Bulletin of the American Physical Society
53rd Annual Meeting of the APS Division of Plasma Physics
Volume 56, Number 16
Monday–Friday, November 14–18, 2011; Salt Lake City, Utah
Session NO8: EOS and IFE |
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Chair: Peter Celliers, Lawrence Livermore National Laboratory Room: Ballroom I |
Wednesday, November 16, 2011 9:30AM - 9:42AM |
NO8.00001: Multiple Spherically Converging Shock Waves in Liquid Deuterium T.R. Boehly, V.N. Goncharov, S.X. Hu, T.J.B. Collins, J.A. Marozas, T.C. Sangster, D.D. Meyerhofer, M.A. Barrios, D.E. Fratanduono, P.M. Celliers, D.G. Hicks, G.W. Collins High-performance ICF target designs use multiple shocks to condition the shell before it is imploded. Accurate timing of these shocks is critical to target performance. We report on experiments on the OMEGA Laser System using directly driven spherical targets filled with liquid deuterium where up to four spherically converging shocks were observed and timed. This technique is the basis for tuning campaigns performed at the National Ignition Facility. The measured shock-velocity profiles exhibit the effects of spherical convergence (pressure increase with decreasing radius) and very high shock velocities (135 km/s). Simulations of these experiments accurately model the shock velocities and timing when a nonlocal electron-transport model is used for heat conduction. The self-emission from these shocks provides the temperature of deuterium shocked to 1 to 5 Mbar. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302. [Preview Abstract] |
Wednesday, November 16, 2011 9:42AM - 9:54AM |
NO8.00002: The Thermal Conductivity of National Ignition Facility Target Materials D.E. Hanson, L.A. Collins, J.D. Kress, M.P. Desjarlais Using quantum (finite-temperature density functional theory) molecular dynamics (QMD), we performed simulations of several important materials in the Inertial Confinement Fusion-National Ignition Facility nominal target designs, comprising various mixtures of proposed ablator materials (Be or CH) with the DT fuel. Simulations were done over a range of temperatures between 5 eV and 20 eV, at densities between 7.5 and 14 g/cc. The QMD program (VASP) produces the Kohn-Sham orbital wavefunctions and associated eigenenergies from which we determine both the electrical and thermal conduction properties from a Chester-Tellung-Kubo-Greenwood formulation. We find that the thermal conductivity is not sensitive to modest density variations but is quite sensitive to the mix fraction. We find that the thermal conductivity of mixed systems can be approximated to within 20\% by the Faber-Ziman equation. We also compare our QMD results to the Hubbard and Lee-More thermal conductivity models. For the conditions of our simulations, the Hubbard model is in reasonable agreement with the QMD results. [Preview Abstract] |
Wednesday, November 16, 2011 9:54AM - 10:06AM |
NO8.00003: Measurement of the EOS of WDM aluminum John Benage, Robert Watt, David Montgomery, Eliseo Gamboa The warm dense matter (WDM) regime is one of the most uncertain in terms of our knowledge of the equation of state (EOS) of materials. This is not only because it is difficult to calculate the properties of WDM, but also because we have so little data from that parameter regime. To address this need, we are developing an experimental platform to measure the EOS of WDM. This platform relies on using the shock and release technique with the addition of non-traditional diagnostic capabilities. Our experiment platform utilizes the Omega laser to drive a very strong shock into an aluminum sample. The shock is then released into 0.2 g/cm$^{3}$ aerogel foam which is used as a pressure standard. A shock breakout measurement is used to determine the shock velocity and pressure in the foam and released sample. We have also developed an imaging x-ray Thomson spectrometer to measure Compton scattered x-rays from the released aluminum sample. This information can be used to determine the temperature and density of the released aluminum, providing the necessary measurements to determine the EOS. Simulations predict the conditions of the released aluminum will be $\sim $ solid density at 10-15 eV. We will present our experimental results of pressure measurements along with preliminary data from the imaging x-ray Thomson spectrometer. [Preview Abstract] |
Wednesday, November 16, 2011 10:06AM - 10:18AM |
