Femtosecond synchrotron radiation pulses generated in the ALS storage ring (open access)

Femtosecond synchrotron radiation pulses generated in the ALS storage ring

Scientists from the Lawrence Berkeley National Laboratory (Berkeley Lab) have generated 300-femtosecond pulses of bend-magnet synchrotron radiation at the Advanced Light Source (ALS) with the aid of a laser ''time-slicing'' technique. This technique allows an ultrashort portion of an electron bunch in the ALS storage ring to be spatially displaced in such a way that the synchrotron radiation from the displaced portion can then be collected separately. Their proof-of-principle experiment demonstrates that this technique is a viable one for producing ultra-short pulses of x-rays. An ALS bend-magnet beamline is already under construction that will be dedicated to time-resolved x-ray diffraction, EXAFS, and other techniques capable of probing the long-range and local structure of matter on a femtosecond time scale. A proposed undulator beamline based on the same technique would further enhance the flux and brightness by orders of magnitude.
Date: April 26, 2000
Creator: Schoenlein, Robert W. & Robinson, Arthur L.
System: The UNT Digital Library
Microstructure Development in Nickel Base Superalloys during Weld Thermal Cycle (open access)

Microstructure Development in Nickel Base Superalloys during Weld Thermal Cycle

Welding plays an important role in the economical reuse and reclamation of used and failed nickel base superalloy blades. Previous research on microstructure development during laser beam welding of a single crystal CMSX4 alloy [Ref. l] showed non-equilibrium y/y{prime} microstructure development. In addition, the y{prime} precipitates were found to be irregular in shape and atom probe field ion microscopy illustrated the presence of diffusional concentration profile within the y phase in the as welded condition. To understand the above microstructure characteristics, y{prime} precipitation from y phase was investigated during continuous cooling from solutionizing temperature.
Date: April 26, 2000
Creator: Babu, S. S. & David, S. A.
System: The UNT Digital Library
Overview of energy storage applications (open access)

Overview of energy storage applications

Sandia National Laboratories has been studying Energy Storage Systems since the late 1970s. Sandia started by applying their defense program battery experience to larger stationary systems, eventually joining in the formation of the Utility Battery Group which has since evolved into the Energy Storage Association. Sandia's role, as a Department of Energy funded program is to look ahead at emerging technologies, perform early R and D and identify applications for Energy Storage Systems that offer significant benefit to the nation's electricity providers and users. In order to identify applications of energy storage, a two-phase Opportunities Analysis was conceptualized in FY94. Phase 1 of the project was completed and published in 1995 (SAND94-2605). Phase 2 of the project is an extension of Phase 1 to reexamine the identified applications in the dynamic environment of today. In a preliminary assessment of national benefits, SNL estimated that generation and transmission applications of storage could represent $17.2B in national benefits. In Phase 1 of the Opportunities Analysis, the T and D benefits were found to be significantly higher than previous estimates Phase 2 of the study, which began in late 1998, includes a refinement of the technical and economic understanding of the role of …
Date: April 26, 2000
Creator: BOYES,JOHN D.
System: The UNT Digital Library
Single Transverse Mode Selectively Oxidized Vertical Cavity Lasers (open access)

Single Transverse Mode Selectively Oxidized Vertical Cavity Lasers

Vertical cavity surface emitting lasers (VCSELs) which operate in multiple transverse optical modes have been rapidly adopted into present data communication applications which rely on multi-mode optical fiber. However, operation only in the fundamental mode is required for free space interconnects and numerous other emerging VCSEL applications. Two device design strategies for obtaining single mode lasing in VCSELs based on mode selective loss or mode selective gain are reviewed and compared. Mode discrimination is attained with the use of a thick tapered oxide aperture positioned at a longitudinal field null. Mode selective gain is achieved by defining a gain aperture within the VCSEL active region to preferentially support the fundamental mode. VCSELs which exhibit greater than 3 mW of single mode output power at 850 nm with mode suppression ratio greater than 30 dB are reported.
Date: April 26, 2000
Creator: Choquette, Kent D.; Geib, Kent M.; Briggs, Ronald D.; Allerman, Andrew A. & Hindi, Jana Jo
System: The UNT Digital Library
Technologies for energy storage flywheels and super conducting magnetic energy storage (open access)

