Bulletin of the American Physical Society
59th Annual Meeting of the APS Division of Plasma Physics
Volume 62, Number 12
Monday–Friday, October 23–27, 2017; Milwaukee, Wisconsin
Session PO5: Warm Dense Matter |
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Chair: Alla Safranova, University of Nevada, Reno Room: 202AB |
Wednesday, October 25, 2017 2:00PM - 2:12PM |
PO5.00001: Measuring warm dense matter properties with spectrally resolved x-ray scattering Siegfried Glenzer We have developed powerful ultrafast pump-probe techniques to measure the structural transformations and the physical properties of matter in extreme conditions. We apply megabar pressures to our samples using high-power laser irradiation followed by X-ray laser pulses from the Linac Coherent Light Source to take femtosecond measurements of the states that result. These experiments deliver data of unprecedented accuracy that allow critical experimental tests of theory in the challenging near-Fermi degenerate warm dense matter regime or in the non-ideal plasma state. We find good agreement with density functional theory simulations and provide predictions for new studies at the highest densities in laboratory plasmas that approach conditions of the interiors of brown dwarfs. [Preview Abstract] |
Wednesday, October 25, 2017 2:12PM - 2:24PM |
PO5.00002: Lattice Stability and Interatomic Potential of Non-equilibrium Warm Dense Gold Z. Chen, M. Mo, L. Soulard, V. Recoules, P. Hering, Y.Y. Tsui, A. Ng, S.H. Glenzer Interatomic potential is central to the calculation and understanding of the properties of matter. A manifestation of interatomic potential is lattice stability$^{\mathrm{1}}$ in the solid-liquid transition. Recently, we have used frequency domain interferometry (FDI) to study the disassembly of ultrafast laser heated warm dense gold nanofoils. The FDI measurement is implemented by a spatial chirped single-shot technique. The disassembly of the sample is characterized by the change in phase shift of the reflected probe resulted from hydrodynamic expansion. The experimental data is compared with the results of two-temperature molecular dynamic simulations based on a highly optimized embedded-atom-method (EAM) interatomic potential$^{\mathrm{2}}$. Good agreement is found for absorbed energy densities of 0.9 to 4.3MJ/kg. This provides the first demonstration of the applicability of an EAM interatomic potential in the non-equilibrium warm dense matter regime. The MD simulations also reveal the critical role of pressure waves in solid-liquid transition in ultrafast laser heated nanofoils. This work is supported by DOE Office of Science, Fusion Energy Science under FWP 100182, and SLAC LDRD program \\T. Ao, \textit{et al,} Phys. Rev. Lett.96, 055001 (2006) \\ H.W. Sheng \textit{et al}, Phys. Rev. B 83, 134118 (2011) [Preview Abstract] |
Wednesday, October 25, 2017 2:24PM - 2:36PM |
PO5.00003: Exploring warm dense water by using Free-Electron-Laser P. Sperling, J. Kim, Z. Chen, M. French, C. Curry, J. Koralek, M. Mo, M. Nakatsutsumi, R. Rodel, R. Redmer, S. Toleikis, P. Zalden, S. H. Glenzer Warm dense water is predicted in the interior of giant planets and has an important impact on planetary evolutions. As such, the electrical and thermal properties in this regime are critically important for modelling astrophysical objects. We present electrical property measurements in warm dense water by using a novel planar water jet compatible with high repetition rate studies. The liquid density water is isochorically and uniformly heated to non-equilibrium warm dense matter by FLASH free-electron laser irradiation ($5.5~$nm, $0.1-20~\mu$J). The dielectric function can be extracted from optical transmission and reflection measurements on the picosecond timescale before significant expansion and subsequent relaxation occurs. The time-dependent dielectric function reveals the electronic properties of water at different temperatures of the electronic and ionic subsystem during the heating and relaxation process, that allow to infer the electron-ion energy coupling. Comparison with 2-temperature density-functional-theory molecular-dynamic simulations show good agreement, that can not be achieved by standard theories of plasma physics. [Preview Abstract] |
Wednesday, October 25, 2017 2:36PM - 2:48PM |
