Bright-Spot Contributions to Hardphoton Continuum K-Shell Yield from Argon and Stainless-Steel Load Implosions on Z

In Z-pinch implosions, K-shell radiation often comes from isolated bright spots, whose density and/or temperature significantly differ from the background plasma parameters [1] - [3] . The prominence of bright spots in many radiating materials raises questions about the applicability of the analytical [4] and numerical predictions of K-shell yields that do not accurately describe small-scale radiating structures. Our study was motivated by the spectroscopic analysis done at Weizmann [5] , indicating high densities and small sizes of K-shell emitting plasmas in wire-array loads on Z. We analyzed the data from argon gas-puff and stainless-steel wire-array shots on Z, which produced high yields in K-shell lines and the hard-photon continuum. We compared the ion densities inferred from the observed K-shell spectra using the CRE model with the average densities of the radiating plasmas. The Ar plasma was determined to be energy-rich, its average parameters being consistent with K-shell yields and spectra. On the contrary, the stainless-steel plasma is energy-poor. Its spectra indicate that the emission comes from bright spots whose density is much greater than the background plasma.