Author: Saeki, T.
Paper Title Page
TUPO030 Precise Evaluation of Characteristic of the Multi-layer Thin-film Superconductor Consisting of NbN and Insulator on Pure Nb Substrate 391
TUOP03   use link to see paper's listing under its alternate paper code  
 
  • 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
  
  In re­cent years, it has been pointed out that the max­i­mum ac­cel­er­at­ing gra­di­ent of a su­per­con­duct­ing RF cav­ity can be pushed up by coat­ing the inner sur­face of the cav­ity with a mul­ti­layer thin-film struc­ture that con­sists of al­ter­nat­ing in­su­lat­ing and su­per­con­duct­ing 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 pen­e­trat­ing into the su­per­con­duc­tor layer, and it is pre­dicted to de­pend on the com­bi­na­tion of the film thick­ness. We made sam­ples that have NbN/SiO2 thin-film struc­ture on pure Nb sub­strate with sev­eral thick­nesses of NbN film de­posited using DC mag­netron sput­ter­ing method. Here, we re­port the mea­sure­ment re­sults of ef­fec­tive Hc1 of the NbN sam­ple with a thick­ness of 200 nm by using the third-har­monic volt­age method. In ad­di­tion, we re­port the pre­lim­i­nary re­sults to eval­u­ate the de­pen­dence of the ef­fec­tive Hc1 on the thick­ness of the NbN film in the range 50 nm-200 nm.  
slides icon Slides TUPO030 [0.305 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO030  
About • paper received ※ 18 September 2018       paper accepted ※ 21 September 2018       issue date ※ 18 January 2019  
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TUPO050 Construction of Thin-film Coating System Toward the Realization of Superconducting Multilayered Structure 445
 
  • R. Ito, T. Nagata
    ULVAC, Inc, Chiba, Japan
  • H. Hayano, T. Kubo, T. Saeki
    KEK, Ibaraki, Japan
  • H. Ito
    Sokendai, Ibaraki, Japan
  • Y. Iwashita, R. Katayama
    Kyoto ICR, Uji, Kyoto, Japan
  • H. Oikawa
    Utsunomiya University, Utsunomiya, Japan
  
  Al­though S-I-S (su­per­con­duc­tor-in­su­la­tor-su­per­con­duc­tor) mul­ti­lay­ered struc­ture is ex­pected to in­crease the max­i­mum ac­cel­er­a­tion gra­di­ent of SRF cav­i­ties, in order for it to func­tion in re­al­ity, it is nec­es­sary to de­velop a coat­ing pro­cess­ing that can re­al­ize high pu­rity and qual­ity su­per­con­duct­ing thin-films. We launched the co-sput­ter­ing sys­tem to cre­ate su­per­con­duct­ing alloy thin-films such as Nb3Sn and to re­search how the char­ac­ter­is­tics of them change de­pend­ing on the coat­ing con­di­tions. The de­po­si­tion rate of two el­e­ments was op­ti­mized by ad­just­ing each input power, so we suc­cess­fully ob­tained an alloy thin-film hav­ing ap­pro­pri­ate com­po­si­tion ratio. In ad­di­tion, we de­vel­oped an­other ex­per­i­men­tal equip­ment for coat­ing on the inner sur­face of the 3GHz TESLA type small cav­i­ties. A cylin­dri­cal shape Nb in which some per­ma­nent mag­nets are in­serted was adopted as the sput­ter­ing tar­get. Glow dis­charge of the tar­get was con­firmed, and the in­ner-sput­ter­ing test was con­ducted. This pre­sen­ta­tion re­ports the spec­i­fi­ca­tions of the two sput­ter­ing ap­pa­ra­tuses and the re­sults of the coat­ing test.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO050  
About • paper received ※ 18 September 2018       paper accepted ※ 08 October 2018       issue date ※ 18 January 2019  
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TUPO065 Improvement of Cavity Performance by Nitrogen Doping at KEK 480
SPWR019   use link to see paper's listing under its alternate paper code  
 
  • T. Okada, Y. Hori, E. Kako, T. Konomi, H. Sakai, K. Umemori, Y. Yamamoto
    Sokendai, Ibaraki, Japan
  • T. Dohmae, Y. Hori, E. Kako, T. Konomi, T. Saeki, T. Saeki, H. Sakai, K. Umemori, Y. Yamamoto
    KEK, Ibaraki, Japan
  • J. Kamiya
    JAEA/J-PARC, Tokai-mura, Japan
  • S. Kurosawa, K. Takeishi
    JAEA, Ibaraki-ken, Japan
  
