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Vapor deposition of copper on stainless steel 304L

Description: Y-12 Plant is seeking to minimize the generation of hazardous wastes in its operations. The standard procedure for electroplating a thin layer of copper on type 304L stainless steel requires several aqueous pretreatment steps which generate Resource Conservation and Recovery Act (RCRA) hazardous wastes. We have evaluated a more environmentally acceptable procedure. Copper was vacuum deposited onto 304L coupons under differing deposition conditions and properties of coatings produced, including microstructure and adhesive strength, were examined. Results indicated that a noncolumnar, fine grain copper coating with high adhesion can be produced using this environmentally more acceptable approach.
Date: August 17, 1993
Creator: Vasofsky, R. W.
Partner: UNT Libraries Government Documents Department

Magnetic circular dichroism in x-ray absorption and core-level photoemission

Description: Here is reported observation of magnetic circular dichroism in both x-ray absorption and core-level photoemission of ultra thin magnetic films using circularly polarized x-rays. Iron films (1--4 ML) grown on a Cu(001) substrate at 150 K and magnetized perpendicular to the surface show dramatic changes in the L{sub 2,3} branching ratio for different x-ray polarizations. For linearly-polarized x-rays perpendicular to the magnetic axis of the sample the branching ratio was 0.75. For films {ge} 2 ML, this ratio varied from 0.64 to 0.85 for photon spin parallel and anti-parallel, respectively, to the magnetic axis. This effect was observed either by changing the x-ray helicity for a fixed magnetic axis, or by reversing the magnetic axis for a fixed x-ray helicity. Our observation can be analyzed within a simple one-electron picture, if the raw branching ratios are no so that the linear value becomes statistical Furthermore, warming the films to {approximately}300 K eliminated this effect, indicating a loss of magnetization in the film over a temperature range of {approximately}30 K. Finally, reversing the relative orientation of the photon spin and the magnetic axis from parallel to anti-parallel allowed measurement of the exchange splitting of the Fe 2p and 3p core levels which were found to be 0.3 eV and 0.2 eV. respectively. These results are consistent with earlier studies, but the use of off-plane circularly-polarized x-rays from a bending magnet monochromator offers {approximately}2 orders of magnitude greater intensity than typical spin-polarization measurements. Finally, we have performed preliminary x-ray absorption studies of UFe{sub 2}, demonstrating the feasibilty of MCD measurements in 5f as well as 3d materials.
Date: March 17, 1993
Creator: Tobin, J. G.; Waddill, G. D.; Gouder, T. H.; Colmenares, C. A. & Pappas, D. P.
Partner: UNT Libraries Government Documents Department

Modular intelligent sensor system

Description: This paper describes a sensor system architecture suitable for application in systems intended for battery powered unattended use. The modularity concept addresses the logical interconnects between modules, the electrical interconnects between modules, and a system for the generalization of data to permit modular processing.
Date: June 17, 1993
Creator: Fuess, D. A.
Partner: UNT Libraries Government Documents Department

Phase screens for the control of the focal irradiance of the Nova laser

Description: The authors report on the design and fabrication of continuous contour (kinoform) phase plates for homogenizing the focal plane irradiance of high-power, inertial confinement fusion laser systems. These kinoform phase plates are designed using an iterative algorithm. They offer the flexibility of controlling the overall shape of the far-field irradiance profile and the ability to concentrate the energy within a central region of the focal profile. These properties make kinoforms superior to the conventional, binary random phase plates for many applications. Potential methods for fabrication of such kinoform phase plates are discussed.
Date: September 17, 1993
Creator: Lawson, J. K.; Dixit, S. N.; Eimerl, D.; Henesian, M. A.; Manes, K. R.; Morgan, A. J. et al.
Partner: UNT Libraries Government Documents Department

A 600 MeV cyclotron for radioactive beam production

Description: The magnetic field design for a 600 MeV proton cyclotron is described. The cyclotron has a single stage, a normal conducting magnet coil and a 9.8 m outside yoke diameter. It has 8 sectors, with a transition to 4 sectors in the center region. The magnetic field design was done using 1958 Harwell rectangular ridge system measurements and was compared with recent 3-dimensional field calculations with the program TOSCA at NSCL. The center region 4--8 sector transition focussing was also checked with TOSCA.
Date: May 17, 1993
Creator: Clark, D. J.
Partner: UNT Libraries Government Documents Department

Development of {sup 129}I AMS for the LLNL spectrometer

Description: The Multi-user Tandem Laboratory at LLNL was designed to be a versatile facility which could be configured to develop new capabilities as determined by the requirements of sponsoring agencies and experimental programs. The initial design made some compromises, driven by both the usual budgetary constraints and uncertainties in program needs and support. We were recently funded by the Office of Arms Control in the US DOE to develop an {sup 129}I AMS capability. The first {sup 129}I measurements were performed this year after upgrades and modifications to the initially installed components were completed. The configuration of the present spectrometer and performance achieved to date will be described. Planned improvements to the injector and high energy spectrometer will be outlined.
Date: September 17, 1993
Creator: Proctor, I. D.; Southon, J. R. & Roberts, M. L.
Partner: UNT Libraries Government Documents Department

