Resource Type

78 Matching Results

Results open in a new window/tab.

Effects of high beam rates on TPC's (open access)

Effects of high beam rates on TPC's

The TPC's (Time Projection Chamber) used in E-810 at the AGS (Alternating Gradient Synchroton) were exposed to silicon ion fluxes equivalent to more than 10{sup 7} minimum ionizing particles per second to measure the distortion of the electric field caused by positive ions in the drift region. Results of these tests are presented and the consequences for the TPC based experiment at RHIC (Relativistic Heavy Ion Collider) are discussed.
Date: February 6, 1992
Creator: Etkin, A.; Eiseman, S. E.; Foley, K. J.; Hackenburg, R. W.; Longacre, R. S.; Love, W. A. et al.
System: The UNT Digital Library
Preliminary Results from the UCLA/SLAC Ultra-High Gradient CerenkovWakefield Accelerator Experiment (open access)

Preliminary Results from the UCLA/SLAC Ultra-High Gradient CerenkovWakefield Accelerator Experiment

The first phase of an experiment to study the performance of dielectric Cerenkov wakefield accelerating structures at extremely high gradients in the GV/m range has been completed. This experiment takes advantage of the unique SLAC FFTB electron beam and its demonstrated ultra-short pulse lengths and high currents (e.g., {sigma}{sub z} = 20 {micro}m at Q = 3 nC). The FFTB electron beam has been successfully focused down and sent through varying lengths of fused silica capillary tubing with two different sizes: ID = 200 {micro}m/OD = 325 {micro}m and ID = 100 {micro}m/OD = 325 {micro}m. The pulse length of the electron beam was varied in the range 20 {micro}m < {sigma}{sub z} < 100 {micro}m which produced a range of electric fields between 2 and 20 GV/m at the inner surface of the dielectric tubes. We observed a sharp increase in optical emissions from the capillaries in the middle part of this surface field range which we believe indicates the transition between sustainable field levels and breakdown. If this initial interpretation is correct, the surfaced fields that were sustained equate to on axis accelerating field of several GV/m. In future experiments we plan to collect and measure coherent Cerenkov …
Date: February 6, 2008
Creator: Thompson, M. C.; Badakov, H.; Rosenzweig, J. B.; Travish, G.; Hogan, M.; Ischebeck, R. et al.
System: The UNT Digital Library
Seismic Waves in Rocks with Fluids and Fractures (open access)

Seismic Waves in Rocks with Fluids and Fractures

Seismic wave propagation through the earth is often strongly affected by the presence of fractures. When these fractures are filled with fluids (oil, gas, water, CO{sub 2}, etc.), the type and state of the fluid (liquid or gas) can make a large difference in the response of the seismic waves. This paper will summarize some early work of the author on methods of deconstructing the effects of fractures, and any fluids within these fractures, on seismic wave propagation as observed in reflection seismic data. Methods to be explored here include Thomsen's anisotropy parameters for wave moveout (since fractures often induce elastic anisotropy), and some very convenient fracture parameters introduced by Sayers and Kachanov that permit a relatively simple deconstruction of the elastic behavior in terms of fracture parameters (whenever this is appropriate).
Date: February 6, 2006
Creator: Berger, E. L.
System: The UNT Digital Library
Volume Independence in Large Nc QCD-like Gauge Theories (open access)

Volume Independence in Large Nc QCD-like Gauge Theories

Volume independence in large N{sub c} gauge theories may be viewed as a generalized orbifold equivalence. The reduction to zero volume (or Eguchi-Kawai reduction) is a special case of this equivalence. So is temperature independence in confining phases. A natural generalization concerns volume independence in ''theory space'' of quiver gauge theories. In pure Yang-Mills theory, the failure of volume independence for sufficiently small volumes (at weak coupling) due to spontaneous breaking of center symmetry, together with its validity above a critical size, nicely illustrate the symmetry realization conditions which are both necessary and sufficient for large N{sub c} orbifold equivalence. The existence of a minimal size below which volume independence fails also applies to Yang-Mills theory with antisymmetric representation fermions [QCD(AS)]. However, in Yang-Mills theory with adjoint representation fermions [QCD(Adj)], endowed with periodic boundary conditions, volume independence remains valid down to arbitrarily small size. In sufficiently large volumes, QCD(Adj) and QCD(AS) have a large N{sub c} ''orientifold'' equivalence, provided charge conjugation symmetry is unbroken in the latter theory. Therefore, via a combined orbifold-orientifold mapping, a well-defined large N{sub c} equivalence exists between QCD(AS) in large, or infinite, volume and QCD(Adj) in arbitrarily small volume. Since asymptotically free gauge theories, such …
Date: February 6, 2007
Creator: Kovtun, Pavel; Unsal, Mithat & Yaffe, Laurence G.
System: The UNT Digital Library
Charm and Charmonium Spectroscopy in BaBar (open access)

