Keyword: resonance
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MOZGBF5 Analysis of Polarization Decay at RHIC Store polarization, emittance, lattice, target 76

• H. Huang, P. Adams, E.C. Aschenauer, A. Poblaguev, W.B. Schmidke
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.
There are polarization losses in RHIC store due to various sources, such as emittance growth and higher order spin resonances. The beam polarization was measured several times over a store by the p-carbon polarimeters situated in both rings. These provide information on the polarization decay over time and also polarization profile development over time. A polarized jet was also used to monitor the polarization continuously through store, though with limited statistical accuracy. These polarization measurements and emittance measurements from the IPM are analyzed and the polarization loss from different sources are reviewed.

Slides MOZGBF5 [4.530 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOZGBF5
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MOPMF004 Spin Dynamics in the JLEIC Alternative Pre-Booster Ring booster, proton, polarization, dipole 87

• J.L. Martinez Marin, B. Mustapha
ANL, Argonne, USA

In order to reduce the foot-print of the JLEIC ion complex, we have designed a more compact and cost-effective octagonal 3-GeV pre-booster ring half the size of the orig-inal figure-8 design. However, this new ring does not preserve ion polarization by design as the figure-8 shape, making it necessary to study the spin dynamics to find the best solution for spin correction. Different codes, Zgoubi and COSY, are used to model and simu-late the spin dynamics in the octagonal 3 GeV ring, in-cluding spin correction with Siberian snakes.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF004
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MOPMF013 eRHIC EIC: Plans for Rapid Acceleration of Polarized Electron Bunch at Cornell Synchrotron polarization, electron, synchrotron, acceleration 108

• F. Méot, E.C. Aschenauer, H. Huang, C. Montag, V. Ptitsyn, V.H. Ranjbar, E. Wang, Z. Zhao
BNL, Upton, Long Island, New York, USA
• I.V. Bazarov, D. L. Rubin
Cornell University, Ithaca, New York, USA
• L. Cultrera, G.H. Hoffstaetter, K.W. Smolenski, R.M. Talman
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
• D. Gaskell, O. Glamazdin, J.M. Grames
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.
An option as an injector into the polarized-electron storage ring of eRHIC EIC is a rapid-cycling synchrotron (RCS). Cornell's 10 GeV RCS injector to CESR presents a good opportunity for dedicated polarized bunch rapid-acceleration experiments, it can also serve as a test bed for source and polarimetry developments in the frame of the EIC R&D, as polarized bunch experiments require disposing of a polarized electron source, and of dedicated polarimetry in the linac region and in the RCS proper. This is as well an opportunity for a pluri-disciplinary collaboration between Laboratories. This paper is an introduction to the topic, and to on-going activities towards that EIC R&D project.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF013
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MOPMF016 Progress on RCS eRHIC Injector Design polarization, emittance, lattice, detector 115

• V.H. Ranjbar, M. Blaskiewicz, J.M. Brennan, S.J. Brooks, D.M. Gassner, H.-C. Hseuh, I. Marneris, F. Méot, M.G. Minty, C. Montag, V. Ptitsyn, K.S. Smith, S. Tepikian, F.J. Willeke, H. Witte, B. P. Xiao, A. Zaltsman
BNL, Upton, Long Island, New York, USA
• I.V. Pogorelov

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
We have refined the design for the Rapid Cycling Synchrotron (RCS) polarized electron injector for eRHIC. The newer design includes bypasses for the eRHIC detectors and definition of the lattice layout in the existing RHIC tunnel. Additionally, we provide more details on the RF, alignment and orbit control, and magnet specifications.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF016
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MOPMF018 Numerical Simulation of Spin Dynamics with Spin Flipper in RHIC dipole, simulation, 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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MOPMF028 A Superconvergent Algorithm for Invariant Spin Field Stroboscopic Calculations simulation, 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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MOPMF032 Nonlinear Correction Strategies for the LHC Using Resonance Driving Terms dipole, optics, insertion, coupling 161

• F.S. Carlier, E.H. Maclean, T. Persson, R. Tomás
CERN, Geneva, Switzerland

The correction of nonlinearities in future colliders is critical to reach operational conditions and pose a significant challenge for commissioning schemes. Several approaches have been succesfully used in the LHC to correct sextupolar and octupolar sources in the LHC insertion regions. Measurements of resonance driving terms at top energy in the LHC have improved and now offer a new observable to calculate and validate nonlinear corrections. This paper reports on measurements of resonance driving terms in the LHC and the relevant strategies used for nonlinear corrections.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF032
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MOPMF033 Probing the Forced Dynamic Aperture in the LHC at Top Energy Using AC Dipoles dipole, dynamic-aperture, insertion, emittance 165

• F.S. Carlier, M. Giovannozzi, E.H. Maclean, T. Persson, R. Tomás
CERN, Geneva, Switzerland

Measurements of the dynamic aperture in colliders are a common method to ensure machine performance and offer an insight in the nonlinear content of the machine. Such direct measurements are very challenging for the LHC and High Luminosity LHC. Forced dynamic aperture has been demonstrated for the first time in the LHC at injection energy as a potential new observable to safely probe the nonlinear content of the machine. This paper presents the first measurements of forced dynamic aperture at top energy and discusses the proposed measurement schemes and challenges.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF033
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MOPMF047 Transverse Coupling Measurements With High Intensity Beams Using Driven Oscillations coupling, dipole, injection, controls 208

• T. Persson, G. Baud, X. Buffat, J.M. Coello de Portugal, E. Fol, K. Fuchsberger, M. Gabriel, M. Gąsior, M. Giovannozzi, G.H. Hemelsoet, M. Hostettler, M. Hruska, D. Jacquet, E.H. Maclean, L. Malina, J. Olexa, P.K. Skowroński, M. Solfaroli Camillocci, M.E. Söderén, R. Tomás, D. Valuch, A. Wegscheider, J. Wenninger
CERN, Geneva, Switzerland

Transverse coupling has been linked to instabilities and reduction in dynamic aperture and is hence a crucial parameter to control in the LHC. In this article we describe the development to use driven oscillations to measure the transverse coupling with high intensity beams. The method relies on the use of the transverse damper to drive an oscillation in a similar way as with an AC-dipole. The calculation of the coupling is based on the turn-by-turn data from all available BPMs gated for the excited bunch.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF047
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MOPMF057 FCC-ee Dynamic Aperture Studies and Frequency Map Analysis alignment, dynamic-aperture, emittance, sextupole 244

• T. Tydecks, S. Aumon, T.K. Charles, B. Härer, B.J. Holzer, K. Oide, Y. Papaphilippou, J. Wenninger
CERN, Geneva, Switzerland

