Conference on Nuclear Energy and Science for the 21st Century: Atoms for Peace Plus Fifty - Washington, D.C., October 2003 (open access)

Conference on Nuclear Energy and Science for the 21st Century: Atoms for Peace Plus Fifty - Washington, D.C., October 2003

This conference's focus was the peaceful uses of the atom and their implications for nuclear science, energy security, nuclear medicine and national security. The conference also provided the setting for the presentation of the prestigious Enrico Fermi Prize, a Presidential Award which recognizes the contributions of distinguished members of the scientific community for a lifetime of exceptional achievement in the science and technology of nuclear, atomic, molecular, and particle interactions and effects. An impressive group of distinguished speakers addressed various issues that included: the impact and legacy of the Eisenhower Administration’s “Atoms for Peace” concept, the current and future role of nuclear power as an energy source, the challenges of controlling and accounting for existing fissile material, and the horizons of discovery for particle or high-energy physics. The basic goal of the conference was to examine what has been accomplished over the past fifty years as well as to peer into the future to gain insights into what may occur in the fields of nuclear energy, nuclear science, nuclear medicine, and the control of nuclear materials.
Date: October 22, 2006
Creator: Pfaltzgraff, Robert L
System: The UNT Digital Library
Silicon Oxynitride Thin Film Barriers for PV Packaging (Poster) (open access)

Silicon Oxynitride Thin Film Barriers for PV Packaging (Poster)

Dielectric, adhesion-promoting, moisture barriers comprised of silicon oxynitride thin film materials (SiOxNy with various material stoichiometric compositions x,y) were applied to: 1) bare and pre-coated soda-lime silicate glass (coated with transparent conductive oxide SnO2:F and/or aluminum), and polymer substrates (polyethylene terephthalate, PET, or polyethylene napthalate, PEN); plus 2) pre- deposited photovoltaic (PV) cells and mini-modules consisting of amorphous silicon (a-Si) and copper indium gallium diselenide (CIGS) thin-film PV technologies. We used plasma enhanced chemical vapor deposition (PECVD) process with dilute silane, nitrogen, and nitrous oxide/oxygen gas mixtures in a low-power (< or = 10 milliW per cm2) RF discharge at ~ 0.2 Torr pressure, and low substrate temperatures < or = 100(degrees)C, over deposition areas ~ 1000 cm2. Barrier properties of the resulting PV cells and coated-glass packaging structures were studied with subsequent stressing in damp-heat exposure at 85(degrees)C/85% RH. Preliminary results on PV cells and coated glass indicate the palpable benefits of the barriers in mitigating moisture intrusion and degradation of the underlying structures using SiOxNy coatings with thicknesses in the range of 100-200 nm.
Date: October 3, 2006
Creator: del Cueto, J. A.; Glick, S. H.; Terwilliger, K. M.; Jorgensen, G. J.; Pankow, J. W.; Keyes, B. M. et al.
System: The UNT Digital Library
The Dark Matter Halos of Massive, Relaxed Galaxy Clusters Observed With Chandra (open access)

The Dark Matter Halos of Massive, Relaxed Galaxy Clusters Observed With Chandra

We use the Chandra X-ray Observatory to study the dark matter halos of 34 massive, dynamically relaxed galaxy clusters, spanning the redshift range 0.06 &lt; z &lt; 0.7. The observed dark matter and total mass (dark-plus-luminous matter) profiles can be approximated by the Navarro Frenk & White (hereafter NFW) model for cold dark matter (CDM) halos; for {approx} 80 percent of the clusters, the NFW model provides a statistically acceptable fit. In contrast, the singular isothermal sphere model can, in almost every case, be completely ruled out. We observe a well-defined mass-concentration relation for the clusters with a normalization and intrinsic scatter in good agreement with the predictions from simulations. The slope of the mass-concentration relation, c {infinity} M{sub vir}{sup a}/(1 + z){sup b} with a = -0.41 {+-} 0.11 at 95 percent confidence, is steeper than the value a {approx} -0.1 predicted by CDM simulations for lower mass halos. With the slope a included as a free fit parameter, the redshift evolution of the concentration parameter, b = 0.54 {+-} 0.47 at 95 percent confidence, is also slower than, but marginally consistent with, the same simulations (b {approx} 1). Fixing a {approx} -0.1 leads to an apparent evolution that …
Date: October 11, 2006
Creator: Schmidt, Robert W.; /Heidelberg, Astron. Rechen Inst.; Allen, S.W. & /KIPAC, Menlo Park
System: The UNT Digital Library
Study of Multi-body Charmless B Decays with the BaBar Experiment (open access)