  Ni­tro­gen dop­ing ex­per­i­ments in sin­gle-cell and 3-cell nio­bium cav­i­ties were car­ried out at KEK. After an­neal­ing at 800 deg C for 3 hours, pure ni­tro­gen gas with a pres­sure of 3 Pa for 20 min­utes and 3 min­utes were in­tro­duced for dop­ing in a fur­nace in J-PARC, re­spec­tively. Re­mov­ing sur­face in 5 um and 20 um by elec­trop­o­l­ish­ing were per­formed prior to the ver­ti­cal tests, re­spec­tively. In­creases of a qual­ity fac­tor at 2K and re­duc­tion of the BCS re­sis­tance with re­spect to an ac­cel­er­at­ing gra­di­ent were ob­served in both cav­i­ties.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO065  
About • paper received ※ 12 September 2018       paper accepted ※ 21 September 2018       issue date ※ 18 January 2019  
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TUPO066 Lower Critical Field Measurement of Thin Film Superconductor 484
 
  • H. Ito
    Sokendai, Ibaraki, 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
  • R. Ito, T. Nagata
    ULVAC, Inc, Chiba, Japan
  • Y. Iwashita, R. Katayama, H. Tongu
    Kyoto ICR, Uji, Kyoto, Japan
  • H. Oikawa
    Utsunomiya University, Utsunomiya, Japan
  
  Funding: The work is supported by Japan Society for the Promotion of Science Grant-in-Aid for Young Scientist (A) No.17H04839.
Su­per­con­duct­ing thin film is the promis­ing tech­nol­ogy to in­crease the per­for­mance of SRF cav­i­ties. The lower crit­i­cal field Hc1, which is one of the im­por­tant phys­i­cal pa­ra­me­ters char­ac­ter­iz­ing a su­per­con­duct­ing ma­te­r­ial, will be en­hanced by coat­ing Nb with thin film su­per­con­duc­tor such as NbN. To in­ves­ti­gate the Hc1, we de­vel­oped the Hc1 mea­sure­ment sys­tem using the third har­monic re­sponse of ap­plied AC mag­netic field. The mea­sure­ment sys­tem con­sists of he­lium cryo­stat with two of GM re­frig­er­a­tors, sam­ple Cu stage, so­le­noid coil Cu mount, so­le­noid coil, tem­per­a­ture sen­sors, and liq­uid he­lium level meter. AC mag­netic field is pro­duced by a coil which is dri­ven by func­tion gen­er­a­tor and power am­pli­fier at around 1 kHz. In order to con­trol the tem­per­a­ture of the sam­ple, we in­stalled heaters and ther­mal an­chors which could be moved by the motor. By this tem­per­a­ture con­trol the sam­ple state can be eas­ily trans­ferred from Meiss­ner state to mixed state. So that the mea­sure­ment is re­peated for var­i­ous ap­plied mag­netic field, and the tran­si­tion curve can be made. In this re­port, mea­sure­ment re­sult of the bulk Nb sam­ple and NbN-SiO2 mul­ti­layer thin film sam­ple will be dis­cussed. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO066  
About • paper received ※ 19 September 2018       paper accepted ※ 20 September 2018       issue date ※ 18 January 2019  
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TUPO067 Study on New Removal Thickness Distribution Improvement Methods for Niobium 9-cell Cavity Vertical Electropolishing with Ninja Cathode 488
 
  • K.N. Nii, V. Chouhan, Y.I. Ida, T.Y. Yamaguchi
    MGH, Hyogo-ken, Japan
  • H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
    KEK, Ibaraki, Japan
  
