Bulletin of the American Physical Society
15th APS Topical Conference on Shock Compression of Condensed Matter
Volume 52, Number 8
Sunday–Friday, June 24–29, 2007; Kohala Coast, Hawaii
Session B3: High Energy Density Physics / Warm Dense Matter |
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Chair: Peter Celliers, Lawrence Livermore National Laboratory Room: Fairmont Orchid Hotel Plaza I |
Monday, June 25, 2007 10:30AM - 10:45AM |
B3.00001: Radical electronic transformation of strongly coupled plasma at megabar pressure ionization, dielectrization and phase transitions Vladimir Fortov The work presents new results of investigation of pressure and temperature ionization of coupled nonideal plasmas generated as a result of multiple shock compression of metals, H2, He, noble gases, S, I, fullerene C60, H2O in the megabar pressure range. The highly time-resolved diagnostics permit us to measure thermodynamical, radiative and mechanical properties of high pressure condensed matter in a broad region of the phase diagram. This data in combination with exploding wire conductivity measurements demonstrate an ionization rate increase up to ten orders of magnitude as a result of compression of degenerate plasmas at p~104-107 bars. Shock compression of H2, Ar, He, Kr, Ne, Xe in initially gaseous and cryogenic liquid state allows measuring the electrical conductivity, Hall effect parameters, equation of state, and emission spectra of strongly nonideal plasma. Thermal and pressure ionization of strongly coupled states of matter is the most prominent effects under the experimental conditions. It was shown that plasma compression strongly deforms the ionization potentials, emission spectra and scattering cross-sections of the neutrals and ions in the strongly coupled plasmas. In contrast to the plasma compression the multiple shock compression of solid Li, Na, Ca shows ``dielectrization'' of the elements. Phase transitions in strongly nonideal plasmas are discussed. [Preview Abstract] |
Monday, June 25, 2007 10:45AM - 11:00AM |
B3.00002: The Equation of State and Optical Conductivity of Warm Dense He and H2 Stephanie Brygoo, Jon H. Eggert, Paul Loubeyre, Ryan S. McWilliams, Damien G. Hicks, Peter M. Celliers, Tom R. Boehly, Raymond Jeanloz, Gilbert W. Collins The determination of the equations of state of helium and hydrogen at very high density is an important problem at the frontier between condensed matter physics and plasma physics with important implications for planetary physics. Due to the limitations of the conventional techniques for reaching extreme densities(static or single shock compression), there are almost no data for the deep interior states of Jupiter. We present here shock compression measurements of helium and hydrogen, precompressed in diamond anvil cells up to 3$\rho_{liquid}$. We report the shock pressure, density and reflectivity up to 2 Mbar for helium and up to 1 Mbar for hydrogen. The data are compared to equations of state models used for astrophysical applications and to recent first principles calculations. This work was performed under the auspices of the U.S. Department of Energy (DOE) by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48. [Preview Abstract] |
Monday, June 25, 2007 11:00AM - 11:30AM |
B3.00003: Simulations of Shocked Hydrogen and Helium and Implications for Giant Planet Interiors Invited Speaker: In 1996 the NOVA laser shock wave experiments at LLNL probed the properties of deuterium at megabar pressure for the first time. These measurements have triggered a large number of theoretical and experimental studies. Recently the combination of static and dynamic compression techniques allowed one to reach even higher densities. In this talk, path integral Monte Carlo and density functional molecular dynamics simulations have been applied to predict the shock states of precompressed hydrogen and helium samples. It will be explained why the precompression leads to a reduction in the compression ratio for both materials [1]. It will also be demonstrated that electronic excitations lead to a much higher compression ratio of 5.24 for shocked helium compared to 4.3 that our simulations predicted for deuterium. Combining our equation of state (EOS) results for shock samples with further first-principles simulation for hydrogen-helium mixtures [2] allowed us to build a model for the interiors of giant planets. Included were corrections to the commonly used linear mixing approximation as well as the increased stability of hydrogen molecules that arises from the presence of helium. Our interior models update the suite of models that were based on the widely used Saumon-Chabrier-Van Horn (SCVH) EOS. Deviations from SCVH are up to about 5 percent depending on the pressure, and thus affect interior models at the same level. Unlike SCVH, the computed DFT-EOS does not predict any first-order thermodynamic discontinuities associated with pressure-dissociation and metallization of hydrogen [2]. We conclude by discussing constraints for the size of Jupiter's rocky core and whether the planet was formed by core accretion. \newline \newline [1] B. Militzer, ``First Principles Calculations of Shock Compressed Fluid Helium,'' Phys. Rev. Lett. 97 (2006) 175501. \newline [2] J. Vorberger, I. Tamblyn, B. Militzer, S.A. Bonev, ``Hydrogen-Helium Mixtures in the Interiors of Giant Planets,'' Phys. Rev. B 75 (2006) 024206. [Preview Abstract] |
