The Effect of Radial Electric Fields on Plasma Formation in Wire Array Z-Pinches

Summary form only given. We will present experimental observations of the effect of the radial electric field on plasma formation and implosion dynamics in wire array Z-pinches. Experiments were performed on the 1 MA MAGPIE generator, with 8 mm diameter Al wire arrays in configurations in which the polarity of the radial electric field was reversed midway along the wires of an array. The wire cores in the two halves of the array have demonstrated a factor of ~2 difference in the ablation rates, resulting in a difference in the implosion times of the two halves. The difference in the ablation rates is correlated with the difference in the size of the wire cores and with the difference in the inward flow velocity of the precursor plasma. The change in the ablation velocity did not change the qualitative features of the implosion dynamics of the two parts of the array. The implosion still starts after formation of gaps in the wire cores and leaves trailing mass behind. Possible mechanisms responsible for the observed effect of polarity of the radial electric field on the ablation rate in wire array implosions will be discussed.