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Relativistic models in nuclear and particle physics

Description: A comparative overview is presented of different approaches to the construction of phenomenological dynamical models that respect basic principles of quantum theory and relativity. Wave functions defined as matrix elements of products of field operators on one hand and wave functions that are defined as representatives of state vectors in model Hilbert spaces are related differently to observables and dynamical models for these wave functions have each distinct advantages and disadvantages 34 refs.
Date: January 1, 1988
Creator: Coester, F.
Partner: UNT Libraries Government Documents Department

Octupole correlations in the heavy elements

Description: The effects of octupole correlations on the nuclear structure of the heavy elements are discussed. The cluster model description of the heavy elements is analyzed. The relevance of 2/sup 6/-pole deformation and fast El transitions to an octupole model is considered. 30 refs., 21 figs., 1 tab.
Date: January 1, 1986
Creator: Chasman, R.R.
Partner: UNT Libraries Government Documents Department

Proceedings of a symposium on the occasion of the 40th anniversary of the nuclear shell model

Description: This report contains papers on the following topics: excitation of 1p-1h stretched states with the (p,n) reaction as a test of shell-model calculations; on Z=64 shell closure and some high spin states of {sup 149}Gd and {sup 159}Ho; saturating interactions in {sup 4}He with density dependence; are short-range correlations visible in very large-basis shell-model calculations ; recent and future applications of the shell model in the continuum; shell model truncation schemes for rotational nuclei; the particle-hole interaction and high-spin states near A-16; magnetic moment of doubly closed shell +1 nucleon nucleus {sup 41}Sc(I{sup {pi}}=7/2{sup {minus}}); the new magic nucleus {sup 96}Zr; comparing several boson mappings with the shell model; high spin band structures in {sup 165}Lu; optical potential with two-nucleon correlations; generalized valley approximation applied to a schematic model of the monopole excitation; pair approximation in the nuclear shell model; and many-particle, many-hole deformed states.
Date: March 1, 1990
Creator: Lee, T. S. H. & Wiringa, R. B. (eds.)
Partner: UNT Libraries Government Documents Department

The fission cross section ratios and error analysis for ten thorium, uranium, neptunium and plutonium isotopes at 14. 74 MeV neutron energy

Description: The error information from the recent measurements of the fission cross section ratios of nine isotopes, /sup 230/Th, /sup 232/Th, /sup 233/U, /sup 234/U, /sup 236/U, /sup 238/U, /sup 237/Np, /sup 239/Pu, and /sup 242/Pu, relative to /sup 235/U at 14.74 MeV neutron energy was used to calculate their correlations. The remaining 36 non-trivial and non-reciprocal cross section ratios and their errors were determined and compared to evaluated (ENDF/B-V) values. There are serious differences but it was concluded that the reduction of three of the evaluated cross sections would remove most of them. The cross sections to be reduced are /sup 230/Th - 13%, /sup 237/Np - 9.6% and /sup 239/Pu - 7.6%. 5 refs., 6 tabs.
Date: March 1, 1987
Creator: Meadows, J.W.
Partner: UNT Libraries Government Documents Department

De Haas-Van Alphen measurements of one-electron and many-body effects in transition metals and intermetallic compounds

Description: Examples are given which demonstrate the power and versatility of the dHvA effect in studying electronic behavior in metals. In transition metals the parametrization schemes give a very complete and consistent picture of the k-dependent and surface averaged electronic properties. Because the one-electron behavior is fairly well known, the many body contribution to the Fermi velocity can be isolated and its detailed anisotropy can be displayed. This kind of information is directly relevant to the calculation of electron-phonon interaction effects and cannot be derived by any other means.
Date: January 1, 1980
Creator: Crabtree, G.W.; Johanson, W.R.; Campbell, S.A.; Dye, D.H.; Karim, D.P. & Ketterson, J.B.
Partner: UNT Libraries Government Documents Department

Comparison of three MHD flow control methods for self-cooled liquid metal blankets

Description: The heat deposition in a blanket is concentrated near the first wall. Uniform liquid-metal velocity in a self-cooled blanket is unattractive, because it leads to low mixed-mean temperature rise through the blanket and reduced power conversion efficiency. The objective of MHD flow control is to use the electromagnetic forces to produce a non-uniform velocity distribution which gives a uniform temperature distribution over the thickness of the blanket. Three methods of MHD flow control are presented here and the MHD pressure drops corresponding to the three methods are compared. One of the methods, although successful at achieving nonuniform velocity profiles, permits a large circulation of electric current which produces a high pressure drop. The analytical results do not indicate a clear choice between the other two methods. The analytical results do point to possible difference in heat transfer performance with the two methods.
Date: January 1, 1986
Creator: Walker, J.S. & Picologlou, B.F.
Partner: UNT Libraries Government Documents Department

