Keyword: space-charge
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MOPML060 Self-Consistent Simulation and Optimization of Space-Charge Limited Thermionic Energy Converters simulation, electron, cathode, feedback 543
 
  • N.M. Cook, J.P. Edelen, C.C. Hall
    RadiaSoft LLC, Boulder, Colorado, USA
  • J.-L. Vay
    LBNL, Berkeley, California, USA
  
  Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC0017162.
Thermionic energy converters (TEC) are an attractive technology for modular, efficient transfer of heat to electrical energy. The steady-state dynamics of a TEC are a function of the emission characteristics of the cathode and anode, an array of intra-gap electrodes and dielectric structures, and the self-consistent dynamics of the electrons in the gap. Proper modeling of these devices requires self-consistent simulation of the electron interactions in the gap. We present results from simulations of these devices using the particle-in-cell code Warp, developed at Lawrence Berkeley National Lab. We consider the role of individual energy loss mechanisms in reducing device efficiency, including kinetic losses, radiative losses, and dielectric charging. We discuss the implementation of an external circuit model to provide realistic feedback. Lastly, we illustrate the potential to use nonlinear optimization to maximize the efficiency of these devices by examining grid transparency. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML060  
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TUXGBF4 ORBIT Simulation, Measurement and Mitigation of Transverse Beam Instability in the Presence of Strong Space Charge in the 3-GeV RCS of J-PARC simulation, impedance, injection, acceleration 620
 
  • P.K. Saha, H. Harada, N. Hayashi, H. Hotchi, Y. Shobuda, F. Tamura
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  
  The transverse impedance of eight extraction pulse kicker magnets (KM) is extremely strong source of transverse beam instability in the 3-GeV RCS (Rapid Cycling Synchrotron) at J-PARC. To realize the designed 1 MW beam power, collective beam dynamics with including the space charge effect for the coupled bunch instabilities excited by the KM impedance and associated measures were studied by incorporating all realistic time-dependent machine parameters in the ORBIT 3-D particle tracking code. The simulation results were all reproduced by measurements and, as a consequence, an acceleration of 1 MW beam power has been successfully demonstrated. In order to maintain variation of the RCS parameters required for multi-user operation, realistic measures for beam instability mitigation were proposed and also been successfully implemented in reality. To further increase the RCS beam power, beam stability issues and possible measures beyond 1 MW beam power are also considered.  
slides icon Slides TUXGBF4 [2.241 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUXGBF4  
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TUPAF024 Impedance and Instability Studies in LEIR with Xenon impedance, coupling, accumulation, injection 720
 
  • N. Biancacci, H. Bartosik, M. Gąsior, S. Hirlaender, V. Kain, T.E. Levens, E. Métral
    CERN, Geneva, Switzerland
  • M. Migliorati
    Rome University La Sapienza, Roma, Italy
  
  In 2017, the LEIR accelerator has been operated with Xe39+ beam for fixed target experiments in the SPS North Area. The different ion species, with respect to the usually operated Pb54+, allowed for additional comparative measurements of tune shift versus intensity at injection energy both in coasting and bunched beams. The fast transverse instability observed for high accumulated intensities has been as well characterized and additional observations relevant to impedance have been collected from longitudinal Schottky signal and BTF measurements. The results of these measurements are summarised and compared to the currently developed machine impedance model.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF024  
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TUPAF048 LIU Space Charge Studies for the LHC Pre-Accelerators injection, proton, resonance, simulation 810
 
  • F. Schmidt, H. Bartosik
    CERN, Geneva, Switzerland
  
  In 2011 a working group has been started to study performance limitations due to Space Charge (SC) in the four LHC pre-accelerators, LEIR, PSB, PS & SPS, in view of the LHC Injector Upgrade (LIU) project. To this end external and in-house simulation tools have been benchmarked for the LIU study cases with the long-term goal of providing a full sequence of tested CERN Space Charge tools. It became clear that SC studies must be combined with trustworthy models of the machines, including linear and non-linear errors. In particular an effective s-dependent non-linear model is required. Recent studies indicate that also the low frequency ripple spectrum due to conventional power supplies might play an important role for the beam dynamics in presence of space charge in the pre-injectors.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF048  
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TUPAF073 Simulation of Integrable Synchrotron with Space-charge and Chromatic Tune-shifts lattice, simulation, optics, synchrotron 894
 
  • J.S. Eldred, A. Valishev
    Fermilab, Batavia, Illinois, USA
  
  We present a nonlinear rapid-cycling synchrotron designed as a high-intensity replacement of the Fermilab Booster. The design incorporates integrable optics, an innovation in particle accelerator design that enables strong nonlinear focusing without generating parametric resonances. We use the Synergia space-charge tracking code to demonstrate the stability of a beam in this lattice with a space-charge tune-shift up to 0.4 and a rms momentum spread up to 0.4\%. We demonstrate the benefit of increased lattice periodicity.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF073  
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TUPAL040 Ion Beam Studies in the FRIB Front End ion-source, ECR, coupling, optics 1094
 
  • T. Yoshimoto, K. Fukushima, S.M. Lidia, T. Maruta, P.N. Ostroumov, G. Pozdeyev, H.T. Ren
    FRIB, East Lansing, USA
  
  Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 and the National Science Foundation under Cooperative Agreement PHY-1102511.
The commissioning of the FRIB Front End with 12 keV/u argon beam started in the spring of 2017*. Beam profile monitors were used to evaluate RMS Twiss parameters in various locations along the beam line. Beam dynamics in the LEBT was simulated using full 3D model of beam optics elements in the tracking codes. We found a good consistency between measured and simulated data. A beam image viewer was used to measure the beam density distribution in the real space. A hollow beam structure was observed in the Ar9+ beam with the current of ~20 eμA. Extensive beam dynamics study with 3D tracking code suggests that the hollow density distribution can be generated by space charge effects of the multi-component, multi-charge state ion beam just after the ECR ion source. This paper reports studies of a mechanism that can produce a hollow beam structure.
*E. Pozdeyev, invited talk at this conference 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL040  
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TUPAL043 Simulations of the Electron Column in IOTA electron, plasma, proton, simulation 1103
 
  • B.T. Freemire
    Northern Illinois University, DeKalb, Illinois, USA
  • S. Chattopadhyay
    Northern Illinois Univerity, DeKalb, Illinois, USA
  • M. Chung
    UNIST, Ulsan, Republic of Korea
  • C.S. Park
    Korea University Sejong Campus, Sejong, Republic of Korea
  • G. Penn
    LBNL, Berkeley, California, USA
  • V.D. Shiltsev, G. Stancari
    Fermilab, Batavia, Illinois, USA
  
  Funding: Work supported by the U.S. Department of Energy, Office of High Energy Physics, under Contract Nos. DE-AC02-07CH11359 and DE-AC02-05CH1123 and General Accelerator Research and Development Program
Future high current proton accelerators will need to minimize beam loss due to space-charge in order to achieve safe operation while achieving the desired physics goals. One method of space-charge compensation to be tested at the Integrable Optics Test Accelerator (IOTA) at Fermilab is the Electron Column. The concept for this device is to allow a circulating beam to ionize a small region of relatively high pressure residual gas, while using electric and magnetic fields to confine and shape the resulting plasma electrons. If the profile of the electrons is matched to the beam profile transversely and longitudinally, the electrons should counteract the space-charge force of the proton beam. Simulations of the IOTA proton beam circulating through the Electron Column have been performed, with the evolution of the electron plasma and its effect on the beam studied. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL043  
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TUPAL054 Experimental Measurements of Resonances near to the ISIS Working Point resonance, experiment, synchrotron, controls 1132
 
  • P.T. Griffin-Hicks, B. Jones, B.G. Pine, C.M. Warsop, M. Wright
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  
  ISIS is the pulsed spallation neutron source located at the Rutherford Appleton Laboratory in the UK. Operation is based on a 50 Hz, 800 MeV proton synchrotron, accelerating up to 3·1013 protons per pulse (ppp), which provides beam to two target stations. ISIS is beam loss limited, so to achieve greater beam intensity and optimal operation, losses must be reduced. Some beam loss may be attributed to resonance lines found in betatron tune space. These could be driven by higher order magnet field components, errors or misalignment. This paper describes work measuring losses against tune space around the ISIS working point. Experiments have been carried out to measure beam loss against tune in the ISIS synchrotron. The experiments were done at low intensity to minimise space charge and intensity effects. Resonance lines that cause beam loss can be clearly identified and provide new information about the machine. The experimental process has been automated in order to decrease experiment duration and to reduce systematic human error. MAD-X models that compare the beam envelope at different points in tune space to the beam pipe aperture are used to distinguish between losses caused by increased envelope size and losses induced by driven resonances.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL054  
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TUPAL056 High Order Image Terms and Harmonic Closed Orbits at the ISIS Synchrotron closed-orbit, simulation, resonance, vacuum 1140
 
  • B.G. Pine, C.M. Warsop
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  
  ISIS is the spallation neutron source at Rutherford Appleton Laboratory in the UK. Protons are accelerated from 70 to 800 MeV in a 50 Hz rapid cycling synchrotron. Due to the intense beam, space charge forces are high during the first part of the acceleration cycle. The vacuum vessel in the synchrotron has a rectangular shape where the apertures are conformal to the design beam envelopes. At high intensities image forces interact with the beam, especially when the closed orbit is large. An analysis of image forces has been made and used to classify higher order image terms. These have been identified using simulations of round beams in rectangular vacuum vessels. The higher order image terms from harmonic closed orbits have been used with single particle resonance theory, taking account of the coherent nature of the beam response. Several predictions of beam resonance have been made. A simulation study has been carried out using a smooth focusing lattice and uniform density beams. Resonant beam behaviour has been observed and explained by the proposed theory.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL056  
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TUPAL058 Studies for Major ISIS Upgrades via Conventional RCS and Accumulator Ring Designs injection, simulation, lattice, emittance 1148
 
