Publications

The 1/f noise of MOS transistors has been measured as a function of total ionizing dose and postirradiation biased annealing time. Comparison to oxide and interface trapped-charge buildup and annealing is discussed. 13 refs., 3 figs.

Significant improvements in CMOSIC quality, reliability, and fabrication yield can be readily achieved in the 1990s by appropriate implementation of tests for quiescent power supply current (I{sub DDQ}). As part of an overall quality management program, I{sub DDQ} testing incorporated with design for testability and modified conventional logic response testing enables 100% stuck-at fault coverage, quality improvement goals of defective levels less than 100 PPM, and reliability greater than 0.999 for 30 years. 9 refs., 2 figs., 1 tab.

Gravitational forces have been found to be an important factor in defining the particle collection efficiency curve of inertial impactors for large particles. In general it was found that if the parameter {cflx G} = gW/V{sub 0}{sup 2} (g is the gravitational acceleration, W is the nozzle diameter and V{sub 0} is the average fluid velocity at the nozzle throat) in greater than 10{sup {minus}3}, the efficiency curve would shift to lower particle sizes. No effect could be seen for lower values of {cflx G}. 1 ref., 1 fig., 1 tab.

The US Department of Energy (DOE) has supported the development of the sodium-sulfur technology since 1973. The programs have focused on progressing core aspects of the technology and completing initial battery engineering for both mobile and stationary applications. An overview of the Office of Energy Management (OEM) activities is contained in this paper. Two major development programs have been active: the first with Ford Aerospace and Communications Corporation (1975 to 1985), and the second with Chloride Silent Power Limited (1985 to 1990). With the completion this year of the qualification of a cell suitable for initial Solar Energy Systems (SES) applications, the emphasis of future DOE/OEM sodium/sulfur programs will shift to SES-battery engineering and development. The initial effort will resolve a number of issues related to the feasibility of utilizing the sodium/sulfur technology in these large-scale applications. This multi-year activity will represent the initial phase of an integrated long-term DOE-supported program to produce a commercially viable battery system.

The integrity of many mechanical assemblies and electrical components depends on small threaded fasteners. The design standards for small (less than {1/4} inch in diameter) screws made of stainless steel are not as well developed as those for larger sizes of high strength steels. The typical design approach is based on the application of static design principals. Steady state accelerations are applied to the component or assembly and sufficient screws are installed in mounting hardware for attachment to the next assembly. These design principals have been used successfully for years in a wide variety of applications. As the parts requiring small screws have continued to decrease in size, some design requirements include greater thread depths and adherence to strict interpretation of the governing thread standards. These design requirements have their origins in the lack of adequate definitions and standards for designs using small threaded fasteners. These design practices have led to significant problems in manufacturing parts with small threaded fasteners by requiring thread depths to four and more diameters of engagement while maintaining thread heights (radial engagement) of 75 percent throughout the thread interfaces. A test program was developed to address questions regarding design and manufacturing issues involving small threaded fasteners which included tensile strength, length of engagement needed to achieve the full strengths of the screws, and verification of the static design principals in dynamic conditions. This paper summarizes the initial results obtained to date from this test program and describes the work-in-progress on the dynamic tests with their related static tests. 2 refs., 4 figs., 4 tabs.

An isotropic continuum damage theory which accounts for the degradation of material strength under quasi-static loading conditions has been developed in the present investigation. The damage mechanism in this theory has been selected to be the interaction and growth of subscale cracks. The development of the theory follows closely the strain-rate dependent dynamic model advanced by the first author and his coworkers. Briefly, the cracks are activated by the maximum principal tensile strain and the density of activated cracks is described by a Weibull statistical distribution. The moduli of a cracked solid derived by Budiansky and O'Connell are then used to represent the global material degradation due to subscale cracking. Two additional material constants have been introduced in this model. These constants are determined from uniaxial tensile test data. The model has been implemented into a finite element code. Sample calculations involving the uniaxial and biaxial responses of plain concrete panels are presented to demonstrate the utility of the model. 7 refs., 2 figs.

The first in a series of multi-factor experiments designed to optimize the chemical cleaning procedure for four types of silicon material used in solar cell fabrication has been completed. The goal of this first experiment (a twenty-two factor main-effects experiment) was to determine the factors associated with chemical cleaning procedures that are most important in obtaining high excess charge-carrier recombination lifetime following a high-temperature furnace oxidation. It was determined that the factors having the strongest influence on charge-carrier lifetime were different for the four different silicon materials considered. In general, the lower the lifetime of the material, the less sensitive the material was to different chemical cleaning steps. The stability of the lifetime was also evaluated with several factors exhibiting a significant effect for high-quality silicon. Chemical cleaning procedures were identified that resulted in stable post-oxidation lifetimes greater than 2 ms for high-resistivity float-zone silicon. 3 refs., 8 figs.

