The nonlinear Poisson-Boltzmann (PB) equation is solved using Pseudo Transient Continuation. The PB solver is constructed by modifying the nonlinear diffusion module of a 3D, massively parallel, unstructured-grid, finite element, radiation-hydrodynamics code. The solver also computes the electrostatic energy and evaluates the force on a user-specified contour. Either Dirichlet or mixed boundary conditions are allowed. The latter specifies surface charges, approximates far-field conditions, or linearizes conditions ''regulating'' the surface charge. The code may be run in either Cartesian, cylindrical, or spherical coordinates. The potential and force due to a conical probe interacting with a flat plate is computed and the result compared with direct force measurements by chemical force microscopy.

The interior voltage of a large metal can with thick walls struck directly by lightning was estimated using diffusion theory, aperture slot voltage theory, and experimental data. The hollow cylinder is closed at both ends. One end has a cap that is welded to the cylinder wall making a continuous electrical interface. The other end consists of a circular plate that is pressed into the cylinder wall and held under pressure with a threaded ring. From our experience with coupling measurements, this joint will be a weak link. It will allow more current to leak into the interior than from diffusion through the walls. Because the joint was designed for mechanical purposes, the electrical properties, such as continuity around the circumference, are not well controlled. Therefore, it is difficult to determine a single voltage attributed to this joint design with varying electrical characteristics. Instead, we will make a best effort of bounding the problem using both analytical calculations and data from tests of similar structures. The calculated internal cylinder voltage subjected to an extreme lightning strike from current diffusing through the wall is 19 volts. We estimate that the press-fit end plate will increase this voltage by a factor of …

This work investigates a control system for HCCI engines, where thermal energy from exhaust gas recirculation (EGR) and compression work in the supercharger are either recycled or rejected as needed. HCCI engine operation is analyzed with a detailed chemical kinetics code, HCT (Hydrodynamics, Chemistry and Transport), that has been extensively modified for application to engines. HCT is linked to an optimizer that determines the operating conditions that result in maximum brake thermal efficiency, while meeting the restrictions of low NO{sub x} and peak cylinder pressure. The results show the values of the operating conditions that yield optimum efficiency as a function of torque and RPM. For zero torque (idle), the optimizer determines operating conditions that result in minimum fuel consumption. The optimizer is also used for determining the maximum torque that can be obtained within the operating restrictions of NO{sub x} and peak cylinder pressure. The results show that a thermally controlled HCCI engine can successfully operate over a wide range of conditions at high efficiency and low emissions.

During the WBS4 review almost a year ago in January, and in more recent discussions of needed capsule characterization, I was struck by three pieces of information related to machined Be capsules: (1) that the speed of sound (and perhaps other properties) in Be grains is markedly different in orthogonal directions, (2) that the grain size in the best refined bulk Be samples is 10 to 15 {micro}m, and that these grains in the best case are randomly oriented, and (3) that we are concerned about capsule homogeneity on the level of 1 part in 10{sup 4}, presumably over angular length scales corresponding to the maximum in the growth curve. It seems to me that the first two points might be inconsistent with the third, and this led me to attempt to model the effect of randomly oriented Be grains on the radially dependent properties of a capsule.

The Inner and Outer modules of the Central Solenoid Model Coil (CSMC) were built by US and Japanese home teams in collaboration with European and Russian teams to demonstrate the feasibility of a superconducting Central Solenoid for ITER and other large tokamak reactors. The CSMC mass is about 120 t, OD is about 3.6 m and the stored energy is 640 MJ at 46 kA and peak field of 13 T. Testing of the CSMC and the CS Insert took place at Japan Atomic Energy Research Institute (JAERI) from mid March until mid August 2000. This paper presents the main results of the tests performed.

We present results from the Sustained Spheromak Physics Experiment (SSPX) at LLNL, which has been built to study energy confinement in spheromak plasmas sustained for up to 2 ms by coaxial DC helicity injection. Peak toroidal currents as high as 600kA have been obtained in the 1m dia. (0.23m minor radius) device using injection currents between 200-400kA; these currents generate edge poloidal fields in the range of 0.2-0.4T. The internal field and current profiles are inferred from edge field measurements using the CORSICA code. Density and impurity control is obtained using baking, glow discharge cleansing, and titanium gettering, after which long plasma decay times ({tau} {ge} 1.5ms) are observed and impurity radiation losses are reduced from {approx}50% to <20% of the input energy. Thomson scattering measurements show peaked electron temperature and pressure profiles with T{sub e} (0){approx}120eV and {beta}{sub e}{approx}7%. Edge field measurements show the presence of n=1 modes during the formation phase, as has been observed in other spheromaks. This mode dies away during sustainment and decay so that edge fluctuation levels as low as 1% have been measured. These results are compared with numerical simulations using the NIMROD code.