Monday, June 25, 2007 11:30AM - 11:45AM |
B3.00004: Equation of state measurements in Ta$_{2}$O$_{5}$ aerogel Joshua Miller, Tom Boehly, David Meyerhofer, Jon Eggert The examination of the equation of state of Ta$_{2}$O$_{5}$ aerogel using laser driven shock compression has been performed at OMEGA. The foams, with densities in the range of 0.1 to 0.25 g/cc, were loaded by shocks with pressures in the range of 50 to 300 Gpa. Hugoniot parameters inferred from mechanical measurements of the shock evolution and temperatures inferred from the shock front self-emission were resolved on the sub-nanosecond time scale during this study. Comparisons between these experimental results and the existing qEOS model show that the aerogel is much more compressible than qEOS predicts at pressures below 100 GPa. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460, the University of Rochester, and the New York 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, June 25, 2007 11:45AM - 12:00PM |
B3.00005: Multi-Megabar pressure and super-dense materials created byinduced micro-explosion inside of transparent solid Eugene Gamaly, Saulius Joudkazis, Hiroaki Misawa, Barry Luther-Davies, Andrei Rode, Ludovic Hallo, Philippe Nicolai, Vladimir Tikhonchuk High pressure and temperature have been produced using a single laser pulse (100 nJ, 800 nm, 200 fs) focused inside transparent dielectrics [1,2]. The laser pulse converts a material within the volume of $\sim $ 0.15 $\mu $m$^{3}$ into plasma in a few fs time. A pressure of $\sim $10 TPa builds up generating strong shock and rarefaction waves and creating a nano-void surrounded by shell of compressed material. Analysis of the size of the void and the shell as a function of laser energy revealed that shell has a density 1.14 times of sapphire. High-density sapphire completely dissolves in 10{\%} solution of hydrofluoric acid while pristine sapphire remains intact. The unique conditions created-- pressure of 10 TPa, temperature of 5x10$^{5}$K, record high heating and cooling rates of 10$^{18}$ Kelvin/s open an exciting research field for studying matter at extreme in well-controlled laboratory environment. \newline [1] S. Joudkazis et al, PRL, 96,166101 (2006).. E. Gamaly et al PRB, \textbf{73}, 214101 (2006). [Preview Abstract] |
Monday, June 25, 2007 12:00PM - 12:15PM |
B3.00006: Charged particle flows in an explosively generated non-ideal plasma C.J. Boswell, J.R. Carney, J. Wilkinson, G.I. Pangilinan, V.H. Whitley Non-ideal plasmas occur as a result of the stimulation of matter by strong shocks, detonation waves, or concentrated laser irradiation. Since all of these methods of generating non-ideal plasmas are already in use to address other problems, we focus on a detailed understanding of this plasma. In particular, we study the flow of charged particles in a non-ideal plasma generated using an explosive to compress the gas into the non- ideal plasma state. The shock wave in the gas is generated by an explosive located at one end of a guide tube filled with the gas. The detonation produces a shock wave strong enough to ionize the gas. Spectral line emission profiles, recorded with a streak emission spectroscopy system, are used to ascertain neutral and ionized gas properties. The electric and magnetic fields are measured by electrostatic probes and magnetic induction coils which permit the measurement of the temperature, density, and electric potential of the non-ideal plasma; as well as the flow of net electric charges respectively. The results demonstrate that a separation of the positive and negative charges occurs in the vicinity of the shock wave. [Preview Abstract] |
Monday, June 25, 2007 12:15PM - 12:30PM |
B3.00007: Material Strength Hohlraum Development Stephen Pollaine, Raymond Smith, Bruce Remington, David Braun, Hye-Sook Park, Gilbert Collins We have demonstrated Omega hohlraums that remain open past 80 ns. These hohlraums deliver a drive that is uniform over a 1 mm$^{2}$ area (1). We also demonstrated hohlraums on Janus, a 2-beam 800 J facility at LLNL, with a uniform area 500 $\mu $m in diameter. These hohlraums drive ICE configurations, in which the hohlraum radiation drive shocks up an ablator, which then unloads across a vacuum gap to quasi-isnetropically drive a metal foil. We have also devised a new technique to measure M-band radiation preheat. These hohlraums will be extended to NIF in 2008. (1) R.F. Smith, S.M. Pollaine, S.J. Moon, H.S. Park, K.T. Lorenz, P.M. Celliers, J.H. Eggert, G.W. Collins, ``High planarity x-ray drive for ultra-fast shockless-compression experiments,'' accepted Physics of Plasmas (2007) [Preview Abstract] |
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