SRF2019 - List of Keywords (gun)

Paper	Title	Other Keywords	Page
MOP004	Preparation of Pb-Photocathodes at National Centre for Nuclear Research in Poland – State of the Art	cathode, electron, plasma, laser	25
	J. Lorkiewicz, I. Cieślik, P.J. Czuma, A.M. Kosińska, R. Nietubyć NCBJ, Świerk/Otwock, Poland J.K. Sekutowicz DESY, Hamburg, Germany
	Funding: We are currently using a financial support within "PolFEL - Polish Free Electron Laser" cofounded by the European Regional Development Fund. R&D activities related to preparation of the superconducting Pb photocathode layer on niobium substrate are ongoing at the National Centre for Nuclear Research (NCBJ) in cooperation with DESY, HZDR, HZB, BNL and other research institutes. The activities are part of the R&D program at DESY for the cw-upgrade of E-XFEL and for the newly approved free electron laser facility PolFEL to be built and operated at NCBJ. The optimization results obtained for the lead deposition on niobium and smoothing of the coated layers are reported. The photocathodes samples were tested for their surface morphology, microstructure and quantum efficiency in terms of the impact on the operation of all-superconducting RF electron injector, proposed for both facilities.
	Poster MOP004 [1.446 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP004
About •	paper received ※ 23 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019
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MOP035	Cryogenic Infrastructure at BESSY II – Current Installations and Future Developments	cryogenics, cavity, storage-ring, radiation	131
	S. Heling, W. Anders, J. Heinrich, A. Hellwig, K. Janke, S. Rotterdam HZB, Berlin, Germany
	In Berlin-Adlershof the Helmholtz-Zentrum Berlin (HZB) is operating the synchrotron radiation source BESSY II. Two superconducting wave-length shifter magnets are built-in the storage ring of BESSY II which are cooled with liquid helium. Additionally several test facilities for superconducting cavities are operated at HZB needing helium at 1.8 K. The required helium is supplied by two helium liquefiers. Parallel to operation of the existing facilities the BERLinPro project will qualify as test facility for ERL science and technology. In order to guarantee the required supply with helium at different temperature levels one of the existing helium liquefiers has been relocated to the new accelerator building and the existing cryogenic infrastructure has been upgraded with a new 10 000 L dewar, three valve boxes, a cold compressor box, warm pumps and a 80 K helium system. This paper specifies the setup of the above described helium cryoplants in detail and gives insight into the challenges of development. The paper concludes with an outlook of the upcoming developments of the cryogenic infrastructure at HZB.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP035
About •	paper received ※ 20 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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MOP065	Upgrade of the S-DALINAC Injector Capture Section	cavity, linac, MMI, target	227
	S. Weih, M. Arnold, J. Enders, N. Pietralla TU Darmstadt, Darmstadt, Germany D.B. Bazyl, H. De Gersem, W.F.O. Müller TEMF, TU Darmstadt, Darmstadt, Germany
	Funding: Work supported by DFG through GRK 2128 "AccelencE" The superconducting injector section of the S-DALINAC (superconducting Darmstadt linear electron accelerator) [1] constists of two cryomodules with three 3-GHz SRF cavities in total. The first cavity of this pre-accelerator is currently a 5-cell structure designed for relativistic particle velocities. Since the gun delivers a 250 keV beam (β=0.74), this cavity is not suited for an efficient capture of the low-energy electron bunches provided by the normal-conducting section of the injector. Beam dynamics simulations and operational experience have shown a large low-energy tail in the phase-space distribution of the bunch downstream of the injector, which arises from the large phase-slippage during the capture in the 5-cell. It is therefore intended to replace the cavity with a beta-adapted 6-cell, re-using most of the cryostat parts. This contribution presents the status of the injector upgrade and the layout and manufacturing status of the new cavity. *N. Pietralla, Nuclear Physics News, Vol. 28, No. 2, 4 (2018)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP065
About •	paper received ※ 21 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019
