100 LPW 800 Lm Warm White LED (open access)

100 LPW 800 Lm Warm White LED

An illumination grade warm white (WW) LED, having correlated color temperature (CCT) between 2800 K and 3500K and capable of producing 800 lm output at 100 lm/W, has been developed in this program. The high power WW LED is an ideal source for use as replacement for incandescent, and Halogen reflector and general purpose lamps of similar lumen value. Over the two year period, we have made following accomplishments: developed a high power warm white LED product and made over 50% improvements in light output and efficacy. The new high power WW LED product is a die on ceramic surface mountable LED package. It has four 1x1 mm{sup 2} InGaN pump dice flip chip attached to a ceramic submount in 2x2 array, covered by warm white phosphor ceramic platelets called Lumiramic™ and an overmolded silicone lens encapsulating the LED array. The performance goal was achieved through breakthroughs in following key areas: (1) High efficiency pump LED development through pump LED active region design and epi growth quality improvement (funded by internal programs). (2) Increase in injection efficiency (IE) represented by reduction in forward voltage (V{sub f}) through the improvement of the silver-based p-contact and a reduction in spreading resistance. The …
Date: October 31, 2010
Creator: Sun, Decai
Object Type: Report
System: The UNT Digital Library
Ion acceleration and cooling in gasless self-sputtering (open access)

Ion acceleration and cooling in gasless self-sputtering

Copper plasma with hyperthermal directed velocity (8.8 eV) but very low temperature (0.6 eV) has been obtained using self-sputtering far above the runaway threshold. Ion energy distribution functions (IEDFs) were simultaneously measured at 34 locations. The IEDFs show the tail of the Thompson distribution near the magnetron target. They transform to shifted Maxwellians with the ions being accelerated and cooled. We deduce the existence of a highly asymmetric, pressure-driven potential hump which acts as a controlling"watershed" between the ion return flux and the expanding plasma.
Date: October 31, 2010
Creator: Horwat, David & Anders, Andre
Object Type: Article
System: The UNT Digital Library
Isotopic Tracking of Hanford 300 Area Derived Uranium in the Columbia River (open access)

Isotopic Tracking of Hanford 300 Area Derived Uranium in the Columbia River

Our objectives in this study are to quantify the discharge rate of uranium (U) to the Columbia River from the Hanford Site's 300 Area, and to follow that U down river to constrain its fate. Uranium from the Hanford Site has variable isotopic composition due to nuclear industrial processes carried out at the site. This characteristic makes it possible to use high-precision isotopic measurements of U in environmental samples to identify even trace levels of contaminant U, determine its sources, and estimate discharge rates. Our data on river water samples indicate that as much as 3.2 kg/day can enter the Columbia River from the 300 Area, which is only a small fraction of the total load of dissolved natural background U carried by the Columbia River. This very low-level of Hanford derived U can be discerned, despite dilution to < 1 percent of natural background U, 350 km downstream from the Hanford Site. These results indicate that isotopic methods can allow the amounts of U from the 300 Area of the Hanford Site entering the Columbia River to be measured accurately to ascertain whether they are an environmental concern, or are insignificant relative to natural uranium background in the Columbia …
Date: October 31, 2010
Creator: Christensen, John N.; Dresel, P. Evan; Conrad, Mark E.; Patton, Gregory W. & DePaolo, Donald J.
Object Type: Article
System: The UNT Digital Library
Low Probability Tail Event Analysis and Mitigation in the BPA Control Area (open access)

Low Probability Tail Event Analysis and Mitigation in the BPA Control Area

This report investigated the uncertainties with the operations of the power system and their contributions to tail events, especially under high penetration of wind. A Bayesian network model is established to quantify the impact of these uncertainties on system imbalance. The framework is presented for a decision support tool, which can help system operators better estimate the need for balancing reserves and prepare for tail events.
Date: October 31, 2010
Creator: Lu, Shuai; Brothers, Alan J.; McKinstry, Craig A.; Jin, Shuangshuang & Makarov, Yuri V.
Object Type: Report
System: The UNT Digital Library
Macroalgae for CO{sub 2} Capture and Renewable Energy - A Pilot Project (open access)

