IPAC2021 - List of Keywords (cavity)

Paper	Title	Other Keywords	Page
MOPAB016	Small Longitudinal Emittance Setup in Injectors with Gold Beam for Beam Energy Scan in RHIC	emittance, operation, luminosity, extraction	90
	H. Huang, C.J. Gardner, C. Liu, V. Schoefer, K. Zeno BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. In recent years, RHIC physics program calls for gold beam collisions with energies at and lower than the nominal RHIC injection energy. To get shorter bunches at the three higher energies (9.8GeV/c, 7.3GeV/c and 4.75GeV/c), RHIC 28MHz cavities were used. The longitudinal emittance out of injectors needs to fit in the 28MHz cavities in RHIC. At two lower energies (4.6 and 3.85 GeV/c), the 9MHz RF cavities were used, which set different requirements from injectors. Extensive beam studies were carried out to establish needed beam parameters, such as bunch intensities and longitudinal emittances. In general, enough intensity can be provided for all energies within the longitudinal emittance constraint. This paper summarizes the recent injector operation experiences for various energies.
	Poster MOPAB016 [2.641 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB016
About •	paper received ※ 16 May 2021 paper accepted ※ 17 August 2021 issue date ※ 01 September 2021
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MOPAB043	Validation of APS-U Beam Dynamics Using 6-GeV APS Beam	HOM, simulation, lattice, impedance	189
	L. Emery, P.S. Kallakuri, R.R. Lindberg, A. Xiao ANL, Lemont, Illinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Several beam measurements at the Advanced Photon Sources were done with a lowered-energy beam of 6 GeV in order to verify or validate calculation codes and some predictions for the APS-U. Though the APS lattice is obviously different from that of the APS-U some aspects of the beams at 6 GeV are similar, for example, the synchrotron radiation damping rate. At 6 GeV, one can also store more current and run with a higher rf bucket allowing the characterization of larger momentum aperture lattices. We report measurements (or plans of measurements) on general instabilities thresholds, lifetime, and other subtle effects. The important topic of ion instabilities at 6 GeV is covered in a separate paper by J. Calvey at this conference.
	Poster MOPAB043 [0.829 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB043
About •	paper received ※ 20 May 2021 paper accepted ※ 23 June 2021 issue date ※ 02 September 2021
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MOPAB045	Measurements and Simulations of High Charge Beam in the APS Booster	booster, injection, simulation, extraction	197
	J.R. Calvey, J.C. Dooling, K.C. Harkay, K.P. Wootton, C. Yao ANL, Lemont, Illinois, USA
	For the APS-Upgrade, swap-out injection will require the booster to support up to 17 nC bunch charge, several times what is used in the present APS. Booster injection efficiency drops sharply at high charge, and is the present bottleneck limiting high charge transport through the injectors. Particle tracking simulations have been used to understand what causes are limiting the injection efficiency, and to guide plans for improving it. In particular, bunch length blowup in the injected beam and beam loading in the RF cavities have been identified as the biggest factors. Simulations and measurements have also been done to characterize beam properties along the booster energy ramp. So far, a bunch charge of 12 nC has been successfully extracted from the booster.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB045
About •	paper received ※ 19 May 2021 paper accepted ※ 26 July 2021 issue date ※ 19 August 2021
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MOPAB046	Plan for Operating the APS-Upgrade Booster with a Frequency Sweep	injection, booster, extraction, emittance	201
	J.R. Calvey, T.G. Berenc, A.R. Brill, L. Emery, T. Fors, K.C. Harkay, T.J. Madden, N. Sereno, U. Wienands ANL, Lemont, Illinois, USA A. Gu UCB, Berkeley, California, USA
	The APS-Upgrade presents several challenging demands to the booster synchrotron. Swap-out injection requires the booster to capture a high charge bunch (up to 17 nC), accelerate it to 6 GeV, and maintain a low emittance at extraction for injection into the storage ring. To accommodate these conflicting demands, the RF frequency will be ramped between injection and extraction. However, the RF cavity tuners will remain static, which means the couplers will need to withstand a high reflected power at extraction. This paper presents a plan for a system that will meet the requirements for injection efficiency, extracted emittance, and equivalent power at the coupler. Results from tracking simulations and beam studies with a frequency ramp will also be shown.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB046
About •	paper received ※ 28 May 2021 paper accepted ※ 02 June 2021 issue date ※ 15 August 2021
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MOPAB050	Spatial Autoresonant Acceleration of Electrons by an Axysimmetric Transverse Electric Field	electron, resonance, acceleration, cyclotron	217
	E.A. Orozco, O. Otero Olarte UIS, Bucaramanga, Colombia
	In this research, The autoresonance acceleration of electrons by an axisymmetric transverse electric field in presence of a stationary inhomogeneous magnetic field is studied. The dynamics of electrons is determined by the numerical solution of the relativistic Newton-Lorentz equation using a finite difference scheme. The inhomogeneous external magnetic field is generated with a three-coil system and calculated using the Biot-Savart law. The electrons move along a TE011 cylinder cavity in a stationary magnetic field whose axis coincides with the cavity axis. The magnetic field profile obtained is such that it keeps the phase difference between the electric field vector of the microwave mode and the velocity vector of the particle within the acceleration band. For an electron injected longitudinally with an energy of 1 keV and that starts at the radial midpoint of the cavity, it is accelerated up to an energy of about 185 keV using an electric field amplitude of 14 kV/cm and a frequency of 2.45 GHz at a distance of 14 cm.
	Poster MOPAB050 [3.298 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB050
About •	paper received ※ 17 May 2021 paper accepted ※ 15 June 2021 issue date ※ 30 August 2021
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MOPAB068	Collective Effects Studies for the SOLEIL Upgrade	impedance, synchrotron, storage-ring, feedback	274
	A. Gamelin, D. Amorim, P. Brunelle, W. Foosang, A. Loulergue, L.S. Nadolski, R. Nagaoka, R. Ollier, M.-A. Tordeux SOLEIL, Gif-sur-Yvette, France
	The SOLEIL upgrade project aims to replace the actual SOLEIL storage ring by a 4th generation light source. The project has just finished its conceptual design report (CDR) phase. Compared to the SOLEIL storage ring, the upgraded storage ring design includes many new features of 4th generation light sources that will impact collective effects, such as reduced beam pipe apertures, a smaller momentum compaction factor and the presence of harmonic cavities (HC). To mitigate them, we rely on several damping mechanisms provided by the synchrotron radiation, the transverse feedback system, and the HC (Landau damping and bunch lengthening). This article presents a first estimate of the collective effects impact of the upgraded design. Conceptual Design Report: Synchrotron SOLEIL Upgrade, 2021, in press.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB068
About •	paper received ※ 17 May 2021 paper accepted ※ 02 June 2021 issue date ※ 20 August 2021
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MOPAB069	Equilibrium Bunch Density Distribution with Multiple Active and Passive RF Cavities	beam-loading, impedance, synchrotron, storage-ring	278
	A. Gamelin SOLEIL, Gif-sur-Yvette, France N. Yamamoto KEK, Ibaraki, Japan
	This paper describes a method to get the equilibrium bunch density distribution with an arbitrary number of active or passive RF cavities in uniform filling. This method is an extension of the one presented by M. Venturini which assumes a passive harmonic cavity and no beam loading in the main RF cavity. M. Venturini, "Passive higher-harmonic rf cavities with general settings and multibunch instabilities in electron storage rings," Physical Review Accelerators and Beams, 2018.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB069
About •	paper received ※ 17 May 2021 paper accepted ※ 23 June 2021 issue date ※ 28 August 2021
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MOPAB070	mbtrack2, a Collective Effect Library in Python	impedance, collective-effects, simulation, synchrotron	282
	A. Gamelin, W. Foosang, R. Nagaoka SOLEIL, Gif-sur-Yvette, France
	This article introduces mbtrack2, a collective effect library written in python3. The idea behind mbtrack2 is to build a coherent object-oriented framework to work on collective effects in synchrotrons. mbtrack2 is composed of different modules allowing to easily write scripts for single bunch or multi-bunch tracking using MPI parallelization in a transparent way. The base of the tracking model of mbtrack2 is inspired by mbtrack, a C multi-bunch tracking code initially developed at SOLEIL. In addition, many tools to prepare or analyse tracking simulations are included. R. Nagaoka, R. Bartolini, and J. Rowland, Studies of Collective Effects in SOLEIL and Diamond Using the Multiparticle Tracking Codes SBTRACK and MBTRACK, in Proc. PAC’09, 2009.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB070
About •	paper received ※ 17 May 2021 paper accepted ※ 06 July 2021 issue date ※ 23 August 2021
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MOPAB072	Single-Bunch Thresholds for the Diamond-II Storage Ring	impedance, simulation, storage-ring, beam-loading	290
	T. Olsson, R.T. Fielder DLS, Oxfordshire, United Kingdom
	The proposed Diamond Light Source upgrade will see the storage ring replaced with a multibend achromat lattice, increasing the capacity of the facility whilst reducing the emittance and providing higher brightness for the users. As part of the design work, tracking studies have been performed to determine the single-bunch thresholds including both the resistive-wall and geometric contributions to the impedance. As the machine design also foresees a third order harmonic cavity, the paper also provides an initial assessment of the effects of bunch lengthening on the single-bunch thresholds.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB072
About •	paper received ※ 18 May 2021 paper accepted ※ 01 June 2021 issue date ※ 18 August 2021
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MOPAB079	Experience of the First Six Years Operations and Plans in NSlS-II	operation, MMI, feedback, vacuum	308
	G.M. Wang BNL, Upton, New York, USA
	NSLS-II is a 3 GeV third-generation synchrotron light source at BNL. The storage ring was commissioned in 2014 and began its routine operations in the December of the same year. Since then, we have been continuously installing and commissioning new insertion devices, their front-ends, and beamlines. At this point, the facility hosts 28 operating beamlines from various radiation sources, including damping wiggler, IVU, EPU, 3PW, and bending magnets for infrared beamlines. Over the past six years, the storage ring performance continuously improved, including 500 mA with limited insertion devices close due to RF power limitation and routinely 400 mA top off operation, >95% operation reliability, maintenance of beam motion short- and long-term stability. In this paper, we report NSLS-II accelerator operations experience and plans for future facility developments.
	Poster MOPAB079 [2.064 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB079
About •	paper received ※ 17 May 2021 paper accepted ※ 21 June 2021 issue date ※ 11 August 2021
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MOPAB092	Project of Wuhan Photon Source	storage-ring, injection, linac, dipole	346
	H.H. Li, Y. Deng, J.H. He, Y. Nie, L. Tang, J. Wang, Y.X. Zhu IAS, Wuhan City, People’s Republic of China
	Wuhan Photon Source (WHPS) has been designed as a fourth-generation light source, which consists of a low energy storage ring (1.5 GeV), a medium energy storage ring (4.0 GeV), and a linac working as a full energy injector. It has been planned to build the low energy light source first as the Phase I project, and then the medium energy light source after its completion. The low energy storage ring has been optimized with the main design parameters as following: An 8-cell, 500 mA storage ring, with a circumference of 180 m and nature emittance 238.4 pm-rad. Based on hybrid-7BA lattice structure, it reaches the soft X-ray diffraction limit. And at the middle of each cell, a 3.5 T superB magnet is used to extend the photon energy to the hard X-ray region. The swap-out injection is chosen due to the small dynamic aperture and a full energy S-band LINAC will be used as its injector. A 3rd harmonic cavity is designed for bunch lengthening to keep a sufficient lifetime. More details of the WHPS phase I project will be described in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB092
About •	paper received ※ 10 June 2021 paper accepted ※ 23 June 2021 issue date ※ 30 August 2021
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MOPAB107	RF Plans for the Diamond-II Upgrade	HOM, linac, booster, gun	391
	C. Christou, P. Gu, P.J. Marten, S.A. Pande, A.F. Rankin DLS, Oxfordshire, United Kingdom
	The RF system for the proposed Diamond-II upgrade will be based on normal-conducting EU HOM-damped cavities powered by high powered solid state amplifiers and controlled by digital low level RF systems built on the microTCA platform. Reasons for these design choices are discussed, and experience of the selected technologies in the Diamond-I ring are reviewed. The storage ring will also include a third harmonic cavity, and the different design options for this device are discussed. RF design of the booster ring is presented, and details are given of an upgraded linac and gun design intended to improve the charge delivered for top-up.
	Poster MOPAB107 [1.703 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB107
About •	paper received ※ 18 May 2021 paper accepted ※ 20 May 2021 issue date ※ 20 August 2021
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MOPAB108	ESRF-EBS 352.37 MHz Radio Frequency System	SRF, operation, MMI, HOM	395
	J. Jacob, P.B. Borowiec, A. D’Elia, G. Gautier, V. Serrière ESRF, Grenoble, France
	The ESRF 352 MHz Radio Frequency (RF) system has been upgraded and tailored to the new 4th Generation Extremely Brilliant Source EBS, that was installed in 2019 and commissioned in 2020. The five former five-cell cavities were replaced with 13 single cell strongly HOM damped cavities that were developed in house, 10 of which are powered from existing 1 MW klystron transmitters. The remaining three cavities are individually fed by three 150 kW solid state amplifiers. All this required a reconstruction in record time of an elaborate WR2300 waveguide network. The low level RF system as well as the cavity and transmitter control system have been rebuilt. The RF design, commissioning and operation experience will be reported, including plans for a 4th harmonic RF system for bunch lengthening to further improve the performance of the new EBS ring.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB108
About •	paper received ※ 19 May 2021 paper accepted ※ 27 May 2021 issue date ※ 28 August 2021
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MOPAB127	Construction of an Impedance Model for Diamond-II	impedance, simulation, lattice, dipole	455
	R.T. Fielder, T. Olsson DLS, Oxfordshire, United Kingdom
	Impedance models for accelerators have traditionally been presented in a static form, usually as tables or spreadsheets which must be read manually. As part of the Diamond-II upgrade work, we have developed an impedance model using a lattice structure. This allows more direct integration with simulation codes while keeping important information easily human readable. We present here a description of this implementation method, along with an overview of the Diamond-II impedance model derived from the latest engineering design.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB127
About •	paper received ※ 18 May 2021 paper accepted ※ 20 May 2021 issue date ※ 27 August 2021
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MOPAB146	Status of the C-Band Engineering Research Facility (CERF-NM) Test Stand Development at LANL	GUI, klystron, controls, radiation	509
	D. Gorelov Private Address, Los Alamos, USA R.L. Fleming, S.K. Lawrence, J.W. Lewellen, D. Perez, M.E. Schneider, E.I. Simakov, T. Tajima LANL, Los Alamos, New Mexico, USA M.E. Middendorf ANL, Lemont, Illinois, USA
	Funding: LDRD-DR Project 20200057DR C-Band structures research is of increasing interest to the accelerator community. The RF frequency range of 4-6 GHz gives the opportunity to achieve significant increase in the accelerating gradient, and having the wakefields at the manageable levels, while keeping the geometric dimensions of the structure technologically convenient. Strong team of scientists, including theorists researching properties of metals under stressful thermal conditions and high electromagnetic fields, metallurgists working with copper as well as alloys of interest, and accelerator scientists developing new structure designs, is formed at LANL to develop a CERF-NM facility. A 50 MW, 5.712 GHz Canon klystron, was purchased in 2019, and laid the basis for this facility. As of Jan-21, the construction of the Test Stand has been finished and the high gradient processing of the waveguide components has been started. Future plans include high gradient testing of various accelerating structures, including benchmark C-band accelerating cavity, a proton ß=0.5 cavity, and cavities made from different alloys. An upgrade to the facility is planned to allow for testing accelerator cavities at cryogenic temperatures.
	Poster MOPAB146 [3.778 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB146
About •	paper received ※ 17 May 2021 paper accepted ※ 26 May 2021 issue date ※ 25 August 2021
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MOPAB155	Magnetic Breakdowns in Side-Coupled X-Band Accelerating Structures	impedance, coupling, simulation, accelerating-gradient	540
	S.P. Antipov, P.V. Avrakhov, S.V. Kuzikov Euclid TechLabs, Solon, Ohio, USA V.A. Dolgashev SLAC, Menlo Park, California, USA C. Jing Euclid Beamlabs, Bolingbrook, USA
	Funding: DOE SBIR Side coupled accelerating structures are popular in the industrial realizations of linacs due to their high shunt impedance and ease of tuning. We designed and fabricated a side-coupled X-band accelerating structure that achieved 133 MOhm/m shut impedance. This structure was fabricated out of two halves using a novel brazeless approach. The two copper halves are joined together using a stainless steel joining piece with knife edges that bite into copper. This structure had been tested at high power at SLAC National Accelerator Laboratory. The performance of the structure had been limited by magnetic breakdowns on the side-coupling cells. In this paper we will present results of the high gradient tests and after-test analysis. Scanning electron microscopy images show a typical magnetic-field induced breakdown.
	Poster MOPAB155 [1.069 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB155
About •	paper received ※ 20 May 2021 paper accepted ※ 23 June 2021 issue date ※ 21 August 2021
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MOPAB187	Design and Calculation of the RF System of DC140 Cyclotron	cyclotron, coupling, simulation, resonance	636
	A.S. Zabanov, V.B. Zarubin JINR/FLNR, Moscow region, Russia J. Franko, G.G. Gulbekyan, I.V. Kalagin, N.Yu. Kazarinov, S.V. Mitrofanov, V.A. Sokolov, K. Verlamov JINR, Dubna, Moscow Region, Russia
	Flerov Laboratory of Nuclear Reaction of Joint Institute for Nuclear Research carries out the works under creating of FLNR JINR Irradiation Facility based on the cyclotron DC140. The facility is intended for SEE testing of microchip, for production of track membranes and for solving of applied physics problems. The main systems of DC140 are based on the DC72 cyclotron ones that now are under reconstruction. The DC140 cyclotron is intended for acceleration of heavy ions with mass-to-charge ratio A/Z within interval from 5 to 5.5 up to two fixed energies 2.124 and 4.8 MeV per unit mass. The intensity of the accelerated ions will be about 1 pmcA for light ions (A<86) and about 0.1 pmcA for heavier ions (A>132). The designed RF-system of the DC-72 cyclotron with a half-wave cavity is not suitable due to the big vertical size. For this reason, a new quarter-wave RF-system was developed for the DC140 cyclotron project. The results of calculating the parameters of the new RF-system are given in this work.
	Poster MOPAB187 [0.488 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB187
About •	paper received ※ 17 May 2021 paper accepted ※ 24 May 2021 issue date ※ 30 August 2021
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MOPAB190	An 8 GeV Linac as the Booster Replacement in the Fermilab Power Upgrade	linac, injection, cryomodule, booster	643
	D.V. Neuffer, S.A. Belomestnykh, M. Checchin, D.E. Johnson, S. Posen, E. Pozdeyev, V.S. Pronskikh, N. Solyak, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. Increasing the Main Injector (MI) beam power above ~1.2 MW requires replacement of the 8 GeV Booster by a higher intensity alternative. Previously, rapid-cycling synchrotron (RCS) and Linac solutions were considered for this purpose. In this paper, we consider the Linac version that produces 8 GeV H⁻ beam for injection into the Recycler Ring (RR) or Main Injector (MI). The Linac takes ~1 GeV beam from the PIP-II Linac and accelerates it to ~2 GeV in a cw SRF linac, followed by a ~2-8 GeV pulsed linac using 1300 MHz cryomodules. The linac components incorporate recent improvements in SRF technology. The linac configuration and beam dynamics requirements are presented. Injection options are discussed. Research needed to implement the Booster replacement is described.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB190
About •	paper received ※ 15 May 2021 paper accepted ※ 28 May 2021 issue date ※ 14 August 2021
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MOPAB191	Method Development for Cavity Failure Compensation in a Superconducting Linac	linac, emittance, lattice, ECR	647
	F. Bouly LPSC, Grenoble Cedex, France
	Reliability is a major challenge within the perspective of improving the performances and sustainability of MegaWatt class accelerators. To optimize the operational costs of such accelerators the availability requirements are becoming more and more challenging. These requirements are even more stringent in the case of Accelerator Driven systems (ADS). As an example, for the MYRRHA (Multipurpose Hybrid Research Reactor for High-tech Applications) ADS demonstrator, the actual availability limit is set to a maximum of 10 beam interruptions (longer than 3 seconds) over a 3-month operating cycle. For this purpose, the accelerator design is based on a redundant and fault-tolerant scheme to enable rapid mitigation of a cavity failure. The adopted strategy is to apply for local compensation: a failed cavity is compensated by several neighboring cavities. Beam dynamics studies and method developments to apply such a failure compensation scheme are here reviewed. First simulation results for superconducting linac retuning and potential future improvements will be discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB191
About •	paper received ※ 19 May 2021 paper accepted ※ 21 May 2021 issue date ※ 30 August 2021
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MOPAB192	LILac Energy Upgrade to 13 MeV	linac, proton, controls, LLRF	651
	B. Koubek, S. Altürk, M. Busch, H. Höltermann, J.D. Kaiser, H. Podlech, U. Ratzinger, M. Schuett, M. Schwarz, W. Schweizer, D. Strehl, R. Tiede, C. Trageser BEVATECH, Frankfurt, Germany A. Brunzel, P. Nonn, H. Schlarb DESY, Hamburg, Germany A.V. Butenko, D.E. Donets, B.V. Golovenskiy, A. Govorov, K.A. Levterov, D.A. Lyuosev, A.A. Martynov, V.A. Monchinsky, D.O. Ponkin, K.V. Shevchenko, I.V. Shirikov, E. Syresin JINR, Dubna, Moscow Region, Russia
	In the frame of the NICA (Nuclotron-based Ion Collider fAcility) ion collider upgrade a new light ion LINAC for protons and ions will be built in collaboration between JINR and BEVATECH GmbH. While ions with a mass-to-charge ratio up to 3 will be fed into the NUCLOTRON ring with an energy of 7 MeV/u, protons are supposed to be accelerated up to an energy of 13 MeV using a third IH structure. This energy upgrade comprises a third IH structure, a dual-use Debuncher cavity as well as an extension of the LLRF control system built on MicroTCA technology.
	Poster MOPAB192 [4.914 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB192
About •	paper received ※ 11 May 2021 paper accepted ※ 31 May 2021 issue date ※ 02 September 2021
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MOPAB194	First 3D Printed IH-Type Linac Structure - Proof-of-Concept for Additive Manufacturing of Linac rf Cavities	vacuum, cyclotron, experiment, linac	654
	H. Hähnel, U. Ratzinger IAP, Frankfurt am Main, Germany
	Additive manufacturing (or "3D printing") has become a powerful tool for rapid prototyping and manufacturing of complex geometries. As technology is evolving, the quality and accuracy of parts manufactured this way is ever improving. Especially interesting for the world of particle accelerators is the process of 3D printing of stainless steel (and copper) parts. We present the first fully functional IH-type drift tube structure manufactured by metal 3D printing. A 433 MHz prototype cavity has been constructed to act as a proof-of-concept for the technology. The cavity is designed to be UHV capable and includes cooling channels reaching into the stems of the DTL structure. We present the first experimental results for this prototype.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB194
About •	paper received ※ 18 May 2021 paper accepted ※ 01 June 2021 issue date ※ 19 August 2021
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MOPAB195	Development of a Disk-and-Washer Cavity for the J-PARC Muon g-2/EDM Experiment	experiment, linac, quadrupole, coupling	658
	Y. Takeuchi, J. Tojo Kyushu University, Fukuoka, Japan E. Cicek, K. Futatsukawa, N. Kawamura, T. Mibe, M. Otani, T. Yamazaki, M. Yoshida KEK, Ibaraki, Japan Y. Iwashita Kyoto ICR, Uji, Kyoto, Japan R. Kitamura, Y. Kondo, T. Morishita JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan Y. Nakazawa Ibaraki University, Hitachi, Ibaraki, Japan N. Saito J-PARC, KEK & JAEA, Ibaraki-ken, Japan Y. Sue, K. Sumi, M. Yotsuzuka Nagoya University, Graduate School of Science, Chikusa-ku, Nagoya, Japan H.Y. Yasuda University of Tokyo, Tokyo, Japan
	At J-PARC, an experiment using muons accelerated by a linac is planned to measure the anomalous magnetic moment of muons and to search for the electric dipole moment. A 1296 MHz disk and washer (DAW) coupled cavity linac (CCL) is being developed for use in the middle beta section of the muon linac. The DAW CCL consists of 14 tanks with 11 cells each. All tanks are connected by bridge couplers and electromagnetic quadrupole doublets for focusing are installed in each bridge coupler. The basic design of the DAW cavity has already been completed, and now detailed cavity design studies and manufacturing process studies are underway. In this poster, we will report about these studies and the preparation status of manufacturing the DAW cavity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB195
About •	paper received ※ 20 May 2021 paper accepted ※ 01 June 2021 issue date ※ 26 August 2021
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MOPAB203	Benchmark of Superconducting Cavity Models at SNS Linac	linac, superconducting-cavity, simulation, operation	671
	A.P. Shishlo ORNL, Oak Ridge, Tennessee, USA
	Funding: This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC0500OR22725 with the U.S. Department of Energy. A benchmark of superconducting cavity models against Time-of-Flight measurements at the SNS linac is presented. The superconducting part of SNS linac (SCL) includes 81 RF cavities that accelerates H⁻ beam from 185.6 MeV to the final energy of 1 GeV. During the operation some of cavities can become unstable, and its amplitudes should be reduced, or they should be completely switched off. In this case, the SCL is retuned by using a linac simulation code. This simulation tool relay on an accuracy of the superconducting cavity model. This paper describes the comparison of the measured beam acceleration by one of the SCL cavities and simulations of this process. Different cavity models are used in simulations. The subject of this study is limited to the longitudinal beam dynamics, so no effects on transverse beam characteristics have been considered.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB203
About •	paper received ※ 14 May 2021 paper accepted ※ 20 May 2021 issue date ※ 28 August 2021
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MOPAB206	The RF Parameters of Heavy Ions Linac	DTL, rfq, linac, MEBT	679
	A. Sitnikov, G. Kropachev, T. Kulevoy, D.N. Selesnev, A.I. Semennikov ITEP, Moscow, Russia M.L. Smetanin, A.V. Telnov, N.V. Zavyalov VNIIEF, Sarov, Russia
	The new linac for A/Z = 8, output energy 4 MeV/u and 3 mA current is under development at NRC "Kurchatov Institute"-ITEP. The linac consists of Radio-Frequency Quadrupole (RFQ) with operating frequency 40 MHz and two sections of Drift Tube Linac (DTL) with operating frequency 80 and 160 MHz, correspondently. Both DTL has a modular structure and consists of separated individually phased resonators with focusing magnetic quadrupoles located between the cavities. The DTL₁ is based on the quarter-wave resonators meanwhile DTL₂ is based on IH 5-gap resonators. The 6D beam matching between RFQ and DTLs is provided by magnetic quadrupole lenses and 2-gaps RF-bunchers. The paper presents results of the radio-frequency (RF) design of linac accelerating structures.
	Poster MOPAB206 [0.559 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB206
About •	paper received ※ 14 May 2021 paper accepted ※ 01 July 2021 issue date ※ 28 August 2021
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MOPAB208	LLRF Measurements and Cu-plating at the First-of-Series Cavity Section of the Alvarez 2.0 at GSI	DTL, operation, simulation, vacuum	686
	M. Heilmann, T. Dettinger, X. Du, L. Groening, S. Mickat, A. Rubin GSI, Darmstadt, Germany
	The Alvarez 2.0 will replace the existing post-stripper DTL of the GSI UNILAC. Today’s GSI comprises the UNILAC and the synchrotron SIS18 and is going to serve as the injector chain for the Facility of Antiproton and Ion Research (FAIR). The new Alvarez-type DTL is operated at 10⁸.4 MHz providing acceleration from 1.4 MeV/u to 11.4 MeV/u along a total length of 55 meters. The first-of-series (FoS) cavity section has 12 RF-gaps along a total length of 1.9 m. It is the first cavity section of the new DTL. All main components were delivered in 2019, followed by successful SAT and installation of the 11 drift tubes and copper-plating. Completion of first low level RF-measurements prior to copper plating and the subsequent plating are major project milestones. These proceedings report on the results and compares them to simulation using CST Microwave Studio.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB208
About •	paper received ※ 18 May 2021 paper accepted ※ 31 May 2021 issue date ※ 23 August 2021
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MOPAB209	Commissioning of SANAEM RFQ Accelerator	rfq, vacuum, plasma, proton	690
	B. Yasatekin, A. Alacakir, A.S. Bolukdemir, I. Kilic, Y. Olgac TENMAK-NUKEN, Ankara, Turkey E. Cicek KEK, Ibaraki, Japan E. Cosgun UNIST, Ulsan, Republic of Korea
	The former SANAEM RFQ is upgraded with a newly manufactured cavity, made of oxygen-free copper (OFC), having the capability of accelerating protons from 20 keV to 1.3 MeV. In the assembling of cavity vanes, flanges, etc., indium wire is preferred over the brazing process providing a more flexible and easy method for vacuum sealing. After assembling the cavity, argon plasma cleaning is performed for the final cleaning and RF pre-conditioning. Vacuum tests revealed that levels of 2·10^-7 mbar could be achieved quite easily. RF power conditioning of the RFQ cavity is successfully completed with the observation of quite few sparks. In the commissioning tests with the proton beam, a magnetic analyzer is used to measure the energy of the particles. This paper presents the strategy and the results concerning the commissioning of the proton beam with special emphasis on the RFQ cavity.
	Poster MOPAB209 [5.076 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB209
About •	paper received ※ 19 May 2021 paper accepted ※ 14 June 2021 issue date ※ 29 August 2021
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MOPAB210	High-Gradient Booster for Enhanced Proton Radiography at LANSCE	linac, booster, proton, focusing	693
	S.S. Kurennoy, Y.K. Batygin LANL, Los Alamos, New Mexico, USA
	Increasing energy of proton beam at LANSCE from 800 MeV to 3 GeV improves radiography resolution ~10 times. We propose accomplishing this energy boost with a compact cost-effective linac based on cryo-cooled normal conducting high-gradient RF accelerating structures. High-gradient structures exceeding 100 MV/m have been developed for electron acceleration and operate with short RF pulse lengths below 1 us. Though such parameters are unusual for typical proton linacs, they fit perfectly for proton radiography (pRad) applications. The pRad limits contiguous trains of beam micro-pulses to less than 80 ns to prevent blur in images. For a compact pRad booster at LANSCE, we develop a staged design: a short section to capture and compress the 800-MeV proton beam followed by the main high-gradient linac. Our beam dynamics study addresses the beam magnetic focusing and minimizing its energy spread, which are challenging in high-gradient structures but very important for successful pRad operation.
	Poster MOPAB210 [0.809 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB210
About •	paper received ※ 10 May 2021 paper accepted ※ 17 August 2021 issue date ※ 23 August 2021
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MOPAB211	Beam Coupling Impedances of Ferrite-Loaded Cavities: Calculations and Measurements	impedance, dipole, resonance, coupling	696
	S.S. Kurennoy, R.C. McCrady LANL, Los Alamos, New Mexico, USA
	We have developed an efficient method of calculating impedances in cavities with dispersive ferrite dampers. The ferrite dispersive properties in the frequency range of interest are fitted in CST, which allows using both wakefield and lossy eigenmode solvers. A simple test cavity with or without ferrite inserts is explored both numerically and experimentally. The resonance frequencies and beam coupling impedances at cavity resonances are calculated with CST to understand the mode structure. The cavity transverse coupling impedances are also measured on a test stand using a two-wire method. We compare results of impedance calculations and measurements for a few different configurations, with and without ferrites, to ensure a complete understanding of the cavity resonances and their damping with ferrite. These results are important to provide adequate damping of undesired transverse modes in induction-linac cells.
	Poster MOPAB211 [1.105 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB211
About •	paper received ※ 10 May 2021 paper accepted ※ 21 May 2021 issue date ※ 19 August 2021
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MOPAB232	Observation of Polarization-Dependent Changes in Higher-Order Mode Responses as a Function of Transverse Beam Position in Tesla-Type Cavities at FAST	HOM, electron, dipole, cryomodule	756
	R.M. Thurman-Keup, D.R. Edstrom, A.H. Lumpkin, P.S. Prieto, J. Ruan Fermilab, Batavia, Illinois, USA J.A. Diaz Cruz UNM-ECE, Albuquerque, USA J.A. Diaz Cruz, B.T. Jacobson, J.P. Sikora, F. Zhou SLAC, Menlo Park, California, USA
	Funding: FNAL supported by U.S. Department of Energy, Office of Science, under contract DE-AC02-07CH11359. SLAC supported by U.S. Department of Energy, Office of Science, under contract DE-AC02-76SF00515. Higher-order modes (HOMs) in superconducting rf cavities present problems for an electron bunch traversing the cavity in the form of long-range wakefields from previous bunches. These may dilute the emittance of the macropulse average, especially with low emittance beams at facilities such as the European X-ray Free-electron Laser (XFEL) and the upgraded Linac Coherent Light Source (LCLS-II). Here we present observations of HOMs driven by the beam at the Fermilab Accelerator Science and Technology (FAST) facility. The FAST facility features two independent TESLA-type cavities (CC1 and CC2) after a photocathode rf gun followed by an 8-cavity cryomodule. The HOM signals were acquired from cavities using bandpass filters of 1.75 ± 0.15 GHz, 2.5 ± 0.2 GHz, and 3.25 ± 0.2 GHz and recorded using an 8-GHz, 20 GSa/s oscilloscope. The frequency resolution obtained is sufficient to separate polarization components of many of the HOMs. These HOM signals were captured from CC1 and cavities 1 and 8 of the cryomodule for various initial trajectories through the cavities, and we observe correlations between trajectory, HOM signals, and which polarization component of a mode is affected.
	Poster MOPAB232 [2.144 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB232
About •	paper received ※ 20 May 2021 paper accepted ※ 25 May 2021 issue date ※ 28 August 2021
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MOPAB236	Ion Beam Dynamics in Linac-100 Facility at Jinr	linac, acceleration, emittance, rfq	767
	S.M. Polozov, V.S. Dyubkov, Y. Lozeev, T.A. Lozeeva, A.V. Samoshin MEPhI, Moscow, Russia
	The heavy-ion linac LINAC-100 is a superconducting driver-accelerator proposed as one of the prospective projects at JINR. Its goal is to accelerate primary stable isotope CW high-intensity beams to energies up to 100 MeV/u. This linac is discussed as the first stage of a new rare isotope facility DERICA (Dubna Electron-Radioactive Ion Collider fAcility), being under development at JINR since 2017. LINAC-100 is supposed to work with a wide range of beams with A/Z 3.5/7, Uranium U³⁴⁺ being the heaviest. Its concept has undergone many changes, mostly considering stripping cells to increase accelerator efficiency. During the latest investigations of various stripping cells [, *], Uranium beam stripping at the energy 10 MeV/u and utilizing three adjacent charge states 59-61+ resulted in 60% output beam intensity preservation (or 30 pA overall output current). The current layout of the LINAC-100 is the following: one or two (separately for light and heavy ions) normal conducting front-end linacs, gas stripper cell at 10 MeV/u, and the SC section. In this paper three charge state Uranium beam dynamics in the current version of SC LINAC-100 section is presented. S Polozov 2020 PhysScr 95 084006 A S Fomichev Phys Usp 62(7) 675-690 2019 Tolstikhina I 2018 Basic At Int of Acc H Ions in Matter 98 1 *** W Barth J Phys Conf Ser 1350:012096
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB236
About •	paper received ※ 20 May 2021 paper accepted ※ 13 August 2021 issue date ※ 17 August 2021
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MOPAB247	Multipacting Studies for the JAEA-ADS Five-Cell Elliptical Superconducting RF Cavities	multipactoring, electron, SRF, simulation	793
	B. Yee-Rendón, Y. Kondo, F.M. Maekawa, S.I. Meigo, J. Tamura JAEA/J-PARC, Tokai-mura, Japan E. Cicek KEK, Ibaraki, Japan
	The Five-cell Elliptical Superconducting Radio-Frequency Cavities (SRFC) provide the final acceleration in the JAEA-ADS linac (from 208 MeV to 1.5 GeV); thus, their performance is essential for the success of the JAEA-ADS project. After their optimization of the cavity geometry to achieve a high acceleration gradient with lower electromagnetic peaks, the next step in the R&D strategy is the accurate estimation of beam-cavity effects which can affect the performance of the cavities. To this end, multipacting studies were developed to investigate its effect in the cavity operation regimen and find countermeasures. The results of this study will help in the development of the SRFC models and in the consolidation of the JAEA-ADS project.
	Poster MOPAB247 [0.599 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB247
About •	paper received ※ 10 May 2021 paper accepted ※ 07 June 2021 issue date ※ 02 September 2021
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MOPAB255	Demonstration of a Novel Longitudinal Phase Space Linearization Method without Higher Harmonics	electron, gun, simulation, laser	805
	R. Stark University of Hamburg, Hamburg, Germany K. Flöttmann, M. Hachmann DESY, Hamburg, Germany F.J. Grüner Center for Free-Electron Laser Science, Universität Hamburg, Hamburg, Germany B. Zeitler CFEL, Hamburg, Germany
	Nonlinear correlations in the longitudinal phase space of electron bunches can be a decisive limitation to the achievable bunch length compression and attainability of small energy spreads. To overcome the restrictions imposed by nonlinear distortions, the longitudinal phase space distribution must be linearized. Previously, a novel linearization procedure based on the controlled expansion of the bunch between two radio frequency cavities operated at the same fundamental frequency has been presented in . A demonstration of this linearization method is presented in this work. B. Zeitler, K. Floettmann, and F. Grüner, "Linearization of the longitudinal phase space without higher harmonic field," Phys. Rev. ST Accel. Beams, vol. 18, p. 120102, 2015.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB255
About •	paper received ※ 18 May 2021 paper accepted ※ 02 June 2021 issue date ※ 12 August 2021
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MOPAB289	Machine Learning Training for HOM reduction and Emittance Preservation in a TESLA-type Cryomodule at FAST	HOM, emittance, electron, controls	916
	J.A. Diaz Cruz UNM-ECE, Albuquerque, USA J.A. Diaz Cruz, A.L. Edelen, B.T. Jacobson, J.P. Sikora SLAC, Menlo Park, California, USA D.R. Edstrom, A.H. Lumpkin, R.M. Thurman-Keup Fermilab, Batavia, Illinois, USA
	Low emittance electron beams are of high importance at facilities like the LCLS-II at SLAC. Emittance dilution effects due to off-axis beam transport for a TESLA-type cryomodule (CM) have been shown at the Fermilab Accelerator Science and Technology facility. The results showed the correlation between the electron beam-induced cavity high-order modes (HOMs) and submacropulse centroid slewing and oscillation downstream of the CM. Mitigation of emittance dilution can be achieved by reducing the HOM signals and the variances in the submacropulse beam positions downstream of the CM. Here we present a Machine Learning based optimization and model construction for HOM signal level reduction using Neural Networks and Gaussian Processes. To gather training data we performed experiments using single bunch and 50 bunch electron beams with charges up to 125 pC/b. We measured HOM signals of all cavities and beam position with a set of BPMs downstream of the CM. The beam trajectory was changed using V/H125 corrector set located upstream of the CM. The results presented here will inform the LCLS-II injector commissioning and will serve as a prototype for HOM reduction and emittance preservation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB289
About •	paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 24 August 2021
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MOPAB290	Machine Learning-Based LLRF and Resonance Control of Superconducting Cavities	controls, LLRF, simulation, SRF	920
	J.A. Diaz Cruz, S. Biedron, M. Martínez-Ramón UNM-ECE, Albuquerque, USA J.A. Diaz Cruz SLAC, Menlo Park, California, USA R. Pirayesh UNM-ME, Albuquerque, New Mexico, USA S. Sosa ODU, Norfolk, Virginia, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics, under award number DE-SC0019468. Superconducting radio frequency (SRF) cavities with high loaded quality factors that operate in continuous wave (CW) and low beam loading are sensitive to microphonics-induced detuning. Cavity detuning can result in an increase of operational power and/or in a cavity quench. Such SRF cavities have bandwidths on the order of 10 Hz and detuning requirements can be as tight as 10 Hz. Passive methods to mitigate vibration sources and their impact in the cryomodule/cavity environment are widely used. Active resonance control techniques that use stepper motors and piezoelectric actuators to tune the cavity resonance frequency by compensating for microphonics detuning have been investigated. These control techniques could be further improved by applying Machine Learning (ML), which has shown promising results in other particle accelerator control systems. In this paper, we describe a Low-level RF (LLRF) and resonance control system based on ML methods that optimally and adaptively tunes the control parameters. We present simulations and test results obtained using a low power test bench with a cavity emulator.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB290
About •	paper received ※ 03 June 2021 paper accepted ※ 11 June 2021 issue date ※ 27 August 2021
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MOPAB291	Design of Cavity BPM Pickup for EuPRAXIA@SPARC_LAB	coupling, GUI, pick-up, simulation	924
	Sh. Bilanishvili INFN/LNF, Frascati (Roma), Italy
	EuPRAXIA@SPARC_LAB will make available at LNF a unique combination offering three different options. A high-brightness electron beam with 1 GeV energy generated in a novel X-band RF linac; A PW-class laser system, and a compact light-source directly driven by a plasma accelerator. Plasma and conventional RF linac driven FEL provide beam with parameters of 30- 200pC charge range, 10-100Hz repetition rate, and 1 GeV electron energy. The control of the charge and the trajectory monitoring at a few pC and a few um is mandatory in this machine. Particularly in the plasma interaction region, where the pickup resolution under 1 um is required. As a possible solution, a cavity beam position monitor (cBPM) is proposed. A prototype in the C-band frequency range has been designed. The pickup was optimized for low charge and single-shot bunches. The poster presents the process to achieve the required specifications. The simulations were performed to study RF properties and the electromagnetic response of the device. Finally, the overall performance of the pickup is discussed, and theoretical resolution is approximated. https://www.researchgate.net/publication/335459394_From_SPARC_LAB_to_EuPRAXIASPARC_LAB **http://www.lnf.infn.it/sis/preprint/detail-new.php?id=5416
	Poster MOPAB291 [16.718 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB291
About •	paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 14 August 2021
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MOPAB322	Electronics for Bead-pull Measurement of Radio Frequency Accelerating Structures in LEHIPA	controls, software, rfq, interface	993
	S. Rosily, S. Krishnagopal Homi Bhbha National Institute (HBNI), DAE, Mumbai, India S. Krishnagopal, S. Singh BARC, Mumbai, India
	For carrying out bead-pull characterisation of RFQ and DTL at the Low Energy High Intensity Proton Accelerator of BARC, a controller for simultaneous motion of 64 axis, tuners or post couplers, was developed. Also, a bead motion controller with integrated phase measurement sensor was developed. The paper discusses the requirements of the system, the architecture of the control systems, operation and results. The results obtained from the sensor was compared to that obtained using an independent USB VNA. The advantages of the system especially with addition of internal phase measurement sensor including minimising position error, flexibility in beadpull to selectively increase resolution at specified locations and ease of implementing auto-tuning algorithms are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB322
About •	paper received ※ 20 May 2021 paper accepted ※ 24 May 2021 issue date ※ 21 August 2021
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MOPAB323	Commissioning of the LCLS-II Prototype HOM Detectors with Tesla-Type Cavities at Fast	HOM, electron, cryomodule, detector	996
	J.P. Sikora, J.A. Diaz Cruz, B.T. Jacobson SLAC, Menlo Park, California, USA J.A. Diaz Cruz UNM-ECE, Albuquerque, USA D.R. Edstrom, A.H. Lumpkin, P.S. Prieto, J. Ruan, R.M. Thurman-Keup Fermilab, Batavia, Illinois, USA
	Funding: Work supported by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy. Work supported by the U.S. Department of Energy, contract DE-AC02-76SF00515. Experiments at the Fermilab Accelerator Science and Technology (FAST) facility detected electron beam-induced high order mode (HOM) signals from Tesla superconducting cavities. This paper describes some of the signal detection hardware used in this experiment, as well as measurements of the HOM signal magnitude versus beam trajectory. These measurements were made both with a single bunch and with a train of 50 bunches at bunch charges from 400 pC/b down to 10 pC/b. The detection hardware is designed for use with the Tesla superconducting cavities of LCLS-II at SLAC** and is based on a prototype already in use at Fermilab. The HOM signal passes through a bandpass filter that is centered on several cavity dipole modes and a zero bias Schottky diode detects its magnitude. Direct comparisons were made between the FNAL chassis and the SLAC prototype for identical beam steering conditions. To support measurements with bunch charges as low as 10 pC, the SLAC detector has RF amplification between the bandpass filter and the diode detector. With this hardware, usable HOM signal measurements are obtained with a single bunch of 10 pC in cryomodule cavities as will be needed for LCLS-II.
	Poster MOPAB323 [2.076 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB323
About •	paper received ※ 17 May 2021 paper accepted ※ 07 June 2021 issue date ※ 25 August 2021
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MOPAB329	Operations of Copper Cavities at Cryogenic Temperatures	coupling, linac, cryogenics, ECR	1020
	H. Wang, U. Ratzinger, M. Schuett IAP, Frankfurt am Main, Germany
	How the anomalous skin effect by copper affects the efficiency of copper- cavities will be studied in the experiment, especially at lower temperatures. The accurate quality factor Q and resonant frequency of three coaxial cavities will be measured over the temperature range from 300 to 22 K. The three coaxial cavities have the same structure, but different lengths, which correspond to resonant frequencies: around 100 MHz, 220 MHz and 340 MHz. The motivation is to check the feasibility of an efficient pulsed, liquid nitrogen cooled ion linac.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB329
About •	paper received ※ 19 May 2021 paper accepted ※ 07 June 2021 issue date ※ 24 August 2021
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MOPAB330	Production and Performance Evaluation of a Compact Deflecting Cavity to Measure the Bunch Length in the cERL	resonance, vacuum, coupling, impedance	1023
	D. Naito, Y. Honda, T. Miyajima, N. Yamamoto KEK, Ibaraki, Japan
	At the KEK compact energy recovery linac, we try to generate an infrared free-electron laser (FEL). To generate the FEL, an electron bunch should be compressed along the longitudinal direction. The measurement of the bunch length is key to optimize the bunch compression. We plan to measure the bunch length by deflecting cavities in the burst mode. The deflecting cavities are required to be a time resolution of 33 fs in order to not only measure the bunch length but also resolve the structure inside the electron bunch. To achieve the requirement, we developed a c-band cavity whose RF input port is compact. The deflecting cavity is a single cell and normal conducting cavity. The deflection mode of the cavity is TM110. The 12 cavities will be located at the exit of undulators. In this presentation, we explain the design of our cavity and report the production of the first cavity. We also report the evaluation of the resonance frequency, the unloaded Q and the external Q of the cavity. From the measurements and simulations, the R/Q is estimated to be 1 mega orms. The time resolution of the cavity is expected to be 400 fs when the input RF power is 1 kW and the beam energy is 20 MeV.
	Poster MOPAB330 [12.920 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB330
About •	paper received ※ 12 May 2021 paper accepted ※ 08 June 2021 issue date ※ 15 August 2021
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MOPAB331	Design Consideration of a Longitudinal Kicker Cavity for Compensating Transient Beam Loading Effect in Synchrotron Light Sources	kicker, resonance, coupling, impedance	1027
	D. Naito, S. Sakanaka, T. Takahashi, N. Yamamoto KEK, Ibaraki, Japan T. Yamaguchi Sokendai, Ibaraki, Japan
	In ultra-low-emittance synchrotron light sources, bunch-lengthening using the combination of main and harmonic cavities is limited by the transient beam-loading (TBL) effect which is caused by gaps in the fill pattern. To manage this effect, we proposed a TBL compensation technique using a wide-band longitudinal kicker cavity. In the future KEK-LS storage ring, for example, the kicker cavity should provide a compensation voltage of 50 kV with a -3dB bandwidth (BW) of about 5 MHz, as well as its higher-order modes (HOM) should be damped sufficiently. In this presentation, we report our conceptual design of the kicker cavity. We employed the single-mode (SM) cavity concept so that harmful HOMs are dumped by rf absorbers on the beam pipes. The distinctive feature of the SM cavity is its simple structure since it has no HOM damper on the cavity. Another feature is its low R/Q by which the TBL effect in the kicker cavity itself can be reduced significantly. We employed a frequency of 1.5 GHz (third-harmonic) and R/Q of 60 orms through optimizations. Using this kicker cavity with a double rf system, a bunch lengthening by a factor of 4.3 (i.e., 40.9 ps) is expected for the KEK-LS case. N.Yamamoto et al., Phys. Rrev. Acc. Beams 21, 012001 (2018)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB331
About •	paper received ※ 19 May 2021 paper accepted ※ 11 June 2021 issue date ※ 10 August 2021
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MOPAB332	Design of 4th Harmonic RF Cavities for ESRF-EBS	HOM, SRF, impedance, coupling	1031
	A. D’Elia, J. Jacob, V. Serrière, X.W. Zhu ESRF, Grenoble, France
	Funding: European Union’s Horizon 2020 research and innovation program under grant #871072 An active 4th harmonic RF system for bunch lengthening is under study at the ESRF to improve the performance of the new EBS storage ring, mainly for few bunch operation with high currents per bunch, by reducing Touschek and intrabeam scattering, thereby increasing the lifetime and limiting the emittance growth. It will also reduce impedance heating of the vacuum chambers. The 4th Harmonic 1.41 GHz normal conducting cavity design takes inspiration from the KEK idea of using a TM020 mode exhibiting a reduced R/Q but a higher unloaded Q with respect to TM010. We propose to use multicell cavities for their compactness, the reduced number of required ancillaries and the ease of control for a reduced number of cavities. The drawback is the complexity of the model and the necessity to damp the lower order TM010 mode (LOM) as well as the higher order modes (HOM). The RF design of a 4th harmonic multicell damped cavity will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB332
About •	paper received ※ 19 May 2021 paper accepted ※ 17 August 2021 issue date ※ 18 August 2021
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MOPAB333	ESRF-EBS 352 MHz HOM Damped RF Cavities	SRF, impedance, HOM, MMI	1034
	A. D’Elia, J. Jacob, V. Serrière ESRF, Grenoble, France
	For the new ESRF-EBS Storage Ring (SR), HOM damped RF cavities were needed to cope with the reduced thresholds for Longitudinal Coupled Bunch Instabilities (LCBI). The 352 MHz cavities were designed at the ESRF based on an improved version of the 500 MHz EU/ALBA/BESSY structures. A short description of the cavity design will be presented as well as an overview of the fabrication, the preparation and the performance of 13 such cavities for the ESRF-EBS SR. A study of the impedance of a whole cavity equipped with its ancillaries (HOM absorbers, ion pump and tuner) will be presented. One of the three HOM absorbers, the smaller one on top of the cavity, was finally not installed on the machine. The reasons and a detailed analysis in terms of HOM impedances that justifies this choice will be reported.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB333
About •	paper received ※ 19 May 2021 paper accepted ※ 07 June 2021 issue date ※ 23 August 2021
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MOPAB334	Status and Recent Development of FAIR Ring RF Systems	LLRF, power-supply, operation, status	1037
	U. Laier, R. Balß, C. Christoph, M. Frey, P. Hülsmann, H. Klingbeil, H.G. König, D.E.M. Lens, J.S. Schmidt, A. Stuhl, K.G. Thomin, T. Winnefeld GSI, Darmstadt, Germany H. Klingbeil TEMF, TU Darmstadt, Darmstadt, Germany
	Funding: GSI Helmholtzzentrum für Schwerionenforschung GmbH Five different Ring RF Systems are required for the operation of FAIR (Facility for Antiproton and Ion Research). These systems have to operate at frequencies between 310 kHz and 3.2 MHz, with gap voltages up to 40 kVp and duty cycles from 5·10^-4 up to cw. All systems will be realized using inductively loaded (ferrite or magnetic alloy) cavities driven by tetrode-based amplifiers fed by switch-mode power supplies. To stabilize the amplitude, resonance frequency and phase, versatile digital feedback and feedforward control will be used. This contribution will present the latest development on the power part and the LLRF of the four RF systems of the SIS100 (SIS100 Acceleration, SIS100 Bunch Compression, SIS100 Barrier Bucket and SIS100 Longitudinal Feedback) as well as the CR Debuncher system which is part of the Collector Ring. The progress of these systems varies by a large degree. This note will give an overview regarding the status of the design, procurement, realization, testing, optimization, commissioning and preparation for installation of these RF systems.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB334
About •	paper received ※ 18 May 2021 paper accepted ※ 07 June 2021 issue date ※ 17 August 2021
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MOPAB337	Design Study of the Spiral Buncher Cavities for the High Current Injector at IUAC	linac, impedance, bunching, rfq	1048
	S. Kedia, R. Ahuja, R. Mehta, C.P. Safvan IUAC, New Delhi, India
	Two high energy beam transport (HEBT) cavities have been designed to provide the longitudinal beam bunching between drift tube linac and superconducting super-buncher of the superconducting linear (SC-LINAC) accelerator. The spiral type cavities were chosen over standard quarter wave-type geometry due to its higher shunt impedance. The TRACE-3D ion-optical codes have been used to determine the bunching voltage and physical location of the cavities. The two-gap RF cavity requires 80 kV/gap to provide the longitudinal beam bunching at the entrance of the superconducting buncher. The CST-MWS simulations were performed to design the spiral type bunching cavities. The various parameters including shunt impedance, quality factor, average accelerating field, and total power loss were determined using CST-MWS simulations. The ratio of drift tube radius to the gap was optimized to achieve the maximum effective electric field with minimum field penetration within the gap. The SolidWorks software has been used to prepare a mechanical model for the fabrication.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB337
About •	paper received ※ 15 May 2021 paper accepted ※ 26 May 2021 issue date ※ 01 September 2021
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MOPAB339	Design Of An X-band 3MeV Standing-wave Accelerating Structure with Nose-cone Structure Made From Two Halves	coupling, impedance, electron, bunching	1051
	F. Liu, H.B. Chen, J. Shi, C.-X. Tang, H. Zha TUB, Beijing, People’s Republic of China
	This work presents an X-band 3MeV standing-wave accelerating structure with nose cones made from two halves. Milling two longitudinally split halves is one economic method to manufacture accelerating structure for decrease of welding, with increasing the difficulty in machining. This linear accelerator includes 4 buncher cavities and 4 accelerating cavities, and nose cone is applied to achieve high shunt impedance. A technical prototype is under fabrication to bring two milled halves manufacture way into practical application.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB339
About •	paper received ※ 19 May 2021 paper accepted ※ 26 May 2021 issue date ※ 17 August 2021
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MOPAB341	First C-Band High Gradient Cavity Testing Results at LANL	proton, GUI, operation, klystron	1057
	E.I. Simakov, R.L. Fleming, D. Gorelov, T.A. Jankowski, M.F. Kirshner, J.W. Lewellen, J.D. Pizzolatto, M.E. Schneider, T. Tajima LANL, Los Alamos, New Mexico, USA X. Lu, E.A. Nanni, S.G. Tantawi SLAC, Menlo Park, California, USA M.E. Middendorf ANL, Lemont, Illinois, USA
	Funding: Los Alamos National Laboratory LDRD Program. This poster will report the results of high gradient testing of the two proton β=0.5 C-band accelerating cavities. The cavities for proton acceleration were fabricated at SLAC and tested at high gradient C-band accelerator test stand at LANL. One cavity was made of copper, and the second was made of a copper-silver alloy. LANL test stand was constructed around a 50 MW, 5.712 GHz Canon klystron and is capable to provide power for conditioning single cell accelerating cavities for operation at surface electric fields up to 300 MV/m. These β=0.5 C-band cavities were the first two cavities tested on LANL C-band test stand. The presentation will report achieved gradients, breakdown probabilities, and other characteristics measured during the high power operation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB341
About •	paper received ※ 19 May 2021 paper accepted ※ 25 May 2021 issue date ※ 15 August 2021
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MOPAB342	Design, Fabrication, and Commissioning of the Mode Launchers for High Gradient C-Band Cavity Testing at LANL	GUI, klystron, simulation, MMI	1060
	E.I. Simakov, J.E. Acosta, D. Gorelov, M.F. Kirshner, J.W. Lewellen LANL, Los Alamos, New Mexico, USA P. Borchard Dymenso LLC, San Francisco, USA M.E. Schneider MSU, East Lansing, Michigan, USA
	Funding: Los Alamos National Laboratory LDRD Program. This poster will report on the design, fabrication, and operation status of the new high gradient C-band TM01 mode launchers for the high gradient C-band test stand at LANL. Modern applications require accelerators with optimized cost of construction and operation, naturally calling for high-gradient acceleration. At LANL we commissioned a test stand powered by a 50 MW, 5.712 GHz Canon klystron. The test is capable of conditioning single cell accelerating cavities for operation at surface electric fields up to 300 MV/m. The rf field is coupled into the cavity from a WR187 waveguide through a mode launcher that converts the fundamental mode of the rectangular waveguide into the TM01 mode of the circular waveguide. Several designs for mode launchers were considered and the final design was chosen based on a compromise between the field enhancements, bandwidth, and simplicity and cost of fabrication. Four mode launchers were fabricated and cold-tested. Two mode launchers with the best transmission characteristics were installed and conditioned to high power. The presentation will report achieved gradients, breakdown probabilities, and other characteristics measured during operation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB342
About •	paper received ※ 19 May 2021 paper accepted ※ 25 May 2021 issue date ※ 27 August 2021
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MOPAB343	Optimization of the Parasitic-Mode Damping on the 1.5 GHz TM020-type Harmonic Cavity	damping, impedance, coupling, simulation	1064
	T. Yamaguchi Sokendai, Ibaraki, Japan D. Naito, S. Sakanaka, T. Takahashi, N. Yamamoto KEK, Ibaraki, Japan
	Bunch-lengthening harmonic cavity is one of the essential tools to mitigate the intrabeam scattering in the 4th-generation synchrotron light sources. For this purpose, we proposed a normal-conducting 1.5 GHz harmonic cavity* of TM020-type*. Thanks to its low R/Q (68 ohms) and high unloaded Q (34, 000), bunch gap transient in the harmonic cavity can be reduced to ~20% as compared to that in a typical TM010 cavity. Furthermore, harmful parasitic modes in this cavity can be heavily damped by installing ferrites where no magnetic fields of TM020-mode exist. However, some of the parasitic modes, e.g. TM021 and TM120 modes, are difficult to damp because their field patterns are similar to that of the TM020 mode. To damp such modes effectively, we optimized the cavity inner shape by tailoring the curvature at the cavity equator, the shape of the nose cones, and introducing "bumps" on the inner wall. Our goals of the coupling impedances are fxR < 2.4[kohm GHz] and RT < 23 kohm/m in the longitudinal and the transverse planes, respectively. As a result of optimization, we almost achieved these goals. To confirm our simulation results, fabrication of a low-power test cavity is in progress. N . Yamamoto et al., Phys. Rev. Acc. Beams 21, 012001 (2018). ** H. Ego et al., Proc. of the 11th Annual Meeting of Particle Accelerator Society of Japan (PASJ2014), MOOL14 (2014).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB343
About •	paper received ※ 19 May 2021 paper accepted ※ 26 May 2021 issue date ※ 27 August 2021
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MOPAB344	Machine Learning Models for Breakdown Prediction in RF Cavities for Accelerators	operation, network, vacuum, linac	1068
	C. Obermair, A. Apollonio, T. Cartier-Michaud, N. Catalán Lasheras, L. Felsberger, W.L. Millar, W. Wuensch CERN, Geneva, Switzerland C. Obermair, F. Pernkopf TUG, Graz, Austria
	Radio Frequency (RF) breakdowns are one of the most prevalent limits in RF cavities for particle accelerators. During a breakdown, field enhancement associated with small deformations on the cavity surface results in electrical arcs. Such arcs degrade a passing beam and if they occur frequently, they can cause irreparable damage to the RF cavity surface. In this paper, we propose a machine learning approach to predict the occurrence of breakdowns in CERN’s Compact LInear Collider (CLIC) accelerating structures. We discuss state-of-the-art algorithms for data exploration with unsupervised machine learning, breakdown prediction with supervised machine learning, and result validation with Explainable-Artificial Intelligence (Explainable AI). By interpreting the model parameters of various approaches, we go further in addressing opportunities to elucidate the physics of a breakdown and improve accelerator reliability and operation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB344
About •	paper received ※ 20 May 2021 paper accepted ※ 16 July 2021 issue date ※ 10 August 2021
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MOPAB347	High Power Coupler Conditioning for bERLinPro Energy Recovery Linac Injector	booster, vacuum, SRF, MMI	1080
	A. Neumann, W. Anders, F. Göbel, A. Heugel, S. Klauke, J. Knobloch, M. Schuster, Y. Tamashevich HZB, Berlin, Germany
	Funding: The work is funded by the Helmholtz-Association, BMBF, the state of Berlin and HZB. Helmholtz Zentrum Berlin is currently finalizing the construction of the demonstrator Energy Recovery Linac bERLinPro . The first part, which will be commissioned, will be the injector consisting of a superconducting RF (SRF) photo-injector (Gun) and a Booster module made up of three two cell SRF cavities. For the latter the 2.3 MeV beam from the gun needs to be accelerated to 6.5 MeV, whereas one Booster cavity will be operated in zero-crossing mode for bunch-shortening. Thus, for the final stage with a 100 mA beam, the twin power couplers of the Booster cavity need to deliver up to 120 kW in travelling continous wave (CW) mode at 1.3 GHz each. To achieve that, a dedicated coupler conditioning setup was installed and commissioned. Here, we will present the first conditioning results with the bERLinPro Booster fundamental power couplers in pulsed and CW regime. M. Abo-Bakr et al., in Proc. 9th Int. Particle Accelerator Conf. (IPAC’18), Vancouver, BC, Canada, Apr. 4,, pp. 4127-4130, doi:10.18429/JACoW-IPAC2018-THPMF034
	Poster MOPAB347 [3.256 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB347
About •	paper received ※ 18 May 2021 paper accepted ※ 08 June 2021 issue date ※ 23 August 2021
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MOPAB350	RF Buncher Cavity for Polarized He-3 Beam at BNL	simulation, alignment, insertion, booster	1090
	T. Kanesue, S.M. Trabocchi BNL, Upton, New York, USA A. Murata TIT, Tokyo, Japan
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. A 100.625 MHz quarter wave resonator type rf buncher cavity was fabricated for polarized He-3 spin rotator beam line at BNL. This cavity will be installed in the existing EBIS-To-Booster beam line to provide effective voltage of more than 40 kV for 2 MeV/u 3He²⁺ beam. This cavity has a large drift tube inner diameter of 80 mm and small gap length of 5 mm. The buncher consists of 3 sections, which are a cavity main body including drift tube, stem, and inner wall, a lid with a power coupler, and a lid with an inductive tuner. The main body was machined from a bulk copper only by CNC machining. The result of low power test agreed well with rf simulation without any alignment. The difference between measured and calculated resonant frequency was <0.1 %, and measured Q value was 92 % of that in simulation. The cavity rf design and test results will be shown.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB350
About •	paper received ※ 26 May 2021 paper accepted ※ 28 May 2021 issue date ※ 25 August 2021
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MOPAB353	Design of a compact Ka-Band Mode Launcher for High-gradient Accelerators	coupling, simulation, quadrupole, accelerating-gradient	1100
	G. Torrisi, G.S. Mauro, G. Sorbello INFN/LNS, Catania, Italy M. Behtouei, L. Faillace, B. Spataro, A. Variola INFN/LNF, Frascati, Italy V.A. Dolgashev SLAC, Menlo Park, California, USA L. Faillace, M. Migliorati Sapienza University of Rome, Rome, Italy M. Migliorati INFN-Roma1, Rome, Italy J.B. Rosenzweig UCLA, Los Angeles, California, USA G. Sorbello University of Catania, Catania, Italy
	In this work, we present the RF design of a table-top Ka-Band mode launcher operating at 35.98 GHz. The structure consists of a symmetrical 4-port WR28 rectangular-TE10-to-circular-TM01 mode converter that is used to couple a peak output RF power of 5 MW (pulse length up to 50 ns and repetition rate up to 100 Hz) in Ka-Band linear accelerator able to achieve very high accelerating gradients (up to 200 MV/m). Numerical simulations have been carried out with the 3D full-wave commercial simulator Ansys HFSS in order to obtain a preliminary tuning of the accelerating field flatness at the operating frequency f0=35.98 GHz. The main RF parameters, such as reflection coefficient, transmission losses, and conversion efficiency are given together with a verification of the field azimuthal symmetry which avoids dipole and quadrupole deflecting modes. To simplify future manufacturing, reduce fabrication costs, and also reduce the probability of RF breakdown, the proposed new geometry has "open" configuration. This geometry eliminates the flow of RF currents through critical joints and allows this device to be milled from metal blocks.
	Poster MOPAB353 [3.131 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB353
About •	paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 11 August 2021
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MOPAB355	Multi-Objective Optimization of RF Structures	impedance, controls, RF-structure, ECR	1103
	S.J. Smith, R. Apsimon, G. Burt, M.J.W. Southerby Cockcroft Institute, Lancaster University, Lancaster, United Kingdom S. Setiniyaz Cockcroft Institute, Warrington, Cheshire, United Kingdom S. Setiniyaz Lancaster University, Lancaster, United Kingdom
	In this work, we apply multi-objective optimization methods to single-cell cavity models generated using non-uniform rational basis splines (NURBS). This modeling method uses control points and a NURBS to generate the cavity geometry, which allows for greater flexibility in the shape, leading to improved performance. Using this approach and multi-objective genetic algorithms (MOGAs) we find the Pareto frontiers for the typical key quantities of interest (QoI) including peak fields, shunt impedance and the modified Poynting vector. Visualizing these results becomes increasingly more difficult as the number of objectives increases, therefore, in order to understand these frontiers, we provide several techniques for analyzing, visualizing and using multi-dimensional Pareto fronts specifically for RF cavity design.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB355
About •	paper received ※ 19 May 2021 paper accepted ※ 15 July 2021 issue date ※ 01 September 2021
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MOPAB356	The ESS MEBT RF Buncher Cavities Conditioning Process	vacuum, controls, MEBT, EPICS	1107
	I. Bustinduy, N. Garmendia, P.J. González, A. Kaftoosian, S. Masa, I. Mazkiaran, L.C. Medina, J.L. Muñoz ESS Bilbao, Zamudio, Spain J. Etxeberria, J.P.S. Martins ESS, Lund, Sweden
	Funding: This work is part of FEDER-TRACKS project, co-funded by the European Regional Development Fund (ERDF) . As part of the 5 MW European Spallation Source (ESS), the Medium Energy Beam Transport (MEBT) was designed, assembled, and installed in the tunnel since May 2020 by ESS-Bilbao. This section of the accelerator is located between the Radio Frequency Quadrupole (RFQ) and the Drift Tube Linac (DTL). The main purpose of the MEBT is to match the incoming beam from the RFQ both transversely and longitudinally into the DTL. The longitudinal matching is achieved by three 352.209 MHz RF buncher cavities. In this paper, we focus on the RF conditioning process for each set of power coupler and buncher cavity. For this purpose, different tools were developed on EPICS and Python as well as electronics hardware such as Fast Interlock Module (FIM) and timing system. These tools served to automatize both the cavity frequency tuning and the power ramp-up process and will be described in detail in the following sections.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB356
About •	paper received ※ 18 May 2021 paper accepted ※ 09 June 2021 issue date ※ 17 August 2021
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MOPAB357	The New Design of the RF System for the SPS-II Light Source	storage-ring, booster, impedance, linac	1110
	N. Juntong, T. Chanwattana, S. Chunjarean, S. Krainara, T. Phimsen, T. Pulampong SLRI, Nakhon Ratchasima, Thailand K. Manasatitpong Synchrotron Light Research Institute (SLRI), Muang District, Thailand
	The new light source facility in Thailand, SPS-II, is a ring-based 3 GeV light source with a circumference of approximately 330 m. The target stored beam current is 300 mA with an emittance of below 1.0 nm rad. The injector has been changed from a full energy linac to a booster injector with 150 MeV linac. The main RF frequency has been reconsidered to a low-frequency range at 119 MHz. Low frequency is chosen with the benefit of low RF voltage for a high RF acceptance together with experience with the present ring RF system of 118 MHz. Details of RF frequency consideration will be discussed. The requirements and details of the RF systems in the booster ring and the storage ring will be presented.
	Poster MOPAB357 [1.696 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB357
About •	paper received ※ 17 May 2021 paper accepted ※ 08 June 2021 issue date ※ 10 August 2021
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MOPAB358	Design and Measurement of the 1.4 GHz Cavity for LEReC Linac	electron, resonance, GUI, HOM	1113
	B.P. Xiao, J.C. Brutus, J.M. Fite, K. Hamdi, D. Holmes, K. Mernick, K.S. Smith, J.E. Tuozzolo, T. Xin, A. Zaltsman BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. The Low Energy RHIC electron Cooler (LEReC) is the first electron cooler based on rf acceleration of electron bunches. To further improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, a normal conducting RF cavity at 1.4 GHz was designed and fabricated for the LINAC that will provide longer electron bunches for the LEReC. It is a single-cell cavity with an effective cavity length shorter than half of the 1.4 GHz wavelength. This cavity was fabricated and tested on-site at BNL to verify RF properties, i.e. the resonance frequency, FPC coupling strength, tuner system performance, and high power tests. In this paper, we report the RF test results for this cavity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB358
About •	paper received ※ 17 May 2021 paper accepted ※ 25 June 2021 issue date ※ 10 August 2021
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MOPAB359	Operational Experience and Redesign of the Tuner without Spring Fingers for the LEReC Warm Cavity	operation, vacuum, SRF, electron	1116
	B.P. Xiao, J.M. Brennan, J.C. Brutus, K. Mernick, S. Polizzo, S.K. Seberg, F. Severino, K.S. Smith, A. Zaltsman BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. A folded coaxial tuner without spring fingers was designed for the Low Energy RHIC electron Cooler (LEReC) 2.1 GHz warm cavity. During RHIC run 2019, this tuner was found to cause cavity trips via different failure modes. After analyzing these failure modes, a new straight coaxial tuner without spring fingers was proposed and was installed. We show the operational experience of the new tuner in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB359
About •	paper received ※ 17 May 2021 paper accepted ※ 25 June 2021 issue date ※ 12 August 2021
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MOPAB361	Threshold in Filling Failure of RF Cavity Caused by Beam Loading in Multipactor	multipactoring, simulation, electron, experiment	1122
	J. Pang USTC/NSRL, Hefei, Anhui, People’s Republic of China Y. Dong Institute of Applied Physics and Computational Mathematics, People’s Republic of China Y. Du Institute of Fluid Physics,, China Academy of Engineering Physics, Mianyang, People’s Republic of China
	Funding: NSFC A pulsed RF cavity would be heavily detuned caused by beam loading of multipactor current in the RF filling process. Multipactor zone would be expended by several times than that in static states with assumptions of fixed voltage and no beam loading. The dynamic of multipactor in the RF filling process was simulated by coupling with parameters of external circuit with the developed simulation code, and test in experiments with a parallel-plate resonator. Threshold of RF voltage, which means the lower boundary of peak voltage of multipactor zone, had been quantified with different cavity parameters. When we increased the gap length, the measured threshold became larger due to the ionization in background gas. Then the secondary emission factor would be increased in simulation for consistence with the experiment results. Additionally, some multipactor phenomenon could not be predicted precisely because the simulation code did not take account of ionization. The hysteresis of phase and energy of ionization electrons would be a new driving factor for the growth of multipactor in certain conditions.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB361
About •	paper received ※ 19 May 2021 paper accepted ※ 24 May 2021 issue date ※ 15 August 2021
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MOPAB363	Design, Characteristics and Dynamic Properties of Mobile Plunger-based Frequency Tuning System for Coaxial Half Wave Resonators	operation, experiment, controls, resonance	1129
	D. Bychanok, S. Huseu, S.A. Maksimenko, A.E. Sukhotski INP BSU, Minsk, Belarus A.V. Butenko, E. Syresin JINR, Dubna, Moscow Region, Russia M. Gusarova, M.V. Lalayan, S.M. Polozov MEPhI, Moscow, Russia V.S. Petrakovsky, A.I. Pokrovsky, A. Shvedov, S.V. Yurevich Physical-Technical Institute of the National Academy of Sciences of Belarus, Minsk, Belarus Y. Tamashevich HZB, Berlin, Germany
	The practical realization of a prototype of the frequency tuning system (FTS) for coaxial half-wave cavities (HWR) for the Nuclotron-based Ion Collider fAcility (NICA) injector is presented. The impact of FTS on electromagnetic parameters of copper HWR prototype is experimentally studied and discussed. The most important parameters like tuning range, tuning sensitivity, the dependence of the resonant frequency on the position of the plungers are estimated. The effective operation algorithms of the proposed FTS are discussed and analyzed. The dynamic characteristics of FTS are investigated and showed the ability to adjust the frequency with an accuracy of about 70 Hz.
	Poster MOPAB363 [3.597 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB363
About •	paper received ※ 18 May 2021 paper accepted ※ 09 June 2021 issue date ※ 28 August 2021
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MOPAB365	Construction and First Test Results of the Barrier and Harmonic RF Systems for the NICA Collider	collider, vacuum, injection, electron	1136
	A.G. Tribendis, Y.A. Biryuchevsky, K.N. Chernov, A.N. Dranitchnikov, E. Kenzhebulatov, A.A. Kondakov, A.A. Krasnov, Ya.G. Kruchkov, S.A. Krutikhin, G.Y. Kurkin, A.M. Malyshev, A.Yu. Martynovsky, N.V. Mityanina, S.V. Motygin, A.A. Murasev, V.N. Osipov, V.M. Petrov, E. Pyata, E. Rotov, V.V. Tarnetsky, I.A. Zapryagaev, A.A. Zhukov BINP SB RAS, Novosibirsk, Russia O.I. Brovko, A.M. Malyshev, I.N. Meshkov, E. Syresin JINR, Dubna, Moscow Region, Russia I.N. Meshkov Saint Petersburg State University, Saint Petersburg, Russia E. Rotov NSU, Novosibirsk, Russia A.G. Tribendis NSTU, Novosibirsk, Russia A.V. Zinkevich Triada-TV, Novosibirsk, Russia
	This paper reports on the design features and construction progress of the three RF systems for the NICA collider being built at JINR, Dubna. Each of the two collider rings has three RF systems named RF1 to 3. RF1 is a barrier bucket system used for particles capturing and accumulation during injection, RF2 and 3 are resonant systems operating at 22nd and 66th harmonics of the revolution frequency and used for the 22 bunches formation. The RF systems are designed and produced by Budker INP. Solid state RF power amplifiers developed by the Triada-TV company, Novosibirsk, are used for driving the RF2 and three cavities. Two RF1 stations were already delivered to JINR, the prototypes of the RF2 and 3 stations were built and successfully tested at BINP. Series production of all eight RF2 and sixteen RF3 stations is in progress. The design modifications and test results are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB365
About •	paper received ※ 18 May 2021 paper accepted ※ 24 May 2021 issue date ※ 19 August 2021
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MOPAB366	Improving Magnetic Materials for RCS Cavity Tuners	solenoid, simulation, booster, synchrotron	1139
	R.L. Madrak, N.M. Curfman, G.V. Romanov, C.-Y. Tan, I. Terechkine Fermilab, Batavia, Illinois, USA G. Das, A.K. Samanta Ceramic Magnetics, Inc., National Magnetics Group, Inc., Bethlehem, USA
	Funding: United States Department of Energy, Contract No. DE-AC02-07CH11359 Within the Lab Directed R&D Program at Fermilab, and in partnership with National Magnetics, we have recently begun to study and attempt to improve the loss parameter in garnet material. This could be used for fast tuner applications such as in rapid cycling synchrotrons.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB366
About •	paper received ※ 19 May 2021 paper accepted ※ 25 May 2021 issue date ※ 23 August 2021
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MOPAB371	A Coupon Tester for Normal Conducting High-Gradient Materials	coupling, vacuum, RF-structure, klystron	1147
	J.W. Lewellen, D. Gorelov, D. Perez, E.I. Simakov LANL, Los Alamos, New Mexico, USA M.E. Schneider Michigan State University, East Lansing, Michigan, USA
	Funding: Los Alamos National Laboratory LDRD Program A coupon tester is an RF structure used to subject a material sample to very high RF fields, with the fields on the sample, or coupon, being higher than elsewhere in the cavity. To date, most such cavities were originally intended to explore the RF properties of superconducting materials, and can expose the sample to strong magnetic fields, but weak to no electric fields. As part of a program to develop materials and structures for high-gradient (> 100 MV/m), low-breakdown-rate normal-conducting accelerators, we have designed a C-band (5.712 GHz) cavity intended to subject samples to both magnetic and electric fields comparable to those experienced in high-gradient structure designs, using a TM-mode cavity; the electric and magnetic fields along the sample coupon can be directly compared to the fields on the iris of high-gradient structures. This poster will present the design criteria for our coupon tester cavity, nominal operating parameters, and our structure concept. The cavity design will be refined over the next several months, and will be constructed and in service near the start of 2022.
	Poster MOPAB371 [0.764 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB371
About •	paper received ※ 17 May 2021 paper accepted ※ 26 May 2021 issue date ※ 25 August 2021
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MOPAB374	Creating Exact Multipolar Fields in Accelerating RF Cavities via an Azimuthally Modulated Design	simulation, quadrupole, dipole, collider	1154
	L.M. Wroe, S.L. Sheehy JAI, Oxford, United Kingdom R. Apsimon Cockcroft Institute, Lancaster University, Lancaster, United Kingdom M. Dosanjh CERN, Meyrin, Switzerland S.L. Sheehy The University of Melbourne, Melbourne, Victoria, Australia
	In this paper, we present a novel method for designing RF structures with specifically tailored multipolar field contributions. This has a range of applications, including the suppression of unwanted multipolar fields or the introduction of wanted terms, such as for quadrupole focusing. In this article, we outline the general design methodology and compare the expected results to 3D CST simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB374
About •	paper received ※ 19 May 2021 paper accepted ※ 08 June 2021 issue date ※ 10 August 2021
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MOPAB376	Design and Fabrication of a Quadrupole Resonator for SRF R&D	SRF, quadrupole, niobium, radio-frequency	1158
	R. Monroy-Villa, W. Hillert, M. Wenskat University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany S. Gorgi Zadeh, P. Putek Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany R. Monroy-Villa, D. Reschke, J.H. Thie DESY, Hamburg, Germany
	As Nb superconducting radio-frequency (SRF) cavities are now approaching the theoretical limits of the material, a variety of different surface treatments have been developed to further improve their performance; although no fully understood theory is yet available. Small superconducting samples are studied to characterize their material properties and their evolution under different surface treatments. To study the RF properties of such samples under realistic SRF conditions at low temperatures, a test cavity called quadrupole resonator (QPR) is currently being fabricated. In this work we report the status of the QPR at Universität Hamburg in collaboration with DESY. Our device is based on the QPRs operated at CERN and at HZB and its design will allow for testing samples under cavity-like conditions, i.e., at temperatures between 2K and 8 K, under magnetic fields up to 120mT and with operating frequencies of 433 MHz, 866 MHz and 1300 MHz. Fabrication tolerance studies on the electromagnetic field distributions and simulations of the static detuning of the device, together with a status report on the current manufacturing process, will be presented.
	Poster MOPAB376 [1.119 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB376
About •	paper received ※ 26 May 2021 paper accepted ※ 09 June 2021 issue date ※ 23 August 2021
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MOPAB379	Topological Optimization on SRF Cavities for Nuclear and High Energy Physics	niobium, superconducting-cavity, radiation, simulation	1162
	H. Gassot Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
	Topology optimization has been developed for more than twenty years. The progress of additive manufacturing boosts the development in topological optimization since the design can be completely innovated and realized by 3D printing. The potential for cost reductions thanks to weight minimization give an interesting perspective for the small production of niobium superconducting radio-frequency cavities, commonly used in accelerators. The traditional manufacturing technologies of cavities are based on multi-stage processes while additive manufacturing technologies can built fully functional parts in a single operation. For modern accelerators that use superconducting linac, including energy recovery linacs (ERLs), it is particularly important to know the perspectives of additive manufacturing for SRF cavities. In this paper, we try to build a preliminary perception of topological optimization in superconducting cavities manufacturing innovation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB379
About •	paper received ※ 11 May 2021 paper accepted ※ 17 August 2021 issue date ※ 17 August 2021
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MOPAB380	Status and Progress of the RF System for High Energy Photon Source	photon, storage-ring, booster, low-level-rf	1165
	P. Zhang, J. Dai, Z.W. Deng, L. Guo, T.M. Huang, D.B. Li, J. Li, Z.Q. Li, H.Y. Lin, Y.L. Luo, Q. Ma, F. Meng, Z.H. Mi, Q.Y. Wang, X.Y. Zhang, F.C. Zhao, H.J. Zheng IHEP, Beijing, People’s Republic of China
	Funding: This work was supported in part by High Energy Photon Source, a major national science and technology infrastructure in China and in part by the Chinese Academy of Sciences. High Energy Photon Source (HEPS) is a 6 GeV diffraction-limited synchrotron light source currently under construction in Beijing. It adopts a double-frequency RF system with 166.6 MHz as fundamental and 499.8 MHz as third harmonic. The fundamental cavity is making use of a superconducting quarter-wave β=1 structure and the third harmonic is of superconducting elliptical single-cell geometry for the storage ring, while normal-conducting 5-cell cavities are chosen for the booster ring. A total of 900 kW RF power shall be delivered to the beam by the 166.6 MHz cavities and the third harmonic cavities are active. All cavities are driven by solid-state power amplifiers and the RF fields are regulated by digital low-level RF control systems. The cavity and ancillaries, high-power RF system and low-level RF control system are in the prototyping phase. This paper presents the current status and progress of the RF system for HEPS.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB380
About •	paper received ※ 09 May 2021 paper accepted ※ 09 June 2021 issue date ※ 12 August 2021
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MOPAB382	Synchrotron Light Shielding for the 166 MHz Superconducting RF Section at High Energy Photon Source	shielding, synchrotron, storage-ring, radiation	1169
	X.Y. Zhang, Z.Q. Li, Q. Ma, P. Zhang IHEP, Beijing, People’s Republic of China
	Funding: This work was supported by High Energy Photon Source, a major national science and technology infrastructure in China. The High Energy Photo Source (HEPS) project has been under construction since 2019, and will be first diffraction-limited synchrotron light source in China. A 6 GeV electron beam with 200 mA current will be stored in the main ring. If synchrotron light produced from this energetic electron beam hits the superconducting cavity’s surface, it would cause thermal breakdown of the superconductivity. In the current lattice design, these lights cannot be fully blocked by the collimator in the upstream lattice cell, therefore a shielding scheme inside the rf section is required. This however brings great challenges to the already limited space. The design of the collimator has been focused on fulfilling shielding requirements while optimizing beam impedance, synchrotron light power density, thermal and mechanical stabilities. Shielding materials are subsequently chosen with dedicated cooling to ensure long-term stable operations. In this paper, a shielding scheme inside the rf section of the HEPS storage ring is presented. The synchrotron light mainly from the upstream bending magnet is successfully block. The sensitivity to beam position movement and installation error is also analyzed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB382
About •	paper received ※ 17 May 2021 paper accepted ※ 11 June 2021 issue date ※ 25 August 2021
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MOPAB383	Pressure Test for Large Grain and Fine Grain Niobium Cavities	niobium, SRF, experiment, FEM	1173
	M. Yamanaka, T. Dohmae, H. Inoue, T. Saeki, K. Umemori, Y. Watanabe, K. Yoshida KEK, Ibaraki, Japan K. Enami Tsukuba University, Ibaraki, Japan
	The pressure test was performed using a fine grain (FG) and a large grain (LG) niobium cavities. The cavity is 1.3 GHz 3-cell TESLA-like shape. The cavity was housed in a steel vessel. Water is supplied into the vessel and the cavity outside is pressurized. The applying pressure and the natural frequency of cavity were measured during the pressure test. The FG and LG cavities were deformed greatly and the pressure dropped suddenly at 3.4 MPa and 1.6 MPa, respectively. The frequency shifted up to 3.4 MHz and 1.3 MHz, respectively. There was no leak after the pressure test, so the cavity did not rupture under above pressure. The result of the pressure at LG cavity is less half than that of the FG cavity. We calculated the stress distribution in the structure by applying outer water pressure using a FEM. The maximum stress at cell when above test pressure is applied, are 146 MPa in FG and 73 MPa in LG, respectively. These stresses are similar to tensile strength of niobium specimen measure by ourselves. The result of pressure tests agrees well with the calculation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB383
About •	paper received ※ 19 May 2021 paper accepted ※ 22 June 2021 issue date ※ 13 August 2021
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Paper

