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.
Conference Proceedings - 10th Anniv., IMTC 1994: Advanced Technologies in I and M. 1994 IEEE Instrumentation and Measurement Technology Conference
Deyst, J.P.; Souders, T.M.; Solomon, O.M.
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.
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.
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.
Conference Record of the 1994 21st International Power Modulator Symposium, MODSYM 1994
Rohwein, G.J.; Babcock, S.R.
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.
Intersociety Energy Conversion Engineering Conference, 1994
Martinez, Gale M.
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.
Proceedings of the 4th International Conference on Computer Integrated Manufacturing and Automation Technology, CIMAT 1994
Chen, Pang C.
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.
Proceedings - International Conference on Tools with Artificial Intelligence, ICTAI
Chen, Pang C.
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.
This paper describes a generic data acquisition system for robotic characterization of DOE production facilities and waste sites. While the specific suite of characterization sensors on the end of a robotic arm or vehicle will depend on site needs, many of the data acquisition, display, archival and interpretation requirements of the sites are common. Therefore, the objective is to create a generic, reusable computing and data acquisition system which can accept a multitude of sensors. This paper discusses the progress to date and future plans for the system.
Finite element calculations of the porosity history of a nuclear waste disposal room for transuranic (TRU) waste in a bedded salt formation have been completed. The analyses include a reduced elastic/secondary creep model for the host halite and a nonlinear consolidation model for the crushed salt backfill. Histories were determined for a 2000 years time period starting from the emplacement of room seals.
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.
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.
Excessive deceleration forces experienced during high speed deployment of parachute systems can cause damage to the payload and the canopy fabric. Conventional reefing lines offer limited relief by temporarily restricting canopy inflation and limiting the peak deceleration load. However, the open-loop control provided by existing reefing devices restrict their use to a specific set of deployment conditions. In this paper, the sensing, processing, and actuation that are characteristic of adaptive structures form the basis of three concepts for active control of parachute inflation. These active control concepts are incorporated into a computer simulation of parachute inflation. Initial investigations indicate that these concepts promise enhanced performance as compared to conventional techniques for a nominal release. Furthermore, the ability of each controller to adapt to off-nominal release conditions is examined.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Mazzoldi, P.; Gonella, F.; Arnold, G.W.; Battaglin, G.; Bertoncello, R.
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.