The equation of state of Invar alloy and systematic uncertainties in modeling the re-shock Hugoniot in quartz

The high-pressure equation of state provides constraint on the material response at extreme conditions relevant to planetary interiors. Invar, a Fe0.64Ni0.36 alloy, helps constrain the properties of the cores of Earth and other terrestrial planets when combined with the EOS of pure Fe and Ni. Furthermore, it is a common alloy frequently used in high-precision optics and electronics due to its low thermal expansion. Measurements of the principal Hugoniot between \textasciitilde 200 and \textasciitilde 1000 GPa using impactors launched via 2-stage light gas gun, magnetically-accelerated flyer plates, and laser-driven shocks are presented. Results demonstrate a systematic difference between direct-impact and laser-driven experiments which can be attributed to use of the quartz release model to calculate the re-shock Hugoniot. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology {\&} Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525.