Insulations are used in metallic glass ribbon cores in pulse power applications to prevent interlaminar eddy currents due to voltages induced between adjacent laminations. These interlaminar eddy currents can greatly increase the losses in cores, and, thereby, decrease the pulse permeability at high magnetization rates. This paper reports results of experiments with various insulation materials and both low and high induced anisotropy energy iron-base metallic glass ribbons. Co-wound insulation films as well as conformal insulations were investigated. Magnetic properties and voltage hold-off strengths are reported. 11 refs., 11 figs., 5 tabs.

When quartz controlled oscillators are required for use in applications demanding precision many factors will ultimately place limitations on the ability of the oscillator to remain at the desired frequency. These factors include temperature, resonator Q, pullability, radiation, output load variability, and the electronic components. This paper addresses the subject of frequency instability of oscillator circuits due to power supply voltage variations. In particular, the primary sources of this instability are described for a Pierce oscillator employing a bipolar transistor and design techniques are presented which minimize these frequency pulling effects. 4 refs., 17 figs.

The three-dimensional structural analysis of reentry vehicles presents a considerable challenge to the analyst. This is due to the mechanics of the problem as well as the incorporation of results from several disciplines into the environmental description of the problem. Separate results from aero-analyses, frequently computed in one-dimensional format must be combined into a three-dimensional format suitable for a structural finite element analysis. Features required for the analysis include the ablated thickness of the heatshield structure, as well as pressure on the vehicle and the temperature distribution through the heatshield. By combining these environments, a complete description of all factors which affect the structural performance of reentry vehicles are included into one analysis. This paper presents a method of analyzing the structural response of reentry vehicles using the complete three-dimensional environmental load description.

Reflection Mass Spectrometry (REMS) consists of a cryo-shrouded mass spectrometer which measures mass-analyzed, line-of-sight chemical fluxes from a growing wafer. It is especially useful during III/V molecular beam epitaxy (MBE) for which there are always substantial group V fluxes and often some group III fluxes leaving the wafer during growth. These fluxes depend sensitively on the instantaneous chemical reactivity of the surface. That chemical reactivity in turn depends on instantaneous alloy composition (III/III ratio), surface stoichiometry (As coverage) and temperature. In this brief summary of our work, we describe two examples of the engineering'' usefulness of REMS, involving MBE of InAlAs and InGaAs and one example of measurements of basic scientific interest. 3 figs.

A program is under way to develop liquid metal heat pipes that can transfer energy from the focal point of a parabolic solar concentrator to the heater tubes of one or more Stirling engines. To design high performance wicks for heat pipe solar receivers, it is necessary to have an accurate assessment of the wick's properties. Procedures for measuring the flow properties of wicks before and after fabrication processes take place are presented. The testing procedures provide a useful method of determining the validity of a wick design before full-scale testing is attempted.

Significant progress is continuing in the development of photovoltaic (PV) concentrator technology. New record cell and module efficiencies have been achieved, and improvements in cells, cell assemblies, and modules are increasing reliability and decreasing cost. The number of firms actively pursuing PV concentrator module technology has increased substantially in the last three years. Two new concentrator systems were installed last year, and we are likely to see more in the near future. This paper describes the most significant developments of the last two years, including descriptions of PV concentrator module development and reliability activities, advances in concentrator cell technology, the new PV concentrator array installations, a new Concentrator Initiative Program, and results of the latest costing study. 26 refs., 9 figs., 1 tab.

Chacahoula salt dome, eight miles southwest of Thibodaux, LA, could be solution mined to create caverns for storing as much as 500 million barrels (MMB) of crude oil, should the Strategic Petroleum Reserve (SPR) require additional storage volume. The salt mass geometry is confirmed by more than 50 oil wells, and also from previous exploratory drilling for sulphur. Top of salt occurs at {minus}1100 ft, and some 1300 acres exist within the {minus}2000 ft salt contour. Frasch mining of 1.35 million long tons of sulphur caused the surface to subside about one foot on the northeastern part of the dome. Creep-induced subsidence averaging {approximately}2.7 ft over 30 yrs is estimated for a 200 MMB cavern array, which would require perimeter diking to control localized perennial flooding. Earthquakes approaching intensity MM 6 have occurred nearby and are expected to recur on the order of {approximately}100 yrs but would not affect cavern stability. Additional study of brine disposal methods and hurricane surge probabilities are needed to establish design parameters and cost estimates for storage. 11 refs., 8 figs., 2 tabs.

