Properties of fluid deuterium under double-shock compression to several Mbar

The compressibility of fluid deuterium up to several Mbar has been probed using laser-driven shock waves reflected from a quartz anvil. Combining high-precision (similar to1%) shock velocity measurements with the double-shock technique, where differences in equation of state (EOS) models are magnified, has allowed better discrimination between theoretical predictions in the second-shock regime. Double-shock results are in agreement with the stiffer EOS models-which exhibit roughly fourfold single-shock compression-for initial shocks up to 1 Mbar and above 2 Mbar, but diverge from these predictions in between. Softer EOS models-which exhibit sixfold single-shock compression at 1 Mbar-overestimate the reshock pressure for the entire range under study. (C) 2004 American Institute of Physics.