托卡马克边缘等离子体密度涨落对低混杂波电流驱动影响的理论研究

Lower hybrid current drive is essential for tokamak to approach steady-state operation, even for the plasma high mode discharge. The density fluctuations at the plasma edge is considered as an important candidate for the quickly decrease of the lower hybrid current drive efficiency in tokamak, where phenomenon of ray wave scattering occurs. In this project, the effect of ray wave scattering that induced by density fluctuations at plasma edge on the lower hybrid current drive efficiency will be discussed. On the one hand, a theoretical analysis of the density fluctuations on the full wave equation will be done based on the Maxwell field equations. On the other hand, we propose a physical model including the plasma density fluctuations at edge, the obtained full wave calculation subroutine is to couple with the ray-tracing code and the Fokker-Planck code, and a careful study of the lower hybrid current drive efficiency in the presence of edge density fluctuation will be carried out. Consequently, an optimization of plasma parameters at the tokamak edge with high current drive efficiency is obtained. The projection is of great significance to the tokamak experiment with lower hybrid wave operation.

低混杂波电流驱动是托卡马克装置稳态高性能运行的重要手段。目前实验上观测到等离子体高密度参数下低混杂波电流驱动效率快速降低被认为与托卡马克边缘等离子体密度涨落密切相关，波射线散射是边缘等离子体密度涨落的重要特征。本项目拟针对边缘等离子体密度涨落现象研究其导致的波射线散射对波传播轨迹、波功率沉积和波驱动电流效率的影响。一方面，基于电磁场麦克斯韦方程组，理论分析推导包含等离子体密度涨落效应的全波方程，获得该方程的数值求解方法；另一方面，根据实验装置参数建立相应的物理模型，根据数值求解获得的全波方程与ray-tracing程序和Fokker-Planck程序模块耦合，通过数值模拟研究边缘等离子体密度涨落的波散射对低混杂波电流驱动效率的影响，获得能够提高低混杂波电流驱动效率的优化的边缘等离子体参数。本项目的研究为托卡马克装置实验提供理论参考。

针对本项目的研究目标和研究内容，开展了积极的理论和数值模拟研究。一方面，建立了包含等离子体密度涨落效应的理论计算模型，并与ray-tracing程序和Fokker-Planck程序模块耦合，获得了计算方程的数值求解方法；另一方面，依托国内外装置，从多方面仔细深入模拟研究了托卡马克等离子体边缘密度涨落对低杂波电流驱动效率的影响。获得了托卡马克边缘等离子体中高低场侧的模拟结果，研究了低混杂波高平行折射率分量对等离子体电流驱动影响，研究了边缘局域模对低混杂波电流驱动的影响，发现了托卡马克边缘即离轴位置上低混杂波与电子回旋波Ohkawa机制联合电流驱动的新协同效应，在EAST托卡马克装置上做了低杂波电流驱动等离子体环向旋转实验研究，并在这些研究中总结了低杂波电流驱动优化方案；同时，也研究了快波电流驱动、螺旋波电流驱动以及旋转磁岛诱发的快离子输运相关的物理问题对托卡马克边缘等离子体的影响，尝试从更深层的角度揭示边缘等离子体密度涨落的物理本质，得出优化低杂波电流驱动效率的方案。总之，完成了项目的各项研究任务。