We present results from searches for top quark production in p[bar p] collisions at the Tevatron collider based on an integrated luminosity of 7.5 pb[sup [minus]1] obtained during the 1992--1993 ran. The present results are confined to decay modes where both the top and anti-top quarks in the event decay semi-leptonically to the ee and e[mu] channels. A lower limit of 103 (99) GeV/c[sup 2] is obtained at 95% confidence level for the top quark mass from the absence of events consistent with standard model top quark decays with background subtraction (no background subtraction). We do however observe one event in the e[mu] channel which cannot be explained by the known backgrounds. While we make no claim that this event is due to top quark decay, it is not inconsistent with a top quark mass in the range 130--170 GeV/c[sup 2]

This brief paper discusses factors that must be considered when defining the [open quotes]normal[close quotes] (as opposed to [open quotes]extreme[close quotes]) loading conditions seen in wind turbines operating within a wind park environment. The author defines the [open quotes]normal[close quotes] conditions to include fatigue damage accumulation as a result of: (1) start/stop cycles, (2) emergency shutdowns, and (3) the turbulence environment associated with site and turbine location. He also interprets [open quotes]extreme[close quotes] loading conditions to include those events that can challenge the survivability of the turbine.

Measurements of jet rates in deep-inelastic muon scattering are presented. The JADE algorithm is used to define jets in the kinematic region 9 < W < 33 GeV. Data taken on a proton target are analyzed within the QCD framework, with the goal of extracting [alpha][sub s]. Results on the Q[sup 2] dependence of the average transverse momentum of jets are used to demonstrate the running of the strong coupling constant [alpha][sub s]. In addition, first measurements of the production of jets from heavy nuclei in the region x[sub B[sub j]] > 0.001 are discussed. Initial results indicate a suppression in the rate of two forward jets in carbon, calcium and lead as compared to deuterium. All results presented are preliminary.

Experiment 789 at Fermilab used the high-rate E605/E772 spectrometer to study low-multiplicity charm and beauty decays. Preliminary results on charm and beauty production are presented based on analysis of [approx] 100% of the charm data and [approx] 50% of the beauty data. A new experiment is proposed to improve charm and beauty sensitivity by several orders of magnitude.

This paper describes a sensor system architecture suitable for application in systems intended for battery powered unattended use. The modularity concept addresses the logical interconnects between modules, the electrical interconnects between modules, and a system for the generalization of data to permit modular processing.

Much progress has been made recently in characterizing the emission from neon-like Yttrium exploding foil x-ray lasers at Lawrence Livermore National Laboratory. Concomitant with that effort, we have carried out detailed modeling to enhance our understanding of the experiments and improve their design. Our modeling includes target hydrodynamics, calculation of gain, and both ray and wave optics propagation. We will describe our modeling of Yt x-ray lasers, including first simulations using a two transverse dimensional gain calculation. Our calculations indicate that the time-integrated signal is very sensitive to the time history of the gain, because of the rapid sweep of the beam in angle measured with respect to the plane of the foil. We have found that better agreement with experiment is achieved if the falloff of the gain with time is made slightly faster than our codes predict. In the vertical direction (normal to exploding foil direction), the experimental beam pattern is typically broader than we calculate. We find that ray and wave optics calculations are in good agreement. The coherence length obtained by a wave optics calculation is larger than seen in experiments; tills is probably due to fluctuations and/or the smooth variation of the pump laser line …

The Advanced Neutron Source is a major new research facility proposed by the Department of Energy for construction over the next six years. The unique set of nuclear safety features selected to give the recently completed conceptual design a high degree of safety are identified and discussed.

In this study, we limited our questions to ORNL, discussing their models with almost a dozen staff members from four divisions. We collected some low-level data about the models, and also tried to gain a sense of the philosophy of the modeler, and how each model fit into the larger perspective of ORNL`s and the scientific community`s efforts. Time and budget prevented us from conducting any larger study, but we have no reason to suppose that conclusions about ORNL`s models and modelers could not be extended to the larger scientific community.

