Some limitations of detailed balance for inverse reaction calculations in the astrophysical p-process (open access)

Some limitations of detailed balance for inverse reaction calculations in the astrophysical p-process

p-Process modeling of some rare but stable proton-rich nuclei requires knowledge of a variety of neutron, charged particle, and photonuclear reaction rates at temperatures of 2 to 3 {times} 10{sup 9} {degrees}K. Detailed balance is usually invoked to obtain the stellar photonuclear rates, in spite of a number of well-known constraints. In this work we attempt to calculate directly the stellar rates for ({gamma},n) and ({gamma},{alpha}) reactions on {sup 151}Eu. These are compared with stellar rates obtained from detailed balance, using the same input parameters for the stellar (n,{gamma}) and ({alpha},{gamma}) reactions on {sup 150}Eu and {sup 147}Pm, respectively. The two methods yielded somewhat different results, which will be discussed along with some sensitivity studies. 16 refs., 7 figs.
Date: December 5, 1990
Creator: Gardner, D. G. & Gardner, M. A.
System: The UNT Digital Library
Simulation of EOR (enhanced oil recovery) processes in stochastically generated permeable media (open access)

Simulation of EOR (enhanced oil recovery) processes in stochastically generated permeable media

Many enhanced oil recovery (EOR) processes involve injecting an agent, such as steam or CO{sub 2}, that is much more mobile than the resident oil. Other EOR processes attempt to improve sweep efficiency by adding polymer or surfactant to the injected water to create a favorable mobility ratio. This study examines the effect of statistically generated heterogeneity on miscible displacements at unfavorable and favorable mobility ratios. The principal goal is to delineate the effects of fingering, dispersion and channeling on volumetric sweep efficiency. Two-dimensional heterogeneous permeability fields are generated with variability (heterogeneity) and spatial correlation as characterizing parameters. Four levels of correlation and three of variability make up a 12 element matrix. At each element of the matrix, a miscible displacement simulation at unit mobility ratio shows the effect of the heterogeneity, and simulations at mobility ratios of 10 and 0.5 show the effect of viscous force differences combined with heterogeneity. 20 refs., 7 figs., 3 tabs.
Date: January 1, 1990
Creator: Waggoner, J. R.; Castillo, J. L. & Lake, L. W.
System: The UNT Digital Library
Diamond tool wear of electrodeposited nickel-phosphorus alloy (open access)

Diamond tool wear of electrodeposited nickel-phosphorus alloy

Nickel-Phosphorus alloys are attractive materials for diamond turning applications such as fabrication of large optics and other high precision parts. Although the mechanism is not understood, diamond tool wear is minimized when the phosphorus content of the deposit is greater than 11% (wgt). In recent years, increased attention has been directed at electrodeposition as an alternate to electroless deposition for producing Ni-P alloys. One principal advantage of the electrodeposition process is that alloys with 14--15% P can be obtained; another is that an order of magnitude greater deposition thickness can be provided if necessary. This paper compares diamond turning results for electrodeposited and electroless Ni-P alloys and shows that the electrodeposited coatings provide promising results. 28 refs., 7 figs., 1 tab.
Date: February 1, 1990
Creator: Dini, J. W.; Donaldson, R. R.; Syn, C. K. & Sugg, D. J.
System: The UNT Digital Library
Green's function Monte Carlo in nuclear physics (open access)

Green's function Monte Carlo in nuclear physics

We review the status of Green's Function Monte Carlo (GFMC) methods as applied to problems in nuclear physics. New methods have been developed to handle the spin and isospin degrees of freedom that are a vital part of any realistic nuclear physics problem, whether at the level of quarks or nucleons. We discuss these methods and then summarize results obtained recently for light nuclei, including ground state energies, three-body forces, charge form factors and the coulomb sum. As an illustration of the applicability of GFMC to quark models, we also consider the possible existence of bound exotic multi-quark states within the framework of flux-tube quark models. 44 refs., 8 figs., 1 tab.
Date: January 1, 1990
Creator: Carlson, J.
System: The UNT Digital Library
Determination of bedrock hydraulic conductivity and hydrochemistry using a wellbore fluid logging method (open access)

