IPAC2019 - List of Keywords (cavity)

Paper	Title	Other Keywords	Page
MOYPLM2	SRF Operation at XFEL: Lessons Learned After More Than One Year	FEL, operation, linac, SRF	12
	D. Kostin, V. Ayvazyan, J. Branlard, W. Decking, L. Lilje, M. Omet, T. Schnautz, E. Vogel, N. Walker DESY, Hamburg, Germany
	The European XFEL is the largest high-field SRF installation in the world and has now been in operation more than a year. It serves as a "prototype" for other facilities being constructed or in the planning stages. Performance of the operation of the SRF system over this period of time and the lessons learned will be discussed.
	Slides MOYPLM2 [4.351 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOYPLM2
About •	paper received ※ 10 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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MOYPLM3	Progress with the High Luminosity LHC Project at CERN	luminosity, operation, quadrupole, collider	17
	L. Rossi, O.S. Brüning CERN, Geneva, Switzerland
	The High Luminosity LHC (HL-LHC) project aims at upgrading the LHC by increasing the peak luminosity by a factor five, to allow to collect 3000 fb-1 for ATLAS and CMS experiments, each, which is ten times more than what is foreseen in the LHC. The upgrade is based on multiple factors. One factor is doubling the beam current, also thanks to the injector upgrade (LIU) project, and another one is operation in levelling mode. The most critical upgrade is the deploying of a stronger inner quadrupole triplet in the low-beta insertions with more than twice-larger aperture w.r.t. present LHC triplet, thanks to the use of Nb₃Sn superconductor, a world first for accelerators, with almost 12 T peak field in the coils. The novel concept of ATS optics allows to utilise the increased aperture efficiently by generating β^* values 3 to 4 times below the nominal values of the LHC. We will make use of compact crab cavities for hadrons (also a novelty in accelerators) to allow almost head-on collisions despite the larger crossing angle. We are developing new collimator insertions in the dispersion suppressor region to handle the losses in the cold part of the machine (the beam halo stores 30 MJ) thanks to the use of a few 11 T dipoles based on Nb₃Sn technology. We also aim at reducing drastically the impedance contribution of collimators by utilizing new materials and coating techniques. Many other technologies are developed for HL-LHC like new SC links of 100 kA: HL-LHC is critical as a technology turning point for HEP colliders as it is for Physics reach. The technologies developed for HL-LHC, namely (but not only) the high field superconducting magnets, are critical for the post-LHC hadron collider, like a High Energy LHC or the 100 km Future Circular Collider
	Slides MOYPLM3 [21.679 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOYPLM3
About •	paper received ※ 19 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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MOZPLM1	Operation Status and Upgrade of CSNS	linac, MMI, rfq, DTL	23
	S. Fu, S. Wang IHEP, Beijing, People’s Republic of China
	China Spallation Neutron Source (CSNS) accelerator complex consists of a front end, an 80MeV DTL linac, and a 1.6GeV Rapid Cycling Synchrotron (RCS).It is designed with a beam power of 100kW in the first phase and reserves upgrade capability to 500kW in the second phase. It has completed initial beam commissioning and has started user operation in 2018. And meanwhile the beam power is quickly going up from the initially above 10kW to 50kW during the user operation, and we can foresee that the designed beam power of 100 kW can be reached in the next year. This talk gives the most recent status of beam power ramping in CSNS, as well as future upgrade plan to increase the beam power up to 500 kW.
	Slides MOZPLM1 [12.157 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOZPLM1
About •	paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOZZPLM1	Beam Commissioning of the Demonstrator Setup for the Superconducting Continuous Wave HIM/GSI-Linac	linac, heavy-ion, cryomodule, solenoid	33
	M. Miski-Oglu, K. Aulenbacher, V. Gettmann, T. Kürzeder HIM, Mainz, Germany K. Aulenbacher, F.D. Dziuba IKP, Mainz, Germany W.A. Barth, C. Burandt, V. Gettmann, M. Heilmann, T. Kürzeder, A. Rubin, A. Schnase, S. Yaramyshev GSI, Darmstadt, Germany W.A. Barth, S. Yaramyshev MEPhI, Moscow, Russia M. Basten, M. Busch, T. Conrad, H. Podlech, M. Schwarz IAP, Frankfurt am Main, Germany
	During successful beam commissioning of the superconducting 15-gap Crossbar H-mode cavity at GSI Helmholtzzentrum für Schwerionenforschung heavy ions up to the design beam energy have been accelerated. The design acceleration gain of 3.5 MeV inside a length of less than 70 cm has been reached with full transmission for heavy ion beams of up to 1.5 particle mueA. The measured beam parameters confirm sufficient beam quality. The machine beam commissioning is a major milestone of the R&D for the superconducting heavy ion continuous wave linear accelerator HELIAC of Helmholtz Institute Mainz (HIM) and GSI developed in collaboration with IAP Goethe-University Frankfurt. The next step is the procurement and commissioning of so called ’Advanced Demonstrator’ - the first of series cryo module for the entire accelerator HELIAC. Results of further Demonstrator beam tests, as well as the status of the Advanced demonstrator project will be reported.
	Slides MOZZPLM1 [3.088 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOZZPLM1
About •	paper received ※ 29 April 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019
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MOPGW002	Longitudinal Kicker Design for Sirius Light Source	kicker, HOM, GUI, feedback	57
	H.O.C. Duarte, A. Barros LNLS, Campinas, Brazil
	An overloaded cavity kicker for the Sirius longitudinal bunch-by-bunch feedback system will be presented in this contribution. 4th generation light sources’ lower aperture of vacuum chambers lead to higher cutoff frequencies, jeopardizing the electromagnetic performance of cavities by trapping higher order modes (HOMs) inside the structure. With the objective of damping longitudinal and transverse HOMs without compromising the kicker shunt impedance, solutions as cavity radius reduction, tapered transitions and other geometry changes are discussed herein.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW002
About •	paper received ※ 15 May 2019 paper accepted ※ 17 May 2019 issue date ※ 21 June 2019
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MOPGW004	Microphonics Suppression in ARIEL ACM1 Cryomodule	GUI, cryomodule, linac, pick-up	65
	Y. Ma, K. Fong, J.J. Keir, D. Kishi, S.R. Koscielniak, D. Lang, R.E. Laxdal, R.S. Sekhon TRIUMF, Vancouver, Canada
	Now the stage of the 30MeV portion of ARIEL (The Advanced Rare Isotope Laboratory) e-Linac is under commissioning which includes an injector cryomodule (ICM) and the 1st accelerator cryomodule (ACM1) with two cavities configuration. The two ACM1 cavities are driven by a single klystron with vector-sum control and running in CW mode. During the commissioning, the ACM1 cavities gradient and stability was limited by ponderomotive effect. Acoustic noise from the environment vibration generated by cooling water system, cryogenic system and vacuum system have been identified to certain external source and some damping has been installed. In this paper, the progress of the microphonics suppression of ACM1 is presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW004
About •	paper received ※ 01 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPGW014	Developing Beam Optics for the BESSY VSR Project	optics, quadrupole, storage-ring, lattice	94
	F. Andreas, M. Abo-Bakr, F. Armborst, P. Goslawski HZB, Berlin, Germany
	At BESSY II due to the continuously increasing interest in short pulse operation, a major upgrade of the ring will enable simultaneous storage of long and short bunches. This Variable pulse-length Storage Ring (VSR) will be achieved by the installation of additional superconducting high gradient cavities. The cavities will be assembled into one cryomodule in one of the straights of the storage ring. As this module needs more space then initially assumed, one possible solution is to remove two quadrupoles to gain available installation length. The quadrupoles were switched off in simulations and the lattice was optimized with regard to the linear order. The best solution found was transferred to the storage ring, where storage of high current with reasonable injection efficiency and lifetime was possible. The proposed optics has to be further optimized in terms of nonlinear beam dynamics, but has shown that an available installation length can be increased.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW014
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW025	Beam Breakup Simulations for the Mainz Energy Recovering Superconducting Accelerator MESA	HOM, cryomodule, simulation, operation	135
	C.P. Stoll, F. Hug KPH, Mainz, Germany
	Funding: This work is supported by DFG through PRISMA+ cluster of excellence EXC 2118/2019, RTG 2128 and by the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No 730871. MESA is a two pass energy recovery linac (ERL) currently under construction at the Johannes Gutenberg-University in Mainz. MESA uses four 1.3 GHz TESLA type cavities with 12.5 MV/m of accelerating gradient in two modified ELBE type cryomodule with improved thermal connection of the HOM antennas and cw operation. In the first stage of MESA operation 1mA of beam current is foreseen, which will later be upgraded to 10mA. One potential limit to maximum beam current in ERLs is the transverse beam breakup (BBU) instability induced by dipole Higher Order Modes (HOMs). These modes can be excited by bunches passing through the cavities off axis. Following bunches are then deflected by the HOMs, which results in even larger offsets for recirculated bunches. This feedback can even lead to beam loss. Simulation results for HOM spectra of a single TESLA cavity are available for example in . It was possible to measure the HOM spectra in the cold, not tuned cavities at DESY and in the cold string tuned to the 1.3 GHz fundamental mode at Mainz. Results for the maximum beam current for MESA, limited by BBU, for the various HOM spectra are presented. "Eigenmode Calculations for the TESLA Cavity Considering Wave-Propagation Losses through Fundamental and Higher-Order Mode Couplers", W. Ackermann, H. De Gersem, C. Liu, and T. Weiland
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW025
About •	paper received ※ 16 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW030	New Analytical Derivation of Group Velocity in TW Accelerating Structures	dipole, simulation, polarization, coupling	155
	M. Behtouei, M. Migliorati, L. Palumbo Sapienza University of Rome, Rome, Italy L. Faillace Universita’ degli Studi di Milano & INFN, Milano, Italy B. Spataro INFN/LNF, Frascati, Italy
	Ultra high-gradient accelerating structures are needed for the next generation of compact light sources. In the framework of the Compact Light XLS project, we are studying a high harmonic traveling-wave accelerating structure operating at a frequency of 35.982 GHz, in order to linearize the longitudinal space phase. In this paper, we propose a new analytical approach for the estimation of the group velocity in the structure and we compare it with numerical electromagnetic simulations that are carried out by using the code HFSS in the frequency domain.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW030
About •	paper received ※ 08 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW039	Investigation of Longitudinal Beam Dynamics With Harmonic Cavities by Using the Code Mbtrack	impedance, operation, synchrotron, beam-loading	178
	N. Yamamoto KEK, Ibaraki, Japan A. Gamelin, R. Nagaoka SOLEIL, Gif-sur-Yvette, France
	In diffraction-limited light sources, the study of collective effects is essential. With harmonic cavities (HCs), the ’flat potential condition’ can be achieved, lengthening the bunch by a factor of ~5. However, the effective rf voltage seen by the beam becomes sensitive to both positions and distributions of all bunches, as the beam-induced voltage of both HCs and fundamental cavities (FCs) contribute. In addition, when there are empty buckets, the transient beam loading induces considerable variations of the rf voltage impacting the beam performance. Here the use of analytical approaches is difficult. Then we introduced the new functions to treat the high-Q resonators driven by either or both of the beams and external generators to the code mbtrack. Using these features, various operating conditions with arbitrary fill patterns can be studied; coupled bunch instability induced by HOMs of the cavity, Robinson instabilities and general beam dynamics with HCs. The growth rates of the instabilities described above are compared with analytical results. The ring performance with HCs in several fill patterns shall be also reported. N.Yamamoto, et al., PRAB, 21, 012001 (2018). **G. Skripka, et al., NIM A806, 221 (2016).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW039
About •	paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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MOPGW040	Beam Optics Design of the Superconducting Region of the JAEA ADS	emittance, linac, controls, lattice	181
	B. Yee-Rendón, Y. Kondo, F.M. Maekawa, S.I. Meigo, J. Tamura JAEA/J-PARC, Tokai-mura, Japan
	The Japan Atomic Energy Agency (JAEA) is proposing an Accelerator Driven Subcritical System (ADS) for the transmutation of the nuclear waste. ADS will consist of a superconducting CW proton linear accelerator of 30MW and a subcritical nuclear reactor core. The main part of the acceleration will take part in the superconducting region using five types of radio frequency cavities. The ADS operation demands a high intensity and reliability of the beam. Therefore, the beam optics design plays a fundamental role to reduce the beam loss, control emittance growth and beam halo.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW040
About •	paper received ※ 17 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW047	Analysis and Simulation of the "After-Pulse" RF Breakdown	simulation, timing, GUI, experiment	196
	X. Lin, H.B. Chen, Z.N. Liu, J. Shi, H. Zha TUB, Beijing, People’s Republic of China X.W. Wu CERN, Meyrin, Switzerland
	During the high power experiment of a single-cell standing-wave accelerating structure, it was observed that many RF breakdowns happen when the field inside cavity is decaying after the input rf pulse is off. The distribution of breakdown timing shows a peak at the moment of RF power switches off. A series of simulation was performed to study the after-pulse breakdown effect in such a standing-wave structure. A method of calculating poynting vector over time is proposed in this article to study the modified poynting vector at critical points in the cavity. Field simulation and thermal simulation were also carried out to analyse possible reasons for the after-pulse breakdown effect.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW047
About •	paper received ※ 14 May 2019 paper accepted ※ 17 May 2019 issue date ※ 21 June 2019
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MOPGW063	Beam Dynamics Optimization in Drift Tube Linear Accelerator With Permanent Quadrupole Magnets	lattice, rfq, quadrupole, DTL	234
	I. Skudnova Saint Petersburg State University, Saint Petersburg, Russia
	The research concerns the design of a drift tube linear accelerator (DTL) with permanent quadrupole magnets (PMQ) placed inside some of the drift tubes for focusing. The study was conducted using Comsol Multiphysics software, where electromagnetic fields and particle dy-namics in the cavity were calculated. The proton beam is accelerated up to 10 MeV. Initial beam is assumed to come from Radio Frequency Quadrupole accelerator (RFQ). Mathematical methods of control theory are used for particles dynamics optimization. Different focusing lattices are examined and variations of the gradient of the magnetic lenses are analyzed with respect to output beam parameters. Effectiveness of the optimization is estimated by the transmission rate and the emittance growth.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW063
About •	paper received ※ 16 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW077	Impedance Reduction in the CERN SPS Through Element Layout Optimisation	impedance, coupling, extraction, quadrupole	277
	A. Farricker, C. Vollinger CERN, Geneva, Switzerland
	The CERN accelerator complex is currently in its long shutdown while the LHC Injector Upgrade is being carried out. The upgrade of the SPS includes but is not limited to: the relocation of the beam dumping system, upgrade of the RF system, replacement of the electrostatic septa and impedance reduction. These major upgrades present an opportunity to perform additional impedance reduction in areas not normally modified due to the large amount of work being performed across the accelerator complex. In this paper, we look at the impedance minimization in the sections near the large aperture quadrupoles of the extraction regions in the CERN SPS. By optimizing the locations of existing equipment and the introduction of a new, more impedance optimised type of bellows, significant reductions in the beam-coupling impedance can be achieved.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW077
About •	paper received ※ 08 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW083	Longitudinal Coupled-Bunch Instability Evaluation for FCC-hh	impedance, emittance, HOM, synchrotron	297
	I. Karpov, E.N. Shaposhnikova CERN, Meyrin, Switzerland
	High-order modes (HOM) of the accelerating rf structures and other machine elements, if not sufficiently damped, can drive longitudinal coupled-bunch instabilities (CBI). Their thresholds can be accurately obtained from macro-particle simulations using the detailed impedance model containing many different contributions. This method, however, is very difficult to apply for synchrotrons with a large number of bunches, as it is the case for the Future Circular hadron-hadron Collider (FCC-hh) with up to 10400 circulating bunches per beam. In this paper the semi-analytical approach is used for calculations of the instability thresholds during the acceleration cycle of the FCC-hh. As the result, we define requirements for the HOM damping that would be sufficient to prevent development of longitudinal CBI in the presence of weak synchrotron radiation damping.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW083
About •	paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW084	Beam Loading Compensation for the Future Circular Hadron-Hadron Collider (FCC-hh)	beam-loading, hadron, collider, impedance	301
	I. Karpov, P. Baudrenghien CERN, Meyrin, Switzerland
	The power consumption of the rf system can be minimised by optimising the cavity detuning and the loaded quality factor. In high-current accelerators, the presence of gaps in the filling results in a modulation of the cavity voltage along the ring (transient beam loading) and as a consequence a spread in the bunch parameters. In addition longitudinal coupled-bunch instabilities can appear, caused by the cavity impedance at the fundamental. Both issues can be mitigated by using an rf feedback around the amplifier and cavity, a technique used in many high intensity machines including the Large Hadron Collider (LHC). Compared to the LHC machine, the energy increase and the radiation loss for the Future Circular hadron-hadron Collider (FCC-hh) will be larger, resulting in a synchronous phase deviating significantly from 180 degrees. The solutions adopted for the LHC must therefore be revisited. This paper evaluates several beam loading compensation schemes for this machine.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW084
About •	paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW094	First Machine Developments Result with HL-LHC Crab Cavities in the SPS	proton, closed-orbit, luminosity, diagnostics	338
	L.R. Carver, A. Alekou, F. Antoniou, H. Bartosik, T. Bohl, R. Calaga, M. Carlà, T.E. Levens, G. Papotti CERN, Meyrin, Switzerland A. Alekou, R.B. Appleby, R.B. Appleby UMAN, Manchester, United Kingdom G. Burt Cockcroft Institute, Warrington, Cheshire, United Kingdom G. Burt, J.A. Mitchell Lancaster University, Lancaster, United Kingdom C.P. Welsch The University of Liverpool, Liverpool, United Kingdom
	Crab cavities are a critical component within the High Luminosity upgrade project for the Large Hadron Collider (HL-LHC). It is foreseen to use crab cavities in order to compensate the geometric luminosity reduction factor (reduction of the luminous region at the Interaction Point [IP]) due to the beam crossing angle (required for minimizing the impact of the long range beam-beam effects on the single particle beam dynamics) and increase the number of collisions per bunch crossing. In 2018 the first beam tests of crab cavities with protons were performed in the Super Proton Synchrotron (SPS) at CERN. Two vertical superconducting cavities of the Double Quarter Wave (DQW) type were fabricated and installed in the SPS to verify some key components of the cavity design and operation. This paper will present some of the first results relating to the proton beam dynamics in the presence of crab cavities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW094
About •	paper received ※ 25 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW095	Beam Dynamics Simulations with Crab Cavities in the SPS Machine	multipole, simulation, luminosity, optics	342
	A. Alekou, A. Alekou, H. Bartosik, H. Bartosik, M. Carlà, Y. Papaphilippou, Y. Papaphilippou, Y. Papaphilippou CERN, Meyrin, Switzerland A. Alekou, A. Alekou, R.B. Appleby, R.B. Appleby UMAN, Manchester, United Kingdom R.B. Appleby Cockcroft Institute, Warrington, Cheshire, United Kingdom
	The LHC Upgrade, called High Luminosity LHC, aims to increase the integrated luminosity by a factor of 10. To achieve this, the project relies on a number of key innovative technologies, including the use of superconducting Crab Cavities with ultra-precise phase control for beam rotation. A set of prototype Crab Cavities has been recently installed in the second largest machine of CERN, the Super Proton Synchrotron (SPS), that operated as a test-bed from May to November of 2018. The tight LHC constraints call for axially non-symmetric cavity designs that introduce high order multipole components. Furthermore, the Crab Cavities in the presence of SPS non-linearities can affect the long term stability of the beam. This paper presents how the SPS dynamic aperture is affected for different cavity, machine and beam configurations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW095
About •	paper received ※ 06 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW099	Vlasov-Fokker-Planck Simulations of Passive Higher-Harmonic Cavity Effects in ALS-U	simulation, impedance, synchrotron, resonance	357
	G. Bassi BNL, Upton, Long Island, New York, USA
	Funding: Work supported by DOE under contract DE-SC0012704 We discuss numerical simulations of the Vlasov-Fokker-Planck equation to model passive higher-harmonic cavity (HHC) effects with parameters of the Advanced Light Source Upgrade (ALS-U. The numerical results, obtained with the SPACE code, are compared with a modal analysis of the coupled-bunch instability theory.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW099
About •	paper received ※ 18 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019
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MOPGW111	Start to End Simulation on Beam Dynamics in Coherent Electron Cooling Accelerator	electron, FEL, bunching, emittance	379
	Y.C. Jing, V. Litvinenko, I. Petrushina, I. Pinayev, K. Shih, Y.H. Wu BNL, Upton, Long Island, New York, USA V. Litvinenko Stony Brook University, Stony Brook, USA I. Petrushina SUNY SB, Stony Brook, New York, USA K. Shih SBU, Stony Brook, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. A Coherent electron Cooling (CeC) has a potential of substantial reducing cooling time of the high-energy hadrons and hence to boost luminosity in high-intensity hadron-hadron and electron-hadron colliders. In a CeC system, a high quality electron beam is generated, propagated and optimized through a beam line which was carefully designed with consideration of space charge effect, wakefields and nonlinear dynamics such as coherent synchrotron radiation and chromatic aberration. In this paper, we present our study on the beam dynamics of such a beam line and compare the simulation result with what was measured in experiment.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW111
About •	paper received ※ 17 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPMP007	Design of a Compact Power Distribution System for the ILC	cryomodule, ECR, acceleration, collider	436
	B. Du, N. Liu Sokendai - Hayama, Hayama, Japan T. Matsumoto, S. Michizono, T. Miura, F. Qiu KEK, Ibaraki, Japan T. Matsumoto, T. Miura, F. Qiu Sokendai, Ibaraki, Japan
	The Local power distribution system (LPDS) of the In-ternational Linear Collider (ILC) is constructed to transmit RF power from the 10 MW klystron to 39 cavi-ties. Each eight or nine 9-cell cavities is assembled in one cryomodule. The variable hybrid is used to adjust the power dividing ratio due to the different required power of each cavity and the variable phase shifter is used to compensate the phase drift caused by the variable hybrid. More compact LPDS is expected to be integrated on the cryomodule decreasing financial cost. We re-design the shorter variable hybrid with a margin of power ratio of ±25% and phase shifter of total phase range being 35° for compensating hybrid and on-crest searching. Fixed phase shifters are designed to adjust the phase difference between adjacent cavities for beam acceleration. Simu-lated results of total compact LPDS can meet the re-quirements of ILC.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP007
About •	paper received ※ 16 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPMP008	Electron Driven Positron Source for International Linear Collider	positron, beam-loading, linac, simulation	439
	M. Kuriki, T. Okugi, T. Omori, M. Satoh, Y. Seimiya, J. Urakawa, K. Yokoya KEK, Ibaraki, Japan H. Nagoshi HU/AdSM, Higashi-Hiroshima, Japan K. Negishi Iwate University, Morioka, Iwate, Japan Y. Sumitomo LEBRA, Funabashi, Japan T. Takahashi Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
	Funding: This work is partly supported by Japan-US Cooperative grant for scientific studies, Grant aid for scientific study by MEXT Japan (KAKENHI) To linear colliders, huge amount of positron has to be provided comparing to ring colliders, because the beam is dumped after the collision. Electron Driven ILC Positron source has been designed as a technical backup of the undulator position source including the beam loading effect, etc. The design of the detail will be presented. To linear colliders, huge amount of positron has to be provided comparing to ring colliders, because the beam is dumped after the collision. Electron Driven ILC Positron source has been designed as a technical backup of the undulator position source including the beam loading effect, etc. The design of the detail will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP008
About •	paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPMP019	High Luminosity LHC Optics and Layout HLLHCV1.4	optics, luminosity, operation, experiment	468
	R. De Maria, R. Bruce, D. Gamba, M. Giovannozzi, F. Plassard CERN, Geneva, Switzerland
	The goal of the High Luminosity Project is the upgrade of the LHC to deliver an integrated luminosity of at least 250 \rm fb^-1 per year in each of the two high-luminosity, general-purpose detectors ATLAS and CMS. This article presents the latest layout design and the corresponding optics features, which comprise optimisation of the orbit corrector and crab cavity systems, and new estimates of the performance reach thanks to the new concept of fully remote alignment. In addition, the new optics version incorporates improvements required by beam instrumentation, dump system, and collimation system, as well as low-beta solutions for the LHCb experiment.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP019
About •	paper received ※ 17 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPMP036	Machine Protection Experience from Beam Tests with Crab Cavity Prototypes in the CERN SPS	machine-protect, beam-losses, betatron, operation	520
	B. Lindstrom, H. Bartosik, T. Bohl, A.C. Butterworth, R. Calaga, L.R. Carver, V. Kain, T.E. Levens, G. Papotti, R. Secondo, J.A. Uythoven, M. Valette, G. Vandoni, J. Wenninger, D. Wollmann, M. Zerlauth CERN, Meyrin, Switzerland
	Funding: Work supported by the High Luminosity LHC project. Crab cavities (CCs) constitute a key component of the High Luminosity LHC (HL-LHC) project. In case of a failure, they can induce significant transverse beam offsets within tens of microseconds, necessitating a fast removal of the circulating beam to avoid damage to accelerator components due to losses from the displaced beam halo. In preparation for the final design to be employed in the LHC, a series of tests were conducted on prototype crab cavities installed in the Super Proton Synchrotron (SPS) at CERN. This paper summarizes the machine protection requirements and observations during the first tests of crab cavities with proton beams in the SPS. In addition, the machine protection implications for future SPS tests and for the use of such equipment in the HL-LHC are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP036
About •	paper received ※ 01 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019
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MOPMP040	US Contributions to the High Luminosity LHC Upgrade - Focusing Quadrupoles and Crab Cavities	luminosity, quadrupole, HOM, SRF	536
	G. Apollinari, G. Ambrosio, R.H. Carcagno, SF. Feher, L. Ristori Fermilab, Batavia, Illinois, USA
	In the early 2000’s, the US High Energy Physics community contributing to the Large Hadron Collider (LHC) launched the LHC Accelerator R&D Program) (LARP), a long-vision focused R&D program, intended to bring the Nb₃Sn and other technologies to a maturity level that would allow applications in HEP machines. Around 2015, the technologies developed by LARP were mature enough to allow the spin-off of a major upgrade project to the LHC complex, the High Luminosity LHC (HL-LHC). This paper will focus on the US contribution to HL-LHC, namely the large-aperture low-beta focusing Nb₃Sn quadrupoles and the Radio Frequency Dipole (RFD) Crab Cavities, located in close proximity to the ATLAS and CMS experiments. This contribution, called the HL-LHC Accelerator Upgrade Project (HL-LHC AUP), focuses on production of these quadrupoles and cavities by sharing the work among a consortium of US Laboratories (FNAL, LBNL, BNL and SLAC) and Universities and in close connection with the CERN-led HL-LHC Collaboration. The collaboration achieved commonality of specifications and uniformity of performance. Final development of design, construction and first results from the prototypes are described to indi-cate the status of these critical components for HL-LHC.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP040
About •	paper received ※ 30 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPMP044	Improving the Luminosity for Beam Energy Scan II at RHIC	operation, electron, space-charge, luminosity	540
	C. Liu, M. Blaskiewicz, K.A. Drees, A.V. Fedotov, W. Fischer, C.J. Gardner, H. Huang, D. Kayran, Y. Luo, G.J. Marr, A. Marusic, K. Mernick, M.G. Minty, C. Montag, I. Pinayev, S. Polizzo, V.H. Ranjbar, D. Raparia, G. Robert-Demolaize, T. Roser, J. Sandberg, V. Schoefer, T.C. Shrey, S. Tepikian, P. Thieberger, A. Zaltsman, K. Zeno, I.Y. Zhang, W. Zhang BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The QCD (Quantum Chromodynamics) phase diagram has many uncharted territories, particularly the nature of the transformation from Quark-Gluon plasma (QGP) to the state of Hadronic gas. The Beam Energy Scan I (BES-I) at the Relativistic Heavy Ion Collider (RHIC) was completed but measurements had large statistical errors. To improve the statistical error and expand the search for first-order phase transition and location of the critical point, Beam Energy Scan II will commence in 2019 with a goal of improving the luminosity by a factor of 3-4. The beam lifetime at low energies was and will be limited by some physical effects of which the most significant are intrabeam scattering, space charge, beam-beam, persistent current effects. This article will review these potential limiting factors and introduce the countermeasures which will be in place to improve BES-II luminosity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP044
About •	paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPMP051	56 MHz SRF System for SPHENIX Experiments at RHIC	operation, SRF, HOM, detector	562
	Q. Wu, M. Blaskiewicz, K. Mernick, S. Polizzo, F. Severino, K.S. Smith, T. Xin BNL, Upton, Long Island, New York, USA
	Funding: Work supported by by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy The sPHENIX experiment is a proposal for a new detector at the Relativistic Heavy Ion Collider (RHIC), that plans to expand on discoveries made by RHIC’s existing STAR and PHENIX research groups. To minimize the luminosity outside the 20 cm vertex detector and keeping the radiation to other detector components as low as possible, a 56 MHz SRF system is added to the existing RHIC RF systems to compress the bunches with less beam loss. The existing 56 MHz SRF cavity was commissioned in previous RHIC runs, and contributed to the luminosity at a voltage of 300kV with thermal limitations from the Higher Order Mode coupler at high field, and at 1MV while using its fundamental damper for HOM damping. In this paper, we will analyze and compare the effect of different RF systems at various scenarios, and discuss possible solutions to the Higher Order Mode (HOM) damping scheme to bring the cavity to 2 MV.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP051
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB006	HOM Damping Options for the Z-Pole Operating Scenario of FCC-ee	HOM, damping, impedance, dipole	590
	S. Gorgi Zadeh Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany R. Calaga CERN, Meyrin, Switzerland T. Flisgen FBH, Berlin, Germany U. van Rienen University of Rostock, Rostock, Germany
	The Z-pole option of FCC-ee is an Ampere class machine with a beam current of 1.39 A. Due to high HOM power and strong HOM damping requirements, the present baseline of FCC-ee considers a single cell cavity at 400 MHz. In this paper, different HOM damping schemes are compared for the Z-pole operating scenario with the aim of lowering the parasitic longitudinal and transverse impedance. The HOM power for each damping scheme is also calculated.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB006
About •	paper received ※ 15 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB017	Development of Inter-Digital H-Mode Drift-Tube Linac Prototype with Alternative Phase Focusing for a Muon Linac in the J-PARC Muon G-2/EDM Experiment	linac, DTL, coupling, experiment	606
	Y. Nakazawa, H. Iinuma Ibaraki University, Ibaraki, Japan K. Hasegawa, Y. Kondo, T. Morishita JAEA/J-PARC, Tokai-mura, Japan N. Hayashizaki RLNR, Tokyo, Japan Y. Iwashita Kyoto ICR, Uji, Kyoto, Japan Y. Iwata NIRS, Chiba-shi, Japan N. Kawamura, T. Mibe, M. Otani, T. Yamazaki, M. Yoshida KEK, Ibaraki, Japan R. Kitamura, H.Y. Yasuda University of Tokyo, Tokyo, Japan N. Saito J-PARC, KEK & JAEA, Ibaraki-ken, Japan Y. Sue Nagoya University, Graduate School of Science, Chikusa-ku, Nagoya, Japan
	Funding: This work is supported by JSPS KAKENHI Grant Numbers JP15H03666, JP18H03707, JP16H03987, and JP16J07784. An inter-digital H-mode drift-tube linac (IH-DTL) is developed in a muon linac at the J-PARC E34 experiment. IH-DTL will accelerate muons from 0.34 MeV to 4.5 MeV at a drive frequency of 324 MHz. Since IH-DTL adopts an APF method, with which the beam is focused in the transverse direction using the RF field only, the proper beam matching of the phase-space distribution is required before the injection into the IH-DTL. Thus, an IH-DTL prototype was fabricated to evaluate the performance of the cavity and beam transmission. As a preparation of the high-power test, a test coupler is designed and fabricated. In this paper, the development of the coupler and the result of the low-power measurement will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB017
About •	paper received ※ 29 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019
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MOPRB018	Conceptual Design of Negative-Muon Decelerator for Material Science	induction, experiment, impedance, power-supply	610
	C. Ohmori, M. Otani, K. Shimomura KEK, Tokai, Ibaraki, Japan T. Takayanagi JAEA/J-PARC, Tokai-mura, Japan
	In 2018, a Negative-Muon Spin Rotation and Relaxation technique was developed in J-PARC Material and Life Science Facility. It is a novel scheme to investigate the motion of hydrogens in the chemicals and materials. To study small samples, the surface of materials and thin foils, a low energy negative muon beam is required. To decelerate intense 300-keV muons to 15-keV, we propose a system which consists of pulse generators and multi-gap induction decelerators. In this design, an inductive adder scheme is considered to use for the high voltage pulse source. High impedance magnetic alloy ring cores will be loaded in the decelerator cells. The high impedance cores which have much larger size than those for public use were developed for J-PARC RF systems and used for many applications including CERN booster RF, anti-proton deceleration and medical accelerator. In this paper, we present a conceptual design of muon deceleration system.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB018
About •	paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPRB022	Current Status of the High-Power RF Systems During Phase2 Operation in SuperKEKB	klystron, operation, GUI, status	619
	K. Watanabe, K. Marutsuka, Ma. Yoshida, S.I. Yoshimoto KEK, Ibaraki, Japan
	The SuperKEKB is an asymmetric-energy two-ring collider consisting of the high-energy ring (HER) for 7 GeV electrons and the low-energy ring (LER) for 4 GeV positrons at KEK. Both the electron and positron beams are injected from the Linac injector complex, which includes a newly constructed 1.1 GeV positron damping ring (DR) to supply a high-quality low emittance positron beam to the LER. The high power RF system has a role to drive the ARES cavities and the superconducting RF cavities for the SuperKEKB. The operating frequency of RF system is 508.9 MHz. The required RF power from the klystron at maximum storage beam current is ~850 kW (CW). The number of RF stations is total 31 for the main ring (MR) and DR. The status of each high power RF components, troubles of them and operation condition that occurred during phase 2 commissioning from Feb 2018 to July 2018 will be reported in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB022
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB027	Progress of HEPS Accelerator System Design	storage-ring, booster, vacuum, lattice	633
	P. He, J.S. Cao, F.S. Chen, J. Chen, H. Dong, D.Y. He, Y. Jiao, W. Kang, C.H. Li, J.Y. Li, F. Long, H.H. Lu, X. Qi, Q. Qin, H. Qu, J.Q. Wang, G. Xu, J.H. Yue, J. Zhang, J.R. Zhang, P. Zhang IHEP, Beijing, People’s Republic of China
	The 4th generation ring-based light sources, HEPS (High Energy Photon Source) 7BA lattice has been de-veloped at IHEP. This is 6Gev, 200mA machine which has horizontal emittance Ɛh around 60pm.rad to gain the high brilliance photon beam. this compact lattice design bring so many engineering challenges for accelerator magnets, vacuum components, beam diagnotice, etc. This paper will present the noval lattice design and subsystem design progress.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB027
About •	paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB033	Preliminary Research of HOM for 100MHz Superconducting Cavity in the Pre-Research Project of HALS	HOM, impedance, damping, simulation	649
	Y.G. Tang, L. Wang, C.-F. Wu USTC/NSRL, Hefei, Anhui, People’s Republic of China
	A 100MHz QWR superconducting cavity is researched in the pre-research project of Hefei Advanced Light Source (HALS). Higher order modes (HOM) damping is a big challenge for synchrotron radiation light source. In this paper, we first apply the novel choke mode structure to the 100MHz QWR (quarter wave resonator) cavity in order to damp the HOM. We identify the main harmful higher order modes. The HOMs in the QWR cavity are suppressed by optimizing the choke dimensions. The broadband HOM impedance spectrum of the cavity was also evaluated by calculating the beam induced wake potential in time domain. The results show that choke mode structure has a good HOM damping effect on the QWR cavity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB033
About •	paper received ※ 25 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB052	Gamma Factory at CERN: Design of a Proof-of-Principle Experiment	photon, laser, experiment, electron	685
	Y. Dutheil, R. Alemany-Fernández, H. Bartosik, N. Biancacci, R. Bruce, P. Czodrowski, V. Fedosseev, B. Goddard, S. Hirlaender, J.M. Jowett, R. Kersevan, M. Kowalska, M. Lamont, D. Manglunki, J. Molson, A.V. Petrenko, M. Schaumann, F. Zimmermann CERN, Geneva, Switzerland S.E. Alden, A. Bosco, S.M. Gibson, L.J. Nevay JAI, Egham, Surrey, United Kingdom A. Apyan ANSL, Yerevan, Armenia E.G. Bessonov LPI, Moscow, Russia A. Bosco, S.M. Gibson, L.J. Nevay Royal Holloway, University of London, Surrey, United Kingdom F. Castelli Università degli Studi di Milano, Milano, Italy F. Castelli, C. Curatolo, L. Serafini INFN-Milano, Milano, Italy K. Kroeger FSU Jena, Jena, Germany A. Martens LAL, Orsay, France V. Petrillo Universita’ degli Studi di Milano, Milano, Italy M. Sapinski, T. Stöhlker GSI, Darmstadt, Germany G. Weber IOQ, Jena, Germany Y.K. Wu FEL/Duke University, Durham, North Carolina, USA
	The Gamma Factory (GF) initiative proposes to create novel research tools at CERN by producing, accelerating and storing highly relativistic partially stripped ion beams in the LHC rings and by exciting their atomic degrees of freedom by lasers, to produce high-energy photon beams. Their intensity would be several orders of magnitude higher than those of the presently operating light sources in the particularly interesting gamma-ray energy domain reaching up to 400 MeV. In this energy domain, the high-intensity photon beams can be used to produce secondary beams of polarized electrons, polarized positrons, polarized muons, neutrinos, neutrons and radioactive ions. Over the years 2017-2018 we have demonstrated that these partially stripped ion beams can be successfully produced, accelerated and stored in the CERN accelerator complex, including the LHC. The next step of the project is to build a proof of principle experiment in the SPS to validate the principal GF concepts. This contribution will present the initial conceptual design of this experiment along with its main challenge - the demonstration of the fast cooling method of partially stripped ion beams.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB052
About •	paper received ※ 19 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB057	An Approach to Alleviating Heavy Beam Loading Effect on the Synchrotron Machine Through the Existed Low Level RF Feedback System	feedback, beam-loading, impedance, simulation	697
	L.-H. Chang, F.Y. 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
	To pursue the highest brightness and intensity of the synchrotron light, the synchrotron machines are pushed to operate with as high as possible of the beam current. To suppress the heavy beam loading effects, the direct RF feedback is currently widely used. This paper provides an another approach to alleviating the heavy beam loading effects on machine operation. Different from the direct RF feedback technique, this approach need not add additional feedback loop to the existed RF feedback system. Applying a proper angle rotation to the I-Q error signals of the cavity voltage, before entering the existed feedback loop, is the only action required in this approach. The paper will explain the working mechanism and investigate the behaviour of this approach, through an example case, with numerical simulation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB057
About •	paper received ※ 16 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019
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MOPRB063	Longitudinal Tomography in a Scaling FFA	synchrotron, experiment, proton, injection	719
	D.J. Kelliher, C. Brown, J.-B. Lagrange, S. Machida, C.R. Prior, C.T. Rogers STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom Y. Ishi, Y. Kuriyama, H. Okita, T. Uesugi Kyoto University, Research Reactor Institute, Osaka, Japan S.L. Sheehy JAI, Oxford, United Kingdom
	In a synchrotron the rate of acceleration is limited by the ramp rate of the bending field. There is no such constraint in a Fixed Field alternating gradient Accelerator (FFA), allowing a much higher repetition rate and novel modes of operation such as beam stacking. It is of interest to obtain a picture of the longitudinal phase space from experimental data in order to diagnose the response of the beam to various RF programmes. Longitudinal tomography, already well established in synchrotrons, involves reconstructing the phase space using bunch monitor data obtained for a sufficient number of turns in a synchrotron oscillation. Here we reconstruct the longitudinal phase space using data from the 150 MeV scaling FFA at KURNS, Osaka, Japan.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB063
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB077	Results From the CBETA Fractional Arc Test	linac, MMI, emittance, betatron	751
	C.M. Gulliford, N. Banerjee, A.C. Bartnik, J.A. Crittenden, P. Quigley 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
	We report on commissioning experiments of the Cornell Brookhaven Energy Recovery Test Accelerator Fractional Arc Test. The beam from the injector is accelerated by a linac with a 36 MeV design energy gain, is transported through a splitter line that uses conventional magnets, and finally into a four cell permanent magnet based fixed field alternating (FFA) gradient arc. We measure beam properties in the injector, calibrate the energy gain and phase of the linac cavities using time of flight to a BPM at the end of the linac. We scan individual cavity phases and pass beam through the cavities to determine the transverse offset of the individual cavities. We scan the beam position in the splitter BPMs to estimate and correct the nonlinearity in the BPM response. We tested our path length adjustment mechanism. We measure the dispersion and R56 in the FFA arc.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB077
About •	paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPRB078	Beam Based Measurements of the CBeta Main Linac Cavity Alignment	linac, cryomodule, survey, acceleration	755
	C.M. Gulliford, A.C. Bartnik, J.A. Crittenden, P. Quigley 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
	Funding: This work was funded by NYSERDA, the New York State Energy Research and Development Agency. Initial attempts at steering the beam through the CBETA main linac indicated the cavities were vertically offset with respect to the BPMs on either side of the linac. In particular, manual alignment of the beam in the first and last cavities suggested a vertical offset of roughly 5 mm. This work presents the results of beam based measurements of the individual cavity offsets taken during the CBETA Fractional Arc Test. With only a single cavity powered at a time, beam was injected at several different vertical offsets, the RF phase was scanned over 360 degrees, and the beam position was measured at the end of the cryomodule. We analyzed the data in two ways. We first compute the RMS spread in the measurements at a given position, and considered the offset with the minimum RMS spread to be the cavity offset. We also fit the measurements at a given phase to a line as a function of initial displacement, and use a model for the transfer matrix of the cavity and downstream drift to compute the offset. The two methods agree well, resulting in an average vertical offset of the main linac cavities of 4.0 plus/minus 1 mm.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB078
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB080	Transient Beam Loading and Mitigation in JLEIC Collider Rings	electron, klystron, luminosity, beam-loading	758
	J. Guo, R.A. Rimmer, H. Wang, S. Wang JLab, Newport News, Virginia, USA J.D. Fox Stanford University, Stanford, California, USA T. Mastoridis CalPoly, San Luis Obispo, California, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177, with additional support from U.S. DOE Award Number DE-SC-0019287 The Jefferson Lab Electron-Ion Collider (JLEIC) is an asymmetric high luminosity ring-ring collider proposed as the next major R&D facility for the nuclear physics community. Both of JLEIC’s electron and ion collider rings have high beam current with gaps serving the pur-poses of beam abort, ion clearing, etc. Such a time-varying beam loading in the RF cavities would generate modulation in cavity RF phase/voltage, causing cyclic shift of collision point and potential luminosity loss. We studied a few approaches to mitigate the RF phase modu-lation and IP shift, such as correcting the RF phase/voltage modulation with traditional LLRF feed-back, one-turn feedback (OTFB), or RF feedforward (FF); optimizing the bunch fill pattern to limit the RF phase/voltage modulation to a small fraction of the bunch trains in the collider ring; or matching the RF phase modulation in the two rings. The preliminary re-sults are discussed in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB080
About •	paper received ※ 23 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019
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MOPRB081	Electron Beam’s Closed Orbit in the Crab Crossing Scheme of Future Electron-Ion Colliders	electron, closed-orbit, luminosity, simulation	762
	Y. Hao, V. Ptitsyn BNL, Upton, Long Island, New York, USA J. Qiang LBNL, Berkeley, California, USA
	In crab-crossing collision geometry the closed orbit of the electron beam will be altered by the beam-beam interaction and the tilted head and tail of the ion beam. We will present the linear model to determine the closed orbit and compare with the simulation. Also, the relation of the closed orbit and the synchro-betatron resonance will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB081
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB082	Scaling Properties of the Synchro-Beta Resonance in Crab Crossing Scheme of Future Electron Ion Collider	luminosity, resonance, electron, simulation	766
	Y. Hao, Y. Luo, V. Ptitsyn BNL, Upton, Long Island, New York, USA J. Qiang LBNL, Berkeley, California, USA
	The synchro - beta resonance due to the beam-beam interaction was predicted by the strong-strong simulation in the future electron-ion collider designs. In this paper, we study the scaling properties of the degradation rate of this unwanted resonance. These studies motivated the possible countermeasures of the luminosity degradation associated with the resonance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB082
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB085	First Results from Commissioning of Low Energy RHIC Electron Cooler (LEReC)	electron, MMI, gun, cathode	769
	D. Kayran, Z. Altinbas, D. Bruno, M.R. Costanzo, K.A. Drees, A.V. Fedotov, W. Fischer, M. Gaowei, D.M. Gassner, X. Gu, R.L. Hulsart, P. Inacker, J.P. Jamilkowski, Y.C. Jing, J. Kewisch, C.J. Liaw, C. Liu, J. Ma, K. Mernick, T.A. Miller, M.G. Minty, L.K. Nguyen, M.C. Paniccia, I. Pinayev, V. Ptitsyn, V. Schoefer, S. Seletskiy, F. Severino, T.C. Shrey, L. Smart, K.S. Smith, A. Sukhanov, P. Thieberger, J.E. Tuozzolo, E. Wang, G. Wang, A. Zaltsman, H. Zhao, Z. Zhao BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The brand new non-magnetized bunched beam electron cooler (LEReC) [1] has been built to provide luminosity improvement for Beam Energy Scan II (BES-II) physics program at the Relativistic Heavy Ion Collider (RHIC) BES-II [2]. The LEReC accelerator includes a photocathode DC gun, a laser system, a photocathode delivery system, magnets, beam diagnostics, a SRF booster cavity, and a set of Normal Conducting RF cavities to provide sufficient flexibility to tune the beam in the longitudinal phase space. This high-current high-power accelerator was successfully commissioned in period of March -September 2018. Beam quality suitable for cooling has been demonstrated. In this paper we discuss beam commissioning results and experience learned during commissioning. [1] A. Fedotov et al., ’Status of bunched beam electron cooler LEReC’ in these proceedings. [2] C.Liu et al., ’Improving luminosity of Beam Energy Scan II at RHIC’ in these proceedings.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB085
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB091	Combined Strong-Strong and Weak-Strong Beam-Beam Simulations for Crabbed Collision in eRHIC	electron, proton, simulation, luminosity	788
	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 K. Ohmi KEK, Ibaraki, Japan 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 eRHIC, to compensate the geometric luminosity loss, local crab cavities on both sides of the interaction points are to adopted. The previous strong-strong beam-beam simulations showed that the luminosity degradation depends on the crab cavity frequency, proton synchrotron tune, proton bunch length and so on. In this article, we apply a combined strong-strong and weak-strong beam-beam simulation to investigate the incoherent and coherent beam motions with crabbed collison, and to calculate more realistic beam emittance growth rates and luminosity degradation rate.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB091
About •	paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB103	A Phase Shifter for Multi-Pass Recirculating Proton LINAC	proton, linac, superconducting-magnet, superconducting-cavity	802
	J. Qiang, L.N. Brouwer, S. Prestemon LBNL, Berkeley, California, USA
	Funding: This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 and used computer resources at the National Energy Research Scientific Computing Center. The multi-pass recirculating proton linac can significantly improve the usage efficiency of RF superconducting cavities by passing the proton beam through the same cavity multiple times. However, in order to achieve the multiple acceleration, synchronous conditions in phase have to be satisfied. In this paper, we propose a fixed field superconducting magnet system as a phase shifter to meet the synchronous conditions.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB103
About •	paper received ※ 09 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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MOPRB109	Cavity Design for the Updated eRHIC Crabbing System	proton, operation, electron, hadron	818
	S. Verdú-Andrés, Q. Wu BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates LLC under contract no. DE-SC0012704 with the U.S. Department of Energy. The electron-ion collider eRHIC proposed by Brookhaven National Laboratory includes a crabbing system to reestablish head-on collisions for a maximum geometric overlap of the colliding bunches. Since the last cavity design, the crossing angle has increased from 22 to 25 mrad to relax the field strength requirement in one of the IR magnets - increasing the deflecting kick required to collider the bunches head on - and one of the considered options is to have both proton and electron crab cavities work at 200 MHz. The present paper discusses the RF design of the 200 MHz crab cavities for the electron and hadron beams of eRHIC.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB109
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPTS001	Operational Experience with a Sled and Multibunch Injection at the Australian Synchrotron	linac, klystron, operation, injection	830
	M.P. Atkinson, G. LeBlanc AS - ANSTO, Clayton, Australia K. Zingre ASCo, Clayton, Victoria, Australia
	The Australian third generation 3 GeV Synchrotron Light Source was originally commissioned with a 100 MeV linear accelerator (LINAC) fed by two 37 MW S band pulsed klystrons. A pulse compressor in form of a SLED cavity was added later to enable single klystron operation for redundancy in case of a modulator failure. The SLED was successfully commissioned in May 2017 including remote selection of single klystron with SLED operation without degradation of beam energy. Two years on there have been some unexpected operational benefits including reduced phase sensitivity and drift allowing repeatable injection based solely on diagnostic phase read backs. Temperature stabilised power amplifiers based on S band GaN radar technology are being trialed in the meantime with a goal to set and inject with minimal operator adjustment. The results from the SLED cavity upgrade are shown and the latest S band radar technology designs are outlined.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS001
About •	paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPTS003	Superconducting LINAC Design Upgrade in View of the 100 MeV MYRRHA Phase I	linac, cryomodule, lattice, emittance	837
	F. Bouly, M.A. Baylac LPSC, Grenoble Cedex, France A. Gatera SCK•CEN, Mol, Belgium D. Uriot CEA-DRF-IRFU, France
	Funding: Part of this work supported by the European Atomic Energy Community (EURATOM) H₂020 Programme under grant agreement n°662186 (MYRTE project). The goal of the MYRRHA project is to demonstrate the technical feasibility of transmutation in a 100 MW Accelerator Driven System (ADS) by building a new flexible irradiation complex at Mol (Belgium). The MYRRHA facility requires a 600 MeV accelerator delivering a maximum proton current of 4 mA in continuous wave operation, with an additional requirement for exceptional reliability. Supported by SCK•CEN and the Belgium government the project has entered in its phase I: which consists in the development and the construction of the linac first part, up to 100 MeV. We review the design updates of the superconducting linac, with its enhanced fault-tolerance capabilities. The linac capabilities at 100 MeV (Phase I) and 600 MeV (ADS operation) are exposed and discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS003
About •	paper received ※ 23 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPTS007	SARAF Equipped Cavity Test Stand (ECTS) at CEA	cryomodule, cryogenics, controls, EPICS	852
	O. Piquet, C. Boulch, D. Chirpaz-Cerbat, G. Ferrand, F. Gohier, T.J. Joannem, G. Monnereau, Th. Plaisant CEA-IRFU, Gif-sur-Yvette, France D. Braud, P. Carbonnier, P. Guiho, L. Maurice, J. Plouin, P. Sahuquet, N. Solenne CEA-DRF-IRFU, France F. Gouit, A. Pérolat CEA, Gif-sur-Yvette, France
	CEA is committed to delivering a Medium Energy Beam Transfer line and a Super Conducting Linac (SCL) for SARAF accelerator in order to accelerate 5mA beam of either protons from 1.3MeV to 35MeV or deuterons from 2.6 MeV to 40.1MeV. The SCL consists in 4 cryomodules separated by warm section housing beam diagnostics. The two first identical cryomodules hosts respectively 6 and 7 half-wave resonator (HWR) low beta (0.091) cavities 176MHz. In order to test the cavity with its tuner and coupler and validate some design consideration, the Equipped Cavity Test Stand (ECTS) has been designed and will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS007
About •	paper received ※ 07 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPTS008	ESS RFQ: Construction Status and Power Couplers Qualification	rfq, vacuum, coupling, pick-up	855
	O. Piquet, A.C. Chauveau, D. Chirpaz-Cerbat, M. Desmons, A.C. France, P. Hamel, B. Pottin CEA-IRFU, Gif-sur-Yvette, France A. Dubois, A. Gaget, Y. Le Noa, L. Napoly, M. Oublaid, G. Perreu CEA-DRF-IRFU, France
	The 352 MHz Radio Frequency Quadrupole (RFQ) for the European Spallation Source ERIC (ESS) will be de-livered during 2019. It is provided by CEA, IRFU, Sac-lay/France. It consists of five sections with a total length of 4.6 m and accelerates the proton beam from 75 keV up to 3.6 MeV. It will be feed with 1.6 MW peak power through two coaxial loop couplers. This paper will present the manufacturing status of the five sections and the qualification test of the RF power couplers.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS008
About •	paper received ※ 07 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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MOPTS015	FoS Cavity of the Alvarez 2.0 DTL as FAIR Injector	DTL, quadrupole, operation, linac	871
	M. Heilmann, X. Du, L. Groening, S. Mickat, C. Mühle, A. Rubin, V. Srinivasan GSI, Darmstadt, Germany
	The Alvarez 2.0 DTL will be the new post-stripper DTL of the UNILAC at GSI. The existing GSI with its LINAC and SIS18 comprise the main operation injector chain for the Facility for Antiproton and Ion Research FAIR. The new Alvarez-DTL has an operation frequency of 10⁸.4 MHz, an input energy of 1.358 MeV/u and the output energy is 11.4 MeV/u with a total length of 55 m. The presented FoS section will be part of the first cavity of the Alvarez 2.0 DTL. The FoS-cavity with 11 drift tubes (including quadrupole singlets) and a total length of 1.9 m will be copper plated in GSI for high power tests. The design of the quadrupole singlet magnet is finalized; a prototype of a fully functional magnet with drift tube and stems will be fabricated within a design study. Empty drift tubes and all components of the tank shall be delivered 2019 for first low level RF investigations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS015
About •	paper received ※ 13 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019
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MOPTS016	Compression and Noise Reduction of Field Maps	DTL, simulation, MMI, extraction	875
	X. Du, L. Groening GSI, Darmstadt, Germany
	Errors from discretization and large data volume of field maps is a concern for beam dynamics simulations with respect to achievable accuracy and to the required amount of time. High-order singular value decomposition (HOSVD) has recently emerged as simple, effective, and adaptive tool to extract the essentials from multidimensional data. This paper is on the feasibility of compression and noise reduction of electromagnetic field map data with HOSVD. The method has been applied to an electric field map of a DTL cavity with 11 m in length comprising 55 rf-gaps. The original field map data of 220 MB was converted into practically noise-free data of just 20 KB. Noise was reduced by 95% as demonstrated using a cubic cavity for which the analytical field map is available.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS016
About •	paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPTS019	End to End Simulations and Error Studies of the FAIR Proton Linac	linac, simulation, rfq, proton	885
	H. Hähnel, U. Ratzinger, M. Syha, R. Tiede IAP, Frankfurt am Main, Germany C.M. Kleffner GSI, Darmstadt, Germany
	The FAIR proton linac is developed as the high current proton injector for the future FAIR antiproton production chain at GSI. It will provide a 70 mA proton beam at an energy of 68 MeV to the SIS18 synchrotron. The linac consists of an ECR ion source, followed by a ladder RFQ and a normalconducting linac based on CH-type cavities. High beam currents and strict beam quality requirements were the main drivers for the beam dynamics design. To ensure matching between the individual sections and validate the injector design as a whole, end to end simulations were performed using TraceWin with 3D fieldmaps of the CH-linac. In this paper, the final cavity design, as well as the results of end to end simulations and error studies are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS019
About •	paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPTS020	Status of the FAIR Proton LINAC	proton, linac, rfq, simulation	889
	C.M. Kleffner, S. Appel, R. Berezov, J. Fils, P. Forck, P. Gerhard, M. Kaiser, K. Knie, A. Krämer, C. Mühle, S. Puetz, A. Schnase, G. Schreiber, A. Seibel, T. Sieber, V. Srinivasan, J. Trüller, W. Vinzenz, M. Vossberg, C. Will GSI, Darmstadt, Germany H. Hähnel, U. Ratzinger, M. Schuett, M. Syha IAP, Frankfurt am Main, Germany
	For the production of Antiproton beams with sufficient intensities, a dedicated high-intensity 325 MHz Proton linac is currently under construction. The Proton linac shall deliver a beam current of up to 70 mA with an energy of 68 MeV for injection into SIS18. The source is designed for the generation of 100 mA beams. The Low-Energy Beam Transport line (LEBT) contains two magnetic solenoid lenses enclosing a diagnostics chamber, a beam chopper and a beam conus. A ladder 4-Rod RFQ and six normal conducting crossbar cavities of CCH and CH type arranged in two sections accelerate the beam to the final energy of 68 MeV. The technical design of the DTL CH cavities are presented and the commissioning measurements of the ion source are described. The construction and the procurement progress, the design and testing results of the key hardware are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS020
About •	paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPTS022	Current Status of the MYRRHA Cavities	resonance, status, operation, vacuum	892
	K. Kümpel, D. Bade, M. Busch, D. Koser, S. Lamprecht, N.F. Petry, H. Podlech, S. Zimmermann IAP, Frankfurt am Main, Germany
	The MYRRHA (Multi-purpose hYbrid Research Reac-tor for High-tech Applications) Project is a planned ac-celerator driven system (ADS) for the transmutation of long-living radioactive waste. In order test the reliability of the planned 17 MeV injector, a shortened injector with 5.9 MeV consisting of the ion source, a 4-Rod RFQ, 2 Quarter Wave Rebunchers (QWRs) and a total of 7 normal conducting CH structures is currently being installed in Louvein-la-Neuve (LLN, Belgium). Before the cavities can be tested with beam, they are subjected to so-called low power tests several times during the individual con-struction stages in order to be able to correct any devia-tions. This paper describes the status of the two Quarter Wave Rebunchers, which are currently in the process of copper plating and final acceptance, as well as the first two CH structures, the first of which is already being conditioned while CH 2 is still in preparation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS022
About •	paper received ※ 10 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPTS023	Conditioning of the Frontline Cavities of the MYRRHA Injector	rfq, electron, multipactoring, MMI	895
	S. Lamprecht, T. Conrad, K. Kümpel, N.F. Petry, H. Podlech IAP, Frankfurt am Main, Germany J. Belmans, D. Davin, W. De Cock, F. Pompon, D. Vandeplassche SCK•CEN, Mol, Belgium
	The MYRRHA Project (Multi-purpose hYbrid Research Reactor for High-tech Applications) in Mol, Belgium, is an upcoming accelerator driven system (ADS) for the transmutation of long-living radioactive waste. In the injector section of the accelerator, consisting of a 4-rod RFQ and a normal conducting CH-cavity section, the protons will be accelerated up to 17 MeV before entering the superconducting gap-spoke cavity section with an output energy of 600 MeV. A shortened test-injector with an output energy of 5.9 MeV is currently being installed at the SCK. CEN in Louvein-la- Neuve, Belgium. This test-injector serves the purpose of testing the reliability of the planned injector. When commissioning a cavity, it first has to be fed very little power to avoid damage to the structure by flashovers, discharges and multipacting. The power is then slowly increased up to full operation level. In this process, the surfaces are cleaned by heating/outgasing so that the effects disturbing operation described above do no longer occur. This paper will report on the status of the conditioning of the 176.1 MHz 4-rod RFQ up to 120 kW of the MYRRHA-injector and additional measurements concerning the gap voltage which are currently being performed at the SCK. CEN.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS023
About •	paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPTS024	Reconstruction of the Longitudinal Phase Portrait for the SC CW Heavy Ion HELIAC at GSI	heavy-ion, linac, proton, quadrupole	898
	S. Lauber, K. Aulenbacher, W.A. Barth, C. Burandt, F.D. Dziuba, V. Gettmann, T. Kürzeder, J. List, M. Miski-Oglu HIM, Mainz, Germany K. Aulenbacher, F.D. Dziuba IKP, Mainz, Germany W.A. Barth, C. Burandt, F.D. Dziuba, P. Forck, V. Gettmann, M. Heilmann, T. Kürzeder, S. Lauber, J. List, M. Miski-Oglu, A. Rubin, T. Sieber, S. Yaramyshev GSI, Darmstadt, Germany H. Podlech, M. Schwarz IAP, Frankfurt am Main, Germany
	At the GSI Helmholtzzentrum für Schwerionenforschung (GSI) in Darmstadt, Germany, the HElmholtz LInear ACcelerator (HELIAC) is currently under construction. The HELIAC comprises superconducting multigap Crossbar H-mode (SC CH) cavities. The input beam is delivered by an already existing High Charge Injector (HLI). For the further development of the accelerator a detailed knowledge of the input beam parameters to the SC section is necessary. A method for beam reconstruction is incorporated, which provides for longitudinal beam characteristics using measurements with a beam shape monitor and a particle simulation code. This finalizes the investigations on 6D beam parameters, following previous measurements in transversal phase space. The reconstruction of the longitudinal phase portrait is presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS024
About •	paper received ※ 24 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPTS027	Conceptual Design of the Proton LINAC for the High Brilliance Neutron Source HBS	linac, rfq, neutron, proton	910
	H. Podlech, M. Droba, K. Kümpel, S. Lamprecht, O. Meusel, N.F. Petry, P.P. Schneider, M. Schwarz IAP, Frankfurt am Main, Germany J. Baggemann, Th. Brückel, T. Cronert, P.-E. Doege, T. Gutberlet, E. Mauerhofer, U. Rücker, P. Zakalek JCNS, Jülich, Germany S. Böhm NET, Aachen, Germany J. Li IEK, Jülich, Germany C. Zhang GSI, Darmstadt, Germany
	Due to the decommissioning of several research reactors there will be a severe drop in available neutrons for research in Europe in the next decade despite the commissioning of the European Spallation Source (ESS). Compact accelerator-based neutron sources (CANS) could close this gap. The High Brilliance Neutron Source (HBS) currently under development at Forschungszentrum Jülich is scalable in terms of beam energy and power due to its modular design. The driver Linac for HBS at will accelerate a 100 mA proton beam to 70 MeV. The Linac is operated with a beam duty cycle of up to 6% (11% RF duty cycle) and can simultaneously deliver three proton pulse lengths (384 Hz@52 mu-s, 96 Hz@208 mu-s and 24 Hz@832 mu-s) for three neutron production targets. In order to minimize the development effort and the technological risk, state-of-the-art technology of the MYRRHA injector is used. The front end of the HBS Linac consists of an ECR source, LEBT and a 2.5 MeV RFQ followed by a CH-DTL with 35 room temperature CH-cavities. All RF structures are operated at 176.1 MHz and are designed for high duty cycle. Solid-state amplifiers up to 500 kW are used as RF drivers. Due to the beam current and the high average beam power of up to 420 kW, particular attention is paid to beam dynamics. In order to minimize losses, a quasi-periodic lattice with constant negative phase is used. The contribution describes the conceptual design and the challenges of such a modern high power proton accelerator with high reliability and availability.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS027
About •	paper received ※ 07 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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MOPTS034	Advanced Beam Dynamics Design for the Superconducting Heavy Ion Accelerator HELIAC	linac, heavy-ion, SRF, acceleration	928
	M. Schwarz, M. Basten, M. Busch, T. Conrad, H. Podlech IAP, Frankfurt am Main, Germany K. Aulenbacher IKP, Mainz, Germany K. Aulenbacher, W.A. Barth, C. Burandt, M. Heilmann, S. Lauber, J. List, A. Rubin, S. Yaramyshev GSI, Darmstadt, Germany K. Aulenbacher, W.A. Barth, C. Burandt, F.D. Dziuba, V. Gettmann, T. Kürzeder, S. Lauber, J. List, M. Miski-Oglu HIM, Mainz, Germany S. Lauber, J. List KPH, Mainz, Germany
	Funding: Work supported by BMBF contr. No. 05P18RFRB1, EU Framework Programme H₂020 662186 (MYRTE) and HIC for FAIR The standalone superconducting (SC) continuous wave (CW) heavy ion linac HELIAC (HElmholtz LInear ACcelerator) is a common project of GSI and HIM under key support of IAP Frankfurt and in collaboration with Moscow Engineering Physics Institute (MEPhI) and Moscow Institute for Theoretical and Experimental Physics (KI-ITEP). It is intended for future experiments with heavy ions near the Coulomb barrier within super-heavy element (SHE) research and aims at developing a linac with multiple CH cavities as key components downstream the High Charge State Injector (HLI) at GSI. The 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 minimum energy spread. In 2017 the first superconducting section of the linac has been successfully commissioned and extensively tested with beam at GSI. 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 with particular emphasis on realistic assumptions of cavity gap and drift lengths as well as gap voltage distributions for CH3’CH11.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS034
About •	paper received ※ 30 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019
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MOPTS035	Recommissioning of SIS18 After FAIR Upgrades	MMI, operation, controls, extraction	932
	D. Ondreka, C. Dimopoulou, H.C. Hüther, H. Liebermann, J. Stadlmann, R.J. Steinhagen GSI, Darmstadt, Germany
	The synchrotron SIS18 of the GSI facility has recently resumed beam operation after a long shutdown, during which major upgrades for the operation of SIS18 in the FAIR facility were realized. This signifies a major milestone for the mission of GSI and FAIR. On one hand, the scientific program of GSI depends strongly on beam from SIS18, including the very important developments of detectors for FAIR experiments. On the other hand, large parts of the existing GSI accelerator facility, including SIS18, are now operated with the FAIR control system, demonstrating its suitability for control of a large scale accelerator facility. Commissioning of the new control system started during the shutdown with a series of dry runs, which proved very useful to establish the basic functionalities. Recommissioning of SIS18 was further facilitated by the fact that the machine model of SIS18, implemented in the modeling framework LSA, had already been tested with beam several years before the shutdown. Thus, all operation modes of SIS18, including multi-turn injection, electron cooling, as well as fast and slow extraction could be successfully commissioned during the first weeks of operation. Other commissioning activities concerned the operation of new devices installed during the shutdown. These devices, mostly installed to prepare SIS18 for the operation with FAIR design parameters, open new possibilities in the standard operation of SIS18. A challenge for the operation of SIS18 is posed by ground motion due to ground water lowering for the nearby FAIR construction site. Surveys revealed that SIS18 subsided by several centimeters during one year. Even though the machine was realigned prior to recommissioning, the dynamics of the ground motion will continue to affect operation of SIS18.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS035
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPTS036	RFQ Electrodes Change and Upgrade Option at the UNILAC HSI Injector	rfq, simulation, operation, MMI	936
	M. Vossberg, P. Gerhard, L. Groening, S. Mickat, H. Vormann, C. Xiao GSI, Darmstadt, Germany V. Bencini, J.M. Garland, J.-B. Lallement, A.M. Lombardi CERN, Geneva, Switzerland
	In order to meet the beam intensity and quality requirements imposed by FAIR, the HSI-RFQ beam dynamics originally dating from 2009 has been re-designed recently at CERN. Front-to-end simulations demonstrated that the new design meets the FAIR targets. Implementation of the new electrodes, initially planned for 2019, will require re-adaption of the RFQ cavity rf-parameters by re-shaping the stems that keep the electrodes. However, during the beam time 2018 the existing RFQ did not reach its nominal voltage most likely due to expired lifetime of the electrodes originating from 2009. In order to shorten the RFQ maintenance period and to minimize any risk for upcoming beam time 2019, it was decided to post-pone the implementation of the new design and rather just re-producing the 2009 design electrodes. This contribution is on the re-production process as short-term solution and on the full implementation of the new design as mid-term solution. CST simulations performed at GSI assure that the resonance frequency with the new electrode geometry is recuperated through corrections of the carrier rings. The status of the exchange of the electrodes and simulations for the adaptation of the new electrode design are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS036
About •	paper received ※ 13 May 2019 paper accepted ※ 17 May 2019 issue date ※ 21 June 2019
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MOPTS037	Comparison Between Measurement and Simulation of a Full Scale Prototype for the Proton Injector at FAIR	simulation, proton, linac, resonance	940
	A. Seibel, C.M. Kleffner, K. Knie, M. Vossberg GSI, Darmstadt, Germany U. Ratzinger IAP, Frankfurt am Main, Germany
	A dedicated 68 MeV, 70 mA proton injector is required for the research program at FAIR (Facility for Antiproton and Ion Research). This 325 MHz linear injector contains a RFQ and six CH structures. The CH (Crossbar H-mode) structures are working in the H₂10 mode. The main acceleration of this room temperature linac will be provided by the CH structures. For the second acceleration from 11.5 MeV to 24.2 MeV a full scale prototype has been built. This structure consists of two individual CH resonators and a coupling cell. Inside the structure there are 17 tuners, they have an impact on the electric field and the frequency. For operation a flat field is required, therefore this tuners must be correctly positioned. Some series of low level tuning and frequency measurements were done to determine the size of the tuners. Low level measurements and simulations will be compared and presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS037
About •	paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPTS049	The First Replacement of the RF Window of the ACS Cavity	linac, vacuum, operation, proton	971
	J. Tamura, Y. Kondo, T. Morishita JAEA/J-PARC, Tokai-mura, Japan F. Naito, M. Otani KEK, Tokai, Ibaraki, Japan Y. Nemoto Nippon Advanced Technology Co., Ltd., Tokai, Japan
	In 2013, the Annular-ring Coupled Structure (ACS) cavities were installed to the Japan Proton Accelerator Research Complex (J-PARC) linac. Since then, the ACS cavities have been stably running. Although any serious problem induced by the ACS RF window has not yet observed, we decided to replace the RF window of one ACS cavity, which is the eighteenth accelerating cavity in the order of beam energy (ACS18), by the newly manufactured one. The major motivations of the replacement are to check the surface condition of the RF window which have been under operation for nearly five years and to confirm the availability of the newly manufactured RF window. By making use of the summer maintenance period of 2018, we carried out the replacement. This was the first experience for us to replace the RF window installed to the ACS cavity in the linac accelerator tunnel. As for the removed RF window, there was no any abnormal warning found with the visual examination. At the starting up of the cavity’s operation after the maintenance period, we investigated how much time would be required for an RF conditioning. It took around fifty hours so that the peak RF power including the beam loading is stably input to the cavity through the new RF window. The ACS cavity with the new RF window is now stably operating.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS049
About •	paper received ※ 01 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPTS050	VSWR Adjustment for ACS Cavity in J-PARC LINAC	coupling, GUI, simulation, linac	974
	J. Tamura, Y. Kondo, T. Morishita JAEA/J-PARC, Tokai-mura, Japan 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, negative hydrogen beams are accelerated from 190 MeV to 400 MeV by twenty-one Annular-ring Coupled Structure (ACS) accelerating cavities. The input coupler of the ACS high-beta cavity, which is the 21st accelerating cavity (ACS21) in the order of beam acceleration, had a comparatively larger value of the Voltage Standing Wave Ratio (VSWR) than those of the other ACS cavities. To adjust the VSWR of the ACS21, we designed and fabricated a rectangular waveguide with a capacitive iris which conduces to a better matching between the cavity and the waveguide. In the 2018 summer maintenance period, we installed the newly fabricated waveguide to the ACS21 in the position between the input coupler and the RF window. Consequently, the VSWR of the ACS21 was successfully decreased to the target value which leads to the critical coupling under the nominal accelerating condition with 50-mA peak beam current.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS050
About •	paper received ※ 01 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019
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MOPTS052	Simulation of Electric and Thermal Behavior of Cryogenic Three-cell Copper Accelerating Cavity for High Gradient Experiments	simulation, cryogenics, coupling, experiment	980
	T. Tanaka, K. Hayakawa, Y. Hayakawa, K. Nogami, T. Sakai, Y. Sumitomo, Y. Takahashi LEBRA, Funabashi, Japan
	A C-band three-cell pi-mode accelerating cavity made of high purity copper is under design for use in ultra-high accelerating gradient experiments at a cavity temperature of 20 K. The basic configuration, consisting of mode converter, short circular waveguide and cells with round periphery, is the same as that which was previously employed in the cold model for a 2.6-cell photocathode electron gun cavity. Though the 0.6-cell part in the previous model is replaced with a full cell having a beam duct, the overall electric property of the cavity will not change significantly. The RF input coupling coefficient is adjusted to around 10 at 20 K, which is expected to be lowered significantly due to the increase in the surface resistance by the rapid temperature rise during a high power RF input. The results of the simulations on the electric field and the temperature rise along the cavity surface during the RF pulse are discussed in the report.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS052
About •	paper received ※ 13 May 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019
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MOPTS056	Optimization of SC Cavity Type for CSNS Linac Upgrade	linac, operation, neutron, acceleration	987
	Y. Wang, M.X. Fan, A.H. Li, B. Li, P.H. Qu IHEP CSNS, Guangdong Province, People’s Republic of China J.P. Dai, H.C. Liu, P. Sha IHEP, Beijing, People’s Republic of China X.L. Wu DNSC, Dongguan, People’s Republic of China
	In order to increase CSNS beam power from 100kW to 500kW, the Linac injection energy need to be increased from 80MeV to 300MeV. The combined layout of superconducting spoke cavities and elliptical cavities will be adopted to accelerate H⁻ beam to 300MeV. Two operation frequency of spoke cavities were compared with single and double spoke structure, a compact 648MHz βg=0.4 single spoke cavity was proposed, and the RF performance was presented, as well as the MP behavior.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS056
About •	paper received ※ 09 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPTS057	SSPA upgrade plan design for CiADS	controls, coupling, klystron, simulation	990
	Q. Chen, Z. Gao, Y. He, G. Huang, R. Huang, T.C. Jiang, S.H. Liu, L.P. Sun, X.W. Wang, Z.J. Wang, W.M. Yue IMP/CAS, Lanzhou, People’s Republic of China
	Funding: Supported by the National natural science foundation of China (Grand No. 11525523 and 91426303) For ADS application, both research and commercial facilities requires extremely large amount of RF power to drive several mega watts beam power, so proper RF power upgrade plan can reduce the budget per phase and increase the valuable experience in engineering. CiADS (China initiative Accelerator Drive System) proposes to employ SSPA (Solid State Power Amplifier) as RF power source for flexible configuring and upgrading in the future. In this paper, from an engineering point of view, it is acceptable if proper matching beam current was selected for adopting fixed-coupling input coupler while only sacrificed some RF power during the upgrade plan. SSPA upgrade plan start with the stablility requirement to determine bandwidth, then combined with other RF power requirements to select output level, finally, checking how much the surplus of selected level SSPA for detuning control. The calculation and evaluation results for a §I{545}{MeV} physical design lattice illustrate that some resonance cavities had very limited surplus RF power left for detuning control that provided necessary optimization direction and guidelines for both physical design and SSPA arrangement.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS057
About •	paper received ※ 30 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPTS059	The Status of CiADS Superconducting LINAC	linac, proton, cryomodule, operation	994
	Z.J. Wang, Y. He, G. Huang, S.H. Liu, T. Tan, Y.Q. Wan, F.F. Wang, W.M. Yue IMP/CAS, Lanzhou, People’s Republic of China
	CiADS (China initiative Accelerator Driven System) approved by Chinese government at 2016 aims to build the first ADS experimental facility to demonstrate the nuclear waste transmutation. The CiADS driving linac can accelerate 5 mA proton beam to 500 MeV at the beam power up to 2.5 MW with the state-of-the-art accelerator technologies. The challenging programs include beam loss control-oriented physics design, high performance CW operated superconducting cavities, SRF cryomod-ules, and highly efficient RF amplifier system. As the driving linac of the ADS system, the RAMI characters will serve as the design philosophy to guide the physics design and the choice of technical routes. The physics design and key technologies of the high-power machine are descried in the paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS059
About •	paper received ※ 14 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019
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MOPTS063	Design and Low Power Test of a Prototype HOM LINAC	DTL, HOM, linac, impedance	1001
	L. Lu, T. He, C.C. Xing, L. Yang IMP/CAS, Lanzhou, People’s Republic of China L. Yang University of Chinese Academy of Sciences, Beijing, People’s Republic of China
	A 325MHz HOM (higher order mode) type linac was proposed and studied for proton or heavy ion acceleration in medium energy region. The cavity was finished the fabrication already by using copper and aluminum material. We will report results of low power test of the HOM linac in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS063
About •	paper received ※ 29 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPTS072	RF DESIGN OF AN 81.25 MHz BENT-VANE TYPE RFQ	rfq, linac, ECR, simulation	1015
	L. Yang, T. He, Y. He, L. Lu, C.C. Xing, L. Yang IMP/CAS, Lanzhou, People’s Republic of China A.H. Li IHEP, Beijing, People’s Republic of China
	The bent-vane type RFQ is proposed at IMP, Chinese Academy of Sciences, which can downsize cross section and has the simple cooling system in low frequency field. The vanes of the four-vane type RFQ are bent to form the new RFQ structure. In order to research its RF properties, the prototype cavity of an 81.25 MHZ bent-vane type RFQ is designed. This paper presents the preliminary RF design of the prototype cavity.
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About •	paper received ※ 17 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPTS075	Design and Experiment of a Window-Type CW Deuteron RFQ	rfq, experiment, operation, Windows	1021
	K. Zhu, M.J. Easton, P.P. Gan, S.L. Gao, H.P. Li, S. Liu, Y.R. Lu, Q.Y. Tan, L. Tao, Z. Wang PKU, Beijing, People’s Republic of China W.P. Dou, Y. He, C. Wang, Q. Wu, H.W. Zhao IMP/CAS, Lanzhou, People’s Republic of China
	A deutron CW RFQ was designed and fabricated in Peking University. It will accelerate 50mA CW deutron beam from 50keV to 1MeV at 162.5MHz. The novel structure of four-vane with window was used to seperate the dipole mode from the working mode. The field tuning of this RFQ was different from conventional four vane RFQ because that the four quadrants of RFQ cavity were coupled. The discipline of field tuning was studied by simulation and experiment. The beam dynamics of the RFQ was designed by equipartation and matching method, limit current effect was considered at the same time. The final design result of the RFQ was: voltage between electrodes was 60kV, transport efficiency of RFQ is 98%, field unflatness is less than 2% after tuning, the deformation of RFQcavity is less than 80um. Only 47 hours was spent to increase CW power of cavity from 0 to 55kW in high power test and The RFQ can working stable at the design voltage. The preliminary H²⁺ beam exeperiment has been done and 1.78mA CW beam was obtained at exit of RFQ. This paper will introduce the detail of design and experiment of the RFQ.
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MOPTS080	Status and Installation Plan of RISP RFQ at Project Site	rfq, site, experiment, resonance	1031
	B.-S. Park, I.S. Hong IBS, Daejeon, Republic of Korea
	Funding: Supported by the Rare Isotope Science Project of Institute for Basic Science funded by the Ministry of Science, ICT (MSIP) and the National Research Foundation (NRF) of Korea (2013M7A1A1075764). The Rare Isotope Science Project (RISP) at Institute for Basic Science (IBS) has been developed a Radio Frequency Quadrupole(RFQ), which was fabricated and commissioned at the off-site test facility. An O+7 beam was accelerated from 10keV/u to 516keV/u as a preliminary beam test. For CW and high power operation, RF conditioning test was also conducted. The RISP RFQ is 5 meters long, 1 meter in diameter and weighs about 16 tons. It was disassembled and transported to the project site, Sin-dong, for installation as the injector system. The installation commenced in April 2019 and the commissioning of the injector system is expected to begin in early 2020. In this paper, the installation status and plans were summarized.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS080
About •	paper received ※ 15 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019
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Paper

