DIELECTRIC-BREAKDOWN OF CF-3 AND A CF-3T CF-3H MIXTURE BY PULSED INFRARED IRRADIATION/

Threshold fluences for dielectric breakdown of pure CF3H and a 0.8 ppm CF3T in CF3H mixture irradiated with pulsed infrared radiation from a CO2 laser have been measured, allowing the effects of homogeneous pre -ionization resulting from beta decay of a tritium-doped gas on dielec tric breakdown to be evaluated for the first time. In both CF3H and th e CF3T/CF3H mixture, breakdown occurs as a result of a cascade process from initiatory electrons present in the gas before radiation is appl ied. The pressure dependence of the breakdown thresholds suggests that recombination is a more important loss mechanism for the cascade elec trons than is diffusion. At all pressures, the threshold measured in t he presence of CF3T was lower than that measured in pure CF3H. However , in both pure CF3H and the CF3T/CF3H mixture, the measured breakdown thresholds are well above the fluences required for laser isotope sepa ration