Keyword: space-charge
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MOPAB028 Estimation of Longitudinal Dimensions of Sub-Picosecond Electron Bunches with the 3-Phase Method booster, electron, simulation, gun 139
 
  • H. Purwar, C. Bruni, A. Gonnin
    LAL, Orsay, France
  • T. Vinatier
    DESY, Hamburg, Germany
  
  An estimation of the longitudinal dimensions for short electron bunches in an accelerating field is an important diagnostic and can be extremely helpful in evaluating the performance of an accelerator. We investigate a method for close estimation of bunch length for sub-picosecond electron bunches from the measurement of their energy spreads. Three or more measurements for the bunch energy spread are made by varying the phase of the accelerating structure and later a reconstruction of the bunch longitudinal dimensions, namely bunch length, initial energy spread and chirp at the entrance of the accelerating structure are obtained using the least square method. A comparison of the obtained results with ASTRA simulations is also included to validate the 3-phase method for sub-ps electron bunches. It is a simple method from both understanding (easy reconstruction using transport matrices) and experimental point of views (multiple measurements of energy spread with varying phase of the accelerating structure).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB028  
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MOPAB039 Development of a Control System Based on Experimental Data for Space Charge Lenses electron, plasma, operation, ion 166
 
  • S. Klaproth, C. Beberweil, M. Droba, O. Meusel, H. Podlech, B.E.J. Scheible, K. Schulte, K.I. Thoma, C. Wagner
    IAP, Frankfurt am Main, Germany
  
  Space charge lenses use a confined electron cloud for the focusing of ion beams. The electron density gives the focusing strength whereas the density distribution influences the mapping quality of the space charge lens and is related to the confinement. The major role of the electron density with respect to the focusing quality has been pointed out many times in the past *,**. With an automated measurement system the radial light density profile, plasma stability and mean value of the electron density have been measured in respect to the confining fields and the pressure. The results are summarized in 3D-maps. The theoretical model approximations for space charge lenses predicts high electron densities then measured. With the automated system the realistic 3D-maps can be considered instead of an approximation of a theoretical density including knowledge of the most stable electron cloud achievable within the parameter range of the lens. The experimental results of the automated measurement system will be presented here and a concept of a control system for this type of space charge lenses will be explained.
* O. Meusel, 'Focussing and transport of ion beams using space charge lenses', PhD thesis, 2006 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB039  
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MOPAB045 Reconstruction of the 3D Charge Distribution of an Electron Bunch Using a Novel Variable-Polarization Transverse Deflecting Structure (TDS) simulation, electron, experiment, laser 188
 
  • D. Marx, R.W. Aßmann, U. Dorda, U. Dorda, B. Marchetti
    DESY, Hamburg, Germany
  • P. Craievich
    PSI, Villigen PSI, Switzerland
  • A. Grudiev, A. Grudiev, A. Grudiev
    CERN, Geneva, Switzerland
  
  A TDS is a well-known device for the characterization of the longitudinal properties of an electron bunch in a linear accelerator. So far, the correlation of the slice properties in the horizontal/vertical planes of the electron bunch distribution has been characterized by using a TDS system deflecting in the vertical/horizontal directions respectively and analysing the image on a subsequent screen*. Recently, an innovative design for a TDS structure has been proposed, which includes the possibility of continuously varying the angle of the transverse streaking field inside a TDS structure**. This allows the beam distribution to be characterized in all transverse directions. By collecting measurements of bunches streaked at different angles and combining them using tomographic techniques, it is possible to retrieve 3D distributions of the charge density. In this paper, a method is proposed and simulation results are presented to show the feasibility of such an approach at the upcoming accelerator R&D facility, SINBAD, at DESY***.
* M. Roehrs et al., Phys. Rev. ST Accel. Beams 12, 050704 (2009).
** A. Grudiev, Report No. CLIC-Note-1067, 2016.
*** B. Marchetti et al. X-band TDS project contribution to these conference proceedings.
 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB045  
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MOPAB048 Simulation of fs Bunch Length Determination with the 3-Phase Method and THz Dielectric Loaded Waveguides injection, linac, simulation, electron 199
 
  • T. Vinatier, R.W. Aßmann, U. Dorda, B. Marchetti
    DESY, Hamburg, Germany
  
  In this paper, we investigate with ASTRA simulations the capability of the 3-phase method to reconstruct the length of a fs electron bunch. We show that a standard 3 GHz travelling wave accelerating structure is not suited for this purpose, because of the too important effect of the space-charge forces and of the too small variations of the induced energy spread with the bunch injection phase. Our simulations demonstrate that the use of dielectric-loaded waveguides driven by THz pulses would allow overcoming these two limitations and possibly achieving an ultimate resolution better than 5% for the determination of a 6.25 fs rms bunch length at 100 MeV energy and 1 pC charge. The next steps of the study to better evaluate, in simulations and experiments, the possible sources of degradation of the 3-phase method resolution are also mentioned.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB048  
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MOPAB137 Validation of a Novel Emittance Diagnostic Method for Beams with Significant Space Charge emittance, focusing, quadrupole, simulation 451
 