Technologies for energy storage flywheels and super conducting magnetic energy storage

A flywheel is an electromechanical storage system in which energy is stored in the kinetic energy of a rotating mass. Flywheel systems under development include those with steel flywheel rotors and resin/glass or resin/carbon-fiber composite rotors. The mechanics of energy storage in a flywheel system are common to both steel- and composite-rotor flywheels. In both systems, the momentum of the rotating rotor stores energy. The rotor contains a motor/generator that converts energy between electrical and mechanical forms. In both types of systems, the rotor operates in a vacuum and spins on bearings to reduce friction and increase efficiency. Steel-rotor systems rely mostly on the mass of the rotor to store energy while composite flywheels rely mostly on speed. During charging, an electric current flows through the motor increasing the speed of the flywheel. During discharge, the generator produces current flow out of the system slowing the wheel down. The basic characteristics of a Flywheel system are shown. Steel flywheel systems are currently being marketed in the US and Germany and can be connected in parallel to provide greater power if required. Sizes range from 40kW to 1.6MW for times of 5--120 seconds. At this time sales are limited but growing. …
Date: April 26, 2000
Creator: BOYES,JOHN D.
System: The UNT Digital Library
Exotic Mesons, Theory and Experiment (open access)

Exotic Mesons, Theory and Experiment

In this talk I summarize the status of exotic mesons, including both theoretical expectations and experimental candidates. The current experimental candidates are ''spin-parity exotics'', since these are most often considered possible hybrid mesons, the theoretical discussion will be mainly concerned with hybrids. The exotic meson candidates discussed are the surprisingly light {pi}{sub 1} (1400) and {pi}{sub 1} (1600).
Date: April 26, 2001
Creator: Barnes, T.
System: The UNT Digital Library
Hybrid Baryons, A Brief Review (open access)

Hybrid Baryons, A Brief Review

This contribution is a brief review of the status of hybrid baryons, which are hypothetical baryons that incorporate a gluonic excitation. We first summarize the status of hybrid mesons, since this closely related topic has seen considerable recent activity with the identification of two exotic candidates. Next we review theoretical expectations for the masses and quantum numbers of hybrid baryons, which have come from studies of the bag model, QCD sum rules and the flux tube model. Finally hybrid baryon experiment is discussed, including suggestions for experimenters at COSY.
Date: April 26, 2001
Creator: Barnes, T.
System: The UNT Digital Library
MESON2000 Conference Summary (open access)

MESON2000 Conference Summary

This short contribution is a lite MESON2000 conference summary. As appropriate for the 600th anniversary of the Jagellonian University, it begins with a brief summary of the last 600 years of European history and its place in hadron physics. Next a ''physicist chirality'' order parameter PC is introduced. When applied to MESON2000 plenary speakers this order parameter illustrates the separation of hadron physicists into disjoint communities. The individual plenary talks in MESON2000 are next sorted according to the subconference associated with each of the 36 plenary speakers. Finally, I conclude with a previously unreported Feynman story regarding the use of models in hadron physics.
Date: April 26, 2001
Creator: Barnes, T.
System: The UNT Digital Library
Very High Resolution Simulations of Compressible, Turbulent Flows (open access)

Very High Resolution Simulations of Compressible, Turbulent Flows

The steadily increasing power of supercomputing systems is enabling very high resolution simulations of compressible, turbulent flows in the high Reynolds number limit, which is of interest in astrophysics as well as in several other fluid dynamical applications. This paper discusses two such simulations, using grids of up to 8 billion cells. In each type of flow, convergence in a statistical sense is observed as the mesh is refined. The behavior of the convergent sequences indicates how a subgrid-scale model of turbulence could improve the treatment of these flows by high-resolution Euler schemes like PPM. The best resolved case, a simulation of a Richtmyer-Meshkov mixing layer in a shock tube experiment, also points the way toward such a subgrid-scale model. Analysis of the results of that simulation indicates a proportionality relationship between the energy transfer rate from large to small motions and the determinant of the deviatoric symmetric strain as well as the divergence of the velocity for the large-scale field.
Date: April 26, 2001
Creator: Woodward, P R; Porter, D H; Sytine, I; Anderson, S E; Mirin, A A; Curtis, B C et al.
System: The UNT Digital Library
Development of CaO coatings by thermal and chemical vapor deposition. (open access)

Development of CaO coatings by thermal and chemical vapor deposition.