Determination of bedrock hydraulic conductivity and hydrochemistry using a wellbore fluid logging method

One of the most challenging tasks faced by environmental engineers is cost effective hydraulic and hydrochemical characterization of a fractured bedrock aquifer by means of exploratory wellbores. To address this problem, a new borehole fluid logging method for rapidly and efficiently determining the vertical distribution of hydraulic conductivity in fractured bedrock aquifers has been developed. This new technique was recently applied near two active landfills in southern New England. The technique involves replacing the standing column of water in a borehole with a uniformly deionized fluid, and then profiling the changes in fluid electrical conductivity in the borehole. These changes occur when the contrasting formation water is drawn back into the borehole by continuous low flow rate pumping or by slug testing. A downhole wireline water-quality tool, which simultaneously measures fluid electrical conducivity, temperature, pH and oxidation-reduction potential (Eh), was employed to profile the physical/chemical changes of the ``emplaced`` fluid. The numerical code BORE, was employed to determine the inflow parameters and fracture-specific fluid electrical conducivity for the hydraulically conductive fractures. Straddle packer testing at 10-foot intervals was conducted to confirm the slug testing results. Some discrepancies were encountered which can be explained by accounting for the volume of formation …
Date: May 1, 1990
Creator: Pedler, W. H.; Barvenik, M. J.; Tsang, C. F. & Hale, F. V.
System: The UNT Digital Library
The plutonium-oxygen phase diagram (open access)

The plutonium-oxygen phase diagram

Identification of products formed by the reaction of plutonium metal with liquid water at 23{degree}C indicates that the plutonium-oxygen phase diagram is similar to the cerium-oxygen and praseodymium-oxygen diagrams. Quantitative measurements of H{sub 2} formation and analytical data suggest that a sequence of hydrolysis reactions produces oxide hydrides of trivalent plutonium, Pu{sub 2}O{sub 3}, mixed-valent oxides and PuO{sub 2}. The intermediate oxides are the n {equals} 7, 9, 10 and 12 members of the Pu{sub n}O{sub 2n{minus}2} homologous series. Properties of the residue formed by thermal decomposition of the initial hydrolysis product, plutonium monoxide monhydride (PuOH), are consistent with the formation of metastable plutonium monoxide. Crystal-chemical, thermodynamic, and kinetic factors are evaluated, but definitive assignment of the equilibrium Pu-O diagram is not possible. 22 refs., 6 figs., 1 tab.
Date: January 1, 1990
Creator: Haschke, J.M.
System: The UNT Digital Library
Laser driven instabilities in inertial confinement fusion (open access)

Laser driven instabilities in inertial confinement fusion

Parametric instabilities excited by an intense electromagnetic wave in a plasma is a fundamental topic relevant to many applications. These applications include laser fusion, heating of magnetically-confined plasmas, ionospheric modification, and even particle acceleration for high energy physics. In laser fusion, these instabilities have proven to play an essential role in the choice of laser wavelength. Characterization and control of the instabilities is an ongoing priority in laser plasma experiments. Recent progress and some important trends will be discussed. 8 figs.
Date: June 4, 1990
Creator: Kruer, W.L.
System: The UNT Digital Library
Tecuamburro Volcano, Guatemala geothermal gradient core hole drilling, operations, and preliminary results (open access)

Tecuamburro Volcano, Guatemala geothermal gradient core hole drilling, operations, and preliminary results

A geothermal gradient core hole (TCB-1) was drilled to a depth of 700+ m at the Tecuamburro geothermal site, Guatemala during February and March, 1990. The core hole is located low on the northern flank of the Tecuamburro Volcano complex. Preliminary analysis of cores (>98% core recovery) indicates that the hydrothermal system may be centered in the 4-km-diameter Chupadero Crater, which has been proposed as the source of pyroxene pumice deposits in the Tecuamburro area. TCB-1 is located 300 m south of a 300-m-diameter phreatic crater, Laguna Ixpaco; the core hole penetrates the thin edge of a tuff ring surrounding Ixpaco and zones of hydrothermal brecciation within the upper 150 m may be related to the phreatic blast, dated at 2,910 {sup 14}C years. At the time of this writing, the unequilibrated temperature at a depth of 570m was 180{degree}C. Data on fracturing, permeability, hydrothermal alteration, and temperature will be presented. 3 refs., 3 figs.
Date: January 1, 1990
Creator: Goff, S.; Heiken, G.; Goff, F.; Gardner, J. (Los Alamos National Lab., NM (USA)); Duffield, W. (Geological Survey, Flagstaff, AZ (USA)); Martinelli, L. et al.
System: The UNT Digital Library
Industrial Consortium for the Utilization of the Geopressured-Geothermal Resource. Volume 2 (open access)

