高功率单孔柱-孔汇聚传输结构的电磁粒子仿真

Electromagnetic particle-in-cell simulation of high-power single-hole post-hole convolute

柱-孔汇聚结构(PHC)附近高功率脉冲电流的损失是脉冲功率技术领域的研究热点,是研制下一代大型脉冲功率装置的技术瓶颈.本文建立了单孔柱-孔汇聚结构的3维仿真模型,采用粒子(PIC)仿真算法,分别在阴极发射电子以及阴极等离子体等情况下,计算了单孔柱-孔汇聚结构的电流传输特性,首次在仿真过程中考虑了阴极负离子的运动对单孔PHC阴阳极间隙闭合的影响.仿真结果表明阴极等离子体导致了阴阳极间距明显地缩短,从而引起电流损失.同时获得了阴极等离子体平均扩展速度为3.76 cm/μs.更为重要的是,当阴极等离子体中含有负离子时,单孔柱-孔汇聚结构电流损失的现象更为显著.同时获得了负离子平均漂移速度约为10 cm/μs.仿真结果显示阴极负离子在PHC阴阳极间隙闭合过程中,同样发挥了显著的作用,是阴阳极间隙闭合的重要因素之一.研究结果有助于深入理解高功率PHC电流损失的物理机理,也可为高功率PHC的设计提供重要理论基础.

The post-hole convolutes(PHCs)are used in pulsed high-power generators to add the output currents of the magnetically insulated transmission lines(MITLs)and deliver the combined current to a single MITL.Then the single MITL delivers the combined current to the load.Magnetic insulation of electron flow is lost near the post-hole convolute(PHC)in the high-power generator.Although cathode plasma and anode ions are widely considered as the factors of the magnetic insulation collapse,there are some other factors that are needed to study.In this paper,the cathode negative ions are considered in the PIC simulation of a single-hole PHC.In this work,we examine the evolution and dynamics of the negative ions in the PHC.The simulation results demonstrate that there are no current losses while the cathode emits only electrons,little current losses(10 kA out of’a total current of 900 kA)while the cathode emits plasma including electrons and ions,and obvious current losses(20 kA out of a total current of 900 kA) while the cathode emits plasma including the electrons,ions and negative ions.The results also indicate that the velocity of the negative ions is about 10 cm/μs,larger than that of the cathode plasma including the electrons and the ions.All results suggest that the cathode negative ions can play an important role in the magnetic insulation collapse,and should be considered carefully in experiment.