Soft X-ray synchrotron radiation investigations of actinidematerials systems utilizing X-ray emission spectroscopy and resonantinelastic X-ray scattering (open access)

Soft X-ray synchrotron radiation investigations of actinidematerials systems utilizing X-ray emission spectroscopy and resonantinelastic X-ray scattering

Synchrotron radiation (SR) methods have been utilized with increasing frequency over the past several years to study topics in actinide science, ranging from those of a fundamental nature to those that address a specifically-targeted technical need. In particular, the emergence of microspectroscopic and fluorescence-based techniques have permitted investigations of actinide materials at sources of soft x-ray SR. Spectroscopic techniques with fluorescence-based detection are useful for actinide investigations since they are sensitive to small amounts of material and the information sampling depth may be varied. These characteristics also serve to simplify both sample preparation and safety considerations. Examples of investigations using these fluorescence techniques will be described along with their results, as well as the prospects for future investigations utilizing these methodologies.
Date: January 3, 2004
Creator: Shuh, D.K.; Butorin, S.M.; Guo, J.-H. & Nordgren, J.
Object Type: Article
System: The UNT Digital Library
An Analysis of Energy Savings Possible Through Advances in Automotive Tooling Technology (open access)

An Analysis of Energy Savings Possible Through Advances in Automotive Tooling Technology

The use of lightweight and highly formable advanced materials in automobile and truck manufacturing has the potential to save fuel. Advances in tooling technology would promote the use of these materials. This report describes an energy savings analysis performed to approximate the potential fuel savings and consequential carbon-emission reductions that would be possible because of advances in tooling in the manufacturing of, in particular, non-powertrain components of passenger cars and heavy trucks. Separate energy analyses are performed for cars and heavy trucks. Heavy trucks are considered to be Class 7 and 8 trucks (trucks rated over 26,000 lbs gross vehicle weight). A critical input to the analysis is a set of estimates of the percentage reductions in weight and drag that could be achieved by the implementation of advanced materials, as a consequence of improved tooling technology, which were obtained by surveying tooling industry experts who attended a DOE Workshop, Tooling Technology for Low-Volume Vehicle Production, held in Seattle and Detroit in October and November 2003. The analysis is also based on 2001 fuel consumption totals and on energy-audit component proportions of fuel use due to drag, rolling resistance, and braking. The consumption proportions are assumed constant over time, but …
Date: December 3, 2004
Creator: Rick Schmoyer, RLS
Object Type: Report
System: The UNT Digital Library
Edge Localized Mode Dynamics and Transport in the Scrape-Off Layer of the DIII-D Tokamak (open access)

Edge Localized Mode Dynamics and Transport in the Scrape-Off Layer of the DIII-D Tokamak

High temporal and spatial resolution measurements in the boundary of the DIII-D tokamak show that edge localized modes (ELMs) are produced in the low field side, are poloidally localized and are composed of fast bursts ({approx}20 to 40 {micro}s long) of hot, dense plasma on a background of less dense, colder plasma ({approx}5 x 10{sup 18} m{sup {+-}3}, 50 eV) possibly created by the bursts themselves. The ELMs travel radially in the scrapeoff layer (SOL), starting at the separatrix at {approx}450 m/s, and slow down to {approx}150 m/s near the wall, convecting particles and energy to the SOL and walls. The temperature and density in the ELM plasma initially correspond to those at the top of the density pedestal but quickly decay with radius in the SOL. The temperature decay length ({approx}1.2 to 1.5 cm) is much shorter than the density decay length ({approx}3 to 8 cm), and the latter decreases with increasing pedestal (and SOL) density. The local particle and energy flux at the midplane wall during the bursts are 10% to 50% ({approx}1 to 2 x 10{sup 21} m{sup {+-}2} s{sup {+-}1}) and 1% to 2 % ({approx}20 to 30 kW/m{sup 2}) respectively of the LCFS average fluxes, …
Date: December 3, 2004
Creator: Boedo, J. A.; Rudakov, D. L.; Hollmann, E.; Gray, D. S.; Burrell, K. H.; Moyer, R. A. et al.
Object Type: Article
System: The UNT Digital Library
Trade Study on Aggregation of Multiple 10-KW Solid Ozide Fuel Cell Power Modules (open access)

