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Prediction of Corrosion of Alloys in Mixed-Solvent Environments (open access)

Prediction of Corrosion of Alloys in Mixed-Solvent Environments

Corrosion is much less predictable in organic or mixed-solvent environments than in aqueous process environments. As a result, US chemical companies face greater uncertainty when selecting process equipment materials to manufacture chemical products using organic or mixed solvents than when the process environments are only aqueous. Chemical companies handle this uncertainty by overdesigning the equipment (wasting money and energy), rather than by accepting increased risks of corrosion failure (personnel hazards and environmental releases). Therefore, it is important to develop simulation tools that would help the chemical process industries to understand and predict corrosion and to develop mitigation measures. To create such tools, we have developed models that predict (1) the chemical composition, speciation, phase equilibria, component activities and transport properties of the bulk (aqueous, nonaqueous or mixed) phase that is in contact with the metal; (2) the phase equilibria and component activities of the alloy phase(s) that may be subject to corrosion and (3) the interfacial phenomena that are responsible for corrosion at the metal/solution or passive film/solution interface. During the course of this project, we have completed the following: (1) Development of thermodynamic modules for calculating the activities of alloy components; (2) Development of software that generates stability diagrams …
Date: June 5, 2003
Creator: A. Anderko, P. Wang, R. D. Young, D. P. Riemer, P. McKenzie and M. M. Lencka (OLI Systems Inc.) & Laboratory), S. S. Babu and P. Angelini (Oak Ridge National
Object Type: Report
System: The UNT Digital Library
Evolution of Defects in Pu during Isochronal Annealing and Self Irradiation (open access)

Evolution of Defects in Pu during Isochronal Annealing and Self Irradiation

We report on the evolution of defects in Pu during isochronal annealing and self irradiation using positron annihilation spectroscopy. Positron annihilation spectroscopy is a sensitive probe (part per million level) for atomic-scale defects. The spectroscopic tools available at LLNL allow the determination of size, concentration, and chemical surroundings of defects in aged Pu samples. Positron lifetime analysis was performed on eight samples aged 7 months to 42 years. All samples except the 7-month old sample contained a high concentration of positron trapping centers. The dominant component yielded a lifetime value of {approx}182 ps. In aged samples, a second longer lifetime component was observed that appears to increase in strength with the age of the sample. The observed lifetime values and their relative strengths are shown in figure 1. The top panel corresponds to the lifetime values and the bottom panel corresponds to the intensity of the long lifetime component. Positron lifetime values are determined by the bubble size and He content. When He is added to a bubble, the positron lifetime is shortened due to the increased electron density. When the size of the bubble is known from an independent measurement, the observed positron lifetime values and the associated first …
Date: February 5, 2003
Creator: Asoka-Kumar, P; Glade, S; Sterne, P A & Howell, R
Object Type: Article
System: The UNT Digital Library
Mechanical Behavior and Fractography of 304 Stainless Steel with High Hydrogen Concentration (open access)

Mechanical Behavior and Fractography of 304 Stainless Steel with High Hydrogen Concentration

Hydrogen embrittlement of 304 stainless steel with different hydrogen concentrations has been investigated. An electrochemical technique was used to effectively charge the high level of hydrogen into 304 stainless steel in a short period of time. At 25 ppm of hydrogen, 304 stainless steel loses 10 percent of its original mechanical strength and 20 percent plasticity. Although the ductile feature dominates the fractography, the brittle crown area near the outer surface shows the intergranular rupture effected by hydrogen. At 60 ppm of hydrogen, 304 stainless steel loses 23 percent of its strength and 38 percent plasticity, where the brittle mode dominates the fracture of the materials. Experimental results show that hydrogen damage to the performance of 304 stainless steel is significant even at very low levels. The fractograph analysis indicates the high penetration ability of hydrogen in 304 stainless steel. This work also demonstrates the advantages of the electrochemical charging technique in the study of hydrogen embrittlement.
Date: February 5, 2003
Creator: Au, M.
Object Type: Article
System: The UNT Digital Library
Characterization and Operation of Liquid Crystal Adaptive Optics Phoropter (open access)

