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Measurement of the angular distribution of electrons from W {right arrow} e{nu} decays observed in p pbar collisions at {squareroot}s = 1.8 TeV
We present a preliminary measurement of the electron angular distribution parameter {alpha}<sub>2</sub> in W {yields} e{nu} events using data collected by the D0 detector during the 1994-1995 Tevatron run. We compare our results with next-to- leading order perturbative QCD, which predicts an angular distribution of (1±{alpha}<sub>1</sub> cos{theta}* +{alpha}<sub>2</sub> cos²{theta}*), where {theta}* is the angle between the charged lepton and the antiproton in the Collins-Soper frame. In the presence of QCD corrections, the parameters {alpha}<sub>1</sub> and {alpha}<sub>2</sub> become functions of p<sup>W</sup><sub>T</sub> , the W boson transverse momentum. We present the first measurement of {alpha}<sub>2</sub> as a function of p<sup>W</sup><sub>T</sub>. This measurement is of importance, because it provides a test of next-to-leading order QCD corrections which are a non-negligible contribution to the W mass measurement.
Date:
July 26, 1999
Creator:
Abbott, B.
Object Type:
Article
System:
The UNT Digital Library
Final report: Efficient thyratron modulator project
The purpose of this program was to examine methods of increasing the efficiency of producing pulses to drive Klystrons in the 150 MW range. This may include 2 Klystrons in the 75 MW range. Specific methods of interest to improve the pulse efficiency were the use of a circuit to add energy to the tail of the pulse, the use of a bipyrimidal transformer, and the use of gas insulation as a means of improving the pulse shape. These methods were investigated using both thyratron and IGBT switching. The low cost designs developed in this work consisted of low voltage designs which don't require the oil immersion. These designs can be ''hot tuned'' based on the use of simple, tunable inductors.
Date:
November 26, 1999
Creator:
Adler, R. J.; Richter-Sand, R. J. & Gregg, C. W.
Object Type:
Report
System:
The UNT Digital Library
Caribbean Basin Enhancement Legislation
Legislation provides Caribbean countries similar tariff benefits as Mexico under the Caribbean and Central American Relief and Economic Stabilization Act. A senate bill provides relief to the hurricane affected countries of Central America. The senate bill is more restrictive than the House bill in the scope of tariff benefits offered.
Date:
March 26, 1999
Creator:
Ahearn, Raymond
Object Type:
Report
System:
The UNT Digital Library
Characterizing Composition Modulations in InAs/AIAs Short-Period Superlattices
The formation of quantum wires has much interest due to their novel electronic properties which may lead to enhanced optoelectronic device performance and greater photovoltaic efficiencies. One method of forming these structures is through spontaneous lateral modulation found during the epitaxial growth of III/V alloys. In this paper, we report and summarize our investigations on the formation of lateral moduation in the MBE grown InAlAs/InP(001) system. This system was grown as a short-period superlattice where n-monolayers of InAs are deposited followed by m-Monolayers of AlAs (with n and m~2) and this sequence is repeated to grown a low strain InAlAs ternary alloy on InP(001) that exhibits lateral modulation. Films were grown under a variety of condition (growth temperature, effective alloy composition, superlattice period, and growth rate). These films have been extensively analyzed using X-ray diffraction, atomic force microscopy, and transmission electron microscopy (TEM) and microcharacterization, in addition to photon-based spectroscopes. Here we present results of several microstructural characterizations using a wide range of TEM-based techniques, and compare them to results from the other methods to obtain a unified understanding of composition modulation. Two strong points consistently emerge: 1) The lateral modulation wavelength is insensitive to growth temperature and effective alloy …
Date:
April 26, 1999
Creator:
Ahrenkiel, S. P.; Follstaedt, D. M.; Jones, E. D.; Lee, S. R.; Mascarenhas, A.; Mirecki-Millunchick, J. et al.
