ERL2019 - List of Keywords (cavity)

Paper	Title	Other Keywords	Page
MOCOXBS02	ERL Operation of S-DALINAC*	operation, linac, beam-loading, MMI	1
	M. Arnold, T. Bahlo, M. Dutine, R. Grewe, J.H. Hanten, L.E. Jürgensen, J. Pforr, N. Pietralla, F. Schließmann, M. Steinhorst, S. Weih TU Darmstadt, Darmstadt, Germany
	Funding: Work supported by DFG through GRK 2128 The S-DALINAC is a superconducting electron accelerator operated at TU Darmstadt. It is running in recirculating operation since 1991. An upgrade done in the years 2015/2016 enables to use the S-DALINAC as an energy-recovery linac (ERL) [1]. The lattice is capable of a once- (up to 34 MeV) or twice-recirculating ERL operation (up to 68 MeV). For both modes dedicated beam dynamics simulations have been conducted. An important aspect is the effect of phase slippage and its influence on the quality of the decelerated beam. Furthermore, investigations regarding specialized diagnostic systems are currently ongoing. This is of great importance especially for the twice-recirculating ERL, where two beams of the same energy are transported through the same beam line. The commissioning of the different ERL modes started in 2017 and will be continued during upcoming beam times. This contribution will give an overview on the ERL modes at S-DALINAC. The beam dynamics simulations as well as diagnostics used will be discussed. Results and operational findings of the different ERL runs will be presented. [1] N. Pietralla, Nuclear Physics News, Vol. 28, No. 2, (2018) 4.*
	Slides MOCOXBS02 [3.807 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-MOCOXBS02
About •	paper received ※ 15 September 2019 paper accepted ※ 31 October 2019 issue date ※ 24 June 2020
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MOCOXBS04	The Berlin Energy Recovery Linac Project BERLinPro - Status, Plans and Future Opportunities	linac, gun, operation, cathode	8
	M. Abo-Bakr, N. Al-Saokal, W. Anders, Y. Bergmann, K. Bürkmann-Gehrlein, A. Bundels, A.B. Büchel, P. Echevarria, A. Frahm, H.-W. Glock, F. Glöckner, F. Göbel, S. Heling, J.G. Hwang, A. Jankowiak, C. Kalus, T. Kamps, G. Klemz, J. Knobloch, J. Kolbe, J. Kühn, B.C. Kuske, J. Kuszynski, A.N. Matveenko, M. McAteer, A. Meseck, S. Mistry, R. Müller, A. Neumann, N. Ohm, K. Ott, F. Pflocksch, L. Pichl, J. Rahn, O. Schüler, M. Schuster, Y. Tamashevich, J. Ullrich, A. Ushakov, J. Völker HZB, Berlin, Germany H. Huck DESY Zeuthen, Zeuthen, Germany
	Funding: Work supported by the German Bundesministerium für Bildung und Forschung, Land Berlin and grants of Helmholtz Association The Helmholtz-Zentrum Berlin is constructing the Energy Recovery Linac Prototype BERLinPro, a SRF based demonstration facility for the science and technology of ERLs for future high power, high brilliance electron beam applications. BERLinPro was designed to accelerate a high current (100 mA, 50 MeV), high brilliance (norm. emittance below 1 mm mrad) cw electron beam. Given the recent prioritization of the BESSY II upgrade to the BESSY VSR variable pulse length storage ring, HZB is forced to reduce the project goals of BERLinPro. As a result, the project had to be rescoped with the goal to maximize its scientific impact within the present boundary conditions. We report on the last year’s progress of the building, the warm and cold infrastructure and on the time line, goals nd opportunities for the remaining project run time.
	Slides MOCOXBS04 [13.980 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-MOCOXBS04
About •	paper received ※ 16 September 2019 paper accepted ※ 06 November 2019 issue date ※ 24 June 2020
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MOCOXBS05	Status of the MESA ERL Project	experiment, linac, electron, MMI	14
	F. Hug, K. Aulenbacher, R.G. Heine, D. Simon KPH, Mainz, Germany K. Aulenbacher GSI, Darmstadt, Germany K. Aulenbacher, S. Friederich HIM, Mainz, Germany S. Friederich, P. Heil, R.F.K. Kempf, C. Matejcek IKP, Mainz, Germany
	Funding: This work has been supported by DFG through the PRISMA+ cluster of excellence EXC 2118/2019 and by the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No 730871. MESA is a recirculating superconducting accelerator under construction at Johannes Gutenberg-Universität Mainz. It can be operated in either external beam or ERL mode and will be used for high precision particle physics experiments. The operating beam current and energy in EB mode is 0.15 mA with polarized electrons at 155 MeV. In ERL mode a polarized beam of 1 mA at 10⁵ MeV will be available. In a later construction stage of MESA the beam current in ERL-mode shall be upgraded to 10 mA (unpolarized). Civil construction and commissioning of components like electron gun, LEBT and SRF modules have been started already. We will give a project overview including the accelerator layout, the current status and an outlook to the next construction and commissioning steps.
	Slides MOCOXBS05 [14.029 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-MOCOXBS05
About •	paper received ※ 14 September 2019 paper accepted ※ 06 November 2019 issue date ※ 24 June 2020
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TUCOXBS04	The LHeC ERL - Optics and Performance Optimizations	linac, optics, emittance, lattice	34
	S.A. Bogacz JLab, Newport News, Virginia, USA
