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General computational spectroscopic framework applied to Z-pinch dynamic hohlraum K-shell argon spectra (open access)

General computational spectroscopic framework applied to Z-pinch dynamic hohlraum K-shell argon spectra

We describe a general computational spectroscopic framework for interpreting observed spectra. The framework compares synthetic spectra with measured spectra, then optimizes the agreement using the Dakota toolkit to minimize a merit function that incorporates established spectroscopic techniques. We generate synthetic spectra using the self-consistent nonlocal thermodynamic equilibrium atomic kinetics and radiative transfer code Cretin, relativistic atomic structure and cross section data from Hullac, and detailed spectral line shapes from Totalb. We test the capabilities of both our synthetic spectra model and general spectroscopic framework by analyzing a K-shell argon spectrum from a Z-pinch dynamic hohlraum inertial confinement fusion capsule implosion experiment. The framework obtains close agreement between an experimental spectrum measured by a time integrated focusing spectrometer and the optimal synthetic spectrum. The synthetic spectra show that considering the spatial extent of the capsule and including the effects of optically thick resonance lines significantly affects the interpretation of measured spectra.
Date: January 10, 2005
Creator: Adams, M L; Sinars, D B & Scott, H A
System: The UNT Digital Library
Microscopic failure behavior of nanoporous Gold (open access)

Microscopic failure behavior of nanoporous Gold

Nanoporous metals have recently attracted considerable interest fueled by potential sensor and actuator applications. One of the key issues in this context is the synthesis of high yield strength materials. Nanoporous Au (np-Au) has been suggested as a candidate due to its monolithic character. The material can be synthesized by dealloying Ag-Au alloys, and exhibits an open sponge-like morphology of interconnecting Au ligaments with a typical pore size distribution on the nanometer length scale. Unfortunately, very little is known about the mechanical properties of np-Au besides a length-scale dependent ductile-brittle transition. A key question in this context is: what causes the macroscopic brittleness of np-Au? Is the normal dislocation-mediated plastic deformation suppressed in nanoscale Au ligaments, or is the brittleness a consequence of the macroscopic morphology? Here, we report on the fracture behavior of nanoporous Au studied by scanning electron microscopy. Specifically, we demonstrate the microscopic ductility of nanometer-sized Au ligaments. The observed fracture behavior seems to be general for nanoporous metals, and can be understood in terms of simple fuse networks.
Date: January 10, 2005
Creator: Biener, J.; Hodge, A. & Hamza, A.
System: The UNT Digital Library
Thermal Analysis of the SAFKEG Package for Long Term Storage (open access)

Thermal Analysis of the SAFKEG Package for Long Term Storage

Interim plutonium storage for up to 10 years in the K-reactor building is currently being planned at Savannah River Site (SRS). SAFKEG package could be used to store Pu metal and oxide (PuO2) in the K-reactor complex with other packagings like 9975. The SAFKEG is designed for carrying Type-B materials across the DOE complex and meets the 10CFR71 requirements. Thermal analyses were performed to ensure that the temperatures of the SAFKEG components will not exceed their temperature limits under the K-reactor storage conditions. Thermal analyses of the SAFKEG packaging with three content configurations using BNFL 3013 outer container (Rocky Flats, SRS bagless transfer cans, and BNFL inner containers) were performed for storage of PuO2 and plutonium metal
Date: January 10, 2005
Creator: NARENDRA, GUPTA
System: The UNT Digital Library
Transverse-momentum dependent modification of dynamic texture in central Au+Au collisions at sqrt(sNN) = 200 GeV (open access)

Transverse-momentum dependent modification of dynamic texture in central Au+Au collisions at sqrt(sNN) = 200 GeV

Correlations in the hadron distributions produced in relativistic Au+Au collisions are studied in the discrete wavelet expansion method. The analysis is performed in the space of pseudorapidity (|{eta}| {le} 1) and azimuth (full 2{pi}) in bins of transverse momentum (p{sub t}) from 0.14 {le} p{sub t} {le} 2.1 GeV/c. In peripheral Au+Au collisions a correlation structure ascribed to minijet fragmentation is observed. It evolves with collision centrality and p{sub t} in a way not seen before which suggests strong dissipation of minijet fragmentation in the longitudinally-expanding medium.
Date: January 10, 2005
Creator: Adams, J.; Aggarwal, M. M.; Ahammed, Z.; Amonett, J.; Anderson, B. D.; Arkhipkin, D. et al.
System: The UNT Digital Library
Electron-Density Scaling of Conversion Efficiency of Laser Energy into L-shell X-rays (open access)

