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15,492 Matching Results
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Heavy residue properties in intermediate energy nuclear collisions with gold
We have measured the target fragment production cross sections and angular distributions for the interaction of 32, 44 and 93 MeV/nucleon argon, 35 and 43 MeV/nucleon krypton with gold. The fragment isobaric yield distributions, moving frame angular distributions and velocities have been deduced from these data. This fission cross section decreases with increasing projectile energy and the heavy residue cross section increases. The ratio v{sub {parallel}}/v{sub cn} increases approximately linearly with mass removed from the target. 21 refs., 8 figs.
Date:
October 1, 1990
Creator:
Aleklett, K.; Sihver, L. (Uppsala Univ., Nykoeping (Sweden). Studsvik Neutron Research Lab.); Loveland, W. (Oregon State Univ., Corvallis, OR (USA)); Liljenzin, J.O. (Chalmers Univ. of Tech., Goeteborg (Sweden)) & Seaborg, G.T. (Lawrence Berkeley Lab., CA (USA). Nuclear Science Div.)
Object Type:
Article
System:
The UNT Digital Library
The BNL 200 MeV H sup minus linac: Performance and upgrades
For the past two years the linac has had reliable operation from the new RFQ preinjector. The performance of this preinjector is described. There is a fast beam chopper in the transport line between the ion source and RFQ. By injecting narrow pulses into the AGS we can obtain an accurate linac energy measurement, or the detailed shape of the linac beam energy distribution, on a single pulse. Some general comment on the linac operation are also presented.
Date:
January 1, 1990
Creator:
Alessi, J. G.; Brennan, J. M.; Kponou, A.; LoDestro, V. & Montemurro, P. A.
Object Type:
Article
System:
The UNT Digital Library
Present status of BNL polarized sources
A review is given of the BNL polarized source development occurring since the 1986 Workshop in Montana, Switzerland. The polarized source in operation for the AGS produces {approx}40 {mu}A of {rvec H}{sup {minus}} with 75--80% polarization. Development of a cold atomic beam for a higher intensity source has concentrated on studies of spin selection and focusing with both a superconducting solenoid and sextupoles. Ionization of H{sup O} by D{sup {minus}} charge exchange using the ring magnetron ionizer seems to be hindered by gas scattering, and work is in progress to improve this.
Date:
January 1, 1990
Creator:
Alessi, J. G.; DeVito, B.; Hershcovitch, A.; Kponou, A. & Meitzler, C. R.
Object Type:
Article
System:
The UNT Digital Library
Isotope and Cs vapor effects in an H sup minus volume source with a toroidal chamber
A volume source of H{sup {minus}} ions, with a full rotational symmetry, has been designed and studied. We have achieved a pulsed H{sup {minus}} current of 50 mA, at a current density of 25 mA/cm{sup 2}. Using a reduced aperture of 1 cm{sup 2}, the emittance of a 10--16 keV beam was measured for different source parameters, and for a beam current of 20 mA it was found to be less than 0.5 {pi} mm mrad (normalized, 4 rms). When operating with deuterium, the D{sup {minus}} output was found to be 50--60% of the H{sup {minus}} current obtained under the same discharge conditions. Adding cesium to the discharge increased the H{sup {minus}} output by a factor of two, while reducing the electron current. After the addition of cesium, greater than 30 mA of H{sup {minus}} could be extracted with I{sub e}/I{sub H}{sup {minus}}.
Date:
January 1, 1990
Creator:
Alessi, J.G. & Prelec, K.
Object Type:
Article
System:
The UNT Digital Library
Status of the Brookhaven National Laboratory (BNL) toroidal volume H sup minus source
A volume H{sup {minus}} source having a toroidal discharge chamber and conical filter field has been developed. Parametric studies of this source have been in progress for two years. Extraction apertures from 0.5 cm{sup 2} to 1.87 cm{sup 2} have been tried, and an H {sup {minus}} current of up to 48 mA has been extracted. The electron-to-H {sup {minus}} current ratio in the extracted beam can be as low as 10 for {approx} 25 mA beam was 0.44{pi}mm mrad. When operating with deuterium, the D{sup {minus}} output wads 50--60% of the H{sup {minus}} current under the same discharge conditions. The addition of cesium to the discharge increased the H{sup {minus}} output and decreased the electron current so that at 30 mA of H{sup {minus}}, one obtained an electron-to-H{sup {minus}} ratio of 1. Using a two gap extractor, with a dipole field in the intermediate electrode, approximately 80% of the extracted electrons could be removed from the primary beam.