	Funding: Work has been authored by Jefferson Science Associates, LLC under Contract No. DE-AC05-06OR23177 with the U.S. Department of Energy. The LHeC 60 GeV ERL baseline design features a racetrack composed of two linacs, completed with 6 return arcs, including vertical spreaders and recombines at the arcs ends. Here, we consider a design strategy aiming at ’downsizing’ the ERL e.g. to 50 GeV, while preserving its performance in terms of synchrotron radiation effects. This results in a significant reduction of accelerator components. The optimization explores tuning of each arc, which takes into account the impact of synchrotron radiation at different energies. At the highest energy, it is crucial to minimize the emittance dilution; therefore, the cells are tuned to minimize the dispersion in the bending sections, as in a theoretical minimum emittance lattice. At the lowest energy, one compensates for the bunch elongation with a negative momentum compaction setup which, additionally, contains the beam size. The intermediate energy arcs are tuned to a double bend achromat lattice, offering a compromise between isochronicity and emittance dilution. Finally, a feasibility of a ’dogbone’ ERL is discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-TUCOXBS04
About •	paper received ※ 16 September 2019 paper accepted ※ 07 November 2019 issue date ※ 24 June 2020
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TUCOXBS05	Beam Timing and Cavity Phasing	linac, acceleration, target, injection	39
	R.M. Koscica, N. Banerjee, G.H. Hoffstaetter, W. Lou, G.T. Premawardhana Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	In a multi-pass Energy Recovery Linac (ERL), each cavity must regain all energy expended from beam acceleration during beam deceleration. The beam should also achieve specific energy targets during each loop that returns it to the linac. To satisfy the energy recovery and loop requirements, one must specify the phase and voltage of cavity fields, and one must control the beam flight times through the return loops. Adequate values for these parameters can be found by using a full scale numerical optimization program. If symmetry is imposed in beam time and energy during acceleration and deceleration, the number of parameters needed decreases, simplifying the optimization. As an example, symmetric models of the Cornell BNL ERL Test Accelerator (CBETA) are considered. Energy recovery results from recent CBETA single-turn tests are presented, as well as multi-turn solutions that satisfy CBETA optimization targets of loop energy and zero cavity loading.
	Slides TUCOXBS05 [5.186 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-TUCOXBS05
About •	paper received ※ 13 September 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020
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TUCOZBS02	A Ferroelectric Fast Reactive Tuner (FE-FRT) to Combat Microphonics	SRF, linac, operation, impedance	42
	N.C. Shipman, J. Bastard, M.R. Coly, F. Gerigk, A. Macpherson, N. Stapley CERN, Geneva, Switzerland I. Ben-Zvi BNL, Upton, New York, USA G. Burt, A. Castilla Lancaster University, Lancaster, United Kingdom C.-J. Jing, A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio, USA E. Nenasheva Ceramics Ltd., St. Petersburg, Russia
	A prototype Fast Reactive Tuner (FRT) for superconducting cavities has been developed, which allows the frequency to be controlled by application of a potential difference across a newly developed ultra-low loss ferro-electric material residing within the tuner. The tuner operates at room temperature, outside of the cryostat and coupled to the cavity via an antenna and co-axial cable. This technique allows for active compensation of microphonics, eliminating the need to design over-coupled fundamental power couplers and thus significantly reducing RF power particularly for low beam current applications. Modelling; simulation; and stability analysis, of the tuner; cavity; measurement system; and feedback loop, have been performed in the frequency and time domain, and are compared to the latest experimental results. The potential benefits of applying this techniques to ERLs, which are seen as one of the major use cases, are detailed both in general and with regards to specific projects. Ideas and designs for an improved next generation FRT are also discussed.
	Slides TUCOZBS02 [5.607 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-TUCOZBS02
About •	paper received ※ 17 September 2019 paper accepted ※ 06 November 2019 issue date ※ 24 June 2020
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TUCOZBS04	Characterization of Microphonics in the cERL Main Linac Superconducting Cavities	controls, LLRF, operation, linac	48
	F. Qiu, D.A. Arakawa, M. Egi, E. Kako, H. Katagiri, T. Konomi, T. Matsumoto, S. Michizono, T. Miura, H. Sakai, K. Umemori KEK, Ibaraki, Japan M. Egi, S. Michizono Sokendai - Hayama, Hayama, Japan E. Kako, T. Konomi, T. Matsumoto, T. Miura, F. Qiu, H. Sakai, K. Umemori Sokendai, Ibaraki, Japan
	In the main linac (ML) of the KEK-cERL, two superconducting cavities with high loaded Q (QL ¿ 1×107) are operated in continuous wave (CW) mode. It is important to control and suppress the microphonics detuning owing to the low bandwidth of the cavities. We evaluated the background microphonics detuning by the low level radio frequency system during the beam operation. Interestingly, a ¿field level dependence microphonics¿ phenomenon was observed on one of the cavities in the ML. Several frequency components were suddenly excited if the cavity field is above a threshold field (~3 MV/m). We found that this threshold field is probably related with the cavity quench limits despite the unclear inherent physical mechanism. Furthermore, in order to optimize the cavity resonance control system for better microphonics rejection, we have measured the mechanical transfer function between the fast piezo tuner and cavity detuning. Finally, we validated this model by comparing the model response with actual system response.
	Slides TUCOZBS04 [7.564 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-TUCOZBS04
About •	paper received ※ 13 September 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020
