Title: Simulation of runaway electron generation in fusion grade tokamak and suppression by impurity injection Show Chinese title

Title: 融合级托卡马克中奔逸电子生成的模拟及通过杂质注入的抑制

Abstract: During disruptions in fusion-grade tokamaks like ITER, large electric fields are induced following the thermal quench (TQ) period which can generate a substantial amount of Runaway Electrons (REs) that can carry up to 10 MA current with energies as high as several tens of MeV [1-3] in current quench phase (CQ). These runaway electrons can cause significant damage to the plasma-facing-components due to their localized energy deposition. To mitigate these effects, impurity injections of high-Z atoms have been proposed [1-3]. In this paper, we use a self-consistent 0D tokamak disruption model as implemented in PREDICT code [6] which has been upgraded to take into account the effect of impurity injections on RE dynamics as suggested in [4-5]. Dominant RE generation mechanisms such as the secondary avalanche mechanism as well as primary RE-generation mechanisms namely Dreicer, hot-tail, tritium decay and Compton scattering (from {\gamma}-rays emitted from activated walls) have been taken into account. In these simulations, the effect of impurities is taken into account considering collisions of REs with free and bound electrons as well as scattering from full and partially-shielded nuclear charge. These corrections were also implemented in the relativistic test particle model to simulate RE-dynamics in momentum space. We show that the presence of impurities has a non-uniform effect on the Runaway Electron Distribution function. We also show that the combined effect of pitch-angle scattering induced by the collisions with impurity ions and synchrotron emission loss results in the faster dissipation of RE-energy distribution function [7]. The variation of different RE generation mechanisms during different phases of the disruption, mainly before and after impurity injections is reported. Show Chinese abstract

Abstract: 在融合级托卡马克装置如ITER发生中断期间，热淬灭（TQ）阶段之后会感应出大的电场，这可能会产生大量奔雷电子（REs），这些电子在电流淬灭阶段（CQ）可以携带高达10 MA的电流，能量高达几十MeV [1-3]。这些奔雷电子由于局部能量沉积，可能对等离子体面对部件造成显著损害。为了减轻这些影响，提出了高Z原子的杂质注入 [1-3]。在本文中，我们使用了在PREDICT代码 [6] 中实现的自洽0D托卡马克中断模型，该模型已升级以考虑杂质注入对RE动力学的影响，如[4-5]中所建议的。考虑了主要的RE生成机制，如二次雪崩机制以及主要的RE生成机制，即Dreicer、热尾、氚衰变和康普顿散射（来自激活壁发射的{\gamma }-rays）。在这些模拟中，考虑了杂质对RE与自由电子和束缚电子碰撞以及从完整和部分屏蔽核电荷散射的影响。这些修正也实施在相对论测试粒子模型中，以模拟动量空间中的RE动力学。我们表明，杂质的存在对奔雷电子分布函数有非均匀的影响。我们还表明，杂质离子碰撞引起的磁倾角散射和同步辐射损失的综合效应导致RE能量分布函数更快地耗散 [7]。报告了在中断的不同阶段，特别是杂质注入前后，不同RE生成机制的变化。