Characterization and Operation of Liquid Crystal Adaptive Optics Phoropter

Adaptive optics (AO), a mature technology developed for astronomy to compensate for the effects of atmospheric turbulence, can also be used to correct the aberrations of the eye. The classic phoropter is used by ophthalmologists and optometrists to estimate and correct the lower-order aberrations of the eye, defocus and astigmatism, in order to derive a vision correction prescription for their patients. An adaptive optics phoropter measures and corrects the aberrations in the human eye using adaptive optics techniques, which are capable of dealing with both the standard low-order aberrations and higher-order aberrations, including coma and spherical aberration. High-order aberrations have been shown to degrade visual performance for clinical subjects in initial investigations. An adaptive optics phoropter has been designed and constructed based on a Shack-Hartmann sensor to measure the aberrations of the eye, and a liquid crystal spatial light modulator to compensate for them. This system should produce near diffraction-limited optical image quality at the retina, which will enable investigation of the psychophysical limits of human vision. This paper describes the characterization and operation of the AO phoropter with results from human subject testing.
Date: February 5, 2003
Creator: Awwal, A.; Bauman, B.; Gavel, D.; Olivier, S.; Jones, S.; Hardy, J. L. et al.
Object Type: Article
System: The UNT Digital Library
A Model for the Behavior of Magnetic Tunnel Junctions (open access)

A Model for the Behavior of Magnetic Tunnel Junctions

A magnetic tunnel junction is a device that changes its electrical resistance with a change in an applied magnetic field. A typical junction consists of two magnetic electrodes separated by a nonmagnetic insulating layer. The magnetizations of the two electrodes can have two possible extreme configurations, parallel and antiparallel. The antiparallel configuration is observed to have the higher measured resistance and the parallel configuration has the lower resistance. To switch between these two configurations a magnetic field is applied to the device which is primarily used to change the orientation of the magnetization of one electrode usually called the free layer, although with sufficient high magnetic field the orientation of the magnetizations of both of the electrodes can be changed. The most commonly used models for describing and explaining the electronic behavior of tunnel junctions are the Simmons model and the Brinkman model. However, both of these models were designed for simple, spin independent tunneling. The Simmons model does not address the issue of applied magnetic fields nor does it address the form of the electronic band structure in the metallic electrodes, including the important factor of spin polarization. The Brinkman model is similar, the main difference between the two …
Date: August 5, 2003
Creator: Baker, Bryan John
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Assessment of Unabated Facility Emission Potentials for Evaluating Airborne Radionuclide Monitoring Requirements at Pacific Northwest National Laboratory - 2003 (open access)

Assessment of Unabated Facility Emission Potentials for Evaluating Airborne Radionuclide Monitoring Requirements at Pacific Northwest National Laboratory - 2003

Assessments were performed to evaluate compliance with the airborne radionuclide emission monitoring requirements in the National Emission Standards for Hazardous Air Pollutants (NESHAP - U.S. Code of Federal Regulations, Title 40, Part 61, Subpart H) and Washington Administrative Code (WAC) 246-247: Radiation Protection - Air Emissions. In these assessments, potential unabated offsite doses were evaluated for emission locations at facilities owned by the U.S. Department of Energy and operated by Pacific Northwest National Laboratory (PNNL) on the Hanford Site. This report describes the inventory-based methods and provides the results for the assessment performed in 2003.
Date: December 5, 2003
Creator: Ballinger, Marcel Y.; Sula, Monte J.; Gervais, Todd L. & Edwards, Daniel L.
Object Type: Report
System: The UNT Digital Library
Investigations of the Electronic Properties and Surface Structures of Aluminium-Rich Quasicrystalline Alloys (open access)

Investigations of the Electronic Properties and Surface Structures of Aluminium-Rich Quasicrystalline Alloys

