IONIZATION AND ATTACHMENT COEFFICIENTS MEASURED IN SF6/AR AND SF6/KR GAS-MIXTURES

The Townsend first ionization coefficient alpha and the electron attachment coefficient eta were measured in SF6-Ar and SF6-Kr gas mixtures using the steady-state Townsend method over the range 15 less-than-or-equal-to E/P less-than-or-equal-to 94 V mm-1 kPa-1 with mixture ratios 10:90, 25:75, 50:50, 75:25 and 90:10. The limiting E/P values of these two gas mixtures were derived from the pre-breakdown current growth measurements. The dielectric strengths of both gas mixtures are found to be almost the same, and they vary linearly with SF6 concentration in the mixture, which is different from the curve pattern for most SF6 gas mixtures.