Electron-Density Scaling of Conversion Efficiency of Laser Energy into L-shell X-rays

Laser-produced plasmas at subcritical densities have proven to be efficient sources for x-ray production. In this context, they obtain new results from experiments performed in Kr and Xe gas-filled targets that were irradiated by the high-power OMEGA (Laboratory for Laser Energetics, University of Rochester) laser. Nearly 40% of the laser energy was converted into x-rays in the L-shell-photon-energy range ({ge} 1.6 keV) by a Kr-filled target. The conversion efficiency measurements were correlated with time-resolved plasma-temperature measurements done by means of a Thomson-scattering diagnostic. The measured range of temperatures, between 2-3.5 keV, is in good agreement with LASNEX radiation-hydrodynamics simulations. X-ray-cooling rates and charge-state distributions were computed using detailed atomic data from the HULLAC suite of codes. X-ray yields predicted by the cooling-rate calculations are compared to measured spectra, and good agreement is found for predictions made with highly-detailed atomic models. They find that x-ray conversion efficiency in Kr-filled targets is a strong function of temperature, and has an optimum density near 10-15% of the laser's critical density.
Date: January 10, 2005
Creator: Fournier, K. B.; Constantin, C.; Back, C. A.; Suter, L.; Chung, H.; Miller, M. C. et al.
System: The UNT Digital Library
build - A Directory Savvy Replacement for Make (open access)

build - A Directory Savvy Replacement for Make

All but the most trivial software packages are generally constructed from multiple source files with many steps being required to generate lexer and parser source files, compile the numerous source files, assemble libraries from object files, and link object files and libraries to form the binary executable application. During the development process, the construction process may be repeated many times as source code is modified requiring the application to be rebuilt. To address this problem the original make tool was developed. However this tool was developed when applications were rather simple with a limited number of source files in single directories. Few header files outside of the standard system header files were used. The graph formed by the file-to-file dependencies was generally simple with little cross branching and limited depth. The increased complexity of modern software systems has made the traditional make tool less capable of managing the problem. Good software development practices have led to more and more source files arranged in directory hierarchies. Modular development of the software has resulted in the proliferation of developer implemented header files and libraries that are part of the application. Code reuse and object oriented design has made the problem even worse …
Date: January 10, 2005
Creator: Reus, J F
System: The UNT Digital Library
Characteristics of a Saturated 18.9 nm Tabletop Laser Operating at 5 Hz Repetition Rate (open access)

Characteristics of a Saturated 18.9 nm Tabletop Laser Operating at 5 Hz Repetition Rate

We report the characteristics of a saturated high repetition rate Ni-like Mo laser at 18.9 nm. This table-top soft x-ray laser was pumped at 5 Hz repetition rate by 8 ps, 1 J optical laser pulses impinging at grazing incidence into a pre-created Mo plasma. The variation of the laser output intensity as a function of the grazing incidence angle of the main pump beam is reported. The maximum laser intensity was observed for an angle of 20 degrees, at which we measured a small signal gain of 65 cm{sup -1} and a gain-length product gxl > 15. Spatial coherence measurements resulting from a Young's double slit interference experiment show the equivalent incoherent source diameter is about 11 {micro}m. The peak spectral brightness is estimated to be of the order of 1 x 10{sup 24} photons s{sup -1} mm{sup -2} mrad{sup -2} within 0.01% spectral bandwidth. This type of practical, small scale, high repetition soft x-ray laser is of interest for many applications. This acts to reduce the sensitivity of burst properties to metallicity. Only the first anomalous burst in one model produces nuclei as heavy as A = 100. For the present choice of nuclear physics and accretion rates, …
Date: January 10, 2005
Creator: Larotonda, M. A.; Luther, B. M.; Wang, Y.; Liu, Y.; Alessi, D.; Berrill, M. et al.
System: The UNT Digital Library