The work presented in this dissertation has investigated three distinct areas of interest in the field of quasicrystals: bulk structure, transport properties, and electronic structure. First, they have described the results of a study which explored the fundamental interactions between the atomic species of the icosahedral Al-Pd-Mn quasicrystal. The goal of this work was to determine whether the pseudo-MacKay or Bergman type clusters have a special stability or are merely a geometric coincidence. This was carried out by using laser vaporization to produce gas-phase metal clusters, which were analyzed using time-of-flight mass spectrometry. Both the kinetic and thermodynamic stabilities of the clusters were probed. The data indicated no special stability for either pseudo-MacKay or Bergman type clusters as isolated units. This, however, is not proof that these clusters are simply a geometric coincidence. It is possible that such clusters only have stability in the framework of the bulk matrix and do not exist as isolated units. Next, they have reported their investigations of the bulk thermal transport properties of a decagonal Al-Ni-Co two dimensional quasicrystal in the temperature range 373K-873K. The properties of a sample oriented along the periodic axis and another oriented along the aperiodic axis were measured. A …
Date: August 5, 2003
Creator: Barrow, Jason A.
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Actinic Mask Inspection at the ALS Initial Design Review (open access)

Actinic Mask Inspection at the ALS Initial Design Review

This report is the first milestone report for the actinic mask blank inspection project conducted at the VNL, which forms sub-section 3 of the Q1 2003 mask blank technology transfer program at the VNL. Specifically this report addresses deliverable 3.1.1--design review and preliminary tool design. The goal of this project is to design an actinic mask inspection tool capable of operating in two modes: high-speed scanning for the detection of multilayer defects (inspection mode), and a high-resolution aerial image mode in which the image emulates the imaging illumination conditions of a stepper system (aerial image or AIM mode). The purpose and objective of these two modes is as follows: (1) Defect inspection mode--This imaging mode is designed to scan large areas of the mask for defects EUV multilayer coatings. The goal is to detect the presence of multilayer defects on a mask blank and to store the co-ordinates for subsequent review in AIM mode, thus it is not essential that the illumination and imaging conditions match that of a production stepper. Potential uses for this imaging mode include: (a) Correlating the results obtained using actinic inspection with results obtained using other non-EUV defect inspection systems to verify that the non-EUV …
Date: March 5, 2003
Creator: Barty, A.; Chapman, H.; Sweeney, D.; Levesque, R.; Bokor, J.; Gullikson, E. et al.
Object Type: Report
System: The UNT Digital Library
Application of Reservoir Characterization and Advanced Technology to Improve Recovery and Economics in a Lower Quality Shallow Shelf San Andres Reservoir. Annual Report: August 3, 2000--August 2, 2001 (open access)

Application of Reservoir Characterization and Advanced Technology to Improve Recovery and Economics in a Lower Quality Shallow Shelf San Andres Reservoir. Annual Report: August 3, 2000--August 2, 2001

The OXY-operated Class 2 Project at West Welch is designed to demonstrate how the use of advanced technology can improve the economics of miscible CO{sub 2} injection projects in lower quality Shallow Shelf Carbonate reservoirs. The research and design phase (Budget Period 1) primarily involved advanced reservoir characterization. The current demonstration phase (Budget Period 2) is the implementation of the reservoir management plan for an optimum miscible CO{sub 2} flood design based on the reservoir characterization. Although Budget Period 1 for the Project officially ended 12/31/96, reservoir characterization and simulation work continued during the Budget Period 2. During the seventh annual reporting period (8/3/00-8/2/01) covered by this report, work continued on interpretation of the interwell seismic data to create porosity and permeability profiles which were distributed into the reservoir geostatistically. The initial interwell seismic CO{sub 2} monitor survey was conducted and the acquired data processed and interpretation started. Only limited well work and facility construction were conducted in the project area. The CO{sub 2} injection initiated in October 1997 was continued, although the operator had to modify the operating plan in response to low injection rates, well performance and changes in CO{sub 2} supply. CO{sub 2} injection was focused in …
Date: May 5, 2003
Creator: Beebe, Tom
Object Type: Report
System: The UNT Digital Library
LARGE AREA FILTERED ARC DEPOSITION OF CARBON AND BORON BASED HARD COATINGS (open access)

