X-RAY SPECTROSCOPY OF HIGH-ENERGY DENSITY INERTIAL CONFINEMENT FUSIONPLASMAS

Analysis is presented of K- and L-shell spectra obtained from Ar and X e dopants seeded into the fuel region of plastic capsules indirectly i mploded using the Nova laser. Stark broadening measurements of the n = 3-1 lines in H- and He-like Ar (Ar Ly-beta and He-beta, respectively) are used to infer fuel electron density, while spatially averaged fue l electron temperature is deduced from the ratio of the intensities of these lines. Systematic variations in Ar spectral features are observ ed as a function of drive conditions. A spectral postprocessing code h as been developed to simulate experimental spectra by taking into acco unt spatial gradients and line transfer effects, and shows good agreem ent with experimental data. It is shown that correct modeling of the x -ray emission requires a proper treatment of the coupled radiative tra nsfer and kinetics problem. Continuum lowering effects are shown not t o affect diagnostic line ratios, within the confines of a simple model . A recently developed diagnostic based on fitting measured line profi les of Ar He-beta and its associated dielectronic satellites to theory is shown to provide a simultaneous measure of electron temperature an d electron density. L-shell Xe spectroscopy is under development as an electron temperature and electron-density diagnostic. Density and tem perature sensitive ratios of spectral features each consisting of many lines have been identified. Observed Xe spectra from imploded cores s how the same qualitative behavior with temperature, as predicted by mo del calculations of Xe emission spectra. Stark broadening of Ne-like X e 4-2 lines appears viable as an electron density diagnostic for N(e) approximately 10(25) CM-3 and is under continuing investigation. (Base d on the invited paper 8I3 at the 1992 APS/DPP annual meeting [Bull. A m. Phys. Soc. 37, 1553 (1992)].)