11,310 Matching Results

Search Results

A 3D Model for Ion Beam Formation and Transport Simulation

Description: In this paper, we present a three-dimensional model forself-consistently modeling ion beam formation from plasma ion sources andtransporting in low energy beam transport systems. A multi-sectionoverlapped computational domain has been used to break the originaltransport system into a number of weakly coupled subsystems. Within eachsubsystem, macro-particle tracking is used to obtain the charge densitydistribution in this subdomain. The three-dimensional Poisson equation issolved within the subdomain after each particle tracking to obtain theself-consistent space-charge forces and the particle tracking is repeateduntil the solution converges. Two new Poisson solvers based on acombination of the spectral method and the finite difference multigridmethod have been developed to solve the Poisson equation in cylindricalcoordinates for the straight beam transport section and in Frenet-Serretcoordinates for the bending magnet section. This model can have importantapplication in design and optimization of the low energy beam line opticsof the proposed Rare Isotope Accelerator (RIA) front end.
Date: February 7, 2006
Creator: Qiang, J.; Todd, D. & Leitner, D.
Partner: UNT Libraries Government Documents Department

3D unstructured mesh ALE hydrodynamics with the upwind discontinuous galerkin method

Description: The authors describe a numerical scheme to solve 3D Arbitrary Lagrangian-Eulerian (ALE) hydrodynamics on an unstructured mesh using a discontinuous Galerkin method (DGM) and an explicit Runge-Kutta time discretization. Upwinding is achieved through Roe's linearized Riemann solver with the Harten-Hyman entropy fix. For stabilization, a 3D quadratic programming generalization of van Leer's 1D minmod slope limiter is used along with a Lapidus type artificial viscosity. This DGM scheme has been tested on a variety of hydrodynamic test problems and appears to be robust making it the basis for the integrated 3D inertial confinement fusion modeling code (ICF3D). For efficient code development, they use C++ object oriented programming to easily separate the complexities of an unstructured mesh from the basic physics modules. ICF3D is fully parallelized using domain decomposition and the MPI message passing library. It is fully portable. It runs on uniprocessor workstations and massively parallel platforms with distributed and shared memory.
Date: May 7, 1999
Creator: Kershaw, D S; Milovich, J L; Prasad, M K; Shaw, M J & Shestakov, A I
Partner: UNT Libraries Government Documents Department

5000 groove/mm multilayer-coated blazed grating with 33percent efficiency in the 3rd order in the EUV wavelength range

Description: We report on recent progress in developing diffraction gratings which can potentially provide extremely high spectral resolution of 105-106 in the EUV and soft x-ray photon energy ranges. Such a grating was fabricated by deposition of a multilayer on a substrate which consists ofa 6-degree blazed grating with a high groove density. The fabrication of the substrate gratings was based on scanning interference lithography and anisotropic wet etch of silicon single crystals. The optimized fabrication process provided precise control of the grating periodicity, and the grating groove profile, together with very short anti-blazed facets, and near atomically smooth surface blazed facets. The blazed grating coated with 20 Mo/Si bilayers demonstrated a diffraction efficiency in the third order as high as 33percent at an incidence angle of 11? and wavelength of 14.18 nm.
Date: July 7, 2009
Creator: Lawrence Berkeley National Laboratory. Advanced Light Source.
Partner: UNT Libraries Government Documents Department

70193-Influence of Clastic Dikes on Vertical Migration of Contaminants in the Vadose Zonde at Hanford

Description: The purpose of this study was to examine the hypothesis that clastic dikes could form a preferential flow path through the vadose zone to the water table at the Hanford Site. Clastic dikes are subvertical structures that form within sedimentary sequences after deposition and cut across the original sedimentary layers. They are common throughout the Hanford Site, often occurring in organized polygonal networks. In the initial phase of the project, we analyzed the large-scale geometry of the clastic dikes and developed an algorithm for simulating their spatial distribution. This result will be useful in providing maps of the potential distribution of clastic dikes in areas where they are not exposed at the surface (e.g., where covered by windblown sand or construction of facilities like tank farms at the surface). In addition to the study of the large-scale distribution of the dikes, a major focus of the project was on field, laboratory, and modeling studies of the hydrogeological properties of the clastic dikes and the effect that they have on transport of water through the vadose zone. These studies were performed at two field locations at the Hanford Site. We performed an extensive series of field and laboratory measurements of a large number of samples from the clastic dikes, linked with infrared (IR) and visual imagery of the clastic dikes and surrounding matrix. We developed a series of correlations from the sample data that allowed us to estimate the unsaturated hydraulic conductivity of the dike and matrix at an extremely high resolution (approximately 1 mm). The resulting grids, each of which measured several meters on a side and included nearly four million grid nodes, were used to study the distribution of moisture between the clastic dike and surrounding matrix, as well as the relative velocities that moisture would have through the ...
Date: April 7, 2004
Creator: Murray, Christopher J; Ward, Anderson L. & Wilson, John L.
Partner: UNT Libraries Government Documents Department

