Publications

We present a theory for transforming the system-theory-based realization models into the corresponding physical coordinate-based structural models. The theory has been implemented into computational procedure and applied to several example problems. Our results show that the present transformation theory yields an objective model basis possessing a unique set of structural parameters from an infinite set of equivalent system realization models. For proportionally damped systems, the transformation directly and systematicaly yields the normal modes and modal damping. Moreover, when nonproportional damping is present, the relative magnitude and phase of the damped mode shapes are separately characterized, and a corrective transformation is then employed to capture the undamped normal modes and nondiagonal modal damping matrix.

No abstract available.

A tunable, high-accelerating-gradient cavity has been designed for use in the rf system of the Low Energy Booster (LEB) at the Superconducting Super Collider (SSC). Details of the cavity design are discussed along with low level, swept frequency, and high pwoer test results.

Three potential methods for measuring the surface tritium content of the TFTR vacuum vessel are described, each based on a different technique for measuring the in situ beta emission from tritium. These methods should be able to provide both a local and a global assessment of the tritium content within the top [approx] 1[mu]m of the inner wall surface.

This paper develops corrections to the impedance per unit length when the conductor cross section includes sharp corners. The case of a right internal angle is treated in detail. Corrections are given for all real positive values of the ratio of internal to external magnetic permeabilities. Both the real and imaginary parts of the corrections are determined. Application of the results to a conductor of square cross section is given. Higher order terms are developed and compared to a numerical solution. These higher order terms are generalized to the conductor of rectangular cross section. © 1994 IEEE

The Robotic All-Terrain Lunar Exploration Rover (RATLER) is a four wheeled all-wheel-drive dual-body vehicle. A uniquely simple method of chassis articulation is employed which allows all four wheels to remain in contact with the ground, even while climbing over step-like obstacles as large as 1.3 wheel diameters. The RATLER design concept began at Sandia National Laboratories in late 1991 with a series of small, proof-of-principle, working scale models. The models proved the viability of the concept for high mobility through mechanical simplicity, and eventually received internal funding at Sandia National Laboratories for full scale, proof-of-concept prototype development. Whereas the proof-of-principle models demonstrated the mechanical design's capabilities for mobility, the full scale proof-of-concept design currently under development is intended to support field operations for experiments in telerobotics, autonomous robotic operations, telerobotic field geology, and advanced man-machine interface concepts. The development program's current status is described, including an outline of the program's work over the past year, recent accomplishments, and plans for follow-on development work.

This paper describes a collision avoidance system using Whole Arm Proximity (WHAP) sensors on a PUMA 560 robot arm. The capacitance-based sensors generate electric fields which can completely encompass the robot arm and detect obstacles as they approach from any direction. The directional obstacle information gathered by the WHAP sensors together with the sensor geometry and robot configuration is used to scale the commanded joint velocities of the robot. A linearized relationship between the WHAP sensor reading and the distance from the obstacle allows direct transformation of perturbations in WHAP readings to perturbations in joint velocities. The WHAP reading is used to directly reduce the component of the command input velocity along the normal axis of the sensor, allowing graceful reductions in speed as the arm approaches the obstacle. By scaling only the component of the velocity vector in the direction of the nearest obstacles, the control system restricts motion in the direction of obstacles while permitting unconstrained motion in other directions.

The computational fluid dynamics code FIDAP (Fluid Dynamics International) is used to perform simulations of the steady laminar flow of an incompressible fluid in a three-dimensional rectangular cavity. Although most previous studies have considered a 'lid-driven' cavity, where a uniform horizontal velocity is imposed on the cavity lid, the flow in the channel above the cavity is explicitly included in the computational domain in these simulations. Simulations are performed for various Reynolds numbers in the range 0 ≤ Re ≤ 1000 and are compared to corresponding two-dimensional results. The three-dimensional flows are seen to exhibit a smooth topology change around Re ≈ 35.

Detection of air-borne environmental contaminants, such as organic solvents, requires unambiguous compound identification and sensitivity to concentrations below those permitted by regulating agencies. One promising detection approach uses a pulsed supersonic molecular beam vacuum expansion in combination with fluorescence signal spectral analysis to identify species in a chemical mixture. This report describes the use and performance of the ultraviolet excitation molecular beam fluorometer.

We have studied a singly-resonant KTP ring OPO pumped by nanosecond pulses from a frequency-doubled NdYAG laser. We present measurements of the temporal and spatial intensity profiles of the incident pump beam and OPO output beams, including the depleted pump, as well as the output energy as a function of pump laser energy. These measurements have been carried out for both injection-seeded and unseeded operation of the OPO The results of these measurements have been compared to the output of a computer model.

The Telemanaged Mobile Security Station (TMSS) was developed at Sandia National Laboratories to investigate the role of mobile robotics in exterior perimeter security systems. A major feature of the system is its capability to perform autonomous patrols of the security site's network of roads. Perimeter security sites are well known, structured environments; the locations of the roads, buildings, and fences are relatively static. A security robot has the advantage of being able to learn its new environment prior to autonomous travel. The TMSS robot combines information from a microwave beacon system and on-board dead reckoning sensors to determine its location within the site. The operator is required to teleoperate the robot in a teach mode over all desired paths before autonomous operations can commence. During this teach phase, TMSS stores points from its position location system at two meter intervals. This map data base is used for planning paths and for reference during path following. Details of the position location and path following systems will be described along with system performance and recommendations for future enhancements.

A method was developed for applying an inorganic conversion coating on that is procedurally similar to chromate conversion coating methods; this method, however does not use or involve hazardous/toxic chemicals. The coating forms by precipitation involving Al{sup 3+} Li{sup +}, OH{sup {minus}}, CO{sub 3}{sup 2}{minus}, and possibly other anions. This polycrystalline coating is continuous, conformal and persistent in aggressive environments. Coating thicknesses range from several tenths to ten micrometers. Although the outer portions of the coating are porous, the pores do not penetrate to the substrate interface. These coatings do not match the levels of performance offered by commercially available chromate conversion coatings, but are capable of meeting many of the corrosion resistance, electrical resistivity, and paint adhesion requirements established in MIL-C-5541E ``Chemical Conversion Coatings on Aluminum and Aluminum Alloys.`` In this paper, methods for producing the talc coating on aluminum alloys 1100 and 6061-T6 are described and compared to traditional chromate conversion coating methods. Resulting coating structure and composition are described. Performance data for the talc coatings in MIL-C-5541E required tests are presented along with data commercial chromate-based coatings.

Fluorescence depolarization studies of polysilane chains in solution have shown that energy transfer along the polymer chains occurs for only a very short time relative to the excited state lifetime and only over short distances before the excited states become trapped in long, low-energy segments. However, in solid films we have shown in previous work that excitons are highly mobile throughout their 600 ps lifetime at room temperature, presumably because energy transfer among neighboring, parallel chain segments becomes possible. In this paper we report that the exciton-exciton annihilation rate constant decreases by only a factor of five between room temperature and 12 K, showing that the excitons do not become trapped even at low temperatures.

Analog-to-digital converters are frequently modeled as a linear polynomial plus a random process. The parameters of the linear polynomial are the familiar gain and offset of the analog-to-digital converter. The output of the random process is uniformly distributed on plus or minus the least significant bit of the analog-to-digital converter. In this paper, the transfer function of an analog-to-digital converter is modeled as a nonlinear polynomial plus a random process. This model can explain the generation of harmonics by the analog-to-digital converter, but the simpler linear model cannot. The parameters of the nonlinear polynomial are estimated from the response to the analog-to-digital converter to a sine wave. The model parameters are used to estimate the nonlinear part of the transfer function of the analog-to-digital converter.

Many safety analyses depend on uncertain inputs and on mathematical models chosen from various alternatives, but give fixed results (implying no uncertainty). Conventional uncertainty analyses help, but are also based on assumptions and models, the accuracy of which may be difficult to assure. Some of the models and assumptions that on cursory examination seem reasonable can be misleading. As a result, quantitative assessments, even those accompanied by uncertainty measures, can give unwarranted impressions of accuracy. Because analysis results can be a major contributor to a safety-measure decision process, risk management depends on relating uncertainty to only the information available. The uncertainties due to abnormal environments are even more challenging than those in normal-environment safety assessments, and therefore require an even more cautious approach. A fuzzy-algebra analysis is proposed in this article that has the potential to appropriately reflect the information available and portray uncertainties well, especially for abnormal environments. © 1994 John Wiley & Sons, Inc.

The blast-induced movement and final location of geologic layers that may cause environmental problems can be predicted using discrete element methods. This prediction capability can be used by mine operators to locate the material in the muck pile during excavation which would allow encapsulation to prevent groundwater infiltration.

In support of the Department of Energy`s Dismantlement Program, the Optoelectronics Characterization and Sensor Development Department 2231 at Sandia National Laboratories/New Mexico has developed an in situ nonintrusive Optoelectronic Inventory System (OIS) that has the potential for application wherever periodic inventory of selected material is desired. Using a network of fiber-optic links, the OIS retrieves and stores inventory signatures from data storage devices (which are permanently attached to material storage containers) while inherently providing electromagnetic pulse immunity and electrical noise isolation. Photovoltaic cells (located within the storage facility) convert laser diode optic power from a laser driver to electrical energy. When powered and triggered, the data storage devices sequentially output their digital inventory signatures through light-emitting diode/photo diode data links for retrieval and storage in a mobile data acquisition system. An item`s exact location is determined through fiber-optic network and software design. The OIS provides an on-demand method for obtaining acceptable inventory reports while eliminating the need for human presence inside the material storage facility. By using modularization and prefabricated construction with mature technologies and components, an OIS installation with virtually unlimited capacity can be tailored to the customer`s requirements.