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MOP100	Design Upgrades of the Next Superconducting RF Gun for ELBE	SRF, cavity, cathode, cryomodule	326
	J. Teichert, A. Arnold, S. Ma, P. Murcek, J. Schaber, H. Vennekate, R. Xiang, P.Z. Zwartek HZDR, Dresden, Germany K. Zhou CAEP/IAE, Mianyang, Sichuan, People’s Republic of China
	Funding: Funding is provided by the China Scholarship Council. At the ELBE user facility a superconducting RF photoinjector has been in operation since several years. The injector is routinely applied for THz radiation production in user beam experiments. For future applications higher bunch charges, shorter pulses and lower transverse emittances are required. Thus it is planned to replace this SRF gun by a next version with an RF cavity reaching a higher acceleration gradient. We also present improvements concerning the SC solenoid and the photocathode exchange system and report on the status of construction and testing of this SRF gun cryomodule.
	Poster MOP100 [2.199 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP100
About •	paper received ※ 27 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019
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MOP105	A Superconducting Magnetic Shield for the Photoelectron Injector of BERLinPro	solenoid, cavity, shielding, operation	335
	J. Völker, A. Frahm, A. Jankowiak, S. Keckert, J. Knobloch, G. Kourkafas, O. Kugeler, A. Neumann, H. Plötz HZB, Berlin, Germany
	Magnetic fields are a big issue for SRF cavities, especially in areas with strong electromagnets or ferromagnetic materials. Magnetic shieldings consisting of metal alloys with high magnetic permeability are often used to reroute the external magnetic flux from the cavity region. Those Mu metal shields are typically designed for weak magnetic fields like Earth’s magnetic field. Next to strong magnetic field sources like superconducting (SC) solenoids, those shields can be easily saturated resulting in a degradation of the shielding efficiency and a permanent magnetization. For the photoinjector of BERLinPro a new SC solenoid will be installed inside the cryomodule next to the SRF gun cavity. Calculations show that the fringe fields of the solenoid during operation can saturate the cavity Mu-metal shields. Therefore we designed an SC magnetic shield placed between solenoid and cavity shield to protect the latter during magnet operation. In this paper we will present the design and first measurements of this SC magnetic shield.
	Poster MOP105 [2.011 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP105
About •	paper received ※ 04 July 2019 paper accepted ※ 14 August 2019 issue date ※ 14 August 2019
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TUP100	Thermal Load Studies on the Photocathode Insert with Exchangeable Plug for the BERLinPro SRF-Photoinjector	cathode, SRF, experiment, cavity	705
	J. Kühn, N. Al-Saokal, M. Bürger, M. Dirsat, A. Frahm, A. Jankowiak, T. Kamps, G. Klemz, S. Mistry, A. Neumann, H. Plötz HZB, Berlin, Germany
	For the operation of an SRF photoinjector a well-functioning and efficient cooling system of the photocathode is necessary. A test experiment was set up of the photocathode cooling system based on the original components, which we call thermal contact experiment (TCX). We present the results of our thermal load studies on the photocathode insert with exchangeable photocathode plug. The goal was to test all components before they are installed in the cold string of the BERLinPro SRF-Photoinjector to ensure the operation of very sensitive semiconductor photocathodes. The tests include the investigation of the cooling performance, the thermal load management and the mechanical stability of the photocathode insert.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP100
About •	paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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THP026	Initial Operation of the LCLS-II Electron Source	cavity, vacuum, cathode, operation	891
	C. Adolphsen, A.L. Benwell, G.W. Brown, M.P. Dunning, S. Gilevich, K. Grouev, X. Liu, J.F. Schmerge, T. Vecchione, F.Y. Wang, F. Zhou SLAC, Menlo Park, California, USA G. Huang, M.J. Johnson, T.H. Luo, F. Sannibale, S.P. Virostek LBNL, Berkeley, California, USA
