Keyword: simulation
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MOPMF006 Test of Stepwise Electron Bunch Replacement in eRHIC Using an Electron Lens in RHIC electron, emittance, proton, experiment 95
 
  • W. Fischer, M.R. Costanzo, A.V. Fedotov, X. Gu, A. Marusic, M.G. Minty, C. Montag, Y. Tan, P. Thieberger
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by U.S. DOE under contract No DE-AC02-98CH10886 with the U.S. Department of Energy.
The electron-ion collider eRHIC requires an electron bunch replacement about every second to maintain both high luminosity and polarization. If the bunch can be replaced in several steps, the requirements for both the electron gun and the electron accelerator are greatly reduced due to the reduced bunch charge. However, a stepwise replacement of electron bunches in eRHIC will give rise to transient effects from the beam-beam interaction that will lead to emittance growth. Such a scheme was tested using one of the RHIC electron lenses with a multiple step increase of the electron current. The test provides an order-of-magnitude estimate of the effect without any further mitigating measures.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF006  
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MOPMF010 Measurement and Simulation of Betatron Coupling Beam Transfer Function in RHIC coupling, betatron, experiment, quadrupole 99
 
  • Y. Luo, W. Fischer, A. Marusic, M.G. Minty
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Transfer function measurements are important for characterizing betatron tunes, betatron coupling, and beam spectrum in the routine operation of the Relativistic Heavy Ion Collider (RHIC). To counteract the linear betatron coupling, we developed a technique to continuously measure the betatron coupling coefficient with a base band phase lock loop tune meter in 2006. Based on this technique, we demonstrated and built a robust tune/coupling feedback in RHIC. In this article, we revisit the BTF measurement with betatron coupling to benchmark our BTF simulation code. We also compared the values of eigenmode projection ratios from BTF with those calculated with the single particle model.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF010  
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MOPMF011 Beam-Beam Issues With Two Interaction Points in eRHIC proton, electron, detector, luminosity 102
 
  • Y. Luo, M. Blaskiewicz, A. He, C. Montag, V. Ptitsyn
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In this article, we study the beam-beam interaction related issues with two interaction points in the current eRHIC ring-ring design. We carried out strong-strong beam-beam simulation in a 2-d bunch intensity scan. We observed coherent beam-beam instability and emittance blowup with 2 collisions per turn at lower bunch intensities than the case with only 1 collision per turn. To deliver collisions to the two experiments simultaneously, we proposed a new bunch filling pattern to avoid 2 collisions per turn for any electron or proton bunch. We proved that the parasitic beam-beam effect with the new bunch filling pattern is negligible.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF011  
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MOPMF012 Study of Crabbed Collision in eRHIC With a Combination of Strong-Strong and Weak-Strong Simulations electron, proton, cavity, luminosity 105
 
  • Y. Luo, G. Bassi, M. Blaskiewicz, W. Fischer, Y. Hao, C. Montag, V. Ptitsyn, V.V. Smaluk, F.J. Willeke
    BNL, Upton, Long Island, New York, USA
  • J. Qiang
    LBNL, Berkeley, California, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In the present design of the future electron-ion collider eRHIC at the Brookhaven National Laboratory, a crossing angle of 22~mrad between the electron and proton orbits at the interaction region is adopted. To compensate the geometric luminosity loss, a local compensation scheme with two sets of crab cavities for each beam is considered. In this article, we first carry out strong-strong beam-beam simulation to study possible coherent beam-beam instability. Under the assumption of no coherent beam-beam motion, we then carry out a weak-strong beam-beam simulation to determine the long-term stability of the proton beam with the equilibrium electron beam sizes extracted from the strong-strong beam-beam simulation.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF012  
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MOPMF014 Polarization at eRHIC Electron Storage Ring, an Ergodic Approach polarization, electron, lattice, storage-ring 112
 
  • F. Méot
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Based on considerations of ergodicity of the dynamical system of an electron bunch at equilibrium, the preservation of polarization in an electron storage ring is estimated from the tracking of a very limited number of electrons. This has a substantial impact on required High Power Computing resources, in noticeable contrast with the method generally used that tracks tens of electron bunches, each comprised of thousands of particles, for several thousands of turns. It is also shown that a minimum number of tracking turns is required in order to ensure the numerical convergence of the linear regressions that yield depolarizing time constant values from tracking, in both methods.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF014  
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MOPMF018 Numerical Simulation of Spin Dynamics with Spin Flipper in RHIC resonance, dipole, polarization, injection 118
 
  • P. Adams, H. Huang, J. Kewisch, F. Méot, P. Oddo, V. Ptitsyn, V.H. Ranjbar, G. Robert-Demolaize, T. Roser
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Spin flipper experiments during RHIC Run 17 were performed to study its effectiveness as a method for polarization sign reversal during stores. Numerical simulations are reported here, which were performed in accompaniment of these, and are being pursued with the aim of accurately reproducing the experimental conditions and providing thorough insight in the role of various key parameters participating in the dynamics of the spin flip, such as the sweep rate of the AC dipole, chromatic orbit control at RHIC snakes, RF parameters, possible effects of non-linear spin resonances, mirror resonance, tolerance on flipper magnet parameters, etc. The ultimate goal is for these simulations to serve as a guidance toward perfect flip to allow routine use during physics Runs.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF018  
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MOPMF022 Luminosity Reduction Caused by the Full-Detuning LLRF Scheme on the HL-LHC Crab Cavities luminosity, cavity, proton, LLRF 129
 
  • E. Yamakawa, R. Apsimon, A.C. Dexter
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • P. Baudrenghien, R. Calaga, F.J. Galindo Guarch
    CERN, Geneva, Switzerland
 
  The High-Luminosity LHC (HL-LHC) crab cavities (CCs) will be installed on both sides of IP1 (ATLAS) and IP5 (CMS) to compensate for the geometric luminosity reduction due to the crossing angle. To cope with the increased beam current (0.55 A DC for LHC, 1.1 A for HL-LHC), the operation of the LLRF system has been changed: rather than fully compensating the transient beam loading, we allow the phase to vary along the turn (100 ps peak-peak with 1.1 A DC). This has been implemented at LHC since July 2017. The CCs have high loaded Q (5e5) and the available RF power is insufficient to follow the bunch phase modulation. The crabbing voltage is not modulated, causing a phase error w.r.t. the individual bunch centroids, leading to transverse kicks of the centroids and an asymmetric crabbing of the bunch cores. We present an analytical model for the resulting luminosity reduction and validate with particle tracking simulations. Due to the symmetry of the bunch filling patterns for the counter-rotating beams, the peak luminosity is reduced by only 2% for nominal HL-LHC parameters at IPs 1 and 5, which is within tolerable limits.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF022  
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MOPMF028 A Superconvergent Algorithm for Invariant Spin Field Stroboscopic Calculations resonance, polarization, storage-ring, lattice 145
 
  • D. Sagan
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Funding: National Science Foundation and the Department of Energy
Stroboscopic averaging can be used to calculate the invariant spin field \bfn for particles with a finite oscillation amplitude in phase space. The standard technique starts with making a guess for \bfn(\bfr), which is a function of the phase space position \bfr. By tracking a particle's orbital position forward in time and then projecting the guessed \bfn backwards to the starting phase space point, the average of the backward projected spins will converge to the invariant spin direction linearly as 1/N where N is the number of turns tracked. The convergence can be accelerated by an iterative method that uses an approximate invariant spin field constructed by averaging the calculated spin field over points that are close in orbital phase space. This superconvergent algorithm has been built into a new program based upon the Bmad toolkit for charged particle and X-ray simulations.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF028  
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MOPMF038 Cleaning Performance of the Collimation System with Xe Beams at the Large Hadron Collider collimation, betatron, heavy-ion, proton 176
 
  • N. Fuster-Martínez, R. Bruce, P.D. Hermes, J.M. Jowett, D. Mirarchi, S. Redaelli
    CERN, Geneva, Switzerland
 
  The LHC heavy-ion program with Pb ions has delivered substantial physics results since the startup of the LHC. There was a Xe run in 2017 in which collimation losses and cleaning were assessed. These studies give a unique opportunity for very valuable benchmark of simulation models with measurements, which could also be very important to understand limitations for future runs with Pb and other species. In this paper, we present collimation loss maps measured in the first ever operation of the LHC with Xe ions. The measurements are compared with simulations and first conclusions are discussed for possible future operation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF038  
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MOPMF040 Crossing Angle Anti-Leveling at the LHC in 2017 luminosity, operation, proton, experiment 184
 
  • N. Karastathis, K. Fuchsberger, M. Hostettler, Y. Papaphilippou, D. Pellegrini
    CERN, Geneva, Switzerland
 
  In 2017, LHC incorporated in operation an anti-leveling procedure of adapting in steps the crossing angle of the colliding beams to increase the integrated luminosity. In this paper, we present the Dynamic Aperture simulations that were employed to identify the operational margins, and therefore define the leveling steps. The results are complemented by observations from nominal operation and projections for the 2018 operation. Additional anti-leveling techniques, investigated in dedicated machine studies are also discussed  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF040  
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MOPMF043 Tuning of CLIC-Final Focus System 3 TeV Baseline Design Under Static and Dynamic Imperfections luminosity, ISOL, collider, linear-collider 196
 
  • E. Marín, A. Latina, J. Pfingstner, D. Schulte, R. Tomás
    CERN, Geneva, Switzerland
  • J. Pfingstner
    University of Oslo, Oslo, Norway
 
  In this paper we present the tuning study of the Compact Linear Collider - Final Focus System (CLIC-FFS) 3~TeV baseline design under static and dynamic imperfections for the first time. The motion of the FFS magnets due to ground motion and the impact of active and passive mechanisms envisaged to stabilize both e- and e+ systems are described. It is found that the Pre-isolator required for stabilization of the Final Doublet drives the performance of the collider at the final stages of the tuning process. The obtained tuning performance depending on the stabilization techniques are discussed in detail.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF043  
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MOPMF044 New Coordination Tools to Prepare Programmed Stops in the LHC and its Injectors hardware, MMI, dipole, FEL 200
 
  • S. Chemli, M. Bernardini, T.W. Birtwistle, A. Bolognesi, B. Brito Da Palma, S.E. Bustamante, J. Coupard, K. Foraz, E. Kleszcz, N. Kotsolakos, T. Krastev, P. A. Kulig, Y. Muttoni, B. Nicquevert, L. Pater, A. Patrascoiu, S. Petit, C. Rauser, A. Wardzinska
    CERN, Geneva, Switzerland
 
  The LHC and its Injectors are submitted to an overall lifecycle of three to four years of physics delivery to Experiments with a two-year long stop, also known as Long Shutdown (LS). The years of physics delivery are ended by a programmed stop for the immediate preventive and corrective maintenance, also known as (Extended)-Year-End Technical Stop - (E)YETS. This regular cycle is to be addressed in parallel with other projects: the upgrade projects to the accelerator complex of the LHC (High-Luminosity project) and to its Injectors (LHC Injectors Upgrade), and the "standard" consolidation tasks. This paper describes the way the programmed stops coordination group prepares the activities to take place during the stop with a set of new tools and processes that ease the communication between the stakeholders of the coordination.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF044  
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MOPMF046 Simulation of Hydrodynamic Tunneling Caused by High Energy Proton Beam in Copper through Coupling of FLUKA and Autodyn target, proton, collider, coupling 204
 
  • Y.C. Nie, A. Bertarelli, F. Carra, C. Fichera, L.K. Mettler, R. Schmidt, D. Wollmann
    CERN, Geneva, Switzerland
 
  For machine protection of high-energy colliders, it is important to assess potential damages caused to accelerator components in case large number of bunches are lost at the same place. The numerical assessment requires an iterative execution of an energy-deposition code and a hydrodynamic code, since the hydrodynamic tunneling effect will likely play an important role in the beam-matter interactions. For proton accelerators at CERN and for the Future Circular Collider (FCC), case studies were performed, coupling FLUKA and BIG2. To compare different hydrocodes and not to rely only on BIG2, FLUKA and a commercial tool, Autodyn, have been used to perform these simulations. This paper reports a benchmarking study against a beam test performed at the HiRadMat (High-Radiation to Materials) facility using beams at 440 GeV from the Super Proton Synchrotron. Good agreement has been found between the simulation results and the test as well as previous simulations with FLUKA and BIG2, particularly in terms of penetration depth of the beam in copper. This makes the coupling of FLUKA and Autodyn an alternative solution to simulating the hydrodynamic tunneling. More case studies are planned for FCC and other high-beam-power accelerators.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF046  
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MOPMF055 Update of the CLIC Positron Source positron, target, linac, electron 236
 
  • Y. Han, L. Ma
    SDU, Shandong, People's Republic of China
  • C. Bayar
    Ankara University, Faculty of Sciences, Ankara, Turkey
  • S. Döbert, A. Latina, D. Schulte
    CERN, Geneva, Switzerland
 
  The baseline positron source of CLIC has been optimised for the 3 TeV c.o.m. energy. Now the first stage of the CLIC is proposed to be at 380 GeV. Recently, the positron transmission efficiency from the tungsten target to the damping rings injection has been improved by 2.5 times. This opened the possibility for an optimisation of the whole positron source, comprising the injector linacs, aimed at improving its performance and its overall power efficiency. In this paper the key parameters of the positron source, which include the current and the energy of the primary electron beam, the thickness of the crystal and amorphous tungsten targets, the distance between the two targets, the adiabatic matching device (AMD) and pre-injector linacs, are optimized to improve the overall power efficiency.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF055  
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MOPMF062 Upgrade of the Dilution System for HL-LHC kicker, operation, Windows, damping 261
 
  • C. Wiesner, W. Bartmann, C. Bracco, M. Calviani, E. Carlier, L. Ducimetière, M.I. Frankl, M.A. Fraser, S.S. Gilardoni, B. Goddard, T. Kramer, A. Lechner, N. Magnin, A. Perillo-Marcone, T. Polzin, E. Renner, V. Senaj
    CERN, Geneva, Switzerland
 
  The LHC Beam Dump System is one of the most critical systems for reliable and safe operation of the LHC. A dedicated dilution system is required to sweep the beam over the front face of the graphite dump core in order to reduce the deposited energy density. The High Luminosity Large Hadron Collider (HL-LHC) project foresees to increase the total beam intensity in the ring by nearly a factor of two, resulting in a correspondingly higher energy deposition in the dump core. In this paper, the beam sweep pattern and energy deposition for the case of normal dilution as well as for the relevant failure cases are presented. The implications as well as possible mitigations and upgrade measures for the dilution system, such as decreasing the pulse-generator voltage, adding two additional kickers, and implementing a retrigger system, are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF062  
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MOPMF068 Quantum Excitation due to Classical Beamstrahlung in Circular Colliders collider, photon, emittance, radiation 281
 
  • M.A. Valdivia García, D. El Khechen, K. Oide, F. Zimmermann
    CERN, Geneva, Switzerland
 
  In the collisions of proposed future circular colliders, like FCC-ee and CEPC, the beamstrahlung regime is classical, i.e. with an "Upsilon parameter" much smaller than 1. In the classical regime, for a constant electromagnetic field a simple relation exists between the average photon energy u and the average squared photon energy u2, which is the same as for standard synchrotron radiation in storage rings. This relation breaks down, however, if the electromagnetic field is not constant in time and position, as is the case for a beam-beam collision. We derive an analytical expression for u2/u2, considering the case of Gaussian-bunch collisions with crossing angle (and possibly crab waist). We compare our result with the photon energies obtained in beam-beam simulation for FCC-ee at beam energies of 45.6 GeV and 175 GeV, using the two independent codes BBWS and Guineapig. Finally, we re-optimize the FCC-ee parameters of a possible mono-chromatization scheme for direct Higgs production at 125 GeV, derived previously, by applying the refined expression for the rms photon energy.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF068  
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MOPMF070 High Voltage Design for the Electrostatic Septum for the Mu2e Beam Resonant Extraction cathode, high-voltage, vacuum, extraction 289
 
  • M.L. Alvarez, C.C. Jensen, D.K. Morris, V.P. Nagaslaev, H. Pham, D.G. Tinsley
    Fermilab, Batavia, Illinois, USA
 
  Two electrostatic septa (ESS) are being designed for the slow extraction of 8GeV proton beam for the Mu2e experiment at Fermilab. Special attention is given to the high voltage components that affect the performance of the septa. The components under consideration are the high voltage (HV) feedthrough, cathode standoff (CS), and clearing electrode ceramic standoffs (CECS). Previous experience with similar HV systems at Fermilab was used to define the evaluation criteria of the design of the high voltage components. Using electric field simulation software, high E-field intensities on the components and integrated field strength along the surface of the dielectric material were minimized. Here we discuss the limitations found and improvements made based on those studies.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF070  
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MOPMF085 Beam-gas Background Characterization in the FCC-ee IR scattering, background, vacuum, optics 322
 
  • M. Boscolo, O.R. Blanco-García
    INFN/LNF, Frascati (Roma), Italy
  • H. Burkhardt, R. Kersevan, M. Lueckhof
    CERN, Geneva, Switzerland
  • F. Collamati
    INFN-Roma1, Rome, Italy
 
  The MDISim toolkit is used to evaluate and characterize the beam-gas induced background in the FCC-ee Interaction Region. MDISim allows a full characterization of this beam background source with the locations where the beam-gas scattering occurs as well as the loss points, as a function of different vacuum conditions and composition, for the nominal optics and parameters. Detailed pressure distribution profiles have been obtained running coupled synchrotron radiation and molecular flow montecarlo codes, as an input to the GEANT4 calculations. The particles hitting the pipe in the IR can be tracked in the detectors with a full Geant-4 simulation. Semi-analytic estimates for the expected rates and lifetime are also performed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF085  
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MOPMF090 First Studies of Ion Collimation for the LHC Using BDSIM collimation, hadron, heavy-ion, proton 341
 
  • A. Abramov, S.T. Boogert, L.J. Nevay, S.D. Walker
    JAI, Egham, Surrey, United Kingdom
 
  At the Large Hadron Collider (LHC) at CERN ion physics runs are performed in addition to proton physics runs. In ion operation the cleaning efficiency of the collimation system is lower than in the case of protons and the ion showering process is more complicated and produces a larger variety of secondary particles. In particular, lighter ion species can be produced as fragmentation products in the collimation system and specialised physics lists are required to simulate their production and propagation in matter. The Geant4 toolkit offers comprehensive physics process lists that extend to the case of arbitrary ion species at high energies. First results from a study of ion collimation for the LHC using the Geant4 physics library in BDSIM are presented here. These include simulations of a full ring loss map and particle spectra for collimator leakage for a Pb beam at injection energy in the LHC.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF090  
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MOPMK010 Study Progress of the Coupling Resonance of the Crab Crossing Scheme in Electron-Ion Collider luminosity, electron, synchrotron, cavity 368
 
  • Y. Hao
    FRIB, East Lansing, USA
  • Y. Luo, V. Ptitsyn
    BNL, Upton, Long Island, New York, USA
  • J. Qiang
    LBNL, Berkeley, California, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Crab crossing scheme is essential collision scheme to achieve high luminosity for the future electron-ion collider (EIC). The bunch length effect of the ion beam cannot be ignored even when cooling is present compared with the wavelength of the crab cavity, therefore, the nonlinear dependence of the crabbing kick may present a challenge to the beam dynamics of the ion beam, hence an impact to the luminosity lifetime. In this paper, we present the result of numerical beam dynamics studies of the crab crossing scheme. The result indicates that there is a special coupling resonance in the nonlinear relation of the crab crossing scheme of the EIC, which dominates the luminosity degradation. And we will discuss the possible remedies for such resonance.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMK010  
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MOPMK012 Electron Cloud Studies in FCC-ee electron, collider, quadrupole, vacuum 374
 
  • E. Belli
    Sapienza University of Rome, Rome, Italy
  • P. Costa Pinto, G. Rumolo, T.F. Sinkovits, M. Taborelli
    CERN, Geneva, Switzerland
  • M. Migliorati
    INFN-Roma1, Rome, Italy
 
  Electron cloud effects are one of the most critical aspects for the LHC and the future circular colliders. In the frame of the electron-positron collider FCC-ee, an estimation of the electron cloud build up in the machine will be discussed in this paper. A preliminary evaluation of the heat load in the arc components and interaction region magnets will be presented, together with possible mitigation strategies.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMK012  
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MOPMK016 Calculations of Beam-Beam Effect and Luminosity for Crab Dynamics Simulations in JLEIC luminosity, collider, electron, beam-beam-effects 386
 
  • H. Huang, V.S. Morozov, A.V. Sy
    JLab, Newport News, Virgina, USA
 
  Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contracts DE-AC05-06OR23177 and DE-AC02-06CH11357.
Crab crossing is an integral part of the Jefferson Lab Electron-Ion Collider (JLEIC) design to achieve high luminosity while meeting the detection and physics pro-gram requirements. The crab crossing scheme provides a head-on beam-beam collision for beams with a nonzero crossing angle. Simulations of crabbing dynamics currently do not include beam-beam effects. We describe a framework for accurate simulation of beam-beam effects on crabbing dynamics by applying a numerical calculation of the Bassetti-Erskine analytic solution to symplectic particle tracking codes. The numerical calculation is benchmarked against the analytic solution by calculating the luminosity reduction for several colliding beam scenarios. Benchmarking results show good agreement be-tween the numerical calculation and analytic solution, paving the way for implementation of the beam-beam kick to Elegant tracking simulations.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMK016  
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MOPML006 Multi-Stage Electron Cooling Scheme for JLEIC emittance, proton, electron, collider 397
 
  • H. Zhang, S.V. Benson, Y.S. Derbenev, Y. Roblin, Y. Zhang
    JLab, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and DE-AC02-06CH11357.
JLEIC is the future electron ion collider under design at Jefferson Lab, which will provide a luminosity up to 1034 cm-2s-1. Electron cooling is essential for JLEIC to overcome the intrabeam scattering effect, reduce the ion beam emittance and thus achieve the high luminosity. The cooling time is approximately in proportion to the square of the energy and the 6D emittance. To avoid the difficulty of cooling the ion beam with large emittance at high energy, a multi-stage cooing scheme was designed for JLEIC. The ion beam was cooled at the low energy to reduce the emittance. Then it was ramped up to the collision energy. During the collision, electron cooling is implemented to maintain the emittance and the luminosity. Simulations for proton beam and lead ion beam at various stages are presented in this paper.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML006  
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MOPML010 Challenges and Status of Tuning Simulations for CLIC Traditional Beam Delivery System luminosity, linear-collider, collider, lattice 412
 
  • R.M. Bodenstein, P. Burrows
    JAI, Oxford, United Kingdom
  • E. Marín
    CERN, Geneva, Switzerland
 
  The beam delivery system (BDS) for the 3 TeV version of the Compact Linear Collider (CLIC) has two main design types. One type is referred to as the local scheme, as it is approximately one kilometer shorter and corrects the chromaticity in both planes. The other type is referred to as the traditional scheme, and separates the chromaticity correction of each plane into different areas. The expectation early in the studies was that the traditional scheme would be easier to tune. This work will address the problems experienced in tuning simulations for the traditional BDS and describe the current state of these simulations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML010  
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MOPML012 Special Collimation System Configuration for the LHC High-Beta Runs background, collimation, detector, experiment 418
 
  • H. Garcia Morales
    Royal Holloway, University of London, Surrey, United Kingdom
  • R. Bruce, H. Burkhardt, M. Deile, S. Jakobsen, A. Mereghetti, S. Redaelli
    CERN, Geneva, Switzerland
 
  Special LHC high-beta optics is required for the forward physics program of TOTEM and ATLAS-ALFA. In this configuration, the beam is de-squeezed (the \beta-function at the collision point is increased) in order to minimize the divergence for measurements at very small scattering angles. In these low beam intensity runs, it is important to place the Roman Pots (RPs) as close as possible to the beam, which demands special collimator settings. During Run I, a significant amount of background was observed in the forward detectors due to particles outscattered from the primary collimator. During Run II, a different collimation configuration was used where a tungsten collimator was used as primary collimator instead of the usual one made of carbon. Using this configuration, a significant reduction of the background at the RPs was observed. In this paper we present a description of the new collimator configuration and the results obtained during the high-beta run carried out in 2016.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML012  
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MOPML020 Numerical Simulations to Evaluate and Compare the Performances of Existing and Novel Degrader Materials for Proton Therapy scattering, emittance, proton, shielding 435
 
  • R. Tesse, A. Dubus, N. Pauly
    ULB - FSA - SMN, Bruxelles, Belgium
  • C. Hernalsteens, W.J.G.M. Kleeven, F. Stichelbaut
    IBA, Louvain-la-Neuve, Belgium
 
  The performance of the energy degrader in terms of beam properties directly impacts the design and cost of cyclotron-based proton therapy centers. The aim of this study is to evaluate the performances of different existing and novel degrader materials. The quantitative estimate is based on detailed Geant4 simulations that analyze the beam-matter interaction and provide a determination of the beam emittance increase and transmission. Comparisons between existing (aluminium, graphite, beryllium) and novel (boron carbide and diamond) degrader materials are provided and evaluated against semi-analytical models of multiple Coulomb scattering. The results showing a potential in emittance reduction for novel materials are presented and discussed in detail.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML020  
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MOPML022 Development of Travelling Wave Accelerating Structure for a 10 MeV E-Linac electron, bunching, radiation, linac 443
 
  • J.H. Yang, Y. Yang
    CIAE, Beijing, People's Republic of China
  • G. Han
    China Institute of Atomic Energy, Beijing, People's Republic of China
 
  Electron irradiation processing is a vital application field of nuclear technology application. China Institute of Atomic Energy (CIAE) developed several 10 MeV high power electron irradiating accelerator successfully, promoting the development of high energy high power irradiating accelerator technology and electron irradiation processing in China. The paper introduced the development of a 10 MeV travelling wave accelerating tube. The tube operates at 2856 MHz in 2π/3 mode. The SUPERFISH and PARMELA are used for the physical design. Several methods are used for microwave parameter measurement and tuning. The high power test shows the beam energy is 10.3 MeV and average beam power is 24.3 kW.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML022  
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MOPML023 Very-High Energy Electron (VHEE) Studies at CERN's CLEAR User Facility experiment, electron, scattering, proton 445
 
  • A. Lagzda, R.M. Jones
    UMAN, Manchester, United Kingdom
  • A. Aitkenhead, K. Kirkby, R. MacKay, M. Van Herk
    The Christie NHS Foundation Trust, Manchester, United Kingdom
  • R. Corsini, W. Farabolini
    CERN, Geneva, Switzerland
 
  Funding: Science and Technology Facilities Council (STFC) - United Kingdom
Here we investigate how inserts of various densities (0.001-2.2 g/cm3) affect the dose distribution properties of VHEE beams at ~150 MeV. A range variation comparison was also made with clinical proton beams using TOPAS/GEANT4 Monte Carlo simulations. In addition, we assess the viability of scattering foils for optimizing the size of VHEE beams for radiotherapy purposes. The experiments were conducted at CERN's CLEAR user facility.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML023  
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MOPML039 Comparison of Two Types of Steerers Applied in Proton Therapy Gantry quadrupole, proton, superconductivity, radiation 488
 
  • Z.F. Zhao, Q.S. Chen, S. Hu, X. Liu, B. Qin, W. Wei
    HUST, Wuhan, People's Republic of China
  • W. Chen
    Huazhong University of Science and Technology, State Key Laboratory of Advanced Electromagnetic Engineering and Technology,, Hubei, People's Republic of China
 
  A proton therapy project HUST-PTF (HUST Proton Therapy Facility) based on a 250MeV isochronous superconducting cyclotron is under development in Huazhong University of Science and Technology (HUST). Based on the optics design of the gantry, the steering magnets need to be placed in a compact structure, as well as meet the magnetic field requirement with a maximum deflection angle of ±5mrad@250MeV. In the paper, two types of steerers (O-shape and H-shape) were introduced and discussed in detail. The magnetic fringe field interference effects between quadrupoles and steerers were studied by using OPERA/TOSCA code. The result based on the contrastive analysis will give us a valuable reference to choose suitable steerers for proton therapy beamline.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML039  
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MOPML052 The Path to Compact, Efficient Solid-State Transistor-Driven Accelerators cavity, electron, linac, impedance 520
 
  • D.C. Nguyen, C.E. Buechler, G.E. Dale, R.L. Fleming, M.A. Holloway, J.W. Lewellen, D. Patrick
    LANL, Los Alamos, New Mexico, USA
  • V.A. Dolgashev, E.N. Jongewaard, E.A. Nanni, J. Neilson, A.V. Sy, S.G. Tantawi
    SLAC, Menlo Park, California, USA
 
  Funding: Research presented in this work is supported by (LANL) Laboratory Directed Research and Development 20170521ER and by (SLAC) Department of Energy contract DE-AC02-76SF00515.
Small, lightweight, few-MeV electron accelerators that can operate with low-voltage power sources, e.g., solid-state transistors running on 50 VDC, instead of high-voltage klystrons, will provide a new tool to enhance existing applications of accelerators as well as to initiate new ones. Recent advances in gallium nitride (GaN) semiconductor technologies * have resulted in a new class of high-power RF solid-state devices called high-electron mobility transistors (HEMTs). These HEMTs are capable of generating a few hundred watts at S-, C- and X-bands at 10% duty factor. We have characterized a number of GaN HEMTs and verified they have suitable RF characteristics to power accelerator cavities **. We have measured energy gain as a function of RF power in a single low-beta C-band cavity. The HEMT powered RF accelerators will be compact and efficient, and they can operate off the low-voltage DC power buses or batteries. These all-solid-state accelerators are also more robust, less likely to fail, and are easier to maintain and operate. In this poster, we present the design of a low-beta, 5.1-GHz cavity and beam dynamics simulations showing continuous energy gain in a ten-cavity C-band prototype.
* See for example, http://www.wolfspeed.com/downloads/dl/file/id/463/product/174/cghv59350.pdf
** J.W. Lewellen et al., Proceedings of LINAC2016, Paper MO3A03
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML052  
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MOPML054 Production and Collection of He-3 and Other Valuable Isotopes using Mu*STAR controls, proton, MMI, interface 527
 
  • R.P. Johnson, R.J. Abrams, M.A. Cummings, T.J. Roberts
    Muons, Inc, Illinois, USA
 
  We propose an example facility based on GEM*STAR, an accelerator-driven molten-salt-fueled graphite-moderated thermal-spectrum reactor that can operate with different fissile fuels and uses a LiF-BeF2 molten eutectic carrier salt. In the first example, they propose using the 6Li in the LiF carrier to produce more than 2 kg/y of tritium (decaying to 3He with 12.3 year half-life) using a 2.5 MWb superconducting proton linac to drive the subcritical 500 MWt reactor burning surplus plutonium. The collection of other valuable fission-product radioisotopes like 133Xe will also benefit from the high temperature and continuous removal and separation afforded by fractional distillation  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML054  
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MOPML055 Preliminary Physics Design of a Linac with the Variable Energy for Industrial Applications linac, electron, gun, beam-loading 530
 
  • Zh. X. Tang
    USTC, Hefei, Anhui, People's Republic of China
  • L. Wang, D.R. Xu
    USTC/NSRL, Hefei, Anhui, People's Republic of China
 
  This paper describes the physics design of a S-band (2856 MHz) linear accelerator (linac) with variable energy tuning. The system consists of a DC gun for generating electron, prebuncher for velocity modulation and two travelling wave (TW) accelerating sections for acceleration. The accelerating structure is a 2'Ð/3 mode constant gradient TW structure, which comprises TW buncher cells, followed by uniform cells. The structure is designed to accelerate 45 keV electron beam from the electron gun to 3.2 MeV, and then 10 MeV. An important feature of the TW linac is that the RF output power of the first linac is as the RF input power of the second linac. Three dimensional transient simulations of the accelerating structure along with the input and output couplers have been performed to explicitly demonstrate this feature. Beam dynamics is performed to calculate the beam parameter.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML055  
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MOPML060 Self-Consistent Simulation and Optimization of Space-Charge Limited Thermionic Energy Converters electron, space-charge, cathode, feedback 543
 
  • N.M. Cook, J.P. Edelen, C.C. Hall
    RadiaSoft LLC, Boulder, Colorado, USA
  • J.-L. Vay
    LBNL, Berkeley, California, USA
 
  Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC0017162.
Thermionic energy converters (TEC) are an attractive technology for modular, efficient transfer of heat to electrical energy. The steady-state dynamics of a TEC are a function of the emission characteristics of the cathode and anode, an array of intra-gap electrodes and dielectric structures, and the self-consistent dynamics of the electrons in the gap. Proper modeling of these devices requires self-consistent simulation of the electron interactions in the gap. We present results from simulations of these devices using the particle-in-cell code Warp, developed at Lawrence Berkeley National Lab. We consider the role of individual energy loss mechanisms in reducing device efficiency, including kinetic losses, radiative losses, and dielectric charging. We discuss the implementation of an external circuit model to provide realistic feedback. Lastly, we illustrate the potential to use nonlinear optimization to maximize the efficiency of these devices by examining grid transparency.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML060  
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MOPML061 Hadron Therapy Machine Simulations Using BDSIM hadron, hadrontherapy, lattice, proton 546
 
  • W. Shields
    JAI, Egham, Surrey, United Kingdom
  • S.T. Boogert, L.J. Nevay
    Royal Holloway, University of London, Surrey, United Kingdom
  • J. Snuverink
    PSI, Villigen PSI, Switzerland
 
  Minimising the background radiation dose in hadron therapy from particle losses and secondary emissions is of the highest importance for patient protection. To achieve this, tracking particles from source to the patient delivery region in a single simulation provides a quantitative description that distinguishes the background radiation from the treatment dose arriving at the gantry's isocentre. We demonstrate the ability to simulate beam transport, particle loss studies, and background radiation tracking in an example hadron therapy machine using BDSIM, a Geant4 based Monte Carlo simulation code for tracking high energy particles within a particle accelerator and its surrounding environment. Machine optics verification is also demonstrated through comparison to existing accelerator tracking codes.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML061  
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MOPML069 Enhancing Hadron Therapy through OMA proton, FEL, medical-accelerators, hadron 568
 
  • C.P. Welsch
    The University of Liverpool, Liverpool, United Kingdom
  • C.P. Welsch
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
 
  Funding: This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie SkłodowskaCurie grant agreement No 675265.
Continued research into the optimization of medical accelerators is urgently required to assure the best possible cancer care for patients and this is one of the central aims of the OMA project which received 4 M€ of funding from the European Commission. A consortium of universities, research and clinical facilities, as well as partners from industry carry out an interdisciplinary R&D program across three closely interlinked scientific work packages. These address the development of novel beam imaging and diagnostics systems, studies into treatment optimization including innovative schemes for beam delivery and enhanced biological and physical models in Monte Carlo codes, as well as R&D into clinical facility design and optimization to ensure optimum patient treatment along with maximum efficiency. Selected research highlights from across these work packages will be presented and the impact on hadron therapy facilities around the world discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML069  
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MOPML070 Thermal and Stress Analysis of an X-Ray Target for 6 MeV Medical Linear Accelerators target, electron, site, photon 572
 
  • Z.H. Wang, H.B. Chen, J. Shi, H. Zha
    TUB, Beijing, People's Republic of China
 
  We present an optimal design of an X-ray target for 6 MeV medical linear accelerators using FLUKA simula-tions. The target is composed of high-atomic number tungsten and high-thermal conductivity copper, corre-sponding water-cooling system is showed too. Further-more, we analyse the temperature and thermal stress re-sponses of the target under transient thermal loads using Ansys Code. For 6 MeV electron beam with 100 uA cur-rent, the results show that the target can achieve 1014 cGy/min at 1meter in front of the target. Within 100 ms, the maximum temperature reaches 512 °C under pulsed heating source with 250 Hz frequency and 1' duty cycle and the number of cycles to failure is estimated as 5.8·108.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML070  
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TUXGBF3 Reduction of the Kicker Impedance Maintaining the Performance of Present Kicker Magnet at RCS in J-PARC kicker, impedance, synchrotron, extraction 616
 
  • Y. Shobuda, Y. Irie, T. Takayanagi, T. Togashi, K. Yamamoto, M. Yamamoto
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
 
  The present kicker at RCS in J-PARC is designed to make a waveform by superposing the forward and backward currents from the power source to extract beams, so that one terminal of the kicker is shorted and the other one is open. On the other hand, the kicker impedance is the dominant source of the beam instability at the RCS. This report proposes a scheme to reduce the kicker impedance, maintaining the beneficial of the superposition of currents with the present kicker magnet.  
slides icon Slides TUXGBF3 [9.951 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUXGBF3  
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TUXGBF4 ORBIT Simulation, Measurement and Mitigation of Transverse Beam Instability in the Presence of Strong Space Charge in the 3-GeV RCS of J-PARC impedance, injection, acceleration, space-charge 620
 
  • P.K. Saha, H. Harada, N. Hayashi, H. Hotchi, Y. Shobuda, F. Tamura
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
 
  The transverse impedance of eight extraction pulse kicker magnets (KM) is extremely strong source of transverse beam instability in the 3-GeV RCS (Rapid Cycling Synchrotron) at J-PARC. To realize the designed 1 MW beam power, collective beam dynamics with including the space charge effect for the coupled bunch instabilities excited by the KM impedance and associated measures were studied by incorporating all realistic time-dependent machine parameters in the ORBIT 3-D particle tracking code. The simulation results were all reproduced by measurements and, as a consequence, an acceleration of 1 MW beam power has been successfully demonstrated. In order to maintain variation of the RCS parameters required for multi-user operation, realistic measures for beam instability mitigation were proposed and also been successfully implemented in reality. To further increase the RCS beam power, beam stability issues and possible measures beyond 1 MW beam power are also considered.  
slides icon Slides TUXGBF4 [2.246 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUXGBF4  
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TUYGBD4 Beam Loss Background and Collimator Design in CEPC Double Ring detector, scattering, background, radiation 632
 
  • S. Bai, J. Gao, H. Geng, D. Wang, Y. Wang, C.H. Yu, Y. Zhang
    IHEP, Beijing, People's Republic of China
 
  The Circular Electron Positron Collider (CEPC) is a proposed Higgs factory with center of mass energy of 240 GeV to measure the properties of Higgs boson and test the standard model accurately. Beam loss background in detectors is an important topic at CEPC. Radiative Bhabha scattering and Beamstrahlung effects are dominant mechanism of the beam induced backgrounds at CEPC due to the beam lifetime. In this paper, we evaluated the beam loss background in simulation and designed a series of collimators to suppress the radiation level on the machine and the detector.  
slides icon Slides TUYGBD4 [0.796 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUYGBD4  
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TUPAF005 Status of AC-Dipole Project at RHIC Injectors for Polarized Helions dipole, booster, resonance, proton 669
 
  • K. Hock, H. Huang, F. Méot, P. Oddo, N. Tsoupas, J.E. Tuozzolo, K. Zeno
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Polarized helions will be used in the eRHIC collider to collide with polarized electrons. To allow efficient transport of polarized helions in the Booster, to rigidities sufficiently high (B rho=10.8 T.m, |G gamma|=10.5) for minimizing the optical perturbations from the two partial helical dipoles in the AGS, an upgrade for overcoming depolarizing intrinsic resonances is needed. An AC-dipole is being designed to induce spin flips through intrinsic resonances. Booster AC-dipole operation will be established with protons while the polarized helion source is being completed. This paper reports the status of the project (which is now well advanced after two years of theoretical and design studies) and provides an overview of proof of principle experiments to take place after successful installation of the AC-dipole, during RHIC Run 19 with polarized proton beams.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF005  
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TUPAF025 Multi-turn Study in FLUKA for the Design of CERN-PS Internal Beam Dumps dumping, experiment, operation, proton 724
 
  • J.A. Briz Monago, M. Calviani, F. Cerutti, J.J. Esala, S.S. Gilardoni, F.-X. Nuiry, G. Romagnoli, G. Sterbini, V. Vlachoudis
    CERN, Geneva, Switzerland
 
  The CERN Proton-Synchrotron (PS) accelerator is currently equipped with two internal beam dumps in operation since the 1970's. An upgrade is required to be able to withstand the beams that will be produced after the end of the LIU (LHC Injector Upgrade) project. For the design of the new dumps, the interaction and transport of beam and all secondary particles generated has been simulated using FLUKA. The working principle of the internal beam dump in the PS ring is very peculiar with respect to the other dumps in the CERN accelerator complex. A moving dump intercepts the circulating beam during few milliseconds like a fast scraper. The moving dump shaving the beam, the multi-turn transport of beam particles in the PS accelerator and a time-dependent energy deposition in the dump were modeled. The methodology and the results obtained in our studies for the dump core and downstream equipment will be reported in this contribution.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF025  
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TUPAF027 CERN PS Kicker for Proton Injection: from Beam-Based Waveform Measurements to Hardware Improvements kicker, injection, emittance, flattop 732
 
  • V. Forte, A. Ferrero Colomo, M.A. Fraser, T. Kramer
    CERN, Geneva, Switzerland
 
