Reactions between Oxide Cathodes and Gases at Very Low Pressures

Abstract

A method is described by which the behaviour of oxide cathodes under the impact of gases at pressures between 10-7 and 10-5mm Hg can be studied. From the cathode under investigation saturated pulsed emission and space-charge-limited emission currents are drawn simultaneously. Whilst the pulsed emission is used as a measure of thermionic emissivity, the space-charge-limited emission is employed for operating an ionization gauge which indicates the gas pressure directly in front of the cathode. The experimental tube is connected to the pump via a capillary, and the rate of gas flowing into the cathode can be determined from measurements of the two pressures at either end of capillary.