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0.7-eV GaInAs Junction for a GaInP/GaAs/GaInAs(1-eV)/GaInAs(0.7-eV) Four-Junction Solar Cell: Preprint (open access)

0.7-eV GaInAs Junction for a GaInP/GaAs/GaInAs(1-eV)/GaInAs(0.7-eV) Four-Junction Solar Cell: Preprint

We discuss recent developments in III-V multijunction solar cells, focusing on adding a fourth junction to the Ga0.5In0.5P/GaAs/Ga0.75In0.25As inverted three-junction cell. This cell, grown inverted on GaAs so that the lattice-mismatched Ga0.75In0.25As third junction is the last one grown, has demonstrated 38% efficiency, and 40% is likely in the near future. To achieve still further gains, a lower-bandgap GaxIn1-xAs fourth junction could be added to the three-junction structure for a four-junction cell whose efficiency could exceed 45% under concentration. Here, we present the initial development of the GaxIn1-xAs fourth junction. Junctions of various bandgaps ranging from 0.88 to 0.73 eV were grown, in order to study the effect of the different amounts of lattice mismatch. At a bandgap of 0.88 eV, junctions were obtained with very encouraging {approx}80% quantum efficiency, 57% fill factor, and 0.36 eV open-circuit voltage. The device performance degrades with decreasing bandgap (i.e., increasing lattice mismatch). We model the four-junction device efficiency vs. fourth junction bandgap to show that an 0.7-eV fourth-junction bandgap, while optimal if it could be achieved in practice, is not necessary; an 0.9-eV bandgap would still permit significant gains in multijunction cell efficiency while being easier to achieve than the lower-bandgap junction.
Date: May 1, 2006
Creator: Friedman, D. J.; Geisz, J. F.; Norman, A. G.; Wanlass, M. W. & Kurtz, S. R.
System: The UNT Digital Library
0.25mm-Thick CCD Packaging for the Dark Energy Survey Camera Array (open access)

0.25mm-Thick CCD Packaging for the Dark Energy Survey Camera Array

Abstract: The Dark Energy Survey Camera focal plane array will consist of 62 2k x 4k CCDs with a pixel size of 15 microns and a silicon thickness of 250 microns for use at wavelengths between 400 and 1000 nm. Bare CCD die will be received from the Lawrence Berkeley National Laboratory (LBNL). At the Fermi National Accelerator Laboratory, the bare die will be packaged into a custom back-side-illuminated module design. Cold probe data from LBNL will be used to select the CCDs to be packaged. The module design utilizes an aluminum nitride readout board and spacer and an Invar foot. A module flatness of 3 microns over small (1 sqcm) areas and less than 10 microns over neighboring areas on a CCD are required for uniform images over the focal plane. A confocal chromatic inspection system is being developed to precisely measure flatness over a grid up to 300 x 300 mm. This system will be utilized to inspect not only room-temperature modules, but also cold individual modules and partial arrays through flat dewar windows.
Date: 2006-06~
Creator: Derylo, Greg; Diehl, H. Thomas & Estrada, Juan
System: The UNT Digital Library
1,2-HOIQO--A highly versatile 1,2-HOPO analog (open access)

1,2-HOIQO--A highly versatile 1,2-HOPO analog

A cyclic, bidentate hydroxamic acid binding unit based on an isoquinoline scaffold has been utilized for the synthesis of a hexadentate tripodal ligand based on the TREN backbone. This prototype for a new class of multidentate chelators forms mononuclear iron(III) complexes and one-dimensional coordination polymers with lanthanide(III) cations. The latter has been determined by single crystal X-ray analysis of the cerium species. The solid state structure in the monoclinic space group P2{sub 1}/c (C{sub 36}H{sub 34}CeN{sub 7}O{sub 11}, a = 12.341(2){angstrom}, b = 26.649(4){angstrom}, c = 10.621(2){angstrom}, {alpha} = {gamma} = 90{sup o}, {beta} = 96.753(3){sup o}, V = 3468.6(9) {angstrom}{sup 3}, Z = 4) exhibits a trigonal-dodecahedral environment around the cerium cation. The proof of concept for the versatility of the new scaffold has been shown by the modification of the crucial precursor 3-carboxyiso-coumarin through electrophilic aromatic substitutions to yield the corresponding chlorosulfonated and nitrated analogs.
Date: August 7, 2006
Creator: Seitz, Michael; Pluth, Michael D. & Raymond, Kenneth N.
System: The UNT Digital Library
3-D Hydrodynamic Modeling in a Geospatial Framework (open access)

