{l_brace}311{r_brace} defects and dislocation loops are formed after ion-implantation and annealing of a silicon wafer. Recent Transmission Electron Microscopy studies by Li and Jones have shown that sub-threshold dislocation loops nucleate from {l_brace}311{r_brace} defects. In our study, the conjugate gradient method with the Stillinger Weber potential is used to relax different configurations such as {l_brace}311{r_brace} defects with a maximum of five chains and perfect dislocation loops. From the formation energies thus obtained we find that there is an optimal width for each length of the {l_brace}311{r_brace} defects. Moreover the relative stability of {l_brace}311{r_brace}s and loops is studied as a function of defect size. We observe that at very small sizes the perfect loops are more stable than the {l_brace}311{r_brace}s. This may provide an explanation for the experimental observation by Robertson et al that, in an annealing study of end of range damage of amorphized samples, 45% of the loops had nucleated in the first 10 minutes of anneal. We propose that homogeneous nucleation, as against unfaulting of the {l_brace}311{r_brace}s, could be the source of these loops.

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.

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 …

Internal combustion engines, both spark ignition and Diesel, are dominant types of vehicle power sources and also provide power for other important stationary applications. Overall, these engines are a central part of power generation in modern society. However, these engines, burning hydrocarbon fuels from natural gas to gasoline and Diesel fuel, are also responsible for a great deal of pollutant emissions to the environment, especially oxides of nitrogen (NO{sub x}) and unburned hydrocarbons (UHC). In recent years, pollutant species emissions from internal combustion engines have been the object of steadily more stringent limitations from various governmental agencies. Engine designers have responded by developing engines that reduce emissions to accommodate these tighter limitations. However, as these limits become ever more stringent, the ability of engine design modifications to meet those limits must be questioned. Production of NO{sub x} in internal combustion engines is primarily due to the high temperature extended Zeldovich reaction mechanism: (1) O + N{sub 2} = NO + N; (2) N + O{sub 2} = NO + O; and (3) N + OH = NO + H. The rates of these reactions become significant when combustion temperatures reach or exceed about 2000K. This large temperature dependence, characterized by …

Aggregates in thin films of conjugated polymers form excimer states and significantly reduce the photo- and electroluminescence efficiency in devices produced from these materials. We have studied the aggregate formation in thin films of MEH-PPV by near-field scanning optical microscopy and spectroscopy. Local photoluminescence spectroscopy and photo-bleaching experiments have been used to show that thin films of MEH-PPV are homogeneously aggregated and do not form aggregated domains.

The present work continues our effort to perform an integrated safety analysis for the HYLIFE-II inertial fusion energy (IFE) power plant design. Recently we developed a base case for a severe accident scenario in order to calculate accident doses for HYLIFE-II. It consisted of a total loss of coolant accident (LOCA) in which all the liquid flibe (Li{sub 2}BeF{sub 4}) was lost at the beginning of the accident. Results showed that the off-site dose was below the limit given by the DOE Fusion Safety Standards for public protection in case of accident, and that his dose was dominated by the tritium released during the accident.

We present results for the 8:1 thermal cavity problem using FIDAP on 3 meshes--each using 3 elements. A brief summary of related results is also included. This contribution comes via the rather versatile and general commercial finite element code, FIDAP. This code still offers the user a wide selection with respect to element choices, statement of governing equations, (e.g., advective form, divergence form) implicit time integrators (variable-step or fixed step, first-order or second-order), and solution techniques for both the nonlinear and linear sets of equations. We have tested quite a number of these variations on this problem; here we report on an interesting subset and will present the remainder at the conference.

Over the course of testing a substantial number of KDP and DKDP crystals from rapid and conventional growth processes, we have discovered that there is a consistent difference in the value of the damage resistance between z-cut and tripler, x-cut and y-cut crystals for a given test fluence. This increase in damage probability for tripler, x and y-cut crystals is consistent for both conventional and rapid growth KDP as well as DKDP. It also holds for unconditioned (S/1) and conditioned (R/l) tests and has values of 2.1 {+-} 0.6 and 1.5 {+-} 0.3 respectively. Testing has also revealed that there is no sensitivity to incident laser polarization. This is in direct contradiction to models based on simple, non-spherical absorbers. This result plus new information on the size and evolution of bulk damage density (see Runkel et al., this proceedings) has led to a reinterpretation of the growth parameter data for rapid growth NIF boules. It now appears that variations in impurity concentration throughout the boule do not affect the damage probability curve as dramatically as previously thought; although, this is still a topic of intensive investigation.

