ERL2019 - Classification: WG3: Electron sources and injectors

Paper	Title	Page
WECOWBS01	Vertical Test Results and Preparation for Horizontal Test of the KEK SRF Gun #2
	T. Konomi KEK, Ibaraki, Japan
	Superconducting 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 WECOWBS01 [18.108 MB]
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WECOWBS02	High Current Polarized Electron Source Development
	L. Cultrera, J. Bae, I.V. Bazarov, A. Galdi, F. Ikponmwen, J.M. Maxson Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: DOE DE-SC0019122 We report on negative electron affinity (NEA) of GaAs using robust layers based on the use of Cs, Sb and Oxygen. A detailed parametric study has been performed on the growth conditions and using the equivalent Sb thickness as main parameter. Our results confirm that dark lifetime (measured as 1/e decay of the quantum efficiency as function of time) of the GaAs activated using this method is improved by a factor 10. More importantly the operating lifetime (measured as 1/e decay of the quantum efficiency as function of the extracted charge) is improved by a factor 40 with respect to Cs-O activated GaAs operated under similar conditions. Such improvements on the lifetime are achieved at expenses of a slightly reduced QE and electron spin polarization.
	Slides WECOWBS02 [36.273 MB]
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WECOWBS03	Using a Protective Layer for Alkali Cathodes
	J. Smedley LANL, Los Alamos, New Mexico, USA
	The photocathode community has been dramatically improving semiconductor cathode performance in recent years, especially in terms of demonstrated mean transverse energy and surface roughness. While the demonstrated QE has also modestly increased, comparatively little effort has been devoted to the parameter most critical to ERL performance - cathode lifetime, especially under high average current operating conditions. This presentation will focus on one approach to improving lifetime - creating a mono-atomic layer of a material with hexagonal pores over the cathode surface. Ideally these pores are too small for Cs to escape the surface, mitigating the effects of both local heating due to the drive laser and ion bombardment induced sputter loss. Further, the coating will limit the diffusion of oxidizers onto the surface, providing some resistance to chemical contamination. The theory of electron transport through the monolayers will be discussed, as well as theory and experimental results for two hexagonal monolayers, graphene and hexagonal BN. The growth of alkali antimonides on both of these materials has been demonstrated, with some loss of QE performance.
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WECOXBS01	Photocathode Preparation and Characterization at HZB.
	S. Mistry, A. Jankowiak, T. Kamps, J. Kühn HZB, Berlin, Germany
	Photoinjector driven electron accelerators place stringent requirements on the photocathodes used. This is primarily due to the fact that the properties of the generated electron bunch are crucially defined by the material properties of the photocathode employed. To generate high brightness and high average current a photocathode with high QE and low intrinsic emittance is required. Furthermore, to be of practical use, the material must be robust and exhibit a long lifetime to deliver stable beam. Bi-alkali antimonides are suitable candidates; they exhibit high quantum efficiencies and can be operated close to the photoemission threshold, thus enabling the generation of high current and low emittance electron beams. At HZB bi-alkali antimonides are the choice photocathode materials to drive the BERLinPro energy recovery linac. In this talk we present studies conducted at HZB to develop the optimal growth procedure for Cs-K-Sb and Na-K-Sb photocathodes with respect to QE and lifetime measurements.
	Slides WECOXBS01 [16.588 MB]
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WECOXBS02	High Current Performance of Alkali Antimonide Photocathode in LEReC DC Gun	61
	M. Gaowei, J. Cen, A.V. Fedotov, D. Kayran, D. Lehn, C.J. Liaw, T. Rao, J.E. Tuozzolo, J. Walsh, E. Wang BNL, Upton, New York, USA
	The bi-alkali antimonide photocathode are chosen as the electron source material for the Low Energy RHIC electron Cooling (LEReC) project at RHIC, BNL based on its requirement for high bunch charge and long-time beam operation. This report presents the design and operation of the cathode deposition and transportation systems for the LEReC photocathodes, the cathode performance under the high current operation in the LEReC DC gun, as well as the characterization of the damaged cathodes from the long-time operation.
	Slides WECOXBS02 [2.804 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-WECOXBS02
About •	paper received ※ 17 September 2019 paper accepted ※ 06 November 2019 issue date ※ 24 June 2020
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WECOXBS03	Bench Test Results of CW 100 mA Electron RF Gun for Novosibirsk ERL based FEL	65
	V. Volkov, V.S. Arbuzov, E. Kenzhebulatov, E.I. Kolobanov, A.A. Kondakov, E.V. Kozyrev, S.A. Krutikhin, I.V. Kuptsov, G.Y. Kurkin, S.V. Motygin, A.A. Murasev, V.K. Ovchar, V.M. Petrov, A.M. Pilan, V.V. Repkov, M.A. Scheglov, I.K. Sedlyarov, S.S. Serednyakov, O.A. Shevchenko, S.V. Tararyshkin, A.G. Tribendis, N.A. Vinokurov BINP SB RAS, Novosibirsk, Russia E.V. Kozyrev, S.S. Serednyakov, N.A. Vinokurov NSU, Novosibirsk, Russia A.G. Tribendis NSTU, Novosibirsk, Russia N.A. Vinokurov KAERI, Daejon, Republic of Korea N.A. Vinokurov UST, Daejeon City, Republic of Korea N.A. Vinokurov University of Science and Technology of Korea (UST), Daejeon, Republic of Korea
	Continuous wave (CW) 100 mA electron rf gun for injecting the high-quality 300-400 keV electron beam in Novosibirsk Energy Recovery Linac (ERL) and driving Free Electron Laser (FEL) was developed, built, and commissioned at BINP SB RAS. The RF gun consists of normal conducting 90 MHz rf cavity with a gridded thermionic cathode unit. Bench tests of rf gun is confirmed good results in strict accordance with our numerical calculations and showed reliable work, unpretentious for vacuum conditions and stable in long-term operation. The design features of different components of the rf gun are presented. Preparation and commissioning experience is discussed. The latest beam results are reported.
	Slides WECOXBS03 [3.201 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-WECOXBS03
About •	paper received ※ 14 September 2019 paper accepted ※ 11 November 2019 issue date ※ 24 June 2020
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WEPNEC03	Thermal Load Studies on the Photocathode Insert with Exchangeable Plug for the BERLinPro SRF-Photoinjector
	N. Al-Saokal, M. Bürger, M. Dirsat, A. Frahm, A. Jankowiak, T. Kamps, G. Klemz, J. Kühn, 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.
	Poster WEPNEC03 [1.703 MB]
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WEPNEC07	Comparison of Two Pareto Optimization Tools Using OPAL and ASTRA for a Dedicated BERLinPro Injector Optimization.
