SOME OBSERVATIONS OF IMPREGNATED TUNGSTEN CATHODES

Scanning microscope studies of a polished impregnated tungsten cathode has shown that active material in such cathodes conducts comparatively poorly at room temperature. The investigation of such cathodes at room-temperature and elevated temperatures using an energy-analysing collection system suggests that such techniques may have important uses in the study of other cathodes of the same type. The application of Auger spectroscopy with a spatial resolution of approximately 16μm has shown considerable spatial variation in the surface composition of impregnated tungsten cathodes. The results suggest the presence of both thick-film and monolayer-type regions at the surface of well-aged cathodes and indicate that the overall emission available from such cathodes is a function of the chemical nature of the barium present at the surface as well as its quantity. © 1979.