Macroalgae for CO{sub 2} Capture and Renewable Energy - A Pilot Project

The objective of this project was to demonstrate, at a pilot scale, the beneficial use of carbon dioxide (CO{sub 2}) through a technology designed to capture CO2 from fossil-fuel fired power plant stack gas, generating macroalgae and converting the macroalgae at high efficiency to renewable methane that can be utilized in the power plant or introduced into a natural gas pipeline. The proposed pilot plant would demonstrate the cost-effectiveness and CO{sub 2}/ NO{sub x} flue-gas removal efficiency of an innovative “algal scrubber” technology where seaweeds are grown out of water on specially-designed supporting structures contained within greenhouses where the plants are constantly bathed by recycled nutrient sprays enriched by flue gas constituents. The work described in this document addresses Phase 1 of the project only. The scope of work for Phase 1 includes the completion of a preliminary design package; the collection of additional experimental data to support the preliminary and detailed design for a pilot scale utilization of CO{sub 2} to cultivate macroalage and to process that algae to produce methane; and a technological and economic analysis to evaluate the potential of the system. Selection criteria for macroalgae that could survive the elevated temperatures and potential periodic desiccation of …
Date: October 31, 2010
Creator: Wiley, Kristine
Object Type: Report
System: The UNT Digital Library
Micro-fluidic (Lab-on the- Chip) PCR Array Cartridge for Biological Screening in a Hand Held Device: FInal Report for CRADA no 264. PNNL-T2-258-RU with CombiMatrix Corp (open access)

Micro-fluidic (Lab-on the- Chip) PCR Array Cartridge for Biological Screening in a Hand Held Device: FInal Report for CRADA no 264. PNNL-T2-258-RU with CombiMatrix Corp

The worldwide emergence of both new and old diseases resulting from human expansion and also human and materials mobility has and will continue to place stress on both medical and clinical diagnostics. The classical approach to bioagents detection involves the use of differential metabolic assays to determine species type in the case of most bacteria, or the use of cell culture and electron microscopy to diagnose viruses and some bacteria that are intracellular parasites. The long-term goal in bioagent detection is to develop a hand-held instrument featuring disposable cartridges which contain all the necessary reagents, reaction chambers, waste chambers, and micro-fluidics to extract, concentrate, amplify, and analyze nucleic acids. This GIPP project began development of a sensory platform using nucleic-acid based probes. Although research was not completed, initial findings indicated that an advanced sensing device could theoretically be built on a DNA/RNA-based technology platform.
Date: October 31, 2010
Creator: Rainina, Evguenia I.
Object Type: Report
System: The UNT Digital Library
QuickSim Analysis Report (open access)

QuickSim Analysis Report

In software tools such as COMcheck, use of the EnergyPlus simulation engine for performance-based code compliance raises a concern about simulation runtime which impacts the dynamic feedback of compliance results to the user. EnergyPlus annual simulations for proposed and code base line building models, and the mechanical equipment sizing runs together increase the annual simulation runtime beyond unacceptable duration, for example, to 5 minutes for a typical small commercial building. This report presents a study undertaken to compare the results of a shortened simulation time period, using 4 weeks of weather data to do a simulation of a full 52 weeks of data. Three representative building types and three climate zones were used for determining the validity of using shortened simulation run period. Further sensitivity analysis and run time comparisons were made to evaluate the robustness and run time savings of using this approach. The results of this analysis show that the shortened simulation run period provides compliance index calculations within 1% of that predicted using annual simulation results, and typically saves about 75% of simulation runtime.
Date: October 31, 2010
Creator: Athalye, Rahul A.; Gowri, Krishnan; Glazer, Jason & Schultz, Robert W.
Object Type: Report
System: The UNT Digital Library
Dense Metal Plasma in a Solenoid for Ion Beam Neutralization (open access)

