Probing thermal transport using Extended X-ray Absorption Fine Structure at the National Ignition Facility

Thermal transport measurements in dynamically compressed materials is important to understand thermal conductivity and equilibration rates in high-energy-density plasmas. In experiments performed at the National Ignition Facility (NIF), Extended X-ray Absorption Fine Structure (EXAFS) has been measured and used to constrain temperature, density, and phase in Cu near 400 GPa. These fine-structure modulations in the x-ray absorption are caused by photoelectron scattering off nearby atoms, and are sensitive to both local atomic spacing and thermal disorder. Measured EXAFS signals reveal an unexpected temperature sensitivity to the material layers adjacent to the Cu sample, and motivate the use of K-edge EXAFS as a temperature probe in thermal conductivity studies.