The picture of laser light absorption and scattering which is emerging from theory and computer simulation studies of laser-plasma interactions is described. On the subject of absorption, we discuss theoretical and experimental evidence that resonance absorption in a steepened density profile is a dominant absorption mechanism. Recent work also indicates the presence of critical surface ripples, which we study using two and three dimensional computer simulations. Predictions of hot electron spectra due to resonance absorption are described, as are effects of plasma outflow. We then discuss two regimes where stimulated scattering may occur. Brillouin scattering is expected in the underdense target blow-off, for long laser pulses, and is limited by ion heating. Raman scattering in the background gas of a reactor target chamber is predicted to be at most a 10 percent effect for 1 ..mu..m lasers.

Motivated by their applicability to gamma-ray spectroscopy experiments in space, quantitative studies of radiation damage effects in high-purity germanium detectors due to high-energy charged particles have been initiated with the irradiation by 6 GeV/c protons of two 1.0 cm thick planar detectors maintained at 88/sup 0/K. The threshold for resolution degradation and the annealing characteristics differs markedly from those previously observed for detectors irradiated by fast neutrons. Under proton bombardment, degradation in the energy resolution was found to begin below 7 x 10/sup 7/ protons/cm/sup 2/, and increased proportionately in both detectors until the experiment was terminated at a total flux of 5.7 x 10/sup 8/ protons/cm/sup 2/, equivalent to about a six year exposure to cosmic-ray protons in space. At the end of the irradiation, the FWHM resolution measured at 1332 keV stood at 8.5 and 13.6 keV, with both detectors of only marginal utility as a spectrometer due to the severe tailing caused by charge trapping. The two detectors displayed a significant difference in proton damage sensitivity, which is consistent with fast neutron damage effects. To ensure that detector variability did not influence the comparison of proton- and neutron-induced damage effects, one of the detectors had been used …

The 120-keV Neutral Beam Test Facility at LBL is fitted with several types of instrumentation to determine the properties of the 10- to 15-A hydrogen and deuterium beams produced in this facility. These include a neutral particle dump for measuring the temperature profile generated by the beam, and a fixed and a moveable ion dump to measure the temperature profiles generated by the various ion components after they have been swept out of the neutral beam by a bending magnet. These several dumps provide enough information to determine the power density profiles and divergences of the neutral beam and the various ion beams for comparison with theoretical calculations, the beam composition, and the neutralization efficiency. The optical beam diagnostic consists of a high-resolution spectrometer coupled with a commercial optical multichannel analyzer. These instruments analyze Doppler-shifted optical radiation from the moving neutral atoms in the beam. Analysis of data so obtained provides the aiming directions and divergences of the various energy components in the neutral beam, as well as the beam composition.

The new Tandem Mirror Experiment (TMX) facility at LLL requires that neutral beams operate for pulse lengths between 25 and 100 ms. The inevitable increase in cost over the present 12-ms pulse length capability dictated that a more economical alternative to the pulse forming networks and the transformer-type arc filament power supplies currently in use be found. A study of the various alternatives and design requirements revealed that battery banks are the most economical alternative. The thermionic arc filaments have relatively simple power-supply requirements in terms of control and regulation. The battery arc filament power supply controls and electromechanical hardware heat the filaments to provide the electrons which produce the plasma. Component testing revealed problems that must be addressed in the finished production design. The battery arc power supply poses a difficult set of requirements for current control. The TMX requires current control accuracy of +-1.0 percent and rise/fall times of 50 ..mu..s. These requirements are met with a novel thyristor switching circuit. The features of the four-section battery bank design, capable of a total of 4000 A at 58 V dc, are detailed. Control hardware compatible with the current generation of pulse-forming network hardware has been developed. The cost …

Observation of x-ray line emissions are valuable for determining the thermodynamic state of the emitting plasma. For laser produced plasmas, diffraction crystals can be used to isolate x-ray monochromes to obtain high resolution spectral measurements. We will describe a versatile multi-crystal high resolution spectrograph used for photon energies from 0.5 to 6 keV. We will discuss a calculational package that tunes the response and sensitivity of the instrument and estimates the effect of source extent on spectral resolution. A scheme using fine slits to obtain spatial resolution with the basic instrument will also be described. An instrument is being built for Shiva diagnostics that incorporates a diffraction crystal and an x-ray streak camera. The design rationale for the crystal stage will be discussed.

