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Fast neutrons incident on rotors : - tantalum.

Description: Reports in the Argonne National Laboratory Nuclear Data and Measurement Series present results of studies in the field of microscopic nuclear data. The primary objective of the series is the dissemination of information in the comprehensive form required for nuclear technology applications. This series is devoted to: (a) measured microscopic nuclear parameters, (b) experimental techniques and facilities employed in measurements, (c) the analysis, correlation and interpretation of nuclear data, and (d) the compilation and evaluation of nuclear data.
Date: March 21, 2005
Creator: Smith, A. B.
Partner: UNT Libraries Government Documents Department

Some personal reflections

Description: This paper analyzes data for fission-energy and fusion-energy development. Neutron reactions with uranium and plutonium are discussed in particular. Instrumentation is also reviewed. (LSP)
Date: January 1, 1988
Creator: Smith, A.B.
Partner: UNT Libraries Government Documents Department

Model for fission-product calculations

Description: Many fission-product cross sections remain unmeasurable thus considerable reliance must be placed upon calculational interpolation and extrapolation from the few available measured cross sections. The vehicle, particularly for the lighter fission products, is the conventional optical-statistical model. The applied goals generally are: capture cross sections to 7 to 10% accuracies and inelastic-scattering cross sections to 25 to 50%. Comparisons of recent evaluations and experimental results indicate that these goals too often are far from being met, particularly in the area of inelastic scattering, and some of the evaluated fission-product cross sections are simply physically unreasonable. It is difficult to avoid the conclusion that the models employed in many of the evaluations are inappropriate and/or inappropriately used. In order to alleviate the above unfortunate situations, a regional optical-statistical (OM) model was sought with the goal of quantitative prediction of the cross sections of the lighter-mass (Z = 30-51) fission products. The first step toward that goal was the establishment of a reliable experimental data base consisting of energy-averaged neutron total and differential-scattering cross sections. The second step was the deduction of a regional model from the experimental data. It was assumed that a spherical OM is appropriate: a reasonable and practical assumption. The resulting OM then was verified against the measured data base. Finally, the physical character of the regional model is examined.
Date: January 1, 1984
Creator: Smith, A.B.
Partner: UNT Libraries Government Documents Department

Energy-averaged nuclear data; measurements and physical interpretations

Description: The objective is an outline of the status of energy-averaged nuclear-data (unresolved-resonance region to 20 MeV) for a diversity of applications. The relevance is primarily to nuclear-energy systems (fission and fusion), and, secondarily, to a wide range of other nuclear applications. Neutron total cross sections, neutron scattering and emission, neutron radiative capture, neutron fission, neutron-induced activities and charged-particle production, and charged-particle processes are reviewed. (WHK)
Date: January 1, 1985
Creator: Smith, A.B.
Partner: UNT Libraries Government Documents Department

Neutron scattering and models: Iron. Nuclear data and measurements series

Description: Differential elastic and inelastic neutron-scattering cross sections of elemental iron are measured from 4.5 to 10 MeV in increments of {approx} 0.5 MeV. At each incident energy the measurements are made at forty or more scattering angles distributed between {approx} 17{degrees} and 160{degrees}, with emphasis on elastic scattering and inelastic scattering due to the excitation of the yrast 2{sup +} state. The measured data is combined with earlier lower-energy results from this laboratory, with recent high-precision {approx} 9.5 {yields} 15 MeV results from the Physilalisch Technische Bundesanstalt and with selected values from the literature to provide a detailed neutron-scattering data base extending from {approx} 1.5 to 26 MeV. This data is interpreted in the context of phenomenological spherical-optical and coupled-channels (vibrational and rotational) models, and physical implications discussed. Deformation, coupling, asymmetry and dispersive effects are explored. It is shown that, particularly in a collective context, a good description of the interaction of neutrons with iron is achieved over the energy range {approx} 0 {yields} 26 MeV, avoiding the dichotomy between high and low-energy interpretations found in previous work.
Date: August 1995
Creator: Smith, A. B.
Partner: UNT Libraries Government Documents Department

Neutron scattering and models: Silver

Description: Differential neutron elastic-scattering cross sections of elemental silver were measured from 1.5 {r_arrow} 10 MeV at {approx} 100 keV intervals up to 3 MeV, at {approx} 200 keV intervals from 3 {r_arrow} 4 MeV, and at {approx} 500 keV intervals above 4 MeV. At {le} 4 MeV the angular range of the measurements was {approx} 20{sup 0} {r_arrow} 160{sup 0} with 10 measured values below 3 MeV and 20 from 3 {r_arrow} 4 MeV at each incident energy. Above 4 MeV {ge} 40 scattering angles were used distributed between {approx} 17{sup 0} and 16{sup 0} All of the measured elastic distributions included some contributions due to inelastic scattering. Below 4 MeV the measurements determined cross sections for ten inelastically-scattered neutron groups corresponding to observed excitations of 328 {+-} 13, 419 {+-} 50, 748 {+-} 25, 908 {+-} 26, 115 {+-} 38, 1286 {+-} 25, 1507 {+-} 20, 1632 {+-} 30, 1835 {+-} 20 and 1944 {+-} 26 keV. All of these inelastic groups probably were composites of contributions from the two isotopes {sup 107}Ag and {sup 109}Ag. The experimental results were interpreted in terms of the spherical optical model and of rotational and vibrational coupled-channels models, and physical implications are discussed. In particular, the neutron-scattering results are consistent with a ground-state rotational band with a quadrupole deformation {Beta}{sub 2} = 0.20 {+-} {approx} 10% for both of the naturally-occurring silver isotopes.
Date: July 1, 1996
Creator: Smith, A.B.
Partner: UNT Libraries Government Documents Department