Results are reported from recently performed bulk-damage, pulse-scaling experiments on DKDP tripler samples taken from NIF-size, rapid-growth boule BD7. The tests were performed on LLNL's Optical Sciences Laser. A matrix of samples was exposed to single shots at 351 mn (3 {omega}) with average fluences from 4 to 8 J/cm{sup 2} for pulse durations of 1, 3 and 10 ns. The damage sites were scatter-mapped after testing to determine the damage evolution as a function of local beam fluence. The average bulk damage microcavity (pinpoint) density varied nearly linearly with fluence with peak values of approximately 16,000 pp/mm{sup 3} at 1 ns, 10,000 pp/mm{sup 3} at 3 ns and 400 pp/mm{sup 3} at 10 ns for fluences in the 8-10 J/cm{sup 2} range. The average size of a pinpoint was 10(+14,-9) {micro}m at 1 ns, 37 {+-} 20 {micro}m at 3 ns and {approx} 110 {micro}m at 10 ns, although all pulse durations produced pinpoints with a wide distribution of sizes. Analysis of the pinpoint density data yielded pulse-scaling behavior of t{sup 0.35}. Significant planar cracking around the pinpoint as was observed for the 10 ns case but not for the 1 and 3 ns pulses. Crack formation around pinpoints …

Hydrocarbon ignition is an important element in many practical combustion systems, including internal combustion engines, detonations, pulse combustors, and flame initiation. The rapid compression machine (RCM) is used frequently to study the kinetics of hydrocarbon autoignition [e.g., 1-7], since the reactive gas temperatures and time histories are similar to those seen in automotive engines during Diesel ignition and end gas autoignition leading to engine knock in spark-ignition engines. The RCM provides a rich environment for study of the theory of hydrocarbon oxidation, including degenerate chain branching, alkylperoxy radical isomerization and effects of thermal feedback [8]. The literature of hydrocarbon oxidation studies in the RCM has been summarized recently [9,10], and many classes of fuels have been studied. Detailed kinetic modeling is another tool available to study hydrocarbon oxidation in the RCM [4,11]. The aim of the present work is to determine experimentally the influence of variations in fuel molecular structure on autoignition, and to use a kinetic model to understand the reasons for those variations. This study is unique in that while other studies have addressed variations in pressure and equivalence ratio on ignition [11], this work addresses effects of variations in fuel molecular structure for all of the isomers …

As an integral part of the plutonium disposition program, formulation and process development is being performed for the immobilization of surplus plutonium in a titanate-based ceramic. Small-scale process prototypic and lab-scale functionally prototypic equipment have been tested to help define the immobilization process. The testing has included non-radioactive surrogates and actual actinide oxides contained in the immobilized form. A summary of the process development studies, as well as the formulation studies relevant to the process, will be provided.

The production of nuclei up to and including the light s-process component at A {approx} 60-90 is calculated for all stages of stable and explosive nuclear burning in stars of 15 and 25 M{sub {circle_dot}}. An extended nuclear reaction network of 480 isotopes is employed along with approximately two dozen recent revisions to key nuclear reaction rates. As noted previously, the new rates suggest a greatly diminished production of {sup 17}O and {sup 18}O in massive stars. {sup 22}Ne is also moderately enhanced. We find that a combination of pre-explosive s-process, {gamma}-process, and (mild) r-processes in massive stars give a consistently solar production of almost all isotopes from mass 64 through 90. However, even after the late stages of evolution are complete and the explosion is over, this same group of elements is overproduced compared to what is needed for the sun, especially in the 25 M{sub {circle_dot}} model.

