Author: Sun, C.
Paper Title Page
MOPAB106 Enhancing the MOGA Optimization Process at ALS-U with Machine Learning 387
 
  • Y. Lu, M.P. Ehrlichman, T. Hellert, S.C. Leemann, H. Nishimura, C. Sun, M. Venturini
    LBNL, Berkeley, California, USA
  
  Funding: This research is funded by the US Department of Energy(BES & ASCR Programs), and supported by the Director of the Office of Science of the US Department of Energy under Contract No. DEAC02-05CH11231.
The bare lat­tice op­ti­miza­tion for the lin­ear and non­lin­ear ALS-U stor­age ring lat­tice, even with­out re­verse bend­ing, com­prises 11 de­grees of free­dom (DoF) and is there­fore a very com­plex and highly time-con­sum­ing process. This de­sign process re­lies heav­ily on multi-ob­jec­tive ge­netic al­go­rithms (MOGA), usu­ally re­quir­ing many months of ex­pe­ri­enced sci­en­tists’ time. The main prob­lem lies in hav­ing to eval­u­ate num­bers of can­di­date lat­tices due to the sto­chas­tic process of MOGA. Al­though al­most all of these can­di­dates are even­tu­ally re­jected, they nev­er­the­less re­quire ex­ten­sive par­ti­cle track­ing to ar­rive at a Pareto front. We there­fore pro­pose a novel Ma­chine Learn­ing (ML) pipeline that non­lin­ear track­ing is re­placed by two well-trained neural net­works (NNs) to pre­dict dy­namic aper­ture (DA) and mo­men­tum aper­ture (MA) for any lat­tice can­di­date. Ini­tial train­ing of these mod­els takes only sev­eral min­utes on con­ven­tional CPUs while pre­dic­tions are then ren­dered near in­stan­ta­neously. We pre­sent this novel method and demon­strate the re­sult­ing or­ders of mag­ni­tude speedup of the ML-en­hanced MOGA process on a 2-DoF prob­lem as well as first re­sults on a more com­plex 11-DoF prob­lem. 		 
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB106  
About • paper received ※ 19 May 2021       paper accepted ※ 01 June 2021       issue date ※ 18 August 2021  
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MOPAB114 Development of a Decoherence Kicker for the ALS Upgrade Project (ALS-U) 414
 
  • C. Sun, S. De Santis, M.P. Ehrlichman, T. Hellert, T. Oliver, G. Penn, C. Steier, M. Venturini, W.L. Waldron
    LBNL, Berkeley, California, USA
  
  The Ad­vanced Light Source (ALS) at Lawrence Berke­ley Na­tional Lab­o­ra­tory is up­grad­ing the ex­ist­ing stor­age-ring lat­tice to a nine-bend-achro­mat lat­tice with on-axis swap-out in­jec­tion. The up­graded stor­age ring will pro­vide a highly fo­cused beam of about 10 um in both hor­i­zon­tal and ver­ti­cal di­rec­tions with a sin­gle bunch train en­ergy of about 60 J at 2.0 GeV. Such a small and in­tense beam could cause dam­age to the trans­fer line vac­uum cham­bers in case of ex­trac­tion el­e­ment fail­ures or dam­age to the stor­age ring vac­uum cham­ber in case of RF fail­ures. To mit­i­gate these po­ten­tial dam­ages, a fast kicker mag­net (so-called de­co­her­ence kicker) will be in­stalled in the ALS-U stor­age ring and ac­ti­vated to di­lute the beam charge den­sity ei­ther on a train to be swapped out a few 100s turns be­fore ex­trac­tion or on the whole beam after RF fail­ures. In this paper, we will pre­sent both physics and en­gi­neer­ing de­signs of this de­co­her­ence kicker.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB114  
About • paper received ※ 19 May 2021       paper accepted ※ 27 May 2021       issue date ※ 20 August 2021  
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MOPAB115 ATS/STA Transfer Line Design for the ALS Upgrade Project (ALS-U) 417
 
  • C. Sun, M.P. Ehrlichman, T. Hellert, M. Juchno, J.-Y. Jung, M. Mardenfeld, J.R. Osborn, G. Penn, C. Steier, C.A. Swenson, M. Venturini
    LBNL, Berkeley, California, USA
  
  At the Ad­vanced Light Source Up­grade (ALS-U), an on-axis swap-out in­jec­tion will be used to re­plen­ish de­pleted bunches in the stor­age ring with re­freshed bunches from the full en­ergy ac­cu­mu­la­tor ring. To im­ple­ment this scheme, two trans­fer lines are re­quired be­tween the stor­age ring and the ac­cu­mu­la­tor ring: the ac­cu­mu­la­tor-to-stor­age-ring (ATS) trans­fer line and the stor­age-ring-to-ac­cu­mu­la­tor (STA) trans­fer line. The de­sign of the ATS/STA trans­fer lines is a chal­leng­ing task as they must fit within a tight in­jec­tion re­gion while also ac­com­mo­dat­ing the stor­age and ac­cu­mu­la­tor rings at dif­fer­ent el­e­va­tions. More­over, the ATS/STA de­sign needs to meet both the bound­ary con­di­tions and op­tics re­quire­ments. In this paper, we will pre­sent a de­sign op­tion for these ATS/STA trans­fer lines.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB115  
About • paper received ※ 19 May 2021       paper accepted ※ 27 May 2021       issue date ※ 15 August 2021  
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MOPAB118 The Impact of Short-Range Wakes on Injection Into the ALS-U Accumulator Ring 429
 
