X-ray diffraction of MgO along the shock Hugoniot

The structure of MgO upon shock compression was interrogated at the Omega Laser at the Laboratory for Laser Energetics, University of Rochester. Laser drives of up to 2 kJ over 7 ns focused onto a polyimide ablator were used to shock compress 50-$\mu{}m$ thick polycrystalline or single-crystal MgO. Scattered He-$\alpha$ X-rays from an Fe backlighter timed with maximum compression were collected using the PXRDiP diagnostic, in which image plates line the inner walls of a box attached to the target package. Other diagnostics utilized were VISAR (velocity history) and Streaked Optical Pyrometry (temperature). We will present experiments probing the $B1$$-$$B2$ phase transition of MgO and discuss the implications for detection of melting.\\[4pt] In collaboration with Thomas Duffy, Ray Smith, Rick Kraus, Federica Coppari, Dayne Fratanduono, Marius Millot, Amy Jenei, Jon Eggert, and Gilbert Collins, Lawrence Livermore National Laboratory.