Transition in X-ray yield, mass scaling observed in the high-wire-number, plasma-shell regime

Summary form only given. Initial calculations, based on classical transport coefficients and carried out to predict the efficiency with which the implosion kinetic energy of aluminum Z pinches could be thermalized and converted into kilovolt X rays, predicted a sharp transition between m/sup 2/ and m yield scaling, where m is the aluminum array mass. Later, when ad hoc increases in the heat conductivity and artificial viscosity were introduced into these calculations and the densities that were achieved on axis were sharply reduced, the transition from m/sup 2/ to m scaling was found to have shifted, but was otherwise still fairly sharp and well-defined. The location of these breakpoint curves defined the locus of implosion velocities at which the yields would obtain their maximum for different mass arrays. The first such mass breakpoint curve that was calculated is termed hard, while the second is termed soft. Early 24, 30, and 42 aluminum wire experiments on the Saturn accelerator at the Sandia National Laboratories confirmed the predictions of the soft breakpoint curve calculations. In this talk, we will present results from a more recent set of aluminum experiments on Saturn, in which the array mass was varied at a fixed array radius and in which the radius was varied for a fixed mass.