Measuring the Thermal Conductivity of Warm Dense Iron at the Omega Laser Facility*

Understanding the thermal conductivity of materials found in the cores of large rocky planets can help us predict planetary evolution and plays a role in determining the existence of a magnetic field. However, significant variations in scientific modeling and a scarcity of experimental measurements limit our understanding of materials at the extremes of temperature and pressure. Here we use our isochoric heating platform developed for the OMEGA 60 Laser System to recreate conditions close to those found in the interiors of Super-Earth planets. Our primary target is an insulated wire composed of a 5 μm Fe/Ni (95/5 %wt) alloy center encased in a 10 μm layer of borosilicate glass, acting as a proxy for the core-mantle boundary. After pressure equilibration, the shape of the density profile across the Fe/Ni-glass interface evolves primarily through thermal conductivity. This profile is measured with a spatial resolution on the order of 1 μm, which enables the accurate extraction of the conductivity scale length^1,2,3.

[1] C. H. Allen et al. Applied Optics 61 2022, 8

[2] M. Oliver et al. Rev. Sci. Instrum. 93 2022, 93502

[3] M. O. Schoelmerich et al. Rev. Sci. Instrum. 94 2023, 13104