Publications

Sandia National Laboratories has developed a variety of alarm communication and display systems for a broad spectrum of users. This paper will briefly describe the latest systems developed for the Department of Energy (DOE), the Department of Defense (DoD), and the Department of State (DOS) applications. Applications covered will vary from relatively small facilities to large complex sites. Ongoing system developments will also be discussed. The concluding section will summarize the practical, implementable state-of-the-art features available in new systems. 6 figs.

The mechanical behavior of microcellular open-cell foams prepared by a thermally induced phase separation process are investigated. The foams studied were prepared from isotactic polystyrene, polyacrylonitrile, and poly(4-methyl-1-pentene) (rigid foams), and polyurethane and Lycra (elastomeric foams). Their densities were in the range 0.04--0.27 g/cm3. Conventional polystyrene foams were used for comparison. The moduli and collapse stresses of these foams were measured in compression and compared with the current constitutive laws which relate mechanical properties to densities. A reinforcement technique based on the in-situ precipitation of silica was used to improve the mechanical properties. 13 refs., 4 figs., 3 tabs.

Ion implantation has been shown to produce unique improvements in the properties of a wide range of materials. This technology has been extensively used for doping of semiconductors, where the required doses and implantation depths are relatively modest and readily achieved with commercial implanters. Other applications of ion implantation currently being pursued at a commercial level include the synthesis of buried second-phase layers in Si and the improvement of metal surface properties such as hardness, friction, wear rate, and corrosion. However, these applications have been severely constrained by the costs of treating large surface areas with the high ion doses required, and by the need to produce modified layers thicker than the range of the sub-MeV ions available from presently available commercial high-flux ion implanters. It therefore seems worthwhile to consider whether pulsed ion accelerators may offer advantages for such applications by providing high ion fluxes at MeV energies. The previously reported applications of pulsed accelerators to materials modification have used sub-MeV ion energies. The purpose of this article is to being these considerations the perspective of materials scientists who use ion implantation. We comment on needed extensions in implantation capabilities while leaving to others the question of whether these needs can be met with pulsed-beam technology. Further, in order to illustrate the kinds of beneficial materials modifications that can be achieved with implantation, we provide examples from recent work at Sandia National Laboratories, where large improvements have been realized in the tribological properties and strengths of Fe and A{ell} alloys. 10 refs., 6 figs.

The natural language technique was just one of many approaches to information system design in 1987. The success of this approach convinced management of the viability of this new'' approach. A group was created to use natural language in information system specifications and designs. Two of the projects undertaken by this group will be reviewed. The first is a quality database that allows for the management of the process that certifies production capabilities for major weapon components and the second tracks command and control status of weapons. A third external project involving nuclear disarmament will also be discussed.

The United States Department of Energy (DOE) plans to use the Waste Isolation Pilot plant (WIPP) in southeastern New Mexico for disposal of transuranic wastes generated by defense programs. The DOE must first demonstrate compliance with the Environmental Protection Agency's (EPA) Environmental Standards for the Management and Disposal of Spent Nuclear Fuel, High-Level and Transuranic Radioactive Wastes (40 CFR Part 191) hereafter called the Standard. The Standard was vacated by a Federal Court of Appeals in 1987 and is undergoing revision; by agreement with the State of New Mexico the DOE will continue to evaluate repository performance with respect to the Standard as first promulgated until a new version is available. This paper reviews the results of a 1989 preliminary demonstration of the performance-assessment methodology that will be used by the WIPP project ultimately to assess compliance with the Standard. The report also describes conceptual and numerical improvements in the performance-assessment methodology made during 1990, and summarizes the progress made toward achieving the probabilistic assessment of repository performance required for regulatory compliance. 13 refs., 4 figs.

Low-density, microcellular polymer foams have numerous applications as structural supports in high-energy physics experiments, in catalysis, ion exchange, and filtration, and for a variety of biomedical uses. A versatile method to prepare such foams is by thermally-induced phase separation (TIPS) of polymer solutions. Demixed solutions can be transformed into a foam by freezing the demixed solution and removing the solvent by freeze-drying. The morphology of these foams is determined by the the thermodynamics and kinetics of phase separation. A model of both the early and late stage structure development for demixed polymer solutions will be presented. For semi-crystalline polymers, gels can be prepared by crystallizing the polymer from solution, either a homogeneous solution or a demixed solution. Foams can be prepared from these gels by the supercritical extraction of the solvent. By understanding and utilizing the phase separation behavior of polymer solutions, engineered microcellular foams can be prepared. To design the foams for any application one must be able to characterize their morphology. Results will be presented on the morphological characterization of these foams and the relationship of the morphology to their processing history. 14 refs., 12 figs.