Trade Study on Aggregation of Multiple 10-KW Solid Ozide Fuel Cell Power Modules

According to the Solid State Energy Conversion Alliance (SECA) program guidelines, solid oxide fuel cells (SOFC) will be produced in the form of 3-10 kW modules for residential use. In addition to residential use, these modules can also be used in apartment buildings, hospitals, etc., where a higher power rating would be required. For example, a hospital might require a 250 kW power generating capacity. To provide this power using the SECA SOFC modules, 25 of the 10 kW modules would be required. These modules can be aggregated in different architectures to yield the necessary power. This report will show different approaches for aggregating numerous SOFC modules and will evaluate and compare each one with respect to cost, control complexity, ease of modularity, and fault tolerance.
Date: December 3, 2004
Creator: Ozpineci, B.
Object Type: Report
System: The UNT Digital Library
High-energy coherent THz radiation from laser wakefieldaccelerated ultrashort electron bunches (open access)

High-energy coherent THz radiation from laser wakefieldaccelerated ultrashort electron bunches

None
Date: May 3, 2004
Creator: van Tilborg, J.; Fubiani, G. J.; Geddes, C. G. R.; Toth, C.; Esarey, E.; Schroeder, C. B. et al.
Object Type: Article
System: The UNT Digital Library
Single ion implantation with scanning probe alignment (open access)

Single ion implantation with scanning probe alignment

None
Date: June 3, 2004
Creator: Persaud, A.; Allen, F. I.; Gicquel, F.; Park, S. J.; Liddle, J. A.; Schenkel, T. et al.
Object Type: Article
System: The UNT Digital Library
Mid infrared observations of Van Maanen 2: no substellar companion. (open access)

Mid infrared observations of Van Maanen 2: no substellar companion.

The results of a comprehensive infrared imaging search for the putative 0.06 M{sub {circle_dot}} astrometric companion to the 4.4 pc white dwarf van Mannen 2 are reported. Adaptive optics images acquired at 3.8 {micro}m reveal a diffraction limited core of 0.09 inch and no direct evidence of a secondary. Models predict that at 5 Gyr, a 50 M{sub J} brown dwarf would be only 1 magnitude fainter than van Maanen 2 at this wavelength and the astrometric analysis suggested a separation of 0.2 inch. In the case of a chance alignment along the line of sight, a 0.4 mag excess should be measured. An independent photometric observation at the same wavelength reveals no excess. In addition, there exist published ISO observations of van Maanen 2 at 6.8 {micro}m and 15.0 {micro}m which are consistent with photospheric flux of a 6750 K white dwarf. If recent brown dwarf models are correct, there is no substellar companion with T{sub eff} {approx}> 500 K.
Date: November 3, 2004
Creator: Farihi, J; Becklin, E & Macintosh, B
Object Type: Article
System: The UNT Digital Library
Hyperspectral Mineral Mapping in Support of Geothermal Exploration: Examples from Long Valley Caldera, CA and Dixie Valley, NV, USA (open access)

Hyperspectral Mineral Mapping in Support of Geothermal Exploration: Examples from Long Valley Caldera, CA and Dixie Valley, NV, USA