Dense Metal Plasma in a Solenoid for Ion Beam Neutralization

Space-charge neutralization is required to compress and focus a pulsed, high-current ion beam on a target for warm dense matter physics or heavy ion fusion experiments. We described approaches to produce dense plasma in and near the final focusing solenoid through which the ion beam travels, thereby providing an opportunity for the beam to acquire the necessary space-charge compensating electrons. Among the options are plasma injection from pulsed vacuum arc sources located outside the solenoid, and using a high current (> 4 kA) pulsed vacuum arc plasma from a ring cathode near the edge of the solenoid. The plasma distribution is characterized by photographic means, by an array of movable Langmuir probes, by a small single probe, and by evaluating Stark broadening of the Balmer H beta spectral line. In the main approach described here, the plasma is produced at several cathode spots distributed azimuthally on the ring cathode. It is shown that the plasma is essentially hollow, as determined by the structure of the magnetic field, though the plasma density exceeds 1014 cm-3 in practically all zones of the solenoid volume if the ring electrode is placed a few centimeters off the center of the solenoid. The plasma is …
Date: October 30, 2010
Creator: Anders, Andre; Kauffeldt, Marina; Oks, Efim M. & Roy, Prabir K.
Object Type: Article
System: The UNT Digital Library
Fiber-Optic Defect and Damage Locator System for Wind Turbine Blades (open access)

Fiber-Optic Defect and Damage Locator System for Wind Turbine Blades

IFOS in collaboration with Auburn University demonstrated the feasibility of a Fiber Bragg Grating (FBG) integrated sensor system capable of providing real time in-situ defect detection, localization and quantification of damage. In addition, the system is capable of validating wind turbine blade structural models, using recent advances in non-contact, non-destructive dynamic testing of composite structures. This new generation method makes it possible to analyze wind turbine blades not only non-destructively, but also without physically contacting or implanting intrusive electrical elements and transducers into the structure. Phase I successfully demonstrated the feasibility of the technology with the construction of a 1.5 kHz sensor interrogator and preliminary instrumentation and testing of both composite material coupons and a wind turbine blade.
Date: October 30, 2010
Creator: Sotoudeh, Dr. Vahid; Black, Dr. Richard J.; Moslehi, Dr. Behzad & Plavsic, Mr. Aleks
Object Type: Report
System: The UNT Digital Library
21st Century Locomotive Technology: Technical Status Report 30 (open access)

21st Century Locomotive Technology: Technical Status Report 30

Analysis of specific missions shows that combining Trip Optimization techniques with Hybrid Energy Storage increases energy savings.
Date: October 29, 2010
Creator: Salasoo, Lembit
Object Type: Report
System: The UNT Digital Library
Estimation of brassylic acid by gas chromatography-mass spectrometry (open access)

Estimation of brassylic acid by gas chromatography-mass spectrometry

The main focus of this work is to estimate Brassylic Acid (BA) using gas chromatography-mass spectrometry (GC-MS). BA is a product obtained from the oxidative cleavage of Erucic Acid (EA). BA has various applications for making nylons and high performance polymers. BA is a 13 carbon compound with two carboxylic acid functional groups at the terminal end. BA has a long hydrocarbon chain that makes the molecule less sensitive to some of the characterization techniques. Although BA can be characterized by NMR, both the starting material (EA) and products BA and nonanoic acid (NA) have peaks at similar {delta}, ppm values. Hence it becomes difficult for the quick estimation of BA during its synthesis.
Date: October 29, 2010
Creator: Mohammed J. Nasrullah, Erica N. Pfarr, Pooja Thapliyal, Nicholas S. Dusek, Kristofer L. Schiele, Christy Gallagher-Lein, and James A. Bahr
Object Type: Article
System: The UNT Digital Library
Final Report for Grant "Direct Writing via Novel Aromatic Ladder Polymer Precursors" (open access)