3-D Hydrodynamic Modeling in a Geospatial Framework

3-D hydrodynamic models are used by the Savannah River National Laboratory (SRNL) to simulate the transport of thermal and radionuclide discharges in coastal estuary systems. Development of such models requires accurate bathymetry, coastline, and boundary condition data in conjunction with the ability to rapidly discretize model domains and interpolate the required geospatial data onto the domain. To facilitate rapid and accurate hydrodynamic model development, SRNL has developed a pre- and post-processor application in a geospatial framework to automate the creation of models using existing data. This automated capability allows development of very detailed models to maximize exploitation of available surface water radionuclide sample data and thermal imagery.
Date: August 24, 2006
Creator: Bollinger, J.; Alfred Garrett, A.; Larry Koffman, L. & David Hayes, D
System: The UNT Digital Library
4-D XRD for strain in many grains using triangulation (open access)

4-D XRD for strain in many grains using triangulation

Determination of the strains in a polycrystalline materialusing 4-D XRD reveals sub-grain and grain-to-grain behavior as a functionof stress. Here 4-D XRD involves an experimental procedure usingpolychromatic micro-beam X-radiation (micro-Laue) to characterizepolycrystalline materials in spatial location as well as with increasingstress. The in-situ tensile loading experiment measured strain in a modelaluminum-sapphire metal matrix composite using the Advanced Light Source,Beam-line 7.3.3. Micro-Laue resolves individual grains in thepolycrystalline matrix. Results obtained from a list of grains sorted bycrystallographic orientation depict the strain states within and amongindividual grains. Locating the grain positions in the planeperpendicular to the incident beam is trivial. However, determining theexact location of grains within a 3-D space is challenging. Determiningthe depth of the grains within the matrix (along the beam direction)involved a triangulation method tracing individual rays that producespots on the CCD back to the point of origin. Triangulation wasexperimentally implemented by simulating a 3-D detector capturingmultiple diffraction images while increasing the camera to sampledistance. Hence by observing the intersection of rays from multiple spotsbelonging to the corresponding grain, depth is calculated. Depthresolution is a function of the number of images collected, grain to beamsize ratio, and the pixel resolution of the CCD. The 4DXRD methodprovides grain morphologies, strain …
Date: December 31, 2006
Creator: Bale, Hrishikesh A.; Hanan, Jay C. & Tamura, Nobumichi
System: The UNT Digital Library
The 8 O'Clock Arc: A Serendipitous Discovery of a Strongly Lensed Lyman Break Galaxy in the SDSS DR4 Imaging Data (open access)

The 8 O'Clock Arc: A Serendipitous Discovery of a Strongly Lensed Lyman Break Galaxy in the SDSS DR4 Imaging Data

We report on the serendipitous discovery of the brightest Lyman Break Galaxy (LBG) currently known, a galaxy at z = 2.73 that is being strongly lensed by the z = 0.38 Luminous Red Galaxy (LRG) SDSS J002240.91+143110.4. The arc of this gravitational lens system, which we have dubbed the ''8 o'clock arc'' due to its time of discovery, was initially identified in the imaging data of the Sloan Digital Sky Survey Data Release 4 (SDSS DR4); followup observations on the Astrophysical Research Consortium (ARC) 3.5m telescope at Apache Point Observatory confirmed the lensing nature of this system and led to the identification of the arc's spectrum as that of an LBG. The arc has a spectrum and a redshift remarkably similar to those of the previous record-holder for brightest LBG (MS 1512-cB58, a.k.a ''cB58''), but, with an estimated total magnitude of (g,r,i) = (20.0,19.2,19.0) and surface brightness of ({mu}{sub g}, {mu}{sub r}, {mu}{sub i}) = (23.3, 22.5, 22.3) mag arcsec{sup -2}, the 8 o'clock arc is thrice as bright. The 8 o'clock arc, which consists of three lensed images of the LBG, is 162{sup o}(9.6'') long and has a length-to-width ratio of 6:1. A fourth image of the LBG--a counter-image--can …
Date: November 1, 2006
Creator: Allam, Sahar S.; Tucker, Douglas L.; Lin, Huan; Diehl, H. Thomas; Annis, James; Buckley-Geer, Elizabeth J. et al.
System: The UNT Digital Library
The 10,000 Year Plan (open access)

