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547 Matching Results
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Alfvenic behavior of alpha particle driven ion cyclotron emission in TFTR
Ion cyclotron emission (ICE) has been observed during D-T discharges in the Tokamak Fusion Test Reactor (TFTR), using rf probes located near the top and bottom of the vacuum vessel. Harmonics of the alpha cyclotron frequency ({Omega}{sub {alpha}}) evaluated at the outer midplane plasma edge are observed at the onset of the beam injection phase of TFTR supershots, and persist for approximately 100-250 ms. These results are in contrast with observations of ICE in JET, in which harmonics of {Omega}{sub {alpha}} evolve with the alpha population in the plasma edge. Such differences are believed to be due to the fact that newly-born fusion alpha particles are super-Alfvenic near the edge of JET plasmas, while they are sub-Alfvenic near the edge of TFTR supershot plasmas. In TFTR discharges with edge densities such that newly-born alpha particles are super-Alfvenic, alpha cyclotron harmonics are observed to persist. These results are in qualitative agreement with numerical calculations of growth rates due to the magnetoacoustic cyclotron instability.
Date:
July 1, 1995
Creator:
Cauffman, S.; Majeski, R. & McClements, K.G.
Object Type:
Report
System:
The UNT Digital Library
Inhomogeneous primordial nucleosynthesis and new abundance constraints on {Omega}{sub b}h{sup 2}
We discuss the upper limit to the baryonic contribution to the closure density. We consider effects of new observational and theoretical uncertainties in the primordial light element abundances, and the effects of fluctuation geometry on the inhomogeneous nucleosynthesis yields. We also consider implications of the possible detection of a high D/H abundance in a Lyman-{alpha} absorption cloud at high redshift and the implied chemical evolution effects of a high deuterium abundance. We show that there exists a region of the parameter space for inhomogeneous models in which a somewhat higher baryonic contribution to the closure density is possible than that allowed in standard homogeneous models. This result is contrary to some other recent studies and is due to both geometry and recently revised uncertainties in primordial light-element abundances, particularly {sup 7}Li. We find that the presently adopted abundance constraints are consistent with a contribution of baryons to the closure density as high as {Omega}{sub b}h{sub 50}{sup 2} {le} 0.11 ({eta} {le} 7 {times} 10{sup {minus}10}). This corresponds to a 20% increase over the limit from standard homogeneous models ({Omega}{sub b}h{sub 50}{sup 2} {le} 0.08, {eta} {le} 5.8 {times} 10{sup {minus}10}). With a high deuterium abundance the upper limits for the …
Date:
July 20, 1995
Creator:
Mathews, G. J.; Kajino, T. & Orito, M.
Object Type:
Report
System:
The UNT Digital Library
Two-stream cyclotron radiative instabilities due to the marginally mirror-trapped fraction for fustion alphas in tokamaks
It is shown here that the marginally mirror-trapped fraction of the newly-born fusion alpha particles in the deuterium-tritium (DT) reaction dominated tokamak plasmas can induce a two-stream cyclotron radiative instability for the fast Alfven waves propagating near the harmonics of the alpha particle cyclotron frequency {omega}{sub c{alpha}}. This can explain both the experimentally observed time behavior and the spatially localized origin of the fusion product ion cyclotron emission (ICE) in TFTR at frequencies {omega} {approx} m{omega}{sub c{alpha}}.
Date:
July 1, 1995
Creator:
Arunasalam, V.
Object Type:
Report
System:
The UNT Digital Library
Inertial confinement fusion target component fabrication and technology development support: Annual report, October 1, 1993--September 30, 1994
On December 30, 1990, the US Department of Energy entered into a contract with General Atomics (GA) to be the Inertial Confinement Fusion (ICF) Target Component Fabrication and Technology Development Support contractor. During the period, GA was assigned 17 tasks in support of the Inertial Confinement Fusion program and its laboratories. This year they achieved full production capabilities for the micromachining, dimensional characterization and gold plating of hohlraums. They fabricated and delivered 726 gold-plated mandrels of 27 different types to LLNL and 48 gold-plated mandrels of two different types to LANL. They achieved full production capabilities in composite capsule production ad delivered in excess of 240 composite capsules. They continuously work to improve performance and capabilities. They were also directed to dismantle, remove, and disposition all equipment at the previous contractor (KMSF) that had radioactive contamination levels low enough that they could be exposed to the general public without radiological constraints. GA was also directed to receive and store the tritium fill equipment. They assisted LANL in the development of techniques for characterization of opaque targets. They developed deuterated and UV-opaque polymers for use by the University of Rochester`s Laboratory for Laser Energetics (UR/LLE) and devised a triple-orifice droplet generator …
Date:
April 1, 1995
Creator:
Hoppe, M.