We have developed CaO coatings that are applied by a thermal and chemical vapor deposition process. Several experiments were conducted to study how the deposition of Ca on a V-4Cr-4Ti substrate alloy is affected by variations in process temperature and time, specimen location, and surface preparation and pretreatment. Results showed that thick adherent coatings can be fabricated by thermal/chemical vapor deposition, especially if a double Ca treatment is applied. Extensive microstructural analysis of the coatings showed almost 100% CaO over a coating thickness of 20-30 {micro}m; electrical resistance (measured by the two-probe method) of the coatings was at least two orders of magnitude higher than the minimum required for blanket application. The results obtained in this study indicate that CaO is a viable coating for V-Li advanced blankets, but that significant additional effort is needed, especially from the standpoint of structure/composition relationship to its electrical resistance and the coating stability in a flowing Li environment. Furthermore, resistance must be measured in situ in Li to simultaneously evaluate coating integrity, resistance, and Li compatibility.
Date: April 26, 2002
Creator: Natesan, K.; Uz, M. & Smith, D. L.
System: The UNT Digital Library
Dynamical x-ray microscopy investigation of electromigration in passivated inlaid Cu interconnect structures (open access)

Dynamical x-ray microscopy investigation of electromigration in passivated inlaid Cu interconnect structures

None
Date: April 26, 2002
Creator: Schneider, G.; Denbeaux, G.; Anderson, E.H.; Bates, B.; Pearson, A.L.; Meyer, M.A. et al.
System: The UNT Digital Library
Fabrication and properties of a tin-lithium alloy. (open access)

Fabrication and properties of a tin-lithium alloy.

A Sn-25 at.% Li alloy has been fabricated by starting with pure Sn and Li. The alloy was cast into various shapes and sent to researchers in several organizations in the United States and abroad for property measurements. The fabrication procedure involved gradual addition of Li from a separate vessel into a vessel that contained Sn; continuous stirring of the mixture during Li addition increased the Li content of the alloy gradually from 0 to the final value of 25 at.%. The melting temperature of the alloy was 334 C; its density was 6.36 g/cm{sup 3}. Results are presented on microstructure, chemical composition, phase distribution, and microhardness of the alloy. Several experiments were conducted to evaluate the chemical reactivity of the alloy with air, water, and steam. Results showed that the alloy undergoes catastrophic oxidation when T >250 C in air and develops an oxide scale in water at temperatures up to 95 C. Exposure in low-pressure steam at 200 C caused significant swelling and cracking of the alloy.
Date: April 26, 2002
Creator: Natesan, K. & Ruther, W.E.
System: The UNT Digital Library
Fabrication of spherical and irregularly shaped powders of Li and Ba titanates from titanium tetrachloride by inorganic sol-gel process. (open access)

Fabrication of spherical and irregularly shaped powders of Li and Ba titanates from titanium tetrachloride by inorganic sol-gel process.

The authors report preparation procedures for some lithium and barium titanate compounds. The procedures utilize inexpensive, commercial TiCl{sub 4} in an aqueous HCl solution. The main preparation steps consist of chloride elimination by distillation with nitric acid, addition of hydroxides of Li (or Ba), evaporation of sols to dry powders, and thermal treatment to titanates. Thermal and X-ray analyses indicate that the formation temperatures are lower than the corresponding temperatures necessary for conventional solid-state reactions. These temperatures can be further decreased by addition of ascorbic acid during formation of Ti nitrate sols. Spherical powders (with particle diameters of < 100 {micro}m) are obtained by solvent extraction of water from sol drops emulsified in 2-ethylheksanol-1. Final correction of the composition of the spherical powders is carried out by an impregnation process.
Date: April 26, 2002
Creator: Deptula, A.; Olczak, T.; Lada, W.; Sartowska, B.; Chmielewski, A. G.; Alvani, C. et al.
System: The UNT Digital Library
Inclined substrate deposition of magnesium oxide for YBCO-coated conductors. (open access)

Inclined substrate deposition of magnesium oxide for YBCO-coated conductors.

