Development of a numerical method for analyzing radio-frequency sheaths in arbitrarily oriented magnetic fields

• Project/Area Number: 19K03793
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 14020:Nuclear fusion-related
• Research Institution: Kyushu Institute of Technology
• Principal Investigator: Kohno Haruhiko 九州工業大学, 大学院情報工学研究院, 准教授 (70710846)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Project Status: Completed (Fiscal Year 2021)
• Budget Amount: ¥3,120,000 (Direct Cost: ¥2,400,000、Indirect Cost: ¥720,000); Fiscal Year 2021: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000); Fiscal Year 2020: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000); Fiscal Year 2019: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
• Keywords: シース / 高周波加熱 / 磁場核融合 / 有限要素法 / RFシース / 磁場閉じ込め核融合 / プラズマ物理学 / 数値解析

Outline of Research at the Start

RF（radio frequency）プラズマが導体壁面に接することにより壁面上に生じるRFシースの制御は，高周波波動加熱を採用する核融合炉において重要な課題である．本研究では，これまで研究代表者が考慮してこなかった磁力線と壁面がなす角度が非常に小さい場合に生じる「電子リッチシース」（シース内に存在する電子の数が正イオンの数よりも多い状態）に対しても適用可能な数値計算コードを開発し，シース内の電圧や電力散逸の空間的な分布をより正しく予測することを目指す．

Outline of Final Research Achievements

To improve the predictive accuracy of the radio-frequency (RF) sheaths on the walls of tokamak fusion reactors using RF heating, a two-dimensional microscale RF sheath model with curved plates on both sides of a plasma-filled domain and a finite element scheme based on this model have been developed. Using this numerical code, it was confirmed that the dimensionless electron and ion admittances are nearly independent of the peak-to-peak amplitude of the sinusoidally curved walls over wide ranges of the dimensionless ion cyclotron frequency and RF frequency under a uniform background magnetic field.

Academic Significance and Societal Importance of the Research Achievements

本研究で開発した2次元マイクロスケールRFシースモデルは，磁力線と壁面の接点が存在せず，かつ，電子に対してMaxwell-Boltzmann近似を適用することができる場合に，任意のイオンサイクロトロン周波数および波動の周波数におけるシース挙動の計算を可能にするものである．マクロスケールにおけるシースとプラズマ波の相互作用を計算する際に，シース幅の時間平均値とシース表面の曲率半径が同程度となるような領域が含まれる場合，従来のシース境界条件をそのような領域の境界に課すことはできないが，本研究の成果はその制約が取り除かれるようにシース境界条件を改良するための指針を与えた．

Research Products

• [Int'l Joint Research] Lodestar Research Corporation(米国)
• [Int'l Joint Research] Lodestar Research Corporation(米国)
• [Int'l Joint Research] Lodestar Research Corporation(米国)
• [Journal Article] Radio frequency wave interactions with a plasma sheath: The role of wave and plasma sheath impedances (2019)
  • Author(s): Myra J. R.、Kohno H.
  • Journal Title: Physics of Plasmas Volume: 26 Issue: 5
  • DOI: 10.1063/1.5088343
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Calculation of RF sheath properties from surface wave-fields: a post-processing method (2019)
  • Author(s): Myra J R、Kohno H
  • Journal Title: Plasma Physics and Controlled Fusion Volume: 61 Issue: 9 Pages: 095003-095003
  • DOI: 10.1088/1361-6587/ab2f41
  • Peer Reviewed
• [Presentation] Investigation of a two-dimensional microscale RF sheath model (2021)
  • Author(s): J. R. Myra, H. Kohno
  • Organizer: 63rd Annual Meeting of the APS Division of Plasma Physics
  • Int'l Joint Research
• [Presentation] Development of a non-linear rf sheath benchmark suite (2021)
  • Author(s): J. C. Wright, C. Migliore, J. R. Myra, D. Curreli, D. N. Smithe, T. G. Jenkins, M. L. Stowell, D. L. Green, C. J. Beers, T. Younkin, S. Shiraiwa, N. Bertelli, M. J. Poulos, H. Kohno
  • Organizer: 63rd Annual Meeting of the APS Division of Plasma Physics
  • Int'l Joint Research
• [Presentation] Numerical analysis of the time-dependent radio-frequency sheath behavior using a two-dimensional microscale model (2021)
  • Author(s): H. Kohno, J. R. Myra
  • Organizer: The 30th International Toki Conference on Plasma and Fusion Research
  • Int'l Joint Research