Keyword: higher-order-mode
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THPAK017 Higher Order Modes in China-ADS Demo Linac dipole, HOM, cavity, linac 3240
 
  • C. Zhang, Y. He, T.C. Jiang, R.X. Wang, S.H. Zhang
    IMP/CAS, Lanzhou, People's Republic of China
  
  Funding: Work supported by Natural Science Foundation of China，No.11505253
The study of higher order modes ex­cited in the China-ADS Linac has been pre­sented in this paper. The ef­fects of the cryo­genic losses and the in­flu­ence on beam of the higher order modes have been in­ves­ti­gated. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK017  
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THPAK113 Cavity Characterization Studies With the Latest Revision of YACS cavity, storage-ring, coupling, superconducting-cavity 3503
 
  • B.D. Isbarn, S. Koetter, B. Riemann, M. Sommer, T. Weis
    DELTA, Dortmund, Germany
  
  Funding: Work supported by the BMBF under contract no. 05K13PEB.
YACS is a 2.5D fi­nite el­e­ment method solver ca­pa­ble of solv­ing for the full 3D eigen­fre­quency spec­tra of res­o­nant ax­isym­met­ric struc­tures while re­duc­ing the com­pu­ta­tional prob­lem to a 2D ro­ta­tion plane. The most re­cent re­vi­sion of YACS now sup­ports ar­bi­trary order basis func­tions for the geom­e­try and field dis­cretiza­tion. In ear­lier re­vi­sions of YACS spu­ri­ous modes were in­tro­duced by in­creas­ing the order of ei­ther the geom­e­try or field basis func­tions. To pre­vent the emer­gence of spu­ri­ous modes, YACS now matches the func­tion spaces of the in-plane and out-plane func­tion basis, and thus yields spu­ri­ous free so­lu­tions. To demon­strate the ca­pa­bil­i­ties of YACS, ex­ten­sive cav­ity char­ac­ter­i­za­tion stud­ies on curved mul­ti­cell mi­crowave cav­i­ties are pre­sented. Due to the com­bined uti­liza­tion of the ro­ta­tion sym­me­try, higher order basis func­tions and curved el­e­ments, eigen­fre­quency spec­tra above 10 GHz for L-band mul­ti­cell struc­tures can be eas­ily ob­tained. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK113  
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THPML012 Simulations and Measurements of the Wakefield Loading Effect in Argonne Wakefield Accelerator Beamline wakefield, experiment, linac, acceleration 4675
 
  • J. Upadhyay, E.I. Simakov
    LANL, Los Alamos, New Mexico, USA
  • M.E. Conde, Q. Gao, N.R. Neveu, J.G. Power, J.H. Shao, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
  • N.R. Neveu
    IIT, Chicago, Illinois, USA
  
  A beam dri­ven ac­cel­er­a­tion ex­per­i­ment in a pho­tonic band gap (PBG) struc­ture is planned at Ar­gonne wake­fied ac­cel­er­a­tor (AWA) fa­cil­ity at Ar­gonne Na­tional Lab­o­ra­tory. We plan to pass a high charge (drive) beam through a trav­el­ling wave 11.7 GHz PBG struc­ture and gen­er­ate a wake­field. This wake­field will be probed by a low charge (wit­ness) beam to demon­strate wake­field ac­cel­er­a­tion and de­cel­er­a­tion. The drive and wit­ness bunches will be ac­cel­er­ated to above 60 MeV in the main ac­cel­er­a­tor at AWA which has fre­quency of 1.3 GHz. The charges used in this ex­per­i­ment could be as high as 20 nC. To mea­sure the ex­clu­sive ef­fect of PBG the struc­ture on ac­cel­er­a­tion and de­cel­er­a­tion of the wit­ness bunch we have to ex­clude the ef­fect of beam load­ing of the main AWA ac­cel­er­a­tor struc­ture. To un­der­stand the wake­field ef­fect in AWA, we con­ducted an ex­per­i­ment where we passed the high charge (10 nC) beam through the ac­cel­er­a­tor struc­ture which was fol­lowed by a 2 nC wit­ness beam sep­a­rated by 4 wave­length. The en­ergy of wit­ness beam was mea­sured in the pres­ence and ab­sence of the drive beam. The beam load­ing was ob­served and quan­ti­fied. The re­sults of this work will be pre­sented in the con­fer­ence.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML012  
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THPML013 Demonstration of the Wakefield Acceleration in an 11.7 GHz Photonic Band Gap Accelerator Structure experiment, wakefield, acceleration, electron 4678
 
