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To Crack or Not to Crack: Strain in High TemperatureSuperconductors

Description: Round wire Bi 2212 is emerging as a viable successor ofNb3Sn in High Energy Physics and Nuclear Magnetic Resonance, to generatemagnetic fields that surpass the intrinsic limitations of Nb3Sn. Ratherbold claims are made on achievable magnetic fields in applications usingBi 2212, due to the materials' estimated critical magnetic field of 100 Tor higher. High transport currents in high magnetic fields, however, leadto large stress on, and resulting large strain in the superconductor. Theeffect of … more
Date: August 22, 2007
Creator: Godeke, Arno
Partner: UNT Libraries Government Documents Department
open access

ECLOUD in PS2, PS+, SPS+: AN UPDATE

Description: We present an update of our results for the electron-cloud build-up for several upgrades proposed for the LHC injectors. Specifically, we have re-examined our published results for the ecloud heat load [1] from the perspective of numerical convergence of the simulations vis-a-vis the integration time step {Delta}t. We repeated most of the simulations with ever smaller values of {Delta}t until we reached stable results, indicating numerical convergence; this was achieved at 200-500 slices per bu… more
Date: May 22, 2007
Creator: Furman, M. A.
Partner: UNT Libraries Government Documents Department
open access

Defect Doping of InN

Description: InN films grown by molecular beam epitaxy have been subjected to 2 MeV He{sup +} irradiation followed by thermal annealing. Theoretical analysis of the electron mobilities shows that thermal annealing removes triply charged donor defects, creating films with electron mobilities approaching those predicted for uncompensated, singly charged donors. Optimum thermal annealing of irradiated InN can be used to produce samples with electron mobilities higher than those of as grown films.
Date: July 22, 2007
Creator: Jones, R. E.; van Genuchten, H. C. M.; Yu, K. M.; Walukiewicz, W.; Li, S. X.; A ger III, J. W. et al.
Partner: UNT Libraries Government Documents Department
open access

Black ring deconstruction

Description: We present a sample microstate for a black ring in four and five dimensional language. The microstate consists of a black string microstate with an additional D6-brane. We show that with an appropriate choice of parameters the piece involving the black string microstate falls down a long AdS throat, whose M-theory lift is AdS_3 x S2. We wrap a spinning dipole M2-brane on the S2 in the probe approximation. In IIA, this corresponds to a dielectric D2-brane carrying only D0-charge. We conjecture t… more
Date: June 22, 2007
Creator: Gimon, Eric; Gimon, Eric G. & Levi, Thomas S.
Partner: UNT Libraries Government Documents Department
open access

Irreversible volume growth in polymer-bonded powder systems: effects of crystalline anisotropy, particle size distribution, and binder strength

Description: Pressed-powdered crystallites of intrinsically anisotropic materials have been shown to undergo irreversible volume expansion when subjected to repeated cycles of heating and cooling. We develop a coarse-grained (micron-scale) interaction Hamiltonian for this system and perform molecular dynamics simulations, which quantitatively reproduce the experimentally observed irreversible growth. The functional form and values of the interaction parameters at the coarse-grained level are motivated by ou… more
Date: August 22, 2007
Creator: Maiti, A.; Gee, R. H.; Hoffman, D. & Fried, L. E.
Partner: UNT Libraries Government Documents Department
open access

Plasma density gradient injection of low absolute momentum spread electron bunches

Description: Plasma density gradients in a gas jet were used to control the wake phase velocity and trapping threshold in a laser wakefield accelerator, producing stable electron bunches with longitudinal and transverse momentum spreads more than ten times lower than in previous experiments (0.17 and 0.02 MeV/c FWHM, respectively) and with central momenta of 0.76 +- 0.02 MeV/c. Transition radiation measurements combined with simulations indicated that the bunches can be used as a wakefield accelerator injec… more
Date: December 22, 2007
Creator: Geddes, C. G. R.; Nakamura, K.; Plateau, G. R.; Toth, Cs.; Cormier-Michel, E.; Esarey, E. et al.
Partner: UNT Libraries Government Documents Department
open access

