Bulletin of the American Physical Society
2005 14th APS Topical Conference on Shock Compression of Condensed Matter
Sunday–Friday, July 31–August 5 2005; Baltimore, MD
Session B3: Focus Session: Ultra-High Pressure Shocks (P>>1 Mbar) |
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Chair: Gilbert Collins, Lawrence Livermore National Laboratory Room: Hyatt Regency Constellation D |
Monday, August 1, 2005 9:00AM - 9:30AM |
B3.00001: Creating Extreme Material Properties with High-Energy Laser Systems Invited Speaker: Laboratory for Laser Energetics, University of Rochester, 250 E. River Rd, Rochester, NY 14623 High-energy laser systems create extreme states of matter by coupling their energy into a target via ablation of the outer layers. In planar experiments on the OMEGA laser system, single-shock pressures can exceed 10 Mbar. In spherical geometry, the compressed target pressures can be significantly higher than 1 Gbar. These pressures will be increased by one or two orders of magnitude on the 1.8-MJ$_{UV}$ National Ignition Facility, under construction at LLNL. The inherent flexibility of multibeam laser systems allows many techniques to be applied to studying the properties of materials under extreme conditions. Recent experiments have used Extended X-ray Absorption Fine Structure to observe shock-induced phase transformations in Fe on the ns time scale. Techniques are being used and/or developed to measure the equation of state of compressed materials, including solids, foams, and liquid D$_{2}$, both on and off the Hugoniot. The coupling of high-energy petawatt (HEPW) lasers to high-energy laser systems will greatly extend the accessible range of material conditions. HEPW lasers produce extremely intense beams of electrons and protons that can be coupled with high-energy compression to access a large region of temperature and density space, for example, by heating a compressed target. These beams, along with the extremely bright x-ray emission, provide new diagnostic opportunities. This presentation will highlight some of the recent advances and future opportunities in creating and measuring extreme materials properties. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-92SF19460, the University of Rochester, and the NY State Energy Research and Development Authority. The support of DOE does not constitute an endorsement by DOE of the views expressed in this article. [Preview Abstract] |
Monday, August 1, 2005 9:30AM - 10:00AM |
B3.00002: Magnetically-Driven Isentropic Compression Status and Future Advances Invited Speaker: Since the development of magnetically driven isentropic compression experiments (ICE) on the Z accelerator by Asay et al, this technique has continued to grow in maturity. At lower pressures, isentropic compression has been employed to identify and then study phase transitions and their kinetics. In addition, experiments have used the same techniques to study re-solidification, the response of explosives, and the crush up of porous materials. Most of these experiments rely on the ability of ICE to generate very smooth ramps that can be applied to multiple samples for relative experiments. For equation of state studies, the intrinsic accuracy and peak pressures continue to demand improvement in understanding, analysis techniques and diagnostics. We have spent significant effort in these areas over the last few years because we believe that we must demonstrate a well characterized and understood method to obtain accurate EOS data with well-behaved materials to give confidence in future comparisons between ICE data and calculations of material properties. In our presentation, we will discuss the status of Z experiments, our recent data at multi-megabar pressures with aluminum and other materials, and the status of our analysis abilities. We will also discuss the need for future improvements in diagnostics plus the anticipated capabilities of the ZR facility and the small pulser. This work was supported by the United States Department of Energy's National Nuclear Security Administration under contract No. DE-AC04-94AL85000. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company.. [Preview Abstract] |
Monday, August 1, 2005 10:00AM - 10:15AM |
B3.00003: Ultra-High Pressure Shock Compression at the Sandia Z Accelerator. Marcus Knudson, R.W. Lemke, M.P. Desjarlais, C. Deeney The Sandia Z accelerator is capable of producing $>$20 MA current pulses with $\sim $200 ns rise-time into short circuit loads, generating intense magnetic fields within the anode-cathode gap. The resulting Lorentz force enables Z to be used very effectively in accelerating plates to ultra-high velocity. Experiments have been directed toward highly accurate dynamic material studies. In particular, emphasis has been placed on launching planar, solid density flyer plates to velocities exceeding 30 km/s for use in equation of state (EOS) studies at high-pressure. Velocities up to 34 km/s have been obtained with aluminum flyer plates several mm in lateral dimensions and a few hundred microns in thickness, enabling highly accurate Hugoniot measurements to multi-Mbar. Emphasis will be placed on predictive magneto-hydrodynamic modeling and EOS results obtained for aluminum and deuterium. [Preview Abstract] |
Monday, August 1, 2005 10:15AM - 10:30AM |
B3.00004: Accuracy and Sensitivity of Hugoniot Measurements at Ultrahigh Pressures W.J. Nellis Achieving ultrahigh shock pressures is straight forward. However, Hugoniot measurements at ultrahigh pressures have neither the accuracy nor the sensitivity to provide useful information about physical phenomena. Be, Al, Cu, Fe, and Mo, for example, have calculated maximum compressions on the Hugoniot of 4.6 to 5.7 fold of initial crystal density at shock pressures of 20 to 100 TPa (100 TPa=1000 Mbar) (1). However, Hugoniot experiments are performed in shock velocity-mass velocity, u$_{s}$(u$_{p})$, space. At 5 fold compression, the uncertainty in compression is 4-fold that in measured u$_{s}$. Above a shock pressure of $\sim $TPa, shock and mass velocities are related by u$_{s}$=Su$_{p}$. For compressions in the range 4.6 to5.7, S is in the range 1.21$<$S$<$1.28. For an ideal gas, limiting shock compression is 4.0 and S=1.33. At ultrahigh shock pressures Hugoniot data have maximum uncertainty and minimum sensitivity to material. To observe such small differences in slope S of u$_{s}$(u$_{p})$ requires extremely high accuracy in shock velocity measurements, accuracies which do not now exist. (1) B. F. Rozsnyai et al, \textit{Phys. Lett. A} \textbf{291} 226 (2001). [Preview Abstract] |
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