Author: Umemori, K.
Paper Title Page
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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TUPO070 Design and Commissioning of KEK New Vacuum Furnace for SRF Cavity Development 496
 
  • K. Umemori, M. Egi, E. Kako, T. Konomi, S. Michizono, H. Sakai
    KEK, Ibaraki, Japan
  
  Re­cently new tech­niques such as Ni­tro­gen-dop­ing and Ni­tro­gen-in­fu­sion have been de­vel­oped to im­prove per­for­mance of SRF (Su­per­con­duct­ing RF) cav­i­ties. We pur­chased a new vac­uum fur­nace, which is key to re­al­ize these tech­niques. Clean­ness of the fur­nace is most im­por­tant issue. The fur­nace has a cryo-pump and whole of vac­uum sys­tem is oil-free sys­tem. Tar­get vac­uum level after cool­ing down is 1x10-6 Pa. Heater, re­flec­tors and sup­port table were made from Molyb­de­num to avoid con­t­a­m­i­na­tion dur­ing heat treat­ment. Metal gas­kets are used for all vac­uum seals, ex­cept big doors. Max­i­mum op­er­a­tion tem­per­a­ture is 1150 de­gree C. Size is around 1 m di­am­e­ter and 2m long for a 1.3 GHz 9-cell cav­ity. En­trance of fur­nace is cov­ered by a clean booth. The fur­nace was fab­ri­cated, as­sem­bled at KEK COI build­ing and com­mis­sioned this year. After sev­eral burn­ing runs, tar­get vac­uum pres­sure was achieved after cool­ing down to room tem­per­a­ture. De­sign of the fur­nace and per­for­mance dur­ing com­mis­sion­ing runs are pre­sented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO070  
About • paper received ※ 19 September 2018       paper accepted ※ 21 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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TUPO072 First Trial of the In-situ Nitrogen Infusion at KEK 503
 
  • T. Konomi, T. Dohmae, E. Kako, S. Michizono, H. Sakai, K. Umemori
    KEK, Ibaraki, Japan
  • T. Okada
    Sokendai, Ibaraki, Japan
  
  The ni­tro­gen in­fu­sion is the new sur­face treat­ment tech­nique for im­prov­ing the RF loss and the max­i­mum ac­cel­er­at­ing gra­di­ent of su­per­con­duct­ing cav­ity. In this process, it is im­por­tant to be car­ried out con­tin­u­ously both the 800 C an­neal­ing in vac­uum and 120 C ni­tro­gen in­fu­sion with­out ex­po­sure to the at­mos­phere. The an­neal­ing serves ac­ti­va­tion process by re­mov­ing the oxide layer. The in-situ ni­tro­gen in­fu­sion sys­tem was pre­pared to in­ves­ti­gate whether ni­tro­gen in­fu­sion ef­fect or some­thing changes hap­pen in the case of ap­ply­ing ni­tro­gen in­fu­sion tech­nique with­out re­mov­ing the oxide layer. It can only in­tro­duce ni­tro­gen into a cav­ity dur­ing 120 C low tem­per­a­ture bak­ing and trans­port a cav­ity to the ver­ti­cal test sys­tem with­out ex­po­sure to the at­mos­phere. We tried to in­fuse ni­tro­gen to a sin­gle cell by keep­ing 120 C and 48 hours with 3 Pa ni­tro­gen. The cav­ity was an­nealed in an­other fur­nace and ap­plied high pres­sure rins­ing be­fore ni­tro­gen in­fu­sion. The ver­ti­cal test re­sult was same Q as the nor­mal 120 C bak­ing with­out ni­tro­gen. It sug­gests that oxide layer pre­vents in­fu­sion of ni­tro­gen. In this poster, the in-situ ni­tro­gen in­fu­sion sys­tem and ver­ti­cal test re­sults will be re­ported.  
poster icon Poster TUPO072 [4.653 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO072  
About • paper received ※ 12 September 2018       paper accepted ※ 21 September 2018       issue date ※ 18 January 2019  
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TUPO073 Niobium Sample Analysis for Nitrogen Infusion and Doping 506
 
