In the manufacture of printed wiring boards (PWB), plasma etchback and desmear processes facilitate the making of good mechanical and electrical bonds of copper inner layers to copper plating. Without sufficient plasma treatment, internal layer copper features receive inadequate polymer removal which results in circuit discontinuity during the plating process. Additionally, the plasma serves to roughen the polymer wall of drilled holes which improves copper adhesion. To ensure proper plasma treatment, careful adherence to strict production guidelines is essential. These guidelines include attention to several critical criteria in placement, pretreatment and treatment of the PWBs during the plasma process; process verification via post plasma testing; and careful process monitoring throughout. In this brief, some guidelines for process monitoring and control will be discussed. A description of a new plasma monitor utilizing optical emission spectroscopy (OES), developed cooperatively between Sandia National Laboratories, National Consortium for Manufacturing Sciences (NCMS) and Texas Instruments Inc., will be discussed along with possible benefits derived from in situ monitoring of plasma systems.
This information package was prepared for both new and experienced users of the SPHINX (Short Pulse High Intensity Nanosecond X-radiator) flash X-Ray facility. It was compiled to help facilitate experiment design and preparation for both the experimenter(s) and the SPHINX operational staff. The major areas covered include: Recording Systems Capabilities,Recording System Cable Plant, Physical Dimensions of SPHINX and the SPHINX Test cell, SPHINX Operating Parameters and Modes, Dose Rate Map, Experiment Safety Approval Form, and a Feedback Questionnaire. This package will be updated as the SPHINX facilities and capabilities are enhanced.
This paper is the first step in the resolution of the direct containment heating (DCH) issue for the Zion nuclear power plant using the risk oriented accident analysis methodology (ROAAM). This paper includes the definition of a probabilistic framework that decomposes the DCH problem into three probability density functions that reflect the most uncertain initial conditions (UO2 mass, zirconium oxidation fraction, and steel mass). Uncertainties in the initial conditions are significant, but our quantification approach is based on establishing reasonable bounds that are not unnecessarily conservative. To this end, we also make use of the ROAAM ideas of enveloping scenarios and 'splintering'. Two causal relations (CRs) are used in this framework: CR1 is a model that calculates the peak pressure in the containment as a function of the initial conditions, and CR2 is a model that returns the frequency of containment failure as a function of pressure within the containment. Uncertainty in CR1 is accounted for by the use of two independently developed phenomenological models, the convection-limited containment heating model and the two-cell equilibrium model, and by probabilistically distributing the key parameter in both, which is the ratio of the melt entrainment time to the system blowdown time constant. The two phenomenological models have been compared with an extensive database including recent integral simulations at two different physical scales (1:10-scale in the Surtsey facility at Sandia National Laboratories and 1:40-scale in the COREXIT facility at Argonne National Laboratory). The loads predicted by these models were significantly lower than those from previous parametric calculations. The containment load distributions do not intersect the containment strength (fragility) curve in any significant way, resulting in containment failure probabilities less than 10-3 for all scenarios considered. Sensitivity analyses did not show any areas of large sensitivity. The feasibility of extrapolating containment loads distributions to most other pressurized water reactors is explored.
The use of hydrous titanium oxide (HTO) ion-exchange materials as supports for iron and chromium based dehydrogenation catalysts is compared to current commercial catalyst systems in order to determine the potential of HTO technology for impacting this important chemical processing area. The best Fe/HTO catalysts synthesized to date achieve ethylbenzene conversions to styrene approaching those of commercial catalysts, even though the Fe/HTO catalysts contain no promoters while the commercial catalysts contain several different promoters, including K, Cr, and Ce. Addition of promoters to Fe/HTO catalyst is expected to result in further conversion improvements such that the activity of the commercial catalysts may be equaled or exceeded. Fe/HTO and Cr/HTO catalysts achieve only modest conversions of isobutane to isobutene that are far below available commercial catalysts. With the Cr/HTO catalysts, however, activity normalized to Cr loading far exceeds that of the commercial catalyst. Since optimum Cr loading conditions have not yet been identified, there is ample room for increases in both Cr loading and catalyst activity. Even if Cr/HTO and Fe/HTO catalysts do not ultimately exceed the performance obtained with commercial catalysts, the ability to cast HTO materials in the form of thin films may present important advantages for catalytic membrane reactor systems. These potential advantages are discussed and evaluated.
