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A Femtosecond-Level Fiber-Optics Timing Distribution System Using Frequency-Offset Interferometry

Description: An optical fiber-based frequency and timing distribution system based on the principle of heterodyne interferometry has been in development at LBNL for several years. The fiber drift corrector has evolved from an RF-based to an optical-based system, from mechanical correctors (piezo and optical trombone) to fully electronic, and the electronics from analog to fully digital, all using inexpensive off-the-shelf commodity fiber components. Short-term optical phase jitter and long-term phase drift … more
Date: October 17, 2009
Creator: Staples, J. W.; Byrd, J.; Doolittle, L.; Huang, G. & Wilcox, R.
Partner: UNT Libraries Government Documents Department
open access

Moving toward multilateral mechanisms for the fuel cycle

Description: Multilateral mechanisms for the fuel cycle are seen as a potentially important way to create an industrial infrastructure that will support a renaissance and at the same time not contribute to the risk of nuclear proliferation. In this way, international nuclear fuel cycle centers for enrichment can help to provide an assurance of supply of nuclear fuel that will reduce the likelihood that individual states will pursue this sensitive technology, which can be used to produce nuclear material dir… more
Date: April 17, 2009
Creator: Panasyuk,A.; Rosenthal,M. & Efremov, G. V.
Partner: UNT Libraries Government Documents Department
open access

Dynamic quantum clustering: a tool for visual exploration of structures in data

Description: A given set of data-points in some feature space may be associated with a Schroedinger equation whose potential is determined by the data. This is known to lead to good clustering solutions. Here we extend this approach into a full-fledged dynamical scheme using a time-dependent Schroedinger equation. Moreover, we approximate this Hamiltonian formalism by a truncated calculation within a set of Gaussian wave functions (coherent states) centered around the original points. This allows for analyt… more
Date: October 17, 2009
Creator: Weinstein, Marvin
Partner: UNT Libraries Government Documents Department
open access

A Search for B^{+} \to \ell^{+} \nu_{\ell} Recoiling Against B^{-} \to D^{(*)0}\ell^{-}\bar{\nu}X

Description: We present a search for the decay B{sup +} {yields} {ell}{sup +} {nu}{sub {ell}} ({ell} = {tau}, {mu}, or e) in (458.9 {+-} 5.1) x 10{sup 6} {Upsilon}(4S) decays recorded with the BABAR detector at the SLAC PEP-IIB-Factory. A sample of events with one reconstructed exclusive semi-leptonic B decay (B{sup -} {yields} D{sup 0} {ell}{sup -}{bar {nu}}X) is selected, and in the recoil a search for B{sup +} {yields} {ell}{sup +}{nu}{sub {ell}} signal is performed. The {tau} is identified in the follow… more
Date: April 17, 2009
Creator: Aubert, Bernard; Bona, M.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prencipe, E. et al.
Partner: UNT Libraries Government Documents Department
open access

Particle-In-Cell/Monte Carlo Simulation of Ion Back BomBardment in a High Average Current RF Photo-Gun

Description: In this paper, we report on study of ion back bombardment in a high average current radio-frequency (RF) photo-gun using a particle-in-cell/Monte Carlo simulation method. Using this method, we systematically studied effects of gas pressure, RF frequency, RF initial phase, electric field profile, magnetic field, laser repetition rate, different ion species on ion particle line density distribution, kinetic energy spectrum, and ion power line density distribution back bombardment onto the photoca… more
Date: October 17, 2009
Creator: Qiang, J.
Partner: UNT Libraries Government Documents Department
open access

