IRON-PHOSPHATE GLASS FOR IMMOBILIZATION OF RADIOACTIVE TECHNETIUM (open access)

IRON-PHOSPHATE GLASS FOR IMMOBILIZATION OF RADIOACTIVE TECHNETIUM

Technetium-99 (Tc-99) can bring a serious environmental threat because of its high fission yield, long half-life, and high solubility and mobility in the ground water. The present work investigated the immobilization of Tc-99 (surrogated by Re) by heat-treating mixtures of an iron-phosphate glass with 1.5 to 6 wt.% KReO{sub 4} at {approx}1000 C. The Re retention in the glass was as high as {approx}1.2 wt. % while the loss of Re by evaporation during melting was {approx}50%. Re was uniformly distributed within the glass. The normalized Re release by the 7-day Product Consistency Test was {approx}0.39 g/m{sup 2}, comparable with that in phosphate-bonded ceramics and borosilicate glasses. These results suggest that iron-phosphate glass can provide a good matrix for immobilizing Tc-99.
Date: March 19, 2012
Creator: AA, KRUGER; PR, HRMA; K, XU; J, CHOI; W, UM & J, HEO
System: The UNT Digital Library
STATUS OF THE DEVELOPMENT OF IN-TANK/AT-TANK SEPARATIONS TECHNOLOGIES FOR FOR HIGH-LEVEL WASTE PROCESSING FOR THE U.S. DEPARTMENT OF ENERGY (open access)

STATUS OF THE DEVELOPMENT OF IN-TANK/AT-TANK SEPARATIONS TECHNOLOGIES FOR FOR HIGH-LEVEL WASTE PROCESSING FOR THE U.S. DEPARTMENT OF ENERGY

Within the U.S. Department of Energy's (DOE) Office of Technology Innovation and Development, the Office of Waste Processing manages a research and development program related to the treatment and disposition of radioactive waste. At the Savannah River (South Carolina) and Hanford (Washington) Sites, approximately 90 million gallons of waste are distributed among 226 storage tanks (grouped or collocated in 'tank farms'). This waste may be considered to contain mixed and stratified high activity and low activity constituent waste liquids, salts and sludges that are collectively managed as high level waste (HLW). A large majority of these wastes and associated facilities are unique to the DOE, meaning many of the programs to treat these materials are 'first-of-a-kind' and unprecedented in scope and complexity. As a result, the technologies required to disposition these wastes must be developed from basic principles, or require significant re-engineering to adapt to DOE's specific applications. Of particular interest recently, the development of In-tank or At-Tank separation processes have the potential to treat waste with high returns on financial investment. The primary objective associated with In-Tank or At-Tank separation processes is to accelerate waste processing. Insertion of the technologies will (1) maximize available tank space to efficiently support …
Date: September 19, 2011
Creator: Aaron, G. & Wilmarth, B.
System: The UNT Digital Library
A Change in the Optical Polarization Associated with a Gamma-Ray Flare in the Blazar 3C 279 (open access)

A Change in the Optical Polarization Associated with a Gamma-Ray Flare in the Blazar 3C 279

It is widely accepted that strong and variable radiation detected over all accessible energy bands in a number of active galaxies arises from a relativistic, Doppler-boosted jet pointing close to our line of sight. The size of the emitting zone and the location of this region relative to the central supermassive black hole are, however, poorly known, with estimates ranging from light-hours to a light-year or more. Here we report the coincidence of a gamma ({gamma})-ray flare with a dramatic change of optical polarization angle. This provides evidence for co-spatiality of optical and {gamma}-ray emission regions and indicates a highly ordered jet magnetic field. The results also require a non-axisymmetric structure of the emission zone, implying a curved trajectory for the emitting material within the jet, with the dissipation region located at a considerable distance from the black hole, at about 10{sup 5} gravitational radii.
Date: August 19, 2011
Creator: Abdo, A. A.
System: The UNT Digital Library
Fermi-LAT Discovery of GeV Gamma-ray Emission from the Young Supernova Remnant Cassiopeia A (open access)

Fermi-LAT Discovery of GeV Gamma-ray Emission from the Young Supernova Remnant Cassiopeia A