Thin films of YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) were grown on MgO buffered metallic substrates by pulsed laser deposition (PLD). The MgO buffer films, which provide the initial biaxial texture, had been grown on polished Hastelloy C276 (HC) tapes using inclined substrate deposition (ISD). The ISD process is promising for the fabrication of coated superconductor wires because it produces biaxially textured template films on nontextured substrate at high deposition rates. Biaxially aligned MgO films were deposited at deposition rates of 20 to 100 {angstrom}/sec. The buffer films were deposited on these template films before ablation of the YBCO films by PLD. The microstructure was studied by scanning electron microscopy and atomic force microscopy. X-ray pole figure analysis and {phi}- and {omega}-scans were used for texture characterization. Good in- and out-of-plane textures were observed on the ISD MgO films ({approx}1.5 {micro}m thick). The full width at half maximums were 9.2{sup o} for the MgO (002) {phi}-scan and 5.4{sup o} for the {omega}-scan. Cube-on-cube epitaxial growth of yttria-stabilized zirconia (YSZ) and ceria (CeO{sub 2}) films on the ISD MgO films was also achieved by PLD. A superconducting critical temperature of 90 K, with a sharp transition, and transport critical current density of …
Date: April 26, 2002
Creator: Ma, B.; Li, M.; Fisher, B. L.; Koritala, R. E.; Dorris, S. E.; Maroni, V. A. et al.
System: The UNT Digital Library
IQARIS : a tool for the intelligent querying, analysis, and retrieval from information systems. (open access)

IQARIS : a tool for the intelligent querying, analysis, and retrieval from information systems.

Information glut is one of the primary characteristics of the electronic age. Managing such large volumes of information (e.g., keeping track of the types, where they are, their relationships, who controls them, etc.) can be done efficiently with an intelligent, user-oriented information management system. The purpose of this paper is to describe a concept for managing information resources based on an intelligent information technology system developed by the Argonne National Laboratory for managing digital libraries. The Argonne system, Intelligent Query (IQ), enables users to query digital libraries and view the holdings that match the query from different perspectives.
Date: April 26, 2002
Creator: Hummel, J. R. & Silver, R. B.
System: The UNT Digital Library
["Mary Cheney joins 'gay-straight' GOP group" article, April 26, 2002] (open access)

["Mary Cheney joins 'gay-straight' GOP group" article, April 26, 2002]

An article written for the Washington Blade about Mary Cheney joining the Republican Unity Coalition's advisory board. The piece includes comments from RUC Co-Chairman Charles C. Francis and also mentions another newer member President Gerald R. Ford.
Date: April 26, 2002
Creator: unknown
System: The UNT Digital Library
Trading of locomotive NO{sub x} emissions : a potential success story. (open access)

Trading of locomotive NO{sub x} emissions : a potential success story.

New US Environmental Protection Agency regulations are forcing locomotive manufacturers and railroads to reduce pollutant emissions from locomotive operation. All new locomotives must meet strict standards when they are built, and existing locomotives must comply when they are rebuilt. Emissions can be reduced either by adjusting combustion parameters, which incurs a fuel penalty, or by turning the diesel engine off when the train is not moving and would otherwise be idling. The latter reduces fuel consumption, but requires installation of a device--such as an auxiliary power unit (APU)--to ensure that the engine can be restarted in cold weather and to supply hotel loads for the crew. Without a financial incentive, capital-short railroads will opt to achieve compliance in the least costly way. However, if they have the option of selling emissions credits from reducing emissions below regulated levels, it would be in their best interest to install additional equipment to minimize emissions. These credits could be purchased by businesses with compliance costs greater than either the cost of the credits or the fines they would have had to pay for non-compliance. The result is a financial benefit for both parties, and a net reduction in emissions, because the seller is …
Date: April 26, 2002
Creator: Gaines, L. L.; Biess, L. J. & Diedrich, G. K.
System: The UNT Digital Library
Ab initio study of low-energy electron collisions withtertafluoroethene, C2F4 (open access)

