Analysis of Diagnostic X-Ray Spectra of Implosions at the NIF

Ge dopant is added to CH ablators of NIF implosions to absorb x-ray preheat. Ge K-shell spectral line emission provides a core/shell-mix diagnostic.\footnote{S. P. Regan, this conference.} K$_{\alpha }$ fluorescence from shell dopant is directly related to the K-edge absorption by the dopant, giving a measure of shell compression. A model of the He-like line and satellite emission is fit to measured spectra to assay the mix mass. Constraints from 1-D simulations are considered. Ge line spectra are fit well by the model at single temperature-density points, giving mix masses that are typically below the 100-ng allowance for hot-spot mix in ignition implosions on the NIF.\footnote{S. W. Haan\textit{ et al.}, Phys. Plasmas \textbf{18}, 051001 (2011).} This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302.