Massive material injection has been proposed as a way to mitigate the formation of a beam of relativistic runaway electrons that may result from a disruption in tokamak plasmas. In this paper we analyse runaway generation observed in eleven ASDEX Upgrade discharges where disruption was triggered using massive gas injection. We present numerical simulations in scenarios characteristic of on-axis plasma conditions, constrained by experimental observations, using a description of the runaway dynamics with self-consistent electric field and temperature evolution in two-dimensional momentum space and zero-dimensional real space. We describe the evolution of the electron distribution function during the disruption, and show that the runaway seed generation is dominated by hot-tail in all of the simulated discharges. We reproduce the observed dependence of the current dissipation rate on the amount of injected argon during the runaway plateau phase. Our simulations also indicate that above a threshold amount of injected argon, the current density after the current quench depends strongly on the argon densities. This trend is not observed in the experiments, which suggests that effects not captured by 0D kinetic modeling -- such as runaway seed transport -- are also important.

中文翻译：

---

在 ASDEX 升级中氩引起的破坏中失控电子生成的动力学建模

大量材料注入已被提议作为减轻托卡马克等离子体中断可能导致的相对论失控电子束形成的一种方式。在本文中，我们分析了在 11 个 ASDEX 升级放电中观察到的失控发电，其中使用大量气体注入触发了中断。我们在受实验观察约束的轴上等离子体条件的场景特征中进行数值模拟，使用二维动量空间和零维真实空间中具有自洽电场和温度演化的失控动力学描述。我们描述了破坏过程中电子分布函数的演变，并表明在所有模拟放电中，失控种子的产生以热尾为主。我们重现了在失控高原阶段观察到的电流耗散率对注入氩气量的依赖性。我们的模拟还表明，高于注入氩气的阈值量，电流猝灭后的电流密度强烈依赖于氩气密度。在实验中没有观察到这种趋势，这表明 0D 动力学模型没有捕捉到的影响 - 例如失控的种子运输 - 也很重要。