Measurement of the ionisation coefficients in binary and ternary mixtures of CO2, N2 and He

Abstract

The Townsend first ionisation coefficient alpha T and the secondary coefficients gamma T have been measured in binary and ternary mixtures of CO2, N2 and He gases by the steady-state Townsend method for E/p0 values from 54 to 215 V cm-1 Torr-1. The results show that the alpha T/p0 value in mixtures of CO2 and N2 increases monotonically with increasing N2 partial pressure whereas in binary mixtures of He and N2, or of He and CO2 there is a maximum value of alpha T/p0 as the partial pressure of He is increased for E/p0>or=108 V cm-1 Torr-1. The alpha T/p0 values of ternary mixtures of these gases are shown on a trigonal prism plot. The value of gamma T is found to decrease rapidly with increase of the component having a small value of gamma T.