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      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      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      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      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      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      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      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      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      issue date ※ 18 January 2019  
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