Developing an experimental platform to benchmark x-ray fluorescence spectroscopy as a temperature diagnostic for high-energy-density plasmas*

Accurate temperature models are critical in modeling planetary interiors and for inertial confinement fusion designs, as temperature affects many important physical properties such as ionization, heat transport, and compressibility. When constructing equation of state (EOS) models for high-energy-density plasmas, temperature measurements add an additional constraint to the more readily available pressure and density data. In this study, we present the development of the experimental platform and initial results for x-ray fluorescence spectroscopy (XFS) at temperatures of 10s of eV to be used as a temperature diagnostic in EOS experiments. The experiments conducted at the OMEGA laser facility use a buried layer of copper (Cu) tamped by plastic (CH) on both sides, the two sides are then irradiated by a symmetric laser drive. Simultaneous measurements using XFS, and x-ray absorption spectroscopy yield independent measures of the temperature. In addition, shock timing experiments on single-sided equivalent dimensioned targets measured with VISAR and SOP on the rear side with quartz window, to inform backlighting of XFS and x-ray absorption spectroscopy measurements. 

This work was performed under the auspices of the U.S. Department of Energy (DOE) by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and supported by Laboratory Directed Research and Development (LDRD) Grant No. 22-ERD-005. This material is based upon work supported by Sandia National Laboratory, managed, and operated by NTESS under DOE National Nuclear Security Administration contract DE-NA0003525.