Ab initio study of low-energy electron collisions withtertafluoroethene, C2F4

We report the results of variational calculations of elastic electron scattering by tetrafluoroethene, C{sub 2}F{sub 4}, with incident electron energies ranging from 0.5 to 20 eV, using the complex Kohn method and effective core potentials. These are the first fully calculations to reproduce experimental angular differential cross sections at energies below 10 eV. Low-energy electron scattering by C{sub 2}F{sub 4} is sensitive to the inclusion of electronic correlation and target-distortion effects. We therefore present results that describe the dynamic polarization of the target by the incident electron. The calculated cross sections are compared with recent experimental measurements.
Date: April 26, 2004
Creator: Trevisan, C. S.; Orel, A. E. & Rescigno, Thomas N.
System: The UNT Digital Library
Development of LLNL Methodology for Nonnuclear Safety Bases (open access)

Development of LLNL Methodology for Nonnuclear Safety Bases

The objective of this paper is to introduce the process and philosophies used to develop LLNL methodology for performing nonnuclear safety bases. Our former approach needed revision in order to implement the new Work Smart Standard (WSS), 'Safety Basis Requirements for Nonnuclear Facilities at Lawrence Livermore National Laboratory Site Specific Standard' (UCRL-ID-150214), approved in 2003 and revised January, 2004. This work relates directly to the following workshop theme: 'Improvements in Chemical, Biological, and Non-nuclear Safety analysis.' A requirements document, Environmental Safety and Health Manual, Document 3.1 provides safety bases methodology 'how-to' for LLNL personnel. This methodology document had to undergo a major revision, and essentially was completely re-written, since the nonnuclear requirements underwent a major change due to the new standard. The new methodology was based on a graded approach respective to risk level for each hazard type and facility classification. The development process included input from a cross-section of representatives of LLNL organizations at every step in the process. The initial methodology was tested in a pilot project that resulted in completed safety basis analyses and documentation for a major facility at LLNL. Feedback from the pilot was used to refine the methodology. The new methodology promotes a graded …
Date: April 26, 2004
Creator: van Warmerdam, C M & Pinkston, D M
System: The UNT Digital Library
Evidence for the predominance of mid-tropopheric aerosols as subtropical anvil nuclei (open access)

Evidence for the predominance of mid-tropopheric aerosols as subtropical anvil nuclei

NASA's recent CRYSTAL-FACE field experiment focused on anvil cirrus clouds, an important but poorly understood element of our climate system. Data obtained include the first comprehensive measurements of aerosols and cloud particles throughout the atmospheric column during the evolution of multiple deep convective storm systems. Coupling these new measurements with detailed cloud simulations that resolve the size distributions of aerosols and cloud particles, we find several lines of evidence that most anvil crystals form on mid-tropospheric rather than boundary layer aerosols. This result defies conventional wisdom and indicates that distant pollution sources may impact anvil clouds more than local sources.
Date: April 26, 2004
Creator: Fridland, Ann; Ackermann, Andy; Jensen, Eric & Stevens, David
System: The UNT Digital Library
Experimental Determination of Thermodynamic Properties of Ion-Exchange in Heulandite: Binary Ion-Exchange Experiments at 55 and 85 oC Involving Ca2+, Sr2+, Na+, and K+ (open access)

Experimental Determination of Thermodynamic Properties of Ion-Exchange in Heulandite: Binary Ion-Exchange Experiments at 55 and 85 oC Involving Ca2+, Sr2+, Na+, and K+

