Research on the Effect of Transients of High-Voltage Power Supplies on the Lifetime of High-Power Vacuum Tubes: A Microscopic Assessment

Electron guns are used as the electron sources in high-power electron tubes. The generated electron beam in electric guns passes through an aperture at the center of the anode. Since the electron beam has considerable kinetic energy, any collision between the electron beam and the anode aperture edge damages the electron gun. Therefore, electron guns are designed to meet the compatibility between the diameters of the electron beam and the anode aperture. However, this compatibility is disrupted during the transient time interval of the gun's power supply. In this article, the cause of failure of the electron gun of high-power electron tubes is investigated for the transient interval of the gun's power supply. The investigations are carried out on a damaged anode; new experiments and computer simulations are also employed. The microscopic assessment shows the studied anode melted several times, proving the role of power supply transients in the failure of the studied gun. Numerical analyses are presented to verify the result of the microscopic assessments. The numerical analysis is carried out using the finite element method (FEM). The result of this study can provide information for proposing the appropriate transient interval of the vacuum tube's high-voltage power supplies.