	J. Völker HZB, Berlin, Germany A. Adelmann PSI, Villigen PSI, Switzerland
	BERLinPro is an Energy Recovery Linac (ERL) Project, currently being set up at the HZB. The accelerator consists of an injector part (SRF photo injector and booster section) and the ERL part (LINAC and recirculator section). Until realization of the final ERL setup further beam applications are under development using only the injector part of BERLinPro, like ultrafast electron diffraction (UED) or tomography experiments. For those cases a dedicated beam optic for the complete injector is required that differ from the standard ERL optics. Especially for UED experiments, an extreme short electron bunch and a tiny transverse emittance are needed. For the optimization of the injector two multi-parameter Pareto optimization tools were used. On the one hand, ASTRA with an external MATLAB optimizer, on the other hand, OPAL** with its new internal optimization tool. In this paper we will present both generic methods and compare their results.
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WEPNEC09	Thz User Operation With 200 pC CW Beam Generated by the ELBE SRF Gun II
	A. Arnold, S. Ma, P. Murcek, J. Schaber, J. Teichert, R. Xiang, P.Z. Zwartek HZDR, Dresden, 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) As a new electron source with higher brilliance, the second superconducting RF photoinjector (SRF Gun II) has been built at the ELBE radiation center for high power radiation sources. One of the main goals of SRF gun II is to achieve a higher bunch charge (>200 pC) and lower emittance (3 mm mrad) than the present ELBE thermionic DC gun. SRF Gun II features a 3.5-cell niobium cavity as well as a superconducting solenoid in the same cryomodule. With Mg photocathodes the gun is able to provide medium current beam with bunch charge of more than 200 pC and sub-ps bunch length at 100 kHz repetition rate. With this contribution we present convincing results from long-term user operation of SRF gun II in combination with the bunching concept of the ELBE accelerator in order to produce THz radiation with much higher stability and power than available using the existing thermionic gun.
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WEPNEC13	Preliminary Investigations and Pre-Research Scheme of High Average Current Electron Injectors at IMP	90
	Q.T. Zhao, J.C. Yang, Z.M. Zhang, H.W. Zhao IMP/CAS, Lanzhou, People’s Republic of China
	High average current electron injectors are desired by high average beam power SRF linacs. With respect to the different linac application, different beam qualities are required. Two kinds of electron gun are planned for future projects at IMP, one is thermionic electron gun dedicated for high average current, and another one is photocathode gun which is for high average current and high beam quality or even with high polarization. Current status and development of the high average current electron source are investigated and summarized. The thermionic gun studies are planned and the feasible types of gun for the future Electron ion collider of China (EicC) project are also proposed. The pre-research scheme of these two kinds of electron guns are schemed, which will be the start of high average current and high-quality electron source development at Institute of modern physics (IMP), Chinese academy of sciences (CAS).
	Poster WEPNEC13 [0.827 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-WEPNEC13
About •	paper received ※ 22 September 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020
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WEPNEC17	Developments in Photocathode R&D at STFC Daresbury Laboratory: New Transverse Energy Spread Measurements and the Development of a Multi-Alkali Photocathode Preparation Facility	103
	L.B. Jones, B.L. Militsyn, T.C.Q. Noakes STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom L.B. Jones, D.P. Juarez-Lopez, B.L. Militsyn, T.C.Q. Noakes, L.A.J. Soomary, C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom D.P. Juarez-Lopez, L.A.J. Soomary, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom
	Photocathode R&D activity within ASTeC is focussed on further development of the tools required for the preparation and characterisation of high performance photocathodes for X-FELs. Our Transverse Energy Spread Spectrometer (TESS)* experimental facility can be used with III-V semiconductor, multi-alkali and metal photocathodes to measure transverse and longitudinal energy distributions of the emitted electrons. Recently TESS has been upgraded to increase the instrument sensitivity for operation with low QE materials under UV illumination. Our R&D facilities also include in-vacuum quantum efficiency measurement, XPS, STM, plus ex-vacuum optical and STM microscopy for surface metrology. Intrinsic photocathode emittance is affected by many factors including illumination wavelength and surface roughness. We present energy distribution measurements for electrons emitted from copper, niobium and zirconium photocathode samples with measured levels of surface roughness under illumination by wavelengths between 256 and 291 nm. We also present an update on progress to establish a multi-alkali photocathode preparation facility to support the CLARA** linear accelerator. * Proc. FEL’13, TUPPS033, 290-293 ** CLARA Conceptual Design Report J. Inst. 9 T05001
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-WEPNEC17
About •	paper received ※ 04 October 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020
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WEPNEC19	Optimisation of the PERLE Injector	107
	B. Hounsell, M. Klein, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom B. Hounsell, B.L. Militsyn, C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom B. Hounsell, W. Kaabi Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France B.L. Militsyn STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	The injector for PERLE, a proposed electron Energy Recovery Linac (ERL) test facility for the LHeC and FCC-eh projects, is intended to deliver 500 pC bunches at a repetition rate of 40.1 MHz for a total beam current of 20 mA. These bunches must have a bunch length of 3 mm rms and an energy of 7 MeV at the entrance to the first linac pass while simultaneously achieving a transverse emittance of less than 6 mm mrad. The injector is based around a DC photocathode electron gun, followed by a focusing and normal conducting bunching section, a booster with 5 independently controllable SRF cavities and a merger into the main ERL. A design for this injector from the photocathode to the exit of the booster is presented. This design was simulated using ASTRA for the beam dynamics simulations and optimized using the many objective optimization algorithm NSGAIII. The use of NSGAIII allows more than three beam parameters to be optimised simultaneously and the trade-offs between them to be explored.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-WEPNEC19
About •	paper received ※ 01 October 2019 paper accepted ※ 11 November 2019 issue date ※ 24 June 2020