Time-resolved velocity interferometry measurements have been made on boron carbide and silicon carbide ceramics to assess dynamic equation-of-state and strength properties of these materials. Hugoniot precursor characteristics, and post-yield shock and release wave properties, indicated markedly different dynamic strength and flow behavior for the two carbides.

To investigate the feasibility of producing a compact, efficient blue laser source, pumped-cavity second harmonic generation of diode lasers was explored. It is desirable to have such lasers to increase optical disk storage density, for color displays and for under-the-sea green-blue optical signal transmission. Based on assumed cavity losses, a cavity was designed and numerical analysis predicted an overall conversion efficiency to the second harmonic wavelength of 76% from a 75 mW diode laser. The diode laser used in these experiments had a single longitudinal and a single transverse mode output at 860 nm. The best conversion efficiency obtained (26%) was less than optimum due to the 2.5% single-pass linear losses associated with the cavity. However, calculations based on these higher losses are in good agreement with the experimentally determined values. In additions, a factor of 1.65 increase in the second harmonic output power is anticipated by reducing the input mirror reflectivity to better impedance-match the cavity. With this relatively low second harmonic conversion, the power to light conversion is 7.8%.

A series of explosive tests were performed to establish containment integrity data for commonly used handling and storage containers of energetic materials at Sandia National Laboratories, Albuquerque, N.M. The tests consisted of two phases: (1) each container was tested for explosive integrity and propagation, and (2) the data were used to evaluate a nominal donor-receptor test matrix for verifying the confinement integrity of a typical explosives service locker.

This study is a comparison of hydraulic fracture models run using test data from the GRI Staged Field Experiment No. 3. Models compared include 2D, pseudo-3D, and 3D codes, run on up to eight different cases. Documented in this comparison are the differences in length, height, width, pressure, and efficiency. The purpose of this study is to provide the completions engineer with a practical comparison of the available models so that rational decisions can be made as to which model is optimal for a given application.

Synthetic Aperture Radar (SAR) from an airborne platform has been proposed for imaging targets beneath the earth`s surface. The propagation of the radar`s energy within the ground, however, is much different than in the earth`s atmosphere. The result is signal refraction, echo delay, propagation losses, dispersion, and volumetric scattering. These all combine to make SAR image formation from an airborne platform much more challenging than a surface imaging counterpart. This report treats the ground as a lossy dispersive half-space, and presents a model for the radar echo based on measurable parameters. The model is then used to explore various imaging schemes, and image properties. Dynamic range is discussed, as is the impact of loss on dynamic range. Modified window functions are proposed to mitigate effects of sidelobes of shallow targets overwhelming deeper targets.

Oxynitrides have been grown by oxidation in N2O in a standard thermal oxidation furnace. Two N2O processes have been studied: Oxidation in N2O only, and two-step oxidation with initial oxidation in O2 followed by oxidation/nitridation in N2O. Results are presented for radiation damage at 80 and 295K, hole trapping, interface trap creation, electron spin resonance, and hole detrapping using thermally-stimulated current analysis. N2O oxydo not appear to have the well-known drawbacks of NH3-annealed oxynitrides. Creation of interface traps during irradiation is reduced in the N2O oxynitrides, with the degree of improvement depending on the fabrication process. © 1994 IEEE

The radiation hardness of commercial Floating Gate 256K E2PROMs from a single diffusion lot was observed to vary between 5 to 25 krad(Si) when irradiated at a low dose rate of 64 mrad(Si)/s. Additional variations in E2PROM hardness were found to depend on bias condition and failure mode (i.e., inability to read or write the memory), as well as the foundry at which the part was manufactured. This variability is related to system requirements, and it is shown that hardness level and variability affect the allowable mode of operation for E2PROMs in space applications. The radiation hardness of commercial I-Mbit CMOS SRAMs from Micron, Hitachi, and Sony irradiated at 147 rad(Si)/s was approximately 12, 13, and 19 krad(Si), respectively. These failure levels appear to be related to increases in leakage current during irradiation. Hardness of SRAMs from each manufacturer varied by less than 20%, but differences between manufacturers are significant. The Qualified Manufacturer's List approach to radiation hardness assurance is suggested as a way to reduce variability and to improve the hardness level of commercial technologies. © 1994 IEEE

This report is divided into: budget, capital equipment requests, general programmatic overview and institutional issues, DOE center of excellence for synthesis and processing of advanced materials, industrial interactions and technology transfer, and research program summaries (new proposals, existing programs). Ceramics, semiconductors, superconductors, interfaces, CVD, tailored surfaces, adhesion, growth and epitaxy, boron-rich solids, nanoclusters, etc. are covered.

Autosim is a software package written to control and trigger the programmable instruments that are used to supply simulated signals to the recording devices on underground nuclear weapons effects tests at the Nevada Test Site. These instruments are located either in the tunnel or at a remote site, and may be controlled from anywhere on the Department 9320 Computer Network. Autosim incorporates commands to control the operation of the Laser Calibrator that is a fiber optic device that transmits a signal from down-hole to the uphole recorders. Autosim also supports the task of characterizing the cable links by communicating to some high bandwidth digitizers that are used to input the pulse of the downhole simulator. To minimize the learning interval, Autosim utilizes menus and offers on-line help on most of the selections in the menu options.

Ceramic chip capacitors can potentially crack due to thermal stresses in a surface mount assembly process. The electrical performance of the cracked capacitors will degrade with time, and they will prematurely short. In high reliability applications, the cracked capacitors must be identified and eliminated. We have developed and demonstrated the temperature-humidity-bias (THB) aging technique to identify cracked capacitors. The initial phase of the study involved setting up automated test equipment to monitor 100 surface mounted capacitors at 85% relative humidity, 85{degree}C with 50 volts dc bias. The capacitors subjected to severe thermal shock were aged along with control samples. Failure mode analysis was done on the failed capacitors. The capacitors with surface cracks short-out within the first 8 hours of aging, whereas the capacitors that failed after a longer aging time (8 to 1000 hours) had a shorting path in an internal void. Internal voids are typical defects introduced during manufacturing of multilayer ceramic (MLC) capacitors. In the second phase of the study, we used the THB aging technique to study the effect of surface mount processes on capacitor cracking and, thus the reliability. The surface mount processes studied were vapor phase, infra-red (IR) and convection belt reflow soldering. The results shoed that 6.3% of vapor phase soldered capacitors, and 1.25% of the IR and convection belt soldered capacitors had cracks. In all capacitors, regardless of the solder process used, an additional 3 to 4% of the capacitors failed due to a shorting path in the internal void. The results of this study confirm that this technique can be used to screen cracked capacitors and compare different solder and manufacturing processes.

The excess base current in an irradiated BJT increases superlinearly with total dose at low-total-dose levels. In this regime, the excess base current depends on the particular charge-trapping properties of the oxide that covers the emitter base junction. The device response is dose-rate-, irradiation-bias-, and technology-dependent in this regime. However, once a critical amount of charge has accumulated in the oxide, the excess base current saturates at a value that is independent of how the charge accumulated. This saturated excess base current depends on the device layout, bulk lifetime in the base region, and the measurement bias. In addition to providing important insight into the physics of bipolar-transistor total-dose response, these results have significant circuit-level implications. For example, in some circuits, the transistor gain that corresponds to the saturated excess base current is sufficient to allow reliable circuit operation. For cases in which the saturated value of current gain is acceptable, and where other circuit elements permit such over-testing, this can greatly simplify hardness assurance for space applications. © 1994 IEEE

This report gives the results of a study of the production of electricity from geothermal energy with particular emphasis on the drilling of geothermal wells. A brief history of the industry, including the influence of the Public Utilities Regulatory Policies Act, is given. Demand and supply of electricity in the United States are touched briefly. The results of a number of recent analytical studies of the cost of producing electricity are discussed, as are comparisons of recent power purchase agreements in the state of Nevada. Both the costs of producing electricity from geothermal energy and the costs of drilling geothermal wells are analyzed. The major factors resulting in increased cost of geothermal drilling, when compared to oil and gas drilling, are discussed. A summary of a series of interviews with individuals representing many aspects of the production of electricity from geothermal energy is given in the appendices. Finally, the implications of these studies are given, conclusions are presented, and program recommendations are made.

In this paper we describe an algorithm by which obstructions and surface features in an underground storage tank can be modeled and used to generate virtual barrier functions for a real-time telerobotic system, which provides an aid to the operator for both real-time obstacle avoidance and for surface tracking. The algorithm requires that the slave's tool and every object in the waste storage tank be decomposed into convex polyhedral primitives, with the waste surface modeled by triangular prisms. Intrusion distance and extraction vectors are then derived at every time step by applying Gilbert's polyhedra distance algorithm, which has been adapted for the task. This information is then used to determine the compression and location of nonlinear virtual spring-dampers whose total force is summed and applied to the manipulator/teleoperator system. Experimental results using a PUMA 560 and a simulated waste surface validate the approach, showing that it is possible to compute the algorithm and generate smooth, realistic pseudo forces for the teleoperator system using standard VME bus hardware.