Growing interest and exploration dollars within the geothermal sector have paved the way for increasingly sophisticated suites of geophysical and geochemical tools and methodologies. The efforts to characterize and assess known geothermal fields and find new, previously unknown resources has been aided by the advent of higher spatial resolution airborne geophysics (e.g. aeromagnetics), development of new seismic processing techniques, and the genesis of modern multi-dimensional fluid flow and structural modeling algorithms, just to name a few. One of the newest techniques on the scene, is hyperspectral imaging. Really an optical analytical geochemical tool, hyperspectral imagers (or imaging spectrometers as they are also called), are generally flown at medium to high altitudes aboard mid-sized aircraft and much in the same way more familiar geophysics are flown. The hyperspectral data records a continuous spatial record of the earth's surface, as well as measuring a continuous spectral record of reflected sunlight or emitted thermal radiation. This high fidelity, uninterrupted spatial and spectral record allows for accurate material distribution mapping and quantitative identification at the pixel to sub-pixel level. In volcanic/geothermal regions, this capability translates to synoptic, high spatial resolution, large-area mineral maps generated at time scales conducive to both the faster pace of …
Date: March 3, 2004
Creator: Pickles, W. L.; Martini, B. A.; Silver, E. A. & Cocks, P. A.
Object Type: Article
System: The UNT Digital Library
Implicit Occluders (open access)

Implicit Occluders

In this paper we propose a novel visibility-culling technique for optimizing the computation and rendering of opaque isosurfaces. Given a continuous scalar field f (x) over a domain D and an isovalue w, our technique exploits the continuity of f to determine conservative visibility bounds implicitly, i.e., without the need for actually computing the isosurface f{sup -1}(w). We generate Implicit Occluders based on the change in sign of f *(x) = f (x)-w, from positive to negative (or vice versa) in the neighborhood of the isosurface. Consider, for example, the sign of f * along a ray r cast from the current viewpoint. The first change in sign of f * within D must contain an intersection of r with the isosurface. Any additional intersection of the isosurface with r is not visible. Implicit Occluders constitute a general concept that can be exploited algorithmically in different ways depending on the framework adopted for visibility computations. In this paper, we propose a simple from-point approach that exploits well-known hardware occlusion queries.
Date: February 3, 2004
Creator: Pesco, S; Lindstrom, P; Pascucci, V & Silva, C T
Object Type: Article
System: The UNT Digital Library
Climate Model Output Rewriter (CMOR) (open access)

Climate Model Output Rewriter (CMOR)

None
Date: June 3, 2004
Creator: Taylor, K E; Doutriaux, C & Peterschmitt, J
Object Type: Report
System: The UNT Digital Library
Arsenic Mobilization from Contaminated Sediments: A Full-scale Experiment in Progress (open access)

Arsenic Mobilization from Contaminated Sediments: A Full-scale Experiment in Progress

The mobilization of arsenic was examined in a system where the deposition of iron and arsenic have been substantially modified by large-scale manipulations. This engineering practice was designed to decrease arsenic concentrations in water supplied to the City of Los Angeles. Accomplishing this objective, however, has resulted in significant accumulation of arsenic and iron in the sediments of a reservoir on the Los Angeles Aqueduct. Arsenic and iron are released into the porewater at depth in the sediment, consistent with reductive dissolution of iron(III) oxyhydroxides. Factors influencing the possible re-sorption of arsenic onto residual iron(III) oxyhydroxides solids have been examined. Reduction of As(V) to As(III) alone cannot account for arsenic mobilization since arsenic occurs in the solid phase as As(III) well above the depth at which it is released into the porewater. Competition from other porewater constituents could suppress re-sorption of arsenic released by reductive dissolution.
Date: February 3, 2004
Creator: O'Day, P A; Campbell, K; Dixit, S & Hering, J G
Object Type: Article
System: The UNT Digital Library
Scientific Presentations: 10th Meeting of the Management Steering Committee of the Riken Bnl Collaboration (Rbrc Scientific Articles, Volume 10) (open access)

Scientific Presentations: 10th Meeting of the Management Steering Committee of the Riken Bnl Collaboration (Rbrc Scientific Articles, Volume 10)

None
Date: September 3, 2004
Creator: Samios, N. P.
Object Type: Report
System: The UNT Digital Library
Strongly Non-Arrhenius Self-Interstitial Diffusion in Vanadium (open access)

