In the first part of this article, the fundamental issues for shock compression are summarized as introductory to increase the interest for non-familiar persons aiming to apply it to various research fields. Recent results are reviewed, as the second part, on typical materials in the Earth and Planetary science at ultrahigh pressures. Recent technical developments enable us to observe and understand material behaviors under extreme conditions where new physics and chemistry are promising.
Since the inauguration in 2012, an X-ray Free Electron Laser (XFEL) facility SACLA has produced a number of significant achievements ranging in ultrafast chemistry, materials science, biology, and x-ray nonlinear optics. High-pressure science to investigate structural dynamics of material, which is compressed by shock waves generated with a high-power laser, is also one of the important applications of XFEL. In this article, current status and future perspectives of SACLA, as well as typical applications for high-pressure sciences, are reviewed.
In this article, a new experimental station is described. The station enables ultrafast X-ray diffraction (XRD) for dynamically compressed material as high as 100 GPa with temporal resolution less than ps. Such ultrashort resolution is obtained by an X-ray free electron laser (XFEL) whose pulse width is less than 10 fs. The station can realize in situ observations of material deformations such as shock wave propagation, formation of shock waves, plastic deformation, and phase transition. The applications of the station to dynamical compression opens unique path ways to explore kinetics of material deformation in context of the condensed matter physics.
In this article, we describe some of our studies which exploit time-resolved X-ray measurement using the X-ray pulse of synchrotron source and nanosecond laser pulse to investigate the real-time structural change of shocked material around Hugoniot Elastic Limit (HEL). Dynamics of lattice response, deformation, and elastic-plastic transition of solid under high-strain rate has not been well known, because the shock compression is an irreversible and extreme phenomena in a short time scale. We measured the lattice response of shocked CdS single crystal under anomalous elastic compression and the intermediate structural change of elastic shock-compressed silica glass using time-resolved X-ray diffraction and scattering. We have also developed sub-nanosecond time-resolved X-ray measurement system using high-power Nd:Glass laser in order to measure a lattice response in an elastic-plastic transition.
Laser-driven dynamic compression is used to study matters in extreme conditions. Warm Dense Matter (WDM) conditions, approximately defined at a solid density and temperatures between 0.1 and 10 eV, are created in materials under the laser-shock compression, of great current interest for high-energy density physics, planetary sciences, and inertial fusion energy research. At the WDM conditions, the micro-structure of material significantly influences the behavior and properties of material. X-ray free electron laser (XFEL) is a powerful tool to directly observe a structure and to reveal the time scale of the structural change under the dynamic high pressures. Here we present recent results of WDM experiments associated with strong shock equation of state and ultrafast observation of lattice dynamics.
The Hugoniot of magnesium oxide (MgO) has been investigated experimentally and computationally at the pressure range between 200 GPa and 1 TPa, where B1 and B2 structures are theoretically stable and liquid exists. The shock velocity is found to be proportional with the particle velocity up to the shock velocity of 15 km s−1, suggesting MgO is in the B1 structure up to a shock pressure of ～350 GPa. Moreover, the Hugoniot data combined with ab initio calculations show two crossovers between the Hugoniot and an extrapolation by the linear relation around 350 GPa (and 8000 K) and 650 GPa (and 14000 K), respectively. The regions separated by the two crossovers are interpreted to be the fields of B1-B2, and B2-liquid transitions, respectively. They are consistent with the results by the ab initio calculations.
In this article, our experimental investigation to study electronic properties of elements under Mbar pressure and low temperature conditions are reviewed. So-called “treasure hunting” has been continued after the finding of superconductivity in elemental mercury at 1911. But complete understanding of the mechanism of appearance of superconductivity is not uncovered yet. Pressure can change the structural distance of atom and the electronic properties, then could be one of the most powerful tool for uncover it. The number of superconducting elements actually increased up to 53 under pressure from 30 at ambient pressure. The aim is to share our idea and experimental struggle process behind the papers already published.
Melting and crystallization of deep Earth materials are the key to understanding the chemical evolution and structure of Earth's deep interior. We investigated melting behaviors of the lower mantle materials by performing high-pressure melting experiments using laser-heated diamond anvil cell, and by conducting chemical analysis of the recovered samples with electron microprobe and dual-energy X-ray CT imaging. Toward deeper understanding of the chemical evolution of the early Earth, we developed a high-pressure in situ X-ray laminography technique using laterally-open diamond anvil cell. In addition, we have developed torsional deformation apparatus based on laterally-open diamond anvil cell. The apparatus enables us to investigate the rheological properties of deep-Earth materials to 135 GPa, covering the entire lower mantle pressure conditions.