Characteristics of positive pulse ARC dischaege in supercritical carbon dioxide

Positive nanosecond pulse arc discharge phenomena in pressurized carbon dioxide under both supercritical and liquid phases were studied. A nanosecond pulsed voltage with a rise time of approximately 90 ns was applied to a needle to plane electrode with a 4.5 mm gap distance. Arc channel appearance was observed by means of a high resolution CMOS camera with attenuating filter. Single or bifurcated arc channels were observed appearing randomly under supercritical and liquid phases; single arc channels were most common, while bifurcated arc channels from the tip of the needle electrode were infrequently observed. The probability of appearance of bifurcated arc channels in the supercritical phase was approximately 2.5 times greater than in the liquid phase.