Modified magnetic ground state in NiMn2O4 thin films (open access)

Modified magnetic ground state in NiMn2O4 thin films

We demonstrate the stabilization of a magnetic ground state in epitaxial NiMn2O4 (NMO) thin films not observed in their bulk counterpart. Bulk NMO exhibits a magnetic transition from a paramagnetic phase to a collinear ferrimagnetic moment configuration below 110 K and to a canted moment configuration below 70 K. By contrast, as-grown NMO films exhibit a single magnetic transition at 60 K and annealed films exhibit the magnetic behavior found in bulk. Cation inversion and epitaxial strain are ruled out as possible causes for the new magnetic ground state in the as-grown films. However, a decrease in the octahedral Mn{sup 4+}:Mn{sup 3+} concentration is observed and likely disrupts the double exchange that produces the magnetic state at intermediate temperatures. X-ray magnetic circular dichroism and bulk magnetometry indicate a canted ferrimagnetic state in all samples at low temperature. Together these results suggest that the collinear ferrimagnetic state observed in bulk NMO at intermediate temperatures is suppressed in the as grown NMO thin films due to a decrease in octahedral Mn{sup 4+} while the canted moment ferrimagnetic ordering is preserved below 60 K.
Date: August 3, 2010
Creator: Nelson-Cheeseman, B. B.; Chopdekar, R. V.; Toney, M. F.; Arenholz, E.; Suzuki, Y. & Iwata, J.M.
Object Type: Article
System: The UNT Digital Library
PROJECT-SPECIFIC TYPE A VERIFICATION FOR THE HIGH FLUX BEAM REACTOR UNDERGROUND UTILITIES REMOVAL PHASE 3 TRENCH 5, BROOKHAVEN NATIONAL LABORATORY UPTON, NEW YORK (open access)

PROJECT-SPECIFIC TYPE A VERIFICATION FOR THE HIGH FLUX BEAM REACTOR UNDERGROUND UTILITIES REMOVAL PHASE 3 TRENCH 5, BROOKHAVEN NATIONAL LABORATORY UPTON, NEW YORK

5098-SR-04-0 PROJECT-SPECIFIC TYPE A VERIFICATION FOR THE HIGH FLUX BEAM REACTOR UNDERGROUND UTILITIES REMOVAL PHASE 3 TRENCH 5, BROOKHAVEN NATIONAL LABORATORY
Date: November 3, 2010
Creator: Weaver, P. C.
Object Type: Report
System: The UNT Digital Library
Adjoint-Based Implicit Uncertainty Analysis for Figures of Merit in a Laser Inertial Fusion Engine (open access)

Adjoint-Based Implicit Uncertainty Analysis for Figures of Merit in a Laser Inertial Fusion Engine

A primary purpose of computational models is to inform design decisions and, in order to make those decisions reliably, the confidence in the results of such models must be estimated. Monte Carlo neutron transport models are common tools for reactor designers. These types of models contain several sources of uncertainty that propagate onto the model predictions. Two uncertainties worthy of note are (1) experimental and evaluation uncertainties of nuclear data that inform all neutron transport models and (2) statistical counting precision, which all results of a Monte Carlo codes contain. Adjoint-based implicit uncertainty analyses allow for the consideration of any number of uncertain input quantities and their effects upon the confidence of figures of merit with only a handful of forward and adjoint transport calculations. When considering a rich set of uncertain inputs, adjoint-based methods remain hundreds of times more computationally efficient than Direct Monte-Carlo methods. The LIFE (Laser Inertial Fusion Energy) engine is a concept being developed at Lawrence Livermore National Laboratory. Various options exist for the LIFE blanket, depending on the mission of the design. The depleted uranium hybrid LIFE blanket design strives to close the fission fuel cycle without enrichment or reprocessing, while simultaneously achieving high discharge …
Date: December 3, 2010
Creator: Seifried, J. E.; Fratoni, M.; Kramer, K. J.; Latkowski, J. F.; Peterson, P. F.; Powers, J. J. et al.
Object Type: Article
System: The UNT Digital Library
Aqueous Homogeneous Reactor Technical Panel Report (open access)