	Funding: This work supported under DOE Contract DE-AC02-76SF00515 The Early Injector Commissioning program for LCLS-II aims to demonstrate CW electron beam production this year in the first two meters of the injector that includes the room-temperature 185.7 MHz single-cell gun and the 1.3 GHz two-cell buncher cavity. These cavities were designed and built by LBNL based on their experience with similar ones for their Advanced Photo-Injector Experiment (APEX) program. With the 258 nm laser system and Cs2Te cathodes, bunches of up to 300 pC are expected at rates as high as 1 MHz. The paper presents results from this program including the vacuum levels achieved, RF processing and field control experience, dark current measurements and laser and beam characterization.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP026
About •	paper received ※ 26 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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THP032	SRF Gun and SRF Linac Driven THz at ELBE Successfully in User Operation	SRF, radiation, electron, linac	915
	R. Xiang, A. Arnold, P.E. Evtushenko, S. Kovalev, U. Lehnert, P.N. Lu, S. Ma, P. Michel, P. Murcek, A.A. Ryzhov, J. Schaber, Ch. Schneider, J. Teichert HZDR, Dresden, Germany H. Vennekate RI Research Instruments GmbH, Bergisch Gladbach, Germany I. Will MBI, Berlin, Germany
	Funding: The work was partly supported by the German Federal Ministry of Education and Research (BMBF) grant 05K12CR1 and Deutsche Forschungsgemeinschaft (DFG) project (XI 10⁶/2-1). The first all-SRF accelerator driven THz source has been operated as a user facility since 2018 at ELBE radiation center. The CW electron beam is extracted from SRF gun II, accelerated to relativistic energies and compressed to sub-ps length in the ELBE SRF linac with a chicane. THz pulses are produced by pass-ing the short electron bunches through a diffraction radiator (CDR) and an undulator. The coherent THz power increases quadratically with bunch charge. The pulse energy up to 10 µJ at 0.3 THz with 100 kHz has been generated.
	Poster THP032 [1.207 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP032
About •	paper received ※ 02 July 2019 paper accepted ※ 04 July 2019 issue date ※ 14 August 2019
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THP080	Status of the All Superconducting Gun Cavity at DESY	cavity, cathode, SRF, niobium	1087
	E. Vogel, S. Barbanotti, A. Brinkmann, Th. Buettner, J.I. Iversen, K. Jensch, D. Klinke, D. Kostin, W.-D. Möller, A. Muhs, J. Schaffran, M. Schmökel, J.K. Sekutowicz, S. Sievers, L. Steder, N. Steinhau-Kühl, A. Sulimov, J.H. Thie, H. Weise, M. Wenskat, M. Wiencek, L. Winkelmann, B. van der Horst DESY, Hamburg, Germany
	At DESY, the development of a 1.6-cell, 1.3 GHz all superconducting gun cavity with a lead cathode attached to its back wall is ongoing. The special features of the structure like the back wall of the half-cell and cathode hole require adaptations of the procedures used for the treatment of nine-cell TESLA cavities. Unsatisfactory test results of two prototype cavities motivated us to re-consider the back-wall design and production steps. In this contribution we present the status of the modified cavity design including accessories causing accelerating field asymmetries, like a pick up antenna located at the back wall and fundamental power- and HOM couplers. Additionally, we discuss preliminary considerations for the compensation of kicks caused by these components.
	Poster THP080 [7.365 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP080
About •	paper received ※ 20 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019
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THP081	A Cryocooled Normal Conducting and Superconducting Hybrid CW RF Gun	cavity, cathode, acceleration, emittance	1091
	H.J. Qian, G. Shu, F. Stephan DESY Zeuthen, Zeuthen, Germany S. Barbanotti, B. Petersen, E. Vogel DESY, Hamburg, Germany A.A. Gorchakov, M. Gusarova MEPhI, Moscow, Russia
	Continuous wave (CW) photoinjectors have seen great progress in the last decades, such as DC gun, superconducting RF (SRF) gun and normal conducting (NC) gun. Developments of Free electron lasers and electron microscopy in the CW mode are pushing for further improvements of CW guns towards higher acceleration gradient, higher beam energy and compatibility with high QE cathodes for better beam brightness. Current SC gun gradient is limited by the cathode cell due to the complication of a cathode back plane and a normal conducting cathode plug, and R&D on SC gun improvement is ongoing. A high gradient cryocooled CW NC gun was proposed to house the high QE cathode, and a SC cavity immediately nearby gives further energy acceleration. In this paper, further RF optimization of the NC gun and ASTRA simulations of such a hybrid photoinjector are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP081
