Liquid crystal spatial light modulator technology appropriate for high-resolution wavefront control has recently become commercially available. Some of these devices have several hundred thousand controllable degrees of freedom, more than two orders of magnitude greater than the largest conventional deformable mirror. We will present results of experiments to characterize the optical properties of these devices and to utilize them to correct aberrations in an optical system. We will also present application scenarios for these devices in high-power laser systems.

Results of experiments with the laser guide star adaptive optics system on the 3-meter Shane telescope at Lick Observatory have demonstrated a factor of 4 performance improvement over previous results. Stellar images recorded at a wavelength of 2 {micro}m were corrected to over 40% of the theoretical diffraction-limited peak intensity. For the previous two years, this sodium-layer laser guide star system has corrected stellar images at this wavelength to {approx}10% of the theoretical peak intensity limit. After a campaign to improve the beam quality of the laser system, and to improve calibration accuracy and stability of the adaptive optics system using new techniques for phase retrieval and phase-shifting diffraction interferometry, the system performance has been substantially increased. The next step will be to use the Lick system for astronomical science observations, and to demonstrate this level of performance with the new system being installed on the 10-meter Keck II telescope.

Electronic sputtering in the interaction of slow (v<v{sub Bohr}), highly charged ions (SHCI) with solid surfaces have been subject of controversial discussions for almost 20 years. We review results from recent studies of total sputtering yields and discuss distinct microscopic mechanisms (such as defect mediated desorption, Coulomb explosions and effects of intense electronic excitation) in the response of insulators and semiconductors to the impact of SHCI. We then describe an application of ions like Xe{sup 44+} and Au{sup 69+} as projectiles in time-of-flight secondary ion mass spectrometry for surface characterization of semiconductors.

In October 1996, the Department of Energy (DOE) and MINATOM agreed to use portable non-destructive assay (NDA) equipment to measure the {sup 235}U enrichment of material subject to the HEU Transparency agreement. A system based on the ''enrichment meter'' method and high-purity germanium (HPGe) detectors had been previously developed for this application. Instead, sodium iodide (NaI) detectors were chosen to measure {sup 235}U enrichment because HPGe systems might reveal sensitive information. Although the accuracy of the NaI systems is less than an HPGe system, it still satisfies the transparency requirements. The equipment consists of a collimated NaI detector, a Canberra Inspector Multi-channel Analyzer, and a laptop computer. The units have been used to confirm the enrichment of material at Russian facilities since January 1997. This paper compares the performance of the NaI systems with the HPGe system and discusses some significant differences.

High energy polarized beam collisions will open up the unique physics opportunities of studying spin effects in hard processes. However, the acceleration of polarized beams in circular accelerators is complicated by the numerous depolarizing spin resonances. Using a partial Siberian Snake and a rf dipole that ensure stable adiabatic spin motion during acceleration has made it possible to accelerate polarized protons to 25 GeV at the Brookhaven AGS. Full Siberian Snakes and polarimeters are being developed for RHIC to make the acceleration of polarized protons to 250 GeV possible.

It is pointed out that creation of a critical assembly by implantation of Pu239 inside an asteroid or comet could produce a substantial force on the asteroid or comet due to either explosive ejection or asymmetric sublimation of material off the surface of the asteroid or comet. This would allow one to make substantial changes in an asteroid`s or comet`s orbital elements using existing launch vehicles and spacecraft technology. It is particularly intriguing that recurrent sublimation induced by plutonium implantation could over a few months time deflect even kilometer-sized earth intersecting objects enough to avoid the earth. For the more distant future, nuclear-powered pulse jets might be a cost-effective way of altering the trajectories of asteroids and comets.

Recent and proposed improvements in spatial resolution, temporal resolution, contrast, and detection efficiency for x-ray framing cameras are discussed in light of present and future laser-plasma diagnostic needs. In particular, improvements in image contrast above hard x-ray background levels is demonstrated by using high aspect ratio tapered pinholes.

