135 Matching Results

Search Results

Results: 1 - 24 next
open access

Exp6-polar thermodynamics of dense supercritical water

Description: We introduce a simple polar fluid model for the thermodynamics of dense supercritical water based on a Buckingham (exp-6) core and point dipole representation of the water molecule. The proposed exp6-polar thermodynamics, based on ideas originally applied to dipolar hard spheres, performs very well when tested against molecular dynamics simulations. Comparisons of the model predictions with experimental data available for supercritical water yield excellent agreement for the shock Hugoniot, iso… more
Date: December 13, 2007
Creator: Bastea, S & Fried, L E
Partner: UNT Libraries Government Documents Department
open access

Ion-Optics Calculations and Preliminary Precision Estimates of the Gas-Capable Ion Source for the 1-MV LLNL BioAMS Spectrometer

Description: Ion-optics calculations were performed for a new ion source and injection beam line. This source, which can accept both solid and gaseous targets, will be installed onto the 1-MV BioAMS spectrometer at the Center for Accelerator Mass Spectrometry, located at Lawrence Livermore National Laboratory and will augment the current LLNL cesium-sputter solid sample ion source. The ion source and its associated injection beam line were designed to allow direct quantification of {sup 14}C/{sup 12}C and {… more
Date: December 13, 2005
Creator: Ognibene, T. J.; Bench, G.; Brown, T. A. & Vogel, J. S.
Partner: UNT Libraries Government Documents Department
open access

Flavorful supersymmetry

Description: Weak scale supersymmetry provides elegant solutions to many of the problems of the standard model, but it also generically gives rise to excessive flavor and CP violation. We show that, if the mechanism that suppresses the Yukawa couplings also suppresses flavor changing interactions in the supersymmetry breaking parameters, essentially all the low energy flavor and CP constraints can be satisfied. The standard assumption of flavor universality in the supersymmetry breaking sector is not necess… more
Date: December 13, 2007
Creator: Nomura, Yasunori; Nomura, Yasunori; Papucci, Michele & Stolarski, Daniel
Partner: UNT Libraries Government Documents Department
open access

Event-by-Event Simulation of Induced Fission

Description: We are developing a novel code that treats induced fission by statistical (or Monte-Carlo) simulation of individual decay chains. After its initial excitation, the fissionable compound nucleus may either deexcite by evaporation or undergo binary fission into a large number of fission channels each with different energetics involving both energy dissipation and deformed scission prefragments. After separation and Coulomb acceleration, each fission fragment undergoes a succession of individual (n… more
Date: December 13, 2007
Creator: Vogt, R. & Randrup, J.
Partner: UNT Libraries Government Documents Department
open access

Evidence for Groundwater Contamination Vulnerability in California?s Central Valley

Description: The California Water Resources Control Board, in collaboration with the US Geological Survey and Lawrence Livermore National Laboratory, has implemented a program to assess the susceptibility of groundwater resources. Advanced techniques such as groundwater age dating using the tritium-helium method, extensive use of oxygen isotopes of the water molecule ({delta}{sup 18}O) for recharge water provenance, and analysis of common volatile organic compounds (VOCs) at ultra-low levels are applied wit… more
Date: December 13, 2005
Creator: Moran, J. E.; Leif, R.; Esser, B. K. & Singleton, M. J.
Partner: UNT Libraries Government Documents Department
open access

Physics of reshock and mixing in single-mode Richtmyer-Meshkov instability

Description: The ninth-order weighted essentially non-oscillatory (WENO) shock-capturing method is used to investigate the physics of reshock and mixing in two-dimensional single-mode Richtmyer-Meshkov instability to late times. The initial conditions and computational domain were adapted from the Mach 1.21 air(acetone)/SF{sub 6} shock tube experiment of Collins and Jacobs [J. Fluid Mech. 464, 113 (2002)]: the growth of the bubble and spike perturbation amplitudes from fifth- and ninth-order WENO simulation… more
Date: December 13, 2006
Creator: Schilling, O; Latini, M & Don, W
Partner: UNT Libraries Government Documents Department
open access

Algorithmic chemistry

Description: In this paper complex adaptive systems are defined by a self- referential loop in which objects encode functions that act back on these objects. A model for this loop is presented. It uses a simple recursive formal language, derived from the lambda-calculus, to provide a semantics that maps character strings into functions that manipulate symbols on strings. The interaction between two functions, or algorithms, is defined naturally within the language through function composition, and results i… more
Date: December 13, 1990
Creator: Fontana, W.
Partner: UNT Libraries Government Documents Department
open access

