Principle and simulation of a high voltage bushing for a repetitive electron accelerator

A cylindrical graded bushing for the electron gun of the ASTRA-M pulsed repetitive accelerator was developed and simulated. In previous tests of the cylindrical graded bushing, primary reasons of electrical breakdown and degradation of dielectric elements were determined. Computational software was used to analyze the electric fields and simulate processes in the voltage grading system of the cylindrical bushing. This enabled proper modification and correction to the insulator structure for known problems. The new bushing has a conical structure instead of cylindrical one. The voltage graduation system uses nonsymmetrical voltage dividing for equal potential distribution along the grading electrodes. The grading electrodes provide shielding of organic dielectric surfaces from accelerated electrons and ultraviolet irradiation. Transmitted energy losses of up to 10% have been estimated in the nonsymmetrical voltage divider of conical bushing by simulating of high voltage pulse of 600 kV amplitude and 400 ns duration.