In this update lecture we focus on laser-driven instabilities in long scalelength underdense plasmas. Particular attention is given to some recent experiments on Raman scattering of intense laser light. Many important features are in accord with theoretical expectations. These features include a correlation of hot electron generation with Raman scattering, an increase in this scattering as the density scale length increases, and collisional suppression of the instability. Some challenging aspects of the growing data base as well as various deficiencies in the understanding are discussed. The role of the plasmon decay instability 2..omega../sub pe/, Brillouin, and filamentation instabilities is also briefly considered.

Four Fe-based superalloys, JBK-75, Incoloy 903, Incoloy 905, and Incoloy 909 were evaluated as tube materials for ICCS Nb/sub 3/Sn superconductors. Evaluation consisted of 4-K tensile and elastic-plastic fracture-toughness testing, and a microstructural characterization of unwelded and autogenously gas-tungsten-arc welded sheet given a simulated postweld processing treatment of 15% cold reduction by rolling followed by a Nb/sub 3/Sn-reaction heat treatment of 96 hours at 700/sup 0/C plus 48 hours at 730/sup 0/C. Results indicate that JBK-75 and Incoloy 903 showed satisfactory combinations of strength and toughness for ICCS tube use requiring long Nb/sub 3/Sn-reaction heat treatments. Incoloy 905 welds and 909 showed unacceptable fracture toughness. Results are discussed in terms of microstructural changes caused by the extended Nb/sub 3/Sn-reaction heat treatment.

The materials accounting system at Los Alamos has evolved from an ''80-column'' card system to a very sophisticated near-real-time computerized nuclear material accountability and safeguards system (MASS). The present hardware was designed and acquired in the late 70's and is scheduled for a major upgrade in fiscal year 1986. The history of the system from 1950 through the DYMAC of the late 70's up to the present will be discussed. The philosophy of the system along with the details of the system will be covered. This system has addressed the integrated problems of management, control, and accounting of nuclear material successfully. 8 refs., 3 figs., 1 tab.

Plastic scintillators can be coupled to light fibers to make small, simple, and inexpensive x-ray detectors. These detectors have been developed for use at the Nevada Test Site (NTS) for the remote detection of x-rays. Light produced in the scintillator can be transmitted by the fiber for several hundred meters to a photodetector, which is usually a streak camera or a photomultiplier tube. The use of a streak camera allows many channels to be recorded simultaneously. A parameter study has been done to measure the sensitivity of these detectors as a function of scintillator geometry, type of scintillator, coupling geometry, and x-ray energy. The results can be qualitatively explained by simple geometric theory. A recent use of these detectors at NTS was the measurement of an x-ray spectrum. System performance for this measurement will be reviewed. 7 refs., 5 figs., 1 tab.

Construction has started on a facility to immobilize high-level radioactive waste in borosilicate glass at the Department of Energy's Savannah River Plant. Type 304L stainless steel is generally sufficient for supply tankage and service lines. It is used as the reference material in chemical reprocessing of reactor target and fuel tubes. Type 304L, however, has unacceptable stress corrosion cracking resistance in solutions containing formic acid and chloride. Scouting tests were performed on twelve commercial nickel-based alloys in simulated process solutions containing halides, sulfates, nitrates, mercury and formic acid. Mercuric ions and halides interact in acidic environments to increase pitting and crevice attack. Alloys with combined chromium plus molybdenum contents greater than 30 percent, that also contain greater than 9 percent molybdenum, were most resistant to pitting and crevice corrosion. Based on this testing, Alloy C-276 has been selected as the reference process equipment material, with Inconel 690 and ALLCORR selected for specialty areas.