  For 2017 operation, the termination mode of the CERN Proton Synchrotron (PS) horizontal injection kicker was permanently changed to short-circuited, to be compliant with the future performances requested by the LHC Injectors Upgrade (LIU) project. An extensive campaign of measurements was performed through a dedicated beam-based technique. The measurements identified possibilities for optimisation of the kicker system and were fundamental to properly tune the PSpice simulation model of the kicker, as well as for validating the hardware changes. The model was finally used to estimate the horizontal emittance growth for the future injection schemes in the PS.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF027  
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TUPAF028 Energy Deposition Studies and Analysis of the Quench Behavior in the Case of Asynchronous Dumps During 6.5 TeV LHC Proton Beam Operation superconducting-magnet, proton, quadrupole, kicker 736
 
  • M.I. Frankl, W. Bartmann, M. Bednarek, C. Bracco, A. Lechner, A.P. Verweij, C. Wiesner, D. Wollmann
    CERN, Geneva, Switzerland
 
  The CERN LHC beam dumping system comprises a series of septa and fast-pulsed kicker magnets for extracting the stored proton beams to the external beam dumps. Different absorbers in the extraction region protect superconducting magnets and other machine elements in case of abnormal beam aborts, where bunches are swept across the machine aperture. During Run 2 of the LHC, controlled beam loss experiments were carried out at 6.5 TeV probing the particle leakage from protection devices under realistic operation conditions. This paper presents particle shower simulations analyzing the energy deposition in superconducting coils and assessing if the observed magnet quenches are compatible with the presently known quench limits.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF028  
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TUPAF030 Electron Cloud Build Up for LHC Sawtooth Vacuum Chamber electron, vacuum, photon, synchrotron 744
 
  • G. Guillermo Cantón, F. Zimmermann
    CERN, Geneva, Switzerland
  • G.H.I. Maury Cuna, E. D. Ocampo
    Universidad de Guanajuato, División de Ciencias e Ingenierías, León, Mexico
 
  At high proton-beam energies, beam-induced synchrotron radiation is an important source of heating, of beam-related vacuum pressure increase, and of primary photoelectrons, which can give rise to an electron cloud. For the arcs of LHC a sawtooth pattern had been imprinted on the horizontally outward side  of the vacuum chamber in order to locally absorb synchrotron radiation photons without dispersing them all around the chamber. Using the combination of the codes Synrad3D and PyCLOUD we examine the effect of realistic absorption distributions with and without sawtooth on the build up of electron clouds.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF030  
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TUPAF031 Beam Simulation Studies for the Upgrade of the SPS Beam Dumping System kicker, dumping, operation, injection 747
 
  • C. Heßler, W. Bartmann, E. Carlier, L. Ducimetière, B. Goddard, F.M. Velotti
    CERN, Geneva, Switzerland
 
  The SPS at CERN currently uses a beam dumping system that is installed in the long straight section 1 (LSS1) of the SPS. This system consists of two beam stopper blocks for low and high energy beams, as well as two vertical and three horizontal kicker magnets, which deflect and dilute the beam on the dumps. Within the frame of the LHC injector upgrade project (LIU) the beam dumping system will be relocated to long straight section 5 (LSS5) and upgraded with an additional vertical kicker, new main switches and a single new beam dump, which covers the full energy range. The impact of a possible increase of the vertical kicker rise time on the beam has been studied in simulations with MAD-X for the different optics in the SPS. Furthermore, the impact on the beam in failure scenarios such as the non-firing of one kicker has been investigated. The results of these studies will be presented and discussed in this paper. Operational mitigation methods to deal with an increased rise time will also be discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF031  
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TUPAF035 Observations of SPS Slow-Extracted Spill Quality Degradation and Possible Improvements extraction, quadrupole, power-supply, experiment 761
 
  • F.M. Velotti, H. Bartosik, K. Cornelis, M.A. Fraser, B. Goddard, S. Hirlaender, V. Kain, O. Michels, M. Pari
    CERN, Geneva, Switzerland
 
  The SPS delivers slow extracted proton and heavy ion spills of several seconds to the North Area fixed target experiments with a very high duty factor. Reduced machine reproducibility due to magnetic history and power supply ripples on the main circuits lead however to frequent degradation of the spill duty factor. In this paper, the measured effect of the SPS magnetic history on spill quality and principal machine parameters is presented. Another detailed measurement campaign was aimed at characterising the frequency content and response of the spill to noise on the main power supplies ripples. The main findings of this study will also be reported. Finally, simulations of possible improvements based on the data acquired are discussed, as well as an extrapolation to the possible spill quality after the implementation of the improvements.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF035  
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TUPAF037 Validation of the CERN PS Eddy Current Injection Septa septum, vacuum, injection, HOM 768
 
  • M. Hourican, B. Balhan, J.C.C.M. Borburgh, T. Masson, A. Sanz Ull
    CERN, Geneva, Switzerland
 
  As part of the upgrade of the CERN PS accelerator from 1.4 GeV to 2 GeV, new injection septa have been developed. The system is comprised of a pulsed eddy current septum magnet and a pulsed eddy current bumper magnet. Both magnets will be housed in a common vacuum vessel and powered by independent power converters. In-depth studies and simulations have been performed to reduce as much as possible the leak field by designing specific magnetic shielding, combined with dual function beam impedance shielding. A prototype magnet was built and measured to validate the simulations. The final complete system will be bake-able at 200C and uses demineralised water for cooling. Closed circuit cooling systems have been integrated to reduce risks of vacuum leaks. This report describes the electromechanical design from the concept and simulation stages to the prototyping and final manufacturing. Results of the initial magnetic measurements, including field homogeneity and leak field mitigation methods are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF037  
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TUPAF039 Electron Cooling Simulation and Experimental Benchmarks at LEIR electron, plasma, experiment, solenoid 776
 
  • A. Latina, H. Bartosik, N. Biancacci, R. Corsini, D. Gamba, S. Hirlaender, A. Huschauer
    CERN, Geneva, Switzerland
 
  A fast and accurate simulation of Electron Cooling has recently been implemented in the tracking code RF-Track. The implementation, which is based on a "hybrid kinetic" model, enables the simulation of a large variety of realistic scenarios, including imperfections such as gradients in the electron density, misalignments of electrons / ions / solenoidal fields, both in the static and in the dynamic regimes. Benchmarks of the simulations against measurements performed at LEIR, using Lead and Xenon ions, are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF039  
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TUPAF040 Beam Loss Measurements for Recurring Fast Loss Events During 2017 LHC Operation Possibly Caused by Macroparticles proton, operation, dipole, insertion 780
 
  • A. Lechner, B. Auchmann, E. Bravin, A.A. Gorzawski, L. K. Grob, E.B. Holzer, B. Lindstrom, T. Medvedeva, D. Mirarchi, R. Schmidt, M. Valette, D. Wollmann
    CERN, Geneva, Switzerland
 
  The availability of the LHC machine was adversely affected in 2017 by tens of beam aborts provoked by frequent loss events in one standard arc cell (16L2). In most of the cases, the dumps were triggered by concurrently developing fast beam instabilities leading to particle losses in the betatron cleaning insertion. Many of the events started with a distinct sub-millisecond loss peak comparable to regular dust particle events, which have been observed along all the LHC since the start-up. In contrast to regular dust events, persistent losses developed in cell 16L2 after the initial peaks which can possibly be explained by a phase transition of macroparticles to the gas phase. In this paper, we summarize the observed loss characteristics such as spatial loss pattern and time profiles measured by Beam Loss Monitors (ionization chambers). Based on the measurements, we estimate the energy deposition in macroparticles and reconstruct proton loss rates as well as the gas densities after the phase transition. Differences between regular dust events and events in 16L2 are highlighted and the ability to induce magnet quenches is discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF040  
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TUPAF046 Conceptual Design of a Collimation System for the CERN Super Proton Synchrotron collimation, optics, proton, injection 802
 
  • M. Patecki, A. Mereghetti, D. Mirarchi, S. Redaelli
    CERN, Geneva, Switzerland
 
  The Super Proton Synchrotron (SPS) is the last accelerator in the LHC Injectors Chain. Its performance is constantly being improved in frame of the LHC Injectors Upgrade (LIU) Project in order to prepare it for the future HL-LHC (High Luminosity LHC) operation. One of the LIU goals is to nearly double the intensity extracted from the SPS, up to 2.32×1011 p/bunch. In recent years, nearly 10% of losses are observed for nominal intensity and LHC-type beams; they grow to about 20% for the intensity approaching the HL-LHC target. Beam losses imply activation and aging of the SPS hardware; the possibility to add a collimation system is being considered to mitigate this problem. In this paper we present studies of a collimation system design for the SPS. The concept is based on a primary horizontal collimator located in an available position with high enough dispersion, and a secondary collimator to intercept the particles leaking out from the primary collimator. Performance of the proposed collimation system is evaluated by means of numerical simulations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF046  
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TUPAF048 LIU Space Charge Studies for the LHC Pre-Accelerators space-charge, injection, proton, resonance 810
 
  • F. Schmidt, H. Bartosik
    CERN, Geneva, Switzerland
 
  In 2011 a working group has been started to study performance limitations due to Space Charge (SC) in the four LHC pre-accelerators, LEIR, PSB, PS & SPS, in view of the LHC Injector Upgrade (LIU) project. To this end external and in-house simulation tools have been benchmarked for the LIU study cases with the long-term goal of providing a full sequence of tested CERN Space Charge tools. It became clear that SC studies must be combined with trustworthy models of the machines, including linear and non-linear errors. In particular an effective s-dependent non-linear model is required. Recent studies indicate that also the low frequency ripple spectrum due to conventional power supplies might play an important role for the beam dynamics in presence of space charge in the pre-injectors.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF048  
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TUPAF051 Investigating Beam Loss Reduction with Octupoles During Slow Extraction in the CERN SPS extraction, octupole, multipole, optics 822
 
  • L.S. Stoel, M. Benedikt, M.A. Fraser, B. Goddard
    CERN, Geneva, Switzerland
  • K.A. Brown
    BNL, Upton, Long Island, New York, USA
 
  Several different methods for reducing beam loss during resonant slow extraction at the CERN Super Proton Synchrotron (SPS) are being studied. One of these methods is the use of multipoles to manipulate the separatrices in order to reduce the fraction of protons hitting the thin wires of the electrostatic extraction septum (ES). In this paper the potential of using octupoles for this purpose is explored. Beam dynamics simulations using both a simplified model and full 6D tracking in MAD-X are presented. The performance reach of such a concept at the SPS is evaluated and the potential of future machine development studies using the octupoles already installed is discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF051  
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TUPAF052 Effects of Electrostatic Septum Alignment on Particle Loss During Slow Extraction at CERN SPS alignment, extraction, operation, septum 826
 
  • J. Prieto, Y. Dutheil, M.A. Fraser, B. Goddard, V. Kain, L.S. Stoel, F.M. Velotti
    CERN, Geneva, Switzerland
  • M.A. Kagan
    SLAC, Menlo Park, California, USA
 
  Slow extraction is an intrinsically lossy process that splits the beam with an electrostatic septum (ES), employing a thin-wire array to delimit the high electric field region that deflects the beam into the extraction channel. At CERN's Super Proton Synchrotron (SPS) the ES is over 16 m long and composed of 5 separate units containing separate wire-arrays that can be moved independently. The tanks are all mounted on a single support structure that can move the ensemble coherently. As a result, the large number of positional degrees of freedom complicates the alignment procedure in operation. Obtaining and maintaining accurate alignment of the ES with the beam is therefore crucial for minimising beam loss. In this paper, we investigate the alignment procedure for different operational scenarios using particle tracking simulations to understand the beam loss along the extraction straight as a function of the relative positions of each of the 5 separate ES units. An important aspect of the study was to understand the required alignment tolerance to achieve optimum extraction efficiency for a given configuration of wire-array thicknesses.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF052  
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TUPAF053 Optimization of Diffuser (Pre-Scatterer) Configurations for Slow Extraction Loss Reduction at Electrostatic Septa septum, scattering, extraction, proton 830
 
  • B. Goddard, B. Balhan, J.C.C.M. Borburgh, M.A. Fraser, L.O. Jorat, V. Kain, C. Lolliot, L.S. Stoel, P. Van Trappen, F.M. Velotti
    CERN, Geneva, Switzerland
  • D. Barna
    Wigner Research Centre for Physics, Institute for Particle and Nuclear Physics, Budapest, Hungary
  • V.P. Nagaslaev
    Fermilab, Batavia, Illinois, USA
 
  Uncontrolled beam loss at the electrostatic septum is a performance limit for several existing or planned high power hadron accelerators delivering slow-extracted spills to fixed targets. A passive diffuser, or pre-scatterer, in a suitable configuration has been shown to reduce such beamloss significantly, with the actual gain factor depending on the parameters and details of the extraction process and hardware. In this paper, the optimization of diffuser configurations is investigated for a range of beam energies and extraction conditions, and the sensitivity to the available parameters explored via simulation results. The advantages and limitations of the diffuser are discussed and conclusions drawn concerning the specific case studies of the 8 GeV Fermilab debuncher ring and 400 GeV CERN SPS.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF053  
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TUPAF054 Slow Extraction Efficiency Measurements at the CERN SPS extraction, proton, operation, septum 834
 
  • M.A. Fraser, K. Cornelis, L.S. Esposito, B. Goddard, V. Kain, F. Roncarolo, L.S. Stoel, F.M. Velotti
    CERN, Geneva, Switzerland
 
  The high efficiency of most slow extraction systems makes quantifying the exact amount of beam lost in the process extremely challenging. This is compounded by the lack of time structure in the extracted beam, as is typically required by the high-energy physics experiments, and the difficulty in accurately calibrating D.C. intensity monitors in the extraction line at count rates of ~ 1013 Hz. As a result, it is common for the extraction inefficiency to be measured by calibrating the beam loss signal induced by the slow extraction process itself. In this paper, measurements of the extraction efficiency performed at the CERN Super Proton Synchrotron for the third-integer resonant slow extraction of 400 GeV protons over recent years will be presented and compared to expectation from simulation. The technique employed will be discussed along with its limitations and an outlook towards a future online extraction efficiency monitoring system will be given.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF054  
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TUPAF055 Progress Toward a Dynamic Extraction Bump for Slow Extraction in the CERN SPS extraction, alignment, septum, closed-orbit 838
 
  • L.S. Stoel, M. Benedikt, M.A. Fraser, B. Goddard, J. Prieto, F.M. Velotti
    CERN, Geneva, Switzerland
 
  The possibility of reducing the angular spread of slow extracted particles with a time-dependent extraction bump at the CERN Super Proton Synchrotron (SPS) is under investigation. In order to create this so-called dynamic bump, two orthogonal knobs were designed to enable independent movements of the beam in position and angle at the upstream end of the electrostatic extraction septum (ES). With the present slow extraction scheme, simulations show that the use of a dynamic bump can reduce the angular spread at the ES by roughly a factor two and reduce beam loss on the ES. A reduction in the angular spread is also a prerequisite to exploit the full potential of other loss reduction techniques being considered for implementation at the SPS, like the active or passive diffusers planned for installation upstream of the ES in 2018. In this paper, the simulated loss reduction with a dynamic bump alone or in combination with other loss reduction techniques will be assessed, the first beam-based tests of the dynamic bump presented, the details of its implementation examined and its potential for future operation at the SPS discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF055  
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TUPAF061 Use of a Massless Septum to Increase Slow-Extraction Efficiency septum, extraction, sextupole, resonance 862
 
  • K. Brunner, M.A. Fraser, B. Goddard, L.S. Stoel, C. Wiesner
    CERN, Geneva, Switzerland
  • D. Barna
    Wigner Research Centre for Physics, Institute for Particle and Nuclear Physics, Budapest, Hungary
 
  The Super Proton Synchrotron (SPS) at CERN provides slow-extracted beam for Fixed Target experiments in the North Area. For the higher extracted beam intensities requested by future experimental proposals, beam-loss induced activation will be one of the limiting factors for the availability of such a facility. In this paper, we present and discuss the concept of using a massless septum magnet to increase the extraction efficiency and decrease losses caused by protons scattering on the electrostatic-septa wires.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF061  
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TUPAF066 Transverse Dynamics and Software Integration of the ESS Low Energy Beam Transport solenoid, MMI, ion-source, proton 882
 
  • N. Milas, K.S. Louisy, D.C. Plostinar
    ESS, Lund, Sweden
 
  The first part of the ESS linac, also called front-end, comprising the Ion Source and the Low Energy Beam Transport (LEBT) section, will be installed and commissioned in 2018. The LEBT is used to focus and correct the proton beam trajectory and clean the head and tail of the proton pulse from the flat top before entering the RFQ. During the ion source and LEBT commissioning a full beam characterization at the RFQ entrance interface is planned. It is thus important to have an application in the control room able to display quantities measured by the diagnostic devices and also to quickly run a simulation including not only centre of mass dynamics but also envelope. This paper presents the efforts in modelling the LEBT elements, as accurately as possible, and implementing the dynamics calculation and integration with diagnostics tools. The final result is a Java FX GUI based on the OpenXAL library.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF066  
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TUPAF073 Simulation of Integrable Synchrotron with Space-charge and Chromatic Tune-shifts lattice, space-charge, optics, synchrotron 894
 
  • J.S. Eldred, A. Valishev
    Fermilab, Batavia, Illinois, USA
 
  We present a nonlinear rapid-cycling synchrotron designed as a high-intensity replacement of the Fermilab Booster. The design incorporates integrable optics, an innovation in particle accelerator design that enables strong nonlinear focusing without generating parametric resonances. We use the Synergia space-charge tracking code to demonstrate the stability of a beam in this lattice with a space-charge tune-shift up to 0.4 and a rms momentum spread up to 0.4\%. We demonstrate the benefit of increased lattice periodicity.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF073  
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TUPAF079 Scaled Alvarez-Cavity Model Investigations for the UNILAC Upgrade DTL, cavity, alignment, pick-up 916
 
  • M. Heilmann, X. Du, L. Groening, M. Kaiser, S. Mickat, M. Vossberg
    GSI, Darmstadt, Germany
  • A. Seibel
    IAP, Frankfurt am Main, Germany
 
  The 1:3 scaled aluminum model of an Alvarez-type cavity with 10 gaps was used for comparison of simulation with measurement for the frequency and the electric field on axis. The scaled frequency is 325.224 MHz and an Alvarez cavity has a small frequency tuning range. With this scaled model it was possible to apply different stem configurations for each drift tube to damp parasitic modes and to increase the field stability. The new drift tubes have an optimized free-formed profile on the end plates in order to increase the shunt impedance. In special the assembly, positioning and alignment of the drift tubes can be tested and the frequency change can be investigated in this respect.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF079  
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TUPAF080 Final Design of the FoS Alvarez-Cavity-Section for the Upgraded UNILAC cavity, DTL, quadrupole, operation 920
 
  • M. Heilmann, X. Du, L. Groening, M. Kaiser, S. Mickat, C. Mühle, A. Rubin, V. Srinivasan
    GSI, Darmstadt, Germany
  • A. Seibel
    IAP, Frankfurt am Main, Germany
 
  The final design describes the First-of-Series (FoS) Alvarez-Cavity-section of the first tank being part of the new post-stripper DTL of the UNILAC. The FoS-cavity has an input energy of 1.358 MeV/u with 11 drift tubes (including quadrupole singlets) in a total length of 1.9 m and a diameter of 2 m with an operation frequency of 108.4 MHz. The drift tubes will have a new shape profile at the end plates. The single layered quadruple singlets inside the drift tubes are pulsed with 10 Hz and will have a maximum field gradient of 51 T/m. The new drift tube design combines the new shape profile with the transverse and longitudinal installation space of the magnet. The FoS Alvarez-cavity will be part of the first section of the new Alvarez DTL. It shall be operated at nominal RF- and magnetic fields prior to procurement of the series.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF080  
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TUPAF086 Adaption of the HSI -RFQ Rf-Properties to an Improved Beam Dynamics Layout rfq, operation, linac, resonance 938
 
  • M. Vossberg, L. Groening, S. Mickat, H. Vormann, C. Xiao
    GSI, Darmstadt, Germany
  • V. Bencini, J.M. Garland, J.-B. Lallement, A.M. Lombardi
    CERN, Geneva, Switzerland
 
  The GSI accelerator facility comprising the linear accelerator UNILAC and the synchrotron SIS18 will be used in future mainly as the injector for the Facility for Anti-Proton and Ion Research (FAIR) being under construction. FAIR requires high beam brilliance and the UNILAC's RFQ electrodes must be upgraded with respect to their beam dynamics design. The new layout is currently being conducted at CERN with the aim of adjusting the electrode voltage according to the design voltage of 123 kV. CST simulations performed at GSI assure that the resonance frequency with the new electrode geometry is recuperated through corrections of the carrier rings. Simulations on the frequency dependence of the rings shapes and their impact on the voltage distribution along the RFQ are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF086  
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TUPAF087 A Two-Stage Splitring-RFQ for High Current Ion Beams at Low Frequencies rfq, impedance, acceleration, resonance 941
 
  • M. Baschke, H. Podlech, A. Schempp
    IAP, Frankfurt am Main, Germany
 
  Funding: HIC for FAIR, BMBF Contr. No. 05P15RFRBA
For several accelerator projects RFQs are the first stage of acceleration. To reach high intensities a new Splitring-RFQ is investigated. Not only a high current and high beam quality/brilliance should be achieved, also a good tuning flexibility and comfort for maintenance are part of the study. The RFQ will consist of two stages with 27 MHz and 54 MHz to accelerate ions with an A/q of 60 up to energies of 200 keV/u. RF simulations with CST MWS have been performed to obtain the quality factor, shunt impedance and voltage distribution as well as tuning possibilities. The results and the status of the project will be presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF087  
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TUPAF089 Initial Measurements on a New 108 MHz 4-Rod CW RFQ Prototype for the HLI at GSI rfq, dipole, linac, resonance 946
 
  • D. Koser, K. Kümpel, H. Podlech
    IAP, Frankfurt am Main, Germany
  • P. Gerhard
    GSI, Darmstadt, Germany
  • O.K. Kester
    TRIUMF, Vancouver, Canada
 
  Funding: Work supported by BMBF Contr. No. 05P15RFBA and HIC for FAIR
The High Charge State Injector (HLI) at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, is one of the two injector linacs for the Universal Linear Accelerator (UNILAC) and is also planned to serve as dedicated injector for a proposed superconducting CW linac for heavy element research. Within the scope of an intended CW upgrade of the HLI front end, a replacement for the existing 4-rod RFQ is desirable since its stable operation and performance is severely impeded by mechanical vibrations of the electrodes and a high thermal sensitivity*. With the aim of suppressing mechanical vibrations and providing efficient cooling considering high power CW operation, a completely new and improved 4-rod design was developed** with a focus on structural mechanical simulations using ANSYS. In order to validate the simulated RF performance, thermal behavior and structural mechanical characteristics, a 6-stem prototype was manufactured***. Initial low power RF measurements and basic piezo actuated mechanical investigations were done and the anticipated properties could be confirmed prior to planned high power RF tests and further mechanical vibration studies.
* D. Koser et al., THPIK021, Proc. of IPAC2017
** D. Koser et al., MOPOY020, Proc. of IPAC2016
*** D. Koser et al., TUPLR057, Proc. of LINAC2016
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF089  
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TUPAF090 Measurements of the MYRRHA-RFQ at the IAP Frankfurt rfq, dipole, controls, resonance 949
 
  • K. Kümpel, D. Koser, S. Lamprecht, N.F. Petry, H. Podlech, A. Schempp, D. Strecker
    IAP, Frankfurt am Main, Germany
  • A. Bechtold
    NTG Neue Technologien GmbH & Co KG, Gelnhausen, Germany
  • C. Zhang
    GSI, Darmstadt, Germany
 
  Funding: Work supported by the EU Framework Programme H2020 662186 (MYRTE)
The MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Applications) Project is a planned accelerator driven system (ADS) which aims to demonstrate the feasibility of large scale transmutation. The first RF structure of the 600 MeV MYRRHA Linac will be a 176.1 MHz 4-Rod RFQ that will accelerate up to 4 mA protons in cw operation from 30 keV up to 1.5 MeV. The voltage along the approximately 4 m long electrodes has been chosen to 44 kV which limits the RF losses to about 25 kW/m. During the design of the structure a new method of dipole compensation has been applied. This paper describes the status of the RFQ and shows the results of the measurements done at IAP Frankfurt such as dipole and flatness measurement, vacuum tests and power tests up to 11 kW.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF090  
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TUPAK007 Simulation of Surface Muon Beamline, Ultra-Slow Muon Production and Extraction for the J-PARC g-2/EDM Experiment target, experiment, laser, proton 970
 
  • M. Otani, N. Kawamura, T. Mibe, T. Yamazaki
    KEK, Tsukuba, Japan
  • K. Ishida
    RIKEN Nishina Center, Wako, Japan
  • G. Marshall
    TRIUMF, Vancouver, Canada
 
  The E34 experiment aims to measure muon anomalous magnetic moment with a precision of 0.1 ppm to cast light on beyond standard model in elementary particle physics. The experiment utilizes a brand new muon beam line in J-PARC (H line), which is designed to have large acceptance to supply an intense muon beam. The surface muons are injected into a silica aerogel target to generate bound state of muon and electron (muonium). Then the muoniums are ionized by lasers and ultra slow (30 meV) muons (USM) are generated. The USM's are extracted by electro-static lens and injected to a muon linac. In this poster, simulation for optics of the surface muon beamline, muonium production and extraction by the electro-static lens, and the estimation of the USM's intensity are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAK007  
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TUPAK008 Longitudinal Bunch Size Measurements with an RF Deflector at J-PARC LINAC radio-frequency, linac, rfq, DTL 974
 
  • M. Otani, K. Futatsukawa
    KEK, Tsukuba, Japan
  • K. Hirano, A. Miura
    JAEA/J-PARC, Tokai-mura, Japan
  • Y. Liu
    KEK/JAEA, Ibaraki-Ken, Japan
  • T. Maruta
    FRIB, East Lansing, USA
 
  Measurement of the longitudinal bunch size is important for the stable beam operation. Especially in a medium energy beam transport (MEBT) located after a radio-frequency quadrupole in J-PARC, it is necessary to measure the bunch size with minimum set of equipment to avoid subsequent emittance growth due to space charge. We had proposed a longitudinal size measurement with an rf deflector normally used for deflecting theμbunch; phase spread is migrated to spatial one if the reference particle arrives at the deflector when the voltage is rising in time and is zero. Then a buncher cavity located upstream of the deflector is utilized to scan the phase spread to measure the longitudinal beam parameters. In this poster, recent measurement results are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAK008  
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TUPAK009 Muon Profile Measurement After Acceleration With a Radio-Frequency Quadrupole Linac experiment, rfq, linac, positron 977
 
  • M. Otani, Y. Fukao, K. Futatsukawa, N. Kawamura, T. Mibe, Y. Miyake, T. Yamazaki
    KEK, Tsukuba, Japan
  • S. Bae, H. Choi, S. Choi, B. Kim, H.S. Ko
    SNU, Seoul, Republic of Korea
  • K. Hasegawa, Y. Kondo, T. Morishita
    JAEA/J-PARC, Tokai-mura, Japan
  • T. Iijima, Y. Sue
    Nagoya University, Graduate School of Science, Chikusa-ku, Nagoya, Japan
  • H. Iinuma, Y. Nakazawa
    Ibaraki University, Ibaraki, Japan
  • K. Ishida
    RIKEN Nishina Center, Wako, Japan
  • R. Kitamura
    University of Tokyo, Tokyo, Japan
  • S. Li
    The University of Tokyo, Graduate School of Science, Tokyo, Japan
  • G.P. Razuvaev
    Budker INP & NSU, Novosibirsk, Russia
  • N. Saito
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
  • E. Won
    Korea University, Seoul, Republic of Korea
 
  Funding: This work is supported by JSPS KAKENHI Grant Numbers JP15H03666, JP16H03987, and JP16J07784.
The E34 experiment aims to measure muon anomalous magnetic moment with a precision of 0.1ppm. The experiment utilizes low emittance muon beam with a muon linac to sweep out beam related uncertainties, which limit the g-2 precision in past experiments. A beam matching with precise beam measurements is required to avoid substantial emittance growth and satisfy the experimental requirement on the beam emittance of around 1.5 pi mm mrad. We conduct profile measurement of muon after acceleration with a radio-frequency quadrupole (RFQ) on December 2017 following a first muon acceleration experiment on October. In the experiment of profile measurement, epi-thermal negative muonium ions are generated by injecting surface muons to a thin metal foil. The muonium ions are accelerated to 5 keV. by an electro-static lens and accelerated to 90 keV by the RFQ. Then the muonium ions are transported to a profile detector consisting of a micro-channel plate and a ccd camera via a quadrupole pair and a bending magnet. In this poster, the experimental result and comparison to the simulation are reported.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAK009  
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TUPAK013 Geant4 Simulation of Radiation Effect on the Deflector of Extraction System in HUST SCC250 septum, proton, neutron, radiation 990
 
  • S. Hu, K. Fan, L.X.F. Li, Z.Y. Mei, Z.J. Zeng, L.G. Zhang
    HUST, Wuhan, People's Republic of China
 
  China has payed extensive attention to the development of proton therapy in recent years. When design a compact, high energy superconducting cyclotron for proton therapy, radiation effect induced by beam losses is a crucial consideration. Since the proton beam is extracted out of HUST SCC250 by electrostatic deflectors, the fierce interaction between proton beam and the deflector septum is the main cause of beam losses, which will bring about radiation effect leading to activation and coil quench. This paper presents simulation results of radiation effect by utilizing Geant4 Monte Carlo code. The energy depositions of proton beam in various septum materials are compared. Meanwhile, the yields, the ener-gy and angular distributions of secondary particles are investigated. Those simulation results based on radiation effect will provide us with valuable implications for the design of this superconducting cyclotron.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAK013  
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TUPAK017 Abandoned Proton Beam Separation Design at MOMENT proton, target, separation-scheme, secondary-beams 1001
 
  • C. Meng, H.T. Jing, Y.P. Song, J.Y. Tang, H. Wang
    IHEP, Beijing, People's Republic of China
 
  Funding: The National Natural Science Foundation of China under Grants 11575217
MOMENT (MuOn-decay MEdium baseline NeuTrino beam facility) is an accelerator-based neutrino beam facility using neutrino from muon decays. The proton driver is a continuous-wave proton linac of 1.5 GeV and 10 mA, which means an extremely high beam power of 15 MW. After bombarding the target, the abandoned proton beam power is very high and should be separate from target station carefully. Because of the energy is not very high and the layout of following transport line isn't linear, we should design special separation line for high momentum proton beam. In this paper the design of separation scheme at MOMENT will be proposed and discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAK017  
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TUPAL009 Studying a Prototype of Dual-beam Drift Tube Linac DTL, cavity, rfq, acceleration 1020
 
  • T. He, L. Lu, W. Ma, L.P. Sun, C.C. Xing, X.B. Xu, L. Yang
    IMP/CAS, Lanzhou, People's Republic of China
 
  For generating high-intensity ion beams from linear ac-celerators, a multi-beam acceleration method which in-volves multiple accelerating beams to suppress the defo-cusing force from space charge effects, then integrating these beams by a beam funneling system, has been pro-posed. An Inter-digital H-mode (IH) two-beam type radio frequency quadrupole (RFQ) with accelerating 108mA (54mA/channel×2) carbon ion from 5 to 60 keV/ u and an IH four-beam RFQ with accelerating 160.8mA (40.2mA/channel×4) carbon ion from 3.6 to 41.6 keV/u had been successfully designed for low energy heavy ion acceleration [1]. In order to demonstrate that an IH dual-beam drift tube linac (DB-DTL) is suitable for high-intensity heavy ion beam acceleration in middle energy region, we has been developing a DB-DTL prototype by using three dimensional electromagnetic CST MicroWave Studio (MWS) and using particles tracking Pi Mode Linac Orbit Calculation (PiMLOC) [2-3]. According to the simulation results, the beam dynamics design and elec-tromagnetic design will be presented in this paper.
* Shota. Iketa et al., Nucl. Instr. and Meth. in Phys. Res. B.239-243 (2017).
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL009  
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TUPAL035 3D Beam Dynamics Modeling of MEBT for the New LANSCE RFQ Injector emittance, rfq, quadrupole, proton 1081
 
  • S.S. Kurennoy
    LANL, Los Alamos, New Mexico, USA
 
  The new RFQ-based proton injector at LANSCE requires a specialized medium-energy beam transfer (MEBT) after the RFQ at 750 keV due to a following long (~3 m) existing common transfer line that also serves for transporting negative-ion beams to the DTL entrance. The horizontal space for MEBT elements is limited because two beam lines merge at 18-degree angle. The MEBT design developed with envelope codes includes two compact quarter-wave RF bunchers and four short quadrupoles with steerers, all within the length of about 1 m. The beam size in the MEBT is large, comparable to the beam-pipe aperture, hence non-linear 3D field effects at large radii become important. Using CST Studio codes, we calculate buncher RF fields and quadrupole magnetic fields and use them to perform particle-in-cell beam dynamics modeling of MEBT with realistic beam distributions from the RFQ. Our results indicate a significant emittance growth not predicted by standard beam dynamics codes. Its origin was traced mainly to the quadrupole edge fields. Quadrupole design modifications are proposed to improve the MEBT performance.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL035  
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TUPAL036 Slow Extraction Techniques at the Marburg Ion-Beam Therapy Centre extraction, synchrotron, controls, resonance 1084
 
  • C. Krantz, T. Fischer, Th. Haberer, B. Kroeck, U. Scheeler, A. Weber, M. Witt
    MIT, Marburg, Germany
  • R. Cee, F. Faber, E. Feldmeier, M. Galonska, Th. Haberer, A. Peters, S. Scheloske, C. Schömers
    HIT, Heidelberg, Germany
  • F. Faber
    Technische Universität Darmstadt (TU Darmstadt, RMR), Darmstadt, Germany
 
  The Marburg Ion-Beam Therapy Centre offers hadron therapy using proton and carbon beams. The accelerator is based on a 65-m ion synchrotron by Danfysik/Siemens Healthcare. Beam extraction from the synchrotron is driven by a transverse RF knock-out (KO) system featuring Dynamic Intensity Control (DIC) of the spill. DIC allows modulation of the extraction rate by factors up to 30 on millisecond time scales. A fast response of the system to the variable intensity set-point can be obtained by careful adjustment of the RF-KO spectrum relative to the machine tune. Tracking simulations of the extraction phase have been conducted to refine that behaviour. Presently, we investigate how fast machine tune shifts, induced by an air-core quadrupole lens, can be used as a way to further improve the spill quality.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL036  
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TUPAL043 Simulations of the Electron Column in IOTA electron, plasma, proton, space-charge 1103
 
  • B.T. Freemire
    Northern Illinois University, DeKalb, Illinois, USA
  • S. Chattopadhyay
    Northern Illinois Univerity, DeKalb, Illinois, USA
  • M. Chung
    UNIST, Ulsan, Republic of Korea
  • C.S. Park
    Korea University Sejong Campus, Sejong, Republic of Korea
  • G. Penn
    LBNL, Berkeley, California, USA
  • V.D. Shiltsev, G. Stancari
    Fermilab, Batavia, Illinois, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of High Energy Physics, under Contract Nos. DE-AC02-07CH11359 and DE-AC02-05CH1123 and General Accelerator Research and Development Program
Future high current proton accelerators will need to minimize beam loss due to space-charge in order to achieve safe operation while achieving the desired physics goals. One method of space-charge compensation to be tested at the Integrable Optics Test Accelerator (IOTA) at Fermilab is the Electron Column. The concept for this device is to allow a circulating beam to ionize a small region of relatively high pressure residual gas, while using electric and magnetic fields to confine and shape the resulting plasma electrons. If the profile of the electrons is matched to the beam profile transversely and longitudinally, the electrons should counteract the space-charge force of the proton beam. Simulations of the IOTA proton beam circulating through the Electron Column have been performed, with the evolution of the electron plasma and its effect on the beam studied.
 
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TUPAL056 High Order Image Terms and Harmonic Closed Orbits at the ISIS Synchrotron closed-orbit, resonance, space-charge, vacuum 1140
 
  • B.G. Pine, C.M. Warsop
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
 
  ISIS is the spallation neutron source at Rutherford Appleton Laboratory in the UK. Protons are accelerated from 70 to 800 MeV in a 50 Hz rapid cycling synchrotron. Due to the intense beam, space charge forces are high during the first part of the acceleration cycle. The vacuum vessel in the synchrotron has a rectangular shape where the apertures are conformal to the design beam envelopes. At high intensities image forces interact with the beam, especially when the closed orbit is large. An analysis of image forces has been made and used to classify higher order image terms. These have been identified using simulations of round beams in rectangular vacuum vessels. The higher order image terms from harmonic closed orbits have been used with single particle resonance theory, taking account of the coherent nature of the beam response. Several predictions of beam resonance have been made. A simulation study has been carried out using a smooth focusing lattice and uniform density beams. Resonant beam behaviour has been observed and explained by the proposed theory.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL056  
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TUPAL058 Studies for Major ISIS Upgrades via Conventional RCS and Accumulator Ring Designs injection, lattice, space-charge, emittance 1148
 
  • C.M. Warsop, D.J. Adams, H.V. Cavanagh, P.T. Griffin-Hicks, B. Jones, B.G. Pine, R.E. Williamson
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
 
  ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK, which provides 0.2 MW of beam power via a 50 Hz, 800 MeV proton RCS. Detailed studies are now under way to find the optimal configuration for a next generation, short pulsed neutron source that will define a major ISIS upgrade in ~2031. Accelerator configurations being considered for the MW beam powers required include designs exploiting FFAG rings as well as conventional accumulator and synchrotron rings. This paper describes work exploring the latter, conventional options, but includes the possibility of pushing further toward intensity limits to reduce facility costs. The scope of planned studies is summarised, looking at optimal exploitation of existing ISIS infrastructure, and incorporating results from recent target studies and user consultations. Results from initial baseline studies for an accumulator ring and RCS located in the existing ISIS synchrotron hall are presented. Injection scheme, foil limits, longitudinal and transverse beam dynamics optimization with related beam loss and activation are outlined, as are results from detailed 3D PIC simulations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL058  
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TUPAL062 Recent Developments for Cyclotron Extraction Foils at TRIUMF electron, extraction, cyclotron, TRIUMF 1159
 
  • Y. Bylinskii, R.A. Baartman, P.E. Dirksen, Y.-N. Rao, V.A. Verzilov
    TRIUMF, Vancouver, Canada
 
  Funding: Funded under a contribution agreement with NRC (National Research Council Canada).
The TRIUMF 500 MeV H− cyclotron employs stripping foils to extract multiple beams for different experimental programs. The upgrades in foil material and foil holders lead to significant improvements in beam quality and foil life time, as well as reduction of Be-7 contamination originated in the foils. Thus, an accumulated beam charge extracted with a single foil increased from ~60 mA·hours to more than 500 mA·hours. A key role that lead to these advances was an understanding of the foil heating mechanism, major contribution to which is paid by the power deposition from electrons stripped by the foil. To further diminish this effect, we recently introduced a foil tilt from the vertical orientation that allows stripped electrons fast escape from the foil, well before losing their original momentum through the heat deposition. Other improvements were related to operational issues. Introduction of a "combo" foil consisting of wide portion and thin wire allowed both high and low intensity beam extraction without foils sacrifice. Deploying a wedge foil for extraction at 100 MeV helped reduction of beam intensity instabilities caused by beam vertical size and position fluctuations.
 
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TUPAL068 The Development of a Nw Fast Harmonic Kicker for the JLEIC Circulator Cooling Ring kicker, cavity, emittance, electron 1171
 
  • G.-T. Park, F. Fors, J. Guo, R.A. Rimmer, H. Wang, S. Wang
    JLab, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
After the first half-scale, 5 harmonic kicker cavity prototyping * for the JLEIC's CCR/ERL electron cooler and the beam dynamic simulation study of the 10-turn CCR **. The optimized circulation cooling turns has been changed to 11 and only 5 odd-harmonic modes from 86.6 MHz to 779.4 MHz plus a DC bias are needed for the harmonic RF kicker system. The new cavity design including the electromagnetic and thermal cooling optimization and its 11 turns beam bunch tracking simulation with the new numerology of RF deflecting voltages will be presented. Further design specifications for its RF harmonic drive and the broadband RF window, coupler and circulator component will be given for handling 5 kW of total RF power.
* Y, Huang, H. Wang et al., Physical Review Accelerators and Beams 19, 122001 (2016).
** Y. Huang, H. Wang et al., Physical Review Accelerators and Beams 19, 084201 (2016).
 
