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Techniques for inelastic x-ray scattering with {mu}eV resolution.

Description: We introduce a novel type of spectrometer that provides a {micro}eV bandpass together with a tunability over a few meV. The technique relies on nuclear resonant scattering (Moessbauer effect) of synchrotrons radiation at the 14.4-keV resonance of {sup 57}Fe. Energy tuning is achieved by the Doppler effect in high speed rotary motion. The resonantly scattered monochromatic radiation is extracted by a polarization filtering technique or by spatial separation due to the ''nuclear lighthouse effect''.
Date: October 23, 1998
Creator: Rohlsberger, R.
Partner: UNT Libraries Government Documents Department

AntiReflection Coating D

Description: Analytical expressions used to optimize AR coatings for single junction solar cells are extended for use in monolithic, series interconnected multi-junction solar cell AR coating design. The result is an analytical expression which relates the solar cell performance (through J{sub sc}) directly to the AR coating design through the device reflectance. It is also illustrated how AR coating design be used to provide an additional degree of freedom for current matching multi-junction devices.
Date: September 23, 1999
Partner: UNT Libraries Government Documents Department

EUV/soft x-ray spectra for low B neutron stars

Description: Recent ROSAT and EUVE detections of spin-powered neutron stars suggest that many emit ``thermal`` radiation, peaking in the EUV/soft X-ray band. These data constrain the neutron stars` thermal history, but interpretation requires comparison with model atmosphere computations, since emergent spectra depend strongly on the surface composition and magnetic field. As recent opacity computations show substantial change to absorption cross sections at neutron star photospheric conditions, we report here on new model atmosphere computations employing such data. The results are compared with magnetic atmosphere models and applied to PSR J0437-4715, a low field neutron star.
Date: May 23, 1995
Creator: Romani, R.W.; Rajagopal, M.; Rogers, F.J. & Iglesias, C.A.
Partner: UNT Libraries Government Documents Department


Description: Last year, the X27A beamline at the National Synchrotron Light Source (NSLS) became dedicated solely to X-Ray Computed Microtomography (XCMT). This is a third-generation instrument capable of producing tomographic volumes of 1-2 micron resolution over a 2-3mm field of view. Recent enhancements will be discussed. These have focused on two issues: the desire for real-time data acquisition and processing and the need for highly monochromatic beam (.1 % energy bandpass). The latter will permit k-edge subtraction studies and will provide improved image contrast from below the Cr (6 keV) up to the Cs (36 keV) k-edge. A range of applications that benefit from these improvements will be discussed as well. These two goals are somewhat counterproductive, however; higher monochromaticity yields a lower flux forcing longer data acquisition times. To balance the two, a more efficient scintillator for X-ray conversion is being developed. Some testing of a prototype scintillator has been performed; preliminary results will be presented here. In the meantime, data reconstruction times have been reduced, and the entire tomographic acquisition, reconstruction and volume rendering process streamlined to make efficient use of synchrotron beam time. A Fast Filtered Back Transform (FFBT) reconstruction program recently developed helped to reduce the time to reconstruct a volume of 150 x 150 x 250 pixels{sup 3} (over 5 million voxels) from the raw camera data to 1.5 minutes on a dual R10,000 CPU. With these improvements, one can now obtain a ''quick look'' of a small tomographic volume ({approximately}10{sup 6}voxels) in just over 15 minutes from the start of data acquisition.
Date: July 23, 1999
Creator: DOWD,B.A.
Partner: UNT Libraries Government Documents Department

