The underlying physics responsible for the formation of an avalanche instability due to the generation of secondary electrons is studied. A careful examination of the momentum space topology of the runaway electron population is carried out with an eye toward identifying how qualitative changes in the momentum space of the runaway electrons is correlated with the avalanche threshold. It is found that the avalanche threshold is tied to the merger of an O and X point in the momentum space of the primary runaway electron population. Such a change of the momentum space topology is shown to be accurately described by a simple analytic model, thus providing a powerful means of determining the avalanche threshold for a range of model assumptions.
二次电子产生导致雪崩不稳定性形成的底层物理机制被研究。对逃逸电子群体的动量空间拓扑结构进行了细致考察，旨在识别逃逸电子动量空间中的定性变化与雪崩阈值之间的关联。研究发现，雪崩阈值与初级逃逸电子群体动量空间中O点和X点的合并相关联。这种动量空间拓扑的变化被证明能够通过一个简单的解析模型精确描述，从而为在多种模型假设下确定雪崩阈值提供了有力工具。