Charm and Charmonium Spectroscopy in BaBar

The BABAR experiment at the PEP-II B-factory offers excellent opportunities in charm and charmonium spectroscopy. The recent observation of new states in the D{sub s} and in the charmonium mass regions revived the interest in this field. Recent BABAR results are presented.
Date: February 6, 2008
Creator: Negrini, M. & U., /Ferrara
System: The UNT Digital Library
The 13th International Symposium on Relations between Homogeneous and Heterogeneous Catalysis -- AnIntroduction (open access)

The 13th International Symposium on Relations between Homogeneous and Heterogeneous Catalysis -- AnIntroduction

Over forty years, there have been major efforts to aim at understanding the properties of surfaces, structure, composition, dynamics on the molecular level and at developing the surface science of heterogeneous and homogeneous catalysis. Since most catalysts (heterogeneous, enzyme and homogeneous) are nanoparticles, colloid synthesis methods were developed to produce monodispersed metal nanoparticles in the 1-10 nm range and controlled shapes to use them as new model catalyst systems in two-dimensional thin film form or deposited in mezoporous three-dimensional oxides. Studies of reaction selectivity in multipath reactions (hydrogenation of benzene, cyclohexene and crotonaldehyde) showed that reaction selectivity depends on both nanoparticle size and shape. The oxide-metal nanoparticle interface was found to be an important catalytic site because of the hot electron flow induced by exothermic reactions like carbon monoxide oxidation.
Date: February 6, 2008
Creator: Somorjai, Gabor A.
System: The UNT Digital Library
Feasibility Evaluation and Retrofit Plan for Cold Crucible Induction Melter Deployment in the Defense Waste Processing Facility at Savannah River Site 8118 (open access)

Feasibility Evaluation and Retrofit Plan for Cold Crucible Induction Melter Deployment in the Defense Waste Processing Facility at Savannah River Site 8118

Cold crucible induction melters (CCIM) have been proposed as an alternative technology for waste glass melting at the Defense Waste Processing Facility (DWPF) at Savannah River Site (SRS) as well as for other waste vitrification facilities. Proponents of this technology cite high temperature operation, high tolerance for noble metals and aluminum, high waste loading, high throughput capacity, and low equipment cost as the advantages over existing Joule Heated Melter (JHM) technology. The CCIM uses induction heating to maintain molten glass at high temperature. A water-cooled helical induction coil is connected to an AC current supply, typically operating at frequencies from 100 KHz to 5 MHz. The oscillating magnetic field generated by the oscillating current flow through the coil induces eddy currents in conductive materials within the coil. Those oscillating eddy currents, in turn, generate heat in the material. In the CCIM, the induction coil surrounds a 'Cold Crucible' which is formed by metal tubes, typically copper or stainless steel. The tubes are constructed such that the magnetic field does not couple with the crucible. Therefore, the field generated by the induction coil couples primarily with the conductive medium (hot glass) within. The crucible tubes are water cooled to maintain their …
Date: February 6, 2008
Creator: Barnes, Allan B.; Iverson, Daniel C.; Adkins, Brannen J. & Tchemitcheff, Eric
System: The UNT Digital Library
ISS-flation (open access)

ISS-flation

Inflation may occur while rolling into the metastable supersymmetry-breaking vacuum of massive supersymmetric QCD. We explore the range of parameters in which slow-roll inflation and long-lived metastable supersymmetry breaking may be simultaneously realized. The end of slow-roll inflation in this context coincides with the spontaneous breaking of a global symmetry, which may give rise to significant curvature perturbations via inhomogeneous preheating. Such spontaneous symmetry breaking at the end of inflation may give rise to observable non-gaussianities, distinguishing this scenario from more conventional models of supersymmetric hybrid inflation.
Date: February 6, 2008
Creator: Craig, Nathaniel J. & /SLAC /Stanford U., ITP
System: The UNT Digital Library
Conference on decontamination and decommissioning of nuclear facilities (open access)

