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Abstract

A scheme to probe the temporal evolution of the K-shell photoabsorption edge in shock compressed aluminum is presented in two components. In the first component, a one dimensional hydrodynamic code coupled to a non-local thermodynamic equilibrium calculation is developed and used to model shock propagation and target preheat in laser irradiated CH-Al-Si multilayer targets. Single and multiple shocks are used to create conditions in the aluminum by which density, temperature and ionization effects on K-shell photoabsorption can be isolated. The final result consists of the optimal laser parameters and target designs for creating well characterized plasma states, necessary for accurate atomic modeling of the K-edge. The second component describes the results of x-ray spectra observed from 12 elements across the periodic table, in search of an emission source to backlight the K-edge measurement. Spectral flatness and high emission levels in the region of 1520-1600 eV around the K-edge of aluminum are the criteria for a suitable backlighter. Lead, gold and yttrium seem promising as backlighter sources, and the emission lines observed in silver provide a convenient spectral calibration source.