Since micromachining technology has raised the prospect of fabricating high performance sensors without the associated high cost and large size, many researchers have investigated micromachined rate gyroscopes. The vast majority of research has focused on single input axis rate gyroscopes, but this paper presents work on a dual input axis micromachined rate gyroscope. The key to successful simultaneous dual axis operation is the quad symmetry of the circular oscillating rotor design. Untuned gyroscopes with mismatched modes yielded random walk as low as 10{degrees}/{radical}hour with cross sensitivity ranging from 6% to 16%. Mode frequency matching via electrostatic tuning allowed performance better than 2{degrees}/{radical}hour, but at the expense of excessive cross sensitivity.
The advanced networking department at Sandia National Laboratories has used the annual Supercomputing conference sponsored by the IEEE and ACM for the past several years as a forum to demonstrate and focus communication and networking developments. At Supercomputing 96, for the first time, Sandia National Laboratories, Los Alamos National Laboratory, and Lawrence Livermore National Laboratory combined their Supercomputing 96 activities within a single research booth under the ASO banner. Sandia provided the network design and coordinated the networking activities within the booth. At Supercomputing 96, Sandia elected: to demonstrate wide area network connected Massively Parallel Processors, to demonstrate the functionality and capability of Sandia`s new edge architecture, to demonstrate inter-continental collaboration tools, and to demonstrate ATM video capabilities. This paper documents those accomplishments, discusses the details of their implementation, and describes how these demonstrations support Sandia`s overall strategies in ATM networking.
Ross developed an analytical relationship to calculate the diversion length of a tilted fine-over-coarse capillary barrier. Oldenburg and Pruess compared simulation results using upstream and harmonic weighting to the diversion length predicted by Ross formula with mixed results; the qualitative agreement is reasonable but the quantitative comparison is poor, especially for upstream weighting. The proximity of the water table to the fine-coarse interface at breakthrough is a possible reason for the poor agreement. In the present study, the Oldenburg and Pruess problem is extended to address the water table issue. When the water table is sufficiently far away from the interface at breakthrough, good qualitative and quantitative agreement is obtained using upstream weighting.
This paper reviews how elements from the theory of fractal functions are employed to construct scaling vectors and multiwavelets. Emphasis is placed on the one-dimensional case, however extensions to IR{sup m} are indicated.
The project addressed the need of the oil and gas industry for real-time information about the drilling process and the formations being drilled. An ideal system would allow measuring while drilling (MWD) and would transmit data to the surface immediately at a rate high enough to support video or televiewer systems. A proposed solution was to use an optical fiber as a link between the surface and the instrumentation package. We explored the use of a disposable MWD telemetry cable, drawing on the technology developed for missile guidance which deploys miles of fiber from a small spool at missile speeds approaching half the speed of sound. Emphasis In was on the questions of survivability of the unarmored fiber in the drill string environment and deployability. Laboratory and field testing showed the concept worked under realistic conditions; a field demonstration transmitted data at 10 kilobits per second from a depth of 3500 feet.
We are testing an anti-weathering preservation strategy that is specific to limestone surfaces. The strategy involves the application of a mineral-specific, bifunctional, passivating/coupling agent that binds to both the limestone surface and to the consolidating inorganic polymer matrix. The sol-gel based reactions form composite materials with desirable conservation and anti-weathering properties. We present the results of our efforts, the highlights of which are: (1) scanning probe microscopy of moisture-free calcite crystals treated with the trisilanol form of silylalkylaminocarboxylate (SAAC), reveals porous agglomerates that offer no significant resistance to the mild leaching action of deionized water. When the crystals are further consolidated with a silica-based consolidant (A2**), no dissolution is seen although the positive role of the passivant molecule is not yet delineated. (2) Modulus of rupture tests on limestone cores treated with an aminoalkylsilane (AEAPS) and A2** showed a 25-35% increase in strength compared to the untreated samples. (3) Environmental scanning electron microscopy of treated limestone subjected to a concentrated acid attack showed degradation of the surface except in areas where thick layers of the consolidant were deposited.
Sandia National Laboratories conducts a comprehensive geothermal drilling research program for the US Department of Energy, Office of Geothermal Technologies. The program currently includes seven areas: lost circulation technology, hard-rock drill bit technology, high-temperature instrumentation, wireless data telemetry, slimhole drilling technology, Geothermal Drilling Organization (GDO) projects, and drilling systems studies. This paper describes the current status of the projects under way in each of these program areas.