About •	paper received ※ 25 June 2019 paper accepted ※ 03 July 2019 issue date ※ 14 August 2019
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THP082	Geometry Dependent Beam Dynamics of a 3.5-cell SRF Gun Cavity at ELBE	SRF, cavity, emittance, electron	1095
	K. Zhou CAEP/IAE, Mianyang, Sichuan, People’s Republic of China A. Arnold, S. Ma, J. Schaber, J. Teichert, R. Xiang HZDR, Dresden, Germany
	In order to optimize the next generation SRF gun at HZDR ELBE radiation source, the impact on beam dynamics from the SRF cavity geometry needs to be investigated. This paper presents an analysis on the electromagnetic fields and output electron beam qualities, by changing the geometry parameters of a 3.5-cell SRF gun cavity. The simulation results show the higher electric field ratio in the first half cell to the TESLA like cell, the better beam parameters we can obtain, which, however, will also lead to a higher Emax/E0 and Bmax/E0.
	Poster THP082 [1.935 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP082
About •	paper received ※ 22 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019
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FRCAB4	Development of High Intensity, High Brightness, CW SRF Gun with Bi-Alkali Photocathode	cathode, SRF, cavity, target	1219
	T. Konomi, Y. Honda, E. Kako, Y. Kobayashi, S. Michizono, T. Miyajima, H. Sakai, K. Umemori, S. Yamaguchi KEK, Ibaraki, Japan
	Superconducting conduction electron guns can realize high acceleration voltage and high beam repetition. KEK has been developing the 1.3 GHz elliptical type 1.5 cell superconducting RF gun to investigate fundamental performance. The surface cleaning methods and tools were developed by using KEK SRF gun cavity #1 and surface peak electric field reached to 75 MV/m without field emission. We will apply this technique to the SRF gun cavity #2 for beam operation. The gun cavity #2 equips the helium jacket, frequency tuner cathode position adjuster to operate the electron beam. The RF structure was designed based on the gun cavity #1. The cathode rod is made of Nb. The photocathode deposited on the cathode rod will be cool down to 2K to minimize thermal emittance. The fabrication of the gun cavity #2 and helium jacket were completed. 4 times vertical tests were carried out. We will report the vertical test results and preparation of the horizontal test.
	Slides FRCAB4 [10.826 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB4
About •	paper received ※ 23 June 2019 paper accepted ※ 03 July 2019 issue date ※ 14 August 2019
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FRCAB5	Performance of 112 MHz SRF Gun at BNL	cathode, electron, SRF, cavity	1223
	T. Xin, I. Ben-Zvi, J.C. Brutus, C. Folz, T. Hayes, P. Inacker, Y.C. Jing, D. Kayran, V. Litvinenko, J. Ma, G.J. Mahler, M. Mapes, K. Mernick, T.A. Miller, G. Narayan, P. Orfin, I. Pinayev, S. Polizzo, T. Rao, F. Severino, J. Skaritka, K.S. Smith, R. Than, J.E. Tuozzolo, E. Wang, G. Wang, Q. Wu, B.P. Xiao, W. Xu, A. Zaltsman BNL, Upton, New York, USA S.A. Belomestnykh Fermilab, Batavia, Illinois, USA C.H. Boulware, T.L. Grimm Niowave, Inc., Lansing, Michigan, USA K. Mihara Stony Brook University, Stony Brook, USA I. Petrushina SUNY SB, Stony Brook, New York, USA K. Shih SBU, Stony Brook, New York, USA
	Funding: This work is funded by the DOE FOA (No. DE-FOA-0000632) and National Science Foundation (Award No. PHY-1415252). A 112 MHz SRF electron photoinjector (gun) was developed at Brookhaven National Laboratory to produce high-brightness and high-bunch-charge bunches for the coherent electron cooling proof-of-principle experiment. The gun is designed to deliver electrons with a kinetic energy of up to 2 MeV. Electrons are generated by illuminating a high quantum efficiency (QE) K2CsSb photoemission layer with a green laser operating at a wavelength of 532 nm. The gun was able to generating 3 nC bunches at 1.7 MeV. The design goals, fabrication, performance and operational experience are reported here.
	Slides FRCAB5 [3.984 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB5
About •	paper received ※ 22 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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Paper

