Bulletin of the American Physical Society
21st Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 64, Number 8
Sunday–Friday, June 16–21, 2019; Portland, Oregon
Session B4: MS: Ramp Compression |
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Chair: Seth Root, SNL Room: Pavilion West |
Monday, June 17, 2019 9:15AM - 9:30AM |
B4.00001: Structural Complexity in Dense Magnesium Jon Eggert, Martin Gorman, Amy Lazicki, David McGonegle, Stanimir Bonev, Sabri Elatresh, Justin Wark, Marc Cormier, Richard Briggs, Amy Coleman, Steve Rothman, Richard Kraus, David Braun, Gilbert Collins, Patrick Heighway, Lisa Peacock, Federica Coppari, Ryan Rygg, Malcolm McMahon As compression increases, the electronic wave functions of the valence electrons begin to overlap and interact with those of the core electrons, resulting in exotic electronic and complex structural behavior. Here we report \textit{in situ} X-ray diffraction measurements of solid magnesium which has been dynamically compressed to pressures up to 1.3 TPa (corresponding to 5.5-fold compression). Our experimental observations show that Mg adopts a series of distorted structures at 0.3, 0.5 and 0.8 TPa, contrary to previous \textit{ab-initio} simulations which find the higher symmetry body centered cubic, face centered cubic and primitive hexagonal structures to be the most stable structures over this pressure range. Our results demonstrate how dynamic compression can be utilized to test theoretical structure calculations at conditions inaccessible by static or shock compression techniques. This work was performed under the auspices of the US Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344 [Preview Abstract] |
Monday, June 17, 2019 9:30AM - 9:45AM |
B4.00002: Dynamic Freezing of Liquid Cerium Under Shock-Ramp Compression Michael Desjarlais, Chris Seagle, Andrew Porwitzky, Brian Jensen We have performed dynamic loading experiments on the Z machine to probe the melt curve and corresponding solidification of polycrystalline cerium following shock melt and subsequent ramp compression. Subtle signs of freezing are found in a small but statistically significant bump in the sound speed suggestive of an elastic wave. Analysis of the sound speed data indicates a very low shear to bulk modulus ratio, characteristic of very ductile material, and a Poisson ratio of approximately 0.45. Density functional calculations exploring a compression isentrope initiating on the Hugoniot exhibit spontaneous freezing to the body centered tetragonal $\epsilon$-Ce phase at pressures very close to the experimental observation of a bump in the sound speed. Corresponding elastic constant calculations performed on full DFT molecular dynamics simulations find values for the longitudinal and bulk sound speeds, shear modulus, and Poisson ratio in very good agreement with experiment. \\ \\ Sandia National Labs is managed and operated by National Technology \& Engineering Solutions of Sandia, LLC, a subsidiary of Honeywell International, Inc., for the U.S Dept. of Energy’s National Nuclear Security Administration under contract DE-NA0003525. [Preview Abstract] |
Monday, June 17, 2019 9:45AM - 10:00AM |
B4.00003: Measuring the Ramp Equation of State of Lithium Fluoride to 1000 GPa Suzanne Ali, Leo Kirsch, David Braun, Dayne Fratanduono, Amalia Fernandez-Panella, Raymond Smith, Michelle Marshall, James McNaney, Jon Eggert The pursuit of accurate, high-pressure data on materials requires well-validated experimental platforms and the precise calibration of equation of state (EOS) standards. Among these standards are window materials used to confine the sample material when the compression wave propagates, as opposed to allowing it to release into vacuum. This facilitates the study of phase transitions on compression and prevents complications such as spall. Lithium fluoride remains transparent at very high pressures, particularly on the isentrope, making it an ideal window material for many experiments. Determination of the hydrodynamic state of the sample material requires knowledge of both the equation of state and density-dependent refractive index of the window material. Using the NIF we have ramp compressed lithium fluoride, measuring the quasi-isentrope to \textasciitilde 1000 GPa. [Preview Abstract] |
Monday, June 17, 2019 10:00AM - 10:15AM |
B4.00004: Crystal Structure and Reflectivity of Laser Ramp-Compressed Sodium Danae Polsin, Xuchen Gong, Linda Crandall, Margaret Huff, Thomas Boehly, Gilbert Collins, Jon Eggert, Amy Lazicki, Marius Millot, Malcolm McMahon, James Rygg Extreme compression can alter the free-electron behavior of ``simple'' metals such as Na. At pressures exceeding 200 GPa, Na was observed to become transparent to visible light under static compression; first-principles calculations suggest this is caused by a transformation to an electride phase where electrons are localized in interstitial positions. Laser-driven ramp compression is used to compress Na into an unexplored pressure regime to investigate the crystalline structure, reflectivity, and melting behavior of Na. X-ray diffraction is used to constrain the crystalline structure and detect melting. Optical reflectivity measurements at 532 nm are used to detect a transition to the predicted insulating electride phase. We show the highest-pressure solid x-ray diffraction and reflectivity data on Na to date. A simple semiconducting Drude picture is used to constrain the band gap and temperature of dense Na. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0003856, the University of Rochester, and the New York State Energy Research and Development Authority. [Preview Abstract] |
Monday, June 17, 2019 10:15AM - 10:30AM |
B4.00005: Analysis of Shocked and Ramp-Compressed Metals to 5 Mbars Jeffrey Nguyen, Minta Akin, Paul Asinow In this report, we present a series of shocked and ramp compressed data on various metals including tantalum, iron and tin. These samples were shocked and ramp-compressed to pressures as high as 5 Mbars with graded density impactors (GDI). To analyze these data, we utilize both backward (characteristics) and forward analyses. The former method does not require a priori knowledge of a pressure drive, and often fails in the presence of strength or phase transition. By using both of these analysis techniques, we can explore the possibility of looking at phase transition and strength during ramp compression. We will also report on recent efforts to characterize GDI in situ impedance profile. This study also gives us insight into the properties of GDI during ramp compression. The results are compared to non-destructive ultra sound scans of GDIs. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 [Preview Abstract] |
Monday, June 17, 2019 10:30AM - 10:45AM |
B4.00006: Dynamic material properties of tantalum under ramp compression (30-160 GPa) Guilin Wang, Zhaohui Zhang, Qizi Sun, Wenjie Yang, Ce Ji, Wenkang Zou, Shuping Feng Material's response has an affinity with microstructure, load path, pressure and temperature, etc. Magnetically driven isentropic compression as a new experimental technique between quasi-static and impact, has low increased entropy and temperature. The Primary Test Stand (PTS) facility is a pulsed power machine capable of delivering currents to loads of 5\textasciitilde 8 MA over times of 200-750 ns. Series of ramp compression experiments of tantalum were performed on PTS facility. The loading peak pressure of the sample exceeded 150 GPa, and the loading average strain rate ranged 4-9*10$^{\mathrm{5}}$ s$^{\mathrm{-1}}$. The strength characteristic data of different process tantalum samples at peak pressure of 29-161 GPa, and the ramp compression strength characteristics of the annealed and cold-rolled regularity knowledge were measured by Photonic Doppler velocimetry (PDV). Experiment results confirmed that the strength of the metal tantalum at 10$^{\mathrm{5-6}}$ s$^{\mathrm{-1}}$ strain rate basically conforms to the SG strength model. [Preview Abstract] |
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