The Power Reactor and Nuclear Fuel Development Corporation (PNC) of Japan and the US Department of Energy (DOE) are cooperating on the development of a remote monitoring system for nuclear nonproliferation efforts. This cooperation is part of a broader safeguards agreement between PNC and DOE. A remote monitoring system is being installed in a spent fuel storage area at PNC`s experimental reactor facility Joyo in Oarai. The system has been designed by Sandia National Laboratories (SNL) and is closely related to those used in other SNL remote monitoring projects. The Joyo project will particularly study the unique aspects of remote monitoring in contribution to nuclear nonproliferation. The project will also test and evaluate the fundamental design and implementation of the remote monitoring system in its application to regional and international safeguards efficiency. This paper will present a short history of the cooperation, the details of the monitoring system and a general schedule of activities.
A double quantum well (QW) subject to in-plane magnetic fields B∥ has the dispersion curves of its two QWs shifted in k-space. When the QWs are strongly coupled, an anticrossing and partial energy gap occur, yielding a tunable multi-component Fermi surface. We report measurements of the resultant features in the conductance, the capacitive density of states and giant deviations in the cyclotron effective masses.
As a part of the International Remote Monitoring Project, during March 1995, a Remote Monitoring System (RMS) was installed at the Embalse Nuclear Power Station in Embalse, Argentina. This system monitors the status of four typical Candu spent fuel dry storage silos. The monitoring equipment for each silo consists of analog sensors for temperature and gamma radiation measurement; digital sensors for motion detection; and electronic fiber-optic seals. The monitoring system for each silo is connected to a wireless Authenticate Item Monitoring System (AIMS). This paper describes the operation of the RMS during the first year of the trial and presents the results of the signals reported by the system compared with the on site inspections conducted by the regulatory bodies, ABACC, IAEA, ENREN. As an additional security feature, each sensor periodically transmits authenticated State-of-Health (SOH) messages. This feature provides assurance that all sensors are operational and have not been tampered with. The details of the transmitted information and the incidents of loss of SOH, referred to as Missing SOH Event, and the possible causes which produced the MSOHE are described. The RMS at the embalse facility uses gamma radiation detectors in a strong radiation field of spent fuel dry storage silos. The detectors are Geiger Muller tubes and Silicon solid state diodes. The study of the thermal drift of electronics in GM detectors and the possible radiation damage in silicon detectors is shown. Since the initial installation, the system has been successfully interrogated from Buenos Aires and Albuquerque. The experience gained, and the small changes made in the hardware in order to improve the performance of the system is presented.
In applications where multiple magnetic modulators are used to drive a single Linear Induction Voltage Adder (LIVA) or Linear Accelerator (LINAC), it is essential that the outputs of the modulators be synchronized. Output rise times are typically in the 10 ns to 20 ns range, often making it necessary to synchronize to within less than 1 ns. Microprocessor and electronic feedback schemes have been developed and demonstrated that achieve the required level of synchronization, however, they are sophisticated and potentially complex. In a quest for simplicity, this work seeks to determine the achievable level of modulator to modulator timing jitter that can be obtained with simple design practices and passive techniques. Sources of output pulse time jitter in magnetic modulators are reviewed and some basic modulator design principles that can be used to minimize the intrinsic time jitter between modulators are discussed. A novel technique for passive synchronization is presented.
Pulsed power offers and efficient, high energy, economical source of x-rays for inertial confinement fusion (ICF) research. We are pursuing two main approaches to ICF driven with pulsed power accelerators: intense light ion beams and z-pinches. This paper describes recent progress in each approach and plans for future development.
Risks in software systems arise from many directions. There are risks that the software is faulty, that the system may be attacked, that safety hazards exist, that the system may be inoperable or untimely, that an abnormal event may cause unexpected actions, etc. Risk analysis tools should support and document risk-mitigation decisions and facilitate understanding of residual risks. These tools must be based on a sound theory of risk, which does not exist today. Probabilistic risk assessment techniques apply to physically-based systems where failure modes and event dependence are fairly well understood. But they cannot be blindly applied to software systems, which do not share these characteristics. Moreover, we need to meld many diverse aspects of risk for software systems. This presentation will explore some thought-provoking ideas about modeling, problem spaces, solution approaches, math, decision friendly output, and the role of risk analysis in the software lifecycle.
The purpose of the Programmatic Risk Management System (PRMS) is to evaluate and manage potential risks associated with proposed projects (i.e., new products or processes, or possible research and technological development projects). Although the PRMS considers some technical aspects of risk, the primary focus of the methodology is programmatic risk. That is, the methodology permits an assessment of risks associated with such issues as the ability to successfully produce a product that performs in accordance with all customer requirements, and the availability and allocation of resources (money, equipment, facilities, skilled personnel). The PRMS process consists of five formalized activities that are essential for effective management of risks associated with proposed projects. These activities include risk assessment, development of appropriate risk mitigation strategies, estimating strategy implementation cost, ranking of risk mitigation strategies for resource allocation, and scheduling of strategy implementing. The PRMS utilizes a ranking system that allows the user to identify the most cost-effective investment of resources of minimizing risk.
