High surface electric fields have been obtained in the first tests of a superconducting rf quadrupole device. The rf quadrupole fields were generated between niobium vanes 6.5 cm in length, with an edge radius of 2 mm, and with a beam aperture of 6 mm diameter. In tests at 4.2 K, the 64 MHz device operated cw at peak surface electric fields of 128 MV/m. Virtually no electron loading was observed at fields below 100 MV/m. It was possible to operate at surface fields of 210 MV/m in pulses of 1 msec duration using a 2.5 kW rf source. For the vane geometry tested, more than 10 square centimeters of surface support a field greater than 90% of the peak field. The present result indicates that electric fields greater than 100 MV/m can be obtained over an appreciable area, sufficient for some accelerator applications. It also shows that superconducting rf technology may provide an extended range of options for rf quadrupole design. 7 refs., 4 figs.

Differential geometry provides a natural family of coordinate systems, the Frenet frame, in which to specify the geometric properties of magnet winding. By a modification of the Euler-Bernoulli thin rod model, the strain energy is defined with respect to this frame. Then it is minimized by a direct method from the calculus of variations. The mathematics, its implementation in a computer program, and some analysis of an SSC dipole by the program will be described. 16 refs.

Interest in interactive 3-D graphics has exploded of late, fueled by (a) the allure of using scientific visualization to go where no-one has gone before'' and (b) by the development of new input devices which overcome some of the limitations imposed in the past by technology, yet which may be ill-suited to the kinds of interaction required by researchers active in scientific visualization. To resolve this tension, we propose a flat 5-D'' environment in which 2-D graphics are augmented by exploiting multiple human sensory modalities using cheap, conventional hardware readily available with personal computers and workstations. We discuss how interactions basic to 3-D scientific visualization, like searching a solution space and comparing two such spaces, are effectively carried out in our environment. Finally, we describe 3DMOVE, an experimental microworld we have implemented to test out some of our ideas. 40 refs., 4 figs.

Sintered bars of Y-Ba-Cu oxide were partially melted using a quartz halogen lamp zone heating apparatus. The resulting multiphase samples showed varying degrees of melt texturing.'' It was found that the addition of YBa{sub 2}CuO{sub 5} powders to the sintered YBa{sub 2}Cu{sub 3}O{sub 7} prior to the zone melting process enhanced the growth of large textured grains. The best value of the critical current density was {approximately}10{sup 3} A/cm{sup 2} at 1.0 T and 77 K for the starting composition of YBa{sub 2}Cu{sub 3}O{sub 7} {sm bullet} (0.2)Y{sub 2}BaCuO{sub 5}. 11 refs., 5 figs.

The remnant magnetic flux distribution in a single crystal and a sintered polycrystal was examined using the magnetic particle decoration technique. The single crystal, which was heavily twinned, showed only local order in the flux lattice. This was probably due to lattice distortions caused by interaction between twin boundaries and fluxons. In the polycrystal, flux pinning effectiveness was seen to vary significantly between grains, depending on size and orientation. Grains with the c axis nearly perpendicular to the applied magnetic field were most effective at pinning flux. Some features of the decoration patterns implied that the flux distribution was influenced by more than just the grains at the sample surface. 7 refs., 6 figs.

Transient electrical potentials can be generated in plasmas by utilizing impulsive mirror-generated forces acting on the plasma electrons together with ion inertia to cause momentary charge imbalance. In the Mirrortron such potentials are generated by applying a rapidly rising (tens of nanoseconds) localized mirror field to the central region of a hot-electron plasma confined between static mirrors. Because of the loss-cone nature of the electron distribution the sudden appearance of the pulsed mirror tends to expel electrons, whereas the ion density remains nearly constant. The quasi-neutrality condition then operates to create an electrical potential the equipotential surfaces of which can be shown theoretically to be congruent with surfaces of constant B. An alternative way of generating transient potentials is to apply a pulse of high-power microwaves to a plasma residing on a magnetic field with a longitudinal gradient. This technique resembles one employed in the Pleiade experiments. At gigawatt power levels, such as those produced by a Free Electron Laser, the production of very high transient potentials is predicted. Fusion-relevant applications of these ideas include heavy-ion drivers for inertial fusion, and the possibility of employing these techniques to enhance the longitudinal confinement of fusion plasmas in multiple-mirror systems. 23 refs., …

Differential-algebraic equation (DAE) boundary value problems arise in a variety of applications, including optimal control and parameter estimation for constrained systems. In this paper we survey these applications and explore some of the difficulties associated with solving the resulting DAE systems. For finite difference methods, the need to maintain stability in the differential part of the system often necessitates the use of methods based on symmetric discretizations. However, these methods can suffer from instability and loss of accuracy when applied to certain DAE systems. We describe a new class of methods, Projected Implicit Runge-Kutta Methods, which overcomes these difficulties. We give convergence and stability results, and present numerical experiments which illustrate the effectiveness of the new methods. 20 refs., 1 tab.

