Author: Liepe, M.
Paper Title Page
MOODA01 Experience with the Cornell ERL Injector SRF Cryomodule during High Beam Current Operation 35
 
  • M. Liepe, D.L. Hartill, G.H. Hoffstaetter, S. Posen, P. Quigley, V. Veshcherevich
    CLASSE, Ithaca, New York, USA
  
  Funding: Supported by NSF award DMR-0807731
Cor­nell Uni­ver­si­ty has de­vel­oped and fab­ri­cat­ed a SCRF in­jec­tor cry­omod­ule for the ac­cel­er­a­tion of high cur­rent, low emit­tance CW beams. This cry­omod­ule is based on su­per­con­duct­ing RF tech­nol­o­gy with five 2-cell SRF cav­i­ties op­er­at­ed in CW mode. Strong High­er-Or­der-Mode (HOM) damp­ing and high power RF input cou­plers sup­port ac­cel­er­at­ing beam cur­rents of tens of mA. The cry­omod­ule is cur­rent­ly under ex­ten­sive test­ing in the Cor­nell ERL in­jec­tor pro­to­type with CW beam cur­rents ex­ceed­ing 25 mA. This paper gives an overview of the ex­pe­ri­ence gained dur­ing the high beam cur­rent op­er­a­tion of the cry­omod­ule, with a focus on the in­trin­sic cav­i­ty qual­i­ty fac­tors, input cou­pler per­for­mance, and HOM damp­ing. 		 
 
MOPC108 Cornell SRF New Materials Program* 328
 
  • S. Posen, M. Liepe, Y. Xie
    CLASSE, Ithaca, New York, USA
  
  Funding: Work supported by NSF Career award PHY-0841213, DOE award ER41628, and the Alfred P. Sloan Foundation
The SRF group at Cor­nell has re­cent­ly pi­o­neered an ex­ten­sive pro­gram to in­ves­ti­gate al­ter­na­tive ma­te­ri­als for su­per­con­duct­ing cav­i­ties. We have de­vel­oped fa­cil­i­ties to fab­ri­cate Nb3Sn, a su­per­con­duc­tor which will the­o­ret­i­cal­ly be able to reach more than twice the max­i­mum ac­cel­er­at­ing field of Nb in a cav­i­ty under the same op­er­at­ing con­di­tions. In ad­di­tion, with the crit­i­cal tem­per­a­ture of Nb3Sn being twice that of Nb, Nb3Sn would allow op­er­a­tion of SRF cav­i­ties with a much high­er cryo­genic ef­fi­cien­cy. We have also man­u­fac­tured two TE cav­i­ties that mea­sure the RF prop­er­ties of small, flat sam­ples, ideal for ma­te­ri­al fab­ri­ca­tion meth­ods in de­vel­op­ment. This paper pre­sents an overview of the ma­te­ri­als re­search pro­gram. First re­sults from tests of Nb3Sn sam­ples are pre­sent­ed. 		 
 
MOPC109 Suppression of Coupler Kicks in 7-Cell Main Linac Cavities for Cornell's ERL 331
 
  • N.R.A. Valles, M. Liepe, V.D. Shemelin
    CLASSE, Ithaca, New York, USA
  
  Funding: Supported by NSF award DMR-0807731
Cor­nell is de­vel­op­ing a 5 GeV En­er­gy Re­cov­ery Linac op­er­at­ing at 100 mA with very small emit­tances (~30 pm at 77 pC bunch charge) in the hor­i­zon­tal and ver­ti­cal di­rec­tions. We in­ves­ti­gate the ef­fect of the fun­da­men­tal RF power cou­plers of the main linac SRF cav­i­ties on the beam using the ACE3P soft­ware pack­age. The cav­i­ties in the ERL main linac will be op­er­at­ed at very high load­ed qual­i­ty fac­tors of up to 6.5·107, cor­re­spond­ing to a full band­width of only 20 Hz. Cav­i­ty mi­cro­phon­ics will de­tune the cav­i­ties by more than one band­width dur­ing op­er­a­tion, there­by caus­ing a time de­pen­dent change of the cou­pler kick in ad­di­tion to its fast os­cil­la­tion at the RF fre­quen­cy. In order to in­ves­ti­gate the de­pen­dence of the cou­pler kick on the cav­i­ty fre­quen­cy, we cal­cu­late the cou­pler kick given to the beam for the case of a de­tuned RF cav­i­ty. We show that a com­pen­sa­tion stub ge­om­e­try lo­cat­ed op­po­site to the input cou­pler port can be op­ti­mized to re­duce the over­all kick given to the beam and the emit­tace growth caused by its time de­pen­dence.