The modalities of speech and gesture have different strengths and weaknesses, but combined they create synergy where each modality corrects the weaknesses of the other. We believe that a multimodal system such a one interwining speech and gesture must start from a different foundation than ones which are based solely on pen input. In order to provide a basis for the design of a speech and gesture system, we have examined the research in other disciplines such as anthropology and linguistics. The result of this investigation was a taxonomy that gave us material for the incorporation of gestures whose meanings are largely transparent to the users. This study describes the taxonomy and gives examples of applications to pen input systems.

Electrical resistance tomography (ERT) using multiple electrodes installed in boreholes has been shown to be useful for both site characterization and process monitoring. In some cases, however, installing multiple downhole electrodes is too costly (e.g., deep targets) or risky (e.g., contaminated sites). For these cases we have examined the possibility of using the steel casings of existing boreholes as electrodes. Several possibilities can be considered. The first case we investigated uses an array of steel casings as electrodes. This results in very few data and thus requires additional constraints to limit the domain of possible inverse solutions. Simulations indicate that the spatial resolution and sensitivity are understandably low but it is possible to coarsely map the lateral extent of subsurface processes such as steam floods. The second case uses an array of traditional point borehole electrodes combined with long-conductor electrodes (steel casings). Although this arrangement provides more data, in many cases it results in poor reconstructions of test targets. Results indicate that this method may hold promise for low resolution imaging where steel casings can be used as electrodes but the merits depend strongly on details of each application. Field tests using these configurations are currently being conducted.

In a new experiment at the Final Focus Test Beam at SLAC a low- emittance 46.6 GeV electron beam is brought into collision with terawatt pulses from a 1.06 {mu} wavelength Nd:glass laser. Peak laser intensities of 10{sup 18} W/cm{sup 2} have been achieved corresponding to a value of 0.6 for the parameter {eta} = {ital eE/mw{sub 0}c}, and to a value of 0.3 for the parameter {Upsilon} = {ital E{sup *}/E{sub crit}} = 2{gamma}{ital ehE}/{ital m}{sup 2}{ital c}{sup 3} in the case of frequency doubled laser pulses. In these circumstances an electron that crosses the center of the laser pulse has near unit interaction probability. Signals are presented for multiphoton Compton scattering in which up to 4 laser photons interact with an electron. High energy backscattered photons of GeV energy can interact within the laser focus to create electron- positron pairs; an excess of 15 positrons above a background of 14 was observed in a run of 6,000 laser shots.

A general method of designing an apochromatic lens by using a triplet of special glasses, in which the buried surfaces concept is used, can be outlined. First, one initially chooses a starting point which is already achromatic. Second, a thick plate or shell is added to the design, where the plate or shell has an index of refraction 1.62, which is similar to the special glass triplet average index of refraction (for example: PSK53A, KZFS1 and TIF6). Third, the lens is then reoptimized to an achromatic design. Fourth, the single element is replace by the special glass triplet. Fifth, only the internal surfaces of the triplet are varied to correct all three wavelengths. Although this step will produce little improvement, it does serve to stabilize further optimization. Sixth and finally, all potential variables are used to fully optimize the apochromatic lens. Microscope objectives, for example, could be designed using this technique. The important concept to apply is the use of multiple buried surfaces in which each interface involves a special glass, after an achromatic design has been achieved. This extension relieves the restriction that all special glasses have a common index of refraction and allows a wider variety of special …

Spatial-filter pinholes and knife-edge samples were irradiated in vacuum by 1053-nm, 5-20 ns pulses at intensities to 500 GW/cm<sup2</sup>. The knife-edge samples were fabricated of plastic, carbon, ahnuinum, stainless steel, molybdenum, tantalum, gold and an absorbing glass. Time-resolved two-beam interferometry with a 40-ns probe pulse was used to observe phase shifts in the expanding laser-induced plasma. For all of these materials, at any time during square-pulse irradiation, the phase shift fell exponentially with distance from the edge of the sample. The expansion was characterized by the propagation velocity V_2x of the contour for a 2(pi) phase shift. To within experimental error, V_2x, was constant during irradiation at a particular intensity, and it increased linearly with intensity for intensities <300 GW/cn². For metal samples, V, exhibited an approximate M^-0.5 dependence where M is the atomic mass. Plasmas of plastic, carbon and absorbing glass produced larger phase shifts, and expanded more rapidly, than plasmas of the heavy metals. The probe beam and interferometer were also used to observe the closing of pinholes. With planar pinholes, accumulation of on-axis plasma was observed along with the advance of plasma away from the edge of the hole. On-axis closure was not observed in square, 4-leaf …