Laser conditioning has been shown to improve the laser damage threshold of some optical coatings by greater than 2x. Debate continues within the damage community regarding laser-conditioning mechanisms, but it is clear that nodular ejection is one of the byproducts of the laser conditioning process. To better understand why laser conditioning is so effective, photothermal microscopy was used to measure absorption of coating defects before and after laser exposure. Although a modest absorption reduction was expected due to the lower electric field peaks within a pit and the absence of potentially absorbing nodular seeds, surprisingly, absorption reductions up to 150x were observed. Photothermal microscopy has also been successfully used to correlate laser-induced damage threshold and absorption of defects in hafnia/silica multilayer optical coatings. Defects with high absorption, as indicated by high photothermal signal, have low damage thresholds. Previously a linear correlation of damage threshold and defect photothermal signal was established with films designed and damage tested at 1{omega} (1053 nm) and Brewster's angle (56.4{sup o}), but characterized by photothermal microscopy at 514.5 nm and near-normal angle of incidence (10{sup o}). In this study coatings designed, characterized by photothermal microscopy, and damage tested at the same wavelength, incident angle, and polarization …

Emission standards for diesel engines in vehicles have been steadily reduced in recent years, and a great deal of research and development effort has been focused on reducing particulate and nitrogen oxide emissions. One promising approach to reducing emissions involves the addition of oxygen to the fuel, generally by adding an oxygenated compound to the normal diesel fuel. Miyamoto et al. [1] showed experimentally that particulate levels can be significantly reduced by adding oxygenated species to the fuel. They found the Bosch smoke number (a measure of the particulate or soot levels in diesel exhaust) falls from about 55% for conventional diesel fuel to less than 1% when the oxygen content of the fuel is above about 25% by mass, as shown in Figure 1. It has been well established that addition of oxygenates to automotive fuel, including both diesel fuel as well as gasoline, reduces NOx and CO emissions by reducing flame temperatures. This is the basis for addition of oxygenates to produce reformulated gasoline in selected portions of the country. Of course, this is also accompanied by a slight reduction in fuel economy. A new overall picture of diesel combustion has been developed by Dec [2], in which …

At the Thirteenth International Symposium on Heavy Ion Inertial Fusion (HIF Symposium), we presented magnet shielding calculations for 72-, 128, 200, and 288-beam versions of the HYLIFE-II power plant design. In all cases, we found the radiation-limited lifetimes of the last set of final focusing magnets to be unacceptably short. Since that time, we have completed follow-on calculations to improve the lifetime of the 72-beam case. Using a self-consistent final focusing model, we vary parameters such as the shielding thicknesses and compositions, focusing length, angle-of-attack to the target, and the geometric representation of the flibe pocket, chamber, and blanket. By combining many of these shielding features, we are able to demonstrate a magnet shielding design that would enable the last set of final focusing magnets to survive for the lifetime of the power plant.

Heavy Ion Fusion (HIF) is considered a promising path to a practical fusion reactor. A driver for a HIF reactor will require a large number of quadrupole arrays to focus heavy ion beams. A conceptual design, and trade off studies of the quadrupole array based on racetracks are presented. A comparison with a conventional shell magnet is given and advantages and disadvantages are discussed. A more detailed design of a single quadrupole for the High Current experiment (HCX) is presented and discussed.

This paper discusses the results of thermal annealing and in-situ second harmonic generation (SHG) damage tests performed on six rapid growth KDP type 1 doubler crystals at 1064 nm (1 {omega}) on the Zeus automated damage test facility. Unconditioned (S/1) and conditioned (R/1) damage probability tests were performed before and after thermal annealing, then with and without SHG on six doubler crystals from the NIF-size, rapid growth KDP boule F6. The tests revealed that unannealed, last-grown material from the boule in either prismatic or pyramidal sectors exhibited the highest damage curves. After thermal annealing at 160 C for seven days, the prismatic sector samples increased in performance ranging from 1.6 to 2.4X, while material from the pyramidal sector increased only modestly, ranging from 1.0 to 1.4X. Second harmonic generation decreased the damage fluence by an average of 20 percent for the S/1 tests and 40 percent for R/1 tests. Conversion efficiencies under test conditions were measured to be 20 to 30 percent and compared quite well to predicted behavior, as modeled by LLNL frequency conversion computer codes. The damage probabilities at the 1 {omega} NIF redline fluence (scaled to 10 ns via t{sup 0.5}) for S/1 tests for the unannealed …

A 24 g aluminum sphere was shot at a sparse array of cylinders with nominal initial projectile velocity of 4 and 5 km/s. Pressure profiles were measured with cased carbon resistor gages at two locations in a projectile impacted water filled cylinder and two of its neighbors on three shots. The pressure maxima were in the 1-13 kbars range. The experiments are modeled with the ALE3D code and several techniques are used to concentrate zoning at places of interest. There is excellent agreement between the measured and calculated pressure profiles for two shots and good agreement for the third. Comparison of the calculated pressure profiles with those from more refined calculations for two shots suggest that we are near convergence with respect to zone size.

