MC7: Accelerator Technology
T06 Room Temperature RF
Paper Title Page
TUXXPLM3 First Operation of a Hybrid e-Gun at the Schlesinger Center for Compact Accelerators in Ariel University 1171
 
  • A. N. Nause, A. Fukasawa, J.B. Rosenzweig, R.J. Roussel
    UCLA, Los Angeles, USA
  • A. Friedman
    Ariel University, Ariel, Israel
  • B. Spataro
    INFN/LNF, Frascati, Italy
 
  Funding: Israel Ministry of Defence Israel Ministry of Science
A novel hybrid photo injector was designed and partially tested at the UCLA Particle Beam Physics Laboratory. It was later commissioned at Ariel University in Israel as an on-going collaboration between the two universities. This unique, new generation design provides a radically simpler approach to RF feeding of a gun/buncher system, leading to a much shorter beam via velocity bunching owed to an attached traveling wave section of the photo-injector. This design results in better performance in beam parameters, providing a high quality electron beam, with energy of 6 MeV, emittance of app 3 μm, and a 150 fs pulse duration at up to 1 nC per pulse. The Hybrid gun is driven by a SLAC XK5 Klystron as the high power RF source, and third harmonic of a fs level IR Laser amplifier (266 nm) to drive the Cathode. The unique e-gun will produce an electron pulse for a THz FEL, which will operate at the super-radiance regime, and therefore requires extraordinary beam properties. This paper briefly describes the gun and presents initial operational results from the gun and its sub-systems.
 
slides icon Slides TUXXPLM3 [9.526 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUXXPLM3  
About • paper received ※ 14 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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WEPRB001 The Effect of the SLED Installation on Extracted and Lost Beam at the Australian Synchrotron Linac. 2794
SUSPFO001   use link to see paper's listing under its alternate paper code  
 
  • P.J. Giansiracusa, T.G. Lucas, R.P. Rassool, M. Volpi
    The University of Melbourne, Melbourne, Victoria, Australia
  • M.J. Boland
    University of Saskatchewan, Saskatoon, Canada
  • M.J. Boland
    CLS, Saskatoon, Saskatchewan, Canada
  • M.P. Lafky
    AS - ANSTO, Clayton, Australia
 
  A recent upgrade to the high power RF network of the linac at the Australian Synchrotron included a SLED Type 1 Pulse Compressor allowing for the operation of its 100 MeV linac using a single klystron. We explore the effects of the SLED installation on the properties of the beam extracted from the linac with a particular focus on the energy spread and bunch train profile. Additionally, the optical fibre beam loss monitor (oBLM), also recently commissioned, was employed to provide shot-by-shot feedback on loss location and intensity to investigate the change in beam losses.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB001  
About • paper received ※ 15 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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WEPRB004 Sawtooth Generation and Regulation with a Single FPGA for TRIUMF’s ARIEL Prebuncher 2801
 
  • X.L. Fu, T. Au, K. Fong, Q. Zheng
    TRIUMF, Vancouver, Canada
 
  TRIUMF’s ARIEL prebuncher is powered by a sawtooth waveform which is the combination of an 11.79MHz, a 23.57MHz and a 35.36MHz components. The generation, control and regulation of these three components are all incorporated digitally inside a single FPGA. This FPGA can be standalone or inserted inside a VXI module. Commands and controls of these components can be directly through Ethernet, or indirectly through register-base or message-base VXI addresses.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB004  
About • paper received ※ 10 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB007 RF Commissioning of the SPIRAL2 RFQ in CW Mode and Beyond Nominal Field 2804
 
  • M. Di Giacomo, R. Ferdinand, H. Franberg, J.-M. Lagniel, G. Normand
    GANIL, Caen, France
  • M. Desmons, P. Galdemard, Y. Lussignol, O. Piquet, S. Sube
    CEA-DRF-IRFU, France
 
  The SPIRAL2 RFQ was recently successfully commissioned at nominal voltage of 114 kV, corresponding to 1.65 Kilpatrick factor. The paper describes limitations of the RFQ main subsystems, cavity conditioning difficulties, as well as changes implemented in the LLRF and automatic procedures to simplify turn on and operation of the whole system.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB007  
About • paper received ※ 26 April 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB008 Design Study of High Gradient Compact S-band TW Accelerating Structure for the ThomX LINAC Upgrade 2807
 
  • M. El Khaldi, M. Alkadi, C. Bruni, L. Garolfi, A. Gonnin, H. Monard
    LAL, Orsay, France
 
  ThomX is a Compton source project in the range of the hard X rays (45/90 keV). The machine is composed of a 50/70 MeV injector Linac and a storage ring where an electron bunch collides with a laser pulse accumulated in a Fabry-Perot resonator. The final goal is to provide an X-rays average flux of 1012-1013 ph/s. A demonstrator was funded and is being built on the Orsay university campus. The S-band injector Linac consists of 2.5 cell photocathode RF gun and a TW accelerating section. During the commissioning phase, a standard LIL S-band accelerating section is able to achieve around 50 MeV corresponding to around 45 keV X-rays energy. Since the maximum targeted X-ray energy is 90 keV, the development of a new S-band accelerating section, intended to replace the LIL structure, will provide an electron beam energy of 70 MeV. This requires essentially the development of more reliable high gradient compact S band accelerating section. Such design is tailored for high gradient operation, low breakdown rates. We present here the RF design of the LINAC upgrade and the performances obtained in terms of beam dynamics.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB008  
About • paper received ※ 02 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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WEPRB010 RF Power Test of the Rebuncher for Saraf-Linac 2815
 
  • L. Zhao, R. Berthier, F. Gougnaud, P. Guiho, N. Solenne, D. Uriot, X.W. Zhu
    CEA-DRF-IRFU, France
  • R. Braud, D. Chirpaz-Cerbat, J. Dumas, R.D. Duperrier, F. Gohier, T.J. Joannem, S. Ladegaillerie, C. Marchand, O. Piquet
    CEA-IRFU, Gif-sur-Yvette, France
  • M. Di Giacomo, J.F. Leyge, M. Michel
    GANIL, Caen, France
  • B. Kaizer, L. Weissman
    Soreq NRC, Yavne, Israel
 
