Bulletin of the American Physical Society
57th Annual Meeting of the APS Division of Plasma Physics
Volume 60, Number 19
Monday–Friday, November 16–20, 2015; Savannah, Georgia
Session TO8: Warm Dense Matter |
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Chair: Dayne Fratanduono, Lawrence Livermore National Laboratory Room: 103/104 |
Thursday, November 19, 2015 9:30AM - 9:42AM |
TO8.00001: Application of Laser-Generated Ion Beams for Isochoric Heating to Study Plasma Mix at Interfaces B.J. Albright, J.C. Fern\'andez, W. Bang, P.A. Bradley, D.C. Gautier, C.E. Hamilton, S. Palaniyappan, M.A. Santiago Cordoba, E.L. Vold, L. Yin, B.M. Hegelich, G. Dyer, R. Roycroft The evolution and mixing of high-Z/low-Z interfaces in plasma media is of profound importance to high energy density physics and inertial fusion experiments. Recent experiments performed at the LANL Trident laser facility as part of the Plasma Interfacial Mix project have applied novel, laser-generated ion beams created under conditions of relativistic induced transparency to the heating of solid-density, multi-material targets isochorically and uniformly (over a few tens of ps), attaining plasma temperatures of several eV. Measurements have been made of the evolving plasma, including location of the material interface and the time-history of the temperature of the medium. Recent data and associated radiation hydrodynamic modeling from our Trident campaigns will be reported. Complementary kinetic simulations of interface evolution, showing anomalously rapid atomic mixing under conditions relevant to ICF experiments, will also be discussed. [Preview Abstract] |
Thursday, November 19, 2015 9:42AM - 9:54AM |
TO8.00002: Visualization of expanding warm dense gold and diamond heated uniformly by laser-generated ion beams W. Bang, B.J. Albright, P.A. Bradley, D.C. Gautier, S. Palaniyappan, E.L. Vold, M.A. Santiago Cordoba, C.E. Hamilton, J.C. Fern\'andez With a laser-generated beam of quasi-monoenergetic ions, a solid density target can be heated uniformly and isochorically. On the LANL Trident laser facility, we have used a beam of quasi-monoenergetic aluminum ions to heat gold and diamond foils. We visualized directly the expanding warm dense gold and diamond with an optical streak camera. Furthermore, we present a new technique to determine the initial temperatures of these heated samples from the measured expansion speeds of gold and diamond into vacuum. These temperatures are in good agreement with the expected temperatures calculated using the total deposited energy into the cold targets and SESAME equation-of-state tables at solid densities. We anticipate the uniformly heated solid density target will allow for direct quantitative measurements of equation-of-state, conductivity, opacity, and stopping power of warm dense matter, benefiting plasma physics, astrophysics, and nuclear physics. *This work is sponsored by the LANL LDRD Program. [Preview Abstract] |
Thursday, November 19, 2015 9:54AM - 10:06AM |
TO8.00003: Streaked optical pyrometry of ion heated compound targets in the study of plasma mix at high density interfaces Gilliss Dyer, Rebecca Roycroft, Craig Wagner, Aaron Bernstein, Todd Ditmire, B. Manuel Hegelich, Brian Albright, Juan Fern\'andez, Woosuk Bang, Paul Bradley, D. Cort Gautier, Christopher Hamilton, Sasi Palaniyappan, Miguel Santiago Cordoba, Erik Vold, Yin Lin The interaction and mixing of different species of plasma at high energy density is of fundamental interest for HED physics and relevant to inertial confinement fusion. An ongoing campaign is underway at the Trident laser facility to study the dynamics at the interface of high and low atomic number materials under warm dense matter conditions. The experiments utilize laser-accelerated ions, such as aluminum, to flash heat solid targets to temperatures \textgreater 1 eV. We report on streaked pyrometry measurements made in a recent experimental run, which shed light on the dynamics of heating induced in various target materials by these ion sources. Timescale as well as spatial extent of the heating can vary greatly depending on the dominant ion species and spectra. [Preview Abstract] |
Thursday, November 19, 2015 10:06AM - 10:18AM |