The FCC-ee Lepton Collider will provide e+e collisions in the beam energy range of 45.6 GeV to 182.5 GeV. FCC-ee will be a precision measurement tool for Z, W, H and t physics with expected luminosities of 2.07× 1036 cm-2 s-1 at the Z-pole and 1.3 × 1034 cm-2 s-1 at the tt- threshold. In order to achieve the foreseen luminosities, a vertical β* of 1 mm to 2 mm is mandatory. Dynamic aperture and frequency map analysis for the 97.75 km machine with such a squeezed accelerator optics are studied. Furthermore, effects of machine misalignments on dynamic and momentum aperture are presented and estimations for the required tolerances are given
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF057
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MOPML007 Analysis of Spin Response Function at Beam Interaction Point in JLEIC collider, polarization, proton, sextupole 400

• V.S. Morozov, Y.S. Derbenev, F. Lin, Y. Zhang
JLab, Newport News, Virginia, USA
• Y. Filatov
MIPT, Dolgoprudniy, Moscow Region, Russia
• A.M. Kondratenko, M.A. Kondratenko
Science and Technique Laboratory Zaryad, Novosibirsk, Russia

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under con-tracts DE-AC05-06OR23177 and DE-AC02-06CH11357.
The spin response function is determined by a collid-er's magnetic lattice and allows one to account for con-tributions of perturbing fields to spin resonance strengths. The depolarizing effect of an incoming beam depends significantly on the response function value at the interaction point (IP). We present an analytic calcula-tion of the response function for protons and deuterons at the IP of Jefferson Lab Electron Ion Collider (JLEIC) over its whole momentum range. We find a good agreement of the analytic calculation with our numerical modeling results obtained using a spin tracking code, Zgoubi.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML007
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MOPML032 Prospects for a Muon Spin Resonace Facility in the Fermilab MuCool Test Area target, linac, experiment, timing 474

• J.A. Johnstone, C. Johnstone
Fermilab, Batavia, Illinois, USA

Funding: Work supported by Fermi Reserach Alliance, LLC under Contract no. DE-AC02-07CH11359 with the United States Department of Energy.
This paper investigates the feasibility of re-purposing the MuCool Test Area beamline and experimental hall to support a Muon Spin Resonance Facility which would make it the only such facility in the US. This report reviews the basic muon production concepts as studied and operationally implemented at TRIUMF, PSI, and RAL and their application in the context of the MTA facility. Two scenarios were determined feasible. One, an initial minimal-shielding and capital-cost investment stage with a single secondary muon beamline that utilizes an existing primary beam absorber and, another, an upgraded stage, that implements an optimized production target, a proximate high-intensity absorber, and optimized secondary muon lines. A unique approach is proposed which chops or strips a macropulse of H beam into a micropulse substructure - a muon creation timing scheme - which allows Muon Spin Resonance experiments in a linac environment. With this timing scheme, and attention to target design and secondary beam collection, the MTA can host enabling and competitive Muon Spin Resonance experiments.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML032
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MOPML035 Betatron Frequencies in Cotangential Trajectory Accelerator for Proton Beam Therapy betatron, alignment, cyclotron, extraction 485

• T. Aoki, F. Ebina, C. Hori, Y. Nakashima, T. Seki
Hitachi Ltd., Ibaraki-ken, Japan
• T. Hae
Hitachi Ltd., Hitachi Research Laboratory, Ibaraki-ken, Japan

It is important that downsizing of an accelerator for spreading proton beam therapy. The synchrotron is the solution of accelerator of proton beam therapy system which can vary energy of extracted beam in the range of from 70 MeV to 235 MeV with a merit of requiring no energy selection system. In order to downsize accelerator with above merit, we suggested smaller variable energy accelerator which have cotangential trajectories. This new type accelerator is expected to realize variability of beam energy with static main magnetic field. One of technological problems of this new type accelerator is stability of betatron oscillation. We plan to utilize week focusing field as main magnetic field, which is decreasing on the radial direction outward and uniform in longitudinal direction, of this new type accelerator. We found the main magnetic field which realizes stable betaron oscillations in the range of from 70 MeV to 235 MeV as the result of estimating the betaron oscillations in this main field by numerical calculation. We report new type accelerator concept and results of analysis of betatron oscillation in cotangential trajectories.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML035
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TUPAF005 Status of AC-Dipole Project at RHIC Injectors for Polarized Helions dipole, booster, proton, simulation 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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TUPAF010 Empty Sweeping Bucket for Slow Extraction extraction, acceleration, hadrontherapy, synchrotron 676

• L. Falbo, E. Bressi, C. Priano
CNAO Foundation, Milan, Italy

The extraction process from a synchrotron is one of the most important aspects of an accelerator devoted to clinical purposes, like the hadrontherapy in which hadron beams are used to treat tumors. Indeed the quality of the dose delivered to the patient, in terms of dose uniformity and precision in the beam characteristics, is defined by the way in which the beam is extracted. The quality of the extracted beam (the so called spill) is strongly affected by the stability of the power supplies of the synchrotron magnets whose field stability creates a ripple in the intensity of the extracted beam itself. When it is not possible to improve the power supply stability, it is needed to apply some additional techniques in order to cure the spill ripple. At CNAO, the italian hadrontherapy facility, it has been thought to improve the Empty Bucket Channelling technique by using an energy-moving bucket instead of a stationary bucket. The paper shows the implementation, the advantages and the efficacy of this RF gymnastic, named 'Empty Sweeping Bucket'.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF010
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TUPAF048 LIU Space Charge Studies for the LHC Pre-Accelerators space-charge, injection, proton, simulation 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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TUPAF061 Use of a Massless Septum to Increase Slow-Extraction Efficiency septum, extraction, sextupole, simulation 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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TUPAF081 Measurements and Simulations of the Spill Quality of Slowly Extracted Beams from the SIS-18 Synchrotron sextupole, extraction, synchrotron, experiment 924

• S. Sorge, P. Forck, R. Singh

In this contribution, results of recent measurements of the spill structure of slowly extracted beams out of the GSI heavy ion synchrotron SIS-18 are presented and compared to results of simulations. Aim of the study is the determination of spill structures at several kHz which arise from ripples in the fields of the accelerator magnets due to imperfections of the magnets' power supplies. The goal of the study is to understand how the ripple is transferred from the magnets to the spill and to find possible ways for spill smoothing. For this purpose a comprehensive simulation model for slow extraction is in preparation which will be validated with beam-based measurements.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF081
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TUPAF086 Adaption of the HSI -RFQ Rf-Properties to an Improved Beam Dynamics Layout simulation, rfq, operation, linac 938

• M. Vossberg, L. Groening, S. Mickat, H. Vormann, C. Xiao
• 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, simulation, impedance, acceleration 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.