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Other Keywords

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MOPAB016

Small Longitudinal Emittance Setup in Injectors with Gold Beam for Beam Energy Scan in RHIC

emittance, operation, luminosity, extraction

90

H. Huang, C.J. Gardner, C. Liu, V. Schoefer, K. Zeno
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In recent years, RHIC physics program calls for gold beam collisions with energies at and lower than the nominal RHIC injection energy. To get shorter bunches at the three higher energies (9.8GeV/c, 7.3GeV/c and 4.75GeV/c), RHIC 28MHz cavities were used. The longitudinal emittance out of injectors needs to fit in the 28MHz cavities in RHIC. At two lower energies (4.6 and 3.85 GeV/c), the 9MHz RF cavities were used, which set different requirements from injectors. Extensive beam studies were carried out to establish needed beam parameters, such as bunch intensities and longitudinal emittances. In general, enough intensity can be provided for all energies within the longitudinal emittance constraint. This paper summarizes the recent injector operation experiences for various energies.

Poster MOPAB016 [2.641 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB016

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paper received ※ 16 May 2021 paper accepted ※ 17 August 2021 issue date ※ 01 September 2021

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MOPAB043

Validation of APS-U Beam Dynamics Using 6-GeV APS Beam

HOM, simulation, lattice, impedance

189

L. Emery, P.S. Kallakuri, R.R. Lindberg, A. Xiao
ANL, Lemont, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
Several beam measurements at the Advanced Photon Sources were done with a lowered-energy beam of 6 GeV in order to verify or validate calculation codes and some predictions for the APS-U. Though the APS lattice is obviously different from that of the APS-U some aspects of the beams at 6 GeV are similar, for example, the synchrotron radiation damping rate. At 6 GeV, one can also store more current and run with a higher rf bucket allowing the characterization of larger momentum aperture lattices. We report measurements (or plans of measurements) on general instabilities thresholds, lifetime, and other subtle effects. The important topic of ion instabilities at 6 GeV is covered in a separate paper by J. Calvey at this conference.

Poster MOPAB043 [0.829 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB043

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paper received ※ 20 May 2021 paper accepted ※ 23 June 2021 issue date ※ 02 September 2021

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MOPAB045

Measurements and Simulations of High Charge Beam in the APS Booster

booster, injection, simulation, extraction

197

J.R. Calvey, J.C. Dooling, K.C. Harkay, K.P. Wootton, C. Yao
ANL, Lemont, Illinois, USA

For the APS-Upgrade, swap-out injection will require the booster to support up to 17 nC bunch charge, several times what is used in the present APS. Booster injection efficiency drops sharply at high charge, and is the present bottleneck limiting high charge transport through the injectors. Particle tracking simulations have been used to understand what causes are limiting the injection efficiency, and to guide plans for improving it. In particular, bunch length blowup in the injected beam and beam loading in the RF cavities have been identified as the biggest factors. Simulations and measurements have also been done to characterize beam properties along the booster energy ramp. So far, a bunch charge of 12 nC has been successfully extracted from the booster.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB045

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paper received ※ 19 May 2021 paper accepted ※ 26 July 2021 issue date ※ 19 August 2021

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MOPAB046

Plan for Operating the APS-Upgrade Booster with a Frequency Sweep

injection, booster, extraction, emittance

201

J.R. Calvey, T.G. Berenc, A.R. Brill, L. Emery, T. Fors, K.C. Harkay, T.J. Madden, N. Sereno, U. Wienands
ANL, Lemont, Illinois, USA
A. Gu
UCB, Berkeley, California, USA

The APS-Upgrade presents several challenging demands to the booster synchrotron. Swap-out injection requires the booster to capture a high charge bunch (up to 17 nC), accelerate it to 6 GeV, and maintain a low emittance at extraction for injection into the storage ring. To accommodate these conflicting demands, the RF frequency will be ramped between injection and extraction. However, the RF cavity tuners will remain static, which means the couplers will need to withstand a high reflected power at extraction. This paper presents a plan for a system that will meet the requirements for injection efficiency, extracted emittance, and equivalent power at the coupler. Results from tracking simulations and beam studies with a frequency ramp will also be shown.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB046

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paper received ※ 28 May 2021 paper accepted ※ 02 June 2021 issue date ※ 15 August 2021

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MOPAB050

Spatial Autoresonant Acceleration of Electrons by an Axysimmetric Transverse Electric Field

electron, resonance, acceleration, cyclotron

217

E.A. Orozco, O. Otero Olarte
UIS, Bucaramanga, Colombia

In this research, The autoresonance acceleration of electrons by an axisymmetric transverse electric field in presence of a stationary inhomogeneous magnetic field is studied. The dynamics of electrons is determined by the numerical solution of the relativistic Newton-Lorentz equation using a finite difference scheme. The inhomogeneous external magnetic field is generated with a three-coil system and calculated using the Biot-Savart law. The electrons move along a TE011 cylinder cavity in a stationary magnetic field whose axis coincides with the cavity axis. The magnetic field profile obtained is such that it keeps the phase difference between the electric field vector of the microwave mode and the velocity vector of the particle within the acceleration band. For an electron injected longitudinally with an energy of 1 keV and that starts at the radial midpoint of the cavity, it is accelerated up to an energy of about 185 keV using an electric field amplitude of 14 kV/cm and a frequency of 2.45 GHz at a distance of 14 cm.

Poster MOPAB050 [3.298 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB050

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paper received ※ 17 May 2021 paper accepted ※ 15 June 2021 issue date ※ 30 August 2021

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MOPAB068

Collective Effects Studies for the SOLEIL Upgrade

impedance, synchrotron, storage-ring, feedback

274

A. Gamelin, D. Amorim, P. Brunelle, W. Foosang, A. Loulergue, L.S. Nadolski, R. Nagaoka, R. Ollier, M.-A. Tordeux
SOLEIL, Gif-sur-Yvette, France

The SOLEIL upgrade project aims to replace the actual SOLEIL storage ring by a 4th generation light source. The project has just finished its conceptual design report (CDR) phase*. Compared to the SOLEIL storage ring, the upgraded storage ring design includes many new features of 4th generation light sources that will impact collective effects, such as reduced beam pipe apertures, a smaller momentum compaction factor and the presence of harmonic cavities (HC). To mitigate them, we rely on several damping mechanisms provided by the synchrotron radiation, the transverse feedback system, and the HC (Landau damping and bunch lengthening). This article presents a first estimate of the collective effects impact of the upgraded design.
* Conceptual Design Report: Synchrotron SOLEIL Upgrade, 2021, in press.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB068

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paper received ※ 17 May 2021 paper accepted ※ 02 June 2021 issue date ※ 20 August 2021

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MOPAB069

Equilibrium Bunch Density Distribution with Multiple Active and Passive RF Cavities

beam-loading, impedance, synchrotron, storage-ring

278

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

This paper describes a method to get the equilibrium bunch density distribution with an arbitrary number of active or passive RF cavities in uniform filling. This method is an extension of the one presented by M. Venturini which assumes a passive harmonic cavity and no beam loading in the main RF cavity*.
*M. Venturini, "Passive higher-harmonic rf cavities with general settings and multibunch instabilities in electron storage rings," Physical Review Accelerators and Beams, 2018.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB069

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paper received ※ 17 May 2021 paper accepted ※ 23 June 2021 issue date ※ 28 August 2021

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MOPAB070

mbtrack2, a Collective Effect Library in Python

impedance, collective-effects, simulation, synchrotron

282

A. Gamelin, W. Foosang, R. Nagaoka
SOLEIL, Gif-sur-Yvette, France

This article introduces mbtrack2, a collective effect library written in python3. The idea behind mbtrack2 is to build a coherent object-oriented framework to work on collective effects in synchrotrons. mbtrack2 is composed of different modules allowing to easily write scripts for single bunch or multi-bunch tracking using MPI parallelization in a transparent way. The base of the tracking model of mbtrack2 is inspired by mbtrack, a C multi-bunch tracking code initially developed at SOLEIL*. In addition, many tools to prepare or analyse tracking simulations are included.
* R. Nagaoka, R. Bartolini, and J. Rowland, Studies of Collective Effects in SOLEIL and Diamond Using the Multiparticle Tracking Codes SBTRACK and MBTRACK, in Proc. PAC’09, 2009.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB070

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paper received ※ 17 May 2021 paper accepted ※ 06 July 2021 issue date ※ 23 August 2021

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MOPAB072

Single-Bunch Thresholds for the Diamond-II Storage Ring

impedance, simulation, storage-ring, beam-loading

290

T. Olsson, R.T. Fielder
DLS, Oxfordshire, United Kingdom

The proposed Diamond Light Source upgrade will see the storage ring replaced with a multibend achromat lattice, increasing the capacity of the facility whilst reducing the emittance and providing higher brightness for the users. As part of the design work, tracking studies have been performed to determine the single-bunch thresholds including both the resistive-wall and geometric contributions to the impedance. As the machine design also foresees a third order harmonic cavity, the paper also provides an initial assessment of the effects of bunch lengthening on the single-bunch thresholds.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB072

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paper received ※ 18 May 2021 paper accepted ※ 01 June 2021 issue date ※ 18 August 2021

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MOPAB079

Experience of the First Six Years Operations and Plans in NSlS-II

operation, MMI, feedback, vacuum

308

G.M. Wang
BNL, Upton, New York, USA

NSLS-II is a 3 GeV third-generation synchrotron light source at BNL. The storage ring was commissioned in 2014 and began its routine operations in the December of the same year. Since then, we have been continuously installing and commissioning new insertion devices, their front-ends, and beamlines. At this point, the facility hosts 28 operating beamlines from various radiation sources, including damping wiggler, IVU, EPU, 3PW, and bending magnets for infrared beamlines. Over the past six years, the storage ring performance continuously improved, including 500 mA with limited insertion devices close due to RF power limitation and routinely 400 mA top off operation, >95% operation reliability, maintenance of beam motion short- and long-term stability. In this paper, we report NSLS-II accelerator operations experience and plans for future facility developments.

