Modeling of DM1 POS and load performance

In this paper, the authors study the performance of the plasma opening switch (POS) and electron-beam diode load on the DM1 pulsed power generator using the transmission-line circuit code BERTHA, the electron/photon-transport code CYLTRAN, and the 2-dimensional particle-in-cell (PIG) code MAGIC. The results suggest that of the 52 kJ required to be delivered to the load to account for the observed radiation, up to 75% is associated with current not flowing in the cathode. This noncathode current cannot be explained by electron vacuum flow only, implying the presence of plasma. Further, the inferred experimental diode impedance, 11 /spl Omega/, is much higher than optimum. Assuming no change in the DM1 conduction current/time and POS performance, an optimum diode impedance of 2 /spl Omega/, and a POS-to-load inductance reduced by 75%, the analysis suggests that the load energy on DM1 can range from 54 kJ to 94 kJ, depending on how much noncathode current reaches the load. The analysis also suggests that to obtain agreement between features of the measurements and calculations, the DM1 flow impedance (gap) must decay after opening and ions must be present in the vacuum transmission line between the POS and load. Understanding of the coupling between the POS and e-beam load remains incomplete.