控制新经典撕裂模大磁岛的ECCD驱动电流阈值的模拟研究

先进托卡马克的稳态运行是国际热核聚变实验堆ITER的重要目标。等离子体大破裂是限制稳态运行的最大威胁。在高比压放电实验中，新经典撕裂模（NTM）引起的大磁岛是造成大破裂的主要原因之一。因此对NTM及控制的研究是托卡马克不稳定性研究的热点课题。在众多控制手段中，电子回旋电流驱动（ECCD）是目前实验上最有效的控制方法之一。磁岛宽度超过阈值之后，ECCD对大磁岛的控制变得困难。驱动电流低于电流阈值将无法完全抑制大磁岛。特别在反磁剪切位形下，控制不当将导致能量爆发现象，而这种爆发与大破裂直接相关。由于实验研究破裂成本过高，因此需通过数值模拟探索实验参数区间来降低成本。本项目的目的是，采用自主开发的三维磁流体程序，在先进托卡马克位形下数值模拟ECCD对NTM大磁岛的控制，通过研究其中驱动电流阈值与磁岛宽度阈值的物理机制以及关键等离子体参数对阈值的影响，为实验上有效控制NTM避免大破裂提供理论支持。

The steady-state operation in advanced tokamaks is one of the most important goals in International Thermonuclear Experimental Reactor (ITER) project. Plasma disruption is the biggest threaten to limit the tokamak steady-state operation. During high-beta discharge experiments, the large magnetic island caused by the neo-classical tearing mode (NTM) is one of the main reasons to result in plasma disruption. Thus, the control of NTM is an intense key topic of instability study in tokamaks recently. Among all the control methods in experiments, electron cyclotron current drive (ECCD) is one of the most effective control techniques at present. As the island width exceeds a threshold, the control of large island becomes difficult. Driven current amplitude less than a threshold will not completely suppress the large island. Especially in reversed magnetic shear (RMS) configuration, inappropriate operations will cause explosive burst of energy which directly related to plasma disruption. Due to the excessive cost of this kind of experimental studies of disruption, the numerical simulation is preferred to lower the cost by exploring the optimum parameter windows for experiments. The purpose of this project is to numerically investigate the control of NTM caused large magnetic islands in RMS using self-developed 3D MHD code. Aiming to provide theoretical supports to the effective control of NTM and thus the avoidance of disruption for experiments by investigating physical mechanisms behind the current threshold and the island width threshold, as well as the influence of different kinds of key plasma parameters on the thresholds.