The Electrical Breakdown of Gases in Non-Uniform Fields at Low Pressure

Abstract

The electrical breakdown of gases between coaxial cylinders at low pressures was studied in air (a gas mixture), hydrogen (a diatomic gas) and in helium (a monatomic gas). The significant secondary ionization processes occurring were correlated with those which are known to occur in uniform fields. The similarity theorem was used to help in the identification of the fundamental collisional processes. The experimental results were consistent with the view that breakdown involves the same primary and secondary ionization processes as in uniform fields: the relative importance of the dominant secondary electron emission processes depends on the nature of the electrodes and the geometry of the system. The effects of traces of impurities in helium were also studied, and the results were accounted for by the action of metastable atoms.