We report on the first detection of GeV high-energy gamma-ray emission from a young supernova remnant with the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope. These observations reveal a source with no discernible spatial extension detected at a significance level of 12.2{sigma} above 500 MeV at a location that is consistent with the position of the remnant of the supernova explosion that occurred around 1680 in the Cassiopeia constellation - Cassiopeia A. The gamma-ray flux and spectral shape of the source are consistent with a scenario in which the gamma-ray emission originates from relativistic particles accelerated in the shell of this remnant. The total content of cosmic rays (electrons and protons) accelerated in Cas A can be estimated as W{sub CR} {approx_equal} (1-4) x 10{sup 49} erg thanks to the well-known density in the remnant assuming that the observed gamma-ray originates in the SNR shell(s). The magnetic field in the radio-emitting plasma can be robustly constrained as B {ge} 0.1 mG, providing new evidence of the magnetic field amplification at the forward shock and the strong field in the shocked ejecta.
Date: August 19, 2011
Creator: Abdo, A. A.
System: The UNT Digital Library
The Spectrum of the Isotropic Diffuse Gamma-Ray Emission Derived From First-Year Fermi Large Area Telescope Data (open access)

The Spectrum of the Isotropic Diffuse Gamma-Ray Emission Derived From First-Year Fermi Large Area Telescope Data

We report on the first Fermi Large Area Telescope (LAT) measurements of the so-called 'extra-galactic' diffuse {gamma}-ray emission (EGB). This component of the diffuse {gamma}-ray emission is generally considered to have an isotropic or nearly isotropic distribution on the sky with diverse contributions discussed in the literature. The derivation of the EGB is based on detailed modelling of the bright foreground diffuse Galactic {gamma}-ray emission (DGE), the detected LAT sources and the solar {gamma}-ray emission. We find the spectrum of the EGB is consistent with a power law with differential spectral index {gamma} = 2.41 {+-} 0.05 and intensity, I(> 100 MeV) = (1.03 {+-} 0.17) x 10{sup -5} cm{sup -2} s{sup -1} sr{sup -1}, where the error is systematics dominated. Our EGB spectrum is featureless, less intense, and softer than that derived from EGRET data.
Date: August 19, 2011
Creator: Abdo, A. A.
System: The UNT Digital Library
Design Methodology and Consideratios for NOVA 53 MHZ RF Cavities (open access)

Design Methodology and Consideratios for NOVA 53 MHZ RF Cavities

The NO?A Experiment will construct a detector optimized for electron neutrino detection in the existing Neutrino at Main Injector (NuMI) beamline. This beamline is capable of operating at 400 kW of primary beam power and the upgrade will allow up to 700 kW. The cavities will operate at 53 MHz and three of them will be installed in the Recycler beamline. Thermal stability of the cavities is crucial since this affects the tuning. Results of finite element thermal and structural analysis involving the copper RF cavity will be presented.
Date: May 19, 2010
Creator: Ader, C. & Wildman, D.W.
System: The UNT Digital Library
CDMSlite: A Search for Low-Mass WIMPs using Voltage-Assisted Calorimetric Ionization Detection in the SuperCDMS Experiment (open access)

CDMSlite: A Search for Low-Mass WIMPs using Voltage-Assisted Calorimetric Ionization Detection in the SuperCDMS Experiment

None
Date: February 19, 2014
Creator: Agnese, R.; Anderson, A. J.; Asai, M.; Balakishiyeva, D.; Thakur, R. Basu; Bauer, D. A. et al.
System: The UNT Digital Library
Fresh Water Generation from Aquifer-Pressured Carbon Storage (open access)

