Keyword: radio-frequency
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TUPAK008 Longitudinal Bunch Size Measurements with an RF Deflector at J-PARC LINAC simulation, linac, rfq, DTL 974
 
  • M. Otani, K. Futatsukawa
    KEK, Tsukuba, Japan
  • K. Hirano, A. Miura
    JAEA/J-PARC, Tokai-mura, Japan
  • Y. Liu
    KEK/JAEA, Ibaraki-Ken, Japan
  • T. Maruta
    FRIB, East Lansing, USA
  
  Mea­sure­ment of the lon­gi­tu­di­nal bunch size is im­por­tant for the sta­ble beam op­er­a­tion. Es­pe­cially in a medium en­ergy beam trans­port (MEBT) lo­cated after a ra­dio-fre­quency quadru­pole in J-PARC, it is nec­es­sary to mea­sure the bunch size with min­i­mum set of equip­ment to avoid sub­se­quent emit­tance growth due to space charge. We had pro­posed a lon­gi­tu­di­nal size mea­sure­ment with an rf de­flec­tor nor­mally used for de­flect­ing theμbunch; phase spread is mi­grated to spa­tial one if the ref­er­ence par­ti­cle ar­rives at the de­flec­tor when the volt­age is ris­ing in time and is zero. Then a buncher cav­ity lo­cated up­stream of the de­flec­tor is uti­lized to scan the phase spread to mea­sure the lon­gi­tu­di­nal beam pa­ra­me­ters. In this poster, re­cent mea­sure­ment re­sults are pre­sented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAK008  
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WEPMF037 HF Free Bipolar Electro-Polishing Studies on Niobium SRF Cavities at Cornell With Faraday Technology cavity, SRF, niobium, MMI 2443
 
  • F. Furuta, M. Ge, T. Gruber, J.J. Kaufman, P.N. Koufalis, M. Liepe, J. Sears
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • T.D. Hall, M.E. Inman, R. Radhakrishnan, S.T. Snyder, E.J. Taylor
    Faraday Technology, Inc., Clayton, Ohio, USA
  
  Cor­nell's SRF group and Fara­day Tech­nol­ogy have been col­lab­o­rat­ing on two phase-II SBIR pro­jects. One of them is the de­vel­op­ment and com­mis­sion­ing of a 9-cell scale HF free Bipo­lar Elec­tro-Pol­ish­ing (BEP) sys­tem. Fara­day Tech­nol­ogy has up­graded their 1.3 GHz sin­gle-cell BEP sys­tem for host­ing 9-cell cav­i­ties. Ini­tial com­mis­sion­ing of the new sys­tem was done with a three sin­gle-cell cav­ity string, and high a gra­di­ent of 40MV/m was demon­strated dur­ing the RF tests at Cor­nell. After this suc­cess with the test string, the 9-cell cav­ity was processed with the new sys­tem at Fara­day and RF test was per­formed at Cor­nell. Here we re­port de­tailed re­sults from these 9-cell scale HF free BEP stud­ies.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF037  
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WEPMF042 A Computational Method for More Accurate Measurements of the Surface Resistance in SRF Cavities cavity, SRF, operation, niobium 2458
 
  • J.T. Maniscalco, M. Liepe
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  The prin­ci­pal loss mech­a­nism for su­per­con­duct­ing RF cav­i­ties in nor­mal op­er­a­tion is Ohmic heat­ing due to the mi­crowave sur­face re­sis­tance in the su­per­con­duct­ing sur­face. The typ­i­cal method for cal­cu­lat­ing this field-de­pen­dent sur­face re­sis­tance Rs(H) from RF mea­sure­ments of qual­ity fac­tor Q0 im­plic­itly re­turns a weighted av­er­age of Rs over the sur­face as a func­tion of peak sur­face mag­netic field H, not the true value of Rs as a func­tion of the local mag­ni­tude of H. In this work we pre­sent a com­pu­ta­tional method to con­vert a mea­sured Q0 vs. Hpeak to a more ac­cu­rate Rs vs. Hlocal, given knowl­edge about cav­ity geom­e­try and field dis­tri­b­u­tion.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF042  
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THPAL015 Evaluation of superconducting characteristics on the thin-film structure by NbN and Insulator coatings on pure Nb substrate cavity, embedded, SRF, electromagnetic-fields 3653
 
  • R. Katayama, Y. Iwashita, H. Tongu
    Kyoto ICR, Uji, Kyoto, Japan
  • C.Z. Antoine
    CEA/IRFU, Gif-sur-Yvette, France
  • A. Four
    CEA/DRF/IRFU, Gif-sur-Yvette, France
  • H. Hayano, T. Kubo, T. Saeki
    KEK, Ibaraki, Japan
  • H. Ito
    Sokendai, Ibaraki, Japan
  • R. Ito, T. Nagata
    ULVAC, Inc, Chiba, Japan
  • H. Oikawa
    Utsunomiya University, Utsunomiya, Japan
  
  Funding: The work is supported by JSPS KAKENHI Grant Numbers JP17H04839, JP26600142 and the Collaborative Research Program of ICR Kyoto University (grant 2016-8, 2017-8, 2017-9).
In re­cent years, it is pointed out that the max­i­mum ac­cel­er­at­ing gra­di­ent of a su­per­con­duct­ing RF cav­ity can be pushed up by coat­ing the inner sur­face of cav­ity with a mul­ti­layer thin-film struc­ture that con­sists of al­ter­nate in­su­la­tor and su­per­con­duc­tive lay­ers. In this struc­ture, the prin­ci­pal pa­ra­me­ter that lim­its the per­for­mance of the cav­ity is the crit­i­cal mag­netic field or ef­fec­tive Hc1 at which vor­tices start pen­e­trate into the first su­per­con­duc­tor layer. We made a sam­ple that has NbN/SiO2 thin-film struc­ture on pure Nb sub­strate by DC mag­netron sput­ter­ing method. In this paper, we will re­port the mea­sure­ment re­sults of ef­fec­tive Hc1 of the sam­ple by the third-har­monic volt­age method. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL015  
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