Keyword: space-charge
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SAPAF02 Optimization of Heavy-Ion Synchrotrons Using Nature-Inspired Algorithms and Machine Learning injection, emittance, simulation, synchrotron 15
 
  • S. Appel, W. Geithner, S. Reimann, M. Sapinski, R. Singh, D.M. Vilsmeier
    GSI, Darmstadt, Germany
  
  The ap­pli­ca­tion of ma­chine learn­ing and na­ture-in­spired op­ti­miza­tion meth­ods, like for ex­am­ple ge­netic al­go­rithms (GA) and par­ti­cle swarm op­ti­miza­tion (PSO) can be found in var­i­ous sci­en­tific/tech­ni­cal areas. In re­cent years, those ap­proaches are find­ing ap­pli­ca­tion in ac­cel­er­a­tor physics to a greater ex­tent. In this re­port, na­ture-in­spired op­ti­miza­tion as well as the ma­chine learn­ing will be shortly in­tro­duced and their ap­pli­ca­tion to the ac­cel­er­a­tor fa­cil­ity at GSI/FAIR will be pre­sented. For the heavy-ion syn­chro­tron SIS18 at GSI, the multi-ob­jec­tive GA/PSO op­ti­miza­tion re­sulted in a sig­nif­i­cant im­prove­ment of multi-turn in­jec­tion per­for­mance and sub­se­quent trans­mis­sion for in­tense beams. An au­to­mated in­jec­tion op­ti­miza­tion with ge­netic al­go­rithms at the CRYRING@​ESR ion stor­age ring has been per­formed. The usage of ma­chine learn­ing for a beam di­ag­nos­tic ap­pli­ca­tion, where re­con­struc­tion of space-charge dis­torted beam pro­files from ion­iza­tion pro­file mon­i­tors is per­formed, will also be shown. First re­sults and the ex­pe­ri­ence gained will be pre­sented.  
slides icon Slides SAPAF02 [2.642 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SAPAF02  
About • paper received ※ 16 October 2018       paper accepted ※ 27 January 2019       issue date ※ 26 January 2019  
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SAPAF03 Comparison of Model-Based and Heuristic Optimization Algorithms Applied to Photoinjectors Using Libensemble simulation, cavity, gun, solenoid 22
 
  • N.R. Neveu
    IIT, Chicago, Illinois, USA
  • S. T. P. Hudson, J.M. Larson
    ANL, Argonne, Illinois, USA
  • L.K. Spentzouris
    Illinois Institute of Technology, Chicago, Illinois, USA
  
  Funding: U.S. DOE, OS, contract DE-AC02-06CH11357 and grant DE-SC0015479.
Ge­netic al­go­rithms are com­mon and often used in the ac­cel­er­a­tor com­mu­nity. They re­quire large amounts of com­pu­ta­tional re­sources and em­pir­i­cal ad­just­ment of hy­per­pa­ra­me­ters. Model based meth­ods are sig­nif­i­cantly more ef­fi­cient, but often la­beled as un­re­li­able for the non­lin­ear or un­smooth prob­lems that can be found in ac­cel­er­a­tor physics. We in­ves­ti­gate the be­hav­ior of both ap­proaches using a pho­toin­jec­tor op­er­ated in the space charge dom­i­nated regime. All op­ti­miza­tion runs are co­or­di­nated and man­aged by the Python li­brary libEnsem­ble, which is de­vel­oped at Ar­gonne Na­tional Lab­o­ra­tory. 		 
slides icon Slides SAPAF03 [0.653 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SAPAF03  
About • paper received ※ 11 November 2018       paper accepted ※ 19 November 2018       issue date ※ 26 January 2019  
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SUPAF04 Symplectic and Self-Consistent Algorithms for Particle Accelerator Simulation plasma, simulation, betatron, resonance 42
 
  • T. Planche, P. M. Jung
    TRIUMF, Vancouver, Canada
  
  This paper is a re­view of al­go­rithms, ap­plic­a­ble to par­ti­cle ac­cel­er­a­tor sim­u­la­tion, which share the fol­low­ing two char­ac­ter­is­tics: (1) they pre­serve to ma­chine pre­ci­sion the sym­plec­tic geom­e­try of the par­ti­cle dy­nam­ics, and (2) they track the evo­lu­tion of the self-field con­sis­tently with the evo­lu­tion of the charge dis­tri­b­u­tion. This re­view in­cludes, but is not lim­ited to, al­go­rithms using a Par­ti­cle-in-Cell dis­cretiza­tion scheme. At the end of this re­view we dis­cuss to pos­si­bil­ity to de­rived al­go­rithms from an elec­tro­sta­tic Hamil­ton­ian.  
slides icon Slides SUPAF04 [0.424 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SUPAF04  
About • paper received ※ 19 October 2018       paper accepted ※ 24 October 2018       issue date ※ 26 January 2019  
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SUPAF07 High-Fidelity Three-Dimensional Simulations of Thermionic Energy Converters simulation, electron, cathode, operation 59
 