Fresh Water Generation from Aquifer-Pressured Carbon Storage

Can we use the pressure associated with sequestration to make brine into fresh water? This project is establishing the potential for using brine pressurized by Carbon Capture and Storage (CCS) operations in saline formations as the feedstock for desalination and water treatment technologies including reverse osmosis (RO) and nanofiltration (NF). Possible products are: Drinking water, Cooling water, and Extra aquifer space for CO{sub 2} storage. The conclusions are: (1) Many saline formation waters appear to be amenable to largely conventional RO treatment; (2) Thermodynamic modeling indicates that osmotic pressure is more limiting on water recovery than mineral scaling; (3) The use of thermodynamic modeling with Pitzer's equations (or Extended UNIQUAC) allows accurate estimation of osmotic pressure limits; (4) A general categorization of treatment feasibility is based on TDS has been proposed, in which brines with 10,000-85,000 mg/L are the most attractive targets; (5) Brines in this TDS range appear to be abundant (geographically and with depth) and could be targeted in planning future CCS operations (including site selection and choice of injection formation); and (6) The estimated cost of treating waters in the 10,000-85,000 mg/L TDS range is about half that for conventional seawater desalination, due to the anticipated pressure …
Date: February 19, 2010
Creator: Aines, R. D.; Wolery, T. J.; Bourcier, W. L.; Wolfe, T. & Haussmann, C.
System: The UNT Digital Library
Constraints on Dark Matter Models From a Fermi LAT Search for High-Energy Cosmic-Ray Electrons from the Sun (open access)

Constraints on Dark Matter Models From a Fermi LAT Search for High-Energy Cosmic-Ray Electrons from the Sun

None
Date: March 19, 2013
Creator: Ajello, M.; Atwood, W. B.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Bellazzini, R. et al.
System: The UNT Digital Library
A Dual Channel X-ray Spectrometer for Fast Ignition Research (open access)

A Dual Channel X-ray Spectrometer for Fast Ignition Research

A new Dual Channel Highly Ordered Pyrolytic Graphite (DC-HOPG) x-ray spectrometer was developed to study laser-generated electron beam transport. The instrument uses a pair of graphite crystals and has the advantage of simultaneously detecting self emission from low-Z materials in first diffraction order and high-Z materials in second order. The emissions from the target are detected using a pair of parallel imaging plates positioned in a such way that the noise from background is minimized and the mosaic focusing is achieved. Initial tests of the diagnostic on Titan laser (I {approx} 10{sup 20} W/cm{sup 2}, {tau} = 0.7 ps) show excellent signal-to-noise ratio (SNR) > 1000 for the low energy channel and SNR > 400 for the high energy channel.
Date: April 19, 2010
Creator: Akli, K. U.; Patel, P. K.; Van Maren, R.; Stephens, R. B.; Key, M. H.; Higginson, D. P. et al.
System: The UNT Digital Library
A Solid-State Nanosecond Beam Kicker Modulator Based on the DSRD Switch (open access)

A Solid-State Nanosecond Beam Kicker Modulator Based on the DSRD Switch

A fast solid-state beam kicker modulator is under development at the SLAC National Accelerator Laboratory. The program goal is to develop a modulator that will deliver 4 ns, {+-}5 kV pulses to the ATF2 damping ring beam extraction kicker. The kicker is a 50 {Omega}, bipolar strip line, 60 cm long, fed at the downstream end and terminated at the upstream end. The bunch spacing in the ring is 5.6 ns, bunches are removed from the back end of the train, and there is a gap of 103.6 ns before the next train. The modulator design is based on an opening switch topology that uses Drift Step Recovery Diodes as the opening switches. The design and results of the modulator development are discussed. There are many applications that benefit from very fast high power switching. However, at MW power levels and nanosecond time scales, solid state options are limited. One option, the Drift Step Recovery Diode (DSRD) has been demonstrated as capable of blocking thousands of volts and switching in nanosecond to sub-nanosecond ranges. When used as an opening switch, the DSRD exhibits a very fast turn off transient. The process is described in detail by its pioneers in [5,6]. …
Date: August 19, 2011
Creator: Akre, R.; Benwell, A.; Burkhart, C.; Krasnykh, A.; Tang, T. & Kardo-Sysoev, A.
System: The UNT Digital Library
A Review of X-ray Diagnostic Calibrations in the 2 to 100 keV Region Using the High Energy X-ray Calibration Facility (HEX) (open access)

A Review of X-ray Diagnostic Calibrations in the 2 to 100 keV Region Using the High Energy X-ray Calibration Facility (HEX)

