低杂波电流驱动抑制EAST装置撕裂模不稳定性的理论研究

In tokamak devices, tearing mode instability is often responsible for degraded plasmas confinement and is considered as a potential threat for the successful operation of burning plasmas experiments. As the most effective method of non-induced current drive in tokamak device, lower hybrid current drive(LHCD) have been widely studied theoretically and experimentally. LHCD is an important instrument to achieve long pulse and steady-state operation for EAST experiments. It is shown theoretically that LHCD can control and suppress the tearing mode instability by means of optimize the plasma current distribution profile. In this project, we will carry out theoretical and numerical studies of tearing mode instability in the Tokamak devices with lower hybrid wave inject. At first, accorrding to the basic principle of plasmas and radio wave in tokamak, together with the magnetohydrodynamic equations, we will propose a theoretical model where the effect of LHCD on the tearing mode in tokamka plasma is considered. Secondly, the effect of magnetic island on the trajectory and the related drive current and power deposition of the lower hybrid wave will be studied carefully by means of numerical simulation through a combination of classical ray-tracing and the three dimensional Fokker-Planck caaulatoion. On the consequence, an effective method of suppressing the tearing modes with lower hybrid wave injection will be obtained through the tearing mode codes simulation.This project is of great significance to the EAST experiments with high performance and steady state operation in the next step.

托卡马克等离子体中的撕裂模不稳定性严重限制了装置的运行参数，甚至导致放电破裂，被认为是制约装置稳态、高性能运行的重要原因。低杂波作为目前最有效的非感应电流驱动方式，理论上和实验上都获得了广泛的关注，是EAST装置长脉冲准稳态运行和实现H模等离子体的重要保障。理论研究表明，低杂波通过控制等离子体电流分布可以抑制撕裂模磁岛增长。本项目拟依托EAST装置开展利用低杂波电流驱动抑制撕裂模不稳定性的研究。首先，根据低杂波与等离子体相互作用原理和磁流体力学基本理论，建立起相关的物理模型，开展理论分析；其次，利用Ray-tracing code和CQL3D code开展大规模数值模拟，研究磁岛对低杂波波迹、驱动电流和功率沉积等的影响；然后，耦合撕裂模计算代码研究驱动电流对磁岛的抑制作用，获得如何利用低杂波抑制撕裂模不稳定性，及影响制稳作用的主要物理因素。本项目的研究为EAST实验提供理论参考。

本项目依托国家大科学工程EAST装置开展了低混杂波电流驱动抑制撕裂模不稳定性的研究。首先，通过平衡叠加扰动的方法，在EAST实验装置gfile平衡数据的基础上获得了含撕裂模磁岛结构的新的磁场平衡位形，耦合ray-tracing程序，数值的获得了磁岛磁场扰动对低混杂波波射线轨迹、波驱动电流剖面和波功率沉积的影响，研究结果表明，扰动磁场明显的改变了低混杂波电流驱动剖面分布。然后，根据波的可近性条件，研究获得了EAST装置高约束模（H模）平台区附近低混杂波快波支和慢波支的转换层，同时，研究结果表明，弱电子朗道阻尼机制下驱动电流效率较低。最后，基于有限体积法的通量差分分裂格式的基本框架，引入高精度HLLD型黎曼求解器，开发了二维磁流体方程组程序，并且研究了托卡马克等离子体双撕裂模不稳定性。此外，还针对HL-2A装置的ITG模和TE模开展了积极的研究。研究结果为国内托卡马克装置相关实验提供了积极的理论参考。