Industrial Consortium for the Utilization of the Geopressured-Geothermal Resource. Volume 2

The Geopressured-Geothermal Program, now in its fifteenth year, is entering the transition period to commercial use. The industry cost-shared proposals to the consortium, represented in the presentations included in these proceedings, attest to the interest developing in the industrial community in utilizing the geopressured-geothermal resource. Sixty-five participants attended these sessions, two-thirds of whom represented industry. The areas represented by cost-shared proposals include (1) thermal enhanced oil recovery, (2) direct process use of thermal energy, e.g., aquaculture and agriculture, (3) conversion of thermal energy to electricity, (4) environment related technologies, e.g., use of supercritical processes, and (5) operational proposals, e.g., a field manual for scale inhibitors. It is hoped that from this array of potential use projects, some will persist and be successful in proving the viability of using the geopressured-geothermal resource. Such industrial use of an alternative and relatively clean energy resource will benefit our nation and its people.
Date: March 1, 1990
Creator: Negus-deWys, J. (ed.)
System: The UNT Digital Library
Proceedings of the workshop on the science of intense radioactive ion beams (open access)

Proceedings of the workshop on the science of intense radioactive ion beams

This report contains the proceedings of a 2-1/2 day workshop on the Science of Intense Radioactive Ion Beams which was held at the Los Alamos National Laboratory on April 10--12, 1990. The workshop was attended by 105 people, representing 30 institutions from 10 countries. The thrust of the workshop was to develop the scientific opportunities which become possible with a new generation intense Radioactive Ion Beam (RIB) facility, currently being discussed within North America. The workshop was organized around five primary topics: (1) reaction physics; (2) nuclei far from stability/nuclear structure; (3) nuclear astrophysics; (4) atomic physics, material science, and applied research; and (5) facilities. Overview talks were presented on each of these topics, followed by 1-1/2 days of intense parallel working group sessions. The final half day of the workshop was devoted to the presentation and discussion of the working group summary reports, closing remarks and a discussion of future plans for this effort.
Date: October 1, 1990
Creator: McClelland, John B. & Vieira, David J.
System: The UNT Digital Library
Study of spin-temperature effects using energy-ordered continuum gamma-ray spectroscopy technique (open access)

Study of spin-temperature effects using energy-ordered continuum gamma-ray spectroscopy technique

We have investigated a new continuum {gamma}-ray spectroscopy technique which is based on the detection of all emitted {gamma} rays in a 4{pi} detector system, and ordering them according to their energies on an event-by-event basis. The technique allows determination of gamma strength functions, and rotational damping width as a function of spin and temperature. Thus, it opens up the possibility of studying the onset of motional narrowing, order-to-chaos transition, and the mapping of the evolution of nuclear collectivity with a spin and temperature. Application of the technique for preferential entry-state population, exit-channel selection, and feeding of the discrete states via selective pathways will be discussed. 20 refs., 4 figs.
Date: January 1, 1990
Creator: Baktash, C.; Halbert, M. L.; Hensley, D. C.; Johnson, N. R.; Lee, I. Y.; McConnell, J. W. et al.
System: The UNT Digital Library
Preliminary observations of lung injury produced by instillation of HF in acidic and neutral buffer (open access)

Preliminary observations of lung injury produced by instillation of HF in acidic and neutral buffer

