Wire array implosion characteristics from determination of load inductance on the Z pulsed-power accelerator

The time-dependent inductance of Z pinches and other loads on the Z pulsed-power accelerator at Sandia National Laboratories [R. B. Spielman , Phys. Plasmas 5, 2105 (1998)] is determined by using electrical measurements and a lumped-circuit analysis. One finds that Sigma(k)alpha(k)V(k)-LI=d(LlIl)/dt, where Sigma(k)alpha(k)V(k) is the weighted sum of the Z-insulator-stack voltages, L is the equivalent inductance of the magnetically insulated transmission lines connecting the stack to the load, I is the added current for those lines, L-l is the load inductance, and I-l is the load current. L-l obtained from this expression is used to reconstruct the motion of the outer edge of wire-array Z-pinch loads, providing an estimate of the time at which the cores start moving significantly from their initial position. Results are consistent with previous optical measurements suggesting that core motion is delayed with respect to a zero-dimensional thin-shell model of the implosion. These results provide useful insights and constraints in experimental and theoretical research of wire arrays precursor and imploding plasma properties. (C) 2004 American Institute of Physics.