  Marui Gal­va­niz­ing Co., Ltd. has been de­vel­op­ing nio­bium 9-cell cav­ity ver­ti­cal elec­trop­o­l­ish­ing (VEP) tech­nolo­gies with Ninja cath­ode in col­lab­o­ra­tion with KEK. Con­ven­tional 9-cell cav­ity VEP had a se­ri­ous prob­lem, which was asym­me­try of re­moval thick­ness dis­tri­b­u­tion. Usu­ally re­moval thick­ness of upper side be­came larger than lower side in case of both in-cell and in­ter-cell. So far, as one so­lu­tion, we pro­posed bub­ble dif­fu­sion pre­ven­tion method and proved it was ef­fec­tive for uni­form re­moval. This time, as other new so­lu­tion, we tried cav­ity flip up­side down and Ninja cath­ode mask­ing VEP meth­ods. In this ar­ti­cle we will re­port the pur­pose, in­ten­tion and VEP ex­per­i­ment re­sult of these meth­ods.  
poster icon Poster TUPO067 [0.858 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO067  
About • paper received ※ 13 September 2018       paper accepted ※ 21 September 2018       issue date ※ 18 January 2019  
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TUPO068 Vertical Electropolishing of 1.3 GHz Niobium Nine-cell SRF Cavity: Bulk Removal and RF Performance 491
 
  • V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi
    MGH, Hyogo-ken, Japan
  • H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
    KEK, Ibaraki, Japan
  • H. Ito
    Sokendai, Ibaraki, Japan
  • H. Oikawa
    Utsunomiya University, Utsunomiya, Japan
  
  Ver­ti­cal elec­trop­o­l­ish­ing (VEP) tech­nique have been suc­cess­fully de­vel­oped for 1.3 GHz nio­bium (Nb) sin­gle cell cav­ity to achieve a smooth sur­face with uni­form re­moval and bet­ter RF per­for­mance as achieved after hor­i­zon­tal EP (HEP) process. VEP pa­ra­me­ters for 1.3 GHz Nb nine-cell cav­i­ties are being stud­ied using a nine-cell coupon cav­ity and our unique Ninja cath­ode. The in­ves­ti­gated VEP pa­ra­me­ters hereto­fore were ap­plied on a 1.3 GHz Tesla shape nine-cell su­per­con­duct­ing RF cav­ity for bulk re­moval of 100 µm fol­lowed by fine re­moval of 20 and 10 µm. The in­te­rior sur­face was found to be smooth and shiny after the VEP process. Our re­cently de­vel­oped dual flow tech­nique, in which the EP acid is flown sep­a­rately in the Ninja cath­ode hous­ing and cav­ity, yielded lower asym­me­try in re­moval along the cav­ity length. The cav­ity was tested in a ver­ti­cal cryo­stat after the final VEP process. The cav­ity achieved 28.3 MV/m at Q0 value of 6.7x109. The cav­ity per­for­mance was al­most the same as in the base­line ver­ti­cal test per­formed after the HEP process.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO068  
About • paper received ※ 13 September 2018       paper accepted ※ 19 September 2018       issue date ※ 18 January 2019  
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TUPO069 Development of Vertical Electropolishing Facility for Nb 9-cell Cavity (2) 494
 
  • Y.I. Ida, V. Chouhan, K.N. Nii
    MGH, Hyogo-ken, Japan
  • T. Akabori, G.M. Mitoya, K. Miyano
    HKK, Morioka, Japan
  • Y. Anetai, F. Takahashi
    WING. Co.Ltd, Iwate-ken, Japan
  • H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
    KEK, Ibaraki, Japan
  
  In IPAC18 (Van­cou­ver, Canada), we re­ported our first step of de­vel­op­ment of nio­bium 9-cell cav­ity ver­ti­cal elec­trop­o­l­ish­ing (VEP) fa­cil­ity. In this ar­ti­cle, we will re­port the method, sys­tem for uni­form pol­ish­ing for nio­bium 9-cell cav­i­ties and the cur­rent sit­u­a­tion of our 9-cell cav­ity VEP fa­cil­ity (The re­sult of pol­ish­ing uni­for­mity, ver­ti­cal test will be pre­sented in other posters of this con­fer­ence). In ad­di­tion, we will show the movie of ex­per­i­ments of VEP-3 with Ninja cath­ode. This fa­cil­ity aims not only for test VEP but also for mass pro­duc­tion and long-time op­er­a­tion.  
poster icon Poster TUPO069 [0.316 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO069  
About • paper received ※ 13 September 2018       paper accepted ※ 19 September 2018       issue date ※ 18 January 2019  
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TUPO071 Study on Nitrogen Infusion for 1.3 GHz SRF Cavities Using J-PARC Furnace 499
 
  • K. Umemori, T. Dohmae, M. Egi, Y. Hori, E. Kako, T. Konomi, S. Michizono, T. Saeki, H. Sakai, Y. Yamamoto
    KEK, Ibaraki, Japan
  • J. Kamiya
    JAEA/J-PARC, Tokai-mura, Japan
  • S. Kurosawa, K. Takeishi
    JAEA, Ibaraki-ken, Japan
  • T. Okada
    Sokendai, Ibaraki, Japan
  