Infrared absorption and photoluminescence have been demonstrated for InAs{sub 1-x}Sb{sub x}/InSb strained-layer superlattices (SLS's) in the 8--15 {eta}m region for As content less than 20%. This extended infrared activity is due to the type II heterojunction band offset in these SLS's. The preparation of the first MOCVD grown p-n junction diode was achieved by using dimethyltellurium as an in-type dopant. Several factors, such as background doping and dopant profiles affect the performance of this device. InSb diodes have been prepared using tetraethyltin. The resulting current-voltage characteristics are improved over those of diodes grown previously using dimethyltellurium. Doping levels of 8 {times} 10{sup 15} to 5 {times} 10{sup 18} cm{sup {minus}3} and mobilities of 6.7 {times} 10{sup 4} to 1.1 {times} 10{sup 4} cm{sup 2}/Vs have been measured for Sn doped InSb. SLS diode structures have been prepared using Sn and Cd as the dopants. Structures prepared with p-type buffer layers are more reproducible. 5 refs., 4 figs.

This paper describes the analysis of the Three Mile Island-2 (TMI-2) standard problem that was performed with MELCOR. The MELCOR computer code is being developed by Sandia National Laboratories for the Nuclear Regulatory Commission for the purpose of analyzing severe accident in nuclear power plants. The primary role of MELCOR is to provide realistic predictions of severe accident phenomena and the radiological source team. The analysis of the TMI-2 standard problem allowed for comparison of the model predictions in MELCOR to plant data and to the results of more mechanistic analyses. This exercise was, therefore valuable for verifying and assessing the models in the code. The major trends in the TMI-2 accident are reasonably well predicted with MELCOR, even with its simplified modeling. Comparison of the calculated and measured results is presented and, based on this comparison, conclusions can be drawn concerning the applicability of MELCOR to severe accident analysis. 5 refs., 10 figs., 3 tabs.

Steady state roughness of surfaces growing by molecular beam epitaxy is investigated by Monte Carlo simulations under conditions where an ion beam is also present which sputters adatoms off the surface. If the sputtering is random, it only increases the roughness. But if the sputtering probability is strongly dependent on the binding energy of an adatom within a cluster or island, the ions can have a smoothening effect. Physical arguments are given in support of the results. 8 refs., 4 figs.

The purpose of this paper is to discuss the current issues of interest in PV concentrator module reliability. Before describing in detail the reliability concerns about PV concentrator modules, it should be emphasized that, with proper design and attention to quality control, there is nothing to prevent concentrator modules from being as reliable as crystalline-silicon flat-plate modules have proven to be. Concentrator modules tested outdoors, as well as in the first-generation systems, have generally been reliable, and no degradation in cell output has been observed. Also, although they are not included in this paper, there are a few items currently of concern with the reliability of other PV module technologies that are not issues with PV concentrator technology, such as the stability of amorphous-silicon efficiencies and concerns about EVA encapsulation.

The deformation and crack initiation behavior of Ti-24Al-11Nb has been examined over a temperature range of 298 to 923 K and for strain rates from 10{sup {minus}4}/s to 10{sup 2}/s. Tests performed in compression indicate much lower strain hardening at 10{sup 2}/s than at either 10{sup {minus}1}/s or 10{sup {minus}4}/s at all temperatures. Associated with this behavior is the occurrence of non-uniform, localized deformation bands at 10{sup 2}/s. An analysis indicates that adiabatic deformation conditions predominate at 10{sup 2}/s and that these result in adiabatic softening. Furthermore, as a result of non-uniform deformation and adiabatic heating, this Ti{sub 3}-Al-based alloy is actually more resistant to strain-induced microcrack initiation at 10{sup 2}/s than at 10{sup {minus}4}/s during room temperature testing. 16 refs., 7 figs.

This paper attempts to give an elementary review of the kinematics of large deformations with a view to illustrating some of the underlying geometric concepts, and then goes on to review some basic features of elastic, hypoelastic, and rate type constitutive equations relevant to their use in numerical methods. Since some recent work has emphasized working in a rotated'' intermediate configuration, one in which the rigid body rotation has been backed out, results relating to this configuration are included, otherwise all of the results have been read off directly from Truesdell and Toupin ( ) or Truesdell and Noll ( ). Finally, results given by Nemat-Nasser ( ) are quoted which reconcile some generalizations of infinitesimal plasticity and some remarks are made relevant to the introduction of tensor internal state variables. Thermodynamic effects, although important in calculations, are omitted to emphasize kinematical effects. Because recent authors have used different names and symbols for stress and strain tensors, it has been found necessary to give a self contained if abbreviated development of the kinematics, which, however, allows a compact discussion of constitutive equations.