We present a new approach for investigating the kinetics of defect migration during annealing of low-energy, ion-implanted silicon, employing a combination of computer simulations and atomic-resolution tunneling microscopy. Using atomically-clean Si(111)-7x7 as a sink for bulk point defects created by 5 keV Xe and Ar irradiation, we observe distinct, temperature-dependent surface arrival rates for vacancies and interstitials. A combination of simulation tools provides a detailed description of the processes that underly the observed temperature-dependence of defect segregation, and the predictions of the simulations agree closely with the experimental observations.

The intense ion beams in a heavy ion Inertial Fusion Energy (IFE) driver and fusion chamber are non-neutral plasmas whose dynamics are largely dominated by space charge. We propose to develop a ''source-to-target'' Heavy Ion Fusion (HIF) beam simulation capability: a description of the kinetic behavior of this complex, nonlinear system which is both integrated and detailed. We will apply this new capability to further our understanding of key scientific issues in the physics of ion beams for IFE. The simulations will entail self-consistent field descriptions that require interprocessor communication, but are scalable and will run efficiently on terascale architectures. This new capability will be based on the integration of three types of simulations, each requiring terascale computing: (1) simulations of acceleration and confinement of the space-charge-dominated ion beams through the driver (accelerator, pulse compression line, and final focusing system) which accurately describe their dynamics, including emittance growth (phase-space dilution) effects; these are particle-in-cell (PIC) models; (2) electromagnetic (EM) and magnetoinductive (Darwin) simulations which describe the beam and the fusion chamber environment, including multibeam, neutralization, stripping, beam and plasma ionization processes, and return current effects; and (3) highly detailed simulations (6f, multispecies PIC, continuum Vlasov), which can examine electron effects …

Linear stability analysis of a two-cylinder approximation to gun injection--one cylinder to represent the confined spheromak and another to represent the gun--is shown to yield equilibria in which tearing modes exist simultaneously at the magnetic axis and at the geometric (gun) axis, as might be required to sustain helicity injection. These equilibria are MHD stable at the two axes but may have localized MHD instability at an interior minimum in the q profile. The theory predicts two tearing thresholds with successively deeper q minima as the gun current is increased at constant bias flux.

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Initial measurements are reported for the Mercury laser system, a scalable driver for rep-rated high energy density physics research. The performance goals include 10% electrical efficiency at 10 Hz and 100 J with a 2-10 ns pulse length.

The utilization of high-power short pulse laser employing chirped-pulse amplification (CPA) for material processing and inertial confinement research is widely increasing. The performance of these high-power CPA laser system continues to be limited by the ability of the pulse compression gratings to hold up to the high-average-power or high-peak-power of the laser. Pulse compression gratings used in transmission and fabricated out of bulk fused silica have intrinsically the highest laser damage threshold when compared with metal or multilayer dielectric gratings that work in reflection. LLNL has developed processing capability to produce high efficiency fused silica transmission gratings at sizes useful to future Petawatt-class systems, and has demonstrated high efficiency at smaller aperture. This report shows that fused silica diffraction exhibiting >95% efficiency into the -1 diffraction order in transmission (90{sup o} deflection of the incident light, at an incidence angle of 45{sup o} to the grating face). The microstructure of this grating consisted of grooves ion-beam etched to a depth of 1.6 microns with a pitch of 0.75 microns, using a holographically produced photoresist mask that was subsequently stripped away in significance to the fabrication of the small scale high efficiency grating was the development of the processing technology and …

We present a method for accelerating time dependent Monte Carlo radiative transfer calculations by using a discretization of the diffusion equation to calculate probabilities that are used to advance particles in regions with small mean free path. The method is demonstrated on problems with on 1 and 2 dimensional orthogonal grids. It results in decreases in run time of more than an order of magnitude on these problems, while producing answers with accuracy comparable to pure IMC simulations. We call the method Implicit Monte Carlo Diffusion, which we abbreviate IMD.

Recent work in heavy-ion fusion accelerators and final focusing systems shows a trend towards less current per beam, and thus, a greater number of beams. Final focusing magnets are susceptible to nuclear heating, radiation damage, and neutron activation. The trend towards more beams, however, means that there can be less shielding for each magnet, Excessive levels of nuclear heating may lead to magnet quench or an intolerable recirculating power for magnet cooling. High levels of radiation damage may result in short magnet lifetimes and low reliability. Finally, neutron activation of the magnet components may lead to difficulties in maintenance, recycling, and waste disposal. The present work expands upon previous, three-dimensional magnet shielding calculations for a modified version of the HYLIFE-I1 IFE power plant design. We present key magnet results as a function of the number of beams.

