(POSTER) In-situ measurements of diamond from 220 to 570 Gpa along the principal hugoniot

Diamond is widely used in high-power laser experiments due to its optical transparency and high strength under compression. The latter of these two properties is not well understood. Previous work indicated conflicting results; high strength maintained to 800GPa (Bradley, 2009), complete loss of strength above the elastic limit (60-81GPa) (McWilliams, 2010), and orientation-dependent strength below the melt line (650 GPa) (Winey, 2020). We used X-ray diffraction to directly measure the in-situ density of single-crystal diamond under shock compression at the Omega EP laser. We used diamond shocked to pressures between 220 and 570 GPa to constrain the in-situ density above the elastic limit and below melting. This is an enhancement over previous studies, which analyzed transmitted shock wave profiles and thus had no mechanism for determining in-situ density. We report pressures (from velocimetry and impedance matching) and densities (from XRD) of diamond, interpret the strength under compression, compare results to known hydrostatic pressure-density relations, and update our uncertain EOS accordingly.