Keyword: cavity
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MOYGB1 Status and Future Strategy for Advanced High Power Microwave Sources for Accelerators klystron, electron, operation, linac 12
 
  • F. Gerigk
    CERN, Geneva, Switzerland
 
  The need for more energy efficient high power microwave devices for accelerator applications continues to increase. This is important for development of cost effective accelerator designs that are coming up in the near future. Efforts are already in place to design new devices that could stretch the limits of RF power conversion to the highest levels possible. Devices including new technologies and design innovations like multi beam, increased number of cavities designs are being considered. Advances in the application of solid state amplifiers to accelerators are also being realized. This invited talk will cover the recent advances and status of such efforts. It will discuss future needs and a strategy for pursuing these efforts on a faster time scale for the benefit of the accelerator community.  
slides icon Slides MOYGB1 [11.575 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOYGB1  
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MOYGB2 The LCLS-II: A High Power Upgrade to the LCLS linac, undulator, cryomodule, electron 18
 
  • J.N. Galayda
    SLAC, Menlo Park, California, USA
 
  Funding: The work is supported by DOE under grant No. DE-AC02-76SF00515
The LCLS-II is an upgrade of the LCLS X-ray FEL based on a 4 GeV superconducting RF linac. The LCLS-II is designed to produce 100's of Watts of X-rays from 200 eV up to 5 keV. The linac uses 1.3 GHz 9-cell cavities processed using the N2-doping technique and will be the first large scale CW SCRF linac with a Q of roughly 3x1010 at a gradient of 16 MV/m. The injector which will be commissioned in spring 2018, is based on the normal conducting CW RF APEX gun developed at LBNL. The LCLS-II will have two undulators: the soft X-ray undulator is a 39 mm period hybrid PM with an adjustable vertical gap to cover the range from 200 eV to 1.5 keV and hard X-ray undulator is a novel adjustable horizontal gap hybrid PM undulator with 26 mm period to generate vertically polarized X-rays from 1 to 5 keV. The talk will review the performance goals as well as the hardware fabrication.
 
slides icon Slides MOYGB2 [11.367 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOYGB2  
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MOZGBD3 Performance of the First LCLS-II Cryomodules: Issues and Solutions cryomodule, HOM, radiation, operation 34
 
  • N. Solyak, E. Cullerton, J. Einstein-Curtis, E.R. Harms, B.D. Hartsell, J.P. Holzbauer, T.N. Khabiboulline, A. Lunin, Y.M. Pischalnikov, R.P. Stanek, G. Wu
    Fermilab, Batavia, Illinois, USA
  • O. Napoly
    CEA/DSM/IRFU, France
 
  LCLS-II 4 GeV linac is on the middle production stage. Linac contains 40 cryomodules of 1.3 GHz and 3 cryomodules of 3.9 GHz, including spares. Fermilab and JLAB share responsibility for cryomodule design, assembly and test. Paper will overview the performance of the cryomodules it the tests, lessons learned and modifications in design to improve performance.  
slides icon Slides MOZGBD3 [8.630 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOZGBD3  
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MOZGBF2 Status of the FAIR Project proton, antiproton, target, dipole 63
 
  • P.J. Spiller, M. Bai, O. Boine-Frankenheim, A. Dolinskyy, F. Hagenbuck, C.M. Kleffner, K. Knie, S. Menke, C. Omet, A. Schuhmann, H. Simon, M. Winkler
    GSI, Darmstadt, Germany
  • J. Blaurock, M. Ossendorf
    FAIR, Darmstadt, Germany
  • I. Koop
    BINP SB RAS, Novosibirsk, Russia
  • D. Prasuhn, R. Tölle
    FZJ, Jülich, Germany
 
  The realization of the new Facility for Antiproton and Ion Research, FAIR at GSI, Germany, has advanced significantly. The civil construction process of the Northern part of the building complex, including the excavation of the SIS100 synchrotron tunnel has been launched end of 2017. On site of the GSI campus, major preparations and upgrade measures for the injector operation of the existing accelerator facilities are ongoing and will be completed mid of 2018. The shielding of the SIS18 accelerator tunnel has been enhanced for the booster operation at high repetition rates and high intensity Proton beams. Two new transformer stations were set-up and commissioned which will provide the required pulse and common power for FAIR. All major contracts for series production of SIS100 components have been signed and a large number of the superconducting SIS100 magnets has been produced and accepted. Major testing infrastructures for superconducting magnets of SIS100 and Super-FRS have been set-up at JINR, CERN and GSI. Also for all other FAIR accelerator systems, the procurement of the components is progressing well  
slides icon Slides MOZGBF2 [4.266 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOZGBF2  
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MOZGBF4 Evolution of the Superconducting Linac Output Energy at the Spallation Neutron Source cryomodule, operation, linac, SRF 73
 
  • S.-H. Kim, D.E. Anderson, M.T. Crofford, M. Doleans, J. Galambos, S.W. Gold, M.P. Howell, M.A. Plum, D.J. Vandygriff
    ORNL, Oak Ridge, Tennessee, USA
  • R. Afanador, D.L. Barnhart, B. DeGraff, J.D. Mammosser, C.J. McMahan, T.S. Neustadt, C.C. Peters, J. Saunders, D.M. Vandygriff
    ORNL RAD, Oak Ridge, Tennessee, USA
 
  Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
The SNS linac output energy has increased since the start of neutron production in FY2007. The various improvements that contributed to the increase of the linac output energy are LLRF/control system improvement, high voltage converter modulator system improvement, high-power RF system improvement, cryomodule repairs, spare cryomodule development and accelerating gradient improvement through in-situ plasma processing. In this paper, the history of the SNS SCL output energy is reported, and plans for the near-term future and for the Proton Power Upgrade (PPU) project are also presented.
 
slides icon Slides MOZGBF4 [34.185 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOZGBF4  
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MOPMF012 Study of Crabbed Collision in eRHIC With a Combination of Strong-Strong and Weak-Strong Simulations simulation, electron, proton, luminosity 105
 
  • Y. Luo, G. Bassi, M. Blaskiewicz, W. Fischer, Y. Hao, C. Montag, V. Ptitsyn, V.V. Smaluk, F.J. Willeke
    BNL, Upton, Long Island, New York, USA
  • J. Qiang
    LBNL, Berkeley, California, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In the present design of the future electron-ion collider eRHIC at the Brookhaven National Laboratory, a crossing angle of 22~mrad between the electron and proton orbits at the interaction region is adopted. To compensate the geometric luminosity loss, a local compensation scheme with two sets of crab cavities for each beam is considered. In this article, we first carry out strong-strong beam-beam simulation to study possible coherent beam-beam instability. Under the assumption of no coherent beam-beam motion, we then carry out a weak-strong beam-beam simulation to determine the long-term stability of the proton beam with the equilibrium electron beam sizes extracted from the strong-strong beam-beam simulation.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF012  
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MOPMF020 Higher Order Mode Coupling Options for the eRHIC Crab Cavity HOM, damping, coupling, impedance 121
 
  • Q. Wu, I. Ben-Zvi, S. Verdú-Andrés, B. P. Xiao
    BNL, Upton, Long Island, New York, USA
  • I. Ben-Zvi
    Stony Brook University, Stony Brook, USA
 
  Funding: This work was supported by the US Department of Energy via Brookhaven Science Associates LLC under contract no. DE-SC0012704.
The eRHIC crab cavity adopts the double quarter wave structure developed at Brookhaven National Lab for the LHC Hi-Lumi upgrade crab cavities. The cavity's fundamental mode is at 338 MHz with the first higher order mode more than 180 MHz above that. We looked into the higher order mode distribution up to 2 GHz, and considered various locations and geometries of the coupling scheme. The cylindrical outer shell of the cavity allowed various possibilities for coupler port openings on all the walls, which were difficult for the narrow waist of the LHC double quarter wave crab cavities. Beam pipe absorbers are also options for simpler high frequency modes damping. Some preliminary high pass filter design will also be discussed in this paper.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF020  
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MOPMF022 Luminosity Reduction Caused by the Full-Detuning LLRF Scheme on the HL-LHC Crab Cavities luminosity, simulation, proton, LLRF 129
 
  • E. Yamakawa, R. Apsimon, A.C. Dexter
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • P. Baudrenghien, R. Calaga, F.J. Galindo Guarch
    CERN, Geneva, Switzerland
 
  The High-Luminosity LHC (HL-LHC) crab cavities (CCs) will be installed on both sides of IP1 (ATLAS) and IP5 (CMS) to compensate for the geometric luminosity reduction due to the crossing angle. To cope with the increased beam current (0.55 A DC for LHC, 1.1 A for HL-LHC), the operation of the LLRF system has been changed: rather than fully compensating the transient beam loading, we allow the phase to vary along the turn (100 ps peak-peak with 1.1 A DC). This has been implemented at LHC since July 2017. The CCs have high loaded Q (5e5) and the available RF power is insufficient to follow the bunch phase modulation. The crabbing voltage is not modulated, causing a phase error w.r.t. the individual bunch centroids, leading to transverse kicks of the centroids and an asymmetric crabbing of the bunch cores. We present an analytical model for the resulting luminosity reduction and validate with particle tracking simulations. Due to the symmetry of the bunch filling patterns for the counter-rotating beams, the peak luminosity is reduced by only 2% for nominal HL-LHC parameters at IPs 1 and 5, which is within tolerable limits.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF022  
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MOPMF034 Layout and Performance of the FCC-ee Pre-Injector Chain linac, emittance, damping, injection 169
 
  • S. Ogur, T.K. Charles, K. Oide, Y. Papaphilippou, L. Rinolfi, F. Zimmermann
    CERN, Geneva, Switzerland
  • A.M. Barnyakov, A.E. Levichev, P.V. Martyshkin, D.A. Nikiforov
    BINP SB RAS, Novosibirsk, Russia
  • I. Chaikovska, R. Chehab
    LAL, Orsay, France
  • K. Furukawa, N. Iida, T. Kamitani, F. Miyahara
    KEK, Ibaraki, Japan
  • E.V. Ozcan
    Bogazici University, Bebek / Istanbul, Turkey
  • S.M. Polozov
    MEPhI, Moscow, Russia
 
  The Future Circular e+e Collider pre-injector chain consists of a 6 GeV S-Band linac, a damping ring at 1.54 GeV and pre-booster ring to reach 20 GeV for injection to the main booster. The electron and positron beams use the same accelerator chain alternatively. The e+ beam is generated from a novel low level RF-gun providing 6.5 nC charge at 11 MeV with 0.5 micron geometric emittance. The e+ beam is produced by the impact of a 4.46 GeV e- beam onto a hybrid target, accelerated in the linac up to 1.54 GeV, and injected to the damping ring for emittance cooling. Simulations on the performance of the DR are presented for reaching the required equilibrium emittances at the required damping time. As an alternative option, a 20 GeV linac is considered utilising C-Band cavities and simulations studies have been undertaken regarding the beam transport and transmission efficiency up to that energy.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF034  
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MOPMF036 FCC-ee Hybrid RF Scheme HOM, impedance, operation, radiation 173
 
  • Sh. Gorgi Zadeh, U. van Rienen
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
  • R. Calaga, F. Gerigk
    CERN, Geneva, Switzerland
 
  Funding: Research supported by the FCC design study
For FCC-ee, the range of beam energies and beam currents is large between each mode of operation, all scaled to an available 50 MW maximum power per beam. The two limiting scenarios for the RF system design are at low energy (45 GeV) with high beam current (1.45 A) and the highest energy (182.5 GeV) with a radiation loss reaching 8.92 GeV per turn. In this paper, RF staging with a hybrid scheme using both 400 MHz and 800 MHz is proposed to mitigate the requirements on the two extremes. Relevant comparisons are made with respect to using only a single frequency for all modes.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF036  
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MOPMF042 Crab Cavity Failures Combined with a Loss of the Beam-Beam Kick in the High Luminosity LHC beam-losses, luminosity, dumping, collimation 192
 
  • B. Lindstrom, H. Burkhardt, V.K.B. Olsen, A. Santamaría García, K.N. Sjobak, M. Valette, D. Wollmann
    CERN, Geneva, Switzerland
 
  Crab cavities are an essential component of the High Luminosity LHC (HL-LHC) project. In case of a failure they can create large transverse kicks on the beam within tens of microseconds and, therefore, require a fast extraction of the circulating beam. In this paper, the effects of different crab cavity failures in combination with the missing beam-beam kick following the dump of only one LHC beam are presented and consequences for the interlocking strategy of crab cavities are discussed.
Work supported by the High Luminosity LHC project.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF042  
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MOPMF061 Emittance Growth in Coast in the SPS at CERN emittance, scattering, experiment, feedback 257
 
  • F. Antoniou, H. Bartosik, T. Bohl, R. Calaga, L.R. Carver, J. Repond, G. Vandoni
    CERN, Geneva, Switzerland
  • A. Alekou
    UMAN, Manchester, United Kingdom
 
  Funding: Research supported by the HL-LHC project.
The HL-LHC prototype crab-cavities are installed in the CERN SPS, which will allow for a comprehensive beam test with high energy protons for the first time. As the time available for experimental beam dynamics studies with the crab cavities installed in the machine will be limited, a very good preparation is required. One of the main concerns is the induced emittance growth, driven by phase amplitude jitter in the crab cavities. In this respect, several machine development (MD) studies were performed during the past years to quantify and characterize the long term emittance evolution of proton beams in the SPS. In these proceedings, the experimental observations from past years are summarized and the MD studies from 2016 and 2017 are presented.
 
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MOPMF076 Energy Spread Compensation in Arbitrary Format Multi-Bunch Acceleration With Standing Wave and Traveling Wave Accelerators beam-loading, acceleration, positron, linac 307
 
  • M. Kuriki
    HU/AdSM, Higashi-Hiroshima, Japan
 
  In the E-driven ILC (International Linear Collider) positron source, the beam is generated and accelerated in a multi-bunch format with mini-trains. The macro-pulse contains 2 to 8 mini-trains with several train gaps, because the pulse format is a copy of a part of the bunch storage pattern in DR (Damping Ring). This pulse format causes a variation of the accelerator field in the pulse due to the transient beam loading and an intensity fluctuation of captured positron. In this article, we discuss the compensation of the energy spread of such beam in standing wave and traveling wave accelerators. For standing wave accelerator, it can be compensated by switching input RF at appropriate timings. For traveling wave accelerator, it can be compensated by amplitude modulation of the input RF.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF076  
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MOPMF077 A Design Study of the Electron-driven ILC Positron Source Including Beam Loading Effect positron, beam-loading, acceleration, booster 311
 
  • H. Nagoshi, M. Kuriki
    HU/AdSM, Higashi-Hiroshima, Japan
  • S. Kashiwagi
    Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
  • K. Negishi
    Iwate University, Morioka, Iwate, Japan
  • T. Omori, M. Satoh, Y. Seimiya, J. Urakawa
    KEK, Ibaraki, Japan
  • Y. Sumitomo
    LEBRA, Funabashi, Japan
  • T. Takahashi
    Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
 
  The International Linear Collider (ILC) is a next-generation accelerator for high-energy physics to study the Higgs and top sector in the Standard Model, and new physics such as supersymmetry and dark matter. ILC positron source based on Electron-driven method has been proposed as a reliable technical backup. In this article, we report the design study of the positron source based on the off-the-shelf RF components. The positron is generated and accelerated in a multi-bunch format. To compensate the energy variation by the transient beam loading effect, we employ AM (Amplitude Modulation) technique and the results were 16.60 ± 0.14 MV (peak-to-peak) for L-band 2m cavity driven by 22.5 MW power and 25.76 ± 0.19 MV (peak-to-peak) for S-band 2m ac-celerator driven by 36 MW power with 0.78 A beam load-ing.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF077  
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MOPMK001 Optics for RF Acceleration Section for the High Energy Large Hadron Collider optics, quadrupole, dipole, instrumentation 345
 
  • L. van Riesen-Haupt, J.L. Abelleira
    University of Oxford, Oxford, United Kingdom
  • J.L. Abelleira, E. Cruz Alaniz, P. Martinez Mirave, A. Seryi
    JAI, Oxford, United Kingdom
  • M. Hofer, F. Zimmermann
    CERN, Geneva, Switzerland
  • D. Zhou
    KEK, Ibaraki, Japan
 
  Funding: Work supported by the Horizon 2020 project EuroCirCol, grant 654305 and by the Science and Technology Facilities Council
As part of the FCC study, the design of the High Energy LHC (HE-LHC) is addressed. A proposed layout for the interaction region for the containing the radio frequency (RF) cavities and various beam instrumentation will be discussed. The higher energy requires more RF cavities, which strongly restricts the space available for optics and instrumentation. Another challenge arises because the beam rigidity increases whilst the LHC geometry has to be conserved. To this end, next generation dipoles have to be used in order to achieve sufficient beam to beam separation. A design that provides enough beam stay clear (BSC) in all the magnets will be presented. The design introduces an additional quadrupole on either side of the RF region to be used for phase advance adjustments that can increase the dynamic aperture.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMK001  
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MOPMK005 HE-LHC Final Focus: Flat Beam Parameters and Energy Deposition Studies optics, luminosity, quadrupole, dipole 356
 
  • J.L. Abelleira, E. Cruz Alaniz, A. Seryi, L. van Riesen-Haupt
    JAI, Oxford, United Kingdom
  • J.L. Abelleira, E. Cruz Alaniz, L. van Riesen-Haupt
    University of Oxford, Oxford, United Kingdom
 
  Funding: Work supported by EuroCircol, EU's Horizon 2020 grant No 654305 & STFC grant to the John Adams Institute
The High Energy LHC (HE-LHC) project is studying the feasibility of a new proton-proton collider with a beam energy of 13.5 TeV. The nominal optics features a β* of 0.25 m and crab-cavities. Here we present a flat-beam optics that can be used with a non-zero crossing angle, in the absence of crab cavities. This is followed by energy deposition studies for the superconducting quadrupoles and dipole separators. The total dose in these magnets coming from the collision debris is evaluated.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMK005  
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MOPMK010 Study Progress of the Coupling Resonance of the Crab Crossing Scheme in Electron-Ion Collider luminosity, electron, synchrotron, simulation 368
 
  • Y. Hao
    FRIB, East Lansing, USA
  • Y. Luo, V. Ptitsyn
    BNL, Upton, Long Island, New York, USA
  • J. Qiang
    LBNL, Berkeley, California, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Crab crossing scheme is essential collision scheme to achieve high luminosity for the future electron-ion collider (EIC). The bunch length effect of the ion beam cannot be ignored even when cooling is present compared with the wavelength of the crab cavity, therefore, the nonlinear dependence of the crabbing kick may present a challenge to the beam dynamics of the ion beam, hence an impact to the luminosity lifetime. In this paper, we present the result of numerical beam dynamics studies of the crab crossing scheme. The result indicates that there is a special coupling resonance in the nonlinear relation of the crab crossing scheme of the EIC, which dominates the luminosity degradation. And we will discuss the possible remedies for such resonance.
 
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MOPMK017 Transient Beam Loading Due to the Bunch Train Gap and Its Compensation Experiments at BEPC-II and ALS experiment, feedback, beam-loading, luminosity 390
 
  • H. Wang, R.A. Rimmer, S. Wang
    JLab, Newport News, Virginia, USA
  • J.P. Dai, Q. Qin, J. Xing, J.H. Yue, Y. Zhang
    IHEP, Beijing, People's Republic of China
  • D. Teytelman
    Dimtel, San Jose, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Non-uniform bunch fill patterns in storage rings, driven by the need to provide gaps for beam aborting and ion clearing cause a large beam loading change in the RF cavities. The induced turn-periodic transient in the cavity voltage modulates longitudinal beam properties along the train, such as synchronous position and bunch length. In the EIC design, due to the asymmetric bunch train structure between the electron and the ion beam, such modulation results in shifting collision point and leads to reduced luminosity. We have carried out the beam based experiments at BEPC-II and ALS using bunch-by-bunch diagnostic capabilities of the coupled-bunch feedback systems to study this transient effect. A modulated bunch filling pattern with higher charge density around the gap has been demonstrated to be effective in partially compensating this transient modulation. Details of the experimental setups and the data analysis will be presented to this conference.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMK017  
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MOPML009 New High Luminosity LHC Baseline and Performance at Ultimate Energy operation, luminosity, optics, emittance 408
 
  • L.E. Medina Medrano
    Universidad de Guanajuato, División de Ciencias e Ingenierías, León, Mexico
  • A. Apollonio, G. Arduini, O.S. Brüning, M. Giovannozzi, L.E. Medina Medrano, S. Papadopoulou, Y. Papaphilippou, S. Redaelli, R. Tomás
    CERN, Geneva, Switzerland
 
  Funding: Research supported by the HL-LHC project and the Beam project (CONACYT, Mexico).
The LHC machine is envisioned to operate eventually at an ultimate beam energy of 7.5 TeV at the end of LHC Run 4, i.e. after commissioning of the HL-LHC systems, a stage falling into the High Luminosity LHC (HL-LHC) era. In this paper we review the latest baseline parameters and performance, and study the potential reach of the HL-LHC with pushed optics at the ultimate beam energy. Results in terms of integrated luminosity and effective pile-up density of both the nominal (5.0×1034 cm-2 s−1) and ultimate (7.5×1034 cm-2 s−1) levelling operations are discussed
 
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MOPML015 Simulations and Measurements of the CCL Modules of the LIGHT Accelerator coupling, linac, proton, GUI 429
 
  • V. F. Khan, G. De Michele, S. Fanella, S. H. Gibson, Ye. Ivanisenko, C. Mellace, J.L. Navarro Quirante, C. Zannini
    AVO-ADAM, Meyrin, Switzerland
  • M. Esposito, P. Gradassi
    CERN, Geneva, Switzerland
 
  A 230 MeV proton LINAC system for medical applications is being developed and commissioned for the LIGHT (Linac Image Guided Hadron Therapy) project by AVO-ADAM. The LINAC system consists of a 750 MHz RFQ (Radio frequency quadrupole) for the low energy proton acceleration, 2998 MHz SCDTL (Side Coupled Drift Tube Linacs) for the medium energy and 2998 MHz CCL (Coupled Cavity Linacs) for the high energy. In particular, the CCL accelerating modules are used in the energy range from 37.5 - 230 MeV. In this paper we discuss the 3D EM (electro-magnetic) simulation results and measurements of the CCL modules.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML015  
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MOPML017 Status and Development of the MYRRHA Injector diagnostics, linac, MMI, rfq 432
 
  • D. Mäder, H. Höltermann, D. Koser, B. Koubek, K. Kümpel, P. Müller, U. Ratzinger, M. Schwarz, W. Schweizer
    BEVATECH, Frankfurt, Germany
  • C. Angulo, J. Belmans, D. Davin, W. De Cock, P. Della Faille, F. Doucet, A. Gatera, Pompon, F.F. Pompon, D. Vandeplassche
    Studiecentrum voor Kernenergie - Centre d'Étude de l'énergie Nucléaire (SCK•CEN), Mol, Belgium
  • M. Busch, H. Hähnel, H. Podlech
    IAP, Frankfurt am Main, Germany
 
  The MYRRHA project aims at coupling a cw 600 MeV, 4 mA proton linac with a sub-critical reactor as the very first prototype nuclear reactor to be driven by a particle accelerator (ADS). Among several applications, MYRRHA main objective is to demonstrate the principle of partitioning and transmutation (P&T) as a viable solution to drastically reduce the radiotoxicity of long-life nuclear waste. For this purpose, the linac needs an unprecedented level of reliability in terms of allowable beam trips. The normal conducting injector delivers 16.6 MeV protons to the superconducting main linac. The first section of the injector (up to 5.9 MeV) consists of an ECR source, a 4-Rod-RFQ and a rebunching line followed by 7 individual CH-type cavities. This entire section will be set up and operated by SCK·CEN in Louvain-la-Neuve, Belgium, for ample performance and reliability testing. The first CH cavity has been sent for power tests to IAP Frankfurt, Germany. The most recent status of all cavities, couplers and the beam diagnostics of the MYRRHA injector is presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML017  
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MOPML034 Development Status of Superconducting RF Transmission Electron Microscope acceleration, LLRF, gun, SRF 481
 
  • N. Higashi, A. Enomoto, Y. Funahashi, T. Furuya, X.J. Jin, Y. Kamiya, S. Michizono, F. Qiu, M. Yamamoto
    KEK, Ibaraki, Japan
  • S. Yamashita
    University of Tokyo, Tokyo, Japan
 
  Now we are developing a new type of transmission electron microscope (TEM) employing the accelerator technologies. In place of a DC thermal gun generally used in conventional TEMs, we apply a photocathode gun and a special-shaped superconducting cavity, named two-mode cavity. The two-mode cavity has two resonant modes of TM010 (1.3 GHz) and TM020 (2.6 GHz). To superimpose these, we can suppress the increase of the energy spread, which is needed for the high-spatial-resolution TEMs. We have already developed some prototypes of the photocathode gun and two-mode cavity, and now in the middle of the performance tests. In this presentation, we will show the latest status of the development.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML034  
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MOPML043 High Gradient Performance of an S-Band Backward Traveling Wave Accelerating Structure for Medical Hadron Therapy Accelerators linac, proton, radiation, accelerating-gradient 491
 
  • A. Vnuchenko, C. Blanch Gutiérrez, D. Esperante Pereira
    IFIC, Valencia, Spain
  • S. Benedetti, N. Catalán Lasheras, A. Grudiev, B. Koubek, G. McMonagle, I. Syratchev, B.J. Woolley, W. Wuensch
    CERN, Geneva, Switzerland
  • A. Faus-Golfe
    LAL, Orsay, France
  • T.G. Lucas, M. Volpi
    The University of Melbourne, Melbourne, Victoria, Australia
  • S. Pitman
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
 
  The high-gradient performance of an accelerating structure prototype for a medical proton linac is presented. The structure was designed and built using technology developed by the CLIC collaboration and the target application is the TULIP (Turning Linac for Proton therapy) proposal developed by the TERA foundation. The special feature of this design is to produce gradient of more than 50 MV /m in low-β accelerating structures (v/c=0.38). The structure was tested in an S-band test stand at CERN. During the tests, the structure reached over above 60 MV/m at 1.2 μs pulse length and breakdown rate of about 5x10-6 bpp. The results presented include ultimate performance, long term behaviour and measurements that can guide future optimization.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML043  
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MOPML052 The Path to Compact, Efficient Solid-State Transistor-Driven Accelerators electron, linac, impedance, simulation 520
 
  • D.C. Nguyen, C.E. Buechler, G.E. Dale, R.L. Fleming, M.A. Holloway, J.W. Lewellen, D. Patrick
    LANL, Los Alamos, New Mexico, USA
  • V.A. Dolgashev, E.N. Jongewaard, E.A. Nanni, J. Neilson, A.V. Sy, S.G. Tantawi
    SLAC, Menlo Park, California, USA
 
  Funding: Research presented in this work is supported by (LANL) Laboratory Directed Research and Development 20170521ER and by (SLAC) Department of Energy contract DE-AC02-76SF00515.
Small, lightweight, few-MeV electron accelerators that can operate with low-voltage power sources, e.g., solid-state transistors running on 50 VDC, instead of high-voltage klystrons, will provide a new tool to enhance existing applications of accelerators as well as to initiate new ones. Recent advances in gallium nitride (GaN) semiconductor technologies * have resulted in a new class of high-power RF solid-state devices called high-electron mobility transistors (HEMTs). These HEMTs are capable of generating a few hundred watts at S-, C- and X-bands at 10% duty factor. We have characterized a number of GaN HEMTs and verified they have suitable RF characteristics to power accelerator cavities **. We have measured energy gain as a function of RF power in a single low-beta C-band cavity. The HEMT powered RF accelerators will be compact and efficient, and they can operate off the low-voltage DC power buses or batteries. These all-solid-state accelerators are also more robust, less likely to fail, and are easier to maintain and operate. In this poster, we present the design of a low-beta, 5.1-GHz cavity and beam dynamics simulations showing continuous energy gain in a ten-cavity C-band prototype.
* See for example, http://www.wolfspeed.com/downloads/dl/file/id/463/product/174/cghv59350.pdf
** J.W. Lewellen et al., Proceedings of LINAC2016, Paper MO3A03
 
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TUXGBF2 Higher-Order-Mode Effects in Tesla-Type Superconducting RF Cavities on Electron Beam Quality HOM, FEL, electron, detector 612
 
  • A.H. Lumpkin, N. Eddy, D.R. Edstrom, P.S. Prieto, J. Ruan, R.M. Thurman-Keup
    Fermilab, Batavia, Illinois, USA
  • K. Bishofberger, B.E. Carlsten
    LANL, Los Alamos, New Mexico, USA
  • O. Napoly
    CEA/DSM/IRFU, France
 
  Funding: *Work at Fermilab supported by FRA, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Dept. of Energy. **Work at LANL supported by U.S. Dept. of Energy through the LANL/LDRD Program.
We report the direct observations of the correlation of higher order modes (HOMs) generated by off-axis electron beam steering in TESLA-type SCRF cavities and sub-macropulse beam centroid shifts (with the concomitant effect on averaged beam size and emittance). The experiments were performed at the Fermilab Accelerator Science and Technology (FAST) facility using its unique configuration of a PC rf gun injecting beam into two separated 9-cell cavities in series with corrector magnets and beam position monitors (BPMs) located before, between, and after them. The ~100-kHz oscillations with up to 300-μm amplitudes at downstream locations were observed in a 3-MHz micropulse repetition rate beam with charges of 500 and 1000 pC/b, although the effects were much reduced at 100 pC/b. The studies were based on HOM detector circuitry targeting the first and second dipole passbands, rf BPM bunch-by-bunch data, and imaging cameras viewing multi-slit images for emittance assessments at 33 MeV. Initial calculations reproduced a key feature of the phenomena. In principle, these results may be scaled to cryomodule configurations of major accelerator facilities.
 
slides icon Slides TUXGBF2 [3.631 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUXGBF2  
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TUYGBF4 Design and Simulation Tools for the High-Intensity Industrial Rhodotron Electron Accelerator dipole, gun, electron, cathode 651
 
  • W.J.G.M. Kleeven, M. Abs, J. Brison, E. Forton, J. M. Hubert, J. Walle
    IBA, Louvain-la-Neuve, Belgium
 
  The Rhodotron is a compact industrial CW recirculating electron accelerator producing intense beams with energies in the range from about 1 to 10 MeV. RF-frequencies are in the range of 100 to 400 MHz. Average beam powers can range from 10 kW to almost 1 MW, depending of the specific type of Rhodotron. Main industrial applications are polymer cross-linking, sterilization, food treatment and container security scanning. Recently, RF pulsing was developed to reduce the average wall power dissipation, thus reducing drastically the energy consumption. Pulsing also permits smaller cavities and higher energies up to 40 MeV, opening the way to applications such as mobile irradiators, or isotopes production by photonuclear reactions, thus offering a compact and high beam duty alternative to linacs. This paper concentrates on some crucial design tools and methods for transverse and longitudinal optics studies, particle tracking with space charge, beam formation studies in the electron gun and dipole magnet design.  
slides icon Slides TUYGBF4 [11.952 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUYGBF4  
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TUPAF001 Requirements for the Cryogenic Refrigerator and the He Distribution System for the MYRRHA 100 Mev Accelerator linac, cryogenics, cryomodule, operation 655
 
  • T. Junquera
    Accelerators and Cryogenic Systems, Orsay, France
  • C. Angulo
    Studiecentrum voor Kernenergie - Centre d'Étude de l'énergie Nucléaire (SCK•CEN), Mol, Belgium
  • D. Vandeplassche
    SCK•CEN, Mol, Belgium
 
  MYRRHA is an ADS demonstrator for the long-lived radioactive waste transmutation. It is composed of a High Energy CW Linac Accelerator (600 MeV - 4mA) coupled to a Subcritical Reactor of 100 MW thermal power. The main challenge of the Linac is a very high reliability performance to limit stress and long restart procedures of the reactor. Within the MYRRHA project phased approach for the construction, a 100 MeV-4 mA Linac (Injector up to 17 MeV and SC Linac between 17 MeV and 100 MeV) will be constructed in the Phase 1, covering 2016-2024. The SC Linac is composed of 58 Single-Spoke SC cavities, housed in 29 cryomodules. The cavities operates at 352 MHz, in a superfluid Helium bath at 2K. In this paper, the requirements for the Linac Cryogenic System are presented. The analysis of high thermal loads induced by the CW mode operation of cavities, leads to a Cryogenic Refrigerator with a power of 2700 W (equiv. power capacity at 4.5 K). Each cryomodule is connected through a dedicated Valve Box to the Helium transfer line running along the Linac tunnel. A description of the cryogenic system features and initial models of the tunnel and associated buildings are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF001  
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TUPAF003 Integrated Prototyping in View of the 100 MeV Linac for Myrrha Phase 1 linac, cryomodule, controls, target 661
 
  • D. Vandeplassche, J. Belmans
    SCK•CEN, Mol, Belgium
  • C. Angulo, D. Davin, W. De Cock, P. Della Faille, F. Doucet, A. Gatera, Pompon, F.F. Pompon
    Studiecentrum voor Kernenergie - Centre d'Étude de l'énergie Nucléaire (SCK•CEN), Mol, Belgium
  • D. Bondoux, F. Bouly
    LPSC, Grenoble Cedex, France
  • H. Höltermann, D. Mäder
    BEVATECH, Frankfurt, Germany
  • C. Joly, G. Olry, H. Saugnac
    IPN, Orsay, France
  • M. Loiselet, N. Postiau, L. Standaert
    UCL, Louvain-la-Neuve, Belgium
  • H. Podlech, U. Ratzinger
    IAP, Frankfurt am Main, Germany
 
  Funding: Work partially supported by the European Commission H2020 programme MYRTE #662186
The MYRRHA project borne by SCK•CEN, the Belgian Nuclear Research Centre, aims at realizing a pre-industrial Accelerator Driven System (ADS) for exploring the transmutation of long lived nuclear waste. The linac for this ADS will be a High Power Proton Accelerator delivering 2.4 MW CW beam at 600 MeV. It has to satisfy stringent requirements for reliability and availability: a beam-MTBF of 250h is targeted. The reliability goal is pursued through a phased approach. During Phase 1, expected till 2024, the MYRRHA linac up to 100 MeV will be constructed. It will allow to evaluate the reliability potential of the 600 MeV linac. It will also feed a Proton Target Facility in which radioisotopes of interest will be collected through an ISOL system. This contribution will focus on the transition to integrated prototyping, which will emphasize (i) a test platform consisting of the initial section of the normal conducting injector (5.9 MeV), (ii) the realization of a complete cryomodule for the superconducting linac and of its cryogenic valve box. The cryomodule will house two 352 MHz single spoke cavities operated at 2K.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF003  
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TUPAF011 Btrain Calibration with RF-Master Method dipole, synchrotron, injection, pick-up 679
 
  • L. Falbo, E. Bressi, M. Pezzetta, C. Priano
    CNAO Foundation, Milan, Italy
 
  CNAO is the only Italian hadrontherapy facility able to treat tumors with beams of protons and carbon ions. It is based on a synchrotron with a 77 m ring equipped with 16 normal conducting dipoles characterized by a long delay in the field stabilization. B-Train system is a fundamental device of the whole machine; it is used in feedback to the dipole power supply in order to regulate the magnetic field reducing the natural stabilization times that would cause long treatments. B-Train system allows to obtain the magnetic field starting from measurements of magnetic field changes: it works as an integrator and then it needs a system to reset the counts compensating the electronic and numerical drift of the system itself. An innovative method has been implemented at CNAO to reset Btrain counts exploiting beam measurements after the RF cavity trapping. This procedure has the advantage to avoid external and additional element like NMR probes. The paper shows the use of B-train system at CNAO and its calibration with this method, called "RF-master method".  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF011  
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TUPAF012 Commissioning of the Lipac Medium Energy Beam Transport Line vacuum, rfq, controls, operation 683
 
  • I. Podadera, J. Castellanos, J.M. García, D. Gavela, A. Ibarra, D. Jiménez-Rey, A. Marqueta, L.M. Martinez Fresno, E. Molina Marinas, J. Mollá, P. Méndez, C. Oliver, D. Regidor, F. Toral, R. Varela, V. Villamayor, M. Weber, C. de la Morena
    CIEMAT, Madrid, Spain
  • P. Cara, A. Marqueta, I. Moya
    Fusion for Energy, Garching, Germany
  • T. Ebisawa, Y. Hirata, A. Ihara, Y. Ikeda, A. Kasugai, T. Kitano, K. Kondo, T. Narita, K. Sakamoto, T. Shinya, M. Sugimoto
    QST, Aomori, Japan
  • D. Gex, A. Jokinen
    F4E, Germany
  • J. Knaster
    IFMIF/EVEDA, Rokkasho, Japan
  • M. Mendez Macias
    7S, Peligros (Granada), Spain
  • O. Nomen
    IREC, Sant Adria del Besos, Spain
  • G. Pruneri
    Consorzio RFX, Associazione Euratom-ENEA sulla Fusione, Padova, Italy
  • F. Scantamburlo
    INFN/LNL, Legnaro (PD), Italy
 
  Funding: This work has been funded by the Spanish Ministry of Economy and Competitiveness under the Agreement as published in BOE, 16/01/2013, page 1988 and the project FIS2013-40860-R.
LIPAc* will be a 9 MeV, 125 mA CW deuteron accelerator which aims to validate the technology to be used as neutron source of the IFMIF facility. Those facilities are essential for future fusion reactors material research. A 175 MHz RFQ will increase the energy up to 5 MeV before a Superconducting RF (SRF) linac with eight 175 MHz Half Wave Resonators brings the particles up to the final energy of 9 MeV. Between both stages, a Medium Energy Beam Transport line (MEBT)** aims at transporting and matching the beam between the RFQ and the SRF linac. The transverse focusing of the beam is controlled by five quadrupole magnets with integrated steerers, grouped in one triplet and one doublet. Two buncher cavities handle the longitudinal dynamics. Two movable scraper systems are included to purify the beam optics coming out the RFQ and avoid losses in the SRF linac. In this contribution, checkout of the beamline and its ancillaries in Japan is reported. Tests carried out on the beamline prior to the MEBT beam commissioning are described, focusing in vacuum tests, magnets powering, buncher conditioning and scrapers movement.
* P. Cara et al., IPAC16, MOPOY057 , p.985, Busan, Korea (2016)
** I. Podadera et al., LINAC2016, TUPLR041, p.554, East Lansing, USA (2016).
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF012  
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TUPAF014 Beam Dynamics Studies For the IFMIF-DONES SRF-Linac linac, SRF, cryomodule, solenoid 687
 
  • L. Du, N. Bazin, N. Chauvin, S. Chel, J. Plouin
    CEA/IRFU, Gif-sur-Yvette, France
 
  The DONES (DEMO oriented neutron source) project is aimed at constructing a DEMO of IFMIF to provide sufficient material damage [1]. In the SRF-Linac of this project, losses can cause harmful material activation and must be maintained much less than 1W/m. It's a challenge to keep losses at such a low level with high beam power and high space charge. This paper presents two designs of the DONES SRF-Linac, one with 4 cryomodules and another with 5 cryomodules. The design details to reduce the losses and the multi-particle simulation results will be shown. The errors studies for these results will also be discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF014  
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TUPAF015 Preliminary Test Results of the First ESS Elliptical Cryomodule Demonstrator cryomodule, cryogenics, vacuum, radiation 691
 
  • F. Peauger, C. Arcambal, S. Berry, P. Bosland, E. Cenni, G. Devanz, T. Hamelin, O. Piquet, B. Renard, P. Sahuquet, T. Trublet
    CEA/DRF/IRFU, Gif-sur-Yvette, France
  • C. Darve
    ESS, Lund, Sweden
  • P. Michelato
    INFN/LASA, Segrate (MI), Italy
  • G. Olivier
    IPN, Orsay, France
  • J.P. Thermeau
    Laboratoire APC, Paris, France
 
  Two ESS elliptical cavities cryomodule prototypes are being developed and will be tested at CEA Saclay before starting the series production. This paper presents the preliminary test results of the first medium beta cavities cryomodule demonstrator M-ECCTD. The measurements of the cryogenic performances at 80 K and 2 K of the different cryomodule components and circuits are given. The first RF test results performed at low power are also reported.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF015  
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TUPAF026 Higher-Harmonic RF System for Landau Damping in the CERN PS damping, flattop, dipole, synchrotron 728
 
  • H. Damerau, A. Lasheen, E.N. Shaposhnikova
    CERN, Geneva, Switzerland
 
  Longitudinal coupled-bunch instabilities after transition crossing and at the flat-top limit the intensity of LHC-type beams in the CERN Proton Synchrotron (PS). A dedicated coupled-bunch feedback for dipole oscillation modes, using a Finemet cavity as wide-band longitudinal kicker, suppresses the instabilities up to an intensity of about 2·1011 particles per bunch at extraction. However, dipole and quadrupole coupled-bunch oscillations are observed beyond this intensity. At the flat-top they were damped with a 40 MHz RF cavity operated as a higher-harmonic RF system to increase Landau damping, in addition to the principal RF system at 10 MHz. The existing 40 MHz RF system, designed for RF manipulations at fixed frequency, does not cover the frequency range required during acceleration. It is therefore proposed to install a tunable RF system with a 5% relative frequency swing. This paper summarizes the observations of instability damping at the flat-top and presents preliminary parameters for the higher-harmonic RF system.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF026  
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TUPAF034 LEIR Injection Efficiency Studies as a Function of the Beam Energy Distribution from Linac3 linac, injection, bunching, optics 758
 