Perfluoroisobutylene (PFIB) is an extremely toxic organofluoride that can be produced during pyrolysis of tetrafluoroethylene polymers, including Teflon{reg sign}. Inhalation of PFIB at very low concentrations causes acute lung injury, the hallmark of which is pulmonary edema. Several lines of evidence have suggested that hydrolysis of PFIB and resulting production of hydrofluoric acid may be responsible for pulmonary damage. In order to investigate the potential involvement of hydrofluoric acid in producing lung injury and its relationship to the mechanism of fluorocarbon toxicity, we have compared the pulmonary injury produced by PFIB, by dissociated (H{sup +} and F{sup {minus}}), and by undissociated (HF) hydrofluoric acid in the deep lung. By delivering hydrofluoric acid by intratracheal instillation in neutral buffer, we demonstrate that F{sup {minus}} produces no significant pulmonary injury as assessed by increased in lung weight and ultrastructural changes. Similarly, instillation of acid buffer alone demonstrated that H{sup +} did not produce detectable lung injury. Instillation of HF produced changes in lung weight and ultrastructure similar to those observed in PFIB-treated rats. However, the ultrastructural studies show that in contrast to inhalation of PFIB, which produces both endothelial and epithelial cell damage, instillation of HF appears to exert its injurious effects …
Date: January 1, 1990
Creator: Brainard, J. R.; Kinkead, S. A.; Kober, E. M.; Sebring, R. J.; Stavert, D. M. & Lehnert, B. E.
System: The UNT Digital Library
Experiments utilizing ICRF heating on TFTR (open access)

Experiments utilizing ICRF heating on TFTR

A variety of experiments have been performed on the TFTR tokamak utilizing ICFR heating. Of special interest has been the insight into plasma performance gained by utilizing a different heating scheme other than the usual NBI. Utilizing ICRF heating allows control over the power deposition profile independent of the plasma fueling profile. In addition, by varying the minority concentration the power split between ion and electron heating can be varied. Confinement has been examined in high recycling gas fueled discharges, low recycling supershot plasmas, and peaked density pellet fueled discharges. Global confinement is found not to be affected by the method or localization of plasma heating, but the calculated local diffusivities vary with the power deposition profile to yield similar local values. In addition, sawtooth stabilization observed with ICRF heating has been investigated and found to occur in qualitative agreement with theory. ICRF sawtooth stabilized discharges exhibit peaked temperature and density profiles and have a safety factor q which appears to fall well below unity on axis. 11 refs., 10 figs.
Date: January 1, 1990
Creator: Wilson, J. R.; Hosea, J. C.; Bell, M. G.; Bitter, M.; Boivin, R.; Fredrickson, E. D. et al.
System: The UNT Digital Library
The Art'' of in situ fluid sampling and the remarkable compositional variations in the wellbore fluid of VC-2B, Valles Caldera, New Mexico (open access)

The Art'' of in situ fluid sampling and the remarkable compositional variations in the wellbore fluid of VC-2B, Valles Caldera, New Mexico

In situ fluid operations were conducted at VC-2B in January 1990 using two flow-through tools of different designs. Of eight attempts, no runs obtained samples from their intended depth of collection or, if they did, the tools gained additional fluid by inward leakage during their trips back to the surface. Interpretation of the salinity and mass of the fluid samples indicates that they were collected from apparent depths of about 204 to 1045 m, at collection temperatures of about 125{degree} to 240{degree}C. The data show a remarkable two-fold increase in fluid salinity (>9000 versus about 4000 mg/kg Cl) near the top of the well and a relatively thin, dilute cap'' of condensed steam at the top of the water column. Various criteria suggest that these salinity gradients are caused by boiling and condensation of steam in the wellbore during a seven month period of logging, stimulation, flow testing, and other in-hole experiments. 8 refs., 3 figs., 5 tabs.
Date: January 1, 1990
Creator: Golf, F.; Gardner, J.N.; Adams, A.; Trujillo, P. E., Jr.; Counce, D. (Los Alamos National Lab., NM (USA)); Solbau, R.D. et al.
System: The UNT Digital Library
Boundary integral methods for unsaturated flow (open access)

