Study on particle generation model of anode in rod-pinch diode

Abstract

<sec>Flash radiography technology is commonly used in detonation physics experiments and nondestructive testing, in which an X-ray diode is an integral part of flash radiography equipment. Its function is to convert the electric energy stored in the front power supply into X-rays through the bremsstrahlung effect. Rod-pinch diode is one of the most commonly used X-ray diodes in 1–4 MV. It has the characteristics of a small focal spot and high imaging resolution. The anode ions of the rod pinch diode come from the anode plasma, and the anode plasma electrons are generated at the same time as the anode plasma ions. Before the establishment of the bipolar current between the anode and cathode of the rod pinch diode, these electrons are mainly absorbed by the anode; however, after the formation of the bipolar current, due to the zero electric field on the anode surface, plasma electrons will accumulate near the anode surface and will not be absorbed. Given the theoretical derivation of bipolar current in the gap between anode and cathode of rod pinch diode in the early stage, it is necessary to study the electrons in anode plasma.</sec><sec>The simulation of the rod-pinch diode is an essential tool for improving the performance of the rod-pinch diode. To improve simulation accuracy, it is necessary to study the emission mechanism of cathode and anode particles and continuously optimize the simulation model. In this paper, PIC and Monte Carlo simulation are used. An anode plasma model is proposed in this work based on the anode ion emission model of the rod-pinch diode and the characteristics of space charge bipolar flow, that is, when the anode plasma environment is fully established, the electric field on the anode surface is zero, and ions and electrons will accumulate on the anode surface. The new model is analyzed in detail and compared with the anode ion emission model in rod-pinch diode current, electromagnetic field distribution between cathode and anode, electron energy spectrum, motion state of electron incident anode rod, dose, and spot size. The results show that the calculation results from the new model are closer to the experimental results, which shows that the role of electrons accumulated near the anode in the plasma cannot be ignored in the numerical calculation of the rod-pinch diode anode rod surface plasma.</sec>