### Session C3: HD-1: Warm Dense Matter

Chair: Thomas Mattson, Sandia National Laboratories
Room: Hermitage C

 Monday, June 29, 2009 11:00AM - 11:30AM C3.00001: Dielectric function of non-equilibrium warm dense gold Invited Speaker: Yuan Ping Warm dense matter lies in a regime where densities are near the solid density and temperatures are between 0.1 and 100 eV. The behavior of such systems is dominated by electron degeneracy, excited electronic states and ion-ion correlations, rendering them a truly daunting many-body problem. Interest in Warm Dense Matter has been growing among broad disciplines as driven by the fundamental urge to understand the convergence between plasma and condensed matter physics, and the practical need to understand dynamic behavior in the transformation of a cold solid into a high energy density plasma. A recent advance in this emerging field is the single state measurements of optical properties of non-equilibrium warm dense gold created by isochoric laser heating. This unveils for the first time the behavior of intraband and interband transitions in warm dense gold at high energy densities, providing a unique opportunity to examine effects of electron band structure and electron distribution. This talk is a review of the experimental technique and the new findings. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. \\[4pt] In collaboration with Andrew Ng, Tadashi Ogitsu, Eric Schwegler, David Prendergast, Byong-ick Cho, Phil Heimann, Tommy Ao, Klaus Widmann, Duncan Hanson, Ingrid Koslow, and Gilbert Collins. Monday, June 29, 2009 11:30AM - 11:45AM C3.00002: Measurements of Beryllium Surface Roughening Due to X-Ray Preheating Scott Greenfield , Eric Loomis , Shengnian Luo We have used Transient Imaging Displacement Interferometry (TIDI) and line VISAR to characterize the response of the ice side'' of thin, planar beryllium targets to M-band x-rays. (The ice side is the one opposite from the drive, which in an ICF capsule will be on the inside, with the D-T ice). These x-rays were generated by the interaction of a 1.2 ns, 200 J laser pulse from the TRIDENT laser facility at Los Alamos with a thin gold foil. Anisotropic expansion of the ice side was measured by TIDI as surface roughening. The roughening begins nearly instantaneously (within a nanosecond); i.e., before the effects of loading on the drive side have propagated to the ice side. Several different types of Be targets were used, including standard polycrystalline (PF-60), equal channel angular extruded (ECAE), single crystal, and sputtered (with various levels of Cu doping). The results show a strong dependence of the roughening on the material microstructure. Hydrocode calculations will be compared to experimental velocity profiles. Implications of the results for the National Ignition Campaign will be discussed. Monday, June 29, 2009 11:45AM - 12:00PM C3.00003: Equation of state of Boron from shock waves measurements Stephanie Brygoo , Michel Naudy , Alexis Casner , Bruno Villette , Laurent Videau , Alain Duval , Stephane Darbon , Bruno Marchet , Isabelle Masclet-Gobin , Catherine Esnault , Jean Eric Fuchs , Paul Loubeyre , Marc Theobald , Olivier Henry , Gaston Thiell , Olivier Lutz , Laurent Chauvel , Herve Graillot , Thierry Chies , Olivier Lobios , Julie Mandar , Christian Thessieux , Vincent Domin , Patrick Arroyo The Ligne d'Integration Laser (LIL) has been completed in 2002 and was first dedicated to laser physics experiments as a prototype for the future Laser MegaJoule. It delivers up to 15 kJ at 351 nm. We will present the last installed standard diagnostic devoted to Equation Of State experiments, which is composed of a pyrometer, a VISAR and a shock breakout measurement. It has been used to measure the equation of state of boron. The shock was generated using direct and indirect drives to explore a large set of pressures up to several Mbar. Quartz and aluminum were used as reference materials. We will discuss experimental data and compare them to simulations. Monday, June 29, 2009 12:00PM - 12:15PM C3.00004: A path to materials science above 10 Mbar on the NIF laser B. Remington , H.-S. Park , S.T. Prisbrey , S.M. Pollaine , R.M. Cavallo , A.G. MacPhee , R.E. Rudd , B. Maddox , M.A. Meyers Solid state dynamics experiments at extreme pressures, P = 5-25 Mbar, and strain rates (1.e6 - 1.e8 1/s) are being developed for the NIF laser, using a ramped pressure drive. Velocity interferometer measurements establish the high pressure conditions. Constitutive models for solid state strength are being tested by comparing 2D continuum simulations with experiments measuring perturbation growth from the Rayleigh- Taylor instability in solid state samples of vanadium and tantalum at $\sim$ 1 Mbar pressures. Simulations using the PTW strength model or a new multi-scale V strength model, suggest that the deformation is largely in the phonon drag regime. Radiography techniques using bursts of 20-40 keV x-rays have been developed to diagnose this perturbation growth in Ta foils. Methods for inferring deformation mechanism (slip vs. twinning, thermal activation vs. phonon drag) will be discussed. Monday, June 29, 2009 12:15PM - 12:30PM C3.00005: Measurements of strain-induced refractive index changes in shocked LiF using laser-driven flyer plates Dayne Fratanduono , Maria Barrios , Tom Boehly , David Meyerhofer , Damien Hicks , Peter Celliers , Jon Eggert , G. Collins The refraction index of compressed LiF directly affects the accuracy of VISAR experiments that use LiF windows. We report on experiments at the LLNL Janus laser that reproduced previous measurements of strain-induced changes to the refractive index. Here laser-driven ramp-compression is used to accelerate aluminum flyer plates that impact a LiF window. The resultant particle velocity is inferred by measuring the flyer velocity just before impact. VISAR measurements through the LiF window provide an `apparent' particle velocity that can be used to infer the refractive index of the shock-compressed LiF. This is the first demonstration of the laser-driven flyer-plate technique applied to a measurement. We discuss how this technique will be implemented on the OMEGA laser to increase the pressures that can be achieved.