The Advanced Limiter-divertor Plasma-facing Systems (ALPS) program was initiated in order to evaluate the potential for improved performance and lifetime for plasma-facing systems. The main goal of the program is to demonstrate the advantages of advanced limiter/divertor systems over conventional systems in terms of power density capability, component lifetime, and power conversion efficiency, while providing for safe operation and minimizing impurity concerns for the plasma. Most of the work to date has been applied to free surface liquids. A multi-disciplinary team from several institutions has been organized to address the key issues associated with these systems. The main performance goals for advanced limiters and diverters are a peak heat flux of >50 MW/m{sup 2},elimination of a lifetime limit for erosion, and the ability to extract useful heat at high power conversion efficiency ({approximately}40%). The evaluation of various options is being conducted through a combination of laboratory experiments, modeling of key processes, and conceptual design studies. The current emphasis for the work is on the effects of free surface liquids on plasma edge performance.

Plutonium production at U.S. Department of Energy Hanford site has created massive amounts of radioactive and mixed wastes. Over 1.3 trillion liters of liquid waste have been discharged into the ground, the largest part of which has been absorbed by the upper soil layers with a small fraction migrating into the groundwater. Approximately 350 million liters of other low and high-level mixed wastes were stored in underground tanks between 1944 and 1980. These tanks contain organic materials that were introduced during the production and processing of plutonium, such as ethylenediametetraacetic acid (EDTA), tributyl phosphate, hexone, paraffin hydrocarbon and other minor organic and inorganic components. The quantity of EDTA is estimated to be 83 metric tons in the underground tanks. Several single-shell tanks are known or suspected to have leaked. It was reported that since 1995, approximately four million liters of mixed waste might have entered the soil beneath the single-shell tanks. This volume of waste is estimated to contain as much as one million curies of radioactivity.

The time-dependence of the wet oxidation of high-Al-content AlGaAs can be either linear, indicating reaction-rate limitation, or parabolic, indicating diffusion-limited rates. The transition from linear to parabolic time dependence can be explained by the increased rate of the formation of intermediate As{sub 2}O{sub 3} vs. its reduction to elemental As. A steadily increasing thickness of the As{sub 2}O{sub 3}-containing region at the oxidation front will shift the process from the linear to the parabolic regime. This shift from reaction-rate-limited (linear) to diffusion-limited (parabolic) time dependence is favored by increasing temperature or increasing Al mole fraction.

Self-aligned JFETs with a carbon-doped p{sup +} region have been reported for the first time. For these JFETs, both the channel and p{sup +} region were grown by metal organic chemical vapor deposition (MOCVD) and are termed epitaxial JFETs in this study. The epitaxial JFETs were compared to ion implanted JFETs of similar channel doping and threshold voltage. Both JFETs were fabricated using the same self-aligned process for doping the source and drain regions of the JFET and for eliminating excess gate capacitance of conventional JFETs. The gate turn-on voltage for the epitaxial JFETs was 1.06 V, about 0.1 V higher than for the implanted JFETs. The reverse breakdown voltage was similar for both JFETs but the reverse gate leakage current of the epitaxial JFETs was 1-3 orders of magnitude less than the implanted JFETs. The epitaxial JFETs also showed higher transconductance and lower knee voltage than the implanted JFETs.

The prospect of using computer simulations to calculate radiation-induced defect production and its influence on microstructure evolution and mechanical property changes during prolonged irradiation of nuclear materials has been a beckoning, yet elusive goal for many years. However, the enormous progress achieved in computational physics for calculating reliable, yet tractable interatomic potentials, coupled with vast improvements in computational power have brought this hope to near reality. In order to develop modeling and simulation tools for predicting the irradiation response of nuclear structural materials, models must be implemented and tested across all relevant length and time scales. We discuss the development and implementation of a modeling methodology that consists of the linkage and hierarchical use of ab initio electronic structure calculations, molecular dynamics (MD) simulations, and kinetic Monte Carlo (KMC) simulations. This methodology can describe length and time scales from nanometers to hundreds of microns and from picoseconds to years, respectively. The ideas are demonstrated in two applications. First, we describe simulations that describe the irradiation and subsequent isochronal annealing of Pb, a low melting point fcc metal, and compare the results to experiments. Second, we show how these methods can be used to investigate damage production and freely migrating defect …