  Funding: SNRC
Three normal conducting rebunchers will be installed at the Medium Energy Beam Transport (MEBT) of the SARAF-LINAC phase II [saraf]. The MEBT line is designed to follow a 1.3 MeV/u RFQ, is about 5 m long, and contains three 176 MHz rebunchers providing a field integral of 105 kV. CEA is in charge of the design and fabrication of the Cu plated stainless steel, 3-gap rebuncher. The high power tests and RF conditioning have been successfully performed at the CEA Saclay on the first cavity. A solid state power amplifier, which has been developed by SNRC and has been used for the RF tests. The cavity has shown a good performance according to calculations, regarding the dissipated power, peak temperatures and coupling factor. RF conditioning was started with a duty cycle of 1\% and increased gradually until continuous wave (CW), which is the nominal working mode in SARAF-LINAC.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB010  
About • paper received ※ 09 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB020 Compact Ultra High-Gradient Ka-Band Accelerating Structure for Research, Medical and Industrial Applications 2842
 
  • L. Faillace
    INFN-Milano, Milano, Italy
  • M. Behtouei
    Sapienza University of Rome, Rome, Italy
  • V.A. Dolgashev
    SLAC, Menlo Park, California, USA
  • B. Spataro, A. Variola
    INFN/LNF, Frascati, Italy
  • G. Torrisi
    INFN/LNS, Catania, Italy
 
  Technological advancements are strongly required to fulfil demands for new accelerators devices from the compact or portable devices for radiotherapy to mo-bile cargo inspections and security, biology, energy and environmental applications, and ultimately for the next generation of colliders. In the frame of the collab-oration with INFN-LNF, SLAC (USA) we are working closely on design studies, fabrication and high-power operation of Ka-band accelerating structures. In par-ticular, new manufacturing techniques for hard-copper structures are being investigated in order to determine the maximum sustainable gradients above 150 MV/m and extremely low probability of RF breakdown. In this paper, the preliminary RF and mechanical design as well as beam dynamics estimations for a Ka-Band accelerating structure at 35 GHz are presented together with discussions on practical accelerating gradients and maximum average beam current throughput.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB020  
About • paper received ※ 08 April 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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WEPRB021 Commissioning of S-band Cavity Test Facility at Elettra for Conditioning of High Gradient Structures for the Fermi Linac Upgrade 2846
 
  • N. Shafqat, L. Giannessi, C. Masciovecchio, M. Milloch, C. Serpico, M. Svandrlik, M. Trovò
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • M. Bopp, R. Zennaro
    PSI, Villigen PSI, Switzerland
  • T.G. Lucas
    The University of Melbourne, Melbourne, Victoria, Australia
 
  FERMI is the seeded Free Electron Laser (FEL) user facility at Elettra laboratory in Trieste, operating in the VUV to soft X-rays spectral range. In order to extend the FEL spectral range to shorter wavelengths, a feasibility study for increasing the Linac energy from 1.5 GeV to 1.8 GeV is actually going on. A short prototype of a new High Gradient (HG) S-band accelerating structure has been built in collaboration with Paul Scherrer Institute (PSI). The new structures are intended to replace the present Backward Travelling Wave (BTW) sections and tailored to be operated at a gradient of 30 MV/m. For RF conditioning and high power testing of prototype, a Cavity Test Facility (CTF) is commissioned at FERMI. The test facility is equipped with RF pulse compressor system and a dedicated diagnostic for breakdown rate (BDR) measurements and events localization. In this paper we present in detail cavity test facility of FERMI and high power testing of the first prototype.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB021  
About • paper received ※ 08 April 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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WEPRB022 RF System Upgrade for Elettra 2.0 2849
 
  • C. Pasotti, M. Bocciai, M. Rinaldi
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
 
  The Elettra 2.0 low emittance light source project has triggered the review of the installed RF system’s performances and the analyses of the new machine requirement. This study includes the imperative revamp of the RF power sources. The trade off between the best theoretical RF system design and the available room for installation and budget for Elettra 2.0 has been translated into the operational plan reported here. The first planned step is the installation of 100 kW 500 MHz solid state based transmitters.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB022  
About • paper received ※ 13 May 2019       paper accepted ※ 18 May 2019       issue date ※ 21 June 2019  
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WEPRB024 Low Power RF Test of a Quadrupole-free X-Band Mode Launcher for High Brightness Applications 2856
 
  • G. Torrisi, L. Celona, S. Gammino, O. Leonardi, G. Sorbello
    INFN/LNS, Catania, Italy
  • G. Castorina
    Sapienza University of Rome, Rome, Italy
  • V.A. Dolgashev
    SLAC, Menlo Park, California, USA
  • L. Faillace
    INFN-Milano, Milano, Italy
  • G.S. Mauro
    INFN/LNL, Legnaro (PD), Italy
  • G. Sorbello
    University of Catania, Catania, Italy
  • B. Spataro
    INFN/LNF, Frascati, Italy
 
  In this work we present the low power RF characterization of a novel TM01 X-band mode launcher for the new generation of high brightness RF photo-injectors. The proposed mode launcher exploits a fourfold symmetry which minimizes both the dipole and the quadrupole fields in order to mitigate the emittance growth in the early stages of the acceleration process. Two identical aluminum mode launchers have been assembled and measured in back-to-back configurations for three different central waveguide lengths. From the back-to-back results we infer the performance of each mode launcher. The low power RF test, performed at the Istituto Nazionale di Fisica Nucleare Laboratori Nazionali del Sud (INFN-LNS), validate both the numerical simulations and the quality of fabrication. An oxygen-free high-conductivity copper version of the device is being manufactured for high power and ultra high vacuum tests that are planned to be conducted at SLAC  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB024  
About • paper received ※ 09 April 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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WEPRB026 Simulations of Beam Loading Compensation in a Wideband Accelerating Cavity Using a Circuit Simulator Including a LLRF Feedback Control 2863
 
  • F. Tamura, M. Nomura, T. Shimada, M. Yamamoto
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  • M. Furusawa, K. Hara, K. Hasegawa, C. Ohmori, Y. Sugiyama, M. Yoshii
    KEK, Tokai, Ibaraki, Japan
 
