Extreme Ultraviolet Laser-based Table-top Aerial Image Metrology of Lithographic Masks (open access)

Extreme Ultraviolet Laser-based Table-top Aerial Image Metrology of Lithographic Masks

We report the first at-wavelength line edge roughness measurements of patterned EUV lithography masks realized using a table-top aerial imaging system based on a table-top {lambda}=13.2 laser.
Date: February 10, 2010
Creator: Brizuela, F.; Carbajo, S.; Sakdinawat, A.; Wang, Y.; Alessi, D.; Martz, D. et al.
System: The UNT Digital Library
Ice Formation in Gas-Diffusion Layers (open access)

Ice Formation in Gas-Diffusion Layers

Under sub-freezing conditions, ice forms in the gas-diffusion layer (GDL) of a proton exchange membrane fuel cell (PEMFC) drastically reducing cell performance. Although a number of strategies exist to prevent ice formation, there is little fundamental understanding of the mechanisms of freezing within PEMFC components. Differential scanning calorimetry (DSC) is used to elucidate the effects of hydrophobicity (Teflon® loading) and water saturation on the rate of ice formation within three commercial GDLs. We find that as the Teflon® loading increases, the crystallization temperature decreases due to a change in internal ice/substrate contact angle, as well as the attainable level of water saturation. Classical nucleation theory predicts the correct trend in freezing temperature with Teflon® loading.
Date: July 10, 2010
Creator: Dursch, Thomas; Radke, Clayton J. & Weber, Adam Z.
System: The UNT Digital Library
Grid-based methods for diatomic quantum scattering problems III: Double photoionization of molecular hydrogen in prolate spheroidal coordinates (open access)

Grid-based methods for diatomic quantum scattering problems III: Double photoionization of molecular hydrogen in prolate spheroidal coordinates

Our previously developed finite-element/ discrete variable representation in prolate spheroidal coordinates is extended to two-electron systems with a study of double ionization of H$_2$ with fixed-nuclei. Particular attention is paid to the development of fast and accurate methods for treating the electron-electron interaction. The use of exterior complex scaling in the implementation offers a simple way of enforcing Coulomb boundary conditions for the electronic double continuum. While the angular distributions calculated in this study are found to be completely consistent with our earlier treatments that employed single-center expansions in spherical coordinates, we find that the magnitude of the integrated cross sections are sensitive to small changes in the initial-state wave function. The present formulation offers significant advantages with respect to convergence and efficiency and opens the way to calculations on more complicated diatomic targets.
Date: June 10, 2010
Creator: Tao, Liang; McCurdy, Bill & Rescigno, Tom
System: The UNT Digital Library
Magnetic frustration effects in uranium intermetallics (open access)

Magnetic frustration effects in uranium intermetallics

The effect of geometrical frustration on the development of the heavy-fermion state and quantum criticality is studied in UAuCu{sub 4}, UAuPt{sub 4}, UAu{sub 3}Ni{sub 2} samples through measurements of their magnetic susceptibility, heat capacity, and electrical resistivity. In addition, since lattice disorder can play a large role in defining magnetic properties in frustrated systems, extended X-ray absorption fine structure (EXAFS) data have also been obtained. The local structure results show a strong correlation with the magnetic properties in these samples.
Date: June 10, 2010
Creator: Jiang, Yu; Booth, C. H.; Tobash, P. H.; Gofryk, K.; Torrez, M. A.; Ronning, F. et al.
System: The UNT Digital Library
Topology-based Feature Definition and Analysis (open access)

Topology-based Feature Definition and Analysis

Defining high-level features, detecting them, tracking them and deriving quantities based on them is an integral aspect of modern data analysis and visualization. In combustion simulations, for example, burning regions, which are characterized by high fuel-consumption, are a possible feature of interest. Detecting these regions makes it possible to derive statistics about their size and track them over time. However, features of interest in scientific simulations are extremely varied, making it challenging to develop cross-domain feature definitions. Topology-based techniques offer an extremely flexible means for general feature definitions and have proven useful in a variety of scientific domains. This paper will provide a brief introduction into topological structures like the contour tree and Morse-Smale complex and show how to apply them to define features in different science domains such as combustion. The overall goal is to provide an overview of these powerful techniques and start a discussion how these techniques can aid in the analysis of astrophysical simulations.
Date: December 10, 2010
Creator: Weber, Gunther H.; Bremer, Peer-Timo; Gyulassy, Attila & Pascucci, Valerio
System: The UNT Digital Library
Progress in Simulating Coulomb Collisions in Particle Codes (open access)

Progress in Simulating Coulomb Collisions in Particle Codes

A method for simulating Coulomb collisions in plasma simulations is described, in which particle weights are changed, instead of particle velocities.
Date: December 10, 2010
Creator: Hinton, F. L.; Yoon, E. S. & Chang, C. S.
System: The UNT Digital Library
Speciation of Heptavalent Technetium in Sulfuric Acid: Structural and Spectroscopic Studies. (open access)

Speciation of Heptavalent Technetium in Sulfuric Acid: Structural and Spectroscopic Studies.