Poster MOPAB079 [2.064 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB079

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paper received ※ 17 May 2021 paper accepted ※ 21 June 2021 issue date ※ 11 August 2021

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MOPAB092

Project of Wuhan Photon Source

storage-ring, injection, linac, dipole

346

H.H. Li, Y. Deng, J.H. He, Y. Nie, L. Tang, J. Wang, Y.X. Zhu
IAS, Wuhan City, People’s Republic of China

Wuhan Photon Source (WHPS) has been designed as a fourth-generation light source, which consists of a low energy storage ring (1.5 GeV), a medium energy storage ring (4.0 GeV), and a linac working as a full energy injector. It has been planned to build the low energy light source first as the Phase I project, and then the medium energy light source after its completion. The low energy storage ring has been optimized with the main design parameters as following: An 8-cell, 500 mA storage ring, with a circumference of 180 m and nature emittance 238.4 pm-rad. Based on hybrid-7BA lattice structure, it reaches the soft X-ray diffraction limit. And at the middle of each cell, a 3.5 T superB magnet is used to extend the photon energy to the hard X-ray region. The swap-out injection is chosen due to the small dynamic aperture and a full energy S-band LINAC will be used as its injector. A 3rd harmonic cavity is designed for bunch lengthening to keep a sufficient lifetime. More details of the WHPS phase I project will be described in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB092

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paper received ※ 10 June 2021 paper accepted ※ 23 June 2021 issue date ※ 30 August 2021

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MOPAB107

RF Plans for the Diamond-II Upgrade

HOM, linac, booster, gun

391

C. Christou, P. Gu, P.J. Marten, S.A. Pande, A.F. Rankin
DLS, Oxfordshire, United Kingdom

The RF system for the proposed Diamond-II upgrade will be based on normal-conducting EU HOM-damped cavities powered by high powered solid state amplifiers and controlled by digital low level RF systems built on the microTCA platform. Reasons for these design choices are discussed, and experience of the selected technologies in the Diamond-I ring are reviewed. The storage ring will also include a third harmonic cavity, and the different design options for this device are discussed. RF design of the booster ring is presented, and details are given of an upgraded linac and gun design intended to improve the charge delivered for top-up.

Poster MOPAB107 [1.703 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB107

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paper received ※ 18 May 2021 paper accepted ※ 20 May 2021 issue date ※ 20 August 2021

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MOPAB108

ESRF-EBS 352.37 MHz Radio Frequency System

SRF, operation, MMI, HOM

395

J. Jacob, P.B. Borowiec, A. D’Elia, G. Gautier, V. Serrière
ESRF, Grenoble, France

The ESRF 352 MHz Radio Frequency (RF) system has been upgraded and tailored to the new 4th Generation Extremely Brilliant Source EBS, that was installed in 2019 and commissioned in 2020. The five former five-cell cavities were replaced with 13 single cell strongly HOM damped cavities that were developed in house, 10 of which are powered from existing 1 MW klystron transmitters. The remaining three cavities are individually fed by three 150 kW solid state amplifiers. All this required a reconstruction in record time of an elaborate WR2300 waveguide network. The low level RF system as well as the cavity and transmitter control system have been rebuilt. The RF design, commissioning and operation experience will be reported, including plans for a 4th harmonic RF system for bunch lengthening to further improve the performance of the new EBS ring.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB108

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paper received ※ 19 May 2021 paper accepted ※ 27 May 2021 issue date ※ 28 August 2021

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MOPAB127

Construction of an Impedance Model for Diamond-II

impedance, simulation, lattice, dipole

455

R.T. Fielder, T. Olsson
DLS, Oxfordshire, United Kingdom

Impedance models for accelerators have traditionally been presented in a static form, usually as tables or spreadsheets which must be read manually. As part of the Diamond-II upgrade work, we have developed an impedance model using a lattice structure. This allows more direct integration with simulation codes while keeping important information easily human readable. We present here a description of this implementation method, along with an overview of the Diamond-II impedance model derived from the latest engineering design.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB127

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paper received ※ 18 May 2021 paper accepted ※ 20 May 2021 issue date ※ 27 August 2021

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MOPAB146

Status of the C-Band Engineering Research Facility (CERF-NM) Test Stand Development at LANL

GUI, klystron, controls, radiation

509

D. Gorelov
Private Address, Los Alamos, USA
R.L. Fleming, S.K. Lawrence, J.W. Lewellen, D. Perez, M.E. Schneider, E.I. Simakov, T. Tajima
LANL, Los Alamos, New Mexico, USA
M.E. Middendorf
ANL, Lemont, Illinois, USA

Funding: LDRD-DR Project 20200057DR
C-Band structures research is of increasing interest to the accelerator community. The RF frequency range of 4-6 GHz gives the opportunity to achieve significant increase in the accelerating gradient, and having the wakefields at the manageable levels, while keeping the geometric dimensions of the structure technologically convenient. Strong team of scientists, including theorists researching properties of metals under stressful thermal conditions and high electromagnetic fields, metallurgists working with copper as well as alloys of interest, and accelerator scientists developing new structure designs, is formed at LANL to develop a CERF-NM facility. A 50 MW, 5.712 GHz Canon klystron, was purchased in 2019, and laid the basis for this facility. As of Jan-21, the construction of the Test Stand has been finished and the high gradient processing of the waveguide components has been started. Future plans include high gradient testing of various accelerating structures, including benchmark C-band accelerating cavity, a proton ß=0.5 cavity, and cavities made from different alloys. An upgrade to the facility is planned to allow for testing accelerator cavities at cryogenic temperatures.

Poster MOPAB146 [3.778 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB146

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paper received ※ 17 May 2021 paper accepted ※ 26 May 2021 issue date ※ 25 August 2021

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MOPAB155

Magnetic Breakdowns in Side-Coupled X-Band Accelerating Structures

impedance, coupling, simulation, accelerating-gradient

540

S.P. Antipov, P.V. Avrakhov, S.V. Kuzikov
Euclid TechLabs, Solon, Ohio, USA
V.A. Dolgashev
SLAC, Menlo Park, California, USA
C. Jing
Euclid Beamlabs, Bolingbrook, USA

Funding: DOE SBIR
Side coupled accelerating structures are popular in the industrial realizations of linacs due to their high shunt impedance and ease of tuning. We designed and fabricated a side-coupled X-band accelerating structure that achieved 133 MOhm/m shut impedance. This structure was fabricated out of two halves using a novel brazeless approach. The two copper halves are joined together using a stainless steel joining piece with knife edges that bite into copper. This structure had been tested at high power at SLAC National Accelerator Laboratory. The performance of the structure had been limited by magnetic breakdowns on the side-coupling cells. In this paper we will present results of the high gradient tests and after-test analysis. Scanning electron microscopy images show a typical magnetic-field induced breakdown.

Poster MOPAB155 [1.069 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB155

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paper received ※ 20 May 2021 paper accepted ※ 23 June 2021 issue date ※ 21 August 2021

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MOPAB187

Design and Calculation of the RF System of DC140 Cyclotron

cyclotron, coupling, simulation, resonance

636

A.S. Zabanov, V.B. Zarubin
JINR/FLNR, Moscow region, Russia
J. Franko, G.G. Gulbekyan, I.V. Kalagin, N.Yu. Kazarinov, S.V. Mitrofanov, V.A. Sokolov, K. Verlamov
JINR, Dubna, Moscow Region, Russia

Flerov Laboratory of Nuclear Reaction of Joint Institute for Nuclear Research carries out the works under creating of FLNR JINR Irradiation Facility based on the cyclotron DC140. The facility is intended for SEE testing of microchip, for production of track membranes and for solving of applied physics problems. The main systems of DC140 are based on the DC72 cyclotron ones that now are under reconstruction. The DC140 cyclotron is intended for acceleration of heavy ions with mass-to-charge ratio A/Z within interval from 5 to 5.5 up to two fixed energies 2.124 and 4.8 MeV per unit mass. The intensity of the accelerated ions will be about 1 pmcA for light ions (A<86) and about 0.1 pmcA for heavier ions (A>132). The designed RF-system of the DC-72 cyclotron with a half-wave cavity is not suitable due to the big vertical size. For this reason, a new quarter-wave RF-system was developed for the DC140 cyclotron project. The results of calculating the parameters of the new RF-system are given in this work.

Poster MOPAB187 [0.488 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB187

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paper received ※ 17 May 2021 paper accepted ※ 24 May 2021 issue date ※ 30 August 2021

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MOPAB190

An 8 GeV Linac as the Booster Replacement in the Fermilab Power Upgrade

linac, injection, cryomodule, booster

643

D.V. Neuffer, S.A. Belomestnykh, M. Checchin, D.E. Johnson, S. Posen, E. Pozdeyev, V.S. Pronskikh, N. Solyak, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
Increasing the Main Injector (MI) beam power above ~1.2 MW requires replacement of the 8 GeV Booster by a higher intensity alternative. Previously, rapid-cycling synchrotron (RCS) and Linac solutions were considered for this purpose. In this paper, we consider the Linac version that produces 8 GeV H⁻ beam for injection into the Recycler Ring (RR) or Main Injector (MI). The Linac takes ~1 GeV beam from the PIP-II Linac and accelerates it to ~2 GeV in a cw SRF linac, followed by a ~2-8 GeV pulsed linac using 1300 MHz cryomodules. The linac components incorporate recent improvements in SRF technology. The linac configuration and beam dynamics requirements are presented. Injection options are discussed. Research needed to implement the Booster replacement is described.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB190

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paper received ※ 15 May 2021 paper accepted ※ 28 May 2021 issue date ※ 14 August 2021

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MOPAB191

Method Development for Cavity Failure Compensation in a Superconducting Linac

linac, emittance, lattice, ECR

647

F. Bouly
LPSC, Grenoble Cedex, France

Reliability is a major challenge within the perspective of improving the performances and sustainability of MegaWatt class accelerators. To optimize the operational costs of such accelerators the availability requirements are becoming more and more challenging. These requirements are even more stringent in the case of Accelerator Driven systems (ADS). As an example, for the MYRRHA (Multipurpose Hybrid Research Reactor for High-tech Applications) ADS demonstrator, the actual availability limit is set to a maximum of 10 beam interruptions (longer than 3 seconds) over a 3-month operating cycle. For this purpose, the accelerator design is based on a redundant and fault-tolerant scheme to enable rapid mitigation of a cavity failure. The adopted strategy is to apply for local compensation: a failed cavity is compensated by several neighboring cavities. Beam dynamics studies and method developments to apply such a failure compensation scheme are here reviewed. First simulation results for superconducting linac retuning and potential future improvements will be discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB191

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paper received ※ 19 May 2021 paper accepted ※ 21 May 2021 issue date ※ 30 August 2021

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MOPAB192

LILac Energy Upgrade to 13 MeV

linac, proton, controls, LLRF

651

B. Koubek, S. Altürk, M. Busch, H. Höltermann, J.D. Kaiser, H. Podlech, U. Ratzinger, M. Schuett, M. Schwarz, W. Schweizer, D. Strehl, R. Tiede, C. Trageser
BEVATECH, Frankfurt, Germany
A. Brunzel, P. Nonn, H. Schlarb
DESY, Hamburg, Germany
A.V. Butenko, D.E. Donets, B.V. Golovenskiy, A. Govorov, K.A. Levterov, D.A. Lyuosev, A.A. Martynov, V.A. Monchinsky, D.O. Ponkin, K.V. Shevchenko, I.V. Shirikov, E. Syresin
JINR, Dubna, Moscow Region, Russia

In the frame of the NICA (Nuclotron-based Ion Collider fAcility) ion collider upgrade a new light ion LINAC for protons and ions will be built in collaboration between JINR and BEVATECH GmbH. While ions with a mass-to-charge ratio up to 3 will be fed into the NUCLOTRON ring with an energy of 7 MeV/u, protons are supposed to be accelerated up to an energy of 13 MeV using a third IH structure. This energy upgrade comprises a third IH structure, a dual-use Debuncher cavity as well as an extension of the LLRF control system built on MicroTCA technology.

Poster MOPAB192 [4.914 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB192

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paper received ※ 11 May 2021 paper accepted ※ 31 May 2021 issue date ※ 02 September 2021

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MOPAB194

First 3D Printed IH-Type Linac Structure - Proof-of-Concept for Additive Manufacturing of Linac rf Cavities

vacuum, cyclotron, experiment, linac

654

H. Hähnel, U. Ratzinger
IAP, Frankfurt am Main, Germany

Additive manufacturing (or "3D printing") has become a powerful tool for rapid prototyping and manufacturing of complex geometries. As technology is evolving, the quality and accuracy of parts manufactured this way is ever improving. Especially interesting for the world of particle accelerators is the process of 3D printing of stainless steel (and copper) parts. We present the first fully functional IH-type drift tube structure manufactured by metal 3D printing. A 433 MHz prototype cavity has been constructed to act as a proof-of-concept for the technology. The cavity is designed to be UHV capable and includes cooling channels reaching into the stems of the DTL structure. We present the first experimental results for this prototype.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB194

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paper received ※ 18 May 2021 paper accepted ※ 01 June 2021 issue date ※ 19 August 2021

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MOPAB195

Development of a Disk-and-Washer Cavity for the J-PARC Muon g-2/EDM Experiment

experiment, linac, quadrupole, coupling

658

Y. Takeuchi, J. Tojo
Kyushu University, Fukuoka, Japan
E. Cicek, K. Futatsukawa, N. Kawamura, T. Mibe, M. Otani, T. Yamazaki, M. Yoshida
KEK, Ibaraki, Japan
Y. Iwashita
Kyoto ICR, Uji, Kyoto, Japan
R. Kitamura, Y. Kondo, T. Morishita
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
Y. Nakazawa
Ibaraki University, Hitachi, Ibaraki, Japan
N. Saito
J-PARC, KEK & JAEA, Ibaraki-ken, Japan
Y. Sue, K. Sumi, M. Yotsuzuka
Nagoya University, Graduate School of Science, Chikusa-ku, Nagoya, Japan
H.Y. Yasuda
University of Tokyo, Tokyo, Japan

At J-PARC, an experiment using muons accelerated by a linac is planned to measure the anomalous magnetic moment of muons and to search for the electric dipole moment. A 1296 MHz disk and washer (DAW) coupled cavity linac (CCL) is being developed for use in the middle beta section of the muon linac. The DAW CCL consists of 14 tanks with 11 cells each. All tanks are connected by bridge couplers and electromagnetic quadrupole doublets for focusing are installed in each bridge coupler. The basic design of the DAW cavity has already been completed, and now detailed cavity design studies and manufacturing process studies are underway. In this poster, we will report about these studies and the preparation status of manufacturing the DAW cavity.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB195

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paper received ※ 20 May 2021 paper accepted ※ 01 June 2021 issue date ※ 26 August 2021

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MOPAB203

Benchmark of Superconducting Cavity Models at SNS Linac

linac, superconducting-cavity, simulation, operation

671

A.P. Shishlo
ORNL, Oak Ridge, Tennessee, USA

Funding: This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC0500OR22725 with the U.S. Department of Energy.
A benchmark of superconducting cavity models against Time-of-Flight measurements at the SNS linac is presented. The superconducting part of SNS linac (SCL) includes 81 RF cavities that accelerates H⁻ beam from 185.6 MeV to the final energy of 1 GeV. During the operation some of cavities can become unstable, and its amplitudes should be reduced, or they should be completely switched off. In this case, the SCL is retuned by using a linac simulation code. This simulation tool relay on an accuracy of the superconducting cavity model. This paper describes the comparison of the measured beam acceleration by one of the SCL cavities and simulations of this process. Different cavity models are used in simulations. The subject of this study is limited to the longitudinal beam dynamics, so no effects on transverse beam characteristics have been considered.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB203

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paper received ※ 14 May 2021 paper accepted ※ 20 May 2021 issue date ※ 28 August 2021

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MOPAB206

The RF Parameters of Heavy Ions Linac

DTL, rfq, linac, MEBT

679

A. Sitnikov, G. Kropachev, T. Kulevoy, D.N. Selesnev, A.I. Semennikov
ITEP, Moscow, Russia
M.L. Smetanin, A.V. Telnov, N.V. Zavyalov
VNIIEF, Sarov, Russia

The new linac for A/Z = 8, output energy 4 MeV/u and 3 mA current is under development at NRC "Kurchatov Institute"-ITEP. The linac consists of Radio-Frequency Quadrupole (RFQ) with operating frequency 40 MHz and two sections of Drift Tube Linac (DTL) with operating frequency 80 and 160 MHz, correspondently. Both DTL has a modular structure and consists of separated individually phased resonators with focusing magnetic quadrupoles located between the cavities. The DTL₁ is based on the quarter-wave resonators meanwhile DTL₂ is based on IH 5-gap resonators. The 6D beam matching between RFQ and DTLs is provided by magnetic quadrupole lenses and 2-gaps RF-bunchers. The paper presents results of the radio-frequency (RF) design of linac accelerating structures.

Poster MOPAB206 [0.559 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB206

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paper received ※ 14 May 2021 paper accepted ※ 01 July 2021 issue date ※ 28 August 2021

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MOPAB208

LLRF Measurements and Cu-plating at the First-of-Series Cavity Section of the Alvarez 2.0 at GSI

DTL, operation, simulation, vacuum

686

M. Heilmann, T. Dettinger, X. Du, L. Groening, S. Mickat, A. Rubin
GSI, Darmstadt, Germany

The Alvarez 2.0 will replace the existing post-stripper DTL of the GSI UNILAC. Today’s GSI comprises the UNILAC and the synchrotron SIS18 and is going to serve as the injector chain for the Facility of Antiproton and Ion Research (FAIR). The new Alvarez-type DTL is operated at 10⁸.4 MHz providing acceleration from 1.4 MeV/u to 11.4 MeV/u along a total length of 55 meters. The first-of-series (FoS) cavity section has 12 RF-gaps along a total length of 1.9 m. It is the first cavity section of the new DTL. All main components were delivered in 2019, followed by successful SAT and installation of the 11 drift tubes and copper-plating. Completion of first low level RF-measurements prior to copper plating and the subsequent plating are major project milestones. These proceedings report on the results and compares them to simulation using CST Microwave Studio.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB208

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paper received ※ 18 May 2021 paper accepted ※ 31 May 2021 issue date ※ 23 August 2021

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MOPAB209

Commissioning of SANAEM RFQ Accelerator

rfq, vacuum, plasma, proton

690

B. Yasatekin, A. Alacakir, A.S. Bolukdemir, I. Kilic, Y. Olgac
TENMAK-NUKEN, Ankara, Turkey
E. Cicek
KEK, Ibaraki, Japan
E. Cosgun
UNIST, Ulsan, Republic of Korea

The former SANAEM RFQ is upgraded with a newly manufactured cavity, made of oxygen-free copper (OFC), having the capability of accelerating protons from 20 keV to 1.3 MeV. In the assembling of cavity vanes, flanges, etc., indium wire is preferred over the brazing process providing a more flexible and easy method for vacuum sealing. After assembling the cavity, argon plasma cleaning is performed for the final cleaning and RF pre-conditioning. Vacuum tests revealed that levels of 2·10^-7 mbar could be achieved quite easily. RF power conditioning of the RFQ cavity is successfully completed with the observation of quite few sparks. In the commissioning tests with the proton beam, a magnetic analyzer is used to measure the energy of the particles. This paper presents the strategy and the results concerning the commissioning of the proton beam with special emphasis on the RFQ cavity.

Poster MOPAB209 [5.076 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB209

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paper received ※ 19 May 2021 paper accepted ※ 14 June 2021 issue date ※ 29 August 2021

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MOPAB210

High-Gradient Booster for Enhanced Proton Radiography at LANSCE

linac, booster, proton, focusing

693

S.S. Kurennoy, Y.K. Batygin
LANL, Los Alamos, New Mexico, USA

Increasing energy of proton beam at LANSCE from 800 MeV to 3 GeV improves radiography resolution ~10 times. We propose accomplishing this energy boost with a compact cost-effective linac based on cryo-cooled normal conducting high-gradient RF accelerating structures. High-gradient structures exceeding 100 MV/m have been developed for electron acceleration and operate with short RF pulse lengths below 1 us. Though such parameters are unusual for typical proton linacs, they fit perfectly for proton radiography (pRad) applications. The pRad limits contiguous trains of beam micro-pulses to less than 80 ns to prevent blur in images. For a compact pRad booster at LANSCE, we develop a staged design: a short section to capture and compress the 800-MeV proton beam followed by the main high-gradient linac. Our beam dynamics study addresses the beam magnetic focusing and minimizing its energy spread, which are challenging in high-gradient structures but very important for successful pRad operation.

Poster MOPAB210 [0.809 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB210

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paper received ※ 10 May 2021 paper accepted ※ 17 August 2021 issue date ※ 23 August 2021

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MOPAB211

Beam Coupling Impedances of Ferrite-Loaded Cavities: Calculations and Measurements

impedance, dipole, resonance, coupling

696

S.S. Kurennoy, R.C. McCrady
LANL, Los Alamos, New Mexico, USA

We have developed an efficient method of calculating impedances in cavities with dispersive ferrite dampers. The ferrite dispersive properties in the frequency range of interest are fitted in CST, which allows using both wakefield and lossy eigenmode solvers. A simple test cavity with or without ferrite inserts is explored both numerically and experimentally. The resonance frequencies and beam coupling impedances at cavity resonances are calculated with CST to understand the mode structure. The cavity transverse coupling impedances are also measured on a test stand using a two-wire method. We compare results of impedance calculations and measurements for a few different configurations, with and without ferrites, to ensure a complete understanding of the cavity resonances and their damping with ferrite. These results are important to provide adequate damping of undesired transverse modes in induction-linac cells.

Poster MOPAB211 [1.105 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB211

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paper received ※ 10 May 2021 paper accepted ※ 21 May 2021 issue date ※ 19 August 2021

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MOPAB232

Observation of Polarization-Dependent Changes in Higher-Order Mode Responses as a Function of Transverse Beam Position in Tesla-Type Cavities at FAST

HOM, electron, dipole, cryomodule

756

R.M. Thurman-Keup, D.R. Edstrom, A.H. Lumpkin, P.S. Prieto, J. Ruan
Fermilab, Batavia, Illinois, USA
J.A. Diaz Cruz
UNM-ECE, Albuquerque, USA
J.A. Diaz Cruz, B.T. Jacobson, J.P. Sikora, F. Zhou
SLAC, Menlo Park, California, USA

Funding: FNAL supported by U.S. Department of Energy, Office of Science, under contract DE-AC02-07CH11359. SLAC supported by U.S. Department of Energy, Office of Science, under contract DE-AC02-76SF00515.
Higher-order modes (HOMs) in superconducting rf cavities present problems for an electron bunch traversing the cavity in the form of long-range wakefields from previous bunches. These may dilute the emittance of the macropulse average, especially with low emittance beams at facilities such as the European X-ray Free-electron Laser (XFEL) and the upgraded Linac Coherent Light Source (LCLS-II). Here we present observations of HOMs driven by the beam at the Fermilab Accelerator Science and Technology (FAST) facility. The FAST facility features two independent TESLA-type cavities (CC1 and CC2) after a photocathode rf gun followed by an 8-cavity cryomodule. The HOM signals were acquired from cavities using bandpass filters of 1.75 ± 0.15 GHz, 2.5 ± 0.2 GHz, and 3.25 ± 0.2 GHz and recorded using an 8-GHz, 20 GSa/s oscilloscope. The frequency resolution obtained is sufficient to separate polarization components of many of the HOMs. These HOM signals were captured from CC1 and cavities 1 and 8 of the cryomodule for various initial trajectories through the cavities, and we observe correlations between trajectory, HOM signals, and which polarization component of a mode is affected.

Poster MOPAB232 [2.144 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB232

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paper received ※ 20 May 2021 paper accepted ※ 25 May 2021 issue date ※ 28 August 2021

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MOPAB236

Ion Beam Dynamics in Linac-100 Facility at Jinr

linac, acceleration, emittance, rfq

767

S.M. Polozov, V.S. Dyubkov, Y. Lozeev, T.A. Lozeeva, A.V. Samoshin
MEPhI, Moscow, Russia

The heavy-ion linac LINAC-100 is a superconducting driver-accelerator proposed as one of the prospective projects at JINR. Its goal is to accelerate primary stable isotope CW high-intensity beams to energies up to 100 MeV/u*. This linac is discussed as the first stage of a new rare isotope facility DERICA (Dubna Electron-Radioactive Ion Collider fAcility), being under development at JINR since 2017**. LINAC-100 is supposed to work with a wide range of beams with A/Z 3.5/7, Uranium U³⁴⁺ being the heaviest. Its concept has undergone many changes, mostly considering stripping cells to increase accelerator efficiency. During the latest investigations of various stripping cells [***, ****], Uranium beam stripping at the energy 10 MeV/u and utilizing three adjacent charge states 59-61+ resulted in 60% output beam intensity preservation (or 30 pA overall output current). The current layout of the LINAC-100 is the following: one or two (separately for light and heavy ions) normal conducting front-end linacs, gas stripper cell at 10 MeV/u, and the SC section. In this paper three charge state Uranium beam dynamics in the current version of SC LINAC-100 section is presented.
*S Polozov 2020 PhysScr 95 084006
**A S Fomichev Phys Usp 62(7) 675-690 2019
***Tolstikhina I 2018 Basic At Int of Acc H Ions in Matter 98 1
**** W Barth J Phys Conf Ser 1350:012096

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB236

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paper received ※ 20 May 2021 paper accepted ※ 13 August 2021 issue date ※ 17 August 2021

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MOPAB247

Multipacting Studies for the JAEA-ADS Five-Cell Elliptical Superconducting RF Cavities

multipactoring, electron, SRF, simulation

793

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

The Five-cell Elliptical Superconducting Radio-Frequency Cavities (SRFC) provide the final acceleration in the JAEA-ADS linac (from 208 MeV to 1.5 GeV); thus, their performance is essential for the success of the JAEA-ADS project. After their optimization of the cavity geometry to achieve a high acceleration gradient with lower electromagnetic peaks, the next step in the R&D strategy is the accurate estimation of beam-cavity effects which can affect the performance of the cavities. To this end, multipacting studies were developed to investigate its effect in the cavity operation regimen and find countermeasures. The results of this study will help in the development of the SRFC models and in the consolidation of the JAEA-ADS project.

Poster MOPAB247 [0.599 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB247

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paper received ※ 10 May 2021 paper accepted ※ 07 June 2021 issue date ※ 02 September 2021

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MOPAB255

Demonstration of a Novel Longitudinal Phase Space Linearization Method without Higher Harmonics

electron, gun, simulation, laser

805

R. Stark
University of Hamburg, Hamburg, Germany
K. Flöttmann, M. Hachmann
DESY, Hamburg, Germany
F.J. Grüner
Center for Free-Electron Laser Science, Universität Hamburg, Hamburg, Germany
B. Zeitler
CFEL, Hamburg, Germany

Nonlinear correlations in the longitudinal phase space of electron bunches can be a decisive limitation to the achievable bunch length compression and attainability of small energy spreads. To overcome the restrictions imposed by nonlinear distortions, the longitudinal phase space distribution must be linearized. Previously, a novel linearization procedure based on the controlled expansion of the bunch between two radio frequency cavities operated at the same fundamental frequency has been presented in *. A demonstration of this linearization method is presented in this work.
*B. Zeitler, K. Floettmann, and F. Grüner, "Linearization of the longitudinal phase space without higher harmonic field," Phys. Rev. ST Accel. Beams, vol. 18, p. 120102, 2015.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB255

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paper received ※ 18 May 2021 paper accepted ※ 02 June 2021 issue date ※ 12 August 2021

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MOPAB289

Machine Learning Training for HOM reduction and Emittance Preservation in a TESLA-type Cryomodule at FAST

HOM, emittance, electron, controls

916

J.A. Diaz Cruz
UNM-ECE, Albuquerque, USA
J.A. Diaz Cruz, A.L. Edelen, B.T. Jacobson, J.P. Sikora
SLAC, Menlo Park, California, USA
D.R. Edstrom, A.H. Lumpkin, R.M. Thurman-Keup
Fermilab, Batavia, Illinois, USA

Low emittance electron beams are of high importance at facilities like the LCLS-II at SLAC. Emittance dilution effects due to off-axis beam transport for a TESLA-type cryomodule (CM) have been shown at the Fermilab Accelerator Science and Technology facility. The results showed the correlation between the electron beam-induced cavity high-order modes (HOMs) and submacropulse centroid slewing and oscillation downstream of the CM. Mitigation of emittance dilution can be achieved by reducing the HOM signals and the variances in the submacropulse beam positions downstream of the CM. Here we present a Machine Learning based optimization and model construction for HOM signal level reduction using Neural Networks and Gaussian Processes. To gather training data we performed experiments using single bunch and 50 bunch electron beams with charges up to 125 pC/b. We measured HOM signals of all cavities and beam position with a set of BPMs downstream of the CM. The beam trajectory was changed using V/H125 corrector set located upstream of the CM. The results presented here will inform the LCLS-II injector commissioning and will serve as a prototype for HOM reduction and emittance preservation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB289

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paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 24 August 2021

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MOPAB290

Machine Learning-Based LLRF and Resonance Control of Superconducting Cavities

controls, LLRF, simulation, SRF

920

J.A. Diaz Cruz, S. Biedron, M. Martínez-Ramón
UNM-ECE, Albuquerque, USA
J.A. Diaz Cruz
SLAC, Menlo Park, California, USA
R. Pirayesh
UNM-ME, Albuquerque, New Mexico, USA
S. Sosa
ODU, Norfolk, Virginia, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics, under award number DE-SC0019468.
Superconducting radio frequency (SRF) cavities with high loaded quality factors that operate in continuous wave (CW) and low beam loading are sensitive to microphonics-induced detuning. Cavity detuning can result in an increase of operational power and/or in a cavity quench. Such SRF cavities have bandwidths on the order of 10 Hz and detuning requirements can be as tight as 10 Hz. Passive methods to mitigate vibration sources and their impact in the cryomodule/cavity environment are widely used. Active resonance control techniques that use stepper motors and piezoelectric actuators to tune the cavity resonance frequency by compensating for microphonics detuning have been investigated. These control techniques could be further improved by applying Machine Learning (ML), which has shown promising results in other particle accelerator control systems. In this paper, we describe a Low-level RF (LLRF) and resonance control system based on ML methods that optimally and adaptively tunes the control parameters. We present simulations and test results obtained using a low power test bench with a cavity emulator.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB290

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paper received ※ 03 June 2021 paper accepted ※ 11 June 2021 issue date ※ 27 August 2021

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MOPAB291

Design of Cavity BPM Pickup for EuPRAXIA@SPARC_LAB

coupling, GUI, pick-up, simulation

924

Sh. Bilanishvili
INFN/LNF, Frascati (Roma), Italy

EuPRAXIA@SPARC_LAB will make available at LNF a unique combination offering three different options. A high-brightness electron beam with 1 GeV energy generated in a novel X-band RF linac; A PW-class laser system, and a compact light-source directly driven by a plasma accelerator*. Plasma and conventional RF linac driven FEL provide beam with parameters of 30- 200pC charge range, 10-100Hz repetition rate, and 1 GeV electron energy**. The control of the charge and the trajectory monitoring at a few pC and a few um is mandatory in this machine. Particularly in the plasma interaction region, where the pickup resolution under 1 um is required. As a possible solution, a cavity beam position monitor (cBPM) is proposed. A prototype in the C-band frequency range has been designed. The pickup was optimized for low charge and single-shot bunches. The poster presents the process to achieve the required specifications. The simulations were performed to study RF properties and the electromagnetic response of the device. Finally, the overall performance of the pickup is discussed, and theoretical resolution is approximated.
* https://www.researchgate.net/publication/335459394_From_SPARC_LAB_to_EuPRAXIASPARC_LAB
**http://www.lnf.infn.it/sis/preprint/detail-new.php?id=5416

Poster MOPAB291 [16.718 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB291

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paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 14 August 2021

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MOPAB322

Electronics for Bead-pull Measurement of Radio Frequency Accelerating Structures in LEHIPA

controls, software, rfq, interface

993

S. Rosily, S. Krishnagopal
Homi Bhbha National Institute (HBNI), DAE, Mumbai, India
S. Krishnagopal, S. Singh
BARC, Mumbai, India

For carrying out bead-pull characterisation of RFQ and DTL at the Low Energy High Intensity Proton Accelerator of BARC, a controller for simultaneous motion of 64 axis, tuners or post couplers, was developed. Also, a bead motion controller with integrated phase measurement sensor was developed. The paper discusses the requirements of the system, the architecture of the control systems, operation and results. The results obtained from the sensor was compared to that obtained using an independent USB VNA. The advantages of the system especially with addition of internal phase measurement sensor including minimising position error, flexibility in beadpull to selectively increase resolution at specified locations and ease of implementing auto-tuning algorithms are discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB322

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paper received ※ 20 May 2021 paper accepted ※ 24 May 2021 issue date ※ 21 August 2021

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MOPAB323

Commissioning of the LCLS-II Prototype HOM Detectors with Tesla-Type Cavities at Fast

HOM, electron, cryomodule, detector

996

J.P. Sikora, J.A. Diaz Cruz, B.T. Jacobson
SLAC, Menlo Park, California, USA
J.A. Diaz Cruz
UNM-ECE, Albuquerque, USA
D.R. Edstrom, A.H. Lumpkin, P.S. Prieto, J. Ruan, R.M. Thurman-Keup
Fermilab, Batavia, Illinois, USA

Funding: *Work supported by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy. **Work supported by the U.S. Department of Energy, contract DE-AC02-76SF00515.
Experiments at the Fermilab Accelerator Science and Technology* (FAST) facility detected electron beam-induced high order mode (HOM) signals from Tesla superconducting cavities. This paper describes some of the signal detection hardware used in this experiment, as well as measurements of the HOM signal magnitude versus beam trajectory. These measurements were made both with a single bunch and with a train of 50 bunches at bunch charges from 400 pC/b down to 10 pC/b. The detection hardware is designed for use with the Tesla superconducting cavities of LCLS-II at SLAC** and is based on a prototype already in use at Fermilab. The HOM signal passes through a bandpass filter that is centered on several cavity dipole modes and a zero bias Schottky diode detects its magnitude. Direct comparisons were made between the FNAL chassis and the SLAC prototype for identical beam steering conditions. To support measurements with bunch charges as low as 10 pC, the SLAC detector has RF amplification between the bandpass filter and the diode detector. With this hardware, usable HOM signal measurements are obtained with a single bunch of 10 pC in cryomodule cavities as will be needed for LCLS-II.

Poster MOPAB323 [2.076 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB323

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paper received ※ 17 May 2021 paper accepted ※ 07 June 2021 issue date ※ 25 August 2021

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MOPAB329

Operations of Copper Cavities at Cryogenic Temperatures

coupling, linac, cryogenics, ECR

1020

H. Wang, U. Ratzinger, M. Schuett
IAP, Frankfurt am Main, Germany

How the anomalous skin effect by copper affects the efficiency of copper- cavities will be studied in the experiment, especially at lower temperatures. The accurate quality factor Q and resonant frequency of three coaxial cavities will be measured over the temperature range from 300 to 22 K. The three coaxial cavities have the same structure, but different lengths, which correspond to resonant frequencies: around 100 MHz, 220 MHz and 340 MHz. The motivation is to check the feasibility of an efficient pulsed, liquid nitrogen cooled ion linac.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB329

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paper received ※ 19 May 2021 paper accepted ※ 07 June 2021 issue date ※ 24 August 2021

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MOPAB330

Production and Performance Evaluation of a Compact Deflecting Cavity to Measure the Bunch Length in the cERL

resonance, vacuum, coupling, impedance

1023

D. Naito, Y. Honda, T. Miyajima, N. Yamamoto
KEK, Ibaraki, Japan

At the KEK compact energy recovery linac, we try to generate an infrared free-electron laser (FEL). To generate the FEL, an electron bunch should be compressed along the longitudinal direction. The measurement of the bunch length is key to optimize the bunch compression. We plan to measure the bunch length by deflecting cavities in the burst mode. The deflecting cavities are required to be a time resolution of 33 fs in order to not only measure the bunch length but also resolve the structure inside the electron bunch. To achieve the requirement, we developed a c-band cavity whose RF input port is compact. The deflecting cavity is a single cell and normal conducting cavity. The deflection mode of the cavity is TM110. The 12 cavities will be located at the exit of undulators. In this presentation, we explain the design of our cavity and report the production of the first cavity. We also report the evaluation of the resonance frequency, the unloaded Q and the external Q of the cavity. From the measurements and simulations, the R/Q is estimated to be 1 mega orms. The time resolution of the cavity is expected to be 400 fs when the input RF power is 1 kW and the beam energy is 20 MeV.

Poster MOPAB330 [12.920 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB330

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paper received ※ 12 May 2021 paper accepted ※ 08 June 2021 issue date ※ 15 August 2021

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MOPAB331

Design Consideration of a Longitudinal Kicker Cavity for Compensating Transient Beam Loading Effect in Synchrotron Light Sources

kicker, resonance, coupling, impedance

1027

D. Naito, S. Sakanaka, T. Takahashi, N. Yamamoto
KEK, Ibaraki, Japan
T. Yamaguchi
Sokendai, Ibaraki, Japan

In ultra-low-emittance synchrotron light sources, bunch-lengthening using the combination of main and harmonic cavities is limited by the transient beam-loading (TBL) effect which is caused by gaps in the fill pattern. To manage this effect, we proposed a TBL compensation technique using a wide-band longitudinal kicker cavity*. In the future KEK-LS storage ring, for example, the kicker cavity should provide a compensation voltage of 50 kV with a -3dB bandwidth (BW) of about 5 MHz, as well as its higher-order modes (HOM) should be damped sufficiently. In this presentation, we report our conceptual design of the kicker cavity. We employed the single-mode (SM) cavity concept so that harmful HOMs are dumped by rf absorbers on the beam pipes. The distinctive feature of the SM cavity is its simple structure since it has no HOM damper on the cavity. Another feature is its low R/Q by which the TBL effect in the kicker cavity itself can be reduced significantly. We employed a frequency of 1.5 GHz (third-harmonic) and R/Q of 60 orms through optimizations. Using this kicker cavity with a double rf system, a bunch lengthening by a factor of 4.3 (i.e., 40.9 ps) is expected for the KEK-LS case.
* N.Yamamoto et al., Phys. Rrev. Acc. Beams 21, 012001 (2018)

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB331

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paper received ※ 19 May 2021 paper accepted ※ 11 June 2021 issue date ※ 10 August 2021

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MOPAB332

Design of 4th Harmonic RF Cavities for ESRF-EBS

HOM, SRF, impedance, coupling

1031

A. D’Elia, J. Jacob, V. Serrière, X.W. Zhu
ESRF, Grenoble, France

Funding: European Union’s Horizon 2020 research and innovation program under grant #871072
An active 4th harmonic RF system for bunch lengthening is under study at the ESRF to improve the performance of the new EBS storage ring, mainly for few bunch operation with high currents per bunch, by reducing Touschek and intrabeam scattering, thereby increasing the lifetime and limiting the emittance growth. It will also reduce impedance heating of the vacuum chambers. The 4th Harmonic 1.41 GHz normal conducting cavity design takes inspiration from the KEK idea of using a TM020 mode exhibiting a reduced R/Q but a higher unloaded Q with respect to TM010. We propose to use multicell cavities for their compactness, the reduced number of required ancillaries and the ease of control for a reduced number of cavities. The drawback is the complexity of the model and the necessity to damp the lower order TM010 mode (LOM) as well as the higher order modes (HOM). The RF design of a 4th harmonic multicell damped cavity will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB332

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paper received ※ 19 May 2021 paper accepted ※ 17 August 2021 issue date ※ 18 August 2021

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MOPAB333

ESRF-EBS 352 MHz HOM Damped RF Cavities

SRF, impedance, HOM, MMI

1034

A. D’Elia, J. Jacob, V. Serrière
ESRF, Grenoble, France

For the new ESRF-EBS Storage Ring (SR), HOM damped RF cavities were needed to cope with the reduced thresholds for Longitudinal Coupled Bunch Instabilities (LCBI). The 352 MHz cavities were designed at the ESRF based on an improved version of the 500 MHz EU/ALBA/BESSY structures. A short description of the cavity design will be presented as well as an overview of the fabrication, the preparation and the performance of 13 such cavities for the ESRF-EBS SR. A study of the impedance of a whole cavity equipped with its ancillaries (HOM absorbers, ion pump and tuner) will be presented. One of the three HOM absorbers, the smaller one on top of the cavity, was finally not installed on the machine. The reasons and a detailed analysis in terms of HOM impedances that justifies this choice will be reported.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB333

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paper received ※ 19 May 2021 paper accepted ※ 07 June 2021 issue date ※ 23 August 2021

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MOPAB334

Status and Recent Development of FAIR Ring RF Systems

LLRF, power-supply, operation, status

1037

U. Laier, R. Balß, C. Christoph, M. Frey, P. Hülsmann, H. Klingbeil, H.G. König, D.E.M. Lens, J.S. Schmidt, A. Stuhl, K.G. Thomin, T. Winnefeld
GSI, Darmstadt, Germany
H. Klingbeil
TEMF, TU Darmstadt, Darmstadt, Germany

Funding: GSI Helmholtzzentrum für Schwerionenforschung GmbH
Five different Ring RF Systems are required for the operation of FAIR (Facility for Antiproton and Ion Research). These systems have to operate at frequencies between 310 kHz and 3.2 MHz, with gap voltages up to 40 kVp and duty cycles from 5·10^-4 up to cw. All systems will be realized using inductively loaded (ferrite or magnetic alloy) cavities driven by tetrode-based amplifiers fed by switch-mode power supplies. To stabilize the amplitude, resonance frequency and phase, versatile digital feedback and feedforward control will be used. This contribution will present the latest development on the power part and the LLRF of the four RF systems of the SIS100 (SIS100 Acceleration, SIS100 Bunch Compression, SIS100 Barrier Bucket and SIS100 Longitudinal Feedback) as well as the CR Debuncher system which is part of the Collector Ring. The progress of these systems varies by a large degree. This note will give an overview regarding the status of the design, procurement, realization, testing, optimization, commissioning and preparation for installation of these RF systems.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB334

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paper received ※ 18 May 2021 paper accepted ※ 07 June 2021 issue date ※ 17 August 2021

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MOPAB337

Design Study of the Spiral Buncher Cavities for the High Current Injector at IUAC

linac, impedance, bunching, rfq

1048

S. Kedia, R. Ahuja, R. Mehta, C.P. Safvan
IUAC, New Delhi, India

Two high energy beam transport (HEBT) cavities have been designed to provide the longitudinal beam bunching between drift tube linac and superconducting super-buncher of the superconducting linear (SC-LINAC) accelerator. The spiral type cavities were chosen over standard quarter wave-type geometry due to its higher shunt impedance. The TRACE-3D ion-optical codes have been used to determine the bunching voltage and physical location of the cavities. The two-gap RF cavity requires 80 kV/gap to provide the longitudinal beam bunching at the entrance of the superconducting buncher. The CST-MWS simulations were performed to design the spiral type bunching cavities. The various parameters including shunt impedance, quality factor, average accelerating field, and total power loss were determined using CST-MWS simulations. The ratio of drift tube radius to the gap was optimized to achieve the maximum effective electric field with minimum field penetration within the gap. The SolidWorks software has been used to prepare a mechanical model for the fabrication.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB337

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paper received ※ 15 May 2021 paper accepted ※ 26 May 2021 issue date ※ 01 September 2021

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MOPAB339

Design Of An X-band 3MeV Standing-wave Accelerating Structure with Nose-cone Structure Made From Two Halves

coupling, impedance, electron, bunching

1051

F. Liu, H.B. Chen, J. Shi, C.-X. Tang, H. Zha
TUB, Beijing, People’s Republic of China

This work presents an X-band 3MeV standing-wave accelerating structure with nose cones made from two halves. Milling two longitudinally split halves is one economic method to manufacture accelerating structure for decrease of welding, with increasing the difficulty in machining. This linear accelerator includes 4 buncher cavities and 4 accelerating cavities, and nose cone is applied to achieve high shunt impedance. A technical prototype is under fabrication to bring two milled halves manufacture way into practical application.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB339

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paper received ※ 19 May 2021 paper accepted ※ 26 May 2021 issue date ※ 17 August 2021

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MOPAB341

First C-Band High Gradient Cavity Testing Results at LANL

proton, GUI, operation, klystron

1057

E.I. Simakov, R.L. Fleming, D. Gorelov, T.A. Jankowski, M.F. Kirshner, J.W. Lewellen, J.D. Pizzolatto, M.E. Schneider, T. Tajima
LANL, Los Alamos, New Mexico, USA
X. Lu, E.A. Nanni, S.G. Tantawi
SLAC, Menlo Park, California, USA
M.E. Middendorf
ANL, Lemont, Illinois, USA

Funding: Los Alamos National Laboratory LDRD Program.
This poster will report the results of high gradient testing of the two proton β=0.5 C-band accelerating cavities. The cavities for proton acceleration were fabricated at SLAC and tested at high gradient C-band accelerator test stand at LANL. One cavity was made of copper, and the second was made of a copper-silver alloy. LANL test stand was constructed around a 50 MW, 5.712 GHz Canon klystron and is capable to provide power for conditioning single cell accelerating cavities for operation at surface electric fields up to 300 MV/m. These β=0.5 C-band cavities were the first two cavities tested on LANL C-band test stand. The presentation will report achieved gradients, breakdown probabilities, and other characteristics measured during the high power operation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB341

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paper received ※ 19 May 2021 paper accepted ※ 25 May 2021 issue date ※ 15 August 2021

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MOPAB342

Design, Fabrication, and Commissioning of the Mode Launchers for High Gradient C-Band Cavity Testing at LANL

GUI, klystron, simulation, MMI

1060

E.I. Simakov, J.E. Acosta, D. Gorelov, M.F. Kirshner, J.W. Lewellen
LANL, Los Alamos, New Mexico, USA
P. Borchard
Dymenso LLC, San Francisco, USA
M.E. Schneider
MSU, East Lansing, Michigan, USA

Funding: Los Alamos National Laboratory LDRD Program.
This poster will report on the design, fabrication, and operation status of the new high gradient C-band TM01 mode launchers for the high gradient C-band test stand at LANL. Modern applications require accelerators with optimized cost of construction and operation, naturally calling for high-gradient acceleration. At LANL we commissioned a test stand powered by a 50 MW, 5.712 GHz Canon klystron. The test is capable of conditioning single cell accelerating cavities for operation at surface electric fields up to 300 MV/m. The rf field is coupled into the cavity from a WR187 waveguide through a mode launcher that converts the fundamental mode of the rectangular waveguide into the TM01 mode of the circular waveguide. Several designs for mode launchers were considered and the final design was chosen based on a compromise between the field enhancements, bandwidth, and simplicity and cost of fabrication. Four mode launchers were fabricated and cold-tested. Two mode launchers with the best transmission characteristics were installed and conditioned to high power. The presentation will report achieved gradients, breakdown probabilities, and other characteristics measured during operation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB342

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paper received ※ 19 May 2021 paper accepted ※ 25 May 2021 issue date ※ 27 August 2021

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MOPAB343

Optimization of the Parasitic-Mode Damping on the 1.5 GHz TM020-type Harmonic Cavity

damping, impedance, coupling, simulation

1064

T. Yamaguchi
Sokendai, Ibaraki, Japan
D. Naito, S. Sakanaka, T. Takahashi, N. Yamamoto
KEK, Ibaraki, Japan

Bunch-lengthening harmonic cavity is one of the essential tools to mitigate the intrabeam scattering in the 4th-generation synchrotron light sources. For this purpose, we proposed a normal-conducting 1.5 GHz harmonic cavity* of TM020-type**. Thanks to its low R/Q (68 ohms) and high unloaded Q (34, 000), bunch gap transient in the harmonic cavity can be reduced to ~20% as compared to that in a typical TM010 cavity. Furthermore, harmful parasitic modes in this cavity can be heavily damped by installing ferrites where no magnetic fields of TM020-mode exist. However, some of the parasitic modes, e.g. TM021 and TM120 modes, are difficult to damp because their field patterns are similar to that of the TM020 mode. To damp such modes effectively, we optimized the cavity inner shape by tailoring the curvature at the cavity equator, the shape of the nose cones, and introducing "bumps" on the inner wall. Our goals of the coupling impedances are fxR < 2.4[kohm GHz] and RT < 23 kohm/m in the longitudinal and the transverse planes, respectively. As a result of optimization, we almost achieved these goals. To confirm our simulation results, fabrication of a low-power test cavity is in progress.
* N . Yamamoto et al., Phys. Rev. Acc. Beams 21, 012001 (2018).
** H. Ego et al., Proc. of the 11th Annual Meeting of Particle Accelerator Society of Japan (PASJ2014), MOOL14 (2014).

