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A Unified Model of Secondary Electron Cascades in Diamond

Description: In this paper we present a detailed and unified theoretical treatment of secondary electron cascades that follow the absorption of an X-ray photon. A Monte Carlo model has been constructed that treats in detail the evolution of electron cascades induced by photoelectrons and by Auger electrons following inner shell ionizations. Detailed calculations are presented for cascades initiated by electron energies between 0.1-10 keV. The present paper expands our earlier work by extending the primary e… more
Date: October 13, 2004
Creator: Ziaja, B; London, R A & Hajdu, J
Partner: UNT Libraries Government Documents Department
open access

Monolithic Nickel (II) Oxide Aerogels Using an Organic Epoxide: The Importance of the Counter Ion

Description: The synthesis and characterization of nickel (II) oxide aerogel materials prepared using the epoxide addition method is described. The addition of the organic epoxide propylene oxide to an ethanolic solution of NiCl{sub 2} 6H{sub 2}O resulted in the formation of an opaque light green monolithic gel and subsequent drying with supercritical CO{sub 2} gave a monolithic aerogel material of the same color. This material has been characterized using powder X-ray diffraction, electron microscopy, elem… more
Date: January 13, 2004
Creator: Gash, A. E.; Satcher, J. H. & Simpson, R. L.
Partner: UNT Libraries Government Documents Department
open access

Intracavity adaptive correction of a 10 kW, solid-state, heat-capacity laser

Description: The Solid-State, Heat-Capacity Laser (SSHCL), under development at Lawrence Livermore National Laboratory (LLNL) is a large aperture (100 cm{sup 2}), confocal, unstable resonator requiring near-diffraction-limited beam quality. There are two primary sources of the aberrations in the system: residual, static aberrations from the fabrication of the optical components and predictable, time-dependent, thermally-induced index gradients within the gain medium. A deformable mirror placed within the ca… more
Date: May 13, 2004
Creator: LaFortune, K N; Hurd, R L; Brase, J M & Yamamoto, R M
Partner: UNT Libraries Government Documents Department
open access

Surrogate Nuclear Reactions and the Origin of the Heavy Elements

Description: An innovative method for indirectly determining reaction cross sections via Surrogate Nuclear Reactions is presented. Exploring indirect approaches for obtaining reaction cross sections is important since a large number of nuclear reactions relevant to astrophysics cannot be measured with currently available techniques. A program is outlined for developing a comprehensive framework for planning and interpreting experiments that can yield the cross sections of interest. The applications will foc… more
Date: July 13, 2004
Creator: Escher, J; Ahle, L; Bernstein, L; Church, J; Dietrich, F; Forssen, C et al.
Partner: UNT Libraries Government Documents Department
open access

Including dislocation flux in a continuum crystal plasticity model to produce size scale effects

Description: A novel model has been developed to capture size scale and gradient effects within the context of continuum crystal plasticity by explicitly incorporating details of dislocation transport, coupling dislocation transport to slip, evolving spatial distributions of dislocations consistent with the flux, and capturing the interactions among various dislocation populations. Dislocation flux and density are treated as nodal degrees of freedom in the finite element model, and they are determined as pa… more
Date: February 13, 2004
Creator: Becker, R.; Arsenlis, A.; Bulatov, V. V. & Parks, D. M.
Partner: UNT Libraries Government Documents Department
open access

The Effect of Small-Size Habitat Disturbances on Population Density and Time to Extinction of the Prairie Vole

Description: We present a study, based on simulations with SERDYCA, a spatially-explicit individual-based model of rodent dynamics, on the relation between population persistence and the presence of numerous isolated disturbances in the habitat. We are specifically interested in the effect of disturbances that do not fragment the environment on population persistence. Our results suggest that the presence of disturbances in the absence of fragmentation can actually increase the average time to extinction of… more
Date: December 13, 2004
Creator: Kostova, T & Carlsen, T
Partner: UNT Libraries Government Documents Department
open access

Femtosecond laser writing of waveguide structures in sodium calcium silicate glasses

Description: Waveguides were written in soda lime silicate glasses with a composition of xNa{sub 2}O xCaO (1-2x)SiO{sub 2}, where x = 15 and 20, using an amplified femtosecond laser. The waveguides formed around, not inside the exposed regions. This is similar to the waveguide behavior our group first observed in a phosphate glass, Schott IOG-1, and is distinctly different from fused silica in which the waveguides are inside the exposed regions. This data supports the rapid quenching theory, i.e. that the e… more
Date: December 13, 2004
Creator: Reichman, W J; Click, C A & Krol, D M
Partner: UNT Libraries Government Documents Department
open access