  Magnetic alloy cavities are employed in the J-PARC RCS to generate high accelerating voltages. The cavity, which is driven by a vacuum tube amplifier, has a wideband frequency response and the beam loading in the cavity is multiharmonic. Therefore, the tube must generate a multiharmonic output current. An LTspice circuit model is developed to analyze the vacuum tube operation and the compensation of the multiharmonic beam loading. The model includes the cavity, tube amplifier, beam current, and LLRF feedback control. The feedback control consists of the I/Q demodulator including low pass filters, PI control, and I/Q modulator. In this presentation, we present the implementation of the LLRF functions in the LTspice simulations. The preliminary simulation results are also presented. The simulations fairly agree with the beam test results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB026  
About • paper received ※ 23 April 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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WEPRB027 Electromagnetic Design and Characterization of an S-band 3-Cell RF Accelerating Cavity 2867
 
  • G.R. Montoya Soto
    Universidad de Guanajuato, División de Ciencias e Ingenierías, León, Mexico
  • C. Duarte Galván, C.A. Valerio
    ECFM-UAS, Culiacan, Sinaloa, Mexico
  • B. Yee-Rendón
    JAEA/J-PARC, Tokai-mura, Japan
 
  An S-Band (2998 MHz) RF cavity to accelerate electrons was developed taking into account the beam space charge, the relativistic change in velocity of the low energy beam particle distribution through the cavity and the emittance growth. The electromagnetic design and geometry optimization were done using the codes Poisson Superfish and CST Studio. In addition, beam dynamics simulations were done using the program Travel to optimize the emittance and take into account the space charge effect. The machining was done in a CNC machining center. Measurements of the cavity resonance frequencies were carried out and compared with the obtained by the simulations with good agreement between them.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB027  
About • paper received ※ 30 April 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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WEPRB030 Commissioning of RF System of the 200 MeV Proton Cyclotron 2877
 
  • G. Chen, C. Chao, G. Liu, X.Y. Long, Z. Peng, C.S. Yu, X. Zhang, Y. Zhao
    ASIPP, Hefei, People’s Republic of China
  • L. Calabretta, A.C. Caruso
    INFN/LNS, Catania, Italy
  • O. Karamyshev, G.A. Karamysheva, G. Shirkov
    JINR, Dubna, Moscow Region, Russia
 
  Funding: (1) National Natural Science Foundation of China under grant No. 11775258, 11575237; (2) International Sci-entific and Technological Cooperation Project of An-hui (grant No. 1704e1002207).
The SC200 superconducting accelerator which is designed for proton therapy is currently under con-struction. The RF (Radio Frequency) system has been designed and constructed as a subsystem of the SC200. To verify the stability of the RF system, a high-power feeding test was performed for the cavity. This paper mainly reports on the overview of RF systems and the prelimary high-power commissioning, as well as the problems found and improvements made during the commissioning process. The results show that the RF system has initially achieved the designed goal, and each loop (amplitude, tuning, phase) can work effec-tively. The cavity can operate in a ~50 kW continuous wave state. Next, the formal RF conditioning will be carried out after the complete assembly of cyclotron, so as to confirm the cavity can run smoothly under 80 kW, which is part of the whole commissioning process.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB030  
About • paper received ※ 22 April 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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WEPRB034 Study on the Design of the X-band Waveguide-damped Structure 2886
 
  • X.X. Huang, W. Fang, Z.T. Zhao
    SSRF, Shanghai, People’s Republic of China
  • A. Grudiev
    CERN, Meyrin, Switzerland
 
  The design of waveguide-damped structure is optimized to reduce the magnitudes of surface electromagnetic fields and strongly suppress long-range transverse wakefields of the 380 GeV Compact Linear Collider facility currently under study. The optimization is mainly discussed with the elliptical shape of the iris, the wall shape of the damping waveguides, the position of the high-order-mode damping loads and the widths of the waveguide openings of the entire sequence of damping waveguides.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB034  
About • paper received ※ 13 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB039 Tuning of a Tapered Ridge-Loaded Waveguide Coupler for a Drift Tube LINAC of the Compact Pulsed Hadron Source 2893
 
  • Y. Lei, C.T. Du, X. Guan, R. Tang, X.W. Wang, Q.Z. Xing, S.X. Zheng
    TUB, Beijing, People’s Republic of China
 
  This paper presents the tuning result of a tapered ridge-loaded waveguide coupler for the drift tube linac (DTL) of the compact pulsed hadron source (CPHS) at Tsinghua University. The coupler has been designed, manufactured, and mounted on the DTL cavity for the cold measurement and tuning. The iris diameter of the coupler which is related to the coupling coefficient needs to be determined in the tuning experiment, due to the difference between the designed and measured quality factors. Meanwhile, we found that the relationship between the coupling coefficient and iris diameter from the traditional analytical design method is not applicable when the iris diameter is relatively large. In this paper, the target coupling coeffi-cient is analysed, and the limit of the original analytical design is presented. The measurement method is intro-duced to improve the measurement efficiency and the tuning process of the coupling coefficient to the target value is described. After several iterations, the coupling coefficient is tuned to 1.54 which is close to the desired value of 1.56.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB039  
About • paper received ※ 30 April 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB042 High Power Test of the First C-band Spherical Pulse Compressor Prototype 2896
 
  • Z.B. Li
    SINAP, Shanghai, People’s Republic of China
  • W. Fang, Q. Gu, X.X. Huang, J.H. Tan, Z.T. Zhao
    SSRF, Shanghai, People’s Republic of China
 
  Funding: National Natural Science Foundation of China (No. 11675249)
Recently, a new C-band (5712 MHz) compact spherical radio frequency (RF) pulse compressor was designed and tested for Shanghai Soft X-ray Free Electron Laser Facili-ty (SXFEL). This pulse compressor utilizes one high Q0 spherical RF resonant cavity that works with two TE1, 1,3 modes and a dual-mode polarized coupler. The peak power multiply factor is 6.1 and average power gain 3.8 in theory. During the high power test, a peak power mul-tiply factor of 5.74 and average power gain of 3.77 was achieved. This paper presents the RF measurement of the C-band spherical pulse compressor and the high power test results.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB042  
About • paper received ※ 19 April 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB043 Wakefield Suppression in the Main LINAC of the Klystron-Based First Stage of CLIC at 380 GeV 2899
SUSPFO064   use link to see paper's listing under its alternate paper code  
 