Study of Multi-body Charmless B Decays with the BaBar Experiment

The authors report recent measurements of charmless B decays to the final states K{sup +}K{sup +}K{sup -}, {phi}{phi}K, {eta}'{eta}'K, M{sub S}{sup 0}K{sub S}{sup 0}K{sub L}{sup 0}, {bar {Lambda}}p{pi}{sup +}, K*{sup +}h{sup +}h{sup -} and KX(inclusive). The results were obtained using a data sample of up to 288.5 fb{sup -1} recorded by the BABAR detector at the PEP-II asymmetric B factory at SLAC.
Date: October 18, 2006
Creator: Latham, Thomas E.
System: The UNT Digital Library
Evaluation of Affordable Prototype Houses at Two Levels of Energy Efficiency (open access)

Evaluation of Affordable Prototype Houses at Two Levels of Energy Efficiency

Two high performance prototype houses were built in Carbondale, Colorado, as part of the U.S. Department of Energy's Building America (BA) Program. Each prototype was a 1256 ft2 (117 m2), 1-story, 3-bedroom house, and met the local requirements for affordable housing. The National Renewable Energy Laboratory (NREL) performed short-term field testing and DOE-2.2 simulations in support of this project at the end of December 2004. We also installed long-term monitoring equipment in one of the houses, and are currently tracking the performance of key building systems under occupied conditions. One of the houses (designated H1) included a package of cost-effective energy efficiency features that placed it well above the Energy Star level, targeting a Home Energy Rating System (HERS) score of 88-89. The other (designated H2) was a BA research house, targeting a HERS score of 94-95, and 45% whole-house energy savings compared to the BA Benchmark. Preliminary results from the field evaluation indicate that the energy savings for both houses will exceed the design targets established for the project, although the performance of certain building systems, including the ventilation and foundation systems, leave some room for improvement.
Date: October 1, 2006
Creator: Hendron, R.; Barker, G.; Hancock, E. & Reeves, P.
System: The UNT Digital Library
The Accelerator Markup Language and the Universal Accelerator Parser (open access)

The Accelerator Markup Language and the Universal Accelerator Parser

A major obstacle to collaboration on accelerator projects has been the sharing of lattice description files between modeling codes. To address this problem, a lattice description format called Accelerator Markup Language (AML) has been created. AML is based upon the standard eXtensible Markup Language (XML) format; this provides the flexibility for AML to be easily extended to satisfy changing requirements. In conjunction with AML, a software library, called the Universal Accelerator Parser (UAP), is being developed to speed the integration of AML into any program. The UAP is structured to make it relatively straightforward (by giving appropriate specifications) to read and write lattice files in any format. This will allow programs that use the UAP code to read a variety of different file formats. Additionally, this will greatly simplify conversion of files from one format to another. Currently, besides AML, the UAP supports the MAD lattice format.
Date: October 6, 2006
Creator: Sagan, D.; Forster, M.; /Cornell U., LNS; Bates, D.A.; /LBL, Berkeley; Wolski, A. et al.
System: The UNT Digital Library
Tests on MgB2 for Application to SRF Cavities (open access)