Physics of supernovae

Description: Presupernova models of massive stars are presented and their explosion by ''delayed neutrino transport'' examined. A new form of long duration Type II supernova model is also explored based upon repeated encounter with the electron-positron pair instability in stars heavier than about 60 Msub solar. Carbon deflagration in white dwarfs is discussed as the probable explanation of Type I supernovae and special attention is paid to the physical processes whereby a nuclear flame propagates through d… more
Date: December 13, 1985
Creator: Woosley, S. E. & Weaver, T. A.
Partner: UNT Libraries Government Documents Department
open access

Behavior of TPC's in a high particle flux environment

Description: TPC's (Time Projection Chamber) used in E-810 at the AGS (Alternating Gradient Synchrotron) were exposed to fluxes equivalent to more than 10{sup 7} minimum ionizing particles per second to find if such high fluxes cause gain changes or distortions of the electric field. Initial results of these and other tests are presented and the consequences for the RHIC (Relativistic Heavy Ion Collider) TPC-based experiments are discussed.
Date: December 13, 1991
Creator: Etkin, A.; Eisemann, S. E.; Foley, K. J.; Hackenburg, R. W.; Longacre, R. S.; Love, W. A. et al.
Partner: UNT Libraries Government Documents Department
open access

Impact analyses after pipe rupture. [PWR; BWR]

Description: Two of the French pipe whip experiments are reproduced with the computer code WIPS. The WIPS results are in good agreement with the experimental data and the French computer code TEDEL. This justifies the use of its pipe element in conjunction with its U-bar element in a simplified method of impact analyses.
Date: December 13, 1983
Creator: Chun, R. C. & Chuang, T. Y.
Partner: UNT Libraries Government Documents Department
open access

Harmonic generation at high peak power

Description: This report reviews progress made in recent years in frequency conversion of laser radiation. By using a material such as potassium dihydrogen phosphate (KDP), intense, coherent light is made available at wavelengths unavailable from the source laser medium. Tests were performed on an array of KDP crystals at the Nova Facility. The tests revealed unexpected losses due to various non-linear effects. (JDH)
Date: December 13, 1985
Creator: Summers, M.A.; Williams, J.D.; Johnson, B.C. & Eimerl, D.
Partner: UNT Libraries Government Documents Department
open access

Behavior of TPC`s in a high particle flux environment

Description: TPC`s (Time Projection Chamber) used in E-810 at the AGS (Alternating Gradient Synchrotron) were exposed to fluxes equivalent to more than 10{sup 7} minimum ionizing particles per second to find if such high fluxes cause gain changes or distortions of the electric field. Initial results of these and other tests are presented and the consequences for the RHIC (Relativistic Heavy Ion Collider) TPC-based experiments are discussed.
Date: December 13, 1991
Creator: Etkin, A.; Eisemann, S. E.; Foley, K. J.; Hackenburg, R. W.; Longacre, R. S.; Love, W. A. et al.
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

Comparison of up-scaling methods in poroelasticity and its generalizations

Description: Four methods of up-scaling coupled equations at the microscale to equations valid at the mesoscale and/or macroscale for fluid-saturated and partially saturated porous media will be discussed, compared, and contrasted. The four methods are: (1) effective medium theory, (2) mixture theory, (3) two-scale and multiscale homogenization, and (4) volume averaging. All these methods have advantages for some applications and disadvantages for others. For example, effective medium theory, mixture theory… more
Date: December 13, 2003
Creator: Berger, E. L.
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

Toward TW-Level, Hard X-Ray Pulses at LCLS

Description: Coherent diffraction imaging of complex molecules such as proteins requires a large number (e.g., {approx} 10{sup 13}/pulse) of hard X-ray photons within a time scale of {approx} 10 fs or less. This corresponds to a peak power of {approx} 1 TW, much larger than that currently generated by LCLS or other proposed X-ray free electron lasers (FELs). We study the feasibility of producing such pulses using a LCLS-like, low charge electron beam, as will be possible in the LCLS-II upgrade project, empl… more
Date: December 13, 2011
Creator: Fawley, W. M.; Frisch, J.; Huang, Z.; Jiao, Y.; Nuhn, H. D.; Pellegrini, C. et al.
Partner: UNT Libraries Government Documents Department
open access

The National Ignition Facility and the Promise of Inertial Fusion Energy

Description: The National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory (LLNL) in Livermore, CA, is now operational. The NIF is the world's most energetic laser system capable of producing 1.8 MJ and 500 TW of ultraviolet light. By concentrating the energy from its 192 extremely energetic laser beams into a mm{sup 3}-sized target, NIF can produce temperatures above 100 million K, densities of 1,000 g/cm{sup 3}, and pressures 100 billion times atmospheric pressure - conditions that ha… more
Date: December 13, 2010
Creator: Moses, E I
Partner: UNT Libraries Government Documents Department
open access