In the analysis of magnetic flux creep experiments it is assumed that, at a given temperature, the pinning energy which must be overcome by thermal activation depends on the magnetic induction and its gradient by U(B,{nabla}B){congruent} U{sub p}(B)(1-{nabla}B/{nabla}B{sub max}){sup n} where U{sub p} is the pinning well depth and {nabla}B{sub max} corresponds to the critical current density with no thermal activation. Customarily, n is assumed to be unity and any unusual temperature dependence of U{sub p} is then ascribed to a distribution of well depths. However, realistic assumptions about the shape of the pinning potential yield 3/2 {approx lt} n {approx lt} 2, which yields an apparent distribution of well depths in the conventional analysis. Simple models will be used to illustrate the characteristics of these two quite different origins for the apparent temperature dependence of well depth obtained from magnetic flux creep rates. 13 refs., 8 figs.

A new heterotic N = 2 string with manifest target space supersymmetry is constructed by combining a conventional N = 2 string in the right-moving sector and a Green-Schwarz-Berkovits type string in the left-moving sector. The corresponding sigma model is then obtained by turning on background fields for the massless excitations. We compute the beta functions and we partially check the OPE's of the superconformal algebra perturbatively in {alpha}{prime}, all in superspace. The resulting field equations describe N = 1 self-dual supergravity.

The compact multi-pass laser design and the extensive use of optical component assemblies as line replaceable units (LRU) are essential to achieve the cost efficiency of the National Ignition Facility design. These design philosophies require a new approach to start-up operation of the NIF 192-beam-line high-energy laser compared to existing fusion laser facilities. The limited access to the beam-line optics and the limited on-line verification and maintenance capability require that extensive component verification and alignment take place in off-line facilities before the LRUÕs are installed in the laser structure. We are developing a detailed plan for the start-up of the NIF facility. This plan includes systematic off-line component and LRU verification tests, LRU installation and prealignment, and sub-system acceptance tests, followed by a well defined set of operational test procedures to verify integrated performance. During integrated performance testing laser performance parameters of individual beam lines will be verified using a precision diagnostic system located in the NIF switchyard. If additional on-line calibration or performance testing is required, the LRU based architecture can accommodate the insertion of specialized in-line diagnostic LRUs at locations that require such additional testing during start-up. Multiple beam focal spot characteristics on disk targets in the NIF …

Differentiating characteristics of magnetic confinement systems having externally generated magnetic fields that are open'' are listed and discussed in the light of their several potential advantages for fusion power systems. It is pointed out that at this stage of fusion research high-Q'' (as deduced from long energy confinement times) is not necessarily the most relevant criterion by which to judge the potential of alternate fusion approaches for the economic generation of fusion power. An example is given of a hypothetical open-geometry fusion power system where low-Q operation is essential to meeting one of its main objectives (low neutron power flux).

The surface thermal lensing technique (STL) successfully resolved and measured the absorptance of transmissive optical components: near- normal angle-of-incidence anti-reflectors and beam splatters. The STL system uses an Ar ion laser to pump the components at 514.5 mn. The absorptance-induced surface deformation diffracts the HeNe probe beam into a photo-detector. The signal intensity was calibrated with a sample of known absorptance. The optical components were designed to function in a copper vapor laser (CVL) transport system, and were previously tested for absorptance with a high power CVL system at 511 rtm. To assure proper absorptance data from the STL system, the pump laser power densities were set at the operational level of the coatings, absorptance time trends were monitored, and absorptance area scans were made. Both types of transmissive optics are more stable than the CVL high reflectors that were measured in another study. Parameter studies based on Fresnel diffraction theory were also performed to optimize experimental condition. The STL system was assessed to have 10 ppb sensitivity for absorption measurement given 2 W of pump power.

