IPAC2019 - List of Keywords (multipactoring)

Paper	Title	Other Keywords	Page
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 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, G. Shu, F. Stephan DESY Zeuthen, Zeuthen, Germany V.V. Paramonov RAS/INR, Moscow, Russia
	A CW upgrade of European XFEL is under consideration, and CW electron injector is under R&D at DESY. One of the injector solutions is the LCLS-II like injector based on a normal conducting CW gun and buncher. RF design of a 1.3 GHz normal conducting buncher structure with accelerating voltage of ~ 400 kV, for such a CW injector is carried out at DESY Zeuthen site. The buncher structures with different geometrical shapes and numbers of cells are studied. The designs are optimized to have higher shunt impedance, higher mode separation and lower thermal power density for CW operation. Multipacting analysis and beam dynamics simulations are also presented.
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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Paper

Title

Other Keywords

Page

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

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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

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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 TUXXPLS3 [5.892 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUXXPLS3

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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

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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.

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

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

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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

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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

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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.

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

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

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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.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB050

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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.

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

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

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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, G. Shu, F. Stephan
DESY Zeuthen, Zeuthen, Germany
V.V. Paramonov
RAS/INR, Moscow, Russia

A CW upgrade of European XFEL is under consideration, and CW electron injector is under R&D at DESY. One of the injector solutions is the LCLS-II like injector based on a normal conducting CW gun and buncher. RF design of a 1.3 GHz normal conducting buncher structure with accelerating voltage of ~ 400 kV, for such a CW injector is carried out at DESY Zeuthen site. The buncher structures with different geometrical shapes and numbers of cells are studied. The designs are optimized to have higher shunt impedance, higher mode separation and lower thermal power density for CW operation. Multipacting analysis and beam dynamics simulations are also presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS012

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paper received ※ 12 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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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.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS007

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

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