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WEPNEC21	Decoupling Cathode and Lattice Emittance Contributions from a 100 pC, 100 MeV Electron Injector System	112
	N.P. Norvell SLAC, Menlo Park, California, USA M.B. Andorf, I.V. Bazarov, C.M. Gulliford, J.M. Maxson Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	We present simulation results to decouple the emittance contributions that are intrinsic from the injector lattice versus emittance contributions due to the quality of the cathode out of a 100 MeV electron injector system. Using ASTRA driven by the NSGA-II genetic algorithm, we optimized the LCLS-II injector system with a zero emittance cathode. We then imposed FEL specific energy constraints and show how the Pareto Front solution shifts. Lastly, we reoptimized at various cathode emittances to map out the dependence of cathode emittance versus final emittance out of the injector system. We then determined the cathode quality needed to hit a 0.1 mm mrad 95% rms transverse emittance specification out of the current LCLS-II injector system.
	Poster WEPNEC21 [3.227 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-WEPNEC21
About •	paper received ※ 01 October 2019 paper accepted ※ 07 November 2019 issue date ※ 24 June 2020
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WEPNEC22	Beam Impedance Study on a Harmonic Kicker for the CCR of JLEIC	116
	G.-T. Park, J. Guo, F. Marhauser, R.A. Rimmer, H. Wang, S. Wang JLab, Newport News, Virginia, USA
	Funding: Work supported by Jefferson Science Associates, LLC under U.S DOE Contract No. DE-AC05-06OR23177 In this report, we present the development of a fast harmonic kicker, a normal conducting deflecting cavity that kicks electron bunches from ERL ring to circulator cooler ring (CCR) in Jefferson Lab Electron Ion Collider (JLEIC). This cavity utilizes 5 harmonic modes to generate a sharp kick to the electron bunch at high frequency of 86.6MHz, which is injection frequency into the CCR. The beam dynamics study and RF design of the hardware was reported in [1],[2]. In this report we present further progress including impedance by higher order mode (HOM) study and mechanical design for fabrication. [1] G. Park, et. al TUPAL068, Proc. of IPAC 2018, Apr 2018, Vancouver, BC Canada [2] G. Park, et. al, Proc. of IPAC2019, May 2019, Melbourne, Australia
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-WEPNEC22
About •	paper received ※ 30 September 2019 paper accepted ※ 04 November 2019 issue date ※ 24 June 2020
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WEPNEC23	Experience With LEReC High Current DC Gun
	X. Gu, Z. Altinbas, D. Bruno, L. Cannizzo, M.R. Costanzo, A.V. Fedotov, D. Kayran, C.J. Liaw, M. Mapes, K. Mernick, C. Mi, T.A. Miller, M.G. Minty, J. Sandberg, L. Smart, P. Thieberger, J.E. Tuozzolo BNL, Upton, New York, USA
	Funding: Work was supported by Brookhaven Science Associates, LLC, under Contract No. DE-SC0012704 with the U.S. Department of Energy. The Low Energy RHIC Electron Cooling (LEReC) ac-celerator was successfully commissioned at BNL. To satisfy the electron beam quality required for cooling, a high voltage DC photocathode gun was chosen as the electron source. The LEReC DC gun system is based on the Cornell University ERL gun. The gun was successfully commissioned with high-current and produced electron beam quality suitable for cooling. Here we describe operational experience with the LEReC gun, as well as experience gained with conditioning of such guns.
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WEPNEC25	Research on Alkali Antimonide Photocathode Fabrication Recipe at PKU	120
	D.M. Ouyang, L.W. Feng, S. Huang, K.X. Liu, S.W. Quan, H.M. Xie, X.K. Zhang, S. Zhao PKU, Beijing, People’s Republic of China
	Low emittance, high QE and long lifetime photocathode is widely studied for X-ray Free Electron Laser (XFEL)and Energy Recovery Linacs (ERL) applications. A deposition system for alkali antimonide photocathode (K2CsSb, Cs3Sb etc.) is being commissioned at Peking University. In this paper, we present our experimental results on alkali antimonide photocathode with this deposition system. We successfully fabricated Cs3Sb photocathode on oxygen free copper, p-type Si (100) and Mo substrates with QE of 1.4%, 2.6% and 2.6% respectively.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-WEPNEC25
About •	paper received ※ 27 September 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020
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THCOYBS01	Metal and Semiconductor Photocathodes in HZDR SRF Gun	142
	R. Xiang, A. Arnold, P. Murcek, J. Schaber, J. Teichert HZDR, Dresden, Germany J. Schaber TU Dresden, Dresden, Germany
	Funding: The work is supported by the German Federal Ministry of Education and Research (BMBF) grant 05K12CR1. Quality of photocathode in a photoinjector is one of the critical issues for the stability and reliability of the whole accelerator facility. In April 2013, the IR FEL lasing was demonstrated for the first time with the electron beam from the SRF gun with Cs2Te at HZDR. Cs2Te photocathode worked in SRF gun-I for more than one year without degradation. Currently, Mg photocathodes with QE up to 0.5% are applied in SRF Gun-II, generating e^- beam with bunch charge up to 300 pC in CW mode with sub-ps bunch length for the high power THz radiation. It is an excellent demonstration that SRF guns can work reliably in a high power user facility.
	Slides THCOYBS01 [3.868 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-THCOYBS01
About •	paper received ※ 18 September 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020
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THCOYBS02	High Charge High Current Beam From BNL 113 MHz SRF Gun	145
	I. Pinayev, I. Ben-Zvi, J.C. Brutus, M. Gaowei, T. Hayes, Y.C. Jing, V. Litvinenko, J. Ma, K. Mihara, G. Narayan, I. Petrushina, F. Severino, K. Shih, J. Skaritka, E. Wang, G. Wang, Y.H. Wu BNL, Upton, New York, USA V. Litvinenko Stony Brook University, Stony Brook, USA I. Petrushina, Y.H. Wu SUNY SB, Stony Brook, New York, USA K. Shih SBU, Stony Brook, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The 113 MHz superconducting gun is used an electron source for the coherent electron cooling experiment. The unique feature of the gun is that a photocathode is held at room temperature. It allowed to preserve the quantum efficiency of Cs2KSb cathode which is adversely affected by cryogenic temperatures. Relatively low frequency permitted fully realize the accelerating field gradient what in turn helps to achieve 10 nC charge and 0.3 microns normalized emittance. We present the achieved performance and operational experience as well.
	Slides THCOYBS02 [4.350 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-THCOYBS02
About •	paper received ※ 03 September 2019 paper accepted ※ 08 July 2020 issue date ※ 24 June 2020
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THCOYBS03	Peking Univ. DC-SC/SRF Gun Progressing
	H.M. Xie PKU, Beijing, People’s Republic of China