Strongly Non-Arrhenius Self-Interstitial Diffusion in Vanadium

None
Date: February 3, 2004
Creator: Zepeda-Ruiz, L A; Rottler, J; Han, S; Ackland, G J; Car, R & Srolovitz, D J
Object Type: Article
System: The UNT Digital Library
Properties of Fluid Deuterium under Double-Shock Compression to Several Mbar (open access)

Properties of Fluid Deuterium under Double-Shock Compression to Several Mbar

The compressibility of fluid deuterium up to several Mbar has been probed using laser-driven shock waves reflected from a quartz anvil. Combining high-precision ({approx} 1 %) shock velocity measurements with the double-shock technique, where differences in equation of state (EOS) models are magnified, has allowed us to accurately discriminate between various theoretical predictions. Our data are consistent with EOS models that show approximately fourfold compression on the principal Hugoniot from 0.7 to 1 Mbar; however, our results indicate that deuterium has a higher compressibility than predicted by these models for single shock pressures between 1 and 2.5 Mbar.
Date: February 3, 2004
Creator: Vianello, E; Celliers, P M; Hicks, D G; Boehly, T R; Collins, T B; Moon, S J et al.
Object Type: Article
System: The UNT Digital Library
Superconducting Combined Function Magnet System for J-PARC Neutrino Experiment. (open access)

Superconducting Combined Function Magnet System for J-PARC Neutrino Experiment.

The J-PARC Neutrino Experiment, the construction of which starts in JFY 2004, will use a superconducting magnet system for its primary proton beam line. The system, which bends the 50 GeV 0.75 MW proton beam by about 80 degrees, consists of 28 superconducting combined function magnets. The magnets utilize single layer left/right asymmetric coils that generate a dipole field of 2.6 T and a quadrupole field of 18.6 T/m with the operation current of about 7.35 kA. The system also contains a few conduction cooled superconducting corrector magnets that serve as vertical and horizontal steering magnets. All the magnets are designed to provide a physical beam aperture of 130 mm in order to achieve a large beam acceptance. Extensive care is also required to achieve safe operation with the high power proton beam. The paper summarizes the system design as well as some safety analysis results.
Date: October 3, 2004
Creator: Ogitsu, T.; Ajima, Y.; Anerella, M.; Escallier, J.; Ganetis, G.; Gupta, R. et al.
Object Type: Article
System: The UNT Digital Library
Parallel Adaptive Multi-Mechanics Simulations using Diablo (open access)

Parallel Adaptive Multi-Mechanics Simulations using Diablo

Coupled multi-mechanics simulations (such as thermal-stress and fluidstructure interaction problems) are of substantial interest to engineering analysts. In addition, adaptive mesh refinement techniques present an attractive alternative to current mesh generation procedures and provide quantitative error bounds that can be used for model verification. This paper discusses spatially adaptive multi-mechanics implicit simulations using the Diablo computer code. (U)
Date: December 3, 2004
Creator: Parsons, D & Solberg, J
Object Type: Article
System: The UNT Digital Library
Indirect Drive Cold-Loaded Ignition Target Design (open access)

Indirect Drive Cold-Loaded Ignition Target Design

This document summarizes the Indirect Drive Cold-Loaded (diffusion-filled) Ignition Target design. These targets include a capsule whose strength is insufficient to withstand the room temperature pressure of the DT fuel. These capsules are diffusion filled with DT gas and then cooled to cryogenic temperature. The target must remain at cryogenic temperature until it is shot. Only features that affect the design of the NIF Cryogenic Target System (NCTS) are presented. The design presented is the current thinking and may evolve further. The NCTS should be designed to accommodate a range of targets and target scales, as described here. The interface location between the target and the NCTS cryostat is at the target base / gripper joint.
Date: September 3, 2004
Creator: Bernat, T. P. & Gibson, C. R.
Object Type: Report
System: The UNT Digital Library
Radiation Resistant Hts Quadrupoles for Ria. (open access)

Radiation Resistant Hts Quadrupoles for Ria.

