Influence of Cathode Boundary and Initial Electron Swarm Width on Electron Swarm Parameter Determination with the Pulsed Townsend Experiment

TL;DR

This paper improves the accuracy of electron swarm parameter determination in Pulsed Townsend experiments by better modeling initial and boundary conditions, enabling more precise extraction of parameters like diffusion coefficients and drift velocity.

Contribution

It introduces an enhanced evaluation method that considers initial and boundary conditions, verified through simulations and experiments, and provides a publicly available curve fitting tool.

Findings

More accurate extraction of electron transport parameters.

Successful validation with experimental and simulation data.

Public availability of the developed analysis code.

Abstract

The Pulsed Townsend experiment enables the extraction of relevant electron transport properties in different gases such as the electron drift velocity $W$ (or equivalently the mobility $\mu$), the longitudinal diffusion coefficient $D_{\mathrm{L}}$, and the effective ionization rate $R_{\mathrm{net}}$ (or equivalently the effective ionization coefficient $\alpha_{\mathrm{eff}}$). Existing analysis techniques lack an accurate representation of the experimental initial and boundary conditions. This work aims to provide an improved evaluation approach by appropriately considering both initial and boundary conditions in order to extract more accurate swarm parameters from measurement data. Simulative and experimental measurement results verify an increased evaluation accuracy. Furthermore, the longitudinal diffusion coefficient $D_{\mathrm{L}}$ can now be accurately extracted from Pulsed Townsend measurements. The developed curve fitting code is made publicly available.