  • S. Hirlaender, R. Alemany-Fernández, H. Bartosik, G. Bellodi, N. Biancacci, V. Kain, R. Scrivens
    CERN, Geneva, Switzerland
 
  High intensities in the CERN Low Energy Ion Ring (LEIR) are achieved using multi-turn injections from the pre-accelerator Linac3 combined with simultaneous stacking in momentum and transverse phase spaces. Up to seven consecutive 200 μs long, 200 ms spaced pulses are injected from Linac3 into LEIR by stacking each of them into the six-dimensional phase-space over 70 turns. An inclined septum magnet allows proper filling of the transverse phase-space plane, while longitudinal stacking requires momentum variation achieved by a shift of mean momentum over time provided by phase shifting a combination of 2 RF cavities at the exit of Linac3. The achievable maximum accumulated intensity depends strongly on the longitudinal beam quality of the injected beam. The longitudinal Schottky signal is used to measure the received energy distribution of the circulating beam which is then correlated with the obtained injection efficiency. This paper presents the experimental studies to understand and further improve the injection reliability and the longitudinal stacking.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF034  
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TUPAF042 Characterization of the Beam Energy Spread at the REX/HIE-ISOLDE Linac ISOL, linac, experiment, detector 787
 
  • M.L. Lozano, N. Bidault, E. Fadakis, M.A. Fraser, E. Matli, J.A. Rodriguez
    CERN, Geneva, Switzerland
 
  ISOLDE is an on-line radioactive isotope separator located at CERN that works by colliding protons accelerated in the PS Booster into a fixed target and by separating the resultant ionized isotopes using a magnetic separator. The completion of the HIE-ISOLDE superconducting linac allows the acceleration of these ions to energy levels that were not reachable before, opening the door to new experiments in different fields. These experiments often have special requirements in terms of beam intensity and purity, transverse emittance or energy spread. A possible way to reduce the energy spread of the beam delivered to the experimental stations is to use one or more of the superconducting cavities as bunchers. The main results of several tests conducted during the last beam commissioning campaign prove that this mode of operation is feasible and will be presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF042  
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TUPAF057 The SPS Tests of the HL-LHC Crab Cavities cryomodule, vacuum, HOM, operation 846
 
  • R. Calaga, O. Capatina, G. Vandoni
    CERN, Geneva, Switzerland
 
  Funding: Research supported by the HL-LHC project
Two superconducting crab cavities in the framework of the High Luminosity (HL-LHC) LHC were built to test for the first time with proton beams in the Super Proton Synchrotron (SPS) at CERN. These tests will address the operation of the crab cavities in a high current and high intensity proton machine through the full energy cycle with a primary focus on cavity transparency, performance and stability, failures modes and long term effects on proton beams. An overview of the SPS cryomodule development towards the SPS tests along with the first test results are presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF057  
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TUPAF063 Beam Dynamics Studies of the ESS LINAC Using a New Multicell Cavity Model linac, emittance, DTL, distributed 870
 
  • R. De Prisco, D.C. Plostinar
    ESS, Lund, Sweden
 
  The European Spallation Source is designed to deliver 5 MW proton beam power on the target while keeping the beam induced losses below 1 W/m throughout the LINAC. This implies the need of accurate models to correctly describe the longitudinal beam dynamics within the multi-cell cavities. In all the previous error studies the cells of a multi-cell cavity were modelled as a sequence of independent gaps and the errors were applied directly on the amplitude of each cell accelerating field, considered as random variable. In this paper, instead, we present a new detailed analysis of the effect of the error tolerances on the beam dynamics including a new model to calculate the amplitude errors of the accelerating field in the multi-cell cavities: errors are applied on the geometrical parameters of each cavity; then the accelerating field is calculated solving the Maxwell equations over all the cavity.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF063  
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TUPAF068 Functional Integration of the RFQ in the ESS Systems rfq, controls, LLRF, vacuum 890
 
  • J.S. Schmidt, E. Bargalló, T. Fay, G. Hulla, B. Lagoguez, R. Montaño, E. Sargsyan, S. Scolari, H. Spoelstra
    ESS, Lund, Sweden
  • A.C. Chauveau, M. Desmons, O. Piquet
    CEA/IRFU, Gif-sur-Yvette, France
  • A.J. Johansson
    Lund University, Lund, Sweden
  • W. Ledda
    Vitrociset s.p.a, Roma, Italy
 
  The 352 MHz Radio Frequency Quadrupole (RFQ) for the European Spallation Source ERIC (ESS) will be delivered during 2018. After delivery, installation and tuning of the cavity, the high power RF conditioning will be performed. At this point all the different systems that are needed to condition and operate the RFQ have to be in place and operational. This paper will give an overview of the system analysis that has been performed for the RFQ. The RFQ requirements for the RF system, including the RF distribution system (RFDS), the Low Level RF (LLRF) and the local RF protection system (RFLPS) will be presented. In addition, the paper covers the system integration of the structure in the ESS control and vacuum systems as well as the outcome of a machine protection analysis.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF068  
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TUPAF079 Scaled Alvarez-Cavity Model Investigations for the UNILAC Upgrade DTL, simulation, alignment, pick-up 916
 
  • M. Heilmann, X. Du, L. Groening, M. Kaiser, S. Mickat, M. Vossberg
    GSI, Darmstadt, Germany
  • A. Seibel
    IAP, Frankfurt am Main, Germany
 
  The 1:3 scaled aluminum model of an Alvarez-type cavity with 10 gaps was used for comparison of simulation with measurement for the frequency and the electric field on axis. The scaled frequency is 325.224 MHz and an Alvarez cavity has a small frequency tuning range. With this scaled model it was possible to apply different stem configurations for each drift tube to damp parasitic modes and to increase the field stability. The new drift tubes have an optimized free-formed profile on the end plates in order to increase the shunt impedance. In special the assembly, positioning and alignment of the drift tubes can be tested and the frequency change can be investigated in this respect.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF079  
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TUPAF080 Final Design of the FoS Alvarez-Cavity-Section for the Upgraded UNILAC DTL, quadrupole, operation, simulation 920
 
  • M. Heilmann, X. Du, L. Groening, M. Kaiser, S. Mickat, C. Mühle, A. Rubin, V. Srinivasan
    GSI, Darmstadt, Germany
  • A. Seibel
    IAP, Frankfurt am Main, Germany
 
  The final design describes the First-of-Series (FoS) Alvarez-Cavity-section of the first tank being part of the new post-stripper DTL of the UNILAC. The FoS-cavity has an input energy of 1.358 MeV/u with 11 drift tubes (including quadrupole singlets) in a total length of 1.9 m and a diameter of 2 m with an operation frequency of 108.4 MHz. The drift tubes will have a new shape profile at the end plates. The single layered quadruple singlets inside the drift tubes are pulsed with 10 Hz and will have a maximum field gradient of 51 T/m. The new drift tube design combines the new shape profile with the transverse and longitudinal installation space of the magnet. The FoS Alvarez-cavity will be part of the first section of the new Alvarez DTL. It shall be operated at nominal RF- and magnetic fields prior to procurement of the series.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF080  
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TUPAF088 Final factory-side Measurements of the Next SC CH-Cavities for the HELIAC-Project linac, resonance, 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
    GSI, Darmstadt, Germany
 
  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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TUPAK002 Advanced Approach for Beam Matching along the Multi-Cavity SC CW Linac at GSI linac, heavy-ion, emittance, proton 955
 
  • S. Yaramyshev, W.A. Barth, M. Heilmann
    GSI, Darmstadt, Germany
  • K. Aulenbacher
    IKP, Mainz, Germany
  • K. Aulenbacher, W.A. Barth, V. Gettmann, T. Kürzeder, M. Miski-Oglu
    HIM, Mainz, Germany
  • M. Basten, M. Busch, H. Podlech, M. Schwarz
    IAP, Frankfurt am Main, Germany
 
  A multi-stage program for the development of a heavy ion superconducting (sc) continuous wave (cw) linac is in progress at HIM (Mainz, Germany) and GSI (Darmstadt, Germany) under support of IAP (Frankfurt, Germany). In 2017 the first section of the CW-Linac has been successfully commissioned at GSI. Beam acceleration at the CW-Linac is foreseen to be performed by up to twelve multi-gap CH cavities. The linac should provide the beam for physics experiments, smoothly varying the output particle energy from 3.5 to 7.3 MeV/u, simultaneously keeping high beam quality. Due to a wide variation of the input- and output -beam energy for each cavity, a longitudinal beam matching to every cavity is of high importance. An advanced algorithm for an optimization of matched beam parameters under variable rf-voltage and rf-phase of each cavity has been developed. The description of the method and the obtained results are presented in the paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAK002  
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TUPAK003 Beam Dynamics Simulations for the New Superconducting CW Heavy Ion LINAC at GSI linac, heavy-ion, cryomodule, solenoid 959
 
  • M. Schwarz, M. Basten, M. Busch, H. Podlech
    IAP, Frankfurt am Main, Germany
  • K. Aulenbacher
    IKP, Mainz, Germany
  • K. Aulenbacher, W.A. Barth, F.D. Dziuba, V. Gettmann, T. Kürzeder, M. Miski-Oglu
    HIM, Mainz, Germany
  • W.A. Barth, M. Heilmann, A. Rubin, A. Schnase, S. Yaramyshev
    GSI, Darmstadt, Germany
 
  Funding: Work supported by BMBF Contr. No. 05P15RFBA and EU Framework Programme H2020 662186 (MYRTE)
For future experiments with heavy ions near the coulomb barrier within the super-heavy element (SHE) research project a multi-stage R&D program of GSI/HIM and IAP is currently in progress. It aims for developing a supercon-ducting (sc) continuous wave (CW) LINAC with multiple CH cavities as key components downstream the High Charge State Injector (HLI) at GSI. The LINAC design is challenging due to the requirement of intense beams in CW mode up to a mass-to-charge ratio of 6, while covering a broad output energy range from 3.5 to 7.3 MeV/u with unchanged minimum energy spread. Testing of the first CH-cavity in 2016 demonstrated a promising maximum accelerating gradient of Ea = 9.6 MV/m; the worldwide first beam test with this sc multi-gap CH-cavity in 2017 was a milestone in the R&D work of GSI/HIM and IAP. In the light of experience gained in this research so far, the beam dynamics layout for the entire LINAC has recently been updated and optimized.
 
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TUPAK004 Superconducting CH-Cavity Heavy Ion Beam Testing at GSI linac, heavy-ion, acceleration, emittance 962
 
  • W.A. Barth, M. Heilmann, A. Rubin, A. Schnase, S. Yaramyshev
    GSI, Darmstadt, Germany
  • K. Aulenbacher
    IKP, Mainz, Germany
  • K. Aulenbacher, F.D. Dziuba, V. Gettmann, T. Kürzeder, M. Miski-Oglu
    HIM, Mainz, Germany
  • M. Basten, M. Busch, H. Podlech, M. Schwarz
    IAP, Frankfurt am Main, Germany
 
  Recently the first section of a standalone superconducting (sc) continuous wave (cw) heavy ion Linac as a demonstration of the capability of 217 MHz multi gap Crossbar H-mode structures (CH) has been commissioned and extensively tested with beam from the GSI- High Charge State Injector. The demonstrator set up reached acceleration of heavy ions up to the design beam energy and beyond. The required acceleration gain was achieved with heavy ion beams even above the design mass to charge ratio at high beam intensity and full beam transmission. This contribution presents systematic beam measurements with varying RF-amplitudes and phases of the CH-cavity, as well as versatile phase space measurements for heavy ion beams with different mass to charge ratio. The worldwide first and successful beam test with a superconducting multi gap CH-cavity is a milestone of the R&D work of Helmholtz Institute Mainz (HIM) and GSI in collaboration with Goethe University Frankfurt (GUF) in preparation of the sc cw heavy ion Linac project and other cw-ion beam applications.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAK004  
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TUPAK005 Upgrade Plan of J-PARC MR - Toward 1.3 MW Beam Power operation, experiment, injection, proton 966
 
  • T. Koseki
    KEK, Ibaraki, Japan
 
  The Main Ring Synchrotron (MR), a 30-GeV slow cycling proton synchrotron, delivers intense proton beam to a long-baseline neutrino oscillation experiment, T2K, by fast extraction and to an experimental facility, which is called hadron hall by slow extraction. The achieved beam intensities for routine operations are 470 kW ( 2.4 x 1014 ppp) for the fast extraction and 44 kW ( 5.1 x 1013 ppp) for the slow extraction. In order to increase the beam intensity, a plan to replace the magnet power supplies are now in progress for operation with a higher repetition rate. After the replacement, the cycle time will be shortened about a half and increase beam intensities two times larger for the fast extraction. In addition, a further upgrade plan for the fast extraction is mainly reinforcement of rf power supplies. The goal of the upgrade plan is reaching 1.3 MW beam power for the neutrino experiment.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAK005  
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TUPAK011 Present Status and Future Upgrades of the J-PARC Ring RF Systems proton, power-supply, operation, controls 984
 
  • M. Yoshii, M. Furusawa, K. Hara, K. Hasegawa, C. Ohmori, Y. Sugiyama
    KEK, Tokai, Ibaraki, Japan
  • M. Nomura, T. Shimada, F. Tamura, M. Yamamoto
    JAEA/J-PARC, Tokai-mura, Japan
 
  J-PARC is the multipurpose research institutes. 10 years have passed since the user operation started. We have been considering the upgrades for the future and the target beam powers for 3 GeV rapid cycling synchrotron (RCS) and 30GeV Main ring (MR) are 1.5MW and 1.3MW. To achieve a 1.5MW of RCS output beam power, increasing the number of Linac proton particles is necessary. For accelerating such higher beam current, the rf systems in the RCS need to upgrade an accelerating voltage and to take account of heavier beam loading. In case of the MR, increasing the number of proton is not appropriate from the viewpoint of space charge effects. We chose to shorten the MR cycle time. The required RF voltages become almost double. All nine systems have been replaced with the higher accelerating gradient RF systems using a newly developed magnetic alloy material. At present, the proton beam of 470kW is being delivered with a cycle time of 2.48s. Beam powers of MR will plan to aim first at 750KW after replacing the magnet power supplies. But, to realize a 1.3MW beam power, upgrading the RF power sources will be necessary. We present the ring RF system status and their upgrades for the future.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAK011  
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TUPAK012 Conceptual Design of a Single-Ended MA Cavity for J-PARC RCS Upgrade acceleration, operation, vacuum, power-supply 987
 
  • M. Yamamoto, M. Nomura, T. Shimada, F. Tamura
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  • M. Furusawa, K. Hara, K. Hasegawa, C. Ohmori, Y. Sugiyama, M. Yoshii
    KEK, Tokai, Ibaraki, Japan
 
  The J-PARC RCS employes Magnetic Alloy (MA) loaded cavities and rf power is fed by vacuum tubes in push-pull operation. The multi-harmonic rf driving and the multi-harmonic beam loading compensation are realized due to the broadband characteristics of the MA. However, the push-pull operation has disadvantages in the multi-harmonics. An unbalance of the anode voltage swing remarkably appears at very high intensity beam acceleration. In order to avoid the unbalance, a single-ended MA cavity is considered for the RCS beam power upgrade because no unbalance arises intrinsically. We will describe the conceptual design of the single-end MA cavity for the RCS upgrade.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAK012  
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TUPAK015 The SARAF-LINAC Project 2018 Status linac, cryomodule, status, controls 994
 
  • N. Pichoff, D. Chirpaz-Cerbat, R. Cubizolles, J. Dumas, R.D. Duperrier, G. Ferrand, B. Gastineau, P. Gastinel, F. Gougnaud, M. Jacquemet, C. Madec, Th. Plaisant, F. Senée, A. Sutra-Fourcade, D. Uriot
    IRFU, CEA, University Paris-Saclay, Gif-sur-Yvette, France
  • D. Berkovits, J. Luner, A. Perry, E. Reinfeld, J. Rodnizki
    Soreq NRC, Yavne, Israel
  • M. Di Giacomo
    GANIL, Caen, France
 
  SNRC and CEA collaborate to the upgrade of the SARAF accelerator to 5 mA CW 40 MeV deuteron and proton beams (Phase 2). CEA is in charge of the design, construction and commissioning of the MEBT line and the superconducting linac (SARAF-LINAC Project). The prototypes of the 176 MHz NC rebuncher, SC cavities, RF coupler and SC Solenoid-Package are under construction and their test stands construction or adaptation is in progress at Saclay. Meanwhile, the cryomodules and the global system just passed their Critical Design Reviews. This paper presents the status of the SARAF-LINAC Project at April 2018.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAK015  
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TUPAL009 Studying a Prototype of Dual-beam Drift Tube Linac DTL, rfq, simulation, acceleration 1020
 
  • T. He, L. Lu, W. Ma, L.P. Sun, C.C. Xing, X.B. Xu, L. Yang
    IMP/CAS, Lanzhou, People's Republic of China
 
  For generating high-intensity ion beams from linear ac-celerators, a multi-beam acceleration method which in-volves multiple accelerating beams to suppress the defo-cusing force from space charge effects, then integrating these beams by a beam funneling system, has been pro-posed. An Inter-digital H-mode (IH) two-beam type radio frequency quadrupole (RFQ) with accelerating 108mA (54mA/channel×2) carbon ion from 5 to 60 keV/ u and an IH four-beam RFQ with accelerating 160.8mA (40.2mA/channel×4) carbon ion from 3.6 to 41.6 keV/u had been successfully designed for low energy heavy ion acceleration [1]. In order to demonstrate that an IH dual-beam drift tube linac (DB-DTL) is suitable for high-intensity heavy ion beam acceleration in middle energy region, we has been developing a DB-DTL prototype by using three dimensional electromagnetic CST MicroWave Studio (MWS) and using particles tracking Pi Mode Linac Orbit Calculation (PiMLOC) [2-3]. According to the simulation results, the beam dynamics design and elec-tromagnetic design will be presented in this paper.
* Shota. Iketa et al., Nucl. Instr. and Meth. in Phys. Res. B.239-243 (2017).
 
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TUPAL011 Low Power Test and Tuning of the LEAF RFQ rfq, quadrupole, dipole, operation 1028
 
  • L. Lu, T. He, Y. He, W. Ma, L.B. Shi, L.P. Sun, C.C. Xing, X.B. Xu, L. Yang, H.W. Zhao
    IMP/CAS, Lanzhou, People's Republic of China
 
  A continuous wave (CW) four-vane radio frequency quadrupole (RFQ) accelerator is under construction for the Low Energy Accelerator Facility (LEAF) at Institute of Modern Physics (IMP). The 5.96 m RFQ will operate with the capability of accelerating all ion species from proton to uranium from 14 keV/u up to 500 keV/u. In this paper, the low power test and tuning results of the RFQ accelerator, including the test of the separate sections and the whole cavity, will be presented. After the final tuning, the relative error of the quadrupole field is within 2% and the admixture of the dipole modes are below 4% of the quadrupole mode.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL011  
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TUPAL012 Design and Fabrication of Hybrid RFQ Prototype DTL, rfq, linac, site 1032
 
  • P.Y. Yu, Y. He, C.X. Li, G.Z. Sun, F.F. Wang, Z.J. Wang, B. Zhang, T.M. Zhu
    IMP/CAS, Lanzhou, People's Republic of China
 
  Hybrid RFQ is proposed as a potential good choice at the low-energy range of linear accelerator. The complexi-ty of mechanical design and difficulty of fabrication are part of reasons impeding application of it and similar structures. In order to explore the practicable structure and research on RF parameters of this accelerating struc-ture, an aluminium prototype is developed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL012  
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TUPAL022 Low-Reflection RF Window for ACS Cavity in J-PARC Linac Windows, linac, proton, impedance 1051
 
  • J. Tamura, Y. Kondo, T. Morishita
    JAEA/J-PARC, Tokai-mura, Japan
  • H. Ao
    FRIB, East Lansing, USA
  • F. Naito, M. Otani
    KEK, Tokai, Ibaraki, Japan
  • Y. Nemoto
    Nippon Advanced Technology Co., Ltd., Tokai, Japan
 
  In the Japan Proton Accelerator Research Complex (J-PARC) linac, the Annular-ring Coupled Structure (ACS) cavities have been stably operating. To maintain this operation availability, we manufactured three backups of the pillbox-type RF windows for the ACS cavities in fiscal year 2015 and 2017. It is desirable to minimize the RF reflection of the RF window to prevent standing waves from exciting between the cavity and the RF window, and not to significantly change the optimized coupling factor between the cavity and the waveguide. To realize the minimization, the relative permittivities of the ceramic disks of the RF windows were evaluated by measuring the resonant frequencies of the pillbox cavity containing the ceramic disk. On the basis of the evaluated relative permittivities, the pillbox-part lengths of the RF windows were determined. The measured Voltage Standing Wave Ratios (VSWRs) of the manufactured RF windows are just about 1.08 and these are applicable for the practical use.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL022  
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TUPAL029 Harmonictron acceleration, proton, operation, synchrotron 1063
 
  • Y. Mori
    Kyoto University, Research Reactor Institute, Osaka, Japan
  • H. Arima, N. Ikeda, Y. Yonemura
    Kyushu University, Department of Applied Quantum Physics and Nuclear Engineering, Fukuoka, Japan
  • Y. Waga
    Kyushu University, Hakozaki, Japan
 
  The possibility of high intensity hadron/lepton accelerator based on a vertical scaling FFAG with harmonic number jump acceleration, named "Harmonictron", has been proposed. The presentation gives a design example of the Harmonictron for accelerating protons from 50 MeV to 500 MeV for generation intense secondary particles such as muon, neutron etc.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL029  
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TUPAL031 Errors Study of a Double-Pass Recirculating Superconducting Proton Linac linac, proton, emittance, quadrupole 1069
 
  • Y. Tao, K. Hwang, J. Qiang
    LBNL, Berkeley, California, USA
 
  The concept of recirculating superconducting proton linac was recently proposed. Beam dynamics simulations were carried out in a double-pass recirculating proton linac using a single bunch. Although all the beam line elements should be installed following the designed values, in reality, there exist machine imperfections that will cause beam off-centering and even particle losses. In this paper, we report on the study of the static and dynamic errors from RF cavities and magnetic focusing elements in the double-pass recirculating proton linac.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL031  
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TUPAL032 A Variable Field Phase-Shifter for Recirculating Proton Linacs linac, dipole, proton, superconducting-cavity 1072
 
  • Y. Tao, J. Qiang
    LBNL, Berkeley, California, USA
 
  The recirculating superconducting proton linac that has a potential to substantially save accelerator cost was re-cently proposed. It consists of three sections to accelerate the continues-wave (CW) beam to multiple GeVs. In the first section, the beam passes the linac two times. In the second and third sections, the beam goes through the linac four and six times. A phase-shifter is needed to meet the synchronous acceleration condition for multi-pass accel-eration using the same RF cavity due to the phase slip-page of the proton beam. Here we present the design of a variable field rectangular bend phase-shifter in which the beam goes to a different path in each pass inside the mag-net to meet the synchronous condition.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL032  
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TUPAL039 Commissioning of the FRIB RFQ rfq, controls, MMI, dipole 1090
 
  • H.T. Ren, J.F. Brandon, N.K. Bultman, M.G. Konrad, H. Maniar, D.G. Morris, P. Morrison, G. Pozdeyev, X. Rao, R. Walker, S. Zhao
    FRIB, East Lansing, USA
 
  Funding: This work is supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 #wei@frib.msu.edu
The radio-frequency quadrupole (RFQ) at the Facility for Rare Isotope Beams (FRIB) is a 4-vane type cavity designed to accelerate heavy ion beams with charge states Q/A between 1/7 and 1/3 from 12 keV/u to 0.5 MeV/u. The RFQ was assembled in the FRIB tunnel in November 2016. Bead-pull measurements and tuning were performed with low RF power. The RFQ has been conditioned to 59 kW in August 2017, which is sufficient to accelerate the Key Performance Parameter (KPP) beams, Argon and Krypton. The RFQ has been successful-ly commissioned with KPP beams in CW regime in Octo-ber 2017. 40Ar9+ and 86Kr17+ beams were accelerated by the FRIB RFQ in the CW regime to the designed energy of 0.5 MeV/u. With the multi-harmonic buncher operation-al, the FRIB RFQ commissioning has been completed with bunched beam in February 2018. The beam trans-mission efficiency through the RFQ was in good agree-ment with PARMTEQ simulation results. The detailed results from the FRIB RFQ tuning, high power condition-ing and beam commissioning will be presented in this paper.
 
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TUPAL045 Towards Operational Scalability for H Laser Assisted Charge Exchange laser, experiment, operation, radiation 1110
 
  • S.M. Cousineau, A.V. Aleksandrov, T.V. Gorlov, Y. Liu, M.A. Plum, A. Rakhman, A.P. Shishlo
    ORNL, Oak Ridge, Tennessee, USA
  • D.E. Johnson, S. Nagaitsev
    Fermilab, Batavia, Illinois, USA
  • M.J. Kay
    UTK, Knoxville, Tennessee, USA
 
  The experimental development of H laser assisted charge exchange, a.k.a. laser stripping, has been ongoing at the SNS accelerator since 2006 in a three-phase approach. The first two phases associated with proof-of-principle and proof-of-practicality experiments have been successfully completed and demonstrated >95% H stripping efficiency for up to 10 us. The final phase is a proof-of-scalability stage to demonstrate that the method can be deployed for realistic beam duty factors. The experimental component of this effort is centered on achieving high efficiency stripping through the use of a laser power amplification scheme to recycle the macropulse laser light at the interaction point of the H stripping. Such a recycling cavity will be necessary for any future operational laser stripping system with at least millisecond duration H pulses. A second component of the proof-of-scalability phase is to develop a conceptual design for a realistic laser stripping scheme. The status of these efforts and challenges associated with deploying the recycling cavity into the laser stripping experiment will be described in this talk.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL045  
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TUPAL049 SNS Proton Power Upgrade Status linac, scattering, proton, injection 1120
 
  • M.A. Plum, G. A. Bloom, M.S. Champion, J. Galambos, M.P. Howell, S.-H. Kim, J. Moss, B.W. Riemer, K.S. White
    ORNL, Oak Ridge, Tennessee, USA
  • R.B. Saethre, R. W. Steffey
    ORNL RAD, Oak Ridge, Tennessee, USA
 
  Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE. This research was supported by the DOE Office of Science, Basic Energy Science, Scientific User Facilities.
The Spallation Neutron Source (SNS) Proton Power Upgrade (PPU) project aims to double the proton accelerator beam power from 1.4 to 2.8 MW. Over the past year PPU has completed the reviews necessary for Critical Decision-1 approval. The baseline design choices are being refined, and a cost-effective approach has been identified. The beam energy will be increased by 30% and the beam current capability improved by ~50%. The sub-system improvements and anticipated schedule will be discussed.
 
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TUPAL050 Progress Work on a CW Deuteron RFQ with Magnetic Coupling Windows rfq, experiment, coupling, Windows 1123
 
  • Q. Fu, M.J. Easton, P.P. Gan, S.L. Gao, H.P. Li, Y.R. Lu, Q.Y. Tan, Z. Wang, K. Zhu
    PKU, Beijing, People's Republic of China
  • W.P. Dou, Y. He
    IMP/CAS, Lanzhou, People's Republic of China
 
  Funding: This work was supported by the National Basic Research Program of China (Grant No. 2014CB845503).
A new 162.5 MHz RFQ has been built for a joint 973 project between Peking University (PKU) and Institute of Modern Physics (IMP). It is designed to deliver 50-mA deuteron beams to 1 MeV in CW mode, with an inter-voltage of 60 kV and a length of 1.809 m. Due to its window-type structure, the RFQ has compact cross-section, sufficient mode separation and high specific shunt impedance. It consists of two segments fabricated and installed at IMP. The assembling error of the cavity is less than 0.05 mm. The RF measurements show good electrical properties of the resonant cavity with a measured unloaded quality factor equal to 96.4% of the simulated value. After tuning, we obtained the nominal frequency and field unbalance within 1.0%. Preparation of high-power test of this RFQ is underway. This paper will cover the fabrication details and RF measurements, as well as the progress of high-power test.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL050  
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TUPAL052 Multi-Physics Analysis of a CW IH-DTL for CIFNEF DTL, neutron, linac, operation 1129
 
  • Q.Y. Tan, M.J. Easton, Q. Fu, P.P. Gan, H.P. Li, Y.R. Lu, Z. Wang
    PKU, Beijing, People's Republic of China
 
  The Compact Intense Fast NEutron Facility (CIFNEF) project aims to produce high intense neutrons via the 7Li (d, n) 8Be reaction using a 5 MeV, 10 mA deuteron linac. The main components of the linac are an ion source, a short radio frequency quadrupole (RFQ) and an interdigi-tal H-mode drift tube linac (IH-DTL). The IH-DTL will accelerate the continuous wave (CW) deuteron beam from 1 MeV to 5 MeV with a total cavity length of 1.25 m using Kombinierte Null Grad Struktur (KONUS) design, achieving an accelerating gradient of 3.2 MV/m. The RF power loss for the whole cavity is estimated to be 85 kW. This high power loss is a significant challenge to the cooling design, as it could cause large rises in tempera-ture, thermal deformation and frequency drift. A detailed multi-physics analysis of the CW IH-DTL is presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL052  
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TUPAL068 The Development of a Nw Fast Harmonic Kicker for the JLEIC Circulator Cooling Ring kicker, emittance, simulation, electron 1171
 
  • G.-T. Park, F. Fors, J. Guo, R.A. Rimmer, H. Wang, S. Wang
    JLab, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
After the first half-scale, 5 harmonic kicker cavity prototyping * for the JLEIC's CCR/ERL electron cooler and the beam dynamic simulation study of the 10-turn CCR **. The optimized circulation cooling turns has been changed to 11 and only 5 odd-harmonic modes from 86.6 MHz to 779.4 MHz plus a DC bias are needed for the harmonic RF kicker system. The new cavity design including the electromagnetic and thermal cooling optimization and its 11 turns beam bunch tracking simulation with the new numerology of RF deflecting voltages will be presented. Further design specifications for its RF harmonic drive and the broadband RF window, coupler and circulator component will be given for handling 5 kW of total RF power.
* Y, Huang, H. Wang et al., Physical Review Accelerators and Beams 19, 122001 (2016).
** Y. Huang, H. Wang et al., Physical Review Accelerators and Beams 19, 084201 (2016).
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL068  
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TUPAL075 Mechanical Design and Error Analysis of a 325 MHz IH-DTL Test Cavity DTL, alignment, simulation, linac 1186
 
  • R. Tang, C.T. Du, X. Guan, K.D. Man, C.-X. Tang, X.W. Wang, Q.Z. Xing, S.X. Zheng
    TUB, Beijing, People's Republic of China
  • J. Li
    NUCTECH, Beijing, People's Republic of China
 
  A 325 MHz interdigital H-mode drift tube linac (IH-DTL) test cavity with a modified KONUS beam dynamics is under fabrication at Tsinghua University. The inner diameter of the tank increases from 196.8 to 232.6 mm. The mechanical design is considered carefully because of its small geometry. A three-piece design has been adopted in the mechanical design. The error analysis is carried out to determine the error requirement of machining and alignment. The details of mechanical design and error analysis is presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL075  
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TUZGBD5 Performance of Nanometre-Level Resolution Cavity Beam Position Monitors at ATF2 feedback, dipole, electron, kicker 1212
 
  • T. Bromwich, D.R. Bett, N. Blaskovic Kraljevic, R.M. Bodenstein, P. Burrows, G.B. Christian, C. Perry, R.L. Ramjiawan
    JAI, Oxford, United Kingdom
  • S. Araki, A. Aryshev, T. Tauchi, N. Terunuma
    KEK, Ibaraki, Japan
  • P. Bambade, S. Wallon
    LAL, Orsay, France
  • S.W. Jang
    Korea University Sejong Campus, Sejong, Republic of Korea
 
  A system of three low-Q cavity beam position monitors (BPMs), installed in the interaction point (IP) region of the Accelerator Test Facility (ATF2) at KEK, has been designed and optimised for nanometre-level beam position resolution. The BPMs are used to provide an input to a low-latency, intra-train beam position feedback system deployed in single-pass, multi-bunch mode with the aim of demonstrating intra-train beam stabilisation on electron bunches of charge ~1 nC separated in time by 280 ns. In 2016 the BPM resolution was demonstrated to be below 50 nm using the raw measured vertical positions at the three BPMs. New results will be presented utilising integrated sampling of the raw waveforms, improved BPM alignment and modified cavities to demonstrate a vertical position resolution on the order of 20 nm.  
slides icon Slides TUZGBD5 [8.557 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUZGBD5  
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TUZGBE4 Toward High-Power High-Gradient Testing of mm-Wave Standing-Wave Accelerating Structures experiment, coupling, accelerating-gradient, diagnostics 1224
 
  • E.A. Nanni, V.A. Dolgashev, A.A. Haase, J. Neilson, S.G. Tantawi
    SLAC, Menlo Park, California, USA
  • S. Jawla, R.J. Temkin
    MIT/PSFC, Cambridge, Massachusetts, USA
  • S. C. Schaub
    MIT, Cambridge, Massachusetts, USA
  • B. Spataro
    INFN/LNF, Frascati (Roma), Italy
 
  Funding: This work is supported in part by Department of Energy contract DE-AC02-76SF00515 (SLAC) and DE-SC0015566 (MIT).
We will preliminary testing results for single-cell accelerating structures intended for high-gradient testing at 110 GHz. The purpose of this work is to study the basic physics of ultrahigh vacuum RF breakdown in high-gradient RF accelerators. The accelerating structures consist of pi-mode standing-wave cavities fed with TM01 circular waveguide mode. We fabricated of two structures one in copper and the other in CuAg alloy. Cold RF tests confirm the design RF performance of the structures. The geometry and field shape of these accelerating structures is as close as practical to single-cell standing-wave X-band accelerating structures more than 40 of which were tested at SLAC. This wealth of X-band data will serve as a baseline for these 110 GHz tests. The structures will be powered with a MW gyrotron oscillator that produces microsecond pulses. One megawatt of RF power from the gyrotron may allow us to reach a peak accelerating gradient of 400 MeV/m.
 
slides icon Slides TUZGBE4 [4.644 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUZGBE4  
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TUZGBE5 A Combined Temperature and Magnetic Field Mapping System for SRF Cavities operation, SRF, niobium, experiment 1228
 
  • J.M. Köszegi, K. Alomari, J. Knobloch, O. Kugeler, B. Schmitz
    HZB, Berlin, Germany
 
  In the past decade, a significant improvement of SRF cavity performance has been achieved, yet a number of performance limiting mechanisms, such as magnetic flux trapping, still exist. We present a diagnostics tool which combines flux expulsion measurement during the superconducting phase transition with temperature mapping during operation. This system has a time resolution for both temperature and magnetic field mapping of 2 ms for full cavity coverage, so that short-lived events, including cavity quenches, can easily be resolved.  
slides icon Slides TUZGBE5 [1.358 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUZGBE5  
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TUZGBF3 Betatron Core Slow Extraction at CNAO betatron, extraction, synchrotron, acceleration 1237
 
  • L. Falbo, E. Bressi, S. Foglio, C. Priano
    CNAO Foundation, Milan, Italy
 
  CNAO is the only Italian hadrontherapy facility able to treat tumors with beams of protons and carbon ions. Beam is extracted with a momentum selection scheme in which beam enters the third order resonance driven by a betatron core. When irradiating a tumor, it is thought as divided in the longitudinal plane in several slices while each slice is divided in the transverse plane in several spots called voxels. Considering the dose uniformity that can be obtained during extraction, the machine must extract an average intensity related to the voxel that requires less dose. Therefore during a treatment, for some slices, a technique is needed to lower the extracted beam intensity with respect to the nominal one. A way to guarantee the correct average intensity according to the treatment planning requirements, is to introduce a mechanical filter (a degrader) that reduces the intensity of the accelerated particles. However this method used in the first treatments at CNAO showed some disadvantages and it has been replaced by what has been called the "dynamic betatron" method. The paper shows the implementations and the advantages of this method in the CNAO treatments.  
slides icon Slides TUZGBF3 [2.146 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUZGBF3  
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TUZGBF5 KlyLac Prototyping for Borehole Logging klystron, linac, feedback, simulation 1244
 
  • A.V. Smirnov, R.B. Agustsson, M.A. Harrison, A.Y. Murokh, A.Yu. Smirnov
    RadiaBeam Systems, Santa Monica, California, USA
  • S. Boucher, T.J. Campese, K.J. Hoyt
    RadiaBeam, Los Angeles, California, USA
  • E.A. Savin
    MEPhI, Moscow, Russia
  • A.A. Zavadtsev
    Nano, Moscow, Russia
 
  Funding: Work supported by the U.S. Department of Energy (award No. DE-SC0015721)
Linac-based system for borehole logging exploits KlyLac approach combing klystron and linac sharing the same electron beam, vacuum volume, and RF network enabling self-oscillation due to a positive feedback. The KlyLac prototype design tailors delivering ~1 MeV electrons in a linac section using part of the beam injected from a sheet beam klystron (SBK). The linac part is based on a very robust, high group velocity, cm-wave, and a standing wave accelerating structure of a 'cross-pin' type supplied by a sampler. The SBK part features a permanent magnet solenoid focusing, relatively low voltage, and high aspect ratio beam. The main SBK characteristics (perveance, power, and efficiency) are expected to be similar to that for a magnetron.
 
slides icon Slides TUZGBF5 [3.280 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUZGBF5  
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TUPMF002 A Cu Photocathode for the Superconducting RF Photoinjector of BERLinPro cathode, gun, SRF, laser 1247
 
  • J. Kühn, M. Bürger, A. Frahm, A. Jankowiak, T. Kamps, G. Klemz, G. Kourkafas, A. Neumann, N. Ohm, M. Schmeißer, M. Schuster, J. Völker
    HZB, Berlin, Germany
  • P. Murcek, J. Teichert
    HZDR, Dresden, Germany
 
  The initial commissioning of the Superconducting RF (SRF) photoinjector is done with a Cu photocathode due to its robustness with regard to interactions with the SRF cavity of the injector. Here we present the preparation and characterization of a Cu photocathode plug and the diagnostics to insert the photocathode in the back wall of the SRF cavity. A polycrystalline bulk Cu plug was polished, particle free cleaned and characterized by x-ray photoelectron spectroscopy. During the transfer of the photocathode insert into the gun module the whole process was controlled by several diagnostic tools monitoring the insert position as well as RF, vacuum and cryogenic signals. We discuss the challenges of the photocathode transfer into an SRF cavity and how they can be tackled.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF002  
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TUPMF003 Dynamic Tuning of the APS-U Booster 5-cell Cavities booster, resonance, 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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TUPMF016 Application of SVD Analysis to Deflecting Cavitiy Space Harmonics simulation, timing, data-analysis, experiment 1283
 
  • C. Yao, L. Emery, D. Hui, H. Shang, Y.P. Sun
    ANL, Argonne, Illinois, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
Singular value decomposition (SVD) analysis is a powerful tool for identifying different spatial and timing variation patterns in many fields of researches. Recently we applied complex SVD method to space harmonic analysis of a 13-cell defecting cavity that is built and installed in the APS linac injector for beam phase space characterization and emittance exchange experiments. Real and imaginary space harmonics components are extracted from CST simulated data. Fields inside the iris were expressed in analytic forms and produced good agreement. Work is underway to implement the results into elegant simulation model.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF016  
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TUPMF032 RF Conceptual Design of Normal Conducting Cavity for an eRHIC Rapid Cycling Synchrotron electron, GUI, coupling, vacuum 1316
 
  • B. P. Xiao, M. Blaskiewicz, J.M. Brennan, D. Holmes, K.S. Smith, T. Xin, A. Zaltsman
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
The Rapid Cycling Synchrotron (RCS) for the eRHIC Ring-Ring design will provide on energy injection (up to 18 GeV) of high charge, polarized electron bunches to the eRHIC electron storage ring. The RF system comprises a large number of 563MHz fundamental cavities, providing up to 45MV per turn. The cavities will operate in pulsed mode with <20% duty factor, at a repetition rate of 1 Hz. In this paper we report the conceptual RF design of the cavity.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF032  
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TUPMF034 Measuring the Electrical Center and Field Flatness of 704 MHz Deflecting Cavity for LEReC with Wire Stretching System simulation, diagnostics, pick-up, experiment 1320
 
  • T. Xin, J.M. Brennan, J.C.B. Brutus, K. Mernick, K.S. Smith, B. P. Xiao, A. Zaltsman
    BNL, Upton, Long Island, New York, USA
  • W. Johnson
    SBU, Stony Brook, New York, USA
  • H. Wang
    JLab, Newport News, Virginia, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
704 MHz deflecting cavity was designed for the Low Energy RHIC electron Cooling (LEReC) project. The cavity will serve as a major component in diagnostic line. In LEReC project the requirement on the energy spread of the electron beam is extremely high (better than 10-4) and the diagnostic system has to to be designed accordingly. The 704 MHz transverse deflecting cavity provides the vertical kick to the beam after it passes through the dispersion dipole so that we can measure the energy spread of the core of the bunch. Traditional way of determining the electrical center of the cavity involves the needle pulling and integration of the signal which is prone to the cumulative error. We present the measurement result from a wire stretching system that is much more efficient and accurate compared to the bead/needle pulling method. Both simulation and experimental results are shown in this paper and the potential in further application is discussed at the end.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF034  
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TUPMF042 Design of a High Dose Rate Micro-Focused X-Ray Source electron, target, emittance, dipole 1346
 