A continuous mode data acquisition technique for proton recoil proportional counter neutron spectrometers

Description: The existing proton recoil proportional counter measurement technique used at FNS for joint FNS-ANL fusion blanket neutron spectroscopy requires that numerous piece-wise (but overlapping) measurements be carried out at a sequence of fixed counter voltages. The composite results of all of these independent measurements are required to construct a single neutron spectrum. This approach has been found to be both inefficient and subject to systematic errors. An alternative approach, in which data is acquired continuously using a slow time modulation of the high voltage bias supply, is here described. The electronics requirements are consistent with the basic detector/amplifier systems now operable at FNS. Some additional hardware including a programmable high voltage bias supply and a random amplitude test pulse generator are necessary. A description of the electronics and data acquisition hardware for these measurements will be provided at a later date. In this report we emphasize the numerical procedures involved to acquire and reduce data, and provide an illustrative example using one of the hardest neutron spectra readily available for this work at ANL. 6 refs., 26 figs.
Date: March 1, 1989
Creator: Bennett, E.F.
Partner: UNT Libraries Government Documents Department

Dynamic polarization of ZF in a fluorinated alcohol

Description: We have studied microwave dynamic cooling of ZF and H nuclei in mixtures of 1,1,1,3,3,3-hexafluoro-2-propanol and water, doped with Cr(V) complex. Equal spin temperatures of the two nuclei are produced, and the highest spin polarizations (/approximately/80%) are found in mixtures near the eutectic ratio. The high fluorine content and polarization make this a suitable material for polarized nuclear scattering experiments. 11 refs., 3 figs., 1 tab.
Date: January 1, 1988
Creator: Hill, D.; Kasprzyk, T.; Jarmer, J.J.; Penttilae, S.; Krumpolc, M.; Hoffmann, G.W. et al.
Partner: UNT Libraries Government Documents Department

Experimental determination of the energy dependence of defect production

Description: The damage function nu(T), i.e., the number of Frenkel pairs as a function of recoil energy is determined for Cu from electron and ion damage-rate measurements. nu(T) shows a plateau at nu = 0.54 which extends up to approx. 7xT/sub d//sup min/. Therefore, simple damage models, such as the modified Kinchin-Pease expression, are inappropriate not only at high recoil energies where stimulated recombination in cascades reduces defect production, but also in the single displacement regime. As a consequence, no simple relation between T/sub d//sup min/ and T/sub d//sup av/ is expected to exist. A procedure is suggested which uses anisotropy measurements in combination with polycrystal electron and ion irradiations to construct absolute damage functions in metals.
Date: January 1, 1982
Creator: Merkle, K.L.; King, W.E.; Baily, A.C.; Haga, K. & Meshii, M.
Partner: UNT Libraries Government Documents Department

Shell structure at high spin and the influence on nuclear shapes

Description: Nuclear structure at high spin is influenced by a combination of liquid-drop and shell-structure effects. For N < 86 both contribute towards the occurrence along the yrast line of high-spin oblate aligned-particle configurations. Shell effects are mainly responsible for the prolate deformation of nuclei with N > 90. The competition between oblate and prolate driving effects leads to a prolate-to-oblate shape transition in /sup 154/Dy/sub 88/. The role of rotation-aligned configurations in the shape change is discussed.
Date: January 1, 1982
Creator: Khoo, T.L.; Chowdhury, P. & Ahmad, I.
Partner: UNT Libraries Government Documents Department

Important material considerations in INTOR

Description: A number of important material-related problems were identified and analyzed during the Phase-I study for INTOR. The first wall and divertor collector plate are subjected to severe normal and off-normal conditions. A melt layer is predicted to develop in a bare stainless steel wall under plasma disruptions. Graphite tiles will not melt but they introduce other serious uncertainties into the design. The design strategy for the divertor collector plate focused on separating the surface and high heat flux problems and on utilizing a novel mechanical design concept for attaching tungsten tiles to a stainless steel (or copper) heat sink.
Date: January 1, 1981
Creator: Abdou, M.A.; Mattas, R.F. & Smith, D.L.
Partner: UNT Libraries Government Documents Department

Discrete nodal integral transport-theory method for multidimensional reactor physics and shielding calculations