The National Ignition Facility (NIF) is a MJ-class glass laser-based facility funded by the Department of Energy which has achieving thermonuclear ignition and moderate gain as one of its main objectives. In the summer of 1998, the project is about 40% complete, and design and construction is on schedule and on cost. The NIF will start firing onto targets in 2001, and will achieve full energy in 2004. The Lawrence Livermore National Laboratory (LLNL), together with the Los Alamos National Laboratory (LANL) have the main responsibility for achieving x-ray driven ignition on the NIF. In the 1990�s, a comprehensive series of experiments on Nova at LLNL, followed by recent experiments on the Omega laser at the University of Rochester, demonstrated confidence in understanding the physics of x-ray drive implosions. The same physics at equivalent scales is used in calculations to predict target performance on the NIF, giving credence to calculations of ignition on the NIF. An integrated program of work in preparing the NIF for x-ray driven ignition in about 2007, and the key issues being addressed on the current ICF facilities [(Nova, Omega, Z at Sandia National Laboratory (SNL), and NIKE at the Naval Research Laboratory (NRL)] are described.

A detector and front-end electronics unit with secure data transmission has been designed and implemented for a fissile mass flow monitoring system for fissile mass flow of gases and liquids in a pipe. The unit consists of 4 bismuth germanate (BGO) scintillation detectors, pulse-shaping and counting electronics, local temperature sensors, and on-board local area network nodes which locally acquire data and report to the master computer via a secure network link. The signal gain of the pulse-shaping circuitry and energy windows of the pulse-counting circuitry are periodicially self calibrated and self adjusted in situ using a characteristic line in the fissile material pulse height spectrum as a reference point to compensate for drift such as in the detector gain due to PM tube aging. The temperature- dependent signal amplitude variations due to the intrinsic temperature coefficients of the PM tube gain and BGO scintillation efficiency have been characterized and real-time gain corrections introduced. The detector and electronics design, measured intrinsic performance of the detectors and electronics, and the performance of the detector and electronics within the fissile mass flow monitoring system are described.

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The authors report a monolithic coupled-resonator vertical-cavity laser with an ion-implanted top cavity and a selectively oxidized bottom cavity which exhibits bistable behavior in the light output versus injection current. Large bistability regions over current ranges as wide as 18 mA have been observed with on/off contrast ratios of greater than 20 dB. The position and width of the bistability region can be varied by changing the bias to the top cavity. Switching between on and off states can be accomplished with changes as small as 250 {micro}W to the electrical power applied to the top cavity. Theoretical analysis suggests that the bistable behavior is the response of the nonlinear susceptibility in the top cavity to the changes in the bottom intracavity laser intensity as the bottom cavity reaches the thermal rollover point.

Terrestrial climate records and historical observations of the Sun suggest that the Sun undergoes aperiodic oscillations in radiative output and size over time periods of centuries and millenia. Such behavior can be explained by the solar convective zone acting as a nonlinear oscillator, forced at the sunspot-cycle frequency by variations in heliomagnetic field strength. A forced variant of the Lorenz equations can generate a time series with the same characteristics as the solar and climate records. The timescales and magnitudes of oscillations that could be caused by this mechanism are consistent with what is known about the Sun and terrestrial climate.

Electromagnetic induction by a magnetic dipole located above a dipping interface is of relevance to the petroleum well-logging industry. The problem is fully three-dimensional (3-D) when formulated as above, but reduces to an analytically tractable one-dimensional (1-D) problem when cast as a small tilted coil above a horizontal interface. The two problems are related by a simple coordinate rotation. An examination of the induced eddy currents and the electric charge accumulation at the interface help to explain the inductive and polarization effects commonly observed in induction logs from dipping geological formations. The equivalence between the 1-D and 3-D formulations of the problem enables the validation of a previously published finite element solver for 3-D controlled-source electromagnetic induction.

