An environmental assessment was conducted to estimate potential impacts or consequences associated with constructing and operating the proposed National Ignition Facility (NIF). The multidisciplinary assessment covered topics ranging from radiological and chemical health and safety to socioeconomic and land-use issues. The impacts of five chemical accidents that could occur at NIF are compared, and the extent of their consequences for workers and off-site populations are discussed. Each of the five accident scenarios was modeled by a chemical release and dispersion model with a toxicological criterion for evaluating potential irreversible human health effects. Results show that most of the chemical release scenarios considered will not impair the general public in taking protective actions in the event of an accidental release. The two exceptions are the mercury release (equipment failure) scenarios for the conceptual design and the enhanced design. In general, the predicted maximum threat zones are significantly less than the distance to the point of nearest public access.

We propose a simple, physically oriented model that explains important characteristics of cyclic combustion variations in spark-ignited engines. A key model feature is the interaction between stochastic, small-scale fluctuations in engine parameters and nonlinear deterministic coupling between successive engine cycles. Prior-cycle effects are produced by residual cylinder gas which alters volume-average in-cylinder equivalence ratio and subsequent combustion efficiency. The model`s simplicity allows rapid simulation of thousands of engine cycles, permitting in-depth statistical studies of cyclic variation patterns. Additional mechanisms for stochastic and prior-cycle effects can be added to evaluate their impact on overall engine performance. We find good agreement with our experimental data.

Interactions between structural defects and metallic impurities were studied in multicrystalline silicon for solar cells applications. The objective was to gain insight into the relationship between solar cell processing, metallic impurity behavior and the resultant effect on material/device performance. With an intense synchrotron x-ray source, high sensitivity x-ray fluorescence measurements were utilized to determine impurity distributions with a spatial resolution of {approx} 1{micro}m. Diffusion length mapping and final solar cell characteristics gauged material/device performance. The materials were tested in both the as-grown state and after full solar cell processing. Iron and nickel metal impurities were located at structural defects in as-grown material, while after solar cell processing, both impurities were still observed in low performance regions. These results indicate that multicrystalline silicon solar cell performance is directly related to metal impurities which are not completely removed during typical processing treatments. A discussion of possible mechanisms for this incomplete removal is presented.

A description of the new ARAC-3 (Atmospheric Release Advisory Capability) modeling system is presented. Among the major new capabilities are a prognostic forecast model and entirely new diagnostic and dispersion models. Various components of the system are being tested to determine their performance both individually and within an integrated setting. When completed in 1999, ARAC-3 will contain all the features of the current ARAC-2 system as well as new capabilities that will enable ARAC to function as a state-of-the-art emergency response system well into the next decade.

Interconnect delays, arising in part from intralevel capacitance, are one of the limiting factors in the performance of advanced integrated circuits. In addition, the problem of filling the spaces between neighboring metal lines with an insulator is becoming increasingly severe as aspect ratios increase. We address these problems by intentionally creating a air gap between closely spaced metal lines. The ends of the air gap and reentrant features are then sealed using a spin on dielectric. The entire structure is then capped with silicon dioxide and planarized . Simple modeling of mechanical test structures on silicon predicts an equivalent dielectric constant of 1.9 on features similar to those expected for 0.25 micron technologies. Metal to metal test structures fabricated in a 0.5 micron CMOS technology show that the process can be readily integrated with chemical mechanical polishing and current standard CMOS processes.

We present recent results of searches for new particles beyond the Standard Model at the Collider Detector at Fermilab (CDF). These include searches for supersymmetric (SUSY) particles, charged Higgs, heavy gauge bosons (Z{prime} and W{prime}), and stable massive charged particles. 19 refs., 12 figs.

D{null} has measured the top quark mass using a sample of 32 single- lepton events selected from approximately 115 pb{sup -1} of {radical}s = 1.8 TeV {ital p}{ital {anti p}} collisions collected from 1992-1996. The result is {ital m}{sub t} = 169 {+-} 8({ital stat}){+-} 8 ({ital syst}) GeV/c{sup 2}. Using a sample of 3 {ital e{mu}} events, D{null} measures {ital m}{sub t} = 158 {+-} 24({ital stat}) {+-} 10({ital syst}) GeV/c{sup 2}.

This workshop was convened to explore what is currently being done in the area of data dissemination via the Internet and to examine ways that future activities in this area within the U.S. nuclear data programs can be better coordinated. Overview talks on the current status, from both the national and international perspectives, were provided. Following these, there were presentations on specific activities in the area of Internet data dissemination which are taking place at seven different institutions. Institutions represented at this meeting were asked to provide written summaries of their programs before the meeting. The talks included actual demonstrations of the electronic methodologies which are under development at these laboratories, and they highlighted the richness and creativity of these programs. This information proved to be very useful in the ensuing general discussions. The main issues that were addressed at this meeting were: (i) how to adapt to rapid evolution of data management and dissemination technologies, (ii) how to provide outside users with some sense of unity in the U.S. nuclear data program and to develop consistent, user-friendly ways to access data without discouraging individual initiatives and the richness which comes from diversity, (iii) how to maintain quality control over …

Thermal management, resonance control, and reliability requirements become predominant when designing ``conventional`` copper coupled- cavity linac (CCL) structures for very high duty factors and accelerating fields. Whereas the outer body of the coupled-cavity drift-tube linac (CCDTL) is in most ways comparable to the CCL, the cooling and support of the added drift tubes present totally new and interesting challenges. Making provisions to limit thermal distortion calls for many cooling passages, high quality materials, and new fabrication schemes and techniques. Thermal designs for a 700 MHz linac are presented, along with results of prototype tests and fabrication developments which offer solutions to all of these problems.