  • J.Y. Liu, H.B. Chen, J. Shi, H. Zha
    TUB, Beijing, People’s Republic of China
  • A. Grudiev
    CERN, Meyrin, Switzerland
 
  An alternative klystron-based scenario for the first stage of Compact Linear Collider (CLIC) at 380 GeV centre-of-mass energy was proposed. To preserve the beam stability and luminosity of CLIC, the beam-induced transverse long-range wakefield in main linac must be suppressed to an acceptable value. The design of klystron-based accelerating structure is based on waveguide damping structure (WDS). The high-order modes (HOMs) propagating into four waveguides are absorbed by HOM damping loads. In this paper, the wakefield suppression in CLIC-K based on GdfidL code simulations are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB043  
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB045 Suppression of Secondary Electron Yield Effect in the 650MHz/800kW Klystron for CEPC 2906
 
  • X. He, C. Meng, S. Pei, J.L. Wang, O. Xiao, N. Zhou
    IHEP, Beijing, People’s Republic of China
 
  The circular electron positron collider (CEPC) is in pre-research, it will need more than two hundred 650MHz/800kW klystrons. The secondary electron yield (SEY) effect suppression is very important for the klystron working stable. The simulation uses an incident primary electron source and considers all the phases and power levels of the input microwave. Two methods are simulated for the SEY suppression. The groove cutting on the nose of cavities is much simple while the TiN coating can suppress better. The effect after groove cutting on nose is also simulated and the corresponding compensations are adopted. For simplify the fabrication progress as well as some experience that can be referenced, the groove cutting method is adopted finally for the first klystron prototype, which is expected to be available in the summer of 2019.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB045  
About • paper received ※ 13 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB046 Development of Flexible Waveguide for High Power High Vacuum Applications in S-band 2909
 
  • X. He, B. Deng, J. Lei, C. Meng, S. Pei
    IHEP, Beijing, People’s Republic of China
 
  A novel flexible waveguide is developed for S band 2856 MHz, which is a standard WR284 waveguide. The surface of the flexible waveguide is plated with Oxygen-free High Conductivity (OFHC) copper for the purpose of welding with the stainless steel flange in the vacuum furnace, for the flexible waveguide itself is made of brass. The prototype has got a certain amount of deformation which will be much more convenient for the connection between two hard waveguides. It also has a good measurement results of the lower power microwave test, and the 72 hours vacuum leakage test shows a satisfactory vacuum performance, no obvious surface collapse is observed. The high power test will be conducted after our high power test facility is available, which will tell us the maximal power level of the flexible waveguide prototype.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB046  
About • paper received ※ 13 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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WEPRB047 High-Power Test of a 12 Cell Accelerating Structure Build in Halves 2912
 
  • M.M. Peng, Y.L. Jiang, J.Y. Liu, Z.N. Liu, X.C. Meng, J. Shi, H. Zha
    TUB, Beijing, People’s Republic of China
 
  An X-band 12 cell travelling-wave accelerating structure has been developed and high-power tested at Tsinghua University in China. This structure works at 2⁄3 π at the frequency of 11.424 GHz. It is a 12-cell constant-impedance structure build in halves and was silver-brazed as a vacuum tight structure. The high power test was conducted at Tsinghua X-band high power test facility [1] with a 50-MW X-band klystron at a repetition rate to 40 Hz. The final input power was 51.23 MW with a 200 ns pulse width, which means an accelerating gradient of 88.58 MV/m was reached. This paper presents the high power test results including the gradient and breakdown history.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB047  
About • paper received ※ 10 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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WEPRB048 Design, Fabricate, and Tuning of X-Band Deflecting Structure for CERN 2915
 
  • J.H. Tan, W. Fang, Q. Gu, X.X. Huang, Z.T. Zhao
    SSRF, Shanghai, People’s Republic of China
 
  A 20-cell x-band deflecting structure for CERN has been finished, and now is under high power conditioning at XBOX of CERN.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB048  
About • paper received ※ 14 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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WEPRB050 Multipacting Studies of the Coaxial Coupler for BNCT DTL 2921
 
  • M.X. Fan, A.H. Li, B. Li, J. Peng, P.H. Qu, A.X. Wang, Y. Wang, X.L. Xiaolei
    IHEP CSNS, Guangdong Province, People’s Republic of China
  • Q. Chen, S. Fu, H.C. Liu
    IHEP, Beijing, People’s Republic of China
  • X.L. Wu
    DNSC, Dongguan, People’s Republic of China
 
  Funding: Youth Innovation Promotion Association of CAS (2015011) Program for GuangDong Introducting Innovative and Enterpreneurial Teams (2017ZT07S225)
Multipacting is a phenomenon in which electrons grow sharply under certain conditions in a RF structure. It may lead to the breakdown or even damage to the equipment. Therefore, it is very important to calculate the Multipact-ing range in the RF equipment design. Since the phe-nomenon is too complicated to use the formula to fully predict it, numerical simulation is employed. There are many computer codes (such as Track3P, MultiPac, CST PS, etc.) used to simulate the phenomenon, but most of them are not commercial. In this paper, theories used in coaxial line for predicting multipacting are introduced; the CST PS is chosen to simulate the multipacting of coaxial coupler for BNCT DTL; finally, methods of sup-pressing multipacting are discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB050  
About • paper received ※ 11 April 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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WEPRB051 MA RF Cavity Design and Simulation for CSNS/RCS Upgrade Project 2925
SUSPFO075   use link to see paper's listing under its alternate paper code  
 
  • B. Wu
    IHEP CSNS, Guangdong Province, People’s Republic of China
  • X. Li, H. Sun
    IHEP, Beijing, People’s Republic of China
 
  The dual harmonic RF system will be adapted for Chi-na Spallation Neutron Source (CSNS) upgrade project. Limited locations in CSNS/RCS are reserved to install additional three 2nd harmonic cavities. The cavity loaded by magnetic alloy (MA) material would be used. Because of the low Q factor of the MA core, the cavity cooling be-comes a very important issue in cavity design. Air-forced, indirect and direct cooling scheme were studied. The fluid thermodynamic of different cooling structure were simu-lated by ANSYS CFX which considered the anisotropy of thermal conductivity of MA core. The limitation of these cooling schemes were discussed in detail based on the simulation results. Indirect cooling experiment was done to assess the cooling efficiency and verify the simulation result. A high power test cavity cooled by water has been designed to estimate the property of the MA core and cooling effectiveness for CSNS/RCS.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB051  
About • paper received ※ 08 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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WEPRB052 Design of Two Types of X-Band High Power Directional Coupler 2928
 
