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 K5: Geophysics and Planetary Science IV |
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Chair: Joshua Townsend, Sandia National Laboratories Room: Regency Ballroom B |
Tuesday, July 11, 2017 2:15PM - 2:30PM |
K5.00001: Stability of hcp-Fe at TPa pressures from in-situ x-ray diffraction and laser-driven ramp compression F. Coppari, R. F. Smith, G. W. Collins, T. S. Duffy, D. E. Fratanduono, A. Lazicki, J. R. Rygg, J. H. Eggert The use of lasers to induce extreme compression states has enabled the study of material properties and equations of state at unprecedented pressure and temperature conditions, existing in the interiors of planets and extra-solar planets. The combination of laser-driven compression and x-ray diffraction provides a unique picture of the transformations taking place in high-energy-density matter. X-ray diffraction is now routinely used at the Omega laser facility (University of Rochester, NY) [1,2,3] to investigate \textit{in-situ }phase transitions occurring on nanosecond time scales. Iron is an important material for geophysics and planetary science and understanding its behavior at extreme pressures and temperatures is paramount to the development of reliable models describing the formation and evolution of planetary bodies. In this work we present x-ray diffraction data of ramp-compressed iron up to TPa pressures, showing that the hexagonal-close-packed (hcp) phase is stable at these conditions. [1] J. R. Rygg et al, RSI 83, 113904 (2012) [2] F. Coppari et al, Nat Geosci 6, 926 (2013) [3] A. Lazicki et al, PRL 115, 075502 (2015) [Preview Abstract] |
Tuesday, July 11, 2017 2:30PM - 2:45PM |
K5.00002: In situ observation of stishovite formation in shock-compressed fused silica Sally June Tracy, Stefan Turneaure, Thomas Duffy Silica, SiO$_{\mathrm{2}}$, has widespread applications ranging from optical components to refractory materials and is of geological importance as one of the major oxide components of the Earth's crust and mantle. The response of silica phases to dynamic loading has long been of interest for understanding the structural evolution of this fundamental oxide. Under shock compression both crystalline quartz and fused silica are characterized by the occurrence of a broad `mixed-phase region' (15-40 GPa) and a dense, high-pressure phase with much lower compressibility. Despite decades of study, the nature of this transformation and the identity of the high-pressure phase(s) remain poorly understood. In situ x-ray diffraction experiments on shock-compressed fused silica were conducted at the Dynamic Compression Sector of the Advanced Photon Source. The lattice-level structure was investigated through time-resolved x-ray diffraction measurements on samples reaching peak stress ranging from 12 to 47 GPa. Our results demonstrate that SiO$_{\mathrm{2}}$ adopts a dense amorphous structure in the `mixed-phase region' and abruptly transforms to stishovite above 34 GPa. These results provide clear evidence that high-pressure crystalline silicate phases can form from amorphous starting materials on the time-scale of laboratory shock experiments. [Preview Abstract] |
Tuesday, July 11, 2017 2:45PM - 3:00PM |
K5.00003: Principal Hugonuot and decaying shock Hugoniot on silicates Toshimori Sekine, Norimasa Ozaki, Ryosuke Kodama, Yuhei Uneda, Tomoko Sato, Kohei Miyanishi, Toyohito Nishikawa Laser shock experiments can achieve warm dense matter conditions applicable to the formation of planets and interior of large planets. The techniques of velocity interferometer system for ant reflector (VISAR) and streaked optical pyrometer (SOP) are used to observe the laser-shocked materials above \textasciitilde 200 GPa, where the shock fronts in most materials become effective reflectors. The VISAR and SOP profiles give shock velocity and temperature directly if the shock structure is one-wave. In the measurement of principal Hugoniot we need one more parameter such as particle velocity that will be determined in a simultaneous measurement of a reference by the impedance match method. In decaying shock measurements, shock velocity and temperature of a sample are monitored simultaneously and pressure will be read using the principal Hugonot relation available as known experimentally or predicted. If two-wave structures appear at phase transition, the analyses are complicated. Therefore we must be careful in applying the decaying shock data to planetary problems. I summarize them by comparing the difference between the principal and decaying Hugoniots of silicates. Sekine et al. (2016) Sci. Adv. 2, e1600157. [Preview Abstract] |
Tuesday, July 11, 2017 3:00PM - 3:15PM |
K5.00004: Leveraging Cababilities of the National Laboratories and Academia to Understand the Properties of Warm Dense MgSiO3 Thomas R. Mattsson, Joshua P. Townsend, Luke Shulenburger, Christopher T. Seagle, Michael D. Furnish, Yingwei Fei For the past seven years, the Z Fundamental Science program has fostered collaboration between scientists at the national laboratories and academic research groups to utilize the Z-machine to explore properties of matter in extreme conditions. A recent example of this involves a collaboration between the Carnegie institution of Washington and Sandia to determine the properties of warm dense MgSiO3 by performing shock experiments using the Z-machine. To reach the higher densities desired, bridgmanite samples are being fabricated at Carnegie using multi-anvil presses. We will describe the preparations under way for these experiments, including pre-shot ab-initio calculations of the Hugoniot and the deployment of dual-layer flyer plates that allow for the measurement of sound velocities along the Hugoniot. 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 DE-AC04-94AL85000. [Preview Abstract] |
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