A class of planar microstructure is proposed which provide high accelerating gradients when excited by an infrared laser pulse. These structures consist of parallel dielectric slabs separated by a vacuum gap; the dielectric or the outer surface coating are spatially modulated at the laser wavelength along the beam direction so as to support a standing wave accelerating field. We have developed numerical and analytic models of the accelerating mode fields in the structure. We show an optimized coupling scheme such that this mode is excited resonantly with a large quality factor. The status of planned experiments on fabricating and measuring these planar structures will be described.

A model of drilling by high radiance pulsed lasers is described. The model involves a one-dimensional description of heat transport below the bottom of the hole, hydrodynamic expansion of the vapor and compressed air, and light propagation through the vapor. The pressure and energy of the vapor are taken from a separate Saha equilibrium code. The boundary conditions at the vaporization surface include the formation of a transition layer within which macroscopic fluid conditions axe reached. The absorption mechanisms are photoionization and inverse bremsstrahlung. The model has been applied to the case of drilling in stainless steel with green copper laser light, for peak input intensities ranging from 10{sup 8} to 4 {times} 10{sup 10} W/cm{sup 2}. Below 3 {times} 10{sup 8} W/cm{sup 2}, there is negligible absorption in the vapor and ablation increases rapidly with intensity. After decreasing for a short interval beyond this point, the ablation rate then increases steadily with power because of a growing electron thermal conduction to the surface. The experimental ablation rate exhibits a somewhat faster overall growth. It appears comparable to the model at low power but is about five times greater at the highest power.

We consider the solution of time-dependent, energy-dependent, discrete ordinates, and nonlinear radiative transfer problems on three-dimensional unstructured spatial grids. We discuss the solution of this class of transport problems, using the code TETON, on large distributed-memory multinode computers having multiple processors per ''node'' (e.g. the IBM-SP). We discuss the use of both spatial decomposition using message passing between ''nodes'' and a threading algorithm in angle on each ''node''. We present timing studies to show how this algorithm scales to hundreds and thousands of processors. We also present an energy group ''batching'' algorithm that greatly enhances cache performance. Our conclusion, after considering cache performance, storage limitations and dependencies inherent in the physics, is that a model that uses a combination of message-passing and threading is superior to one that uses message-passing alone. We present numerical evidence to support our conclusion.

A statistical analysis of shaped charge jet break-up was carried out in order to investigate the role of nonlinear instabilities leading to the particulation of the jet. Statistical methods generally used for studying fluctuations in nonlinear dynamical systems are applied to experimentally measured velocities of the individual particles. In particular we present results suggesting the deviation of non-Gaussian behavior for interparticle velocity correlations, characteristic of nonlinear dynamical systems. Results are presented for two silver shaped charge jets that differ primarily in their material processing. We provide evidence that the particulation of a jet is not random, but has its origin in a deterministic dynamical process involving the nonlinear coupling of two oscillators analogous to the underling dynamics observed in Rayleigh-Benard convection and modeled in the return map of Curry and Yorke.

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Traditionally law enforcement agencies have relied on basic measurement and imaging tools, such as tape measures and cameras, in recording a crime scene. A disadvantage of these methods is that they are slow and cumbersome. The development of a portable system that can rapidly record a crime scene with current camera imaging, 3D geometric surface maps, and contribute quantitative measurements such as accurate relative positioning of crime scene objects, would be an asset to law enforcement agents in collecting and recording significant forensic data. The purpose of this project is to develop a feasible prototype of a fast, accurate, 3D measurement and imaging system that would support law enforcement agents to quickly document and accurately record a crime scene.

Maintaining a contamination free sample preparation lab for biological 14 C AMS requires the same or more diligence as a radiocarbon dating prep lab. Isotope ratios of materials routinely range over 4-8 orders of magnitude in a single experiment, dosing solutions contain thousands of DPM and gels used to separate proteins possess 14 C ratios of 1pMC. Radiocarbon contamination is a legacy of earlier tracer work in most biological laboratories, even if they were never hot labs. Removable surface contamination can be found and monitored using swipes. Contamination can be found on any surface routinely touched: door knobs, light switches, drawer handles, water faucets. In general, all surfaces routinely touched need to be covered with paper, foil, or plastic that can be changed frequently. Shared air supplies can also present problems by distributing hot aerosols throughout a building. Aerosols can be monitored for 14 C content using graphitized coal or fullerene soot mixed with metal powder as an absorber. The monitors can be set out in work spaces for 1-2 weeks and measured by AMS with regular samples. Frequent air changes help minimize aerosol contamination in many cases. Cross contamination of samples can be minimized by using disposable plastic or …