A Progressive Subdivision Paradigm (PSP)

Description: The increasing rate of growth in size of currently available datasets is a well known issue. The possibility of developing fast and easy to implement frameworks able to visualize at least part of a tera-sized volume is a challenging task. Subdivision methods in recent years have been one of the most successful techniques applied to the multiresolution representation and visualization of surface meshes. Extensions of these techniques to the volumetric case presents positive effects and major cha… more
Date: December 13, 2004
Creator: Borgo, R.; Scopigno, R.; Cignoni, P. & Pascucci, V.
Partner: UNT Libraries Government Documents Department
open access

Structure, Stability and ELM Dynamics of the H-Mode Pedestal in DIII-D

Description: Experiments are described that have increased understanding of the transport and stability physics that set the H-mode edge pedestal width and height, determine the onset of Type-I edge localized modes (ELMs), and produce the nonlinear dynamics of the ELM perturbation in the pedestal and scrape-off layer (SOL). Predictive models now exist for the n{sub e} pedestal profile and the p{sub e} height at the onset of Type-I ELMs, and progress has been made toward predictive models of the T{sub e} ped… more
Date: October 13, 2004
Creator: Fenstermacher, M. E.; Leonard, A. W.; Osborne, T. H.; Snyder, P. B.; Thomas, D. M.; Boedo, J. A. et al.
Partner: UNT Libraries Government Documents Department
open access

An assesment of yttrium optical constants in the EUV using Mo/Y multilayers designed as linear polarizers

Description: We have produced and characterized Mo/Y multilayers designed as linear-polarizers for use near {lambda} {approx} 8 nm. By depositing these films directly onto silicon photodiodes, we are able to measure both reflectance and transmittance in the EUV using synchrotron radiation. These measurements have been used to access the accuracy of yttrium optical constants in this wavelength range. We describe our experimental results and discuss the prospects for the future development of efficient EUV po… more
Date: September 13, 2004
Creator: Kjornrattanawanich, B; Soufli, R; Bajt, S; Windt, D L & Seely, J F
Partner: UNT Libraries Government Documents Department
open access

A Filter-Fluorescer Diagnostic System (FFLEX) for the National Ignition Facility (NIF)

Description: An early Filter-Fluorescer Diagnostic System (FFLEX) is being fielded at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) to measure the amount of hard x-rays (20 < hv < 150 keV) generated in laser fusion experiments. From these measurements we hope to quantify the number of hot (20 to 50 keV) electrons produced in laser fusion experiments. The Measurement of hot electron production is important for ignition experiments because these electrons can preh… more
Date: April 13, 2004
Creator: McDonald, J. W.; Kauffman, R. L.; Celeste, J. R.; Rhodes, M. A.; Lee, F. D.; Suter, L. J. et al.
Partner: UNT Libraries Government Documents Department
open access

On Multigrid for Overlapping Grids

Description: The solution of elliptic partial differential equations on composite overlapping grids using multigrid is discussed. An approach is described that provides a fast and memory efficient scheme for the solution of boundary value problems in complex geometries. The key aspects of the new scheme are an automatic coarse grid generation algorithm, an adaptive smoothing technique for adjusting residuals on different component grids, and the use of local smoothing near interpolation boundaries. Other im… more
Date: January 13, 2004
Creator: Henshaw, W
Partner: UNT Libraries Government Documents Department
open access

Current Status of Radiation Transport Tools for Proliferation and Terrorism Prevention

Description: We present the current status and future plans for the set of calculational tools and data bases developed and maintained at LLNL. The calculational tools include the Monte Carlo codes TART and COG as well as the deterministic code ARDRA. In addition to these codes presently in use there is a major development effort for a new massively parallel transport code. An important part of the capability we're developing is a sophisticated user interface, based on a commercial 3-D modeling product, to … more
Date: September 13, 2004
Creator: Sale, K E
Partner: UNT Libraries Government Documents Department
open access

Non-Scaling Fixed Field Gradient Optimization.

Description: Optimization of the non-scaling FFAG lattice for the specific application of the muon acceleration with respect to the minimum orbit offsets, minimum path length and smallest circumference is described. The short muon lifetime requires fast acceleration. The acceleration is in this work assumed to be with super-conducting cavities. This sets up a condition of acceleration at the top of the sinusoidal RF wave.
Date: October 13, 2004
Creator: Trbojevic, D.
Partner: UNT Libraries Government Documents Department
open access

Proposal for Reduction of Transverse Emittance of Bnl 200 Mev Linac.

