IPAC2019 - List of Keywords (bunching)

Paper	Title	Other Keywords	Page
MOPGW017	Feedback Design for Control of the Micro-Bunching Instability based on Reinforcement Learning	storage-ring, feedback, electron, controls	104
	T. Boltz, T. Asfour, M. Brosi, E. Bründermann, B. Härer, P. Kaiser, A.-S. Müller, C. Pohl, P. Schreiber, M. Yan KIT, Karlsruhe, Germany
	The operation of ring-based synchrotron light sources with short electron bunches increases the emission of coherent synchrotron radiation (CSR) in the THz frequency range. However, the micro-bunching instability resulting from self-interaction of the bunch with its own radiation field limits stable operation with constant intensity of CSR emission to a particular threshold current. Above this threshold, the longitudinal charge distribution and thus the emitted radiation vary rapidly and continuously. Therefore, a fast and adaptive feedback system is the appropriate approach to stabilize the dynamics and to overcome the limitations given by the instability. In this contribution, we discuss first efforts towards a longitudinal feedback design that acts on the RF system of the KIT storage ring KARA (Karlsruhe Research Accelerator) and aims for stabilization of the emitted THz radiation. Our approach is based on methods of adaptive control that were developed in the field of reinforcement learning and have seen great success in other fields of research over the past decade. We motivate this particular approach and comment on different aspects of its implementation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW017
About •	paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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MOPGW018	Perturbation of Synchrotron Motion in the Micro-Bunching Instability	electron, synchrotron, storage-ring, radiation	108
	T. Boltz, M. Brosi, E. Bründermann, B. Härer, A.-S. Müller, P. Schreiber, P. Schönfeldt, M. Yan KIT, Karlsruhe, Germany
	Short electron bunches in a storage ring are subject to complex longitudinal dynamics due to self-interaction with their own CSR. Above a particular threshold current, this leads to the formation of dynamically changing micro-structures within the bunch, generally known as the micro-bunching instability. The longitudinal dynamics of this phenomenon can be simulated by solving the Vlasov-Fokker-Planck equation, where the CSR self-interaction can be added as a perturbation to the Hamiltonian. This contribution particularly focuses on the comprehension of synchrotron motion in the micro-bunching instability and how it relates to the formation of the occurring micro-structures. Therefore, we adopt the perspective of a single particle and comment on its implications for collective motion. We explicitly show how the shape of the parallel plates CSR wake potential breaks homogeneity in longitudinal phase space and propose a quadrupole-like mode as potential seeding mechanism of the micro-bunching instability. The gained insights are verified using the passive particle tracking method of the Vlasov-Fokker-Planck solver Inovesa.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW018
About •	paper received ※ 15 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019
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MOPGW020	Numerical Calculation of Micro Bunching in BERLinPro Due to Space Charge and CSR Effects	space-charge, linac, emittance, optics	116
	B.C. Kuske, A. Meseck HZB, Berlin, Germany
	Funding: Work supported by the German Bundesministerium für Bildung und Forschung, Land Berlin and grants of the Helmholtz Association BERLinPro is an Energy Recovery Linac Project, currently being set up at the Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany. BERLinPro is a small demonstrator for ERL technology and applications. Due to the low energy of 50, resp. 32MeV, space charge plays a dominant role in the beam dynamics. Micro-bunching, due to unavoidable shot noise from the cathode in combination with space charge, is seen in the merger as well as in the recirculator. Coherent synchrotron radiation (CSR) can amplify this bunching, as well as micro-bunching can enhance CSR losses. With the release of OPAL 2.0** in May 2018, for the first time, an open source, highly parallel tracking code is available, that is capable of numerically calculating both effects, space charge and CSR, simultaneously. The calculations are compared to earlier results, that used analytical formulas on tracked, space charge dominated bunches. "On space charge driven microbunching instability in BERLinPro", PhD thesis, S.D.Rädel, Humboldt Universität zu Berlin, 2017 ** http://amas.web.psi.ch/docs/opal/opal_user_guide-2.0.0.pdf
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW020
About •	paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW111	Start to End Simulation on Beam Dynamics in Coherent Electron Cooling Accelerator	electron, FEL, emittance, cavity	379
	Y.C. Jing, V. Litvinenko, I. Petrushina, I. Pinayev, K. Shih, Y.H. Wu BNL, Upton, Long Island, New York, USA V. Litvinenko Stony Brook University, Stony Brook, USA I. Petrushina 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. A Coherent electron Cooling (CeC) has a potential of substantial reducing cooling time of the high-energy hadrons and hence to boost luminosity in high-intensity hadron-hadron and electron-hadron colliders. In a CeC system, a high quality electron beam is generated, propagated and optimized through a beam line which was carefully designed with consideration of space charge effect, wakefields and nonlinear dynamics such as coherent synchrotron radiation and chromatic aberration. In this paper, we present our study on the beam dynamics of such a beam line and compare the simulation result with what was measured in experiment.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW111
About •	paper received ※ 17 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPMP015	Longitudinal Particle Dynamics in NICA Collider	collider, injection, accumulation, acceleration	455
	E. Syresin, A.V. Eliseev, A.V. Smirnov JINR, Dubna, Moscow Region, Russia N.V. Mityanina, V.M. Petrov, E. Rotov, A.G. Tribendis BINP SB RAS, Novosibirsk, Russia
	A specific feature of the NICA acceleration complex is high luminosity of colliding beams. Three types of RF stations will be used in the NICA Collider to reach the necessary beam parameters. The first one is for accumulation of particles in the longitudinal phase space with the moving burrier buckets under action of stochastic and/or electron cooling systems. The second and third RF stations are for formation of the final bunch size in the colliding regime. This report presents numerical simulations of longitudinal beam dynamics which taken into account the longitudinal space charge effect during the accumulation and bunching procedures. Influence of space effects leads to some decrease in the accumulation efficiency and requires special manipulation with the 2nd and 3rd RF stations during the adiabatic capture and bunching procedures.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP015
About •	paper received ※ 29 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB028	Application of WCM in Beam Commissioning of RCS in CSNS	proton, neutron, MMI, target	636
	M.T. Li, F. Li IHEP CSNS, Guangdong Province, People’s Republic of China Y.W. An, S.Y. Xu, T.G. Xu IHEP, Beijing, People’s Republic of China
	Wall Current Monitor (WCM) is the only beam instru-ment in RCS of CSNS. It is utilized to derive many kinds of physics parameters during beam commissioning. The longitudinal phase distribution of the bunch over the boosting time is deduced for our future analyzation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB028
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPTS067	The Progress in Physics Design of HEPS LINAC	linac, wakefield, electron, emittance	1008
	C. Meng, D.Y. He, X. He, J.Y. Li, Y.M. Peng, S.C. Wang, O. Xiao, J.R. Zhang, S.P. Zhang IHEP, Beijing, People’s Republic of China