Kaon electroproduction on deuterium and hydrogen targets has been measured at beam energies of 3.245 and 2.445 GeV and momentum transfer Q{sup 2}=0.38 and 0.5 GeV{sup 2}. Associated {Lambda} production off a proton in the deuteron exhibits a quasifree production mechanism. The production of {Sigma}{sup {minus}} off the neutron could be extracted for the first time with reasonable errors.

Detonation of an insensitive high explosive formulated with a fluorine containing binder produces a large amount of condensed carbon and gaseous HF product, which transforms into CF{sub 4} as the pressure is increased. The former (carbon condensation) is characterized by slow energy release, while the latter (HF) has no shockwave data. We have identified that these two items are the key factors, which make reliable prediction of the performance of an insensitive high explosive very difficult. This paper describes physical models to address these issues and apply the models to analyze experimental data of LX-17.

The room-temperature elastic moduli, fracture strength, and fracture toughness of dense, fine-grained, pure Ce{sub 0.9}Gd{sub 0.1}O{sub 1.95} and composites containing 1.3 and 9.1 wt. % Al{sub 2}O{sub 3} were investigated. Addition of 9.1 wt.% Al{sub 2}O{sub 3} to Ce{sub 0.9}Gd{sub 0.1}O{sub 1.95} changed the fracture mode from intergranular to transgranular and increased room-temperature fracture strength from 65 to 125 MPa and fracture toughness from 1.3 to 1.6 MPam{sup 1/2}. In addition, steady-state compressive creep was measured for Ce{sub 0.9}Gd{sub 0.1}O{sub 1.95} and the Ce{sub 0.9}Gd{sub 0.1}O{sub 2{minus}x} + 9.1 wt.% Al{sub 2}O{sub 3} composite. The stress exponent {approx}1.3 and the activation energy {approx}480 kJ/mole for Ce{sub 0.9}Gd{sub 0.1}O{sub 1.95} suggested diffusional flow controlled by the cations. There was no difference in creep rate between Ce{sub 0.9}Gd{sub 0.1}O{sub 2{minus}x} and the composite.

The basic mechanisms of single-event upset are reviewed, including charge collection in silicon junctions and transistors, and properties of single-event upset in CMOS static random access memory (SRAM) cells. The mechanisms are illustrated through the use of three-dimensional device and circuit simulations. Technology trends and implications for commercial devices are discussed.

The cryogenic characteristics in energy extraction of the four fifteen-meter-diameter superconducting solenoids of the g-2 magnet are reported in this paper. The energy extraction tests at full-current and half-current of its operating value were deliberately carried out for the quench analyses and evaluation of the cryogenic system. The temperature profiles of each coil mandrel and pressure profiles in its helium cooling tube during the energy extraction are discussed. The low peak temperature and pressure as well as the short recovery time indicated the desirable characteristics of the cryogenic system.

One reliable and convenient way of processing the cross sections in the resolved energy region is by use of the generalized pole representation, whereby the Doppler-broadening calculation can be carried out rigorously using the analytical approach. So far, its applications have been limited to cases with resonance parameters specified by the Reich-Moore formalism. Although such an approach, in principle, can be extended to all three remaining representations of resolved resonance parameters specified by the ENDF data format, there is no computational tool for handling such a task at present. Given that Breit-Wigner formalisms are probably the most widely used by any evaluated nuclear data library to represent cross sections, a special effort has to be made to convert the single level and multilevel Breit-Wigner resonance parameters to pole parameters. A FORTRAN computer code BW2PR has been developed for this purpose. Extensive calculations have been performed to demonstrate that the proposed method ensures the conservation of the information contained originally in Breit-Wigner resonance parameters. This will make it possible to apply the exact Doppler-broadening method to a larger collection of nuclides.