Date:
January 1, 1990
Creator:
Alessi, J.G. & Prelec, K.
Object Type:
Article
System:
The UNT Digital Library
Design and cost estimate of an 800 MVA superconducting power transmission
Numerous studies involving cost estimates have been performed for superconducting power transmission systems. As these systems were usually aimed at providing transmission from large clusters of generation the base power rating of the corridor was very high; in the case of the most comprehensive study it was 10,000 MVA. The purpose of this study is to examine a system which is very closely based on the prototype 1000 MVA system which was operated at Brookhaven National Laboratory over a four year period. The purpose of the study is to provide cost estimates for the superconducting system and to compare these estimates with a design based on the use of advanced but conventional cable designs. The work is supported by funding from the Office of Energy Research's Industry/Laboratory Technology Exchange Program. This program is designed to commercialize energy technologies. The technical design of the superconducting system was prepared by the BNL staff, the design of the 800 MVA conventional cable system was done by engineers from Underground Systems Incorporated. Both institutions worked on the cost estimate of the superconducting system. The description and cost estimate of the conventional cable system is given in the Appendix. 5 refs.
Date:
October 18, 1990
Creator:
Alex, P.; Ernst, A. (Underground Systems, Inc., Armonk, NY (USA)); Forsyth, E.; Gibbs, R.; Thomas, R. & Muller, T. (Brookhaven National Lab., Upton, NY (USA))
Object Type:
Report
System:
The UNT Digital Library
Reactor production of sup 252 Cf and transcurium isotopes
Berkelium, californium, einsteinium, and fermium are currently produced in the High Flux Isotope Reactor (HFIR) and recovered in the Radiochemical Engineering Development Center (REDC) at the Oak Ridge National Laboratory (ORNL). All the isotopes are used for research. In addition, {sup 252}Cf, {sup 253}Es, and {sup 255}Fm have been considered or are used for industrial or medical applications. ORNL is the sole producer of these transcurium isotopes in the western world. A wide range of actinide samples were irradiated in special test assemblies at the Fast Flux Test Facility (FFTF) at Hanford, Washington. The purpose of the experiments was to evaluate the usefulness of the two-group flux model for transmutations in the special assemblies with an eventual goal of determining the feasibility of producing macro amounts of transcurium isotopes in the FFTF. Preliminary results from the production of {sup 254g}Es from {sup 252}Cf will be discussed. 14 refs., 5 tabs.
Date:
January 1, 1990
Creator:
Alexander, C.W.; Halperin, J.; Walker, R.L. & Bigelow, J.E.
Object Type:
Article
System:
The UNT Digital Library
Ion-induced grain growth in multilayer and coevaporated metal alloy thin films
Irradiation experiments were conducted on multilayer (ML) and coevaporated (CO) thin films in order to examine the role that the heat of mixing ({Delta}H{sub mix}) has in ion-induced grain growth. Room temperature irradiations using 1.7 MeV Xe were performed in the High Voltage Electron Microscope at Argonne National Laboratory. The alloys studied (Pt-Ti, Pt-V, Pt-Ni, Au-Co and Ni-Al) spanned a large range of {Delta}H{sub mix} values. Comparison of grain growth rates between ML and CO films of a given alloy confirmed a heat of mixing effect. Differences in grain growth rates between ML and CO films scaled according to the sign and magnitude of {Delta}H{sub mix} of the system (with exception of the Pt-V system). Substantial variations in growth rates among CO alloy films experiencing similar irradiation damage demonstrated that a purely collisional approach is inadequate for describing ion-induced grain growth and consideration must also be given to material-specific properties. Results from CO alloy films were consistent with a thermal spike model of ion-induced grain growth. The grain boundary mobility was observed to be proportional to the thermal spike-related parameter, (F{sub D}{sup 2})/({Delta}H{sub coh}{sup 3}), where F{sub D} is the deposited damage energy and {Delta}H{sub coh} is the cohesive energy.
