ERL2019 - Classification: WG2: ERL beam dynamics and instrumentation

Paper	Title	Page
TUCOWBS01	Longitudinal Phase Space Dynamics in ERLs
	S.V. Benson, C. Tennant JLab, Newport News, Virginia, USA D. Douglas Douglas Consulting, York, Virginia, USA P.E. Evtushenko HZDR, Dresden, Germany
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 Both the dynamics and the architecture of an energy recovery linac are primarily determined by the longitudinal match. This match can be manipulated by both the magnetic lattice and the RF systems. Here we will present a few examples of systems and the longitudinal solutions found for each. The first application is a free-electron laser application where a short bunch and high peak current are required. The laser increases the energy spread and lowers the energy and this must be compensated in the ERL design. The second application is for an internal target experiment where the need was for small energy spread rather than a short bunch. The third example is for an electron cooler where the bunch must be very long with extremely small energy spread. The beam disruption due to cooling is small but CSR and microbunching effects are a real challenge. In the FEL, the longitudinal matching is mainly accomplished via lattice matching while in the cooler application the RF system is the dominant method to control the phase space. The internal target can be addressed either way.
	Slides TUCOWBS01 [3.666 MB]
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TUCOWBS02	Beyond the Limits of 1D Coherent Synchrotron Radiation
	P.H. Williams STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Collective effects such as coherent synchrotron radiation (CSR) can have a strong influence of the properties of an electron bunch. In particular, CSR experienced by a bunch on a curved trajectory can increase the transverse emittance of a beam. In this contribution, we present an extension to the well-established 1D theory of CSR by accounting fully for the forces experienced in the entrance and exit transients of a bending magnet. A new module of the General Particle Tracer (GPT) tracking code was developed for this study, showing good agreement with theory. In addition to this analysis, we present experimental measurements of the emittance growth experienced in the FERMI bunch compressor chicane as a function of bunch length. When the bunch undergoes extreme compression, the 1D theory breaks down and is no longer valid. A comparison between the 1D theory, experimental measurements and a number of codes which simulate CSR differently are presented, showing better agreement when the transverse properties of the bunch are taken into account.
	Slides TUCOWBS02 [1.146 MB]
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TUCOWBS03	CSR Phase Space Dilution in CBETA
	W. Lou, G.H. Hoffstaetter, D. Sagan Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA C.E. Mayes SLAC, Menlo Park, California, USA
	While Energy Recovery Linac (ERLs) give promise to deliver unprecedentedly high beam current with simultaneously small emittance, Coherent Synchrotron Radiation (CSR) can pose detrimental effect on the beam at high bunch charges and short bunch lengths. CBETA, the Cornell BNL ERL Test Accelerator, will be the first multi-turn ERL with SRF accelerating cavities and Fixed Field Alternating gradient (FFA) beamline. To investigate the CSR effects on CBETA, the established simulation code Bmad has been used to track a bunch with different CSR parameters. We found that CSR causes phase space dilution, and the effect becomes more significant as the bunch charge and recirculation pass increase. Convergence tests have been performed for the CSR parameters to validate the observed micro-bunching instability. Potential ways to mitigate the effect involving vacuum chamber shielding and increasing bunch length are also being investigated.
	Slides TUCOWBS03 [5.215 MB]
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TUCOXBS01	Beam Halo in Energy Recovery Linacs	23
	O.A. Tanaka KEK, Ibaraki, Japan
	The beam halo mitigation is a very important challenge for reliable and safe operation of a high energy machine. Since Energy Recovery Linacs (ERLs) are known to produce high energy electron beams of high virtual power and high density, the beam halo and related beam losses should be properly mitigated to avoid a direct damage of the equipment, an unacceptable increase in the vacuum pressure, a radiation activation of the accelerator components etc. To keep the operation stable, one needs to address all possible beam halo formation mechanisms, including those unique to each machine that can generate beam halo. Present report is dedicated to the beam halo related activities at the Compact ERL at KEK, and our operational experience with respect to the beam halo.
	Slides TUCOXBS01 [4.480 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-TUCOXBS01
About •	paper received ※ 16 September 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020
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TUCOXBS03	Beam Dynamics Layout of the MESA ERL	28
	F. Hug, K. Aulenbacher, D. Simon, C.P. Stoll, S.D.W. Thomas KPH, Mainz, Germany K. Aulenbacher GSI, Darmstadt, Germany K. Aulenbacher HIM, 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. The MESA project is currently under construction at Johannes Gutenberg-Universität Mainz. It will be used for high precision particle physics experiments in two different operation modes: external beam (EB) mode (0.15 mA; 155 MeV) and energy recovery (ERL) mode (1 mA; 10⁵ MeV). The recirculating main linac follows the concept of a double sided accelerator design with vertical stacking of return arcs. Up to three recirculations are possible. Acceleration is done by four TESLA/XFEL 9-cell SRF cavities located in two modified ELBE cryomodules. Within this contribution the recirculation optics for MESA will be presented. Main goals are achieving best energy spread at the experimental setups in recirculating ERL and non-ERL operation and providing small beta-functions within the cryomodules for minimizing HOM excitation at high beam currents.
	Slides TUCOXBS03 [5.077 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-TUCOXBS03
About •	paper received ※ 16 September 2019 paper accepted ※ 06 November 2019 issue date ※ 24 June 2020
