高功率单孔柱-孔汇聚传输结构阴阳极间隙闭合速度理论分析

Analysis on Cathode-Anode Gap Closing Speed of High-Power Single-Hole Post-Hole Convolute Based on Effective Collisions

针对阴极负离子在柱孔汇聚结构(post-hole convolute,PHC)的阴阳极间隙闭合过程中发挥的作用,基于有效碰撞机制分析了阴极负离子流的运动特性。通过计算推导,获得了阴极负离子流扩散速度的表达式,分析了阴极负离子流扩散的特性。研究结果表明,PHC处的工作电压和负载阻抗是显著影响阴极负离子流扩散速度的重要因素。结合单孔PHC电磁场仿真结果,理论估算了单孔PHC阴极负离子流的扩散速度。结果表明,在“强光一号”加速器驱动下,阴极负离子流的扩散速度理论估算值为5.45~14.53 cm·μs^(-1)。理论估算结果与单孔PHC的粒子仿真计算和实验结果相近。最终的研究结果表明,阴极负离子的产生和演化是导致PHC阴阳极间隙闭合的重要因素。

Motion of plasma is main principle of cathode-anode(AK)gap closure.There are negative ions in the cathode plasma under the high linear current density.In recent research,the cathode negative ions are found playing an important role in the process of AK gap closure in the post-hole convolute(PHC).In this paper,we tried to analyze the motion characteristic of cathode negative ion flow based on effective collision principle.From the analysis,diffusion velocity expressions of cathode negative ion flow and its characteristics are obtained and analyzed.The results show that the operating voltage at the PHC and the load impedance are important factors that significantly affect the diffusion velocity of the negative ion flow.Combining the electromagnetic field simulation of the single-hole PHC which works in“Qianguang-I”accelerator,theoretical estimation value of diffusion velocity of cathode negative ion flow is 5.45~14.53 cm·μs^(-1),which are close to the results from the particle-in-cell simulation and the experiments of the single-hole PHC.Finally,the results show that the generation and evolution of cathode negative ions is an important factor to the closure of the AK gap in the PHC.