The 10,000 Year Plan

Pallavi Pharkya thinks a lot about the future. Pharkya, a Ph.D. candidate in materials science and engineering, works in the area of corrosion science, predicting how materials will perform over extended periods of time. Her particular focus is a nickel-chromium-molybdenum alloy called C-22, a highly corrosion-resistant metal. Pharkya's aim is to help determine whether containers made from C-22 can be used to store high-energy nuclear waste--for 10,000 years and longer. Pharkya's work is part of a plan by the U.S. Department of Energy to consolidate the country's nuclear waste in a single proposed repository. The proposed repository is in Yucca Mountain located in a remote Nevada desert. Currently about 70,000 metric tons of spent nuclear fuel and high-level radioactive waste are divided between approximately 100 sites around the country. The undertaking, Pharkya emphasizes, is massive. To study just the corrosion aspects of the packaging, Case is collaborating with eight other universities, five national labs and Atomic Energy of Canada Limited. Even with so many players, the study will likely take several years to complete. Heading the entire group is Joe Payer, a professor of materials science and engineering at Case and Pharkya's mentor. ''I came here to have the opportunity …
Date: February 10, 2006
Creator: Srisaro, L.
System: The UNT Digital Library
THE 10,000 YEAR PLAN (open access)

THE 10,000 YEAR PLAN

Pharkya, a Ph.D. candidate in materials science and engineering, works in the area of corrosion science, predicting how materials will perform over extended periods of time. Her particular focus is a nickel-chromium-molybdenum alloy called C-22, a highly corrosion-resistant metal. Pharkya's aim is to help determine whether containers made from C-22 can be used to store high-energy nuclear waste--for 10,000 years and longer. Pharkya's work is part of a plan by the U.S. Department of Energy to consolidate the country's nuclear waste in a single proposed repository. The proposed repository is in Yucca Mountain located in a remote Nevada desert. Currently about 70,000 metric tons of spent nuclear fuel and high-level radioactive waste are divided between approximately 100 sites around the country. The undertaking, Pharkya emphasizes, is massive. To study just the corrosion aspects of the packaging, Case is collaborating with eight other universities, five national labs and Atomic Energy of Canada Limited. Even with so many players, the study will likely take several years to complete. Heading the entire group is Joe Payer, a professor of materials science and engineering at Case and Pharkya's mentor. ''I came here to have the opportunity to work with Dr. Payer, an expert in …
Date: February 10, 2006
Creator: Srisuro, L.
System: The UNT Digital Library
A 15-T Pulsed Solenoid for a High-Power Target Experiment (open access)

A 15-T Pulsed Solenoid for a High-Power Target Experiment

The MERIT experiment, to be run at CERN in 2007, is a proof-of-principle test for a target system that converts a 4-MW proton beam into a high-intensity muon beam for either a neutrino factory complex or a muon collider. The target system is based on a free mercury jet that intercepts an intense proton beam inside a 15-T solenoidal magnetic field. Here, we describe the design and initial performance of the 15-T, liquid-nitrogen-precooled, copper solenoid magnet.
Date: June 26, 2006
Creator: Kirk, H. G.; Efthymiopoulos, I.; Fabich, A.; Haug, R.; Titus, P.; McDonald, K. T. et al.
System: The UNT Digital Library
20 - 50 GeV muon storage rings for a neutrino factory (open access)

