IPAC2021 - List of Keywords (flattop)

Paper	Title	Other Keywords	Page
TUPAB121	Photoinjector Drive Laser Temporal Shaping for Shanghai Soft X-Ray Free Electron Laser	laser, electron, cathode, FEL	1674
	C.L. Li, X.T. Wang, W.Y. Zhang Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China X.L. Dai SSRF, Shanghai, People’s Republic of China H.X. Deng, L. Feng, B. Liu, J.G. Wang SARI-CAS, Pudong, Shanghai, People’s Republic of China
	Shanghai soft X ray free electron laser (SXFEL) initial designed shape of the photocathode driver laser is flattop produced by α-BBO stacking. The advantage of this design is attractive in producing electron bunch with low initial emittance and high uniformity along the electron bunch. However, some unavoidable modulations are generated along the laser pulse which trigger the electron bunch modulation generated at the source, which is due to the fast response time (tens of femtosecond) of copper cathode. In order to eliminate the modulation of electron bunch, temporal Gaussian driver laser was designed and tested, measurement results show the electron bunch longitudinal modulation was removed. In this paper, we present two kinds of driver laser pulse temporal shaping methods based on α-BBO stacking and UV grating pair shaping. Moreover, corresponding electron bunch temporal profile are also presented.
	Poster TUPAB121 [2.469 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB121
About •	paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 25 August 2021
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TUPAB283	Feasibility Study of ChDR Diagnostic Device in the LHC	radiation, diagnostics, proton, electron	2139
	K. Łasocha Jagiellonian University, Kraków, Poland M. Bergamaschi, M. Krupa, K. Łasocha, T. Lefèvre, S. Mazzoni, N. Mounet, E. Senes CERN, Geneva, Switzerland D.M. Harryman JAI, Egham, Surrey, United Kingdom P. Karataev Royal Holloway, University of London, Surrey, United Kingdom A. Potylitsyn TPU, Tomsk, Russia A. Schloegelhofer TU Vienna, Wien, Austria
	In recent years Cherenkov Diffraction Radiation (ChDR) has been reported as a phenomenon suitable for various types of particle accelerator diagnostics. As it would typically work best for highly relativistic beam, past studies and experiments have been mostly focusing on the lepton machines. This contribution investigates the prospects on the utilization of ChDR as a diagnostic tool for the Large Hadron Collider (LHC). Based on theoretical considerations and simulation results we estimate the properties of the expected radiation, both in the incoherent and coherent domain, and we compare them with the requirements of the existing diagnostic systems. We also address the potential problem of the use of dielectric radiators in circular machines, where secondary electrons could potentially lead to the creation of electron clouds inside the beam pipe that may affect the radiator.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB283
About •	paper received ※ 14 May 2021 paper accepted ※ 18 June 2021 issue date ※ 02 September 2021
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WEPAB040	Characterization of Low Emittance Electron Beams Generated by Transverse Laser Beam Shaping	laser, emittance, electron, cathode	2690
	M. Groß, N. Aftab, P. Boonpornprasert, G.Z. Georgiev, J. Good, C. Koschitzki, M. Krasilnikov, X. Li, O. Lishilin, D. Melkumyan, S.K. Mohanty, R. Niemczyk, A. Oppelt, H.J. Qian, G. Shu, F. Stephan, G. Vashchenko DESY Zeuthen, Zeuthen, Germany Y. Chen, G. Loisch DESY, Hamburg, Germany I. Will MBI, Berlin, Germany
	Linac based X-ray free electron laser demand a high beam quality from the electron source, therefore RF photoinjectors are used to generate the electron bunches for state of the art beam brightness. One important figure of merit for these injectors is the transverse emittance of the generated electron beam, which can be minimized by shaping the photocathode laser pulses. Best performance can be achieved with ellipsoidal laser pulses, but 3D shaping is technically challenging. Typically, a quasi-uniform transverse laser profile is truncated from the Gaussian profile generated by the laser with an aperture to reduce the transverse nonlinear space charge forces. This is investigated in detail by optimizing the laser transverse profile at the Photoinjector Test facility at DESY in Zeuthen (PITZ), where photoinjector R&D is conducted for the E-XFEL and FLASH free electron lasers at DESY in Hamburg. In this contribution we present experimental results at high acceleration gradients (up to 60 MV/m) for both 250 pC and 500 pC. For a bunch charge of 500 pC an emittance reduction of about 30% compared to the commonly used transverse flat-top laser distribution was achieved.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB040
About •	paper received ※ 17 May 2021 paper accepted ※ 02 June 2021 issue date ※ 19 August 2021
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WEPAB178	Non-Adiabatic Longitudinal Bunch Manipulation at Flattop of the J-PARC MR	bunching, extraction, kicker, experiment	3023
	F. Tamura JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan C. Ohmori, Y. Sugiyama, M. Yoshii KEK, Tokai, Ibaraki, Japan
	The J-PARC MR delivers the high-intensity proton beams for the neutrino experiment. Eight bunches of high peak current are extracted by the extraction kickers, therefore the neutrino beam has a similar time structure. The new Intermediate Water Cherenkov Detector (IWCD) will be constructed for the future neutrino experiment and a low peak time structure is desired by the IWCD. Thus, we consider bunch manipulation at flattop of the MR for reducing the peak current. The manipulation requires a longer repetition period to extend the flattop. This reduces the output beam power. The manipulation should be quickly done to minimize the loss of the beam power. Also, the beam gap must be kept for the rise time of the extraction kicker. We propose a non-adiabatic bunch manipulation using the multiharmonic rf voltage. By using the neighbor harmonic of the accelerating harmonic, the first and eighth bunches can be decelerated and accelerated, respectively. After a certain period, the rf phase is flipped to pi for debunching. Thanks to the initial deceleration and acceleration, the beam gap for the kickers is kept. We present the concept and the longitudinal simulation result.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB178
