Boltzmann equation analyses of electron swarm parameters in Hg/Ar gas mixtures: effect of metastable Hg and Ar atoms

The steady-state electron swarm parameters in Hg/Ar mixtures are analysed using a Boltzmann equation in which the collision terms providing generation of secondary electrons via metastable Hg and Ar atoms presented in the preceding paper (see Y. Sakai et al., ibid., vol.22, p.276, 1989) are taken into consideration. The ratio of the Townsend first ionisation coefficient to the electric field strength, alpha /SiE, calculated using the present equation for E/N values from 5 to 1412 Td in Ar with various admixtures of Hg vapour (K=ratio of Hg to total gas atom concentrations from 2*10-4 to 2*10-2) is in good agreement with the experimental values of Burgmans and Smeets (1983). For E/N below 100 Td and K above 6*10-3 ionisation collision between two metastable Hg atoms is found to be the dominant process for electron multiplication. The influence of electron concentration on the swarm behaviour is discussed quantitatively.