  • X. He, S.Q. Liao, J. Long, J. Shi, W. Wang, L. Yang
    CAEP/IFP, Mainyang, Sichuan, People's Republic of China
 
  High energy X-ray computer tomography has wide application in industry, especially in quality control of complicated high-tech equipment. In many applications, higher spatial resolution is needed to discover smaller defects. Decreasing the spot size of the X-Ray source is a promising way to get higher spatial resolution. Rhodotron have been used to produce high power CW electron beam in hundreds of kilowatts level. In this paper, we propose to use an improved Rhodotron to generate high brightness electron beam with high average power. Beam dynamics study shows that when producing tens of kilowatts electron beam, the normalized RMS emittance can be lower than 10 μm, and the relative RMS energy spread can be lower than 0.2%. The beam can be focused to a spot size of about 100μm by using a series of quadruple, and converted to X-Ray by using a rotating target within several kilowatts beam power. Improved Rhodotron proposed in this paper is a good candidate of X-ray source for high resolution high energy industrial CT systems.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF042  
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TUPMF048 On-Axis Beam Accumulation Based on a Triple-Frequency RF System for Diffraction-Limited Storage Rings injection, simulation, accumulation, photon 1359
 
  • S.C. Jiang, Z. Duan, G. Xu
    IHEP, Beijing, People's Republic of China
 
  Since the multi-bend achromats have been applied to lattice design in the future light source to achieve ultralow emittance, strong sextupoles and concomitant nonlinearities restrict its performance to a certain extent. The empirical understanding is the exclusion of conventional off-axis injection scheme on these light sources. In this paper, we will present a new on-axis beam accumulation scheme, which is based on the triple-frequency RF system. By means of delicate superposition of RF voltage with fundamental and two other harmonic frequencies, a commodious and steady main bucket is able to be formed. The electron bunch from the injector will be kicked into the main bucket on-axis with a reasonable time offset to the circular bunch, and this process may make the minimal disturbance to the experiment users while operating on the top-up mode. The application of this scheme to the High Energy Photon Source (HEPS) will be discussed in the paper, corresponding simulation results are also presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF048  
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TUPMF074 Control of Collective Effects by Active Harmonic Cavity in an MBA-based Light Source with Application to the PETRA Upgrade impedance, emittance, lattice, synchrotron 1433
 
  • Y.-C. Chae, J. Keil
    DESY, Hamburg, Germany
 
  Based on the reference lattice for PETRA IV* we investigated collective effects with non-zero current. Out of many possibilities we firstly computed the intrabeam-scattering (IBS) effects on the emittance as well as lifetime as a function of current. The result indicated that PETRA IV would benefit from the reduced peak current when the harmonic cavity lengthens the bunch. The operating point of harmonic cavity was explored by tracking simulations as well as analytic formula. In order to compute the energy spread and bunch length we had used the known impedance function of the APS**. In this way more realistic estimation of IBS effects was expected. However, because of the complex nature of PETRA IV lattice, which includes achromatic cells for undulators, arc cells of octants and straight sectors for damping wigglers, we simplify the longitudinal dynamics by assuming the ring made of 92 multi-bend-achromat (MBA) cells. The optics is approximated as a linear-chromatic transfer map enabling fast tracking and the ring impedance is concatenated into the one location. The detailed collective effects with and without harmonic cavities are presented in the paper.
* J. Keil, "A PETRA IV Lattice Based on Hybrid Seven Bend Achromats", these proceedings.
** Y.-C. Chae and Y. Wang, "Impedance Database II for the Advanced Photon Source Storage Ring", Proc. PAC2007.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF074  
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TUPMF080 Progress on Multibunch FEL Performance at FLASH operation, FEL, controls, accelerating-gradient 1452
 
  • T. Hellert, Ch. Schmidt
    DESY, Hamburg, Germany
 
  At the SASE-FEL user facility FLASH, superconducting TESLA-type cavities are used for acceleration. The high achievable duty cycle allows for operating with long bunch-trains, hence considerably increasing the efficiency of the machine. However, RF induced intra-bunch-train trajectory variations were found to be responsible for significant variations of the SASE intensity within one bunch train. This work presents the latest achievements in improving the multi-bunch FEL performance by reducing the intra-bunch-train variation of RF parameters. Particular attention is given to the static and dynamic detuning of the cavities. It will be shown that the current level of LLRF control is suitable to limit the variation of RF parameters considerably.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF080  
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TUPMF081 Microphonic Detuning Induced Coupler Kick Variation at LCLS-II linac, laser, free-electron-laser, beam-loading 1456
 
  • T. Hellert
    DESY, Hamburg, Germany
  • W. Ackermann, H. De Gersem
    TEMF, TU Darmstadt, Darmstadt, Germany
  • C. Adolphsen, Z. Li, C.E. Mayes
    SLAC, Menlo Park, California, USA
 
  The LCLS-II free-electron laser will be an upgrade of the existing Linac Coherent Light Source (LCLS), including a 4 GeV CW superconducting linac based on the TESLA technology. The high quality factor of the cavity makes it very sensitive to vibrations. The shift of its eigenfrequency (i.e., detuning) will be compensated by the power source in order to assure a constant accelerating voltage. Significant variations of the forward power are expected which result in coupler kick variations induced by the fundamental power coupler. In this work we estimate the magnitude of trajectory jitter caused by these variations. High precision 3D field maps including standing and traveling-wave components for a cavity with the LCLS-II coupler design are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF081  
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TUPMF086 Status of the ARES RF Gun at SINBAD: From its Characterization and Installation towards Commissioning gun, linac, status, electron 1474
 
  • B. Marchetti, R.W. Aßmann, S. Baark, F. Burkart, U. Dorda, K. Flöttmann, I. Hartl, J. Hauser, J. Herrmann, M. Hüning, K. Knebel, O. Krebs, G. Kube, W. Kuropka, S. Lederer, F. Lemery, F. Ludwig, D. Marx, F. Mayet, M. Pelzer, I. Peperkorn, F. Poblotzki, S. Pumpe, J. Rothenburg, H. Schlarb, M. Titberidze, G. Vashchenko, T. Vinatier, P.A. Walker, L. Winkelmann, K. Wittenburg, S. Yamin, J. Zhu
    DESY, Hamburg, Germany
 
  The SINBAD facility (Short and INnovative Bunches and Accelerators at DESY) is foreseen to host multiple experiments relating to the production of ultra-short electron bunches and novel high gradient acceleration techniques. The SINBAD-ARES linac will be a conventional S-band linear RF accelerator allowing the production of low charge (0.5 pC - tens pC) ultra-short electron bunches (FWHM length =< 1 fs - few fs) with 100 MeV energy. The installation of the linac will proceed in stages. In this paper we report on the status of the characterization of the ARES RF gun and the installations of the related infrastructure.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF086  
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TUPMK006 Sub-fs Electron Bunch Generation Using Emittance Exchange Compressor emittance, simulation, sextupole, electron 1501
 
  • J.M. Seok, M. Chung
    UNIST, Ulsan, Republic of Korea
  • M.E. Conde, J.G. Power
    ANL, Argonne, Illinois, USA
  • G. Ha
    PAL, Pohang, Republic of Korea
 
  Sub-fs electron bunch has been pursued in the last decade using several different methods. These methods rely on one of the velocity difference or path length difference to compress a long bunch to sub-fs bunch. Here, we introduce a new method to generate the compression. Emittance Exchange (EEX) beamline makes transverse-to-longitudinal exchange of phase space. In this beamline, a transverse focusing at the upstream introduces a longitudinal compression at the downstream due to the exchange. Since this exchange scheme does not rely on the velocity or the path length differences, it does not require any longitudinal manipulation (e.g. chirp), and it could generate a short bunch with well-controlled nonlinear effects using nonlinear magnets. We present preliminary simulation results of EEX based bunch compression and sub-fs bunch generation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMK006  
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TUPML053 The BERLinPro SRF Photoinjector System - From First RF Commissioning to First Beam cathode, SRF, operation, solenoid 1660
 
  • A. Neumann, D. Böhlick, M. Bürger, P. Echevarria, A. Frahm, H.-W. Glock, F. Göbel, S. Heling, K. Janke, A. Jankowiak, T. Kamps, S. Klauke, G. Klemz, J. Knobloch, G. Kourkafas, J. Kühn, O. Kugeler, N. Leuschner, N. Ohm, E. Panofski, H. Plötz, S. Rotterdam, M.A.H. Schmeißer, M. Schuster, H. Stein, Y. Tamashevich, J. Ullrich, A. Ushakov, J. Völker
    HZB, Berlin, Germany
 
  Funding: The work is funded by the Helmholtz-Association, BMBF, the state of Berlin and HZB.
Helmholtz-Zentrum Berlin (HZB) is currently constructing a high average current superconducting (SC) ERL as a prototype to demonstrate low normalized beam emittance of 1 mm-mrad at 100 mA and short pulses of about 2 ps. To attain the required beam properties, an SRF based photo-injector system was developed and during the past year underwent RF commissioning and was setup within a dedicated diagnostics beamline called Gunlab to analyze beam dynamics of both, a copper cathode and a Cs2KSb cathode as well as their quantum efficiency at UV and green light respectively. The medium power prototype - a first stage towards the final high power 100 mA design - presented here features a 1.4 x λ/2 cell SRF cavity with a normal-conducting, high quantum efficiency CsK2Sb cathode, implementing a modified HZDR-style cathode insert. This injector potentially allows for 6 mA beam current and up to 3.5 MeV kinetic energy, limited by the modified twin TTF-III fundamental power couplers. In this contribution, the first RF commissioning results of the photo-injector module will be presented including dark current analysis as well as measured beam properties with an initially installed Copper cathode.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML053  
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TUPML054 Microbeam Irradiation System with a Dielectric Laser Accelerator for Radiobiology Research laser, electron, accelerating-gradient, radiation 1664
 
  • K. Koyama
    KEK, Ibaraki, Japan
  • Z. Chen
    The University of Tokyo, Tokyo, Japan
  • T. Takahashi
    The University of Tokyo, The School of Engineering, Tokyo, Japan
  • M. Uesaka
    The University of Tokyo, Nuclear Professional School, Ibaraki-ken, Japan
 
  Funding: This work was supported by KAKENHI (Grant-in-Aid for Scientific Research)15H03595 and partly supported by NIMS Nanofabrication Platform in Nanotechnology Platform Project sponsored by the MEXT, Japan.
A laser micro-irradiation (LMI) system is widely used in the field of radiobiology because of its acceptably small size. However, damage in a cell nucleus caused by the LMI system does not necessarily simulate a radiation effect. If the laser of the LMI system is replaced with a small-scale 1MeV-class accelerator such as a dielectric laser accelerator (DLA), experiments might be performed under conditions that are more realistic. The desirable configuration of the DLA for a compact micro-beam irradiation system is that laser pulses are transported to a dielectric structure by single-mode optical fibers and the laser energy is accumulated in an accelerator channel. The long and low-intensity laser pulse of 100 MW/cm2, 10ps and a resonator with Q=104 are capable of producing the light intensity of 1 TW/cm2. The long laser pulse, i.e., low laser induced damage threshold intensity, decreases the acceleration gradient to about 1/3 of the ultra-short pulse irradiation of 100 fs. The length of the accelerator at long-laser pulse might be within the allowable range of several cm. The resonator scheme is useful only for the sub-relativistic regime because of the acceleration gradient.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML054  
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TUPML066 Progress on Beam-Plasma Effect Simulations in Muon Ionization Cooling Lattices plasma, simulation, emittance, scattering 1696
 
  • P. Snopok
    Illinois Institute of Technology, Chicago, Illinois, USA
  • J.S. Ellison
    IIT, Chicago, Illinois, USA
 
  Funding: Work supported by the Department of Energy.
New computational tools are essential for accurate modeling and simulation of the next generation of muon-based accelerators. One of the crucial physics processes specific to muon accelerators that has not yet been simulated in detail is beam-induced plasma effect in liquid, solid, and gaseous absorbers. We report here on the development of required simulation tools and their applications to studying the properties of plasma and its effects on the beam in muon ionization cooling channels.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML066  
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WEXGBF1 Testing of the ESS MB-IOT Prototypes klystron, linac, operation, electron 1759
 
  • M. Jensen
    ESS, Lund, Sweden
  • C. Bel, A. Beunas, D. Bussiere, P. Cacheux, V. Hermann, J.C. Racamier, C. Robert
    TED, Thonon, France
  • M. Boyle, H. Schult
    L-3, Williamsport, Pennsylvania, USA
  • G. Cipolla, E. Montesinos, M.S.B. Sanchez Barrueta
    CERN, Geneva 23, Switzerland
  • T. Kimura, P.E. Kolda, P. Krzeminski, L. Kurek, S. Lenci, O.S. Sablic, L. Turek, C. Yates
    CPI, Palo Alto, California, USA
  • M.F. Kirshner
    LANL, Los Alamos, New Mexico, USA
  • R.D. Kowalczyk, A.V. Sy, B.R. Weatherford
    SLAC, Menlo Park, California, USA
  • A. Zubyk
    L3 EDD, Williamsport, USA
 
  ESS is considering the use of MB-IOTs for parts of the high-beta linac. Two prototypes have been built by indus-try, namely L3 and CPI/Thales and have passed the factory acceptance test with excellent results. Both tubes will go through further extensive testing at CERN for ESS follow-ing delivery and a final decision on tube technology will be taken in April 2018. This invited talk presents the back-ground for the technical decision of IOTs vs klystrons, associated impact for ESS, and latest plans for industrial production of these IOTs for ESS.  
slides icon Slides WEXGBF1 [9.836 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEXGBF1  
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WEXGBF3 RF System for FRIB Accelerator controls, LLRF, rfq, linac 1765
 
  • D.G. Morris, J. Brandon, N.K. Bultman, K.D. Davidson, A. Facco, P.E. Gibson, L. Hodges, M.G. Konrad, T.L. Larter, H. Maniar, P. Morrison, P.N. Ostroumov, J.T. Popielarski, G. Pozdeyev, H.T. Ren, T. Russo, K. Schrock, R. Walker, J. Wei, T. Xu, Y. Xu, S. Zhao
    FRIB, East Lansing, USA
  • A. Facco
    INFN/LNL, Legnaro (PD), Italy
 
  The RF system of the FRIB driver accelerator includes solid state amplifiers up to 18 kW operating at frequencies from 80.5 MHz to 322 MHz. Much higher power is required for the normal conducting RFQ, ~100 kW, and it is based on vacuum tubes. This invited talk presents the performance of solid state amplifiers and LLRF in off-line testing and on-line testing of the RFQ amplifier.  
slides icon Slides WEXGBF3 [14.107 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEXGBF3  
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WEYGBD1 12 GeV CEBAF Initial Operational Experience and Challenges operation, MMI, cryomodule, experiment 1771
 
  • M. F. Spata
    JLab, Newport News, Virginia, USA
 
  The 12 GeV Upgrade for the Continuous Electron Beam Accelerator Facility (CEBAF) achieved CD-4B, or Project Completion, on September 27, 2017. The 13-year $338M project doubled the beam energy of the CEBAF accelerator while also adding a fourth experimental hall. The scope of work for the accelerator complex was completed in 2014. Over the subsequent three years the upgrades for the experimental halls were completed, beamlines and spectrometers commissioned and transitions made to production running for the Nuclear Physics program. This paper will present an overview of the operational experience gained during initial accelerator commissioning through the recent achievements of simultaneous 4-Hall operations at full beam power.  
slides icon Slides WEYGBD1 [15.178 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEYGBD1  
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WEYGBF3 Nb3Sn Multicell Cavity Coating at JLab niobium, factory, SRF, superconductivity 1798
 
  • U. Pudasaini, M.J. Kelley
    The College of William and Mary, Williamsburg, Virginia, USA
  • G. Ciovati, G.V. Eremeev, M.J. Kelley, C.E. Reece
    JLab, Newport News, Virginia, USA
  • M.J. Kelley
    Virginia Polytechnic Institute and State University, Blacksburg, USA
  • I.P. Parajuli, MNS. Sayeed
    ODU, Norfolk, Virginia, USA
 
  Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics.
Following encouraging results with Nb3Sn-coated R&D cavities, the existing coating system was upgraded to allow for Nb3Sn coating of CEBAF accelerator cavities. The upgrade was designed to allow Nb3Sn coating of original CEBAF 5-cell cavities with the vapor diffusion technique. Several CEBAF cavities were coated in the upgraded system to investigate vapor diffusion coatings on extended structures. Witness samples coated along with the cavities were characterized with material science techniques, while coated cavities were measured at 4 and 2 K. The progress, lessons learned, and the pathforward are discussed.
 
slides icon Slides WEYGBF3 [2.381 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEYGBF3  
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WEPAF018 Proposed BPM-Based Bunch Crabbing Angle Monitor simulation, site, electron, diagnostics 1860
 
  • P. Thieberger, M.G. Minty, C. Montag
    BNL, Upton, Long Island, New York, USA
 
  Funding: This work was supported by Brookhaven Science Associates, LLC, under Contract No. DE-AC02-98CH10886 with the US Department of Energy.
A tilted bunch traversing a button beam profile monitor will produce signals on opposite pickup electrodes that will have different degrees of distortion depending on the tilt angle. In particular, the zero-crossing time difference between the two signals will be approximately proportional to the tilt angle. We perform simulations to study this effect as a possible diagnostic tool for measuring the crabbing angles in a future electron-ion collider.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF018  
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WEPAF027 Low Q Cavity BPM Study for the Beam Position Measurement of Nanosecond Spaced Electron Bunches FEL, dipole, electron, coupling 1881
 
  • L. Yang, X. He, L.W. Zhang
    CAEP/IFP, Mainyang, Sichuan, People's Republic of China
  • S.S. Cao, Y.B. Leng, L.Y. Yu, R.X. Yuan
    SINAP, Shanghai, People's Republic of China
 
  Funding: National natural science foundation of China, 11705184
Low Q cavity BPM is a key to distinguish closely spaced electron bunches allowing precise beam handling for XFEL facilities operating in a multi-bunch mode at high repetition rate up to hundreds MHz. The inter-bunch signal pollution issue becomes significant when bunch separation is down to nanosecond and causes the position detection to be increasingly overestimated. Solely relying on extreme low Q to achieve sufficient decay within bunch interval leads to appreciable interference from non-signal modes due to strong overcoupling of antenna design is required. The error imposed on measured position raises a challenge to meet the goal of high resolution. Alternatively, a concept is proposed to remove the dominant part of signal pollution at the moment of sampling by intentionally shifting the phase of the last bunch signal 90degree respect to that of current bunch signal, where signal sampling is normally taken for nanosecond spaced bunches. This quadrature phase shift is defined by properly choosing the operational frequency of dipole mode regarding to the bunch frequency. A low Q cavity BPM prototype to identify technical challenges and verify this concept is under development in the R&D plan for future XFEL with high repetition rate
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF027  
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WEPAF042 Measurement of Beam yz Crabbing Tilt Due to Wake Fields Using Streak Camera at CESR wakefield, storage-ring, positron, coupling 1905
 
  • S. Wang, D. L. Rubin
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Funding: This research was supported by NSF PHYS-1068662, PHYS-1416318 and DMR-1332208.
Transverse vertical wake fields can increase the vertical emittance and distort the phase space of a bunch in a storage ring. Recently, we observed charge-dependent vertical beam size growth with a single scraper inserted through the top of the storage ring vacuum chamber. This apparent growth was due in large part to the yz coupling (vertical crabbing) induced by the wake field from the asymmetric scraper configuration. Here, we report a direct measurement of a small beam yz crabbing tilt using a streak camera. The recorded images (projected beam profiles in yz plane) are analyzed with three different methods, which yield consistent beam yz tilts. We found the directly-measured current-dependent beam tilts by the streak camera are consistent with the beam tilts calculated from a wake field model.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF042  
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WEPAF046 RF Electronics for the Measurement of Beam Induced Higher Order Modes (HOM) Implemented in the MicroTCA.4 Form Factor HOM, dipole, electron, electronics 1916
 
  • S. Jabłoński, N. Baboi, U. Mavrič, H. Schlarb
    DESY, Hamburg, Germany
 
  Higher order modes (HOM) excited in RF accelerating cavities by a particle beam can be used for electron beam diagnostics. Phase of a monopole HOM provides information about the beam phase relative to the externally induced RF field in a cavity (BPhM) [1]. Furthermore, the amplitude of a dipole mode is proportional to the beam position in the cavity, hence it can be used for beam position monitoring (BPM). In this paper we present a prototype of an instrument implemented in the MicoTCA.4 form factor for the measurement of the HOMs at FLASH and Eu-XFEL. The prototype consists of an analog module, which is used for filtering and conditioning of the selected modes, and a digital module responsible for digitization and signal processing. We present the instruments performance and discuss its influence on the precision of the HOM-based diagnostics.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF046  
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WEPAF050 Simulations of 3D Charge Density Measurements for Commissioning of the PolariX-TDS simulation, electron, MMI, lattice 1930
 
  • D. Marx, R.W. Aßmann, R.T.P. D'Arcy, B. Marchetti
    DESY, Hamburg, Germany
 
  The prototype of a novel X-band transverse deflection structure, the Polarizable X-band (PolariX) TDS*, is currently being prepared for installation in the FLASHForward beamline** at DESY in early 2019. This structure will have the novel feature of variable polarization of the deflecting mode, allowing bunches to be streaked at any transverse angle, rather than at just one angle as in a conventional cavity. By combining screen profiles from several streaking angles using tomographic reconstruction techniques, the full 3D charge density of a bunch can be obtained***. It is planned to perform this measurement for the first time during commissioning of the structure. In this paper, simulations of this measurement are presented and the effects of jitter are discussed.
*P Craievich et al. paper THPAL068, this conference
**A Aschikhin et al. Nucl. Instr. Meth. Phys. Res. A., vol.806, pp.175-183, 2018
***D Marx et al. J. Phys.: Conf. Ser., vol.874, p.012077, 2017
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF050  
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WEPAF052 High QL and High Gradient CW Operation of Tesla SCRF 9-Cell Cavity feedback, operation, controls, FEL 1937
 
  • K.P. Przygoda, V. Ayvazyan, L. Butkowski, M. Hierholzer, R. Rybaniec, H. Schlarb, Ch. Schmidt, J.K. Sekutowicz
    DESY, Hamburg, Germany
 
  In the paper we would like to present Tesla SCRF 9-Cell cavity operated at CW regime with extremely high QL at gradients above 23 MV/m. The design hardware and firmware components as well as developed high level software procedures allows automatic procedure of cavity trip from low to high gradient operation. The microphonics as well as a pendoromotive effects are sensed, identify and applied for cavity detuning correction. The RF and piezo feedbacks performance are demonstrated and preliminary results are briefly discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF052  
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WEPAF063 RF Manipulations for Special LHC-Type Beams in the CERN PS extraction, emittance, brightness, flattop 1971
 
  • H. Damerau, S. Hancock, A. Lasheen, D. Perrelet
    CERN, Geneva, Switzerland
 
  Beams with special longitudinal characteristics for the Large Hadron Collider (LHC) have been produced in the Proton Synchrotron (PS) and CERN. The flexibility of its RF systems consisting of in total 25 RF cavities at frequencies from 400 kHz to 200 MHz allows a variety of longitudinal beam manipulations. In particular the main RF system is split into three independent groups tunable from 2.8 MHz to 10 MHz. It is used to merge, split and change the spacing between bunches by applying different voltage and phase programs to the three groups of cavities at different harmonic numbers simultaneously. The batch compression, merging and splitting (BCMS) process has been operationally used for LHC fillings since 2016. To mitigate issues with long bunch trains in the LHC in 2017, short gaps of four bunch positions have been introduced between mini-batches of eight bunches (8b4e). A higher brightness version resulting in four mini-batches per PS extraction has been delivered for luminosity production in the LHC. This paper summarizes the operational experience and indicates possible future RF manipulation schemes.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF063  
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WEPAF068 Frequency Scanning Interferometry as New Solution for on-Line Monitoring Inside a Cryostat for the HL-LHC project target, vacuum, monitoring, dipole 1986
 
  • H. Mainaud Durand, T. Dijoud, J. Gayde, F. Micolon, M. Sosin
    CERN, Geneva, Switzerland
  • M. Duquenne, V. Rude
    ESGT-CNAM, Le Mans, France
 
  Funding: Research supported by the HL-LHC project
For the HL-LHC project, the cryostats of the key components will be equipped permanently with an on-line position monitoring system based on Frequency Scanning Interferometry (FSI). Such a system, based on absolute distance measurement, will determine the position of the inner triplet cold masses w.r.t. their cryostat and the position of the crab cavities also inside their cryostat, within an uncertainty of measurement of 0.1 mm, in a harsh environment: cold temperature of 2 K and high radiation level of the order of 1 MGy. The FSI system was validated first successfully on one LHC dipole cryostat and its associated cold mass to undergo qualification tests under different conditions: warm, vacuum and cold (2K). The FSI system also equips the first crab cavities prototype cryostat. The configuration of the FIS system chosen after simulations, the conditions of tests as well as their results and analysis are presented in this paper.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF068  
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WEPAF069 Evaluation of Frequency Scanning Interferometer Performances for Surveying, Alignment and Monitoring of Physics Instrumentation alignment, laser, target, luminosity 1990
 
  • J. Gayde, S.W. Kamugasa
    CERN, Geneva, Switzerland
 
  During the last three years, the performance of Frequency Scanning Interferometry, accurate to a few micrometres, has been evaluated at CERN in the frame of the PACMAN project. Improvements have been studied and tested to make it better suited for typical alignment and survey conditions in accelerators and experiments. The results of these developments and tests, coupled with the multi-channel capability of the system, and its compactness which eases its integration in the area to be surveyed, offer a wide scope of possible applications for in-situ large scale metrology for physics equipment and facility elements. Furthermore, the fact that the system electronics can be placed far away from the position to be measured, allows the system to be used in confined and hazardous spaces. This paper briefly describes the system and its improvements. It gives the precision obtained for distance measurements and for the 3D point reconstruction based on FSI observations in the case of CLIC component fiducialisation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF069  
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WEPAF086 Latest Developments and Updates of the ESS Linac Simulator DTL, linac, solenoid, space-charge 2051
 
  • J.F. Esteban Müller, E. Laface
    ESS, Lund, Sweden
 
  A fast and accurate online model is required for optimal commissioning and reliable operation of the high-power proton linac at the European Spallation Source. The Open XAL framework, initially developed at SNS, is used at ESS for the development of high-level physics applications. The online model we use, known as ESS Linac Simulator (JELS), extends the Open XAL model with several features. This paper describes the latest updates carried out to JELS. Two new elements have been implemented: a solenoid field map for the LEBT and a DTL Tank element that automatically calculates each gap phase. All calculations are now done in the laboratory frame, in agreement with Open XAL convention. A thorough benchmark of the model against TraceWin, which is the tool used for the lattice design, is also presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF086  
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WEPAG002 Tunable Q-Factor Gas-Filled RF Cavity coupling, hadron, plasma, simulation 2064
 
  • M.D. Balcazar, A. Moretti, A.V. Tollestrup, A.C. Watts, K. Yonehara, R.M. Zwaska
    Fermilab, Batavia, Illinois, USA
  • M.A. Cummings, A. Dudas, R.P. Johnson, G.M. Kazakevich, M.L. Neubauer
    Muons, Inc, Illinois, USA
 
  Funding: Work supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359 and DOE STTR Grant, No. DE-SC0013795.
Fermilab is the main institution to produce the most powerful and wide-spectrum neutrino beam. From that respective, a radiation robust beam diagnostic system is a critical element in order to maintain the quality of the neutrino beam. Within this context, a novel radiation-resistive beam profile monitor based on a gas-filled RF cavity has been proposed. The goal of this measurement is to study a tunable Q-factor RF cavity to determine the accuracy of the RF signal as a function of the quality factor. Specifically, the measurement error of the Q-factor in the RF calibration is investigated. Then, the RF system will be improved to minimize signal error.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAG002  
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WEPAG003 Hadron Beam Monitor Design with Gas-Filled RF Resonators in Intense Neutrino Source hadron, scattering, target, radiation 2067
 
  • M.D. Balcazar, K. Yonehara
    Fermilab, Batavia, Illinois, USA
 
  Funding: Work supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359 and DOE STTR Grant, No. DE-SC0013795.
For the future Long Baseline Neutrino Facility at Fermilab, a new radiation-robust hadron beam profile monitor has been proposed consisting of an interface of gas-filled radiofrequency cavity detectors in the backward region of the LBNF decay pipe. A tailored monitor layout will be used along with the new RF instrumentation. Proposed designs for the detector configuration include a variety of radially symmetric arrangements of RF resonators located at the position of maximum gradient in the beam distribution across the monitor. Until the final detector cavities are available, a prototype tunable Q-factor RF cavity will provide functional emulation for studies of the monitor layout configurations presented here.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAG003  
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WEPAK001 Intense Neutrino Source Front End Beam Diagnostics System R&D detector, plasma, target, hadron 2077
 
  • K. Yonehara, M.D. Balcazar, A. Moretti, A.V. Tollestrup, A.C. Watts, R.M. Zwaska
    Fermilab, Batavia, Illinois, USA
  • M.A. Cummings, A. Dudas, R.P. Johnson, G.M. Kazakevich, M.L. Neubauer
    Muons, Inc, Illinois, USA
 
  Funding: Work supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359 and DOE STTR Grant, No. DE-SC0013795.
We overview the front end beam diagnostic system R&D to prepare operation of a multi-MW proton beam for intensity frontier Neutrino experiments. One of critical issues is shorter life time of a detector with higher beam intensity due to radiation damage. We show a possible improvement of the existing ion chamber based detector, and a study of a conceptually new radiation-robust detector which is based on a gas-filled RF resonator.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAK001  
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WEPAK006 Bunch Shape Measurements at the GSI CW-Linac Prototype linac, heavy-ion, bunching, emittance 2091
 
  • T. Sieber, W.A. Barth, P. Forck, V. Gettmann, M. Heilmann, H. Reeg, A. Reiter, S. Yaramyshev
    GSI, Darmstadt, Germany
  • F.D. Dziuba, T. Kürzeder, M. Miski-Oglu
    HIM, Mainz, Germany
  • A. Feschenko, S.A. Gavrilov
    RAS/INR, Moscow, Russia
 
  The existing GSI accelerator will become the injector for FAIR. To preserve and enhance the current experimental program at UNILAC, a new Linac is under development, which shall run in parallel to the FAIR injector, providing cw-beams of ions at energies from 3.5 - 7.3 MeV/u. For this cw-Linac a superconducting prototype cavity has been developed and was first operated with beam in summer 2017. The resonator is a cross-bar H-structure (CH) of 0.7 m length, with a resonant frequency of 216.8 MHz. It has been installed behind the GSI High Charge State Injector (HLI), which provided 108 MHz bunches of 1.4 MeV/u Ar6+/9+/11+ ions at a duty cycle of 25 %. Due to the frequency jump and small longitudinal acceptance of the CH, proper matching of the HLI beam to the prototype was required. The bunch properties of the injected beam as well as the effect of different phase- and amplitude-settings of the cavity were measured in detail with a bunch shape monitor (BSM) fabricated at INR, Moscow, while the mean energy was analyzed by time of flight method. In this contribution, the bunch shape measurements are described and the capabilities of the used BSM measurement principle are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAK006  
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WEPAK012 Developing Kalman Filter Based Detuning Control with a Digital SRF CW Cavity Simulator controls, SRF, FPGA, LLRF 2114
 
  • A. Ushakov, P. Echevarria, A. Neumann
    HZB, Berlin, Germany
 
  Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of the Helmholtz Association
Continuous wave operated superconducting cavities experiencing small net beam loading and thus operate potentially at narrow bandwidth require precise detuning control to reach the high stability requirements for RF fields within facilities as FEL or ERL based photon sources. Especially microphonics compensation down to sub-hertz detuning regime besides improving stability reduces the risk of rise of Lorentz force detuning driven ponderomotive instabilities. Usually the complex and second order nature of the mechanical to RF detuning transfer functions of cavity and cavity-tuner system require for more advanced control schemes. In this paper we will show the application of a Kalman filter based detuning estimator algorithm first introduced during IPAC2017 [1] to the SRF cavity simulator developed at Helmholtz Zentrum Berlin [2]. Results using the algorithm in observer mode to detuning compensation attempts in closed loop mode are presented.
* A. Ushakov, P. Echevarria, A. Neumann, Proc. of IPAC 2017, Copenhagen, Denmark
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAK012  
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WEPAK013 SRF Cavity Simulator for LLRF Algorithms Debugging controls, SRF, LLRF, FPGA 2118
 
  • P. Echevarria, J. Knobloch, A. Neumann, A. Ushakov
    HZB, Berlin, Germany
  • E. Aldekoa, J. Jugo
    University of the Basque Country, Faculty of Science and Technology, Bilbao, Spain
 
  Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association
The availability of niobium superconducting cavities, ei-ther due to a lack of a real cavity or due to the time needed for the experiment set up (vacuum, cryogenics, cabling, etc.), is limited, and thus it can block or delay the develop-ment of new algorithms such as low level RF control. Hardware-in-the-loop simulations, where an actual cavity is replaced by an electronics system, can help to solve this issue. In this paper we present a Cavity Simulator imple-mented in a National Instruments PXI equipped with an FPGA module. This module operates with one intermedi-ate frequency input which is IQ-demodulated and fed to the electrical cavity's model, where the transmitted and re-flected voltages are calculated and IQ-modulated to gener-ate two intermediate frequency outputs. Some more ad-vanced features such as mechanical vibration modes driven by Lorentz-force detuning or external microphonics have also been implemented. This Cavity Simulator is planned to be connected to an mTCA chassis to close the loop with a LLRF control system.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAK013  
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WEPAL001 LLRF Control and Master Oscillator System for Damping Ring at SuperKEKB controls, LLRF, injection, linac 2137
 
  • T. Kobayashi, K. Akai, A. Kabe, K. Nakanishi, M. Nishiwaki, J.-I. Odagiri
    KEK, Ibaraki, Japan
  • H. Deguchi, K. Hayashi, J. Mizuno
    Mitsubishi Electric TOKKI Systems, Amagasaki, Hyogo, Japan
  • K. Hirosawa
    Sokendai, Ibaraki, Japan
 
  For SuperKEKB, new low level RF (LLRF) control systems has ben developed and they worked successfully in the first beam commissioning (Phase-1) of SuperKEKB, which was accomplished in 2016. Damping ring (DR) was newly constructed for positron beam injection, in order to make significantly emittance smaller for SuperKEKB. The beam commissioning of DR will be conducted in JFY2017 for the Phase-2 commissioning. Phase-2 is scheduled in the last quater of JFY2017. DR has an RF station, and two cavities (or three cavities in future) are driven by a klystron. New LLRF control system for DR (DR-LLRF) was also developed and installed. RF frequency of DR operation is common with the main storage rings (MR) of SuperKEKB. The good performance of DR-LLRF was demonstrated in test operation, and RF conditioning of the pair of two cavities was successfully completed in June 2017. This paper reports the detail of the performance results of DR-LLRF controls, and also the other some relevant issues in LLRF controls for DR, including the master oscillator system (synchronization with the injection linac), are introduced.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL001  
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WEPAL003 Baseband Simulation Model of the Vector RF Voltage Control System for the J-PARC RCS controls, feedback, simulation, software 2144
 
  • F. Tamura, M. Nomura, T. Shimada, M. Yamamoto
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  • M. Furusawa, K. Hara, K. Hasegawa, C. Ohmori, Y. Sugiyama, M. Yoshii
    KEK, Tokai, Ibaraki, Japan
 
  Vector rf voltage feedback control for the wideband magnetic alloy cavity of the J-PARC RCS is considered to be employed to compensate the heavy beam loading caused by high intensity proton beams. A prototype system of multiharmonic rf vector voltage control has been developed and is under testing. To characterize the system performance, full rf simulations could be performed by software like Simulink, while the software is proprietary and expensive. Also, it requires much computing power and time. We performed the simplified baseband simulations of the system in z-domain by using free software, Scilab and Python control library. It seems to be beneficial for searching the parameters that the baseband simulation can be performed quickly. In this presentation, we present the setup and results of the simulations. The simulations well reproduce the open and closed loop responses of the prototype system.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL003  
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WEPAL008 Low-level RF System for The Chinese ADS Front-end Demo Linac controls, LLRF, linac, interface 2159
 
  • J.Y. Ma, Z. Gao, G. Huang, L.P. Sun
    IMP/CAS, Lanzhou, People's Republic of China
 
  The Chinese ADS Front-end Demo Linac (FDL) is constructed to demonstrate the technology of superconducting linac with high proton beam loading of CW 10mA. The low-level RF (LLRF) control system for the ADS FDL is developed by IMP, and the cooperation with TRIUMF. In the normal conducting (NC) section, the normal RF feedback control loop is used. In order to stable the superconducting (SC) cavity with loaded high RF power, the self excited loop with phase locked mode was used on the SC linac. This paper introduces the LLRF control system for buncher, SC linac, and the structures of hardware and the functions of software of these LLRF systems. The operating status of the LLRF systems is also reported.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL008  
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WEPAL012 Measurements with the ELI-NP Cavity Beam Position Monitor Read-out Electronics at FLASH electron, instrumentation, electronics, FEL 2169
 
  • G. Franzini, D. Pellegrini, M. Serio, A. Stella, A. Variola
    INFN/LNF, Frascati (Roma), Italy
  • B.B. Baricevic, M. Cargnelutti
    I-Tech, Solkan, Slovenia
  • D. Lipka
    DESY, Hamburg, Germany
  • M. Marongiu
    INFN-Roma, Roma, Italy
  • A. Mostacci
    Sapienza University of Rome, Rome, Italy
 
  The Extreme Light Infrastructure - Nuclear Physics Gamma Beam Source (ELI-NP GBS) will be installed and commissioned starting within the next year in Magurele, Romania. It will generate gamma beam through Compton back-scattering of a recirculated laser and a multi-bunch electron beam, produced by a 720 MeV LINAC. In order to obtain bunch by bunch position measurements, four cavity beam position monitors (cBPM) near the two interaction points are foreseen. Extensive tests on the cBPM read-out electronics, recently developed by Instrumentation Technologies and acquired for ELI-NP GBS, were performed in laboratory at INFN-LNF and at FLASH in DESY, during the user operation. In the latter case, three cBPMs installed along the LINAC, with similar features as the ones of ELI-NP GBS, were used as measuring devices and signal sources for the read-out electronics under test. We present here the measurements collected and the related analysis, with a particular focus on the beam position measurement resolution.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL012  
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WEPAL014 Non-Distructive 2-D Beam Profile Monitor Using Gas Sheet in J-PARC LINAC linac, injection, electron, vacuum 2177
 
  • J. Kamiya, Y. Hikichi, M. Kinsho, A. Miura, N. Ogiwara
    JAEA/J-PARC, Tokai-mura, Japan
 
  We have been developed a beam profile monitor using interaction between the beam and the gas molecules distributed in sheet shape*. Generated luminescence or ions by passing the beam through the gas sheet has the information of cross-section shape of the beam. The gas sheet beam monitor will become a useful tool to measure the profile of high power beams because it has no breakable element such as wires and a 2-D beam profile at a certain position of beam line can be immediately obtained by just injecting the gas. Previously, the development of the gas sheet generator and successful demonstration of the beam profile measurement were reported. This time, we applied a gas sheet monitor to J-PARC LINAC, where the negative hydrogen atoms (H) are accelerated to the energy of 400 MeV in the normal operation. Most challenging factor was the development of the gas sheet monitor system, which generates the enough dense gas sheet to detect the clear image of the beam profile without harmful effect on the ultra-high vacuum in the beam line. We will report the gas sheet beam monitor system for J-PARC LINAC and the results of the first measurement of the beam profile.
* N. Ogiwara, et al., Proceedings of IPAC2016, p.2102.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL014  
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WEPAL016 Tensile Fracture Test of Metallic Wire of Beam Profile Monitors linac, electron, beam-loading, controls 2183
 
  • A. Miura, Y. Kawane, K. Moriya
    JAEA/J-PARC, Tokai-mura, Japan
  • S. Fukuoka
    Nihon Koshuha Co. Ltd, Yokohama, Japan
  • K. Futatsukawa, T. Miyao
    KEK, Ibaraki, Japan
 
  In order to mitigate the beam loss during a beam transportation in a high-brilliant accelerator facilities, wire-based profile monitors are used to measure by both transverse and longitudinal beam profiles using wire-scanner monitors (WSMs) and bunch-shape monitors (BSMs) for the tuning of quadrupole magnets and bunching cavities. Signals are come from the direct interaction between a metallic wire and beam. We have used the tungsten wire as a high melting-point material by estimation of heat loading during the impact of beam particles. In addition, a spring is applied for the relaxing a sag under wire's own weight. A tensile fracture test is conducted by supplying an electrical current as a simulated beam-heat loading. As the results, we obtained the relation between the thermal limit to break down and tension loading of tungsten wire.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL016  
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WEPAL017 Adaptive Feedforward Control Design Based on Simulink for the J-PARC LINAC LLRF System controls, LLRF, linac, simulation 2187
 
  • S. Li
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
  • Z. Fang, Y. Fukui, K. Futatsukawa, F. Qiu
    KEK, Ibaraki, Japan
  • S. Mizobata, Y. Sato, S. Shinozaki
    JAEA/J-PARC, Tokai-mura, Japan
 
