Background As a high-energy radiation source, X-ray sources have been widely used in many research areas, such as radiation detection, radiation effects and surface thermodynamic effects. Bremsstrahlung diodes can produce X-ray sources with adjustable energy spectrum and pulse width.

Purpose In order to improve the quality of X-ray source, the physical process of electron beam generation and transmission to target in Bremsstrahlung diode needs to be studied deeply.

Methods In this paper, the generation and transmission characteristics of the electron beam in a bremsstrahlung diode which is called the low impedance nested double-ring diode are numerically simulated using the all electromagnetic PIC(Particle-in-Cell) code. Evolution of the electron beam propagation characteristics during the voltage pulse rise process is investigated emphatically, and the physical characteristics and operation principles of the diode are analyzed and summarized.

Results When the peak diode voltage is 1.5 MV, simulation results showed that the total beam current obtained on the target is about 2.47 MA, the impedance is 0.6 Ω and the maximum intensity of the self-magnetic field in the diode reaches 1.7 T. The typical physical images such as the spatial distribution of electric field and angular self-magnetic field in the diode, the distribution of electrons in real space and phase space, the distribution of electron numbers versus the electron energy, the radial position, and impact angles on the anode target surface are given by simulations. The influence of diode voltage waveform and end axial gap length on diode impedance, current and electron beam trajectory are also obtained by simulations when the other structural parameters are fixed.

Conclusions The simulation results will be used as the input parameters for subsequent calculation of X-ray dose and spatial distribution generated by electron bremsstrahlung using the Monte Carlo (MC) code.