The DIII-D tokamak employs eight neutral beam systems for plasma heating and current drive experiments. These positive ion source neutral beam systems have gone through several improvements in operational technique and in system hardware since the start of conditioning of the first long pulse ion source in December 1986. These improvements have led to the routine operation in deuterium at beam power levels of 20 MW. The improvements in operational technique include filament power supply operating mode, accelerator grid voltage holding capability, mid changes in grid potential gradients. The hardware improvements include installation of arc notching, arc discharge density regulation, and control of neutralizer gas puffing. Each of these improvements are discussed in this paper. Successful testing and operation of the ion source at 93 kV deuterium beam energy, well above the design value of 80 kV, also led to the possibility of enhancing system capability to 28 MW power level, nearly twice the original design value. Upgrading of the beam system to 60 second pulse duration at the currently achieved power level is under consideration. Studies have shown that this pulse length extension can be achieved with improvements in beamline heat handling components and auxiliary systems, especially the power …

Two different requirements are driving engineering studies and hardware development to improve LAMPF. The first is concerned with component and system improvements to increase beam availability during the LAMPF production cycle. Hardware changes in RF, power supplies, and magnets are being implemented to increase mean time between failure and reduce time to replace or repair failed units. A joint LAMPF-Industry project is on-going to improve reliability of RF components. A component test stand is being refurbished to include significant development capability. The second approach includes several changes that will increase the duty factor of the existing accelerator. Major changes are being evaluated for replacing the front end of the accelerator. Other changes improving high brightness capability could result in a new performance plateau for LAMPF.

Polarized neutron reflection was used to determine the magnetic structure of two different antiferromagnetically coupled multilayer systems, Fe/Gd and Fe/Cr. In Fe/Gd, the Fe and Gd moments are coupled antiparallel at the interface. At low temperatures a surface induced magnetic phase transition was found. In Fe/Cr, annealing at temperatures of up to 425{degrees}C, resulted in the degrading of antiferromagnetic coupling between Fe layers and in the formation of ferromagnetically coupled regions.

Research is underway at SLAC to develop accelerator structures for the next generation linear collider. An important feature of the design is a detuning of the dipole modes of the cells to suppress the long-range transverse wakefield by two orders of magnitude. This paper describes a facility, called ASSET, that will be incorporated into the SLAC Linear Collider (SLC) to test the long-range wakefield suppression and also to measure the other components of the wakefields generated in accelerator test structures.

The overall objective of the current Task 6 under Contract AC21-90MC27168 is to develop understanding as well as quantification of cell ohmic resistance in carbonate fuel cell. The important resistance-contributing interfaces and elements are being investigated in high-temperature out-of-cell resistance experiments, using an AC-impedance technique. Ohmic resistance loss in a state-of-the-art carbonate fuel cell contributes about 65 mV loss at BOL (beginning-of-life). It may increase to about as much as 145 mV after 40,000 hours. Its reduction will offer further improvement in fuel cell power plant efficiency. The important resistance contributing elements/interfaces are illustrated in Figure 1. The majority of the ohmic loss attributed to electrolyte matrix (ionic) and cathode-side hardware (electronic). The ohmic loss due to anode-side hardware can generally be neglected because the anode-side hardware is surface protected resulting in very little surface oxide formation. The ohmic resistance of the electrodes is also negligible. The matrix ionic resistance is influenced by many factors: electrolyte conductivity, matrix porosity, tortuosity, electrolyte fill level and matrix thickness. At present, matrix contributes to > 300 m{Omega}cm{sup 2} (>70% of the total cell ohmic resistance) and is the major resistance contributor.

Temperature dependent studies of ion channeling in high-quality, high-Tc single-crystals are summarized. The measurements revealed an abrupt change across Tc in displacements in the a-b plane of the Cu(I and 2) and 0(4) atoms; normal Debye-like'' vibrations were found for the Y and Ba atoms. The anomalous atomic displacements were found for both proton and He channeling, and manifested themselves as an abrupt increase in the critical angle and a simultaneous decrease in the minimum yield. The anomalous change in Cu-0 displacements shifted directly with stoichiometry-induced changes in Tc, implying a causal fink between the observed phonon anomaly and the superconducting state. An apparently identical anomaly was found in (Bi{sub 1.7}Pb{sub 0.3})Sr{sub 2}CaCu{sub 2}O{sub x}, indicating that it is a general feature of high-T, superconductivity. A comparison with other experimental measurements in YBa{sub 2}Cu{sub 3}O{sub 7-x}, including a detailed neutron diffraction study, indicates that the anomaly is not due to an overall reduction in average vibrational amplitude, but arises instead from a strongly correlated sequence of Cu(1 and 2) and 04 displacements that appears with the onset of superconductivity. These strongly correlated displacements are either dynamic, or they are static distortions that fail to preserve the overall crystal symmetry.