Low energy Ar and Xe ion bombardment of Ge (001) produces large numbers of point defects on the Ge surface and in the near-surface regions. Defect concentrations on the surface are detected and quantified in real time during bombardment using in situ Reflection High Energy Electron Diffraction (RHEED). We report the energy dependence of the defect yield for 70-500 eV Ar and Xe ion bombardment, and the temperature dependence of the defect yield (defects/ion) during 200 eV ion bombardment. The defect yield drops rapidly as the substrate temperature during bombardment is varied from 175 K to 400 K. We attribute the yield reduction to surface recombination of adatoms and vacancies produced in the same collision cascade.

Least-squares sine-fit algorithms are used extensively in signal processing applications. The parameter estimates produced by such algorithms are subject to both random and systematic errors when the record of input samples consists of a fundamental sine wave corrupted by harmonic distortion or noise. The errors occur because, in general, such sine-fits will incorporate a portion of the harmonic distortion or noise into their estimate of the fundamental. Bounds are developed for these errors for least-squares four-parameter (amplitude, frequency, phase, and offset) sine-fit algorithms. The errors are functions of the number of periods in the record, the number of samples in the record, the harmonic order, and fundamental and harmonic amplitudes and phases. The bounds do not apply to cases in which harmonic components become aliased.

FPT0 is the first of six tests that are scheduled to be conducted in an experimental reactor in Cadarache, France. The test apparatus consists of an in-pile fuel bundle, an upper plenum, a hot leg, a steam generator, a cold leg, and a small containment. Thus, the test is integral in the sense that it attempts to simulate all of the processes that would be operative in a severe nuclear accident. In FPT0, the fuel will be trace irradiated; in subsequent tests high burn-up fuel will be used. This report discusses separate pretest analyses of the FPT0 fuel bundle and primary circuit have been conducted using the USNRC`s source term code, VICTORIA-92. Predictions for release of fission product, control rod, and structural elements from the test section are compared with those given by CORSOR-M. In general, the releases predicted by VICTORIA-92 occur earlier than those predicted by CORSOR-M. The other notable difference is that U release is predicted to be on a par with that of the control rod elements; CORSOR-M predicts U release to be about 2 orders of magnitude greater.

DC and pulsed-DC electromigration tests were performed at the wafer level using standard and self-stressing test structures. DC characterization tests over a very large temperature range (180 to 560 °C) were consistent with an interface diffusion mechanism in parallel with lattice diffusion. That data allowed for extraction of the respective activation energies and the diffusion coefficient of the rapid mechanism. The ability to extract simultaneously a defect-based diffusion coefficient and activation energy is significant given the extreme difficulty in making those measurements in aluminum. The pulsed-DC experiments were conducted over a range that includes the highest frequency to date, from DC to 500 MHz. Measurements were also made as a function of duty factor from 15% to 100% at selected frequencies. The data shows that the pulsed-DC lifetime is consistent with the average current density model at high (>10 MHz) frequencies and showed no additional effects at the highest frequency tested (500 MHz). At low frequencies, we attribute the lessened enhancement to thermal effects rather than vacancy relaxation effects. Finally, the deviation in lifetime from the expected current density dependence, characterized over 1 1/2 orders of magnitude in current density, is explained in terms of a shift in the boundary condition for electromigration as the current density is decreased.

This report identifies and describes emerging nondestructive inspection (NDI) methods that can potentially be used to inspect commercial transport and commuter aircraft for structural damage. The nine categories of emerging NDI techniques are: acoustic emission, x-ray computed tomography, backscatter radiation, reverse geometry x-ray, advanced electromagnetics, including magnetooptic imaging and advanced eddy current techniques, coherent optics, advanced ultrasonics, advanced visual, and infrared thermography. The physical principles, generalized performance characteristics, and typical applications associated with each method are described. In addition, aircraft inspection applications are discussed along with the associated technical considerations. Finally, the status of each technique is presented, with a discussion on when it may be available for use in actual aircraft maintenance programs. It should be noted that this is a companion document to DOT/FAA/CT-91/5, Current Nondestructive Inspection Methods for Aging Aircraft.

This report describes efforts conducted under Tasks 3 and 4 of the second phase of the project to develop a single-element stretched-membrane dish concept to reduce the cost of a high-performance concentrating solar collector. We completed the detailed design for such a collector suitable to drive a 25-kWe Stirling motor generator. The design includes the collectors, optical element, the drive, and support systems. The aperture of the optical element was sized to provide the required energy to the engine based on test data and analytical models of the concentrator receiver, and engine. The design of the optical element was improved based on experience gained from the design, fabrication, and testing of several prototypes.

Thin films of amorphous carbon/hydrogen, also known as diamond-like carbon or DLC, are of interest as an economical alternative to diamond in a variety of coatings applications. We have investigated the thermal stability of DLC films deposited onto tungsten and aluminum substrates via plasma CVD of methane. These films contain approximately 40 atom % hydrogen, and based on Auger spectra the carbon in the films is estimated to be approximately 60% sp3 hybridized and 40% sp2 hybridized. Thermal desorption, Auger, and Raman measurements all indicate that the DLC films are stable to 250-300 °C. Between 300 and 500 °C, thermal evolution of hydrogen from the films is accompanied by the conversion of carbon from sp3 to sp2 hybridization, and Raman spectra indicate the conversion of the overall film structure from DLC to micro-crystalline graphite or so-called `glassy' carbon. These results suggest that DLC of this type is potentially useful for applications in which the temperature does not exceed 250 °C.

This manual is intended to act as a working guide for setting up a Science Fair Volunteer Support Committee at your school. The Science Fair Volunteer Support Committee, or SFVSC, is the key component of the Science Fair Self-Help program, which was developed by Sandia National Laboratories and is designed to support a school`s science activities. The SFVSC is a team of parents and community volunteers who work in concert with a school`s teaching staff to assist and manage all areas of a school Science and Engineering Fair. The main advantage of creating such a committee is that it frees the science teachers from the organizational aspects of the fair and lets them concentrate on their job of teaching science. This manual is based on information gained through a Self-Help Development pilot program that was developed by Sandia National Laboratories during the 1991--92 school year at three Albuquerque, NM, middle schools. The manual describes the techniques that were successful in the pilot program and discusses how these techniques might be implemented in other schools. This manual also discusses problems that may be encountered, including suggestions for how they might be resolved.

The code HORSMIC was written to solve the problem of calculating the shape of hydrocarbon (gas or liquid) storage caverns formed by solution mining in bedded salt formations. In the past many storage cavems have been formed by vertically drilling into salt dome formations and solution mining large-aspect-ratio, vertically-axisymmetric caverns. This approach is generally not satisfactory for shallow salt beds because it would result in geomechanically-unstable, pancake-shaped caverns. In order to produce a high aspect ratio cavern in the horizontal direction a more complicated strategy must be employed. This report describes one such strategy, and documents the use of the computer model HORSMIC which can be used to estimate the shape of the cavern produced by a prescribed leaching schedule. Multiple trials can then be used to investigate the effects of various pipe hole configurations in order to optimize over the cavern shape.

The objective of the ``Hydrodynamics of Maneuvering Bodies`` LDRD project was to develop a Lagrangian, vorticity-based numerical simulation of the fluid dynamics associated with a maneuvering submarine. Three major tasks were completed. First, a vortex model to simulate the wake behind a maneuvering submarine was completed, assuming the flow to be inviscid and of constant density. Several simulations were performed for a dive maneuver, each requiring less than 20 cpu seconds on a workstation. The technical details of the model and the simulations are described in a separate document, but are reviewed herein. Second, a gridless method to simulate diffusion processes was developed that has significant advantages over previous Lagrangian diffusion models. In this model, viscous diffusion of vorticity is represented by moving vortices at a diffusion velocity, and expanding the vortices as specified by the kinematics for a compressible velocity field. This work has also been documented previously, and is only reviewed herein. The third major task completed was the development of a vortex model to describe inviscid internal wave phenomena, and is the focus of this document. Internal wave phenomena in the stratified ocean can affect an evolving wake, and thus must be considered for naval applications. The vortex model for internal wave phenomena includes a new formulation for the generation of vorticity due to fluid density variations, and a vortex adoption algorithm that allows solutions to be carried to much longer times than previous investigations. Since many practical problems require long-time solutions, this new adoption algorithm is a significant step toward making vortex methods applicable to practical problems. Several simulations are described and compared with previous results to validate and show the advantages of the new model. An overview of this project is also included.