Aqueous Homogeneous Reactor Technical Panel Report

Considerable interest has been expressed for developing a stable U.S. production capacity for medical isotopes and particularly for molybdenum- 99 (99Mo). This is motivated by recent re-ductions in production and supply worldwide. Consistent with U.S. nonproliferation objectives, any new production capability should not use highly enriched uranium fuel or targets. Conse-quently, Aqueous Homogeneous Reactors (AHRs) are under consideration for potential 99Mo production using low-enriched uranium. Although the Nuclear Regulatory Commission (NRC) has guidance to facilitate the licensing process for non-power reactors, that guidance is focused on reactors with fixed, solid fuel and hence, not applicable to an AHR. A panel was convened to study the technical issues associated with normal operation and potential transients and accidents of an AHR that might be designed for isotope production. The panel has produced the requisite AHR licensing guidance for three chapters that exist now for non-power reactor licensing: Reac-tor Description, Reactor Coolant Systems, and Accident Analysis. The guidance is in two parts for each chapter: 1) standard format and content a licensee would use and 2) the standard review plan the NRC staff would use. This guidance takes into account the unique features of an AHR such as the fuel being in solution; …
Date: December 3, 2010
Creator: Diamond, David; Bajorek, Stephen; Bakel, Allen; Flanagan, George; Mubayi, Vinod; Skarda, Raymond et al.
Object Type: Report
System: The UNT Digital Library
Experimental Study of High-Z Gas Buffers in Gas-Filled ICF Engines (open access)

Experimental Study of High-Z Gas Buffers in Gas-Filled ICF Engines

ICF power plants, such as the LIFE scheme at LLNL, may employ a high-Z, target-chamber gas-fill to moderate the first-wall heat-pulse due to x-rays and energetic ions released during target detonation. To reduce the uncertainties of cooling and beam/target propagation through such gas-filled chambers, we present a pulsed plasma source producing 2-5 eV plasma comprised of high-Z gases. We use a 5-kJ, 100-ns theta discharge for high peak plasma-heating-power, an electrode-less discharge for minimizing impurities, and unobstructed axial access for diagnostics and beam (and/or target) propagation studies. We will report on the plasma source requirements, design process, and the system design.
Date: December 3, 2010
Creator: Rhodes, M A; Kane, J; Loosmore, G; DeMuth, J & Latkowski, J
Object Type: Article
System: The UNT Digital Library
Final report SI 08-SI-004: Fusion application targets (open access)

Final report SI 08-SI-004: Fusion application targets

Complex target structures are necessary to take full advantage of the unique laboratory environment created by inertial confinement fusion experiments. For example, uses-of-ignition targets that contain a thin layer of a low density nanoporous material inside a spherical ablator shell allow placing dopants in direct contact with the DT fuel. The ideal foam for this application is a low-density hydrocarbon foam that is strong enough to survive wetting with cryogenic hydrogen, and low enough in density (density less than {approx}30 mg/cc) to not reduce the yield of the target. Here, we discuss the fabrication foam-lined uses-of-ignition targets, and the development of low-density foams that can be used for this application. Much effort has been directed over the last 20 years toward the development of spherical foam targets for direct-drive and fast-ignition experiments. In these targets, the spherical foam shell is used to define the shape of the cryogenic DT fuel layer, or acts as a surrogate to simulate the cryogenic fuel layer. These targets are fabricated from relatively high-density aerogels (>100 mg/cc) and coated with a few micron thick permeation barrier. With exception of the above mentioned fast ignition targets, the wall of these targets is typically larger than 100 …
Date: December 3, 2010
Creator: Biener, J.; Kucheyev, S. O.; Wang, M. Y.; Dawedeit, C.; Worsley, M. A.; Kim, S. H. et al.
Object Type: Report
System: The UNT Digital Library
DOSE TO CURIE DETERMINATION FOR CONTAINERS WITH MEASURABLE CS-137 (open access)