A thin boron film has been applied to the DIII-D tokamak plasma facing surfaces to reduce impurity influx, particularly oxygen and carbon. A direct result of this surface modification was the observation of a regime of very high energy confinement, VH-mode, with confinement times from 1.5 to 2 times greater than predicted by H-mode scaling relation for the same set of parameters. VH-mode discharges are characterized by low ohmic target densities, low edge neutral pressure, and reduced cycling. These conditions have reduced the collisionality, {nu}*, in the edge region producing a higher edge pressure gradient and a significant bootstrap current, up to 30% of the total current. We will describe the edge plasma properties after boronization including reductions in recycling inferred from measurements of {tau}{sup p}*. In particular we will discuss the edge plasma conditions necessary for access to VH-mode including the boronization process and properties of the deposited film.

ISOCELL{sup TM} cryogenic technology is designed to immobilize buried hazardous, radioactive, and mixed waste and contaminated soil by creating a block of frozen waste and soil that can be safely retrieved, stored, transported, and treated with a minimum of dust or aerosol production. A proof-of-concept'' test of the ISOCELL process was conducted in clean soil by RKK, Ltd., for the Idaho National Engineering Laboratory (INEL). Results indicate ISOCELL technology successfully froze moist soil into a solid block capable of being lifted and retrieved. Test conditions were compared to characteristics of possible buried waste sites in the INEL.

Many theoretical models have been employed to described the structure of the nucleus {sup 24}Mg. Among these are the Cranked Shell model (CSM), the Cranked Cluster Model (CCM), and calculations have also been performed using the Hartree-Fock formalism. One very striking prediction of these calculations is that in this nucleus there exist very unusual configurations, with structures reminiscent of linear chains of alpha particles. In the CSM, for instance, such a configuration is identified with a pronounced minimum in the potential energy energy at very large prolate deformation. In the CCM, several very different alpha-particle duster configurations are identified, many having rather large deformations. These cluster configurations can be associated with the different potential-energy minima obtained in the CSM results. In the case of the CCM, a 6{alpha} chain-like configuration is predicted to occur at excitation energies between 40 and 50 MeV, with predicted rotational spacing given by {Dirac h}{sup 2}/2I=22 keV. At this excitation energy, such a chain configuration would lie well above the threshold for the decay of {sup 24}Mg into 6 alpha particles, and its identification poses a difficult experimental challenge. This report discusses this challenge.

A study has been conducted on the recent progress of the three-terminal devices with transistor-like characteristics fabricated from the high-{Tc} superconducting materials. This study explored the operating principles and characteristics of these devices in relation to the relevant materials and techniques. A comparison of a variety of techniques for superconducting thin film deposition will be given. This study indirates that the feasibility of fabricating hybrid devices composed of semiconductors and superconductors appear to be the key issue to push forward the applications of high-{Tc} superconductors in microelectronics. The junction field-effect transistors with a semiconductor base controlled by the proximity effect are likely to be more manufacturable. The factors that influence the operating reliability of devices and the problems arising from integrating and packaging the devices will also be discussed.

Each year the Geothermal Division of the US Department of Energy conducts an in-depth review of its entire geothermal R D program. The conference serves several purposes: a status report on current R D activities, an assessment of progress and problems, a review of management issues, and a technology transfer opportunity between DOE and the US geothermal city. This year's conference, Program Review X, was held in San Francisco on March 24--26, 1992. The theme of the review, Geothermal Energy and the Utility Market -- The Opportunities and Challenges for Expanding Geothermal Energy in a Competitive Supply Market,'' focused on the needs of the electric utility sector. Geothermal energy, with its power capacity potential of 10 GWe by the year 2010, can provide reliable, enviromentally clean electricity which can help offset the projected increase in demand. Program Review X consisted of seven sessions including an opening session with presentations by Mr. Vikram Budhraja, Vice President of System Planning and Operations, Southern California Edison Company, and Mr. Richard Jaros, President and Chief Operating Officer, California Energy Company. The six technical sessions included presentations by the relevant field researchers covering DOE-sponsored R D in hydrothermal, hot dry rock, and geopressured energy. Individual …