PO5.00004: Isochoric heating and adiabatic expansion of WDM with intense relativistic electrons Josh Coleman, J. Colgan, N.B. Ramey, T. Schmidt, H.L. Andrews, J.O. Perry, D.R. Welch A \textasciitilde 100-ns-long electron bunch with an energy of 19.8 MeV and current of 1.7 kA has been used to isochorically heat thin foils of Cu or Ti to T$_{\mathrm{e}}$\textit{ \textgreater }1 eV. Adiabatic expansion of these warm dense plasmas has been observed, which fits well with the analytical point source solution. After 100 ns of heating, the plasma expands and the opacity drops emitting Ti-I or Cu-I, which indicates the measured density ranges from 1-3 x \quad 10$^{\mathrm{17}}$ cm$^{\mathrm{-3}}$. Additional efforts are underway to model the hydrodynamic expansion and deploy several diagnostics to measure the WDM. These include a Bragg spectrometer for K-shell emission, a PDV probe for hydro disassembly time and an indirect measurement of the plasma pressure, and a single pass density diagnostic. Preliminary measurements will be presented which are critical for characterizing the warm dense phase and providing a map of the EOS across a density range of 10$^{\mathrm{16}}$ \textit{\textless }n$_{\mathrm{e}}$ (cm$^{\mathrm{-3}})$ \textit{\textless }10$^{\mathrm{23}}$ This work was supported by the National Nuclear Security Administration of the U.S. Department of Energy under Contract No. DE-AC52-06NA25396. [Preview Abstract] |
Wednesday, October 25, 2017 2:48PM - 3:00PM |
PO5.00005: X-Ray Thomson Scattering and Radiography from Spherical Implosions on the OMEGA Laser A. M. Saunders, A. Laziki-Jenei, T. Doeppner, O. L. Landen, M. MacDonald, J. Nilsen, D. Swift, R. W. Falcone X-ray Thomson scattering (XRTS) is an experimental technique that directly probes the physics of warm dense matter by measuring electron density, electron temperature, and ionization state [1]. XRTS in combination with x-ray radiography offers a unique ability to measure an absolute equation of state (EOS) from material under compression [1,2]. Recent experiments highlight uncertainties in EOS models and the predicted ionization of compressed matter, suggesting more validation of models is needed [3,4]. We present XRTS and x-ray radiography measurements taken at the OMEGA Laser Facility from directly-driven solid carbon spheres at densities on the order of 1x10$^{\mathrm{24}}$ g cm$^{\mathrm{-3}}$ and temperatures on the order of 30 eV. The results shed light on the equations of state of matter under compression. [1] S. H. Glenzer and R. Redmer. Rev. Mod. Phys. \textbf{81}, 1625 (2009). [2] A. L. Kritcher et al., J. Phys. Conf., \textbf{688}, 102055 (2016). [3] D. Kraus et al., Phys. Rev. E. \textbf{94}, 011202(R) (2016). [4] L. B. Fletcher et al., Phys. Rev. Lett. \textbf{112}, 145004 (2014). [Preview Abstract] |
Wednesday, October 25, 2017 3:00PM - 3:12PM |
PO5.00006: First-Principles Equation of State and Shock Compression of Warm Dense Aluminum and Hydrocarbons Kevin Driver, Francois Soubiran, Shuai Zhang, Burkhard Militzer Theoretical studies of warm dense plasmas are a key component of progress in fusion science, defense science, and astrophysics programs. Path integral Monte Carlo (PIMC) and density functional theory molecular dynamics (DFT-MD), two state-of-the-art, first-principles, electronic-structure simulation methods, provide a consistent description of plasmas over a wide range of density and temperature conditions. Here, we combine high-temperature PIMC data with lower-temperature DFT-MD data to compute coherent equations of state (EOS) for aluminum and hydrocarbon plasmas. Subsequently, we derive shock Hugoniot curves from these EOSs and extract the temperature-density evolution of plasma structure and ionization behavior from pair-correlation function analyses. Since PIMC and DFT-MD accurately treat effects of atomic shell structure, we find compression maxima along Hugoniot curves attributed to K-shell and L-shell ionization, which provide a benchmark for widely-used EOS tables, such as SESAME and LEOS, and more efficient models. LLNL-ABS-734424. Funding provided by the DOE (DE-SC0010517) and in part under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Computational resources provided by Blue Waters (NSF ACI1640776) and NERSC. [Preview Abstract] |
Wednesday, October 25, 2017 3:12PM - 3:24PM |