	The High Energy Photon Source (HEPS) is a 6-GeV, ultralow-emittance light source to be built in China. The injector is composed of a 500-MeV Linac and a full energy booster. According to the study and com-missioning consideration of on-axis swap-out injec-tion system, a high bunch charge injector is desirable and a Linac that can provide 7nC per bunch electron beam to booster is needed. This paper present different bunching system schemes and the performance of different schemes are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS067
About •	paper received ※ 14 May 2019 paper accepted ※ 17 May 2019 issue date ※ 21 June 2019
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MOPTS073	Bunching System Optimization Based on MOGA	linac, emittance, electron, solenoid	1018
	S.P. Zhang, J.Y. Li, C. Meng IHEP, Beijing, People’s Republic of China
	Multiobjective Genetic Algorithms (MOGA) is effective in dealing with optimization problems with multiple objectives. The bunching system of the High Energy Photon Source (HEPS) linac adopts a traditional bunching system for compressing electron beams with a pulse charge of 4 nC. The bunching system is optimized using MOGA. The optimization include minimizing the normalized emittance and maximizing transmission efficiency. The optimization results have reached the design target, and are presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS073
About •	paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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TUPGW045	Lattice Design for the Reversible SSMB	radiation, electron, emittance, storage-ring	1507
	C.L. Li SINAP, Shanghai, People’s Republic of China A. Chao SLAC, Menlo Park, California, USA C. Feng, B.C. Jiang Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China
	Steady State Microbunching (SSMB) aiming at producing high average power radiation in the electron storage ring has been proposed by Ratner and Chao years ago. Reversible seeding scheme is one of the promising scenarios with less challenges on the storage ring lattice design. The key problem for reversible SSMB is the precise cancelation of the laser modulation which will allow producing turn-by-turn coherent radiation without spoiling the transverse emittances and energy spread. In this paper the lattice design for the microbunching generation and its cancelation will be presented. Also a storage ring lattice design will be shown.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW045
About •	paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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TUPGW089	Tunable Bunch Train Generation Using Emittance Exchange Beamline With Transverse Wiggler	wiggler, controls, simulation, emittance	1612
	G. Ha, M.E. Conde, J.G. Power, J.H. Shao, E.E. Wisniewski ANL, Argonne, Illinois, USA
	Funding: This work is supported by LDRD program at Argonne National Laboratory and Department of Energy, Office of High Energy Physics, under Contract No. DE-AC02-06CH11357. Emittance exchange beamline provides a unique correlation between the upstream transverse momentum and downstream longitudinal timing. Similar to the bunch train generation concept using energy modulation and chicane, the emittance exchange beamline can convert the transverse momentum modulation to the temporal modulation at the end of the beamline. The beam can obtain this transverse modulation from alternating magnet array (e.g. 90 degree rotated undulator). While most of other methods provide only one knob to control both micro-bunch length and bunch-to-bunch spacing or hard to control one of the knobs, this method provides separated knobs for the micro-bunch length and spacing and they are easy to control. These knobs enable to separately control the fundamental frequency of the radiation and its bandwidth. We plan to demonstrate this method at Argonne Wakefield Accelerator facility (AWA). This poster present progress on this new method and its demonstration at AWA.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW089
About •	paper received ※ 21 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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TUPRB001	Nanosecond Pulsing for Tandem Accelerator	controls, linac, experiment, injection	1673
	P. Linardakis, N.R. Lobanov, D.C. Tempra Research School of Physics and Engineering, Australian National University, Canberra, Australian Capitol Territory, Australia
	Funding: The Australian Federal Government Superscience/EIF funding under the NCRIS mechanism A pulsed system capable of delivering up to a few microampere bursts of ions with mass range M=1 - 100 amu with a duration of approximately 1 ns is described. The system consists of a negative ion source, three frequency harmonic buncher - which uses the entire tandem electrostatic accelerator as a drift path to produce bunched ion bursts at the targets or linac entry - and high energy choppers. The buncher consists of a single acceleration gap with aligned retractable grids.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB001
About •	paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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TUPRB013	Simulation Studies for a EEHG seeded FEL in the XUV	laser, electron, FEL, simulation	1705
	V. Grattoni, S. Ackermann, R.W. Aßmann, B. Faatz, T. Lang, C. Lechner, M.M. Mohammad Kazemi, G. Paraskaki, J. Zemella DESY, Hamburg, Germany W. Hillert University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany S. Reiche PSI, Villigen PSI, Switzerland
	Echo-enabled harmonic generation (EEHG) is a promising technique for seeded free electron lasers (FELs) not only to go down to wavelengths of 4 nm, but also to simplify the schemes that are currently used to achieve a similar wavelength range (double cascade HGHG). Thus a study optimizing the EEHG performance in the wavelength range from 60 to §I{4}{nm} has been performed. The more critical working point, at 4 nm, is here analyzed in terms of seed laser energy stability for two different seed laser frequencies: visible and UV.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB013
About •	paper received ※ 30 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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TUPRB057	THz-Pump and UV-Probe Scheme Based on Storage Ring	laser, electron, radiation, storage-ring	1811
	H.R. Zhang, Z.G. He, S.M. Jiang, W.X. Wang USTC/NSRL, Hefei, Anhui, People’s Republic of China
	We propose a THz-pump and UV-probe scheme based on storage ring for ultra-fast dynamics experiment. In which, two sequential laser pulses, one of which has a periodic intensity envelope, simultaneously interact with different parts of the long electron beam in a modulator; after a chicane, the part that interacts with the periodic pulse will bunch at THz domain and radiate through a bend magnet, another based on high-harmonic generation will bunch at UV domain and radiate at a radiator. The electron beam can be utilized circularly in the storage ring, which will increase its average power. The feasibility of this THz-pump and UV-probe scheme is verified in both theory and simulation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB057
About •	paper received ※ 30 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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TUPRB070	A Peak Finding Algorithm for FEL Spectra Characterization	FEL, electron, laser, background	1827
	M.A. Pop MAX IV Laboratory, Lund University, Lund, Sweden E. Allaria Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	We present a software tool aimed at investigating the spectra of photon sources in order to detect any instabilities in the electron beam that have a clear effect on the spectrum. The method has been developed for FERMI@Elettra but with a general approach on the particularities of FEL machines such as a high repetition frequency and significant shot to shot fluctuations. The software has two operating options: a mode, aimed at online usage, which only detects peaks and their corresponding valleys, offering no information about the peaks themselves; and a more comprehensive mode that fits peak functions (Gaussian, Lorentzian etc…) to the spectrum based on initial guesses of the fitting parameters. The algorithm can provide a collection of simple but valuable variables such as number of peaks, peak separation and ratio between peak heights, as well as more specialized variables like peak width statistics and decomposition of the raw spectrum in basic components. Project done in collaboration with FERMI@Elettra
