Isentropic-Compression Equation-of-State Experiments Using the OMEGA Laser

Quasi-isentropic compression of materials can improve the understanding of equation of state (EOS) by providing off-Hugoniot measurements.~ Quasi-isentropic compression was used on the OMEGA Laser System to achieve peak pressures $>$10 Mbar in diamond and at relatively low temperatures of $<$1 eV. We report on a technique that uses this compression to study structural and optical properties of materials' high pressures. The reflectivity of aluminum samples is observed to dramatically decrease when compressed to $\sim $1 Mb. Several explanations for this will be discussed. This work was supported by U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302.