A Nuisance Alarm Data System (NADS) was developed to gather long- term background alarm data on exterior intrusion detectors as part of their evaluation. Since nuisance alarms play an important part in the selection of intrusion detectors for use at Department of Energy (DOE) facilities, an economical and reliable way to monitor and record there alarms was needed. NADS consists of an IBM Personal Computer and printer along with other commercial units to communicate with detectors, to gather weather data and to record video for assessment. Each alarm, its assessment and the weather conditions occurring at alarm time are placed into a database that is used in the evaluation of the detector. The operating software is written in Turbo Pascal for easy maintenance and modification. A portable system, based on the NADS design, has been built and shipped to other DOE locations to do on-site alarm monitoring. This has been valuable for the comparison of different detectors in the on-site environment and for testing new detectors when the appropriate conditions do not exist or cannot be simulated at the Exterior Intrusion Detection Testbed.

X-ray microanalysis by analytical electron microscopy (AEM) has proven to be a powerful tool for characterizing the spatial distribution of solute elements in materials. True compositional variations over spatial scales smaller than the actual resolution for microanalysis can be determined if the measured composition profile is deconvoluted. Explicit deconvolutions of such data, via conventional techniques such as Fourier transforms, are not possible due to statistical noise in AEM microanalytical data. Hence, the method of choice is to accomplish the deconvolution via iterative convolutions. In this method, a function describing the assumed true composition profile, calculated by physically permissible thermodynamic and kinetic modeling is convoluted with the x-ray generation function and the result compared to the measured composition profile. If the measured and calculated profiles agree within experimental error, it is assumed that the true compositional profile has been determined. If the measured and calculated composition profiles are in disagreement, the assumptions in the physical model are adjusted and the convolution process repeated. To employ this procedure it is necessary to calculate the x-ray generation function explicitly. While a variety of procedures are available for calculating this function, the most accurate procedure is to use Monte Carlo modeling of electron scattering. 9 refs., 1 fig.

TNF-doped Mylar is a new radiation-hard dielectric that has recently been qualified as a viable substitute for Mylar in capacitors. The advantage of TNF-doped Mylar is that it satisfies both the nuclear safety and radiation hardness requirements of weapons. Mylar is not radiation-hard. Aging and compatibility studies were carried out to insure that (1) TNF does not diffuse from the film during fabrication of the capacitor or during storage; and (2) there are no compatibility problems with aluminum foil (the conductor) or Fluorinert (the secondary dielectric). Losses of TNF were barely detectable during the vacuum bakes used in fabricating capacitors or during accelerated aging tests carried out below T{sub g} (70C) over a two year period in air. In other accelerated tests, no compatibility problems were detected with aluminum or Fluorinert. TNF-doped Mylar is now being used in the MC-4109 capacitor that was called out for use in SRAM II. We anticipate no age-related or compatibility-related problems with TNF-doped Mylar.

The equilibrium swelling of a number of elastomeric seals, commonly used in weapon components, was determined after they were exposed to a saturated solvent environment. The dimensional stability of these elastomers in the solvents varied considerably. Reasons for this are discussed and a method by which one may estimate the degree of swelling that these elastomers will undergo in a solvent environment is presented. 5 refs.

This paper surveys a few of the current issues in sol-gel reaction kinetics. Many times seemingly modest changes in reactants or reaction conditions can lead to substantial differences in the overall reaction rates and pathways. For example, qualitative features of the reaction kinetics can depend on catalyst concentration. At very high acid-catalyst concentrations, reverse are significant for TMOS sol-gels, while for moderate acid-catalyst concentrations, reverse reactions are substantially reduced. The reaction kinetics are substantially reduced. The reaction kinetics of two similar tetraalkoxysilanes: tetramethoxysilane (TMOS) and tetraethoxysilane (TEOS), can be markedly different under identical reaction conditions. Under acid-catalyzed reaction conditions, a TMOS sol-gel undergoes both water-and alcohol-producing condensation reactions while a TEOS sol-gel undergoes only water-producing condensation. The early time hydrolysis and condensation reactions of a TMOS sol-gel are statistical in nature and can be quantitatively described by a few simple reaction rate constants while the reaction behavior of a TEOS sol-gel is markedly nonstatistical. A comprehensive theory of sol-gel kinetics must address diverse experimental findings. 9 refs., 3 figs., 1 tab.