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TUPAL069 Experimental Demonstration of Ion Beam Cooling with Pulsed Electron Beam electron, experiment, synchrotron, data-analysis 1174
 
  • Y. Zhang, A. Hutton, K. Jordan, T. Powers, R.A. Rimmer, M. F. Spata, H. Wang, S. Wang, H. Zhang
    JLab, Newport News, Virginia, USA
  • J. Li, X.M. Ma, L.J. Mao, M.T. Tang, J.C. Yang, X.D. Yang, H. Zhao, H.W. Zhao
    IMP/CAS, Lanzhou, People's Republic of China
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Cooling ion beams at high energy is presently considered for several ion colliders, in order to achieve high luminosities by enabling a significant reduction of emittance of hadron beams. Electron beam at cooling channel in a few to tens MeV can be accelerated by a RF/SRF linac, and thus using bunched electrons to cool bunched ions. To study such cooling process, the DC electron gun of EC35 cooler at the storage ring CSRm, IMP was modified by pulsing the grid voltage. A 0.07-3.5 micro-second pulse length with a repetition frequency of less than 250 kHz and synchronized with the ion revolution frequency was obtained. The first experimental demonstration of cooling of a coasting and bunched ion beam by a pulsed electron beam was carried out. Data analysis indicates the bunch length shrinkage and the momentum spread reduction of bunched 12C+6 ion beam as evidence of cooling. A longitudinal grouping effect of the coasting ion beam by the electron pulses has also been observed*. In this paper, we will present experimental results and comparison to the simulation modelling, particularly on the bunched electron cooling data after carefully analyzing the beam diagnostic signals.
* L.J. Mao et al., Experimental Demonstration of Electron Cooling with Bunched Electron Beam, TUP15, Proceedings of COOL2017, Bonn, Germany
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL069  
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TUPAL075 Mechanical Design and Error Analysis of a 325 MHz IH-DTL Test Cavity DTL, alignment, cavity, linac 1186
 
  • R. Tang, C.T. Du, X. Guan, K.D. Man, C.-X. Tang, X.W. Wang, Q.Z. Xing, S.X. Zheng
    TUB, Beijing, People's Republic of China
  • J. Li
    NUCTECH, Beijing, People's Republic of China
 
  A 325 MHz interdigital H-mode drift tube linac (IH-DTL) test cavity with a modified KONUS beam dynamics is under fabrication at Tsinghua University. The inner diameter of the tank increases from 196.8 to 232.6 mm. The mechanical design is considered carefully because of its small geometry. A three-piece design has been adopted in the mechanical design. The error analysis is carried out to determine the error requirement of machining and alignment. The details of mechanical design and error analysis is presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL075  
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TUPAL076 Result of the First Muon Acceleration with Radio Frequency Quadrupole rfq, acceleration, experiment, target 1190
 
  • R. Kitamura
    University of Tokyo, Tokyo, Japan
  • S. Bae, B. Kim
    SNU, Seoul, Republic of Korea
  • Y. Fukao, K. Futatsukawa, N. Kawamura, T. Mibe, Y. Miyake, M. Otani, T. Yamazaki
    KEK, Tsukuba, Japan
  • K. Hasegawa, Y. Kondo, T. Morishita
    JAEA/J-PARC, Tokai-mura, Japan
  • H. Iinuma, Y. Nakazawa
    Ibaraki University, Ibaraki, Japan
  • G.P. Razuvaev
    Budker INP & NSU, Novosibirsk, Russia
  • N. Saito
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
  • Y. Sue
    Nagoya University, Graduate School of Science, Chikusa-ku, Nagoya, Japan
 
  Funding: This work is supported by JSPS KAKENHI Grant Numbers JP15H03666, JP16H03987, and JP16J07784.
J-PARC E34 experiment aims to measure the muon g-2/EDM precisely with novel techniques including the muon linear accelerator. Slow muon source by the metal foil method in order to cool the muon beam has been developed for the muon acceleration test with RF accelerator, because the muon beam derived from the proton driver was the tertiary beam and has a large emittance. The first verification test of the muon acceleration with RFQ was carried out at the muon test beam line of J-PARC MLF in October 2017. The incident surface muons were decelerated by the thin metal foil target and produced the negative muonium ions (Mu-), which is the bound stat of a positive muon and two electrons. After Mu- were extracted by a electrostatic accelerator as the injector of the RFQ, they were accelerated with RFQ to 88.6 keV. The accelerated Mu- were identified by the momentum selection with the bending magnet after the RFQ, and the measurement of the Time-Of-Flight. Accelerated Mu- were easily distinguished from penetrated positive muons by the difference of the polarity. The latest analysis result of the world's first muon acceleration with RFQ will be reported in this paper.
 
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TUPAL077 2D-3D PIC Code Benchmarking/Anchoring Comparisons For a Novel RFQ/RFI LINAC Design rfq, space-charge, linac, experiment 1194
 
  • S.J. Smith, S. Biedron, A. M. N. Elfrgani, E. Schamiloglu
    University of New Mexico, Albuquerque, USA
  • M.S. Curtin, B. Hartman, T. Pressnall, D.A. Swenson
    Ion Linac Systems, Inc., Albuquerque, USA
  • K. Kaneta
    CICS, Tokyo, Japan
 
  Funding: *The study at the University of New Mexico was supported in part by DARPA Grant N66001-16-1-4042 and gift to the University of New Mexico Foundation by ILS.
In this study, comparisons are made between several particle dynamics codes (namely CST Particle Studio, GPT, and upgraded PARMILA codes) in order to benchmark them. The structure used for the simulations is a novel 200 MHz, 2.5 MeV, CW RFQ/RFI LINAC designed by Ion Linac Systems (ILS). The structure design and parameters are provided, simulation techniques are explained, and results from all three code families are presented. These results are then compared with each other, identifying similarities and differences. Numerous parameters for comparison are used, including the transmission efficiency, Q-factor, E-field on axis, and beam properties. Preliminary anchoring between modeling and simulation performance predictions and experimental measurements will be provided.
 
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TUZGBF5 KlyLac Prototyping for Borehole Logging klystron, linac, cavity, feedback 1244
 
  • A.V. Smirnov, R.B. Agustsson, M.A. Harrison, A.Y. Murokh, A.Yu. Smirnov
    RadiaBeam Systems, Santa Monica, California, USA
  • S. Boucher, T.J. Campese, K.J. Hoyt
    RadiaBeam, Los Angeles, California, USA
  • E.A. Savin
    MEPhI, Moscow, Russia
  • A.A. Zavadtsev
    Nano, Moscow, Russia
 
  Funding: Work supported by the U.S. Department of Energy (award No. DE-SC0015721)
Linac-based system for borehole logging exploits KlyLac approach combing klystron and linac sharing the same electron beam, vacuum volume, and RF network enabling self-oscillation due to a positive feedback. The KlyLac prototype design tailors delivering ~1 MeV electrons in a linac section using part of the beam injected from a sheet beam klystron (SBK). The linac part is based on a very robust, high group velocity, cm-wave, and a standing wave accelerating structure of a 'cross-pin' type supplied by a sampler. The SBK part features a permanent magnet solenoid focusing, relatively low voltage, and high aspect ratio beam. The main SBK characteristics (perveance, power, and efficiency) are expected to be similar to that for a magnetron.
 
slides icon Slides TUZGBF5 [3.285 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUZGBF5  
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TUPMF005 Simulation of Inverse Compton Scattering and Its Implications on the Scattered Linewidth electron, emittance, laser, scattering 1254
 
  • N. Ranjan, B. Terzić
    ODU, Norfolk, Virginia, USA
  • I. Drebot, L. Serafini
    Istituto Nazionale di Fisica Nucleare, Milano, Italy
  • G.A. Krafft
    JLab, Newport News, Virginia, USA
  • V. Petrillo
    Universita' degli Studi di Milano & INFN, Milano, Italy
 
  Funding: This paper is authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Compton scattering, though first described some one hundred years ago, has recently experienced a surge of interest due to the search for energy sources that are capable of yielding low emission bandwidths. In particular, the desire for hard x-rays with energies greater than 10 keV has led to increased study of inverse Compton sources. The rise in interest concerning inverse Compton sources has increased the need for efficient models that properly quantify the behavior of scattered radiation given a set of interaction parameters. The current, state-of-the-art, simulations rely of Monte Carlo-based methods, which may fail to properly model collisions of bunches in low-probability regions of the spectrum. Furthermore, the random sampling of the simulations may lead to inordinately high runtimes. Our methods can properly model behaviors exhibited by the collisions by integrating over the emissions of the electrons in the bunch in a lessened amount of time. Analytical simulations of Gaussian laser beams closely verify the behavior predicted by an analytically derived scaling law describing bandwidth of scattered radiation.
Current affiliation of primary author (Nalin Ranjan) is Princess Anne High, Virginia Beach, VA 23452, USA.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF005  
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TUPMF012 Determination of the Ground Motion Orbit Amplification Factors Dependence on the Frequency for the APS Upgrade Storage Ring ground-motion, factory, lattice, storage-ring 1272
 
  • V. Sajaev, C.A. Preissner
    ANL, Argonne, Illinois, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Advanced Photon Source (APS) is pursuing an upgrade to the storage ring that will provide electron beam with extremely low emittance. To allow users to take advantage of this small beam size, the beam orbit motion has to be kept stable to within a fraction of the beam size, which translates to sub-micron orbit stability requirement. Ground motion provides significant contribution to the overall expected beam motion, especially at lower frequencies where the ground motion has larger amplitudes. At the same time, the lattice amplification factors reduce when the ground motion becomes coherent at low frequencies. In this paper, we will present simulation of the lattice amplification factor dependence on the ground motion coherence length and show results of the ground motion coherence measurements at APS. After that, we will determine the lattice amplification factors dependence on the ground motion frequency, that can be used to calculate the expected effect of the ground motion on the orbit stability.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF012  
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TUPMF016 Application of SVD Analysis to Deflecting Cavitiy Space Harmonics cavity, timing, data-analysis, experiment 1283
 
  • C. Yao, L. Emery, D. Hui, H. Shang, Y.P. Sun
    ANL, Argonne, Illinois, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
Singular value decomposition (SVD) analysis is a powerful tool for identifying different spatial and timing variation patterns in many fields of researches. Recently we applied complex SVD method to space harmonic analysis of a 13-cell defecting cavity that is built and installed in the APS linac injector for beam phase space characterization and emittance exchange experiments. Real and imaginary space harmonics components are extracted from CST simulated data. Fields inside the iris were expressed in analytic forms and produced good agreement. Work is underway to implement the results into elegant simulation model.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF016  
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TUPMF018 Simulation Studies of the Helical Superconducting Undulator Installed at APS multipole, undulator, operation, storage-ring 1290
 
  • A. Xiao, V. Sajaev, Y.P. Sun
    ANL, Argonne, Illinois, USA
 
  A multi-year project at APS has resulted in construction of a helical superconducting undulator (HSCU) for installation in the ring. Before installation, simulation studies were done to ensure that APS performance will not be compromised. This paper describes the method used for calculating the HSCU's perturbation effects and the simulation results for both calculated and measured field map.
Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF018  
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TUPMF021 Investigation of Options for Damping Trapped IVU Resonances resonance, impedance, damping, undulator 1296
 
  • R.T. Dowd
    AS - ANSTO, Clayton, Australia
  • W.J. Chi, D. Pelz
    RFS, Kilsyth, Australia
 
  Trapped resonances have been observed within the three In-Vacuum Undulators (IVUs) insertion devices at the Australian Synchrotron. These resonances can create vertical beam instability if not controlled through transverse feedback systems. Similar resonances have been observed at other synchrotron light sources around the world. Under certain conditions of undulator gap, these resonances can couple quite strongly to the beam, requiring high feedback gain. An investigation of the resonances has been carried out using 3D eigenmode and wakefield simulations to understand the resonances and determine the effectiveness of various schemes for modifying the damping the resonances.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF021  
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TUPMF034 Measuring the Electrical Center and Field Flatness of 704 MHz Deflecting Cavity for LEReC with Wire Stretching System cavity, diagnostics, pick-up, experiment 1320
 
  • T. Xin, J.M. Brennan, J.C.B. Brutus, K. Mernick, K.S. Smith, B. P. Xiao, A. Zaltsman
    BNL, Upton, Long Island, New York, USA
  • W. Johnson
    SBU, Stony Brook, New York, USA
  • H. Wang
    JLab, Newport News, Virginia, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
704 MHz deflecting cavity was designed for the Low Energy RHIC electron Cooling (LEReC) project. The cavity will serve as a major component in diagnostic line. In LEReC project the requirement on the energy spread of the electron beam is extremely high (better than 10-4) and the diagnostic system has to to be designed accordingly. The 704 MHz transverse deflecting cavity provides the vertical kick to the beam after it passes through the dispersion dipole so that we can measure the energy spread of the core of the bunch. Traditional way of determining the electrical center of the cavity involves the needle pulling and integration of the signal which is prone to the cumulative error. We present the measurement result from a wire stretching system that is much more efficient and accurate compared to the bead/needle pulling method. Both simulation and experimental results are shown in this paper and the potential in further application is discussed at the end.
 
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TUPMF048 On-Axis Beam Accumulation Based on a Triple-Frequency RF System for Diffraction-Limited Storage Rings cavity, injection, accumulation, photon 1359
 
  • S.C. Jiang, Z. Duan, G. Xu
    IHEP, Beijing, People's Republic of China
 
  Since the multi-bend achromats have been applied to lattice design in the future light source to achieve ultralow emittance, strong sextupoles and concomitant nonlinearities restrict its performance to a certain extent. The empirical understanding is the exclusion of conventional off-axis injection scheme on these light sources. In this paper, we will present a new on-axis beam accumulation scheme, which is based on the triple-frequency RF system. By means of delicate superposition of RF voltage with fundamental and two other harmonic frequencies, a commodious and steady main bucket is able to be formed. The electron bunch from the injector will be kicked into the main bucket on-axis with a reasonable time offset to the circular bunch, and this process may make the minimal disturbance to the experiment users while operating on the top-up mode. The application of this scheme to the High Energy Photon Source (HEPS) will be discussed in the paper, corresponding simulation results are also presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF048  
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TUPMF053 Longitudinal Impedance Measurement of the Strip-Line Kicker for High Energy Photon Source (HEPS) impedance, kicker, coupling, distributed 1379
 
  • S.K. Tian, J. Chen, Y. Jiao, H. Shi, L. Wang, N. Wang
    IHEP, Beijing, People's Republic of China
 
  The High Energy Photon Source (HEPS) is a 6-GeV, kilometer-scale storage ring light source to be built in China. One of the main design challenges of the storage ring is to minimize collective instabilities associated with the impedance of small-aperture vacuum components. In this paper we present beam coupling impedance measurements obtained by the well known coaxial wire method, for the HEPS Strip-Line kicker. The frequency dependent real and imaginary parts of the distributed impedance are obtained from the measured S-parameters.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF053  
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TUPMF059 Error Study of HEPS Booster closed-orbit, booster, multipole, lattice 1398
 
  • C. Meng, D. Ji, J.L. Li, Y.M. Peng
    IHEP, Beijing, People's Republic of China
 
  The High Energy Photon Source (HEPS) is a 6-GeV, ultralow-emittance light source to be built in China. The injector is composed of a 500-MeV linac and a full energy booster with 1 Hz repetition frequency. The detailed error study of the booster will be presented, including misalignment errors and closed orbit correc-tion, magnetic field errors and power supply errors. The effect of errors on closed orbit, tune, chromaticity and dynamic aperture will be discussed. The dynamic aperture with multipole errors will be presented also.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF059  
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TUPMF073 Impedance Optimization of Small Gap Chambers for the High Single Bunch Current Operation at the Undulator Based Light Sources impedance, lattice, undulator, ECR 1430
 
  • Y.-C. Chae
    DESY, Hamburg, Germany
 
  In the undulator based light sources the intensity limit of single bunch is often determined by the strong vertical instability caused by the wakefield in the ring, where the undulator itself is large impedance source. The optimization of transition from the large aperture to undulator's small-gap chamber is on-going research topic in an effort to reduce the vertical impedance; at the same time, the demand on single-bunch current is high from the timing-mode x-ray user community. In this paper, after showing the results obtained by exploring the parameter space guided by Stupakov's formula, we propose the linearly-segmented transition which can reduce the impedance down to 60% or less of the original linear taper. The reduction can be utilized either to increase the bunch current substantially or to install a smaller gap chamber without impacting the bunch current limit. For the definite result we considered the transition between two ellipses, namely, (a, b) = (42 mm, 21 mm) and (18 mm, 4 mm) over the length 15-30 cm in beam direction.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF073  
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TUPMF076 Temporal X-ray Reconstruction Using Temporal and Spectral Measurements electron, photon, FEL, laser 1440
 
  • F. Christie, J. Rönsch-Schulenburg, M. Vogt
    DESY, Hamburg, Germany
  • Y. Ding, Z. Huang, J. Krzywinski, A.A. Lutman, T.J. Maxwell, D.F. Ratner
    SLAC, Menlo Park, California, USA
  • V. A. Jhalani
    CALTECH, Pasadena, California, USA
 
  Transverse deflecting structures (TDS) are widely used in accelerator physics to measure the longitudinal density of particle bunches. When used in combination with a dispersive section, the whole longitudinal phase space density can be imaged. At the Linac Coherent Light Source (LCLS), the installation of such a device downstream of the undulators enables the reconstruction of the X-ray temporal intensity profile by comparing longitudinal phase space distributions with lasing on and lasing off*. However, the resolution of this TDS is limited to around 1 fs rms (root mean square), and therefore, in most cases, it is not possible to resolve single self-amplified spontaneous emission (SASE) spikes within one photon pulse. By combining the intensity spectrum from a high resolution photon spectrometer** and the temporal structure from the TDS, the overall resolution is enhanced, thus allowing the observation of temporal, single SASE spikes. The combined data from the spectrometer and the TDS is analyzed using an iterative algorithm to obtain the actual intensity profile. In this paper, we present the reconstruction algorithm as well as analyzed data obtained from simulations which shows the reliability of this method. Real data will be published at a later stage.
*Y. Ding et al., Phys. Rev. ST AB, 14, 120701, 2011.
**D. Zhu et al., Appl. Phys. Lett., 101, 034103, 2012.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF076  
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TUPMF078 Control of FEL Radiation Properties by Tailoring the Seed Pulses FEL, laser, experiment, electron 1444
 
  • V. Grattoni, R.W. Aßmann, J. Bödewadt, I. Hartl, C. Lechner, B. Manschwetus, M.M. Mohammad Kazemi
    DESY, Hamburg, Germany
  • A. Azima, W. Hillert, V. Miltchev, J. Roßbach
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • S. Khan, T. Plath
    DELTA, Dortmund, Germany
 
  Seeded free-electron lasers (FELs) produce intense, ultrashort and fully coherent X-ray pulses. These seeded FEL pulses depend on the initial seed properties. Therefore, controlling the seed laser allows tailoring the FEL radiation for phase-sensitive experiments. In this contribution, we present detailed simulation studies to characterize the FEL process and to predict the operation performance of seeded pulses. In addition, we show experimental data on the temporal characterization of the seeded FEL pulses performed at the sFLASH experiment in Hamburg.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF078  
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TUPMK002 First Tests of the Apple II Undulator for the LOREA Insertion Device and Front End vacuum, undulator, optics, insertion-device 1488
 
  • J. Campmany, L.G.O. Garcia-Orta, J. Marcos, Z. Martí, V. Massana, M. Quispe
    ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
 
  ALBA synchrotron is currently installing the new beamline LOREA (Low-Energy Ultra-High-Resolution Angular Photoemission for Complex Materials at ALBA). It operates in the range of 10 - 1500 eV with polarized light. To produce the light for the beamline, an Apple II undulator with a period of 125 mm has been chosen. It can operate as an undulator at low energies and as a wiggler at high energies, providing a wide energy range. The device was built by KYMA, delivered on February 2017 and installed in August 2017. We present the magnetic measurements made during SAT as well as the simulations of the influence of the ID in the electron beam dynamics and the first measurements with beam. On the other hand, the high demanding characteristics of the beamline lead to a device providing high power and wide beam in some working modes. This situation has been a challenge for the Front End (FE) thermal load. It has been built by the companies RMP and TVP, and the FE modules have been installed in the tunnel along autumn 2017. We present the Site Acceptance Tests results as well as the technical solutions adopted, especially in terms of mechanical design and used materials.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMK002  
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TUPMK004 Using Decoherence to Prevent Damage to the Swap-Out Dump for the APS Upgrade emittance, kicker, electron, storage-ring 1494
 
  • M. Borland, J.C. Dooling, R.R. Lindberg, V. Sajaev, A. Xiao
    ANL, Argonne, Illinois, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Advanced Photon Source (APS) is pursuing an upgrade of the storage ring to a hybrid seven-bend-achromat* design, which will operate in swap-out mode. The ultra-low emittance (about 30 pm in both planes) combined with the desire to provide high charge (15 nC) in individual bunches, entails very high energy density in the beam. Simple estimates, confirmed by simulation, indicate that interaction of such a bunch with the dump material will result in localized melting. Over time, it is possible that the beam would drill through the dump and vent the ring vacuum. This would seem to prevent extraction and dumping of bunches as part of swap out, and also suggests that transferring of bunches out of the ring carries significant risk. We devised an idea for using a pre-kicker to cause decoherence of the target bunch emittances, making it safe to extract. Simulations show that the concept works very well.
*L. Farvacque et al., IPAC13, 79 (2013).
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMK004  
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TUPMK005 CSR Shielding Effect in Dogleg and EEX Beamlines shielding, dipole, experiment, emittance 1498
 
  • G. Ha, M.E. Conde, J.G. Power, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
 
  Funding: Department of Energy, Office of HEP and BES under Contract No. DE-AC02-06CH11357.
CSR shielding is a well-known CSR suppression scheme which works by cutting off the low frequency CSR radiation. Although the shielding scheme is well known, its effects on the beam has been rarely studied. We investigate the CSR effect on the beam emittance when passing through a dogleg and a double dogleg type EEX beamline. An experimental study is planned at the Argonne Wakefield Accelerator facility where we can generate a 0.1-100 nC electron beam with an energy of 50 MeV and have a double dogleg EEX beamline. Tunable shielding plates are installed at the dipole magnet chambers of the EEX beamline to vary the shielding condition. Transverse and longitudinal phase space measurement systems are prepared to characterize the beam-CSR interaction, and bolometer and interferometry are prepared to characterize CSR. We present simulation results and preliminary experimental results.
 
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TUPMK006 Sub-fs Electron Bunch Generation Using Emittance Exchange Compressor emittance, sextupole, cavity, electron 1501
 
  • J.M. Seok, M. Chung
    UNIST, Ulsan, Republic of Korea
  • M.E. Conde, J.G. Power
    ANL, Argonne, Illinois, USA
  • G. Ha
    PAL, Pohang, Republic of Korea
 
  Sub-fs electron bunch has been pursued in the last decade using several different methods. These methods rely on one of the velocity difference or path length difference to compress a long bunch to sub-fs bunch. Here, we introduce a new method to generate the compression. Emittance Exchange (EEX) beamline makes transverse-to-longitudinal exchange of phase space. In this beamline, a transverse focusing at the upstream introduces a longitudinal compression at the downstream due to the exchange. Since this exchange scheme does not rely on the velocity or the path length differences, it does not require any longitudinal manipulation (e.g. chirp), and it could generate a short bunch with well-controlled nonlinear effects using nonlinear magnets. We present preliminary simulation results of EEX based bunch compression and sub-fs bunch generation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMK006  
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TUPMK009 Electron Beam Optics for the ASU Compact XFEL dipole, FEL, electron, laser 1507
 
  • C. Zhang, W.S. Graves, M.R. Holl, L.E. Malin
    Arizona State University, Tempe, USA
  • E.A. Nanni
    SLAC, Menlo Park, California, USA
 
  Funding: National Science Foundation Division of Physics (Accelerator Science) award 1632780, award 1231306. DOE grant DE-AC02-76SF00515.
Arizona State University (ASU) is pursuing a new concept for a compact x-ray FEL (CXFEL) as a next phase of compact x-ray light source (CXLS). We describe the electron beam optics design for the ASU compact XFEL. In previous experiments we introduced a grating diffraction method to generate a spatially modulated beam. We plan to combine a telescope imaging system with emittance exchange (EEX) to magnify/demagnify the modulated beam and transfer it from transverse modulation into a longitudinal one to make it an ideal seed for phase-coherent XFEL. The simulation results of the beam line setup will be demonstrated. Our first goal is to successfully image the modulated beam with desired magnification then we will investigate various magnification and magnets combinations and optimize aberration correction.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMK009  
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TUPMK014 Dipole Fringe Field Analysis of the NSLS-II Storage Ring dipole, storage-ring, optics, lattice 1519
 
  • J. Choi, Y. Hidaka, T.V. Shaftan, C.J. Spataro, G.M. Wang
    BNL, Upton, Long Island, New York, USA
 
  Funding: DOE Contract No. DE-SC0012704
In the NSLS-II storage ring, the effect of the dipole fringe field is not negligible and was considered already at the design phase. Especially in the vertical direction, the standard simulation codes are using the parameter called FINT (fringe Field INTegral) and, if there is no specific information, it is usually set to 0.5 which is considered as the reasonable average. With the hall-probe measurement data of the NSLS-II storage ring dipoles, we evaluated measured FINTs and applied them to the beam simulation. The paper shows the resulting FINTs and their effects.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMK014  
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TUPMK015 Initial Studies into Longitudinal Ionization Cooling for the Muon g-2 Experiment emittance, experiment, storage-ring, target 1522
 
  • J. Bradley
    Edinburgh University, Edinburgh, United Kingdom
  • J.D. Crnkovic
    BNL, Upton, Long Island, New York, USA
  • D. Stratakis, M.J. Syphers
    Fermilab, Batavia, Illinois, USA
  • M.J. Syphers
    Northern Illinois University, DeKalb, Illinois, USA
 
  Fermilab's Muon g-2 experiment aims to measure the anomalous magnetic moment of the muon to an unprecedented precision of 140 ppb. It relies on large numbers of muons surviving many turns in the storage ring without colliding with the sides, at least long enough for the muons to decay. Longitudinal ionization cooling is introduced with respect to Fermilab's Muon g-2 experiment in an attempt to increase storage and through this the statistics and quality of results. The ionization cooling is introduced to the beam through a material wedge, an initial simulation study is made into the positioning, material, and geometrical parameters of this wedge using G4Beamline. Results suggest a significant increase of 20 - 30% in the number of stored muons when the optimal wedge is included in the simulation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMK015  
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TUPML004 Correction of Emittance Growth Due to Quad Components in Solenoids With Quad Correctors at AWA emittance, solenoid, linac, electron 1536
 
  • L.M. Zheng, C.-X. Tang
    TUB, Beijing, People's Republic of China
  • M.E. Conde, D.S. Doran, W. Gai, W. Liu, J.G. Power, J.H. Shao, C. Whiteford, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
 
  An asymmetrical electron beam is observed on the drive beamline at Argonne Wakefield Accelerator (AWA) due to the quad components in the solenoids. An ASTRA simulation shows that the emittance will increase when the electron beam passes through solenoids with quad errors. We use two quad correctors to correct this emittance growth. A preliminary emittance correction result is presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML004  
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TUPML007 Short Pulse High Power RF Generation with an X-Band Dielectric Power Extractor experiment, acceleration, linear-collider, collider 1546
 
  • J.H. Shao, M.E. Conde, D.S. Doran, W. Gai, W. Liu, N.R. Neveu, J.F. Power, C. Whiteford, E.E. Wisniewski, L.M. Zheng
    ANL, Argonne, Illinois, USA
  • C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio, USA
 
  Short pulse high power rf generation is one of the key technologies for the Argonne Flexible Linear Collider (AFLC), a proposed 3 TeV electron-positron linear collider based on two-beam acceleration (TBA) scheme. Compared with metallic power extractors, dielectric structures have the potential to achieve lower fabrication cost and to withstand higher gradient. Recently, an X-band dielectric power extractor (a.k.a, DPETS) has been developed at the Argonne Wakefield Accelerator (AWA) facility and achieved 105 MW output power when driven by a high charge 8-bunch train separated by 770 ps. The design, the cold test measurement, the preliminary high power test results, and the structure inspection will be presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML007  
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TUPML009 Design and Test Plan for a Prototype Corrugated Waveguide GUI, wakefield, experiment, electron 1550
 
  • G.J. Waldschmidt, D.S. Doran, G. Ha, R. Kustom, A. Nassiri, J.G. Power, A. Zholents
    ANL, Argonne, Illinois, USA
  • A.E. Siy
    UW-Madison/PD, Madison, Wisconsin, USA
 
  A cylindrical, corrugated wakefield accelerating structure with a 1 mm radius bore is being designed to facilitate sub-terahertz Čerenkov radiation produced by an elec-tron bunch propagating along the waveguide. A 220 GHz axial mode for the wakefield is being considered. The waveguide is being optimized to maximize the trailing wakefield potential while maintaining a ratio of the trail-ing potential to the peak decelerating voltage in the bunch, or transformer ratio, of approximately 5 for the door step peak current distribution [1]. In order to evalu-ate the manufacturing tolerances and perform rf and electron beam testing of the waveguide, a 21 GHz proto-type waveguide structure will be built consisting of re-configurable parts allowing modelling of various fabrica-tion errors. Measurements with an electron beam will be performed at the Argonne Wakefield Accelerator (AWA) test facility. Analysis of the experimental layout has been performed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML009  
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TUPML015 Influence of Ionization and Beam Quality on Interaction of Tw-Peak Co2 Laser With Hydrogen Plasma laser, plasma, electron, experiment 1560
 
  • P. Kumar, V. Samulyak
    SBU, Stony Brook, USA
  • V. Samulyak, K. Yu
    BNL, Upton, Long Island, New York, USA
 
  3D numerical simulations of the interaction of a powerful CO2 laser with hydrogen jets demonstrating the role of ionization and laser beam quality are presented. Simulations are performed in support of the plasma wakefield accelerator experiments being conducted at the BNL Accelerator Test Facility (ATF). The CO2 laser at BNL ATF has several potential advantages for laser wakefield acceleration compared to widely used solid-state lasers. SPACE, a parallel relativistic Particle-in-Cell code, developed at SBU and BNL, has been used in these studies. A novelty of the code is its set of efficient atomic physics algorithms that compute ionization and recombination rates on the grid and transfer them to particles. The primary goal of the initial BNL experiments was to characterize the plasma density by measuring the sidebands in the spectrum of the probe laser. Simulations, that resolve hydrogen ionization and laser spectra, help explain several trends that were observed in the experiments.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML015  
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TUPML017 Longitudinal Phase Space Reconstruction at FLASHForward Using a Novel Transverse Deflection Cavity, PolariX-TDS plasma, experiment, dipole, lattice 1567
 
  • R.T.P. D'Arcy, A. Aschikhin, P. González Caminal, V. Libov, J. Osterhoff
    DESY, Hamburg, Germany
 
  The FLASHForward project at DESY is an innovative beam-driven plasma-wakefield acceleration (PWFA) experiment, aiming to accelerate electron beams to GeV energies over a few centimeters of ionized gas. These accelerated beams are assessed for their capability to drive a free-electron laser. The ultra short, low emittance, and low energy spread properties of bunches produced from certain PWFA injection schemes naturally lend themselves to this task. However, these bunch lengths, typically in the few femtosecond range, are difficult to temporally resolve with traditional diagnostic methods. In order to longitudinally diagnose these bunches it is necessary to utilise the properties of a transverse RF deflecting cavity operating in a high-frequency regime. It is proposed that this type of X-band transverse deflection system, styled the PolariX-TDS due to its novel variable polarisation feature, will be introduced to the FLASHForward beam line in order to perform these single-shot longitudinal phase space measurements. This paper will concern itself with the efficacy of longitudinally reconstructing PWFA-bunches expected at FLASHForward with this TDS, with a focus on the variable bunch properties expected from early commissioning of the experiment.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML017  
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TUPML028 Photocathodes R&D for High Brightness and Highly Polarized Electron Beams at Cornell University electron, cathode, emittance, gun 1601
 
  • L. Cultrera, J. Bae, A.C. Bartnik, I.V. Bazarov, R. Doane, A. Galdi, C.M. Gulliford, W. H. Li, J.M. Maxson, S.A. McBride, T.P. Moore, C. M. Pierce, C. Xu
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Cornell University is a leader in the development of photocathode materials for the production of high brightness electron beam sources for applications in large scale accelerators and small scale electron scattering experiments. During the last year we have also included Mott polarimetry to investigate long lifetime spin-polarized photocathodes materials. Another thrust of our laboratory is the exploration of ultra low emittance photocathodes at cryogenic temperatures, for which we are building a novel LHe cryogenic electron source. We will review updates from our lab across each of these areas.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML028  
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TUPML029 Novel Photocathode Geometry Optimization: Field Enhancing Photoemission Tips cathode, emittance, electron, solenoid 1605
 
  • W. H. Li, I.V. Bazarov, C.M. Gulliford, J.M. Maxson
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Funding: This work was supported by the U.S. National Science Foundation under award PHY-1549132, the Center for Bright Beams.
For photoemission sources, the extraction electric field defines the maximum achievable emission current, and hence the maximum achievable beam brightness. Recently, interest has been growing in studying photocathodes with non-flat geometries to produce local field enhancements in excess of what can be achieved with large area flat cathodes. However, such geometries cause image charge effects which require self-consistent field solvers to correctly simulate. We present a novel simulation framework which combines a full particle in cell field solver (WARP) with a fast adaptive mesh space charge particle tracker (GPT) and a parallel multi-objective genetic optimizer to explore photocathode geometries for ultra high brightnesses. A first application of this technique is also shown, namely the use of field enhanced photoemission tips to create bright beams for ultra-fast electron diffraction.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML029  
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TUPML039 First Order Sensitivity Analysis of Electron Acceleration in Dual Grating Type Dielectric Laser Accelerator Structures laser, electron, experiment, emittance 1626
 
  • F. Mayet, R.W. Aßmann, U. Dorda, W. Kuropka
    DESY, Hamburg, Germany
  • W. Kuropka, F. Mayet
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  Funding: Gordon and Betty Moore Foundation. Grant GBMF4744
Symmetrically driven dual-grating type DLA (Dielectric Laser Accelerator) linac structures allow for in-channel electric field gradients on the order of GV/m at optical wavelengths. In this work we study the sensitivity of important final beam parameters like mean energy, energy spread and transverse emittance on DLA drive laser as well as input beam parameters. To this end a fast specialized particle tracking code (DLATracker) is used to compute the so called first order sensitivity indices based on a large number of Monte Carlo simulation runs of an exemplary external injection based DLA experiment. The results of this work point out important stability constraints on the drive laser setup and the externally injected electron beam.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML039  
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TUPML042 Accurate Modeling of the Hose Instability in Plasma Based Accelerators plasma, electron, damping, wakefield 1638
 
  • T.J. Mehrling, C. Benedetti, E. Esarey, W. Leemans, C.B. Schroeder
    LBNL, Berkeley, USA
 
  Funding: US Department of Energy Contract No. DE-AC02-05CH11231
The hose instability is a long standing challenge for plasma-based accelerators. It is seeded by initial transverse asymmetries of the beam or plasma phase space distributions. The beam centroid displacement is thereby amplified during the propagation in the plasma, which can lead to an unstable acceleration process. A witness beam can itself cause hosing and/or may be affected by the hosing of the drive beam. The accurate study of hosing including a witness beam is of utmost importance to facilitate stable plasma-based accelerators. In this contribution, we discuss novel methods for the mitigation of hosing and present a new model for the evolution of the plasma centroid, which enables the accurate investigation of the hose instability of drive and witness beam pair in the nonlinear blowout regime. This work enables more precise and comprehensive studies of hosing and hence, for the potential stabilization of future compact plasma-based accelerators.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML042  
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TUPML051 Studies of Collision and Compression of Pulsed Plasmas Generated by Coaxial Accelerators plasma, electron, experiment, ion-source 1653
 
  • T. Manegold, C. Benzing, M. Iberler, J. Jacoby, P. Mahmoodi Tavana, A. Müller-Münster, B. Podßus
    IAP, Frankfurt am Main, Germany
 
  This contribution is about our recent studies of collision and compression of plasma sheaths, generated by coaxial plasma accelerators. One application is the development of a pulsed ion source producing high ion currents, coming along with high electron densities. The experiment is built up of an energy storage with up to 1,35kJ with a 2% Hydrogen in Helium gas mixture as working gas. The small fraction of Hydrogen is necessary to use the linear Stark-broadening of the H-line to determine the electron density, which is in the range up to 1015cm-3. By the collision of two plasma sheaths in an angle of 180°, the electron density has been increased by a factor of 2.5 compared to the single plasma sheath. As an alternative, the compression of the plasma by funnel geometries has been studied. As has been found, the achieved electron densities are more than a magnitude higher, compared to the values of the plasma collision. Thus, the H-line is broadened too high to be used. Alternatively, the broadening of a copper line by the quadratic Stark-effect has been calibrated and used to determine those high electron densities of about 1018cm-3.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML051  
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TUPML052 Characterisation of the Second Stable Orbit Generated by Transverse Resonance Island Buckets (TRIBs) optics, resonance, experiment, emittance 1656
 
  • F. Kramer, P. Goslawski, A. Jankowiak, M. Ries, M. Ruprecht, A. Schälicke
    HZB, Berlin, Germany
 
  Funding: Federal Ministry of Education and Research
Operating the storage ring near a transverse tune resonance can generate TRIBs in the corresponding phase space, providing a second orbit twisting around the standard orbit. TRIBs as a bunch separation scheme in combination with the proposed variable bunch length storage ring BESSY VSR* represent a promising alternative to dedicated single or few bunch operation modes. The injection efficiency and stability of the two orbits at BESSY II and MLS are almost on par with and the lifetime at about 70 % of the standard user mode. Results from simulations and measurements of our present island optics will be presented. Beam parameters like the betatron motion, dispersion and emittance of both the core and island orbit will be discussed as well as the separation between the island and the core orbit. At BESSY II a dedicated test week together with the friendly users took place in the first week of February, 2018.
* A. Jankowiak et al., eds., BESSY VSR Technical Design Study, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Germany, June 2015. DOI: 10.5442/R0001
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML052  
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TUPML059 Slice Energy Spread Optimization for a 5 GeV Laser-Plasma Accelerator plasma, laser, beam-loading, electron 1670
 
  • X. Li, P.A.P. Nghiem
    IRFU, CEA, University Paris-Saclay, Gif-sur-Yvette, France
  • A. Mosnier
    CEA/IRFU, Gif-sur-Yvette, France
 
  GeV-scale laser-plasma accelerating modules can be integrated into a multi-staged plasma linac for driving compact X-ray light sources or future colliders. Such a plasma module, operating in the quasi-linear regime, has been designed for the 5 GeV laser plasma acceleration stage (LPAS) of the EuPRAXIA project. Although it can be employed to optimize the total energy spread, the beam loading effect introduces an non-negligible slice energy spread to the beam. In this paper, we study the slice energy spread from linear theory, establishing a relationship between it and the laser-plasma parameters. To reduce the slice energy spread, simulations have been carried out for various plasma densities and laser strengths. The results will be discussed and compared with the theory.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML059  
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TUPML062 A Wedge Test in MICE emittance, experiment, beam-cooling, collider 1680
 
  • T.A. Mohayai
    IIT, Chicago, Illinois, USA
  • D.V. Neuffer
    Fermilab, Batavia, Illinois, USA
  • P. Snopok
    Illinois Institute of Technology, Chicago, Illlinois, USA
  • D.J. Summers
    UMiss, University, Mississippi, USA
 
  Emittance exchange mediated by wedge absorbers is required for longitudinal ionization cooling and for final transverse emittance minimization for a muon collider. A wedge absorber within the MICE cooling channel could serve as a demonstration of the type of emittance exchange needed for 6-D cooling, including the configurations needed for muon colliders. Parameters for this test have been explored in simulation and applied to experimental configurations using a wedge absorber in the MICE beam. A wedge absorber has been constructed and placed in MICE and data has been collected for both direct emittance exchange, where the longitudinal emittance decreases, and reverse emittance exchange, where the transverse emittance decreases. The simulation studies that led to the magnet configurations and beam configurations are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML062  
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TUPML063 A Non-parameteric Density Estimation Approach to Measuring Beam Cooling in MICE emittance, beam-cooling, experiment, solenoid 1684
 
  • T.A. Mohayai
    IIT, Chicago, Illinois, USA
  • D.V. Neuffer
    Fermilab, Batavia, Illinois, USA
  • P. Snopok
    Illinois Institute of Technology, Chicago, Illlinois, USA
 
  The goal of the international Muon Ionization Cooling Experiment (MICE) is to demonstrate muon beam ionization cooling for the first time. It constitutes a key part of the R&D towards a future neutrino factory or muon collider. The intended MICE precision requires development of analysis tools that can account for any effects (e.g., nonlinearities) which may lead to inaccurate cooling measurements. Non-parametric density estimation techniques, in particular, kernel density estimation (KDE), allow very precise calculations of the muon beam phase-space density and its increase as a result of cooling. In this study, these density estimation techniques and their application to measuring the reduction in muon beam phase-space volume and amplitude in MICE are investigated.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML063  
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TUPML065 Phase Space Density Evolution in MICE emittance, factory, experiment, collider 1692
 
  • D. Rajaram
    Illinois Institute of Technology, Chicago, Illinois, USA
  • V. Blackmore
    Imperial College of Science and Technology, Department of Physics, London, United Kingdom
 
  Funding: STFC, DOE, NSF, INFN, and CHIPP
The Muon Ionization Cooling Experiment (MICE) collaboration will demonstrate the feasibility of ionization cooling, the technique proposed to cool the muon beam at a future neutrino factory or muon collider. The muon beam parameters are measured before and after the cooling cell using high precision scintillating-fibre trackers in a solenoidal magnetic field. Position and momentum reconstruction of each muon in MICE allows the development of several alternative figures of merit in addition to emittance. Contraction of the phase-space volume of the sample, or equivalently the increase in phases-pace density at its core, is an unequivocal cooling signature. Single-particle amplitude, defined as a weighted distance to the sample centroid, can be used to probe the change in density in the core of the beam. Alternatively, non-parametric statistics provide reliable methods to estimate the entire phase-space density distribution and reconstruct probability contours. The aforementioned techniques, robust to transmission losses and sample non linearities, are ideal candidates for a cooling measurement in MICE. Preliminary results are presented here*.
*Submitted by the MICE Speakers bureau, to be prepared and presented by a MICE member to be selected in due course
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML065  
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TUPML066 Progress on Beam-Plasma Effect Simulations in Muon Ionization Cooling Lattices plasma, emittance, scattering, cavity 1696
 
  • P. Snopok
    Illinois Institute of Technology, Chicago, Illinois, USA
  • J.S. Ellison
    IIT, Chicago, Illinois, USA
 
  Funding: Work supported by the Department of Energy.
New computational tools are essential for accurate modeling and simulation of the next generation of muon-based accelerators. One of the crucial physics processes specific to muon accelerators that has not yet been simulated in detail is beam-induced plasma effect in liquid, solid, and gaseous absorbers. We report here on the development of required simulation tools and their applications to studying the properties of plasma and its effects on the beam in muon ionization cooling channels.
 
