Author: Li, Z.
Paper Title Page
WEPWO072 HOM Damping Coupler Design for the 400-MHz RF Dipole Compact Crab Cavity for the LHC HiLumi Upgrade 2468
 
  • Z. Li, L. Ge
    SLAC, Menlo Park, California, USA
  • S.U. De Silva, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  
  Funding: Work partially supported by the US DOE through the US LHC Accelerator Research Program (LARP), and by US DOE under contract number DE-AC02-76SF00515.
Crab cav­i­ties are adapted as the base­line de­sign for the LHC Hi­Lumi up­grade to achieve head-on beam-beam col­li­sions for fur­ther im­prove­ment in lu­mi­nos­ity. A 400-MHz com­pact RF di­pole crab cav­ity de­sign was de­vel­oped by a joint ef­fort be­tween Old Do­min­ion Uni­ver­sity and SLAC under the sup­port of US LARP pro­gram. This de­sign has shown very fa­vor­able RF pa­ra­me­ters and can fit into the avail­able beam­line spac­ing for ei­ther ver­ti­cal and hor­i­zon­tal crab­bing schemes. A nio­bium pro­to­type cav­ity based on such a de­sign has been man­u­fac­tured for ver­ti­cal test. In ad­di­tion, there are strin­gent wake­field re­quire­ments that needed to be met for such a cav­ity in order to pre­serve the qual­ity of the cir­cu­lat­ing beams. In this paper, we will dis­cuss dif­fer­ent damp­ing schemes for such a com­pact de­sign and pre­sent the HOM cou­pler de­signs to meet the damp­ing re­quire­ments. 		 
 
WEPWO076 Development of Ultra High Gradient and High Q0 Superconducting Radio Frequency Cavities 2474
 
  • R.L. Geng, W.A. Clemens, J. Follkie, T. Harris, D. Machie, R. Martin, A.D. Palczewski, E. Perry, G. Slack, R.S. Williams
    JLAB, Newport News, Virginia, USA
  • C. Adolphsen, Z. Li
    SLAC, Menlo Park, California, USA
  • J.K. Hao, Y.M. Li, K.X. Liu
    PKU, Beijing, People's Republic of China
  • P. Kushnick
    JLab, Newport News, Virginia, USA
  
  Funding: Work supported by DOE. Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
We re­port on the re­cent progress at Jef­fer­son Lab in de­vel­op­ing ultra high gra­di­ent and high Q0 su­per­con­duct­ing radio fre­quency (SRF) cav­i­ties for fu­ture SRF based ma­chines. A new 1300 MHz 9-cell pro­to­type cav­ity is being fab­ri­cated. This cav­ity has an op­ti­mized shape in terms of the ratio of the peak sur­face field (both mag­netic and elec­tric) to the ac­cel­er­a­tion gra­di­ent, hence the name low sur­face field (LSF) shape. The goal of the ef­fort is to demon­strate an ac­cel­er­a­tion gra­di­ent of 50 MV/m with Q0 of 1010 at 2 K in a 9-cell SRF cav­ity. Fine-grain nio­bium ma­te­r­ial is used. Con­ven­tional form­ing, ma­chin­ing and elec­tron beam weld­ing method are used for cav­ity fab­ri­ca­tion. New tech­niques are adopted to en­sure re­peat­able, ac­cu­rate and in­ex­pen­sive fab­ri­ca­tion of com­po­nents and the full as­sem­bly. The com­pleted cav­ity is to be first me­chan­i­cally pol­ished to a mir­ror-fin­ish, a newly ac­quired in-house ca­pa­bil­ity at JLab, fol­lowed by the proven ILC-style pro­cess­ing recipe es­tab­lished al­ready at JLab. In par­al­lel, new sin­gle-cell cav­i­ties made from large-grain nio­bium ma­te­r­ial are made to fur­ther ad­vance the cav­ity treat­ment and pro­cess­ing pro­ce­dures, aim­ing for the demon­stra­tion of an ac­cel­er­a­tion gra­di­ent of 50 MV/m with Q0 of 2·1010 at 2K.
The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes. 		 
 
WEPFI073 A Modular Cavity for Muon Ionization Cooling R&D 2860
 
  • D.L. Bowring, A.J. DeMello, A.R. Lambert, D. Li, S.P. Virostek, M.S. Zisman
    LBNL, Berkeley, California, USA
  • C. Adolphsen, L. Ge, A.A. Haase, K.H. Lee, Z. Li, D.W. Martin
    SLAC, Menlo Park, California, USA
  • D.M. Kaplan
    Illinois Institute of Technology, Chicago, Illinois, USA
  • T.H. Luo, D.J. Summers
    UMiss, University, Mississippi, USA
  • A. Moretti, M.A. Palmer, R.J. Pasquinelli, Y. Torun
    Fermilab, Batavia, USA
  • R.B. Palmer
    BNL, Upton, Long Island, New York, USA
  
  The Muon Ac­cel­er­a­tor Pro­gram (MAP) col­lab­o­ra­tion is de­vel­op­ing an ion­iza­tion cool­ing chan­nel for muon beams. Ion­iza­tion cool­ing chan­nel de­signs call for the op­er­a­tion of high-gra­di­ent, nor­mal-con­duct­ing RF cav­i­ties in multi-Tesla so­le­noidal mag­netic fields. How­ever, strong mag­netic fields have been shown to limit the max­i­mum achiev­able gra­di­ent in RF cav­i­ties. This gra­di­ent limit is char­ac­ter­ized by RF break­down and dam­age to the cav­ity sur­face. To study this issue, we have de­vel­oped an ex­per­i­men­tal pro­gram based on a mod­u­lar pill­box cav­ity op­er­at­ing at 805 MHz. The mod­u­lar cav­ity de­sign al­lows for the eval­u­a­tion of dif­fer­ent cav­ity ma­te­ri­als - such as beryl­lium - which may ame­lio­rate or cir­cum­vent RF break­down trig­gers. Mod­u­lar cav­ity com­po­nents may fur­ther­more be pre­pared with dif­fer­ent sur­face treat­ments, such as high-tem­per­a­ture bak­ing or chem­i­cal pol­ish­ing. This poster pre­sents the de­sign and ex­per­i­men­tal sta­tus of the mod­u­lar cav­ity, as well as fu­ture plans for the ex­per­i­men­tal pro­gram.  
 
WEPFI083 High Power Tests of the 2-Pin Waveguide Structures 2890
 
  • F.Y. Wang, Z. Li
    SLAC, Menlo Park, California, USA
  
  An X-band Two-Pin Wave­guide Struc­ture has been de­signed to study the in­flu­ence of power flow on rf break­down. Three dif­fer­ent sets of pins will be tested at SLAC. These sets were de­signed to achieve a sim­i­lar peak sur­face elec­tric field on one of the pins for input rf power lev­els that vary by about an order of mag­ni­tude (the other pin is used for match­ing). Two sets of pins have been tested so far, and the break­down rate was found to be strongly de­pen­dent on the power flow. In this paper, we re­view the ex­per­i­men­tal setup, the com­plete set of re­sults and their im­pli­ca­tions.