Improvement of Electron Gun Breakdown Performance Through Surface Flashover and Discharge Studies

The reliable and uninterrupted operation of electron gun for refractory metal melting application requires a systematic study of surface flashover and electron beam-generated plasma discharge (EB-GPD) characteristics. These are highly influenced by insulator and target material characteristics. However, both lead to high-voltage (HV) breakdown of electron gun due to electric field intensification, insulator failure due to its sputtering and coating by backscattered electrons as well as secondary emitted electrons from the target material. This article deals with performance optimization of 2700-bent directly heated electron gun (DHEG) for device improvement. To achieve this, systematic study and analysis of insulator and target materials have been done through: 1) detailed 3-D simulations to study surface flashover by investigating electric field intensification in electron gun and 2) detailed study of discharge characteristics to investigate backscattered and secondary emitted electrons. The 3-D electrostatic, electromagnetic, and particle tracking simulations are done by using the Computer Simulation Technology (CST) Studio Particle tracking module. Discharge properties are evaluated by using disk-type Langmuir probe (LP) measurements accompanied by detailed mathematical calculations. This work helps to address the HV breakdown issue in electron gun, which is of great practical significance.