  • T. Konomi, E. Kako, S. Michizono, H. Sakai, K. Umemori
    KEK, Ibaraki, Japan
  • T. Nagata
    ULVAC, Inc., Tsukuba, Japan
  • T. Nojima
    Tohoku University, Sendai, Japan
  
  KEK has been in­ves­ti­gat­ing the bet­ter con­di­tions of the heat treat­ment in ni­tro­gen, which are called as ni­tro­gen dop­ing and ni­tro­gen in­fu­sion. We have tried to un­der­stand the high gra­di­ent per­for­mance of the cav­ity from the analy­ses of sam­ples which were pre­pared in the same con­di­tions for the cav­ity. The main tools are D-SIMS for the depth pro­file of the el­e­men­tal con­cen­tra­tion, XPS for com­po­si­tion analy­sis and SQUID mag­ne­tom­e­try for the crit­i­cal DC mag­netic field mea­sure­ment. The dif­fer­ence in the depth pro­files of the ni­tro­gen, car­bon and oxy­gen be­tween the heat treat­ment con­di­tions was ob­served in vac­uum and fur­nace tem­per­a­ture of ni­tro­gen in­fu­sion by D-SIMS and XPS. Such a dif­fer­ence cor­re­lates with the vor­tex pen­e­tra­tion field mea­sured by SQUID. In par­tic­u­lar, that of ni­tro­gen dop­ing sam­ple was greatly de­graded, while that of ni­tro­gen in­fu­sion sam­ple was slightly im­proved. The ten­dency is sim­i­lar to the RF high gra­di­ent test re­sults. De­tails of the sam­ple analy­sis are shown in this pre­sen­ta­tion.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO073  
About • paper received ※ 18 September 2018       paper accepted ※ 21 September 2018       issue date ※ 18 January 2019  
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TUPO074 Design and Fabrication of KEK Superconducting RF Gun #2 510
 
  • T. Konomi, Y. Honda, E. Kako, Y. Kobayashi, S. Michizono, T. Miyajima, H. Sakai, K. Umemori, S. Yamaguchi, M. Yamamoto
    KEK, Ibaraki, Japan
  
  Su­per­con­duct­ing RF gun can re­al­ize high ac­cel­er­a­tion volt­age and high beam rep­e­ti­tion. KEK has been de­vel­op­ing the 1.3 GHz el­lip­ti­cal type 1.5 cell su­per­con­duct­ing RF gun to in­ves­ti­gate fun­da­men­tal per­for­mance. A sur­face clean­ing method and tools are de­vel­oped by using KEK SR­F­GUN #1 and high sur­face peak gra­di­ent 75 MV/m was achieved with­out field emis­sion. SR­F­GUN #2 which equips the he­lium jacket and can be op­er­ated with elec­tron beam was de­signed based on the SR­F­GUN #1. It can be op­er­ated with trans­mit type pho­to­cath­ode which in­clude su­per­con­duct­ing trans­par­ent ma­te­r­ial. The cath­ode plug is cooled by ther­mal con­duct­ing from the 2 K he­lium jacket and pho­to­cath­ode will be kept around 2K to main­tain su­per­con­duc­tiv­ity. Bulk nio­bium pho­to­cath­ode plug and sub­strate will used for the fun­da­men­tal per­for­mance test. In par­al­lel, the pho­to­cath­ode de­po­si­tion cham­ber for multi-al­kali pho­to­cath­ode will be pre­pared.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO074  
About • paper received ※ 12 September 2018       paper accepted ※ 20 September 2018       issue date ※ 18 January 2019  
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WE2A03 Construction Status of the Superconducting Linac at RIKEN RIBF 620
 
  • N. Sakamoto, H. Imao, O. Kamigaito, K. Kusaka, H. Okuno, K. Ozeki, K. Suda, T. Watanabe, Y. Watanabe, K. Yamada
    RIKEN Nishina Center, Wako, Japan
  • H. Hara, T. Yanagisawa
    MHI, Hiroshima, Japan
  • E. Kako, H. Nakai, H. Sakai, K. Umemori
    KEK, Ibaraki, Japan
  • A. Miyamoto, K. Sennyu
    MHI-MS, Kobe, Japan
  
