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Chemical Solution Processing of Strontium Bismuth Tantalate Films

Description: We describe Chemical Solution Deposition (CSD) processes by which Strontium Bismuth Tantalate (SBT) thin films can be prepared at temperatures as low as 550 C. In this paper, we will present strategies used to optimize the properties of the films including solution chemistry, film composition, the nature of the substrate (or bottom electrode) used, and the thermal processing cycle. Under suitable conditions, {approximately} 1700 {angstrom} films can be prepared which have a large switchable polarization (2P{sub r} > 10{micro}C/cm{sup 2}), and an operating voltage, defined as the voltage at which 0.80 x 2P{sub r} max is switched, 2.0V. We also describe an all-alkoxide route to SBT films from which SBT can be crystallized at 550 C.
Date: December 21, 1998
Creator: Boyle, T.J. & Lakeman, C.D.E.
Partner: UNT Libraries Government Documents Department

Ba{sub 1{minus}x}Sr{sub x}TiO{sub 3} thin film sputter-growth processes and electrical property relationships for high frequency devices

Description: Precise control of Ba{sub 1{minus}x}Sr{sub x}Ti0{sub 3} (BST) film composition is critical for the production of high-quality BST thin films. Specifically, it is known that nonstoichiometry greatly affects the electrical properties of BST film capacitors. The authors are investigating the composition-microstructure-electrical property relationships of polycrystalline BST films produced by magnetron sputter-deposition using a single target with a Ba/Sr ratio of 50/50 and a (Ba+Sr)/Ti ratio of 1.0. It was determined that the (Ba+Sr)/Ti ratios of these BST films could be adjusted from 0.73 to 0.98 by changing the total (Ar+O{sub 2}) process pressure, while the O{sub 2}/Ar ratio did not strongly affect the metal ion composition. The crystalline quality as well as the measured dielectric constant, dielectric tunability, and electrical breakdown voltage of BST films have been found to be strongly dependent on the composition of the BST films, especially the (Ba+Sr)/Ti ratio. The authors discuss the impact of BST film composition control, through film deposition and process parameters, on the electrical properties of BST capacitors for high frequency devices.
Date: December 21, 1999
Creator: Im, J.; Auciello, O.; Streiffer, S. K.; Baumann, P. K.; Eastman, J. A.; Kaufman, D. Y. et al.
Partner: UNT Libraries Government Documents Department

Neutron transfer kernels in the resonance domain in the harmonic crystal model.

Description: To describe neutron scattering the resonance domain of the nuclear fuel isotopes, the static model is widely in use in nuclear data processing codes. With this model the influence of chemical binding on the transfer cross section is not taken into account since the nucleus is considered to be in rest and isolated in the laboratory system. Further, the application of the free gas model to the resonant scattering of neutrons shows that the up-scattering probability is strongly dependent on the incident neutron energy. If the latter is smaller than the resonance energy then the free gas model predicts an enormous chance for the neutron to gain energy after collision. Neither the static nor free gas model is adequate to describe the resonant scattering of neutrons in a crystal. This fact can induce non-negligible errors in reactor calculations and, in particular, in the estimation of the Doppler coefficient. In the present paper the author proposes the theoretical study of the possibility to estimate the neutron transfer cross sections in the harmonic crystal approximation.
Date: December 21, 1999
Creator: Naberejnev, D. G.
Partner: UNT Libraries Government Documents Department

Collectivity of the ''Three-Phonon'' Region in {sup 100}Ru

Description: We have studied the quadrupole degree of freedom in a typical vibrational nucleus, {sup 100}Ru. From inelastic neutron scattering at the Van de Graaff accelerator of the University of Kentucky, lifetimes of states in {sup 100}Ru were determined. Absolute transition rates or limits thereon were extracted and compared to the theoretical description of this nucleus.
Date: December 21, 1999
Creator: Genilloud, L.; Brown, T.B.; Corminboeuf, G & Garrett, P.
Partner: UNT Libraries Government Documents Department