  • G. Penn, M.P. Ehrlichman, T. Hellert, C. Steier, C. Sun, M. Venturini, D. Wang
    LBNL, Berkeley, California, USA
  
  Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DEAC02-05CH11231.
As part of the ALS-U de­sign, bunches with small charge will be added to the ac­cu­mu­la­tor ring in a man­ner that ini­tially leaves both the stored and in­jected bunches dis­placed from the nom­i­nal orbit. While the beam cur­rent is below in­sta­bil­ity thresh­olds, tran­sient ef­fects due to the com­bi­na­tion of short-range wake fields and large ini­tial dis­place­ments can have an im­pact on in­jec­tion ef­fi­ciency. In this paper, the im­pact of wake fields on the two bunches is de­tailed using the el­e­gant sim­u­la­tion code, and dif­fer­ent tech­niques to op­ti­mize the in­jec­tion ef­fi­ciency are ex­plored. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB118  
About • paper received ※ 19 May 2021       paper accepted ※ 31 May 2021       issue date ※ 12 August 2021  
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WEPAB123 Multi-Bunch Resistive Wall Wake Field Tracking via Pseudomodes in the ALS-U Accumulator Ring 2893
 
  • M.P. Ehrlichman, S. De Santis, T. Hellert, S.C. Leemann, G. Penn, C. Steier, C. Sun, M. Venturini, D. Wang
    LBNL, Berkeley, California, USA
  
  For the ALS-U pro­ject, par­ti­cles will be in­jected from the booster to the ac­cu­mu­la­tor ring uti­liz­ing an in­jec­tion scheme that leaves the stored and in­jected par­ti­cles with a non-triv­ial tran­sient. This tran­sient re­quires that multi­bunch feed­back be masked for those buck­ets into which charge is in­jected. The mask­ing sig­nif­i­cantly di­min­ishes the damp­ing ca­pa­bil­ity of the multi­bunch feed­back sys­tem. This prob­lem is ex­ac­er­bated by the large in­jec­tion tran­sient. The higher order re­sis­tive wall wake fields in the ac­cu­mu­la­tor ring ex­ceed the ra­di­a­tion damp­ing time. To study whether the beam will re­main multi­bunch sta­ble dur­ing an in­jec­tion cycle, a multi­bunch track­ing sim­u­la­tion is used that sim­u­lates the multi­bunch feed­back sys­tem and also pseudo­mode rep­re­sen­ta­tion of re­sis­tive wall wake fields.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB123  
About • paper received ※ 20 May 2021       paper accepted ※ 01 September 2021       issue date ※ 23 August 2021  
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WEPAB124 The Three Dipole Kicker Injection Scheme for the ALS-U Accumulator Ring 2896
 
  • M.P. Ehrlichman, T. Hellert, S.C. Leemann, G. Penn, C. Steier, C. Sun, M. Venturini, D. Wang
    LBNL, Berkeley, California, USA
  
  The ALS-U light source will im­ple­ment on-axis swap-out in­jec­tion of in­di­vid­ual trains em­ploy­ing an ac­cu­mu­la­tor be­tween the booster and stor­age rings. The ac­cu­mu­la­tor ring de­sign is a twelve pe­riod triple-bend achro­mat that will be in­stalled along the inner cir­cum­fer­ence of the stor­age-ring tun­nel. A non-con­ven­tional in­jec­tion scheme will be uti­lized for top-off off-axis in­jec­tion from the booster into the ac­cu­mu­la­tor ring meant to ac­com­mo­date a rel­a­tively nar­row vac­uum-cham­ber aper­ture while max­i­miz­ing in­jec­tion ef­fi­ciency. The scheme in­cor­po­rates three di­pole kick­ers dis­trib­uted over three sec­tors, with two kick­ers per­turb­ing the stored beam and the third af­fect­ing both the stored and the in­jected beam tra­jec­to­ries. This paper de­scribes this ‘‘3DK’’ in­jec­tion scheme, how it was cho­sen, de­signed and op­ti­mized, and how we eval­u­ated its fit­ness as a so­lu­tion for booster-to-ac­cu­mu­la­tor ring in­jec­tion against al­ter­nate in­jec­tion schemes.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB124  
About • paper received ※ 20 May 2021       paper accepted ※ 01 July 2021       issue date ※ 13 August 2021  
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