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TUCOZBS05	Low Level RF ERL Experience at the S-DALINAC*	operation, controls, beam-loading, linac	52
	M. Steinhorst, M. Arnold, T. Bahlo, R. Grewe, L.E. Jürgensen, J. Pforr, N. Pietralla, F. Schließmann, S. Weih TU Darmstadt, Darmstadt, Germany
	Funding: Supported by the DFG through GRK 2128. The recirculating superconducting Darmstadt linear accelerator S-DALINAC [1] is one of the main research instruments at the institute for nuclear physics at the TU Darmstadt. It is operating in cw mode at beam currents of up to 20 uA with energies of up to 130 MeV using a thrice recirculating scheme. In 2010 the present digital low-level rf (LLRF) control system was set into operation. Since 2017 the S-DALINAC can be used as an energy recovery linac (ERL). The ERL mode is adjusted by shifting the phase of the beam by 180° in the second recirculation. The current setup of the LLRF control system is not optimized for the usage in an ERL operation. Therefore investigations in regard of the rf control performance have to be done. The first successful one turn ERL operation was set up in August 2017 where the rf control performance was investigated the first time in this new mode. In this talk the LLRF control system of the S-DALINAC is presented and its perfomance during an ERL operation is discussed. [1] N. Pietralla, Nucl. Phys. News 28 No. 2, 4 (2018).
	Slides TUCOZBS05 [26.760 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-TUCOZBS05
About •	paper received ※ 13 September 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020
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TUCOZBS06	Cryomodules for the Mainz Energy-Recovering Superconducting Accelerator (MESA)	cryomodule, HOM, operation, radiation	56
	T. Stengler, K. Aulenbacher, F. Hug, D. Simon, C.P. Stoll, S.D.W. Thomas KPH, Mainz, Germany K. Aulenbacher HIM, Mainz, Germany K. Aulenbacher GSI, Darmstadt, Germany
	Funding: This work is supported by the German Research Foundation (DFG) under the Cluster of Excellence "PRISMA+" EXC 2118/2019} The Mainz Energy-recovering Superconducting Accelerator (MESA) will be an electron accelerator allowing c.w. operation in energy-recovery (ER) mode. The energy gain of 50 MeV will be provided by two modified ELBE/Rossendorf-type cryomodules. The MESA-cryomodules are delivered and tested. The test results will be discussed.
	Slides TUCOZBS06 [10.644 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-TUCOZBS06
About •	paper received ※ 16 September 2019 paper accepted ※ 11 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	cathode, gun, radiation, electron	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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WEPNEC11	X-Ray ICS Source Based on Modified Push-Pull ERLs	electron, photon, radiation, linac	84
	I. Drebot, A. Bacci, S. Cialdi, L. Faillace, D. Giannotti, M. Rossetti Conti, A.R. Rossi, L. Serafini, M. Statera, V. Torri INFN-Milano, Milano, Italy A. Bosotti, F. Broggi, D. Giove, P. Michelato, L. Monaco, R. Paparella, D. Sertore INFN/LASA, Segrate (MI), Italy P. Cardarelli, M. Gambaccini, G. Paternò, A. Taibi INFN-Ferrara, Ferrara, Italy A. Esposito, A. Gallo, C. Vaccarezza INFN/LNF, Frascati, Italy G. Galzerano POLIMI, Milano, Italy M. Gambaccini UNIFE, Ferrara, Italy G. Mettivier, P. Russo UniNa, Napoli, Italy V. Petrillo, F. Prelz Universita’ degli Studi di Milano & INFN, Milano, Italy E. Puppin Politecnico/Milano, Milano, Italy A. Sarno INFN-Napoli, Napoli, Italy
	We present the conceptual designs of BriXS and BriXSino (a minimal test-bench demonstrator of proof of principle) for a compact X-ray Source based on innovative push-pull ERLs. BriXS, the first stage of the Marix project, is a Compton X-ray source based on superconducting cavity technology with energy recirculation and on a laser system in Fabry-Pérot cavity at a repetition rate of 100 MHz, producing 20-180 keV radiation for medical applications. The energy recovery scheme based on a modified folded push-pull CW-SC twin Linac ensemble allows to sustain MW-class beam power with almost just one hundred kW active power dissipation/consumption.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-WEPNEC11
About •	paper received ※ 20 September 2019 paper accepted ※ 06 November 2019 issue date ※ 24 June 2020
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WEPNEC14	Electromagnetic Design of a Superconducting dual axis Spoke Cavity*	linac, SRF, radiation, acceleration	94
	Ya.V. Shashkov, N.Yu. Samarokov MEPhI, Moscow, Russia I.V. Konoplev JAI, Oxford, United Kingdom
	Funding: The reported study was funded by RFBR according to the research project 18-302-00990 Dual axis superconducting spoke cavity for Energy Recovery Linac application is proposed. Conceptual design of the cavity is shown and preliminary optimiza-tions of the proposed structure have been carried out to minimize the ratio of the peak magnetic and electric fields to the accelerating voltage. The new design and future work are discussed
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-WEPNEC14
About •	paper received ※ 01 October 2019 paper accepted ※ 06 November 2019 issue date ※ 24 June 2020
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WEPNEC19	Optimisation of the PERLE Injector	booster, emittance, gun, electron	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	emittance, cathode, electron, FEL	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	impedance, HOM, kicker, simulation	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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THCOWBS06	Beam Breakup Limit Estimations and Higher Order Mode Characterisation for MESA	HOM, dipole, cryomodule, simulation	134
	C.P. Stoll, F. Hug KPH, Mainz, Germany