DOSE TO CURIE DETERMINATION FOR CONTAINERS WITH MEASURABLE CS-137

The Next Generation Retrieval (NGR) project will retrieve suspect transuranic (TRU) waste containers from Trenches 17 and 27 in the 218-E-12B (12B) burial ground. The trenches were in operation from May 1970 through October 1972. A portion of the retrieved containers that will require shipment to and acceptance at a treatment, storage, and disposal (TSD) facility and the containers will be either remote-handled (RH) and/or contact-handled (CH). The method discussed in this document will be used for the RH and some of the CH containers to determine the radionuclide inventory. Waste disposition (shipment and TSD acceptance) requires that the radioactive content be characterized for each container. Source-term estimates using high resolution, shielded, gamma-ray scan assay techniques cannot be performed on a number of RH and other containers with high dose rates from {sup 137}Cs-{sup 137m}Ba. This document provides the method to quantify the radioactive inventory of fission product gamma emitters within the containers based on the surface dose rate measurements taken in the field with hand-held survey instruments.
Date: December 3, 2010
Creator: LA, RATHBUN; JD, ANDERSON & RJ, SWAN
Object Type: Report
System: The UNT Digital Library
Final Report: Human Capacity Building Grant for Renewable Energy Development (open access)

Final Report: Human Capacity Building Grant for Renewable Energy Development

Warm Springs Power and Water Enterprise (WSPWE), a Corporate Entity of the Confederated Tribes of Warm Springs Oregon, developed and distributed written materials, held workshops and field trips to educate tribal members on renewable energy projects that are a possibility utilizing resources on reservation. In order to build stronger public and Tribal Council support for the development of renewable energy projects on the reservation, WSPWE conducted a 12 month public education and technical expertise development program. The objectives of this program were to: • To build a knowledge base within the tribal community regarding renewable energy development potential and opportunities on reservation lands. • To educate the tribal community regarding development process, impacts and benefits. • To increase the technical expertise of tribal government and Tribal Council.
Date: January 3, 2010
Creator: Sando, Wil
Object Type: Report
System: The UNT Digital Library
Micrometeorite Impacts in Beringian Mammoth Tusks and a Bison Skull (open access)

Micrometeorite Impacts in Beringian Mammoth Tusks and a Bison Skull

We have discovered what appear to be micrometeorites imbedded in seven late Pleistocene Alaskan mammoth tusks and a Siberian bison skull. The micrometeorites apparently shattered on impact leaving 2 to 5 mm hemispherical debris patterns surrounded by carbonized rings. Multiple impacts are observed on only one side of the tusks and skull consistent with the micrometeorites having come from a single direction. The impact sites are strongly magnetic indicating significant iron content. We analyzed several imbedded micrometeorite fragments from both tusks and skull with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and X-ray fluorescence (XRF). These analyses confirm the high iron content and indicate compositions highly enriched in nickel and depleted in titanium, unlike any natural terrestrial sources. In addition, electron microprobe (EMP) analyses of a Fe-Ni sulfide grain (tusk 2) show it contains between 3 and 20 weight percent Ni. Prompt gamma-ray activation analysis (PGAA) of a particle extracted from the bison skull indicates ~;;0.4 mg of iron, in agreement with a micrometeorite ~;;1 mm in diameter. In addition, scanning electron microscope (SEM) images and XRF analyses of the skull show possible entry channels containing Fe-rich material. The majority of tusks (5/7) have a calibrated weighted mean 14C …
Date: February 3, 2010
Creator: Hagstrum, Jonathon T.; Firestone, Richard B; West, Allen; Stefanka, Zsolt & Revay, Zsolt
Object Type: Article
System: The UNT Digital Library
Genetic Engineering Workshop Report, 2010 (open access)

