The ability to study material response during isentropic compression has been a grand challenge of the scientific community for several decades. However, development of precision techniques for producing isentropic compression at high pressures has been limited. The revolutionary advance for using planar magnetic loading on the Z accelerator accelerated this goal by enabling quasi-isentropic studies on macroscopically sized materials to over 5 Mbar. In addition, the accelerator is easily configured to launch flyer plates to velocities more than four times higher than possible with conventional launchers, thus allowing shock compression studies in the laboratory to pressures exceeding 20 Mbar.

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Laser-driven dynamic compression has been used to study extreme conditions of various materials. Very high pressures and temperatures can be generated up to more than 10³ GPa and 10⁵ K, respectively. This approach, which has been developed as a strong driving force in the inertial confinement fusion research, now provides a very wide range of pressures, densities and even low temperatures. This review presents a part of the past 10-year works on Hugoniot based equation-of-state (EOS), current trends of the off-Hugoniot generation and measurements, and a future perspective of high-pressure condensed matter research toward undiscovered metallic materials in the Osaka University.

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Dynamics of materials under laser shock compression has been studied by using nanosecond time-resolved Raman spectroscopy. Laser shock is induced by focusing 10-ns pulse laser and Raman scattering is induced by 25-ps pulse laser. Liquid-solid phase transition of benzene under shock compression at 3.7 GPa has been observed within 20 ns by using time-resolved coherent anti-Stokes Raman scattering. Structural phase transition of polytetrafluoroethylene from spiral structure to planar zigzag structure has been observed at 1 GPa within 10 ns.

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Through the determination of Hugoniot parameters, we can get useful information about high-pressure phase transition, equations of state (EOS), etc. of solids, without pressure calibration. We have performed the Hugoniot-measurement experiments on various kinds of hard materials of chalcogenides, oxides, nitrides and borides by using a high time-resolution streak camera system (inclined-mirror method) to investigate the yielding property, phase transition and EOS. It was found that almost all brittle materials behave as an elasto-isotropic solid unlike metals (elasto-plastic solid), except TiB₂. The high-pressure phase transitions were observed for ZnS, ZnSe, TiO₂, ZrO₂, Gd₃Ga₅O₁₂, AlN and B₄C. Some oxide materials showed virtually incompressible property in the high-pressure phase region. Here, the Hugoniot-compression data are reviewed, and the yield property and phase transition of these hard materials are discussed, as well as the EOS of the high-pressure phase.

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This paper is the history of the discovery of metallic, fluid hydrogen at 3000 K achieved with a two-stage light-gas gun (2SG) at the Lawrence Livermore National Laboratory (LLNL). The temperature is low in that the electrons are highly degenerate and the experimental lifetime is long in that the fluid is in thermal equilibrium. The necessary technology and experimental data were developed over a period of twenty-five years without realizing the end result would be metallic fluid hydrogen. The requirements for success were physical intuition, creative thinking concerning experiments to be performed and how to interpret results, persistence, a willingness to take risks, and luck. Knowing where to look is not luck, but the cooperation of nature is required to make any discovery. The biggest impediment was the funding system, which discourages risk.

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Current trends in research on shock experiments to understand the fundamentals of impact phenomena were briefly reviewed. It was addressed that dynamic behavior of volatile-bearing materials is important although many experimental difficulties are recognized technically. The subject under various initial conditions will become more critical for detailed understanding of the impact phenomena in the universe. Overhauling of the current attitude in this research area and new development with a long-term perspective are required in Japan.

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In this article, current research trends and the future in dynamic processing of materials are reviewed. Some fundamentals and recent topics in the related issues are introduced for explosive welding, explosive powder compaction and shock-induced reaction synthesis, which are mainly based on some research works made at the Shock Wave and Condensed Matter Research Center, Kumamoto University.

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In this article, the contents of my doctoral thesis are briefly reviewed. I have developed 10 GPa class micro diamond anvil cell (DAC) in order to investigate high-pressure effect on filled skutterudite compounds. In addition, a way of setting up for high-pressure resistivity measurements using a four-probe method was established. Here, I focus on the heavy fermion superconductor PrOs₄Sb₁₂ and present pressure and magnetic field effects on the electrical resistivity by using the newly developed DAC with pressures up to 10 GPa.

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According to the liquid-liquid critical point hypothesis of water, liquid water separates into low- and high-density liquid phases at low temperature and high pressure, and these liquid phases become the known low- and high-density amorphous ices below their glass transition temperatures. An accumulation of experimental and theoretical results seems to support this hypothesis, and this hypothesis may virtually explain "the mysteries of water" including the density maximum at 277 K. Aqueous solutions and the confined water appear to be readily interpreted on the hypothesis.

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