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TUCOXBS04	The LHeC ERL - Optics and Performance Optimizations	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	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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WEPNEC02	Investigation and Mitigation of the Mie-Scattering on the Surface of the First Objective Lens for Coronagraph-Based Halo Monitor
	J.G. Hwang, J. Kuszynski HZB, Berlin, Germany
	Funding: This work was supported by the German Bundesministerium für Bildung und Forschung, Land Berlin and grants of Helmholtz Association. Since, due to the heat capacity of the cryogenics, additional heat load on a cryogenic system as a result of uncontrolled beam losses is only allowed to be below 50 W which corresponds to 10^-5 respected to the full power of BERLinPro, the development of diagnostics which can measure the intensity in the order of 10^-5 is crucial. In our previous beam test of the coronagraph-based halo monitor with various operation modes of the BESSY II storage ring, the limitation of the measurement of the halo distribution was to be 10^-4 respected to the core intensity due to the noise produced by scattered light from digs and scratches of the first objective lens. In order to mitigate the noise level produced from the surface of the objective lens to reach 10^-5 to 10^-6, the Mie-scattering effect was investigated, and furthermore, a high-quality surface lens was purchased.
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WEPNEC06	Radiation Protection Instrumentation of BERLinPro
	L. Pichl, Y. Bergmann, A. Bundels, K. Ott HZB, Berlin, Germany
	Funding: Work supported by the German Bundesministerium für Bildung und Forschung, Land Berlin and grants of Helmholtz Association The Energy Recovery Linac project BERLinPro is a test facility to study the beam parameter range necessary for an ERL as synchrotron light source [1]. It is currently under construction and is designed to operate with the maximum beam parameters of 50 MeV and 100 mA cw current. Even if the electron losses within the recirculator are limited to 0.6 % due to the available rf power, (at higher losses an immediate beam break-up occurs because of the ERL principle) the beam loss power can be by orders of magnitude higher than in electron storage rings used for synchrotron radiation. The Fluka [2,3] calculations of the resulting activations of machine components and air activations have been discussed in earlier papers [4,5]. In this work we present the components of the ambient dosimetry, the measurement system of air activations and their inclusion in the personal safety system. Additionally we present recent calculations of the activation of cooling water and the method of storing and measuring it in case of a leakage. 1 M Abo-Bakr et al SRF2009 Berlin 2 G Battistoni et al AIP Conf. Proc. 896 2007 3 A Fasso et al CERN-2005-10 2005 4 M Helmecke et al RADSYNCH2013 BNL 5 K Ott et al RADSYNCH2015 DESY
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WEPNEC08	Dispersion Matching With Space Charge in MESA	74
	A. Khan, O. Boine-Frankenheim TEMF, TU Darmstadt, Darmstadt, Germany K. Aulenbacher IKP, Mainz, Germany
	Funding: Supported by the DFG through GRK 2128. For intense electron bunches traversing through bends, as for example the recirculation arcs of an Energy-Recovery Linac (ERL), dispersion matching with space charge of an arc into the subsequent radio-frequency (RF) structure is essential to maintain the beam quality. We show that beam envelopes and dispersion along the bends and recirculation arcs of an ERL, including space charge forces, can be matched to adjust the beam to the parameters of the subsequent section. The present study is focused on a small-scale, double-sided recirculating linac Mainz Energy-recovering Superconducting Accelerator (MESA). MESA is an under construction two pass ERL at the Johannes Gutenberg-Universit\"at Mainz, which should deliver a continuous wave (CW) beam at 10⁵ MeV for physics experiments with a pseudo-internal target. In this work, a coupled transverse-longitudinal beam matrix approach for matching with space charge in MESA is employed.
	Poster WEPNEC08 [1.190 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-WEPNEC08
About •	paper received ※ 12 September 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020
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WEPNEC10	Investigation on the Ion Clearing of Multi-Purpose Electrodes of BERLinPro	80
	G. Pöplau COMPAEC e.G., Rostock, Germany A. Meseck KPH, Mainz, Germany A. Meseck HZB, Berlin, Germany
	High-brightness electron beams provided by modern accelerators require several measures to preserve their high quality and to avoid instabilities. The mitigation of the impact of residual ions is one of these measures. It is particularly important if high bunch charges in combination with high repetition rates are aimed for. This is because ions can be trapped in the strong negative electrical potential of the electron beam causing emittance blow-up, increased beam halo and longitudinal and transverse instabilities. One ion-clearing strategy is the installation of clearing electrodes. Of particular interest in this context is the performance of multi-purpose electrodes, which are designed such that they allow for a simultaneous ion-clearing and beam-position monitoring. Such electrodes will be installed in the BERLinPro facility. In this contribution, we present numerical studies of the performance of multi-purpose clearing-electrodes planned for BERLinPro, i.e. we investigate the behavior of ions generated by electron bunches while passing through the field of the electrodes. Hereby, several ion species and configurations of electrodes are considered.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-WEPNEC10
About •	paper received ※ 11 October 2019 paper accepted ※ 06 November 2019 issue date ※ 24 June 2020
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WEPNEC12	Beam Optics of Bunch Compression at Compact ERL
	M. Shimada, Y. Honda, R. Kato, T. Miyajima, N. Nakamura, T. Obina KEK, Ibaraki, Japan
	Short electron bunch is essential for THz coherent transition radiation or FEL oscillation. Therefore, the bunch compression is studied at the compact ERL in KEK site. We demonstrated it and experimentally evaluated the bunch length and the transverse emittance. The results of the optics and beam commissioning will be presented.