Spatial Bias in Field-Estimated Unsaturated Hydraulic Properties

Description: Hydraulic property measurements often rely on non-linear inversion models whose errors vary between samples. In non-linear physical measurement systems, bias can be directly quantified and removed using calibration standards. In hydrologic systems, field calibration is often infeasible and bias must be quantified indirectly. We use a Monte Carlo error analysis to indirectly quantify spatial bias in the saturated hydraulic conductivity, K{sub s}, and the exponential relative permeability parameter, {alpha}, estimated using a tension infiltrometer. Two types of observation error are considered, along with one inversion-model error resulting from poor contact between the instrument and the medium. Estimates of spatial statistics, including the mean, variance, and variogram-model parameters, show significant bias across a parameter space representative of poorly- to well-sorted silty sand to very coarse sand. When only observation errors are present, spatial statistics for both parameters are best estimated in materials with high hydraulic conductivity, like very coarse sand. When simple contact errors are included, the nature of the bias changes dramatically. Spatial statistics are poorly estimated, even in highly conductive materials. Conditions that permit accurate estimation of the statistics for one of the parameters prevent accurate estimation for the other; accurate regions for the two parameters do not overlap in parameter space. False cross-correlation between estimated parameters is created because estimates of K{sub s} also depend on estimates of {alpha} and both parameters are estimated from the same data.
Date: December 21, 2000
Creator: HOLT,ROBERT M.; WILSON,JOHN L. & GLASS JR.,ROBERT J.
Partner: UNT Libraries Government Documents Department

Search for SUSY with missing E{sub T} and jets at CDF

Description: Events with signatures involving large missing transverse energy (E{sub T}) are among the quintessential search modes for R-parity conserving supersymmetry. CDF has conducted two recent analyses for supersymmetry which use E{sub T} and jets. The E{sub T} and monojet signature is employed to determine process independent limits for the production of new physics beyond the Standard Model and then applied to models of spontaneous breaking of supersymmetry to determine limits on the supersymmetry breaking parameter and the gravitino mass. Direct searches for scalar top and scalar bottom quarks within the framework of supersymmetric models are performed using a signature of E{sub T} and two heavy flavor jets. Since the data is found to be consistent with Standard Model expectations, limits are determined in the mass planes m({tilde {chi}}{sub 1}{sup 0})-m({tilde t}{sub 1}) and m({tilde {chi}}{sub 1}){sup 0}-m({tilde b}{sub 1}).
Date: December 21, 2000
Creator: CDF, Search for SUSY with Missing ET and Jets at
Partner: UNT Libraries Government Documents Department

A beamline matching application based on open source software

Description: An interactive Beamline Matching application has been developed using beamline and automatic differentiation class libraries. Various freely available components were used; in particular, the user interface is based on FLTK, a C++ toolkit distributed under the terms of the GNU Public License (GPL). The result is an application that compiles without modifications under both X-Windows and Win32 and offers the same look and feel under both operating environments. In this paper, we discuss some of the practical issues that were confronted and the choices that were made. In particular, we discuss object-based event propagation mechanisms, multithreading, language mixing and persistence.
Date: December 21, 2000
Partner: UNT Libraries Government Documents Department

Dense optical-electrical interface module

Description: The DOIM (Dense Optical-electrical Interface Modules) is a custom-designed optical data transmission module employed in the upgrade of Silicon Vertex Detector of CDF experiment at Fermilab. Each DOIM module consists of a transmitter (TX) converting electrical differential input signals to optical outputs, a middle segment of jacketed fiber ribbon cable, and a receiver (RX) which senses the light inputs and converts them back to electrical signals. The targeted operational frequency is 53 MHz, and higher rate is achievable. This article outlines the design goals, implementation methods, production test results, and radiation hardness tests of these modules.
Date: December 21, 2000
Creator: Chang, Paul
Partner: UNT Libraries Government Documents Department