The precise and accurate measurement of X-rays in the 2 keV to 100 keV region is crucial to the understanding of HED plasmas and warm dense matter in general. With the emergence of inertially confined plasma facilities as the premier platforms for ICF, laboratory astrophysics, and national security related plasma experiments, the need to calibrate diagnostics in the high energy X-ray regime has grown. At National Security Technologies High Energy X-ray Calibration Facility (HEX) in Livermore, California, X-ray imagers, filter-fluorescer spectrometers, crystal spectrometers, image plates, and nuclear diagnostics are calibrated. The HEX can provide measurements of atomic line radiation, X-ray flux (accuracy within 10%), and X-ray energy (accuracy within 1%). The HEX source is comprised of a commercial 160 kV X-ray tube, a fluorescer wheel, a filter wheel, and a lead encasement. The X-ray tube produces a Tungsten bremsstrahlung spectrum which causes a foil to fluoresce line radiation. To minimize bremsstrahlung in the radiation for calibration we also provide various foils as filters. For experimental purposes, a vacuum box capable of 10{sup -7} Torr, as well as HPGe and CdTe radiation detectors, are provided on an optical table. Most geometries and arrangements can be changed to meet experimental needs.
Date: May 19, 2010
Creator: Ali, Zaheer; Pond, T.; Buckles, R. A.; Maddox, B. R.; Chen, C. D.; DeWald, E. L. et al.
System: The UNT Digital Library
Tunable Plasmonic Nanogap Resonator (open access)

Tunable Plasmonic Nanogap Resonator

None
Date: June 19, 2012
Creator: BOnd, T.; Bora, M.; Chang, A. & Miles, R.
System: The UNT Digital Library
Quantification of thin film crystallographic orientation using X-ray diffraction with an area detector (open access)

Quantification of thin film crystallographic orientation using X-ray diffraction with an area detector

As thin films become increasingly popular (for solar cells, LEDs, microelectronics, batteries), quantitative morphological information is needed to predict and optimize the film's electronic, optical and mechanical properties. This quantification can be obtained quickly and easily with X-ray diffraction using an area detector and synchrotron radiation in two simple geometries. In this paper, we describe a methodology for constructing complete pole figures for thin films with fiber texture (isotropic in-plane orientation). We demonstrate this technique on semicrystalline polymer films, self-assembled nanoparticle semiconductor films, and randomly-packed metallic nanoparticle films. This method can be immediately implemented to help understand the relationship between film processing and microstructure, enabling the development of better and less expensive electronic and optoelectronic devices.
Date: February 19, 2010
Creator: Baker, Jessica L; Jimison, Leslie H; Mannsfeld, Stefan; Volkman, Steven; Yin, Shong; Subramanian, Vivek et al.
System: The UNT Digital Library
Simulations for experimental study of warm dense matter and inertial fusion energy applications on NDCX-II (open access)

Simulations for experimental study of warm dense matter and inertial fusion energy applications on NDCX-II

The Neutralized Drift Compression Experiment II (NDCX II) is an induction accelerator planned for initial commissioning in 2012. The final design calls for a {approx}3 MeV, {approx}30 A Li{sup +} ion beam, delivered in a bunch with characteristic pulse duration of 1 ns, and transverse dimension of order 1 mm. The purpose of NDCX II is to carry out experimental studies of material in the warm dense matter regime, and ion beam/hydrodynamic coupling experiments relevant to heavy ion based inertial fusion energy. In preparation for this new machine, we have carried out hydrodynamic simulations of ion-beam-heated, metallic solid targets, connecting quantities related to observables, such as brightness temperature and expansion velocity at the critical frequency, with the simulated fluid density, temperature, and velocity. We examine how these quantities depend on two commonly used equations of state.
Date: March 19, 2010
Creator: Barnard, J. J.; Armijo, J.; Bieniosek, F. M.; Friedman, A.; Hay, M. J.; Henestroza, E. et al.
System: The UNT Digital Library
Characterization of the effects of x-ray irradiation on the hierarchical structure and mechanical properties of human cortical bone (open access)

Characterization of the effects of x-ray irradiation on the hierarchical structure and mechanical properties of human cortical bone