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB343

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paper received ※ 19 May 2021 paper accepted ※ 26 May 2021 issue date ※ 27 August 2021

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MOPAB344

Machine Learning Models for Breakdown Prediction in RF Cavities for Accelerators

operation, network, vacuum, linac

1068

C. Obermair, A. Apollonio, T. Cartier-Michaud, N. Catalán Lasheras, L. Felsberger, W.L. Millar, W. Wuensch
CERN, Geneva, Switzerland
C. Obermair, F. Pernkopf
TUG, Graz, Austria

Radio Frequency (RF) breakdowns are one of the most prevalent limits in RF cavities for particle accelerators. During a breakdown, field enhancement associated with small deformations on the cavity surface results in electrical arcs. Such arcs degrade a passing beam and if they occur frequently, they can cause irreparable damage to the RF cavity surface. In this paper, we propose a machine learning approach to predict the occurrence of breakdowns in CERN’s Compact LInear Collider (CLIC) accelerating structures. We discuss state-of-the-art algorithms for data exploration with unsupervised machine learning, breakdown prediction with supervised machine learning, and result validation with Explainable-Artificial Intelligence (Explainable AI). By interpreting the model parameters of various approaches, we go further in addressing opportunities to elucidate the physics of a breakdown and improve accelerator reliability and operation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB344

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paper received ※ 20 May 2021 paper accepted ※ 16 July 2021 issue date ※ 10 August 2021

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MOPAB347

High Power Coupler Conditioning for bERLinPro Energy Recovery Linac Injector

booster, vacuum, SRF, MMI

1080

A. Neumann, W. Anders, F. Göbel, A. Heugel, S. Klauke, J. Knobloch, M. Schuster, Y. Tamashevich
HZB, Berlin, Germany

Funding: The work is funded by the Helmholtz-Association, BMBF, the state of Berlin and HZB.
Helmholtz Zentrum Berlin is currently finalizing the construction of the demonstrator Energy Recovery Linac bERLinPro *. The first part, which will be commissioned, will be the injector consisting of a superconducting RF (SRF) photo-injector (Gun) and a Booster module made up of three two cell SRF cavities. For the latter the 2.3 MeV beam from the gun needs to be accelerated to 6.5 MeV, whereas one Booster cavity will be operated in zero-crossing mode for bunch-shortening. Thus, for the final stage with a 100 mA beam, the twin power couplers of the Booster cavity need to deliver up to 120 kW in travelling continous wave (CW) mode at 1.3 GHz each. To achieve that, a dedicated coupler conditioning setup was installed and commissioned. Here, we will present the first conditioning results with the bERLinPro Booster fundamental power couplers in pulsed and CW regime.
* M. Abo-Bakr et al., in Proc. 9th Int. Particle Accelerator Conf. (IPAC’18), Vancouver, BC, Canada, Apr. 4,, pp. 4127-4130, doi:10.18429/JACoW-IPAC2018-THPMF034

Poster MOPAB347 [3.256 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB347

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paper received ※ 18 May 2021 paper accepted ※ 08 June 2021 issue date ※ 23 August 2021

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MOPAB350

RF Buncher Cavity for Polarized He-3 Beam at BNL

simulation, alignment, insertion, booster

1090

T. Kanesue, S.M. Trabocchi
BNL, Upton, New York, USA
A. Murata
TIT, Tokyo, Japan

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
A 100.625 MHz quarter wave resonator type rf buncher cavity was fabricated for polarized He-3 spin rotator beam line at BNL. This cavity will be installed in the existing EBIS-To-Booster beam line to provide effective voltage of more than 40 kV for 2 MeV/u 3He²⁺ beam. This cavity has a large drift tube inner diameter of 80 mm and small gap length of 5 mm. The buncher consists of 3 sections, which are a cavity main body including drift tube, stem, and inner wall, a lid with a power coupler, and a lid with an inductive tuner. The main body was machined from a bulk copper only by CNC machining. The result of low power test agreed well with rf simulation without any alignment. The difference between measured and calculated resonant frequency was <0.1 %, and measured Q value was 92 % of that in simulation. The cavity rf design and test results will be shown.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB350

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paper received ※ 26 May 2021 paper accepted ※ 28 May 2021 issue date ※ 25 August 2021

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MOPAB353

Design of a compact Ka-Band Mode Launcher for High-gradient Accelerators

coupling, simulation, quadrupole, accelerating-gradient

1100

G. Torrisi, G.S. Mauro, G. Sorbello
INFN/LNS, Catania, Italy
M. Behtouei, L. Faillace, B. Spataro, A. Variola
INFN/LNF, Frascati, Italy
V.A. Dolgashev
SLAC, Menlo Park, California, USA
L. Faillace, M. Migliorati
Sapienza University of Rome, Rome, Italy
M. Migliorati
INFN-Roma1, Rome, Italy
J.B. Rosenzweig
UCLA, Los Angeles, California, USA
G. Sorbello
University of Catania, Catania, Italy

In this work, we present the RF design of a table-top Ka-Band mode launcher operating at 35.98 GHz. The structure consists of a symmetrical 4-port WR28 rectangular-TE10-to-circular-TM01 mode converter that is used to couple a peak output RF power of 5 MW (pulse length up to 50 ns and repetition rate up to 100 Hz) in Ka-Band linear accelerator able to achieve very high accelerating gradients (up to 200 MV/m). Numerical simulations have been carried out with the 3D full-wave commercial simulator Ansys HFSS in order to obtain a preliminary tuning of the accelerating field flatness at the operating frequency f0=35.98 GHz. The main RF parameters, such as reflection coefficient, transmission losses, and conversion efficiency are given together with a verification of the field azimuthal symmetry which avoids dipole and quadrupole deflecting modes. To simplify future manufacturing, reduce fabrication costs, and also reduce the probability of RF breakdown, the proposed new geometry has "open" configuration. This geometry eliminates the flow of RF currents through critical joints and allows this device to be milled from metal blocks.

Poster MOPAB353 [3.131 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB353

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paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 11 August 2021

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MOPAB355

Multi-Objective Optimization of RF Structures

impedance, controls, RF-structure, ECR

1103

S.J. Smith, R. Apsimon, G. Burt, M.J.W. Southerby
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
S. Setiniyaz
Cockcroft Institute, Warrington, Cheshire, United Kingdom
S. Setiniyaz
Lancaster University, Lancaster, United Kingdom

In this work, we apply multi-objective optimization methods to single-cell cavity models generated using non-uniform rational basis splines (NURBS). This modeling method uses control points and a NURBS to generate the cavity geometry, which allows for greater flexibility in the shape, leading to improved performance. Using this approach and multi-objective genetic algorithms (MOGAs) we find the Pareto frontiers for the typical key quantities of interest (QoI) including peak fields, shunt impedance and the modified Poynting vector. Visualizing these results becomes increasingly more difficult as the number of objectives increases, therefore, in order to understand these frontiers, we provide several techniques for analyzing, visualizing and using multi-dimensional Pareto fronts specifically for RF cavity design.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB355

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paper received ※ 19 May 2021 paper accepted ※ 15 July 2021 issue date ※ 01 September 2021

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MOPAB356

The ESS MEBT RF Buncher Cavities Conditioning Process

vacuum, controls, MEBT, EPICS

1107

I. Bustinduy, N. Garmendia, P.J. González, A. Kaftoosian, S. Masa, I. Mazkiaran, L.C. Medina, J.L. Muñoz
ESS Bilbao, Zamudio, Spain
J. Etxeberria, J.P.S. Martins
ESS, Lund, Sweden

Funding: This work is part of FEDER-TRACKS project, co-funded by the European Regional Development Fund (ERDF) .
As part of the 5 MW European Spallation Source (ESS), the Medium Energy Beam Transport (MEBT) was designed, assembled, and installed in the tunnel since May 2020 by ESS-Bilbao. This section of the accelerator is located between the Radio Frequency Quadrupole (RFQ) and the Drift Tube Linac (DTL). The main purpose of the MEBT is to match the incoming beam from the RFQ both transversely and longitudinally into the DTL. The longitudinal matching is achieved by three 352.209 MHz RF buncher cavities. In this paper, we focus on the RF conditioning process for each set of power coupler and buncher cavity. For this purpose, different tools were developed on EPICS and Python as well as electronics hardware such as Fast Interlock Module (FIM) and timing system. These tools served to automatize both the cavity frequency tuning and the power ramp-up process and will be described in detail in the following sections.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB356

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paper received ※ 18 May 2021 paper accepted ※ 09 June 2021 issue date ※ 17 August 2021

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MOPAB357

The New Design of the RF System for the SPS-II Light Source

storage-ring, booster, impedance, linac

1110

N. Juntong, T. Chanwattana, S. Chunjarean, S. Krainara, T. Phimsen, T. Pulampong
SLRI, Nakhon Ratchasima, Thailand
K. Manasatitpong
Synchrotron Light Research Institute (SLRI), Muang District, Thailand

The new light source facility in Thailand, SPS-II, is a ring-based 3 GeV light source with a circumference of approximately 330 m. The target stored beam current is 300 mA with an emittance of below 1.0 nm rad. The injector has been changed from a full energy linac to a booster injector with 150 MeV linac. The main RF frequency has been reconsidered to a low-frequency range at 119 MHz. Low frequency is chosen with the benefit of low RF voltage for a high RF acceptance together with experience with the present ring RF system of 118 MHz. Details of RF frequency consideration will be discussed. The requirements and details of the RF systems in the booster ring and the storage ring will be presented.

Poster MOPAB357 [1.696 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB357

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paper received ※ 17 May 2021 paper accepted ※ 08 June 2021 issue date ※ 10 August 2021

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MOPAB358

Design and Measurement of the 1.4 GHz Cavity for LEReC Linac

electron, resonance, GUI, HOM

1113

B.P. Xiao, J.C. Brutus, J.M. Fite, K. Hamdi, D. Holmes, K. Mernick, K.S. Smith, J.E. Tuozzolo, T. Xin, A. Zaltsman
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
The Low Energy RHIC electron Cooler (LEReC) is the first electron cooler based on rf acceleration of electron bunches. To further improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, a normal conducting RF cavity at 1.4 GHz was designed and fabricated for the LINAC that will provide longer electron bunches for the LEReC. It is a single-cell cavity with an effective cavity length shorter than half of the 1.4 GHz wavelength. This cavity was fabricated and tested on-site at BNL to verify RF properties, i.e. the resonance frequency, FPC coupling strength, tuner system performance, and high power tests. In this paper, we report the RF test results for this cavity.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB358

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paper received ※ 17 May 2021 paper accepted ※ 25 June 2021 issue date ※ 10 August 2021

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MOPAB359

Operational Experience and Redesign of the Tuner without Spring Fingers for the LEReC Warm Cavity

operation, vacuum, SRF, electron

1116

B.P. Xiao, J.M. Brennan, J.C. Brutus, K. Mernick, S. Polizzo, S.K. Seberg, F. Severino, K.S. Smith, A. Zaltsman
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
A folded coaxial tuner without spring fingers was designed for the Low Energy RHIC electron Cooler (LEReC) 2.1 GHz warm cavity. During RHIC run 2019, this tuner was found to cause cavity trips via different failure modes. After analyzing these failure modes, a new straight coaxial tuner without spring fingers was proposed and was installed. We show the operational experience of the new tuner in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB359

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paper received ※ 17 May 2021 paper accepted ※ 25 June 2021 issue date ※ 12 August 2021

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MOPAB361

Threshold in Filling Failure of RF Cavity Caused by Beam Loading in Multipactor

multipactoring, simulation, electron, experiment

1122

J. Pang
USTC/NSRL, Hefei, Anhui, People’s Republic of China
Y. Dong
Institute of Applied Physics and Computational Mathematics, People’s Republic of China
Y. Du
Institute of Fluid Physics,, China Academy of Engineering Physics, Mianyang, People’s Republic of China

Funding: NSFC
A pulsed RF cavity would be heavily detuned caused by beam loading of multipactor current in the RF filling process. Multipactor zone would be expended by several times than that in static states with assumptions of fixed voltage and no beam loading. The dynamic of multipactor in the RF filling process was simulated by coupling with parameters of external circuit with the developed simulation code, and test in experiments with a parallel-plate resonator. Threshold of RF voltage, which means the lower boundary of peak voltage of multipactor zone, had been quantified with different cavity parameters. When we increased the gap length, the measured threshold became larger due to the ionization in background gas. Then the secondary emission factor would be increased in simulation for consistence with the experiment results. Additionally, some multipactor phenomenon could not be predicted precisely because the simulation code did not take account of ionization. The hysteresis of phase and energy of ionization electrons would be a new driving factor for the growth of multipactor in certain conditions.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB361

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paper received ※ 19 May 2021 paper accepted ※ 24 May 2021 issue date ※ 15 August 2021

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MOPAB363

Design, Characteristics and Dynamic Properties of Mobile Plunger-based Frequency Tuning System for Coaxial Half Wave Resonators

operation, experiment, controls, resonance

1129

D. Bychanok, S. Huseu, S.A. Maksimenko, A.E. Sukhotski
INP BSU, Minsk, Belarus
A.V. Butenko, E. Syresin
JINR, Dubna, Moscow Region, Russia
M. Gusarova, M.V. Lalayan, S.M. Polozov
MEPhI, Moscow, Russia
V.S. Petrakovsky, A.I. Pokrovsky, A. Shvedov, S.V. Yurevich
Physical-Technical Institute of the National Academy of Sciences of Belarus, Minsk, Belarus
Y. Tamashevich
HZB, Berlin, Germany

The practical realization of a prototype of the frequency tuning system (FTS) for coaxial half-wave cavities (HWR) for the Nuclotron-based Ion Collider fAcility (NICA) injector is presented. The impact of FTS on electromagnetic parameters of copper HWR prototype is experimentally studied and discussed. The most important parameters like tuning range, tuning sensitivity, the dependence of the resonant frequency on the position of the plungers are estimated. The effective operation algorithms of the proposed FTS are discussed and analyzed. The dynamic characteristics of FTS are investigated and showed the ability to adjust the frequency with an accuracy of about 70 Hz.

Poster MOPAB363 [3.597 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB363

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paper received ※ 18 May 2021 paper accepted ※ 09 June 2021 issue date ※ 28 August 2021

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MOPAB365

Construction and First Test Results of the Barrier and Harmonic RF Systems for the NICA Collider

collider, vacuum, injection, electron

1136

A.G. Tribendis, Y.A. Biryuchevsky, K.N. Chernov, A.N. Dranitchnikov, E. Kenzhebulatov, A.A. Kondakov, A.A. Krasnov, Ya.G. Kruchkov, S.A. Krutikhin, G.Y. Kurkin, A.M. Malyshev, A.Yu. Martynovsky, N.V. Mityanina, S.V. Motygin, A.A. Murasev, V.N. Osipov, V.M. Petrov, E. Pyata, E. Rotov, V.V. Tarnetsky, I.A. Zapryagaev, A.A. Zhukov
BINP SB RAS, Novosibirsk, Russia
O.I. Brovko, A.M. Malyshev, I.N. Meshkov, E. Syresin
JINR, Dubna, Moscow Region, Russia
I.N. Meshkov
Saint Petersburg State University, Saint Petersburg, Russia
E. Rotov
NSU, Novosibirsk, Russia
A.G. Tribendis
NSTU, Novosibirsk, Russia
A.V. Zinkevich
Triada-TV, Novosibirsk, Russia

This paper reports on the design features and construction progress of the three RF systems for the NICA collider being built at JINR, Dubna. Each of the two collider rings has three RF systems named RF1 to 3. RF1 is a barrier bucket system used for particles capturing and accumulation during injection, RF2 and 3 are resonant systems operating at 22nd and 66th harmonics of the revolution frequency and used for the 22 bunches formation. The RF systems are designed and produced by Budker INP. Solid state RF power amplifiers developed by the Triada-TV company, Novosibirsk, are used for driving the RF2 and three cavities. Two RF1 stations were already delivered to JINR, the prototypes of the RF2 and 3 stations were built and successfully tested at BINP. Series production of all eight RF2 and sixteen RF3 stations is in progress. The design modifications and test results are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB365

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paper received ※ 18 May 2021 paper accepted ※ 24 May 2021 issue date ※ 19 August 2021

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MOPAB366

Improving Magnetic Materials for RCS Cavity Tuners

solenoid, simulation, booster, synchrotron

1139

R.L. Madrak, N.M. Curfman, G.V. Romanov, C.-Y. Tan, I. Terechkine
Fermilab, Batavia, Illinois, USA
G. Das, A.K. Samanta
Ceramic Magnetics, Inc., National Magnetics Group, Inc., Bethlehem, USA

Funding: United States Department of Energy, Contract No. DE-AC02-07CH11359
Within the Lab Directed R&D Program at Fermilab, and in partnership with National Magnetics, we have recently begun to study and attempt to improve the loss parameter in garnet material. This could be used for fast tuner applications such as in rapid cycling synchrotrons.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB366

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paper received ※ 19 May 2021 paper accepted ※ 25 May 2021 issue date ※ 23 August 2021

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MOPAB371

A Coupon Tester for Normal Conducting High-Gradient Materials

coupling, vacuum, RF-structure, klystron

1147

J.W. Lewellen, D. Gorelov, D. Perez, E.I. Simakov
LANL, Los Alamos, New Mexico, USA
M.E. Schneider
Michigan State University, East Lansing, Michigan, USA

Funding: Los Alamos National Laboratory LDRD Program
A coupon tester is an RF structure used to subject a material sample to very high RF fields, with the fields on the sample, or coupon, being higher than elsewhere in the cavity. To date, most such cavities were originally intended to explore the RF properties of superconducting materials, and can expose the sample to strong magnetic fields, but weak to no electric fields. As part of a program to develop materials and structures for high-gradient (> 100 MV/m), low-breakdown-rate normal-conducting accelerators, we have designed a C-band (5.712 GHz) cavity intended to subject samples to both magnetic and electric fields comparable to those experienced in high-gradient structure designs, using a TM-mode cavity; the electric and magnetic fields along the sample coupon can be directly compared to the fields on the iris of high-gradient structures. This poster will present the design criteria for our coupon tester cavity, nominal operating parameters, and our structure concept. The cavity design will be refined over the next several months, and will be constructed and in service near the start of 2022.

Poster MOPAB371 [0.764 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB371

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paper received ※ 17 May 2021 paper accepted ※ 26 May 2021 issue date ※ 25 August 2021

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MOPAB374

Creating Exact Multipolar Fields in Accelerating RF Cavities via an Azimuthally Modulated Design

simulation, quadrupole, dipole, collider

1154

L.M. Wroe, S.L. Sheehy
JAI, Oxford, United Kingdom
R. Apsimon
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
M. Dosanjh
CERN, Meyrin, Switzerland
S.L. Sheehy
The University of Melbourne, Melbourne, Victoria, Australia

In this paper, we present a novel method for designing RF structures with specifically tailored multipolar field contributions. This has a range of applications, including the suppression of unwanted multipolar fields or the introduction of wanted terms, such as for quadrupole focusing. In this article, we outline the general design methodology and compare the expected results to 3D CST simulations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB374

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paper received ※ 19 May 2021 paper accepted ※ 08 June 2021 issue date ※ 10 August 2021

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MOPAB376

Design and Fabrication of a Quadrupole Resonator for SRF R&D

SRF, quadrupole, niobium, radio-frequency

1158

R. Monroy-Villa, W. Hillert, M. Wenskat
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
S. Gorgi Zadeh, P. Putek
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
R. Monroy-Villa, D. Reschke, J.H. Thie
DESY, Hamburg, Germany

As Nb superconducting radio-frequency (SRF) cavities are now approaching the theoretical limits of the material, a variety of different surface treatments have been developed to further improve their performance; although no fully understood theory is yet available. Small superconducting samples are studied to characterize their material properties and their evolution under different surface treatments. To study the RF properties of such samples under realistic SRF conditions at low temperatures, a test cavity called quadrupole resonator (QPR) is currently being fabricated. In this work we report the status of the QPR at Universität Hamburg in collaboration with DESY. Our device is based on the QPRs operated at CERN and at HZB and its design will allow for testing samples under cavity-like conditions, i.e., at temperatures between 2K and 8 K, under magnetic fields up to 120mT and with operating frequencies of 433 MHz, 866 MHz and 1300 MHz. Fabrication tolerance studies on the electromagnetic field distributions and simulations of the static detuning of the device, together with a status report on the current manufacturing process, will be presented.

Poster MOPAB376 [1.119 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB376

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paper received ※ 26 May 2021 paper accepted ※ 09 June 2021 issue date ※ 23 August 2021

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MOPAB379

Topological Optimization on SRF Cavities for Nuclear and High Energy Physics

niobium, superconducting-cavity, radiation, simulation

1162

H. Gassot
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France

Topology optimization has been developed for more than twenty years. The progress of additive manufacturing boosts the development in topological optimization since the design can be completely innovated and realized by 3D printing. The potential for cost reductions thanks to weight minimization give an interesting perspective for the small production of niobium superconducting radio-frequency cavities, commonly used in accelerators. The traditional manufacturing technologies of cavities are based on multi-stage processes while additive manufacturing technologies can built fully functional parts in a single operation. For modern accelerators that use superconducting linac, including energy recovery linacs (ERLs), it is particularly important to know the perspectives of additive manufacturing for SRF cavities. In this paper, we try to build a preliminary perception of topological optimization in superconducting cavities manufacturing innovation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB379

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paper received ※ 11 May 2021 paper accepted ※ 17 August 2021 issue date ※ 17 August 2021

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MOPAB380

Status and Progress of the RF System for High Energy Photon Source

photon, storage-ring, booster, low-level-rf

1165

P. Zhang, J. Dai, Z.W. Deng, L. Guo, T.M. Huang, D.B. Li, J. Li, Z.Q. Li, H.Y. Lin, Y.L. Luo, Q. Ma, F. Meng, Z.H. Mi, Q.Y. Wang, X.Y. Zhang, F.C. Zhao, H.J. Zheng
IHEP, Beijing, People’s Republic of China

Funding: This work was supported in part by High Energy Photon Source, a major national science and technology infrastructure in China and in part by the Chinese Academy of Sciences.
High Energy Photon Source (HEPS) is a 6 GeV diffraction-limited synchrotron light source currently under construction in Beijing. It adopts a double-frequency RF system with 166.6 MHz as fundamental and 499.8 MHz as third harmonic. The fundamental cavity is making use of a superconducting quarter-wave β=1 structure and the third harmonic is of superconducting elliptical single-cell geometry for the storage ring, while normal-conducting 5-cell cavities are chosen for the booster ring. A total of 900 kW RF power shall be delivered to the beam by the 166.6 MHz cavities and the third harmonic cavities are active. All cavities are driven by solid-state power amplifiers and the RF fields are regulated by digital low-level RF control systems. The cavity and ancillaries, high-power RF system and low-level RF control system are in the prototyping phase. This paper presents the current status and progress of the RF system for HEPS.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB380

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paper received ※ 09 May 2021 paper accepted ※ 09 June 2021 issue date ※ 12 August 2021

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MOPAB382

Synchrotron Light Shielding for the 166 MHz Superconducting RF Section at High Energy Photon Source

shielding, synchrotron, storage-ring, radiation

1169

X.Y. Zhang, Z.Q. Li, Q. Ma, P. Zhang
IHEP, Beijing, People’s Republic of China

Funding: This work was supported by High Energy Photon Source, a major national science and technology infrastructure in China.
The High Energy Photo Source (HEPS) project has been under construction since 2019, and will be first diffraction-limited synchrotron light source in China. A 6 GeV electron beam with 200 mA current will be stored in the main ring. If synchrotron light produced from this energetic electron beam hits the superconducting cavity’s surface, it would cause thermal breakdown of the superconductivity. In the current lattice design, these lights cannot be fully blocked by the collimator in the upstream lattice cell, therefore a shielding scheme inside the rf section is required. This however brings great challenges to the already limited space. The design of the collimator has been focused on fulfilling shielding requirements while optimizing beam impedance, synchrotron light power density, thermal and mechanical stabilities. Shielding materials are subsequently chosen with dedicated cooling to ensure long-term stable operations. In this paper, a shielding scheme inside the rf section of the HEPS storage ring is presented. The synchrotron light mainly from the upstream bending magnet is successfully block. The sensitivity to beam position movement and installation error is also analyzed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB382

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paper received ※ 17 May 2021 paper accepted ※ 11 June 2021 issue date ※ 25 August 2021

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MOPAB383

Pressure Test for Large Grain and Fine Grain Niobium Cavities

niobium, SRF, experiment, FEM

1173

M. Yamanaka, T. Dohmae, H. Inoue, T. Saeki, K. Umemori, Y. Watanabe, K. Yoshida
KEK, Ibaraki, Japan
K. Enami
Tsukuba University, Ibaraki, Japan

The pressure test was performed using a fine grain (FG) and a large grain (LG) niobium cavities. The cavity is 1.3 GHz 3-cell TESLA-like shape. The cavity was housed in a steel vessel. Water is supplied into the vessel and the cavity outside is pressurized. The applying pressure and the natural frequency of cavity were measured during the pressure test. The FG and LG cavities were deformed greatly and the pressure dropped suddenly at 3.4 MPa and 1.6 MPa, respectively. The frequency shifted up to 3.4 MHz and 1.3 MHz, respectively. There was no leak after the pressure test, so the cavity did not rupture under above pressure. The result of the pressure at LG cavity is less half than that of the FG cavity. We calculated the stress distribution in the structure by applying outer water pressure using a FEM. The maximum stress at cell when above test pressure is applied, are 146 MPa in FG and 73 MPa in LG, respectively. These stresses are similar to tensile strength of niobium specimen measure by ourselves. The result of pressure tests agrees well with the calculation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB383

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paper received ※ 19 May 2021 paper accepted ※ 22 June 2021 issue date ※ 13 August 2021

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MOPAB384

Nb₃Sn Coating of Twin Axis Cavity for Accelerator Applications

linac, niobium, SRF, dipole

1175

J.K. Tiskumara, S.U. De Silva, J.R. Delayen, H. Park
ODU, Norfolk, Virginia, USA
J.R. Delayen, H. Park, U. Pudasaini, C.E. Reece
JLab, Newport News, Virginia, USA
G.V. Eremeev
Fermilab, Batavia, Illinois, USA

Funding: Research supported by DOE Office of Science Accelerator Stewardship Program Award DE- SC0019399. Partially authored by Jefferson Science Associates under contract no. DEAC0506OR23177
A Superconducting twin axis cavity consisting of two identical beam pipes that can accelerate and decelerate beams within the same structure has been proposed for the Energy Recovery Linac (ERL) applications. There are two niobium twin axis cavities at JLab fabricated with the intention of later Nb₃Sn coating and now we are progressing to coat them using vapor diffusion method. Nb₃Sn is a potential alternate material for replacing Nb in SRF cavities for better performance and reducing operational costs. Because of advanced geometry, larger surface area, increased number of ports and hard to reach areas of the twin axis cavities, the usual coating approach developed for typical elliptical single-axis cavities must be evaluated and requires to be adjusted. In this contribution, we report the first results from the coating of a twin axis cavity and discuss current challenges with an outlook for the future.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB384

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paper received ※ 19 May 2021 paper accepted ※ 24 May 2021 issue date ※ 20 August 2021

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MOPAB385

An Overview of RF Systems for the EIC

SRF, electron, HOM, luminosity

1179

R.A. Rimmer, J.P. Preble
JLab, Newport News, Virginia, USA
K.S. Smith, A. Zaltsman
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under DOE Contract No. DE-SC0012704, by Jefferson Science Associates under contract DE-SC0002769, and by SLAC under Contract No. DE-AC02-76SF00515.
The Electron Ion Collider (EIC) to be constructed at Brookhaven National Laboratory in the USA will be a complex system of accelerators providing high luminosity, high polarization, variable center of mass energy collisions between electrons and protons or ions. To achieve this a variety of RF systems are required. They must provide for capture, formation and storage of Ampere-class beams in the electron and hadron storage rings (ESR and HSR), fast acceleration of high-charge polarized electron bunches in the rapid cycling synchrotron (RCS), provision of cold high current electron bunches in the high-energy cooler ERL and precise high-gradient crabbing of electrons and hadrons either side of the interaction point. The challenges include strong HOM damping in the storage ring cavities and cooler ERL, very high fundamental mode power in the ESR and cooler injector, extremely stable low-noise operation of the crab cavities, mitigation of transient beam loading from gaps, and operating over a wide range of energies and beam currents. We describe the high-level system parameters and principal design choices made and progress on the R&D plan to develop these state of the art systems.

Poster MOPAB385 [1.268 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB385

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paper received ※ 18 May 2021 paper accepted ※ 31 May 2021 issue date ※ 22 August 2021

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MOPAB386

Development of Nitrogen-Doping Technology for SHINE

SRF, niobium, ECR, linac

1182

Y. Zong, X. Huang, Z. Wang
SINAP, Shanghai, People’s Republic of China
J.F. Chen, H.T. Hou, D. Wang, J.N. Wu, Y.X. Zhang
SARI-CAS, Pudong, Shanghai, People’s Republic of China
P.C. Dong
Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China
Y.W. Huang
ShanghaiTech University, Shanghai, People’s Republic of China
J. Rong
SSRF, Shanghai, People’s Republic of China

The Shanghai HIgh repetition rate XFEL aNd Extreme light facility (SHINE) is under construction, which needs six hundred 1.3GHz cavities with high quality factor. In this paper, we present the newest studies on single cell cavities with nitrogen doping and cold EP treatment, showing an obvious improvement compared with the previous results.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB386

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paper received ※ 21 May 2021 paper accepted ※ 08 June 2021 issue date ※ 12 August 2021

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MOPAB388

Status of the High Power Couplers for ESS Elliptical Cavities

cryomodule, simulation, vacuum, SRF

1186

C. Arcambal, P. Bosland, G. Devanz, T. Hamelin, C. Madec, C. Marchand, M. Oublaid, G. Perreu, C. Servouin, C. Simon
CEA-IRFU, Gif-sur-Yvette, France
M. Baudrier, C. Mayri, S. Regnaud, T.V. Vacher
CEA-DRF-IRFU, France

In the framework of the European Spallation Source (ESS), CEA Paris-Saclay is responsible for the delivery of 30 cryomodules (9 medium beta (β = 0.67) and 21 high beta (β = 0.86) ones). Each cryomodule contains 4 elliptical cavities equipped with a radio frequency power coupler. The ESS nominal pulse is 1.1 MW maximum peak power over a width of 3.6 ms at a repetition rate of 14 Hz. The design of the couplers for medium beta and for high beta cavities is the same, except a small difference of the antenna penetration to adjust the Q_ext. The mass production of the 120 couplers started and all the medium beta couplers have been conditioned at room temperature. The first cryomodules equipped with the power couplers were successfully tested at high RF power and with cavities at 2K reaching the ESS nominal pulse. The main issue at the start of the series production could be fixed and it was due to bad TiN coatings that caused abnormal dielectric losses in the window. Thus, this paper deals with the TiN coating defect, presents the conditioning procedure and gives a conditioning report of these 36 couplers.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB388

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paper received ※ 19 May 2021 paper accepted ※ 24 May 2021 issue date ※ 30 August 2021

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MOPAB390

Development of a 166.6 MHz Low-Level RF System by Direct Sampling for High Energy Photon Source

LLRF, controls, photon, pick-up

1189

D.B. Li, H.Y. Lin, Q.Y. Wang, P. Zhang
IHEP, Beijing, People’s Republic of China

Funding: This work was supported by High Energy Photon Source, a major national science and technology infrastructure in China.
A digital low-level radio frequency (LLRF) system by direct sampling has been proposed for 166.6 MHz superconducting cavities at High Energy Photon Source (HEPS). The RF field inside the cavities has to be controlled better than ±0.1% (peak to peak) in amplitude and ±0.1 deg (peak to peak) in phase. Considering that the RF frequency is 166.6 MHz, which is well within the analog bandwidth of modern high-speed ADCs and DACs, direct RF sampling and direct digital modulation can be achieved. A digital LLRF system utilizing direct sampling has therefore been developed with embedded experimental physics and industrial control system (EPICS) in the field programmable gate array (FPGA). The performance in the lab has been characterized in a self-closed loop with a residual peak-to-peak noise of ±0.05% in amplitude and ±0.03 deg in phase, which is well below the HEPS specifications. Further tests on a warm 166.6 MHz cavity in the lab are also presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB390

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paper received ※ 17 May 2021 paper accepted ※ 09 June 2021 issue date ※ 11 August 2021

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MOPAB391

Conduction Cooling Methods for Nb₃Sn SRF Cavities and Cryomodules

SRF, controls, accelerating-gradient, simulation

1192

N.A. Stilin, A.T. Holic, M. Liepe, R.D. Porter, J. Sears, Z. Sun
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Rapid progress in the performance of Nb₃Sn SRF cavities during the last few years has made Nb₃Sn an energy efficient alternative to traditional Nb cavities, thereby initiating a fundamental shift in SRF technology. These Nb₃Sn cavities can operate at significantly higher temperatures than Nb cavities while simultaneously requiring less cooling power. This critical property enables the use of new, robust, turn-key style cryogenic cooling schemes based on conduction cooling with commercial cryocoolers. Cornell University has developed and tested a 2.6 GHz Nb₃Sn cavity assembly which utilizes such cooling methods. These tests have demonstrated stable RF operation at 10 MV/m and the measured thermal dynamics match what is found in numerical simulations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB391

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paper received ※ 20 May 2021 paper accepted ※ 10 June 2021 issue date ※ 17 August 2021

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MOPAB392

Alternative RF Tuning Methods Performed on Spoke Cavities for ESS and MYRRHA Projects

operation, target, simulation, experiment

1196

P. Duchesne, S. Blivet, G. Olivier, G. Olry, T. Pépin-Donat
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France

In order to obtain the target frequency in operation, the resonant frequency of superconducting radiofrequency cavities is controlled and adjusted from the manufacturing to the end of preparation phase. Reaching this right frequency can be challenging due to the narrow frequency range defined by the tuning sensitivity of the cavity and the capability of the tuner. Mechanical deformation until plasticity is attained is of great interest to tune SRF cavities when large frequency shift is needed. But once a cavity is dressed with its helium tank, the only accessible part is its beam pipe, reducing the mechanical action to a push/pull action. This limited possibility has hence to be skilfully associated with chemical etching. An original mechanical tuning of Spoke dressed cavities consists in increasing the pressure inside the helium tank to induce a permanent deformation of the cavity walls. The frequency shift induced by nonlinear deformation is numerically evaluated in order to determine the pressure increments. Both methods were successfully performed on the cavities of the ESS accelerator and of the Myrrha project.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB392

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paper received ※ 20 May 2021 paper accepted ※ 25 June 2021 issue date ※ 02 September 2021

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MOPAB393

Design of an RF-Dipole Crabbing Cavity System for the Electron-Ion Collider

HOM, cryomodule, impedance, electron

1200

S.U. De Silva, J.R. Delayen
ODU, Norfolk, Virginia, USA
J. Henry, F. Marhauser, H. Park, R.A. Rimmer
JLab, Newport News, Virginia, USA

The Electron-Ion Collider requires several crabbing systems to facilitate head-on collisions between electron and proton beams in increasing the luminosity at the interaction point. One of the critical rf systems is the 197 MHz crabbing system that will be used in crabbing the proton beam. Many factors such as the low operating frequency, large transverse voltage requirement, tight longitudinal and transverse impedance thresholds, and limited beam line space makes the crabbing cavity design challenging. The rf-dipole cavity design is considered as one of the crabbing cavity options for the 197 MHz crabbing system. The cavity is designed including the HOM couplers, FPC and other ancillaries. This paper presents the detailed electromagnetic design, mechanical analysis, and conceptual cryomodule design of the crabbing system.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB393

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paper received ※ 26 May 2021 paper accepted ※ 02 June 2021 issue date ※ 11 August 2021

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MOPAB394

Preliminary BCP Flow Field Investigation by CFD Simulations and PIV in a Transparent Model of a SRF Elliptical Low Beta Cavity

experiment, simulation, SRF, laser

1204

A. D’Ambros, M. Bertucci, A. Bosotti, A.T. Grimaldi, P. Michelato, L. Monaco, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
F. Cozzi, G. Pianello
Politecnico di Milano, Milano, Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy

Standard vertical Buffered Chemical Polishing (BCP) is one of the main surface treatment for Superconducting Radiofrequency (SRF) cavities. A finite element Computational Fluid Dynamic (CFD) model has been developed. Uncertainties in the solution of fluid simulations are not negligible due to the complex geometry of a SRF cavity; thus without an experimental validation, results from this type of simulations cannot be confidently used to improve the process. To this aim, an experimental study was started to investigate the fluid dynamics of the BCP process by means of Particle Image Velocimetry (PIV) technique. Similitude on Reynolds number and Refractive Index Matching (RIM) technique were also implemented to replace the dangerous BCP mixture with a glycerine-water mixture. The paper describes the preliminary results from simulations and experiment.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB394

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paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 14 August 2021

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MOPAB396

Measurements of Magnetic Field Penetration in Superconducting Materials for SRF Cavities

SRF, experiment, solenoid, accelerating-gradient

1208

I.H. Senevirathne, J.R. Delayen, A.V. Gurevich
ODU, Norfolk, Virginia, USA
J.R. Delayen, A-M. Valente-Feliciano
JLab, Newport News, Virginia, USA

Funding: This work is supported by NSF Grants PHY-1734075 and PHY-1416051, and DOE Award DE-SC0010081 and DE-SC0019399
Superconducting radiofrequency (SRF) cavities used in particle accelerators operate in the Meissner state. To achieve high accelerating gradients, the cavity material should stay in the Meissner state under high RF magnetic field without penetration of vortices through the cavity wall. The field onset of flux penetration into a superconductor is an important parameter of merit of alternative superconducting materials other than Nb which can enhance the performance of SRF cavities. There is a need for a simple and efficient technique to measure the onset of field penetration into a superconductor directly. We have developed a Hall probe experimental setup for the measurement of the flux penetration field through a superconducting sample placed under a small superconducting solenoid magnet which can generate magnetic fields up to 500 mT. The system has been calibrated and used to measure different bulk and thin film superconducting materials. This system can also be used to study SIS multilayer coatings that have been proposed to enhance the vortex penetration field in Nb cavities.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB396

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paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 11 August 2021

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MOPAB400

Development of Helium Vessel Welding Process for SNS PPU Cavities

proton, cryomodule, neutron, accelerating-gradient

1212

P. Dhakal, E. Daly, G.K. Davis, J.F. Fischer, N.A. Huque, K. Macha, P.D. Owen, K.M. Wilson, M. Wiseman
JLab, Newport News, Virginia, USA

Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The Spallation Neutron Source Proton Power Upgrade cavities are produced by Research Instrument with all the cavity processing done at vendor sites with final chemistry applied to the cavity to be electropolishing. Cavities are delivered to Jefferson Lab, ready to be tested. One of the tasks to be completed before the arrival of production-ready PPU cavities is to develop a robust helium vessel welding protocol. We have successfully developed the process and applied it to three six-cell high beta cavities. Here, we present the summary of RF results, welding process development, and post helium vessel RF results.

Poster MOPAB400 [1.313 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB400

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paper received ※ 18 May 2021 paper accepted ※ 26 May 2021 issue date ※ 11 August 2021

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MOPAB401

In-Situ EXAFS Investigations of Nb-Treatments in N₂, O₂ and N₂-O₂ Mixtures at Elevated Temperatures

vacuum, site, experiment, niobium

1214

P. Rothweiler, B. Bornmann, J. Klaes, D. Lützenkirchen-Hecht, R. Wagner
University of Wuppertal, Wuppertal, Germany

Funding: We gratefully acknowledge financial support by the German Federal Ministry of Education and Research (BMBF) under project No. 05H18PXRB1.
Smooth polycrystalline Nb metal foils were treated in dilute gas atmospheres using a temperature of 900 °C. Transmission mode X-ray absorption spectroscopy (EX-AFS) at the Nb K-edge was used to investigate changes in the atomic short-range order structure of the bulk Nb-material in-situ. The experiments were performed in a dedicated high-vacuum cell that allows treatments in a dilute gas atmosphere and temperatures of up to 1200 °C. Typical treatments include (i) pre-heating at 900 °C under high-vacuum, (ii) gas exposure at the desired pressure and temperature, and (iii) cooldown to room temperature under vacuum. EXAFS data were collected during the entire procedure with a time resolution of 1 s. For the treatments in N₂ at T = 900°C, the data show subtle changes in the Nb-EXAFS, that are compatible with N-doping of the bulk Nb, and the results suggest Nb uptake on octahedral interstitial sites. However, even a small O2-partial pressure leads to distinct oxidation of the Nb. The results will be discussed in more detail in the presentation.

