Being a three body problem, the scattering of an incoming antiproton (p{sup -}) by a hydrogen atom (H, consisting of an electron, e{sup -}, bound to a proton, p) is one of the simplest problems in quantum mechanics that requires a numerical solution. An appropriate choice of calculational method for this system depends on the energy of the p{sup -}. Described and compared here are three methods, valid in essentially separate energy ranges from zero energy through MeV energies. In spite of its seeming simplicity, much effort is required in terms of mathematical manipulation and use of approximations to render this problem capable of numerical solution.

This case study provides examples of how some simple decisions the authors made in structuring their algorithms for handling cell-centered data can dramatically influence the results. Although they all know that these decisions produce variations in results, they think that they underestimate the potential magnitude of the differences. More importantly, the users of the codes may not be aware that these choices have been made or what they mean to the resulting visualizations of their data. This raises the question of whether or not these decisions are inadvertently distorting user interpretations of data sets.

During the last 20 years there has been a tremendous increase in computational capabilities. It seems to accelerate every year. Models are now constructed with millions of degrees of freedom. Sandia National Laboratories recently computed modes and transient response for a 4,000,000 degree of freedom model. There is also an increase in the cost of testing as the unit price of test items increases and manpower costs escalate. One is reminded of Augustine's Laws, ``Simple systems are not feasible because they require infinite testing.'' Or conversely, extremely complex systems require no testing. In his discussion he uses data from actual systems to show how increasing complexity of systems appears to require less testing. A hundred dollar item required several thousand developments tests, where a ten million dollar item required a few tens of development tests. Of course, this results from the large increase in test costs caused in large part by the large cost of the test hardware that comes with increasing complexity. The complex system (costly) is coupled with the perceived need to reduce nonessential costs. At Sandia National Laboratories they are also faced with the prospect that some of the tests they ran in the past are not …

Experimentation, theory, and modeling have all played vital roles in defining what is known about microstructural evolution and the effects of microstructure on material properties. Recently, technology has become an enabling factor, allowing significant advances to be made on several fronts. Experimental evidence of crystallographic slip and the basic theory of crystal plasticity were established in the early 20th century, and the theory and models evolved incrementally over the next 60 years. During this time, modeling was primarily concerned with the average response of polycrystalline aggregates. While some detailed finite element modeling (FEM) with crystal plasticity constitutive relations was performed in the early 1980's, such simulations over taxed the capacity of the available computer hardware. Advances in computer capabilities led to a flurry of activity in finite element modeling in the next 10 years, thus increasing understanding of lattice orientation evolution and generating detailed predictions of spatial orientation distributions that could not be readily validated with existing experimental characterization methods. Significant advancements in material characterization, particularly automated electron backscatter diffraction (EBSD), have made it possible to conduct detailed validation studies of the FEM predictions. The data collected are extensive, and many questions about the evolution of microstructure and its role …

The effects of electron-hole interaction on the optical properties of a variety of materials have been calculated using an ab initio method based on solving the Bethe-Salpeter equation. Results on selected semiconductors, insulators, and semiconducting polymers are presented. In the cases of alpha-quartz (SiO2) and poly-phenylene-vinylene, resonant excitonic states qualitatively alter the absorption spectra.

None

None

An instrument combining an array of Cadmium-Zinc-Telluride (CZT) detectors, a NaI scintillator, and two {sup 3}He neutron detectors has been constructed. The instrument uses the CZT array to identify radioactive materials. As an example of this application, the 3 {sigma} Minimum Detectable Activity for the 375 keV peak of {sup 238}Pu is less than 1 gram at a distance of 20 cm for a 100-second counting time. The 2 x 2 NaI scintillator has a dual purpose. First, it is used to supplement the CZT array for identification of high-energy gammas, such as those from {sup 60}Co. Second, the principle use of the NaI scintillator is to help search for radioactive material and to find a suitable measurement location on a suspect package for the CZT-based isotope-identification measurement. This detector also produces energy-corrected exposure-rate data. The {sup 3}He neutron detectors provide an additional confirmation of the presence of some plutonium isotopes. The neutron sensitivity is 90 counts per second at 20 cm from a moderated {sup 252}Cf neutron source.

Numerical modeling of the urban boundary layer is complicated by the need to describe airflow patterns outside of the computational domain. These patterns have an impact on how successfully the simulation is able to model the turbulence associated with the urban boundary layer. This talk presents experiments with the model boundary conditions for simulations that were done to support two Department of Energy observational programs involving the Salt Lake City basin. The Chemical/Biological Non-proliferation Program (CBNP) is concerned with the effects of buildings on influencing dispersion patterns in urban environments. The Vertical Transport and Mixing Program (VTMX) investigating mixing mechanisms in the stable boundary layer and how they are influenced by the channeling caused by drainage flows or by obstacles such as building complexes. Both of these programs are investigating the turbulent mixing caused by building complexes and other urban obstacles.

