Impulse ratios of uniform and non-uniform field gaps in compressed gases

Impulse ratios of nearly uniform field gaps were measured in compressed N2, SF6 and in ambient air surrounded by an insulating cylinder. For a 5-mm sphere gap irradiated by a mercury-are lamp an erroneous impulse ratio as high as 2.5 was recorded in both air and N2, while a considerably lower impulse ratio (? 1.5) was obtained in SF6, all measurements being made at 100 kPa. When 1 mCi caesium was used as an irradiation source the impulse ratio for the sphere gap in N2 and SF6 became unity at 100 kPa and slightly above unity at 400 kPa. For a 30mm point-sphere gap impulse ratios were measured in He, N2, CO, CO2 and SF6. Impulse ratio as high as approx. 2.9 was recorded in both He and N2 under negative polarity and as low as 0.62 was obtained in SF6 within the corona-stabilized pressure range. Also, in weakly attaching gases, CO and CO2, impulse ratios lower than unity were found in some pressure ranges under positive polarity.