EAST托卡马克中性束快离子压强剖面演化的模拟研究

A lot of experimental results indicate that the transport level of the fast ions from neutral beam injection (NBI) in tokamak plasmas is usually as small as the neoclassical level. The “anomalous” transport of fast ions is usually due to various MHD instabilities, which include the fishbone modes, the sawtooth oscillations, and the various Alfvén eigenmodes. This project plans to investigate the fast ions transport induced by the Alfvén eigenmodes. By using a kinetic/MHD hybrid code, we investigate the time evolution of the pressure profile of fast ions on the slowing down time scale of the fast ions. The simulation will include the nonlinear interaction between the Alfvén eigenmodes and the fast ions, the collisions of the fast ions with background plasmas, and the source and loss of the fast ions. The results will be compared with the measurements of the fast ions D-alpha diagnostic (FIDA) and fast ions loss detectors (FILD) on EAST tokamak. The results of this project will help to explain and predict the possible "anomalous" transport of fast ions on EAST tokamak.

大量实验表明托卡马克快离子的输运通常满足新经典输运规律，而快离子的“反常”输运是由各种磁流体不稳定性引起。常见的与快离子输运有关的磁流体不稳定性包括：低频的鱼骨模、锯齿振荡，及频率较高的各种阿尔芬本征模。本项目拟考虑阿尔芬本征模作用下的中性束快离子输运，计算快离子与阿尔芬本征模的非线性相互作用引起的快离子压强剖面在慢化时间尺度上的演化。计算中将包含中性束持续注入产生的快离子源、快离子与主等离子体的碰撞、热化及边界损失过程。计算结果将与EAST托卡马克上的快离子D-alpha诊断及快离子损失探测器诊断数据比较，解释并预测相关现象。

实验表明托卡马克中性束快离子输运通常满足新经典碰撞输运规律，而快离子的“反常”输运是由各种尺度较大（大于微湍流空间尺度（热离子的回旋半径尺度））的磁流体不稳定性引起。常见的与快离子输运有关的磁流体不稳定性包括:低频的鱼骨模、锯齿振荡,及频率较高的各种阿尔芬本征模。此外，EAST托卡马克上安装的共振磁扰动线圈产生的三维的磁扰动也可以显著增强快离子输运。本项目研究了共振磁扰动及阿尔芬本征模作用下的中性束快离子输运，计算了快离子压强剖面在慢化时间尺度上的演化。计算中包含中性束持续注入产生的快离子源、快离子与主等离子体的碰撞、热化及边界损失过程。开发了一个较完备的模拟中性束注入及快离子输运过程的数值程序。此模拟程序已经在分析EAST快离子实验中获得应用。