Six different techniques were used to delineate 40 year old trench boundary at Los Alamos National Laboratory. Data from historical aerial photographs, a magnetic gradient survey, airborne multispectral and thermal infra-red imagery, seismic refraction, DC resistivity, and total field magnetometry were utilized in this process. Each data set indicated a southern and northern edge for the trench. Average locations and 95% confidence limits for each edge were determined along a survey line perpendicular to the trench. Trench edge locations were fairly consistent among all six techniques. Results from a modeling effort performed with the total magnetic field data was the least consistent. However, each method provided unique and complementary information, and the integration of all this information led to a more complete characterization of the trench boundaries and contents.

We review the differences in first order phase transition of single and multi-component systems, and then discuss the crystalline structure expected to exist in the mixed confined deconfined phase of hadronic matter. The particular context of neutron stars is chosen for illustration. The qualitative results are general and apply for example to the vapor-liquid transition in subsaturated asymmetric nuclear matter.

The theory and experimental approach for a new technique used to determine the Poisson`s ratio of thin films are presented. The method involves taking the ratio of curvatures of cantilever beams and plates micromachined out of the film of interest. Curvature is induced by a through-thickness variation in residual stress, or by depositing a thin film under residual stress onto the beams and plates. This approach is made practical by the fact that the two curvatures air, the only required experimental parameters, and small calibration errors cancel when the ratio is taken. To confirm the accuracy of the technique, it was tested on a 2.5 {mu}m thick film of single crystal silicon. Micromachined beams 1 mm long by 100 {mu} wide and plates 700 {mu}m by 700 {mu}m were coated with 35 nm of gold and the curvatures were measured with a scanning optical profilometer. For the orientation tested ([100] film normal, [011] beam axis, [0{bar 1}1] contraction direction) silicon`s Poisson`s ratio is 0.064, and the measured result was 0.066 {+-} 0.043. The uncertainty in this technique is due primarily to variation in the measured curvatures, and should range from {+-} 0.02 to 0.04 with proper measurement technique.

Supernova 1987A focused attention on the critical role of hydrodynamic instabilities in the evolution of supernovae. To test the modeling of these instabilities we are developing laboratory experiments of hydrodynamic mixing under conditions relevant to supernovae. The target consists of two-layer planar package composed on 85 micron Cu backed by 500 micron CH2, having a single mode sinusoidal perturbation at the interface, with gamma = 200 microns, nuo + 20 microns. The Nova laser is used to generate a 10-15 Mbar (10- 15x10{sup 12} dynes/cm2) shock at the interface, which triggers perturbation growth, due to the Richtmyer-Meshov instability followed by the Raleigh-Taylor instability as the interface decelerates. This resembles the hydrodynamics of the He-H interface of a Type II supernova at the intermediate times, up to a few x10{sup 3} s. The experiment is modeled using the hydrodynamic codes HYADES and CALE, and the supernova code PROMETHEUS. We are designing experiments to test the differences in the growth of 2D vs 3D single mode perturbations; such differences may help explain the high observed velocities of radioactive core material in SN1987A. Results of the experiments and simulations are presented.

The Li(Si)/FeS{sub 2} and Li(Si)/CoS{sub 2} couples were evaluated with a low-melting LiBr-KBr-LiF eutectic and all-Li LiCl-LiBr-LiF electrolyte for a battery application that required both high energy and high power for short duration. Screening studies were carried out with 1.25 inch-dia. triple cells and with 10-cell batteries. The Li(Si)/LiCl-LiBr-LiF/CoS{sub 2} couple performed the best under the power load and the Li(Si)/LiCl-LiBr-LiF/FeS{sub 2} was better under the energy load. The former system was selected as the best overall performer for the wide range of temperatures for both loads, because of the higher thermal stability of CoS{sub 2}.

This paper will concentrate on the progression of the bioassay and dose evaluation programs at Savannah River Site.