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MOYPLM2

SRF Operation at XFEL: Lessons Learned After More Than One Year

FEL, operation, linac, SRF

12

D. Kostin, V. Ayvazyan, J. Branlard, W. Decking, L. Lilje, M. Omet, T. Schnautz, E. Vogel, N. Walker
DESY, Hamburg, Germany

The European XFEL is the largest high-field SRF installation in the world and has now been in operation more than a year. It serves as a "prototype" for other facilities being constructed or in the planning stages. Performance of the operation of the SRF system over this period of time and the lessons learned will be discussed.

Slides MOYPLM2 [4.351 MB]

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MOYPLM3

Progress with the High Luminosity LHC Project at CERN

luminosity, operation, quadrupole, collider

17

L. Rossi, O.S. Brüning
CERN, Geneva, Switzerland

The High Luminosity LHC (HL-LHC) project aims at upgrading the LHC by increasing the peak luminosity by a factor five, to allow to collect 3000 fb-1 for ATLAS and CMS experiments, each, which is ten times more than what is foreseen in the LHC. The upgrade is based on multiple factors. One factor is doubling the beam current, also thanks to the injector upgrade (LIU) project, and another one is operation in levelling mode. The most critical upgrade is the deploying of a stronger inner quadrupole triplet in the low-beta insertions with more than twice-larger aperture w.r.t. present LHC triplet, thanks to the use of Nb₃Sn superconductor, a world first for accelerators, with almost 12 T peak field in the coils. The novel concept of ATS optics allows to utilise the increased aperture efficiently by generating β^* values 3 to 4 times below the nominal values of the LHC. We will make use of compact crab cavities for hadrons (also a novelty in accelerators) to allow almost head-on collisions despite the larger crossing angle. We are developing new collimator insertions in the dispersion suppressor region to handle the losses in the cold part of the machine (the beam halo stores 30 MJ) thanks to the use of a few 11 T dipoles based on Nb₃Sn technology. We also aim at reducing drastically the impedance contribution of collimators by utilizing new materials and coating techniques. Many other technologies are developed for HL-LHC like new SC links of 100 kA: HL-LHC is critical as a technology turning point for HEP colliders as it is for Physics reach. The technologies developed for HL-LHC, namely (but not only) the high field superconducting magnets, are critical for the post-LHC hadron collider, like a High Energy LHC or the 100 km Future Circular Collider

Slides MOYPLM3 [21.679 MB]

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MOZPLM1

Operation Status and Upgrade of CSNS

linac, MMI, rfq, DTL

23

S. Fu, S. Wang
IHEP, Beijing, People’s Republic of China

China Spallation Neutron Source (CSNS) accelerator complex consists of a front end, an 80MeV DTL linac, and a 1.6GeV Rapid Cycling Synchrotron (RCS).It is designed with a beam power of 100kW in the first phase and reserves upgrade capability to 500kW in the second phase. It has completed initial beam commissioning and has started user operation in 2018. And meanwhile the beam power is quickly going up from the initially above 10kW to 50kW during the user operation, and we can foresee that the designed beam power of 100 kW can be reached in the next year. This talk gives the most recent status of beam power ramping in CSNS, as well as future upgrade plan to increase the beam power up to 500 kW.

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MOZZPLM1

Beam Commissioning of the Demonstrator Setup for the Superconducting Continuous Wave HIM/GSI-Linac

linac, heavy-ion, cryomodule, solenoid

33

M. Miski-Oglu, K. Aulenbacher, V. Gettmann, T. Kürzeder
HIM, Mainz, Germany
K. Aulenbacher, F.D. Dziuba
IKP, Mainz, Germany
W.A. Barth, C. Burandt, V. Gettmann, M. Heilmann, T. Kürzeder, A. Rubin, A. Schnase, S. Yaramyshev
GSI, Darmstadt, Germany
W.A. Barth, S. Yaramyshev
MEPhI, Moscow, Russia
M. Basten, M. Busch, T. Conrad, H. Podlech, M. Schwarz
IAP, Frankfurt am Main, Germany

During successful beam commissioning of the superconducting 15-gap Crossbar H-mode cavity at GSI Helmholtzzentrum für Schwerionenforschung heavy ions up to the design beam energy have been accelerated. The design acceleration gain of 3.5 MeV inside a length of less than 70 cm has been reached with full transmission for heavy ion beams of up to 1.5 particle mueA. The measured beam parameters confirm sufficient beam quality. The machine beam commissioning is a major milestone of the R&D for the superconducting heavy ion continuous wave linear accelerator HELIAC of Helmholtz Institute Mainz (HIM) and GSI developed in collaboration with IAP Goethe-University Frankfurt. The next step is the procurement and commissioning of so called ’Advanced Demonstrator’ - the first of series cryo module for the entire accelerator HELIAC. Results of further Demonstrator beam tests, as well as the status of the Advanced demonstrator project will be reported.

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MOPGW002

Longitudinal Kicker Design for Sirius Light Source

kicker, HOM, GUI, feedback

57

H.O.C. Duarte, A. Barros
LNLS, Campinas, Brazil

An overloaded cavity kicker for the Sirius longitudinal bunch-by-bunch feedback system will be presented in this contribution. 4th generation light sources’ lower aperture of vacuum chambers lead to higher cutoff frequencies, jeopardizing the electromagnetic performance of cavities by trapping higher order modes (HOMs) inside the structure. With the objective of damping longitudinal and transverse HOMs without compromising the kicker shunt impedance, solutions as cavity radius reduction, tapered transitions and other geometry changes are discussed herein.

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MOPGW004

Microphonics Suppression in ARIEL ACM1 Cryomodule

GUI, cryomodule, linac, pick-up

65

Y. Ma, K. Fong, J.J. Keir, D. Kishi, S.R. Koscielniak, D. Lang, R.E. Laxdal, R.S. Sekhon
TRIUMF, Vancouver, Canada

Now the stage of the 30MeV portion of ARIEL (The Advanced Rare Isotope Laboratory) e-Linac is under commissioning which includes an injector cryomodule (ICM) and the 1st accelerator cryomodule (ACM1) with two cavities configuration. The two ACM1 cavities are driven by a single klystron with vector-sum control and running in CW mode. During the commissioning, the ACM1 cavities gradient and stability was limited by ponderomotive effect. Acoustic noise from the environment vibration generated by cooling water system, cryogenic system and vacuum system have been identified to certain external source and some damping has been installed. In this paper, the progress of the microphonics suppression of ACM1 is presented.

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MOPGW014

Developing Beam Optics for the BESSY VSR Project

optics, quadrupole, storage-ring, lattice

94

F. Andreas, M. Abo-Bakr, F. Armborst, P. Goslawski
HZB, Berlin, Germany

At BESSY II due to the continuously increasing interest in short pulse operation, a major upgrade of the ring will enable simultaneous storage of long and short bunches. This Variable pulse-length Storage Ring (VSR) will be achieved by the installation of additional superconducting high gradient cavities. The cavities will be assembled into one cryomodule in one of the straights of the storage ring. As this module needs more space then initially assumed, one possible solution is to remove two quadrupoles to gain available installation length. The quadrupoles were switched off in simulations and the lattice was optimized with regard to the linear order. The best solution found was transferred to the storage ring, where storage of high current with reasonable injection efficiency and lifetime was possible. The proposed optics has to be further optimized in terms of nonlinear beam dynamics, but has shown that an available installation length can be increased.