  • C.M. Warsop, D.J. Adams, H.V. Cavanagh, P.T. Griffin-Hicks, B. Jones, B.G. Pine, R.E. Williamson
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  
  ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK, which provides 0.2 MW of beam power via a 50 Hz, 800 MeV proton RCS. Detailed studies are now under way to find the optimal configuration for a next generation, short pulsed neutron source that will define a major ISIS upgrade in ~2031. Accelerator configurations being considered for the MW beam powers required include designs exploiting FFAG rings as well as conventional accumulator and synchrotron rings. This paper describes work exploring the latter, conventional options, but includes the possibility of pushing further toward intensity limits to reduce facility costs. The scope of planned studies is summarised, looking at optimal exploitation of existing ISIS infrastructure, and incorporating results from recent target studies and user consultations. Results from initial baseline studies for an accumulator ring and RCS located in the existing ISIS synchrotron hall are presented. Injection scheme, foil limits, longitudinal and transverse beam dynamics optimization with related beam loss and activation are outlined, as are results from detailed 3D PIC simulations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL058  
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TUPAL077 2D-3D PIC Code Benchmarking/Anchoring Comparisons For a Novel RFQ/RFI LINAC Design rfq, simulation, linac, experiment 1194
 
  • S.J. Smith, S. Biedron, A. M. N. Elfrgani, E. Schamiloglu
    University of New Mexico, Albuquerque, USA
  • M.S. Curtin, B. Hartman, T. Pressnall, D.A. Swenson
    Ion Linac Systems, Inc., Albuquerque, USA
  • K. Kaneta
    CICS, Tokyo, Japan
  
  Funding: *The study at the University of New Mexico was supported in part by DARPA Grant N66001-16-1-4042 and gift to the University of New Mexico Foundation by ILS.
In this study, comparisons are made between several particle dynamics codes (namely CST Particle Studio, GPT, and upgraded PARMILA codes) in order to benchmark them. The structure used for the simulations is a novel 200 MHz, 2.5 MeV, CW RFQ/RFI LINAC designed by Ion Linac Systems (ILS). The structure design and parameters are provided, simulation techniques are explained, and results from all three code families are presented. These results are then compared with each other, identifying similarities and differences. Numerous parameters for comparison are used, including the transmission efficiency, Q-factor, E-field on axis, and beam properties. Preliminary anchoring between modeling and simulation performance predictions and experimental measurements will be provided. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL077  
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WEPAF086 Latest Developments and Updates of the ESS Linac Simulator DTL, linac, cavity, solenoid 2051
 
  • J.F. Esteban Müller, E. Laface
    ESS, Lund, Sweden
  
  A fast and accurate online model is required for optimal commissioning and reliable operation of the high-power proton linac at the European Spallation Source. The Open XAL framework, initially developed at SNS, is used at ESS for the development of high-level physics applications. The online model we use, known as ESS Linac Simulator (JELS), extends the Open XAL model with several features. This paper describes the latest updates carried out to JELS. Two new elements have been implemented: a solenoid field map for the LEBT and a DTL Tank element that automatically calculates each gap phase. All calculations are now done in the laboratory frame, in agreement with Open XAL convention. A thorough benchmark of the model against TraceWin, which is the tool used for the lattice design, is also presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF086  
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WEPAK008 Reconstructing Space-Charge Distorted IPM Profiles with Machine Learning Algorithms electron, simulation, GUI, network 2099
 
  • D.M. Vilsmeier, M. Sapinski, R. Singh
    GSI, Darmstadt, Germany
  • J.W. Storey
    CERN, Geneva, Switzerland
  
  Measurements of undistorted transverse profiles via Ionization Profile Monitors (IPMs) may pose a great challenge for high brightness or high energy beams due to interaction of ionized electrons or ions with the electromagnetic field of the beam. This contribution presents application of various machine learning algorithms to the problem of reconstructing the actual beam profile from measured profiles that are distorted by beam space-charge interaction. (Generalized) linear regression, artificial neural network and support vector machine algorithms are trained with simulation data, obtained from the Virtual-IPM simulation tool, in order to learn the relation between distorted profiles and original beam dimension. The performance of different algorithms is assessed and the obtained results are very promising for testing with simulation data.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAK008  
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WEPAL044 ENSOLVE : A Simulation Code for FXR LIA Downstream Section emittance, solenoid, target, electron 2271
 
  • Y.H. Wu, Y.-J. Chen
    LLNL, Livermore, California, USA
  
  Funding: This work was performed under the auspi-ces of the U.S. Department of Energy by Law-rence Livermore National Laboratory under Contract DE-AC52-07NA27344.
In this paper, we describe an envelope code, ENSOLVE. It solves the rms beam envelope equation by including space change depression of the potential, spherical aberration of the so-lenoidal lens, emittance growth and focusing effects of backstreaming ions in the final focus region. In this paper, we focus on the physics included for beam transport simulations in the downstream section of flash x-ray radiography linear induction accelerators, such as FXR LIA. We have used ENSOLVE to design final focus tunes for FXR LIA downstream section 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL044  
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WEPAL065 Development of a Gas Sheet Beam Profile Monitor for IOTA simulation, detector, proton, plasma 2326
 
  • S. Szustkowski, B.T. Freemire
    Northern Illinois University, DeKalb, Illinois, USA
  • S. Chattopadhyay
    Northern Illinois Univerity, DeKalb, Illinois, USA
  • D.J. Crawford
    Fermilab, Batavia, Illinois, USA
  
