Bremsstrahlung X-ray measurement of energetic electrons at the current-drive by multiple harmonic electron cyclotron waves

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K03510
• 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 University
• Principal Investigator: Onchi Takumi 九州大学, 応用力学研究所, 助教 (00727216)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 球状トカマク / 電子サイクロトロン加熱 / 制動放射

Outline of Final Research Achievements

In spherical tokamaks, owing to the strong gradient of toroidal field, multiple harmonic resonance layers for electron cyclotron (EC) waves can coexist in plasma confinement region. EC waves resonate with energetic electrons in broad area due to the relativistic Doppler effect. In this research, a two-dimensional hard X-ray (HXR) detector was developed to observe spatial profile of bremsstrahlung radiation from energetic electrons. In the experiment in the QUEST spherical tokamak, HXR patterns, which is attributed to energetic electrons moving the current-drive side, have been observed. Energetic trapped-electrons hit the tungsten limiter so that the strong HXR is also observed from that.

Free Research Field

核融合学

Academic Significance and Societal Importance of the Research Achievements

近年発展が顕著な二次元X線検出器（検出エネルギー200 keV以下）を導入し，球状トカマクに適用して観測データを得た．特に電流を担う高エネルギー電子群によるX線の空間分布観測は新規性があると考えられる．金属構造に対する高エネルギー電子の衝突による放射強度が高く，またプラズマ内部からの制度放射と重なって検出されるため，Ｘ線空間分布計測の難易度が高いことが実験的に明らかになった．これらの結果は今後の計測器開発に重要な知見であると考えられる．