The problem of plasma expansion into a vacuum is revisited with the addition of a finite boundary condition; an electrically insulated surface. As plasma expands towards a charge-accumulating surface, the leading electron cloud charges the surface negatively, which in turn repels electrons and attracts ions. This plasma–surface interaction is shown to result in a feedback process which accelerates the plasma expansion. In addition, we examine the decrease in (negative) surface potential and associated near-surface electron density. To investigate this plasma coupling with an electrically floating surface, we develop an analytic model including four neighbouring plasma regions: (i) undisturbed plasma, (ii) quasi-neutral self-similar expansion, (iii) ion front boundary layer and (iv) electron cloud. A key innovation in our approach is a self-contained analytic approximation of the ion front boundary layer, providing a spatially continuous electric field model for the early phase of bounded plasma expansion.

中文翻译：

---

电绝缘表面的等离子体膨胀

通过添加有限边界条件，重新讨论了等离子体膨胀到真空中的问题；电绝缘表面。当等离子体向电荷积累表面扩展时，领先的电子云使表面带负电，这反过来又排斥电子并吸引离子。这种等离子体-表面相互作用被证明会导致加速等离子体膨胀的反馈过程。此外，我们检查了（负）表面电位和相关的近表面电子密度的降低。为了研究这种等离子体与电浮动表面的耦合，我们开发了一个分析模型，包括四个相邻的等离子体区域：（i）未受干扰的等离子体，（ii）准中性自相似膨胀，（iii）离子前边界层和（iv）电子云。