  • N.M. Cook, J.P. Edelen, C.C. Hall, M.V. Keilman, P. Moeller, R. Nagler
    RadiaSoft LLC, Boulder, Colorado, USA
  • J.-L. Vay
    LBNL, Berkeley, California, USA
  
  Funding: This work is supported the US DOE Office of Science, Office of High Energy Physics: DE-SC0017162.
Thermionic en­ergy con­vert­ers (TEC) are a class of ther­mo­elec­tric de­vices, which promise im­prove­ments to the ef­fi­ciency and cost of both small- and large-scale elec­tric­ity gen­er­a­tion. A TEC is com­prised of a nar­rowly-sep­a­rated thermionic emit­ter and an anode. Sim­ple struc­tures are often space-charge lim­ited as op­er­at­ing tem­per­a­tures pro­duce cur­rents ex­ceed­ing the Child-Lang­muir limit. We pre­sent re­sults from 3D sim­u­la­tions of these de­vices using the par­ti­cle-in-cell code Warp, de­vel­oped at Lawrence Berke­ley Na­tional Lab. We demon­strate im­prove­ments to the Warp code per­mit­ting high fi­delity sim­u­la­tions of com­plex de­vice geome­tries. These im­prove­ments in­clude mod­el­ing of non-con­for­mal geome­tries using mesh re­fine­ment and cut-cells with a di­elec­tric solver. We also con­sider self-con­sis­tent ef­fects to model Schot­tky emis­sion near the space-charge limit for ar­rays of shaped emit­ters. The ef­fi­ciency of these de­vices is com­puted by mod­el­ing dis­tinct loss chan­nels, in­clud­ing ki­netic losses, ra­dia­tive losses, and di­elec­tric charg­ing. We demon­strate many of these fea­tures within an open-source, browser-based in­ter­face for run­ning 3D elec­tro­sta­tic sim­u­la­tions with Warp, in­clud­ing de­sign and analy­sis tools, as well as stream­lined sub­mis­sion to HPC cen­ters. 		 
slides icon Slides SUPAF07 [6.097 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SUPAF07  
About • paper received ※ 01 November 2018       paper accepted ※ 19 November 2018       issue date ※ 26 January 2019  
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SUPAG01 Space Charge and Transverse Instabilities at the CERN SPS and LHC coupling, simulation, optics, impedance 80
 
  • E. Métral, D. Amorim, G. Arduini, H. Bartosik, E. Benedetto, H. Burkhardt, K.S.B. Li, A. Oeftiger, D. Quatraro, G. Rumolo, B. Salvant, C. Zannini
    CERN, Geneva, Switzerland
  
  At the CERN ac­cel­er­a­tor com­plex, it seems that only the high­est en­ergy ma­chine in the se­quence, the LHC, with space charge (SC) pa­ra­me­ter close to one, sees the pre­dicted ben­e­fi­cial ef­fect of SC on trans­verse co­her­ent in­sta­bil­i­ties. In the other cir­cu­lar ma­chines of the LHC in­jec­tor chain (PSB, PS and SPS), where the SC pa­ra­me­ter is much big­ger than one, SC does not seem to play a major (sta­bil­is­ing) role, and it is maybe the op­po­site in the SPS. All the mea­sure­ments and sim­u­la­tions per­formed so far in both the SPS and LHC will be re­viewed and analysed in de­tail.  
slides icon Slides SUPAG01 [37.523 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SUPAG01  
About • paper received ※ 20 October 2018       paper accepted ※ 19 November 2018       issue date ※ 26 January 2019  
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SUPLG01 Computational Accelerator Physics: On the Road to Exascale simulation, plasma, optics, radiation 113
 
  • R.D. Ryne
    LBNL, Berkeley, USA
  
  The first con­fer­ence in what would be­come the ICAP se­ries was held in 1988. At that time the most pow­er­ful com­puter in the world was a Cray YMP with 8 proces­sors and a peak per­for­mance of 2 gi­gaflops. Today the fastest com­puter in the world has more than 2 mil­lion cores and a the­o­ret­i­cal peak per­for­mance of nearly 200 petaflops. Com­pared to 1988, per­for­mance has in­creased by a fac­tor of 100 mil­lion, ac­com­pa­nied by huge ad­vances in mem­ory, net­work­ing, big data man­age­ment and an­a­lyt­ics. By the time of the next ICAP in 2021 we will be at the dawn of the Ex­as­cale era. In this talk I will de­scribe the ad­vances in Com­pu­ta­tional Ac­cel­er­a­tor Physics that brought us to this point and de­scribe what to ex­pect in re­gard to High Per­for­mance Com­put­ing in the fu­ture. This writeup as based on my pre­sen­ta­tion at ICAP’18 along with some ad­di­tional com­ments that I did not in­clude orig­i­nally due to time con­straints.  
slides icon Slides SUPLG01 [25.438 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SUPLG01  
About • paper received ※ 14 November 2018       paper accepted ※ 07 December 2018       issue date ※ 26 January 2019  
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TUPAF20 Mean-Field Density Evolution of Bunched Particles With Non-Zero Initial Velocity electron, simulation, emittance, distributed 233
 