A sodium carbonate salt transport system is required to support the Molten Salt Oxidation system being constructed at Lawrence Livermore National Laboratory. We are embarking on a project to create a national test bed for evaluating mixed waste destruction technologies. This project is called the Mixed Waste Management Facility. It is currently in the second phase of design and will be operational in 1998. One of the first technologies demonstrated in this facility is Molten Salt Oxidation. Molten Salt Oxidation is a thermal process that destroys the organic constituents of mixed and hazardous wastes. Sodium carbonate salt is heated in a reactor vessel to approximately 950{degrees}C. Organic wastes, along with oxidant air, are injected under the pool of molten salt. A catalytic reaction occurs converting the organics into CO{sub 2} and water. Inorganic constituents in the salt such as metals, silica, alumina, and radionuclides remain captured in the salt. Chlorides in the waste feed are converted in the salt to sodium chloride. As these impurities build up in the salt, the salt must be recycled to remove them or else the reaction rate is reduced. Spent salt is periodically taken from the reactor and transported to a salt recycle system. …

The calculations with the broad-group cross-section library Bugle-96, and atom displacement (dpa) cross sections for iron, both derived from ENDF/B-VI data, result in higher calculated fast neutron fluxes, better agreement of calculations with radiometric dosimeter measurements, and significantly slower dpa rate attenuation through pressure vessel walls relative to the results with their predecessors: the Sailor library and ASTM iron dpa cross sections.

Low power Electromagnetic (EM) Wave sensors can measure general properties of human speech articulator motions, as speech is produced. See Holzrichter, Burnett, Ng, and Lea, J.Acoust.Soc.Am. 103 (1) 622 (1998). Experiments have demonstrated extremely accurate pitch measurements (< 1 Hz per pitch cycle) and accurate onset of voiced speech. Recent measurements of pressure-induced tracheal motions enable very good spectra and amplitude estimates of a voiced excitation function. The use of the measured excitation functions and pitch synchronous processing enable the determination of each pitch cycle of an accurate transfer function and, indirectly, of the corresponding articulator motions. In addition, direct measurements have been made of EM wave reflections from articulator interfaces, including jaw, tongue, and palate, simultaneously with acoustic and glottal open/close signals. While several types of EM sensors are suitable for speech articulator measurements, the homodyne sensor has been found to provide good spatial and temporal resolution for several applications.

The objective of this talk is to compare the CDF W+ {ge} 3 Jets data with Monte Carlo predictions using the standard model with the top quark. The data is seen to be consistent with these predictions using the t{bar t} production rate indicated by the SVX b-tagging and the previously reported top mass.

Large amounts of data obtained from surveillance capsules and test reactor experiments are needed, comprising many different materials and different irradiation conditions, to develop generally applicable damage prediction models that can be used for industry standards and regulatory guides. Version 1 of the Embrittlement Data Base (EDB) [I] is such a comprehensive collection of such data resulting from the merging of the Power Reactor Embrittlement Data Base (PR-EDB) [2] and the Test Reactor Embrittlement Data Base (TR-EDB) [3]. Fracture toughness data were also integrated into Version 1 of the EDB. The EDB data files are in dBASE format and can be accessed with a personal computer using the DOS or WINDOWS operating system. A utility program has been written to investigate radiation embrittlement using this data base. The utility program is used to retrieve and select specific data, manipulate data, display data to the screen or printer, and to tit and plot Charpy impact data.

Electric and hybrid-electric vehicles are being developed and commercialized around the world at a rate never before seen. These efforts are driven by the prospect of vehicles with lower emissions and higher fuel efficiencies. The widespread adaptation of such vehicles promises a cleaner environment and a reduction in the rate of accumulation of greenhouse gases, Critical to the success of this technology is the use of electrochemical power sources such as batteries and fuel cells, which can convert chemical energy to electrical energy more efficiently and quietly than internal combustion engines. This overview will concentrate on the work being conducted in the US to develop advanced propulsion systems for the electric and hybrid vehicles, This work is spearheaded by the US Advanced Battery Consortium (USABC) for electric vehicles and the Partnership for a New Generation of Vehicle (PNGV) for hybrid-electric vehicles, both of which can be read about on the world wide web (www.uscar.tom). As is commonly known, electric vehicles rely strictly on batteries as their source of power. Hybrid-electric vehicles, however, have a dual source of power. An internal combustion engine or eventually a fuel cell supplies the vehicle with power at a relatively constant rate. A battery pack …

In this paper, a single-stage G-M refrigerator with the regenerator set outside the cylinder is presented. The experimental system for testing the performance of the cryocooler was constructed. The lowest temperature was 14K when the operating frequency was 0.6 Hz. The cooling capacity of 4.4W has been obtained at 20K. The effects of operating parameters of the refrigerator on cooling performance were also experimentally studied.