20 - 50 GeV muon storage rings for a neutrino factory

Muon decay rings are under study as part of an International Scoping Study (ISS) for a future Neutrino Factory. Both isosceles triangle- and racetrack-shaped rings are being considered for a 20 GeV muon energy, but with upgrade potentials of 40 or 50 GeV. Both rings are designed with long straights to optimize directional muon decay. The neutrinos from muon decay pass to one or two distant detectors; the racetrack ring has one very long production straight aligned with one detector while the triangular ring has two straights which can be aligned with two detectors. Decay ring specifications and lattice studies are the primary topic of this paper. Injection, collimation, and the RF system are covered in a second contribution to these proceedings.
Date: July 1, 2006
Creator: Rees, G. H.; Johnstone, C. & Meot, F.
System: The UNT Digital Library
A 30 ps Timing Resolution for Single Photons with Multi-pixel Burle MCP-PMT (open access)

A 30 ps Timing Resolution for Single Photons with Multi-pixel Burle MCP-PMT

We have achieved {approx}30 psec single-photoelectron and {approx}12ps for multi-photoelectron timing resolution with a new 64 pixel Burle MCP-PMT with 10 micron microchannel holes. We have also demonstrated that this detector works in a magnetic field of 15kG, and achieved a single-photoelectron timing resolution of better than 60 psec. The study is relevant for a new focusing DIRC RICH detector for particle identification at future Colliders such as the super B-factory or ILC, and for future TOF techniques. This study shows that a highly pixilated MCP-PMT can deliver excellent timing resolution.
Date: July 5, 2006
Creator: Va'vra, J.; Benitez, J.; Coleman, J.; Leith, D. W. G. S.; Mazaheri, G.; Ratcliff, B. et al.
System: The UNT Digital Library
100,000-Mile Evaluation of Transit Buses Operated on Biodiesel Blends (B20) (open access)

100,000-Mile Evaluation of Transit Buses Operated on Biodiesel Blends (B20)

Evaluates the emissions, fuel economy, and maintenance of five 40-foot transit buses operated on B20 compared to four on petroleum diesel.
Date: November 1, 2006
Creator: Proc, K.; Barnitt, R.; Hayes, R. R.; Ratcliff, M.; McCormick, R. L.; Ha, L. et al.
System: The UNT Digital Library
201 MHz Cavity R&D for MUCOOL and MICE (open access)

201 MHz Cavity R&D for MUCOOL and MICE

We describe the design, fabrication, analysis and preliminary testing of the prototype 201 MHz copper cavity for a muon ionization cooling channel. Cavity applications include the Muon Ionization Cooling Experiment (MICE) as well as cooling channels for a neutrino factory or a muon collider. This cavity was developed by the US muon cooling (MUCOOL) collaboration and is being tested in the MUCOOL Test Area (MTA) at Fermilab. To achieve a high accelerating gradient, the cavity beam irises are terminated by a pair of curved, thin beryllium windows. Several fabrication methods developed for the cavity and windows are novel and offer significant cost savings as compared to conventional construction methods. The cavity's thermal and structural performances are simulated with an FEA model. Preliminary high power RF commissioning results will be presented.
Date: June 23, 2006
Creator: Li, Derun; Virostek, Steve; Zisman, Michael; Norem, Jim; Bross,Alan; Moretti, Alfred et al.
System: The UNT Digital Library
225-kW Dynamometer for Testing Small Wind Turbine Components (open access)

225-kW Dynamometer for Testing Small Wind Turbine Components

Poster for WindPower 2006 held June 4-7, 2006, in Pittsburgh, PA, describing the 225-kW dynamometer for testing small wind turbine components.
Date: June 1, 2006
Creator: Green, J.
System: The UNT Digital Library
225-kW Dynamometer for Testing Small Wind Turbine Components: Preprint (open access)

225-kW Dynamometer for Testing Small Wind Turbine Components: Preprint

This paper describes NREL's new 225-kW dynamometer facility that is suitable for testing a variety of components and subsystems for small wind turbines and discusses opportunities for industry partnerships with NREL for use of the facility.
Date: June 1, 2006
Creator: Green, J.
System: The UNT Digital Library
The 300 Kpc Long X-Ray Jet in PKS 1127-145, Z=1.18 Quasar: Constraining X-Ray Emission Models (open access)

The 300 Kpc Long X-Ray Jet in PKS 1127-145, Z=1.18 Quasar: Constraining X-Ray Emission Models