	Funding: Work supported by the German Research Foundation (DFG) under the Cluster of Excellence "PRISMA+" EXC 2118/2019, through RTG2128 Accelence and by ARIES. MESA is a two pass energy recovery linac (ERL) currently under construction at the Johannes Gutenberg-University in Mainz. MESA uses two 1.3 GHz TESLA type cavities with 12.5 MV/m of accelerating gradient in a modified ELBE type cryomodule in c.w. operation. One potential limit to maximum beam current in ERLs is the transverse beam breakup (BBU) instability induced by dipole HOMs. These modes can be excited by bunches passing through the cavities off axis. Following bunches are then deflected by the HOMs, which results in even larger offsets for recirculated bunches. This feedback can even lead to beam loss. To measure the quality factors and frequencies for the dressed as well as undressed cavities improves the validity of any current limit estimation done.
	Slides THCOWBS06 [3.256 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-THCOWBS06
About •	paper received ※ 18 September 2019 paper accepted ※ 04 November 2019 issue date ※ 24 June 2020
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THCOXBS02	Development of HOM Coupler with C-Shaped Waveguide for ERL Operation	HOM, insertion, GUI, cryomodule	138
	M. Sawamura, R. Hajima QST, Tokai, Japan M. Egi, K. Enami, T. Furuya, H. Sakai, K. Umemori KEK, Ibaraki, Japan
	HOM damping in the superconducting cavities has been becoming increasingly important for high current beam acceleration. Though some HOM damping devices have already been used with success at moderate currents, they have some inherent disadvantages for high current in principle. We have proposed the new type of the HOM coupler using the C-shaped wave guide (CSWG). The CSWG is structured by topologically transforming a rectangular waveguide into coaxial-like structure whose inner and outer conductors are connected with a plate. Similar to the rectangular waveguide, the CSWG has cutoff frequency whose half wave length is approximately equal to the mean circumference. This enables a smaller low-pass filter than the rectangular waveguide. Since the inner conductor can be easily cooled through the plate and the outer conductor, this prevents the connector for HOM power extraction from temperature rising. These characteristics of the CSWG-type HOM coupler can solve the disadvantages of the conventional damping devices. The properties of sufficient HOM damping were confirmed by the measurements with the CSWG-type HOM couplers equipped to the cavity models.
	Slides THCOXBS02 [7.418 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-THCOXBS02
About •	paper received ※ 13 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	cathode, gun, SRF, laser	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	cathode, gun, laser, electron	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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FRCOWBS04	Essential Instrumentation for the Characterization of ERL Beams	diagnostics, radiation, linac, operation	150
	N. Banerjee, A.C. Bartnik, K.E. Deitrick, J. Dobbins, C.M. Gulliford, G.H. Hoffstaetter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA J.S. Berg, S.J. Brooks, R.J. Michnoff BNL, Upton, New York, USA
	Funding: This work was performed through the support of New York State Energy Research and Development Agency (NYSERDA). The typical requirement of Energy Recovery Linacs to produce beams with high repetition rate and high bunch charge presents unique demands on beam diagnostics. ERLs being quite sensitive to time of flight effects necessitate the use of beam arrival time monitors along with typical position detection. Being subjected to a plethora of dynamic effects, both longitudinal and transverse phase space monitoring of the beam becomes quite important. Additionally, beam halo plays an important role determining the overall transmission. Consequently, we also need to characterize halo both directly using sophisticated beam viewers and indirectly using radiation monitors. In this talk, I will describe the instrumentation essential to ERL operation using the Cornell-BNL ERL Test Accelerator (CBETA) as a pertinent example.
	Slides FRCOWBS04 [7.129 MB]
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FRCOXBS03	Beam Dynamics Simulations for the Twofold ERL Mode at the S-DALINAC*	linac, electron, acceleration, GUI	155
	F. Schließmann, M. Arnold, M. Dutine, J. Pforr, N. Pietralla, M. Steinhorst TU Darmstadt, Darmstadt, Germany
	Funding: Work supported by DFG through GRK 2128 and BMBF through grant No. 05H18RDRB2 The recirculating superconducting electron accelerator S-DALINAC [1] at TU Darmstadt is capable to run as a onefold or twofold Energy Recovery Linac (ERL) with a maximum energy of approximately 34 or 68 MeV in ERL mode, respectively. Since the maximum kinetic energy for the twofold ERL mode at injection is less than 8 MeV (v/c<0.9982) and since several multi-cell cavities designed for v/c=1 are used in the main accelerator, the electrons suffer from the effect of phase slippage. Therefore, beam dynamics simulations for the 6D phase space were performed in order to provide a sufficient beam guiding. [1] N. Pietralla, Nuclear Physics News, Vol. 28, No. 2, 4 (2018).*
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-FRCOXBS03
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FRCOYBS04	Working Group Summary: Superconducting RF	HOM, controls, operation, cryomodule	177
	F. Gerigk CERN, Meyrin, Switzerland P.A. McIntosh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	To be added
	Slides FRCOYBS04 [17.955 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-FRCOYBS04
About •	paper received ※ 20 September 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020
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Paper