Tests on MgB2 for Application to SRF Cavities

Magnesium diboride (MgB{sub 2}) has a transition temperature (T{sub c}) of {approx} 40 K, i.e., about 4 times higher than niobium (Nb). Studies in the last 3 years have shown that it could have about one order of magnitude less RF surface resistance (R{sub s}) than Nb at 4 K and seems to have much less power dependence than high-T{sub c} materials such as YBCO. However, it was also found that it will depend on the way you deposit the film. The result from on-axis pulsed laser deposition (PLD) showed rapid increase in R{sub s} with higher surface magnetic fields compared to the film deposited with reactive evaporation method.
Date: October 6, 2006
Creator: Tajima, T.; Canabal, A.; Alamos, /Los; Zhao, Y.; U., /Wollongong; Romanenko, A. et al.
System: The UNT Digital Library
Matrix Formalism of Synchrobetatron Coupling (open access)

Matrix Formalism of Synchrobetatron Coupling

In this paper we present a complete linear synchrobetatron coupling formalism by studying the transfer matrix which describes linear horizontal and longitudinal motions. With the technique established in the linear horizontal-vertical coupling study [D. Sagan and D. Rubin, Phys. Rev. ST Accel. Beams 2, 074001 (1999)], we found a transformation to block diagonalize the transfer matrix and decouple the betatron motion and the synchrotron motion. By separating the usual dispersion term from the horizontal coordinate first, we were able to obtain analytic expressions of the transformation under reasonable approximations. We also obtained the perturbations to the betatron tune and the Courant-Snyder functions. The closed orbit changes due to finite energy gains at rf cavities and radiation energy losses were also studied by the 5 x 5 extended transfer matrix with the fifth column describing kicks in the 4-dimension phase space.
Date: October 6, 2006
Creator: Huang, Xiaobiao
System: The UNT Digital Library
The First Generation of Stars in Lambda-CDM Cosmology (open access)

The First Generation of Stars in Lambda-CDM Cosmology

We have performed a large set of high-resolution cosmological simulations using smoothed particle hydrodynamics (SPH) to study the formation of the first luminous objects in the {Lambda}CDM cosmology. We follow the collapse of primordial gas clouds in eight early structures and document the scatter in the properties of the first star-forming clouds. Our first objects span formation redshifts from z {approx} 10 to z {approx} 50 and cover an order of magnitude in halo mass. We find that the physical properties of the central star-forming clouds are very similar in all of the simulated objects despite significant differences in formation redshift and environment. This suggests that the formation path of the first stars is largely independent of the collapse redshift; the physical properties of the clouds have little correlation with spin, mass, or assembly history of the host halo. The collapse of proto-stellar objects at higher redshifts progresses much more rapidly due to the higher densities, which accelerates the formation of molecular hydrogen, enhances initial cooling and shortens the dynamical timescales. The mass of the star-forming clouds cover a broad range, from a few hundred to a few thousand solar masses, and exhibit various morphologies: some have disk-like structures which …
Date: October 10, 2006
Creator: Gao, Liang; Abel, T.; Frenk, C. S.; Jenkins, A.; Springel, V. & Yoshida, N.
System: The UNT Digital Library
Understanding Limitations in the Determination of the Diffuse Galactic Gamma-ray Emission (open access)

Understanding Limitations in the Determination of the Diffuse Galactic Gamma-ray Emission

We discuss uncertainties and possible sources of errors associated with the determination of the diffuse Galactic {gamma}-ray emission using the EGRET data. Most of the issues will be relevant also in the GLAST era. The focus here is on issues that impact evaluation of dark matter annihilation signals against the diffuse {gamma}-ray emission of the Milky Way.
Date: October 3, 2006
Creator: Moskalenko, Igor V.; /Stanford U., HEPL /KIPAC, Menlo Park; Digel, S.W.; /SLAC /KIPAC, Menlo Park; Porter, T.A.; /UC, Santa Cruz et al.
System: The UNT Digital Library
Measurement of Direct CP Asymmetries in Charmless Hadronic B Decays (open access)

Measurement of Direct CP Asymmetries in Charmless Hadronic B Decays

We present recent results on time integrated and time dependent CP violation for charmless hadronic B decays using BABAR detector at the PEP-II B-factory.
Date: October 11, 2006
Creator: Di Marco, Emanuele
System: The UNT Digital Library
CP Violation Measurements in B to Charm Decays at BaBar (open access)

