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Self-consistent core-edge nonlinear transport simulations with CORSICA 2

Description: The coupled core-edge nonlinear transport code CORSICA 2 is introduced and the structure of its iterative coupling algorithm is briefly discussed. Selected application results are reported that reproduce equilibria in DIII-D discharges with plasma profiles initialized from the experimental data. Simulations for an L-H transition and for a gas puffing experiment in DIII-D plasmas are presented.
Date: January 17, 1996
Creator: Tarditi, A.; Cohen, R.H. & Craddock, G.G.
Partner: UNT Libraries Government Documents Department

Reliable software systems via chains of object models with provably correct behavior

Description: This work addresses specification and design of reliable safety-critical systems, such as nuclear reactor control systems. Reliability concerns are addressed in complimentary fashion by different fields. Reliability engineers build software reliability models, etc. Safety engineers focus on prevention of potential harmful effects of systems on environment. Software/hardware correctness engineers focus on production of reliable systems on the basis of mathematical proofs. The authors think that correctness may be a crucial guiding issue in the development of reliable safety-critical systems. However, purely formal approaches are not adequate for the task, because they neglect the connection with the informal customer requirements. They alleviate that as follows. First, on the basis of the requirements, they build a model of the system interactions with the environment, where the system is viewed as a black box. They will provide foundations for automated tools which will (a) demonstrate to the customer that all of the scenarios of system behavior are presented in the model, (b) uncover scenarios not present in the requirements, and (c) uncover inconsistent scenarios. The developers will work with the customer until the black box model will not possess scenarios (b) and (c) above. Second, the authors will build a chain of several increasingly detailed models, where the first model is the black box model and the last model serves to automatically generated proved executable code. The behavior of each model will be proved to conform to the behavior of the previous one. They build each model as a cluster of interactive concurrent objects, thus they allow both top-down and bottom-up development.
Date: May 17, 1996
Creator: Yakhnis, A. & Yakhnis, V.
Partner: UNT Libraries Government Documents Department

Modeling of filamentation damage induced in silica by 351-nm laser pulses

Description: A major risk factor that must be considered in design of the National Ignition Facility is the possibility for catastrophic self-focusing of the 351-nm beam in the silica optical components that are in the final section of the laser. Proposed designs for the laser are analyzed by the beam-propagation code PROP92. A 351-nm self-focusing experiment, induction of tracking damage, was done to provide data for validation of this code. The measured self-focusing lengths were correctly predicted by the code.
Date: October 17, 1996
Creator: Milam, D.; Manes, K.R. & Williams, W.H.
Partner: UNT Libraries Government Documents Department

Quark masses, chiral symmetry, and the U(1) anomaly

Description: The author discusses the mass parameters appearing in the gauge theory of the strong interactions, concentrating on the two flavor case. He shows how the effect of the CP violating parameter {theta} is simply interpreted in terms of the state of the aether via an effective potential for meson fields. For degenerate flavors he shows that a first order phase transition is expected at {theta} = {pi}. The author speculates on the implications of this structure for Wilson`s lattice fermions.
Date: September 17, 1996
Creator: Creutz, M.
Partner: UNT Libraries Government Documents Department

Amplitude and phase modulation with waveguide optics

Description: We have developed amplitude and phase modulation systems for glass lasers using integrated electro-optic modulators and solid state high- speed electronics. The present and future generation of lasers for Inertial Confinement Fusion require laser beams with complex temporal and phase shaping to compensate for laser gain saturation, mitigate parametric processes such as transverse stimulated Brillouin scattering in optics, and to provide specialized drive to the fusion targets. These functions can be performed using bulk optoelectronic modulators, however using high-speed electronics to drive low voltage integrated optical modulators has many practical advantages. In particular, we utilize microwave GaAs transistors to perform precision, 250 ps resolution temporal shaping. Optical bandwidth is generated using a microwave oscillator at 3 GHz amplified by a solid state amplifier. This drives an integrated electrooptic modulator to achieve laser bandwidths exceeding 30 GHz.
Date: December 17, 1996
Creator: Burkhart, S.C.; Wilcox, R.B.; Browning, D. & Penko, F.A.
Partner: UNT Libraries Government Documents Department

Hypertools in image and volume visualization

Description: This paper describes our experience in image and volume visualization at the Lawrence Livermore National Laboratory. After an introduction on visualization issues, we present a new software approach to the analysis and visualization of images and volumes. The efficiency of the visualization process is improved by letting the user combine small and reusable applications by the means of a machine-independent interpreted language such as Tcl/Tk. These hypertools can communicate with each other over a network, which has a direct impact on the design of graphical interfaces. We first describe the implementation of a flexible gray-scale image widget that can handle large data sets, provides complete control of the color palette and allows for manual and semi-interactive segmentation. This visualization tool can be embedded in a data-flow image processing environment to assess the quality of acquisition, preprocessing and filtering of raw data. This approach combines the simplicity of visual programming with the power of a high-level interpreted language. We show how hypertools can be used in surface and volume rendering and how they increase the interaction efficiency by performing complex or tedious tasks automatically. One biomedical application is presented.
Date: June 17, 1996
Creator: Bossart, P.L.
Partner: UNT Libraries Government Documents Department