An experimental study of electrokinetic effects (streaming potential) in earth materials was undertaken. The objective was to evaluate the measurement of electrokinetic effects as a method of monitoring and predicting the movement of groundwater, contaminant plumes, and other fluids in the subsurface. The laboratory experiments verified that the electrokinetic effects in earth materials are prominent, repeatable, and can be described well to first order by a pair of coupled differential equations.
Photonic system and device technologies have claimed a significant share of the current high-tech market. In particular, laser systems and optical devices impact a broad range of technological areas including telecommunications, optical computing, optical data storage, integrated photonics, remote environmental sensing and biomedical applications. Below we present an overview of photonics research being conducted within the Lasers, Optics and Remote Sensing department of the Physical and Chemical Sciences Center at Sandia National Laboratories. Recent results in the fields of photosensitive materials and devices, binary optics device applications, wavelength generation using optical parametric oscillators, and remote sensing are highlighted. 11 refs., 6 figs.
Vertical Cavity Surface Emitting Lasers (VCSELs) offer many benefits over conventional edge-emitting lasers including economical microelectronic batch processing, easy extension to 2-D arrays, and of interest here, very large intrinsic bandwidths due to reduced cavity volume. Results of electrical characterization of a 19 GHz bandwidth 850 nm VCSEL are presented. Small-signal characterization and modeling of the frequency response and device impedance is presented. Large signal performance is studied using two-tone RF and high-speed digital measurements. Appropriate drive conditions for high-speed digital applications are demonstrated.
Multiple-wavelength VCSEL and photodetector arrays are useful for wavelength-multiplexed fiberoptic networks, and for optical crosstalk isolation in parallel, free-space interconnects. Multiple wavelength VCSEL arrays have been obtained by varying the growth rate using thermal gradients caused by a backside-patterned substrate, by growth enhancement on a patterned substrate, and by varying the cavity length through anodic oxidation and selective etching of the wafer. We show here for the first time both the enhancement and the reduction of the growth rate of the entire VCSEL structure on a topographically patterned substrate, and demonstrate the controlled variation of the lasing wavelengths of a VCSEL array over an extended spectral range.
Capillary barriers, consisting of tilted fine-over-coarse layers under unsaturated conditions, have been suggested as landfill covers to divert water infiltration away from sensitive underground regions, especially for arid and semi-arid regions. The Hydrological Evaluation of Landfill Performance (HELP) computer code is an evaluation tool for landfill covers used by designers and regulators. HELP is a quasi-two-dimensional model that predicts moisture movement into and through the underground soil and waste layers. Processes modeled within HELP include precipitation, runoff, evapotranspiration, unsaturated vertical drainage, saturated lateral drainage, and leakage through liners. Unfortunately, multidimensional unsaturated flow phenomena that are necessary for evaluating tilted capillary barriers are not included in HELP. Differences between the predictions of the HELP and those from a multidimensional unsaturated flow code are presented to assess the two different approaches. Comparisons are presented for the landfill covers including capillary barrier configurations at the Alternative Landfill Cover Demonstration (ALCD) being conducted at Sandia.
The thermomechanical fatigue failure of solder joints is increasingly becoming an important reliability issue for electronic packages. The purpose of this Laboratory Directed Research and Development (LDRD) project was to develop computational tools for simulating the behavior of solder joints under strain and temperature cycling, taking into account the microstructural heterogeneities that exist in as-solidified near eutectic Sn-Pb joints, as well as subsequent microstructural evolution. The authors present two computational constitutive models, a two-phase model and a single-phase model, that were developed to predict the behavior of near eutectic Sn-Pb solder joints under fatigue conditions. Unique metallurgical tests provide the fundamental input for the constitutive relations. The two-phase model mathematically predicts the heterogeneous coarsening behavior of near eutectic Sn-Pb solder. The finite element simulations with this model agree qualitatively with experimental thermomechanical fatigue tests. The simulations show that the presence of an initial heterogeneity in the solder microstructure could significantly degrade the fatigue lifetime. The single-phase model was developed to predict solder joint behavior using materials data for constitutive relation constants that could be determined through straightforward metallurgical experiments. Special thermomechanical fatigue tests were developed to give fundamental materials input to the models, and an in situ SEM thermomechanical fatigue test system was developed to characterize microstructural evolution and the mechanical behavior of solder joints during the test. A shear/torsion test sample was developed to impose strain in two different orientations. Materials constants were derived from these tests. The simulation results from the two-phase model showed good fit to the experimental test results.