Double-Diffusive Finger Convection: Flow Field Evolution in a Hele-Shaw Cell

Description: Double-diffusive finger convection is a hydrodynamic instability that can occur when two components with different diffusivities are oppositely stratified with respect to the fluid density gradient as a critical condition is exceeded. Laboratory experiments were designed using sodium chloride and sucrose solutions in a Hele-Shaw cell. A high resolution, full field, light transmission technique was used to study the development of the instability. The initial buoyancy ratio (R{sub p}), which is a ratio of fluid density contributions by the two solutes, was varied systematically in the experiments so that the range of parameter space spanned conditions that were nearly stable (R{sub p} = 2.8) to those that were moderately unstable (R{sub p} = 1.4). In systems of low R{sub p}, fingers develop within several minutes, merge with adjacent fingers, form conduits, and stall before newer-generated fingers travel through the conduits and continue the process. Solute fluxes in low R{sub p} systems quickly reach steady state and are on the order of 10{sup {minus}6} m{sup 2} sec{sup {minus}1}. In the higher R{sub p} experiments, fingers are slower to evolve and do not interact as dynamically as in the lower R{sub p} systems. Our experiment with initial R{sub p} = 2.8 exhibited flux on the order of that expected for a similar diffusive system (i.e., 10{sup {minus}7} m{sup 2} sec{sup {minus}1}), although the structures were very different than the pattern of transport expected in a diffusing system. Mass flux decayed as t{sup 1/2} in two experiments each with initial R{sub p} = 2.4 and 2.8.
Date: December 21, 2000
Creator: Cooper, Clay A.; Glass, Robert J., Jr. & Tyler, Scott W.
Partner: UNT Libraries Government Documents Department

From a {nu} factory to {mu} super + mu super {minus} Colliders

Description: An important feature of a {mu}-storage ring {nu}-source is that it can be extended to the possibility of a future high-energy muon collider. The neutrino source provides a useful physics device that initiates key technologies required for future {mu}{sup +}-{mu}{sup {minus}} Colliders, but with much less demanding parameter requirements. These technologies include high-intensity {mu}-production, {mu}-capture, {mu}-cooling, {mu}-acceleration and multiturn {mu} storage rings. {mu}{sup +}-{mu}{sup {minus}} colliders require a similar number of muons, but they require that the muons be cooled to a much smaller phase space and formed into a small number of bunches, and both positive and negative bunches must be simultaneously captured. These differences are discussed, and the extension of the {nu}-source to {mu}{sup +}-{mu}{sup {minus}} collider specifications is described.
Date: December 21, 2000
Creator: Neuffer, David
Partner: UNT Libraries Government Documents Department

Dijet production by double pomeron exchange at the Tevatron

Description: The authors report the observation of dijet events with a Double Pomeron Exchange topology produced in {bar p}p collisions at {radical}s = 1,800 GeV. The events are characterized by a leading antiproton, two jets in the central pseudorapidity region, and a rapidity gap on the outgoing proton side. Results on kinematics, production rates, and comparisons with corresponding results from single diffractive and inclusive dijet production are presented.
Date: December 21, 2000
Creator: Terashi, Koji
Partner: UNT Libraries Government Documents Department

Search for second and third generation leptoquarks at CDF

Description: The authors report the results of a search for second and third generation leptoquarks using 88 pb{sup {minus}1} of data recorded by the Collider Detector at Fermilab. Color triplet technipions, which play the role of scalar leptoquarks, are investigated due to their potential production in decays of strongly coupled color octet technirhos. Events with a signature of two heavy flavor jets and missing energy may indicate the decay of a second (third) generation leptoquark to a charm (bottom) quark and a neutrino. As the data is found to be consistent with Standard Model expectations, mass limits are determined.
Date: December 21, 2000
Creator: Haas, Richard
Partner: UNT Libraries Government Documents Department

The underlying event in large transverse momentum charged jet and Z-boson production

Description: The authors study the behavior of the underlying event in large transverse momentum charged jet and Z-boson production at 1.8 TeV and compare with the QCD Monte-Carlo models. The data indicate that neither ISAJET or HERWIG produce enough charged particles (with p{sub T} > 0.5 GeV/c) from the beam-beam remnant component and that ISAJET produces too many charged particle from initial-state radiation. PYTHIA which uses multiple parton scattering to enhance the underlying event does the best job describing the data.
Date: December 21, 2000
Creator: Field, Rick
Partner: UNT Libraries Government Documents Department

