Although the feasibility of using PZT and PLZT films for optical data processing applications, such as optical storage disks, image comparators, and spatial light modulators, has clearly been established, most of the critical parameters related to the storage and readout processes still need to be evaluated. Optical readout techniques capable of nondestructively determining the value of polarization are based either on the quadratic electrooptic effect or on a photocurrent response. In reflection, large electrooptic retardations (>60{degrees}) have now been achieved with thin PZT films ({approx equal} 0.5 {mu}m) under conditions that optimize interference effects. These results are quite attractive for device applications. Model calculations, based on the equations of reflection ellipsometry, have been used to develop a framework for understanding those results. The magnitude of the photocurrent response has also been used to determine the polarization state. However, the photocurrent always has the same sign, regardless of the sign of the polarization, which suggests the presence of a strong bias field due to at least one of the interfaces. In addition, the accumulation of space charge after a succession of measurements suppresses the photocurrent transient, which severely limits the utility of a photocurrent based readout. 7 refs., 9 figs.
The contact of aluminum-based melts with liquid water has been shown to be explosive in many experiments performed by the aluminum industry and in several nuclear reactor experiments and accidents. In order to obtain quantitative information relating to the fuel-coolant interactions that might occur with aluminum-based fuel, a laboratory-scale experimental study is being performed at Sandia National Laboratories. The overall objective of this research program is to provide an understanding of the mechanism of steam explosions with the melt compositions expected in several hypothetical core meltdown accident scenarios in production reactors. In this program it has been demonstrated that rapid exothermic metal-water reactions can accompany the steam explosions under certain conditions resulting in enhanced energy release and in the concomitant generation of hydrogen. 4 refs., 2 figs.
The INTEROP Achievement Award will be given to those customer organizations that make the most effective use of internetworking technology to further their own specific business aims. This paper is an application for this award by Sandia National Laboratories. Given are the network application, topology, and the types of systems to which it is applied.(JEF)
One problem with electromagnetic time domain finite-difference simulations in cylindrical coordinates is the rapidly decreasing characteristic dimension of the cells as r approaches zero. In order to satisfy the Courant stability condition a small time step is needed to insure stability, which is undesirable because it increases the cost of the simulation. In our presentation, we will describe a method which uses a rectangular grid and an annular cylindrical grid which overlap to perform electromagnetic simulations of cylindrical geometries. The two grids are connected by interpolating the field at the grid points of one grid using field values from the second grid. 2 refs.
The strength of deuterium bonding to the walls of closed cavities within Si was determined in ion-beam experiments. These studies circumvented an inherent indeterminacy in the analysis of external-surface desorption and thereby allowed the Si-H surface bond energy to be quantified for the first time. The bond energy is 2.5 {plus minus} 0.2 eV for submonolayer coverages. 14 refs., 3 figs.
Scan path testing and debugging offers a structured, proven way to debug and test arbitrarily complex electronic systems. The interface and equipment requirements are far lower than traditional debug and test techniques. The system is also completely testable even when physically remote from the lab where it was originally developed. This report describes our experience using scan techniques to debug the EPSILON-2 processor board, a system with over 300 ICs and over 2500 independently controllable and observable test points. The debug time of the circuit was greatly reduced by the adoption of scan path methodology. The use of expensive test equipment was drastically reduced, and the level of control of the circuitry increased. We have run tests on the processor from physically remote sites. Our experiences are described, and the adoption of scan path techniques is shown to be simple enough that it should be useful in all electronic projects. 8 refs., 12 figs.
Sandia National Laboratories is a large multi-program DOE laboratory. The Recorded Information Management Division (RIM) has an expanding mission to meet Sandia's needs for cost-effective management in information from creation to final disposition in accordance with applicable regulations and requirements. An analysis based on the need to meet requirements and to improve business practice was successful in convincing management to allocate increased resources to the RIM Compliance Project.
Historically, the electronics industry has always attempted to increase the speed of electronic components and decrease the size of electronic assemblies by developing and manufacturing smaller and faster basic level components (e.g., integrated circuits). However, it is now becoming apparent that the next significant advancement in electronic assembly size and speed may come not as a result of smaller and faster devices, but rather as a consequence of smaller and more closely spaced packages. This increased packaging density will occur at early levels of assembly as industry moves towards multichip modules. It will also occur at later packaging steps as industry continues to expand the use of surface mount technology (SMT) and mixed mounting technology (through hole attachment as well as SMT on one circuit board). Furthermore, there will be an increased propensity to use higher packaging density on printed wiring boards (PWB) and to place more PWB's in a given volume at yet the next level of packaging. One class of materials on which this advanced packaging technology will place severe new demands will be the alloys used to join assemblies and subassemblies (e.g. solders and brazes). These materials will be taxed both from the perspective of enhanced manufacturability as well as greater in-service robustness. It is the objective of this paper, through the use of selected case studies, to illustrate how advanced microstructural characterization techniques can be used to improve packaging technology. The specific case studies discussed are: (1) Microstructural Characterization of Solders, (2) Microstructural Characterization of Solder Joint Embrittlement of Leaded, Surface Mount Transistors (3) Microstructural Characterization of Metal/Ceramic Brazes in Electronic Applications, and (4) Microstructural Characterization of Direct Brazing of Graphite to Copper. 25 refs., 16 figs.
