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19,325 Matching Results
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Atomic processes in plasmas under ultra-intense laser irradiation
Lasers delivering subpicosecond pulses with energies of a fraction of a Joule have made it possible to generate irradiance levels approaching 10{sup 20} W/cm{sup 2}. We presently operate two such systems, a KrF based excimer laser capable of producing a few 10{sup 17} W/cm{sup 2} at 248 nm with a repetition rate of 3--5 Hz and a XeCl based excimer laser capable of producing mid 10{sup 19} W/cm{sup 2} at 308 nm and 1 Hz. We will discuss some experimental results and the theory and modeling of the interaction of such intense laser pulses with aluminum. Because of a small ASE prepulse the high intensity interaction is not at the solid surface but rather at the n{sub e} = 2 {times} 10{sup 22} cm{sup {minus}3} critical density of the blowoff plasma generated by the ASE. The transient behavior of the plasma following the energy deposition by the intense subpicosecond pulse can be viewed as the energy-impulse response of the plasma. Experimental results and modeling of the x-ray emission from this plasma will be presented. 15 refs., 8 figs.
Date:
November 1, 1989
Creator:
Schappert, G. T.; Casperson, D. E.; Cobble, J. A.; Comly, J. C.; Jones, L. A.; Kyrala, G. A. et al.
Object Type:
Article
System:
The UNT Digital Library
Cadmium sulfide/copper sulfide heterojunction cell research. Quarterly technical progress report, June 1-September 30, 1979
Off-stoiciometry CdS coatings with resistivities of about 10..cap omega..-cm have been deposited by a cyclic reactive sputtering process where the H/sub 2/S injection is periodically switched on and off. Cells with CdS layer fabricated in this way have yielded efficiencies of about 0.6% with short circuit currents of about 3.5 mA/cm/sup 2/, open circuit voltages of about 0.43V, and fill factors of about 0.40. CdS resistivity control by In doping has been achieved both by diffusion from a pre-deposited In layer and by using an In-doped Cd sputtering target. Resistivities of about 30..cap omega..-cm are achieved in CdS coatings about 5 um thick deposited at 250/sup 0/C over 50 nm thick In layers. A Cd cathode doped with 1 atomic percent In has yielded CdS coatings with resistivities of about 0.1 ..cap omega..-cm at substrate temperatures in the 100 to 300/sup 0/C range. Cells fabricated from the 0.1 ..cap omega..-cm CdS with a 0.5 um undoped layer adjacent to the junction have yielded encouraging diode characteristics with a strong photovoltaic effect and will be used to an optimization study. Cu/sub x/S coatings deposited onto CdS under various conditions have been found to have the same properties as those deposited onto …
Date:
November 30, 1979
Creator:
Thornton, J.A.
Object Type:
Report
System:
The UNT Digital Library
Boundary plasma transport studies on TFTR
In this report we summarize the experimental and theoretical investigations supported under the DOE Transport Initiative Contract on the subject of Boundary Plasma Transport Studies on TFTR. This work can be logically separated into two areas of investigations and therefore the report included here is divided into two parts. First, in Section I, detailed boundary plasma data obtained from TFTR in an Ohmic density scan has been compared with results from the LIM Impurity Production and Transport Code. Second, in Section II, experimental results taken with the newly-purchased (specifically for this Initiative) intensified CCD camera are presented, which, after comparison with simple modeling, reveals a new and important effect that has implications for limiter and divertor plate design.
Date:
November 1, 1991
Creator:
Pitcher, C.S. & Stangeby, P.C.
Object Type:
Report
System:
The UNT Digital Library
Von Neumann stability of the WONDY wavecode for thermodynamic equations of state
Previous analyses of the von Neumann stability of the WONDY wavecode (based on the von Neumann--Richtmyer artificial viscosity method) assumed a mechanical stress--strain relation; i.e., they assumed the stress, p, to depend only on the mass density, rho. In a thermodynamic equation of state p is allowed to depend also on the specific entropy, S (or on the specific internal energy, epsilon). If p does not depend on epsilon (or S), then the Grueneisen parameter, GAMMA, is zero. Herein a von Neumann stability analysis of WONDY is done for the more general case when GAMMA is not equal to 0. The result of this analysis is the requirement that the timestep be less than the product of the material increment and a certain function f of the acoustic impedance (a); artificial viscosity coefficient, ..lambda..; and GAMMA. In a region of compression, if ..lambda.. GAMMA is greater than 0, then f(a,..lambda..,GAMMA) is smaller than f(a,..lambda..,0). Therefore, the more general stability analysis yields the result that the timestep restriction now in WONDY may be insufficient for stability in certain regions of certain calculations.
