# Experimental observation and simulation of the equilibration of electron swarms in a scanning drift tube

## TL;DR

This study combines experimental measurements and Monte Carlo simulations to analyze how electron swarms in argon gas reach equilibrium in a scanning drift tube, revealing the spatial scales of energy balance.

## Contribution

It provides the first detailed experimental and simulation-based investigation of electron swarm equilibration in a homogeneous electric field near an emitting boundary.

## Key findings

- Electron swarms equilibrate over specific length scales depending on electric field strength.
- Monte Carlo simulations agree well with experimental results.
- Transport properties become spatially invariant after equilibration.

## Abstract

We investigate the spatially and temporally resolved electron kinetics in a homogeneous electric field in argon gas, in the vicinity of an emitting boundary. This (transient) region, where the electron swarm exhibits non-equilibrium character with energy gain and loss processes taking place at separate positions (in space and time), is monitored experimentally in a scanning drift tube apparatus. Depending on the strength of the reduced electric field we observe the equilibration of the swarm over different length scales, beyond which the energy gain and loss mechanism becomes locally balanced and transport properties become spatially invariant. The evolution of the electron swarm in the experimental apparatus is also described by Monte Carlo simulations, of which the results are in good agreement with the experimental observations, over the domains of the reduced electric field and the gas pressure covered.