IONIZATION AND ATTACHMENT COEFFICIENTS MEASURED IN NITROGEN AND DIFLUORODICHLOROMETHANE GAS-MIXTURES

In view of contradiction in the dielectric strength of the CF2Cl2/N2 gas mixture reported by different investigators, the authors report the Townsend first ionisation coefficient alpha and the electron attachment coefficient eta measured in that gas mixture with various mixing ratios using the steady-state Townsend method over the range 40<or=E/p<or=140 V cm‒ Torr-1. The limiting E/p values derived from pre-breakdown current growth were in good agreement with static breakdown experiments. In contrast to the SF6/N2 gas mixture, the dielectric strength of the CF2Cl2/N2 mixture as a function of CF2Cl2 concentration is quite close to a straight line similar to that of CF2Cl2/CO2. © 1990 IOP Publishing Ltd.