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB070
About •	paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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TUPRB071	Considerations on Implementing EEHG with a Strong Linear Chirp	electron, FEL, linac, radiation	1830
	M.A. Pop, S. Werin MAX IV Laboratory, Lund University, Lund, Sweden
	As the ECHO enabled harmonic generation (EEHG) scheme draws such intense focus from the FEL community, we conduct simulations to evaluate the challenges of implementing said scheme in different FEL layouts. Nonlinear processes such as this require extensive simulations to harmonize all system specific properties like seed lasers and electron beam properties. Along with optimizing the original EEHG scheme* one can consider, for example, altering the seed laser pulse to optimize the bunching for a machine specific chirp. We study the EEHG as a possible seeding method aimed at increasing coherence of the photon beam for the prospective SXL FEL beamline at MAXIV. The particular chirp of the electron beam through the MAXIV LINAC generates some specific requirements in implementing EEHG but may also offer an opportunity for exotic operation modes of this FEL. * Xiang D. and Stupakov G. Echo-enabled harmonic generation free electron laser 10.1103/PhysRevSTAB.12.030702
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB071
About •	paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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TUPRB091	Study of XFEL Third Harmonic Radiation at LCLS	undulator, FEL, radiation, experiment	1875
	C. Emma, M.W. Guetg, A. Halavanau, A.A. Lutman, G. Marcus, T.J. Maxwell, C. Pellegrini SLAC, Menlo Park, California, USA
	Funding: This work was supported by the U.S. Department of Energy Contract No. DE-AC02-76SF00515. In this paper, we focus on characterization of the nonlinear third harmonic radiation properties at Linac Coherent Light Source (LCLS). In addition, we experimentally perform third harmonic self-seeding, using diamond crystal attenuator in the hard X-ray self-seeding chicane. We discuss warm beam effects in such scheme, justifying recently proposed two bunch configuration for harmonic lasing.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB091
About •	paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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TUPTS052	Conceptual Design of a High-Performance Injector Based on Rf-Gated Gridded Thermionic Gun for Thz Fel	gun, electron, linac, cathode	2046
	P. Yang, H.M. Chen, T. Hu, J.J. Li, Y. Lu HUST, Wuhan, People’s Republic of China G.Y. Feng, S.C. Zhang USTC/NSRL, Hefei, Anhui, People’s Republic of China
	Free-Electron Laser (FEL) has higher requirements on electron beam properties, for example, low transverse emittance, small energy spread, short bunch length and high peak current. Taking compactness and economy into account, we aim to design a high-performance linear accelerator based on a RF-gated gridded thermionic electron gun, which will be used as the injector of the oscillator-type THz FEL facility at Huazhong University of Science and Technology of China. The RF-gated grid will be modulated with the fundamental and 3rd harmonic microwave of the LINAC frequency, which will be very helpful to get high electron capture efficiency and short bunch length. Concerning velocity bunching effect in the LINAC, electron bunch with good symmetry of current profile and bunch length less than 10 ps can be obtained at the exit of the injector. In this paper, design and beam dynamics simulation for the high-performance injector are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS052
About •	paper received ※ 26 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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WEPGW017	Continuous Bunch-by-Bunch Reconstruction of Short Detector Pulses	detector, storage-ring, experiment, simulation	2501
	J.L. Steinmann, M. Brosi, M. Caselle, B. Kehrer, M. Martin, A.-S. Müller, M.M. Patil, P. Schreiber KIT, Karlsruhe, Germany
	Funding: This work is funded by the BMBF contract number: 05K16VKA The KAPTURE system (KArlsruhe Pulse Taking and Ultrafast Readout Electronics), developed at the Karlsruhe Institute of Technology (KIT), was designed to digitize detector pulses during multi-bunch operation at the KIT storage ring KARA (Karlsruhe Research Accelerator). KAPTURE provides digitization for pulses at rates of 500 MHz using up to 4 sampling points per pulse to record each bunch and each turn for potentially unlimited time. The new KAPTURE-2 system now provides eight sampling points per pulse, including baseline sampling between pulses, which allows improved reconstruction of the pulse shape. The advanced reconstruction of the pulse shape is realized with a highly parallelised implementation on GPU. The system will be used for the investigation on longitudinal beam dynamics e.g. by measuring instability induced CSR fluctuations or arrival time oscillations. This contribution will report on first results of the KAPTURE-2 system at KARA.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW017
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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WEPRB055	Design of 3 MeV S-band Electron Linac Structure With 2.5 Bunching Cells	electron, linac, coupling, simulation	2934
	Y. Joo, P. Buaphad, H.R. Lee University of Science and Technology of Korea (UST), Daejeon, Republic of Korea Y. Kim KAERI, Daejon, Republic of Korea J.Y. Lee, S. Lee Korea Atomic Energy Research Institute (KAERI), Daejeon, Republic of Korea
	Funding: UST (University of Science and Technology), KAERI (Korea Atomic Energy Research Institute) The Korea Atomic Energy Research Institute (KAERI) has been designing several 3 MeV S-band RF electron linear accelerators (linacs) for non-destructive testing. Until now, the bunching cell of the linac has a full-cell geometry. However, to maximize the acceleration of electrons after emission from the electron gun, the geometry of the first bunching cell is modified from a full-cell to a half cell. To accelerate electron beams more gently, recently, we increased the total number of bunching cells from 1.5 to 2.5. In this paper, we describe design concepts and detailed optimization processes of a 3 MeV linac with the 2.5 bunching cells to optimize RF parameters such as the quality factor, resonance frequency, and uniformity of electric field distribution along the linac. Lastly, we will discuss the application of 3 MeV linac.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB055
About •	paper received ※ 04 June 2019 paper accepted ※ 16 June 2019 issue date ※ 21 June 2019
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WEPRB095	Microbunching Plasma-Cascade Instability	plasma, simulation, electron, focusing	3035
	V. Litvinenko Stony Brook University, Stony Brook, USA T. Hayes, Y.C. Jing, D. Kayran, J. Ma, T.A. Miller, G. Narayan, I. Pinayev, F. Severino, G. Wang BNL, Upton, Long Island, New York, USA I. Petrushina 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 and NSF Grant No. PHY-141525 We present a new type of longitudinal microbunching instability entitled ’Plasma-Cascade Instability’. This instability could occur in beams propagating along a straight section with external focusing elements. We present a theoretical description of this instability as well as self-consistent 3D simulations. Finally, we present results of experimental observation of Plasma-Cascade Instability at frequencies up to 10 THz using SRF linear accelerator built for Coherent electron Cooling experiment . Commissioning of FEL-based Coherent electron Cooling system, V.N. Litvinenko et al., In proc. of 38th Int. Free Electron Laser Conf.(FEL’17), Santa Fe, NM, USA, August 20-25, 2017, p. 132
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB095
About •	paper received ※ 18 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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WEPTS015	Synchronous Measurements of Electron Bunches Under the Influence of the Microbunching Instability	synchrotron, radiation, simulation, storage-ring	3119