None

The electrical properties of semi-insulating (SI) Gallium Arsenide (GaAs) have been investigated for some time, particularly for its application as a substrate in microelectronics. Of late this material has found a variety of applications other than as an isolation region between devices, or the substrate of an active device. High resistivity SI GaAs is increasingly being used in charged particle detectors and photoconductive semiconductor switches (PCSS). PCSS made from these materials operating in both the linear and non-linear modes have applications such as firing sets, as drivers for lasers, and in high impedance, low current Q-switches or Pockels cells. In the non-linear mode, it has also been used in a system to generate Ultra-Wideband (UWB) High Power Microwaves (HPM). The choice of GaAs over silicon offers the advantage that its material properties allow for fast, repetitive switching action. Furthermore photoconductive switches have advantages over conventional switches such as improved jitter, better impedance matching, compact size, and in some cases, lower laser energy requirement for switching action. The rise time of the PCSS is an important parameter that affects the maximum energy transferred to the load and it depends, in addition to other parameters, on the bias or the average field …

The high energy physics experiment CDF, located in the anti-proton-proton collider at Fermilab, will write data in Run 2 at a rate of 20 MByte/s, twenty times the rate of Run 1. The offline production system must be able to handle this rate. Components of that system include a large PC farm, I/O systems to read/write data to and from mass storage, and a system to split the reconstructed data into physics streams which are required for analysis. All of the components must work together seamlessly to ensure the necessary throughput. A description will be given of the overall hardware and software design for the system. A small prototype farm has been used for about one year to study performance, to test software designs and for the first Mock Data Challenge. Results from the tests and experience from the first Mock Data Challenge will be discussed. The hardware for the first production farm is in place and will be used for the second Mock Data Challenge. Finally, the possible scaling of the system to handle larger rates foreseen later in Run 2 will be described.

In principle, the energy released by a fission can be converted directly into electricity by using the charged fission fragments. The first theoretical treatment of direct energy conversion (DEC) appeared in the literature in 1957. Experiments were conducted over the next ten years, which identified a number of problem areas. Research declined by the late 1960's due to technical challenges that limited performance. Under the Nuclear Energy Research Initiative the authors are determining if these technical challenges can be overcome with todays technology. The authors present the basic principles of DEC reactors, review previous research, discuss problem areas in detail, and identify technological developments of the last 30 years that can overcome these obstacles. As an example, the fission electric cell must be insulated to avoid electrons crossing the cell. This insulation could be provided by a magnetic field as attempted in the early experiments. However, from work on magnetically insulated ion diodes they know how to significantly improve the field geometry. Finally, a prognosis for future development of DEC reactors will be presented .

Future high energy colliders along with their physics potential, and relationship to new laser technology are discussed. Experimental approaches and requirements for New Physics exploration are also described.

H-Morph is a new automatic algorithm for the generation of a hexahedral-dominant finite element mesh for arbitrary volumes. The H-Morph method starts with an initial tetrahedral mesh and systematically transforms and combines tetrahedral into hexahedra. It uses an advancing front technique where the initial front consists of a set of prescribed quadrilateral surface facets. Fronts are individually processed by recovering each of the six quadrilateral faces of a hexahedron from the tetrahedral mesh. Recovery techniques similar to those used in boundary constrained Delaunay mesh generation are used. Tetrahedral internal to the six hexahedral faces are then removed and a hexahedron is formed. At any time during the H-Morph procedure a valid mixed hexahedral-tetrahedral mesh is in existence within the volume. The procedure continues until no tetrahedral remain within the volume, or tetrahedral remain which cannot be transformed or combined into valid hexahedral elements. Any remaining tetrahedral are typically towards the interior of the volume, generally a less critical region for analysis. Transition from tetrahedral to hexahedra in the final mesh is accomplished through pyramid shaped elements. Advantages of the proposed method include its ability to conform to an existing quadrilateral surface mesh, its ability to mesh without the need to …

A method for decomposing a volume with a prescribed quadrilateral surface mesh, into a hexahedral-dominated mesh is proposed. With this method, known as Hex-Morphing (H-Morph), an initial tetrahedral mesh is provided. Tetrahedral are transformed and combined starting from the boundary and working towards the interior of the volume. The quadrilateral faces of the hexahedra are treated as internal surfaces, which can be recovered using constrained triangulation techniques. Implementation details of the edge and face recovery process are included. Examples and performance of the H-Morph algorithm are also presented.

Many parallel applications require periodic redistribution of workloads and associated data. In a distributed memory computer, this redistribution can be difficult if limited memory is available for receiving messages. The authors propose a model for optimizing the exchange of messages under such circumstances which they call the minimum phase remapping problem. They first show that the problem is NP-Complete, and then analyze several methodologies for addressing it. First, they show how the problem can be phrased as an instance of multi-commodity flow. Next, they study a continuous approximation to the problem. They show that this continuous approximation has a solution which requires at most two more phases than the optimal discrete solution, but the question of how to consistently obtain a good discrete solution from the continuous problem remains open. Finally, they devise a simple and practical approximation algorithm for the problem with a bound of 1.5 times the optimal number of phases.