The speciation of Tc(VII) in 12 M sulfuric acid was studied by NMR, UV-visible and XAFS spectroscopy, experimental results were supported by DFT calculation and were in agreement with the formation of TcO{sub 3}OH(H{sub 2}O){sub 2}. In summary, the speciation of heptvalent technetium has been investigated in sulfuric acid. In 12 M H{sub 2}SO{sub 4}, a yellow solution is observed, and its {sup 99}Tc NMR spectrum is consistent with a heptavalent complex. The yellow solution was further characterized by EXAFS spectroscopy, and results are consistent with the formation of TcO{sub 3}(OH)(H{sub 2}O){sub 2}. No technetium heptoxide or sulfato- complexes were detected in these conditions. The molecular structure of TcO{sub 3}(OH)(H{sub 2}O){sub 2} has been optimized by DFT techniques, and the structural parameters are well in accordance with those found by XAFS spectroscopy. The experimental electronic spectra exhibit ligand-to-metal charge transfer transitions that have been assigned using TDDFT methods. Calculations demonstrate the theoretical electronic spectrum of TcO{sub 3}(OH)(H{sub 2}O){sub 2} to be in very good agreement with the experimental one. Recent experiments in 12 M H{sub 2}SO{sub 4} show the yellow solution to be very reactive in presence of reducing agents presumably forming low valent Tc species. Current spectroscopic works focus …
Date: June 10, 2010
Creator: Poineau, Frederic; Weck, Philippe F.; German, Konstantin; Maruk, Alesya; Kirakosyan, Gayane; Lukens, Wayne et al.
System: The UNT Digital Library
SOLUBILITY OF URANIUM AND PLUTONIUM IN ALKALINE SAVANNAH RIVER SITE HIGH LEVEL WASTE SOLUTIONS (open access)

SOLUBILITY OF URANIUM AND PLUTONIUM IN ALKALINE SAVANNAH RIVER SITE HIGH LEVEL WASTE SOLUTIONS

Five actual Savannah River Site tank waste samples and three chemically-modified samples were tested to determine solubility limits for uranium and plutonium over a one year time period. Observed final uranium concentrations ranged from 7 mg U/L to 4.5 g U/L. Final plutonium concentrations ranged from 4 {micro}g Pu/L to 12 mg Pu/L. Actinide carbonate complexation is believed to result in the dramatic solubility increases observed for one sample over long time periods. Clarkeite, NaUO{sub 2}(O)OH {center_dot} H{sub 2}O, was found to be the dominant uranium solid phase in equilibrium with the waste supernate in most cases.
Date: March 10, 2010
Creator: King, W.; Hobbs, D.; Wilmarth, B. & Edwards, T.
System: The UNT Digital Library
EM-31 ALTERNATIVE AND ENHANCED CHEMICAL CLEANING PROGRAM FOR SLUDGE HEEL REMOVAL - 11220 (open access)

EM-31 ALTERNATIVE AND ENHANCED CHEMICAL CLEANING PROGRAM FOR SLUDGE HEEL REMOVAL - 11220

Mixtures of oxalic acid with nitric acid have been shown to be superior to oxalic acid alone for the dissolution of iron-rich High Level Waste sludge heels. Optimized conditions resulting in minimal oxalate usage and stoichiometric iron dissolution (based on added oxalate ion) have been determined for hematite (a primary sludge iron phase) in oxalic/nitric acid mixtures. The acid mixtures performed better than expected based on the solubility of hematite in the individual acids through a synergistic effect in which the preferred 1:1 Fe:oxalate complex is formed. This allows for the minimization of oxalate additions to the waste stream. Carbon steel corrosion rates were measured in oxalic/nitric acid mixtures to evaluate the impacts of chemical cleaning with these solutions on waste tank integrity. Manageable corrosion rates were observed in the concentration ranges of interest for an acid contact timescale of 1 month. Kinetics tests involving hematite and gibbsite (a primary sludge aluminum phase) have confirmed that {ge}90% solids dissolution occurs within 3 weeks. Based on these results, the chemical cleaning conditions recommended to promote minimal oxalate usage and manageable corrosion include: 0.5 wt. % oxalic acid/0.175 M nitric acid mixture, 50 C, 2-3 week contact time with agitation.
Date: December 10, 2010
Creator: King, W.; Hay, M.; Wiersma, B. & Pennebaker, F.
System: The UNT Digital Library
A Programmable Beam Shaping System for Tailoring the Profile of High Fluence Laser Beams (open access)