Extremely high radiation, levels with accumulated doses comparable to those in nuclear reactors than in accelerators, and very high heat loads ({approx}15 kw) make the quadrupole magnets in the fragment separator one of the most challenging elements of the proposed Rare Isotope Accelerator (RIA). Removing large heat loads, protecting the superconducting coils against quenching, the long term survivability of magnet components, and in particular, insulation that can retain its functionality in such a harsh environment, are the major challenges associated with such magnets. A magnet design based on commercially available high temperature superconductor (HTS) and stainless steel tape insulation has been developed. HTS will efficiently remove these large heat loads and stainless steel can tolerate these large radiation doses. Construction of a model magnet has been started with several coils already built and tested. This paper presents the basic magnet design, results of the coil tests, the status and the future plans. In addition, preliminary results of radiation calculations are also presented.
Date: October 3, 2004
Creator: Gupta, R.; Anerella, M.; Harrison, M. & Al., Et
Object Type: Article
System: The UNT Digital Library
Pulse duration measurements of a picosecond laser-pumped 14.7 nm x-ray laser (open access)

Pulse duration measurements of a picosecond laser-pumped 14.7 nm x-ray laser

The temporal dependence of the 14.7 nm Ni-like Pd ion x-ray laser is measured as a function of the laser drive conditions with a fast sub-picosecond x-ray streak camera. The chirped pulse amplification laser beam that pumps the inversion process is varied from 0.5 - 27 ps (FWHM) to determine the effect on the x-ray laser pulse duration. The average x-ray laser pulse duration varies by a relatively small factor of 2.5 times from 3.6 ps to 8.1 ps with traveling wave (TW) irradiation conditions. Slightly shorter pulse durations approaching 2 ps are observed with the x-ray laser operating below saturation. The x-ray laser is found to be 4 - 5 times transform-limited for 6 - 13 ps laser pumping conditions.
Date: August 3, 2004
Creator: Dunn, J; Smith, R F; Shepherd, R; Booth, R; Nilsen, J; Hunter, J R et al.
Object Type: Article
System: The UNT Digital Library
Constraints and Casimirs for Super Poincare and Supertranslation Algebras in various dimensions (open access)

Constraints and Casimirs for Super Poincare and Supertranslation Algebras in various dimensions

We describe, for arbitrary dimensions the construction of a covariant and supersymmetric constraint for the massless Super Poincare algebra and we show that the constraint fixes uniquely the representation of the algebra. For the case of finite mass and in the absence of central charges we discuss a similar construction, which generalizes to arbitrary dimensions the concept of the superspin Casimir. Finally we discuss briefly the modifications introduced by central charges, both scalar and tensorial.
Date: November 3, 2004
Creator: Zumino, Bruno
Object Type: Article
System: The UNT Digital Library
Mechanisms of Strontium and Uranium Removal From Radioactive Waste Simulant Solutions by the Sorbent Monosodium Titanate (open access)

Mechanisms of Strontium and Uranium Removal From Radioactive Waste Simulant Solutions by the Sorbent Monosodium Titanate

High-Level Radioactive Waste (HLW) is the priority problem for the U.S. Dept. of Energy's Environmental Management Program. Current HLW treatment processes at the Savannah River Site (Aiken, SC) include the use of monosodium titanate (MST, similar to NaTi{sub 2}O{sub 5}xH{sub 2}O) to concentrate radioactive strontium (Sr) and actinides. Mechanistic information about radionuclide uptake will provide us with insight about the reliability of MST treatments. We characterized the morphology of MST and the chemistry of sorbed Sr{sup 2+} and uranium [U(VI)] on MST with x-ray based spectroscopic and electron microscopic techniques. Sorbed Sr{sup 2+} exhibited specific adsorption as partially-hydrated species, whereas sorbed U exhibited site-specific adsorption as monomeric and dimeric U(VI)-carbonate complexes. These differences in site specificity and mechanism may account for the difficulties associated with predicting MST loading and removal kinetics.
Date: December 3, 2004
Creator: Duff, Martine
Object Type: Article
System: The UNT Digital Library
On the Sensitivity of Atmospheric Model Implied Ocean Heat Transport to the Dominant Terms of the Surface Energy Balance (open access)

