Evaluation of liquid equation of state for deuterium oxide (D2O) and perfluorooctane (C8F18) via tamped Richtmyer–Meshkov instability experiments

Window materials in shock compression experiments maintain shock stresses in samples and enable optical velocimetry measurements of the sample–window interface. Transparent liquids present unique opportunities as negligible-strength window materials that conform to nonuniform surfaces without adhesives or gaps. The equation of state (EOS) and dynamic strength of shock-loaded materials must be defined to accurately predict their behavior. Traditionally, these properties are characterized through separate experiments, including uniaxial-strain shock compression experiments for EOS and pressure-shear experiments for dynamic strength. More recently, the tamped Richtmyer–Meshkov instability (RMI) method was developed to measure dynamic strength through combined experiment and simulation. Here, we improve the tamped RMI method by directly determining the shock-compressed state of liquid tamper materials from dynamic radiographs. Impact experiments driving shock waves across corrugated metal–liquid interfaces at 2.5–5.2 km/s were recorded using x-ray phase contrast imaging. Radiographs of the tamper response were analyzed to define the EOS of D2O and C8F18. Material interface and shock wave locations were tracked to obtain shock and particle velocities, which calibrated linear shock-particle velocity Hugoniot relationships serving as reference curves for EOS surfaces, such as the Mie–Grüneisen EOS. The resulting EOS is compared to prior data and can be used in designing and analyzing experiments employing D2O and C8F18 as liquid windows. This method extends the utility of the tamped RMI method by allowing measurement of a sample EOS in addition to dynamic strength.