Conference on decontamination and decommissioning of nuclear facilities

A brief history of Decontamination and Decommissioning (D and D) experience at the Idaho National Engineering Laboratory is presented as an introduction to the status of current projects. Details are then presented as an introduction to the status of current projects. Details are then presented on a project to remove sodium from some major components of the Hallam reactor and on the Organic Moderated Reactor Experiment (OMRE) decommissioning project. Cost, schedule, waste volume, and other technical data from these projects are presented. In addition, a brief summary of the future INEL D and D program is presented.
Date: February 6, 1979
Creator: Meservey, R.H.
System: The UNT Digital Library
Capturing asteroids into bound orbits around the earth: Massive early return on an asteroid terminal defense system (open access)

Capturing asteroids into bound orbits around the earth: Massive early return on an asteroid terminal defense system

Nuclear explosives may be used to capture small asteroids (e.g., 20--50 meters in diameter) into bound orbits around the earth. The captured objects could be used for construction material for manned and unmanned activity in Earth orbit. Asteroids with small approach velocities, which are the ones most likely to have close approaches to the Earth, require the least energy for capture. They are particularly easy to capture if they pass within one Earth radius of the surface of the Earth. They could be intercepted with intercontinental missiles if the latter were retrofit with a more flexible guiding and homing capability. This asteroid capture-defense system could be implemented in a few years at low cost by using decommissioned ICMs. The economic value of even one captured asteroid is many times the initial investment. The asteroid capture system would be an essential part of the learning curve for dealing with larger asteroids that can hit the earth.
Date: February 6, 1992
Creator: Hills, J.G.
System: The UNT Digital Library
Techniques for the generation and monitoring of vapors (open access)

Techniques for the generation and monitoring of vapors

Controlled test atmospheres can be produced using a variety of techniques. Gases are usually generated by using flow dilution methods while vapors are produced by using solvent injection and vaporization, saturation, permeation and diffusion techniques. The resulting gas mixtures can be monitored and measured using flame ionization, photoionization, electrochemical and infrared analytical systems. An ideal system for the production of controlled test atmospheres would not only be able to generate controlled test atmospheres, but also monitor all pertinent environmental parameters, such as temperature, humidity, and air flow.
Date: February 6, 1981
Creator: Nelson, G.O.
System: The UNT Digital Library
Structural and thermal requirements for the tandem-mirror fusion-test-facility magnet system (open access)

Structural and thermal requirements for the tandem-mirror fusion-test-facility magnet system

Structural requirements for the magnet system include unique spatial constraints and materials restrictions to meet the operational needs of the unusual configuration. All of the magnets are liquid helium cooled which represents about 1500 tonnes of 4.5 K structure in the vacuum environment of the large vessel. Magnet support structures must satisfy complex load conditions, including electromagnetic (both normal-operating and fault conditions) and seismically induced. Improved plasma confinement, characterized by long particle lifetimes, requires attention to coil alignment and field errors. Continued monitoring of field accuracy and possible adjustment during operation are contemplated. Operating conditions for the magnet system include rapid cooldown and warm-up to minimize down time for maintenance.
Date: February 6, 1981
Creator: VanSant, J. H. & Bulmer, R. H.
System: The UNT Digital Library
Noncontact material testing using laser energy deposition and interferometry (open access)

Noncontact material testing using laser energy deposition and interferometry

A technique is described for the noncontact testing of materials using laser deposition to generate a stress pulse and interferometry to record the transient surface displacement. The dilatational wave speed can be measured and, in the particular case of rod or plate specimens, sufficient information can be obtained to evaluate the two elastic constants of an isotropic material. Several applications illustrating the advantages of the approach are summarized.
Date: February 6, 1978
Creator: Calder, C.A. & Wilcox, W.W.
System: The UNT Digital Library
Effect of propagation of coherent pulses on multiple-photon excitation (open access)

Effect of propagation of coherent pulses on multiple-photon excitation

The influence of laser pulse propagation on multiple-photon excitation of many-level absorbers, and the significance of SIRF for SF/sub 6/ dissociation are discussed.
Date: February 6, 1980
Creator: Shore, B. W.; Eberly, J. H. & Konopnicki, M. J.
System: The UNT Digital Library
Capturing asteroids into bound orbits around the earth: Massive early return on an asteroid terminal defense system (open access)

Capturing asteroids into bound orbits around the earth: Massive early return on an asteroid terminal defense system

