Dynamic Temperature and Emissivity Determination in Shock Compressed Mineral Samples

Shock compression studies of minerals allow for the experimental measurement of properties necessary for accurately determining equations of state, including predicting a mineral’s behavior within planetary interiors. However, while pressure and volume can be measured precisely, temperature measurements are subject to assumptions of materials properties that produce varied results. One of the most predominant issues in accurate temperature determination is the emissivity of the shocked material. We have performed a series of gas gun compression experiments on forsterite (Mg₂SiO₄), quartz (SiO₂), and iron (Fe) utilizing discrete wavelength pyrometry, as well as streaked optical pyrometry using a xenon flashlamp light source to gather time- and wavelength-resolved reflectivity information. Our results show the assumption of constant emissivity with respect to both temperature and wavelength is not always valid, but can be retrieved from in-situ measurements or modeled preemptively. We will discuss the development of these techniques, target design, and options for situations where in-situ reflectivity determination is not possible.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.