A number of models that predict the impulse generated in solid targets by short high-intensity radiation loads are described. It is shown that the impulse is insensitive to the details of the energy deposition and interaction processes. Thus with the proper nondimensionalization and normalization, all the models are known to be very nearly equivalent. 5 refs., 5 figs., 1 tab.
The radiation produced by a 15.5-MeV monoenergetic electron beam incident on optimized and nonoptimized bremsstrahlung targets is characterized using the ITS Monte Carlo code and measurements with equilibrated and non-equilibrated TLD dosimetry. Comparisons between calculations and measurements verify the calculations and demonstrate that the code can be used to predict both bremsstrahlung production and TLD response for radiation fields that are characteristic of those produced by pulsed simulators of gamma rays. At optimum bremsstrahlung production, the predicted total forward radiation fluence detected in equilibrated TLD dosimetry agrees with that measured within the {plus minus}6% uncertainty of the measurement. The absolute comparisons made here provide independent confirmation of the validity of the TLD calibration for photon fields characteristic of gamma-ray simulators. The empirical Martin equation, which is often used to calculate radiation dose from optimized bremsstrahlung targets, is examined, and its range of validity is established from the data presented. 23 refs., 11 figs., 2 tabs.
Acoustic emissions and conventional strain measurements were used to follow the evolution of the damage surface and the plastic potential in a limestone under conditions of triaxial compressions. Confining pressures were chosen such that macroscopically, the limestone exhibited both brittle and ductile behavior. The parameters thus derived are useful for modeling the deformation of a pressure-dependent material and for computing when localization would occur. 10 refs., 8 figs.
The Gaseous Electronics Conference (GEC) RF Reference Cell was developed to enhance studies of radiofrequency (rf) discharge systems analogous to those used to fabricate microelectronic devices. The Reference Cell concept includes both a standard discharge-chamber design and a set of diagnostic tools that can be used to verify that different Cells behave similarly. Voltage and current measurements in Reference Cells in the United States show that, with proper care, plasmas that behave in a similar manner can be generated in different Cells. The versatility of the Reference Cell is illustrated by results on the use of planar laser-induced fluorescence imaging to obtain two-dimensional spatial profiles of SO{sub 2} in an SF{sub 6}/O{sub 2} rf discharge. 4 refs., 5 figs.
We have used the highly sensitive technique of Photothermal Deflection Spectroscopy (PDS) to measure changes in the infrared absorption spectra of MEHPPV, P3HT and Polydiacetylene-4BCMU induced by pumping these polymers with light above the {pi}--{pi}* transition energy. In contrast to previous chopped light transmission measurements of these effects, the PDS technique can directly measure the buildup or decay of the absorption coefficient, {alpha}, on the time scale of second to days. In the case of MEHPPV we observe that the time scale of seconds to days. In the case of MEHPPV we observe that above-gap light causes the appearance of a broad infrared peak in {alpha}, which continues to grow-in hours after the pump light is first applied. For this polymer the general shape of the absorption spectra in the unpumped state mimics the photo-induced changes, suggesting that remnant photo-induced states determine the maximum transparency observed under normal experimental conditions. For P3HT and to a lesser extent, MEHPPV, we also observe irreversible photo-induced absorption components which we tentatively identify with photo-induced oxidation of the polymer matrix. 10 refs., 8 figs.
Present practice in most computer codes intended for the solution of dynamic mechanics problems is to use the classical infinitesimal plasticity relations together with the Jaumann stress rate to account for finite rotations. Use of the Jaumann stress rate is known to lead to oscillating stress-strain response in simple shear at large deformations for elastic and some plastic relations, and is limited to isotropic material descriptions. Formulations of finite deformation plasticity based on the Lagrangian reference configuration and an unrotated configuration have been proposed which, in principle, should overcome these limitations. The latter has been implemented in a finite element computer code. In this paper, it is shown how a Lagrangian description based on the reference configuration may be implemented in computer codes, and how it may be translated into a corresponding Eulerian description based on the current configuration and a description based on the unrotated configuration for comparison with currently used descriptions. 11 refs.