Performance measurements of sealed-tube electron beam windows

Description: This paper describes the performance of the thin-film windows used in a new sealed-tube electron gun. Measurements include beam current, power, and power density along with window transmission, temperature, electron scattering and window life tests. A number of novel beam diagnostic tools were developed as part of this effort. Results are compared to Monte Carlo computer predictions and show good agreement. Transmitted beam powers in excess of 200 watts have been achieved, with current densities exceeding 30 milliamperes per square centimeter at sixty kilovolts beam energy. Predicted window wearout time exceeds several thousand hours at a current density of two milliamperes per square centimeter and a beam accelerating voltage of 60 kilovolts. This work was carried out under a Cooperative Research and Development Agreement (CRADA) between Lawrence Livermore National Laboratory and American International Technologies, Inc.
Date: February 23, 1996
Creator: Myers, B.R.; Chen, H.L.; Meyer, G. & Wakalopulos, G.
Partner: UNT Libraries Government Documents Department

Shock loading of Ta: yield and hardening behavior of polycrystalline and oriented single crystals

Description: We are undertaking a series of shock compression experiments on polycrystalline and oriented single crystal Ta to investigate the fundamental mechanisms controlling dislocation behavior in Ta and other bcc metals at high strain rate. We compare experimental results to those calculated using an explicit 1-D computer code using the Steinberg-Guinan-Lund rate dependent model (Steinberg and Lund [1989]) to describe the strength properties of Ta in these calculation
Date: October 23, 1998
Creator: Fiske, P. S.; Holmes, N. C. & Lassila, D. H.
Partner: UNT Libraries Government Documents Department

Waste minimization applications at a remediation site

Description: The Fernald Environmental Management Project (FEMP) owned by the Department of Energy was used for the processing of uranium. In 1989 Fernald suspended production of uranium metals and was placed on the National Priorities List (NPL). The site`s mission has changed from one of production to environmental restoration. Many groups necessary for producing a product were deemed irrelevant for remediation work, including Waste Minimization. Waste Minimization does not readily appear to be applicable to remediation work. Environmental remediation is designed to correct adverse impacts to the environment from past operations and generates significant amounts of waste requiring management. The premise of pollution prevention is to avoid waste generation, thus remediation is in direct conflict with this premise. Although greater amounts of waste will be generated during environmental remediation, treatment capacities are not always available and disposal is becoming more difficult and costly. This creates the need for pollution prevention and waste minimization. Applying waste minimization principles at a remediation site is an enormous challenge. If the remediation site is also radiologically contaminated it is even a bigger challenge. Innovative techniques and ideas must be utilized to achieve reductions in the amount of waste that must be managed or dispositioned. At Fernald the waste minimization paradigm was shifted from focusing efforts on source reduction to focusing efforts on recycle/reuse by inverting the EPA waste management hierarchy. A fundamental difference at remediation sites is that source reduction has limited applicability to legacy wastes but can be applied successfully on secondary waste generation. The bulk of measurable waste reduction will be achieved by the recycle/reuse of primary wastes and by segregation and decontamination of secondary wastestreams. Each effort must be measured in terms of being economically and ecologically beneficial.
Date: January 23, 1995
Creator: Allmon, L.A.
Partner: UNT Libraries Government Documents Department

A Phase-Field Model for Grain Growth

Description: A phase-field model for grain growth is briefly described. In this model, a poly-crystalline microstructure is represented by multiple structural order parameter fields whose temporal and spatial evolutions follow the time-dependent Ginzburg-Landau (TDGL) equations. Results from phase-field simulations of two-dimensional (2D) grain growth will be summarized and preliminary results on three-dimensional (3D) grain growth will be presented. The physical interpretation of the structural order parameter fields and the efficient and accurate semi-implicit Fourier spectral method for solving the TDGL equations will be briefly discussed.
Date: December 23, 1998
Creator: Chen, L.Q.; Fan, D.N. & Tikare, V.
Partner: UNT Libraries Government Documents Department

The Quantum Mixed-Spin Heme State of Barley Peroxidase: A Paradigm for Class III Peroxidases