  In j-parc linac, for dealing with high beam loading effect, an adaptive feedforward control method which based on iterative learning control was put forward. At the same time, in order to verify its effectiveness before it is officially put into use, an llrf system simulation model was built in simulink, matlab. In this paper, the architecture of llrf system simulation model will be introduced. The result of iterative learning control (ILC) is summarized.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL017  
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WEPAL021 Study of a Tuner for a High-Accuracy Bunch Shape Monitor linac, insertion, resonance, 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, electron, controls, resonance 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.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL024  
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WEPAL025 Development of a Low-Latency, High-Precision, Beam-Based Feedback System Based on Cavity BPMs at the KEK ATF2 feedback, dipole, kicker, extraction 2212
 
  • R.L. Ramjiawan, D.R. Bett, N. Blaskovic Kraljevic, R.M. Bodenstein, T. Bromwich, P. Burrows, G.B. Christian, C. Perry
    JAI, Oxford, United Kingdom
 
  A low-latency, intra-train feedback system employing cavity beam position monitors (BPMs) has been developed and tested at the Accelerator Test Facility (ATF2) at KEK. The feedback system can be operated with either position information from a single BPM to provide local beam stabilisation, or by using position information from two BPMs to stabilise the beam at an intermediate location. The correction is implemented using a stripline kicker and a custom power amplifier, with the feedback calculations being performed on a digital board built around a Field Programmable Gate Array (FPGA). The addition of indium sealing to the BPMs to increase the cavities' Q-values has led to improvements to the BPM system resolution, with current measurements of the resolution of order 20 nm. The feedback performance was tested with beam trains of two bunches, separated by 280 ns and with a charge of ~1 nC. For single- (two-)BPM feedback, stabilisation of the beam has been demonstrated to below 50 nm (41 nm). Ongoing work to improve the feedback performance further will be discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL025  
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WEPAL029 FLUTE Diagnostics Integration controls, diagnostics, interface, linac 2227
 
  • M. Yan, A. Bernhard, E. Bründermann, S. Funkner, A. Malygin, S. Marsching, W. Mexner, A. Mochihashi, A.-S. Müller, M.J. Nasse, G. Niehues, R. Ruprecht, T. Schmelzer, M. Schuh, N.J. Smale, P. Wesolowski, S. Wüstling
    KIT, Karlsruhe, Germany
  • I. Križnar
    Cosylab, Ljubljana, Slovenia
 
  FLUTE (Ferninfrarot Linac- Und Test-Experiment) will be a new compact versatile linear accelerator at KIT. Its primary goal is to serve as a platform for a variety of accelerator studies as well as to generate strong ultra-short THz pulses for photon science. The machine consists of an RF gun, a traveling wave linac and a D-shaped bunch compressor chicane with corresponding diagnostics sections. In this contribution, we report on the latest developments of the diagnostics components. An overview of the readout and control system integration will be given.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL029  
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WEPAL031 RF Interlock Implementation Using Digital LLRF System for 100 MeV Proton Linac at KOMAC pick-up, LLRF, controls, proton 2233
 
  • H.S. Jeong, Y.-S. Cho, H.S. Kim, J.H. Kim, S.G. Kim, H.-J. Kwon, Y.G. Song
    Korea Atomic Energy Research Institute (KAERI), Gyeongbuk, Republic of Korea
 
  Funding: This work has been supported through KOMAC (Korea Multi-purpose Accelerator Complex) operation fund of KAERI by MSIT (Ministry of Science and ICT)
KOMAC (Korea Multi-purpose Accelerator Complex) already has operated 100 MeV proton linear accelerator with high availability since 2013. This accelerator is composed of Ion source, LEBT, RFQ and DTL systems to transport proton particles to the target. Total 9 klystrons with 1.6 MWpeak are used to provide controlled RF power to the accelerator cavities with 350 MHz of operating frequency. These klystrons are driven by LLRF systems that the LLRF systems should control the RF and protect the amplifiers and cavities from the abnormal RF. In this article, the RF interlock using cavity pickup signal introduced. When the cavity pickup amplitude breaks away from the adjustable upper or lower limit window, the digital LLRF system interrupts the LLRF output. These implementations were conducted by upgrading the FPGA (Field Programmable Gate Array) logics of the existing digital LLRF system.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL031  
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WEPAL039 LCLS-II Gun/Buncher LLRF System Design gun, LLRF, SRF, controls 2258
 
  • G. Huang, K.S. Campbell, L.R. Doolittle, J.A. Jones, Q. Qiang, C. Serrano
    LBNL, Berkeley, California, USA
  • S. Babel, A.L. Benwell, M. Boyes, G.W. Brown, D. Cha, J.H. De Long, J.A. Diaz Cruz, B. Hong, A. McCollough, A. Ratti, C.H. Rivetta, D. Rogind, F. Zhou
    SLAC, Menlo Park, California, USA
  • R. Bachimanchi, C. Hovater, D.J. Seidman
    JLab, Newport News, Virginia, USA
  • B.E. Chase, E. Cullerton, J. Einstein-Curtis, D.W. Klepec
    Fermilab, Batavia, Illinois, USA
  • J.A. Diaz Cruz
    CSU, Fort Collins, Colorado, USA
 
  Funding: This work was supported by the LCLS-II Project and the U.S. Department of Energy, Contract n. DE-AC02-05CH11231.
For a free electron laser, the stability of injector is critical to the final electron beam parameters, e.g., beam energy, beam arrival time, and eventually it determines the photon quality. The LCLS-II project's injector contains a VHF copper cavity as the gun and a two-cell L-band copper cavity as its buncher. The cavity designs are inherited from the APEX design, but requires more field stability than demonstrated in APEX operation. The gun LLRF system design uses a connectorized RF front end and low noise digitizer, together with the same general purpose FPGA carrier board used in the LCLS-II SRF LLRF system. The buncher LLRF system directly adopts the SRF LLRF chassis design, but programs the controller to run the normal conducting cavities. In this paper, we describe the gun/buncher LLRF system design, including the hardware design, the firmware design and bench test.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL039  
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WEPAL041 FPGA Based Optical Phase Control for Coherent Laser Pulse Stacking controls, experiment, FPGA, laser 2265
 
  • Y. Yang, L.R. Doolittle, Q. Du, G. Huang, W. Leemans, R.B. Wilcox, T. Zhou
    LBNL, Berkeley, California, USA
  • A. Galvanauskas
    University of Michigan, Ann Arbor, Michigan, USA
 
  Coherent temporal pulse stacking combines the energy from a train of pulses into one pulse through a series of optical cavities. To stabilize the output energy, the cavity roundtrip phases must be precisely locked to particular values. Leveraging the LLRF expertise we have for conventional accelerators, a FPGA-based control system has been developed for optical cavity phase control. A phase measurement method, ''Modulated Impulse Response'', has been developed and implemented on FPGA. An experiment demonstrated that it can measure and lock the optical phases of four stacking cavities, leading to combination of 25 pulses into one pulse with 1.5 % RMS stability over 30 hours.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL041  
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WEPAL046 A New Digital Feedback and Feedforward Controller for Cavity Field Control of the LANSCE Accelerator controls, feedback, LLRF, FPGA 2277
 
  • S. Kwon, L.J. Castellano, D.J. Knapp, J.T.M. Lyles, M.S. Prokop, A. Scheinker, P.A. Torrez
    LANL, Los Alamos, New Mexico, USA
 
  Funding: Work Supported by DOE
A new digital low-level RF system was designed and has been deployed on the drift-tube-linac section of the Los Alamos Neutron Science Center(LANSCE) proton accelerator. This new system is part of a modernization of the existing analog cavity-field controls that were originally developed and put into service forty-five years ago. For stabilization of the cavity field amplitude and phase during beam loading, a proportional-integral feedback controller, a static beam feedforward controller, and an iterative learning controller working in parallel have been implemented. In this paper, the controller architecture is described, and the performances of the three controllers when beam is being actively accelerated is presented.
 
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WEPAL053 Dynamic Signal Analysis Based on FPGA for NSRRC DLLRF FPGA, LLRF, controls, feedback 2295
 
  • F.Y. Chang, L.-H. Chang, M.H. Chang, S.W. Chang, L.J. Chen, F.-T. Chung, Y.T. Li, M.-C. Lin, Z.K. Liu, C.H. Lo, Ch. Wang, M.-S. Yeh, T.-C. Yu
    NSRRC, Hsinchu, Taiwan
 
  As DLLRF control system designs for SRF cavities have greatly matured and the FPGA technology has im-proved as well, it is possible now to think about incorporating dynamic signal analysis (DSA). Implementation of a DSA in the FPGA is desired to study the frequency response of the open/closed loop gain in a SRF system. Open loop gain is useful to observe the stability of a SRF system while closed loop gain can be applied to investi-gate the operational bandwidth of the system feedback and also to configure the performance of a PID controller. The DSA function was confirmed by analyzing the frequency response of a digital filter and the results of the analysis will be compared with MATLAB simulations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL053  
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WEPAL054 Digital Low Level Radio Frequency System for the Booster Ring of the Taiwan Photon Source LLRF, controls, operation, booster 2298
 
  • Z.K. Liu, F.Y. Chang, L.-H. Chang, M.H. Chang, S.W. Chang, L.J. Chen, F.-T. Chung, Y.T. Li, M.-C. Lin, C.H. Lo, Ch. Wang, M.-S. Yeh, T.-C. Yu
    NSRRC, Hsinchu, Taiwan
 
  The purpose of a Low-Level Radio Frequency (LLRF) system is to control the accelerating cavity field amplitude and phase. For the Taiwan Photon Source (TPS) at NSRRC, the currently operating LLRF systems are based on analog technology. To have better RF field stability, precise con-trol and high noise reduction, a digital LLRF control sys-tems based on Field Programmable Gate Arrays (FPGA) was developed. We replaced the analog LLRF system with the digital version for the TPS booster ring at the beginning of 2018, and we will replace those in the storage rings in the future. Test results and operational performance of the TPS booster DLLRF system are reported here.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL054  
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WEPAL057 Methods to Detect Error Sources and Their Application at the TPS photon, kicker, storage-ring, injection 2305
 
  • C.H. Huang, Y.-S. Cheng, P.C. Chiu, K.T. Hsu, K.H. Hu, C.Y. Wu
    NSRRC, Hsinchu, Taiwan
 
  For a low-emittance photon light source, beam stability is a very important property to attain a high-quality photon beam. While it is hard to avoid beam perturbations in a storage ring, it is more important to quickly find the source locations and to remove or eliminate the sources as soon as possible. In this report, we develop a method to identify the locations of multiple sources. For a source with a particular frequency, the relative phase between sources can also be obtained. This method has been a useful tool during TPS operation and its methodology and practical applications are described in this report.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL057  
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WEPAL069 Reentrant Cavity Resonator for Low Intensities Proton Beam Measurements simulation, pick-up, resonance, scattering 2341
 
  • S. Srinivasan, P.-A. Duperrex
    PSI, Villigen PSI, Switzerland
 
  A non-interceptive beam current monitor has been developed to investigate the measurement possibilities of low-intensity beams down to 1 nA for proton therapy machines without the drawback of interceptive monitors. This works on the principle of a reentrant cavity resonator such that its fundamental mode resonance frequency of 145.7 MHz matches the second harmonic of the pulse repetition rate of the cyclotron beam i.e. 72.85 MHz. The Driven Modal analysis from the simulation tool ANSYS HFSS was used for parametric model development and to optimize design parameters such as e.g. the position of the inductively coupled pick-ups. A ceramic plate has been inserted in the resonator gap to relax the precision required during manufacturing. A test bench has been designed and constructed for the characterization tests of the prototype. Comparison of the simulated and the experimental scattering parameter from the test bench shows a good agreement.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL069  
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WEPMF002 Operational Experience with IOTs at Alba Synchrotron cathode, electron, operation, controls 2372
 
  • J.R. Ocampo, B. Bravo, R. Fos, F. Pérez, A. Salom, P. Solans
    ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
  • S. Bethuys, A. Beunas, M. Grezaud, P. Reynaud
    TED, Velizy-Villacoublay, France
  • M. Boyle, J. Cipolla, W.F. Coyle, H. Schult
    L-3, Williamsport, Pennsylvania, USA
 
  ALBA is a 3 GeV Synchrotron light source in operation since 2012. The RF systems are based in Inductive Output Tube (IOT) transmitters. A total of 13 80 kW IOT amplifiers are used to power the Storage Ring and Booster cavities at 500 MHz. The transmitters were initially configured to operate the TH-793-1 and TH-794 IOT from THALES Electron devices. On 2015, the amplifiers have been adapted to operate also the TH-795 from THALES and the L4444-C from L3 Communications. In this paper, a brief overview of the differences between these IOT models will be presented, as well as operation results for each type of IOT from the point of view of performance, reliability and durability.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF002  
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WEPMF004 The Saclay Test Stand for Conditioning the ESS RFQ Power Couplers at High RF Power rfq, vacuum, linac, interface 2375
 
  • N. Misiara, A.C. Chauveau, D. Chirpaz-Cerbat, P. Daniel-Thomas, M. Lacroix, L. Maurice
    CEA/IRFU, Gif-sur-Yvette, France
  • M. Desmons, A. Dubois, A. Gaget, L. Napoly, M. Oublaid, G. Perreu, O. Piquet, B. Pottin, Y. Sauce
    CEA/DRF/IRFU, Gif-sur-Yvette, France
 
  The RF power coupler system for the RFQ of the ESS LINAC will feed 1.6 MW peak power through two coaxial loop couplers for a 352.21 MHz operation at the expected duty cycle. A specific test stand has been designed to condition the power couplers, and test the different auxiliary components in the nominal conditions of the RFQ. The power couplers were successfully assembled, installed and instrumented on the test cavity. This paper presents the general layout of the test stand, the installation and preparation of the power couplers for their conditioning at high RF power up to the ESS nominal conditions.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF004  
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WEPMF005 Design and Testing of a 12 kW, 352 MHz Solid State rf System at the Advanced Photon Source controls, operation, GUI, simulation 2378
 
  • D. Horan, D.J. Bromberek, A. Goel, T.J. Madden, A. Nassiri, G.J. Waldschmidt
    ANL, Argonne, Illinois, USA
 
  A 12 kW, 352 MHz rf power amplifier system was designed and constructed at the Advanced Photon Source as a research and development test bed for eventual development of a 200 kW cw rf system capable of supporting accelerator beam operation. The system utilizes six 2 kW laterally diffused metal oxide field effect transistor (MOSFET) rf amplifiers, an output cavity combiner terminated with a WR2300 waveguide output flange, and a monitoring system based on programmable logic controller technology. The combining cavity has a total capacity of 108 two-kilowatt inputs to support eventual operation up to 216kW maximum output power. Design details and operational performance of the 12 kW system will be discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF005  
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WEPMF009 Influence of Argon-Ion Irradiation on Field Emission from Polycrystalline Cu and Large-Grain NB Surfaces radiation, niobium, experiment, vacuum 2384
 
  • S. Soykarci
    University of Wuppertal, Wuppertal, Germany
  • D. Lützenkirchen-Hecht, V. Porshyn, P. Serbun
    Bergische Universität Wuppertal, Wuppertal, Germany
 
  Funding: This work is funded by the BMBF project 05H15PXRB1.
In the present work, systematic investigations of the enhanced field emission (EFE) from polycrystalline copper and large grain niobium surfaces before and after argon-ion irradiation with an energy of 5 keV were performed with a variation of the irradiation time. Results show that the suppression of the EFE might be achievable.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF009  
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WEPMF010 Laser Treatment of Niobium Surface for SRF Aplications laser, niobium, experiment, electron 2387
 
  • V. Porshyn, D. Lützenkirchen-Hecht, P. Serbun
    Bergische Universität Wuppertal, Wuppertal, Germany
  • H. Bürger, S. Soykarci
    University of Wuppertal, Wuppertal, Germany
 
  Funding: The research was funded by the German Federal Ministry of Education and Research (BMBF) under project number 05H15PXRB1.
We report on a laser surface treatment of high purity niobium (110) single crystals. Typical surface defects like scratches, pits, sharp rims and holes were eliminated by a focused pulsed ns-laser beam. A laser fluence of about 0.68 J/cm2 and 40 - 80 pulses per spot were required to induce well detectable surface modifications. The remelted surface was sufficiently smooth, but exhibited also a number of wave structures. Thus, the surface roughness slightly increased with increasing number of pulses. Finally, boiling traces and μm-deep ablation were observed and studied as well. Local field electron emission measurements showed no emission up to 700 MV/m from a moderate remelted area below the boiling point.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF010  
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WEPMF011 Design and Status of Sirius Light Source RF Systems storage-ring, booster, LLRF, lattice 2391
 
  • R.H.A. Farias, A.P.B. Lima, L. Liu, F.S. Oliveira
    LNLS, Campinas, Brazil
 
  Sirius is the new synchrotron light source currently under construction at the site of the Brazilian Synchro-tron Light Laboratory (LNLS) in Campinas, Brazil. The facility comprises a 3 GeV electron storage ring, a full energy booster and a 150 MeV linac. This work provides a brief description of the RF system of the booster and storage ring, presenting their main characteristics and specification goals.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF011  
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WEPMF012 Power Requirement and Preliminary Coupler Design for the eRHIC Crab Cavity System operation, proton, electron, SRF 2394
 
  • S. Verdú-Andrés, I. Ben-Zvi, D. Holmes, Q. Wu
    BNL, Upton, Long Island, New York, USA
  • I. Ben-Zvi
    Stony Brook University, Stony Brook, USA
 
  Funding: Work supported by Brookhaven Science Associates LLC under contract no. DE-SC0012704 with the U.S. Department of Energy.
Crab cavities are deflecting cavities operated in such a way that the bunch center is in synchronism with the zero-crossing kick voltage. In that case, beam loading is zero for an on-axis beam. The crab cavity system of the future electron-ion collider eRHIC will manipulate 275 GeV proton beams. At high energies, the beam offset can be as large as 2 mm (including mechanical and electrical offset tolerances). The beam loading resulting from such offset can greatly incur in large power requirements to the RF amplifier. The choice of external Q for the Fundamental Power Coupler (FPC) is critical to limit the power requirement to practical values. The loaded Q of the eRHIC crab cavities is mainly governed by the external Q of the FPC, so the external Q will also define the cavity bandwidth and thus the tuning requirements to counteract frequency transients from external perturbations. This paper discusses the choice of external Q for the FPC of the eRHIC crab cavities and introduces the design of a preliminary FPC antenna concept that would provide the appropriate external Q.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF012  
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WEPMF022 Coulped Multiphysics Simulation for the Water Cooling Layout of a Rhodotron Cavity simulation, operation, vacuum, electron 2416
 
  • L. Yang, X. He, H. Li, S.Q. Liao
    CAEP/IFP, Mainyang, Sichuan, People's Republic of China
 
  A Rhodotron-based electron accelerator served as micro-focused X-ray source is under development at IFP, CAEP. The RF-cavity, running in long pulse/ CW mode, will deliver 9 MeV energy to electron beams after multiple accelerations within the same field at a frequency of 107.5MHz. A substantial amount of average power loss with tens of kW will be dissipated on the RF surface of the cavity to maintain the operational field level. Efficient water cooling is critical to prevent large scale temperature rise for stable operation sake. Reasonable prediction of temperature rise becomes essential to assess a certain cooling layout in the design phase. The frequency drift and thermal stress on account of temperature variation and gradient on cavity wall respectively, could be computed accordingly. This paper presents a comprehensive coupled simulation involving electromagnetic, thermal and structural for the RF-cavity of Rhodotron.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF022  
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WEPMF030 Optimization of Klystron Efficiency with MOGA klystron, electron, simulation, bunching 2419
 
  • C. Meng, X. He, S. Pei, S.C. Wang, O. Xiao, Z.S. Zhou
    IHEP, Beijing, People's Republic of China
 
  As the very important element of accelerator the klystron provide power to cavities for accelerating. Considering the accelerator cost of construction and running, the improvement of klystron efficiency is one developing hotspot of klystron research. In this paper the optimization method of klystron efficiency with MOGA based on 1D simulation program is proposed and the influences on klystron efficiency will be discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF030  
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WEPMF033 RF Study And Cold Test of an S-band Spherical Cavity Pulse Compressor coupling, simulation, vacuum, klystron 2429
 
  • J. Lei, X. He, M. Hou, X.P. Li, G. Pei, H. Wang, J.B. Zhao
    IHEP, Beijing, People's Republic of China
  • S. Shu
    Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
 
  An S-band (2856 MHz) spherical cavity pulse compressor has been designed, fabricated and tested in the Institute of High Energy Physics (IHEP), Chinese Academy of Sciences (CAS). The pulse compressor consists of a special 3 dB coupler and only one spherical energy storage cavity, two TE114 modes are chosen to oscillate in which for fairly high unload Q factor. The prototype was made of aluminum for studying the performance of the pulse compressor and checking the validity of the simulations. The cold test results of the aluminum cavity are also presented. The copper coating on the whole internal surface of the aluminum spherical cavity is in progress and the test results will also be presented in the future.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF033  
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WEPMF034 Development of Superconducting RF Double Spoke Cavity at IHEP coupling, target, electron, proton 2432
 
  • Z.Q. Zhou, H.F.S. Feisi, W.M. Pan
    IHEP, Beijing, People's Republic of China
 
  Funding: State Key Development Program for Basic Research of China (Grant No.2014CB845500)
The China Initiative Accelerator Driven System (CiADS) has been approved to transmute long-lived radi-oisotopes in used nuclear fuel into shorter-lived fission products. IHEP is developing a 325MHz double spoke cavity at β0 of 0.5 for the CiADS linac. The cavity shape was optimized to minimize Ep/Ea while keeping Bp/Ep reasonably low, while the multipacting was analyzed. Meanwhile, mechanical design was applied to check stress, Lorentz force detuning and microphonic effects, and to minimize pressure sensitivity. A new RF coupling scheme was proposed to avoid electrons hitting directly on ceramic window. The detailed design for the cavity is addressed in this paper.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF034  
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WEPMF035 Investigating the Effect of Inhomogeneous Resistivity on Bulk RRR and Heat Conductivity Using a Lattice Green's Functions Method network, niobium, lattice, HOM 2436
 
  • N.C. Shipman, A. Macpherson
    CERN, Geneva, Switzerland
  • G. Burt
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • J.A. Mitchell
    Lancaster University, Lancaster, United Kingdom
 
  A method was developed to calculate the bulk RRR (residual resistivity ratio) which would be measured on a superconducting cavity or sample with an inhomogeneous resistivity and arbitrary geometry. The method involves modelling the object as a network of resistors and employs lattice Green's functions. A further adaptation of the method which allows the heat transport characteristics of such an object to be predicted is also described.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF035  
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WEPMF036 RF Test Result of a BNL N-Doped 500 MHz B-Cell Cavity at Cornell SRF, vacuum, superconducting-cavity, niobium 2440
 
  • F. Furuta, M. Ge, T. Gruber, J.J. Kaufman, M. Liepe, J.T. Maniscalco, J. Sears
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • F. Gao, J. Rose
    BNL, Upton, Long Island, New York, USA
 
  Cornell's SRF group has collaborated with Brookhaven National Laboratory (BNL) on one 500 MHz CESR type SRF "B-cell" cavity (BNL B-cell) for the National Synchrotron Light Source II. Cornell has been responsible for RF surface preparation, vertical testing, and short cavity string assembly. As a state-of-the-art surface preparation protocol, Cornell selected Nitrogen doping for the BNL B-cell. N-doping has been well demonstrated and established to push the cavity quality factor (Q0) higher in 1.3GHz SRF cavities at many laboratories. Cornell calculated that N-doping could also be beneficial on a 500MHz SRF cavity, with a potential to increase its Q0 by a factor of two compared with the traditional chemical polishing based surface preparation protocol. Here we report on the detailed surface preparation and vertical test result of the BNL B-cell.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF036  
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WEPMF037 HF Free Bipolar Electro-Polishing Studies on Niobium SRF Cavities at Cornell With Faraday Technology SRF, niobium, MMI, radio-frequency 2443
 
  • F. Furuta, M. Ge, T. Gruber, J.J. Kaufman, P.N. Koufalis, M. Liepe, J. Sears
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • T.D. Hall, M.E. Inman, R. Radhakrishnan, S.T. Snyder, E.J. Taylor
    Faraday Technology, Inc., Clayton, Ohio, USA
 
  Cornell's SRF group and Faraday Technology have been collaborating on two phase-II SBIR projects. One of them is the development and commissioning of a 9-cell scale HF free Bipolar Electro-Polishing (BEP) system. Faraday Technology has upgraded their 1.3 GHz single-cell BEP system for hosting 9-cell cavities. Initial commissioning of the new system was done with a three single-cell cavity string, and high a gradient of 40MV/m was demonstrated during the RF tests at Cornell. After this success with the test string, the 9-cell cavity was processed with the new system at Faraday and RF test was performed at Cornell. Here we report detailed results from these 9-cell scale HF free BEP studies.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF037  
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WEPMF038 Microphonics Suppression in the CBETA Linac Cryomodules linac, cryomodule, SRF, controls 2447
 
  • N. Banerjee, J. Dobbins, F. Furuta, G.H. Hoffstaetter, R.P.K. Kaplan, M. Liepe, P. Quigley, E.N. Smith, V. Veshcherevich
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Funding: This work was performed through the support of New York State Energy Research and Development Agency. The linac cryomodules were constructed with funding from the National Science Foundation.
The Cornell-BNL ERL Test Accelerator (CBETA) is a new multi-turn energy recovery linac currently under construction at Cornell University. It uses two superconducting linacs, both of which are susceptible to microphonics detuning. The high-current injector accelerates electrons to 6 MeV and the main linac accelerates and decelerates electrons by 36 MeV. In this paper, we discuss various measures taken to reduce vibrations caused by instabilities and flow transients in the cryogenic system of the main linac cryomodule. We further describe the use of a Least Mean Square algorithm in establishing a stable Active Microphonics Compensation system for operation of the main linac cavities.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF038  
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WEPMF039 Experimental Results on the Field and Frequency Dependence of the Surface Resistance of Niobium Cavities niobium, vacuum, experiment, electron 2451
 
  • P.N. Koufalis, M. Liepe, J.T. Maniscalco, T.E. Oseroff
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  We investigate the field and frequency dependence of the surface resistance of single-cell niobium cavities as a function of surface treatment at 1.3, 2.6, and 3.9 GHz. The surface resistance is broken down into two parts: the temperature-independent residual resistance and the temperature-dependent BCS resistance. While the low-field BCS resistance is known to vary quadratically with frequency, the exact dependence of the BCS and residual resistances on field at higher frequencies are important topics for further investigation. We offer results on a systematic experimental study of the residual and BCS resistance as a function of frequency and field for clean niobium and high-temperature nitrogen-doped niobium.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF039  
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WEPMF041 Insights into the Role of C, N, and O Introduced by Low Temperature Baking on Niobium Cavity Performance niobium, experiment, ECR, superconductivity 2455
 
  • P.N. Koufalis, M. Liepe
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Previous experiments have shown that introducing nitrogen gas during low temperature bakes (120-160 C) of niobium cavities introduces C, N, and O impurities to the first 10-100 nm of the surface. This new treatment results in higher quality factors and even 'anti-Q-slope' in some cases. However, it is not entirely clear the role that each of these impurities plays in the performance enhancement of the cavities. It has been suggested that interstitial N within the first few nm of the surface is solely responsible for the observed enhancement, but little work has been done on the role of C and O. Because both C and O are abundant in much higher quantities than N near the surface, it is important to understand whether they are beneficial or detrimental to cavity performance. We provide further insight into the effects of C and O on cavity performance by baking in an ambient atmosphere rich in CO2 as opposed to N2.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF041  
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WEPMF042 A Computational Method for More Accurate Measurements of the Surface Resistance in SRF Cavities SRF, operation, niobium, radio-frequency 2458
 
  • J.T. Maniscalco, M. Liepe
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  The principal loss mechanism for superconducting RF cavities in normal operation is Ohmic heating due to the microwave surface resistance in the superconducting surface. The typical method for calculating this field-dependent surface resistance Rs(H) from RF measurements of quality factor Q0 implicitly returns a weighted average of Rs over the surface as a function of peak surface magnetic field H, not the true value of Rs as a function of the local magnitude of H. In this work we present a computational method to convert a measured Q0 vs. Hpeak to a more accurate Rs vs. Hlocal, given knowledge about cavity geometry and field distribution.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF042  
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WEPMF043 Frequency Tuner Development at Cornell for the RAON Half Wave Resonators cryogenics, cryomodule, controls, operation 2461
 
  • M. Ge, F. Furuta, T. Gruber, S.W. Hartman, M. Liepe, J.T. Maniscalco, T.I. O'Connell, P.J. Pamel, J. Sears, V. Veshcherevich
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • B.H. Choi, J. Joo, J.W. Kim, W.K. Kim, J. Lee, I. Shin
    IBS, Daejeon, Republic of Korea
 
  The superconducting half-wave-resonators for the RAON project require a slow frequency tuner that can provide at least 80 kHz tuning range. Cornell University has designed, prototyped, and tested a tuner for these half-wave-resonators. In this paper, we present the tuner design, prototype fabrication, test insert preparation, long-term testing and tuner performance test results at cryogenic temperature. The performance of the tuner is analyzed in detail.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF043  
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WEPMF044 Updates on the DC Field Dependence Cavity niobium, multipactoring, SRF, simulation 2465
 
  • J.T. Maniscalco, M. Liepe
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Work at Cornell has demonstrated good agreement between a theoretical model by A. Gurevich of the anti-Q-slope (a field-dependent decrease of the microwave surface resistance) and experimental results from impurity-doped niobium. As a corollary, the model predicts that a strong DC magnetic field applied parallel to the RF surface will produce a similar decrease in surface resistance. In order to explore this prediction for many materials, we have designed a new coaxial cavity with a strong, uniform DC field superimposed over a weak RF field on a removable and replaceable niobium sample. Here we present updates on the progress of this new cavity.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF044  
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WEPMF045 Performance of the Prototype SRF Half-Wave-Resonators Tested at Cornell for the RAON Project SRF, multipactoring, pick-up, radiation 2468
 
  • M. Ge, F. Furuta, T. Gruber, S.W. Hartman, M. Liepe, J.T. Maniscalco, T.I. O'Connell, P.J. Pamel, J. Sears, V. Veshcherevich
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • B.H. Choi, J. Joo, J.W. Kim, W.K. Kim, J. Lee, I. Shin
    IBS, Daejeon, Republic of Korea
 
  Two prototype superconducting half-wave-resonator (162.5 MHz and β=0.12) for the RAON project have been successfully tested at Cornell University. Detailed vertical performance testing included (1) test of the bare cavity without the helium tank, and (2) test of the dressed cavity with a helium tank. In this paper, we report on the development of the test infrastructure, test results, and performance data analysis, showing that the specifications for RAON were met.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF045  
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WEPMF046 Modeling of the Frequency and Field Dependence of the Surface Resistance of Impurity-Doped Niobium niobium, experiment, ECR, SRF 2471
 
  • J.T. Maniscalco, P.N. Koufalis, M. Liepe
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  The anti-Q-slope, a field-dependent decrease in surface resistance observed in impurity-doped niobium, has been investigated extensively in 1.3 GHz cavities. New early research into this effect has recently been performed at higher and lower frequencies, revealing an additional dependence on frequency: the anti-Q-slope is stronger at higher frequencies and weaker at lower frequencies. Several models have been proposed to explain the anti-Q-slope, with varying success in this new frequency-dependent regime. In this work, we analyze recent experimental data from a low-temperature-doped 1.3 GHz cavity and a high-temperature nitrogen-doped 2.6 GHz cavity and discuss the implications of these results on the proposed models.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF046  
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WEPMF047 Performance of Samples With Novel SRF Materials and Growth Techniques SRF, superconducting-RF, niobium, site 2475
 
  • T.E. Oseroff, M. Ge, M. Liepe, J.T. Maniscalco, R.D. Porter
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • S.R. McNeal
    Ultramet, Pacoima, California, USA
  • M.J. Sowa
    Veeco-CNT, Medford, USA
 
  Novel materials are currently being studied in an attempt to push accelerating superconducting RF cavities to support higher accelerating fields and to operate with lower power loss. Growing layers of these materials of the quality necessary has proven to be difficult. In this work, we present the SRF performance of planar samples of the promising materials, NbN and Nb¬3Sn, grown using atomic layer deposition (ALD) and chemical vapor deposition (CVD) respectively. Results are promising.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF047  
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WEPMF050 Update on Nb3Sn Progress at Cornell University niobium, SRF, accelerating-gradient, site 2479
 
  • R.D. Porter, J. Ding, D.L. Hall, M. Liepe
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • T.A. Arias, P. Cueva, D.A. Muller, N. Sitaraman
    Cornell University, Ithaca, New York, USA
 
  Niobium-3 Tin (Nb3Sn) is the most promising alternative material for SRF accelerator cavities. The material can achieve higher quality factors, higher temperature operation and potentially higher accelerating gradients compared to conventional niobium. Cornell University has a leading program to produce 2 - 3 micrometer thick coatings of Nb3Sn on Nb for SRF applications using vapor diffusion. This program has been the first to produce quality factors higher than achievable with conventional Nb at usable accelerating gradients. Here we present an update on progress at Cornell University, including studies of the formation of the Nb3Sn layer, density functional theory calculations of Nb3Sn growth, and designs for a sample host cavity for measuring the quench field of Nb3Sn.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF050  
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WEPMF054 Design and Status of the MicroTCA.4 Based LLRF System for TARLA controls, LLRF, hardware, operation 2490
 
  • Gumus, C. Gumus, M. Hierholzer, K.P. Przygoda, H. Schlarb, Ch. Schmidt
    DESY, Hamburg, Germany
  • A.A. Aksoy, A. Aydin
    Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey
 
  The Turkish Accelerator and Radiation Laboratory in Ankara (TARLA) is constructing a 40 MeV Free Electron Laser with continuous wave (CW) RF operation. In order to control and monitor the four superconducting (SC) TESLA type cavities as well as the two normal conducting (NC) buncher cavities, a MicroTCA.4 based LLRF system is foreseen. This highly modular system is further used to control the mechanical tuning of the SC cavities by control of piezo actuators and mechanical motor tuners. This paper focuses on giving brief overview on hardware and software components of LLRF control of TARLA, as well as updates on the ongoing integration tests at DESY.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF054  
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WEPMF058 Anomaly Detection for Cavity Signals - Results from the European XFEL flattop, FEL, beam-loading, simulation 2502
 
  • A.S. Nawaz, S. Pfeiffer
    DESY, Hamburg, Germany
  • G. Lichtenberg
    HAW, Hamburg, Germany
  • P. Rostalski
    Institute for Electrical Engineering in Medicine, Lübeck, Germany
 
  The data throughput of the European XFEL DAQ is about 1.5 Gb/s. Data depicting the cavity signal behavior is currently only saved manually. This either happens, when cavity tests are being performed, or an operator detects a fault in the cavity system, that has to be further investigated. Those instances of interest are neither systematically nor automatically stored. It can therefore be assumed that unwanted or degraded cavity behavior is detected late or not at all. It is proposed to change the focus from detecting known faults (such as quenches) to additionally detect anomalies in the cavity system behavior. In order to detect anomalies in the cavity signals, an algorithm is proposed using a cavity model. It aims on finding those data sets, which diverge from the nominal cavity behavior, saving those instances for later analysis. The nominal behavior is defined by the cavity electromagnetic resonance model with beam loading as well as the model for the mechanical oscillations due to the Lorentz Forces. By using such an approach, the detection of anomalies, as well as faults could be automated. This contribution aims to summarize the influence of beam loading on the detection and gives examples for anomalies that were found in several cavities.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF058  
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WEPMF062 Simulation of Cavity Conditioning for the Diamond SCRF Cavity GUI, coupling, simulation, operation 2509
 
  • S.A. Pande, C. Christou, P. Gu
    DLS, Oxfordshire, United Kingdom
 
  Diamond SCRF cavities are pulse conditioned every week in order to keep them operating reliably. During conditioning, the cavities are detuned in order to sweep the standing wave through the waveguide. To match these cavities at lower voltage (typically < 1.4 MV) and at higher power, 3 stub tuners are used in the waveguide feed. Simulations with CST studio show that a strong SW field exists between the RF window and the matching posts. As the cavity is detuned the electric field maximum passes through the window causing heating of the ceramic. Temperature measurements with thermal camera reveal that the temperature of the window increases to maximum when the cavity is detuned towards higher frequency. Based on the simulation results and the measurements, it was decided to reduce the conditioning voltage. These results are summarised.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF062  
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WEPMF065 High Efficiency, High Power, Resonant Cavity Amplifier For PIP-II coupling, impedance, network, operation 2518
 
  • M.P.J. Gaudreau, N. Butler, D.B. Cope, P. H. Gordon, E.G. Johnson, M.K. Kempkes, R.E. Simpson
    Diversified Technologies, Inc., Bedford, Massachusetts, USA
 
  Funding: Funded under US DOE grant no. DE-SC0015780
Diversified Technologies, Inc. (DTI) is developing an integrated resonant-cavity combined solid-state amplifier for the Proton Improvement Plan-II (PIP-II) at Fermilab. The prototype has demonstrated multiple-transistor combining at 71% efficiency, at 675 watts per transistor at 650 MHz. The design simplifies solid-state transmitters to create straightforward scaling to high power levels. A crucial innovation is the reliable "soft-failure" mode of operation; a failure in one or more of these myriad combined transistors has negligible performance impact. The design couples the transistor drains directly to the cavity without first transforming to 50 Ohms, avoiding the otherwise-necessary multitude of circulators, cables, and connectors. DTI's design increases the power level at which it is cost-effective to employ a solid-state transmitter. DTI is upgrading the system to accommodate more transistors in each cavity module, and then will design and build a complete 100 kW-class transmitter which will consist of four such cavity modules and a combiner.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF065  
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WEPMF068 Inexpensive Brazeless Accelerator Prototype gun, vacuum, operation, electron 2528
 
  • S.P. Antipov, R.A. Kostin, S.V. Kuzikov
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • A.A. Vikharev
    IAP/RAS, Nizhny Novgorod, Russia
 
  Funding: DOE SBIR
A simple, inexpensive way to manufacture a standard radio frequency (RF) driven particle accelerator is presented. The simplification comes from two innovations: utilization of LCLS gun type RF design to avoid an expensive brazing process and copper plating of stainless steel that further reduces manufacturing cost. This is realized by a special structure design where accelerating structure cells are made out of copper plated stainless steel with knife edges and structure irises - copper disks acts also as gaskets for vacuum and RF seal. Besides the reduced cost, brazeless assembly allows integration of effective cooling and magnet optics elements into accelerator cells. Here we report on manufacturing and testing of brazeless accelerator prototype.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF068  
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WEPMF069 High Shunt Impedance Accelerating Structure with Distributed Microwave Coupling coupling, GUI, distributed, impedance 2531
 
  • S.P. Antipov, R.A. Kostin, S.V. Kuzikov
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • V.A. Dolgashev
    SLAC, Menlo Park, California, USA
 
  Funding: DOE SBIR
Conventional traveling wave or pi-phase advance standing wave structures use coupling of the microwave power through the beam pipe. This feature constrains the cavity shunt impedance (efficiency) to relatively small values. As microwave power flows through the accelerating cells in such structures, the probability of breakdown in high gradient operation is greatly increased. In this paper we present results from an accelerating structure prototype with distributed microwave coupling, an approach invented at SLAC. These structures include one or more parallel waveguides which are loaded by accelerating cavities. In this configuration accelerating cavities are fed independently and completely isolated at the beam pipe. Thus there is no microwave power flow through the accelerating cavity, making this geometry favorable for high gradient operation and maximizing the shunt impedance.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF069  
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WEPMF074 High Power Conditioning of X-Band RF Components operation, vacuum, hardware, GUI 2545
 
  • N. Catalán Lasheras, H. Damerau, R.L. Gerard, A. Grudiev, G. McMonagle, J. Paszkiewicz, A. Solodko, I. Syratchev, B.J. Woolley, W. Wuensch, V. del Pozo Romano
    CERN, Geneva, Switzerland
  • T.G. Lucas, M. Volpi
    The University of Melbourne, Melbourne, Victoria, Australia
  • S. Pitman
    Lancaster University, Lancaster, United Kingdom
  • A. Vnuchenko
    IFIC, Valencia, Spain
 
  As part of the effort to qualify CLIC accelerating struc-tures prototypes, new X-band test facilities have been built and commissioned at CERN in the last years. In this context, a number of RF components have been designed and manufactured aiming at stable operation above 50 MW peak power and several kW of average power. All of them have been tested now in the X-band facility at CERN either as part of the facility or in dedicated tests. Here, we describe shortly the main design and manufac-turing steps for each component, the testing and eventual conditioning as well as the final performance they achieved.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF074  
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WEPMF078 Assembly of the DQW Crab Cavity Cryomodule for SPS Test cryomodule, vacuum, controls, alignment 2561
 
  • M. Garlaschè, K. Artoos, R. Calaga, O. Capatina, T. Capelli, N. El Kbiri, D. Lombard, P.F. Marcillac, P. Minginette, M. Narduzzi, L.R.A. Renaglia, J. Roch, J.S. Swieszek
    CERN, Geneva, Switzerland
  • A. Krawczyk, B. Prochal
    IFJ-PAN, Kraków, Poland
 