LARGE AREA FILTERED ARC DEPOSITION OF CARBON AND BORON BASED HARD COATINGS

This document is a final report covering work performed under Contract No. DE-FG02-99ER82911 from the Department of Energy under a SBIR Phase II Program. Wear resistant, hard coatings can play a vital role in many engineering applications. The primary goal of this project was to develop coatings containing boron and carbon with hardness greater than 30 GPa and evaluate these coatings for machining applications. UES has developed a number of carbon and boron containing coatings with hardness in the range of 34 to 65 GPa using a combination of filtered cathodic arc and magnetron sputtering. The boron containing coatings were based on TiB2, TiBN, and TiBCN, while the carbon containing coatings ere TiC+C and hydrogen free diamond-like-carbon. Machining tests were performed with single and multilayer coated tools. The turning and milling tests were run at TechSolve Inc., under a subcontract at Ohio State University. Significant increases in tool lives were realized in end milling of H-13 die steel (8X) and titanium alloy (80%) using the TiBN coating. A multilayer TiBN/TiN performed the best in end-milling of highly abrasive Al-Si alloys. A 40% increase in life over the TiAlN benchmark coating was found. Further evaluations of these coatings with commercialization partners …
Date: December 5, 2003
Creator: Bhattacharya, Rabi S.
Object Type: Report
System: The UNT Digital Library
Phenomenological aspects of heterotic orbifold models at one loop (open access)

Phenomenological aspects of heterotic orbifold models at one loop

We provide a detailed study of the phenomenology of orbifold compactifications of the heterotic string within the context of supergravity effective theories. Our investigation focuses on those models where the soft Lagrangian is dominated by loop contributions to the various soft supersymmetry breaking parameters. Such models typically predict non-universal soft masses and are thus significantly different from minimal supergravity and other universal models. We consider the pattern of masses that are governed by these soft terms and investigate the implications of certain indirect constraints on supersymmetric models, such as flavor-changing neutral currents, the anomalous magnetic moment of the muon and the density of thermal relic neutralinos. These string-motivated models show novel behavior that interpolates between the phenomenology of unified supergravity models and models dominated by the superconformal anomaly.
Date: August 5, 2003
Creator: Birkedal-Hansen, A.; Binetruy, P.; Mambrini, Y. & Nelson, B.
Object Type: Report
System: The UNT Digital Library
Recommendations for SZ/TSPA Model Uncertainty Analysis Concerning the Yucca Mountain Project (open access)

Recommendations for SZ/TSPA Model Uncertainty Analysis Concerning the Yucca Mountain Project

This report considers the problem of how best to evaluate the stability (i.e., sampling reliability) of Monte Carlo outputs obtained for two Yucca Mountain Project (YMP) modeling components, namely, outputs for the Saturated Zone (SZ) model, and for the Total System Performance Assessment (TSPA) model. One approach considered is the one that has been employed to date, namely, the application of Monte Carlo methods. Also considered in this context are potential improvements that might be obtained by the additional use of a Monte Carlo ''quitting rule'', such as that defined by Woo (1991), to select the number of Monte Carlo sample runs to perform. By the Monte Carlo approach, each output-value sample (realization) is calculated as a function of a sample-value vector of stochastic realizations, each of which in turn corresponds to a value of a corresponding distributed input variable. Abstractions from the SZ model and the Biosphere model are both used as input to the TSPA model. Sets of stochastic realizations required for SZ and TSPA abstractions ''expensive'' to generate, so the practical issue addressed by a ''quitting rule'' is how to determine what number of realizations is ''enough'' for the purpose of characterizing sampling error in the Monte …
Date: November 5, 2003
Creator: Bogen, K T
Object Type: Report
System: The UNT Digital Library
Speciation, Mobility and Fate of Actinides in the Groundwater at the Hanford Site (open access)

