Bulletin of the American Physical Society
16th APS Topical Conference on Shock Compression of Condensed Matter
Volume 54, Number 8
Sunday–Friday, June 28–July 3 2009; Nashville, Tennessee
Session V2: HD-3: Multi-Megabar Issues |
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Chair: Clint Hall, Sandia National Laboratories Room: Hermitage AB |
Thursday, July 2, 2009 1:30PM - 1:45PM |
V2.00001: Hugoniot and sound speed of alpha-Quartz in the 90-1200 GPa regime Marcus Knudson, Michael Desjarlais The development of an ultra-high velocity flyer plate capability at the Sandia Z Machine has enabled multi-Mbar experiments with unprecedented accuracy. Here we present the results of both Hugoniot and sound speed measurements on z-cut, alpha-quartz in the 90-1200 GPa regime, inclusive of the pressure range over which silica transitions from a molecular to atomic fluid. Measurement of both the Hugoniot and the sound speed along the Hugoniot allows for extraction of the behavior of the thermodynamic gamma and provides an excellent test case for comparison with first principles calculations of melt and dissociation. Quantum molecular dynamics (QMD) calculations are in excellent agreement with the experimental data. These experimental and theoretical results provide a foundation for the use of quartz as an extremely accurate standard for use in multi-Mbar shock wave experiments. [Preview Abstract] |
Thursday, July 2, 2009 1:45PM - 2:00PM |
V2.00002: High-precision measurements of the equation of state (EOS) of polymers at 100-1000 GPa using laser-driven shock waves M.A. Barrios, D.E Fratanduono, T.R. Boehly, D.D. Meyerhofer, D.G. Hicks, J. Eggert, P. Cellier, G. Collins The behavior of polymer materials at high-pressure ($>$100 GPa) is important for the design inertial-confinement-fusion capsules and the effect of stoichiometry at high-pressures. To address these we performed EOS measurements on polystyrene (CH), polypropylene (CH$_{2})$, and GDP (C$_{43}$H$_{56}$O) at shock pressures of $\sim $100-1000 GPa. These experiments use laser-driven shocks to drive impedance-match measurements using alpha quartz as a standard material. Shock velocities in these transparent samples \underline {and} the standard can be measured to $\sim $1{\%} or precision. This refines the impedance-match technique for laser-driven shock experiments to produce precise data at extreme pressures. A novel method for also acquiring re-shock data is presented. These data are compared to various EOS models and other experiments driven by gas guns and lasers. [Preview Abstract] |
Thursday, July 2, 2009 2:00PM - 2:15PM |
V2.00003: Hugoniot measurements for tantalum up to impact velocity of $\sim $10 km/s on a three-stage gun Jianbo Hu, Hua Tan, Chengda Dai, Xiang Wang, Jinsong Bo, Yun Ma, Qingsong Wang, Guoqiang Luo, Qiang Shen A ``three-stage gun'' was developed at LSD by mounting an accelerating tube on a two-stage gun. A Ta flyer (32 mm diameter by 0.5 mm thick) was driven by a graded-density impactor (GDI) up to $\sim $9.61 km/s for Hugoniot measurements. The velocity of the Ta flyer was measured using a Doppler probe system, or determined from 1D hydrodynamic code calculations based on the projectile velocity measured by using optical beam break technique. The incident and transmitted time of shock front through the Ta specimen was detected by electric shorting-pins. The Hugoniot states of Ta specimen were determined using impedance-match method. The preheating effect resulting from the GDI driving on the Ta flyer was estimated by model calculations. Two data pairs of shock velocity versus particle velocity were obtained and consistent with the extrapolation of reported data. [Preview Abstract] |
Thursday, July 2, 2009 2:15PM - 2:30PM |
V2.00004: Investigation of near critical point states of lithium, sodium and aluminium by pulse heating during launching Dmitry Nikolaev, Vladimir Ternovoi, Alexei Pyalling, Sergey Kvitov, Vladimir Fortov The results of experimental investigation of near - critical point states of liquid-vapour phase transition of of lithium, sodium and aluminium are presented. The metal foil samples were launched by explosively driven steel plate in Helium atmosphere; Li and Na -- by direct impact and Al -- by impact through the layer of helium. The heating of the Li and Na foils were performed by heat exchange with shocked He layer from the free side of sample; Al -- by heating by multiple-shocked He from the back side of the foil [1]. The temperature of sample surface was measured by fast multi-channel optical pyrometer. The 1-D simulation of the process of launching was performed. The obtained experimental information allowed to evaluate liquid spinodal line, and the position of critical point on pressure - temperature plane.\\[4pt] [1] V.Ya.Ternovoi, V.E.Fortov et.al. High Temp.-High Pres. 2002, v.34, pp.73-79 [Preview Abstract] |
Thursday, July 2, 2009 2:30PM - 2:45PM |
V2.00005: Equation of State Effects in Hypervelocity Impact Simulations Robert Nance, Michael Worsham, John Cogar Hydrocodes are frequently employed to obtain high-fidelity predictions of hypervelocity impacts. The accuracy of these codes in predicting the hydrodynamic characteristics of such impacts, including debris clouds, has been demonstrated over the past 20 years for a variety of applications. However, greater uncertainty is associated with the detailed thermodynamic state of impact-induced debris clouds. Appropriate equations of state (EOSs) are a key factor in predicting these characteristics, including temperature distribution and degree of vaporization. However, significant differences may exist between EOSs in the modeling employed for different phenomena (such as vaporization and ionization), the construction of the liquid-vapor coexistence region, or the density-temperature resolution used to construct the tables. This paper will demonstrate these influences on hypervelocity impact predictions. We will use established computational shock-physics techniques, tabular EOSs, and in-house-developed analysis tools, to analyze impacts on aluminum between 5 and 11 km/s. A better understanding of the observed EOS-related differences will ultimately yield improved models for problems where thermodynamic details of the expanded state are important. [Preview Abstract] |
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