Bulletin of the American Physical Society
19th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 60, Number 8
Sunday–Friday, June 14–19, 2015; Tampa, Florida
Session U2: Experimental Developments VIII: Optical Diagnostics |
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Chair: Jennifer Gottfried, Army Research Laboratory, Michael Armstrong, Lawrence Livermore National Laboratory Room: Grand F |
Thursday, June 18, 2015 2:15PM - 2:30PM |
U2.00001: Anisotropic Transverse Stress in Calcite and Sapphire Measured Using Birefringence Gareth R. Tear, David J. Chapman, Daniel E. Eakins, William G. Proud Many significant geological minerals have anisotropic crystal structures leading to material properties that are anisotropic, including compressive elastic behaviour. A non-invasive approach to investigate the directional dependence of transverse stress in these materials during shock compression would supplement current understanding. As many geological minerals are transparent and hence optically anisotropic, measuring the change in birefringence induced by transverse stress in the material offers the possibility of a fast, non-invasive approach to probe transverse behaviour. Shock compression experiments have been performed on a-cut calcite and a-cut sapphire for strain rates of order 105 s-1 and up to longitudinal stresses of 2 GPa for calcite and 12 GPa for sapphire. We present measured changes in birefringence for these materials under shock compression, comparing with current and past literature as well as an in house optical model. The authors would like to thank Mr Steve Johnson and Mr David Pittman for technical support. [Preview Abstract] |
Thursday, June 18, 2015 2:30PM - 2:45PM |
U2.00002: Multi-Frame Imaging of Shock Propagation Leora Cooper, David Veysset, Brandt Pein, Alexei Maznev, Steven Kooi, Keith Nelson We have developed a platform to generate and image shock propagation through quasi-2D materials. A thin material (5-50 $\mu $m) is pressed between two glass plates, confining it in one dimension. A sub-nanosecond laser pulses is focused into a ring of 100 $\mu $m radius, launching a shock wave that propagates and focuses towards the circle's center. The high pressure of the shock wave causes changes in the refractive index of the material that can be observed with Shlieren imaging using a train of femtosecond pulses. A Fabry-Perot cavity is used to generate a train of imaging pulses spaced 5 ns apart. Using a high-speed multi-frame camera we have been able to take up to sixteen frames with 5 ns intervals of the same shock wave. This single-shot imaging method allows us to investigate irreversible processes in materials including phase transitions, cracking and decomposition in energetic materials, and cavitation and crack formation in water following the shock front. [Preview Abstract] |
Thursday, June 18, 2015 2:45PM - 3:00PM |
U2.00003: Implementation of Single-Shot Ellipsometry on Gas Gun Experiments Sean Grant, Tommy Ao, Aaron Bernstein, Jean-Paul Davis, Todd Ditmire, Daniel Dolan, Jung-Fu Lin, Christopher Seagle We have built and implemented a time-resolved ellipsometry diagnostic for dynamic testing at Sandia National Laboratories. This diagnostic measures refractive index of a sample under dynamic conditions with a time resolution of a few nanoseconds. We show and discuss results from our first dynamic experiments on a gas gun. Future work will study geophysical materials under relevant pressure-temperature conditions. 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. SAND2015-0376 A [Preview Abstract] |
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