This paper presents information on measures taken by Sandia National Laboratories to prepare for environmental, safety, and health compliance assessments conducted by Tiger Teams'' at Department of Energy facilities.
Woven Kevlar fabrics exhibit a number of beneficial mechanical properties which include strength, flexibility, and relatively low density. The desire to engineer or design Kevlar fabrics for specific applications has stimulated interest in the development of theoretical models which relate their effective mechanical properties to specific aspects of the fabric morphology and microstructure. In this work the author provides a theoretical investigation of the large deformation elastic response of a plane woven Kevlar fabric and compares these theoretical results with experimental data obtained from uniaxially loaded Kevlar fabrics. The theoretical analysis assumes the woven fabric to be a regular network of orthogonal interlaced yarns and the individual yarns are modeled as extensible elastica, thus coupling stretching and bending effects at the outset. This comparison of experiment with theory indicates that the deformation of woven fabric can be quite accurately predicted by modeling the individual yarns as extensible elastica. 2 refs., 1 fig.
The Modular Integrated Video System (MIVS) Image Processing System (MIPS) was developed to assist the International Atomic Energy Agency (IAEA) Inspectorate in the safeguards review of MIVS surveillance data. MIPS is designed to review MIVS surveillance data automatically; firstly detecting significantly changed images and secondly identifying if the changed images show IAEA defined objects of safeguards interest. To achieve this, MIPS uses both digital image processing and neural network techniques. A change detector uses image processing techniques to identify significantly changed images. The MIPS neural network classifier detects images which may show an important object(s). The neural network is trained , i.e., given example images showing the objects that it must recognize, for each different facility. The MIPS change detection algorithms reduce the original MIVS data by eliminating images without significant activity. The MIPS neural network algorithms further reduce this data by eliminating images which may not show a safeguards significant object. The images analyzed by both the change detector and the neural network are available for inspector review. The MIPS algorithms are implemented in commercially available hardware. A high-level menu-driven system interface allows inspectors to train the neural network and to operate both the change detection and neural network classification. An evaluation program was conducted jointly by Sandia National Laboratories (SNL) and the IAEA to determine the systems capabilities on a variety of MIVS data. The MIPS processing techniques and the user interface were evaluated by IAEA inspectors. Performance tests were also completed on a variety of MIVS data. This paper provides a description of the Class II MIPS and the evaluation program and reports on the results of this joint evaluation. 7 refs., 4 figs., 3 tabs.
Betavoltaic power sources operate by converting the nuclear decay energy of beta-emitting radioisotopes into electricity. Since they are not chemically driven, they could operate at temperatures which would either be to hot or too cold for typical chemical batteries. Further, for long lived isotopes, they offer the possibility of multi-decade active lifetimes. Two approaches are being investigated: direct and indirect conversion. Direct conversion cells consist of semiconductor diodes similar to photovoltaic cells. Beta particle directly bombard these cells, generating electron-hole pairs in the semiconductor which are converted to useful power. Many using low power flux beta emitters, wide bandgap semiconductors are required to achieve useful conversion efficiencies. The combination of tritium, as the beta emitter, and gallium phosphide (GaP), as the semiconductor converter, was evaluated. Indirect conversion betacells first convert the beta energy to light with a phosphor, and then to electricity with photovoltaic cells. An indirect conversion power source using a tritium radioluminescent (RL) light is being investigated. Our analysis indicates that this approach has the potential for significant volume and cost savings over the direct conversion method. 7 refs., 11 figs.
Over the past three years, several experiments have been conducted at the Brookhaven National Laboratory Radiation Effects Facility. These experiments have been investigations of proton induced radiation effects in individual electronic components, circuits, operational subsystems and full systems. Our investigations using 170--200 MeV protons have included total dose effects up to 12 Mrad, dose rate effects of the ionizing radiation in the 10{sup 5} to 10{sup 8} rad/s range, the displacement damage effects of the protons up to 10{sup 15} p/cm{sup 2}, and the proton induced thermal shift and thermal-rate effects. The target thickness of many test devices was an appreciable fraction of the range of 200 MeV protons. In our proton beam testing experiments at BNL, dosimetry placed downstream of the target consistently yielded higher dose in rad and in particle fluence than in dosimetry placed upstream of the target. We designed and performed an experiment to study this dose enhancement. The objective of the experiment was to determine the effect of sample thickness on our three methods of dosimetry. The data from the PIN diodes and tantalum calorimeters were consistent and followed the expected DE/DX curve. They show a dose enhancement effect. The proton beam interacts and loses energy as it travels through thick targets. The exiting lower energy beam deposits more energy into the dosimetry because the stopping power increases with decreasing proton energy.