A model for the physics of exploding pusher targets is presented which compares favorably with the predictions of the complex simulation code, LASNEX.

The rapid deterioration of concrete bridge decks as a result of the increased use of deicing salts is one of the most severe problems facing the highway industry today. One possible solution to the problem is the use of concrete polymer materials. The materials of prime interest are polymer-impregnated concrete (PIC) and polymer concrete (PC), both of which have excellent durability and strength properties. Three potential applications: repair of deteriorated bridge decks, polymer impregnation of new bridge deck surfaces, and full impregnation of precast deck panels have been studied in laboratory and field tests and the results have been encouraging. These results and economic considerations are described.

Experiments have been performed by LLL which indicate a definite density profile steepening. One possible mechanism for this effect is the ponderomotive force. LASNEX has been modified to include the light momentum deposition in the form rho dv/dt = -nabla P - nabla(radical epsilon + radical 1/epsilon) I/2c. Results will be presented from numerical simulations on spherical glass targets at laser intensities from 10/sup 14/ to 10/sup 16/ watts/cm/sup 2/. Emphasis is placed on the nature of the density profile near the critical region as a function of laser intensity and plasma conditions. The existence of this sharp step, whose scale length is of the order of a micrometer may imply a local reduction in the thermal conductivity.

At Brookhaven National Laboratory data telecommunication for remote job entry, interactive time sharing, networking, graphics, and special purpose links became increasingly important--they now rival the more traditional over-the-counter traffic. The BNL Central Scientific Computing Facility (CSCF) responded to this need with a number of developments. The latest and most comprehensive of these is a ''front-end'' communications system built around MODCOMP II computers. To put this project into its proper framework, some historical background is presented describing predecessor systems, the development of specifications, and the factors considered in the decision to turn to MODCOMP. The hardware is based around dual MODCOMP II-233 processors with a specially developed link to the larger CSCF machines, two Control Data 6600 computers and one CDC 7600. The MODCOMP software is based upon an existing system developed by Chrysler Corporation, running under MAXCOM. On the Control Data side Scope 3.4/INTERCOM 4 is used as a basis. The developments and modifications, both hardware and software, necessary for these components to meet Brookhaven's specifications are described. Certain related special-purpose data link applications are described. Among them are a research project in national resource sharing networks using ARPANET, and a connection to the National Weather Service machines in Suitland, …

A ''Lead-Glass Wall,'' consisting of 318 lead-glass Cherenkov shower counters and three wire spark chambers, has been added to one octant of the SPEAR Mark I Magnetic Detector. The wall covers a solid angle of approximately 6 percent of 4..pi.. steradians and has been used to identify and measure the energies of electrons and photons produced in electron-positron collisions. The design, calibration, gain-monitoring, and performance of the system are described.

In the present ISABELLE design, the luminosity at each insertion will be the same, unless special efforts are taken to get a low-..beta.. insertion or reduced crossing angle. These can only change the luminosity by factors of 2 to 4 from insertion to insertion. An estimation of the range of desired luminosities is given.

The time resolution capabilities of prototype microchannel plate and static crossed-field photomultipliers have been investigated. Measurements were made of electron transit time, rise time, time response, single photoelectron time spread and multiphotoelectron time spread for LEP HR350 proximity focused high gain curved microchannel plate and VPM-154A/1.6L static crossed-field photomultipliers. The experimental data have been compared with results obtained with conventionally designed RCS 8850 and C31024 high speed photomultipliers. Descriptions are given of both the measuring techniques and the measuring systems.

