HL-2A等离子体破裂期间逃逸电子演化模拟

Simulation of runaway electron evolution during disruptions in HL-2A tokamak

采用数值模拟方法对托卡马克等离子体破裂期间的逃逸电子（RE）演化行为进行研究。程序所使用的物理模型包含了初级和次级两种RE产生机制,并耦合了麦克斯韦方程组。模拟结果显示：在等离子体破裂开始0.1-0.2ms后感应产生了很强的环向电场,持续约0.1ms之后该环向电场达到最大值,但是在大致2.5ms内逐渐衰减。同时模拟结果也证明了RE产生于等离子体中心处的局部区域,并且在破裂之后约1ms时间内就形成了RE束,实验中等离子体破裂之后出现的几十毫秒的电流平台主要是由RE携带的。从理论模拟与实验的对比中可以得出：HL-2A 15335次放电等离子体破裂期间欧姆电流转化为逃逸电流（RC）的转化率在40%-60%。次级产生机制在RE束的形成过程当中起到了关键作用。

The simulation of runaway electron（RE） and electric field evolution during HL-2A disruption is presented using a self-consistent model, which is constituted by Maxwell＇s equations and generation rate equation. The generation rate equation includes Dreicer and avalanche generation mechanisms of REs. The simulation shows that the electric field increases rapidly from 0.1-0.2ms after the disruption, reaches the maximum about 0.1 ms later, and lasts about 2.5ms. The simulation results also show that REs are produced mostly in the region around the magnetic axis and a RE beam forms at 1ms after disruption, tens of milliseconds steady-state current appearing after disruption is carried mainly by REs. Further, comparing between the simulation and the experimental results, it is found that 40%-60% of the Ohmic current is converted into runaway current（RC） during the disruption（discharge No. 15335） in HL-2A. Although the avalanche generation rate of REs is weaker than Dreicer generation mechanism in HL-2A, it plays a key role because of its larger action time than Dreicer generation mechanism.