Final Report for Grant "Direct Writing via Novel Aromatic Ladder Polymer Precursors"

This report describes activities and findings under the above entitled grant. These pertain to the development of new synthetic routes to novel precursor polymers and oligomers that are applicable for conversion from electrical insulators to electrical conductors under the application of light (e.g. direct photolithographic writing)
Date: October 29, 2010
Creator: Gorman, C. B.
Object Type: Report
System: The UNT Digital Library
INDEPENDENT TECHNICAL REVIEW OF THE C-400 INTERIM REMEDIAL PROJECT PHASE I RESULTS, PADUCAH, KENTUCKY (open access)

INDEPENDENT TECHNICAL REVIEW OF THE C-400 INTERIM REMEDIAL PROJECT PHASE I RESULTS, PADUCAH, KENTUCKY

The groundwater and soil in the vicinity of the C-400 Building at the Paducah Gaseous Diffusion Plant (PGDP), is contaminated with substantial quantities of industrial solvents, primarily trichoroethene (TCE). This solvent 'source' is recognized as a significant challenge and an important remediation target in the overall environmental cleanup strategy for PGDP. Thus, the cleanup of the C-400 TCE Source is a principal focus for the Department of Energy (DOE) and its contractors, and for PGDP regulators and stakeholders. Using a formal investigation, feasibility study and decision process, Electrical Resistance Heating (ERH) was selected for the treatment of the soil and groundwater in the vicinity of C-400. ERH was selected as an interim action to remove 'a significant portion of the contaminant mass of TCE at the C-400 Cleaning Building area through treatment' with the longer term goal of reducing 'the period the TCE concentration in groundwater remains above its Maximum Contaminant Level (MCL).' ERH is a thermal treatment that enhances the removal of TCE and related solvents from soil and groundwater. The heterogeneous conditions at PGDP, particularly the high permeability regional gravel aquifer (RGA), are challenging to ERH. Thus, a phased approach is being followed to implement this relatively expensive …
Date: October 29, 2010
Creator: Looney, B.; Rossabi, J.; Stewart,L. & Richards, W.
Object Type: Report
System: The UNT Digital Library
Oxidative cleavage of erucic acid for the synthesis of brassylic acid (open access)

Oxidative cleavage of erucic acid for the synthesis of brassylic acid

The main focus of this work is to synthesize Brassylic Acid (BA) using oxidative cleavage of Erucic Acid (EA). Crambe (Crambe abyssinica) is an industrial oilseed grown in North Dakota. Crambe has potential as an industrial fatty acid feedstock as a source of Erucic acid (EA). It has approximately 50-60 % of EA, a C{sub 22} monounsaturated fatty acid. Oxidative cleavage of unsaturated fatty acids derived from oilseeds produces long chain (9, 11, and 13 carbon atoms) dibasic and monobasic acids. These acids are known commercial feedstocks for the preparation of nylons, polyesters, waxes, surfactants, and perfumes. Other sources of EA are Rapeseed seed oil which 50-60 % of EA. Rapeseed is grown outside USA. The oxidative cleavage of EA was done using a high throughput parallel pressure reactor system. Kinetics of the reaction shows that BA yields reach a saturation at 12 hours. H{sub 2}WO{sub 4} was found to be the best catalyst for the oxidative cleavage of EA. High yields of BA were obtained at 80 C with bubbling of O{sub 2} or 10 bar of O{sub 2} for 12 hours.
Date: October 29, 2010
Creator: Nasrullah, Mohammed J.; Thapliyal, Pooja; Pfarr, Erica N.; Dusek, Nicholas S.; Schiele, Kristofer L. & Bahr, James A.
Object Type: Article
System: The UNT Digital Library
Post-Shot Radiation Environment Following Low-Yield Shots Inside the National Ignition Facility (open access)

Post-Shot Radiation Environment Following Low-Yield Shots Inside the National Ignition Facility