  Funding: US Department of Energy, Office of High Energy Physics, General Accelerator Research and Development (GARD) Program
A nitrogen gas sheet will measure the two dimensional transverse profile of the 2.5 MeV proton beam in IOTA. The beam lifetime is limited by the interaction with the gas, thus a minimally invasive instrument is required. To produce a gas sheet with the desired density and thickness, various nozzle types are being investigated, including rectangular capillary tubes for gas injection and skimmers for final shaping of the gas. It is essential to meet vacuum requirements in the interaction chamber while maintaining the precise thickness and density of the gas, without significantly affecting the beam lifetime. The current design of a gas sheet beam profile monitor and present status will be discussed. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL065  
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THPAF021 Start to End Simulation of the CBETA Energy Recovery Linac linac, lattice, simulation, optics 2993
 
  • W. Lou, A.C. Bartnik, J.A. Crittenden, C.M. Gulliford, G.H. Hoffstaetter, D. Sagan
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • J.S. Berg, S.J. Brooks, F. Méot, D. Trbojevic, N. Tsoupas
    BNL, Upton, Long Island, New York, USA
  • C.E. Mayes
    SLAC, Menlo Park, California, USA
  
  Funding: This manuscript has been authored by employees of Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
CBETA is an energy recovery linac accelerating from 6 MeV to 150 MeV in four linac passes, using a single return line accepting all energies from 42 MeV to 150 MeV. We simulate a 6-dimensional particle distribution from the injector through the end of the dump line. Space charge forces are taken into account at the low energy stages. We compare results using field maps to those using simpler magnet models. We introduce random and systematic magnet errors to the lattice, apply an orbit correction algorithm, and study the impact on the beam distribution. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF021  
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THPAF024 Understanding and Compensating Emittance Diluting Effects in Highly Optimized Ultrafast Electron Diffraction Beamlines emittance, electron, cathode, gun 3004
 
  • C. M. Pierce, I.V. Bazarov, C.M. Gulliford, J.M. Maxson
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • S. Baturin
    Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA
  • M.A. Gordon, Y.K. Kim
    University of Chicago, Chicago, Illinois, USA
  
  Funding: This work was supported by the Center for Bright Beams, NSF PHY-1549132 and Department of Energy grant DE-SC0014338.
The application of Multiobjective Genetic Algorithm optimization (MOGA) to photoemission based ultrafast electron diffraction (UED) beamlines featuring extremely low cathode mean transverse energies has lead to designs with emittances as low as 1 nm for sub-picosecond bunches with 105 electrons*. Analysis of these results shows significant emittance growth during transport: with emittance dilution as high as a factor of 200-4000% for various designs and optics settings. In this study we quantify and model the individual sources of emittance growth (slice mismatches and space charge), and explore the use of the core emittance as a strong invariant.
C. Gulliford, A. Bartnik, and I. Bazarov. Multi-
objective optimizations of a novel cryocooled dc gun based
UED beam line. Phys. Rev. Ac-
celerators and Beams, 19(9):093402, 2016. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF024  
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THPAF033 Degradation of Electron Beam Quality for a Compact Laser-Based FEL electron, FEL, emittance, laser 3029
 
  • A.Y. Molodozhentsev, L. Pribyl
    Czech Republic Academy of Sciences, Institute of Physics, Prague, Czech Republic
  • K.O. Kruchinin
    ELI-BEAMS, Prague, Czech Republic
  
  Laser wake field acceleration (LWFA) mechanism allows to produce extremely short electron bunches of a few fs length with the energy up to a few GeV in extremely compact geometries providing unique electron beam parameters, in particular, transverse beam emittance (order of 1pi mm mrad), extremely short bunch length and high beam charge (up to 100pC) . This novel acceleration method therefore opens a new way to develop compact 'laser-based' FELs. In the frame of this report we analyze effects, which lead to degradation of an electron beam quality. The chromatic and collective effects are analyzed for a compact dedicated electron beam line to transport the electron beam to an undulator. In addition, the SASE FEL performance has been discussed taking into consideration the degradation of the electron beam quality.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF033  
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THPAF054 Characterization of Losses and Emittance Growth for Ion Beams on the SPS Injection Plateau emittance, resonance, injection, scattering 3091
 
  • Á. Saá Hernández, F. Antoniou, H. Bartosik, A. Huschauer
    CERN, Geneva, Switzerland
  
  Losses and transverse emittance growth in the Super Protron Synchrotron (SPS) impose presently the main performance limitation on the Large Hadron Collider (LHC) ion injector chain. In this paper we present the measurements performed in 2016 with Pb82+ ions and the analysis to characterize the observations of beam degradation during the long injection plateau. Residual gas scattering, intrabeam scattering (IBS) and resonance excitation have been studied.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF054  
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THPAF055 Space Charge Studies on LEIR resonance, emittance, simulation, lattice 3095
 
  • Á. Saá Hernández, H. Bartosik, N. Biancacci, S. Hirlaender, A. Huschauer, D. Moreno Garcia
    CERN, Geneva, Switzerland
  