Femtosecond X-ray Pulse Temporal Characterization in Free-Electron Lasers Using a Transverse Deflector

Description: We propose a novel method to characterize the temporal duration and shape of femtosecond x-ray pulses in a free-electron laser (FEL) by measuring the time-resolved electron-beam energy loss and energy spread induced by the FEL process, with a transverse radio-frequency deflector located after the undulator. Its merits are simplicity, high resolution, wide diagnostic range, and non-invasive to user operation. When the system is applied to the Linac Coherent Light Source, the first hard x-ray fre… more
Date: December 13, 2011
Creator: Ding, Y.; Behrens, C.; Emma, P.; Frisch, J.; Huang, Z.; Loos, H. et al.
Partner: UNT Libraries Government Documents Department
open access

A Proposal for Study of Structure and Dynamics of Energy/Matter Based on Production of Gamma-Ray at SLAC Facility

Description: The success of this proposal will open new areas of Chemistry with antimatter: (1) new chemical dynamics; (2) exclusive production of parent ions by energy-tuning the positrons; (3) formation of antimatter compounds; (4) nano- and microscopic imaging of molecules, cells, and tumors (5) multi-positron systems and their thermodynamics and chemical kinetics. Also with o-Ps and p-Ps physics including speculations of dark mater (PAMELA & ATIC reported excesses in the e{sup +}e{sup -} cosmic rays).
Date: December 13, 2011
Creator: Decker, F. -J.; Krasnykh, Anatoly; Perelstein, M. & Shramenko, B.
Partner: UNT Libraries Government Documents Department
open access

Thermal Acoustic Sensor for High Pulse Energy X-ray FEL Beams

Description: The pulse energy density of X-ray FELs will saturate or destroy conventional X-ray diagnostics, and the use of large beam attenuation will result in a beam that is dominated by harmonics. We present preliminary results at the LCLS from a pulse energy detector based on the thermal acoustic effect. In this type of detector an X-ray resistant material (boron carbide in this system) intercepts the beam. The pulse heating of the target material produces an acoustic pulse that can be detected with hi… more
Date: December 13, 2011
Creator: Smith, T. J.; Frisch, J. C.; Kraft, E. M.; Loos, J. & Bentsen, G. S.
Partner: UNT Libraries Government Documents Department
open access

A Comprehensive Study of Nanometer Resolution of the IPBPM at ATF2

Description: High-resolution beam position monitors (IPBPMs) have been developed in order to measure the electron beam position at the focus point of ATF2 to a few nanometers in the vertical plane. To date, the IPBPM system has operated in test mode with a highest demonstrated resolution of 8.7 nm in the ATF extraction line during 2008. After expected noise source calculations there still remains 7.9 nm of noise of unexplained origin. We summarize the experimental work on the IPBPM system since this measure… more
Date: December 13, 2011
Creator: Kim, Y. I.; Park, H.; U., /Kyungpook Natl.; Boogert, S. T.; /Oxford U., JAI; Frisch, J. et al.
Partner: UNT Libraries Government Documents Department
open access

First Beam to FACET

Description: The SLAC 3km linear electron accelerator has been reconfigured to provide a beam of electrons to the new Facility for Advanced Accelerator Experimental Tests (FACET) while simultaneously providing an electron beam to the Linac Coherent Light Source (LCLS). On June 23, 2011, the first electron beam was transported through this new facility. Commissioning of FACET is in progress. On June 23, 2011, an electron beam was successfully transported through the new FACET system to a dump in Sector 20 in… more
Date: December 13, 2011
Creator: Erickson, R.; Clarke, C.; Colocho, W.; Decker, F. -J.; Hogan, M.; Kalsi, S. et al.
Partner: UNT Libraries Government Documents Department
open access

Gamma-Ray Observations of the Supernova Remnant RX J0852.0-4622 with the Fermi LAT

Description: We report on gamma-ray observations of the supernova remnant (SNR) RX J0852.0-4622 with the Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope. In the Fermi LAT data, we find a spatially extended source at the location of the SNR. The extension is consistent with the SNR size seen in other wavelengths such as X-rays and TeV gamma rays, leading to the identification of the gamma-ray source with the SNR. The spectrum is well described as a power law with a photon index of {Lamb… more
Date: December 13, 2011
Creator: Tanaka, T.; Allafort, A.; /Stanford U., HEPL /KIPAC, Menlo Park; Ballet, J.; /Saclay; Funk, S. et al.
Partner: UNT Libraries Government Documents Department
Back to Top of Screen