A detailed model of the Target Bay (TB) at the National Ignition Facility (NIF) has been developed to estimate the post-shot radiation environment inside the facility. The model includes large number of structures and diagnostic instruments present inside the TB. These structures and instruments are activated by the few nanosecond pulse of neutrons generated during a shot and the resultant gamma dose rates are estimated at various decay times following the shot. The results presented in this paper are based on a low-yield D-T shot of 10{sup 16} neutrons. General environment dose rates drop to below 3 mrem/h within three hours following a shot with higher dose rates observed at contact with some of the components. Dose rate maps of the different TB levels were generated to aid in estimating worker stay-out times following a shot before entry is permitted into the TB.
Date: October 29, 2010
Creator: Sitaraman, S.; Brereton, S.; Dauffy, L.; Hall, J.; Hansen, L.; Khater, H. et al.
Object Type: Article
System: The UNT Digital Library
Real time intelligent process control system for thin film solar cell manufacturing (open access)

Real time intelligent process control system for thin film solar cell manufacturing

This project addresses the problem of lower solar conversion efficiency and waste in the typical solar cell manufacturing process. The work from the proposed development will lead toward developing a system which should be able to increase solar panel conversion efficiency by an additional 12-15% resulting in lower cost panels, increased solar technology adoption, reduced carbon emissions and reduced dependency on foreign oil. All solar cell manufacturing processes today suffer from manufacturing inefficiencies that currently lead to lower product quality and lower conversion efficiency, increased product cost and greater material and energy consumption. This results in slower solar energy adoption and extends the time solar cells will reach grid parity with traditional energy sources. The thin film solar panel manufacturers struggle on a daily basis with the problem of thin film thickness non-uniformity and other parameters variances over the deposited substrates, which significantly degrade their manufacturing yield and quality. Optical monitoring of the thin films during the process of the film deposition is widely perceived as a necessary step towards resolving the non-uniformity and non-homogeneity problem. In order to enable the development of an optical control system for solar cell manufacturing, a new type of low cost optical sensor is …
Date: October 29, 2010
Creator: Atanasoff, George
Object Type: Report
System: The UNT Digital Library
Science and Technology Review December 2010 (open access)

Science and Technology Review December 2010

This month's issue has the following articles: (1) More Insight to Better Understand Climate Change - Commentary by Tomas Diaz de la Rubia; (2) Strengthening Our Understanding of Climate Change - Researchers at the Center for Accelerator Mass Spectrometry are working to better understand climate variation and sharpen the accuracy of predictive models; (3) Precision Diagnostics Tell All - The National Ignition Facility relies on sophisticated diagnostic instruments for measuring the key physical processes that occur in high-energy-density experiments; (4) Quick Detection of Pathogens by the Thousands - Livermore scientists have developed a device that can simultaneously identify thousands of viruses and bacteria within 24 hours; and (5) Carbon Dioxide into the Briny Deep - A proposed technique for burying carbon dioxide underground could help mitigate the effects of this greenhouse gas while producing freshwater.
Date: October 29, 2010
Creator: Blobaum, K M
Object Type: Report
System: The UNT Digital Library
Standing-wave excited soft x-ray photoemission microscopy: application to Co microdot magnetic arrays (open access)

Standing-wave excited soft x-ray photoemission microscopy: application to Co microdot magnetic arrays

We demonstrate the addition of depth resolution to the usual two-dimensional images in photoelectron emission microscopy (PEEM), with application to a square array of circular magnetic Co microdots. The method is based on excitation with soft x-ray standing-waves generated by Bragg reflection from a multilayer mirror substrate. Standing wave is moved vertically through sample simply by varying the photon energy around the Bragg condition. Depth-resolved PEEM images were obtained for all of the observed elements. Photoemission intensities as functions of photon energy were compared to x-ray optical calculations in order to quantitatively derive the depth-resolved film structure of the sample.
Date: October 29, 2010
Creator: Gray, Alexander; Kronast, Florian; Papp, Christian; Yang, See-Hun; Cramm, Stefan; Krug, Ingo P. et al.
Object Type: Article
System: The UNT Digital Library
DEVELOPMENT AND DEPLOYMENT OF VACUUM SALT DISTILLATION AT THE SAVANNAH RIVER SITE (open access)