Nuclear explosives may be used to capture small asteroids (e.g., 20--50 meters in diameter) into bound orbits around the earth. The captured objects could be used for construction material for manned and unmanned activity in Earth orbit. Asteroids with small approach velocities, which are the ones most likely to have close approaches to the Earth, require the least energy for capture. They are particularly easy to capture if they pass within one Earth radius of the surface of the Earth. They could be intercepted with intercontinental missiles if the latter were retrofit with a more flexible guiding and homing capability. This asteroid capture-defense system could be implemented in a few years at low cost by using decommissioned ICMs. The economic value of even one captured asteroid is many times the initial investment. The asteroid capture system would be an essential part of the learning curve for dealing with larger asteroids that can hit the earth.
Date: February 6, 1992
Creator: Hills, J. G.
System: The UNT Digital Library
A Source-to-Source Architecture for User-Defined Optimizations (open access)

A Source-to-Source Architecture for User-Defined Optimizations

The performance of object-oriented applications often suffers from the inefficient use of high-level abstractions provided by underlying libraries. Since these library abstractions are user-defined and not part of the programming language itself only limited information on their high-level semantics can be leveraged through program analysis by the compiler and thus most often no appropriate high-level optimizations are performed. In this paper we outline an approach based on source-to-source transformation to allow users to define optimizations which are not performed by the compiler they use. These techniques are intended to be as easy and intuitive as possible for potential users; i.e. for designers of object-oriented libraries, people most often only with basic compiler expertise.
Date: February 6, 2003
Creator: Schordan, M & Quinlan, D
System: The UNT Digital Library
Metastable metallic hydrogen glass (open access)

Metastable metallic hydrogen glass

The quest for metallic hydrogen has been going on for over one hundred years. Before hydrogen was first condensed into a liquid in 1898, it was commonly thought that condensed hydrogen would be a metal, like the monatomic alkali metals below hydrogen in the first column of the Periodic Table. Instead, condensed hydrogen turned out to be transparent, like the diatomic insulating halogens in the seventh column of the Periodic Table. Wigner and Huntington predicted in 1935 that solid hydrogen at 0 K would undergo a first-order phase transition from a diatomic to a monatomic crystallographically ordered solid at {approx}25 GPa. This first-order transition would be accompanied by an insulator-metal transition. Though searched for extensively, a first-order transition from an ordered diatomic insulator to a monatomic metal is yet to be observed at pressures up to 120 and 340 GPa using x-ray diffraction and visual inspection, respectively. On the other hand, hydrogen reaches the minimum electrical conductivity of a metal at 140 GPa, 0.6 g/cm{sup 3}, and 3000 K. These conditions were achieved using a shock wave reverberating between two stiff sapphire anvils. The shock wave was generated with a two-stage light-gas gun. This temperature exceeds the calculated melting temperature …
Date: February 6, 2001
Creator: Nellis, W J
System: The UNT Digital Library
The National Ignition Facility (open access)

The National Ignition Facility

The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory is a stadium-sized facility containing a 192-beam, 1.8-Megajoule, 500-Terawatt, ultraviolet laser system together with a 10-meter-diameter target chamber and room for 100 diagnostics. NIF is the world's largest and most energetic laser experimental system, providing a scientific center to study inertial confinement fusion and matter at extreme energy densities and pressures. NIF's energetic laser beams will compress fusion targets to conditions required for thermonuclear burn, liberating more energy than required to initiate the fusion reactions. Other NIF experiments will study physical processes at temperatures approaching 10{sup 8} K and 10{sup 11} bar; conditions that exist naturally only in the interior of stars and planets. NIF has completed the first phases of its laser commissioning program. The first four beams of NIF have generated 106 kilojoules in 23-ns pulses of infrared light and over 16 kJ in 3.5-ns pulses at the third harmonic (351 nm). NIF's target experimental systems are being commissioned and experiments have begun. This paper provides a detailed look the NIF laser systems, laser and optical performance, and results from recent laser commissioning shots. We follow this with a discussion of NIF's high-energy-density and inertial fusion experimental capabilities, …
Date: February 6, 2004
Creator: Miller, G H; Moses, E I & Wuest, C R
System: The UNT Digital Library
Fabrication and Test Results of a Nb3Sn Superconducting Racetrack Dipole Magnet (open access)