Neutrons and antimony physical measurements and interpretations

Description: New experimental information for the elastic and inelastic scattering of {approx} 4--10 MeV neutrons from elemental antimony is presented. The differential measurements are made at {approx} 40 or more scattering angles and at incident neutron-energy intervals of {approx} 0.5 MeV. The present experimental results, those previously reported from this laboratory and as found in the literature are comprehensively interpreted using spherical optical-statistical and dispersive-optical models. Direct vibrational processes via core-excitation, isospin and shell effects are discussed. Antimony models for applications are proposed and compared with global, regional, and specific models reported in the literature.
Date: May 23, 2000
Creator: Smith, A. B.
Partner: UNT Libraries Government Documents Department

Elemental ABAREX -- a user's manual.

Description: ELEMENTAL ABAREX is an extended version of the spherical optical-statistical model code ABAREX, designed for the interpretation of neutron interactions with elemental targets consisting of up to ten isotopes. The contributions from each of the isotopes of the element are explicitly dealt with, and combined for comparison with the elemental observables. Calculations and statistical fitting of experimental data are considered. The code is written in FORTRAN-77 and arranged for use on the IBM-compatible personal computer (PC), but it should operate effectively on a number of other systems, particularly VAX/VMS and IBM work stations. Effort is taken to make the code user friendly. With this document a reasonably skilled individual should become fluent with the use of the code in a brief period of time.
Date: May 26, 1999
Creator: Smith, A.B.
Partner: UNT Libraries Government Documents Department

Neutron scattering and models : molybdenum.

Description: A comprehensive interpretation of the fast-neutron interaction with elemental and isotopic molybdenum at energies of {le} 30 MeV is given. New experimental elemental-scattering information over the incident energy range 4.5 {r_arrow} 10 MeV is presented. Spherical, vibrational and dispersive models are deduced and discussed, including isospin, energy-dependent and mass effects. The vibrational models are consistent with the ''Lane potential''. The importance of dispersion effects is noted. Dichotomies that exist in the literature are removed. The models are vehicles for fundamental physical investigations and for the provision of data for applied purposes. A ''regional'' molybdenum model is proposed. Finally, recommendations for future work are made.
Date: May 26, 1999
Creator: Smith, A.B.
Partner: UNT Libraries Government Documents Department

Neutron interaction with doubly-magic {sup 40}Ca

Description: Differential neutron elastic and inelastic-scattering cross sections of elemental calcium (96.94% doubly-magic {sup 40}Ca) are measured from {approx} 1.5 to 10 MeV with sufficient detail to determine their energy-averaged behavior in the highly fluctuating environment. These results, combined with values previously reported in the literature, are assessed in the contexts of optical-statistical, dispersive optical, and coupled-channels models, applicable to the energy domain 0 {yields} 30+ MeV, with particular emphasis on the lower energies where the interpretations are sensitive to the dispersion relationship and the effective mass. The interpretations define the energy dependencies of the potential parameters (resolving prior ambiguities), suggest that previous estimates of the prominent low-energy (n,p) and (n,a) reactions are too large, reasonably describe observables to at least 30 MeV, and provide a vehicle for extrapolation into the bound-state regime that gives a good description of hole- and particle-state binding energies. The resulting real-potential parameters (in contrast to many {sup 40}Ca parameters reported in the literature) are shown consistent with global trends.
Date: November 1, 1993
Creator: Smith, A.B.
Partner: UNT Libraries Government Documents Department

Fast-neutrons incident on gadolinium.

Description: Reports in the Argonne National Laboratory Nuclear Data and Measurement Series present results of studies in the field of microscopic nuclear data. The primary objective of the series is the dissemination of information in the comprehensive form required for nuclear technology applications. This Series is devoted to: (a) measured microscopic nuclear parameters, (b) experimental techniques and facilities employed in measurements, (c) the analysis, correlation and interpretation of nuclear data, and (d) the compilation and evaluation of nuclear data. Contributions to this Series are reviewed to assure technical competence and, unless otherwise stated, the contents can be formally referenced. This Series does not supplant formal journal publication, but it does provide the more extensive information required for technological applications (e.g., tabulated numerical data) in a timely manner.
Date: May 24, 2004
Creator: Smith, A. B.
Partner: UNT Libraries Government Documents Department

Nuclear data and measurements series.