Genetic Engineering Workshop Report, 2010

The Lawrence Livermore National Laboratory (LLNL) Bioinformatics group has recently taken on a role in DTRA's Transformation Medical Technologies (TMT) program. The high-level goal of TMT is to accelerate the development of broad-spectrum countermeasures. To achieve this goal, there is a need to assess the genetic engineering (GE) approaches, potential application as well as detection and mitigation strategies. LLNL was tasked to coordinate a workshop to determine the scope of investments that DTRA should make to stay current with the rapid advances in genetic engineering technologies, so that accidental or malicious uses of GE technologies could be adequately detected and characterized. Attachment A is an earlier report produced by LLNL for TMT that provides some relevant background on Genetic Engineering detection. A workshop was held on September 23-24, 2010 in Springfield, Virginia. It was attended by a total of 55 people (see Attachment B). Twenty four (44%) of the attendees were academic researchers involved in GE or bioinformatics technology, 6 (11%) were from DTRA or the TMT program management, 7 (13%) were current TMT performers (including Jonathan Allen and Tom Slezak of LLNL who hosted the workshop), 11 (20%) were from other Federal agencies, and 7 (13%) were from industries …
Date: November 3, 2010
Creator: Allen, J. & Slezak, T.
Object Type: Report
System: The UNT Digital Library
Native SrTiO3 (001) surface layer from resonant Ti L2,3 reflectance spectroscopy (open access)

Native SrTiO3 (001) surface layer from resonant Ti L2,3 reflectance spectroscopy

We quantitatively model resonant Ti L2,3 reflectivity Rs,p(q, hn) from several SrTiO3 (001) single crystals having different initial surface preparations and stored in ambient conditions before and between measurements. All samples exhibit unexpected 300 K Rs(hn) - Rp(hn) anisotropy corresponding to weak linear dichroism and tetragonal distortion of the TiO6 octahedra indicating a surface layer with properties different from cubic SrTiO3. Oscillations in Rs(q) confirm a ubiquitous surface layer 2-3 nm thick that evolves over a range of time scales. Resonant optical constant spectra derived from Rs,p(hn) assuming a uniform sample are refined using a single surface layer to fit measured Rs(q). Differences in surface layer and bulk optical properties indicate that the surface is significantly depleted in Sr and enriched in Ti and O. While consistent with the tendency of SrTiO3 surfaces toward non-stoichiometry, this layer does not conform simply to existing models for the near surface region and apparently forms via room temperature surface reactions with the ambient. This new quantitative spectral modeling approach is generally applicable and has potential to study near-surface properties of a variety of systems with unique chemical and electronic sensitivities.
Date: November 3, 2010
Creator: Valvidares, Manuel; Huijben, Mark; Yu, Pu; Ramesh, Ramamoorthy & Kortright, Jeffrey
Object Type: Article
System: The UNT Digital Library
Using Dimmable Lighting for Regulation Capacity and Non-Spinning Reserves in the Ancillary Services Market. A Feasibility Study. (open access)

Using Dimmable Lighting for Regulation Capacity and Non-Spinning Reserves in the Ancillary Services Market. A Feasibility Study.

The objective of this Feasibility Study was to identify the potential of dimmable lighting for providing regulation capacity and contingency reserves if massively-deployed throughout the State. We found that one half of the total electric lighting load in the California commercial sector is bottled up in larger buildings that are greater an 50,000 square feet. Retrofitting large California buildings with dimmable lighting to enable fast DR lighting would require an investment of about $1.8 billion and a"fleet" of about 56 million dimming ballasts. By upgrading the existing installed base of lighting and controls (primarily in large commercial facilities) a substantial amount of ancillary services could be provided. Though not widely deployed, today's state-of-the art lighting systems, control systems and communication networks could be used for this application. The same lighting control equipment that is appropriate for fast DR is also appropriate for achieving energy efficiency with lighting on a daily basis. Thus fast DR can leverage the capabilities that are provided by a conventional dimming lighting control system. If dimmable lighting were massively deployed throughout large California buildings (because mandated by law, for example) dimmable lighting could realistically supply 380 MW of non-spinning reserve, 47percent of the total non-spinning reserves …
Date: December 3, 2010
Creator: Rubinstein, Francis; Xiaolei, Li & Watson, David S.
Object Type: Report
System: The UNT Digital Library
A Direct, Biomass-Based Synthesis of Benzoic Acid: Formic Acid-Mediated Deoxygenation of the Glucose-Derived Materials Quinic Acid and Shikimic Acid (open access)

