Surface Flashover Mechanism of Alumina Ceramics in High Temperature Cesium Vapor

The cesium vapor in the alumina ceramic gap of the metal ceramic unit of thermionic energy converter is prone to surface flashover under the action of emitter voltage. In order to study the surface flashover mechanism of alumina ceramics in high temperature cesium vapor, special experimental samples were designed and manufactured, and a surface flashover test platform was designed and built. The key flashover voltage data were obtained by carrying out surface flashover test. The test results show that cesium vapor can cause surface resistance of alumina ceramic to drop exponentially, and cesium vapor pressure has no direct effect on the surface flashover voltage at working temperature. The surface flashover voltage of alumina ceramics in cesium vapor is calculated by the dynamic arc model of contamination flashover. The comparison between the calculated results and the test data shows that the cesium contamination layer formed by the adhesion of cesium vapor is the main factor of surface flashover. Based on the SEEA model and Townsend gas discharge theory, it is shown that cesium vapor can promote the collision ionization of the space and cathode surface, and is conducive to the formation of surface flashover of alumina ceramics.