Keyword: multipactoring
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MOPRB069 Generation of High Power Short Rf Pulses using an X-Band Metallic Power Extractor Driven by High Charge Multi-Bunch Train pick-up, experiment, acceleration, simulation 734
 
  • J.H. Shao, M.E. Conde, D.S. Doran, G. Ha, W. Liu, J.G. Power, C. Whiteford, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
  • H.B. Chen, M.M. Peng, J. Shi, H. Zha
    TUB, Beijing, People’s Republic of China
  • C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • J. Seok
    UNIST, Ulsan, Republic of Korea
 
  Short pulse two-beam acceleration (TBA) is a structure wakefield acceleration (SWFA) approach aiming to achieve gradient above 250 MV/m using rf pulses less than 20 ns. An X-band 11.7 GHz metallic power extractor has been developed as the power source to test accelerating structures in this extreme regime. The power extractor is designed to be driven by high charge bunches separated by 769.2 ps (9 times the X-band period) on an L-band 1.3 GHz beamline. In the recent experiment, ~280 MW rf pulses with 3 ns flat-top have been measured by a coaxial rf pickup when driven by 8-bunch trains with a total charge of ~500 nC. The power level is ~50% lower than the theoretical prediction and simulation. Experimental investigation suggests that the missing power was mainly caused by the multipacting issue inside the rf pickup, which could be eliminated by a newly-designed directional coupler.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB069  
About • paper received ※ 19 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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MOPTS023 Conditioning of the Frontline Cavities of the MYRRHA Injector rfq, cavity, electron, MMI 895
 
  • S. Lamprecht, T. Conrad, K. Kümpel, N.F. Petry, H. Podlech
    IAP, Frankfurt am Main, Germany
  • J. Belmans, D. Davin, W. De Cock, F. Pompon, D. Vandeplassche
    SCK•CEN, Mol, Belgium
 
  The MYRRHA Project (Multi-purpose hYbrid Research Reactor for High-tech Applications) in Mol, Belgium, is an upcoming accelerator driven system (ADS) for the transmutation of long-living radioactive waste. In the injector section of the accelerator, consisting of a 4-rod RFQ and a normal conducting CH-cavity section, the protons will be accelerated up to 17 MeV before entering the superconducting gap-spoke cavity section with an output energy of 600 MeV. A shortened test-injector with an output energy of 5.9 MeV is currently being installed at the SCK. CEN in Louvein-la- Neuve, Belgium. This test-injector serves the purpose of testing the reliability of the planned injector. When commissioning a cavity, it first has to be fed very little power to avoid damage to the structure by flashovers, discharges and multipacting. The power is then slowly increased up to full operation level. In this process, the surfaces are cleaned by heating/outgasing so that the effects disturbing operation described above do no longer occur. This paper will report on the status of the conditioning of the 176.1 MHz 4-rod RFQ up to 120 kW of the MYRRHA-injector and additional measurements concerning the gap voltage which are currently being performed at the SCK. CEN.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS023  
About • paper received ※ 13 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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TUXXPLS3 The Design Optimization of the Dielectric Assist Accelerating Structure for Better Heat and Gas Transfer cavity, vacuum, embedded, lattice 1179
 
  • S. Mori, M. Yoshida
    KEK, Ibaraki, Japan
  • D. Sato
    AIST, Tsukuba, Ibaraki, Japan
 
  The dielectric-assist accelerating (DAA) structure is a dielectric-inserted normal-conducting cavity, which provides high Q value at room temperature. This accelerating structure is composed of dielectric disks and a dielectric cylindrical layer inserted in a copper cavity. For the realistic operation, the removal of heat from the dielectric cells and the vacuum evacuation of gas inside the cylindrical layers have not considered yet. In order to solve the problems, we propose the optimized design of the DAA structure, where the extended part of the dielectric disk is embedded in the copper cavity and the choke structure is applied. We show the result of the electromagnetic-field simulation of the extended DAA structure and the thermal simulation to clarify the relation between a duty factor and maximum temperature of the dielectric cells.  
slides icon Slides TUXXPLS3 [5.892 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUXXPLS3  
About • paper received ※ 30 April 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPMP051 MULTIPACTOR SUPPRESSION BY LASER ABLATION SURFACE ENGINEERING FOR SPACE APPLICATIONS electron, laser, GUI, controls 1365
 
  • R. Valizadeh, A.N. Hannah, O.B. Malyshev, B.S. Sian
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • J.S. Colligon
    University of Huddersfield, Huddersfield, United Kingdom
  • Y. Dan
    Hitachi High-Technologies Corp., Ibaraki-ken, Japan
  • V. R. Dhanak
    The University of Liverpool, Liverpool, United Kingdom
  • J. Mutch
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  • B.S. Sian
    UMAN, Manchester, United Kingdom
  • N. Sykes
    Micronanics Laser Solution Center, Didcot, United Kingdom
 
  Developing a surface with low Secondary Electron Yield (SEY) is one of the main ways of mitigating electron cloud and beam-induced electron multipacting in high-energy charged particle accelerators and space-borne RF equipment for communication purposes. In this study we report on the secondary electron yield (SEY) measured from silver coated aluminium alloy as-received and after laser ablation surface engineering (LASE). Analysis shows the SEY can be reduced by 43% using LASE. EDX and SEM analysis shows it is possible to reduce the SEY whilst maintaining the original surface composition.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP051  
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPTS013 Characterization of an Electron Gun Test Setup Based on Multipacting cavity, electron, cathode, gun 1961
 
  • C. Henkel, W. Hillert, V. Miltchev
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • K. Flöttmann
    DESY, Hamburg, Germany
 