We report formation of several small colloidal metal catatlysts in inverted micelle (oil-continuous) systems. These materials have demonstrated catalytic activity in situ (i.e. unsupported). The range of solvents possible in this process is large, including all saturated hydrocarbons, cyclic hydrocarbons (e.g. cyclohexane) and aromatics (e.g. toluene, xylene). Three classes of micelle system were investigated, nonionic, anionic, and cationic. Nonionic types allow precise size control but in general do not act as strong stabilizing agents at high temperatures. Cationics can be chosen to provide this permanent stability, providing both charge and steric stabilization. Metal systems formed include Rh, Ni, NiB, MoO{sub 2}, Pd, Au and Ag and alloys. Selected examples are given. 4 figs.

This paper presents an analytical and numerical analysis which evaluates the core-structure heat-up and subsequent relocation of molten core materials during a NWR short-term station blackout accident with ADS. A simplified one-dimensional approach coupled with bounding arguments is first presented to establish an estimate of the temperature differences within a BWR assembly at the point when structural material first begins to melt. This analysis leads to the conclusions that the control blade will be the first structure to melt and that at this point in time, overall temperature differences across the canister-blade region will not be more than 200 K. Next, a three-dimensional heat-transfer model of the canister-blade region within the core is presented that uses a diffusion approximation for the radiation heat transfer. This is compared to the one-dimensional analysis to establish its compatibility. Finally, the extension of the three-dimensional model to include melt relocation using a porous media type approximation is described. The results of this analysis suggest that under these conditions significant amounts of material will relocate to the core plate region and refreeze, potentially forming a significant blockage. The results also indicate that a large amount of lateral spreading of the melted blade and canister material into the fuel rod regions will occur during the melt progression process. 22 refs., 18 figs., 1 tab.

Fatigue life estimates for wind turbine components can be extremely variable due to both inherently random and uncertain parameters. A structural reliability analysis is used to qualify the probability that the fatigue life will fall short of a selected target. Reliability analysis also produces measures of the relative importance of the various sources of uncertainty and the sensitivity of the reliability to each input parameter. The process of obtaining reliability estimates is briefly outlined. An example fatigue reliability calculation for a blade joint is formulated; reliability estimates, importance factors, and sensitivities are produced. Guidance in selecting distribution functions for the random variables used to model the random and uncertain parameters is also provided. 5 refs., 9 figs., 1 tab.

Photovoltaic concentrator collectors are an attractive option for utility-scale photovoltaic power plants. This paper reviews the current status of photovoltaic concentrator collector and cell development. Included in the review is a discussion of the economic motivation for concentrators, a summary of recent concentrator collector and cell development, and a description of a major new program to accelerate development and commercial introduction of concentrator collectors. 21 refs., 1 fig., 3 tabs.

Physical security specialists have been attracted to the concept of video motion detection for several years. Claimed potential advantages included additional benefit from existing video surveillance systems, automatic detection, improved performance compared to human observers, and cost effectiveness. In recent years significant advances in image processing dedicated hardware and image analysis algorithms and software have accelerated the successful application of video motion detection systems to a variety of physical security applications. Currently Sandia is developing several advanced systems that employ image processing techniques for a broader set of safeguards and security applications. TCATS (Target Cueing and Tracking System) uses a set of powerful, flexible, modular algorithms and software to alarm on purposeful target motion. Custom TCATS hardware optimized for perimeter security applications is currently being evaluated with video input. VISDTA (Video Imaging System for Detection, Tracking, and Assessment) uses some of the same TCATS algorithms and operates with a thermal imager input. In the scan mode, VISDTA detects changes in a scene from the previous image at a given scan point; in the stare mode, VISDTA detects purposeful motion similar to TCATS.

Many of the properties associated with ceramic materials such as high hardness, high dielectric constant, refractoriness, and good optical properties will play a critical role in the development of devices for new and emerging technologies. In many cases, the combination of properties that is required demands that a composite material be designed to fulfill these complex materials needs. The increasing emphasis upon composite materials design and performance necessarily focuses greater attention upon the structure and properties of interfaces in ceramic materials. One on the most important aspects of interfacial behavior is the adhesive stability. As an example, high hardness ceramic coatings for tribological applications require a high degree of interfacial adhesion with the underlying substate material. Alternatively it has been shown that fiber reinforced ceramic composites that are designed for high fracture toughness must contain weak interfaces that allow for fiber pull-out to toughen the instrinsically brittle ceramic matrix. Our ability to design ceramic interfaces for specific interfacial adhesive behavior dictates that we develop a full understanding of the factors that control the adhesive bond in these systems. We report on the use of continuum fracture mechanics techniques to identify the molecular source of adhesion between oxide surfaces and introduce a new approach to measuring interfacial adhesive forces using an Interfacial Force Microscope.