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TUPML074 Resonant Excitation of Accelerating Field in Dielectric Corrugated Waveguide wakefield, experiment, electron, GUI 1715
 
  • A. Lyapin, S.T. Boogert, K. Lekomtsev
    JAI, Egham, Surrey, United Kingdom
  • A. Aryshev
    KEK, Ibaraki, Japan
  • A.A. Tishchenko
    MEPhI, Moscow, Russia
 
  Funding: This project has received funding from the European Union Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 655179.
Beam driven dielectric wakefield accelerators (DWAs) [*] typically operate in the terahertz frequency range, which pushes the plasma breakdown threshold for surface electric fields into the multi GV/m range. DWA technique allows one to accommodate a significant amount of charge per bunch, and opens access to conventional fabrication techniques for the accelerating structures. Resonant excitation of coherent Cherenkov radiation in DWA by a multi-bunch beam was used for selective resonant mode excitation [**] and enhancement of accelerating wakefield [***]. We investigate the resonant excitation of Cherenkov Smith-Purcell radiation [****] in a corrugated cylindrical waveguide by a multi-bunch electron beam. The accelerating field is calculated using Particle in Cell simulations and some basic post-processing is done in order to estimate the possible enhancement of the accelerating field. The aim of this work is to investigate regimes of the resonant excitation that can potentially produce accelerating gradients above 1 GV/m.
* C. Jing, Rev. Acc. Phys. and Tech. 9, 127 (2016).
** G. Andonian, APL 98, 202901 (2011).
*** J.G. Power, PRSTAB 3, 101302 (2000).
**** A.A. Ponomarenko, A.A. Tishchenko, NIMB 309, 223 (2013).
 
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TUPML077 Development of Physical Processes in Geant4 for Simulation of ISOL Target-Ion-Source System target, proton, ISOL, ion-source 1724
 
  • P. Lee, Y.-S. Cho, J.J. Dang, H.S. Kim, H.-J. Kwon, S. Lee, Y.G. Song, S.P. Yun
    Korea Atomic Energy Research Institute (KAERI), Gyeongbuk, Republic of Korea
 
  Funding: This work has been supported through KOMAC operation fund of KAERI and the NRF of Korea grant funded by the Korea government (MSIT) (No. NRF-2017M2A2A6A02071070).
Geant4 physical processes for simulating diffusion and effusion of radioactive ions in matter have been developed for optimizing ISOL target-ion-source (TIS) system. The developed processes simulate motions of radioactive ions with sub-eV kinetic energy in the TIS geometry. The processes consist of diffusion, effusion, and radioactive decay modules, and they are designed to work seamlessly with other implemented physics lists, extending capability of the Geant4 toolkit to more complicated applications in the field of nuclear physics. The diffusion probability is analytically calculated by using the well-known Fick's formula. The effusive flow of neutral atoms is interpreted in terms of kinetic molecular theory of gases, where the interaction between atoms and the wall of a target container is described by employing Lorentz-Lambert model. By the help of newly implemented processes, it is able to simulate the release of radioactive ions from the irradiation of a proton beam on the TIS system with different geometrical parameters in a single environment. Here, we present the status of the development and plans for further improvements.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML077  
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WEXGBE3 IBS Studies at BESSY II and MLS emittance, scattering, radiation, damping 1755
 
  • T. Mertens
    Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
  • T. Atkinson, J. Feikes, P. Goslawski, J.G. Hwang, A. Jankowiak, J. Li, D. Malyutin, Y. Petenev, M. Ries, I. Seiler
    HZB, Berlin, Germany
 
  Intrabeam Scattering (IBS) effects will become a limiting factor for the attainable emittances and single-bunch currents in future electron storage rings and light sources. IBS studies were performed for BESSY II at the Helmholtz-Zentrum Berlin (HZB) and for the Metrology Light Source (MLS) at the Physikalisch-Technische Bundesanstalt (PTB) to quantify the IBS contributions to equilibrium beam sizes in these machines and make predictions for the BESSY II upgrade project, BESSY VSR. The energy dependence of IBS effects (γ −4 ) makes especially the MLS machine susceptible to IBS effects due to the relatively low energy ranges at which it can be operated (50 MeV-630 MeV). We compare experimental data with simulations and present IBS simulation results for BESSY VSR.  
slides icon Slides WEXGBE3 [0.922 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEXGBE3  
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WEPAF003 Beamline Architect interface, quadrupole, software, solenoid 1812
 
  • J.D. Kunz, C.M. Conrad, L.M. Romero
    Anderson University, Anderson, USA
 
  Funding: Indiana Space Grant Fellowship Program 2015-2018, subaward number 4103-82252
Beamline Architect is a new particle accelerator simulation tool. Currently, two of the most widely used tools in this field are G4beamline and COSY Infinity. While these codes are fast and quite accurate, sometimes their interfaces can be time-consuming for students to learn, particularly undergraduate students or students whose primary field is not accelerator physics. Without Beamline Architect, each code has its own high-level language that must be manually written into a file and then executed on the command line. Moreover, sometimes the use of both simulation tools is warranted in order to check for consistency between the codes. Writing the codes by hand or translating between software can sometimes be cumbersome, even for experts. Furthermore, knowledge of an additional language, such as Python, is required in order to analyze the outputs of the codes (which may be in different formats from one another). Beamline Architect is a tool that provides a graphical user interface to G4beamline and COSY Infinity. This lets the user build a particle accelerator channel in 3D with or without using code. The channel may then be saved, exported, translated, or run. Any output data will be plotted in Beamline Architect using Python, since it is both flexible aesthetically and quite standard in the particle accelerator community. For undergraduate and non-accelerator students, Beamline Architect allows a hands-on experience with accelerator simulations. Some applications for these students include health physics radiation dosimetry problems, medical imaging mechanics, security scanner simulations, and (of course) accelerator channel design for particle physics experiments. For experts, Beamline Architect provides visual confirmation of the channel and a faster, more consistent way of cross-referencing results between the codes.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF003  
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WEPAF014 Commissioning the Superconducting Magnetic Inflector System for the Muon g-2 Experiment storage-ring, experiment, injection, MMI 1844
 
  • N.S. Froemming
    CENPA, Seattle, Washington, USA
  • K.E. Badgley, H. Nguyen, D. Stratakis
    Fermilab, Batavia, Illinois, USA
  • J.D. Crnkovic
    BNL, Upton, Long Island, New York, USA
  • L.E. Kelton
    UKY, Kentucky, USA
  • M.J. Syphers
    Northern Illinois University, DeKalb, Illinois, USA
 
  The Fermilab muon g-2 experiment aims to measure the muon anomalous magnetic moment with a precision of 140 ppb - a fourfold improvement over the 540 ppb precision obtained in the BNL muon g-2 experiment. Both of these high-precision experiments require an extremely uniform magnetic field in the muon storage ring. A superconducting magnetic inflector system is used to inject beam into the storage ring as close as possible to the design orbit while minimizing disturbances to the storage-region magnetic field. The Fermilab experiment is currently in its first data-taking run, where the Fermilab inflector system is the refurbished BNL inflector system. This discussion reviews the Fermilab inflector system refurbishment and commissioning.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF014  
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WEPAF018 Proposed BPM-Based Bunch Crabbing Angle Monitor cavity, site, electron, diagnostics 1860
 
  • P. Thieberger, M.G. Minty, C. Montag
    BNL, Upton, Long Island, New York, USA
 
  Funding: This work was supported by Brookhaven Science Associates, LLC, under Contract No. DE-AC02-98CH10886 with the US Department of Energy.
A tilted bunch traversing a button beam profile monitor will produce signals on opposite pickup electrodes that will have different degrees of distortion depending on the tilt angle. In particular, the zero-crossing time difference between the two signals will be approximately proportional to the tilt angle. We perform simulations to study this effect as a possible diagnostic tool for measuring the crabbing angles in a future electron-ion collider.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF018  
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WEPAF019 Fast Readout Algorithm for Cylindrical Beam Position Monitors Providing Good Accuracy for Particle Bunches with Large Offsets FPGA, electron, collider, pick-up 1864
 
  • P. Thieberger, D.M. Gassner, R.L. Hulsart, R.J. Michnoff, T.A. Miller, M.G. Minty, Z. Sorrell
    BNL, Upton, Long Island, New York, USA
  • A.C. Bartnik
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Funding: This work was supported by Brookhaven Science Associates, LLC, under Contract No. DE-AC02-98CH10886 with the US Department of Energy.
A simple, analytically correct algorithm is developed for calculating 'pencil' beam coordinates using the signals from an ideal cylindrical beam position monitor (BPM) with four pickup electrodes (PUEs) of infinitesimal widths. The algorithm is then applied to simulations of realistic BPMs with finite width PUEs. Surprisingly small deviations are found. Simple empirically determined correction terms reduce the deviations even further. Finally, the algorithm is used to study the impact of beam-size upon the precision of BPMs in the non-linear region. As an example of the data acquisition speed advantage, a FPGA-based BPM readout implementation of the new algorithm has been developed and characterized
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF019  
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WEPAF036 Energy Independence in Optical Transition Radiation Imaging radiation, electron, diagnostics, optics 1898
 
  • J. Wolfenden, R.B. Fiorito, C.P. Welsch
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • R.B. Fiorito, C.P. Welsch, J. Wolfenden
    The University of Liverpool, Liverpool, United Kingdom
 
  Funding: This work was supported by the EU under Grant Agreement No. 624890 and the STFC Cockcroft Institute core Grant No. ST/G008248/1.
The exploitation of optical transition radiation (OTR) in imaging-based diagnostics for charged particle beams is a well-established technique. Simulations of the expected OTR transverse beam profiles are therefore important in both the design of such imaging systems and the analysis of the data. Simulating OTR images is relatively straightforward for low energy electron beams. However, in the near future electron machines will be using high-energy and low-emittance beams. Using such parameters can be challenging to simulate, and can be limiting in their account of practical factors, e.g. chromatic aberrations. In this work we show systematically that the use of low-energy parameters in high-energy OTR image simulations induces little deviation in the resulting transverse beam profiles. Simulations therefore become much easier to perform, and further analysis may be performed. This opens up exciting opportunities to perform simulations quicker and with reduced demands on the computation requirements. It will be shown in this contribution how this approach will enable enhanced ways to optimize OTR diagnostics.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF036  
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WEPAF041 Use of Dimension-Reduction Techniques With Multi-Objective Genetic Algorithms to Improve the Vertical Emittance and Orbit at CESR emittance, storage-ring, lattice, electron 1901
 
  • W.F. Bergan, I.V. Bazarov, C.J. Duncan, D. L. Rubin
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • D. Liarte, J.P. Sethna
    Cornell University, Ithaca, New York, USA
 
  Funding: DOE DE-SC0013571 NSF DGE-1650441
In order to reduce the vertical emittance at the Cornell Electron Storage Ring (CESR), we first measure and correct the vertical orbit, dispersion, and coupling. However, due to the finite resolution of our optics measurements, we still retain a significant residual emittance. In order to correct this further, we made use of the theory of sloppy models, according to which certain high-dimensionality systems can be modeled with significantly fewer "eigenparameters" that still contain most of the effect on the desired objective, in this case, the emittance.* However, we noted that using these knobs for tuning often resulted in increased vertical orbit errors. In an attempt to constrain these, we have applied multi-objective genetic algorithms to this problem. We have found that it can be more efficient to run such algorithms using our eigenparameters as the genes to be varied, as opposed to the raw magnet values. When running with the first 8 such knobs as genes, we can get either orbits or beam sizes as good as we obtain with our regular emittance-tuning algorithm which uses all the corrector magnets.
*K.S. Brown and J.P. Sethna, Phys. Rev. E 68, 021904 (2003).
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF041  
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WEPAF050 Simulations of 3D Charge Density Measurements for Commissioning of the PolariX-TDS cavity, electron, MMI, lattice 1930
 
  • D. Marx, R.W. Aßmann, R.T.P. D'Arcy, B. Marchetti
    DESY, Hamburg, Germany
 
  The prototype of a novel X-band transverse deflection structure, the Polarizable X-band (PolariX) TDS*, is currently being prepared for installation in the FLASHForward beamline** at DESY in early 2019. This structure will have the novel feature of variable polarization of the deflecting mode, allowing bunches to be streaked at any transverse angle, rather than at just one angle as in a conventional cavity. By combining screen profiles from several streaking angles using tomographic reconstruction techniques, the full 3D charge density of a bunch can be obtained***. It is planned to perform this measurement for the first time during commissioning of the structure. In this paper, simulations of this measurement are presented and the effects of jitter are discussed.
*P Craievich et al. paper THPAL068, this conference
**A Aschikhin et al. Nucl. Instr. Meth. Phys. Res. A., vol.806, pp.175-183, 2018
***D Marx et al. J. Phys.: Conf. Ser., vol.874, p.012077, 2017
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF050  
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WEPAF060 Non-Invasive Bunch Length Diagnostics for High Intensity Beams detector, radiation, electron, real-time 1964
 
  • S.V. Kuzikov, S.P. Antipov
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • S.V. Kuzikov, A.A. Vikharev
    IAP/RAS, Nizhny Novgorod, Russia
 
  Modern particle accelerators utilize photoinjectors and compression schemes to produce short high peak current electron bunches for various applications like x-ray free electron lasers, high gradient beam driven acceleration and others. Bunch length detection is a desired diagnostics for such machines. In this paper we describe a non-invasive, real-time detector which can be retrofitted into an existing beamline and measure the bunch length in real time using interferometric methods. Diffraction radiation is the mechanism to be used to produce a measurable signal without intercepting the beam. This became possible as sensitivity of pyrodetectors improved over the years, while peak beam power grew. For high peak current beams there is a possibility of a single shot measurement. This can be done with a pair of closely placed vacuum breaks that create a spatial correlation of the generated signals which can be measured by a pyro-detector array or a THz camera. The bunch length is determined from the correlation data using an iterative beam profile recovery algorithm.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF060  
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WEPAF076 Availability Studies Comparing Drive Beam and Klystron Options for the Compact Linear Collider klystron, operation, linac, software 2013
 
  • O. Rey Orozko, S. Döbert, M. Jonker
    CERN, Geneva, Switzerland
 
  The initial proposal for the Compact Linear Collider (CLIC) is based on a two beam-scheme to accelerate the main colliding beams. For low collision energies, the main beam could also be accelerated by powering the accelerating structures with klystrons instead of the two-beam scheme. This paper studies the feasibility of this new alternative in terms of machine availability. An implemented bottom-up availability model considers the components failure modes to estimate the overall availability of the system. The model is defined within a Common Input Format scheme and the AvailSim3 software package is used for availability simulations. This paper gives an overview of the systems affecting the beam powering availability and makes recommendations for availability improvements.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF076  
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WEPAG002 Tunable Q-Factor Gas-Filled RF Cavity cavity, coupling, hadron, plasma 2064
 
  • M.D. Balcazar, A. Moretti, A.V. Tollestrup, A.C. Watts, K. Yonehara, R.M. Zwaska
    Fermilab, Batavia, Illinois, USA
  • M.A. Cummings, A. Dudas, R.P. Johnson, G.M. Kazakevich, M.L. Neubauer
    Muons, Inc, Illinois, USA
 
  Funding: Work supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359 and DOE STTR Grant, No. DE-SC0013795.
Fermilab is the main institution to produce the most powerful and wide-spectrum neutrino beam. From that respective, a radiation robust beam diagnostic system is a critical element in order to maintain the quality of the neutrino beam. Within this context, a novel radiation-resistive beam profile monitor based on a gas-filled RF cavity has been proposed. The goal of this measurement is to study a tunable Q-factor RF cavity to determine the accuracy of the RF signal as a function of the quality factor. Specifically, the measurement error of the Q-factor in the RF calibration is investigated. Then, the RF system will be improved to minimize signal error.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAG002  
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WEPAK008 Reconstructing Space-Charge Distorted IPM Profiles with Machine Learning Algorithms electron, space-charge, GUI, network 2099
 
  • D.M. Vilsmeier, M. Sapinski, R. Singh
    GSI, Darmstadt, Germany
  • J.W. Storey
    CERN, Geneva, Switzerland
 
  Measurements of undistorted transverse profiles via Ionization Profile Monitors (IPMs) may pose a great challenge for high brightness or high energy beams due to interaction of ionized electrons or ions with the electromagnetic field of the beam. This contribution presents application of various machine learning algorithms to the problem of reconstructing the actual beam profile from measured profiles that are distorted by beam space-charge interaction. (Generalized) linear regression, artificial neural network and support vector machine algorithms are trained with simulation data, obtained from the Virtual-IPM simulation tool, in order to learn the relation between distorted profiles and original beam dimension. The performance of different algorithms is assessed and the obtained results are very promising for testing with simulation data.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAK008  
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WEPAK010 Simulations and Measurements of the BPM Non Linearity and Kicker Timing Influence on the Tune Shift With Amplitude (TSWA) Measurement at BESSY II kicker, optics, factory, diagnostics 2107
 
  • F. Kramer, P. Goslawski, J.G. Hwang, A. Jankowiak, P. Kuske, M. Ruprecht, A. Schälicke
    HZB, Berlin, Germany
 
  The Tune Shift With Amplitude (TSWA) does not only determine the position of the stable fix points for the Transverse Resonant Island Buckets (TRIBs) but also represents a global observable for the nonlinear optics in general. For theoretical investigations of the TRIBs a reliable nonlinear optics of the machine is required and thus all measurable global observables for the nonlinear optics are of great interest. The measurement of the TSWA for the BESSY II standard optics was performed using an injection kicker to excite high amplitude betatron oscillations and then extract the amplitude dependant frequency from the synchrotron radiation damped oscillation with a Hilbert transformation. With TRIBs optics the injection kicker was not able to sufficienty excite the beam. The impact and correctability of the BPM nonlinearity at the reached amplitudes and the reason for the failure of the excitation method for our TRIBs optics shall be looked onto in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAK010  
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WEPAL003 Baseband Simulation Model of the Vector RF Voltage Control System for the J-PARC RCS controls, feedback, cavity, software 2144
 
  • F. Tamura, M. Nomura, T. Shimada, M. Yamamoto
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  • M. Furusawa, K. Hara, K. Hasegawa, C. Ohmori, Y. Sugiyama, M. Yoshii
    KEK, Tokai, Ibaraki, Japan
 
  Vector rf voltage feedback control for the wideband magnetic alloy cavity of the J-PARC RCS is considered to be employed to compensate the heavy beam loading caused by high intensity proton beams. A prototype system of multiharmonic rf vector voltage control has been developed and is under testing. To characterize the system performance, full rf simulations could be performed by software like Simulink, while the software is proprietary and expensive. Also, it requires much computing power and time. We performed the simplified baseband simulations of the system in z-domain by using free software, Scilab and Python control library. It seems to be beneficial for searching the parameters that the baseband simulation can be performed quickly. In this presentation, we present the setup and results of the simulations. The simulations well reproduce the open and closed loop responses of the prototype system.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL003  
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WEPAL013 Design of the Diagnostic Stations for the ELI-NP Compton Gamma Source radiation, electron, optics, linac 2173
 
  • M. Marongiu
    INFN-Roma, Roma, Italy
  • M. Castellano, E. Chiadroni, G. Di Pirro, G. Franzini, A. Giribono, V. Shpakov, A. Stella, A. Variola
    INFN/LNF, Frascati (Roma), Italy
  • A. Cianchi
    Università di Roma II Tor Vergata, Roma, Italy
  • A. Mostacci, L. Palumbo
    Sapienza University of Rome, Rome, Italy
 
  A high brightness electron Linac is being built in the Compton Gamma Source at the ELI Nuclear Physics facility in Romania. To achieve the design luminosity, a train of 32 bunches, 16 ns spaced, with a nominal charge of 250 pC will collide with the laser beam in the interaction point. Electron beam spot size is measured with optical transition radiation (OTR) profile monitors. Furthermore, OTR angular distribution strongly depends on beam energy. Since OTR screens are typically placed in several positions along the Linac to monitor beam envelope, one may perform a distributed energy measurement along the machine. This will be useful, for instance, during the commissioning phase of the GBS in order to verify the correct functionality of the C-Band accelerating structures, due to the fact that there are OTR screens after each accelerating module. This paper deals with the studies of different optic configurations to achieve the field of view, resolution and accuracy in order to measure the energy of the beam. Several configurations of the optical detection line will be studied with simulation tools (e.g. Zemax).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL013  
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WEPAL017 Adaptive Feedforward Control Design Based on Simulink for the J-PARC LINAC LLRF System controls, LLRF, cavity, linac 2187
 
  • S. Li
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
  • Z. Fang, Y. Fukui, K. Futatsukawa, F. Qiu
    KEK, Ibaraki, Japan
  • S. Mizobata, Y. Sato, S. Shinozaki
    JAEA/J-PARC, Tokai-mura, Japan
 
  In j-parc linac, for dealing with high beam loading effect, an adaptive feedforward control method which based on iterative learning control was put forward. At the same time, in order to verify its effectiveness before it is officially put into use, an llrf system simulation model was built in simulink, matlab. In this paper, the architecture of llrf system simulation model will be introduced. The result of iterative learning control (ILC) is summarized.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL017  
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WEPAL028 Study of the Influence of the CSR Impedance on the Synchronous Phase Shift at KARA impedance, synchrotron, storage-ring, radiation 2223
 
  • P. Schönfeldt, E. Blomley, M. Brosi, E. Bründermann, J. Gethmann, B. Kehrer, A.-S. Müller, A.I. Papash, J.L. Steinmann
    KIT, Karlsruhe, Germany
 
  Funding: This work has been supported by the German Federal Ministry of Education and Research (Grant No. 05K16VKA) and the Helmholtz Association (Contract No. VH-NG-320).
Measurements of the bunch current dependent synchronous phase shift are a standard method to characterize the impedance of a storage ring. To study this shift, different experimental approaches can be used. In this contribution, we first derive the phase shift caused by the impedance describing the emission of coherent synchrotron radiation (CSR) based on numerical simulations of the longitudinal phase space. The predicted shift is compared to measurement results obtained by time-correlated single photon counting.
 
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WEPAL030 Deep Learning Based Predictive Control for RFT-30 Cyclotron controls, cyclotron, network, operation 2230
 
  • Y.B. Kong, M.G. Hur, E.J. Lee, J.H. Park, H.S. Song, S.D. Yang
    KAERI, Jeongeup-si, Republic of Korea
 
  Successful construction of the control system is an important problem in the accelerator. The RFT-30 cyclotron is 30 MeV cyclotron for radioisotope production and fundamental researches. To operate the RFT-30 cyclotron for beam irradiation, the human operators should carefully manipulate the control parameters. If the control does not function properly, it becomes difficult to handle the cyclotron and cannot perform the accurate operations for the control. In this work, we propose a deep learning based model predictive control approach for the RFT-30 cyclotron. The proposed approach is composed of two steps: system identification and a control design. In the system identification procedure, the proposed approach constructs the predictive model of the accelerator using the deep learning approach. In the control design stage, the controller finds the optimal control inputs by solving the optimization problem. To analyze the performance of the proposed approach, we applied the approach into the RFT-30 cyclotron.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL030  
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WEPAL033 Development of Real-Time Mass Analysis System with Permanent Magnet for Ion Beam ion-source, extraction, permanent-magnet, ECR 2236
 
  • Y. Takeuchi, Y. Iwashita, H. Tongu
    Kyoto ICR, Uji, Kyoto, Japan
 
  In order to analyze time variation of the ion species in a pulse, we are developing a mass analysis system that has multiple collector electrodes to detect several ion species simultaneously. Strong permanent magnets can generate 1T magnetic field and the size of the analyzing magnet system can be compact. The detected signals are scanned by a fast multiplexer. The scanning rate is 2 MHz, so that all electrode signals of the 16 channels are scanned in 8 μs period. In this paper, details of the design of the analysis system, and preliminary beam extraction test results with prototype of the system are described.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL033  
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WEPAL037 Simulation Study on Luminosity Feedback for Horizontal Beam Stabilization at Superkekb luminosity, feedback, ground-motion, monitoring 2250
 
  • C.G. Pang, P. Bambade
    LAL, Orsay, France
  • Y. Funakoshi, S. Uehara
    KEK, Ibaraki, Japan
 
  The SuperKEKB e+ e- collider uses highly focused ultra-low emittance bunches colliding every 4 ns to reach a very high luminosity of 8× 1035 cm-2s-1. It is quite essential to have an orbit feedback system at the Interaction Point (IP) to maintain the optimum overlap between the colliding beams in the presence of ground motion disturbances. For the horizontal motion, a luminosity monitoring system, based on measuring the rate of the Bhabha process at vanishing scattering angle, is developed as input signal to the feedback system. The relative precision needed for this monitor is studied in detail, for the different successive stages of luminosity operation, based on a full simulation of this system, including the detector, DAQ, lock-in amplifier, and feedback control.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL037  
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WEPAL038 First Tests of Superkekb Fast Luminosity Monitors During 2018 Phase-2 Commissioning luminosity, monitoring, detector, feedback 2254
 
  • C.G. Pang, P. Bambade, S. Di Carlo, D. Jehanno, V. Kubytskyi, Y. Peinaud, C. Rimbault
    LAL, Orsay, France
  • Y. Funakoshi, S. Uehara
    KEK, Ibaraki, Japan
 
  The SuperKEKB e+e- collider aims to reach a very high luminosity of 8× 1035 cm-2s-1, by using highly focused ultra-low emittance bunches colliding every 4 ns, it is essential to have an orbit feedback system at the Interaction Point (IP) to maintain the optimum overlap between two colliding beams. Luminosity monitoring systems including LumiBelle2 and ZDLM as input to dithering feedback system used to stabilize the horizontal orbit at the IP were developed and will be described, including the detectors, mechanical set-up, DAQ. Preliminary measurements and analysis of background and first stage luminosity monitoring data collected will be reported and compared with simulation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL038  
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WEPAL049 Simulating Non-Relativistic Beams Using Helical Pulse Lines impedance, site, ECR, GUI 2288
 
  • C.J. Richard
    NSCL, East Lansing, Michigan, USA
  • S.M. Lidia
    FRIB, East Lansing, USA
 
  Funding: Work supported by the US Department of Energy, Office of Science, High Energy Physics under Cooperative Agreement award number DE-SC0018362.
Benchtop calibration of capacitive beam position monitors (BPMs) in low energy beamlines is challenging due to non-relativistic effects. Typical benchtop calibrations cannot account for these effects because they rely on speed of light fields transmitted along a straight wire. However, it is possible to replicate the electromagnetic fields generated by non-relativistic beams using a helical line pulse instead of a straight wire. In order to properly replicate the fields from a beam, a method must be developed for tailoring input pulses into the helical line to match bunch shape and a model of the impedance of the helix should be developed to assist with matching. This paper uses the sheath helix model to analyze signal propagation along a helical line in the time domain, with attention to dispersive effects and impedance matching. The results from this model are then compared to Microwave Studio simulations.
 
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WEPAL065 Development of a Gas Sheet Beam Profile Monitor for IOTA detector, space-charge, proton, plasma 2326
 
  • S. Szustkowski, B.T. Freemire
    Northern Illinois University, DeKalb, Illinois, USA
  • S. Chattopadhyay
    Northern Illinois Univerity, DeKalb, Illinois, USA
  • D.J. Crawford
    Fermilab, Batavia, Illinois, USA
 
  Funding: US Department of Energy, Office of High Energy Physics, General Accelerator Research and Development (GARD) Program
A nitrogen gas sheet will measure the two dimensional transverse profile of the 2.5 MeV proton beam in IOTA. The beam lifetime is limited by the interaction with the gas, thus a minimally invasive instrument is required. To produce a gas sheet with the desired density and thickness, various nozzle types are being investigated, including rectangular capillary tubes for gas injection and skimmers for final shaping of the gas. It is essential to meet vacuum requirements in the interaction chamber while maintaining the precise thickness and density of the gas, without significantly affecting the beam lifetime. The current design of a gas sheet beam profile monitor and present status will be discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL065  
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WEPAL069 Reentrant Cavity Resonator for Low Intensities Proton Beam Measurements pick-up, cavity, resonance, scattering 2341
 
  • S. Srinivasan, P.-A. Duperrex
    PSI, Villigen PSI, Switzerland
 
  A non-interceptive beam current monitor has been developed to investigate the measurement possibilities of low-intensity beams down to 1 nA for proton therapy machines without the drawback of interceptive monitors. This works on the principle of a reentrant cavity resonator such that its fundamental mode resonance frequency of 145.7 MHz matches the second harmonic of the pulse repetition rate of the cyclotron beam i.e. 72.85 MHz. The Driven Modal analysis from the simulation tool ANSYS HFSS was used for parametric model development and to optimize design parameters such as e.g. the position of the inductively coupled pick-ups. A ceramic plate has been inserted in the resonator gap to relax the precision required during manufacturing. A test bench has been designed and constructed for the characterization tests of the prototype. Comparison of the simulated and the experimental scattering parameter from the test bench shows a good agreement.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL069  
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WEPAL072 A Novel Longitudinal Laserwire to Non-Invasively Measure 6-Dimensional Bunch Parameters at High Current Hydrogen Ion Accelerators laser, emittance, detector, linac 2349
 
  • S.M. Gibson, A. Bosco
    Royal Holloway, University of London, Surrey, United Kingdom
  • S.E. Alden, A. Bosco, S.M. Gibson
    JAI, Egham, Surrey, United Kingdom
  • A.P. Letchford
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  • J.K. Pozimski
    Imperial College of Science and Technology, Department of Physics, London, United Kingdom
  • J.K. Pozimski
    STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
 
  Funding: We acknowledge funding by the STFC Grant ST/P003028/1 and the John Adams Institute at Royal Holloway, University of London.
Optical methods for non-invasive beam diagnostics of high current H ion accelerators have been developed in recent years*, **. Such laserwires typically measure a 1D beam profile and/or 2D transverse emittance from the products of photo-detached ions as a laser beam is scanned across the H beam. For laser pulse durations (~80ns) longer than the RF period (~3ns), the detector integrates many complete bunches, enabling only transverse beam monitoring. This paper presents a new technique to capture a series of time resolved transverse emittance measurements along the bunch train. A fast (~10ps) pulsed laser photo-detaches ions within each bunch and is synchronized to sample consecutive bunches at certain longitudinal positions along each bunch. A fast detector records the spatial distribution and time-of-flight of the neutralized H0, thus both the transverse and longitudinal emittance are reconstructed. We present simulations of a time varying pulsed laser field interacting within an H bunch, and estimate the yield, spatial and time distributions of H0 arriving at the detector. We summarise the design of a recently funded longitudinal laserwire being installed in FETS at RAL, UK.
* NIM-A, 830, p526-531, T. Hofmann et al
** T. Hofmann et al, 'Commissioning of the Operational Laser Emittance Monitors for LINAC4 at CERN' IPAC18.
 
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WEPMF005 Design and Testing of a 12 kW, 352 MHz Solid State rf System at the Advanced Photon Source cavity, controls, operation, GUI 2378
 
  • D. Horan, D.J. Bromberek, A. Goel, T.J. Madden, A. Nassiri, G.J. Waldschmidt
    ANL, Argonne, Illinois, USA
 
  A 12 kW, 352 MHz rf power amplifier system was designed and constructed at the Advanced Photon Source as a research and development test bed for eventual development of a 200 kW cw rf system capable of supporting accelerator beam operation. The system utilizes six 2 kW laterally diffused metal oxide field effect transistor (MOSFET) rf amplifiers, an output cavity combiner terminated with a WR2300 waveguide output flange, and a monitoring system based on programmable logic controller technology. The combining cavity has a total capacity of 108 two-kilowatt inputs to support eventual operation up to 216kW maximum output power. Design details and operational performance of the 12 kW system will be discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF005  
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WEPMF019 Conceptual Design of the eRHIC Storage Ring Magnets storage-ring, dipole, sextupole, quadrupole 2407
 
  • H. Witte, J.S. Berg, S. Tepikian
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Presently the electron-ion collider eRHIC is under design, which aims to provide a facility with a peak luminosity of 1034cm-2sec-1. Part of the eRHIC accelerator is the addition of an electron storage ring to the existing tunnel. This paper describes the magnets required for this storage ring. The necessary bending is provided by a triplet of dipole magnets, which generate excess bending to create additional radiation damping to allow a larger beam-beam tune shift. Each triplet consists of two long, low field magnets and a short, high-field magnet. This paper also describes the quadrupole and sextupole magnets necessary for this machine. All magnets require a large aperture to accommodate the beam-pipe.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF019  
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WEPMF022 Coulped Multiphysics Simulation for the Water Cooling Layout of a Rhodotron Cavity cavity, operation, vacuum, electron 2416
 
  • L. Yang, X. He, H. Li, S.Q. Liao
    CAEP/IFP, Mainyang, Sichuan, People's Republic of China
 
  A Rhodotron-based electron accelerator served as micro-focused X-ray source is under development at IFP, CAEP. The RF-cavity, running in long pulse/ CW mode, will deliver 9 MeV energy to electron beams after multiple accelerations within the same field at a frequency of 107.5MHz. A substantial amount of average power loss with tens of kW will be dissipated on the RF surface of the cavity to maintain the operational field level. Efficient water cooling is critical to prevent large scale temperature rise for stable operation sake. Reasonable prediction of temperature rise becomes essential to assess a certain cooling layout in the design phase. The frequency drift and thermal stress on account of temperature variation and gradient on cavity wall respectively, could be computed accordingly. This paper presents a comprehensive coupled simulation involving electromagnetic, thermal and structural for the RF-cavity of Rhodotron.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF022  
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WEPMF030 Optimization of Klystron Efficiency with MOGA klystron, cavity, electron, bunching 2419
 
  • C. Meng, X. He, S. Pei, S.C. Wang, O. Xiao, Z.S. Zhou
    IHEP, Beijing, People's Republic of China
 
  As the very important element of accelerator the klystron provide power to cavities for accelerating. Considering the accelerator cost of construction and running, the improvement of klystron efficiency is one developing hotspot of klystron research. In this paper the optimization method of klystron efficiency with MOGA based on 1D simulation program is proposed and the influences on klystron efficiency will be discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF030  
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WEPMF031 Development of a High-Power High-Directivity Directional Coupler and Four Power Dividers for S-Band coupling, GUI, vacuum, MMI 2422
 
  • X. He, J. Lei, J.R. Zhang
    IHEP, Beijing, People's Republic of China
 
  A novel Bethe-hole S band directional coupler has been designed based on some structural optimizations, the prototype has been tested with a Directivity of more than 30 dB. The new directional coupler can also hold higher power compared to the old type, which is more useful for the future accelerator applications. Four power dividers using different structures are studied and the best one is chosen for fabrication. The prototype with matching rod in the middle has got qualified microwave cold test results and has been used during the whole microwave commissioning of an accelerating structure, the performance is quite stable.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF031  
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WEPMF033 RF Study And Cold Test of an S-band Spherical Cavity Pulse Compressor cavity, coupling, vacuum, klystron 2429
 
  • J. Lei, X. He, M. Hou, X.P. Li, G. Pei, H. Wang, J.B. Zhao
    IHEP, Beijing, People's Republic of China
  • S. Shu
    Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
 
  An S-band (2856 MHz) spherical cavity pulse compressor has been designed, fabricated and tested in the Institute of High Energy Physics (IHEP), Chinese Academy of Sciences (CAS). The pulse compressor consists of a special 3 dB coupler and only one spherical energy storage cavity, two TE114 modes are chosen to oscillate in which for fairly high unload Q factor. The prototype was made of aluminum for studying the performance of the pulse compressor and checking the validity of the simulations. The cold test results of the aluminum cavity are also presented. The copper coating on the whole internal surface of the aluminum spherical cavity is in progress and the test results will also be presented in the future.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF033  
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WEPMF044 Updates on the DC Field Dependence Cavity cavity, niobium, multipactoring, SRF 2465
 
  • J.T. Maniscalco, M. Liepe
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Work at Cornell has demonstrated good agreement between a theoretical model by A. Gurevich of the anti-Q-slope (a field-dependent decrease of the microwave surface resistance) and experimental results from impurity-doped niobium. As a corollary, the model predicts that a strong DC magnetic field applied parallel to the RF surface will produce a similar decrease in surface resistance. In order to explore this prediction for many materials, we have designed a new coaxial cavity with a strong, uniform DC field superimposed over a weak RF field on a removable and replaceable niobium sample. Here we present updates on the progress of this new cavity.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF044  
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WEPMF051 Multipacting in an RF Window: Simulations and Measurements multipactoring, electron, resonance, gun 2483
 
  • M. Bousonville, S. Choroba
    DESY, Hamburg, Germany
 
  Electron guns are used in the accelerators of the European XFEL and FLASH. They are operated at 1.3 GHz. The RF peak power is 5 MW at 650 us pulse width and 10 Hz repetition rate. In order to understand the multipacting that occurs during conditioning, it was simulated in the RF window type that is used for the electron gun in the XFEL. The reduction in secondary emission yield associated with conditioning was taken into account. Since the RF windows are tested with high power on a test stand before their use, without the electron gun, measurement results are available which are compared with the simulation results. The main advantage of the simulation compared to the measurement is that the locations of multipacting can be determined in the RF window. This could be helpful for the development of high-power RF components in the future, in order to detect pronounced multipacting resonances even before production and to avoid them by design changes.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF051  
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WEPMF058 Anomaly Detection for Cavity Signals - Results from the European XFEL cavity, flattop, FEL, beam-loading 2502
 
  • A.S. Nawaz, S. Pfeiffer
    DESY, Hamburg, Germany
  • G. Lichtenberg
    HAW, Hamburg, Germany
  • P. Rostalski
    Institute for Electrical Engineering in Medicine, Lübeck, Germany
 
  The data throughput of the European XFEL DAQ is about 1.5 Gb/s. Data depicting the cavity signal behavior is currently only saved manually. This either happens, when cavity tests are being performed, or an operator detects a fault in the cavity system, that has to be further investigated. Those instances of interest are neither systematically nor automatically stored. It can therefore be assumed that unwanted or degraded cavity behavior is detected late or not at all. It is proposed to change the focus from detecting known faults (such as quenches) to additionally detect anomalies in the cavity system behavior. In order to detect anomalies in the cavity signals, an algorithm is proposed using a cavity model. It aims on finding those data sets, which diverge from the nominal cavity behavior, saving those instances for later analysis. The nominal behavior is defined by the cavity electromagnetic resonance model with beam loading as well as the model for the mechanical oscillations due to the Lorentz Forces. By using such an approach, the detection of anomalies, as well as faults could be automated. This contribution aims to summarize the influence of beam loading on the detection and gives examples for anomalies that were found in several cavities.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF058  
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WEPMF062 Simulation of Cavity Conditioning for the Diamond SCRF Cavity cavity, GUI, coupling, operation 2509
 
  • S.A. Pande, C. Christou, P. Gu
    DLS, Oxfordshire, United Kingdom
 
  Diamond SCRF cavities are pulse conditioned every week in order to keep them operating reliably. During conditioning, the cavities are detuned in order to sweep the standing wave through the waveguide. To match these cavities at lower voltage (typically < 1.4 MV) and at higher power, 3 stub tuners are used in the waveguide feed. Simulations with CST studio show that a strong SW field exists between the RF window and the matching posts. As the cavity is detuned the electric field maximum passes through the window causing heating of the ceramic. Temperature measurements with thermal camera reveal that the temperature of the window increases to maximum when the cavity is detuned towards higher frequency. Based on the simulation results and the measurements, it was decided to reduce the conditioning voltage. These results are summarised.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF062  
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WEPMF075 Performance Measurements and Analysis of Jitter Like Events for the PS Injection Kicker System kicker, controls, operation, injection 2549
 
  • A. Ferrero Colomo, J.C.C.M. Borburgh, L. Ducimetière, L.M.C. Feliciano, V. Forte, M.A. Fraser, T. Kramer, L. Sermeus
    CERN, Geneva, Switzerland
 