Bone comprises a complex structure of primarily collagen, hydroxyapatite and water, where each hierarchical structural level contributes to its strength, ductility and toughness. These properties, however, are degraded by irradiation, arising from medical therapy or bone-allograft sterilization. We provide here a mechanistic framework for how irradiation affects the nature and properties of human cortical bone over a range of characteristic (nano to macro) length-scales, following x-­ray exposures up to 630 kGy. Macroscopically, bone strength, ductility and fracture resistance are seen to be progressively degraded with increasing irradiation levels. At the micron-­scale, fracture properties, evaluated using in-situ scanning electron microscopy and synchrotron x-ray computed micro-tomography, provide mechanistic information on how cracks interact with the bone-matrix structure. At sub-micron scales, strength properties are evaluated with in-situ tensile tests in the synchrotron using small-/wide-angle x-ray scattering/diffraction, where strains are simultaneously measured in the macroscopic tissue, collagen fibrils and mineral. Compared to healthy bone, results show that the fibrillar strain is decreased by ~40% following 70 kGy exposures, consistent with significant stiffening and degradation of the collagen. We attribute the irradiation-­induced deterioration in mechanical properties to mechanisms at multiple length-scales, including changes in crack paths at micron-­scales, loss of plasticity from suppressed fibrillar sliding …
Date: August 19, 2011
Creator: Barth, Holly; Zimmermann, Elizabeth; Schaible, Eric; Tang, Simon; Alliston, Tamara & Ritchie, Robert
System: The UNT Digital Library
High statistics analysis using anisotropic clover lattices: (III) Baryon-baryon interactions (open access)

High statistics analysis using anisotropic clover lattices: (III) Baryon-baryon interactions

Low-energy baryon-baryon interactions are calculated in a high-statistics lattice QCD study on a single ensemble of anisotropic clover gauge-field configurations at a pion mass of m{sub {pi}} {approx} 390 MeV, a spatial volume of L{sup 3} {approx} (2.5 fm){sup 3}, and a spatial lattice spacing of b {approx} 0.123 fm. Luescher's method is used to extract nucleon-nucleon, hyperon-nucleon and hyperon-hyperon scattering phase shifts at one momentum from the one- and two-baryon ground-state energies in the lattice volume. The isospin-3/2 N{Sigma} interactions are found to be highly spin-dependent, and the interaction in the {sup 3}S{sub 1} channel is found to be strong. In contrast, the N{Lambda} interactions are found to be spin-independent, within the uncertainties of the calculation, consistent with the absence of one-pion-exchange. The only channel for which a negative energy-shift is found is {Lambda}{Lambda}, indicating that the {Lambda}{Lambda} interaction is attractive, as anticipated from model-dependent discussions regarding the H-dibaryon. The NN scattering lengths are found to be small, clearly indicating the absence of any fine-tuning in the NN-sector at this pion mass. This is consistent with our previous Lattice QCD calculation of NN interactions. The behavior of the signal-to-noise ratio in the baryon-baryon correlation functions, and in the ratio …
Date: January 19, 2010
Creator: Beane, S; Detmold, W; Lin, H; Luu, T; Orginos, K; Savage, M et al.
System: The UNT Digital Library
Common Origin of the Circular-dichroism Pattern in ARPES of SrTiO3 and CuxBi2Se3 (open access)

Common Origin of the Circular-dichroism Pattern in ARPES of SrTiO3 and CuxBi2Se3

We investigate circular dichroism in the angular distribution (CDAD) of photoelectrons from SrTiO{sub 3}:Nb and Cu{sub x}Bi{sub 2}Se{sub 3} recorded by 7-eV laser ARPES. In addition to the well-known node that occurs in CDAD when the incidence plane matches the mirror plane of the crystal, we show that another type of node occurs when the mirror plane of the crystal is vertical to the incidence plane and the electronic state is two dimensional. The flower-shaped CDAD's occurring around the Fermi level of SrTiO{sub 3}:Nb and around the Dirac point of Cu{sub x}Bi{sub 2}Se{sub 3} are explained on equal footings. A surface-state-to-surface-resonance transition is indicated for the topological state of Cu{sub x}Bi{sub 2}Se{sub 3}.
Date: August 19, 2011
Creator: Bell, Christopher
System: The UNT Digital Library
Control of Electronic Conduction at an Oxide Heterointerface using Surface Polar Adsorbates (open access)

