Keyword: bunching
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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/opaluserguide-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. 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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