9978 AND 9975 TYPE B PACKAGING INTERNAL DATA COLLECTION FEASIBILITY TESTING

Description: The objective of this report is to document the findings from a series of proof-of-concept tests performed by Savannah River National Laboratory (SRNL) R and D Engineering, for the DOE Packaging Certification Program to determine if a viable radio link could be established from within the stainless steel confines of several drum-style DOE certified Type B radioactive materials packagings. Two in-hand, off-the-shelf radio systems were tested. The first system was a Wi-Fi Librestream Onsight{trademark} camera with a Fortress ES820 Access Point and the second was the On-Ramp Wireless Ultra-Link Processing{trademark} (ULP) radio system. These radio systems were tested within the Model 9975 and 9978 Type B packagings at the SRNL. This report documents the test methods and results. A path forward will also be recommended.
Date: May 7, 2012
Creator: Fogle, R.
Partner: UNT Libraries Government Documents Department

An Ab Initio Approach Towards Engineering Fischer-Tropsch Surface Chemistry

Description: One of the greatest societal challenges over the next decade is the production of cheap, renewable energy for the 10 billion people that inhabit the earth. This will require the development of various different energy sources potentially including fuels derived from methane, coal, and biomass and alternatives sources such as solar, wind and nuclear energy. One approach will be to synthesize gasoline and other fuels from simpler hydrocarbons such as CO derived from methane or other U.S. based sources such as coal. Syngas (CO and H{sub 2}) can be readily converted into higher molecular weight hydrocarbons through Fischer-Tropsch synthesis. Fischer-Tropsch synthesis involves the initiation or activation of CO and H{sub 2} bonds, the subsequent propagation steps including hydrogenation and carbon-carbon coupling, followed by chain termination reactions. Commercially viable catalysts include supported Co and Co-alloys. Over the first two years of this project we have used ab initio methods to determine the adsorption energies for all reactants, intermediates, and products along with the overall reaction energies and their corresponding activation barriers over the Co(0001) surface. Over the third year of the project we developed and advanced an ab initio-based kinetic Monte Carlo simulation code to simulate Fischer Tropsch synthesis. This report details our work over the last year which has focused on the derivation of kinetic parameters for the elementary steps involved in FT synthesis from ab initio density functional theoretical calculations and the application of the kinetic Monte Carlo algorithm to simulate the initial rates of reaction for FT over the ideal Co(0001) surface. The results from our simulations over Co(0001) indicate the importance of stepped surfaces for the activation of adsorbed CO. In addition, they demonstrate that the dominant CH{sub x}* surface intermediate under steady state conditions is CH*. This strongly suggests that hydrocarbon coupling occurs through reaction with ...
Date: May 7, 2006
Creator: Neurock, Matthew & Walthall, David A.
Partner: UNT Libraries Government Documents Department

Ab-Initio Study on Plutonium Compounds Pu3M (M=Al, Ga, In), PuNp and Elemental Neptunium

Description: Using spin-polarized relativistic density functional theory the electronic and magnetic structures for the plutonium compounds Pu{sub 3}M(M = Al; Ga; In) and PuNp have been investigated. For the first group of compounds the enhanced hybridization between Pu 5f and p-states of alloying element, as it has been found in spin-polarized calculations, is believed to be the main reason for the higher formation energies obtained in such kind of studies in comparison with the non-spin-polarized case. Also, comparative analysis of the actinides U, Np, Pu, Am, and Cm has been performed based on their electronic and magnetic structure. Some noticeable difference in the calculated magnetic structure was discovered between the actinide with local magnetic moments (Cm) and the actinides (Pu, Am) in which magnetic moments were found only in the calculations.
Date: September 7, 2005
Creator: Kutepov, A L
Partner: UNT Libraries Government Documents Department

[ABC Visiting WBAP-TV]

Description: Photograph of five men surrounding one man seated on a saddled wooden saw horse on the set of "Davy Crockett's Opry House."
Date: July 7, 1949
Creator: WBAP-TV (Television station : Fort Worth, Tex.)
Partner: UNT Libraries Special Collections

Abortion: Legislative Response

Description: The primary focus of this issue brief is legislative action in the 107th Congress with respect to abortion. However, discussion of those legislative proposals necessarily involves a brief discussion of the leading U.S. Supreme Court decisions concerning a woman’s right to choose whether to terminate her pregnancy. For a more detailed discussion of the relevant case law, see CRS Report 95-724, Abortion Law Development: A Brief Overview.
Date: January 7, 2003
Creator: Lewis, Karen J.; Shimabukuro, Jon O. & Ely, Dana
Partner: UNT Libraries Government Documents Department

