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Study on Stabilization of Resistive Wall Modes in RFP's with the use of Rotating Helical Field

Research Project

Project/Area Number13680558
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field プラズマ理工学
Research InstitutionKYOTO INSTITUTE OF TECHNOLOGY

Principal Investigator

MASAMUNE Sadao  Department of Electronics and Information Science, Professor, 工芸学部, 教授 (00157182)

Co-Investigator(Kenkyū-buntansha) IIDA Motomi  Department of Electronics and Information Science, Associate Professor, 工芸学部, 助教授 (80211712)
Project Period (FY) 2001 – 2002
Project Status Completed(Fiscal Year 2002)
Budget Amount *help
¥3,200,000 (Direct Cost : ¥3,200,000)
Fiscal Year 2002 : ¥1,300,000 (Direct Cost : ¥1,300,000)
Fiscal Year 2001 : ¥1,900,000 (Direct Cost : ¥1,900,000)
KeywordsReversed Field Pinch / Tearing Mode (Instability) / External Kink Mode (Instability) / Resistive Wall Modes / Rotating Resonant Helical Field / Mode Rotation / Plasma Rotation / Control of MHD Mode Dynamics / モード安定化 / 磁気閉じ込め核融合 / MHD不安定性 / 回転ヘリカル磁場 / テアリングモード / フィードバック制御
Research Abstract

Three critical MHD issues are to be addressed in the course of development of a reversed field pinch (RFP) fusion reactor. The first one is the internal tearing mode that plays essential roles in the RFP dynamics. In future RFP's inevitably equipped with resistive wall, control or suppression of this mode remains very important. The other two are ideal kink modes that grow with the time scale of field penetration time of the wall. Internal kink modes are unstable for flat current profile, while external kinks become unstable for peaked current profile. In STE-2 RFP [R/a=0.4m/0.1m], efforts have been made to actively control the resistive wall modes with resonant rotating helical field (RHF). The machine has been operated only with a SS vacuum vessel whose field penetration time(tw) is about 0.15 ms.Typical plasma current is 60 kA with discharge duration of 0.7 ms. In low pinch parameter (8) regime where θ=2, core resonant modes (with m=1/n=8,9) growing with time scale of tw are identif … More ied as the resistive wall tearing modes. When operated in high ? Regime (θ>2), m=1/n=3,4 modes grow with time scale of tw, and these are identified as resistive wall kink modes. We have installed pulsed oscillators so that RHF can be applied with constant amplitude during RFP discharge duration. The frequency can be changed from 10 kHz to 30 kHz, with maximum current of 1 kA. The perturbation amplitude of radial component at the edge [Bm] is about 15G (for helical current of 1 kA) at f=1O kHz, while it decreases to 5 G at f=30 kHz. The resonant surface of or interest lies near r/a=0.4, and the perturbation amplitude there is 4 G even at f=25 kHz, which would produce the magnetic island with the width of 10 % of the minor radius. In standard RFP plasmas in STE-2, the dominant m=1/n=8 and lower (n<8) modes are almost locked to the wall, while the higher modes (n>9) sometimes rotate in the opposite direction to the plasma current (CTR direction). When we apply the RHF, the resonant mode tends to rotate in the same direction as the applied RHF. The mode rotation velocity is lower than the applied RHF. In addition to the resonant m=l/n=8 mode, rotation of the neighboring m=l modes and m=0 modes also, are influenced by the RHF. When we increase the parturbation amplitude higher than 0.6% (to as high as 1%), a clear mode rotation can be seen in raw data of magnetic fluctuations. In addition, the pitch parameter θ sometimes tends to increase to higher than 2.5. In this high-θ regime, the resonant mode sometimes rotates at the same velocity as the applied RHF. The time-averaged fluctuation level of the dominant mode reduces by 30-50%. The lower level of core resonant modes indicates less active RFP dynamo, consistent with the higher θ trend. Although the plasma current increases and the discharge resistance decreases, no appreciable improvement is evident in RFP characteristics, which may be due to the lack of sufficient equilibraium control with increased plasma current. The present results have shown the possible use of RHF for the control of tearing modes with resistive wall. Less

Report

(3results)
  • 2002 Annual Research Report   Final Research Report Summary
  • 2001 Annual Research Report

Research Products

(22results)

