Primary Ionization Coefficient Measurements in Penning Mixtures

Measurements have been made of the electron ionization coefficient $\ensuremath{\eta}$ in helium-hydrogen and neon-hydrogen gas mixtures over an extended range of $\frac{E}{{p}_{0}}$ values. The present results show a variation of $\ensuremath{\eta}$ with $\frac{E}{{p}_{0}}$ and hydrogen concentration similar to that previously obtained by Kruithof and Penning for the case of neon-argon mixtures. The maximum values of $\ensuremath{\eta}$ observed of 0.0302 and 0.0285 ${\mathrm{V}}^{\ensuremath{-}1}$ were obtained for hydrogen concentrations of 0.1% and at $\frac{E}{{p}_{0}}$ (V/cm\ifmmode\times\else\texttimes\fi{}Torr) values of 15.0 and 3.0 for helium-hydrogen and neon-hydrogen mixtures, respectively. Comparison is made of these results with the neon-argon measurements of Kruithof and Penning. In addition, the present data are compared with ionization measurements obtained using other techniques.