The characteristics of pulsed laser ablation for epitaxial film growth are reviewed. New developments in the growth of heteroepitaxial multilayers, stabilization of metastable phases, and growth of semiconductor alloys with continuously variable composition, are described.

Helium refrigerator performance degrades rapidly when it has to handle a varying or pulsed heat load. A novel scheme is presented to handle highly pulsed 4.5 K cryogenic loads with a standard helium refrigerator by isolating it from these pulses. The scheme uses a relatively simple arrangement of control valves, heat exchangers, and a storage dewar. Applications include pulsed tokamak machines such as TPX (Tokamak Physics Experiment) and ITER (International Thermonuclear Experimental Reactor). For example, the TPX (currently in the conceptual design phase in a DoE contract) requires an average 4.5 K refrigerator capacity of about 10 kW; however, pulsed loads caused by eddy current and nuclear heating will exceed 100 kW. The scheme presented here provides a method for handling these pulsed loads. Because of the simple and proven nature of the components involved and the thermodynamic properties of the helium, the system could be implemented for projects such as TPX or ITER with little or no development.

Superlattices composed of YBa{sub 2}CU{sub 3}O{sub 7} and PrBa{sub 2}Cu{sub 3}O{sub 7} have been studied extensively experimentally and several theoretical attempts to correlate the resistivity as a function of temperature with the superlattice structure have appeared in the literature. The theoretical interest in such structures comes about primarily because of insight into dimensionality effects, interlayer coupling, and interlayer charge redistribution in high-T {sub c}, superconductors. On the experimental side, there are possibilities for device applications that are just now beginning to be explored. After an overview of the experimental work and a discussion of charge transfer calculations, a description of how the experimental data can be explained using a model that incorporates Kosterlitz-Thouless (vortex-antivortex unbinding) and Azlamazov-Larkin (fluctuation-enhanced conductivity) theories in the resistive transition region and charge-transfer effects, variable-range hopping, etc. in the normal state. Difficulty in disentangling charge transfer and dimensionality effects in determining the nominal transition temperature is pointed out and other mechanisms that influence the width of the resistive transition are considered.

X-ray Absorption Spectroscopy (XAS) of the Rare Earth (RE) 3d levels yields sharp peaks near the edges as a result of strong, quasi-atomic 3d{sup 10}4f{sup n} {yields} 3d-{sup 9}4f{sup n+1} transitions and these transitions exhibit a wealth of spectroscopic features. The XAS measurements of single crystal REPO{sub 4} (RE = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er) at the 3d edge were performed in the total yield mode at beam line 8-2 at the Stanford Synchrotron Radiation Laboratory (SSRL). The XAS spectra of the RE ions in the orthophosphate matrix generally resemble the XAS of the corresponding RE metal. This is not unexpected and emphasizes the major contribution of the trivalent state to the electronic transitions at the RE 3d edges. These spectra unequivocally identify the transitions originating from well-characterized RE cores and correlate well with previous theoretical investigations.

The Remote Area Monitoring System was developed by Los Alamos National Laboratory (LANL) for DOE test directors at the Nevada Test Site (NTS) to verify radiological conditions are safe after a nuclear test. In the unlikely event of a venting as a result of a nuclear test, this system provides radiological and meteorological data to Weather Service Nuclear Support Office (WSNSO) computers where mesoscale models are used to predict downwind exposure rates. The system uses a combination of hardwired radiation sensors and satellite based data acquisition units with their own radiation sensors to measure exposure rates in remote areas of the NTS. The satellite based data acquisition units are available as small, Portable Remote Area Monitors (RAMs) for rapid deployment, and larger, Semipermanent RAMs that can have meteorological towers. The satellite based stations measure exposure rates and transmit measurements to the GOES (Geostationary Operational Environmental Satellite) where they are relayed to Direct Readout Ground Stations (DRGS) at the NTS and Los Alamos. Computers process the data and display results in the NTS Operations Coordination Center. Los Alamos computers and NTS computers are linked together through a wide area network, providing remote redundant system capability. Recently, LANL, expanded the system to …