CP Violation Measurements in B to Charm Decays at BaBar

This article summarizes measurements of time-dependent CP asymmetries in decays of neutral B mesons to charm final states using data collected by the BABAR detector at the PEP-II asymmetric-energy B factory. All results are preliminary unless otherwise stated.
Date: October 11, 2006
Creator: George, Katherine A.
System: The UNT Digital Library
X-ray Pulse Length Characterization using the Surface Magneto Optic Kerr Effect (open access)

X-ray Pulse Length Characterization using the Surface Magneto Optic Kerr Effect

It will be challenging to measure the temporal profile of the hard X-ray SASE beam independently from the electron beam in the LCLS and other 4th generation light sources. A fast interaction mechanism is needed that can be probed by an ultrafast laser pulse in a pump-probe experiment. It is proposed to exploit the rotation in polarization of light reflected from a thin magnetized film, known as the surface magneto optic Kerr effect (SMOKE), to witness the absorption of the x-ray pulse in the thin film. The change in spin orbit coupling induced by the x-ray pulse occurs on the subfemtosecond time scale and changes the polarization of the probe beam. The limitation to the technique lies with the bandwidth of the probe laser pulse and how short the optical pulse can be made. The SMOKE mechanism will be described and the choices of materials for use with 1.5 {angstrom} x-rays. A schematic description of the pump-probe geometry for x-ray diagnosis is also described.
Date: October 4, 2006
Creator: Krejcik, P.
System: The UNT Digital Library
Performance and Aging Studies of BaBar Resistive Plate Chambers (open access)

Performance and Aging Studies of BaBar Resistive Plate Chambers

The BaBar detector is currently operating nearly 200 Resistive Plate Chambers (RPCs), constructed as part of an upgrade of the forward endcap muon detector in 2002. Although the average RPC efficiency remains high, numerous changes in the RPC performance (increased currents and rates) have been observed. A few of the highest rate RPCs have suffered efficiency losses of more than 15%. Several types of efficiency loss have been observed. Tests with humidified gas have shown that some of the lost efficiency is recoverable. However, efficiency losses in the highest rate regions have not yet improved with humid gases.
Date: October 13, 2006
Creator: Band, H. R.; Hollar, J.; Tan, P.; Anulli, F.; Baldini, R.; Calcaterra, A. et al.
System: The UNT Digital Library
Directional Detection of a Neutron Source. (open access)

Directional Detection of a Neutron Source.

Advantages afforded by the development of new directional neutron detectors and imagers are discussed. Thermal neutrons have mean free paths in air of about 20 meters, and can be effectively imaged using coded apertures. Fission spectrum neutrons have ranges greater than 100 meters, and carry enough energy to scatter at least twice in multilayer detectors which can yield both directional and spectral information. Such strategies allow better discrimination between a localized spontaneous fission source and the low, but fluctuating, level of background neutrons generated by cosmic rays. A coded aperture thermal neutron imager will be discussed as well as a proton-recoil double-scatter fast-neutron directional detector with time-of-flight energy discrimination.
Date: October 23, 2006
Creator: Vanier, P. E. & Forman, L.
System: The UNT Digital Library
Evidence for the Importance of Resonance Scattering in X-Ray Emission Line Profiles of the O Star Zeta Puppis (open access)

Evidence for the Importance of Resonance Scattering in X-Ray Emission Line Profiles of the O Star Zeta Puppis

We fit the Doppler profiles of the He-like triplet complexes of O VII and N VI in the X-ray spectrum of the O star {zeta} Pup, using XMM-Newton RGS data collected over {approx} 400 ks of exposure. We find that they cannot be well fit if the resonance and intercombination lines are constrained to have the same profile shape. However, a significantly better fit is achieved with a model incorporating the effects of resonance scattering, which causes the resonance line to become more symmetric than the intercombination line for a given characteristic continuum optical depth {tau}{sub *}. We discuss the plausibility of this hypothesis, as well as its significance for our understanding of Doppler profiles of X-ray emission lines in O stars.
Date: October 10, 2006
Creator: Leutenegger, M.A.; U., /Columbia; Owocki, S.P.; Inst., /Bartol Research; Kahn, S.M.; /KIPAC, Menlo Park et al.
System: The UNT Digital Library
Black Hole Entropy, Marginal Stability and Mirror Symmetry (open access)