About •	paper received ※ 17 May 2021 paper accepted ※ 25 June 2021 issue date ※ 28 August 2021
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WEPAB343	Inductive Adder Prototype for FCC-hh Injection Kicker System	kicker, injection, simulation, collider	3494
	D. Woog, M.J. Barnes, T. Kramer CERN, Geneva, Switzerland H. De Gersem TEMF, TU Darmstadt, Darmstadt, Germany
	The future circular collider (FCC) requires a highly reliable injection kicker system. Present day kicker systems often rely on thyratron-based pulse generators and a pulse forming network or line: the thyratron is susceptible to self-triggering. Hence, an alternative pulse generator topology, based on fast semiconductor switches, is considered for the FCC. One possibility is an inductive adder (IA). A prototype IA has been designed and built: the main challenges are the fast rise time, high output current, low system impedance and a 2.3 us pulse duration combined with low droop. This paper presents the results of measurements on the prototype IA where the rated output current and output voltage were achieved separately. Suggested improvements to the IA hardware are identified and proposals are presented that could help improve the kicker system performance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB343
About •	paper received ※ 16 May 2021 paper accepted ※ 01 July 2021 issue date ※ 17 August 2021
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WEPAB351	Requirements for an Inductive Voltage Adder as Driver for a Kicker Magnet with Short Circuit Termination	kicker, impedance, simulation, timing	3521
	J. Ruf, M.J. Barnes, T. Kramer CERN, Geneva 23, Switzerland M. Sack KIT, Karlsruhe, Germany
	At CERN pulse generators based on Thyratron switches and SF6 gas filled pulse forming lines, used for driving kicker magnets, are to be replaced with semiconductor technology. Preliminary investigations show the inductive voltage adder is suitable as a pulse generator for this application. To increase the magnetic field without raising the system voltage, a short-circuit termination is often applied to a kicker magnet. Because of the electrical length of a transmission line magnet, wave propagation needs to be considered. To allow for the wavefront reflected from the short-circuit termination back to the generator, a novel approach for an inductive adder architecture has been investigated. It is based on a modified generator interface, circulating the current back into the load, until the stored energy is absorbed at the end of the pulse. This approach allows for a smaller magnetic core size compared to a conventional design with a matched load. Moreover, it enables more energy-efficient operation involving smaller storage capacitors. This paper summarizes the conceptual design features and furthermore gives an overview of the parameter space for possible applications at CERN.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB351
About •	paper received ※ 18 May 2021 paper accepted ※ 11 June 2021 issue date ※ 17 August 2021
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THPAB286	Quadrupole Focusing Lenses for Heavy Ion Linac	DTL, focusing, quadrupole, operation	4359
	V. Skachkov, A.V. Kozlov, G. Kropachev, T. Kulevoy, D.A. Liakin, O.S. Sergeeva, V.S. Skachkov, Yu. Stasevich ITEP, Moscow, Russia
	Simulation results of pulsed current electromagnet quadrupoles with integral of the magnetic field gradient up to 7 T are presented. Magnets for the DTL and MEBT focusing channels are designing for the heavy-ion linac in Institute for Theoretical and Experimental Physics (ITEP - NRC "Kurchatov Institute"). Appropriate conditions which promise getting the magnetic lens parameters required at restrictions on the overall length <130 mm as well as on the beam aperture >45 mm are defined. It is shown that the channel acceptance to beam emittance ratio desired not less than 3 can be provided by conventional low-carbon steel up to a magnetic aperture of 50 mm in diameter while beyond this size permendur is out of competition. Some aspects of the pulsed power supply system are considered and main parameters of the pulse current generator (PCG) are given.
	Poster THPAB286 [0.701 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB286
About •	paper received ※ 14 May 2021 paper accepted ※ 30 June 2021 issue date ※ 02 September 2021
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THPAB331	High-Power Test of a Highly Over-Coupled X-Band RF Gun Driven by Short RF Pulses	gun, cathode, electron, wakefield	4432
	J.H. Shao, D.S. Doran, W. Liu, J.G. Power, C. Whiteford, E.E. Wisniewski ANL, Lemont, Illinois, USA C.-J. Jing, S.V. Kuzikov Euclid TechLabs, Solon, Ohio, USA X. Lu, P. Piot, W.H. Tan Northern Illinois University, DeKalb, Illinois, USA
	Beam brightness, a key figure of merit of RF photocathode guns, can be improved by increasing the cathode surface field which suppresses emittance growth from space charge. The surface field in normal-conducting structures is mainly limited by RF breakdown and it has been experimentally discovered that RF breakdown rate exponentially depends on RF pulse length. A highly over-coupled 1.5-cell X-band photocathode gun has been developed to be powered by 9 ns RF pulses with 3 ns rising time, 3 ns flat-top, and 3 ns falling time generated by an X-band metallic power extractor. In the recent experiment at Argonne Wakefield Accelerator facility, cathode surface field up to ~350 MV/m with a low breakdown rate has been obtained under ~250 MW input power. Strong beam loading from dark current was observed during RF conditioning and quickly recovered to a negligible level after the gun reached the maximum gradient. Detailed high-power test results and data analysis will be reported in this manuscript.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB331
About •	paper received ※ 25 May 2021 paper accepted ※ 14 July 2021 issue date ※ 23 August 2021
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Paper