  • R.B. Fiorito, C.P. Welsch, H.D. Zhang
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • M.E. Conde, N.R. Neveu, J.F. Power
    ANL, Argonne, Illinois, USA
  • O. Mete Apsimon
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • A.G. Shkvarunets
    UMD, College Park, Maryland, USA
  
  Funding: Work supported by the EU under grant agreement 624890, the STFC Cockcroft Institute Core Grant No. ST/G008248/1.
Exact knowledge of beam emittance is of central importance for essentially every accelerator. However, there are only few methods to determine it when the beam has significant space charge. We report on our progress to validate a novel diagnostic method that has been proposed to determine the RMS emittance of an electron beam with space charge. This method uses RMS divergence and beam size data measured at a screen placed in a free drift region for selected values of magnetic focusing strength. A novel algorithm is then used to determine the cross correlation term and consequently the RMS emittance of the beam. Simulations, quadrupole scans, phase space tomography and optical diffraction-dielectric foil radiation interferometry are currently being employed to determine and compare the horizontal (x) and vertical (y) emittances of the 14 MeV witness electron beam at Argonne National Laboratory's Wakefield Accelerator. The results of simulations and current measurements are presented and the advantages of the new technique are discussed. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB137  
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MOPIK075 Design, Simulation and Compare of Flat Cathode Electron Guns with Spherical Cathode Electron Guns for Industrial Accelerators cathode, gun, electron, simulation 702
 
  • M. Nazari, F. Abbasi
    Shahid Beheshti University, Tehran, Iran
  • S. Ahmadiannamin
    ILSF, Tehran, Iran
  • F. Ghasemi
    NSTRI, Tehran, Iran
  • S. Haghtalab
    IPM, Tehran, Iran
  
  In this article, electron guns with flat and spherical cathodes have been designed and simulated for industrial accelerators. After checking the different features of each cathode geometry, there has been discussed about optimum values of this features. The most important features in selecting the best cathode geometry for industrial accelerators are beam waist radius, beam waist position, current density and price. Finally after comparing the different features of both geometries with each other, suitable geometry was selected.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK075  
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MOPIK113 Beam Phase Space Tomography for FXR LIA emittance, simulation, solenoid, electron 801
 
  • Y.H. Wu, Y.-J. Chen
    LLNL, Livermore, California, USA
  
  Funding: This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Knowing the initial beam parameters entering an accelerator or a downstream beamline allows us to select transport tunes optimized for a desired accelerator performance. In this study, we report unfolding LLNL's FXR [1] beam parameters by using the tomography technique [2, 3] to construct the beam phase space along the accelerator's downstream beamline. The unfolded phase spaces from tomography and simulations are consistent. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK113  
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TUPAB142 Tracking of Electrons Created at Wrong RF Phases in the RHIC Low Energy Cooler electron, cathode, cavity, laser 1666
 
  • J. Kewisch, A.V. Fedotov, D. Kayran, S. Seletskiy
    BNL, Upton, Long Island, New York, USA
  
  Funding: Work supported by the US Department of Energy under contract No. DE-SC0012704.
The RHIC Low Energy Cooler will be based on a 400 keV DC electron gun with a photo-cathode and a 2.2 MeV SRF booster cavity. Electron that leave the cathode at the wrong time may be decelerated and turned around in the booster and return to the cathode with energies up to 1 MeV. On the way back these electron will encounter the defocussing EM fields up to nine following electron bunches. Such electrons may be created for various reasons: Cosmic rays, stray laser light including a catastrophic failure of the laser timing system or as secondaries of returning electrons. We present tracking results from the GPT program* and discuss the consequences for the machine protection system.
* www.pulsar.nl 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB142  
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TUPAB143 Dependence of LEReC Beam Energy Spread on Photocathode Laser Modulation laser, electron, impedance, flattop 1669
 
  • S. Seletskiy, M. Blaskiewicz, A.V. Fedotov, D. Kayran, J. Kewisch, M.G. Minty, B. Sheehy, Z. Zhao
    BNL, Upton, Long Island, New York, USA
  • B. Sheehy
    Sheehy Scientific Consulting, Wading River, New York, USA
  