This report documents results of a series of scoping experiments on boiling from downward-facing surfaces in support of the Sandia New Production Reactor, Vessel-Pool Boiling Heat Transfer task. Quenching experiments have been performed to examine the boiling processes from downward-facing surfaces using two 61-centimeter diameter test masses, one with a flat test surface and one with a curved test surface having a radius of curvature of 335 cm, matching that of the Cylindrical Boiling facility test vessel. Boiling curves were obtained for both test surfaces facing horizontally downward. The critical beat flux was found to be essentially the same, having an average value of approximately 0.5 MW/m{sup 2}. This value is substantially higher than current estimates of the heat dissipation rates required for in-vessel retention of core debris in the Heavy Water New Production Reactor as well as some of the advanced light water reactors under design. The nucleate boiling process was found to be cyclic with four relatively distinct phases: direct liquid/solid contact, nucleation and growth of bubbles, coalescence, and ejection.

We demonstrate the use of HAST and Assembly Test Chips to evaluate the susceptability of epoxy molding compounds to moisture induced corrosion of Al conductors. We show that the procedure is sufficiently sensitive to discriminate between assembly processes used by different molding facilities. Our data show that the location in time of the 'knee' in the failure distribution is dependent on material properties of the epoxy. Reducing the failure rate in the early or 'extrinsic' region of the time-failure distribution is key to achieving high reliability. We examine the failure modes in the extrinsic region for test chips encapsulated with a number of high quality molding compounds in an attempt to better understand this region.

This report describes the instrumentation locations of the Tore Supra Phase III Outboard Limiter, including the locations and signal names of the flowmeters and thermocouples. Shot 11044 was evaluated in some detail. The heat loads in the fourteen cooling tubes that form the limiter head were calculated from the data and the results compared with the heat loads predicted using a 3-D model heat transfer calculation that calculates the distribution of power on the limiter based upon the power scrape-off length, the mag magnetic configuration and the shape of the limiter.

We are studying carbon thin films by using a pulsed excimer laser to ablate pyrolytic graphite targets to form highly tetrahedral coordinated amorphous carbon (at-C) films. These films have been grown on room temperature p-type Si (100) substrates without the intentional incorporation of hydrogen. In order to understand and optimize the growth of at-C films, parametric studies of the growth parameters have been performed. We have also introduced various background gases (H2, N2 and Ar) and varied the background gas pressure during deposition. The residual compressive stress levels in the films have been measured and correlated to changes in the Raman spectra of the at-C band near 1565 cm-1. The residual compressive stress falls with gas pressure, indicating a decreasing atomic sp3-bonded carbon fraction. We find that reactive gases such as hydrogen and nitrogen significantly alter the Raman spectra at higher pressures. These effects are due to a combination of chemical incorporation of nitrogen and hydrogen into the film as well as collisional cooling of the ablation plume. In contrast, films grown in non-reactive Ar background gases show much less dramatic changes in the Raman spectra at similar pressures.

Granular salt can be used to construct high performance permanent seals in boreholes which penetrate rock salt formations. These seals are described as seal systems comprised of the host rock, the seal material, and the seal rock interface. The performance of these seal systems is defined by the complex interactions between these seal system components through time. The interactions are largely driven by the creep of the host formation applying boundary stress on the seal forcing consolidation of the granular salt. The permeability of well constructed granular salt seal systems is expected to approach the host rock permeability (<10-21 m2 (10"9 darcy)) with time. The immediate permeability of these seals is dependent on the emplaced density. Laboratory test results suggest that careful emplacement techniques could result in immediate seal system permeability on the order of 10'16 m2 to 10*1* m2 (10*4 darcy to 10"^ darcy). The visco-plastic behavior of the host rock coupled with the granular salts ability to "heal" or consolidate make granular salt an ideal sealing material for boreholes whose permanent sealing is required.

The Department of Energy’s Solar Thermal Electric Program is managed by the Solar Thermal and Biomass Power Division, which is part of the Office of Utility Technologies. The focus of the Program is to commercialize solar electric technologies. In this regard, three major projects are currently being pursued in trough, central receiver, and dish/Stirling electric power generation. This paper describes these three projects and the activities at the National Laboratories that support them.

Northern Research and Engineering Corp. (NREC) is currently under contract to Sandia National Laboratories to solarize a 30 kWe Brayton engine that is based on turbo-charger technology. This program is also supported by the German Aerospace Research Establishment (DLR), which is supplying the solar receiver through an agreement with the International Energy Agencyl Solar PACES. The engine is a low pressure, highly recuperated engine. The turbo-machinery is built up from commercial turbo-chargers, which ensures low cost and high reliability. A combustor will be included in the system to allow for full power production during cloud transients. Current estimates are that the engine/alternator thermal-to-electric efficiency will be 30+%. The solar receiver to be supplied by DLR will be an advanced version of their VOBREC volumetric receiver. This receiver has a parabolic quartz window and ceramic foam absorber. The estimated efficiency of the receiver is 9W%. Sandia has developed an economic model to estimate the levelized energy cost (LEC) of energy produced by dish/engine systems. The model includes both the operating characteristics of the dishes and engines as well as a detailed economic model. The results of the analysis indicate that the dish/Brayton systems compare favorably with dishlstirling systems.

The National Ignition Facility (NIF), which is expected to resolve important Defense Program and inertial fusion energy issues for energy production in the future, will consist of a laser system with 192 independent beamlets transported to a target chamber. The target chamber is a multi-purpose structure that provides the interface between the target and the laser optics. The chamber must be capable of achieving moderate vacuum levels in reasonable times; it must remain dimensionally stable within micron tolerances, provide support for the optics, diagnostics, and target positioner; it must minimize the debris from the x-ray and laser light environments; and it must be capable of supporting external neutron shielding. The chamber must also be fabricated from a low neutron activation material. This paper describes the conceptual design of the target chamber, target positioner, and shielding for the NIF.

Highly tetrahedral-coordinated-amorphous-carbon (a-tC) films deposited by pulsed-laser deposition (PLD) on silicon substrates are studied. These films are grown at room-temperatures in a high-vacuum ambient. a-tC films grown in this manner have demonstrated stability to temperatures in excess of T = 1000 °C, more than sufficient for any post-processing treatment or application. Film surfaces are optically smooth as determined both visually and by atomic-force microscopy. PLD growth parameters can be controlled to produce films with a range of sp2 - sp3 carbon-carbon bond ratios. Films with the highest yield of sp3 C-C bonds have high resistivity, with a dielectric permittivity constant ε to approximately 4, measured capacitively at low frequencies (1 - 100 kHz). These a-tC films are p-type semiconductors as grown. Schottky barrier diode structures have been fabricated.

Pool-boiler reflux receivers have been considered as an alternative to heat pipes for the input of concentrated solar energy to Stirling-cycle engines in dish-Stirling electric generation systems. Pool boilers offer simplicity in design and fabrication. The operation of a full-scale pool-boiler receiver has been demonstrated for short periods of time. However, to generate cost-effective electricity, the receiver must operate without significant maintenance for the entire system life, as much as 20 to 30 years. Long-term liquid-metal boiling stability and materials compatibility with refluxing NaK-78 is not known and must be determined for the pool boiler receiver. No boiling system has been demonstrated for a significant duration with the current porous boiling enhancement surface and materials. At least one theory explaining lncipientboiling behavior of alkali metals indicates that favorable start-up behavior should deteriorate over time. Many factors affect the stability and startup behavior of the boiling system. Therefore, it is necessary to simulate the full-scale pool boiler design as much as possible, including flux levels, materials, and operating cycles. On-sun testing is impractical because of the limited test time available. A test vessel was constructed with a Friction Coatings Inc, porous boiling enhancement surface. The boiling surface consisted of a brazed stainless steel powder with about 50% porosity. The vessel was heated with a quartz lamp array providing about 90 Wlcm2 peak incident thermal flux. The vessel was charged with NaK-78, which is liquid at room temperature. This allows the elimination of costly electric preheating, both on this test and on fullscale receivers. The vessel was fabricated from Haynes 230 alloy, selected for its high temperature strength and oxidation resistance. The vessel operated at 750°C around the clock, with a 112-hour shutdown cycle to ambient every 8 hours. Temperature data was continually collected. The test completed 7500 hours of lamp-on operation time, and over 1000 startups from ambient. The test was terminated when a small leak in an lnconel 600 thermowell was detected. The test design and data are presented here. Metallurgical analysis of virgin and tested materials has begun, and initial results are also presented.

In attempt to ultimately control the characteristics of the PZT films, we have decided to investigate some of the basic chemistry associated with these solutions. Frequently, these solutions have been generated from Group IV metal alkoxides in acetic acid (HOAc). Therefore, studies of the simple reactivity between M(OCHMe2)4 (M = Ti, Zr) and HOAc have been undertaken. These reactions were monitored by 1H, 13C, 17O NMR, FT-IR, TGA/DTA, and single crystal X-ray studies. Films were produced from spin-coat deposition of crystalline material (from the titanium reaction) in toluene and aged solutions as well.

This paper describes three applications of the boundary element method and their implementations on the Intel Paragon supercomputer. Each of these applications sustains over 99 Gflops/s based on wall-clock time for the entire application and an actual count of flops executed; one application sustains over 140 Gflops/s! Each application accepts the description of an arbitrary geometry and computes the solution to a problem of commercial and research interest. The common kernel for these applications is a dense equation solver based on LU factorization. It is generally accepted that good performance can be achieved by dense matrix algorithms, but achieving the excellent performance demonstrated here required the development of a variety of special techniques to take full advantage of the power of the Intel Paragon.