	Stable operation of 3.5 cell DC-SRF photoinjector has been realized with average beam current of ~1mA at Peking university. A new 1.5 cell DC-SRF photoinjector has been designd and now is being constructed. In this talk we will give a brief introduction on the low emittance simulation of the new photoinjector, which indicates that emittance less than 0.5 um could be achieved at 100 pC bunch charge. Laser shaping, bi-alkali photocathode are all in progress.
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THCOZBS01	Novosibirsk ERL injector
	O.A. Shevchenko, V.S. Arbuzov, K.N. Chernov, I.V. Davidyuk, O.I. Deichuli, E.N. Dementyev, B.A. Dovzhenko, Ya.V. Getmanov, A.A. Kondakov, V.R. Kozak, E.V. Kozyrev, S.A. Krutikhin, G.N. Kulipanov, E.A. Kuper, I.V. Kuptsov, G.Y. Kurkin, A.S. Matveev, L.E. Medvedev, S.V. Motygin, V.N. Osipov, V.K. Ovchar, V.M. Petrov, A.M. Pilan, V.M. Popik, V.V. Repkov, T.V. Salikova, M.A. Scheglov, I.K. Sedlyarov, S.S. Serednyakov, A.N. Skrinsky, S.V. Tararyshkin, V.G. Tcheskidov, A.G. Tribendis, N.A. Vinokurov, V. Volkov BINP SB RAS, Novosibirsk, Russia I.V. Davidyuk, Ya.V. Getmanov, E.V. Kozyrev, S.S. Serednyakov, N.A. Vinokurov NSU, Novosibirsk, Russia A.G. Tribendis NSTU, Novosibirsk, Russia
	The Novosibirsk ERL is the first in the world multi-orbit ERL with high average current. It is used as a source of electron bunches for three powerful FEL-oscillators which operate in CW mode. In present configuration the ERL Injector comprises a 300-kV electrostatic gun with thermionic cathode, as well as one bunching and two accelerating cavities separated by the drift space which is used for bunch compression. In near future the new RF gun will be added to this configuration. The basic requirement for the injector is to provide beam parameters necessary for FEL operation. These parameters include bunch charge more than 1 nQ and repetition rate about 10 MHz. Very small emittance and very short pulse duration are not required in our case because of long FEL radiation wavelength and low RF frequency of the main linac. We present detailed description of the injector setup and results of beam parameters measurements. The measured parameters are compared with simulation results. We also discuss future upgrade which includes installation of the new RF gun.
	Slides THCOZBS01 [18.483 MB]
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THCOZBS02	Status of SRF Gun for BERLinPro
	A. Neumann, N. Al-Saokal, D. Böhlick, A.B. Büchel, M. Bürger, P. Echevarria, A. Frahm, H.-W. Glock, F. Göbel, S. Heling, K. Janke, A. Jankowiak, T. Kamps, S. Klauke, G. Klemz, J. Knobloch, G. Kourkafas, J. Kühn, O. Kugeler, N. Leuschner, A.N. Matveenko, S. Mistry, N. Ohm, E. Panofski, H. Plötz, S. Rotterdam, M.A.H. Schmeißer, M. Schuster, H. Stein, Y. Tamashevich, J. Ullrich, A. Ushakov, J. Völker HZB, Berlin, Germany T. Kamps HU Berlin, Berlin, Germany
	Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association Helmholtz-Zentrum Berlin (HZB) is on the final round to complete an high average current superconducting (SC) ERL as a prototype to demonstrate low normalized beam emittance of 1 mm·mrad at 100mA and short pulses of about 2 ps. The high brilliance beam will originate from an 1.4 x λ/2 cell SRF cavity with a normal-conducting, high quantum efficiency CsK2Sb cathode, implementing a modified HZDR-style cathode insert. This prototype injector potentially allows for 6 mA beam current and up to 3.5 MeV beam kinetic energy, limited by the modified twin TTF-III fundamental power couplers. In this contribution the operation of the SRF injector cavity with a Copper cathode within a dedicated beam test experiment called Gunlab will be presented. The second half of the talk will give an overview about on-going activities to refurbish and reinstall the SRF gun module in the accelerator hall in BERLinPro. Also an insight into the repair attempts of the first cavity suffering from field emission will be given.
	Slides THCOZBS02 [21.091 MB]
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THCOZBS03	Magnetized Beam Generated from DC Gun for JLEIC Electron Cooler
	S.V. Benson, P.A. Adderley, J.F. Benesch, D.B. Bullard, J.M. Grames, J. Guo, F.E. Hannon, J. Hansknecht, C. Hernandez-Garcia, R. Kazimi, G.A. Krafft, M.A. Mamun, M. Poelker, R. Suleiman, M.G. Tiefenback, Y.W. Wang, S. Zhang JLab, Newport News, Virginia, USA J.R. Delayen ODU, Norfolk, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 Bunched-beam electron cooling is a key feature of all proposed designs of the future electron-ion collider, and a requirement for achieving the specified collision luminosity of the order 1034 cm^-2s⁻¹. For the Jefferson Lab Electron Ion Collider (JLEIC), fast cooling of ion beams will be accomplished via so-called ’magnetized electron cooling’, where the cooling process will occur inside a long solenoid field, which will be part of the collider ring and facilitated using a circulator ring and Energy Recovery Linac (ERL). In this contribution, we describe recent achievements that include the generation of picosecond-bunch magnetized beams at average currents up to 28 mA with exceptionally long photocathode lifetime, and independent demonstrations of magnetized beam with high bunch charge up to 700 pC at 10s of kHz repetition rates using a compact 300 kV DC high voltage photogun with an inverted insulator geometry and alkali-antimonide photocathodes. Magnetization characterization including beam rotation and drift emittance were also presented for various gun bias voltages and laser spot sizes at the photocathode using 532 nm lasers with DC and RF time structure. These accomplishments mark important steps toward demonstrating the feasibility of a technically challenging JLEIC cooler design using magnetized beams.
	Slides THCOZBS03 [14.025 MB]
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THCOZBS04	Injector Development at KEK
	T. Miyajima KEK, Ibaraki, Japan
	Since 2013, we have operated the compact ERL (cERL) injector at KEK to demonstrate hardware and beam performances for future ERL accelerator. The injector consists of a 500 kV DC photocathode gun, solenoid magnets, a normal conducting buncher and three 2-cell superconducting cavities. In beam operation, the DC gun with GaAS photocathode is very stable with DC 500 kV, and can generate stable CW 1 mA electron beam. For low bunch charge operation, we achieved designed beam performance with low emittance and short bunch length in the injector. From 2017, we started high bunch charge operation with 60 pC bunch charge toward an infrared free electron laser (IR FEL) test. In June 2019, we achieved the requirements of injector beam performance for the IR FEL test, which were < 3 mm mrad normalized emittance and 4 ps RMS bunch length.
	Slides THCOZBS04 [4.475 MB]
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FRCOYBS03	Working Group Summary: Electron Sources and Injectors
	E. Wang BNL, Upton, New York, USA L. Cultrera Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	To be added
	Slides FRCOYBS03 [34.567 MB]
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Paper