Advantage of STEM is that no model structures are required to interpret the images to first order, so that unexpected interfacial phenomena will be immediately apparent, such as in CoSi{sub 2}/Si(100) interface made by Co implantation/annealing. By depositing two monolayer Ge marker layers during growth of Si{sub 0. 5}Ge{sub 0.5} alloy layer, a misfit dislocation was found to nucleate to relieve the strain. Hole concentration profiles can be measured in YBCO superconductor, using the pre-edge of the oxygen K EELS spectrum. Future directions of this combination of atomic-resolution imaging and analysis on a single microscope are discussed briefly.

High-order harmonic generation from atoms and ions cuts off in accord with the simple rule: E{sub c} {approximately} I{sub p} + 3U{sub p}. This cutoff rule as well as the lack of a cutoff in high- order electron energy spectra can be understood via a simple extension of existing two step quasi-classical models.

These presentations from the June 1993 quarterly meeting cover He-3 target/blanket design, experiment status, and accelerator design. For the helium targets: physics, mechanical design and safety, engineering support, and tritium processing are described. Materials and thermal-hydraulics of planned experiments are discussed. For the overall accelerator design: accelerator physics, engineering, rf power systems, power conditioning, beam transport and beam stops, operations and safety are outlined. Also, site layout and containment considerations are made.

Cu/Cu-Zr multilayer foils were fabricated and indented to determine the degree to which multilayer hardness is enhanced by increasing the volume fraction of the harder phase. Using sputter deposition and thermal processing a series of foils was fabricated in which the thicknesses of the Cu layers remained fixed while the thicknesses of the alternate Cu-Zr layers varied. These samples were then indented both parallel and normal to their layering. In general hardness increased as the volume fraction of the harder Cu-Zr phase rose. When the films were loaded parallel to their layering, the measured hardnesses were higher and the dependencies on volume fraction of the Cu-Zr phase were stronger than when the films were loaded nominal to their layering. These results agree with predictions based on isostress and isostrain theories. The relations between hardness and volume fraction are used to compare the hardnesses of the Cu-Zr phases: amorphous Cu-Zr, Cu{sub 51}Zr{sub 14} and Cu{sub 9}Zr{sub 2}, and to show that the hardness of the textured, as-deposited Zr layers is highly anisotropic.

Munitions materials can accumulate or cycle in terrestrial environs at production and manufacturing facilities and thus pose potential heath and environmental concerns. To address questions related to food chain accumulation, the environmental behavior of energetic compounds (2,4,6-trinitrotoluene,TNT; hexahydro-1,3,5-trinitro-1,3,5-triazine, RDX; 2,4,6-trinitrophenylmethylnitramine, tetryl) was evaluated. Emphasis was placed on determining the potential for soil/plant transfer of munitions residues, translocation and distribution within the plant, the extent to which compounds were metabolized following accumulation, and the chemical nature and form of accumulated residues. Both TNT and tetryl undergo extensive chemical transformation in soil, forming aminodinitrotoluene isomers and N-methyl-2,4,6-trinitroaniline residues, respectively, along with a series of unknowns. After 60 days, only 30% of the amended TNT and 8% of the amended tetryl remained unchanged in the soil. In contrast, 78% of the soil-amended RDX remained unchanged after 60 days. After 60 days, plants grown in soils containing 10 ppm residues contained from 5 {mu}g TNT/g to 600 {mu}g RDX/G fresh wt. tissue. TNT and tetryl residues were primarily accumulated in roots (75%), while RDX was concentrated in leaves and seed. The principal transport form for TNT (root to shoot) was an acid labile conjugate of aminodinitrotoluene; RDX was transported unchanged. On accumulation in roots …