Heulandite is a common rock-forming zeolite that exhibits wide solid solution of extra framework cations, presumably due to ready ion exchange with aqueous solutions. In order to provide a quantitative basis for interpreting and predicting the distribution of aqueous species between heulandite and aqueous solutions, ion exchange equilibrium between heulandite and aqueous solutions with respect to the binary cation pairs Ca{sup 2+} - K{sup +}, Ca{sup 2+} - Na{sup +}, K{sup +} - Na{sup +}, K{sup +} - Sr{sup 2+}, Na{sup +} - Sr{sup 2+}, and Ca{sup 2+} - Sr{sup 2+} was investigated. Homoionic Ca-, K-, and Na-heulandites prepared from natural heulandite were equilibrated with 0.1 N Cl{sup -} solutions containing various proportions of the cations in a given binary pair at 55 and 85 C to define isotherms describing partitioning of the cations over a wide range of heulandite and solution composition with respect to the cations in each pair. In general, the experiments equilibrated rapidly, within 11-15 weeks at 55 C and 3-4 weeks at 85 C. The exception was the Ca{sup 2+} - Sr{sup 2+} binary exchange, which did not equilibrate even after 3 months at 55 C and 4 weeks at 85 C. Slow exchange of …
Date: April 26, 2004
Creator: Fridriksson, T.; Neuhoff, P. S.; Viani, B. E. & Bird, D. K.
System: The UNT Digital Library
Geothermal Prospecting using Hyperspectral Imaging and Field Observations, Dixie Meadows, NV (open access)

Geothermal Prospecting using Hyperspectral Imaging and Field Observations, Dixie Meadows, NV

In an ongoing project to relate surface hydrothermal alteration to structurally controlled geothermal aquifers, we mapped a 16 km swath of the eastern front of the Stillwater Range using Hyperspectral fault and mineral mapping techniques. The Dixie Valley Fault system produces a large fractured aquifer heating Pleistocene aged groundwater to a temperature of 285 C at 5-6 km. Periodically over the last several thousand years, seismic events have pushed these heated fluids to the surface, leaving a rich history of hydrothermal alteration in the Stillwater Mountains. At Dixie Hot Springs, the potentiometric surface of the aquifer intersects the surface, and 75 C waters flow into the valley. We find a high concentration of alunite, kaolinite, and dickite on the exposed fault surface directly adjacent to a series of active fumaroles on the range front fault. This assemblage of minerals implies interaction with water in excess of 200 C. Field spectra support the location of the high temperature mineralization. Fault mapping using a Digital Elevation Model in combination with mineral lineation and field studies shows that complex fault interactions in this region are improving permeability in the region leading to unconfined fluid flow to the surface. Seismic studies conducted 10 km …
Date: April 26, 2004
Creator: Kennedy-Bowdoin, T; Silver, E; Martini, B & Pickles, W
System: The UNT Digital Library
LLNL Microsensors Program (open access)

LLNL Microsensors Program

The Microsensors Program was born out the need for enhanced sensor technology in support of the Weapons Program. In the interest of expanded diagnostic capabilities to provide true performance characteristics of weapon assemblies in flight and ground tests, a suite of sensor requirements was proposed. These potential new sensor technologies were envisioned to be completely unobtrusive and allow for the development of test vehicles (mock warheads and bomb assemblies) that were designed to mechanical and electrical specifications as close to the stockpile weapon design configuration as possible. The closeness of a test vehicle design to the respective stockpile weapon design is referred to as ''fidelity,'' with the term ''high-fidelity'' to mean all components are designed to emulate, very closely, the true system design. These efforts were in line with many activities associated with Stockpile Stewardship and were intended to enable better modeling and performance assessment without the need for underground testing. Several weapons are currently undergoing Life Extension Programs (LEP) to lengthen each weapon system's respective service life. The ability to assess the projected life of these complex assemblies is crucial to the success of the LEP activities.
Date: April 26, 2004
Creator: Lavietes, A
System: The UNT Digital Library
Making european-style community wind power development work in theUnited States (open access)

Making european-style community wind power development work in theUnited States

Once primarily a European phenomenon, community wind power development--defined here as one or more locally owned, utility-scale wind turbines interconnected on either the customer or utility side of the meter--is gaining a foothold in an increasing number of states throughout the United States. This article describes the various policies and incentives that Minnesota, Wisconsin, Iowa, and Massachusetts are using to support community wind power development, and how state and federal support influences the types of projects and ownership structures that are being developed. Experience in these states demonstrates that, with an array of incentives and creative financing schemes targeted at community-scale projects, there are opportunities to make community wind work in the United States.
Date: April 26, 2004
Creator: Bolinger, Mark A.
System: The UNT Digital Library