  Present requirements to the photocathode DC gun of the low energy RHIC electron cooling (LEReC) project is to produce 100 ps long bunch of electrons with 130 pC charge. The laser pulse of required length will be produced with the stacking of multiple few picosecond long sub-pulses. Depending on the choice of the laser sub-pulse length and on the relative delay between these sub-pulses one can obtain laser pulse with various longitudinal intensity modulations. The longitudinal modulation of laser intensity creates longitudinal modulation of electron bunch charge. Such modulation is known to cause the growth of e-beam uncorrelated energy spread in photoinjectors - the effect we would like to avoid. In this paper we estimate growth of e-beam energy spread due to its initial density modulation and set requirements to the maximum allowable depth of longitudinal modulation of photocathode laser intensity.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB143  
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TUPVA059 Overcoming the Space Charge Limit: Development of an Electron Lens for SIS18 electron, ion, gun, injection 2211
 
  • D. Ondreka, P.J. Spiller
    GSI, Darmstadt, Germany
  • P. Apse-Apsitis
    Riga Technical University, Riga, Latvia
  • K. Schulte
    IAP, Frankfurt am Main, Germany
  
  The 'Facility for Anti-Proton and Ion Research' (FAIR) presently under construction will deliver intense ion beams to its experimental users. The requested intensities require filling the existing synchrotron SIS18, which serves as injector to FAIR, up to the space charge (SC) limit. Operation under these conditions is challenging due to the large tune footprint of the beam, demanding delicate control of adverse effects caused by machine imperfections to avoid emittance growth and beam loss. To facilitate the high intensity operation, the installation of an electron lens for SC compensation into SIS18 is foreseen. This requires an electron beam of a current of several amperes with longitudinal and transverse distributions matched to those of the ion beam during the cycle. The electron beam needs to be RF modulated at a bandwidth of a few MHz with time varying amplitude ranging from DC to fully modulated, while the transverse size needs to be continuously adapted to the adiabatically shrinking ion beam. This contribution reports on the requirements on an electron lens for SC compensation in SIS18.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA059  
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TUPVA140 Space charge effects of catch-up collision in a CW double-pass proton linac simulation, linac, proton, cavity 2429
 
  • Y. Tao, K. Hwang, J. Qiang
    LBNL, Berkeley, California, USA
  
  Recirculating superconducting proton linac has an advantage to reduce the number of cavities and the resulting accelerator construction/operation costs. Beam dynamics simulations were done recently in a double pass recirculating proton linac using a single bunch. For continuous wave (CW) operation, the high energy proton beam bunch during the second pass will catch up and collide with the low energy proton bunch at a number of locations inside the superconducting linac. In this paper, we report on the study of the space-charge effects during a collision on both beams through the rest of the linac.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA140  
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WEXB1 Studies and Observations of Beam Dynamics Near a Sum Resonance resonance, synchrotron, emittance, simulation 2503
 
  • G. Franchetti
    GSI, Darmstadt, Germany
  • S.S. Gilardoni, A. Huschauer, F. Schmidt, R. Wasef
    CERN, Geneva, Switzerland
  
  The effect of space charge on bunches stored for long term in a can be severe for beam survival. This may be the case in projects as SIS100 at GSI or LIU at CERN. In the past decade systematic simulation studies and experiments performed at CERN and GSI have highlighted the space charge induced periodic crossing of “one dimensional” resonances as the underlying mechanism of long term beam loss or emittance growth. However only in 2012, for the first time, the effect of space charge on a normal third order coupled resonance was investigated at the CERN-PS. The experimental results have highlighted an unprecedented asymmetric beam response where in the horizontal plane the beam exhibits a thick halo, whereas the vertical profile has only core growth. The quest for explaining these results requires a journey thorough the 4 dimensional dynamics of the coupled resonance investigating the fix-lines, and requires a detailed code-experiment benchmarking also including beam profile benchmarking. This study shows that the experimental results of the 2012 PS measurements can be explained by the dynamics the fixed lines also including the effect of the dispersion.  
slides icon Slides WEXB1 [18.195 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEXB1  
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WEPAB031 OCELOT as a Framework for Beam Dynamics Simulations of X-Ray Sources simulation, wakefield, FEL, electron 2642
 
  • S.I. Tomin
    XFEL. EU, Hamburg, Germany
  • I.V. Agapov, M. Dohlus, I. Zagorodnov
    DESY, Hamburg, Germany
  
  We describe the OCELOT open source project focusing on new beam dynamics simulation capabilities of the whole machine in modern electron-based x-ray sources. Numerical approaches for particle tracking and field calculations are discussed. In developing of the full-dimensional numerical modeling we pursue two important competitive aspects: the simulation has to be fast and has to include accurate estimations of collective effects. The simulation results for the European XFEL [1] are presented. The results have been benchmarked agains other codes and some of such benchmarks are shown.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB031  
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WEPAB118 High Power Sub-Femtosecond X-Ray Pulse Study for the LCLS undulator, electron, simulation, photon 2848
 
  • J.P. MacArthur
    Stanford University, Stanford, California, USA
  • J.P. Duris, Z. Huang, A. Marinelli
    SLAC, Menlo Park, California, USA
  