Date:
September 1, 1990
Creator:
Alexander, D. E.; Was, G. S. & Rehn, L. E.
Object Type:
Article
System:
The UNT Digital Library
Three dimensional visualization breakthrough in analysis and communication of technical information for nuclear waste management
Computer graphics systems that provide interactive display and manipulation of three-dimensional data are powerful tools for the analysis and communication of technical information required for characterization and design of a geologic repository for nuclear waste. Greater understanding of site performance and repository design information is possible when performance-assessment modeling results can be visually analyzed in relation to site geologic and hydrologic information and engineering data for surface and subsurface facilities. In turn, this enhanced visualization capability provides better communication between technical staff and program management with respect to analysis of available information and prioritization of program planning. A commercially-available computer system was used to demonstrate some of the current technology for three-dimensional visualization within the architecture of systems for nuclear waste management. This computer system was used to interactively visualize and analyze the information for two examples: (1) site-characterization and engineering data for a potential geologic repository at Yucca Mountain, Nevada; and (2) three-dimensional simulations of a hypothetical release and transport of contaminants from a source of radionuclides to the vadose zone. Users may assess the three-dimensional distribution of data and modeling results by interactive zooming, rotating, slicing, and peeling operations. For those parts of the database where information is …
Date:
November 1, 1990
Creator:
Alexander, D. H.; Cerny, B. A.; Hill, E. R.; Krupka, K. M.; Smoot, J. L.; Smith, D. R. et al.
Object Type:
Article
System:
The UNT Digital Library
The effect of aging at 343 degrees C on type 308 stainless steel weldments
The effect of long-term aging at intermediate temperatures on the mechanical properties of stainless steel welds has been studied. Three type 308 multipass shielded metal-arc welds with ferrite levels of 4, 8, and 12% were aged up to 343{degrees}C. Tensile tests showed little effect of aging on either the yield or ultimate tensile strengths, but the impact toughness was significantly degraded. The extent of the degradation increased with increasing ferrite content and increasing aging time. Examination of the microstructure with transmission electron microcscopy and atom probe field-ion microscopy revealed that the ferrite phase had undergone spinodal decomposition as a result of aging. In addition, G-phase particles were observed at dislocations, and finer G-phase particles were homogeneously distributed throughout the ferrite phase. The changes in the mechanical properties and the fractography are discussed in light of the observed changes in the microstructure. 19 refs., 7 figs., 2 tabs.
Date:
January 1, 1990
Creator:
Alexander, D. J.; Alexander, K. B.; Miller, M. K. & Nanstad, R. K.
Object Type:
Article
System:
The UNT Digital Library
Thermal spike model of ion-induced grain growth
A thermal spike model has been developed to describe the phenomenon of ion irradiation-induced grain growth in metal alloy thin films. In single phase films where the driving force for grain growth is the reduction of grain boundary curvature, the model shows that ion-induced grain boundary mobility, M{sub ion}, is proportional to the quantity F{sub D}{sup 2}/{Delta}H{sub coh}{sup 3}, where F{sub D} is the deposited ion damage energy and {Delta}H{sub coh} is the cohesive energy of the element or alloy. Experimental strain growth results from ion irradiated coevaporated binary alloy films compare favorably with model predictions. 11 refs., 1 fig., 1 tab.