	M. Brosi, T. Boltz, E. Bründermann, S. Funkner, B. Kehrer, A.-S. Müller, M.J. Nasse, G. Niehues, M.M. Patil, P. Schreiber, P. Schönfeldt, J.L. Steinmann KIT, Karlsruhe, Germany
	Funding: This work has been supported by the German Federal Ministry of Education and Research (Grant No. 05K16VKA). We acknowledge the support by the Helmholtz International Research School for Teratronics. The microbunching instability is a longitudinal collective instability which occurs for short electron bunches in a storage ring above a certain threshold current. The instability leads to a charge modulation in the longitudinal phase space. The resulting substructures on the longitudinal bunch profile vary over time and lead to fluctuations in the emitted power of coherent synchrotron radiation (CSR). To study the underlying longitudinal dynamics on a turn-by-turn basis, the KIT storage ring KARA (Karlsruhe Research Accelerator) provides a wide variety of diagnostic systems. By synchronizing the single-shot electro-optical spectral decoding setup (longitudinal profile), the bunch-by-bunch THz detection systems (THz power) and the horizontal bunch size measurement setup (energy spread), three important properties of the bunch during this instability can be measured at every turn for long time scales. This allows a deep insight into the dynamics of the bunch under the influence of the microbunching instability. This contribution will discuss effects like the connection between the emitted CSR power and the deformations in the longitudinal bunch profile on the time scale of the instability.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS015
About •	paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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WEPTS028	Transverse-Longitudinal Coupling for Harmonic Generation and Bunch Length Manipulation	emittance, coupling, lattice, storage-ring	3160
	X.J. Deng, W.-H. Huang, C.-X. Tang, Y. Zhang TUB, Beijing, People’s Republic of China A. Chao SLAC, Menlo Park, California, USA
	A general harmonic generation and bunch length manipulation scheme using transverse-longitudinal coupling is presented. The method makes use of the freedom in projecting the three beam eigen-emittances into different physical dimensions. A realization of this coupling lattice, a PEHG variant, is given as an example. For the purpose of harmonic generation and bunch compression, this method is advantageous when the transverse emittance is small. The combination with sawtooth waveform modulation is proposed to boost the bunching further. Transverse-longitudinal coupling in storage rings are briefly discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS028
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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WEPTS034	Generation of Sub-Femtosecond Electron Beams and Electron Bunch Trains With High Form Factor Using Wake Field Structures	electron, wakefield, space-charge, simulation	3174
	Z. Dong, H. Chen, X.J. Deng, Y.C. Du, Z. Zhou TUB, Beijing, People’s Republic of China
	In this paper, we propose two beam manipulation methods with wakefield structures in a photo-injector. First, we propose a simple scheme to compensate non-linear effects during ballistic bunching by using a wakefield structure. Simulations have shown beams of 1 pC charge can be compressed to 1.56 fs rms, and even shorter beams (a few hundred attoseconds) can be obtained with bunch charge well below 1 pC. In the second part, a method of producing bunch trains with high form factor is proposed by using multiple wake-field structures. Simulation results have shown the production of a train with a form factor of 0.5 using a 1 nC beam at few-MeV energy.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS034
About •	paper received ※ 11 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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WEPTS040	Energy Dependence of the Reproducibility and Injection Efficiency of the LINAC3-LEIR Complex	linac, cavity, injection, operation	3188
	S. Hirlaender ATI, Vienna, Austria H. Bartosik, G. Bellodi, N. Biancacci, V. Kain, A. Saá Hernández, R. Scrivens CERN, Geneva, Switzerland
	High intensities in the CERN Low Energy Ion Ring (LEIR) are achieved by stacking several multi-turn injections from the pre-accelerator LINAC3. Up to seven consecutive 200 μs long, 200 ms spaced pulses are injected from LINAC3 into LEIR. An inclined septum magnet combined with a collapsing horizontal orbit bump allows a 6-D phase space painting via a linearly ramped mean momentum along with the LINAC3 pulse and injection at high dispersion. The injected energy distribution measured by the LEIR longitudinal Schottky is correlated with the obtained injection efficiency in this paper. Studies in 2018 revealed that the achievable accumulated intensity of LEIR strongly depends on the longitudinal distribution from LINAC3, which does not stay constant. This paper summarises the experimental results and means to further improve reproducibility and high injection efficiency.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS040
About •	paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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WEPTS089	Microbunching Instability Mitigation via Multi-Stage Cancellation	electron, linac, laser, impedance	3321
	J. Qiang, B. Li LBNL, Berkeley, California, USA
	Funding: This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 and used computer resources at the National Energy Research Scientific Computing Center. The microbunching instability driven by beam collective effects in the linear accelerator of a free electron laser (FEL) facility can significantly degrade electron beam quality and FEL performance. Understanding and control of the instability is a priority for the design of modern high-brightness electron accelerators. In this paper, we study an instability cancellation phenomenon due to 180 degree phase slippage of the current modulations between different amplification stages. A case study of using a nonisochronous dogleg section in a double compression scheme to cancel the current modulation is illustrated.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS089
About •	paper received ※ 07 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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WEPTS090	Suppression of Microbunching Instability Through Dispersive Lattice	electron, linac, quadrupole, simulation	3325
	J. Qiang, B. Li LBNL, Berkeley, California, USA
	Funding: This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 and used computer resources at the National Energy Research Scientific Computing Center. The microbunching instability from the initial small modulation such as shot-noise can be amplified by longitudinal space-charge force and causes significant electron beam quality degradation at the exit of accelerator for the next generation x-ray free electron laser. In the paper, we present analytical and numerical simulation studies of a novel method using dispersion leakage from some quadrupoles inside a chicane.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS090
About •	paper received ※ 26 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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THPTS038	There-Dimensional Simulation of a C-Band 32-Beam Klystron	klystron, electron, cavity, simulation	4190
	Z.N. Liu, H.B. Chen, J. Shi, H. Zha TUB, Beijing, People’s Republic of China
	A 32-beam klystron working at 5.712 GHz has been designed with efficiency of 70% and output power of 3.4 MW. Core oscillations method (COM) is chosen to bunch electrons. The code KlyC is used for 1-D and 1.5-D calculation and a series of parameters are given after optimizing, including the position, frequency, R/Q, Q₀ and Qe of cavities. CST/PIC is used to make the final design and coaxial cavities are used. This paper describes 1-D, 1.5-D and 3-D beam dynamics of the klystron, compares their differences, and analyses effect of these differences on efficiency.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS038
About •	paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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Paper

