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Amplification of an ultra short pulse laser by stimulated Raman scattering of a 1 ns pulse in a low density plasma

Description: Experiments are described in which a 1mJ, 1ps, 1200 nm seed laser beam is amplified by interaction with an intersecting 350 J, 1ns, 1054 nm pump beam in a low density (1 x 10{sup 19}/cm{sup 3}) plasma. The transmission of the seed beam is observed to be enhanced by > {approx} 25 x when the plasma is near the resonant density for stimulated Raman scattering (SRS), compared to measured transmissions at wavelengths just below the resonant value. The amplification is observed to increase rapidly… more
Date: October 8, 2007
Creator: Kirkwood, R. K.; Dewald, E.; Niemann, C.; Meezan, N.; Wilks, S. C.; Price, D. W. et al.
Partner: UNT Libraries Government Documents Department
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Stringy Instantons in IIB Brane Systems

Description: No Description Available.
Date: April 8, 2008
Creator: Kachru, Shamit; Simic, Dusan & /Stanford U., Phys. Dept. /SLAC
Partner: UNT Libraries Government Documents Department
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Transverse Effect Due to Short Range Resistive Wall Wakefield

Description: For accelerator designs with ultra short electron beams, beam dynamics study has to invoke the short-range wakefields. In this paper, we first obtain the short-range dipole mode resistive wall wakefield. Analytical approach is then developed to study the single bunch transverse beam dynamics due to this short-range resistive wall wake. The results are applied to the LCLS undulator.
Date: January 8, 2008
Creator: Delayen, J. R.; Chao, Alexander Wu & Wu, J.
Partner: UNT Libraries Government Documents Department
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Neutron Bang Time Detector Based on a Light Pipe

Description: A neutron bang time detector consisting of a scintillator, light pipe, photomultiplier tube (PMT), and high-bandwidth oscilloscope has been implemented on the 60-beam, 30-kJ OMEGA Laser Facility at the University of Rochester's Laboratory for Laser Energetics. Light from the scintillator, located 23 cm from the target, is transmitted outside the target bay through a 9.6-m-long, 2-in.-diam polished stainless steel pipe to the PMT. The PMT signal is recorded by two channels of a 6-GHz, 10-GS/s Te… more
Date: May 8, 2008
Creator: Glebov, V. Y.; Moran, M.; Stoeckl, C.; Sangster, T. C. & Cruz, M.
Partner: UNT Libraries Government Documents Department
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Self Consistent Monte Carlo Method to Study CSR Effects in Bunch Compressors

Description: In this paper we report on the results of a self-consistent calculation of CSR effects on a particle bunch moving through the benchmark Zeuthen bunch compressors. The theoretical framework is based on a 4D Vlasov-Maxwell approach including shielding from the vacuum chamber. We calculate the fields in the lab frame, where time is the independent variable, and evolve the phase space density/points in the beam frame, where arc length, s, along a reference orbit, is the independent variable. Some d… more
Date: January 8, 2008
Creator: Warnock, R. L.; Bassi, G.; Ellison, J. A. & Heinemann, K. A.
Partner: UNT Libraries Government Documents Department
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Wetting of metals and glasses on Mo

Description: The wetting of low melting point metals and Si-Ca-Al-Ti-O glasses on molybdenum has been investigated. The selected metals (Au, Cu, Ag) form a simple eutectic with Mo. Metal spreading occurs under nonreactive conditions without interdiffusion or ridge formation. The metals exhibit low (non-zero) contact angles on Mo but this requires temperatures higher than 1100 C in reducing atmospheres in order to eliminate a layer of adsorbed impurities on the molybdenum surface. By controlling the oxygen a… more
Date: January 8, 2008
Creator: Saiz, Eduardo; Tomsia, Antoni P.; Saiz, Eduardo; Lopez-Esteban, Sonia; Benhassine, Mehdi; de Coninck, Joel et al.
Partner: UNT Libraries Government Documents Department
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Nuclear diffractive structure functions at high energies

Description: A future high-energy electron-ion collider would explore the non-linear weakly-coupled regime of QCD, and test the Color Glass Condensate (CGC) approach to high-energy scattering. Hard diffraction in deep inelastic scattering off nuclei will provide many fundamental measurements. In this work, the nuclear diffractive structure function F{sub 2,A}{sup D} is predicted in the CGC framework, and the features of nuclear enhancement and suppression are discussed.
Date: August 8, 2008
Creator: Marquet,C.; Kowalski, H.; Lappi, T. & Venugopalan, R.
Partner: UNT Libraries Government Documents Department
open access

