Precision Measurements of the Townsend Energy Ratio for Electron Swarms in Highly Uniform Electric Fields

Abstract

A detailed account is given of the solution to the problems associated with the use of the Townsend–Huxley method of measuring the ratio of drift speed to diffusion coefficient for very low energy electron swarms. The elimination of radial components of the electric field within the diffusion chamber is shown to be the major experimental problem, especially in the case of the comparatively weak electric fields which must be used for some of the measurements in the near· thermal region. The experimental techniques and procedures, which are described in some detail, enable measurements to be made in this region with an accuracy comparable to that which has been achieved at higher electron energies.