  The desire to resolve sub-femtosecond electron dynamics has pushed FEL facilities to shorter pulse lengths. However, current short-pulse schemes provide low pulse energy and a gain-length limited lower bound on the pulse duration. The X-ray Laser-Enhanced Attosecond Pulses (XLEAP) project at SLAC is designed implement an Enhanced Self Amplified Spontaneous Emission (ESASE) scheme, which produces sub-fs current spikes by modulating and compressing the electron beam. We show through a series of Genesis simulations that the current spike is capable of producing sub-fs pulses with a peak power well above 100 GW. Space-charge induced beam chirp can decrease pulse lengths below 400 as, and multi-stage schemes can increase peak x-ray powers to around 1 TW.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB118  
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WEPIK014 Coupled Bunch Instability and Its Cure at J-PARC RCS impedance, kicker, emittance, injection 2946
 
  • Y. Shobuda, H. Harada, H. Hotchi, P.K. Saha, T. Takayanagi, F. Tamura, N. Tani, T. Togashi, Y. Watanabe, K. Yamamoto, M. Yamamoto
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  • Y.H. Chin, Y. Irie, T. Toyama
    KEK, Ibaraki, Japan
  
  The RCS at J-PARC is a kicker-impedance dominant machine, which violates the impedance budget from a classical viewpoint. Nevertheless, we have recently succeeded to accelerate a 1-MW equivalent beam by making maximum use of the space charge effect on the beam instabilities. In this report, we explain the manipulation to suppress the beam instability, at first. Then, we discuss some issues to suppress the beam instabilities for beams with much smaller transverse emittance, as well as the present status of our efforts to reduce the kicker impedance toward the realization of the higher beam power at the RCS.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK014  
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WEPIK074 Twiss Parameter Measurement and Application to Space Charge Dynamics resonance, betatron, emittance, lattice 3101
 
  • K. Ohmi, S. Igarashi, T. Toyama
    KEK, Ibaraki, Japan
  • H. Harada, S. Hatakeyama
    JAEA/J-PARC, Tokai-mura, Japan
  • N. Kuroo
    UTTAC, Tsukuba, Ibaraki, Japan
  • Y. Sato
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
  • R. Tomás, A. Wegscheider
    CERN, Geneva, Switzerland
  
  We are looking for feasible and quantitative method to evaluate space charge induced beam loss in J-PARC MR. One possible way is space charge simulation and theory based on measured Twiss parameter. Twiss parameter measurement using turn-by-turn monitors is presented. Resonance strengths of lattice magnets and space charge force are estimated by the measured Twiss parameters. Emittance growth and beam loss under the resonance strengths are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK074  
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WEPIK094 LEIR Impedance Model and Coherent Beam Instability Observations impedance, ion, injection, electron 3159
 
  • N. Biancacci, H. Bartosik, A. Huschauer, E. Métral, T.L. Rijoff, B. Salvant, R. Scrivens
    CERN, Geneva, Switzerland
  • M. Migliorati
    University of Rome La Sapienza, Rome, Italy
  
  The LEIR machine is the first synchrotron in the ion acceleration chain at CERN and it is responsible to deliver high intensity ion beams to the LHC. Following the recent progress in the understanding of the intensity limitations, detailed studies of the machine impedance started. In this work we describe the present LEIR impedance model, detailing the contribution to the total longitudinal and transverse impedance of several machine element. We then compare the machine tune shift versus intensity predictions against measurements at injection energy and summarize the coherent instability observations in absence of transverse damper feedback.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK094  
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WEPIK101 Novel Implementation of Quadrupole and Higher Order Fringe Fields to Accelerator Design quadrupole, multipole, sextupole, dipole 3184
 
  • B.D. Muratori
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  
  Until recently, in the initial design phase of any accelerator project, it was not possible to have an adequate description of quadrupole and higher order multipole fringe fields. We report on the latest developments in analytical fringe fields for multipoles, particularly for quadrupoles and sextupoles. We show how they can be used to improve accelerator codes and make them both faster and more precise. We also show how the analytical formulae for the fringe fields yield expressions for both the scalar and vector potentials in electromagnetism. We conclude by discussing the application of both potentials to the design of multipole magnets as well as the implementation of symplectic kick approximations for fringe fields in thin lens models that could be used in accelerator codes.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK101  
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WEPVA037 Machine Development Studies in the CERN PS Booster, in 2016 injection, emittance, extraction, booster 3339
 
  • E. Benedetto, S.C.P. Albright, M.E. Angoletta, W. Bartmann, J.M. Belleman, A. Blas, M. Cieslak-Kowalska, G.P. Di Giovanni, A. Findlay, V. Forte, A. Garcia-Tabares, G. Guidoboni, S. Hancock, M. Jaussi, B. Mikulec, J.C. Molendijk, A. Oeftiger, T.L. Rijoff, F. Schmidt, P. Zisopoulos
    CERN, Geneva, Switzerland
  • M. Cieslak-Kowalska
    EPFL, Lausanne, Switzerland
  • P. Zisopoulos
    Uppsala University, Uppsala, Sweden
  