Cl{sub 2}+Ar Reactive-Ion-Beam Etching is demonstrated for anisotropic, low-damage etching of InAlGaAs semiconductor alloys for use as optical transmission modulators at 1.32 {mu}m wavelength.
Two thin-walled Al tubes were filled with epoxy which were cured isothermally; one tube was instrumented with strain gauges, and the other with thermocouples. Finite element codes were used. Predicted and measured centerline hoop strains are shown; predictions and measurements agree. This is being applied to encapsulated components.
The primary research objective of the work described here is to design, synthesize, and characterize new materials for use as chemical sensor interfaces, integrate these materials, using appropriate transducers, into sensor arrays, and then develop appropriate mathematical algorithms for interpreting the array response. In this paper, we will discuss two new types of materials we have developed that are ideally suited for use as chemically sensitive interfaces for array-based chemical sensing applications, since they: (1) provide general specificity towards classes of functional groups rather than individual compounds; (2) are intermediate in structure between monolayers and polymers; (3) exhibit both endo- and exo-recognition. The first class of materials is surface-confined dendrimers and the second is hyperbranched polymers.
We have studied the different driving forces behind syneresis in MTES/TEOS gels by aging them in different H{sub 2}O/EtOH pore fluids. We show using shrinkage, density, contact angle, and N{sub 2} sorption measurements, the influence of gel/solvent interactions on the microstructural evolution during drying. Competing effects of syneresis (that occurs during aging) and drying shrinkage resulted in the overall linear shrinkage of the organically modified gels to be constant at {approximately}50%. Increasing the hydrophobicity of the gels caused the driving force for syneresis to change from primarily condensation reactions to a combination of condensation and solid/liquid interfacial energy. In addition the condensation driven shrinkage was observed to be irreversible, whereas the interfacial free energy driven shrinkage was observed to be partially reversible. Nitrogen sorption experiments show that xerogels with the same overall extent of shrinkage can have vastly different microstructures due to the effects of microphase separation.
Solar dish/Stirling systems using sodium heat pipe receivers are being developed by industry and government laboratories here and abroad. The unique demands of this application lead to heat pipe wicks with very large surface areas and complex three-dimensional flow patterns. These characteristics can enhance the mass transport and concentration of constituents of the wick material, resulting in wick corrosion and plugging. As the test times for heat pipe receivers lengthen, we are beginning to see these effects both indirectly, as they affect performance, and directly in post-test examinations. We are also beginning to develop corrective measures. In this paper, we report on our test experiences, our post-test examinations, and on our initial effort to ameliorate various problems.
A unifying framework is developed for the analysis of brittle materials. Heretofore diverse classes of models result from different choices for unspecified coefficient and distribution functions in the unified theory. Material response is described in terms of expectation integrals of transverse symmetry tensors. First, a canonical body containing cracks of all the same orientation is argued to possess macroscopic transverse isotropy. An orthogonal basis for the linear subspace consisting of all double-symmetric transversely-isotropic fourth-order tensors associated with a given material vector is introduced and applied to deduce the explicit functional dependence of the compliance of such contrived materials on the shared crack orientation. A principle of superposition of strain rates is used to write the compliance for a more realistic material consisting of cracks of random size and orientation as an expectation integral of the transverse compliance for each orientation times the joint distribution function for the size and orientation. Utilizing an evolving (initially exponential) size- dependence in the joint distribution, the general theory gives unprecedented agreement with measurements of the dynamic response of alumina to impact loading, especially upon release where the calculations predict the development of considerable deformation- induced anisotropy, challenging the conventional notion of shocks as isotropic phenomena.
This paper describes the design, implementation and performance of a port of the Argonne National Laboratory/Mississippi State University MPICH implementation of the Message Passing Interface standard to the Cray T3D massively parallel processing system. A description of the factors influencing the design and the various stages of implementation are presented. Performance results revealing superior bandwidth and comparable latency as compared to other full message passing systems on the T3D are shown. Further planned improvements and optimizations, including an analysis of a port to the T3E, are mentioned.
Development of this pyrotechnic occurred because of the need for a static insensitive material to meet personnel safety requirements and related system safety issues in nuclear weapon energetic material component designs. Ti subhydride materials are made by the thermal dehydrding of commercial Ti hydride powder to the desired equivalent hydrogen composition in the Ti lattice. These Ti subhydrides, when blended with K perchlorate, meet the static insensitivity requirement of not being initiated from an equivalent human body electrostatic discharge. Individual material and blend qualification requirements provide a reproducible material from lot to lot. These pyrotechnic formulations meet the high reliability requirements (0.9995) for initiation and performance parameters and have the necessary stability and compatibility to meet long lived requirements of more than 25 years. Various experiences and problems are also discussed that have led to a mature technology for Ti subhydride/K perchlorate during its use in energetic material component designs.