Speciation, Mobility and Fate of Actinides in the Groundwater at the Hanford Site

Plutonium and other actinides represent important contaminants in the groundwater and vadose zone at Hanford and other DOE sites. The distribution and migration of these actinides in groundwater must be understood so that these sites can be carefully monitored and effectively cleaned up, thereby minimizing risks to the public. The objective of this project was to obtain field data on the chemical and physical forms of plutonium in groundwater at the Hanford site. We focused on the 100-k and 100-n areas near the Columbia River, where prior reactor operations and waste storage was in close proximity to the river. In particular, a unique set of technical approaches were combined to look at the details of Pu speciation in groundwater, as thus its chemical affinity for soil surfaces and solubility in groundwater, as these impact directly the migration rates off site and possible mitigation possibilities one might undertake to control, or at least better monitor these releases.
Date: November 5, 2003
Creator: Buesseler, K. O.; Dai, M.; Repeta, D.; Wacker, J. F. & Kelley, J. M.
Object Type: Report
System: The UNT Digital Library
Planned Disposition of Material in the Savannah River Site High Level Waste System (open access)

Planned Disposition of Material in the Savannah River Site High Level Waste System

Since the early 1950's Savannah River Site (SRS) has received over 100 million gallons of waste into the F and H Tank Farms, commonly known as the High Level Waste System (HLW) system. This waste was neutralized, insoluble sludge settled, and supernate was evaporated to form saltcake such that as of January 2003 only 37 million gallons of waste is stored in F and H tank farm. This waste contains approximately 417 million curies of radioactivity and includes approximately 3 million gallons of sludge and 34 million gallons of salt waste. Additionally, 5 million curies have already been dispositioned by the Defense Waste Processing Facility (DWPF) into glass canisters. The Accelerated Clean-up Plan (ACP)1 will result in the acceleration of risk reduction by emptying HLW tanks sooner, shipping HLW glass canisters and Transuranic Waste (TRU) to their geologic repositories sooner and decommissioning the F Canyon facilities and other excess facilities sooner. This document discusses the planned disposition of the material currently stored in the HLW System.
Date: May 5, 2003
Creator: Carter, J.
Object Type: Report
System: The UNT Digital Library
Time-Reversal Analysis for Scatterer Characterization (open access)

Time-Reversal Analysis for Scatterer Characterization

Only the simplest monopole scattering behavior has usually been treated in previous time-reversal analyses. A new application of time-reversal processing of wave scattering data permits characterization of scatterers by analyzing the number and nature of the singular functions (or eigenfunctions) associated with individual scatterers when they have multiple contributions from monopole, dipole and/or quadrupole scattering terms. We discuss acoustic, elastic, and electromagnetic scattering problems for low frequencies (ka < 1, k being the wavenumber and a the radius of the scatterer). Specific examples for electromagnetic scattering from one of a number of small conducting spheres show that each sphere can have up to six distinct time-reversal eigenfunctions associated with it.
Date: November 5, 2003
Creator: Chambers, D H & Berryman, J G
Object Type: Article
System: The UNT Digital Library
Addressing Problems with Scene-Based Wave Front Sensing (open access)

Addressing Problems with Scene-Based Wave Front Sensing

Scene-Based Wave Front Sensing uses the correlation between successive subimages to determine phase aberrations which blur digital images. Adaptive Optics technology uses deformable mirrors to correct for these phase aberrations and make the images clearer. The correlation between temporal subimages gives tip-tilt information. If these images do not have identical image content, tip-tilt estimations may be incorrect. Motion detection is necessary to help avoid errors initiated by dynamic subimage content. In this document, I will discuss why edge detection fails as a motion detection method on low resolution images and how thresholding the normalized variance of individual pixels is successful for motion detection.
Date: August 5, 2003
Creator: Chan, C
Object Type: Report
System: The UNT Digital Library
smesh User's Guide (open access)