Object Type:
Article
System:
The UNT Digital Library
Subsurface imaging using the spectral polarization difference technique and NIR illumination
A subsurface imaging system is utilized to test the ability of the spectral polarization difference imaging technique for deep subsurface imaging in tissues. The illumination of the system is derived from compact class III lasers in the red and NIR spectral region and, alternatively, from a white light source and selection of the appropriate illumination wavelength using band-pass optical filters. The experimental results demonstrate detection and imaging of a high-scattering object located up to 1.5 cm underneath the surface of a host chicken tissue.
Date:
January 26, 1999
Creator:
Alfano, R R; Demos, S G & Radousky, H B
Object Type:
Article
System:
The UNT Digital Library
Beam Tilt and Angular Dispersion in Broad-Bandwidth, Nanosecond Optical Parametric Oscillators
We show that the signal and idler beams generated by certain types of unseeded, nanosecond optical parametric oscillators are tilted and angularly dispersed and have anomalously large bandwidths. This effect is demonstrated in both laboratory measurements and a numerical model. We show how the optical cavity design influences the tilts and how they can be eliminated or minimized. We also determine the conditions necessary to injection seed these parametric oscillators.
Date:
January 26, 1999
Creator:
Alford, W. J.; Arisholm, G.; Gehr, R. J.; Schmitt, R. L. & A.V., Smith.
Object Type:
Article
System:
The UNT Digital Library
The Oklahoma Daily (Norman, Okla.), Vol. 83, No. 91, Ed. 1 Tuesday, January 26, 1999
Student newspaper of the University of Oklahoma in Norman, Oklahoma that includes national, local, and campus news along with advertising.
Date:
January 26, 1999
Creator:
Allam, Heather
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
The Oklahoma Daily (Norman, Okla.), Vol. 83, No. 114, Ed. 1 Friday, February 26, 1999
Student newspaper of the University of Oklahoma in Norman, Oklahoma that includes national, local, and campus news along with advertising.
Date:
February 26, 1999
Creator:
Allam, Heather
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
The Oklahoma Daily (Norman, Okla.), Vol. 83, No. 127, Ed. 1 Friday, March 26, 1999
Student newspaper of the University of Oklahoma in Norman, Oklahoma that includes national, local, and campus news along with advertising.
Date:
March 26, 1999
Creator:
Allam, Heather
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
The Oklahoma Daily (Norman, Okla.), Vol. 83, No. 150, Ed. 1 Monday, April 26, 1999
Student newspaper of the University of Oklahoma in Norman, Oklahoma that includes national, local, and campus news along with advertising.
Date:
April 26, 1999
Creator:
Allam, Heather
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Development of Characterization Tools for Reliability Testing of MicroElectroMechanical System Actuators
Characterization tools have been developed to study the performance characteristics and reliability of surface micromachined actuators. These tools include (1) the ability to electrically stimulate or stress the actuator, (2) the capability to visually inspect the devices in operation, (3) a method for capturing operational information, and (4) a method to extract performance characteristics from the operational information. Additionally, a novel test structure has been developed to measure electrostatic forces developed by a comb drive actuator.
Date:
July 26, 1999
Creator:
Allen, James J.; Eaton, William P.; Smith, Norman F. & Tanner, Danelle M.
Object Type:
Article
System:
The UNT Digital Library
Novel InGaAsN pn Junction for High-Efficiency Multiple-Junction Solar Cells
We report the application of a novel material, InGaAsN, with bandgap energy of 1.05 eV as a junction in an InGaP/GaAs/InGaAsN/Ge 4-junction design. Results of the growth and structural, optical, and electrical properties were demonstrated, showing the promising perspective of this material for ultra high efficiency solar cells. Photovoltaic properties of an as-grown pn diode structure and improvement through post growth annealing were also discussed.
Date:
March 26, 1999
Creator:
Allerman, A. A.; Chang, P. C.; Gee, J. M.; Hammons, B. E.; Hou, H. Q.; Jones, E. D. et al.