The ARAC Client System allows users (such as emergency managers and first responders) with commonly available desktop and laptop computers to utilize the central ARAC system over the Internet or any other communications link using Internet protocols. Providing cost-effective fast access to the central ARAC system greatly expands the availability of the ARAC capability. The ARAC Client system consists of (1) local client applications running on the remote user's computer, and (2) ''site servers'' that provide secure access to selected central ARAC system capabilities and run on a scalable number of dedicated workstations residing at the central facility. The remote client applications allow users to describe a real or potential them-bio event, electronically sends this information to the central ARAC system which performs model calculations, and quickly receive and visualize the resulting graphical products. The site servers will support simultaneous access to ARAC capabilities by multiple users. The ARAC Client system is based on object-oriented client/server and distributed computing technologies using CORBA and Java, and consists of a large number of interacting components.

The mesoscale sea breeze has important consequences for many densely populated coastal environments, including convection initiation, aviation safety, and air quality. The sea breeze characteristics before and after sunset are markedly different (Sha et al 1993). A gravity current will form during the early afternoon due to the relatively large density difference between the land and sea air. During the afternoon, as the lighter land air is forced upward by the cooler dense sea air, Kelvin-Helmholtz (KH) billows often form along the interface, as well as thin regions of turbulent rising air, playing a crucial role in the mixing process (Simpson 1994). After sunset, the frontal zone expands as longwave radiation cools the surface which reduces vertical mixing. With further inland penetration, the sea breeze encounters increasingly stable air near the ground, resulting in the formation of an undular bore or cutoff vortex (Sha et al. 1993). It has been demonstrated that large-scale winds have profound effects on both the strength and inland penetration of sea breezes (Arritt 1993, among others). In general, offshore flow results in a sharper frontal discontinuity and less inland penetration, while onshore flow produces weaker fronts which may penetrate further inland. Most sea breeze studies …

In the second half of the 1990`s, LLNL and others anticipate designing and beginning construction of the National Ignition Facility (NIF). The NIF will be capable of producing the worlds first laboratory scale fusion ignition and bum reaction by imploding a small target. The NIF will utilize approximately 192 simultaneous laser beams for this purpose. The laser will be capable of producing a shaped energy pulse of at least 1.8 million joules (MJ) with peak power of at least 500 trillion watts (TV). In total, the facility will require more than 7,000 large optical components. The performance of a high power laser of this kind can be seriously degraded by the presence of low amplitude, periodic modulations in the surface and transmitted wavefronts of the optics used. At high peak power, these phase modulations can convert into large intensity modulations by non-linear optical processes. This in turn can lead to loss in energy on target via many well known mechanisms. In some cases laser damage to the optics downstream of the source of the phase modulation can occur. The database described here contains wavefront phase maps of early prototype optical components for the NIF. It has only recently become possible …

Plasma rockets are being considered for both Earth-orbit and interplanetary missions because their extremely high exhaust velocity and ability to modulate thrust allow very efficient use of propellant mass. In such rockets, a hydrogen or helium plasma is RF-heated and confined by axial magnetic fields produced by coils around the plasma chamber. HTS coils cooled by the propellant are desirable to increase the energy efficiency of the system. We describe a set of prototype high-temperature superconducting (HTS) coils that are being considered for the VASIMR ( Variable Specific Impulse Magnetoplasma Rocket) thruster proposed for testing on the Radiation Technology Demonstration (RTD) satellite. Since this satellite will be launched by the Space Shuttle, for safety reasons liquid helium will be used as propellant and coolant. The coils must be designed to operate in the space environment at field levels of 1 T. This generates a unique set of requirements. Details of the overall winding geometry and current density, as well as the challenging thermal control aspects associated with a compact, minimum weight design will be discussed.