Publications

We report in this paper a study of the effective mass in thin oxide Si-MOSFETs, using the temperature dependence of the Shubnikov-de Haas (SdH) effect and following the methodology developed by Smith and Stiles.

Plasma, vapor and debris associated with an impact or explosive event have been demonstrated in the laboratory to produce radiofrequency and optical electromagnetic emissions that can be diagnostic of the event. Such effects could potentially interfere with communications or remote sensing equipment if an impact occurred, for example, on a satellite. More seriously, impact generated plasma could end the life of a satellite by mechanisms that are not well understood and not normally taken into account in satellite design. For example, arc/discharge phenomena resulting from highly conductive plasma acting as a current path across normally shielded circuits may have contributed to the loss of the Olympus experimental communications satellite on August 11, 1993. The possibility of significant storm activity during the Leonid meteor showers of November 1998, 1999 and 2000 (impact velocity, 72 km/s) has heightened awareness of potential vulnerabilities from hypervelocity electromagnetic effects to orbital assets. The concern is justified. The amount of plasma, electrostatic charge and the magnitude of the resulting currents and electric fields scale nearly as the cube of the impact velocity. Even for microscopic Leonid impacts, the amount of plasma approaches levels that could be dangerous to spacecraft electronics. The degree of charge separation that occurs during hypervelocity impacts scales linearly with impactor mass. The resulting magnetic fields increase linearly with impactor radius and could play a significant role in our understanding of the paleomagnetism of planetary surfaces. The electromagnetic properties of plasma produced by hypervelocity impact have been exploited by researchers as a diagnostic tool, invoked to potentially explain the magnetically jumbled state of the lunar surface and blamed for the loss of the Olympus experimental communications satellite. The production of plasma in and around an impact event can lead to several effects: (1) the plasma provides a significant perturbation to the ambient magnetic field via the electromagnetic pulse; (2) it supports the production of transient radiofrequency electromagnetic fields; (3) it charges ejected debris which, because of inertial separation, leads to significant electrostatic and magnetostatic field production; and (4) its high electrical conductivity provides a convenient path for discharge of the resulting high electrostatic fields. Effects (1) and (2) have been discussed by the authors elsewhere. Effects (3) and (4) will be discussed here. Typical studies of kinetic energy warheads focus on lethality as a function of impactor momentum or energy as they couple mechanically to the target. At high enough energies, however, additional physical processes come into play. Vaporization plays an important role and a partially ionized plasma can form. Impact-generated plasma, charged debris and magnetic fields have been characterized by laboratory hypervelocity impact experiments and are shown to be more abundant when certain easily ionized materials (such as alkali metals) are used in either projectile or target.

The Waste Isolation Pilot Plant (WIPP) is a deep underground nuclear waste repository certified by the U.S. Environmental Protection Agency ,(EPA) to store transuranic defense-related waste contaminated by small amounts of radioactive materials. Located at a depth of about 655 meters below the surface, the facility is sited in southeastern New Mexico, about 40 Department of Energy underground facilities, waste disposal. kilometers east of the city of Carlsbad, New Mexico. The U.S. (DOE) managed the design and construction of the surface and and remains responsible for operation and closure following The managing and operating contractor for the DOE at the WIPP, Westinghouse Electric Corporation, maintains two rechmiant seismic monitoring systems located at the surface and in the underground. This report discusses two earthquakes detected by the seismic monitoring system, one a duratior magnitude 5.0 (Md) event located approximately 60 km east-southeast of the facility, and another a body-wave magnitude 5.6 (rob) event that occurred approximately 260 kilometers to the south-southeast.

Abstract not provided.

As an ongoing part of the collaborative efforts between the Cooperative Monitoring Center (CMC) at Sandia National Laboratories, the United States Arms Control and Disarmament Agency (ACDA), and U.S. Department of Energy (DOE), staff from the CMC served as faculty in conducting a workshop in Shanghai, China. Sponsor of the workshop was the Regional Centre for Strategic Studies (RCSS) based in Colombo, Sri Lanka. The workshop included participants from throughout South Asia and China. The CMC presented four sessions related to the role of monitoring technologies in promoting regional security and building confidence among nations. Participation in these workshops supports U.S. efforts to further regional cooperation and promote arms control, nonproliferation and other cooperative securily measures and supplements efforts funded by DOE and ACDA over the past four years. The RCSS Shanghai meeting permitted a continued CMC involvement in regionally conducted training for anew generation of leaders in government, the military, and academia throughout South Asia and China. Nuclear issues are clearly a dominant South Asian concern since the nuclear tests of May 1998. However, there remains a strong interest in identifying opportunities for increased trade and reduced tensions in other areas. The RCSS and other regional organizations are enthusiastic about continued CMC involvement in future regional courses.