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MOPGW025

Beam Breakup Simulations for the Mainz Energy Recovering Superconducting Accelerator MESA

HOM, cryomodule, simulation, operation

135

C.P. Stoll, F. Hug
KPH, Mainz, Germany

Funding: This work is supported by DFG through PRISMA+ cluster of excellence EXC 2118/2019, RTG 2128 and by the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No 730871.
MESA is a two pass energy recovery linac (ERL) currently under construction at the Johannes Gutenberg-University in Mainz. MESA uses four 1.3 GHz TESLA type cavities with 12.5 MV/m of accelerating gradient in two modified ELBE type cryomodule with improved thermal connection of the HOM antennas and cw operation. In the first stage of MESA operation 1mA of beam current is foreseen, which will later be upgraded to 10mA. One potential limit to maximum beam current in ERLs is the transverse beam breakup (BBU) instability induced by dipole Higher Order Modes (HOMs). These modes can be excited by bunches passing through the cavities off axis. Following bunches are then deflected by the HOMs, which results in even larger offsets for recirculated bunches. This feedback can even lead to beam loss. Simulation results for HOM spectra of a single TESLA cavity are available for example in *. It was possible to measure the HOM spectra in the cold, not tuned cavities at DESY and in the cold string tuned to the 1.3 GHz fundamental mode at Mainz. Results for the maximum beam current for MESA, limited by BBU, for the various HOM spectra are presented.
* "Eigenmode Calculations for the TESLA Cavity Considering Wave-Propagation Losses through Fundamental and Higher-Order Mode Couplers", W. Ackermann, H. De Gersem, C. Liu, and T. Weiland

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MOPGW030

New Analytical Derivation of Group Velocity in TW Accelerating Structures

dipole, simulation, polarization, coupling

155

M. Behtouei, M. Migliorati, L. Palumbo
Sapienza University of Rome, Rome, Italy
L. Faillace
Universita’ degli Studi di Milano & INFN, Milano, Italy
B. Spataro
INFN/LNF, Frascati, Italy

Ultra high-gradient accelerating structures are needed for the next generation of compact light sources. In the framework of the Compact Light XLS project, we are studying a high harmonic traveling-wave accelerating structure operating at a frequency of 35.982 GHz, in order to linearize the longitudinal space phase. In this paper, we propose a new analytical approach for the estimation of the group velocity in the structure and we compare it with numerical electromagnetic simulations that are carried out by using the code HFSS in the frequency domain.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW030

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paper received ※ 08 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW039

Investigation of Longitudinal Beam Dynamics With Harmonic Cavities by Using the Code Mbtrack

impedance, operation, synchrotron, beam-loading

178

N. Yamamoto
KEK, Ibaraki, Japan
A. Gamelin, R. Nagaoka
SOLEIL, Gif-sur-Yvette, France

In diffraction-limited light sources, the study of collective effects is essential. With harmonic cavities (HCs), the ’flat potential condition’ can be achieved, lengthening the bunch by a factor of ~5. However, the effective rf voltage seen by the beam becomes sensitive to both positions and distributions of all bunches, as the beam-induced voltage of both HCs and fundamental cavities (FCs) contribute. In addition, when there are empty buckets, the transient beam loading induces considerable variations of the rf voltage impacting the beam performance*. Here the use of analytical approaches is difficult. Then we introduced the new functions to treat the high-Q resonators driven by either or both of the beams and external generators to the code mbtrack**. Using these features, various operating conditions with arbitrary fill patterns can be studied; coupled bunch instability induced by HOMs of the cavity, Robinson instabilities and general beam dynamics with HCs. The growth rates of the instabilities described above are compared with analytical results. The ring performance with HCs in several fill patterns shall be also reported.
* N.Yamamoto, et al., PRAB, 21, 012001 (2018).
**G. Skripka, et al., NIM A806, 221 (2016).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW039

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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MOPGW040

Beam Optics Design of the Superconducting Region of the JAEA ADS

emittance, linac, controls, lattice

181

B. Yee-Rendón, Y. Kondo, F.M. Maekawa, S.I. Meigo, J. Tamura
JAEA/J-PARC, Tokai-mura, Japan

The Japan Atomic Energy Agency (JAEA) is proposing an Accelerator Driven Subcritical System (ADS) for the transmutation of the nuclear waste. ADS will consist of a superconducting CW proton linear accelerator of 30MW and a subcritical nuclear reactor core. The main part of the acceleration will take part in the superconducting region using five types of radio frequency cavities. The ADS operation demands a high intensity and reliability of the beam. Therefore, the beam optics design plays a fundamental role to reduce the beam loss, control emittance growth and beam halo.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW040

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paper received ※ 17 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW047

Analysis and Simulation of the "After-Pulse" RF Breakdown

simulation, timing, GUI, experiment

196

X. Lin, H.B. Chen, Z.N. Liu, J. Shi, H. Zha
TUB, Beijing, People’s Republic of China
X.W. Wu
CERN, Meyrin, Switzerland

During the high power experiment of a single-cell standing-wave accelerating structure, it was observed that many RF breakdowns happen when the field inside cavity is decaying after the input rf pulse is off. The distribution of breakdown timing shows a peak at the moment of RF power switches off. A series of simulation was performed to study the after-pulse breakdown effect in such a standing-wave structure. A method of calculating poynting vector over time is proposed in this article to study the modified poynting vector at critical points in the cavity. Field simulation and thermal simulation were also carried out to analyse possible reasons for the after-pulse breakdown effect.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW047

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paper received ※ 14 May 2019 paper accepted ※ 17 May 2019 issue date ※ 21 June 2019

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MOPGW063

Beam Dynamics Optimization in Drift Tube Linear Accelerator With Permanent Quadrupole Magnets

lattice, rfq, quadrupole, DTL

234

I. Skudnova
Saint Petersburg State University, Saint Petersburg, Russia

The research concerns the design of a drift tube linear accelerator (DTL) with permanent quadrupole magnets (PMQ) placed inside some of the drift tubes for focusing. The study was conducted using Comsol Multiphysics software, where electromagnetic fields and particle dy-namics in the cavity were calculated. The proton beam is accelerated up to 10 MeV. Initial beam is assumed to come from Radio Frequency Quadrupole accelerator (RFQ). Mathematical methods of control theory are used for particles dynamics optimization. Different focusing lattices are examined and variations of the gradient of the magnetic lenses are analyzed with respect to output beam parameters. Effectiveness of the optimization is estimated by the transmission rate and the emittance growth.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW063

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paper received ※ 16 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW077

Impedance Reduction in the CERN SPS Through Element Layout Optimisation

impedance, coupling, extraction, quadrupole

277

A. Farricker, C. Vollinger
CERN, Geneva, Switzerland

The CERN accelerator complex is currently in its long shutdown while the LHC Injector Upgrade is being carried out. The upgrade of the SPS includes but is not limited to: the relocation of the beam dumping system, upgrade of the RF system, replacement of the electrostatic septa and impedance reduction. These major upgrades present an opportunity to perform additional impedance reduction in areas not normally modified due to the large amount of work being performed across the accelerator complex. In this paper, we look at the impedance minimization in the sections near the large aperture quadrupoles of the extraction regions in the CERN SPS. By optimizing the locations of existing equipment and the introduction of a new, more impedance optimised type of bellows, significant reductions in the beam-coupling impedance can be achieved.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW077

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paper received ※ 08 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW083

Longitudinal Coupled-Bunch Instability Evaluation for FCC-hh

impedance, emittance, HOM, synchrotron

297

I. Karpov, E.N. Shaposhnikova
CERN, Meyrin, Switzerland

High-order modes (HOM) of the accelerating rf structures and other machine elements, if not sufficiently damped, can drive longitudinal coupled-bunch instabilities (CBI). Their thresholds can be accurately obtained from macro-particle simulations using the detailed impedance model containing many different contributions. This method, however, is very difficult to apply for synchrotrons with a large number of bunches, as it is the case for the Future Circular hadron-hadron Collider (FCC-hh) with up to 10400 circulating bunches per beam. In this paper the semi-analytical approach is used for calculations of the instability thresholds during the acceleration cycle of the FCC-hh. As the result, we define requirements for the HOM damping that would be sufficient to prevent development of longitudinal CBI in the presence of weak synchrotron radiation damping.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW083

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paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW084

Beam Loading Compensation for the Future Circular Hadron-Hadron Collider (FCC-hh)

beam-loading, hadron, collider, impedance

301

I. Karpov, P. Baudrenghien
CERN, Meyrin, Switzerland

The power consumption of the rf system can be minimised by optimising the cavity detuning and the loaded quality factor. In high-current accelerators, the presence of gaps in the filling results in a modulation of the cavity voltage along the ring (transient beam loading) and as a consequence a spread in the bunch parameters. In addition longitudinal coupled-bunch instabilities can appear, caused by the cavity impedance at the fundamental. Both issues can be mitigated by using an rf feedback around the amplifier and cavity, a technique used in many high intensity machines including the Large Hadron Collider (LHC). Compared to the LHC machine, the energy increase and the radiation loss for the Future Circular hadron-hadron Collider (FCC-hh) will be larger, resulting in a synchronous phase deviating significantly from 180 degrees. The solutions adopted for the LHC must therefore be revisited. This paper evaluates several beam loading compensation schemes for this machine.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW084

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paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW094

First Machine Developments Result with HL-LHC Crab Cavities in the SPS

proton, closed-orbit, luminosity, diagnostics

338

L.R. Carver, A. Alekou, F. Antoniou, H. Bartosik, T. Bohl, R. Calaga, M. Carlà, T.E. Levens, G. Papotti
CERN, Meyrin, Switzerland
A. Alekou, R.B. Appleby, R.B. Appleby
UMAN, Manchester, United Kingdom
G. Burt
Cockcroft Institute, Warrington, Cheshire, United Kingdom
G. Burt, J.A. Mitchell
Lancaster University, Lancaster, United Kingdom
C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom

Crab cavities are a critical component within the High Luminosity upgrade project for the Large Hadron Collider (HL-LHC). It is foreseen to use crab cavities in order to compensate the geometric luminosity reduction factor (reduction of the luminous region at the Interaction Point [IP]) due to the beam crossing angle (required for minimizing the impact of the long range beam-beam effects on the single particle beam dynamics) and increase the number of collisions per bunch crossing. In 2018 the first beam tests of crab cavities with protons were performed in the Super Proton Synchrotron (SPS) at CERN. Two vertical superconducting cavities of the Double Quarter Wave (DQW) type were fabricated and installed in the SPS to verify some key components of the cavity design and operation. This paper will present some of the first results relating to the proton beam dynamics in the presence of crab cavities.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW094

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paper received ※ 25 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW095

Beam Dynamics Simulations with Crab Cavities in the SPS Machine

multipole, simulation, luminosity, optics

342

A. Alekou, A. Alekou, H. Bartosik, H. Bartosik, M. Carlà, Y. Papaphilippou, Y. Papaphilippou, Y. Papaphilippou
CERN, Meyrin, Switzerland
A. Alekou, A. Alekou, R.B. Appleby, R.B. Appleby
UMAN, Manchester, United Kingdom
R.B. Appleby
Cockcroft Institute, Warrington, Cheshire, United Kingdom

The LHC Upgrade, called High Luminosity LHC, aims to increase the integrated luminosity by a factor of 10. To achieve this, the project relies on a number of key innovative technologies, including the use of superconducting Crab Cavities with ultra-precise phase control for beam rotation. A set of prototype Crab Cavities has been recently installed in the second largest machine of CERN, the Super Proton Synchrotron (SPS), that operated as a test-bed from May to November of 2018. The tight LHC constraints call for axially non-symmetric cavity designs that introduce high order multipole components. Furthermore, the Crab Cavities in the presence of SPS non-linearities can affect the long term stability of the beam. This paper presents how the SPS dynamic aperture is affected for different cavity, machine and beam configurations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW095

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paper received ※ 06 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW099

Vlasov-Fokker-Planck Simulations of Passive Higher-Harmonic Cavity Effects in ALS-U

simulation, impedance, synchrotron, resonance

357

G. Bassi
BNL, Upton, Long Island, New York, USA

Funding: Work supported by DOE under contract DE-SC0012704
We discuss numerical simulations of the Vlasov-Fokker-Planck equation to model passive higher-harmonic cavity (HHC) effects with parameters of the Advanced Light Source Upgrade (ALS-U. The numerical results, obtained with the SPACE code, are compared with a modal analysis of the coupled-bunch instability theory.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW099

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paper received ※ 18 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019

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MOPGW111

Start to End Simulation on Beam Dynamics in Coherent Electron Cooling Accelerator

electron, FEL, bunching, emittance

379

Y.C. Jing, V. Litvinenko, I. Petrushina, I. Pinayev, K. Shih, Y.H. Wu
BNL, Upton, Long Island, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA
I. Petrushina
SUNY SB, Stony Brook, New York, USA
K. Shih
SBU, Stony Brook, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
A Coherent electron Cooling (CeC) has a potential of substantial reducing cooling time of the high-energy hadrons and hence to boost luminosity in high-intensity hadron-hadron and electron-hadron colliders. In a CeC system, a high quality electron beam is generated, propagated and optimized through a beam line which was carefully designed with consideration of space charge effect, wakefields and nonlinear dynamics such as coherent synchrotron radiation and chromatic aberration. In this paper, we present our study on the beam dynamics of such a beam line and compare the simulation result with what was measured in experiment.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW111

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paper received ※ 17 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPMP007

Design of a Compact Power Distribution System for the ILC

cryomodule, ECR, acceleration, collider

436

B. Du, N. Liu
Sokendai - Hayama, Hayama, Japan
T. Matsumoto, S. Michizono, T. Miura, F. Qiu
KEK, Ibaraki, Japan
T. Matsumoto, T. Miura, F. Qiu
Sokendai, Ibaraki, Japan

The Local power distribution system (LPDS) of the In-ternational Linear Collider (ILC) is constructed to transmit RF power from the 10 MW klystron to 39 cavi-ties. Each eight or nine 9-cell cavities is assembled in one cryomodule. The variable hybrid is used to adjust the power dividing ratio due to the different required power of each cavity and the variable phase shifter is used to compensate the phase drift caused by the variable hybrid. More compact LPDS is expected to be integrated on the cryomodule decreasing financial cost. We re-design the shorter variable hybrid with a margin of power ratio of ±25% and phase shifter of total phase range being 35° for compensating hybrid and on-crest searching. Fixed phase shifters are designed to adjust the phase difference between adjacent cavities for beam acceleration. Simu-lated results of total compact LPDS can meet the re-quirements of ILC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP007

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paper received ※ 16 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPMP008

Electron Driven Positron Source for International Linear Collider

positron, beam-loading, linac, simulation

439

M. Kuriki, T. Okugi, T. Omori, M. Satoh, Y. Seimiya, J. Urakawa, K. Yokoya
KEK, Ibaraki, Japan
H. Nagoshi
HU/AdSM, Higashi-Hiroshima, Japan
K. Negishi
Iwate University, Morioka, Iwate, Japan
Y. Sumitomo
LEBRA, Funabashi, Japan
T. Takahashi
Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan

Funding: This work is partly supported by Japan-US Cooperative grant for scientific studies, Grant aid for scientific study by MEXT Japan (KAKENHI)
To linear colliders, huge amount of positron has to be provided comparing to ring colliders, because the beam is dumped after the collision. Electron Driven ILC Positron source has been designed as a technical backup of the undulator position source including the beam loading effect, etc. The design of the detail will be presented. To linear colliders, huge amount of positron has to be provided comparing to ring colliders, because the beam is dumped after the collision. Electron Driven ILC Positron source has been designed as a technical backup of the undulator position source including the beam loading effect, etc. The design of the detail will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP008

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paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPMP019

High Luminosity LHC Optics and Layout HLLHCV1.4

optics, luminosity, operation, experiment

468

R. De Maria, R. Bruce, D. Gamba, M. Giovannozzi, F. Plassard
CERN, Geneva, Switzerland

The goal of the High Luminosity Project is the upgrade of the LHC to deliver an integrated luminosity of at least 250 \rm fb^-1 per year in each of the two high-luminosity, general-purpose detectors ATLAS and CMS. This article presents the latest layout design and the corresponding optics features, which comprise optimisation of the orbit corrector and crab cavity systems, and new estimates of the performance reach thanks to the new concept of fully remote alignment. In addition, the new optics version incorporates improvements required by beam instrumentation, dump system, and collimation system, as well as low-beta solutions for the LHCb experiment.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP019

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paper received ※ 17 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPMP036

Machine Protection Experience from Beam Tests with Crab Cavity Prototypes in the CERN SPS

machine-protect, beam-losses, betatron, operation

520

B. Lindstrom, H. Bartosik, T. Bohl, A.C. Butterworth, R. Calaga, L.R. Carver, V. Kain, T.E. Levens, G. Papotti, R. Secondo, J.A. Uythoven, M. Valette, G. Vandoni, J. Wenninger, D. Wollmann, M. Zerlauth
CERN, Meyrin, Switzerland

Funding: Work supported by the High Luminosity LHC project.
Crab cavities (CCs) constitute a key component of the High Luminosity LHC (HL-LHC) project. In case of a failure, they can induce significant transverse beam offsets within tens of microseconds, necessitating a fast removal of the circulating beam to avoid damage to accelerator components due to losses from the displaced beam halo. In preparation for the final design to be employed in the LHC, a series of tests were conducted on prototype crab cavities installed in the Super Proton Synchrotron (SPS) at CERN. This paper summarizes the machine protection requirements and observations during the first tests of crab cavities with proton beams in the SPS. In addition, the machine protection implications for future SPS tests and for the use of such equipment in the HL-LHC are discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP036

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paper received ※ 01 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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MOPMP040

US Contributions to the High Luminosity LHC Upgrade - Focusing Quadrupoles and Crab Cavities

luminosity, quadrupole, HOM, SRF

536

G. Apollinari, G. Ambrosio, R.H. Carcagno, SF. Feher, L. Ristori
Fermilab, Batavia, Illinois, USA

In the early 2000’s, the US High Energy Physics community contributing to the Large Hadron Collider (LHC) launched the LHC Accelerator R&D Program) (LARP), a long-vision focused R&D program, intended to bring the Nb₃Sn and other technologies to a maturity level that would allow applications in HEP machines. Around 2015, the technologies developed by LARP were mature enough to allow the spin-off of a major upgrade project to the LHC complex, the High Luminosity LHC (HL-LHC). This paper will focus on the US contribution to HL-LHC, namely the large-aperture low-beta focusing Nb₃Sn quadrupoles and the Radio Frequency Dipole (RFD) Crab Cavities, located in close proximity to the ATLAS and CMS experiments. This contribution, called the HL-LHC Accelerator Upgrade Project (HL-LHC AUP), focuses on production of these quadrupoles and cavities by sharing the work among a consortium of US Laboratories (FNAL, LBNL, BNL and SLAC) and Universities and in close connection with the CERN-led HL-LHC Collaboration. The collaboration achieved commonality of specifications and uniformity of performance. Final development of design, construction and first results from the prototypes are described to indi-cate the status of these critical components for HL-LHC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP040

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paper received ※ 30 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPMP044

Improving the Luminosity for Beam Energy Scan II at RHIC

operation, electron, space-charge, luminosity

540

C. Liu, M. Blaskiewicz, K.A. Drees, A.V. Fedotov, W. Fischer, C.J. Gardner, H. Huang, D. Kayran, Y. Luo, G.J. Marr, A. Marusic, K. Mernick, M.G. Minty, C. Montag, I. Pinayev, S. Polizzo, V.H. Ranjbar, D. Raparia, G. Robert-Demolaize, T. Roser, J. Sandberg, V. Schoefer, T.C. Shrey, S. Tepikian, P. Thieberger, A. Zaltsman, K. Zeno, I.Y. Zhang, W. Zhang
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The QCD (Quantum Chromodynamics) phase diagram has many uncharted territories, particularly the nature of the transformation from Quark-Gluon plasma (QGP) to the state of Hadronic gas. The Beam Energy Scan I (BES-I) at the Relativistic Heavy Ion Collider (RHIC) was completed but measurements had large statistical errors. To improve the statistical error and expand the search for first-order phase transition and location of the critical point, Beam Energy Scan II will commence in 2019 with a goal of improving the luminosity by a factor of 3-4. The beam lifetime at low energies was and will be limited by some physical effects of which the most significant are intrabeam scattering, space charge, beam-beam, persistent current effects. This article will review these potential limiting factors and introduce the countermeasures which will be in place to improve BES-II luminosity.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP044

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paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPMP051

56 MHz SRF System for SPHENIX Experiments at RHIC

operation, SRF, HOM, detector

562

Q. Wu, M. Blaskiewicz, K. Mernick, S. Polizzo, F. Severino, K.S. Smith, T. Xin
BNL, Upton, Long Island, New York, USA

Funding: Work supported by by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy
The sPHENIX experiment is a proposal for a new detector at the Relativistic Heavy Ion Collider (RHIC), that plans to expand on discoveries made by RHIC’s existing STAR and PHENIX research groups. To minimize the luminosity outside the 20 cm vertex detector and keeping the radiation to other detector components as low as possible, a 56 MHz SRF system is added to the existing RHIC RF systems to compress the bunches with less beam loss. The existing 56 MHz SRF cavity was commissioned in previous RHIC runs, and contributed to the luminosity at a voltage of 300kV with thermal limitations from the Higher Order Mode coupler at high field, and at 1MV while using its fundamental damper for HOM damping. In this paper, we will analyze and compare the effect of different RF systems at various scenarios, and discuss possible solutions to the Higher Order Mode (HOM) damping scheme to bring the cavity to 2 MV.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP051

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB006

HOM Damping Options for the Z-Pole Operating Scenario of FCC-ee

HOM, damping, impedance, dipole

590

S. Gorgi Zadeh
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
R. Calaga
CERN, Meyrin, Switzerland
T. Flisgen
FBH, Berlin, Germany
U. van Rienen
University of Rostock, Rostock, Germany

The Z-pole option of FCC-ee is an Ampere class machine with a beam current of 1.39 A. Due to high HOM power and strong HOM damping requirements, the present baseline of FCC-ee considers a single cell cavity at 400 MHz. In this paper, different HOM damping schemes are compared for the Z-pole operating scenario with the aim of lowering the parasitic longitudinal and transverse impedance. The HOM power for each damping scheme is also calculated.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB006

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paper received ※ 15 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB017

Development of Inter-Digital H-Mode Drift-Tube Linac Prototype with Alternative Phase Focusing for a Muon Linac in the J-PARC Muon G-2/EDM Experiment

linac, DTL, coupling, experiment

606

Y. Nakazawa, H. Iinuma
Ibaraki University, Ibaraki, Japan
K. Hasegawa, Y. Kondo, T. Morishita
JAEA/J-PARC, Tokai-mura, Japan
N. Hayashizaki
RLNR, Tokyo, Japan
Y. Iwashita
Kyoto ICR, Uji, Kyoto, Japan
Y. Iwata
NIRS, Chiba-shi, Japan
N. Kawamura, T. Mibe, M. Otani, T. Yamazaki, M. Yoshida
KEK, Ibaraki, Japan
R. Kitamura, H.Y. Yasuda
University of Tokyo, Tokyo, Japan
N. Saito
J-PARC, KEK & JAEA, Ibaraki-ken, Japan
Y. Sue
Nagoya University, Graduate School of Science, Chikusa-ku, Nagoya, Japan

Funding: This work is supported by JSPS KAKENHI Grant Numbers JP15H03666, JP18H03707, JP16H03987, and JP16J07784.
An inter-digital H-mode drift-tube linac (IH-DTL) is developed in a muon linac at the J-PARC E34 experiment. IH-DTL will accelerate muons from 0.34 MeV to 4.5 MeV at a drive frequency of 324 MHz. Since IH-DTL adopts an APF method, with which the beam is focused in the transverse direction using the RF field only, the proper beam matching of the phase-space distribution is required before the injection into the IH-DTL. Thus, an IH-DTL prototype was fabricated to evaluate the performance of the cavity and beam transmission. As a preparation of the high-power test, a test coupler is designed and fabricated. In this paper, the development of the coupler and the result of the low-power measurement will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB017

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paper received ※ 29 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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MOPRB018

Conceptual Design of Negative-Muon Decelerator for Material Science

induction, experiment, impedance, power-supply

610

C. Ohmori, M. Otani, K. Shimomura
KEK, Tokai, Ibaraki, Japan
T. Takayanagi
JAEA/J-PARC, Tokai-mura, Japan

In 2018, a Negative-Muon Spin Rotation and Relaxation technique was developed in J-PARC Material and Life Science Facility. It is a novel scheme to investigate the motion of hydrogens in the chemicals and materials. To study small samples, the surface of materials and thin foils, a low energy negative muon beam is required. To decelerate intense 300-keV muons to 15-keV, we propose a system which consists of pulse generators and multi-gap induction decelerators. In this design, an inductive adder scheme is considered to use for the high voltage pulse source. High impedance magnetic alloy ring cores will be loaded in the decelerator cells. The high impedance cores which have much larger size than those for public use were developed for J-PARC RF systems and used for many applications including CERN booster RF, anti-proton deceleration and medical accelerator. In this paper, we present a conceptual design of muon deceleration system.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB018

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paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPRB022

Current Status of the High-Power RF Systems During Phase2 Operation in SuperKEKB

klystron, operation, GUI, status

619

K. Watanabe, K. Marutsuka, Ma. Yoshida, S.I. Yoshimoto
KEK, Ibaraki, Japan

The SuperKEKB is an asymmetric-energy two-ring collider consisting of the high-energy ring (HER) for 7 GeV electrons and the low-energy ring (LER) for 4 GeV positrons at KEK. Both the electron and positron beams are injected from the Linac injector complex, which includes a newly constructed 1.1 GeV positron damping ring (DR) to supply a high-quality low emittance positron beam to the LER. The high power RF system has a role to drive the ARES cavities and the superconducting RF cavities for the SuperKEKB. The operating frequency of RF system is 508.9 MHz. The required RF power from the klystron at maximum storage beam current is ~850 kW (CW). The number of RF stations is total 31 for the main ring (MR) and DR. The status of each high power RF components, troubles of them and operation condition that occurred during phase 2 commissioning from Feb 2018 to July 2018 will be reported in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB022

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB027

Progress of HEPS Accelerator System Design

storage-ring, booster, vacuum, lattice

633

P. He, J.S. Cao, F.S. Chen, J. Chen, H. Dong, D.Y. He, Y. Jiao, W. Kang, C.H. Li, J.Y. Li, F. Long, H.H. Lu, X. Qi, Q. Qin, H. Qu, J.Q. Wang, G. Xu, J.H. Yue, J. Zhang, J.R. Zhang, P. Zhang
IHEP, Beijing, People’s Republic of China

The 4th generation ring-based light sources, HEPS (High Energy Photon Source) 7BA lattice has been de-veloped at IHEP. This is 6Gev, 200mA machine which has horizontal emittance Ɛh around 60pm.rad to gain the high brilliance photon beam. this compact lattice design bring so many engineering challenges for accelerator magnets, vacuum components, beam diagnotice, etc. This paper will present the noval lattice design and subsystem design progress.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB027

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paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB033

Preliminary Research of HOM for 100MHz Superconducting Cavity in the Pre-Research Project of HALS

HOM, impedance, damping, simulation

649

Y.G. Tang, L. Wang, C.-F. Wu
USTC/NSRL, Hefei, Anhui, People’s Republic of China

A 100MHz QWR superconducting cavity is researched in the pre-research project of Hefei Advanced Light Source (HALS). Higher order modes (HOM) damping is a big challenge for synchrotron radiation light source. In this paper, we first apply the novel choke mode structure to the 100MHz QWR (quarter wave resonator) cavity in order to damp the HOM. We identify the main harmful higher order modes. The HOMs in the QWR cavity are suppressed by optimizing the choke dimensions. The broadband HOM impedance spectrum of the cavity was also evaluated by calculating the beam induced wake potential in time domain. The results show that choke mode structure has a good HOM damping effect on the QWR cavity.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB033

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paper received ※ 25 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB052

Gamma Factory at CERN: Design of a Proof-of-Principle Experiment

photon, laser, experiment, electron

685

Y. Dutheil, R. Alemany-Fernández, H. Bartosik, N. Biancacci, R. Bruce, P. Czodrowski, V. Fedosseev, B. Goddard, S. Hirlaender, J.M. Jowett, R. Kersevan, M. Kowalska, M. Lamont, D. Manglunki, J. Molson, A.V. Petrenko, M. Schaumann, F. Zimmermann
CERN, Geneva, Switzerland
S.E. Alden, A. Bosco, S.M. Gibson, L.J. Nevay
JAI, Egham, Surrey, United Kingdom
A. Apyan
ANSL, Yerevan, Armenia
E.G. Bessonov
LPI, Moscow, Russia
A. Bosco, S.M. Gibson, L.J. Nevay
Royal Holloway, University of London, Surrey, United Kingdom
F. Castelli
Università degli Studi di Milano, Milano, Italy
F. Castelli, C. Curatolo, L. Serafini
INFN-Milano, Milano, Italy
K. Kroeger
FSU Jena, Jena, Germany
A. Martens
LAL, Orsay, France
V. Petrillo
Universita’ degli Studi di Milano, Milano, Italy
M. Sapinski, T. Stöhlker
GSI, Darmstadt, Germany
G. Weber
IOQ, Jena, Germany
Y.K. Wu
FEL/Duke University, Durham, North Carolina, USA

The Gamma Factory (GF) initiative proposes to create novel research tools at CERN by producing, accelerating and storing highly relativistic partially stripped ion beams in the LHC rings and by exciting their atomic degrees of freedom by lasers, to produce high-energy photon beams. Their intensity would be several orders of magnitude higher than those of the presently operating light sources in the particularly interesting gamma-ray energy domain reaching up to 400 MeV. In this energy domain, the high-intensity photon beams can be used to produce secondary beams of polarized electrons, polarized positrons, polarized muons, neutrinos, neutrons and radioactive ions. Over the years 2017-2018 we have demonstrated that these partially stripped ion beams can be successfully produced, accelerated and stored in the CERN accelerator complex, including the LHC. The next step of the project is to build a proof of principle experiment in the SPS to validate the principal GF concepts. This contribution will present the initial conceptual design of this experiment along with its main challenge - the demonstration of the fast cooling method of partially stripped ion beams.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB052

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paper received ※ 19 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB057

An Approach to Alleviating Heavy Beam Loading Effect on the Synchrotron Machine Through the Existed Low Level RF Feedback System

feedback, beam-loading, impedance, simulation

697

L.-H. Chang, F.Y. 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

To pursue the highest brightness and intensity of the synchrotron light, the synchrotron machines are pushed to operate with as high as possible of the beam current. To suppress the heavy beam loading effects, the direct RF feedback is currently widely used. This paper provides an another approach to alleviating the heavy beam loading effects on machine operation. Different from the direct RF feedback technique, this approach need not add additional feedback loop to the existed RF feedback system. Applying a proper angle rotation to the I-Q error signals of the cavity voltage, before entering the existed feedback loop, is the only action required in this approach. The paper will explain the working mechanism and investigate the behaviour of this approach, through an example case, with numerical simulation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB057

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paper received ※ 16 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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MOPRB063

Longitudinal Tomography in a Scaling FFA

synchrotron, experiment, proton, injection

719

D.J. Kelliher, C. Brown, J.-B. Lagrange, S. Machida, C.R. Prior, C.T. Rogers
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
Y. Ishi, Y. Kuriyama, H. Okita, T. Uesugi
Kyoto University, Research Reactor Institute, Osaka, Japan
S.L. Sheehy
JAI, Oxford, United Kingdom

In a synchrotron the rate of acceleration is limited by the ramp rate of the bending field. There is no such constraint in a Fixed Field alternating gradient Accelerator (FFA), allowing a much higher repetition rate and novel modes of operation such as beam stacking. It is of interest to obtain a picture of the longitudinal phase space from experimental data in order to diagnose the response of the beam to various RF programmes. Longitudinal tomography, already well established in synchrotrons, involves reconstructing the phase space using bunch monitor data obtained for a sufficient number of turns in a synchrotron oscillation. Here we reconstruct the longitudinal phase space using data from the 150 MeV scaling FFA at KURNS, Osaka, Japan.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB063

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB077

Results From the CBETA Fractional Arc Test

linac, MMI, emittance, betatron

751

C.M. Gulliford, N. Banerjee, A.C. Bartnik, J.A. Crittenden, P. Quigley
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

We report on commissioning experiments of the Cornell Brookhaven Energy Recovery Test Accelerator Fractional Arc Test. The beam from the injector is accelerated by a linac with a 36 MeV design energy gain, is transported through a splitter line that uses conventional magnets, and finally into a four cell permanent magnet based fixed field alternating (FFA) gradient arc. We measure beam properties in the injector, calibrate the energy gain and phase of the linac cavities using time of flight to a BPM at the end of the linac. We scan individual cavity phases and pass beam through the cavities to determine the transverse offset of the individual cavities. We scan the beam position in the splitter BPMs to estimate and correct the nonlinearity in the BPM response. We tested our path length adjustment mechanism. We measure the dispersion and R56 in the FFA arc.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB077

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPRB078

Beam Based Measurements of the CBeta Main Linac Cavity Alignment

linac, cryomodule, survey, acceleration

755

C.M. Gulliford, A.C. Bartnik, J.A. Crittenden, P. Quigley
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

Funding: This work was funded by NYSERDA, the New York State Energy Research and Development Agency.
Initial attempts at steering the beam through the CBETA main linac indicated the cavities were vertically offset with respect to the BPMs on either side of the linac. In particular, manual alignment of the beam in the first and last cavities suggested a vertical offset of roughly 5 mm. This work presents the results of beam based measurements of the individual cavity offsets taken during the CBETA Fractional Arc Test. With only a single cavity powered at a time, beam was injected at several different vertical offsets, the RF phase was scanned over 360 degrees, and the beam position was measured at the end of the cryomodule. We analyzed the data in two ways. We first compute the RMS spread in the measurements at a given position, and considered the offset with the minimum RMS spread to be the cavity offset. We also fit the measurements at a given phase to a line as a function of initial displacement, and use a model for the transfer matrix of the cavity and downstream drift to compute the offset. The two methods agree well, resulting in an average vertical offset of the main linac cavities of 4.0 plus/minus 1 mm.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB078

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB080

Transient Beam Loading and Mitigation in JLEIC Collider Rings

electron, klystron, luminosity, beam-loading

758

J. Guo, R.A. Rimmer, H. Wang, S. Wang
JLab, Newport News, Virginia, USA
J.D. Fox
Stanford University, Stanford, California, USA
T. Mastoridis
CalPoly, San Luis Obispo, California, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177, with additional support from U.S. DOE Award Number DE-SC-0019287
The Jefferson Lab Electron-Ion Collider (JLEIC) is an asymmetric high luminosity ring-ring collider proposed as the next major R&D facility for the nuclear physics community. Both of JLEIC’s electron and ion collider rings have high beam current with gaps serving the pur-poses of beam abort, ion clearing, etc. Such a time-varying beam loading in the RF cavities would generate modulation in cavity RF phase/voltage, causing cyclic shift of collision point and potential luminosity loss. We studied a few approaches to mitigate the RF phase modu-lation and IP shift, such as correcting the RF phase/voltage modulation with traditional LLRF feed-back, one-turn feedback (OTFB), or RF feedforward (FF); optimizing the bunch fill pattern to limit the RF phase/voltage modulation to a small fraction of the bunch trains in the collider ring; or matching the RF phase modulation in the two rings. The preliminary re-sults are discussed in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB080

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paper received ※ 23 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019

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MOPRB081

Electron Beam’s Closed Orbit in the Crab Crossing Scheme of Future Electron-Ion Colliders

electron, closed-orbit, luminosity, simulation

762

Y. Hao, V. Ptitsyn
BNL, Upton, Long Island, New York, USA
J. Qiang
LBNL, Berkeley, California, USA

In crab-crossing collision geometry the closed orbit of the electron beam will be altered by the beam-beam interaction and the tilted head and tail of the ion beam. We will present the linear model to determine the closed orbit and compare with the simulation. Also, the relation of the closed orbit and the synchro-betatron resonance will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB081

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB082

Scaling Properties of the Synchro-Beta Resonance in Crab Crossing Scheme of Future Electron Ion Collider

luminosity, resonance, electron, simulation

766

Y. Hao, Y. Luo, V. Ptitsyn
BNL, Upton, Long Island, New York, USA
J. Qiang
LBNL, Berkeley, California, USA

The synchro - beta resonance due to the beam-beam interaction was predicted by the strong-strong simulation in the future electron-ion collider designs. In this paper, we study the scaling properties of the degradation rate of this unwanted resonance. These studies motivated the possible countermeasures of the luminosity degradation associated with the resonance.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB082

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB085

First Results from Commissioning of Low Energy RHIC Electron Cooler (LEReC)

electron, MMI, gun, cathode

769

D. Kayran, Z. Altinbas, D. Bruno, M.R. Costanzo, K.A. Drees, A.V. Fedotov, W. Fischer, M. Gaowei, D.M. Gassner, X. Gu, R.L. Hulsart, P. Inacker, J.P. Jamilkowski, Y.C. Jing, J. Kewisch, C.J. Liaw, C. Liu, J. Ma, K. Mernick, T.A. Miller, M.G. Minty, L.K. Nguyen, M.C. Paniccia, I. Pinayev, V. Ptitsyn, V. Schoefer, S. Seletskiy, F. Severino, T.C. Shrey, L. Smart, K.S. Smith, A. Sukhanov, P. Thieberger, J.E. Tuozzolo, E. Wang, G. Wang, A. Zaltsman, H. Zhao, Z. Zhao
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The brand new non-magnetized bunched beam electron cooler (LEReC) [1] has been built to provide luminosity improvement for Beam Energy Scan II (BES-II) physics program at the Relativistic Heavy Ion Collider (RHIC) BES-II [2]. The LEReC accelerator includes a photocathode DC gun, a laser system, a photocathode delivery system, magnets, beam diagnostics, a SRF booster cavity, and a set of Normal Conducting RF cavities to provide sufficient flexibility to tune the beam in the longitudinal phase space. This high-current high-power accelerator was successfully commissioned in period of March -September 2018. Beam quality suitable for cooling has been demonstrated. In this paper we discuss beam commissioning results and experience learned during commissioning.
[1] A. Fedotov et al., ’Status of bunched beam electron cooler LEReC’ in these proceedings.
[2] C.Liu et al., ’Improving luminosity of Beam Energy Scan II at RHIC’ in these proceedings.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB085

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB091

Combined Strong-Strong and Weak-Strong Beam-Beam Simulations for Crabbed Collision in eRHIC

electron, proton, simulation, luminosity

788

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
K. Ohmi
KEK, Ibaraki, Japan
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 eRHIC, to compensate the geometric luminosity loss, local crab cavities on both sides of the interaction points are to adopted. The previous strong-strong beam-beam simulations showed that the luminosity degradation depends on the crab cavity frequency, proton synchrotron tune, proton bunch length and so on. In this article, we apply a combined strong-strong and weak-strong beam-beam simulation to investigate the incoherent and coherent beam motions with crabbed collison, and to calculate more realistic beam emittance growth rates and luminosity degradation rate.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB091

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paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB103

A Phase Shifter for Multi-Pass Recirculating Proton LINAC

proton, linac, superconducting-magnet, superconducting-cavity

802

J. Qiang, L.N. Brouwer, S. Prestemon
LBNL, Berkeley, California, USA

Funding: This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 and used computer resources at the National Energy Research Scientific Computing Center.
The multi-pass recirculating proton linac can significantly improve the usage efficiency of RF superconducting cavities by passing the proton beam through the same cavity multiple times. However, in order to achieve the multiple acceleration, synchronous conditions in phase have to be satisfied. In this paper, we propose a fixed field superconducting magnet system as a phase shifter to meet the synchronous conditions.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB103

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paper received ※ 09 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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MOPRB109

Cavity Design for the Updated eRHIC Crabbing System

proton, operation, electron, hadron

818

S. Verdú-Andrés, Q. Wu
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates LLC under contract no. DE-SC0012704 with the U.S. Department of Energy.
The electron-ion collider eRHIC proposed by Brookhaven National Laboratory includes a crabbing system to reestablish head-on collisions for a maximum geometric overlap of the colliding bunches. Since the last cavity design, the crossing angle has increased from 22 to 25 mrad to relax the field strength requirement in one of the IR magnets - increasing the deflecting kick required to collider the bunches head on - and one of the considered options is to have both proton and electron crab cavities work at 200 MHz. The present paper discusses the RF design of the 200 MHz crab cavities for the electron and hadron beams of eRHIC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB109

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS001

Operational Experience with a Sled and Multibunch Injection at the Australian Synchrotron

linac, klystron, operation, injection

830

M.P. Atkinson, G. LeBlanc
AS - ANSTO, Clayton, Australia
K. Zingre
ASCo, Clayton, Victoria, Australia

The Australian third generation 3 GeV Synchrotron Light Source was originally commissioned with a 100 MeV linear accelerator (LINAC) fed by two 37 MW S band pulsed klystrons. A pulse compressor in form of a SLED cavity was added later to enable single klystron operation for redundancy in case of a modulator failure. The SLED was successfully commissioned in May 2017 including remote selection of single klystron with SLED operation without degradation of beam energy. Two years on there have been some unexpected operational benefits including reduced phase sensitivity and drift allowing repeatable injection based solely on diagnostic phase read backs. Temperature stabilised power amplifiers based on S band GaN radar technology are being trialed in the meantime with a goal to set and inject with minimal operator adjustment. The results from the SLED cavity upgrade are shown and the latest S band radar technology designs are outlined.

