The Measurement of the Drift Velocity of Electrons Through Gases by the Electron Shutter Method

Abstract

The behaviour of an electron shutter apparatus such as that used by Neilsen and Bradbury for the measurement of electron velocities is analysed, taking into account the effect of electron diffusion. A relation between shutter frequency and drift velocity, and a relation giving the accuracy obtainable by the method in terms of the chamber length and gas pressure are derived. It is thus shown that neglect of the influence of diffusion can lead to large errors, but that these can be reduced to any desired degree by increasing the chamber length or the gas pressure. Numerical examples are given.