Title

Other Keywords

Page

TUPAB121

Photoinjector Drive Laser Temporal Shaping for Shanghai Soft X-Ray Free Electron Laser

laser, electron, cathode, FEL

1674

C.L. Li, X.T. Wang, W.Y. Zhang
Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China
X.L. Dai
SSRF, Shanghai, People’s Republic of China
H.X. Deng, L. Feng, B. Liu, J.G. Wang
SARI-CAS, Pudong, Shanghai, People’s Republic of China

Shanghai soft X ray free electron laser (SXFEL) initial designed shape of the photocathode driver laser is flattop produced by α-BBO stacking. The advantage of this design is attractive in producing electron bunch with low initial emittance and high uniformity along the electron bunch. However, some unavoidable modulations are generated along the laser pulse which trigger the electron bunch modulation generated at the source, which is due to the fast response time (tens of femtosecond) of copper cathode. In order to eliminate the modulation of electron bunch, temporal Gaussian driver laser was designed and tested, measurement results show the electron bunch longitudinal modulation was removed. In this paper, we present two kinds of driver laser pulse temporal shaping methods based on α-BBO stacking and UV grating pair shaping. Moreover, corresponding electron bunch temporal profile are also presented.

Poster TUPAB121 [2.469 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB121

About •

paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 25 August 2021

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TUPAB283

Feasibility Study of ChDR Diagnostic Device in the LHC

radiation, diagnostics, proton, electron

2139

K. Łasocha
Jagiellonian University, Kraków, Poland
M. Bergamaschi, M. Krupa, K. Łasocha, T. Lefèvre, S. Mazzoni, N. Mounet, E. Senes
CERN, Geneva, Switzerland
D.M. Harryman
JAI, Egham, Surrey, United Kingdom
P. Karataev
Royal Holloway, University of London, Surrey, United Kingdom
A. Potylitsyn
TPU, Tomsk, Russia
A. Schloegelhofer
TU Vienna, Wien, Austria