A compact, easily transportable, pulse generator has been developed for a variety of applications that require a pulse duration in the range of 1p sec., voltages from 150 to 300 KV and current levels from 2,000 to 3,000 amps. The generator has a simple cylindrical configuration and modular construction to facilitate assembly and service. The generator may be operated single-pulse or repetitively at pulse repetition rates to 50 Hz in a burst mode.

A wideband EMF' tester consisting of a high voltage modulator, transmission line, high voltage peaking switch, and a "EM test cell has been developed that delivers repetitive high frequency EMF' pulses to an RF-sealed double-test volume of about 1 k3. The pulse shape is rectangular, has a duration of 4 ns and a risetime of 120 ps. The system can be operated at pulse repetition rates up to 1500 Hz and electric field levels up to 125 kV/m. Both voltage and pulse rate are continuously adjustable over these ranges and may be operated in any combination.

High-temperature post-oxidation annealing of poly-Si/SiO2/Si structures such as metal-oxide-semiconductor capacitors and metal-oxide-semiconductor field effect transistors is known to result in enhanced radiation sensitivity, increased 1/f noise, and low field breakdown. We have studied the origins of these effects from a spectroscopic standpoint using electron paramagnetic resonance (EPR) and atomic force microscopy. One result of high temperature annealing is the generation of three types of paramagnetic defect centers, two of which are associated with the oxide close to the Si/SiO2 interface (oxygen-vacancy centers) and the third with the bulk Si substrate (oxygen-related donors). In all three cases the origin of the defects may be attributed to out-diffusion of O from the SiO2 network into the Si substrate with associated reduction of the oxide. We present a straightforward model for the interfacial region which assumes the driving force for O out-diffusion is the chemical potential difference of the O in the two phases (SiO2 and the Si substrate). Experimental evidence is provided to show that enhanced hole trapping and interface-trap and border-trap generation in irradiated high-temperature annealed Si/SiO2/Si systems are all related either directly, or indirectly, to the presence of oxygen vacancies.

The Geothermal Heat Pump (GHP) concept was originally developed in the 1940's. Recently, because of increasing energy costs, utility interest, and the development of simple and durable ground source heat exchangers, GHP's have gained international attention as a proven means of energy conservation and electrical peak power demand reduction. GHP systems require installation of a buried heat exchanger to utilize the nearly constant ground temperature making them more efficient than conventional air source heat pumps. However, the high installation cost for both residential and commercial applications is a major obstacle to their market penetration. Sandia National Laboratories (SNL) through its sponsors, the Department of Energy (DOE) and the Department of Defense (DOD), has embarked on a research program to find ways to reduce GHP installation costs and improve performance, thereby increasing their market penetration. The major elements of the program are: data acquisition to quantify the performance of GHP's, research and development (R&D) of the ground source heat exchanger aimed at reducing installation costs, and support of DOE efforts to market the GHP concept. This paper describes the current status of our program, some experimental and analytical results, and plans for future activities.

Path planning needs to be fast to facilitate real-time robot programming. Unfortunately, current planning techniques are still too slow to be effective, as they often require several minutes, if not hours of computation. To overcome this difficulty, we present an adaptive algorithm that uses past experience to speed up future performance. It is a learning algorithm suitable for automating flexible manufacturing in mirementally-changing environments. The algorithm allows the robot to adapt to its environment by having two ezperience manipulation schemes: For minor environmental change, we use an object-attached experience abstraction scheme to increase the Flexibility of the learned experience; for major environmental change, we use an on-demand experience repair scheme to retain those experiences that remain valid and useful. Using this algorithm, we can effectively reduce the overall robot planning time by re-using the computation result for one task to plan a path for another.

Path planning needs to be fast to facilitate real-time robot programming. Unfortunately, current planning techniques are still too slow to be effective, as they often require several minutes, if not hours of computation. To overcome this difficulty, we present an adaptive algorithm that uses past experience to speed up future performance. It is a learning algorithm suitable for incrementally-changing environments such as those encountered in manufacturing of evolving prod-ucts and waste-site remediation. The algorithm allows the robot to adapt to its environment by having two experience manipulation schemes: For minor environmental change, we use an object-attached experience abstraction scheme to increase the flexibility of the learned experience; for major environmental change, we use an on-demand experience repair scheme to retain those experiences that remain valid and useful. Using this algorithm, we can effectively reduce the overall robot planning time by re-using the computation result for one task to plan a path for another.

Property scaling becomes an issue whenever heterogeneous media properties are measured at one scale but applied at another (i.e., data is collected at the core scale but analysis is conducted at the grid block scale). A research program has been established to challenge current understanding of property scaling with the aim of developing and testing models that describe scaling behavior in a quantitative manner. Scaling of constitutive rock properties is investigated through physical experimentation involving the collection of gas-permeability data measured over a range of discrete scales. The approach is to systematically isolate those factors that influence property scaling and investigate their relative contributions to overall scaling behavior. Two blocks of rock, each exhibiting differing heterogeneity structure, have recently been examined. The two samples were found to yield different scaling behavior, as exhibited by changes in the distribution functions and semivariograms. Simple models have been fit to the measured scaling behavior that are of similar functional form but of different magnitude.

A computer code has been developed to determine the size of a ground-launched, multistage missile which can intercept a theater ballistic missile before it leaves the atmosphere. Typical final conditions for the inteceptor are 450 km range, 60 km altitude, and 80 sec flight time. Given the payload mass (35 kg), which includes a kinetic kill vehicle, and achievable values for the stage mass fractions (0.85), the stage specific impulses (290 sec), and the vehicle density (60 lb/ft3), the launch mass is minimized with respect to the stage payload mass ratios, the stage burn times, and the missile angle of attack history subject to limits on the angle of attack (10 deg), the dynamic pressure (60,000 psf), and the maneuver load (200,000 psf deg). For a conical body, the minimum launch mass is approximately 1900 kg. The missile has three stages, and the payload coasts for 57 sec. A trade study has been performed by varying the flight time, the range, and the dynamic pressure limits. With the results of a sizing study for a 70 lb payload and qmar = 35,000 psf, a more detailed design has been carried out to determine heat shield mass, tabular aerodynamics, and altitude dependent thrust. The resulting missile has approximately 100 km less range than the sizing program predicted primarily because of the additional mass required for heat protection. On the other hand, launching the same missile from an aircraft increases its range by approximately 100 km. Sizing the interceptor for air launch with the same final conditions as the ground-launched missile reduces its launch mass to approximately 1000 kg.

Factors that control phase evolution, microstructural development and ferroelectric domain assemblage are evaluated for chemically prepared lead zirconate titanate (PZT) thin films. Zirconium to titanium stoichiometry is shown to strongly influence microstructure. As Ti content increases, there is an apparent enhancement of the perovskite phase nucleation rate, grain size becomes smaller, and the amount of pyrochlore phase, if present, decreases. While the pyrochlore matrix microstructure for near morphotropic phase boundary composition thin films consists of two interpenetrating nanophases (pyrochlore and an amorphous phase); the pyrochlore microstructure for PZT 20/80 films deposited on MgO substrates is single phase and consists of 10 nm grains. Zirconium to titanium stoichiometry also has a substantial influence on process integration. Near morphotropic phase boundary films exhibit extensive reaction with underlying Ti02 diffusion barriers; conversely, there is no chemical reaction for identically processed PZT 20/80 thin films. We have attempted to directly correlate the optical quality of PZT thin films to the following microstructural features: 1) presence of a second phase, 2) domain orientation, and 3) nanometer surface morphology. © 1994, Taylor & Francis Group, LLC. All rights reserved.

A dual-element, stretched-membrane central receiver heliostat was designed and manufactured in 1989, by a private US company engaged in the development of commercial central receiver solar technology. The two-module collector, with a collection area of 97.5 m{sup 2}, extends stretched-membrane mirror technology on several fronts with face-down stow capability and a digital controller that integrates tracking and focusing control on a single programmable control board. The solar collector was installed at Sandia`s National Solar Thermal Test Facility in Albuquerque, New Mexico and evaluated over a three-and-a-half year period which ended in September 1993. The measured performance and the operational and maintenance characteristics of this commercial prototype are the subject of this report. The results of beam quality measurements, tracking repeatability tests, measurements of beam movement in elevated winds, performance tests of the focusing system, and all-day beam quality and tracking tests are presented, and the authors offer a detailed discussion of the knowledge gained through operation and maintenance and of the improvements made or suggested to the heliostat`s design.

This report presents the results of an inspection around fastener holes in simulated lap splice specimens using a Nortec-30 Eddyscan inspection system. The inspector performing the tests had no prior knowledge of the extent or location of cracks in the specimens examined. The results of the inspection are presented in terms of various probability of detection curve models and are compared to various other eddy current inspections performed on the same set of test specimens. Results indicate that the system is capable, with high confidence, of detecting 60 to 70 mil cracks from under countersink fasteners.