In the testing of active microwave components, a common test procedure is to evaluate a device's performance when subjected to an all-phase, constant-standing-wave-ratio (APCS) load pull. Such a test specification is useful in verifying a device's stability and mismatch performance. Typically, APCS pulls are tediously performed by hand, with manually operated tuners. However, with the advent of mechanical, computer-controlled tuners, it is how possible to automate this procedure. At Sandia, the goal was to integrate an APCS pull capability into a multi-test, single-connection tester. (The single-connection concept implies that many test, such as network analysis, spectral analysis, and noise figure measurements can be made from a one-time, device-to-tester connection). Consequently, the slide-screw tuner was the obvious choice due to its removable probe capability. Hence, it became necessary to develop a custom algorithm capable of utilizing the tuner in an impedance-finding mode. The general concept used in implementing this capability was to empirically characterize the tuner over and acceptable range of tuner positions, and then use this characterization to intelligently predict the tuner positions needed to present the desired impedance. 4 figs.

Conductor development is one of the major long term goals in high temperature superconductor research. In this paper we report on two promising processing technologies that have been utilized to produce superconducting HTS conductors. First, melt spun YBa{sub 2}Cu{sub 3}O{sub 7} fibers rapid thermal processed for 1--8 sec at 950 to 1075{degree}C have {Tc}'s to 92 K, J{sub c}'s to 1100 A/cm{sup 2} and the orthorhombic twinned morphology typical for high quality YBa{sub 2}Cu{sub 3}O{sub 7}. A processing matrix of time, temperature and composition for these fibers shows that slightly CuO-rich starting compositions give the best results. Second, silver tube encapsulated wires of Bi{sub 1.7}Pb{sub 0.3}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} have been made by extrusion, wire drawing and cold rolling. The resulting tapes show orientation of the crystallites, zero resistance up to 100K and improved magnetic hysteresis above 50 K. The combination of mechanical reprocessing and extended thermal anneals near 850{degree}C appears to significantly improve these materials. 13 refs., 7 figs.

This paper discusses the ability of an adaptive line enhancer (ALE) driven by the least-mean-squares (LMS) algorithm to track the frequency of a chirping signal in broadband noise. The dynamic behavior of the weights is described and a weight tracking error bound is derived in terms in chirp rate. Frequency tracking and weight behavior are illustrated in examples. 6 refs., 7 figs.

A series-array voltage standard containing 2,076 Josephson junctions has been operated in a liquid helium bath maintained within a refrigerated Dewar over the temperature range 1.56K ≤ T ≤ 4.54K. No systematic variation in the array voltage near 1.018V with temperature was detected over this entire range, indicating that any temperature coefficient of the array voltage must be less than 2×10-8 V/K. The critical current and gap energy of the weakest junction within the array in the absence of millimeter wave power were measured as a function of temperature over this same range. The noise sensitivity of the array was observed to change abruptly but by a small amount as the helium bath was pumped superfluid. Voltage calibrations were unaffected by the bath's superfluid transition. © 1990.

As computers become increasingly powerful, the constitutive models used in structural analysis codes become increasingly sophisticated. With the current generation of supercomputers, it now seems reasonable to consider incorporating relatively detailed representations of the multiaxial deformation response of engineering alloys. To aid in the development of such models and to allow measurement of their constituent parameters, we have designed a complex multiaxial deformation test system. The system to be described has been developed to perform non-proportional cycling of thin-walled metal tubes using internal/external fluid pressure and tensile/compressive axial loading. It has been added to an existing MTS 490 kN load frame with a PDP 11/34-based computer control system. Features of interest include; specimen grips, the high pressure chamber, the hydraulic intensifier and controller, and associated valving and switching. Initial software for this system has been written on the PDP 11/34 in the MTS MultiUser-BASIC language to perform simple proportional multiaxial cyclic deformation to a prescribed effective plastic strain limit.

This paper explains the newly implemented new material (NM) sampling rationale for weapon production developed by Frank W. Mueller, SNL/7266, and approved by DOE. Our experience with weapon production programs has been primarily limited to production lengths of five years or less. As more recent programs, such as the W80, are moving toward increasingly longer production phases, it has become apparent that our previous sampling rationale may have required excessive new material samples. 3 refs.