PO5.00007: Toward Sodium X-Ray Diffraction in the High-Pressure Regime X. Gong, D.N. Polsin, J.R. Rygg, T.R. Boehly, L. Crandall, B.J. Henderson, S.X. Hu, M. Huff, R. Saha, G.W. Collins, R. Smith, J. Eggert, A.E. Lazicki, M. McMahon We are working to quasi-isentropically compress sodium into the terapascal regime to test theoretical predictions that sodium transforms to an electride.\footnote{M. Gatti, I. V. Tokatly, and A. Rubio, Phys. Rev. Lett. \textbf{104}, 216404 (2010).}$^{\mathrm{,\thinspace }}$\footnote{E. Geregoryanz \textit{et al.}, Phys. Rev. Lett \textbf{94}, 185502 (2005).} A series of hydrodynamic simulations have been performed to design experiments to investigate the structure and optical properties of sodium at pressures up to 500 GPa. We show preliminary results where sodium samples, sandwiched between diamond plates and lithium-fluoride windows, are ramp compressed by a gradual increase in the drive-laser intensity. The low sound speed in sodium makes it particularly susceptible to forming a shock; therefore, it is difficult to compress without melting the sample. Powder x-ray diffraction\footnote{J. R. Rygg \textit{et al.}, Rev. Sci. Instrum. \textbf{83}, 113904 (2012).} is used to provide information on the structure of sodium at these high pressures. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944. [Preview Abstract] |
Wednesday, October 25, 2017 3:24PM - 3:36PM |
PO5.00008: Stopping Power of Warm Dense Matter from Ehrenfest Molecular Dynamics Attila Cangi, Daniel S. Jensen, Stephanie B. Hansen, Andrew D. Baczewski Recent experimental advances enabled the precise measurement of the stopping power of fusion products in warm dense matter. We assess the ability of real-time time-dependent density functional theory to reproduce these results. Our approach facilitates the prediction of the stopping power in future experiments from first principles and advances our empirical and phenomenological understanding of transport properties in this technologically challenging thermodynamic regime. [Preview Abstract] |
Wednesday, October 25, 2017 3:36PM - 3:48PM |
PO5.00009: Optical conductivity of magnetized warm dense matter using time-dependent density functional theory Daniel Jensen, Andrew Baczewski, Attila Cangi, Stephanie Hansen In magnetized liner inertial fusion (MagLIF), matter is subjected to 10-30 T magnetic fields that are then flux compressed to strengths greater than 1 kT [Slutz et al, Phys. Rev. Lett. 108, 025003 (2012)]. The determination of transport properties in such extreme fields and the warm dense regime are of vital importance to experimental design. We show how time-dependent density functional theory (TDDFT) can be used to extract optical conductivities in and beyond the linear response regime. Building on work studying scalar linear perturbations to warm dense matter [Baczewski et al., Phys. Rev. Lett. 116, 115004 (2016)], we present the necessary theoretical modifications as well as some preliminary results. [Preview Abstract] |
Wednesday, October 25, 2017 3:48PM - 4:00PM |
PO5.00010: First Principles Simulation of the Dynamics of Warm Dense Matter during Femtosecond Laser Damage using a Particle-in-Cell Method with Pair-Potential Interactions and Direct Comparison to Experiment Alex Russell, Kyle Kafka, Enam Chowdhury, Douglass Schumacher Understanding of the warm dense matter (WDM) state is of fundamental importance in the modeling of femtosecond laser damage because laser electron coupling and subsequent electron lattice coupling can rapidly increase the material temperature at the laser focal region to on the order of an eV, producing WDM not well described by standard liquid and solid equations of state. By modifying the particle-in-cell formalism designed for plasmas to include a pair-potential interaction model, we have created the first fundamental simulation method for modelling ultrashort pulse laser damage that can treat large scale (micron sized) damage morphology and resolves dynamics spanning over six orders of magnitude in time from the femtosecond to the nanosecond scale. We confirm the accuracy of our algorithm by comparing simulated crater profiles on copper against those produced from precision experiment and then show the dynamics of transient warm dense matter formation in aluminum. This material is based upon work supported by the Air Force Office of Scientific Research under award number FA9550-16-1-0069 and computing time from the Ohio Supercomputer Center. [Preview Abstract] |
Wednesday, October 25, 2017 4:00PM - 4:12PM |