Tests of quark mass textures

Description: The classic hints on the structure of the quark mass matrices are shortly reviewed and the possibility of obtaining further information through precise texture analysis is discussed with the aid of a specific example.
Date: December 21, 2000
Partner: UNT Libraries Government Documents Department

Disorder-driven nonequilibrium melting studied by electron diffraction, brillouis scattering, and molecular dynamics

Description: In the present paper, a brief overview of the electron diffraction, Brillouin scattering and molecular dynamics studies of radiation-induced amorphization of ordered intermetallic compounds is presented. In these studies, measured changes in the velocity of surface acoustic phonons, lattice constant, and the Bragg-Williams long-range order parameter induced by irradiation were compared with the results of computer simulations of defect-induced amorphization. The results indicate that progressive chemical disordering of the superlattice structure during irradiation is accompanied by an expansion of the lattice and a large change in sound velocity corresponding to a {approximately} 50% decrease in the average shear modulus. The onset of amorphization occurs when the average shear modulus of the crystalline compound becomes equal to that of the amorphous phase. This elastic softening criterion for the onset of amorphization and the dependence of the average shear modulus on the long-range-order parameter are in excellent agreement with molecular dynamics simulations. Both the experimental observations and computer simulations confirm the predictions of the generalized Lindemann melting criterion which stipulates that thermodynamic melting of a defective crystal occurs when the sum of the dynamic and static mean-square atomic displacements reaches a critical value identical to that for melting of the defect-free crystal. In this broader view of melting, the crystal-to-glass transformation is a disorder-driven nonequilibrium melting process occurring at temperatures below the Kauzmann isentropic glass-transition temperature.
Date: December 21, 1999
Creator: Okamoto, P. R.; Lam, N. Q. & Grimsditch, M.
Partner: UNT Libraries Government Documents Department

Safe venting of ``red oil`` runaway reactions

Description: Calorimetry testing of Tri-n-butyl phosphate (TBP) saturated with strong nitric acid was performed to determine the relationship between vent size and pressure buildup in the event of a runaway reaction. These experiments show that runaway can occur in an open system, but that even when runaway is induced in the TBP/HN0{sub 3} system, dangerous pressure buildup will be prevented with practical vent size.
Date: December 21, 1994
Creator: Paddleford, D.F. & Fauske, H.K.
Partner: UNT Libraries Government Documents Department

Long-term operating experience for the ATLAS superconducting resonators

Description: Portions of the ATLAS accelerator have been operating now for over 21 years. The facility has accumulated several million resonator-hours of operation at this point and has demonstrated the long-term reliability of RF superconductivity. The overall operating performance of the ATLAS facility has established a level of beam quality, flexibility, and reliability not previously achieved with heavy-ion accelerator facilities. The actual operating experience and maintenance history of ATLAS are presented for ATLAS resonators and associated electronics systems. Solutions to problems that appeared in early operation as well as current problems needing further development are discussed.
Date: December 21, 1999
Creator: Pardo, R. & Zinkann, G.
Partner: UNT Libraries Government Documents Department

Incorporation of radionuclides from the electrometallurgical treatment of spent fuel into a ceramic waste form.

Description: An electrometallurgical process is being developed at Argonne National Laboratory to treat spent metallic nuclear fuel. In this process, the spent nuclear fuel is electrorefined in a molten salt to separate uranium from the other constituents of the fuel. The treatment process generates a contaminated chloride salt that is incorporated into a ceramic waste form. The ceramic waste form, a composite of socialite and glass, contains the fission products (rare earths, alkalis, alkaline earth metals, and halides) and transuranic radionuclides that accumulated in the electrorefiner salt. These radionuclides are incorporated into zeolite A, which can fully accommodate the salt in its crystal structure. The radionuclides are incorporated into the zeolite by high-temperature blending or by ion exchange. In the blending process the salt and zeolite are simply tumbled together at >450 C (723 K), but in the ion exchange process, which yields a product more highly concentrated in fission products, the molten salt is passed through a bed of the zeolite. In either case, the salt-loaded zeolite A is mixed with glass frit and hot isostatically pressed to produce a monolithic leach resistant waste form. Zeolite is converted to sodalite during hot pressing. This paper presents experimental results on the fission product uptake of the zeolite as a function of time and salt composition.
Date: December 21, 1998
Creator: Pereira, C.
Partner: UNT Libraries Government Documents Department

