Statistical Delay Times in Small Gas Spark Gaps

Statistical times were measured as a function of overvoltage and gap conditioning in small (0.127 mm) flowing-gas spark gaps. Results for air, nitrogen, oxygen, and helium are reported here. Statistical time was determined by averaging 60 measurements of the time between application of a step voltage to the gap and breakdown of the gap. These times, ranging from 100 ns to over 100 ¿s, were measured with 10-ns resolution. Conditioning was done by breaking down the spark gap 40 times per second until the desired number of pulses was obtained (5000, 50 000, 500 000). Conditioning increased the breakdown voltage of gaps filled with air, nitrogen, and oxygen, but had little effect when helium was used. The functional dependence of the statistical time on electric-field strength was not changed by conditioning. Limited results showed statistical time increased with pressure in air-filled spark gaps.