TO8.00004: The One Component Plasma: a paradigm for Warm Dense Matter jean Clerouin, Philippe Arnault, Christopher Ticknor, Joel Kress, Lee Collins We study the static and dynamical properties of plasmas using orbital free molecular dynamics simulations in the hot and dense regime. Because such simulations do not make any assumptions on ionization and screening we call them real plasmas. Thanks to a systematic comparison with the one component plasma (OCP) structure we define an effective OCP (eOCP) from which a coupling parameter $\Gamma $e and an effective ionization Qe are deduced. It is shown that, while eOCP is relevant for the short-range structure at high temperatures, screening manifests itself at long range. Dynamical properties are characterized by different frequencies of oscillation that can be reconciled using a renormalized mass. Since the short time scales and the relaxation times are similar, transport properties can be derived through a connection to the eOCP. Collective modes confirm that screening is important at low wavenumber k (long distance) allowing for the definition of a sound speed, but that eOCP behavior is recovered at high k (short distance) conditions. [Preview Abstract] |
Thursday, November 19, 2015 10:18AM - 10:30AM |
TO8.00005: Excited-state PAW Potentials: Modelling Hot-Dense Plasmas From First Principles Patrick Hollebon, Sam Vinko, Orlando Ciricosta, Justin Wark Finite temperature density functional theory has proven to be a successful means of modelling warm and hot dense plasma systems, including the calculation of transport properties [1], equation of state [2] and ionization potential depression [3]. Such methods take into account the non-negligible influence of quantum mechanics on the electronic structure of these strongly coupled systems. We apply excited state frozen core potentials to model general core-hole states in high density plasma, allowing for the calculation of the electronic structure of a range of ionic configurations. The advantages of using excited-state potentials are explored and we investigate their application towards various response function calculations, with the results shown to be in good agreement with all-electron calculations at finite-temperatures. \\[4pt] [1] F. Lambert {\it et al.}, Physics of Plasmas, {\bf 18}, 056306 (2011). \newline [2] Jean Cl\'{e}rouin {\it et al.}, Phys. Rev. B {\bf 71}, 064203 (2005). \newline [3] S.M. Vinko {\it et al.}, Nat. Commun, 5:3533 (2014). [Preview Abstract] |
(Author Not Attending)
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TO8.00006: Time evolution of electron structure in femtosecond heated warm dense molybdenum. V. Recoules, F. Dorchies, J. Bouchet, C. Fourment, P.M. Leguay, B.I. Cho, K. Engelhorn, M. Nakatsutsumi, C. Ozkan, T. Tshentscher, M. Harmand, S. Toleikis, M. Stormer, E. Galtier, H.J. Lee, B. Nagler, P.A. Heimann, J. Gaudin The time evolution of the electron structure is investigated in a molybdenum foil heated up to the warm dense matter regime by a femtosecond laser pulse, through time-resolved XANES spectroscopy. Spectra are measured with independent control of temperature and density. They are successfully compared with ab initio quantum molecular dynamic calculations and an analytical model. We demonstrate that the observed white line in the L3-edge reveals the time evolution of the electron density of state from the solid to the hot (a few eV) and expanding liquid. [Preview Abstract] |
Thursday, November 19, 2015 10:42AM - 10:54AM |
TO8.00007: Interband and intraband electron kinetics in non-thermal warm dense gold Shaughnessy Brennan Brown, Zhijiang Chen, Chandra Curry, Philippe Hering, Matthias C. Hoffmann, Andrew Ng, Matthew Reid, Ying Y. Tsui, Siegfried H. Glenzer Single-state warm dense matter may be produced via isochoric heating of thin metal foils using ultrafast high-power lasers. Previous experiments have confirmed that electron temperatures exceed ion temperatures during the initial picoseconds following excitation; however, electron kinetics in non-thermal states preceding establishment of a well-defined electron thermal distribution remain little understood. X-ray and optical probing techniques provide necessary resolution to investigate these electronic properties. Here, we will present a study of electron kinetics in warm dense gold produced by irradiating free-standing 30 nm Au foils with a 400 nm FWHM, 45 fs Ti:Sapphire laser system at SLAC National Accelerator Laboratory. The temporal evolutions of AC conductivity for 400 nm and 800 nm laser pulses are simultaneously determined with sub-100 fs resolution, providing insight into the 5$d$-6$s$/$p$ interband and 6$s/p$ intraband transitions respectively. Our results suggest that Auger decay and three-body recombination play important roles in electron thermalization of warm dense gold. [Preview Abstract] |
