Effects of a Xe dopant on an Ar gas-puff implosion on Z

Two Ar gas-puff experiments, each using loads consisting of two annuli and a center jet, were recently performed on Sandia National Laboratories' Z machine. These shots had the same load except that one of them (Z2603) employed a Xe dopant of 0.8% by number in the jet, which was not present in the otherwise identical Z2605. The extensive diagnostics deployed in these experiments reveal that the presence of this small fraction of Xe had a profound effect on both the emitted radiation and hydrodynamic evolution of the pinch. Use of the Xe dramatically reduced the Ar K-shell yield from 373 ± 9% to 129 ± 9% kJ. However, the total yield increased slightly, from 1.02 ± 17% to 1.14 ± 17% MJ. Also, the K-shell power pulse for Z2603 exhibited two nearly equal peaks separated by ∼ 5 ns, but that of Z2605 consisted of a more conventional single peak. Analysis of time- and space-resolved K-shell spectra using a detailed atomic model indicates that a much greater fraction of the load mass was heated to the K-shell in the non-Xe shot Z2605. Previous average-ion calculations of Xe cooling rates [1] show that radiative cooling of the small 0.8% Xe fraction is nonetheless significant compared to that of the Ar and is therefore likely responsible for the differences in the shots.