Testing activities today at LLNL occur at three different locations: Livermore, Site 300, and the Nevada Test Site. At the Livermore location, there are three gas guns, two of which are used primarily for materials studies and scientific experiments on materials. The third gun is located in the High Explosive Applications Facility (HEAF) and fires into a chamber rated for 10 kg of explosive containment. The HEAF gun is used primarily for impact studies on explosives. Also within HEAF are five other containment chambers for explosive testing. Each is instrumented to varying degrees to supply the necessary information of explosive behavior. These include high speed optics, Fabry Perot velocimetry and radiography. The descriptions of the three gas guns and a summary of the HEAF facility are presented in the accompanying figures.

The Global Nuclear Vision Project is examining, using scenario building techniques, a range of long-term nuclear energy futures. The exploration and assessment of optimal nuclear fuel-cycle and material strategies is an essential element of the study. To this end, an established global E{sup 3} (energy/economics/environmental) model has been adopted and modified with a simplified, but comprehensive and multi-regional, nuclear energy module. Consistent nuclear energy scenarios are constructed using this multi-regional E{sup 3} model, wherein future demands for nuclear power are projected in price competition with other energy sources under a wide range of long-term demographic (population, workforce size and productivity), economic (price-, population-, and income-determined demand for energy services, price- and population-modified GNP, resource depletion, world-market fossil energy prices), policy (taxes, tariffs, sanctions), and top-level technological (energy intensity and end-use efficiency improvements) drivers. Using the framework provided by the global E{sup 3} model, the impacts of both external and internal drivers are investigated. The ability to connect external and internal drivers through this modeling framework allows the study of impacts and tradeoffs between fossil- versus nuclear-fuel burning, that includes interactions between cost, environmental, proliferation, resource, and policy issues.

We present a magnetic force microscopy (MFM) analysis of arrays of submicron-scale Co dots fabricated by interference lithography. The dots are thin (180--300 Å) and elliptical in shape. MFM reveals that these structures relax into highly ordered remanent states whose symmetry and configuration are governed by their shape anisotropy. In particular, when the dots are saturated along their long-axis, a uniformly magnetized state persists at remanence. However, when the dots are saturated along their short-axis, they relax into a single-vortex state in which the circulation can have either sign. Both states are characterized by smoothly varying magnetization patterns and a high degree of uniformity across the array. We attribute the ordered behavior of these.structures to the film microstructure, which allows the shape anisotropy to dominate over magnetocrystalline anjsotropy. By imaging a series of minor-loop remanent states, we show that magnetization reversal in these structures occurs via the nucleation and annihilation of a single vortex. Magnetic hysteresis loop measurements are consistent with these observations and provide additional details. Furthermore, we present the results of micromagnetic simulations, which are in excellent agreement with both the MFM images and the hysteresis loop measurements. © 1998 Elsevier Science B.V. All rights reserved.

We present estimates of the energy gain of highly charged ions approaching a LiF surface, based on a modified classical-over-barrier model for insulators. The analysis includes the energy gain by image acceleration as well as the deceleration due to charge-up of the surface in a staircase sequence. The role of the frequency-dependent dielectric response of LiF is emphasized. The resulting velocity dependent total energy gain is studied in detail and the results are compared with experimental data.

At Lawrence Livermore National Laboratory (LLNL), Python has proven to be a convenient language for the development of graphical user interfaces (GUIs) which allow scientists to view, plot, and analyze scientific data. Two such applications are described in this paper. The first, EOSView, is a browser application for an equation of state data library at LLNL. EOSView is used by scientists throughout the laboratory who use simulation codes that access the data library, or who need equation of state data for other purposes. EOSView provides graphical visualization capabilities, as well as the capability to analyze the data in many different ways. The second application, Zimp, is a GUI that allows interactive use of the Stark Line Shape Database. It is used to access and plot data. The quick construction of Zimp from elements of the EOSView code provides a useful lesson in code reuse, and illustrates how the object-oriented nature of Python facilitates this goal. In general, Python has proven to be an appropriate choice of language for applications of this type for several reasons, including the easy access to GUI functionality provided by Tkinter, the ease with which C functions can be called from Python, and the convenient handling …

The authors compare the results of a computer simulated flow field around building 170 (B170) at Lawrence Livermore National Laboratory (LLNL) with field measurements. In order to aid in the setup of the field experiments, the simulations were performed first. B170 was chosen because of its architectural complexity and because a relatively simple fetch exists upwind (a field lies southwest of the site). Figure 1 shows a computational model of the building which retains the major architectural features of the real building (e.g., courtyard, alcoves, and a multi-level roof). Several important characteristics of the cases presented here are: (1) the flow was assumed neutral and no heat flux was imposed at the ground, representing cloudy or morning conditions, (2) a simple canopy parameterization was used to model the effect of a large row of eucalyptus trees which is located to the northeast of the building, (3) the wind directions studied were 200, 225, 250 degrees measured clockwise from true north (the prevailing winds at LLNL are from the southwest in the summer), (4) the incoming wind profile was modeled as logarithmic with a maximum of about 3 meters per second. In addition, note that the building is rotated counterclockwise by …