DEVELOPMENT AND DEPLOYMENT OF VACUUM SALT DISTILLATION AT THE SAVANNAH RIVER SITE

The Savannah River Site has a mission to dissolve fissile materials and disposition them. The primary fissile material is plutonium dioxide (PuO{sub 2}). To support dissolution of these materials, the Savannah River National Laboratory (SRNL) designed and demonstrated a vacuum salt distillation (VSD) apparatus using both representative radioactive samples and non-radioactive simulant materials. Vacuum salt distillation, through the removal of chloride salts, increases the quantity of materials suitable for processing in the site's HB-Line Facility. Small-scale non-radioactive experiments at 900-950 C show that >99.8 wt % of the initial charge of chloride salt distilled from the sample boat with recovery of >99.8 wt % of the ceric oxide (CeO{sub 2}) - the surrogate for PuO{sub 2} - as a non-chloride bearing 'product'. Small-scale radioactive testing in a glovebox demonstrated the removal of sodium chloride (NaCl) and potassium chloride (KCl) from 13 PuO{sub 2} samples. Chloride concentrations were distilled from a starting concentration of 1.8-10.8 wt % to a final concentration <500 mg/kg chloride. Initial testing of a non-radioactive, full-scale production prototype is complete. A designed experiment evaluated the impact of distillation temperature, time at temperature, vacuum, product depth, and presence of a boat cover. Significant effort has been devoted to …
Date: October 28, 2010
Creator: Pierce, R.; Pak, D. & Edwards, T.
Object Type: Article
System: The UNT Digital Library
Electronic structure of fully epitaxial Co2TiSn thin films (open access)

Electronic structure of fully epitaxial Co2TiSn thin films

In this article we report on the properties of thin films of the full Heusler compound Co{sub 2}TiSn prepared by DC magnetron co-sputtering. Fully epitaxial, stoichiometric films were obtained by deposition on MgO (001) substrates at substrate temperatures above 600 C. The films are well ordered in the L2{sub 1} structure, and the Curie temperature exceeds slightly the bulk value. They show a significant, isotropic magnetoresistance and the resistivity becomes strongly anomalous in the paramagnetic state. The films are weakly ferrimagnetic, with nearly 1 {mu}{sub B} on the Co atoms, and a small antiparallel Ti moment, in agreement with theoretical expectations. From comparison of x-ray absorption spectra on the Co L{sub 3,2} edges, including circular and linear magnetic dichroism, with ab initio calculations of the x-ray absorption and circular dichroism spectra we infer that the electronic structure of Co{sub 2}TiSn has essentially non-localized character. Spectral features that have not been explained in detail before, are explained here in terms of the final state band structure.
Date: October 28, 2010
Creator: Meinert, Markus; Schmalhorst, Jan; Wulfmeier, Hendrik; Reiss, Gunter; Arenholz, Elke; Graf, Tanja et al.
Object Type: Article
System: The UNT Digital Library
Evolution of organic aerosol mass spectra upon heating: implications for OA phase and partitioning behavior (open access)

Evolution of organic aerosol mass spectra upon heating: implications for OA phase and partitioning behavior