smesh User's Guide

''smesh'' is a general purpose, interactive, 2D unstructured mesh generator based on Overture. It supports three kinds of mesh generation techniques: structured patches with transfinite interpolation (TFI); unstructured triangles based on an advancing front technique; and a Cartesian cutcell/triangle hybrid method. Meshes are generated in a generalized ''multi-block'' manner where each ''block'', or region, can be one of the three mesh types. Geometry definitions can be created interactively by placing points and interpolating curves. Spacing information is provided by both the curve discretization (which can be stretched) and a user specified preferred grid spacing for a region. A mesh optimization procedure is available for the non-TFI regions for mesh quality improvement. Each mesh region is given an unique identifier and an optional string name. Meshes are exported to a modified ''ingrid'' format including mesh region identifiers and names. Facilities for command scripting and batch running are available.
Date: May 5, 2003
Creator: Chand, K. K.
Object Type: Report
System: The UNT Digital Library
An Overview of Neutrino Masses and Mixing in SO(10) Models. (open access)

An Overview of Neutrino Masses and Mixing in SO(10) Models.

We review in this talk various SUSY SO(10) models. Specifically, we discuss how small neutrino masses are generated in and generic predictions of different SO(10) models. A comparison of the predictions of these models for sin{sup 2} {theta}{sub 13}is given.
Date: June 5, 2003
Creator: Chen, M. C. & Mahanthappa, K. T.
Object Type: Article
System: The UNT Digital Library
The Electric and Optical Properties of Doped Small Molecular Organic Light-Emitting Devices (open access)

The Electric and Optical Properties of Doped Small Molecular Organic Light-Emitting Devices

Organic light-emitting devices (OLEDs) constitute a new and exciting emissive display technology. In general, the basic OLED structure consists of a stack of fluorescent organic layers sandwiched between a transparent conducting-anode and metallic cathode. When an appropriate bias is applied to the device, holes are injected from the anode and electrons from the cathode; some of the recombination events between the holes and electrons result in electroluminescence (EL). Until now, most of the efforts in developing OLEDs have focused on display applications, hence on devices within the visible range. However some organic devices have been developed for ultraviolet or infrared emission. Various aspects of the device physics of doped small molecular OLEDs were described and discussed. The doping layer thickness and concentration were varied systematically to study their effects on device performances, energy transfer, and turn-off dynamics. Low-energy-gap DCM2 guest molecules, in either {alpha}-NPD or DPVBi host layers, are optically efficient fluorophores but also generate deep carrier trap-sites. Since their traps reduce the carrier mobility, the current density decreases with increased doping concentration. At the same time, due to efficient energy transfer, the quantum efficiency of the devices is improved by light doping or thin doping thickness, in comparison with …
Date: August 5, 2003
Creator: Cheon, Kwang-Ohk
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Quantum dynamics via Planck-scale-stepped action-carrying 'Graph Paths' (open access)

Quantum dynamics via Planck-scale-stepped action-carrying 'Graph Paths'

A divergence-free, parameter-free, path-based discrete-time quantum dynamics is designed to not only enlarge the achievements of general relativity and the standard particle model, by approximations at spacetime scales far above Planck scale while far below Hubble scale, but to allow tackling of hitherto inaccessible questions. ''Path space'' is larger than and precursor to Hilbert-space basis. The wave-function-propagating paths are action-carrying structured graphs-cubic and quartic structured vertices connected by structured ''fermionic'' or ''bosonic'' ''particle'' and ''nonparticle'' arcs. A Planck-scale path step determines the gravitational constant while controlling all graph structure. The basis of the theory's (zero-rest-mass) elementary-particle Hilbert space (which includes neither gravitons nor scalar bosons) resides in particle arcs. Nonparticle arcs within a path are responsible for energy and rest mass.
Date: May 5, 2003
Creator: Chew, Geoffrey F.
Object Type: Report
System: The UNT Digital Library
Heterogeneous Shallow-Shelf Carbonate Buildups in the Paradox Basin, Utah and Colorado: Targets for Increased Oil Production and Reserves Using Horizontal Drilling Techniques (open access)