This report presents a provisional lifetime prediction method which attempts to account for creep- fatigue interactions typically encountered in the design of solar central receivers that spend a considerable fraction of their operating periods subjected to compressive stresses at elevated temperature. During its operating life, a solar central receiver will be exposed to a large number of startup/shut- down cycles (relative to other power-producing systems), along with only short periods (up to 10-12 hrs.) of steady-state operation during each daily cycle. As such, fatigue-related deformation is expected to dominate the damage leading to failure in the high temperature alloys used for such as receiver. Thus, the provisional method concentrates on a fatigue-based damage approach, with direct accounting for the effects of thermo-mechanical fatigue and hold times at elevated temperatures. Note that creep damage is treated in an implicit way only, by means of the hold time correction. The starting point for the methodology is the isothermal low cycle fatigue data set used to develop fatigue design curves for ASME Boiler and Pressure Vessel Code Case N-47. Since the original data were not available for materials of interest (316 Stainless Steel and Alloy 800H), we attempted to estimate the original data sets by stripping away the safety factors of 2 on Δϵ and 20 on N₁ from the N-47 design curves. These "baseline data curves" for N₁ versus Δϵ, which represent the mean low cycle fatigue properties for each alloy at a given temperature, are tabulated in the Appendix in both tabular format and by means of sixth-order polynomial equations. The baseline data curves are first reduced to account for the effects of frequency and hold time. Comparison of hold time data for both 316 SS and 800H have indicated that additional factors of safety are required to make the frequency and hold time reductions conservative for all data considered. Therefore, safety factors of 1.5 on Δϵ and 4.5 on N₁ are used, and these are shown to give generally conservative predictions. Finally, reductions for thermomechanical fatigue damage are made which are a function of f, the fraction of thermally imposed strain to the total imposed strain. It is expected that the resulting fatigue design curves should yield reasonable life predictions for the design of solar central receivers.

Performance assessment calculations are based on geochemical models that assume that interactions among radionuclides, rocks and groundwaters under natural conditions, can be estimated or bound by data obtained from laboratory-scale studies. The data include radionuclide distribution coefficients, measured in saturated batch systems of powdered rocks, and retardation factors measured in short-term column experiments. Traditional approaches to model validation cannot be applied in a straightforward manner to the simple reactive transport models that use these data. An approach to model validation in support of performance assessment is described in this paper. It is based on a recognition of different levels of model validity and is compatible with the requirements of current regulations for high-level waste disposal. Activities that are being carried out in support of this approach include (1) laboratory and numerical experiments to test the validity of important assumptions inherent in current performance assessment methodologies,(2) integrated transport experiments, and (3) development of a robust coupled reaction/transport code for sensitivity analyses using massively parallel computers.

We report the synthesis and optical properties of Rb[Ti{sub 1-2x}Ln{sub x}Nb{sub x}]OAsO{sub 4}. The solid solubility of lanthanide ions in the materials decreases exponentially as the size of the lanthanide ion increases. The materials exhibit absorption spectra characteristic of the particular lanthanide ion in the structure. The spectral regions between absorption peaks are transparent and will allow the transmission of fundamental and second-harmonic radiation. The charge transfer band is red-shifted 0 to 27 nm relative to RbTiOAsO{sub 4} (midpoint 331 nm). Second-harmonic intensities measured at 532 nm decrease exponentially as lanthanide ion concentration increases.

Saturation profiles resulting from TOUGH2 numerical simulations of water infiltration into a tuff matrix from a saturated vertical fracture have been compared to experimental results. The purpose was to determine the sensitivity of the infiltration on local heterogeneities and different representations of two-phase characteristic curves used by the model. Findings indicate that the use of simplified (linearized) capillary pressure curves with rigorous (van Genuchten) relative permeability curves resulted in a more computationally efficient solution without a loss in accuracy. However, linearized forms of the relative permeability functions produced poor results, regardless of the form of the capillary pressure function. In addition, numerical simulations revealed that the presence of local heterogeneities in the tuff caused non-uniform saturation distributions and wetting fronts in the in matrix.

As Sandia National Laboratories and the Physical and Chemical Sciences Center develop an increasingly diverse set of customers, research partners, and Cooperative Research and Development Agreements (CRADA`s) with industry, there is a need for providing more concise information describing their technical achievements and capabilities. This publication, Research Briefs, is designed to inform the present and potential partners in research and technology advancement. Their research emphasizes semiconductor physics, electronic materials, surface physics and chemistry, plasma and chemical processing sciences, lasers and optics, vision science, ion-solid interactions and defect physics, and advanced materials physics. The specific programs they pursue are driven by the research goals which are greatly influenced by interactions with the government and industrial customers.

Tests were performed to evaluate the corrosivity of several nitrate salt mixtures on the containment materials likely to be used in a molten-salt solar central receiver power plant. Objective was to determine if common salt impurities (e.g., chloride) aggravate corrosion. The test was conducted for 7008 hours on A36 carbon steel at 320C and 304 and 316 stainless steels at 570C. Seven salt mixture containing a variety of impurity concentrations were used. Corrosion rates were determined by descaled weight loss for coupons removed periodically from the melts. The nitrate mixtures were analyzed for changes in impurity levels and accumulation of soluble corrosion products. Test results indicate generally that corrosion is slow and that impurities do not contribute dramatically to corrosion rates of carbon and stainless steels.

Ion implantation in insulators causes modifications in the refractive-index as a result of radiation damage, phase separation, or compound formation. As a consequence, light waveguides may be formed with interesting applications in the field of optoelectronics. Recently implantation of metals ions (e.g. silver, copper, gold, lead,...) showed the possibility of small radii colloidal particles formation, in a thin surface layer of the glass substrate. These particles exhibit an electron plasmon resonance which depends on the optical constants of the implanted metal and on the refractive-index of the glass host. The non-linear optical properties of such colloids, in particular the enhancement of optical Kerr susceptibility, suggest that the, ion implantation technique may play an important role for the production of all-optical switching devices. In this paper an analysis of the state-of-the-art of the research in this field will be presented in the framework of ion implantation in glass physics and chemistry.

Copper implantations (90 keV, 5{times}10{sup 16} ions/cm{sup 2}) were made into fused silica, borosilicate glasses and soda-lime glass. The copper distribution has been found to vary according to glass type. The optical absorption band characteristic of the implanted metal optical properties was observed only for copper-implanted fused silica. Absorption for all the other samples was either not observable or was negligibly small, however very small metallic particles are present also in soda-lime glass. Subsequent nitrogen implantation (100 keV, 1.5{times}10{sup 17} ions/cm{sup 2}) completely eliminated the copper-colloid induced absorption in the copper-implanted fused silica, while it facilitated formation of copper-colloids in soda-lime glass.

One important application for the Fe-29Ni-17Co (Kovar{trademark}) alloy in wire form is in brazed feed through assemblies which are integral parts of vacuum electronic devices. Since Cu metal brazes are performed at process temperatures of about 1100{degrees}C, there is opportunity for significant grain growth to occur during the brazing operation. Additional high temperature exposure includes decarburization of the Fe-29Ni-17Co alloy wire in wet hydrogen for 30 min. at 1000{degrees}C prior to the Cu brazing operation. Two approaches have been used to characterize grain growth in two lots of Fe-29Ni-17Co alloy: (1) a once-through processing study to study the effect of one-time-only device thermal processing on the resulting grain size, and (2) an isothermal grain growth study involving various times at 800--1100{degrees}C. The results of the once-through processing study indicate that acceptable grain sizes are obtained from both cold worked and mill-annealed wire lots following Cu brazing. The isothermal grain growth study indicates that the linear intercept distance for Fe-29Ni-17Co can be described with a power law function of time, and that thermal exposure must be controlled at temperatures in excess of 900{degrees}C in order to avoid excessive grain growth. A second study has characterized the oxidation kinetics of Fe-29Ni-17Co alloy wire in air at temperatures ranging from 550--700{degrees}C. This study indicates the parabolic growth law applies for this material, and between 550 and 700{degrees}C, oxidation in this alloy occurs at an activation energy of 27.9 kcal/mole. Other oxidation studies at higher temperatures ({ge}750{degrees}C) indicate an activation energy of 52.2 kcal/mole for oxidation of Fe-29Ni-17Co alloy at temperatures greater than 790{degrees}C. Quantitative point analyses of the oxide scale formed at 600{degrees}C suggest that a significant fraction of the scale is close to the stoichiometry of the Fe{sub 2}O{sub 3}-type oxide.

The Natural Excitation Technique (NExT) was used to analyze STARS launch data during first and second stage flight using telemetered acceleration data. A continuous track of modal frequencies and modal damping was acquired for the first and second elastic modes of the system during first stage flight and for the first mode during second stage flight. The results from this modal analysis of launch data allowed a final quantification of the inherent bias errors which result from ground-based modal tests. Also, NExT is shown to be an important new tool for analyzing structural dynamics data during launch.

Alkylene-bridge polygerm- and polygermsilsequioxanes have been formed by hydrolysis-condensation of their corresponding (EtO){sub 3}M(CH{sub 2}){sub n}Ge(OEt){sub 3} monomers under HCl- and NEt{sub 3}-catalyzed conditions in ethanol. Solid state {sup 13}C and {sup 29}Si NMR indicate the retention of the alkylene bridging moiety during polymerization. The resulting aerogels are mesoporous materials with high surface areas. Incorporation of the short ethylene bridging unit results in higher surface areas than when heylene bridges are present. The porous nature of hexylene-bridged hybrid network [Si(CH{sub 2}){sub 6}GeO{sub 3}]{sub n} appears insensitive to the acidic or basic nature of the catalyst employed in it formation, in contrast to its polysilsesquioxane counterpart. Work is underway to determine the origin of porosity in these materials, and to characterize xerogel materials generated from these monomers.