Vacuum Ultraviolet (VUV) photoionization mass spectrometry has been used to measure the evolution of chemical composition for two distinct organic aerosol types as they are passed through a thermodenuder at different temperatures. The two organic aerosol types considered are primary lubricating oil (LO) aerosol and secondary aerosol from the alpha-pinene + O3 reaction (alphaP). The evolution of the VUV mass spectra for the two aerosol types with temperature are observed to differ dramatically. For LO particles, the spectra exhibit distinct changes with temperature in which the lower m/z peaks, corresponding to compounds with higher vapor pressures, disappear more rapidly than the high m/z peaks. In contrast, the alphaP aerosol spectrum is essentially unchanged by temperature even though the particles experience significant mass loss due to evaporation. The variations in the LO spectra are found to be quantitatively in agreement with expectations from absorptive partitioning theory whereas the alphaP spectra suggest that the evaporation of alphaP derived aerosol appears to not be governed by partitioning theory. We postulate that this difference arises from the alphaP particles existing as in a glassy state instead of having the expected liquid-like behavior. To reconcile these observations with decades of aerosol growth measurements, which indicate …
Date: October 28, 2010
Creator: Davis, UC; Cappa, Christopher D. & Wilson, Kevin R.
Object Type: Article
System: The UNT Digital Library
Improvement of Laser Damage Resistance and Diffraction Efficiency of Multilayer Dielectric Diffraction Gratings by HF-Etchback Linewidth Tailoring (open access)

Improvement of Laser Damage Resistance and Diffraction Efficiency of Multilayer Dielectric Diffraction Gratings by HF-Etchback Linewidth Tailoring

Multilayer dielectric (MLD) diffraction gratings for Petawatt-class laser systems possess unique laser damage characteristics. Details of the shape of the grating lines and the concentration of absorbing impurities on the surface of the grating structures both have strong effects on laser damage threshold. It is known that electric field enhancement in the solid material comprising the grating lines varies directly with the linewidth and inversely with the line height for equivalent diffraction efficiency. Here, they present an overview of laser damage characteristics of MLD gratings, and describe a process for post-processing ion-beam etched grating lines using very dilute buffered hydrofluoric acid solutions. This process acts simultaneously to reduce grating linewidth and remove surface contaminants, thereby improving laser damage thresholds through two pathways.
Date: October 28, 2010
Creator: Nguyen, H T; Larson, C C & Britten, J A
Object Type: Article
System: The UNT Digital Library
Simulation of Infrared Laser Heating of Silica Using Heat Conduction and Multifrequency Radiation Diffusion Equations Adapted for Homogeneous Refractive Lossy Media (open access)

Simulation of Infrared Laser Heating of Silica Using Heat Conduction and Multifrequency Radiation Diffusion Equations Adapted for Homogeneous Refractive Lossy Media

Localized, transient heating of materials using micro-scale, highly absorbing laser light has been used in many industries to anneal, melt and ablate material with high precision. Accurate modeling of the relative contributions of conductive, convective and radiative losses as a function of laser parameters is essential to optimizing micro-scale laser processing of materials. In bulk semi-transparent materials such as silicate glass melts, radiation transport is known to play a significantly larger role as the temperature increases. Conventionally, radiation is treated in the frequency-averaged diffusive limit (Rosseland approximation). However, the role and proper treatment of radiative processes under rapidly heated, high thermal gradient conditions, often created through laser-matter interactions, is at present not clear. Starting from the radiation transport equation for homogeneous, refractive lossy media, they derive the corresponding time-dependent multi-frequency diffusion equations. Zeroth and first moments of the transport equation couple the energy density, flux and pressure tensor. The system is closed by neglecting the temporal derivative of the flux and replacing the pressure tensor by its diagonal analogue. The radiation equations are coupled to a diffusion equation for the matter temperature. They are interested in modeling infrared laser heating of silica over sub-millimeter length scales, and at possibly rapid …
Date: October 28, 2010
Creator: Shestakov, A I; Matthews, M J; Vignes, R M & Stolken, J S
Object Type: Article
System: The UNT Digital Library
Study of the neutron damage on electronics at the National Ignition Facility (open access)

Study of the neutron damage on electronics at the National Ignition Facility

The NIF environment is very complex leading to a large and non trivial radiation background. A shield surrounding the electronics is required to lower the neutron background to less than 1e7 n/cm{sup 2}. Moving electronics to behind the 6 foot-thick target bay wall is the best shield.
Date: October 28, 2010
Creator: Dauffy, L S; Mcnaney, J M & Khater, H Y
Object Type: Article
System: The UNT Digital Library