Synchrotron radiation images from runaway electrons (REs) in an ASDEX Upgrade discharge disrupted by argon injection are analysed using the synchrotron diagnostic tool Soft and coupled fluid-kinetic simulations. We show that the evolution of the runaway distribution is well described by an initial hot-tail seed population, which is accelerated to energies between 25–50 MeV during the current quench, together with an avalanche runaway tail which has an exponentially decreasing energy spectrum. We find that, although the avalanche component carries the vast majority of the current, it is the high-energy seed remnant that dominates synchrotron emission. With insights from the fluid-kinetic simulations, an analytic model for the evolution of the runaway seed component is developed and used to reconstruct the radial density profile of the RE beam. The analysis shows that the observed change of the synchrotron pattern from circular to crescent shape is caused by a rapid redistribution of the radial profile of the runaway density.

中文翻译：

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ASDEX升级中断中同步加速器图像失控分布函数的时空分析

使用同步加速器诊断工具软耦合流体动力学模拟分析来自 ASDEX 升级放电中失控电子 (RE) 的同步加速器辐射图像，该放电被氩注入破坏。我们表明，失控分布的演变可以通过初始热尾种子群得到很好的描述，在当前淬火过程中，热尾种子群被加速到 25-50 MeV 之间的能量，以及具有指数下降能谱的雪崩失控尾巴。我们发现，虽然雪崩分量承载了绝大多数电流，但支配同步加速器发射的是高能种子残余物。根据流体动力学模拟的见解，开发了失控种子分量演变的分析模型，并用于重建 RE 束的径向密度剖面。