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TUPAF088 Final factory-side Measurements of the Next SC CH-Cavities for the HELIAC-Project cavity, linac, heavy-ion, factory 943

• M. Basten, M. Busch, H. Podlech, M. Schwarz
IAP, Frankfurt am Main, Germany
• K. Aulenbacher, W.A. Barth, V. Gettmann, T. Kürzeder, M. Miski-Oglu
HIM, Mainz, Germany
• W.A. Barth, F.D. Dziuba, M. Heilmann, S. Yaramyshev

Funding: Work supported by the EU Framework Programme H2020 662186 (MYRTE); Work supported by BMBF Contr. No. 05P15RFBA;
The upcoming FAIR project (Facility for Antiproton and Ion Research) at GSI will use the existing UNILAC (UNIversal Linear Accelerator) as an injector to provide high intensity heavy ion beams at low repetition rates. As a consequence a new superconducting (sc) continous wave (cw) high intensity heavy ion Linac is required to provide ion beams above the coulomb barrier to keep the Super Heavy Element (SHE) physics program at GSI competitive on an international level. The fundamental Linac design comprises a high performance ion source, the High Charge State Injector (HLI) upgraded for cw-operation and a matching line (1.4 MeV/u) followed by a sc Drift Tube Linac (DTL). Four cryo modules each equipped with three Crossbar-H-mode (CH) structures provide for acceleration up to 7.3 MeV/u. The first section of this ambitious accelerator project has been successfully commissioned and tested with heavy ion beam from the HLI in 2017. It comprises two sc 9.3 T solenoids and a sc 217 MHz CH-cavity with 15 equidistant gaps as a demonstrator. The construction of the next two sc 217 MHz 8 gap CH-cavities is nearly finished and final factory-side measurements will be presented.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF088
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TUPAF089 Initial Measurements on a New 108 MHz 4-Rod CW RFQ Prototype for the HLI at GSI rfq, simulation, dipole, linac 946

• D. Koser, K. Kümpel, H. Podlech
IAP, Frankfurt am Main, Germany
• P. Gerhard
• O.K. Kester

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, simulation, controls 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

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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TUPAL036 Slow Extraction Techniques at the Marburg Ion-Beam Therapy Centre extraction, synchrotron, simulation, controls 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

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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TUPAL051 Program for High-Intensity RFQ Design With Matched and Equipartitioned Design Strategy rfq, emittance, linac, ISOL 1126

• H.P. Li, M.J. Easton, Q. Fu, P.P. Gan, Y.R. Lu, Q.Y. Tan, Z. Wang, K. Zhu
PKU, Beijing, People's Republic of China

The deuteron driver accelerator of the Beijing Iso-tope Separation On-Line (BISOL) facility will acceler-ate and deliver a 20 mA deuteron beam to the targets with an energy of 40 MeV. As the injector of the driver linac, an RFQ is required to bunch and accelerate the 20 mA deuteron beam to 3 MeV with very high beam quality. In order to fulfil these requirements and re-duce time spent on optimization, an RFQ design pro-gram named RFQEP has been developed to generate the input file for the PARMTEQM code. In this program, the ‘matched and equipartitioned' design strategy is adopted to prevent halo formation and to avoid struc-ture resonances in high intensity RFQs. The detailed design aspects are studied in this paper and simulation results are given for an RFQ designed by this code, which shows the accuracy and the merits of the new program.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL051
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TUPAL054 Experimental Measurements of Resonances near to the ISIS Working Point experiment, synchrotron, controls, space-charge 1132

• P.T. Griffin-Hicks, B. Jones, B.G. Pine, C.M. Warsop, M. Wright
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

ISIS is the pulsed spallation neutron source located at the Rutherford Appleton Laboratory in the UK. Operation is based on a 50 Hz, 800 MeV proton synchrotron, accelerating up to 3·1013 protons per pulse (ppp), which provides beam to two target stations. ISIS is beam loss limited, so to achieve greater beam intensity and optimal operation, losses must be reduced. Some beam loss may be attributed to resonance lines found in betatron tune space. These could be driven by higher order magnet field components, errors or misalignment. This paper describes work measuring losses against tune space around the ISIS working point. Experiments have been carried out to measure beam loss against tune in the ISIS synchrotron. The experiments were done at low intensity to minimise space charge and intensity effects. Resonance lines that cause beam loss can be clearly identified and provide new information about the machine. The experimental process has been automated in order to decrease experiment duration and to reduce systematic human error. MAD-X models that compare the beam envelope at different points in tune space to the beam pipe aperture are used to distinguish between losses caused by increased envelope size and losses induced by driven resonances.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL054
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TUPAL056 High Order Image Terms and Harmonic Closed Orbits at the ISIS Synchrotron closed-orbit, simulation, 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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TUPAL064 Extended-Domain Tune-Scans for the HL-LHC Dynamic Aperture in Presence of Beam-Beam Effects lattice, octupole, dynamic-aperture, beam-beam-effects 1163

• D. Kaltchev
• N. Karastathis, Y. Papaphilippou, D. Pellegrini
CERN, Geneva, Switzerland

We report simulations of the HL-LHC dynamic aperture (DA) at collision energy in the presence of beam-beam effects (weak-strong approximation) aiming to determine its dependence on the working point in tune space. Both linear domains working points are explored, spanning over (0.028 – 0.33) in horizontal tune, and two-dimensional ones which focus on more promising sub-regions near the diagonal. The range of parameters, such as bunch intensity and emittance, are chosen to correspond to the more important HL-LHC scenarios. A comparison with the LHC as built is also made. Direct benefit from these studies is the possible identification of working points alternative to the nominal one (in terms of dynamic aperture). They also help to understand the dependence of DA on particular resonance lines present in the vicinity of the footprint. In this work, the necessary resources were provided by the LHC@home project, based on the BOINC-SixTrack platform for distributed Computing.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL064
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TUPMF003 Dynamic Tuning of the APS-U Booster 5-cell Cavities booster, cavity, extraction, coupling 1251

• G.J. Waldschmidt, M. Abliz, T.G. Berenc, D. Horan, U. Wienands
ANL, Argonne, Illinois, USA

The booster synchrotron for the APS-U is being upgraded to accommodate high-charge bunches, up to 20 nC, for extraction into the MBA lattice. The booster is required to operate at 85% efficiency in order to achieve bunch swap-out into the storage ring. In order to compensate for significant beam-loading effects as well as support a frequency ramp to achieve higher efficiency, a ferrite tuner is being considered to dynamically adjust the cavity frequency. A tuner design will be presented that spans 60 kHz and utilizes a low-loss YIG garnet similar to that used in the Recycler Ring at Fermilab.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF003
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TUPMF011 Calculation of Expected Orbit Motion Due to Girder Resonant Vibration at the APS Upgrade ground-motion, factory, lattice, quadrupole 1269

• V. Sajaev, Z. Liu, J. Nudell, 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. To keep the beam orbit stable on a sub-micron level, one needs to carefully design magnet supports/girders so that the ground motion does not lead to excessive orbit motion due to resonant modes of magnet supports. In this paper, we will describe the process of calculating the expected orbit motion due to girder resonant vibration. First, we will present the simulation results for the girder resonant modes, then we will calculate the orbit amplification factors for the girder deformation modes, then calculate the expected orbit motion using measured ground motion spectrum. This process can be used to evaluate the design of the magnet supports.