Defining Requirements for Improved Photovoltaic System Reliability

Description: Reliable systems are an essential ingredient of any technology progressing toward commercial maturity and large-scale deployment. This paper defines reliability as meeting system fictional requirements, and then develops a framework to understand and quantify photovoltaic system reliability based on initial and ongoing costs and system value. The core elements necessary to achieve reliable PV systems are reviewed. These include appropriate system design, satisfactory component reliability, and proper installation and servicing. Reliability status, key issues, and present needs in system reliability are summarized for four application sectors.
Date: December 21, 1998
Creator: Maish, A.B.
Partner: UNT Libraries Government Documents Department

Precision measurements at a muon collider

Description: We discuss the potential for making precision measurements of M{sub W} and M{sub T} at a muon collider and the motivations for each measurement. A comparison is made with the precision measurements expected at other facilities. The measurement of the top quark decay width is also discussed.
Date: December 21, 1995
Creator: Dawson, S.
Partner: UNT Libraries Government Documents Department

Testing and Development of a 30-kVA Hybrid Inverter: Lessons Learned and Reliability Implications

Description: A 30-kVA Trace Technologies hybrid power processor was specified and tested at the Sandia inverter test facility. Trace Technologies involving the control system, in response to suggestions made modifications, primarily by Sandia and Arizona Public Service (APS) personnel. The modifications should make the inverter more universally applicable and less site-specific so that it can be applied in various sites with minimal field interaction required from the design engineer. The project emphasized the importance of battery management, generator selection, and site load management to the performance and reliability of hybrid power systems.
Date: December 21, 1998
Creator: Ginn, J.W.
Partner: UNT Libraries Government Documents Department

Solar Heat-Pipe Receiver Wick Modeling

Description: Stirling-cycle engines have been identified as a promising technology for the conversion of concentrated solar energy into usable electrical power. In previous experimented work, we have demonstrated that a heat pipe receiver can significantly improve system performance-over a directly-illuminated heater head. The design and operating conditions of a heat pipe receiver differ significantly from typical laboratory heat pipes. New wick structures have been developed to exploit the characteristics of the solar generation system. Typically, these wick structures allow vapor generation within the wick. Conventional heat pipe models do not handle this enhancement yet it can more than double the performance of the wick. In this study, I develop a steady-state model of a boiling-enhanced wick for a solar heat pipe receiver. The model is used for design-point calculations and is written in FORTRAN90. Some limited comparisons have been made with actual test data.
Date: December 21, 1998
Creator: Andraka, C.E.
Partner: UNT Libraries Government Documents Department

Fate of neptunium in an anaerobic, methanogenic microcosm.

Description: Neptunium is found predominantly as Np(IV) in reducing environments, but Np(V) in aerobic environments. However, currently it is not known how the interplay between biotic and abiotic processes affects Np redox speciation in the environment. In order to evaluate the effect of anaerobic microbial activity on the fate of Np in natural systems, Np(V) was added to a microcosminoculated with anaerobic sediments from a metal-contaminated fresh water lake. The consortium included metal-reducing, sulfate-reducing, and methanogenic microorganisms, and acetate was supplied as the only exogenous substrate. Addition of more than 10{sup {minus}5} M Np did not inhibit methane production. Total Np volubility in the active microcosm, as well as in sterilized control samples, decreased by nearly two orders of magnitude. A combination of analytical techniques, including VIS-NIR absorption spectroscopy and XANES, identified Np(IV) as the oxidation state associated with the sediments. The similar results from the active microcosm and the abiotic controls suggest that microbian y produced Mn(II/HI) and Fe(II) may serve as electron donors for Np reduction.
Date: December 21, 1998
Creator: Banaszak, J. E.
Partner: UNT Libraries Government Documents Department