Object Type:
Report
System:
The UNT Digital Library
Magnetic viscosity by localized shear flow instability in magnetized accretion disks
Differentially rotating disks are subject to the axisymmetric instability for perfectly conducting plasma in the presence of poloidal magnetic fields. For nonaxisymmetric perturbations, the authors find localized unstable eigenmodes whose eigenfunction is confined between two Alfven singularities at {omega}{sub d} = {+-} {omega}{sub A}, where {omega}{sub d} is the Doppler-shifted wave frequency, and {omega}{sub A} = k{parallel}v{sub A} is the Alfven frequency. The radial width of the unstable eigenfunction is {Delta}x {approximately} {omega}{sub A}/(Ak{sub y}), where A is the Oort`s constant, and k{sub y} is the azimuthal wave number. The growth rate of the fundamental mode is larger for smaller value of k{sub y}/k{sub z}. The maximum growth rate when k{sub y}/k{sub z} {approximately} 0.1 is {approximately} 0.2{Omega} for the Keplerian disk with local angular velocity {Omega}. It is found that the purely growing mode disappears when k{sub y}/k{sub z} > 0.12. In a perfectly conducting disk, the instability grows even when the seed magnetic field is infinitesimal. Inclusion of the resistivity, however, leads to the appearance of an instability threshold. When the resistivity {eta} depends on the instability-induced turbulent magnetic fields {delta}B as {eta}([{delta}B{sup 2}]), the marginal stability condition self-consistently determines the {alpha} parameter of the angular momentum transport …
Date:
January 1, 1995
Creator:
Matsumoto, R. & Tajima, T.
Object Type:
Report
System:
The UNT Digital Library
Optimization of magnetite carrier precipitation process for transuranic waste reduction
Transuranic (TRU) waste that is being generated at Argonne National Laboratory has a TRU activity ranging from 10{sup 2} to 10{sup 7} nCi/g with a wide variety of chemical compositions. Currently, the waste is stored in highly acidic solutions that must be neutralized for intermediate storage. A magnetite carrier precipitation process has been adapted to concentrate TRU isotopes in a noncorrosive solid phase. In this paper, the authors report the results of a series of laboratory tests done to optimize the process. The parameters they optimized included (1) magnetite concentration used to precipitate the TRUs from solution, (2) formation of magnetite (in situ or ex situ), (3) processing pH, and (4) temperature and mixing time of the carrier precipitation. They also studied the effects of anions, cations, and complexing agents in the waste solutions on the carrier precipitation and the effect of magnetite solids loading on the filtration equipment. An overview is given of the planned full-scale process, which will be operated in a glovebox.
Date:
December 31, 1995
Creator:
Slater, S.A.; Chamberlain, D.B.; Aase, S.A.; Babcock, B.D.; Conner, C.; Sedlet, J. et al.
Object Type:
Article
System:
The UNT Digital Library
An update on measurements of helium-production reactions with a spallation neutron source
This report gives the status, updated since the last Research Coordination Meeting, of alpha-particle production cross sections, emission spectra and angular distributions which we are measuring at the spallation source of fast neutrons at the Los Alamos Meson Physics Facility (LAMPF). Detectors at angles of 30, 60, 90 and 135{degrees} are used to identify alpha particles, measure their energy spectra, and indicate the time-of-flight, and hence the energy, of the neutrons inducing the reaction. The useful neutron energy ranges from less than 1 MeV to approximately 50 MeV for the present experimental setup. Targets under study at present include C, N, 0, {sup 27}Al, Si, {sup 51}V, {sup 56}Fe, {sup 59}CO, {sup 58,60}Ni, {sup 89}Y and {sup 93}Nb. Data for {sup 59}Co have been re-analyzed. The results illustrate the capabilities of the approach, agreement with literature values, and comparisons with nuclear reaction model calculations.