Description: Electronic absorption and resonance Raman (RR) spectra of the ferric form of barley grain peroxidase (BP 1) at various pH values both at room temperature and 20 K are . reported, together with EPR spectra at 10 K. The ferrous forms and the ferric complex with fluoride have also been studied. A quantum mechanically mixed-spin (QS) state has been identified. The QS heme species co-exists with 6- and 5-cHS heroes; the relative populations of these three spin states are found to be dependent on pH and temperature. However, the QS species remains in all cases the dominant heme spin species. Barley peroxidase appears to be further characterized by a splitting of the two vinyl stretching modes, indicating that the vinyl groups are differently conjugated with the porphyrin. An analysis of the presently available spectroscopic data for proteins from all three peroxidase classes suggests that the simultaneous occurrence of the QS heme state as well as the splitting of the two vinyl stretching modes is confined to class III enzymes. The former point is discussed in terms of the possible influences of heme deformations on heme spin state. It is found that moderate saddling alone is probably not enough to cause the QS state, although some saddling maybe necessary for the QS state.
Date: March 23, 1999
Creator: Howes, B.D.; Ma, J.; Marzocchi, M.P.; Schiodt, C.B.; Shelnutt, J.A.; Smulevich, G. et al.
Partner: UNT Libraries Government Documents Department

X-ray tomography of preserved samples from the Geysers scientific corehole

Description: Approximately 800 ft. of continuous core was recovered from borehole SB-15 D (on unit 15, near the site of the abandoned Geysers Resort) during a recently completed drilling operation. Sections of this core were collected at 50 ft intervals for subsequent examination as drilling proceeded. Five foot sections were not removed at the drill site, but were sealed in the innermost sleeve of a triple tube coring system to minimize drying and disturbance of the core. All cores remained sealed and were radiographed within 72 hours of drilling: the five foot core from near 1400 ft. was scanned within 18 hours of drilling. A third generation x-ray scanner, which uses high energy radiation to penetrate the aluminum sleeve and 3.5 inch cores, was used to make preliminary radiographs and to collect multiple views of the sample as the core is rotated in front of the beam. True three dimensional tomographs are then reconstructed from the data. The images have a spatial resolution of approximately 140 micrometers and can resolve contrast differences of 0.2%. The tomographs clearly show differences in lithology with depth in the reservoir. Partially filled fractures, vein selvage and vuggy porosity are all evident in parts of the core. A principle goal is to determine the fluid content of the reservoir. Important questions to investigate include water loss during core recovery, infiltration of drilling fluid, and the heterogeneous distribution of pore fluid. Images show that radial gradients in x-ray attenuation commonly occur in jacketed cores. Regions of excess attenuation extend about halfway into the 3.5 in. core, and are probably caused by mud invasion induced by capillarity of the small scale porosity of the graywacke matrix. X-ray measurements will be coordinated with other independent measurements of fluid content underway in separate studies, particularly NMR spectroscopy of frozen `pressure ...
Date: January 23, 1995
Creator: Bonner, B.P.; Roberts, J.J.; Schneberk, D.J.; Marsh, A.; Ruddle, C. & Updike, E.
Partner: UNT Libraries Government Documents Department

Second-order method for interface reconstruction in orthogonal coordinate systems

Description: We present a method in two-dimensions for reconstructing an interface from a distribution of volume fractions in a general orthogonal coordinate system. The method, in a cell by cell fashion, approximates the interface curve by a linear pro le. The approach requires only local volume fraction information for the reconstruction. An integral formulation is used that accounts for the orthogonal coordinate system in a natural way. We use nit different to approximate the slop of the required interface while retaining at worst second order accuracy for general interface orientations and an exact representation for coordinate system aligned o
Date: December 23, 1998
Creator: Colella, P.; Graves, D. T. & Greenough, J. G.
Partner: UNT Libraries Government Documents Department

Summary: Working Group on QCD and Strong Interactions

Description: In this summary of the considerations of the QCD working group at Snowmass 2001, the roles of quantum chromodynamics in the Standard Model and in the search for new physics are reviewed, with empahsis on frontier areas in the field. We discuss the importance of, and prospects for, precision QCD in perturbative and lattice calculations. We describe new ideas in the analysis of parton distribution functions and jet structure, and review progress in small-x and in polarization experiments.
Date: December 23, 2002
Creator: al., Edmond L. Berger et
Partner: UNT Libraries Government Documents Department