Control of Electronic Conduction at an Oxide Heterointerface using Surface Polar Adsorbates

We study the effect of the surface adsorption of a variety of common laboratory solvents on the conductivity at the interface between LaAlO{sub 3} and SrTiO{sub 3}. This interface possesses a range of intriguing physics, notably a proposed connection between the surface state of the LaAlO{sub 3} and the conductivity buried in the SrTiO{sub 3}. We show that the application of chemicals such as acetone, ethanol, and water can induce a large change (factor of three) in the conductivity. This phenomenon is observed only for polar solvents. These data provide experimental evidence for a general polarization-facilitated electronic transfer mechanism.
Date: August 19, 2011
Creator: Bell, Christopher
System: The UNT Digital Library
Intrinsic Spin-Orbit Coupling in Superconducting Delta-Doped SrTiO3 Heterostructures (open access)

Intrinsic Spin-Orbit Coupling in Superconducting Delta-Doped SrTiO3 Heterostructures

We report the violation of the Pauli limit due to intrinsic spin-orbit coupling in SrTiO{sub 3} heterostructures. Via selective doping down to a few nanometers, a two-dimensional superconductor is formed, geometrically suppressing orbital pair-breaking. The spin-orbit scattering is exposed by the robust in-plane superconducting upper critical field, exceeding the Pauli limit by a factor of 4. Transport scattering times several orders of magnitude higher than for conventional thin film superconductors enables a new regime to be entered, where spin-orbit coupling effects arise non-perturbatively.
Date: August 19, 2011
Creator: Bell, Christopher
System: The UNT Digital Library
Structural Comparison of n-type and p-type LaAlO3/SrTiO3 Interfaces (open access)

Structural Comparison of n-type and p-type LaAlO3/SrTiO3 Interfaces

Using a surface x-ray diffraction technique, we investigated the atomic structure of two types of interfaces between LaAlO{sub 3} and SrTiO{sub 3}, that is, p-type (SrO/AlO{sub 2}) and n-type (TiO{sub 2}/LaO) interfaces. Our results demonstrate that the SrTiO{sub 3} in the sample with the n-type interface has a large polarized region, while that with the p-type interface has a limited polarized region. In addition, the atomic intermixing was observed to extend deeper into STO substrate at the n-type interface than at the p-type. These differences result in different degrees of band bending, which likely contributes to the striking difference in electrical conductivity between the two types of interfaces.
Date: August 19, 2011
Creator: Bell, Christopher
System: The UNT Digital Library
N >= 4 Supergravity Amplitudes from Gauge Theory at One Loop (open access)

N >= 4 Supergravity Amplitudes from Gauge Theory at One Loop

We expose simple and practical relations between the integrated four- and five-point one-loop amplitudes of N {ge} 4 supergravity and the corresponding (super-)Yang-Mills amplitudes. The link between the amplitudes is simply understood using the recently uncovered duality between color and kinematics that leads to a double-copy structure for gravity. These examples provide additional direct confirmations of the duality and double-copy properties at loop level for a sample of different theories.
Date: August 19, 2011
Creator: Bern, Z.; Boucher-Veronneau, C. & Johansson, H.
System: The UNT Digital Library
The BlackHat Library for One-Loop Amplitudes (open access)

The BlackHat Library for One-Loop Amplitudes

None
Date: February 19, 2014
Creator: Bern, Z.; Dixon, L. J.; Cordero, F. Febres; Hoeche, S.; Ita, H.; Kosower, D. A. et al.
System: The UNT Digital Library
Ntuples for NLO events at Hadron Colliders (open access)

Ntuples for NLO events at Hadron Colliders

None
Date: February 19, 2014
Creator: Bern, Z.; Dixon, L.J.; Cordero, F.Febres; Hoeche, S.; Ita, H.; Kosower, D.A. et al.
System: The UNT Digital Library