The 6th International Conference on Matter and Radiation at Extremes (ICMRE2023)

76 / 2023-04-12 23:04:43

Study on the Equation of State and Sound Velocity of Warm Dense Matter Produced by Extreme Shock Compression of Gases and Solids

High Pressure Physics and Materials Science > Dynamic behavior of materials under compression-II

The thermodynamic properties of materials under extremely high pressure-temperature (P-T) conditions are of great significance largely due to the key applications for geophysics, planetary science, and inertial confinement fusion (ICF). Generating such extreme conditions in the laboratory remains highly challenging and is still the subject of ongoing attention and exploration. Based on the gas gun experimental platform, we have developed the multiple reflection compression technique of shockwave and the three-stage gas gun hypervelocity launch techniques based on the gradient density impactor (GDI), which can produce shock pressures of several hundred GPa and TPa in dense gases and solids, respectively. We have conducted multiple reflection compression and hypervelocity shock experiments on low-Z gases such as hydrogen [1], krypton [2], deuterium-helium mixtures [3], and high-Z metals such as gold and platinum. For the low-Z gases, we obtained equation of state (EOS) data up to about 200 GPa and 50,000 K, and using the quasi-adiabatic characteristics of the late stage of multiple reflection compression, we obtained sound velocity data for low-Z gases in the megabar pressure range. For high-Z metals, the obtained Hugoniot data reached a maximum pressure of 1.1 TPa, and we discovered the "softening" behavior in the Hugoniot above ~0.6 TPa caused by thermal excitation (ionization) of the 5d electrons in gold under extreme shock compression. These results will greatly promote the understanding of warm dense matter (WDM), as well as the construction and verification of theoretical models in WDM regime.