Title

Other Keywords

Page

MOP004

Preparation of Pb-Photocathodes at National Centre for Nuclear Research in Poland – State of the Art

cathode, electron, plasma, laser

25

J. Lorkiewicz, I. Cieślik, P.J. Czuma, A.M. Kosińska, R. Nietubyć
NCBJ, Świerk/Otwock, Poland
J.K. Sekutowicz
DESY, Hamburg, Germany

Funding: We are currently using a financial support within "PolFEL - Polish Free Electron Laser" cofounded by the European Regional Development Fund.
R&D activities related to preparation of the superconducting Pb photocathode layer on niobium substrate are ongoing at the National Centre for Nuclear Research (NCBJ) in cooperation with DESY, HZDR, HZB, BNL and other research institutes. The activities are part of the R&D program at DESY for the cw-upgrade of E-XFEL and for the newly approved free electron laser facility PolFEL to be built and operated at NCBJ. The optimization results obtained for the lead deposition on niobium and smoothing of the coated layers are reported. The photocathodes samples were tested for their surface morphology, microstructure and quantum efficiency in terms of the impact on the operation of all-superconducting RF electron injector, proposed for both facilities.

Poster MOP004 [1.446 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP004

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paper received ※ 23 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019

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MOP035

Cryogenic Infrastructure at BESSY II – Current Installations and Future Developments

cryogenics, cavity, storage-ring, radiation

131

S. Heling, W. Anders, J. Heinrich, A. Hellwig, K. Janke, S. Rotterdam
HZB, Berlin, Germany

In Berlin-Adlershof the Helmholtz-Zentrum Berlin (HZB) is operating the synchrotron radiation source BESSY II. Two superconducting wave-length shifter magnets are built-in the storage ring of BESSY II which are cooled with liquid helium. Additionally several test facilities for superconducting cavities are operated at HZB needing helium at 1.8 K. The required helium is supplied by two helium liquefiers. Parallel to operation of the existing facilities the BERLinPro project will qualify as test facility for ERL science and technology. In order to guarantee the required supply with helium at different temperature levels one of the existing helium liquefiers has been relocated to the new accelerator building and the existing cryogenic infrastructure has been upgraded with a new 10 000 L dewar, three valve boxes, a cold compressor box, warm pumps and a 80 K helium system. This paper specifies the setup of the above described helium cryoplants in detail and gives insight into the challenges of development. The paper concludes with an outlook of the upcoming developments of the cryogenic infrastructure at HZB.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP035

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paper received ※ 20 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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MOP065

Upgrade of the S-DALINAC Injector Capture Section

cavity, linac, MMI, target

227

S. Weih, M. Arnold, J. Enders, N. Pietralla
TU Darmstadt, Darmstadt, Germany
D.B. Bazyl, H. De Gersem, W.F.O. Müller
TEMF, TU Darmstadt, Darmstadt, Germany

Funding: Work supported by DFG through GRK 2128 "AccelencE"
The superconducting injector section of the S-DALINAC (superconducting Darmstadt linear electron accelerator) [1] constists of two cryomodules with three 3-GHz SRF cavities in total. The first cavity of this pre-accelerator is currently a 5-cell structure designed for relativistic particle velocities. Since the gun delivers a 250 keV beam (β=0.74), this cavity is not suited for an efficient capture of the low-energy electron bunches provided by the normal-conducting section of the injector. Beam dynamics simulations and operational experience have shown a large low-energy tail in the phase-space distribution of the bunch downstream of the injector, which arises from the large phase-slippage during the capture in the 5-cell. It is therefore intended to replace the cavity with a beta-adapted 6-cell, re-using most of the cryostat parts. This contribution presents the status of the injector upgrade and the layout and manufacturing status of the new cavity.
*N. Pietralla, Nuclear Physics News, Vol. 28, No. 2, 4 (2018)

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP065

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paper received ※ 21 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019

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MOP100

Design Upgrades of the Next Superconducting RF Gun for ELBE

SRF, cavity, cathode, cryomodule

326

J. Teichert, A. Arnold, S. Ma, P. Murcek, J. Schaber, H. Vennekate, R. Xiang, P.Z. Zwartek
HZDR, Dresden, Germany
K. Zhou
CAEP/IAE, Mianyang, Sichuan, People’s Republic of China