Recent electroweak precision measurements fro {ital e}{sup +}{ital e}{sup -} and {ital p{anti p}} colliders are presented. Some emphasis is placed on the recent developments in the heavy flavor sector. The measurements are compared to predictions from the Standard Model of electroweak interactions. All results are found to be consistent with the Standard Model. The indirect constraint on the top quark mass from all measurements is in excellent agreement with the direct {ital m{sub t}} measurements. Using the world`s electroweak data in conjunction with the current measurement of the top quark mass, the constraints on the Higgs` mass are discussed.

This paper addresses the problem of improving detection, assessment, and response capabilities of security systems. Our approach combines two state-of-the-art technologies: volumetric video motion detection (VVMD) and virtual reality (VR). This work capitalizes on the ability of VVMD technology to provide three-dimensional (3D) information about the position, shape, and size of intruders within a protected volume. The 3D information is obtained by fusing motion detection data from multiple video sensors. The second component involves the application of VR technology to display information relating to the sensors and the sensor environment. VR technology enables an operator, or security guard, to be immersed in a 3D graphical representation of the remote site. VVMD data is transmitted from the remote site via ordinary telephone lines. There are several benefits to displaying VVMD information in this way. Because the VVMD system provides 3D information and because the sensor environment is a physical 3D space, it seems natural to display this information in 3D. Also, the 3D graphical representation depicts essential details within and around the protected volume in a natural way for human perception. Sensor information can also be more easily interpreted when the operator can `move` through the virtual environment and explore the …

Advances in parallel supercomputing now make possible molecular-based engineering and science calculations that will soon revolutionize many technologies, such as those involving polymers and those involving aqueous electrolytes. We have developed a suite of message-passing codes for classical molecular simulation of such complex fluids and amorphous materials and have completed a number of demonstration calculations of problems of scientific and technological importance with each. In this paper, we will focus on the molecular simulation of rheological properties, particularly viscosity, of simple and complex fluids using parallel implementations of non-equilibrium molecular dynamics. Such calculations represent significant challenges computationally because, in order to reduce the thermal noise in the calculated properties within acceptable limits, large systems and/or long simulated times are required.

We have measured gain and saturation in sing;e mode Yb:silica fiber, and developed fiber lasers and amplifiers at 1053 nm. The lasers are tunable over 10`s of nanometers, with amplifier gain flattened by fiber gratings or dielectric filters.

Newspaper article from The Houston Chronicle, discussing new evidence uncovered about the beginning of the Holocaust in 1941.

A Fission Track Analysis (FTA) method for assessing 239Pu in urine samples was first developed at Brookhaven National Laboratory (BNL) in 1988; it then had a detection limit of 100 aCi (3.7 {micro}Bq). Since that time, several steps were introduced that increased chemical recovery and lowered the detection limit to less than 1O aCi per sample. These improvements include a process of micro-column separation of plutonium in the final stages. The improved FTA method was applied to 22 urine samples from male staff at BNL. The results showed that 239Pu from fallout excreted in urine was 33 +/- 11 aCi (1.2 {micro}Bq) per day.

Recent advances in compound semiconductor technology utilize a variety of metal thin films fabricated by thermal and electron-beam evaporation, and electroplating. An overview of metal processes used by Sandia`s Compound Semiconductor Research Laboratory is presented. Descriptions of electrical n-type and p-type ohmic contact alloys, interconnect metal, and metal layers specifically included for packaging requirements are addressed. Several illustrations of devices incorporating gold plated air bridges are included. ``Back-end`` processes such as flip-chip under bump metallurgy with fluxless solder reflow and plated solder processes are mentioned as current research areas.

Fast and thermal neutron activation analysis with sealed neutron generators has been used to detect oil (oil logging), hazardous waste, fissile material, explosives, and contraband (drugs). Sealed neutron generators, used in the above applications, must be small and portable, have good electrical efficiency and long life. The ion sources used in the sealed neutron tubes require high gas utilization efficiencies or low pressure operation with high ionization efficiencies. In this paper, the authors compare a number of gas ion sources that can be used in sealed neutron tubes. The characteristics of the most popular ion source, the axial Penning discharge will be discussed as part of the zetatron neutron generator. Other sources to be discussed include the SAMIS source and RF ion source.

The US Department of Energy`s Atmospheric Release Advisory Capability (ARAC) provides real-time dose assessments of airborne pollutant releases. Diverse data assimilation techniques are required to meet the needs of a new generation of ARAC models and to take advantage of the rapidly expanding availability of meteorological data. We are developing a hierarchy of algorithms to provide gridded meteorological fields which can be used to drive dispersion codes or to provide initial fields for mesoscale models. Data to be processed include winds, temperature, moisture, and turbulence.

Based on a mixed variational principle and the finite element method, a model for efficiently generating mass-consistent wind fields over continuous terraing has been developed. Two numerical examples are presented to demonstrate the applicability of the model.