NO8.00004: An Analytic Screening Potential for Dense, Strongly-Coupled Plasmas Liam Stanton, Michael Murillo, Frank Graziani Characterizing warm dense matter (WDM) has gained renewed interest due to advances in powerful lasers and next generation light sources. Because WDM is strongly coupled and moderately degenerate, we must often rely on simulations of WDM, which are necessarily based on molecular dynamics of ions interacting through a screened potential. Almost always, a Debye- (Yukawa-) like interaction is assumed; however, it is well known that such long wavelength models over-screen. Here, we present a new effective ion-ion interaction, which recovers the exact fermionic linear response in the long-wave limit while retaining a pair-potential functionally similar to that of the Yukawa form. This new potential not only improves the accuracy of screening effects without contributing to the computational complexity of the model, but it also adds physics entirely missing from Yukawa models (such as the onset of Friedel oscillations). Simulations of the ion structure factor are compared to XRTS data for Be and C in the WDM regime. [Preview Abstract] |
Wednesday, November 16, 2011 10:18AM - 10:30AM |
NO8.00005: Semiclassical Simulation of Electron Scattering in Warm Dense Plasma Conditions Andreas Markmann, Paul Grabowski, Michael Murillo, Frank Graziani, Victor Batista We introduce an efficient algorithm for dynamics simulation of particles with attractive potentials developed within the Cimarron Project, where electron-proton scattering is to be treated explicitly. Such simulations provide valuable insights and guidance for current experimental efforts at the National Ignition Facility. Electrons rapidly transition between bound and free states, while their environment changes rapidly, requiring simulations to account for quantum effects. Large scale simulations modeling quantum effects need to be tuned by comparison to high accuracy quantum or semiclassical simulations. Our algorithm is applied to semiclassical simulations of electron-proton scattering processes in the Wigner-transform time-dependent picture. Heisenberg uncertainty and interference are compared to exact quantum dynamics. Protons are modeled through full Coulomb potentials and screened Coulomb (Yukawa) potentials, respectively. The relative importance of quantum effects such as uncertainty and interference is inferred from the results. [Preview Abstract] |
Wednesday, November 16, 2011 10:30AM - 10:42AM |
NO8.00006: Elastic-plastic behavior in laser-shock-compressed Mo using time-resolved 17 keV Bragg diffraction Brian Maddox, Nathan Barton, Hye-sook Park, Shon Prisbrey, Allen Elsholz, James Hawreliak, Rick Gross, Robert Rudd, Bruce Remington, Andrew Comley Time-resolve diffraction during the rapid loading of crystalline samples is fast becoming a powerful new tool for diagnosing the lattice dynamics of materials under high-pressure, high-strain rate conditions. The information contained in this diffraction data can yield important information about the sample including strength, phase, and timescales associated with dislocation-driven plastic deformation. We have developed high-energy, time-resolved Bragg diffraction on the Omega EP laser using a short-pulse driven K$\alpha $ backlighter as the gated x-ray source. We used the 17 keV x-rays from a Mo foil backlighter to probe shock-compressed Mo (111) single crystals as a function of time and pressure from 0.08 Mbar to 0.37 Mbar. We find that at low shock pressure ($<$0.15 Mbar) the lattice response is essentially elastic with a transition to plastically relaxed behavior above 0.15 Mbar. We also put an upper bound on the plastic relaxation timescale that is consistent with similar measurements of BCC Ta using time-resolved diffraction (see Comley \textit{et al.}). We also infer the shear strength above the plastic transition as a function of pressure up to 0.37 Mbar on the hugoniot. [Preview Abstract] |
Wednesday, November 16, 2011 10:42AM - 10:54AM |
