同心度对杆箍缩二极管物理特性的影响

Physical characteristics of rod-pinch diode with different concentricity

闪光X射线照相是获得高凝聚态物质内部物理图像的重要手段,阳极杆箍缩二极管是X射线源的重要组成部分之一,其设计直接影响X射线源稳定性。由于受装置结构及真空等因素的影响,使得阴阳极几何中心同心存在一定的困难。因此,评估同心偏差对二极管物理特性的影响,对提高闪光X射线源稳定性具有重要的意义。针对阴阳极几何中心同心偏差问题开展实验研究,分别取三种同心偏差度(小于1%,15.02%和22.92%)状态。在1MV电压下获得了不同同心偏差度下二极管电参数特性,并在此基础上结合理论模型分析了同心偏差度对二极管物理特性及电极等离子体扩散速度的影响。研究结果表明,随着同心偏差度增加,磁绝缘阶段阻抗下降率及等离子体扩散速度呈非线性增加,同时造成该阶段二极管阻抗与脉冲驱动源输出阻抗失配严重,降低了二极管与脉冲驱动源的能量耦合效率。

The rod-pinch diode is a cylindrical pinched beam diode that generates an intense pulsed small diameter bremsstrahlung source for flash radiography. If the pulse power source has the inductive voltage adder structure in vacuum vessels, the mechanical deformation caused by its long cantilever arm and air pressure could induce visible concentricity deviation to the anode and cathode structure. To evaluate that the concentricity of the cathode and anode geometrical centers does have some effect on the physical characteristics of the rod-pinch diode and the gap closure, a positive polarity rod-pinch diode was designed to work at 1 MV, and three different values of eccentricity were used in experiment： less than 1%, 15.06%, 22.92%. The experimental results show that the diode impedance decay rate is increased with a larger concentricity deviation. This implies that the electrode plasma expansion is fast. A larger concentricity deviation results in the impedance mismatch and decrease in energy coupling efficiency between the diode and pulse power source at the magnetically limited phase.