This report discusses the recovery from the February 9, 1991 small scale explosion in a custom processing dissolver at the Idaho Chemical Processing Plant. Custom processing is a small scale dissolution facility which processes nuclear material in an economical fashion. The material dissolved in this facility was uranium metal, uranium oxides, and uranium/fissium alloy in nitric acid. The paper explained the release of fission material, and the decontamination and recovery of the fuel material. The safety and protection procedures were also discussed. Also described was the chemical analysis which was used to speculate the most probable cause of the explosion. (MB)

For high energy pp collisions, the concepts 4{pi}'' and full acceptance'' are distinct. At the SSC, the appropriate variables for describing phase space are the lego variables: pseudorapidity {eta} and azimuthal angle {phi}. While most of 4{pi} is covered by pseudorapidities less than 3 or 4 in magnitude, at the SSC there is very interesting physics out to {eta}'s of 9 to 12. For over a year I have been attempting to encourage an initiative at the SSC to provide a detector which could cover the missing acceptance of the two big detectors, which in particular have no appreciable charged particle tracking with good momentum resolution beyond rapidities of 2.5 or so. The nonnegotiable criteria for an FAD are for me the following: 1. All charged particles are seen and their momenta measured well, provided pt is not too large. 2. All photons are seen and their momenta are measured well. 3. The physics of rapidity-gaps is not compromised. This means angular coverage from 90{degrees} down to tens of microradians. The above criteria cannot be met on day one of SSC commissioning with the amount of funds available. But I believe a staged approach is feasible, with a lot of …

The Grand Canyon region of the American Southwest is an interesting region meteorologically, but because of its isolated location, the lack of major population centers in the region, and the high cost of meteorological field experiments, it has historically received little observational attention. In recent years, however, attention has been directed to episodes of visibility degradation in many of the US National parks, and two recent field studies focused on this visibility problem have greatly increased the meteorological data available for the Grand Canyon region. The most recent and comprehensive of these studies is the Navajo Generating Station Winter Visibility Study of 1989--90. This study investigated the sources of visibility degradation in Grand Canyon National Park and the meteorological mechanisms leading to low visibility episodes. In this paper we present analyses of this rich data set to gain a better understanding of the key wintertime meteorological features of the Grand Canyon region.

Argonne National Laboratory (ANL) has developed two- and three-dimensional computer programs to predict hydrodynamics in complex fluid/solids systems including atmospheric and pressurized bubbling and circulating fluidized-bed combustors and gasifiers, concentrated suspension (slurry) piping systems and advanced particle-bed reactors for space-based applications, for example. The computer programs are based upon phenomenological mechanistic models and can predict frequency of bubble formation, bubble size and growth, bubble frequency and rise-velocity, solids volume fraction, gas and solids velocities and low dimension chaotic attracters. The results of these hydrodynamic calculations are used as inputs to mechanistic models to predict heat transfer and erosion and have been used to produce simplified models and guidelines to assist in design and scaling. An extensive coordinated effort involving industry, government, and university laboratory data has served to validate the various models. Babcock Wilcox (B W), in close collaboration with ANL, has developed the three dimensional FORCE2 computer program which is both transient as well as steady-state.

Preliminary design for the SLAC Next Linear Collider Test Accelerator (NLCTA) requires a pulse power source to produce a 600 kV, 600 A, 1.4 {mu}s, 0.1% flat top pulse with rise and fall times of approximately 100 ns to power an X-Band klystron with a microperveance of 1.25 at {approx} 100 MW peak RF power. The design goals for the modulator, including those previously listed, are peak modulator pulse power of 340 MW operating at 120 Hz. A three-stage darlington pulse-forming network, which produces a >100 kV, 1.4 {mu}s pulse, is coupled to the klystron load through a 6:1 pulse transformer. Careful consideration of the transformer leakage inductance, klystron capacitance, system layout, and component choice is necessary to produce the very fast rise and fall times at 600 kV operating continuously at 120 Hz.

This paper has discussed some considerations important to making a successful transition from R D to manufacturing. It has described a product commercialization framework and discussed the importance of business analyses, especially product cost analysis, in determining the future potential of an emerging technology. Careful attention to the major elements discussed in this report should help both developers and venture sponsors to reduce the risks inherent in new business ventures.

