| In the field of Inertial Confinement Fusion (ICF), a major goal of spectroscopy is to uncover as much information as possible from a limited set of data. This work is focused on extracting temperature and density gradients, or spatial profiles, from data. At the University of Rochester's Laboratory for Laser Energetics, indirect and direct drive implosions of Ar-doped and D2-filled plastic microballoon targets were performed. Imaging of the implosion cores was provided by the Multi-Monochromatic X-ray Imager (MMI), which recorded Ar Lybeta, Hebeta, and Lyalpha narrow-band line and continuum images, as well as x-ray line spectra. Objective techniques have been developed in an IDL environment to process the data. Three spectroscopic methods are used to characterize the core gradients. One technique is a multi-objective search and reconstruction which utilizes a genetic algorithm to search for the temperature and density gradients. The other techniques are analyses involving the emissivity ratio of Lybeta/Hebeta to extract temperature, followed by the solution of either emissivity or intensity equations based on the Lybeta or Hebeta line to infer density. In particular, the idea of solving intensity equations permits the consideration of the opacity effect, which turns out to be sizeable even for quasi-optically thin lines (i.e. Lybeta and Hebeta). In order to further extract the mixing spatial profile and account for its effect on density, the optically-thick Lybeta line is brought into the analysis. To connect with a theoretical methodology, two independent mix models have been used to independently estimate the level of mixing in these experiments. Reasonable agreement between the results of the mix models and the experimental data analysis substantiate our ability to investigate mixing in ICF implosion cores. |
