In the present experiments, we measured the thermal radiation from water in an incident shock wave and a shock wave reflected from a barrier with higher dynamic stiffness—a transparent window of lithium fluoride or sapphire. The range of the incident shock pressures was 28–36 GPa. The purpose of this work was to obtain new data for verification of the equation of state of water at lower temperatures than those on the Hugoniot at the same pressures.

In double-shock compression up to 79 GPa, the temperature was found up to 2.8 kK. Temperature values measured by the brightness and color method are well consistent with each other.

The temperature and heat capacity behind the front of the first and second shock waves were calculated using an equation-of-state model, in which the coefficients were selected so as to match the data on shock compression of water in one shock wave, including the results of previous temperature measurements and the data of the present work. This equation-of-state model provided an adequate description of the new experimental data on the Hugoniot of repeated shock compression in the reflected wave.