The three-dimensional diagnostic wind field model (MATHEW) and the particle-in-cell atmospheric transport and diffusion model (ADPIC) are used by the Atmospheric Release Advisory Capability to estimate the environmental consequences of accidental releases of radioactivity into the atmosphere. These models have undergone extensive evaluations against field experiments conducted in a variety of environmental settings ranging from relatively flat to very complex terrain areas. Simulations of tracer experiments conducted in a complex mountain valley setting revealed that 35 to 50% of the comparisons between calculated and measured tracer concentrations were within a factor of 5. This may be compared with a factor of 2 for 50% of the comparisons for relatively flat terrain. This degradation of results in complex terrain is due to a variety of factors such as the limited representativeness of measurements in complex terrain, the limited spatial resolution afforded by the models, and the turbulence parameterization based on sigma/sub theta/ measurements to evaluate the eddy diffusivities. Measurements of sigma/sub theta/ in complex terrain exceed those measured over flat terrain by a factor of 2 to 3 leading to eddy diffusivities that are unrealistically high. The results of model evaluations are very sensitive to the quality and the representativeness of …

The performance of a streak camera recording system is strongly linked to the technique used to amplify, detect and quantify the streaked image. At the Lawrence Livermore National Laboratory (LLNL) streak camera images have been recorded both on film and by fiber-optically coupling to charge-coupled devices (CCD's). During the development of a new process for recording these images (lens coupling the image onto a cooled CCD) the definitions of important performance characteristics such as resolution and dynamic range were re-examined. As a result of this development, these performance characteristics are now presented to the streak camera user in a more useful format than in the past. This paper describes how these techniques are used within the Laser Fusion Program at LLNL. The system resolution is presented as a modulation transfer function, including the seldom reported effects that flare and light scattering have at low spatial frequencies. Data are presented such that a user can adjust image intensifier gain and pixel averaging to optimize the useful dynamic range in any particular application.

Experimental techniques are described for shock waves in liquids: Hugoniot equation-of-state, shock temperature and emission spectroscopy, electrical conductivity, and Raman spectroscopy. Experimental data are reviewed and presented in terms of phenomena that occur at high densities and temperatures in shocked He, Ar, N/sub 2/, CO, SiO/sub 2/-aerogel, H/sub 2/O, and C/sub 6/H/sub 6/. The superconducting properties of Nb metal shocked to 100 GPa (1 Mbar) and recovered intact are discussed in terms of prospects for synthesizing novel, metastable materials. Ultrahigh pressure data for Cu is reviewed in the range 0.3 to 6TPa (3 to 60 Mbar). 56 refs., 9 figs., 1 tab.

Early researchers recogniZed the desirable features of the linear Z-pinch configuration as a magnetic fusion scheme. In particular, a Z-pinch reactor might not require auxiliary heating or external field coils, and could constitute an uncomplicated, high plasma ..beta.. geometry. The simple Z pinch, however, exhibited gross MHD instabilities that disrupted the plasma, and the linear Z pinch was abandoned in favor of more stable configurations. Recent advances in pulsed-power technology and an appreciation of the dynamic behavior of an ohmically heated Z pinch have led to a reexamination of the Z pinch as a workable fusion concept.

The transmission coefficient of a wavepacket traversing a potential barrier can be determined by steady state calculations carried out in imaginary time instead of by real time dynamical calculations. The general argument is verified for the Eckart barrier potential by a comparison of transmission coefficients calculated from real and imaginary time solutions of the Schroedinger equation. The correspondence demonstrated here allows a formulation for the reaction rate that avoids difficulties due to both rare events and explicitly time dependent calculations. 5 refs., 2 figs.

The desirable features of cells in suspension will necessarily be dependent upon the use for which the cells were prepared. Adequate cell yield or recovery is defined by the measurement to be performed. Retention of cellular morphology is important for microscopic identification of cell types in a heterogenous cell suspension, and may be used to determine whether the cells in suspension are representative of those in the tumor in situ. Different dispersal protocols may yield cells with different degrees of clonogenicity, as well as altered biochemical features, such as loss of cellular proteins, surface antigens, nucleotide pools, etc. The quality of the cell suspension can be judged by the degree of cell clumping and level of cellular debris, both of which impact on flow cytometric measurements and studies in which the number of cells be known accurately. Finally, if the data measured on the cells in suspension are to be extrapolated to phenomena occurring in the tumor in situ, it is desirable that the cells in suspension are representative of those in the solid tumor in vivo. This report compares characteristics of tumor cell suspensions obtained by different types of selected disaggregation methods. 33 refs., 2 figs., 4 tabs.

