NUMERICAL INVESTIGATION OF PLASMA EVOLUTION IN MAGNETICALLY INSULATED TRANSMISSION LINES

摘要

The formation and evolution of plasma from metal surfaces in high power vacuum discharges was studied using the particle-in cell simulation code LSP** a fully 3D parallel, electromagnetic PIC code designed for large-scale plasma simulations. It can be used in ID and 2D geometries and either Cartesian or cylindrical coordinate systems. Here, we present results from 2D cylindrical systems for a current waveform and an electrode configuration similar to those employed in ongoing experiments at the University of Nevada, Reno (UNR). It is observed in the experiments [0] that for sufficiently small anode cathode gaps, the MITL short circuits. We report on studies which attempt to simulate this behavior. Two distinct operating regimes are considered. The first considers the role of the MITL flow electrons on the heating of the anode surface and the subsequent emission of ions from the anode. In the second, a plasma layer is initialized on the anode side of the MITL (prior to arrival of the peak pulse). It is shown that for the case with just electron and ion emission from the MITL surfaces, the sheath currents provide only a few percent of the total current running in the MITL and thus cannot be responsible for MITL closure. When a plasma layer is placed on the anode side of MITL, however, this can result in nearly 50% of the main current being shorted across the A-K gap.