Boundary integral methods for unsaturated flow

Many large simulations may be required to assess the performance of Yucca Mountain as a possible site for the nations first high level nuclear waste repository. A boundary integral equation method (BIEM) is described for numerical analysis of quasilinear steady unsaturated flow in homogeneous material. The applicability of the exponential model for the dependence of hydraulic conductivity on pressure head is discussed briefly. This constitutive assumption is at the heart of the quasilinear transformation. Materials which display a wide distribution in pore-size are described reasonably well by the exponential. For materials with a narrow range in pore-size, the exponential is suitable over more limited ranges in pressure head. The numerical implementation of the BIEM is used to investigate the infiltration from a strip source to a water table. The net infiltration of moisture into a finite-depth layer is well-described by results for a semi-infinite layer if {alpha}D > 4, where {alpha} is the sorptive number and D is the depth to the water table. the distribution of moisture exhibits a similar dependence on {alpha}D. 11 refs., 4 figs.,
Date: December 31, 1990
Creator: Martinez, M.J. & McTigue, D.F.
System: The UNT Digital Library
Global Warming: A Northwest Perspective (open access)

Global Warming: A Northwest Perspective

The Northwest Power Planning Council convened a symposium in Olympia, Washington, on the subject of global climate change ( the greenhouse effect'') and its potential for affecting the Pacific Northwest. The symposium was organized in response to a need by the Power Council to understand global climate change and its potential impacts on resource planning and fish and wildlife planning for the region, as well as a need to understand national policy developing toward climate change and the Pacific Northwest's role in it. 40 figs., 15 tabs.
Date: February 1990
Creator: Scott, M. J. & Counts, C. A.
System: The UNT Digital Library
Historical Perspectives on Near-Death Phenomena (open access)

Historical Perspectives on Near-Death Phenomena

Abstract: The authors present an introductory overview of the history of near-death phenomena, followed by a synopsis of near-death research representative of three historical eras: 1880s-1930s; 1930s-1960; and 1960 to the present.
Date: Winter 1990
Creator: Walker, Barbara A. & Serdahely, William J.
System: The UNT Digital Library
Fermilab experiment E-687: Recent results on charm (open access)

Fermilab experiment E-687: Recent results on charm

About 10{sup 4} charm decays have been reconstructed from first-run data of Fermilab experiment E687 using the Fermilab Wide-Band Photon Spectrometer with the world's highest energy photon beam. Charm selection strategies and preliminary results are discussed. Lifetime values are (.50 {plus minus} .06 {plus minus} .03)ps for the D{sub s}{sup +} and (.20 {plus minus} .03 {plus minus} .03)ps for the {Lambda}{sub c}{sup +}. Preliminary D{sup +} and D{sup 0} lifetimes are consistent with current world averages. Signals for charm baryon and Cabibbo-suppressed charm meson decays are shown. Preliminary branching ratios are: B(D{sup 0} {yields} {pi}{sup +}{pi}{sup {minus}}{pi}{sup +}{pi}{sup {minus}})/B(D{sup 0} {yields} K{sup {minus}}{pi}{sup +}{pi}{sup +}{pi}{sup {minus}}) = .10 {plus minus} .02 {plus minus} .02; B(D{sup 0} {yields} {bar K}{sup 0}K{sup +}K{sup {minus}})/B(D{sup 0} {yields} {bar K}{sup 0}{pi}{sup +}{pi}{sup {minus}}) = .20 {plus minus} .06(stat); B(D{sup 0} {yields} {bar K}{sup 0}{phi})/B(D{sup 0} {yields} {bar K}{sup 0}{pi}{sup +}{pi}{sup {minus}}) = .16 {plus minus} .06(stat). Preliminary results are given on D*{sup {plus minus}} and D{sup {plus minus},0} photoproduction for photon energies from 100 to 350 GeV. 13 refs., 3 figs.
Date: December 1, 1990
Creator: Shephard, W.D. (Notre Dame Univ., IN (USA))
System: The UNT Digital Library
Savannah River Region: Transition between the Gulf and Atlantic Coastal Plains. Proceedings (open access)

Savannah River Region: Transition between the Gulf and Atlantic Coastal Plains. Proceedings