Funding: Funding is provided by the China Scholarship Council.
At the ELBE user facility a superconducting RF photoinjector has been in operation since several years. The injector is routinely applied for THz radiation production in user beam experiments. For future applications higher bunch charges, shorter pulses and lower transverse emittances are required. Thus it is planned to replace this SRF gun by a next version with an RF cavity reaching a higher acceleration gradient. We also present improvements concerning the SC solenoid and the photocathode exchange system and report on the status of construction and testing of this SRF gun cryomodule.

Poster MOP100 [2.199 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP100

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paper received ※ 27 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019

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MOP105

A Superconducting Magnetic Shield for the Photoelectron Injector of BERLinPro

solenoid, cavity, shielding, operation

335

J. Völker, A. Frahm, A. Jankowiak, S. Keckert, J. Knobloch, G. Kourkafas, O. Kugeler, A. Neumann, H. Plötz
HZB, Berlin, Germany

Magnetic fields are a big issue for SRF cavities, especially in areas with strong electromagnets or ferromagnetic materials. Magnetic shieldings consisting of metal alloys with high magnetic permeability are often used to reroute the external magnetic flux from the cavity region. Those Mu metal shields are typically designed for weak magnetic fields like Earth’s magnetic field. Next to strong magnetic field sources like superconducting (SC) solenoids, those shields can be easily saturated resulting in a degradation of the shielding efficiency and a permanent magnetization. For the photoinjector of BERLinPro a new SC solenoid will be installed inside the cryomodule next to the SRF gun cavity. Calculations show that the fringe fields of the solenoid during operation can saturate the cavity Mu-metal shields. Therefore we designed an SC magnetic shield placed between solenoid and cavity shield to protect the latter during magnet operation. In this paper we will present the design and first measurements of this SC magnetic shield.

Poster MOP105 [2.011 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP105

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paper received ※ 04 July 2019 paper accepted ※ 14 August 2019 issue date ※ 14 August 2019

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TUP100

Thermal Load Studies on the Photocathode Insert with Exchangeable Plug for the BERLinPro SRF-Photoinjector

cathode, SRF, experiment, cavity

705

J. Kühn, N. Al-Saokal, M. Bürger, M. Dirsat, A. Frahm, A. Jankowiak, T. Kamps, G. Klemz, S. Mistry, A. Neumann, H. Plötz
HZB, Berlin, Germany

For the operation of an SRF photoinjector a well-functioning and efficient cooling system of the photocathode is necessary. A test experiment was set up of the photocathode cooling system based on the original components, which we call thermal contact experiment (TCX). We present the results of our thermal load studies on the photocathode insert with exchangeable photocathode plug. The goal was to test all components before they are installed in the cold string of the BERLinPro SRF-Photoinjector to ensure the operation of very sensitive semiconductor photocathodes. The tests include the investigation of the cooling performance, the thermal load management and the mechanical stability of the photocathode insert.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP100

About •

paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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THP026

Initial Operation of the LCLS-II Electron Source

cavity, vacuum, cathode, operation

891

C. Adolphsen, A.L. Benwell, G.W. Brown, M.P. Dunning, S. Gilevich, K. Grouev, X. Liu, J.F. Schmerge, T. Vecchione, F.Y. Wang, F. Zhou
SLAC, Menlo Park, California, USA
G. Huang, M.J. Johnson, T.H. Luo, F. Sannibale, S.P. Virostek
LBNL, Berkeley, California, USA

Funding: This work supported under DOE Contract DE-AC02-76SF00515
The Early Injector Commissioning program for LCLS-II aims to demonstrate CW electron beam production this year in the first two meters of the injector that includes the room-temperature 185.7 MHz single-cell gun and the 1.3 GHz two-cell buncher cavity. These cavities were designed and built by LBNL based on their experience with similar ones for their Advanced Photo-Injector Experiment (APEX) program. With the 258 nm laser system and Cs2Te cathodes, bunches of up to 300 pC are expected at rates as high as 1 MHz. The paper presents results from this program including the vacuum levels achieved, RF processing and field control experience, dark current measurements and laser and beam characterization.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP026