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WEPNEC16	Electron Outcoupling System of Novosibirsk Free Electron Laser Facility - Beam Dynamics Calculation and the First Experiments	98
	Ya.V. Getmanov, A.S. Matveev, O.A. Shevchenko, N.A. Vinokurov BINP SB RAS, Novosibirsk, Russia Ya.V. Getmanov, A.S. Matveev, N.A. Vinokurov NSU, Novosibirsk, Russia
	The radiation power of the FEL with optical cavity can be limited by the overheating of reflecting mirrors. In the electron outcoupling scheme electron beam radiates the main power at a slight angle to the optical axis. For this, it is necessary to divide undulator by a dipole magnet at least in two parts - the first for the electron beam bunching in the field of the main optical mode, and the second for the power radiation by deflected beam. Electron outcoupling system is installed on the third FEL based on the multiturn energy recovery linac of the Novosibirsk Free Electron Laser facility (NovoFEL). It consists of three undulators, dipole correctors and two quadrupole lenses assembled between them. There are two different configurations of the system since the electrons can be deflected in either the second or the third undulator. The electron beam dynamics calculations and the results of the first experiments are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-WEPNEC16
About •	paper received ※ 01 October 2019 paper accepted ※ 06 November 2019 issue date ※ 24 June 2020
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WEPNEC18	Analytic Longitudinal Phase Space Solutions for Multipass Energy Recovery Linacs
	P.H. Williams STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom I.R. Bailey, P.H. Williams Cockcroft Institute, Warrington, Cheshire, United Kingdom I.R. Bailey Lancaster University, Lancaster, United Kingdom T.K. Charles The University of Melbourne, Melbourne, Victoria, Australia T.K. Charles CERN, Geneva, Switzerland G. Perez-Segurana Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
	The longitudinal solution space of an energy recovery linac is an under-constrained system. For applications where we wish to compress the bunches for delivery to, for example, a free-electron laser or an interaction point, and simultaneously ensure full recovery it is useful to be able to rapidly ascertain and assess the possible solutions. Moreover, when we consider multi-pass ERLS, we quickly conclude that a trial-and-error approach to deriving such solutions (through for example one-dimensional particle tracking) is impractical. Here we extend an analytic recurrence method of deriving phase space solutions in multistage compression schemes, due to Zagorodnov & Dohlus, to multi-pass energy recovery linac systems. We use this method to categorise classes of solutions, and explore the implications of the energy recovery condition.
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WECOYBS04	Commissioning of theBERLinPro Diagnostics Line using Machine Learning Techniques	123
	B.C. Kuske HZB, Berlin, Germany A. Adelmann PSI, Villigen PSI, Switzerland
	Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin and grants of Helmholtz Association BERLinPro is an Energy Recovery Linac (ERL) project currently being set up at HZB, Berlin. Commissioning is planned for early 2020. HZB triggered and supported the development of release 2.0 of the particle tracking code OPAL, that is now also applicable to ERLs. OPAL is set up as an open source, highly parallel tracking code for large accelerator systems and many particles. Thus, it is idially suited to serve attempts of applying machine learning approaches to beam dynamics, as demonstrated in [1]. OPAL is used to calculate hundreds of randomized machines close to the commissioning optics of BERLinPro. This data base will be used to train a neural network, to establish a surrogate model of BERLinPro, much faster than any physical model including particle tracking. First steps, like the setup of the sampler and a sensitivity analysis of the resulting data are presented. The ultimate goal of this work is to use machine learning techniques during the commissioning of BERLinPro. Future steps are outlined. [1] A. Edelen, A. Adelmann, N. Neveu, Y. Huber, M. Frey, ’Machine Learning to enable orders of magnitude speedup in multi-objective optimization of particle accelerator systems’
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-WECOYBS04
About •	paper received ※ 30 October 2019 paper accepted ※ 07 November 2019 issue date ※ 24 June 2020
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FRCOWBS02	Design and Commissioning Experience with State of the Art MPS for LEReC Accelerator
	S. Seletskiy, Z. Altinbas, D. Bruno, M.R. Costanzo, K.A. Drees, A.V. Fedotov, D.M. Gassner, X. Gu, L.R. Hammons, J. Hock, R.L. Hulsart, P. Inacker, J.P. Jamilkowski, D. Kayran, J. Kewisch, C. Liu, K. Mernick, T.A. Miller, M.G. Minty, M.C. Paniccia, W.E. Pekrul, I. Pinayev, V. Ptitsyn, T.C. Shrey, L. Smart, K.S. Smith, R. Than, P. Thieberger, J.E. Tuozzolo, W. Xu, Z. Zhao BNL, Upton, New York, USA
	The Low Energy RHIC Electron Cooler (LEReC), the world’s first electron cooler to employ an RF electron accelerator, has been recently fully commissioned. The LEReC is a high-current, high-brightness accelerator featuring ~100 m of beamline and is designed to operate with 1.6-2.6 MeV electron beams of up to 140 kW beam power. The LEReC requires a dedicated machine protection system (MPS) capable of interlocking electron beam within 40 us and is equipped with multiple levels of protection. In this paper we summarize our experience with designing, building, and operating the LEReC MPS.
	Slides FRCOWBS02 [2.031 MB]
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FRCOWBS03	Beam Commissioning Experience at Low Energy RHIC Electron Cooler (LEReC)