Description: A coarse-mesh discrete nodal integral transport theory method has been developed for the efficient numerical solution of multidimensional transport problems of interest in reactor physics and shielding applications. The method, which is the discrete transport theory analogue and logical extension of the nodal Green's function method previously developed for multidimensional neutron diffusion problems, utilizes the same transverse integration procedure to reduce the multidimensional equations to coupled one-dimensional equations. This is followed by the conversion of the differential equations to local, one-dimensional, in-node integral equations by integrating back along neutron flight paths. One-dimensional and two-dimensional transport theory test problems have been systematically studied to verify the superior computational efficiency of the new method.
Date: January 1, 1980
Creator: Lawrence, R.D. & Dorning, J.J.
Partner: UNT Libraries Government Documents Department

Electron capture in ion-molecule collisions at intermediate energy

Description: Recent progress of theoretical charge transfer study in ion-molecule collisions at the intermediate energy is reviewed. Concept of close and distant collisions obtained from extensive ion-atom collision studies is identified so that it can be utilized to model two distinct collision processes. For a close collision, explicit representation of the whole collision complex is necessary to describe collision dynamics correctly, while a model potential approach for molecule is appropriate for a distant collision. It is shown that these two distinct models are indeed capable of reproducing experimental charge transfer cross sections. Some remarks for further theoretical study of ion-molecule collisions are also given. 21 refs., 8 figs.
Date: January 1, 1986
Creator: Kumura, M.
Partner: UNT Libraries Government Documents Department

New possibilities for exotic hadrons

Description: New theoretical ideas and experimental evidence for exotic hadrons are presented. A new exciting candidate is an anticharmed baryon; i.e., a bound state of a nucleon and an F (now called D3). New experimental evidence for four-quark exotic mesons presented at this conference is discussed. The confusion in the E-iota region and the pseudoscalar spectrum still await further experimental clarification.
Date: May 12, 1987
Creator: Lipkin, H.J.
Partner: UNT Libraries Government Documents Department

Nuclear dependence of structure functions in the shadowing region of deep inelastic scattering

Description: A discussion of nuclear shadowing in deep inelastic lepton scattering is presented. We show that the parton recombination model suggests that shadowing should begin to occur at larger values of Bjorken x as A increases. This expectation as well as that of weak dependence on Q/sup 2/, and the trend of the x dependence of the shadowing phenomenon are consistent with recent data. Shadowing at small x is combined with nuclear bound state effects, responsible for nuclear dependence at larger x, to provide description of the A dependence of the structure function for the entire range of x. 21 refs., 5 figs.
Date: July 27, 1988
Creator: Berger, E.L. & Qiu, Jianwei
Partner: UNT Libraries Government Documents Department

Momentum distributions in hcp, bcc, and liquid /sup 4/He

Description: Using Deep Inelastic Neutron Scattering we have measured the nuclear momentum distribution in hcp, bcc and liquid /sup 4/He at constant density over a temperature range 0.96K < T < 4.0K. We find no temperature dependence of the momentum distribution in the hcp solid or the liquid. We also find no difference between the hcp, bcc and liquid phases. The average kinetic energy per atom is lower than the best present theories predict.
Date: May 1, 1984
Creator: Sokol, P.E.; Simmons, R.O.; Price, D.L. & Hilleke, R.O.
Partner: UNT Libraries Government Documents Department

Heavy flavor production at fixed target and collider energies

Description: A review is presented of heavy quark production in /bar p/p, p, and pp interactions at fixed target and collider energies. Calculations of total cross sections are described including contributions through next-to-leading order in QCD perturbation theory. Comparisons with available data on charm and bottom quark production show good agreement for reasonable values of charm and bottom quark masses and other parameters. Open issues in the interpretation of results are summarized. A discussion is presented of signatures, backgrounds, and expected event rates for top quark production. 19 refs., 4 figs.
Date: October 13, 1988
Creator: Berger, E.L.
Partner: UNT Libraries Government Documents Department

A measurement of intermediate vector boson production in 1. 8 TeV /bar p/p collisions

Description: The cross section for the production and subsequent decay to electron and neutrino of the W intermediate vector boson has been measured in 1.8 TeV /bar p/p collisions at the Collider Detector at Fermilab. An analysis of events with missing transverse energy greater than 25 GeV and an electron of transverse energy greater than 15 GeV from a data sample of 25nb/sup /minus/1/ gives sigma/center dot/B = 2.57 +- 0.56 +- 0.46nb, in agreement with theoretical predictions. 10 refs., 4 figs.
Date: June 27, 1988
Creator: St.Denis, R.D.
Partner: UNT Libraries Government Documents Department

Two-phase-flow models and their limitations

Description: An accurate prediction of transient two-phase flow is essential to safety analyses of nuclear reactors under accident conditions. The fluid flow and heat transfer encountered are often extremely complex due to the reactor geometry and occurrence of transient two-phase flow. Recently considerable progresses in understanding and predicting these phenomena have been made by a combination of rigorous model development, advanced computational techniques, and a number of small and large scale supporting experiments. In view of their essential importance, the foundation of various two-phase-flow models and their limitations are discussed in this paper.
Date: January 1, 1982
Creator: Ishii, M. & Kocamustafaogullari, G.
Partner: UNT Libraries Government Documents Department