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPTS003

Superconducting LINAC Design Upgrade in View of the 100 MeV MYRRHA Phase I

linac, cryomodule, lattice, emittance

837

F. Bouly, M.A. Baylac
LPSC, Grenoble Cedex, France
A. Gatera
SCK•CEN, Mol, Belgium
D. Uriot
CEA-DRF-IRFU, France

Funding: Part of this work supported by the European Atomic Energy Community (EURATOM) H₂020 Programme under grant agreement n°662186 (MYRTE project).
The goal of the MYRRHA project is to demonstrate the technical feasibility of transmutation in a 100 MW Accelerator Driven System (ADS) by building a new flexible irradiation complex at Mol (Belgium). The MYRRHA facility requires a 600 MeV accelerator delivering a maximum proton current of 4 mA in continuous wave operation, with an additional requirement for exceptional reliability. Supported by SCK•CEN and the Belgium government the project has entered in its phase I: which consists in the development and the construction of the linac first part, up to 100 MeV. We review the design updates of the superconducting linac, with its enhanced fault-tolerance capabilities. The linac capabilities at 100 MeV (Phase I) and 600 MeV (ADS operation) are exposed and discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS003

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paper received ※ 23 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS007

SARAF Equipped Cavity Test Stand (ECTS) at CEA

cryomodule, cryogenics, controls, EPICS

852

O. Piquet, C. Boulch, D. Chirpaz-Cerbat, G. Ferrand, F. Gohier, T.J. Joannem, G. Monnereau, Th. Plaisant
CEA-IRFU, Gif-sur-Yvette, France
D. Braud, P. Carbonnier, P. Guiho, L. Maurice, J. Plouin, P. Sahuquet, N. Solenne
CEA-DRF-IRFU, France
F. Gouit, A. Pérolat
CEA, Gif-sur-Yvette, France

CEA is committed to delivering a Medium Energy Beam Transfer line and a Super Conducting Linac (SCL) for SARAF accelerator in order to accelerate 5mA beam of either protons from 1.3MeV to 35MeV or deuterons from 2.6 MeV to 40.1MeV. The SCL consists in 4 cryomodules separated by warm section housing beam diagnostics. The two first identical cryomodules hosts respectively 6 and 7 half-wave resonator (HWR) low beta (0.091) cavities 176MHz. In order to test the cavity with its tuner and coupler and validate some design consideration, the Equipped Cavity Test Stand (ECTS) has been designed and will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS007

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paper received ※ 07 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS008

ESS RFQ: Construction Status and Power Couplers Qualification

rfq, vacuum, coupling, pick-up

855

O. Piquet, A.C. Chauveau, D. Chirpaz-Cerbat, M. Desmons, A.C. France, P. Hamel, B. Pottin
CEA-IRFU, Gif-sur-Yvette, France
A. Dubois, A. Gaget, Y. Le Noa, L. Napoly, M. Oublaid, G. Perreu
CEA-DRF-IRFU, France

The 352 MHz Radio Frequency Quadrupole (RFQ) for the European Spallation Source ERIC (ESS) will be de-livered during 2019. It is provided by CEA, IRFU, Sac-lay/France. It consists of five sections with a total length of 4.6 m and accelerates the proton beam from 75 keV up to 3.6 MeV. It will be feed with 1.6 MW peak power through two coaxial loop couplers. This paper will present the manufacturing status of the five sections and the qualification test of the RF power couplers.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS008

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paper received ※ 07 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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MOPTS015

FoS Cavity of the Alvarez 2.0 DTL as FAIR Injector

DTL, quadrupole, operation, linac

871

M. Heilmann, X. Du, L. Groening, S. Mickat, C. Mühle, A. Rubin, V. Srinivasan
GSI, Darmstadt, Germany

The Alvarez 2.0 DTL will be the new post-stripper DTL of the UNILAC at GSI. The existing GSI with its LINAC and SIS18 comprise the main operation injector chain for the Facility for Antiproton and Ion Research FAIR. The new Alvarez-DTL has an operation frequency of 10⁸.4 MHz, an input energy of 1.358 MeV/u and the output energy is 11.4 MeV/u with a total length of 55 m. The presented FoS section will be part of the first cavity of the Alvarez 2.0 DTL. The FoS-cavity with 11 drift tubes (including quadrupole singlets) and a total length of 1.9 m will be copper plated in GSI for high power tests. The design of the quadrupole singlet magnet is finalized; a prototype of a fully functional magnet with drift tube and stems will be fabricated within a design study. Empty drift tubes and all components of the tank shall be delivered 2019 for first low level RF investigations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS015

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paper received ※ 13 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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MOPTS016

Compression and Noise Reduction of Field Maps

DTL, simulation, MMI, extraction

875

X. Du, L. Groening
GSI, Darmstadt, Germany

Errors from discretization and large data volume of field maps is a concern for beam dynamics simulations with respect to achievable accuracy and to the required amount of time. High-order singular value decomposition (HOSVD) has recently emerged as simple, effective, and adaptive tool to extract the essentials from multidimensional data. This paper is on the feasibility of compression and noise reduction of electromagnetic field map data with HOSVD. The method has been applied to an electric field map of a DTL cavity with 11 m in length comprising 55 rf-gaps. The original field map data of 220 MB was converted into practically noise-free data of just 20 KB. Noise was reduced by 95% as demonstrated using a cubic cavity for which the analytical field map is available.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS016

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paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPTS019

End to End Simulations and Error Studies of the FAIR Proton Linac

linac, simulation, rfq, proton

885

H. Hähnel, U. Ratzinger, M. Syha, R. Tiede
IAP, Frankfurt am Main, Germany
C.M. Kleffner
GSI, Darmstadt, Germany

The FAIR proton linac is developed as the high current proton injector for the future FAIR antiproton production chain at GSI. It will provide a 70 mA proton beam at an energy of 68 MeV to the SIS18 synchrotron. The linac consists of an ECR ion source, followed by a ladder RFQ and a normalconducting linac based on CH-type cavities. High beam currents and strict beam quality requirements were the main drivers for the beam dynamics design. To ensure matching between the individual sections and validate the injector design as a whole, end to end simulations were performed using TraceWin with 3D fieldmaps of the CH-linac. In this paper, the final cavity design, as well as the results of end to end simulations and error studies are discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS019

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paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS020

Status of the FAIR Proton LINAC

proton, linac, rfq, simulation

889

C.M. Kleffner, S. Appel, R. Berezov, J. Fils, P. Forck, P. Gerhard, M. Kaiser, K. Knie, A. Krämer, C. Mühle, S. Puetz, A. Schnase, G. Schreiber, A. Seibel, T. Sieber, V. Srinivasan, J. Trüller, W. Vinzenz, M. Vossberg, C. Will
GSI, Darmstadt, Germany
H. Hähnel, U. Ratzinger, M. Schuett, M. Syha
IAP, Frankfurt am Main, Germany

For the production of Antiproton beams with sufficient intensities, a dedicated high-intensity 325 MHz Proton linac is currently under construction. The Proton linac shall deliver a beam current of up to 70 mA with an energy of 68 MeV for injection into SIS18. The source is designed for the generation of 100 mA beams. The Low-Energy Beam Transport line (LEBT) contains two magnetic solenoid lenses enclosing a diagnostics chamber, a beam chopper and a beam conus. A ladder 4-Rod RFQ and six normal conducting crossbar cavities of CCH and CH type arranged in two sections accelerate the beam to the final energy of 68 MeV. The technical design of the DTL CH cavities are presented and the commissioning measurements of the ion source are described. The construction and the procurement progress, the design and testing results of the key hardware are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS020

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPTS022

Current Status of the MYRRHA Cavities

resonance, status, operation, vacuum

892

K. Kümpel, D. Bade, M. Busch, D. Koser, S. Lamprecht, N.F. Petry, H. Podlech, S. Zimmermann
IAP, Frankfurt am Main, Germany

The MYRRHA (Multi-purpose hYbrid Research Reac-tor for High-tech Applications) Project is a planned ac-celerator driven system (ADS) for the transmutation of long-living radioactive waste. In order test the reliability of the planned 17 MeV injector, a shortened injector with 5.9 MeV consisting of the ion source, a 4-Rod RFQ, 2 Quarter Wave Rebunchers (QWRs) and a total of 7 normal conducting CH structures is currently being installed in Louvein-la-Neuve (LLN, Belgium). Before the cavities can be tested with beam, they are subjected to so-called low power tests several times during the individual con-struction stages in order to be able to correct any devia-tions. This paper describes the status of the two Quarter Wave Rebunchers, which are currently in the process of copper plating and final acceptance, as well as the first two CH structures, the first of which is already being conditioned while CH 2 is still in preparation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS022

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paper received ※ 10 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS023

Conditioning of the Frontline Cavities of the MYRRHA Injector

rfq, electron, multipactoring, MMI

895

S. Lamprecht, T. Conrad, K. Kümpel, N.F. Petry, H. Podlech
IAP, Frankfurt am Main, Germany
J. Belmans, D. Davin, W. De Cock, F. Pompon, D. Vandeplassche
SCK•CEN, Mol, Belgium

The MYRRHA Project (Multi-purpose hYbrid Research Reactor for High-tech Applications) in Mol, Belgium, is an upcoming accelerator driven system (ADS) for the transmutation of long-living radioactive waste. In the injector section of the accelerator, consisting of a 4-rod RFQ and a normal conducting CH-cavity section, the protons will be accelerated up to 17 MeV before entering the superconducting gap-spoke cavity section with an output energy of 600 MeV. A shortened test-injector with an output energy of 5.9 MeV is currently being installed at the SCK. CEN in Louvein-la- Neuve, Belgium. This test-injector serves the purpose of testing the reliability of the planned injector. When commissioning a cavity, it first has to be fed very little power to avoid damage to the structure by flashovers, discharges and multipacting. The power is then slowly increased up to full operation level. In this process, the surfaces are cleaned by heating/outgasing so that the effects disturbing operation described above do no longer occur. This paper will report on the status of the conditioning of the 176.1 MHz 4-rod RFQ up to 120 kW of the MYRRHA-injector and additional measurements concerning the gap voltage which are currently being performed at the SCK. CEN.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS023

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paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPTS024

Reconstruction of the Longitudinal Phase Portrait for the SC CW Heavy Ion HELIAC at GSI

heavy-ion, linac, proton, quadrupole

898

S. Lauber, K. Aulenbacher, W.A. Barth, C. Burandt, F.D. Dziuba, V. Gettmann, T. Kürzeder, J. List, M. Miski-Oglu
HIM, Mainz, Germany
K. Aulenbacher, F.D. Dziuba
IKP, Mainz, Germany
W.A. Barth, C. Burandt, F.D. Dziuba, P. Forck, V. Gettmann, M. Heilmann, T. Kürzeder, S. Lauber, J. List, M. Miski-Oglu, A. Rubin, T. Sieber, S. Yaramyshev
GSI, Darmstadt, Germany
H. Podlech, M. Schwarz
IAP, Frankfurt am Main, Germany

At the GSI Helmholtzzentrum für Schwerionenforschung (GSI) in Darmstadt, Germany, the HElmholtz LInear ACcelerator (HELIAC) is currently under construction. The HELIAC comprises superconducting multigap Crossbar H-mode (SC CH) cavities. The input beam is delivered by an already existing High Charge Injector (HLI). For the further development of the accelerator a detailed knowledge of the input beam parameters to the SC section is necessary. A method for beam reconstruction is incorporated, which provides for longitudinal beam characteristics using measurements with a beam shape monitor and a particle simulation code. This finalizes the investigations on 6D beam parameters, following previous measurements in transversal phase space. The reconstruction of the longitudinal phase portrait is presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS024

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paper received ※ 24 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS027

Conceptual Design of the Proton LINAC for the High Brilliance Neutron Source HBS

linac, rfq, neutron, proton

910

H. Podlech, M. Droba, K. Kümpel, S. Lamprecht, O. Meusel, N.F. Petry, P.P. Schneider, M. Schwarz
IAP, Frankfurt am Main, Germany
J. Baggemann, Th. Brückel, T. Cronert, P.-E. Doege, T. Gutberlet, E. Mauerhofer, U. Rücker, P. Zakalek
JCNS, Jülich, Germany
S. Böhm
NET, Aachen, Germany
J. Li
IEK, Jülich, Germany
C. Zhang
GSI, Darmstadt, Germany

Due to the decommissioning of several research reactors there will be a severe drop in available neutrons for research in Europe in the next decade despite the commissioning of the European Spallation Source (ESS). Compact accelerator-based neutron sources (CANS) could close this gap. The High Brilliance Neutron Source (HBS) currently under development at Forschungszentrum Jülich is scalable in terms of beam energy and power due to its modular design. The driver Linac for HBS at will accelerate a 100 mA proton beam to 70 MeV. The Linac is operated with a beam duty cycle of up to 6% (11% RF duty cycle) and can simultaneously deliver three proton pulse lengths (384 Hz@52 mu-s, 96 Hz@208 mu-s and 24 Hz@832 mu-s) for three neutron production targets. In order to minimize the development effort and the technological risk, state-of-the-art technology of the MYRRHA injector is used. The front end of the HBS Linac consists of an ECR source, LEBT and a 2.5 MeV RFQ followed by a CH-DTL with 35 room temperature CH-cavities. All RF structures are operated at 176.1 MHz and are designed for high duty cycle. Solid-state amplifiers up to 500 kW are used as RF drivers. Due to the beam current and the high average beam power of up to 420 kW, particular attention is paid to beam dynamics. In order to minimize losses, a quasi-periodic lattice with constant negative phase is used. The contribution describes the conceptual design and the challenges of such a modern high power proton accelerator with high reliability and availability.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS027

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paper received ※ 07 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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MOPTS034

Advanced Beam Dynamics Design for the Superconducting Heavy Ion Accelerator HELIAC

linac, heavy-ion, SRF, acceleration

928

M. Schwarz, M. Basten, M. Busch, T. Conrad, H. Podlech
IAP, Frankfurt am Main, Germany
K. Aulenbacher
IKP, Mainz, Germany
K. Aulenbacher, W.A. Barth, C. Burandt, M. Heilmann, S. Lauber, J. List, A. Rubin, S. Yaramyshev
GSI, Darmstadt, Germany
K. Aulenbacher, W.A. Barth, C. Burandt, F.D. Dziuba, V. Gettmann, T. Kürzeder, S. Lauber, J. List, M. Miski-Oglu
HIM, Mainz, Germany
S. Lauber, J. List
KPH, Mainz, Germany

Funding: Work supported by BMBF contr. No. 05P18RFRB1, EU Framework Programme H₂020 662186 (MYRTE) and HIC for FAIR
The standalone superconducting (SC) continuous wave (CW) heavy ion linac HELIAC (HElmholtz LInear ACcelerator) is a common project of GSI and HIM under key support of IAP Frankfurt and in collaboration with Moscow Engineering Physics Institute (MEPhI) and Moscow Institute for Theoretical and Experimental Physics (KI-ITEP). It is intended for future experiments with heavy ions near the Coulomb barrier within super-heavy element (SHE) research and aims at developing a linac with multiple CH cavities as key components downstream the High Charge State Injector (HLI) at GSI. The 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 minimum energy spread. In 2017 the first superconducting section of the linac has been successfully commissioned and extensively tested with beam at GSI. 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 with particular emphasis on realistic assumptions of cavity gap and drift lengths as well as gap voltage distributions for CH3’CH11.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS034

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paper received ※ 30 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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MOPTS035

Recommissioning of SIS18 After FAIR Upgrades

MMI, operation, controls, extraction

932

D. Ondreka, C. Dimopoulou, H.C. Hüther, H. Liebermann, J. Stadlmann, R.J. Steinhagen
GSI, Darmstadt, Germany

The synchrotron SIS18 of the GSI facility has recently resumed beam operation after a long shutdown, during which major upgrades for the operation of SIS18 in the FAIR facility were realized. This signifies a major milestone for the mission of GSI and FAIR. On one hand, the scientific program of GSI depends strongly on beam from SIS18, including the very important developments of detectors for FAIR experiments. On the other hand, large parts of the existing GSI accelerator facility, including SIS18, are now operated with the FAIR control system, demonstrating its suitability for control of a large scale accelerator facility. Commissioning of the new control system started during the shutdown with a series of dry runs, which proved very useful to establish the basic functionalities. Recommissioning of SIS18 was further facilitated by the fact that the machine model of SIS18, implemented in the modeling framework LSA, had already been tested with beam several years before the shutdown. Thus, all operation modes of SIS18, including multi-turn injection, electron cooling, as well as fast and slow extraction could be successfully commissioned during the first weeks of operation. Other commissioning activities concerned the operation of new devices installed during the shutdown. These devices, mostly installed to prepare SIS18 for the operation with FAIR design parameters, open new possibilities in the standard operation of SIS18. A challenge for the operation of SIS18 is posed by ground motion due to ground water lowering for the nearby FAIR construction site. Surveys revealed that SIS18 subsided by several centimeters during one year. Even though the machine was realigned prior to recommissioning, the dynamics of the ground motion will continue to affect operation of SIS18.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS035

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS036

RFQ Electrodes Change and Upgrade Option at the UNILAC HSI Injector

rfq, simulation, operation, MMI

936

M. Vossberg, P. Gerhard, L. Groening, S. Mickat, H. Vormann, C. Xiao
GSI, Darmstadt, Germany
V. Bencini, J.M. Garland, J.-B. Lallement, A.M. Lombardi
CERN, Geneva, Switzerland

In order to meet the beam intensity and quality requirements imposed by FAIR, the HSI-RFQ beam dynamics originally dating from 2009 has been re-designed recently at CERN. Front-to-end simulations demonstrated that the new design meets the FAIR targets. Implementation of the new electrodes, initially planned for 2019, will require re-adaption of the RFQ cavity rf-parameters by re-shaping the stems that keep the electrodes. However, during the beam time 2018 the existing RFQ did not reach its nominal voltage most likely due to expired lifetime of the electrodes originating from 2009. In order to shorten the RFQ maintenance period and to minimize any risk for upcoming beam time 2019, it was decided to post-pone the implementation of the new design and rather just re-producing the 2009 design electrodes. This contribution is on the re-production process as short-term solution and on the full implementation of the new design as mid-term solution. CST simulations performed at GSI assure that the resonance frequency with the new electrode geometry is recuperated through corrections of the carrier rings. The status of the exchange of the electrodes and simulations for the adaptation of the new electrode design are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS036

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paper received ※ 13 May 2019 paper accepted ※ 17 May 2019 issue date ※ 21 June 2019

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MOPTS037

Comparison Between Measurement and Simulation of a Full Scale Prototype for the Proton Injector at FAIR

simulation, proton, linac, resonance

940

A. Seibel, C.M. Kleffner, K. Knie, M. Vossberg
GSI, Darmstadt, Germany
U. Ratzinger
IAP, Frankfurt am Main, Germany

A dedicated 68 MeV, 70 mA proton injector is required for the research program at FAIR (Facility for Antiproton and Ion Research). This 325 MHz linear injector contains a RFQ and six CH structures. The CH (Crossbar H-mode) structures are working in the H₂10 mode. The main acceleration of this room temperature linac will be provided by the CH structures. For the second acceleration from 11.5 MeV to 24.2 MeV a full scale prototype has been built. This structure consists of two individual CH resonators and a coupling cell. Inside the structure there are 17 tuners, they have an impact on the electric field and the frequency. For operation a flat field is required, therefore this tuners must be correctly positioned. Some series of low level tuning and frequency measurements were done to determine the size of the tuners. Low level measurements and simulations will be compared and presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS037

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPTS049

The First Replacement of the RF Window of the ACS Cavity

linac, vacuum, operation, proton

971

J. Tamura, Y. Kondo, T. Morishita
JAEA/J-PARC, Tokai-mura, Japan
F. Naito, M. Otani
KEK, Tokai, Ibaraki, Japan
Y. Nemoto
Nippon Advanced Technology Co., Ltd., Tokai, Japan

In 2013, the Annular-ring Coupled Structure (ACS) cavities were installed to the Japan Proton Accelerator Research Complex (J-PARC) linac. Since then, the ACS cavities have been stably running. Although any serious problem induced by the ACS RF window has not yet observed, we decided to replace the RF window of one ACS cavity, which is the eighteenth accelerating cavity in the order of beam energy (ACS18), by the newly manufactured one. The major motivations of the replacement are to check the surface condition of the RF window which have been under operation for nearly five years and to confirm the availability of the newly manufactured RF window. By making use of the summer maintenance period of 2018, we carried out the replacement. This was the first experience for us to replace the RF window installed to the ACS cavity in the linac accelerator tunnel. As for the removed RF window, there was no any abnormal warning found with the visual examination. At the starting up of the cavity’s operation after the maintenance period, we investigated how much time would be required for an RF conditioning. It took around fifty hours so that the peak RF power including the beam loading is stably input to the cavity through the new RF window. The ACS cavity with the new RF window is now stably operating.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS049

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paper received ※ 01 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS050

VSWR Adjustment for ACS Cavity in J-PARC LINAC

coupling, GUI, simulation, linac

974

J. Tamura, Y. Kondo, T. Morishita
JAEA/J-PARC, Tokai-mura, Japan
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, negative hydrogen beams are accelerated from 190 MeV to 400 MeV by twenty-one Annular-ring Coupled Structure (ACS) accelerating cavities. The input coupler of the ACS high-beta cavity, which is the 21st accelerating cavity (ACS21) in the order of beam acceleration, had a comparatively larger value of the Voltage Standing Wave Ratio (VSWR) than those of the other ACS cavities. To adjust the VSWR of the ACS21, we designed and fabricated a rectangular waveguide with a capacitive iris which conduces to a better matching between the cavity and the waveguide. In the 2018 summer maintenance period, we installed the newly fabricated waveguide to the ACS21 in the position between the input coupler and the RF window. Consequently, the VSWR of the ACS21 was successfully decreased to the target value which leads to the critical coupling under the nominal accelerating condition with 50-mA peak beam current.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS050

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paper received ※ 01 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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MOPTS052

Simulation of Electric and Thermal Behavior of Cryogenic Three-cell Copper Accelerating Cavity for High Gradient Experiments

simulation, cryogenics, coupling, experiment

980

T. Tanaka, K. Hayakawa, Y. Hayakawa, K. Nogami, T. Sakai, Y. Sumitomo, Y. Takahashi
LEBRA, Funabashi, Japan

A C-band three-cell pi-mode accelerating cavity made of high purity copper is under design for use in ultra-high accelerating gradient experiments at a cavity temperature of 20 K. The basic configuration, consisting of mode converter, short circular waveguide and cells with round periphery, is the same as that which was previously employed in the cold model for a 2.6-cell photocathode electron gun cavity. Though the 0.6-cell part in the previous model is replaced with a full cell having a beam duct, the overall electric property of the cavity will not change significantly. The RF input coupling coefficient is adjusted to around 10 at 20 K, which is expected to be lowered significantly due to the increase in the surface resistance by the rapid temperature rise during a high power RF input. The results of the simulations on the electric field and the temperature rise along the cavity surface during the RF pulse are discussed in the report.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS052

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paper received ※ 13 May 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019

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MOPTS056

Optimization of SC Cavity Type for CSNS Linac Upgrade

linac, operation, neutron, acceleration

987

Y. Wang, M.X. Fan, A.H. Li, B. Li, P.H. Qu
IHEP CSNS, Guangdong Province, People’s Republic of China
J.P. Dai, H.C. Liu, P. Sha
IHEP, Beijing, People’s Republic of China
X.L. Wu
DNSC, Dongguan, People’s Republic of China

In order to increase CSNS beam power from 100kW to 500kW, the Linac injection energy need to be increased from 80MeV to 300MeV. The combined layout of superconducting spoke cavities and elliptical cavities will be adopted to accelerate H⁻ beam to 300MeV. Two operation frequency of spoke cavities were compared with single and double spoke structure, a compact 648MHz βg=0.4 single spoke cavity was proposed, and the RF performance was presented, as well as the MP behavior.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS056

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paper received ※ 09 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS057

SSPA upgrade plan design for CiADS

controls, coupling, klystron, simulation

990

Q. Chen, Z. Gao, Y. He, G. Huang, R. Huang, T.C. Jiang, S.H. Liu, L.P. Sun, X.W. Wang, Z.J. Wang, W.M. Yue
IMP/CAS, Lanzhou, People’s Republic of China

Funding: Supported by the National natural science foundation of China (Grand No. 11525523 and 91426303)
For ADS application, both research and commercial facilities requires extremely large amount of RF power to drive several mega watts beam power, so proper RF power upgrade plan can reduce the budget per phase and increase the valuable experience in engineering. CiADS (China initiative Accelerator Drive System) proposes to employ SSPA (Solid State Power Amplifier) as RF power source for flexible configuring and upgrading in the future. In this paper, from an engineering point of view, it is acceptable if proper matching beam current was selected for adopting fixed-coupling input coupler while only sacrificed some RF power during the upgrade plan. SSPA upgrade plan start with the stablility requirement to determine bandwidth, then combined with other RF power requirements to select output level, finally, checking how much the surplus of selected level SSPA for detuning control. The calculation and evaluation results for a §I{545}{MeV} physical design lattice illustrate that some resonance cavities had very limited surplus RF power left for detuning control that provided necessary optimization direction and guidelines for both physical design and SSPA arrangement.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS057

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paper received ※ 30 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS059

The Status of CiADS Superconducting LINAC

linac, proton, cryomodule, operation

994

Z.J. Wang, Y. He, G. Huang, S.H. Liu, T. Tan, Y.Q. Wan, F.F. Wang, W.M. Yue
IMP/CAS, Lanzhou, People’s Republic of China

CiADS (China initiative Accelerator Driven System) approved by Chinese government at 2016 aims to build the first ADS experimental facility to demonstrate the nuclear waste transmutation. The CiADS driving linac can accelerate 5 mA proton beam to 500 MeV at the beam power up to 2.5 MW with the state-of-the-art accelerator technologies. The challenging programs include beam loss control-oriented physics design, high performance CW operated superconducting cavities, SRF cryomod-ules, and highly efficient RF amplifier system. As the driving linac of the ADS system, the RAMI characters will serve as the design philosophy to guide the physics design and the choice of technical routes. The physics design and key technologies of the high-power machine are descried in the paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS059

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paper received ※ 14 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019

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MOPTS063

Design and Low Power Test of a Prototype HOM LINAC

DTL, HOM, linac, impedance

1001

L. Lu, T. He, C.C. Xing, L. Yang
IMP/CAS, Lanzhou, People’s Republic of China
L. Yang
University of Chinese Academy of Sciences, Beijing, People’s Republic of China

A 325MHz HOM (higher order mode) type linac was proposed and studied for proton or heavy ion acceleration in medium energy region. The cavity was finished the fabrication already by using copper and aluminum material. We will report results of low power test of the HOM linac in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS063

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paper received ※ 29 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPTS072

RF DESIGN OF AN 81.25 MHz BENT-VANE TYPE RFQ

rfq, linac, ECR, simulation

1015

L. Yang, T. He, Y. He, L. Lu, C.C. Xing, L. Yang
IMP/CAS, Lanzhou, People’s Republic of China
A.H. Li
IHEP, Beijing, People’s Republic of China

The bent-vane type RFQ is proposed at IMP, Chinese Academy of Sciences, which can downsize cross section and has the simple cooling system in low frequency field. The vanes of the four-vane type RFQ are bent to form the new RFQ structure. In order to research its RF properties, the prototype cavity of an 81.25 MHZ bent-vane type RFQ is designed. This paper presents the preliminary RF design of the prototype cavity.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS072

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paper received ※ 17 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS075

Design and Experiment of a Window-Type CW Deuteron RFQ

rfq, experiment, operation, Windows

1021

K. Zhu, M.J. Easton, P.P. Gan, S.L. Gao, H.P. Li, S. Liu, Y.R. Lu, Q.Y. Tan, L. Tao, Z. Wang
PKU, Beijing, People’s Republic of China
W.P. Dou, Y. He, C. Wang, Q. Wu, H.W. Zhao
IMP/CAS, Lanzhou, People’s Republic of China

A deutron CW RFQ was designed and fabricated in Peking University. It will accelerate 50mA CW deutron beam from 50keV to 1MeV at 162.5MHz. The novel structure of four-vane with window was used to seperate the dipole mode from the working mode. The field tuning of this RFQ was different from conventional four vane RFQ because that the four quadrants of RFQ cavity were coupled. The discipline of field tuning was studied by simulation and experiment. The beam dynamics of the RFQ was designed by equipartation and matching method, limit current effect was considered at the same time. The final design result of the RFQ was: voltage between electrodes was 60kV, transport efficiency of RFQ is 98%, field unflatness is less than 2% after tuning, the deformation of RFQcavity is less than 80um. Only 47 hours was spent to increase CW power of cavity from 0 to 55kW in high power test and The RFQ can working stable at the design voltage. The preliminary H²⁺ beam exeperiment has been done and 1.78mA CW beam was obtained at exit of RFQ. This paper will introduce the detail of design and experiment of the RFQ.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS075

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paper received ※ 22 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019

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MOPTS080

Status and Installation Plan of RISP RFQ at Project Site

rfq, site, experiment, resonance

1031

B.-S. Park, I.S. Hong
IBS, Daejeon, Republic of Korea

Funding: Supported by the Rare Isotope Science Project of Institute for Basic Science funded by the Ministry of Science, ICT (MSIP) and the National Research Foundation (NRF) of Korea (2013M7A1A1075764).
The Rare Isotope Science Project (RISP) at Institute for Basic Science (IBS) has been developed a Radio Frequency Quadrupole(RFQ), which was fabricated and commissioned at the off-site test facility. An O+7 beam was accelerated from 10keV/u to 516keV/u as a preliminary beam test. For CW and high power operation, RF conditioning test was also conducted. The RISP RFQ is 5 meters long, 1 meter in diameter and weighs about 16 tons. It was disassembled and transported to the project site, Sin-dong, for installation as the injector system. The installation commenced in April 2019 and the commissioning of the injector system is expected to begin in early 2020. In this paper, the installation status and plans were summarized.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS080

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paper received ※ 15 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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MOPTS090

Beam-Based Measurement of the Skew-Sextupolar Component of the Radio Frequency Field of a HL-LHC-Type Crab-Cavity

betatron, sextupole, damping, experiment

1066

M. Carlà, A. Alekou, H. Bartosik, L.R. Carver
CERN, Geneva, Switzerland

Two High Luminosity Large Hadron Collider (LHC) type crab-cavities have been installed in the CERN SPS for testing purposes. An attempt to characterize the skew-sextupolar component of the radio frequency field of the crab-cavity (a3) has been carried out by means of beam-based techniques using turn-by-turn monitoring of the betatron motion. The skew nature of a3 couples the horizontal and vertical betatron motions through a non-linear term. Therefore by exciting the horizontal betatron motion it was possible to observe a spectral line in the vertical beam motion driven by the non-linear coupling at the characteristic frequency 2Qx. A measurement of the magnitude of a3 was thus obtained by characterizing amplitude and phase of such line. The results of the measurements are discussed here.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS090

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paper received ※ 06 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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MOPTS092

Numerical and Experimental Evaluation of the DQW Crab Cavity Cryomodule Thermal Budget

cryomodule, HOM, radiation, experiment

1074

F. Carra, K. Brodzinski, E. Cano-Pleite, O. Capatina
CERN, Meyrin, Switzerland

Funding: Research supported by the HL-LHC project
One of the key devices of the HL-LHC project are SRF Crab Cavities. A cryomodule with two Double Quarter Wave (DQW) crab cavities has been fabricated at CERN in 2017 and successfully tested with beam in the Super Proton Synchrotron (SPS) in 2018. The aim of the present study is to present and compare the estimation of the thermal budget for the different components of the cryomodule, performed with numerical and semi-analytical methods, with the experimental measurements carried out on the cryomodule after installation in the SPS.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS092

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paper received ※ 12 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS106

Barrier Bucket Studies in the CERN PS

proton, LLRF, ISOL, kicker

1128

M. Vadai, A. Alomainy
QMUL, London, United Kingdom
H. Damerau
CERN, Geneva, Switzerland

Part of the residual beam loss during the Multi-Turn Extraction (MTE) of fixed target beams from the CERN Proton Synchrotron (PS) can be attributed to kicker magnets switching while the beam is coasting with the main RF systems off before extraction. Generating a barrier bucket to deplete the longitudinal line density of the coasting beam during the kicker rise time can reduce these losses. Beam tests have been performed with an existing Finemet cavity in the PS, which is normally operated as a wideband feedback kicker. To drive the cavity, a beam synchronous waveform synthesizer based on programmable logic has been developed. It produces a pre-distorted signal which ideally results in a single period sinusoidal voltage pulse with programmable parameters at the gap of the cavity, once or multiple times per revolution. The modelling of the behavior of the power amplifier and the cavity is essential to achieve an anti-symmetric voltage pulse with little pre- and post-pulse ripple. The design of the beam-synchronous waveform generator is presented together with results from initial beam studies with the created barrier buckets in the PS.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS106

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paper received ※ 18 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPTS107

Beam Manipulations With Barrier Buckets in the CERN PS

extraction, synchrotron, proton, operation

1132

M. Vadai, A. Alomainy
QMUL, London, United Kingdom
H. Damerau, S.S. Gilardoni, M. Giovannozzi, A. Huschauer
CERN, Geneva, Switzerland

A barrier bucket scheme is being considered to reduce losses during the Multi-Turn Extraction from the CERN Proton Synchrotron to the Super Proton Synchrotron for the fixed-target physics programme. For effective loss reduction, the extraction kicker has to be triggered during the gap at the time of the longitudinal barrier. Initial beam studies at injection energy and with low intensity beams allowed to fully qualify an existing wide-band cavity to generate one or multiple beam synchronous pulses per turn. Bunch-length stretching and shortening have been exercised with barriers moving in azimuth with respect to the beam. The encouraging results obtained at injection energy guided the implementation of a de-bunching manipulation at higher energy to move all bunches into a single barrier bucket. Beam measurements at a momentum of 14GeV/c, varying intensity and the width of the barrier, demonstrate that a quasi-constant longitudinal line density and an almost fully depleted gap can be achieved at highest intensities. The contribution summarises the results of the beam studies at high energy together with some observations related to the Multi-Turn Extraction.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS107

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paper received ※ 18 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS111

Primary Beam Dynamics Design of a Heavy-Ion IH-DTL With Electromagnetic Quadrupoles

DTL, quadrupole, focusing, rfq

1140

P.F. Ma, X. Guan, R. Tang, X.W. Wang, Q.Z. Xing, X.D. Yu, S.X. Zheng
TUB, Beijing, People’s Republic of China

A new IH-DTL beam dynamics scheme, IH-EMQ (ElectroMagnetic Quadrupole) is presented to obtain a large longitudinal acceptance. In this scheme, electromagnetic quadrupoles are installed inside the drift tubes of IH-DTL. A large-longitudinal-acceptance heavy-ion IH-DTL design is described in this paper. With the limit current of 25 mA, the 90% normalized longitudinal acceptance reaches 87.8 pi.deg. MeV for the 60 MeV 107Au³⁰⁺, which is 8 times of the input emittance.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS111

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paper received ※ 09 April 2019 paper accepted ※ 17 May 2019 issue date ※ 21 June 2019

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MOPTS114

Upgrades for Subsystems of the 200 MeV H⁻ Linac at BNL

linac, controls, power-supply, DTL

1152

D. Raparia, G. Atoian, D.M. Gassner, D. Goldberg, O. Gould, T. Lehn, V. LoDestro, M. Mapes, M. Mapes, I. Marneris, S. Polizzo, J. Ritter, A. Zaltsman, A. Zelenski
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
To increase the average current for isotope production by factor of two, we have undertaken several upgrades for our 50-year-old 200 MeV H⁻ linac. Average current will be double by increasing the beam pulse length. We are testing the DTL tanks reliability by increasing RF pulse length and replacing weak RF joints. We are in the process of replace 50-year old ion pumps and a new PLC based vacuum I&C system for the DTL tanks. We are also upgrading/replacing/adding LLRF, diagnostics, machine protection system, and quadrupole power supply. Paper will present status of these activity and future plan.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS114

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPTS117

Exploration of High-Gradient Structures for 4th Generation Light Sources

FEL, linac, cryogenics, electron

1155

S.J. Smith, S. Biedron, S.I. Sosa Guitron
University of New Mexico, Albuquerque, USA
T.B. Bolin
Element Aero, Chicago, USA
B.E. Carlsten, F.L. Krawczyk
LANL, Los Alamos, New Mexico, USA
J.R. Cary, D.M. Cheatham
Tech-X, Boulder, Colorado, USA

As the energy, scale and therefore the cost of large-scale accelerator projects, such as X-ray free-electron lasers (XFELs) increases, new technologies must be developed in order to minimize costs and maximize efficiency wherever possible. One obvious way to reduce costs is to reduce the length of accelerating sections by utilizing higher accelerating gradients. Here we present the results of a study into the various structure options for FEL linacs, contrasting different frequencies, geometries and operating modes. An investigation into the possibility of using cryo-cooled travelling wave (TW) electron structures which allow for higher gradient operation by exploiting the anomalous skin effect is also detailed. Finally, we give simulation results from a number of commercial codes including VSim 9, for a hypothetical TW high gradient C-band structure design employing cryo-cooled technology. Breakdown effects, pulsed heating, tolerances, efficiencies and potential rf sources are also explored, all within the framework of typical FELs and their requirements.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS117

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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TUXXPLM2

SRF Cavity Fault Classification Using Machine Learning at CEBAF

cryomodule, SRF, operation, GUI

1167

A.D. Solopova, A. Carpenter, T. Powers, Y. Roblin, C. Tennant
JLab, Newport News, Virginia, USA
K.M. Iftekharuddin, L. Vidyaratne
ODU, Norfolk, Virginia, USA

The Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab is the first large high power CW recirculating electron accelerator which makes use of SRF accelerating structures configured in two antiparallel linacs. Each linac consists of twenty C20/C50 cryomodules each containing eight 5-cell cavities and five C100 upgrade cryomodules each containing eight 7-cell cavities. Accurately classifying the source of cavity faults is critical for improving accelerator performance. In addition to archived signals sampled at 10 Hz, a cavity fault triggers a waveform acquisition process where 16 waveform records sampled at 5 kHz are recorded for each of the 8 cavities in the effected cryomodule. The waveform record length is sufficiently long for transient microphonic effects to be observable. Significant time is required by a subject matter expert to analyze and identify the intra-cavity signatures of imminent faults. This paper describes a path forward that utilizes machine learning for automatic fault classification. Post-training identification of the physical origins of faults are discussed, as are potential machine-trained model-free implementations of trip avoidance procedures. These methods should provide new insights into cavity fault mechanisms and facilitate intelligent optimization of cryomodule performance

Slides TUXXPLM2 [4.404 MB]

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUXXPLS3

The Design Optimization of the Dielectric Assist Accelerating Structure for Better Heat and Gas Transfer

vacuum, multipactoring, embedded, lattice

1179

S. Mori, M. Yoshida
KEK, Ibaraki, Japan
D. Sato
AIST, Tsukuba, Ibaraki, Japan

The dielectric-assist accelerating (DAA) structure is a dielectric-inserted normal-conducting cavity, which provides high Q value at room temperature. This accelerating structure is composed of dielectric disks and a dielectric cylindrical layer inserted in a copper cavity. For the realistic operation, the removal of heat from the dielectric cells and the vacuum evacuation of gas inside the cylindrical layers have not considered yet. In order to solve the problems, we propose the optimized design of the DAA structure, where the extended part of the dielectric disk is embedded in the copper cavity and the choke structure is applied. We show the result of the electromagnetic-field simulation of the extended DAA structure and the thermal simulation to clarify the relation between a duty factor and maximum temperature of the dielectric cells.

Slides TUXXPLS3 [5.892 MB]

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paper received ※ 30 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPMP006

Cryogenic Tests of the SPIRAL2 LINAC Systems

cryomodule, cryogenics, linac, operation

1240

A. Ghribi, P.-E. Bernaudin, R. Ferdinand, A.V. Vassal
GANIL, Caen, France

Two full cool-down of the SPIRAL2 superconducting LINAC have been performed in 2017 and 2018 respectively, followed by a total of around 5 months of tests at 4 K. Several cool-down strategies were tested, in order to minimize 100 K effect on the SC cavities. Helium bath regulations (level and pressure) have been tested and optimized. Effects of pressure instabilities and coupling with the cryogenic plant have also been observed. Cryogenic performances of each cryomodule have been measured. Low-level RF measurements were also performed on all cavities and showed unidentified modulations at frequencies around 5Hz. These turned out to be thermoacoustic oscillations (TAO) on the cryogenic lines, which generate important pressure instabilities. Several solutions to remove TAO and cure these instabilities have been tested and one has been successfully deployed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP006

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paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPMP048

Current Status of Turkish Accelerator and Radiation Laboratory

electron, radiation, FEL, status

1359

A.A. Aksoy, O.F. Elçim
Ankara University Institute of Accelerator Technologies, Golbasi, Turkey
Ö. Karslı, C. Kaya, B. Koc
Ankara University, Accelerator Technologies Institute, Golbasi, Turkey

Funding: T.R. Presidency Strategy and Budget Office Grand No: 2006K-120470
Turkish Accelerator and Radiation Laboratory (TARLA) which is designed to deliver various accelerator based radiation sources, aims to be outstanding research instrument for users from both Turkey and region. Within the current scope of TARLA its superconducting accelerator will drive two of free electron laser (FEL) beamlines in order to provide Continuous Wave (CW) tunable radiation of high brightness in the mid- and far-infrared range as well as a Bremmstrahlung radiation station. Main components of TARLA, such as injector, superconducting accelerating modules and cryoplant are under commissioning currently. In this paper commissioning results and current status of facility are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP048

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPGW008

PERLE: A High Power Energy Recovery Facility

linac, cryomodule, injection, gun

1396

W. Kaabi, I. Chaikovska, A. Stocchi, C. Vallerand
LAL, Orsay, France
D. Angal-Kalinin, J.W. McKenzie, B.L. Militsyn, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
S.A. Bogacz, A. Hutton, F. Marhauser, R.A. Rimmer, C. Tennant
JLab, Newport News, Virginia, USA
S. Bousson, D. Longuevergne, G. Olivier, G. Olry
IPN, Orsay, France
O.S. Brüning, R. Calaga, L. Dassa, F. Gerigk, E. Jensen, P.A. Thonet
CERN, Geneva, Switzerland
B. Hounsell, M. Klein, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
E.B. Levichev, Yu.A. Pupkov
BINP SB RAS, Novosibirsk, Russia

PERLE is a proposed high power Energy Recovery Linac, designed on multi-turn configuration, based on SRF technology, to be hosted at Orsay-France in a col-laborative effort between local laboratories: LAL and IPNO, together with an international collaboration involv-ing today: CERN, JLAB, STFC ASTeC Daresbury, Liverpool University and BINP Novosibirsk. PERLE will be a unique leading edge facility designed to push advances in accelerator technology, to provide intense and highly flexible test beams for component development. In its final configuration, PERLE provides a 500 MeV elec-tron beam using high current (20 mA) acceleration during three passes through 801.6 MHz cavities. This presenta-tion outlines the technological choices, the lattice design and the main component descriptions.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW008

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paper received ※ 19 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPGW019

Progress of the BESSY VSR Cold String Development and Testing

GUI, simulation, experiment, vacuum

1434

H.-W. Glock, V. Dürr, F. Glöckner, J. Knobloch, M. Tannert, A.V. Vélez, D. Wolk, N. Wunderer
HZB, Berlin, Germany
J. Guo, R.A. Rimmer, H. Wang
JLab, Newport News, Virginia, USA

The so-called VSR (Variable Storage Ring) upgrade of the 3rd gen. light source BESSY II will provide the capability to simultaneously store long (about 20 ps rms length) and short (1 ps or less) bunches in the ring. This will be accomplished by inserting a module with four superconducting cavities, two of them operating at 1.5 GHz as the third harmonic of the 500 MHz driving RF, two at 1.75 GHz. The "cold" string of those four cavities also includes supporting and connecting devices, as there will be: - three intermediate bellows, all shielded against leaking fundamental mode cavity fields, one additionally acting as a collimator for incident synchrotron light; - two tuneable bellows at the module ends; - two warm end groups outside the module, housing toroidal dielectric wake field absorbers, another bellow and a vacuum pump connection. The recent design progress of those components will be reported, including a description of a beam test planned for the central collimating shielded bellow.

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paper received ※ 22 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPGW023

Incorporation of a MESA Linac Modules into BERLinPro

linac, optics, operation, HOM

1449

B.C. Kuske, W. Anders, A. Jankowiak, A. Neumann
HZB, Berlin, Germany
K. Aulenbacher
IKP, Mainz, Germany
K. Aulenbacher
HIM, Mainz, Germany
F. Hug, T. Stengler, C.P. Stoll
KPH, Mainz, Germany

Funding: Work supported by the German Bundesministerium für Bildung und Forschung, Land Berlin, grants of the Helmholtz Association and grants of Helmholtz Association and the DFG within GRK 2128
BERLinPro is an Energy Recovery Linac (ERL) project, currently being set up at the Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany. BERLinPro is designed as - and for - experiments in accelerator physics and as a test bed for novel ERL components. MESA is an ERL project under construction at the Johannes Gutenberg-Universität, Mainz, Germany. MESA is designed as a user facility to perform experiments in dark matter physics and precision measurements of natural constants. Despite the diverse goals, the main linac, providing the larger part of the particles energy, is fairly compatible. It is planned to test and run the MESA linac module in BERLinPro, prior to its usage in MESA. The goals and benefits of this unique cooperation for both projects are outlined in this paper. The necessary adaptions in BERLinPro, including hardware aspects, the new optics, and the scope of performance are described.

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paper received ※ 30 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPGW028

Low Energy Beam Transport System for MESA

emittance, laser, experiment, solenoid

1461

C. Matejcek, K. Aulenbacher, S. Friederich
IKP, Mainz, Germany

An important part of the new accelerator MESA (Mainz Energy-recovering Superconducting Accelerator) is the low energy beam transport system connecting the 100 keV electron source with the injector accelerator. The present setup includes the chopper- and bunching system. The devices are of most importance in order to achieve sufficient bunch compression particularely at higher bunch charges and currents. With the circular deflecting cavity of the chopper system it is possible to measure the longitudinal dimension of the bunches upstream of the buncher whereas downstream the longitudinal size will be measured by Smith Purcell radiation. Based on experimental results obtained from this setup we will discuss the beam parameter and compare them with simulations of the beamline.

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paper received ※ 30 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPGW032

Mode-Locked Pulse Oscillation of a Self-Resonating Enhancement Optical Cavity

laser, resonance, controls, feedback

1471

Y. Hosaka
QST/Takasaki, Takasaki, Japan
Y. Honda, T. Omori, J. Urakawa
KEK, Ibaraki, Japan
A. Kosuge
ISSP, Kashiwa-shi, Japan
K. Sakaue
The University of Tokyo, The School of Engineering, Tokyo, Japan
T. Takahashi
Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
Y. Uesugi
Tohoku University, Institute of Multidisciplinary Research for Advanced Materials, Sendai, Japan
M. Washio
Waseda University, Tokyo, Japan

A power enhancement optical cavity is a compelling means of realizing a pulsed laser with a high peak power and high repetition frequency, which is not feasible using a simple amplifier scheme. However, a precise feedback system is necessary for maintaining the narrow resonance condition of the optical cavity; this has become a major technical issue in developing such cavities. We have developed a new approach that does not require any active feedback system, by placing the cavity in the outer loop of a laser amplifier. We report on the first demonstra-tion of a mode-locked pulse oscillation using the new system.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW032

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paper received ※ 15 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPGW035

A Highly Brilliant Compact 3 GeV Light Source Project in Japan

emittance, storage-ring, injection, linac

1478

N. Nishimori
National Institutes for Quantum and Radiological Science and Technology (QST), Sayo-cho, Japan
H. Tanaka
RIKEN SPring-8 Center, Hyogo, Japan
T. Watanabe
JASRI/SPring-8, Hyogo, Japan

A highly brilliant compact 3 GeV light source project was proposed in Japan. The light source would be constructed in Sendai, north-east part of Japan. It provides brilliant soft X-ray beam to widely cover wavelengths ranging from EUV to hard X-ray in Japan together with SPring-8. The accelerator system is now mostly designed except for several linac components and so on. We have chosen a 4-bend achromat lattice to achieve a low emittance keeping a small circumference with a rather relaxed space issue. The number of cells is 16 and the ring circumference is about 350 m. Number of available beam lines are 26 including short straight sections for multi-pole wigglers. Horizontal emittance is expected to be around 1.1 nmrad, and the maximum brilliance may exceed 10²¹ at 1 - 3 keV region with a stored current of 400 mA. The designs of many components such as vacuum chambers, magnets and monitors are employed from those studied for SPring-8 upgrade project. A full energy injector linac equipped with a thermionic gun and C-band accelerating structures is employed to produce sufficiently low emittance beams for efficient beam injections. The C-band system is adopted from those developed for XFEL SACLA with some modifications. In the future, the injector would be upgraded as an electron driver for SXFEL. Details of the project and accelerator system will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW035

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paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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TUPGW036

1 mA Stable Energy Recovery Beam Operation with Small Beam Emittance

operation, emittance, linac, gun

1482

T. Obina, D.A. Arakawa, M. Egi, T. Furuya, K. Haga, K. Harada, T. Honda, Y. Honda, T. Honma, E. Kako, R. Kato, H. Kawata, Y. Kobayashi, Y. Kojima, T. Konomi, H. Matsumura, T. Miura, T. Miyajima, S. Nagahashi, H. Nakai, N. Nakamura, K. Nakanishi, K.N. Nigorikawa, T. Nogami, F. Qiu, H. Sagehashi, H. Sakai, S. Sakanaka, M. Shimada, M. Tadano, T. Takahashi, R. Takai, O.A. Tanaka, Y. Tanimoto, T. Uchiyama, K. Umemori, M. Yamamoto
KEK, Ibaraki, Japan
R. Hajima, R. Nagai, M. Sawamura
QST, Tokai, Japan
N. Nishimori
National Institutes for Quantum and Radiological Science and Technology (QST), Sayo-cho, Japan

A compact energy-recovery linac (cERL) have been operating since 2013 at KEK to develop critical components for ERL facility. Details of design, construction and the result of initial commissioning are already reported*. This paper will describe the details of further improvements and researches to achieve higher averaged beam current of 1 mA with continuous-wave (CW) beam pattern. At first, to keep the small beam emittance produced by 500 kV DC-photocathode gun, tuning of low-energy beam transport is essential. Also, we found some components degrades the beam quality, i.e., a non-metallic mirror which disturbed the beam orbit. Other important aspects are the measurement and mitigation of the beam losses. Combination of beam collimator and tuning of the beam optics can improve the beam halo enough to operate with 1 mA stably. The cERL has been operated with beam energy at 20 MeV or 17.5 MeV and with beam rep-rate of 1300 MHz or 162.5 MHz depending on the purpose of experiments. In each operation, the efficiency of the energy recovery was confirmed to be better than 99.9 %.
* S. Sakanaka, et.al., Nucl. Instr. and Meth. A 877 (2017)197, https://doi.org/10.1016/j.nima.2017.08.051

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPGW059

Studies of The Electron Beam Lifetime in Solaris Electron Storage Ring

electron, storage-ring, scattering, vacuum

1541

R. Panas, A.M. Marendziak, A.I. Wawrzyniak, M. Wisniowski
Solaris National Synchrotron Radiation Centre, Jagiellonian University, Kraków, Poland

Solaris storage ring is a recently constructed and commissioned machine operated in decay mode. With total accumulated beam dose near to 1000 A.h the measured total lifetime has reached 16 h for 270mA of a stored current. In this paper, the beam lifetime studies are presented using measured residual gas analysis and vertical scraper position for tuned and detuned Landau cavities. It shows that for stable beam the lifetime is dominated by the interaction of the electron with residual gas (vacuum lifetime) and between electrons interaction within a bunch (Touschek lifetime). The estimated vacuum, Touschek and total beam lifetimes from theoretical analysis are also compared with the measured beam lifetime.