Laser driven hydrodynamic instability experiments. Revision 1

Description: An extensive series of experiments has been conducted on the Nova laser to measure hydrodynamic instabilities in planar foils accelerated by x-ray ablation. Single mode experiments allow a measurement of the fundamental growth rates from the linear well into the nonlinear regime. Two-mode foils allow a first direct observation of mode coupling. Surface-finish experiments allow a measurement of the evolution of a broad spectrum of random initial modes.
Date: February 17, 1993
Creator: Remington, B. A.; Weber, S. V.; Haan, S. W.; Kilkenny, J. D.; Glendinning, S. G.; Wallace, R. J. et al.
Partner: UNT Libraries Government Documents Department

Direct probability mapping of contaminants

Description: Exhaustive characterization of a contaminated site is a physical and practical impossibility. Descriptions of the nature, extent, and level of contamination, as well as decisions regarding proposed remediation activities, must be made in a state of uncertainty based upon limited physical sampling. Geostatistical simulation provides powerful tools for investigating contaminant levels, and in particular, for identifying and using the spatial interrelationships among a set of isolated sample values. This additional information can be used to assess the likelihood of encountering contamination at unsampled locations and to evaluate the risk associated with decisions to remediate or not to remediate specific regions within a site. Past operation of the DOE Feed Materials Production Center has contaminated a site near Fernald, Ohio, with natural uranium. Soil geochemical data have been collected as part of the Uranium-in-Soils Integrated Demonstration Project. These data have been used to construct a number of stochastic images of potential contamination for parcels approximately the size of a selective remediation unit. Each such image accurately reflects the actual measured sample values, and reproduces the univariate statistics and spatial character of the extant data. Post-processing of a large number of these equally likely, statistically similar images produces maps directly showing the probability of exceeding specified levels of contamination. Evaluation of the geostatistical simulations can yield maps representing the expected magnitude of the contamination for various regions and other information that may be important in determining a suitable remediation process or in sizing equipment to accomplish the restoration.
Date: September 17, 1993
Creator: Rautman, C. A.
Partner: UNT Libraries Government Documents Department

Emission from ferroelectric cathodes

Description: We have recently initiated an investigation of electron emission from ferroelectric cathodes. Our experimental apparatus consisted of an electron diode and a 250 kV, 12 ohm, 70 ns pulsed high voltage power source. A planar triode modulator driven by a synthesized waveform generator initiates the polarization inversion and allows inversion pulse tailoring. The pulsed high voltage power source is capable of delivering two high voltage pulses within 50 ns of each other and is capable of operating at a sustained repetition rate of 5 Hz. Our initial measurements indicate that emission current densities above the Child-Langmuir Space Charge Limit are possible. We explain this effect to be based on a non-zero initial energy of the emitted electrons. We also determined that this effect is strongly coupled to relative timing between the inversion pulse and application of the main anode-cathode pulse. We also have initiated brightness measurements of the emitted beam. As in our previous measurements at this Laboratory, we performed the measurement using a pepper pot technique. Beam-let profiles are recorded with a fast phosphor and gated cameras. We describe our apparatus and preliminary measurements.
Date: May 17, 1993
Creator: Sampayan, S. E.; Caporaso, G. J.; Holmes, C. L.; Lauer, E. J.; Prosnitz, D.; Trimble, D. O. et al.
Partner: UNT Libraries Government Documents Department

Combining nonlinear multiresolution system and vector quantization for still image compression

Description: It is popular to use multiresolution systems for image coding and compression. However, general-purpose techniques such as filter banks and wavelets are linear. While these systems are rigorous, nonlinear features in the signals cannot be utilized in a single entity for compression. Linear filters are known to blur the edges. Thus, the low-resolution images are typically blurred, carrying little information. We propose and demonstrate that edge-preserving filters such as median filters can be used in generating a multiresolution system using the Laplacian pyramid. The signals in the detail images are small and localized to the edge areas. Principal component vector quantization (PCVQ) is used to encode the detail images. PCVQ is a tree-structured VQ which allows fast codebook design and encoding/decoding. In encoding, the quantization error at each level is fed back through the pyramid to the previous level so that ultimately all the error is confined to the first level. With simple coding methods, we demonstrate that images with PSNR 33 dB can be obtained at 0.66 bpp without the use of entropy coding. When the rate is decreased to 0.25 bpp, the PSNR of 30 dB can still be achieved. Combined with an earlier result, our work demonstrate that nonlinear filters can be used for multiresolution systems and image coding.
Date: December 17, 1993
Creator: Wong, Y.
Partner: UNT Libraries Government Documents Department

Workforce diversity in a research and development environment -- a model that works