The electric field dependence of radiation-induced interface- and oxide-trap charge (ΔVot and ΔVit) generation for polysilicon- and metal-gate MOS transistors is investigated at electric fields (Eox) from −4.2 MV/cm to +4.7 MV/cm. If electron-hole recombination effects are taken into account, the absolute value of ΔVot and the saturated value of ΔVit for both polysilicon- and metal-gate transistors are shown to follow an approximate E−1/2 field dependence for Eox ≥ 0.4 MV/cm. An E−1/2 dependence for the saturated value of ΔVit was also observed for negative-bias irradiation followed by a constant positive-bias anneal. This field dependence does not appear to be consistent with interface-trap formation due to hydrogen ion (H+) release in the bulk of the oxide and subsequent drift to the Si/SiO2 interface, proposed by McLean to be the likely cause of interface-trap buildup in metal-gate capacitors. The E−1/2 field dependence observed in this work suggests that the total number of interface traps created in these devices may be determined by hole trapping near the Si/SiO2 interface for positive-bias irradiation, or near the gate/SiO2 interface for negative bias irradiation, though H+ drift remains the likely rate-limiting step in the process. Based on these results, we propose a hole-trapping/hydrogen transport (HT)2 model—involving hole trapping and subsequent near-interfacial H+ release, transport, and reaction at the interface—as a possible explanation of ΔVit buildup in these polysilicon- and metal-gate transistors. © 1990 IEEE

The Direct Absorption Receiver (DAR) concept was proposed in the mid-1970s as an alternative advanced receiver concept to simplify and reduce the cost of solar central receiver systems. Rather than flowing through tubes exposed to the concentrated solar flux, the heat absorbing fluid (molten nitrate salt) would flow in a thin film down a flat, nearly vertical panel and absorb the flux directly. Potential advantages of the DAR over conventional tubular designs include a substantially simplified design, improved thermal performance, increased reliability and operating life, as well as reduced capital and operating costs. However, before commercial-scale designs can be realized, a method for controlling droplet ejection from the panel must be developed. In this paper, we present a new DAR design, which has the potential to control these droplets. The design employs four flat panels that are sloped backwards 5 degrees, wind spoilers, and air curtains. A systems analysis is presented indicating that the levelized-energy cost of the quad geometry should be very similar to cylindrical geometry that was originally proposed for the DAR concept. 19 refs., 5 figs., 3 tabs.

A molten salt cavity receiver was solar tested at Sandia National Laboratories during a year-long test program. Upon completion of testing, an analysis was performed to determine the effect of thermal cycling on the receiver. The results indicate substantial fatigue damage accumulation for the receiver when the relatively short test time is considered. This paper describes the methodology used to analyze the cycling, the results, and how they affect future receiver design. The test receiver was configured as a C-shaped cavity with eight multipass heat absorption panels. The tubes were Alloy 800. The heat exchange medium was a molten nitrate salt mixture (60% sodium nitrate, 40% potassium nitrate by weight). The operating temperature range was from 288°C to 566°C.

A sodium reflux pool-boiler solar receiver has been tested on a nominal 75-kWt parabolic dish concentrator. The purpose was to demonstrate the feasibility of reflux receiver technology for application to Stirling engine dish electric systems. In this application, pool boilers (and more generally liquid metal reflux receivers) have advantages over directly illuminated tube receivers. The advantages include more uniform temperature, which results in longer lifetime and higher temperature available to the engine. The absorber was a 70° half-angle spherical segment with an 8.63 inches radius, positioned behind an 8.65 inches diameter aperture. The relatively small size of this receiver, which minimized thermal losses, fabrication costs, and sodium inventory, was possible because of its excellent internal heat transfer characteristics. Tests were run at sodium temperatures up to 800°C and receiver input power levels as high as 67 kWt. At maximum input power, the peak in the solar flux distribution on the absorber was calculated to be 73 Wt/cm2. Receiver efficiency was about 90% when the input power and sodium temperature were at their maximum values. To promote stable boiling, the receiver design included 35 equally spaced artificial cavities in the absorber wetted surface. In all tests, stable boiling was always observed. Under certain conditions during both real and simulated cloud transients, high incipient boiling superheats were observed. This behavior could be suppressed either actively by momentarily increasing the thermal load on the receiver or passively by the addition of a small amount of xenon into the boiler.

Over the next several decades, it is expected that the use of renewable energy technologies will greatly expand as these technologies mature, as the cost of conventional energy supply increases, and as the environmental impact of fossil fuel usage is better understood. A critical question is whether the impact of renewables, in terms of displaced fossil fuel use and reduced environmental effects, can be significant. Certainly, public policy will have dramatic effects on this question. Given a positive policy environment, renewables have the potential to displace a significant fraction of projected energy use within 30-40 years. For the United States, renewables could contribute as much as 25-55 exajoules of energy annually by the year 2030, or 15-35{percent} of the projected total US energy consumption. 12 refs., 6 figs.