Title

Page

WECOWBS01

Vertical Test Results and Preparation for Horizontal Test of the KEK SRF Gun #2

T. Konomi
KEK, Ibaraki, Japan

Superconducting 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 WECOWBS01 [18.108 MB]

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WECOWBS02

High Current Polarized Electron Source Development

L. Cultrera, J. Bae, I.V. Bazarov, A. Galdi, F. Ikponmwen, J.M. Maxson
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: DOE DE-SC0019122
We report on negative electron affinity (NEA) of GaAs using robust layers based on the use of Cs, Sb and Oxygen. A detailed parametric study has been performed on the growth conditions and using the equivalent Sb thickness as main parameter. Our results confirm that dark lifetime (measured as 1/e decay of the quantum efficiency as function of time) of the GaAs activated using this method is improved by a factor 10. More importantly the operating lifetime (measured as 1/e decay of the quantum efficiency as function of the extracted charge) is improved by a factor 40 with respect to Cs-O activated GaAs operated under similar conditions. Such improvements on the lifetime are achieved at expenses of a slightly reduced QE and electron spin polarization.

Slides WECOWBS02 [36.273 MB]

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WECOWBS03

Using a Protective Layer for Alkali Cathodes

J. Smedley
LANL, Los Alamos, New Mexico, USA

The photocathode community has been dramatically improving semiconductor cathode performance in recent years, especially in terms of demonstrated mean transverse energy and surface roughness. While the demonstrated QE has also modestly increased, comparatively little effort has been devoted to the parameter most critical to ERL performance - cathode lifetime, especially under high average current operating conditions. This presentation will focus on one approach to improving lifetime - creating a mono-atomic layer of a material with hexagonal pores over the cathode surface. Ideally these pores are too small for Cs to escape the surface, mitigating the effects of both local heating due to the drive laser and ion bombardment induced sputter loss. Further, the coating will limit the diffusion of oxidizers onto the surface, providing some resistance to chemical contamination. The theory of electron transport through the monolayers will be discussed, as well as theory and experimental results for two hexagonal monolayers, graphene and hexagonal BN. The growth of alkali antimonides on both of these materials has been demonstrated, with some loss of QE performance.

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WECOXBS01

Photocathode Preparation and Characterization at HZB.

S. Mistry, A. Jankowiak, T. Kamps, J. Kühn
HZB, Berlin, Germany

Photoinjector driven electron accelerators place stringent requirements on the photocathodes used. This is primarily due to the fact that the properties of the generated electron bunch are crucially defined by the material properties of the photocathode employed. To generate high brightness and high average current a photocathode with high QE and low intrinsic emittance is required. Furthermore, to be of practical use, the material must be robust and exhibit a long lifetime to deliver stable beam. Bi-alkali antimonides are suitable candidates; they exhibit high quantum efficiencies and can be operated close to the photoemission threshold, thus enabling the generation of high current and low emittance electron beams. At HZB bi-alkali antimonides are the choice photocathode materials to drive the BERLinPro energy recovery linac. In this talk we present studies conducted at HZB to develop the optimal growth procedure for Cs-K-Sb and Na-K-Sb photocathodes with respect to QE and lifetime measurements.

Slides WECOXBS01 [16.588 MB]

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WECOXBS02

High Current Performance of Alkali Antimonide Photocathode in LEReC DC Gun

61

M. Gaowei, J. Cen, A.V. Fedotov, D. Kayran, D. Lehn, C.J. Liaw, T. Rao, J.E. Tuozzolo, J. Walsh, E. Wang
BNL, Upton, New York, USA

The bi-alkali antimonide photocathode are chosen as the electron source material for the Low Energy RHIC electron Cooling (LEReC) project at RHIC, BNL based on its requirement for high bunch charge and long-time beam operation. This report presents the design and operation of the cathode deposition and transportation systems for the LEReC photocathodes, the cathode performance under the high current operation in the LEReC DC gun, as well as the characterization of the damaged cathodes from the long-time operation.

Slides WECOXBS02 [2.804 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-WECOXBS02

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paper received ※ 17 September 2019 paper accepted ※ 06 November 2019 issue date ※ 24 June 2020

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WECOXBS03

Bench Test Results of CW 100 mA Electron RF Gun for Novosibirsk ERL based FEL

65

V. Volkov, V.S. Arbuzov, E. Kenzhebulatov, E.I. Kolobanov, A.A. Kondakov, E.V. Kozyrev, S.A. Krutikhin, I.V. Kuptsov, G.Y. Kurkin, S.V. Motygin, A.A. Murasev, V.K. Ovchar, V.M. Petrov, A.M. Pilan, V.V. Repkov, M.A. Scheglov, I.K. Sedlyarov, S.S. Serednyakov, O.A. Shevchenko, S.V. Tararyshkin, A.G. Tribendis, N.A. Vinokurov
BINP SB RAS, Novosibirsk, Russia
E.V. Kozyrev, S.S. Serednyakov, N.A. Vinokurov
NSU, Novosibirsk, Russia
A.G. Tribendis
NSTU, Novosibirsk, Russia
N.A. Vinokurov
KAERI, Daejon, Republic of Korea
N.A. Vinokurov
UST, Daejeon City, Republic of Korea
N.A. Vinokurov
University of Science and Technology of Korea (UST), Daejeon, Republic of Korea

Continuous wave (CW) 100 mA electron rf gun for injecting the high-quality 300-400 keV electron beam in Novosibirsk Energy Recovery Linac (ERL) and driving Free Electron Laser (FEL) was developed, built, and commissioned at BINP SB RAS. The RF gun consists of normal conducting 90 MHz rf cavity with a gridded thermionic cathode unit. Bench tests of rf gun is confirmed good results in strict accordance with our numerical calculations and showed reliable work, unpretentious for vacuum conditions and stable in long-term operation. The design features of different components of the rf gun are presented. Preparation and commissioning experience is discussed. The latest beam results are reported.

Slides WECOXBS03 [3.201 MB]

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paper received ※ 14 September 2019 paper accepted ※ 11 November 2019 issue date ※ 24 June 2020

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WEPNEC03

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

N. Al-Saokal, M. Bürger, M. Dirsat, A. Frahm, A. Jankowiak, T. Kamps, G. Klemz, J. Kühn, 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.

