Measurement of breakdown potentials and Townsend ionization coefficients for the Penning mixtures of neon and xenon

The Townsend primary (α) and secondary (γ) coefficients and Paschen curves for neon, xenon, and their mixtures are reported. The primary coefficient was determined by measuring the variation in the luminous flux in a self-sustained Townsend discharge between two parallel-plate nickel electrodes spaced 21.5 mm apart. The values of the reduced primary coefficient, αp₀, for Ne and Xe are about 10-20% lower than published values obtained by the classical method of Townsend. The αp₀ values obtained for Ne agree with previous work using the same luminous-flux method. The ionization efficiency function η η=αE, where E is the electric field) has a maximum value for Ne and 0.01% Xe. Also, the value of η for this gas mixture is larger than that for Ne + 0.1% Ar, especially at small values of Ep₀ (1-10 V cm^-1 Torr^-1).