Description: The Lawrence Livermore National Laboratory (LLNL) Engineering Directorate is in the third year of a diversity process that has changed the culture of the organization in many ways. This work outlines progress toward realizing the LLNL Engineering Diversity Model. Currently recommendations are being implemented that have been formulated through a problem resolution process, described in this work, in which employees helped identify problems, recommend solutions, and work with managers in focus groups. The process of arriving at the recommendations and the lessons learned through the problem resolution process are discussed. Ongoing actions, short-term goals, and long-term goals of the program are described.
Date: November 17, 1993
Creator: McDavid, S.
Partner: UNT Libraries Government Documents Department

{sup 41}Ca as a tracer for calcium uptake and deposition in heart tissue during ischemia and reperfusion

Description: We have developed techniques and are commencing experiments using enriched {sup 41}Ca as a tracer in isolated rabbit heart preparations. The aims of the study are to measure calcium uptake and deposition in response to cardiac ischemia and reperfusion, and to investigate events and mechanism leading to irreversible myocyte injury.
Date: September 17, 1993
Creator: Southon, J. R.; Bishop, M. S. & Kost, G. J.
Partner: UNT Libraries Government Documents Department

Two dimensional self-consistent fluid simulation of rf inductive sources

Description: The two-dimensional (R - Z) electromagnetic code FMRZ has been written to model inductive sources self-consistently in time. The code models an argon plasma with momentum-transfer, excitation and ionization as electron-neutral reactions and scattering and charge-exchange for the ion-neutral reactions. The electrons and ions are treated as Maxwellian fluid species and a reduced set of Maxwell`s equations is used to advance the electromagnetic fields. The set of equations used in FMRZ is not subject to typical numerical constraints present in many time dynamic codes allowing one to choose appropriate the and space scales to resolve only the frequencies and scale lengths of interest. The model retains nonlinear driving terms which give rise to a pondermotive force that distorts the density profile. Density and power profiles will be used to illustrate the physical effects of various terms in the equations. Trends in average density and temperature compare well with an analytic model.
Date: November 17, 1993
Creator: DiPeso, G.; Vahedi, V.; Hewett, D. W. & Rognlien, T. D.
Partner: UNT Libraries Government Documents Department

Fast pulsars, compact stars, and the strange matter hypothesis

Description: Part one of this paper deals with the recent finding of the possible existence of a mixed phase of baryon matter and quark matter inside neutron stars. In part two we review the theoretically determined minimum rotational periods of neutron stars, which serve to distinguish between pulsars that can be understood as rotating neutron stars and those that can not. Likely candidates for the latter are hypothetical strange stars. Their mass-radius relationship is discussed in the last part. It is pointed out that strange stars with a nuclear crust can give rise to the observed phenomena of pulsar glitches, thus passing the only astrophysical test of the strange-matter hypothesis existing to date.
Date: March 17, 1993
Creator: Weber, F. & Glendenning, N. K.
Partner: UNT Libraries Government Documents Department

System modeling for the longitudinal beam dynamics control problem in heavy ion induction accelerators

Description: We address the problem of developing system models that are suitable for studying the control of the longitudinal beam dynamics in induction accelerators for heavy ions. In particular, we present the preliminary results of our efforts to devise a general framework for building detailed, integrated models of accelerator systems consisting of pulsed power modular circuits, induction cells, beam dynamics, and control system elements. Such a framework will permit us to analyze and design the pulsed power modulators and the control systems required to effect precise control over the longitudinal beam dynamics.
Date: May 17, 1993
Creator: Payne, A. N.
Partner: UNT Libraries Government Documents Department

Preliminary results of the comparison of ATSR measurements with in situ sea temperatures

Description: During October and November, 1991, the NATO Research Vessel Alliance sailed from Amsterdam into the western Mediterranean Sea and during this time measurements were made for the validation of ATSR data. This document reports the initial comparison between ATSR measurements and sea-surface temperatures (SSTs) taken along the ship's track by an in situ thermometer at a depth of about 3m.
Date: March 17, 1993
Creator: Minnett, P.J.
Partner: UNT Libraries Government Documents Department

The first data from the MACHO experiment

Description: MAssive Compact Halo Objects such as brown dwarfs, Jupiters, and black holes are prime candidates to comprise the dark halo of our galaxy. Paczynski noted that objects (dubbed MACHOS) with masses in the range 10{sup {minus}6} M{circle_dot} < M {approx_lt} 100M{circle_dot} can be detected via gravitational microlensing of stars in the Magellanic Clouds with the caveat that only about one in 10{sup 6} stars will be lensed at any given time. Our group has recently begun a search for microlensing using a refurbished 1.27 meter telescope at the Mount Stromlo Observatory in Australia. Since the summer of 1992, we have been imaging up to 10{sup 7} stars a night in the Large Magellanic Cloud using our large format two-color 3.4 {times} 10{sup 7} pixel CCD camera. Here I report on our first results based on an analysis of {approximately}10{sup 6} of these stars. Although this is not enough data to make definitive statements about the nature of the dark matter, we are able to conclude that the rate of variable star background events is not larger than the expected MACHO signal.
Date: March 17, 1993
Creator: Bennett, D. P.; Cook, K. H.; Akerlof, C.; Perlmutter, S.; Sutherland, W.; Alcock, C. et al.
Partner: UNT Libraries Government Documents Department