Poster WEPNEC03 [1.703 MB]

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WEPNEC07

Comparison of Two Pareto Optimization Tools Using OPAL and ASTRA for a Dedicated BERLinPro Injector Optimization.

J. Völker
HZB, Berlin, Germany
A. Adelmann
PSI, Villigen PSI, Switzerland

BERLinPro is an Energy Recovery Linac (ERL) Project, currently being set up at the HZB. The accelerator consists of an injector part (SRF photo injector and booster section) and the ERL part (LINAC and recirculator section). Until realization of the final ERL setup further beam applications are under development using only the injector part of BERLinPro, like ultrafast electron diffraction (UED) or tomography experiments. For those cases a dedicated beam optic for the complete injector is required that differ from the standard ERL optics. Especially for UED experiments, an extreme short electron bunch and a tiny transverse emittance are needed. For the optimization of the injector two multi-parameter Pareto optimization tools were used. On the one hand, ASTRA with an external MATLAB optimizer, on the other hand, OPAL** with its new internal optimization tool. In this paper we will present both generic methods and compare their results.

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WEPNEC09

Thz User Operation With 200 pC CW Beam Generated by the ELBE SRF Gun II

A. Arnold, S. Ma, P. Murcek, J. Schaber, J. Teichert, R. Xiang, P.Z. Zwartek
HZDR, Dresden, 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)
As a new electron source with higher brilliance, the second superconducting RF photoinjector (SRF Gun II) has been built at the ELBE radiation center for high power radiation sources. One of the main goals of SRF gun II is to achieve a higher bunch charge (>200 pC) and lower emittance (3 mm mrad) than the present ELBE thermionic DC gun. SRF Gun II features a 3.5-cell niobium cavity as well as a superconducting solenoid in the same cryomodule. With Mg photocathodes the gun is able to provide medium current beam with bunch charge of more than 200 pC and sub-ps bunch length at 100 kHz repetition rate. With this contribution we present convincing results from long-term user operation of SRF gun II in combination with the bunching concept of the ELBE accelerator in order to produce THz radiation with much higher stability and power than available using the existing thermionic gun.

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WEPNEC13

Preliminary Investigations and Pre-Research Scheme of High Average Current Electron Injectors at IMP

90

Q.T. Zhao, J.C. Yang, Z.M. Zhang, H.W. Zhao
IMP/CAS, Lanzhou, People’s Republic of China

High average current electron injectors are desired by high average beam power SRF linacs. With respect to the different linac application, different beam qualities are required. Two kinds of electron gun are planned for future projects at IMP, one is thermionic electron gun dedicated for high average current, and another one is photocathode gun which is for high average current and high beam quality or even with high polarization. Current status and development of the high average current electron source are investigated and summarized. The thermionic gun studies are planned and the feasible types of gun for the future Electron ion collider of China (EicC) project are also proposed. The pre-research scheme of these two kinds of electron guns are schemed, which will be the start of high average current and high-quality electron source development at Institute of modern physics (IMP), Chinese academy of sciences (CAS).

Poster WEPNEC13 [0.827 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-WEPNEC13

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paper received ※ 22 September 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020

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WEPNEC17

Developments in Photocathode R&D at STFC Daresbury Laboratory: New Transverse Energy Spread Measurements and the Development of a Multi-Alkali Photocathode Preparation Facility

103

L.B. Jones, B.L. Militsyn, T.C.Q. Noakes
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
L.B. Jones, D.P. Juarez-Lopez, B.L. Militsyn, T.C.Q. Noakes, L.A.J. Soomary, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
D.P. Juarez-Lopez, L.A.J. Soomary, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom

Photocathode R&D activity within ASTeC is focussed on further development of the tools required for the preparation and characterisation of high performance photocathodes for X-FELs. Our Transverse Energy Spread Spectrometer (TESS)* experimental facility can be used with III-V semiconductor, multi-alkali and metal photocathodes to measure transverse and longitudinal energy distributions of the emitted electrons. Recently TESS has been upgraded to increase the instrument sensitivity for operation with low QE materials under UV illumination. Our R&D facilities also include in-vacuum quantum efficiency measurement, XPS, STM, plus ex-vacuum optical and STM microscopy for surface metrology. Intrinsic photocathode emittance is affected by many factors including illumination wavelength and surface roughness. We present energy distribution measurements for electrons emitted from copper, niobium and zirconium photocathode samples with measured levels of surface roughness under illumination by wavelengths between 256 and 291 nm. We also present an update on progress to establish a multi-alkali photocathode preparation facility to support the CLARA** linear accelerator.
* Proc. FEL’13, TUPPS033, 290-293
** CLARA Conceptual Design Report J. Inst. 9 T05001

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reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-WEPNEC17

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paper received ※ 04 October 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020

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WEPNEC19

Optimisation of the PERLE Injector

107

B. Hounsell, M. Klein, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
B. Hounsell, B.L. Militsyn, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
B. Hounsell, W. Kaabi
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

The injector for PERLE, a proposed electron Energy Recovery Linac (ERL) test facility for the LHeC and FCC-eh projects, is intended to deliver 500 pC bunches at a repetition rate of 40.1 MHz for a total beam current of 20 mA. These bunches must have a bunch length of 3 mm rms and an energy of 7 MeV at the entrance to the first linac pass while simultaneously achieving a transverse emittance of less than 6 mm mrad. The injector is based around a DC photocathode electron gun, followed by a focusing and normal conducting bunching section, a booster with 5 independently controllable SRF cavities and a merger into the main ERL. A design for this injector from the photocathode to the exit of the booster is presented. This design was simulated using ASTRA for the beam dynamics simulations and optimized using the many objective optimization algorithm NSGAIII. The use of NSGAIII allows more than three beam parameters to be optimised simultaneously and the trade-offs between them to be explored.

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reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-WEPNEC19

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paper received ※ 01 October 2019 paper accepted ※ 11 November 2019 issue date ※ 24 June 2020

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WEPNEC21

Decoupling Cathode and Lattice Emittance Contributions from a 100 pC, 100 MeV Electron Injector System

112

N.P. Norvell
SLAC, Menlo Park, California, USA
M.B. Andorf, I.V. Bazarov, C.M. Gulliford, J.M. Maxson
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

We present simulation results to decouple the emittance contributions that are intrinsic from the injector lattice versus emittance contributions due to the quality of the cathode out of a 100 MeV electron injector system. Using ASTRA driven by the NSGA-II genetic algorithm, we optimized the LCLS-II injector system with a zero emittance cathode. We then imposed FEL specific energy constraints and show how the Pareto Front solution shifts. Lastly, we reoptimized at various cathode emittances to map out the dependence of cathode emittance versus final emittance out of the injector system. We then determined the cathode quality needed to hit a 0.1 mm mrad 95% rms transverse emittance specification out of the current LCLS-II injector system.