  RF Crab Cavities are an essential part of the High Luminosity Upgrade of the LHC accelerating complex. Two concepts of such superconducting systems are being developed: the Double Quarter Wave (DQW) and the RF Dipole (RFD). A prototype cryomodule - hosting two DQW cavities - has been fabricated and assembled for validation tests to be carried out in the Super Proton Synchrotron (SPS) at CERN. An overview of the main cryomodule components is presented, together with the system features and main fabrication requirements. The preparatory measures for cryomodule assembly, the execution and lessons learned are also discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF078  
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WEPMK007 INFN-LASA Design and Prototyping Activity for PIP-II HOM, coupling, operation, linac 2640
 
  • A. Bignami, M. Bertucci, A. Bosotti, J.F. Chen, P. Michelato, L. Monaco, R. Paparella, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
  • S. Pirani
    ESS, Lund, Sweden
 
  The design of the PIP-II medium-β, 5-cell, 650 MHz SRF elliptical cavity and the first steps of its prototyping activity are here presented. A design based on a three dies fabrication model has been chosen and fully characterized in terms of electromagnetic and mechanical parameters. Goal of the optimization has been to realize a highly performant cavity for CW operation with reasonably good performances when pulsed. A prototyping phase started with the production of three single-cell cavities used to validate the LASA model and to develop an optimal recipe for RF surface treatment according to the state-of-the-art of the high-Q frontier.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK007  
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WEPMK008 In-Depth Analysis of the Vertical Test Results of the Third-Harmonic Cavities for the E-XFEL Injector FEL, experiment, feedback, SRF 2644
 
  • M. Bertucci, A. Bignami, A. Bosotti, J.F. Chen, C.G. Maiano, P. Michelato, L. Monaco, R. Paparella, P. Pierini, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • C.G. Maiano, P. Pierini
    ESS, Lund, Sweden
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
 
  The results of the vertical tests performed at LASA on the 3.9 GHz third-harmonic cavities for the E-XFEL injector are here discussed. Analysis of experimental data allows to confirm that such high frequency cavity, prepared with standard BCP treatment and 800°C annealing treatment, suffers an intrinsic performance limitation at around 22 MV/m (@ 2 K) due to a global thermal dissipation mechanism. A quantitative interpretation of the high field Q slope is also presented according to the latest theoretical models of field-dependent surface resistance.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK008  
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WEPMK010 LCLS-II Cryomodules Production at Fermilab cryomodule, vacuum, FEL, controls 2652
 
  • T.T. Arkan, J.N. Blowers, C.M. Ginsburg, C.J. Grimm, J.A. Kaluzny, A. Lunin, Y.O. Orlov, K.S. Premo, R.P. Stanek, G. Wu
    Fermilab, Batavia, Illinois, USA
 
  Funding: DOE
LCLS-II is a planned upgrade project for the linear coherent light source (LCLS) at SLAC. The LCLS-II linac will consist of thirty-five 1.3 GHz and two 3.9 GHz superconducting RF continuous wave (CW) cryomodules that Fermilab and Jefferson Lab are currently producing in collaboration with SLAC. The LCLS-II 1.3 GHz cryomodule design is based on the European XFEL pulsed-mode cryomodule design with modifications needed for CW operation. Two prototype cryomodules had been assembled and tested. After prototype cryomodule tests, both laboratories have increased cryomodule production rate to meet the challenging LCLS-II project installation schedule requirements of approximately one cryomodule per month per laboratory. Fermilab is at half point for the production, meaning that 6 cryomodules are fully assembled and tested. This paper presents Fermilab Cryomodule Assembly Facility (CAF) infrastructure for the LCLS-II cryomodules assembly, production experience at the half point emphasizing the challenges and mitigations.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK010  
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WEPMK012 Update on Plasma Processing R&D for LCLS-II plasma, HOM, experiment, SRF 2656
 
  • P. Berrutti, A. Grassellino, T.N. Khabiboulline, M. Martinello
    Fermilab, Batavia, Illinois, USA
  • M. Doleans, S.-H. Kim, K.E. Tippey
    ORNL, Oak Ridge, Tennessee, USA
  • D. Gonnella, G. Lanza, M.C. Ross
    SLAC, Menlo Park, California, USA
 
  Funding: Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE
SRF cavities performance preservation is crucial, from vertical test to accelerator operation. Field emission is still one of the main problems to overcome and plasma cleaning has been proven successful by SNS, in cleaning field emitters and increasing the work function of Nb. A collaboration has been established between FNAL, SLAC and ORNL with the purpose of applying plasma processing to LCLS-II cavities, in order to minimize and overcome field emission without affecting the high Q of N-doped cavities. The recipe will follow the neon-oxygen active plasma adopted at SNS, allowing in-situ processing of cavities and cryomodules from hydrocarbon contaminants. A novel method for plasma ignition has been developed at FNAL: a plasma glow discharge is ignited using high order modes to overcome limitations imposed by the fundamental power coupler. The results of experiments on 9-cell LCLS-II cavity are presented, along with plasma ignition studies. In addition the RF system is shown and N-doped Nb samples studies are discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK012  
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WEPMK014 A New Design for the Hilumi Radio-Frequency Dipole Bare Cavity niobium, GUI, resonance, 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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WEPMK015 Optimization of Vertical Electro-Polishing Process: Experiments with Updated Cathode on Single-Cell Cavity and Performance Achieved in Vertical Test cathode, SRF, linac, superconductivity 2662
 
  • F. Éozénou, L. Maurice
    CEA/DSM/IRFU, France
  • P. Carbonnier, C. Madec, Th. Proslier, C. Servouin
    CEA/DRF/IRFU, Gif-sur-Yvette, France
  • V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi
    MGH, Hyogo-ken, Japan
  • H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
    KEK, Ibaraki, Japan
 
  Marui Galvanizing Co.Ltd., and CEA have been studying Vertical Electro-Polishing (VEP) on Nb single-cell accelerating superconducting accelerator cavity with the goal of mass-production and cost-reduction, in collaboration with KEK within TYL-FJPPL Particle Physics Laboratory. Marui has invented and patented a rotative cathode called ‘i-Ninja'. The version 5 has been tested for the first time in Europe at CEA Saclay. The four wings of the cathode remove efficiently, bubbles of hydrogen, and the chosen parameters make it possible to achieve better surface and uniform material removal compared to VEP with a fixed cathode. The effect of the temperature of the cavity walls on current oscillations has been precisely studied. Two single-cell cavities have been electro-polished and tested at 2 K in vertical cryostat and the results will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK015  
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WEPMK016 New Insight on Nitrogen Infusion Revealed by Successive Nanometric Material Removal SRF, accelerating-gradient, factory, niobium 2665
 
  • M. Checchin, A. Grassellino, M. Martinello, O.S. Melnychuk, S. Posen, A.S. Romanenko, D.A. Sergatskov
    Fermilab, Batavia, Illinois, USA
 
  In this study we present new insight on low temperature nitrogen infusion on bulk niobium superconducting radio-frequency (SRF) cavities. Nitrogen infusion is a thermal treatment recently discovered at Fermilab that allows to reach high accelerating gradients, of the order of 45MV/m, with high Q-factors, of the order of 2 · 1010. Detailed depth dependent RF studies (by means of subsequent HF rinses) and comparisonwith SIMS results pinpointed interstitial nitrogen as the responsible for the improved performance and uncovered the extension of its profile inside the material.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK016  
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WEPML001 Passive Microphonics Mitigation during LCLS-II Cryomodule Testing at Fermilab cryomodule, cryogenics, controls, resonance 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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WEPML002 Design of 650 MHz Tuner for PIP-II Project interface, simulation, experiment, linac 2671
 
  • Y.M. Pischalnikov, S. Cheban, J.C. Yun
    Fermilab, Batavia, Illinois, USA
 
  Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
The Proton Improvement Plan (PIP) II project at Fermilab is a proton driver linac which will use of five different cavity geometries including a 650 MHz 5-cell elliptical cavities that will operate in RF-pulse mode. Detuning of these cavities by Lorentz Forces will be large and strongly depend of the stiffness of the cavity's tuner. First prototype tuner built and tested warm [1,2]. Measured stiffness of the prototype tuner was below 30kN/mm instead of expected from simulation 70kN/mm [2]. Significant effort has been invested into understanding discrepancy between simulation and experimental data that led to newest tuner design. Updated 'dressed cavity-helium vessel-tuner' model provided consistent results between ANSYS simulations and experiment results. Modified tuner design and analysis in limitations for overall 'cavity/tuner system' stiffness will be presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML002  
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WEPML003 Precision Q0 Measurement of an SRF Cavity with a Digital RF Techniques coupling, SRF, impedance, GUI 2674
 
  • J.P. Holzbauer, B.M. Hanna, Y.M. Pischalnikov, W. Schappert, D.A. Sergatskov, A.I. Sukhanov
    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.
Direct measurement of the quality factor of SRF cavity using traditional RF techniques is essential for cavity production and development. Systematic effects of the measurement can contribute significant amounts of error to these measurements if not accounted for. This paper will present measurements taken at Fermilab using a digital RF system to characterize and correct for these systematic effects and directly measure the quality factor versus gradient curve for a single spoke resonator in the Spoke Test Cryostat at Fermilab. These measurements will be compared to traditional calorimetric measurements, and a discussion of improving/extending these techniques to other testing situations will be included.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML003  
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WEPML004 Production Tuner Testing for LCLS-II Cryomodule Production cryomodule, LLRF, interface, SRF 2678
 
  • J.P. Holzbauer, Y.M. Pischalnikov, W. Schappert, J.C. Yun
    Fermilab, Batavia, Illinois, USA
  • C. Contreras-Martinez
    FRIB, East Lansing, 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.
LCLS-II 1.3 GHz cryomodule production is well underway at Fermilab. Several dozen cavity/tuner systems have been tested, including tuning to 1.3 GHz, cold landing frequency, range/sensitivity of the slow tuner, and range/sensitivity of the fast tuner. All this testing information as well as lessons learned from tuner installation will be presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML004  
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WEPML005 Testing of SSR1 Production Tuner for PIP-II linac, SRF, niobium, cryomodule 2681
 
  • J.P. Holzbauer, D. Passarelli, Y.M. Pischalnikov
    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 PIP-II project at Fermilab is a proton driver linac calling for the use of five different, novel cavity geometries. Prototyping at Fermilab is in the advanced stages for the low-beta single-spoke resonator (SSR1) and associated technologies. A production tuner design has been fabricated and tested, both warm and cold in the Spoke Test Cryostat (STC). This paper will present the detailed studies on this tuner, including slow motor/piezoelectric tuner range and hysteresis as well as dynamic mechanical system characterization.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML005  
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WEPML006 Modified Slow Tuner Design for Cavity 1 Inside LCLS II Cryomodules cryomodule, interface, SRF, simulation 2684
 
  • Y.M. Pischalnikov, T.T. Arkan, S. Cheban, J.P. Holzbauer, J.A. Kaluzny, Y.O. Orlov, J.C. Yun
    Fermilab, Batavia, Illinois, USA
 
  Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
Initial LCLS-II cryomodule testing at Fermilab showed microphonics on the furthest upstream cavity (number 1) at least factor 2 larger than on the rest of the cavities. Testing indicated that this was a difference in the mechanical support of cavity 1, not a local acoustic source. Further investigation pointed to the upstream beam-pipe of the cavity 1. The upstream cavity flange has a solid spool piece connection to the beamline gate valve unlike the other cavities, which all connect through bellows. The gate valve's weight is supported by sliding system (free in z-axis) connected to large diameter Helium gas return pipe. The tuner design was modified to transform interface between cavity#1 and gate valve. Arms of the tuner for cavity 1 were extended and became the support structure for gate valve, eliminating the connection to the helium return pipe. Modification of the tuner design and results in microphonics mitigations will be presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML006  
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WEPML007 Active Microphonics Compensation for LCLS-II controls, resonance, 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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WEPML008 Tuner Testing of a Dressed 3.9 GHz Cavity for LCLS-II at Fermilab SRF, operation, background, FEL 2690
 
  • J.P. Holzbauer, S. Aderhold, T.N. Khabiboulline, Y.M. Pischalnikov, W. Schappert, J.C. Yun
    Fermilab, Batavia, Illinois, USA
  • C. Contreras-Martinez
    FRIB, East Lansing, 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.
Fermilab is responsible for the design of the 3.9 GHz cryomodule for LCLS-II. Integrated acceptance testing of a dressed 3.9 GHz cavity for the LCLS-II project has been done at the Fermilab Horizontal Test Stand. This test included a slim blade tuner (based on INFN & XFEL designs) with integrated piezoelectric fast/fine tuner. This paper will present results of the mechanical setup, cold testing, and cold function of this tuner including fast and slow tuner range, sensitivity, and hysteresis.
 
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WEPML010 Operation Regime Analysis of Conduction Cooled Cavities Through Multi-Physics Simulation operation, SRF, simulation, niobium 2697
 
  • R.A. Kostin, R. Dhuley, M.G. Geelhoed, R.D. Kephart, T.K. Kroc, O.V. Prokofiev, J.C.T. Thangaraj
    Fermilab, Batavia, Illinois, USA
  • A. Kanareykin
    Euclid TechLabs, LLC, Solon, Ohio, USA
 
  Funding: Department of Energy
Euclid Techlabs in collaboration with Fermilab IARC (Batavia, IL) is developing industrial superconducting 10MeV electron linac. Conduction cooling is used for cooling instead of liquid helium bath to simplify linac maintenance. The cavity linked to commercially available cryo-cooler cold head through highly conductive aluminium strips. However, this solution raises a problem of contact thermal resistance. This paper shows some results of Comsol multyphysics simulations of the cavity cooling by AL strips. Some insight was obtained on the acceptable range of contact resistance. Operation regimes were obtained at different accelerating gradients and cavity temperatures. The results of simulation are presented and discussed.
 
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WEPML011 Garnet Ring Measurements for the Fermilab Booster 2nd Harmonic Cavity booster, controls, solenoid, simulation 2700
 
  • R.L. Madrak, J.E. Dey, K.L. Duel, J. Kuharik, A.V. Makarov, W. Pellico, J. Reid, G.V. Romanov, M. Slabaugh, D. Sun, C.-Y. Tan, I. Terechkine
    Fermilab, Batavia, Illinois, USA
 
  A perpendicularly biased tuneable 2nd harmonic cavity is being constructed for use in the Fermilab Booster. The cavity's tuner uses National Magnetics AL800 garnet as the tuning media. For quality control, the magnetic properties of the material and the uniformity of the properties within the tuner must be assessed. We describe two tests which are performed on the rings and on their corresponding witness samples.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML011  
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WEPML012 Progress on the Construction of the Perpendicularly Biased 2nd Harmonic Cavity for the Fermilab Booster HOM, booster, damping, impedance 2703
 
  • R.L. Madrak, J.E. Dey, K.L. Duel, M.R. Kufer, J. Kuharik, A.V. Makarov, R.D. Padilla, W. Pellico, J. Reid, G.V. Romanov, M. Slabaugh, D. Sun, C.-Y. Tan, I. Terechkine
    Fermilab, Batavia, Illinois, USA
 
  A perpendicularly biased tuneable 2nd harmonic cavity, designed for the Fermilab Booster, is being assembled for testing this summer (2018). The cavity will work at twice the frequency of the fundamental cavities, and will be on only during the injection and transition (or extraction) periods. The main purpose of adding this cavity is to improve beam capture and reduce losses as required by Fermilab's Proton Improvement Plan (PIP). After three years of testing and optimization, the cavity design has now been finalized and all constituent parts have been received. We report on the cavity final design and on the status of the construction.  
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WEPML013 Anti-Q-slope enhancement in high-frequency niobium cavities ECR, niobium, SRF, experiment 2707
 
  • M. Martinello, S. Aderhold, S.K. Chandrasekaran, M. Checchin, A. Grassellino, O.S. Melnychuk, S. Posen, A.S. Romanenko, D.A. Sergatskov
    Fermilab, Batavia, Illinois, USA
 
  N-doped 1.3 GHz niobium cavities showed for the first time the so-called anti-Q-slope, i.e. the increasing of the Q-factor as a function of the accelerating field. It was verified that the anti-Q-slope is consequence of the decreasing of the temperature-dependent component of the surface resistance as a function of the field. This trend is opposite compared to the increasing of the surface resistance previously observed in 1.3 GHz standard (EP, BCP, 120 C baked) niobium cavities. The effect of the different state-of-the-art surface treatments on the field dependence of the surface resistance is studied for 650 MHz, 1.3 GHz, 2.6 GHz and 3.9 Ghz cavities. This proceeding shows that the field dependence of the temperature-dependent component of the surface resistance has a strong frequency dependence and that the anti-Q-slope may appear even in clean niobium cavities if the resonant frequency is high enough, suggesting new routes toward the understanding of the anti-Q-slope effect.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML013  
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WEPML014 Tooling Systems for the Assembly and Integration of the SSR1 Cryomodule for PIP-II Project at Fermilab cryomodule, solenoid, vacuum, insertion 2710
 
  • D. Passarelli, F. Di Ciocchis, M. Parise, V. Roger
    Fermilab, Batavia, Illinois, USA
 
  In this paper we present the assembly strategy and tooling design for the SSR1 cryomodule from the cavity string to the final module. Several challenging aspects were considered to minimize undesired stresses on critical components, to preserve the alignment of cavities and solenoids during final assembly, and ultimately to meet the technical requirements of the PIP-II project at Fermilab.  
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WEPML015 Preparation and Qualification of Jacketed SSR1 Cavities for String Assembly at Fermilab vacuum, cryomodule, multipactoring, controls 2714
 
  • D. Passarelli, P. Berrutti, S.K. Chandrasekaran, J.P. Ozelis, M. Parise, L. Ristori, A.M. Rowe, A.I. Sukhanov
    Fermilab, Batavia, Illinois, USA
 
  The qualification of dressed 325 MHz Single Spoke Resonators type 1 (SSR1) to meet technical requirements is an important milestone in the development of the SSR1 cryomodule for the PIP-II Project at Fermilab. This paper reports the procedures and lessons learned in processing and preparing these cavities for horizontal cold testing prior to integration into a cavity string assembly.  
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WEPML016 Development of Nb3Sn Coatings for Superconducting RF Cavities at Fermilab SRF, factory, superconductivity, network 2718
 
  • S. Posen, S.K. Chandrasekaran, O.S. Melnychuk, D.A. Sergatskov, B. Tennis, Y. Trenikhina
    Fermilab, Batavia, Illinois, USA
  • J. Lee
    NU, Evanston, Illinois, USA
 
  Nb3Sn films are a promising alternative material for su-perconducting RF cavities, with proven high quality factors at medium fields and predictions for increased superheating field as well. In this contribution, we de-scribe the latest results from the Fermilab Nb3Sn SRF program. Early experiments have been focused on single cell 1.3 GHz cavities. We briefly review efforts to bring the parameters used in the coating process into a range where they produce uniform surfaces without regions showing signs of excess tin or thin/uncoated areas. We then present the latest cavity results, after modifications to the coating recipe based on feedback from film appear-ance and RF performance. These results show high Q0 at medium fields and a maximum field of ~18 MV/m.  
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WEPML022 3.9 GHz Power Coupler Design and Tests for LCLS-II Project simulation, resonance, cryomodule, diagnostics 2727
 
  • N. Solyak, I.V. Gonin, C.J. Grimm, E.R. Harms, T.N. Khabiboulline, A. Lunin, O.V. Prokofiev, G. Wu
    Fermilab, Batavia, Illinois, USA
 
  LCLS-II linac requires two 3.9 GHz cryomodules (eight cavities per CM), operating up to 16MV/m in cw regime. Fermilab has designed and built few prototypes of the cavity and auxiliaries and tested them at the vertical and horizontal cryostats. Fundamental power coupler, based on existing design (FLASH, XFEL) was redesign for 2kW average power. We built three prototypes and tested them at room temperature test stand. One coupler was assembled on the cavity and tested at horizontal cryostat as part of design verification program. Test results and comparison with simulations are discussed in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML022  
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WEPML023 Design and Test Results of the 3.9 GHz Cavity for LCLS-II radiation, cryomodule, operation, FEL 2730
 
  • N. Solyak, S. Aderhold, S.K. Chandrasekaran, C.J. Grimm, T.N. Khabiboulline, A. Lunin, O.V. Prokofiev, G. Wu
    Fermilab, Batavia, Illinois, USA
 
  The LCLS-II project uses sixteen 3.9 GHz superconduct-ing cavities to linearize energy distribution before the bunch compressor. To meet LCLS-II requirements origi-nal FNAL design used in FLASH and XFEL was signifi-cantly modified to improve performance and provide reliable operation up to 16 MV/m in cw regime [1-3]. Four prototype cavities were built and tested at vertical cryo-stat. After dressing, one cavity was assembled and tested at horizontal cryostat as part of design verification pro-gram. All auxiliaries (magnetic shielding, power and HOM couplers, tuner) were also re-designed and tested with this cavity. In this paper we will discuss cavity and coupler design and test results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML023  
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WEPML031 The New Broadband Accelerating System for the SIS18 Upgrade at GSI operation, impedance, controls, resonance 2755
 
  • P. Hülsmann, R. Balß, H. Klingbeil, U. Laier, K.-P. Ningel, C. Thielmann, B. Zipfel
    GSI, Darmstadt, Germany
 
  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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WEPML032 The FAIR-SIS100 Bunch Compressor RF Station power-supply, controls, coupling, electronics 2759
 
  • H.G. König, R. Balß, P. Hülsmann, H. Klingbeil, P.J. Spiller
    GSI, Darmstadt, Germany
  • R. Gesche, J.H. Scherer
    Aurion Anlagentechnik GmbH, Seligenstadt, Germany
  • A. Morato, C. Morri, G.T. Taddia
    OCEM, Valsamoggia, Italy
 
  In the frame of the Facility for Antiproton and Ion Research (FAIR) 9 bunch compressor RF stations were ordered for the first stage of realization of the SIS100 synchrotron. For RF gymnastics referred to as bunch rotation, one RF station has to provide a sudden rise in gap voltage of up to 40 kVp within less than 30 μs. The system is designed for a maximum RF burst of 3 ms per second. The RF frequency will be pre-selectable between 310 kHz and 560 kHz at a harmonic number of h=2 with respect to the beam. Compressed bunches with a peak current > 150 A and a width < 50 ns are the goal. For this purpose, a 1.218 m long cavity was designed using iron-based magnetic alloy cores. Variable vacuum capacitors are attached for tuning. The cavity is driven by a cross-coupled push-pull tetrode amplifier. This scheme minimizes the influence of the tetrode's DC current at the working point to the cores. The energy for the pulsed system is stored in a relatively small capacitor bank which will be charged semi-continuously and a voltage-stabilizing device is added. Cavity and power amplifier were realized by AURION Anlagentechnik GmbH ' the power supply unit is designed and built by OCEM Power Electronics.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML032  
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WEPML033 The FAIR-SIS100 Accelerating RF Station controls, feedback, operation, power-supply 2762
 
  • H.G. König, R. Balß, H. Klingbeil, U. Laier, D.E.M. Lens, P.J. Spiller
    GSI, Darmstadt, Germany
  • G. Blokesch, F. Wieschenberg
    Ampegon PPT GmbH, Dortmund, Germany
  • K. Dunkel, M. Eisengruber, J.H. Hottenbacher
    RI Research Instruments GmbH, Bergisch Gladbach, Germany
  • C. Hiltbrunner
    Ampegon AG, Turgi, Switzerland
 
  For the Facility for Antiproton and Ion Research (FAIR) 14 ferrite loaded accelerating RF stations are planned for the first stage of realization of the SIS100 synchrotron. Each RF station has to provide a total peak gap voltage of up to 20 kVp in CW operation - tuneable in the range of 1.1 MHz up to 3.2 MHz to allow ion beam acceleration and beam gymnastics at different harmonic numbers and energy levels in the new facility. Each RF station consists of a tuneable ferrite cavity, a single ended tetrode amplifier and a dedicated power supply and control unit (PSU) ' including two bias current supplies for cavity- and control-grid(G1)-circuit-tuning. The ferrite cavity is based on the SIS18 cavity concept but has to provide a 1.25 times higher gap voltage of 20 kVp over a total length of 3 meters. The realization is done by a consortium consisting of RI Research Instruments GmbH as consortium leader and manufacturer of the cavity, Ampegon PPT GmbH (for the tetrode amplifier) and Ampegon AG (for the power supply unit). In this contribution, the system design is discussed, and commissioning results are presented. All main parameters are achieved with the RF station described.  
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WEPML034 Design and Commissioning of the RF System of the Collector Ring at FAIR controls, power-supply, MMI, operation 2765
 
  • U. Laier, R. Balß, A. Dolinskyy, P. Hülsmann, H. Klingbeil, T. Winnefeld
    GSI, Darmstadt, Germany
  • G. Blokesch, F. Wieschenberg
    Ampegon PPT GmbH, Dortmund, Germany
  • K. Dunkel, M. Eisengruber, J.H. Hottenbacher
    RI Research Instruments GmbH, Bergisch Gladbach, Germany
  • C. Morri, M.P. Pretelli, G.T. Taddia
    OCEM, Valsamoggia, Italy
 
  The Collector Ring (CR), a storage ring intended to perform efficient cooling of secondary beams, is under construction at GSI in the scope of the FAIR project. The RF system of the CR has to provide a frequency range from 1.1 to 1.5 MHz and pulsed gap voltages of up to 200 kVp (0.2 to 1 Hz, max. 10-3 duty cycle) and up to 10 kVp in CW operation. Five identical RF stations will be built. Each RF station consists of an inductively loaded cavity, a tetrode based power amplifier, a semiconductor driver amplifier, a switch mode power supply and two digital feedback loops. The main components of the RF station are designed, built and commissioned in close collaboration between GSI and three companies: RI Research Instruments GmbH, Ampegon PPT GmbH and OCEM Energy Technology SRL. In 2016, the first of five RF stations has been integrated at GSI. In 2017 the system was successfully commissioned to demonstrate that all envisaged parameters have been achieved. This contribution will present the requirements imposed the system, the principal design of the overall system as well as of its key components, and the results of the commissioning of the first RF station.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML034  
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WEPML039 Design of the Two-Gap Superconducting Re-Buncher heavy-ion, linac, simulation, proton 2779
 
  • M. Gusarova, W.A. Barth, S. Yaramyshev
    MEPhI, Moscow, Russia
  • W.A. Barth, S. Yaramyshev
    GSI, Darmstadt, Germany
  • W.A. Barth, M. Miski-Oglu
    HIM, Mainz, Germany
  • M. Basten, M. Busch
    IAP, Frankfurt am Main, Germany
  • M. Gusarova
    JINR, Dubna, Moscow Region, Russia
 
  A new design of a spoke cavity for low relative velocities of heavy ions has been elaborated. Simulation results for a 2-gap spoke cavity with a resonance frequency of 216.816 MHz and a relative velocity of 0.07с are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML039  
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WEPML040 Further Tests on the Final State of the SC 325 MHz CH-Cavity and Coupler Test Bench Update linac, heavy-ion, framework, SRF 2783
 
  • M. Busch, M. Basten, J. List, P. Müller, H. Podlech, M. Schwarz
    IAP, Frankfurt am Main, Germany
  • W.A. Barth, J. List
    GSI, Darmstadt, Germany
  • W.A. Barth
    HIM, Mainz, Germany
  • W.A. Barth
    MEPhI, Moscow, Russia
 
  Funding: Work supported by BMBF Contr. No. 05P15RFBA
At the Institute for Applied Physics, Goethe-University Frankfurt, a sc 325 MHz CH-cavity has been developed and successfully tested up to 14.1 mV/m and has now reached the final production stage with the helium vessel welded to the frontal joints of the cavity and final processing steps have been performed. Further tests in a vertical and horizontal environment are being prepared for intensive studies. This cavity is a prototype for envisaged beam tests with a pulsed ion beam at 11.4 AMeV. In this contribution the results of the performed RF tests are being presented. Furthermore, first measurements of the recently installed 217 MHz coupler test bench are shown.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML040  
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WEPML041 Comparative Study of Low Beta Multi-Gap Superconducting Bunchers linac, heavy-ion, proton, accelerating-gradient 2786
 
  • K.V. Taletskiy, W.A. Barth, M. Gusarova, S. Yaramyshev
    MEPhI, Moscow, Russia
  • W.A. Barth, S. Yaramyshev
    GSI, Darmstadt, Germany
  • W.A. Barth, M. Miski-Oglu
    HIM, Mainz, Germany
  • M. Basten, M. Busch
    IAP, Frankfurt am Main, Germany
  • M. Gusarova
    JINR, Dubna, Moscow Region, Russia
 
  The results of a comparative study of low beta multi-gap superconducting bunchers for 216.816 MHz and a relative velocity of 0.07с with dedicated limitations of the overall geometrical dimensions are presented. A comparison of electrodynamic, mechanical and thermal properties of 3-gap and 2-gap cavities is shown.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML041  
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WEPML043 RF Simulations of the Injector Section from CH8 to CH15 for MYRRHA simulation, impedance, resonance, MMI 2790
 
  • P. Müller, M. Busch, H. Hähnel, K. Kümpel, D. Mäder, N.F. Petry, H. Podlech
    IAP, Frankfurt am Main, Germany
 
  Funding: Work supported by the EU Framework Programme H2020 662186 (MYRTE) and HIC for FAIR
MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Applications) is the first prototype of an accelerator driven nuclear reactor dealing with the transmutation of long-living nuclear waste. Beam quality and reliability are crucial for the reactor. The injector design is done by IAP, Goethe-University, and has been adapted to the final magnet design and voltage distributions. The energy section from 5.87 MeV up to 16.6 MeV has been changed to normal conducting CH cavities as in the lower energy part of the injector. For beam adjustment a 5-gap CH cavity rebuncher at 5.87 MeV as well as two doublet magnets forming the new MEBT-2 section between CH7 and CH8 have been added. Starting parameters for the RF simulations have been given by beam dynamics results calculated with LORASR. RF simulations of these structures consisting of flatness and tuning optimizations will be presented within this contribution.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML043  
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WEPML044 Design of HOM Couplers for Superconducting 400 MHz RF Cavities HOM, collider, proton, simulation 2793
 
  • N.F. Petry, M. Busch, K. Kümpel, O. Meusel, H. Podlech
    IAP, Frankfurt am Main, Germany
 
  The Future Circular Collider (FCC) is one possible future successor of the Large Hadron Collider (LHC). The proton-proton collider center-of-mass collision energy is set to 100 TeV with a beam current of 0.5 A. To reach this goal a stable acceleration is critical and therefore higher order modes (HOM) need to be damped. To avoid a high power level in the HOM dampers, further described as couplers, the loaded Q-factor should be below 1000 for the cavity with mounted HOM couplers. Besides a low Q-factor the R/Q value should also be in the range of 1 Ω or below. Two different types of couplers are used to achieve a high damping. The two types are a narrowband Hook-type HOM coupler and a broadband Probe-type HOM coupler. The recent results of the design of the HOM couplers attached to a superconducting 400 MHz RF cavity will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML044  
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WEPML045 Infrastructure for Superconducting CH-Cavity Preparation at HIM linac, vacuum, SRF, heavy-ion 2796
 
  • T. Kürzeder, K. Aulenbacher, W.A. Barth, F.D. Dziuba, V. Gettmann, M. Miski-Oglu, E. Riehn
    HIM, Mainz, Germany
  • K. Aulenbacher, R.G. Heine, T. Stengler
    IKP, Mainz, Germany
  • W.A. Barth, S. Yaramyshev
    GSI, Darmstadt, Germany
  • F. Hug
    KPH, Mainz, Germany
 
  A superconducting cw LINAC for heavy ions is currently under development at GSI in Darmstadt and HIM in Mainz. This Linac is based on 217 MHz multigap bulk niobium Crossbar H-mode RF-cavities. In order to treat and prepare RF-cavities with such a complex geometry a new cleanroom facility has been already built at the Helmholtz-Institut in Mainz. All tools and machines inside the cleanroom can handle cavities with up to 800 mm in diameter and with up to 1300 mm in length. In its ISO-class 6 and 4 zones, respectively it features a large ultrasonic and conductance rinsing bath, a high pressure rinsing (HPR) cabinet and a vacuum oven. The HPR cabinet has an inside clearance of 1.4 m. The large cavities sit on a rotating table, while the rising wand moves vertically up and down. Due to the crossbar structure of the RF-cavities the HPR device allows for off axis-rinsing in their quadrants. For RF testing a 52 m² (4 m x 13 m) concrete shielded area with sufficient liquid helium and nitrogen supply is located next to the cleanroom and the cryo-module assembly area. We will report on the new SRF infrastructure in Mainz and the commissioning of the new high pressure rinsing cabinet.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML045  
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WEPML046 Multipactor Discharge in Superconducting Accelerating CH Cavities multipactoring, electron, linac, heavy-ion 2800
 
  • M. Gusarova, D. I. Kiselev
    MEPhI, Moscow, Russia
  • F.D. Dziuba, T. Kürzeder, M. Miski-Oglu
    HIM, Mainz, Germany
  • M. Gusarova
    JINR, Dubna, Moscow Region, Russia
 
  The results of numerical simulations of multipacting discharge in a superconducting accelerating CH cavity are presented in this paper. The localization of multipactor trajectories in the 15-gap 217 MHz superconducting (sc) CH cavity at various levels of accelerating voltage is considered.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML046  
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WEPML047 Study on RF Coupler Kicks of SRF Cavities in the BESSY VSR Module SRF, storage-ring, HOM, GUI 2804
 
  • A.V. Tsakanian, T. Mertens
    Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
  • H.-W. Glock, J. Knobloch, M. Ries, A.V. Vélez
    HZB, Berlin, Germany
 
  The BESSY VSR upgrade of the BESSY II light source represents a novel approach to simultaneously store long (ca. 15ps) and short (ca. 1.7ps) bunches in the storage ring with the standard user optics. This challenging goal requires installation of four new SRF multi-cell cavities (2x1.5GHz and 2x1.75GHz) equipped with strong waveguide HOM dampers ensuring tolerable beam coupling impedance, necessary for stable operation. These cavities will operate at high 20MV/m in CW mode and at the zero-crossing phase according to the accelerating voltage. Consequently the transverse voltages will be maximum and can impact the transverse beam dynamics. The asymmetric character of those transverse kicks are caused by cavity fundamental power couplers (FPC) with strong monopole terms, introducing transverse kick to on-axis particles. Different FPC orientations were analyzed to optimize the net coupler kick from the four cavity chain. The coupler kick strength of each cavity is estimated taking into account accelerating mode amplitudes and phases required for operation in VSR mode.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML047  
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WEPML048 HOM Power Levels in the BESSY VSR Cold String HOM, SRF, simulation, GUI 2808
 
  • A.V. Tsakanian, T. Flisgen
    Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
  • H.-W. Glock, J. Knobloch, A.V. Vélez
    HZB, Berlin, Germany
 
  The BESSY VSR upgrade of the BESSY II light source represents a novel approach to simultaneously store long (ca. 15ps) and short (ca. 1.7ps) bunches in the storage ring. This challenging goal requires installation of four new SRF cavities (2x1.5 GHz and 2x1.75 GHz) in one module for installation in a single straight. These cavities are equipped with strong waveguide HOM dampers necessary for stable operation. The expected HOM power and spectrum has been analyzed for the complete cold string. The cold string is a combination of various elements such as SRF cavities, bellows with and without shielding, warm HOM beampipe absorbers and UHV pumping domes. The presented study is performed for various BESSY VSR bunch filling patterns with 300 mA beam current. The contribution of each component to the total HOM power is presented. In addition the optimization of different cavity arrangements in the module is performed in order to reach the optimal operation conditions with equally distributed power levels along the string and tolerable beam coupling impedance.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML048  
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WEPML049 The Challenge to Measure nΩ Surface Resistance on SRF Samples SRF, quadrupole, pick-up, simulation 2812
 
  • S. Keckert, T. Junginger, J. Knobloch, O. Kugeler
    HZB, Berlin, Germany
  • T. Junginger
    Lancaster University, Lancaster, United Kingdom
 
  Systematic research on fundamental limits of superconducting materials for SRF applications and their intrinsic material properties relevant for use in an accelerator requires studies in a wide parameter space of temperature, RF field and frequency. The Quadrupole Resonator at HZB enables precision measurements on planar samples at temperatures of 1.8 K to >20 K, RF fields of up to 120 mT, and frequencies of 420 MHz, 850 MHz and 1285 MHz. In the past years the capabilities of the setup were studied intensively and developed further. Sources of systematic errors, such as microphonics or misalignment have been identified and eliminated. In this contribution the current status of the QPR and its systematic limitations are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML049  
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WEPML051 Improvement of the Chopper System for rf Deflector at the J-PARC Linac controls, timing, linac, operation 2816
 
  • K. Futatsukawa, Z. Fang, Y. Fukui
    KEK, Ibaraki, Japan
  • Y. Sato
    Nippon Advanced Technology Co., Ltd., Tokai, Japan
  • S. Shinozaki
    JAEA/J-PARC, Tokai-mura, Japan
 
  In the J-PARC linac, the RF deflector has been operated to kick the wasted beam and to shape the intermediate-pulse like the comb structure. Then about 50% of the beam current is removed by leading the scraper and the rest beam current is injected to the downstream synchrotron ring RCS. The fast rising time and falling time, the cavity with low loading Q value in the chopper system are required to decrease the incomplete kicked beam. However, there was the ringing of the RF field on the chopper cavity, and it influenced the beam rising time. The chopper controllers, which has the fast RF -switch to make the particular RF according to the intermediate-pulses, were improved for the RF falling time by outputting short pulses with inverting phase. The beam study for the new system was successfully done. In this paper, I would like to introduce this system and to show the results of the beam study.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML051  
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WEPML055 Simulation Study of Parasitic-Mode Damping Methods for a 1.5-GHz TM020-Mode Harmonic Cavity impedance, damping, coupling, radiation 2822
 
  • N. Yamamoto, S. Sakanaka, T. Takahashi
    KEK, Ibaraki, Japan
 
  Design study of parasitic-mode (PM) damped structures has been conducted for the purpose to realize a normal conducting 1.5 GHz harmonic cavity which is based on the TM020 resonant mode*. We have investigated the performances of two PM-damping mechanisms, that are, rod-type antennas** and annular slots. The rod-type antennas locate at the node of electric field of the TM020 mode while the annular slots locate at the node of magnetic field. As a result of 3D electromagnetic simulations, suitable performances of PMs were confirmed by employing either of the PM-damping mechanisms. It was also shown that the slot-type structure is superior in PM-damping performance and in the unloaded Q of the TM020 mode.
* N. Yamamoto et al., IPAC'17, paper THOPIK037; N. Yamamoto Phys. Rev. Accel. Beams, 21, 1, 012001.
** T. Takahashi et al., IPAC'17, paper THPIK036.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML055  
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WEPML067 Second Sound Quench Detection on Superconducting Cavities detector, site, SRF, superconducting-cavity 2843
 
  • Z.C. Liu, S. Bai, J. Gao, F.S. He, H.Y. Lin, P. Zhang
    IHEP, Beijing, People's Republic of China
 
  Second sound is an effective way to detect the quench position on superconducting cavity. A second sound quench site detection system is under developing for the PAPS. High gradient is very important for superconducting cavity, however it may be limited by quench on the cavity high field region. Quench can be caused by various reasons. To locate the position is the key to reveal the mysteries of quench. Now we are developing the quench position detection system by RTD sensors such as Cernox and OST sensors.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML067  
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WEPML078 Development of a Superconducting Double-Spoke Cavity at IMP accelerating-gradient, SRF, ion-source, niobium 2869
 
  • T.C. Jiang, H. Guo, Y. He, C.L. Li, L.B. Liu, T. Tan, P.R. Xiong, Z.M. You, W.M. Yue, S.H. Zhang, S.X. Zhang
    IMP/CAS, Lanzhou, People's Republic of China
 
  Superconducting multi-spoke cavities are well-known optional choice for acceleration of heavy ions in medium velocity regimes. The paper describes the design, fabrication and test results of the superconducting double-spoke cavity developed at IMP. After Buffered Chemical Polishing and High pressure Rinsing, one cavity has undergone high gradient RF testing at 4 K in the Vertical Test Stand. We present measurements of the quality factor as a function of accelerating field and maximum field on the surface. Accelerating gradient of more than 15 MV/m is reached with peak electric field of 61 MV/m, and peak magnetic field of 118 mT.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML078  
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THXGBD1 The Upgrade of the Advanced Photon Source lattice, feedback, controls, simulation 2872
 
  • M. Borland, M. Abliz, N.D. Arnold, T.G. Berenc, J.M. Byrd, J.R. Calvey, J.A. Carter, J. Carwardine, H. Cease, Z.A. Conway, G. Decker, J.C. Dooling, L. Emery, J.D. Fuerst, K.C. Harkay, A.K. Jain, M.S. Jaski, P.S. Kallakuri, M.P. Kelly, S.H. Kim, R.M. Lill, R.R. Lindberg, J. Liu, Z. Liu, J. Nudell, C.A. Preissner, V. Sajaev, N. Sereno, X. Sun, Y.P. Sun, S. Veseli, J. Wang, U. Wienands, A. Xiao, C. Yao
    ANL, Argonne, Illinois, USA
  • A. Blednykh
    BNL, Upton, Long Island, New York, USA
 
  After decades of successful operation as a 7-GeV synchrotron radiation source, the Advanced Photon Source is pursing a major upgrade that involves replacement of the storage ring with an ultra-low emittance multi-bend achromat design. Using a seven-bend hybrid multi-bend achromat with reverse bending magnets gives a natural emittance of 42 pm operated at 6 GeV. The x-ray brightness is predicted to increase by more than two orders of magnitude. Challenges are many, but appear manageable based on thorough simulation and in light of the experience gained from world-wide operation of 3\text{rd}-generation light sources. The upgraded ring will operate in swap-out mode, which has allowed pushing the performance beyond the limits imposed by conventional operation.  
slides icon Slides THXGBD1 [14.684 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THXGBD1  
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THXGBF2 Beam Commissioning of the IFMIF EVEDA Very High Power RFQ rfq, MMI, vacuum, operation 2902
 
  • E. Fagotti, L. Antoniazzi, L. Bellan, D. Bortolato, M. Comunian, A. Facco, M.G. Giacchini, F. Grespan, M. Montis, A. Palmieri, A. Pisent, F. Scantamburlo
    INFN/LNL, Legnaro (PD), Italy
  • B. Bolzon, N. Chauvin, R. Gobin
    CEA/IRFU, Gif-sur-Yvette, France
  • P. Cara
    IFMIF/EVEDA, Rokkasho, Japan
  • H. Dzitko, D. Gex, A. Jokinen, G. Phillips
    F4E, Germany
  • T. Ebisawa, A. Kasugai, K. Kondo, K. Sakamoto, T. Shinya, M. Sugimoto
    QST, Aomori, Japan
  • R. Heidinger, A. Marqueta, I. Moya
    Fusion for Energy, Garching, Germany
  • P. Mereu
    INFN-Torino, Torino, Italy
  • G. Pruneri
    Consorzio RFX, Associazione Euratom-ENEA sulla Fusione, Padova, Italy
  • M. Weber
    CIEMAT, Madrid, Spain
 
  IFMIF, the International Fusion Materials Irradiation Facility, is an accelerator-based neutron source that will use Li(d, xn) reactions to generate a flux of neutrons with a broad peak at 14 MeV equivalent to the conditions of the Deuterium-Tritium reactions in a fusion power plant. IFMIF is conceived for fusion materials testing. The IFMIF prototype linear accelerator (LIPAc) is jointly developed by Europe and Japan within the IFMIF EVEDA project: it is composed of an ion source, a LEBT, an RFQ, a MEBT and a SC linac, with a final energy of 9 MeV. The 4-vane Radio Frequency Quadrupole (RFQ), developed by INFN in Italy, will accelerate a 130 mA deuteron beam from 0.1 to 5 MeV in continuous wave, for a beam power of 650 kW. The 9.8 m long 175 MHz cavity is composed of 18 x 0.54 m long modules flanged together and aligned within 0.3 mm tolerance. The RFQ was completed, delivered and assembled at the Rokkasho site and is presently under extended RF tests. The second phase of beam commissioning (up to 2.5 MeV/u) was scheduled to start at the end of 2017. Several unexpected issues and incidents significantly delayed the original program, which is however proceeding step by step toward the full achievement of its goals.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THXGBF2  
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THYGBD1 FCC: Colliders at the Energy Frontier collider, luminosity, hadron, injection 2908
 
  • M. Benedikt, F. Zimmermann
    CERN, Geneva, Switzerland
 
  The international Future Circular Collider study, launched in 2014, is finalizing a multi-volume conceptual design report. The FCC develops high-energy circular collider options based on a new 100 km tunnel. Long-term goal is a 100 TeV proton-proton collider (FCC-hh). The study also includes a high-luminosity electron-positron collider (FCC-ee), and it also examines lepton-hadron scenarios (FCC-he). Civil engineering and technical infrastructure studies were carried out. Global programs advance the development of high-field superconducting magnet technology based on Nb3Sn, the optimization of a suitable large superconducting RF system, and schemes for synchrotron radiation handling. In addition, the FCC study includes the design of the HE-LHC, housed in the LHC tunnel, and based on the same high-field magnet technology as the FCC-hh. The FCC study further includes an elaboration of the physics cases, including for heavy-ion collisions, and detector concepts, as well as staging and implementation scenarios. The FCC collaboration has grown to more than 120 institutes from 30 countries around the world. This invited talk summarizes the study achievements and the final designs.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THYGBD1  
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THYGBE3 RF Controls for High-Q Cavities for the LCLS-II LLRF, controls, cryomodule, EPICS 2929
 
  • C. Serrano, K.S. Campbell, L.R. Doolittle, G. Huang, A. Ratti
    LBNL, Berkeley, California, USA
  • R. Bachimanchi, C. Hovater
    JLab, Newport News, Virginia, USA
  • A.L. Benwell, M. Boyes, G.W. Brown, D. Cha, G. Dalit, J.A. Diaz Cruz, J. Jones, R.S. Kelly, A. McCollough
    SLAC, Menlo Park, California, USA
  • B.E. Chase, E. Cullerton, J. Einstein-Curtis, J.P. Holzbauer, D.W. Klepec, Y.M. Pischalnikov, W. Schappert
    Fermilab, Batavia, Illinois, USA
  • L.R. Dalesio, M.A. Davidsaver
    Osprey DCS LLC, Ocean City, USA
 
  Funding: This work was supported by the LCLS-II Project and the U.S. Department of Energy, Contract n. DE-AC02-76SF00515.
The SLAC National Accelerator Laboratory is building LCLS-II, a new 4 GeV CW superconducting (SCRF) Linac as a major upgrade of the existing LCLS. The LCLS-II Low-Level Radio Frequency (LLRF) collaboration is a multi-lab effort within the Department of Energy (DOE) accelerator complex. The necessity of high longitudinal beam stability of LCLS-II imposes tight amplitude and phase stability requirements on the LLRF system (up to 0.01% in amplitude and 0.01° in phase RMS). This is the first time such requirements are expected of superconducting cavities operating in continuous-wave (CW) mode. Initial measurements on the Cryomodule test stands at partner labs have shown that the early production units are able to meet the extrapolated hardware requirements to achieve such levels of performance. A large effort is currently underway for system integration, Experimental Physics and Industrial Control System (EPICS) controls, transfer of knowledge from the partner labs to SLAC and the production and testing of 76 racks of LLRF equipment.
 