We present a {approx} 100 ksec Chandra X-ray observation and new VLA radio data of the large scale, 300 kpc long X-ray jet in PKS 1127-145, a radio loud quasar at redshift z=1.18. With this deep X-ray observation we now clearly discern the complex X-ray jet morphology and see substructure within the knots. The X-ray and radio jet intensity profiles are seen to be strikingly different with the radio emission peaking strongly at the two outer knots while the X-ray emission is strongest in the inner jet region. The jet X-ray surface brightness gradually decreases by an order of magnitude going out from the core. The new X-ray data contain sufficient counts to do spectral analysis of the key jet features. The X-ray energy index of the inner jet is relatively flat with {alpha}{sub x} = 0.66 {+-} 0.15 and steep in the outer jet with {alpha}{sub x} = 1.0 {+-} 0.2. We discuss the constraints implied by the new data on the X-ray emission models and conclude that ''one-zone'' models fail and at least a two component model is needed to explain the jet's broad-band emission. We propose that the X-ray emission originates in the jet proper while the …
Date: November 20, 2006
Creator: Siemiginowska, Aneta; Stawarz, Lukasz; Cheung, C. C.; Harris, D. E.; Sikora, Marek; Aldcroft, Thomas L. et al.
System: The UNT Digital Library
13C-Tracer Experiments in DIII-D Preliminary to Thermal Oxidation Experiments to Understand Tritium Recovery in DIII-D, JET, C-Mod, and MAST (open access)

13C-Tracer Experiments in DIII-D Preliminary to Thermal Oxidation Experiments to Understand Tritium Recovery in DIII-D, JET, C-Mod, and MAST

Retention of tritium in carbon co-deposits is a serious concern for ITER. Developing a reliable in-situ removal method of the co-deposited tritium would allow the use of carbon plasma-facing components which have proven reliable in high heat flux conditions and compatible with high performance plasmas. Thermal oxidation is a potential solution, capable of reaching even hidden locations. It is necessary to establish the least severe conditions to achieve adequate tritium recovery, minimizing damage and reconditioning time. The first step in this multi-machine project is {sup 13}C-tracer experiments in DIII-D, JET, C-Mod and MAST. In DIII-D and JET, {sup 13}CH{sub 4} has been (and in C-Mod and MAST, will be) injected toroidally symmetrically, facilitating quantification and interpretation of the results. Tiles have been removed, analyzed for {sup 13}C content and will next be evaluated in a thermal oxidation test facility in Toronto with regard to the ability of different severities of oxidation exposure to remove the different types of (known and measured) {sup 13}C co-deposit. Removal of D/T from B on Mo tiles from C-Mod will also be tested. OEDGE interpretive code analysis of the {sup 13}C deposition patterns is used to generate the understanding needed to apply findings to ITER. …
Date: June 19, 2006
Creator: Stangeby, P.; Allen, S.; Bekris, N.; Brooks, N.; Christie, K.; Chrobak, C. et al.
System: The UNT Digital Library
16th Workshop on Crystalline Silicon Solar Cells and Modules: Materials and Processes; Program, Extended Abstracts, and Papers (open access)

16th Workshop on Crystalline Silicon Solar Cells and Modules: Materials and Processes; Program, Extended Abstracts, and Papers

The National Center for Photovoltaics sponsored the 16th Workshop on Crystalline Silicon Solar Cells and Modules: Materials and Processes held August 6-9, 2006 in Denver, Colorado. The workshop addressed the fundamental properties of PV-Si, new solar cell designs, and advanced solar cell processing techniques. It provided a forum for an informal exchange of technical and scientific information between international researchers in the photovoltaic and relevant non-photovoltaic fields. The Workshop Theme was: "Getting more (Watts) for Less ($i)". A combination of oral presentations by invited speakers, poster sessions, and discussion sessions reviewed recent advances in crystal growth, new cell structures, new processes and process characterization techniques, and cell fabrication approaches suitable for future manufacturing demands. The special sessions included: Feedstock Issues: Si Refining and Purification; Metal-impurity Engineering; Thin Film Si; and Diagnostic Techniques.
Date: August 1, 2006
Creator: Sopori, B. L.
System: The UNT Digital Library
17th International Conference on Arabidopsis Research (open access)