In this paper we review three proposed mechanisms for GaAs ALE and review or present data support or contradiction of these mechanisms. Surface chemistry results clearly demonstrated that TMGa irreversibly chemisorbs on the Ga-rich GaAs(100) surface. The reactive sticking coefficient (RSC) of TMGa on the adsorbate-free Ga-rich GaAs(100) surface was measured to be {approximately}0.5, conclusively demonstrating that the selective adsorption'' mechanism of ALE is not valid. We describe kinetic evidence for methyl radical desorption in support of the adsorbate inhibition'' mechanism. The methyl radical desorption rates determined by temperature programmed desorption (TPD) demonstrate that desorption is at least a factor of {approximately}10 faster from the As-rich c(2 {times} 8)/(2 {times} 4) surface than from the Ga-rich surface. It is disparity in CH{sub 3} desorption rates between the As-rich and Ga-rich surfaces that is largely responsible for GaAs ALE behavior. A gallium alkyl radical (e.g. MMGa) is also observed during TPD and molecular beam experiments, in partial support of the flux balance'' mechanism. Stoichiometry issues of ALE are also discussed. We have discovered that arsine exposures typical of atmospheric pressure and reduced pressure ALE lead to As coverages {ge} 1 ML, which provides the likely solution to the stoichiometry question regarding the arsine cycle. 32 refs., 6 figs.
A procedure was developed to use solder technology in the assembly of a single-crystal quartz accelerometer. 87.5Au-12.5Ge (wt.%) solder films 0.5 {times} 10{sup {minus}6}, 1.0 {times} 10{sup {minus}6}, and 2.0 {times} 10{sup {minus}}6 m thick were formed by the electron beam deposition of individual layers of Au and Ge with thicknesses so that the bulk film composition equals the eutectic composition. Interdiffusion of the Au and Ge formed the solder; thermal-physical measurements showed the multilayer films to behave similarly to bulk 87.5Au-12.5Be solder in process thermal cycles. The 2.0 {times} 10{sup {minus}6}m thick quartz/Au-Ge/quartz bonds had an adhesive tensile strength of 17 {plus minus} 2 MPa. The strength increased to 29 {plus minus} 3 MPa and 27 {plus minus} 12 MPa after thermal shock and thermal cycle exposures respectively. The 1.0 {times} 10{sup {minus}6} m thick bonds exhibited strengths of 16 {plus minus} 3 MPa, 16 MPa and 15 {plus minus} 8 MPa in the as-fabricated, post-thermal shock, and post-thermal cycled samples, respectively. The 0.5 {times} 10{sup {minus}6} m joints produced a large degree of scatter in the strength values. Accelerometers assembled with the 2.0 {times} 10{sup {minus}6} m thick joints demonstrated a significant improvement in temperature performance as opposed to units fabricated with a polyimide adhesive. 8 refs., 12 figs., 8 tabs.
This paper is about the spatial resolution of x-ray microanalysis in thin foils. The theory of the scattering of an electron beam with a thin foil is discussed.
Upon becoming Secretary of the Department of Energy (DOE), Admiral Watkins first pledged to Congress that he would clean-up'' the nuclear weapons production complexes and then initiated many changes in the way DOE facilities are operated. He generated new orders regarding environments, safety, and health and created investigation units called Tiger Teams'' to check on how well his orders were being followed. During the spin-up of this massive undertaking, DOE decided to include all its facilities and not just the ones involved in nuclear production. This resulted in research and development labs, such as Lawrence Livermore, Los Alamos, and Sandia National Laboratories being subjected to more stringent regulations. This paper addresses the action Sandia National Laboratories has taken during the past year, particularly in regard to its pulsed-power accelerators, to come into compliance with the new DOE orders. 2 tabs.
The measurement and understanding of the fracture toughness of ductile cast irons, DCI, are critical to the analysis of nuclear transportation casks made from these alloys. Cask containment must be assured for all loading events from normal handling to accidents during which high loads can be delivered at elevated rates. Cask walls are commonly in the range of 20 to 50 cm thick (or greater) in order to provide requisite nuclear shielding, and this requires that associated mechanical constraint effects must be considered. At elevated temperatures (i.e., in the vicinity of ambient) DCI behaves in an elastic-plastic manner, even for large section sizes (B>20 cm) and moderately high loading rates. However, as the temperature is lowered or the loading rate is increased, ferritic DCI alloys exhibit a relatively sharp transition to linear elastic behavior, with a significant decrease in the fracture toughness. The fracture toughness of a DCI alloy has been measured using linear elastic and elastic-plastic experimental techniques. Measurements have been made as a function of temperature, loading rate and section size. The loading rates span the range which a cask could experience during normal transport and handling, as well as accident events. 15 refs., 7 figs., 4 tabs.