Optimization of Insulator and Shield Geometry of 225 kV Electron Gun

In this paper, the electrical performance of 225 kV electron gun is optimized based on the avalanche theory of secondary electron emission. Due to the electron gun shield, the Angle between the electric field direction of the electron gun insulator and the insulator surface changes in positive and negative directions. Different discussions should be made on the insulators in the acting area of the shield and other areas. Bessel curve and spline curve were selected to parameterize the model of insulator and shield. The ratio of normal electric field and tangential electric field of insulator outer contour, integral value of tangential electric field of insulator outer contour along the outer contour and maximum field intensity of shield surface were taken as the optimization objective function, and the Nelder-Mead approximate gradient algorithm method was used to solve the problem. After optimization, the maximum electric field strength on the shield surface is reduced by 37.3%, the field strength at the cathode triple junction (CTJ) is reduced by 76.7%, and the maximum electric field strength on the insulator surface is reduced by 25.5%. The tangential electric field distribution on the insulator surface is also optimized.