Effect of fast electron transport on neoclassical tearing mode stabilization by electron cyclotron current drive
Effect of fast electron transport on neoclassical tearing mode stabilization by electron cyclotron current drive
复制标题
电子回旋电流驱动快速电子传输对新古典撕裂模式稳定的影响
DOI：
10.1088/1741-4326/ac55b9
复制
发表时间：
2022
期刊：
影响因子：
--
通讯作者：
H.Q. Liu
中科院分区：
文献类型：
--
作者：
X.J. Wang;Y.Zhang;X.D. Zhang;L.Q.Hu;H.Q. Liu
最近的研究表明，当注入的电子回旋波束被等离子体密度涨落展宽时，ITER中电子回旋电流驱动（ECCD）对新经典撕裂模（NTMs）的稳定作用可能受到阻碍。本文首先利用修正的卢瑟福方程（MRE）分析了ECCD对NTM的稳定作用。结果表明，与宽波沉积，模式稳定的最有效的方法是应用调制ECCD早在模式生长时的磁岛是小的，正如预期的。基于简化的磁流体动力学方程进行了数值模拟，其结果与MRE得到的结果一致。然而，考虑到在数值模拟中，快电子的垂直输运，被发现显着降低调制ECCD的模式稳定。模式稳定所需的调制驱动电流与快电子的垂直扩散率的平方根成正比，并且当扩散率由于等离子体湍流而达到异常输运水平时增加数倍。当驱动电流与谐振面的径向偏离达到等离子体小半径的0.4%时，模式稳定性会大大降低，这取决于波沉积宽度和快电子的垂直扩散系数。
Recent studies have shown that the stabilization of neoclassical tearing modes (NTMs) by electron cyclotron current drive (ECCD) in ITER may be impeded when the injected electron cyclotron wave beam is broadened by plasma density fluctuations. This paper starts with the analysis of NTM stabilization by ECCD using the modified Rutherford equation (MRE). It is shown that with a wide wave deposition, the most effective approach for mode stabilization is to apply modulated ECCD early during the mode growth when the magnetic island is small, as expected. Numerical simulations based on reduced magnetohydrodynamic equations have been further carried out, and the results show the same trend as those obtained from the MRE. However, the perpendicular transport of fast electrons, taken into account in numerical simulations, is found to significantly degrade the mode stabilization by modulated ECCD. The modulated driven current required for mode stabilization is proportional to the square root of the perpendicular diffusivity of fast electrons and is increased by several times when the diffusivity reaches the anomalous transport level due to plasma turbulence. If the radial misalignment of the driven current from the resonant surface reaches∼ 4% of the plasma minor radius, the mode stabilization can be degraded to a great extent, depending on the wave deposition width and the perpendicular diffusivity of fast electrons.