Although computational aerodynamics simulation has been taking more responsibility during recent years, wind tunnel experimentation has continued to play the major role in flight vehicle analysis and design.This role, however, is changing because of the great strides in the capability and confidence in numerical simulations. For a small, well defined, class of supersonic and hypersonic flow problems, high quality numerical solutions are now believed to represent the physics of the problem more accurately than a wind tunnel experimental can simulate the free flight conditions. An example of this is the supersonic or hypersonic, laminar, perfect gas flow over a spherically blunted cone at low angle of attack. In this paper, aerodynamic force and moment measurements and flow visualization results are presented for a reentry vehicle configuration at Mach 8. All of the results were obtained in the Sandia Mach 8 long duration, blow-down, hypersonic wind tunnel. The basic vehicle configuration is a spherically blunted cone with a slice parallel with the axis of the vehicle. Onto the slice portion of the vehicle can be attached flaps with three different deflection angles, 10, 20 and 30 deg. Flow visualization results include surface oil flow, spark Schlieren, and liquid crystal photographs. 1 ref., 7 figs.

An AlGaAs window layer is used in high-efficiency GaAs solar cells to reduce carrier recombination at the front surface. Free surfaces of III-V semiconductors have a high density of surface states that serve as recombination sites and create a depletion region at the front surface. We have performed a theoretical investigation of front-surface recombination that includes the effect of a surface space-charge layer. It was found that the surface space-charge layer can have a profound effect on front-surface recombination for thin or lightly doped window layers. 15 refs., 5 figs., 1 tab.

Transport by groundwater within the Culebra Dolomite, an aquifer above the Waste Isolation Pilot Plant (WIPP), is the most probable mechanism for long-term release of radionuclides to the accessible environment. Radionuclides could be retarded by sorption if the groundwater is exposed to sufficient amounts of fracture-lining clays. In this natural-analog study, distributions of U and trace metals have been examined to constrain the strength of clay/solute interactions within the Culebra. Uranium solid/liquid distribution ratios, calculated from U concentrations of groundwaters and consanguineous fracture-filling clays, range from {approximately}80 to 800 m{ell}/g and imply retardation factors of 60 to 500 using a fracture-flow model. Retardation factors inferred from uranium-series disequilibria and {sup 14}C ages in Culebra groundwaters alone are much lower ({approximately}10), implying that clays may contain a significant unreactive component of U. Such a possibility is corroborated by Rb/Sr ages; these imply long-term stability of the clays,with resetting occurring more than 250 Ma ago. Factor analysis and mass-balance calculations suggest, however, that Mg-rich clays are dissolving in Pleistocene-age groundwaters and/or are converting to Na-rich smectites, and that B and Li are taken up from the water by the clays. Apparently, the solution chemistry reflects gradual equilibration of clays with groundwater, but thus far the bulk of the clays remain structurally intact. Measurements of the distribution of U in the Culebra will be more meaningful if the inert and exchangeable components of the U content of the clays can be quantified. 26 refs., 3 figs., 2 tabs.

Computer simulation of low-energy ion-solid processes has greatly broadened in scope in recent years. In particular, realistic descriptions of the ion-solid and solid-solid interactions can now be utilized. The molecular dynamics technique, in which the equations of motion of the interacting atoms are numerically integrated, can now be used to characterize ion-solid interactions in a range of model material systems. Despite practical limitations of this procedure, a number of substantial results have appeared. The available results are examined to investigate the qualitative influence that chemical interactions have on low-energy ion-solid processes. 26 refs., 4 figs.

Good quality, low temperature silicon nitride and oxynitride films were deposited downstream from an electron cyclotron resonance (ECR) plasma source using SiH{sub 4} and N{sub 2} gas mixtures. The Si/N ratio and H content in the deposited films were determined using Rutherford backscattering spectrometry (RBS)and elastic recoil detection (ERD). The H concentration was minimum for films with compositions closest to that of stoichiometric Si{sub 3}N{sub 4}. The optimum conditions for producing a stoichiometric Si{sub 3}N{sub 4}were: a SiH{sub 4}/N{sub 2} flow ratio between 0.1 and 0.2, and an electrically isolated sample far from the ECR source. Infrared absorption spectra showed that as the film composition changed from N rich to Si rich the dominant bonds associated with H changed from N-H to Si-H. The addition of O{sub 2} to the background gas formed an oxynitride with a low H content similar to the stoichiometric Si{sub 3}N{sub 4} 10 refs., 4 figs., 2 tabs.