  The performance of the CERN Low Energy Ion Ring with electron cooled ion beams is presently limited by losses occurring once the beam has been captured in the RF buckets. An intense machine study program was started by the end of 2015 to mitigate the losses and improve the performance of the accelerator. The measurements pointed to the interplay of direct space charge forces and excited betatron resonances as the most plausible driving mechanism of these losses. In this paper, we present the systematic space-charge measurements performed in 2017 and compare them to space-charge tracking simulations based on an adaptive frozen potential.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF055  
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THPAF064 Beam Dynamics with Covariant Hamiltonians multipole, octupole, wakefield, software 3123
 
  • B.T. Folsom, E. Laface
    ESS, Lund, Sweden
  
  We demonstrate covariant beam-physics simulation through multipole magnets using Hamiltonians relying on canonical momentum. Space-charge integration using the Lienard–Wiechert potentials is also discussed. This method is compared with conventional nonlinear Lie-operator tracking and the TraceWin software package.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF064  
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THPAF075 Numerical Simulations of Space Charge Compensation with an Electron Lens electron, lattice, simulation, emittance 3154
 
  • E.G. Stern, Y.I. Alexahin, J.F. Amundson, A.V. Burov, A. Macridin, V.D. Shiltsev
    Fermilab, Batavia, Illinois, USA
  
  The future high energy physics program at Fermilab requires that the proton complex operate with beam bunch intensities four times larger than is currently handled. At these intensities space charge nonlinear defocussing effects cause unacceptable particle losses especially in the low energy rapid-cycling-synchrotron (RCS) Booster. Focusing electron lens elements may offer a solution by providing partial space charge compensation but there is a need for detailed simulations as this technique has not been demonstrated. We report on high fidelity numerical 6D space charge simulations in a model accelerator lattice with a record high space charge tune shift approaching unity.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF075  
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THPAK002 Updated Model of the Resistive Wall Impedance for the Main Ring of J-PARC impedance, kicker, hadron, injection 3204
 
  • B. Yee-Rendón, Y.H. Chin, H. Kuboki, T. Toyama
    KEK, Ibaraki, Japan
  • M. Schenk
    CERN, Geneva, Switzerland
  
  The resistive wall impedance is one of the major contributors of the impedance in the Main Ring of J-PARC. The present model assumes round chambers of stainless steel with perfect magnet boundary conditions for its surroundings. This work presents the model of the resistive wall impedances taking into account the different chamber geometries of Main Ring, the materials and more realistic surroundings. The models were benchmarked with measurements of the coherent tune shift of the Main Ring of J-PARC. The simulation of beam instabilities is a helpful tool to evaluate potential threats against the machine protection of the high intensity beams.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK002  
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THPAK008 Space Charge and Microbunching Studies for the Injection Arc of MESA bunching, simulation, injection, lattice 3221
 
  • A. Khan, O. Boine-Frankenheim
    Institut Theorie Elektromagnetischer Felder, TU Darmstadt, Darmstadt, Germany
  • C.P. Stoll
    IKP, Mainz, Germany
  
  For intense electron bunches traversing through bends, as for example the recirculation arcs of an ERL, space charge (SC) may result in beam phase space deterioration. SC modifies the electron transverse dynamics in dispersive regions along the beam line and causes emittance growth for mismatched beams or for specific phase advances. On the other hand, longitudinal space charge together with dispersion can lead to the microbunching instability. The present study focuses on the 180° low energy (5 MeV) injection arc lattice for the multi-turn Mainz Energy-recovering Superconducting Accelerator (MESA), which should deliver a CW beam at 105 MeV for physics experiments with an internal target. We will discuss matching conditions with space charge together with the estimated microbunching gain for the arc. The implication for the ERL operation will be outlined, using 3D envelope and tracking simulations.
Supported by the DFG through GRK 2128 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK008  
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THPAK035 Numerical Tools for Modeling Nonlinear Integrable Optics in IOTA with Intense Space Charge Using the Code IMPACT-Z optics, lattice, simulation, proton 3290
 
  • C.E. Mitchell, J. Qiang
    LBNL, Berkeley, California, USA
  
  Funding: This work is supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
The Integrable Optics Test Accelerator (IOTA) is a novel storage ring under commissioning at Fermi National Accelerator Laboratory designed to investigate the dynamics of beams with large transverse tune spread in the presence of strongly nonlinear integrable optics. Several new numerical tools have been implemented in the code IMPACT-Z to allow for high-fidelity modeling of the IOTA ring during Phase II operation with intense proton beams. A primary goal is to ensure symplectic treatment of both single-particle and collective dynamics. We describe these tools and demonstrate their application to modeling nonlinear integrable dynamics with space charge in IOTA. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK035  
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THPAK042 On Long-Term Space-Charge Tracking Simulation simulation, emittance, lattice, optics 3305
 
  • J. Qiang
    LBNL, Berkeley, California, USA
  
  The nonlinear space-charge effects in high intensity accelerator can degrade beam quality and cause particle losses. Self-consistent macroparticle tracking simulations have been widely used to study these space-charge effects. However, it is computationally challenging for long-term tracking simulation of these effects. In this paper, we study a fully symplectic self-consistent particle-in-cell model and numerical methods to mitigate numerical emittance growth. We also discuss about a fast alternative frozen space-charge model that has a potential to improve computational speed significantly.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK042  
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THPAK044 Self-Consistent Modeling using a Lienard-Wiechert Particle-Mesh Method simulation, radiation, synchrotron, emittance 3313
 