Inelastic nuclear scattering of X-rays from the 14.413 keV nuclear resonance of {sup 57}Fe was employed to measure directly the Fe-projected phonon density of states (DOS) in MBE-grown Fe/Cr(00l) superlattices on MgO(001). The Moessbauer-inactive {sup 56}Fe isotope was used in the Fe layers. A 1{angstrom} thick Moessbauer-active {sup 57}Fe-probe layer (95% enriched) was placed at different locations within the Fe layers. This procedure permits one to distinguish phonon density of states at the Fe-Cr-interface from that at the center of the Fe-film. Distinct differences have been observed in the DOS of our samples. The phonon DOS of an amorphous Tb{sub 33}Fe{sub 67} alloy film was found to be a broad and structureless hump, contrary to that of an epitaxial TbFe{sub 2} film, which exhibits characteristic features.

Multiple current limiting mechanisms exist from the nanometer to millimeter scale in Ag-sheathed (Bi,Pb)-2223 tapes. Recent studies of the zero-field critical current density (J{sub c} (0T, 77K)), the irreversibility field (H*) and the crack microstructure elucidate these properties. We show that H*(77K) can vary significantly over the range {approximately}120-260 mT, independently of J{sub c} (0T, 77K). Cracks, actual or incipient, exist on the sub to several hundred micron scale. Surface magneto optical imaging of whole tapes, correlated to subsequent ultrasonic fracture analysis of. the bare 2223 filaments extracted by dissolving away the Ag shows that even composites having J{sub c} (0T, 77K) values of 60 kA/cm{sup 2} exhibit strong signs of unhealed rolling damage. These combined studies show that today's very best 2223 tapes are still far from full optimization.

The new generation of powerful DSM and SMP cluster computers enables simulations of fluid dynamics at sufficient resolution to compute the complex nonlinear interactions of small-scale turbulent motions with a large-scale driving flow. With a new programming model of hierarchical shared memory multitasking, it is possible to exploit these new systems without disrupting the flow of small and medium-sized jobs that makes their existence possible.

Effective seismic interrogation of the near subsurface requires that measured parameters, such as compressional and shear velocities and attenuation, be related to important soil properties. Porosity, composition (clay content), fluid content and type are of particular interest. The ultrasonic (100-500 kHz) pulse transmission technique was used to collect data for highly attenuating materials appropriate to the vadose zone. Up to several meters of overburden were simulated by applying low uniaxial stress of 0 to about 0.1 MPa to the sample. The approach was to make baseline measurements for pure quartz sand, because the elastic properties are relatively well known except at the lowest pressures. Clay was added to modify the sample microstructure and ultrasonic measurements were made to characterize the effect of the admixed second phase. Samples were fabricated from Ottawa sand mixed with a swelling clay (Wyoming bentonite). The amount of clay added was 1 to 40% by mass. Compressional (P) velocities are low (228-483 m/s), comparable to the sound velocity in air. Shear (S) velocities are about half of the compressional velocity (120-298 m/s), but show different sensitivity to microstructure. Adding clay increases the shear amplitude dramatically with respect to P, and also changes the sensitivity of the …

Construction of a single-pass free-electron laser (FEL) based on the self-amplified spontaneous emission (SASE) mode of operation is nearing completion at the Advanced Photon Source (APS) with initial experiments imminent. The APS SASE FEL is a proof-of-principle fourth-generation light source. As of January 1999 the undulator hall, end-station building, necessary transfer lines, electron and optical diagnostics, injectors, and initial undulatory have been constructed and, with the exception of the undulatory, installed. All preliminary code development and simulations have also been completed. The undulator hall is now ready to accept first beam for characterization of the output radiation. It is the project goal to push towards fill FEL saturation, initially in the visible, but ultimately to W and VUV, wavelengths.

