Designs for spherically-converging shock experiments to measure wider ranges of states*

Radiographic experiments with spherically-converging shocks can access a wider range of pressures and off-Hugoniot states by altering the target design and drive pulse, while still providing absolute equation of state (EOS) measurements. Shaping the laser pulse to drive the sample with a controlled ramp behind the initial shock, it thus strengthens more in the outer region of the sample before convergence effects dominate, exploring a wider range of shock pressures with a single shot. We have also started analyzing the outgoing shock, which in principle provides information on a family of double-shocked states though with larger uncertainty. By inserting a central ball of higher-impedance material, an earlier, reflected outgoing shock is produced which is easier to analyze, providing off-Hugoniot data needed to interpret relative EOS measurements from our Mach wave platform. The shock transmitted into the ball, reflecting from the center, provides an integrated measurement of the EOS at even higher pressures. Finally, a gap or low density region between the ball and shell provides the potential to compress the ball to much higher densities along paths between the Hugoniot and isentrope.