  The paper presents the outstanding studies performed in 2016 in preparation of the PS Booster upgrade, within the LHC Injector Upgrade project (LIU), to provide twice higher brightness and intensity to the High-Luminosity LHC. Major changes include the increase of injection and extraction energy, the implementation of a H− charge-exchange injection system, the replacement of the present Main Power Supply and the deployment of a new RF system (and related Low-Level), based on the Finemet technology. Although the major improvements will be visible only after the upgrade, the present machine can already benefit of the work done, in terms of better brightness, transmission and improved reproducibility of the present operational beams. Studies address the space-charge limitations at low energy, for which a detailed optics model is needed and for which mitigation measurements are under study, and the blow-up reduction at injection in the downstream machine, for which the beams need careful preparation and transmission. Moreover they address the requirements and the reliability of new beam instrumentation and hardware that is being installed in view of LIU.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA037  
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WEPVA067 Preliminary Results on the Resonant Excitation of THz Wakefield in a Multi-Mode Dielectric Loaded Waveguide by Bunch Train electron, wakefield, radiation, experiment 3426
 
  • D. Wang, Y.-C. Du, W. Gai, W.-H. Huang, L. Niu, X.L. Su, C.-X. Tang, Q.L. Tian, L.X. Yan
    TUB, Beijing, People's Republic of China
  • S.P. Antipov
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • Y.F. Liang
    Tsinghua University, Beijing, People's Republic of China
  
  Funding: Work supported by the National Nature Science Foundation of China (NSFC Grants No.11475097) and the National Key Scientific Instrument and Equipment Development Project of China (Grants No. 2013YQ12034504)
We report the preliminary experimental results on the resonant excitation of THz wakefield in a multi-mode dielectric loaded waveguide (DLW) by electron bunch train at the Tsinghua University accelerator beamline. The bunch train with certain longitudinal periodicity was generated based on nonlinear longitudinal space charge oscillation [1]. By passing such bunch train through a multi-mode DLW, we observed selective excitation of the fifth longitudinal mode (TM05 mode) was resonantly excited. Future experiment plan is to tune the bunch train interval with a chicane in the beamline in order to selectively excite arbitrary mode for tunable THz radiation source with multi-mode DLWs.
*wangdan16@mail.tsinghua.edu.cn
*yanlx@mail.tsinghua.edu.cn
 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA067  
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THOAA2 Research on Compensation of Superconducting Cavity Failures in C-ADS Injector-I FPGA, hardware, cavity, linac 3635
 
  • J.P. Dai, C. Meng, Y. Shao, Z. Xue, F. Yan
    IHEP, Beijing, People's Republic of China
  
  Funding: Work supported by Natural Science Foundation of China (11575216)
For the proton accelerators such as the China Accelerator Driven subcritical System(C-ADS), it is essential and difficult to achieve extremely high performance reliability requirement. In order to achieve this performance reliability requirement, in addition to hardware improvement, a failure tolerant design is mandatory. A compensation mechanism to cope with hardware failure, mainly RF failures of superconducting cavities, will be in place in order to maintain the high uptime, short recovery time and extremely low frequency of beam loss. This paper proposes an innovative and challenging way for compensation and rematch of cavity failure with the hardware implementation of the scheme using fast electronic devices and Field Programmable Gate Arrays (FPGAs). A method combined building an equivalent model for the FPGA with an improved genetic algorithm has been developed. Results based on the model and algorithm are compared with TRACEWIN simulation to show the precision and correctness of the mechanism. 		 
slides icon Slides THOAA2 [2.414 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THOAA2  
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THPAB013 A Fast Particle Tracking Tool for the Simulation of Dielectric Laser Accelerators simulation, laser, GPU, plasma 3716
 
  • F. Mayet, R.W. Aßmann, U. Dorda, W. Kuropka
    DESY, Hamburg, Germany
  • W. Kuropka, F. Mayet
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  
  Funding: GBMF - Gordon and Betty Moore Foundation
In order to simulate the beam dynamics in grating based Dielectric Laser Accelerators (DLA) fully self-consistent PIC codes are usually employed. These codes model the evolution of both the electromagnetic fields inside a laser-driven DLA and the beam phase space very accurately. The main drawback of these codes is that they are computationally very expensive. While the simulation of a single DLA period is feasible with these codes, long multi-period structures cannot be studied without access to HPC clusters. We present a fast particle tracking tool for the simulation of long DLA structures. DLATracker is a parallelized code based on the analytical reconstruction of the in-channel electromagnetic fields and a Boris/Vay-type particle pusher. It computational kernel is written in OpenCL and can run on both CPUs and GPUs. The main code is following a modular approach and is written in Python 2.7. This way the code can be easiliy extended for different use cases. In order to benchmark the code, simulation results are compared to results obtained with the PIC code VSim 7.2. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB013  
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THPAB027 Symplectic Multi-Particle Tracking Using Cuda GPU, simulation, kicker, emittance 3756
 