A multi-attribute utility analysis is applied to the decision to select a treatment method for the management of aluminum-based spent nuclear i%el (A1-SNF) owned by the United States Department of Energy (DOE). DOE will receive, treat, and temporarily store Al- SNF, most of which is composed of highly enriched uranium, at its Savannah River Site in South Carolina. DOE intends ultimately to send the treated Al-SNJ? to a geologic repository for permanent disposal. DOE initially considered ten treatment alternatives for the management of A1-SNF, and has narrowed the choice to two of these the direct disposal and melt and dilute alternatives. The decision analysis presented in this document focuses on a decision between these two remaining alternatives.

The HI616 shipping container is a certified type B(U) packaging used by the Department of Energy (DOE) to ship tritium in support of defense programs. During the 1997 recertification of the container, DOE became concerned about the possible cracking of the polyurethane foam in the overpacks of the 2300 containers currently in service. In response, Sandia National Laboratories (SNL) initiated a radiographic inspection program to determine if cracking of the foam was occurring in the H1616 overpacks. SNL developed the radiographic technique for inspecting the foam and contracted the Savannah River Site's Tritium Engineering division to inspect a representative sample of overpacks in service. This report details the development process and the results of all of the radiography performed both at SNL and Savannah River.

As computing assumes a more central role in managing the nuclear stockpile, the consequences of an erroneous computer simulation could be severe. Computational failures are common in other endeavors and have caused project failures, significant economic loss, and loss of life. This report examines the causes of software failure and proposes steps to mitigate them. A formal verification and validation program for scientific software is recommended and described.

The research summarized in this report is the result of a two-year effort that has focused on evaluating the viability of wavelet bases for the solution of partial differential equations. The primary objective for this work has been to establish a foundation for hierarchical/wavelet simulation methods based upon numerical performance, computational efficiency, and the ability to exploit the hierarchical adaptive nature of wavelets. This work has demonstrated that hierarchical bases can be effective for problems with a dominant elliptic character. However, the strict enforcement of orthogonality was found to be less desirable than weaker semi-orthogonality or bi-orthogonality for solving partial differential equations. This conclusion has led to the development of a multi-scale linear finite element based on a hierarchical change of basis. The reproducing kernel particle method has been found to yield extremely accurate phase characteristics for hyperbolic problems while providing a convenient framework for multi-scale analyses.

Early in 1994, the Department of Energy assigned Sandia National Laboratories the responsibility for designing and providing the welding system for the girth weld for the AT-400A containment vessel. (The AT-400A container is employed for the shipment and long-term storage of the nuclear weapon pits being returned from the nation's nuclear arsenal.) Mason Hanger Corporation's Pantex Plant was chosen to be the production facility. The project was successfully completed by providing and implementing a turnkey welding system and qualified welding procedure at the Pantex Plant. The welding system was transferred to Pantex and a pilot lot of 20 AT-400A containers with W48 pits was welded in August 1997. This document is intended to bring together the AT-400A welding system and product (girth weld) requirements and the activities conducted to meet those requirements. This document alone is not a complete compilation of the welding development activities but is meant to be a summary to be used with the applicable references.

The goal is the development of materials that are highly sensitive and selective for chid chemicals and biochemical (such as insecticides, herbicides, proteins, and nerve agents) to be used as sensors, catalysts and separations membranes. Molecular modeling methods are being used to tailor chiral molecular recognition sites with high affinity and selectivity for specified agents. The work focuses on both silicate and non-silicate materials modified with chirally-pure fictional groups for the catalysis or separations of enantiomerically-pure molecules. Surfactant and quaternary amine templating is being used to synthesize porous frameworks, containing mesopores of 30 to 100 angstroms. Computer molecukw modeling methods are being used in the design of these materials, especially in the chid surface- modi~ing agents. Molecular modeling is also being used to predict the catalytic and separations selectivities of the modified mesoporous materials. The ability to design and synthesize tailored asymmetric molecular recognition sites for sensor coatings allows a broader range of chemicals to be sensed with the desired high sensitivity and selectivity. Initial experiments target the selective sensing of small molecule gases and non-toxic model neural compounds. Further efforts will address designing sensors that greatly extend the variety of resolvable chemical species and forming a predictive, model-based method for developing advanced sensors.