Date:
November 1, 1977
Creator:
Hicks, D.L.
Object Type:
Report
System:
The UNT Digital Library
Energy and technology review
Separate abstracts were prepared for three papers in this review. (LEW)
Date:
November 1, 1983
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Annual review of cultural resource investigations by the Savannah River Archaeological Research Program, fiscal year 1990
The Savannah River Archaeological Research Program (SRARP) of the South Carolina Institute of Archaeology and Anthropology, University of South Carolina, is funded through a direct contract with the United States Department of Energy to provide services required under federal law for the protection and management of archaeological resources on the Savannah River Site (SRS). Because the significance of most archaeological resources is dependent upon research potential, the SRARP is guided by research objectives. An on-going research program provides the problems, methods and means of assessing site significance within the compliance process specified by law. In addition, the SRARP maintains an active program of public education to disseminate knowledge about prehistory and history, and to enhance public awareness about historic preservation. The following report summarizes the management, research and public education activities of the SRARP during Fiscal Year 1990.
Date:
November 1, 1990
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
TFTR initial operations
The Tokamak Fusion Test Reactor (TFTR) has operated since December 1982 with ohmically heated plasmas. Routine operation with feedback control of plasma current, position, and density has been obtained for plasmas with I/sub p/ approx. = 800 kA, a = 68 cm, R = 250 cm, and B/sub t/ = 27 kG. A maximum plasma current of 1 MA was achieved with q approx. = 2.5. Energy confinement times of approx. 150 msec were measured for hydrogen and deuterium plasmas with anti n/sub e/ approx. = 2 x 10/sup 13/ cm/sup -3/, T/sub e/ (0) approx. = 1.5 keV, T/sub i/ (0) approx. = 1.5 keV, and Z/sub eff/ approx. = 3. The preliminary results suggest a size-cubed scaling from PLT and are consistent with Alcator C scaling where tau approx. nR/sup 2/a. Initial measurements of plasma disruption characteristics indicate current decay rates of approx. 800 kA in 8 ms which is within the TFTR design requirement of 3 MA in 3 ms.
Date:
November 1, 1983
Creator:
Young, K.M.; Bell, M.; Blanchard, W.R.; Bretz, N.; Cecchi, J.; Coonrod, J. et al.
Object Type:
Report
System:
The UNT Digital Library
Starting an ODE solver. [Selection of initial step size]
A scheme is developed for the automatic selection of the initial step size for an ODE solver. Additional devices are developed to increase the reliability and efficiency of the selection for stiff problems. The question of starting the integration with zero initial values when a pure relative error control is desired is answered for some kinds of codes. Some numerical results are given to illustrate the devices and support some of the conclusions.
Date:
November 1, 1977
Creator:
Shampine, L.F.
Object Type:
Report
System:
The UNT Digital Library
Composition of eta carbide in Hastelloy N after aging 10,000 hr at 815/sup 0/C
The composition of the eta carbide in Hastelloy N containing 0.7 wt percent Si in the alloy approaches M/sub 12/C, rather than M/sub 6/C as indicated in the alloy literature. The silicon content of the eta phase in this case was about 25 at. percent, much higher than has been observed in less highly alloyed material. The data do not permit a definition of the limiting compositions of the phases.
Date:
November 1, 1977
Creator:
Leitnaker, J. M.; Potter, G. A.; Bradley, D. J.; Franklin, J. C. & Laing, W. R.
Object Type:
Report
System:
The UNT Digital Library
Improved methods for computing masses from numerical simulations
An important advance in the computation of hadron and glueball masses has been the introduction of non-local operators. This talk summarizes the critical signal-to-noise ratio of glueball correlation functions in the continuum limit, and discusses the case of (q{bar q} and qqq) hadrons in the chiral limit. A new strategy for extracting the masses of excited states is outlined and tested. The lessons learned here suggest that gauge-fixed momentum-space operators might be a suitable choice of interpolating operators. 15 refs., 2 tabs.
