Effect of discrete wires on the implosion dynamics of wire array Z pinches

A phenomenological model of wire array Z-pinch implosions, based on the ana lysis of experimental data obtained on the mega-ampere generator for plasma implosion experiments (MAGPIE) generator [I. H. Mitchell , Rev. Sci. Instr um. 67, 1533 (1996)], is described. The data show that during the first sim ilar to 80% of the implosion the wire cores remain stationary in their init ial positions, while the coronal plasma is continuously jetting from the wi re cores to the array axis. This phase ends by the formation of gaps in the wire cores, which occurs due to the nonuniformity of the ablation rate alo ng the wires. The final phase of the implosion starting at this time occurs as a rapid snowplow-like implosion of the radially distributed precursor p lasma, previously injected in the interior of the array. The density distri bution of the precursor plasma, being peaked on the array axis, could be a key factor providing stability of the wire array implosions operating in th e regime of discrete wires. The modified "initial" conditions for simulatio ns of wire array Z-pinch implosions with one-dimension (1D) and two-dimensi ons (2D) in the r-z plane, radiation-magnetohydrodynamic (MHD) codes, and a possible scaling to a larger drive current are discussed. (C) 2001 America n Institute of Physics.