The equation of state of Invar alloy: a comparison of drive techniques

The high-pressure equation of state provides constraint on the material response at extreme conditions relevant to planetary interiors. Invar, a Fe_0.64Ni_0.36 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. We present measurements of the Hugoniot, overtaking-wave sound velocity, and release of Invar alloy between ~200 and ~1000 GPa using impactors launched via 2-stage light gas gun, magnetically-accelerated flyer plates, and laser-driven shocks. Results are compared between platforms to identify potential systematic uncertainties in the techniques.