The Townsend Ionization Coefficients for Ni and Al Cathodes in an Atmosphere of Hydrogen

Measurements of the first and second Townsend coefficients for ionization by collision have been carried out for surfaces of Ni and Al in an atmosphere of hydrogen. The Al surface was evaporated in an atmosphere of argon and is estimated to be a few hundred molecular layers thick. The values found for the α- and γ-coefficients are compared with the results previously reported for a Pt surface in hydrogen. The values of αp, in pure hydrogen, plotted as a function of X/p show a decreasing characteristic between values of X/p from 900 to 1400. The curves of values of γ plotted as a function of X/p show a characteristic photo-emission peak at an X/p of 131, and a gradual rise at the higher values of X/p. Sparking potential curves are calculated from the γ-values and are compared with the experimentally determined curves.