Title

Other Keywords

Page

MOPGW017

Feedback Design for Control of the Micro-Bunching Instability based on Reinforcement Learning

storage-ring, feedback, electron, controls

104

T. Boltz, T. Asfour, M. Brosi, E. Bründermann, B. Härer, P. Kaiser, A.-S. Müller, C. Pohl, P. Schreiber, M. Yan
KIT, Karlsruhe, Germany

The operation of ring-based synchrotron light sources with short electron bunches increases the emission of coherent synchrotron radiation (CSR) in the THz frequency range. However, the micro-bunching instability resulting from self-interaction of the bunch with its own radiation field limits stable operation with constant intensity of CSR emission to a particular threshold current. Above this threshold, the longitudinal charge distribution and thus the emitted radiation vary rapidly and continuously. Therefore, a fast and adaptive feedback system is the appropriate approach to stabilize the dynamics and to overcome the limitations given by the instability. In this contribution, we discuss first efforts towards a longitudinal feedback design that acts on the RF system of the KIT storage ring KARA (Karlsruhe Research Accelerator) and aims for stabilization of the emitted THz radiation. Our approach is based on methods of adaptive control that were developed in the field of reinforcement learning and have seen great success in other fields of research over the past decade. We motivate this particular approach and comment on different aspects of its implementation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW017

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paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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MOPGW018

Perturbation of Synchrotron Motion in the Micro-Bunching Instability

electron, synchrotron, storage-ring, radiation

108

T. Boltz, M. Brosi, E. Bründermann, B. Härer, A.-S. Müller, P. Schreiber, P. Schönfeldt, M. Yan
KIT, Karlsruhe, Germany

Short electron bunches in a storage ring are subject to complex longitudinal dynamics due to self-interaction with their own CSR. Above a particular threshold current, this leads to the formation of dynamically changing micro-structures within the bunch, generally known as the micro-bunching instability. The longitudinal dynamics of this phenomenon can be simulated by solving the Vlasov-Fokker-Planck equation, where the CSR self-interaction can be added as a perturbation to the Hamiltonian. This contribution particularly focuses on the comprehension of synchrotron motion in the micro-bunching instability and how it relates to the formation of the occurring micro-structures. Therefore, we adopt the perspective of a single particle and comment on its implications for collective motion. We explicitly show how the shape of the parallel plates CSR wake potential breaks homogeneity in longitudinal phase space and propose a quadrupole-like mode as potential seeding mechanism of the micro-bunching instability. The gained insights are verified using the passive particle tracking method of the Vlasov-Fokker-Planck solver Inovesa.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW018

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paper received ※ 15 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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MOPGW020

Numerical Calculation of Micro Bunching in BERLinPro Due to Space Charge and CSR Effects

space-charge, linac, emittance, optics

116

B.C. Kuske, A. Meseck
HZB, Berlin, Germany

Funding: Work supported by the German Bundesministerium für Bildung und Forschung, Land Berlin and grants of the Helmholtz Association
BERLinPro is an Energy Recovery Linac Project, currently being set up at the Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany. BERLinPro is a small demonstrator for ERL technology and applications. Due to the low energy of 50, resp. 32MeV, space charge plays a dominant role in the beam dynamics. Micro-bunching, due to unavoidable shot noise from the cathode in combination with space charge, is seen in the merger as well as in the recirculator. Coherent synchrotron radiation (CSR) can amplify this bunching, as well as micro-bunching can enhance CSR losses. With the release of OPAL 2.0** in May 2018, for the first time, an open source, highly parallel tracking code is available, that is capable of numerically calculating both effects, space charge and CSR, simultaneously. The calculations are compared to earlier results*, that used analytical formulas on tracked, space charge dominated bunches.
* "On space charge driven microbunching instability in BERLinPro", PhD thesis, S.D.Rädel, Humboldt Universität zu Berlin, 2017
** http://amas.web.psi.ch/docs/opal/opal_user_guide-2.0.0.pdf

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW020

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paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW111

Start to End Simulation on Beam Dynamics in Coherent Electron Cooling Accelerator

electron, FEL, emittance, cavity

379

Y.C. Jing, V. Litvinenko, I. Petrushina, I. Pinayev, K. Shih, Y.H. Wu
BNL, Upton, Long Island, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA
I. Petrushina
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.
A Coherent electron Cooling (CeC) has a potential of substantial reducing cooling time of the high-energy hadrons and hence to boost luminosity in high-intensity hadron-hadron and electron-hadron colliders. In a CeC system, a high quality electron beam is generated, propagated and optimized through a beam line which was carefully designed with consideration of space charge effect, wakefields and nonlinear dynamics such as coherent synchrotron radiation and chromatic aberration. In this paper, we present our study on the beam dynamics of such a beam line and compare the simulation result with what was measured in experiment.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW111

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paper received ※ 17 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPMP015

Longitudinal Particle Dynamics in NICA Collider

collider, injection, accumulation, acceleration

455

E. Syresin, A.V. Eliseev, A.V. Smirnov
JINR, Dubna, Moscow Region, Russia
N.V. Mityanina, V.M. Petrov, E. Rotov, A.G. Tribendis
BINP SB RAS, Novosibirsk, Russia

A specific feature of the NICA acceleration complex is high luminosity of colliding beams. Three types of RF stations will be used in the NICA Collider to reach the necessary beam parameters. The first one is for accumulation of particles in the longitudinal phase space with the moving burrier buckets under action of stochastic and/or electron cooling systems. The second and third RF stations are for formation of the final bunch size in the colliding regime. This report presents numerical simulations of longitudinal beam dynamics which taken into account the longitudinal space charge effect during the accumulation and bunching procedures. Influence of space effects leads to some decrease in the accumulation efficiency and requires special manipulation with the 2nd and 3rd RF stations during the adiabatic capture and bunching procedures.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP015

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paper received ※ 29 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB028

Application of WCM in Beam Commissioning of RCS in CSNS

proton, neutron, MMI, target

636

M.T. Li, F. Li
IHEP CSNS, Guangdong Province, People’s Republic of China
Y.W. An, S.Y. Xu, T.G. Xu
IHEP, Beijing, People’s Republic of China

Wall Current Monitor (WCM) is the only beam instru-ment in RCS of CSNS. It is utilized to derive many kinds of physics parameters during beam commissioning. The longitudinal phase distribution of the bunch over the boosting time is deduced for our future analyzation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB028

