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Experimental results are presented of ionisation ( alpha ) and electron attachment (( eta ) coefficients evaluated from the steady-state Townsend current growth curves for SF6N2 and CCl2F2-N2 mixtures over the range 60

The ratio of the electron attachment coefficient eta to the gas pressure p (reduced to 0 degrees C) evaluated from the Townsend current growth curves in binary mixtures of electronegative gases (SF6, CCl2F2, CO2) and buffer gases (N2, Ar, air) clearly indicate that the eta /p ratios do not scale as the partial pressure of electronegative gas in the mixture. Extensive calculations carried out using data experimentally obtained have shown that the attachment coefficient of the mixture eta mix can be expressed as eta mix= eta (1-exp- beta F/(100-F)) where eta is the attachment coefficient of the 100% electronegative gas, F is the percentage of the electronegative gas in the mixture and beta is a constant. The results of this analysis explain to a high degree of accuracy the data obtained in various mixtures and are in very good agreement with the data deduced by Itoh and co-workers (1980) using the Boltzmann equation method.

Measurements of the ratio of diffusion coefficient to mobility (D/ mu ) of electrons in SF6-N2 and CCl2F2-N2 mixtures over the range 80