Object Type:
Article
System:
The UNT Digital Library
Flux effects on defect production and damage accumulation in cu and fe exposed to IFE-like conditions
Radiation damage production and accumulation in solids can be divided into two stages. In the production stage, the impinging particle gradually gives off its kinetic energy to lattice atoms in the form of energetic recoils. These deposit their energy by generating secondary and higher order recoils that result in a displacement collision cascade. The outcome of this stage, of the time scale of a few to 100 picoseconds, is a population of point or clustered defects known as the primary state of damage. In the second stage, which can extend over seconds, defects that survive recombination within their nascent cascade migrate over long distances, interacting with the microstructure. These freely migrating defects (FMD) are responsible for the changes in the macroscopic properties of metals under irradiation, such as void swelling, embrittlement, radiation enhanced diffusion, etc. Such changes in mechanical properties are most often detrimental and severely limit the flexibility in materials choice and operating temperature when designing a fusion power plant. Under most conditions, such as those that would be present in a magnetic fusion energy plant, or when bombarding with fission or spallation neutrons, irradiation takes place at a certain dose rate and temperature, but in a continuous manner. …
Date:
August 26, 1999
Creator:
Alonso, E. A.; Caturla, M. J.; Diaz de la Rubia, T.; Perlado, J. M. & Stoller, R. E.
Object Type:
Article
System:
The UNT Digital Library
The design of a liquid lithium lens for a muon collider.
The last stage of ionization cooling for the muon collider requires a multistage liquid lithium lens. This system uses a large ({approximately}0.5 MA) pulsed current through liquid lithium to focus the beam while energy loss in the lithium removes momentum which is replaced by linacs. The beam optics are designed to maximize the 6 dimensional transmission from one lens to the next while minimizing emittance growth. The mechanical design of the lithium vessel is constrained by a pressure pulse due to the sudden ohmic heating, and the stress on the Be window. The authors describe beam optics, the liquid lithium pressure vessel, pumping, power supplies, as well as the overall optimization of the system.
Date:
March 26, 1999
Creator:
Balbekov, V.; Geer, S.; Hassanein, A.; Holtkamp, N.; Lebrun, P.; Neuffer, D. et al.
Object Type:
Article
System:
The UNT Digital Library
An ep collider with E{sub cm} = 1 TeV in a VLHC booster tunnel.
The low field option for the VLHC includes a 3 TeV proton booster with a circumference of 34 km. The authors are studying the option of an electron ring to fit in this tunnel which can produce ep collisions with a luminosity of 1 fb{sup {minus}1}/yr with a center of mass energy of 1 TeV. The machine would utilize superconducting rf and small low field magnets for the {approximately} 80 GeV electron beam. They describe the vacuum chamber/magnet system, rf power supply requirements, vacuum chamber cooling, interaction regions and installation of the facility in the tunnel, as well as provide preliminary estimates of beam stability and lifetimes.
Date:
March 26, 1999
Creator:
Barber, D. P.; Chojnacki, E.; Derrick, M.; Friedsam, H.; Gorski, A.; Hanuska, S. et al.
Object Type:
Article
System:
The UNT Digital Library
News Bulletin (Castroville, Tex.), Vol. 41, No. 34, Ed. 1 Thursday, August 26, 1999
Weekly newspaper from Castroville, Texas that includes local, state, and national news along with extensive advertising.
