A5042325572- Muon and positron interactions and applications
- High-pressure geophysics and materials
- Physics of Superconductivity and Magnetism
- Atomic and Molecular Physics
- Advanced Chemical Physics Studies
- Advanced Condensed Matter Physics
- Laser-Plasma Interactions and Diagnostics
- Fusion materials and technologies
- Graphene research and applications
- Laser-induced spectroscopy and plasma
- Magnetic properties of thin films
- Magnetic and transport properties of perovskites and related materials
- Surface and Thin Film Phenomena
- Intermetallics and Advanced Alloy Properties
- Ion-surface interactions and analysis
- X-ray Spectroscopy and Fluorescence Analysis
- Diamond and Carbon-based Materials Research
- Copper Interconnects and Reliability
- Rare-earth and actinide compounds
- Advanced Materials Characterization Techniques
- Thermodynamic and Structural Properties of Metals and Alloys
- Metallurgical and Alloy Processes
- Chemical Synthesis and Characterization
- Ammonia Synthesis and Nitrogen Reduction
- Metallic Glasses and Amorphous Alloys
Lawrence Livermore National Laboratory
2016-2025
Lawrence Livermore National Security
2012
Applied Energetics (United States)
2012
Sandia National Laboratories
2012
General Atomics (United States)
2012
Swarthmore College
2006
Faculty of 1000 (United States)
2003
Lawrence University
2003
University of California, Davis
1993-1999
Oak Ridge National Laboratory
1988-1996
We review the application of finite element (FE) method to ab initio electronic structure calculations in solids. The FE is a general approach for solution differential and integral equations which uses strictly local, piecewise-polynomial basis. Because basis composed polynomials, completely its accuracy systematically improvable. local real space, allows variable resolution space; produces sparse, structured matrices, enabling effective use iterative methods; well suited parallel...
Capsule implosions on the National Ignition Facility (NIF) [Lindl et al., Phys. Plasmas 11, 339 (2004)] are underway with goal of compressing deuterium-tritium (DT) fuel to a sufficiently high areal density (ρR) sustain self-propagating burn wave required for fusion power gain greater than unity. These driven carefully tailored sequence four shock waves that must be timed very precision in order keep DT low adiabat. Initial experiments measure strength and relative timing these shocks have...
Recent indirect drive inertial confinement fusion implosions on the National Ignition Facility (NIF) [Spaeth et al., Fusion Sci. Technol. 69, 25 (2016)] have crossed threshold of ignition. However, performance has been variable due to several factors. One leading sources variability is quality high-density carbon (HDC) shells used as ablators in these experiments. In particular, can a number defects that found correlate with appearance ablator mix into hot spot and degradation nuclear yield....
Producing a burning plasma in the laboratory has been long-standing milestone for physics community. A is state where alpha particle deposition from deuterium–tritium (DT) fusion reactions leading source of energy input to DT plasma. Achieving these high thermonuclear yields an inertial confinement (ICF) implosion requires efficient transfer driving source, e.g., lasers, fuel. In indirect-drive ICF, fuel loaded into spherical capsule which placed at center cylindrical radiation enclosure,...
This work introduces an ab initio approach to calculate the ionization degree directly from dynamic electrical conductivity in matter at extreme conditions. The method is demonstrated for high-density carbon plasmas and provides different values what usually reported
Abstract Transport properties of high energy density matter affect the evolution many systems, ranging from geodynamo in Earth’s core, to hydrodynamic instability growth inertial confinement fusion capsules. Large uncertainties these are present warm dense regime where both plasma models and condensed become invalid. To overcome this limit, we devise an experimental platform based on x-ray differential heating time-resolved refraction-enhanced radiography coupled a deep neural network. We...
We present an approach to solid-state electronic-structure calculations based on the finite-element method. In this method, basis functions are strictly local, piecewise polynomials. Because is composed of polynomials, method completely general and its convergence can be controlled systematically. local in real space, allows for variable resolution space; produces sparse, structured matrices, enabling effective use iterative solution methods; well suited parallel implementation. The thus...
The electronic structure of three-dimensional nanostructures (aerogels) is studied by soft x-ray absorption near-edge (XANES) spectroscopy. High-resolution O -edge and Sn - XANES spectra monolithic nanocrystalline rutile aerogels with different surface areas (i.e., surface-to-volume atom fractions) are compared full-density tetragonal SnO. Spectra interpreted based on the densities states in calculated both cluster (self-consistent real-space multiple scattering) band-structure (linear...
The cleaved surfaces of untwinned, single-crystal ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{6.9}$ have been probed with synchrotron-radiation photoemission, utilizing both high energy and angular resolution. Acute spectral structure was observed, at the Fermi higher binding energies, particularly near high-symmetry points two-dimensional Brillouin zone, \ensuremath{\Gamma}\ifmmode\bar\else\textasciimacron\fi{}, X\ifmmode\bar\else\textasciimacron\fi{},...
We report the computation and measurement of equation state a plastic with composition CH${}_{1.36}$. The computational scheme employed is density functional theory based molecular dynamics, at conditions: 1.8 g/cm${}^{3}$ $<\ensuremath{\rho}<10$ g/cm${}^{3}$, 4000 K $<T<$ 100 000 K. Experimental measurements are shock speeds in geometry which directly abutting different material, liquid deuterium, from release wave behavior can be deduced. After fitting our computed pressure internal energy...
The near vacuum campaign on the National Ignition Facility has concentrated its efforts over last year finding optimum target geometry to drive a symmetric implosion at high convergence ratio (30×). As hohlraum walls are not tamped with gas, is filling gold plasma and challenge resides in depositing enough energy before it fills up. Hohlraum believed cause symmetry swings late pulse that detrimental of hot spot convergence. This paper describes series experiments carried out examine effect...
We have developed an experimental platform for the National Ignition Facility that uses spherically converging shock waves absolute equation-of-state (EOS) measurements along principal Hugoniot. In this Letter, we present one indirect-drive implosion experiment with a polystyrene sample employs radiographic compression over range of pressures reaching up to 60 Mbar (6 TPa). This significantly exceeds previously published results obtained on Nova laser [R. Cauble et al., Phys. Rev. Lett. 80,...
Abstract
Heat transport across interfaces is a ubiquitous phenomenon with many unresolved aspects. In particular, it unknown if an interfacial thermal resistance (ITR) occurs in matter high-energy-density where free electrons dominate the heat conduction. Here, we report on first experimental evidence that significant barrier present between two different regions of matter: strongly heated tungsten wire and surrounding plastic layer stays relatively cold. We use diffraction-enhanced imaging to track...
The authors describe the electronic structure of Gd within local spin density functional approximation treating 4f electrons on equal footing with s, p, d valence electrons. This band model is solved LMTO-ASA method, which includes spin-orbit coupling and polarisation. gives a reasonable description properties such as magnetic moment Fermi surface. Total energy calculations indicate that experimentally observed HCP favoured over both FCC DHCP structures. Freezing 5p semi-core states...
The electronic structure of La2CuO4 and YBa2Cu3O7 has been evaluated within the local density approximation, using LMTO-ASA method. calculated lattice parameter for La-based oxide is 1% experimental value. Theoretical photoemission inverse spectra (XPA BIS) are presented. dominated by emission from Cu sites show a d band strongly affected bonding with O p levels.