Photomultiplier Studies of the Temporal Growth of Ionization during the Formative Time of Spark Breakdown in Nitrogen

Abstract

THE purpose of the present communication is to report the use of a photomultiplier technique to record the temporal growth of ionization in a pulsed Townsend discharge in nitrogen, with high values of the parameter pd (pressure × gap length) of ∼ 1,000 mm mercury cm. The object of the investigation was to examine the secondary ionization processes leading to the sparkover of uniform-field gaps, and to test current growth theory¹ under the aforementioned conditions, where the formative time lags are of the order of microseconds at low over-voltages and evaluation of the growth constant λ¹ requires measurement of the rate of growth of the discharge for currents up to 10⁻⁵ amp at which space-charge distortion becomes important.