	D. Kayran, Z. Altinbas, K.A. Drees, A.V. Fedotov, M. Gaowei, X. Gu, R.L. Hulsart, P. Inacker, J.P. Jamilkowski, Y.C. Jing, J. Kewisch, C. Liu, J. Ma, K. Mernick, T.A. Miller, M.G. Minty, M.C. Paniccia, I. Pinayev, V. Ptitsyn, V. Schoefer, S. Seletskiy, F. Severino, A. Sukhanov, P. Thieberger, J.E. Tuozzolo, E. Wang, G. Wang, H. Zhao, Z. Zhao BNL, Upton, 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 high-current high-brightness electron accelerator for cooling of RHIC ions at low energy (LEReC) was successfully commissioned at BNL. A beam quality suitable for electron cooling has been achieved. Cooling of single ion bunches in RHIC using a new approach of bunched-beam electron cooling was demonstrated during 2019. To achieve such a cooling with non-magnetized electron beams and RF acceleration required proper beam manipulation in the longitudinal phase space while preserving transverse emittances. Electron beam with kinetic energy of 1.6 MeV with beam quality suitable for cooling was successfully propagated through 100 meters of beam lines including dispersion sections and maintained through both cooling sections in RHIC. The LEReC accelerator includes a photocathode DC gun, a laser system, a photocathode delivery system, magnets, beam diagnostics, a SRF booster cavity, and a set of Normal Conducting RF cavities to provide sufficient flexibility to tune the beam in the longitudinal phase space. In this paper we discuss experience learned during LEReC beam commissioning.
	Slides FRCOWBS03 [24.527 MB]
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FRCOWBS04	Essential Instrumentation for the Characterization of ERL Beams	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]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-FRCOWBS04
About •	paper received ※ 19 September 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020
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FRCOXBS01	Electronic Modulation of the FEL-Oscillator Radiation Power Driven by ERL
	O.A. Shevchenko, E.V. Bykov, Ya.V. Getmanov, S.S. Serednyakov, S.V. Tararyshkin BINP SB RAS, Novosibirsk, Russia M.V. Fedin, S.L. Veber International Tomography Center, SB RAS, Novosibirsk, Russia Ya.V. Getmanov, S.S. Serednyakov NSU, Novosibirsk, Russia
	Funding: RSF grant no. 17-13-01412 FEL oscillators usually operate in CW mode and produce periodic train of radiation pulses but some user experiments require modulation of radiation power. Conventional way to obtain this modulation is using of mechanical shutters however it cannot provide very short switching time and may lead to decreasing of the radiation beam quality. Another way could be based on the electron beam current modulation but it cannot be used in the ERL. We propose a simple way of fast control of the FEL lasing which is based on periodic phase shift of electron bunches with respect to radiation stored in optical cavity. The phase shift required to suppress lasing is relatively small and it does not change significantly repetition rate. This approach has been realized at NovoFEL facility. It allows to generate radiation macropulses of desirable length down to several microseconds (limited by quality factor of optical cavity and FEL gain) which can be synchronized with external trigger. We present detailed description of electronic power modulation scheme and discuss the results of experiments.
	Slides FRCOXBS01 [7.025 MB]
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FRCOXBS03	Beam Dynamics Simulations for the Twofold ERL Mode at the S-DALINAC*	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
About •	paper received ※ 17 October 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020
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FRCOXBS04	Status of the Control System for the Energy Recovery Linac BERLinPro at HZB	159
	T. Birke, P. Echevarria, D. Eichel, R. Fleischhauer, J.G. Hwang, G. Klemz, R. Müller, C. Schröder, E. Suljoti, A. Ushakov HZB, Berlin, Germany
	BERLinPro is an energy recovery linac (ERL) demonstrator project built at HZB. It features CW SRF technology for the low emittance, high brightness gun, the booster module and the recovery linac. Construction and civil engineering are mostly completed. Synchronized with the device integration the EPICS based control system is being set-up for testing, commissioning and finally operation. In the warm part of the accelerator technology is used that is already operational at BESSY and MLS (e.g. CAN-bus and PLC/OPCUA). New implementations like the machine protection system and novel major subsystems (e.g. LLRF, Cryo-Controls, photo cathode laser) need to be integrated. The first RF transmitters have been tested and commissioned. Around the time of this workshop the first segment of the accelerator is scheduled to become online. For commissioning and operation of the facility the standard set of EPICS tools form the back-bone. A set of generic python applications already developed at BESSY/MLS will be adapted to the specifics of BERLinPro. Scope and current project status are described in this paper.
	Slides FRCOXBS04 [11.021 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-FRCOXBS04
About •	paper received ※ 05 September 2019 paper accepted ※ 11 November 2019 issue date ※ 24 June 2020
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FRCOXBS05	Adjusting BERLinPro Optics to Commissioning Needs	165
	B.C. Kuske, M. McAteer HZB, Berlin, Germany
	Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin and grants of Helmholtz Association BERLinPro is an Energy Recovery Linac (ERL) project currently being set up at HZB, Berlin. During the turn of the project, many adaptations of the optics to changing hardware realities were necessary. To name only one, commissioning of the recirculator will now be realized with the superconducting linac module fabricated for the Mainz ERL project MESA, as the BERLinPro linac is delayed. The Mainz linac will supply roughly 60% of the energy planned for the BERLinPro linac module and will be limited by higher order modes in the cavities to few mA of current. While the adapted optics shows similar parameters as the original 50MeV optics, studies of longitudinal space charge and coherent synchrotron radiation show that the energy leads to large emittance blow up due toμbunching. Furthermore, preparations for commissioning with gun fields much lower than the original 30MV/m in the 1.4 cell SRF gun are introduced and according optics are presented.
	Slides FRCOXBS05 [9.766 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-FRCOXBS05
About •	paper received ※ 19 September 2019 paper accepted ※ 04 November 2019 issue date ※ 24 June 2020
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FRCOYBS02	Working Group Summary: ERL Beam Dynamics and Instrumentation
	G.H. Hoffstaetter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA P.E. Evtushenko HZDR, Dresden, Germany
	To be added
	Slides FRCOYBS02 [5.605 MB]
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Paper

