Surface studies on the impregnated tungsten thermionic cathode

Abstract

Auger spectroscopy, work function measurements, and residual gas analysis are the techniques used in this study of an active cathode operated at nominal values of emission and temperature. The surface properties of conventional impregnated cathodes are investigated by the use of Auger spectroscopy and work function measurements, and these are compared with a synthesized barium or barium oxide coated tungsten surface. The latter surface is prepared by evaporating barium from a KIC barium getter in an ultra high vacuum system on to a tungsten surface which can be heated to elevated temperatures. Multilayer or monolayer coverages can be investigated using this technique. The results of these measurements show the surface of an impregnated tungsten cathode is identical to that observed for a synthesized monolayer of barium on tungsten, using the criteria of identical Auger patterns and work functions.