Date:
November 1, 1990
Creator:
Alexander, D.E. (Argonne National Lab., IL (USA)) & Was, G.S. (Michigan Univ., Ann Arbor, MI (USA). Dept. of Nuclear Engineering)
Object Type:
Article
System:
The UNT Digital Library
Materials for cold neutron sources: Cryogenic and irradiation effects
Materials for the construction of cold neutron sources must satisfy a range of demands. The cryogenic temperature and irradiation create a severe environment. Candidate materials are identified and existing cold sources are briefly surveyed to determine which materials may be used. Aluminum- and magnesium-based alloys are the preferred materials. Existing data for the effects of cryogenic temperature and near-ambient irradiation on the mechanical properties of these alloys are briefly reviewed, and the very limited information on the effects of cryogenic irradiation are outlined. Generating mechanical property data under cold source operating conditions is a daunting prospect. It is clear that the cold source material will be degraded by neutron irradiation, and so the cold source must be designed as a brittle vessel. The continued effective operation of many different cold sources at a number of reactors makes it clear that this can be accomplished. 46 refs., 8 figs., 2 tab.
Date:
January 1, 1990
Creator:
Alexander, D.J.
Object Type:
Article
System:
The UNT Digital Library
Effect of whisker surface treatments and processing conditions on the SiC/Al sub 2 O sub 3 interface
Various electron microscopy techniques have been used to evaluate the microstructural and interfacial characteristics of silicon carbide whisker-reinforced alumina composites. The effects of subjecting whiskers to oxidizing and reducing treatments prior to composite fabrication were examined. Whisker/matrix interfaces in which carbon coatings were applied to whiskers prior to specimen fabrication were also examined. Physical and thermodynamic arguments can be used to explain why it is difficult to greatly modify the physical nature of the whisker/matrix interface. 7 refs., 7 figs.
Date:
January 1, 1990
Creator:
Alexander, K.B.; Angelini, P. & Becher, P.F.
Object Type:
Article
System:
The UNT Digital Library
A 1. 5--4 Kelvin detachable cold-sample transfer system: Application to inertially confined fusion with spin-polarized hydrogens fuels
A compact cold-transfer apparatus for engaging and retrieving samples at liquid helium temperatures (1.5--4K), maintaining the samples at such temperatures for periods of hours, and subsequently inserting them in diverse apparatuses followed by disengagement, is described. The properties of several thermal radiation-insulating shrouds, necessary for very low sample temperatures, are presented. The immediate intended application is transportable target-shells containing highly spin-polarized deuterons in solid HD or D{sub 2} for inertially confined fusion (ICF) experiments. The system is also valuable for unpolarized high-density fusion fuels, as well as for other applications which are discussed. 9 refs., 6 figs.
Date:
January 1, 1990
Creator:
Alexander, N.; Barden, J.; Fan, Q. & Honig, A.
Object Type:
Report
System:
The UNT Digital Library
Astronomy at Ultra-High Energies: Results From the CYGNUS Experiment
The CYGNUS experiment is composed of an air-shower array and muon detectors, located in Los Alamos, NM, and operating at energies above 50 TeV. Recent results include a search for emission from Cygnus X-3 during the radio outbursts of June and July 1989, preliminary results from a search for diffuse emission from the galactic plane, and preliminary results from a search for emission from possible northern hemisphere point sources, both known and unknown. 3 refs., 4 figs.
Date:
January 1, 1990
Creator:
Alexandreas, D. E.; Allen, R. C.; Biller, S. D.; Dion, G. M.; Lu, X-Q.; Vishwanath, P. R. et al.
Object Type:
Article
System:
The UNT Digital Library
Search for UHE emission from 4U0115+63
We report here the preliminary results of our observations of the sporadic x-ray binary system 4U0115 + 63. The CYGNUS air shower array has been collecting data since April 1986. No significant excess is seen from the direction of this source, nor any correlation with its 24-day orbital period. A 90% confidence-level upper limit on the flux from 4U0115 + 63 is 2.8 {times} 10{sup {minus}13} cm{sup {minus}2} s{sup {minus}1} above 50 TeV. This flux limit is considerably lower than those reported by other UHE experiments. Search for periodicity at the neutron star frequency is in progress. 12 refs., 3 figs., 1 tab.
Date:
January 1, 1990
Creator:
Alexandreas, D. E.; Allen, R. C.; Biller, S. D.; Dion, G. M.; Lu, X.-Q.; Vishwanath, P. R. et al.