  In the framework of the LIU project, several modifications have been made to the CERN PS injection kicker system during the winter stop 2016-2017 (EYETS). Current waveform and beam-based measurements were carried out in 2017 to validate the implemented design changes by observing the magnetic field impact on the beam. During these long-term measurements, increased values for the rise and fall times were observed when compared to single shot observations of the current waveform. An unknown source of jitter-like pre-firing in the main switch has been identified, creating an additional challenge to meet the already tight system rise and fall time specifications. This paper briefly describes the efforts made to fine tune the pulse generator after the EYETS, summarises the optimised configuration and analyses the observed jitter events. A new triggering system design is briefly outlined to address the issue.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF075  
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WEPMF082 Design and Construction of the CERN PS Booster Charge Exchange Injection Chicane Bumpers injection, vacuum, septum, linac 2575
 
  • B. Balhan, C. Baud, J.C.C.M. Borburgh, M. Hourican
    CERN, Geneva, Switzerland
 
  In the framework of the LIU project and the connection from LINAC4 to PS Booster, the 160 MeV H beam will be injected horizontally into the PSB by means of one charge-exchange injection system for each PSB ring. A set of four outside vacuum pulsed dipole magnets (BSW) creating the required injection bump has been designed and built. The dynamic requirements for the bump ramp down determine, to a large extent, the field homogeneity due to the eddy currents induced in the corrugated Inconel vacuum chamber. Magnetic simulations were performed to determine the field harmonics during bump ramp down, and the results subsequently used for the dynamic tracking of the beam during injection. The mechanical design and construction of the magnets will be briefly outlined, and the article will conclude with the magnetic measurements of the magnets. The magnetic performance of the as built magnets will be compared with the simulations and the influence of the vacuum chambers on the magnetic field will be quantified.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF082  
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WEPMF089 Measurements of Electromagnetic Properties of Ferrites as a Function of Frequency and Temperature kicker, impedance, injection, coupling 2592
 
  • A. Chmielinska, M.J. Barnes, F. Caspers, B.K. Popovic, C. Vollinger
    CERN, Geneva, Switzerland
 
  Fast kicker magnets are used to inject beam into and extract beam out of the CERN accelerator rings. These kickers are often ferrite loaded transmission line type magnets with a rectangular shaped aperture through which the beam passes. The interaction of the beam with the resistive part of the longitudinal beam coupling impedance leads to power dissipation and heating of different elements in the accelerator ring. In particular, power deposition in the kicker magnets can be a limitation: if the temperature of the ferrite yoke exceeds the Curie temperature, the beam will not be properly deflected. In addition, the imaginary portion of the beam coupling impedance contributes to beam instabilities. A good knowledge of electromagnetic properties of materials up to GHz frequency range is essential for a correct impedance evaluation. This paper presents the results of transmission line measurements of complex initial permeability and permittivity for different ferrite types. We present an approach for deriving electromagnetic properties as a function of both frequency and temperature; this information is required for simulating ferrite behaviour under realistic operating conditions.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF089  
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WEPMG001 Engineering Design and Prototyping of the New LIU PS Internal Beam Dumps vacuum, interface, proton, operation 2600
 
  • G. Romagnoli, J.A. Briz Monago, M.E.J. Butcher, M. Calviani, D.G. Cotte, Y. C. Coutron, J.J. Esala, E. Grenier-Boley, J. Hansen, A. Huschauer, A. Masi, F.-X. Nuiry, D. Steyart, V. Vlachoudis
    CERN, Geneva, Switzerland
 
  For the LHC Injectors Upgrade (LIU) at CERN, the two Proton Synchrotron (PS) internal dumps are redesigned and upgraded for the new high intensity/brightness beams. The dumps are installed as active elements in the lattice in straight sections between the main bending magnets. The dumps are moved into the beam when requested by operation and shave the circulating beam turn by turn stopping the beam after about 6 ms. The shaving induces a very localized beam energy deposition on the dump surface in a thickness of tens of microns. A completely new approach has been developed with FLUKA to simulate beam shaving, coupled with ANSYS to define a new dump core design. This paper presents the design of the dump based on operational constraints such as cycling 200 000 times per year for 20 years, limited access for maintenance or reaching the beam trajectory in 150 ms. These constraints had a major impact on the technological choices. The new dump core is made of a low-density graphite block followed by a denser copper alloy (CuCr1Zr) one. Water circuits, bonded with Hot Isostatic Pressing, are cooling the core in ultra-high vacuum. The core is moved by a spring-based actuation mechanism.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMG001  
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WEPMG002 Beam Dump Facility Target: Design Status and Beam Tests in 2018 target, radiation, operation, experiment 2604
 
  • E. Lopez Sola, O. Aberle, P. Avigni, L. Bianchi, J. Busom, M. Calviani, M. Casolino, J.P.C. Espadanal, M.A. Fraser, S. Girod, B. Goddard, D. Grenier, M. Guinchard, C. Heßler, R. Illan Fiastre, R. Jacobsson, M. Lamont, A. Ortega Rolo, B. Riffaud, G. Romagnoli, L. Zuccalli
    CERN, Geneva, Switzerland
 
  The Beam Dump Facility (BDF) Project, currently in its design phase, is a proposed general-purpose fixed target facility at CERN, dedicated to the Search for Hidden Particles (SHiP) experiment in its initial phase. At the core of the installation resides the target/dump assembly, whose aim is to fully absorb the high intensity 400 GeV/c SPS beam and produce charmed mesons. In addition to high thermo-mechanical loads, the most challenging aspects of the proposed installation lie in very high energy and power density deposition that are reached during operation. In order to validate the design of the BDF target, a scaled prototype is going to be tested during 2018 in the North Area at CERN, upstream the existing beryllium primary targets. The prototype testing under representative beam scenarios will allow having an insight of the material response in an unprecedented regime. Online monitoring and an extensive Post Irradiation Experimental (PIE) campaign are foreseen. The current contribution will detail the design and handling aspects of the innovative Target Complex as well as the design of the BDF target/dump core and the design and construction of the prototype target assembly.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMG002  
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WEPMG003 Analysis and Operational Feedback of the New High-Energy Beam Dump in the CERN SPS operation, MMI, shielding, monitoring 2608
 
  • A. Perillo-Marcone, M. Calviani, R. Illan Fiastre, P. Rios Rodriguez, G. Romagnoli
    CERN, Geneva, Switzerland
 
  The CERN Super Proton Synchrotron (SPS) high-energy internal dump (TIDVG) is used to intercept beam dumps from 102.2 to 450 GeV. An inspection in 2013 revealed significant beam induced damage to the aluminium absorbing block, resulting in operational limitations to minimize the risk of reproducing this phenomenon. Additionally, in 2016 a vacuum leak was detected in the dump assembly, which imposed further limitations, i.e., a reduction of the beam intensity that could be dumped. In the winter stop of 2016-2017, a new version of the TIDVG (featuring several design modifications) was installed. This paper analyses the performance of the dump observed during the commissioning period and subsequent operation in 2017 of the most recent installed version of the TIDVG. The temperature measurements recorded during this time were used to benchmark numerical models that allow predicting the performance of the dump under different conditions. After several iterations, a good agreement between simulations and real measurements was obtained; resulting in numerical models that can produce reliable results for this and other devices with similar design.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMG003  
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WEPMG004 Design of the Future High Energy Beam Dump for the CERN SPS operation, shielding, dumping, kicker 2612
 
  • S. Pianese, J.A. Briz Monago, M. Calviani, D. Grenier, P.B. Heckmann, J. Humbert, R. Illan Fiastre, A. Perillo-Marcone, G. Romagnoli, S. Sgobba, D. Steyart, V. Vlachoudis
    CERN, Geneva, Switzerland
 
  The future CERN Super Proton Synchrotron (SPS) internal dump (Target Internal Dump Vertical Graphite, known as TIDVG#5), to be installed during CERN's Long Shutdown 2 (2019-2020), will be required to intercept beam dumps from 26 to 450 GeV, with increased intensity and repetition rates with respect to its predecessor (TIDVG#4). The beam power to be managed by the dump will increase by approximately a factor of four; resulting in new challenges in terms of design in order to fulfil the highly demanding specification, which is based on guaranteeing a good performance of the machine with little or no limitations imposed by this device. This paper presents the proposed design, including material selection, manufacturing techniques and thermo-mechanical simulations under different operational scenarios expected during the lifetime of the device.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMG004  
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WEPMK002 Longitudinal Impedance Analysis of an Upgraded LHC Injection Kicker Magnet impedance, kicker, injection, vacuum 2628
 
  • V. Vlachodimitropoulos, M.J. Barnes, L. Vega Cid, W.J.M. Weterings
    CERN, Geneva, Switzerland
 
  Prior to Long Shutdown 1 (LS1) one of the LHC injection kickers (MKIs) occasionally exhibited high temperatures leading to significant turnaround times. After a successful impedance mitigation campaign during LS1, the MKI ferrite yokes have remained below their Curie point and have not limited LHC's availability. However, for HL-LHC operation the MKI yokes are expected to exceed their Curie temperatures after long physics runs. To ensure uninterrupted future HL-LHC operation, a modified beam screen design, relocating some of the heat load to more easily cooled parts, and a suitable cooling system are under development as the current baseline for the HL-LHC upgrade of the MKIs. An upgraded beam screen providing such relocation has been designed, simulated and compared to the existing model. To validate simulations, two longitudinal beam coupling impedance measurement techniques have been used and the results are compared to predictions. The modified beam screen was implemented in an upgraded MKI installed in the LHC during the Year End Technical Stop (YETS) 2017/18.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK002  
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WEPML002 Design of 650 MHz Tuner for PIP-II Project cavity, interface, experiment, linac 2671
 
  • Y.M. Pischalnikov, S. Cheban, J.C. Yun
    Fermilab, Batavia, Illinois, USA
 
  Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
The Proton Improvement Plan (PIP) II project at Fermilab is a proton driver linac which will use of five different cavity geometries including a 650 MHz 5-cell elliptical cavities that will operate in RF-pulse mode. Detuning of these cavities by Lorentz Forces will be large and strongly depend of the stiffness of the cavity's tuner. First prototype tuner built and tested warm [1,2]. Measured stiffness of the prototype tuner was below 30kN/mm instead of expected from simulation 70kN/mm [2]. Significant effort has been invested into understanding discrepancy between simulation and experimental data that led to newest tuner design. Updated 'dressed cavity-helium vessel-tuner' model provided consistent results between ANSYS simulations and experiment results. Modified tuner design and analysis in limitations for overall 'cavity/tuner system' stiffness will be presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML002  
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WEPML006 Modified Slow Tuner Design for Cavity 1 Inside LCLS II Cryomodules cavity, cryomodule, interface, SRF 2684
 
  • Y.M. Pischalnikov, T.T. Arkan, S. Cheban, J.P. Holzbauer, J.A. Kaluzny, Y.O. Orlov, J.C. Yun
    Fermilab, Batavia, Illinois, USA
 
  Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
Initial LCLS-II cryomodule testing at Fermilab showed microphonics on the furthest upstream cavity (number 1) at least factor 2 larger than on the rest of the cavities. Testing indicated that this was a difference in the mechanical support of cavity 1, not a local acoustic source. Further investigation pointed to the upstream beam-pipe of the cavity 1. The upstream cavity flange has a solid spool piece connection to the beamline gate valve unlike the other cavities, which all connect through bellows. The gate valve's weight is supported by sliding system (free in z-axis) connected to large diameter Helium gas return pipe. The tuner design was modified to transform interface between cavity#1 and gate valve. Arms of the tuner for cavity 1 were extended and became the support structure for gate valve, eliminating the connection to the helium return pipe. Modification of the tuner design and results in microphonics mitigations will be presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML006  
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WEPML010 Operation Regime Analysis of Conduction Cooled Cavities Through Multi-Physics Simulation cavity, operation, SRF, niobium 2697
 
  • R.A. Kostin, R. Dhuley, M.G. Geelhoed, R.D. Kephart, T.K. Kroc, O.V. Prokofiev, J.C.T. Thangaraj
    Fermilab, Batavia, Illinois, USA
  • A. Kanareykin
    Euclid TechLabs, LLC, Solon, Ohio, USA
 
  Funding: Department of Energy
Euclid Techlabs in collaboration with Fermilab IARC (Batavia, IL) is developing industrial superconducting 10MeV electron linac. Conduction cooling is used for cooling instead of liquid helium bath to simplify linac maintenance. The cavity linked to commercially available cryo-cooler cold head through highly conductive aluminium strips. However, this solution raises a problem of contact thermal resistance. This paper shows some results of Comsol multyphysics simulations of the cavity cooling by AL strips. Some insight was obtained on the acceptable range of contact resistance. Operation regimes were obtained at different accelerating gradients and cavity temperatures. The results of simulation are presented and discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML010  
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WEPML011 Garnet Ring Measurements for the Fermilab Booster 2nd Harmonic Cavity cavity, booster, controls, solenoid 2700
 
  • R.L. Madrak, J.E. Dey, K.L. Duel, J. Kuharik, A.V. Makarov, W. Pellico, J. Reid, G.V. Romanov, M. Slabaugh, D. Sun, C.-Y. Tan, I. Terechkine
    Fermilab, Batavia, Illinois, USA
 
  A perpendicularly biased tuneable 2nd harmonic cavity is being constructed for use in the Fermilab Booster. The cavity's tuner uses National Magnetics AL800 garnet as the tuning media. For quality control, the magnetic properties of the material and the uniformity of the properties within the tuner must be assessed. We describe two tests which are performed on the rings and on their corresponding witness samples.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML011  
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WEPML022 3.9 GHz Power Coupler Design and Tests for LCLS-II Project cavity, resonance, cryomodule, diagnostics 2727
 
  • N. Solyak, I.V. Gonin, C.J. Grimm, E.R. Harms, T.N. Khabiboulline, A. Lunin, O.V. Prokofiev, G. Wu
    Fermilab, Batavia, Illinois, USA
 
  LCLS-II linac requires two 3.9 GHz cryomodules (eight cavities per CM), operating up to 16MV/m in cw regime. Fermilab has designed and built few prototypes of the cavity and auxiliaries and tested them at the vertical and horizontal cryostats. Fundamental power coupler, based on existing design (FLASH, XFEL) was redesign for 2kW average power. We built three prototypes and tested them at room temperature test stand. One coupler was assembled on the cavity and tested at horizontal cryostat as part of design verification program. Test results and comparison with simulations are discussed in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML022  
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WEPML039 Design of the Two-Gap Superconducting Re-Buncher cavity, heavy-ion, linac, proton 2779
 
  • M. Gusarova, W.A. Barth, S. Yaramyshev
    MEPhI, Moscow, Russia
  • W.A. Barth, S. Yaramyshev
    GSI, Darmstadt, Germany
  • W.A. Barth, M. Miski-Oglu
    HIM, Mainz, Germany
  • M. Basten, M. Busch
    IAP, Frankfurt am Main, Germany
  • M. Gusarova
    JINR, Dubna, Moscow Region, Russia
 
  A new design of a spoke cavity for low relative velocities of heavy ions has been elaborated. Simulation results for a 2-gap spoke cavity with a resonance frequency of 216.816 MHz and a relative velocity of 0.07с are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML039  
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WEPML043 RF Simulations of the Injector Section from CH8 to CH15 for MYRRHA cavity, impedance, resonance, MMI 2790
 
  • P. Müller, M. Busch, H. Hähnel, K. Kümpel, D. Mäder, N.F. Petry, H. Podlech
    IAP, Frankfurt am Main, Germany
 
  Funding: Work supported by the EU Framework Programme H2020 662186 (MYRTE) and HIC for FAIR
MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Applications) is the first prototype of an accelerator driven nuclear reactor dealing with the transmutation of long-living nuclear waste. Beam quality and reliability are crucial for the reactor. The injector design is done by IAP, Goethe-University, and has been adapted to the final magnet design and voltage distributions. The energy section from 5.87 MeV up to 16.6 MeV has been changed to normal conducting CH cavities as in the lower energy part of the injector. For beam adjustment a 5-gap CH cavity rebuncher at 5.87 MeV as well as two doublet magnets forming the new MEBT-2 section between CH7 and CH8 have been added. Starting parameters for the RF simulations have been given by beam dynamics results calculated with LORASR. RF simulations of these structures consisting of flatness and tuning optimizations will be presented within this contribution.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML043  
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WEPML044 Design of HOM Couplers for Superconducting 400 MHz RF Cavities HOM, cavity, collider, proton 2793
 
  • N.F. Petry, M. Busch, K. Kümpel, O. Meusel, H. Podlech
    IAP, Frankfurt am Main, Germany
 
  The Future Circular Collider (FCC) is one possible future successor of the Large Hadron Collider (LHC). The proton-proton collider center-of-mass collision energy is set to 100 TeV with a beam current of 0.5 A. To reach this goal a stable acceleration is critical and therefore higher order modes (HOM) need to be damped. To avoid a high power level in the HOM dampers, further described as couplers, the loaded Q-factor should be below 1000 for the cavity with mounted HOM couplers. Besides a low Q-factor the R/Q value should also be in the range of 1 Ω or below. Two different types of couplers are used to achieve a high damping. The two types are a narrowband Hook-type HOM coupler and a broadband Probe-type HOM coupler. The recent results of the design of the HOM couplers attached to a superconducting 400 MHz RF cavity will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML044  
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WEPML048 HOM Power Levels in the BESSY VSR Cold String HOM, cavity, SRF, GUI 2808
 
  • A.V. Tsakanian, T. Flisgen
    Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
  • H.-W. Glock, J. Knobloch, A.V. Vélez
    HZB, Berlin, Germany
 
  The BESSY VSR upgrade of the BESSY II light source represents a novel approach to simultaneously store long (ca. 15ps) and short (ca. 1.7ps) bunches in the storage ring. This challenging goal requires installation of four new SRF cavities (2x1.5 GHz and 2x1.75 GHz) in one module for installation in a single straight. These cavities are equipped with strong waveguide HOM dampers necessary for stable operation. The expected HOM power and spectrum has been analyzed for the complete cold string. The cold string is a combination of various elements such as SRF cavities, bellows with and without shielding, warm HOM beampipe absorbers and UHV pumping domes. The presented study is performed for various BESSY VSR bunch filling patterns with 300 mA beam current. The contribution of each component to the total HOM power is presented. In addition the optimization of different cavity arrangements in the module is performed in order to reach the optimal operation conditions with equally distributed power levels along the string and tolerable beam coupling impedance.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML048  
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WEPML049 The Challenge to Measure nΩ Surface Resistance on SRF Samples SRF, quadrupole, pick-up, cavity 2812
 
  • S. Keckert, T. Junginger, J. Knobloch, O. Kugeler
    HZB, Berlin, Germany
  • T. Junginger
    Lancaster University, Lancaster, United Kingdom
 
  Systematic research on fundamental limits of superconducting materials for SRF applications and their intrinsic material properties relevant for use in an accelerator requires studies in a wide parameter space of temperature, RF field and frequency. The Quadrupole Resonator at HZB enables precision measurements on planar samples at temperatures of 1.8 K to >20 K, RF fields of up to 120 mT, and frequencies of 420 MHz, 850 MHz and 1285 MHz. In the past years the capabilities of the setup were studied intensively and developed further. Sources of systematic errors, such as microphonics or misalignment have been identified and eliminated. In this contribution the current status of the QPR and its systematic limitations are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML049  
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WEPML069 Fast Kicker and Pulser R&D for the HEPS on-Axis Injection System kicker, injection, impedance, vacuum 2846
 
  • H. Shi, J. Chen, Z. Duan, L. Huo, P. Liu, X.L. Shi, G. Wang, L. Wang, N. Wang
    IHEP, Beijing, People's Republic of China
 
  The HEPS plans to adopt on-axis injection scheme because the dynamic aperture of machine is not large enough for off-axis injection for its baseline 7BA lattice design. A sets of super fast kicker and pulser of ±15kV amplitude, 15ns pulse bottom width are needed for bunch spacing of 10ns to minimize perturbation on adjacent bunches. To achieve these requirement, a multifaceted R&D program including the strip-line kicker and HV pulser, was initiated last 2 years. So far, the prototype development of a 750mm long strip-line kicker and a DSRD pulser was completed and the preliminary test results show they can meet the baseline requirement of the HEPS.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML069  
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THXGBD1 The Upgrade of the Advanced Photon Source lattice, feedback, controls, cavity 2872
 
  • M. Borland, M. Abliz, N.D. Arnold, T.G. Berenc, J.M. Byrd, J.R. Calvey, J.A. Carter, J. Carwardine, H. Cease, Z.A. Conway, G. Decker, J.C. Dooling, L. Emery, J.D. Fuerst, K.C. Harkay, A.K. Jain, M.S. Jaski, P.S. Kallakuri, M.P. Kelly, S.H. Kim, R.M. Lill, R.R. Lindberg, J. Liu, Z. Liu, J. Nudell, C.A. Preissner, V. Sajaev, N. Sereno, X. Sun, Y.P. Sun, S. Veseli, J. Wang, U. Wienands, A. Xiao, C. Yao
    ANL, Argonne, Illinois, USA
  • A. Blednykh
    BNL, Upton, Long Island, New York, USA
 
  After decades of successful operation as a 7-GeV synchrotron radiation source, the Advanced Photon Source is pursing a major upgrade that involves replacement of the storage ring with an ultra-low emittance multi-bend achromat design. Using a seven-bend hybrid multi-bend achromat with reverse bending magnets gives a natural emittance of 42 pm operated at 6 GeV. The x-ray brightness is predicted to increase by more than two orders of magnitude. Challenges are many, but appear manageable based on thorough simulation and in light of the experience gained from world-wide operation of 3\text{rd}-generation light sources. The upgraded ring will operate in swap-out mode, which has allowed pushing the performance beyond the limits imposed by conventional operation.  
slides icon Slides THXGBD1 [14.689 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THXGBD1  
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THXGBE1 6D Beam Measurement, Challenges and Possibilities rfq, experiment, quadrupole, linac 2890
 
  • A.V. Aleksandrov, S.M. Cousineau, A.P. Zhukov
    ORNL, Oak Ridge, Tennessee, USA
  • B.L. Cathey
    ORNL RAD, Oak Ridge, Tennessee, USA
 
  A system to measure the full 6D beam parameters (not 3x2D) has been built at the SNS RFQ test stand. Such a measurement will allow detailed analysis of the beam physics from a properly measured input term. This invited provides an overview of the principles and design of this system, and reports on status and results.  
slides icon Slides THXGBE1 [4.476 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THXGBE1  
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THYGBD2 Results of UFO Dynamics Studies with Beam in the LHC experiment, emittance, proton, beam-losses 2914
 
  • B. Lindstrom, A. Apollonio, P. Bélanger, M. Dziadosz, A.A. Gorzawski, L. K. Grob, E.B. Holzer, A. Lechner, R. Schmidt, M. Valette, D. Valuch, D. Wollmann
    CERN, Geneva, Switzerland
 
  Micrometer sized particles entering the LHC beam (the so-called Unidentified Falling Objects or UFOs) are a known cause of localized beam losses since the beginning of high intensity beam operation, however the origin of these particles is not fully known. Their effect limits LHC availability by causing premature dumps due to excessive beam losses and occasionally even magnet quenches. This could become an important limitation for future accelerators such as the High Luminosity upgrade of the LHC (HL-LHC) and the Future Circular Collider (FCC). The dynamics of these UFOs was investigated in two dedicated experiments. In the first experiment, it was shown that the transverse movements of these particles can be studied by observing bunch-by-bunch losses from bunches with different horizontal and vertical emittances. In the second experiment, UFO-like events around the 16L2 interconnect in the LHC, which has seen intense UFO activity in 2017, were studied with the above method. This paper summarizes the results of both experiments.  
slides icon Slides THYGBD2 [1.361 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THYGBD2  
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THYGBE4 Early Phase 2 Results of LumiBelle2 for the SuperKEKB Electron Ring luminosity, background, electron, photon 2934
 
  • S. Di Carlo, P. Bambade, D. Jehanno, V. Kubytskyi, C.G. Pang, Y. Peinaud, C. Rimbault
    LAL, Orsay, France
 
  We report on the early SuperKEKB Phase 2 operations of the fast luminosity monitor (LumiBelle2 project). Fast luminosity monitoring is required by the dithering feedback system, which is used to stabilize the beam in the presence of horizontal vibrations. In this report, we focus on the operations related to the electron side of LumiBelle2. Diamond sensors are located 30 meters downstream of the IP, just above, beside, and below the electron beam pipe. During early Phase 2, the sensors are used to measure the background, arising from beam-gas scattering. We present the hardware design, the detection algorithm, and the analysis of the background measurements taken up-to-date. The results are then compared with a detailed simulation of the background, in order to well understand the physical processes involved. The simulation is performed using SAD for generation and tracking purposes, while Geant4 is used to calculate the energy deposition in the diamond sensors.  
slides icon Slides THYGBE4 [3.096 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THYGBE4  
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THPAF005 Simulations of Modulator for Coherent Electron Cooling electron, bunching, plasma, quadrupole 2953
 
  • J. Ma, V. Litvinenko, G. Wang
    BNL, Upton, Long Island, New York, USA
  • V. Litvinenko
    Stony Brook University, Stony Brook, USA
 
  Highly resolved numerical simulations have been performed using the code SPACE for the modulator, the first section of the Coherent electron cooling (CeC) device installed in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL). Simulation results have been benchmarked with analytical solution using uniform electron beam with realistic thermal velocities. Electron bunches with Gaussian distribution and quadrupole field with realistic settings have been applied in the simulations to predict the modulation process and final bunching factors induced by ions with reference and off-reference energies in the CeC experiment at BNL RHIC.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF005  
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THPAF006 Simulations of Cooling Rate and Diffusion for Coherent Electron Cooling Experiment electron, FEL, kicker, bunching 2957
 
  • J. Ma, V. Litvinenko, G. Wang
    BNL, Upton, Long Island, New York, USA
  • V. Litvinenko
    Stony Brook University, Stony Brook, USA
 
  Start-to-end numerical simulations have been performed using the code SPACE and GENESIS for the single pass of gold ions through the coherent electron cooling (CeC) device installed in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL). Cooling rate of CeC experiment has been predicted using off-reference energy ions in a finite Gaussian electron beam through a realistic beam-line, in which settings of quadrupoles and free-electron laser (FEL) device are relevant to BNL RHIC.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF006  
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THPAF010 Reduction of Coherent Betatron Oscillations Using RF Electric Fields in the Fermilab Muon g-2 Experiment dipole, quadrupole, experiment, betatron 2961
 
  • O. Kim, S. Hacıömeroğlu, Y.I. Kim, Y.K. Semertzidis
    CAPP/IBS, Daejeon, Republic of Korea
  • Y.F. Orlov
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  The Fermilab Muon g-2 experiment aims to measure the muon anomalous magnetic moment with a 140 parts-per-billion precision to investigate the greater than 3 standard deviation difference between the Standard Model prediction and the previous measurement by the BNL Muon g-2 experiment. The coherent betatron oscillation (CBO) beam effects must be corrected for in the decay-positron time spectra fits used in high precision muon storage ring based anomalous magnetic moment measurements. This MC simulation study indicates that the application of radio frequency (RF) electric fields to the muon storage ring beam can reduce the CBO amplitude by up to a factor of 10, as well to increase the symmetry of the beam phase space. This is achieved by correcting the mismatched oscillation phases between the high and low momentum muon populations by modulating the muon beam betatron oscillation frequencies with off-resonance RF fields.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF010  
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THPAF012 The Influence of Chromaticity on Transverse Single-Bunch Instability in the Booster of HEPS booster, damping, injection, radiation 2968
 
  • H.S. Xu, N. Wang
    IHEP, Beijing, People's Republic of China
 
  The study of the transverse single-bunch instability has been carried out for the HEPS booster to double check whether the required single-bunch charge can be achieved. The chromaticity has been varied in our study to see how the threshold changes accordingly. Usually, the slightly positive chromaticity is expected for stabilizing the beam. However, our simulations show that the single-bunch threshold current drops significantly when the chromaticity becomes non-zero. We present the simulation methods and results in details in this paper. The analysis of the simulation results is also presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF012  
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THPAF015 Beam Tracking Studies of Electron Cooling in ELENA electron, proton, antiproton, emittance 2975
 
  • B. Veglia, J.R. Hunt, J. Resta-López, V. Rodin, C.P. Welsch
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • J.R. Hunt, J. Resta-López, V. Rodin, C.P. Welsch
    The University of Liverpool, Liverpool, United Kingdom
 
  Funding: This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 721559.
The Extra Low ENergy Antiproton storage ring (ELENA), which is currently being commissioned at CERN, will further decelerate antiprotons extracted from the Antiproton Decelerator (AD) from 5.3 MeV to energies as low as 100 keV. It will provide high quality beams for the antimatter experiments located within the AD hall. At such low energies, it is important to correctly evaluate the long term beam stability. To provide a consistent explanation of the different physical phenomena affecting the beam, tracking simulations have been performed and the results will be presented in this contribution. These include electron cooling and various scattering effects under realistic conditions. The effects of several imperfections in the electron cooling process will also be discussed. In addition, analytical approximations of the temporal variation of emittance under these conditions will be presented, and compared with numerical simulation results.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF015  
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THPAF016 3D Tracking Methods in a GEANT4 Environment Through Electrostatic Beamlines quadrupole, experiment, proton, antiproton 2979
 
  • J.R. Hunt, J. Resta-López, V. Rodin, B. Veglia, C.P. Welsch
    The University of Liverpool, Liverpool, United Kingdom
  • J.R. Hunt, J. Resta-López, V. Rodin, B. Veglia, C.P. Welsch
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
 
  Funding: Work supported by the EU under Grant Agreement 721559 and the STFC Cockcroft Institute core Grant No. ST/G008248/1.
Due to the relatively infrequent use of electrostatic beamline elements compared with their magnetic counterparts, there are few particle tracking codes which allow for the straightforward implementation of such beamlines. In this contribution, we present 3D tracking methods for beamlines containing electrostatic elements utilising a modified version of the Geant4 based tracking code 'G4beamline'. In 2020 transfer lines will begin transporting extremely low energy (100 keV) antiproton beams from the Extra Low Energy Antiproton (ELENA) ring to the antimatter experiments at CERN. Electrostatic bending and focusing elements have been chosen for the beamlines due to their mass independence and focusing efficiency in the low energy regime. These beamlines form the basis of our model which is benchmarked against simplified tracking simulations. Realistic beam distributions obtained via tracking around ELENA in the presence of collective effects and electron cooling will be propagated along the optimised 3D transfer model to achieve the best beam quality possible for the experiments.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF016  
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THPAF017 Improvement of RF Field Phase and Amplitude Errors Simulations in TraceWin Code cavity, linac, diagnostics, beam-losses 2983
 
  • D. Uriot
    IRFU, CEA, University Paris-Saclay, Gif-sur-Yvette, France
 
  Funding: This work is supported by the European Atomic Energy Community's (EURATOM) H2020 Programme under grant agreement n°662186 (MYRTE project)
RF field phase and amplitude errors are usually not correctly simulated and it is a serious problem especially when in high intensity linear accelerators, the main losses are due to particle leaving the beam acceptance. This new development implemented in TraceWin fixes this issue. The objective is to improve the longitudinal beam dynamics simulation methods, by including more close-to-real models for the cavities tuning procedure. By this way, clear distinction should be done between static and dynamic errors and longitudinal diagnostics accuracy can be clearly defined according to beam dynamics results.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF017  
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THPAF021 Start to End Simulation of the CBETA Energy Recovery Linac linac, lattice, optics, space-charge 2993
 
  • W. Lou, A.C. Bartnik, J.A. Crittenden, C.M. Gulliford, G.H. Hoffstaetter, D. Sagan
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • J.S. Berg, S.J. Brooks, F. Méot, D. Trbojevic, N. Tsoupas
    BNL, Upton, Long Island, New York, USA
  • C.E. Mayes
    SLAC, Menlo Park, California, USA
 
  Funding: This manuscript has been authored by employees of Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
CBETA is an energy recovery linac accelerating from 6 MeV to 150 MeV in four linac passes, using a single return line accepting all energies from 42 MeV to 150 MeV. We simulate a 6-dimensional particle distribution from the injector through the end of the dump line. Space charge forces are taken into account at the low energy stages. We compare results using field maps to those using simpler magnet models. We introduce random and systematic magnet errors to the lattice, apply an orbit correction algorithm, and study the impact on the beam distribution.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF021  
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THPAF022 Beam Breakup Studies for the 4-Pass Cornell-Brookhaven Energy Recovery Linac Test Accelertor HOM, cavity, lattice, dipole 2996
 
  • W. Lou, G.H. Hoffstaetter
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Cornell University and Brookhaven National Laboratory are currently designing the Cornell-BNL ERL-FFAG Test Accelerator (CBETA). To be built at Cornell Wilson Lab, CBETA utilizes the existing ERL injector and main linac cryomodule (MLC). As the electron bunches pass through the MLC cavities, higher order modes (HOMs) fields are excited. The recirculating bunches interact with the HOMs, which can give rise to beam-breakup instability (BBU). We would present simulation results on how BBU limits the maximum achievable current, and potential ways to improve the threshold current.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF022  
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THPAF025 Progress in Measurement and Modeling of Electron Cloud Effects at CesrTA electron, dipole, emittance, positron 3007
 
  • S. Poprocki, S.W. Buechele, J.A. Crittenden, D. L. Rubin
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Funding: This work is supported by the US National Science Foundation PHY-0734867, PHY-1002467 and the US Department of Energy DE-FC02-08ER41538, DE-SC0006505.
The synchrotron-radiation-induced buildup of low-energy electron densities in positron and proton storage rings limits performance by causing betatron tune shifts and incoherent emittance growth. The Cornell Electron Storage Ring (CESR) Test Accelerator project includes extensive measurement and modeling programs to quantify such effects and apply the knowledge gained to the design of future accelerator projects. We report on improved measurements of betatron tune shifts along a train of positron bunches, now accurate in both horizontal and vertical planes. Improved electron cloud buildup modeling uses detailed information on photoelectron production properties obtained from recently developed simulations and successfully describes the measurements after determining ring-wide secondary-yield properties of the vacuum chamber by fitting the model to data with a multi-objective optimizer. Cloud splitting in dipole magnetic fields is seen to be the source of horizontal tune shifts decreasing at higher bunch populations.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF025  
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THPAF026 Modeling Studies for Synchrotron-Radiation-Induced Electron Production in the Vacuum Chamber Walls at CesrTA photon, electron, vacuum, site 3011
 
  • S. Poprocki, J.A. Crittenden, D. L. Rubin, D. Sagan
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Funding: This work is supported by the US National Science Foundation PHY-0734867, PHY-1002467 and the US Department of Energy DE-FC02-08ER41538, DE-SC0006505.
We report on calculations of electron production by synchrotron radiation absorbed in the vacuum chamber walls of the Cornell Electron Storage Ring (CESR). These electrons are the source of electron clouds which limit the performance of storage rings by causing betatron tune shifts, instabilities and emittance growth. Until now, cloud buildup modeling codes have used ad hoc models of the production of the seed electrons. We have employed the photon scattering code Synrad3D to quantify the pattern of absorbed photons around the CESR ring, including the transverse distribution on the wall of the beam-pipe. These distributions in absorbed photon energy and incident angle are used as input to Geant4-based simulations of electron emission from the walls. The average quantum efficiency is found to vary dramatically with the location of the absorption site, owing to the distribution in impact energies and angles. The electron production energy spectrum plays an important role in the modeling of electron cloud buildup, where the interplay of production energy and acceleration by the beam bunches determines the time structure and multipacting characteristics of the cloud.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF026  
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THPAF032 Simulation Study of an RF Injector for the LWFA Configuration at EuPRAXIA linac, injection, plasma, emittance 3025
 
  • J. Zhu, R.W. Aßmann, A. Ferran Pousa, B. Marchetti, P.A. Walker
    DESY, Hamburg, Germany
 
  The Horizon 2020 Project EuPRAXIA (EuropeanPlasma Research Accelerator with eXcellence In Applications) aims at producing a design report of a highly compact and cost-effective European facility with multi-GeV electron beams using a plasma accelerator. LWFA with external injection from an RF accelerator is one of the most promising configurations. In order to achieve the goal parameters for the 5 GeV, 30 pC electron beam at the entrance of the undulator, a high-quality electron beam with bunch length of less than 10 fs (FWHM) and matched beta functions (~1 mm) at the plasma entrance is required. In addition, from the compactness point of view, the injection energy is desired to be as low as possible. A hybrid compression scheme is considered in this paper and a detailed start-to-end simulation is presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF032  
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THPAF034 Studies of Horizontal Instabilities in the CERN SPS octupole, optics, damping, impedance 3032
 
  • M.S. Beck, H. Bartosik, M. Carlà, K.S.B. Li, G. Rumolo, M. Schenk
    CERN, Geneva, Switzerland
  • U. van Rienen
    Rostock University, Faculty of Engineering, Rostock, Germany
 
  In the framework of the LHC Injectors Upgrade (LIU), beams with double intensity with respect to the present values will have to be successfully accelerated by the CERN Super Proton Synchrotron (SPS) and extracted towards the Large Hadron Collider (LHC). However, first experience running with intensity higher than the nominal LHC beam has shown that coherent instabilities in the horizontal plane may develop, becoming a potential intensity limitation for the future high intensity operation. To understand the mechanism of these instabilities, the PyHEADTAIL code has been used to check if the SPS impedance model reproduces the observations. The instability growth rates have been studied for different machine models and different chromaticity settings. In addition, the effect of other stabilizing methods, like the octupoles and the transverse damper, has also been investigated. Measurements are presented to benchmark the simulations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF034  
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THPAF041 Uncontrolled Longitudinal Emittance Blow-Up during RF Manipulations in the CERN PS impedance, cavity, emittance, controls 3056
 
  • A. Lasheen, H. Damerau, G. Favia
    CERN, Geneva, Switzerland
 
  The CERN Proton Synchrotron (PS) determines the basic bunch spacing for the Large Hadron Collider (LHC) by means of rf manipulations. Several rf systems in a frequency range from 2.8 MHz to 200 MHz are available for beam acceleration and manipulations. Each of the six bunches injected from the PS Booster is split in several steps into 12 bunches spaced by 25 ns, yielding a batch of 72 bunches at transfer to the Super Proton Synchrotron (SPS). In the framework of the LHC Injector Upgrade (LIU) project the bunch intensity must be doubled. However, with most of the planned upgrades already in place this intensity has not yet been achieved due to collective effects. One of them is uncontrolled longitudinal emittance blow-up during the bunch splittings. In this contribution, measurements of the blow-up during the splitting process are presented and compared with particle simulations using the present PS impedance model. Beam-based measurements of the impedances of the rf cavities have been performed. They revealed that to reproduce the instability an additional impedance source is required in the PS impedance model.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF041  
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THPAF051 Beam Impedance Evaluation for CERN PS Gate Valves by Simulation and Benchmark Measurement impedance, wakefield, resonance, coupling 3080
 
  • B.K. Popovic, C. Vollinger
    CERN, Geneva, Switzerland
 
  The CERN High Luminosity LHC project calls for a doubling of beam intensity which requires a clear identification of possible longitudinal instability sources in the injector chain. This requirement yields the need to further improve the longitudinal impedance model for the Proton Synchrotron (PS). In this impedance model it is necessary to include not only obvious impedance sources, such as RF cavities and kickers but also seemingly innocuous elements like certain vacuum components. Individually these vacuum elements would give only a small impedance contribution, however, due to the large number of these elements in the machine, their resultant combined impedances impact the overall impedance budget. This paper presents the electromagnetic simulation analysis of the PS sector gate valves along with EM measurements confirming the simulation model. These measurements are especially crucial in this case since no complete mechanical model or drawings are available and assumptions had to be made regarding its interior mechanical structure.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF051  
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THPAF053 Lower-Harmonic RF System in the CERN SPS emittance, impedance, cavity, proton 3087
 
  • J. Repond, H. Damerau, A. Lasheen, E.N. Shaposhnikova
    CERN, Geneva, Switzerland
 
  Significant beam losses increasing with intensity are observed at capture and along the SPS flat bottom for the LHC-type proton beam. The intensity should be doubled for HL-LHC and high losses may be a major performance limitation. Bunches extracted from the PS, the SPS injector, are produced in a 40 MHz RF system applying a bunch rotation at the end of the cycle and therefore cannot be perfectly matched to the 200 MHz SPS RF bucket. The possibility of using a lower harmonic additional RF capture system in the SPS was already proposed after the LEP era in preparation for transfer of the LHC beam but the bunch rotation was the preferred solution, since the induced voltage in the SPS 200 MHz RF system would be too large to ensure stability in a low harmonic system without mitigation measures. However, the use of the upgraded one-turn feedback and the 200 MHz RF system as a Landau cavity could help to improve stability. The feasibility of this scenario to reduce capture losses in the SPS is analysed and presented in this paper. The choice of an optimum RF frequency and voltage is also discussed. The transfer to the main 200 MHz is simulated using a realistic bunch distribution.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF053  
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THPAF055 Space Charge Studies on LEIR resonance, space-charge, emittance, lattice 3095
 
  • Á. Saá Hernández, H. Bartosik, N. Biancacci, S. Hirlaender, A. Huschauer, D. Moreno Garcia
    CERN, Geneva, Switzerland
 