We have used a Tl-Ca-Ba-Cu-O superconducting flux flow transistor (SFFT) as an active impedance converter between Josephson and FET circuitry. The input of the flux flow device is a control line of low impedance that can be driven by a tunnel junction. The output is the signal across the SFFT which is made of a parallel array of weak links. The output impedance is typically greater than 5 {Omega} with a maximum voltage swing of over 100 mV into a 50 {Omega} system. The switching of an all-Nb junction induced a 90 mV voltage swing at the FET input and over 200 mV at the FET output. The line driver can operate anywhere between 4.2K and 85K with minor changes in speed ({plus minus}5 ps) and output level ({plus minus}10 mV). The switching time measured was about 100 ps and was fixture limited. 13 refs., 5 figs.

Archimedes is a prototype mechanical assembly system which generates and executes robot assembly programs from a CAD model input. The system addresses the unrealized potential for flexibility in robotic mechanical assembly applications by automating the programming task. Input is a solid model of the finished assembly. Parts relationships and geometric constraints are deduced from the solid model. A rule-based planner generates a generic'' assembly plan that satisfies the geometric constraints, as well as other constraints embodied in the rules. A retargetable plan compiler converts the generic plan into code specific to an application environment. Execution of the compiled plan in a workcell containing an Adept Two robot, a vision system, and other parts handling equipment will be shown on videotape.

This concept brings a condensed source of tritium into close proximity with an inorganic phosphor. That source may thus become the equivalent of many atmospheres of tritium gas pressure. If both phosphor and tritium source material are optically clear, then a lamp's brightness may be made to scale with optical path length. Proof of principle of this concept has been demonstrated and will be described. A theoretical treatment is presented for the results here and for results from aerogel experiments.

Pressurized water reactor pressure vessels operate under US Nuclear Regulatory Commission (NRC) rules and regulatory guides that are intended to maintain a low probability of vessel failure. The NRC has also addressed neutron embrittlement of pressurized water reactor pressure vessels by imposing regulations on plant operation. Plants failing to meet the operating criteria specified by these rules and regulations are required, among other things, to analytically demonstrate fitness for service in order to continue safe operation. The initial flaw size or distribution of initial vessel flaws is a key input to the required vessel integrity analyses. A fracture mechanics sensitivity study was performed to quantify the effect of the assumed flaw distribution on the predicted vessel performance under a specified pressurized thermal shock transient and to determine the critical crack size. Results of the analysis indicate that vessel performance in terms of the estimated probability of failure is very sensitive to the assumed flaw distribution. 20 refs., 3 figs., 2 tabs.

Short communication.

Inorganic zeolites show promise as an alternative to traditional tritium gas tube light sources. Greater proximity of tritium atoms and luminescing centers, as well as greater tritium loading density, have been obtained within the zeolite aluminosilicate matrix. Zeolites are in addition optically clear and radiation stable. The zeolite radioluminescence program is described. Procedures for obtaining light sources are presented and results are discussed. 12 refs., 1 fig.

The microstructure of Al ion-implanted at room temperature with 17 at. % 0 has been characterized with TEM. The alloy has extremely small (1.5--3.5 nm) oxide precipitates whose crystal structure is interpreted to be a disordered version of {gamma}-Al{sub 2}O{sub 3} having a fcc lattice of O{sup 2{minus}} ions with Al{sup 3+} ions in random interstitial sites. The small sizes can account for the exceptionally high strength of as-implanted alloys: 2500--3300 MPa. Larger precipitates are found when the alloy is annealed 1/2 hour at 550{degree}C, which is consistent with its somewhat lower strength: 800--1600 MPa. 4 figs.

Solderability of Class II environmentally exposed Ni-Sn plated Cu substrates was evaluated with 60Sn-40Pb solder. Tin thickness were 10, 50, and 150 {mu}in. The 10 {mu}in. plating gave the smallest solder meniscus rise. A general decrease in contact angle, or increase in wettability, was observed with increasing Sn plating. The environmental exposures retarded the wetting rate and increased the time to maximum wetting, particularly with only 10 {mu}in. of Sn. Although the solderability of the 50 and 150 {mu}in. surfaces were not significantly affected by the test conditions, an intermediate plating thickness of 100 {mu}in. is preferred for processing flexibility. 13 refs., 6 figs., 1 tab.

SICADS is a generic command, control and display software package which provides the capability to generate security systems which employ different hardware and system configurations, but which are controlled by the same software. SICADS was designed to avoid the task of developing new software for each site. By reusing software, expenses are reduced and software quality is increased. Tested software can be reused without modifications. Configurations of security systems vary from site to site. In many systems, a seemingly minor change in configuration has required significant software modifications. SICADS has been designed to isolate site specific information into data files so that it can be easily tailored to fit a site's requirements without changing the software. Using SICADS, it is possible to generate systems which distribute processing and control over several computers and consoles. 1 fig.

