Boltzmann equation analysis of the electron swarm development in SF6and nitrogen mixtures

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Abstract
The ionisation alpha and electron attachment eta coefficients and other electron swarm parameters are calculated for SF6 and nitrogen gas mixtures for E/p0=75-200 V cm-1 Torr-1 by a Boltzmann equation method, in which the effect of generation and loss of free electrons due to ionisation and attachment are fully considered, for the steady-state Townsend (SST) experiment. The results show that the deduced values of the effective ionisation coefficient alpha (= alpha - eta ) are in good to fair agreement with those measured by Itoh et al. (1979) by a SST method, but agreement is less satisfactory with the experimental values of Aschwanden (1979) by a pulse method. The limiting E/p0 value, at which alpha = eta , is also calculated to give slightly higher values than previous experiments. The variation of the electron energy distribution, electron drift velocity, diffusion coefficient and mean energy, and the excitation frequency to C3 Pi u of nitrogen, as a function of the partial SF6 pressure, are calculated and discussed.