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TUPMF021 Investigation of Options for Damping Trapped IVU Resonances impedance, damping, undulator, simulation 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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TUPMF068 Beam Dynamics on a Coupling Resonance at PETRA III coupling, optics, lattice, injection 1417

• I.V. Agapov, J. Keil, G. Kube, G.K. Sahoo, R. Wanzenberg
DESY, Hamburg, Germany
• Y.-C. Chae
ANL, Argonne, Illinois, USA
• A.I. Novokshonov
TPU, Tomsk, Russia

Working on a coupling resonance is a usual way of producing round beams in a synchrotron. The beam dynamics in this regime is however more complicated, and the emittance is sensitive to the working point, coupling correction, and bunch current drop with time, which complicates the operation. We present experience with optics setup for working on a coupling resonance in PETRA III, including linear and nonlinear beam optics characteristics, and the measurement of the horizontal and vertical beam emittances with a 2D interferometer. Beam dynamics on a coupling resonance for PETRA IV, the MBA upgrade of PETRA III currently under consideration, is also presented.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF068
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TUPMK001 Removal of RF-Fingers at the Edges of the Injection Kickers impedance, kicker, storage-ring, injection 1485

• T.F.G. Günzel, N. Ayala, F.F.B. Fernández, U. Iriso, M. Pont
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

The ALBA storage ring injection kickers are equipped with RF-fingers to close a 2.5 mm gap between the ceramic tube and the metallic flange. After two distortion incidents that required the replacement of the fingers, their removal was decided. The decision could be supported by the observation that most of the additional impedance is created above the cut-off frequency of the beam pipe. This was later confirmed by a temperature decrease in that zone after the removal. Furthermore it was checked that the thresholds of the longitudinal coupled bunch instabilities of modes trapped around the resulting open gap are above the maximal applied beam current of 400 mA.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMK001
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TUPMK018 Round Beam Studies at NSLS-II coupling, emittance, lattice, experiment 1529

• Y. Hidaka, W.X. Cheng, Y. Li, T.V. Shaftan, G.M. Wang
BNL, Upton, Long Island, New York, USA

Funding: The study is supported by U.S. DOE under Contract No. DE-AC02-98CH10886.
Instead of typical flat beam, some synchrotron light us-ers prefer round beam, i.e., with equal horizontal and vertical emittance, for various reasons (e.g., simplified optics, smaller fraction of photons getting discarded, better phase space match between photon and e-beam). Several future upgrade storage rings such as APS-U, ALS-U, and SLS-2 currently plan to operate in round beam mode. We report our beam study results on round beam operating at NSLS-II by driving linear difference cou-pling resonance.

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TUPML052 Characterisation of the Second Stable Orbit Generated by Transverse Resonance Island Buckets (TRIBs) optics, experiment, emittance, simulation 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

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WEPAF015 Commissioning the Muon g-2 Experiment Electrostatic Quadrupole System quadrupole, storage-ring, experiment, positron 1848

• J.D. Crnkovic, V. Tishchenko
BNL, Upton, Long Island, New York, USA
• K.E. Badgley, H. Nguyen, E. Ramberg
Fermilab, Batavia, Illinois, USA
• E. Barlas Yucel, M. Yucel
Istanbul Technical University, Maslak, Istanbul, Turkey
• J.M. Grange
ANL, Argonne, Illinois, USA
• A.T. Herrod
Cockcroft Institute, Warrington, Cheshire, United Kingdom
• A.T. Herrod
The University of Liverpool, Liverpool, United Kingdom
• J.L. Holzbauer, W. Wu
UMiss, University, Mississippi, USA
• H.D. Sanders
APP, Freeville, New York, USA
• H.D. Sanders
Sanders Pulsed Power LLC, Batavia, Illinois, USA
• N.H. Tran
BUphy, Boston, Massachusetts, USA

The Fermilab Muon g-2 experiment aims to measure the muon anomaly with a precision of 140 parts-per-billion (ppb) - a fourfold improvement over the 540 ppb precision obtained by the BNL Muon g-2 experiment. These high precision experiments both require a very uniform muon storage ring magnetic field that precludes the use of vertical-focusing magnetic quadrupoles. The Fermilab Electrostatic Quadrupole System (EQS) is the refurbished and upgraded BNL EQS, where this overview describes the Fermilab EQS and its recent operations.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF015
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WEPAF017 Correction of ID-Induced Transverse Linear Coupling at NSLS-II coupling, emittance, operation, quadrupole 1856

• Y. Hidaka, Y. Li, T.V. Shaftan, T. Tanabe, Y. Tian, G.M. Wang
BNL, Upton, Long Island, New York, USA

Funding: The study is supported by U.S. DOE under Contract No. DE-AC02-98CH10886.
Sizeable lifetime jumps have been observed sporadically since March 2016 at NSLS-II. These jumps were found to coincide with insertion device (ID) gap motions. Particularly, one of the in-vacuum undulators (IVUs) at Cell 17 was discovered to have large localized skew quadrupole component variation with gap. To allow the machine to operate stably in the low-emittance mode, a global coupling feedforward system has been recently implemented and successfully deployed. After installation of a new additional skew quadrupole, coupling compensation of this ID is now performed by a local coupling feedforward system. Furthermore, the maximum gap limit of all the existing IVUs has been decreased from 40 mm to 25 mm to limit the skew component variation during user operation.

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WEPAF058 Detection of X-Rays and Charged Particles via Detuning of the Microwave Resonator coupling, monitoring, network, experiment 1958

• S.P. Antipov
Euclid TechLabs, LLC, Solon, Ohio, USA
• S.V. Kuzikov
Euclid Beamlabs LLC, Bolingbrook, USA
• S. Stoupin
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
• A.A. Vikharev
IAP/RAS, Nizhny Novgorod, Russia

Funding: DOE SBIR
Critically coupled microwave resonator is a finely balanced system, reflection at the resonance is virtually zero. Small changes in dielectric properties of resonator parts destroy this balance, small reflection can be detected from the resonator. This measurement is used in electron paramagnetic resonance studies. In this paper we discuss two accelerator - related applications of this technology. First is related to beam halo measurement taking advantage of high sensitivity of the microwave measurement. High energy particles crossing the diamond inside of a tuned resonator induce a weak conductivity in the sensing material. This small change results in resonator decoupling providing a signal proportional to a number of particles crossing the diamond plate. Second application considered is the x-ray flux monitoring. In this case it is x-ray induced photoconductivity which alters resonator coupling and produces a signal. Interestingly, sensing dielectric material embedded in a resonator can be a diamond or kapton window, refractive lens or part of a silicon monochromator. Thus an inevitable x-ray absorption on optical elements of the beamline is used to monitor x-ray flux online.

