Performance of magnetically injected plasma opening switches for the Particle Beam Fusion Accelerator 2 (PBFA 2)

Plasma opening switch experiments using a magnetically injected plasma have been in progress since October 1988. Plasma densities of 1 x 1012 to 2 x 1013 e/cm3 have been injected from the anode side into the 8 cm gap of the 20 ohm magnetically insulated transmission line of PBFA II using a slowly rising Br,z magnetic field. This field confines the azimuthally-uniform plasma to produce switches up to 30 cm in length. Four MIP geometries have been investigated to find a higher electrical impedance when the switch opens. These studies have shown that a separation of 10 to 20 cm from the load is important to keep the POS from affecting the load performance. With such a separation, 20 to 30 TW of power at 7 to 11 MV has been delivered to electron and ion diode loads. Data on switch performance with various loads and factors that improve performance are discussed. 4 refs., 6 figs