Developing x-ray Fresnel Diffractive-Refractive Radiography for Measuring Thermal Conductivity in Warm Dense Matter

Transport properties in warm dense matter (WDM), such as thermal conductivity, have extensive theoretical predictions but lack experimental benchmarking [1]. We have developed a Fresnel Diffractive Radiography (FDR) platform at the Omega Laser Facility, which enables high spatial resolution measurements of the evolution of an isochorically-heated WDM interface [2]. Novel 1 µm-wide slits provide a spatially coherent x-ray source that, in the presence of sharp density gradients, result in distinct diffraction fringes. Isochoric x-ray heating of CH-coated metal wires sets up a temperature differential at the material interface. After pressure equilibration, the interface is hydrodynamically-stable, and the evolution of the interface is driven primarily through thermal conduction, which modifies the temperature and density profiles. From the resulting shape of the diffraction fringes the thermal conductivity of the materials can be inferred.

[1] P.E. Grabowski et al. HEDP 37, 100905 (2020).

[2] C. H. Allen et al. AO 61, 1987 (2022).