EAST上离子回旋波参量衰变不稳定性的模拟研究

Radiofrequency wave in ion cyclotron range of frequency (ICRF) is an important way for heating plasma, driving current and implementing plasma control in the magnetic fusion devices such as EAST and ITER, etc. During the high power ICRF injection experiments, it is found that the performance of the injected wave was significantly affected by the parametric decay instability (PDI), and the fast ions with high energy at the keV level were observed in the tokamak edge region. The generation mechanism of the fast ions remains unclear. In this proposed project, the simulation studies of the PDIs of ICRF in EAST tokamak will be carried out via the self-consistent particle-in-cell method for the first time. The dependence of the PDI decay channels on the plasma parameters, such as plasma density, density profile, magnetic field and ratio of minority ion, will also be explored. We plans to analyze the effects of PDIs on the formation of edge fast ions, and propose the valuable experiment scenario to suppress or avoid these kinds of PDIs. The results of this proposed project will be beneficial to understand the energy transfer between the wave and particle in the PDI processes, and reveal the formation mechanism of edge fast ions observed in the high power ICRF injection experiments. Accordingly, the proposal for eliminating or reducing this edge ion heating effects can be provided.

离子回旋波（ICRF）是磁约束聚变装置（EAST和ITER等）中加热等离子体、驱动电流和实现等离子体控制的重要方式。在高功率ICRF注入实验中，发现参量衰变不稳定性（PDI）会严重影响入射波的性能，并观测到能量高达keV量级的快离子在托卡马克的边界区域产生，但其产生机制尚无定论。本项目将首次针对EAST的实验参数，利用PIC方法自洽地模拟研究ICRF的PDI过程，探索PDI的衰变通道对等离子体参数（包括密度、密度剖面、磁场和少数离子份额等）的依赖关系，分析PDI对边界快离子形成的影响，并提出抑制或避免这些PDI过程的实验方案。本项目的研究结果将有助于理解PDI中波与粒子的能量传递过程；有助于揭示高功率ICRF注入实验中观察到的边界快离子的产生机理，为消除或降低这种边界离子加热效应提供参考依据。

离子回旋波是EAST和ITER等磁约束聚变装置中加热等离子体、驱动电流和实现等离子体控制的重要方式。在高功率离子回旋注入实验中，发现参量衰变不稳定性会严重影响入射波的性能，并观测到能量高达keV量级的快离子在托卡马克的边界区域产生，但其产生机制尚无定论。本项目针对EAST上离子回旋加热实验参数，分析了参量衰变不稳定性衰变通道的匹配条件，结果显示，等离子体密度剖面，平行波数和磁场显著影响参量衰变的匹配条件，而少数离子份额和密度影响较小。模拟结果表明，参量衰变过程可将边界区域的离子由几十eV加热到几个keV量级。同时开展了包含EAST真实离子回旋天线结构的三维模拟研究，结果表明，天线结构，截止层宽度和环向曲率显著影响耦合过程。此外，本项目开展了EAST反剪切安全因子剖面下激发鱼骨模的线性和非线性特征研究。针对CFETR参数，研究了低杂波参量衰变不稳定性过程和螺旋波的耦合过程。本项目的研究成果有助于理解EAST上离子回旋波的参量衰变过程，并揭示了高功率离子回旋波注入实验中观测到的边界快离子的产生机制。此外，本项目研究成果还可为EAST上离子回旋波耦合效率的提高和CFETR中低杂波和螺旋波的参数设计提供参考。