A Direct, Biomass-Based Synthesis of Benzoic Acid: Formic Acid-Mediated Deoxygenation of the Glucose-Derived Materials Quinic Acid and Shikimic Acid

An alternative biomass-based route to benzoic acid from the renewable starting materials quinic acid and shikimic acid is described. Benzoic acid is obtained selectively using a highly efficient, one-step formic acid-mediated deoxygenation method.
Date: May 3, 2010
Creator: Arceo, Elena; Ellman, Jonathan & Bergman, Robert
Object Type: Article
System: The UNT Digital Library
Stellarator Coil Design and Plasma Sensitivity (open access)

Stellarator Coil Design and Plasma Sensitivity

The rich information contained in the plasma response to external magnetic perturbations can be used to help design stellarator coils more effectively. We demonstrate the feasibility by first devel- oping a simple, direct method to study perturbations in stellarators that do not break stellarator symmetry and periodicity. The method applies a small perturbation to the plasma boundary and evaluates the resulting perturbed free-boundary equilibrium to build up a sensitivity matrix for the important physics attributes of the underlying configuration. Using this sensitivity information, design methods for better stellarator coils are then developed. The procedure and a proof-of-principle application are given that (1) determine the spatial distributions of external normal magnetic field at the location of the unperturbed plasma boundary to which the plasma properties are most sen- sitive, (2) determine the distributions of external normal magnetic field that can be produced most efficiently by distant coils, (3) choose the ratios of the magnitudes of the the efficiently produced magnetic distributions so the sensitive plasma properties can be controlled. Using these methods, sets of modular coils are found for the National Compact Stellarator Experiment (NCSX) that are either smoother or can be located much farther from the plasma boundary than those …
Date: November 3, 2010
Creator: Ku, Long-Poe & Boozer, Allen H.
Object Type: Report
System: The UNT Digital Library
Neptunium Transport Behavior in the Vicinity of Underground Nuclear Tests at the Nevada Test Site (open access)

Neptunium Transport Behavior in the Vicinity of Underground Nuclear Tests at the Nevada Test Site

We used short lived {sup 239}Np as a yield tracer and state of the art magnetic sector ICP-MS to measure ultra low levels of {sup 237}Np in a number of 'hot wells' at the Nevada National Security Site (NNSS), formerly known as the Nevada Test Site (NTS). The results indicate that {sup 237}Np concentrations at the Almendro, Cambric, Dalhart, Cheshire and Chancellor sites, are in the range of 3 x 10{sup -5} to 7 x 10{sup -2} pCi/L and well below the MCL for alpha emitting radionuclides (15 pCi/L) (EPA, 2009). Thus, while Np transport is believed to occur at the NNSS, activities are expected to be well below the regulatory limits for alpha-emitting radionuclides. We also compared {sup 237}Np concentration data to other radionuclides, including tritium, {sup 14}C, {sup 36}Cl, {sup 99}Tc, {sup 129}I, and plutonium, to evaluate the relative {sup 237}Np transport behavior. Based on isotope ratios relative to published unclassified Radiologic Source Terms (Bowen et al., 1999) and taking into consideration radionuclide distribution between melt glass, rubble and groundwater (IAEA, 1998), {sup 237}Np appears to be substantially less mobile than tritium and other non-sorbing radionuclides, as expected. However, this analysis also suggests that {sup 237}Np mobility is …
Date: December 3, 2010
Creator: Zhao, P.; Tinnacher, R. M.; Zavarin, M.; Williams, R. W. & Kersting, A. B.
Object Type: Report
System: The UNT Digital Library
Sythesis of metal sulfide nanomaerials via thermal decomposition of single-source percursors (open access)