Effective use of a parallel computer requires that a calculation be carefully divided among the processors. This load balancing problem appears in many guises and has been a fervent area of research for the past decade or more. Although great progress has been made, and useful software tools developed, a number of challenges remain. It is the conviction of the author that these challenges will be easier to address if programmers first come to terms with some significant shortcomings in their current perspectives. This paper tries to identify several areas in which the prevailing point of view is either mistaken or insufficient. The goal is to motivate new ideas and directions for this important field.

Preliminary Monte Carlo simulations have demonstrated that passive Nuclear Materials Identification System (NMIS) measurements can be used to determine the mass of Pu in AT400-R containers with measurement times as short as a few minutes. The sensitivity of the proposed detectors to gamma rays should enhance this measurement method because the gamma rays from fission, induced or spontaneous, escape this container more easily than neutrons. In these calculations, the container contained two Pu spheres with mass varying between 0.5 and 2 Kg with {approximately}6 wt% {sup 240 }Pu.

The concept of a muon storage ring based Neutrino Source (Neutrino Factory) has sparked considerable interest in the High Energy Physics community. Besides providing a first phase of a muon collider facility, it would generate more intense and well collimated neutrino beams than currently available. The BNL-AGS or some other proton driver would provide an intense proton beam that hits a target, produces pions that decay into muons. The muons must be cooled, accelerated and injected into a storage ring with a long straight section where they decay. The decays occurring in the straight sections of the ring would generate neutrino beams that could be directed to detectors located thousands of kilometers away, allowing studies of neutrino oscillations with precisions not currently accessible. For example, with the neutrino source at BNL, detectors at Soudan, Minnesota (1,715 km), and Gran Sasso, Italy (6,527 km) become very interesting possibilities. The feasibility of constructing and operating such a muon-storage-ring based Neutrino-Factory, including geotechnical questions related to building non-planar storage rings (e.g. at 8{degree} angle for BNL-Soudan, and 3{degree} angle for BNL-Gran Sasso) along with the design of the muon capture, cooling, acceleration, and storage ring for such a facility is being explored by …

We have performed x-ray spectroscopic experiments in homogeneous gas bag plasmas where we independently measure the temperature with Thomson scattering. We find that collisional radiative (kinetics) modeling of the intensities of the He-{beta} line and its dielectronic capture satellites is generally in agreement with the measured spectra. On the other hand, for the particular case of satellites arising from inner-shell electron collisional excitation, we find discrepancies of up to a factor of two between experiment and kinetics models. We have ruled out possible effects on the line emission due to plasma gradients, radiative transport, and suprathermal electron excitation leaving errors in the atomic physics modeling to be the most likely explanation. The determination that there are problems with the collisionally populated states is important for the interpretation of inertial confinement fusion capsule implosions where electron densities and temperature have been measured using the spectral line shape of the He-{beta} transition of Ar XVII. The analysis of the implosion data has required Stark broadening calculations coupled to a kinetics model to calculate the detailed line intensities and widths. Despite remaining discrepancies, the good agreement between the experimental dielectronic capture satellites and the HULLAC calculations suggests that HULLAC is a more appropriate …

This work points out that the costates are actually discontinuous functions of time for optimal control problems with Coloumb friction. In particular these discontinuities occur at the time points where the velocity of the system changes sign. To the authors knowledge, this has not been noted before. This phenomenon is demonstrated on a minimum-time problem with Coloumb friction and the consistency of discontinuous costates and switching functions with respect to the input switches is shown.

Thin resist films (< 1500 {angstrom}) based on DUV chemical approaches have been demonstrated for use in EUV lithography. Resists with good sensitivity (5--6 mJ/cm{sup 2}) were observed but imaging mechanisms, in particular as they affect sensitivity, are poorly understood. To clarify mechanisms leading to photosensitivity, acid-generation efficiency at both EUV and DUV wavelengths was measured for the most promising EUV resist compositions as well as initial radiation damage experiments. In previous work, polymer composition was found to be more important in determining the relative dose to print of resists to EUV and DUV radiation than was PAG composition. Here, acid generating efficiency for several polymers upon exposure to EUV and DW are compared to gain insight into the role of the polymer and PAG in converting the incident EUV photon energy into resist images. It is shown that acid generation efficiencies at EUV do not track efficiencies measured on identical films with DUV exposures, and is attributable to polymer and polymer/PAG interactions. No particular structural feature of the polymer could be correlated to the acid generation results. Radiation damage studies showed that polymers that create acid in different yields at EUV do not show differences in radiation damage, as …

This paper presents a new approach to a gesture-tracking system using real-time range on-demand. The system represents a gesture-controlled interface for interactive visual exploration of large data sets. The paper describes a method performing range processing only when necessary and where necessary. Range data is processed only for non-static regions of interest. This is accomplished by a set of filters on the color, motion, and range data. The speedup achieved is between 41% and 54%. The algorithm also includes a robust skin-color segmentation insensitive to illumination changes. Selective range processing results in dynamic regional range images (DRRIs). This development is also placed in a broader context of a biological visual system emulation, specifically redundancies and attention mechanisms.