Fabrication and Test Results of a Nb3Sn Superconducting Racetrack Dipole Magnet

A 'proof-of-principle' Nb{sub 3}Sn superconducting dual-bore dipole magnet was built from racetrack coils, as a first step in a program to develop an economical, 15 Tesla, accelerator-quality magnet. The mechanical design and magnet fabrication procedures are discussed. No training was required to achieve temperature-dependent plateau currents, despite several thermal cycles that involved partial magnet disassembly and substantial pre-load variations. Subsequent magnets are expected to approach 15 Tesla with substantially improved conductor.
Date: February 6, 2000
Creator: Chow, K.; Dietderich, D. R.; Gourlay, S. A.; Gupta, R.; Harnden, W.; Lietzke, A. F. et al.
System: The UNT Digital Library
Microseismic monitoring of the Chaveroo oil field, New Mexico (open access)

Microseismic monitoring of the Chaveroo oil field, New Mexico

Microseismicity was monitored in the Chaveroo oil field in southeastern New Mexico during, and for 5 weeks following, a pressurized stimulation of a well being prepared as an injector for a water flood operation. Three-thousand barrels of water were injected into the reservoir over a 5.5-hour period. Little seismicity was detected during the stimulation. Intermittent monitoring over a 5-week period following the injection indicated detectable seismicity occurring with activity levels varying in time. The most active period recorded occurred just after production resumed in the immediate area of the monitor well. Mapping the microearthquakes using the hodogram technique indicates the events occur along linear trends which corroborate known structural trends of the field. Seismicity trends were defined both parallel and perpendicular to the regionally defined maximum horizontal stress direction. Seventy-three good quality events were recorded, in a cumulative 24 hour period, from which structures were mapped up to 3000 ft from the monitor well. 13 refs., 9 figs.
Date: February 6, 1990
Creator: Rutledge, J. T. & Albright, J. N.
System: The UNT Digital Library
Kinematical and Dynamical Aspects of Higher-Spin Bound-State Equations in Holographic QCD (open access)

Kinematical and Dynamical Aspects of Higher-Spin Bound-State Equations in Holographic QCD

None
Date: February 6, 2013
Creator: de Teramond, Guy F.; Dosch, Hans Gunter & Brodsky, Stanley J.
System: The UNT Digital Library
Thick target measurement of the 40Ca(alpha,gamma)44Ti reaction rate (open access)

Thick target measurement of the 40Ca(alpha,gamma)44Ti reaction rate

The thick-target yield for the {sup 40}Ca({alpha},{gamma}){sup 44}Ti reaction has been measured for E{sub beam} = 4.13, 4.54, and 5.36 MeV using both an activation measurement and online {gamma}-ray spectroscopy. The results of the two measurements agree. From the measured yield a reaction rate is deduced that is smaller than statistical model calculations. This implies a smaller {sup 44}Ti production in supernova compared to recently measured {sup 40}Ca({alpha},{gamma}){sup 44}Ti reaction rates.
Date: February 6, 2009
Creator: Sheets, S A; Burke, J T; Scielzo, N D; Phair, L; Bleuel, D; Norman, E B et al.
System: The UNT Digital Library
NIF Target Fabrication (open access)

NIF Target Fabrication

None
Date: February 6, 2013
Creator: Hamza, A V
System: The UNT Digital Library
Chemical and electronic characterization of cobalt in Lanthanumperovskites. Effects of Strontium substitution (open access)

Chemical and electronic characterization of cobalt in Lanthanumperovskites. Effects of Strontium substitution

Two different cobaltites, LaCoO{sub 3} and La{sub 0.5}Sr{sub 0.5}CoO{sub 3-{delta}}, have been prepared and characterized by means of high energy Co K-edge and low energy O K-edge X-ray absorption spectroscopy (XAS). The partial substitution of La(III) by Sr(II) species induces important changes in the reactivity and electronic state of the perovskite, while little or no changes can be detected in the formal oxidation state of cobalt atoms. The presence of strontium cations induces two main effects in the chemical and electronic behavior of the perovskite. The charge balance with Sr(II) species is reached by the formation of oxygen vacancies throughout the network, which increases the reactivity of the perovskite, now more reducible than the original LaCoO{sub 3} perovskite. O K-edge XAS experiments indicate that the Sr(II) species cause d electrons of cobalt cations to change from low to high spin configuration. Our data allow us to propose that this change in spin multiplicity is induced by the bigger size of Sr(II) cations, which aligns the Co-O-Co atoms, and favors the overlapping of {pi}-symmetry cobalt and oxygen orbitals, reducing the splitting energy of e{sub g} and t{sub 2g} levels.
Date: February 6, 2009
Creator: Hueso, Jose L.; Holgado, Juan P.; Pereniguez, Rosa; Mun, Simon; Salmeron, Miquel & Caballero, Alfonso
System: The UNT Digital Library