Black Hole Entropy, Marginal Stability and Mirror Symmetry

We consider the superconformal quantum mechanics associated to BPS black holes in type IIB Calabi-Yau compactifications. This quantum mechanics describes the dynamics of D-branes in the near-horizon attractor geometry of the black hole. In many cases, the black hole entropy can be found by counting the number of chiral primaries in this quantum mechanics. Both the attractor mechanism and notions of marginal stability play important roles in generating the large number of microstates required to explain this entropy. We compute the microscopic entropy explicitly in a few different cases, where the theory reduces to quantum mechanics on the moduli space of special Lagrangians. Under certain assumptions, the problem may be solved by implementing mirror symmetry as three T-dualities: this is essentially the mirror of a calculation by Gaiotto, Strominger and Yin. In some simple cases, the calculation may be done in greater generality without resorting to conjectures about mirror symmetry. For example, the K3 x T{sub 2} case may be studied precisely using the Fourier-Mukai transform.
Date: October 6, 2006
Creator: Aspinwall, Paul S.; Maloney, Alexander & Simons, Aaron
System: The UNT Digital Library
Observation of CP violation in B^0 to eta' K^0 (open access)

Observation of CP violation in B^0 to eta' K^0

The authors present measurements of the time-dependent CP-violation parameters S and C in B{sup 0} {yields} K{sup 0} decays. The data sample corresponds to 384 million B{bar B} pairs produced by e{sup +}e{sup -} annihilation at the {Upsilon}(4S). The results are S = 0.58 {+-} 0.10 {+-} 0.03, and C = -0.16 {+-} 0.07 {+-} 0.03. They observe mixing-induced CP violation with a significance of 5.5 standard deviations in this b {yields} s penguin dominated mode.
Date: October 6, 2006
Creator: Aubert, B.
System: The UNT Digital Library
Gamma-Ray Burst Physics with GLAST (open access)

Gamma-Ray Burst Physics with GLAST

The Gamma-ray Large Area Space Telescope (GLAST) is an international space mission that will study the cosmos in the energy range 10 keV-300 GeV, the upper end of which is one of the last poorly observed region of the celestial electromagnetic spectrum. The ancestor of the GLAST/LAT was the Energetic Gamma Ray Experiment Telescope (EGRET) detector, which flew onboard the Compton Gamma Ray Observatory (CGRO). The amount of information and the step forward that the high energy astrophysics made thanks to its 9 years of observations are impressive. Nevertheless, EGRET uncovered the tip of the iceberg, raising many questions, and it is in the light of EGRET's results that the great potential of the next generation gamma-ray telescope can be appreciated. GLAST will have an imaging gamma-ray telescope, the Large Area Telescope (LAT) vastly more capable than instruments own previously, as well as a secondary instrument, the GLAST Bursts Monitor, or GBM, to augment the study of gamma-ray bursts. Gamma-Ray Bursts (GRBs) science is one of the most exciting challenges for the GLAST mission, exploring the high energy emission of one of the most intense phenomena in the sky, shading light on various problems: from the acceleration of particles to …
Date: October 6, 2006
Creator: Omodei, N.
System: The UNT Digital Library
Electromagnetic and Hadron Calorimeters in the MIPP Experiment (open access)

Electromagnetic and Hadron Calorimeters in the MIPP Experiment

The purpose of the MIPP experiment is to study the inclusive production of photons, pions, kaons, and nucleons produced in π, K, and p interactions on various targets using beams from the Main Injector at Fermilab. The purpose of the calorimeters is to measure the production of forward-going photons and neutrons. The electromagnetic calorimeter consists of 10 lead plates interspersed with proportional chambers followed by the hadron calorimeter with 64 steel plates interspersed with scintillator. We collected data with a variety of targets with beam energies from 5 GeV/c up to 120 GeV/c. The energy calibration of both calorimeters with electrons, pions, kaons and protons is discussed. The performance of the calorimeters was tested on a neutron sample.
Date: October 1, 2006
Creator: Nigmanov, T. S.; Gustafson, H. R.; Longo, M. J. & Collaboration), D. Rajaram (MIPP
System: The UNT Digital Library
Proposed Few-optical Cycle Laser-driven ParticleAccelerator Structure (open access)