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS067

The Progress in Physics Design of HEPS LINAC

linac, wakefield, electron, emittance

1008

C. Meng, D.Y. He, X. He, J.Y. Li, Y.M. Peng, S.C. Wang, O. Xiao, J.R. Zhang, S.P. Zhang
IHEP, Beijing, People’s Republic of China

The High Energy Photon Source (HEPS) is a 6-GeV, ultralow-emittance light source to be built in China. The injector is composed of a 500-MeV Linac and a full energy booster. According to the study and com-missioning consideration of on-axis swap-out injec-tion system, a high bunch charge injector is desirable and a Linac that can provide 7nC per bunch electron beam to booster is needed. This paper present different bunching system schemes and the performance of different schemes are discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS067

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paper received ※ 14 May 2019 paper accepted ※ 17 May 2019 issue date ※ 21 June 2019

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MOPTS073

Bunching System Optimization Based on MOGA

linac, emittance, electron, solenoid

1018

S.P. Zhang, J.Y. Li, C. Meng
IHEP, Beijing, People’s Republic of China

Multiobjective Genetic Algorithms (MOGA) is effective in dealing with optimization problems with multiple objectives. The bunching system of the High Energy Photon Source (HEPS) linac adopts a traditional bunching system for compressing electron beams with a pulse charge of 4 nC. The bunching system is optimized using MOGA. The optimization include minimizing the normalized emittance and maximizing transmission efficiency. The optimization results have reached the design target, and are presented in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS073

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPGW045

Lattice Design for the Reversible SSMB

radiation, electron, emittance, storage-ring

1507

C.L. Li
SINAP, Shanghai, People’s Republic of China
A. Chao
SLAC, Menlo Park, California, USA
C. Feng, B.C. Jiang
Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China

Steady State Microbunching (SSMB) aiming at producing high average power radiation in the electron storage ring has been proposed by Ratner and Chao years ago. Reversible seeding scheme is one of the promising scenarios with less challenges on the storage ring lattice design. The key problem for reversible SSMB is the precise cancelation of the laser modulation which will allow producing turn-by-turn coherent radiation without spoiling the transverse emittances and energy spread. In this paper the lattice design for the microbunching generation and its cancelation will be presented. Also a storage ring lattice design will be shown.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW045

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paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPGW089

Tunable Bunch Train Generation Using Emittance Exchange Beamline With Transverse Wiggler

wiggler, controls, simulation, emittance

1612

G. Ha, M.E. Conde, J.G. Power, J.H. Shao, E.E. Wisniewski
ANL, Argonne, Illinois, USA

Funding: This work is supported by LDRD program at Argonne National Laboratory and Department of Energy, Office of High Energy Physics, under Contract No. DE-AC02-06CH11357.
Emittance exchange beamline provides a unique correlation between the upstream transverse momentum and downstream longitudinal timing. Similar to the bunch train generation concept using energy modulation and chicane, the emittance exchange beamline can convert the transverse momentum modulation to the temporal modulation at the end of the beamline. The beam can obtain this transverse modulation from alternating magnet array (e.g. 90 degree rotated undulator). While most of other methods provide only one knob to control both micro-bunch length and bunch-to-bunch spacing or hard to control one of the knobs, this method provides separated knobs for the micro-bunch length and spacing and they are easy to control. These knobs enable to separately control the fundamental frequency of the radiation and its bandwidth. We plan to demonstrate this method at Argonne Wakefield Accelerator facility (AWA). This poster present progress on this new method and its demonstration at AWA.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW089

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paper received ※ 21 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPRB001

Nanosecond Pulsing for Tandem Accelerator

controls, linac, experiment, injection

1673

P. Linardakis, N.R. Lobanov, D.C. Tempra
Research School of Physics and Engineering, Australian National University, Canberra, Australian Capitol Territory, Australia

Funding: The Australian Federal Government Superscience/EIF funding under the NCRIS mechanism
A pulsed system capable of delivering up to a few microampere bursts of ions with mass range M=1 - 100 amu with a duration of approximately 1 ns is described. The system consists of a negative ion source, three frequency harmonic buncher - which uses the entire tandem electrostatic accelerator as a drift path to produce bunched ion bursts at the targets or linac entry - and high energy choppers. The buncher consists of a single acceleration gap with aligned retractable grids.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB001

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPRB013

Simulation Studies for a EEHG seeded FEL in the XUV

laser, electron, FEL, simulation

1705

V. Grattoni, S. Ackermann, R.W. Aßmann, B. Faatz, T. Lang, C. Lechner, M.M. Mohammad Kazemi, G. Paraskaki, J. Zemella
DESY, Hamburg, Germany
W. Hillert
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
S. Reiche
PSI, Villigen PSI, Switzerland

Echo-enabled harmonic generation (EEHG) is a promising technique for seeded free electron lasers (FELs) not only to go down to wavelengths of 4 nm, but also to simplify the schemes that are currently used to achieve a similar wavelength range (double cascade HGHG). Thus a study optimizing the EEHG performance in the wavelength range from 60 to §I{4}{nm} has been performed. The more critical working point, at 4 nm, is here analyzed in terms of seed laser energy stability for two different seed laser frequencies: visible and UV.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB013

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paper received ※ 30 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPRB057

THz-Pump and UV-Probe Scheme Based on Storage Ring

laser, electron, radiation, storage-ring

1811

H.R. Zhang, Z.G. He, S.M. Jiang, W.X. Wang
USTC/NSRL, Hefei, Anhui, People’s Republic of China

We propose a THz-pump and UV-probe scheme based on storage ring for ultra-fast dynamics experiment. In which, two sequential laser pulses, one of which has a periodic intensity envelope, simultaneously interact with different parts of the long electron beam in a modulator; after a chicane, the part that interacts with the periodic pulse will bunch at THz domain and radiate through a bend magnet, another based on high-harmonic generation will bunch at UV domain and radiate at a radiator. The electron beam can be utilized circularly in the storage ring, which will increase its average power. The feasibility of this THz-pump and UV-probe scheme is verified in both theory and simulation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB057

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TUPRB070

A Peak Finding Algorithm for FEL Spectra Characterization

FEL, electron, laser, background

1827

M.A. Pop
MAX IV Laboratory, Lund University, Lund, Sweden
E. Allaria
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

We present a software tool aimed at investigating the spectra of photon sources in order to detect any instabilities in the electron beam that have a clear effect on the spectrum. The method has been developed for FERMI@Elettra but with a general approach on the particularities of FEL machines such as a high repetition frequency and significant shot to shot fluctuations. The software has two operating options: a mode, aimed at online usage, which only detects peaks and their corresponding valleys, offering no information about the peaks themselves; and a more comprehensive mode that fits peak functions (Gaussian, Lorentzian etc…) to the spectrum based on initial guesses of the fitting parameters. The algorithm can provide a collection of simple but valuable variables such as number of peaks, peak separation and ratio between peak heights, as well as more specialized variables like peak width statistics and decomposition of the raw spectrum in basic components.
Project done in collaboration with FERMI@Elettra