Use of the MIT-SNL Period-Generated Minimum Time Control Laws for the automated increase of neutronic power from subcritical conditions has recently been demonstrated. The use of these laws is advantageous because they provide the speed at which a control device should be withdrawn in order to generate a specified period. Two strategies were investigated. The first was the direct use of the MIT-SNL laws for the entire transient, startup plus operation at power. The second was to add reactivity at a constant rate until criticality was achieved and then to transfer control to the MIT-SNL laws. Each was evaluated by both simulation and actual experiment under conditions of closed-loop digital control on the Annular Core Research Reactor that is operated by the Sandia National Laboratories. Both approaches were shown to be feasible. The former has the advantage that the power profile will be known during the startup. Its drawback is that an excessively high rate of reactivity change may be needed to initiate the transient. 16 refs., 9 figs.

An experimental study is described that evaluates the potential for using an acoustic borehole television technique to measure fracture dimensions in lost circulation zones encountered in geothermal drilling. A simulated wellbore was constructed of sandstone blocks with adjustable, inclined fractures, stacked in a barrel filled with water. A slim-hole televiewer was used to log the wellbore, and a computer was used to digitize and analyze the data. Televiewer signal perturbations caused by the fractures were studied to evaluate the effects of fracture thickness and signal amplification on the width of the signal perturbation in the digital record. It was found that the signal amplification is applied. Two techniques for determining the correct amplification are described. With the televiewer used in the present study, fractures thicker than 0.15 inch in a 5.1-inch wellbore can be measured to within an accuracy of 5--15%. Fractures as small as 0.031 inch can be detected but cannot be accurately and reliably measured. 1 ref., 15 figs.

We are continuing to see significant progress in the development of photovoltaic (PV) concentrator technology. New record cell and module efficiencies have been achieved, and improvements in cells, cell assemblies, and modules are increasing reliability and decreasing cost. The number of firms actively pursuing PV concentrator module technology has increased substantially in the last three years. Two new concentrator systems were installed last year, and more are likely to be installed in the near future. This paper describes the most significant developments of the last two years, including descriptions of advances in PV concentrator cell technology, module development and reliability activities, the new installations, a new Concentrator Initiative Program, and results of the latest costing study. 26 refs., 8 figs., 1 tab.

The cost goals and calculations in the Five-Year Plan for the National Photovoltaics Program assume that photovoltaic (PV) concentrator modules will have a reliable output and an operational life expectancy of 30 years.'' Although the modules in the few PV concentrator systems fielded to date have so far been reliable, they have not been in the field long enough to establish performance levels for 30 years and are not necessarily representative of newer concentrator designs. Thus, extensive testing and analysis are required to evaluate and establish the reliability of current concentrator module designs. Considerable research has been done to establish appropriate qualification tests, to understand component failure mechanisms, and to obtain reliable materials and designs. Surveys of fielded systems have been conducted and new test and analysis techniques have been developed in the process. This paper discusses the reliability of photovoltaic concentrator modules with an emphasis on the issues that are currently of most concern. 12 refs., 5 figs.

Erosion of POCO graphite by helium in PISCES-A was measured by carbon spectroscopy for a temperature range from 900{degree}-- 2000{degree}C, ion energies of 30--300 eV, ion fluxes of 1 {minus} 6 {times} 10{sup 22} m{sup {minus}2} s{sup {minus}1} and electro temperatures of 4--22 eV. Yields at low energies were higher than predicted in current models. The role of redeposition is discussed. 15 refs., 4 figs.

Under compressive stresses, brittle polycrystalline materials fail as the result of the growth, interaction and coalesence of microcracks. To predict the deformation of damaging material, constitutive laws developed for such materials must incorporate the effects of crack size, density, orientation, and interaction.A method of incorporating the accumulation and growth of microcracks into a continuum model is to use a measure of microcrack growth and interaction defined as damage. Although a number of damage theories have been proposed, there is no generally accepted experimental technique for detecting and measuring damage. Acoustic emissions (AE) have been correlated with microcrack nucleation and growth. We propose that AE locations and density are useful measures of damage that can be correlated with calculated damage. Our approach is to use acoustic emissions (AE) and computer modeling to study the development of damage in geomaterials.