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paper received ※ 26 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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THP032

SRF Gun and SRF Linac Driven THz at ELBE Successfully in User Operation

SRF, radiation, electron, linac

915

R. Xiang, A. Arnold, P.E. Evtushenko, S. Kovalev, U. Lehnert, P.N. Lu, S. Ma, P. Michel, P. Murcek, A.A. Ryzhov, J. Schaber, Ch. Schneider, J. Teichert
HZDR, Dresden, Germany
H. Vennekate
RI Research Instruments GmbH, Bergisch Gladbach, Germany
I. Will
MBI, Berlin, Germany

Funding: The work was partly supported by the German Federal Ministry of Education and Research (BMBF) grant 05K12CR1 and Deutsche Forschungsgemeinschaft (DFG) project (XI 10⁶/2-1).
The first all-SRF accelerator driven THz source has been operated as a user facility since 2018 at ELBE radiation center. The CW electron beam is extracted from SRF gun II, accelerated to relativistic energies and compressed to sub-ps length in the ELBE SRF linac with a chicane. THz pulses are produced by pass-ing the short electron bunches through a diffraction radiator (CDR) and an undulator. The coherent THz power increases quadratically with bunch charge. The pulse energy up to 10 µJ at 0.3 THz with 100 kHz has been generated.

Poster THP032 [1.207 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP032

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paper received ※ 02 July 2019 paper accepted ※ 04 July 2019 issue date ※ 14 August 2019

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THP080

Status of the All Superconducting Gun Cavity at DESY

cavity, cathode, SRF, niobium

1087

E. Vogel, S. Barbanotti, A. Brinkmann, Th. Buettner, J.I. Iversen, K. Jensch, D. Klinke, D. Kostin, W.-D. Möller, A. Muhs, J. Schaffran, M. Schmökel, J.K. Sekutowicz, S. Sievers, L. Steder, N. Steinhau-Kühl, A. Sulimov, J.H. Thie, H. Weise, M. Wenskat, M. Wiencek, L. Winkelmann, B. van der Horst
DESY, Hamburg, Germany

At DESY, the development of a 1.6-cell, 1.3 GHz all superconducting gun cavity with a lead cathode attached to its back wall is ongoing. The special features of the structure like the back wall of the half-cell and cathode hole require adaptations of the procedures used for the treatment of nine-cell TESLA cavities. Unsatisfactory test results of two prototype cavities motivated us to re-consider the back-wall design and production steps. In this contribution we present the status of the modified cavity design including accessories causing accelerating field asymmetries, like a pick up antenna located at the back wall and fundamental power- and HOM couplers. Additionally, we discuss preliminary considerations for the compensation of kicks caused by these components.

Poster THP080 [7.365 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP080

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paper received ※ 20 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019

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THP081

A Cryocooled Normal Conducting and Superconducting Hybrid CW RF Gun

cavity, cathode, acceleration, emittance

1091

H.J. Qian, G. Shu, F. Stephan
DESY Zeuthen, Zeuthen, Germany
S. Barbanotti, B. Petersen, E. Vogel
DESY, Hamburg, Germany
A.A. Gorchakov, M. Gusarova
MEPhI, Moscow, Russia

Continuous wave (CW) photoinjectors have seen great progress in the last decades, such as DC gun, superconducting RF (SRF) gun and normal conducting (NC) gun. Developments of Free electron lasers and electron microscopy in the CW mode are pushing for further improvements of CW guns towards higher acceleration gradient, higher beam energy and compatibility with high QE cathodes for better beam brightness. Current SC gun gradient is limited by the cathode cell due to the complication of a cathode back plane and a normal conducting cathode plug, and R&D on SC gun improvement is ongoing. A high gradient cryocooled CW NC gun was proposed to house the high QE cathode, and a SC cavity immediately nearby gives further energy acceleration. In this paper, further RF optimization of the NC gun and ASTRA simulations of such a hybrid photoinjector are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP081

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paper received ※ 25 June 2019 paper accepted ※ 03 July 2019 issue date ※ 14 August 2019