In recent years Cherenkov Diffraction Radiation (ChDR) has been reported as a phenomenon suitable for various types of particle accelerator diagnostics. As it would typically work best for highly relativistic beam, past studies and experiments have been mostly focusing on the lepton machines. This contribution investigates the prospects on the utilization of ChDR as a diagnostic tool for the Large Hadron Collider (LHC). Based on theoretical considerations and simulation results we estimate the properties of the expected radiation, both in the incoherent and coherent domain, and we compare them with the requirements of the existing diagnostic systems. We also address the potential problem of the use of dielectric radiators in circular machines, where secondary electrons could potentially lead to the creation of electron clouds inside the beam pipe that may affect the radiator.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB283

About •

paper received ※ 14 May 2021 paper accepted ※ 18 June 2021 issue date ※ 02 September 2021

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reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPAB040

Characterization of Low Emittance Electron Beams Generated by Transverse Laser Beam Shaping

laser, emittance, electron, cathode

2690

M. Groß, N. Aftab, P. Boonpornprasert, G.Z. Georgiev, J. Good, C. Koschitzki, M. Krasilnikov, X. Li, O. Lishilin, D. Melkumyan, S.K. Mohanty, R. Niemczyk, A. Oppelt, H.J. Qian, G. Shu, F. Stephan, G. Vashchenko
DESY Zeuthen, Zeuthen, Germany
Y. Chen, G. Loisch
DESY, Hamburg, Germany
I. Will
MBI, Berlin, Germany

Linac based X-ray free electron laser demand a high beam quality from the electron source, therefore RF photoinjectors are used to generate the electron bunches for state of the art beam brightness. One important figure of merit for these injectors is the transverse emittance of the generated electron beam, which can be minimized by shaping the photocathode laser pulses. Best performance can be achieved with ellipsoidal laser pulses, but 3D shaping is technically challenging. Typically, a quasi-uniform transverse laser profile is truncated from the Gaussian profile generated by the laser with an aperture to reduce the transverse nonlinear space charge forces. This is investigated in detail by optimizing the laser transverse profile at the Photoinjector Test facility at DESY in Zeuthen (PITZ), where photoinjector R&D is conducted for the E-XFEL and FLASH free electron lasers at DESY in Hamburg. In this contribution we present experimental results at high acceleration gradients (up to 60 MV/m) for both 250 pC and 500 pC. For a bunch charge of 500 pC an emittance reduction of about 30% compared to the commonly used transverse flat-top laser distribution was achieved.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB040

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paper received ※ 17 May 2021 paper accepted ※ 02 June 2021 issue date ※ 19 August 2021

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WEPAB178

Non-Adiabatic Longitudinal Bunch Manipulation at Flattop of the J-PARC MR

bunching, extraction, kicker, experiment

3023

F. Tamura
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
C. Ohmori, Y. Sugiyama, M. Yoshii
KEK, Tokai, Ibaraki, Japan

The J-PARC MR delivers the high-intensity proton beams for the neutrino experiment. Eight bunches of high peak current are extracted by the extraction kickers, therefore the neutrino beam has a similar time structure. The new Intermediate Water Cherenkov Detector (IWCD) will be constructed for the future neutrino experiment and a low peak time structure is desired by the IWCD. Thus, we consider bunch manipulation at flattop of the MR for reducing the peak current. The manipulation requires a longer repetition period to extend the flattop. This reduces the output beam power. The manipulation should be quickly done to minimize the loss of the beam power. Also, the beam gap must be kept for the rise time of the extraction kicker. We propose a non-adiabatic bunch manipulation using the multiharmonic rf voltage. By using the neighbor harmonic of the accelerating harmonic, the first and eighth bunches can be decelerated and accelerated, respectively. After a certain period, the rf phase is flipped to pi for debunching. Thanks to the initial deceleration and acceleration, the beam gap for the kickers is kept. We present the concept and the longitudinal simulation result.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB178

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paper received ※ 17 May 2021 paper accepted ※ 25 June 2021 issue date ※ 28 August 2021

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WEPAB343

Inductive Adder Prototype for FCC-hh Injection Kicker System

kicker, injection, simulation, collider

3494

D. Woog, M.J. Barnes, T. Kramer
CERN, Geneva, Switzerland
H. De Gersem
TEMF, TU Darmstadt, Darmstadt, Germany

The future circular collider (FCC) requires a highly reliable injection kicker system. Present day kicker systems often rely on thyratron-based pulse generators and a pulse forming network or line: the thyratron is susceptible to self-triggering. Hence, an alternative pulse generator topology, based on fast semiconductor switches, is considered for the FCC. One possibility is an inductive adder (IA). A prototype IA has been designed and built: the main challenges are the fast rise time, high output current, low system impedance and a 2.3 us pulse duration combined with low droop. This paper presents the results of measurements on the prototype IA where the rated output current and output voltage were achieved separately. Suggested improvements to the IA hardware are identified and proposals are presented that could help improve the kicker system performance.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB343