SmartWeld is a concurrent engineering system that integrates product design and processing decisions within an electronic desktop engineering environment. It is being developed to provide designers, process engineers, researchers and manufacturing technologists with transparent access to the right process information, process models, process experience and process experts, to realize``right the first time`` manufacturing. Empirical understanding along with process models are synthesized within a knowledge-based system to identify robust fabrication procedures based on cost, schedule, and performance. Integration of process simulation tools with design tools enables the designer to assess a number of design and process options on the computer rather than on the manufacturing floor. Task models and generic process models are being embedded within user friendly GUI`s to more readily enable the customer to use the SmartWeld system and its software tool set without extensive training. The integrated system architecture under development provides interactive communications and shared application capabilities across a variety of workstation and PC-type platforms either locally or at remote sites.
Compared to other metrology approaches, electrical test structures for the measurement of dimensional characteristics such as linewidth and overlay directly relate to the electrical performance of the circuits being fabricated. The inherent disadvantage of electrical techniques is that they can be applied only to the extraction of the dimensions of features patterned in electrically-conducting materials. They can not be directly applied to patterned resist films or dielectric material layers. In the case of narrow on-wafer features patterned in resist, for example, linewidths are preferably extracted by electron-beam methods. These methods are sufficiently repeatable for monitoring fabrication-process variations. However, the traceability of the units in which linewidth is expressed is thwarted by the unavailability of suitable calibration artifacts. In the case of overlay metrology, the same limitations as regards electrical conduction apply. However, similar advantages accrue in principle to electrical overlay methods when they can be utilized. It is the electrical quality of the overlay of a conducting via relative to underlying or overlying conducting material which is of driving importance for circuit functionality. This may differ from the overlay values extracted from the same patterns by commonly-used optical overlay tools. Further refinements in the state of the art in both electrical linewidth and electrical overlay metrologies are desirable as feature sizes and spacings continue to shrink in emerging generations of devices. This paper discusses some recent innovations which have been recently introduced and indicates new roles for electrical metrology in low-cost certification of reference materials for both linewidth and overlay applications.
Dynamic compaction of mine-run salt is being investigated for the Waste Isolation Pilot Plant (WIPP), where compacted salt is being considered for repository sealing applications. One large-scale and two intermediate-scale dynamic compaction demonstrations were conducted. Initial fractional densities of the compacted salt range form 0.85 to 0.90, and permeabilities vary. Dynamically-compacted specimens were further consolidated in the laboratory by application of hydrostatic pressure. Permeability as a function of density was determined, and consolidation microprocesses were studied. Experimental results, in conjunction with modeling results, indicate that the compacted salt will function as a viable seal material.
As part of the demonstration of compliance with federal regulations, a shaft seal system has been designed for the Waste Isolation Pilot Plant. The system completely fills the 650 m shafts with components consisting of the common engineering materials, each of which possesses low permeability, longevity, and can be constructed using available technology. Design investigations couple rock mechanics and fluid flow analysis and tests of these materials within the natural geological setting, and demonstrate the effectiveness of the design.
Because many of the phenomenologically based codes used to support risk assessments require lone execution times, it is important to have a rationally based means for optimizing the choice of parameter values that are input to the code calculations. For this reason, we have developed a method for intelligently searching the space of parameter values to deduce, with as few computations as possible, the values that are most likely to lead to high risk. We have applied the method to a problem involving electrical initiation of an explosive due to the response of the system to fires. We have shown that our method can locate potential risk vulnerabilities with far fewer time-consuming physical response computations than would be necessary using standard sampling approaches.
The status of nuclear materials in both the U.S. and Former Soviet Union is changing based upon the execution of agreements relative to weapons materials production and weapon dismantlement. The result of these activities is that a considerably different emphasis is being placed on how nuclear materials are viewed and utilized. Even though much effort is being expended on the final disposition of these materials, the interim need for storage and security of the material is increasing. Both safety and security requirements exist to govern activities when these materials are placed in storage. These requirements are intended to provide confidence that the material is not being misused and that the storage operations are conducted safely. Both of these goals can be significantly enhanced if technological monitoring of the material is performed. This paper will briefly discuss the traditional manual methods of U.S. and international material monitoring and then present approaches and technology that are available to achieve the same goals under the evolving environment.