Date:
October 1, 1995
Creator:
Haight, R. C.; Bateman, F. B. & Chadwick, M. B.
Object Type:
Report
System:
The UNT Digital Library
Integrated data base report - 1994: US spent nuclear fuel and radioactive waste inventories, projections, and characteristics
The Integrated Data Base Program has compiled historic data on inventories and characteristics of both commercial and U.S. Department of Energy (DOE) spent nuclear fuel and commercial and U.S. government-owned radioactive wastes. Except for transuranic wastes, inventories of these materials are reported as of December 31, 1994. Transuranic waste inventories are reported as of December 31, 1993. All spent nuclear fuel and radioactive waste data reported are based on the most reliable information available from government sources, the open literature, technical reports, and direct contacts. The information forecasted is consistent with the latest DOE/Energy Information Administration (EIA) projections of U.S. commercial nuclear power growth and the expected DOE-related and private industrial and institutional activities. The radioactive materials considered, on a chapter-by-chapter basis, are spent nuclear fuel, high-level waste, transuranic waste, low-level waste, commercial uranium mill tailings, DOE Environmental Restoration Program contaminated environmental media, commercial reactor and fuel-cycle facility decommissioning wastes, and mixed (hazardous and radioactive) low-level waste. For most of these categories, current and projected inventories are given through the calendar-year 2030, and the radioactivity and thermal power are calculated based on reported or estimated isotopic compositions.
Date:
September 1, 1995
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Nineteenth annual actinide separations conference: Conference program and abstracts
This report contains the abstracts from the conference presentations. Sessions were divided into the following topics: Waste treatment; Spent fuel treatment; Issues and responses to Defense Nuclear Facility Safety Board 94-1; Pyrochemical technologies; Disposition technologies; and Aqueous separation technologies.
Date:
December 31, 1995
Creator:
Bronson, M.
Object Type:
Article
System:
The UNT Digital Library
Barrier/Cu contact resistivity
The specific contact resistivity of Cu with ({alpha} + {beta})-Ta, TiN, {alpha}-W, and amorphous-Ta{sub 36}Si{sub 14}N{sub 50} barrier films is measured using a novel four-point-probe approach. Geometrically, the test structures consist of colinear sets of W-plugs to act as current and voltage probes that contact the bottom of a planar Cu/barrier/Cu stack. Underlying Al interconnects link the plugs to the current source and voltmeter. The center-to-center distance of the probes ranges from 3 to 200 {micro}m. Using a relation developed by Vu et al., a contact resistivity of roughly 7 {times} 10{sup {minus}9} {Omega} cm{sup 2} is obtained for all tested barrier/Cu combinations. By reflective-mode small-angle X-ray scattering, the similarity in contact resistivity among the barrier films may be related to interfacial impurities absorbed from the deposition process.
Date:
October 17, 1995
Creator:
Reid, J.S.; Nicolet, M.A.; Angyal, M.S.; Lilienfeld, D.; Shacham-Diamand, Y. & Smith, P.M.
Object Type:
Report
System:
The UNT Digital Library
Global Alfven eigenmodes in WELDELSTEIN 7-AS
In the presence of fast particle populations marginally stable global modes in the shear Alfven branch can be destabilized by wave particle resonances. This is particularly of concern in future large devices, where losses of resonant particles ({alpha}-particles in a reactor) may then limit the available heating power and also may cause damage of the first wall. In tokamaks TAE modes inside toroidicity induced gaps of the shear Alfven continua have been found. In stellarators with very weak shear like W7-AS low-n TAE-gaps do not occur but gaps below the shear Alfven continua with mode numbers m and n, if the resonant values {tau} = n/m do not exist in the plasma volume (k{sub {parallel}} = (m{sm_bullet}{tau} - n )/R {ne} 0 ). Under these conditions GAE modes with frequencies {omega}{sub GAE} < (k{sub {parallel}}{sm_bullet}V{sub A}){sub min} are the favoured modes. The investigation of GAE modes could also be of relevance in the case of advanced tokamak equilibria with flat or inverted q-profiles in the central region.