A Programmable Beam Shaping System for Tailoring the Profile of High Fluence Laser Beams

Customized spatial light modulators have been designed and fabricated for use as precision beam shaping devices in fusion class laser systems. By inserting this device in a low-fluence relay plane upstream of the amplifier chain, 'blocker' obscurations can be programmed into the beam profile to shadow small isolated flaws on downstream optical components that might otherwise limit the system operating energy. In this two stage system, 1920 x 1080 bitmap images are first imprinted on incoherent, 470 nm address beams via pixilated liquid crystal on silicon (LCoS) modulators. To realize defined masking functions with smooth apodized shapes and no pixelization artifacts, address beam images are projected onto custom fabricated optically-addressable light valves. Each valve consists of a large, single pixel liquid cell in series with a photoconductive Bismuth silicon Oxide (BSO) crystal. The BSO crystal enables bright and dark regions of the address image to locally control the voltage supplied to the liquid crystal layer which in turn modulates the amplitude of the coherent beams at 1053 nm. Valves as large as 24 mm x 36 mm have been fabricated with low wavefront distortion (<0.5 waves) and antireflection coatings for high transmission (>90%) and etalon suppression to avoid spectral and …
Date: November 10, 2010
Creator: Heebner, J.; Borden, M.; Miller, P.; Stolz, C.; Suratwala, T.; Wegner, P. et al.
System: The UNT Digital Library
The interplay between magnetism, structure, and strong electron-phonon coupling in binary FeAs under pressure (open access)

The interplay between magnetism, structure, and strong electron-phonon coupling in binary FeAs under pressure

Unlike the ferropnictide superconductors, which crystallize in a tetragonal crystal structure, binary FeAs forms in an orthorhombic crystal structure, where the local atomic environment resembles a highly distorted variant of the FeAs{sub 4} tetrahedral building block of the ferropnictide superconductors. However, like the parent compounds of the ferropnictide superconductors, FeAs undergoes magnetic ordering at low temperatures, with no evidence favoring a superconducting ground state at ambient pressure. We employ pressure-dependent electrical transport and x-ray diffraction measurements using diamond anvil cells to characterize the magnetic state and the structure as a function of pressure. While the structure persists up to 25 GPa, compressing continuously with pressure, magnetotransport measurements suggests that the magnetic state is destroyed near 11 GPa. The magnetic transition temperature is found to be remarkably robust under pressure, and transport measurements suggest that a dynamical structural instability coupled to the Fermi surface via a strong electron-phonon interaction may play an important role in enabling magnetism in FeAs.
Date: November 10, 2010
Creator: Jeffries, J R; Butch, N P; Cynn, H; Saha, S R; Kirshenbaum, K; Weir, S T et al.
System: The UNT Digital Library
Exploration of Resource and Transmission Expansion Decisions in the Western Renewable Energy Zone Initiative (open access)

Exploration of Resource and Transmission Expansion Decisions in the Western Renewable Energy Zone Initiative

The Western Renewable Energy Zone (WREZ) initiative brings together a diverse set of voices to develop data, tools, and a unique forum for coordinating transmission expansion in the Western Interconnection. In this paper we use a new tool developed in the WREZ initiative to evaluate possible renewable resource selection and transmission expansion decisions. We evaluate these decisions under a number of alternative future scenarios centered on meeting 33percent of the annual load in the Western Interconnection with new renewable resources located within WREZ-identified resource hubs. Our analysis finds that wind energy is the largest source of renewable energy procured to meet the 33percent RE target across nearly all scenarios analyzed (38-65percent). Solar energy is almost always the second largest source (14-41percent). We find several load zones where wind energy is the least cost resource under a wide range of sensitivity scenarios. Load zones in the Southwest, on the other hand, are found to switch between wind and solar, and therefore to vary transmission expansion decisions, depending on uncertainties and policies that affect the relative economics of each renewable option. Further, we find that even with total transmission expenditures of $17-34 billion these costs still represent just 10-19percent of the total …
Date: June 10, 2010
Creator: Mills, Andrew D.; Phadke, Amol A. & Wiser, Ryan H.
System: The UNT Digital Library
International Conference on the Cell and Molecular Biology of Chlamydomonas (open access)

