Advanced Dispenser Cathodes
Controlled porosity reservoir cathodes offer significantly improved performance over conventional impregnated cathodes. Optimized performance requires additional design to achieve reduced barium deposition on adjacent surfaces, increased lifetime, and high current density emission. This paper describes the achievable performance and the associated design requirements.
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.
Investigation of recovery characteristics after ion bombardment on scandate cathode
The scandate cathode has excellent electron emission capability. However, applications in vacuum electron devices are limited because of nonuniform emission and weak resistance to ion bombardment. A new method has been adopted for making scandate cathode. This type of scandate cathode showed more uniform emission and fast recovery characteristics after ion bombardment comparing with conventional impregnated scandate cathode. The results of XPS analysis before and after ion bombardment are presented.