  A multipacting electron gun (MEG) is a micro-pulse electron source, based on secondary electron emission in a resonant microwave cavity structure, for the generation of low emittance electron bunches in continuous wave operation. Based on numerical simulations, an experimental test setup for low-energy electron beams at 3 GHz has been established. In this contribution we show a detailed description and characterization of the RF test stand, supported by first results on charge collection measurements of the output current with respect to important operational parameters like power transmission and modifiable mechanical dimensions in the assembly of the experiment. This is a milestone in the development of a MEG setup for higher energetic electron beams and subsequent investigation of essential beam characteristics like emittance and energy distribution for the optimization with regard to best possible beam quality and future fields of application.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS013  
About • paper received ※ 30 April 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB030 Commissioning of RF System of the 200 MeV Proton Cyclotron cavity, cyclotron, MMI, coupling 2877
 
  • G. Chen, C. Chao, G. Liu, X.Y. Long, Z. Peng, C.S. Yu, X. Zhang, Y. Zhao
    ASIPP, Hefei, People’s Republic of China
  • L. Calabretta, A.C. Caruso
    INFN/LNS, Catania, Italy
  • O. Karamyshev, G.A. Karamysheva, G. Shirkov
    JINR, Dubna, Moscow Region, Russia
 
  Funding: (1) National Natural Science Foundation of China under grant No. 11775258, 11575237; (2) International Sci-entific and Technological Cooperation Project of An-hui (grant No. 1704e1002207).
The SC200 superconducting accelerator which is designed for proton therapy is currently under con-struction. The RF (Radio Frequency) system has been designed and constructed as a subsystem of the SC200. To verify the stability of the RF system, a high-power feeding test was performed for the cavity. This paper mainly reports on the overview of RF systems and the prelimary high-power commissioning, as well as the problems found and improvements made during the commissioning process. The results show that the RF system has initially achieved the designed goal, and each loop (amplitude, tuning, phase) can work effec-tively. The cavity can operate in a ~50 kW continuous wave state. Next, the formal RF conditioning will be carried out after the complete assembly of cyclotron, so as to confirm the cavity can run smoothly under 80 kW, which is part of the whole commissioning process.
 
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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WEPRB032 Superconducting Elliptical Cavities Developed in IMP for the CiADS cavity, HOM, operation, simulation 2883
 
  • Y.L. Huang, Y. He, R. Huang, T.C. Jiang, L.B. Liu, S.H. Liu, T. Tan, R.X. Wang, Z.J. Wang, S.H. Zhang, S.X. Zhang
    IMP/CAS, Lanzhou, People’s Republic of China
 
  Multicell superconducting radio frequency (SRF) ellip-tical cavities are proposed for efficient acceleration of proton beam in the Chinese initiative Accelerator Driven Subcritical System (CiADS). Two families of such cavities will be used in the driver SRF Linac, the first family corresponding to βopt=0.62 cavities that will be used to accelerate the H+ beam from 175 MeV to 377 MeV and the second family corresponding to βopt=0.82 cavities that will accelerate the H+ beam from 377 MeV to 500 MeV, with the possibility to upgrade to 1 GeV and higher. The electromagnetic optimization of the cavities with the HOM, wakefield and multipacting analysis will be dis-cussed in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB032  
About • paper received ※ 14 May 2019       paper accepted ※ 23 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 cavity, klystron, simulation, electron 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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WEPRB050 Multipacting Studies of the Coaxial Coupler for BNCT DTL simulation, DTL, impedance, neutron 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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WEPRB058 Combined Field Emission and Multipactor Simulation in High Gradient RF Accelerating Structures electron, simulation, cavity, GUI 2940
 
  • D. Banon-Caballero
    IFIC, Valencia, Spain
  • N. Catalán Lasheras, K. T. Szypula, W. Wuensch
    CERN, Geneva, Switzerland
  • A. Faus-Golfe
    LAL, Orsay, France
  • B. Gimeno
    UVEG, Burjasot (Valencia), Spain
 
  Field emitted electrons have important consequences in the operation of high-gradient RF accelerating structures both by generating so-called dark currents and initiating RF breakdown. The latter is an important limitation of the performance in such devices. Another kind of vacuum discharge that primarily affects the operation of lower-field RF components, for example those used in space applications, is multipactor. Theoretical simulations using CST Particle Studio, show that field emitted electrons generated in the high field regions of high-gradient accelerating cavities migrate to low field regions under ponderomotive forces potentially triggering multipactor there. This phenomenon is an interplay between high field and low field processes which may have as a consequence that multipactor actually affects to the performance of high-gradient cavities because field emitted electrons might reduce the timescales for the onset of multipactor.  
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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WEPTS012 RF Design Studies of a 1.3 GHz Normal Conducting CW Buncher for European X-FEL simulation, impedance, coupling, cavity 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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THPTS007 MYRRHA 80 kW CW RF Coupler Design cavity, electron, vacuum, simulation 4115
 
  • Y. Gómez Martínez, M.A. Baylac, D. Bondoux, F. Bouly, P.-O. Dumont
    LPSC, Grenoble Cedex, France
  • S. Blivet, C. Joly, J. Lesrel, H. Saugnac
    IPN, Orsay, France
  • W. Kaabi
    LAL, Orsay, France
 
  MYRRHA [1] (Multi Purpose Hybrid Reactor for High Tech Applications) is an Accelerator Driven System (ADS) project. Its superconducting linac will provide a 600 MeV - 4 mA proton beam. The first project phase based on a 100 MeV linac is launched. The Radio-Frequency (RF) couplers have been designed to handle 80 kW CW at 352.2 MHz. This paper describes the thermal, mechanical and RF studies leading to the final design of the RF coupler.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS007  
About • paper received ※ 10 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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