The In-situ Permeable Flow Sensor is a new type of implantable instrument under development at Sandia National Laboratories that uses thermal boundary layer pertubation techniques to rapidly determine the three-dimensional velocity vector of groundwater flow in soils or permeable geologic media. This sensor is based on the refinement of previous technology, the Convective Heat Flow Probe, developed for the scientific study of the flow of geothermal fluids in thermally active regions of the earth's crust. The Convective Heat Flow Probe was designed as a logging tool for use in open or uncased boreholes. The newer In-situ Permeable Flow Sensor is based on the same theoretical principles but is designed to be permanently buried at waste or cleanup sites where long term monitoring of groundwater flow is of interest. This instrument is sensitive to permeable flows as low as a few meters per year.

Simplified ATPG and fault simulation algorithms, reduced test set sizes, and increased fault coverage are achieved with I {sub DDQ} testing for stuck-at faults. In addition, I {sub DDQ} testing will detect logically redundant and multiple stuck-at faults, and improve the detection of non-stuck-at fault defects. 17 refs., 6 figs., 6 tabs.

The Department of Energy's Multiwell Experiment (MWX) is a field laboratory in the Piceance Basin of Colorado which has two overall objectives: to characterize the low permeability gas reservoirs in the Mesaverde Formation and to develop technology for their production. Different depositional environments have created distinctly different reservoirs in the Mesaverde, and MWX has addressed each of these in turn. This report presents a comprehensive summary of results from the fluvial interval which lies between 4400 ft and 6000 ft at the MWX site. The reservoirs consist of heterogeneous, amalgamated point-bar sequences which form broad meanderbelts which create irregular, but roughly tabular, reservoirs with widths of 1000--2500 ft. Separate sections of this report are background and summary; site descriptions and operations; geology; log analysis; core analysis; in situ stress; well testing, stimulation, fracture diagnostics, and reservoir evaluation in two separate sandstones; stress, fracture diagnostic, and stimulation experiments in an additional sandstone; supporting laboratory studies; and a bibliography. Additional detailed data, results, analyses, and data file references are presented as appendices which are included on microfiche. The results show that stimulation of fluvial reservoirs can be successful if proper care is taken to minimize damage to the natural fracture system. Both an accelerated leakoff phenomenon and the ability to alter the in situ stress were quantified. Overall, the fluvial interval offers the highest production potential of the three nonmarine intervals studied. 116 refs., 230 figs., 28 tabs.

This paper presents a discussion of the use of the Nijssen Information Analysis Methodology (NIAM) in the design of an experimenters database. This database is used by physicists and technicians to describe the configuration and diagnostic systems used on Sandia National Laboratories Particle Beam Fusion Accelerator II (PBFA II). The design of this database presented some unique challenges because of the large degree of flexibility required to enable timely response to changing experimental configurations. The NIAM user-oriented technique proved to be invaluable in translating experimenter's requirements into an information model and then to a normalized relational design.

The theory and practice of information engineering is being actively developed at Sandia National Laboratories. The main output of Sandia is information. Information is created, analyzed and distributed. It is the life blood of our design laboratory. The proper management of information will have a large, positive impact on staff productivity. In order to achieve the potential benefits of shared information a commonly understood approach is needed, and the approach must be implemented in a CASE (Computer-Aided Software Engineering) tool that spans the entire life cycle of information. The commonly understood approach used at Sandia is natural language. More specifically, it is a structured subset of English. Users and system developers communicate requirements and commitments that they both understand. The approach is based upon NIAM (Nijssen's Information Analysis Methodology). In the last three years four NIAM training classes have been given at Sandia. The classes were all at the introductory level, with the latest class last October having an additional seminar highlighting successful projects. The continued growth in applications using NIAM requires an advanced class. The class will develop an information model for the Ultimate CASE Tool.'' This paper presents the requirements that have been established for the Ultimate CASE Tool'' and presents initial models. 4 refs., 1 tab.

Consideration is given to the problem of stabilizing a plant using a suboptimal stable compensator of fixed order. The resulting equations are a modified form of the optimal projection equations, with the separation principle not holding in either the full- or reduced-order case. An overbounding technique on the state covariance guarantees that the compensator is stable if nonnegative definite solutions exist to the design equations.

Sandia National Laboratories joined with two other laboratories, Los Alamos National Laboratory and Naval Research Laboratory, to study and implement a highly parallelized tracker/correlator algorithm. Significant progress was made at Sandia on a specific algorithm and code. This report summarizes the accomplishments by Sandia during FY '89 on this project. 12 refs., 4 figs., 2 tabs.