Description: BNL has a plan to upgrade the AGS proton beam from the current 0.14 MW to higher than 1.0 MW and beyond for a neutrino facility which consists of two major subsystems. First is a 1.45 GeV superconducting linac (SCL) to replace the Booster as injector for the AGS. Second is the performance upgrade for the AGS itself for the higher intensity and repetition rate. For high intensity proton accelerators, such as the upgraded AGS, there are very stringent limitations on uncontrolled beam losses. A di… more
Date: August 13, 2004
Creator: Raparia, D.; Alessij.; Beebe-Wang, J. & Weng, W. T.
Partner: UNT Libraries Government Documents Department
open access

Preliminary Performance Measurements for a Streak Camera with a Large-Format Direct-Coupled CCD Readout

Description: Livermore's ICF Program has a large inventory of optical streak cameras built in the 1970s and 1980s. The cameras are still very functional, but difficult to maintain because many of their parts are obsolete including the original streak tube and image-intensifier tube. The University of Rochester's Laboratory for Laser Energetics is leading an effort to develop a fully automated, large-format streak camera that incorporates modern technology. Preliminary characterization of a prototype camera … more
Date: April 13, 2004
Creator: Lerche, R. A.; McDonald, J. W.; Griffith, R. L.; de Dios, G. V.; Andrews, D. S.; Huey, A. W. et al.
Partner: UNT Libraries Government Documents Department
open access

Recent Results From Optimization Studies of Linear Non-Scaling Ffags for Muon Acceleration.

Description: Because of the highly repetitive nature and simple cell structure of FFAG lattices, it is possible to automatically design these lattices. In designing an FFAG lattice, one will try to meet certain constraints and then minimize some cost function by varying any remaining free parameters. I will first review previously published work on optimized FFAG design. Then I will describe recent advances in the understanding of linear non-scaling FFAG design that have come from these optimization techniq… more
Date: October 13, 2004
Creator: Berg, J. S.
Partner: UNT Libraries Government Documents Department
open access

How to study weakly coupled neutral vector bosons

Description: A weakly coupled new neutral gauge boson, forming a narrow resonance, can be efficiently produced at e{sup +}e{sup -} colliders through radiative return processes if the collider energy is larger than the gauge boson mass. This contribution analyzes the sensitivity of a future linear collider for weakly coupled gauge bosons and briefly discusses how, in case of discovery, its properties can be determined with high precision.
Date: August 13, 2004
Creator: afreitas@fnal.gov, Ayres Freitas
Partner: UNT Libraries Government Documents Department
open access

Global analysis of inclusive B decays

Description: In light of the large amount of new experimental data, we revisit the determination of |V{sub cb}| and m{sub b} from inclusive semileptonic and radiative B decays. We study shape variables to order {Lambda}{sub QCD}{sup 3}/m{sub b}{sup 3} and {alpha}{sub s}{sup 2}{beta}{sub 0}, and include the order {alpha}{sub s} {Lambda}{sub QCD}/m{sub b} correction to the hadron mass spectrum in semileptonic decay, which improves the agreement with the data. We focus on the 1S and kinetic mass schemes for th… more
Date: August 13, 2004
Creator: Bauer, Christian W.; Ligeti, Zoltan; Luke, Michael; Manohar, Aneesh & Trott, Michael
Partner: UNT Libraries Government Documents Department
open access

Complete photo-fragmentation of the deuterium molecule

Description: All properties of molecules, from binding and excitation energies to their geometry, are determined by the highly correlated initial state wavefunction of the electrons and nuclei. Perhaps surprisingly, details of these correlations can be revealed by studying the break-up of these systems into their constituents. The fragmentation might be initiated by the absorption of a single photon [1, 2, 3, 4, 5, 6], collision with a charged particle [7, 8] or exposure to a strong laser pulse [9, 10]. If … more
Date: May 13, 2004
Creator: Weber, Thorsten; Czasch, Achim O.; Jagutzki, Ottmar; Muller, Alkis K.; Mergel, Volker; Kheifets, A. et al.
Partner: UNT Libraries Government Documents Department
open access

Immiscibility in the NiFe2O4-NiCr2O4 Spinel Binary

Description: The solid solution behavior of the Ni(Fe{sub 1-n}Cr{sub n}){sub 2}O{sub 4} spinel binary is investigated in the temperature range 400-1200 C. Non-ideal solution behavior, as exhibited by non-linear changes in lattice parameter with changes in n, is observed in a series of single-phase solids air-cooled from 1200 C. Air-annealing for one year at 600 C resulted in partial phase separation in a spinel binary having n = 0.5. Spinel crystals grown from NiO, Fe{sub 2}O{sub 3} and Cr{sub 2}O{sub 3} re… more
Date: August 13, 2004
Creator: Ziemniak, S
Partner: UNT Libraries Government Documents Department
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