Effect of Penning ionisation on the Townsend first ionisation coefficient of pulsed and steady-state Townsend experiments in Ar/Ne mixtures

Abstract

The Townsend first ionisation coefficient alpha defined in pulsed Townsend (PT) experiments in Ar/Ne mixtures are analysed using a Boltzmann equation in which the influence of generation of secondary electrons through Penning ionisation in a discharge is taken properly into consideration. It is found that the values of alpha /E, where E is the electric field strength, for PT experiments differ considerably from those for steady-state Townsend (SST) experiments especially in the E/N range, where N is the gas atom concentration, in which Penning ionisation affects the SST values of alpha /E considerably (Sakai et al. 1986). This difference of the alpha /E is shown to be a peculiar phenomenon in Penning gases and to occur due to difference between the observation method for the metastable Ne and the electron concentrations in a swarm of PT and SST experiments.