Under Executive Order 12898, Federal Actions to Address Environmental Justice in Minority Populations and Low-Income Populations, the Department of Energy (DOE) and Sandia National Laboratories New Mexico (SNL) are required to identify and address, as appropriate, disproportionately high, adverse human health or environmental effects of their activities on minority and low-income populations. The National Environmental Policy Act (NEPA) also requires that environmental justice issues be identified and addressed. This presents a challenge for SNL because it is located in a culturally diverse area. Successfully addressing potential impacts is contingent upon accurately identifying them through objective analysis of demographic information. However, an effective public participation process, which is necessarily subjective, is also needed to understand the subtle nuances of diverse populations that can contribute to a potential impact, yet are not always accounted for in a strict demographic profile. Typically, there is little or no coordination between these two disparate processes. This report proposes a five-step method for reconciling these processes and uses a hypothetical case study to illustrate the method. A demographic analysis and community profile of the population within 50 miles of SNL were developed to support the environmental justice analysis process and enhance SNL`s NEPA and public involvement programs. This report focuses on developing a methodology for identifying potentially impacted populations. Environmental justice issues related to worker exposures associated with SNL activities will be addressed in a separate report.
The Land Use, Air Quality, and Transportation Integrated Modeling Environment (LATIME) represents an integrated approach to computer modeling and simulation of land use allocation, travel demand, and mobile source emissions for the Albuquerque, New Mexico, area. This environment provides predictive capability combined with a graphical and geographical interface. The graphical interface shows the causal relationships between data and policy scenarios and supports alternative model formulations. Scenarios are launched from within a Geographic Information System (GIS), and data produced by each model component at each time step within a simulation is stored in the GIS. A menu-driven query system is utilized to review link-based results and regional and area-wide results. These results can also be compared across time or between alternative land use scenarios. Using this environment, policies can be developed and implemented based on comparative analysis, rather than on single-step future projections. 16 refs., 3 figs., 2 tabs.
Due to inter-quantum well tunneling, coupled double quantum wells (DQWs) contain an extra degree of electronic freedom in the growth direction, giving rise to new transport phenomena not found in single electron layers. This report describes work done on coupled DQWs subject to inplane magnetic fields B{sub {parallel}}, and is based on the lead author`s doctoral thesis, successfully defended at Oregon State University on March 4, 1997. First, the conductance of closely coupled DQWs in B{sub {parallel}} is studied. B{sub {parallel}}-induced distortions in the dispersion, the density of states, and the Fermi surface are described both theoretically and experimentally, with particular attention paid to the dispersion anticrossing and resulting partial energy gap. Measurements of giant distortions in the effective mass are found to agree with theoretical calculations. Second, the Landau level spectra of coupled DQWs in tilted magnetic fields is studied. The magnetoresistance oscillations show complex beating as Landau levels from the two Fermi surface components cross the Fermi level. A third set of oscillations resulting from magnetic breakdown is observed. A semiclassical calculation of the Landau level spectra is then performed, and shown to agree exceptionally well with the data. Finally, quantum wires and quantum point contacts formed in DQW structures are investigated. Anticrossings of the one-dimensional DQW dispersion curves are predicted to have interesting transport effects in these devices. Difficulties in sample fabrication have to date prevented experimental verification. However, recently developed techniques to overcome these difficulties are described.
This report details characterization and development activities in electronic packaging for high temperature applications. This project was conducted through a Department of Energy sponsored Cooperative Research and Development Agreement between Sandia National Laboratories and General Motors. Even though the target application of this collaborative effort is an automotive electronic throttle control system which would be located in the engine compartment, results of this work are directly applicable to Sandia`s national security mission. The component count associated with the throttle control dictates the use of high density packaging not offered by conventional surface mount. An enabling packaging technology was selected and thermal models defined which characterized the thermal and mechanical response of the throttle control module. These models were used to optimize thick film multichip module design, characterize the thermal signatures of the electronic components inside the module, and to determine the temperature field and resulting thermal stresses under conditions that may be encountered during the operational life of the throttle control module. Because the need to use unpackaged devices limits the level of testing that can be performed either at the wafer level or as individual dice, an approach to assure a high level of reliability of the unpackaged components was formulated. Component assembly and interconnect technologies were also evaluated and characterized for high temperature applications. Electrical, mechanical and chemical characterizations of enabling die and component attach technologies were performed. Additionally, studies were conducted to assess the performance and reliability of gold and aluminum wire bonding to thick film conductor inks. Kinetic models were developed and validated to estimate wire bond reliability.