CXX is a facility for extending Python using C++. Recently, the authors have substantially revised and improved the way in which you create extension objects and extension modules in C++. The method is now much more natural and has much less overhead, both in the code generated and in the effort needed to create the objects and extensions.

The Protein Crystallography Beamline at Berkeley Lab's Advanced Light Source is a facility that is being used to solve the structure of proteins. The software that is being used to control this beamline uses Java for user interface applications which communicate via CORBA with workstations that control the beamline hardware. We describe the software architecture for the beamline and our experiences after two years of operation.

Spectroscopic techniques are ideal for characterization and process control of electron beam generated vapor plumes. Absorption based techniques work well for a wide variety of applications, but are difficult to apply to optically dense or opaque vapor plumes. We describe an approach for monitoring optically dense vapor plumes that is based on measuring the group velocity delay of a laser beam near an optical transition to determine the vapor density. This technique has a larger dynamic range than absorption spectroscopy. We describe our progress towards a robust system to monitor aluminum vaporization in an industrial environment. Aluminum was chosen because of its prevalence in high performance aircraft alloys. In these applications, composition control of the alloy constituents is critical to the deposition process. Data is presented demonstrating the superior dynamic range of the measurement. In addition, preliminary data demonstrating aluminum vapor rate control in an electron beam evaporator is presented. Alternative applications where this technique could be useful are discussed. Keywords: Group velocity delay spectroscopy, optical beat signal, optical heterodyne, index of refraction, laser absorption spectroscopy, external cavity diode laser (ECDL), electron beam vaporization, vapor density, vapor phase manufacturing, process control

The authors use a solid mechanics approach to investigate hydride formation and cracking in zirconium-niobium alloys used in the pressure tubes of CANDU nuclear reactors. In this approach, the forming hydride is assumed to be purely elastic and its volume dilation is accommodated by elasto-plastic deformation of the surrounding matrix material. The energetics of the hydride formation is revisited and the terminal solid solubility of hydrogen in solution is defined on the basis of the total elasto-plastic work done on the system by the forming hydride and the external loads. Hydrogen diffusion and probabilistic hydride formation coupled with the material deformation are modeled at a blunting crack tip under plane strain loading. A full transient finite element analysis allows for numerical monitoring of the development and expansion of the hydride zone as the externally applied loads increase. Using a Griffith fracture criterion for fracture limitiation, the reduced fracture resistance of the alloy can be predicted and the factors affecting fracture toughness quantified.

As American textile and nonwovens companies participate in an increasingly competitive world market, technology is playing an ever-growing role in production of new, improved, and more cost competitive products and processes. But the same competitive pressures which drive the need for advanced manufacturing technology also reduce the resources available for necessary research and development activities. Technology resources and manufacturing expertise, unmatched in the world, are available to American industry at the Oak Ridge Centers for Manufacturing Technology (ORCMT). Bottom-line benefits from ORCMT technology solutions are already in the hundreds of millions of dollars. This presentation will describe a sampling of the technologies and expertise available, present examples of previous solutions, and explain how a company can benefit from the wealth of resources available.

Microelectromechanical Systems (MEMS) packaging is much different from conventional integrated circuit (IC) packaging. Many MEMS devices must interface to the environment in order to perform their intended function, and the package must be able to facilitate access with the environment while protecting the device. The package must also not interfere with or impede the operation of the MEMS device. The die attachment material should be low stress, and low outgassing, while also minimizing stress relaxation overtime which can lead to scale factor shifts in sensor devices. The fabrication processes used in creating the devices must be compatible with each other, and not result in damage to the devices. Many devices are application specific requiring custom packages that are not commercially available. Devices may also need media compatible packages that can protect the devices from harsh environments in which the MEMS device may operate. Techniques are being developed to handle, process, and package the devices such that high yields of functional packaged parts will result. Currently, many of the processing steps are potentially harmful to MEMS devices and negatively affect yield. It is the objective of this paper to review and discuss packaging challenges that exist for MEMS systems and to …