The highly successful safe remediation of the Fernald waste pits undertaken under the privatization model

Description: Remediation of eight waste pits at the Department of Energy (DOE) Fernald site, located northwest of Cincinnati, Ohio, involves excavating approximately one million tonnes in-situ of low-level waste which were placed in pits during Fernald's production era. This unique project, one of the largest in the history of CERCLA/Superfund, includes uranium and thorium contaminated waste, soils and sludges. These wet soils and sludges are thermally dried in a processing facility to meet Department of Transportation (DOT) transportation and disposal facility waste acceptance criteria, loaded into railcars and shipped to the Envirocare waste disposal facility at Clive, Utah. This project is now approximately 60% complete with more than 415,000 tonnes (460,000 tons) of waste material safely shipped in 74 unit trains to Envirocare. Work is scheduled to be completed in early 2005. Success to date demonstrates that a major DOE site remediation project can be safely and successfully executed in partnership with private industry, utilizing proven commercial best practices, existing site labor resources and support of local stakeholders. In 1997 under the DOE's privatization initiative, Fluor Fernald, Inc. (Fluor Fernald) solicited the services of the remediation industry to design, engineer, procure, construct, own and operate a facility that would undertake the remediation of the waste pits. The resulting procurement was awarded to IT Corporation, currently Shaw Environmental and Infrastructure, Inc. (Shaw). The contractor was required to finance the procurement and construction of its facilities and infrastructure. The contract was performance-based and payment would be made on the successful loadout of the waste from the facility on a per-ton basis meeting the Envirocare waste acceptance criteria. This paper details the performance to date, the challenges encountered, and the seamless partnering between DOE, the Environmental Protection Agency (EPA), Fluor Fernald, Shaw, labor un ions, and the local community in creating and executing a ...
Date: February 23, 2003
Creator: Cherry, Mark; Lojek, Dave & Murphy, Con
Partner: UNT Libraries Government Documents Department


Description: The National Nuclear Security Administration is developing methods for nonproliferation assessments to support the development and implementation of U.S. nonproliferation policy. This paper summarizes the key results of that effort. Proliferation resistance is the degree of difficulty that a nuclear material, facility, process, or activity poses to the acquisition of one or more nuclear weapons. A top-level measure of proliferation resistance for a fuel cycle system is developed here from a hierarchy of metrics. At the lowest level, intrinsic and extrinsic barriers to proliferation are defined. These barriers are recommended as a means to characterize the proliferation characteristics of a fuel cycle. Because of the complexity of nonproliferation assessments, the problem is decomposed into: metrics to be computed, barriers to proliferation, and a finite set of threats. The spectrum of potential threats of nuclear proliferation is complex and ranges from small terrorist cells to industrialized countries with advanced nuclear fuel cycles. Two general categories of methods have historically been used for nonproliferation assessments: attribute analysis and scenario analysis. In the former, attributes of the systems being evaluated (often fuel cycle systems) are identified that affect their proliferation potential. For a particular system under consideration, the attributes are weighted subjectively. In scenario analysis, hypothesized scenarios of pathways to proliferation are examined. The analyst models the process undertaken by the proliferant to overcome barriers to proliferation and estimates the likelihood of success in achieving a proliferation objective. An attribute analysis approach should be used at the conceptual design level in the selection of fuel cycles that will receive significant investment for development. In the development of a detailed facility design, a scenario approach should be undertaken to reduce the potential for design vulnerabilities. While, there are distinctive elements in each approach, an analysis could be performed that utilizes aspects of each approach.
Date: June 23, 2003
Partner: UNT Libraries Government Documents Department


Description: A high-energy CO{sub 2} laser is channeled in a capillary discharge. Plasma dynamic simulations confirm occurrence of guiding conditions at the relatively low axial plasma density 1 {divided_by} 4 x 10{sup 17} cm{sup -3}. A relativistic electron beam transmitted through the capillary changes its properties depending upon the plasma density. We observe focusing, defocusing or steering of the e-beam. Counter-propagation of the electron and laser beams in the plasma channel results in generation of intense picosecond x-ray pulses.
Date: June 23, 2002
Partner: UNT Libraries Government Documents Department

Experimental challenges for QCD - the past and the future.