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WEPAK007 Slow Extraction Spill Characterization From Micro to Milli-Second Scale extraction, power-supply, experiment, betatron 2095

• R. Singh, P. Boutachkov, P. Forck, S. Sorge, H. Welker

This contribution deals with the topic of slow extraction spill quality characterization based on the measurements performed at GSI SIS-18. The sensitivity of the spill to power supply ripples are studied by introducing external ripples. An estimate of sources of inherent power supply ripples along with ripple magnitude are thus obtained. Spill characterization in time and frequency domain are discussed and exemplified by a typical spill and the differences from an ideal or Poisson spill. An appropriate spill characterization aims to provide a suitable abstraction for communication about the spill quality requirements between accelerator operations and users.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAK007
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WEPAL021 Study of a Tuner for a High-Accuracy Bunch Shape Monitor linac, insertion, cavity, electron 2200

• K. Moriya, Y. Kawane, A. Miura
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
• K. Futatsukawa, T. Miyao
KEK, Ibaraki, Japan

In the J-PARC Linac, development and higher precision of Bunch Shape Monitor (BSM) have been progressed for measuring the longitudinal beam distribution. To transform a longitudinal beam-profile into transverse one with an rf field, we need the field having an acceleration synchronizing frequency. An rf deflector of BSM consists of a half λ cylindrical cavity and two electrodes for deflection. In general, the resonance frequency can be tuned by adjusting the electrode length. We designed the new tuner with CST Studio. We can control the resonance frequency by Adjusting not only the electrode length but the cavity volume. We found the optimum lengths of electrode and volume for tuning. We introduce development of the new rf tuner for BSM in this paper.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL021
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WEPAL024 High Precision Beam Parameter Stabilization for P2 at MESA experiment, cavity, electron, controls 2209

• R.F.K. Kempf, J. Diefenbach
IKP, Mainz, Germany
• K. Aulenbacher
HIM, Mainz, Germany

Funding: Cluster of Excellence PRISMA (EXC 1098/2014) German Research Foundation DFG (GRK 2128)
The experiment P2 will measure the weak mixing angle with an all-time high precision via electron-proton scattering. The measured physics asymmetry and its uncertainty has to be corrected by the apparatus' asymmetry, which is generated by helicity correlated fluctuations of the beam parameters position, angle, intensity and energy. This Poster will describe how the high precision of 0.1 ppb of the parity violating asymmetry can be provided by the high precision measurements of the parameters position, angle and intensity.

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WEPAL066 Determination of RF Resonator Axis Inclination to Beam Axis in Electron-Positron Storage Ring experiment, kicker, electron, positron 2330

• Leshenok D. Leshenok
NSU, Novosibirsk, Russia
• S.A. Nikitin
BINP SB RAS, Novosibirsk, Russia

We proposed and tested the method that allows obtaining of an upper limit for an angle of the RF resonator axis inclination relative to a beam axis. Such disturbance gives an additional contribution to separation of electron and positron orbits due to action of the transverse component of the electric field. In the horizontal plane, this effect can lead to increase of the difference between electrons and positrons spin precession frequencies in a storage mono-ring collider. This effect can play a great role in FCC. At the angular disturbance of axis in the certain VEPP-4M RF resonators ~10-3 rad, the difference between the spin frequencies is about 10-8. Our method is based on resonant excitation of betatron oscillations using phase modulation of the master oscillator of the RF system. The maximal amplitude of the enforced oscillations is measured by the counting rate of the VEPP-4M Touschek polarimeter scintillation counters. Comparison of the obtained results with the data of the special calibration experiment allows estimating the value of the inclination angle. In this calibrated experiment the betatron oscillations excite using the VEPP-4M kicker.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL066
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WEPAL069 Reentrant Cavity Resonator for Low Intensities Proton Beam Measurements simulation, pick-up, cavity, 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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WEPMF051 Multipacting in an RF Window: Simulations and Measurements multipactoring, electron, simulation, 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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WEPMK014 A New Design for the Hilumi Radio-Frequency Dipole Bare Cavity cavity, niobium, GUI, SRF 2659

• M. Parise, P. Berrutti, L. Ristori
Fermilab, Batavia, Illinois, USA

Crabbing cavities are one of the technological landmark that will allow the LHC to optimize its per-formance and maximize its integrated luminosity by allowing a head-on collision between the bunches despite the non-zero crossing angle. A total of 8 crab cavities will be installed in the interaction region of each of the two experiments, ATLAS and CMS. In the last years, the two types of crab cavities were de-signed, built and tested under the US-LARP R&D pro-gram. Horizontal crabbing is obtained with a radio-frequency dipole cavity (RFD) designed by Old Do-minion University (ODU), SLAC and Fermilab (FNAL). In this paper a new mechanical design, that uses passive stiffeners, is presented. This design leads to a decrease of the Lorentz Force Detuning frequency shift, satisfy the requirements on pressure sensitivity, validate the structural integrity and increase the tuner sensitivity and the maximum elastic tuning range. Furthermore, it will be possible to greatly simplify the shape of the magnetic shield and Helium vessel with respect to the current design.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK014
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WEPML001 Passive Microphonics Mitigation during LCLS-II Cryomodule Testing at Fermilab cryomodule, cavity, cryogenics, controls 2668

• J.P. Holzbauer, B.E. Chase, J. Einstein-Curtis, B.J. Hansen, E.R. Harms, J.A. Kaluzny, A.L. Klebaner, M.W. McGee, Y.O. Orlov, T.J. Peterson, Y.M. Pischalnikov, W. Schappert, R.P. Stanek, J. Theilacker, M.J. White, G. Wu
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 LCLS-II project calls for cryomodule production and testing at both Fermilab and JLab. Due to low beam loading and high cavity quality factor, the designed peak detuning specification is 10 Hz. Initial testing showed peak detuning up to 150 Hz with a complex and varying time-structure, showing both fast (1-2 second) and slow (1-2 hour) drifts in amplitude and spectrum. Extensive warm and cold testing showed Thermoacoustic Oscillations in the cryogenic valves were the primary source of the microphonics. This was mitigated by valve wipers and valve re-plumbing, resulting in a greatly improved cavity detuning environment. Additional modifications were made to the cavity mechanical supports and Fermilab test stand to improve detuning performance. These modifications and testing results will be presented.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML001
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WEPML007 Active Microphonics Compensation for LCLS-II cavity, controls, LLRF, cryomodule 2687

• J.P. Holzbauer, B.E. Chase, J. Einstein-Curtis, Y.M. Pischalnikov, W. Schappert
Fermilab, Batavia, Illinois, USA
• L.R. Doolittle, C. Serrano
LBNL, Berkeley, California, 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.
Testing of early LCLS-II cryomodules showed microphonics-induced detuning levels well above specification. As part of a risk-mitigation effort, a collaboration was formed between SLAC, LBNL, and Fermilab to develop and implement active microphonics compensation into the LCLS-II LLRF system. Compensation was first demonstrated using a Fermilab FPGA-based development system compensating on single cavities, then with the LCLS-II LLRF system on single and multiple cavities simultaneously. The primary technique used for this effort is a bank of narrowband filter set using the piezo-to-detuning transfer function. Compensation automation, optimization, and stability studies were done. Details of the techniques used, firmware/software implementation, and results of these studies will be presented.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML007
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WEPML022 3.9 GHz Power Coupler Design and Tests for LCLS-II Project cavity, simulation, 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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WEPML031 The New Broadband Accelerating System for the SIS18 Upgrade at GSI cavity, operation, impedance, controls 2755