Comprehensive management of the battle-space has created new requirements in information management, communication, and interoperability as they effect surveillance and situational awareness. The objective of this proposal is to expand intelligent controls theory to produce a uniquely powerful implementation of distributed ground-based measurement incorporating both local collective behavior, and interoperative global optimization for sensor fusion and mission oversight. By using a layered hierarchal control architecture to orchestrate adaptive reconfiguration of autonomous robotic agents, we can improve overall robustness and functionality in dynamic tactical environments without information bottlenecks. In this concept, each sensor is equipped with a miniaturized optical reflectance modulator which is interactively monitored as a remote transponder using a covert laser communication protocol from a remote mothership or operative. Robot data-sharing at the ground level can be leveraged with global evaluation criteria, including terrain overlays and remote imaging data. Information sharing and distributed intelli- gence opens up a new class of remote-sensing applications in which small single-function autono- mous observers at the local level can collectively optimize and measure large scale ground-level signals. AS the need for coverage and the number of agents grows to improve spatial resolution, cooperative behavior orchestrated by a global situational awareness umbrella will be an essential ingredient to offset increasing bandwidth requirements within the net. A system of the type described in this proposal will be capable of sensitively detecting, tracking, and mapping spatial distributions of measurement signatures which are non-stationary or obscured by clutter and inter- fering obstacles by virtue of adaptive reconfiguration. This methodology could be used, for example, to field an adaptive ground-penetrating radar for detection of underground structures in urban environments and to detect chemical species concentrations in migrating plumes. Given is our research in these areas and a status report of our progress.

This report describes the results of a Sandia Laboratov Directed Research & Development project to develop a technique that can identifi atoms in atomically engineered nanostructures. The report provides a detailed description of the experimental measurement techniques and subsequent image analysis procedures used in the identification process, followed by examples of the technique's successful application to several atomic surface features. Use of this technique requires the experimental measurement of both constant-current topographic and multi-bias conductance data from an atomic surface with the scanning tunneling microscope. These measurements are rendered as a collection of topographic and single-bias conductance images of the surface. Image pixels are then grouped into classes by a computed grouping algorithm, according to the shared conductance characteristics exhibited at each pixel. The image pixels are then color-coded by class to produce a false-color image of the scanned surface that chemically distinguishes surface electronic features over the entire area of the measured atomic surface.

Technical support for the Hanford Tank Closure Program focused on evaluation of concepts for immobilization of residual contaminants in the Hanford AX tanks and underlying soils, and identification of cost-effective approaches to improve long-term performance of AX tank farm cIosure systems. Project objectives are to develop materials or engineered systems that would significantly reduce the radionuclide transport to the groundwater from AX tanks containing residual waste. We pursued several studies that, if implemented, would help achieve these goals. They include: (1) tank fill design to reduce water inilltration and potential interaction with residual waste; (2) development of in-tank getter materials that would specifically sorb or sequester radionuclides; (3) evaluation of grout emplacement under and around the tanks to prevent waste leakage during waste retrieval or to minimize water infiltration beneath the tanks; (4) development of getters that will chemically fix specific radionuclides in soils under tanks; and (5) geochemical and hydrologic modeling of waste-water-soil-grout interactions. These studies differ in scope from the reducing grout tank fill employed at the Savannah River Site in that our strategy improves upon tank fill design by providing redundancy in the barriers to radionuclide migration and by modification the hydrogeochemistry external to the tanks.

Abstract not provided.

Sol-gel chemistry has been the focus of much attention in the design and preparation of highly crosslinked polysiloxane gels. Preparation of sol-gel processed silica or polysilesquioxane gels is carried out by the hydrolysis and condensation of alkoxysilyl monomers, usually in the presence of catalytic acid or base and an excess of water. Removal of the alcohol and water byproducts of the condensation reactions, in addition to the alcohol needed to co-dissolve the hydrophobic monomers with water, leads to substantial shrinkage during drying of the resulting gels. This limits the utility of sol-gel processing for applications requiring net-shape casting of artifacts, crack free coatings, or low vaporous organic contaminants (VOCs). It would be advantageous to have a sol-gel process based on an organosilicon monomer that would not require water as a reactant or produce water and alcohol condensation products and still result in siloxane network polymers capable of forming gels. Here, the authors show the synthesis and preparation of a novel sol-gel monomer which can easily be polymerized by ring opening polymerization to give highly crosslinked polysiloxane gels with no condensation byproducts.

An air sparging and high vacuum extraction was installed as an alternative to a containment pump and treat system to reduce the long-term remediation schedule. The site is located at the DOE Mound facility in Miamisburg, Ohio, just south of Dayton. The air sparging system consists of 23 wells interspersed between 17 soil vapor extraction wells. The SVE system has extracted about 1,500 lbs of VOCs in five months. The air sparging system operated for about 6 weeks before shutdown due to suspected biochemical fouling. Technical data are presented on the operating characteristics of the system.

Advanced radiographic applications require a constant source size less than 1 mm. To study the time history of a relativistic electron beam as it interacts with a bremsstrahlung converter, one of the diagnostics they use is a multi-frame time-resolved hard x-ray camera. They are performing experiments on the ETA-II accelerator at Lawrence Livermore National Laboratory to investigate details of the electron beam/converter interactions. The camera they are using contains 6 time-resolved images, each image is a 5 ns frame. By starting each successive frame 10 ns after the previous frame, they create a 6-frame movie from the hard x-rays produced from the interaction of the 50-ns electron beam pulse.