The ion-hose instability can catastrophically disrupt a classical electron beam propagating in the ion-focussed regime (IFR). Ion hose is driven by a resonant interaction between the smooth electron-betatron and ion-betatron orbits. In a classical beam phase correlations decay secularly in time c(t)/c(t{sub 0}) {approximately} (t{sub 0}/t){sup n} (0 < n {le} 2). In a stochastic electron beam the electron orbits are chaotic. Such a beam can be immune to resonant instabilities because phase correlations decay exponentially fast c(t)/c(0) {approximately} e{sup {minus}ht} thus destroying the coherence of the electron response on the growth time 1/{gamma}{sub g} if h {approximately} {gamma}{sub g}. Using the same principles we can also envision a stochastic damping cell in which electron phase correlations damp exponentially c(z)/c(0) {approximately} e{sup {minus}hz} thus centering and conditioning a beam more effectively than a classical phase-mixing cell in which c(z)/c(z{sub 0}) {approximately} (z{sub 0}/z){sup n}. A triple-Bennett'' IFR system and the analogous triple-wire'' damping cell are analyzed. The K-entrophy is introduced as a figure-of-merit for such stochastic electron beam systems. 16 refs., 7 figs.

The chemical bonding and isochronal annealing of H implanted into GaAs at 80 K has been investigated by infrared absorption measurements. Based upon the frequency shift when deuterium is substituted for H, and an equivalent band formation in InAs, assignment of a new band at 2029 cm{sup {minus}1} is made to As-H centers. Bonding of H at interstitial As of and As-vacancy pair which anneals between 150 and 250K is suggested as the structure for the defect. A previously-reported absorption band at 1834 cm{sup {minus}1} assigned to Ga-H centers in H-implanted GaAS increase in intensity when H is released from As-H centers. 15 refs., 5 figs.

Strained layer structures have received a great deal of attention due both to their possible application in electronic devices and their intrinsic interest. The study of strained layer quantum wells grown using lattice mismatched materials has been widely developed for III-V semiconductors. Strained layer quantum wells grown using II-VI materials have not been studied nearly so much as those from III-V, but they are a rapidly growing field of semiconductor research. The wide gap II-VI materials are of interest because they are generally direct gap materials. This makes them attractive for optoelectronic devices. The majority of the work on strained layer structures in the wide gap tellurium based materials has focused in two areas. The first is the inclusion of Mn to produce dilute magnetic semiconductors (DMS) strained layers and superlattices. The other area is CdTe/ZnTe quantum wells and superlattices. Some related work has been done with CdZnTe/ZnTe structures. For the CdZnTe/CdTe very little work has been done and the majority of that used very small amounts of Zn. In this paper we will present the growth and optical characterization of Cd{sub 1-x}Zn{sub x}Te/CdTe strained single quantum wells (SSQW) where the Zn concentration ranges from about 10 to 50%. 10 refs., 3 figs.

Apollo's OmniBack backup system provides a convenient and effective way of storing network backup information on 8mm tape. In addition it has a journaling facility to write extensive log files, recording the backup process in almost any degree of detail desired. The directory structure and file names used are logical and well-defined. Summary files announce the degree of success of the backup as specified in the work file. The system will run unattended under the UNIX cron command, allowing the backup to be performed during the night when user demands on the network are small and most user files are free.

Agencies that are prime contractors to the Department of Energy (DOE) have developed and are currently instituting a quality initiative which applies a QML-like methodology to a complete discrete semiconductor process. Our goal is to demonstrate that improving the quality of this process is a more efficient method than screening to improve the quality of the semiconductor. The QML methodology, MIL-I-38535, is used to achieve this goal for integrated circuits. Our methods, for discrete semiconductor, applies many of the principles found in this specification to provide structured continuous improvement. Improvement in product performance reduces incoming inspection requirements, resulting in reduced cost and product lead time. This paper describes our methodology for this initiative, which consists of a certification, qualification, and monitoring (CQM) program for the complete semiconductor process. This process includes all technical and administrative activities that effect the quality of a device, beginning with circuit design and ending with the installation of the manufactured device into the electronic component assembly. For the initial application, our CQM program is being implemented on a small signal transistor. Four companies are involved in the partnership: Sandia National Laboratories, a design agency and prime contractor to the DOE; Allied-Signal Aerospace Company, Kansas City Division, a production agency and prime contractor to the DOE (for electronic component assembly); Alliance Electronics, a prime contractor and supplier (for procurement and testing); and Motorola Inc., Semiconductor Products Sector, a manufacturer. 2 refs.

