POWER-FLOW BETWEEN A PLASMA-OPENING SWITCH AND A LOAD SEPARATED BY A HIGH-INDUCTANCE MAGNETICALLY INSULATED TRANSMISSION-LINE

Results are presented from particle-in-cell simulations of the electro n flow launched from a plasma opening switch (POS) into a magnetically insulated transmission line (MITL) as the POS opens. The opening proc ess of the POS is treated by removing plasma from a fixed anode-cathod e gap with an opening time of tau(rise). To be similar to opening swit ch experiments at Physics International, the simulations were performe d with the same inductance L(MITL) between the POS and load. When L(MI TL)/tau(rise) is large compared to the POS flow impedance, this induct ance effectively isolates the POS from the load during the opening pro cess and the POS voltage is insensitive to changes in the load impedan ce. Analysis and simulations show that the peak load power is maximize d when the load impedance is equal to the POS flow impedance. In contr ast to previous theories and simulations of magnetically insulated flo ws, a large amount of electron flow in the MITL is concentrated near t he anode. This is a result of the high effective impedance imposed on the POS by the inductive load which causes a significant electron curr ent loss in the POS. As a result, many electrons lose insulation on th e load side of the POS gap and those that do flow into the MITL have b een accelerated to nearly the full POS potential. Electrons then EXB d rift on equipotential lines close to the anode as they enter the MITL and flow toward the load. Current losses in the MITL are observed due to the proximity of the electron flow to the anode. Some electrons flo w from the MITL directly into the load and are registered as load curr ent while others EXB drift back toward the POS along the cathode surfa ce. This is possible because the electron flow launched into the MITL from the POS is large enough to cause sufficient positive image charge s on the cathode so that the electric field points out of the cathode surface.