Description: The past leaves the surprising experimental successes of the simple constituent quark model to be explained by QCD. The future opens the way to new insight into QCD from heavy flavor experiments.
Date: October 23, 2002
Creator: Lipkin, H. J.
Partner: UNT Libraries Government Documents Department

Enhanced Plutonium Mobility During Long-Term Transport Through an Unsaturated Subsurface Environment

Description: Plutonium moved more rapidly through vadose zone sediments than previous thought possible. Based on field studies conducted for up to 11 years and supplemental laboratory studies, it was hypothesized that periodic sediment drying caused the very slow release of tightly bound Pu into the mobile aqueous phase, presumably by oxidation of Pu(IV) to the more mobile Pu(V). Of particular interest, was that this release occurred in sediments, that when saturated with groundwater, promoted rapid reduction of Pu to the less mobile form, Pu(IV). Accurate prediction of Pu transport through the vadose zone is important because this region is expected to provide an important buffer between disposed nuclear waste and the biosphere.
Date: January 23, 2004
Creator: Kaplan, D.I.
Partner: UNT Libraries Government Documents Department

Numerical Models of Waste Glass Models Part II Computational Modeling of DWPF

Description: Computational fluid-dynamics numerical models are developed for joule-heated slurry fed waste glass melters, such as the Defense Waste Processing Facility Melter. An important feature of the analyses is the simulation of the cold cap region with its thermally resistant foamy layer. Using a simplified model which describes the foam void fraction as a function of temperature, based on laboratory sample testing, characteristic features of the cold cap are simulated. Two- and three-dimensional models are presented.
Date: April 23, 2003
Creator: Bickford, D.F.
Partner: UNT Libraries Government Documents Department


Description: Two, 111 GBq (3 Curie) radium-beryllium (RaBe) sources were in underground storage at the Brookhaven National Laboratory (BNL) since 1988. These sources originated from Princeton Plasma Physics Laboratory (PPPL) where they were used to calibrate neutron detection diagnostics. In 1999, PPPL and BNL began a collaborative effort to expand the use of an innovative pilot-scale technology and bring it to full-scale deployment to shield these sources for eventual transport and burial at the Hanford Burial site. The transport/disposal container was constructed of depleted uranium oxide encapsulated in polyethylene to provide suitable shielding for both gamma and neutron radiation. This new material can be produced from recycled waste products (DU and polyethylene), is inexpensive, and can be disposed with the waste, unlike conventional lead containers, thus reducing exposure time for workers. This paper will provide calculations and information that led to the initial design of the shielding. We will also describe the production-scale processing of the container, cost, schedule, logistics, and many unforeseen challenges that eventually resulted in the successful fabrication and deployment of this shield. We will conclude with a description of the final configuration of the shielding container and shipping package along with recommendations for future shielding designs.
Date: February 23, 2003
Partner: UNT Libraries Government Documents Department

Superconducting drift-tube cavity development for the RIA driver.

Description: This paper reports the design and development of two intermediate-velocity superconducting cavities and design of an associated cryomodule for the RIA driver linac. The two cavity types are a 115 MHz, {beta}{sub GEOM} = 0.15 quarter-wave resonant (QWR) cavity, and a 173 MHz, {beta}{sub GEOM} = 0.26 half-wave loaded cavity. Both cavities are well-corrected for dipole and quadrupole asymmetries in the accelerating field. The cryomodule is being designed to incorporate a separate vacuum system for cavity vacuum to provide a particulate-free environment for the superconducting cavities.
Date: September 23, 2002
Creator: Shepard, K. W.; Kelly, M. P. & Fuerst, J. D.
Partner: UNT Libraries Government Documents Department