The Influence of a D.C. Crossed Magnetic Field on the Electrical Discharge Characteristics of Gases in the Townsend Region

摘要

The influence of a crossed magnetic field on a gaseous Townsend discharge in nitrogen, hydrogen, argon and ethane for uniform field gap distances between 0.3 and 1.2 cm at pressures from 0.5 to 700 Torr using a magnetic field up to 7500 gauss, can be adequately accounted for by the equivalent pressure concept. On this basis formulae for the sparking voltage in a crossed magnetic field are derived which agree well with the experimental results. A new method for determining the important electron-molecule collision frequency from sparking voltage data is described; the values so derived for N2 and H2 agree with those reported in the literature and those for Ar and C2H6 are new. Pre-breakdown ionization current measurements were made in Ar and N2 for H/p up to 2000 G/Torr and for 30 or = E/p or = 1000 V/cm/Torr. The measured values of the primary ionization coefficient in N2 agree well with the calculated ones for 200 or = E/p or = 500. Finally a probe method is described to study the lateral movement of a Townsend discharge; this should make it possible to determine the discharge propagation velocity at a later stage. (Author)