  • G. Wang, X. Lin, Y.G. Tang, C.-F. Wu
    USTC/NSRL, Hefei, Anhui, People’s Republic of China
 
  The directional coupler is one of the most widely used components in many microwave systems, which is used to distribute the power of the input microwave signal according to a desired ratio. Directional coupler may be a three-port component or a four-port component with certain specification such as frequencies, bandwidth and structure. To meet the requirements of stable coupling degree and high directivity, we designed two types of directional coupler working at 11.424 GHz with high power handling capacity. One consists of two parallel rectangular waveguides with four holes drilled along the central line of the narrow-wall for coupling the electromagnetic power from the main-waveguide to the sub-waveguide which is called H-plane directional coupler. Simulations show that the coupling degree of H-face directional coupler is 49.9 dB and the directivity is 54.5 dB .The peak electric field is about 29MV/m while operating at 200 MW peak power. The other consists of a circular main-waveguide transmitting TM01 mode and a rectangular sub-waveguide transmitting TE10 mode, called circular-rectangle waveguide directional coupler. These two waveguide are connected by six holes drilled on the side of the circular main-waveguide and along the central line of the wide-wall of the sub-waveguide. The coupling degree of this directional coupler is 50.14 dB and the directivity is 37.93 dB due to the simulation. The bandwidth is about 800MHz. The peak electric field is 404.5V/m while operating at 200 MW peak power. Comparing with the H-plane directional coupler, peak electric field of this directional coupler is lower. Low peak electric field can reduce the risk of RF breakdown and the Multipactor effect, which ensures the stable high power operation of the directional coupler.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB052  
About • paper received ※ 27 April 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB055 Design of 3 MeV S-band Electron Linac Structure With 2.5 Bunching Cells 2934
 
  • Y. Joo, P. Buaphad, H.R. Lee
    University of Science and Technology of Korea (UST), Daejeon, Republic of Korea
  • Y. Kim
    KAERI, Daejon, Republic of Korea
  • J.Y. Lee, S. Lee
    Korea Atomic Energy Research Institute (KAERI), Daejeon, Republic of Korea
 
  Funding: UST (University of Science and Technology), KAERI (Korea Atomic Energy Research Institute)
The Korea Atomic Energy Research Institute (KAERI) has been designing several 3 MeV S-band RF electron linear accelerators (linacs) for non-destructive testing. Until now, the bunching cell of the linac has a full-cell geometry. However, to maximize the acceleration of electrons after emission from the electron gun, the geometry of the first bunching cell is modified from a full-cell to a half cell. To accelerate electron beams more gently, recently, we increased the total number of bunching cells from 1.5 to 2.5. In this paper, we describe design concepts and detailed optimization processes of a 3 MeV linac with the 2.5 bunching cells to optimize RF parameters such as the quality factor, resonance frequency, and uniformity of electric field distribution along the linac. Lastly, we will discuss the application of 3 MeV linac.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB055  
About • paper received ※ 04 June 2019       paper accepted ※ 16 June 2019       issue date ※ 21 June 2019  
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WEPRB058 Combined Field Emission and Multipactor Simulation in High Gradient RF Accelerating Structures 2940
SUSPFO091   use link to see paper's listing under its alternate paper code  
 
  • D. Banon-Caballero
    IFIC, Valencia, Spain
  • N. Catalán Lasheras, K. T. Szypula, W. Wuensch
    CERN, Geneva, Switzerland
  • A. Faus-Golfe
    LAL, Orsay, France
  • B. Gimeno
    UVEG, Burjasot (Valencia), Spain
 
  Field emitted electrons have important consequences in the operation of high-gradient RF accelerating structures both by generating so-called dark currents and initiating RF breakdown. The latter is an important limitation of the performance in such devices. Another kind of vacuum discharge that primarily affects the operation of lower-field RF components, for example those used in space applications, is multipactor. Theoretical simulations using CST Particle Studio, show that field emitted electrons generated in the high field regions of high-gradient accelerating cavities migrate to low field regions under ponderomotive forces potentially triggering multipactor there. This phenomenon is an interplay between high field and low field processes which may have as a consequence that multipactor actually affects to the performance of high-gradient cavities because field emitted electrons might reduce the timescales for the onset of multipactor.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB058  
About • paper received ※ 27 April 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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WEPRB059 Dark Current Analysis at CERN’s X-band Facility 2944
 
  • D. Banon-Caballero, M. Boronat, V. Sánchez Sebastián, A. Vnuchenko
    IFIC, Valencia, Spain
  • N. Catalán Lasheras, S. Pitman, M. Widorski, W. Wuensch, V. del Pozo Romano
    CERN, Meyrin, Switzerland
  • A. Faus-Golfe
    LAL, Orsay, France
  • B. Gimeno
    UVEG, Burjasot (Valencia), Spain
  • T.G. Lucas, M. Volpi
    The University of Melbourne, Melbourne, Victoria, Australia
  • W.L. Millar
    Lancaster University, Lancaster, United Kingdom
  • J. Paszkiewicz
    University of Oxford, Oxford, United Kingdom
 
  Dark current is particularly relevant during operation in high-gradient linear accelerators. Resulting from the capture of field emitted electrons, dark current produces additional radiation that needs to be accounted for in experiments. In this paper, an analysis of dark current is presented for four accelerating structures that were tested and conditioned in CERN’s X-band test facility for CLIC. The dependence on power, and therefore on accelerating gradient, of the dark current signals is presented. The Fowler-Nordheim equation for field emission seems to be in accordance with the experimental data. Moreover, the analysis shows that the current intensity decreases as a function of time due to conditioning, but discrete jumps in the dark current signals are present, probably caused by breakdown events that change the emitters’ location and intensity.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB059  
About • paper received ※ 10 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB060 HOM Damped Normal Conducting 1.5 GHz Cavity Design Evolution for the 3rd Harmonic System of the ALBA Storage Ring 2948
 
  • A. Salom, J.M. Alvarez, B. Bravo, F. Pérez
    ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
 