Sythesis of metal sulfide nanomaerials via thermal decomposition of single-source percursors

In this report, we present a synthetic method for the formation of cuprous sulfide (Cu2S) and lead sulfide (PbS) nanomaterials directly on substrates from the thermolysis of single-source precursors. We find that the final morphology and arrangement of the nanomaterials may be controlled through the concentration of the dissolved precursors and choice of solvent. One-dimensional (1-D) morphologies may also be grown onto substrates with the addition of a metal catalyst layer through solution-liquid-solid (SLS) growth. These synthetic techniques may be expanded to other metal sulfide materials.
Date: June 3, 2010
Creator: Jen-La Plante, Ilan; Zeid, Tahani W.; Yang, Peidong & Mokari, Taleb
Object Type: Article
System: The UNT Digital Library
Exact Magnetic Diffusion Solutions for Magnetohydrodynamic Code Verification (open access)

Exact Magnetic Diffusion Solutions for Magnetohydrodynamic Code Verification

In this paper, the authors present several new exact analytic space and time dependent solutions to the problem of magnetic diffusion in R-Z geometry. These problems serve to verify several different elements of an MHD implementation: magnetic diffusion, external circuit time integration, current and voltage energy sources, spatially dependent conductivities, and ohmic heating. The exact solutions are shown in comparison with 2D simulation results from the Ares code.
Date: December 3, 2010
Creator: Miller, D. S.
Object Type: Article
System: The UNT Digital Library
Fermi Surface Evolution Across Multiple Charge Density Wave Transitions in ErTe3 (open access)

Fermi Surface Evolution Across Multiple Charge Density Wave Transitions in ErTe3

None
Date: May 3, 2010
Creator: Moore, R. G.
Object Type: Article
System: The UNT Digital Library
HANFORD TANK CLEANUP UPDATE APRIL 2010 (open access)

HANFORD TANK CLEANUP UPDATE APRIL 2010

None
Date: May 3, 2010
Creator: Berriochoa, M. V.
Object Type: Report
System: The UNT Digital Library
The hierarchy of multiple many-body interaction scales in high-temperature superconductors (open access)

The hierarchy of multiple many-body interaction scales in high-temperature superconductors

To date, angle-resolved photoemission spectroscopy has been successful in identifying energy scales of the many-body interactions in correlated materials, focused on binding energies of up to a few hundred meV below the Fermi energy. Here, at higher energy scale, we present improved experimental data from four families of high-T{sub c} superconductors over a wide doping range that reveal a hierarchy of many-body interaction scales focused on: the low energy anomaly ('kink') of 0.03-0.09eV, a high energy anomaly of 0.3-0.5eV, and an anomalous enhancement of the width of the LDA-based CuO{sub 2} band extending to energies of {approx} 2 eV. Besides their universal behavior over the families, we find that all of these three dispersion anomalies also show clear doping dependence over the doping range presented.
Date: May 3, 2010
Creator: Meevasana, W.
Object Type: Article
System: The UNT Digital Library
Glass Composition Constraint Recommendations for Use in Life-Cycle Mission Modeling (open access)

Glass Composition Constraint Recommendations for Use in Life-Cycle Mission Modeling