• P. Hülsmann, R. Balß, H. Klingbeil, U. Laier, K.-P. Ningel, C. Thielmann, B. Zipfel

In this contribution, a new SIS18 rf accelerating system is presented whose cavities are based on magnetic alloy materials. The rf system works at harmonic number h=2 (f=0,43- to 2,8 MHz) and provides the necessary accelerating voltage (up to 50kVp) for SIS18 injector operation for FAIR with high intensity heavy ion beams in a fast operation mode with up to three cycles per second. The paper focusses on the cavity part and its cooling issues as well as the broadband characteristics. Due the lossy magnetic alloy ring core filling, which consists of high permeability Finemet FT3M ring cores (HITACHI), the cavities show a broadband behaviour and thus no cavity tuning during the acceleration ramp is necessary. To keep the bandwidth of the cavities as broad as possible they are cooled by a special mineral oil with low permittivity. Also the beam impedance and the power consumption of the rf system are discussed.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML031
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WEPML043 RF Simulations of the Injector Section from CH8 to CH15 for MYRRHA simulation, cavity, impedance, 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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WEPML064 Design of the Trim Coil for the Superconducting Cyclotron Extraction extraction, cyclotron, controls, flattop 2840

• L.G. Zhang, K. Fan, S. Hu, Z.Y. Mei, Z.J. Zeng
HUST, Wuhan, People's Republic of China

A proton therapy system is being developed at Huazhong university of science and technology (HUST). A 250 MeV superconducting cyclotron with an average magnetic filed of 3.1 T in the extraction region is selected to reduce the machine size, which creates difficulties for beam extraction because of the small turn separation of the beam orbits in the extraction region. To obtain high extraction efficiency, a carefully controlled magnetic perturbation is introduced to excite resonance when beam passes through the νr =1 resonance. The first-order perturbation in the magnetic field is generated by trim coils within confined regions. The profile of the trim coil and the resultant perturbation fields are optimized iteratively with orbit tracking. Simulation shows that sufficient turn separation can be obtained with the proper setting of trim coils.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML064
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WEPML070 The Status of the CSNS/RCS Power Supply System power-supply, dipole, neutron, network 2850

• X. Qi, Z. Hao, W. Zhang
IHEP, Beijing, People's Republic of China

The 1.6GeV proton synchrotron proposed in the CSNS Project is a 25Hz rapid-cycling synchrotron (RCS) with injection energy of 80MeV. Beam power is aimed to 100kW at 1.6GeV. In this year, the neutron beam was successfully obtained for the first time. This paper will introduce the commission statues of RCS Power Supply System status in the last year.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML070
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THYGBD3 Beam-beam Studies for Super Proton-Proton Collider luminosity, closed-orbit, collider, proton 2918

• L.J. Wang, J.Y. Tang
IHEP, Beijing, People's Republic of China
• K. Ohmi
KEK, Ibaraki, Japan

In China, a two-stage circular collider project, CEPC-SPPC has been proposed. The first stage, CEPC (Circular Electron Positron Collier, a so-called Higgs factory) is focused on the Higgs physics, and the second stage, SPPC (Super Proton-Proton Collider) will be an energy frontier collider and a discovery machine. Luminosity is a key factor for any particle-physics colliders. With the increasing bunch population, beam-beam interaction is increasingly become the limit factor of luminosity improvement. The finite crossing angle scheme is considered firstly. Meanwhile, long-range interaction is another significant source of luminosity degrade. In this report, firstly, we don't consider long-range interactions and study luminosity degrade with crossing angle and without crossing angle for horizontal crossing and horizontal-vertical crossing. Secondly we discuss luminosity decay with long-range interactions for horizontal crossing and horizontal-vertical crossing. Thirdly, we talk about emittance growth and luminosity degradation using resonance analysis for different scenarios. Finally the resulting beam-beam limit will be concluded for SPPC.
Slides THYGBD3 [1.379 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THYGBD3
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THPAF051 Beam Impedance Evaluation for CERN PS Gate Valves by Simulation and Benchmark Measurement impedance, simulation, wakefield, 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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THPAF052 Impedance Analysis of New PS Internal Dump Design impedance, HOM, coupling, vacuum 3083

• B.K. Popovic, L. Teofili, C. Vollinger
CERN, Geneva, Switzerland

The High Luminosity Large Hadron Collider (HL-LHC) project at CERN calls for increasing beam intensity in the injector chain. In the Proton Synchrotron (PS), a pre-injector of the LHC, these intensities can result in beam instabilities and potential RF heating of machine components, such that impedance mitigation measures are required. To study these intensity effects, the PS impedance model has been developed and is continuously updated. Each new machine element that is to be added into the accelerator requires an impedance study to minimize its contribution with respect to the machine's overall impedance budget. In such a context, this paper presents the impedance analysis of the new design of the internal beam dump for the PS, showing the design process required to reduce the impedance contribution of this element. Furthermore, the impedance analysis of the currently installed beam dump is analysed in order to compare the impedance contributions of the two designs.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF052
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THPAF054 Characterization of Losses and Emittance Growth for Ion Beams on the SPS Injection Plateau emittance, space-charge, injection, scattering 3091

• Á. Saá Hernández, F. Antoniou, H. Bartosik, A. Huschauer
CERN, Geneva, Switzerland

Losses and transverse emittance growth in the Super Protron Synchrotron (SPS) impose presently the main performance limitation on the Large Hadron Collider (LHC) ion injector chain. In this paper we present the measurements performed in 2016 with Pb82+ ions and the analysis to characterize the observations of beam degradation during the long injection plateau. Residual gas scattering, intrabeam scattering (IBS) and resonance excitation have been studied.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF054
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THPAF055 Space Charge Studies on LEIR space-charge, emittance, simulation, 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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THPAF063 Identification of Imperfections in Impedance Shields on the SPS-QF Flanges via Non-Intrusive Measurements impedance, shielding, coupling, cavity 3119

• A. Farricker, P. Kramer, B.K. Popovic, E. Sunar, C. Vollinger, M. Wendt
CERN, Geneva, Switzerland