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THYGBE3  
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THYGBF4 Accelerator Physics Advances in FRIB (Facility for Rare Isotope Beams) linac, MMI, ECR, ECRIS 2950
 
  • P.N. Ostroumov, N.K. Bultman, M. Ikegami, S.M. Lidia, S.M. Lund, G. Machicoane, T. Maruta, A.S. Plastun, G. Pozdeyev, X. Rao, J. Wei, T. Xu, T. Yoshimoto, Q. Zhao
    FRIB, East Lansing, USA
  • C.Y. Wong
    NSCL, East Lansing, Michigan, USA
 
  Funding: Work supported by the U.S. DOE Office of Science under Cooperative Agreement DE-SC0000661 and the NSF under Cooperative Agreement PHY-1102511, the State of Michigan and Michigan State University.
This paper presents recent developments of accelerator physics related topics for the Facility for Rare Isotope Beams (FRIB) being built at Michigan State University. While extensive beam dynamics simulations including all known errors do not show uncontrolled beam losses in the linac, ion beam contaminants extracted from the ECR ion source together with main ion beam can produce significant losses after the charge stripper. These studies resulted in development of beam collimation system at relatively low energy of 16 MeV/u and room temperature bunchers instead of originally planned superconducting ones. Commissioning of the Front End enabled detailed beam physics studies accompanied with the simulations using several beam dynamics codes. Settings of beam optics devices from the ECR to MEBT has been developed and applied to meet important project milestones. Similar work is planned for the beam commissioning of the first 3 cryomodules in the superconducting linac.
 
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THYGBF4  
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THPAF017 Improvement of RF Field Phase and Amplitude Errors Simulations in TraceWin Code simulation, linac, diagnostics, beam-losses 2983
 
  • D. Uriot
    IRFU, CEA, University Paris-Saclay, Gif-sur-Yvette, France
 
  Funding: This work is supported by the European Atomic Energy Community's (EURATOM) H2020 Programme under grant agreement n°662186 (MYRTE project)
RF field phase and amplitude errors are usually not correctly simulated and it is a serious problem especially when in high intensity linear accelerators, the main losses are due to particle leaving the beam acceptance. This new development implemented in TraceWin fixes this issue. The objective is to improve the longitudinal beam dynamics simulation methods, by including more close-to-real models for the cavities tuning procedure. By this way, clear distinction should be done between static and dynamic errors and longitudinal diagnostics accuracy can be clearly defined according to beam dynamics results.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF017  
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THPAF019 Initial Performance of the Magnet System in the Splitter/Combiner Section of the Cornell-Brookhaven Energy-Recovery Linac Test Accelerator linac, quadrupole, dipole, optics 2986
 
  • J.A. Crittenden, A.C. Bartnik, R.M. Bass, D.C. Burke, J. Dobbins, C.M. Gulliford, Y. Li, D. Sagan, K.W. Smolenski, Turco, J. Turco
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • J.S. Berg
    BNL, Upton, Long Island, New York, USA
  • D. Jusic
    Cornell University, Ithaca, New York, USA
 
  Funding: This work is supported by NSF award DMR-0807731, DOE grant DE-AC02- 76SF00515, and New York State Energy Research and Development Authority.
The Cornell-Brookhaven Energy-recovery Linac Test Accelerator is a four-pass, 150-MeV electron accelerator with a six-cell 1.3 GHz superconducting-RF linear accelerator and a fixed-field alternating-gradient (FFAG) return loop made up of Halbach-style quadrupole magnets. The optics matching between the linear accelerator and the return loop is achieved with a conventional magnet system comprised of 50 dipole magnets and 64 quadrupole magnets in four beamlines at each end of the linac. The 42-, 78-, 114- and 150-MeV electron beams are separated into independent vacuum chambers in order to allow for the path-length adjustment required by energy recovery. We report on the first beam tests of the initial installation of the splitter/combiner section at the exit of the linac. The vacuum system of the 42-MeV S1 line was installed during the first week of April. Nine dipole and four quadrupole magnets were installed and surveyed into position the following week, and the water cooling system was commissioned. A 6-MeV beam passed through the line on April~11 with no need for adjusting pre-set magnet excitation currents. One week later, time-of-flight measurements were used to calibrate and phase the individual superconducting RF cavities. The S1 magnet settings were then scaled up to achieve 5-cavity, 42-MeV operation through the first nine FFAG permanent-magnet quadrupoles. This initial Fractional Arc Test will conclude on May 18, when the installation of the remaining seven splitter/combiner lines and the return loop will begin. CBETA operations are scheduled to begin in early 2019.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF019  
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THPAF020 Measurement of Transverse Impedance of Specific Components in CESR Using BPM Measurements of Pinged Bunches impedance, undulator, experiment, betatron 2990
 
  • M.P. Ehrlichman, J.P. Shanks, S. Wang
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  A beam-based technique is applied to determine the quadrupole impedance of large-impedance components of the CESR storage ring. Two bunches separated by ~1/3 of the ring circumference are charged to 0.85 and 0.3 mA. Each bunch is given a single kick, either horizontal or vertical. Turn-by-turn, bunch-by-bunch position information is recorded for ~16 k turns. BPM-by-BPM phase is calculated using the All-phase FFT method of spectral analysis. The difference in the BPM-to-BPM phase advance between the two bunches is a measurement of the local transverse impedance. The impedances of the small-aperture in-vacuum undulators, collimators, scrapers, RF cavities, electrostatic separators, and bulk impedance of the remaining ring are determined in this manner.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF020  
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THPAF022 Beam Breakup Studies for the 4-Pass Cornell-Brookhaven Energy Recovery Linac Test Accelertor HOM, simulation, lattice, dipole 2996
 
  • W. Lou, G.H. Hoffstaetter
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Cornell University and Brookhaven National Laboratory are currently designing the Cornell-BNL ERL-FFAG Test Accelerator (CBETA). To be built at Cornell Wilson Lab, CBETA utilizes the existing ERL injector and main linac cryomodule (MLC). As the electron bunches pass through the MLC cavities, higher order modes (HOMs) fields are excited. The recirculating bunches interact with the HOMs, which can give rise to beam-breakup instability (BBU). We would present simulation results on how BBU limits the maximum achievable current, and potential ways to improve the threshold current.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF022  
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THPAF039 IP Orbit Correction Update for HL-LHC alignment, quadrupole, optics, dipole 3048
 
  • D. Gamba, R. De Maria
    CERN, Geneva, Switzerland
 
  Funding: Research supported by the HL-LHC project.
The HL-LHC design foresees a substantial modification of the LHC layout next to the low beta Interaction Points (IPs), namely IP1 and IP5. The inner triplets will be replaced by larger aperture ones to achieve lower beta at the IPs and crab cavities (CCs) will be installed. This will add new constraints to the orbit control, which required a careful choice of location and strength of the new orbit correctors to be installed in the area. The new orbit correction system will need to correct for the unavoidable imperfections, but also provide the necessary flexibility for implementing and optimising the crossing scheme. Detailed studies of the HL-LHC layout versions HLLHCV1.0 and HLLHCV1.1 were already performed. This paper is the continuation of these works and is based on the latest layout HLLHCV1.3. A simplification of the previous analysis is proposed that helps to identify the dominant imperfections. The expected performance and tolerances of the present layout are presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF039  
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THPAF041 Uncontrolled Longitudinal Emittance Blow-Up during RF Manipulations in the CERN PS impedance, emittance, simulation, controls 3056
 
  • A. Lasheen, H. Damerau, G. Favia
    CERN, Geneva, Switzerland
 
  The CERN Proton Synchrotron (PS) determines the basic bunch spacing for the Large Hadron Collider (LHC) by means of rf manipulations. Several rf systems in a frequency range from 2.8 MHz to 200 MHz are available for beam acceleration and manipulations. Each of the six bunches injected from the PS Booster is split in several steps into 12 bunches spaced by 25 ns, yielding a batch of 72 bunches at transfer to the Super Proton Synchrotron (SPS). In the framework of the LHC Injector Upgrade (LIU) project the bunch intensity must be doubled. However, with most of the planned upgrades already in place this intensity has not yet been achieved due to collective effects. One of them is uncontrolled longitudinal emittance blow-up during the bunch splittings. In this contribution, measurements of the blow-up during the splitting process are presented and compared with particle simulations using the present PS impedance model. Beam-based measurements of the impedances of the rf cavities have been performed. They revealed that to reproduce the instability an additional impedance source is required in the PS impedance model.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF041  
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THPAF042 Improvement of the Longitudinal Beam Transfer from PS to SPS at CERN acceleration, emittance, controls, proton 3060
 
  • A. Lasheen, H. Damerau, J. Repond, M. Schwarz, E.N. Shaposhnikova
    CERN, Geneva, Switzerland
 
  The beam transfer from the Proton Synchrotron (PS) to the Super Proton Synchrotron (SPS) at CERN is a critical process for the production of beams for the Large Hadron Collider (LHC). A bunch-to-bucket transfer is performed with the main drawback that the rf frequency in the SPS (200 MHz) is five times higher than the one in the PS (40 MHz). The PS bunches are therefore shortened non-adiabatically before extraction by applying a fast rf voltage increase (bunch rotation) to fit them into the short rf buckets in the SPS. However, particles with large amplitude of synchrotron oscillations in the PS longitudinal phase space are not properly captured in the SPS. They contribute to losses at the injection plateau and at the start of acceleration in the SPS. In this contribution, we present measurements and simulations performed to identify the source of the uncaptured particles. The tails of the particle distribution were characterized by applying longitudinal shaving during acceleration. Furthermore, the rotated bunch distribution was improved by linearizing the rf voltage using a higher-harmonic rf cavity.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF042  
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THPAF053 Lower-Harmonic RF System in the CERN SPS emittance, impedance, simulation, proton 3087
 
  • J. Repond, H. Damerau, A. Lasheen, E.N. Shaposhnikova
    CERN, Geneva, Switzerland
 
  Significant beam losses increasing with intensity are observed at capture and along the SPS flat bottom for the LHC-type proton beam. The intensity should be doubled for HL-LHC and high losses may be a major performance limitation. Bunches extracted from the PS, the SPS injector, are produced in a 40 MHz RF system applying a bunch rotation at the end of the cycle and therefore cannot be perfectly matched to the 200 MHz SPS RF bucket. The possibility of using a lower harmonic additional RF capture system in the SPS was already proposed after the LEP era in preparation for transfer of the LHC beam but the bunch rotation was the preferred solution, since the induced voltage in the SPS 200 MHz RF system would be too large to ensure stability in a low harmonic system without mitigation measures. However, the use of the upgraded one-turn feedback and the 200 MHz RF system as a Landau cavity could help to improve stability. The feasibility of this scenario to reduce capture losses in the SPS is analysed and presented in this paper. The choice of an optimum RF frequency and voltage is also discussed. The transfer to the main 200 MHz is simulated using a realistic bunch distribution.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF053  
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THPAF063 Identification of Imperfections in Impedance Shields on the SPS-QF Flanges via Non-Intrusive Measurements resonance, impedance, shielding, coupling 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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THPAF065 Semi-Empirical Hamiltonian Model for Elliptical Cavities linac, simulation, linear-dynamics, proton 3127
 
  • E. Laface, J. F. Esteban Müller
    ESS, Lund, Sweden
 
  We propose to use the sum of TM0m0 modes to treat a radio-frequency superconducting elliptical cavity as a pill-box cavity with variable radius. The amplitudes of the different modes are obtained interpolating the field-map of the cavity with the model. Once the field is calculated, the Hamiltonian of the cavity is constructed and used to evaluate the transfer matrices associated to each step of the field-map. The multi-particle non-linear dynamics can also be evaluated using the Lie Transform of the Hamiltonian. The results are benchmarked against the ESS Linac Simulator contained in the OpenXAL suite.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF065  
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THPAF083 LINAC-Multitool - an Open Source Java-Toolkit linac, GUI, MMI, simulation 3179
 
  • M. Schwarz, D. Bade, J. Corbet, H. Podlech
    IAP, Frankfurt am Main, Germany
 
  Funding: Work supported by BMBF contr. No. 05P15RFRBA and HIC for FAIR.
Dedicating more precious time to advanced research instead of spending it towards time-consuming routine tasks is a desirable goal in particle accelerator simulation and development. Requirements engineering was started at IAP in order to identify routine processes at our institute's R&D that can be automated or simplified. Results indicated that there were several areas to consider: Bead pull measurements, data processing and visualization for the beam dynamics code LORASR, CST field map processing for the use with TraceWin, conversion between different particle distribution data formats and more. Subsequently development of the LINAC-Multitool started to rationalize these processes and replace preexisting scripts also to ensure consistency of results and increase transparency and reliability of computation. In order to guarantee maintainability, expandability and platform independence, LINAC-Multitool is programmed using Java and will be open source. This contribution presents the current state of development.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF083  
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THPAF084 Impact of RF Coupler Kicks on Beam Dynamics in BESSY VSR simulation, kicker, SRF, lattice 3182
 
  • T. Mertens
    Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
  • T. Atkinson, F. Glöckner, A. Jankowiak, M. Ries, A.V. Tsakanian
    HZB, Berlin, Germany
 
  The expected BESSY II upgrade to BESSY VSR requires the installation of a superconducting RF system, consisting of four cavities. Two cavities will operate at 1.5 GHz and two at 1.75 GHz. Each of them is equipped with a Fundamental Power Coupler and with Higher Order Mode (HOM) damping waveguide couplers. Dedicated simulations of these cavities and couplers have shown that at the location of the FPC the beam will see a transverse kick [*], perturbing the closed orbit and affecting transverse beam dynamics. We present the results of simulations and experiments of the impact on transverse beam dynamics of these coupler induced kicks for different FPC orientations.
[*] Study on RF Coupler Kicks of SRF Cavities in the BESSY VSR Module
A. Tsakanian#, H.-W. Glock, T. Mertens, M. Ries, A. Velez, J. Knobloch
IPAC18
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF084  
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THPAF085 Estimation of Dielectric Losses in the Bessy VSR Warm Beam Pipe Absorbers HOM, GUI, storage-ring, wakefield 3185
 
  • T. Flisgen
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
  • H.-W. Glock
    HZB, Berlin, Germany
  • A.V. Tsakanian
    Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
 
  Funding: Work supported by the German Bundesministerium für Bildung und Forschung, Land Berlin and grants of Helmholtz Association.
Currently Helmholtz Zentrum Berlin prepares the update of the BESSY II ring to BESSY VSR. The updated ring will be capable to simultaneously store short and long bunches to satisfy the various user demands. For this sake, a cryomodule accommodating two 1.5 GHz and two 1.75 GHz superconducting cavities will be installed into the storage ring. The cavity string will be equipped with warm dielectric absorber rings at both ends. Together with the waveguide dampers of the cavities, these rings damp electromagnetic fields excited by the beam. This contribution presents the estimation of the dielectric losses in the beam pipe absorber rings of the BESSY VSR module. The presented approach is based on determining a broad band impedance of the dielectric ring by exciting the numerical model with a single broad band Gaussian bunch. Subsequently, the power deposited into the ring is estimated in frequency domain by multiplying the impedance with the square of the beam current for all considered harmonics of the beam. Finally, these power contributions are added up. In addition to details of the scheme, the contribution presents results for the recent absorber layout of the BESSY VSR string.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF085  
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THPAF087 Multi-Objective Optimization of an SRF Photoinjector with Booster Section for High Brightness Beam Performance booster, emittance, brightness, gun 3193
 
  • E. Panofski, A. Jankowiak, T. Kamps, A. Neumann
    HZB, Berlin, Germany
 
  Several future accelerator projects, light sources and user experiments require high brightness electron beams. SRF photoinjectors operating in continuous-wave (cw) mode hold the potential to serve as an electron source generating beams of high average brightness and short bunch lengths. Different operation and design parameters of the SRF photoinjector impact the beam dynamics and thus the beam brightness. A universal multi-objective optimization program based on a genetic algorithm was developed to extract optimum gun parameter settings from Pareto-optimum solutions. After getting the first optimum results, the photoinjector is supplemented with a booster section downstream. The new optimization results are presented. Further, the optimization program is applied to evaluate the impact of the field flatness of the gun cavity on the high brightness performance.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF087  
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THPAK005 Measuring the Coupling Impedance of Vacuum Components for the Advanced Photon Source Upgrade Using a Goubau Line impedance, simulation, vacuum, coupling 3211
 
  • M.P. Sangroula
    IIT, Chicago, Illinois, USA
  • R.M. Lill, R.R. Lindberg, R.B. Zabel
    ANL, Argonne, Illinois, USA
 
  The Planned upgrade of the Advanced Photon Source to a multi-bend achromat (MBA) will increase the x-ray brightness by two to three orders of magnitude. Storing such an intense beam stably inside the narrow gap vacuum chambers requires sophisticated and appropriately designed rf-components that helps to minimize rf heating and collective instabilities associated with the impedance of these small-aperture vacuum components. As part of this effort, my research focuses on impedance measurement and simulation of various MBA vacuum components. In this paper, we briefly introduce the novel Goubau line (G-line) test fixture for the impedance measurement, at first, and then present our measurements data along with simulations with simulations for various vacuum components designed for the APS Upgrade.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK005  
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THPAK016 Measurement and Analysis of Synchrotron Tune Variation with Beam Current in BEPCII synchrotron, positron, electron, impedance 3237
 
  • N. Wang, Z. Duan, G. Xu, H.S. Xu, C.H. Yu, Y. Zhang
    IHEP, Beijing, People's Republic of China
 
  Coherent synchrotron frequency shift is observed during machine studies in BEPCII (Beijing Electron Positron Collider Upgrade). The results show that the synchrotron frequency varies parabolically with the increase of the beam current. This phenomenon is supposed to be induced by the interaction of the beam with the fundamental mode of the accelerating cavity. In order to explain this phenomenon, a simple physical model is developed from the couple bunch instability theory. The analytical estimations based on the physical model show good agreement with the measurements.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK016  
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THPAK017 Higher Order Modes in China-ADS Demo Linac dipole, HOM, linac, higher-order-mode 3240
 
  • C. Zhang, Y. He, T.C. Jiang, R.X. Wang, S.H. Zhang
    IMP/CAS, Lanzhou, People's Republic of China
 
  Funding: Work supported by Natural Science Foundation of China,No.11505253
The study of higher order modes excited in the China-ADS Linac has been presented in this paper. The effects of the cryogenic losses and the influence on beam of the higher order modes have been investigated.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK017  
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THPAK018 Recent Developments in DEMIRCI for RFQ Design rfq, software, simulation, multipole 3243
 
  • E. Celebi
    IBU, Istanbul, Turkey
  • O. Cakir, G. Turemen
    Ankara University, Faculty of Sciences, Ankara, Turkey
  • G. Turemen
    TAEK, Ankara, Turkey
  • G. Unel
    UCI, Irvine, California, USA
 
  Funding: This project has been supported by TUBITAK with project number 114F106 and 117F143.
DEMIRCI software aims to aid RFQ design efforts by making the process easy, fast and accurate. In this report, DEMIRCI 8-term potential results are compared with the results provided by other commercially available simulation software. Computed electric fields are compared to the re- sults from simulations of a recently produced 352 MHz RFQ. Recent developments like the inclusion of space charge ef- fects in DEMIRCI beam dynamics are also discussed. More- over, further terms are added to 8-term potential to simulate possible vane production errors. The FEM solver was also improved to mesh the cells with errors.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK018  
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THPAK028 Beam Dynamics Simulations in the Dubna SC202 Superconducting Cyclotron for Hadron Therapy extraction, cyclotron, proton, simulation 3270
 
  • O. Karamyshev, G.A. Karamysheva, D.V. Popov, G. Shirkov, S.G. Shirkov
    JINR, Dubna, Moscow Region, Russia
  • V. Malinin
    JINR/DLNP, Dubna, Moscow region, Russia
 
  In 2015 the joint project JINR (Dubna, Russia) - ASIPP (Hefei, China) on design and construction of supercon-ducting proton cyclotron SC202 was started. Two cyclo-trons are planned to be manufactured in China, according to the Collaboration Agreement between JINR and ASIPP. The first cyclotron will be used for proton therapy in Hefei and the second one will replace the Phasotron in the research and treatment program on proton therapy in Dubna. New schema of extraction system and results of beam acceleration and extraction simulations for Dubna cyclotron are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK028  
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THPAK031 Suppression of Longitudinal Coupled Bunch Instability by Harmonic Cavity in UVSOR Electron Storage Ring damping, synchrotron, storage-ring, HOM 3280
 
  • A. Mochihashi
    KIT, Eggenstein-Leopoldshafen, Germany
  • M. Fujimoto, K. Hayashi, M. Katoh
    UVSOR, Okazaki, Japan
  • J. H. Hasegawa, M. Hosaka, M. Hosaka, Y. Takashima, Y. Takashima
    Nagoya University, Nagoya, Japan
  • M. Hosaka, Y. Takashima
    Aichi Synchrotron Radiation Center, Aichi, Japan
  • M. Katoh
    Sokendai - Okazaki, Okazaki, Aichi, Japan
 
  In the UVSOR electron storage ring, which is dedicated for a VUV synchrotron radiation light source, a longitudinal coupled bunch instability (LCBI) is observed in multi-bunch operation. To suppress the LCBI, we routinely operate a third harmonic cavity (HCV) in a passive mode. By properly tuning HCV, the instability is almost completely suppressed. Because of the lower beam energy (750 MeV) and brilliant beam emittance (17.5 nm-rad), the Touschek effect becomes severe in the UVSOR. To guarantee enough beam lifetime, we also apply HCV for lengthening the bunch. The suppression of the instability and increasing the beam lifetime are crucial benefits by HCV for the UVSOR. However, not only the origin of the LCBI but also the Landau damping effect by HCV has not been understood systematically yet. We have noticed that one of the HOMs at HCV itself could cause the LCBI and observed the behavior of the instability, which strongly depends on the beam current. From the experiment we have discussed the cause of the instability with the HOM theory. We have also tried to observe synchrotron tune spread and discussed a competition between the Landau damping and the instability growth.
Present affiliation of the first auther : Karlsruhe Institute of Technology
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK031  
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THPAK037 Beam-Loading Transients and Bunch Shape in the Operation of Passive Harmonic Cavities in the ALS-U simulation, beam-loading, impedance, controls 3298
 
  • Z. Pan, S. De Santis, C. Steier, C. Sun, M. Venturini
    LBNL, Berkeley, USA
  • T. Hellert
    DESY, Hamburg, Germany
  • C.-X. Tang
    TUB, Beijing, People's Republic of China
 
  The ALS-U is a major upgrade of the LBNL ALS to a diffraction limited light source. The current plan is to replace all the vacuum and magnet components while retaining the existing 500 MHz main and third-harmonic, passively operated, rf cavities, but replacement of the existing rf cavities is also being considered. A new feature, is represented by beam-loading transients associated with a beam consisting of 11 bunch trains separated by 10 ns gaps as needed to enable on-axis swap-out injection. In this paper we study these transients and the associated bunch-to-bunch phase, length, and profile variations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK037  
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THPAK062 Bunch Compression of Flat Beams emittance, simulation, experiment, booster 3368
 
  • A. Halavanau, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • D.J. Crawford, D.R. Edstrom, D. Mihalcea, S. Nagaitsev, P. Piot, A.L. Romanov, J. Ruan, V.D. Shiltsev
    Fermilab, Batavia, Illinois, USA
 
  Funding: This work is supported by the DOE contract No.DEAC02-07CH11359 to the Fermi Research Alliance LLC. A.H. is supported by the DOE under contract No. DE-SC0011831 with Northern Illinois University.
Flat beams can be produced via a linear manipulation of canonical angular momentum (CAM) dominated beams using a set of skew-quadrupole magnets. Recently such beams were produced at Fermilab Accelerator Science and Technology (FAST) facility. In this paper, we report the results of flat beam compression study in a magnetic chicane at an energy of E~32 MeV. Additionally, we investigate the effect of energy chirp in the round-to-flat beam transform. The experimental results are compared with numerical simulations.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK062  
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THPAK069 Open XAL Status Report 2018 linac, MMI, diagnostics, GUI 3388
 
  • A.P. Zhukov, C.K. Allen, A.P. Shishlo
    ORNL, Oak Ridge, Tennessee, USA
  • C.P. Chu, Y. Li
    IHEP, Beijing, People's Republic of China
  • J.F. Esteban Müller, E. Laface, Y. Levinsen, N. Milas, C. Rosati
    ESS, Lund, Sweden
  • P. Gillette, G. Normand, A. Savalle
    GANIL, Caen, France
  • X.H. Lu
    CSNS, Guangdong Province, People's Republic of China
 
  The Open XAL accelerator physics software platform is being developed through an international collaboration among several facilities since 2010. The goal of the collaboration is to establish Open XAL as a multi-purpose software platform supporting a broad range of tool and application development in accelerator physics and high-level control (Open XAL also ships with a suite of general purpose accelerator applications). This paper discusses progress in beam dynamics simulation, new RF models, and updated application framework along with new generic accelerator physics applications. We present the current status of the project, a roadmap for continued development and an overview of the project status at each participating facility.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK069  
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THPAK070 Coupled Bunch Instability from JLEIC Crab Cavity Higher Order Modes HOM, impedance, luminosity, feedback 3392
 
  • S.I. Sosa Guitron, S.U. De Silva, J.R. Delayen, H. Park
    ODU, Norfolk, Virginia, USA
  • R. Li, V.S. Morozov, H. Park
    JLab, Newport News, Virginia, USA
 
  Particle bunches traveling in a ring can excite wakefields inside any radio-frequency element present. These electromagnetic modes can resonate long enough and interact with subsequent passing bunches. A coherent oscillation between bunches can quickly become an instability and needs to be addressed. The Jefferson Lab electron ion collider has a large 50 mrad crossing angle and thus relies on bunch crabbing to achieve high luminosity. Bunch crabbing is done with compact superconducting rf dipole cavities. We study coupled bunch oscillations driven by the higher order modes of multicell RFD crab cavities under study for JLEIC, we calculate the instability growth time assuming a symmetric beam spectrum, identify the HOMs driving the instability and discuss mitigation measures.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK070  
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THPAK077 Feasibility of Non-Metal Vacuum Chamber for Storage Rings impedance, vacuum, insertion-device, insertion 3411
 
  • T.-Y. Lee
    PAL, Pohang, Kyungbuk, Republic of Korea
 
  This paper studies if the vacuum chamber of an elec-tron storage ring can be made of dielectric non-meta materials such as ceramics or glass. The purpose of this study is to substantially reduce the broadband imped-ance of the vacuum chamber and consequently mitigate single bunch instabilities. This theoretical study examines how these materials can reduce the impedance and pro-poses how to resolve technical problems to occur.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK077  
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THPAK105 Construction Progress of Two Superconducting Cyclotrons for Proton Therapy and Proton Irradiation at CIAE cyclotron, proton, extraction, controls 3477
 
  • T.J. Zhang, S. An, H.R. Cai, L.C. Cao, X.L. Cao, T. Cui, X.L. Fu, T. Ge, P.F. Gong, F.P. Guan, L.L. Guan, S.G. Hou, B. Ji, X.L. Jia, M. Li, X.L. Li, Y.Q. Li, J. Lin, J.Y. Liu, X.T. Lu, Y.L. Lv, C. Wang, F. Wang, F. Wang, L. Wang, J.Y. Wei, S.M. Wei, J.S. Xing, G. Yang, J.J. Yang, M. Yin, Z.G. Yin, D.S. Zhang, S.P. Zhang, X. Zhen
    CIAE, Beijing, People's Republic of China
  • K. Fong
    TRIUMF, Vancouver, Canada
 
  Funding: Supported partly by the National Natural Science Foundation of China (Grant No. 11375273 and 11475269) and by the Ministry of Science and Technology under Grant 2016YFC0105300.
There are very strong demand for mid-energy of proton machine recent years due to the surging cancer patients and fast progress of the space science in China. For the applications of proton therapy and proton irradiation, the energy range of proton beam usually is from 200 MeV to 250 MeV, or even higher for astronavigation. Based on the R&D starting from 2009, two construction projects of 230 MeV and 250 MeV superconducting cyclotron, which have been implemented recently at China Institute of Atomic Energy(CIAE). That was started in Jan 2015 for the 230 MeV machine, for the program of proton therapy and space science launched by China National Nuclear Corporation (CNNC), and in Jan 2016 for the 250 MeV machine, for the program of proton therapy launched by the Ministry of Science and Technology of China (MOST). In this paper, the designs for the two SC cyclotrons and their key components, including the main magnet, SC coils, RF system, internal ion source and central region, extraction system, etc, and the construction progress of the machines will be presented.
 
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THPAK113 Cavity Characterization Studies With the Latest Revision of YACS storage-ring, coupling, superconducting-cavity, higher-order-mode 3503
 
  • B.D. Isbarn, S. Koetter, B. Riemann, M. Sommer, T. Weis
    DELTA, Dortmund, Germany
 
  Funding: Work supported by the BMBF under contract no. 05K13PEB.
YACS is a 2.5D finite element method solver capable of solving for the full 3D eigenfrequency spectra of resonant axisymmetric structures while reducing the computational problem to a 2D rotation plane. The most recent revision of YACS now supports arbitrary order basis functions for the geometry and field discretization. In earlier revisions of YACS spurious modes were introduced by increasing the order of either the geometry or field basis functions. To prevent the emergence of spurious modes, YACS now matches the function spaces of the in-plane and out-plane function basis, and thus yields spurious free solutions. To demonstrate the capabilities of YACS, extensive cavity characterization studies on curved multicell microwave cavities are presented. Due to the combined utilization of the rotation symmetry, higher order basis functions and curved elements, eigenfrequency spectra above 10 GHz for L-band multicell structures can be easily obtained.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK113  
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THPAK115 Numerical Multiparticle Tracking Studies on Coupled-Bunch Instabilities in the Presence of RF Phase Modulation wakefield, impedance, synchrotron, damping 3511
 
  • M. Sommer, B.D. Isbarn, S. Koetter, B. Riemann, T. Weis
    DELTA, Dortmund, Germany
 
  Funding: Work supported by the BMBF under contract no. 05K13PEB.
Since 2008, longitudinal coupled-bunch instabilities are suppressed at DELTA by a modulation of the phase of the accelerating RF field inside the cavity. To achieve a deeper understanding of the interaction of both effects, experimental studies have been made in 2016. These studies show a quadratic dependency of the coupled-bunch mode damping rates on the phase modulation amplitude. Recently, a numerical particle tracking code has been developed to confirm the experimental results. It is based on long range wake field effects produced inside an RF cavity acting on multi particle bunches of arbitrary charge, together with phase focusing by a phase modulated accelerating field. The numerical results confirm the quadratic dependency of damping rates on the phase shift obtained in experimental studies before.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK115  
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THPAK118 Beam Dynamics Studies for a Strong-Focusing Cyclotron dipole, focusing, cyclotron, betatron 3522
 
  • J. Gerity, S. Assadi, P.M. McIntyre, A. Sattarov
    Texas A&M University, College Station, USA
 
  Results are presented from end-to-end simulation of a 100 MeV strong focusing cyclotron (SFC). The develop-ment of the high-current SFC is motivated by applica-tions for production of medical isotopes and for a proton driver for subcritical fission. It uses a novel superconducting cavity to provide suffi-cient energy gain to fully separate all turns. An arc-contour F-D doublet, trim dipole winding, and sextupole are located along each turn within the aperture of each sector dipole to control the betatron and synchrotron motion and to stabilize non-linear dynamics with high-current operation. The phase space evolution of a proton bunch in the SFC was simulated using both the code OPAL and an ad hoc Runge-Kutta tracker. Iterative optimization of the dipole, quadrupole, and sextupole fields was used to provide precise isochronicity, favorable betatron phase advance, and cancellation of dispersion in each cell.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK118  
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THPAK122 Longitudinal Coupled Bunch Instability in JLEIC HOM, impedance, electron, resonance 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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THPAK123 Updates on Collective Effects Estimations for JLEIC electron, impedance, collider, luminosity 3533
 
  • R. Li, K. E. Deitrick, T.J. Michalski
    JLab, Newport News, Virginia, USA
 
  Funding: This work is supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
JLEIC is the high luminosity and high polarization electron-ion collider (EIC) currently under active design at Jefferson Lab. It aims at high luminosity (1033~1034 cm-2s−1) for a wide range of ion species and center-of-mass energies. This luminosity performance relies sensibly on beam stability with high intensity electron and ion beam operation. The impedance budget analysis and the estimations of the single and multibunch instabilities are currently underway. In this paper, we present the update status of estimations for the longitudinal and transverse coherent instabilities, and identify areas or parameter regimes where special attentions for instability mitigations are required.
 
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THPAK131 Investigation of Two-Bunch Train Compression by Velocity Bunching bunching, electron, emittance, experiment 3548
 
  • D. Wang, Y. C. Du, W.-H. Huang, X. Liu, X.L. Su, C.-X. Tang, Q.L. Tian, L.X. Yan
    TUB, Beijing, People's Republic of China
  • H. Zhang
    Tsinghua University, Beijing, People's Republic of China
 
  Two electron beamlets, also referred as two-bunch train with adjustable time and energy spacing are popular in many applications such as two color FEL and pump-probe experiments. We investigate compression of two-bunch train via velocity bunching scheme in a traveling wave accelerator (TWA) tube by varying the phase of TWA tube in a very large range. Beam dynamics simulations show that when the phase injected into the accelerator tube for the beam is set to ≪-100 degree, velocity bunching occurs in a deep over-compression mode, where two-bunch train is continuously tunable in time and in energy space, and the emittance of each sub-bunch is also preserved. In the experiment, we use energy spectrum and defecting cavity to diagnose the train's energy space and time space respectively, the measurements demonstrated that two-bunch train through deep over-compression scheme is separated both in time and in energy space, which also agree well with the predictions.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK131  
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THPAL002 RF System Operation of High Current RFQ in ADS Project rfq, operation, coupling, LLRF 3613
 
  • L.P. Sun, R. Huang, C.X. Li, L. Lu, A. Shi, L.B. Shi, W.B. Wang, X.B. Xu, H.W. Zhao
    IMP/CAS, Lanzhou, People's Republic of China
  • Y. Hu
    TUB, Beijing, People's Republic of China
 
  Funding: Work supported by Natural Science Foundation of China, No.11505253
New RF system has been upgraded several times for high-current operation, especially for extra beam power and detuning angle. The current was increased gradually resulting in more and more frequency detuning, and an effective method is to tune the temperature of cavity to compromise detuning. Of course, the power dissipated in cavity and high intensity beam are approximately 120kW resulting in too many power modules operated in the high risk of failure. The specific analysis and simulation were introduced in detail.
 