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPGW066

Exploring the Potential of the Swiss Light Source

emittance, storage-ring, operation, damping

1554

M. Aiba, M. Böge, A. Citterio, M.M. Dehler, A. Lüdeke, C. Ozkan Loch, L. Stingelin, A. Streun
PSI, Villigen PSI, Switzerland

Swiss Light Source (SLS) has been on-line since 2001. Although its performance meets the specifications, it still has a potential to achieve better storage ring beam parameters. We explore two possible improvements. The first one is for the beam lifetime. There are 480 rf buckets while normally 390 bunches are stored. The gap in filing pattern (90 empty buckets) is held to suppress ion instability. After many years of operation, however, the vacuum condition is much better than that of the time when the SLS was turned on. Hence it is possible to shorten the gap. The beam lifetime can then be prolonged due to less bunch current while keeping the net beam current. The study may be also useful to predict possible filling patter in SLS2, which is the SLS upgrade planned. The second one is for the beam emittance. The nominal energy closed orbit coincides with the axes of quadrupole magnets. An off-momentum closed orbit is therefore off-centered through quadrupoles, resulting in a damping partition shift. The beam emittance can be decreased at the expense of a larger energy spread. This was successfully achieved in the ESRF booster. We study whether it is applicable to the SLS storage ring.

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paper received ※ 13 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPGW078

Harmonic Cavity Design Choice for Lifetime Increase in Diamond-II

simulation, beam-loading, lattice, storage-ring

1585

T. Olsson, R. Bartolini, I.P.S. Martin
DLS, Oxfordshire, United Kingdom

The ongoing trend towards synchrotron light storage rings with ultralow emittance leads to a requirement for strong magnet gradients, which reduce the dynamic aperture and thus the Touschek lifetime of the machine. This is also the case for the planned upgrade of the Diamond Light Source. One option to increase the Touschek lifetime is to lengthen the electron bunches with a harmonic cavity operated close to a harmonic of the fundamental RF frequency. This paper presents studies of a harmonic cavity for Diamond-II with the focus on maximising the lifetime increase. It is foreseen that the ring will have to operate with a gap in the fill pattern to avoid instabilities and therefore multiparticle tracking was used to determine the effect on stability and lifetime for various cavity parameters taking into account transient beam loading.

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paper received ※ 14 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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TUPGW082

Impedance of the Flange Joints With the RF Contact Spring in NSLS-II

impedance, storage-ring, vacuum, damping

1597

A. Blednykh, B. Bacha, G. Bassi, C. Hetzel, B.N. Kosciuk, T.V. Shaftan, V.V. Smaluk, G.M. Wang
BNL, Upton, Long Island, New York, USA

Funding: This work was supported by Department of Energy Contract No. DE-SC0012704
Since the beginning of the NSLS-II commissioning, temperature of the vacuum components has been moni-tored by the Resistance Temperature Detectors located predominantly outside of the vacuum enclosure and at-tached to the chamber body. Temperature map helps us to control overheating of the vacuum components around the ring especially during the current ramp-up. The average current of 475mA has been achieved with two main 500MHz RF cavities and w/o harmonic cavities. Effect of the RF shielded flanges on local heat and on the longitu-dinal beam dynamics is discussed in details.

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPGW084

Multi-pass ERL in a ’Dogbone’ Topology

linac, optics, dipole, focusing

1601

S.A. Bogacz
JLab, Newport News, Virginia, USA

Funding: Work has been authored by Jefferson Science Associates, LLC under Contract No. DE-AC05-06OR23177 with the U.S. Department of Energy.
The main thrust of a multi-pass RLA is its very efficient usage of expensive linac structures. That efficiency can be further enhanced by configuring an RLA in a ’dogbone’ topology, which further boosts the RF efficiency by factor of two (compare to a corresponding racetrack). However, the ’dogbone’ configuration requires the beam to traverse the linac in both directions, while being accelerated. This can be facilitated by a special ’bisected’ linac Optics. Here, the quadrupole gradients scale up with momentum to maintain periodic FODO structure for the lowest energy pass in the first half of the linac and then the quadrupole strengths are mirror reflected in the second linac half. The virtue of this optics is the appearance of distinct nodes in the beta beat-wave at the ends of each pass (where the droplet arcs begin), which limits the growth of initial betas at the beginning of each subsequent droplet arc. Furthermore, ‘bisected’ linac optics naturally supports energy recovery in the ’dogbone’ topology. In this paper, we present a-proof-of-principle lattice design of a multi-pass ’dogbone’ ERL.

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paper received ※ 08 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPGW086

Energy and RF Cavity Phase Symmetry Enforcement in Multi-Turn ERL Models

linac, acceleration, target, electron

1606

R.M. Koscica, N. Banerjee, C.M. Gulliford, G.H. Hoffstaetter, W. Lou
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

In a multi-pass Energy Recovery Linac (ERL), each cavity must regain all energy expended from beam acceleration during beam deceleration, and the beam should achieve specific energy targets during each loop that returns it to the linac. For full energy recovery, and for every returning beam to meet loop energy requirements, we must optimize the phase and voltage of cavity fields in addition to selecting adequate flight times. If we impose symmetry in time and energy during acceleration and deceleration, fewer parameters are needed, simplifying the optimization. As an example, we present symmetric models of the Cornell BNL ERL Test Accelerator (CBETA) with solutions that satisfy the optimization targets of loop energy and zero cavity loading.

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paper received ※ 14 May 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019

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TUPGW092

Working Impedance Model and Its Effect on the Intensity Limitation of Petra-IV Storage Ring

impedance, feedback, emittance, storage-ring

1623

Y.-C. Chae
DESY, Hamburg, Germany

We made sufficient progress in modeling the imped-ance of the PETRA-IV storage ring. The result was ap-plied to estimate the impedance-based single and multi-bunch intensity limit. Due to the extremely small emit-tance of the beam the intrabeam scattering (IBS) effects will be significant unless they are reduced by bunch lengthening. The 3rd harmonic cavity was proposed to dilute the bunch density which resulted in the small syn-chrotron frequency with a large spread. Because of the complexity introduced by impedance and harmonic cavity we used broadband impedance up to 200 GHz to compute the parameters such as bunch length and energy spread at different currents. We found that the microwave instability started very early in current less than 0.5 mA. Even if it is small, the prediction by tracking simulation was consistent with another diffraction-limited storage ring (DLSR) when the Keil-Schnell criterion was used to predict one from the other. Then, we present the single-bunch current limit which had included the effect of geometric and resistive wall impedances of the NEG-coated chamber. Finally, we present the emittance and lifetime which can be realistically achieved in the ring with the above collective effects included.

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPGW097

Design Progress of ALS-U, the Soft X-ray Diffraction Limited Upgrade of the Advanced Light Source

emittance, lattice, storage-ring, vacuum

1639

C. Steier, Ph. Amstutz, K.M. Baptiste, P.A. Bong, E.S. Buice, P.W. Casey, K. Chow, S. De Santis, R.J. Donahue, M.P. Ehrlichman, J.P. Harkins, T. Hellert, M.J. Johnson, J.-Y. Jung, S.C. Leemann, R.M. Leftwich-Vann, D. Leitner, T.H. Luo, O. Omolayo, J.R. Osborn, G. Penn, G.J. Portmann, 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 project to upgrade the Advanced Light Source to a multi bend achromat lattice received CD-1 approval in 2018 marking the end of its conceptual design phase. The ALS-U 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 magnitude 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 presents recent design progress of the accelerator, as well as new results of the mature R&D program.

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paper received ※ 21 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPGW099

Superconducting Crab Cavity Options for Short X-Ray Pulse Generation in SPEAR3

sextupole, GUI, impedance, HOM

1647

F. Toufexis, V.A. Dolgashev, X. Huang, Z. Li
SLAC, Menlo Park, California, USA

Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515.
We are exploring methods to generate short X-ray pulses in SPEAR3 on the order of 1 ps to enable studying ultrafast processes in materials. We are developing a 2-frequency crab cavity scheme with two sets of crab cavities* at the 6th and 6.5th harmonics of the 476 MHz ring RF frequency. In previous work we studied a normal conducting crab cavity for SPEAR3**. In this work we explored two superconducting cavity options: a traditional elliptical cavity and the Quasi-waveguide Resonator***. We found that the Quasi-waveguide Resonator cannot meet our field uniformity specifications due to higher order multipole fields. We then optimized a traditional elliptical cavity with the input, Lower Order Modes, and Higher Order Modes couplers following the Argonne Advanced Photon Source design.
* A. Zholents, et al, Nucl. Instrum. Methods Phys. Res., Sect. A, Vol. 425 (1999), p. 385.
** Z. Li, et al, Proceedings of IPAC17.
*** A. Lunin, et al, Proceedings of HOMSC14.

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paper received ※ 11 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPGW107

Overview of Collective Effects in SLS 2.0

impedance, operation, simulation, damping

1658

M.M. Dehler, M. Aiba, A. Citterio, L. Stingelin
PSI, Villigen PSI, Switzerland

At the end of 2017, the conceptual design for an upgrade of the Swiss Light Source was finished, promising a 40 fold smaller emittance and a corresponding increase of the spectral brightness from the current value. From the point of view of collective effects, the main changes in the new design are a reduced chamber size, fully coated with NEG, and operation at small and negative momentum compaction with low synchrotron frequency. We give an overview of the latest results for the ring. Most critical is the threshold for the longitudinal single bunch instability. Taking into account the combined effect of wake impedances and CSR, we have to rely on bunch stretching by a higher harmonic system to achieve stable operation at nominal current.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW107

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPGW110

Improvement of Touschek Lifetime by Higher Harmonic RF Cavity in the SPS Storage Ring

storage-ring, operation, synchrotron, scattering

1669

T. Phimsen, N. Juntong, P. Sudmuang
SLRI, Nakhon Ratchasima, Thailand
B.C. Jiang
Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China
Z.T. Zhao
SSRF, Shanghai, People’s Republic of China

Siam Photon Source (SPS), located at Nakhon Ratchasima, Thailand, is a synchrotron light source with the beam energy of 1.2 GeV. User operation is performed in beam decay mode with the maximum current of 150 mA. Beam lifetime is about 12 hours at the beam current of 100 mA. Beam injection is carried out twice a day, and even with full energy, it takes roughly 30 minutes. Beam lifetime in the SPS storage ring is limited by Touschek scattering and strongly depends on operation conditions. Higher harmonic RF cavity is a proven method to increase the beam lifetime and suppressing coupled bunch instabilities through Landau damping effect. If the beam lifetime is increased for examples, to be double, only one injection per day would be needed. In this study, an improvement of Touschek lifetime by passive harmonic RF cavity is investigated.

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPRB002

The Conceptual Design of a 36 GHz RF Undulator

undulator, electron, GUI, photon

1676

D. Zhu
ASCo, Clayton, Victoria, Australia
A.W. Cross, L. Zhang
USTRAT/SUPA, Glasgow, United Kingdom
Y.E. Tan
AS - ANSTO, Clayton, Australia

The CompactLight project supported by European H₂020 is to design a hard X-ray FEL facility beyond today’s state of the art. The project integrates photo injector, X-band acceleration and innovative compact short-period undulators together to make the machine more compact. RF undulator has an extraordinary advantage of working at very short undulator period. A conceptual design for a RF undulator at 36 GHz using a corrugated cylindrical waveguide operating in the HE11 mode is presented in this paper. Based on beam dynamics simulation and photon beam radiation simulations, the possibility of RF undulator to be used in CompactLight project is evaluated.

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPRB010

FIRST DESIGN STUDIES OF A NC CW RF GUN FOR EUROPEAN XFEL

gun, cathode, simulation, FEL

1698

G. Shu, Y. Chen, S. Lal, H.J. Qian, H. Shaker, F. Stephan
DESY Zeuthen, Zeuthen, Germany

After the successful commissioning of the European XFEL in pulsed mode, continuous wave (CW) mode operation of European X-ray Free-Electron Laser (XFEL) is under considerations for future upgrade. DESY is push-ing R&D on CW electron sources. A fully superconducting CW gun is under experimental development at DESY in Hamburg, and a normal conducting (NC) CW gun is under physics design at the Photo Injector Test facility at DESY in Zeuthen (PITZ) as a backup option. A 217 MHz NC CW gun is developed from the LBNL 187 MHz VHF gun, with enhancement on both cathode gradient and gun voltage to further improve beam brightness. This paper presents the cavity RF design, multipacting (MP) simula-tions and beam dynamics studies.

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paper received ※ 17 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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TUPRB035

Stimulated Emission of THz Coherent Diffraction Radiation in an Optical Cavity by a Multibunch Electron Beam

experiment, radiation, resonance, electron

1763

Y. Honda, A. Aryshev, R. Kato, T. Miyajima, T. Obina, M. Shimada, R. Takai, T. Uchiyama, N. Yamamoto
KEK, Ibaraki, Japan

Funding: JSPS KAKENHI
Accelerator-based terahertz (THz) radiation has been expected to realize a high-power broad-band source. Employing a low-emittance and short-bunch electron beam at a high repetition rate, a scheme to resonantly excite optical cavity modes of THz spectrum range via coherent diffraction radiation has been proposed. The confocal cavity design is the special case that resonance conditions of all the eigen modes coincide, resulting in realizing broad-band excitation. But in general cases of non-confocal cavities, the resonance condition depends on the mode, and the resonance peak becomes wide and weak. We performed an experiment with a non-confocal cavity as a follow-up experiment of that we have done with a confocal cavity. The result confirmed that the confocal design is the key for a broad-band source.

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paper received ※ 26 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPRB039

Research of Coherent Edge Radiation Generated by Electron Beams Oscillating Free-Electron Lasers

FEL, electron, radiation, experiment

1772

N. Sei, H. Ogawa
AIST, Tsukuba, Ibaraki, Japan
K. Hayakawa, Y. Hayakawa, K. Nogami, T. Sakai, Y. Sumitomo, Y. Takahashi, T. Tanaka
LEBRA, Funabashi, Japan
H. Ohgaki, H. Zen
Kyoto University, Kyoto, Japan

Funding: JSPS KAKENHI Grant Number JP16H03912
We have studied far-infrared coherent radiation with an S-band linac at Laboratory for Electron Beam Research and Application (LEBRA) at Nihon University. We have already developed a couple of terahertz-wave sources based on coherent synchrotron radiation and coherent transition radiation*, which have been applied to spectroscopic research**. Moreover, we developed coherent edge radiation (CER) at the downstream bending magnets in the FEL sections. Because the edge radiation has an annular shape distribution characterized by the asymmetric first-order Laguerre-Gaussian mode, the CER can be extracted from an optical cavity of the FEL system without a diffraction loss of the FEL beam***. The root-mean-squared bunch length of the electron beam was evaulated by measuring the CER spectra, which was about the same level as the FEL micropulse width. Although the infrared FELs at LEBRA had a long slippage length, the CER intensity can be a guidepost enhancing the FEL power because of the existence of their correlation. In this presentation, the characteristics of the CER including correlation between the CER and the FEL will be reported.
* N. Sei et al., Jpn. J. Appl. Phys. 56, (2017) 032401.
** N. Sei et al., J. Opt. Soc. Am. B, 31, (2014) 2150.
*** N. Sei et al., Phys. Lett. A in press.

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paper received ※ 19 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPRB041

Simulation of Short-Pulse Generation from a Dynamically Detuned IR-FEL Oscillator and Pulse Stacking at an External Cavity

FEL, electron, simulation, radiation

1778

Y. Sumitomo, Y. Hayakawa, T. Sakai
LEBRA, Funabashi, Japan
R. Hajima
QST, Tokai, Japan

Funding: Q-LEAP program supported by Ministry of Education, Culture, Sports, Science and Technology, Japan
At the LEBRA facility of Nihon U., we have an IR-FEL oscillator to generate radiations in the range of wavelengths 1-6 um for various experiments. A research program has been established to explore the application of the IR-FEL to generate attosecond UV and X-ray pulses through the high harmonic generation (HHG) in noble gases, where the IR-FEL pulses must have a high-peak power and a short-pulse duration. The property of generated FEL pulse is affected by the cavity length detuning of FEL oscillator as well as the small signal gain and the cavity loss. The operation at a small- or zero-detuning length is necessary to generate a FEL pulse shorter than the bunch length, although it requires a long macro-pulse to reach the saturation. For the short FEL pulse generation within a limited macro-pulse length at the LEBRA LINAC, we apply a dynamical modulation to the electron bunch repetition, that is equivalent to a dynamical detuning of the FEL cavity length. We illustrate the potential performance of the IR-FEL with the dynamical detuning by time-dependent 3D FEL simulations. We also evaluate the enhancement of the FEL pulses by an external cavity stacking for the sake of the HHG application.

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paper received ※ 29 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPRB042

Design Study of Nonlinear Energy Chirp Correction Using Sextupole Magnets at the Soft X-Ray Free-Electron Laser Beamline of SACLA

sextupole, FEL, electron, linac

1782

K. Togawa, T. Hara, H. Tanaka
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

At the x-ray free-electron laser (FEL) facility, SACLA, a soft x-ray FEL beamline (SCSS+) is driven by a dedicated 800-MeV electron accelerator and being operated in parallel with two hard x-ray FEL beamlines. Responding to the demands of short laser pulses from users, a nonlinearity correction system using sextupole magnets is under consideration to obtain shorter electron bunches. Since the frequency of the SCSS+ injector is S-band, the nonlinearity correction of a bunch compression process using a harmonic correction cavity is not so efficient as the SACLA injector, whose frequency of the injector is L-band. Instead of a complex and costly correction cavity system, the sextupole magnets are simply installed in a dispersive section of the first bunch compressor chicane. In this report, we will present the basic design concept and some detail studies of the nonlinear correction.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB042

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPRB045

Stimulated Excitation by Seeding With Cherenkov Radiation in an Optical Cavity

radiation, electron, GUI, ion-source

1785

S.M. Jiang, Z.G. He, Q.K. Jia, W.W. Li, L. Wang
USTC/NSRL, Hefei, Anhui, People’s Republic of China
D. He
Anhui Electrical Engineering Professional Technique College, Hefei, People’s Republic of China

Funding: Work supported by National Foundation of Natural Sciences of China (11775216, 11705198, 11675178), and Fundamental Research Funds for the Central Universities (WK2310000061).
By seeding with narrow-band Cherenkov radiation from a dielectric loaded waveguide(DLW), stimulated excitation in an optical cavity is presented. The evolution and energy loss of the field oscillating in optical cavity is analysed by the theoretical and numerical calculation. The results show that the high order TM modes of the Cherenkov radiation can be better preserved after a large number of roundtrips in the optical cavity and this scheme offers a potential method of realizing high power Terahertz radiation source in a compact facility.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB045

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paper received ※ 30 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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TUPRB059

Solid State Amplifier of SC Linac for Shine

linac, LLRF, hardware, factory

1814

Y.B. Zhao, Q. Chang, K. Xu, Zh.G. Zhang, S.J. Zhao, X. Zheng
SINAP, Shanghai, People’s Republic of China

Shanghai HIgh repetition rate XFEL aNd Extreme light facility （SHINE）is a platform for technique and science research which energy is 8GeV, operated in CW-mode and beam current is 0.2mA. It include a LINAC of 8GeV, three undulator lines, three beam lines and ten experiment stations. SHINE is located underground 30 meters. The lengths of facility is 3kM and the length of LINAC is 1.2km. The acceleration architecture of LINAC consists of six hundred 1.3GHz and sixteen 3.9GHz TELSA type cavities. The 5.2kW SSA will drive the 1.3GHz superconductive cavities and 2kW SSA will power the 3.9GHz superconductive cavities. Four 1.3GHz prototypes of SSA have already been produced, the design and performance are showed in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB059

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paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPRB074

Start-to-End Simulations of the Compact Light Project Based on an S-Band Injector and an X-Band LINAC

lattice, linac, FEL, electron

1836

E. Marín, R. Muñoz Horta, F. Pérez
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
A.A. Aksoy
Ankara University, Accelerator Technologies Institute, Golbasi, Turkey
S. Di Mitri
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
A. Latina
CERN, Geneva, Switzerland
S.B. van der Geer
Pulsar Physics, Eindhoven, The Netherlands

Funding: This project has received funding from the European Union’s Horizon2020 research and innovation programme under grant agreement No 777431
In this paper we report the start-to-end simulation results of one of the options under consideration for the CompactLight Project (XLS). The XLS is a hard X-ray Free Electron Laser under design, using the latest concepts for bright electron photo injectors, very high-gradient X-band structures, and innovative short-period undulators. Presently there exist various tracking codes to conduct the design process. Therefore identifying the most convenient code is of notable importance. This paper compares the tracking codes, Placet and General Particle Tracer, using the XLS lattice based on a S and X-band Injector. The calculation results in terms of beam quality and tracking performance of a full 6-D simulation are presented.
[*] The CompactLight Design Study Project, IPAC2019 proceedings.

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paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPRB075

Higher Order Mode Spectra Study of 3.9 GHz Superconducting Radio Frequency Cavities for the European XFEL

HOM, simulation, electron, FEL

1840

L. Shi, S. Reiche
PSI, Villigen PSI, Switzerland
N. Baboi, A. Sulimov, E. Vogel, T. Wamsat
DESY, Hamburg, Germany
R.M. Jones, N.Y. Joshi
UMAN, Manchester, United Kingdom
P. Pierini
ESS, Lund, Sweden

Funding: The work is part of EuCARD2 and was partly funded by the European Commission, GA 312453.
It is important to verify both by simulation and experiments the wakefields in superconducting radio frequency (SRF) cavities, which can degrade the electron beam quality considerably or impose excessive heat load if left undamped. In this paper, we investigate the Higher Order Mode (HOM) spectra of the 3.9 GHz SRF cavities, which are assembled in a cryogenic module and are used to linearize the longitudinal phase space of the electron beam in the injector of the European XFEL. The HOM spectra are significantly different from the ones from a single cavity due to the coupling of the modes amongst cavities. The measurements not only provide direct input for the beam dynamics studies but also for the beam instrumentation utilizing these modes. The mode spectra are also investigated with a number of numerical simulations and the comparison with measurements shows favorable agreement.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB075

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paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPRB096

Test of an X-ray Cavity using Double-Bunches from the LCLS Cu-Linac

FEL, electron, laser, free-electron-laser

1887

K.-J. Kim, L. Assoufid, R.R. Lindberg, X. Shi, D. Shu, Yu. Shvyd’ko, M. White
ANL, Argonne, Illinois, USA
F.-J. Decker, Z. Huang, G. Marcus, T.O. Raubenheimer, D. Zhu
SLAC, Menlo Park, California, USA

Funding: This work is supported by U.S. DOE, Office of Science, Office of BES, under Contract No. DE-AC02-06CH11357 (ANL) and DE-AC02-76SF00515 (SLAC).
We discuss a proposal to test the operation of an X-ray cavity consisting of Bragg reflectors. The test will con-stitute a major step demonstrating the feasibility of either an X-ray regenerative amplifier FEL or an X-ray FEL Oscillator. These cavity-based X-ray FELs will provide the full temporal coherence lacking in the SA-SE FELs. An X-ray cavity of rectangular path will be constructed around the first seven LCLS-II undulator units. The Cu-linac will produce a pair of electron bunches separated by the cavity-round-trip distance during each linac cycle. The X-ray pulse produced by the first bunch is deflected into the cavity and returns to the undulator where it is amplified due to the presence of the second bunch. The key challenges are: the preci-sion of the cavity mechanical construction, the quality of the diamond crystals, and the electron beam stability. When the LCLS-II super-conducting linac becomes available, the cavity can then be used for high-repetition rate studies of the X-ray RAFEL and XFELO concepts.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB096

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPRB097

Recent Progress on the Design of Normal Conducting APEX-II VHF CW Electron Gun

gun, electron, cathode, brightness

1891

D. Li, H.Q. Feng, D. Filippetto, M.J. Johnson, A.R. Lambert, T.H. Luo, C.E. Mitchell, J. Qiang, F. Sannibale, J.W. Staples, S.P. Virostek, R.P. Wells
LBNL, Berkeley, California, USA
H.Q. Feng
TUB, Beijing, People’s Republic of China

Funding: Director of Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
We report recent progress on the design of a normal conducting CW electron gun, APEX-II (Advanced Photo-injector EXperiment-II) at Lawrence Berkeley National Laboratory. APEX-II is an upgrade of the successful APEX gun and the LCLS-II (Linac Coherent Light Source-II) injector, aiming at applications for Free electron laser (FEL) such as LCLS-II High Energy upgrade, UED (Ultrafast Electron Diffraction) and UEM (Ultrafast Electron Microscopy). The APEX-II adopted a two-cell cavity design with resonant frequency of 162.5 MHz. The APEX-II gun is targeting to achieve exceeding 30 MV/m of launch gradient at the cathode and output energy above 1.5 MeV with transverse emittance of 0.1 um at 100 pC. Advanced MOGA optimization technique has been used for both the RF cavity design and extensive beam dynamics studies using APEX-like and LCLS-II like injector layout. Detailed RF designs, beam dynamics studies, preliminary engineering design and FEA analysis will be presented, with cavity features that were demonstrated to be crucial in the operation of the APEX gun.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB097

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPRB103

The FHI FEL Upgrade Design

FEL, undulator, dipole, operation

1903

A.M.M. Todd
AMMTodd Consulting, Princeton Junction, New Jersey, USA
W.B. Colson
NPS, Monterey, California, USA
M. De Pas, S. Gewinner, H. Junkes, G. Meijer, W. Schöllkopf, G. von Helden
FHI, Berlin, Germany
S.C. Gottschalk
STI Magnetics LLC, Woodinville, USA
J. Rathke, T. Schultheiss
AES, Medford, New York, USA
L.M. Young
LMY Technology, Lincolnton, Georgia, USA

Since coming on-line in November 2013, the Fritz-Haber-Institut (FHI) der Max-Planck-Gesellschaft (MPG) Free-Electron Laser (FEL) has provided intense, tunable infrared radiation to FHI user groups. It has enabled experiments in diverse fields ranging from bio-molecular spectroscopy to studies of clusters and nanoparticles, nonlinear solid-state spectroscopy, and surface science, resulting in 50 peer-reviewed publications so far. The MPG has now funded a significant upgrade to the original FHI FEL. A second short Rayleigh range undulator FEL beamline is being added that will permit lasing from < 5 microns to > 160 microns. Additionally, a 500 MHz kicker cavity will permit simultaneous two-color operation of the FEL from both FEL beamlines over an optical range of 5 to 50 microns by deflecting alternate 1 GHz pulses into each of the two undulators. We will describe the upgraded FHI FEL physics and engineering design and present the plans for two-color FEL operations in November 2020.
A.M.M. Todd, L.M. Young, J.W Rathke, W.B. Colson, T.J Schultheiss and S. Gottschalk are Consultants to the Fritz-Haber-Institut

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB103

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paper received ※ 02 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPRB117

Disk and Washer Coupled Cavity Linac Design and Cold-Model for Muon Linac

linac, acceleration, emittance, operation

1924

M. Otani, N. Saito
J-PARC, KEK & JAEA, Ibaraki-ken, Japan
K. Futatsukawa, T. Mibe, F. Naito
KEK, Ibaraki, Japan
K. Hasegawa, T. Ito, Y. Kondo, T. Morishita
JAEA/J-PARC, Tokai-mura, Japan
H. Iinuma, Y. Nakazawa
Ibaraki University, Ibaraki, Japan
Y. Iwashita
Kyoto ICR, Uji, Kyoto, Japan
R. Kitamura
University of Tokyo, Tokyo, Japan

Funding: This work was supported by JSPS KAKENHI Grant Numbers JP15H03666, JP 16H03987, JP18H03707.
A disk and washer (DAW) coupled cavity linac (CCL) has been developed for a middle velocity part in a muon linac at the J-PARC E34 experiment. It will accelerate muons from v/c = 0.3 to 0.7 at an operational frequency of 1296 MHz. In this poster, the cavity designs, beam dynamics designs, and the cold-model measurements will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB117

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paper received ※ 30 April 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019

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TUPTS006

Tests at High RF Power of the ESS Medium Beta Cryomodule Demonstrator

cryomodule, cryogenics, linac, status

1940

P. Bosland, C. Arcambal, F. Ardellier, S. Berry, A. Bouygues, E. Cenni, G. Devanz, T. Hamelin, X. Hanus, O. Piquet, J.P. Poupeau, B. Renard, P. Sahuquet
CEA-DRF-IRFU, France
C. Darve
ESS, Lund, Sweden
P. Michelato
INFN/LASA, Segrate (MI), Italy
G. Olivier, J.P. Thermeau
IPN, Orsay, France

CEA is in charge of the 30 elliptical medium and high-beta cryomodules to be installed in the ESS tunnel in Lund, Sweden. Before launching the assembly of the series cryomodules, CEA developed a medium-beta cryomodule technology demonstrator in a collaboration with IPNO, LASA and ESS. This paper briefly presents the cryomodule assembly and summarizes the main results of the high RF power tests performed in 2018 in a dedicated test stand in CEA Saclay. The main ESS requirements were reached: E_acc = 16.7 MV/m in cavities, Pforward = 1.1 MW in power couplers, RF pulses length = 3.6 ms at 14 Hz. The piezo tuners efficiently compensated the Lorentz forces detuning and could stabilize the accelerating field better than 1% over the full length of the expected ESS 2.86 ms beam pulse without any LLRF regulation system. Following this successful validation CEA started the assembly of the first ESS medium-beta series cryomodule

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS006

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paper received ※ 06 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPTS013

Characterization of an Electron Gun Test Setup Based on Multipacting

electron, cathode, multipactoring, gun

1961

C. Henkel, W. Hillert, V. Miltchev
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
K. Flöttmann
DESY, Hamburg, Germany

A multipacting electron gun (MEG) is a micro-pulse electron source, based on secondary electron emission in a resonant microwave cavity structure, for the generation of low emittance electron bunches in continuous wave operation. Based on numerical simulations, an experimental test setup for low-energy electron beams at 3 GHz has been established. In this contribution we show a detailed description and characterization of the RF test stand, supported by first results on charge collection measurements of the output current with respect to important operational parameters like power transmission and modifiable mechanical dimensions in the assembly of the experiment. This is a milestone in the development of a MEG setup for higher energetic electron beams and subsequent investigation of essential beam characteristics like emittance and energy distribution for the optimization with regard to best possible beam quality and future fields of application.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS013

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paper received ※ 30 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPTS015

Design Steps Towards an Electron Source for Ultrafast Electron Diffraction at DELTA

electron, laser, gun, space-charge

1968

D. Krieg, S. Khan
DELTA, Dortmund, Germany
T.J. Albert, K. Sokolowski-Tinten
Universität Duisburg-Essen, Duisburg, Germany

Funding: MERCUR Pr-2017-0002
Ultrafast electron diffraction (UED) is a pump-probe technique to explore the structural dynamics of matter, combining sub-angstrom De-Broglie wavelength of electrons with femtosecond time resolution. UED experiments require ultrashort laser pulses to pump a sample, electron bunches with small emittance and ultrashort length to analyze the state of the sample and excellent control of the delay between them. Electrons accelerated to a few MeV in a photocathode gun offer significant advantages compared to keV electrons from electrostatic electron sources regarding emittance, bunch length and, due to the reduction of space charge effects, bunch charge. Furthermore, thicker samples and hence a wider range of possible materials are enabled by the longer mean free path of MeV electrons. In this paper, design steps towards a university-based UED facility with ultrashort and low-emittance MeV electron bunches are presented, including the transverse and longitudinal focusing schemes, which minimize space charge effects and nonlinearities.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS015

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPTS035

Vacuum Tube Operation Analysis for 1.2 MW Beam Acceleration in J-PARC RCS

acceleration, vacuum, operation, power-supply

2017

M. Yamamoto, M. Nomura, T. Shimada, F. Tamura
JAEA/J-PARC, Tokai-mura, Japan
M. Furusawa, K. Hara, K. Hasegawa, C. Ohmori, Y. Sugiyama, M. Yoshii
KEK, Tokai, Ibaraki, Japan

The J-PARC RCS has successfully accelerated 1 MW proton beam, matching the designed beam power. Therefore, we have considered acceleration beyond the designed beam power, with the next target being 1.2 MW. An issue for 1.2 MW beam acceleration is the rf system. The present anode power supply is limited by its output current, and the vacuum tube amplifier suffers from an unbalance of the anode voltage swing, arising from the combination of multi-harmonic rf driving and push-pull operation. We have investigated the mitigation of the maximum anode currents and unbalanced tubes by choosing appropriate circuit parameters of the rf cavity with the tube amplifier. We describe the analysis results of the vacuum tube operation for 1.2 MW beam acceleration in the RCS.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS035

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paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPTS045

Simulation Analysis of LLRF Feedforward Compensation to Beam Loading for CiADS LINAC

simulation, beam-loading, controls, feedback

2027

X.C. Xu, J.Y. Ma
IMP/CAS, Lanzhou, People’s Republic of China

A simulation is coded to calculate the beam loading in the cavity of CiADS and the response of the LLRF system. In the pulse operating mode, the fluctuation of amplitude and phase of the cavity field contributed by the transient beam loading is traced. During the simulation the effect of beam current fluctuation, and timing jitter were determined. The deviation margin of relational parameters is lined out to meet the requirement for cavity stability with amplitude 0.1% and phase 0.1°.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS045

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paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPTS046

Commissioning of a Compact THz Source Based on FEL

linac, FEL, undulator, radiation

2030

Y.J. Pei, G. Feng, X.Y. He, Y. Hong, D. Jia, P. Lu, S. Lu, L. Shang, B.G. Sun, Zh.X. Tang, W. Wang, X.Q. Wang, W. Wei
USTC/NSRL, Hefei, Anhui, People’s Republic of China
L. Cao, Q.S. Chen, Q. Fu, T. Hu, P. Tan, Y.Q. Xiong
HUST, Wuhan, People’s Republic of China
G. Huang
IMP/CAS, Lanzhou, People’s Republic of China
L.G. Shen, F. Zhang
USTC/PMPI, Hefei, Anhui, People’s Republic of China

The layout of the THz source based on FEL was de-scribed in this paper. The THz source was based on a FEL which was composed of a compact 8-14MeV LINAC, undulator, optical resonance, THz wave measurement system and so on. The facility was designed in 2013 and the typical running parameter got in 2017 were as the following: energy is of 12.7MeV, energy spread is of 0.3%, macro-pulse is of 4 μs, pulse length of micro-pulse is of 6ps, emittance is of 24 mm.mrad. After that the ma-chine was commissioning for production THz radiation. In November 2018, the THz wave was test and got THz wave signal, the spectrum was also got. This year, we plan to measure the output power of the THz source.

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paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPTS053

Design of a 217 MHz VHF Gun at Tsinghua University

gun, cathode, electron, simulation

2050

L.M. Zheng, H. Chen, Y.C. Du, W.-H. Huang, R.K. Li, Z.Z. Li, C.-X. Tang
TUB, Beijing, People’s Republic of China
B. Gao
IHEP, Beijing, People’s Republic of China

A 217 MHz VHF gun operating in CW mode is designing at Tsinghua University. The cathode gradient is designed to be 30 MV/m to accelerate the electron bunches up to 878 keV. The cavity profile is optimized in CST to minimize the input power, peak surface electric field, and peak wall power density. The multipacting analysis and the thermal analysis are also presented in this paper. Further gun shape optimization and mechanical design are ongoing.

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paper received ※ 15 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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TUPTS054

1st+2nd Harmonic Photocathode Bimodal Gun R&D

gun, emittance, cathode, electron

2054

L. Wang
SINAP, Shanghai, People’s Republic of China
W. Fang, Z.T. Zhao
SSRF, Shanghai, People’s Republic of China
J.L. Hirshfield
Yale University, Physics Department, New Haven, CT, USA
J.L. Hirshfield, S.V. Shchelkunov
Omega-P, Inc., New Haven, Connecticut, USA
Y. Jiang, S.V. Shchelkunov
Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA
L. Wang
University of Chinese Academy of Sciences, Beijing, People’s Republic of China

Funding: U.S. Dept. of Energy
A novel Bimodal Electron Gun is designed to apply microwaves at two harmonically-related frequency in a 0.6 cell RF gun to increase the RF breakdown threshold and enhance the beam quality. This stratagem is intended to allow the RF gun structure to support a high accelera-tion gradient as well as to manipulate the emittance evolution in the half cell. By selecting a proper ampli-tude ratio and phase relationship between the first and second harmonic RF field components in the gun cavity, the superposition of the harmonic field components can provide a flat-top like RF profile to omitting the RF emittance component in the gun, while increase the RF breakdown threshold. The recent status of the Bimodal Electron Gun R&D is presented, including the designs of the novel two frequency RF structure and the simulation of the beam dynamic.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS054

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPTS059

Conceptual Design of the SC230 Superconducting Cyclotron for Proton Therapy

cyclotron, proton, acceleration, simulation

2058

O. Karamyshev, S. Gurskiy, G.A. Karamysheva, D.V. Popov, G. Shirkov, S.G. Shirkov, V.L. Smirnov, S.B. Vorozhtsov
JINR, Dubna, Moscow Region, Russia

Physical design of the compact superconducting cyclotron SC230 (91.5MHz) has been performed. The cyclotron will deliver up to 230 MeV beam for proton therapy and medico-biological research. We have performed simulations of magnetic and accelerating systems of the SC230 cyclotron and specified the main parameters of the accelerator.

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paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPTS065

RF Conditioning of the CLARA 400 Hz Photoinjector

GUI, controls, vacuum, operation

2067

L.S. Cowie, D.J. Scott
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Automated conditioning of the 400 Hz photoinjector for CLARA was begun and the conditioning program refined. The conditioning was performed at 100 Hz. Masks were used to detect breakdowns in the reflected power and phase, and the breakdown rate was limited to 5x106 breakdowns per pulse. The cavity gradient and breakdown rate evolution over the conditioning time is presented. Post-pulse multipactor and other evidence of electron effects were detected. Possible mechanisms for this are discussed. The conditioning was interrupted by breakdown in the waveguide after reaching 2.5 MW, and will be resumed after the planned 6 month shutdown of CLARA.

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paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPTS069

A Plasmonic Niobium Photocathode for SRF Gun Applications

cathode, gun, laser, photon

2079

F.E. Hannon
JLab, Newport News, Virginia, USA
G. Andonian, L.H. Harris
RadiaBeam, Marina del Rey, California, USA

The typical quantum efficiency of niobium is of the order 10^-4, whilst also requiring UV lasers for emission. This paper presents the results of a plasmonic niobium surface that operates with IR laser via multiphoton emission.