  • R.D. Ryne, C.E. Mitchell, J. Qiang
    LBNL, Berkeley, California, USA
  • B.E. Carlsten
    LANL, Los Alamos, New Mexico, USA
  
  In this paper we describe a parallel, large-scale simulation capability using a Lienard-Wiechert Particle-Mesh (LWPM) method. The approach is a natural extension of the convolution-based technique to solve the Poisson equation in space-charge codes. It provides a unified method to compute both Coulomb-like self-fields and radiative phenomena like coherent synchrotron radiation (CSR). The approach brings together several mathematical and computational capabilities including the use of integrated Green function (IGF) methods and adaptive quadrature methods. We will describe the theoretical model and our progress to date.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK044  
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THPAK056 Resonance Identification Studies at the CERN PS resonance, sextupole, experiment, synchrotron 3350
 
  • F. Asvesta
    NTUA, Athens, Greece
  • H. Bartosik, A. Huschauer, Y. Papaphilippou, G. Sterbini
    CERN, Geneva, Switzerland
  
  In view of the LHC Injectors Upgrade (LIU) and the challenging high brightness target beam parameters, a broad range of possible working points for the Proton Synchrotron (PS) is being investigated. High order resonances have been identified, both structural resonances driven by space charge due to the lattice harmonics of the PS, and resonances excited by multipolar components in the machine. This paper provides a summary of the performed tune scan studies, covering both experimental and simulation results. Furthermore, non-linear analysis techniques have been used to characterize the resonances and their effect on the beam in presence of space charge.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK056  
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THPAK076 Development and Benchmarking of the IMPACT-T Code rfq, linac, SRF, simulation 3408
 
  • H.P. Li, M.J. Easton, Y.R. Lu, Z. Wang
    PKU, Beijing, People's Republic of China
  • J. Qiang
    LBNL, Berkeley, California, USA
  
  The multi-particle tracking code IMPACT-T is widely used to calculate the particle motion in high intensity linacs. The code is a self-consistent three-dimensional beam dynamics simulation toolbox that utilizes the particle-in-cell method in the time domain. In the collaboration between PKU and LBNL, an RFQ module was implemented to the IMPACT-T code, which enables simulations of the accelerator front-end. In order to benchmark the newly developed module in the IMPACT-T code, we have simulated the beam transport in Beijing Isotope Separation On-Line (BISOL) high intensity deuteron driver linac. It consists of a 3 MeV RFQ and 40 MeV superconducting HWR linac with five cryomodules. After comparing the simulation results with PARMTEQM, TraceWin and Toutatis, we obtained a very good agreement, which represents the validation of the new code.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK076  
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THPAK083 An s-Based Symplectic Spectral Space Charge Algorithm optics, simulation, plasma, proton 3425
 
  • N.M. Cook, D.T. Abell, D.L. Bruhwiler, J.P. Edelen, C.C. Hall, S.D. Webb
    RadiaSoft LLC, Boulder, Colorado, USA
  
  Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC001340.
Traditional finite-difference particle-in-cell methods for modeling self-consistent space charge introduce non-Hamiltonian effects that make long-term tracking in storage rings unreliable. Foremost of these is so-called grid heating. Particularly for studies where the Hamiltonian invariants are critical for understanding the beam dynamics, such as nonlinear integrable optics, these spurious effects make interpreting simulation results difficult. To remedy this, we present a symplectic spectral space charge algorithm that is free of non-Hamiltonian numerical effects and, therefore, suitable for long-term tracking studies. We present initial results demonstrating the implementation of the algorithm, using a spectral representation of the fields and macro particles to preserve Hamiltonian structures. We then discuss applications to the Integrable Optics Test Accelerator (IOTA), currently under construction at Fermilab. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK083  
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THPAK085 3D Space Charge in Bmad simulation, software, lattice, brightness 3428
 
  • C.E. Mayes
    SLAC, Menlo Park, California, USA
  • R.D. Ryne
    LBNL, Berkeley, California, USA
  • D. Sagan
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  We present a parallel fast Fourier transform based 3D space charge software library based on integrated Green functions. The library is open-source, and has been structured to easily be used by existing beam dynamics codes. We demonstrate this by incorporating it with the Bmad toolkit for charged particle simulation, and compare with analytical formulas and well-established space charge codes.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK085  
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THPAK086 A 2D Steady-State Space Charge Solver for Azimuthally Symmetric Problems of Arbitrary Degree gun, cathode, electromagnetic-fields, distributed 3431
 
  • A.R. Gold, A. R. Gold, S.G. Tantawi
    SLAC, Menlo Park, California, USA
  
  Correctly and rapidly simulating the steady-state interaction between particle beams and electromagnetic fields is crucial to the design and optimization of accelerator and radiofrequency (RF) source components. Iteratively solving for the self-consistent interaction between particles and fields can prove challenging and highly susceptible to numerical noise and mesh induced instabilities. We present herein two new approaches to solving the self-consistent trajectories of particles in the presence of external and self fields. The first method reformulates the integrated self field contribution as a path integral. The second method uses a hybrid Eulerian framework and produces an interpolated continuous current density, resulting in 1-2 orders of magnitude fewer particles required to obtain an accurate solution. We conclude with benchmarking results which show this method is as accurate as state of the art PIC solvers, while running 80-120X faster.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK086  
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THPAK107 Space-Charge Hamiltonian with a Space Coordinate as Independent Variable plasma, TRIUMF, vacuum, synchrotron 3484
 