Vertical cavity surface emitting laser (VCSEL) sources have been adopted into Gigabit Ethernet applications in a remarkably short time period. VCSELs are particularly suitable for multimode optical fiber local area networks (LANs), due to their reduced threshold current, circular output beam, and inexpensive and high volume manufacture. Moreover, selectively oxidized VCSELs are nearly ideal LAN sources since the oxide aperture within the laser cavity produces strong electrical and optical confinement which enables high electrical to optical conversion efficiency and minimal modal discrimination allowing emission into multiple transverse optical modes. In addition to the large demand for multimode lasers, VCSELs which emit into a single optical mode are also increasingly sought for emerging applications, which include data communication with single mode optical fiber, bar code scanning, laser printing, optical read/write heads, and modulation spectroscopy. To achieve single mode selectively oxidized VCSELs is a challenging task, since the inherent index confinement within these high performance lasers is very large.

A new method for measuring the wavelength dependence of the transit time, material dispersion, and attenuation of an optical fiber is described. The authors inject light from a 4-ns risetime pulsed broad-band flashlamp into various length fibers and record the transmitted signals with a time-resolved spectrograph. Segments of data spanning an approximately 3,000 {angstrom} range are recorded from a single flashlamp pulse. Comparison of data acquired with short and long fibers enables the determination of the transit time and the material dispersion as functions of wavelength dependence for the entire recorded spectrum simultaneously. The wavelength dependent attenuation is also determined from the signal intensities. The method is demonstrated with experiments using a step index 200-{micro}m-diameter SiO{sub 2} fiber. The results agree with the transit time determined from the bulk glass refractive index to within {+-} 0.035% for the visible (4,000--7,200 {angstrom}) spectrum and 0.12% for the ultraviolet (2,650--4,000 {angstrom}) spectrum, and with the attenuation specified by the fiber manufacturer to within {+-} 10%.

The impressive performance improvements of laterally oxidized VCSELs come at the expense of increased fabrication complexity for 2-dimensional arrays. Since the epitaxial layers to be wet-thermally oxidized must be exposed, non-planarity can be an issue. This is particularly important in that electrical contact to both the anode and cathode of the diode must be brought out to a package. They have investigated four fabrication sequences suitable for the fabrication of 2-dimensional VCSEL arrays. These techniques include: mesa etched polymer planarized, mesa etched bridge contacted, mesa etched oxide isolated (where the electrical trace is isolated from the substrate during the oxidation) and oxide/implant isolation (oxidation through small via holes) all of which result in VCSELs with outstanding performance. The suitability of these processes for manufacturing are assessed relative to oxidation uniformity, device capacitance, and structural ruggedness for packaging.

Previously, an effective index optical model was introduced for the analysis of lateral waveguiding effects in vertical-cavity surface-emitting lasers. The authors show that the resultant transverse equation is almost identical to the one typically obtained in the analysis of dielectric waveguide problems, such as a step-index optical fiber. The solution to the transverse equation yields the lateral dependence of the optical field and, as is recognized in this paper, the discrete frequencies of the microcavity modes. As an example, they apply this technique to the analysis of vertical-cavity lasers that contain thin-oxide apertures. The model intuitively explains the experimental data and makes quantitative predictions in good agreement with a highly accurate numerical model.

The authors report preliminary results from a study of {Lambda}{sup 0} polarization in the exclusive reaction pp {r_arrow} p{sub f} ({Lambda}{sup 0} K{sup +}) at 800 GeV/c. These data are a part of the 5 x 10{sup 9} diffractive event sample collected by Fermilab E690. They observe a large dependence of the polarization on the {Lambda}{sup 0} K{sup +} invariant mass. This observation confirms the result of the CERN ISR R608 experiment and extends the range over which the effect is observed.

Shock loading techniques are often used to determine material response along a specific pressure loading curve referred to as the Hugoniot. However, many technological and scientific applications require accurate determination of dynamic material response that is off-Hugoniot, covering large regions of the equation-of-state surface. Unloading measurements from the shocked state provide off-Hugoniot information, but experimental techniques for measuring compressive off-Hugoniot response have been limited. A new pulsed magnetic loading technique is presented which provides previously unavailable information on isentropic loading of materials to pressures of several hundred kbar. This smoothly increasing pressure loading provides a good approximation to the high-pressure material isentrope centered at ambient conditions. The approach uses high current densities to create ramped magnetic loading to a few hundred kbar over time intervals of 100--200 ns. The method has successfully determined the isentropic mechanical response of copper to about 200 kbar and has been used to evaluate the kinetics of the alpha-epsilon phase transition occurring in iron at 130 kbar. With refinements in progress, the method shows promise for performing isentropic compression experiments to multi-Mbar pressures.

