EAST低杂波电流驱动与电子回旋波电流驱动协同效应的数值模拟与实验研究

Lower hybrid current drive (LHCD) is characterized by the highest current drive efficiency. On the other hand, electron cyclotron current drive (ECCD) is known to provide highly localized current, and is therefore usually used to control the magnetohydrodynamic (MHD) instabilities. Combined schemes, in which LHCD and ECCD are used together, should play an important role in steady-state long pulse operation, confinement improvement and MHD control in EAST plasmas. In particular, owning to the synergy effect exerted during the combination of LHCD and ECCD, the power requirements should be substantially reduced, and thus makes the current drive systems significantly more economical. In this project, the synergy effect with different wave and plasma parameters will be calculated and analyzed in a self-consistent way using the LHCD and ECCD codes coupled to the transport code, which provides references for the experimental design. Then, our research will focus on the releated experiments performed in EAST based on the simulated results and the exploration of synergy effect dependence on wave and plasma parameters. Sequentially, the requirements for optimal synergy effect should be obtained. This project will be helpful to improve current drive efficiency and current drive system economy, and thus to broaden the range of operation parameters in EAST.

低杂波电流驱动最大的特点是具有非常高的驱动效率，而电子回旋波驱动的电流则具有很好的局域性，因此常用来控制磁流体不稳定性。二者的共同作用将在EAST长脉冲稳态等离子体运行、改善约束和抑制磁流体不稳定性方面发挥重要意义。更重要的是二者共同作用产生的协同效应将大大减少所需的功率，从而使得电流驱动系统更加的经济性。本课题将低杂波程序和电子回旋波程序与输运程序耦合在一起，自洽地计算、分析不同等离子体参数、波参数条件下的双波协同效应，为实验设计提供参考依据。基于数值模拟结果，然后重点在EAST上开展双波协同作用的物理实验，探索协同效应与波参数和等离子体参数之间的依赖关系，从而获得产生最佳协同效应所需的物理条件。这有助于提高电流驱动效率和电流驱动系统的经济性，从而拓宽EAST实验参数区间。

完善和发展了EAST低杂波和电子回旋波电流驱动计算程序和波物理相关诊断。利用升级后的程序对不同低杂波初始平行折射率、不同电子回旋波入射角度、以及双波功率相对大小条件下的双波协同情况做了模拟分析。研究了低杂波驱动效率随密度的变化趋势，比较分析了EAST上不同频率的低杂波电流驱动和加热特性；验证了较高的波源频率有利于改善高密度电流驱动效率。基于模拟结果，通过实验研究了两波功率沉积位置、功率值大小、低杂波的平行折射率和电子温度、密度等参数对协同效应的影响。发现双波协同效应对低杂波的平行折射率有较强的依赖关系，当低杂波的相位为180度时，双波协同加热效果最明显，而当相位为90度时，驱动效果最佳。此结果对EAST高电子温度长脉冲放电具有十分重要的意义。