Developing a high-flux, high-energy continuum backlighter for extended X-ray absorption fine structure measurements at the National Ignition Facility*

Extended X-ray absorption fine structure (EXAFS) spectroscopy is a powerful tool for in-situ characterization of matter in the high energy density regime. An EXAFS platform is currently being developed on the National Ignition Facility (NIF). Development of a suitable X-ray backlighter involves minimizing the temporal duration and source size while maximizing spectral smoothness and brightness. One approach involves imploding a spherical shell, which generates a high-flux X-ray flash at stagnation. We present results from a series of experiments comparing the X-ray source properties produced by imploded empty and Ar-filled glow discharge polymer (GDP) capsules. We find that 1 atm and 4 atm fill pressures produce similar X-ray spectra compared to empty GDP capsules with a significant reduction in spot size.