  • Zh.C. Liu
    IHEP, Beijing, People's Republic of China
  • J. Qiang
    LBNL, Berkeley, California, USA
  
  Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 and the Ministry of Science and Technology of China under Grant No.2014CB845501.
The symplectic tracking model can preserve phase space structure and reduce non-physical effects in long term simulation. Though this model is computationally expensive, it is very suitable for parallelization and can be accelerated significantly by using Graphic Processing Units (GPUs). Using a single GPU, the code achieves a speedup of more than 400 compared with the time on a single CPU core. It also shows good scalability on a GPU cluster at Oak Ridge Leadership Computing Facility. In this paper, we report on the GPU code implement, the performance test on both single-GPU and multi-GPU cluster, and an application of beam dynamics simulation. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB027  
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THPAB049 Progress in the Understanding of the Performance Limitations in the CERN Low Energy Ion Ring resonance, ion, sextupole, optics 3819
 
  • A. Huschauer, H. Bartosik, S. Hancock, V. Kain
    CERN, Geneva, Switzerland
  
  The performance of heavy ion beams in the CERN Low Energy Ion Ring is mainly limited by beam loss occuring during the radio-frequency capture and the first part of acceleration. Since October 2015, the driving mechanism of these losses has been studied in detail and an interplay of direct space charge forces and excited betatron resonances was identified as the most plausible explanation of the phenomenon. In this paper we summarize the current understanding of the loss mechanism by presenting recent experimental and simulation studies. We discuss strategies to mitigate beam loss and further improve the performance of the accelerator in the future.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB049  
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THPAB050 Simulations of Beam-Beam Interactions With RF-Track for the AWAKE Primary Beam Lines electron, proton, simulation, plasma 3823
 
  • J.S. Schmidt, A. Latina
    CERN, Geneva, Switzerland
  
  The AWAKE project at CERN will use a high-energy proton beam at 400 GeV/c to drive wake'elds in a plasma. The amplitude of these wake'elds will be probed by injecting into the plasma a low-energy electron beam (10-20 MeV/c), which will be accelerated to several GeV. Upstream of the plasma cell the two beams will either be transported coaxially or with an o'set of few millimetres for about 6 m. The interaction between the two beams in this beam line has been investigated in the past, with a dedicated simulation code tracking particles under the in'uence of direct space-charge e'ects. These simulations have recently been crosschecked with a new simulation code called RF-Track, developed at CERN to simulate low energy accelerators. RF-Track can track multiple-specie beams at arbitrary energies, taking into account the full electromagnetic particle-to-particle inter-action. For its characteristics RF-Track seems an ideal tool to study the AWAKE two-beam interaction. The results of these studies are presented in this paper and compared to the previous results. The implications for the facility performance are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB050  
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THPAB059 CSR and Space Charge Studies for the CLARA Phase 1 Beamline dipole, electron, simulation, linac 3851
 
  • B.S. Kyle, R.B. Appleby
    UMAN, Manchester, United Kingdom
  • J.K. Jones, P.H. Williams
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • M.J. de Loos, S.B. van der Geer
    Pulsar Physics, Eindhoven, The Netherlands
  
  The installation of Phase 1 of CLARA, the UK's new FEL test facility, is currently underway at Daresbury Laboratory. When completed, it will be able to deliver 45 MeV electron beams to the pre-existing VELA beamline, which runs parallel. Phase 1 consists of a 10 Hz photocathode gun, a 2 m long S-band travelling wave linac, a spectrometer line, and associated optics and diagnostics. A detailed study into the beam dynamics of the lattice is presented, with a focus towards the effects of space charge and coherent synchrotron radiation on the electron bunch. Simulations disagreed with predictions from a one-dimensional model of coherent radiation, and this disagreement is believed to be due to a violation of the Derbenev criterion.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB059  
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THPAB081 The Effects of Space-Charge on the Dynamics of the Ion Booster in the Jefferson Lab EIC (JLEIC) booster, resonance, injection, emittance 3906
 