I discuss the role of anomalies in the modern development of quantum field theory and their implications for physics.

The matrix elements of the four quark operators needed to predict many weak interaction processes can be evaluated using the large N{sub c} limit of quantum chromodynamics. At leading order in the large N{sub c} expansion, the weak matrix elements of four quark operators factorize into independent matrix elements of two quark operators, a common approximation being used today. At the next leading order, the weak matrix elements acquire the leading scale and scheme dependence expected for these matrix elements in full QCD. They discuss methods to evaluate these matrix elements which involve matching perturbative QCD calculations at short distance to non-perturbative hadronic matrix elements at long distance.

Sandia National Laboratories (SNL) designs mechanical systems with components that must survive high frequency shock environments including pyrotechnic shock. These environments have not been simulated very well in the past at the payload system level because of weight limitations of traditional pyroshock mechanical simulations using resonant beams and plates. A new concept utilizing tuned resonators attached to the payload system and driven with the impact of an airgun projectile allow these simulations to be performed in the laboratory with high precision and repeatability without the use of explosives. A tuned resonator has been designed and constructed for a particular payload system. Comparison of laboratory responses with measurements made at the component locations during actual pyrotechnic events show excellent agreement for a bandwidth of DC to 4 kHz. The bases of comparison are shock spectra. This simple concept applies the mechanical pyroshock simulation simultaneously to all components with the correct boundary conditions in the payload system and is a considerable improvement over previous experimental techniques and simulations.

Condensate flow rate is an important factor in designing dehumidifiers or evaporators. In this paper, the latentj fimtor is used to analyze the dehumidification performance of two plate-fin tube heat exchangers. This latent j factor, analogous to the total j factor, is a flmction of the mass transfa coefllcient, the volumetric air flow rate, and the Schmidt number. This latent j factor did predict condensate flow rate more directly and accurately than any other sensiblej factor method. The Iatentj factor has been used in the present study because the sensible j factor correlations presented in the literature failed to predict the condensate flow rate at high Reynolds numbers. Results show that the latent j i%ctor em be simply correlated as a fhnction of the Reynolds number based on the tube outside diameter and number of rows of the heat exchanger.

Using the EBIT facility in Livermore we produce definitive atomic data for input into spectral synthesis codes. Recent, measurements of line excitation and dielectronic recombination of highly charged K-shell and L-shell ions are presented to illustrate this point.

Micromachined beams are commonly used to measure material properties in MEMS. Such measurements are complicated by the fact that boundary effects at the ends of the beams have a significant effect on the properties being measured. In an effort to improve the accuracy and resolution of such measurements, we are conducting a study of support post compliance in cantilever and fixed-fixed beams. Three different support post designs have been analyzed by finite element modeling. The results are then compared to measurements made on actual devices using interferometry. Using this technique, the accuracy of measurements of Young's modulus has been improved. Continuing work will also improve the measurement of residual stress.

We have designed, fabricated, tested and modeled a first generation small area test structure for MEMS fracture studies by electrostatic rather than mechanical probing. Because of its small area, this device has potential applications as a lot monitor of strength or fatigue of the MEMS structural material. By matching deflection versus applied voltage data to a 3-D model of the test structure, we develop high confidence that the local stresses achieved in the gage section are greater than 1 GPa. Brittle failure of the polycrystalline silicon was observed.