  An up­grade pro­ject of the RIKEN Heavy-Ion Linac, RILAC, is under going, which aims at the fur­ther in­ves­ti­ga­tion of the su­per-heavy el­e­ments and pro­duc­tion of ra­dioac­tive iso­topes for med­ical ap­pli­ca­tions. In this pro­ject, a new su­per­con­duct­ing ECR ion source and su­per­con­duct­ing RF (SRF) booster linac are being de­vel­oped and con­structed. The SRF linac con­sists of 10 quar­ter-wave­length res­onator op­er­ated at 73 MHz, that are con­tained in three cry­omod­ules. The con­struc­tion sta­tus, in­clud­ing the first ver­ti­cal test re­sults, will be given in this paper.  
slides icon Slides WE2A03 [23.169 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-WE2A03  
About • paper received ※ 14 September 2018       paper accepted ※ 17 October 2018       issue date ※ 18 January 2019  
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THPO002 Investigation of SRF Elliptical Cavities Made by New Nb Materials in KEK 676
 
  • T. Dohmae, K. Umemori, Y. Watanabe, M. Yamanaka
    KEK, Ibaraki, Japan
  • T. Okada
    Sokendai, Ibaraki, Japan
  
  Cost re­duc­tion for cav­ity fab­ri­ca­tion is cur­rently main issue to re­al­ize in­ter­na­tional lin­ear col­lider. Cav­ity fab­ri­ca­tion fa­cil­ity (CFF) in KEK is ap­proach­ing this issue from a point of view of ma­te­ri­als for cav­i­ties. CFF had fab­ri­cated SRF el­lip­ti­cal cav­i­ties made by two types of nio­bium; one is high tan­ta­lum con­tained and low RRR (< 100) fine grain nio­bium, and the other is high tan­ta­lum con­tained and RRR < 300 large grain (LG) nio­bium. For­mer was melted two times (nor­mally five times) which re­sults RRR re­cov­ery up to around 300, and used for cell parts. Two 3-cell cav­i­ties were fab­ri­cated for each ma­te­r­ial re­spec­tively and ver­ti­cal tested. One of these cav­ity made by LG achieved ac­cel­er­a­tor gra­di­ents of more than 40 MV/m. In this re­port, cav­ity ma­te­ri­als and ver­ti­cal test re­sults are pre­sented in de­tail.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-THPO002  
About • paper received ※ 12 September 2018       paper accepted ※ 20 September 2018       issue date ※ 18 January 2019  
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THPO008 Long-term 0peration with Beam and Cavity Performance Degradation in Compact-ERL Main Linac at KEK 695
 
  • H. Sakai, T. Furuya, E. Kako, T. Konomi, T. Miura, F. Qiu, K. Umemori
    KEK, Ibaraki, Japan
  
  We de­vel­oped ERL main linac cry­omod­ule for Com­pact ERL (cERL) in KEK. The mod­ule con­sists of two 9-cell 1.3 GHz su­per­con­duct­ing cav­i­ties. After con­struc­tion of cERL re­cir­cu­la­tion loop, beam op­er­a­tion was started in 2013 Dec. First elec­tron beam of 20 MeV suc­cess­fully passed the main linac cav­i­ties. Beam cur­rent in­creased step by step and cur­rently reached to 1mA (CW). En­ergy re­cov­ery has suc­cess­fully achieved. How­ever, field emis­sion was one of the prob­lems for long term op­er­a­tion. There­fore, the per­for­mance of the SRF cav­i­ties through long term beam op­er­a­tion has been in­ves­ti­gated. In this paper, we ex­press the mea­sure­ment of the cav­ity per­for­mances and its degra­da­tion dur­ing long term beam op­er­a­tion. We also de­scribed the de­tails of the cav­ity per­for­mance degra­da­tion and some trial for the cav­ity per­for­mance re­cov­ery.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-THPO008  
About • paper received ※ 11 September 2018       paper accepted ※ 20 September 2018       issue date ※ 18 January 2019  
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