  In a collaboration framework with CERN, ALBA has designed a normal conducting active 1.5 GHz cavity which could serve as main RF system for the Damping Ring of CLIC and as an active third harmonic cavity for the ALBA Storage Ring. The third harmonic cavity at ALBA will be used to increase the bunch length in order to improve the beam lifetime and increase the beam stability thresholds. The main advantage of an active third harmonic cavity is that optimum conditions can be reached for any beam current. This paper presents the evolution of the preliminary design of this cavity and its trans-dampers: high order modes coaxial dampers with waveguide transitions to N, which allows extracting the power of the high order modes induced by the beam outside of the cavity and to dissipate it using standard loads. This approach has two main advantages: no ferrites brazing is needed and they provide a diagnostic to analyze the beam dynamics. The new features of the design, together with electromagnetic simulations, mechanical and thermal stress analysis will be presented in this paper as well as the first stages of the prototype production status.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB060  
About • paper received ※ 15 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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WEPRB062 Spatially Resolved Dark Current in High Gradient Traveling Wave Structures 2956
SUSPFO106   use link to see paper's listing under its alternate paper code  
 
  • J. Paszkiewicz, W. Wuensch
    CERN, Meyrin, Switzerland
  • P. Burrows
    JAI, Oxford, United Kingdom
  • P. Burrows
    Oxford University, Physics Department, Oxford, Oxon, United Kingdom
 
  High-gradient accelerating structures are known to produce field-emitted current from regions of high surface field, which are captured and accelerated by the fields within the structure. This current is routinely measured in structures under test in the CLIC high-gradient test stands using Faraday cups. This paper presents a novel technique to spatially resolve the longitudinal distribution of field emitted current by analysing downstream Faraday cup signals when the structure is fed with RF pulses much shorter than its filling time. Results from this method applied to X-band cavities operating at 100 MV/m are presented, and are compared to breakdown position distributions. A decay in emitted current as conditioning progressed in regions with a low breakdown rate and large jumps in regions with a large breakdown rate are observed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB062  
About • paper received ※ 29 April 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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WEPRB063 Connection of 12 GHz High Power RF from the XBOX 1 High Gradient Test Stand to the CLEAR Electron LINAC 2960
 
  • A.V. Edwards
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • N. Catalán Lasheras, S. Gonzalez Anton, G. McMonagle, S. Pitman, B.J. Woolley, V. del Pozo Romano
    CERN, Meyrin, Switzerland
 
  A new RF system is being established at XBOX1 to drive two §I{100}{MV/m} CLIC structures in the CLEAR electron linac. In the past, these structures had been powered by RF from PET structures excited by a drive beam. This drive beam is no longer available. The upgrade will reroute power from the §I{50}{MW} klystron and pulse compressor which was previously used to power the structure in XBOX1. During the upgrade, the LLRF system will be optimised to improve the modulation of the output signals and down-mixing of the returning signals to obtain accurate phase and amplitude information. The design of the improved LLRF and software, along with phase noise measurements and comparisons with the old system are made in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB063  
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB064 High Power Conditioning of X-Band Variable Power Splitter and Phase Shifter 2964
 
  • V. del Pozo Romano, H. Bursali, N. Catalán Lasheras, A. Grudiev, S. Pitman, I. Syratchev
    CERN, Meyrin, Switzerland
  • C. Serpico
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • M. Volpi
    The University of Melbourne, Melbourne, Victoria, Australia
 
  The three X-band test facilities currently at CERN aim at qualifying CLIC structures prototypes but are also exten- sively used to qualify X-band components operation at high power. In order to upgrade one of the facilities from a single test line to a double test line facility, a high power variable splitter and variable phase shifter have been designed and manufactured at CERN. They have been power tested, first in a dedicated test and also in their final configuration, to en- sure stable power operation before installing them together with an accelerating structure. In this paper, we broadly describe the RF and mechanical design, manufacturing and low power measurements agreement with simulations. We report the high power qualification of both components and their suitability to be used in existing and planned X-band facilities.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB064  
About • paper received ※ 10 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB066 Utilizing the High Shunt Impedance TM020-Mode Cavity in the Double RF Systems for the Storage Ring of the Thailand New Light Source 2972
 
  • N. Juntong, T. Phimsen
    SLRI, Nakhon Ratchasima, Thailand
  • N. Chulakham, S. Malichan
    Udon Thani Rajabhat University, Udon Thani, Thailand
 
  The utilization of the TM020-mode cavity for the storage ring based light source was pioneered by SPring-8 with its high quality factor and hence its high shunt impedance. KEK-LS has also studied the possibility of using this type of cavity for their storage ring. The TM020-mode cavity has larger transverse dimension compared to the traditional TM010-mode cavity, but with its higher shunt impedance it can be designed to fit in the new low emittance storage ring regardless. The new storage ring based light source project in Thailand aims to optimum the low emittance beam in nano-meters region with the energy of 3 GeV. The TM020-mode cavity was considered as the main cavity and the harmonic cavity for the storage ring. They have been designed to have their pipe aperture fits the storage ring beam ducts. The main cavity has a high shunt impedance of 8.3 Mega Ohms with the 51,000 unloaded quality factor. The harmonic cavity has a high shunt impedance and an unloaded quality factor of 2.45 Mega Ohms and 36,000, respectively. The damping mechanism of the parasitic modes and the tuning mechanism of the operating mode of these cavities were also studied. There will be four main cavities and six harmonic cavities in the new storage ring. Detailed design and study of these cavities will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB066  
About • paper received ※ 29 April 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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WEPRB068 Ka-Band Linearizer Studies for a Compact Light Source 2976
 
  • A. Castilla, G. Burt, W.L. Millar
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • A. Latina, X. Liu, W.L. Millar, X.W. Wu, W. Wuensch
    CERN, Geneva, Switzerland
 
  Funding: This project has received funding from the European Union’s Horizon2020 research and innovation programme under grant agreement No 777431.
The CompactLight project is currently developing the design of a next generation hard X-ray FEL facility, based on high-gradient X-band (12 GHz) structures, bright electron photo-injectors, and compact short period undulators. However, to improve the brightness limitations due to the non-linear energy spread of the electron bunches, a K-band (36 GHz) linearizer is being considered to provide a harmonic compensation during the bunch compression. In this paper, we analyze the feasibility of such linearizer.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB068  
About • paper received ※ 15 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB069 Wakefield Suppression in a Manifold Damped and Detuned Structure for a 380 GeV CLIC Staged Design 2980
 