The authors report 77K operation of an optically pumped vertical cavity surface emitting laser with an Sb-based cavity. The structure consists of 15 and 20 pair AlGaAsSb/AlAsSb top and bottom reflectors and a bulk InGaAs active region.

The authors present an agent-oriented mechanism that uses a central ontology as a means to conduct complex distributed transactions. This is done by instantiating a template object motivated solely by the ontology, then automatically and explicitly linking each temple element to an independently constructed interface component. Validation information is attached directly to the links so that the agent need not know a priori the semantics of data validity, merely how to execute a general validation process to satisfy the conditions given in the link. Ontological leveling is critical: all terms presented to informants must be semantically coherent within the central ontology. To illustrate this approach in an industrial setting, they discuss an existing implementation that conducted international commercial transactions on the World-Wide Web. Agents operating within a federated architecture construct, populate by Web-based elicitation, and manipulate a distributed composite transaction object to effect transport of goods over the US/Mexico border.

ALEGRA is a coupled physics framework originally written to simulate inertial confinement fusion (ICF) experiments being conducted at the PBFA-II facility at Sandia National Laboratories. It has since grown into a large software development project supporting a number of computational programs at Sandia. As the project has grown, so has the development team, from the original two authors to a group of over fifteen programmers crossing several departments. In addition, ALEGRA now runs on a wide variety of platforms, from large PCs to the ASCI Teraflops massively parallel supercomputer. The authors discuss the reasons for ALEGRA`s success, which include the intelligent use of object-oriented techniques and the choice of C++ as the programming language. They argue that the intelligent use of development tools, such as build tools (e.g. make), compiler, debugging environment (e.g. dbx), version control system (e.g. cvs), and bug management software (e.g. ClearDDTS), is nearly as important as the choice of language and paradigm.

The authors improved a self-aligned emitter etchback technique that requires only a single emitter diffusion and no alignments to form self-aligned, patterned-emitter profiles. Standard commercial screen-printed gridlines mask a plasma-etchback of the emitter. A subsequent PECVD-nitride deposition provides good surface and bulk passivation and an antireflection coating. The authors used full-size multicrystalline silicon (mc-Si) cells processed in a commercial production line and performed a statistically designed multiparameter experiment to optimize the use of a hydrogenation treatment to increase performance. They obtained an improvement of almost a full percentage point in cell efficiency when the self-aligned emitter etchback was combined with an optimized 3-step PECVD-nitride surface passivation and hydrogenation treatment. They also investigated the inclusion of a plasma-etching process that results in a low-reflectance, textured surface on multicrystalline silicon cells. Preliminary results indicate reflectance can be significantly reduced without etching away the emitter diffusion.

The Direct Simulation Monte Carlo (DSMC) technique is employed to evaluate several configurations of thermal transpiration and accommodation pumps. There is renewed interest in these rarefied flow pumping concepts for Micro-Electro-Mechanical Systems (MEMS) due to advances in micro-fabrication. The simulation results are compared with existing data to understand gas-surface interaction uncertainties in the experiments. Parametric studies are performed to determine the effects of Knudsen number and surface temperature and roughness on the maximum pump pressure ratio.

This paper describes a method of modeling swarms of UAVs and/or fighter aircraft using particle simulation concepts. Recent investigations into the use of genetic algorithms to design neural networks for the control of autonomous vehicles (i.e., robots) led to the examination of methods of simulating large collections of robots. This paper describes the successful implementation of a model of swarm dynamics using particle simulation concepts. Several examples of the complex behaviors achieved in a target/interceptor scenario are presented.

A novel Monte Carlo (MC) model of Zener pinning has been developed. It differs from previous MC models in that it does not simulate polycrystalline grain growth. Instead a single boundary moving through an array of particles is simulated. The boundary curvature defines the driving force acting on the boundary; this is constant throughout the simulation. By incrementally increasing the volume fraction of particles, the pinning force is gradually increased. The boundary is eventually pinned when driving force equals the pinning force. This defines the Zener criterion and enables the volume fraction dependence of the model to be determined. The value of this approach is that there is no limit imposed on either the volume fraction of particles or their size. Simulations have been carried out over a range of volume fractions, from 0 < f < 0.25 for particles with volumes of 27 sites. The pinning force exerted by particles on a boundary is related to the characteristic shape during bypass, the so called dimple. When the simulation temperature is T{prime} = 0, dimples are not formed, the boundaries experience an artificially strong pinning force and the model exhibits an f{sup {minus}1/2} dependence. When T{prime} is greater than a critical value dimples are formed and the model shows an f{sup {minus}1} volume fraction dependence. The implications of this result for previously MC models of Zener pinning is discussed.