Modeling of Barium Coverage and Electron Emission From a Controlled-Porosity Dispenser Cathode

A mathematical model was developed to estimate the dynamic coverage of barium on the surface of a controlled-porosity dispenser (CPD) cathode. This model considers the cumulative barium coverage due to all the neighboring pores and loss of barium due to evaporation. The zero field emission current density and work function obtained from synthesized current-voltage characteristics were derived from barium coverage data. The effect of tungsten wire size on these emission parameters has been studied. The optimum diameter of tungsten wire, used in the fabrication of the CPD cathode, has been determined.