In order to achieve the highest beam intensities possible in the LHC the highest quality beam possible has to be supplied by the injector chain. The Super Proton Synchrotron (SPS) at CERN is the last accelerator in the injector chain of the LHC. One factor that is currently known to limit the intensity of the beam for injection to the LHC, is the longitudinal beam-coupling impedance in the SPS. One known source of multi-bunch instability is the vacuum flanges and campaigns to mechanically shield this source were completed in the year 2000. However, today it cannot be excluded that some of these shields may have partial or indeed full failures. Since these flanges are next to a QF magnet and are in most cases connected to a BPH (Beam Position Monitor Horizontal), it is possible to carry out via the BPH an in-situ measurement of the effectiveness of the shields. In this paper we present a methodology as well as measurement results taken with this non-intrusive in-situ method. From measurements, it is possible to identify if the flanges are without any impedance shield, equipped with either a fully functioning shield or a shield exhibiting non-ideal properties.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF063
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THPAF069 Particle Tracking Simulation of Collective Modes - Parametric Landau Damping Off Coupling Resonance damping, coupling, simulation, 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, simulation, 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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THPAF080 SIS100 Beam Dynamics Challenges Related to the Magnet System dipole, quadrupole, sextupole, extraction 3172

• V. Kornilov, O. Boine-Frankenheim, V. Chetvertkova, S. Sorge, P.J. Spiller

The SIS100 synchrotron is the central accelerator of the upcoming FAIR project at GSI, Darmstadt, Germany. The major challenges of the future operation are related to high-intensity, low beam loss operation for a wide range of ion species and charge states, for different operational cycles and extraction schemes. The magnet system consists of 108 dipole, 166 quadrupole and additional correction superconducting superferric magnets. The magnets are presently under production and testing, with detailed measurements of the magnetic field imperfections. This results in the construction of a complete database for the SIS100 magnet system. We analyse implications of the magnetic field imperfections for the single-particle stability, space charge induced tune-shifts and resonance crossing for the different SIS100 operation modi. Resonance compensation and magnet sorting schemes are discussed as possible measures.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF080
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THPAK024 A new method to measure the Beta function in a Paul trap dipole, experiment, lattice, emittance 3262

• L. Martin, S.L. Sheehy
JAI, Oxford, United Kingdom
• K. Ito, H. Okamoto
• D.J. Kelliher
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
• S. Machida
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

The Simulator of Particle Orbit Dynamics (S-POD) is a linear Paul trap at Hiroshima University, Japan, used to study beam physics. S-POD has so far been used to study resonances in high intensity beams, predominantly using a simple alternating gradient lattice configuration. Recently a similar apparatus, the Intense Beam Experiment (IBEX), has been constructed at the Rutherford Appleton Lab in the UK. To use either of these experiments to study beam dynamics in more complex lattice configurations in the future further diagnostic techniques must be developed for Paul traps. Here we describe a new method to measure the beta function and emittance at a given time in a Paul trap.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK024
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THPAK056 Resonance Identification Studies at the CERN PS space-charge, sextupole, experiment, synchrotron 3350

• F. Asvesta
NTUA, Athens, Greece
• H. Bartosik, A. Huschauer, Y. Papaphilippou, G. Sterbini
CERN, Geneva, Switzerland

In view of the LHC Injectors Upgrade (LIU) and the challenging high brightness target beam parameters, a broad range of possible working points for the Proton Synchrotron (PS) is being investigated. High order resonances have been identified, both structural resonances driven by space charge due to the lattice harmonics of the PS, and resonances excited by multipolar components in the machine. This paper provides a summary of the performed tune scan studies, covering both experimental and simulation results. Furthermore, non-linear analysis techniques have been used to characterize the resonances and their effect on the beam in presence of space charge.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK056
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THPAK103 Pragmatic Method of Deducing a Wake Function for a General 3D Structure impedance, wakefield, simulation, vacuum 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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THPAK108 Fourier Coefficients of Long-Range Beam-Beam Hamiltonian via Two-Dimensional Bessel functions lattice, optics, emittance, TRIUMF 3486

• D. Kaltchev

The two-dimensional coefficients (resonance basis) in the Fourier expansion of the long-range beam-beam Hamiltonian have been expressed through the (less familiar) generalized modified Bessel functions of two arguments. We describe an efficient method to compute these coefficients based on the above representation. The method has been applied to HL-LHC lattices and benchmarked against MadX simulations of detuning.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK108
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THPAK110 Correction of νrz=1 Resonance in TRIUMF Cyclotron coupling, cyclotron, TRIUMF, simulation 3492

• Y.-N. Rao, R.A. Baartman, T. Planche

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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THPAK117 Space Charge Limitations for Bunch Compression in Synchrotrons space-charge, simulation, emittance, synchrotron 3518

• Y.S. Yuan, O. Boine-Frankenheim
• G. Franchetti, I. Hofmann

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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THPAK122 Longitudinal Coupled Bunch Instability in JLEIC HOM, cavity, impedance, electron 3530

• R. Li, J. Guo, F. Marhauser, S. Wang
JLab, Newport News, Virginia, USA

Funding: This work is supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The luminosity performance of the JLEIC design is achieved by using a high bunch repetition rate (476MHz) with moderate bunch charges, similar to the strategy employed in modern lepton colliders. Such a bunch configuration will make single bunch instabilities less probable, yet makes the machine more prone to the onset of longitudinal and transverse coupled bunch instabilities. Consequently, this will set higher demands on the bunch-by-bunch feedback systems to mitigate the multi-bunch instabilities. In this paper we present our detailed analysis of the growth rate of the coupled bunch instabilities for beams in both the electron and ion rings in JLEIC at the collision scenario. The implication of the growth rate on the feedback system will be discussed.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK122
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THPAK137 Beam-Based Sextupolar Nonlinearity Mapping in CESR sextupole, simulation, experiment, 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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THPAK139 Lost Muon Studies for the Muon g-2 Experiment at Fermilab positron, experiment, storage-ring, background 3573

• S. Ganguly, K. T. Pitts
University of Illinois at Urbana-Champaign, Urbana, USA
• J.D. Crnkovic
BNL, Upton, Long Island, New York, USA
• C. C. Polly
Fermilab, Batavia, Illinois, USA

The Fermilab Muon g-2 experiment aims to measure the muon anomalous magnetic moment aµ with an unprecedented precision of 140 parts per billion (ppb), a four-fold improvement over the 540~ppb precision obtained by the BNL Muon g-2 Experiment. This study presents preliminary work on estimating the muon losses by using double coincidences in the calorimeters.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK139
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THPAL059 TEMPERATURE ISSUES OF THE TPS BPMS impedance, wakefield, simulation, site 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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THPAL064 Burst-Mode UV Enhancement Cavity for Laser-Assisted Hydrogen Ion Beam Stripping at SNS cavity, laser, experiment, controls 3799

• A. Rakhman, Y. Liu
ORNL, Oak Ridge, Tennessee, USA

Funding: This work has been supported in part by U.S. DOE grant DE-FG02-13ER41967. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
Recent success of laser-assisted charge exchange for 10 µs duration Hydrogen ion beams at SNS motivates laser development necessary for efficient stripping of 1.0 ms duration beam at full duty cycle. To overcome the laser power challenge, the interaction point was chosen inside an optical cavity. A doubly-resonant enhancement cavity and a novel locking technique have been developed, and a coherent enhancement of 402.5 MHz, 50 ps, 1.05 MW peak power ultraviolet (355 nm) laser pulses operating at 10-μs/10-Hz burst mode has been demonstrated. This will enable 1.0 ms duration laser macropulses at 60 Hz to be stored inside such a cavity to achieve efficient stripping at SNS.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL064
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THPAL113 The Design of 1 MeV Proton LINAC Operating in CW cavity, linac, proton, simulation 3905