Date:
September 1, 1995
Creator:
Weller, A.; Goerner, C. & Jaenicke, R.
Object Type:
Article
System:
The UNT Digital Library
Decomposable Mandrel Project. Progress report
We report on our progress in developing a new technology to produce both Nova and NIF scale capsules using a depolymerizable mandrel. In this technique we use poly({alpha}-methylstyrene) (PAMS) beads or shells as mandrels which are overcoated with plasma polymer. The poly({alpha}-methylstyrene) mandrel is then thermally depolymerized to gas phase monomer which diffuses away through the more thermally stable plasma polymer coating, leaving a hollow shell. Since our last report we have concentrated on characterization of the final shell. Starting with PAMS bead mandrels leads to distorted pyrolyzed shells because of thermally induced creep of the CH coating. We found that plasma polymer coatings on hollow shell mandrels shrink isotropically during pyrolysis and maintain sphericity. We are now concentrating our efforts on the use of microencapsulated shells to prepare targets with buried diagnostic layers or inner wall surface texture.
Date:
May 8, 1995
Creator:
Letts, S. A.; Fearon, E.; Allison, L.; Buckley, S.; Saculla, M. & Cook, R.
Object Type:
Report
System:
The UNT Digital Library
High resolution interface nanochemistry and structure. Progress report, December 1, 1994--November 30, 1995
Progress is described in the following research areas concerned with high resolution interface nanochemistry and structure: ceramic interfaces and grain boundaries; metal/alpha (6H)-SiC(0001) interfaces; oxygen distributions in monolithic silicon carbide; SiC/nitride and metal on nitride interfaces; and interface synthesis.
Date:
August 15, 1995
Creator:
Carpenter, R.W.
Object Type:
Report
System:
The UNT Digital Library
Development of radiation detectors based on hydrogenated amorphous silicon and its alloys
Hydrogenated amorphous silicon and related materials have been applied to radiation detectors, utilizing their good radiation resistance and the feasibility of making deposits over a large area at low cost. Effects of deposition parameters on various material properties of a-Si:H have been studied to produce a material satisfying the requirements for specific detection application. Thick(-{approximately}50 {mu}m), device quality a-Si:H p-i-n diodes for direct detection of minimum ionizing particles have been prepared with low internal stress by a combination of low temperature growth, He-dilution of silane, and post annealing. The structure of the new film contained voids and tiny crystalline inclusions and was different from the one observed in conventional a-Si:H. Deposition on patterned substrates was attempted as an alternative to controlling deposition parameters to minimize substrate bending and delamination of thick a-Si:H films. Growth on an inversed-pyramid pattern reduced the substrate bending by a factor of 3{approximately}4 for the same thickness film. Thin (0.1 {approximately} 0.2 {mu}m) films of a-Si:H and a-SiC:H have been applied to microstrip gas chambers to control gain instabilities due to charges on the substrate. Light sensitivity of the a-Si:H sheet resistance was minimized and the surface resistivity was successfully` controlled in the range of 10{sup …
Date:
April 1, 1995
Creator:
Hong, Wan-Shick
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
A cross section measurement of charm hyperons {Xi}{sub c}{sup +} and {Xi}{sub c}{sup 0} in 250 GeV p/K/{pi}-nucleon interactions
Fermilab Experiment 769 used a charge-selected, hadron beam of mean energy 250 GeV/c, composed of pions, kaons, and protons, impinging on beryllium, aluminum, copper and tungsten targets. Using a sample of approximately 4000 {Xi}{sub s}{sup {minus}} {yields} {Lambda}{sup 0}{pi}{sup {minus}} decays, measurements of the charm baryon forward cross sections times branching ratio {pi}{sup {+-}}N {yields} {Xi}{sub c}{sup +}X and {pi}{sup {+-}}N {yields} {Xi}{sub c}{sup 0}X are presented. Upper limits on {alpha} x BR are also determined for the states {Xi}{sub c}{sup +} {yields} {Xi}{sub s}{sup {minus}}{pi}{sup +}{pi}{sup +} and {Xi}{sub c}{sup 0} {yields} {Xi}{sub s}{sup {minus}}{pi}{sup +} produced in (p, {pi}{sup +}, {pi}{sup {minus}}, K{sup +}, K{sup {minus}})-nucleon interactions.