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPTS076

RF Design of APEX2 Cavities

gun, cathode, electron, brightness

2094

T.H. Luo, H.Q. Feng, D. Filippetto, M.J. Johnson, A.R. Lambert, D. Li, C.E. Mitchell, F. Sannibale, J.W. Staples, S.P. Virostek, R.P. Wells
LBNL, Berkeley, California, USA
H.Q. Feng
TUB, Beijing, People’s Republic of China

Funding: Director of Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231
APEX2 is a proposed high repetition rate, high brightness electron source based on CW normal conducting RF cavities, aiming to further extend the brightness performance for FEL and UED/UEM beyond APEX. APEX2 consists of two cavities, one gun cavity for generating photo-electrons and one following cavity for beam energy boosting. In this paper, we present the RF design of the APEX2 cavities. The design has considered both beam dynamics requirements and engineering feasibility. A novel geometry optimization method with Genetic Algorithm has been implemented in the design procedure.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS076

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPTS079

Overcoming Multipacting Barriers in SRF Photoinjectors

gun, electron, cathode, SRF

2105

I. Petrushina
SUNY SB, Stony Brook, New York, USA
V. Litvinenko, G. Narayan, I. Pinayev, F. Severino, K.S. Smith
BNL, Upton, Long Island, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA

Superconducting RF (SRF) photoinjectors are considered to be a potential breakthrough in the area of high brightness electron sources. However, there is always the very important question of the compatibility of SRF cavities and high quantum efficiency (QE) photocathodes. A deposition of active elements from high QE photocathodes on the surface of a cavity makes it more vulnerable to multipacting (MP) and could affect the operation of an SRF gun. On the other side, MP can significantly reduce the lifetime of a photocathode. It is well known in the SRF community that a strong coupling, high forward power and sufficient cleanliness of cavity walls are the key components to overcome a low-level MP zone. In this paper we present a theoretical model of passing a MP barrier which could help estimate the desirable conditions for successful operation of an SRF gun. We demonstrate our results for the 113 MHz SRF photo-injector for Coherent electron Cooling (CeC) alongside with the experimental observations and 3D simulations of the MP discharge in the cavity. The results of the theoretical model and simulations show good agreement with the experimental results, and demonstrate that, if approached carefully, MP zones can be easily passed without any harm to the photocathode.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS079

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPTS083

Simulations and Experimental Plans for a High-Repetition-Rate Field-Enhanced Conduction-Cooled Superconducting RF Electron Source

electron, cathode, SRF, simulation

2113

O. Mohsen, A. McKeown, D. Mihalcea, P. Piot, I. Salehinia
Northern Illinois University, DeKalb, Illinois, USA
R. Dhuley, M.G. Geelhoed, D. Mihalcea, P. Piot, J.C.T. Thangaraj
Fermilab, Batavia, Illinois, USA

Funding: Work supported by DOE awards DE-SC0018367 with NIU and DE-AC02-07CH11359 with Fermilab.
We present a novel RF design for a field enhanced electron source driven by field emission cathodes. The proposed electron source relies on the enhanced high electric field gradients at the cathode to simultaneously extract and accelerate electrons. The system will be tested in a conduction-cooled superconducting radio-frequency cavity recently demonstrated at Fermilab. In this paper, we present electromagnetic and thermal simulations of the setup that support the feasibility of the design.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS083

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paper received ※ 18 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPTS106

First Commissioning of LCLS-II CW Injector Source

gun, operation, electron, vacuum

2171

F. Zhou, C. Adolphsen, A.L. Benwell, G.W. Brown, W.S. Colocho, Y. Ding, M.P. Dunning, K. Grouev, B.T. Jacobson, X. Liu, T.J. Maxwell, J.F. Schmerge, T.J. Smith, T. Vecchione, F.Y. Wang, C.M. Zimmer
SLAC, Menlo Park, California, USA
G. Huang, F. Sannibale
LBNL, Berkeley, California, USA

Funding: The work is supported by DOE under grant No. DE-AC02-76SF00515
The LCLS-II injector source includes a 186MHz CW rf-gun, a 1.3 GHz CW rf-buncher, a loadlock system for photocathode change, two main solenoids, and a few essential diagnostics. The electron beam is designed to operate at a high repetition rate, up to 1-MHz. Since summer of 2018 we started LCLS-II injector source commissioning immediately after the major installation was completed. Initial commissioning showed the rf-gun was severely contaminated with hydrocarbons and very limited power <600W could be fed into the gun cavity. After a few significant processes, we eventually removed the hydrocarbons and successfully delivered desired rf power of 80 kW to the gun. This paper reports first com-missioning results including gun bakeout and vacuum processing, CW RF-gun and buncher operation with nom-inal power, and measurements of rf stability and dark current.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS106

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paper received ※ 10 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPTS112

Stand-alone Accelerator System Based on SRF Quarter-wave Resonators

cryomodule, SRF, operation, vacuum

2185

S.V. Kutsaev, R.B. Agustsson, R.D. Berry, D. Chao
RadiaBeam, Santa Monica, California, USA
Z.A. Conway
ANL, Argonne, Illinois, USA

Funding: This material is based upon work supported by the U.S. Department of Energy under contracts DE-SC0017101 and DE-AC02-06CH11357. This research used resources of DOE ANL’s ATLAS facility.
Superconducting accelerators are large and complex systems requiring a central refrigerator and distributed transfer systems to supply 2-4 K liquid helium. Stand-alone, cryocooler-based systems are of interest both to scientific facilities and industrial applications, as they do not require large cryogenic infrastructure and trained specialists for operation. Here we present our approach to the challenge of using low-power commercially available cryocoolers to operate niobium superconducting resonators at 4.4 K with high accelerating voltages and several watts of heating. Engineering and design results from RadiaBeam Systems, collaborating with Argonne National Laboratory, for a stand-alone liquid-cooled cryomodule with 10 Watts of 4.4 K cooling capacity housing a 72.75 MHz quarter-wave resonator operating at 2 MV for synchronous ions travelling at 7.7% of speed of light will be discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS112

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paper received ※ 30 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPTS113

Microwave Thermionic Electron Gun for Synchrotron Light Sources

gun, cathode, electron, coupling

2189

S.V. Kutsaev, R.B. Agustsson, R.D. Berry, D. Chao, O. Chimalpopoca, A.Yu. Smirnov, K.V. Taletski, A. Verma
RadiaBeam, Santa Monica, California, USA
M. Borland, A. Nassiri, Y. Sun, G.J. Waldschmidt, A. Zholents
ANL, Argonne, Illinois, USA

Funding: This work was supported by the U.S. Department of Energy, Office of Basic Energy Science, under contracts DE-SC0015191 and DE- AC02-06CH11357.
Thermionic RF guns are the source of electrons used in many practical applications, such as drivers for synchrotron light sources, preferred for their compactness and efficiency. RadiaBeam Technologies has developed a new thermionic RF gun for the Advanced Photon Source at Argonne National Laboratory, which would offer substantial improvements in reliable operations with a robust interface between the thermionic cathode and the cavity, as well as better RF performance, compared to existing models. This improvement became possible by incorporating new pi-mode electromagnetic design, robust cavity back plate design, and a cooling system that will allow stable operation for up to 1 A of beam current and 100 Hz rep rate at 1.5 μs RF pulse length, and 70 MV/m peak on-axis field in the cavity. In this paper, we discuss the electromagnetic and engineering design of the cavity and provide the test results of the new gun.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS113

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paper received ※ 30 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPTS118

LASA Activities on Surface Treatment of Low-beta Elliptical Cavities

SRF, FEL, cathode, superconductivity

2207

M. Bertucci, A. Bignami, A. Bosotti, M. Chiodini, A. D’Ambros, P. Michelato, L. Monaco, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy
D. Rizzetto, M. Rizzi
Ettore Zanon S.p.A., Schio, Italy
L. Sagliano
ESS, Lund, Sweden

This paper describes the efforts made by LASA on the development of surface treatments for low-beta elliptical cavities, for the current series production of ESS and the foreseen series production of PIP-II. The traditional techniques of buffered chemical polishing and electropolishing are here discussed taking into account the industrial environment, the practical issues due to the size and geometry of such cavities and according to the required qualification values for quality factor and accelerating gradient.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS118

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paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPTS119

Status of the ESS Medium Beta Cavities at INFN - LASA

status, controls, HOM, niobium

2211

P. Michelato, M. Bertucci, A. Bignami, A. Bosotti, M. Chiodini, A. D’Ambros, L. Monaco, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
S. Aurnia, O. Leonardi, A. Miraglia, G. Vecchio
INFN/LNS, Catania, Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy
L. Sagliano
ESS, Lund, Sweden

INFN-LASA contributes in-kind to the European Spallation Source ERIC with 36 6-cell cavities for the Medium Beta section of the Superconducting Linac. After having developed the electromagnetic and mechanical models, few prototypes have been produced and tested. Based on this experience, we are now supervisioning the cavity production at the industry, the resonators test at DESY and the delivery to CEA at Saclay. In this paper, we report on the status of the overall INFN-LASA contribution including also document handling, interface data exchange and QA/QC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS119

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPTS120

Status of the PIP-II Activities at INFN-LASA

niobium, linac, interface, SRF

2215

R. Paparella, M. Bertucci, A. Bignami, A. Bosotti, M. Chiodini, A. D’Ambros, P. Michelato, L. Monaco, C. Pagani, D. Sertore
INFN/LASA, Segrate (MI), Italy
J.F. Chen
SARI-CAS, Pudong, Shanghai, People’s Republic of China
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy
L. Sagliano
ESS, Lund, Sweden

INFN-LASA joined the international effort for the PIP-II project in Fermilab and it is expected to build the 650 MHz superconducting cavities required by the low-beta section of the 800 MeV front-end proton linac, as recently signed by US DOE and Italian MIUR. After developing the electro-magnetic and mechanical design, INFN-Milano started the prototyping phase by producing five single-cells and two complete 5-cells cavities. In a joint effort with Fermilab the road for the optimal surface treatment for such low-beta resonators has started in order to approach the existing state-of-the-art performances of beta 1 cavities. This paper reports the status of PIP-II activities at INFN-LASA summarizing manufacturing experience and preliminary experimental results.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS120

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paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEXXPLS1

Magnetron R&D for High Efficiency CW RF Sources of Particle Accelerators

injection, electron, controls, klystron

2233

H. Wang, R.M. Nelson, R.A. Rimmer
JLab, Newport News, Virginia, USA
B.R.L. Coriton, C.P. Moeller
GA, San Diego, California, USA
A. Dudas, M.L. Neubauer
Muons, Inc, Illinois, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177, DOE OS/NP STTR Grant DE-SC0013203 and DOE OS/HEP Accelerator Stewardship award 2019-2021.
The scheme of using a high efficiency magnetron to drive a superconducting or normal conducting radio frequency accelerator cavity needs not only injection phase locking but also amplitude modulation to compensate for the cavity’s microphonics, frequency change, variations of cavity voltage and beam current. To be able to do a fast and efficient modulation and to compensate the frequency pushing effect due to the anode current change, the magnetron’s magnetic field has to be trimmed by an external coil*. To facilitate this, a low eddy current magnetron body has been designed and built**. This paper will present the experimental results of such modulation on a conventional 2.45 GHz magnetron at the R&D test stand. In addition, the progresses on the injection lock test to a new 1497 MHz, 13kW magnetron prototype aimed for the CEBAF klystron replacement with newly built low level RF (LLRF) controller for the amplitude modulation will be reported. Based on these R&D results, a 915MHz, 2×75kW CW industrial heating type magnetron system is being developed to be used for the high efficiency (>80%) RF source to the electron accelerator for industrial applications.
* H. Wang, et al,THPAL145, proceedings of IPAC 2018.
** M. Neubauer, et al,THPAL042, proceedings of IPAC 2018.

Slides WEXXPLS1 [8.033 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEXXPLS1

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEYPLM1

Status of Circular Electron-Positron Collider and Super Proton-Proton Collider

collider, injection, luminosity, booster

2244

C.H. Yu, S. Bai, X. Cui, J. Gao, H. Geng, D.J. Gong, D. Ji, Y.D. Liu, C. Meng, Q. Qin, J.Y. Tang, D. Wang, N. Wang, Y. Wang, Y. Wei, J.Y. Zhai, Y. Zhang, H.J. Zheng, Y.S. Zhu
IHEP, Beijing, People’s Republic of China

Circular electron-positron collider (CEPC) is a dedi-cated project proposed by China to research the Higgs boson. The collider ring provides e⁺ e⁻ collision at two interaction points (IP). The luminosity for the Higgs mode at the beam energy of 120GeV is 3*10³⁴ cm^-2s^-1 at each IP while the synchrotron radiation (SR) power per beam is 30MW. Furthermore, CEPC is compatible with W and Z experiments, for which the beam energies are 80 GeV and 45.5 GeV respectively. The luminosity at the Z mode is higher than 1.7*10³⁵ cm^-2s^-1 per IP. Top-up operation is available during the data taking of high energy physics. Super Proton-Proton Collider (SPPC) is envisioned to be an extremely powerful machine, with centre mass energy of 75 TeV, a nominal luminosity of 1.0*10³⁵ cm^-2s^-1 per IP, and an integrated luminosity of 30 ab^-1 assuming 2 interaction points and ten years of running. The status of CEPC and SPPC will be introduced in detail in this paper.

Slides WEYPLM1 [11.814 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEYPLM1

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paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEYPLS1

Building the Impedance Model of a Real Machine

impedance, simulation, wakefield, coupling

2249

B. Salvant, D. Amorim, S.A. Antipov, S. Arsenyev, M.S. Beck, N. Biancacci, O.S. Brüning, J.V. Campelo, E. Carideo, F. Caspers, A. Farricker, A. Grudiev, T. Kaltenbacher, E. Koukovini-Platia, P. Kramer, A. Lasheen, M. Migliorati, N. Mounet, E. Métral, N. Nasr Esfahani, S. Persichelli, B.K. Popovic, T.L. Rijoff, G. Rumolo, E.N. Shaposhnikova, V.G. Vaccaro, C. Vollinger, N. Wang, C. Zannini, B. Zotter
CERN, Geneva, Switzerland
D. Amorim
Grenoble-INP Phelma, Grenoble, France
T. Dalascu
EPFL, Lausanne, Switzerland
M. Migliorati
Sapienza University of Rome, Rome, Italy
R. Nagaoka
SOLEIL, Gif-sur-Yvette, France
V.V. Smaluk
BNL, Upton, Long Island, New York, USA
B. Spataro
INFN/LNF, Frascati, Italy
N. Wang
IHEP, Beijing, People’s Republic of China
S.M. White
ESRF, Grenoble, France

A reliable impedance model of a particle accelerator can be built by combining the beam coupling impedances of all the components. This is a necessary step to be able to evaluate the machine performance limitations, identify the main contributors in case an impedance reduction is required, and study the interaction with other mechanisms such as optics nonlinearities, transverse damper, noise, space charge, electron cloud, beam-beam (in a collider). The main phases to create a realistic impedance model, and verify it experimentally, will be reviewed, highlighting the main challenges. Some examples will be presented revealing the levels of precision of machine impedance models that have been achieved.

Slides WEYPLS1 [5.648 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEYPLS1

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paper received ※ 10 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPMP053

Operational Results of Simultaneous Four-Beam Delivery at Jefferson Lab

laser, operation, experiment, gun

2454

R. Kazimi, A. Freyberger, J.M. Grames, J. Hansknecht, A.S. Hofler, T.E. Plawski, M. Poelker, M.F. Spata, Y.W. Wang
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
A concept for simultaneous beam delivery to all four CEBAF experimental halls from a single injector and a single main accelerator for the 12 GeV era was proposed in 2012. The original 12 GeV beam delivery plan was for a maximum of three experimental halls at a time as in the 6 GeV era. Therefore, the new concept increases the po-tential beam time for the experiments up to 33%. This change, although a major improvement in operational capabilities, required only limited modifications to the existing machine. The modifications were mainly timing and pattern changes to the beams in the injector, adding a fourth laser to the photo-cathode gun, and the addition of new RF separators to the highest pass of CEBAF. These changes are now complete and, for the first time, the full system is operating, producing four simultaneous beams through the accelerator to four different destinations. In this paper, in addition to presenting the results of the full system commissioning, we will discuss important details about the new configuration plus some of our operational challenges.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP053

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPGW034

Development of L-band Cavity BPM for STF

electron, electronics, linac, simulation

2547

S.W. Jang, E.-S. Kim
KUS, Sejong, Republic of Korea
H. Hayano
KEK, Ibaraki, Japan

We developed a L-band beam position monitor with position resolution of few hundred nano meter for Superconducting Test Faciliy(STF) in KEK. The L-band BPM was developed to install inside the superconducting cryomodule of STF in KEK and it’s test was performed at Accelerator Test Facility in KEK. The three L-band BPM are fabricated and installed at the end of Linac of ATF. The position resolution measurement was performed with new L-band BPM electronics. In this talk, we will describe about the development of L-band BPM and its beam test results of nano meter level beam position resolution with new electronics system.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW034

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paper received ※ 15 May 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019

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WEPGW044

Study on the Influence of Beam Transverse Position on the Cavity Bunch Length Measurement

simulation, dipole, electron, laser

2578

Q. Wang, S.M. Jiang, Q. Luo, B.G. Sun
USTC/NSRL, Hefei, Anhui, People’s Republic of China

Funding: Work supported by National Key R&D Program of China (Grant No. 2016YFA0401900 and No. 2016YFA0401903) and The National Natural Science Foundation of China (Grant No. U1832169 and No. 11575181).
Monopole modes in the resonant cavity are wildly used to obtain the beam current and the bunch length, while dipole modes are used to measure the beam transverse position. It is generally recognized that the monopole modes are independent of the beam transverse offset. In this paper, the influence of beam transverse offset on the bunch length measurement using monopole modes is analyzed. The simulation results show that the relative error of the bunch length measurement is less than 1 % when the beam offset is within 1 mm.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW044

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paper received ※ 25 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPGW075

Coupling Impedance Studies of the Current Transformers at ALBA

impedance, resonance, simulation, factory

2647

T.F.G. Günzel, U. Iriso, A.A. Nosych
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

ALBA is equipped with two different current transformers (FCT and DCCT), and a third one (ICT) is now in design stage to be installed in 2019. A comparative study of the different currents transformers was carried out in order to characterize their contribution to longitudinal and transverse impedance. The gap in the vacuum chamber of the current transformers was varied in order to study its effect on the heat deposited by the beam in the corresponding device and on the resonance in the longitudinal impedance spectrum. The simulation results are compared to the experience with the existing current transformers in operation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW075

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paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPGW083

Quadrated Dielectric-Filled Reentrant Cavity Resonator as a Proton Beam Position Diagnostic

dipole, pick-up, proton, simulation

2676

S. Srinivasan, P.-A. Duperrex, J.M. Schippers
PSI, Villigen PSI, Switzerland

Funding: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sk³odowska-Curie grant agreement No 675265
Low proton beam intensities (0.1-40 nA) are used for medical treatment of tumours at the PROSCAN facility in Paul Scherrer Institut (PSI). A cavity resonator using four quadrants operating in a dipole mode resonance has been developed to measure beam positions at these low intensities. The TM110 resonance frequency of 145.7 MHz is matched to the second harmonic of the beam pulse repetition rate (i.e.72.85 MHz). HFSS (High Frequency Structural Simulator) provides the BPM geometry and important parameters such as pickup position; dielectric dimensions etc. Comparison of test bench measurement and simulation provides good agreement. The measured position and signal sensitivity are limited by the noise, so that a position signal can be derived at beam intensities of at least 10 nA . We will discuss potential methods to increase the sensitivity. The dipole cavity resonator can be a promising candidate as a non-invasive position di-agnostic at the low proton beam intensities used in pro-ton therapy

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paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPGW109

Double Quarter Wave Deflector Cavity Design & Simulation

coupling, operation, simulation, diagnostics

2749

M.S. Stefani
ODU, Norfolk, Virginia, USA
G.-T. Park
JLab, Newport News, Virginia, USA

Funding: This manuscript has been authored by Jefferson Science Associates, LLC under Contract No. DE-AC05-06OR23177 with the U.S. Department of Energy.
A Double Quarter Wave (DQW) Cavity has been designed, tested and installed for use in longitudinal measurements as part of a diagnostic beamline. This report will describe the design and testing used to characterize this cavity before its use in the study of a magnetized electron beam.

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPGW115

Radiation Robust RF Gas Beam Detector R&D for Intensity Frontier Experiments

detector, GUI, plasma, electron

2770

K. Yonehara, A. Moretti
Fermilab, Batavia, Illinois, USA
M.A. Cummings, R.P. Johnson, G.M. Kazakevich
Muons, Inc, Illinois, USA

A novel radiation robust RF gas beam detector has been demonstrated by using the Main Injector beam at Fermilab. The detector demonstrated a stable signal gain, fast response time, and high radiation resistivity with intense proton beams. The plasma process in the detector is studied to validate the plasma physics model. The result suggests that the detector is applicable for Long Baseline Neutrino Facility at Fermilab. To prepare for the LBNF, a proto type detector will be made and applied for the Neutrino at Main Injector target system. Progress of the project will be given in the presentation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW115

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paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPRB003

Parametric Pumped Oscillation by Lorentz Force in Superconducting Rf Cavity

feedback, controls, acceleration, klystron

2798

K. Fong, R. Leewe
TRIUMF, Vancouver, Canada

Mechanical instabilities have been observed in superconducting RF cavities, when multiple cavities are driven by a single klystron and these cavities are regulated by vector-summing the outputs from these cavities. A nonlinear theory has been developed to study the source of this mechanical instability, which is due to the coupling between Lorentz force detuning and mechanical oscillation by parametric pumping. Analytical and numerical analysis of this model show regions of stability, limit cycles and instabilities. These results are in agreement with the observed oscillations by TRIUMF eLinac Acceleration Module.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB003

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paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPRB004

Sawtooth Generation and Regulation with a Single FPGA for TRIUMF’s ARIEL Prebuncher

controls, LLRF, FPGA, pick-up

2801

X.L. Fu, T. Au, K. Fong, Q. Zheng
TRIUMF, Vancouver, Canada

TRIUMF’s ARIEL prebuncher is powered by a sawtooth waveform which is the combination of an 11.79MHz, a 23.57MHz and a 35.36MHz components. The generation, control and regulation of these three components are all incorporated digitally inside a single FPGA. This FPGA can be standalone or inserted inside a VXI module. Commands and controls of these components can be directly through Ethernet, or indirectly through register-base or message-base VXI addresses.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB004

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paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPRB007

RF Commissioning of the SPIRAL2 RFQ in CW Mode and Beyond Nominal Field

LLRF, rfq, controls, vacuum

2804

M. Di Giacomo, R. Ferdinand, H. Franberg, J.-M. Lagniel, G. Normand
GANIL, Caen, France
M. Desmons, P. Galdemard, Y. Lussignol, O. Piquet, S. Sube
CEA-DRF-IRFU, France

The SPIRAL2 RFQ was recently successfully commissioned at nominal voltage of 114 kV, corresponding to 1.65 Kilpatrick factor. The paper describes limitations of the RFQ main subsystems, cavity conditioning difficulties, as well as changes implemented in the LLRF and automatic procedures to simplify turn on and operation of the whole system.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB007

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paper received ※ 26 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPRB010

RF Power Test of the Rebuncher for Saraf-Linac

EPICS, controls, linac, MEBT

2815

L. Zhao, R. Berthier, F. Gougnaud, P. Guiho, N. Solenne, D. Uriot, X.W. Zhu
CEA-DRF-IRFU, France
R. Braud, D. Chirpaz-Cerbat, J. Dumas, R.D. Duperrier, F. Gohier, T.J. Joannem, S. Ladegaillerie, C. Marchand, O. Piquet
CEA-IRFU, Gif-sur-Yvette, France
M. Di Giacomo, J.F. Leyge, M. Michel
GANIL, Caen, France
B. Kaizer, L. Weissman
Soreq NRC, Yavne, Israel

Funding: SNRC
Three normal conducting rebunchers will be installed at the Medium Energy Beam Transport (MEBT) of the SARAF-LINAC phase II [saraf]. The MEBT line is designed to follow a 1.3 MeV/u RFQ, is about 5 m long, and contains three 176 MHz rebunchers providing a field integral of 10⁵ kV. CEA is in charge of the design and fabrication of the Cu plated stainless steel, 3-gap rebuncher. The high power tests and RF conditioning have been successfully performed at the CEA Saclay on the first cavity. A solid state power amplifier, which has been developed by SNRC and has been used for the RF tests. The cavity has shown a good performance according to calculations, regarding the dissipated power, peak temperatures and coupling factor. RF conditioning was started with a duty cycle of 1\% and increased gradually until continuous wave (CW), which is the nominal working mode in SARAF-LINAC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB010

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paper received ※ 09 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPRB011

PVD Depostion of Nb₃Sn Thin Film on Copper Substrate from an Alloy Nb₃Sn Target

niobium, site, interface, HOM

2818

R. Valizadeh, S. Aliasghari, A.N. Hannah, O.B. Malyshev
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
K. Dawson, V.R. Dhanak
The University of Liverpool, Liverpool, United Kingdom
G.B.G. Stenning
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
D. Turner
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
D. Turner
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom

In this study we report on the PVD deposition of Nb₃Sn on Cu substrates with and without a thick Nb interlayer to produce Cu/Nb/Nb₃Sn and Cu/Nb₃Sn multilayer structures. The Nb₃Sn was sputtered directly from an alloy target at room and elevated temperatures. The dependence of the superconducting properties of the total structure on deposition parameters has been determined. The films have been characterized via SEM, XRD, EDX and SQUID magnetometer measurements. Analysis showed that the composition at both room and elevated temperature was within the desired stoichiometry of 24’25 at%. However, superconductivity was only observed for deposition at elevated temperature or post annealing at 650 °C. The critical temperature was determined to be in the range of 16.8 to 17.4 K. In the case of bilayer deposition, copper segregation from the interface all the way to the surface was observed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB011

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB012

Overview on SC CH-Cavity Development

linac, SRF, heavy-ion, status

2822

M. Busch, M. Basten, T. Conrad, P. Müller, H. Podlech, M. Schwarz
IAP, Frankfurt am Main, Germany
W.A. Barth, F.D. Dziuba, M. Miski-Oglu
GSI, Darmstadt, Germany
W.A. Barth, F.D. Dziuba, M. Miski-Oglu
HIM, Mainz, Germany
W.A. Barth
MEPhI, Moscow, Russia
F.D. Dziuba
IKP, Mainz, Germany

Funding: Work supported by GSI, HIC for FAIR, BMBF Contr. No. 05P18RFRB1
During the last decades an enermous effort has been put into the development of low beta structures for hadron acceleration worldwide. Since hadrons exhibit a very inert velocity gain due to their high mass this change in speed has to be taken into account when utilizing low beta cavities. At the Institute of Applied Physics (IAP), Frankfurt, Germany, five multi-cell CH-cavities (Crossbar H-Mode) have been developed and tested for different kind of applications so far. In addition to the successfully tested original 360 MHz prototype further structures envisaged for beam operation have been fabricated and tested. Overview, status and outlook of this cavity technology is topic of this contribution.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB012

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paper received ※ 08 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPRB014

Further RF Measurements on the Superconducting 217 MHz CH Demonstrator Cavity for a CW Linac at GSI

linac, heavy-ion, MMI, operation

2826

F.D. Dziuba, K. Aulenbacher, W.A. Barth, C. Burandt, V. Gettmann, T. Kürzeder, S. Lauber, J. List, M. Miski-Oglu
HIM, Mainz, Germany
K. Aulenbacher
IKP, Mainz, Germany
K. Aulenbacher, W.A. Barth, C. Burandt, V. Gettmann, M. Heilmann, T. Kürzeder, S. Lauber, J. List, M. Miski-Oglu, J. Salvatore, A. Schnase, S. Yaramyshev
GSI, Darmstadt, Germany
M. Basten, M. Busch, T. Conrad, H. Podlech, M. Schwarz
IAP, Frankfurt am Main, Germany
S. Lauber, J. List
KPH, Mainz, Germany

Funding: Work supported by GSI, HIM, BMBF Contr. No. 05P18UMRB2
Recently, the first section of the superconducting (sc) continuous wave (cw) Linac has been extensively tested with heavy ion beam from the GSI High Charge State Injector (HLI). During this testing phase, the reliable operability of 217 MHz multi gap crossbar-H-mode (CH) cavities has been successfully demonstrated. The sc 217 MHz CH cavity (CH⁰) of the demonstrator setup accelerated heavy ions up to the design beam energy and even beyond at high beam intensities and full transmission. This worldwide first beam test with a sc CH cavity is a major milestone on the way realizing the entire sc cw Linac project. In this contribution further RF measurements on the cavity are presented providing full characterization of the RF structure.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB014

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paper received ※ 26 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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WEPRB015

Cleanroom Installations for SRF Cavities at the Helmholtz-Institut Mainz

operation, vacuum, heavy-ion, SRF

2830

T. Kürzeder, K. Aulenbacher, W.A. Barth, C. Burandt, F.D. Dziuba, V. Gettmann, R.G. Heine, S. Lauber, J. List, M. Miski-Oglu
HIM, Mainz, Germany
K. Aulenbacher, F.D. Dziuba
IKP, Mainz, Germany
W.A. Barth, C. Burandt, V. Gettmann, M. Miski-Oglu, S. Yaramyshev
GSI, Darmstadt, Germany
J. Conrad
TU Darmstadt, Darmstadt, Germany
R.G. Heine, F. Hug, T. Stengler
KPH, Mainz, Germany

At the Helmholtz-Institut Mainz (HIM) a cleanroom has been equipped with new tools and installations for the planned treatment of different superconducting RF-cavities. At first TESLA/XFEL type 9-cell cavities for the Mainz Energy-Recovering Superconducting Accelerator (MESA) project or 217 MHz multigap Crossbar H-mode cavities for the HElmholtz LInear ACcelerator (HELIAC) under development by HIM and GSI will be treated. The cleanroom installations, including the greyroom, cover an area of about 155 sqm. In its ISO-class 6 area a large ultrasonic and a conductance rinsing bath has been installed recently. A high pressure rinsing cabinet (HPR) has been implemented between the ISO-class 6 and 4 cleanroom. A RF-cavity can be loaded and unloaded from both sides. HPR treatments are possible for cavities of up to 1.4 m length and about 0.7 m diameter. For drying the ISO-class 4 clean room is equipped with a 160 C vacuum oven. New cleanroom lifters allow the handling of up to 200 kg heavy objects. A rail system in the cleanroom floor is installed to move out the entire cold string of the cleanroom after assembly and leak testing. First operational experiences with this facility will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB015

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paper received ※ 29 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPRB016

Simulation of Quench Detection Algorithms for Helmholtz Zentrum Berlin SRF Cavities

SRF, FPGA, LLRF, controls

2834

P. Echevarria, A. Neumann, A. Ushakov
HZB, Berlin, Germany
B. Garcia
UPV-EHU, Leioa, Spain
J. Jugo
University of the Basque Country, Faculty of Science and Technology, Bilbao, Spain

The Helmholtz Zentrum Berlin is carrying out two accelerator projects which make use of high gradient SRF cavities: BERLinPro* and BESSY-VSR**. In both projects, a prompt detection of a quench is crucial to avoid damages in the cryomodules and cavities themselves. In this paper, the response of real time estimation of the cavity parameters*** using the transmitted and forward RF signals is simulated, in order to perform the quench detection. The time response of the estimated half bandwidth is compared with the dissipated power in the cavity walls for the different type of SRF cavities used in both projects, i.e., BERLinPro’s photoinjector, booster and linac, and BESSY-VSR 1.5 GHz and 1.75 GHz cavities. As an intermediate step prior to the implementation in an mTCA.4 system together with the LLRF control and test with a real cavity, the algorithm has been implemented using a National Instruments FPGA board to check the its proper behavior.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB016

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paper received ※ 16 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPRB017

Operational Experiences with X-Ray Tomography for SRF Cavity Shape and Surface Control

controls, gun, detector, simulation

2838

H.-W. Glock, J. Knobloch, A. Neumann, Y. Tamashevich
HZB, Berlin, Germany
M. Böhnel, N. Reims
Fraunhofer IIS EZRT, Fürth, Germany
J. Kinzinger
X-RAY LAB, Sachsenheim, Germany

X-ray tomography has established as a non-destructive three-dimensional analysis tool, commercially offered by industrial vendors. Typical applications cover shape control and failure detection (voids, cracks) deep inside of complicated bulk pieces like engine blocks, bearings, turbine blades etc. We evaluated the applicability of the process for superconducting radio frequency cavities, in particular the 1.4-cell 1.3 GHz BERLinPro electron gun cavity and the 1.5 GHz single-cell VSR cavity prototype. The former experienced severe shape modifications during its tuning process and features a complicated internal stiffening construction. Thus it is a demanding challenge to measure its actual internal cavity surface shape after the complete preparation process with a resolution, sufficiently high (better than 0.2 mm) to serve as input for meaningful comparative field simulations. First tests with a vendor’s on-site X-ray source, operating at X-ray energies up to 590 keV revealed an insufficient resolution of the inner surface, attributed to the unfavorable X-ray damping characteristics of niobium. This was overcome with the aid of an accelerator-based source (X-ray spectrum up to 9 MeV), operated by Fraunhofer IIS, Fürth, Germany. Results both show significant, while understood, shape changes and indicate partial inner surface modifications of the gun cavity. Further the data evaluation process, which was needed to provide input for field simulations, raised issues because of the data set size and complexity, which are discussed in the paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB017

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paper received ※ 17 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB021

Commissioning of S-band Cavity Test Facility at Elettra for Conditioning of High Gradient Structures for the Fermi Linac Upgrade

LLRF, FEL, hardware, linac

2846

N. Shafqat, L. Giannessi, C. Masciovecchio, M. Milloch, C. Serpico, M. Svandrlik, M. Trovò
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
M. Bopp, R. Zennaro
PSI, Villigen PSI, Switzerland
T.G. Lucas
The University of Melbourne, Melbourne, Victoria, Australia

FERMI is the seeded Free Electron Laser (FEL) user facility at Elettra laboratory in Trieste, operating in the VUV to soft X-rays spectral range. In order to extend the FEL spectral range to shorter wavelengths, a feasibility study for increasing the Linac energy from 1.5 GeV to 1.8 GeV is actually going on. A short prototype of a new High Gradient (HG) S-band accelerating structure has been built in collaboration with Paul Scherrer Institute (PSI). The new structures are intended to replace the present Backward Travelling Wave (BTW) sections and tailored to be operated at a gradient of 30 MV/m. For RF conditioning and high power testing of prototype, a Cavity Test Facility (CTF) is commissioned at FERMI. The test facility is equipped with RF pulse compressor system and a dedicated diagnostic for breakdown rate (BDR) measurements and events localization. In this paper we present in detail cavity test facility of FERMI and high power testing of the first prototype.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB021

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paper received ※ 08 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPRB022

RF System Upgrade for Elettra 2.0

storage-ring, HOM, LLRF, klystron

2849

C. Pasotti, M. Bocciai, M. Rinaldi
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

The Elettra 2.0 low emittance light source project has triggered the review of the installed RF system’s performances and the analyses of the new machine requirement. This study includes the imperative revamp of the RF power sources. The trade off between the best theoretical RF system design and the available room for installation and budget for Elettra 2.0 has been translated into the operational plan reported here. The first planned step is the installation of 100 kW 500 MHz solid state based transmitters.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB022

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paper received ※ 13 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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WEPRB023

Vertical Test of ESS Medium Beta Cavities

HOM, cryomodule, vacuum, linac

2852

A. Bosotti, M. Bertucci, A. Bignami, P. Michelato, L. Monaco, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
D. Reschke, A. Sulimov, M. Wiencek
DESY, Hamburg, Germany

The Medium beta (β=0.67) section of the European Spallation Source (ESS) Linac is composed of 36 six-cell elliptical superconducting (SC) cavities. As a part to the in kind contribution of Italy to the ESS project, INFN-LASA is in charge of the development and of the industrial production of the whole set of 36 resonators plus two spares. The production activity is now ongoing at ZANON. To qualify the cavities power tests in vertical cryostat has been committed to DESY. During the qualification tests, where the cavities provided with He tanks are pushed to their electromagnetic limits, recording their main electromagnetics parameters such as quality factor Q₀ vs E_acc. In this paper we report about the qualification tests performed on the first part of the quality production.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB023

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paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPRB025

High Density Mapping for Superconducting Cavities

cryogenics, radiation, status, operation

2860

Y. Iwashita, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan
Y. Fuwa
Kyoto University, Research Reactor Institute, Osaka, Japan
R.L. Geng
JLab, Newport News, Virginia, USA
H. Hayano
KEK, Ibaraki, Japan

High density mapping system for superconducting cavities are under development. Testing on the stiffener X-ray mapping system at JLAB showed consistent results in comparison with simultaneously taken GM tube or ion chamber output signals. The system provides better visi-bility as shown by data briefly reported here. In addition to the temperature and the X-ray mapping, a sensitive magnetic field mapping system with high spatial density is also under development. The magnetic field sensor is AF755B, whose operations at cryogenic temperatures are already reported by other group. Our development status using the magnetic field sensor will be reported.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB025

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paper received ※ 19 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPRB026

Simulations of Beam Loading Compensation in a Wideband Accelerating Cavity Using a Circuit Simulator Including a LLRF Feedback Control

controls, feedback, simulation, vacuum

2863

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

Magnetic alloy cavities are employed in the J-PARC RCS to generate high accelerating voltages. The cavity, which is driven by a vacuum tube amplifier, has a wideband frequency response and the beam loading in the cavity is multiharmonic. Therefore, the tube must generate a multiharmonic output current. An LTspice circuit model is developed to analyze the vacuum tube operation and the compensation of the multiharmonic beam loading. The model includes the cavity, tube amplifier, beam current, and LLRF feedback control. The feedback control consists of the I/Q demodulator including low pass filters, PI control, and I/Q modulator. In this presentation, we present the implementation of the LLRF functions in the LTspice simulations. The preliminary simulation results are also presented. The simulations fairly agree with the beam test results.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB026

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paper received ※ 23 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPRB027

Electromagnetic Design and Characterization of an S-band 3-Cell RF Accelerating Cavity

emittance, simulation, electron, acceleration

2867

G.R. Montoya Soto
Universidad de Guanajuato, División de Ciencias e Ingenierías, León, Mexico
C. Duarte Galván, C.A. Valerio
ECFM-UAS, Culiacan, Sinaloa, Mexico
B. Yee-Rendón
JAEA/J-PARC, Tokai-mura, Japan

An S-Band (2998 MHz) RF cavity to accelerate electrons was developed taking into account the beam space charge, the relativistic change in velocity of the low energy beam particle distribution through the cavity and the emittance growth. The electromagnetic design and geometry optimization were done using the codes Poisson Superfish and CST Studio. In addition, beam dynamics simulations were done using the program Travel to optimize the emittance and take into account the space charge effect. The machining was done in a CNC machining center. Measurements of the cavity resonance frequencies were carried out and compared with the obtained by the simulations with good agreement between them.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB027

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paper received ※ 30 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPRB028

Electromagnetic Design of the Low Beta Cavities for the JAEA ADS

SRF, linac, proton, superconductivity

2870

B. Yee-Rendón, Y. Kondo, F.M. Maekawa, S.I. Meigo, J. Tamura
JAEA/J-PARC, Tokai-mura, Japan

The Japan Atomic Energy Agency (JAEA) is designing a superconducting CW proton linear accelerator for the ADS project. The superconducting region will use five types of radio frequency cavities. In the region from 2 to 180 MeV the acceleration will be done using Half Wave Resonator (HWR) and Single Spokes (SS) cavities. HWR cavities will accelerate the beam from 2 to 10 MeV with a geometrical beta of 0.08 and the SS ones will do from 10 to 180 MeV using two cavity families with geometrical betas of 0.16 and 0.43. The results of electromagnetic model design are presented and the comparison with similar cavities from other projects are included.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB028

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paper received ※ 19 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB029

Design of the Elliptical Superconducting Cavities for the JAEA ADS

superconducting-cavity, SRF, simulation, acceleration

2873

B. Yee-Rendón, Y. Kondo, F.M. Maekawa, S.I. Meigo, J. Tamura
JAEA/J-PARC, Tokai-mura, Japan

The superconducting CW proton linear accelerator for an Accelerator Driven Subcritical System (ADS) proposed by Japan Atomic Energy Agency (JAEA) employs elliptical cavities for the final acceleration of 180 MeV to 1.5 GeV. Since this energy region implies a change of beta from 0.55 to 1, two cavity models were developed using the geometrical betas of 0.68 and 0.89 to improve the acceleration efficiency. The study of the electromagnetic design was simulated using SUPERFISH (SF) code and python program to do variable scan, the results were benchmarked with CST Microwave Studio program (CST).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB029

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paper received ※ 18 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPRB030

Commissioning of RF System of the 200 MeV Proton Cyclotron

cyclotron, multipactoring, MMI, coupling

2877

G. Chen, C. Chao, G. Liu, X.Y. Long, Z. Peng, C.S. Yu, 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, G. Shirkov
JINR, Dubna, Moscow Region, Russia

Funding: (1) National Natural Science Foundation of China under grant No. 11775258, 11575237; (2) International Sci-entific and Technological Cooperation Project of An-hui (grant No. 1704e1002207).
The SC200 superconducting accelerator which is designed for proton therapy is currently under con-struction. The RF (Radio Frequency) system has been designed and constructed as a subsystem of the SC200. To verify the stability of the RF system, a high-power feeding test was performed for the cavity. This paper mainly reports on the overview of RF systems and the prelimary high-power commissioning, as well as the problems found and improvements made during the commissioning process. The results show that the RF system has initially achieved the designed goal, and each loop (amplitude, tuning, phase) can work effec-tively. The cavity can operate in a ~50 kW continuous wave state. Next, the formal RF conditioning will be carried out after the complete assembly of cyclotron, so as to confirm the cavity can run smoothly under 80 kW, which is part of the whole commissioning process.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB030

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paper received ※ 22 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB031

SRF Trip Caused by the Tuner in BEPCII

SRF, electron, operation, collider

2880

J.P. Dai, Z.H. Mi, P. Sha, Y. Sun, Q.Y. Wang, L.G. Xiao
IHEP, Beijing, People’s Republic of China

Funding: Work support by Natural Science Foundation of China (11575216)
The stability and reliability of the Superconducting RF system (SRF) is generally a key issue in a large scale accelerator such as Beijing Electron Positron Collider II (BEPCII). In the past several years, SRF is one of the main factors limiting the availability of BEPCII, and many efforts have been made to fix the SCRF troubles. This paper focuses on the details of the SCRF trip caused by the tuner, which is one of the most persistent troubles and figured out till the summer of 2018.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB031

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paper received ※ 08 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPRB032

Superconducting Elliptical Cavities Developed in IMP for the CiADS

HOM, multipactoring, operation, simulation

2883

Y.L. Huang, Y. He, R. Huang, T.C. Jiang, L.B. Liu, S.H. Liu, T. Tan, R.X. Wang, Z.J. Wang, S.H. Zhang, S.X. Zhang
IMP/CAS, Lanzhou, People’s Republic of China

Multicell superconducting radio frequency (SRF) ellip-tical cavities are proposed for efficient acceleration of proton beam in the Chinese initiative Accelerator Driven Subcritical System (CiADS). Two families of such cavities will be used in the driver SRF Linac, the first family corresponding to βopt=0.62 cavities that will be used to accelerate the H⁺ beam from 175 MeV to 377 MeV and the second family corresponding to βopt=0.82 cavities that will accelerate the H⁺ beam from 377 MeV to 500 MeV, with the possibility to upgrade to 1 GeV and higher. The electromagnetic optimization of the cavities with the HOM, wakefield and multipacting analysis will be dis-cussed in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB032

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB037

Development of EP System at IHEP

controls, MMI, power-supply, cathode

2890

S. Jin, J.P. Dai, J. Dai, H.F.S. Feisi, J. Gao, D.J. Gong, Z.Q. Li, Z.C. Liu, W.M. Pan, P. Sha, Y. Sun, J.Y. Zhai, P. Zhang
IHEP, Beijing, People’s Republic of China

Electropolishing (EP) is a necessary technology for high quality cavities including both high accelerating gradient and high quality factor cavities, which will be used for several future large projects such as CEPC, Shanghai hard X-ray FEL, ILC, and so on. An EP system was development at IHEP, CAS. In last years, we finished all the engineering design and fabrication including functional circulation loops design, system parameters choices, key equipment choice or design, components test and fabrication. According to the functions of various components, the whole system were divided into three main units: electrolyte mixing, acid solution and mechanical platform, and several key components such as rotation sleeves, DC power supply and so on. Since the system is designed for both R&D and mass production, several characteristics comparing with those in other labs in the world can be realized, including dozens of solution circulations, electrolyte mixing, new and old acid separation, cavity outside water cooling, cathode vertical assembly, and compatible for several types of cavities. We will report them in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB037

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paper received ※ 21 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB042

High Power Test of the First C-band Spherical Pulse Compressor Prototype

GUI, FEL, electron, linac

2896

Z.B. Li
SINAP, Shanghai, People’s Republic of China
W. Fang, Q. Gu, X.X. Huang, J.H. Tan, Z.T. Zhao
SSRF, Shanghai, People’s Republic of China

Funding: National Natural Science Foundation of China (No. 11675249)
Recently, a new C-band (5712 MHz) compact spherical radio frequency (RF) pulse compressor was designed and tested for Shanghai Soft X-ray Free Electron Laser Facili-ty (SXFEL). This pulse compressor utilizes one high Q₀ spherical RF resonant cavity that works with two TE1, 1,3 modes and a dual-mode polarized coupler. The peak power multiply factor is 6.1 and average power gain 3.8 in theory. During the high power test, a peak power mul-tiply factor of 5.74 and average power gain of 3.77 was achieved. This paper presents the RF measurement of the C-band spherical pulse compressor and the high power test results.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB042

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paper received ※ 19 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPRB044

Microphonics Simulation and Parameters Design of the SRF Cavities for CiADS

simulation, linac, beam-loading, proton

2903

J.Y. Ma, G. Huang
IMP/CAS, Lanzhou, People’s Republic of China

The CiADS (China initiative Accelerator Driven System) proton Linac is designed to accelerate CW beams of up to 500 MeV and 5mA, which is delivered to the spallation target. Since the beam power will eventually reach 2.5 MW, the beam loss should be restricted, which is sensitive to the SC cavity stability. On CW operating mode, the main perturbation to the cavity is microphonics. This paper will describe a set of tools developed to simulate performance of the cavity and its LLRF control system in order to ensure proper cavity operation under microphonics. The simulation tools describe a relationship between microphonics and the RF parameters. The microphonics effect to the cavity is simulated. The tolerated intensity of microphonics is determined by simulation, in order to satisfy the stability of amplitude and phase with 0.1% and 0.1 degree respectively.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB044

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPRB045

Suppression of Secondary Electron Yield Effect in the 650MHz/800kW Klystron for CEPC

klystron, simulation, electron, multipactoring

2906

X. He, C. Meng, S. Pei, J.L. Wang, O. Xiao, N. Zhou
IHEP, Beijing, People’s Republic of China

The circular electron positron collider (CEPC) is in pre-research, it will need more than two hundred 650MHz/800kW klystrons. The secondary electron yield (SEY) effect suppression is very important for the klystron working stable. The simulation uses an incident primary electron source and considers all the phases and power levels of the input microwave. Two methods are simulated for the SEY suppression. The groove cutting on the nose of cavities is much simple while the TiN coating can suppress better. The effect after groove cutting on nose is also simulated and the corresponding compensations are adopted. For simplify the fabrication progress as well as some experience that can be referenced, the groove cutting method is adopted finally for the first klystron prototype, which is expected to be available in the summer of 2019.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB045

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paper received ※ 13 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPRB048

Design, Fabricate, and Tuning of X-Band Deflecting Structure for CERN

simulation, GUI, free-electron-laser, electron

2915

J.H. Tan, W. Fang, Q. Gu, X.X. Huang, Z.T. Zhao
SSRF, Shanghai, People’s Republic of China