Description: Results of measurements of neutron scattering from elemental rhenium are presented over two incident-energy regions: (1) 0.3-1.5 MeV, and (2) 4.5-10.0 MeV. The first of these supplements previously-reported work at this Laboratory, and the second consists of information in an entirely new energy range. These experimental results are interpreted in terms of optical-statistical and coupled-channels models, including consideration of dispersive effects, and of scalar and vector potentials. Some basic and applied physical implications of these considerations are discussed. Comparisons are made with other regional and/or global models, and with evaluated nuclear-data files used in applications.
Date: August 13, 2003
Creator: Smith, A. B.
Partner: UNT Libraries Government Documents Department

Note on the elastic-scattering of few-MeV neutrons from elemental calcium

Description: Neutron differential-elastic-scattering cross sections of elemental calcium are measured from < 1.5 to 4.0 MeV at intervals of approx. = 50 to 100 keV. Scattering angles are distributed between 20 and 160/sup 0/. Incident-neutron energy resolutions are approximately 50 to 100 keV. The experimental results are compared with values given in ENDF/B-V and are examined in the context of shielding applications. An optical potential is deduced from the measured values and its possible implications are discussed.
Date: March 1, 1982
Creator: Smith, A.B. & Guenther, P.T.
Partner: UNT Libraries Government Documents Department

Fast-neutron scattering cross sections of elemental silver

Description: Differential neutron elastic- and inelastic-scattering cross sections of elemental silver are measured from 1.5 to 4.0 MeV at intervals of less than or equal to 200 keV and at 10 to 20 scattering angles distributed between 20 and 160/sup 0/. Inelastically-scattered neutron groups are observed corresponding to the excitation of levels at; 328 +- 13, 419 +- 50, 748 +- 25, 908 +- 26, 1150 +- 38, 1286 +- 25, 1507 +- 20, 1623 +- 30, 1835 +- 20 and 1944 +- 26 keV. The experimental results are used to derive an optical-statistical model that provides a good description of the observed cross sections. The measured values are compared with corresponding quantities given in ENDF/B-V.
Date: May 1, 1982
Creator: Smith, A.B. & Guenther, P.T.
Partner: UNT Libraries Government Documents Department

Some fundamental aspects of the optical potential for the interaction of fast neutrons with cobalt

Description: Differential elastic- and inelastic-scattering cross sections, measured from approx.1.5 to 10.0 MeV, are interpreted in terms of spherical-optical-statistical (OM) and coupled-channels models. A successful description of the differential elastic scattering below 10 MeV and the total cross section to 20.0 MeV is achieved using the spherical OM with energy-dependent strengths and geometries. These energy dependencies are large below approx.7.0 MeV, but become smaller and similar to those reported for /open quotes/global/close quotes/ potentials at higher energies. This change in the energy dependence of the parameters probably marks the onset of the Fermi surface anomaly approx.19 MeV above the Fermi energy. Inelastic scattering to the levels below 1.8 MeV displays a forward-peaked behavior. This nonstatistical component is interpreted using the weak-coupling model in which the f/sub 7/2 proton hole is coupled to the 2/sup /plus// state in /sup 60/Ni. This model provides an explanation of the unusual energy dependence and relatively small radius found for the imaginary OM potential. The coupling also contributes to the large value of this potential. The real spherical OM potential derived from the neutron-scattering results is extrapolated to bound energies by using the dispersion relationship and the method of moments. The resulting real-potential strength and radius peak at approx.-10.0 MeV, whereas the real diffuseness is at a minimum at this energy. The extrapolated potential is approx.8% larger than that implied by reported particle-state energies, and approx.13% smaller than indicated by hole-state energies. 42 refs., 8 figs.
Date: January 1, 1988
Creator: Smith, A.B. & Lawson, R.D.
Partner: UNT Libraries Government Documents Department

Neutron sources: Present practice and future potential

Description: The present capability and future potential of accelerator-based monoenergetic and white neutron sources are outlined in the context of fundamental and applied neutron-nuclear research. The neutron energy range extends from thermal to 500 MeV, and the time domain from steady-state to pico-second pulsed sources. Accelerator technology is summarized, including the production of intense light-ion, heavy-ion and electron beams. Target capabilities are discussed with attention to neutron-producing efficiency and power-handling capabilities. The status of underlying neutron-producing reactions is summarized. The present and future use of neutron sources in: fundamental neutron-nuclear research, nuclear data acquisition, materials damage studies, engineering tests, and biomedical applications are discussed. Emphasis is given to current status, near-term advances well within current technology, and to long-range projections. 90 refs., 4 figs.
Date: January 1, 1988
Creator: Cierjacks, S. & Smith, A.B.
Partner: UNT Libraries Government Documents Department

Fast-neutron scattering from elemental cadmium

Description: Neutron differential-elastic-scattering cross sections of elemental cadmium are measured from approx. = 1.5 to 4.0 MeV at incident-neutron energy intervals of 50 to 200 keV and at 10 to 20 scattering angles distributed between approx. = 20 and 160 degrees. Concurrently, lumped-level neutron inelastic-excitation cross sections are measured. The experimental results are used to deduce parameters of an optical-statistical model that is descriptive of the observables and are compared with corresponding quantities given in ENDF/B-V.
Date: July 1, 1982
Creator: Smith, A.B. & Guenther, P.T.
Partner: UNT Libraries Government Documents Department