This project focused on the fabrication and evaluation of supported inorganic membranes for hydrogen and oxygen separation in petrochemical processes. A variety of fabrication techniques, including CVD (Chemical Vapor Deposition), electroless plating, solution deposition and conventional ceramic processing methods were used for membrane fabrication. For the oxygen separation membrane materials studied, the high surface roughness of the commercially available (and chemically compatible) MgO supports for high flux oxygen materials (SrCo{sub 0.5}FeO{sub x} and SrCo{sub 0.8}Fe{sub 0.2}O{sub x}) hindered the development of supported membranes of these materials. More encouraging results were obtained for the supported hydrogen separation membranes. Both dense palladium (prepared by CVD and electroless plating) and ultramicroporous silica (prepared by solution deposition) membranes were fabricated onto porous alumina supports. Gas separation characteristics and reactor performance of the membranes were both studied. Of the two classes of membranes, when incorporated into a membrane reactor the silica membranes demonstrated the best performance. Propane and isobutane dehydrogenation processes were studied and the silica membrane reactors displayed modest improvements in performance compared to the conventional reactors. In propane dehydrogenation, an increase in propylene yield of 34% was obtained with the membrane reactor (compared to the conventional reactor); in isobutane dehydrogenation, an increase in isobutylene yield of 40% at 525 C was obtained. However, these performance gains decreased somewhat with time on stream, due to membrane instability. Further improvements in membrane stability and permselectivity, as well as catalyst stability are needed before membrane reactors can be considered as a realistic alternative to the existing conventional technology.
A hydrologic modeling study was performed to gain insight into the flow mechanisms around Room Q. A summary of hydrologic and structural data and of predictive fluid flow models from Room Q are provided. Six years of measured data are available from the time of excavation. No brine accumulation in Room Q was measured in the first two years following excavation. However, there is considerable uncertainty associated with this early-time data due to inadequate sealing of the room. Brine may have been lost to evaporation or it may have flowed into newly created disturbed rock zone (DRZ) porosity resulting from excavation. Non-zero brine accumulation rates were measured from 2--5 years, but brine accumulation within the room dropped to zero after 5.5 years. A conceptual model for brine inflow to Room Q was developed which assumes far-field Darcy flow combined with an increasing DRZ pore volume. Numerical simulations employed TOUGH28W and used predictive DRZ porosity increase with time from SPECTROM-32 rock deformation simulations. Simulated brine inflow showed good agreement with measured brine accumulation rates for the first five years. Two important conclusions were drawn from the simulation results: (1) early-time brine inflow to the room can be reduced to zero if the DRZ pore volume increases with time, and (2) brine accumulation (inflow) rates from 2 to 5 years suggest a far-field permeability of 5 {times} 10{sup {minus}22} m{sup 2} with a bulk rock compressibility of 5.4 {times} 10{sup {minus}12} Pa{sup {minus}1}.
This report describes a project to develop a flow probe to monitor gas movement in the vadose zone due to passive venting or active remediation efforts such as soil vapor extraction. 3-D and 1-D probes were designed, fabricated, tested in known flow fields under laboratory conditions, and field tested. The 3-D pores were based on technology developed for ground water flow monitoring. The probes gave excellent agreement with measured air velocities in the laboratory tests. Data processing software developed for ground water flow probes was modified for use with air flow, and to accommodate various probe designs. Modifications were made to decrease the cost of the probes, including developing a downhole multiplexer. Modeling indicated problems with flow channeling due to the mode of deployment. Additional testing was conducted and modifications were made to the probe and to the deployment methods. The probes were deployed at three test sites: a large outdoor test tank, a brief vapor extraction test at the Chemical Waste landfill, and at an active remediation site at a local gas station. The data from the field tests varied markedly from the laboratory test data. All of the major events such as vapor extraction system turn on and turn off, as well as changes in the flow rate, could be seen in the data. However, there were long term trends in the data which were much larger than the velocity signals, which made it difficult to determine accurate air velocities. These long term trends may be due to changes in soil moisture content and seasonal ground temperature variations.
Volatile organic compound (VOC) emission to the atmosphere is of great concern to semiconductor manufacturing industries, research laboratories, the public, and regulatory agencies. Some industries are seeking ways to reduce emissions by reducing VOCs at the point of use (or generation). This paper discusses the requirements, design, calibration, and use of a sampling inlet/quadrupole mass spectrometer system for monitoring VOCs in a semiconductor manufacturing production line. The system uses chemical ionization to monitor compounds typically found in the lithography processes used to manufacture semiconductor devices (e.g., acetone, photoresist). The system was designed to be transportable from tool to tool in the production line and to give the operator real-time feedback so the process(es) can be adjusted to minimize VOC emissions. Detection limits ranging from the high ppb range for acetone to the low ppm range fore other lithography chemicals were achieved using chemical ionization mass spectroscopy at a data acquisition rate of approximately 1 mass spectral scan (30 to 200 daltons) per second. A demonstration of exhaust VOC monitoring was performed at a working semiconductor fabrication facility during actual wafer processing.