The rate at which elements can be transported in groundwater systems is governed in part by the solubility of the element in the groundwater. This report documents plutonium solubility experiments in a brine simulant relevant to the Waste Isolation Pilot Plant. Approximately 1 to 2.5 mL of five stock solutions containing single oxidation states of plutonium (Pu(IV)-polymer, Pu{sup 3+}, Pu{sup 4+}, PuO{sub 2}{sup +}, and PuO{sub 2}{sup 2+}) were added to {approximately}75 mL of synthetic H-17 Brine in five reaction vessels. Initial plutonium concentrations ranged from 1.3 {times} l0{sup {minus}4} to 5.l {times} l0{sup {minus}4} M (moles per liter) total plutonium. Because these initial concentrations were far above the plutonium solubility limit in H-17 Brine, plutonium-containing solids precipitated. Aqueous plutonium concentrations were measured over time until steady-state was reached, requiring over 300 days in H-17 Brine.

The development of high peak power simulators, laser drivers, free electron lasers, and Inertial Confinement Fusion drivers is being extended to high average power short-pulse machines with the capabilities of performing new roles in environmental cleanup and industrial manufacturing processes. We discuss a new class of short-pulse, high average power accelerator that achieves megavolt electron and ion beams with 10`s of kiloamperes of current and average power levels in excess of 100 KW. Large treatment areas are possible with these systems because kilojoules of energy are available in each output pulse. These systems can use large area x-ray converters for applications requiring greater depth of penetration such as food pasteurization and waste treatment. The combined development of this class of accelerators and applications, at Sandia National Laboratories, is called Quantum Manufacturing.

This report discusses the possibility of human intrusion into the WIPP facility, an undergound disposal facility for alpha-bearing wastes. The probability of exploratory drilling occurring at the site is described.

Force reconstruction is a procedure in which the externally applied force is inferred from measured structural response rather than directly measured. In a recently developed technique, the response acceleration time-histories are multiplied by scalar weights and summed to produce the reconstructed force. This reconstruction is called the Sum of Weighted Accelerations Technique (SWAT). One step in the application of this technique is the calculation of the appropriate scalar weights. In this paper a new method of estimating the weights, using measured frequency response function data, is developed and contrasted with the traditional SWAT method of inverting the mode-shape matrix. The technique uses frequency response function data, but is not based on deconvolution. An application that will be discussed as part of this paper is the impact into a rigid barrier of a weapon system with an energy-absorbing nose. The nose had been designed to absorb the energy of impact and to mitigate the shock to the interior components.

This paper focuses on the development of an approximate time-optimal feedback strategy for conducting rest-to-rest maneuvers of a magnetically levitated table. Classical switching curves are modified to account for the complexities of magnetic actuation as well as the coupling of the rigid body modes through the control. A smooth blend of time-optimal and proportional-derivative controls is realized near the destination point to correct for inaccuracies produced by the approximate time-optimal strategy. Detailed computer simulations of the system indicate that this hybrid control strategy provides a significant reduction in settling time as compared to proportional-derivative control alone.

Arithmetic averaging is simple, stable, and can be very effective in attenuating the undesirable components in a complex signal, thereby providing smoothing or trend removal. An arithmetic average is easy to calculate. However, the resulting modifications to the data, in both the time and frequency domains, are not well understood by many experimentalists. This paper discusses the following aspects of averaging: (1) types of averages -- simple, cumulative, and moving; and (2) time and frequency domain effects of the averaging process.

Charge storage devices in which non-equilibrium depletion regions represent stored charge are sensitive to ionizing radiation. This results since the radiation generates electron-hole pairs that neutralize excess ionized dopant charge. Silicon structures, such as dynamic RAM or CCD cells are particularly sensitive to radiation since carrier diffusion lengths in this material are often much longer than the depletion width, allowing collection of significant quantities of charge from quasi-neutral sections of the device. For GaAs the situation is somewhat different in that minority carrier diffusion lengths are shorter than in silicon, and although mobilities are higher, we expect a reduction of radiation sensitivity as suggested by observations of reduced quantum efficiency in GaAs solar cells. Dynamic memory cells in GaAs have potential increased retention times. In this paper, we report the response of a novel GaAs dynamic memory element to transient ionizing radiation. The charge readout technique is nondestructive over a reasonable applied voltage range and is more sensitive to stored charge than a simple capacitor.

Ab initio electronic-structure calculations are combined with empirical bond-additivity corrections to yield thermochemical properties of gas-phase molecules. A self-consistent set of heats of formation for molecules in the Si-H, Si-H-Cl, Si-H-F, Si-N-H and Si-N-H-F systems is presented, along with preliminary values for some Si-O-C-H species.

Realistic computer prediction of high-velocity impact and penetration events involving composite materials requires a knowledge of the material behavior under large compressive stresses at high rates of deformation. As an aid to the development of constitutive models for composites under these conditions, methods for numerical simulation of the material response at the microstructural level are being developed. At present, the study is confined to glass fiber/epoxy composites. The technique uses a numerical model of a representative sample of the microstructure with randomly distributed fibers. By subjecting the boundary of this numerical sample to prescribed loading histories, a statistical interpretation allows prediction of the global material response. Because the events at the microstructural scale involve locally large deformation, and because of the constantly changing picture with regard to contact between the fibers, the Eulerian code CTH is used for these calculations. Certain aspects of material failure can also be investigated using this approach. The method allows the mechanical behavior of composite materials to be studied with fewer assumptions about constituent behavior and morphology than typically required in analytical efforts.

Experimental measurements of force into a ``rigid`` test item representing a typical system level vibration test were conducted to evaluate several methods of force measurements. The methods evaluated included: (1) Direct measurement with force gages between the test item and the fixturing; (2) Measurement of the force at the shaker/fixture interface and correcting the force required to drive the fixturing using two methods, (a) mass subtraction and (b) SWAT (sum of weighted accelerations technique), (3) Force deduced from voltage and current needed to drive the test item. All of the methods worked over a limited frequency range of five to a few hundred Hertz. The widest bandwidth was achieved with force at the shaker/fixture interface with SWAT corrections and from the voltage and current measurements.

Densifying non-mined diamond powder precursors with diamond produced by chemical vapor infiltration (CVI) is an attractive approach for forming thick diamond deposits that avoids many potential manufacturability problems associated with predominantly chemical vapor deposition (CVD) processes. The authors have developed two techniques: electrophoretic deposition and screen printing, to form nonmined diamond powder precursors on substrates. They then densify these precursors in a hot filament assisted reactor. Analysis indicated that a hot filament assisted chemical vapor infiltration process forms intergranular diamond deposits with properties that are to some degree different from predominantly hot-filament-assisted CVD material.

The National Center for Advanced Information Components Manufacturing (NCAICM) projects focus on manufacturing processes, materials, user facilities, standard tools, and equipment for large area emissive flat panel displays and microelectronics. Two types of projects are funded; (1) precompetitive projects done at the Center and (2) joint industry/national laboratory projects, which may carry intellectual property rights, where the work will be done at the appropriate industry or laboratory site. A summary of the NCAICM projects will be presented.

The organometallic chemical vapor deposition of transition metal carbides (M = Ti, Zr, Hf, and Cr) from tetraneopentyl-metal precursors has been carried out. Metal carbides can be deposited on Si, Al{sub 2}O{sub 3}, and stainless steel substrates from M[CH{sub 2}C(CH{sub 3}){sub 3}]{sub 4} at temperatures in the range of 300 to 750 C and pressures from 10{sup {minus}2} to 10{sup {minus}4} Torr. Thin films have also been grown using a carrier gas (Ar, H{sub 2}). The effects of variation of the metal center, deposition conditions, and reactor design on the resulting material have been examined by SEM, XPS, XRD, ERD and AES. Hydrocarbon fragments generated in the deposition chamber have been studied in by in-situ mass spectrometry. Complementary studies examining the UHV surface decomposition of Zr[CH{sub 2}C(CH{sub 3}){sub 3}]{sub 4} have allowed for a better understanding of the mechanism leading to film growth.

The Intelligent Systems and Robotics Center at Sandia National Laboratories is developing technologies for the automation of processes associated with environmental remediation and information-driven manufacturing. These technologies, which focus on automated planning and programming and sensor-based and model-based control, are used to build intelligent systems which are able to generate plans of action, program the necessary devices, and use sensors to react to changes in the environment. By automating tasks through the use of programmable devices tied to computer models which are augmented by sensing, requirements for faster, safer, and cheaper systems are being satisfied. However, because of the need for rapid cost-effective prototyping and multi-laboratory teaming, it is also necessary to define a consistent approach to the construction of controllers for such systems. As a result, the Generic Intelligent System Controller (GISC) concept has been developed. This concept promotes the philosophy of producing generic tool kits which can be used and reused to build intelligent control systems.

