Bulletin of the American Physical Society
20th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 62, Number 9
Sunday–Friday, July 9–14, 2017; St. Louis, Missouri
Session E5: Geophysics and Planetary Science II |
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Chair: Arianna Gleason, Los Alamos National Laboratory/Stanford University Room: Regency Ballroom B |
Monday, July 10, 2017 3:30PM - 3:45PM |
E5.00001: Recent research on stishovite: Hugoniot and partial release Z experiments and DFT EOS calculations Michael Furnish, Luke Shulenburger, Michael Desjarlais, Yingwei Fei We have conducted a series of ride-along experiments on the Z facility to ascertain the Hugoniot of silica centered in the stishovite phase over a range 0.4 - 1.0 TPa, together with partial release states produced at the interface between the sample and a fused silica window. The stishovite samples were synthesized in a large-volume multi-anvil press at 15 GPa and 1773 K, with an initial density of 4.29 gm/cc. The new Z experiments on stishovite fill in a gap between gas gun experiments and NIF experiments. The states are compared with the Hugoniots of quartz and fused silica for inferences as to EOS. They are generally consistent with Sesame 7360 predictions. Sound speed constraints from these data are discussed. The new Hugoniot data cross over the melting curve of stishovite, providing insight into the properties of solid and liquid under extreme conditions in conjunction with predictions from density-functional theory modeling. These data are fundamentally important for understanding the interior of silicate-based super-Earths. [Preview Abstract] |
Monday, July 10, 2017 3:45PM - 4:00PM |
E5.00002: Single-shot Ellipsometry of Shocked Iron to 275 GPa Sean Grant, Tommy Ao, Aaron Bernstein, Jean-Paul Davis, Todd Ditmire, Daniel Dolan, Jung-Fu Lin, Andrew Porwitzky, Christopher Seagle We have studied the properties of iron under shock conditions using time-resolved ellipsometry, a technique that probes the dielectric value of materials under dynamic conditions, on the STAR gas gun facility at Sandia National Laboratories. We performed experiments on a two-stage gas gun ranging from the $\alpha - \epsilon$ transition (75 GPa) to the solid-liquid transition (275 GPa). For the first time, we report the dielectric results of shocked iron at those conditions. In addition, the time-resolved ellipsometry diagnostic is being implemented on the Sandia pulsed power Z-machine. The goal of upcoming Z experiments will be to employ the “shock-ramp” technique to reach pressure and temperature conditions relevant to the Earth core, and to use ellipsometry to obtain the iron electric conductivities needed for benchmarking material models. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000. SAND2017-1952 A [Preview Abstract] |
Monday, July 10, 2017 4:00PM - 4:30PM |
E5.00003: Dynamic compression of liquids and applications in geophysics and planetary science Invited Speaker: Paul Asimow Shock and dynamic ramp compression offer a number of distinct advantages for the study of the liquid state at elevated pressure, including absolute density measurement without diffraction, absolute pressure measurement without reference to uncertain high-temperature calibrants, and absolute internal energy measurements to define thermodynamic states. Given the essential roles of silicate and metallic liquids in terrestrial planet formation and evolution, dynamic studies focused on properties of such liquids inform numerous debates in geophysics and planetary science. In this talk, I will review the current understanding of compression mechanisms of silicate liquids and the constraints obtained from simulation, dynamic experiments and static experiments. We will consider the precision necessary to answer key questions about density crossovers between liquids and their coexisting solids in multicomponent systems, the vexing question of silicate liquid heat capacity under planetary interior conditions, and the universal behavior of the Gr\"{u}neisen parameter in such liquids. Applications include magma ocean evolution and seismic anomalies at the core-mantle boundary. Turning to metallic liquids, we will consider how simultaneous density and sound speed measurements in Fe alloy liquids can help to resolve the uncertain composition of Earth's core. Overtaking experiments on the Hugoniot, pre-heated ramp compression experiments with graded density impactors, and detailed release wave profiles all carry information about the sound speed and can be performed along the isentropes most likely to characterize the outer core. [Preview Abstract] |
Monday, July 10, 2017 4:30PM - 4:45PM |
E5.00004: Shock states of solid Mg$_{\mathrm{2}}$SiO$_{\mathrm{4}}$ Joshua Townsend, Luke Shulenburger To date there have been thousands of planets discovered outside our solar system. Forsterite, the magnesium end-member of olivine, ((Mg,Fe)$_{\mathrm{2}}$SiO$_{\mathrm{4}})$ is abundant in the Earth's mantle, and is likely a common planetary building block throughout the galaxy. Despite extensive investigation under terrestrial pressure and temperature regimes, the behavior of the Mg$_{\mathrm{2}}$SiO$_{\mathrm{4}}$ system at higher pressures and temperatures (P\textgreater 100 GPa, T\textgreater 4000 K) remains poorly understood. To better understand the behavior of planetary impact processes and the structure of massive planets we investigated the high pressure and high temperature properties of Mg$_{\mathrm{2}}$SiO$_{\mathrm{4}}$ using combined shock compression experiments on the Z-machine at Sandia National Laboratories, and \textit{ab-initio} molecular dynamics simulations. We compare our results to other recent experiments on shocked forsterite. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract No. DE-AC04-94AL85000. SAND2017-1987 C. [Preview Abstract] |
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