Title

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TUCOWBS01

Longitudinal Phase Space Dynamics in ERLs

S.V. Benson, C. Tennant
JLab, Newport News, Virginia, USA
D. Douglas
Douglas Consulting, York, Virginia, USA
P.E. Evtushenko
HZDR, Dresden, Germany

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
Both the dynamics and the architecture of an energy recovery linac are primarily determined by the longitudinal match. This match can be manipulated by both the magnetic lattice and the RF systems. Here we will present a few examples of systems and the longitudinal solutions found for each. The first application is a free-electron laser application where a short bunch and high peak current are required. The laser increases the energy spread and lowers the energy and this must be compensated in the ERL design. The second application is for an internal target experiment where the need was for small energy spread rather than a short bunch. The third example is for an electron cooler where the bunch must be very long with extremely small energy spread. The beam disruption due to cooling is small but CSR and microbunching effects are a real challenge. In the FEL, the longitudinal matching is mainly accomplished via lattice matching while in the cooler application the RF system is the dominant method to control the phase space. The internal target can be addressed either way.

Slides TUCOWBS01 [3.666 MB]

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TUCOWBS02

Beyond the Limits of 1D Coherent Synchrotron Radiation

P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Collective effects such as coherent synchrotron radiation (CSR) can have a strong influence of the properties of an electron bunch. In particular, CSR experienced by a bunch on a curved trajectory can increase the transverse emittance of a beam. In this contribution, we present an extension to the well-established 1D theory of CSR by accounting fully for the forces experienced in the entrance and exit transients of a bending magnet. A new module of the General Particle Tracer (GPT) tracking code was developed for this study, showing good agreement with theory. In addition to this analysis, we present experimental measurements of the emittance growth experienced in the FERMI bunch compressor chicane as a function of bunch length. When the bunch undergoes extreme compression, the 1D theory breaks down and is no longer valid. A comparison between the 1D theory, experimental measurements and a number of codes which simulate CSR differently are presented, showing better agreement when the transverse properties of the bunch are taken into account.

Slides TUCOWBS02 [1.146 MB]

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TUCOWBS03

CSR Phase Space Dilution in CBETA

W. Lou, G.H. Hoffstaetter, D. Sagan
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
C.E. Mayes
SLAC, Menlo Park, California, USA

While Energy Recovery Linac (ERLs) give promise to deliver unprecedentedly high beam current with simultaneously small emittance, Coherent Synchrotron Radiation (CSR) can pose detrimental effect on the beam at high bunch charges and short bunch lengths. CBETA, the Cornell BNL ERL Test Accelerator, will be the first multi-turn ERL with SRF accelerating cavities and Fixed Field Alternating gradient (FFA) beamline. To investigate the CSR effects on CBETA, the established simulation code Bmad has been used to track a bunch with different CSR parameters. We found that CSR causes phase space dilution, and the effect becomes more significant as the bunch charge and recirculation pass increase. Convergence tests have been performed for the CSR parameters to validate the observed micro-bunching instability. Potential ways to mitigate the effect involving vacuum chamber shielding and increasing bunch length are also being investigated.

Slides TUCOWBS03 [5.215 MB]

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TUCOXBS01

Beam Halo in Energy Recovery Linacs

23

O.A. Tanaka
KEK, Ibaraki, Japan

The beam halo mitigation is a very important challenge for reliable and safe operation of a high energy machine. Since Energy Recovery Linacs (ERLs) are known to produce high energy electron beams of high virtual power and high density, the beam halo and related beam losses should be properly mitigated to avoid a direct damage of the equipment, an unacceptable increase in the vacuum pressure, a radiation activation of the accelerator components etc. To keep the operation stable, one needs to address all possible beam halo formation mechanisms, including those unique to each machine that can generate beam halo. Present report is dedicated to the beam halo related activities at the Compact ERL at KEK, and our operational experience with respect to the beam halo.

Slides TUCOXBS01 [4.480 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-TUCOXBS01

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paper received ※ 16 September 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020

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TUCOXBS03

Beam Dynamics Layout of the MESA ERL

28

F. Hug, K. Aulenbacher, D. Simon, C.P. Stoll, S.D.W. Thomas
KPH, Mainz, Germany
K. Aulenbacher
GSI, Darmstadt, Germany
K. Aulenbacher
HIM, 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.
The MESA project is currently under construction at Johannes Gutenberg-Universität Mainz. It will be used for high precision particle physics experiments in two different operation modes: external beam (EB) mode (0.15 mA; 155 MeV) and energy recovery (ERL) mode (1 mA; 10⁵ MeV). The recirculating main linac follows the concept of a double sided accelerator design with vertical stacking of return arcs. Up to three recirculations are possible. Acceleration is done by four TESLA/XFEL 9-cell SRF cavities located in two modified ELBE cryomodules. Within this contribution the recirculation optics for MESA will be presented. Main goals are achieving best energy spread at the experimental setups in recirculating ERL and non-ERL operation and providing small beta-functions within the cryomodules for minimizing HOM excitation at high beam currents.

