Investigation of the pressure-volume-temperature equation of state for dense hydrogen-helium mixture using multi-shock compression method

Abstract

The multi-shock Hugoniot and shock temperatures of gaseous hydrogen-helium equimolar mixture with initial pressure and temperature of～30MPa and～90 K have been measured up to 140 GPa using two-stage light gas gun and shock reverberation technique. Two kinds of multi-channel pyrometer systems with different sensitivities, were used in experiment for diagnostics, because the thermal radiation of the sample in the first-shock state is lower than that in the multi-shocked states by a magnitude of one to two orders. The measured pressure, volume and temperature are respectively 5GPa, 12.0cm3/mol and 3030 K in the first-shock state, 27GPa, 6.7cm3/mol and 5070K in the second -shock state, and 105GPa, 4.0cm3/mol and 5090K in the fourth-shock state. The results for the first- and second-shock states are well described by the fluid perturbation theory and dissociation model. It demonstrates that the dissociation of molecular hydrogen of the compressed sample is negligible in the first-shock state, while about 7% and 32% of molecular hydrogen undergo dissociation in the second-and fourth-shock states, respectively. The fourth-shock temperature measured was lower than the prediction for～2000K.