Date:
August 26, 1999
Creator:
Barnes, Thomas
Object Type:
Newspaper
System:
The Portal to Texas History
GaN CVD Reactions: Hydrogen and Ammonia Decomposition and the Desorption of Gallium
Isotopic labeling experiments have revealed correlations between hydrogen reactions, Ga desorption, and ammonia decomposition in GaN CVD. Low energy electron diffraction (LEED) and temperature programmed desorption (TPD) were used to demonstrate that hydrogen atoms are available on the surface for reaction after exposing GaN(0001) to deuterium at elevated temperatures. Hydrogen reactions also lowered the temperature for Ga desorption significantly. Ammonia did not decompose on the surface before hydrogen exposure. However, after hydrogen reactions altered the surface, N<sup>15</sup>H<sub>3</sub> did undergo both reversible and irreversible decomposition. This also resulted in the desorption of N<sub>2</sub> of mixed isotopes below the onset of GaN sublimation, This suggests that the driving force of the high nitrogen-nitrogen bond strength (226 kcal/mol) can lead to the removal of nitrogen from the substrate when the surface is nitrogen rich. Overall, these findings indicate that hydrogen can influence G-aN CVD significantly, being a common factor in the reactivity of the surface, the desorption of Ga, and the decomposition of ammonia.
Date:
May 26, 1999
Creator:
Bartram, Michael E. & Creighton, J. Randall
Object Type:
Article
System:
The UNT Digital Library
Cesaro-One Summability and Uniform Convergence of Solutions of a Sturm-Liouville System
Galerkin methods are used in separable Hilbert spaces to construct and compute L{sup 2} [0,{pi}] solutions to large classes of differential equations. In this note a Galerkin method is used to construct series solutions of a nonhomogeneous Sturm-Liouville problem defined on [0,{pi}]. The series constructed are shown to converge to a specified du Bois-Reymond function f in L{sup 2} [0,{pi}]. It is then shown that the series solutions can be made to converge uniformly to the specified du Bois-Reymond function when averaged by the Ces{'a}ro-one summability method. Therefore, in the Ces{'a}ro-one sense, every continuous function f on [0,{pi}] is the uniform limit of solutions of nonhomogeneous Sturm-Liouville problems.
Date:
January 26, 1999
Creator:
Baty, R.S. & Tucker, D.H.
Object Type:
Article
System:
The UNT Digital Library
Thermal Barrier Coatings for Low Emission, High Efficiency Diesel Engine Applications
Thermal efficiencies of 54% have been demonstrated by single cylinder engine testing of advanced diesel engine concepts developed under Department of Energy funding. In order for these concept engines to be commercially viable, cost effective and durable systems for insulating the piston, head, ports and exhaust manifolds will be required. The application and development of new materials such as thick thermal barrier coating systems will be key to insulating these components. Development of test methods to rapidly evaluate the durability of coating systems without expensive engine testing is a major objective of current work. In addition, a novel, low cost method for producing thermal barrier coated pistons without final machining of the coating has been developed.
Date:
April 26, 1999
Creator:
Beardsley, M. B.; Happoldt, P. G.; Kelley, K. C.; Rejda, E. F. & Socie, D. F.
Object Type:
Article
System:
The UNT Digital Library
Assembly conductance measurements: halthane vent path testing
The purpose of this test was to characterize the conductance of different configurations of vent paths put into weapons assemblies through application of Halthane 88-3 precoats onto the parts. Conductance is a measure of the ease of gas flow in an assembly. It is the inverse of resistance which may be more familiar to most readers. It is defined as the resultant of the gas flow (torr-1/sec) divided by the pressure drop (torr) in the assembly. Its dimensions are thus liters per second. The conductance paths are put into the precoats to allow pumpdown of weapon assemblies and communication during stockpile life. They are put into the precoats by applying tape of the desired width onto the part prior to coating. The Halthane 88-3 is then rolled onto the part and when the tape is removed the vent paths are left. To keep this report unclassified some of the description of the situation has been abbreviated. For a more complete description of the device configuration and conductance issue, see the final report on WDW 9009-A and -B (CODT 98-0809).