Poster WEPNEC21 [3.227 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-WEPNEC21

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paper received ※ 01 October 2019 paper accepted ※ 07 November 2019 issue date ※ 24 June 2020

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WEPNEC22

Beam Impedance Study on a Harmonic Kicker for the CCR of JLEIC

116

G.-T. Park, J. Guo, F. Marhauser, R.A. Rimmer, H. Wang, S. Wang
JLab, Newport News, Virginia, USA

Funding: Work supported by Jefferson Science Associates, LLC under U.S DOE Contract No. DE-AC05-06OR23177
In this report, we present the development of a fast harmonic kicker, a normal conducting deflecting cavity that kicks electron bunches from ERL ring to circulator cooler ring (CCR) in Jefferson Lab Electron Ion Collider (JLEIC). This cavity utilizes 5 harmonic modes to generate a sharp kick to the electron bunch at high frequency of 86.6MHz, which is injection frequency into the CCR. The beam dynamics study and RF design of the hardware was reported in [1],[2]. In this report we present further progress including impedance by higher order mode (HOM) study and mechanical design for fabrication.
[1] G. Park, et. al TUPAL068, Proc. of IPAC 2018, Apr 2018, Vancouver, BC Canada
[2] G. Park, et. al, Proc. of IPAC2019, May 2019, Melbourne, Australia

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paper received ※ 30 September 2019 paper accepted ※ 04 November 2019 issue date ※ 24 June 2020

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WEPNEC23

Experience With LEReC High Current DC Gun

X. Gu, Z. Altinbas, D. Bruno, L. Cannizzo, M.R. Costanzo, A.V. Fedotov, D. Kayran, C.J. Liaw, M. Mapes, K. Mernick, C. Mi, T.A. Miller, M.G. Minty, J. Sandberg, L. Smart, P. Thieberger, J.E. Tuozzolo
BNL, Upton, New York, USA

Funding: Work was supported by Brookhaven Science Associates, LLC, under Contract No. DE-SC0012704 with the U.S. Department of Energy.
The Low Energy RHIC Electron Cooling (LEReC) ac-celerator was successfully commissioned at BNL. To satisfy the electron beam quality required for cooling, a high voltage DC photocathode gun was chosen as the electron source. The LEReC DC gun system is based on the Cornell University ERL gun. The gun was successfully commissioned with high-current and produced electron beam quality suitable for cooling. Here we describe operational experience with the LEReC gun, as well as experience gained with conditioning of such guns.

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WEPNEC25

Research on Alkali Antimonide Photocathode Fabrication Recipe at PKU

120

D.M. Ouyang, L.W. Feng, S. Huang, K.X. Liu, S.W. Quan, H.M. Xie, X.K. Zhang, S. Zhao
PKU, Beijing, People’s Republic of China

Low emittance, high QE and long lifetime photocathode is widely studied for X-ray Free Electron Laser (XFEL)and Energy Recovery Linacs (ERL) applications. A deposition system for alkali antimonide photocathode (K2CsSb, Cs3Sb etc.) is being commissioned at Peking University. In this paper, we present our experimental results on alkali antimonide photocathode with this deposition system. We successfully fabricated Cs3Sb photocathode on oxygen free copper, p-type Si (100) and Mo substrates with QE of 1.4%, 2.6% and 2.6% respectively.

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paper received ※ 27 September 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020

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THCOYBS01

Metal and Semiconductor Photocathodes in HZDR SRF Gun

142

R. Xiang, A. Arnold, P. Murcek, J. Schaber, J. Teichert
HZDR, Dresden, Germany
J. Schaber
TU Dresden, Dresden, Germany

Funding: The work is supported by the German Federal Ministry of Education and Research (BMBF) grant 05K12CR1.
Quality of photocathode in a photoinjector is one of the critical issues for the stability and reliability of the whole accelerator facility. In April 2013, the IR FEL lasing was demonstrated for the first time with the electron beam from the SRF gun with Cs2Te at HZDR. Cs2Te photocathode worked in SRF gun-I for more than one year without degradation. Currently, Mg photocathodes with QE up to 0.5% are applied in SRF Gun-II, generating e^- beam with bunch charge up to 300 pC in CW mode with sub-ps bunch length for the high power THz radiation. It is an excellent demonstration that SRF guns can work reliably in a high power user facility.

Slides THCOYBS01 [3.868 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-THCOYBS01

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paper received ※ 18 September 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020

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THCOYBS02

High Charge High Current Beam From BNL 113 MHz SRF Gun

145

I. Pinayev, I. Ben-Zvi, J.C. Brutus, M. Gaowei, T. Hayes, Y.C. Jing, V. Litvinenko, J. Ma, K. Mihara, G. Narayan, I. Petrushina, F. Severino, K. Shih, J. Skaritka, E. Wang, G. Wang, Y.H. Wu
BNL, Upton, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA
I. Petrushina, Y.H. Wu
SUNY SB, Stony Brook, New York, USA
K. Shih
SBU, Stony Brook, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The 113 MHz superconducting gun is used an electron source for the coherent electron cooling experiment. The unique feature of the gun is that a photocathode is held at room temperature. It allowed to preserve the quantum efficiency of Cs2KSb cathode which is adversely affected by cryogenic temperatures. Relatively low frequency permitted fully realize the accelerating field gradient what in turn helps to achieve 10 nC charge and 0.3 microns normalized emittance. We present the achieved performance and operational experience as well.

Slides THCOYBS02 [4.350 MB]

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paper received ※ 03 September 2019 paper accepted ※ 08 July 2020 issue date ※ 24 June 2020

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THCOYBS03

Peking Univ. DC-SC/SRF Gun Progressing

H.M. Xie
PKU, Beijing, People’s Republic of China

Stable operation of 3.5 cell DC-SRF photoinjector has been realized with average beam current of ~1mA at Peking university. A new 1.5 cell DC-SRF photoinjector has been designd and now is being constructed. In this talk we will give a brief introduction on the low emittance simulation of the new photoinjector, which indicates that emittance less than 0.5 um could be achieved at 100 pC bunch charge. Laser shaping, bi-alkali photocathode are all in progress.