PO5.00011: Magnetic anvil cells driven by pulsed-power generators P.-A. Gourdain, M. B. Adams, M. Evans, R. D. McBRide, A. B. Sefkow, C. E. Seyler, G. Collins Magnetic anvil cells (MAC) use a gas, foam or solid damper to compress a material sample via magnetic pinch forces. Unlike diamond anvil cells (DAC), which are limited by the material strength of diamond, MAC have no mechanical limits. Only the amount of current that can be delivered to the MAC limits the final pressure at which a material sample can be compressed. Another main advantage of MAC over DAC is the ability to heat the sample, allowing to produce warm dense matter. The damper that surrounds the material sample has several functions. Initially, it diverts the current away from the sample, preventing electrothermal instabilities inside the sample. When the damper has fully imploded, the current commutes from the damper to the sample in less than 10 ns. Since the current is already on its way to reach a maximum, hundreds of kilobars are suddenly applied to the sample, limiting plasma ablation and surface inhomogeneity, which can later seed magnetic Rayleigh-Taylor instabilities. This work shows that the phase and chemical composition of the damper is critical to the homogeneity of the compressed sample and will change depending on the current level required to reach the final pressure. [Preview Abstract] |
Wednesday, October 25, 2017 4:12PM - 4:24PM |
PO5.00012: Two-temperature equilibration in warm dense hydrogen measured with x-ray scattering from the LCLS Luke Fletcher Understanding the properties of warm dense hydrogen plasmas is critical for modeling stellar and planetary interiors, as well as for inertial confinement fusion (ICF) experiments. Of central importance are the electron-ion collision and equilibration times that determine the microscopic properties in a high energy density state. Spectrally and angularly resolved x-ray scattering measurements from fs-laser heated hydrogen have resolved the picosecond evolution and energy relaxation from a two-temperature plasma towards thermodynamic equilibrium in the warm dense matter regime. The interaction of rapidly heated cryogenic hydrogen irradiated by a 400 nm, 5x1017 W/cm2, 70 fs-laser is visualized with ultra-bright 5.5 kev x-ray pulses from the Linac Coherent Light (LCLS) source in 1 Hz repetition rate pump-probe setting. We demonstrate that the energy relaxation is faster than many classical binary collision theories that use ad hoc cutoff parameters used in the Landau-Spitzer determination of the Coulomb logarithm. [Preview Abstract] |
Wednesday, October 25, 2017 4:24PM - 4:36PM |
PO5.00013: Dynamic Conductivity and Partial Ionization in Warm, Dense Hydrogen M. Zaghoo, I. F. Silvera A theoretical description for optical conduction experiments in dense fluid hydrogen is presented. Different quantum statistical approaches are used to describe the mechanism of electron transport in hydrogen's high-temperature dense phase. We show that at the onset of the metallic transition, optical conduction could be described by a strong rise in the atomic polarizability, resulting from increased ionization; whereas in the highly degenerate limit, the Ziman weak-scattering model better describes the observed saturation of reflectance. In the highly degenerate region, the inclusion of partial ionization effects provides excellent agreement with experimental results. Hydrogen's fluid metallic state is revealed to be a partially ionized free-electron plasma. These results provide a crucial benchmark for \textit{ab initio} calculations as well as an important guide for future experiments. Research supported by DOE Stockpile Stewardship Academic Alliance Program, Grant DE-FG52-10NA29656, and NASA Earth and Space Science Fellowship Program, Award NNX14AP17H. [Preview Abstract] |
Wednesday, October 25, 2017 4:36PM - 4:48PM |
PO5.00014: Abstract Withdrawn
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Wednesday, October 25, 2017 4:48PM - 5:00PM |
PO5.00015: Thermal conductivity measurements of proton-heated warm dense aluminum A. Mckelvey, G. Kemp, P. Sterne, A. Fernandez, R. Shepherd, M. Marinak, A. Link, G. Collins, H. Sio, J. King, R. Freeman, R. Hua, C. McGuffey, J. Kim, F. Beg, Y. Ping We present the first thermal conductivity measurements of warm dense aluminum at 0.5-2.7 g/cc and 2-10 eV, using a recently developed platform of differential heating. A temperature gradient is induced in a Au/Al dual-layer target by proton heating, and subsequent heat flow from the hotter Au to the Al rear surface is detected by two simultaneous time-resolved diagnostics. A systematic data set allows for constraining both thermal conductivity and equation-of-state models. Simulations using Purgatorio model or Sesame S27314 for Al thermal conductivity and LEOS for Au/Al release equation-of-state show good agreement with data after 15 ps. Predictions by other models, such Lee-More, Sesame 27311 and 29373, are outside of experimental error bars. Discrepancy still exists at early time 0-15 ps, likely due to non-equilibrium conditions. (Y. Ping et al. Phys. Plasmas, 2015, A. Mckelvey, et al. Sci. Reports 2017). [Preview Abstract] |
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