杆箍缩二极管阳极杆粒子生成模型研究

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

杆箍缩二极管的模拟工作是指导杆箍缩二极管性能改进的重要工具,为提升模拟的准确性,本文对阳极等离子体产生机制开展研究.采用particle in cell和蒙特卡洛的模拟计算方法,在杆箍缩二极管阳极离子发射模型的基础上,根据空间电荷双极性流特性,着重研究等离子体电子的作用,提出阳极等离子体模型.本文以目前的实验结果为基础,以数值计算为主要手段对新模型进行了详细的分析,并在杆箍缩二极管电流、杆箍缩二极管阴阳极间隙电场分布、电子能谱、电子入射阳极杆的运动状态、X射线剂量及成像焦斑计算等方面与阳极离子发射模型进行详细对比.研究表明,新模型计算结果更接近实验测量结果,描述杆箍缩二极管物理过程不能忽视阳极等离子体电子的作用.

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.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.