Using IOR to analyze the I/O Performance for HPC Platforms

Description: The HPC community is preparing to deploy petaflop-scale computing platforms that may include hundreds of thousands to millions of computational cores over the next 3 years. Such explosive growth in concurrency creates daunting challenges for the design and implementation of the I/O system. In this work, we first analyzed the I/O practices and requirements of current HPC applications and used them as criteria to select a subset of microbenchmarks that reflect the workload requirements. Our analy… more
Date: June 8, 2007
Creator: Shan, Hongzhang & Shalf, John
Partner: UNT Libraries Government Documents Department
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Bond stretching phonon softening and angle-resolved photoemission kinks in optimally doped Bi2Sr1:6La0:4Cu2O6+sigma superconductors

Description: We report the first measurement of the Cu-O bond stretching phonon dispersion in optimally doped Bi2Sr1.6La0.4Cu2O6+delta using inelastic x-ray scattering. We found a softening of this phonon at q=(0.25,0,0) from 76 to 60 meV, similar to the one reported in other cuprates. A comparison with angle-resolved photoemission data on the same sample revealed an excellent agreement in terms of energy and momentum between the angle-resolved photoemission nodal kink and the soft part of the bond stretchi… more
Date: May 8, 2008
Creator: Graf, Jeff; d'Astuto, M.; Jozwiak, C.; Garcia, D.R.; Saini, N.L.; Krisch, M. et al.
Partner: UNT Libraries Government Documents Department
open access

A low-energy linear oxygen plasma source

Description: A new version of a Constricted Plasma Source is described,characterized by all metal-ceramic construction, a linear slit exit of180 mm length, and cw-operation (typically 50 kHz) at an average power of1.5 kW. The plasma source is here operated with oxygen gas, producingstreaming plasma that contains mainly positive molecular and atomic ions,and to a much lesser degree, negative ions. The maximum total ion currentobtained was about 0.5 A. The fraction of atomic ions reached more than10 percent o… more
Date: January 8, 2007
Creator: Anders, Andre & Yushkov, Georgy Yu.
Partner: UNT Libraries Government Documents Department
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Discovery of an Unusual Optical Transient with the Hubble Space Telescope

Description: We present observations of SCP 06F6, an unusual optical transient discovered during the Hubble Space Telescope Cluster Supernova Survey. The transient brightened over a period of ~;;100 days, reached a peak magnitude of ~;;21.0 in both i_775 and z_850, and then declined over a similar timescale. There is no host galaxy or progenitor star detected at the location of the transient to a 3 sigma upper limit of i_775 = 26.4 and z_850 = 26.1, giving a corresponding lower limit on the flux increase of… more
Date: September 8, 2008
Creator: Project, The Supernova Cosmology; Barbary, Kyle; Dawson, Kyle S.; Tokita, Kouichi; Aldering, Greg; Amanullah, Rahman et al.
Partner: UNT Libraries Government Documents Department
open access

First principles calculations of the effect of Pt on NiAl surfaceenergy and the site preference of Pt

Description: Pt-modified NiAl is widely used as a coating material in industry. In this study, the surface energies of NiAl with and without Pt are investigated using first-principles calculations. The presence of Pt in NiAl takes the surface electronic states to higher energies, resulting in an increased surface energy, which explains some of the beneficial effects of Pt on the oxidation resistance of NiAl. The electronic structure of NiAl-Pt alloys is also analyzed in terms of the site preference of Pt in… more
Date: March 8, 2007
Creator: Yu, Rong & Hou, Peggy Y.
Partner: UNT Libraries Government Documents Department
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Breakdown of Electrostatic Predictions for the Nonlinear Dispersion Relation of a Stimulated Raman Scattering-Driven Plasma Wave

Description: The kinetic nonlinear dispersion relation, and frequency shift {delta}{omega}{sub srs}, of a plasma wave driven by stimulated Raman scattering (SRS) are presented. Our theoretical calculations are fully electromagnetic, and use an adiabatic expression for the electron susceptibility which accounts for the change in phase velocity as the wave grows. When k{lambda}{sub D} {approx}> 0.35 (k being the plasma wave number and {lambda}{sub D} the Debye length), {delta}{omega}{sub srs} is significan… more
Date: May 8, 2007
Creator: Benisti, D; Strozzi, D J & Gremillet, L
Partner: UNT Libraries Government Documents Department
open access

Coherent Synchrotron Radiation and Space Charge for a 1-D Bunch on an Arbitrary Planar Orbit

Description: Realistic modeling of coherent synchrotron radiation (CSR) and the space charge force in single-pass systems and rings usually requires at least a two-dimensional (2-D) description of the charge/current density of the bunch. Since that leads to costly computations, one often resorts to a 1-D model of the bunch for first explorations. This paper provides several improvements to previous 1-D theories, eliminating unnecessary approximations and physical restrictions.
Date: January 8, 2008
Creator: Warnock, R. L.
Partner: UNT Libraries Government Documents Department
open access