Wilson fermions at finite temperature

Description: The author conjectures on the phase structure expected for lattice gauge theory with two flavors of Wilson fermions, concentrating on large values of the hopping parameter. Numerous phases are expected, including the conventional confinement and deconfinement phases, as well as an Aoki phase with spontaneous breaking of flavor and parity and a large hopping phase corresponding to negative quark masses.
Date: September 17, 1996
Creator: Creutz, M.
Partner: UNT Libraries Government Documents Department

Application of MXCD to magnetic thin-film sensors

Description: While Magnetic X-ray Circular Dichroism (MXCD) has been applied extensively to the extraction of elemental magnetic moments in various magnetic multilayers, the configuration of actual devices imposes certain constraints on the application of MXCD to devices. Using a set of real, thin-film spin valve devices with varying Cu spacer layer thicknesses, we demonstrate the correlation between MXCD and R-H measurements on those devices as well as the restrictions on the interpretation of MXCD data imposed by both the device topology and the formulation of realistic error estimates.
Date: May 17, 1996
Creator: Bedrossian, P.J.; Tobin, J.G. & Jankowski, A.F.
Partner: UNT Libraries Government Documents Department

Materials performance in a high-level radioactive waste vitrification system

Description: The Defense Waste Processing Facility (DWPF) is a Department of Energy Facility designed to vitrify highly radioactive waste. An extensive materials evaluation program has been completed on key components in the DWPF after twelve months of operation using nonradioactive simulated wastes. Results of the visual inspections of the feed preparation system indicate that the system components, which were fabricated from Hastelloy C-276, should achieve their design lives. Significant erosion was observed on agitator blades that process glass frit slurries; however, design modifications should mitigate the erosion. Visual inspections of the DWPF melter top head and off gas components, which were fabricated from Inconel 690, indicated that varying degrees of degradation occurred. Most of the components will perform satisfactorily for their two year design life. The components that suffered significant attack were the borescopes, primary film cooler brush, and feed tubes. Changes in the operation of the film cooler brush and design modifications to the feed tubes and borescopes is expected to extend their service lives to two years. A program to investigate new high temperature engineered materials and alloys with improved oxidation and high temperature corrosion resistance will be initiated.
Date: June 17, 1996
Creator: Imrich, K.J. & Chandler, G.T.
Partner: UNT Libraries Government Documents Department

Report of the Supersymmetry Theory Subgroup

Description: We provide a mini-guide to some or the possible manifestations of weak scale supersymmetry. For each of six scenarios we provide: a brief description of the theoretical underpinnings, the adjustable parameters, a qualitative description of the associated phenomenology at future colliders, comments on how to simulate each scenario with existing event generators,
Date: September 17, 1996
Creator: Amundson, J.; Anderson, G. & Baer, H.
Partner: UNT Libraries Government Documents Department

A low power, tight seal, polyimide electrostatic microvalve

Description: An electrostatically-actuated polyimide microvalve is developed with sub-micron gaps between the electrodes to provide high force with low power consumption (< 1 mW). Built-in residual stress results in a curled bimorph cantilever which allows for a n-Licroactuator with large displacement. This microactuator is used to open and close a fluid path hole etched in silicon for a microvalve. The microactuator can be actuated with 25V for a displacement of 200 {mu}m. The cantilever actuator is mainly composed of polyimide, which is flexible enough to conform over the flow hole, thereby eliminating the need for the design of a valve seat.
Date: April 17, 1996
Creator: Lee, A.P.; Hamilton, J. & Trevino, J.
Partner: UNT Libraries Government Documents Department

X-ray spectra from convective photospheres of neutron stars

Description: We present first results of modeling convective photospheres of neutron stars. We show that in photospheres composed of the light elements convection arises only at relatively low effective temperatures ({le}3 - 5 x 10{sup 4} K), whereas in the case of iron composition it arises at T{sub eff}{le} 3 x 10{sup 5}K. Convection changes the depth dependence of the photosphere temperature and the shapes of the emergent spectra. Thus, it should be taken into account for the proper interpretation of EUV/soft-X-ray observations of the thermal radiation from neutron stars.
Date: January 17, 1996
Creator: Zavlin, V.E.; Pavlov, G.G.; Shibanov, Yu.A.; Rogers, F.J. & Iglesias, C.A.
Partner: UNT Libraries Government Documents Department