• N.V. Avreline

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, simulation, TRIUMF 3908

• N.V. Avreline

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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THPMF070 Non-Linear Optics and Low Alpha Operation at the Storage Ring KARA at KIT wiggler, operation, octupole, injection 4235

• A.I. Papash, E. Blomley, M. Brosi, J. Gethmann, B. Kehrer, A.-S. Müller, M. Schuh, P. Schönfeldt, J.L. Steinmann
KIT, Karlsruhe, Germany

The storage ring Karlsruhe Research Accelerator (KARA) at KIT operate in a wide energy range from 0.5 to 2.5 GeV. Different non-linear effects, in particular, residual octupole components of the magnetic field of the CATACT wiggler at high field level (2.5 T), proximity of the working point to a vertical sextupole resonance Qy=8/3 and weak coupling octupole resonance 2Qx+2Qy=19, high chromaticity, etc. decrease the beam life time. This is because of the reduced dynamic aperture and momentum acceptance for off-momentum particles. A new operation point at high vertical tune Qy=2.81 was tested. For this, injection and ramping tables have been modified. First the values were optimized by simulations, then during beam tests, to minimize betatron tune shaking during beam-energy ramps. It stabilized high-current beams by the fast-feedback system the whole process: injection at 0.5 GeV, ramping, and operation at 1.3 GeV cycles. It essentially improved life time and beam current. In addition, new low-alpha tables have been created and tested, resulting in the reduction of the momentum compaction factor to 10-4. Short bunch operation at 0.5GeV injection energy was also tested successfully.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF070
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THPMK048 The Design and Construction of a Novel Dual-Mode Dual-Frequency Linac Design operation, impedance, cavity, acceleration 4391

• M.H. Nasr, S.G. Tantawi
SLAC, Menlo Park, California, USA

One promising approach in boosting accelerators efficiency is dual-mode simultaneous operation. In our work, the topic of dual-mode acceleration is studied from a wider perspective with new approaches and tools. We present a new type of accelerator structures that operates simultaneously with two modes and two frequencies. The frequencies are not constrained to be harmonically related, but rather have a common sub-harmonic. These designs will utilize a newly developed parallel-feeding network that feeds each individual accelerating cell independently using a distributed feeding network. As a result, the design problem converges to a single-cell design with identical cells. The cells are designed for maximum efficiency using new geometrical optimization that utilizes nonuniform rational B-spline (NURBS) with a series of control points. We will present a study on the topic for S-band simultaneous operation with C-band or X-band.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK048
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THPMK111 Negative Electron Affinity Gallium Arsenide Photocathodes Based on Optically Resonant Nanostructure cathode, electron, experiment, simulation 4575

• S. Zhang, M. Poelker, M.L. Stutzman
JLab, Newport News, Virginia, USA
• X. Peng, J. Zou
East China University of Science and Technology, Shanghai, People's Republic of China

Funding: DOE
We report the design and fabrication of a new type of negative electron affinity (NEA) gallium arsenide (GaAs) photocathode with optically resonant nanostructures. We observed a significant enhancement of the quantum effi-ciency (QE) from the GaAs photocathode with nanowire arrays (NWA) due to the Mie resonance effect within the intended wavelength range. Theoretical calculations of the expected reflectance behaviour together with experi-mental results of optical and photoemission characteris-tics are presented.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK111
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THPML082 Reflected Power Based Extremum Seeking Control Algorithm to Tune the Resonance Frequency of Room Temperature Cavities cavity, controls, TRIUMF, ISAC 4844

• R. Leewe, K. Fong, Z. Shahriari
• M. Moallem

A sliding mode extremum seeking algorithm to tune the resonance frequency was implemented in two of TRIUMF's DTL tanks. The tuning algorithm searches for the minimum reflected power point and was developed to eliminate the highly temperature dependent phase measurement, which was previously used to tune the resonance frequency. Short and long term measurement results show that the tuning algorithm compensates for the RF heating effect as well as for diurnal temperature variations. Reflected power measurements of TRIUMF's DTL tank 3 were taken for both cases of operating the phase based tuning system and the reflected power based tuning system, with an outcome of a higher tuning accuracy of the newly developed system. Another advantage is a quick cavity start up time, as the reflected power based system does not rely on a reference set point which has do be adjusted manually. The sliding mode extremum seeking control loop is currently commissioned in further room temperature cavities of the TRIUMF's ISAC I facility.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML082
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THPML088 Cavity Impedance Reduction Strategies During Multi Cavity Operation in the SIS100 High Intensity Hadron Synchrotron cavity, controls, emittance, acceleration 4863

• D. Mihailescu Stoica, D. Domont-Yankulova
• D. Domont-Yankulova, H. Klingbeil
• H. Klingbeil, D.E.M. Lens

Funding: Supported by GSI Helmholtzzentrum für Schwerionenforschung GmbH
The planned SIS100 heavy ion synchrotron at the GSI Helmholtzzentrum für Schwerionenforschung will possess twenty ferrite accelerating cavities in its final stage of extension. As at injection and at flat top during slow extraction of the planned acceleration cycles the RF voltage will be relatively low, not all cavities will be active in this part of operation. It is important to analyse the impact of the inactive cavities on the overall RF voltage and subsequently their implication on the longitudinal particle dynamics. Classical approaches for reducing the beam impedance consist of active detuning of the cavities to pre-described parking frequencies. The fact that two out of ten buckets have to stay empty in all SIS100 scenarios is of particular interest as additional frequency components appear in the excitatory beam current, which have to be considered when the cavity is detuned. Therefore multi-cavity particle tracking simulations, consisting of twenty cavities and their attached LLRF control systems, are carried out in order to analyse different possibilities to minimize the impact on the beam dynamics and emittance growth.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML088
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THPML117 Study of the Impact of Linear Coupling on Off-Axis Injection coupling, injection, dynamic-aperture, quadrupole 4943

• X. Huang
SLAC, Menlo Park, California, USA
• T. Zhang
USTC/NSRL, Hefei, Anhui, People's Republic of China

The next generation of storage ring light sources will likely operate with high linear coupling, which could potentially prevent the use of off-axis injection as large horizontal oscillation of the injected beam is coupled to the vertical plane. We did experiments on the SPEAR3 storage ring to study how linear coupling impact the dynamic aperture and the off-axis injection efficiency. The results show that the dynamic aperture is significantly reduced and injection efficiency can drop to zero when operated on the coupling resonance. However, with large nonlinear detuning, the dynamic aperture and high injection efficiency can survive with the stored beam at full coupling because the injected beam is shifted away from the coupling resonance.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML117
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