  The performance of the CERN Low Energy Ion Ring with electron cooled ion beams is presently limited by losses occurring once the beam has been captured in the RF buckets. An intense machine study program was started by the end of 2015 to mitigate the losses and improve the performance of the accelerator. The measurements pointed to the interplay of direct space charge forces and excited betatron resonances as the most plausible driving mechanism of these losses. In this paper, we present the systematic space-charge measurements performed in 2017 and compare them to space-charge tracking simulations based on an adaptive frozen potential.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF055  
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THPAF057 Instability Observations in the Large Hadron Collider During Run 2 coupling, operation, electron, hadron 3099
 
  • L.R. Carver, D. Amorim, S. A. Antipov, N. Biancacci, X. Buffat, G. Iadarola, K.S.B. Li, E.H. Maclean, L. Mether, E. Métral, B. Salvant, M. Schenk
    CERN, Geneva, Switzerland
  • L. Mether, M. Schenk
    EPFL, Lausanne, Switzerland
 
  Instabilities of many different types and characteristics have been observed in the LHC during Run 2. The origin of these instabilities come from a variety of stabilising and destabilising mechanisms. Efforts to understand these instabilities and prevent their occurrence has improved the performance of the LHC in all stages of the machine cycle. This paper aims to give an overview into some of the instability observations and details the operational steps to prevent them.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF057  
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THPAF062 Impact of Superconducting Magnet Protection Equipment on the Circulating Beam in HL-LHC dipole, quadrupole, shielding, experiment 3115
 
  • M. Valette, L. Bortot, A.M. Fernandez Navarro, B. Lindstrom, M. Mentink, R. Schmidt, E. Stubberud, A.P. Verweij, D. Wollmann
    CERN, Geneva, Switzerland
  • E. Ravaioli
    LBNL, Berkeley, California, USA
 
  Funding: Work supported by the HL-LHC project.
The new superconducting quadrupole and dipole magnets for the High Luminosity LHC (HL-LHC) will rely on quench heaters or Coupling-Loss Induced Quench (CLIQ) units or a combination of both to protect the magnet coils in case of a quench. After the detection of a quench, the quench heater power supplies will discharge currents of several hundreds of amperes into the quench heater strips glued to the coils, and the CLIQ units will discharge an oscillating current in the order of 1~kA directly into the coils. These currents can have a significant effect on the circulating beam if the discharge occurs before the beam is dumped. In the HL-LHC inner triplet quadrupole magnets and 11 T dipole magnets, which will be installed in the collimation region dispersion suppressor, this effect will even be stronger due to the larger number of quench heaters and use of CLIQ units (triplet magnets only) as well as due to the greater value of beta function in comparison with the present LHC. In this paper, the expected effects of quench heater and CLIQ discharges on the circulating beam are summarized, and several mitigation methods are proposed and evaluated.
Matthieu. Valette@cern.ch
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF062  
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THPAF065 Semi-Empirical Hamiltonian Model for Elliptical Cavities cavity, linac, linear-dynamics, proton 3127
 
  • E. Laface, J. F. Esteban Müller
    ESS, Lund, Sweden
 
  We propose to use the sum of TM0m0 modes to treat a radio-frequency superconducting elliptical cavity as a pill-box cavity with variable radius. The amplitudes of the different modes are obtained interpolating the field-map of the cavity with the model. Once the field is calculated, the Hamiltonian of the cavity is constructed and used to evaluate the transfer matrices associated to each step of the field-map. The multi-particle non-linear dynamics can also be evaluated using the Lie Transform of the Hamiltonian. The results are benchmarked against the ESS Linac Simulator contained in the OpenXAL suite.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF065  
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THPAF068 Suppression of Instabilities Generated by an Anti-Damper With a Nonlinear Magnetic Element in IOTA experiment, lattice, optics, damping 3134
 
  • E.G. Stern, J.F. Amundson, A. Macridin
    Fermilab, Batavia, Illinois, USA
 
  Funding: US Department of Energy
The Integrable Optics Test Accelerator (IOTA) storage ring is being constructed at Fermilab as a testbed for new accelerator concepts. One important series of experiments tests the use of a novel nonlinear magnetic insert to damp coherent instabilities. To test the damping power of the ele- ment, an instability of desired strength may be intentionally excited with an anti-damper. We report on simulations of beam stabilization using the Synergia modeling framework over ranges of driving and damping strengths.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF068  
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THPAF069 Particle Tracking Simulation of Collective Modes - Parametric Landau Damping Off Coupling Resonance damping, coupling, resonance, synchrotron 3137
 
  • A. Macridin, J.F. Amundson, A.V. Burov, P. Spentzouris, E.G. Stern
    Fermilab, Batavia, Illinois, USA
 
  Employing Synergia simulations with the DMD method we investigate the Landau damping of space charge modes in bunched beams. The simulations reveal two instances of the parametric damping mechanism in bunched beams. The first example occurs in the proximity of coupling resonance and is due to the oscillation of particles' amplitudes in the transverse plane. This oscillation modulates the mode-particle coupling with particle dependent trapping frequency. The second example is due to the modulation of the mode-particle coupling in one transverse plane by the oscillatory motion in the other plane.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF069  
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THPAF071 McMillan Lens in a System with Space Charge emittance, resonance, quadrupole, lattice 3143
 
  • I. Lobach
    University of Chicago, Chicago, Illinois, USA
  • S. Nagaitsev, E.G. Stern, T. Zolkin
    Fermilab, Batavia, Illinois, USA
 
  Space charge (SC) in a circulating beam in a ring produces both betatron tune shift and betatron tune spread. These effects make some particles move on to a machine resonance and become unstable. Linear elements of beam optics cannot reduce the tune spread induced by SC because of its intrinsic nonlinear nature. We investigate the possibility to mitigate it by a thin McMillan lens providing a nonlinear axially symmetric kick, which is qualitatively opposite to the accumulated kick by SC. Experimentally, the proposed concept can be tested in Fermilab's IOTA ring. A thin McMillan lens can be implemented by a short (70 cm) insertion of an electron beam with specifically chosen density distribution in transverse directions. In this article, to see if McMillan lenses reduce the tune spread induced by SC, we make several simulations with particle tracking code Synergia. We choose such beam and lattice parameters that tune spread is roughly 0.5 and a beam instability due to the half-integer resonance 0.5 is observed. Then, we try to reduce emittance growth by shifting betatron tunes by adjusting quadrupoles and reducing the tune spread by McMillan lenses.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF071  
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THPAF075 Numerical Simulations of Space Charge Compensation with an Electron Lens space-charge, electron, lattice, emittance 3154
 
  • E.G. Stern, Y.I. Alexahin, J.F. Amundson, A.V. Burov, A. Macridin, V.D. Shiltsev
    Fermilab, Batavia, Illinois, USA
 
  The future high energy physics program at Fermilab requires that the proton complex operate with beam bunch intensities four times larger than is currently handled. At these intensities space charge nonlinear defocussing effects cause unacceptable particle losses especially in the low energy rapid-cycling-synchrotron (RCS) Booster. Focusing electron lens elements may offer a solution by providing partial space charge compensation but there is a need for detailed simulations as this technique has not been demonstrated. We report on high fidelity numerical 6D space charge simulations in a model accelerator lattice with a record high space charge tune shift approaching unity.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF075  
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THPAF076 Using Graphic-Turtle with the Particle Beam Optics Laboratory (PBO Lab) optics, scattering, software, quadrupole 3158
 
  • G.H. Gillespie
    G.H. Gillespie Associates, Inc., Del Mar, California, USA
 
  A Particle Beam Optics Laboratory (PBO Lab) module has been developed for the Paul Scherrer Institute (PSI) version of the TURTLE program commonly known as Graphic-Turtle. The PSI-TURTLE version extends the original TURTLE program by including several unique beam optics capabilities, as well as by providing a self-contained graphics package. The unique optics modeling, together with the data visualization enhancements, make the PSI-TURTLE program ideal for certain types of beam simulations. The PBO Lab environment provides a single graphic user interface (GUI) that features an easy-to-learn and easy-to-use drag-and-drop beamline construction kit. Underlying the GUI is a sophisticated object model developed specifically for the accelerator community. PBO Lab provides a common interface for multiple charged particle optics codes. Modules have been developed for a number of popular beam optics programs that cover a range of accelerator types and applications. The PSI-TURTLE Module extends those capabilities. The module is described and its main capabilities and limitations are summarized.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF076  
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THPAF077 Ion-optical Measurements at CRYRING@ESR during Commissioning MMI, acceleration, injection, closed-orbit 3161
 
  • O. Geithner, Z. Andelkovic, M. Bai, A. Bräuning-Demian, V. Chetvertkova, O. Chorniy, C. Dimopoulou, W. Geithner, O.E. Gorda, F. Herfurth, M. Lestinsky, S.A. Litvinov, S. Reimann, A. Reiter, M. Sapinski, R. Singh, T. Stöhlker, G. Vorobjev, U. Weinrich
    GSI, Darmstadt, Germany
  • A. Källberg
    Stockholm University, Stockholm, Sweden
 
  CRYRING@ESR is a heavy ion storage ring, which can cool and decelerate highly charged ions down to a few 100 keV/u. It has been relocated from Sweden to GSI, downstream of the experimental storage ring (ESR), within the FAIR project. The ring will be used as a test facility for FAIR technologies as well as for physics experiments with slow exotic ion beams for several FAIR collaborations: SPARC, BioMat, FLAIR and NUSTAR. CRYRING@ESR is in its commissioning phase since summer 2016. Several ion-optical measurements such as tunes, tune diagram, dispersion, chromaticity and orbit response matrix were performed at the ring. The measurements will be used for several purposes such as improvement of the theoretical model, closed orbit control and correction of unacceptable misalignments, calibration coefficients and field errors.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF077  
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THPAF078 Expected Performance of the Stochastic Cooling and RF System in the Collector Ring bunching, proton, antiproton, emittance 3165
 
  • O.E. Gorda, C. Dimopoulou, A. Dolinskyy
    GSI, Darmstadt, Germany
  • T. Katayama
    Nihon University, Narashino, Chiba, Japan
 
  The Collector Ring is designed for stochastic cooling of antiprotons or radioactive ions at FAIR. Simulations of the cooling process in combination with the required RF beam manipulations have been done taking into account the improved and recently fixed ion-optics. The measured RF properties of the first of series debuncher system have been considered to evaluate the performance of the bunch rotation, de-bunching and re-bunching process within the planned CR operation cycle. The expected beam parameters and matching at extraction to the HESR storage ring are discussed in this paper. The latest hardware developments of the stochastic cooling system components are also presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF078  
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THPAF079 Landau Damping and Tune-Spread Requirements for Transverse Beam Stability octupole, damping, impedance, quadrupole 3168
 
  • V. Kornilov, O. Boine-Frankenheim
    GSI, Darmstadt, Germany
 
  Passive mitigation methods are effective cures for collective instabilities in ring accelerators. For decades, octupole magnets have been used as an established and well-understood passive mitigation method. Present and the future accelerator facilities, like FAIR or FCC, impose new challenges on the passive mitigation due to higher energies and smaller beam emittances. Lattice resonances usually restrict the tolerable tune-spreads which are essential for the passive mitigation methods. We study the stability of transverse bunch oscillations provided by octupole magnets and radio-frequency quadrupoles. The special focus of our study is on the interplay and role of decoherence, phase-mixing and Landau damping for the different mitigation schemes. Particle tracking simulations are performed and the tune spreads for the different mechanisms are compared with each other and also with analytical dispersion relations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF079  
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THPAF082 Frequency Jump at Low Energies rfq, linac, emittance, bunching 3176
 
  • C. Zhang
    GSI, Darmstadt, Germany
  • H. Podlech
    IAP, Frankfurt am Main, Germany
 
  One or more radio-frequency jumps are usually necessary for realizing a ≥100 AMeV/u proton or ion driver linac. Typically, such jumps happen in the range of β = 0.2-0.6 between the resonator structures fitting to this β-range, e.g. DTL, HWR, CCL or elliptical cavities. We propose to perform the first frequency jump already at low energies (β ≤ 0.1) between two RFQ accelerators, which can bring some unique advantages. First studies have been performed and the results proved that this idea is feasible and promising. Many efforts have been and are being made to address the most critical issue for the jumps i.e. the beam matching at the transition.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF082  
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THPAF083 LINAC-Multitool - an Open Source Java-Toolkit linac, cavity, GUI, MMI 3179
 
  • M. Schwarz, D. Bade, J. Corbet, H. Podlech
    IAP, Frankfurt am Main, Germany
 
  Funding: Work supported by BMBF contr. No. 05P15RFRBA and HIC for FAIR.
Dedicating more precious time to advanced research instead of spending it towards time-consuming routine tasks is a desirable goal in particle accelerator simulation and development. Requirements engineering was started at IAP in order to identify routine processes at our institute's R&D that can be automated or simplified. Results indicated that there were several areas to consider: Bead pull measurements, data processing and visualization for the beam dynamics code LORASR, CST field map processing for the use with TraceWin, conversion between different particle distribution data formats and more. Subsequently development of the LINAC-Multitool started to rationalize these processes and replace preexisting scripts also to ensure consistency of results and increase transparency and reliability of computation. In order to guarantee maintainability, expandability and platform independence, LINAC-Multitool is programmed using Java and will be open source. This contribution presents the current state of development.
 
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THPAF084 Impact of RF Coupler Kicks on Beam Dynamics in BESSY VSR cavity, kicker, SRF, lattice 3182
 
  • T. Mertens
    Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
  • T. Atkinson, F. Glöckner, A. Jankowiak, M. Ries, A.V. Tsakanian
    HZB, Berlin, Germany
 
  The expected BESSY II upgrade to BESSY VSR requires the installation of a superconducting RF system, consisting of four cavities. Two cavities will operate at 1.5 GHz and two at 1.75 GHz. Each of them is equipped with a Fundamental Power Coupler and with Higher Order Mode (HOM) damping waveguide couplers. Dedicated simulations of these cavities and couplers have shown that at the location of the FPC the beam will see a transverse kick [*], perturbing the closed orbit and affecting transverse beam dynamics. We present the results of simulations and experiments of the impact on transverse beam dynamics of these coupler induced kicks for different FPC orientations.
[*] Study on RF Coupler Kicks of SRF Cavities in the BESSY VSR Module
A. Tsakanian#, H.-W. Glock, T. Mertens, M. Ries, A. Velez, J. Knobloch
IPAC18
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF084  
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THPAK001 Impedance Evaluation of In-Vacuum Undulator at KEK Photon Factory impedance, undulator, factory, vacuum 3200
 
  • O. Tanaka, M. Adachi, R. Kato, N. Nakamura, T. Obina, S. Sakanaka, R. Takai, K. Tsuchiya, N. Yamamoto
    KEK, Ibaraki, Japan
 
  The estimate of impedance and kick factors of the recently installed at KEK Photon Factory (PF) four In-Vacuum Undulators (IVU) is currently a very important issue, because they could be considerable contributors to the total impedance of PF. Moreover, the coupling impedance of the IVUs could lead to the beam energy loss, changes in the bunch shape, betatron tune shifts and, finally, to the various beam instabilities. Using the simulation tool (CST Particle Studio), longitudinal and transverse impedances of the IVUs were evaluated and compared to analytical formulas and measurement results. The study provides guidelines for mitigation of unwanted impedance, for the accurate estimate of its effects on the beam quality and beam instabilities and also for the impedance budget of a newly designed next-generation machine which has many IVUs and small-aperture beam pipes.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK001  
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THPAK005 Measuring the Coupling Impedance of Vacuum Components for the Advanced Photon Source Upgrade Using a Goubau Line impedance, cavity, vacuum, coupling 3211
 
  • M.P. Sangroula
    IIT, Chicago, Illinois, USA
  • R.M. Lill, R.R. Lindberg, R.B. Zabel
    ANL, Argonne, Illinois, USA
 
  The Planned upgrade of the Advanced Photon Source to a multi-bend achromat (MBA) will increase the x-ray brightness by two to three orders of magnitude. Storing such an intense beam stably inside the narrow gap vacuum chambers requires sophisticated and appropriately designed rf-components that helps to minimize rf heating and collective instabilities associated with the impedance of these small-aperture vacuum components. As part of this effort, my research focuses on impedance measurement and simulation of various MBA vacuum components. In this paper, we briefly introduce the novel Goubau line (G-line) test fixture for the impedance measurement, at first, and then present our measurements data along with simulations with simulations for various vacuum components designed for the APS Upgrade.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK005  
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THPAK008 Space Charge and Microbunching Studies for the Injection Arc of MESA space-charge, bunching, injection, lattice 3221
 
  • A. Khan, O. Boine-Frankenheim
    Institut Theorie Elektromagnetischer Felder, TU Darmstadt, Darmstadt, Germany
  • C.P. Stoll
    IKP, Mainz, Germany
 
  For intense electron bunches traversing through bends, as for example the recirculation arcs of an ERL, space charge (SC) may result in beam phase space deterioration. SC modifies the electron transverse dynamics in dispersive regions along the beam line and causes emittance growth for mismatched beams or for specific phase advances. On the other hand, longitudinal space charge together with dispersion can lead to the microbunching instability. The present study focuses on the 180° low energy (5 MeV) injection arc lattice for the multi-turn Mainz Energy-recovering Superconducting Accelerator (MESA), which should deliver a CW beam at 105 MeV for physics experiments with an internal target. We will discuss matching conditions with space charge together with the estimated microbunching gain for the arc. The implication for the ERL operation will be outlined, using 3D envelope and tracking simulations.
Supported by the DFG through GRK 2128
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK008  
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THPAK009 Benchmark Analyses of Electrostatic Devices for SPIRAL2-DESIR Beam Lines quadrupole, optics, emittance, electrostatic-devices 3225
 
  • L. Perrot, M. Kemel, S. Rousselot
    IPN, Orsay, France
 
  Funding: French ANR, Investissements d'Avenir, EQUIPEX. Contract number ANR-11-EQPX-0012.
The new ISOL facility SPIRAL2 is currently being built at GANIL, Caen France. The commissioning of the accelerator is in progress since 2015. SPIRAL2 will produce a large number of new radioactive ion beams (RIB) at high intensities. In 2023, the DESIR facility will receive beams from the upgraded SPIRAL1 facility of GANIL (stable beam and target fragmentation), from the S3 Low Energy Branch (fusion-evaporation and deep-inelastic reactions). In order to deliver the RIB to the experimental set-ups installed in the DESIR hall, 140 meters of beam line are studied since 2014. The transfert lines are today fully design and building will start in 2018. Electrostatic devices (quadrupoles, steerers and deflectors) have been intensively study using various tools. This paper will focus on the detail results of a benchmark using OPERA3D and Comsol Multiphysics apply to the DESIR quadrupole conception.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK009  
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THPAK014 Analytical Estimation of the Beam Ion Instability in HEPS operation, brightness, damping, electron 3231
 
  • N. Wang, Z. Duan, S.K. Tian, H.S. Xu
    IHEP, Beijing, People's Republic of China
 
  The High Energy Photon Source (HEPS) is a new designed photon source at beam energy of 6 GeV, with natural beam emittance less than 100pm. Due to the small transverse beam size, beam ion instability is one of the potential issues for HEPS. The growth time of the instability is estimated analytically for different operation scenarios. The results show considerably good agreement with the wake strong simulations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK014  
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THPAK015 Impedance and Heat Load Analysis of the Stripline Kicker in HEPS kicker, impedance, coupling, injection 3234
 
  • N. Wang, J. Chen, Z. Duan, H. Shi, S.K. Tian, L. Wang, H.S. Xu
    IHEP, Beijing, People's Republic of China
 
  In the High Energy Photon Source (HEPS), strip-line kickers are adopted for beam injection and extraction. Beam coupling impedance contribution from the strip-line kicker is calculated. Detailed studies on the heat load dissipation have been performed. The peak electric field on the blade and the induced voltage on the feedthroughs due to the beam passage are also calculated.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK015  
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THPAK018 Recent Developments in DEMIRCI for RFQ Design rfq, software, multipole, cavity 3243
 
  • E. Celebi
    IBU, Istanbul, Turkey
  • O. Cakir, G. Turemen
    Ankara University, Faculty of Sciences, Ankara, Turkey
  • G. Turemen
    TAEK, Ankara, Turkey
  • G. Unel
    UCI, Irvine, California, USA
 
  Funding: This project has been supported by TUBITAK with project number 114F106 and 117F143.
DEMIRCI software aims to aid RFQ design efforts by making the process easy, fast and accurate. In this report, DEMIRCI 8-term potential results are compared with the results provided by other commercially available simulation software. Computed electric fields are compared to the re- sults from simulations of a recently produced 352 MHz RFQ. Recent developments like the inclusion of space charge ef- fects in DEMIRCI beam dynamics are also discussed. More- over, further terms are added to 8-term potential to simulate possible vane production errors. The FEM solver was also improved to mesh the cells with errors.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK018  
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THPAK021 Design of High Resolution Mass Spectrometer for SPES dipole, HOM, emittance, high-voltage 3252
 
  • M. Comunian, C. Baltador, L. Bellan, M. Cavenago, A. Pisent
    INFN/LNL, Legnaro (PD), Italy
  • E. Khabibullina
    ITEP, Moscow, Russia
  • E. Khabibullina
    MEPhI, Moscow, Russia
 
  Within the framework of the SPES (Selective Production of Exotic Species) project at National Institute of Nuclear Physics (INFN laboratory, Legnaro, Italy) the High Resolution Mass Spectrometer (HRMS) will be build. HRMS needs to provide full separation of the ions with mass resolution 1/20000 for the following breeding and acceleration on ALPI Linac. In this article the main design choice of the HRMS and of the transport channel will be reported.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK021  
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THPAK022 Beam Dynamic Simulation for the Beam Line from Charge Breeder to ALPI for SPES Project rfq, linac, experiment, quadrupole 3255
 
  • M. Comunian, L. Bellan, A. Pisent
    INFN/LNL, Legnaro (PD), Italy
  • A.V. Ziiatdinova
    ITEP, Moscow, Russia
  • A.V. Ziiatdinova
    MEPhI, Moscow, Russia
 
  The SPES project (Selective Production of Exotic Species) is under development at INFN-LNL. This facility is intended for production of neutron-rich Radioactive Ion Beams (RIBs) by ISOL method. The +1 charged beam will be transformed to n+ charge by Charge Breeder (Electron Cyclotron resonance ion source) and reaccelerated by the ALPI (Acceleratore Lineare Per Ioni) superconducting Linac . This paper includes results of beam dynamic simulation at the beam line from Charge Breeder to ALPI.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK022  
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THPAK025 Recent Developments in Beam Delivery Simulation - BDSIM dipole, radiation, sextupole, interface 3266
 
  • L.J. Nevay, A. Abramov, S.T. Boogert, H. Garcia Morales, S.M. Gibson, W. Shields, S.D. Walker
    JAI, Egham, Surrey, United Kingdom
  • J. Snuverink
    PSI, Villigen PSI, Switzerland
 
  Funding: Work supported by Science and Technology Research council grant 'The John Adams Institute for Accelerator Science' ST/P00203X/1 and Impact Acceleration Account.
Beam Delivery Simulation (BDSIM) is a program to seamlessly simulate the passage of particles in an accelerator, the surrounding environment and detectors. It uses a suite of high energy physics software including Geant4, CLHEP and ROOT to create a 3D model from an optical description of an accelerator and simulate the interaction of particles with matter as well as the production of secondaries. BDSIM is used to simulate energy deposition and charged particle backgrounds in a variety of accelerators worldwide. The latest developments are presented including low-energy tracking extension, more detailed geometry, support for ion beams and improved magnetic fields. A new analysis suite that allows scalable event by event analysis is described for advanced analysis such as the trace back of energy deposition to primary particle impacts.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK025  
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THPAK028 Beam Dynamics Simulations in the Dubna SC202 Superconducting Cyclotron for Hadron Therapy extraction, cyclotron, proton, cavity 3270
 
  • O. Karamyshev, G.A. Karamysheva, D.V. Popov, G. Shirkov, S.G. Shirkov
    JINR, Dubna, Moscow Region, Russia
  • V. Malinin
    JINR/DLNP, Dubna, Moscow region, Russia
 
  In 2015 the joint project JINR (Dubna, Russia) - ASIPP (Hefei, China) on design and construction of supercon-ducting proton cyclotron SC202 was started. Two cyclo-trons are planned to be manufactured in China, according to the Collaboration Agreement between JINR and ASIPP. The first cyclotron will be used for proton therapy in Hefei and the second one will replace the Phasotron in the research and treatment program on proton therapy in Dubna. New schema of extraction system and results of beam acceleration and extraction simulations for Dubna cyclotron are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK028  
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THPAK030 Studies of Longitudinal Dynamics in the Micro-Bunching Instability Using Machine Learning longitudinal-dynamics, bunching, synchrotron, vacuum 3277
 
  • T. Boltz, M. Brosi, E. Bründermann, A.-S. Müller, P. Schönfeldt, M. Yan
    KIT, Karlsruhe, Germany
  • M. Schwarz
    CERN, Geneva, Switzerland
 
  The operation of synchrotron light sources with short electron bunches increases the emitted CSR power in the THz frequency range. However, the spatial compression leads to complex longitudinal dynamics, causing the formation of micro-structures in the longitudinal bunch profiles. The fast temporal variation and small scale of these micro-structures put challenging demands on their observation. At the KIT storage ring KARA (KArlsruhe Research Accelerator), diagnostics have been developed allowing direct observation of the dynamics by an electro-optical setup, and indirect observation by measuring the fluctuation of the emitted CSR. In this contribution, we present studies of the micro-structure dynamics on simulated data, obtained using the numerical Vlasov-Fokker-Planck solver Inovesa, and first applications on measured data. To deal with generated data sets in the order of terabytes in size, we apply the machine learning technique k-means to identify the dominant micro-structures in the longitudinal bunch profiles. Following this approach, new insights on the correlation of the CSR power fluctuation to the underlying longitudinal dynamics can be gained.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK030  
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THPAK032 Elaborated Modeling of Synchrotron Motion in Vlasov-Fokker-Planck Solvers synchrotron, electron, storage-ring, damping 3283
 
  • P. Schönfeldt, T. Boltz, A. Mochihashi, A.-S. Müller, J.L. Steinmann
    KIT, Karlsruhe, Germany
 
  Funding: Funded by the German Federal Ministry of Education and Research (Grant No. 05K16VKA) & Initiative and Networking Fund of the Helmholtz Association (contract number: VH-NG-320).
Solving the Vlasov-Fokker-Planck equation is a well-tested approach to simulate dynamics of electron bunches self-interacting with their own wake-field. Typical implementations model the dynamics of a charge density in a damped harmonic oscillator, with a small perturbation due to collective effects. This description imposes some limits to the applicability: Because after a certain simulation time coherent synchrotron motion will be damped down, effectively only the incoherent motion is described. Furthermore - even though computed - the tune spread is typically masked by the use of a charge density instead of individual particles. As a consequence, some effects are not reproduced. In this contribution, we present methods that allow to consider single-particle motion, coherent synchrotron oscillation, non-linearities of the accelerating voltage, higher orders of the momentum compaction factor, as well as modulations of the accelerating voltage. We also provide exemplary studies - based on the KIT storage ring KARA (KArlsruhe Research Accelerator) - to show the potential of the methods.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK032  
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THPAK035 Numerical Tools for Modeling Nonlinear Integrable Optics in IOTA with Intense Space Charge Using the Code IMPACT-Z space-charge, optics, lattice, proton 3290
 
  • C.E. Mitchell, J. Qiang
    LBNL, Berkeley, California, USA
 
  Funding: This work is supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
The Integrable Optics Test Accelerator (IOTA) is a novel storage ring under commissioning at Fermi National Accelerator Laboratory designed to investigate the dynamics of beams with large transverse tune spread in the presence of strongly nonlinear integrable optics. Several new numerical tools have been implemented in the code IMPACT-Z to allow for high-fidelity modeling of the IOTA ring during Phase II operation with intense proton beams. A primary goal is to ensure symplectic treatment of both single-particle and collective dynamics. We describe these tools and demonstrate their application to modeling nonlinear integrable dynamics with space charge in IOTA.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK035  
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THPAK037 Beam-Loading Transients and Bunch Shape in the Operation of Passive Harmonic Cavities in the ALS-U cavity, beam-loading, impedance, controls 3298
 
  • Z. Pan, S. De Santis, C. Steier, C. Sun, M. Venturini
    LBNL, Berkeley, USA
  • T. Hellert
    DESY, Hamburg, Germany
  • C.-X. Tang
    TUB, Beijing, People's Republic of China
 
  The ALS-U is a major upgrade of the LBNL ALS to a diffraction limited light source. The current plan is to replace all the vacuum and magnet components while retaining the existing 500 MHz main and third-harmonic, passively operated, rf cavities, but replacement of the existing rf cavities is also being considered. A new feature, is represented by beam-loading transients associated with a beam consisting of 11 bunch trains separated by 10 ns gaps as needed to enable on-axis swap-out injection. In this paper we study these transients and the associated bunch-to-bunch phase, length, and profile variations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK037  
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THPAK040 Bunched Beam Envelope Instability in a Periodic Focusing Channel emittance, focusing, lattice, solenoid 3301
 
  • J. Qiang
    LBNL, Berkeley, California, USA
 
  The space-charge driven envelope instability presents a great danger in high intensity accelerator design. In this paper, we report on the study of bunched beam envelope instability in a periodic focusing channel using three-dimensional envelope model for a 3D uniform Waterbag distribution and a 3D Gaussian distribution. Our results show that the envelope instability stopband becomes broader with the increase of longitudinal focusing and are not sensitive to the type of distribution. Self-consistent macroparticle simulations using both distributions show similar structure in emittance growth but also extra instability stopbands. The emittance growth from the Waterbag distribution has larger stopband than that from the Gaussian distribution.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK040  
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THPAK042 On Long-Term Space-Charge Tracking Simulation space-charge, emittance, lattice, optics 3305
 
  • J. Qiang
    LBNL, Berkeley, California, USA
 
  The nonlinear space-charge effects in high intensity accelerator can degrade beam quality and cause particle losses. Self-consistent macroparticle tracking simulations have been widely used to study these space-charge effects. However, it is computationally challenging for long-term tracking simulation of these effects. In this paper, we study a fully symplectic self-consistent particle-in-cell model and numerical methods to mitigate numerical emittance growth. We also discuss about a fast alternative frozen space-charge model that has a potential to improve computational speed significantly.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK042  
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THPAK043 Performance Optimization of a Beam Dynamics PIC Code On Hybrid Computer Architectures GPU, kicker, plasma, HOM 3309
 
  • Zh.C. Liu
    IHEP, Beijing, People's Republic of China
  • J. Qiang
    LBNL, Berkeley, California, USA
 
  The self-consistent multi-particle tracking based on particle-in-cell method (PIC) has been widely used in particle accelerator beam dynamics study. However, the PIC simulation is time-consuming and needs to use modern parallel computers for high resolution applications. In this paper, we implemented and optimized a parallel beam dynamics PIC code on two types of hybrid parallel computer architectures: one is the GPU and GPU cluster, while the other is the "Knight Landing" CPU cluster.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK043  
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THPAK044 Self-Consistent Modeling using a Lienard-Wiechert Particle-Mesh Method space-charge, radiation, synchrotron, emittance 3313
 
  • R.D. Ryne, C.E. Mitchell, J. Qiang
    LBNL, Berkeley, California, USA
  • B.E. Carlsten
    LANL, Los Alamos, New Mexico, USA
 
  In this paper we describe a parallel, large-scale simulation capability using a Lienard-Wiechert Particle-Mesh (LWPM) method. The approach is a natural extension of the convolution-based technique to solve the Poisson equation in space-charge codes. It provides a unified method to compute both Coulomb-like self-fields and radiative phenomena like coherent synchrotron radiation (CSR). The approach brings together several mathematical and computational capabilities including the use of integrated Green function (IGF) methods and adaptive quadrature methods. We will describe the theoretical model and our progress to date.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK044  
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THPAK046 The Ion-Hose Instability in High-Current Multi-Pulse Induction Linacs electron, induction, vacuum, experiment 3320
 
  • C. Ekdahl
    LANL, Los Alamos, New Mexico, USA
 
  The ion-hose instability has long been considered a danger for long-pulse, high-current electron linear induction accelerators (LIAs)*. This instability is enabled by beam-electron ionization of residual background gas in the accelerator. The space-charge of the high-energy beam ejects low-energy electrons from the ionized channel, leaving a positively-charged ion channel that attracts the electron beam. The beam can oscillate in the potential well around the channel position. Likewise, the electron beam attracts the ions, which can oscillate about the beam position. Because of the vast differences in particle mass, the oscillations are out of phase, and the amplitudes grow unstably. The number of instability e-foldings is proportional to the channel ion density*, which in turn is proportional to the background pressure and pulse length. This scaling of the instability growth was demonstrated on the long-pulse DARHT-II linear induction accelerator (LIA) at Los Alamos**. The ion-hose instability is also problematic for high-current multi-pulse LIAs, because ion recombination times are so very long at typical background pressures. Moreover, because of low ion channel ion densities, and massive ions, channel expansion is too slow to reduce the instability growth by very much. In particular, the ion channel is expected to persist and its density to increase during the 3-microsecond duration of a four-pulse burst from the 2-kA, 20-MeV Scorpius LIA now being developed. Recent simulations with an experimentally validated code that was used to predict DARHT-II growth rates have shown that the magnetic focusing field designed for Scorpius will be strong enough to inhibit ion-hose instability if the background pressure is kept below a value that is readily attainable with the present designs of induction cells and other accelerator components. Details and results of these calculations are the subject of this presentation.
*H. L. Buchanan, Phys. Fluids, vol. 30, pp. 221 - 231, 1987
**C. A. Ekdahl, et al., IEEE Trans. Plasma Sci., vol. 34, pp. 460-466, 2006
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK046  
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THPAK047 Comparison of Profile Measurements and TRANSPORT Beam Envelope Predictions Along the 80-m LANSCE pRad Beamline linac, emittance, proton, diagnostics 3323
 
  • P.K. Roy, C. Pillai, C.E. Taylor
    LANL, Los Alamos, New Mexico, USA
 
  Funding: *Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE-AC52-06NA25396.
The Proton Radiography (pRad) experimental facility beam transport line is over 80 meters in length starting from the end of the LANSCE linear accelerator. The 800-MeV beam is transported through a beam line containing many bending and focusing elements before it reaches the pRad beam optics system where the beam spot size requirement is nominally 2 mm (RMS). Here we discuss the efforts to reconcile the beam transport inconsistencies (sizes) seen between comparisons of the beam sizes obtained using the LANL version of the beam envelope code TRANSPORT with those measured along the beam line. The transverse input beam parameters for the code were extracted from a fit to several wire-scanner measurements located in the downstream portion of the LINAC. The longitudinal input beam parameters were extrapolated from lower-energy information. Recently, new measurements were made of the beam line element locations and compared with legacy drawings. Beam envelope measurements made at various locations throughout the beam line using wire scanners and gated imaging systems were compared to the calculated results. The predicted beam envelopes and measured data agree within expected errors.
*Los Alamos National Laboratory (LA-UR-17-30876)
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK047  
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THPAK049 Simulation Code Design for the Interpreted Language Using the Compiled Module interface, EPICS, linac, lattice 3327
 
  • K. Fukushima, M.A. Davidsaver, Z.Q. He, M. Ikegami, G. Shen, T. Yoshimoto, T. Zhang
    FRIB, East Lansing, USA
  • J. Qiang
    LBNL, Berkeley, California, USA
 
  Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DESC0000661.
We are planning to use two types of the accelerator simulation codes for FRIB (Facility for Rare Isotope Beams). One is the linear envelope tracking code "FLAME" for fast simulations. FLAME can calculate the FRIB-linac beam envelope within an order of ms. This is useful in systematic surveys, wide range optimizations and so forth. This code, written in C++, was designed with Python interface from the beginning. On the other hand, "Advanced-IMPACT" is the particle tracking code dedicated for precise and realistic calculations, which can simulate the particle losses, nonlinear and space-charge effects. This code is refactored from the Fortran code IMPACT-Z developed in LBNL. Both codes provide the compiled modules for Python to support flexible inputs and direct outputs management in memory. In other words, they can be directly connected to the modern scientific tools through the Python interface without delay in the data transport. In addition, these modules can accomplish the interactive simulation processes without losing computational efficiency. We report the knowledges applicable for other accelerator simulation codes among those obtained through these developments and designs.
 
