Measurement of Temperature and Thermal Properties of Shocked LiF

Lithium fluoride (LiF) is commonly used as an optical window for velocimetry and pyrometry measurements in shock wave experiments due to its ability to remain transparent at very high pressures. In the latter, the sample/LiF window interface temperature is determined directly by measuring the amount of light emitted by it. However, inferring the temperature in the interior (or bulk) of the sample requires knowing the LiF temperature, as well as the thermal transport properties of both the sample and the window at the high P-T conditions realized in the experiment. In this work, we measured temperature and thermal diffusivity of LiF at high pressures by putting a thin (~300 nm) layer of emitter between two LiF anvils and shock compressing this assembly. For temperature measurement, graphite was used as an emitter, while for thermal conductivity measurement, we used tin. Graphite was used because it is closely impedance matched with LiF, reaches similar temperatures as LiF, and can be approximated as a blackbody. In the experiment with tin (Sn), Sn and LiF act as a heat source and a heat sink, respectively. Therefore, thermal diffusivity of LiF was determined by recording Sn/LiF interface temperature. In my talk, I will discuss the results from these experiments.