Poster MOPAB401 [2.032 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB401

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paper received ※ 19 May 2021 paper accepted ※ 26 May 2021 issue date ※ 28 August 2021

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TUXA07

Beam Dynamics Study in a Dual Energy Storage Ring for Ion Beam Cooling*

storage-ring, electron, focusing, emittance

1290

B. Dhital, G.A. Krafft
ODU, Norfolk, Virginia, USA
Y.S. Derbenev, D. Douglas, A. Hutton, G.A. Krafft, F. Lin, V.S. Morozov, Y. Zhang
JLab, Newport News, Virginia, USA

Funding: * Work supported by the U.S. Department of Energy, Office of Science, and Office of Nuclear Physics under Contracts DE-AC05-06OR23177 and DE-AC02-06CH11357. / Jefferson Lab EIC Fellowship2020.
A dual energy storage ring designed for beam cooling consists of two closed rings with significantly different energies: the cooling and damping rings. These two rings are connected by an energy recovering superconducting RF structure that provides the necessary energy difference. In our design, the RF acceleration has a main linac and harmonic cavities both running at crest that at first accelerates the beam from low energy E_L to high energy E_H and then decelerates the beam from E_H to E_L in the next pass. The purpose of the harmonic cavities is to extend the bunch length in a dual energy storage ring as such a longer bunch length may be very useful in a cooling application. Besides these cavities, a bunching cavity running on zero-crossing phase is used outside of the common beamline to provide the necessary longitudinal focusing for the system. In this paper, we present a preliminary lattice design along with the fundamental beam dynamics study in such a dual energy storage ring.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXA07

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paper received ※ 19 May 2021 paper accepted ※ 07 June 2021 issue date ※ 25 August 2021

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TUXB04

Fabrication and Tuning of a THz-Driven Electron Gun

gun, electron, GUI, resonance

1297

S.M. Lewis, A.A. Haase, J.W. Merrick, E.A. Nanni, M.A.K. Othman, S.G. Tantawi
SLAC, Menlo Park, California, USA
S.M. Lewis
Fermilab, Batavia, Illinois, USA

Funding: This work was supported by the Department of Energy Contract No. DE-AC02-76SF00515 (SLAC) and by NSF Grant No. PHY-1734015.
We have developed a THz-driven field emission electron gun and beam characterization assembly. The two cell standing-wave gun operates in the pi mode at 110.08 GHz. It is designed to produce 360 keV electrons with 500 kW of input power supplied by a 110 GHz gyrotron. Multiple gun structures were electroformed in copper using a high precision diamond-turned mandrel. The field emission cathode is a rounded copper tip located in the first cell. The cavity resonances were mechanically tuned using azimuthal compression. This work will discuss details of the fabrication and tuning and present the results of low power measurements.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXB04

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paper received ※ 18 May 2021 paper accepted ※ 22 June 2021 issue date ※ 28 August 2021

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TUXC03

Ferro-Electric Fast Reactive Tuner Applications for SRF Cavities

SRF, beam-loading, operation, controls

1305

N.C. Shipman, A. Castilla, M.R. Coly, F. Gerigk, A. Macpherson, N. Stapley, H. Timko
CERN, Geneva, Switzerland
I. Ben-Zvi
BNL, Upton, New York, USA
G. Burt, A. Castilla
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
C.-J. Jing, A. Kanareykin
Euclid TechLabs, Solon, Ohio, USA

A Ferro-Electric fast Reactive Tuner (FE-FRT) is a novel type of RF cavity tuner containing a low loss ferroelectric material. FE-FRTs have no moving parts and allow cavity frequencies to be changed extremely quickly (on the timescale of 100s of ns or less). They are of particular interest for SRF cavities as they can be placed outside the liquid helium environment and without an FE-FRT it’s typically very difficult to tune SRF cavities quickly. FE-FRTs can be used for a wide variety of use cases including microphonics suppression, RF switching, and transient beam loading compensation. This promises entirely new operational capabilities, increased performance and cost savings for a variety of existing and proposed accelerators. An overview of the theory and potential applications will be discussed in detail.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXC03

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paper received ※ 19 May 2021 paper accepted ※ 02 August 2021 issue date ※ 01 September 2021

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TUPAB016

ESS RFQ: Installation and Tuning at Lund

rfq, quadrupole, insertion, coupling

1372

P. Hamel, D. Chirpaz-Cerbat, M. Desmons, A.C. France, O. Piquet
CEA-IRFU, Gif-sur-Yvette, France
A. Dubois, Y. Le Noa
CEA-DRF-IRFU, France

The 352 MHz Radio Frequency Quadrupole (RFQ) for the European Spallation Source ERIC (ESS) has been delivered by the end of 2019. It has been provided by CEA, IRFU, Saclay/France. It consists of five sections with a total length of 4.6 m and accelerates the 70 mA proton beam from 75 keV up to 3.6 MeV. It will be fed with 900 kW peak power through two coaxial loop couplers. The installation process (alignment, vacuum test), as well as the tuning process based on bead-pull measurements, is presented in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB016

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paper received ※ 18 May 2021 paper accepted ※ 06 July 2021 issue date ※ 30 August 2021

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TUPAB017

Study of Conduction-Cooled Superconducting Quadrupole Magnets Combined with Dipole Correctors for the ILC Main Linac

quadrupole, dipole, linac, SRF

1375

Y. Arimoto, S. Michizono, Y. Morikawa, N. Ohuchi, T. Oki, H. Shimizu, K. Umemori, X. Wang, A. Yamamoto, Y. Yamamoto, Z.G. Zong
KEK, Ibaraki, Japan
V.S. Kashikhin
Fermilab, Batavia, Illinois, USA

A superconducting rf (SRF) cryomodule for International Linear Collider(ILC) Main Linac equips focus/steering magnets. The magnets are "superferric" magnets with four superconducting (SC) race track coils conductively cooled from the cryomodule LHe supply pipe. The quadrupole field gradient and dipole field are 40 T/m and 0.1 T, respectively. The magnet length and iron-pole radius are 1 m and 0.045 m, respectively. It is known that dark current is generated at SRF cavities and accelerated through the following linac string. The dark current reaches and heats the SC magnets. It is estimated that the power deposition in the magnet may reach more than a few watts and temperature of the SC coils may locally reach to critical temperature of NbTi. It is important to make the magnet not reach quench with sufficient conduction cooling. We aim to realize the SC magnet which can stably operate under such condition. We plan to develop test coils made of three types of SC materials, NbTi, Nb₃Sn, and MgB₂ and study thermal characteristics and stability . We will develop a short model magnet, based on the test coil results. Here, we will present the magnet design study and the R&D plan.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB017

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paper received ※ 19 May 2021 paper accepted ※ 16 June 2021 issue date ※ 20 August 2021

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TUPAB019

A High-Resolution, Low-Latency, Bunch-by-Bunch Feedback System for Nano-Beam Stabilization

feedback, dipole, kicker, collider

1378

R.L. Ramjiawan, D.R. Bett, N. Blaskovic Kraljevic, T. Bromwich, P. Burrows, G.B. Christian, C. Perry
JAI, Oxford, United Kingdom
D.R. Bett
CERN, Geneva, Switzerland
N. Blaskovic Kraljevic
ESS, Lund, Sweden
G.B. Christian
DLS, Oxfordshire, United Kingdom

A low-latency, bunch-by-bunch feedback system employing high-resolution cavity Beam Position Monitors (BPMs) has been developed and tested at the Accelerator Test Facility (ATF2) at the High Energy Accelerator Research Organization (KEK), Japan. The feedback system was designed to demonstrate nanometer-level vertical stabilization at the focal point of the ATF2 and can be operated using either a single BPM to provide local beam stabilization, or by using two BPMs to stabilize the beam at an intermediate location. The feedback correction is implemented using a stripline kicker and the feedback calculations are performed on a digital board constructed around a Field Programmable Gate Array (FPGA). The feedback performance was tested with trains of two bunches, separated by 280ns, at a charge of ~1nC, where the vertical offset of the first bunch was measured and used to calculate the correction to be applied to the second bunch. The BPMs have been demonstrated to achieve an operational resolution of ~20nm. With the application of single-BPM and two-BPM feedback, beam stabilization of below 50nm and 41nm respectively has been achieved with a latency of 232ns.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB019

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paper received ※ 18 May 2021 paper accepted ※ 09 June 2021 issue date ※ 02 September 2021

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TUPAB020

A Sub-Micron Resolution, Bunch-by-Bunch Beam Trajectory Feedback System and Its Application to Reducing Wakefield Effects in Single-Pass Beamlines

feedback, wakefield, electron, kicker

1382

D.R. Bett, P. Burrows, C. Perry, R.L. Ramjiawan
JAI, Oxford, United Kingdom
D.R. Bett
CERN, Geneva, Switzerland
K. Kubo, T. Okugi, N. Terunuma
KEK, Ibaraki, Japan

A high-precision intra-bunch-train beam orbit feedback correction system has been developed and tested at the KEK Accelerator Test Facility, ATF2. The system uses the vertical position of the bunch measured at two beam position monitors to calculate a pair of kicks which are applied to the next bunch using two upstream kickers, thereby correcting both the vertical position and trajectory angle. Using trains of two electron bunches separated in time by 187.6ns, the system was optimised so as to stabilize the beam offset at the feedback BPMs to better than 350nm, yielding a local trajectory angle correction to within 250nrad. The quality of the correction was verified using three downstream witness BPMs and the results were found to be in agreement with the predictions of a linear lattice model used to propagate the beam trajectory from the feedback region. This same model predicts a corrected be am jitter of c.1nm at the focal point of the accelerator. Measurements with a beam size monitor at this location demonstrate that reducing the trajectory jitter of the beam by a factor of 4 also reduces the increase in the measured beam size as a function of beam charge by a factor of ~1.6.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB020

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paper received ※ 13 May 2021 paper accepted ※ 01 July 2021 issue date ※ 22 August 2021

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TUPAB035

ESS Medium Beta Cavities Status at INFN LASA

SRF, linac, multipactoring, controls

1420

D. Sertore, M. Bertucci, M. Bonezzi, A. Bosotti, A. D’Ambros, A.T. Grimaldi, P. Michelato, L. Monaco, R. Paparella
INFN/LASA, Segrate (MI), Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy

INFN Milano contributes in-kind to the ESS ERIC Superconducting Linac supplying 36 cavities for the Medium Beta section of the proton accelerator. The production has reached completion, being all the cavities mechanical fabricated, BCP treated and, for most of them, also qualified with vertical test at cold. In this paper, we report on the results and lessons learnt and the actions taken both for quality control managing and recovery of the few cavities that did not reach the project goal after the first qualification test.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB035

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paper received ※ 19 May 2021 paper accepted ※ 14 June 2021 issue date ※ 15 August 2021

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TUPAB037

The Design of a High Charge Polarized Preinjector for the Electron-Ion Collider

cathode, gun, linac, electron

1428

E. Wang, W. Liu, V.H. Ranjbar, J. Skaritka, N. Tsoupas
BNL, Upton, New York, USA
J.M. Grames, J. Guo
JLab, Newport News, Virginia, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy
The design of the electron pre-injector of the Electron-Ion Collider (EIC) project to generate 4 x 7 nC bunch has been advancing to meet the requirements for injection into the Rapid Cycling Synchrotron (RCS). The major challenges are high charge transport and achieving small energy spread from 3 GHz traveling-wave plate(TWP). The designed preinjector includes the polarized electron source, bunching section, TWP Linac, zigzag phase space manipulation and spin rotator. In this report, we will discuss the RF frequency selection and the way to reduce energy spread down to 0.2% by longitudinal phase space manipulate. We will also report the results of beamline simulation using space charge code and the conceptual design of spin rotator.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB037

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paper received ※ 16 May 2021 paper accepted ※ 15 June 2021 issue date ※ 31 August 2021

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TUPAB038

Simulation of the Filling Pattern Dependent Regenerative Beam Breakup Instabilities in Energy Recover Linacs

HOM, linac, simulation, electron

1431

S. Setiniyaz, P.H. Williams
Cockcroft Institute, Warrington, Cheshire, United Kingdom
R. Apsimon
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

The interaction of a transversely displaced beam with the higher modes (HOM) of the accelerating cavities causes building up HOM voltages in the cavity, which in turn kicks the beam and increases the offset further. This is known as regenerative beam breakup (BBU) instability and it sets the beam threshold current for the stable beam operation. A study by Setiniyaz et al.~[Setiniyaz2020] showed the filling pattern and recombination schemes of multi-turn energy recovery linacs (ERLs) can create many different beam loading transients, which can have a big impact on the cavity fundamental mode voltage and RF stabilizes. In this work, we extend the study of the filling pattern and recombination schemes to the BBU instabilities and threshold current. In the ERLs, the accelerated and decelerated bunches can be ordered differently while they pass through the cavity and form different filling patterns. Each pattern has a unique bunch energy sequence and bunch arrival times and hence interacts with cavity uniquely and thus drives BBU differently. In this paper, we introduce a simulation tool to investigate the filling pattern dependence of the ERL BBU instability.
* S. Setiniyaz, R. Apsimon, and P. H. Williams, Phys. Rev. Accel. Beams 23, 072002, 2020.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB038

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paper received ※ 20 May 2021 paper accepted ※ 09 June 2021 issue date ※ 13 August 2021

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TUPAB041

Detector Solenoid Compensation for the Electron-Ion Collider

solenoid, coupling, electron, detector

1439

B.R. Gamage, T.J. Michalski, V.S. Morozov, R. Rajput-Ghoshal, A. Seryi, W. Wittmer, Y. Zhang
JLab, Newport News, Virginia, USA
E. Gianfelice-Wendt
Fermilab, Batavia, Illinois, USA
A. Kiselev, H. Lovelace III, B. Parker, S. Peggs, S. Tepikian, F.J. Willeke, H. Witte, Q. Wu
BNL, Upton, New York, USA

Funding: Jefferson Science Associates, LLC Contract No. DE-AC05-06OR23177, Fermi Research Alliance, LLC Contract No. DE-AC02-07CH11359, and Brookhaven Science Associates, LLC Contract No. DE-SC0012704
The central detector in the present EIC design includes a 4 m long solenoid with an integrated strength of up to 12 Tm. The electron beam passes on-axis through the solenoid, but the hadron beam has an angle of 25 mrad. Thus the solenoid couples horizontal and vertical betatron motion in both electron and hadron storage rings, and causes a vertical closed orbit excursion in the hadron ring. The solenoid also couples the transverse and longitudinal motions of both beams, when crab cavities are also considered. In this paper, we present schemes for closed orbit correction and coupling compensation at the IP, including crabbing.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB041

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paper received ※ 28 May 2021 paper accepted ※ 22 August 2021 issue date ※ 31 August 2021

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TUPAB045

The Low Energy Injector Design for the Southern Advanced Photon Source

electron, linac, gun, bunching

1450

Y. Han
IHEP CSNS, Guangdong Province, People’s Republic of China
Y. Jiao, B. Li, X. Liu, S. Wang
IHEP, Beijing, People’s Republic of China

The Southern Advanced Photon Source (SAPS) is a project under design, which aims at constructing a 4th generation storage ring with emittance below 100 pm.rad at the electron beam energy of around 3.5 GeV. At present, two injector options are under consideration. One is a full energy booster plus a low energy injector, and another is a full energy linac injector. In this paper, a preliminary design of the low energy injector is presented, which consists of an DC thermionic electron gun, a bunching section and an accelerating section. The beam energy at the end of the injector is about 150 MeV.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB045

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paper received ※ 17 May 2021 paper accepted ※ 09 June 2021 issue date ※ 21 August 2021

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TUPAB053

Design Progress of ALS-U 3rd-Harmonic Cavity

HOM, damping, impedance, simulation

1481

T.H. Luo, K.M. Baptiste, S. De Santis, D. Li, J.W. Staples, M. Venturini
LBNL, Berkeley, California, USA
H.Q. Feng
TUB, Beijing, People’s Republic of China

Funding: Director, Office of Science, Office of Basic Energy Sciences, and LDRD Program of Lawrence Berkeley National Laboratory, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
A higher-harmonic rf cavity (HHC) system is required in the ALS-U storage ring to lengthen the bunches, reduce intrabeam-scattering effects, and improve Touschek beam lifetime. A 3rd harmonic, normal conducting, passive-cavity system has been chosen based on beam-dynamics requirements and cost considerations. We have explored two options for ALS-U 3HC system: a high-R/Q re-entrant cavity with waveguide HOM dampers, and a low-R/Q system with two elliptical cavities and HOM beam line absorbers. In this paper, we present the recent progress on the cavity design and related beam dynamics studies.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB053

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paper received ※ 19 May 2021 paper accepted ※ 11 June 2021 issue date ※ 18 August 2021

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TUPAB072

The Status of a Grating Monochromator for Soft X-Ray Self-Seeding Experiment at SHINE

electron, laser, FEL, free-electron-laser

1532

K.Q. Zhang
SSRF, Shanghai, People’s Republic of China
H.X. Deng, C. Feng, B. Liu, T. Liu
SARI-CAS, Pudong, Shanghai, People’s Republic of China

The research status of a grating monochromator for soft X-ray self-seeding experiment at SHINE has been presented in this paper. The monochromator system includes the vacuum cavity, optical elements, and mechanical movement devices. Until now, the vacuum cavity has finished the manufactured process completely, the optical mirrors have finished machining and measured by the longitudinal trace profiler (LTP) and atomic force microscope (AFM). To make sure the monochromator system can achieve an optical resolution of 1/10000 at the photon energy of 700-1300eV, the system has been integrated and tested recently. In this year, the previous online experiment will be performed in the shanghai soft X-ray free-electron laser (FEL) user facility.

Poster TUPAB072 [0.717 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB072

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paper received ※ 11 May 2021 paper accepted ※ 09 June 2021 issue date ※ 01 September 2021

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TUPAB074

S-Band Transverse Deflecting Structure Design for CompactLight

klystron, FEL, operation, impedance

1540

X.W. Wu, W. Wuensch
CERN, Meyrin, Switzerland
S. Di Mitri
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
N. Thompson
Cockcroft Institute, Warrington, Cheshire, United Kingdom

The CompactLight project is currently developing the design of a next generation hard X-ray FEL facility, which is based on high-gradient X-band (12 GHz) structures. However, to carry out pump-and-probe experiments in the project, two-bunch operation with a spacing of 10 X-band rf cycles is proposed. A sub-harmonic transverse deflecting structure working at S-band is proposed to direct the two bunches into two separate FEL lines. The two FEL pulses will have independently tunable wavelengths and can be combined in a single experiment with a temporal delay between pulses of ± 100 fs. The rf design of the transverse deflector is presented in this paper.

Poster TUPAB074 [1.557 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB074

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paper received ※ 19 May 2021 paper accepted ※ 10 June 2021 issue date ※ 11 August 2021

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TUPAB077

Novel Open Cavity for Rotating Mode SLED-Type RF Pulse Compressors

coupling, klystron, GUI, linear-collider

1547

X.W. Wu, A. Grudiev
CERN, Meyrin, Switzerland

A new X-band high-power rotating mode SLAC Energy Doubler (SLED)-type rf pulse compressor is proposed. It is based on a novel cavity type, a single open bowl-shape energy storage cavity with high Q₀ and compact size, which is coupled to the waveguide using a compact rotating mode launcher. The novel cavity type is applied to the rf pulse compression system of the main linac rf module of the klystron-based option of the Compact Linear Collider (CLIC). Quasi-spherical rotating modes of \rm{TE}_1,2,4 and \rm{TE}_1,2,13 are proposed for the correction cavity and storage cavity of the rf pulse compression system respectively. The storage cavity working at \rm{TE}_1,2,13 has a Q₀ of 240000 and a diameter less than 33 cm. The design of the pulse compressor and in particular of the high-Q cavity will be presented in detail.

Poster TUPAB077 [1.229 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB077

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paper received ※ 19 May 2021 paper accepted ※ 10 June 2021 issue date ※ 12 August 2021

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TUPAB098

Recent Progress Toward a Conduction-Cooled Superconducting Radiofrequency Electron Gun

simulation, SRF, electron, accelerating-gradient

1604

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

Funding: This work was supported by the US Department of Energy (DOE) under contract DE-SC0018367
High-repetition-rate electron sources have widespread applications. This contribution discusses the progress toward a proof-of-principle demonstration for a conduction-cooled electron source. The source consists of a simple modification of an elliptical cavity that enhances the field electric field at the photocathode surface. The source was cooled to cryogenic temperatures and preliminary measurements for the quality factor and accelerating field were performed. Additionally, we present future plans to improve the source along with simulated beam-dynamics performances.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB098

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paper received ※ 29 May 2021 paper accepted ※ 17 June 2021 issue date ※ 14 August 2021

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TUPAB105

Simulation Studies for Dark Current Signature From DLS RF Gun

simulation, electron, solenoid, cathode

1630

J. Karmakar, M. Aggarwal, S. Ghosh, B. Karmakar, P. Patra, B.K. Sahu, A. Sharma
IUAC, New Delhi, India

The Delhi Light source (DLS) is an upcoming compact THz facility at IUAC, New Delhi, based on pre-bunched FEL. RF conditioning of the 2.6 cell S-band RF gun is presently carried out with a Cu photo-cathode (PC) plug and dark current is produced when substantial accelerating field is reached inside the cavity. To identify the possible field emission sites contributing to dark current, single electron ASTRA simulations are done with a phase scan of the RF field. The simulation is extended to include multi-particle emission from the PC edge as a ring. The energies present in the dark current is analysed from the the Fowler Nordheim current plot and energy phase scan plot. The distribution of few dark current energies and their respective trajectories upto the YAG screen at a given solenoid setting is traced and shown in the simulations. We also present the dark current images captured during the initial RF conditioning and try to compare it with the simulations.

Poster TUPAB105 [0.742 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB105

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paper received ※ 19 May 2021 paper accepted ※ 17 August 2021 issue date ※ 28 August 2021

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TUPAB109

Characterization of the X-Ray Angular Pointing Jitter in the LCLS Hard X-ray Undulator Line

undulator, FEL, electron, detector

1640

R.A. Margraf, Z. Huang, J.P. MacArthur, G. Marcus, T. Sato, D. Zhu
SLAC, Menlo Park, California, USA
Z. Huang
Stanford University, Stanford, California, USA

Funding: This work was supported by the Department of Energy, Laboratory Directed Research and Development program at SLAC National Accelerator Laboratory, under contract DE-AC02-76SF00515.
The angular pointing jitter of X-ray pulses produced by an X-ray Free-Electron Laser (XFEL) depends on both intrinsic properties of the SASE (Self-amplified spontaneous emission) process and jitters in beamline variables such as electron orbit. This jitter is of interest to the Cavity-Based XFEL (CBXFEL)* project at SLAC, which will lase seven undulators inside an X-ray cavity of four diamond Bragg mirrors. The CBXFEL cavity has a narrow angular bandwidth, thus large angular jitters cause X-rays to leak out of the cavity and degrade cavity efficiency. To understand contributors to angular pointing jitter, we studied the pointing jitter of the Linac Coherent Light Source (LCLS) Hard X-ray Undulator line (HXU). Monochromatic and pink X-rays were characterized at the X-ray Pump Probe (XPP) instrument. We found pulses with high monochromatized pulse energy and small electron beam orbit in the undulator have the lowest angular pointing jitter. We present here our measurement results, discuss why these factors correlate with pointing stability, and propose a strategy for CBXFEL to reduce angular pointing jitter and account for angular pointing jitter in cavity efficiency measurements.
*Gabriel Marcus et al. "CBXFEL Physics Requirements Document for the Optical cavity Based X-Ray Free Electron Lasers Research and Development Project." SLAC-I-120-103-121-00. Apr 2020.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB109

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paper received ※ 19 May 2021 paper accepted ※ 14 June 2021 issue date ※ 18 August 2021

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TUPAB110

Measurement and Correction of RF Kicks in the LCLS Accelerator to Improve Two-Bunch Operation

electron, FEL, klystron, experiment

1644

R.A. Margraf, F.-J. Decker, Z. Huang, G. Marcus
SLAC, Menlo Park, California, USA
Z. Huang
Stanford University, Stanford, California, USA

Funding: This work was supported by the Department of Energy, Laboratory Directed Research and Development program at SLAC National Accelerator Laboratory, under contract DE-AC02-76SF00515.
RF kicks, caused by a misalignment of an electron beam and acceleration structure, produce an electron orbit in the accelerator which decreases the final energy of the accelerated electron beam and is detrimental to lasing electron bunches in an X-ray Free Electron Laser (XFEL). RF kicks can depend on the RF waveform of the accelerating structure, so controlling this effect is particularly important when two or more electron bunches are accelerated within an RF fill time. Multibunch modes have been successfully developed for the Linac Coherent Light Source (LCLS) accelerator at SLAC,* and are being continually improved to accommodate new experiments. One such experiment, the Cavity-Based XFEL (CBXFEL)** project will require two electron bunches separated by 218.5 ns which must be identical in energy and orbit. To reduce variation in energy and orbit between the two bunches, we studied the RF kicks produced by each of 75 accelerator segments in the LCLS linac at several RF timings. Here, we discuss these measurements and propose a method to correct RF kicks in the LCLS accelerator using corrector dipoles and quadrupoles.
* F.-J. Decker, et al. Recent Developments and Plans for Two Bunch Operation, Proc. of FEL2017, TUP023.
** Gabriel Marcus et al. CBXFEL Physics Requirements Document. SLAC-I-120-103-121-00. 2020.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB110

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paper received ※ 19 May 2021 paper accepted ※ 15 June 2021 issue date ※ 25 August 2021

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TUPAB127

Spare Gun Multi-Physics Analysis for LCLS-II

gun, cathode, simulation, electron

1688

L. Xiao, C. Adolphsen, A. Cedillo, E.N. Jongewaard, X. Liu, C.-K. Ng, F. Zhou
SLAC, Menlo Park, California, USA

LBNL APEX VHF normal conducting gun was adopted for LCLS-II CW operation to provide ultra-bright high repetition rate X-ray pulses. The initial LCLS-II gun and injector commissioning showed excessive dark current dominated by field emission around the cathode plug outer diameter and the gun cavity nose. There is a concern that the dark current may get worse with time of operation. It is planning to build a spare rf gun largely based on the current LCLS-II gun to replace current LCLS-II gun. The proposed spare gun has a reduced the peak electrical fields around the cathode plug corner and cavity nose by 10% through further optimizing APEX gun cavity shape. In addition, there are some moderate modifications on the engineering design to increase mechanical robustness and vacuum performance. SLAC developed parallel finite-element electromagnetic code suite ACE3P is used to apply for the spare gun modeling including RF, thermal and structural analysis at static and transient states to ensure its successful operation in LCLS-II. In this paper, the spare gun multi-physics analysis is described.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB127

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paper received ※ 19 May 2021 paper accepted ※ 20 August 2021 issue date ※ 25 August 2021

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TUPAB133

Brazing free RF Pulse Compressor for High Gradient Accelerators

GUI, coupling, simulation, vacuum

1700

L. Kankadze, D. Alesini, F. Cardelli, G. Di Raddo, M. Diomede
INFN/LNF, Frascati, Italy

EURPRAXIA@SPARC\_LAB, is a proposal to upgrade the SPARC\_LAB test facility (at LNF, Frascati) to a soft X-ray user facility based on plasma acceleration and high-gradient X-band (11.9942 GHz) accelerating modules. Each module is made up of a group of 4 TW sections assembled on a single girder and fed by one klystron by means of one rf pulse compressor system and a low attenuation circular waveguide network that transports the rf power to the input hybrids of the sections. The pulse compressor is based on a single Barrel Open Cavity (BOC). The BOC use a ’whispering gallery’ mode which has an intrinsically high quality factor and operates in a resonant rotating wave regime. Compared to the conventional SLED scheme it requires a single cavity instead of two cavities and a 3-dB hybrid. A new brazeless mechanical design has been proposed and is described in the present paper together with the electro-magnetic and thermo-mechanical simulations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB133

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paper received ※ 21 May 2021 paper accepted ※ 15 June 2021 issue date ※ 27 August 2021

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TUPAB166

A New Design of a Dressed Balloon Cavity with Superior Mechanical Properties

multipactoring, SRF, linac, software

1769

R.A. Kostin, C. Jing, S. Ross
Euclid Beamlabs, Bolingbrook, USA
I.V. Gonin, T.N. Khabiboulline, G.V. Romanov, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA
M.P. Kelly
ANL, Lemont, Illinois, USA
R.E. Laxdal
TRIUMF, Vancouver, Canada

Funding: Work supported by the SBIR program of the U.S. Department of Energy, under grant DE-SC0020781
Superconducting spoke cavities are prone to multipactor - resonant raise of a number of electrons due to secondary emission. Recently proposed and tested by TRIUMF balloon-type spoke cavity showed an outstanding multipactor (MP) suppression property but unfortunately serious Q degradation at high fields. A new fully developed design of a dressed balloon cavity which can be used for any proton linac SSR2 section is developed. The design incorporates additional EP ports for high Q-factor demonstration. Superior properties are demonstrated, such as effective multipactor suppression, 40% lower Lorentz force coefficient, zero sensitivity to external pressure. This paper presents the results of coupled structural Multiphysics analysis, and engineering design of the dressed balloon cavity with EP ports.

Poster TUPAB166 [1.394 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB166

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paper received ※ 15 May 2021 paper accepted ※ 21 June 2021 issue date ※ 12 August 2021

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TUPAB167

Status of Conduction Cooled SRF Photogun for UEM/UED

gun, SRF, cryomodule, shielding

1773

R.A. Kostin, C. Jing
Euclid Beamlabs, Bolingbrook, USA
P.V. Avrakhov, A. Liu, Y. Zhao
Euclid TechLabs, Solon, Ohio, USA

Funding: DOE #DE-SC0018621
Benefiting from the rapid progress on RF photogun technologies in the past two decades, the development of MeV range ultrafast electron diffraction/microscopy (UED and UEM) has been identified as an enabling instrumentation. UEM or UED use low power electron beams with modest energies of a few MeV to study ultrafast phenomena in a variety of novel and exotic materials. SRF photoguns become a promising candidate to produce highly stable electrons for UEM/UED applications because of the ultrahigh shot-to-shot stability compared to room temperature RF photoguns. SRF technology was prohibitively expensive for industrial use until two recent advancements: Nb₃Sn and conduction cooling. The use of Nb₃Sn allows to operate SRF cavities at higher temperatures (4K) with low power dissipation which is within the reach of commercially available closed-cycle cryocoolers. Euclid is developing a continuous wave (CW), 1.5-cell, MeV-scale SRF conduction cooled photogun operating at 1.3 GHz. In this paper, the technical details of the design and first experimental data are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB167

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paper received ※ 29 May 2021 paper accepted ※ 21 June 2021 issue date ※ 31 August 2021

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TUPAB168

Beam Commissioning of a 325 MHz Proton IH-DTL at XiPAF

DTL, proton, emittance, linac

1777

P.F. Ma, X. Guan, R. Tang, M.W. Wang, X.W. Wang, Q.Z. Xing, W.B. Ye, S.X. Zheng
TUB, Beijing, People’s Republic of China
W. Chen, W.L. Liu, W. Lv, M.T. Qiu, B.C. Wang, D. Wang, M.C. Wang, Z.M. Wang, Y.H. Yan, Y. Yang, M.T. Zhao
NINT, Xi’an, People’s Republic of China

The Inter-Digital H-mode Drift Tube Linac (IH-DTL) is widely used as the main component of injectors for medical synchrotrons. This paper describes the beam commissioning of a compact 325 MHz IH-DTL with modified KONUS beam dynamics at Tsinghua University (THU). This IH-DTL accelerates the proton beam from 3 MeV to 7 MeV in 1m. The average energy of the beam is 7.0 MeV with the energy spread range of -0.6 MeV to 0.3 MeV. The output transverse normalized RMS emittance of the beam is 0.58 (x)/0.58 (y) pi mm mrad with the input emittance of 0.43 (x)/0.37 (y) pi mm mrad. The beam test results show good agreement with the beam dynamics design.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB168

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paper received ※ 08 May 2021 paper accepted ※ 16 June 2021 issue date ※ 13 August 2021

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TUPAB170

Decouple Transverse Coupled Beam in the DTL with Tilted PMQs

emittance, coupling, DTL, rfq

1785

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
Y.H. Pu, J. Qiao, C.P. Wang, X.C. Xie, F. Yang
Shanghai APACTRON Particle Equipment Company Limited, Shanghai, People’s Republic of China

The coupling of the beam is widely studied in the accelerator physics field. Projected transverse emittances easily grow up if the beam is transversely-coupled. If we decouple the transverse coupled beam, the transverse emittance can be small. The matrix approach based on the symplectic transformation theory for decoupling the coupled beam is summarized. For a proton accelerator, the transverse coupled beam is introduced by an RFQ tilted by 45°. The beam is decoupled with the first five tilted quadrupoles mounted in the DTL section. A study on the gradient choice of the quadrupoles and the space charge effect is given in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB170

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paper received ※ 08 May 2021 paper accepted ※ 21 June 2021 issue date ※ 01 September 2021

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TUPAB173

ESS Drift Tube Linac Manufacturing, Assembly and Tuning

DTL, linac, alignment, emittance

1797

F. Grespan, L. Antoniazzi, A. Baldo, C. Baltador, A. Battistello, L. Bellan, P. Bottin, M. Comunian, D. Conventi, E. Fagotti, L. Ferrari, A. Palmieri, R. Panizzolo, A. Pisent, D. Scarpa
INFN/LNL, Legnaro (PD), Italy
R.A. Baron
ESS, Lund, Sweden
T. Bencivenga, P. Mereu, C. Mingioni, M. Nenni, E. Nicoletti
INFN-Torino, Torino, Italy
A.G. Colombo
INFN- Sez. di Padova, Padova, Italy
B. Jones
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

The Drift Tube Linac (DTL) for the ESS Linac will accelerate H⁺-beams of up to 62.5 mA peak current from 3.62 to 90 MeV. The structure consists of five cavities. The first cavity (DTL1) is a 7.6 m long tank containing 60 drift tubes, 23 fixed tuners, 3 movable tuners and 24 post-couplers, operating at a frequency of 352.21 MHz and an average accelerating field of 3.0 MV/m. The cavity is now assembled at ESS, the results of alignment and tuning are here presented. The DTL1 "as-built" as been analyzed from the beam dynamics point of view. The manufacturing of DTL4 and DTL3 is completed and they are now under assembly at ESS. DTL2 and DTL5 manufacturing will be completed within 2021. The paper describes the production and assembly stages, with a focus on the statistics of quality check in terms of metrology, alignment, leak tests.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB173

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paper received ※ 19 May 2021 paper accepted ※ 27 May 2021 issue date ※ 15 August 2021

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TUPAB198

ESS DTL Tuning Using Machine Learning Methods

network, DTL, linac, proton

1872

J.S. Lundquist, N. Milas, E. Nilsson
ESS, Lund, Sweden
S. Werin
Lund University, Lund, Sweden

The European Spallation Source, currently under construction in Lund, Sweden, will be the world’s most powerful neutron source. It is driven by a proton linac with a current of 62.5 mA, 2.86 ms long pulses at 14 Hz. The final section of its normal-conducting front-end consists of a 39 m long drift tube linac (DTL) divided into five tanks, designed to accelerate the proton beam from 3.6 MeV to 90 MeV. The high beam current and power impose challenges to the design and tuning of the machine and the RF amplitude and phase have to be set within 1% and 1 degree of the design values. The usual method used to define the RF set-point is signature matching, which can be a time consuming and challenging process, and new techniques to meet the growing complexity of accelerator facilities are highly desirable. In this paper we study the usage of Machine Learning to determine the RF optimum amplitude and phase. The data from a simulated phase scan is fed into an artificial neural network in order to identify the needed changes to achieve the best tuning. Our test for the ESS DTL1 shows promising results, and further development of the method will be outlined.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB198

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paper received ※ 17 May 2021 paper accepted ※ 21 June 2021 issue date ※ 10 August 2021

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TUPAB211

The Accelerator System of IFMIF-DONES Multi-MW Facility

linac, rfq, SRF, cryomodule

1910

I. Podadera, A. Ibarra, D. Jimenez-Rey, J. Mollá, C. Oliver, D. Regidor, R. Varela, C. de la Morena
CIEMAT, Madrid, Spain
F. Arbeiter, V. Hauer
KIT, Eggenstein-Leopoldshafen, Germany
N. Bazin, J. Dumas, L. Seguí
CEA-IRFU, Gif-sur-Yvette, France
L. Bellan, E. Fagotti, A. Palmieri, A. Pisent
INFN/LNL, Legnaro (PD), Italy
N. Chauvin, S. Chel, J. Plouin
CEA-DRF-IRFU, France
G. Duglue, H. Dzitko
F4E, Germany
W.C. Grabowski, A. Wysocka-Rabin
NCBJ, Świerk/Otwock, Poland
M. Jaksic, T. Tadic
RBI, Zagreb, Croatia
W. Królas
IFJ-PAN, Kraków, Poland
R. López, A. Muñoz, C. Prieto
Empresarios Agrupados, Madrid, Spain
O. Nomen, M. Sanmartí, F.J. Saura Esteban, B.K. Singh, D. Sánchez-Herranz
IREC, Sant Adria del Besos, Spain

Funding: Work carried out within EUROfusion Consortium and DONES-PreP and received funding from the Euratom research and training programme 2014-2018 & 2019-2020 under grants agreement No. 633053 & 870186
The IFMIF-DONES (DEMO-Oriented Neutron Early Source) facility has passed the preliminary design phase and the detailed design phase is very much advanced. Next step will be the preparation phase for the construction of the facility. The DONES facility aims at developing a database of fusion-like radiation effects on materials to be used in future fusion reactors up to damage levels expected in the EU DEMO. It will be based on an intense neutron source created by an accelerated deuteron beam (125 mA CW, 40 MeV) impinging on a liquid lithium curtain. The DONES Accelerator Systems (AS) will be responsible of delivering this 5 MW D⁺ beam with very high availability. The beam acceleration will be performed by several stages: an ion source and LEBT, an RFQ, a MEBT, an SRF Linac and a HEBT transporting and delivering an optimized profile down to the target. A high power RF system and several ancillaries will ensure the equipment is properly operated. This contribution will report the present status of the AS design, the main challenges faced, the R&D programme to overcome them, and the prospects for the construction and commissioning of the DONES accelerator in Granada (Spain).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB211

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paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 13 August 2021

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TUPAB220

Longitudinal Dynamics with Harmonic Cavities under the Over-stretching Conditions

detector, beam-loading, longitudinal-dynamics, bunching

1939

J.Y. Xu, H.S. Xu
IHEP, Beijing, People’s Republic of China

Higher harmonic cavities (HHCs) are often used to lengthen the bunches, mainly for increasing the Touschek lifetime or for suppressing the coupled-bunch instabilities in electron storage rings. There have been quite many studies on the beam dynamics with the consideration of HHCs. We revisited the basic longitudinal dynamics with HHCs. The derivation of the longitudinal equations of motion with HHCs will be presented in this paper. The difference in the number of fixed points at different HHC settings (mainly under the over-stretching conditions) is also discussed.

Poster TUPAB220 [1.082 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB220

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paper received ※ 19 May 2021 paper accepted ※ 02 August 2021 issue date ※ 18 August 2021

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TUPAB237

Symplectic Tracking Through Field Maps

quadrupole, dipole, ion-source, radio-frequency

1992

S.D. Webb
RadiaSoft LLC, Boulder, Colorado, USA
B.T. Folsom, E. Laface, R. Miyamoto
ESS, Lund, Sweden

For many applications, it is necessary to track particles using field maps, instead of an analytic representation of the fields which is typically not available. These field maps come about while designing elements such as realistic magnets or radiofrequency cavities, and represent the field geometry on a mesh in space. However, simple interpolation of the fields from the field maps does not guarantee that the resulting tracking scheme satisfies the symplectic condition. Here we present a general method to decompose the field-map potential in the sum of interpolating functions that produces, by construction, a symplectic integrator.

Poster TUPAB237 [0.307 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB237

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paper received ※ 19 May 2021 paper accepted ※ 22 July 2021 issue date ※ 18 August 2021

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TUPAB241

Characterization of the RF-Cavities geometry in Order to Optimize the Beam Parameters in S-Band On-Axis LINACs

electron, target, emittance, impedance

2005

A. Khosravi, B. Shokri
LAPRI, Tehran, Iran
N. Khosravi
ILSF, Tehran, Iran

The RF characteristics of an accelerating tube are primarily assigned to geometrical features of a cavity. As a consequence of this geometry, the final electric field will make the shape of our Gaussian bunch and the final dose. The accelerating field can be studied considering the nose cone, gap, and bore radius. In dual electron linacs, the role of input power and bunch current is inevitable. Therefore, the geometrical issues of RF-cavities are studied in a 6MeV electron on-axis SW tube. To make an accurate comparison, each RF-cavity is designed and optimized by POISSON SU-PERFISH. The optimized cavities are imported to the PIC solver of CST. Then the beam characteristics are studied on a predefined target.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB241

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paper received ※ 18 May 2021 paper accepted ※ 14 June 2021 issue date ※ 13 August 2021

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TUPAB242

The Beam-Study of the Side and On-Axis RF Cavities in S-Band 6 MeV LINACs

target, emittance, coupling, impedance

2008

A. Khosravi, B. Shokri
LAPRI, Tehran, Iran
N. Khosravi
ILSF, Tehran, Iran

The geometry of side and on-axis RF cavities are two magnetic-coupled designs for the different LINAC applications. The electromagnetic fields, RF power, beam parameters, thermal stability, and manufacturing costs are the most critical factors in cavity type selection in each application. In this article, both RF-cavities are optimized in POISSON SUPERFISH code to compare the beam parameters accurately. Then the optimized cavities are making a tube and compare in ASTRA 1D code and CST 3D software. At last, the thermal sensitivity of both models is studied in MPHYSICS module of the CST. As a result, the final decision can be achieved on the side or on-axis cavities considering the input power, costs, beam properties, and thermal stability for the different applications of the LINACs

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB242

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paper received ※ 18 May 2021 paper accepted ※ 21 June 2021 issue date ※ 26 August 2021

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TUPAB243

Investigation of the Buncher Effect on Beam Properties in SW 3-6 MeV LINACs

electron, emittance, target, impedance

2012

A. Khosravi, B. Shokri
LAPRI, Tehran, Iran
N. Khosravi
ILSF, Tehran, Iran

The best quality of an electron beam is the primary goal of a linear accelerator design. Beam-study on a buncher section can lead us to a better perspective of the modulation and acceleration of a beam to optimize the final Gaussian beam. Five setups of different bunchers are designed, optimized, and presented in this article. A more brilliant and converged beam with a higher current, transverse emittance and smaller beam size is the study’s goal.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB243

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paper received ※ 18 May 2021 paper accepted ※ 14 June 2021 issue date ※ 12 August 2021

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TUPAB248

A Parallel Time Domain Thermal Solver for Transient Analysis of Accelerator Cavities

gun, simulation, background, software

2030

C.-K. Ng, L. Ge, Z. Li, L. Xiao
SLAC, Menlo Park, California, USA

Funding: Work supported by US DOE under contract AC02-76SF00515.
Simulation of thermal effects in accelerator cavity is normally performed assuming steady state solution where a static thermal solver suffices to evaluate temperature gradients and impacts on mechanical design. However, during the rf pulse ramp up or the machine system cool-down process, when the field in the cavity changes rapidly, transient effects need to be taken into account. A parallel time domain thermal solver has been developed in the finite element multi-physics code suite ACE3P with integrated electromagnetic, thermal and mechanical modeling capabilities. The implementation takes advantage of the parallel computation infrastructure of ACE3P and shares most of the ingredients in mesh generation, matrix assembly, time advancement scheme and postprocessing. In this paper, we will outline the finite element formulation of the transient thermal problem and verify the implementation against analytical solutions and existing numerical results. The thermal solver has also been coupled to ACE3P mechanical solver, allowing stress and strain analysis during the transient stage. Application of the transient thermal solver to realistic accelerator cavities will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB248

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paper received ※ 19 May 2021 paper accepted ※ 18 August 2021 issue date ※ 25 August 2021

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TUPAB254

Limiting Coherent Longitudinal Beam Oscillations in the EIC Electron Storage Ring

feedback, electron, emittance, hadron

2046

B. Podobedov
Brookhaven National Laboratory (BNL), Electron-Ion Collider, Upton, New York, USA
M. Blaskiewicz
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
We study coherent longitudinal beam oscillations in the EIC electron storage ring (ESR). We show that to avoid unacceptable hadron emittance growth due to finite crossing angle, the amplitude of these oscillations needs to be limited to a fraction of a millimeter. Using an analytical model we estimate the amplitude of these oscillations under the two scenarios: 1) the beam is passively stable and the oscillations are driven by RF phase noise only; 2) a coupled-bunch instability, presently expected in the ESR, is damped by a longitudinal feedback system. We show that, for the 2nd scenario, comfortable specifications for RF phase noise and feedback sensor noise will be sufficient to maintain the oscillation amplitude within the required limits.

Poster TUPAB254 [1.347 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB254

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paper received ※ 12 May 2021 paper accepted ※ 18 June 2021 issue date ※ 26 August 2021

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TUPAB256

Investigation of Damping Effects of the Crab Cavity Noise Induced Emittance Growth

emittance, simulation, impedance, experiment

2054

N. Triantafyllou, L.R. Carver, A. Wolski
The University of Liverpool, Liverpool, United Kingdom
F. Antoniou, H. Bartosik, P. Baudrenghien, X. Buffat, R. Calaga, Y. Papaphilippou, N. Triantafyllou
CERN, Meyrin, Switzerland
L.R. Carver
ESRF, Grenoble, France
T. Mastoridis
CalPoly, San Luis Obispo, California, USA

Crab cavities will be installed at the two main interaction points (IP1 and IP5) of the High Luminosity LHC (HL-LHC) in order to minimize the geometric reduction of the luminosity due to the crossing angle. Two prototype crab cavities have been installed into the SPS machine and were tested with a proton beam in 2018, to study the expected emittance growth induced by RF noise. The measured emittance growth was found to be a factor 2-3 lower than predicted from the available analytical and computational models. Damping mechanisms from the transverse impedance, which is not included in the available theories, are studied as a possible explanation for the observed discrepancy.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB256

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paper received ※ 18 May 2021 paper accepted ※ 18 June 2021 issue date ※ 23 August 2021

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TUPAB261

The Ferrite Loaded Cavity Impedance Simulation

impedance, simulation, MMI, synchrotron

2070

L. Huang, X. Li, S. Wang, S.Y. Xu
IHEP, Beijing, People’s Republic of China
B. Wu
IHEP CSNS, Guangdong Province, People’s Republic of China

Funding: Work supported by NNSF of China: N0. U1832210
The Rapid Cycling Synchrotron of the China Spallation Neutron Source is a high-intensity proton accelerator, it accumulates the 80 MeV proton beam and accelerates it to 1.6 GeV in 20 ms. The transverse coupling bunch instability is observed in beam commissioning. The source has been investigating from the commissioning. The RF acceleration system consists of eight ferrite-loaded cavities. The impedance is simulated and there is a narrow-band impedance of the ferrite cavity at about 17 MHz

Poster TUPAB261 [1.145 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB261

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paper received ※ 13 May 2021 paper accepted ※ 31 May 2021 issue date ※ 28 August 2021

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TUPAB263

The Phase Loop Status of the RF System in CSNS/RCS

proton, feedback, space-charge, MMI

2076

L. Huang, X. Li, S. Wang
IHEP, Beijing, People’s Republic of China
M.T. Li, H.Y. Liu
IHEP CSNS, Guangdong Province, People’s Republic of China
Y. Liu
DNSC, Dongguan, People’s Republic of China

The Rapid Cycling Synchrotron (RCS) of the China Spallation Neutron Source (CSNS) is a high intensity proton accelerator. The acceleration system consists of eight ferrite loaded cavities. The RCS is the space charge dominant machine and it is mitigated through the bunch factor optimization in the beam commissioning, so the injected beam will occupy a larger bucket size and unavoidable mismatch with the bucket, thus the dipole oscillation is excited. The phase loop scheme is designed to restrict the oscillation in the RF system, but the transmission efficiency is reduced by the phase loop and the bunch factor also increases, so the phase loop scheme is studied. To keep the phase loop but also maintain the transmission efficiency, we optimized the original phase loop scheme, but the beam loss still increases small when the loop on.

Poster TUPAB263 [1.548 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB263

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paper received ※ 13 May 2021 paper accepted ※ 02 June 2021 issue date ※ 24 August 2021

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TUPAB265

Bunch Lengthening of the HALF Storage Ring in the Presence of Passive Harmonic Cavities

storage-ring, simulation, damping, emittance

2082

T.L. He, Z.H. Bai, G.Y. Feng, W. Li, W.W. Li, G. Liu, L. Wang, H. Xu, S.C. Zhang
USTC/NSRL, Hefei, Anhui, People’s Republic of China

A passive 3^rd harmonic RF system, being necessary for the Hefei Advanced Light Facility (HALF) storage ring under design, will be employed to lengthen the bunches for suppressing the intrabeam scattering and improving the beam lifetime. However, the transient beam loading due to the fundamental mode may significantly reduce the bunch lengthening. Since the scale of transient effects is proportional to R/Q, the effects of R/Q on bunch lengthening, in uniform fill pattern with the near-optimum condition fulfilled, are analyzed by multibunches multiparticles tracking simulation. It indicates that the passive superconducting harmonic cavity with a lower R/Q is preferred by HALF.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB265

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paper received ※ 16 May 2021 paper accepted ※ 18 June 2021 issue date ※ 21 August 2021

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TUPAB266

Periodic Transient Beam Loading Effects Predicted by a Semi-Analytical Method

beam-loading, storage-ring, wakefield, simulation

2086

T.L. He, Z.H. Bai, G. Feng, W. Li, W.W. Li, G. Liu, L. Wang, H. Xu, S.C. Zhang
USTC/NSRL, Hefei, Anhui, People’s Republic of China

In this paper, we improve a semi-analytical method, which can be not only used for bunch lengthening under equilibrium conditions, but also applied to the prediction of a periodic transient beam loading effect. This periodic transient is induced by the presence of the passive harmonic cavity and might be encountered under specific conditions for a ultra-low emittance storage ring with a higher beam current.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB266

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paper received ※ 16 May 2021 paper accepted ※ 21 June 2021 issue date ※ 10 August 2021

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TUPAB272

Observation of Long-Range Wakefield Effects Generated in an Off-Resonance Tesla-Type Cavity

HOM, electron, resonance, wakefield

2101

A.H. Lumpkin, D.R. Edstrom, A. Lunin, P.S. Prieto, J. Ruan, R.M. Thurman-Keup
Fermilab, Batavia, Illinois, USA
J.A. Diaz Cruz
UNM-ECE, Albuquerque, USA
J.A. Diaz Cruz, B.T. Jacobson, J.P. Sikora
SLAC, Menlo Park, California, USA

Funding: Work supported by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics
The interest in controlling emittance dilution effects due to off-axis beam transport in accelerator cavities and the resulting dipolar modes is especially important for the facilities with lower emittance beams. The Fermilab Accelerator Science and Technology (FAST) facility has a unique configuration of two single cavities after the photocathode rf gun followed by a cryomodule. The second capture cavity (CC2) was run 15 kHz off resonance and without rf power while a 25-MeV beam was injected into it. The beam centroid effects were tracked by 10 rf button BPMs with bunch-by-bunch position readout capability downstream in a 12-m drift. Possible LRW effects seemed to dominate our previously observed near-resonant HOM effects at mode 14 in this cavity. This mode also shifted in frequency compared to that of the tuned case based on direct measurements. Submacropulse vertical position slewing of 1400 microns at 11 m downstream was observed with a 125 pC/bunch, 50 bunches per macropulse, and 25-MeV beam. The y-position slew amplitudes as a function of z were also measured. Horizontal positions also showed a slew effect. Both are emittance-dilution effects which one wants to mitigate.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB272

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paper received ※ 18 May 2021 paper accepted ※ 09 June 2021 issue date ※ 16 August 2021

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TUPAB273

Observations on Submicropulse Electron-Beam Effects From Short-Range Wakefields in Tesla-Type Superconducting Rf Cavities

electron, wakefield, laser, HOM

2105

A.H. Lumpkin, D.R. Edstrom, P.S. Prieto, J. Ruan, R.M. Thurman-Keup
Fermilab, Batavia, Illinois, USA
J.A. Diaz Cruz
UNM-ECE, Albuquerque, USA
J.A. Diaz Cruz, A.L. Edelen, B.T. Jacobson, F. Zhou
SLAC, Menlo Park, California, USA

Funding: Work supported by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
In previous experiments at the Fermilab Accelerator Science and Technology (FAST) facility, the effects of higher-order modes (HOMs) in TESLA-type cavities on submacropulse centroid motion were elucidated*. We now have extended our investigations to short-range wakefields (SRWs) in these cavities. The latter result in submicropulse effects where the transverse wakefields cause head-tail centroid shifts. We used a Hamamatsu C5680 UV-visible synchroscan streak camera to synchronously sum the OTR from each of the 50 micropulses in the macropulse. We generated the y-t effect in the 41-MeV beam by purposely steering the beam off axis in y at the entrance of the first capture cavity. The head-tail transverse kicks within the 11-ps-long micropulses of 500 pC each were observed at the 100-micron level for steering off-axis in one cavity and several 100 microns for two cavities. These SRW results will be compared to simulations from the ASTRA model of a single micropulse in FAST. Since the SRW kicks go inversely with energy, these emittance-dilution effects are particularly relevant to the LCLS-II injector commissioning plans where <1 MeV beam will be injected into a TESLA-type cryomodule.
* A.H. Lumpkin et al, Phys. Rev. Accel. and Beams 23, 054401 (2020).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB273

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paper received ※ 18 May 2021 paper accepted ※ 09 June 2021 issue date ※ 02 September 2021

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TUPAB274

Investigations of Long-Range Wakefield Effects in a TESLA-type Cryomodule at FAST

HOM, electron, cryomodule, wakefield

2109

A.H. Lumpkin, D.R. Edstrom, P.S. Prieto, J. Ruan, R.M. Thurman-Keup
Fermilab, Batavia, Illinois, USA
J.A. Diaz Cruz
UNM-ECE, Albuquerque, USA
J.A. Diaz Cruz, B.T. Jacobson, J.P. Sikora, F. Zhou
SLAC, Menlo Park, California, USA

Funding: *Work supported by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
The preservation of low emittance of electron beams during transport in the accelerating structures of large facilities is an ongoing challenge. In the cases of the TESLA-type superconducting rf cavities currently used in the European X-ray Free-electron Laser (XFEL) and the under-construction Linac Coherent Light Source upgrade (LCLS-II), off-axis beam transport may result in emittance dilution due to transverse long-range wakefields (LRWs) and short-range wakefields (SRW)***. To investigate such effects, experiments were performed at the Fermilab Accelerator Science and Technology (FAST) facility with its unique configuration of two TESLA-type cavities after the photocathode rf gun followed by an 8-cavity cryomodule CM). We generated beam trajectory changes with the H/V125 corrector set located 4 m upstream of the cryomodule. At 125 pC/bunch, 50 bunches, 25-MeV input, and 100-MeV exit energy, we observed for the first time submacropulse position slews of up to 500 microns at locations ~3 m after the CM and a centroid oscillation at a difference frequency of 240 kHz further downstream. Both are emittance-dilution effects which we mitigated with selective upstream beam steering.
***W.K.H. Panofsky and M. Bander, Rev. Sci. Instr. 39, 206 (1968).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB274

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paper received ※ 18 May 2021 paper accepted ※ 09 June 2021 issue date ※ 18 August 2021

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TUPAB292

Automation of the ReAccelerator Linac Phasing

detector, controls, interface, linac

2170

D.J. Barofsky, A.I. Henriques, T.J. Kabana, A.S. Plastun
FRIB, East Lansing, Michigan, USA
D.B. Crisp, A. Lapierre, S. Nash, A.C.C. Villari
NSCL, East Lansing, Michigan, USA

Funding: This work is supported by the National Science Foundation under Grant No. PHY-1565546
The ReAccelerator (ReA) at the National Superconducting Cyclotron Laboratory at Michigan State University is a unique facility, as it offers the possibility to reaccelerate not only stable, but rare-isotope beams produced by fast-projectile fragmentation or fission. At ReA, beams are accelerated using a Radio-Frequency-Quadrupole and a superconducting linear accelerator before being delivered to experiments. Beam preparation time plays a major role in the availability of beams to experiments. One of the major time consuming tasks is the linac phasing, since there are 23 resonator cavities to be phased, usually with very low beam intensities. This procedure was automated using a combination of EPICS (Experimental Physics and Industrial Controls System) In/Output Controllers (IOCs) and IOC triggered scripts to scan the resonator phase delay and measure the change in beam energy. We have developed user-friendly tools to phase the linac, which have been tested, making the task of phasing substantially easier. In this presentation, we will present our methodology, challenges faced, tools developed, and initial results of the application for automating the phasing of the ReA linac.