Date:
May 2, 1995
Creator:
Francisco, J. & Vergara, A.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Lawrence Livermore National Laboratory offsite hazardous waste shipment data validation report
The U.S. Department of Energy Headquarters requested this report to verify that Lawrence Livermore National Laboratory (LLNL) properly categorized hazardous waste shipped offsite from 1984 to 1991. LLNL categorized the waste shipments by the new guidelines provided on the definition of radioactive waste. For this validation, waste that has had no radioactivity added by DOE operations is nonradioactive. Waste to which DOE operations has added or concentrated any radioactivity is radioactive. This report documents findings from the review of available LLNL hazardous waste shipment information and summarizes the data validation strategy. The report discusses administrative and radiological control procedures in place at LLNL during the data validation period. It also describes sampling and analysis and surface survey procedures used in determining radionuclide concentrations for offsite release of hazardous waste shipments. The evaluation team reviewed individual items on offsite hazardous waste shipments and classified them, using the DOE-HQ waste category definitions. LLNL relied primarily on generator knowledge to classify wastes. Very little radioanalytical information exists on hazardous wastes shipped from LLNL. Slightly greater than one-half of those hazardous waste items for which the documentation included radioanalytical data showed concentrations of radioactivity higher than the LLNL release criteria used from 1989 to …
Date:
September 1, 1995
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
The Rambler (Fort Worth, Tex.), Ed. 1 Wednesday, November 15, 1995
Weekly student newspaper from Texas Wesleyan University in Fort Worth, Texas that includes campus and local news along with advertising.
Date:
November 15, 1995
Creator:
Kim Laster
Object Type:
Newspaper
System:
The Portal to Texas History
The Rattler (San Antonio, Tex.), Vol. 81, No. 12, Ed. 1 Wednesday, March 29, 1995
Biweekly student newspaper from St. Mary's University in San Antonio, Texas that includes campus news along with advertising.
Date:
March 29, 1995
Creator:
St. Mary's University (San Antonio, Tex.)
Object Type:
Newspaper
System:
The Portal to Texas History
Hilltop Views (Austin, Tex.), Vol. 9, No. 12, Ed. 1 Thursday, February 9, 1995
Semimonthly student newspaper from St. Edward's University in Austin, Texas that includes news and information of interest to the college community along with advertising.
Date:
February 9, 1995
Creator:
unknown
Object Type:
Newspaper
System:
The Portal to Texas History
The Optimist (Abilene, Tex.), Vol. 83, No. 34, Ed. 1, Wednesday, February 1, 1995
Weekly student newspaper from Abilene Christian University in Abilene, Texas that includes local, state and campus news along with advertising.
Date:
February 1, 1995
Creator:
unknown
Object Type:
Newspaper
System:
The Portal to Texas History
[Program: Twelfth Annual Black Music and the Civil Rights Movement Concert]
Program for the twelfth annual Black Music and the Civil Rights Movement hosted by the Junior Black Academy of Arts and Letters on January 15, 1995 at the Morton H. Meyerson Symphony Center.
Date:
January 1995
Creator:
Junior Black Academy of Arts and Letters
Object Type:
Pamphlet
System:
The UNT Digital Library
San Antonio Register (San Antonio, Tex.), Vol. 64, No. 1, Ed. 1 Thursday, June 1, 1995
Weekly newspaper from San Antonio, Texas that includes local, state, and national news along with advertising.
Date:
June 1, 1995
Creator:
unknown
Object Type:
Newspaper
System:
The Portal to Texas History
The Oklahoma Daily (Norman, Okla.), Vol. 79, No. 142, Ed. 1 Monday, April 10, 1995
Student newspaper of the University of Oklahoma in Norman, Oklahoma that includes national, local, and campus news along with advertising.
Date:
April 10, 1995
Creator:
Pape, Tiffany A.
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
The Optimist (Abilene, Tex.), Vol. 83, No. 52, Ed. 1, Wednesday, April 19, 1995
Weekly student newspaper from Abilene Christian University in Abilene, Texas that includes local, state and campus news along with advertising.
Date:
April 19, 1995
Creator:
unknown
Object Type:
Newspaper
System:
The Portal to Texas History