NO8.00007: High pressure, high strain rate material strength studies B.A. Remington, A. Arsenlis, N. Barton, J. Belof, R. Cavallo, B. Maddox, H.-S. Park, S. Prisbrey, R. Rudd, A. Comley, M. Meyers, J. Wark Constitutive models for material strength are currently being tested at high pressures by comparing 2D simulations with experiments measuring the Rayleigh-Taylor (RT) instability evolution in solid-state samples of vanadium (V), tantalum (Ta), and iron (Fe). The multiscale strength models being tested combine molecular dynamics, dislocation dynamics, and continuum simulations. Our analysis for the V experiments suggests that the material deformation at these conditions falls into the phonon drag regime, whereas for Ta, the deformation resides mainly in the thermal activation regime. Recent Fe-RT experiments suggest perturbation growth about the alpha-epsilon (bcc-hcp) phase transition threshold has been observed. Using the LLNL multiscale models, we decompose the strength as a function of strain rate into its dominant components of thermal activation, phonon drag, and work hardening. We have also developed a dynamic diffraction diagnostic technique to measure strength directly from shock compressed single crystal samples. Finally, recovery experiments allow a comparison of residual dislocation density with predictions from the multiscale model. [Preview Abstract] |
Wednesday, November 16, 2011 10:54AM - 11:06AM |
NO8.00008: Studying Ta material strength under high pressure and high strain rate using plasma drives Hye-Sook Park, N.R. Barton, R.M. Cavallo, B.R. Maddox, M.J. May, S.M. Pollaine, S.T. Prisbrey, B.A. Remington, R.E. Rudd, A.J. Comley We are studying material strength under high pressures ($>$1 Mbar) and high strain rates (10$^{6}$ - 10$^{8}$ sec$^{-1})$ in Ta. The strength is inferred from the growth measurements of the pre-imposed sinusoidal ripples on the sample via Rayleigh-Taylor (RT) instability properties. The material strength can greatly suppress RT growth rate [1]. Our recent experiments include the study of any grain size dependence of strength under these high pressures and strain rates. There are neither existing experimental data nor theoretical predictions of the expected Hall-Petch effect under the extreme conditions of our RT experiments. Three different samples of 0.25 $\mu $m, 15 $\mu $m and 90 $\mu $m average grain sizes are fabricated and their corresponding RT-induced ripple growth factors are measured. The details of the measurements, target characteristics, analysis, and final results will be presented. Designs that extend this experiment by an order of magnitude in pressure on NIF will also be presented \\[4pt] [1] H. S. Park et al., PRL. 104, 135504 (2010). [Preview Abstract] |
Wednesday, November 16, 2011 11:06AM - 11:18AM |
NO8.00009: Lattice Dynamics of Shocked, Single-Crystal Tantalum Characterized using Dynamic White-Light Laue X-ray Diffraction A.J. Comley, B.R. Maddox, J.A. Hawreliak, H.-S. Park, S.T. Prisbrey, R.E. Rudd, B.A. Remington, P.A. Rosen, S. Rothman, N. Park, J.M. Foster, A. Higginbotham, M. Suggit, J.S. Wark We report on recent experiments at the Omega laser facility that demonstrate the use of broadband x-ray diffraction to probe the lattice dynamics of tantalum crystals under a range of shock-loaded conditions (1 -- 2.2MBar). In the experiments, an implosion capsule x-ray backlighter (approx 150 ps duration) driven by 44 Omega beams (22 kJ total in a 1 ns square pulse) was employed to produce the white light diffraction pattern. VISAR was employed simultaneously to infer the high-pressure conditions in the shocked Ta crystal. We show how the residual strain present in a 1D-to-3D relaxed lattice can be obtained from the x-ray diffraction data. This information, when combined with an elastic constant calculated from first principles for the pressure as determined from VISAR, allows the strength of the crystal to be inferred. [Preview Abstract] |
Wednesday, November 16, 2011 11:18AM - 11:30AM |
NO8.00010: X-ray Scattering Measurement of the Heat Capacity Ratio in Shock Compressed Matter C. Fortmann, H.J. Lee, Tilo Doeppner, A.L. Kritcher, O.L. Landen, R.W. Falcone, S.H. Glenzer We developed accurate x-ray scattering techniques to measure properties of matter under extreme conditions of density and temperature in intense laser-solid interaction experiments. We report on novel applications of x-ray scattering to measure the heat-capacity ratio $\gamma=c_p/c_v$ of a Be plasma which determines the equation of state of the system. Ultraintense laser radiation is focussed onto both sides of a Be foil, creating two counterpropagating planar shock waves that collide in the target center. A second set of lasers produces Zn He-$\alpha$ radiation of 8.9 keV energy that scatters from the shock-compressed matter. We observe temperatures of $10\,\textrm{eV}$ and $15\,\textrm{eV}$ and mass densities of $5\,\textrm{g/cm}^{3}$ and $11\,\textrm{g/cm}^{3}$ before and after the shock collision. Applying the Rankine-Hugoniot relations for counterpropagating shocks we then infer $\gamma$ as a function of density using only the measured mass compression ratios. Our results agree with equation of state models and DFT simulations. [Preview Abstract] |
