Ignitron discharge growth during high-current pulses

Glass ignitrons were studied carrying up to 21,000 amperes with rise times as short as 1.25 μsec (microseconds). Kerr-Cell photographs show discharge growth, constrictions, and an expanding circle of arc spots with speeds up to 2 × 106 cm/sec (centimeters per second). The peak velocity varied with the 0.7 power of capacitor voltage and directly with the peak non-inductive component of anode voltage. Arc-front propagation, by ionic charging of a dielectric film, is discussed and is consistent with the measurements.