Poster TUPAB292 [1.140 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB292

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paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 11 August 2021

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TUPAB302

Arrival Time Stabilization at Flash Using the Bunch Arrival Corrector Cavity (BACCA)

electron, feedback, laser, SRF

2194

B. Lautenschlager, L. Butkowski, M.K. Czwalinna, B. Dursun, M. Hierholzer, S. Pfeiffer, H. Schlarb, Ch. Schmidt
DESY, Hamburg, Germany

For pump-probe and seeding experiments at free electron lasers, a femtosecond precise bunch arrival time stability is mandatory. To stabilize the arrival times a fast longitudinal intra bunch-train feedback (L-IBFB) using bunch arrival time monitors is applied. The electron bunch energy prior to a bunch compression chicane is modulated by superconducting radio frequency (SRF) cavities to compensate fast arrival time fluctuations of the subsequent bunches. A broadband normal conducting RF cavity was installed in front of the first bunch compression chicane at FLASH. The L-IBFB uses the normal conducting cavity for small but fast energy corrections together with the SRF cavities for larger and slower corrections. Current measurements show arrival time stabilities of the electron bunches towards 5 fs (rms) at the end of the linac, if the normal conducting cavity acts together with the SRF cavities in the L-IBFB system.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB302

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paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 12 August 2021

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TUPAB306

Status of Beam-Based Feedback Research and Development for Continuous Wave SRF Linac ELBE

controls, electron, feedback, LLRF

2200

A. Maalberg, M. Kuntzsch
HZDR, Dresden, Germany
E. Petlenkov
TalTech, Tallinn, Estonia

The superconducting electron linear accelerator ELBE at Helmholtz-Zentrum Dresden-Rossendorf is a versatile light source operated in continuous wave mode. As the demand on the beam stability increases, the improvement of the beam control schemes currently installed at ELBE becomes highly relevant. This improvement can be achieved by an upgrade of the existing digital MicroTCA.4-based LLRF control scheme by beam-based feedback. By presenting both the design and implementation details of the new control scheme this contribution reports the status of the work in progress.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB306

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 19 August 2021

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TUPAB328

Machine Learning for Time Series Prediction of an Accelerator Beam to Recognize Equipment Malfunction

SRF, linac, ion-source, neutron

2272

C.C. Peters
ORNL RAD, Oak Ridge, Tennessee, USA
W. Blokland, D.L. Brown, F. Liu, C.D. Long, D. Lu, P. Ramuhalli, D.E. Womble, J. Zhang, A.P. Zhukov
ORNL, Oak Ridge, Tennessee, USA

Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05- 00OR22725 for the U.S. Department of Energy.
The Spallation Neutron Source (SNS) is an accelerator based pulsed neutron source based on a 1 GeV pulsed proton Superconducting Radio Frequency (SRF) linear accelerator (linac). Since beginning high power beam operation in 2006 correlations have been found linking abrupt beam loss events to SRF cavity instabilities. With the planned upgrades to double the beam power we expect increased rates of degradation and the importance of minimizing these beam loss events will become ever more important. To further limit degradation, we are developing machine learning approaches to monitor the beam and to detect, predict and prevent beam loss events. Initial research has shown that precursors to beam loss events are detectable. The initial steps are to use ML-based classification to recognize anomalies and to use Long Short-Term Memory (LSTM) autoencoders to predict beam loss. In this paper, we describe recent progress in applying machine learning for recognizing anomalies and predicting beam loss and present initial results of our research using acquired data from different diagnostics and the Machine Protection System (MPS).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB328

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paper received ※ 23 May 2021 paper accepted ※ 28 May 2021 issue date ※ 23 August 2021

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TUPAB329

Pattern Based Parameter Setup of the SNS Linac

linac, DTL, operation, beam-losses

2276

C.C. Peters
ORNL RAD, Oak Ridge, Tennessee, USA
A.P. Shishlo
ORNL, Oak Ridge, Tennessee, USA

Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05- 00OR22725 for the U.S. Department of Energy.
Theoretical and practical aspects of beam tuning procedures used for the SNS linac are discussed. The SNS linac includes two sections of beam acceleration. Acceleration in the first section up to 185.5 MeV is done with a room temperature copper linac which consists of both Drift Tube Linac (DTL) and Coupled Cavity Linac (CCL) Radio Frequency (RF) cavities. The second section consists of 81 Superconducting RF (SRF) cavities which accelerate the beam to the final beam energy of 1 GeV. The linac is currently capable of delivering an average beam power output of 1.44 MW with typical yearly operating hours of around 4500 hours. Due to the high power output and high availability of the linac, activation of accelerator equipment is a significant concern. The linac tuning process consists of three stages: model based setup of amplitudes and phases of the RF cavities, empirical beam loss reduction, and then documentation of the final amplitudes and phases of RF cavities after the empirical tuning. The final step is needed to ensure fast recovery from an SRF cavity failure. This paper discusses models, algorithms, diagnostic tools, software, and practices that are used for these stages.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB329

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paper received ※ 22 May 2021 paper accepted ※ 28 May 2021 issue date ※ 26 August 2021

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TUPAB333

Status of PIP-II 650 MHz Prototype Dressed Cavity Qualification

SRF, cryomodule, status, superconductivity

2279

G.V. Eremeev, D.J. Bice, C. Boffo, S.K. Chandrasekaran, S. Cheban, F. Furuta, I.V. Gonin, C.J. Grimm, S. Kazakov, T.N. Khabiboulline, A. Lunin, M. Martinello, N. Nigam, J.P. Ozelis, Y.M. Pischalnikov, K.S. Premo, O.V. Prokofiev, O.V. Pronitchev, G.V. Romanov, N. Solyak, A.I. Sukhanov, G. Wu
Fermilab, Batavia, Illinois, USA
M. Bagre, V. Jain, A. Puntambekar, S. Raghvendra, P. Shrivastava
RRCAT, Indore (M.P.), India
P. Bhattacharyya, S. Ghosh, S. Seth
VECC, Kolkata, India
R. Kumar
BARC, Mumbai, India
J. Lewis, P.A. McIntosh, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
C. Pagani, R. Paparella
INFN/LASA, Segrate (MI), Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy
T. Reid
ANL, Lemont, Illinois, USA
A.D. Shabalina
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
Low-beta and high-beta sections of PIP-II linac will use nine low-beta cryomodules with four cavities each and four high-beta cryomodules with six cavities each. These cavities will be produced and qualified in collaboration between Fermilab and the international partner labs. Prior to their installation into prototype cryomodules, several dressed cavities, which include jacketed cavities, high power couplers, and tuners, will be qualified in STC horizontal test bed at Fermilab. After qualification of bare β = 0.9 cavities at Fermilab, several pre-production β = 0.92 and β = 0.61 cavities have been and are being fabricated and qualified. Procurements have also been started for high power couplers and tuners. In this contribution we present the current status of prototype dressed cavity qualification for PIP-II.

Poster TUPAB333 [6.247 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB333

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paper received ※ 23 May 2021 paper accepted ※ 19 July 2021 issue date ※ 25 August 2021

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TUPAB338

Surface Roughness Reduction of Nb₃Sn Thin Films via Laser Annealing for Superconducting Radio-Frequency Cavities

laser, SRF, superconductivity, HOM

2283

Z. Sun, M. Ge, M. Liepe, T.E. Oseroff, R.D. Porter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
A.B. Connolly, M.O. Thompson
Cornell University, Ithaca, USA

Superconducting radio frequency (SRF) cavities, a key component of particle accelerators, await new SRF materials beyond the state-of-the-art niobium. Nb₃Sn is one of the most competitive candidates, since it increases the superheating field, allows the operation temperature up to 4K, and improves cavity efficiency. Surface roughness and grain boundaries, however, significantly affect the RF performance of current Nb₃Sn cavities. Here, we explore a post laser annealing technique to reduce the surface roughness. In doing so, we deposited a TiN laser-absorber on Nb₃Sn and Nb surfaces, and then annealed the samples by laser scanning via different laser systems. The Nb₃Sn surface roughness was minimized to 101 nm (Ra) by laser annealing via 308 nm, 35 ns pulses. Surface imaging and Fourier analysis revealed laser annealing is able to remove sharp edges and <1 um wavelength features.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB338

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paper received ※ 20 May 2021 paper accepted ※ 09 June 2021 issue date ※ 19 August 2021

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TUPAB339

High Power Test of the Antenna Adjustable Power Coupler for 325 MHz Superconducting Cavities

vacuum, multipactoring, electron, pick-up

2286

J.Y. Yoon, E.-S. Kim, C.S. Park, S.H. Park
KUS, Sejong, Republic of Korea
J. Bahng
Korea University Sejong Campus, Sejong, Republic of Korea
E. Kako
KEK, Ibaraki, Japan
K.R. Kim
PAL, Pohang, Republic of Korea

Funding: The Ministry of Education (South Korea)
The power coupler is development at Korea University for a Single Spoke Resonator (SSR) of heavy ion accelerator. Our power coupler is a coaxial capacitive type based on a conventional 3-1/8 inch electronic industries alliance (EIA) 50 Ω coaxial transmission line with a titanium nitride (TiN) coated single ceramic window. A high power test is rectangular test cavity with high vacuum and various measuring equipment, such as an arc detector, a power meter, and an electron pick-up probe. The interlock system under vacuum and arc instrumentations prevent the RF window from breaking the power coupler window during the high power test. We conduct high power tests for more than 12 hrs at 12 kW in a 325 MHz continous wave (CW) mode to verify the performance of the designed power coupler.
*Superconducting, *Power Coupler

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB339

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paper received ※ 12 May 2021 paper accepted ※ 21 June 2021 issue date ※ 22 August 2021

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TUPAB340

Design of the Magnetic Shielding for 166 MHz and 500 MHz Superconducting RF Cavities at High Energy Photon Source

shielding, simulation, photon, superconducting-cavity

2289

L. Guo, Y. Chen, J. Li, Z.Q. Li, Q. Ma, P. Zhang, X.Y. Zhang, H.J. Zheng
IHEP, Beijing, People’s Republic of China

Funding: This work was supported by High Energy Photon Source, a major national science and technology infrastructure in China.
Five 166 MHz quarter-wave β=1 superconducting cavities and two 500 MHz single-cell elliptical superconducting cavities have been designed for the storage ring of High Energy Photon Source (HEPS). It is necessary to shield magnetic field for superconducting cavities to reduce the residual surface resistance due to magnetic flux trapping during cavity cool down. The magnetic shielding for both 166 MHz and 500 MHz superconducting cavities have been designed. The residual magnetic field inside the cavities have been calculated by using Opera-3D simulation software. The geographic location of the cavity being installed at the HEPS site and the fringe field of the upstream magnet are considered. These are reported in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB340

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paper received ※ 18 May 2021 paper accepted ※ 17 June 2021 issue date ※ 20 August 2021

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TUPAB341

Optimization of Two-Cell Cavities for the W and H Working Points of the FCC-ee Considering Higher-Order Mode Effects

HOM, impedance, damping, ECR

2292

S. Udongwo, S.G. Zadeh, U. van Rienen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
R. Calaga
CERN, Meyrin, Switzerland

Funding: The European Organization for Nuclear Research (CERN)
The lepton collider of the future circular collider (FCC-ee) aims at conducting precision measurements on the Z, W, and H bosons and the top quark. The present RF baseline considers single-cell cavities at 400 MHz for the high current Z-pole working point, four-cell 400 MHz cavities for the W and H working points, and a hybrid RF system composed of four-cell 400 MHz and five-cell 800 MHz cavities for the high energy tt working point. The W working point has shown limitations in the achievable HOM damping for beam stability requirements using four-cell cavities. A two-cell cavity is studied as an alternative scenario for the current W- and H-RF setups with a special focus on HOM damping during the optimization of the RF geometry.

Poster TUPAB341 [1.580 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB341

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 02 September 2021

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TUPAB342

Preliminary Cryogenic Cold Test Results of the First 9-Cell LSF Shape Cavity

niobium, SRF, multipactoring, laser

2296

R.L. Geng, W.A. Clemens, R.S. Williams
JLab, Newport News, Virginia, USA
S.A. Belomestnykh
Fermilab, Batavia, Illinois, USA
Y. Fuwa
JAEA/J-PARC, Tokai-mura, Japan
H. Hayano
KEK, Ibaraki, Japan
Y. Iwashita
Kyoto ICR, Uji, Kyoto, Japan
Z. Li
SLAC, Menlo Park, California, USA
V.D. Shemelin
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Supplemental support by US-Japan Collaboration on HEP.
Following successful prototyping and testing of single- & 5-cell LSF shape cavities *, **, the first 9-cell LSF shape cavity LSF9-1 was successfully constructed using an innovative process at JLab with the in-house facilities. The cavity was then shipped to KEK for post-fabrication mechanical adjustment and ILC TDR style treatment and surface processing. Cold testing was carried out at the JLab VTA facility, instrumented with a suite of Kyoto instruments. Favorable values for the bath pressure detuning sensitivity and Lorentz force detuning coefficient were experimentally measured, validating the design improvement in cell stiffeners. Pass-band measurements indicate 4 out of 9 cells reaching gradient capability of > 45 MV/m, including 2 cells reaching 51 MV/m. Cornell OST detectors identified the cell and location responsible for the current hard quench limit. Multipacting-like barriers observed in end cells are investigated both analytically and numerically. The cavity was shipped to FNAL and received a light EP at the joint ANL/FNAL facility for further cold testing at Jlab. Two new 9-cell LSF cavities are being constructed including one made of large-grain niobium material.
* R. L. Geng et al.,WEPWI013, IPAC15.
** R. L. Geng et al., MOP064, SRF’19.

Poster TUPAB342 [1.600 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB342

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paper received ※ 09 May 2021 paper accepted ※ 14 June 2021 issue date ※ 30 August 2021

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TUPAB343

Final Design Studies for the VSR DEMO 1.5 GHz Coupler

multipactoring, SRF, operation, electron

2300

E. Sharples-Milne, V. Dürr, P. Echevarria, J. Knobloch, A. Neumann, A.V. Vélez
HZB, Berlin, Germany

With the 1.5 GHz couplers for the Variable pulse length Storage Ring (VSR) DEMO now in the manufacturing stages, the studies that led to the final coupler design will be presented. The system specific constraints and design modifications that combat the challenges of thermomechanical stresses, higher order mode (HOM) propagation and dimensional constraints are explored. This includes S-Parameter analysis, an in-depth study of the coupling factor, and multipacting studies for the average (1.5 kW) and peak (16 kW) power.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB343

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paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 01 September 2021

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TUPAB344

Evaluation of Anisotropic Magnetoresistive (AMR) Sensors for a Magnetic Field Scanning System for SRF Cavities

SRF, experiment, niobium, MMI

2304

I.P. Parajuli, G. Ciovati, J.R. Delayen, A.V. Gurevich
ODU, Norfolk, Virginia, USA
G. Ciovati, J.R. Delayen
JLab, Newport News, Virginia, USA

Funding: Work supported by NSF Grant 100614-010. G. C. is supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
One of the significant causes of residual losses in superconducting radio-frequency (SRF) cavities is trapped magnetic flux. The flux trapping mechanism depends on many factors that include cool-down conditions, surface preparation techniques, and ambient magnetic field orientation. Suitable diagnostic tools are not yet available to quantitatively correlate such factors’ effect on the flux trapping mechanism. A magnetic field scanning system (MFSS) consisting of AMR sensors, fluxgate magnetometers, or Hall probes is recently commissioned to scan the local magnetic field of trapped vortices around 1.3 GHz single-cell SRF cavities. In this contribution, we will present results from sensitivity calibration and the first tests of AMR sensors in the MFSS.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB344

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paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 25 August 2021

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TUPAB345

Availability Modeling of the Solid-State Power Amplifiers for the CERN SPS RF Upgrade

operation, simulation, MMI, SRF

2308

L. Felsberger, A. Apollonio, T. Cartier-Michaud, E. Montesinos, J.C. Oliveira, J.A. Uythoven
CERN, Geneva, Switzerland

Funding: This project has received funding from the Euratom research and training programme 2019-2020 under grant agreement No 945077.
As part of the LHC Injector Upgrade program a complete overhaul of the Super Proton Synchrotron Radio-Frequency (RF) system took place. New cavities have been installed for which the solid-state technology was chosen to deliver a combined RF power of 2 MW from 2560 RF amplifiers. This strategy promises high availability as the system continues operation when some of the amplifiers fail. This study quantifies the operational availability that can be achieved with this new installation. The evaluation is based on a Monte Carlo simulation of the system using the novel AvailSim4 simulation software. A model based on lifetime estimations of the RF modules is compared against data from early operational experience. Sensitivity analyses have been made, that give insight to the chosen operational scenario. With the increasing use of solid-state RF power amplifiers, the findings of this study provide a useful reference for future application of this technology in particle accelerators.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB345

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paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 02 September 2021

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TUPAB346

Development of a 500-MHz 150-kW Solid-State Power Amplifier for High Energy Photon Source

GUI, controls, photon, booster

2312

Y.L. Luo, T.M. Huang, J. Li, H.Y. Lin, Q. Ma, Q.Y. Wang, P. Zhang, F.C. Zhao
IHEP, Beijing, People’s Republic of China

A 500-MHz 150-kW solid-state power amplifier (SSA) has been developed to test the 500-MHz normal conducting cavities for High Energy Photon Source (HEPS) booster ring. It will also be used to power normal conducting cavities in the initial beam commissioning stage of the HEPS storage ring. A total number of 96 amplifier modules are combined initially by coaxial and later by waveguide combiners to deliver the 150-kW RF power. The final output is of EIA standard WR1800 rectangular waveguide. Each amplifier module consists four transistors equipped with individual circulator and load and outputs 2-kW RF power. Modularity, redundancy and satisfactory RF performance are demonstrated. In the final stage of HEPS project, this 150-kW amplifier will be modified to a 100-kW amplifier to join the other five 100-kW SSAs for normal operation of the booster cavities. The development and test results are presented in this paper.

Poster TUPAB346 [1.870 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB346

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 12 August 2021

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TUPAB347

Development of a 166-MHz 260-kW Solid-State Power Amplifier for High Energy Photon Source

controls, photon, status, power-supply

2315

Y.L. Luo, T.M. Huang, J. Li, H.Y. Lin, Q. Ma, Q.Y. Wang, P. Zhang, F.C. Zhao
IHEP, Beijing, People’s Republic of China

166-MHz 260-kW solid-state power amplifiers have been chosen to drive the 166.6-MHz superconducting cavities for the storage ring of High Energy Photon Source. Highly modular yet compact are desired. A total number of 112 amplifier modules of 3 kW each are combined in a multi-stage power combining topology. The final output is of 9-3/16" 50 Ω coaxial rigid line. Each amplifier module consists of 3 LDMOS transistors with individual circulator and load. Thermal simulations of the amplifier module have been conducted to optimize cooling capabilities for both travelling-wave and full-reflection operation scenarios. High efficiency, sufficient redundancy and excellent RF performances of the 260-kW system are demonstrated. A control system is also integrated and EPICS is used to manage the monitored data. The design and test results of the amplifier system are presented in this paper.

Poster TUPAB347 [1.972 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB347

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 19 August 2021

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TUPAB348

Magnetron R&D for High Efficiency CW RF Sources for Industrial Accelerators

injection, experiment, GUI, MMI

2318

H. Wang, K. Jordan, R.M. Nelson, R.A. Rimmer, S.O. Solomon
JLab, Newport News, Virginia, USA
B.R.L. Coriton, C.P. Moeller, K.A. Thackston
GA, San Diego, California, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177, and DOE OS/HEP Accelerator Stewardship award 2019-2021.
The scheme of using high-efficiency magnetrons to drive radiofrequency accelerators has been demonstrated at 2450 MHz in CW mode *. Magnetron test stands at JLab and GA have been set up to further test the noise figure and the locking speed of the injection phase-lock method. For higher power applications, power combining experiments using a TM010 cavity-type combiner and a magic tee for the binary combiner while using a single clean injection signal has been carried out at 2450 MHz. The frequency pulling effect between the magnetron and a low-Q cavity has been shown to enhance the frequency locking bandwidth compared to the injection phase-lock alone. The principle has been studied by the equivalent circuit simulation, analytical model, and finally confirmed experimentally on the magnetrons. Due to the pandemic delay in 2020, the equivalent high power tests using a 75kW, 915MHz industrial magnetron will be done in 2021 and will be reported in a future paper.
* H. Wang, et al, Magnetron R&Ds for High-Efficiency CW RF Sources of Particle Accelerators, WEXXPLS1, proceedings of IPAC 2019, Melbourne, Australia, May 19 -24, 2019.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB348

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paper received ※ 22 May 2021 paper accepted ※ 21 June 2021 issue date ※ 16 August 2021

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TUPAB349

High Efficiency, Low Cost RF Sources for Accelerators and Colliders

klystron, controls, simulation, electron

2322

R.L. Ives, T. Bui, G. Collins, H. Freund, T.W. Habermann, D. Marsden, M.E. Read
CCR, San Mateo, California, USA
B.E. Chase, J. Reid
Fermilab, Batavia, Illinois, USA
N. Chaudhary, J.R. Conant, T. Cox, R. Ho, C. McVey, C.M. Walker
CPI, Palo Alto, California, USA
J.C. Frisch, L. Ma
SLAC, Menlo Park, California, USA
A. Jensen
Leidos Corp, Billerica, MA, USA
J.M. Potter
JP Accelerator Works, Los Alamos, New Mexico, USA
W. Sessions
Georgia Tech Research Institute, Smyrna, Georgia, USA

Funding: U.S. Department of Energy
Calabazas Creek Research, Inc. (CCR) and its collaborators are developing high efficiency, low cost RF sources. Phase and Amplitude Controlled Magnetrons: CCR, Fermilab, and Communications & Power Industries, LLC (CPI) recently developed a 100 kW, 1.3 GHz magnetron system with amplitude and phase control. The system operated at more than 80% efficiency and demonstrated rapid control of amplitude and phase. Multiple Beam Triodes: CCR, in collaboration with CPI and JP Accelerator Works, Inc., is developing 200 kW, pulsed and CW RF sources from 350 to 700 MHz with projected efficiencies exceeding 80% and cost of $0.50/Watt. Prototype tubes are scheduled for tests in spring 2021. High Efficiency Klystrons:CCR, CPI, and Leidos, Inc. are building a 1.3 GHz, 100 kW klystron operating at 80% efficiency. High power testing is scheduled for summer 2021. Multiple Beam IOTs: CCR and Georgia Tech Research Institute are developing MBIOTs with simplified input coupling and high efficiency. Simulations indicate that 3rd harmonic drive power can increase the efficiency 8-10 %. The program is developing a prototype tube to produce 200 kW peak, 100 kW average power at 704 MHz.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB349

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paper received ※ 18 May 2021 paper accepted ※ 01 June 2021 issue date ※ 24 August 2021

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TUPAB354

352-MHz Solid State RF System Development at the Advanced Photon Source

GUI, controls, PLC, klystron

2335

D. Horan, D.J. Bromberek, N.P. DiMonte, A. Goel, T.J. Madden, A. Nassiri, G. Trento, G.J. Waldschmidt
ANL, Lemont, Illinois, USA

Development effort is underway on a 352MHz, 200kW solid state rf system intended as the base design to replace the existing klystron-based rf systems presently in use at the Advanced Photon Source (APS). A sixteen-input, 200kW final combining cavity was designed, built, and successfully tested to 29kW CW in combiner mode, and to 200kW CW in back-feed mode, where an external klystron was used to transmit power into the combining cavity. A four-port waveguide combiner was also tested in both backfeed and combiner mode to 193kW and 26kW respectively. Slow and fast interlock systems were designed and implemented to support the testing process. An EPICS and Programmable Logic Controller (PLC)-based system was developed to control, communicate with, and monitor the rf amplifiers used in the combiner-mode test, and to monitor and log system performance parameters relating to the combining cavity. Low-level rf control of the cavity in 29kW combiner-mode operation was achieved using the existing APS analog low-level rf hardware. Test data and design details are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB354

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paper received ※ 18 May 2021 paper accepted ※ 31 May 2021 issue date ※ 24 August 2021

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TUPAB355

Design and Implementation of a Production Model Bias Tee

multipactoring, high-voltage, MMI, linac

2339

T.L. Larter, E. Gutierrez, S.H. Kim, D.G. Morris, J.T. Popielarski, T. Xu, S. Zhao
FRIB, East Lansing, Michigan, USA

Funding: This work is supported by the US Department of Energy Office of Science under Cooperative Agreement DE-SC0000661, the State of Michigan and Michigan State University.
The Facility for Rare Isotope Beams (FRIB) includes two types of half wave SC resonators (HWR) operating at 322MHz. The fundamental power couplers used to transmit RF power into the HWRs commonly suffer from multipacting which can result in long conditioning times. A bias tee can be used to apply a high voltage to the couplers to help alleviate multipacting. A production version of the bias tee was commissioned for use at FRIB. The bias tee went through several design revisions to diagnose and correct thermal dissipation issues. This paper will discuss details of design and challenges faced during production validation of the bias tee.

Poster TUPAB355 [0.630 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB355

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paper received ※ 19 May 2021 paper accepted ※ 28 May 2021 issue date ※ 14 August 2021

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TUPAB356

Electron Beam Driven Cavities

electron, simulation, linac, klystron

2342

M. Schuett, U. Ratzinger
IAP, Frankfurt am Main, Germany

State of the art high power feeder for RF cavities used as accelerators generally require RF amplifiers consisting of a vacuum tube, such as a klystron or Grid Tubes. In addition, a number of cost intensive RF auxiliary devices are needed: Modulator, waveguides, circulator, power dump and couplers. The equipment requires significant floor space within the linac building. Alternatively, we propose a direct driven system. Aμbunched electron beam is injected directly into the cavity. A high perveance bunched electron beam can be generated by a standard electron gun combined with a deflecting beam chopper*, an off-the-shelf IOT or klystron, respectively. The pulse rate is determined by the resonance frequency of the cavity. The resonator hereby acts like the output cavity of a klystron: Within its propagation through the cavity the beam is decelerated increasing the stored energy of the accelerator. We present 3D particle PIC simulations evaluating the geometry and beam properties in order to optimize the coupling efficiency and cavity excitation of state-of-art CH particle accelerator structures.
* S. Setzer, T. Weiland and U. Ratzinger, A Chopped Electron Beam Driver for H-Type Cavities, 20th ‘International Linac Conference, Monterey, California, August 21-25, 2000, pp. 1001-1003

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB356

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 21 August 2021

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TUPAB358

Novel 500 MHz Solid State Power Amplifier Module Development at Sirius

operation, impedance, synchrotron, storage-ring

2349

M.H. Wallner, R.H. Farias, A.P.B. Lima, F. Santiago de Oliveira
LNLS, Campinas, Brazil

A new solid state power amplifier (SSPA) module is being developed at the Brazilian Center for Research in Energy and Materials (CNPEM) to drive one of the superconducting RF cavities to be installed at Sirius, its new 3 GeV fourth generation synchrotron light source. Several prototypes have been built and tested in-house, and a planar balun was designed to achieve a push-pull configuration at deep class AB operation. Efforts to optimize heat exchange in various ways have been made. Results obtained thus far are presented and the next steps concerning development are discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB358

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paper received ※ 19 May 2021 paper accepted ※ 18 June 2021 issue date ※ 18 August 2021

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TUPAB395

Vacuum System Models for Minerva Linac Design

vacuum, linac, rfq, MEBT

2443

S. Rey, M.A. Baylac, F. Bouly, E. Froidefond
LPSC, Grenoble Cedex, France
F. Davin, D. Vandeplassche
SCK•CEN, Mol, Belgium
L. Perrot, H. Saugnac
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France

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 Belgian federal government the project has entered in its phase I: this includes the development and the construction of the linac first part, up to 100 MeV. We here review the MINERVA linac vacuum system modelling studies that enabled to validate the choice of materials and vacuum equipment. The strengths and weaknesses of the vacuum design, highlighted by the models, will be discussed as well as the required improvements.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB395

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paper received ※ 19 May 2021 paper accepted ※ 01 June 2021 issue date ※ 12 August 2021

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TUPAB399

RF Characterisation of New Coatings for Future Circular Collider Beam Screens

impedance, laser, collider, electron

2453

P. Krkotić, F. Pérez, M. Pont, N.D. Tagdulang
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
S. Calatroni
CERN, Meyrin, Switzerland
X. Granados, J. Gutierrez, T. Puig, A. Romanov, G.T. Telles
ICMAB, Bellatera, Spain
A.N. Hannah, O.B. Malyshev, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
J.M. O’Callaghan Castella
Universitat Politécnica de Catalunya, Barcelona, Spain
D. Whitehead
The University of Manchester, Laser Processing Research Center, Manchester, United Kingdom

For the future high energy colliders being under the design at this moment, the choice of a low surface impedance beam screen coating material has become of fundamental importance to ensure sufficiently low beam impedance and consequently guaranteed stable operation at high currents. We have studied the use of high-temperature superconducting coated conductors as possible coating materials for the beam screen of the FCC-hh. In addition, amorphous carbon coating and laser-based surface treatment techniques are effective surface treatments to lower the secondary electron yield and minimise the electron cloud build-up. We have developed and adapted different experimental setups based on resonating structures at frequencies below 10 GHz to study the response of these coatings and their modified surfaces under the influence of RF fields and DC magnetic fields up to 9 T. Taking the FCC-hh as a reference, we will show that the surface resistance for REBCO-CCs is much lower than that of Cu. Further we show that the additional surface modifications can be optimised to minimise their impact on the surface impedance. Results from selected coatings will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB399

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paper received ※ 19 May 2021 paper accepted ※ 25 June 2021 issue date ※ 16 August 2021

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TUPAB417

Pushing Spatial Resolution Limits In Single-Shot Time-Resolved Transmission Electron Microscopy at the UCLA Pegasus Laboratory

electron, space-charge, gun, simulation

2506

P.E. Denham, P. Musumeci
UCLA, Los Angeles, USA

Funding: This work was supported by DOESTTR grant No. DE-SC0013115 and by by the National Science Foundation under STROBE Science and Technology Center Grant No. DMR-1548924
We present the design of a high-speed single shot relativistic electron microscope planned for implementation at the UCLA PEGASUS Laboratory capable of imaging with less than 30~nm spatial resolution and image acquisition time on the order of 10~ps. This work is based on a multi-cavity acceleration scheme for producing relativistic beams (3.75 MeV) with suppressed rms energy spread (σ_δ ≈5e-5), and a means to reduce smooth space charge aberrations by generating a quasi-optimal 4D particle distribution at the sample plane. start-to-end simulation results are used to validate the entire setup. Ultimately, a feasible working point is demonstrated.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB417

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paper received ※ 19 May 2021 paper accepted ※ 28 July 2021 issue date ※ 12 August 2021

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WEXA01

Successful Crabbing of Proton Beams

luminosity, collider, emittance, impedance

2510

R. Calaga
CERN, Meyrin, Switzerland

Funding: Research supported by the HL-LHC project and by the DOE and UK-STFC.
Many future particle colliders require beam crabbing to recover the geometric luminosity loss from the non-zero crossing angle at the interaction point. A first demonstration experiment of crabbing with hadron beams was successfully carried out with high energy protons. This breakthrough result is fundamental to achieve the physics goals of the high luminosity LHC upgrade project (HL-LHC) and the future circular collider (FCC). The expected peak luminosity gain (related to collision rate) is 65% for HL-LHC, and even greater for the FCC. Novel beam physics experiments with proton beams in CERN’s Super Proton Synchrotron (SPS) were performed to demonstrate several critical aspects for the operation of crab cavities in the future HL-LHC including transparency with a pair of cavities, a full characterization of the cavity impedance with high beam currents and controlled emittance growth from crab cavity induced RF noise.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXA01

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paper received ※ 14 May 2021 paper accepted ※ 28 July 2021 issue date ※ 15 August 2021

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WEXA02

Operational Electron Cooling in the Relativistic Heavy Ion Collider

electron, operation, collider, cathode

2516

A.V. Fedotov, K.A. Drees, W. Fischer, X. Gu, D. Kayran, J. Kewisch, C. Liu, K. Mernick, M.G. Minty, V. Schoefer, H. Zhao
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
Since the invention of the electron cooling technique its application to cool hadron beams in colliders was considered for numerous accelerator physics projects worldwide. However, achieving the required high-brightness electron beams of required quality and cooling of ion beams in collisions was deemed to be challenging. An electron cooling of ion beams employing a high-energy approach with RF-accelerated electron bunches was recently successfully implemented at BNL. It was used to cool ion beams in both collider rings with ion beams in collision. Electron cooling in RHIC became fully operational during the 2020 physics run and led to substantial improvements in luminosity. This presentation will discuss implementation, optimization and challenges of electron cooling for colliding ion beams in RHIC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXA02

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paper received ※ 18 May 2021 paper accepted ※ 15 June 2021 issue date ※ 13 August 2021

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WEXB01

The ESS Elliptical Cavity Cryomodules Production at CEA

cryomodule, status, site, vacuum

2536

C. Madec
CEA, Gif-sur-Yvette, France
C. Arcambal, S. Berry, A. Bouygues, G. Devanz, C. Mayri, P. Sahuquet, T. Trublet
CEA-DRF-IRFU, France
P. Bosland, E. Cenni, C. Cloué, T. Hamelin, O. Piquet
CEA-IRFU, Gif-sur-Yvette, France
P. Pierini
ESS, Lund, Sweden

CEA in Kind contribution to the ESS superconducting LINAC includes 30 elliptical medium and high-beta cryomodules. CEA is in charge of the production of all the components (except the cavities delivered by LASA and STFC) as well as the assembly of the cryomodules and a few cryogenic and RF tests. The power couplers operating at a maximum power of 1.1MW on a 3.6ms pulse at 14Hz are conditioned at high RF power on a dedicated stand. The assembly of the cryomodules is performed at CEA by a private Company under the supervision of CEA. This paper presents the status of the cryomodules production and the infrastructure dedicated to this project at CEA Saclay.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXB01

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paper received ※ 18 May 2021 paper accepted ※ 19 July 2021 issue date ※ 21 August 2021

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WEXB06

Development of an APF IH-DTL in the J-PARC Muon g-2/EDM Experiment

DTL, linac, experiment, focusing

2544

Y. Nakazawa, H. Iinuma
Ibaraki University, Hitachi, Ibaraki, Japan
E. Cicek, N. Kawamura, T. Mibe, M. Yoshida
KEK, Ibaraki, Japan
N. Hayashizaki
RLNR, Tokyo, Japan
Y. Iwata
NIRS, Chiba-shi, Japan
R. Kitamura, Y. Kondo, T. Morishita
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
M. Otani, N. Saito
J-PARC, KEK & JAEA, Ibaraki-ken, Japan
Y. Sue, K. Sumi, M. Yotsuzuka
Nagoya University, Graduate School of Science, Chikusa-ku, Nagoya, Japan
Y. Takeuchi
Kyushu University, Fukuoka, Japan
T. Yamazaki
KEK, Tokai Branch, Tokai, Naka, Ibaraki, Japan
H.Y. Yasuda
University of Tokyo, Tokyo, Japan

An inter-digital H-mode drift-tube linac (IH-DTL) is under development in a muon linac at the J-PARC muon g-2/EDM experiment. It accelerates muons from 0.34 MeV to 4.3 MeV at an operating frequency of 324 MHz. The cavity can be miniaturized by introducing the alternative phase focusing (APF) method that enables transverse focusing only with an E-field. The APF IH-DTL cavity was modeled by a three-dimensional field analysis, and the beam dynamics were evaluated numerically. The beam emittance was calculated as 0.316pi and 0.189pi mm mrad in the horizontal and vertical directions, respectively. It satisfies the experimental requirement. Actually, the field error due to the fabrication errors and thermal expansion during operation causes an emittance growth. It was evaluated that the optimized tuners can suppress the emittance growth to less than 10%. In this paper, the detailed design of the APF IH-DTL including the tuner will be reported.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXB06

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paper received ※ 19 May 2021 paper accepted ※ 29 July 2021 issue date ※ 20 August 2021

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WEXC03

Review of Superconducting Radio Frequency Gun

cathode, gun, SRF, operation

2556

R. Xiang
HZDR, Dresden, Germany

The success of proposed high power free-electron lasers (FELs) and energy recovery linac (ERL) largely depends on the development of the electron source, which requires the best beam quality and CW operation. An elegant way to realize this average brilliance is to combine the high beam quality of mature normal conducting radio frequency photoinjector with the quick developing superconducting radio frequency technology, to build superconducting rf photoinjectors (SRF guns). In last decade, several SRF gun programs based on different approaches have achieved promising progress, even succeeded in routine operation at BNL and HZDR [*,**]. In the near future SRF guns are expected to play an important role for hard X-ray FEL facilities. In this contribution, we will review the design concepts, parameters, and the status of the major SRF gun projects.
*I. Petrushina et al., Phys. Rev. Lett. 124, 244801
**J. Teichert at al., Phys. Rev. Accel. Beams 24, 033401

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXC03

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paper received ※ 19 May 2021 paper accepted ※ 28 June 2021 issue date ※ 11 August 2021

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WEPAB006

EIC Crab Cavity Multipole Analysis

multipole, dynamic-aperture, collider, simulation

2589

Q. Wu, Y. Luo, B.P. Xiao
BNL, Upton, New York, USA
S.U. De Silva
ODU, Norfolk, Virginia, USA
J.A. Mitchell
CERN, Geneva, Switzerland

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
Crab cavities are specialized RF devices designed for colliders targeting high luminosities. It is a straightforward solution to retrieve head-on collision with crossing angle existing to fast separate both beams after collision. The Electron Ion Collider (EIC) has a crossing angle of 25 mrad, and will use local crabbing to minimize the dynamic aperture requirement throughout the rings. The current crab cavity design for the EIC lacks axial symmetry. Therefore, their higher order components of the fundamental deflecting mode have a potential of affecting the long-term beam stability. We present here the multipole analysis and preliminary particle tracking results from the current crab cavity design.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB006

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paper received ※ 18 May 2021 paper accepted ※ 25 June 2021 issue date ※ 12 August 2021

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WEPAB009

Study of Harmonic Crab Cavity in EIC Beam-Beam Simulations

simulation, resonance, betatron, electron

2595

D. Xu, Y. Hao
FRIB, East Lansing, Michigan, USA
Y. Luo, C. Montag
BNL, Upton, New York, USA
J. Qiang
LBNL, Berkeley, California, USA

In the Electron-Ion Collider (EIC) design, crab cavities are adopted to compensate the geometric luminosity loss from the crossing angle. From previous studies, higher-order synchro-betatron resonances are excited since the hadron beam is long and the crossing angle is large. To reduce the luminosity degradation rate, different combinations of harmonic crab cavities are studied with both weak-strong and strong-strong simulation methods. The frequency map analysis (FMA) is also used for comparison. This study helps determine the crab cavity parameters for the future EIC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB009

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paper received ※ 17 May 2021 paper accepted ※ 23 June 2021 issue date ※ 30 August 2021

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WEPAB010

Full Range Tune Scan Studies Using Graphics Processing Units with CUDA in EIC Beam-Beam Simulations

simulation, resonance, betatron, GPU

2598

D. Xu, Y. Hao
FRIB, East Lansing, Michigan, USA
Y. Luo, C. Montag
BNL, Upton, New York, USA
J. Qiang
LBNL, Berkeley, California, USA

The hadron beam in the Electron-Ion Collider (EIC) suffers high order betatron and synchro-betatron resonances. In this paper, we present a weak-strong full range (0.0~0.5) fractional tune scan with a step size as small as 0.001. Multiple Graphics Processing Units (GPUs) are used to speed up the simulation. A code parallelized with MPI and CUDA is implemented. The good tune region from weak-strong scan is further checked by the self-consistent strong-strong simulation. This study provides beam dynamics guidance in choosing proper working points for the future EIC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB010

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paper received ※ 17 May 2021 paper accepted ※ 23 June 2021 issue date ※ 23 August 2021

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WEPAB019

RF Harmonic Kicker R&D Demonstration and Its Application to the RCS Injection of the EIC

kicker, injection, electron, operation

2632

G.-T. Park, M.W. Bruker, J.M. Grames, J. Guo, R.A. Rimmer, S.O. Solomon, H. Wang
JLab, Newport News, Virginia, USA

The Rapid Cycling Synchrotron (RCS) of the Electron-Ion Collider (EIC) at Brookhaven National Laboratory (BNL) * is an accelerating component of the electron injection complex, which provides polarized electrons in electron-ion collisions in the main Electron Storage Ring (ESR). We present the injection scheme into the RCS based on an ultra-fast harmonic kicker, whose "five odd-harmonic modes" prototype was developed in the context of the Jefferson Lab EIC (JLEIC) conceptual design **. In its early stage of R&D, the sharp (~3 ns width) waveform construction, beam dynamics, and pulsed power operation with short ramping time (~10 us) will be discussed together with the fabrication work of the JLEIC prototype ***.
* BNL, "Electron Ion Collider Conceptual Design Report", 2020
** G. Park et. al, JLAB-TN-044
*** G. Park et. al., JLAB-TN-046

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB019

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paper received ※ 17 May 2021 paper accepted ※ 22 June 2021 issue date ※ 27 August 2021

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WEPAB020

The Relation Between Field Flatness and the Passband Frequency in the Elliptical Cavities

SRF, simulation, gun, accelerating-gradient

2636

G.-T. Park, R.A. Rimmer, H. Wang
JLab, Newport News, Virginia, USA

A technique that predicts the field flatness of the operating pi-mode based on the passband frequency is highly desirable when the direct measurement of the field is not available. Such a technique was developed for the SNS-PPU cavity, a 6-cell SRF cavity whose field flatness is important for cold operation. In this paper, we will present the theory on the relations between field profile and passband frequencies of the arbitrary deformed cavities, the simulation studies, and comparison with the experimental measurements.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB020

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paper received ※ 17 May 2021 paper accepted ※ 24 June 2021 issue date ※ 31 August 2021

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WEPAB038

Commissioning of a New X-Band, Low-Noise LLRF System

klystron, LLRF, MMI, linac

2683

A.V. Edwards, M. Boronat Arevalo, N. Catalán Lasheras, G. McMonagle
CERN, Meyrin, Switzerland
A.C. Dexter
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom

To increase beam energy in the CLEAR facility at CERN and study the CLIC accelerating structure prototype in operating conditions, the first X-band test facility at CERN was upgraded in 2020. Both, the acquisition and software systems at X-band test stand 1 (Xbox1) were upgraded to exhibit low phase noise which is relevant to klystron based CLIC and to the use of crab cavities in the beam delivery system. The new LLRF uses down-conversion which necessitates a local oscillator which can be produced by two different methods. The first is a PLL, a commonly used technique which has been previously employed at the other X-band facilities at CERN. The second is a novel application of a single sideband up-convertor. The up-convertor system has demonstrated reduced phase noise when compared with the PLL. The commissioning of the new system began in late 2020 with the conditioning of a 50 MW Klystron. Measurements of the quality of the new LLRF will be shown. These will compare the PLL and up-convertor with particular attention on the quality of the phase measurements. Also, a preliminary study of phase shifts in the waveguide network due to temperature changes will be presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB038

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paper received ※ 13 May 2021 paper accepted ※ 05 July 2021 issue date ※ 23 August 2021

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WEPAB041

Testing of the Milliampere Booster Prototype Cavity

linac, vacuum, operation, solenoid

2693

R.G. Heine
KPH, Mainz, Germany

The Milliampere Booster (MAMBO) is the injector linac for the Mainz Energy-recovering Superconducting Accelerator MESA. MESA is a multi-turn energy recovery linac with beam energies in the 100 MeV regime currently designed and built at Institut für Kernphysik (KPH) of Johannes Gutenberg-Universität Mainz. The main accelerator consists of two superconducting Rossendorf type modules, while the injector MAMBO relies on normal conducting technolgy. The MAMBO RF cavities are bi-periodic pi/2 structures with 33 cells and 37 cells, respectively. In this paper we present the results of the commissioning and testing of a 13 cell prototype structure.

