Time-resolved resistance during spark gap breakdown

The breakdown voltage and the time derivative of the current through a spark gap terminating a transmission line were measured as a function of 4 gas species, 3 gap pressures, and 2 gap spacings. From these measurements, the time-varying channel resistance, the power, and the energy dissipated in the discharge can be determined for the first 1500 ps of breakdown. Data were obtained with a 74-cm-long transmission line, open at the charging end, and terminated by a spark gap at the other end. The line was pulse charged with a 2-µs rise time pulse having a maximum voltage of 3 kV. The breakdown voltage was determined by monitoring the charge voltage waveform while a
di/dt
probe close to the spark gap provided a sampling oscilloscope with the other desired signal. The latter waveform was then digitized and the data were reconstructed using Fourier techniques on a computer to account for the frequency response of the required signal delay line.