Neutron reflectivity is among the few techniques able to probe a buried interface. Through the use of isotopic labeling, complicated interface structures may be determined with a resolution on the order of 5 {angstrom}. However, for highly complex thin film and interface structures, it is often necessary to perform complementary experiments to reduce the number of unknown variables, and thus enable an unambiguous interpretation of the neutron reflectivity. To this end, the authors have combined X-ray and neutron reflectivity to study changes in a metal/polymer interface (molybdenum/polyurethane, hereafter Mo/PU) upon exposure to a humid environment. In particular, the authors have tracked the adsorption of moisture to the interface and variations in the density of the interphase. This information was obtained as a function of the concentration of a silane coupling agent added to the bulk of the PU. Adhesion of the Mo/PU interface is important to programs in the DOE complex. This paper reports the first results of this study.

A novel CFD/structural analysis was performed to predict functionality of a cross parachute under loadings near the structural limits of the parachute. The determination of parachute functionality was based on the computed structural integrity of the canopy and suspension lines. In addition to the standard aerodynamic pressure loading on the canopy, the structural analysis considered the reduction in fabric strength due to the computed aerodynamic heating. The intent was to illustrate the feasibility of such an analysis with the commercially available software PATRAN.

Short communication.

FALCON is a high-power, steady-state, nuclear reactor-pumped laser (RPL) concept that is being developed by the Department of Energy. The FALCON program has experimentally demonstrated reactor-pumped lasing in various mixtures of xenon, argon, neon, and helium at at wavelengths of 585, 703, 725, 1271, 1733, 1792, 2032, 2630, 2650, and 3370 nm with intrinsic efficiency as high as 2.5%. The major strengths of a reactor-pumped laser are continuous high-power operation, modular construction, self-contained power, compact size, and a variety of wavelengths (from visible to infrared). These characteristics suggest numerous applications not easily accessible to other laser types. A ground-based RPL could beam its power to space for such activities as illuminating geosynchronous communication satellites in the earth`s shadow to extend their lives, beaming power to orbital transfer vehicles, removing space debris, and providing power (from earth) to a lunar base during the long lunar night. The compact size and self-contained power also makes an RPL very suitable for ship basing so that power-beaming activities could be situated around the globe. The continuous high power of an RPL opens many potential manufacturing applications such as deep-penetration welding and cutting of thick structures, wide-area hardening of metal surfaces by heat treatment or cladding application, wide-area vapor deposition of ceramics onto metal surfaces, production of sub-micron sized particles for manufacturing of ceramics, wide-area deposition of diamond-like coatings, and 3-D ceramic lithography.

The purpose of this paper is to document a few of the many environmental information systems that currently exist worldwide. The paper is not meant to be a comprehensive list; merely a discussion of a few of the more technical environmental database systems that are available. Regulatory databases such as US Environmental Protection Agency`s (EPA`s) RODS (Records of Decision System) database [EPA, 1993] and cost databases such as EPA`s CORA (Cost of Remedial Action) database [EPA, 1993] are not included in this paper. Section 2 describes several US Department of Energy (DOE) Environmental Restoration and Waste Management (EM) information systems and databases. Section 3 discusses several US EPA information systems on waste sites and technologies. Section 4 summarizes a few of the European Community environmental information systems, networks, and clearinghouses. And finally, Section 5 provides a brief overview of Geographical Information Systems. Section 6 contains the references, and the Appendices contain supporting information.

Sandia National Laboratories is a vertically multi-disciplined research and development laboratory with a long history of designing and developing d electro-mechanical products in the national interest. Integrating new technologies into the prototyping phase of our development cycle is necessary to reduce the cycle time from initial design to finished product. The introduction of rapid prototyping machines into the marketplace promises to revolutionize the process of producing prototype parts with relative speed and production-like quality. Issues of accuracy, feature definition, and surface finish continue to drive research and development of these processes. Sandia uses Stereolithography (SL) and Selective Laser Sintering (SLS) capabilities to support internal product development efforts. The primary use of SL and SLS is to produce patterns for investment casting in support of a Sandia managed program called FASTCAST that integrates computational technologies and experimental data into the investment casting process. These processes are also used in the design iteration process to produce proof-of-concept models, hands-on models for design reviews, fit-check models, visual aids for manufacturing, and functional parts in assemblies. This presentation will provide an overview of the SL and SLS processes and an update of our experience and success in integrating these technologies into the product development cycle. Also presented will be several examples of prototype parts manufactured using SL and SLS with a focus on application, accuracy, surface and feature definition.

An investigation has been performed to evaluate the capabilities of the Annular Core Research Reactor and its supporting Hot Cell Facility for the production of {sup 99}Mo and its separation from the fission product stream. Various target irradiation locations for a variety of core configurations were investigated, including the central cavity, fuel and reflector locations, and special target configurations outside the active fuel region. Monte Carlo techniques, in particular MCNP using ENDF B-V cross sections, were employed for the evaluation. The results indicate that the reactor, as currently configured, and with its supporting Hot Cell Facility, would be capable in meeting the current US demand if called upon. Modest modifications, such as increasing the capacity of the external heat exchangers, would permit significantly higher continuous power operation and even greater {sup 99}Mo production ensuring adequate capacity for future years.

The Automated Sensor Tester (AST) is being developed by Sandia National Laboratories for the Department of Energy (DOE) to be a tool to aid in testing exterior intrusion detection sensors in a fixed site security system. This is accomplished by automatically performing a simulated intrusion test of the sensors installed in the Perimeter Intrusion Detection and Assessment System (PIDAS). During the test, a target is moved across the detection zone of the sensor, simulating a human moving through the detection zone. The first phase of this project concentrated on automatically testing the bi-static microwave exterior intrusion detection sensor in one sector of a PIDAS. This sensor was selected because it is commonly used, and the test target has been determined and is presently in use. The goal of the AST project is to provide consistent test results, automatic data logging, easier data reduction and reduced manpower to perform the DOE mandated and frequent intrusion detection sensor tests. The AST will help to determine that the intrusion sensor being tested is functional and has even and adequate detection along its entire detection zone. The AST consists of two vehicles and a data logger. The Mother Vehicle contains the processing and navigation capability and deployed and retrieved the Target Vehicle. The Target Vehicle provided the alarm stimulus. The Alarm Interface/Data Logger was connected to the intrusion sensors alarm signal and recorded the test results. This system will autonomously conduct a series of tests on an entire PIDAS sector. This paper describes the three elements of the AST system and their operation.

We are studying the boron nitride system using a pulsed excimer laser to ablate from hexagonal BN (cBN) targets to form cubic BN (cBN) films. We are depositing BN films on heated (25--800C) Si (100) surfaces and are using a broad-beam ion source operated with Ar and N{sub 2} source gases to produce BN films with a high percentage of sp{sup 3}-bonded cBN. In order to optimize growth and nucleation of cBN films, parametric studies of the growth parameters have been performed. The best films to date show >85% sp{sup 3}-bonded BN as determined from Fourier-transform infrared (FTIR) reflection spectroscopy. High resolution transmission electron microscopy (TEM) and selected area electron diffraction confirm the presence of cBN in these samples. The films are polycrystalline and show grain sizes up to 30--40 mn. We find from both the FTIR and TEM analyses that the cBN content in these films evolves with growth time. Initially, the films are deposited as hBN and the cBN nucleates on this hBN underlayer. Importantly, the position of the cBN IR phonon also changes with growth time. Initially this mode appears near 1130 cm{sup {minus}1} and the position decreases with growth time to a constant value of 1085 cm{sup {minus}1}. Since in bulk cBN this IR mode appears at 1065 cm{sup {minus}1}, a large compressive stress induced by the ion bombardment is suggested. In addition, we report on the variation in cBN percentage with temperature.

The physical properties of in-situ produced composites, such as the TEOS-polysiloxane based systems, are directly related to the complex interaction of structural features from the nano- to macro-scopic scales. The nature of these structural interactions are a key element in understanding and controlling mechanical properties in these systems. We believe that the smallest scale structures, in the nanometer range, correlate with properties such as the modulus while large-scale structures on the micron scale effect failure in these materials. This paper discusses techniques for analysis of structural features and interrelation of structural features over these wide ranges of size using small-angle light, x-ray and neutron scattering. Combination of data from different instruments allows for characterization of the interaction between these different size scale features.

Short communication.

In 1992 and 1993, numerous innovative and emerging technologies for characterizing metal and mixed waste contaminants and their migration beneath landfills in and environments were field tested at Sandia`s Chemical Waste Landfill. Many of these technologies are being evaluated as part of the Landfill Characterization System (LCS). The LCS emphasizes minimally intrusive technologies and downhole sensors that strive to be cheaper, better, safer and faster than conventional methods. Major aims of the LCS are to demonstrate, test and evaluate these technologies, and determine whether substantial cost saving over traditional baseline methods can be realized. To achieve these goals, the LCS uses an integrated systems approach that stresses the application of complementary and compatible technologies. Successful field demonstrations combined with favorable economics, will greatly assist the commercialization of these technologies to the private sector and to Environmental Restoration groups throughout the DOE Complex. In this paper, a technical and economic evaluation of selected technologies that comprise the LCS is presented. Because sampling and analysis is the most costly part of a characterization effort, the economic evaluation presented here focuses specifically on these activities. LCS technologies discussed include the ``Smart Sampling Methodology`` and two field screening analytical methods, stripping voltammetry and x-ray fluorescence.