Higher-Twist Dynamics in Large Transverse Momentum Hadron Production

Description: A scaling law analysis of the world data on inclusive large-p{sub {perpendicular}} hadron production in hadronic collisions is carried out. A significant deviation from leading-twist perturbative QCD predictions at next-to-leading order is reported. The observed discrepancy is largest at high values of x{sub {perpendicular}} = 2p{sub {perpendicular}}/{radical}s. In contrast, the production of prompt photons and jets exhibits the scaling behavior which is close to the conformal limit, in agreeme… more
Date: December 17, 2009
Creator: Arleo, Francois; Brodsky, Stanley J.; Hwang, Dae Sung & Sickles, Anne M.
Partner: UNT Libraries Government Documents Department
open access

Construction of Large Period Symplectic Maps by Interpolative Methods

Description: The goal is to construct a symplectic evolution map for a large section of an accelerator, say a full turn of a large ring or a long wiggler. We start with an accurate tracking algorithm for single particles, which is allowed to be slightly non-symplectic. By tracking many particles for a distance S one acquires sufficient data to construct the mixed-variable generator of a symplectic map for evolution over S, given in terms of interpolatory functions. Two ways to find the generator are conside… more
Date: December 17, 2009
Creator: Warnock, Robert; Cai, Yunhai & Ellison, James A.
Partner: UNT Libraries Government Documents Department
open access

Polarized Antenna Splitting Functions

Description: We consider parton showers based on radiation from QCD dipoles or 'antennae'. These showers are built from 2 {yields} 3 parton splitting processes. The question then arises of what functions replace the Altarelli-Parisi splitting functions in this approach. We give a detailed answer to this question, applicable to antenna showers in which partons carry definite helicity, and to both initial- and final-state emissions.
Date: October 17, 2009
Creator: Larkoski, Andrew J. & Peskin, Michael E.
Partner: UNT Libraries Government Documents Department
open access

Digital Divide in Sub-Saharan African Universities: Recommendations and Monitoring

Description: The Digital Divide prevents Africa from taking advantages of new information technologies. One of the most urgent priorities is to bring the Internet in African Universities, Research, and Learning Centers to the level of other regions of the world. eGY-Africa, and the Sharing Knowledge Foundation are two bottom-up initiatives by scientists to secure better cyber-infrastructure and Internet facilities in Africa. Recommendations by the present scientific communities are being formulated at natio… more
Date: December 17, 2009
Creator: Barry, Boubakar; Chukwuma, Victor; Petitdidier, Monique; Cottrell, Les & Bartons, Charles
Partner: UNT Libraries Government Documents Department
open access

VITRIFICATION OF HIGH LEVEL WASTE AT THE SAVANNAH RIVER SITE

Description: The objective of this study was to experimentally measure the properties and performance of a series of glasses with compositions that could represent high level waste Sludge Batch 5 (SB5) as vitrified at the Savannah River Site Defense Waste Processing Facility. These data were used to guide frit optimization efforts as the SB5 composition was finalized. Glass compositions for this study were developed by combining a series of SB5 composition projections with a group of candidate frits. The st… more
Date: June 17, 2009
Creator: Fox, K. & Peeler, D.
Partner: UNT Libraries Government Documents Department
open access

ASSESSMENTOF BETA PARTICLE FLUX FROM SURFACE CONTAMINATION AS A RELATIVE INDICATOR FOR RADIONUCLIDE DISTRIBUTION ON EXTERNAL SURFACES OF A MULTI-STORY BUILDING IN PRIPYAT

Description: How would we recover if a Radiological Dispersion Device (e.g., dirty bomb) or Improvised Nuclear Device were to detonate in a large city? In order to assess the feasibility of remediation following such an event, several issues would have to be considered, including the levels and characteristics of the radioactive contamination, the availability of the required resources to accomplish decontamination, and the planned future use of the city's structures and buildings. Presently little is known… more
Date: November 17, 2009
Creator: Farfan, E.
Partner: UNT Libraries Government Documents Department
open access

