Simulation of Cathode Spots Crater Formation on Zirconium Electrode

Abstract

The model of cathode spot including internal physical process is improved on pure zirconium (Zr) cathode, mass equation, momentum equation, heat transfer equation, potential equation are considered in current model. The mean charge state is 2.6 instead of an integer, so the Mackeown equation is shown. In simulation result, the discharge current can reach 7A, the potential can reach 0.23V, the maximum temperature is about 4300K and the maximum electron field is about 5×109V/m. Ablation rate in cathode spot crater development stage is calculated by different ways, simulation result shows that mass loss caused by evaporation can be ignored, most of metal corresponding to cathode spot crater leaves on cathode, droplets are the main reason for cathode ablation, and the ablation rates calculated by droplets are on the same order of magnitude with experiment results. In addition, when liquid metal rings break into droplets, the radius of droplets should be a little larger than the width of the liquid metal rings.