Uniform-field sparking voltages of gases in crossed magnetic fields

The influence of a crossed magnetic field on sparking voltages in nitrogen, hydrogen, argon and ethane has been investigated theoretically and experimentally for a uniform-field gap distance between 0.3 and 1.2cm at gas pressures from 0.5 to 700torr using a magnetic field of up to 7500Gs. It is found that the influence of the magnetic field is greatest at low pressures and can adequately be accounted, for by the equivalent-pressure concept. The magnetic field tilts the electron avalanche and its successors through an angle ¿, so that the discharge path is increased and the effective field is reduced, thus increasing the strength of the gases, particularly at low pressure. Using these concepts, formulas are derived which agree well with the experimental results. A new method is presented whereby the important electron-molecule collision frequency can be determined from the present sparking data; values so derived agree well with the few reported in the literature.