Towards a Dynamic Thermal Conductivity Measurement: Temperature Convergence of Iron Coatings to a Bulk Temperature Source

The thermal conductivity of iron under Earth’s core temperatures and pressures is a critical parameter in models of the geophysical history of Earth’s core. Recent DAC measurements and first principles calculations have presented conflicting trends in the thermal conductivity as a function of temperature and pressure, leading to large uncertainties in the predicted age of Earth’s solid inner core. Confidently resolving this discrepancy requires corroborative conductivity measurements using multiple experimental methodologies, however dynamic compression experiments have so far suffered from uncontrolled systematics. We present the results of gas gun experiments testing the convergence of coating temperatures to a bulk temperature source. A series of experiments were performed at 50 and 120 GPa, where Fe and Sn were used as coating and temperature source materials. Temperature of the coating material was measured using optical pyrometry, and simulations were performed which show matching trends in the observed temperature data for a range of input thermal conductivity values.