International Conference on the Cell and Molecular Biology of Chlamydomonas

The 2010 Conference on the Cell and Molecular Biology of Chlamydomonas was held June 6-10 near Boston, MA, and attracted a record 273 participants, 146 from US labs, 10 from Canada, and the remainder from 18 other countries. The single-celled algal protist Chlamydomonas is a key research organism for many investigators, including those who study photosynthesis, cell motility, adaptation to environmental stresses, the evolution of multicellularity, and the production of biofuels. Chlamydomonas researchers gather every two years at a research conference to exchange methods, develop collaborative efforts, disseminate recent findings, and plan large-scale studies to improve the usefulness of this unique research organism. This conference provides the only opportunity for Chlamydomonas scientists who work on different research problems to meet face to face, and greatly speeds progress in their respective fields. An important function of these Chlamydomonas conferences is to promote and showcase the work of younger scientists, and to attract new investigators into the Chlamydomonas community. DOE award SC0004085 was used to offset the travel and registration costs for 18 young investigators, 9 of whom were women, including one African American. Most of these scientists would not have been able to attend the conference without DOE support. A total …
Date: June 10, 2010
Creator: Miller, Stephen
System: The UNT Digital Library
Robust Algorithm for Computing Statistical Stark Broadening of Spectral Lines (open access)

Robust Algorithm for Computing Statistical Stark Broadening of Spectral Lines

A method previously developed to solve large-scale linear systems is applied to statistical Stark broadened line shape calculations. The method is formally exact, numerically stable, and allows optimization of the integration over the quasi-static field to assure numerical accuracy. Furthermore, the method does not increase the computational effort and often can decrease it compared to the conventional approach.
Date: February 10, 2010
Creator: Iglesias, C A & Sonnad, V
System: The UNT Digital Library
Type Ia Supernova Intrinsic Magnitude Dispersion and the Fitting of Cosmological Parameters (open access)

Type Ia Supernova Intrinsic Magnitude Dispersion and the Fitting of Cosmological Parameters

I present an analysis for fitting cosmological parameters from a Hubble Diagram of a standard candle with unknown intrinsic magnitude dispersion. The dispersion is determined from the data themselves, simultaneously with the cosmological parameters. This contrasts with the strategies used to date. The advantages of the presented analysis are that it is done in a single fit (it is not iterative), it provides a statistically founded and unbiased estimate of the intrinsic dispersion, and its cosmological-parameter uncertainties account for the intrinsic dispersion uncertainty. Applied to Type Ia supernovae, my strategy provides a statistical measure to test for sub-types and assess the significance of any magnitude corrections applied to the calibrated candle. Parameter bias and differences between likelihood distributions produced by the presented and currently-used fitters are negligibly small for existing and projected supernova data sets.
Date: December 10, 2010
Creator: Kim, Alex G
System: The UNT Digital Library
The CGC and the Glasma: Two Lectures at the Yukawa Institute (open access)

The CGC and the Glasma: Two Lectures at the Yukawa Institute

These lectures present the theory of the Color Glass Condensate (CGC) and the Glasma in an elementary and intuitive manner. This matter controls the high energy limit of QCD. The CGC is the universal limit for the components of a hadron wavefunction important for high energy scattering processes. It is a highly coherent, extremely high energy density ensemble of gluon states. The Glasma is matter produced in the collision of CGCs of two hadrons. It has properties much different from those of the CGC, and is produced in a very short time after the collision. It eventually evolves from the the Color Glass Condensate initial conditions into a Quark Gluon Plasma. We can visualize the collision of two high energy hadrons as shown in Fig. 1. Before the collision, two hadrons appear as Lorentz contracted sheets approaching one another at near light speed. These we will later describe as two sheets of Colored Glass. In a very short time, the sheets of Color Glass interpenetrate one another. This we think of as the initial singularity for the collision. This is of course not a real singularity for finite collision energy, but we will see it becomes one in the limit …
Date: August 10, 2010
Creator: McLerran, L.
System: The UNT Digital Library
The response of the HMX-based material PBXN-9 to thermal insults: thermal decomposition kinetics and morphological changes (open access)

The response of the HMX-based material PBXN-9 to thermal insults: thermal decomposition kinetics and morphological changes