Poster WEPAB041 [2.824 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB041

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paper received ※ 18 May 2021 paper accepted ※ 23 June 2021 issue date ※ 23 August 2021

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WEPAB048

Design of an Optical Cavity for Generating Intense THz Pulse Based on Coherent Cherenkov Radiation

electron, radiation, gun, experiment

2711

P. Wang, Y. Koshiba, T. Murakami, K. Murakoshi, K. Sakaue, Y. Tadenuma, M. Washio
Waseda University, Tokyo, Japan
R. Kuroda
AIST, Tsukuba, Japan
K. Sakaue
The University of Tokyo, Graduate School of Engineering, Bunkyo, Japan

We have been studying terahertz (THz) generation via Cherenkov radiation with high-quality electron beams from a photocathode rf (radio frequency) gun. In our early studies, we have succeeded in the generation of coherent Cherenkov radiation by controlling the tilt of the electron beam using an rf-deflector. For further enhancement, we are planning to stack the THz pulses in an optical cavity. Multi-bunch operation of the rf-gun will generate electron beams with a repetition rate of 119 MHz, and THz pulses as well. These pulses will be accumulated in the cavity for up to 150 pulses. In this conference, we report the design study of the enhancement cavity and discuss the performance of the THz source.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB048

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paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 22 August 2021

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WEPAB065

Studies of the Energy Recovery Performance of the PERLE Project

linac, HOM, electron, radiation

2744

K.D.J. André, B.J. Holzer
CERN, Geneva, Switzerland
S.A. Bogacz
JLab, Newport News, Virginia, USA

The Powerful Energy Recovery Linac for Experiments (PERLE) is an accelerator facility for the development and application of the energy recovery technique for an intense 500 MeV electron beam. The paper presents the studies that have been performed to assess the quality of the ERL lattice design and beam optics. The studies include the Coherent Synchrotron Radiation (CSR) emission and wakefields in the superconducting radio-frequency structures of the linacs. The lattice design and optics principles of the ERL structure are discussed, involving the vertical deflection system and the 180° arcs. Finally, the results of the front-to-end tracking simulations that consider the complete multi-turn energy recovery process are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB065

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paper received ※ 18 May 2021 paper accepted ※ 24 June 2021 issue date ※ 14 August 2021

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WEPAB079

Optics Studies on the Operation of a New Wiggler and Bunch Shortening at the DELTA Storage Ring

wiggler, optics, storage-ring, operation

2772

B. Büsing, P. Hartmann, A. Held, S. Khan, C. Mai, D. Schirmer, G. Schmidt
DELTA, Dortmund, Germany

Funding: Work supported by Deutsche Forschungsgemeinschaft via project INST 212/330-1 AOBJ: 619186
The 1.5-GeV electron storage ring DELTA is a synchrotron light source operated by the TU Dortmund University. Radiation from hard X-rays to the THz regime is provided by dipole magnets and insertion devices like undulators and wigglers. To provide even shorter wavelengths, a new 22-pole superconducting 7-T wiggler has been installed. The edge focusing of the wiggler has a large impact on the linear optics of the storage ring. Measurements regarding its influence and simulations were performed. In addition, a second radiofrequency (RF) cavity has been installed to compensate the increased energy loss per turn due to the new wiggler. As a consequence of the higher RF power, the electron bunches are shorter compared to the old setup with only one cavity. In view of reducing the bunch length even more, studies of the storage ring optics with reduced momentum compaction factor were performed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB079

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paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 22 August 2021

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WEPAB081

The Broad-Band Impedance Budget in the Storage Ring of the ALS-U Project

impedance, vacuum, wakefield, storage-ring

2779

D. Wang, K.L.F. Bane, R. Bereguer, T. Cui, S. De Santis, P. Gach, D. Li, T.H. Luo, T. Miller, T. Oliver, O. Omolayo, C. Steier, T.L. Swain, M. Venturini, G. Wang
LBNL, Berkeley, California, USA

Design work is underway for the upgrade of the Advanced Light Source (ALS-U) to a diffraction-limited soft x-rays radiation source. Like other 4th-generation light source machines, the ALS-U multiple-bend achromat storage-ring (SR) is potentially sensitive to beam-coupling impedance effects. This paper presents the SR broad-band impedance budget in both the longitudinal and transverse planes. In our modeling we follow the commonly accepted approach of separating the resistive-wall and the geometric parts of the impedance, the former being described by analytical formulas and the latter obtained by numerical electromagnetic codes (primarily CST Studio software) assuming perfectly conducting materials. We discuss the main sources of impedance. Results of our analysis are the basis for the single bunch instability study and would feedback on the design of critical vacuum components.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB081

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paper received ※ 20 May 2021 paper accepted ※ 01 July 2021 issue date ※ 14 August 2021

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WEPAB082

Single Bunch Instability Simulations in the Storage Ring of the ALS-U Project

impedance, simulation, storage-ring, operation

2783

D. Wang, K.L.F. Bane, S. De Santis, M.P. Ehrlichman, D. Li, T.H. Luo, O. Omolayo, G. Penn, C. Steier, M. Venturini
LBNL, Berkeley, California, USA

As the broad-band impedance modeling and the vacuum chamber design of the new Advanced Light Source storage ring (ALS- U) reach maturity, we report on progress in single-bunch collective effects studies. A pseudo-Green function wake representing the entire ring was earlier obtained by numerical and analytical methods. Macroparticle simulations using the computer code "elegant" and this wake function are used to determine the instability thresholds for longitudinal and transverse motion. We consider various operating conditions, such as without/with higher-harmonic RF cavities, zero/finite linear chromaticity, and without/with a transverse bunch-by-bunch feedback system. Results show enough margin for the broadband impedance budget when the single-bunch instability thresholds are compared with the design bunch charge.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB082

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paper received ※ 20 May 2021 paper accepted ※ 01 July 2021 issue date ※ 18 August 2021

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WEPAB090

Higher Order Mode Damping for 166 MHz and 500 MHz Superconducting RF Cavities at High Energy Photon Source

HOM, impedance, damping, storage-ring

2798

H.J. Zheng, Z.Q. Li, F. Meng, N. Wang, H.S. Xu, P. Zhang, X.Y. Zhang
IHEP, Beijing, People’s Republic of China

Funding: This work was supported in part by High Energy Photon Source, in part by the National Natural Science Foundation of China under Grant No. 11905232.
Superconducting rf cavities have been chosen for High Energy Photon Source, a 6 GeV diffraction-limited synchrotron light source under construction in Beijing. The main accelerating cavity adopted a quarter-wave β=1 structure operating at 166 MHz while the third harmonic cavity utilized the single-cell elliptical geometry at 500 MHz for the storage ring. The high beam current (200 mA) requires a strong damping of higher order modes (HOMs) excited in the superconducting cavities. To meet the beam stability requirements, enlarged beam pipes with a diameter of 505 mm for the 166 MHz cavity and 300 mm for the 500 MHz cavity were chosen to allow all HOMs to propagate along the beam tubes and to be damped by beam-line absorbers. This paper presents the HOM damping scheme and the cavity impedance analysis results. In addition, power losses due to HOMs were also evaluated for various operation modes (high charge and high luminosity) of the HEPS.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB090

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paper received ※ 17 May 2021 paper accepted ※ 22 June 2021 issue date ※ 11 August 2021

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WEPAB098

Cryogenic Component and Material Testing for Compact Electron Beamlines

cryogenics, cathode, electron, gun

2818

G.E. Lawler, N. Majernik, J.B. Rosenzweig
UCLA, Los Angeles, California, USA

Funding: This work was supported by the Center for Bright Beams, National Science Foundation Grant No. PHY-1549132 and DOE Contract DE-SC0020409
Cryogenic regimes of operation are, for various reasons, highly advantageous for normal conducting accelerator structures. Liquid cryogen-based systems are costly to implement and maintain. As a result, developing cryogenic test facilities at a smaller more cost effective scale using cryo-coolers is attractive. Before real implementations of a cryo-cooler based beamline, a significant amount of information is necessary regarding the behavior and properties of various components and materials at cryogenic temperatures. Finding this information lacking for our particular beamline case and by extension similar electron beamlines, we endeavor to generate a thorough beamline-relevant material and component properties down to the range of a liquid nitrogen temperatures (77 K) and the nominal operating temperature of a modest Gifford-McMahon cryocooler (45 K).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB098

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paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 18 August 2021

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WEPAB110

Solid-State Driven X-Band Linac for Electron Microscopy

electron, linac, simulation, gun

2853

A. Dhar, E.A. Nanni, M.A.K. Othman, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: This work was supported by the Department of Energy Contract No. DE-AC02-76SF00515.
Microcrystal electron diffraction (MicroED) is a technique used by scientists to image molecular crystals with cryo-electron microscopy (cryo-EM)*. However, cryo-EMs remain expensive, limiting MicroED’s accessibility. Current cryo-EMs accelerate electrons to 200-300 keV using DC electron guns with a nA of current and low emittance. However at higher voltages these DC guns rapidly grow in size. Replacing these electron guns with a compact linac powered by solid-state sources could lower cost while maintaining beam quality, thereby increasing accessibility. Utilizing compact high shunt impedance X-band structures ensures that each RF cycle contains at most a few electrons, preserving beam coherence. CW operation of the RF linac is possible with distributed solid-state architectures** that use 100W solid-state amplifiers at X-band frequencies. We present an initial design for a prototype low-cost CW RF linac for high-throughput MicroED producing 200 keV electrons with a standing-wave architecture where each cell is individually powered by a solid-state amplifier. This design also provides an upgrade path for future compact MeV-scale sources on the order of 1 meter in size.
* Jones, C. G. et al. ACS central science 4, 1587-1592 (2018).
** D. C. Nguyen et al, Proc. 9th International Particle Accelerator Conference (IPAC’18), no. 9, pp. 520-523

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB110

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paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 19 August 2021

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WEPAB138

Superconducting RF Gun with High Current and the Capability to Generate Polarized Electron Beams

gun, SRF, electron, cathode

2936

I. Petrushina
SUNY SB, Stony Brook, New York, USA
S.A. Belomestnykh, S. Kazakov, T.N. Khabiboulline, M. Martinello, Y.M. Pischalnikov, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA
J.C. Brutus, P. Inacker, Y.C. Jing, V. Litvinenko, J. Skaritka, E. Wang
BNL, Upton, New York, USA
J.M. Grames, M. Poelker, R. Suleiman, E.J-M. Voutier
JLab, Newport News, Virginia, USA

High-current low-emittance CW electron beams are indispensable for nuclear and high-energy physics fixed target and collider experiments, cooling high energy hadron beams, generating CW beams of monoenergetic X-rays (in FELs) and gamma-rays (in Compton sources). Polarization of electrons in these beams provides extra value by opening a new set of observables and frequently improving the data quality. We report on the upgrade of the unique and fully functional CW SRF 1.25 MeV SRF gun, built as part of the Coherent electron Cooling (CeC) project, which has demonstrated sustained CW operation with CsK2Sb photocathodes generating electron bunches with record-low transverse emittances and record-high bunch charge exceeding 10 nC. We propose to extend the capabilities of this system to high average current of 100 milliampere in two steps: increasing the current 30-fold at each step with the goal to demonstrate reliable long-term operation of the high-current low-emittance CW SRF guns. We also propose to test polarized GaAs photocathodes in the ultra-high vacuum (UHV) environment of the SRF gun, which has never been successfully demonstrated in RF accelerators.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB138

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paper received ※ 25 May 2021 paper accepted ※ 29 July 2021 issue date ※ 23 August 2021

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WEPAB148

RF Design of an X-Band TM02 Mode Cavity for Field Emitter Testing

electron, coupling, insertion, multipactoring

2961

Z. Li, S.G. Tantawi
SLAC, Menlo Park, California, USA
S.V. Baryshev, T. Posos, M.E. Schneider
Michigan State University, East Lansing, Michigan, USA

Funding: Work at SLAC was supported by DOE under contract No. DE-AC02-76SF00515. Work at MSU was supported by DOE under Award No. DE-SC0020429 and under Cooperative Agreement Award No. DE-SC0018362.
Planar polycrystalline synthetic diamond with nitrogen-doping/incorporation was found to be a remarkable field emitter. It is capable of generating a high charge beam and handling moderate vacuum conditions. Integrating it with an efficient RF cavity could therefore provide a compact electron source for RF injectors. Understanding the performance metrics of the emitter in RF fields is essential toward developing such a device. We investigated a test setup of the field emitter at the X-band frequency. The setup included an X-band cavity operating at the TM02 mode. The field emitter material will be plated on the tip of a insertion rod on the cavity back plate. Part of the back plate and the emitter rod are demountable, allowing for exchange of the field emitters. The TM02 mode was chosen such that the design of the demountable back plate does not induce field enhancement at the installation gap. The cavity were optimized to achieve a high surface field at the emitter tip and a maximum energy gain of the emitted electrons at a given input power. We will present the RF and mechanical design of such a TM02 X-band cavity for field emitter testing.

Poster WEPAB148 [1.642 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB148

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paper received ※ 14 May 2021 paper accepted ※ 12 July 2021 issue date ※ 25 August 2021

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WEPAB149

The RF Gun for the Siberian Circular Light Source "SKIF"

gun, cathode, electron, linac

2965

V. Volkov, A.M. Batrakov, S.M. Gurov, S.E. Karnaev, A.A. Kondakov, S.A. Krutikhin, G.Y. Kurkin, A.E. Levichev, O.I. Meshkov, V.K. Ovchar, A.V. Pavlenko, O.A. Pavlov, A.G. Tribendis, N.G. Vasileva
BINP SB RAS, Novosibirsk, Russia
A.E. Levichev, A.V. Pavlenko
NSU, Novosibirsk, Russia
A.G. Tribendis
NSTU, Novosibirsk, Russia

The Siberian Circular Light Source is a new medium-energy high brightness synchrotron light facility that is under construction on the Budker Institute of Nuclear Physics (BINP) in Russia, Novosibirsk. The accelerator facility is divided for convenience into three components; a 3 GeV storage ring, a full-energy booster synchrotron, and a 200 MeV injector linac with a thermionic gridded RF gun electron source. This paper describes the RF gun design and plans for operations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB149

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paper received ※ 19 May 2021 paper accepted ※ 07 June 2021 issue date ※ 10 August 2021

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WEPAB150

Monotron Beam Break Up Instability Analysis

HOM, klystron, dipole, resonance

2968

V. Volkov, V.M. Petrov
BINP SB RAS, Novosibirsk, Russia

New features of monotron beam break up (BBU) instability such as the typing of high order monopole modes (HOMs)in each cavity by two classes one of them are stable and other ones are unstable, HOM effective quality factor depending on average beam current, and normalized invariable threshold current individually characterizes each HOM are investigated in this article in detail.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB150

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paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 10 August 2021

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WEPAB151

Regenerative Beam Break Up Instability Analysis

HOM, dipole, linac, experiment

2971

V. Volkov, V.M. Petrov
BINP SB RAS, Novosibirsk, Russia

New features of regenerative beam break up (BBU) instability such as the typing of high order dipole modes (HOMs)in each cavity by two classes, one of them are stable and other ones are unstable, HOM effective quality factor depending on average beam current, and normalized invariable threshold current individually characterizes each HOM are investigated in this article in detail.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB151

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paper received ※ 19 May 2021 paper accepted ※ 22 June 2021 issue date ※ 10 August 2021

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WEPAB165

Metamaterial Waveguide HOM Loads for SRF Accelerating Cavities

HOM, GUI, vacuum, SRF

2994

S.V. Kuzikov
Euclid TechLabs, Solon, Ohio, USA

Suppression of beam induced HOMs is necessary for most SRF accelerating cavities driven with high currents. One of the problems in design of a HOM load is that vacuum compatible materials with high enough imaginary part of the dielectric permittivity, which provides absorption, have also a high real part of the permittivity. This does not allow absorbing RF radiation at short distance and in broad frequency band. We propose considering artificial metamaterials where besides lossy dielectric pieces, an absorber with high magnetic permeability is included. In our proposal, we suggest composing a waveguide HOM load of a metamaterial consisted of well-known ceramic and ferrite plates placed periodically in a stack. Such a design provides low return losses, compactness and broad frequency range of the operation.

Poster WEPAB165 [1.844 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB165

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paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 15 August 2021

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WEPAB177

Consideration of Triple-Harmonic Operation for the J-PARC RCS

operation, bunching, injection, simulation

3020

H. Okita
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
M. Furusawa, Y. Sugiyama
KEK, Tokai, Ibaraki, Japan
K. Hara, K. Hasegawa, M. Nomura, C. Ohmori, T. Shimada, F. Tamura, M. Yamamoto, M. Yoshii
KEK/JAEA, Ibaraki-Ken, Japan

The wideband magnetic alloy (MA) cavities are employed in the J-PARC RCS. The dual-harmonic operation, in which each MA cavity is driven by superposition of the fundamental accelerating voltage and the second harmonic voltage, significantly improves the bunching factor and is indispensable for acceleration of the high intensity beams. The original LLRF control system was replaced with the new system in 2019, which can control the amplitudes of the higher harmonics as well as the fundamental and second harmonics. Therefore we consider to use additionally the third harmonic voltage for further improvement of the bunching factor during acceleration. By the triple-harmonic operation, the flat RF bucket can be realized with a higher synchronous phase and improvement of the bunching factor is expected. In this presentation, we describe the longitudinal simulation studies of the triple-harmonic operation. Also the preliminary test results are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB177

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paper received ※ 18 May 2021 paper accepted ※ 25 June 2021 issue date ※ 18 August 2021

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WEPAB209

Review of Medical Accelerator Development at Sameer, India

linac, electron, photon, acceleration

3113

T.S. Dixit, N. Bansode, A.P. Bhagwat, S.T. Chavan, A.P. Deshpande, G. Gaikwad, S. Ghosh, R. Krishnan, C.S. Nainwad, G.D. Panchal, S.N. Pethe, K.A. Thakur, V.B. Ukey, M.M. Vidwans
SAMEER, Mumbai, India

Funding: Ministry of Electronics and Information Technology (MeitY), Government of India
At the Medical Electronics Division of SAMEER, R&D for the development of a 4 MeV energy electron linac for Cancer therapy was taken up in the late ’80s. An S-band standing wave side coupled structure operating at pi/2 mode was developed for electron acceleration. The linac was integrated with other subsystems in collaboration with CSIO and PGIMER and the first machine was commissioned at PGI, Chandigarh in 1990. Thereafter, a lot of modifications like energy, dose rate, iso-center height etc. were made in the system, and later 4 more machines were commissioned in hospitals for treatment. More than 1,50,000 patients have been treated using SAMEER’s 6 MeV oncology system. Subsequently, development of dual-mode and variable energy electron and photon output machines was undertaken. Two-photon energies of 6 and 15 MV and multiple electron energies starting from 6 to 18 MeV for treatment was offered from the linac. The electron energy variation was done using plunger mechanism in the side coupling cavity. This linac was successfully baked and RF tested for various parameters. This paper describes the experimental parameters achieved for both low and high energy dual-mode linac.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB209

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paper received ※ 14 May 2021 paper accepted ※ 07 July 2021 issue date ※ 01 September 2021

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WEPAB244

Optimization and Machine Learning Applied to the RF Manipulations of Proton Beams in the CERN PS

beam-loading, operation, extraction, simulation

3201

A. Lasheen, H. Damerau, S.C. Johnston
CERN, Meyrin, Switzerland

The 25 ns bunch spacing in the LHC is defined by a sequence of RF manipulations in the Proton Synchrotron (PS). Multiple RF systems covering a large range of revolution harmonics (7 to 21, 42, 84, 168) allow performing RF manipulations such as beam splitting, and non-adiabatic bunch shortening. For the nominal beam sent to LHC, each bunch is split in 12 in the PS. The relative amplitude and phase settings of the RF systems need to be precisely adjusted to minimize the bunch-by-bunch variations in intensity, longitudinal emittance, and bunch shape. However, due to transient beam-loading, the ideal settings, as well as the best achievable beam quality, vary with beam intensity. Slow drifts of the hardware may also affect beam quality. In this paper, automatized optimization routines based on particle simulations with intensity effects are presented, together with the first considerations of machine learning. The optimization routines are used to assess the best achievable longitudinal beam quality expected with the PS RF systems upgrades, in the framework of the LHC Injector Upgrade project.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB244

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paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 19 August 2021

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WEPAB254

Design of a 10 MeV Beamline at the Upgraded Injector Test Facility for e-Beam Irradiation

electron, radiation, solenoid, focusing

3232

X. Li, H. Baumgart, G. Ciovati
ODU, Norfolk, Virginia, USA
G. Ciovati, F.E. Hannon, S. Wang
JLab, Newport News, Virginia, USA

Funding: Jefferson lab LDRD.
Electron beam irradiation near 10 MeV is suitable for wastewater treatment. The Upgraded Injector Test Facility (UITF) at Jefferson Lab is a CW superconducting linear accelerator capable of providing an electron beam of energy up to 10 MeV and up to 100 µA current. This contribution presents the beam transport simulations for a beamline to be used for the irradiation of wastewater samples at the UITF. The simulations were done using the code General Particle Tracer with the goal of obtaining an 8 MeV electron beam of radius (3-σ) of ~2.4 cm. The achieved energy spread is ~74.5 keV. The space charge effects were investigated when the bunch charge is varied to be up to 1000 times and the results showed that they do not affect the beam quality significantly.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB254

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paper received ※ 20 May 2021 paper accepted ※ 25 June 2021 issue date ※ 18 August 2021

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WEPAB258

Beam Dynamics Design of a 162.5 MHz Superconducting RFQ Accelerator

rfq, emittance, accelerating-gradient, focusing

3248

Ying. Xia, H.P. Li, Y.R. Lu, Q.Y. Tan, Z. Wang
PKU, Beijing, People’s Republic of China
Y.R. Lu
IAP, Frankfurt am Main, Germany

Superconducting(SC) RFQ has lower power consumption, larger aperture and higher accelerating gradient than room temperature RFQ. We plan to design a 162.5MHz SC RFQ to accelerate the 30 mA proton beams from 35 keV to 2.5 MeV, which will be used as a neutron source for BNCT and neutron imaging project. At an inter-vane voltage of 180kV, the beam dynamics design was carried out with acceptable peak surface electric field, high transmission efficiency, and relatively short cavity length.

Poster WEPAB258 [1.251 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB258

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paper received ※ 17 May 2021 paper accepted ※ 06 July 2021 issue date ※ 13 August 2021

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WEPAB293

The Trip Event Logger for Online Fault Diagnosis at the European XFEL

controls, FEL, operation, EPICS

3344

J.H.K. Timm, J. Branlard, A. Eichler, H. Schlarb
DESY, Hamburg, Germany

The low-level RF (LLRF) system at the European XFEL, DESY, is of major importance for a high-performant and reliable operation. Faults here can jeopardize the overall operation. Therefore, the trip event logger is currently developped, - a fault diagnosis tool to detect errors online, inform the operators and trigger automatic supervisory actions. Further goals are to provide information for a fault tree and event tree analysis as well as a database of labeled faulty data sets for offline analysis. The tool is based on the C++ framework ChimeraTK Application Core. With this close interconnection to the control system it is possible not only to monitor but also to intervene as it is of great importance for supervisory tasks. The core of the tool consists of fault analysis modules ranging from simple ones (e.g., limit checking) to advanced ones (model-based, machine learning, etc.). Within this paper the architecture and the implementation of the trip event logger are presented.

Poster WEPAB293 [7.919 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB293

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paper received ※ 19 May 2021 paper accepted ※ 02 July 2021 issue date ※ 21 August 2021

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WEPAB295

Parameter Estimation of Short Pulse Normal-Conducting Standing Wave Cavities

gun, coupling, RF-structure, resonance

3351

S. Pfeiffer, J. Branlard, F. Burkart, M. Hoffmann, H. Schlarb
DESY, Hamburg, Germany

The linear accelerator ARES (Accelerator Research Experiment at SINBAD) is a new research facility at DESY. Electron bunches with a maximum repetition rate of 50 Hz are accelerated to a target energy of 155 MeV. The facility aims for ultra-stable sub-femtosecond arrival-times and high peak-currents at the experiment, placing high demands on the reference distribution and field regulation of the RF structure. In this contribution, we present the physical parameter estimation of key RF properties such as cavity detuning not directly measurable on the RF field decay. The method can be used as a fast monitor of inner cell temperature. The estimated properties are finally compared with the measured ones.

Poster WEPAB295 [0.860 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB295

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paper received ※ 19 May 2021 paper accepted ※ 05 July 2021 issue date ※ 10 August 2021

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WEPAB297

A Recent Upgrade on Phase Drift Compensation System for a Stable Beam Injection at J-PARC Linac

linac, DTL, injection, controls

3357

E. Cicek, Z. Fang, Y. Fukui, K. Futatsukawa
KEK, Ibaraki, Japan
T. Hirane, S. Shinozaki
JAEA/J-PARC, Tokai-mura, Japan
Y. Sato
Nippon Advanced Technology Co., Ltd., Tokai, Japan

J-PARC linac, consisting of 324 MHz and 972 MHz acceleration sections, delivers H⁻ beam to the rapid cycling synchrotron (RCS). The drift in the beam injection momentum from linac to RCS was measured to be highly dependent on the humidity at the klystron gallery. Also, changes in both temperature and humidity strongly affect the rf field phase controlled within the digital feedback (DFB) system. To cope with this, a unique phase drift compensation system, namely the phase drift monitor (PDM) system, is implemented in the MEBT2B1 station as the first step at the linac. However, the compensation of the drift correction could not be achieved directly since two different frequencies were used. The new PDM, which adapts the direct sampling method using the Radio Frequency System-on-Chip (RFSoC), will pave the way to ensure rf phase stability at all stations simultaneously. Here we present the effects of temperature and humidity on the rf field phase, along with performance and preliminary test results concerning the phase drift compensation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB297

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paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 30 August 2021

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WEPAB299

Spallation Neutron Source Proton Power Upgrade Low-Level RF Control System Development

controls, LLRF, operation, neutron

3363

M.T. Crofford, J.A. Ball, J.E. Breeding, M.P. Martinez, J.S. Moss, M. Musrock
ORNL, Oak Ridge, Tennessee, USA
L.R. Doolittle, C. Serrano, V.K. Vytla
LBNL, Berkeley, California, USA
J. Graham, C.K. Roberts, J.W. Sinclair, Z. Sorrell, S. Whaley
ORNL RAD, Oak Ridge, Tennessee, USA

Funding: * This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract number DE-AC05-00OR22725.
The Proton Power Upgrade (PPU) Project is approved for the Spallation Neutron Source at Oak Ridge National Laboratory and will double the proton beam power capability from 1.4 MW to 2.8 MW with 2 MW beam power available to the first target station. A second target station is planned and will utilize the remaining beam power in the future. The proton power increase will be supported with the addition of twenty-eight new superconducting cavities powered by 700 kW peak power klystrons to increase beam energy while increases to the beam current will be done with a combination of existing RF margin, and DTL HPRF upgrades. The original low-level RF control system has proven to be reliable over the past 15 years of operations, but obsolescence issues mandate a replacement system be developed for the PPU project. The replacement system is realized in a µTCA.4 platform using a combination of commercial off-the-shelf boards and custom hardware to support the requirements of PPU. This paper presents the prototype hardware, firmware, and software development activities along with preliminary testing results of the new system.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB299

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paper received ※ 18 May 2021 paper accepted ※ 21 June 2021 issue date ※ 12 August 2021

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WEPAB300

Python Based Tools for FRIB LLRF Operation and Management

controls, LLRF, EPICS, linac

3367

S.R. Kunjir, D.G. Morris, S. Zhao
FRIB, East Lansing, Michigan, USA

Funding: This work is supported by the US Department of Energy Office of Science under Cooperative Agreement DE-SC0000661, the State of Michigan and Michigan State University.
Some Python based tools have been developed at the Facility for Rare Isotope Beams (FRIB) for the ease of operation and management of the low level radio frequency (LLRF) controllers. Utilizing the rich features in Python, some tasks can be easily applied to a whole segment, one type of cryomodule (CM), a specific cryomodule or individual cavities grouped by a complex custom query. The tasks include, for example, 1) testing interface connections between various sub-systems prior to an operational run; 2) setting, checking and saving/restoring parameters during and after an operational run; 3) updating LLRF controller firmware and software during maintenance. With these tools, routine manual tasks are streamlined to achieve significantly greater efficiency in terms of scalability, time, memory and network resources. Considering channel access security, beam on/off status etc., the strategy of choosing either input/output controller (IOC) or Python for the implementation of certain tasks is also discussed in the paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB300

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paper received ※ 18 May 2021 paper accepted ※ 01 July 2021 issue date ※ 29 August 2021

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WEPAB301

Design of an X-Band LLRF System for TEX Test Facility at LNF-INFN

LLRF, klystron, insertion, GUI

3371

L. Piersanti, D. Alesini, M. Bellaveglia, S. Bini, B. Buonomo, F. Cardelli, C. Di Giulio, M. Diomede, A. Falone, G. Franzini, A. Gallo, A. Liedl, S. Pioli, S. Quaglia, L. Sabbatini, M. Scampati, G. Scarselletta, A. Stella
INFN/LNF, Frascati, Italy

Funding: Latino is a project co-funded by Regione Lazio within POR-FESR 2014-2020 program
In the framework of LATINO project (Laboratory in Advanced Technologies for INnOvation) funded by Lazio regional government, a TEst stand for X-band (TEX) is being commissioned at Frascati National Laboratories (LNF) of INFN. TEX is born as a collaboration with CERN, aimed at carrying out high power tests of X-band accelerating structure prototypes and waveguide components, and it is of paramount importance in view of the construction of EuPRAXIA@SPARC_LAB facility at LNF. In order to generate, manipulate and measure the RF pulses needed to feed the RF power unit (solid state ScandiNova K400 modulator, CPI 50 MW 50 Hz klystron) an X-band low level RF system has been developed, making use of a commercial S-band (2.856 GHz) Libera digital LLRF (manufactured by Instrumentation Technologies) with a newly designed up/down conversion stage and a reference generation/distribution system, which is able to produce coherent reference frequencies for the American S-band (2.856 GHz) and European X-band (11.994 GHz). In this paper the main features of such systems will be reviewed together with preliminary laboratory measurement results.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB301

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paper received ※ 19 May 2021 paper accepted ※ 12 July 2021 issue date ※ 16 August 2021

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WEPAB322

Status of Digital BPM Signal Processor for SHINE

FPGA, FEL, electron, electronics

3430

L.W. Lai, F.Z. Chen, Y.B. Leng, T. Wu, Y.M. Zhou
SSRF, Shanghai, People’s Republic of China
J. Wan
SINAP, Shanghai, People’s Republic of China

Funding: Youth Innovation Promotion Association, CAS (Grant No. 2019290); The National Key Research and Development Program of China (Grant No. 2016YFA0401903).
Digital signal processors that can handle 1MHz bunch rate BPM signal processing are under development for SHINE. Two different processors have been developed at the same time, including an intermediate frequency signal processor with a sampling rate higher than 500MHz, which can be used in general BPM applications; and a direct RF sampling processor, which can directly sample the C band cavity BPM signal without analog down-conversion modules and greatly simplifies the cavity BPM system. This paper will introduce the design, development status, and performance evaluations of the processors.

Poster WEPAB322 [1.919 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB322

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paper received ※ 20 May 2021 paper accepted ※ 10 June 2021 issue date ※ 24 August 2021

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WEPAB329

LCLS-II Average Current Monitor

vacuum, coupling, simulation, network

3443

P. Borchard, J.S. Hoh
Dymenso LLC, San Francisco, USA

The LCLS-II project at SLAC is a high power upgrade to the existing free-electron laser facility. The LCLS-II Accelerator System will include a new 4 GeV continuous-wave superconducting linear accelerator in the first kilometer of the SLAC linear accelerator tunnel and supplements the existing low power pulsed linac. Average Current Monitors (ACMs) are needed to protect against excessive beam power which might otherwise cause damage to the beam dumps. The ACM cavities are pillbox-shaped stainless steel RF cavity with two radial probe ports with couplers, one radial test port with a coupler, and a mechanism for mechanically fine-tuning the cavity resonant frequency. The ACM RF cavities will be located at points of known or constrained beam energy and will monitor the beam current, a safety system will trip off the beam if the beam power exceeds the allowed value.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB329

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paper received ※ 19 May 2021 paper accepted ※ 16 June 2021 issue date ※ 12 August 2021

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WEPAB358

Development of Low-Z Collimator for SuperKEKB

impedance, electron, positron, operation

3537

S. Terui, T. Abe, Y. Funakoshi, T. Ishibashi, H.N. Nakayama, K. Ohmi, D. Zhou
KEK, Ibaraki, Japan
A. Natochii
University of Hawaii, Honolulu,, USA

Collimator jaws for SuperKEKB main ring, which is an electron-positron collider, installed to suppress background noise in a particle detector complex named Belle II. The collimators are successful to reduce backgrounds when the collimator was closed. But, in high current operations with 500 mA or more, jaws were occasionally damaged by hitting abnormal beams. This trouble is a low-frequency, which is once-a-commissioning period currently, but a high-consequence one because we are not able to apply high voltage on detectors in Belle II by high backgrounds. Low-Z collimator jaw, that is durable through hitting uncontrollable beam, have been designed due to protect important component as the solution of the trouble. The low-Z collimator jaws are installable in a present collimator chamber, have a pair of vertically opposed movable jaws. One pair of low-Z collimator jaws was installed. The paper is to describe what did we calculate and measure to make a low-Z collimator, how did we make a low-Z collimator, the impact of the installed low-Z collimator, mainly transverse mode coupling instability.

Poster WEPAB358 [0.788 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB358

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paper received ※ 16 May 2021 paper accepted ※ 22 July 2021 issue date ※ 31 August 2021

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WEPAB381

Multipactor Simulations for MYRRHA Spoke Cavity: Comparison Between SPARK3D, MUSICC3D, CST PIC and Measurement

multipactoring, electron, simulation, niobium

3606

N. Hu, M. Chabot, J.-L. Coacolo, D. Longuevergne, G. Olry
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
M.B. Belhaj
ONERA, Toulouse, France

The multipactor effect can lead to thermal breakdown (quench), high field emission and limited accelerating gradient in superconducting accelerator devices. To determine the multipactor breakdown power level, multipactor simulations can be performed. The objective of this study is to compare the results given by different simulation codes with the results of vertical testing of SRF cavities. In this paper, Spark3D, MUSICC3D and CST Studio PIC solver have been used to simulate the multipactor effect in Spoke cavity developed within the framework of MYRRHA project. Then, a benchmark of these three simulation codes has been made. The breakdown power level, the multipactor order and the most prominent location of multipactor are presented. Finally, the simulation results are compared with the measurements done during the vertical tests.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB381

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paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 30 August 2021

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WEPAB394

Development of a New Interlock and Data Acquisition for the RF System at High Energy Photon Source

controls, EPICS, FPGA, PLC

3630

Z.W. Deng, J.P. Dai, H.Y. Lin, Q.Y. Wang, P. Zhang
IHEP, Beijing, People’s Republic of China

Funding: This work was supported by High Energy Photon Source, a major national science and technology infrastructure in China.
A new interlock and data acquisition (DAQ) system is being developed for the RF system at High Energy Photon Source (HEPS) to protect essential devices as well as to locate the fault. Various signals collected and pre-processed by the DAQ system and individual interlock signals from solid-state power amplifiers, low-level RFs, arc detectors, etc. are sent to the interlock system for logic decision to control the RF switch. Programmable logic controllers (PLC) are used to collect slow signals like temperature, water flowrate, etc., while fast acquisition for RF signals is realized by dedicated boards with down-conversion frontend and digital signal processing boards. In order to improve the response time, field programmable gate array (FPGA) has been used for interlock logic implementation with an embedded experimental physics and industrial control system (EPICS). Data storage is managed by using EPICS Archiver Appliance and an operator interface is developed by using Control System Studio (CSS) running on a standalone computer. This paper presents the design and the first test of the new interlock and DAQ for HEPS RF system.

Poster WEPAB394 [2.140 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB394

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paper received ※ 16 May 2021 paper accepted ※ 14 July 2021 issue date ※ 31 August 2021

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WEPAB402

Status and Progress of the High-Power RF System for High Energy Photon Source

booster, photon, GUI, storage-ring

3653

T.M. Huang, J. Li, H.Y. Lin, Y.L. Luo, Q. Ma, W.M. Pan, P. Zhang, F.C. Zhao
IHEP, Beijing, People’s Republic of China

Funding: Work was supported in part by High Energy Photon Source, a major national science and technology infrastructure in China, and in part by the National Natural Science Foundation of China(12075263).
High Energy Photon Source is a 6-GeV diffraction-limited synchrotron light source currently under construction in Beijing. Three types of high-power RF systems are used to drive the booster and the storage ring. For the booster ring, a total of 600-kW continuous-wave (CW) RF power is generated by six 500-MHz solid-state power amplifiers (SSA) and fed into six normal-conducting copper cavities. Concerning the storage ring, five CW 260-kW SSAs at 166 MHz and two CW 260-kW SSAs at 500-MHz are used to drive five fundamental and two third-harmonic superconducting cavities respectively. The RF power distributions are realized by 9-3/16" rigid coaxial line for the 166-MHz system and EIA standard WR1800 waveguide for the 500-MHz one. High-power circulators and loads are installed at the outputs of all SSAs to further protect the power transmitters from damages due to reflected power although each amplifier module is equipped with individual isolators. The overall system layout and the progress of the main components are presented in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB402

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paper received ※ 18 May 2021 paper accepted ※ 02 July 2021 issue date ※ 29 August 2021

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THPAB002

Lattice Design for BEPCII Upgrade

lattice, quadrupole, dynamic-aperture, electron

3756

H. Geng, W.B. Liu, J. Qiu, J. Xing, C.H. Yu, Y. Zhang
IHEP, Beijing, People’s Republic of China

The Beijing Electron Positron Collider II (BEPCII) has achieved a series of achievements in high-energy physics study. Along with the deepening of the research, more important physics is expected in higher energy regions (>2.1 GeV). As the upper limit of BEPCII design energy is 2.1GeV, an urgent upgrade is required for BEPCII. To achieve a higher luminosity at higher energy, the number of RF cavities is expected to be doubled. In this paper, the lattice design for the upgrade of BEPCII is studied. The dynamic aperture tracking result shows that the lattice could meet the injection requirement of the BEPCII beam with a reasonable margin.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB002

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paper received ※ 14 May 2021 paper accepted ※ 17 June 2021 issue date ※ 01 September 2021

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THPAB007

Technology Spinoff and Lessons Learned from the 4-Turn ERL CBETA

permanent-magnet, radiation, SRF, linac

3762

K.E. Deitrick, N. Banerjee, A.C. Bartnik, D.C. Burke, J.A. Crittenden, J. Dobbins, C.M. Gulliford, G.H. Hoffstaetter, Y. Li, W. Lou, P. Quigley, D. Sagan, K.W. Smolenski
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
J.S. Berg, S.J. Brooks, R.L. Hulsart, G.J. Mahler, F. Méot, R.J. Michnoff, S. Peggs, T. Roser, D. Trbojevic, N. Tsoupas
BNL, Upton, New York, USA
T. Miyajima
KEK, Ibaraki, Japan

The Cornell-BNL ERL Test Accelerator (CBETA) developed several energy-saving measures: multi-turn energy recovery, low-loss superconducting radiofrequency (SRF) cavities, and permanent magnets. With green technology becoming imperative for new high-power accelerators, the lessons learned will be important for projects like the FCC-ee or new light sources, where spinoffs and lessons learned from CBETA are already considered for modern designs.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB007

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paper received ※ 20 May 2021 paper accepted ※ 05 July 2021 issue date ※ 28 August 2021

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THPAB014

Matlab Simulations of the Helium Liquefier in the FREIA Laboratory

simulation, HOM, interface, coupling

3781

E. Waagaard, R.J.M.Y. Ruber, V.G. Ziemann
Uppsala University, Uppsala, Sweden

We describe simulations that track a state vector with pressure, temperature, and gas flow through the helium liquefier in the FREIA laboratory. Most components, including three-way heat exchangers, are represented by matrices that allow us to track the state through the system. The only non-linear element is the Joule-Thomson valve, which is represented by a non-linear map for the state variables. Realistic properties for the enthalpy and other thermodynamic quantities are taken into account with the help of the Coolprop library. The resulting system of equations is rapidly solved by iteration and shows good agreement with the observed LHe yield with and without nitrogen pre-cooling.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB014

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paper received ※ 13 May 2021 paper accepted ※ 14 July 2021 issue date ※ 21 August 2021

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THPAB015

Studies of the Imperfection in Crab Crossing Scheme for Electron-Ion Collider

electron, solenoid, luminosity, proton

3784

Y. Hao, J.S. Berg, D. Holmes, Y. Luo, C. Montag
BNL, Upton, New York, USA
V.S. Morozov
JLab, Newport News, Virginia, USA
J. Qiang
LBNL, Berkeley, California, USA
D. Xu
FRIB, East Lansing, Michigan, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
Crab crossing scheme is the essential scheme that accommodates large crossing angle without loss of luminosity in the design of Electron-Ion collider (EIC). The ideal optics and phase advances of the crab cavity pair are set to create a local crabbing bump in the interaction region (IR). However, there are always small errors in the actual lattice of IR. In this article, we will present the simulation and analytical studies on the imperfections in the crab crossing scheme in the EIC design. The tolerance of the imperfection and the possible remedies can be concluded from these studies.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB015

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paper received ※ 17 May 2021 paper accepted ※ 16 July 2021 issue date ※ 30 August 2021

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THPAB029

Dynamic Aperture Evaluation for the Hadron Storage Ring in the Electron-Ion Collider

dynamic-aperture, electron, proton, dipole

3812

Y. Luo, J.S. Berg, M. Blaskiewicz, W. Fischer, X. Gu, H. Lovelace III, C. Montag, R.B. Palmer, S. Peggs, V. Ptitsyn, F.J. Willeke, H. Witte
BNL, Upton, New York, USA
Y. Hao, D. Xu
FRIB, East Lansing, Michigan, USA
H. Huang
ODU, Norfolk, Virginia, USA
V.S. Morozov, E.A. Nissen, T. Satogata
JLab, Newport News, Virginia, USA
J. Qiang
LBNL, Berkeley, California, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The Electron-Ion Collider (EIC) is aiming at a design luminosity of 1e34 cm^-2s⁻¹. To maintain such a high luminosity, both beams in the EIC need an acceptable beam lifetime in the presence of the beam-beam interaction. For this purpose, we carried out weak-strong element-by-element particle tracking to evaluate the long-term dynamic aperture for the hadron ring lattice design. We improved our simulation code SimTrack to treat some new lattice design features, such as radially offset on-momentum orbits, coordinate transformations in the interaction region, etc. In this article, we will present the preliminary dynamic aperture calculation results with β^*- function scan, radial orbit shift, crossing angle collision, and magnetic field errors.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB029

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paper received ※ 17 May 2021 paper accepted ※ 31 August 2021 issue date ※ 01 September 2021

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THPAB067

Simulation of the APS-U Orbit Motion Due to RF Noise

simulation, synchrotron, resonance, photon

3911

V. Sajaev
ANL, Lemont, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
APS Upgrade storage ring will keep the same rf system that is presently used at APS. This rf system has amplitude and phase noise dominated by the lines at 60, 180, and 360 Hz. APS presently operates with synchrotron frequency close to 2 kHz, which is far away from the rf noise frequencies, and still the rf system noise contributes over 2 micrometers rms into the horizontal orbit noise due to beam energy variation. APS-U will operate with a bunch-lengthening cavity, which will lower the synchrotron frequency down to about 200 Hz. This could potentially lead to large orbit noise and other negative consequences due to energy variation caused by the rf system noise. In this paper, we will present simulations of the rf noise-induced orbit motion at APS and APS-U and define the rf amplitude and phase noise requirements that need to be achieved for APS-U operation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB067

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paper received ※ 12 May 2021 paper accepted ※ 13 July 2021 issue date ※ 22 August 2021

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THPAB069

Design Concepts for a High-Gradient C-Band Linac

FEL, electron, linac, accelerating-gradient

3919

T.B. Bolin, S.I. Sosa Guitron
UNM-ECE, Albuquerque, USA
S. Biedron
UNM-ME, Albuquerque, New Mexico, USA
J.R. Cary
Tech-X, Boulder, Colorado, USA
M. Dal Forno
SLAC, Menlo Park, California, USA

Funding: This work was performed under Contract No. 89233218CNA000001, supported by the U.S. DOE’s National Nuclear Security Administration, for the operation of Los Alamos National Laboratory (LANL).
During the last decade, the production of soft to hard x-rays (up to 25 keV) at XFEL facilities has enabled new developments in a broad range of disciplines. One caveat is that these instruments can require a large amount of real estate. For example, the XFEL driver is typically an electron beam linear accelerator (LINAC) and the need for higher electron beam energies capable of generating higher energy X-rays can require longer linacs; costs quickly become prohibitive, requiring state of art methods. One cost-saving measure is to produce a high accelerating gradient while reducing cavity size. Compact accelerating structures are also high-frequency. Here, we describe design concepts for a high-gradient, cryo-cooled LINAC for XFEL facilities in the C-band regime (~4-8 GHz). We are also exploring C-band for different applications including drivers for security applications. We investigate 2 different traveling wave (TW) geometries optimized for high-gradient operation as modeled with VSim software.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB069

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paper received ※ 20 May 2021 paper accepted ※ 02 July 2021 issue date ※ 13 August 2021

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THPAB081

High-Power Prototype Canon Coupler for APS-U Booster Cavities

booster, GUI, coupling, injection

3956

G.J. Waldschmidt, D.J. Bromberek, D. Horan, G. Trento, U. Wienands
ANL, Lemont, Illinois, USA
T. Harada, H. Oikawa, H. Takahashi
CETD, Tochigi, Japan

The Advanced Photon Source Upgrade (APS-U) plans to achieve a beam capture efficiency above 90% at 17 nC bunch charge into the Booster. Due to large beam loading at injection, the 352-MHz Booster cavities will be significantly detuned necessitating effective-power handling much greater than the 100kW effective power rating of the present coupler. Canon Electron Tubes & Devices Co., Ltd. (CETD) has designed and built a compact coupler for the APS-U Booster using a high-power ceramic disk window design in addition to accommodating significant space restrictions and additional diagnostics and cooling requirements. The coupler design was modified from an existing 500MHz, 800kW coupler that has been in routine operation at KEKB. The APS-U coupler has been installed and tested in the high-power 352-MHz test stand at the APS. The details of the design and testing of the prototype coupler will be reported in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB081

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paper received ※ 18 May 2021 paper accepted ※ 28 July 2021 issue date ※ 26 August 2021

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THPAB083

Measurement of the Longitudinal Phase-Space of the APS Photo-Injector Beam

linac, gun, dipole, lattice

3963

Y. Sun
ANL, Lemont, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
An S-band photo-cathode RF gun (PCG) exists at the front of the linac. The high-brightness photoinjector beam is accelerated by the linac and and can be used for accelerator technology and beam physics R&D experiments in the Linac Extension Area (LEA). For some applications, the beam needs to be compressed by a magnetic bunch compressor in the middle of the linac. An S-band transverse-mode cavity (Tcav) is available at the end of the linac for beam longitudinal phase-space diagnostics. Beam commissioning experience of the Tcav is reported in this paper. The cavity rf conditioning and calibration was performed. There is a horizontally bending dipole magnet downstream of the Tcav, which kicks beam in the vertical plane. Beam image on a YAG screen downstream of the Tcav and dipole magnet contains the single-shot information of the longitudinal phase-space of the photo-injector beam. The first measurements of the longitudinal phase-space of the compressed and non-compressed photoinjector beam are discussed. Improvements of the measurement resolution are planned.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB083

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paper received ※ 25 May 2021 paper accepted ※ 12 July 2021 issue date ※ 26 August 2021

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THPAB106

Optimization of a High Bunch Charge ERL Injection Merger for PERLE

emittance, linac, space-charge, booster

3983

B. Hounsell, M. Klein, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
S.A. Bogacz
JLab, Newport News, Virginia, USA
C. Bruni, B. Hounsell, W. Kaabi
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
B. Hounsell, B.L. Militsyn, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Delivery of high charge electron bunches into the main loop of an ERL (energy recovery linac) while preserving the emittance is challenging. This is because at the typical injection momentum, space charge forces still have a significant effect on the beam dynamics. In this work we consider the design of the merger for PERLE, an ERL test facility to be based at IJCLab in France. Previous simulations have shown that the baseline DC gun based injector can achieve the required emittance at the booster linac exit. The quality of the 500 pC bunches must then be preserved with space charge through the merger at total beam energy of 7 MeV keeping the emittance below 6 mm mrad. The beam dynamics in the merger were simulated using the code OPAL and optimised using a genetic algorithm. Three possible merger schemes were investigated. The goal of the optimisation was to minimise the emittance growth while also achieving the required Twiss parameters to match onto the spreader at the main linac exit. A three dipole solution is then examined in more detail.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB106

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paper received ※ 19 May 2021 paper accepted ※ 16 July 2021 issue date ※ 02 September 2021

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THPAB121

Plasma Muon Beam Cooling for HEP

plasma, focusing, simulation, emittance

3999

M.A. Cummings, R.J. Abrams, R.P. Johnson, S.A. Kahn, T.J. Roberts
Muons, Inc, Illinois, USA
V.S. Morozov, A.V. Sy
JLab, Newport News, Virginia, USA
K. Yonehara
Fermilab, Batavia, Illinois, USA

Ionization cooling has the potential to shrink the phase space of a muon beam by a factor of 10⁶ within the muons’ short lifetime (2.2 µs) because the collision frequency in a cooling medium is extremely high compared to conventional beam cooling methods. It has been realized that ionization cooling inherently produces a plasma of free electrons inside the absorber material, and this plasma can have an important effect on the muon beam. In particular, under the right circumstances, it can both improve the rate of cooling and reduce the equilibrium emittance of the beam. This has the potential to improve the performance of muon facilities based on muon cooling; in particular a future muon collider. We describe how this project will integrate Plasma muon beam cooling into both the basic Helical Cooling Channel (HCC) and extreme Parametric-resonance Ionization Cooling (PIC) techniques. This potentially whole new approach to muon cooling has exciting prospects for significantly reduced muon beam emittance.

