OPTIMIZATION OF K-SHELL EMISSION IN ALUMINUM Z-PINCH IMPLOSIONS - THEORY VERSUS EXPERIMENT

Two sets of z-pinch experiments were recently completed at the Saturn and Phoenix facilities of Sandia National Laboratories and the Naval S urface Warfare Center, respectively, using aluminum wire arrays of dif ferent wire and array diameters. Measurements of the total x-ray yield from the K shell of aluminum were made. In this paper, a comparison o f these measurements is made to both theoretical predictions and to a similar set of earlier measurements that were made at the Double Eagle facility of Physics International Company, These three sets of yield measurements have points of agreement with predicted yields and with e ach other, but they also show points of mutual disagreement, whose sig nificance is discussed. The data are analyzed using a slightly revised version of a previously published K-shell yield scaling law, and they support the existence of a reasonably well defined region in (load ma ss)-(implosion velocity) space in which plasma kinetic energy is effic iently converted into K-shell x rays. Furthermore, a correlation is ob served between the inferred conversion efficiencies and the times in w hich the implosions occur relative to the times when each generator's short-circuit current reaches its peak value. Finally, unlike the Doub le Eagle experiments, the largest measured yields in the new experimen ts were observed to occur at the upper velocity boundary of the effici ent emission region. Moreover, the observed yields are in fairly good quantitative agreement with an earlier scaling law prediction of the m aximum K-shell x-ray yield from aluminum as a function of load mass as suming kinetic energy conversion alone.