The focus of the this conference of Coastal Plains geologists was on the Savannah River region of Georgia and South Carolina, and particularly on the geology of the US Department of Energy`s 300 square mile Savannah River Site (SRS) in western South Carolina. Current geological studies indicate that the Mesozoic-Cenozoic section in the Savannah River region is transitional between that of the Gulf Coastal Plain to the southwest and that of the Atlantic Coastal Plain to the northeast. With the transitional aspect of the region as its theme, the first session was devoted to overviews of Cretaceous and Paleogene geology in the Gulf and Atlantic Coastal Plains. Succeeding presentations and resulting discussions dealt with more specific problems in structural, lithostratigraphic, hydrological, biostratigraphic, and cyclostratigraphic analysis, and of correlation to standard stratigraphic frameworks. For these conference proceedings, individual papers have been processed separately for the Energy Data Base.
Date: December 31, 1990
Creator: Zullo, V. A.; Harris, W. B. & Price, V.
System: The UNT Digital Library
Formulating Energy Policies Related to Fossil Fuel Use: Critical Uncertainties in the Global Carbon Cycle (open access)

Formulating Energy Policies Related to Fossil Fuel Use: Critical Uncertainties in the Global Carbon Cycle

The global carbon cycle is the dynamic interaction among the earth's carbon sources and sinks. Four reservoirs can be identified, including the atmosphere, terrestrial biosphere, oceans, and sediments. Atmospheric CO{sub 2} concentration is determined by characteristics of carbon fluxes among major reservoirs of the global carbon cycle. The objective of this paper is to document the knowns, and unknowns and uncertainties associated with key questions that if answered will increase the understanding of the portion of past, present, and future atmospheric CO{sub 2} attributable to fossil fuel burning. Documented atmospheric increases in CO{sub 2} levels are thought to result primarily from fossil fuel use and, perhaps, deforestation. However, the observed atmospheric CO{sub 2} increase is less than expected from current understanding of the global carbon cycle because of poorly understood interactions among the major carbon reservoirs. 87 refs.
Date: 1990~
Creator: Post, W. M.; Dale, V. H.; DeAngelis, D. L.; Mann, L. K.; Mulholland, P. J.; O'Neill, R. V. et al.
System: The UNT Digital Library
Determination of bedrock hydraulic conductivity and hydrochemistry using a wellbore fluid logging method (open access)

Determination of bedrock hydraulic conductivity and hydrochemistry using a wellbore fluid logging method

One of the most challenging tasks faced by environmental engineers is cost effective hydraulic and hydrochemical characterization of a fractured bedrock aquifer by means of exploratory wellbores. To address this problem, a new borehole fluid logging method for rapidly and efficiently determining the vertical distribution of hydraulic conductivity in fractured bedrock aquifers has been developed. This new technique was recently applied near two active landfills in southern New England. The technique involves replacing the standing column of water in a borehole with a uniformly deionized fluid, and then profiling the changes in fluid electrical conductivity in the borehole. These changes occur when the contrasting formation water is drawn back into the borehole by continuous low flow rate pumping or by slug testing. A downhole wireline water-quality tool, which simultaneously measures fluid electrical conducivity, temperature, pH and oxidation-reduction potential (Eh), was employed to profile the physical/chemical changes of the emplaced'' fluid. The numerical code BORE, was employed to determine the inflow parameters and fracture-specific fluid electrical conducivity for the hydraulically conductive fractures. Straddle packer testing at 10-foot intervals was conducted to confirm the slug testing results. Some discrepancies were encountered which can be explained by accounting for the volume of formation …
Date: May 1, 1990
Creator: Pedler, W. H.; Barvenik, M. J. (GZA GeoEnvironmental, Inc., Newton Upper Falls, MA (United States)); Tsang, C. F. & Hale, F. V. (Lawrence Berkeley Lab., CA (United States))
System: The UNT Digital Library
An assessment of the lifetime of Faraday shield elements (open access)