A number of high-level radioactive waste (HLW) safety issues have been identified at the Hanford Site in southeastern Washington State. Resolution of these issues is one of the Highest Priorities of the US Department of Energy. The most urgent issues are the potential for explosions in certain tanks (due to periodic venting of large quantities of flammable gases, or the presence of substantial quantities of ferrocyanide and/or organic compounds in combination with nitrates-nitrites). Other safety issues have been identified as well, such as the requirement for periodic water additions to one tank to control its temperature and the release of noxious vapors from a number of tanks. Substantial progress has been made toward safety issue resolution. Potential mechanisms have been identified for the generation, retention and periodic venting of flammable gas mixtures; potential methods for controlling the periodic release behavior have been identified and in-tank testing will be initiated in 1992. Research is being conducted to determine the initiation temperatures, energetics, reaction sequences and effects of catalysts and initiators on ferrocyanide-nitrate/nitrite reactions; waste characterization on a tank-by-tank basis will be required to identify whether ferrocyanide-containing wastes are safe to store as-is or will require further treatment to eliminate safety concerns. …

Chemical reactivity is one of the few methods currently available for investigating the geometrical structure of isolated transition metal clusters. In this paper we summarize what is currently known about the structures of clusters of four transition metals, Fe, Co, Ni, and Cu, in the size range from 13 to 180 atoms. Chemical probes used to determine structural information include reactions with H{sub 2}(D{sub 2}), H{sub 2}0, NH{sub 3} and N{sub 2}. Measurements at both low coverage and at saturation are discussed.

The US Army established the Army Tactical Command and Control System (ATCCS) Experimentation Site (AES) to provide a place where material and combat developers could experiment with command and control systems. The AES conducts fundamental and applied research involving command and control issues using a number of research methods, ranging from large force-level experiments, to controlled laboratory experiments, to studies and analyses. The work summarized in this paper was done by Pacific Northwest Laboratory under task order from the Army Tactical Command and Control System Experimentation Site. The purpose of the task was to develop the functional requirements for army engineer automation and support software, including MCS-ENG. A client, such as an army engineer, has certain needs and requirements of his or her software; these needs must be presented in ways that are readily understandable to the software developer. A requirements analysis then, such as the one described in this paper, is simply the means of communication between those who would use a piece of software and those who would develop it. The analysis from which this paper was derived attempted to bridge the communications gap'' between army combat engineers and software engineers. It sought to derive and state the …

The kinetics of chemical reactions of cobalt clusters Co{sub n} with deuterium are described. Absolute rate constants have been measured in the cluster range n = 7--68 at 293 K. The rate constants are found to be a strong function of cluster size, varying by up to three orders of magnitude. This size , dependence is most prominent in the n = 7--25 size range: CO{sub 15} is the most reactive cluster, and CO{sub 7-9} and CO{sub 19--20} are particularly unreactive. Abrupt changes in the rate constants from one cluster size to the next are observed. For the clusters above n = 25, the rate constants show several less prominent maxima and minima superimposed on a slow, nearly monotonic increase with cluster size.

Selected perovskite solid electrolytes incorporated into research size fuel cells have shown stability for > 4000 hours at 600{degrees}C. Perovskite lattice requirements which favor low E{sub a} for ionic conduction include (i) that the perovskite lattice possess a moderate enthalpy of formation, (ii) perovskite lattice possess large free volumes, (iii) that the lattice minimally polarizes the mobile ion and (iv) that the crystallographic saddle point r{sub c} for ionic conduction is {approx equal} 1.

Shared virtual memory (SVM) is a virtual memory layer with a single address space on top of a distributed real memory on parallel computers. We examine the behavior and performance of SVM running a parallel program with medium-grained, loop-level parallelism on top of it. A simulator for the underlying parallel architecture can be used to examine the behavior of SVM more deeply. The influence of several parameters, such as the number of processors, page size, cold or warm start, and restricted page replication, is studied.

Three examples of magnetic coupling across metallic spacer layers are considered. Fe/Nb sputtered superlattices are observed to have as many as five antiferromagnetic oscillations, but a weak magnetoresistive anomaly. Epitaxial trilayers of Fe/Mo/Fe grown on Mo(100) and Co/Cu/Co grown on Cu(100) are observed to have short- and long-period oscillations, respectively. The trilayers are grown with wedged spacer layers and characterized in-situ by means of the magneto-optic Kerr effect.