Development of a Cell-Based Fluorescence Resonance Energy Transfer Reporter for Bacillus anthracis Lethal Factor Protease

Description: We report the construction of a cell-based fluorescent reporter for anthrax lethal factor (LF) protease activity using the principle of fluorescence resonance energy transfer (FRET). This was accomplished by engineering an Escherichia coli cell line to express a genetically encoded FRET reporter and LF protease. Both proteins were encoded in two different expression plasmids under the control of different tightly controlled inducible promoters. The FRET-based reporter was designed to contain a … more
Date: March 22, 2007
Creator: Kimura, R H; Steenblock, E R & Camarero, J A
Partner: UNT Libraries Government Documents Department
open access

Ab Initio Study of 40Ca with an Importance Truncated No-Core Shell Model

Description: We propose an importance truncation scheme for the no-core shell model, which enables converged calculations for nuclei well beyond the p-shell. It is based on an a priori measure for the importance of individual basis states constructed by means of many-body perturbation theory. Only the physically relevant states of the no-core model space are considered, which leads to a dramatic reduction of the basis dimension. We analyze the validity and efficiency of this truncation scheme using differen… more
Date: May 22, 2007
Creator: Roth, R & Navratil, P
Partner: UNT Libraries Government Documents Department
open access

U.S. and Russian Collaboration in the Area of Nuclear Forensics

Description: Nuclear forensics has become increasingly important in the fight against illicit trafficking in nuclear and other radioactive materials. The illicit trafficking of nuclear materials is, of course, an international problem; nuclear materials may be mined and milled in one country, manufactured in a second country, diverted at a third location, and detected at a fourth. There have been a number of articles in public policy journals in the past year that call for greater interaction between the U.… more
Date: October 22, 2007
Creator: Kristo, M J
Partner: UNT Libraries Government Documents Department
open access

Study of low-lying resonant states in 16F using an 15O radioactiveion beam

Description: A 120 MeV {sup 15}O radioactive ion beam with an intensity on target of 4.5 x 10{sup 4} pps has been developed at the 88-inch cyclotron at the Lawrence Berkeley National Laboratory. This beam has been used to study the level structure of {sup 16}F at low energies via the p({sup 15}O,p) reaction using the thick target inverse kinematics method on a polyethylene target. The experimental excitation function was analyzed using R-matrix calculations. Significantly improved values for the level width… more
Date: January 22, 2007
Creator: Lee, D. W.; Perajarvi, K.; Powell, J.; O'Neil, J. P.; Moltz, D. M.; Goldberg, V. Z. et al.
Partner: UNT Libraries Government Documents Department
open access

Review of Understanding the Micro to Macro Behaviour of Rock FluidSystems

Description: The book consists of a series of summaries of studies supported by the Natural Environmental Research Council's thematic program of the same name. The objective of this research initiative was to improve understanding and characterization of subsurface fluid flow over a wide range of spatial scales through field investigations, laboratory studies, and computer simulations of these processes.
Date: January 22, 2007
Creator: Cortis, A.; Dobson, P. F. & Liu, H. H.
Partner: UNT Libraries Government Documents Department
open access

Diffusion of a Highly-Charged Supramolecular Assembly: Direct Observation of Ion-Association in Water

Description: Understanding the solution behavior of supramolecular assemblies is essential for a full understanding of the formation and chemistry of synthetic host-guest systems. While the interaction between host and guest molecules is generally the focus of mechanistic studies of host-guest complexes, the interaction of the host-guest complex with other species in solution remains largely unknown, although in principle accessible by diffusion studies. Several NMR techniques are available to monitor diffu… more
Date: October 22, 2007
Creator: University of California, Berkeley; Laboratory, Lawrence Berkeley National; Raymond, Kenneth; Pluth, Michael D.; Tiedemann, Bryan E.F.; van Halbeek, Herman et al.
Partner: UNT Libraries Government Documents Department
open access