The large Nd:glass laser-fusion systems, such as Argus and Shiva, require short-pulse oscillators that are very reliable and predictable. The requirements go well beyond what can reasonably be expected from a passively mode-locked laser. An actively mode-locked and Q-switched oscillator has now been developed that is extremely reliable and predictable, and satisfies all the requirements for the present Nd:glass laser systems. These systems require pulses that are adjustable from less than 100 ps to more than 1 ns, with less than 5% shot-to-shot variation in pulse energy and pulse width. Single-pulse energy from 100 ..mu..J to 1 mJ is sufficient. In this paper we will describe the principle of operation of this short-pulse oscillator, describe the Argus laser configuration, and the results obtained with this oscillator. We will then indicate further developments for the Shiva oscillator and discuss the performance of this laser.

The conceptual design of a laser fusion power plant has been undertaken to exploit recent developments in target design. Advanced high-gain targets which have been developed make it possible to significantly relax the laser and optical system requirements. The power plant design features a reactor concept which utilizes a thick falling region of liquid lithium to protect the first-wall from the neutrons, x-rays, and charged particles that are produced in the thermonuclear microexplosion. The lithium waterfall has also been designed to be thick enough to significantly reduce the effects of 14 MeV neutrons and cyclical stresses on the blanket structure; thereby allowing us to consider smaller blanket structures which could last the lifetime of the plant. Fusion targets producing 700 MJ of thermonuclear energy are ignited by a 2 percent efficient, 1 MJ laser system at the rate of 1.4 Hz. Schemes for protecting the final focusing optics are described which are both compatible with this reactor system, and show promise of surviving a full year in order to minimize costly downtime.

Higher focusable power in neodymium glass fusion lasers can be obtained through the use of new materials with lower nonlinear index (n/sub 2/) and better energy storage capabilities than the presently employed silicate glass. Silicate, phosphate, fluorophosphate, and beryllium fluoride glasses are discussed in terms of fusion laser requirements, particularly those for the proposed Nova laser. Examples of the variation in spectroscopic and optical properties obtainable with compositional changes are given. Results of a system evaluation of potential laser materials show that fluorophosphate glasses have many of the desired properties for use in Nova. These glasses are now being cast in large sizes (30-cm diameter) and will be tested in prototype amplifiers in 1978.

A new approach towards the understanding of hitherto unknown, non-elemental acceptors and donors which can limit the purity of ultra-pure germanium has been explored for a specific pair of shallow centers, designated A/sub 2/ and D. Using photoelectric spectroscopy, we have demonstrated that an isotope shift in the ground-state binding energy occurs when the germanium crystals are grown in pure deuterium instead of in the usual pure hydrogen atmosphere. This isotope shift is the most direct proof of the presence of hydrogen atoms in the centers A/sub 2/ and D. Applying uniaxial stress to Ge samples containing A/sub 2/ and D, we show that the symmetry and structure of the centers can be explored. The knowledge of the chemical composition and the structure of the non-elemental centers will allow development of methods to reduce and keep their concentrations to acceptable levels.

The Lawrence Livermore Laboratory Shiva laser-target interaction facility is designed for experiments at 20 to 30 terawatts. At this power level there will be larger fluxes of neutrons, x-rays, electrons and ions than have been previously measured. The measurements of energy converted into the various reaction products is crucial both in target design and performance analysis of the actual experiment. The total energy absorbed is measured by a box calorimeter surrounding the target except for beam input holes. This measurement prevents the use of other diagnostics, so for normal operation an energy balance module was designed for location on ports on the Shiva target chamber. This module monitors the energy in scattered light at 10640 A and 5320 A or 7118 A. It also contains a faraday cup and plasma and x-ray calorimeters. The distribution of energy in scattered light, plasma and x-rays will be mapped by 58 such modules.

Longer wavelength (e.g., lambda = 10.5 ..mu..m) laser radiation generates relatively large fluxes of superthermal electrons that penetrate and preheat the cores of such pellets at early times in their implosion history, precluding their efficient subsequent compression. It has been proposed to separate the outermost shell of such pellets (onto which the laser light is directed) from its inner regions by a vacuum layer, thereby ''insulating'' these inner portions from superthermal electron degradation. We consider this proposal analytically and computationally, and find it to be questionable, due to the rapid penetration of the vacuum insulation layer by plasma streamers from the laser heated shells, which are accelerated to velocities of the order of those of the superthermal electrons by an electrostatic analog of the Rayleigh-Taylor instability. Results of such considerations are presented. The results developed also apply to a variety of formally similar phenomena, ranging from the relativistic edge of supernova photospheres to diode breakdown in REB machines.