Post-growth thermal annealing effects on InAs/GaAs quantum dots (QDs) near Stransky-Krastanow transformation were investigated. Self-assembled QDs of average size of about 10 nm were grown by metal organic vapour phase epitaxy. The photoluminescence (PL) due to emission from QDs as well as two peaks due to emission from the strained InAs wetting layer (WL) were observed in as-grown samples. Bimodal structure of the WL PL was attributed to WL regions of different thickness. There was almost no difference in the PL spectrum after 30 s annealing at 600 C. However, annealing at temperatures in the range between 700 C and 950 C resulted in quenching of the PL from QDs and the thinner WL. The PL peak from the new, thicker WL blue-shifted and narrowed with increasing annealing temperature. This behavior was in agreement with TEM observations. Complete dissolution of the QDs and substantial broadening of the WL was observed. All our results indicate that thermally induced modifications of the WL rather than QDs can be responsible for the blue-shift and narrowing of the PL peaks in structures containing InAs QDs.

Visapult is a prototype application and framework for remote visualization of large scientific datasets. We approach the technical challenges of tera-scale visualization with a unique architecture that employs high speed WANs and network data caches for data staging and transmission. This architecture allows for the use of available cache and compute resources at arbitrary locations on the network. High data throughput rates and network utilization are achieved by parallelizing I/O at each stage in the application, and by pipe-lining the visualization process. On the desktop, the graphics interactivity is effectively decoupled from the latency inherent in network applications. We present a detailed performance analysis of the application, and improvements resulting from field-test analysis conducted as part of the DOE Combustion Corridor project.

Post-growth thermal annealing effects on InAs/GaAs quantum dots (QDs) near Stransky-Krastanow transformation were investigated. Self-assembled QDs of average size of about 10 nm were grown by metal-organic vapor phase epitaxy. The photoluminescence (PL) due to emission from QDs as well as two peaks due to emission from the strained InAs wetting layer (WL) were observed in as-grown samples. Bimodal structure of the WL PL was attributed to WL regions of different thickness. There was almost no difference in the PL spectrum after 30 s annealing at 600 C. However, annealing at temperatures in the range between 700 C and 950 C resulted in quenching of the PL from QDs and the thinner WL. The PL peak from the new, thicker WL blue-shifted and narrowed with increasing annealing temperature. This behavior was in agreement with TEM observations. Complete dissolution of the QDs and substantial broadening of the WL was observed. All our results indicate that thermally induced modifications of the WL rather than QDs can be responsible for the blue-shift and narrowing of the PL peaks in structures containing InAs QDs.

Soft proton-antiproton interactions are selected from events collected with the CDF minimum-bias trigger at {radical}(s) = 1800 and 630 GeV. The analysis of their properties compared at the two energies reveals important and unexpected invariances. This paper describes an attempt to address the problem and the study of the properties of genuine soft interactions. These are identified as a subsample of proton antiproton interactions collected with the CDF minimum bias trigger. In the analysis a splitting procedure of the full minimum bias sample in two subsamples, one highly enriched in soft interactions and the other enriched in hard interactions, is applied. The two subsamples are analyzed separately through the compared measures of some inclusive distributions and final state correlations at different c.m.s. energies. The results evidence some interesting unobserved properties of the isolated soft sample and, in particular, a remarkably unpredicted invariance of some of the measured correlations and spectra between 630 and 1800 GeV.

A thin metallic beam pipe reinforced by multi-layer spiral metallic ribs is proposed for rapid cycling proton synchrotrons. The pipe is made of Inconel 718 with thickness of a few tenths of mm. Each spiral rib has a cross section of about 0.3 mm{sup 2} and can be bonded to the pipe by using laser deposition technique (e.g., precision metal deposition, or PMD). Compared with other designs (e.g., ceramic beam pipe with a metallic cage used in the ISIS at the RAL), this new pipe will reduce the magnet aperture significantly, which, in turn, reduces the construction and operating cost of a synchrotron. Numerical simulations and analytical modeling are used to investigate the structural strength and deformation, and the eddy current effects, including heating, magnetic field distortion and the electro-magnetic force on the beam pipe. The results show that this new beam pipe will work. It can be employed to high intensity rapid cycling proton synchrotrons, such as the proton driver at FERMILAB and the JHF at JAERI/KEK. Effort to build a prototype is under way.