The relative density of BCl radicals has been measured in a modified Applied Materials DPS metal etch chamber using laser-induced fluorescence. In plasmas containing mixtures of BCl{sub 3} with Cl{sub 2}, Ar and/or N{sub 2}, the relative BCl density was measured as a function of source and bias power, pressure, flow rate, BCl{sub 3}/Cl{sub 2} ratio and argon addition. To determine the influence of surface materials on the bulk plasma properties, the relative BCl density was measured using four different substrate types; aluminum, alumina, photoresist, and photoresist-patterned aluminum. In most cases, the relative BCl density was highest above photoresist-coated wafers and lowest above blanket aluminum wafers. The BCl density increased with increasing source power and the ratio of BCl{sub 3} to Cl{sub 2}, while the addition of N{sub 2} to a BCl{sub 3}/Cl{sub 2} plasma resulted in a decrease in BCl density. The BCl density was relatively insensitive to changes in the other plasma parameters.

Changes in physical and chemical characteristics of aquatic habitats made to reduce or eliminate ecological risks can sometimes have unforeseen consequences. Environmental management activities on the U.S. Dept. of Energy reservation in Oak Ridge, Tennessee,have succeeded in improving water quality in streams impacted by discharges fi-om industrial facilities and waste disposal sites. The diversity and abundance of pollution-sensitive components of the benthic macroinvertebrate communities of three streams improved after new waste treatment systems or remedial actions reduced inputs of various toxic chemicals. Two of the streams were known to be mercury-contaminated from historical spills and waste disposal practices. Waterborne mercury concentrations in the third were typical of uncontaminated systems. In each case, concentrations of mercury in fish, or the apparent biological availability of mercury increased over the period during which ecological metrics indicated improved water quality. In the system where waterborne mercury concentrations were at background levels, increased mercury bioaccumulation was probably a result of reduced aqueous selenium concentrations; however, the mechanisms for increased mercury accumulation in the other two streams remain under investigation. In each of the three systems, reduced inputs of metals and inorganic anions was followed by improvements in the health of aquatic invertebrate communities. However, this …

It is difficult to accurately predict actinide behavior during the alkaline leaching of Hanford's radioactive sludges due to the diverse chemical and radiolytic conditions existing in these wastes. The results of Pu dissolution during experimental washing of sludge simulants from the BiPO{sub 4} Redox, and PUREX processes shows that {le} 2.l% Pu is dissolved during contact with alkaline media, but up to 65.5% Pu may be dissolved in acidic media. The dissolution of Cr, Fe, Nd, and Mn has also been observed, and the results of solid state, radioanalytical, and spectroscopic investigations are detailed.

Capacitor designs for DOE and/or DoD applications are now driven by two major factors; first, the need to reduce component volumes (attain higher energy density) to permit inclusion of additional components and/ or sensors in systems and second, the continuing budget constraints. The reduced volume and cost must be achieved with no sacrifices in functionality, reliability and safety. Since this study was initiated, we have seen a general, continuous increase in resulting short-time breakdown (STB) values, with particular improvements noted on thermal cycled capacitors. Process and results support our prediction that a 50Y0-650A volume reduction can be achieved with no reduction in performance and reliability.

Backfills have been part of Sandia National Laboratories' [Sandia's] Waste Isolation Pilot Plant [WIPP] designs for over twenty years. Historically, backfill research at Sandia has depended heavily on the changing mission of the WIPP facility. Early testing considered heat producing, high level, wastes. Bentonite/sand/salt mixtures were evaluated and studies focused on developing materials that would retard brine ingress, sorb radionuclides, and withstand elevated temperatures. The present-day backfill consists of pure MgO [magnesium oxide] in a pelletized form and is directed at treating the relatively low contamination level, non-heat producing, wastes actually being disposed of in the WIPP. It's introduction was motivated by the need to scavenging CO{sub 2} [carbon dioxide] from decaying organic components in the waste. However, other benefits, such as a substantial desiccating capacity, are also being evaluated. The MgO backfill also fulfills a statutory requirement for assurance measures beyond those needed to demonstrate compliance with the US Environmental Protection Agency [EPA] regulatory release limits. However, even without a backfill, the WIPP repository design still operates within EPA regulatory release limits.

Article on electronic transport in extended systems and the application to carbon nanotubes.

Article on mechanical deformations and coherent transport in carbon nanotubes.