Poster THPAB121 [1.214 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB121

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paper received ※ 19 May 2021 paper accepted ※ 12 July 2021 issue date ※ 26 August 2021

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THPAB138

FEbreak: A Comprehensive Diagnostic and Automated Conditioning Interface for Analysis of Breakdown and Dark Current Effects

controls, FPGA, real-time, software

4027

M.E. Schneider, S.V. Baryshev
Michigan State University, East Lansing, Michigan, USA
R.L. Fleming, D. Gorelov, J.W. Lewellen, E.I. Simakov
LANL, Los Alamos, New Mexico, USA
E. Jevarjian
MSU, East Lansing, Michigan, USA

Funding: DE-AC02-06CH11357, No. DE-SC0018362, DE-NA-0003525, DE-AC52-06NA25396, LA-UR-21-20613
As the next generation of accelerator technology pushes towards being able to achieve higher and higher gradients there is a need to develop high-frequency structures that can support these fields *. The conditioning process of the structures and waveguides to high gradient is a labor-intensive process, its length increases as the maximum gradient is increased. This results in the need to automate the conditioning process. This automation must allow for high accuracy calculations of the breakdown probabilities associated with the conditioning process which can be used to instruct the conditioning procedure without the need for human intervention. To automate the conditioning process at LANL’s high gradient C-band accelerator test stand we developed FEbreak that is a breakout probability and conditioning automation software that is a part of the FEmaster series **, ***, ****. FEbreak directly interfaces with the rest of FEmaster to automate the data collection and data processing to not only analyze the breakdown probability but also the dark current effects associated with these high gradient structures.
* E. I. Simakov Nuc. Inst. and Meth, in Phy. Research Section A: Acc. Spec, 907 221 (2019)
** E. Jevarjian arXiv:2009.13046
*** T. Y. Posos arXiv:2012.03578
**** M. Schneider arXiv:2012.10804

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB138

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paper received ※ 18 May 2021 paper accepted ※ 02 July 2021 issue date ※ 23 August 2021

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THPAB145

Cold Test of a Novel S-Band 1.6 Cell Photocathode RF Gun

gun, coupling, cathode, simulation

4045

Zh.X. Tang, S.X. Dong, Y.J. Pei, B.F. Wei
USTC/NSRL, Hefei, Anhui, People’s Republic of China

Funding: Work supported by National Natural Science Foundation of China(Grant No. 11805199 and U1832135) and Fundamental Research Funds for the Central Universities (Grant No. WK2310000072)
The photocathode RF gun is one of the most critical components for high quality electron beam sources. The asymmetric multi-pole field contributes to the transverse emittance growth and degrades the beam quality. In order to overcome the problem, we propose a novel rotationally symmetric 1.6 cell RF gun to construct the symmetric field in this paper. The concrete proposal is that a coaxial cell cavity with a symmetrical distribution of four grooves is concatenated to the photocathode end of the traditional 0.6 cell cavity to form the novel 0.6 cell cavity. Through the detailed design study, the profile of the RF gun is optimized to improve the shunt impedance and mode separation and make the surface peak electric field at the photocathode end. Considering the filling time, a coupling slot is designed to couple input power into the RF gun. The RF cavity is machined by numerical control machine tool, and the tuning and low power RF measurement are carried out. The experimental results are consistent with the simulation results.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB145

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paper received ※ 09 May 2021 paper accepted ※ 30 August 2021 issue date ※ 02 September 2021

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THPAB146

Preliminary Study of Femtosecond Electron Source Based on THz Acceleration and Field Emission

electron, FEM, cathode, gun

4048

Zh.X. Tang, G. Feng, B.F. Wei
USTC/NSRL, Hefei, Anhui, People’s Republic of China

Funding: Work supported by National Natural Science Foundation of China (Grant No. U1832135 and 11805199) and Fundamental Research Funds for the Central Universities (Grant No. WK2310000072)
In this paper, we propose a novel electron gun based on THz acceleration and field emission to generate femtosecond electron bunches. The field emission cathode is placed in the center of the cavity, and the standing wave field is established in the cavity to achieve the field emission conditions and extract the electron beam. Because the period of THz band is about picosecond, the femtosecond bunch is formed by controlling the field strength and the pulse width of the extracted beam. We analyzed the feasibility of field emission and the length of the pulse beam. The surface peak field intensity of the structure of the cavity with different emitters are simulated by CST software.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB146

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paper received ※ 09 May 2021 paper accepted ※ 18 August 2021 issue date ※ 02 September 2021

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THPAB147

Preliminary Study of 500 MHz HOM-Free RF Cavity

HOM, coupling, GUI, damping

4050

Zh.X. Tang
USTC/NSRL, Hefei, Anhui, People’s Republic of China

Funding: Work supported by National Natural Science Foundation of China(Grant No. U1832135 and 11805199)}
In this paper, we study the microwave characteristics of 500 MHz RF cavity, including the optimization of cavity structure, the simulation design of high-order mode (HOM) absorption structure and the design of coupler. The cavity structure is simulated by CST. The absorption waveguide is designed and optimized. The coupler is designed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB147

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paper received ※ 09 May 2021 paper accepted ※ 16 July 2021 issue date ※ 23 August 2021

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THPAB153

Design, Construction and Tests of the Cooling System with a Cryocooler for Cavity Testing

cryogenics, SRF, vacuum, simulation

4056

P. Pizzol, J.W. Lewellen, E.R. Olivas, E.I. Simakov, T. Tajima
LANL, Los Alamos, New Mexico, USA

Cryogenically cooled normal-conducting cavities have shown higher gradients than those operated at room temperature. We are constructing a compact cooling system with a cryocooler to test C-band normal-conducting cavities and 1.3 GHz superconducting cavities. This paper describes the design, construction, and cooling test results as well as some low-power cavity Q measurement results.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB153

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paper received ※ 17 May 2021 paper accepted ※ 21 June 2021 issue date ※ 12 August 2021

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THPAB156

Built-in Thermionic Electron Source for an SRF Linacs

cathode, electron, gun, SRF

4062

I.V. Gonin, S. Kazakov, R.D. Kephart, T.N. Khabiboulline, T.H. Nicol, N. Solyak, J.C.T. Thangaraj, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

The design of a thermionic electron source connected directly to a superconducting cavity, the key part of an SRF gun, is described. The results of beam dynamics optimization are presented which allow lack of beam current intercepting in the superconducting cavity. The electron source concept is presented including the cathode-grid assembly, thermal insulation of the cathode from the cavity, and the gun resonator design. The cavity thermal load caused by the gun is analyzed including the static heat load, black body radiation, backward electron heating, etc.

Poster THPAB156 [0.670 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB156

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paper received ※ 19 May 2021 paper accepted ※ 12 July 2021 issue date ※ 28 August 2021

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THPAB167

Technical Design of an RFQ Injector for the IsoDAR Cyclotron

rfq, cyclotron, simulation, coupling

4075

H. Höltermann, D. Koser, B. Koubek, H. Podlech, U. Ratzinger, M. Schuett, M. Syha
BEVATECH, Frankfurt, Germany
J.M. Conrad, J. Smolsky, L.H. Waites, D. Winklehner
MIT, Cambridge, Massachusetts, USA

For the IsoDAR (Isotope Decay-At-Rest) experiment, a high intensity (10 mA CW) primary proton beam is needed. To generate this beam, H²⁺ is accelerated in a cyclotron and stripped into protons after extraction. An RFQ, partially embedded in the cyclotron yoke, will be used to bunch and axially inject H²⁺ ions into the main accelerator. The strong RFQ bunching capabilities will be used to optimize the overall injection efficiency. To keep the setup compact the distance between the ion source and RFQ can be kept very short as well. In this paper, we describe the technical design of the RFQ. We focus on two critical aspects: 1. The use of a split-coaxial structure, necessitated by the low frequency of 32.8 MHz (matching the cyclotron RF) and the desired small tank diameter; 2. The high current, CW operation, requiring a good cooling concept for the RFQ tank and vanes.

Poster THPAB167 [2.162 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB167

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paper received ※ 14 May 2021 paper accepted ※ 27 July 2021 issue date ※ 22 August 2021

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THPAB170

RF Deflector Design for Rapid Proton Therapy

proton, simulation, polarization, quadrupole

4086

E.J.C. Snively, G.B. Bowden, V.A. Dolgashev, Z. Li, E.A. Nanni, D.T. Palmer, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: This work is supported by US Department of Energy Contract No. DE-AC02-76SF00515.
Pencil beam scanning of charged particle beams is a key technology enabling high dose rate cancer therapy. The potential benefits of high-speed dose delivery include not only a reduction in total treatment time and improvements to motion management during treatment but also the possibility of enhanced healthy tissue sparing through the FLASH effect, a promising new treatment modality. We present here the design of an RF deflector operating at 2.856 GHz for the rapid steering of 150 MeV proton beams. The design utilizes a TE11-like mode supported by two posts protruding into a pillbox geometry to form an RF dipole. This configuration provides a significant enhancement to the efficiency of the structure, characterized by a transverse shunt impedance of 68 MOhm/m, as compared to a conventional TM11 deflector. We discuss simulations of the structure performance for several operating configurations including the addition of a permanent magnet quadrupole to amplify the RF-driven deflection. In addition to simulation studies, we will present preliminary results from a 3-cell prototype fabricated using four copper slabs to accommodate the non-axially symmetric cell geometry.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB170

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paper received ※ 19 May 2021 paper accepted ※ 14 July 2021 issue date ※ 28 August 2021

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THPAB173

Fundamental Study on Electromagnetic Characteristics of Half-Wave Resonator for 200 MeV Energy Upgrade of KOMAC Proton Linac

simulation, linac, proton, SRF

4098

J.J. Dang, Y.-S. Cho, H.S. Kim, H.-J. Kwon, S. Lee
Korea Atomic Energy Research Institute (KAERI), Gyeongbuk, Republic of Korea

Funding: This work has been supported through KOMAC operation fund of KAERI by the Korea government (MSIT).
A superconducting linac has been developed at KOrea Multi-purpose Accelerator Complex (KOMAC). A goal of the SRF linac is to increase proton beam energy from 100 MeV to 200 MeV. 350 MHz medium beta half-wave resonator (HWR) should provide 3.6 MV accelerating voltage to achieve the energy upgrade. An electromagnetic (EM) analysis on the parametrically designed HWR cavity was conducted. The cavity design was optimized to reduce a peak electric field and a peak magnetic field while satisfying the required acerating voltage. In addition, a mechanical-EM coupled simulation was conducted to estimate a helium pressure sensitivity. Also, Lorentz force detuning was simulated. The design is being optimized to minimize the frequency detuning due to the helium pressure and Lorentz force.

Poster THPAB173 [0.800 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB173

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 22 August 2021

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THPAB183

New Longitudinal Beam Production Methods in the CERN Proton Synchrotron Booster

space-charge, emittance, proton, resonance

4130

S.C.P. Albright, F. Antoniou, F. Asvesta, H. Bartosik, C. Bracco, E. Renner
CERN, Meyrin, Switzerland
E. Renner
TU Vienna, Wien, Austria

As part of the LHC Injectors Upgrade (LIU) project, significant improvements were made to the CERN Proton Synchrotron Booster (PSB) during the 2019/2020 long shutdown, including a new Finemet-based wideband RF system, renovated longitudinal beam control, and a new magnetic cycle. To meet the requirements of the diverse experimental program, the PSB provides beams with intensities spanning three orders of magnitude and a large range of longitudinal emittances. To maximize the brightness, in particular for the LHC beams, the voltages at low energy are designed to reduce the impact of transverse space charge using a second RF harmonic in bunch lengthening mode. At high energies, the risk of longitudinal microwave instability is avoided by optimizing the longitudinal distribution to raise the instability threshold. RF phase noise is applied to provide controlled longitudinal emittance blow-up and to shape the longitudinal distribution. This paper discusses the design of the RF functions used to meet the beam specifications, whilst ensuring longitudinal stability.

Poster THPAB183 [6.692 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB183

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paper received ※ 18 May 2021 paper accepted ※ 22 July 2021 issue date ※ 01 September 2021

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THPAB187

Determination of Required Tolerances and Stop Band Width for Cells Manufacturing and Tuning in Compensated High Energy Accelerating Structures

coupling, linac, hadron, factory

4139

I.V. Rybakov, V.V. Paramonov
RAS/INR, Moscow, Russia

The required value of the spread for accelerating field distribution comes from the beam dynamics conditions and for cavities in high energy hadron linacs is ~1%. The standard deviation of the accelerating field distribution depends on the spread in frequencies of accelerating and coupling cells, stop bandwidth and deviations in coupling coefficients. The deviations in frequencies for accelerating, coupling cells, coupling coefficients, are directly related to tolerances manufacturing tolerances for cells. The stop bandwidth should be adjusted with cell tuning. Relations between the standard deviation of field distribution and deviations in cells parameters* are known. Together with the relation between deviations in cells dimensions and cells parameters** recommendations for cells manufacturing tolerances could be obtained. In relation to the coupling coefficient of compensated accelerating structures (ACS, SCS, CDS, DAW) for high-energy parts of linacs some recommendations for the determination of optimal manufacturing tolerances and acceptable stopband are presented.
* V.F. Vikulov and V.E. Kalyuzhny // Tech. Phys., v. 50, 1980, pp. 773-779
** I.V. Rybakov, V.V. Paramonov, A.K. Skassyrskaya // Proc. RuPAC 2016, pp. 291-293

Poster THPAB187 [0.649 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB187

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paper received ※ 18 May 2021 paper accepted ※ 25 June 2021 issue date ※ 11 August 2021

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THPAB200

Cavity Control Modelling for SPS-to-LHC Beam Transfer Studies

controls, beam-loading, simulation, injection

4168

L.E. Medina Medrano, T. Argyropoulos, P. Baudrenghien, H. Timko
CERN, Geneva, Switzerland

Funding: Research supported by the HL-LHC project.
To accurately simulate injection losses in the LHC and the High-Luminosity LHC era, a realistic beam distribution model at SPS extraction is needed. To achieve this, the beam-loading compensation by the SPS cavity controller has to be included, as it modulates the bunch positions with respect to the rf buckets. This dynamic cavity control model also allows generating a more realistic beam halo, from which the LHC injection losses will mainly originate. In this paper, the implementation of the present SPS cavity controller in CERN’s Beam Longitudinal Dynamics particle tracking code is described. Just like in the machine, the feedback and feedforward controls are included in the simulation model, as well as the generator-beam-cavity interaction. Benchmarking against measurements of the generated beam distributions at SPS extraction are presented.

Poster THPAB200 [4.164 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB200

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paper received ※ 18 May 2021 paper accepted ※ 27 July 2021 issue date ※ 15 August 2021

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THPAB219

Beam Dynamics in Coherent Electron Cooling Accelerator

electron, simulation, linac, emittance

4216

Y.C. Jing, V. Litvinenko, I. Petrushina, I. Pinayev, K. Shih, Y.H. Wu
BNL, Upton, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA
I. Petrushina, Y.H. Wu
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.
Coherent electron Cooling (CeC) has the potential to substantially reduce the cooling time of the high-energy hadrons and hence to boost luminosity in high-intensity hadron-hadron and electron-hadron colliders. Recent development in CeC cooling theory requires the accelerator to deliver high-quality electron bunches with low beam noise. In this paper, we present our design of the CeC accelerator to achieve the electron beam requirements and compare our findings with the experimental observations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB219

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paper received ※ 27 May 2021 paper accepted ※ 27 July 2021 issue date ※ 20 August 2021

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THPAB220

Multibunch Studies for LCLS-II High Energy Upgrade

dipole, linac, emittance, HOM

4219

R.J. England, K.L.F. Bane, Z. Li, T.O. Raubenheimer, M.D. Woodley
SLAC, Menlo Park, California, USA
M. Borland
ANL, Lemont, Illinois, USA
A. Lunin
Fermilab, Batavia, Illinois, USA

Funding: The work is supported in part by DOE Contract No. DE-AC02-76SF00515.
The Linac Coherent Light Source (LCLS) X-ray free-electron laser at SLAC is being upgraded to LCLS-II with a superconducting linac and 1 MHz bunch repetition rate. The proposed high-energy upgrade (LCLS-II-HE) will increase the beam energy from 4 to 8 GeV, extending the reach of accessible X-ray photon energies. With the increased repetition rate and longer linac of LCLS-II-HE, multi-bunch effects are of greater concern. We use recently introduced capabilities in the beam transport code ELEGANT to study dipole and monopole beam breakup effects for LCLS-II HE beam parameters. The results indicate that resonant dipole kicks have steady-state settle times on the order of 500 bunches or less and appear manageable. We also consider a statistical variation of the cavity frequencies and transverse offsets of cavities and quadrupoles. Resonant emittance growth driven by monopole kicks is found to be disrupted by frequency variation between cavities.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB220

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paper received ※ 19 May 2021 paper accepted ※ 15 July 2021 issue date ※ 16 August 2021

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THPAB221

Multi-Objective Optimization with ACE3P and IMPACT

cathode, simulation, lattice, interface

4223

D.A. Bizzozero, J. Qiang
LBNL, Berkeley, California, USA
L. Ge, Z. Li, C.-K. Ng, L. Xiao
SLAC, Menlo Park, California, USA

Funding: This work is supported by the Director of the Office of Science of the US Department of Energy under contracts DE-AC02-05-CH11231 and DE-AC02-76-SF00515.
Photo injector design is an important consideration in the construction of next-generation accelerators. In current injector optimization, components (e.g. RF cavities) are individually shape-optimized for performance subject to requirements such as peak surface field, shunt impedance, and resonant frequency. Once these component shapes are determined, beam dynamics simulations optimize the injector lattice by adjusting parameters such as the amplitude and phase of the driving fields. However, this form of beam dynamics optimization is restricted by the fixed geometry and field profile of the components. To optimize accelerator design more generally, a coupled optimization of the cavity shape and beam parameters is required. For this coupled optimization problem, we have created an integrated ACE3P-IMPACT workflow. Within this workflow, component geometries are adjusted, field modes are computed with Omega3P (a module in the ACE3P suite), and beam dynamics are simulated with IMPACT-T. This workflow is encapsulated into a multi-objective optimization algorithm using the DEAP* and libEnsemble** Python libraries to yield a Pareto-optimal set of solutions for a simple injector model.
* F.-A. Fortin et al, DEAP: Evolutionary Algorithms Made Easy, J Mach Learn Res, 13, 2171-2175, July 2012
** S. Hudson et al, libEnsemble User Manual, Argonne National Laboratory, Rev 0.7.1, 2020

Poster THPAB221 [1.842 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB221

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paper received ※ 19 May 2021 paper accepted ※ 02 August 2021 issue date ※ 26 August 2021

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THPAB244

Design of Interdigital H-Mode Re-Buncher at KoBRA Beamline

bunching, heavy-ion, impedance, simulation

4285

Y. Lee, E.-S. Kim
KUS, Sejong, Republic of Korea

KOrea Broad acceptance Recoil spectrometer & Apparatus (KOBRA) is an experimental facility for low energy nuclear physics in the heavy ion accelerator complex RAON. Two re-buncher systems at KOBRA beamline are required to longitudinally focus the 40Ar⁹⁺ with 27MeV/u. The normal conducting IH resonator with seven-gap as the re-buncher structure was chosen because of the reduction in the risk of particulate contamination and total power consumption. In this paper, the detailed design results of the 162.5 MHz IH re-buncher cavity will be presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB244

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paper received ※ 19 May 2021 paper accepted ※ 27 July 2021 issue date ※ 13 August 2021

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THPAB268

Hierarchical Intelligent Real-Time Optimal Control for LLRF Using Time Series Machine Learning Methods and Transfer Learning

controls, LLRF, network, simulation

4329

R. Pirayesh, S. Biedron
UNM-ME, Albuquerque, New Mexico, USA
S. Biedron, J.A. Diaz Cruz, M. Martínez-Ramón
UNM-ECE, Albuquerque, USA
J.A. Diaz Cruz
SLAC, Menlo Park, California, USA

Funding: supported by DOE, Office of Science, Office of High Energy Physics, under award number DE-SC0019468, Contract No. DE-AC02-76SF00515, also supported Office of Basic Energy Sciences. ALCF, Element Aero
Machine learning (ML) has recently been applied to Low-level RF (LLRF) control systems to keep the voltage and phase of Superconducting Radiofrequency (SRF) cavities stable within 0.01 degree in phase and 0.01% amplitude as constraints. Model predictive control (MPC) uses an optimization algorithm offline to minimize a cost function with constraints on the states and control input. The surrogate model optimally controls the cavities online. Time series deep ML structures including recurrent neural network (RNN) and long short-term memory (LSTM) can model the control input of MPC and dynamics of LLRF as a surrogate model. When the predicted states diverge from the measured states more than a threshold at each time step, the states’ measurements from the cavity fine-tune the surrogate model with transfer learning. MPC does the optimization offline again with the updated surrogate model, and, next, transfer learning fine-tunes the surrogate model with the new data from the optimal control inputs. The surrogate model provides us with a computationally faster and accurate modeling of MPC and LLRF, which in turn results in a more stable control system.
Machine learning, Surrogate model, control, LLRF, MPC, Transfer learning

Poster THPAB268 [0.377 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB268

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paper received ※ 16 May 2021 paper accepted ※ 13 July 2021 issue date ※ 28 August 2021

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THPAB271

JLAB LLRF 3.0 Development and Tests

LLRF, controls, FPGA, cryomodule

4340

T.E. Plawski, R. Bachimanchi, S. Higgins, C. Hovater, J. Latshaw, C.I. Mounts, D.J. Seidman, J. Yan
JLab, Newport News, Virginia, USA

The Jefferson Lab LLRF 3.0 system is being developed to replace legacy LLRF systems in the CEBAF accelerator. The new design builds upon 25 years of design and operational RF control experience, and our recent collaboration in the design of the LCLSII LLRF system. The new cavity control algorithm is a fully functional phase and amplitude locked Self Exciting Loop (SEL). This paper discusses the progress of the LLRF 3.0 hardware design, FPGA firmware development, User Datagram Protocol (UDP) operation, and recent LLRF 3.0 system tests on the CEBAF Booster cryomodule in the Upgrade Injector Test Facility (UITF).

Poster THPAB271 [1.940 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB271

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paper received ※ 14 May 2021 paper accepted ※ 06 July 2021 issue date ※ 11 August 2021

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THPAB272

Validation of Two Re-Buncher Cavities under High Beam Loading for LIPAc

LLRF, beam-loading, operation, MEBT

4343

D. Gavela, I. Podadera, F. Toral
CIEMAT, Madrid, Spain
I. Moya
Fusion for Energy, Garching, Germany
F. Scantamburlo
IFMIF/EVEDA, Rokkasho, Japan

Funding: Work partially supported by the Spanish Ministry of Science and Innovation under project AIC-A-2011-0654 and FIS2013-40860-R
Two re-buncher cavities were installed at the Medium Energy Beam Transport line of the LIPAc accelerator, presently being commissioned at Rokkasho (Japan). They are IH-type cavities with five gaps providing an effective voltage of 350 kV at 175 MHz for a nominal operation of 125 mA CW deuterons at 5 MeV. After full conditioning and beamline integration in Europe, the cavities were installed in the accelerator with special care given to the alignment with respect to the rest of the components. The RF line, cooling circuits, and instrumentation were also mounted. The cavities were operated with an FPGA-based LLRF system. A re-conditioning of the cavities was performed in the first place, followed by tests with a pulsed beam with increasing currents. A maximum pulsed beam current of 100 mA was reached while operating the buncher cavities, under which they reached voltages up to 340 kV and 260 kV respectively. As expected, the beam loading was significant, leading to a series of difficulties and required strategies for a good operation that are discussed in this paper. The effect on the beam dynamics, measured by beam position monitors downstream of the bunchers is also discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB272

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paper received ※ 19 May 2021 paper accepted ※ 02 September 2021 issue date ※ 02 September 2021

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THPAB287

Providing Computing Power for High Level Controllers in MicroTCA-based LLRF Systems via PCI Express Extension

controls, LLRF, software, Ethernet

4363

P. Nonn, A. Eichler, S. Pfeiffer, H. Schlarb, J.H.K. Timm
DESY, Hamburg, Germany

It is possible to connect the PCIe bus of a high performance computer to a MicroTCA crate. This allows the software on the computer to communicate with the modules in the crate, as if they were peripherals of the computer. This article will discuss the use of this feature in respect to accelerator control with a focus on High Level Controllers.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB287

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paper received ※ 19 May 2021 paper accepted ※ 26 July 2021 issue date ※ 26 August 2021

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THPAB296

The Spallation Neutron Source Normal Conducting Linac RF System Design for the Proton Power Upgrade Project

DTL, GUI, klystron, linac

4383

J.S. Moss, M.T. Crofford, S.W. Lee, G.D. Toby
ORNL, Oak Ridge, Tennessee, USA
M.E. Middendorf
ORNL RAD, Oak Ridge, Tennessee, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract number DE-AC05-00OR22725.
The Proton Power Upgrade (PPU) project at the Spallation Neutron Source will double the available proton beam power from 1.4 to 2.8 MW by increasing the beam energy from 1.0 to 1.3 GeV and the beam current from 26 to 38 mA. The increase in beam current resulted in the need to redesign the existing normal conducting linac (NCL) RF Systems. High-power testing of the existing NCL RF Systems configured to accelerate PPU-level beam provided the data used to make the final design decisions. This paper describes the development and execution of those in-situ tests and the subsequent results.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB296

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paper received ※ 17 May 2021 paper accepted ※ 22 July 2021 issue date ※ 18 August 2021

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THPAB317

Experiment and Simulation Study on the Capture and Acceleration Process of XiPAF Synchrotron

acceleration, synchrotron, experiment, proton

4409

Y. Li, X. Guan, X.Y. Liu, M.W. Wang, X.W. Wang, Q.Z. Xing, Y. Yang, H.J. Yao, W.B. Ye, S.X. Zheng
TUB, Beijing, People’s Republic of China
W.L. Liu, D. Wang, Z.M. Wang, Y. Yang, M.T. Zhao
NINT, Shannxi, People’s Republic of China

The beam commissioning of the capture and acceleration process on the XiPAF (Xi’an 200MeV Proton Application Facility) synchrotron has been carried out. The efficiency of the experiment results has been compared with the simulation results. At present, the efficiency of the capture process with single-harmonic is about 73%, and the acceleration efficiency is about 82%, and the simulation results are 77% and 96% without space charge effect, respectively. In order to improve efficiency, dual-harmonic was used during the capture and acceleration process. During the experiment, the capture efficiency was increased by 5%, and the acceleration efficiency was increased by 4%. The capture efficiency decreases with the increase of the maximum RF voltages. We analyzed the reasons for the decrease in capture efficiency. In the next step, further verification will be carried out through experiments under different conditions.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB317

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paper received ※ 19 May 2021 paper accepted ※ 08 July 2021 issue date ※ 19 August 2021

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THPAB320

ALD-Based NbTiN Studies for SIS R&D

site, plasma, SRF, niobium

4420

I. González Díaz-Palacio, R.H. Blick, R. Zierold
University of Hamburg, Hamburg, Germany
W. Hillert, M. Wenskat
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Superconductor-Insulator-Superconductor multilayers improve the performance of SRF cavities providing magnetic screening of the bulk cavity and lower surface resistance. In this framework NbTiN mixtures stand as a potential material of interest. Atomic layer deposition (ALD) allows for uniform coating of complex geometries and enables tuning of the stoichiometry and precise thickness control in sub-nm range. In this talk, we report about NbTiN thin films deposited by plasma-enhanced ALD on insulating AlN buffer layer. The deposition process has been optimized by studying the superconducting electrical properties of the films. Post-deposition thermal annealing studies with varying temperatures, annealing times, and gas atmospheres have been performed to further improve the thin film quality and the superconducting properties. Our experimental studies show an increase in Tc by 87.5% after thermal annealing and a maximum Tc of 13.9 K has been achieved for NbTiN of 23 nm thickness. Future steps include lattice characterization, using XRR/XRD/EBSD/PALS, and SRF measurements to obtain Hc1 and the superconducting gap.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB320

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paper received ※ 24 May 2021 paper accepted ※ 23 July 2021 issue date ※ 26 August 2021

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THPAB322

Transient Beam Loading in the CBETA Multi-Turn ERL

linac, beam-loading, operation, SRF

4422

N. Banerjee
Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA
G.H. Hoffstaetter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: This work was supported by NSF Grant No. DMR0807731, DOE Award No. DE-SC0012704, and NYSERDA Agreement No. 102192.
The Cornell-BNL ERL Test Accelerator (CBETA) is the first superconducting multi-turn ERL that has been commissioned at Cornell University in a low current mode. In this paper, we first discuss a new model of beam loading which is valid for the low injection energies used in CBETA. Using this model, we explore the effect of bunch patterns, beam turn-on, and turn-off transients on the fundamental mode of the 7-cell SRF cavities used in the main linac. In particular, we examine the operational constraints on the rf system at the design current of 40 mA.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB322

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paper received ※ 20 May 2021 paper accepted ※ 29 July 2021 issue date ※ 26 August 2021

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THPAB336

Novel Magnetron Operation and Control Methods for Superconducting RF Accelerators

controls, injection, operation, SRF

4442

G.M. Kazakevich, R.P. Johnson
Muons, Inc, Illinois, USA
T.N. Khabiboulline, G.V. Romanov, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

High power magnetrons designed and optimized for industrial heating, being injection-locked, have been suggested to power superconducting RF cavities for accelerators due to lower cost and higher efficiency. However, standard operation methods do not provide high efficiency with wideband control suppressing microphonics. We have developed and experimentally verified novel methods of operating and controlling the magnetron that provide stable RF generation with higher efficiency and lower noise than other RF sources. By our method the magnetrons operate with the anode voltage notably lower than the self-excitation threshold improving its performance. This is also a promising way to increase tube reliability and longevity. A magnetron operating with the anode voltage lower than the self-excitation threshold, in so-called stimulated coherent generation mode has special advantage for pulse operation with a gated injection-locking signal. This eliminates the need for expensive pulsed HV modulators and additionally increases the magnetron RF source efficiency due to absence of losses in HV modulators.

Poster THPAB336 [0.960 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB336

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paper received ※ 15 May 2021 paper accepted ※ 08 July 2021 issue date ※ 18 August 2021

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THPAB337

Resonance Control System for the PIP-II IT HWR Cryomodule

controls, feedback, cryomodule, resonance

4446

P. Varghese, B.E. Chase, P.M. Hanlet, H. Maniar, D.J. Nicklaus, S. Sankar Raman
Fermilab, Batavia, Illinois, USA
L.R. Doolittle, S. Paiagua, C. Serrano
LBNL, Berkeley, California, USA

The HWR (half-wave-resonator) cryomodule is the first one in the superconducting section of the PIP-II LINAC project at Fermilab. PIP-II IT is a test facility for the project where the injector, warm front-end, and the first two superconducting cryomodules are being tested. The HWR cryomodule comprises 8 cavities operating at a frequency of 162.5 MHz and accelerating beam up to 10 MeV. Resonance control of the cavities is performed with a pneumatically operated slow tuner which compresses the cavity at the beam ports. Helium gas pressure in a bellows mounted to an end wall of the cavity is controlled by two solenoid valves, one on the pressure side and one on the vacuum side. The resonant frequency of the cavity can be controlled in one of two modes. A pressure feedback control loop can hold the cavity tuner pressure at a fixed value for the desired resonant frequency. Alternately, the feedback loop can regulate the cavity tuner pressure to bring the RF detuning error to zero. The resonance controller is integrated into the LLRF control system for the cryomodule. The control system design and performance of the resonance control system are described in this paper.

Poster THPAB337 [4.426 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB337

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paper received ※ 12 May 2021 paper accepted ※ 26 July 2021 issue date ※ 15 August 2021

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THPAB338

Performance of the LLRF System for the Fermilab PIP-II Injector Test

controls, LLRF, resonance, cryomodule

4450

P. Varghese, B.E. Chase, P.M. Hanlet, H. Maniar, D.J. Nicklaus
Fermilab, Batavia, Illinois, USA
L.R. Doolittle, C. Serrano
LBNL, Berkeley, California, USA

PIP-II IT is a test facility for the PIP-II project where the injector, warm front-end, and the first two superconducting cryomodules are being tested. The 8-cavity half-wave-resonator (HWR) cryomodule operating at 162.5 MHz is followed by the 8-cavity single-spoke resonator(SSR1) cryomodule operating at 325 MHz. The LLRF systems for both cryomodules are based on a common SOC FPGA-based hardware platform. The resonance control systems for the two cryomodules are quite different, the first being a pneumatic system based on helium pressure and the latter a piezo/stepper motor type control. The data acquisition and control system can support both CW and Pulsed mode operations. Beam loading compensation is available which can be used for both manual/automatic control in the LLRF system. The user interfaces include EPICS, Labview, and ACNET. Testing of the RF system has progressed to the point of being ready for a 2 mA beam to be accelerated to 25 MeV. The design and performance of the field control and resonance control system operation with beam are presented in this paper.

Poster THPAB338 [5.482 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB338

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paper received ※ 13 May 2021 paper accepted ※ 27 July 2021 issue date ※ 19 August 2021

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THPAB343

Test Results of the Prototype SSR1 Cryomodule for PIP-II at Fermilab

cryomodule, SRF, vacuum, focusing

4461

D. Passarelli, J. Bernardini, C. Boffo, B.M. Hanna, S. Kazakov, T.N. Khabiboulline, A. Lunin, J.P. Ozelis, M. Parise, Y.M. Pischalnikov, V. Roger, B. Squires, A.I. Sukhanov, G. Wu, V.P. Yakovlev, S. Zorzetti
Fermilab, Batavia, Illinois, USA
C. Contreras-Martinez
FRIB, East Lansing, Michigan, USA

Funding: Work supported by Fermi Research Alliance, LLC under Contract No. DEAC02- 07CH11359 with the United States Department of Energy
A prototype cryomodule containing eight Single Spoke Resonators type-1 (SSR1) operating at 325 MHz and four superconducting focusing lenses has been successfully assembled and cold tested in the framework of PIP-II project at Fermilab. The performance of cavities and focusing lenses along with test results of other cryomodule’s key parameters are presented in this contribution.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB343

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paper received ※ 20 May 2021 paper accepted ※ 08 August 2021 issue date ※ 26 August 2021

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THPAB347

Status of Sirius Storage Ring RF System

operation, storage-ring, MMI, controls

4470

A.P.B. Lima, D. Daminelli, R.H.A. Farias, F.K.G. Hoshino, F.S. Oliveira, R.R.C. Santos, M.H. Wallner
LNLS, Campinas, Brazil

The design configuration of the Sirius Light Source RF System is based on two superconducting RF cavities and eight 60 kW solid state amplifiers operating at 500 MHz. The current configuration, based on a 7-cell room temperature cavity, was initially planned for commissioning and initial tests of the beamlines. However, it will have to remain in operation longer than planned. Sirius has been operating in decay mode for beamline tests with an initial current of 70 mA. We present an overview of the first-year operation of the RF system and the preparations for the installation of the two superconducting cavities, which is expected to take place in 2023.

Poster THPAB347 [1.322 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB347

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paper received ※ 16 May 2021 paper accepted ※ 23 July 2021 issue date ※ 16 August 2021

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THPAB348

INFN-LASA for the PIP-II LB650 Linac

SRF, linac, experiment, cryogenics

4474

R. Paparella, M. Bertucci, M. Bonezzi, A. Bosotti, A. D’Ambros, A.T. Grimaldi, P. Michelato, L. Monaco, D. Sertore
INFN/LASA, Segrate (MI), Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy

INFN joined the international effort for the PIP-II project at Fermilab and it’s going to contribute to the low-beta section of the PIP-II proton linac. In particular, INFN-LASA is finalizing its commitment to deliver in kind the full set of the LB650 cavities, namely 36 plus spares 5-cell cavities at 650 MHz and geometrical beta 0.61. All cavities, designed by INFN-LASA, will be produced and surface treated in industry, qualified through vertical cold test, and delivered as ready for string installation. This paper reports the status of INFN’s contribution to PIP-II and of ongoing activities toward the experimental qualifications of infrastructures and prototypes.

Poster THPAB348 [4.076 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB348

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paper received ※ 16 May 2021 paper accepted ※ 01 July 2021 issue date ※ 01 September 2021

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THPAB351

INFN-LASA Experimental Activities on PIP-II Low-Beta Cavity Prototypes

target, experiment, SRF, superconductivity

4481

M. Bertucci, A. Bosotti, A. D’Ambros, A.T. Grimaldi, P. Michelato, L. Monaco, C. Pagani, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
A. Gresele, A. Torri
Ettore Zanon S.p.A., Nuclear Division, Schio, Italy
M. Rizzi
Ettore Zanon S.p.A., Schio, Italy

This paper reports on the first results obtained by INFN-LASA on PIP-II low-beta cavity prototypes. The goal of this activity was to validate the reference surface treatment based on Electropolishing as a bulk removal step. The cavity treatment procedures are here presented together with the strategy used for their optimization. The experimental results of cavity cold tests for a single cell prototype are presented and discussed. Having this cavity achieved the requested performance, the baseline procedure is considered as validated and a plan for a future high-Q cavity surface treatment is proposed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB351

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paper received ※ 19 May 2021 paper accepted ※ 23 July 2021 issue date ※ 22 August 2021

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THPAB352

Computer Vision Techniques Used to Monitor the Alignment of Cavities and Solenoids in the PIP-II Prototype SSR1 Cryomodule

solenoid, alignment, target, cryomodule

4485

S. Zorzetti, J. Bernardini, D. Passarelli
Fermilab, Batavia, Illinois, USA

The alignment of the SRF PIP-II string components is studied as the acceptable beam deflection, offset and defocusing, which may otherwise cause beam loss. Simulations and measurements established that the maximum deviation of the beam pipe from the reference orbit should not exceed a small fraction of the beam aperture. To observe the translations and rotations of each single component within the cryomodule, optical instruments (H-BCAM) surveying highly reflective targets, installed in the internal assembly of the module were used. The alignment monitoring concept for the PIP II SSR1 prototype cryomodule, along with relevant measurements of the components’ position monitoring during coldmass cooldown is presented in this contribution. This development paves the way to new computer vision applications in the field of cryomodule assemblies in cleanroom environment, in which robotically-assisted operations have the potential to dramatically reduce the risk of chemical and particulate contamination.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB352

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paper received ※ 19 May 2021 paper accepted ※ 02 August 2021 issue date ※ 28 August 2021

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THPAB369

Research and Design of an X-Band 100-MeV Compact Electron Accelerator for Very High Energy Electron Therapy in Tsinghua University

electron, gun, linac, klystron

4502

X. Lin, H.B. Chen, J. Shi, C.-X. Tang, H. Zha, L.Y. Zhou
TUB, Beijing, People’s Republic of China

A 100-MeV Compact Electron Accelerator scheme based on the Tsinghua X-band (11.424 GHz) High Power Test stand (TPot-X) was proposed for Very High Energy Electron (VHEE) radiotherapy. A pulse compressor with correction cavity chain was designed to compress the 50 MW, 1500 ns microwave pulse from the X-band klystron to 120 MW, 300 ns. The acceleration system consists of 3 parts, a buncher which bunches and boosts the electron from a thermionic cathode gun to 8 MeV, and two accelerating structure which further boost the electron energy to 100MeV. The detailed design and consideration are presented in this article.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB369

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paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 17 August 2021

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FRXB02

Development of 36 GHz RF Systems for RF Linearisers

klystron, HOM, linac, impedance

4518

A. Castilla, G. Burt
Lancaster University, Lancaster, United Kingdom
M. Behtouei, B. Spataro
INFN/LNF, Frascati, Italy
G. Burt
Cockcroft Institute, Warrington, Cheshire, United Kingdom
J.C. Cai, A. Castilla, A. Latina, X. Liu, I. Syratchev, X.W. Wu, W. Wuensch
CERN, Geneva, Switzerland
J.C. Cai, A. Castilla
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
A.W. Cross, L. Zhang
USTRAT/SUPA, Glasgow, United Kingdom
L.J.R. Nix
University of Strathclyde, Glasgow, United Kingdom

Funding: This project has received funding from the European Union’s Horizon2020 research and innovation programme under grant agreement No 777431.
As part of the deign studies, the CompactLight project plans to use an injector in the C-band. Which constitutes a particular complication for the harmonic system in charge of linearising the beam’s phase space, since it means its operation frequency could be higher than the standard X-band RF technologies. In the present work, we investigated a 36 GHz (Ka-band) as the ideal frequency for the harmonic system. A set of structure designs are presented as candidates for the lineariser, based on different powering schemes and pulse compressor technologies. The comparison is made both in terms of beam dynamics and RF performance. Given the phase stability requirements for the MW class RF sources needed for this system, we performed careful studies of a Gyro-Klystron and a multi-beam klystron as potential RF sources, with both showing up to 3 MW available power using moderate modulator voltages. Alternatives for pulse compression at Ka-band are also discussed in this work.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXB02

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paper received ※ 17 May 2021 paper accepted ※ 19 July 2021 issue date ※ 24 August 2021

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FRXC01

Superconducting Radio-Frequency Cavity Fault Classification Using Machine Learning at Jefferson Laboratory

cryomodule, network, SRF, radio-frequency

4535

C. Tennant, A. Carpenter, T. Powers, L.S. Vidyaratne
JLab, Newport News, Virginia, USA
K.M. Iftekharuddin, M. Rahman
ODU, Norfolk, Virginia, USA
A.D. Shabalina
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

Funding: This work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under Contract No. DE-AC05-06OR23177.
We report on the development of machine learning models for classifying C100 superconducting radiofrequency (SRF) cavity faults in the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab. Of the 418 SRF cavities in CEBAF, 96 are designed with a digital low-level RF system configured such that a cavity fault triggers recordings of RF signals for each of eight cavities in the cryomodule. Subject matter experts analyze the collected time-series data and identify which of the eight cavities faulted first and classify the type of fault. This information is used to find trends and strategically deploy mitigations to problematic cryomodules. However, manually labeling the data is laborious and time-consuming. By leveraging machine learning, near real-time - rather than postmortem - identification of the offending cavity and classification of the fault type has been implemented. We discuss the performance of the machine learning models during a recent physics run. We also discuss efforts for further insights into fault types through unsupervised learning techniques and present preliminary work on cavity and fault prediction using data collected prior to a failure event.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXC01

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paper received ※ 16 May 2021 paper accepted ※ 01 July 2021 issue date ※ 11 August 2021

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FRXC06

Development of the Prototype of the Cavity BPM System for SHINE

FEL, experiment, electron, controls

4552

J. Chen, Y.B. Leng, R.X. Yuan
SSRF, Shanghai, People’s Republic of China
S.S. Cao
SINAP, Shanghai, People’s Republic of China
L.W. Lai
SARI-CAS, Pudong, Shanghai, People’s Republic of China

The Shanghai high repetition rate XFEL and extreme light facility (SHINE) under construction is designed as one of the most advanced FEL facilities in the world, which will produce coherent x-rays with wavelengths from 0.05 to 3 nm and maximum repetition rate of 1MHz. In order to achieve precise, stable alignment of the electron and photo beams in the undulator, the prototype of the cavity beam position monitors (CBPM) including C-band and X-band have been designed and fabricated for the SHINE. And the requirement of the transverse position resolution is better than 200 nm for a single bunch of 100 pC at the dynamic range of ±100 µm. In this paper, we present the design of the cavity with high loaded Q and the RF front-end with low noise-figure, adjustable gain, single-stage down-conversion and phase-locked with reference clock, and also described the structure and specifications of the home-made data acquisition (DAQ) system. The construction of the experiment platform and preliminary measurement result with beam at Shanghai Soft X-ray FEL facility (SXFEL) will be addressed as well.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXC06

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paper received ※ 20 May 2021 paper accepted ※ 06 July 2021 issue date ※ 14 August 2021

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