Status of ParaDyn: DYNA3D for parallel computing

Description: The evolution of DYNA3D from a vector supercomputer code into a parallel code is reviewed. Current status and target applications, especially those of interest to the Department of Defense.
Date: April 17, 1996
Creator: Goudreau, G.L.; Hoover, C.G.; DeGrout, A.J. & Raboin, P.J.
Partner: UNT Libraries Government Documents Department

Laser aperture diagnostics system for gain and wavefront measurements on NIF/LMJ amplifiers

Description: We are in the midst of constructing an amplifier laboratory (Arnplab) that will be the physics and engineering proving ground for fill sized segmented glass amplifiers of designs that will outfit the National Ignition Facility (NIF) and Laser Megajoule (LMJ) projects. Amplab will demonstrate the cornerstone mechanical, electrical and optical concepts that support the NW and LMJ amplifier schemes. Here we address the optical diagnostics that will be used to characterize optical performance of the amplifiers. We describe, the apparatus that will be used in pulsed measurements of gain distribution and wave-front distortions. The large aperture diagnostic system or LADS, is now being built through a collaborative effort between CEL-V and LLNL. The LADS will provide measurements of gain and wave front distortions over the fill extracting aperture of the NIF and LMJ prototype amplifiers. The LADS will be able to address each of eight apertures via motorized stages and following semi-automated alignment, take data on the aperture of interest. The LADS should be operational in mid-1997 at LLNL and will be used to characterize the optical performance of the very first fill scale prototype 4 x 2 NIF and LMJ amplifiers. It will be transported to Bordeaux, France to make similar measurements during activation of the first 8-aperture LMJ-like facility (LIL) that is planned to start in the near future.
Date: December 17, 1996
Creator: Zapata, L. E., LLNL
Partner: UNT Libraries Government Documents Department

Optical and thermo-optical characterization of KTP and its isomorphs for 1.06 {micro}m pumped OPO`s

Description: The need to protect personnel from inadvertent eye trauma from fielded laser sources dictates that the highest externally accessible fluences produced by these systems be kept below the maximum permissible exposure (MPE) for intra-beam viewing. The large MPE value for a typical Q-switched (10 ns pulsewidth) source is 1 J/cm{sup 2} for wavelengths in the range of 1.5--1.8 microns, while the MPE for a similar pulsewidth Nd:YAG source is 5 {micro}J/cm{sup 2}. This 5 order of magnitude difference in the MPE is one reason for the trend towards shifting the output of near infrared sources used for remote sensing or ranging to the eyesafe wavelength region, even at the expense of overall system efficiency. There are 5 nonlinear optical crystals available with apertures of at least 10 x 10 mm{sup 2} which are also highly transparent in the 1.5 micron region; LiNbO{sub 3}, KNbO{sub 3}, KTP, KTA, and RTA. All 5 crystals are capable of 1,555 nm generation in an orientation with a favorable nonlinear optical coupling. However, KTP, KTA, or RTA are preferred materials, given that the generated signal of the OPO should remain at a fixed wavelength, insensitive to angular or thermal variations. The authors have characterized the phasematching angle, linewidth, thermal conductivity, and d{lambda}/dT for KTP, KTA, and RTA optical parametric oscillators.
Date: February 17, 1996
Creator: Ebbers, C.A. & Velsko, S.P.
Partner: UNT Libraries Government Documents Department

A separate SU(2) for the third family: Topflavor

Description: The authors consider the extended electroweak gauge group SU(2){sub 1}xSU(2){sub x}xU(1){sub Y} where the first and second families of fermions couple to SU(2){sub 1} while the third family couples to SU(2){sub 2}. Bounds based on precision electroweak observables and heavy gauge boson searches are placed on the new parameters of the theory. The extra gauge bosons can be as light as about a TeV and can be discovered at future colliders such as the NLC and LHC for a wide range of the parameter space. FCNC interactions are also considered.
Date: October 17, 1996
Creator: Muller, D. J. & Nandi, S.
Partner: UNT Libraries Government Documents Department

Compact IR laser for calibration of space based sensors

Description: An Er:YAG laser, operating at 2.94 microns, has been developed for in-theater calibration of space based infrared sensors. The laser is used to illuminate a spaceborne sensor focal plane from a surveyed ground reference point. The known reference point is compared to the laser position reported by the sensor, and boresight corrections are made. The Er:YAG laser is side pumped by a InGaAs diode array and is tuned to an atmospheric microwindow with and intracavity etalon. This technology is being directly applied to meet Army requirements for enhanced deep strike targeting information supplied to theater weapons systems.
Date: April 17, 1996
Creator: Kietrick, K. M.; Dezenberg, G.; Hamilton, C.; Vann, J. & LaSala, J.
Partner: UNT Libraries Government Documents Department

[The Daily Texan]

Description: A news piece on a lawsuit regarding the firing of an employee with AIDS.
Date: June 17, 1996
Partner: UNT Libraries Special Collections