This paper and a companion paper show the traditional limits on amplitude and frequency that can be generated in a laboratory test on a vibration exciter can be substantially extended. This is accomplished by attaching a device to the shaker that permits controlled metal to metal impacts that generate high frequency, high acceleration environment on a test surface. A companion paper (Reference 1) shows that a sinusoidal or random shaker input can be used to generate a random vibration environment on the test surface. This paper derives the three response components that occur on the test surface due to an impact on the bottom surface and the base driven response from the shaker input. These response components are used to generate impulse response functions and frequency response functions which are used in the companion paper to derive power spectral density functions for the overall response. 9 refs., 8 figs.

High average power magnetic pulse compression systems are now being considered for use in several applications such as the High Power Radiation Source (HiPoRS) project. Such systems will require high reliability magnetic switches (saturable inductors) that are very efficient and have long lifetimes. One of the weakest components in magnetic switches is their interlaminar insulation. Considerations related to dielectric breakdown, thermal management of compact designs, and economical approaches for achieving these needs must be addressed. Various dielectric insulation and coating materials have been applied to Metglas foil in an attempt to solve the complex technical and practical problems associated with large magnetic switch structures. This work reports various needs, studies, results, and proposals in selecting and evaluating continuous coating approaches for magnetic foil. Techniques such as electrophoretic polymer deposition and surface chemical oxidation are discussed. We also propose continuous photofabrication processes for applying dielectric ribs or spacers to the foil which permit circulation of dielectric liquids for cooling during repetitive operation. 10 refs., 8 figs., 11 tabs.

This paper and a companion paper show that the traditional limits on amplitude and frequency that can be generated in a laboratory test on a vibration exciter can be substantially extended. This is accomplished by attaching a device to the shaker that permits controlled metal to metal impacts that generate a high acceleration, high frequency environment on a test surface. A companion paper derives some of the mechanical relations for the system. This paper shows that a sinusoidal shaker input can be used to excite deterministic chaotic dynamics of the system yielding a random vibration environment on the test surface, or a random motion of the shaker can be used to generate a random vibration environment on the test surface. Numerical examples are presented to show the kind of environments that can be generated in this system. 9 refs., 9 figs.

Charged-particle simulations in three dimensions are now performed routinely in the Pulsed Power Sciences Directorate at Sandia with the QUICKSILVER suite of codes. QUICKSILVER is a multitasked, finite-difference, three-dimensional, fully relativistic, electromagnetic, particle-in-cell code developed at Sandia. It is targeted for use on current and near-term supercomputers, such as the Cray X-MP/416, which are characterized by large, shared central memories and multiple processors. QUICKSILVER has already been used to simulate ion diodes, magnetically insulated transmission lines, microwave devices, and electron beam propagation. QUICKSILVER is actually a suite of codes; in addition to the main simulation code there are several support codes. The problem geometry is generated with a preprocessor and the simulation results are examined with one or more postprocessors. The MERCURY preprocessor assists the user in defining the mesh, boundary conditions, and other input parameters. The FLASH and AVS postprocessors are used to examine a wide variety of simulation output, including 3D rendering of particle positions, conductor surfaces, and scalar and vector quantities. The PLOTPFF postprocessor displays 2D slices and 1D pencils derived from 3D scalar and vector quantities. Additionally, time histories of various simulation quantities can be examined and manipulated with the IDR postprocessor. This paper describes the suite in detail. 9 refs., 4 figs.

This is a brief report about a Sandia National Laboratory facility which can provide high-thermal flux for simulation of nuclear thermal flash, measurements of the effects of aerodynamic heating on radar transmission, etc

This paper summarizes a cost-benefit assessment of the seismic design of the waste-handling facilities associated with the prospective high-level waste repository at Yucca Mountain, Nevada. It provides a very brief description of the methodology used and the costs and benefits of varying design levels for vibratory ground motions and surface fault displacements for structures, components, and equipment that are important to safety in the waste-handling facilities. 3 refs., 7 figs.

The semiconductor product engineers job requires knowledge and expertise related to many different subjects. This report provides guidance for newcomers to product engineering and is a consise reference for all others involved in product engineering. Subjects addressed are Customer/Supplier interactions, component development sequence, production schedule support, component characterization, product specifications, test equipment requirements, product qualification, characterization and development reports, preferred parts list, standard packaging, and finally, classification and security considerations. This guide is intended to help standardize and simplify the component development sequence presently used in the semiconductor product engineering department. 3 figs., 2 tabs.