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Saeki, T.

Paper Title Page
WEPEC023 Surface Study on Niobium Stain after Electro-polishing for Super-conducting RF Cavity 2941
 
  • M. Nishiwaki, H. Hayano, S. Kato, T. Saeki, M. Sawabe
    KEK, Ibaraki
  • P.V. Tyagi
    Sokendai, Ibaraki
  
 

In de­vel­op­ment of su­per­con­duct­ing ra­dio-fre­quen­cy nio­bi­um cav­i­ties, there are prob­lems in low per­for­mances of elec­tro-pol­ished (EP) cav­i­ties with a fresh EP so­lu­tion due to stains on the sur­faces with dis­col­oration. Al­though the stain prob­lems have been known from the past re­search­es, the de­tailed study with sur­face anal­y­sis has not been car­ried out. In this study, the stains on the nio­bi­um sur­faces were ob­served with x-ray pho­to­elec­tron spec­troscopy (XPS), Auger elec­tron spec­troscopy and scan­ning elec­tron mi­cro­scope. Ac­cord­ing to re­sults of XPS, there are some dif­fer­ences in atom­ic com­po­nents at the stained and non-stained sur­faces, ex, a lit­tle amount of flu­o­rine and no metal oxide were found only at the stained sur­face. In this ar­ti­cle, we will de­scribe the de­tail of the XPS re­sults.

  
WEPEC027 Long-period Monitoring of Electro-polishing Electrolyte in EP Facility at KEK 2947
 
  • M. Sawabe., H. Hayano, S. Kato, M. Nishiwaki, T. Saeki
    KEK, Ibaraki
  • P.V. Tyagi
    Sokendai, Ibaraki
  
 

We have con­struct­ed an Elec­tro-pol­ish­ing (EP) Fa­cil­i­ty in the Su­per­con­duct­ing RF Test Fa­cil­i­ty (STF) at KEK in 2008. The EP fa­cil­i­ty has been used for the EP pro­cess of Su­per­con­duct­ing RF (SRF) 9-cell cav­i­ties for more than one year. In the EP fa­cil­i­ty, the ca­pac­i­ty of the EP-elec­trolyte reser­voir tank is 2,000 L. This size is rel­a­tive­ly large if com­pared with EP fa­cil­i­ties in other lab­o­ra­to­ries. It means that the qual­i­ty con­trol of EP elec­trolyte is more dif­fi­cult be­cause the sta­tus of EP-elec­trolyte changes as the aging of EP-elec­trolyte pro­ceeds. In the real EP-pro­cess op­er­a­tions, we cir­cu­lat­ed the EP elec­trolyte of 1,100 L which was first­ly de­liv­ered into the tank in Jan­uary 2008 and was dis­posed in May 2009. Dur­ing this pe­ri­od, we per­formed the EP pro­cess­es 40 times and pe­ri­od­i­cal­ly mea­sured the con­cen­tra­tion of Nb ,Al ,HF in the EP elec­trolyte. In this ar­ti­cle, we re­port the de­tailed re­sults of the EP-elec­trolyte mon­i­tor­ing as well as the ob­ser­va­tion of chang­ing elec­tron­ic cur­rent os­cil­la­tion in the EP pro­cess­es dur­ing this pe­ri­od in the EP fa­cil­i­ty at STF/KEK.

  
WEPEC034 Various Rinsing Effects to Mitigate Contaminates Brought by BCP on Niobium SRF Cavity Surface 2968
 
  • P.V. Tyagi
    Sokendai, Ibaraki
  • H. Hayano, S. Kato, M. Nishiwaki, T. Saeki, M. Sawabe
    KEK, Ibaraki
  
 

Buffered chem­i­cal pol­ish­ing (BCP) has been wide­ly used as a final recipe of the sur­face treat­ment for nio­bi­um cav­i­ties and there is still much room to im­prove this tech­nol­o­gy since it is en­vi­ron­ment friend­ly, cheap­er and sim­pler than elec­tro-pol­ish­ing. To ex­am­ine BCPed sur­face in de­tail, we car­ried out BCP ex­per­i­ment fol­lowed by var­i­ous rins­ing meth­ods on a se­ries of nio­bi­um sam­ples at KEK. As a re­sult of the BCP pro­cess some con­tam­i­nants like flu­o­rine, car­bon, etc. have been de­tect­ed at the sur­faces which may be the promi­nent cause of lim­it­ing the per­for­mance of SRF cav­i­ties. To re­move these con­tam­i­nants, var­i­ous rins­ing pro­cess­es such as ultra pure water rinse, ul­tra­son­ic pure water rinse, al­co­holic rinse, de­ter­gent rinse, high pres­sure water rinse (HPR) had been test­ed after the BCP. The pre­lim­i­nary re­sults show that, only HPR had po­ten­tial to mit­i­gate these con­tam­i­nants. In this ar­ti­cle, we de­scribe the sur­face anal­y­sis re­sults using X-ray photo elec­tron spec­troscopy etc and a com­par­a­tive study of nio­bi­um BCPed sam­ples fol­lowed by above men­tioned rins­ing pro­cess­es.

  
WEPE008 Construction of the S1-Global Cryomodules for ILC 3356
 
  • N. Ohuchi, H. Hayano, N. Higashi, E. Kako, Y. Kondou, H. Nakai, S. Noguchi, T. Saeki, M. Satoh, M. Sawabe, T. Shidara, T. Shishido, A. Terashima, K. Tsuchiya, K. Watanabe, A. Yamamoto, Y. Yamamoto, K. Yokoya
    KEK, Ibaraki
  • T.T. Arkan, S. Barbanotti, H. Carter, M.S. Champion, R.D. Kephart, J.S. Kerby, D.V. Mitchell, Y. Orlov, T.J. Peterson, M.C. Ross
    Fermilab, Batavia
  • A. Bosotti, C. Pagani, R. Paparella, P. Pierini
    INFN/LASA, Segrate (MI)
  • D. Kostin, L. Lilje, A. Matheisen, W.-D. Möller, H. Weise
    DESY, Hamburg
  
 

In an at­tempt at demon­strat­ing an av­er­age field gra­di­ent of 31.5 MV/m as per the de­sign ac­cel­er­at­ing gra­di­ent for ILC, a pro­gram called S1-Glob­al is in progress as an in­ter­na­tion­al re­search col­lab­o­ra­tion among KEK, INFN, FNAL, DESY and SLAC. The S1-Glob­al cry­omod­ule will con­tain eight su­per­con­duct­ing cav­i­ties from FNAL, DESY and KEK. The cry­omod­ule will be con­struct­ed by join­ing two half-size cry­omod­ules, each 6 m in length. The mod­ule con­tain­ing four cav­i­ties from FNAL and DESY has been con­struct­ed by INFN. The mod­ule for four KEK cav­i­ties is being mod­i­fied at pre­sent. The as­sem­bly of the cry­omod­ules is sched­uled from Jan­uary 2010, and the op­er­a­tion of the sys­tem is sched­uled from June 2010 at the KEK-STF. In this paper, the con­struc­tion of the S1-Glob­al cry­omod­ule will be pre­sent­ed.