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THPAK050 MuSim, a User-Friendly Interface for Multiple Simulation Codes interface, proton, real-time, controls 3330
 
  • T.J. Roberts
    Muons, Inc, Illinois, USA
 
  MuSim is a new and innovative graphical framework that permits the user to construct, explore, optimize, analyze, and evaluate nuclear, accelerator, and other particle-based systems efficiently and effectively. It is designed for both students and experienced scientists to use in dealing with the many modeling tools and their different description languages and data formats. Graphical interfaces are used throughout, making it easy to construct the system graphically, display the system with particle tracks, analyze results, and use on-screen controls to vary parameters and observe their effects in (near) real time. Such exploration is essential to give users insight into how systems behave, and is valuable to both new users and experienced system designers. The use of URL-based component libraries will encourage collabor-ation among geographically diverse teams. This project will facilitate access to advanced modeling and simulation tools for inexperienced users and provide workflow management for them and advanced users.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK050  
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THPAK051 Computer Simulation of Explosive Emission Electrons Acceleration and X-ray Quantum Generation in Pulse Coaxial Diode System with Interior Anode cathode, electron, radiation, target 3333
 
  • V.I. Rashchikov, A.A. Isaev, A.E. Shikanov, E.A. Shikanov
    MEPhI, Moscow, Russia
 
  Computer simulation of electrons from explosive emission acceleration and X-ray quantum generation in pulse coaxial diode system with interior anode, which is used in accelerating tube of compact X-ray generator* with Tesla transformer as high voltage source, was done. The results obtained allow us to choose accelerating tube diode system geometry for different running modes. Comparison of numerical results with experimental data of dose rate dependence on the distance from vacuum tube anode and energy at first circuit Tesla transformer was fulfilled.
*Patent RF N71817, 03.10.2007
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK051  
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THPAK052 Single Bunch Instabilities in FCC-ee impedance, collider, electron, vacuum 3336
 
  • E. Belli
    Sapienza University of Rome, Rome, Italy
  • G. Castorina, M. Migliorati
    INFN-Roma1, Rome, Italy
  • G. Rumolo
    CERN, Geneva, Switzerland
  • B. Spataro, M. Zobov
    INFN/LNF, Frascati (Roma), Italy
 
  FCC-ee is a high luminosity lepton collider with a centre-of-mass energy from 91 to 365 GeV. Due to the machine parameters and pipe dimensions, collective effects due to electromagnetic fields produced by the interaction of the beam with the vacuum chamber can be one of the main limitations to the machine performance. In this frame, an impedance model is required to analyze these instabilities and to find possible solutions for their mitigation. This paper will present the contributions of specific machine components to the total impedance budget and their effects on the beam stability. Single bunch instability thresholds will be estimated in both transverse and longitudinal planes.   
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK052  
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THPAK061 Magnetized and Flat Beam Generation at the Fermilab's FAST Facility quadrupole, emittance, cathode, solenoid 3364
 
  • A. Halavanau, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • D.J. Crawford, D.R. Edstrom, D. Mihalcea, S. Nagaitsev, P. Piot, A.L. Romanov, J. Ruan, V.D. Shiltsev
    Fermilab, Batavia, Illinois, USA
 
  Funding: This work is supported by the DOE contract No.DEAC02-07CH11359 to the Fermi Research Alliance LLC. A.H. is supported by the DOE under contract No. DE-SC0011831 with Northern Illinois University.
Canonical angular momentum (CAM) dominated beams can be formed in photoinjectors by applying an axial magnetic field on the photocathode surface. Such a beam possess asymmetric eigenemittances and is characterized by the measure of its magnetization. CAM removal using a set skew-quadrupole magnets maps the beam eigenemittances to the conventional emittance along each transverse degree of freedom thereby yielding flat beam with asymmetric transverse emittance. In this paper we report on the experimental generation of CAM dominated beam and their subsequent transformation into flat beams at the Fermilab Accelerator Science and Technology (FAST) facility. Our results are compared with numerical simulations and possible applications of the produced beams are discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK061  
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THPAK062 Bunch Compression of Flat Beams emittance, experiment, cavity, booster 3368
 
  • A. Halavanau, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • D.J. Crawford, D.R. Edstrom, D. Mihalcea, S. Nagaitsev, P. Piot, A.L. Romanov, J. Ruan, V.D. Shiltsev
    Fermilab, Batavia, Illinois, USA
 
  Funding: This work is supported by the DOE contract No.DEAC02-07CH11359 to the Fermi Research Alliance LLC. A.H. is supported by the DOE under contract No. DE-SC0011831 with Northern Illinois University.
Flat beams can be produced via a linear manipulation of canonical angular momentum (CAM) dominated beams using a set of skew-quadrupole magnets. Recently such beams were produced at Fermilab Accelerator Science and Technology (FAST) facility. In this paper, we report the results of flat beam compression study in a magnetic chicane at an energy of E~32 MeV. Additionally, we investigate the effect of energy chirp in the round-to-flat beam transform. The experimental results are compared with numerical simulations.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK062  
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THPAK064 Theoretical Modeling of Electromagnetic Field from Electron Bunches in Periodic Wire Medium radiation, electron, lattice, FEL 3376
 
  • S.S. Chuchurka, A.I. Benediktovitch
    BSU, Minsk, Belarus, Belarus
  • S.N. Galyamin, V.V. Vorobev
    Saint Petersburg State University, Saint Petersburg, Russia
  • A. Halavanau
    Northern Illinois University, DeKalb, Illinois, USA
 
  Funding: Work supported by the Grant from Russian Foundation for Basic Research (No. 17-52-04107).
The interaction of relativistic electrons with periodic structures results in radiation by a number of mechanisms. In case of crystals one obtains parametric X-ray radiation, its frequency is determined by distance between crystallographic planes and direction of electron beam. If instead of crystal one considers a periodic structure of metallic wires with period of the order of mm, one can expect emission of THz radiation. In the present contribution we consider theoretical approaches for modeling of the distribution of electromagnetic field from electron bunches in lattice formed by metallic wires. The analytical description is possible for the case of wires with small radius, the range of validity is checked by numerical simulations. The intensity of radiation will be significantly increased if the electrons in the bunch could radiate coherently. Two possibilities will be discussed: the prebunching of the beam and the self-modulation of the beam due to interaction with radiated field.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK064  
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THPAK065 Application of Transverse-to-Longitudinal Phase-Space-Exchanged Beam Produced from a Nano-Structure Photocathode to a Soft X-Ray Free-Electron Laser cathode, acceleration, quadrupole, laser 3379
 
  • A. Lueangaramwong, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • G. Andonian
    RadiaBeam, Santa Monica, California, USA
  • P. Piot
    Fermilab, Batavia, Illinois, USA
 
  Nano-structured cathodes can form transversely modulated beams which can be subsequently converted to temporally modulated beam via a transverse-to-longitudinal phase space-exchanging beamline. We demonstrate via numerical simulation the generation of transversely modulated beam at the nm scale and investigate the corresponding enhancement in a soft-X-ray SASE free-electron laser. Our study is supported by start-to-end simulation combining WARP, IMPACT-T and GENESIS(FEL process) and focuses on the optimization of the beamline to preserve initial modulation at the nanometer level. We also discuss the scaling of the concept to shorter-wavelengths.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK065  
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THPAK067 Progress Toward a Self-Consistent Beam at the Spallation Neutron Source injection, solenoid, kicker, quadrupole 3382
 
  • J.A. Holmes, S.M. Cousineau, T.V. Gorlov, M.A. Plum
    ORNL, Oak Ridge, Tennessee, USA
  • N.J. Evans
    ORNL RAD, Oak Ridge, Tennessee, USA
 
  Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the US DOE. This research was supported by the DOE Office of Science, Accelerator and Detector Research Program.
We have proposed to inject a self-consistent "rotating" beam into the Spallation Neutron Source (SNS). Self-consistent beam distributions are defined to be ellipsoidal, or elliptical in 2D, distributions that have uniform density and that retain these properties under all linear transformations. We have made much progress since the original proposal. We have demonstrated computationally the feasibility of injecting a rotating beam under realistic physics assumptions. We have optimized the injection scheme with respect to beam loss and to minimum necessary hardware changes. We have also determined how existing SNS beam diagnostic equipment can be used to verify the self-consistency of the injected beam. This paper will report the details of this work as well as the status of plans to carry out the self-consistency experiments.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK067  
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THPAK071 Simulation Study of the Magnetized Electron Beam solenoid, cathode, electron, gun 3395
 
  • S.A.K. Wijethunga, J.R. Delayen, G.A. Krafft
    ODU, Norfolk, Virginia, USA
  • J. F. Benesch, F.E. Hannon, G.A. Krafft, M.A. Mamun, M. Poelker, R. Suleiman
    JLab, Newport News, Virginia, USA
 
  Funding: This work is supported by the Department of Energy, Laboratory Directed Research and Development funding, under contract DE-AC05-06OR23177
Electron cooling of the ion beam plays an important role in electron ion colliders to obtain the required high luminosity. This cooling efficiency can be enhanced by using a magnetized electron beam, where the cooling process occurs inside a solenoid field. This paper compares the predictions of ASTRA and GPT simulations to measurements made using a DC high voltage photogun producing magnetized electron beam, related to beam size and rotation angles as a function of the photogun magnetizing solenoid and other parameters.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK071  
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THPAK072 Generation of Flat Ultra-Low Emittance Beams quadrupole, emittance, cathode, permanent-magnet 3398
 
  • N.R. Bell
    UCLA, Los Angeles, USA
  • L. Phillips
    PBPL, Los Angeles, USA
 
  By placing a cathode in a longitudinal magnetic field generated by a solenoid or permanent magnet, angular-momentum dominated electron beams can be produced. Such beams can be uncoupled using a skew-quadrupole channel to remove the angular momentum and yield flat beams with an ultralow emittance in one of the transverse dimensions. Flat beams have immediate relevance in our pursuit of ultrahigh brightness in two dimensions for dielectric laser accelerator (DLA) or slab beam applications. We are currently investigating the possibility of implementing flat beam generation at the UCLA Pegasus beamline. We utilize particle tracking simulations to optimize the transverse emittance ratio and normalized transverse emittance. Our simulations show emittance ratios of more than 100 and normalized emittances in the <5 nm range in the vertical dimension, matching analytic estimates. In addition to simulation results, experimental plans to implement and test the flat beam transform (FBT) are also discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK072  
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THPAK075 Simulation of Particle Interactions in a High Intensity Radio-Frequency Quadrupole for Molecular Hydrogen Ions rfq, proton, electron, acceleration 3405
 
  • M.J. Easton, H.P. Li, Y.R. Lu, Z. Wang
    PKU, Beijing, People's Republic of China
  • J. Qiang
    LBNL, Berkeley, California, USA
 
  High-intensity deuteron accelerators run the risk of deuteron-deuteron interactions leading to activation. For this reason, in the commissioning phase, a molecular hydrogen ion (H2+) beam is often used as a model for the deuteron beam without the radiation risk. However, composite ions are susceptible to particle interactions that do not affect single ions, such as stripping of electrons and charge exchange. Such interactions affect the beam dynamics results, and may lead to production of secondary particles, which in high-intensity beams may cause damage to the accelerator and reduce the quality of the beam. In order to understand these effects, we have modified the IMPACT-T particle tracking code to include particle interactions during the tracking simulation through a high-intensity continuous-wave (CW) radio-frequency quadrupole (RFQ). This code is also designed to be easily extensible to other interactions, such as collisions or break-up of heavier ions. Preliminary results and possibilities for future development will be discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK075  
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THPAK076 Development and Benchmarking of the IMPACT-T Code rfq, linac, SRF, space-charge 3408
 
  • H.P. Li, M.J. Easton, Y.R. Lu, Z. Wang
    PKU, Beijing, People's Republic of China
  • J. Qiang
    LBNL, Berkeley, California, USA
 
  The multi-particle tracking code IMPACT-T is widely used to calculate the particle motion in high intensity linacs. The code is a self-consistent three-dimensional beam dynamics simulation toolbox that utilizes the particle-in-cell method in the time domain. In the collaboration between PKU and LBNL, an RFQ module was implemented to the IMPACT-T code, which enables simulations of the accelerator front-end. In order to benchmark the newly developed module in the IMPACT-T code, we have simulated the beam transport in Beijing Isotope Separation On-Line (BISOL) high intensity deuteron driver linac. It consists of a 3 MeV RFQ and 40 MeV superconducting HWR linac with five cryomodules. After comparing the simulation results with PARMTEQM, TraceWin and Toutatis, we obtained a very good agreement, which represents the validation of the new code.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK076  
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THPAK078 GPT-CSR: a New Simulation Code for CSR Effects radiation, emittance, electromagnetic-fields, linac 3414
 
  • S.B. van der Geer, M.J. de Loos
    Pulsar Physics, Eindhoven, The Netherlands
  • A.D. Brynes, P.H. Williams
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • I.D. Setija, P.W. Smorenburg
    ASML Netherlands B.V., Veldhoven, The Netherlands
 
  For future applications of high-brightness electron beams, including the design of next generation FEL's, correct simulation of Coherent Synchrotron Radiation (CSR) is essential as it potentially degrades beam quality to unacceptable levels. However, the long interaction lengths compared to the bunch length, numerical cancellation, and difficult 3D retardation conditions make accurate simulation of CSR effects notoriously difficult. To ease the computational burden, CSR codes often make severe simplifications such as an ultra-relativistic bunch travelling on a prescribed reference trajectory. Here we report on a new CSR model implemented in the General Particle Tracer (GPT) code that avoids most of the usual assumptions: It directly evaluates the Liénard'Wiechert potentials based on the stored history of the beam. It makes no assumptions about reference trajectories, and also takes into account the transverse size of the beam. Example results demonstrating normalised emittance growth in the first bunch compressor of FERMI@Elettra are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK078  
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THPAK079 New Algorithms in Zgoubi dipole, proton, polarization, factory 3418
 
  • D.T. Abell
    RadiaSoft LLC, Boulder, Colorado, USA
  • F. Méot
    BNL, Upton, Long Island, New York, USA
 
  Funding: This work was supported in part by the US Department of Energy, Office of Science, Office of Nuclear Physics under Award No. DE-SC0017181.
The particle tracking code Zgoubi*,** is used for a broad array of accelerator design studies, including FFAGs*** and EICs****,*****. In this paper, we describe recent work aimed at improving Zgoubi's speed and flexibility. In particular, we describe a new implementation of the Zgoubi tracking algorithm that requires significantly less memory and arithmetic. And we describe a new algorithm that performs symplectic tracking through field maps. In addition, we describe the current efforts to parallelize Zgoubi.
*https://sourceforge.net/projects/zgoubi/
**F. Méot, FERMILAB-TM-2010, 1997
***F. Lemuet et al., NIM-A, 547:638, 2005
****F. Méot et al., eRHIC/45, 2015
*****F. Lin et al., IPAC17, WEPIK114, 2017
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK079  
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THPAK082 Simulation of Perturbative Effects in IOTA lattice, optics, octupole, emittance 3422
 
  • C.C. Hall, D.L. Bruhwiler, N.M. Cook, J.P. Edelen, S.D. Webb
    RadiaSoft LLC, Boulder, Colorado, USA
 
  The Integrable Optics Test Accelerator (IOTA) is being commissioned at Fermi National Laboratory for study of the concept of nonlinear integrable optics. The use of a special nonlinear magnetic element introduces large tune spread with amplitude while constraining the idealized dynamics by two integrals of motion. The nonlinear element should provide suppression of instabilities through nonlinear decoherence. We examine the case of a bunch injected off-axis and the resulting damping of centroid oscillations from decoherence. A simple model of the damping is described and compared to simulation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK082  
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THPAK083 An s-Based Symplectic Spectral Space Charge Algorithm space-charge, optics, plasma, proton 3425
 
  • N.M. Cook, D.T. Abell, D.L. Bruhwiler, J.P. Edelen, C.C. Hall, S.D. Webb
    RadiaSoft LLC, Boulder, Colorado, USA
 
  Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC001340.
Traditional finite-difference particle-in-cell methods for modeling self-consistent space charge introduce non-Hamiltonian effects that make long-term tracking in storage rings unreliable. Foremost of these is so-called grid heating. Particularly for studies where the Hamiltonian invariants are critical for understanding the beam dynamics, such as nonlinear integrable optics, these spurious effects make interpreting simulation results difficult. To remedy this, we present a symplectic spectral space charge algorithm that is free of non-Hamiltonian numerical effects and, therefore, suitable for long-term tracking studies. We present initial results demonstrating the implementation of the algorithm, using a spectral representation of the fields and macro particles to preserve Hamiltonian structures. We then discuss applications to the Integrable Optics Test Accelerator (IOTA), currently under construction at Fermilab.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK083  
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THPAK085 3D Space Charge in Bmad space-charge, software, lattice, brightness 3428
 
  • C.E. Mayes
    SLAC, Menlo Park, California, USA
  • R.D. Ryne
    LBNL, Berkeley, California, USA
  • D. Sagan
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  We present a parallel fast Fourier transform based 3D space charge software library based on integrated Green functions. The library is open-source, and has been structured to easily be used by existing beam dynamics codes. We demonstrate this by incorporating it with the Bmad toolkit for charged particle simulation, and compare with analytical formulas and well-established space charge codes.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK085  
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THPAK087 Software-Computing System for Numerical Modelling of Beam Dynamics in Accelerators software, experiment, controls, interface 3435
 
  • E. Krushinevskii, E. Sboeva
    Saint Petersburg State University, Saint Petersburg, Russia
  • S.N. Andrianov, A.N. Ivanov, N.V. Kulabukhova
    St. Petersburg State University, St. Petersburg, Russia
 
  The spectrum of software packages for the physics of charged particles beams is extremely wide. From most popular and effective systems can be allocated such programs as COSY Infinity, MAD X, MARYLIE, TRANSPORT. Heterogeneous individual formats of input and output data, the lack of a common and user-friendly interface and the narrow specialization of these programs poses a number of challenges for the modern researchers. It significantly reduces the effectiveness and quality of corresponding computational experiments. In this article we present a universal tool for automation and acceleration of computing experiments. The authors consider a method for developing the concept and prototype of a corresponding software package that would combine the advantages of existing (non-commercial) systems. This software will be able to unify the input and output data format for certain programs, visualize the information in various ways, provide reference and training information for "beginners". The results obtained within the developed framework will be a significant contribution both to the development of numerical and symbolical methods for solving evolution nonlinear equations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK087  
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THPAK088 Matrix Representation of Lie Transform in TensorFlow network, storage-ring, GPU, linear-dynamics 3438
 
  • A.N. Ivanov, S.N. Andrianov, N.V. Kulabukhova, A.A. Sholokhova
    St. Petersburg State University, St. Petersburg, Russia
  • E. Krushinevskii, E. Sboeva
    Saint Petersburg State University, Saint Petersburg, Russia
 
  In the article, we propose an implementation of the matrix representation of Lie transform using TensorFlow as a computational engine. TensorFlow allows easy description of deep neural networks and provides automatic code execution on both single CPU/GPU and cluster architectures. In this research, we demonstrate the connection of the matrix Lie transform with polynomial neural networks. The architecture of the neural network is described and realized in code. In terms of beam dynamics, the proposed technique provides a tool for both simulation and analysis of experimental results using modern machine learning techniques. As a simulation technique one operates with a nonlinear map up to the necessary order of nonlinearity. On the other hand, one can utilize TensorFlow engine to run map optimization and system identification problems.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK088  
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THPAK091 Design of the New Proton Synchrotron Booster Absorber Scraper (PSBAS) in the Framework of the Large Hadron Collider Injection Upgrade (LIU) Project impedance, vacuum, proton, booster 3444
 
  • L. Teofili, M. Migliorati
    Sapienza University of Rome, Rome, Italy
  • J.A. Briz Monago, M. Calviani, N. Chritin, J.J. Esala, S.S. Gilardoni, I. Lamas Garcia, J. Maestre, T. Polzin, T.L. Rijoff
    CERN, Geneva, Switzerland
  • T.L. Rijoff
    TU Darmstadt, Darmstadt, Germany
 
  The Large Hadron Collider (LHC) Injector Upgrade (LIU)Project at CERN calls for increasing beam intensity for the LHC accelerator chain. Some machine components will not survive the new beam characteristics and need to be rebuilt for the new challenging scenario. This is particularly true for beam intercepting devices (BIDs) such as dumps, collimators, and absorber/scrapers, which are directly exposed to beam impacts. In this context, this work summarizes conceptual design studies on the new Proton Synchrotron Booster (PSB) Absorber/Scraper (PSBAS), a device aimed at cleaning the beam halo at the very early stage of the PSB acceleration. This paper outlines the steps performed to fulfil the component design requirements. It discusses thermo-mechanical effects as a consequence of the beam-matter collisions, simulated with the FLUKA Monte Carlo code and ANSYS finite element software; and the impedance minimization study performed to prevent beam instabilities and to reduce RF-heating on the device.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK091  
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THPAK092 Analysis on the Mechanical Effects Induced by Beam Impedance Heating on the HL-LHC Target Dump Injection Segmented (TDIS) Absorber impedance, injection, HOM, shielding 3448
 
  • L. Teofili, M. Migliorati
    Sapienza University of Rome, Rome, Italy
  • M. Calviani, D. Carbajo Perez, S.S. Gilardoni, F. Giordano, I. Lamas Garcia, G. Mazzacano, A. Perillo-Marcone
    CERN, Geneva, Switzerland
 
  The High Luminosity Large Hadron Collider (HL-LHC) Project at CERN calls for increasing beam brightness and intensity. In such a scenario, critical accelerator devices need to be redesigned and rebuilt. Impedance is among the design drivers, since its thermo-mechanical effects could lead to premature device failures. In this context, the current work reports the results of a multiphysics study to assess the electromagnetic and thermo-mechanical behaviour of the Target Dump Injection Segmented (TDIS). It first discusses the outcomes of the impedance analysis performed to characterise the resistive wall and the high order resonant modes (HOMs) trapped in the TDIS structures. Then, their RF-heating effects and the related temperature distribution are considered. Finally, mechanical stresses induced by thermal gradients are studied in order to give a final validation on the design quality.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK092  
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THPAK093 A Multi-Physics Approach to Simulate the RF Heating 3D Power Map Induced by the Proton Beam in a Beam Intercepting Device impedance, HOM, injection, proton 3452
 
  • L. Teofili, M. Migliorati
    Sapienza University of Rome, Rome, Italy
  • D. Carbajo Perez, F. Giordano, I. Lamas Garcia, G. Mazzacano
    CERN, Geneva, Switzerland
 
  The project High Luminosity Large Hadron Collider (HL- LHC) calls for a streaking beam intensity and brightness in the LHC machine. In such a scenario, beam-environment electromagnetic interactions are a crucial topic: they could lead to uneven power deposition in machine equipment. The resulting irregular temperature distribution would gener- ates local thermal gradients, this would create mechanical stresses which could lead to cracks and premature failure of accelerator devices. This work presents a method to study this phenomenon by means of coupled electro-thermo- mechanical simulations. Further, examples of applications on real HL-LHC devices is also discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK093  
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THPAK100 Design and Fabrication of a Combined Function Magnet Prototype for Siam Photon Source quadrupole, dipole, multipole, synchrotron 3466
 
  • P. Sunwong, B. Boonwanna, S. Chaichuay, P. Klysubun, A. Kwankasem, C.P. Preecha, V. Sooksrimuang
    SLRI, Nakhon Ratchasima, Thailand
 
  A prototype of combined function magnet has been developed for a new facility of Siam Photon Source (SPS). The magnet is a combined dipole and quadrupole with the required dipole field and quadrupole gradient of 0.6 T and 30 T/m, respectively. The high field gradient is attained from an offset quadrupole design pioneered by the European Synchrotron Radiation Facility (ESRF). The prototype magnet is fabricated and tested in-house. Magnetic field quality is characterized by the field homogeneity in the central field region and multipole components of the magnetic field. Calculated results show that the gradient deviation and the normalized multipole error are less than 0.01 within the good field region of ±8 mm. Preliminary measurements show a good agreement with the calculation, although further measurements are required to verify the results and the multipole error of magnetic field.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK100  
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THPAK103 Pragmatic Method of Deducing a Wake Function for a General 3D Structure impedance, wakefield, vacuum, resonance 3469
 
  • G. Skripka
    CERN, Geneva, Switzerland
  • R. Nagaoka
    SOLEIL, Gif-sur-Yvette, France
 
  A key quantity in simulating collective beam instabilities is the wake potential of a bunch of particles whose charge distribution is continuously evolving in time. However, obtaining such wake potential is only possible if a wake excited by a single particle in the surrounding environment is known. A practical self-consistent approach was developed to obtain an effective wake function from a numerical wake potential computed for a finite length bunch. The wake potential is processed to a numerical impedance which is decomposed into a set of well-known analytical wake functions. The decomposed impedance is then transformed back into time domain and, thus, converted into an effective wake function which is by nature physical and most consistent with the numerical wake potential. Though the method is limited by the initial numerical impedance data and the choice of impedance decomposition, the retrieved wake function can be used in instability simulations with a bunch whose length is comparable to that used in the electromagnetic field solver. We show that the method can be applied to a general 3D structure, which allows finding effective wake functions of realistic vacuum chambers.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK103  
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THPAK109 Improved Simulation for Centre Region of TRIUMF 500 MeV Cyclotron with Space Charge space-charge, TRIUMF, focusing, cyclotron 3489
 
  • Y.-N. Rao, R.A. Baartman, T. Planche
    TRIUMF, Vancouver, Canada
 
  Funding: TRIUMF receives federal funding via a contribution agreement through the National Research Council of Canada
The TRIUMF 500 MeV cyclotron delivered routinely a total current up to 200 µA protons for 15 years till 2001. Since 2002, developments towards 300 µA total extraction became compelling because of the ISAC expansion. To meet future requirements (for addition of a new beam-line), a total extraction of 310 − 450 µA shall be envisioned. With such an increase of beam current, the space charge effect becomes a major concern in the centre region, as it limits the maximum amount of beam current achievable out of the machine. Therefore, numerical simulation on beam orbits with the space charge force has has been initiated, starting from the injection gap. This study is focused on the beam bunches which are very long compared with transverse size (because TRIUMF extraction is by stripping of H-minus and separated turns are not required). In order to achieve an improved understanding of the space charge effect, we worked to validate the simulations performed without and with the space charge force, using realistic centre region geometry. Our goal is to work out the space charge limits and their dependence upon the bunchers, rf voltage, and matching. In this paper we present our recent progress in this study.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK109  
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THPAK110 Correction of νrz=1 Resonance in TRIUMF Cyclotron resonance, coupling, cyclotron, TRIUMF 3492
 
  • Y.-N. Rao, R.A. Baartman, T. Planche
    TRIUMF, Vancouver, Canada
 
  Funding: TRIUMF receives federal funding via a contribution agreement through the National Research Council of Canada
The second order linear coupling resonance nur-nuz=1 is driven by an asymmetry in the median plane of the cyclotron due to presence of the first harmonic in Br component. In TRIUMF cyclotron, this resonance is encountered at about 166 MeV and 291 MeV, where nur=1.2 and nuz=0.2. When the beam is off-centered radially to pass through this resonance, the radial oscillation gets converted into vertical oscillation, which can cause beam loss to occur, though these loss modes do not reduce the machine transmission under normal operation. In this paper, we present the results of simulations and measurements that we have performed to correct this resonance by using the existing harmonic coils.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK110  
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THPAK111 Envelope Calculations on the Ion Beam Injection and Extraction of CANREB EBIS electron, injection, extraction, TRIUMF 3496
 
  • M.H. Pereira-Wilson
    UW/Physics, Waterloo, Ontario, Canada
  • R.A. Baartman, S. Saminathan
    TRIUMF, Vancouver, Canada
 
  An electron beam ion source (EBIS) is being developed as a charge state breeder for the production of highly charged ions in the CANREB (CANadian Rare isotope facility with Electron Beam ion source) project at TRIUMF. The multiple tunable electrodes of the EBIS, coupled with the necessity of directing both an electron beam and an ion beam of varying charge, impose a challenging task for the optimization of the beam optics. With this in mind, beam envelope simulations have been performed to determine the acceptance of the EBIS and the emittance of the extracted ion beam. The electric field of the different EBIS electrodes were modelled using finite element analysis software and the envelope simulations were executed using beam envelope code TRANSOPTR. Preliminary results show envelope calculation as a viable candidate for tuning the injection and extraction optics of the EBIS.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK111  
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THPAK112 Toward an End-to-End Model for ISAC-I Accelerators ISAC, rfq, linac, TRIUMF 3500
 
  • O. Shelbaya, O.K. Kester
    TRIUMF, Vancouver, Canada
 
  Diurnal-like transmission variations in the ISAC-I warm accelerator system necessitates periodic retuning by operators. While beam loss points are well known, re-tuning nevertheless results in additional downtime and reduced count rates at experiments. This has motivated the development of an end-to-end simulation of the ISAC-I linear accelerator (linac) system to understand and characterize the nature of transmission instabilities spanning several hours to days.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK112  
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THPAK116 Modeling Surface Roughness Effects and Emission Properties of Bulk and Layered Metallic Photocathode electron, emittance, experiment, cathode 3515
 
  • D.A. Dimitrov, G.I. Bell
    Tech-X, Boulder, Colorado, USA
  • I. Ben-Zvi, J. Smedley
    BNL, Upton, Long Island, New York, USA
  • J. Feng, S.S. Karkare, H.A. Padmore
    LBNL, Berkeley, California, USA
 
  Funding: This work was supported by the Office of Science, Office of Basic Energy Sciences of the U.S. Department of Energy under Contract Nos. DE-SC0013190, DE-AC02-05CH11231, and KC0407-ALSJNT-I0013.
The thermal limit of the intrinsic emittance of photocathodes represents an important property to measure experimentally and to understand theoretically. Detailed measurements of intrinsic emittance have become possible in momentatron experiments. Moreover, recent developments in material design have allowed growing photoemissive layers with controlled surface roughness. Although analytical formulations of the effects of roughness have been developed, a full theoretical model and experimental verification are lacking. We aim to bridge this gap by developing realistic models for different materials in the three-dimensional VSim particle-in-cell code. We have recently implemented modeling of electron photo-excitation, transport, and emission from photoemissive layers grown on a substrate. We report results from simulations with these models on electron emission from antimony and gold. We consider effects due to density of states, photoemissive layer thickness, surface roughness and how they affect the spectral response of quantum yield and intrinsic emittance.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK116  
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THPAK117 Space Charge Limitations for Bunch Compression in Synchrotrons space-charge, resonance, emittance, synchrotron 3518
 
  • Y.S. Yuan, O. Boine-Frankenheim
    TEMF, TU Darmstadt, Darmstadt, Germany
  • G. Franchetti, I. Hofmann
    GSI, Darmstadt, Germany
 
  Bunch compression achieved via a fast bunch rotation in longitudinal phase space is a well-accepted scheme to generate short, intense ion bunches for various applications. During bunch compression, coherent beam instabilities and incoherent single particle resonances can occur because of increasing space charge, resulting in an important limitation for the bunch intensity. We present an analysis of the relevant space charge driven beam instability and resonance phenomena during bunch compression. A coupled longitudinal-transverse envelope approach is compared with Particle-In-Cell (PIC) simulations. Two distinct cases of crossing are discussed and applied to the GSI SIS18 heavy-ion synchrotron. It is shown that during bunch compression, the 90° condition of phase advance is associated with a fourth order single particle resonance and the 120° condition with the recently discovered dispersion-induced instability. The agreement between the envelope and PIC results indicates that the stop band is defined by the 120° dispersion instability, which should be avoided during bunch compression.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK117  
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THPAK127 Toroidal Merger Simulations for the JLEIC Bunched Beam Electron Cooler Ring electron, emittance, solenoid, space-charge 3540
 
  • A.V. Sy
    JLab, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The bunched beam electron cooler ring for the Jefferson Lab Electron-Ion Collider (JLEIC) requires a merger system to transport magnetized electron beams of two different energies to the same energy recovery linac (ERL) beamline. The system is especially challenging compared to existing mergers for ERL or hadron cooling applications (as at COSY) due to the small separation in energy between the two beams; for the JLEIC bunched beam cooler, the two beam energies may only differ by a factor of 4. An additional complication is the use of a magnetized beam. A toroidal merger system is studied using G4Beamline/GEANT4. Preservation of the quality of the low energy beam from the injector is especially vital for efficient cooling performance and compatibility with the ERL. Effects of the toroidal system on transverse and longitudinal emittances of the magnetized beams, as well as space charge effects, are presented and discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK127  
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THPAK137 Beam-Based Sextupolar Nonlinearity Mapping in CESR sextupole, experiment, resonance, lattice 3565
 
  • L. Gupta, Y.K. Kim
    University of Chicago, Chicago, Illinois, USA
  • S. Baturin
    Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA
  • M.P. Ehrlichman, J.M. Maxson, R.E. Meller, D. L. Rubin, D. Sagan, J.P. Shanks
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Funding: Work supported by the U.S. National Science Foundation under Award No. PHY-1549132, the Center for Bright Beams
In order to maintain beam quality during transport through a storage ring, sextupole magnets are used to make chromatic corrections, but necessarily introduce deleterious effects such as nonlinear resonances and reduced dynamic aperture. Implementing intricate sextupole distributions to mitigate these effects will rely on precision beam-based measurement of the applied sextupole distribution. In this work, we generalize previous sextupole mapping techniques by using resonant phase-locked excitation of the beam at the Cornell Electron Storage Ring (CESR), which accounts for variations in the normal mode tunes on a turn by turn basis. The methods presented here are applied to simulation and actual turn by turn data in CESR for both simplified and realistic sextupole distributions.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK137  
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THPAK138 Development of Efficient Tree-Based Computation Methods for the Simulation of Beam Dynamics in Sparsely Populated Phase Spaces electron, FEL, bunching, HOM 3569
 
  • Ph. Amstutz
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • M. Vogt
    DESY, Hamburg, Germany
 
  Collective instabilities pose a major threat to the quality of the high brightness electron beams needed for the operation of a free electron laser. Multi-stage bunch compression schemes have been identified as a possible source of such an instability. The dispersive sections in these compressors translate energy inhomogeneities within the bunch into longitudinal charge density inhomogeneities. In conjunction with a collective force driving locally density-dependent energy modulations this leads to intricate longitudinal beam dynamics. As a consequence of the thin shape those bunches form in the longitudinal phase space, efficient simulation of such systems is not straight forward. At high resolutions, the numerical representation of the phase space density on a uniform grid is too wasteful, due to the large unpopulated phase space regions. In this contribution we present advances made in the development of a simulation code that addresses the problem of sparsely populated phase spaces by means of quadtree domain decomposition. A focus lies on the explanation of the underlying tree data structure.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK138  
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THPAK140 Pyroelectric Detection of Coherent Radiation on the CLARA Phase 1 Beamline radiation, electron, dipole, detector 3577
 
  • B.S. Kyle
    University of Manchester, Manchester, United Kingdom
  • R.B. Appleby, T.H. Pacey
    UMAN, Manchester, United Kingdom
  • P.H. Williams
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • J. Wolfenden
    The University of Liverpool, Liverpool, United Kingdom
 
  The impacts of coherent synchrotron radiation (CSR) and space charge in the bunch compressor section of the CLARA Free Electron Laser (FEL) are expected to be significant, given the relatively high charge and short bunch lengths expected. The General Particle Tracer (GPT) code allows for the modelling of these effects in tandem, presenting an opportunity to more reliably estimate their effects on the CLARA beam. To provide confidence in future studies using GPT, a benchmarking study on the CLARA Phase 1 beamline is presented alongside relevant simulations. This study will make use of pyroelectric detectors to measure the emitted coherent power of the CLARA beam as it passes through a dispersive section whilst varying the chirp imparted on the bunches longitudinal phase space (LPS). Simulations presented demonstrate the viability of such a study, with energies between ∼ 10-100 nJ per pulse expected to be incident upon the detector face.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK140  
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THPAK141 Initial Tests of Nonlinear Quasi-Integrable Optics at the University of Maryland Electron Ring octupole, electron, optics, experiment 3581
 
  • H. Baumgartner, B.L. Beaudoin, I. Haber, T.W. Koeth, D.B. Matthew, K.J. Ruisard
    UMD, College Park, Maryland, USA
 
  Funding: Funding for this project and travel is provided by DOE-HEP, NSF GRFP and NSF Accelerator Science Program.
An octupole channel has been inserted into the University of Maryland Electron Ring (UMER), in order to investigate the mitigation of destructive resonances as a novel approach in high-intensity beam transport. The individual octupole magnets have been characterized using our in-house 3-dimensional magnet mapping stage, with a measured gradient of 51.6 ± 1.5 T/m3/A. A single section (20°) of an 18-cell FODO lattice has been replaced by a longitudinally-varying octupole channel constructed from seven flexible printed circuits (PCBs). We present the design of the channel and preliminary beam based measurements on the ring.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK141  
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THPAL004 Research and Development of RF System for SC200 Cyclotron cavity, LLRF, cyclotron, acceleration 3616
 
  • G. Chen, C. Chao, G. Liu, X.Y. Long, Z. Peng, Y. Song, Y.S. Wang, C.S. Wei, M. Xu, Q. Yang, X. Zhang, Y. Zhao
    ASIPP, Hefei, People's Republic of China
  • L. Calabretta, A.C. Caruso
    INFN/LNS, Catania, Italy
  • O. Karamyshev, G.A. Karamysheva, N.A. Morozov, E. Samsonov, G. Shirkov
    JINR, Dubna, Moscow Region, Russia
 
  A 200MeV compact isochronous superconducting cyclotron, named SC200, for proton therapy is under development by collaboration of ASIPP (Hefei, China) and JINR (Dubna, Russia). The radio frequency (RF) system as one of most significant subsystems in cyclotron consists of acceleration cavity, low level RF, RF source and transmission network. SC200 has two cavities connected in the centre, which are operated at 91.5 MHz with second harmonic. To meet the required acceleration voltage, the cavities have been carefully designed with comprised choices between several aspects, such as Q factor, mechanic stability and so on. The low-level RF (LLRF) system has been implemented by using the FPGA to achieve the significant accelerating voltage with an amplitude stability of <0.2% and a phase stability of < 0.1 degree. The cavity and LLRF system have been tested outside of cyclotron, the results will be presented. For future, the commissioning of whole RF system will be started after the assembly of SC200 at the end of 2019.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL004  
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THPAL017 From design to alignment of ThomX quadrupoles quadrupole, multipole, HOM, alignment 3660
 
  • C. Vallerand, R. Marie, H. Monard
    LAL, Orsay, France
  • J. Campmany, J. Marcos, V. Massana
    ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
  • J. Chavanne, G. Le Bec
    ESRF, Grenoble, France
  • M.-E. Couprie, A. Lestrade, A. Loulergue, F. Marteau, M. Ros
    SOLEIL, Gif-sur-Yvette, France
 
  Quadrupoles for Thomx Facility have been carefully designed and measured due to high constraints of the storage ring. The need of a compact accelerator, 70 m2 on floor, as well as a beam life time of 20 ms, led to the following requirements for the quadrupole : a gradient of 5 T/m with 20.5 mm radius bore, harmonic content better than few 1.10-3 at the reference radius of 18 mm, no cross-talk with sextupole placed within 5 cm and a precision of the magnetic axis of 100 µm and the roll angle of 300 µrad for measurements and alignment. Total of 41 quadrupoles have been built and all measured by a rotating coil at ALBA and SOLEIL, providing multipole components, transfer function and magnetic center. Cross-check measurements have also been carried out with a versatile stretched wire from ESRF at LAL. This paper mainly describes results of simulations with OPERA and RADIA and provides the results of measurements with these three benches. These results will be compared and highlighted important points for the alignment and installation of quadrupoles in an accelerator.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL017  
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THPAL018 DQW HOM Coupler Design for the HL-LHC HOM, impedance, cavity, GUI 3663
 
  • J.A. Mitchell
    Lancaster University, Lancaster, United Kingdom
  • G. Burt
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • R. Calaga
    CERN, Geneva, Switzerland
  • S. Verdú-Andrés, B. P. Xiao
    BNL, Upton, Long Island, New York, USA
 
  HOMs in the DQW crab cavity can produce large heat loads and beam instabilities as a result of the high current HL-LHC beams. The DQW crab cavity has on-cavity, coaxial HOM couplers to damp the HOMs whilst providing a stop-band response to the fundamental mode. Manufacturing experience and further simulations give rise to a set of desirable coupler improvements. This paper will assess the performance of the current HOM coupler design, present operational improvements and propose an evolved design for HL-LHC.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL018  
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THPAL020 Design of Asymmetric Quadrupole Gradient Bending R&D Magnet for the Advanced Light Source Upgrade (ALS-U) dipole, quadrupole, multipole, lattice 3667
 
  • J.-Y. Jung, M. Leitner, N. Li, E.R. San Mateo, C. Steier, C.A. Swenson, M. Venturini
    LBNL, Berkeley, California, USA
 
  Lawrence Bekerley National Laboratory (LBNL) is en-gaged in the development of magnets for the upgrade of the ALS synchrotron (ALS-U) [1]. The proposed ALS-U lattice is a 9-bend achromat reproducing the existing 12-fold symmetric ALS foot print. The ALS-U lattice requires strong focusing elements and the dipole magnet requires high gradient larger than 46 T/m. This paper presents the detailed design of the R&D dipoles under construction.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL020  
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THPAL023 Assessing the Continued Suitability of an Existing Water System for an Accelerator Upgrade operation, neutron, interface, HOM 3673
 
  • W.C. Barkley, C.E. Buechler, E.N. Pulliam
    LANL, Los Alamos, New Mexico, USA
 
  This paper assesses the continued suitability of an existing Water Cooling System (WCS) for cooling intermediate and high-power RF power amplifiers at the Los Alamos Neutron Science Center (LANSCE). At LANSCE, the high-power and intermediate power amplifiers installed in the 70s were at end-of-life with obsolete parts and no suitable replacements available to extend their life. The LANSCE Refurbishment Project was initiated (now complete) to replace these amplifiers and to utilize already existing WCSs. Two existing WCSs were repurposed and one new WCS was designed and installed. Unscheduled, intermittent water system trips on one of the WCSs has prompted the engineering group to drill down into the original decision, build a flow model and assess some of the legacy components' suitability to solve the problem. This paper discusses the general approach, troubleshooting and solution recommendations to be made for resolution of the intermittent issues.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL023  
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THPAL024 A Simple Variable Focus Lens for Field Emitter Cathodes cathode, emittance, focusing, laser 3677
 
  • R.L. Fleming, H.L. Andrews, K. Bishofberger, D. Kim, J.W. Lewellen, K.E. Nichols, D.Y. Shchegolkov, E.I. Simakov
    LANL, Los Alamos, New Mexico, USA
 
  Funding: Los Alamos National Laboratory LDRD Program
We present the design for a simple, variable-focus solenoidal lens with integrated emittance filtering. The design was developed as a first-iteration injection optics solution for transport of a beam from a field-emitter cathode into a dielectric laser accelerator structure. The design is easy to fabricate and, while based on permanent magnets, can readily be modified to allow for remote control of the focal length. The emittance is controlled via selection of collimating irises. The focal length can be changed by altering the spacing between two permanent ring magnets. Results from fabrication and initial testing will be presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL024  
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THPAL033 Measurement of the Internal Dark Current in a High Gradient Accelerator Structure at 17 GHz multipactoring, acceleration, electron, experiment 3705
 
  • H. Xu, M.A. Shapiro, R.J. Temkin
    MIT/PSFC, Cambridge, Massachusetts, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of High Energy Physics, under Grant No. DE-SC0015566
We report a study of internal dark current generation by multipactor inside a 17 GHz single cell standing wave disk-loaded waveguide accelerator structure. The multipactor takes place on the side wall of the central cell, driven by the local rf electric and magnetic fields. Theory indicates that a resonant multipactor mode with two rf cycles can be excited near 45 MV/m gradient and a single rf cycle multipactor mode near 60 MV/m. The accelerator structure had two thin slits opened on the side wall of the central cell to directly extract and measure the internal dark current. The dark current was measured as a function of the gradient up to a gradient of 70 MV/m. The experimental results agreed well with theory, showing the two predicted multipactor modes. To further study the effect of the central cell side wall surface properties on the structure performance, we prepared and tested a second structure with the central cell side wall coated with a layer of diamond-like carbon. The comparison of the results showed that the coating reduced the internal dark current and thus enhanced the structure performance considerably.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL033  
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THPAL041 Power Coupler Design for the LUCRECE Project cavity, SRF, coupling, linac 3732
 
  • H. Guler, D. Auguste, J. Bonis, O. Bouras, M. El Khaldi, W. Kaabi, P. Lepercq
    LAL, Orsay, France
 
  The LUCRECE project aims at developing an elementary RF system (cavity, power source, LLRF and controls) suitable for continuous (CW) operation at 1.3 GHz. This effort is made in the framework of the advanced and compact FEL project LUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation), using superconducting linac technology for high repetition rate and multi-user operation (www.lunex5.com). In this context, based on its large experience on coupler design and RF conditioning, LAL Laboratory is in charge of the design and the fabrication of RF couplers that could operate at up to 15-20 kW in CW mode. For this purpose, geometry based on CORNELL 65kW CW couplers will me modified to fulfil the LCLS2 type cavity with the high necessary coupling level. Electromagnetic simulations and optimisation and associated thermal heating will be discussed. Methods to decrease the thermal impact, and strategy for RF conditioning will be considered.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL041  
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THPAL043 Dipole Magnets for the Technological Electron Accelerators dipole, electron, permanent-magnet, radiation 3739
 
  • I.S. Guk, O.M. Bovda, V.O. Bovda, A.N. Dovbnya, S.G. Kononenko, V.N. Ljashchenko, A. Mytsykov, L.V. Onishchenko, A.Y. Zelinsky
    NSC/KIPT, Kharkov, Ukraine
 