An assessment of the lifetime of Faraday shield elements

The interaction of plasma with rf fields from an ion cyclotron range of frequencies (ICRF) antenna has been studied to estimate the amount of Faraday shield erosion expected in normal ICRF heating operation. Plasma parameters and ion energies have been measured in the near field of an antenna and used in a model to estimate the erosion rate of the Faraday shield surface. Experiments were conducted on the RF Test Facility, a magnetic mirror device at Oak Ridge National Laboratory, using a single-strap resonant loop antenna with a two-tier Faraday shield. The outer tier, facing the plasma, was layered with graphite tiles. The antenna was operated at currents and voltages within 50% of those expected in tokamaks. The time-varying floating potential was measured with a capacitively coupled probe, and the time-averaged floating potential, electron temperature, and electron density were measured with a Langmuir probe. Ion energies were measured with a gridded energy analyser located below the antenna, and samples of silicon were placed on the Faraday shield surface to estimate the incident ion energy. The capacitive probe measurements show that the rf floating potential follows the magnetic field pattern of the antenna, indicating that the electromagnetic fields are responsible for …
Date: January 1, 1990
Creator: Caughman, J. B. O., II; Ruzic, D. N.; Hoffman, D. J.; Langley, R. A.; Lewis, M. B. & Ryan, P. M.
System: The UNT Digital Library
H- Enhancement Process in a Multicusp Ion Source Operated with a Barium Insert Structure (open access)

H- Enhancement Process in a Multicusp Ion Source Operated with a Barium Insert Structure

It has been demonstrated that the H{sup -} output current from a small multicusp source can be substantially enhanced if the hydrogen plasma is seeded with barium. Operating with a barium washer insert at the extraction aperture, it is found that the extractable H{sup -} current is increased by a factor of three if the insert bias potential is optimized. By use of a mixture of xenon and hydrogen gas, it is further demonstrated that the positive hydrogen ions are responsible for the observed H{sup -} enhancement.
Date: May 1, 1990
Creator: Leung, K. N.; Van Os, C. F. A. & Kunkel, W. B.
System: The UNT Digital Library
Recent Results on Charm From Fermilab Experiment E-687 (open access)

Recent Results on Charm From Fermilab Experiment E-687

About 10{sup 4} charm decays have been reconstructed from first-run data of Fermilab experiment E687 using the Fermilab Wide-Band Photon Spectrometer with the world's highest energy photon beam. The success of techniques for isolating and reconstructing charm event samples based on two complementary vertexing strategies is illustrated. Preliminary results are presented. These include lifetime value of (0.50 {plus minus} 0.06 {plus minus} 0.03)ps for the D{sub s}{sup +}, and (0.20 {plus minus} 0.03 {plus minus} 0.03)ps for the {Lambda}{sub c}{sup +}. Preliminary values for the D{sup +} and D{sup 0} lifetimes are consistent with currently accepted world averages. Signals for the Cabibbo-suppressed decays D{sup 0} {yields} {pi}{sup +}{pi}{sup {minus}}{pi}{sup +}{pi}{sup {minus}}, D{sup +} {yields} K{sup +}K{sup {minus}}{pi}{sup +}, and D{sup +} {yields} {phi}{pi}{sup +} are shown; for B(D{sup 0} {yields} {pi}{sup +}{pi}{sup {minus}}{pi}{sup +}{pi}{sup {minus}})/B(D{sup 0} {yields} K{sup {minus}}{pi}{sup +}{pi}{sup +}{pi}{sup {minus}}) our preliminary value is 0.10 {plus minus} 0.02 {plus minus} 0.02. Preliminary values for ratios B(D{sup 0} {yields} {ovr K}{sup 0}K{sup +}K{sup {minus}})/B(D{sup 0} {yields} {ovr K}{sup 0}{pi}{sup +}{pi}{sup {minus}}) and B(D{sup 0} {yields} {ovr K}{sup 0}{phi})/B(D{sup 0} {yields} {ovr K}{sup 0}{pi}{sup +}{pi}{sup {minus}}) are 0.20 {plus minus} 0.06 and 0.16 {plus minus} 0.06. Preliminary results are given …
Date: December 1, 1990
Creator: Buchholz, D.; Gourlay, S.; Moroni, L.; Ratti, S .P. & Shephard, W. D.
System: The UNT Digital Library