Study on physics mechanism of vacuum discharge toward electrostatic accelerator of the energy higher than 1 MeV

2007 Fiscal Year Final Research Report Summary

• Project/Area Number: 18560807
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Nuclear engineering
• Research Institution: Japan Atomic Energy Agency
• Principal Investigator: INOUE Takashi Japan Atomic Energy Agency, Fusion R & D Directorate, Principal Research Engineer (00354639)
• Co-Investigator(Kenkyū-buntansha): WATANABE Kazuhiro Japan Atomic Energy Agency, Fusion R & D Directorate, Principal Research Engineer (90354638) ; KASHIWAGI Mieko Japan Atomic Energy Agency, Fusion R & D Directorate, Research Engineer (50354642) ; UMEDA Naotaka Japan Atomic Energy Agency, Fusion R & D Directorate, Scientist (40354659)
• Project Period (FY): 2006 – 2007
• Keywords: Accelerator / Plasma / Vacuum discharge / Vacuum insulation / Clump theory / Triple junction / Organic insulation material

Research Abstract

Using a MeV accelerainr being developed for neutral beam injector ofITER, experiments on vacuum insulation have been carried out to establish physics and engineering basis toward general purpose electrostatic accelerator of the beam energy more than 1MeV.
● A large bore FRP (glass fiber reinforced epoxy) insulator was tested its applicability toward the accelerator of more than 1MeV. Prevention of surface flashover was demonstrated by reducing the stress at cathode side triple junction (interface of vacuum metal and dielectric insulator) below 1kV/mm.
● Data base on vacuum insulation was established for a range of vacuum gap width in real accelerator geometries.
(1) Achievable voltage as a function of gap length seems to follow to Clump theory
(2) Achievable voltages in the real accelerator geometries are about a half of that achieved with a quasi-ideal Rogowsky electrode, even the vacuum gap length were the same in both cases.
(3) The deterioration of voltage holding in the real accelerator geometries are probably due to local electric field concentration in the accelerators, such as corner of the grid support or junction between grids and grid support structures.
● Extrapolation of achievable voltage in the accelerator at various gas pressure suggests possibility of vacuum and glow discharge prevention even the voltage was 2MV by maintaining the pressure at 0.02Pa, though necessary vacuum gap length would be as long as 2m.

Research Products

• [Journal Article] ITER NBI用SINGAP-MAMuG加速器の性能比較試験 (2009)
  • Author(s): 谷口正樹, 柏木美恵子, 梅田尚孝, 大楽正幸, 渡邉和弘, 井上多加志, Hubert de Esch, Lennart Svensson
  • Journal Title: 日本原子力研究開発機構研究開発報告書JAEA-Research 2008-121 Pages: 1-26
  • Description: 「研究成果報告書概要(和文)」より
  • Peer Reviewed
• [Journal Article] Development of 1MeV accelerator and HV bushing at JAEA toward ITER Neutral Beam system(web公開済) (2009)
  • Author(s): N. Umeda, M. Taniguchi, M. Kashiwagi, M. Dairaku, M. Hanada, H. Tobari, K. Watanabe, K. Sakamoto, T. Inoue
  • Journal Title: Fusion Engineering and Design 84 Pages: 1875-1880
  • Description: 「研究成果報告書概要(和文)」より
  • Peer Reviewed
• [Journal Article] High energy, high current accelerator development for ITER NBI at JADA(web公開済) (2009)
  • Author(s): M. Kashiwagi, M. Taniguchi, M. Dairaku, H. P. L. de Esch, L. R. Grisham, L. Svensson, H. Tobari, N. Umeda, K. Watanabe, K. Sakamoto, T. Inoue
  • Journal Title: Nuclear Fusion 49(印刷中)
  • Description: 「研究成果報告書概要(和文)」より
  • Peer Reviewed
• [Journal Article] H. P. L. de Esch, L. Svensson (2009)
  • Author(s): M. Taniguchi, M. Kashiwagi, N. Umeda, M. Dairaku, K Watanabe, T. Inoue
  • Journal Title: Japan Atomic Energy Agency Research Report JAEA-Research 2008-121 Pages: 1-26
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Development of 1MeV accelerator and HV bushing at JAEA toward ITER Neutral Beam system (2009)
  • Author(s): N. Umeda, M. Taniguchi, M. Kashiwagi, M. Dairaku, M. Hanada, H. Tobari, K. Watanabe, K. Sakamoto, T. Inoue
  • Journal Title: Fusion Engineering Design (in electronic journal))
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] High energy, high current accelerator development for ITER NBI at JADA (2009)
  • Author(s): M. Kashiwagi, M. Taniguchi, M. Dairaku, H. P. L. de Esch, L. R. Grisham, L. Svensson, H. Tobari, N. Umeda, K. Watanabe, K. Sakamoto, T. Inoue
  • Journal Title: Nuclear Fusion (in electronic journal)
  • Description: 「研究成果報告書概要(欧文)」より
• [Presentation] High energy, high current accelerator development for ITER NBI at JADA (2008)
  • Author(s): M. Kashiwagi, M. Taniguchi, M. Dairaku, H. P. L. de Esch, L. R. Grisham, L. Svensson, H. Tobari, N. Umeda, K. Watanabe, K. Sakamoto, T. Inoue
  • Organizer: 22nd IAEA Fusion Energy Conference
  • Place of Presentation: ジュネーブ(スイス)
  • Year and Date: 20081013-20081018
  • Description: 「研究成果報告書概要(和文)」より
• [Presentation] High energy, high current accelerator development for ITER NBI at JADA (2008)
  • Author(s): M. Kashiwagi, M. Taniguchi, M. Dairaku, H. P. L. de Esch, L. R. Grisham, L. Svensson, H. Tobari, N. Umeda, K. Watanabe, K. Sakamoto, T. Inoue
  • Organizer: 22nd LAEA Fusion Energy Conference
  • Place of Presentation: Geneva, Switzerland
  • Year and Date: 20081013-20081018
  • Description: 「研究成果報告書概要(欧文)」より
• [Presentation] Development of 1MeV H^-ion accelerator at JAEA for ITER NB (2008)
  • Author(s): 谷口正樹, 柏木美恵子, Hubertde Esch, Svensson Lennart, 梅田尚孝, 渡邉和弘, 戸張博之, 大楽正幸, 坂本慶司, 井上多加志
  • Organizer: 1st International conference on negative ions, beams and sources
  • Place of Presentation: エクスアンプロバンス(フランス)
  • Year and Date: 2008-09-10
  • Description: 「研究成果報告書概要(和文)」より
• [Presentation] Development of 1MeV H^- ion accelerator at JAEA for ITER NB (2008)
  • Author(s): M. Taniguchi, M. Kashiwagi, H. P. L. de Esch, L. Svensson, N. Umeda, K. Watanabe, H. Tobari, M. Dairaku, K. Sakamoto, T. Inoue
  • Organizer: 1st International conference on negative ions, beams and sources
  • Place of Presentation: Aix en Provence, France
  • Year and Date: 2008-09-10
  • Description: 「研究成果報告書概要(欧文)」より
• [Remarks] 「研究成果報告書概要(和文)」より
  • URL: http://www.naka.jaea.go.jp/nbi/NBI_Home.html