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB070

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPRB071

Considerations on Implementing EEHG with a Strong Linear Chirp

electron, FEL, linac, radiation

1830

M.A. Pop, S. Werin
MAX IV Laboratory, Lund University, Lund, Sweden

As the ECHO enabled harmonic generation (EEHG) scheme draws such intense focus from the FEL community, we conduct simulations to evaluate the challenges of implementing said scheme in different FEL layouts. Nonlinear processes such as this require extensive simulations to harmonize all system specific properties like seed lasers and electron beam properties. Along with optimizing the original EEHG scheme* one can consider, for example, altering the seed laser pulse to optimize the bunching for a machine specific chirp. We study the EEHG as a possible seeding method aimed at increasing coherence of the photon beam for the prospective SXL FEL beamline at MAXIV. The particular chirp of the electron beam through the MAXIV LINAC generates some specific requirements in implementing EEHG but may also offer an opportunity for exotic operation modes of this FEL.
* Xiang D. and Stupakov G. Echo-enabled harmonic generation free electron laser 10.1103/PhysRevSTAB.12.030702

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TUPRB091

Study of XFEL Third Harmonic Radiation at LCLS

undulator, FEL, radiation, experiment

1875

C. Emma, M.W. Guetg, A. Halavanau, A.A. Lutman, G. Marcus, T.J. Maxwell, C. Pellegrini
SLAC, Menlo Park, California, USA

Funding: This work was supported by the U.S. Department of Energy Contract No. DE-AC02-76SF00515.
In this paper, we focus on characterization of the nonlinear third harmonic radiation properties at Linac Coherent Light Source (LCLS). In addition, we experimentally perform third harmonic self-seeding, using diamond crystal attenuator in the hard X-ray self-seeding chicane. We discuss warm beam effects in such scheme, justifying recently proposed two bunch configuration for harmonic lasing.

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paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPTS052

Conceptual Design of a High-Performance Injector Based on Rf-Gated Gridded Thermionic Gun for Thz Fel

gun, electron, linac, cathode

2046

P. Yang, H.M. Chen, T. Hu, J.J. Li, Y. Lu
HUST, Wuhan, People’s Republic of China
G.Y. Feng, S.C. Zhang
USTC/NSRL, Hefei, Anhui, People’s Republic of China

Free-Electron Laser (FEL) has higher requirements on electron beam properties, for example, low transverse emittance, small energy spread, short bunch length and high peak current. Taking compactness and economy into account, we aim to design a high-performance linear accelerator based on a RF-gated gridded thermionic electron gun, which will be used as the injector of the oscillator-type THz FEL facility at Huazhong University of Science and Technology of China. The RF-gated grid will be modulated with the fundamental and 3rd harmonic microwave of the LINAC frequency, which will be very helpful to get high electron capture efficiency and short bunch length. Concerning velocity bunching effect in the LINAC, electron bunch with good symmetry of current profile and bunch length less than 10 ps can be obtained at the exit of the injector. In this paper, design and beam dynamics simulation for the high-performance injector are presented.

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paper received ※ 26 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPGW017

Continuous Bunch-by-Bunch Reconstruction of Short Detector Pulses

detector, storage-ring, experiment, simulation

2501

J.L. Steinmann, M. Brosi, M. Caselle, B. Kehrer, M. Martin, A.-S. Müller, M.M. Patil, P. Schreiber
KIT, Karlsruhe, Germany

Funding: This work is funded by the BMBF contract number: 05K16VKA
The KAPTURE system (KArlsruhe Pulse Taking and Ultrafast Readout Electronics), developed at the Karlsruhe Institute of Technology (KIT), was designed to digitize detector pulses during multi-bunch operation at the KIT storage ring KARA (Karlsruhe Research Accelerator). KAPTURE provides digitization for pulses at rates of 500 MHz using up to 4 sampling points per pulse to record each bunch and each turn for potentially unlimited time. The new KAPTURE-2 system now provides eight sampling points per pulse, including baseline sampling between pulses, which allows improved reconstruction of the pulse shape. The advanced reconstruction of the pulse shape is realized with a highly parallelised implementation on GPU. The system will be used for the investigation on longitudinal beam dynamics e.g. by measuring instability induced CSR fluctuations or arrival time oscillations. This contribution will report on first results of the KAPTURE-2 system at KARA.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW017

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPRB055

Design of 3 MeV S-band Electron Linac Structure With 2.5 Bunching Cells

electron, linac, coupling, simulation

2934

Y. Joo, P. Buaphad, H.R. Lee
University of Science and Technology of Korea (UST), Daejeon, Republic of Korea
Y. Kim
KAERI, Daejon, Republic of Korea
J.Y. Lee, S. Lee
Korea Atomic Energy Research Institute (KAERI), Daejeon, Republic of Korea

Funding: UST (University of Science and Technology), KAERI (Korea Atomic Energy Research Institute)
The Korea Atomic Energy Research Institute (KAERI) has been designing several 3 MeV S-band RF electron linear accelerators (linacs) for non-destructive testing. Until now, the bunching cell of the linac has a full-cell geometry. However, to maximize the acceleration of electrons after emission from the electron gun, the geometry of the first bunching cell is modified from a full-cell to a half cell. To accelerate electron beams more gently, recently, we increased the total number of bunching cells from 1.5 to 2.5. In this paper, we describe design concepts and detailed optimization processes of a 3 MeV linac with the 2.5 bunching cells to optimize RF parameters such as the quality factor, resonance frequency, and uniformity of electric field distribution along the linac. Lastly, we will discuss the application of 3 MeV linac.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB055

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paper received ※ 04 June 2019 paper accepted ※ 16 June 2019 issue date ※ 21 June 2019

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WEPRB095

Microbunching Plasma-Cascade Instability

plasma, simulation, electron, focusing

3035

V. Litvinenko
Stony Brook University, Stony Brook, USA
T. Hayes, Y.C. Jing, D. Kayran, J. Ma, T.A. Miller, G. Narayan, I. Pinayev, F. Severino, G. Wang
BNL, Upton, Long Island, New York, USA
I. Petrushina
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 and NSF Grant No. PHY-141525
We present a new type of longitudinal microbunching instability entitled ’Plasma-Cascade Instability’. This instability could occur in beams propagating along a straight section with external focusing elements. We present a theoretical description of this instability as well as self-consistent 3D simulations. Finally, we present results of experimental observation of Plasma-Cascade Instability at frequencies up to 10 THz using SRF linear accelerator built for Coherent electron Cooling experiment *.
* Commissioning of FEL-based Coherent electron Cooling system, V.N. Litvinenko et al., In proc. of 38th Int. Free Electron Laser Conf.(FEL’17), Santa Fe, NM, USA, August 20-25, 2017, p. 132

