Optimization of dispenser cathode

Abstract

The problem of optimization of emission properties of industrial thermionic dispenser cathodes is lying in its complexity and difficulty of experimental identification of elemental processes and structural aspects of the cathode technology and its usage. As a rule the functioning of most efficient barium-oxygen molecular layer cathodes is looked upon only as a process of supplying of the cathode surface with barium atoms needed for the maintenance of the Ba-O-Ne layer by the Knudsen flow through the cathode body pores without due attention to the questions of BaO or O movement via surface migration and possible chemical reactions on the cathode surface and in the cathode volume. In the present report we try to widen means of model understanding of the processes by using of an approach consisted in computer simulation of the main processes taking place in the volume and the surface of the cathode. In the report will be presented results of studying the dynamic equilibrium between the surface layer composition and the main branches of the particle flow; the Knudsen flow and the particle surface migration processes as well as the possibility of chemical reactions taking place parallely. One of the main conclusions of this study is that the Knudsen flow coexisting with surface migration in a simple system as parallel transport agents can not raise the delivery of adsorbing atoms to the cathode surface and only leads to deterioration of its emission properties and the working life.