Wednesday, November 16, 2011 11:30AM - 11:42AM |
NO8.00011: Validating equation of state models in the ablative Richtmyer-Meshkov regime for indirect-drive inertial confinement fusion capsules Eric Loomis, Dave Braun, Steve Batha, Charles Sorce, Otto Landen Recent simulations have shown that isolated features on the outer surface of Inertial Confinement Fusion (ICF) ignition capsules can profoundly impact capsule performance by leading to mixing in the hotspot. Controlling the growth of these artifacts is complicated due to uncertainties in equation of state (EOS) models used in simulation codes. Here we report on measurements pertaining to the growth of isolated defects due to ablative Richtmyer-Meshkov in CH capsules in order to validate these models. Face-on transmission radiography was used to measure the evolution of Gaussian bump arrays in plastic targets. Au halfraums heated to radiation temperatures near 70 eV using 15 beams in a 5 ns pulse from the Omega laser (Laboratory for Laser Energetics, University of Rochester, NY) indirectly drove the samples. Shock speed measurements made with Omega's Active Shock BreakOut (ASBO) diagnostic in conjunction with the x-ray flux recorded by a soft x-ray power diagnostic (DANTE) were used to determine drive conditions in the target. These measurements show that SESAME 7592 is in closer agreement with shock speed and bump growth data compared to LEOS 5310. [Preview Abstract] |
Wednesday, November 16, 2011 11:42AM - 11:54AM |
NO8.00012: ABSTRACT WITHDRAWN |
Wednesday, November 16, 2011 11:54AM - 12:06PM |
NO8.00013: Integrated systems for pulsed-power driven inertial fusion energy M.E. Cuneo, S.A. Slutz, W.A. Stygar, M.C. Herrmann, D.B. Sinars, R.D. McBride, R.A. Vesey, A.B. Sefkow, M.G. Mazarakis, J.P. VanDevender, E.M. Waisman, D.L. Hansen, A.C. Owen, J.F. Jones, J.A. Romero, J. McKenney Pulsed power fusion concepts integrate: (i) directly-magnetically-driven fusion targets that absorb large energies (10 MJ), (ii) efficient, rep-rated driver modules, (iii) compact, scalable, integrated driver architectures, (iv) driver-to-target coupling techniques with standoff and driver protection, and (v) long lifetime fusion chambers shielded by vaporizing blankets and thick liquid walls. Large fusion yields (3-30 GJ) and low rep-rates (0.1-1 Hz) may be an attractive path for IFE. Experiments on the ZR facility are validating physics issues for magnetically driven targets. Scientific breakeven (fusion energy = fuel energy) may be possible in the next few years. Plans for system development and integration will be discussed. [Preview Abstract] |
Wednesday, November 16, 2011 12:06PM - 12:18PM |
NO8.00014: Hybrid Kinetic-Fluid Electromagnetic Simulations of Imploding High Energy Density Plasmas for IFE Dale Welch, Dave Rose, Carsten Thoma, Thomas Genoni, Nichelle Bruner, Robert Clark, William Stygar, Ramon Leeper A new simulation technique is being developed to study high current and moderate density-radius product ($\rho $R) z-pinch plasmas relevant to Inertial Fusion Energy (IFE). Fully kinetic, collisional, and electromagnetic simulations of the time evolution of up to 40-MA current (deuterium and DT) z-pinches, but with relatively low $\rho $R, have yielded new insights into the mechanisms of neutron production.\footnote{D. R. Welch, \textit{et al., }Phys. Rev. Lett. \textbf{103}, 255002 (2009).} At fusion relevant conditions ($\rho $R $>$ 0.01 gm/cm$^{2})$, however, this technique requires a prohibitively large number of cells and particles. A new hybrid implicit technique has been developed that accurately describes high-density and magnetized imploding plasmas. The technique adapts a recently published algorithm,\footnote{T. C. Genoni, \textit{et al.}, Open Plasma Phys. J. \textbf{3}, 36 (2010).} that enables accurate descriptions of highly magnetized particle orbits, to high density plasmas and also makes use of an improved kinetic particle remap technique. We will discuss the new technique, stable range of operation, and application to an IFE relevant z-pinch design at 60 MA. [Preview Abstract] |
Wednesday, November 16, 2011 12:18PM - 12:30PM |
NO8.00015: ABSTRACT WITHDRAWN |
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