The present study of the interstellar formyl ion HCO/sup +/ is the first attempt to investigate dissociative recombination for a triatomic molecular ion using an entirely theoretical approach. We describe a number of fairly extensive electronic structure calculations that were performed to determine the reaction mechanism of the e-HCO/sup +/ process. Similar calculations for the isoelectronic ions HOC/sup +/ and HN/sub 2//sup +/ are in progress. 60 refs.

The 14 MeV neutron work at Lawrence Livermore National Laboratory (LLNL) covers two main areas of interest to this Symposium: (1) measurements and calculations of differential cross sections; and (2) integral measurements of the neutron and gamma emission spectra. In both areas a large number of materials have been studied, spanning a wide mass range (6 < A < 239), of interest to fusion and hybrid reactors. In this presentation a brief description of the experimental techniques and calculational analysis is given for each of the above areas and the measured and calculated cross sections are discussed. 28 refs., 7 figs., 3 tabs.

The dissociation of water to hydrogen and oxygen requires energy ..delta..G/sub 298/ = 228 kJ/mole. By irradiating a semiconductor with light of energy greater than this amount, one may produce electrons in the excited state and electron vacancies at the surface that can perform the photochemical reduction (2H/sup +/ + 2e/sup -/ ..-->.. 2H ..-->.. H/sub 2/) and oxidation (20H/sup -/ + 2/sup +/ ..-->.. H/sub 2/O/sub 2/ ..-->.. H/sub 2/O + (1/2)O/sub 2/). There are several semiconductors, SrTiO/sub 3/, TiO/sub 2/, CdS, and Fe/sub 2/O/sub 3/ among them, that can photodissociate water. Some possess sites for both reduction and oxidation, while others carry out the two processes at different surfaces. A reversible solid state reaction that involves changes in the transition metal and ion oxidation state must accompany the splitting of water. Platinum, rhodium, and ruthenium oxide, when deposited on the semiconductor, serve as catalysts that accelerate the water photodissociation. These additives accelerate the recombination of hydrogen and oxygen atoms, shift the semiconductor Fermi level to a more favorable position that improves the thermodynamic feasibility for the process, accelerate electron transport, and inhibit side reactions like the photoreduction of oxygen. Many of the elementary reaction steps leading to photoproduction …

The effect of ion bombardment on several grades of alumina was investigated. Changes in the electrical resistance of the substrate as a function of incoming ion energy were of particular interest. Attention was also paid to the sputter particle distribution as a function of ambient pressure. This distribution was found to be dependent on the ion to substrate mass ratio. In general, the distribution follows a curve of growth; approximating a cosine distribution at the lower pressures and mass ratio, becoming isotropic at higher pressures. Pressures in the range of 10/sup -2/ to 10/sup -4/ Pascals have been used along with mass ratios in the range of 0.40 to 1.3. Samples of up to 80 cm/sup 2/ were subjected to a 10 cm diameter ion beam at energies of up to 6.25 keV. Average ion current densities of 1ma/cm/sup 2/ were used. Substrate temperatures while subjected to the ion beam were also monitored.

The feasibility of performing x-ray fluorescence trace element determinations at concentrations substantially below the ppM level for biological materials is demonstrated. Conditions for achieving optimum sensitivity were ascertained. Results achieved for five standard reference materials were, in most cases, in excellent agreement with listed values. Minimum detectable limits of 20 ppM were measured for most elements.

A formalism is presented by means of which the propagation and imaging characteristics of synchrotron radiation can be studied, taking into account the effects of diffraction, electron beam emittance, and the transverse and longitudinal extent of the source. An important quantity in this approach is the Wigner distribution of the electric fields, which can be interpreted as a phase-space distribution of photon flux, and thus can be identified with the brightness. When integrated over the angular variables, the brightness becomes the intensity distribution in the spatial variables and when integrated over the spatial variables, it becomes the intensity distribution in angular variables. The brightness so defined transforms through a general optical medium in exactly the same way as in the case of a collection of geometric rays. Finally, the brightness of different electrons adds in a simple way. Optical characteristics of various synchrotron radiation sources - bending magnets, wigglers and undulators, are analyzed using this formalism.