On the Sensitivity of Atmospheric Model Implied Ocean Heat Transport to the Dominant Terms of the Surface Energy Balance

The oceanic meridional heat transport (T{sub o}) implied by an atmospheric General Circulation Model (GCM) can help evaluate a model's readiness for coupling with an ocean GCM. In this study we examine the T{sub o} from benchmark experiments of the Atmospheric Model Intercomparison Project, and evaluate the sensitivity of T{sub o} to the dominant terms of the surface energy balance. The implied global ocean TO in the Southern Hemisphere of many models is equatorward, contrary to most observationally-based estimates. By constructing a hybrid (model corrected by observations) T{sub o}, an earlier study demonstrated that the implied heat transport is critically sensitive to the simulated shortwave cloud radiative effects, which have been argued to be principally responsible for the Southern Hemisphere problem. Systematic evaluation of one model in a later study suggested that the implied T{sub o} could be equally as sensitive to a model's ocean surface latent heat flux. In this study we revisit the problem with more recent simulations, making use of estimates of ocean surface fluxes to construct two additional hybrid calculations. The results of the present study demonstrate that indeed the implied T{sub o} of an atmospheric model is very sensitive to problems in not only the …
Date: November 3, 2004
Creator: Gleckler, P J
Object Type: Article
System: The UNT Digital Library
A multi-scale approach to molecular dynamics simulations of shock waves (open access)

A multi-scale approach to molecular dynamics simulations of shock waves

Study of the propagation of shock waves in condensed matter has led to new discoveries ranging from new metastable states of carbon [1] to the metallic conductivity of hydrogen in Jupiter, [2] but progress in understanding the microscopic details of shocked materials has been extremely difficult. Complications can include the unexpected formation of metastable states of matter that determine the structure, instabilities, and time-evolution of the shock wave. [1,3] The formation of these metastable states can depend on the time-dependent thermodynamic pathway that the material follows behind the shock front. Furthermore, the states of matter observed in the shock wave can depend on the timescale on which observation is made. [4,1] Significant progress in understanding these microscopic details has been made through molecular dynamics simulations using the popular non-equilibrium molecular dynamics (NEMD) approach to atomistic simulation of shock compression. [5] The NEMD method involves creating a shock at one edge of a large system by assigning some atoms at the edge a fixed velocity. The shock propagates across the computational cell to the opposite side. The computational work required by NEMD scales at least quadratically in the evolution time because larger systems are needed for longer simulations to prevent the …
Date: September 3, 2004
Creator: Reed, E. J.; Fried, L. E.; Manaa, M. R. & Joannopoulos, J. D.
Object Type: Book
System: The UNT Digital Library
Finite Pressure Effects on Reversed Shear Alfven Eigenmodes (open access)

Finite Pressure Effects on Reversed Shear Alfven Eigenmodes

The inclusion of finite pressure in ideal-magnetohydrodynamic (MHD) theory can explain the Reversed magnetic Shear Alfven Eigenmodes (RSAE) (or Alfven cascades) that have been observed in several large tokamaks without the need to invoke the energetic particle mechanism for the existence of these modes. The chirping of the RSAEs is cased by changes in the minimum of the magnetic safety factor, q(sub)min, while finite pressure effects explains the observed non-zero minimum frequency of the RSAE when qmin has a rational value. Finite pressure effects also play a dominant role in the existence of the downward chirping RSAE branch.
Date: September 3, 2004
Creator: Kramer, G. J.; Gorelenkov, N. N.; Nazikian, R. & Cheng, C. Z.
Object Type: Report
System: The UNT Digital Library