Interpretation and prediction of gaseous electrical-breakdown characteristics in a crossed magnetic field

Breakdown characteristics in a crossed magnetic field are analysed with the aid of the equivalent-reduced-electric-field (e.r.e.f.) concept. Individual contributions to the secondary ionisation process can be separated, and, in argon, the contribution is mainly due to photons and/or metastable atoms; in ethane, it is wholly due to positive ions; and in hydrogen and nitrogen, a mixture of these two processes exists. For the first time, Somerville´s formula for electron recapture by the cathode on account of the crossed magnetic field is shown to work, and also Haydon´s suggestion that the secondary ionisation process by photons in subject to the e.r.e.f. principle is substantiated. There is evidence to suggest that secondary electrons leave the cathode under positive-ion bombardment with almost zero energy, whereas, under photon and/or metastable action, the secondary electrons are considered to have a substantial escape velocity which, it is calculated, reduces their probability of being recaptured by the cathode. The use of e.r.e.f. allows successful analysis and prediction of breakdown characteristics in a crossed magnetic field, and the whole subject is shown to be soundly based and to form a harmonious and sell-consistent topic.