All Other

All Publications

  • [Publications] 政宗 貞男: "RFPにおけるベータ限界の研究"プラズマ・核融合学会誌. Vol.79, No.2. 152-156 (2003)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] S.Masamune, M.Iida: "Resistive wall mode studies in an RFP with rotating helical field"J. Plasma and Fusion Research Ser.. Vol.5. 509-513 (2003)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] M.Nagata, S.Masamune et al.: "Self-Reversal Phenomena of Toroidal Current by Reversing the External Toroidal Field in Helicity-driven Toroidal Plasmas"Physical Review Letters. Vol.90(in press). (2003)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] S.Maki, S.Masamune et al.: "Diffusion process of fast electrons in a reversed field pinch"Journal of Physical Society of Japan. Vol.71, No.7. 1680-1683 (2002)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] S.Masamune, M.Iida: "Control of RFP dynamics using external helical fields"Mem. Fac. Eng. and Design, Kyoto Institute of Technology. Vol.50. 37-54 (2002)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] S.Maki, S.Masamune et al.: "Formation Mechanism of Reversed Toroidal Current in an RFP"Journal of Physical Society of Japan. Vol.70, No.2. 415-420 (2001)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] S. Masamune: "Recent Progress in High-beta Studies in RFP"J. Plasma and Fusion Research. VOL.79, NO.2. 152-156 (2003)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] S. Masamune, M. Iida: "Resistive Wall Mode Studies in an RFP with Ro1atirgHdical Field"J. Plasma and Fusion Research. Series 5. 509-513 (2003)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] M. Nagata, S. Masamune et al.: "Self-Reversal Phenomena of Toroidal Current by Reversing the External Toroidal Field in Helicity-Driven Toroidal Plasmas Phys."Rev. Lett.. in press. 92 (2003)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] S. Maki, S. Masamune et al: "Diffusion Process of Fast Electrons in a Reversed Field Pinch"J. Phys. Soc. Jpn.. 71,7. 1680-1683 (2002)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] S. Masamune, M. Iida: "Control of RFP Dynamics Using External Helical Fields"Mem. Fac. Eng. Design, Kyoto Institute of Technology. 50. 37-54 (2002)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] S. Maki, S. Masamune et al: "Formation Mechanism of Reversed Toroidal Current in an RFP"J. Phys. Soc. Jpn.. 70,2. 415-420 (2001)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] S. Masamune, M. Iida et al.: "Control of RFP Dynamics with Rotating Helical Fields"Proc. 18th IAEA Fusion Energy Conference. IAEA-F1-CN-77/EXP3/11. (2001)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] 政宗 貞男: "RFPにおけるベータ限界の研究"プラズマ・核融合学会誌. Vol.79,No.2. 152-156 (2003)

    • Related Report
      2002 Annual Research Report
  • [Publications] S.Masamune, M.Iida: "Resistive wall mode studies in an RFP with rotating helical field"J.Plasma and Fusion Research Ser.. Vol.5(in press). (2003)

    • Related Report
      2002 Annual Research Report
  • [Publications] M.Nagata, S.Masamune et al.: "Coaxial helicity injection and n=1 relaxation activity in the HIST spherical torus"Proc.19^<th> LAEA Fusion Energy Conference. IAEA-CN-94-EX. 4-17 (2002)

    • Related Report
      2002 Annual Research Report
  • [Publications] S.Maki, S.Masamune et al.: "Diffusion process of fast electrons in a reversed field pinch"Journal of Physical Society of Japan. Vol.71, No.7. 1680-1683 (2002)

    • Related Report
      2002 Annual Research Report
  • [Publications] S.Masamune, M.Iida: "Control of RFP dynamics using external helical fields"Mem.Fac.Eng.and Design, Kyoto Institute of Technology. Vol.50. 37-54 (2002)

    • Related Report
      2002 Annual Research Report
  • [Publications] S.Masamune, M.Iida et al.: "Control of RFP Dynamics with Rotating Helical Fields"Proc.18^<th> IAEA Fusion Energy Conference LAEA-CN-77/EXP3/11. EXP3/11. (2001)

    • Related Report
      2001 Annual Research Report
  • [Publications] S.Maki, S.Masamune et al.: "Formation Mechanism of Reversed Toroidal Current in an RFP"J.Phys.Soc.Jpn.. Vol.70 No.2. 415-420 (2001)

    • Related Report
      2001 Annual Research Report
  • [Publications] K.Yukimura, S.Masamune: "Shunting Arc As a Pulsed Ion Source for Solid-State Materials for Plasma Based Ion Implantation"Surface and Coatings Technology. 136. 56-59 (2001)

    • Related Report
      2001 Annual Research Report
  • [Publications] 政宗貞男(分担執筆): "電気学会技術報告「プラズマイオン注入法とその応用」"電気学会. 60 (2001)

    • Related Report
      2001 Annual Research Report

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Published : 2001-04-01   Modified : 2016-04-21  

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