# Effect of partially-screened nuclei on fast-electron dynamics

## TL;DR

This paper investigates how partially-screened nuclei influence fast-electron behavior in plasmas, deriving analytical formulas that show significant effects on deflection and slowing-down frequencies, impacting runaway electron control in tokamaks and atmospheric discharges.

## Contribution

It provides new analytical expressions for electron deflection and slowing-down frequencies considering partial screening effects.

## Key findings

- Partially-screened nuclei increase deflection and slowing-down frequencies.
- Modifications are equally important for runaway current evolution.
- Results impact mitigation strategies in tokamaks and atmospheric discharges.

## Abstract

We analyze the dynamics of fast electrons in plasmas containing partially ionized impurity atoms, where the screening effect of bound electrons must be included. We derive analytical expressions for the deflection and slowing-down frequencies, and show that they are increased significantly compared to the results obtained with complete screening, already at sub-relativistic electron energies. Furthermore, we show that the modifications to the deflection and slowing down frequencies are of equal importance in describing the runaway current evolution. Our results greatly affect fast-electron dynamics and have important implications, e.g. for the efficacy of mitigation strategies for runaway electrons in tokamak devices, and energy loss during relativistic breakdown in atmospheric discharges.