Confidence building measures (CBMs), particularly military ones, that address the security needs of North and South Korea could decrease the risk of conflict on the Korean Peninsula and help create an environment in which to negotiate a peace regime. The Korea Institute for Defense Analyses (KIDA) and the Cooperative Monitoring Center (CMC) of Sandia National Laboratories collaborated to identify potential CBMs and define associated monitoring. The project is a conceptual analysis of political and technical options for confidence building that might be feasible in Korea at some future time. KIDA first analyzed current security conditions and options for CBMs. Their conclusions are presented as a hypothetical agreement to strengthen the Armistice Agreement by establishing Limited Force Deployment Zones along the Military Demarcation Line. The goal of the hypothetical agreement is to increase mutual security and build confidence. The CMC then used KIDA`s scenario to develop a strategy for cooperative monitoring the agreement. Cooperative monitoring is the collecting, analyzing and sharing of agreed information among parties to an agreement and typically relies on the use of commercially available technology. A cooperative monitoring regime must be consistent with the agreement`s terms; the geographic, logistic, military, and political factors in the Korean setting; and the capabilities of monitoring technologies. This report describes the security situation on the Korean peninsula, relevant precedents from other regions, the hypothetical agreement for reducing military tensions, a monitoring strategy for the hypothetical Korean agreement, examples of implementation, and a description of applicable monitoring technologies and procedures.
The disposition of the large back-log of plutonium residues at the Rocky Flats Environmental Technology Site (Rocky Flats) will require interim storage and subsequent shipment to a waste repository. Current plants call for disposal at the Waste Isolation Pilot Plant (WIPP) and the transportation to WIPP in the TRUPACT-II. The transportation phase will require the residues to be packaged in a container that is more robust than a standard 55-gallon waste drum. Rocky Flats has designed the Pipe Overpack Container to meet this need. The tests described here were performed to qualify the Pipe Overpack Container as a waste container for shipment in the TRUPACT-II. Using a more robust container will assure the fissile materials in each container can not be mixed with the fissile material from the other containers and will provide criticality control. This will allow an increase in the payload of the TRUPACT-II from 325 fissile gram equivalents to 2,800 fissile gram equivalents.
This study is a continuation of earlier work that evaluated 1969-1981 and 1984-1994 events affecting commercial light-water reactors. One-hundred nine operational events that affected 51 reactors during 1982 and 1983 and that are considered to be precursors to potential severe core damage are described. All these events had conditional probabilities of subsequent severe core damage greater than or equal to 1.0 x 10{sup {minus}6}. These events were identified by first computer screening the 1982-83 licensee event reports from commercial light-water reactors to select events that could be precursors to core damage. Candidates underwent engineering evaluation that identified, analyzed, and documented the precursors. This report discusses the general rationale for the study, the selection and documentation of events as precursors, and the estimation of conditional probabilities of subsequent severe core damage for the events.
Sealing fractures in nuclear waste repositories concerns all programs investigating deep burial as a means of disposal. Because the most likely mechanism for contaminant migration is by dissolution and movement through groundwater, sealing programs are seeking low-viscosity sealants that are chemically, mineralogically, and physically compatible with the host rock. This paper presents the results of collaborative work directed by Sandia National Laboratories (SNL) and supported by Whiteshell Laboratories, operated by Atomic Energy of Canada, Ltd. The work was undertaken in support of the Waste Isolation Pilot Plant (WIPP), an underground nuclear waste repository located in a salt formation east of Carlsbad, NM. This effort addresses the technology associated with long-term isolation of nuclear waste in a natural salt medium. The work presented is part of the WIPP plugging and sealing program, specifically the development and optimization of an ultrafine cementitious grout that can be injected to lower excessive, strain-induced hydraulic conductivity in the fractured rock termed the Disturbed Rock Zone (DRZ) surrounding underground excavations. Innovative equipment and procedures employed in the laboratory produced a usable cement-based grout; 90% of the particles were smaller than 8 microns and the average particle size was 4 microns. The process involved simultaneous wet pulverization and mixing. The grout was used for a successful in situ test underground at the WIPP. Injection of grout sealed microfractures as small as 6 microns (and in one rare instance, 3 microns) and lowered the gas transmissivity of the DRZ by up to three orders of magnitude. Following the WIPP test, additional work produced an improved version of the grout containing particles 90% smaller than 5 microns and averaging 2 microns. This grout will be produced in dry form, ready for the mixer.