Title

Other Keywords

Page

MOCOXBS02

ERL Operation of S-DALINAC*

operation, linac, beam-loading, MMI

1

M. Arnold, T. Bahlo, M. Dutine, R. Grewe, J.H. Hanten, L.E. Jürgensen, J. Pforr, N. Pietralla, F. Schließmann, M. Steinhorst, S. Weih
TU Darmstadt, Darmstadt, Germany

Funding: *Work supported by DFG through GRK 2128
The S-DALINAC is a superconducting electron accelerator operated at TU Darmstadt. It is running in recirculating operation since 1991. An upgrade done in the years 2015/2016 enables to use the S-DALINAC as an energy-recovery linac (ERL) [1]. The lattice is capable of a once- (up to 34 MeV) or twice-recirculating ERL operation (up to 68 MeV). For both modes dedicated beam dynamics simulations have been conducted. An important aspect is the effect of phase slippage and its influence on the quality of the decelerated beam. Furthermore, investigations regarding specialized diagnostic systems are currently ongoing. This is of great importance especially for the twice-recirculating ERL, where two beams of the same energy are transported through the same beam line. The commissioning of the different ERL modes started in 2017 and will be continued during upcoming beam times. This contribution will give an overview on the ERL modes at S-DALINAC. The beam dynamics simulations as well as diagnostics used will be discussed. Results and operational findings of the different ERL runs will be presented.
[1] N. Pietralla, Nuclear Physics News, Vol. 28, No. 2, (2018) 4.

Slides MOCOXBS02 [3.807 MB]

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MOCOXBS04

The Berlin Energy Recovery Linac Project BERLinPro - Status, Plans and Future Opportunities

linac, gun, operation, cathode

8

M. Abo-Bakr, N. Al-Saokal, W. Anders, Y. Bergmann, K. Bürkmann-Gehrlein, A. Bundels, A.B. Büchel, P. Echevarria, A. Frahm, H.-W. Glock, F. Glöckner, F. Göbel, S. Heling, J.G. Hwang, A. Jankowiak, C. Kalus, T. Kamps, G. Klemz, J. Knobloch, J. Kolbe, J. Kühn, B.C. Kuske, J. Kuszynski, A.N. Matveenko, M. McAteer, A. Meseck, S. Mistry, R. Müller, A. Neumann, N. Ohm, K. Ott, F. Pflocksch, L. Pichl, J. Rahn, O. Schüler, M. Schuster, Y. Tamashevich, J. Ullrich, A. Ushakov, J. Völker
HZB, Berlin, Germany
H. Huck
DESY Zeuthen, Zeuthen, Germany

Funding: Work supported by the German Bundesministerium für Bildung und Forschung, Land Berlin and grants of Helmholtz Association
The Helmholtz-Zentrum Berlin is constructing the Energy Recovery Linac Prototype BERLinPro, a SRF based demonstration facility for the science and technology of ERLs for future high power, high brilliance electron beam applications. BERLinPro was designed to accelerate a high current (100 mA, 50 MeV), high brilliance (norm. emittance below 1 mm mrad) cw electron beam. Given the recent prioritization of the BESSY II upgrade to the BESSY VSR variable pulse length storage ring, HZB is forced to reduce the project goals of BERLinPro. As a result, the project had to be rescoped with the goal to maximize its scientific impact within the present boundary conditions. We report on the last year’s progress of the building, the warm and cold infrastructure and on the time line, goals nd opportunities for the remaining project run time.

Slides MOCOXBS04 [13.980 MB]

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MOCOXBS05

Status of the MESA ERL Project

experiment, linac, electron, MMI

14

F. Hug, K. Aulenbacher, R.G. Heine, D. Simon
KPH, Mainz, Germany
K. Aulenbacher
GSI, Darmstadt, Germany
K. Aulenbacher, S. Friederich
HIM, Mainz, Germany
S. Friederich, P. Heil, R.F.K. Kempf, C. Matejcek
IKP, Mainz, Germany

Funding: This work has been supported by DFG through the PRISMA+ cluster of excellence EXC 2118/2019 and by the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No 730871.
MESA is a recirculating superconducting accelerator under construction at Johannes Gutenberg-Universität Mainz. It can be operated in either external beam or ERL mode and will be used for high precision particle physics experiments. The operating beam current and energy in EB mode is 0.15 mA with polarized electrons at 155 MeV. In ERL mode a polarized beam of 1 mA at 10⁵ MeV will be available. In a later construction stage of MESA the beam current in ERL-mode shall be upgraded to 10 mA (unpolarized). Civil construction and commissioning of components like electron gun, LEBT and SRF modules have been started already. We will give a project overview including the accelerator layout, the current status and an outlook to the next construction and commissioning steps.

