Author: Delayen, J.R.
Paper Title Page
WEPA17 Improved Electrostatic Design of the Jefferson Lab 300 kV DC Photogun and the Minimization of Beam Deflection 655
 
  • M.A. Mamun, D.B. Bullard, J.M. Grames, C. Hernandez-Garcia, G.A. Krafft, M. Poelker, R. Suleiman
    JLab, Newport News, Virginia, USA
  • J.R. Delayen, G.A. Krafft, G.G. Palacios Serrano, S.A.K. Wijethunga
    ODU, Norfolk, Virginia, USA
  
  Funding: This work is supported by the Department of Energy, under contract DE-AC05-06OR23177, JSA initiatives fund program, and the Laboratory Directed Research and Development program.
An elec­tron beam with high bunch charge and high rep­e­ti­tion rate is re­quired for elec­tron cool­ing of the ion beam to achieve the high lu­mi­nos­ity re­quired for the pro­posed elec­tron-ion col­lid­ers. An im­proved de­sign of the 300 kV DC high volt­age pho­to­gun at Jef­fer­son Lab was in­cor­po­rated to­ward over­com­ing the beam loss and space charge cur­rent lim­i­ta­tion ex­pe­ri­enced in the orig­i­nal de­sign. To reach the bunch charge goal of ~ few nC within 75 ps bunches, the ex­ist­ing DC high volt­age pho­to­gun elec­trodes and an­ode-cath­ode gap were mod­i­fied to in­crease the lon­gi­tu­di­nal elec­tric field (Ez) at the pho­to­cath­ode. The an­ode-cath­ode gap was re­duced to in­crease the Ez at the pho­to­cath­ode, and the anode aper­ture was spa­tially shifted with re­spect to the beam­line lon­gi­tu­di­nal axis to min­i­mize the beam de­flec­tion in­tro­duced by the geo­met­ric asym­me­try of the in­verted in­su­la­tor pho­to­gun. The elec­tro­sta­tic de­sign and beam dy­nam­ics sim­u­la­tions were per­formed to de­ter­mine the re­quired mod­i­fi­ca­tion. Beam-based mea­sure­ment from the mod­i­fied gun con­firmed the re­duc­tion of the beam de­flec­tion, which is pre­sented in this con­tri­bu­tion. 		 
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DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA17  
About • Received ※ 23 July 2022 — Revised ※ 28 July 2022 — Accepted ※ 05 August 2022 — Issue date ※ 11 August 2022
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WEPA26 197 MHz Waveguide Loaded Crabbing Cavity Design for the Electron-Ion Collider 679
 
  • S.U. De Silva, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  • J. Guo, R.A. Rimmer
    JLab, Newport News, Virginia, USA
  • Z. Li
    SLAC, Menlo Park, California, USA
  • B.P. Xiao
    BNL, Upton, New York, USA
  
  The Elec­tron-Ion Col­lider will re­quire crab­bing sys­tems at both hadron and elec­tron stor­age rings in order to reach the de­sired lu­mi­nos­ity goal. The 197 MHz crab cav­ity sys­tem is one of the crit­i­cal rf sys­tems of the col-lider. The crab cav­ity, based on the rf-di­pole de­sign, ex-plores the op­tion of wave­guide load damp­ing to sup­press the higher order modes and meet the tight im­ped­ance spec­i­fi­ca­tions. The cav­ity is de­signed with com­pact dog-bone wave­guides with tran­si­tions to rec­tan­gu­lar wave-guides and wave­guide loads. This paper pre­sents the com­pact 197 MHz crab cav­ity de­sign with wave­guide damp­ing and other an­cil­lar­ies.  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA26  
About • Received ※ 08 August 2022 — Revised ※ 09 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 06 September 2022
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WEPA31 Lower Temperature Annealing of Vapor Diffused Nb3Sn for Accelerator Cavities 695
 
  • J.K. Tiskumara, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  • G.V. Eremeev
    Fermilab, Batavia, Illinois, USA
  • U. Pudasaini
    JLab, Newport News, Virginia, USA
  
  Nb3Sn is a next-gen­er­a­tion su­per­con­duct­ing ma­te­r­ial for the ac­cel­er­a­tor cav­i­ties with higher crit­i­cal tem­per­a­ture and su­per­heat­ing field, both twice com­pared to Nb. It promises su­pe­rior per­for­mance and higher op­er­at­ing tem­per­a­ture than Nb, re­sult­ing in sig­nif­i­cant cost re­duc­tion. So far, the Sn vapor dif­fu­sion method is the most pre­ferred and suc­cess­ful tech­nique to coat nio­bium cav­i­ties with Nb3Sn. Al­though sev­eral post-coat­ing tech­niques (chem­i­cal, elec­tro­chem­i­cal, me­chan­i­cal) have been ex­plored to im­prove the sur­face qual­ity of the coated sur­face, an ef­fec­tive process has yet to be found. Since there are only a few stud­ies on the post-coat­ing heat treat­ment at lower tem­per­a­tures, we an­nealed Nb3Sn-coated sam­ples at 800 C - 1000 C to study the ef­fect of heat treat­ments on sur­face prop­er­ties, pri­mar­ily aimed at re­mov­ing sur­face Sn residues. This paper dis­cusses the sys­tem­atic sur­face analy­sis of coated sam­ples after an­neal­ing at tem­per­a­tures be­tween 850 C and 950 C.  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA31  
About • Received ※ 02 August 2022 — Revised ※ 05 August 2022 — Accepted ※ 07 August 2022 — Issue date ※ 02 September 2022
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