There are many options for the handling and storage of spent nuclear fuel from naval vessels. This paper summarizes the options that are available and explores the issues that are involved. In many cases choices have been made, not on the basis of which is the best engineering solution or the most cost-effective, but based on the political realities involved. For example, currently it seems that the most prevalent solution for spent fuel interim storage is in dual-purpose (transport-storage) casks. These casks are robust and, politically, they offer the visible evidence that the fuel is ''road-ready'' to be moved from the local area where the fuel is being stored in the interim. However, dual-purpose casks are the most expensive of the storage mediums. Drywell storage (storage in below grade or bermed pipes), on the other hand, the least expensive and most flexible storage option, suffers from an image of permanence (not politically acceptable) and from being improperly implemented in the past. Though these issues are easily resolved from a technical perspective, the option is often not seriously considered because of this past history. It wasn't too many years ago that spent fuel pools were the storage medium of choice. The …

This paper describes a study undertaken to explain the risk profile differences in the results of PRAs of two similar WER-1000 nuclear power plants. The risk profile differences are particularly significant in the area of small steam/feedwater line breaks, small-small LOCAs, support system initiators and containment bypass initiators. A top level (limited depth) approach was used in which we studied design differences, major assumptions, data differences, and also compared the two PRA analyses on an element-by-element basis in order to discern the major causative factors for the risk profile differences. We conclude that the major risk profile differences are due to differences in assumptions and engineering judgment (possibly combined with some design and data differences) involved in treatment of uncertain physical phenomena (primarily sump plugging in LOCAs and turbine building steaming effects in secondary system breaks). Additional major differences are attributable to support system characteristics.

We have synthesized a series of Ti-Si-N coatings with 0 to 20 at. % Si by high-density plasma-assisted vapor-phase deposition. Composition, structure, and atomic short-range order were characterized by Rutherford Backscattering Spectrometry (RBS), Transmission Electron Microscopy (TEM), {Theta}-2{Theta} X-ray Diffraction (XRD), and X-ray Absorption Near Edge Structure (XANES) spectroscopy. The mechanical properties of these coatings were characterized by instrumented nanoindentation, and compared to those of B1-TiN. Our experiments show that the present series of Ti-Si-N coatings are nanocomposites, consisting of a nm-scale mixture of crystalline titanium nitride (TiN) and amorphous silicon nitride (a-Si:N). The mechanical response of the present series of Ti-Si-N coatings was found to be essentially independent of the Si composition, and similar to that of B1-TiN.

Grids comprise an infrastructure that enables scientists to use a diverse set of distributed remote services and resources as part of complex scientific problem-solving processes. We analyze some of the challenges involved in deploying software and components transparently in Grids. We report on three practical solutions used by the Globus Project. Lessons learned from this experience lead us to believe that it is necessary to support a variety of software and component deployment strategies. These strategies are based on the hosting environment.

Deep centers and dislocation densities in undoped n GaN, grown by hydride vapor phase epitaxy (HVPE), were characterized as a function of the layer thickness by deep level transient spectroscopy and transmission electron microscopy, respectively. As the layer thickness decreases, the variety and concentration of deep centers increase, in conjunction with the increase of dislocation density. Based on comparison with electron irradiation induced centers, some dominant centers in HVPE GaN are identified as possible point defects.

Resistance upset welding is used to attach small diameter machined tubes to small gas vessels. Recently there has been interest in determining the level of residual stresses caused by this attachment method and its influence on environmental interactions. A test program was initiated to determine the residual stresses present due to welding using the nominal weld parameters and varying the interference between the foot and the counter bore. In this paper, the residual stress measurement technique is described, the welding conditions are provided, and the residual stress due to welding at the nominal conditions are presented.

Recent progresses in the study of jet modification in hotmedium and their consequences in high-energy heavy-ion collisions are reviewed. In particular, I will discuss energy loss for propagating heavy quarks and the resulting modified fragmentation function. Medium modification of the parton fragmentation function due to quark recombination are formulated within finite temperature field theory and their implication on the search for deconfined quark-gluon plasma is also discussed.