We present tests of the flavor independence of strong interactions via preliminary measurements of the ratios {alpha}{sub s}/{sub alpha}{sub s}(udsc) and {alpha}{sub s}(uds)/{alpha}{sub s}(bc) using data collected by the SLD experiment at SLAC during the 1992 SLD/SLC run. In addition, we have measured the difference in charged particle multiplicity between Z{sup 0} {yields} b{bar b} and Z{sup 0} {yields} u{bar u}, d{bar d}, s{bar s} events, and find that it supports the prediction of perturbative QCD that the multiplicity difference be independent of center-of-mass energy. We have also made a preliminary study of jet polarization and find, using a charge-signed definition, a small net handedness in our sample of hadronic jets.

The authors report the results of a high-resolution Electron-Energy Loss Spectroscopy (EELS) investigation of Be(0001) surface. Two dispersive surface vibrational modes are observed in the {bar {Gamma}} to {bar M} direction: a sagittal-plane mode (the Rayleigh wave) and a shear horizontal mode. They have compared their experimental results to a 300-layer slab calculation and to a semi-infinite Green`s function calculation of Sameth and Mele. Compared with the experimental results, both calculations predict a higher energy for the Rayleigh wave and lower energy for the shear horizontal mode. These results are consistent with stronger in-plane bonding and weaker interplanar bonding at the surface, in accord with other theoretical predictions.

This report discusses the scientific and economic feasibility of fusion energy, especially in regards to the tokamak reactor.

Global warming is likely to result in a variety of environmental effects ranging from impacts on species diversity, changes in population size in flora and fauna, increases in sea level and possible impacts on the primary productivity of the sea. Potential impacts on human health and welfare have included possible increases in heat related mortality, changes in the distribution of disease vectors, and possible impacts on respiratory diseases including hayfever and asthma. Most of the focus thus far is on effects which are directly related to increases in temperature, e.g., heat stress or perhaps one step removed, e.g., changes in vector distribution. Some of the more severe impacts are likely to be much less direct, e.g., increases in migration due to agricultural failure following prolonged droughts. This paper discusses two possible approaches to the study of these less-direct impacts of global warming and presents information from on-going research using each of these approaches.

We review many of the recently developed applications of Heavy Quark Effective Theory techniques. After a brief update on Luke`s theorem, we describe striking relations between heavy baryon form factors, and how to use them to estimate the accuracy of the extraction of {vert_bar}V{sub cb}{vert_bar}. We discuss factorization and compare with experiment. An elementary presentation, with sample applications, of reparametrization invariance comes next. The final and most extensive chapter in this review deals with phenomenological lagrangians that incorporate heavy-quark spin-flavor as well as light quark chiral symmetries. We compile many interesting results and discuss the validity of the calculations.

Imaging optics in a soft x-ray projection lithography (SXPL) system must meet stringent requirements to achieve high throughput and diffraction limited performance. Errors in the surface figure must be kept to less than {approximately}1 nm and the rms surface roughness must be less than 0.1 nm. The ML coatings must provide high reflectivity (> 60%) at wavelengths in the vicinity of 13 nm. The reflectivity bandpasses of the optics must be aligned within 0.05 nm. Each coating must be uniform across the surface of the optic to within 0.5%. These specifications challenge the limits of the current capabilities in optics fabrication and ML deposition. Consequently a set of qualified SXPL imaging optics is expected to be expensive, costing in the range of 100--250 k$. If the lifetime of the imaging optics is short, the replacement cost could significantly impact the economic competitiveness of the technology. The most likely failure modes for the imaging optics are mechanisms that degrade the ML coatings, but which leave the substrates intact. A potentially low cost solution for salvaging the imaging optics could be to strip the damaged ML coating to recover the substrate and then deposit a new coating. In this paper the authors …