Slides TUCOXBS03 [5.077 MB]

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paper received ※ 16 September 2019 paper accepted ※ 06 November 2019 issue date ※ 24 June 2020

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TUCOXBS04

The LHeC ERL - Optics and Performance Optimizations

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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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

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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paper received ※ 13 September 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020

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WEPNEC02

Investigation and Mitigation of the Mie-Scattering on the Surface of the First Objective Lens for Coronagraph-Based Halo Monitor

J.G. Hwang, J. Kuszynski
HZB, Berlin, Germany

Funding: This work was supported by the German Bundesministerium für Bildung und Forschung, Land Berlin and grants of Helmholtz Association.
Since, due to the heat capacity of the cryogenics, additional heat load on a cryogenic system as a result of uncontrolled beam losses is only allowed to be below 50 W which corresponds to 10^-5 respected to the full power of BERLinPro, the development of diagnostics which can measure the intensity in the order of 10^-5 is crucial. In our previous beam test of the coronagraph-based halo monitor with various operation modes of the BESSY II storage ring, the limitation of the measurement of the halo distribution was to be 10^-4 respected to the core intensity due to the noise produced by scattered light from digs and scratches of the first objective lens. In order to mitigate the noise level produced from the surface of the objective lens to reach 10^-5 to 10^-6, the Mie-scattering effect was investigated, and furthermore, a high-quality surface lens was purchased.

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WEPNEC06

Radiation Protection Instrumentation of BERLinPro

L. Pichl, Y. Bergmann, A. Bundels, K. Ott
HZB, Berlin, Germany

Funding: Work supported by the German Bundesministerium für Bildung und Forschung, Land Berlin and grants of Helmholtz Association
The Energy Recovery Linac project BERLinPro is a test facility to study the beam parameter range necessary for an ERL as synchrotron light source [1]. It is currently under construction and is designed to operate with the maximum beam parameters of 50 MeV and 100 mA cw current. Even if the electron losses within the recirculator are limited to 0.6 % due to the available rf power, (at higher losses an immediate beam break-up occurs because of the ERL principle) the beam loss power can be by orders of magnitude higher than in electron storage rings used for synchrotron radiation. The Fluka [2,3] calculations of the resulting activations of machine components and air activations have been discussed in earlier papers [4,5]. In this work we present the components of the ambient dosimetry, the measurement system of air activations and their inclusion in the personal safety system. Additionally we present recent calculations of the activation of cooling water and the method of storing and measuring it in case of a leakage.
1 M Abo-Bakr et al SRF2009 Berlin
2 G Battistoni et al AIP Conf. Proc. 896 2007
3 A Fasso et al CERN-2005-10 2005
4 M Helmecke et al RADSYNCH2013 BNL
5 K Ott et al RADSYNCH2015 DESY

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WEPNEC08

Dispersion Matching With Space Charge in MESA

74

A. Khan, O. Boine-Frankenheim
TEMF, TU Darmstadt, Darmstadt, Germany
K. Aulenbacher
IKP, Mainz, Germany

Funding: Supported by the DFG through GRK 2128.
For intense electron bunches traversing through bends, as for example the recirculation arcs of an Energy-Recovery Linac (ERL), dispersion matching with space charge of an arc into the subsequent radio-frequency (RF) structure is essential to maintain the beam quality. We show that beam envelopes and dispersion along the bends and recirculation arcs of an ERL, including space charge forces, can be matched to adjust the beam to the parameters of the subsequent section. The present study is focused on a small-scale, double-sided recirculating linac Mainz Energy-recovering Superconducting Accelerator (MESA). MESA is an under construction two pass ERL at the Johannes Gutenberg-Universit\"at Mainz, which should deliver a continuous wave (CW) beam at 10⁵ MeV for physics experiments with a pseudo-internal target. In this work, a coupled transverse-longitudinal beam matrix approach for matching with space charge in MESA is employed.

Poster WEPNEC08 [1.190 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-WEPNEC08

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paper received ※ 12 September 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020

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WEPNEC10

Investigation on the Ion Clearing of Multi-Purpose Electrodes of BERLinPro

80

G. Pöplau
COMPAEC e.G., Rostock, Germany
A. Meseck
KPH, Mainz, Germany
A. Meseck
HZB, Berlin, Germany

High-brightness electron beams provided by modern accelerators require several measures to preserve their high quality and to avoid instabilities. The mitigation of the impact of residual ions is one of these measures. It is particularly important if high bunch charges in combination with high repetition rates are aimed for. This is because ions can be trapped in the strong negative electrical potential of the electron beam causing emittance blow-up, increased beam halo and longitudinal and transverse instabilities. One ion-clearing strategy is the installation of clearing electrodes. Of particular interest in this context is the performance of multi-purpose electrodes, which are designed such that they allow for a simultaneous ion-clearing and beam-position monitoring. Such electrodes will be installed in the BERLinPro facility. In this contribution, we present numerical studies of the performance of multi-purpose clearing-electrodes planned for BERLinPro, i.e. we investigate the behavior of ions generated by electron bunches while passing through the field of the electrodes. Hereby, several ion species and configurations of electrodes are considered.

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reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-WEPNEC10

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paper received ※ 11 October 2019 paper accepted ※ 06 November 2019 issue date ※ 24 June 2020

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WEPNEC12

Beam Optics of Bunch Compression at Compact ERL

M. Shimada, Y. Honda, R. Kato, T. Miyajima, N. Nakamura, T. Obina
KEK, Ibaraki, Japan

Short electron bunch is essential for THz coherent transition radiation or FEL oscillation. Therefore, the bunch compression is studied at the compact ERL in KEK site. We demonstrated it and experimentally evaluated the bunch length and the transverse emittance. The results of the optics and beam commissioning will be presented.