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

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WEPAB351

Requirements for an Inductive Voltage Adder as Driver for a Kicker Magnet with Short Circuit Termination

kicker, impedance, simulation, timing

3521

J. Ruf, M.J. Barnes, T. Kramer
CERN, Geneva 23, Switzerland
M. Sack
KIT, Karlsruhe, Germany

At CERN pulse generators based on Thyratron switches and SF6 gas filled pulse forming lines, used for driving kicker magnets, are to be replaced with semiconductor technology. Preliminary investigations show the inductive voltage adder is suitable as a pulse generator for this application. To increase the magnetic field without raising the system voltage, a short-circuit termination is often applied to a kicker magnet. Because of the electrical length of a transmission line magnet, wave propagation needs to be considered. To allow for the wavefront reflected from the short-circuit termination back to the generator, a novel approach for an inductive adder architecture has been investigated. It is based on a modified generator interface, circulating the current back into the load, until the stored energy is absorbed at the end of the pulse. This approach allows for a smaller magnetic core size compared to a conventional design with a matched load. Moreover, it enables more energy-efficient operation involving smaller storage capacitors. This paper summarizes the conceptual design features and furthermore gives an overview of the parameter space for possible applications at CERN.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB351

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paper received ※ 18 May 2021 paper accepted ※ 11 June 2021 issue date ※ 17 August 2021

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THPAB286

Quadrupole Focusing Lenses for Heavy Ion Linac

DTL, focusing, quadrupole, operation

4359

V. Skachkov, A.V. Kozlov, G. Kropachev, T. Kulevoy, D.A. Liakin, O.S. Sergeeva, V.S. Skachkov, Yu. Stasevich
ITEP, Moscow, Russia

Simulation results of pulsed current electromagnet quadrupoles with integral of the magnetic field gradient up to 7 T are presented. Magnets for the DTL and MEBT focusing channels are designing for the heavy-ion linac in Institute for Theoretical and Experimental Physics (ITEP - NRC "Kurchatov Institute"). Appropriate conditions which promise getting the magnetic lens parameters required at restrictions on the overall length <130 mm as well as on the beam aperture >45 mm are defined. It is shown that the channel acceptance to beam emittance ratio desired not less than 3 can be provided by conventional low-carbon steel up to a magnetic aperture of 50 mm in diameter while beyond this size permendur is out of competition. Some aspects of the pulsed power supply system are considered and main parameters of the pulse current generator (PCG) are given.

Poster THPAB286 [0.701 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB286

About •

paper received ※ 14 May 2021 paper accepted ※ 30 June 2021 issue date ※ 02 September 2021

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THPAB331

High-Power Test of a Highly Over-Coupled X-Band RF Gun Driven by Short RF Pulses

gun, cathode, electron, wakefield

4432

J.H. Shao, D.S. Doran, W. Liu, J.G. Power, C. Whiteford, E.E. Wisniewski
ANL, Lemont, Illinois, USA
C.-J. Jing, S.V. Kuzikov
Euclid TechLabs, Solon, Ohio, USA
X. Lu, P. Piot, W.H. Tan
Northern Illinois University, DeKalb, Illinois, USA

Beam brightness, a key figure of merit of RF photocathode guns, can be improved by increasing the cathode surface field which suppresses emittance growth from space charge. The surface field in normal-conducting structures is mainly limited by RF breakdown and it has been experimentally discovered that RF breakdown rate exponentially depends on RF pulse length. A highly over-coupled 1.5-cell X-band photocathode gun has been developed to be powered by 9 ns RF pulses with 3 ns rising time, 3 ns flat-top, and 3 ns falling time generated by an X-band metallic power extractor. In the recent experiment at Argonne Wakefield Accelerator facility, cathode surface field up to ~350 MV/m with a low breakdown rate has been obtained under ~250 MW input power. Strong beam loading from dark current was observed during RF conditioning and quickly recovered to a negligible level after the gun reached the maximum gradient. Detailed high-power test results and data analysis will be reported in this manuscript.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB331

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paper received ※ 25 May 2021 paper accepted ※ 14 July 2021 issue date ※ 23 August 2021

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