Date:
November 22, 1989
Creator:
Kronfeld, A.S.
Object Type:
Article
System:
The UNT Digital Library
ORNL ALICE: a statistical model computer code including fission competition. [In FORTRAN]
A listing of the computer code ORNL ALICE is given. This code is a modified version of computer codes ALICE and OVERLAID ALICE. It allows for higher excitation energies and for a greater number of evaporated particles than the earlier versions. The angular momentum removal option was made more general and more internally consistent. Certain roundoff errors are avoided by keeping a strict accounting of partial probabilities. Several output options were added.
Date:
November 1, 1977
Creator:
Plasil, F.
Object Type:
Report
System:
The UNT Digital Library
Cladding creepdown under compression. [BWR; PWR]
Light-water power reactors use Zircaloy tubing as cladding to contain the UO/sub 2/ fuel pellets. In-service operating conditions impose an external hydrostatic force on the cladding, causing it to creep down into eventual contact with the fuel. Knowledge of the rate of such creepdown is of great importance to modelers of fuel element performance. An experimental system was devised for studying creepdown that meets several severe requirements by providing (1) correct stress state, (2) multiple positions for measuring radial displacement of the cladding surface, (3) high-precision data, and (4) an experimental configuration compact enough to fit in-reactor. A microcomputer-controlled, eddy-current monitoring system was developed for this study and has proven highly successful in measuring cladding deformation with time at temperatures of 371/sup 0/C (700/sup 0/F) and higher, and at pressures as high as 21 MPa (3000 psig).
Date:
November 9, 1977
Creator:
Hobson, D.O.
Object Type:
Article
System:
The UNT Digital Library
Study of electron density and pressure profile behavior in a tokamak plasma
Simultaneous determinations of local electron density and magnetic flux surface in a tokamak plasma have been made feasible with multichannel interferometry using a new asymmetric Abel inversion method. This new method takes advantage of interferometry by measuring the electron density profile as a function of time. The derived electron density parameters, such as the total number of electrons, peak density, and the profile shape factor, have been extremely useful in tokamak plasma experiments. In addition, by suing measured time-dependent electron temperatures from electron cyclotron emission, similar parameters for the electron pressure can be studied. 16 refs., 3 figs.
Date:
November 1, 1989
Creator:
Park, H.K.; Goldston, R.J. & Taylor, G.
Object Type:
Report
System:
The UNT Digital Library
Task plan for TARA-II compaction and grouting demonstration
This task directly supports the corrective measures evaluation for the closure of Solid Waste Storage Area (SWSA) 6 but also supports technology development for the closure of other Oak Ridge National Laboratory (ORNL) SWSAs and waste management units. Previous demonstrations have established the effectiveness of dynamic compaction and in situ grouting in stabilizing burial trenches against subsidence, which would otherwise compromise the support of infiltration barrier structures designed to protect buried waste from leaching. In situ grouting with polyacrylamide has also been demonstrated to improve the hydrologic isolation of buried waste. Both of these stabilization techniques have been demonstrated on burial trenches that are situated well above the water table and, hence, are in a chronic unsaturated moisture regime. Further demonstrations of these shallow-land burial trench stabilization techniques are necessary to establish their effectiveness and safety when applied to burial trenches that are chronically inundated with groundwater.
Date:
November 1, 1991
Creator:
Spalding, B. P.
Object Type:
Report
System:
The UNT Digital Library
Compressible gas properties of UF/sub 6/ for isentropic, normal shock, and oblique shock conditions
Isentropic, normal shock, and oblique shock tables are given for the real gas UF/sub 6/ for Mach numbers up to 22. An evaluation of the real gas effects is given. A computer program listing is included.
Date:
November 1, 1984
Creator:
Harloff, G.J.
Object Type:
Report
System:
The UNT Digital Library
Storage and flow of solids. Bulletin No. 123; Vol. 53, No. 26, November 1964
Information is presented on: the concepts of flowability of bulk solids and of channels and the flow-no flow postulate; equipment and procedures for testing the flow of bulk solids; and bulk flow equipment design. This information should be sufficient to enable the engineer to design storage plants and flow channels for unobstructed bulk flow. Only an outline of the theory of flow is included. (LCL)
Date:
November 1, 1976
Creator:
Jenike, A. W.