  • B.S. Zerbe, P.M. Duxbury
    MSU, East Lansing, Michigan, USA
  
  Funding: NSF Grant 1625181 NSF Grant RC108666 MSU Col. Nat. Sci., Provost Off., Col. Comm. Art and Sci.
Reed (2006) pre­sented a 1D mean-field model of ini­tially cold pan­cake-beam ex­pan­sion demon­strat­ing that the evo­lu­tion of the en­tire spa­tial dis­tri­b­u­tion can be solved for all time where the 1D as­sump­tion holds. This model is rel­e­vant to ul­tra-fast elec­tron mi­croscopy as it de­scribes the evo­lu­tion of the dis­tri­b­u­tion within the pho­to­elec­tron gun, and this model is sim­i­lar to An­der­son’s sheet beam den­sity time de­pen­dence (An­der­son 1987) ex­cept that Reed’s the­ory ap­plies to freely ex­pand­ing beams in­stead of beams within a fo­cussing chan­nel. Our re­cent work (Zerbe 2018) gen­er­al­ized Reed’s analy­sis to cylin­dri­cal and spher­i­cal geome­tries demon­strat­ing the pres­ence of a shock that is seen in the Coulomb ex­plo­sion lit­er­a­ture under these geome­tries and fur­ther dis­cussed the ab­sence of a shock in the 1D model. This work is rel­e­vant as it of­fers a mech­a­nis­tic ex­pla­na­tion of the ring-like den­sity shock that arises in non-equi­lib­rium pan­cake-beams within the pho­to­elec­tron gun; more­over, this shock is co­in­ci­dent with a re­gion of high-tem­per­a­ture elec­trons pro­vid­ing an ex­pla­na­tion for why ex­per­i­men­tally aper­tur­ing the elec­tron bunch re­sults in a greater than 10-fold im­prove­ment in beam emit­tance(Williams 2017), pos­si­bly even re­sult­ing in bunch emit­tance below the in­trin­sic emit­tance of the cath­ode. How­ever, this the­ory has been de­vel­oped for cold-bunches, i.e. bunches of elec­trons with 0 ini­tial mo­men­tum. Here, we briefly re­view this new the­ory and ex­tend the cylin­dri­cal- and spher­i­cal- sym­met­ric dis­tri­b­u­tion to en­sem­bles that have non-zero ini­tial mo­men­tum dis­tri­b­u­tions that are sym­met­ric but oth­er­wise un­re­stricted demon­strat­ing how ini­tial ve­loc­ity dis­tri­b­u­tions cou­ple to the shocks seen in the less gen­eral for­mu­la­tion. Fur­ther, we de­rive and demon­strate how the lam­i­nar con­di­tion may be prop­a­gated through beam foci. 		 
slides icon Slides TUPAF20 [1.396 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF20  
About • paper received ※ 19 October 2018       paper accepted ※ 15 December 2018       issue date ※ 26 January 2019  
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WEPLG01 Analysis of Emittance Growth in a Gridless Spectral Poisson Solver for Fully Symplectic Multiparticle Tracking emittance, lattice, plasma, simulation 335
 
  • C.E. Mitchell, J. Qiang
    LBNL, Berkeley, California, USA
  
  Funding: This work was supported by the Director, Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Grid­less spec­tral meth­ods for self-con­sis­tent sym­plec­tic space charge mod­el­ing pos­sess sev­eral ad­van­tages over tra­di­tional mo­men­tum-con­serv­ing par­ti­cle-in-cell meth­ods, in­clud­ing the ab­sence of nu­mer­i­cal grid heat­ing and the pres­ence of an un­der­ly­ing multi-par­ti­cle Hamil­ton­ian. Nev­er­the­less, ev­i­dence of col­li­sional par­ti­cle noise re­mains. For a class of such 1D and 2D al­go­rithms, we pro­vide an­a­lyt­i­cal mod­els of the nu­mer­i­cal field error, the op­ti­mal choice of spec­tral modes, and the nu­mer­i­cal emit­tance growth per timestep. We com­pare these re­sults with the emit­tance growth mod­els of Struck­meier, Hoff­man, Kest­ing, and oth­ers. 		 
slides icon Slides WEPLG01 [11.804 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-WEPLG01  
About • paper received ※ 18 October 2018       paper accepted ※ 28 January 2019       issue date ※ 26 January 2019  
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