  • N.Y. Joshi, R.M. Jones
    UMAN, Manchester, United Kingdom
 
  The first stage of the Compact Linear Collider (CLIC) project aims to collide electrons and positrons at a 380 GeV center of mass energy. In the baseline design the main linacs for this staged approach are required to achieve a gradient of 72 MeV/m, with the surface electromagnetic fields (EM) and the transverse long-range wakefields bound by beam dynamics constraints. The baseline design utilizes heavy damping in a traveling wave (TW) structure. Here we report on an alternate design, which adopts moderate damping along with strong detuning of the individual cell frequencies. In the context of this Damped and Detuned Structure (DDS) design, we study Gaussian and hyperbolic secant dipole distributions, together with interleaving of successive structures, to effect long-range transverse wakefield suppression. Both analytic and modal summation approaches, in the quasi-coupled approximation, produce consistent results. In the optimisation scheme we opt for a dipole frequency bandwidth of 17.7 % (2.92 GHz)  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB069  
About • paper received ※ 13 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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WEPRB072 Ultra-High Gradient Short RF Pulse Gun 2987
 
  • S.P. Antipov, P.V. Avrakhov, S.V. Kuzikov, A. Liu
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • G. Ha, J.G. Power
    ANL, Argonne, Illinois, USA
 
  Funding: DOE SBIR DE-SC0018709
High brightness beams enable novel applications like x-ray free electron lasers and ultrafast electron microscopes. High brightness beams essentially consist of a large number of electrons in a small phase space volume, i.e. a high peak current. When such beams are generated from the cathode, there is a strong space charge force, which elongates the bunch and reduces its brightness. An optimal solution is to raise the accelerating voltage in the gun. However, the maximum gradient is limited by the effects of RF breakdown. The probability of RF breakdown is reduced as the RF pulse length decreases. We present a development of an electron photoinjector operating with short RF pulse, 10 ns scale. We have designed an X-band gun including the RF design, beam quality optimization, and engineering. The gun will be fed by 10 ns, 300 MW RF pulse generated at the Argonne Wakefield Accelerator Facility for two-beam acceleration experiments. We also manufactured an aluminum prototype and measured its microwave properties, most importantly, fill time. The proposed high brightness beam source can be used as the main beam in wakefield accelerators. It will find commercial applications in ultrafast electron diffraction and microscopy systems.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB072  
About • paper received ※ 21 May 2019       paper accepted ※ 24 May 2019       issue date ※ 21 June 2019  
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WEPRB073 CW Room Temperature Accelerating Structures 2990
 
  • S.P. Antipov, P.V. Avrakhov, E. Gomez, S.V. Kuzikov
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • A.A. Vikharev
    IAP/RAS, Nizhny Novgorod, Russia
 
  To this day CW linear electron accelerators were based only on expensive and bulky (embedded in a cryostat) superconducting accelerating structures. CW regime can in principle be realized with normal conducting structures provided the shunt impedance is high. Such structures can be designed using dielectrics (ultra-pure ceramics in C-band and diamond in mm-waves) with ultra-low loss tangent (~10-6). The use of dielectrics allows to concentrate the electromagnetic energy density in the dielectric region and thus minimize fields and ohmic loss on metallic walls. The thermal loss in dielectric can be relatively low given the loss tangent is small. We report here the design of structures with shunt impedance on the order of 104 MOhm/m, which is several orders of magnitude higher than shut impedance in copper structures in GHz and THz range. High shunt impedance makes it possible to accelerate electrons to 1 MeV using kW-level CW RF sources like magnetrons in C-band and gyrotrons in THz range. Such CW accelerators will find applications in sterilization, food irradiation, industrial radiography and cargo inspection.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB073  
About • paper received ※ 21 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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WEPRB075 Optimizing Room Temperature RF Structures for Accelerator Driven System Operations 2993
 
  • D.L. Brown, M.T. Crofford
    ORNL, Oak Ridge, Tennessee, USA
  • C.C. Peters
    ORNL RAD, Oak Ridge, Tennessee, USA
 
  Funding: This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. 
Minimizing beam trip rates is one of the key operational goals at the Spallation Neutron Source (SNS). Trip rates are closely monitored, and real-time statistics are kept during beam operations for immediate analysis. Beam trips are automatically binned by the length of the trip along with the cause for each trip. The shortest beam trips occur with the highest frequency and those trip rates are dominated by the room temperature RF structures. There can be many causes for the RF structure malfunctions, but one area that has had a major impact on trip rates is improvement in how RF processing is done on structures after extended maintenance periods. Details about the improvement in RF conditioning will be discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB075  
About • paper received ※ 13 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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WEPRB080 Optimization of RF Cavities Using MOGA for ALS-U 3007
 
  • H.Q. Feng, K.M. Baptiste, D. Li, T.H. Luo
    LBNL, Berkeley, California, USA
  • H.Q. Feng, W.-H. Huang, Z.N. Liu, C.-X. Tang
    TUB, Beijing, People’s Republic of China
 
  Funding: Director of Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
A multi-objective genetic algorithm-based optimiza-tion process has been applied to optimize the RF design of a 500 MHz main cavity and a 1.5 GHz Higher Harmon-ic Cavity (HHC) for the Advanced Light Source upgrade (ALS-U) in Lawrence Berkeley National Laboratory (LBNL). For the main cavity, a significant improvement, compared with the existing ALS cavity, has been achieved in cavity shunt impedance and power loss den-sity simultaneously. The field strengths and distribution of the optimized structure are analysed for further re-search. For the HHC, a cavity with low R/Q has been pre-liminary designed to mitigate the beam instability. This study also serves as an example of how a genetic algo-rithm can be used for optimizing RF cavities.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB080  
About • paper received ※ 16 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB081 Design Study on Higher Harmonic Cavity for ALS-U 3011
 
  • H.Q. Feng, K.M. Baptiste, S. De Santis, D. Li, T.H. Luo
    LBNL, Berkeley, California, USA
  • H.Q. Feng, W.-H. Huang, Z.N. Liu, C.-X. Tang
    TUB, Beijing, People’s Republic of China
 
