Breakdown phenomena of gas‐insulated gaps with nanosecond pulses

Breakdown phenomena of gas‐insulated gaps with nanosecond pulses were examined under the spot illumination of the ultraviolet rays on the cathode surface in the atmospheric gases such as air, N2, and O2. Our investigation reveals that the 50% probability of flashover voltage obtained under the spot illumination of the ultraviolet rays shows very close values under the entire illumination on the cathode surface, and the observed time lag of flashover may be explained by the conventional avalanche‐to‐streamer development theory.