Growth of ionization currents in carbon tetrafluoride and hexafluoroethane

Abstract

Values of the ionization coefficient α and attachment coefficient η have been obtained in CF 4 and C 2 F 6 at 20°C using the modified Townsend method. In CF 4 the reduced field E/p was varied from 40 to 90 V cm −1 torr −1 and the reduced coefficients α/ p and η/ p were found to be independent of pressure from 5 to 20 torr. In C 2 F 6 the range of E/p was from 70 to 190 V cm −1 torr −1 and the pressure was varied from 2·5 to 30 torr. Values of α/ p and η/ p are in good agreement at the lower pressures but at 30 torr it was necessary to assume a small detachment coefficient δ/ p similar, equals2 × 10 −3 cm −1 torr −1 , in order to obtain consistent results.