Heterogeneous Shallow-Shelf Carbonate Buildups in the Paradox Basin, Utah and Colorado: Targets for Increased Oil Production and Reserves Using Horizontal Drilling Techniques

The Paradox Basin of Utah, Colorado, Arizona, and New Mexico contains nearly 100 small oil fields producing from carbonate buildups within the Pennsylvanian (Desmoinesian) Paradox Formation. These fields typically have one to 10 wells with primary production ranging from 700,000 to 2,000,000 barrels (111,300-318,000 m{sup 3}) of oil per field and a 15 to 20 percent recovery rate. At least 200 million barrels (31.8 million m{sup 3}) of oil will not be recovered from these small fields because of inefficient recovery practices and undrained heterogeneous reservoirs. Several fields in southeastern Utah and southwestern Colorado are being evaluated as candidates for horizontal drilling and enhanced oil recovery from existing vertical wells based upon geological characterization and reservoir modeling case studies. Geological characterization on a local scale is focused on reservoir heterogeneity, quality, and lateral continuity, as well as possible reservoir compartmentalization, within these fields. This study utilizes representative cores, geophysical logs, and thin sections to characterize and grade each field's potential for drilling horizontal laterals from existing development wells. The results of these studies can be applied to similar fields elsewhere in the Paradox Basin and the Rocky Mountain region, the Michigan and Illinois Basins, and the Midcontinent region. This report …
Date: October 5, 2003
Creator: Chidsey, Thomas C.; McClure, Kevin & Morgan, Craig D.
Object Type: Report
System: The UNT Digital Library
Effects of Point Sources in Trench Disposal of Radioactive Waste (open access)

Effects of Point Sources in Trench Disposal of Radioactive Waste

At the U. S. Department of Energy Savannah River Site, disposal of radioactive wastes in shallow trenches was simulated with vadose zone models and decoupled aquifer models. The vadose zone models provided contaminant fluxes to the aquifer models.
Date: February 5, 2003
Creator: Collard, L.B.
Object Type: Article
System: The UNT Digital Library
All Fiber Technology for High-Energy Petawatt Front End Laser Systems (open access)

All Fiber Technology for High-Energy Petawatt Front End Laser Systems

We are developing an all fiber front end for the next generation high-energy petawatt (HEPW) laser at Lawrence Livermore National Laboratory (LLNL). The ultimate goal of the LLNL HEPW effort is to generate 5-kJ pulses capable of compression to 5ps at 1053nm, enabling advanced x-ray backlighters and possible demonstration of fast ignition. We discuss the front-end of the laser design from the fiber master oscillator, which generates the mode-locked 20nm bandwidth initial pulses through the 10mJ output of the large flattened mode (LFM) fiber amplifier. Development of an all fiber front end requires technological breakthroughs in the key areas of the master oscillator and fiber amplification. Chirped pulse amplification in optical fibers has been demonstrated to 1mJ. Further increase is limited by the onset of stimulated Raman scattering (SRS). We have recently demonstrated a new flattened mode fiber technology, which reduces peak power for a given energy and thus the onset of SRS. Controlled experiments with 1st generation fibers yielded 0.5mJ of energy while significantly increasing the point at which nonlinear optical effects degrade the amplified pulse. In this paper we will discuss our efforts to extend this work to greater than 20mJ using our large flattened mode fiber amplifier.
Date: September 5, 2003
Creator: Dawson, J W; Liao, Z M; Jovanovic, I; Wattellier, B; Beach, R; Payne, S A et al.
Object Type: Article
System: The UNT Digital Library
Chemistry and Materials Science, A Collection of Articles from Science & Technology Review (open access)

Chemistry and Materials Science, A Collection of Articles from Science & Technology Review

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Date: February 5, 2003
Creator: Diaz de la Rubia, T
Object Type: Report
System: The UNT Digital Library