We are currently developing a component based, parallel visualization and graphical analysis tool for visualizing and analyzing data on two- and three-dimensional (20, 30) meshes. The tool consists of three primary components: a graphical user interface (GUI), a viewer, and a parallel compute engine. The components are designed to be operated in a distributed fashion with the GUI and viewer typically running on a high performance visualization server and the compute engine running on a large parallel platform. The viewer and compute engine are both based on the Visualization Toolkit (VTK), an open source object oriented data manipulation and visualization library. The compute engine will make use of parallel extensions to VTK, based on MPI, developed by Los Alamos National Laboratory in collaboration with the originators of P K . The compute engine will make use of meta-data so that it only operates on the portions of the data necessary to generate the image. The meta-data can either be created as the post-processing data is generated or as a pre-processing step to using VisIt. VisIt will be integrated with the VIEWS' Tera-Scale Browser, which will provide a high performance visual data browsing capability based on multi-resolution techniques.

A broad baseline study of the levels and distributions of trace metals and PCB compounds in sediments has been undertaken. PCB concentrations in surface sediments reflect the source of these contaminates in the region. The highest PCB concentrations as Aroclor 1260 (approximately 10 ng g{sup -1}) were found in sediments near the outflow of the Po river. The lowest concentrations (1.5 ng g{sup -1} dry) were associated with the sediments from the Jabuka Pit in the Middle Adriatic. These values are quite similar to total PCBs (<1.0-17) measured in surface sediments sampled off the coast of Croatia in 1977-78. Thus, based on the limited amount of new data available, it appears that there has been little, if any, decrease in PCB loading in Adriatic sediments over the past 15 years. Downcore profiles of PCBs in sediment cores are also discussed from a pollution history standpoint. Likewise, total mercury in surface sediments was also highest at stations off the Po (403-499 ng g{sup -1} dry) and lowest (67-224 ng g{sup -1}) in the Jabuka Pit. In one core located just south of the Po outflow, total Hg concentrations at all depths were relatively high decreasing gradually from approximately 400 ng g{sup …

A set of twenty-three 20-L crystallizer runs exploring the importance of several engineering variables found that growth temperature is the most important variable controlling damage resistance of DKDP over the conditions investigated. Boules grown between 45 C and room temperature have a 50% probability of 3{omega} bulk damage that is 1.5 to 2 times higher than boules grown between 65 and 45 C. This raises their damage resistance above the NIF tripler specification for 8 J/cm{sup 2} operation by a comfortable margin. Solution impurity levels do not correlate with damage resistance for iron less than 200 ppb and aluminum less than 2000 ppb. The possibility that low growth temperatures could increase damage resistance in NIF-scale boules was tested by growing a large boule in a 1000-L crystallizer with a supplemental growth solution tank. Four samples representing early and late pyramid and prism growth are very close to the specification as best it is understood at the present. Implications of low temperature growth for meeting absorbance, homogeneity, and other material specifications are discussed.

Iron ions provide many valuable plasma diagnostics for cosmic plasmas. The accuracy of these diagnostics, however, often depends on an accurate understanding of the ionization structure of the emitting gas. Dielectronic recombination (DR) is the dominant electron-ion recombination mechanism for most iron ions in cosmic plasmas. Using the heavy-ion storage ring at the Max-Planck-Institute for Nuclear Physics in Heidelberg, Germany, we have measured the low temperature DR rates for Fe{sup q+} where q = 15, 17, 18, and 19. These rates are important for photoionized gases which form in the media surrounding active galactic nuclei, X-ray binaries, and cataclysmic variables. Our results demonstrate that commonly used theoretical approximations for calculating low temperature DR rates can easily under- or over-estimate the DR rate by a factor of {approx} 2 or more. As essentially all DR rates used for modeling photoionized gases are calculated using these approximations, our results indicate that new DR rates are needed for almost all charge states of cosmically abundant elements. Measurements are underway for other charge states of iron.

Ecological risk assessment (ERA) is a tool used by many regulatory agencies to evaluate the impact to ecological receptors from changes in environmental conditions. Widespread use of ERAs began with the United States Environmental Protection Agency's Superfund program to assess the ecological impact from hazardous chemicals released to the environment. Many state hazardous chemical regulatory agencies have adopted the use of ERAs, and several state regulatory agencies are evaluating the use of ERAs to assess ecological impacts from releases of petroleum and gas-related products. Typical ERAs are toxicologically-based, use conservative assumptions with respect to ecological receptor exposure duration and frequency, often require complex modeling of transport and exposure and are very labor intensive. In an effort to streamline the ERA process, efforts are currently underway to develop default soil screening levels, to identify ecological screening criteria for excluding sites from formal risk assessment, and to create risk-based corrective action worksheets. This should help reduce the time spent on ERAs, at least for some sites. Work is also underway to incorporate bioavailability and spatial considerations into ERAs. By evaluating the spatial nature of contaminant releases with respect to the spatial context of the ecosystem under consideration, more realistic ERAs with respect …