  • E.W. Nissen, S.A. Bogacz
    JLab, Newport News, Virginia, USA
  
  Funding: Notice: This manuscript has been authored by Jefferson Science Associates, LLC under Contract No. DE-AC05-06OR23177 with the U.S. Department of Energy.
Optimization of the booster synchrotron design to operate in the extreme space-charge dominated regime is proposed. This study is motivated by the ultra-high luminosity promised by the JLEIC accelerator complex, which poses several beam dynamics and lattice design challenges for its individual components. We examine the effects of space charge on the dynamics of the booster synchrotron for the proposed JLEIC electron ion collider. This booster will inject and accumulate protons and heavy ions at an energy of 280 MeV and then engage in a process of acceleration and electron cooling to bring it to its extraction energy of 8 GeV. This would then be sent into the ion collider ring part of JLEIC. In order to examine the effects of space charge on the dynamics of this process we use the software SYNERGIA. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB081  
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THPVA004 Pushing the Space Charge Limit: Electron Lenses in High-Intensity Synchrotrons? electron, synchrotron, ion, resonance 4417
 
  • W.D. Stem, O. Boine-Frankenheim
    TEMF, TU Darmstadt, Darmstadt, Germany
  • O. Boine-Frankenheim
    GSI, Darmstadt, Germany
  
  Funding: Work is supported by BMBF contract FKZ:05P15RDRBA
Several accelerator projects require an increase in the number of particles per bunch, which is constrained by the space charge limit. Above this limit the transverse space charge force in combination with the lattice structure causes beam quality degradation and beam loss. Proposed devices to mitigate this beam loss in ion beams are electron lenses. An electron lens imparts a nonlinear, localized focusing kick to counteract the (global) space-charge forces in the primary beam. This effort is met with many challenges, including a reduced dynamic aperture (DA), resonance crossing, and beam-beam alignment. This contribution provides a detailed study of idealized electron lens use in high-intensity particle accelerators, including a comparison between analytical calculations and pyORBIT particle-in-cell (PIC) simulations. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA004  
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THPVA005 Investigation of Electron Beam Assisted Density Boosting in Plasma Traps Using the Example of a Gabor Plasma Lens electron, plasma, simulation, experiment 4421
 
  • C. Beberweil, M. Droba, S. Klaproth, O. Meusel, D. Noll, H. Podlech, K. Schulte, K.I. Thoma
    IAP, Frankfurt am Main, Germany
  • S. Gammino, D. Mascali
    INFN/LNS, Catania, Italy
  • L. Malferrari, A. Montanari, F. Odorici
    INFN-Bologna, Bologna, Italy
  
  Gabor lenses are plasma traps that can be used for focusing an ion beam linearly without aberrations* by the electric field of a confined electron cloud. They combine strong electrostatic focusing with the possibility of space charge compensation and provide an attractive alternative to conventional ion beam optics in a LEBT section. The focusing performance strongly depends on the density and distribution of the enclosed electron plasma*. As the Gabor lens is usually operated close to the ion source, residual gas ionization is supposed to be the central electron generation mechanism. An electron source is introduced in order to investigate the possibility of boosting the electron density in plasma traps using the example of a Gabor lens. This way, a Gabor lens could be operated under XUHV conditions, where residual gas ionization is suppressed. The particle in cell code bender** was used to simulate the injection into the confining fields of the space charge lens in different geometrical configurations and a prototype experiment was constructed consisting of a Gabor lens and an electron source system. In this contribution, simulations and measurements will be presented.
* Schulte, K., et al. Electron cloud dynamics in a Gabor space charge lens. 2012
** Noll, D., et al. The particle-in-cell code bender and its application to non-relativistic beam transport. 2015 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA005  
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THPVA019 Self-consistent Space Charge Tracking Method based on Lie Transform simulation, proton, sextupole, emittance 4454
 
  • E. Laface, J. F. Esteban Müller
    ESS, Lund, Sweden
  
  In this paper we propose to describe the self-force of a particles beam, known as space charge, as an Hamiltonan term dependent on the distribution of the particles' coordinates: Hsc = Hsc(ρ(x,y,z)). This Hamiltonian is then used, together with the kinetic component Hk in a Lie transform to generate a transport map by e-L:Hk +Hsc: where the Lie operator :Hk + Hsc: is defined according to the Dragt's notation [1]. Then the Lie transform is used to transport directly the distribution function ρ(x, y, z) in a self-consistent iterative algorithm. The result of this proof-of-concept idea is verified on a drift space and on a FODO channel and compared with a traditional multi-particles simulation code.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA019  
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THPVA021 Dynamics of Spectator Particles in Space-Charge Fields of Mismatched Beams With Cross-Plane Coupling lattice, coupling, simulation, proton 4462
 
  • M. Holz, V.G. Ziemann
    Uppsala University, Uppsala, Sweden
  
  In accelerators with high beam power, even moderate beam losses must be avoided. These losses are due to particles reaching large transverse amplitudes that form a low density halo orbiting the beam core. To study the beam halo formation, we place a spectator particle outside the beam core and let it interact with the core's electric field. The core, we model by a self-consistent transverse Gaussian beam including non-linear space charge forces and cross-plane coupling.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA021  
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THPVA023 Studies of Longitudinal Beam Stability in CERN PS Booster After Upgrade impedance, simulation, emittance, injection 4469
 