Abortion Services and Military Medical Facilities

Description: The purpose of this report is to describe and discuss the provisions for providing abortion services to military personnel, their dependents, and other military health care beneficiaries at military medical facilities. The report describes the history of these provisions, with particular emphasis on legislative actions. Finally, this report discusses a number of proposals to modify the law, as well as other related legislative and administrative actions.
Date: June 7, 2012
Creator: Burrelli, David F.
Partner: UNT Libraries Government Documents Department

Absolute measurements of the high-frequency magnetic dynamics in high-{Tc} superconductors

Description: The authors review recent measurements of the high-frequency dynamic magnetic susceptibility in the high-T{sub c} superconducting systems La{sub 2{minus}x}Sr{sub x}CuO{sub 4} and YBa{sub 2}Cu{sub 3}O{sub 6+x}. Experiments were performed using the chopper spectrometers HET and MARI at the ISIS spallation source. The authors have placed their measurements on an absolute intensity scale, this allows systematic trends to be seen and comparisons with theory to be made. They find that the insulating S = 1/2 antiferromagnetic parent compounds show a dramatic renormalization in the spin wave intensity. The effect of doping on the response is to cause broadenings in wave vector and large redistributions of spectral weight in frequency.
Date: August 7, 1997
Creator: Hayden, S.M.; Aeppli, G.; Dai, P.; Mook, H.A.; Perring, T.G.; Cheong, S.W. et al.
Partner: UNT Libraries Government Documents Department

AN ACCELERATED RATE CALORIMETRY STUDY OF CAUSTIC-SIDE SOLVENT EXTRACTION SOLVENT WITHOUT EXTRACTANT

Description: This study found that 4 - 48 part per thousand (ppth) of Caustic Side Solvent Extraction (CSSX) solvent without extractant in caustic salt solution at evaporator-relevant temperatures result in no process-significant energetic events. However, the data suggest a chemical reaction (possible decomposition) in the CSSX solvent near 140 C. This concentration of entrained solvent is believed to markedly exceed the amount of solvent that will pass from the Modular Caustic Side Solvent Unit (MCU) through the downstream Defense Waste Processing Facility and enter the evaporator through routine tank farm operations. The rate of pressure rise at 140 C differs appreciably - i.e., is reduced - for salt solution containing the organic from that of the same solution without solvent. This behavior is due to a reaction between the CSSX components and the salt solution simulant.
Date: March 7, 2006
Creator: Fondeur, F & Samuel Fink, S
Partner: UNT Libraries Government Documents Department

Acceleration Characteristics of a Turbojet Engine With Variable-Position Inlet Guide Vanes

Description: Report presenting a study of the acceleration characteristics of a turbojet engine equipped with variable-position inlet guide vanes in the altitude test chamber. Maximum acceleration values for 3 engines of the same model were also obtained during testing and were found to differ as much as 50 percent. Results regarding the effect of fuel step size and inlet guide vane on acceleration, effect of flight condition, reproducibility of engine acceleration, compressor pressure ratio in relation to acceleration, and acceleration with inlet air distortion are provided.
Date: July 7, 1955
Creator: Dobson, W. F. & Wallner, Lewis E.
Partner: UNT Libraries Government Documents Department

ACCELERATION FOR A HIGH ENERGY MUON COLLIDER

Description: The authors describe a method for designing the acceleration systems for a muon collider, with particular application and examples for a high energy muon collider. This paper primarily concentrates on design considerations coming from longitudinal motion, but some transverse issues are briefly discussed.
Date: April 7, 2000
Creator: BERG,J.S
Partner: UNT Libraries Government Documents Department

Acceleration using total internal reflection

Description: This report considers the use of a dielectric slab undergoing total internal reflection as an accelerating structure for charged particle beams. We examine the functional dependence of the electromagnetic fields above the surface of the dielectric for polarized incident waves. We present an experimental arrangement for testing the performance of the method, using apparatus under construction for the Grating Acceleration experiment at Brookhaven National Laboratory. 13 refs., 4 figs., 2 tabs.
Date: June 7, 1991
Creator: Fernow, R.C.
Partner: UNT Libraries Government Documents Department

Access to Broadband Networks: The Net Neutrality Debate

Description: This report discusses the current debate over "net neutrality." While there is no single accepted definition of "net neutrality," most agree that any such definition should include the general principles that owners of the networks that compose and provide access to the Internet should not control how consumers lawfully use that network, and they should not be able to discriminate against content provider access to that network.
Date: July 7, 2010
Creator: Gilroy, Angele A.
Partner: UNT Libraries Government Documents Department