PBXN-9, an HMX-formulation, is thermally damaged and thermally decomposed in order to determine the morphological changes and decomposition kinetics that occur in the material after mild to moderate heating. The material and its constituents were decomposed using standard thermal analysis techniques (DSC and TGA) and the decomposition kinetics are reported using different kinetic models. Pressed parts and prill were thermally damaged, i.e. heated to temperatures that resulted in material changes but did not result in significant decomposition or explosion, and analyzed. In general, the thermally damaged samples showed a significant increase in porosity and decrease in density and a small amount of weight loss. These PBXN-9 samples appear to sustain more thermal damage than similar HMX-Viton A formulations and the most likely reasons are the decomposition/evaporation of a volatile plasticizer and a polymorphic transition of the HMX from {beta} to {delta} phase.
Date: December 10, 2010
Creator: Glascoe, E. A.; Hsu, P. C.; Springer, H. K.; DeHaven, M. R.; Tan, N. & Turner, H. C.
System: The UNT Digital Library
Room-temperature scintillation properties of cerium-doped REOX (RE=Y, La, Gd, and Lu; X=F, Cl, Br, and I) (open access)

Room-temperature scintillation properties of cerium-doped REOX (RE=Y, La, Gd, and Lu; X=F, Cl, Br, and I)

The scintillation properties of cerium-doped oxyhalides following the general formula REOX (RE=Y, La, Gd, and Lu; X=F, Cl, Br, and I) are reported. These materials were synthesized under dry conditions as microcrystalline powders from conventional solid state reactions. The room temperature X-ray excited emission and scintillation decay curves were measured and analyzed for each material. Additionally, the hygroscopic nature of the oxychlorides and oxybromides was compared to that of their corresponding rare earth halides. The yttrium, lanthanum, and gadolinium oxychlorides, and all of the oxybromides and oxyiodides are found to be activated by Ce{sup 3+}. GdOBr doped with 0.5% Ce{sup 3+} has the highest light output with a relative luminosity of about one-half that of LaBr{sub 3}: Ce{sup 3+}. It displays a single exponential decay of 30 ns.
Date: December 10, 2010
Creator: Eagleman, Yetta; Bourret-Courchesne, Edith & Derenzo, Stephen
System: The UNT Digital Library
COMPARISON OF EXTRACTION AND BEAM TRANSPORT SIMULATIONS WITH EMITTANCE MEASUREMENTS FROM THE ECR ION SOURCE VENUS (open access)

COMPARISON OF EXTRACTION AND BEAM TRANSPORT SIMULATIONS WITH EMITTANCE MEASUREMENTS FROM THE ECR ION SOURCE VENUS

None
Date: November 10, 2010
Creator: Winklehner, D.; Todd, D.; Benitez, J.; Strohmeier, M.; Grote, D. & Leitner, D.
System: The UNT Digital Library
Improving Reproducibility in Sputtered Beryllium and Graded Copper Doped Beryllium Capsules (open access)

Improving Reproducibility in Sputtered Beryllium and Graded Copper Doped Beryllium Capsules

None
Date: February 10, 2010
Creator: Youngblood, K.; Hayes, J.; Moreno, K.; Nikoo, A.; Xu, H.; Alford, C. et al.
System: The UNT Digital Library
Measure Of Quasi-Static Toughness And Fracture Parameters For Mock Explosive And Insensitive High Explosive LX-17 (open access)

Measure Of Quasi-Static Toughness And Fracture Parameters For Mock Explosive And Insensitive High Explosive LX-17

None
Date: March 10, 2010
Creator: Ferranti, L., Jr.; Gagliardi, F. J.; Cunningham, B. J. & Vandersall, K. S.
System: The UNT Digital Library
Modeling Blood Flow in a Tilted IVC Filter: Does Tilt Adversely Affect Hemodynamics? (open access)

Modeling Blood Flow in a Tilted IVC Filter: Does Tilt Adversely Affect Hemodynamics?

None
Date: February 10, 2010
Creator: Singer, M. A. & Wang, S. L.
System: The UNT Digital Library
Plasma transport in stochastic magnetic field caused by vacuum resonant magnetic perturbations at diverted tokamak edge (open access)

Plasma transport in stochastic magnetic field caused by vacuum resonant magnetic perturbations at diverted tokamak edge

None
Date: September 10, 2010
Creator: Park, G.; Chang, C. S.; Joseph, I. & Moyer, R. A.
System: The UNT Digital Library
Processing of spectrally-resolved x-ray images of ICF implosion cores recorded with MMI instruments (open access)

Processing of spectrally-resolved x-ray images of ICF implosion cores recorded with MMI instruments

None
Date: September 10, 2010
Creator: Nagayama, T; Mancini, R C; Florido, R; Tommasini, R; Koch, J; Delettez, J A et al.
System: The UNT Digital Library