Corrosion tests of DOE-owned spent nuclear fuel are performed at Argonne National Laboratory to support the license application for the Yucca Mountain Repository. The tests are designed to determine corrosion rates and degradation products formed when fuel is reacted at elevated temperature in different aqueous environments, including vapor, dripping water, submersion, and liquid film contact. Corrosion rates are determined from the quantity of radionuclides released from wetted fuel and from the weight loss of the test fuel specimen as a function of time. Degradation products include secondary mineral phases and dissolved, adsorbed, and colloidal species. Solid phase examinations determine fuel/mineral interface relationships, characterize radionuclide incorporation into secondary phases, and determine corrosion mechanisms at grain interfaces within the fuel. Leachate solution analyses quantify released radionuclides and determine the size and charge distribution of colloids. This paper presents selected results from corrosion tests on metallic fuels.

The possibility of colloid generation from spent fuel in an unsaturated environment has significant implications for storage of these fuels in the proposed repository at Yucca Mountain. Because colloids can act as a transport medium for sparingly soluble radionuclides, it might be possible for colloid-associated radionuclides to migrate large distances underground and present a human health concern. This study examines the nature of colloidal materials produced during corrosion of metallic uranium fuel in simulated groundwater at elevated temperature in an unsaturated environment. Colloidal analyses of the leachates from these corrosion tests were performed using dynamic light scattering and transmission electron microscopy. Results from both techniques indicate a bimodal distribution of small discrete particles and aggregates of the small particles. The average diameters of the small, discrete colloids are {approximately}3--12 nm, and the large aggregates have average diameters of {approximately}100--200 nm. X-ray diffraction of the solids from these tests indicates a mineral composition of uranium oxide or uranium oxy-hydroxide.

The intrinsic chirality of metal surfaces with kinked steps (e.g. Pt(643)) endows them with enantiospecific adsorption properties (D. S. Shell, Langmuir, 14, 1998, 862). To understand these properties quantitatively the impact of thermally-driven step wandering must be assessed. The authors derive a lattice-gas model of step motion on Pt(111) surfaces using diffusion barriers from Density Functional Theory. This model is used to examine thermal fluctuations of straight and kinked steps.

This report summarizes the activities of the Parton Distributions Working Group of the QCD and Weak Boson Physics workshop held in preparation for Run II at the Fermilab Tevatron. The main focus of this working group was to investigate the different issues associated with the development of quantitative tools to estimate parton distribution functions uncertainties. In the conclusion, the authors introduce a Manifesto that describes an optimal method for reporting data.

The work in the past 6 months has involved three areas of magnetic thin films: (1) amorphous rare earth-transition metal alloys, (2) epitaxial Co-Pt and Ni-Pt alloy thin films, and (3) collaborative work on heat capacity measurements of magnetic thin films, including nanoparticles and CMR materials. A brief summary of work done in each area is given.

Using interracial force microscopy (IFM), the tribological properties of self-assembled monolayer (SAM) on Si surfaces produced by a new chemical strategy are investigated and compared to those of classical SAM systems, which include alkanethiols on Au and alkylsilanes on SiO{sub x}. The new SAM films are prepared by depositing n-alkyl chains with OH-terminations onto Cl-terminated Si substrates. The chemical nature of the actual lubricating molecules, n-dodecyl, is kept constant in all three thin film systems for direct comparison and similarities and differences in tribological properties are observed. The adhesion strength is virtually identical for all three systems; however, frictional properties differ due to differences in film packing. Differences in the chemical bonds that attach the lubricant molecules to the substrate are also discussed as they influence variations in film wear and durability. It is demonstrated that the new SAM films are capable of controlling the friction and adhesion of Si surfaces as well as the classical SAMs in addition to providing a greater potential to be more reproducible and more durable.