Thursday, November 19, 2015 10:54AM - 11:06AM |
TO8.00008: Broadband AC Conductivity of XUV Excited Warm Dense Gold Z. Chen, Y. Tsui, S. Toleikis, P. Hering, S. Brown, C. Curry, T. Tanikawa, H. Hoeppner, M. Levy, S. Goede, B. Ziaja-Motyka, B. Rethfeld, Vanina Recoules, A. Ng, S. Glenzer The properties of ultrafast laser excited warm dense gold have been extensively studied in the past decade [1, 2]. In those studies, a 400nm ultrashort laser pulse was used to excite the 5$d$ electrons in gold to 6s/p state. Here we will present our recent study of warm dense gold with 245eV, 70fs pulses to selectively excite 4$f$ electrons using the XUV-FEL at FLASH. The AC conductivity of the warm dense gold was measured at different wavelengths (485nm, 520nm, 585nm, 640nm and 720nm) to cover the range from 5$d$-6$s/p$ interband transitions to 6$s$/$p$ intraband transitions. Preliminary result suggests that the onset of 5$d$-6$s/p$ band transition shifts from 2.3eV to $\sim$ 2eV, which is in agreement with the study of 400nm laser pulse excited warm dense gold [3]. More detailed analysis of our data will also be presented.\\[4pt] [1] Z. Chen \textit{et. al}, \textit{PRL }\textbf{110}, 135001 (2013)\\[0pt] [2] T. Ao \textit{et. al}, \textit{PRL }\textbf{96}$, $055001 (2006)\\[0pt] [3] Y. Ping \textit{et. al}, \textit{PRL} \textbf{96}, 255003 (2006) [Preview Abstract] |
Thursday, November 19, 2015 11:06AM - 11:18AM |
TO8.00009: Electron conductivity in warm and hot dense matter Charles Starrett, Marc Charest, David Feinblum, Daniel Burrill The electronic conductivity of warm and hot dense matter is investigated by combining the Ziman-Evans approach with the recently developed pseudo-atom molecular dynamics (PAMD) method. PAMD gives an accurate description of the electronic and ionic structure of the plasma. The Ziman-Evans approach to conductivity, which takes the electronic and ionic structures as inputs, has been widely used but with numerous different assumptions on these inputs. Here we present a systematic study of these assumptions by comparing results to gold-standard QMD results that are thought to be accurate but are very expensive to produce. The study reveals that some assumptions yield very inaccurate results and should not be used, while others give consistently reasonable results. Finally, we show that the Thomas-Fermi version of PAMD can also be used to give accurate conductivities very rapidly, taking a few minutes per point on a single processor. [Preview Abstract] |
Thursday, November 19, 2015 11:18AM - 11:30AM |
TO8.00010: Transport properties of a high Z, low Z mixtures with varying concentration Christopher Ticknor, Lee Collins, Joel Kress, Jean Clerouin, Gregory Robert, Philippe Arnault Large-scale molecular dynamics (MD) simulations in an orbital-free (OF) density-functional theory (DFT) formulation have been performed for pure and mixed species over a broad range of temperatures and densities that includes the warm, dense matter and high-energy density physics regimes. A finite-temperature Thomas-Fermi-Dirac form with a local-density exchange-correlation potential and a regularized electron-ion interaction represents the quantum nature of the electrons. We examine the mass transport (diffusion, shear viscosity) properties of a mixture of light and heavy elements. We focus on Hydrogen-Silver mixtures with varying concentration at fixed pressure and temperature. These results will be fitted to simple functions of mass density and temperature, functions suitable for use in large-scale hydrodynamics simulation codes. [Preview Abstract] |
Thursday, November 19, 2015 11:30AM - 11:42AM |
