Quantum Kinetics of Fast-Electron Inelastic Collisions in Partially-Ionized Plasmas

TL;DR

This paper develops a quantum kinetic model for fast-electron energy loss in partially ionized plasmas, highlighting the importance of inelastic energy diffusion in accurately predicting runaway-electron generation.

Contribution

It introduces a Fokker-Planck operator derived from ab initio simulations to account for energy diffusion effects in fast-electron kinetics.

Findings

Neglecting inelastic energy diffusion underestimates runaway-electron production by several orders of magnitude.

The model improves understanding of energy straggling and diffusion effects in partially ionized plasmas.

Inelastic collision effects are crucial for accurate predictions in plasma physics applications.

Abstract

Fast electrons in partially ionized plasmas lose energy through inelastic collisions with bound electrons. While the mean energy loss is well described by stopping-power theory, fluctuations associated with discrete excitation and ionization events produce energy straggling and an additional longitudinal diffusion in momentum space. We incorporate this effect into fast-electron kinetics through a derived Fokker-Planck operator whose coefficients are obtained from ab initio quantum many-body simulations. We demonstrate that neglecting inelastic energy diffusion in partially ionized D-Ar plasmas can underestimate primary runaway-electron generation by several orders of magnitude.