  • T. Planche, P. M. Jung, S.D. Rädel
    TRIUMF, Vancouver, Canada
  
  We present a version of the Low Lagrangian tailored to treat space-charge effects in particle accelerators: the Lagrangian is relativistic and uses a space coordinate as the independent variable. From this Lagrangian we obtain the corresponding Hamiltonian. From the Hamiltonian we obtain equations of motion for the 8 canonical variables, which can be plugged into a symplectic numerical integrator. We will finally discuss the possibility of numerically solving this problem using an explicit symplectic integrator.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK107  
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THPAK109 Improved Simulation for Centre Region of TRIUMF 500 MeV Cyclotron with Space Charge TRIUMF, simulation, focusing, cyclotron 3489
 
  • Y.-N. Rao, R.A. Baartman, T. Planche
    TRIUMF, Vancouver, Canada
  
  Funding: TRIUMF receives federal funding via a contribution agreement through the National Research Council of Canada
The TRIUMF 500 MeV cyclotron delivered routinely a total current up to 200 μA protons for 15 years till 2001. Since 2002, developments towards 300 μA total extraction became compelling because of the ISAC expansion. To meet future requirements (for addition of a new beam-line), a total extraction of 310 − 450 μA shall be envisioned. With such an increase of beam current, the space charge effect becomes a major concern in the centre region, as it limits the maximum amount of beam current achievable out of the machine. Therefore, numerical simulation on beam orbits with the space charge force has has been initiated, starting from the injection gap. This study is focused on the beam bunches which are very long compared with transverse size (because TRIUMF extraction is by stripping of H-minus and separated turns are not required). In order to achieve an improved understanding of the space charge effect, we worked to validate the simulations performed without and with the space charge force, using realistic centre region geometry. Our goal is to work out the space charge limits and their dependence upon the bunchers, rf voltage, and matching. In this paper we present our recent progress in this study. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK109  
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THPAK117 Space Charge Limitations for Bunch Compression in Synchrotrons resonance, simulation, emittance, synchrotron 3518
 
  • Y.S. Yuan, O. Boine-Frankenheim
    TEMF, TU Darmstadt, Darmstadt, Germany
  • G. Franchetti, I. Hofmann
    GSI, Darmstadt, Germany
  
  Bunch compression achieved via a fast bunch rotation in longitudinal phase space is a well-accepted scheme to generate short, intense ion bunches for various applications. During bunch compression, coherent beam instabilities and incoherent single particle resonances can occur because of increasing space charge, resulting in an important limitation for the bunch intensity. We present an analysis of the relevant space charge driven beam instability and resonance phenomena during bunch compression. A coupled longitudinal-transverse envelope approach is compared with Particle-In-Cell (PIC) simulations. Two distinct cases of crossing are discussed and applied to the GSI SIS18 heavy-ion synchrotron. It is shown that during bunch compression, the 90° condition of phase advance is associated with a fourth order single particle resonance and the 120° condition with the recently discovered dispersion-induced instability. The agreement between the envelope and PIC results indicates that the stop band is defined by the 120° dispersion instability, which should be avoided during bunch compression.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK117  
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THPAK127 Toroidal Merger Simulations for the JLEIC Bunched Beam Electron Cooler Ring electron, emittance, solenoid, simulation 3540
 
  • A.V. Sy
    JLab, Newport News, Virginia, USA
  
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The bunched beam electron cooler ring for the Jefferson Lab Electron-Ion Collider (JLEIC) requires a merger system to transport magnetized electron beams of two different energies to the same energy recovery linac (ERL) beamline. The system is especially challenging compared to existing mergers for ERL or hadron cooling applications (as at COSY) due to the small separation in energy between the two beams; for the JLEIC bunched beam cooler, the two beam energies may only differ by a factor of 4. An additional complication is the use of a magnetized beam. A toroidal merger system is studied using G4Beamline/GEANT4. Preservation of the quality of the low energy beam from the injector is especially vital for efficient cooling performance and compatibility with the ERL. Effects of the toroidal system on transverse and longitudinal emittances of the magnetized beams, as well as space charge effects, are presented and discussed. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK127  
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THPAK129 Modeling Challenges for Energy Recovery Linacs With Long, High Charge Bunches bunching, electron, recirculation, lattice 3544
 
  • C. Tennant
    JLab, Newport News, Virginia, USA
  
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Historically, nearly all energy recovery linacs (ERLs) built and operated were used to drive a free-electron laser (FEL). The requirement for high peak current bunches necessitates bunch compression and handling the attendant beam dynamical challenges. In recent years, ERLs have turned from being drivers of light sources toward applications for nuclear physics experiments, Compton backscattering sources and strong electron cooling. Unlike an FEL, these latter uses require long, high charge bunches with small energy spread. The electron bunch must maintain a small projected energy spread and therefore must avoid gross distortion due to CSR and longitudinal space charge over a single (or multiple) recirculations. Accurately modeling the relevant collective effects in the system 'space charge, microbunching instability, CSR and the effect of shielding' in addition to beam dynamical processes such as halo, presents a formidable challenge. Absent a code that models all of these effects, we outline an approach towards the design, analysis and optimization of the high-energy electron cooler for the Jefferson Lab Electron-Ion Collider and survey widely used codes and their capabilities. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK129  
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THPAK154 Beam Parameter Optimization for UEM Facility with Photo-Emission S-band RF Gun electron, gun, laser, emittance 3610
 
