Diffusion and drift of electrons in SF6

Abstract

Measurements have been made of the drift velocities and the ratios of the diffusion coefficient to mobility (D/μ) of electrons in SF6 over the range 115<E/p<210 V cm−1 Torr−1 normalized to 20°C with gas pressures in the range 0·6 to 2 Torr and for diffusion gap distances of 3, 5 and 7 cm. In the derivation of the D/μ values, Townsend's primary ionization and electron attachment coefficients reported by Bhalla and Craggs (for the range 110 <E/p<160) and Moruzzi (for the range 160 <E/p<210) were used. The close agreement obtained between the D/μ values at various pressures and gap lengths supports the data of these workers. Anomalous diffusion of electrons was observed particularly at high pressures for E/p<130.