Slides MOCOXBS05 [14.029 MB]

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TUCOXBS04

The LHeC ERL - Optics and Performance Optimizations

linac, optics, emittance, lattice

34

S.A. Bogacz
JLab, Newport News, Virginia, USA

Funding: Work has been authored by Jefferson Science Associates, LLC under Contract No. DE-AC05-06OR23177 with the U.S. Department of Energy.
The LHeC 60 GeV ERL baseline design features a racetrack composed of two linacs, completed with 6 return arcs, including vertical spreaders and recombines at the arcs ends. Here, we consider a design strategy aiming at ’downsizing’ the ERL e.g. to 50 GeV, while preserving its performance in terms of synchrotron radiation effects. This results in a significant reduction of accelerator components. The optimization explores tuning of each arc, which takes into account the impact of synchrotron radiation at different energies. At the highest energy, it is crucial to minimize the emittance dilution; therefore, the cells are tuned to minimize the dispersion in the bending sections, as in a theoretical minimum emittance lattice. At the lowest energy, one compensates for the bunch elongation with a negative momentum compaction setup which, additionally, contains the beam size. The intermediate energy arcs are tuned to a double bend achromat lattice, offering a compromise between isochronicity and emittance dilution. Finally, a feasibility of a ’dogbone’ ERL is discussed.

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TUCOXBS05

Beam Timing and Cavity Phasing

linac, acceleration, target, injection

39

R.M. Koscica, N. Banerjee, G.H. Hoffstaetter, W. Lou, G.T. Premawardhana
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

In a multi-pass Energy Recovery Linac (ERL), each cavity must regain all energy expended from beam acceleration during beam deceleration. The beam should also achieve specific energy targets during each loop that returns it to the linac. To satisfy the energy recovery and loop requirements, one must specify the phase and voltage of cavity fields, and one must control the beam flight times through the return loops. Adequate values for these parameters can be found by using a full scale numerical optimization program. If symmetry is imposed in beam time and energy during acceleration and deceleration, the number of parameters needed decreases, simplifying the optimization. As an example, symmetric models of the Cornell BNL ERL Test Accelerator (CBETA) are considered. Energy recovery results from recent CBETA single-turn tests are presented, as well as multi-turn solutions that satisfy CBETA optimization targets of loop energy and zero cavity loading.

Slides TUCOXBS05 [5.186 MB]

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TUCOZBS02

A Ferroelectric Fast Reactive Tuner (FE-FRT) to Combat Microphonics

SRF, linac, operation, impedance

42

N.C. Shipman, J. Bastard, M.R. Coly, F. Gerigk, A. Macpherson, N. Stapley
CERN, Geneva, Switzerland
I. Ben-Zvi
BNL, Upton, New York, USA
G. Burt, A. Castilla
Lancaster University, Lancaster, United Kingdom
C.-J. Jing, A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
E. Nenasheva
Ceramics Ltd., St. Petersburg, Russia

A prototype Fast Reactive Tuner (FRT) for superconducting cavities has been developed, which allows the frequency to be controlled by application of a potential difference across a newly developed ultra-low loss ferro-electric material residing within the tuner. The tuner operates at room temperature, outside of the cryostat and coupled to the cavity via an antenna and co-axial cable. This technique allows for active compensation of microphonics, eliminating the need to design over-coupled fundamental power couplers and thus significantly reducing RF power particularly for low beam current applications. Modelling; simulation; and stability analysis, of the tuner; cavity; measurement system; and feedback loop, have been performed in the frequency and time domain, and are compared to the latest experimental results. The potential benefits of applying this techniques to ERLs, which are seen as one of the major use cases, are detailed both in general and with regards to specific projects. Ideas and designs for an improved next generation FRT are also discussed.

Slides TUCOZBS02 [5.607 MB]

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TUCOZBS04

Characterization of Microphonics in the cERL Main Linac Superconducting Cavities

controls, LLRF, operation, linac

48

F. Qiu, D.A. Arakawa, M. Egi, E. Kako, H. Katagiri, T. Konomi, T. Matsumoto, S. Michizono, T. Miura, H. Sakai, K. Umemori
KEK, Ibaraki, Japan
M. Egi, S. Michizono
Sokendai - Hayama, Hayama, Japan
E. Kako, T. Konomi, T. Matsumoto, T. Miura, F. Qiu, H. Sakai, K. Umemori
Sokendai, Ibaraki, Japan

In the main linac (ML) of the KEK-cERL, two superconducting cavities with high loaded Q (QL ¿ 1×107) are operated in continuous wave (CW) mode. It is important to control and suppress the microphonics detuning owing to the low bandwidth of the cavities. We evaluated the background microphonics detuning by the low level radio frequency system during the beam operation. Interestingly, a ¿field level dependence microphonics¿ phenomenon was observed on one of the cavities in the ML. Several frequency components were suddenly excited if the cavity field is above a threshold field (~3 MV/m). We found that this threshold field is probably related with the cavity quench limits despite the unclear inherent physical mechanism. Furthermore, in order to optimize the cavity resonance control system for better microphonics rejection, we have measured the mechanical transfer function between the fast piezo tuner and cavity detuning. Finally, we validated this model by comparing the model response with actual system response.