  • H.R. Lee, P. Buaphad, Y. Joo
    University of Science and Technology of Korea (UST), Daejeon, Republic of Korea
  • S.C. Cha, Y. Kim
    KAERI, Daejon, Republic of Korea
  • B.L. Cho
    KRISS, Daejeon, Republic of Korea
  • H. Suk
    GIST, Gwangju, Republic of Korea
  
  Ultrafast Electron Microscopy (UEM) can provide snapshot images of a dynamic process in samples with an ultrafast time resolution, which is shorter than picosecond. The Future Accelerator R&D Team at KAERI has been preparing a UEM facility with a photo-emission S-band (= 2856 MHz) RF gun by collaborating with GIST and KRISS. To achieve a higher spatial resolution as well as a higher time resolution, the transverse beam emittance, beam divergence, and energy spread should be smaller, and the bunch length should be shorter. Beam dynamics simulations with ASTRA code is used to optimize those beam parameters in the RF gun. In this paper, we describe ASTRA optimizations of the S-band RF gun to achieve high spatial-temporal resolutions for the UEM facility.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK154  
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THPAL122 Beam Performance Study of an RF Structure to Accelerate or Bunch Low Energy Ion Beams booster, rfq, ISAC, bunching 3931
 
  • S.D. Rädel, S. Kiy, R.E. Laxdal, O. Shelbaya
    TRIUMF, Vancouver, Canada
  
  The 35.4MHz Radio Frequency Quadrupole (RFQ) at the ISAC-I facility at TRIUMF is designed to accelerate ions from an energy of 2.04 keV/u to 150 keV/u for a large range of mass-to-charge ratios (A/Q). A multi-harmonic, 11.8MHz, buncher is used to provide a time focus at the RFQ entrance. Due to limits in the ion source HV platform a boost in the energy is required for higher mass beams (20 ≤ A/Q ≤ 30) to provide energy matching into the RFQ. To achieve this, a 3-gap, 11.8 MHz RF booster has been installed into the ISAC-I facility downstream of the buncher and upstream of the RFQ. The device can operate as an accelerator to match into the RFQ or as a second pre-buncher to improve capture in the RFQ and reduce sensitivity to space charge. Proof-of-principle measurements demonstrating various aspects of the performance will be reported and compared against expectations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL122  
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THPMK054 Analysis of 1D FEL Sideband Instability with Inclusion of Energy Detune and Space Charge FEL, electron, undulator, laser 4410
 
  • C.-Y. Tsai, J. Wu, C. Yang, G. Zhou
    SLAC, Menlo Park, California, USA
  • M. Yoon
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  
  Funding: The work was supported by the US Department of Energy (DOE) under contract DE- AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
It has been known that free-electron laser (FEL) is capable of generating a coherent high-power radiation over a broad spectrum. Recently there is a great interest in pursuing higher peak power (for example, at terawatt level) in FEL that can enable coherent diffraction imaging and probe fundamental high-field physics. The FEL radiation power can be increased by virtue of undulator tapering. However the FEL sideband signal begins to exponentially grow in the post-saturation regime. In this paper we extend our sideband analysis* by including both the energy detune due to discrete undulator tapering and longitudinal space charge in an effective 1-D model. A dispersion relation with explicit energy detune and space charge is derived. The study is carried out semi-analytically and compared with simulations. The impact of energy detune and space charge is analyzed.
* C.-Y. Tsai et al., Analysis of the sideband instability based on a one-dimensional high-gain free electron laser model, PRAB (accepted) 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK054  
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THPMK097 First Conceptual Design Studies of an Electron Source for Ultrafast Electron Diffraction at DELTA electron, cavity, laser, gun 4530
 
  • D. Krieg, S. Khan
    DELTA, Dortmund, Germany
  • K. Sokolowski-Tinten
    Universität Duisburg-Essen, Duisburg, Germany
  
  Funding: MERCUR Pr-2017-0002
Ultrafast electron diffraction (UED) is a technique to study the structural dynamics of matter, combining diffraction of electrons with sub-angstrom De-Broglie wavelength with femtosecond time resolution. The method is complementary to X-ray scattering at free-electron lasers. UED pump-probe experiments require ultrashort laser pulses to pump a sample, electron bunches with small emittance and ultrashort length to analyze the state of the sample by diffraction, as well as excellent control of the delay between them. While most UED systems are based on electrostatic electron sources in the keV regime, electrons accelerated to a few MeV in a radiofrequency photocathode gun offer significant advantages regarding emittance and bunch length due to the reduction of space charge effects. Furthermore, the longer mean free path of MeV electrons allows for thicker samples and hence a broader range of possible materials. In this paper, a first conceptual design and simulation results for a university-based UED facility with ultrashort and low-emittance MeV electron bunches are presented. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK097  
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