An experimental study of the combustion of two isomers of pentane, n-pentane and iso-pentane, in laminar cool flames has been carried out. Three flames were studied, one with n-pentane, the second with iso-pentane, and the third with an equimolar mixture of the two isomers. Particular attention has been given to the low temperature region ahead of the hot region of the flame and the cool flame chemistry occurring there. A unique experimental facility has been used to provide access to this cool flame region. Comparisons are made of the structures of the three flames, with particular attention on the different intermediate species produced and the correlations between the fuel molecule structure and the specific intermediates produced.

We are continuing with the development of fast ({approx} 12 MeV) neutron imaging techniques for use in NDE applications. Our goal is to develop a neutron imaging system capable of detecting sub-mm-scale cracks, cubic-mm-scale voids and other structural defects in heavily-shielded low-Z materials within thick sealed objects. The final system will be relatively compact (suitable for use in a small laboratory) and capable of acquiring both radiographic and full tomographic image sets. The design of a prototype imaging detector will be reviewed and results from several recent imaging experiments will be presented. The concurrent development of an intense, accelerator-driven neutron source suitable for use with the final production imaging system will also be discussed.

Calibration of hydroacoustic stations for nuclear explosion monitoring is important for increasing monitoring capability and confidence from newly installed stations and from existing stations. Calibration of hydroacoustic stations is herein defined as the near-field precision location of the hydrophones and determination of the amplitude response; and the regional-scale calibration of acoustic traveltimes, bathymetric shadowing, diffraction, and reflection as recorded at a particular station. An important type of calibration not considered here is ocean-basin-scale calibration of a hydroacoustic monitoring system. To understand how to best conduct hydroacoustic station calibrations, an experiment was conducted in May 1999 at Ascension Island in the South Atlantic Ocean. The experiment made use of a British oceanographic research vessel towing an airgun array and collected data over three MILS hydrophones that were in use by the National Data Center and the International Data Center. From the towed airgun data we were able to determine the location for each of the three hydrophones to accuracy better than 100 meters in latitude, longitude, and depth. The agreement with the nominal locations was excellent in depth and to within 1 km in latitude and longitude. The depths determined for the hydrophones and the ocean bottom depths determined from the …

A common coil design for a high-field accelerator dipole magnet using a Nb{sub 3}Sn cable with the React-and-Wind approach is pursued by a collaboration between Fermilab and LBNL. The design requirements for the cable include a high operating current so that a field of 10-11 T can be produced, together with a low critical current degradation due to bending around a 90 mm radius. A program, using ITER strands of the internal tin type, was launched to develop the optimal cable design for React-and-Wind common coil magnets. Three prototype cable designs, all 15 mill wide, were fabricated: a 41-strand cable with 0.7 mm diameter strands; a 57-strand cable with 0.5 mm diameter strands; and a 259 strand multi-level cable with a 6-around-1 sub-element using 0.3 mm diameter wire. Two versions of these cables were fabricated: one with no core and one with a stainless steel core. Additionally, the possibility of a wide (22 mm) cable made from 0.7 mm strand was explored. This paper describes the first results of the cable program including reports on cable fabrication and reaction, first winding tests and first results of the measurement of the critical current degradation due to cabling and bending.

The problem of generating light neutrinos within supersymmetric models is discussed. It is shown that the hierarchy of scales induced by supersymmetry breaking can give rise to suppression factors of the correct order of magnitude to produce experimentally allowed neutrino spectra.

This paper presents our early results in applying data mining techniques to the problem of finding radio-emitting galaxies with a bent-double morphology. In the past, astronomers on the FIRST (Faint Images of the Radio Sky at Twenty-cm) survey have detected such galaxies by first inspecting the radio images visually to identify probable bent-doubles, and then conducting observations to confirm that the galaxy is indeed a bent-double. Our goal is to replace this visual inspection by a semi-automated approach. In this paper, we present a brief overview of data mining, describe the features we use to discriminate bent-doubles from non-bent-doubles, and discuss the challenges faced in defining meaningful features in a robust manner. Our experiments show that data mining, using decision trees, can indeed be a viable alternative to the visual identification of bent-double galaxies.