Slides TUCOZBS04 [7.564 MB]

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TUCOZBS05

Low Level RF ERL Experience at the S-DALINAC*

operation, controls, beam-loading, linac

52

M. Steinhorst, M. Arnold, T. Bahlo, R. Grewe, L.E. Jürgensen, J. Pforr, N. Pietralla, F. Schließmann, S. Weih
TU Darmstadt, Darmstadt, Germany

Funding: *Supported by the DFG through GRK 2128.
The recirculating superconducting Darmstadt linear accelerator S-DALINAC [1] is one of the main research instruments at the institute for nuclear physics at the TU Darmstadt. It is operating in cw mode at beam currents of up to 20 uA with energies of up to 130 MeV using a thrice recirculating scheme. In 2010 the present digital low-level rf (LLRF) control system was set into operation. Since 2017 the S-DALINAC can be used as an energy recovery linac (ERL). The ERL mode is adjusted by shifting the phase of the beam by 180° in the second recirculation. The current setup of the LLRF control system is not optimized for the usage in an ERL operation. Therefore investigations in regard of the rf control performance have to be done. The first successful one turn ERL operation was set up in August 2017 where the rf control performance was investigated the first time in this new mode. In this talk the LLRF control system of the S-DALINAC is presented and its perfomance during an ERL operation is discussed.
*[1] N. Pietralla, Nucl. Phys. News 28 No. 2, 4 (2018).

Slides TUCOZBS05 [26.760 MB]

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TUCOZBS06

Cryomodules for the Mainz Energy-Recovering Superconducting Accelerator (MESA)

cryomodule, HOM, operation, radiation

56

T. Stengler, K. Aulenbacher, F. Hug, D. Simon, C.P. Stoll, S.D.W. Thomas
KPH, Mainz, Germany
K. Aulenbacher
HIM, Mainz, Germany
K. Aulenbacher
GSI, Darmstadt, Germany

Funding: This work is supported by the German Research Foundation (DFG) under the Cluster of Excellence "PRISMA+" EXC 2118/2019}
The Mainz Energy-recovering Superconducting Accelerator (MESA) will be an electron accelerator allowing c.w. operation in energy-recovery (ER) mode. The energy gain of 50 MeV will be provided by two modified ELBE/Rossendorf-type cryomodules. The MESA-cryomodules are delivered and tested. The test results will be discussed.

Slides TUCOZBS06 [10.644 MB]

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WECOXBS03

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

cathode, gun, radiation, electron

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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WEPNEC11

X-Ray ICS Source Based on Modified Push-Pull ERLs

electron, photon, radiation, linac

84

I. Drebot, A. Bacci, S. Cialdi, L. Faillace, D. Giannotti, M. Rossetti Conti, A.R. Rossi, L. Serafini, M. Statera, V. Torri
INFN-Milano, Milano, Italy
A. Bosotti, F. Broggi, D. Giove, P. Michelato, L. Monaco, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
P. Cardarelli, M. Gambaccini, G. Paternò, A. Taibi
INFN-Ferrara, Ferrara, Italy
A. Esposito, A. Gallo, C. Vaccarezza
INFN/LNF, Frascati, Italy
G. Galzerano
POLIMI, Milano, Italy
M. Gambaccini
UNIFE, Ferrara, Italy
G. Mettivier, P. Russo
UniNa, Napoli, Italy
V. Petrillo, F. Prelz
Universita’ degli Studi di Milano & INFN, Milano, Italy
E. Puppin
Politecnico/Milano, Milano, Italy
A. Sarno
INFN-Napoli, Napoli, Italy

We present the conceptual designs of BriXS and BriXSino (a minimal test-bench demonstrator of proof of principle) for a compact X-ray Source based on innovative push-pull ERLs. BriXS, the first stage of the Marix project, is a Compton X-ray source based on superconducting cavity technology with energy recirculation and on a laser system in Fabry-Pérot cavity at a repetition rate of 100 MHz, producing 20-180 keV radiation for medical applications. The energy recovery scheme based on a modified folded push-pull CW-SC twin Linac ensemble allows to sustain MW-class beam power with almost just one hundred kW active power dissipation/consumption.

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WEPNEC14

Electromagnetic Design of a Superconducting dual axis Spoke Cavity*

linac, SRF, radiation, acceleration

94

Ya.V. Shashkov, N.Yu. Samarokov
MEPhI, Moscow, Russia
I.V. Konoplev
JAI, Oxford, United Kingdom

Funding: The reported study was funded by RFBR according to the research project 18-302-00990
Dual axis superconducting spoke cavity for Energy Recovery Linac application is proposed. Conceptual design of the cavity is shown and preliminary optimiza-tions of the proposed structure have been carried out to minimize the ratio of the peak magnetic and electric fields to the accelerating voltage. The new design and future work are discussed

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WEPNEC19

Optimisation of the PERLE Injector

booster, emittance, gun, electron

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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WEPNEC21

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

emittance, cathode, electron, FEL

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

impedance, HOM, kicker, simulation

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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reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-WEPNEC22