Object Type:
Article
System:
The UNT Digital Library
The showerfront time-structure of anomalous muon'' events associated with Hercules X-1
The 11 in-phase'' source events from the 1986 muon-rich bursts associated with Hercules X-1 (previously reported by this group) have been studied for indications of further anomalous behavior. The most significant effect observed resulted from an analysis of the showerfront time-structures of these events. This analysis was then applied a priori to the rest of the source day, where an additional {approximately}9 signal events are expected to remain. The same effect was observed at a chance probability level of {approximately}0.1%. 1 ref., 7 figs.
Date:
January 1, 1990
Creator:
Alexandreas, D. E.; Allen, R. C.; Biller, S. D.; Dion, G. M.; Lu, X.-Q.; Vishwanath, P. R. et al.
Object Type:
Article
System:
The UNT Digital Library
Synchrotron radiation power calculations and bending radius choice for LER (Low Energy Ring)
This note will discuss ways of choosing a bending radius and synchrotron radiation absorber design. We would like to decrease the synchrotron radiation power density on the absorber's surfaces, yet we would like to reduce the LER's bending radius for better matching with the HER (beam-beam interaction criteria). We will consider two cases, both based on the PEP structure. One with 96 periods, containing 1 bending magnet per period and the other 2 bends per period. The case of synchrotron radiation absorbers outside of the bending magnet will considered also. 2 refs., 13 figs.
Date:
August 17, 1990
Creator:
Alexandrov, A.; Hutton, A. & Logatchev, P.
Object Type:
Report
System:
The UNT Digital Library
Hot nuclei -- Landau theory, thermal fluctuations and dissipation
The basic ideas and theoretical methods used in the description of hot nuclei are reviewed. In particular, a macroscopic approach to shape transitions is discussed in the framework of the Landau theory in which the quadrupole shape degrees of freedom play the role of the order parameters. This theory describes the universal features of the nuclear shape evolution with temperature and spin. A unified description of fluctuations in all five quadrupole degrees of freedom is introduced and plays an important role in the calculation of physical observables. A macroscopic approach to the giant dipole resonance (GDR) in hot nuclei is developed. With all parameters fixed by the zero temperature nuclear properties, the theory predicts both the GDR cross-section and angular anisotropy of the {gamma}-rays in very good agreement with recent experiments. The intrinsic shape fluctuations are the main cause for the resonance broadening at higher temperatures, while the orientation fluctuations are responsible for the observed attenuation in the angular anisotropy. Dissipation at finite temperature is discussed in the framework of a Langevin-like equation describing the time-dependent shape fluctuations. Non-adiabatic effects may cause motional narrowing of the resonance.
Date:
December 31, 1990
Creator:
Alhassid, Y.
Object Type:
Article
System:
The UNT Digital Library
Hot nuclei -- Landau theory, thermal fluctuations and dissipation
The basic ideas and theoretical methods used in the description of hot nuclei are reviewed. In particular, a macroscopic approach to shape transitions is discussed in the framework of the Landau theory in which the quadrupole shape degrees of freedom play the role of the order parameters. This theory describes the universal features of the nuclear shape evolution with temperature and spin. A unified description of fluctuations in all five quadrupole degrees of freedom is introduced and plays an important role in the calculation of physical observables. A macroscopic approach to the giant dipole resonance (GDR) in hot nuclei is developed. With all parameters fixed by the zero temperature nuclear properties, the theory predicts both the GDR cross-section and angular anisotropy of the {gamma}-rays in very good agreement with recent experiments. The intrinsic shape fluctuations are the main cause for the resonance broadening at higher temperatures, while the orientation fluctuations are responsible for the observed attenuation in the angular anisotropy. Dissipation at finite temperature is discussed in the framework of a Langevin-like equation describing the time-dependent shape fluctuations. Non-adiabatic effects may cause motional narrowing of the resonance.
Date:
January 1, 1990
Creator:
Alhassid, Y.