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THPAL004 Research and Development of RF System for SC200 Cyclotron LLRF, cyclotron, simulation, acceleration 3616
 
  • G. Chen, C. Chao, G. Liu, X.Y. Long, Z. Peng, Y. Song, Y.S. Wang, C.S. Wei, M. Xu, Q. Yang, X. Zhang, Y. Zhao
    ASIPP, Hefei, People's Republic of China
  • L. Calabretta, A.C. Caruso
    INFN/LNS, Catania, Italy
  • O. Karamyshev, G.A. Karamysheva, N.A. Morozov, E. Samsonov, G. Shirkov
    JINR, Dubna, Moscow Region, Russia
 
  A 200MeV compact isochronous superconducting cyclotron, named SC200, for proton therapy is under development by collaboration of ASIPP (Hefei, China) and JINR (Dubna, Russia). The radio frequency (RF) system as one of most significant subsystems in cyclotron consists of acceleration cavity, low level RF, RF source and transmission network. SC200 has two cavities connected in the centre, which are operated at 91.5 MHz with second harmonic. To meet the required acceleration voltage, the cavities have been carefully designed with comprised choices between several aspects, such as Q factor, mechanic stability and so on. The low-level RF (LLRF) system has been implemented by using the FPGA to achieve the significant accelerating voltage with an amplitude stability of <0.2% and a phase stability of < 0.1 degree. The cavity and LLRF system have been tested outside of cyclotron, the results will be presented. For future, the commissioning of whole RF system will be started after the assembly of SC200 at the end of 2019.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL004  
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THPAL007 Upgrade of PIAVE Superconducting RFQs at INFN-Legnaro rfq, SRF, operation, superconducting-RF 3623
 
  • G. Bisoffi, E. Bissiato, D. Bortolato, F. Chiurlotto, T. Contran, E. Fagotti, A. Minarello, P. Modanese, E. Munaron, D. Scarpa
    INFN/LNL, Legnaro (PD), Italy
  • V. Andreev
    ITEP, Moscow, Russia
  • A. Bosotti, R. Paparella
    INFN/LASA, Segrate (MI), Italy
  • L.M.A. Ferreira
    CERN, Geneva, Switzerland
  • K. Kasprzak
    IFJ-PAN, Kraków, Poland
  • R.C. Pardo
    ANL, Argonne, Illinois, USA
 
  Superconducting RFQs (SRFQs), the first SC RFQs ever made operational for users, have been operated on the PIAVE SC heavy ion linac injector at INFN-Legnaro since 2006. The structure is split into two resonators and is limited to the accelerating RFQ sections. The resonators had never exceeded 80% of the design accelerating fields. In 2015, an upgrade plan started, aimed at increasing the accelerating fields, while improving their slow and fast tuning systems, repairing degraded components, imple-menting a LASER alignment method. The upgrade plan was successfully concluded in summer 2017. The resona-tors were kept stably locked for days at a field larger than the nominal one. Eventually, a test beam was accelerated successfully for 72 hours, with negligible locking issues. SRFQs entered once again routine operation in December 2017. The new features will allow to accelerate heavy ions with an A/q value as high as 8.5 (versus a former maximum A/q=7.5), allowing operation of the very first accelerated uranium beams at INFN-LNL, after the relat-ed authorizations shall have been issued.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL007  
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THPAL012 Soft Chemical Polishing and Surface Analysis of Niobium Samples niobium, SRF, linac, operation 3641
 
  • J. Conrad, L. Alff, M. Arnold, S. Flege, R. Grewe, M. Major, N. Pietralla
    TU Darmstadt, Darmstadt, Germany
  • F. Hug
    IKP, Mainz, Germany
 
  Funding: Work supported by the German Federal Ministry for Education and Research (BMBF) under Grant No. 05H15RDRBA
The Superconducting Darmstadt Linear Accelerator S-DALINAC uses twelve Niobium Cavities with a RRR of 280 which are operated at 2 K. The operating frequency is 3 GHz; the design value of the accelerating gradient is 5 MV/m. To achieve the target value of 3 x 10˄9 for Q0, different surface preparation methods were applied and systematically tested using a vertical 2 K cryostat. A well-established technique is the so called Darmstadt Soft Chemical Polishing, which consists of an ultrasonic cleaning of the cavity with ultrapure water followed by oxidizing the inner surface with nitric acid. After rinsing with water the niobium oxide layer is removed with hydrofluoric acid in a separate second step. Finally the structure is rinsed and then dried by a nitrogen flow. Until now each cavity in operation was chemically treated with a proven record of success. In order to understand and to optimize the process on the niobium surface, systematic tests with samples were performed and analyzed using material science techniques like SEM, SIMS and EDX. We will report on the results of our research and we will give a review on our experiences with varied chemical procedures.
 
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THPAL015 Evaluation of superconducting characteristics on the thin-film structure by NbN and Insulator coatings on pure Nb substrate embedded, SRF, radio-frequency, electromagnetic-fields 3653
 
  • R. Katayama, Y. Iwashita, H. Tongu
    Kyoto ICR, Uji, Kyoto, Japan
  • C.Z. Antoine
    CEA/IRFU, Gif-sur-Yvette, France
  • A. Four
    CEA/DRF/IRFU, Gif-sur-Yvette, France
  • H. Hayano, T. Kubo, T. Saeki
    KEK, Ibaraki, Japan
  • H. Ito
    Sokendai, Ibaraki, Japan
  • R. Ito, T. Nagata
    ULVAC, Inc, Chiba, Japan
  • H. Oikawa
    Utsunomiya University, Utsunomiya, Japan
 
  Funding: The work is supported by JSPS KAKENHI Grant Numbers JP17H04839, JP26600142 and the Collaborative Research Program of ICR Kyoto University (grant 2016-8, 2017-8, 2017-9).
In recent years, it is pointed out that the maximum accelerating gradient of a superconducting RF cavity can be pushed up by coating the inner surface of cavity with a multilayer thin-film structure that consists of alternate insulator and superconductive layers. In this structure, the principal parameter that limits the performance of the cavity is the critical magnetic field or effective Hc1 at which vortices start penetrate into the first superconductor layer. We made a sample that has NbN/SiO2 thin-film structure on pure Nb substrate by DC magnetron sputtering method. In this paper, we will report the measurement results of effective Hc1 of the sample by the third-harmonic voltage method.
 
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THPAL018 DQW HOM Coupler Design for the HL-LHC HOM, impedance, simulation, GUI 3663
 
  • J.A. Mitchell
    Lancaster University, Lancaster, United Kingdom
  • G. Burt
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • R. Calaga
    CERN, Geneva, Switzerland
  • S. Verdú-Andrés, B. P. Xiao
    BNL, Upton, Long Island, New York, USA
 
  HOMs in the DQW crab cavity can produce large heat loads and beam instabilities as a result of the high current HL-LHC beams. The DQW crab cavity has on-cavity, coaxial HOM couplers to damp the HOMs whilst providing a stop-band response to the fundamental mode. Manufacturing experience and further simulations give rise to a set of desirable coupler improvements. This paper will assess the performance of the current HOM coupler design, present operational improvements and propose an evolved design for HL-LHC.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL018  
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THPAL025 New Drift-Tube Linac RF Systems at LANSCE DTL, controls, LLRF, detector 3680
 
  • J.T.M. Lyles, R.E. Bratton, M.S. Prokop, D. Rees
    LANL, Los Alamos, New Mexico, USA
 
  Funding: Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE-AC52-06NA25396.
LANSCE has restored the proton drift-tube linac (DTL) to high-power capability after the original RF-power tube manufacturer could no longer supply devices that consistently met our high-average power requirement. Thales TH628L Diacrodes® now supply RF power to three of the four DTL tanks. These tetrodes reused the existing infrastructure including water-cooling systems, coaxial transmission lines, high-voltage power supplies and capacitor banks. Each transmitter uses a combined pair of power amplifiers to produce up to 3- MW peak and 360- kW of mean power. A new intermediate power amplifier was simultaneously developed using a TH781 tetrode. Design and prototype testing of the high-power stages was completed in 2012, with commercialization following in 2013. Each installation was accomplished during a 4 to 5 month beam outage each year from 2014-2016. A new digital low-level RF control system was designed, built and placed into operation in 2016. The interaction of the dual power amplifiers, the I/Q LLRF, and the DTL cavities provided many challenges that were overcome. The replacement RF systems have completely met our accelerator requirements.
 
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THPAL028 Commissioning of the Bunch-by-Bunch Feedback System in the MAX IV 1.5 GeV Ring feedback, storage-ring, kicker, synchrotron 3688
 
  • D. Olsson, Å. Andersson, F.J. Cullinan, P.F. Tavares
    MAX IV Laboratory, Lund University, Lund, Sweden
 
  The MAX IV 1.5 GeV ring is an electron storage ring for production of synchrotron light in the IR to soft X-ray spectral range. The ring will deliver light to its first users during 2018. Bunch-By-Bunch (BBB) feedback has been needed to suppress coupled-bunch mode instabilities (CBMIs), and the feedback has this far been provided in all three planes by a single stripline kicker. This is done by combining the horizontal and vertical baseband feedback signals with the longitudinal feedback signal that is upconverted to the 150 MHz - 250 MHz range. The combined signal is then fed to two stripline electrodes. The layout of the BBB feedback system in the MAX IV 1.5 GeV ring is presented in this paper. Results from instability studies are also discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL028  
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THPAL029 Comparison of Horizontal and Vertical Electropolishing Methods using Niobium Single-Cell Coupon Cavity cathode, niobium, accumulation, experiment 3692
 
  • V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi
    MGH, Hyogo-ken, Japan
  • H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
    KEK, Ibaraki, Japan
 
  Horizontal electropolishing (HEP) is an established tech-nique for surface treatment of niobium accelerating cavi-ties. Vertical electropolishing (VEP), in which the cavity is electropolished in the vertical posture, is in R&D phase for parameter optimization. We performed HEP and VEP of a niobium single-cell coupon cavity to compare the effect of both the methods on surface state and removal at different positions of the cavity. HEP was performed at STF, KEK with the standard EP parameters. VEP was performed at Marui Galvanizing Company with a cathode called 'Ninja cathode' that can be rotated during the VEP process. The optimized cathode design and VEP parame-ters resulted in symmetric removal as obtained with the HEP technique and yielded a smooth inner surface of the entire cavity  
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THPAL030 Vertical Electropolishing of 1.3 GHz Niobium 9-Cell Cavity: Parameter Study and Cavity Performance cathode, accumulation, niobium, linac 3695
 
  • V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi
    MGH, Hyogo-ken, Japan
  • H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
    KEK, Ibaraki, Japan
  • H. Ito
    Sokendai, Ibaraki, Japan
  • H. Oikawa
    Utsunomiya University, Utsunomiya, Japan
 
  VEP parameters and process have been already optimized with single-cell 1.3 GHz niobium cavity at Marui Galva-nizing Company working in collaboration with KEK. A unique cathode called 'Ninja cathode' with an optimized shape was applied to single-cell cavities. The cathode was effective to stop the bubble accumulation in the upper half-cell of the cavity and yielded smooth surface and uniform removal in the cell. This work shows parameter study with the Ninja cathode and a 9-cell coupon cavity which contains totally 9 coupons and viewports in the first, fifth, and ninth cells. Effects of temperature and acid flow in the cathode housing were studied using coupon currents and by observing bubbles through the viewports. The adequate parameters found with 9-cell coupon cavity were applied on a 9-cell cavity to be tested in vertical cryostat. The VEP and vertical test results are reported.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL030  
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THPAL031 Development of a Vertical Electropolishing Facility for Nb 9-Cell Cavity niobium, cathode, controls, site 3699
 
  • Y.I. Ida, V. Chouhan, K.N. Nii
    MGH, Hyogo-ken, Japan
  • akabori. Akabori, G.M. Mitoya, K. Miyano
    HKK, Morioka, Japan
  • Y. Anetai, F. Takahashi
    WING. Co.Ltd, Iwate-ken, Japan
  • H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
    KEK, Ibaraki, Japan
 
  Our Nb accelerating cavity vertical electropolishing (VEP) facility development group which was led by KEK started single-cell VEP facility development from 2014. This is based on horizontal electropolishing (HEP) techniques developed by KEK over 10 years and stainless steel electropolishing techniques developed by Marui over 30 years. We have reported results of Nb cavity VEP with Ninja cathode so far. In order to achieve international linear collider (ILC) construction, it is said that cost reduction and productivity improvement are necessary, however in case of 9-cell cavity, uniform inner surface polishing is difficult, as well known to predecessors. In this article, we will present the first report of VEP facility development from initial transparent plastic mock-up to improvement for Nb 9-cell cavity.  
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THPAL032 1.3GHz Nb Single-Cell Cavity Vertical Electropolishing with Ninja Cathode and Results of Vertical Test cathode, accelerating-gradient, experiment, factory 3702
 
  • K.N. Nii, V. Chouhan, Y.I. Ida, T.Y. Yamaguchi
    MGH, Hyogo-ken, Japan
  • H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
    KEK, Ibaraki, Japan
  • H. Ito
    Sokendai, Ibaraki, Japan
  • H. Oikawa
    Utsunomiya University, Utsunomiya, Japan
 
  Marui Galvanizing Co., Ltd. has been developing Nb cavity vertical electropolishing (VEP) technologies in collaboration with KEK. Until now, we reported that inner surface state and removal thickness distribution were improved in VEP with Ninja cathode and coupon cavity. This time, a 1.3GHz Nb single-cell cavity VEP with Ninja cathode was performed in Marui and vertical test was performed in KEK. The inner surface state and removal thickness distribution were satisfactory. And as a result of vertical test, the accelerating gradient of 32MV/m (Q0=8.0E9) was achieved.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL032  
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THPAL034 Dynamic Tuner Development for Medium β Superconducting Elliptical Cavities linac, operation, SRF, superconducting-RF 3709
 
  • C. Contreras-Martinez, P.N. Ostroumov
    FRIB, East Lansing, USA
  • E. Borissov, S. Cheban, Y.M. Pischalnikov, V.P. Yakovlev, J.C. Yun
    Fermilab, Batavia, Illinois, USA
 
  Funding: Work supported by U.S. DOE SCGSR program under contract number DE-SC0014664, Michigan State University, and Fermi Research Alliance under contract N. DEAC02-07CH11959 with the U.S. DOE
The Facility for Rare Isotope Beams (FRIB) is developing a 5-cell 644 MHz βopt=0.65 elliptical cavity for a future linac energy upgrade to 400 MeV/u for the heaviest uranium ions. Superconducting elliptical cavities operated in continuous wave, such as the ones for FRIB, are prone to microphonics which can excite mechanical modes of the cavities. It has been shown that the detuning due to microphonics can be mitigated with the use of piezo actuators (fast tuner) as opposed to the costly option of increasing the input RF power. The FRIB slow/fast dynamic tuner will be based on the Fermilab experience with similar tuners like those developed for the linac coherent light source (LCLS) II and proton improvement plan (PIP) II. This paper will present the results of tuner properties on the bench.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL034  
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THPAL035 Design of β=0.65, 5 Cells, 644 MHz Elliptical Cavity for FRIB Upgrade linac, cryomodule, niobium, operation 3712
 
  • M. Xu, C. Compton, C. Contreras-Martinez, W. Hartung, S.H. Kim, S.J. Miller, P.N. Ostroumov, A.S. Plastun, J.T. Popielarski, L. Popielarski, M.A. Reaume, K. Saito, A. Taylor, J. Wei, T. Xu, Q. Zhao
    FRIB, East Lansing, USA
  • I.V. Gonin, T.N. Khabiboulline, V.P. Yakovlev
    Fermilab, Batavia, Illinois, USA
 
  Funding: Work supported by the U.S. DOE Office of Science under Cooperative Agreement DE-SC0000661 and the NSF under Cooperative Agreement PHY-1102511, the State of Michigan and Michigan State University.
The superconducting (SC) linac of the Facility for Rare Isotope Beams (FRIB) under construction will deliver 200 MeV/u, 400 kW beam to the target for producing rare isotopes at Michigan State of University (MSU). For further beam energy upgrade, we have designed the β = 0.65, 5 cells, 644 MHz elliptical cavity. The beam energy can be upgraded to 400 MeV/u by installing 11 cryomodules to the available space in the FRIB tunnel.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL035  
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THPAL036 Nb3Sn Thin Films for the Production of Higher Gradient SRF Cavities at Reduced Cost niobium, SRF, superconductivity, site 3716
 
  • S.A. Kahn, M.A. Cummings
    Muons, Inc, Illinois, USA
  • E.Z. Barzi, D. Turrioni
    Fermilab, Batavia, Illinois, USA
  • S. Falletta
    Politecnico di Torino, Torino, Italy
  • A. Kikuchi
    NIMS, Tsukuba, Ibaraki, Japan
 
  High gradient superconducting cavities (SRF) will be needed for future accelerators. The higher gradient can achieve the high energy with fewer cavities. However the accelerating field of niobium cavities is limited by the peak magnetic field on the cavity surface. Cavities coated with Nb3Sn have a significantly larger Hc2 allowing the cavity to achieve a larger gradient. Measurements of Nb3Sn coated cavities have achieved about half the theoretical predicted gradient. It is possible to improve Nb3Sn plated cavity performance.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL036  
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THPAL038 Phase Grouping of Larmor Electrons by a Synchronous Wave in Controlled Magnetrons controls, electron, operation, cathode 3723
 
  • G.M. Kazakevich, R.P. Johnson
    Muons, Inc, Illinois, USA
  • V.A. Lebedev, V.P. Yakovlev
    Fermilab, Batavia, Illinois, USA
 
  A simplified analytical model based on the charge drift approximation has been developed. It considers the resonant interaction of the synchronous wave with the flow of Larmor electrons in a magnetron. The model predicts stable coherent generation of the tube above and below the threshold of self-excitation. This occurs if the magnetron is driven by a sufficient resonant injected signal (up to -10 dB). The model substantiates precise stability, high efficiency and low noise at the range of the magnetron power control over 10 dB by variation of the magnetron current. The model and the verifying experiments with 2.45 GHz, 1 kW magnetrons are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL038  
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THPAL039 Improved Magnetron Stability and Reduced Noise in Efficient Transmitters for Superconducting Accelerators controls, SRF, feedback, experiment 3726
 
  • G.M. Kazakevich, R.P. Johnson
    Muons, Inc, Illinois, USA
  • V.A. Lebedev, V.P. Yakovlev
    Fermilab, Batavia, Illinois, USA
 
  State of the art high-current superconducting accelerators require efficient RF sources with a fast dynamic phase and power control. This allows for compensation of the phase and amplitude deviations of the accelerating volt-age in the Superconducting RF (SRF) cavities caused by microphonics, etc. Efficient magnetron transmitters with fast phase and power control are attractive RF sources for this application. They are more cost effective than traditional RF sources such as klystrons, IOTs and solid-state amplifiers used with large scale accelerator projects. However, unlike traditional RF sources, controlled magnetrons operate as forced oscillators. Study of the impact of the controlling signal on magnetron stability, noise and efficiency is therefore important. This paper discusses experiments with 2.45 GHz, 1 kW tubes and verifies our analytical model which is based on the charge drift approximation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL039  
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THPAL041 Power Coupler Design for the LUCRECE Project simulation, SRF, coupling, linac 3732
 
  • H. Guler, D. Auguste, J. Bonis, O. Bouras, M. El Khaldi, W. Kaabi, P. Lepercq
    LAL, Orsay, France
 
  The LUCRECE project aims at developing an elementary RF system (cavity, power source, LLRF and controls) suitable for continuous (CW) operation at 1.3 GHz. This effort is made in the framework of the advanced and compact FEL project LUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation), using superconducting linac technology for high repetition rate and multi-user operation (www.lunex5.com). In this context, based on its large experience on coupler design and RF conditioning, LAL Laboratory is in charge of the design and the fabrication of RF couplers that could operate at up to 15-20 kW in CW mode. For this purpose, geometry based on CORNELL 65kW CW couplers will me modified to fulfil the LCLS2 type cavity with the high necessary coupling level. Electromagnetic simulations and optimisation and associated thermal heating will be discussed. Methods to decrease the thermal impact, and strategy for RF conditioning will be considered.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL041  
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THPAL042 Injection Locked 1497 MHz Magnetron injection, superconducting-cavity, site, medical-accelerators 3736
 
  • M.L. Neubauer, A. Dudas, S.A. Kahn
    Muons, Inc, Illinois, USA
  • R.A. Rimmer, H. Wang
    JLab, Newport News, Virginia, USA
 
  A novel injection-locked 1497 MHz 13 kW AM magnetron design is presented. The anode design to minimized eddy currents due to the changing magnetic field is presented. Thermal calculations of two design options are also presented. An extra degree of freedom in the anode construction is made possible by the fact that the magnetron is injection locked. This fact presents some additional design details that can be utilized in the cooling network for the magnetron anode.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL042  
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THPAL045 Determination of the Electron Bunch Length With Third Harmonic Cavity for the Taiwan Photon Source operation, simulation, SRF, electron 3745
 
  • Z.K. Liu, F.Y. Chang, L.-H. Chang, M.H. Chang, S.W. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, C.H. Lo, Ch. Wang, M.-S. Yeh, T.-C. Yu
    NSRRC, Hsinchu, Taiwan
 
  The Taiwan Photon Source (TPS) is a modern 3 GeV low emittance light source with RMS bunch lengths of about 3 mm at a beam current of 500 mA and operating gap voltage of 3.2 MV. With a higher harmonic cavity, we could increase the Touschek lifetime and lower the heat load of in-vacuum undulators by lengthening the bunch lengths. Preliminary studies show that for full and uni-form fill patterns, the bunch lengths could be increased by a factor of four. However, this calculation ignores phase transient effects and may overestimate the effect of harmonic cavities. A multi-bunch, multi-particle tracking method has been developed to determine the bunch lengths for non-uniform fill patterns, which also takes phase transient effects into account and the expected maximum bunch lengthening factor for different TPS operation conditions are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL045  
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THPAL060 Advanced Modeling of Klystrons by the Tesla-Family of Large-Signal Codes klystron, impedance, experiment, simulation 3785
 
  • I.A. Chernyavskiy, D.K. Abe, B. Levush, A.N. Vlasov
    NRL, Washington, DC, USA
  • T.M. Antonsen
    UMD, College Park, Maryland, USA
  • T.M. Antonsen
    Leidos Corp, Billerica, MA, USA
  • J. Rodgers
    Naval Research Laboratory (NRL), Washington, USA
 
  Funding: US Office of the Naval Research
Klystrons and IOTs are widely used or proposed to be used in accelerators as high-power RF sources. Development and optimization of klystron and IOT designs is aided by the use of different simulation tools, including highly efficient large-signal codes. We present an overview of the advances in the code development and modeling using Naval Research Laboratory (NRL) set of TESLA-family of large-signal codes, suitable for the modeling of single-beam and multiple beam klystrons and IOTs. Original 2D large-signal algorithm of the code TESLA* was developed for the modeling of klystrons based on (relatively) high Q resonators and is applicable to the multiple-beam devices in an approximation of identical beams/beam-tunnels. Parallel extension of TESLA algorithm (code TESLA-MB**) enabled an accurate, quasi-3D modeling of multiple-beam devices with non-identical beams/beam-tunnels. Recently developed more general TESLA-Z algorithm*** is based on the impedance matrix approach and enabled geometry-driven large-signal modeling. Examples of applications of TESLA-family of codes to the modeling of advanced single-beam and multiple-beam klystrons (and IOTs) will be presented.
*A.N. Vlasov, et al,IEEE TPS, v.30(3), 1277-1291, June 2002
**I.A. Chernyavskiy, et al.,IEEE TPS, v.36(3), 670-681, June 2008
***I.A. Chernyavskiy, et al.,IEEE TED, v.64(2), 536-542, Feb 2017
 
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THPAL061 Simulation of Pulsed Temperature Rise in Cryogenic Copper RF Cavity Achieving a Very High Accelerating Field simulation, accelerating-gradient, coupling, cryogenics 3788
 
  • T. Tanaka, K. Hayakawa, Y. Hayakawa, K. Nogami, T. Sakai, Y. Sumitomo
    LEBRA, Funabashi, Japan
 
  A cryogenic C-band photocathode RF electron gun cavity has been studied at Nihon University LEBRA in cooperation with KEK. The RF properties of a cold model measured at 20 K have shown good agreement with those expected from computer simulations using the cavity surface resistance predicted by the theory of the anomalous skin effect. Recent studies on the vacuum RF breakdown at high electric fields suggest that the temperature in the cavity surface during the high power RF pulse has a significant effect on the behavior of the breakdown rate. In order to investigate the breakdown property of the cryogenic cavity aiming at a very high accelerating field with as low breakdown rate as possible, one-dimensional simulations of the temperature rise in the cavity surface have been done for various combinations of the RF pulse width and the peak input RF power. The evaluation will be taken into consideration in the design of a new high power cryogenic cavity that has basically the same configuration with the cold model.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL061  
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THPAL063 RF and Thermo-Mechanical Considerations in Designing the Waveguide Iris Coupler for the Drift Tube Linac in the ORNL Spallation Neutron Source GUI, DTL, simulation, vacuum 3796
 
  • S.W. Lee, Y.W. Kang
    ORNL, Oak Ridge, Tennessee, USA
 
  Funding: This work was supported by SNS through UT Battelle, LLC, under contract DE AC05 00OR22725 for the U.S.DOE
The Spallation Neutron Source (SNS) employs tapered ridge waveguide iris couplers to power six drift tube linac (DTL) cavity structures with pulsed RF systems using 2.5MW klystrons at 402.5MHz. All DTL iris couplers have been operating continuously for more than a decade without replacement. Transferring high RF energy to the cavities requires robust RF and mechanical performances with respect to power dissipation, electrical breakdown, and vacuum pressure. Considering the upcoming full 1.4MW operation and the future proton power upgrade (PPU) project, the structural design and the material selection needed to be reviewed for potential spare manufacturing. The existing design and the modified design with improvements to the coupler have been numerically studied. For the study, 3D models were used for RF and structural characterizations of the waveguide iris couplers on the DTL cavity. RF and thermo-mechanical co-simulations were performed to assess the effects of using the different materials and the structural modification.
 
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THPAL064 Burst-Mode UV Enhancement Cavity for Laser-Assisted Hydrogen Ion Beam Stripping at SNS laser, resonance, 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.
 
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THPAL065 Improving the Work Function of Nitrogen-Doped Niobium Surfaces for SRF Cavities by Plasma Processing plasma, niobium, SRF, accelerating-gradient 3802
 
  • K.E. Tippey, R. Afanador, M. Doleans, S.-H. Kim, J.D. Mammosser, C.J. McMahan
    ORNL, Oak Ridge, Tennessee, USA
  • M. Martinello
    Fermilab, Batavia, Illinois, USA
 
  Funding: DOE research grant FWP-ERKCSA2; DOE contract DE-AC05-00OR22725
Work function and surface chemistries of SiC-polished, electropolished, and nitrogen-doped niobium coupons were analyzed before and after plasma processing using a neon-oxygen gas mixture. These studies represent an initial enquiry into the feasibility of applying the plasma processing technique designed at ORNL for the Spallation Neutron Source (SNS) to the nitrogen-doped Nb cavities for the Coherent Light Source II (LCLS-II). Work function of all measured samples was increased after plasma processing, which indicates the strong potential of the plasma processing technique as a tool for increasing the accelerating gradient of nitrogen-doped cavities.
 
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THPAL067 Room Temperature Measurements of Higher Order Modes for the SPS Prototype RF-Dipole Crabbing Cavity HOM, dipole, simulation, luminosity 3805
 
  • S.U. De Silva, J.R. Delayen, H. Park
    ODU, Norfolk, Virginia, USA
  • P. Berrutti
    Fermilab, Batavia, Illinois, USA
  • N.A. Huque, H. Park
    JLab, Newport News, Virginia, USA
 
  LHC High Luminosity Upgrade will be developing two local crabbing systems to increase the luminosity of the colliding bunches at the ATLAS and CMS experiments. One of the crabbing systems uses the rf-dipole cavity design that will be crabbing the beam in the horizontal plane. The fully integrated crabbing cavity has two higher order mode couplers in damping those excited modes. Currently two sets of HOM couplers have been fabricated at Jefferson Lab for prototyping and testing with the LARP crabbing cavities. This paper presents the measurements of the higher order modes with the prototype HOM couplers carried out at room temperature.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL067  
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THPAL070 Multi-Physics Analysis of Two Bunchers for CIFNEF simulation, beam-transport, target, neutron 3815
 
  • Q.Y. Tan, M.J. Easton, Q. Fu, P.P. Gan, H.P. Li, Y.R. Lu, Z. Wang
    PKU, Beijing, People's Republic of China
 
  CIFNEF(Compact Intense Fast NEutron Facility) project will accelerate and deliver a 5 MeV deuteron beam to the targets to produce high-intense neutrons. A 2.5 MHz pulsed deuteron beam with bunch width within 2 ns is needed on the targets at last. To fulfill the special requirements of the beam dynamics, two types of bunchers are adopted in the CIFNEF. One is a 10.156 MHz buncher used in the low energy beam transport (LEBT) line to longitudinally focus the 50 keV deuteron beam to the RFQ longitudinal acceptance with 4 kV effective voltage. A lumped element model is adopted because of the low frequency and it consists of an inductance coil in parallel with the capacitance of drift tube. The other one is an 81.25 MHz buncher used in the high energy beam transport (HEBT) line to longitudinally focus the 5 MeV deuteron beam to 2 ns. A QWR cavity with 2-gaps is used to provide 150 kV effective voltage. Thermal and structural analyses have been carried out on these two bunchers. Details of simulations of these two bunchers are presented and discussed in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL070  
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THPAL074 Numerical Studies of Normal Conducting Deflecting Cavity Designs for the ELBE Accelerator HOM, electron, experiment, impedance 3824
 
  • T.G. Hallilingaiah, U. van Rienen
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
  • A. Arnold, U. Lehnert, P. Michel
    HZDR, Dresden, Germany
 
  Currently, in the electron linac ELBE there is a single beam line. Therefore, at any given time only single user can use the beam. Moreover, as different user experiments require distinct beam intensity settings, not all the experiments fully utilize the 13 MHz CW beam capability of the facility. To utilize the full beam capacity, multiple beam lines can be established by using an array of transverse deflecting structures. For that, an RF cavity was the design choice due to its inherent advantages with respect to repeatability of the kick voltage amplitude and phase, and the possibility of CW operation in the MHz range. Potential design candidates are the CEBAF RF separator, the three proposed crab cavities for the HL-LHC upgrade project, and a novel NC deflecting cavity design. In this comparative study, the figures of merit of the cavities are computed from electromagnetic field simulations for a transverse voltage of 300 kV. This comparative study supported our selection of the deflecting cavity design for ELBE.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL074  
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THPAL076 Experimental Methods for the Assessment of NEG Pumps Working in Dust-Sensitive Environments vacuum, SRF, experiment, background 3828
 
  • T. Porcelli, E. Maccallini, P. Manini, M. Mura, M.F. Urbano
    SAES Getters S.p.A., Lainate, Italy
 
  NEG pumps have been widely adopted by many accelerator facilities since decades. However, their use in dust-sensitive areas - such as superconductive radio frequency (SRF) cavities - has always been limited by concerns about accidental dust emission, which could induce detrimental field emission. As future machines will necessarily rely on highly-efficient SRF cavities, able to supply very high accelerating gradients, requirements in terms of particle release from vacuum components (e.g., pumps and valves) are becoming more and more stringent. At the same time, achieving stable ultra-high vacuum conditions is crucial, as condensed residual gas might also be a potential source of field emission. At present, a unified standard procedure to assess dust generation and propagation along a machine is still missing and discussions are ongoing in the vacuum community. Recent experimental measurements demonstrated the compatibility of sintered NEG pumps with ultra-clean environments, due to their intrinsic very low dust release. In parallel, in-situ tests performed at different accelerator facilities showed absence of dust contamination from NEGs and no impact on cavities efficiency.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL076  
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THPAL080 Parallel-Feed SRF Accelerator Structures SRF, coupling, simulation, impedance 3835
 
  • P.B. Welander, Z. Li, M.H. Nasr, S.G. Tantawi
    SLAC, Menlo Park, California, USA
 
  Funding: This work is supported by the Department of Energy, Laboratory Directed Research and Development program at SLAC National Accelerator Laboratory, under contract DE-AC02-76SF00515.
Development of SRF accelerator technology that enables both higher gradient and higher efficiency is crucial for future machines. While much of the recent R&D focus has been on materials and surface science, our aim is to optimize the cavity geometry to maximize performance with current materials. The recent demonstration of a highly efficient parallel-feed NCRF structure at SLAC has served as a proof-of-concept. Applied to SRF, such a structure could dramatically reduce power consumption while boosting the achievable gradient. Instead of coupled elliptical cells, our structure employs isolated reentrant cells. To feed RF power to the cavities, each cell is directly coupled to an integrated manifold. The structure is made in two parts, split along the beam axis, which are then joined. Such a structure has been fabricated from bulk Cu and tested at SLAC - designed for X-band, it operates at a record gradient of 150 MV/m. Adapting to SRF at 1.3 GHz and fabricating from Nb, such a cavity could achieve more than 50% lower RF loss and 40% higher gradient compared to the TESLA cavity. We will describe our simulations and propose an experimental roadmap for demonstrating this technology.
 
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THPAL081 A 3 GHz SRF Reduced-beta Cavity for the S-DALINAC linac, SRF, operation, electron 3838
 
  • D.B. Bazyl, H. De Gersem, W.F.O. Müller
    TEMF, TU Darmstadt, Darmstadt, Germany
  • J. Enders, S. Weih
    TU Darmstadt, Darmstadt, Germany
 
  Funding: Work supported by DFG through GRK 2128
In order to reduce the energy spread and to be able to use a 200 keV spin-polarized electron source, the initial part of the injector linac of the superconducting Darmstadt electron linear accelerator S-DALINAC needs to be upgraded. The decisions on the cavity type, number of cells and value of geometric beta are motivated. The main part of this work is dedicated to the mechanical design of the cavity. A precise evaluation of the mechanical characteristics of an SRF cavity is necessary during the design stage. The dependence of the resonant frequency of the fundamental mode on external mechanical loads needs to be investigated for developing the tuning procedures. The results of the multiphysics simulations and of the optimization of the mechanical design are presented.
 
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THPAL084 An X-Band Lineariser for the CLARA FEL FEL, simulation, wakefield, klystron 3848
 
  • L.S. Cowie, A.D. Brynes, J.K. Jones, A.E. Wheelhouse, P.H. Williams
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • R. Apsimon, G. Burt, W.L. Millar
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • Ö. Mete
    UMAN, Manchester, United Kingdom
  • A.J. Moss
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
 
  The CLARA FEL at Daresbury Laboratory will employ four S-band linacs to accelerate electron bunches to 250 MeV/c. In order to compress the bunch sufficiently to achieve peak currents suitable for FEL lasing, one must compensate for curvature imprinted on the longitudinal phase space of the bunch. For CLARA a harmonic RF linearization system has been designed to achieve this requirement. The linearization will be achieved by an X-band travelling wave cavity of the PSI/CERN design, which incorporates wake-field monitoring of the bunch position. A five-axis mover will align the cavity to the beam axis. Pulse compression of a 6 MW klystron pulse will provide the required power to achieve a 30 MV/m operational gradient.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL084  
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THPAL085 High Power RF Conditioning on CLARA vacuum, linac, solenoid, multipactoring 3852
 
  • L.S. Cowie, D.J. Scott
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • G. Burt, W.L. Millar
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
 
  The CLARA accelerator at Daresbury Laboratory will have 8 normal conducting RF cavities. Automating the high power RF conditioning of these cavities will mean a repeatable, research-lead process is followed. An auto-mated algorithm has been written in Python. A prototype algorithm was used to condition the first CLARA travel-ling wave linac in October 2017. The linac was success-fully conditioned over approximately 12 million pulses up to 27 MW for a 750 ns pulse. A more complex and robust algorithm was used to re-condition the standing wave 10 Hz photoinjector after a cathode change. The photoinjec-tor was conditioned to 10 MW for a 2.5 μs pulse in Feb-ruary 2018 over 2.1 million pulses. Conditioning method; differences for travelling and standing wave structures; difficulties and interesting phenomena are all discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL085  
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THPAL086 Superconducting Thin Film RF Measurements SRF, vacuum, niobium, operation 3856
 
  • P. Goudket, L. Bizel-Bizellot, L. Gurran, O.B. Malyshev, S.M. Pattalwar, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • G. Burt, L. Gurran
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • P. Goudket, T. Junginger, O.B. Malyshev, S.M. Pattalwar, R. Valizadeh
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • L. Gurran, T. Junginger
    Lancaster University, Lancaster, United Kingdom
 
  As part of an ongoing programme of SRF Thin Films development, a radiofrequency (RF) cavity and cryostat dedicated to the measurement of superconducting coatings at GHz frequencies was designed to evaluate surface resistive losses on a flat sample. The resonator has now been used for measurements on Thin Film samples. Results from a test on a sample previously tested at Cornell University are presented. In order to simplify the measurements and achieve a faster turnaround, the experiment will be moved to a new cryostat fitted with a cryocooler. This will limit the measurements to low power only, but will allow a much faster sorting of samples to identify those that would benefit from further investigation. A description of the system and initial results will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL086  
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THPAL089 Design, Assembly and Commissioning of a New Cryogenic Facility for Complex Superconducting Thin Film Testing SRF, experiment, site, operation 3859
 
  • O.B. Malyshev, L. Bizel-Bizellot, K.D. Dumbell, P. Goudket, N. Pattalwar, S.M. Pattalwar, P. Pizzol, P.A. Smith, R. Valizadeh, S. Wilde
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • P. Pizzol
    The University of Liverpool, Liverpool, United Kingdom
 
  An ongoing study on the superconducting thin films for future superconducting RF cavities requires an intense testing of various superconducting properties. We have designed, built and tested a new facility for complex superconducting thin film testing that includes: (1) RRR measurement with and without magnetic field, (2) planar and (3) tubular magnetic field penetration experiments, (4) a superconducting coaxial resonator for bulk niobium and superconducting thin film characterisation. The system is based on a closed cycle refrigerator, eliminating the need for liquid helium, thus making it simple and safe to operate. The details of the design and commissioning will be presented at the conference.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL089  
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THPAL101 Longitudinal Effects of Trapped Homs in Shanghai Coherent Light Facility HOM, linac, impedance, FEL 3872
 
  • J.J. Guo, Q. Gu, H.T. Hou, J.H. Tan, M. Zhang
    SINAP, Shanghai, People's Republic of China
 
  Funding: Shanghai Institute of Applied Physics, Chinese Academy of Sciences
Shanghai Coherent Light Facility (SCLF), a superconducting accelerated structure-baesd FEL device, is now under development at Shanghai Institute of Applied Physics, Chinese Academy of Sciences. We investigate effects of cryogenic losses caused by trapped longitudinal high order modes (HOM). Results of calculations are presented for losses caused by HOMs excitation in the acceleration RF system of the continues-wave (CW) linac of SCLF.
 