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WEPNEC16

Electron Outcoupling System of Novosibirsk Free Electron Laser Facility - Beam Dynamics Calculation and the First Experiments

98

Ya.V. Getmanov, A.S. Matveev, O.A. Shevchenko, N.A. Vinokurov
BINP SB RAS, Novosibirsk, Russia
Ya.V. Getmanov, A.S. Matveev, N.A. Vinokurov
NSU, Novosibirsk, Russia

The radiation power of the FEL with optical cavity can be limited by the overheating of reflecting mirrors. In the electron outcoupling scheme electron beam radiates the main power at a slight angle to the optical axis. For this, it is necessary to divide undulator by a dipole magnet at least in two parts - the first for the electron beam bunching in the field of the main optical mode, and the second for the power radiation by deflected beam. Electron outcoupling system is installed on the third FEL based on the multiturn energy recovery linac of the Novosibirsk Free Electron Laser facility (NovoFEL). It consists of three undulators, dipole correctors and two quadrupole lenses assembled between them. There are two different configurations of the system since the electrons can be deflected in either the second or the third undulator. The electron beam dynamics calculations and the results of the first experiments are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-WEPNEC16

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paper received ※ 01 October 2019 paper accepted ※ 06 November 2019 issue date ※ 24 June 2020

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WEPNEC18

Analytic Longitudinal Phase Space Solutions for Multipass Energy Recovery Linacs

P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
I.R. Bailey, P.H. Williams
Cockcroft Institute, Warrington, Cheshire, United Kingdom
I.R. Bailey
Lancaster University, Lancaster, United Kingdom
T.K. Charles
The University of Melbourne, Melbourne, Victoria, Australia
T.K. Charles
CERN, Geneva, Switzerland
G. Perez-Segurana
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom

The longitudinal solution space of an energy recovery linac is an under-constrained system. For applications where we wish to compress the bunches for delivery to, for example, a free-electron laser or an interaction point, and simultaneously ensure full recovery it is useful to be able to rapidly ascertain and assess the possible solutions. Moreover, when we consider multi-pass ERLS, we quickly conclude that a trial-and-error approach to deriving such solutions (through for example one-dimensional particle tracking) is impractical. Here we extend an analytic recurrence method of deriving phase space solutions in multistage compression schemes, due to Zagorodnov & Dohlus, to multi-pass energy recovery linac systems. We use this method to categorise classes of solutions, and explore the implications of the energy recovery condition.

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WECOYBS04

Commissioning of theBERLinPro Diagnostics Line using Machine Learning Techniques

123

B.C. Kuske
HZB, Berlin, Germany
A. Adelmann
PSI, Villigen PSI, Switzerland

Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin and grants of Helmholtz Association
BERLinPro is an Energy Recovery Linac (ERL) project currently being set up at HZB, Berlin. Commissioning is planned for early 2020. HZB triggered and supported the development of release 2.0 of the particle tracking code OPAL, that is now also applicable to ERLs. OPAL is set up as an open source, highly parallel tracking code for large accelerator systems and many particles. Thus, it is idially suited to serve attempts of applying machine learning approaches to beam dynamics, as demonstrated in [1]. OPAL is used to calculate hundreds of randomized machines close to the commissioning optics of BERLinPro. This data base will be used to train a neural network, to establish a surrogate model of BERLinPro, much faster than any physical model including particle tracking. First steps, like the setup of the sampler and a sensitivity analysis of the resulting data are presented. The ultimate goal of this work is to use machine learning techniques during the commissioning of BERLinPro. Future steps are outlined. [1] A. Edelen, A. Adelmann, N. Neveu, Y. Huber, M. Frey, ’Machine Learning to enable orders of magnitude speedup in multi-objective optimization of particle accelerator systems’

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paper received ※ 30 October 2019 paper accepted ※ 07 November 2019 issue date ※ 24 June 2020

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FRCOWBS02

Design and Commissioning Experience with State of the Art MPS for LEReC Accelerator

S. Seletskiy, Z. Altinbas, D. Bruno, M.R. Costanzo, K.A. Drees, A.V. Fedotov, D.M. Gassner, X. Gu, L.R. Hammons, J. Hock, R.L. Hulsart, P. Inacker, J.P. Jamilkowski, D. Kayran, J. Kewisch, C. Liu, K. Mernick, T.A. Miller, M.G. Minty, M.C. Paniccia, W.E. Pekrul, I. Pinayev, V. Ptitsyn, T.C. Shrey, L. Smart, K.S. Smith, R. Than, P. Thieberger, J.E. Tuozzolo, W. Xu, Z. Zhao
BNL, Upton, New York, USA

The Low Energy RHIC Electron Cooler (LEReC), the world’s first electron cooler to employ an RF electron accelerator, has been recently fully commissioned. The LEReC is a high-current, high-brightness accelerator featuring ~100 m of beamline and is designed to operate with 1.6-2.6 MeV electron beams of up to 140 kW beam power. The LEReC requires a dedicated machine protection system (MPS) capable of interlocking electron beam within 40 us and is equipped with multiple levels of protection. In this paper we summarize our experience with designing, building, and operating the LEReC MPS.