The current capabilities of kinetic modeling of hydrocarbon oxidation in shock waves are discussed. The influence of molecular size and structure on ignition delay times are stressed. The n-paraffin fuels from CH/sub 4/ to n-C/sub 5/H/sub 12/ are examined under shock tube conditions, as well as the branched chain fuel isobutane, and the computed results are compared with available experimental data. The modeling results show that it is important in the reaction mechanism to distinguish between abstraction of primary, secondary and tertiary H atom sites from the fuel molecule. This is due to the fact that both the rates and the product distributions of the subsequent alkyl radical decomposition reactions depend on which H atoms were abstracted. Applications of the reaction mechanisms to shock tube problems and to other practical problems such as engine knock are discussed.

Alterations in regional epithelial permeability were assessed in 22 retired West Virginia coal miners' lungs by measuring the clearance of inhaled 0.5-..mu..m Tc-99m DTPA aerosol. Activity was measured in both lungs and in regions of interest placed over the lung periphery in the apical, middle, and basal portions of each lung. Clearance rates (T/sub 1/2/) for 5 nonsmokers, 8 ex-smokers, and 9 smokers were significantly faster than for comparable subjects measured elsewhere, who were not coal miners. Regional apex-to-base distributions of DTPA were measured as a function of clearance time and compared with regional ventilation and perfusion. Regional, as well as overall lung clearance curves of 8 smokers and 4 ex-smokers had two components, with overall T/sub 1/2/ of <7 min for the faster one. No correlations were found between T/sub 1/2/ and DLCO or with P(A-a)O/sub 2/. The results of our study suggest that measurement of DTPA clearance is a potentially useful noninvasive technique to assess lung injury in miners exposed to coal dust. 14 refs., 6 figs., 2 tabs.

The underlying concepts of nonequilibrium statistical mechanics, and of irreversible thermodynamics, will be described. The question at hand is then, how are these concepts to be realize in computer simulations of many-particle systems. The answer will be given for dissipative deformation processes in solids, on three hierarchical levels: heterogeneous plastic flow, dislocation dynamics, an molecular dynamics. Aplication to the shock process will be discussed.

It often occurs that, in a rare-earth compound having a singlet electronic ground state, a long-range magnetically ordered state is formed by coupling of the nuclear spins with the electrons through the hyperfine interaction, at millikelvin temperatures. Neutron scattering has been used to measure the details of the magnetization processes of both the electrons and the nuclear spins in the coupled state in PrSn/sub 3/, HoVO/sub 4/, and PrCu/sub 2/. The polarized nuclear spins could be observed through spin dependent nuclear scattering by /sup 141/Pr and /sup 165/Ho. The experimental results for PrSn/sub 3/ and HoVO/sub 4/ can be explained very well based on mean field considerations. For PrCu/sub 2/, a recent experiment indicates that a sinusoidal screw structure is realized simultaneously both in the electronic and nuclear spin systems of this material.

Current leak detection practices in 74 operating nuclear reactors have been reviewed. Existing leak detection systems are adequate to ensure a leak-before-break scenario in most situations, but no currently available, single method combines optimal leakage detection sensitivity, leak-locating ability, and leakage measurement accuracy. Simply tightening current leakage limits may produce an unacceptably large number of unnecessary shutdowns. The use of commercially available acoustic monitoring systems or moisture-sensitive tape may improve leak detection capability at specific sites. However, neither of these methods currently provides source discrimination (e.g., to distinguish between leaks from pipe cracks and valves) or leak-rate information (a small leak may saturate the system). A field-implementable acoustic leak detection system is being developed to address these limitations. 5 refs., 3 figs.

Recent studies have shown that significant compositional redistribution in irradiated alloys can be induced by the gradients in the atomic displacement rates resulting from nonuniform defect production, in addition to the commonly-observed solute segregation at defect sinks. This process gives rise to complex local phase transformations during light-ion bombardment or irradiation with focused electron beams in the high-voltage electron microscope. Results of our theoretical and experimental investigations of this phenomenon in Ni-Al and Ni-Si are discussed. The implications of the observed effect in a number of areas of materials science are assessed.

It is suggested that Hall steps in the fractional quantum Hall effect are physically similar to those in the ordinary quantum Hall effect. This proposition leads to a simple scaling diagram containing a new type of fixed point, which is identified with the destruction of the fractional states by disorder. 15 refs., 3 figs.