  • J. Upadhyay, E.I. Simakov
    LANL, Los Alamos, New Mexico, USA
  • M.E. Conde, Q. Gao, N.R. Neveu, J.G. Power, J.H. Shao, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
  
  We plan to con­duct a beam dri­ven ac­cel­er­a­tion ex­per­i­ment in a pho­tonic band gap (PBG) ac­cel­er­a­tor struc­ture op­er­at­ing at 11.7 GHz at Ar­gonne Wake­field Ac­cel­er­a­tor (AWA) fa­cil­ity. For the ex­per­i­ment, the PBG struc­ture will be ex­cited by a high charge (up to 10 nC) elec­tron bunch, and a sec­ond smaller charge wit­ness bunch will be ac­cel­er­ated. Be­cause the PBG struc­ture was fab­ri­cated with elec­tro­form­ing, the AWA beam­line in­cludes a Be win­dow placed be­fore the PBG struc­ture that pro­tects the cath­ode from con­t­a­m­i­na­tion due to pos­si­ble out­gassing from the elec­tro­formed cop­per. The di­am­e­ter of the Be win­dow is 9 mm and the beam tube di­am­e­ter of the PBG struc­ture is 6.4 mm. The size of the high charge elec­tron beam on Be win­dow has to be min­i­mized to min­i­mize scat­ter­ing. The pa­ra­me­ters of the beam­line had to be ad­justed to achieve good prop­a­ga­tion of the beam. An OPAL sim­u­la­tion for the AWA beam­line was per­formed for 1, 5, and 10 nC beams. The beam size was ex­per­i­men­tally mea­sured at dif­fer­ent po­si­tions in the beam­line for dif­fer­ent charges to ver­ify sim­u­la­tions. Fi­nally, the high charge elec­tron beam was passed through the PBG struc­ture and ac­cel­er­a­tion of the wit­ness bunch was mea­sured  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML013  
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THPML125 Efficiency Analysis of High Average Power Linacs for Environmental and Industrial Applications linac, impedance, beam-loading, coupling 4970
 
  • M. Shumail, V.A. Dolgashev
    SLAC, Menlo Park, California, USA
  
  Funding: U.S. Department of Energy, HEP under Research Opportunities in Accelerator Stewardship: LAB 16-1438.
We pre­sent com­pre­hen­sive ef­fi­ciency equa­tions and use­ful scal­ing laws to op­ti­mally de­ter­mine de­sign pa­ra­me­ters for high ef­fi­ciency rf linacs. For the first time we have in­cor­po­rated the par­a­sitic losses due to the higher order cav­ity modes into the ef­fi­ciency analy­sis of the stand­ing wave (SW) and trav­el­ling wave (TW) ac­cel­er­a­tors. We have also de­rived the ef­fi­ciency equa­tions for a new kind of at­ten­u­a­tion-in­de­pen­dent-im­ped­ance trav­el­ling wave (ATW) ac­cel­er­a­tors where the shunt im­ped­ance can be op­ti­mized in­de­pen­dent of the group ve­loc­ity. We have ob­tained scal­ing laws which re­late the rf to beam ef­fi­ciency to the linac length, beam aper­ture ra­dius , phase ad­vance per cell, and the type of ac­cel­er­at­ing struc­ture: SW ver­sus TW, disk-loaded (DL) ver­sus nose-cone (NC). We give an ex­am­ple of using these scal­ing laws to de­ter­mine a fea­si­ble set of pa­ra­me­ters for a 10 MeV, 10 MW linac with 97.2% ef­fi­ciency. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML125  
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