The component concentration limits that most influence the predicted Hanford life-cycle HLW glass volume by HTWOS were re-evaluated. It was assumed that additional research and development work in glass formulation and melter testing would be performed to improve the understanding of component effects on the processability and product quality of these HLW glasses. Recommendations were made to better estimate the potential component concentration limits that could be applied today while technology development is underway to best estimate the volume of HLW glass that will eventually be produced at Hanford. The limits for concentrations of P2O5, Bi2O3, and SO3 were evaluated along with the constraint used to avoid nepheline formation in glass. Recommended concentration limits were made based on the current HLW glass property models being used by HTWOS (Vienna et al. 2009). These revised limits are: 1) The current ND should be augmented by the OB limit of OB ≤ 0.575 so that either the normalized silica (NSi) is less that the 62% limit or the OB is below the 0.575 limit. 2) The mass fraction of P2O5 limit should be revised to allow for up to 4.5 wt%, depending on CaO concentrations. 3) A Bi2O3 concentration limit of 7 …
Date: May 3, 2010
Creator: McCloy, John S. & Vienna, John D.
Object Type: Report
System: The UNT Digital Library
THE ODTX SYSTEM FOR THERMAL IGNITION AND THERMAL SAFETY STUDY OF ENERGETIC MATERIALS (open access)

THE ODTX SYSTEM FOR THERMAL IGNITION AND THERMAL SAFETY STUDY OF ENERGETIC MATERIALS

Understanding the response of energetic material to thermal event is very important for the storage and handling of energetic materials. The One Dimensional Time to Explosion (ODTX) system at the Lawrence Livermore National Laboratory (LLNL) can precisely measure times to explosion and minimum ignition temperatures of energetic materials at elevated temperatures. These measurements provide insight into the relative ease of thermal ignition and allow for the determination of kinetic parameters. The ODTX system can potentialy be a good tool to measure violence of the thermal ignition by monitoring the size of anvil cavity. Recent ODTX experimental data on various energetic materials (solid and liquids) are reported in this paper.
Date: March 3, 2010
Creator: Hsu, P C; Hust, G; Howard, M & Maienschein, J L
Object Type: Article
System: The UNT Digital Library
RAPID SEPARATION METHOD FOR ACTINIDES IN EMERGENCY AIR FILTER SAMPLES (open access)

RAPID SEPARATION METHOD FOR ACTINIDES IN EMERGENCY AIR FILTER SAMPLES

A new rapid method for the determination of actinides and strontium in air filter samples has been developed at the Savannah River Site Environmental Lab (Aiken, SC, USA) that can be used in emergency response situations. The actinides and strontium in air filter method utilizes a rapid acid digestion method and a streamlined column separation process with stacked TEVA, TRU and Sr Resin cartridges. Vacuum box technology and rapid flow rates are used to reduce analytical time. Alpha emitters are prepared using cerium fluoride microprecipitation for counting by alpha spectrometry. The purified {sup 90}Sr fractions are mounted directly on planchets and counted by gas flow proportional counting. The method showed high chemical recoveries and effective removal of interferences. This new procedure was applied to emergency air filter samples received in the NRIP Emergency Response exercise administered by the National Institute for Standards and Technology (NIST) in April, 2009. The actinide and {sup 90}Sr in air filter results were reported in {approx}4 hours with excellent quality.
Date: February 3, 2010
Creator: Maxwell, S.; Noyes, G. & Culligan, B.
Object Type: Article
System: The UNT Digital Library
Angle-resolved photoemission studies of lattice polaron formation in the cuprate Ca2CuO2Cl2 (open access)

Angle-resolved photoemission studies of lattice polaron formation in the cuprate Ca2CuO2Cl2

To elucidate the nature of the single-particle excitations in the undoped parent cuprates, we have performed a detailed study of Ca{sub 2}CuO{sub 2}Cl{sub 2} using photoemission spectroscopy. The photoemission lineshapes of the lower Hubbard band are found to be well-described by a polaron model. By comparing the lineshape and temperature dependence of the lower Hubbard band with additional O 2p and Ca 3p states, we conclude that the dominant broadening mechanism arises from the interaction between the photohole and the lattice. The strength of this interaction was observed to be strongly anisotropic and may have important implications for the momentum dependence of the first doped hole states.
Date: May 3, 2010
Creator: Shen, K.M.
Object Type: Article
System: The UNT Digital Library