A 20-cell x-band deflecting structure for CERN has been finished, and now is under high power conditioning at XBOX of CERN.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB048

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paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPRB049

HOM Analysis of the 4-cell Superconducting Cavity on CTFEL Facility

HOM, FEL, simulation, electron

2918

X. Luo, T.H. He, C.L. Lao, L.J. Shan, X.M. Shen, D. Wu, K. Zhou
CAEP/IAE, Mianyang, Sichuan, People’s Republic of China
F. Wang
PKU, Beijing, People’s Republic of China

The higher order modes (HOMs) of the 1.3GHz 4-cell cavity on CTFEL facility is analyzed in this paper. The passbands of the HOMs in the 4-cell cavity were simulat-ed, and the most harmful modes were determined. The power of the wakefields was estimated. By microwave test at room temperature, the frequencies of the HOMs were measured, as well as the external Q’s of the HOM cou-plers. Besides, a frequency distribution measurement system was built. The HOM signal excited by beam at 2 K temperature is measured, and some preliminary results are obtained. The measurement techniques and results of the HOM damping performance are presented in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB049

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPRB051

MA RF Cavity Design and Simulation for CSNS/RCS Upgrade Project

simulation, experiment, synchrotron, detector

2925

B. Wu
IHEP CSNS, Guangdong Province, People’s Republic of China
X. Li, H. Sun
IHEP, Beijing, People’s Republic of China

The dual harmonic RF system will be adapted for Chi-na Spallation Neutron Source (CSNS) upgrade project. Limited locations in CSNS/RCS are reserved to install additional three 2nd harmonic cavities. The cavity loaded by magnetic alloy (MA) material would be used. Because of the low Q factor of the MA core, the cavity cooling be-comes a very important issue in cavity design. Air-forced, indirect and direct cooling scheme were studied. The fluid thermodynamic of different cooling structure were simu-lated by ANSYS CFX which considered the anisotropy of thermal conductivity of MA core. The limitation of these cooling schemes were discussed in detail based on the simulation results. Indirect cooling experiment was done to assess the cooling efficiency and verify the simulation result. A high power test cavity cooled by water has been designed to estimate the property of the MA core and cooling effectiveness for CSNS/RCS.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB051

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paper received ※ 08 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB056

Design Study of 325MHz RF Power Coupler for Superconducting Cavity

impedance, superconducting-cavity, resonance, simulation

2937

J.Y. Yoon, H.J. Cha, S.W. Jang, E.-S. Kim, K.R. Kim, C.S. Park, S.H. Park
KUS, Sejong, Republic of Korea
J. Bahng
Korea University Sejong Campus, Sejong, Republic of Korea
K.R. Kim
PAL, Pohang, Kyungbuk, Republic of Korea

We present the design study of the RF input power coupler for 325 MHz superconducting cavities. The power coupler, based on a conventional coaxial transmission line, provides RF powers to the cavity up to 12kW in CW mode. The thermal interceptors are considered as 4.5 K and 40 K or 4.5 K and 77 K corresponding to the usage of liquid Helium only or both liquid Helium and Nitrogen for cryogenic temperature to reduce the thermal load. The transition box (T-box), which is assembled with power coupler, is designed and applied for impedance matching and inner conductor cooling.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB056

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB058

Combined Field Emission and Multipactor Simulation in High Gradient RF Accelerating Structures

electron, multipactoring, simulation, GUI

2940

D. Banon-Caballero
IFIC, Valencia, Spain
N. Catalán Lasheras, K.T. Szypula, W. Wuensch
CERN, Geneva, Switzerland
A. Faus-Golfe
LAL, Orsay, France
B. Gimeno
UVEG, Burjasot (Valencia), Spain

Field emitted electrons have important consequences in the operation of high-gradient RF accelerating structures both by generating so-called dark currents and initiating RF breakdown. The latter is an important limitation of the performance in such devices. Another kind of vacuum discharge that primarily affects the operation of lower-field RF components, for example those used in space applications, is multipactor. Theoretical simulations using CST Particle Studio, show that field emitted electrons generated in the high field regions of high-gradient accelerating cavities migrate to low field regions under ponderomotive forces potentially triggering multipactor there. This phenomenon is an interplay between high field and low field processes which may have as a consequence that multipactor actually affects to the performance of high-gradient cavities because field emitted electrons might reduce the timescales for the onset of multipactor.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB058

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paper received ※ 27 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPRB060

HOM Damped Normal Conducting 1.5 GHz Cavity Design Evolution for the 3rd Harmonic System of the ALBA Storage Ring

GUI, HOM, simulation, insertion

2948

A. Salom, J.M. Alvarez, B. Bravo, F. Pérez
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

In a collaboration framework with CERN, ALBA has designed a normal conducting active 1.5 GHz cavity which could serve as main RF system for the Damping Ring of CLIC and as an active third harmonic cavity for the ALBA Storage Ring. The third harmonic cavity at ALBA will be used to increase the bunch length in order to improve the beam lifetime and increase the beam stability thresholds. The main advantage of an active third harmonic cavity is that optimum conditions can be reached for any beam current. This paper presents the evolution of the preliminary design of this cavity and its trans-dampers: high order modes coaxial dampers with waveguide transitions to N, which allows extracting the power of the high order modes induced by the beam outside of the cavity and to dissipate it using standard loads. This approach has two main advantages: no ferrites brazing is needed and they provide a diagnostic to analyze the beam dynamics. The new features of the design, together with electromagnetic simulations, mechanical and thermal stress analysis will be presented in this paper as well as the first stages of the prototype production status.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB060

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB061

The Integration and RF Conditioning of the ESS Double-Spoke Prototype Cryomodule at FREIA

vacuum, software, proton, cryomodule

2952

H. Li, K. Fransson, K.J. Gajewski, L. Hermansson, A. Miyazaki, R.J.M.Y. Ruber, R. Santiago Kern
Uppsala University, Uppsala, Sweden

ESS, the European Spallation Source, will adopt a single family of double-spoke cavities for accelerating the proton beam from the normal conducting section to the first family of the elliptical superconducting cavities. They will be the first double-spoke cavities in the world to be commissioned for a high power proton accelerator. The first double-spoke cavity cryomodule for the ESS project is under high power test at Uppsala University. This paper presents the integration, RF conditioning and experience of this prototype cryomodule.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB061

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paper received ※ 26 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPRB065

Multi-physics Computation and Deformation Testing of a Shell-type 1.5-GHz Cavity

SRF, experiment, resonance, synchrotron

2968

M.-C. Lin, C.H. Lo
NSRRC, Hsinchu, Taiwan
M.-R. Lu, M.-K. Yeh
NTHU, Hsinchu, Taiwan

Funding: Work supported by the Ministry of Science and Technology, R. O. C. (Taiwan) under grant NSC-100-2628-E-213-001-MY3.
A copper prototype of a 1.5-GHz cavity was manufac-tured to simulate a superconducting radio-frequency cavity for technique development. Frequency tuning with longitudinal compression of this prototype and cryogenic cooling with liquid nitrogen were performed to examine the numerical results from finite-element models, mainly the corresponding shifts of the fundamental resonant frequency. An appropriate element option improved the accuracy of the resonant frequency and the distribution of the magnetic field. Effects of geometry distortion of an uneven length on the frequency shift of this shell-type cavity as loaded on longitudinal compression are also examined and discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB065

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paper received ※ 25 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPRB066

Utilizing the High Shunt Impedance TM020-Mode Cavity in the Double RF Systems for the Storage Ring of the Thailand New Light Source

storage-ring, impedance, coupling, damping

2972

N. Juntong, T. Phimsen
SLRI, Nakhon Ratchasima, Thailand
N. Chulakham, S. Malichan
Udon Thani Rajabhat University, Udon Thani, Thailand

The utilization of the TM020-mode cavity for the storage ring based light source was pioneered by SPring-8 with its high quality factor and hence its high shunt impedance. KEK-LS has also studied the possibility of using this type of cavity for their storage ring. The TM020-mode cavity has larger transverse dimension compared to the traditional TM010-mode cavity, but with its higher shunt impedance it can be designed to fit in the new low emittance storage ring regardless. The new storage ring based light source project in Thailand aims to optimum the low emittance beam in nano-meters region with the energy of 3 GeV. The TM020-mode cavity was considered as the main cavity and the harmonic cavity for the storage ring. They have been designed to have their pipe aperture fits the storage ring beam ducts. The main cavity has a high shunt impedance of 8.3 Mega Ohms with the 51,000 unloaded quality factor. The harmonic cavity has a high shunt impedance and an unloaded quality factor of 2.45 Mega Ohms and 36,000, respectively. The damping mechanism of the parasitic modes and the tuning mechanism of the operating mode of these cavities were also studied. There will be four main cavities and six harmonic cavities in the new storage ring. Detailed design and study of these cavities will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB066

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paper received ※ 29 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPRB070

Facile Deposition of Superconducting MgB₂ Thin Films on Substrates: A Comparative Investigation of Electrochemical Deposition and Magnetron Sputtering Techniques

site, superconductivity, target, FEL

2984

N. Misra, A.N. Hannah, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
R. Valizadeh
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: Authors acknowledge the funding received under the Rutherford International Postdoctoral Fellowship Programme
Coating of Copper cavities with a superconducting layer of MgB₂ thin film is an attractive alternative to bulk Nb cavities. In this work, we investigate the application of two approaches-electrochemical deposition and magnetron sputtering of MgB₂, to fabricate MgB₂ films with potential accelerator applications. In the first approach, MgB₂ powder dispersed in acetone was used as an electrolytic medium. Application of a DC voltage of 400 V between a graphite anode and a Copper film (serving as cathode), with the electrode distance maintained at ~2cm, resulted in the electrochemical deposition of MgB₂ on the Cu surface. In an alternate approach, MgB₂ in powder form was used directly for sputtering based deposition. The powder was initially compacted to form a thin layer that served as the magnetron target. Application of a pulsed DC power of 25W for 4 hours yielded MgB₂ thin film on Si substrates. Samples were characterized by XPS analysis to ascertain their elemental composition, which confirmed the presence of Mg and B, in addition to traces of C and O as impurities. Surface morphology was determined using SEM characterization technique. Further work to determine the superconducting properties of the samples and fine tune the deposition processes for large scale MgB₂ deposition inside actual RF cavities is in progress.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB070

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPRB075

Optimizing Room Temperature RF Structures for Accelerator Driven System Operations

vacuum, operation, RF-structure, DTL

2993

D.L. Brown, M.T. Crofford
ORNL, Oak Ridge, Tennessee, USA
C.C. Peters
ORNL RAD, Oak Ridge, Tennessee, USA

Funding: This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy.
Minimizing beam trip rates is one of the key operational goals at the Spallation Neutron Source (SNS). Trip rates are closely monitored, and real-time statistics are kept during beam operations for immediate analysis. Beam trips are automatically binned by the length of the trip along with the cause for each trip. The shortest beam trips occur with the highest frequency and those trip rates are dominated by the room temperature RF structures. There can be many causes for the RF structure malfunctions, but one area that has had a major impact on trip rates is improvement in how RF processing is done on structures after extended maintenance periods. Details about the improvement in RF conditioning will be discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB075

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paper received ※ 13 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPRB076

Analysis of Higher Order Multipoles of the 952.6 Mhz RF-Dipole Crabbing Cavity for the Jefferson Lab Electron-Ion Collider

multipole, dipole, HOM, electron

2996

S.U. De Silva, J.R. Delayen, S. Sosa
ODU, Norfolk, Virginia, USA
V.S. Morozov, H. Park
JLab, Newport News, Virginia, USA

The crabbing system is a key feature in the Jefferson Lab Electron-Ion Collider (JLEIC) required to increase the luminosity of the colliding bunches. A local crabbing system will be installed with superconducting rf-dipole crabbing cavities operating at 952.6 MHz. The field non-uniformity across the beam aperture in the crabbing cavities produces higher order multipole components, similar to that which are present in magnets. Knowledge of higher order mode multipole field effects is important for accurate beam dynamics study for the crabbing system. In this paper, we quantify the multipole components and analyse their effects on the beam dynamics.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB076

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paper received ※ 20 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB077

Simulation and Measurements of HOM Filter of the LARP Prototype RF-Dipole Crabbing Cavity Using an RF Test Box

HOM, dipole, luminosity, damping

2999

S.U. De Silva, J.R. Delayen
ODU, Norfolk, Virginia, USA
Z. Li
SLAC, Menlo Park, California, USA

The RF-Dipole Crabbing Cavity designed for the LHC High Luminosity Upgrade includes two higher order mode (HOM) couplers. One of the HOM couplers is an rf filter, which is a high pass filter designed to couple to the horizontal dipole modes and accelerating modes up to 2 GHz, while rejecting the fundamental operating mode at 400 MHz. The coupler consists of a high pass filter circuit where the rejection of the operating mode and transmission of HOMs are sensitive to dimensional deviations. An rf test box has been designed to measure the transmission of the rf filter in order to qualify the fabricated HOM coupler and to tune the coupler. This paper presents the measurements of the HOM coupler with the rf test box.

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paper received ※ 20 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPRB078

RF Commissioning and Performance in the CBETA ERL

operation, controls, linac, LLRF

3003

N. Banerjee, K.E. Deitrick, J. Dobbins, G.H. Hoffstaetter, R.P.K. Kaplan, M. Liepe, C.W. Miller, 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 supported by the New York State Energy Research and Development Authority, Contract No. DE-SC0012704 with the U.S. Department of Energy and NSF award DMR-0807731.
The Cornell-BNL ERL Test Accelerator (CBETA) is a new multi-turn energy recovery linac currently being commissioned at Cornell University. It uses a superconducting main linac to accelerate electrons by 36 MeV and recover their energy. The energy recovery process is sensitive to fluctuations in the accelerating field of all cavities. In this paper, we outline our semi-automated RF commissioning procedure, which starts from automatic coarse tuning of the cavity all the way to adjusting the field control loops. We show some results of using these tools and describe the recent performance of the RF system during our ongoing commissioning phase.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB078

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPRB080

Optimization of RF Cavities Using MOGA for ALS-U

impedance, simulation, controls, gun

3007

H.Q. Feng, K.M. Baptiste, D. Li, T.H. Luo
LBNL, Berkeley, California, USA
H.Q. Feng, W.-H. Huang, Z.N. Liu, C.-X. Tang
TUB, Beijing, People’s Republic of China

Funding: Director of Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
A multi-objective genetic algorithm-based optimiza-tion process has been applied to optimize the RF design of a 500 MHz main cavity and a 1.5 GHz Higher Harmon-ic Cavity (HHC) for the Advanced Light Source upgrade (ALS-U) in Lawrence Berkeley National Laboratory (LBNL). For the main cavity, a significant improvement, compared with the existing ALS cavity, has been achieved in cavity shunt impedance and power loss den-sity simultaneously. The field strengths and distribution of the optimized structure are analysed for further re-search. For the HHC, a cavity with low R/Q has been pre-liminary designed to mitigate the beam instability. This study also serves as an example of how a genetic algo-rithm can be used for optimizing RF cavities.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB080

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paper received ※ 16 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPRB081

Design Study on Higher Harmonic Cavity for ALS-U

impedance, higher-order-mode, simulation, wakefield

3011

H.Q. Feng, K.M. Baptiste, S. De Santis, D. Li, T.H. Luo
LBNL, Berkeley, California, USA
H.Q. Feng, W.-H. Huang, Z.N. Liu, C.-X. Tang
TUB, Beijing, People’s Republic of China

Funding: Director of Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
The ALS upgrade (ALS-U) to a diffraction-limited light source [1] depends on the ability to lengthen the stored bunches to limit the emittance growth and increase the beam life time. Higher harmonic cavities (HHCs), also known as Landau cavities, have been proposed to in-crease beam lifetime and Landau damping by lengthen-ing the bunch. We present an optimized 1.5 GHz normal conducting HHC design for the ALS-U with a supercon-ducting-like geometry using multi-objective genetic algorithm (MOGA) for lower R/Q. The optimization goal is to reach the required shunt impedance while maintain-ing a relatively high Q value of the cavities. To minimize the coupled bunch instabilities, higher-order mode (HOM) of the HHC as well as corresponding impedance are explored and characterized.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB081

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paper received ※ 16 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPRB084

Mechanical Design and Analysis of the Proposed APEX2 VHF CW Electron Gun

gun, vacuum, electron, cathode

3014

A.R. Lambert, H.Q. Feng, D. Filippetto, M.J. Johnson, D. Li, T.H. Luo, C.E. Mitchell, F. Sannibale, J.W. Staples, S.P. Virostek, R.P. Wells
LBNL, Berkeley, California, USA

Funding: Work supported by the Office of Science, U.S. Department of Energy under DOE contract number DEAC02-05CH11231
Normal conducting radio-frequency (RF) guns resonating in the very high frequency (VHF) range (30-300 MHz) and operating in continuous wave (CW) mode have successfully achieved the targeted brightness and reliability necessary for upgrading the performance of current lower repetition rate accelerator-based instruments such as X-ray free electron lasers (FELs), and ultra-fast electron diffraction (UED) and microscopy (UEM). The APEX2 (Advanced Photo-injector Experiment 2) electron gun is a proposed upgrade for the current LCLS-II injector, which was based on the original APEX design. In contrast, APEX2 is designed as a two-cell cavity operating at 162.5 MHz with a launching field at the cathode equal to 34 MV/m, producing a beam energy of 1.5 to 2 MeV, more than double APEX. Operation of the gun in this condition will require upwards of 200 kW of RF power, thus proper thermal management is crucial to achieve target performance. This paper describes the current design, thermal performance and tuning methods.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB084

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paper received ※ 13 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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WEPRB087

High-gradient SRF Cavity R&D at Cornell University

SRF, collider, linear-collider, vacuum

3017

M. Ge, T. Gruber, J.J. Kaufman, P.N. Koufalis, G. Kulina, M. Liepe, J.T. Maniscalco
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Achieving high accelerating field is a critical R&D topic for superconducting RF cavities for future accelerators including the International Linear collider (ILC). The ILC requires an average accelerating field of 35MV/m with a Q₀ of at least 8.9·10⁹ at 2K. In this paper, we report the latest results from high-gradient research at Cornell, which focusses on 75C vacuum baking to improve maximum (quench) fields. We demonstrate that such low temperature bakes can significantly improve quench fields in certain cases by mitigating localized defects. We further report on high-pulsed power results of these cavities before and after baking.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB087

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paper received ※ 23 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019

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WEPRB089

Theoretical Analysis of Quasiparticle Overheating, Positive Q-Slope, and Vortex Losses in SRF Cavities

SRF, niobium, electron, experiment

3020

J.T. Maniscalco, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
T. Arias, D. Liarte, J.P. Sethna, N. Sitaraman
Cornell University, Ithaca, New York, USA

The surface resistance of an SRF cavity is an important measure of its performance and utility: lower resistance leads directly to lower cryogenic losses and power consumption. This surface resistance comprises two components, namely the ‘‘BCS resistance’’, which depends strongly on the quasiparticle temperature, and a temperature-independent ‘‘residual resistance’’, which is often dominated by losses due to trapped magnetic vortices. Both components are generally dependent on the RF field strength. Here we present a summary of recent theoretical advances in understanding the microscopic mechanisms of the surface resistance, in particular addressing niobium hydride formation and quasiparticle overheating (using the tools of density functional theory) and discussing issues with existing models of the positive Q-slope, a field-dependent decrease in the BCS resistance, and possible paths for improvement of these models. We also discuss trapped flux losses using ideas from collective weak pinning theory.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB089

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paper received ※ 20 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPRB090

The Design of Parallel-Feed SC RF Accelerator Structure

SRF, coupling, niobium, alignment

3024

M.H. Nasr, Z. Li, S.G. Tantawi, P.B. Welander
SLAC, Menlo Park, California, USA

Funding: Research funded by a SLAC Laboratory-Directed Research and Development award, supported by the U.S. Department of Energy, contract number DE-AC02-76SF00515
Development of superconducting RF (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 normal-conducting RF structure at SLAC has served as a proof-of-concept. Instead of coupled elliptical cells, the structure employs isolated re-entrant 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. Applied to SRF, simulations suggest such a structure could nearly double the achievable gradient, while reducing cryogenic RF loss by more than half. We are experimentally verifying the concept using an X-band SRF design to be tested at SLAC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB090

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paper received ※ 24 May 2019 paper accepted ※ 27 May 2019 issue date ※ 21 June 2019

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WEPRB093

Design of a Proof-of-principle Crabbing Cavity for the Jefferson Lab Electron-ion Collider

electron, HOM, collider, luminosity

3027

H. Park, S.U. De Silva, J.R. Delayen, S.I. Sosa Guitron
ODU, Norfolk, Virginia, USA
J.R. Delayen, H. Park
JLab, Newport News, Virginia, USA

The Jefferson Lab design for an electron-ion collider (JLEIC) requires crabbing of the electron and ion beams in order to achieve the design luminosity. A number of options for the crabbing cavities have been explored, and the one which has been selected for the proof-of-principle is a 952 MHz, 2-cell rf-dipole (RFD) cavity. This paper summarizes the electromagnetic design of the cavity and its HOM characteristics.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB093

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paper received ※ 22 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019

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WEPRB094

Measurements of the Electrical Axes of the CeC PoP RF Cavities

cathode, gun, SRF, electron

3031

I. Petrushina
SUNY SB, Stony Brook, New York, USA
Y.C. Jing, V. Litvinenko, J. Ma, I. Pinayev, K. Shih, G. Wang
BNL, Upton, Long Island, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA
K. Shih
SBU, Stony Brook, New York, USA

It is common knowledge that every mode in an SRF cavity has a so-called electrical axis, and only in an ideal cavity would this axis align exactly with the geometrical axis of the device. The misalignment of the electrical axis creates an additional undesirable transverse kick to the beam, which has to be corrected to achieve the designed beam parameters. In this paper we present the two methods which have been used in order to determine the electrical axes in the RF cavities of the Coherent electron Cooling (CeC) Proof of Principle (PoP) accelerator. The electron accelerator for the CeC PoP consists of the three main RF components: the 113 MHz SRF gun, the two normal-conducting 500 MHz bunching cavities, and the 704 MHz SRF 5-cell elliptical cavity. We discuss, in detail, the specifics of the measurement for each cavity and provide the corresponding results. In addition, we describe the influence of the field asymmetry in the 500 MHz bunchers on the beam dynamics, which was observed experimentally and confirmed by simulations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB094

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paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPRB097

Understanding and Mitigation of Field Emission in CEBAF SRF Linacs

cryomodule, linac, operation, vacuum

3039

R.L. Geng, A. Freyberger, R.A. Rimmer
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
We will present current understanding of field emission in two 1.1 GeV CW SRF linacs at CEBAF and its mitigation for improved CEBAF energy reach and operation reliability. This contribution will provide a review of CEBAF gradient evolution since 2014, the impact of field emission, the effort in understanding the root cause of field emission in operational SRF cavities including the recently installed C100 cavities. We will evaluate the effect of initial mitigations implemented since 2016, aimed at reducing generation and transportation of new field emitting particulates. Effects of cavity thermal cycling aimed at abating activation of settled field emitting particulates will be evaluated as well. Remaining issues toward predictable control of field emission in operational SRF cavities will be discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB097

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paper received ※ 19 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB098

Cryogenic RF Performance of Double-Quarter Wave Cavities Equipped with HOM Filters

HOM, operation, cryogenics, SRF

3043

S. Verdú-Andrés, I. Ben-Zvi, Q. Wu, B.P. Xiao
BNL, Upton, Long Island, New York, USA
I. Ben-Zvi
Stony Brook University, Stony Brook, USA
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
G. Burt, J.A. Mitchell
Lancaster University, Lancaster, United Kingdom
R. Calaga, O. Capatina
CERN, Geneva, Switzerland
N.A. Huque, E.A. McEwen, H. Park, T. Powers
JLab, Newport News, Virginia, USA
Z. Li, A. Ratti
SLAC, Menlo Park, California, USA

Funding: Work supported by US DOE through BSA LLC under contracts No. DE-AC02-98CH10886, No. DE-SC0012704, and the US LHC Accelerator Research Program (LARP) and by the EU HL-LHC Project.
Crab cavities are one of the several components included in the luminosity upgrade of the Large Hadron Collider (HL-LHC). The cavities have to provide a nominal deflecting kick of 3.4 MV per cavity while the cryogenic load per cavity stays below 5 W. Cold RF tests confirmed the required performances in bare cavities, with several cavities exceeding the required voltage by more than 50%. However, the first tests of a Double-Quarter Wave (DQW) cavity with one out of three HOM filters did not reach the required voltage. The present paper describes the studies and tests conducted on a DQW cavity with HOM filter to understand the limiting factor. The recipe to meet the performance specification and exceed the voltage requirement by more than 35% is discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB098

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPRB099

Status Update of a Harmonic Kicker Development for JLEIC

kicker, multipole, coupling, simulation

3047

G.-T. Park, J. Guo, J. Henry, M. Marchlik, F. Marhauser, 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.
An effort to develop the second prototype of the harmonic kicker for the Circulator Cooler Ring (CCR) of the Jefferson Lab Electron-Ion Collider (JLEIC) is under way. After beam dynamics studies and completion of a conceptual RF design of the kicker [1], further progress has been made toward the final mechanical design including the input power coupler (loop) design, tuner ports, multipacting studies. Furthermore, concerning the kicker’s compatibility with beam dynamics, the impact of RF multipole components was investigated and a scheme was developed to cancel out detrimental beam effects.
1. G. Park, et al, The Development of a New Fast Harmonic Kicker for the JLEIC Circulator Cooler Ring, TUPAL068, proceedings of IPAC 2018.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB099

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB102

Correction of Crosstalk Effect in the LEReC Booster Cavity

electron, booster, resonance, HOM

3051

B.P. Xiao, K. Mernick, F. Severino, K.S. Smith, T. Xin, W. Xu
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 Linac of Low Energy RHIC electron Cooler (LEReC) is designed to deliver a 1.6 MeV to 2.6 MeV electron beam, with peak-to-peak dp/p less than 7·10^-4. The booster cavity is the major accelerating component in LEReC, which is a 0.4 cell cavity operating at 2 K, with a maximum energy gain of 2.2 MeV. It is modified from the Energy Recovery Linac (ERL) photocathode gun, with fundamental power coupler (FPC), pickup coupler (PU) and higher order mode (HOM) coupler close to each other. The direct coupling between FPC and PU induced crosstalk effect in this cavity. This effect is simulated and measured, and is further corrected using low level RF (LLRF) to meet the energy spread requirement.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB102

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB107

The New 1-18 MHz Wideband RF System for the CERN PS Booster

vacuum, electronics, electron, impedance

3063

M.M. Paoluzzi, L. Arnaudon, V. Bretin, Y. Cuvet, J. Daricou, S. Energico, M. Haase, A.J. Jones, D. Landré, C. Rossi
CERN, Meyrin, Switzerland
C. Ohmori
KEK/JAEA, Ibaraki-Ken, Japan

The LHC Injector Upgrade (LIU) project at CERN prepares the injectors to meet the requirements of the High Luminosity LHC. For protons, it includes the new Linac4, PS Booster (PSB), PS and SPS. Among the major changes concerning the PSB, the extraction energy increase from 1.4 GeV to 2 GeV and the higher beam intensity, made possible by the Linac4 together with the new charge exchange injection system into the PSB (2·10¹³ protons) strongly affect the RF system requirements. To deal with this more demanding beam operation, a new RF system was designed. It is based on modern magnetic alloy loaded cavities driven by solid-state amplifiers. Its wideband frequency response (1 MHz to 18 MHz) covers all the required frequency schemes. This new RF system has been produced in 2017 and 2018; installation is planned during 2019, the first year of Long Shutdown 2 (LS2) and commissioning foreseen in 2020. Most of the production and testing was outsourced to industry; parts acceptance, cavities assembly and pre-testing was done in-house. A quality assurance plan was established to achieve the required high reliability. This paper describes the procurement, production and testing strategies and methodologies. It also reports the achieved results, system performances and relevant statistics.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB107

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paper received ※ 26 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB110

Recent Results from Nb₃Sn-Coated Single-cell Cavities Combined with Sample Studies at Jefferson Lab

experiment, SRF, superconductivity, niobium

3066

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
I.P. Parajuli
ODU, Norfolk, Virginia, USA

Funding: Partially authored by Jefferson Science Associates under contract no. DEAC0506OR23177. Supported by Office of High Energy Physics under grants DE-SC-0014475 and DE-SC-0018918.
The critical temperature (~ 18 K) and superheating field (~ 425 mT) of Nb₃Sn are almost twice that of niobium, thereby promising the higher quality factor and accelerating gradient at any given temperature compared to traditional SRF cavities made of niobium. It can enable higher temperature for cavity operation (4 K Vs. 2 K), resulting in significant reduction in both capital and operating cost for the cryoplant. Several single-cell cavities along with witness samples were coated with Nb₃Sn to explore, understand and improve the coating process for betterment of cavity performance. RF measurements of coated cavities combined with material characterization of witness samples were employed to update the coating process. Following some modifications to the existing coating process, we were able to produce Nb₃Sn cavity with quality factor ≥ 2.10¹⁰ for accelerating gradient up to 15 MV/m at 4 K, without any significant Q-slope. In this article, we will discuss recent results from several Nb₃Sn coated single-cell cavities combined with material studies of witness samples.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB110

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paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPRB111

Development of Nb₃Sn Multicell Cavity Coatings

niobium, HOM, factory, cryomodule

3070

G.V. Eremeev
JLab, Newport News, Virginia, USA
U. Pudasaini
The College of William and Mary, Williamsburg, Virginia, USA

Funding: Co-Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics.
Nb₃Sn films have the potential to augment niobium in SRF cavities. Besides single-cell cavity efforts to improve Nb₃Sn films, we are working to replicate single-cell results onto the practical 5-cell CEBAF cavities. High quality factors (10¹¹ at 2.0K and 10^zEhNZeHn at 4.3 K) have been measured, but the cavities are typically limited by strong low-field Q-slopes and early quenches. Two of the cavities were selected to be assembled into a ’mock-up’ cavity pair unit, the standard step before installation into a cryomodule. Comparison of test results between VTA and pair test offered the first glimpse into post-processing effects on the cavity performance.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB111

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paper received ※ 16 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPRB114

Understanding and Pushing the Limits of Nitrogen Doping

SRF, niobium, experiment, ECR

3078

D. Bafia, M. Checchin, A. Grassellino, M. Martinello, O.S. Melnychuk, S. Posen, A.S. Romanenko, D.A. Sergatskov
Fermilab, Batavia, Illinois, USA
D. Bafia, J. Zasadzinski
IIT, Chicago, Illinois, USA
D. Gonnella
SLAC, Menlo Park, California, USA
A.D. Palczewski
JLab, Newport News, Virginia, USA

This work will describe Fermilab experiments that focus on the optimization of doping parameters to achieve low sensitivity to trapped magnetic flux while maintaining very high Q characteristic of nitrogen doped cavities and same or higher quench fields. Working partially in the context of LCLS-2 higher energy upgrade, new doping recipes are pursued and have been found to vary the mean free path of the resonator which is related to the sensitivity to trapped magnetic flux. Moreover, a correlation has been found between lighter doping and higher quench fields while maintaining sufficiently low surface resistance.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB114

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paper received ※ 18 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB115

Development of RF Interlock and Diagnostics Systems in SOLARIS Storage Ring

network, storage-ring, synchrotron, betatron

3082

M.A. Knafel, M. Madura
Solaris National Synchrotron Radiation Centre, Jagiellonian University, Kraków, Poland
A.I. Wawrzyniak
SOLARIS, Kraków, Poland

The purpose of this document is to describe and asses the operation of various devices that have been developed, constructed and tested by RF team in NSRC SOLARIS . One of those devices is used as additional safety interlock for the tuning mechanism of main 100MHz active cavities. The other is a stripline feeding network, that in cooperation with BPM receiving network will excite the beam providing the diagnostics group with a new option for tune measurement. Each device shall have its principle of operation explained and construction details revealed. Finally, all devices will be assesed over their operational lifetime in our facility.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB115

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS010

Beam Dynamics Errors Studies for the IFMIF-DONES SRF-LINAC

linac, SRF, solenoid, cryomodule

3103

N. Chauvin, N. Bazin, J. Plouin
CEA-DRF-IRFU, France
S. Chel, L. Du
CEA-IRFU, Gif-sur-Yvette, France

The goal of the IFMIF-DONES (International Fusion Materials Irradiation Facility-DEMO Oriented Neutron Source) project is to build an irradiation facility that will provide a sufficient neutron flux to study and characterize structure materials foreseen for future fusion power plant. In order to accelerate the required 125mA/40 MeV continuous deuteron beam from 5 MeV to 40 MeV, a superconducting radio-frequency (SRF) linac, housed in five cryomodules, is proposed. The design is based on two beta families (β=0.11 and β=0.17) of half-wave resonators (HWR) at 175MHz. The transverse focusing is achieved using one solenoid coil per focusing period. This paper presents the extensive multiparticle beam dynamics simulations that have been performed to adapt the beam along the SRF-linac in such a high space charge regime. As one of the constraints of the IFMIF linac is a low level of beam losses, specific optimizations have been done to minimize the beam occupancy in the line (halo). A Monte Carlo error analysis has also been carried out to study the effects of misalignments or field imperfections (static errors) and also vibrations or power supplies ripple (dynamic errors). The results of these errors studies are presented and discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS010

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paper received ※ 21 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPTS011

Intra-Beam Scattering Effect in the SOLEIL Storage Ring Upgrade

emittance, lattice, coupling, simulation

3106

A. Vivoli, A. Bence, P. Brunelle, A. Gamelin, L. Hoummi, A. Loulergue, L.S. Nadolski, R. Nagaoka, M.-A. Tordeux
SOLEIL, Gif-sur-Yvette, France

As the work on the design of the upgrade of SOLEIL storage ring advances, the study of the impact of Intra-Beam Scattering (IBS) on the equilibrium emittance is also progressing, showing a significant contribution of this effect. Different measures can be taken to mitigate the emittance dilution, like operating the machine with full transverse coupling and using harmonic cavities to increase bunch length. The calculation of the IBS effect needs then to take into account the different beam dynamics and its effect on the particle distribution. In this paper the current state of the ongoing study is presented, reporting on the results obtained for the different options considered, and comparing the results of different codes and their implicit assumptions.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS011

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paper received ※ 14 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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WEPTS012

RF Design Studies of a 1.3 GHz Normal Conducting CW Buncher for European X-FEL

multipactoring, simulation, impedance, coupling

3109

S. Lal, Y. Chen, H.J. Qian, H. Shaker, G. Shu, F. Stephan
DESY Zeuthen, Zeuthen, Germany
V.V. Paramonov
RAS/INR, Moscow, Russia

A CW upgrade of European XFEL is under consideration, and CW electron injector is under R&D at DESY. One of the injector solutions is the LCLS-II like injector based on a normal conducting CW gun and buncher. RF design of a 1.3 GHz normal conducting buncher structure with accelerating voltage of ~ 400 kV, for such a CW injector is carried out at DESY Zeuthen site. The buncher structures with different geometrical shapes and numbers of cells are studied. The designs are optimized to have higher shunt impedance, higher mode separation and lower thermal power density for CW operation. Multipacting analysis and beam dynamics simulations are also presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS012

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paper received ※ 12 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS016

Longitudinal Beam Manipulation by RF Phase Modulation at the Karlsruhe Research Accelerator

simulation, experiment, synchrotron, beam-loading

3123

A. Mochihashi, E. Blomley, T. Boltz, E. Huttel, B. Kehrer, A.-S. Müller, M. Schuh
KIT, Karlsruhe, Germany
D. Teytelman
Dimtel, San Jose, USA

At the storage ring KARA (Karlsruhe Research Accelerator) of the Karlsruhe Institute of Technology (KIT) we have installed a function for the RF phase modulation to the low-level RF system. By choosing proper conditions of the modulation, the electron distribution on the longitudinal phase space can be changed in a large range. There are several applications of this longitudinal manipulation to the accelerator operation: an improvement of the beam lifetime and suppression of collective instabilities. We have performed tracking simulations for the longitudinal beam manipulation by the RF phase modulation. The results have implied that the longitudinal phase space distribution strongly depends on the modulation frequency. We have also performed experiments, which aimed at improving the beam lifetime in 2.5 GeV KARA multi-bunch operations. In this contribution, the low-level RF system at KARA, the simulation and experimental results under the RF phase modulation will be presented. As one of the options of the modulation, we consider manipulation of the internal fine structure in the longitudinal phase space by the modulation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS016

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPTS031

The Beam Dynamics Design of the Proton Synchrotron Linear Injector for Proton Therapy

DTL, rfq, proton, linac

3167

J. Qiao, Y.H. Pu, X.C. Xie
SINAP, Shanghai, People’s Republic of China

A compact room-temperature injector is designed to accelerate 20 mA proton beam from 30 keV to 7.0 MeV for the purpose of Proton Synchrotron Linear Injector for Proton Therapy. The main feature of this linac injector is that the 4-vane Radio Frequency Quadrupole (RFQ) and the Drift Tube Linac (DTL) section are matched by one triplet and powered by one RF power source. The beam is matched from the first RFQ section to the second DTL section in traverse and longitudinal directions. The overall accelerating gradient of this design has reached up to 1.6 MV/m with transmission efficiency of 96%.This injector combines a 3 m long 4-vane RFQ from 30 keV to 3.0 MeV with a 0.8 m long H-type DTL section to 7.0 MeV. In general, the design meets the requirements of the Pro-ton Synchrotron and the Terminal treatment.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS031

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS038

New RFQ and Field Map Model for the ESS Linac Simulator

rfq, linac, space-charge, simulation

3181

J.F. Esteban Müller, E. Laface
ESS, Lund, Sweden

The Java ESS Linac Simulator (JELS) is an extension of the Open XAL online model that is a fundamental part of the accelerator control system. The model is used by high-level physics applications for commissioning, tuning, and machine development activities at the European Spallation Source (ESS). This paper summarizes the upgrades done to JELS during the last year. An RFQ model is under development. The RFQ was the only element of the linac missing in the online model. The electromagnetic field map model has been refactored to ease implementation of new elements (rf cavities and magnets), and to allow the superposition of more than one field map and other elements. Further improvements have also been done in the treatment of corrector magnets and space charge for continuous beam in the Low-Energy Beam Transport (LEBT). Finally, the machine description can now include arbitrary aperture definitions.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS038

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS039

Momentum Slip-Stacking in CERN SPS for the Ion Beams

simulation, optics, operation, emittance

3184

T. Argyropoulos, T. Bohl, A. Lasheen, G. Papotti, D. Quartullo, E.N. Shaposhnikova
CERN, Geneva, Switzerland

The LHC Injectors Upgrade (LIU) project at CERN aims at doubling the total intensity of the lead ion beam for the High-Luminosity (HL) LHC. Achieving this goal requires using momentum slip-stacking in the SPS, the LHC injector. Slip-stacking will be applied on an intermediate energy plateau to interleave two batches, reducing the bunch spacing from 100 ns to 50 ns and thus increasing the total number of bunches injected into the LHC. Realistic macro-particle simulations, with the present SPS impedance model are used to study and design this complicated beam manipulation. Slip-stacking can be tested experimentally only after the upgrade of the SPS 200 MHz RF system, in 2021. Preliminary, slip-stacking related beam measurements were performed at the end of 2018. In this paper both macro-particle simulations and beam measurements are reported with emphasis given on optimisation of the process, crucial to achieve the required HL-LHC parameters (bunch lengths, beam losses).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS039

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPTS040

Energy Dependence of the Reproducibility and Injection Efficiency of the LINAC3-LEIR Complex

linac, injection, bunching, operation

3188

S. Hirlaender
ATI, Vienna, Austria
H. Bartosik, G. Bellodi, N. Biancacci, V. Kain, A. Saá Hernández, R. Scrivens
CERN, Geneva, Switzerland

High intensities in the CERN Low Energy Ion Ring (LEIR) are achieved by stacking several multi-turn injections from the pre-accelerator LINAC3. Up to seven consecutive 200 μs long, 200 ms spaced pulses are injected from LINAC3 into LEIR. An inclined septum magnet combined with a collapsing horizontal orbit bump allows a 6-D phase space painting via a linearly ramped mean momentum along with the LINAC3 pulse and injection at high dispersion. The injected energy distribution measured by the LEIR longitudinal Schottky is correlated with the obtained injection efficiency in this paper. Studies in 2018 revealed that the achievable accumulated intensity of LEIR strongly depends on the longitudinal distribution from LINAC3, which does not stay constant. This paper summarises the experimental results and means to further improve reproducibility and high injection efficiency.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS040

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS054

Pyg4ometry : A Tool to Create Geometries for Geant4, BDSIM, G4Beamline and FLUKA for Particle Loss and Energy Deposit Studies

interface, simulation, detector, shielding

3244

S.T. Boogert, A. Abramov, J. Albrecht, G. D’Alessandro, L.J. Nevay, W. Shields, S.D. Walker
JAI, Egham, Surrey, United Kingdom

Studying the energy deposits in accelerator components, mechanical supports, services, ancillary equipment and shielding requires a detailed computer readable description of the component geometry. The creation of geometries is a significant bottleneck in producing complete simulation models and reducing the effort required will provide the ability of non-experts to simulate the effects of beam losses on realistic accelerators. The paper describes a flexible and easy to use Python package to create geometries usable by either Geant4 (and so BDSIM or G4Beamline) or FLUKA either from scratch or by conversion from common engineering formats, such as STEP or IGES created by industry standard CAD/CAM packages. The conversion requires an intermediate conversion to STL or similar triangular or tetrahedral tessellation description. A key capability of pyg4ometry is to mix GDML/STEP/STL geometries and visualisation of the resulting geometry and determine if there are any geometric overlaps. An example conversion of a complex geometry used in Geant4/BDSIM is presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS054

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paper received ※ 19 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPTS066

Suppression of Correlated Energy Spread Using Emittance Exchange

linac, controls, simulation, electron

3275

J. Seok, M. Chung
UNIST, Ulsan, Republic of Korea
M.E. Conde, G. Ha, J.G. Power
ANL, Argonne, Illinois, USA

An emittance exchange (EEX) provides a precise longitudinal phase space manipulation of electron bunch. It has been studied for an easy and precise control of temporal distribution, but controls of energy distribution have not been explored. Since the energy control using EEX is under the identical principle to the temporal control, the EEX beamline can control a correlated energy spread of the electron bunch. This would benefit accelerator facilities requiring a low energy spread such as X-ray Free Electron Laser Oscil-lator (XFELO). In this paper, we present principle and preliminary simulation work on the suppression of correlated energy spread using the EEX beamline. ing the EEX beamline.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS066

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paper received ※ 21 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPTS073

Beam-Beam Effect: Crab Dynamics Calculation in JLEIC

simulation, luminosity, collider, electron

3293

H. Huang, F. Lin, V.S. Morozov, Y. Roblin, A.V. Sy, Y. Zhang
JLab, Newport News, Virgina, USA
I. Neththikumara, S. Sosa, B. Terzić
ODU, Norfolk, Virginia, USA

The electron and ion beams of a future Electron Ion Collider (EIC) must collide at an angle for detection, machine and engineering design reasons. To avoid associated luminosity reduction, a local crabbing scheme is used where each beam is crabbed before collision and de-crabbed after collision. The crab crossing scheme then provides a head-on collision for beams with a non-zero crossing angle. We develop a framework for accurate simulation of crabbing dynamics with beam-beam effects by combining symplectic particle tracking codes with a beam-beam model based on the Bassetti-Erskine analytic solution. We present simulation results using our implementation of such a framework where the beam dynamics around the ring is tracked using Elegant and the beam-beam kick is modeled in Python.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS073

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paper received ※ 16 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS082

Luminosity Studies of Asymmetric Crab Crossing in JLEIC

luminosity, ECR, collider, electron

3311

E.A. Nissen
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The U.S. Government retains a non-exclusive, world-wide license to publish or reproduce this manuscript.
The proposed Jefferson Lab Electron Ion Collider (JLE-IC) currently plans to use a crab crossing scheme to max-imize the available luminosity. It had been suggested that space and cost savings, as well as hadron beam quality improvements, could be realized by leaving the ion beam un-crabbed and increasing the crabbing angle of the elec-tron beam. This and variations in-between equal and totally one-sided crabbing are examined for both JLEIC and LHC parameters, with various changes in crabbing angle and frequency studied to maximize luminosity.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS082

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paper received ※ 14 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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WEPTS083

Multipass Simulations of Space Charge Compensation using Electron Columns at IOTA

space-charge, electron, simulation, proton

3313

C.S. Park, E.G. Stern
Fermilab, Batavia, Illinois, USA
S. Chattopadhyay, B.T. Freemire
Northern Illinois University, DeKalb, Illinois, USA
C.E. Mitchell, R.D. Ryne
LBNL, Berkeley, California, USA

Defocusing repulsive forces due to self space charge fields lead to degradation of high-intensity particle beams. Being of particular concern for low- and medium-energy proton beams, they result in emittance growth, beam halo formation, and beam loss. They set stringent limits on the intensity of frontier accelerators; therefore, the mitigation of space charge effects is a crucial challenge to improve proton beam intensity. The space charge effects in a positively charged proton beam can be effectively compensated using negatively charged electron columns. In this paper, we present the results of simulations using Synergia of the Electron Column lattice for IOTA. Beam loss due to space charge effects and aperture restrictions have been studied, as well as bunch formation and matching using an adiabatic ramp of the RF cavity. The results show the need for space charge compensation, and provide the basis for integration of the Synergia and Warp codes in order to form a complete simulation of space charge compensation using an Electron Column in IOTA.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS083

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paper received ※ 16 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS088

Integration of Cavity Design and Beam Dynamics Simulation Using the Parallel IMPACT and the ACE3P Codes

simulation, emittance, electron, gun

3317

J. Qiang, D.A. Bizzozero
LBNL, Berkeley, California, USA
L. Ge, Z. Li, C.-K. Ng, L. Xiao
SLAC, Menlo Park, California, USA

Funding: This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 and DE-AC02-76SF00515,
The 3D parallel code suite IMPACT has been extensively used in the beam dynamics study of photoinjectors while the 3D parallel code ACE3P has been extensively used in the RF cavity design. In this paper, we propose integrating the ACE3P cavity design and the IMPACT beam dynamics simulation into a single work flow. Such a workflow enables efficient simulation of 3D effects(e.g. RF coupler) on high performance computers.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS088

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paper received ※ 07 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS096

Open XAL Status Report 2019

LEBT, linac, framework, status

3341

A.P. Zhukov, C.K. Allen, A.P. Shishlo
ORNL, Oak Ridge, Tennessee, USA
B.E. Bolling, J.F. Esteban Müller, E. Laface, Y. Levinsen, N. Milas, C. Rosati
ESS, Lund, Sweden
C.P. Chu, Y. Li
IHEP, Beijing, People’s Republic of China
T. Dodson
University of Tennessee, Knoxville, USA
P. Gillette, P. Laurent, G. Normand, A. Savalle
GANIL, Caen, France
M.T. Li, X.H. Lu, J. Peng
IHEP 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. 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.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS096

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPTS118

Results of CEA Tests of SARAF Couplers Prototypes

vacuum, EPICS, linac, controls

3382

G. Ferrand, Y. Baron, S. Bouaziz, D. Chirpaz-Cerbat, R. Cubizolles, F. Gohier, S. Ladegaillerie, A. Lotode, C. Madec, G. Monnereau, N. Pichoff, O. Piquet
CEA-IRFU, Gif-sur-Yvette, France
C. Boulch, E. Fayette, P. Guiho, Y. Lussignol, C. Servouin
CEA-DRF-IRFU, France

CEA is committed to delivering a Medium Energy Beam Transfer line and a superconducting linac (SCL) for SARAF accelerator in order to accelerate 5 mA beam of either protons from 1.3 MeV to 35 MeV or deuterons from 2.6 MeV to 40 MeV. The SCL consists in 4 cryomodules. The first two cryomodules host 6 and 7 half-wave resonator (HWR) low beta cavities (β = 0.09) at 176 MHz. The last two identical cryomodule will host 7 HWR high-beta cavities (β = 0.18) at 176 MHz. The maximal required power to be transmitted to the beam is 11.4 kW for high-beta cavity couplers. This document presents the results of the coupler tests and conditioning.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS118

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paper received ※ 23 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THYPLS1

RF Controls Towards Femtosecond and Attosecond Precision

LLRF, controls, detector, FEL

3414

F. Ludwig, J. Branlard, L. Butkowski, M.K. Czwalinna, M. Hierholzer, M. Hoffmann, M. Killenberg, T. Lamb, J. Marjanovic, U. Mavrič, J.M. Müller, S. Pfeiffer, H. Schlarb, Ch. Schmidt, L. Springer
DESY, Hamburg, Germany
M. Kuntzsch, K. Zenker
HZDR, Dresden, Germany

In the past two decades, RF controls have improved by two orders in magnitude achieving meanwhile sub-10 fs phase stabilities and 10^-4 amplitude precision. Advances are through improved field detection methods and massive usage of digital signal procession on very powerful field programmable gate arrays (FPGAs). The question rise, what can be achieved in the next 10 years? In this talk, a review is given of existing systems and strategies, current stability limitations of RF control system and new technologies with the potential to achieve attosecond resolutions.