  Funding: Director of Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
The ALS upgrade (ALS-U) to a diffraction-limited light source [1] depends on the ability to lengthen the stored bunches to limit the emittance growth and increase the beam life time. Higher harmonic cavities (HHCs), also known as Landau cavities, have been proposed to in-crease beam lifetime and Landau damping by lengthen-ing the bunch. We present an optimized 1.5 GHz normal conducting HHC design for the ALS-U with a supercon-ducting-like geometry using multi-objective genetic algorithm (MOGA) for lower R/Q. The optimization goal is to reach the required shunt impedance while maintain-ing a relatively high Q value of the cavities. To minimize the coupled bunch instabilities, higher-order mode (HOM) of the HHC as well as corresponding impedance are explored and characterized.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB081  
About • paper received ※ 16 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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WEPRB084 Mechanical Design and Analysis of the Proposed APEX2 VHF CW Electron Gun 3014
 
  • A.R. Lambert, H.Q. Feng, D. Filippetto, M.J. Johnson, D. Li, T.H. Luo, C.E. Mitchell, F. Sannibale, J.W. Staples, S.P. Virostek, R.P. Wells
    LBNL, Berkeley, California, USA
 
  Funding: Work supported by the Office of Science, U.S. Department of Energy under DOE contract number DEAC02-05CH11231
Normal conducting radio-frequency (RF) guns resonating in the very high frequency (VHF) range (30-300 MHz) and operating in continuous wave (CW) mode have successfully achieved the targeted brightness and reliability necessary for upgrading the performance of current lower repetition rate accelerator-based instruments such as X-ray free electron lasers (FELs), and ultra-fast electron diffraction (UED) and microscopy (UEM). The APEX2 (Advanced Photo-injector Experiment 2) electron gun is a proposed upgrade for the current LCLS-II injector, which was based on the original APEX design. In contrast, APEX2 is designed as a two-cell cavity operating at 162.5 MHz with a launching field at the cathode equal to 34 MV/m, producing a beam energy of 1.5 to 2 MeV, more than double APEX. Operation of the gun in this condition will require upwards of 200 kW of RF power, thus proper thermal management is crucial to achieve target performance. This paper describes the current design, thermal performance and tuning methods.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB084  
About • paper received ※ 13 May 2019       paper accepted ※ 18 May 2019       issue date ※ 21 June 2019  
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WEPRB099 Status Update of a Harmonic Kicker Development for JLEIC 3047
 
  • G.-T. Park, J. Guo, J. Henry, M. Marchlik, F. Marhauser, R.A. Rimmer, H. Wang, S. Wang
    JLab, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
An effort to develop the second prototype of the harmonic kicker for the Circulator Cooler Ring (CCR) of the Jefferson Lab Electron-Ion Collider (JLEIC) is under way. After beam dynamics studies and completion of a conceptual RF design of the kicker [1], further progress has been made toward the final mechanical design including the input power coupler (loop) design, tuner ports, multipacting studies. Furthermore, concerning the kicker’s compatibility with beam dynamics, the impact of RF multipole components was investigated and a scheme was developed to cancel out detrimental beam effects.
1. G. Park, et al, The Development of a New Fast Harmonic Kicker for the JLEIC Circulator Cooler Ring, TUPAL068, proceedings of IPAC 2018.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB099  
About • paper received ※ 15 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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WEPRB105 Design of an X-Band Constant Impedance LINAC for Compact Light Project 3055
 
  • J.M. Arnesano, A. Mostacci, L. Palumbo
    Sapienza University of Rome, Rome, Italy
  • M. Diomede, M. Marongiu
    INFN/LNF, Frascati, Italy
  • L. Ficcadenti
    INFN-Roma, Roma, Italy
 
  Within the framework of Horizon 2020 project, Compact Light, in order to provide a high performance, high-gradient X-band technology, for the new generation of hard X-ray FEL, a travelling wave (TW) Linac, working on 2pi/3 mode at 11.9952 GHz, fed by two types of asymmetrically couplers, has been designed. The design was performed using CST Microwave Studio frequency domain solver. First, simulations have been conduct in order to obtain the best trade-off between single cell’s parameters, varying iris aperture. Then, the both couplers, with and without pumping port, has been tuned to avoid reflections at the input port. Finally, the entire structure, with 5 cells, was simulated. The main structure parameters will be present and we will also show and discuss the acceleranting gradient obtained vary with linac lenght and input power.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB105  
About • paper received ※ 15 May 2019       paper accepted ※ 24 May 2019       issue date ※ 21 June 2019  
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WEPRB115 Development of RF Interlock and Diagnostics Systems in SOLARIS Storage Ring 3082
 
  • M.A. Knafel, M. Madura
    Solaris National Synchrotron Radiation Centre, Jagiellonian University, Kraków, Poland
  • A.I. Wawrzyniak
    SOLARIS, Kraków, Poland
 
  The purpose of this document is to describe and asses the operation of various devices that have been developed, constructed and tested by RF team in NSRC SOLARIS . One of those devices is used as additional safety interlock for the tuning mechanism of main 100MHz active cavities. The other is a stripline feeding network, that in cooperation with BPM receiving network will excite the beam providing the diagnostics group with a new option for tune measurement. Each device shall have its principle of operation explained and construction details revealed. Finally, all devices will be assesed over their operational lifetime in our facility.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB115  
About • paper received ※ 15 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPTS012 RF Design Studies of a 1.3 GHz Normal Conducting CW Buncher for European X-FEL 3109
 
  • S. Lal, Y. Chen, H.J. Qian, H. Shaker, S. Shu, F. Stephan
    DESY Zeuthen, Zeuthen, Germany
  • V.V. Paramonov
    RAS/INR, Moscow, Russia
 
  A CW upgrade of European XFEL is under consideration, and CW electron injector is under R&D at DESY. One of the injector solutions is the LCLS-II like injector based on a normal conducting CW gun and buncher. RF design of a 1.3 GHz normal conducting buncher structure with accelerating voltage of ~ 400 kV, for such a CW injector is carried out at DESY Zeuthen site. The buncher structures with different geometrical shapes and numbers of cells are studied. The designs are optimized to have higher shunt impedance, higher mode separation and lower thermal power density for CW operation. Multipacting analysis and beam dynamics simulations are also presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS012  
About • paper received ※ 12 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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