Challenges in Whole-Genome Annotation of Pyrosequenced Eukaryotic Genomes

Description: Pyrosequencing technologies such as 454/Roche and Solexa/Illumina vastly lower the cost of nucleotide sequencing compared to the traditional Sanger method, and thus promise to greatly expand the number of sequenced eukaryotic genomes. However, the new technologies also bring new challenges such as shorter reads and new kinds and higher rates of sequencing errors, which complicate genome assembly and gene prediction. At JGI we are deploying 454 technology for the sequencing and assembly of ever-… more
Date: April 17, 2009
Creator: Kuo, Alan & Grigoriev, Igor
Partner: UNT Libraries Government Documents Department
open access

Towards a PEBB-Based Design Approach for a Marx-Topology ILC Klystron Modulator

Description: Introduced by the U.S. Navy more than a decade ago, the concept of Power Electronic Building Blocks (PEBBs) has been successfully applied in various applications. It is well accepted within the power electronics arena that this concept offers the potential to achieve increased levels of modularity and compactness. This approach is thus ideally suited for applications where easy serviceability and high availability are key, such as the ILC. This paper presents a building block approach for desig… more
Date: October 17, 2009
Creator: Macken, K
Partner: UNT Libraries Government Documents Department
open access

The Evolution of Swift/BAT blazars and the origin of the MeV background

Description: We use 3 years of data from the Swift/BAT survey to select a complete sample of X-ray blazars above 15 keV. This sample comprises 26 Flat-Spectrum Radio Quasars (FSRQs) and 12 BL Lac objects detected over a redshift range of 0.03 < z < 4.0. We use this sample to determine, for the first time in the 15-55 keV band, the evolution of blazars. We find that, contrary to the Seyfert-like AGNs detected by BAT, the population of blazars shows strong positive evolution. This evolution is comparabl… more
Date: October 17, 2009
Creator: Ajello, M.; /SLAC /KIPAC, Menlo Park; Costamante, L.; /Stanford U., HEPL /KIPAC, Menlo Park; Sambruna, R.M.; Gehrels, N. et al.
Partner: UNT Libraries Government Documents Department
open access

Measurements of the LCLS Laser Heater and its impact on the x-ray FEL Performance

Description: The very bright electron beam required for an x-ray free-electron laser (FEL), such as the Linac Coherent Light Source (LCLS), is susceptible to a microbunching instability in the magnetic bunch compressors, prior to the FEL undulator. The uncorrelated electron energy spread in the LCLS can be increased by an order of magnitude to provide strong Landau damping against the instability without degrading the FEL performance. To this end, a 'laser-heater' system has been installed in the LCLS injec… more
Date: December 17, 2009
Creator: Huang, Zhirong; Brachmann, A.; Decker, F. J.; Ding, Y.; Dowell, D.; Emma, P. et al.
Partner: UNT Libraries Government Documents Department
open access

Femtosecond isomerization dynamics in the ethylene cation measured in an EUV-pump NIR-probe configuration

Description: Dynamics in the excited ethylene cation C{sub 2}H{sub 4}{sup +} lead to isomerization to the ethylidene configuration (HC-CH{sub 3}){sup +}, which is predicted to be a transient configuration for electronic relaxation. With an intense femtosecond EUV (extreme ultraviolet) pump pulse to populate the excited state, and an NIR (near infrared) probe pulse to produce the fragments CH{sup +} and CH{sub 3}{sup +} (which provides a direct signature of ethylidene), we measure optimum fragment yields at … more
Date: March 17, 2009
Creator: van Tilborg, Jeroen; Allison, Tom; Wright, Travis; Hertlein, Marc; Falcone, Roger; Liu, Yanwei et al.
Partner: UNT Libraries Government Documents Department
open access

Next Generation Fast RF Interlock Module and ATCA Adapter for ILC High Availability RF Test Station Demonstration

Description: High availability interlocks and controls are required for the ILC (International Linear Collider) L-Band high power RF stations. A new F3 (Fast Fault Finder) VME module has been developed to process both fast and slow interlocks using FPGA logic to detect the interlock trip excursions. This combination eliminates the need for separate PLC (Programmable Logic Controller) control of slow interlocks. Modules are chained together to accommodate as many inputs as needed. In the next phase of develo… more
Date: October 17, 2009
Creator: Larsen, R.
Partner: UNT Libraries Government Documents Department
open access