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

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THCOWBS06

Beam Breakup Limit Estimations and Higher Order Mode Characterisation for MESA

HOM, dipole, cryomodule, simulation

134

C.P. Stoll, F. Hug
KPH, Mainz, Germany

Funding: Work supported by the German Research Foundation (DFG) under the Cluster of Excellence "PRISMA+" EXC 2118/2019, through RTG2128 Accelence and by ARIES.
MESA is a two pass energy recovery linac (ERL) currently under construction at the Johannes Gutenberg-University in Mainz. MESA uses two 1.3 GHz TESLA type cavities with 12.5 MV/m of accelerating gradient in a modified ELBE type cryomodule in c.w. operation. One potential limit to maximum beam current in ERLs is the transverse beam breakup (BBU) instability induced by dipole HOMs. These modes can be excited by bunches passing through the cavities off axis. Following bunches are then deflected by the HOMs, which results in even larger offsets for recirculated bunches. This feedback can even lead to beam loss. To measure the quality factors and frequencies for the dressed as well as undressed cavities improves the validity of any current limit estimation done.

Slides THCOWBS06 [3.256 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-THCOWBS06

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paper received ※ 18 September 2019 paper accepted ※ 04 November 2019 issue date ※ 24 June 2020

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THCOXBS02

Development of HOM Coupler with C-Shaped Waveguide for ERL Operation

HOM, insertion, GUI, cryomodule

138

M. Sawamura, R. Hajima
QST, Tokai, Japan
M. Egi, K. Enami, T. Furuya, H. Sakai, K. Umemori
KEK, Ibaraki, Japan

HOM damping in the superconducting cavities has been becoming increasingly important for high current beam acceleration. Though some HOM damping devices have already been used with success at moderate currents, they have some inherent disadvantages for high current in principle. We have proposed the new type of the HOM coupler using the C-shaped wave guide (CSWG). The CSWG is structured by topologically transforming a rectangular waveguide into coaxial-like structure whose inner and outer conductors are connected with a plate. Similar to the rectangular waveguide, the CSWG has cutoff frequency whose half wave length is approximately equal to the mean circumference. This enables a smaller low-pass filter than the rectangular waveguide. Since the inner conductor can be easily cooled through the plate and the outer conductor, this prevents the connector for HOM power extraction from temperature rising. These characteristics of the CSWG-type HOM coupler can solve the disadvantages of the conventional damping devices. The properties of sufficient HOM damping were confirmed by the measurements with the CSWG-type HOM couplers equipped to the cavity models.

Slides THCOXBS02 [7.418 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-THCOXBS02

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paper received ※ 13 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

cathode, gun, SRF, laser

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

cathode, gun, laser, electron

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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reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-THCOYBS02

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

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FRCOWBS04

Essential Instrumentation for the Characterization of ERL Beams

diagnostics, radiation, linac, operation

150

N. Banerjee, A.C. Bartnik, K.E. Deitrick, J. Dobbins, C.M. Gulliford, G.H. Hoffstaetter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
J.S. Berg, S.J. Brooks, R.J. Michnoff
BNL, Upton, New York, USA

Funding: This work was performed through the support of New York State Energy Research and Development Agency (NYSERDA).
The typical requirement of Energy Recovery Linacs to produce beams with high repetition rate and high bunch charge presents unique demands on beam diagnostics. ERLs being quite sensitive to time of flight effects necessitate the use of beam arrival time monitors along with typical position detection. Being subjected to a plethora of dynamic effects, both longitudinal and transverse phase space monitoring of the beam becomes quite important. Additionally, beam halo plays an important role determining the overall transmission. Consequently, we also need to characterize halo both directly using sophisticated beam viewers and indirectly using radiation monitors. In this talk, I will describe the instrumentation essential to ERL operation using the Cornell-BNL ERL Test Accelerator (CBETA) as a pertinent example.

Slides FRCOWBS04 [7.129 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-FRCOWBS04

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paper received ※ 19 September 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020

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FRCOXBS03

Beam Dynamics Simulations for the Twofold ERL Mode at the S-DALINAC*

linac, electron, acceleration, GUI

155

F. Schließmann, M. Arnold, M. Dutine, J. Pforr, N. Pietralla, M. Steinhorst
TU Darmstadt, Darmstadt, Germany

Funding: *Work supported by DFG through GRK 2128 and BMBF through grant No. 05H18RDRB2
The recirculating superconducting electron accelerator S-DALINAC [1] at TU Darmstadt is capable to run as a onefold or twofold Energy Recovery Linac (ERL) with a maximum energy of approximately 34 or 68 MeV in ERL mode, respectively. Since the maximum kinetic energy for the twofold ERL mode at injection is less than 8 MeV (v/c<0.9982) and since several multi-cell cavities designed for v/c=1 are used in the main accelerator, the electrons suffer from the effect of phase slippage. Therefore, beam dynamics simulations for the 6D phase space were performed in order to provide a sufficient beam guiding.
[1] 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-ERL2019-FRCOXBS03

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paper received ※ 17 October 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020

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FRCOYBS04

Working Group Summary: Superconducting RF

HOM, controls, operation, cryomodule

177

F. Gerigk
CERN, Meyrin, Switzerland
P.A. McIntosh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

To be added

Slides FRCOYBS04 [17.955 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-FRCOYBS04

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paper received ※ 20 September 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020

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