Object Type:
Report
System:
The UNT Digital Library
Investigating the impact of drilling mud and its major components on bivalve species of Georges bank. Progress report No. 2, February 28, 1979-November 1, 1979
Results described in progress report No. 1 indicate that 0.3-1.0 grams of drilling mud/liter of seawater can stress bivalve molluscs and that metallic components of drilling muds are assimilated by these organisms. The results posed questions about the short- and long-term effects of stress on energy stores, reproduction, and metal assimilation; accordingly, this year's research program has focused on these three areas and on a continued chemical characterization of the drilling muds used.
Date:
November 1, 1979
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Long pulse microsphere experiments at 3 TW
Previous 1.06 ..mu..m laser implosion experiments have explored the parameter space associated with microsphere targets of typically less than 100 psec. Exploding pusher experiments have now been performed using long pulses (100 to 200 psec FWHM), and large diameter (100 to 150 ..mu..m) targets on the 3 TW Argus laser facility. Absorption, transport, implosion and neutron and ..cap alpha.. yield characteristics are discussed and compared with earlier short pulse results. The observed neutron yields are discussed in light of the temporal mismatch between the absorption and implosion time scales imposed by the large diameter, long pulse conditions.
Date:
November 1, 1977
Creator:
Boyle, M. J.; Attwood, D. T. & Brooks, K. M.
Object Type:
Article
System:
The UNT Digital Library
Coal liquefaction process streams characterization and evaluation
This study clearly demonstrated the usefulness of liquid- and solid-state {sup 13}C- and {sup 1}H-NMR for the examination of process-derived materials from direct coal liquefaction. The techniques can provide data not directly obtainable by other methods to examine the saturation of aromatic rings and to determine the modes of hydrogen utilization during coal liquefaction. In addition, these methods can be used to infer the extent of condensation and retrograde reactions occurring in the direct coal liquefaction process. Five NMR techniques were employed. Solid-state {sup 13}C-NMR measurements were made using the Cross Polarization Magic Angle Spinning (CP/MAS) and Single Pulse (SP) techniques. Solid-state {sup 1}H-NMR measurements were made using the technique of Combined Rotation and Multiple-Pulse spectroscopy (CRAMPS). Conventional liquid-state {sup 12}C- and {sup 1}H-NMR techniques were employed as appropriate. Interpretation of the NMR data, once obtained, is relatively straightforward. Combined with other information, such as elemental analyses and process conversion data, the NMR data prove to be a powerful tool for the examination of direct coal liquefaction process-derived material. Further development and more wide-spread application of this analytical method as a process development tool is justified on the basis of these results.
Date:
November 1, 1991
Creator:
Miknis, F.P. (Western Research Inst., Laramie, WY (United States))
Object Type:
Report
System:
The UNT Digital Library
Initial characterization of a BGO-photodiode detector for high resolution positron emission tomography
Spatial resolution in positron emission tomography is currently limited by the resolution of the detectors. This work presents the initial characterization of a detector design using small bismuth germanate (BGO) crystals individually coupled to silicon photodiodes (SPDs) for crystal identification, and coupled in groups to phototubes (PMTs) for coincidence timing. A 3 mm x 3 mm x 3 mm BGO crystal coupled only to an SPD can achieve a 511 keV photopeak resolution of 8.7% FWHM at -150/sup 0/C, using a pulse peaking time of 10 ..mu..s. When two 3 mm x 3 mm x 15 mm BGO crystals are coupled individually to SPDs and also coupled to a common 14 mm diam PMT, the SPDs detect the 511 keV photopeak with a resolution of 30% FWHM at -76/sup 0/C. In coincidence with an opposing 3 mm wide BGO crystal, the SPDs are able to identify the crystal of interaction with good signal-to-noise ratio, and the detector pair resolution is 2 mm FWHM. 32 references, 7 figures, 3 tables.
Date:
November 1, 1983
Creator:
Derenzo, S.E.