TO8.00011: Melting and band gap-dynamics of shock-compressed graphite diagnosed by x-ray scattering at the LCLS Ulf Zastrau, Hae Ja Lee The diversity of the electronic properties of carbon makes it of key interest to the material science community; By contrast, at the high pressures typical of planetary and stellar interiors, the behavior of carbon is poorly understood with large uncertainties in the conductivity and even the material phase. Tremendous efforts have been made to measure properties of warm dense matter (WDM) in extreme conditions, e.g. temperatures in excess of 1000 K of temperature and pressures in the Mbar regime. In laboratory experiments, practical issues with gradients in the temperature and density of shock compressed matter have hindered accurate measurement and further from distinguishing theoretical models. Here, we present measurements of melting of graphite upon coalescence of two counter-propagating shocks using combinations of spatially and spectrally resolved x-ray scattering methods at the LCLS free electron laser. The MEC nanosecond lasers launch counter-propagating shock waves into graphite. At shock coalescence, pressures in excess of 1 Mbar are reached. At given time delay, we measure scattering from the sample using 5070 eV x-ray pulses. We employed curved mosaic and perfect imaging crystals for spatially resolved x-ray scattering. Compared with hydrodynamics simulations, we present data on plasmon dispersion, axial compression gradients and finally carbon melting at shock coalescence. We have indication for a widening of the band gap during compression of the solid, while the band gab fully closes in the melt. [Preview Abstract] |
Thursday, November 19, 2015 11:42AM - 11:54AM |
TO8.00012: The dynamic response of high pressure phase of Si using phase contrast imaging and X-ray diffraction H.J. Lee, E. Galtier, Z. Xing, A. Gleason, E. Granados, F. Tavella, A. Schropp, F. Seiboth, C. Schroer, A. Higginbotham, S. Brown, B. Arnold, R. Curiel, D. Peterswright, A. Fry, B. Nagler Static compression studies have revealed that crystalline silicon undergoes phase transitions from a cubic diamond structure to a variety of phases including body-centered tetragonal phase, an orthorhombic phase, and a hexagonal primitive phase [1]. However, the dynamic response of silicon at high pressure is not well understood. Phase contrast imaging has proven to be a powerful tool for probing density changes caused by the shock propagation into a material [2, 3]. With respect to the elastic and plastic compression, we image shock waves in Si with high spatial resolution using the LCLS X-ray free electron laser and Matter in Extreme Conditions instrument. In this study, the long pulse optical laser with pseudoflat top shape creates high pressures up to 60 GPa. We also measure the crystal structure by observing the X-ray diffraction orthogonal to the shock propagation direction over a range of pressure. In this talk, we will present the capability of simultaneously performing phase contrast imaging and in situ X-ray diffraction during shock loading and will discuss the dynamic response of Si in high pressure phases [1] Jamieson, Science, 139, 762 (1963); Hu et al. Phys. Rev.B 34, 4679 (1986) [2] B. Nagler et al. J. Synchrotron Rad. 22 (2015) doi: 10.1107/S1600577515004865 [3] A. Schropp et al. Scientific Reports 5, 11089 (2015) doi:10.1038/srep11089 [Preview Abstract] |
Thursday, November 19, 2015 11:54AM - 12:06PM |
TO8.00013: Design of an Extreme Ultraviolet Spectrometer Suite for Isochoric-Heated Warm-Dense-Matter Studies S. Ivancic, C.R. Stillman, P.M. Nilson, D.H. Froula An ultrafast streaked extreme ultraviolet (XUV) spectrometer (5 to 35 nm) is in development for the measurement of warm dense matter (WDM). In contrast to other forms of pyrometry where the temperature is inferred from bulk x-ray emission, XUV emission is restricted to the sample surface, allowing for the measurement of temperature at the material--vacuum interface. The measurement of the surface temperature is of particular importance in constraining models for the release of WDM. The divergence of surface and bulk temperature measurements may indicate gradients in temperature in the target. Coupling the XUV spectrometer to an ultrafast streak camera allows for the observation of picosecond time-scale evolution of the surface layer temperature. Two high-throughput XUV spectrometers are being designed to measure the time-resolved and absolute XUV emission. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944. [Preview Abstract] |
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