Modeling of concrete response at high temperature

Description: A rate-type creep law is implemented into the computer code TEMP-STRESS for high temperature concrete analysis. The disposition of temperature, pore pressure and moisture for the particular structure in question is provided as input for the thermo-mechanical code. The loss of moisture from concrete also induces material shrinkage which is accounted for in the analytical model. Examples are given to illustrate the numerical results.
Date: January 1, 1984
Creator: Pfeiffer, P. & Marchertas, A.
Partner: UNT Libraries Government Documents Department

Spin models of the proton

Description: We have constructed a model of the proton spin based on a broken SU(6) parameterization for the spin-weighted valence quark distributions in a longitudinally polarized proton. The polarized sea and gluon distributions are assumed to have simple relations to the corresponding unpolarized structure functions. The sum rules, which involve the non-singlet components of the structure function xg/sub 1/, imply that the valence quarks carry about 78% of the proton spin, while the spin carried by sea quarks is negative. Recent EMC data suggest a model in which the sea quarks carry a large negative polarization, whereas certain theoretical arguments favor a model with a smaller negatively polarized sea. These models are discussed with reference to the sum rules. Experiments are suggested which will discriminate between these models. 24 refs., 4 figs.
Date: October 20, 1988
Creator: Ramsey, G.P.
Partner: UNT Libraries Government Documents Department

Sputtering properties of copper-lithium alloys at reactor-level temperatures and surface erosion rates

Description: Previous experiments on copper-lithium alloys at temperatures up to 250/sup 0/C and with erosion rates of .01 to .1 monolayer per second have shown that in the electric and magnetic field environment of a magnetic-confinement fusion reactor, it is possible to maintain a lithium overlayer which will significantly reduce the copper erosion rate. We have extended these experiments to the reactor-relevant regime of 350 to 400/sup 0/C, with erosion rates approaching one monolayer per second. By comparison with the lower flux experiments, it is found that radiation damage effects start to dominate both the surface concentration and depth profile of the lithium. The subsurface region of enhanced lithium concentration is broadened, while the surface concentration is not depleted as rapidly per incident ion as in the low flux case. The time-dependent lithium depth profile is calculated using a computer code developed at Argonne which includes both Gibbsian segregation and radiation-induced effects. The experimental results are compared with these calculations. It is found that the sputtering behavior of the copper-lithium alloy is highly dependent on the mass and energy spectrum of the incident particles, the sample temperature, subsurface structure, and the partial sputtering yields of the alloy components.
Date: January 1, 1984
Creator: Krauss, A.R.; Gruen, D.M.; Lam, N.Q. & DeWald, A.B.
Partner: UNT Libraries Government Documents Department

/sup 127/I Moessbauer study of Chevrel-phase superconductors Mo/sub 6/X/sub 6/I/sub 2/ (X = S,Te)

Description: The Chevrel-phase compounds Mo/sub 6/X/sub 6/I/sub 2/ (X = S,Te) exhibit very interesting superconducting behvior. The transition temperatures dramatically increase in both Mo/sub 6/X/sub 8/ structures be replacing 2 of the X atoms with iodine atoms. This enhancement in superconducting behavior is closely related to the number of electrons on the Mo/sub 6/ cluster in these compounds. The iodine atoms in these compounds preferentially occupy the 2c sites while the remaining X atoms occupy the 6f sites. We have performed the Moessbauer effect measurements using the 57.6-keV transition in /sup 127/I to evaluate the charge on the iodine. Assuming the charge on S to be -2, the experimental value of nearly -1 charge on iodine leaves 22.3 electrons per Mo/sub 6/ cluster which is close to that predicted in SnMo/sub 6/S/sub 8/). In Mo/sub 6/Te/sub 6/I/sub 2/, assuming Te to have nearly -1 charge, we obtain 28.3 electrons per Mo/sub 6/ cluster. The observation of superconductivity in this compound then reflects a significantly distinct band structure of tellurides compared to those of sulphides. The quadrupole interactions at the odine nucleus in Mo/sub 6/S/sub 6/I/sub 2/ and Mo/sub 6/Te/sub 6/I/sub 2/ are small but have opposite signs signifying bonding differences between these compounds.
Date: January 1, 1981
Creator: Subba Rao, G.V.; Niarchos, D.; Shenoy, G.K.; Cashion, J.D.; Hinks, D.; Umarji, A.M. et al.
Partner: UNT Libraries Government Documents Department