Object Type:
Article
System:
The UNT Digital Library
Study of the defect structure of ''pure'' and doped nonstoichiometric CeO/sub 2/. Final report, January 1, 1965--May 31, 1977
The defect structure and transport properties of defects in nonstoichiometric oxides was studied based on their electrical and thermodynamic behavior. Similar studies were also made on doped-nonstoichiometric oxides to determine the effect of the ionic radii, valence and concentration of the dopant cation on the nonstoichiometric defect structure and the transport properties of these defects. The thermodynamic and electrical property study on ''pure'' and doped-nonstoichiometric CeO/sub 2//sub -x/ is reviewed. The combined study of the electrical conductivity, ionic transference, and thermodynamic measurements initiated on CaO-doped CeO/sub 2/ as a function of temperature, oxygen pressure and CaO content is discussed. The results of similar measurements on CeO/sub 2/ doped with other oxides (e.g., ThO/sub 2/, Ta/sub 2/O/sub 5/, etc.) which have cations with different valences and ionic radii are also discussed. The primary objective of these studies was to determine the effect of ionic radii, valence and concentration of the dopant cation on (1) the nonstoichiometric behavior, (2) the thermodynamic quantities ..delta..antiH/sub O/sub 2// and ..delta..antiS/sub O/sub 2//, (3) the nonstoichiometric defect structure, (4) the electronic and ionic conductivities, and (5) the mobility of electrons and oxygen vacancies in doped CeO/sub 2//sub -x/.
Date:
November 1, 1977
Creator:
Blumenthal, R.N.
Object Type:
Report
System:
The UNT Digital Library
Charge states of high Z atoms in a strong laser field
We present a numerical solution of the Thomas-Fermi atom in the presence of a static electric field as a model of the adiabatic response of a heavy atom in the presence of a strong laser field. In this semiclassical approach, we calculate the resulting charge state of the atom and its induced dipole moment after the field is turned on. Due to the scaling properties of the Thomas-Fermi approach, the resulting total atomic charge and dipole moment can be expressed as a universal function of the field. We compare our results with recent ionization experiments performed on noble gases using laser fields. 7 refs., 5 figs.
Date:
November 1, 1989
Creator:
Susskind, S. M.; Valeo, E. J.; Oberman, C. R.; Bernstein, I. B. (Princeton Univ., NJ (USA). Plasma Physics Lab. & Yale Univ., New Haven, CT (USA))
Object Type:
Report
System:
The UNT Digital Library
LOFT suppression tank spray system piping: heat exchanger BS-H-31 piping modifications
A stress analysis of the piping modification, resulting from relocation of heat exchanger BS-H-31 of the LOFT Blowdown Suppressing Tank Spray System, was performed. The piping, fittings, and supports were found to comply with the criteria of Section III of the ASME Boiler and Pressure Vessel Code, 1974.
Date:
November 7, 1977
Creator:
Blandford, R.K.
Object Type:
Report
System:
The UNT Digital Library
Thin films of InP for photovoltaic energy conversion. First quarterly technical progress report, July 5, 1979-September 28, 1979
A research study is in progress to develop a low-cost high-efficiency thin-film InP heterojunction solar cell, using the metalorganic chemical vapor deposition (MO-CVD) technique for InP film growth on suitable low-cost substrates. Heterostructure devices of CdS/InP and indium tin oxides (ITO)/InP are to be prepared by Stanford University under subcontract, using the InP films grown by MO-CVD. The first quarter's work is summarized. An existing reactor system was modified and upgraded, with provision for growth of GaAs intermediate layers and p-type doping capability using a premixed metalorganic Zn compound source, as well as a dilution system common to the dopants and the Group III and Group V reactants. The all-fused-quartz deposition chamber was redesigned to permit use of larger susceptors and to facilitate assembly, disassembly, and cleaning. Initial attempts to prepare p-type epitaxial InP films on single-crystal InP substrates met with only limited success until a new source of diethylzinc (DEZn) was obtained and installed on the system, after which active Zn concentrations (i.e., measured hole concentrations) in the 10/sup 17/ cm/sup -3/ range were produced in epitaxial films on (100), 111A), and (111B) InP substrates in the deposition temperature range 715 to 730/sup 0/C. The films have been characterized …
Date:
November 1, 1979
Creator:
Manasevit, H. M.; Ruth, R. P.; Moudy, L. A.; Yang, J. J. J. & Johnson, R. E.
Object Type:
Report
System:
The UNT Digital Library