The Department of Energy (DOE) is investigating the use of ductile cast iron (DCI) as a candidate material for radioactive material transportation cask construction. The investigation will include materials testing and full-scale cask testing. The major effort will focus on materials qualification and cask evaluation of the 9 meter and puncture drop test events. The test plan shall include a series of drop tests, and several core bars will be removed from the casting wall for material properties testing. Of particular interest is the evaluation of the material microstructure and fracture toughness parameters. Test instrumentation, used to define cask deceleration loads and strain during the drop tests, will be strategically placed in areas of the greatest structural interest. Part of the testing will include placement of an induced flaw. At the conclusion of the cask drop tests, the induced flaw(s) will be sectioned from the cask body for metallurgical examination. All test results will be documented in the safety analysis report for packaging for submission to the US Nuclear Regulatory Commission (NRC). The goal of this program is a certificate of compliance for DCI from the NRC to transport high-level radioactive materials. The acceptance of DCI within the USA cask design community will offer an alternative to present-day materials for cask construction, and its entry has the potential of providing significant cost-savings.

A three generation family of CMOS silicon test chips for packaging diagnostics has been developed. These Assembly Test Chips (ATC) contain sensors that measure a number of variables associated with assembled IC degradation, including the degree of IC corrosion, handling damage, ESD threat, ppm, moisture, mechanical stress, mobile ion density, bond pad cratering, and high speed logic degradation. The ATC family are intended to give manufacturing feedback in four ways: direct feedback in evaluation of an Assembly Manufacturing Line in an objective, non-intrusive way; before and after comparisons on an assembly production line when an individual process, material, or piece of equipment has been changed; resident lifetime monitor for system package aging and ongoing reliability projection and thermal, mechanical, dc electrical, and high frequency mock-up evaluation of packaging (including multichip) schemes. 14 refs., 6 figs., 2 tabs.

Infrared reflectance and transmittance measurements between 500 and 1800 cm{sup {minus}1} were obtained on boron carbides with between 10 and 20 atomic percent carbon. Measurements on both boron and carbon isotopically enriched samples indicate that all prominent modes involve boron motion, and that all but a mode near 950 cm{sup {minus}1} involve carbon motion. Since the spectrum remains qualitatively unaltered as a function of carbon concentration, its prominent features must have a common structural origin. 5 refs., 4 figs., 2 tabs.

The thermal neutron absorption cross sections of geologic materials are of first-order importance to the interpretation of pulsed neutron porosity logs and of second-order importance to the interpretation of steady-state porosity logs using dual detectors. Even in the latter case, uncertainties in log response can be excessive whenever formations are encountered that possess absorption properties appreciably greater than the limestones used in most tool calibrations. These effects are of importance to logging operations directed at geothermal applications where formation vary from igneous to sedimentary and which may contain solution-deposited minerals with very large cross-section values. Most measurements of cross-section values for geologic materials have been made for hydrocarbon production applications. Hence, the specimen materials are sedimentary and clean in the sense that they are not altered by geothermal fluids. This investigation was undertaken to measure cross-section values from a sequence of igneous materials obtained from a single hole drilled in an active hydrothermal system. 3 refs., 1 fig.

An automatic optical track identification/counting system has been developed for counting the total number of fission tracks on a fused quartz solid state track recorder. The system is capable of analyzing up to twenty recorders a day with an operator input of less than two hours. The uncertainty introduced by the counting system is about one percent. 6 refs., 2 figs.

A new runaway electron suppression paddle was designed with the PTA code package to reduce the runaway electron population in the Advanced Toroidal Facility (ATF), Oak Ridge National Laboratory. The PTA code package is a unique application of PATRAN, the Integrated TIGER Series, and ABAQUS for modeling high energy electron impact on magnetic fusion components and materials. By its nature, ATF is susceptible to runaway electron formation and confinement resulting in the production of a high level of hard x-rays near the machine. Four previous stainless steel paddles proved effective in reducing the runaway electron population; however, electrons above 15 MeV have still been observed. Melting and bending were observed in each of the previous paddles, reducing their effectiveness. Scoping experiments are under way to further characterize the runaway electrons in ATF. Data from these experiments will provide insight into runaway electron damage mechanisms. Proposals for the insertion of a new paddle in ATF are being considered. These analyses add to the knowledge of runaway electron damage and will aid in the design of future components to withstand runaway electron discharges in all magnetic fusion devices, including tokamaks. 8 refs., 3 figs., 1 tab.