Slides FRCOWBS02 [2.031 MB]

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FRCOWBS03

Beam Commissioning Experience at Low Energy RHIC Electron Cooler (LEReC)

D. Kayran, Z. Altinbas, K.A. Drees, A.V. Fedotov, M. Gaowei, X. Gu, R.L. Hulsart, P. Inacker, J.P. Jamilkowski, Y.C. Jing, J. Kewisch, C. Liu, J. Ma, K. Mernick, T.A. Miller, M.G. Minty, M.C. Paniccia, I. Pinayev, V. Ptitsyn, V. Schoefer, S. Seletskiy, F. Severino, A. Sukhanov, P. Thieberger, J.E. Tuozzolo, E. Wang, G. Wang, H. Zhao, Z. Zhao
BNL, Upton, 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 high-current high-brightness electron accelerator for cooling of RHIC ions at low energy (LEReC) was successfully commissioned at BNL. A beam quality suitable for electron cooling has been achieved. Cooling of single ion bunches in RHIC using a new approach of bunched-beam electron cooling was demonstrated during 2019. To achieve such a cooling with non-magnetized electron beams and RF acceleration required proper beam manipulation in the longitudinal phase space while preserving transverse emittances. Electron beam with kinetic energy of 1.6 MeV with beam quality suitable for cooling was successfully propagated through 100 meters of beam lines including dispersion sections and maintained through both cooling sections in RHIC. The LEReC accelerator includes a photocathode DC gun, a laser system, a photocathode delivery system, magnets, beam diagnostics, a SRF booster cavity, and a set of Normal Conducting RF cavities to provide sufficient flexibility to tune the beam in the longitudinal phase space. In this paper we discuss experience learned during LEReC beam commissioning.

Slides FRCOWBS03 [24.527 MB]

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FRCOWBS04

Essential Instrumentation for the Characterization of ERL Beams

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

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FRCOXBS01

Electronic Modulation of the FEL-Oscillator Radiation Power Driven by ERL

O.A. Shevchenko, E.V. Bykov, Ya.V. Getmanov, S.S. Serednyakov, S.V. Tararyshkin
BINP SB RAS, Novosibirsk, Russia
M.V. Fedin, S.L. Veber
International Tomography Center, SB RAS, Novosibirsk, Russia
Ya.V. Getmanov, S.S. Serednyakov
NSU, Novosibirsk, Russia

Funding: RSF grant no. 17-13-01412
FEL oscillators usually operate in CW mode and produce periodic train of radiation pulses but some user experiments require modulation of radiation power. Conventional way to obtain this modulation is using of mechanical shutters however it cannot provide very short switching time and may lead to decreasing of the radiation beam quality. Another way could be based on the electron beam current modulation but it cannot be used in the ERL. We propose a simple way of fast control of the FEL lasing which is based on periodic phase shift of electron bunches with respect to radiation stored in optical cavity. The phase shift required to suppress lasing is relatively small and it does not change significantly repetition rate. This approach has been realized at NovoFEL facility. It allows to generate radiation macropulses of desirable length down to several microseconds (limited by quality factor of optical cavity and FEL gain) which can be synchronized with external trigger. We present detailed description of electronic power modulation scheme and discuss the results of experiments.

Slides FRCOXBS01 [7.025 MB]

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FRCOXBS03

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

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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FRCOXBS04

Status of the Control System for the Energy Recovery Linac BERLinPro at HZB

159

T. Birke, P. Echevarria, D. Eichel, R. Fleischhauer, J.G. Hwang, G. Klemz, R. Müller, C. Schröder, E. Suljoti, A. Ushakov
HZB, Berlin, Germany

BERLinPro is an energy recovery linac (ERL) demonstrator project built at HZB. It features CW SRF technology for the low emittance, high brightness gun, the booster module and the recovery linac. Construction and civil engineering are mostly completed. Synchronized with the device integration the EPICS based control system is being set-up for testing, commissioning and finally operation. In the warm part of the accelerator technology is used that is already operational at BESSY and MLS (e.g. CAN-bus and PLC/OPCUA). New implementations like the machine protection system and novel major subsystems (e.g. LLRF, Cryo-Controls, photo cathode laser) need to be integrated. The first RF transmitters have been tested and commissioned. Around the time of this workshop the first segment of the accelerator is scheduled to become online. For commissioning and operation of the facility the standard set of EPICS tools form the back-bone. A set of generic python applications already developed at BESSY/MLS will be adapted to the specifics of BERLinPro. Scope and current project status are described in this paper.

Slides FRCOXBS04 [11.021 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-FRCOXBS04

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paper received ※ 05 September 2019 paper accepted ※ 11 November 2019 issue date ※ 24 June 2020

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FRCOXBS05

Adjusting BERLinPro Optics to Commissioning Needs

165

B.C. Kuske, M. McAteer
HZB, Berlin, Germany

Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin and grants of Helmholtz Association
BERLinPro is an Energy Recovery Linac (ERL) project currently being set up at HZB, Berlin. During the turn of the project, many adaptations of the optics to changing hardware realities were necessary. To name only one, commissioning of the recirculator will now be realized with the superconducting linac module fabricated for the Mainz ERL project MESA, as the BERLinPro linac is delayed. The Mainz linac will supply roughly 60% of the energy planned for the BERLinPro linac module and will be limited by higher order modes in the cavities to few mA of current. While the adapted optics shows similar parameters as the original 50MeV optics, studies of longitudinal space charge and coherent synchrotron radiation show that the energy leads to large emittance blow up due toμbunching. Furthermore, preparations for commissioning with gun fields much lower than the original 30MV/m in the 1.4 cell SRF gun are introduced and according optics are presented.

Slides FRCOXBS05 [9.766 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-FRCOXBS05

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paper received ※ 19 September 2019 paper accepted ※ 04 November 2019 issue date ※ 24 June 2020

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FRCOYBS02

Working Group Summary: ERL Beam Dynamics and Instrumentation

G.H. Hoffstaetter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
P.E. Evtushenko
HZDR, Dresden, Germany

To be added

Slides FRCOYBS02 [5.605 MB]

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