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THPAL108 In-Situ Characterization of Normal Conducting RF Cavities in Solaris Light Source Storage Ring HOM, storage-ring, simulation, ISOL 3891
 
  • P.B. Borowiec, A.I. Wawrzyniak
    Solaris National Synchrotron Radiation Centre, Jagiellonian University, Kraków, Poland
  • J. Björklund Svensson
    Lund University, Division of Atomic Physics, Lund, Sweden
 
  The SOLARIS 1.5 GeV storage ring is equipped with two 100 MHz active cavities and two 3rd harmonic passive cavities. They are in operation since 2015. For control of their respective working points, knowledge about cavity voltage and higher order mode (HOM) frequency spec-trum is mandatory. After their installation in the storage ring and connection of the RF feeder to a high power isolator and a transmitter, the influence of the external elements on the quality factor and the HOM spectrum should be verified with respect to simulations of a simpli-fied model of a stand-alone cavity. This paper will pre-sent results of in-situ cavity measurements to qualify the HOM placement and their quality factor. HOM meas-urements have been performed in the range 100 MHz to 1.3 GHz for active cavities and 300 MHz to 1.5 GHz for 3rd harmonic cavities at three different temperatures under ultra-high vacuum conditions for each cavity separately. The measurement and analysis methodology will also be presented  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL108  
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THPAL109 The New 118 MHz Cavity for RF Development Activities of the RF for Accelerator Laboratory at SLRI simulation, HOM, coupling, impedance 3895
 
  • N. Juntong, K. Kittimanapun, P. Sunwong
    SLRI, Nakhon Ratchasima, Thailand
  • A. Sutchada
    Walailak University, Nakhon Si Thammarat, Thailand
 
  The RF for accelerator laboratory is established at SLRI to perform RF related development activities of the current light source and the future synchrotron light facility in Thailand. One of activities is to build an in-house RF cavity. It will be used for testing of RF amplifier unit and the developed LLRF system. The cavity is a nose-cone pill-box cavity operating at 118 MHz and aiming at 100 kV gap voltage. Details of designing in particular the inner surface profile, the RF properties, the higher order modes properties, the RF power coupler, and the tuning mechanism will be presented with the manufacturing timeline.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL109  
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THPAL110 High-Power RF Test of Coaxial Couplers for the Injection Linac of XiPAF vacuum, multipactoring, coupling, linac 3899
 
  • Y. Lei, X. Guan, R. Tang, X.W. Wang, Q.Z. Xing, H.Y. Zhang, S.X. Zheng
    TUB, Beijing, People's Republic of China
  • J. Jiang, H. Li, C. Yu
    Beijing Aerospace Guagntong Technology Co., Beijing, People's Republic of China
 
  For the high-power RF test of the coaxial couplers which will be employed on the linac injector of the XiPAF (Xi'an Proton Application Facility) project, a high-power conditioning cavity was designed and manufactured [1]. There are some optimized aspects on the cavity and couplers to obtain better RF performance during the high-power testing process. The traveling-wave test and full-power-reflection test were executed to check whether the coupler can afford the enough power level for the linac operation, and whether only one coupler can afford the total power for the RFQ. The construction of the testing stand, optimization of RF parameters and results of high-power RF test are presented in this paper.  
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THPAL113 The Design of 1 MeV Proton LINAC Operating in CW linac, proton, simulation, resonance 3905
 
  • N.V. Avreline
    TRIUMF, Vancouver, Canada
 
  Experimental results and computer simulations of electrodynamic and thermodynamic characteristics are presented for an accelerating structure that is excited in the TM010 mode and that has the accelerating channel of URAN-1M located in the diametric plane. The idea of using this structure in the particle accelerator URAN-1M, located at the Baikov Institute of Metallurgy and Materials Science, with the goal of increasing the average beam current is explored.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL113  
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THPAL118 Critical Fields of SRF Materials niobium, FEL, interface, superconductivity 3921
 
  • T. Junginger
    TRIUMF, Vancouver, Canada
  • T. Prokscha, Z. Salman, A. Suter
    PSI, Villigen PSI, Switzerland
  • A-M. Valente-Feliciano
    JLab, Newport News, Virginia, USA
 
  Nb3Sn and NbTiN are two potential alternative materials to niobium for superconducting RF cavities. In this study direct measurements of the magnetic penetration depth using the low energy muon spin rotation technique are presented, from which the lower critical field and the superheating field are derived. Comparison with RF data confirms that the lower critical field is not a fundamental limitation and predict a potential performance clearly exceeding current state of the art of niobium technology if the superheating field can be achieved. As a potential pathway to avoid premature vortex penetration and reaching the superheating field it is suggested to use a bilayer structure with the outer layer having a larger magnetic penetration depth.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL118  
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THPAL123 Fabrication and Test of β=0.3 325MHz Balloon Single Spoke Resonator multipactoring, niobium, linac, TRIUMF 3934
 
  • Z.Y. Yao, J.J. Keir, D. Kishi, D. Lang, R.E. Laxdal, H.L. Liu, Y. Ma, B. Matheson, B.S. Waraich, Q. Zheng, V. Zvyagintsev
    TRIUMF, Vancouver, Canada
 
  A novel balloon variant of the single spoke resonator (SSR) has been designed, fabricated and tested at TRIUMF. The cavity is the β=0.3 325 MHz SSR1 prototype for the Rare Isotope Science Project (RISP) in Korea. The balloon variant is specifically designed to reduce the likelihood of multipacting barriers near the operating point. A systematic multipacting study led to a novel geometry, a spherical cavity with re-entrant irises plus a spoke. The balloon cavity provides competitive RF parameters and a robust mechanical structure. Cold tests demonstrated the principle of the balloon concept. The fabrication experience and the preliminary test results will be reported in this paper.  
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THPAL126 Nitrogen Bake-out Procedures at the Vertical High-Temperature UHV-Furnace of the S-DALINAC SRF, vacuum, niobium, linac 3937
 
  • R. Grewe, L. Alff, M. Arnold, J. Conrad, S. Flege, M. Major, N. Pietralla
    TU Darmstadt, Darmstadt, Germany
  • F. Hug
    IKP, Mainz, Germany
 
  Funding: Work supported by the Federal Ministry of Education and Research through grant No. 05H15RDRBA.
As the performance limits of bulk Nb srf cavities are reached, our research is focused on materials with superior srf properties like Nb3Sn and NbN. Research on NbN resulted in the "nitrogen-doping" process used for increasing the quality factors of srf cavities for the LCLS-II project. This process leads to delta-phase Nb-N, a phase with higher critical sc parameters than bulk Nb. This phase is formed at temperatures of 800°C in nitrogen atmospheres of 10-2 mbar. Other crystalline phases of NbN have even better sc parameters. We concentrate our research on applicability of delta-phase NbN for cavities. The delta-phase forms at temperatures of above 1300°C, which is more than most of the furnaces at accelerator facilites are capable of. Since 2005 the Institute for Nuclear Physics at the Technische Universität Darmstadt operates a high temperature vacuum furnace which has been upgraded to allow temperatures of up to 1750°C and bakeouts of niobium samples and cavities in nitrogen atmospheres. We will report on the current status of our research on nitrogen bake-out procedures on Nb samples. The samples have been analyzed at the Material Science Departement with SIMS, REM and XRD.
 
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THPAL127 Structural Investigations of Nitrogen-Doped Niobium for Superconducting RF Cavities niobium, vacuum, ECR, experiment 3940
 
  • M. Major, L. Alff, M. Arnold, J. Conrad, S. Flege, R. Grewe, M. Mahr, N. Pietralla
    TU Darmstadt, Darmstadt, Germany
  • F. Hug
    KPH, Mainz, Germany
 
  Funding: Work supported by the German Federal Ministry for Education and Research (BMBF) through grant 05H15RDRBA.
Niobium is the standard material for superconducting RF (SRF) cavities. Superconducting materials with higher critical temperature or higher critical magnetic field allow cavities to work at higher operating temperatures or higher accelerating fields, respectively. Enhancing the surface properties of the superconducting material in the range of the penetration depth is also beneficial. One direction of search for new materials with better properties is the modification of bulk niobium by nitrogen doping. In the Nb-N phase diagram the cubic delta-phase of NbN has the highest critical temperature (16 K). Already slight nitrogen doping of the alpha-Nb phase results in higher quality factors.* Nb samples were N-doped at the refurbished UHV furnace at IKP Darmstadt. Reference samples were annealed in 1 bar nitrogen atmosphere at different temperatures. In this contribution the results on the structural investigations (x-ray diffraction and pole figure, secondary ion mass spectroscopy, scanning electron microscopy) at the Materials Research Department of TU Darmstadt will be presented.
*Grassellino et al., Proc. SRF2015, MOBA06, 48.
 
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THPAL129 Magnetron Sputtering of Nb3Sn for SRF Cavities SRF, site, target, controls 3946
 
  • MNS. Sayeed, H. Elsayed-Ali
    ODU, Norfolk, Virginia, USA
  • G.V. Eremeev, M.J. Kelley, C.E. Reece
    JLab, Newport News, Virginia, USA
  • M.J. Kelley, U. Pudasaini
    The College of William and Mary, Williamsburg, Virginia, USA
  • M.J. Kelley
    Virginia Polytechnic Institute and State University, Blacksburg, USA
 
  Nb3Sn is a potential candidate for surface material of SRF cavities since it can enable the cavity to operate at higher temperatures with high quality factor and at an increased accelerating gradient. Nb-Sn films were deposited using magnetron sputtering of individual Nb and Sn targets onto Nb and sapphire substrates. The as-deposited films were annealed at 1200 °C for 3 hours. The films were characterized for their structure by X-ray Diffraction (XRD), morphology by Field Emission Scanning Electron Microscopy (FESEM), and composition by Energy Dispersive X-ray Spectroscopy (EDS) and Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS). The surface resistivity was measured down to cryogenic temperature to determine the superconducting transition temperature and its width. The composition of the multilayered films was controlled by varying the thickness of the Nb and Sn layers. The films showed crystalline Nb3Sn phases with Tc up to 17.6 K.  
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THPAL130 Effect of Deposition Temperature and Duration on Nb3Sn Diffusion Coating SRF, niobium, experiment, superconductivity 3950
 
  • U. Pudasaini, M.J. Kelley
    The College of William and Mary, Williamsburg, Virginia, USA
  • G.V. Eremeev, M.J. Kelley, C.E. Reece
    JLab, Newport News, Virginia, USA
  • M.J. Kelley, J. Tuggle
    Virginia Polytechnic Institute and State University, Blacksburg, USA
 
  Funding: Partially authored by Jefferson Science Associates under contract no. DE¬AC05¬06OR23177. Work at College of William & Mary supported by Office of High Energy Physics under grant SC0014475.
Nb3Sn is a potential candidate to replace Nb in SRF accelerator cavities to reduce cost and advance perfor-mance. Tin vapor diffusion is the preferred technique to realize such cavities by growing a few microns thick Nb3Sn coating on the interior surface of the niobium cavity. The coating process typically uses temperatures of 1100-1200 °C for 3-6 hours. It is important to better understand the coating process, and optimize the coating parameters to overcome the current limitation on the performance of Nb3Sn coated SRF cavities. We investi-gate Nb3Sn coatings prepared in the temperature range of 900-1200 °C and duration of 3 - 12 hours using various material characterization tools. Variation of these pa-rameters appears to have notable effect on microstructure and topography of the obtained surface.
 
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THPAL131 Studies of Electropolishing and Oxypolishing Treated Diffusion Coated Nb3Sn Surfaces niobium, SRF, experiment, superconductivity 3954
 
  • U. Pudasaini, M.J. Kelley
    The College of William and Mary, Williamsburg, Virginia, USA
  • G.V. Eremeev, M.J. Kelley, C.E. Reece
    JLab, Newport News, Virginia, USA
  • M.J. Kelley, J. Tuggle
    Virginia Polytechnic Institute and State University, Blacksburg, USA
 
  The Nb3Sn-coated cavities aim to enhance perfor-mance and significantly reduce cost. Their fabrication involves tin vapor diffusion coating of Nb3Sn on the interior surface of a Nb cavity. Controlled removal of first few layers to obtain a smoother and cleaner surface could be desirable to improve the high field RF perfor-mance. Our first results from the application of elec-tropolishing and oxypolishing techniques on Nb3Sn-coated surfaces indicated reduced surface roughness, and the surface composition appeared nominally unchanged. Systematic studies explore the effect of different polish-ing parameters into the roughness and composition. We present the latest results from SEM/EDS and AFM studies of Nb3Sn-coated samples treated with electropolishing and oxypolishing.  
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THPAL133 LASE Surfaces for Mitigation of Electron Cloud in Accelerators electron, laser, vacuum, experiment 3958
 
  • B.S. Sian
    UMAN, Manchester, United Kingdom
  • O.B. Malyshev, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  Vacuum chamber surface characteristics such as the photon and secondary electron yields (PEY and SEY) are critical parameters in the formation of an electron cloud, a serious problem that limits the performance of proton and positron accelerators. A few years ago it was discovered by the Vacuum Solutions Group at Daresbury laboratory that Laser Ablation Surface Engineering (LASE) could provide surfaces with SEY<1 [1,2]. The LASE surfaces are considered as a baseline solution for electron cloud miti-gation in the Future Circular Collider (FCC). However, these surfaces are undergoing further optimisation for the FCC application. While keeping SEY<1 the surfaces should meet the following criteria: Low outgassing, Low particulate generation and low surface resistance. In this paper we will report a number of new surfaces created using the LASE technique with different laser parameters (wavelength, scan speed, pitch, repetition rate, power, and pulse length) and their effect on the SEY, surface re-sistance and vacuum properties, etc  
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THPAL134 Commissioning of the Prototype C75 Cavities in a CEBAF Cryomodule cryomodule, MMI, HOM, operation 3961
 
  • M.A. Drury, G. Cheng, G. Ciovati, E. Daly, G.K. Davis, J. Guo, R.A. Legg, F. Marhauser, T. Powers, A.V. Reilly, R.A. Rimmer
    JLab, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
Prototype cavities have been built at Jefferson Lab to increase the energy of future refurbished CEBAF cryomodules to 75 MeV in the most cost efficient way. Three such cavities, named "C75", have been built from ingot Nb material of different purity and have been processed and tested. The two better performing cavities have been assembled into a "cavity pair" and installed in the latest refurbished original CEBAF cryomodule. The cryomodule was installed and commissioned in CEBAF. The results from the commissioning of the C75 cavities, compared with the original CEBAF cavities, are presented in this article. The vertical test performance of the C75 cavities was preserved in the cryomodule with one of the cavities achieving the performance specification of an accelerating gradient of 19 MV/m with a quality factor of ~8×109 at 2.07 K. The performance in terms of microphonics and tuner operation was similar to that of original CEBAF cavities, as expected, and the high-order modes are properly damped. The quality factor of the two C75 cavities was the highest achieved in a CEBAF cryomodule, possibly due to the better magnetic flux expulsion of ingot Nb than standard fine-grain Nb.
 
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THPAL137 Acceptance Testing of the First Group of LCLS II Cryomodules at Jefferson Lab cryomodule, operation, HOM, radiation 3965
 
  • M.A. Drury, E. Daly, N.A. Huque, L.K. King, M.D. McCaughan, A.D. Solopova
    JLab, Newport News, Virginia, USA
  • J. Nelson
    SLAC, Menlo Park, California, USA
 
  Funding: This work was supported by the LCLS-II Project and the US Department of Energy, Contract DE-AC02-76SF00515.
The Thomas Jefferson National Accelerator Facility is currently engaged, along with several other Department of Energy (DOE) national laboratories, The Thomas Jefferson National Accelerator Facility is currently engaged, along with several other Department of Energy (DOE) national laboratories, in the Linac Co-herent Light Source II project (LCLS II). The SRF Insti-tute at Jefferson Lab is currently building 17 cryomod-ules for this project. The cryomodules are TESLA style cryomodules that have been modified for continuous wave (CW) operation and for other LCLS II specifica-tions. Each cryomodule contains eight 9-cell cavities with coaxial power couplers operating at 1.3 GHz. The cryomodules also contains a magnet package that con-sists of a quadrupole and two correctors. These cryomod-ules will be tested in the Cryomodule Test Facility (CMTF) at Jefferson Lab before shipment to the Stanford Linear Accelerator (SLAC). Acceptance testing of the LCLS II cryomodules began in December 2016. Seven cryomodules have currently completed Acceptance test-ing. This paper will summarize the results of those tests.
 
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THPAL140 Rework Recipe Development, Analysis and Results of Select 9-Cell Cavities for LCLS-II embedded, niobium, site, linac 3968
 
  • A.D. Palczewski, K. Macha, H. Park, C.E. Reece, K.M. Wilson
    JLab, Newport News, Virginia, USA
  • A. Burrill, D. Gonnella
    SLAC, Menlo Park, California, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The SLAC National Accelerator Laboratory is currently constructing a major upgrade to its accelerator, the Linac Coherent Light Source II (LCLS-II). Several Department of Energy laboratories, including the Thomas Jefferson National Accelerator Facility (JLab) and Fermi National Accelerator Laboratory (FNAL), are collaborating in this project. The cryomodules for this project each consist of eight 1.3-GHz cavities produced by two vendors, Research Instruments GmbH in Germany (RI*) and Ettore Zanon S.p.a. in Italy (EZ*), using niobium cell material from Tokyo Denkai Co., Ltd. (TD) and Ningxia Orient Tantalum Industry Co., Ltd. (OTIC/NX)). During the initial production run, cavity performance from one of the vendors (Vendor A) was far below expectation. All the cavities had low Q0, later attributed to minimal EP as well as high-flux-trapping NX material, early quench behaviour below 18 MV/m, with many having Q0 roll-off at 12-16 MV/m. Production was stopped multiple times over the following 6 months, with test batches of cavities being made to ascertain the root cause of the problem. The final root cause of the problem was found to be inappropriate grinding of the RF surface prior to welding which left normal conducting inclusions in the surface. In addition, most cavities showed internal and external weld spatter which required post weld grinding and a very rough surface from operating the electropolishing machine in an etching rather than polishing regime. All issues have been corrected on new cavities and rework is underway on the originally effected cavities.
 
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THPAL141 Optimizing Procurement Strategies for LCLS-II cryomodule, niobium, HOM, status 3972
 
  • K.M. Wilson, G. Cheng, E. Daly, J.A. Fitzpatrick, N.A. Huque, M.L. Laney, F. Marhauser, A.D. Palczewski, H. Park, T. Peshehonoff, G. Tenbusch, M. Torres
    JLab, Newport News, Virginia, USA
 
  Funding: This work was supported by the LCLS-II Project and the U.S. Department of Energy, Contract DE-AC02-76SF00515
The SLAC National Accelerator Laboratory is currently constructing a major upgrade to its accelerator, the Linac Coherent Light Source II (LCLS-II). Several Department of Energy national laboratories, including the Thomas Jefferson National Accelerator Facility (JLab), are participating in this project. JLab is responsible for procuring a number of critical components. Over the course of this project, JLab has evolved several procurement strategies to minimize risk and improve performance while working within the constraints of budget and schedule. This paper discusses the impact of procurement choices on project technical success.
 
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THPAL143 Commissioning of JLab Vertical Cavity Processing System for SRF Nb Single Cell and Multicell Cavity With HF-Free Pulse-Reverse Electopolishing SRF, controls, niobium, MMI 3978
 
  • H. Tian, M. Lester, J. Musson, H.L. Phillips, C.E. Reece, C. Seaton
    JLab, Newport News, Virginia, USA
 
  Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177
Pulse reversed electropolishing of niobium SRF cavities, using a dilute aqueous H2SO4 electrolyte without HF yields equivalent RF performance with traditional EP. Comparing with present EP process for Nb SRF cavity which uses 1:10 volume ratio of HF (49%) and H2SO4 (98%), pulse reverse EP (also known as bipolar EP (BPEP)) is ecologically friendly and uses relatively benign electrolyte options for cavity processing. In this study, we report the commissioning of a new vertical cavity processing system for SRF Nb single cell and multi-cell cavities with HF-free pulse-reverse electropolishing at Jefferson Lab, together with RF test of cavities being processed. We report the scale-up challenges and interpretations from process R&D to implementation.
 
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THPAL144 952.6 MHz SRF Cavity Development for JLEIC HOM, damping, electron, SRF 3982
 
  • R.A. Rimmer, W.A. Clemens, F. Fors, J. Guo, F.E. Hannon, J. Henry, F. Marhauser, L. Turlington, H. Wang, S. Wang
    JLab, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
JLab is developing new SRF cavity designs at 952.6 MHz for the proposed Jefferson Lab Electron-Ion Collider (JLEIC). New cavities will be required for the ion ring, cooler ERL and booster and eventually for an upgrade of the electron ring to allow the highest possible bunch collision rate. The challenges include the need for high fundamental mode power couplers and strong HOM damping, with high HOM power capability. Initial focus is on the cooler ERL 5-cell cavity as this is a critical component for the strong, high energy, bunched-beam cooling concept. 1-cell and 5-cell Nb prototype cavities have been designed and fabricated. Details concerning the cavity fabrication and test results will be presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL144  
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THPAL145 Magnetron R&D toward the Amplitude Modulation Control for SRF Accelerator injection, controls, simulation, SRF 3986
 
  • R.A. Rimmer, T. E. Plawski, H. Wang
    JLab, Newport News, Virginia, USA
  • A. Dudas, S.A. Kahn, M.L. Neubauer
    Muons, Inc, Illinois, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and SBIR grant DE-SC0013203
The scheme of using a high efficiency magnetron to drive a superconducting radio frequency (SRF) accelerator cavity needs not only the injection phase locking but also the amplitude modulation to compensate the cavity's microphomics caused cavity voltage change and the beam loading variation. To be able to do a fast and efficient modulation, the magnetron's magnetic field has to be trimmed by an external coil to compensate the frequency pushing effect due to the anode current change [1]. A low eddy current magnetron body has been designed and built [2]. This paper will present the analytical prediction, simulation and experimental results on the 2.45 GHz magnetron test stand with the modulation frequency up to 1 kHz. In addition, the progresses on the injection lock to a copper cavity, new 1497 MHz magnetron prototype, 13 kW high power magnetron test stand development and newly built low level RF (LLRF) controller for the amplitude modulation will be reported.
[1] M. Neubauer et al, THPIK123, Proceedings of IPAC 2017, Copenhagen, Denmark
[2] S. A. Kahn et al, THPIK121, Proceedings of IPAC 2017, Copenhagen, Denmark
 
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THPAL146 802 MHz ERL Cavity Design and Development SRF, collider, electron, hadron 3990
 
  • F. Marhauser, S. Castagnola, W.A. Clemens, J.G. Dail, P. Dhakal, F. Fors, J. Henry, R.A. Rimmer, L. Turlington, R.S. Williams
    JLab, Newport News, Virginia, USA
  • R. Calaga, K.M. Dr. Schirm, E. Jensen
    CERN, Geneva, Switzerland
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177, and CERN Contract NR. KE3080/ATS
In the framework of a collaboration between CERN and JLab, an SRF accelerating cavity for energy recovery linacs operating at 802 MHz was developed in the context of the CERN's Large Hadron electron Collider (LHeC) design study. A single-cell and a five-cell cavity from fine grain high RRR niobium were built at JLab to validate the basic RF design in vertical tests. Two copper single-cell cavities were produced in parallel for R&D purposes at CERN. The cavity design has since been adapted as baseline for the main linac cavities in the proposed Powerful Energy Recovery Linac Experiment facility (PERLE) at Orsay. Details concerning the cavity fabrication and test results for the Nb cavities are presented.
 
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THPAL148 Status of High Efficiency Klystron Development in TETD klystron, electron, simulation, bunching 3993
 
  • Y. Okubo, S. Fujii, K. Suzuki, T.E. Tanaka
    Toshiba Electron Tubes & Devices Co., Ltd (TETD), Tochigi, Japan
 
  TETD (Toshiba Electron Tubes and Devices Co., Ltd.) has been developing a high efficiency klystron improved bunch quality by the multi-stage of core oscillation design. For feasibility study, an S-band 7.5 MW klystron has been designed with the efficiency of more than 60% at 1.8μperveance. The first prototype was fabricated by modifying the interaction section of a commercial model to enhance the efficiency from 45% to 60%. The klystron was tested in June 2017, and 57% of efficiency at 6 MW output power was demonstrated. We are developing the second prototype which has the improved design for the higher efficiency at 7.5 WM output power. The design details and the test results of the first prototypes are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL148  
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THPAL151 Progress in Understanding Breakdown Characteristics of X-Band Choke-Mode Structures timing, experiment, HOM, operation 4002
 
  • X.W. Wu, D.Z. Cao, H.B. Chen, J. Shi, H. Zha
    TUB, Beijing, People's Republic of China
  • T. Abe, T. Higo, S. Matsumoto
    KEK, Ibaraki, Japan
 
  Funding: National Natural Science Foundation of China (Grant No. 11135004).
As one of the higher-order-mode (HOM) damping structures, X-band choke-mode accelerating structures had been studied for several years. However, the breakdown characteristics of the X-band choke are still unknown. Five different single-cell choke-mode accelerating structures and one reference structure were designed, fabricated and high-gradient tested to study the related RF breakdown characteristics. The absence of field emission current flash was proposed to be the sign of breakdowns occurring inside the choke, this was verified by the post-mortem observation. Evaluation of the breakdown rate revealed that there is memory effect with pulse width and electric field. The breakdown rate in a single RF pulse did not have the 5th order pulse width and 30th order electric field dependency predicted by the empirical formula.
 
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THPAL152 Study of X-Band Phase Shifter Using Ferrite Material GUI, simulation, coupling, insertion 4005
 
  • Y.L. Jiang, D.Z. Cao, H.B. Chen, J. Shi, P. Wang, H. Zha
    TUB, Beijing, People's Republic of China
 
  Ferrite has the feature of the permeability depended on the external static magnetic field, thus could be used to shift the phase of the propagating radio frequency (RF) signal. In this paper, we introduce a novel design of ferrite-based RF phase shifter. The design changes the resonant frequency of a ferrite-filled pill-box cavity to implement the phase changing. This design has a lower local RF field and a higher sensitivity on the phase changing than those of waveguide phase shifter, which may bring advantages such as higher power capacity, fast changing speed and lower insertion loss. Theory and simulation results are also presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL152  
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THPAL153 High Power Test of the S-Band Spherical Pulse Compressor at Tsinghua University FEL, coupling, polarization, klystron 4008
 
  • P. Wang, D.Z. Cao, H.B. Chen, C. Cheng, J. Shi, Z.H. Wang, H. Zha
    TUB, Beijing, People's Republic of China
 
  We designed, fabricated and high power tested an S-band spherical pulse compressor for the high-power test facility at Tsinghua University. The pulse compressor comprises a spherical resonant cavity with an unloaded quality factor of 100, 000 and an RF polarizer with two rectangular ports and a circular port. To achieve high efficiency and large power gain, the coupling coefficient was optimized to 8 with input pulse length of 3.6 us and compression ratio of 12. After conditioning the RF system, the pulse compressor generated RF pulses with peak power of more than 400MW. And during the operation, the pulse compressor has very low breakdown rate and was extremely stable.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL153  
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THPAL155 Fabrication and Cold Test of the Correction Cavity Chain for Klystron-Based CLIC operation, polarization, klystron, linear-collider 4014
 
  • P. Wang, D.Z. Cao, H.B. Chen, J. Shi, Z.H. Wang, H. Zha
    TUB, Beijing, People's Republic of China
 
  A proposed RF scheme based on correction cavity chain and storage cavity (CC-SC scheme) for klystron-based CLIC has the ability to generate flat output pulses. In the scheme, the correction cavity chain modulates the amplitude of the input pulse, while the storage cavity compresses the amplitude-modulated pulse. Resonant cavities of the correction cavity chain are of a relatively low unloaded quality factor and of small size, which results in the compactness of the RF scheme. The first prototype of a correction cavity chain was fabricated and cold tested at Tsinghua University and then delivered to CERN for high power test. Both the results of the cold and high power tests show that the correction cavity chain is of good performance. Feasibility and stability of the pulse compression system based on CC-SC scheme were demonstrated.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL155  
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THPAL157 Investigation of Transverse Wakefield and Beam Break Up Effect in Irradiation Linacs wakefield, experiment, linac, simulation 4020
 
  • X.C. Meng, H.B. Chen, J. Shi, Z.H. Wang, H. Zha, S.X. Zheng
    TUB, Beijing, People's Republic of China
  • G.H. Li, J.S. Liu, Y.H. Liu
    NUCTECH, Beijing, People's Republic of China
 
  Study of beam break up effect in linacs has been done in recent years. The beam-induced high order dipolar modes, especially the TM11-like mode were investigated for the linacs both in travelling wave and backward trav-elling wave. Measurements of beam-break up in a travel-ling wave linac were carried out and results are discussed. Moreover, a theoretical model was developed for the irradiation linacs to study the detailed interaction be-tween the transverse wakefield and the electron beam.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL157  
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THPAL158 Development of an Half-Cell Accelerating Structure in Tsinghua simulation, GUI, alignment, radiation 4023
 
  • M.M. Peng, W. Gai, J. Shi, Z.H. Wang, H. Zha
    TUB, Beijing, People's Republic of China
 
  The half-cell high gradient accelerating structure is attractive for its easy manufacturing and good alignment. A structure with 12 cells has been designed for the frequency of 11.424 GHz and a cold test will be conducted. Two different mechanical factory manufacture with same machining drawing and the results will be compared.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL158  
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THPMF007 Commissioning of the Hybrid Superconducting/Normal Conducting RF System in the Diamond Storage Ring storage-ring, operation, LLRF, HOM 4042
 
  • C. Christou, A.G. Day, P. Gu, P.J. Marten, S.A. Pande, D. Spink, A. Tropp
    DLS, Oxfordshire, United Kingdom
 
  Two 500 MHz HOM damped normal conducting cavities have been installed in the Diamond storage ring to ensure continuity of operation of Diamond in the event of a failure of one of the two existing superconducting cavities. Following receipt from the manufacturer, the cavities were incorporated into an assembly including vacuum pumping, cooling and interlocked diagnostics and then tested for vacuum integrity and RF performance. Both cavities were then conditioned up to high power in Diamond's RF test facility before being installed in the storage ring in August and November 2017. Conditioning and operation has been carried out using a new digital LLRF system. Results of acceptance tests and commissioning with power and beam are presented, together with the current status of the hybrid RF system and options for further improvement of the system in the near future.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF007  
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THPMF024 Commissioning and Operation of FAST Electron Linac at Fermilab electron, cryomodule, experiment, MMI 4096
 
  • A.L. Romanov, C.M. Baffes, D.R. Broemmelsiek, K. Carlson, D.J. Crawford, N. Eddy, D.R. Edstrom, E.R. Harms, J. Hurd, M.J. Kucera, J.R. Leibfritz, I.L. Rakhno, J. Reid, J. Ruan, J.K. Santucci, V.D. Shiltsev, G. Stancari, R.M. Thurman-Keup, A. Valishev, A. Warner
    Fermilab, Batavia, Illinois, USA
 
  We report results of the beam commissioning and first operation of the 1.3 GHz superconducting RF electron linear accelerator at Fermilab Accelerator Science and Technology (FAST) facility. Construction of the linac was completed and the machine was commissioned with beam in 2017. The maximum total beam energy of about 300 MeV was achieved with the record energy gain of 250 MeV in the ILC-type SRF cryomodule. The pho-toinjector was tuned to produce trains of 200 pC bunches with a frequency of 3 MHz at a repetition rate of 1 Hz. This report describes the aspects of machine commission-ing such as tuning of the SRF cryomodule and beam optics optimization. We also present highlights of an experimental program carried out parasitically during the two-month run, including studies of wake-fields, and advanced beam phase space manipulation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF024  
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THPMF028 Coherent Stacking Scheme for Inverse-Compton Scattering at MHz Repetition Rates laser, simulation, coupling, feedback 4103
 
  • P. Piot, D. Mihalcea
    Northern Illinois University, DeKalb, Illinois, USA
  • T.J. Campese, A.Y. Murokh
    RadiaBeam Systems, Santa Monica, California, USA
  • D. Mihalcea, P. Piot, J. Ruan
    Fermilab, Batavia, Illinois, USA
 
  Funding: Work sponsored by the DNDO award 2015-DN-077-ARI094 to Northern Illinois University and US DOE contract DE-AC02-07CH11359 to Fermilab.
An experiment to produce 1-MeV gamma rays via Compton back-scattering of infrared photons on 250-MeV electron bunches is currently in preparation at the Fermilab Accelerator Science & Technology (FAST) facility. To increase the gamma-ray flux the energy of the infrared laser pulses are planned to be amplified within the interaction region using a resonant cavity. This passive amplifier composed of a Fabry-Perot cavity will allow the laser pulse bunches to coherently and constructively stack. Our estimates, based on theoretical models, show that the laser pulse energy can be increased from approximately 1-2 mJ at the exit of the last active amplifier to 5 -10 mJ at the interaction point when the laser repetition rate is set at the nominal value of 3 MHz. This paper details the cavity design option(s) and associated wave-optic simulations.
 
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THPMF030 VSR Injector Upgrade at BESSY II booster, injection, storage-ring, kicker 4110
 
  • T. Atkinson, P. Goslawski, J.G. Hwang, M. Ries
    HZB, Berlin, Germany
  • T. Flisgen, T. Mertens
    Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
 
  BESSY VSR is a fully funded project at the Helmholtz-Zentrum in Berlin (HZB). The objective is to produce simultaneously both long and short pulses in the storage ring. The implications for the existing injector systems and the upgrade strategy are presented. Envisaged is a global upgrade which includes additional accelerating structures to reduce the bunch length in the booster, orbit measurements and implementing longitudinal feedback.  
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THPMF032 Preparation and Testing of the BERLinPro Gun 1.1 Cavity gun, cathode, pick-up, niobium 4117
 
  • H.-W. Glock, J. Knobloch, A. Neumann, Y. Tamashevich
    HZB, Berlin, Germany
 
  Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of the Helmholtz Association
For the BERLinPro energy recovery LINAC, HZB is developing a superconducting 1.4-cell electron gun, which, in its final version, is planned to be capable of CW 1.3 GHz operation with 77 pC/bunch. For this purpose a series of three superconducting cavities, denoted as Gun 1.0, Gun 1.1 (both designed for 6 mA) and Gun 2.0 (100 mA) is foreseen. Here the status of the Gun 1.1 cavity is described, including results of the recent vertical testing. Lessons learned from the production and preparation process are summarized, also in order to identify issues critical for the production of Gun 2.0.
 
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THPMF033 Design of the Beamline Elements in the BESSY VSR Cold String synchrotron, HOM, shielding, operation 4123
 
  • H.-W. Glock, F. Glöckner, J. Knobloch, E. Sharples, A.V. Tsakanian, A.V. Vélez
    HZB, Berlin, Germany
  • T. Flisgen
    Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
 
  Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of the Helmholtz Association
The four SRF cavities in the BESSY VSR module will be linked by bellows, which will be equipped with inner coaxial shielding pipes to prevent both parasitic fundamental mode losses and beam-induced heating. The central bellow will also act as a collimator for synchrotron radiation generated in the closest upstream dipole magnet. Additional bellows at the module's ends are needed to connect with the warm BESSY beam pipe. Outside the module the beam pipe cross section transitions will be located, which will be equipped with toroidal HOM absorbing elements. In the paper the recent design considerations and specifications for all those components will be described.
 
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THPMF034 Status Report of the Berlin Energy Recovery Linac Project BERLinPro gun, SRF, cathode, vacuum 4127
 
  • M. Abo-Bakr, W. Anders, Y. Bergmann, K.B. Bürkmann-Gehrlein, A.B. Büchel, P. Echevarria, A. Frahm, H.-W. Glock, F. Glöckner, F. Göbel, B.D.S. Hall, S. Heling, H.-G. Hoberg, A. Jankowiak, C. Kalus, T. Kamps, G. Klemz, J. Knobloch, J. Kolbe, G. Kourkafas, J. Kühn, B.C. Kuske, J. Kuszynski, A.N. Matveenko, M. McAteer, A. Meseck, R. Müller, A. Neumann, N. Ohm, K. Ott, E. Panofski, F. Pflocksch, L. Pichl, J. Rahn, M.A.H. Schmeißer, O. Schüler, M. Schuster, J. Ullrich, A. Ushakov, J. Völker
    HZB, Berlin, Germany
  • A. Bundels
    Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
 
  Funding: Work supported by the German Bundesministerium für Bildung und Forschung, Land Berlin and grants of Helmholtz Association
The Helmholtz-Zentrum Berlin is constructing the Energy Recovery Linac Prototype BERLinPro, a demonstration facility for the science and technology of ERLs for future light source applications. BERLinPro is designed to accelerate a high current (100 mA, 50 MeV), high brilliance (norm. emittance below 1 mm mrad) cw electron beam. We report on the last year's progress, including the comissioning of the gun module as the first SRF component to be installed in BERLinPro.
 
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THPMF036 Status of the Conceptual Design of ALS-U lattice, emittance, vacuum, kicker 4134
 
  • C. Steier, A.P. Allézy, A. Anders, K.M. Baptiste, E.S. Buice, K. Chow, G.D. Cutler, S. De Santis, R.J. Donahue, D. Filippetto, J.P. Harkins, T. Hellert, M.J. Johnson, J.-Y. Jung, S.C. Leemann, D. Leitner, M. Leitner, T.H. Luo, H. Nishimura, T. Oliver, O. Omolayo, J.R. Osborn, G.C. Pappas, S. Persichelli, M. Placidi, G.J. Portmann, S. Reyes, D. Robin, F. Sannibale, C. Sun, C.A. Swenson, M. Venturini, S.P. Virostek, W.L. Waldron, E.J. Wallén
    LBNL, Berkeley, California, USA
 
  Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
The ALS-U conceptual design promises to deliver diffraction limited performance in the soft x-ray range by lowering the horizontal emittance to about 70 pm rad resulting in two orders of brightness increase for soft x-rays compared to the current ALS. The design utilizes a nine bend achromat lattice, with reverse bending magnets and on-axis swap-out injection utilizing an accumulator ring. This paper shows some aspects of the completed conceptual design of the accelerator, as well as some results of the R&D program that has been ongoing for the last years.
 
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THPMF038 Status of the BESSY VSR Project vacuum, operation, SRF, electron 4138
 
  • P. Schnizer, W. Anders, Y. Bergmann, P. Goslawski, H. Hartmut, A. Jankowiak, J. Knobloch, A. Neumann, K. Ott, M. Ries, A. Schälicke, A.V. Vélez
    HZB, Berlin, Germany
 
  BESSY VSR is set out to provide a variable pulse pattern to the BESSY II users. This project is now fully funded and heading into its implementation phase. The pulse pattern, consisting of long and short pulses, require inserting cavities providing a 3rd and a 3.5th harmonic of the fundamental harmonic of the ring. Therefore 1.5 and 1.75 GHz cavities are developed with appropriate higher order mode damping spectrum. Similarly the BESSY II ring and injector chain has to be upgraded to provide appropriate diagnostics and increase the injection efficiency. In this paper we give the current status of the project and give an overview of scientific challenges currently being tackled.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF038  
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THPMF039 Study of Magnesium Photocathodes for Superconducting RF Photoinjectors laser, gun, cathode, SRF 4142
 
  • R. Xiang, A. Arnold, P.N. Lu, P. Murcek, J. Teichert, H. Vennekate
    HZDR, Dresden, Germany
 
  Funding: The work is supported by the German Federal Ministry of Education and Research (BMBF) grant 05K12CR1.
The superconducting RF photoinjector (SRF Gun II) has successfully served for the ELBE user facility at HZDR. Nevertheless, the quality of photocathodes is one of the most critical issues in improving the stability and reliability for its application. Magnesium has a comparably low work function (3.6 eV) and shows a quantum efficiency up to 0.3% after laser cleaning. However, the present cleaning process with a high intensity laser beam is time consuming and produces unwanted surface roughness, which leads to a higher thermal emittance. Thermal treatment and Excimer laser cleaning for Mg cathodes are investigated as alternative methods. In this work, the new cleaning procedures are tested and optimized, and the quantum efficiency of Mg samples with different microstructure, composition and suppliers are compared.
 
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THPMF041 Low Emittance Lattice for PF-AR optics, emittance, injection, operation 4148
 
  • N. Higashi, K. Harada, S. Nagahashi, N. Nakamura, T. Obina, R. Takai, H. Takaki
    KEK, Ibaraki, Japan
  • K. Hirano
    Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
 
  PF-AR is a synchrotron-type 6.5 GeV light source in KEK. The user-run was started in 1987, and the lattice is almost the same as the original one. Now we consider the emittance improvement to enlarge the horizontal tune advance in the normal cell. Thanks to this manipulation, the emittance will be improved to about a half of the current value.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF041  
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THPMF056 Optimisation Study of the Fabry-Pérot Optical Cavity for the MARIX/BRIXS Compton X-Ray Source laser, electron, gun, photon 4192
 
  • I. Drebot, A. Bacci, F. Broggi, S. Cialdi, C. Curatolo, D. Giannotti, D. Giove, A.R. Rossi, L. Serafini, M. Statera, V. Torri
    Istituto Nazionale di Fisica Nucleare, Milano, Italy
  • A. Bosotti, P. Michelato, L. Monaco, R. Paparella, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • R. Calandrino, A. Delvecchio
    HSP, Milan, Italy
  • P. Cardarelli, M. Gambaccini, G. Paternò, A. Taibi
    INFN-Ferrara, Ferrara, Italy
  • A. Esposito, L. Faillace, A. Gallo, C. Vaccarezza
    INFN/LNF, Frascati (Roma), Italy
  • G. Galzerano, E. Puppin, A. Tagliaferri
    Politecnico/Milano, Milano, Italy
  • G. Mettivier, P. Russo
    UniNa, Napoli, Italy
  • V. Petrillo, F. Prelz, M. Rossetti Conti
    Universita' degli Studi di Milano & INFN, Milano, Italy
  • M. Placidi, G. Turchetti
    Bologna University, Bologna, Italy
  • A. Sarno
    INFN-Napoli, Napoli, Italy
 
  We present the study of the optimization of the optical cavity parameters, in order to maximise the flux of scattered photons in the Compton scattering process. In the optimisation, we compensate the losses of the photon number due to the elliptical shape of the laser pulse in optical cavity with a high focusing electron beam.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF056  
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THPMF057 Multi Colour X-Gamma Ray Inverse Compton Back-Scattering Source laser, electron, radiation, photon 4196
 
  • I. Drebot, S. Cialdi, D. Giannotti, L. Serafini
    Istituto Nazionale di Fisica Nucleare, Milano, Italy
  • R. Calandrino
    HSP, Milan, Italy
  • P. Cardarelli, M. Gambaccini, G. Paternò, A. Taibi
    INFN-Ferrara, Ferrara, Italy
  • G. Galzerano
    Politecnico/Milano, Milano, Italy
  • V. Petrillo
    Universita' degli Studi di Milano & INFN, Milano, Italy
 
  We present a simple and new scheme for producing multi colour Thomson/Compton radiation with the possibility of controlling separately their polarization, based on the interaction of one single electron beam with two and more laser pulses that can come from the same laser setup or from two different lasers system and that collide with the electrons at different angle inside one optical cavity. One of the most interesting cases for medical applications is to provide two X-ray pulses across the iodine K-edge at 33.2 keV. The iodine is used as contrast medium in various imaging techniques and the availability of two spectral lines accross the K-edge allows one to produce subtraction images with a great increase in accuracy.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF057  
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THPMF058 The MariX source (Multidisciplinary Advanced Research Infrastructure with X-rays) electron, FEL, gun, radiation 4199
 
  • V. Petrillo, N. Piovella
    Universita' degli Studi di Milano, Milano, Italy
  • A. Bacci, F. Castelli, S. Cialdi, C. Curatolo, I. Drebot, D. Giannotti, D. Giove, C. Meroni, A.R. Rossi, L. Serafini, M. Statera, V. Torri
    Istituto Nazionale di Fisica Nucleare, Milano, Italy
  • A. Bosotti, F. Broggi, F. Groppi, P. Michelato, L. Monaco, R. Paparella, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • R. Calandrino, A. Delvecchio
    HSP, Milan, Italy
  • F. Camera, S. Coelli, G. Onida, B. Paroli, L. Perini, F. Prelz, M. Rossetti Conti, F. Tomasi
    Universita' degli Studi di Milano & INFN, Milano, Italy
  • P. Cardarelli, M. Gambaccini, G. Paternò, A. Taibi
    INFN-Ferrara, Ferrara, Italy
  • A. Castoldi, G. Ghiringhelli, C. Guazzoni, M. Moretti, E. Pinotti
    Polytechnic of Milan, Milano, Italy
  • S. Di Mitri