17th International Conference on Arabidopsis Research

The 17th International Conference on Arabidopsis Research was held at the University of Madison, Wisconsin from June 27- July 2, 2006. ICAR-2006 included approximately 625 scientists from across the world. The scientific program was of excellent quality featuring 73 talks, including 30 from invited speakers. There were also 6 community-organized workshops (facilitated by conference staff) featuring additional talks on topics including ‘Submitting data to long-term repositories,’ ‘TAIR introductory workshop,’ ‘Web services and demonstration,’ ‘Public engagement: broadening the impact of your research,’ ‘Systems biology approaches to analysis of metabolic and regulatory networks of Arabidopsis,’ and ‘Mechanotransduction in Arabidopsis.’ Approximately 440 posters were presented in general topic areas including, among others, Development, Modeling/Other Systems, Energy, Environment, and Genetic/Epigenetic mechanisms. Graduate students, postdoctoral researchers, junior faculty, and underrepresented minorities made up a significant portion of the oral presentations thereby promoting the training of young scientists and facilitating important career development opportunities for speakers. Several poster sessions provided an opportunity for younger participants to freely meet with more established scientists. The North American Arabidopsis Steering Committee (NAASC) continued its outreach effort and again sponsored two special luncheons to encourage personal and professional development of young scientists and also underrepresented minorities. The ‘Emerging Scientists Luncheon’ …
Date: July 1, 2006
Creator: Bender, Judith
System: The UNT Digital Library
An 18th Century Near-Death Experience: The Case of George de Benneville (open access)

An 18th Century Near-Death Experience: The Case of George de Benneville

Article discussing the near-death experience (NDE) of George de Benneville during the 18th century, regarding his autobiographical account of the religious vision he had during his experience. It also compares the account to other ancient and modern NDEs.
Date: Autumn 2006
Creator: Vincent, Ken R. & Morgan, John C.
System: The UNT Digital Library
2005 Applied and Environmental Microbiology Gordon Conference July 24-29, 2005 (open access)

2005 Applied and Environmental Microbiology Gordon Conference July 24-29, 2005

This report is about Applied and Environmental Microbiology on Gordon Conference
Date: April 14, 2006
Creator: Kenneth Nealson, Nancy Ryan Gray
System: The UNT Digital Library
2005 Cellulases and Cellulosomes Gordon Research Conferences (open access)

2005 Cellulases and Cellulosomes Gordon Research Conferences

This report is on Cellulases and Cellulosomes on Gordon Research Conferences.
Date: June 1, 2006
Creator: Gray, Nancy Ryan & Warren, Richard
System: The UNT Digital Library
2005 Chemical Reactions at Surfaces (open access)

2005 Chemical Reactions at Surfaces

The Gordon Research Conference (GRC) on 2005 Chemical Reactions at Surfaces was held at Ventura Beach Marriott, Ventura California from February 13, 2005 through February 18, 2005. The Conference was well-attended with 124 participants (attendees list attached). The attendees represented the spectrum of endeavor in this field coming from academia, industry, and government laboratories, both U.S. and foreign scientists, senior researchers, young investigators, and students. In designing the formal speakers program, emphasis was placed on current unpublished research and discussion of the future target areas in this field. There was a conscious effort to stimulate lively discussion about the key issues in the field today. Time for formal presentations was limited in the interest of group discussions. In order that more scientists could communicate their most recent results, poster presentation time was scheduled. Attached is a copy of the formal schedule and speaker program and the poster program. In addition to these formal interactions, 'free time' was scheduled to allow informal discussions. Such discussions are fostering new collaborations and joint efforts in the field.
Date: March 14, 2006
Creator: Friend, Cynthia M.
System: The UNT Digital Library
The 2005 National Conference of Black Physics Students (open access)

The 2005 National Conference of Black Physics Students

This proposal funded the 19th Annual National Conference of Black Physics Students. This conference provided physics students with the opportunity to interact with world-class researchers and the facilities at which they work. The conference supports the well established need for the US to foster a larger and stronger scientific workforce through the recruitment and retention of science and engineering students.
Date: September 26, 2006
Creator: Reid, David D.
System: The UNT Digital Library