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THP082

Geometry Dependent Beam Dynamics of a 3.5-cell SRF Gun Cavity at ELBE

SRF, cavity, emittance, electron

1095

K. Zhou
CAEP/IAE, Mianyang, Sichuan, People’s Republic of China
A. Arnold, S. Ma, J. Schaber, J. Teichert, R. Xiang
HZDR, Dresden, Germany

In order to optimize the next generation SRF gun at HZDR ELBE radiation source, the impact on beam dynamics from the SRF cavity geometry needs to be investigated. This paper presents an analysis on the electromagnetic fields and output electron beam qualities, by changing the geometry parameters of a 3.5-cell SRF gun cavity. The simulation results show the higher electric field ratio in the first half cell to the TESLA like cell, the better beam parameters we can obtain, which, however, will also lead to a higher Emax/E0 and Bmax/E0.

Poster THP082 [1.935 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP082

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paper received ※ 22 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019

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FRCAB4

Development of High Intensity, High Brightness, CW SRF Gun with Bi-Alkali Photocathode

cathode, SRF, cavity, target

1219

T. Konomi, Y. Honda, E. Kako, Y. Kobayashi, S. Michizono, T. Miyajima, H. Sakai, K. Umemori, S. Yamaguchi
KEK, Ibaraki, Japan

Superconducting conduction electron guns can realize high acceleration voltage and high beam repetition. KEK has been developing the 1.3 GHz elliptical type 1.5 cell superconducting RF gun to investigate fundamental performance. The surface cleaning methods and tools were developed by using KEK SRF gun cavity #1 and surface peak electric field reached to 75 MV/m without field emission. We will apply this technique to the SRF gun cavity #2 for beam operation. The gun cavity #2 equips the helium jacket, frequency tuner cathode position adjuster to operate the electron beam. The RF structure was designed based on the gun cavity #1. The cathode rod is made of Nb. The photocathode deposited on the cathode rod will be cool down to 2K to minimize thermal emittance. The fabrication of the gun cavity #2 and helium jacket were completed. 4 times vertical tests were carried out. We will report the vertical test results and preparation of the horizontal test.

Slides FRCAB4 [10.826 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB4

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paper received ※ 23 June 2019 paper accepted ※ 03 July 2019 issue date ※ 14 August 2019

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FRCAB5

Performance of 112 MHz SRF Gun at BNL

cathode, electron, SRF, cavity

1223

T. Xin, I. Ben-Zvi, J.C. Brutus, C. Folz, T. Hayes, P. Inacker, Y.C. Jing, D. Kayran, V. Litvinenko, J. Ma, G.J. Mahler, M. Mapes, K. Mernick, T.A. Miller, G. Narayan, P. Orfin, I. Pinayev, S. Polizzo, T. Rao, F. Severino, J. Skaritka, K.S. Smith, R. Than, J.E. Tuozzolo, E. Wang, G. Wang, Q. Wu, B.P. Xiao, W. Xu, A. Zaltsman
BNL, Upton, New York, USA
S.A. Belomestnykh
Fermilab, Batavia, Illinois, USA
C.H. Boulware, T.L. Grimm
Niowave, Inc., Lansing, Michigan, USA
K. Mihara
Stony Brook University, Stony Brook, USA
I. Petrushina
SUNY SB, Stony Brook, New York, USA
K. Shih
SBU, Stony Brook, New York, USA

Funding: This work is funded by the DOE FOA (No. DE-FOA-0000632) and National Science Foundation (Award No. PHY-1415252).
A 112 MHz SRF electron photoinjector (gun) was developed at Brookhaven National Laboratory to produce high-brightness and high-bunch-charge bunches for the coherent electron cooling proof-of-principle experiment. The gun is designed to deliver electrons with a kinetic energy of up to 2 MeV. Electrons are generated by illuminating a high quantum efficiency (QE) K2CsSb photoemission layer with a green laser operating at a wavelength of 532 nm. The gun was able to generating 3 nC bunches at 1.7 MeV. The design goals, fabrication, performance and operational experience are reported here.

Slides FRCAB5 [3.984 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB5

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paper received ※ 22 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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