阳极杆箍缩二极管的理论模型及物理特性

闪光X射线源是获得高凝聚态物质内部物理图像的重要手段，阳极杆箍缩二极管(RPD)作为其重要组成部分之一，直接影响闪光X射线源照相质量。研究RPD物理特性对二极管物理结构优化设计及实验调试具有重要意义。分析了RPD空间电荷限制、弱箍缩和磁绝缘阶段物理模型。基于PIC模拟技术，编写了计算程序，研究了RPD不同阶段的电子电流、离子电流及电子束箍缩物理特性。通过理论分析，获得了特定几何结构RPD物理模型修正系数及各个阶段离子电流与电子电流比，验证了粒子模拟代码的有效性。模拟结果表明:空间电荷限制阶段，粒子模拟结果与双极性流计算结果一致；在弱箍缩和磁绝缘阶段，粒子模拟得到的总电流与磁绝缘模型计算结果一致，且与文献给出的经验拟合表达式计算结果一致；磁绝缘阶段离子电流与电子电流之比与电压和二极管几何结构相关，给出了离子电子电流比增大系数η与电压和阴阳极半径比的关系，该系数受电子、离子在不同结构二极管渡越时间的影响，随电压和阴阳极半径比增加而逼近恒定值。

Theoretical modeling and physical characteristics of rod-pinch diode

The rod-pinch diode (RPD) is a cylindrical pinched beam diode being developed as an intense pulsed small diameter bremsstrahlung source for flash X-ray radiography.The studying significance of the physical characteristics lies in optimizing geometry structure of RPD.Using PIC program and numerical simulation, a model of the rod-pinch diode operation based on space limited current at low voltage and self-magnetically limited current at high voltage is researched.Analysis shows that the diode characteristic is determined by space charge limited current at low voltage and self-magnetically limited critical current at high voltage.The simulation result is consistent with reference.Under the special conditions (space charge limited, weakly pinched and self-magnetically limited), the ratios of ion current to electron current are studied.The coefficient for calculating the self-magnetically limited ion to electron current ratio in the self-magnetically limited condition is affected by the electron and ion transit time and free from the high voltage.