Study of interaction between energetic ions and MHD instabilities in a helical plasma

螺旋等离子体中高能离子与 MHD 不稳定性之间相互作用的研究

• 批准号: 12480127
• 负责人: TOI Kazuo
• 金额: $ 5.89万
• 依托单位: National Institute for Fusion Science
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12480127/
• 关键词: energetic ions; Alfven eigenmodes; helical devices; energetic ion loss; shear Alfven soectrum; core-localized TAEs; helicity induced Alfven eigenmodes (HAEs); Alfven eigenmode spectroscopy; ヘリカルプラズマ; 高速イオン励起; HAE; バースト的モード; 内部輸送障壁; 高速周波数掃引

Characteristics of energetic ion driven MHD modes and their effects on energetic ion transport were studied in neutral-beam-injection (NBI) heated plasmas of the Large Helical Device(LHD). The following new and important results were obtained.(1) Two types of toroidicity-induced Alfven eigenmodes (TAEs) were observed. One is a core-localized TAE(C-TAE) of which TAE gap location is near the plasma center with low magnetic shear. The other is a global TAE of which gap location is in the outer portion of the minor plasma radius. In a few shots, C-TAEs with even and odd parity were simultaneously excited.(2) When the rotational transform at the plasma center exceeds a certain value, the relevant C-TAE has been converted to two global Alfven eigenmodes (GAEs) because the TAE gap is removed. This mode transition from C-TAE to GAE is also observed in a reversed shear configuration of the JT-60U tokamak.(3) In high beta plasmas, high frequency Alfven eigenmodes of which frequency is by eight times higher than the TAE gap frequency were observed. Comparison of the modes with the calculated shear Alfven spectra suggests that the high frequency mode is a helicity-induced Alfven eigenmode (HAE).(4) About 30-50 % of total energetic ions generated by NBI is transiently lost by bursting TAEs with rapid frequency chirping. The bursting TAEs often trigger the formation of internal transport barrier.In the Compact Helical system (CHS) heliotron/torsatron, TAEs were excited by external magnetic perturbations generated by the inserted electrodes into a low density and low temperature plasma without energetic ions. This experiment was carried out as a basic study ofAlfven eigenmodes in a helical plasma.This research project has demonstrated that the Alfven eigenmode spectroscopy using energetic ions and externally applied magnetic perturbations is very useful to study MHD properties of a helical plasma.

在大型螺旋装置（LHD）的中性束注入（NBI）加热等离子体中研究了高能离子驱动MHD模式的特征及其对高能离子输运的影响。获得了以下新的重要结果：(1)观察到了两种类型的环形诱导的阿尔芬本征模(TAE)。一种是核心局域TAE（C-TAE），其TAE间隙位置靠近等离子体中心，具有低磁剪切。另一种是全局 TAE，其间隙位置位于小等离子体半径的外部。在几次发射中，具有偶数和奇数宇称的C-TAE同时被激发。（2）当等离子体中心的旋转变换超过一定值时，相关的C-TAE已转换为两个全局阿尔芬本征模（GAE），因为TAE 间隙被消除。这种从 C-TAE 到 GAE 的模式转变也在 JT-60U 托卡马克的反向剪切配置中观察到。(3) 在高 β 等离子体中，高频阿尔文本征模的频率比 TAE 间隙频率高 8 倍观察到。将这些模式与计算的剪切阿尔文谱进行比较表明，高频模式是螺旋引起的阿尔文本征模式 (HAE)。 (4) NBI 产生的总高能离子中大约 30-50% 会因快速的 TAE 爆发而瞬时损失。频率啁啾。爆炸的TAE通常会触发内部传输势垒的形成。在紧凑螺旋系统（CHS）日射管/扭转管中，TAE被插入电极产生的外部磁扰动激发成没有高能离子的低密度和低温等离子体。该实验是作为螺旋等离子体中阿尔文本征模的基础研究而进行的。该研究项目证明，使用高能离子和外部施加的磁扰动的阿尔文本征模光谱对于研究螺旋等离子体的 MHD 特性非常有用。

项目成果

K.Toi: "Impact of Energetic Ion Driven Global Modes on Toroidal Plasma Confinement"Journal of Plasma and Fusion Research. SERIES 5. 50-56 (2002)

K.Toi：“高能离子驱动全局模式对环形等离子体约束的影响”等离子体与聚变研究杂志。

M.Takechi: "Transition of Toroidal Alfven Eigenmode to Global Alfven Eigenmode in CHS Heliotron/Torsatron"Journal of Plasma and Fusion Research. 78. 1273-1274 (2002)

M.Takechi：“CHS Heliotron/Torsatron 中环形阿尔文本征模式到全局阿尔文本征模式的转变”等离子体与聚变研究杂志。

S.Ohdachi: "High-Speed Tangentially Viewing Soft X-Ray Camera to Study Magnetohydrodynamic Fluctuations in Toroidally Confined Plasma"Reviews of Scientific Instruments. 74. 2136-2143 (2003)

S.Ohdachi：“高速切向观察软 X 射线相机研究环形受限等离子体中的磁流体动力波动”科学仪器评论。

K.Toi: "Energetic ion driven MHD instabilities observed in the heliotron/torsatron devices Compact Helical System and Large Helical Device"Nuclear Fusion. 40・7. 1349-1362 (2000)

K.Toi：“在日射管/扭转管装置紧凑螺旋系统和大型螺旋装置中观察到的高能离子驱动 MHD 不稳定性”核聚变 40・7 (2000)。

M. Takechi: "Transition of Toroidal Alfven Eigenmode to Global Alfven Eigenmode in CHS Heliotron/Torsatron"Jounal of Plasma and Fusion Research. Vol.78. 1273-1274 (2002)

M. Takechi：“CHS Heliotron/Torsatron 中环形阿尔文本征模式到全局阿尔文本征模式的转变”等离子与聚变研究杂志。