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Interactive computer graphics is an excellent approach to many types of applications. It is an exciting method of doing geographic analysis when desiring to rapidly examine existing geographically related data or to display specially prepared data and base maps for publication. One such program is the interactive thematic mapping system called CARTE, which combines polygonal base maps with statistical data to produce shaded maps using a variety of shading symbolisms on a variety of output devices. A polygonal base map is one where geographic entities are described by points, lines, or polygons. It is combined with geocoded data to produce special subject or thematic maps. Shading symbolisms include texture shading for areas, varying widths for lines, and scaled symbols for points. Output devices include refresh and storage CRTs and auxiliary Calcomp or COM hardcopy. The system is designed to aid in the quick display of spatial data and in detailed map design.

Most of the components of the Neutral Beam Lines of the Tokamak Fusion Test Reactor (TFTR) will be enclosed in a 50 cubic meter box-shaped vacuum chamber. The chamber will have a number of unorthodox features to accomodate both neutral beam and TFTR requirements. The design constraints, and the resulting chamber design, are presented.

Currently, liquid dominated geothermal systems hold the maximum promise for exploiting geothermal energy in the United States. The principal characteristic of such systems is that most of the heat is transferred by flowing water, which also controls subsurface fluid pressures and stress changes. The reduction in pore pressures brought about by geothermal fluid extraction is potentially capable of causing appreciable deformation of the reservoir rocks leading to displacements at the land surface. In order to foresee the pattern and magnitude of potential ground displacements in and around producing liquid dominated geothermal fields, a numerical model has been developed. Conceptually, the simulator combines conductive and convective heat transfer in a general three dimensional heterogeneous porous medium with a one-dimensional deformation of the reservoir rocks. The capabilities of the model and its potential applicability to field cases are illustrated with examples considering the effects of temperature and pressure dependent properties, material heterogeneities and previous stress history.

Preliminary design and performance test results for fast optical shutters intended for use in the Nova high power fusion laser system are briefly described. Both an opening shutter to protect the pellet target from amplified spontaneous emission (ASE), and a closing shutter to protect the laser from light reflected back from the target are discussed. Faraday rotators, synchronized by a 400 Hz oscillator, provide an opening shutter mechanism with an opening time of approximately 10 ..mu..s. A plasma closing shutter, employing electrical sublimation of a foil, provide a shutter closing time of 70 ns +- 20 ns. Energy for foil sublimation is provided by discharge of a 42 J capacitor bank. Implementation of these shutter techniques in the Nova system is anticipated to improve laser output power and efficiency. (RME)

Double-folding heavy-ion potentials are conventionally generated by folding the densities of projectile and target with a nucleon--nucleon interaction. The success of the folding method has recently been explained by Fleckner and Mosel (Nucl. Phys. A277, 170 (1977)) in terms of a cancellation effect between two types of approximations, namely, the effects of neglecting the antisymmetrization between the ions and the polarization of the densities due to the (Coulomb and nuclear) forces between the ions. The validity of the above justification of folding potentials was here investigated by studying distortion and antisymmetrization effects in the heavy-ion interaction energy for a number of different nucleon--nucleon interactions. In particular, the change in the energy expectation value induced by neglecting the antisymmetrization between both ions, the sign of that change, and its sensitivity to the strength, range, and exchange terms of the nucleon--nucleon interaction chosen were examined. Calculations were done for the /sup 16/O + /sup 16/O system. It was found that a general statement about the effect of the antisymmetrization on the heavy-ion interaction energy cannot be made. For some nucleon--nucleon forces the energy increases; for others, it decreases. The magnitude and sign of the net effect depend very sensitively on the range, …