Date:
March 26, 1999
Creator:
Beat, T G & Kervin, J E
Object Type:
Article
System:
The UNT Digital Library
Rapid thermal outgassing of component samples
This paper/presentation describes the rapid thermal outgassing tests that were ran to provide an inventory of all gasses present in the weld channel during the weld. The component samples tested were of all materials that are exposed to the channel during the temperature excursion due to the welding operation. The temperature ramps were determined from previous weld tests. The test equipment, test procedures, and the data collection system is described. They present the data and their interpretation of it.
Date:
March 26, 1999
Creator:
Beat, T G & Moffitt, K
Object Type:
Article
System:
The UNT Digital Library
Experimental test of nuclear magnetization distribution and nuclear structure models
Models exist that ascribe the nuclear magnetic fields to the presence of a single nucleon whose spin is not neutralized by pairing it up with that of another nucleon; other models assume that the generation of the magnetic field is shared among some or all nucleons throughout the nucleus. All models predict the same magnetic field external to the nucleus since this is an anchor provided by experiments. The models differ, however, in their predictions of the magnetic field arrangement within the nucleus for which no data exist. The only way to distinguish which model gives the correct description of the nucleus would be to use a probe inserted into the nucleus. The goal of our project was to develop exactly such a probe and to use it to measure fundamental nuclear quantities that have eluded experimental scrutiny. The need for accurately knowing such quantities extends far beyond nuclear physics and has ramifications in parity violation experiments on atomic traps and the testing of the standard model in elementary particle physics. Unlike scattering experiments that employ streams of free particles, our technique to probe the internal magnetic field distribution of the nucleus rests on using a single bound electron. Quantum …
Date:
February 26, 1999
Creator:
Beirsdorfer, P; Crespo-Lopez-Urrutia, J R & Utter, S B
Object Type:
Report
System:
The UNT Digital Library
Hydrologic resources management program, FY 1998 progress report
This report presents the results from FY 1998 technical studies conducted by Lawrence Livermore National Laboratory (LLNL) as part of the Hydrology and Radionuclide Migration Program (HRMP) and Underground Test Area (UGTA) project. The HRMP is sponsored by Defense Programs (DP) of the U.S. Department of Energy, Nevada Operations Office (DOE/NV), and supports DP operations at the Nevada Test Site (NTS) through studies of radiochemistry and resource management related to the defense programs mission. Other participating organizations include the Los Alamos National Laboratory (LANL), the United States Geological Survey (USGS), the Desert Research Institute (DRI) of the University of Nevada, the United States Environmental Protection Agency (EPA), and Bechtel-Nevada (BN). The UGTA project is an Environmental Management (EM) activity of DOE/NV that supports a Federal Facilities Agreement and Consent Order between the Department of Energy, the Department of Defense, and the State of Nevada. UGTA's primary function is to address the legacy release of hazardous constituents at the Nevada Test Site, the Tonopah Test Range, and off-Nevada Test Site underground nuclear testing areas. Participating contractors include LLNL (Earth and Environmental Sciences Directorate, Analytical and Nuclear Chemistry Division), LANL, DRI, USGS, BN, HSI-GeoTrans, and IT Corporation. The FY 1998 HRMP and …
Date:
July 26, 1999
Creator:
Benedict, F.C.; Criss, R.E.; Davisson, M.L.; Eaton, G.F.; Hudson, G.B.; Kenneally, J.M. et al.
Object Type:
Report
System:
The UNT Digital Library
Development of a 3D FEL code for the simulation of a high-gain harmonic generation experiment.
Over the last few years, there has been a growing interest in self-amplified spontaneous emission (SASE) free-electron lasers (FELs) as a means for achieving a fourth-generation light source. In order to correctly and easily simulate the many configurations that have been suggested, such as multi-segmented wigglers and the method of high-gain harmonic generation, we have developed a robust three-dimensional code. The specifics of the code, the comparison to the linear theory as well as future plans will be presented.
Date:
February 26, 1999
Creator:
Biedron, S. G.
Object Type:
Article
System:
The UNT Digital Library