Cryogenic Neutron Spectrometer Development

Description: Cryogenic microcalorimeter detectors operating at temperatures around {approx}0.1 K have been developed for the last two decades, driven mostly by the need for ultra-high energy resolution (<0.1%) in X-ray astrophysics and dark matter searches [1]. The Advanced Detector Group at Lawrence Livermore National Laboratory has developed different cryogenic detector technologies for applications ranging from X-ray astrophysics to nuclear science and non-proliferation. In particular, we have adapted… more
Date: March 8, 2006
Creator: Niedermayr, T.; Hau, I. D.; Friedrich, S.; Burger, A.; Roy, U. N. & Bell, Z. W.
Partner: UNT Libraries Government Documents Department
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Fourth-Order Method for Numerical Integration of Age- and Size-Structured Population Models

Description: In many applications of age- and size-structured population models, there is an interest in obtaining good approximations of total population numbers rather than of their densities. Therefore, it is reasonable in such cases to solve numerically not the PDE model equations themselves, but rather their integral equivalents. For this purpose quadrature formulae are used in place of the integrals. Because quadratures can be designed with any order of accuracy, one can obtain numerical approximation… more
Date: January 8, 2008
Creator: Iannelli, M; Kostova, T & Milner, F A
Partner: UNT Libraries Government Documents Department
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Substrate-induced band gap opening in epitaxial graphene

Description: Graphene has shown great application potential as the hostmaterial for next-generation electronic devices. However, despite itsintriguing properties, one of the biggest hurdles for graphene to beuseful as an electronic material is the lack of an energy gap in itselectronic spectra. This, for example, prevents the use of graphene inmaking transistors. Although several proposals have been made to open agap in graphene's electronic spectra, they all require complexengineering of the graphene layer… more
Date: September 8, 2007
Creator: Zhou, S. Y.; Gweon, G.-H.; Fedorov, A. V.; First, P. N.; de Heer, W. A.; Lee, D.-H. et al.
Partner: UNT Libraries Government Documents Department
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Experimental measurements of the 15O(alpha,gamma)19Ne reaction rate and the stability of thermonuclear burning on accreting neutron stars

Description: Neutron stars in close binary star systems often accrete matter from their companion stars. Thermonuclear ignition of the accreted material in the atmosphere of the neutron star leads to a thermonuclear explosion which is observed as an X-ray burst occurring periodically between hours and days depending on the accretion rate. The ignition conditions are characterized by a sensitive interplay between the accretion rate of the fuel supply and its depletion rate by nuclear burning in the hot CNO c… more
Date: May 8, 2007
Creator: Fisker, J.; Tan, W.; Goerres, J.; Wiescher, M. & Cooper, R.
Partner: UNT Libraries Government Documents Department
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Distance-Two Interpolation for Parallel Algebraic Multigrid

Description: Algebraic multigrid (AMG) is one of the most efficient and scalable parallel algorithms for solving sparse linear systems on unstructured grids. However, for large three-dimensional problems, the coarse grids that are normally used in AMG often lead to growing complexity in terms of memory use and execution time per AMG V-cycle. Sparser coarse grids, such as those obtained by the Parallel Modified Independent Set coarsening algorithm (PMIS) [7], remedy this complexity growth, but lead to non-sc… more
Date: May 8, 2007
Creator: De Sterck, H; Falgout, R; Nolting, J & Yang, U M
Partner: UNT Libraries Government Documents Department
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AC Loss Analysis on the Superconducting Coupling Magnet in MICE

Description: A pair of coupling solenoids is used in MICE experiment to generate magnetic field which keeps the muons within the iris of thin RF cavity windows. The coupling solenoids have a 1.5-meter inner diameter and will produce 7.4 T peak magnetic field. Three types of AC losses in coupling solenoid are discussed. The affect of AC losses on the temperature distribution within the cold mass during charging and rapid discharging process is analyzed also. The analysis result will be further confirmed by t… more
Date: July 8, 2008
Creator: Wu, Hong; Wang, Li; Green, Michael; Li, LanKai; Xu, FengYu; Liu, XiaoKun et al.
Partner: UNT Libraries Government Documents Department
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A Molecular Assessment of Phylogenetic Relationships and LineageDiversification Within the Family Salamandridae (Amphibia, Caudata)

Description: Phylogenetic relationships among species of the salamanderfamily Salamandridae are investigated using nearly 3000 nucleotide basesof newly reported mitochondrial DNA sequence data from the mtDNA genicregion spanning the genes tRNALeu-COI. This study uses nearlycomprehensive species-level sampling to provide the first completephylogeny for the Salamandridae. Deep phylogenetic relationships amongthe three most divergent lineages in the family Salamandrina terdigitata,a clade comprising the "True"… more
Date: August 8, 2005
Creator: Weisrock, David W.; Papenfuss, Theodore J.; Macey, J. Robert; Litvinchuk, Spartak N.; Polymeni, Rosa; Ugurtas, Ismail H. et al.
Partner: UNT Libraries Government Documents Department
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