3-D Modeling and Experimental Studies for a Thermionic Dispenser Cathode Activation Process

Abstract

The activation of dispenser cathodes while heating up to their brightness temperatures is a highly nonlinear and specific process. Since the cathode surface temperature is a crucial factor, controlling it and determining the physical and chemical factors affecting this parameter gives the opportunity to design dispenser cathodes more efficiently. Barium transport mechanism with temperature values can also be modeled. Thus, the extra time can be gained for activating cathode and it gives the advantages of determining cathode parameters that affecting directly emission quality and lifetime of the cathode. For this purpose, this article presents a 3-D modeling solution that is novel and very reliable for the analysis of this process. It has been obtained by the 3-D cathode model based on COMSOL Multiphysics simulations with heat transfer module environment. In addition to this, the degrees of temperature on the surface of our fabricated cathode have been measured experimentally as a function of delivered power for comparison with simulated data. The obtained results have been compared with MATLAB execution and also verified by values of a commercial-type cathode. The results show that the simulation data obtained by COMSOL have given a more realistic approach than theoretical ones. Thus, it has been observed that the activation process can be performed by the COMSOL model as a preliminary approach before heating a cathode physically.