  Permanent magnets made of rare earth elements alloys allow to develop compact dipole magnets for the applied electron accelerator. These devices can be used for the beam trajectory bending as well as for the beam characteristics measurements. For NSC KIPT linear accelerator «EPOS» a dipole magnet on the base of Nd-Fe-B alloy has been designed and developed. The magnet provides 90 degrees bend of 23 MeV electron beam. The design value of magnetic field at the beam design trajectory is 0.5 Т. The magnet effective length is 242 mm. The magnet temperature can be changed with thermos-stabilization system. For NSC KIPT 10 MeV LU-10 applied accelerator a dipole magnet of Sm2Co17 alloy has been manufactured. The maximum magnet field of the magnet is 0.3 Т. The magnet layout allows easy magnet assembling at the accelerator chamber. The magnet is used for the beam energy measurement and accelerator beam energy turning. After energy turning the magnet should be removed from the accelerator lattice.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL043  
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THPAL045 Determination of the Electron Bunch Length With Third Harmonic Cavity for the Taiwan Photon Source cavity, operation, SRF, electron 3745
 
  • Z.K. Liu, F.Y. Chang, L.-H. Chang, M.H. Chang, S.W. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, C.H. Lo, Ch. Wang, M.-S. Yeh, T.-C. Yu
    NSRRC, Hsinchu, Taiwan
 
  The Taiwan Photon Source (TPS) is a modern 3 GeV low emittance light source with RMS bunch lengths of about 3 mm at a beam current of 500 mA and operating gap voltage of 3.2 MV. With a higher harmonic cavity, we could increase the Touschek lifetime and lower the heat load of in-vacuum undulators by lengthening the bunch lengths. Preliminary studies show that for full and uni-form fill patterns, the bunch lengths could be increased by a factor of four. However, this calculation ignores phase transient effects and may overestimate the effect of harmonic cavities. A multi-bunch, multi-particle tracking method has been developed to determine the bunch lengths for non-uniform fill patterns, which also takes phase transient effects into account and the expected maximum bunch lengthening factor for different TPS operation conditions are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL045  
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THPAL049 Power Supply Decoupling Design controls, power-supply, coupling, electron 3751
 
  • Y.T. Li, F.Y. Chang
    NSRRC, Hsinchu, Taiwan
 
  After an actual operation of the phase-shifted magnet's power supply was conducted, it was found that the currents in the two modules of magnets would be coupled each other. In order to solve this mutual coupling current, a decoupling controller is designed. From the experiment results indicate that it does not only solve the issue of coupling current but also shorten the rising time of the power supply current. This helps to increase the power supply bandwidth.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL049  
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THPAL052 Finite Element Analysis on Beam-Induced Heat Load in in-Vacuum Undulators with a Small Magnet Gap undulator, synchrotron, vacuum, synchrotron-radiation 3760
 
  • J.-C. Chang, Y.-H. Liu
    NSRRC, Hsinchu, Taiwan
 
  In-vacuum undulators with a small gap and short period have been applied in synchrotron accelerators for hard X-rays users for years. However, beam-induced heat load resulted from synchrotron radiation or the image current will not only degrade the performance of undulator but damage the magnet foil. It is difficult to quantitatively study heat transfer phenomenon of the magnet foil through physical experiment. In this study, finite element analysis was applied to study the effect of beam-induced heat load on an in-vacuum undulator.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL052  
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THPAL055 A Novel High Step-down DC-DC Converter with Isolated Transformer and Switched Capacitor Techniques for Corrector Magnet Bulk Power in Taiwan Photon Source ISOL, power-supply, high-voltage, operation 3769
 
  • Y.S. Wong, K.-B. Liu
    NSRRC, Hsinchu, Taiwan
  • J.F. Chen
    NCKU, Tainan city, Taiwan
 
  In this study, a high step down DC-DC converter was successfully integrated using switch capacitor and isolated transformer techniques. Switching capacitor techniques has use of capacitor parallel energy storage and series release of the way to improve the voltage conversion ratio. In addition, the output voltage ripple will be smaller due to the input current being continuous, the inductance is an element to prevent a surge current. The isolated transformer techniques has use of inductor coil turns ratio to achieve high conversion ratio. But, the leakage inductor and parasitic capacitance on the power switch will be resonant to generate a surge voltage spike when the power switch S is turned off. So that, additional a passive clamp circuit, energy of leakage inductor will be recycled to clamp capacitor and voltage stress of main power switch. The power switch S can be selected a lower Rds(on) components and reduce the conduction losses to improve power converter efficiency. Step down mode operation principle and steady-state analysis were discussed in this paper. Finally, simulation and prototype circuit is implemented in this laboratory to verify the performance, the step-down DC-DC converter is input voltage 400-V, output voltage 48-V and output power 960-W.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL055  
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THPAL059 TEMPERATURE ISSUES OF THE TPS BPMS impedance, wakefield, site, resonance 3781
 
  • Y.T. Huang, C.-C. Chang, C.M. Cheng, P.J. Chou, Y.C. Yang
    NSRRC, Hsinchu, Taiwan
 
  Since the TPS is capable to operate at higher currents, long-term 400mA conditioning runs were conducted. Current-dependent temperature data of BPMs were collected and analysed for both, aluminium and stainless steel BPM chambers. To better understand beam coupling effects in different types of TPS BPMs, electromagnetic and thermal simulation models were established. In this paper, we discuss associated results of such studies.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL059  
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THPAL060 Advanced Modeling of Klystrons by the Tesla-Family of Large-Signal Codes klystron, cavity, impedance, experiment 3785
 
  • I.A. Chernyavskiy, D.K. Abe, B. Levush, A.N. Vlasov
    NRL, Washington, DC, USA
  • T.M. Antonsen
    UMD, College Park, Maryland, USA
  • T.M. Antonsen
    Leidos Corp, Billerica, MA, USA
  • J. Rodgers
    Naval Research Laboratory (NRL), Washington, USA
 
  Funding: US Office of the Naval Research
Klystrons and IOTs are widely used or proposed to be used in accelerators as high-power RF sources. Development and optimization of klystron and IOT designs is aided by the use of different simulation tools, including highly efficient large-signal codes. We present an overview of the advances in the code development and modeling using Naval Research Laboratory (NRL) set of TESLA-family of large-signal codes, suitable for the modeling of single-beam and multiple beam klystrons and IOTs. Original 2D large-signal algorithm of the code TESLA* was developed for the modeling of klystrons based on (relatively) high Q resonators and is applicable to the multiple-beam devices in an approximation of identical beams/beam-tunnels. Parallel extension of TESLA algorithm (code TESLA-MB**) enabled an accurate, quasi-3D modeling of multiple-beam devices with non-identical beams/beam-tunnels. Recently developed more general TESLA-Z algorithm*** is based on the impedance matrix approach and enabled geometry-driven large-signal modeling. Examples of applications of TESLA-family of codes to the modeling of advanced single-beam and multiple-beam klystrons (and IOTs) will be presented.
*A.N. Vlasov, et al,IEEE TPS, v.30(3), 1277-1291, June 2002
**I.A. Chernyavskiy, et al.,IEEE TPS, v.36(3), 670-681, June 2008
***I.A. Chernyavskiy, et al.,IEEE TED, v.64(2), 536-542, Feb 2017
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL060  
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THPAL061 Simulation of Pulsed Temperature Rise in Cryogenic Copper RF Cavity Achieving a Very High Accelerating Field cavity, accelerating-gradient, coupling, cryogenics 3788
 
  • T. Tanaka, K. Hayakawa, Y. Hayakawa, K. Nogami, T. Sakai, Y. Sumitomo
    LEBRA, Funabashi, Japan
 
  A cryogenic C-band photocathode RF electron gun cavity has been studied at Nihon University LEBRA in cooperation with KEK. The RF properties of a cold model measured at 20 K have shown good agreement with those expected from computer simulations using the cavity surface resistance predicted by the theory of the anomalous skin effect. Recent studies on the vacuum RF breakdown at high electric fields suggest that the temperature in the cavity surface during the high power RF pulse has a significant effect on the behavior of the breakdown rate. In order to investigate the breakdown property of the cryogenic cavity aiming at a very high accelerating field with as low breakdown rate as possible, one-dimensional simulations of the temperature rise in the cavity surface have been done for various combinations of the RF pulse width and the peak input RF power. The evaluation will be taken into consideration in the design of a new high power cryogenic cavity that has basically the same configuration with the cold model.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL061  
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THPAL063 RF and Thermo-Mechanical Considerations in Designing the Waveguide Iris Coupler for the Drift Tube Linac in the ORNL Spallation Neutron Source cavity, GUI, DTL, vacuum 3796
 
  • S.W. Lee, Y.W. Kang
    ORNL, Oak Ridge, Tennessee, USA
 
  Funding: This work was supported by SNS through UT Battelle, LLC, under contract DE AC05 00OR22725 for the U.S.DOE
The Spallation Neutron Source (SNS) employs tapered ridge waveguide iris couplers to power six drift tube linac (DTL) cavity structures with pulsed RF systems using 2.5MW klystrons at 402.5MHz. All DTL iris couplers have been operating continuously for more than a decade without replacement. Transferring high RF energy to the cavities requires robust RF and mechanical performances with respect to power dissipation, electrical breakdown, and vacuum pressure. Considering the upcoming full 1.4MW operation and the future proton power upgrade (PPU) project, the structural design and the material selection needed to be reviewed for potential spare manufacturing. The existing design and the modified design with improvements to the coupler have been numerically studied. For the study, 3D models were used for RF and structural characterizations of the waveguide iris couplers on the DTL cavity. RF and thermo-mechanical co-simulations were performed to assess the effects of using the different materials and the structural modification.
 
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THPAL067 Room Temperature Measurements of Higher Order Modes for the SPS Prototype RF-Dipole Crabbing Cavity HOM, cavity, dipole, luminosity 3805
 
  • S.U. De Silva, J.R. Delayen, H. Park
    ODU, Norfolk, Virginia, USA
  • P. Berrutti
    Fermilab, Batavia, Illinois, USA
  • N.A. Huque, H. Park
    JLab, Newport News, Virginia, USA
 
  LHC High Luminosity Upgrade will be developing two local crabbing systems to increase the luminosity of the colliding bunches at the ATLAS and CMS experiments. One of the crabbing systems uses the rf-dipole cavity design that will be crabbing the beam in the horizontal plane. The fully integrated crabbing cavity has two higher order mode couplers in damping those excited modes. Currently two sets of HOM couplers have been fabricated at Jefferson Lab for prototyping and testing with the LARP crabbing cavities. This paper presents the measurements of the higher order modes with the prototype HOM couplers carried out at room temperature.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL067  
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THPAL069 Simulation of a 10 mm Diameter Cascaded Plasma Window plasma, cathode, vacuum, experiment 3812
 
  • P.P. Gan, S. Huang, Y.R. Lu, S.Z. Wang, K. Zhu
    PKU, Beijing, People's Republic of China
 
  As a windowless vacuum device, the 10 mm diameter 60 mm long plasma window designed by Peking University only achieved to separate 28.8 kPa from 360 Pa experimentally with 50 A direct current and 2.5 kW power. Based on our 10 mm diameter plasma window, we have proposed a cascaded plasma window to achieve the isolation of atmosphere and high vacuum. In this paper, a numerical 2D FLUENT-based magneto-hydrodynamic simulation on 10 mm diameter cascaded plasma window was developed. The gas inlet, arc creation and plasma expansion segments are all contained in this model. A set of parameters including pressure, temperature, velocity and current distribution were obtained and analysed. In our first simulation, the isolation of 100 kPa and 50 Pa pressure has been realised, and some interesting phenomena occurred.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL069  
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THPAL070 Multi-Physics Analysis of Two Bunchers for CIFNEF cavity, beam-transport, target, neutron 3815
 
  • Q.Y. Tan, M.J. Easton, Q. Fu, P.P. Gan, H.P. Li, Y.R. Lu, Z. Wang
    PKU, Beijing, People's Republic of China
 
  CIFNEF(Compact Intense Fast NEutron Facility) project will accelerate and deliver a 5 MeV deuteron beam to the targets to produce high-intense neutrons. A 2.5 MHz pulsed deuteron beam with bunch width within 2 ns is needed on the targets at last. To fulfill the special requirements of the beam dynamics, two types of bunchers are adopted in the CIFNEF. One is a 10.156 MHz buncher used in the low energy beam transport (LEBT) line to longitudinally focus the 50 keV deuteron beam to the RFQ longitudinal acceptance with 4 kV effective voltage. A lumped element model is adopted because of the low frequency and it consists of an inductance coil in parallel with the capacitance of drift tube. The other one is an 81.25 MHz buncher used in the high energy beam transport (HEBT) line to longitudinally focus the 5 MeV deuteron beam to 2 ns. A QWR cavity with 2-gaps is used to provide 150 kV effective voltage. Thermal and structural analyses have been carried out on these two bunchers. Details of simulations of these two bunchers are presented and discussed in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL070  
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THPAL078 In-Vacuum Lambertson Septum for SPEAR3 Low Emittance Injection septum, vacuum, storage-ring, injection 3831
 
  • M.A.G. Johansson, J. Langton, J.A. Safranek
    SLAC, Menlo Park, California, USA
  • S.C. Gottschalk
    STI Magnetics LLC, Woodinville, USA
 
  Funding: Work supported by DOE Contract No. DE-AC02-76SF00515
A new in-vacuum Lambertson septum magnet is being designed for the SPEAR3 storage ring, intended to replace the existing septum to allow injection into a new lower emittance operation mode for SPEAR3. The new septum design is constrained to fit in the same length and have the same bend angle as the existing injection septum, so as to minimize changes to surrounding storage ring and transfer line components, while also meeting stringent requirements on the stored beam leakage field. This has led to a design using Vanadium Permendur alloy for the septum pole pieces, with shaping of the inner profile of the stored beam channel to minimize the leakage fields indicated in 2D and 3D magnetic simulations.
 
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THPAL080 Parallel-Feed SRF Accelerator Structures cavity, SRF, coupling, impedance 3835
 
  • P.B. Welander, Z. Li, M.H. Nasr, S.G. Tantawi
    SLAC, Menlo Park, California, USA
 
  Funding: This work is supported by the Department of Energy, Laboratory Directed Research and Development program at SLAC National Accelerator Laboratory, under contract DE-AC02-76SF00515.
Development of SRF accelerator technology that enables both higher gradient and higher efficiency is crucial for future machines. While much of the recent R&D focus has been on materials and surface science, our aim is to optimize the cavity geometry to maximize performance with current materials. The recent demonstration of a highly efficient parallel-feed NCRF structure at SLAC has served as a proof-of-concept. Applied to SRF, such a structure could dramatically reduce power consumption while boosting the achievable gradient. Instead of coupled elliptical cells, our structure employs isolated reentrant cells. To feed RF power to the cavities, each cell is directly coupled to an integrated manifold. The structure is made in two parts, split along the beam axis, which are then joined. Such a structure has been fabricated from bulk Cu and tested at SLAC - designed for X-band, it operates at a record gradient of 150 MV/m. Adapting to SRF at 1.3 GHz and fabricating from Nb, such a cavity could achieve more than 50% lower RF loss and 40% higher gradient compared to the TESLA cavity. We will describe our simulations and propose an experimental roadmap for demonstrating this technology.
 
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THPAL084 An X-Band Lineariser for the CLARA FEL cavity, FEL, wakefield, klystron 3848
 
  • L.S. Cowie, A.D. Brynes, J.K. Jones, A.E. Wheelhouse, P.H. Williams
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • R. Apsimon, G. Burt, W.L. Millar
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • Ö. Mete
    UMAN, Manchester, United Kingdom
  • A.J. Moss
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
 
  The CLARA FEL at Daresbury Laboratory will employ four S-band linacs to accelerate electron bunches to 250 MeV/c. In order to compress the bunch sufficiently to achieve peak currents suitable for FEL lasing, one must compensate for curvature imprinted on the longitudinal phase space of the bunch. For CLARA a harmonic RF linearization system has been designed to achieve this requirement. The linearization will be achieved by an X-band travelling wave cavity of the PSI/CERN design, which incorporates wake-field monitoring of the bunch position. A five-axis mover will align the cavity to the beam axis. Pulse compression of a 6 MW klystron pulse will provide the required power to achieve a 30 MV/m operational gradient.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL084  
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THPAL092 Test Particle Monte Carlo Simulation of NEG Coated Narrow Tubular Samples vacuum, ECR, experiment, SRF 3862
 
  • O. Seify, A.N. Hannah, O.B. Malyshev, Sirvinskaite, R. Sirvinskaite, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • Sirvinskaite, R. Sirvinskaite
    Loughborough University, Loughborough, Leicestershire, United Kingdom
 
  The pumping properties of the NEG coated vacuum chambers play an important role in the efficiency of vac-uum system of accelerators. The sticking probability of the NEG films is one the most important parameters to characterise the pumping properties of the NEG coated vacuum chambers. In order to investigate the NEG film sticking probability, Test Particle Monte-Carlo (TPMC) models were used. The models were based on the design of the installed experimental setup in ASTeC Vacuum Science group laboratory at Daresbury Laboratory (DL). The results of the simulations have been used for inter-preting the results of the measurements in the experi-mental setup.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL092  
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THPAL105 Lower Critical Field Measurement System of Thin Film Superconductor controls, experiment, SRF, embedded 3882
 
  • H. Ito
    Sokendai, Ibaraki, Japan
  • C.Z. Antoine
    CEA/IRFU, Gif-sur-Yvette, France
  • A. Four
    CEA/DRF/IRFU, Gif-sur-Yvette, France
  • H. Hayano, T. Kubo, T. Saeki
    KEK, Ibaraki, Japan
  • R. Ito, T. Nagata
    ULVAC, Inc, Chiba, Japan
  • Y. Iwashita, R. Katayama, H. Tongu
    Kyoto ICR, Uji, Kyoto, Japan
  • H. Oikawa
    Utsunomiya University, Utsunomiya, Japan
 
  Funding: The work is supported by Japan Society for the Promotion of Science Grant-in-Aid for Young Scientist (A) No.17H04839.
Superconducting thin film is the promising technology to increase the performance of SRF cavities. The lower critical field Hc1, which is one of the important physical parameters characterizing a superconducting material, will be enhanced by coating Nb with thin film superconductor such as NbN. To investigate the performance of thin film, we developed the Hc1 measurement system using the third harmonic response of applied AC magnetic field. The measurement system consists of helium cryostat with two of GM refrigerators, sample Cu stage, solenoid coil Cu mount, solenoid coil, temperature sensors, and liquid helium level meter. AC magnetic field is produced by a coil which is driven by function generator and power amplifier at around 1 kHz. In order to control the temperature of the sample stage and coil mount, the depth of thermal anchors attached to the stage and the mount can be moved by the motor. By this temperature control the sample state can be easily transferred from Meissner state to mixed state. So that the measurement is repeated for various applied magnetic field, and the transition curve can be made. In this report, performance of the measurement system is described.
 
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THPAL108 In-Situ Characterization of Normal Conducting RF Cavities in Solaris Light Source Storage Ring cavity, HOM, storage-ring, ISOL 3891
 
  • P.B. Borowiec, A.I. Wawrzyniak
    Solaris National Synchrotron Radiation Centre, Jagiellonian University, Kraków, Poland
  • J. Björklund Svensson
    Lund University, Division of Atomic Physics, Lund, Sweden
 
  The SOLARIS 1.5 GeV storage ring is equipped with two 100 MHz active cavities and two 3rd harmonic passive cavities. They are in operation since 2015. For control of their respective working points, knowledge about cavity voltage and higher order mode (HOM) frequency spec-trum is mandatory. After their installation in the storage ring and connection of the RF feeder to a high power isolator and a transmitter, the influence of the external elements on the quality factor and the HOM spectrum should be verified with respect to simulations of a simpli-fied model of a stand-alone cavity. This paper will pre-sent results of in-situ cavity measurements to qualify the HOM placement and their quality factor. HOM meas-urements have been performed in the range 100 MHz to 1.3 GHz for active cavities and 300 MHz to 1.5 GHz for 3rd harmonic cavities at three different temperatures under ultra-high vacuum conditions for each cavity separately. The measurement and analysis methodology will also be presented  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL108  
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THPAL109 The New 118 MHz Cavity for RF Development Activities of the RF for Accelerator Laboratory at SLRI cavity, HOM, coupling, impedance 3895
 
  • N. Juntong, K. Kittimanapun, P. Sunwong
    SLRI, Nakhon Ratchasima, Thailand
  • A. Sutchada
    Walailak University, Nakhon Si Thammarat, Thailand
 
  The RF for accelerator laboratory is established at SLRI to perform RF related development activities of the current light source and the future synchrotron light facility in Thailand. One of activities is to build an in-house RF cavity. It will be used for testing of RF amplifier unit and the developed LLRF system. The cavity is a nose-cone pill-box cavity operating at 118 MHz and aiming at 100 kV gap voltage. Details of designing in particular the inner surface profile, the RF properties, the higher order modes properties, the RF power coupler, and the tuning mechanism will be presented with the manufacturing timeline.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL109  
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THPAL112 RF Matching Circuit for CANREB RFQ rfq, TRIUMF, network, pick-up 3902
 
  • T. Au, B. Barquest, J.J. Keir, V. Zvyagintsev
    TRIUMF, Vancouver, Canada
 
  A RF matching circuit has been developed to provide two phase RF voltage of 1.2 kVpp at 3 MHz and 6 MHz for the CANREB RFQ structure with an equivalent capacitive load of 300 pF. The RF matching circuit utilizes pi-network with two phase transformer. Beyond RF drive the CANREB structure requires pulse DC bias with amplitude up to 500 V. Results of development and testing of RF matching circuit and filters are presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL112  
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THPAL113 The Design of 1 MeV Proton LINAC Operating in CW cavity, linac, proton, resonance 3905
 
  • N.V. Avreline
    TRIUMF, Vancouver, Canada
 
  Experimental results and computer simulations of electrodynamic and thermodynamic characteristics are presented for an accelerating structure that is excited in the TM010 mode and that has the accelerating channel of URAN-1M located in the diametric plane. The idea of using this structure in the particle accelerator URAN-1M, located at the Baikov Institute of Metallurgy and Materials Science, with the goal of increasing the average beam current is explored.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL113  
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THPAL114 The Analytical Model of the Helical Accelerating Structure of Linac with Helix Outside of the Vacuum Chamber vacuum, experiment, resonance, TRIUMF 3908
 
  • N.V. Avreline
    TRIUMF, Vancouver, Canada
 
  An analytical model of the helical RF resonator for the single charged 250 keV nitrogen ion implanter operating in CW was developed. The analytical model allowed to determine the geometry of the accelerating structure and to construct CST Microwave Studio and ANSYS HFSS models based on this analytical model. Results obtained from the analytical model and simulations were within 5% of each other. The experimental investigation of the accelerating section confirmed that the models are correct. The accelerating section was tuned and verified for the right accelerating field distribution and operating frequency. Finally, the section was successfully tested in 2 kW CW RF power.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL114  
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THPAL115 The Design of 1.1 MW RF Dummy Load for the RF System of 520 MeV Cyclotron cyclotron, TRIUMF, pick-up, controls 3911
 
  • N.V. Avreline, Y. Bylinskii, B. Jakovljevic, Y. Ma, V. Zvyagintsev
    TRIUMF, Vancouver, Canada
 
  The RF System of 520-MeV Cyclotron is operating at 23 MHz with 1 MW CW RF power. The RF dummy load is required to troubleshoot and tune the RF amplifier. The RF system is being constantly improved and the future goal is to increase cyclotron's beam current up to 400 μA, which requires increasing the RF amplifier's power. As a part of this goal, a new RF dummy load was designed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL115  
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THPAL145 Magnetron R&D toward the Amplitude Modulation Control for SRF Accelerator injection, controls, cavity, SRF 3986
 
  • R.A. Rimmer, T. E. Plawski, H. Wang
    JLab, Newport News, Virginia, USA
  • A. Dudas, S.A. Kahn, M.L. Neubauer
    Muons, Inc, Illinois, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and SBIR grant DE-SC0013203
The scheme of using a high efficiency magnetron to drive a superconducting radio frequency (SRF) accelerator cavity needs not only the injection phase locking but also the amplitude modulation to compensate the cavity's microphomics caused cavity voltage change and the beam loading variation. To be able to do a fast and efficient modulation, the magnetron's magnetic field has to be trimmed by an external coil to compensate the frequency pushing effect due to the anode current change [1]. A low eddy current magnetron body has been designed and built [2]. This paper will present the analytical prediction, simulation and experimental results on the 2.45 GHz magnetron test stand with the modulation frequency up to 1 kHz. In addition, the progresses on the injection lock to a copper cavity, new 1497 MHz magnetron prototype, 13 kW high power magnetron test stand development and newly built low level RF (LLRF) controller for the amplitude modulation will be reported.
[1] M. Neubauer et al, THPIK123, Proceedings of IPAC 2017, Copenhagen, Denmark
[2] S. A. Kahn et al, THPIK121, Proceedings of IPAC 2017, Copenhagen, Denmark
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL145  
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THPAL148 Status of High Efficiency Klystron Development in TETD klystron, cavity, electron, bunching 3993
 
  • Y. Okubo, S. Fujii, K. Suzuki, T.E. Tanaka
    Toshiba Electron Tubes & Devices Co., Ltd (TETD), Tochigi, Japan
 
  TETD (Toshiba Electron Tubes and Devices Co., Ltd.) has been developing a high efficiency klystron improved bunch quality by the multi-stage of core oscillation design. For feasibility study, an S-band 7.5 MW klystron has been designed with the efficiency of more than 60% at 1.8μperveance. The first prototype was fabricated by modifying the interaction section of a commercial model to enhance the efficiency from 45% to 60%. The klystron was tested in June 2017, and 57% of efficiency at 6 MW output power was demonstrated. We are developing the second prototype which has the improved design for the higher efficiency at 7.5 WM output power. The design details and the test results of the first prototypes are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL148  
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THPAL152 Study of X-Band Phase Shifter Using Ferrite Material cavity, GUI, coupling, insertion 4005
 
  • Y.L. Jiang, D.Z. Cao, H.B. Chen, J. Shi, P. Wang, H. Zha
    TUB, Beijing, People's Republic of China
 
  Ferrite has the feature of the permeability depended on the external static magnetic field, thus could be used to shift the phase of the propagating radio frequency (RF) signal. In this paper, we introduce a novel design of ferrite-based RF phase shifter. The design changes the resonant frequency of a ferrite-filled pill-box cavity to implement the phase changing. This design has a lower local RF field and a higher sensitivity on the phase changing than those of waveguide phase shifter, which may bring advantages such as higher power capacity, fast changing speed and lower insertion loss. Theory and simulation results are also presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL152  
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THPAL157 Investigation of Transverse Wakefield and Beam Break Up Effect in Irradiation Linacs cavity, wakefield, experiment, linac 4020
 
  • X.C. Meng, H.B. Chen, J. Shi, Z.H. Wang, H. Zha, S.X. Zheng
    TUB, Beijing, People's Republic of China
  • G.H. Li, J.S. Liu, Y.H. Liu
    NUCTECH, Beijing, People's Republic of China
 
  Study of beam break up effect in linacs has been done in recent years. The beam-induced high order dipolar modes, especially the TM11-like mode were investigated for the linacs both in travelling wave and backward trav-elling wave. Measurements of beam-break up in a travel-ling wave linac were carried out and results are discussed. Moreover, a theoretical model was developed for the irradiation linacs to study the detailed interaction be-tween the transverse wakefield and the electron beam.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL157  
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THPAL158 Development of an Half-Cell Accelerating Structure in Tsinghua cavity, GUI, alignment, radiation 4023
 
  • M.M. Peng, W. Gai, J. Shi, Z.H. Wang, H. Zha
    TUB, Beijing, People's Republic of China
 
  The half-cell high gradient accelerating structure is attractive for its easy manufacturing and good alignment. A structure with 12 cells has been designed for the frequency of 11.424 GHz and a cold test will be conducted. Two different mechanical factory manufacture with same machining drawing and the results will be compared.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL158  
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THPMF012 Tapered Flying Radiofrequency Undulator undulator, electron, FEL, ECR 4059
 
  • S.P. Antipov, S.V. Kuzikov, A. Liu
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • S.V. Kuzikov, A.V. Savilov, A.A. Vikharev
    IAP/RAS, Nizhny Novgorod, Russia
 
  Funding: DOE SBIR DE-SC0017145
The x-ray free electron laser (x-FEL) efficiency, measured as a fraction of the electron beam power converted into light, is typically below 0.1% for most of the x-FEL facilities presently in operation. Undulator tapering techniques can be used to improve the conversion efficiency by 1-2 orders of magnitude. However at present there are no robust tapered undulator x-FEL schemes operating at 10% efficiency. In this paper we report on the development of tapered radiofrequency (RF) undulator. An RF undulator is a microwave waveguide in which strong RF field is excited that interacts with a charged particle beam forcing it to radiate coherent x-rays while undergoing a wiggling motion. RF undulators are attractive for use in x-FELs due to their large beam aperture and a short undulator period. Strongly tapered RF undulators (with tapering of a wavelength) due to non-resonant trapping regime allow keeping high overall XFEL efficiency being driven by laser plasma accelerated beams usually having high enough current but large energy spread (1-10%).
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF012  
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THPMF022 Study of Possible Beam Losses After Post-Linac Collimation at European XFEL undulator, radiation, FEL, vacuum 4092
 
  • S. Liu, W. Decking
    DESY, Hamburg, Germany
  • F. Wolff-Fabris
    XFEL. EU, Schenefeld, Germany
 
  The European XFEL has been operating with the undulator beam line SASE1 and SASE3 since April 2017 and February 2018, respectively. Despite of the fact that the post-linac collimation has collimated the beam halo to ~20 σ level*, relative high radiation doses have been measured especially in the diagnostic undulator (DU) section**. In order to find the sources of beam losses after post-linac collimation, BDSIM simulations have been performed. In this paper, we will first present the possible losses generated by the wire scanners upstream of the undulators during a scan. The simulation results will be compared with the measured doses along SASE1 and SASE3 undulators. Based on the simulation results, we will estimate the frequency for wire scanner opera-tions. Besides, the simulations with large extension of beam halo hitting the vacuum chamber aperture transition will also be presented. Finally, other possible radiation dose sources will be discussed.
* S. Liu et al., in Proc. of FEL 2017, Santa-Fe, USA, Aug. 2017, paper TUP003.
** F. Wolff-Fabris et al.,IPAC-2018 contribution.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF022  
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THPMF028 Coherent Stacking Scheme for Inverse-Compton Scattering at MHz Repetition Rates laser, cavity, coupling, feedback 4103
 
  • P. Piot, D. Mihalcea
    Northern Illinois University, DeKalb, Illinois, USA
  • T.J. Campese, A.Y. Murokh
    RadiaBeam Systems, Santa Monica, California, USA
  • D. Mihalcea, P. Piot, J. Ruan
    Fermilab, Batavia, Illinois, USA
 
  Funding: Work sponsored by the DNDO award 2015-DN-077-ARI094 to Northern Illinois University and US DOE contract DE-AC02-07CH11359 to Fermilab.
An experiment to produce 1-MeV gamma rays via Compton back-scattering of infrared photons on 250-MeV electron bunches is currently in preparation at the Fermilab Accelerator Science & Technology (FAST) facility. To increase the gamma-ray flux the energy of the infrared laser pulses are planned to be amplified within the interaction region using a resonant cavity. This passive amplifier composed of a Fabry-Perot cavity will allow the laser pulse bunches to coherently and constructively stack. Our estimates, based on theoretical models, show that the laser pulse energy can be increased from approximately 1-2 mJ at the exit of the last active amplifier to 5 -10 mJ at the interaction point when the laser repetition rate is set at the nominal value of 3 MHz. This paper details the cavity design option(s) and associated wave-optic simulations.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF028  
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THPMF048 Bunch Length Measurements Using CTR at the AWA with Comparison to Simulation experiment, laser, gun, electron 4166
 
  • N.R. Neveu
    IIT, Chicago, Illinois, USA
  • S.P. Antipov
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • A. Halavanau, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • P. Piot
    Fermilab, Batavia, Illinois, USA
  • J.G. Power, C. Whiteford, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
  • L.K. Spentzouris
    Illinois Institute of Technology, Chicago, Illinois, USA
 
  Funding: This work is funded by the DOE Office of Science, grant no. DE-SC0015479, and contract No. DE-AC02- 06CH11357.
In this paper we present electron bunch length measurements at the Argonne Wakefield Accelerator (AWA) photoinjector facility. The AWA accelerator has a large dynamic charge density range, with electron beam charge varying between 0.1 nC - 100 nC, and laser spot size diameter at the cathode between 0.1 mm - 18 mm. The bunch length measurements were taken at different charge densities using a metallic screen and a Martin-Puplett interferometer to perform autocorrelation scans of the corresponding coherent transition radiation (CTR). A liquid helium-cooled 4K bolometer was used to register the interferometer signal. The experimental results are compared with Impact-T and OPAL-T numerical simulations.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF048  
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THPMF049 Photoinjector Optimization Studies at the AWA emittance, laser, experiment, gun 4169
 
  • N.R. Neveu
    IIT, Chicago, Illinois, USA
  • J. Larson, J.G. Power
    ANL, Argonne, Illinois, USA
  • L.K. Spentzouris
    Illinois Institute of Technology, Chicago, Illinois, USA
 
  Funding: This work is funded by the DOE Office of Science, grant no. DE-SC0015479, and contract No. DE-AC02- 06CH11357.
With a variable charge range of 0.1 nC - 100 nC, the Argonne Wakefield Accelerator facility (AWA) has a unique and dynamic set of operating parameters. Adjustment of the optics and occasionally the rf phases is required each time the bunch charge is changed. Presently, these adjustments are done by the operator during each experiment. This is time consuming and inefficient, more so at high charge and for complex experimental set ups. In an attempt to reduce the amount of time spent adjusting parameters by hand, several optimization methods in simulation are being explored. This includes using the well-known Genetic Algorithm (NSGA-II), incorporated into OPAL-T. We have also investigated a model-based method and novel structure based algorithms developed at ANL. Ongoing efforts include using these optimization methods to improve operations at the AWA. Simulation results will be compared to measured beam parameters at the AWA, and one optimization method will be selected for use in guiding operations going forward.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF049  
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THPMF055 Ion Instability Simulation in the HEPS Storage Ring electron, storage-ring, emittance, lattice 4189
 
  • S.K. Tian, Y. Jiao, N. Wang
    IHEP, Beijing, People's Republic of China
  • K. Ohmi
    KEK, Ibaraki, Japan
 
  The High Energy Photon Source (HEPS), a kilometre scale storage ring light source, with a beam energy of 6 GeV and transverse emittances of a few tens of pm.rad, is to be built in Beijing and now is under design. We investigate the ion instability in the storage ring with high beam intensity and low-emittance. We performe a weak-strong simulation to show characteristic phenomena of the instability in the storage ring.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF055  
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THPMF059 Simulation Studies of Beam Commissioning and Expected Performance of the SPring-8-II Storage Ring emittance, quadrupole, lattice, sextupole 4203
 
  • Y. Shimosaki
    JASRI, Hyogo, Japan
  • K. Soutome, M. Takao
    JASRI/SPring-8, Hyogo-ken, Japan
  • H. Tanaka
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
 
  In the SPring-8 upgrade project, the 5-bend achromat lattice is adopted for achieving a very low emittance of 157 pm.rad at 6 GeV. Since the dynamic aperture (DA) and the beam performance become sensitive against errors due to the strong quadrupoles and sextupoles, we carried out tracking simulations to evaluate the tolerance of machine imperfections such as the misalignment, magnetic field errors, the BPM offset, etc. It is found that the first-turn-steering (FTS) with the use of single-pass BPM's is indispensable because even under strict (but attainable) tolerances the beam cannot be stored without steering kicks. We then confirmed that after the FTS a sufficiently large DA can be obtained for accumulating the beam by the off-axis injection. By performing the orbit and optics corrections for the stored beam, we can finally achieve an emittance value of 160 ~ 180 pm.rad, being close to the design value. We also found that a naive application of the SVD algorithm to orbit corrections yields unwanted local bumps between BPM's and this deteriorates the vertical emittance. A possible scheme to avoid such local bumps by effectively interpolating the measured orbit will be discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF059  
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THPMF060 Touschek Beam Loss Simulation for Light Source Storage Rings electron, scattering, storage-ring, coupling 4206
 
  • M. Takao, K. Soutome
    JASRI/SPring-8, Hyogo-ken, Japan
  • Y. Shimosaki
    JASRI, Hyogo, Japan
  • K. Soutome, H. Tanaka
    RIKEN SPring-8 Center, Hyogo, Japan
 
  In light source storage rings, it is important to know the distribution of lost electrons due to the Touschek scattering for protecting insertion devices (IDs) from radiation damage. This will become crucial especially in future light sources where narrow gap in-vacuum IDs are normally used. While the Touschek scattered electron begins to oscillate in the horizontal direction with the amplitude proportional to the dispersion at the scattering point and to the momentum deviation after scattering, the motion is converted into the vertical direction due to the betatron coupling and some of the scattered electrons are lost at the narrow gaps of in-vacuum IDs. The momentum deviation by the Touschek scattering reaches 5% more, and according to which the vertical oscillation is more excited. Hence electrons even scattered at small horizontal dispersion are also lost at narrow gap IDs. We carried out computer simulations by taking the present SPring-8 storage ring and a planned 3GeV low-emittance ring as examples. The results and possible measures for ID protection will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF060  
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THPMF069 Perturbation to Stored Beam by Pulse Sextupole Magnet and Disturbance of the Sextupole Magnetic Field in Aichi Synchrotron Radiation Center synchrotron, radiation, synchrotron-radiation, injection 4232
 
  • A. Mochihashi
    KIT, Eggenstein-Leopoldshafen, Germany
  • M. Fujimoto, M. Katoh
    UVSOR, Okazaki, Japan
  • M. Hosaka, M. Hosaka, Y. Takashima, Y. Takashima, K. Y. Yamamura
    Nagoya University, Nagoya, Japan
  • M. Hosaka, H. Ohkuma, Y. Takashima
    Aichi Synchrotron Radiation Center, Aichi, Japan
  • M. Katoh
    Sokendai - Okazaki, Okazaki, Aichi, Japan
  • H. Ohkuma
    JASRI/SPring-8, Hyogo-ken, Japan
 
  In the Aichi synchrotron radiation center (Aichi-SR), a pulse sextupole magnet (PSM) has been installed as a pulse magnet for beam injection. This leads to the injection scheme without using a bump orbit and stable supply of the synchrotron radiation. In Aichi-SR we have performed usual injection scheme with 4 kicker magnets and making the bump. Because the circumference of the Aichi-SR is only 72 m, 3 beam lines are inside the bump. The Aichi-SR has performed top-up operation since its public open, so it is a crucial subject to eliminate the disturbance of the synchrotron radiation during the injection. We have installed the PSM in 2015 and developed the beam study continuously. At present, however, a perturbation to the stored beam by the PSM still has been observed and is not acceptable. We have performed beam diagnostic experiment and concluded that an additional dipole kick affects the beam. From the magnetic field measurement data, we have discussed the source of the additional kick; most likely is an eddy current on the Ti coating inside the ceramics duct of the PSM. The beam diagnostics experiment and the magnetic field measurement will be discussed in the presentation.
Present affiliation of the first auther : Karlsruhe Institute of Technology
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF069  
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THPMF074 Study of the Saturation of Radiation Energy Caused by the Space Charge Effect in a Compact THz Coherent Radiation Source electron, radiation, undulator, laser 4245
 
  • S. Krainara, Chatani, S. Chatani, T. Kii, H. Ohgaki, H. Zen
    Kyoto University, Kyoto, Japan
 
  Funding: Institute of Advanced Energy, Kyoto University
To generate an intense quasi-monochromatic Terahertz Coherent Undulator Radiation (THz-CUR), a compact linac system, which employs a magnetic electron bunch compressor with a beam energy of 4.6 MeV, has been constructed at Kyoto University. The THz-CUR has suc-cessfully been generated in a frequency range from 0.16 to 0.65 THz with a bunch charge of 60 pC. The maximum micro-pulse energy of THz radiation was observed higher than 1 µJ at 0.16 THz with 160 pC. However, when a bunch charge was higher than 80 pC, the micro-pulse energy of THz radiation gradually went to the saturation and obviously at the bunch charge higher than 110 pC because of the bunch lengthening and degradation of electron beam quality due to the space charge effect. The dependence of a bunch length on a bunch charge has been studied by GPT simulation and compared with CTR and CUR experiments. The trends of the measured results from CUR and CTR are in good agreement with the GPT simulation.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF074  
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THPMF078 Simulation of Trajectory Correction in Early Commissioning of the Advanced Light Source Upgrade MMI, lattice, sextupole, closed-orbit 4256
 
  • T. Hellert, J.-Y. Jung, S.C. Leemann, H. Nishimura, D. Robin, F. Sannibale, C. Steier, C. Sun, C.A. Swenson, M. Venturini
    LBNL, Berkeley, California, USA
 
  Funding: *Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231.
The ALS upgrade into a diffraction-limited soft x-rays light source requires a small emittance, which is achieved by much stronger focusing than in the present ALS. Very strong focusing elements and a relatively small vacuum chamber make the required rapid commissioning a significant challenge. This paper will describe the progress towards a start-to-end simulation of the machine commissioning and present first simulation results.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF078  
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