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB095

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paper received ※ 18 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPTS015

Synchronous Measurements of Electron Bunches Under the Influence of the Microbunching Instability

synchrotron, radiation, simulation, storage-ring

3119

M. Brosi, T. Boltz, E. Bründermann, S. Funkner, B. Kehrer, A.-S. Müller, M.J. Nasse, G. Niehues, M.M. Patil, P. Schreiber, P. Schönfeldt, J.L. Steinmann
KIT, Karlsruhe, Germany

Funding: This work has been supported by the German Federal Ministry of Education and Research (Grant No. 05K16VKA). We acknowledge the support by the Helmholtz International Research School for Teratronics.
The microbunching instability is a longitudinal collective instability which occurs for short electron bunches in a storage ring above a certain threshold current. The instability leads to a charge modulation in the longitudinal phase space. The resulting substructures on the longitudinal bunch profile vary over time and lead to fluctuations in the emitted power of coherent synchrotron radiation (CSR). To study the underlying longitudinal dynamics on a turn-by-turn basis, the KIT storage ring KARA (Karlsruhe Research Accelerator) provides a wide variety of diagnostic systems. By synchronizing the single-shot electro-optical spectral decoding setup (longitudinal profile), the bunch-by-bunch THz detection systems (THz power) and the horizontal bunch size measurement setup (energy spread), three important properties of the bunch during this instability can be measured at every turn for long time scales. This allows a deep insight into the dynamics of the bunch under the influence of the microbunching instability. This contribution will discuss effects like the connection between the emitted CSR power and the deformations in the longitudinal bunch profile on the time scale of the instability.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS015

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paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPTS028

Transverse-Longitudinal Coupling for Harmonic Generation and Bunch Length Manipulation

emittance, coupling, lattice, storage-ring

3160

X.J. Deng, W.-H. Huang, C.-X. Tang, Y. Zhang
TUB, Beijing, People’s Republic of China
A. Chao
SLAC, Menlo Park, California, USA

A general harmonic generation and bunch length manipulation scheme using transverse-longitudinal coupling is presented. The method makes use of the freedom in projecting the three beam eigen-emittances into different physical dimensions. A realization of this coupling lattice, a PEHG variant, is given as an example. For the purpose of harmonic generation and bunch compression, this method is advantageous when the transverse emittance is small. The combination with sawtooth waveform modulation is proposed to boost the bunching further. Transverse-longitudinal coupling in storage rings are briefly discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS028

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPTS034

Generation of Sub-Femtosecond Electron Beams and Electron Bunch Trains With High Form Factor Using Wake Field Structures

electron, wakefield, space-charge, simulation

3174

Z. Dong, H. Chen, X.J. Deng, Y.C. Du, Z. Zhou
TUB, Beijing, People’s Republic of China

In this paper, we propose two beam manipulation methods with wakefield structures in a photo-injector. First, we propose a simple scheme to compensate non-linear effects during ballistic bunching by using a wakefield structure. Simulations have shown beams of 1 pC charge can be compressed to 1.56 fs rms, and even shorter beams (a few hundred attoseconds) can be obtained with bunch charge well below 1 pC. In the second part, a method of producing bunch trains with high form factor is proposed by using multiple wake-field structures. Simulation results have shown the production of a train with a form factor of 0.5 using a 1 nC beam at few-MeV energy.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS034

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paper received ※ 11 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPTS040

Energy Dependence of the Reproducibility and Injection Efficiency of the LINAC3-LEIR Complex

linac, cavity, injection, operation

3188

S. Hirlaender
ATI, Vienna, Austria
H. Bartosik, G. Bellodi, N. Biancacci, V. Kain, A. Saá Hernández, R. Scrivens
CERN, Geneva, Switzerland

High intensities in the CERN Low Energy Ion Ring (LEIR) are achieved by stacking several multi-turn injections from the pre-accelerator LINAC3. Up to seven consecutive 200 μs long, 200 ms spaced pulses are injected from LINAC3 into LEIR. An inclined septum magnet combined with a collapsing horizontal orbit bump allows a 6-D phase space painting via a linearly ramped mean momentum along with the LINAC3 pulse and injection at high dispersion. The injected energy distribution measured by the LEIR longitudinal Schottky is correlated with the obtained injection efficiency in this paper. Studies in 2018 revealed that the achievable accumulated intensity of LEIR strongly depends on the longitudinal distribution from LINAC3, which does not stay constant. This paper summarises the experimental results and means to further improve reproducibility and high injection efficiency.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS040

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS089

Microbunching Instability Mitigation via Multi-Stage Cancellation

electron, linac, laser, impedance

3321

J. Qiang, B. Li
LBNL, Berkeley, California, USA

Funding: This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 and used computer resources at the National Energy Research Scientific Computing Center.
The microbunching instability driven by beam collective effects in the linear accelerator of a free electron laser (FEL) facility can significantly degrade electron beam quality and FEL performance. Understanding and control of the instability is a priority for the design of modern high-brightness electron accelerators. In this paper, we study an instability cancellation phenomenon due to 180 degree phase slippage of the current modulations between different amplification stages. A case study of using a nonisochronous dogleg section in a double compression scheme to cancel the current modulation is illustrated.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS089

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paper received ※ 07 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPTS090

Suppression of Microbunching Instability Through Dispersive Lattice

electron, linac, quadrupole, simulation

3325

J. Qiang, B. Li
LBNL, Berkeley, California, USA

Funding: This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 and used computer resources at the National Energy Research Scientific Computing Center.
The microbunching instability from the initial small modulation such as shot-noise can be amplified by longitudinal space-charge force and causes significant electron beam quality degradation at the exit of accelerator for the next generation x-ray free electron laser. In the paper, we present analytical and numerical simulation studies of a novel method using dispersion leakage from some quadrupoles inside a chicane.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS090

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paper received ※ 26 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPTS038

There-Dimensional Simulation of a C-Band 32-Beam Klystron

klystron, electron, cavity, simulation

4190

Z.N. Liu, H.B. Chen, J. Shi, H. Zha
TUB, Beijing, People’s Republic of China

A 32-beam klystron working at 5.712 GHz has been designed with efficiency of 70% and output power of 3.4 MW. Core oscillations method (COM) is chosen to bunch electrons. The code KlyC is used for 1-D and 1.5-D calculation and a series of parameters are given after optimizing, including the position, frequency, R/Q, Q₀ and Qe of cavities. CST/PIC is used to make the final design and coaxial cavities are used. This paper describes 1-D, 1.5-D and 3-D beam dynamics of the klystron, compares their differences, and analyses effect of these differences on efficiency.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS038

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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