Circuit-code modeling of the PBFA Z for z-pinch experiments

The SCREAMER and the TL codes were used to design the z-pinch modification of PBFA II, which is now called Z. In the design phase an equivalent voltage was used to initiate the simulations. Good agreement between the measured waveforms and design simulations has been achieved. Full-circuit, shortened-circuit, and equivalent-circuit simulations have been used. All use a loss model that discards the plasma current in the vacuum magnetically insulated transmission lines (MITLs) at the post hole convolute (PHC). Voltage measurements provide an equivalent voltage which is used as a starting point for four-level circuit and equivalent-circuit simulations. Both full-circuit and shortened-circuit simulations use a four-line model. The thirty-six lines are lumped into four, nine-line equivalent circuits. The full circuit includes the erected Marx bank, the intermediate store water capacitor, the laser-triggered spark gap, the line 1, 2 and 3 pulse forming lines, the coax to biplate transition, the water biplates, the vacuum stack with water and vacuum flares, the MITLs, the PHC, and the z-pinch load. Because of the difficulty in making load current measurements, the model has been used to infer load current and implosion characteristics. The model has also been used to predict optimal pinch load configurations.