System tuning often occurs in response to observed changes in key performance indicators. But, how do we determine if a change is significant Our indicators are random variables. They display a natural'' variation. This presentation reviews techniques that may provide a great deal of assistance in determining the significance of a change -- and more importantly -- when and what to tune. The techniques were developed by Dr. William Shewhart at Bell Labs and refined by internationally known quality specialist W. Edwards Deming. Although founded on statistical theory, the techniques are easy to use, require no formal statistical training, and may help you

The US Department of Energy National Photovoltaics Program considers the photovoltaic (PV) concentrator technology as a viable entity, likely to penetrate the utility market in the foreseeable future. To achieve this, it has launched the National Photovoltaic Concentrator Initiative under the management of Sandia National Laboratories. The objective of this program is to encourage PV concentrator system design and manufacture, with a view to bringing the energy cost to $0.12/kWh in the next four years and to $0.06/kWh by the year 2000. To achieve these goals, the systems have to perform reliably for 20 to 30 years. This necessitates a stringent quality assurance/quality control (QA/QC) program in all phases of PV concentrator design, production, and installation. In order to assist the PV industry in this effort a project was initiated to provide a generic QA/QC guide, capable of being adapted by any PV concentrator industry to prepare its individual QA/QC plan. The draft plan of the guide was prepared and circulated to various government laboratories and industries involved in PV concentrator work. Their input is now being incorporated into a final document, which will serve as an industry standard. 1 ref., 1 fig.

The design-basis, defense-related, transuranic (TRU) waste to be emplaced in the Waste Isolation Pilot Plant (WIPP) could, if sufficient H{sub 2}O and nutrients were present, produce as much as 1,500 moles of gas per drum of waste. Gas production could pressurize the repository to 150 atm (lithostatic pressure) and perhaps higher. Anoxic corrosion of Fe and Fe-base alloys and microbial degradation of cellulosics are the processes of greatest concern, but radiolysis of brine could also be important. The proposed backfill additives CaCO{sub 3}, CaO, CuSO{sub 4}, KOH, and NaOH may remove or prevent the production of some of the expected gases. Because of the heterogeneous nature of design-basis waste, the Eh and pH of any brine present in WIPP disposal rooms could vary significantly over short distances after reacting with the waste. The WIPP Project is investigating the consequences of gas production and considering engineered alternatives, including reprocessing the waste, to reduce gas production rates or potentials. Reprocessing would also reduce the range of Eh and pH expected for the repository. 12 refs.

More than 20 years ago, a philosophy was developed for the design and analysis of hardware systems to ensure that they would perform in a predictably safe manner, even in severe abnormal environments. This philosophy has been scrutinized and tested during the intervening years, and has proved successful in practice. A requirement guiding the development of the philosophy was that the resulting design must be simple enough to be amenable to analysis. The inherent simplicity is a safety attribute, because complex analyses, such as those represented by fault trees containing hundreds of branches, are extremely susceptible to error. There are many examples where such errors led analysts to believe systems were safe when they were not, with disastrous consequences. The purpose of this workshop problem is to determine whether the principles developed to ensure hardware safety are applicable in any way to safety-critical software systems. It is possible that hardware associations with software will need to be considered, but whether or not this is true is left as an aspect of the investigation. In order to put the ground rules in perspective, it will be necessary to establish some framework.

We present here the SMILE modification of the RADLAC II accelerator which enabled us to produce high quality 12--14 MV, 100 kA beams. It consists of replacing the 40-kA 4-MV beam injector, magnetic vacuum transport and accelerating gaps by a long cathode shank which adds up the voltages of the 8 pulse forming lines. The beam now is produced at the end of the accelerator and is free of all the possible instabilities associated with accelerating gaps and magnetic vacuum transport. Annular beams with {beta}{perpendicular} {le} 0.1 and radius r{sub b} {le} 2 cm are routinely obtained and extracted from a small magnetically immersed foilless electron diode. Results of the experimental evaluation are presented and compared with design parameters and numerical simulation predictions. 6 refs., 7 figs., 1 tab.

A diode employing a thermionic cathode has produced 80 A beams at 200 kV for at least 6 {mu}s. Moreover, the diode operates at rates as high as 1 Hz. EGUN simulations of the experimental geometry agree with the experiments. Finally, simulation of a proposed diode geometry predicts a 1 kA, 500 kV beam.

An algorithm is presented or rendering scalar field data which reduces rendering times by as much as two orders of magnitude over traditional full resolution image. Less than full resolution sampling of the scalar field is performed using a fast ray tracing method. The sampling grid points are output as a set of screen based gouraud shaded polygons which are rendered in hardware by a graphics workstation. A gradient based variable resolution algorithm is presented which further improves rendering speed. Several examples are presented. 16 refs., 8 figs., 2 tabs.