Author: Hernandez-Garcia, C.
Paper Title Page
MOPAB324 High Voltage Design and Evaluation of Wien Filters for the CEBAF 200 keV Injector Upgrade 1000
 
  • G.G. Palacios Serrano, P.A. Adderley, J.F. Benesch, D.B. Bullard, J.M. Grames, C. Hernandez-Garcia, A.S. Hofler, D. Machie, M. Poelker, M.L. Stutzman, R. Suleiman
    JLab, Newport News, Virginia, USA
  • H. Baumgart, G.G. Palacios Serrano
    ODU, Norfolk, Virginia, USA
  
  Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
High-en­ergy nu­clear physics ex­per­i­ments at the Jef­fer­son Lab Con­tin­u­ous Elec­tron Beam Ac­cel­er­a­tor Fa­cil­ity (CEBAF) re­quire highly spin-po­lar­iza­tion elec­tron beams, pro­duced from strained su­per-lat­tice GaAs pho­to­cath­odes, ac­ti­vated to neg­a­tive elec­tron affin­ity in a pho­to­gun op­er­at­ing at 130 kV dc. A pair of Wien fil­ter spin ro­ta­tors in the in­jec­tor de­fines the ori­en­ta­tion of the elec­tron beam po­lar­iza­tion at the end sta­tion tar­get. An up­grade of the CEBAF in­jec­tor to bet­ter sup­port the up­com­ing MOLLER ex­per­i­ment re­quires in­creas­ing the elec­tron beam en­ergy to 200 keV, to re­duce un­wanted he­lic­ity cor­re­lated in­ten­sity and po­si­tion sys­tem­at­ics and pro­vide pre­cise con­trol of the po­lar­iza­tion ori­en­ta­tion. Our con­tri­bu­tion de­scribes de­sign, fab­ri­ca­tion and test­ing of the high volt­age sys­tem to up­grade the Wien spin ro­ta­tor to be com­pat­i­ble with the 200 keV beam. This re­quired Solid­works mod­el­ing, CST and Opera elec­tro- and mag­ne­to­sta­tic sim­u­la­tions, up­grad­ing HV vac­uum feedthroughs, and as­sem­bly tech­niques for im­prov­ing elec­trode align­ment. The elec­tric and mag­netic fields re­quired by the Wien con­di­tion and the suc­cess­ful HV char­ac­ter­i­za­tion under vac­uum con­di­tions are also pre­sented. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB324  
About • paper received ※ 19 May 2021       paper accepted ※ 24 May 2021       issue date ※ 29 August 2021  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPAB092 Redesign of the Jefferson Lab -300 kV DC Photo-Gun for High Bunch Charge Operations 2802
 
  • S.A.K. Wijethunga, J.R. Delayen, G.A. Krafft, G.G. Palacios Serrano
    ODU, Norfolk, Virginia, USA
  • J.F. Benesch, J.R. Delayen, C. Hernandez-Garcia, G.A. Krafft, M.A. Mamun, M. Poelker, R. Suleiman
    JLab, Newport News, Virginia, USA
  
  Funding: The U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177, JSA initiatives fund program and Laboratory Directed Research and Development program.
Pro­duc­tion of high bunch charge beams for the Elec­tron-Ion Col­lider (EIC) is a chal­leng­ing task. High bunch charge (a few nC) elec­tron beam stud­ies at Jef­fer­son Lab using an in­verted in­su­la­tor DC high volt­age photo-gun showed ev­i­dence of space charge lim­i­ta­tions start­ing at 0.3 nC, lim­it­ing the max­i­mum de­liv­ered bunch charge to 0.7 nC for beam at -225 kV, 75 ps (FWHM) pulse width, and 1.64 mm (rms) laser spot size. The low ex­tracted charge is due to the mod­est lon­gi­tu­di­nal elec­tric field (Ez) at the pho­to­cath­ode lead­ing to beam loss at the anode and down­stream beam pipe. To reach the few nC high bunch charge goal, and to cor­rect the beam de­flec­tion ex­erted by the non-sym­met­ric na­ture of the in­verted in­su­la­tor photo-gun the ex­ist­ing photo-gun was mod­i­fied. This con­tri­bu­tion dis­cusses the elec­tro­sta­tic de­sign of the mod­i­fied photo-gun ob­tained using CST Stu­dio Suite’s elec­tro­mag­netic field solver. Beam dy­nam­ics sim­u­la­tions per­formed using Gen­eral Par­ti­cle Tracer (GPT) with the re­sult­ing elec­tro­sta­tic field map ob­tained from the mod­i­fied elec­trodes con­firmed the va­lid­ity of the new de­sign. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB092  
About • paper received ※ 20 May 2021       paper accepted ※ 02 June 2021       issue date ※ 17 August 2021  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPAB104 Improving the Operational Lifetime of the CEBAF Photo-Gun by Anode Biasing 2840
 
  • J.T. Yoskowitz, G.A. Krafft, G.G. Palacios Serrano, S.A.K. Wijethunga
    ODU, Norfolk, Virginia, USA
  • J.M. Grames, J. Hansknecht, C. Hernandez-Garcia, M. Poelker, M.L. Stutzman, R. Suleiman
    JLab, Newport News, Virginia, USA
  • S.B. van der Geer
    Pulsar Physics, Eindhoven, The Netherlands
  
  Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
The op­er­at­ing life­time of GaAs-based pho­to­cath­odes in DC high volt­age elec­tron photo-guns is dom­i­nated by the ion­iza­tion rate of resid­ual beam­line gas mol­e­cules. In this work, ex­per­i­ments were per­formed to quan­tify the im­prove­ment in pho­to­cath­ode charge life­time by bi­as­ing the photo-gun anode with a pos­i­tive volt­age, which re­pels ions gen­er­ated down­stream of the anode. The photo-cath­ode charge life­time im­proved by al­most a fac­tor of two when the anode was bi­ased com­pared to the usual grounded con­fig­u­ra­tion. Sim­u­la­tions were per­formed using the par­ti­cle track­ing code Gen­eral Par­ti­cle Tracer (GPT) with a new cus­tom el­e­ment. The sim­u­la­tion re­sults showed that both the num­ber and en­ergy of ions play a role in the pat­tern of QE degra­da­tion. The ex­per­i­ment re­sults and con­clu­sions sup­ported by GPT sim­u­la­tions will be pre­sented. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB104  
About • paper received ※ 20 May 2021       paper accepted ※ 02 June 2021       issue date ※ 18 August 2021  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)