Proposed Few-optical Cycle Laser-driven ParticleAccelerator Structure

We describe a transparent dielectric grating accelerator structure that is designed for ultra-short laser pulse operation. The structure is based on the principle of periodic field reversal to achieve phase synchronicity for relativistic particles, however to preserve ultra-short pulse operation it does not resonate the laser field in the vacuum channel. The geometry of the structure appears well suited for application with high average power lasers and high thermal loading. Finally, it shows potential for an unloaded gradient of 10 GeV/m with 10 fsec laser pulses and the possibility to accelerate 10{sup 6} electrons per bunch at an efficiency of 8%. The fabrication procedure and a proposed near term experiment with this accelerator structure are presented.
Date: October 6, 2006
Creator: Plettner, T.; Lu, P.; Byer, R.L. & /Stanford U., Ginzton Lab.
System: The UNT Digital Library
Observation of a New D_s Meson Decaying to D K at a Mass of 2.86 GeV/c^2 (open access)

Observation of a New D_s Meson Decaying to D K at a Mass of 2.86 GeV/c^2

The authors observe a new D{sub s} meson with mass (2856.6 {+-} 1.5{sub stat.} {+-} 5.0{sub syst.}) MeV/c{sup 2} and width (48 {+-} 7{sub stat.} {+-} 10{sub syst.}) MeV/c{sup 2} decaying into D{sup 0}K{sup +} and D{sup +}K{sub S}{sup 0}. In the same mass distributions they also observe a broad structure with mass (2688 {+-} 4{sub stat.} {+-} 3{sub syst.}) MeV/c{sup 2} and width (112 {+-} 7{sub stat.} {+-} 36{sub syst.}) MeV/c{sup 2}. To obtain this result they use 240 fb{sup -1} of data recorded by the BABAR detector at the PEP-II asymmetric e{sup +}e{sup -} storage rings at the Stanford Linear Accelerator Center running at center-of-mass energies near 10.6 GeV.
Date: October 4, 2006
Creator: Aubert, B.
System: The UNT Digital Library
Computing Criticality of Lines in Power Systems (open access)

Computing Criticality of Lines in Power Systems

We propose a computationally efficient method based onnonlinear optimization to identify critical lines, failure of which cancause severe blackouts. Our method computes criticality measure for alllines at a time, as opposed to detecting a single vulnerability,providing a global view of the system. This information on criticality oflines can be used to identify multiple contingencies by selectivelyexploring multiple combinations of broken lines. The effectiveness of ourmethod is demonstrated on the IEEE 30 and 118 bus systems, where we canvery quickly detect the most critical lines in the system and identifysevere multiple contingencies.
Date: October 13, 2006
Creator: Pinar, Ali; Reichert, Adam & Lesieutre, Bernard
System: The UNT Digital Library
Welding of dissimilar alloys for high temperature heat exchangers for SOFC (open access)

Welding of dissimilar alloys for high temperature heat exchangers for SOFC

Reduction in the cost of balance of plant applications is one of the top priority focus areas for the successful implementation of solid oxide fuel cell technology. High temperature heat exchangers are employed to heat cathode air utilizing either hot gases coming from the anode side of the stack or other hot gases generated by external processes. In order to reduce the cost of heat exchangers, it may be necessary to apply several different materials, each in a different temperature zone, for the construction of the heat exchanger. This technique would require the joining of dissimilar materials in the construction. In this work, welding of commercial candidate dissimilar materials is explored. Filler materials were identified using equilibrium phase diagrams and thermodynamic simulation software. Autogenous welding was performed and the welding defects were characterized. Finally, experimental weld microstructures were compared to phases predicted by the simulations.
Date: October 1, 2006
Creator: Wilson, R. D.; Hatem, J.; Dogan, O. N. & King, P. E.
System: The UNT Digital Library