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THCOZBS01

Novosibirsk ERL injector

O.A. Shevchenko, V.S. Arbuzov, K.N. Chernov, I.V. Davidyuk, O.I. Deichuli, E.N. Dementyev, B.A. Dovzhenko, Ya.V. Getmanov, A.A. Kondakov, V.R. Kozak, E.V. Kozyrev, S.A. Krutikhin, G.N. Kulipanov, E.A. Kuper, I.V. Kuptsov, G.Y. Kurkin, A.S. Matveev, L.E. Medvedev, S.V. Motygin, V.N. Osipov, V.K. Ovchar, V.M. Petrov, A.M. Pilan, V.M. Popik, V.V. Repkov, T.V. Salikova, M.A. Scheglov, I.K. Sedlyarov, S.S. Serednyakov, A.N. Skrinsky, S.V. Tararyshkin, V.G. Tcheskidov, A.G. Tribendis, N.A. Vinokurov, V. Volkov
BINP SB RAS, Novosibirsk, Russia
I.V. Davidyuk, Ya.V. Getmanov, E.V. Kozyrev, S.S. Serednyakov, N.A. Vinokurov
NSU, Novosibirsk, Russia
A.G. Tribendis
NSTU, Novosibirsk, Russia

The Novosibirsk ERL is the first in the world multi-orbit ERL with high average current. It is used as a source of electron bunches for three powerful FEL-oscillators which operate in CW mode. In present configuration the ERL Injector comprises a 300-kV electrostatic gun with thermionic cathode, as well as one bunching and two accelerating cavities separated by the drift space which is used for bunch compression. In near future the new RF gun will be added to this configuration. The basic requirement for the injector is to provide beam parameters necessary for FEL operation. These parameters include bunch charge more than 1 nQ and repetition rate about 10 MHz. Very small emittance and very short pulse duration are not required in our case because of long FEL radiation wavelength and low RF frequency of the main linac. We present detailed description of the injector setup and results of beam parameters measurements. The measured parameters are compared with simulation results. We also discuss future upgrade which includes installation of the new RF gun.

Slides THCOZBS01 [18.483 MB]

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THCOZBS02

Status of SRF Gun for BERLinPro

A. Neumann, N. Al-Saokal, D. Böhlick, A.B. Büchel, M. Bürger, P. Echevarria, A. Frahm, H.-W. Glock, F. Göbel, S. Heling, K. Janke, A. Jankowiak, T. Kamps, S. Klauke, G. Klemz, J. Knobloch, G. Kourkafas, J. Kühn, O. Kugeler, N. Leuschner, A.N. Matveenko, S. Mistry, N. Ohm, E. Panofski, H. Plötz, S. Rotterdam, M.A.H. Schmeißer, M. Schuster, H. Stein, Y. Tamashevich, J. Ullrich, A. Ushakov, J. Völker
HZB, Berlin, Germany
T. Kamps
HU Berlin, Berlin, Germany

Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association
Helmholtz-Zentrum Berlin (HZB) is on the final round to complete an high average current superconducting (SC) ERL as a prototype to demonstrate low normalized beam emittance of 1 mm·mrad at 100mA and short pulses of about 2 ps. The high brilliance beam will originate from an 1.4 x λ/2 cell SRF cavity with a normal-conducting, high quantum efficiency CsK2Sb cathode, implementing a modified HZDR-style cathode insert. This prototype injector potentially allows for 6 mA beam current and up to 3.5 MeV beam kinetic energy, limited by the modified twin TTF-III fundamental power couplers. In this contribution the operation of the SRF injector cavity with a Copper cathode within a dedicated beam test experiment called Gunlab will be presented. The second half of the talk will give an overview about on-going activities to refurbish and reinstall the SRF gun module in the accelerator hall in BERLinPro. Also an insight into the repair attempts of the first cavity suffering from field emission will be given.

Slides THCOZBS02 [21.091 MB]

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THCOZBS03

Magnetized Beam Generated from DC Gun for JLEIC Electron Cooler

S.V. Benson, P.A. Adderley, J.F. Benesch, D.B. Bullard, J.M. Grames, J. Guo, F.E. Hannon, J. Hansknecht, C. Hernandez-Garcia, R. Kazimi, G.A. Krafft, M.A. Mamun, M. Poelker, R. Suleiman, M.G. Tiefenback, Y.W. Wang, S. Zhang
JLab, Newport News, Virginia, USA
J.R. Delayen
ODU, Norfolk, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
Bunched-beam electron cooling is a key feature of all proposed designs of the future electron-ion collider, and a requirement for achieving the specified collision luminosity of the order 1034 cm^-2s⁻¹. For the Jefferson Lab Electron Ion Collider (JLEIC), fast cooling of ion beams will be accomplished via so-called ’magnetized electron cooling’, where the cooling process will occur inside a long solenoid field, which will be part of the collider ring and facilitated using a circulator ring and Energy Recovery Linac (ERL). In this contribution, we describe recent achievements that include the generation of picosecond-bunch magnetized beams at average currents up to 28 mA with exceptionally long photocathode lifetime, and independent demonstrations of magnetized beam with high bunch charge up to 700 pC at 10s of kHz repetition rates using a compact 300 kV DC high voltage photogun with an inverted insulator geometry and alkali-antimonide photocathodes. Magnetization characterization including beam rotation and drift emittance were also presented for various gun bias voltages and laser spot sizes at the photocathode using 532 nm lasers with DC and RF time structure. These accomplishments mark important steps toward demonstrating the feasibility of a technically challenging JLEIC cooler design using magnetized beams.

Slides THCOZBS03 [14.025 MB]

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THCOZBS04

Injector Development at KEK

T. Miyajima
KEK, Ibaraki, Japan

Since 2013, we have operated the compact ERL (cERL) injector at KEK to demonstrate hardware and beam performances for future ERL accelerator. The injector consists of a 500 kV DC photocathode gun, solenoid magnets, a normal conducting buncher and three 2-cell superconducting cavities. In beam operation, the DC gun with GaAS photocathode is very stable with DC 500 kV, and can generate stable CW 1 mA electron beam. For low bunch charge operation, we achieved designed beam performance with low emittance and short bunch length in the injector. From 2017, we started high bunch charge operation with 60 pC bunch charge toward an infrared free electron laser (IR FEL) test. In June 2019, we achieved the requirements of injector beam performance for the IR FEL test, which were < 3 mm mrad normalized emittance and 4 ps RMS bunch length.

Slides THCOZBS04 [4.475 MB]

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FRCOYBS03

Working Group Summary: Electron Sources and Injectors

E. Wang
BNL, Upton, New York, USA
L. Cultrera
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

To be added

Slides FRCOYBS03 [34.567 MB]

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