Shock compression of liquid helium to 360 GPa

Data for the shock equation of state of helium are obtained up to 360 G Pa , nearly doubling the pressure of previous experimental measurements. The helium samples are first precompressed to 0.35–0.42 g c m − 3 in a diamond anvil cell prior to laser-driven shock compression at the Omega Laser Facility. Time-resolved Doppler velocimetry and pyrometry reveal significant reflectivity and greater compressibility compared to the predictions of existing broad-range tabular equation of state models, which may be caused by the onset of ionization. These experimental observations, however, are largely captured with molecular-dynamics simulations based on density functional theory, affirming the ability of first-principles techniques to capture complex physics, while enabling critical insight for the behavior of warm dense helium in Jovian interiors and white dwarf atmospheres.