Object Type:
Article
System:
The UNT Digital Library
Phosphazene polymer containing composites and method for making phosphazene polymer containing composites
The object of the invention is to provide a composite material comprised of phosphazene polymer. A feature of phosphazene-containing composites is their superior stiffness, thermal stability, and hardness which is lacking in more typical composite constituents. An advantage of using phosphazene composites is a wider range of applications, including uses in harsh environments. Another object of the present invention provides a method for producing phosphazene-containing composite materials through a pultrusion process. In brief, these and other objects are achieved by a composite produced by first coating a reinforcing material with an inorganic phosphazene compound and then polymerizing the phosphazene compound so as to confer superior thermal, physical and chemical resistance qualities to the composite. 2 figs., 6 tabs.
Date:
December 31, 1990
Creator:
Allen, C. A.; Grey, A. E.; McCaffrey, R. R.; Simpson, B. M. & Stone, M. L.
Object Type:
Patent
System:
The UNT Digital Library
In situ study of effects of ion-irradiation on solid state crystallization of cobalt disilicide thin films
Results of a continuing in situ study of the ion-irradiation-modified crystallization of amorphous CoSi{sub 2} thin films are discussed. 1.5 MeV Kr ion irradiation is employed at 90 K to mix'' nominally amorphous, as-deposited material for subsequent epitaxial regrowth at 450 K. The ion irradiation also is employed at 300 K to produce ion-assisted crystallization. The average degree of transformation per ion is approximately 4 {times} 10{sup {minus}20} cm{sup 3} per ion. The resultant number density of crystals, however, depends sensitively on prior treatment of the film. For example, 300 kV electron irradiation at 300 K prior to ion irradiation may result in a large number density of crystal nuclei. Low dose Kr irradiation at 300 K may also cause a slight increase in the number density of crystals formed subsequently at 450 K, while large Kr doses at 300 K (> 3 {times} 10{sup 14} cm{sup {minus}2}) may double the subsequent thermal growth rate at 450 K. These results are discussed qualitatively in terms of nucleation and growth theory. 8 refs., 6 figs.
Date:
January 1, 1990
Creator:
Allen, C.W. (Argonne National Lab., IL (USA)) & Smith, D.A. (International Business Machines Corp., Yorktown Heights, NY (USA). Thomas J. Watson Research Center)
Object Type:
Article
System:
The UNT Digital Library
In situ study of the effects of heavy-ion irradiation on co-evaporated CoSi sub 2 films
The in situ ion irradiation capability of Argonne's HVEM-Tandem User Facility has been employed to determine the effects of 1.5 MeV Kr{sup +} irradiation and 300 kV electron irradiation on the crystallization of as-deposited and of partially crystallized 40 nm thick films of CoSi{sub 2}. Ion fluxes ranged from 8.5 {times} 10{sup 14} to 6.8 {times} 10{sup 15} m{sup {minus}2}s{sup {minus}1} for which beam heating effects may be neglected. The maximum electron flux at 300 kV was 0.8 {times} 10{sup 23} m{sup {minus}2}s{sup {minus}1}. The maximum temperature at which crystalline CoSi{sub 2} is amorphized by the ion irradiation of flux = 6.8 {times} 10{sup 15} m{sup {minus}2}s{sup {minus}1} is between 250 and 280 K. At higher temperatures amorphous material crystallizes by growth of any preexisting crystals and by classical nucleation and growth, with radial growth rates which are proportional to ion flux. The average degree of transformation per ion is 4 {times} 10{sup {minus}26} m{sup 3} per ion. Thermally induced crystallization of as-deposited films occurs above approximately 420 K. For ion doses at least as low as 3.4 {times} 10{sup 16} m{sup {minus}2} ion irradiation at 300 K promotes thermal crystallization at 450 K, by virtue of enhanced apparant nucleation …
Date:
November 1, 1990
Creator:
Allen, C.W. (Argonne National Lab., IL (USA)) & Smith, D.A. (International Business Machines Corp., Yorktown Heights, NY (USA). Thomas J. Watson Research Center)
Object Type:
Article
System:
The UNT Digital Library
Setting-Basin Separating Device
Patent for Settling Basin-Separating Devices. This device improves the issue of unwanted discharge shown in prior devices
Date:
May 11, 1990
Creator:
Allen, Charles
Object Type:
Patent
System:
The Portal to Texas History