Particle Simulation of Coulomb Collisions: Comparing the Methods of Takizuka & Abe and Nanbu

Description: The interactions of charged particles in a plasma are in a plasma is governed by the long-range Coulomb collision. We compare two widely used Monte Carlo models for Coulomb collisions. One was developed by Takizuka and Abe in 1977, the other was developed by Nanbu in 1997. We perform deterministic and stochastic error analysis with respect to particle number and time step. The two models produce similar stochastic errors, but Nanbu's model gives smaller time step errors. Error comparisons betwe… more
Date: May 22, 2007
Creator: Wang, C.; Lin, T.; Caflisch, R.; Cohen, B. & Dimits, A.
Partner: UNT Libraries Government Documents Department
open access

ABSOLUTE BUNCH LENGTH MEASUREMENTS AT THE ALS BY INCOHERENTSYNCHROTRON RADIATION FLUCTUATION ANALYSIS

Description: By analysing the pulse to pulse intensity fluctuations ofthe radiation emitted by a charge particle in the incoherent part of thespectrum, it is possible to extract information about the spatialdistribution of the beam. At the Advanced Light Source (ALS) of theLawrence Berkeley National Laboratory, we have developed and tested asimple scheme based on this principle that allows for the absolutemeasurement of the bunch length. A description of the method and theexperimental results are presented.
Date: June 22, 2007
Creator: Sannibale, Fernando; Zolotorev, Max S.; Filippetto, Daniele & Stupakov, Gennady V.
Partner: UNT Libraries Government Documents Department
open access

Development of a Novel Depleted Uranium Treatment Process at Lawrence Livermore National Laboratory

Description: A three-stage process was developed at Lawrence Livermore National Laboratory to treat potentially pyrophoric depleted uranium metal wastes. The three-stage process includes waste sorting/rinsing, acid dissolution of the waste metal with a hydrochloric and phosphoric acid solution, and solidification of the neutralized residuals from the second stage with clay. The final product is a solid waste form that can be transported to and disposed of at a permitted low-level radioactive waste disposal … more
Date: January 22, 2007
Creator: Gates-Anderson, D.; Bowers, J.; Laue, C. & Fitch, T.
Partner: UNT Libraries Government Documents Department
open access

Global Cooling: Effect of Urban Albedo on Global Temperature

Description: In many urban areas, pavements and roofs constitute over 60% of urban surfaces (roof 20-25%, pavements about 40%). The roof and the pavement albedo can be increased by about 0.25 and 0.10, respectively, resulting in a net albedo increase for urban areas of about 0.1. Many studies have demonstrated building cooling-energy savings in excess of 20% upon raising roof reflectivity from an existing 10-20% to about 60%. We estimate U.S. potential savings in excess of $1 billion (B) per year in net ann… more
Date: May 22, 2007
Creator: Akbari, Hashem; Menon, Surabi & Rosenfeld, Arthur
Partner: UNT Libraries Government Documents Department
open access

Nonlocal exchange correlation in screened-exchange densityfunctional methods

Description: We present a systematic study on the exchange-correlationeffects in screened-exchange local density functional method. Toinvestigate the effects of the screened-exchange potential in the bandgap correction, we have compared the exchange-correlation potential termin the sX-LDA formalism with the self-energy term in the GWapproximation. It is found that the band gap correction of the sX-LDAmethod primarily comes from the downshift of valence band states,resulting from the enhancement of bonding a… more
Date: April 22, 2007
Creator: Lee, Byounghak; Wang, Lin-Wang; Spataru, Catalin D. & Louie,Steven G.
Partner: UNT Libraries Government Documents Department
open access

Progress on Modeling of Ultrafast X-Ray Streak Cameras

Description: Streak cameras continue to be useful tools for studying phenomena on the picoseconds time scale. We have employed accelerator modeling tools to understand and possibly improve the time resolution of present and future streak cameras. This effort has resulted in an end-to-end model of the camera. This model has contributed to the recent measurement of 230 fsec (FWHM) resolution measured at 266 nm in the Advanced Light Source Streak Camera Laboratory. We describe results from this model that show… more
Date: June 22, 2007
Creator: Huang, G.; Byrd, J.M.; Feng, J.; Qiang, J. & Wang, W.
Partner: UNT Libraries Government Documents Department
open access