  • D. Quartullo, S.C.P. Albright, E.N. Shaposhnikova
    CERN, Geneva, Switzerland
  
  The CERN PS Booster, comprised of four superposed rings, is the first synchrotron in the LHC proton injection chain. In 2021, after major upgrades, the injection and extraction beam energies, as well as the acceleration rate, will be increased. The required beam intensities should be a factor of two higher for nominal LHC and fixed-target beams, and the currently used narrow-band ferrite systems will be replaced by broad-band Finemet cavities in all four rings. Future beam stability was investigated using simulations with the Beam Longitudinal Dynamics (BLonD) code. The simulation results for existing situation were compared with beam measurements and gave a good agreement. An accurate impedance model, together with a careful estimation of the longitudinal space charge, was used in simulations of the future acceleration cycle in single and double RF, with phase and radial loops and controlled longitudinal emittance blow-up. Since the beam is not ultra-relativistic and fills the whole ring (h=1), the front and multi-turn back wakes were taken into account, as well as the RF feedbacks which reduce the effect of the Finemet impedance at the revolution frequency harmonics.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA023  
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THPVA032 Space-Charge Simulation of Integrable Rapid Cycling Synchrotron lattice, sextupole, optics, resonance 4501
 
  • J.S. Eldred, A. Valishev
    Fermilab, Batavia, Illinois, USA
  
  Integrable optics is an innovation in particle accelerator design that enables strong nonlinear focusing without generating parametric resonances. We use a Synergia space-charge simulation to investigate the application of integrable optics to a high-intensity hadron ring that could replace the Fermilab Booster. We find that incorporating integrability into the design suppresses the beam halo generated by a mismatched KV beam. Our integrable rapid cycling synchrotron (iRCS) design includes other features of modern ring design such as low momentum compaction factor and harmonically canceling sextupoles. Experimental tests of high-intensity beams in integrable lattices will take place over the next several years at the Fermilab Integrable Optics Test Accelerator (IOTA) and the University of Maryland Electron Ring (UMER).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA032  
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THPVA037 Injection of a Self-Consistent Beam at the Spallation Neutron Source injection, simulation, closed-orbit, target 4516
 
  • J.A. Holmes, S.M. Cousineau, T.V. Gorlov, M.A. Plum
    ORNL, Oak Ridge, Tennessee, USA
  
  Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. This research was supported by the DOE Office of Science, Basic Energy Science.
We plan to demonstrate the injection of a self-consistent beam into the Spallation Neutron Source (SNS). Self-consistent beams are defined to be ellipsoidal distributions with uniform density and to retain these properties under all linear transformations. Self-consistent distributions may generate very little halo if realized in practice. Some may also be manipulated to generate flat beams. Self-consistent distributions involve very special relationships between the phase space coordinates, making them difficult to realize experimentally. One self-consistent distribution, the 2D rotating distribution, can be painted into the SNS ring, with slight modification of the lattice. However, it is unknown how robust self-consistent distributions will be under real world transport in the presence of nonlinearities and other collective effects. This paper studies these issues and the mitigation of unwanted effects by applying realistic detailed computational models to the simulation of the injection of rotating beams into SNS. The result is a feasible prescription for the injection of a rotating self-consistent distribution into the SNS ring. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA037  
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THPVA086 Beam Dynamics Studies of an Accelerating Tube for 6 MeV Electron LINAC emittance, electron, simulation, linac 4657
 
  • S. Zarei
    Nuclear Science and Technology Research, InstituteRadiation Application School, Tehran, Iran
  • F. Abbasi
    Shahid Beheshti University, Tehran, Iran
  • S. Ahmadiannamin
    ILSF, Tehran, Iran
  • F. Ghasemi
    NSTRI, Tehran, Iran
  • M. Lamehi
    IPM, Tehran, Iran
  
  Side coupled standing wave accelerating tubes are widely used in a low energy linear accelerator because of relatively high accelerating gradient and low sensitivity to construction tolerances. The effective interaction of particles and electromagnetic fields is important for accelerate electrons to intended energy with the greatest efficiency and beam quality output. In this paper, we present the beam dynamics of a 6 MeV Side coupled standing wave accelerating tube using a space charge tracking algorithm (ASTRA). The designed accelerating tube that feeds by a maximum power of 2.6 MW resonant at frequency of 2998.5 MHz in pi/2 mode. 37.5 percent capture efficiency, 6.82 pi-mm-mrad horizontal emittance, 6.78 pi-mm-mrad vertical emittance, 2.24 mm horizontal and vertical beam size and 1079 keV energy spread of the output beam have been determined from the results of beam dynamics studies in ASTRA  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA086  
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