Slides THYPLS1 [10.328 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THYPLS1

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPMP013

Challenges Towards Industrialization of the ERL-FEL Light Source for EUV Lithography

FEL, SRF, cathode, undulator

3478

N. Nakamura, E. Kako, R. Kato, H. Kawata, T. Miyajima, H. Sakai, K. Umemori
KEK, Ibaraki, Japan

EUV Lithography is going to HVM (high volume manufacturing) stage with 250-W-class laser-produced plasma sources and it is important to develop a new-type EUV light source to meet future demand for higher power. Energy-recovery linac based free-electron lasers (ERL-FELs) are possible candidates of a high-power EUV light source that can distribute 1 kW power to multiple scanners simultaneously. In Japan, an ERL-FEL based EUV light source has been designed using available technologies without much development to demonstrate generation of EUV power more than 10 kW and the EUV-FEL Light Source Study Group for Industrialization has been established since 2015 to realize industrialization of the light source and the related items. For industrialization, high availability is essential as well as high power and reduction of the light source size is also required. In this paper, we will report an overview of the designed ERL-FEL light source for EUV lithography and some activities for the industrialization and describe considerations and developments for obtaining high availability and size reduction of the light source.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP013

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paper received ※ 13 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPMP016

Design of the Condenser System and Imaging System for a UEM

electron, gun, experiment, cathode

3485

T. Chen, W. Li, Y.J. Pei
USTC/NSRL, Hefei, Anhui, People’s Republic of China

The ultrafast electron microscope provides a useful tool for exploring fine structure and observing dynamic process at nanometer and picosecond scale, which has been extensively applied in chemistry and biological field. After emitting from the electron gun, electron beams are focused on the stage sample by the condenser system and then be projected by the imaging system on the screen. In the present study, a two-lens condenser system is simulated by Parmela and a three-lens imaging system is designed using thin-lens approximation. Besides, the shape factor of metallic spheres which have different radius for perturbation method is measured, which is conductive to measuring the Z/Q parameter and the electric field along the axis of the C-band 3MeV photocathode gun for the UEM.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP016

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPMP049

Sequential Excitation Scheme for Laser Stripping of Hydrogen Ion Beams

laser, photon, electron, proton

3558

Y. Liu, A.V. Aleksandrov, S.M. Cousineau, T.V. Gorlov, A. Rakhman
ORNL, Oak Ridge, Tennessee, USA

Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
Resonant laser excitation of the electron in a hydrogen atom is essential to achieve high-efficiency laser stripping of hydrogen ion (H⁻) beam. In the laser stripping experiments recently carried out at SNS, an ultra-violet (UV) laser was used to excite the electrons in 1-GeV hydrogen atoms from the n=1 state to the n=3 state. In this talk, we propose a sequential resonant excitation scheme by using two laser beams to excite electrons in a sequence of two steps: from the n=1 state to the n=2 state and from the n=2 state to any higher state. The advantages of the sequential resonant excitation scheme include (1) lower laser power requirement due to higher transition probability in the first excitation step and (2) possibility of shifting the stripping laser wavelength from UV regime to longer wavelengths. An application of the sequential resonant excitation scheme in combination with the double-resonance optical cavity technology to the laser stripping of 1.3-GeV H⁻ beam (envisioned in the SNS proton power upgrade project) will be described.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP049

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paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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THPGW047

Cylindrical Cavity Design and Particle-Tracking Simulation in Cyclotron Auto-Resonance Accelerator

electron, cyclotron, resonance, acceleration

3689

Y.T. Yuan
HUST, Wuhan, People’s Republic of China
K. Fan
Huazhong University of Science and Technology, State Key Laboratory of Advanced Electromagnetic Engineering and Technology,, Hubei, People’s Republic of China
Y. Jiang
Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA

The Cyclotron Auto-Resonance Accelerator (CARA) is a novel concept of accelerating continuous-wave (CW) charged-particle beams. This type of accelerator has ap-plications in environment improvement area and genera-tion of high-power microwaves. In CARA, the CW elec-tron beam follows a gyrating trajectory while undergoing the interaction with a rotating TE11-mode RF field and tapered static magnetic field. The cylindrical cavity oper-ating at TE11p-mode is adapted to accelerate electron beam. The cavity size is optimized to obtain a beam with designed energy, then a design method of the TE11p-mode acceleration cavity is described here. Moreover, regard-less of space charge effect, several particle-tracking simu-lations of CARAs are showed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW047

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paper received ※ 16 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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THPGW078

Prototyping of Brazed mm-Wave Accelerating Structures

resonance, simulation, GUI, RF-structure

3764

M.A.K. Othman, B.J. Angier, A.A. Haase, E.A. Nanni, M.R. Roux, A.V. Sy
SLAC, Menlo Park, California, USA

Funding: This work was supported by Department of Energy contract DE-AC02-76SF00515. This work was also supported by NSF grants PHY-1734015.
Advanced fabrication and prototyping of metallic RF structures play a fundamental role in advancing accelerator technologies particularly at mm-wave and THz frequencies. With the scaling of the RF structure up to these frequencies, conventional fabrication techniques do not achieve the required accuracy and tolerances. Improved manufacturing techniques including diffusion bonding, brazing or clamping split-block geometries produce high quality structures when successfully implemented. However, in most schemes the resulting gap and irregularities at the iris result in a local field enhancement which is not desirable for high-gradient operation. Development of advanced split-block braze technique for THz accelerators was required for high quality miniature accelerators. A new braze technique was developed for W-band structures to control the flow of braze alloy, enabling fabrication of the first high-gradient brazed structures at mm-wave frequencies. This fabrication process has the potential to overcome consistent fabrication defects around the cell iris. Thin spacers were used to set the final gap between blocks during the braze process; while braze foil thickness is varied with minimal impact on the resulting frequency. To demonstrate the robustness of this technique, testing after the various manufacturing steps was done to monitor and track frequency change throughout the process. This technique is further pushed to produce G-band RF structures, operating at 300 GHz.

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPGW080

Initial Results of High-Gradient Breakdown Tests for W-Band Accelerating Structures

experiment, electron, laser, vacuum

3769

M.A.K. Othman, V.A. Dolgashev, A.A. Haase, E.A. Nanni, J. Neilson, S.G. Tantawi
SLAC, Menlo Park, California, USA
S. Jawla, J.F. Picard, R.J. Temkin
MIT/PSFC, Cambridge, Massachusetts, USA
S.C. Schaub
MIT, Cambridge, Massachusetts, USA
B. Spataro
INFN/LNF, Frascati, Italy

Funding: This work was supported by Department of Energy contract DE-AC02-76SF00515 (SLAC) and grant DE-SC0015566 (MIT). This work was also supported by NSF grants PHY-1734015.
Emerging accelerator technology at mm-wave and THz frequencies has recently shown notable progress. Indeed, metallic and dielectric accelerating structures at THz frequencies are plausible candidates toward miniaturization of accelerators. RF breakdown in such structures is a major factor limiting their performance. Therefore, comprehensive analysis of RF breakdown physics in mm-wave accelerating structures is needed, which includes understanding of dependencies of the breakdown rate on geometric, electromagnetic and material properties. In this work we report on high power tests of a 110 GHz single-cell standing wave accelerating structure powered by a 1 MW gyrotron. The RF power is coupled from the gyrotron into the accelerating structure with a Gaussian to TM01 mode converter through a quasi-optical setup. We demonstrate coupling of 10 ns, 100s of kilowatt pulses into the structure using a fast switch and achieving ~150 MV/m accelerating gradients. Measurements of RF signals and field-emitted currents allow for complete comprehensive of the high-gradient behavior of W-band structures, including breakdown probability.

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPGW094

Phasing of Superconductive Cavities of the REX/HIE-ISOLDE LINAC

detector, linac, ISOL, dipole

3786

E. Matli, N. Bidault, E. Piselli, J.A. Rodriguez
CERN, Geneva, Switzerland

ISOLDE is a facility dedicated to the production of a large variety of Radioactive Ion Beams. The facility is located at the European Organization for Nuclear Research (CERN). In addition to two target stations followed by low energy separators, the facility includes a post-accelerating linac with both normal conducting (REX) and superconducting (HIE-ISOLDE) sections. The HIE-ISOLDE section consists of four cryomodules with five SRF cavities each that need to be phased individually. In this paper, we will describe the procedure and the software applications developed to phase each of the cavities as well as improvements that will be introduced in the near future to reduce the time it takes to complete the process.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW094

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paper received ※ 02 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB007

Ponderomotive Instability of Self-Excited Cavity

resonance, feedback, SRF, controls

3808

S.R. Koscielniak
TRIUMF, Vancouver, Canada

The electro-magnetic fields within a super-conducting radio frequency (SRF) cavity can be sufficiently strong to deform the cavity shape, which may lead to a ponderomotive instability. Stability criteria for the self-excited mode of cavity operation were given in 1978 by Delayen. The treatment was based on the Routh-Hurwitz analysis of the characteristic polynomial. With the Wolfram modern analytical tool, "Mathematica", we revisit the criteria for an SRF cavity equipped with amplitude and phase loops and a single microphonic mechanical mode.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB007

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB008

Ponderomotive Instability of Two Self-Excited Cavities

resonance, controls, linac, coupling

3812

S.R. Koscielniak
TRIUMF, Vancouver, Canada

We consider the ponderomotive instability of two superconducting RF cavities self-driven from a single RF source with vector-sum control.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB008

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPRB009

Vector Sum & Diffference Control of SRF Cavities

controls, resonance, coupling, linac

3816

S.R. Koscielniak
TRIUMF, Vancouver, Canada

We consider the ponderomotive instability of multiple superconducting RF cavities driven from a single RF source. We add vector difference control to the usual the technique of vector sum control, in order to increase the accelerating gradient threshold for ponderomotive instability.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB009

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB010

Ponderomotive Instability of Generator-Driven Cavity

resonance, controls, SRF, feedback

3820

S.R. Koscielniak
TRIUMF, Vancouver, Canada

The electro-magnetic fields within a super-conducting radio frequency (SRF) cavity can be sufficiently strong to deform the cavity shape, which may lead to a ponderomotive instability. Stability criteria for the generator-driven mode of cavity operation were given in 1971 by Schulze. The treatment side-stepped the Routh-Hurwitz analysis of the characteristic polynomial. With the Wolfram modern analytical tool, ’Mathematica’, we revisit the criteria for an SRF cavity equipped with amplitude and phase loops and a single microphonic mechanical mode.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB010

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paper received ※ 14 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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THPRB011

Norm-optimal Iterative Learning Control to Cancel Beam Loading Effect on the Accelerating Field

controls, beam-loading, simulation, feedback

3824

Z. Shahriari, K. Fong
TRIUMF, Vancouver, Canada
G.A. Dumont
UBC, Vancouver, Canada

Iterative learning control (ILC) is an open loop control strategy that improves the performance of a repetitive system through learning from previous iterations. ILC can be used to compensate for a repetitive disturbance like the beam loading effect in resonators. In this work, we aim to use norm-optimal ILC to cancel beam loading effect. Norm-optimal ILC updates the control signal with the goal of minimizing a performance index, which results in monotonic convergence. Simulation results show that this controller improves beam loading compensation compared to a PI controller.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB011

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paper received ※ 14 May 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019

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THPRB012

Toward Autonomous Phasing of ISAC Heavy Ion LINACs

ISAC, linac, controls, cryomodule

3827

O. Shelbaya, R.A. Baartman, O.K. Kester, S. Kiy
TRIUMF, Vancouver, Canada

Ongoing development work at TRIUMF aims to implement a model-based tuning approach for accelerators, with the goal of automation of tuning tasks and minimizing tuning times. As a part of this, work is underway toward the development of an analytical model of the linacs using the methodology of Hamiltonian based beam envelope dynamics. The TRIUMF High-Level Applications (HLA) project has been developing software that allows direct interfacing with the control system. The envelope code TRANSOPTR is now being extended to simulate the ISAC-II Superconducting Linac. Within the emerging HLA framework, this will allow for automated phasing and tuning of the linac. The steps of the model development will be presented in this contribution.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB012

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paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB022

Sensitivity Analysis of Feedforward Beam Current Compensation for Improved Beam Loading Robustness

emittance, controls, injection, simulation

3850

D. Mihailescu Stoica, D. Domont-Yankulova
RMR, TU Darmstadt, Darmstadt, Germany
D. Domont-Yankulova, H. Klingbeil
TEMF, TU Darmstadt, Darmstadt, Germany
H. Klingbeil, D.E.M. Lens
GSI, Darmstadt, Germany

The planned SIS100 heavy ion synchrotron at the Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany will possess twenty ferrite accelerating cavities in its final stage of extension. During the intended acceleration cycles, the cavities will encounter significant beam loading effects, which have to be handled by the control systems. As both the generator- and beam-current act on the same system input, a feedforward disturbance compensation can be a promising approach to improve beam qualities and suppress instabilities induced by the beam current. Particle tracking simulations, incorporating twenty ferrite cavities and their attached LLRF control systems, are performed to analyse the sensitivity of the beam quality with respect to errors in the feedforward beam current compensation. The main focus lies on the time after injection from a pre-accelerator, where most cavities in the SIS100 do not provide any gap voltage and thus are particularly sensitive to induced voltages by beam currents if the cavities are not or only partly short-circuited.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB022

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paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB024

Piezo Controls For The European XFEL

controls, FEL, linac, LLRF

3856

K.P. Przygoda, J. Branlard, L. Butkowski, M.K. Grecki, M. Hierholzer, M. Omet, H. Schlarb
DESY, Hamburg, Germany

The European X-Ray Free Electron Laser (E-XFEL) accelerator is a pulse machine. The typical time duration of a radio frequency (RF) pulse is about 1.3 ms. The RF power transmitted to the superconducting RF (SCRF) cavity as a set of successive pulses (10 Hz repetition rate), causes strong mechanical stresses inside the cavity. The mechanical deformations of the RF cavity are typically caused by the Lorentz force detuning (LFD). The cavity can be tuned to a 1.3 GHz resonance frequency during the RF pulse using fast piezo tuners. Since the E-XFEL will use around 800 cavities (each cavity with double piezos), a distributed architecture with multi-channel digital and analog control circuits seems to be essential. The most sought-after issue is high-voltage, high-current piezo driving circuit dedicated to multi-channel configuration. The driving electronics should allow a maximum piezo protection against any kind of failure. The careful automation of the piezo tuners control and its demonstration for the high gradient conditions a real challenge. The first demonstration of piezo controls applied for chosen RF stations of the E-XFEL linear accelerator (linac) are presented and obtained results are briefly discussed within this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB024

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paper received ※ 30 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB025

New MicroTCA Piezo Driver (PZT4)

high-voltage, controls, operation, power-supply

3860

K.P. Przygoda, L. Butkowski, M. Fenner, M. Hierholzer, R. Rybaniec, H. Schlarb, Ch. Schmidt
DESY, Hamburg, Germany
R. Rybaniec
PSI, Villigen PSI, Switzerland

In the paper we would like to present a new Micro Telecommunication Computing Architecture (MicroTCA) piezo driver (PZT4). The piezo driver module is capable of driving of 4 piezo actuators with high voltages up to 160 Vpp. It is also possible to measure cavity mechanical vibrations using 4 analog to digital converters (ADC) ported to the driver electronics. The new piezo driver can be supplied using internal 12 V payload power provided by the MicroTCA standard. For the applications that need more than 30 W of the input power, the external power supply module can be provided. In order to protect the piezo driver electronics against output short condition a dedicated supervision circuit is designed. The piezo driver module has been setup at Cryo Module Test Bench (CMTB) facility in Deutsches-Elektronen Synchrotron (DESY) as a part of the single cavity low-level radio frequency (LLRF) controls. The LLRF control system has been used to demonstrate the radio frequency (RF) field stabilization and cavity tuning capabilities for continuous (CW) and pulse modes of operation of 1.3 GHz superconducting resonant RF (SCRF) cavity. The preliminary results are demonstrated and briefly discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB025

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paper received ※ 08 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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THPRB049

MODELING AND SIMULATION FOR MULTI-FEEDING CAVITY WITHOUT BEAM LOADING

electron, impedance, simulation, beam-loading

3921

K. Liu, Q. Gu, L. Li, Ch. Wang, M.H. Zhao
SINAP, Shanghai, People’s Republic of China
Q. Gu
SSRF, Shanghai, People’s Republic of China

The Multi-feeding cavity usually be applied in super-conducting and normal-conducting RF cavity. The differences between multiple input couplers in coupler coefficient, incident power and phase will cause the cavity field stabilities can not meet the requirements. For explore the influences of these differences and develop equations for measurement, a multi-feeding LCR transient model was developed. As two-feeding cavity, the VHF photocathode electron gun was model and simulated in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB049

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paper received ※ 06 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB050

LLRF System Modelling and Controller Design in UED

LLRF, electron, controls, cathode

3924

Y.Q. Li, K. Fan, Y. Song
HUST, Wuhan, People’s Republic of China

In the Ultrafast Electron Diffraction (UED) facility for investigating material structure, drifts of amplitude and phase in cavity have different effects on beam quality. So it is critical for pump-probe experiments in the UED to keep accurate synchronization between the laser and electron. To achieve the desired 50fs resolution, the Low Level Radio Frequency (LLRF) controller in S-band normal conducting cavity needs to satisfy the stability: ±0.01% (rms) for the amplitude and ±0.01° (rms) for the phase, respectively. Then we can study the performance of the RF control system by simulating the LLRF system. In the simulation program, feedback, feed-forward algorithms, and beam current variations can be simulated in a Matlab/Simulink environment. This paper shows that a model-based controller design can meet the necessary requirements of the field regulation and implement the algorithms.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB050

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paper received ※ 20 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB063

Field Control Challenges for Different LINAC Types

controls, linac, FEL, electron

3946

O. Troeng, A.J. Johansson
Lund University, Lund, Sweden
M. Eshraqi
ESS, Lund, Sweden
S. Pfeiffer
DESY, Hamburg, Germany

Linacs for free-electron lasers typically require cavity field stabilities of 0.01\% and 0.01 degree, while the requirements for high-intensity proton linacs are on the order of 0.1–1\% and 0.1–1 degrees. From these numbers it is easy to believe that the field control problem for proton linacs is many times easier than for free-electron lasers linacs. In this contribution we explain why this is not necessarily the case, and discuss the factors that make field control challenging. We also discuss the drivers for field stability, and how high-level decisions on the linac design affect the difficulty of the field control problem.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB063

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB066

Beam Based Measurements of Relative RF Phase

alignment, acceleration, booster, proton

3950

S.C.P. Albright
CERN, Geneva, Switzerland
M.D. Kuczynski
LPCT, Vandoeuvre-lès-Nancy Cedex, France

The ferrite loaded RF cavities of the CERN Proton Synchrotron Booster will be replaced with FinemetTM loaded cavities during Long Shutdown 2 2019-2020). To fully realise the potential of the new cavities, the relative RF phases must be aligned along the acceleration ramp, where the revolution frequency changes by nearly a factor of 2. A beam based method of measuring the relative phase between the cavities is desired to give the best possible compensation for the frequency dependent phase shift. In this paper we present an operationally viable method to measure the phase shift as a function of RF frequency. The relative phase of the RF cavities can be aligned to within a few degrees, giving an error on the voltage seen by the beam of less than 1%.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB066

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paper received ※ 08 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB082

The CERN SPS Low Level RF upgrade Project

LLRF, controls, feedback, acceleration

4005

G. Hagmann, P. Baudrenghien, J.D. Betz, J. Egli, G. Kotzian, M. Rizzi, L. Schmid, A. Spierer, T. Włostowski
CERN, Meyrin, Switzerland
F.J. Galindo Guarch
Universitat Politécnica de Catalunya, Barcelona, Spain

The High Luminosity LHC project (HL-LHC) calls for the doubling of the beam intensity injected from the Super Proton Synchrotron (SPS). This is not possible with the present RF system consisting of four 200 MHz cavities. An upgrade was therefore launched, consisting of the installation of two more cavities during the machine shutdown in 2019-2020 (LS2). Installation of more cavities requires the installation of extra Low Level RF (LLRF) electronics. The present LLRF system consists of the original equipment installed in the 1970s, plus some additions dating from the late 1990s when the SPS was commissioned as LHC injector. The High-Power RF up-grade has motivated a complete renovation of the LLRF during LS2; use of a MicroTCA platform, use of a digital deterministic link for synchronization (the so-called White Rabbit), use of an absolute clock for the processing, new algorithms for reducing the cavity impedance, and a complete re-design of the beam control loops and slip-stacking.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB082

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paper received ※ 13 May 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019

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THPRB094

Study of the System Stability for the Digital Low Level RF System Operated at High Beam Currents

LLRF, controls, feedback, simulation

4042

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 amplitude and phase of the field in the accelerating cavity. A digital LLRF (DLLRF) system will be installed in the Taiwan Photon Source (TPS) storage ring in 2019. The system stability depends much on the feedback parameters. An instability of the cavity voltage controlled by a DLLRF was observed during machine tests with high beam current and low feedback gain. A simulation model for the digital LLRF system with beam-cavity interaction was developed to investigate this instability and simulations and machine test results will be presented here.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB094

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paper received ※ 07 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPRB097

Analysis of RF System Stability on CLARA

klystron, gun, linac, controls

4053

N.Y. Joshi, J.K. Jones, A.J. Moss, E.W. Snedden, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
A.C. Dexter, J. Henderson
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
J.K. Jones
Cockcroft Institute, Warrington, Cheshire, United Kingdom

The Compact Linear Accelerator for Research and Applications (CLARA) facility at STFC Daresbury Laboratory will test underpinning concepts and technology for a next generation X-ray free electron laser (FEL). CLARA will use four S-band normal conducting traveling wave linacs to accelerate electron bunches to a maximum energy of 250 MeV. The amplitude and phase stability of the collected RF systems is critical in enabling CLARA to achieve low (10 fs) shot-to-shot timing jitter of the photon output. Here we present initial measurements and model of the amplitude and phase jitter of the CLARA RF systems, achieved by experimentally correlating the klystron output with controls from modulator, driver, and other environment parameters. The effect of the RF jitter on the CLARA beam momentum is also integrated in the model.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB097

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paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB115

MicroTCA Based LLRF Control Systems for TARLA and NICA

LLRF, controls, operation, electron

4089

P. Nonn, C. Gümüş, C.K. Kampmeyer, H. Schlarb, Ch. Schmidt, T. Walter
DESY, Hamburg, Germany

The MicroTCA Technology Lab (A Helmholtz Innovation Lab) is preparing two turn-key Low Level RF control systems for facilities outside of DESY. The Turkish Accelerator and Radiation Laboratory in Ankara (TARLA) is a 40 MeV electron accelerator with continuous wave (CW) RF operation. The MicroTCA based LLRF control system is responsible for two normal conducting and four superconducting cavities, controlling the RF as well as cavity tuning via motors and piezos. The Light Ion Linac (LILAC) is one of the injectors for the Nuclotron-based Ion Collider Facility (NICA) in Dubna, Russia. It will provide a 7 MeV/u pulsed, polarized proton or deuteron beam. The MicroTCA based LLRF control system will control five normal conducting cavities, consisting of one RFQ, one buncher, one debuncher and two IH-cavities. MicroTCA Technology Lab is cooperating with BEVATECH GmbH, Frankfurt, Germany, who designed the cavities. This paper gives a brief overview of the design of both LLRF systems as well as the status of their assembly.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB115

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPTS006

Upgrade of the Canadian Light Source Booster RF System to Solid State

booster, controls, operation, klystron

4112

J.M. Patel, D. Bertwistle, J. Stampe
CLS, Saskatoon, Saskatchewan, Canada
A. Bachtior, A. Borisov, N. Pupeter
CRE, Wuppertal, Germany
P. Hartmann
DELTA, Dortmund, Germany

Funding: CFI, NSERC, NRC, CIHR, the Province of Saskatchewan, WD, and the University of Saskatchewan
The Canadian Light Source synchrotron (CLS) had first light in 2004. For the last 14 years of operation we have exclusively used klystrons to provide RF power to our linac, booster, and storage ring. The klystrons represent a single point of failure for the operation of our booster and storage ring. This is especially poignant in the case of our booster ring klystron which is no longer manufactured. We have chosen to move to solid state amplifier (SSA) RF technology for its implicit high redundancy, modularity, ease of maintenance, and efficiency. Herein we review the performance parameters of our upgraded booster RF to a 100 kW 500 MHz transmitter built by Cryoelectra.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS006

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paper received ※ 08 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPTS007

MYRRHA 80 kW CW RF Coupler Design

multipactoring, electron, vacuum, simulation

4115

Y. Gómez Martínez, M.A. Baylac, D. Bondoux, F. Bouly, P.-O. Dumont
LPSC, Grenoble Cedex, France
S. Blivet, C. Joly, J. Lesrel, H. Saugnac
IPN, Orsay, France
W. Kaabi
LAL, Orsay, France

MYRRHA [1] (Multi Purpose Hybrid Reactor for High Tech Applications) is an Accelerator Driven System (ADS) project. Its superconducting linac will provide a 600 MeV - 4 mA proton beam. The first project phase based on a 100 MeV linac is launched. The Radio-Frequency (RF) couplers have been designed to handle 80 kW CW at 352.2 MHz. This paper describes the thermal, mechanical and RF studies leading to the final design of the RF coupler.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS007

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paper received ※ 10 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPTS008

Prospects of Additive Manufacturing for Accelerators

vacuum, niobium, detector, GUI

4118

N. Delerue, S. Jenzer
LAL, Orsay, France
H.C. Carduner
SUBATECH, Nantes, France
R.L. Gerard
CERN, Meyrin, Switzerland
P.M. Manil
CEA-DRF-IRFU, France
P.R. Repain
LPNHE, Paris, France
A. Simar
UCL, Louvain-la-Neuve, Belgium

Funding: Université Paris-SAclay, Labex P2IO and P2I departement
Additive manufacturing allows the production of mechanical components often much faster than traditional manufacturing. Several accelerators components built using additive manufacturing have already been qualified for use in accelerator. A workshop was held in Orsay in December 2018 to discuss the prospects of using additive manufacturing for particle accelerators and particle detectors. We report here on the prospects as far as accelerators are concerned.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS008

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paper received ※ 20 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPTS013

Further Designs of HOM Couplers for Superconducting 400 MHz RF Cavities

HOM, simulation, impedance, proton

4132

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) at CERN. The proton-proton collider center-of-mass collision energy is set to 100 TeV with a beam current of 0.5 A. To achieve this energy a stable acceleration is critical and therefore higher order modes (HOM) need to be damped. HOM dampers, further characterized as couplers, need to fulfill several criteria to be efficient. As a first property the couplers should assure a longitudinal impedance of higher order modes of below 10 kW. Furthermore, the loaded Q-factor should be below 1000 and the corresponding R/Q value should be in the range of 10 Ω. Besides the Hook-type and Probe-type HOM coupler two additional designs were simulated. The recent results of the different couplers attached to a superconducting 400 MHz RF cavity will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS013

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paper received ※ 09 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPTS019

Design of Beam Position Monitoring System for IPM Low Energy Electron LINAC

electron, simulation, software, linac

4394

N. Messbah, F. Abbasi Davani
Shahid Beheshti University, Tehran, Iran
S. Ahmadiannamin
ILSF, Tehran, Iran
H. Shaker, M. Shirshekan
IPM, Tehran, Iran

A beam position monitor (BPM) is a common device used in particle accelerators to measure the position of a beam of charged-particles. The goal of this project is to simulate and build prototype of different parts to be used for IPM low energy electron Linac being developed at Institute for Research in Fundamental Sciences. The IPM low energy electron Linac will initially be operated at a 7𝜇sec pulse duration and 250 Hz repetition rate with 2.998 GHz bunching frequency. A 4.5-MeV electron beam will be available in the second phase of commissioning. The device is composed of two pickup S-band cavities and a detection circuit to read out the electron beam’s position. The electrode pickup sensors will sense the mode strength generated by the passing beam of electrons. The working modes are TM110 (dipole) for the so called position cavity and TM010 (monopole) for the reference cavity. When the beam crosses the two cavity gaps it induces signals proportional to the product of charge and position offset in the position cavity, and to the charge only in the reference cavity. the position cavity has four rectangular waveguides that couple to the dipole mode while rejecting the monopole mode that would otherwise limit the resolution of the electronics. This signal will be input to a detection circuit that will be used to calculate the signals detected by four antennas arranged. A 180 degree hybrid at the first stage reduce the monopole and a heterodyne receiver principle was used to down-convert the signal frequency in about MHz IF frequency. These signals can then be used to determine the beam’s displacement from the center.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS019

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paper received ※ 15 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019

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THPTS038

There-Dimensional Simulation of a C-Band 32-Beam Klystron

klystron, electron, simulation, bunching

4190

Z.N. Liu, H.B. Chen, J. Shi, H. Zha
TUB, Beijing, People’s Republic of China

A 32-beam klystron working at 5.712 GHz has been designed with efficiency of 70% and output power of 3.4 MW. Core oscillations method (COM) is chosen to bunch electrons. The code KlyC is used for 1-D and 1.5-D calculation and a series of parameters are given after optimizing, including the position, frequency, R/Q, Q₀ and Qe of cavities. CST/PIC is used to make the final design and coaxial cavities are used. This paper describes 1-D, 1.5-D and 3-D beam dynamics of the klystron, compares their differences, and analyses effect of these differences on efficiency.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS038

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPTS058

New 50 KW SSPA Transmitter for the ALBA Booster

operation, booster, ISOL, synchrotron

4237

P. Solans, B. Bravo, J.R. Ocampo, F. Pérez, A. Salom
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
J.V. Balboa, I. Fernández, D. Iriarte, J. Lluch, A. Mellado, C. Rosa, F. Sierra, E. Ugarte
BTESA, Leganés, Spain

ALBA is a 3th generation 3 GeV synchrotron light source located in Barcelona and operating with users since May 2012. The IOT based transmitter for the booster cavity has been replaced by a Solid State Power Amplifier (SSPA) of 50 kW at 500 MHz in August 2018. The new transmitter is made of 96 active devices, which are divided in 12 modules of 8 transistors each one. The modules are combined in groups of four using the Gysel topology and two hybrid combiners are used for the final combining stage. The design allows the transmitter to provide enough power even when multiple transistor fails occur, in the same module or in different ones, and it also presents power supplies redundancy. These modules can be hot swapped, i.e., the module can be replaced by a spare at any time, even when the transmitter is providing power without affecting the operation. After two months of operation, the transmitter fulfills very well the design specifications regarding power, efficiency and gain; and although minor problems have arisen due to infant mortality in some components, the operation of the transmitter has never been affected due to the high redundancy.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS058

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paper received ※ 15 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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THPTS059

Development of a 1.5 GHz, 1 KW Solid State Power Amplifier for 3rd Harmonic System of the Alba Storage Ring

storage-ring, network, ISOL, operation

4240

Z. Hazami, F. Pérez, A. Salom, P. Solans
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

ALBA is the Spanish third generation synchrotron light source, located near Barcelona, in operation since 2012. In order to improve the operation, a third harmonic system has been designed for the Storage Ring in order to stretch the bunch length, and so, improve the beam life time and increase the stability current thresholds. The design of the system consist of four Higher Order Mode (HOM) damped normal conductive active cavities at 1.5 GHz*, feed with 20 kW of RF power each cavity, in order to provide the voltage of 1 MV to the electron beam. The 20 kW RF power transmitter system is based on 250 W solid state power amplifier modules added in parallel by a tree combination technique. The selected combination tree divides the 20 kW overall power per cavity in twenty 1 kW crates. This paper presents the designs of the 250 W power amplifier modules, of the splitter and of the combiner, as well as the measurement results of a 1 kW prototype crate.
* HOM Damped Normal Conducting 1.5 GHz Cavity for the 3rd Harmonic System of the ALBA Storage Ring. IPAC 2019 proceedings

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS059

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPTS060

Sirius Digital LLRF

LLRF, controls, FPGA, booster

4244

A. Salom, F. Pérez
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
R.H.A. Farias, F.K.G. Hoshino, A.P.B. Lima
LNLS, Campinas, Brazil

Sirius is a Synchrotron Light Source Facility based on a 4th generation low emittance storage ring. The facility is presently under construction in Campinas, Brazil, and comprises a 3 GeV electron storage ring, a full energy booster synchrotron and a 120 MeV linac. The booster RF system is based on a single 5-cell cavity driven by a 50 kW amplifier at 500MHz and is designed to operate at 2 Hz rate. The storage ring RF system will start with 1 normal conducting 7-cell cavity. In the final configuration, the system will comprise 2 superconducting cavities, each one driven by a 240 kW RF amplifier. A digital LLRF system based on ALBA LLRF has been designed and commissioned to control 3 different types of cavities: 2 normal conducting single cell cavities, one multi-cell cavity driven by 2 amplifiers and one superconducting cavity driven by 4 amplifiers. The first LLRF System was installed and commissioned in the Sirius Booster in 2019. The performance of the control loops with beam, together with other utilities of the system like automatic start-up, conditioning, fast interlocks and post-mortem analysis will be presented in this paper, as well as possible upgrades for the future

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS060

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPTS063

Development of a W-Band Power Extraction Structure

undulator, electron, GUI, extraction

4252

F. Toufexis, B.J. Angier, D. Gamzina, A. McGuire, M. Shumail, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515, and the National Science Foundation under Contract No. PHY-1415437.
We are modifying the X-Band Test Accelerator at SLAC to operate as an Extreme Ultra Violet (EUV) light source*. The existing photo electron gun will be replaced by a thermionic X-Band injector which utilizes RF bunch compression. The beam is accelerated up to 129 MeV using an X-Band traveling wave structure followed by a novel high shunt impedance standing wave structure. The beam then goes through a mm-wave undulator with a period of 1.75 mm, producing EUV radiation around 13.5 nm. The undulator is powered by a W-Band decelerator structure, which extracts the RF power from the electron beam. In this work we present the mechanical design and fabrication of the 91.392 GHz decelerator structure, as well as structural characterization of its cavities using SEM and 3D microscopy.
* F. Toufexis, et al, "A Compact EUV Light Source using a mm-wave Undulator", Proceedings of IPAC17.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS063

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paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPTS075

Performance Tests of a Digital Low-Level Rf-System at the TPS

LLRF, beam-loading, storage-ring, controls

4292

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

A digital low-level RF (DLLRF) control system for the cavity gap voltage is now common throughout the world. At the Taiwan Photon Source (TPS) we installed and operated a DLLRF in the booster ring in 2018 successfully and plan to install it also in the storage ring in 2019. Operational and beam loading tests of the DLLRF at the storage ring are ongoing. The performance of the DLLRF in the presence of a large number of 60 Hz harmonics and its stability for gap voltage and phase will be discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS075

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paper received ※ 10 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPTS081

Novel Apparatus and Technique for Measuring RR Resistivity of Tube Coatings at Cryogenic Temperatures

cryogenics, lattice, experiment, vacuum

4304

A. Hershcovitch, J.M. Brennan, R. Than, S. Verdú-Andrés, Q. Wu
BNL, Upton, Long Island, New York, USA
A.X. Custer, M.Y. Erickson, H.J. Poole
PVI, Oxnard, California, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy
A unique apparatus for measuring RF resistivity of tubes and coated tubes at cryogenic temperatures is operational at BNL, which to our knowledge is the first of its kind. A folded quarter wave resonator structure of 300 mm length accesses a wide range of frequencies. The structure is cooled in liquid He bath at 4 K. All internal resonator components (except for test samples) were fabricated out of superconducting materials. Consequently, when the resonator is cooled, the bulk of the losses are due to the copper coating. The RF resistivity is determined from Q measurements, since for a fixed geometry the quality factor of a resonant cavity is proportional to the square root of the conductivity. The RF input loop and the output signal antenna are adjustable when cold via bellows to control matching to each cavity mode. The Q values of 10 resonant modes between 180 and 2500 MHz are deduced from the bandwidth of the S21 response Network Analyzer measurements. CST MicroWave Studio is used to extract the resistivity of the samples from the Q measurements. Resistivity results of solid Cu tube, 2, 5, & 10 μm Cu coated 316LN stainless steel RHIC beam tubes will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS081

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPTS095

High Efficiency High Power Resonant Cavity Amplifier For PIP-II

coupling, impedance, network, operation

4335

M.P.J. Gaudreau, D.B. Cope, E.G. Johnson, M.K. Kempkes, R.E. Simpson, N.A. Stuart
Diversified Technologies, Inc., Bedford, Massachusetts, USA

Funding: Work 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 70% efficiency, at 675 watts per transistor at 650 MHz. The patent pending design simplifies solid-state transmitters to create straightforward scaling to 200 kW and higher high power levels. A crucial innovation is the reliable "soft-failure" mode of operation; a failure in one or more of the transistors has negligible performance impact. This design couples the transistor drains directly to the cavity without first transforming to 50 Ohms, avoiding the circulators, cables, and connectors that would normally be required. Under an ongoing SBIR grant from the US Department of Energy, DTI designed the system to accommodate over 96 transistors in each 50 kW cavity, with minimal RF, DC, and cooling connections. By the end of the SBIR, DTI will build and demonstrate a complete 100 kW-class (~200 kW) transmitter by combining four cavity modules to show the expandability of the design to very high power levels, comparable to large VEDs.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS095

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paper received ※ 19 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPTS102

Radio Frequency Power Stations for ESS LINAC Spoke Section

operation, controls, power-supply, site

4346

C. Pasotti, M. Cautero, T.N. Gucin
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
C.A. Martins, R.A. Yogi
ESS, Lund, Sweden

26 equivalent 400 kW Radio Frequency Power Station (RFPS) units will be provided by Elettra as part of the Italian in kind contribution to ESS. They will be installed in the LINAC "Spoke Section". Each RFPS will power a single superconducting spoke cavity in pulsed operation at 352.21 MHz. The RFPS is a complete system that operates unmanned, based on a combination of solid state and tetrode amplification’s stages. The tender specification, the RFPS main features and requested performances are reported here.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS102

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paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPTS116

The SARAF-LINAC Project 2019 Status

linac, MEBT, cryomodule, status

4352

N. Pichoff, R.D. Duperrier, G. Ferrand, B. Gastineau, F. Gougnaud, M. Jacquemet, C. Madec, O. Piquet, Th. Plaisant, F. Senée, D. Uriot
CEA-IRFU, Gif-sur-Yvette, France
D. Berkovits, J. Luner, A. Perry, E. Reinfeld
Soreq NRC, Yavne, Israel

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 have been tested recently. Meanwhile, the cryomodules technical specifications have been written and called for tender. This paper presents the status of the SARAF-LINAC Project at April 2019.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS116

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paper received ※ 13 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPTS117

Results of CEA Tests of SARAF Cavities Prototypes

pick-up, target, linac, detector

4356

G. Ferrand, G. Jullien, S. Ladegaillerie, F. Leseigneur, C. Madec, N. Misiara, N. Pichoff, O. Piquet, L. Zhao
CEA-IRFU, Gif-sur-Yvette, France
P. Carbonnier, F. Éozénou, E. Fayette, L. Maurice, C. Servouin
CEA-DRF-IRFU, France
A. Pérolat
CEA, Gif-sur-Yvette, France

CEA is committed to delivering a Medium Energy Beam Transfer line and a superconducting linac (SCL) for SARAF accelerator in order to accelerate 5mA beam of either protons to 35 MeV or deuterons to 40 MeV. The SCL consists in 4 cryomodules. The first two cryomodules host 6 & 7 half-wave resonator (HWR) low beta cavities (β = 0.09) at 176 MHz, and the last two crymodules host 7 HWR medium beta cavities (β = 0.18). The low beta prototype was qualified, the medium beta is being qualified. The results of the RF tests will be presented in this poster.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS117

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paper received ※ 23 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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