The carbon aerogel/carbon paper composites have physical properties similar to those of monolithic carbon aerogels but do not require supercritical extraction during fabrication. The resorcinol-formaldehyde based carbon aerogel phase is intertwined between the fibers of a commercial carbon paper. The resulting composites have variable densities (0.4-0.6 g/cc), high surface areas (300-600 m{sup 2}/g), and controllable pore sizes and pore distribution. The effects of the resorcinol-formaldehyde concentrations (50-70% w/v) and the pyrolysis temperature (600-1050 C) were studied in an attempt to tailor the aerogel microstructure and properties. The composite physical properties and structure were analyzed by transmission electron microscopy and multipoint-BET analyses and related to electrochemical capacitive data in 5M KOH. These thin carbon aerogel/carbon paper composite electrodes are used in experiments with electrochemical double-layer capacitors and capacitive deionization.

We report on the raw disk i/o performance of a set of Compaq StorageWorks RAID arrays connected to our cluster of Compaq ES40 computers via Fibre Channel. The best cumulative peak sustained data rate is l17MB/s per node for reads and 77MB/s per node for writes. This value occurs for a configuration in which a node has two Fibre Channel interfaces to a switch, which in turn has two connections to each of two Compaq StorageWorks RAID arrays. Each RAID array has two HSG80 RAID controllers controlling (together) two 5+p RAID chains. A 10% more space efficient arrangement using a single 1l+p RAID chain in place of the two 5+P chains is 25% slower for reads and 40% slower for writes.

A thick flowing layer of liquid (e.g., flibe-a molten salt, or Sn{sub 80}Li{sub 20}--a liquid metal) protects the structural walls of the magnetic fusion configuration so that they can last the life of the plant even with intense 14 MeV neutron bombardment from the D-T fusion reaction, The surface temperature of the liquid rises as it passes from the inlet nozzles to the exit nozzles due to absorption of line and bremsstrahlung radiation, and neutrons. The surface temperature can be reduced by enhanced turbulent convection of hot surface liquid into the cooler interior. This surface temperature is affected by the temperature of liquid from a heat transport and energy recovery system. The evaporative flux from the wall driven by the surface temperature must also result in an acceptable impurity level in the core plasma. The shielding of the core by the edge plasma is modeled with a 2D-transport code for the DT and impurity ions; these impurity ions are either swept out to the divertor, or diffuse to the hot plasma core. An auxiliary plasma between the edge plasma and the liquid wall may further attenuate evaporating flux of atoms and molecules by ionization near the wall.

The testing reported here was performed on K East Basin consolidated sludge samples to generate data needed for the evaluation and design of the systems that will be used to disposition the K Basin sludge to T-Plant for interim storage. The tests were conducted by Pacific Northwest National Laboratory from May through November 1999 under the direction of the Spent Nuclear Fuel (SNF) Project. The samples used in the work discussed here were collected by the SNF Characterization Project from the KE Basin floor and canisters during March and April 1999. These samples (3 from the floor and 3 from the canisters) were shipped to the storage pool at the Postirradiation Testing Laboratory (327 Building) and later transferred to the PNNL Radiochemical Processing Laboratory (325 Building), where they were recovered for testing and analysis. Testing activities presented in this report include particle size measurement via wet sieving, sludge settling and sludge density measurements, sludge shear strength measurement, and measurement of sludge dissolution enthalpy to ascertain the uranium metal content of the sludge. Section 1.0 provides the summary and conclusions to date. Section 2.0 describes the consolidated sample container system, the sample collection and transfer, inspection, and recovery of the samples …

Over 200 single-pass flow-through experiments were completed with LAWABP1 glass, the reference glass for the 2001 Immobilized Low-Activity Waste Performance Assessment. These data provided the kinetic rate law parameters and Na ion-exchange rate needed to conduct long-term performance analyses using the reactive chemical transport code STORM. Pressurized unsaturated flow (PUF) experiments with five prototypic LAW glasses were also performed. The PUF test provides a means to dramatically accelerate the weathering process in a simulated vadose zone environment. The performance of these five next generation LAW glasses in the PUF test (and other accelerated tests) improved dramatically from earlier glass compositions that were being developed by BNFL, Inc. No autocatalytic corrosion rate accelerations were observed in tests that were conducted for over 1 year. SPFT and PUF experiments were run with a commercial humic acid solution, 25 to 50 times more concentrated than expected in Hanford vadose zone pore water. No difference in glass dissolution rate versus the rate measured in deionized water could be detected within experimental error. Initial development and testing of a parallelized lattice-Boltzmann method for solving reactive chemical transport problems in complex geometries was completed. This method is being examined as a means to dramatically decrease the …