Impact of Eliminating Mercury Removal Pretreatment on the Performance of a High Level Radioactive Waste Melter Offgas System

Description: The Defense Waste Processing Facility at the Savannah River Site processes high-level radioactive waste from the processing of nuclear materials that contains dissolved and precipitated metals and radionuclides. Vitrification of this waste into borosilicate glass for ultimate disposal at a geologic repository involves chemically modifying the waste to make it compatible with the glass melter system. Pretreatment steps include removal of excess aluminum by dissolution and washing, and processing… more
Date: March 17, 2009
Creator: Zamecnik, J. & Alexander Choi, A.
Partner: UNT Libraries Government Documents Department
open access

High harmonic phase in molecular nitrogen

Description: Electronic structure in atoms and molecules modulates the amplitude and phase of high harmonic generation (HHG). We report measurements of the high harmonic spectral amplitude and phase in N{sub 2}. The phase is measured interferometrically by beating the N{sub 2} harmonics with those of an Ar reference oscillator in a gas mixture. A rapid phase shift of 0.2{pi} is observed in the vicinity of the HHG spectral minimum, where a shift of {pi} had been presumed [J. Itatani et al., Nature 432, 867 (… more
Date: October 17, 2009
Creator: McFarland, Brian K.
Partner: UNT Libraries Government Documents Department
open access

Binary Pseudo-Random Gratings and Arrays for Calibration of Modulation Transfer Function of Surface Profilometers

Description: In the present work, we describe application of binary pseudo-random gratings (BPRG) and arrays (BPRA) as effective 1D and 2D test surfaces suitable for calibration of different surface profilometers, including a number of interferometric microscopes and scatterometers.
Date: June 17, 2009
Creator: Barber, Samuel K.; Anderson, Erik D.; Cambie, Rossana; McKinney, Wayne R.; Takacs, Peter Z.; Stover, John C. et al.
Partner: UNT Libraries Government Documents Department
open access

Progress in Beam Focusing and Compression for Target Heating and Warm Dense Matter Experiments

Description: The Heavy-Ion Fusion Sciences Virtual National Laboratory is pursuing an approach to target heating experiments in the warm dense matter regime, using space-charge-dominated ion beams that are simultaneously longitudinally bunched and transversely focused. Longitudinal beam compression by large factors has been demonstrated in the Neutralized Drift Compression Experiment (NDCX) with controlled ramps and forced neutralization. Using an injected 30 mA K{sup +} ion beam with initial kinetic energy… more
Date: April 17, 2009
Creator: Seidl, Peter A.; Anders, A.; Bieniosek, F. M.; Barnard, J. J.; Cohen, R. H.; Coleman, J. E. et al.
Partner: UNT Libraries Government Documents Department
open access

The Quasiparticle Puzzle: Reconciling ARPES and FTSTS Studies of Bi2212

Description: Angle Resolved Photoemission Spectroscopy (ARPES) probes the momentum-space electronic structure of materials, and provides invaluable information about the high-temperature superconducting cuprates. Likewise, cuprates real-space, inhomogeneous electronic structure is elucidated by Scanning Tunneling Spectroscopy (STS). Recently, STS has exploited quasiparticle interference (QPI) - wave-like electrons scattering off impurities to produce periodic interference patterns - to infer properties of t… more
Date: December 17, 2009
Creator: Vishik, I. M.; Nowadnick, E. A.; Lee, W. S.; Shen, Z. X.; /Stanford U., Materials Sci. Dept. /SLAC /Stanford U., Geballe Lab. /Stanford U., Appl. Phys. Dept. /Stanford U., Phys. Dept.; Moritz, B. et al.
Partner: UNT Libraries Government Documents Department
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