Oscillographic Observations on Ultra-High-Frequency Sparks

Abstract

EXPERIMENTS are in progress on the mechanism of the breakdown of gases at centimetre wavelengths, some of which have already been reported¹. In the previous communication reference was made to the mid-gap streamers which, at atmospheric pressure, seem to constitute the birth-stage of a spark in a resonator energized at 2,800 megacycles per second. These streamers are regularly produced when a narrow beam of short-wave ultra-violet light, from a spark gap, is passed through the gas between the electrodes immediately before the 1·4-micro-second pulse reaches the resonator (Fig. 1). Photoelectrons in the gas itself execute oscillations of small amplitude in the electric field, and cause breakdown if the field is strong enough.