Pressure-Dependent Breakdown Potentials in Penning Mixtures

Measurements have been made of the primary and secondary electron ionization coefficients in neon-hydrogen, helium-hydrogen, and neon-argon mixtures using the Townsend technique. In these experiments, measurements have been conducted over a considerable range of pressures at the E/p0 value corresponding to the maximum of the Penning effect and for the optimum concentrations. Examination of the prebreakdown current growth indicated at fixed E/p0 a pressure-dependent breakdown potential. Measurements of the primary coefficient as a function of pressure showed no significant pressure variation. Measurements of the secondary ionization coefficient, however, indicated that γ decreased with increasing pressure consistent with the observed breakdown potential variation.