Life model of coated and uncoated thermionic dispenser cathodes

The life model for uncoated and coated (with osmium, indium film or film made from their alloys with refractory metals) thermionic dispenser cathodes has been developed based on the study of physical and chemical processes taking place within the volume and on the surface of these cathodes, depending on the operating temperature and the time of the operation as well as on the film systems simulating the operation of these cathodes. The model presented here, as well as the life models of the dispenser cathodes described earlier is based on the statement that the electron emission and lifetime of the dispenser cathodes at operating temperatures largely depend on the degree of their emitting surface coating with a film consisting of co-adsorbed atoms of barium and oxygen as well as the crystallographic structure and electronic properties of a refractory substrate material and the value of barium and oxygen atom flow from the volume to the surface of the cathode.