  Ni­tro­gen in­fu­sion (N-in­fu­sion) is new sur­face treat­ment tech­nique for nio­bium SRF (Su­per­con­duct­ing RF) cav­i­ties. After cool­ing down from 800 de­gree C heat treat­ment, a vac­uum fur­nace and cav­i­ties are kept 120 de­gree C, 48 hours with about 3 Pa Ni­tro­gen. Im­prove­ment of Q-value and ac­cel­er­at­ing gra­di­ent is ex­pected. We used J-PARC fur­nace, since N-in­fu­sion pro­ce­dure re­quires clean vac­uum fur­nace. It has a cryo-pump and turbo mol­e­c­u­lar pumps and its vac­uum sys­tem is oil-free sys­tem. Six times of N-in­fu­sion tests were car­ried out, while chang­ing vac­uum con­di­tion, N-in­fu­sion tem­per­a­ture, Ni­tro­gen pres­sure, nio­bium ma­te­r­ial and so on. Nio­bium caps were mounted on cav­i­ties to avoid con­t­a­m­i­na­tions on inner sur­faces. Some of tri­als were suc­cess­ful and ver­ti­cal test re­sults showed im­prove­ment of Q-val­ues and ac­cel­er­at­ing gra­di­ent. How­ever, some of them were not. Most of bad cases showed degra­da­tion of Q-val­ues above 5 MV/m. De­tails of heat treat­ment pro­ce­dure in­clud­ing N-in­fu­sion and ver­ti­cal test re­sults are shown in this pre­sen­ta­tion.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO071  
About • paper received ※ 20 September 2018       paper accepted ※ 20 September 2018       issue date ※ 18 January 2019  
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TUPO076 An Innovative Nb3Sn Film Approach and Its Potential for SRF Applications 513
 
  • E.Z. Barzi, D. Turrioni, C. Ciaccia
    Fermilab, Batavia, Illinois, USA
  • G.V. Eremeev, R.L. Geng, R.A. Rimmer, A-M. Valente-Feliciano
    JLab, Newport News, Virginia, USA
  • S. Falletta
    Politecnico di Torino, Torino, Italy
  • H. Hayano, T. Saeki
    KEK, Ibaraki, Japan
  • H. Ito
    Sokendai, Ibaraki, Japan
  • A. Kikuchi
    NIMS, Tsukuba, Ibaraki, Japan
  
  Funding: Work supported by U.S. DOE contract No. DE-AC02-07CH11359
A novel elec­tro-chem­i­cal tech­nique to pro­duce Nb3Sn films on Nb sub­strates was de­vel­oped and op­ti­mized at Fer­mi­lab. The Nb3Sn phase is ob­tained in a two-elec­trode cell, by elec­trode­po­si­tion from aque­ous so­lu­tions of Sn lay­ers and Cu in­ter­me­di­ate lay­ers onto Nb sub­strates. Sub­se­quent ther­mal treat­ments in inert at­mos­phere are re­al­ized at a max­i­mum tem­per­a­ture of 700°C to ob­tain the Nb3Sn su­per­con­duct­ing phase. Sev­eral su­per­con­duct-ing Nb3Sn films were ob­tained on Nb sub­strates by study-ing and op­ti­miz­ing most pa­ra­me­ters of the elec­tro-plat­ing process. Sam­ples were char­ac­ter­ized at Fer­mi­lab, NIMS, KEK and JLAB, in­clud­ing EPMA analy­ses, DC and in-duc­tive tests of crit­i­cal tem­per­a­ture Tc0, and lower crit­i­cal field Hc1(4.2 K) by SQUID. In par­al­lel to sam­ple de­vel-op­ment and fab­ri­ca­tion at FNAL, at JLAB and KEK ef­fort was put into etch­ing and elec­tro-pol­ish­ing tech­niques ad­e­quate to re­move the Cu and bronze phases from the sam­ples’ outer sur­face. This is nec­es­sary prior to meas-ure­ments at JLAB of the sur­face im­ped­ance of flat sam-ples in a setup that make use of an RF host cav­ity. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO076  
About • paper received ※ 21 September 2018       paper accepted ※ 08 October 2018       issue date ※ 18 January 2019  
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