Progress on H5Part: A Portable High Performance Parallel DataInterface for Electromagnetics Simulations

Description: Significant problems facing all experimental andcomputationalsciences arise from growing data size and complexity. Commonto allthese problems is the need to perform efficient data I/O ondiversecomputer architectures. In our scientific application, thelargestparallel particle simulations generate vast quantitiesofsix-dimensional data. Such a simulation run produces data foranaggregate data size up to several TB per run. Motived by the needtoaddress data I/O and access challenges, we have impleme… more
Date: June 22, 2007
Creator: Adelmann, Andreas; Gsell, Achim; Oswald, Benedikt; Schietinger,Thomas; Bethel, Wes; Shalf, John et al.
Partner: UNT Libraries Government Documents Department
open access

Measurements of the intercombination and forbidden lines from helium-like ions in Tokamaks and Electron Beam Ion Traps

Description: The paper reviews the results from tokamak experiments for the line ratios x/w, y/w, and z/w from helium-like ions with Z in the range from 14 to 28. With exception of the DITE experiments, where these line ratios were found to be in agreement with theoretical predictions, all other tokamak experiments yielded values that were significantly larger than predicted. The reasons for these discrepancies are not yet understood. It is possible that radial profile effects were not properly taken into a… more
Date: August 22, 2007
Creator: Bitter, M.; Hill, K. W.; Von Goeler, S.; Stodiek, W.; Beiersdorfer, P.; Rice, J. E. et al.
Partner: UNT Libraries Government Documents Department
open access

EVALUATION OF FLOWSHEET CHANGES FOR THE HIGHLY ENRICHED URANIUM BLENDDOWN PROGRAM

Description: H Canyon is considering a flowsheet change for Plutonium (Pu) Contaminated Scrap (PuCS) material. The proposed change is to route dissolved PuCS material directly to a uranium (U) storage tank. As a result, the PuCS solution will bypass Head End and First U Cycle, and will be purified by solvent extraction in Second U Cycle. The PuCS solution contains appreciable amounts of boron (B) and fluoride (F{sup -}), which are currently at trace levels in the U storage tank. Though unlikely, if the B co… more
Date: October 22, 2007
Creator: Crowder, M.; Rudisill, T.; Laurinat, J. & Mickalonis, J.
Partner: UNT Libraries Government Documents Department
open access

Performance of the Anti-Coincidence Detector on the GLAST Large Area Telescope

Description: The Anti-Coincidence Detector (ACD), the outermost detector layer in the Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT), is designed to detect and veto incident cosmic ray charged particles, which outnumber cosmic gamma rays by 3-4 orders of magnitude. The challenge in ACD design is that it must have high (0.9997) detection efficiency for singly-charged relativistic particles, but must also have a low probability for self-veto of high-energy gammas by backsplash radiati… more
Date: October 22, 2007
Creator: Thompson, D. J.; Charles, E.; Hartman, R. C.; Moiseev, A. A. & Ormes, J. F.
Partner: UNT Libraries Government Documents Department
open access

Large-Format X-Ray Pinhole Camera

Description: National Security Technologies, LLC, has successfully implemented many scientific and engineering innovations in the new Large-Format Pinhole Camera (LFPHC), which have dramatically increased the detection sensitivity and reliability of the camera in exotic locations, such as the Sandia National Laboratories Z-facility. Quality improvements of the LFPHC have been demonstrated in its fielding at Z, where high-quality images were recorded. A major improvement was the development of a new, user-fr… more
Date: June 22, 2007
Creator: Joseph, Nathan; Tibbits, Aric; Wu, Ming & Chandler, Gordon
Partner: UNT Libraries Government Documents Department
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