skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Effect of preequilibrium spin distribution on {sup 48}Ti +n cross sections

Abstract

Nuclear model calculations of discrete {gamma}-ray production cross sections produced in {sup 48}Ti(n,n{sup '}{gamma}{sub i}){sup 48}Ti and {sup 48}Ti(n,2n{gamma}{sub i}){sup 47}Ti reactions were made as a function of incident neutron energy from E{sub n}=1 MeV to 35 MeV and compared with new experimental results using the large-scale Compton-suppressed germanium array for neutron induced excitations (GEANIE) at LANSCE. The Hauser-Feshbach reaction code GNASH, incorporating the spin distribution for the preequilibrium process calculated with the Feshbach-Kerman-Koonin (FKK) quantum-mechanical preequilibrium theory, was used to calculate partial {gamma}-ray transition cross sections. The comparisons of calculated and experimental data demonstrate that, the FKK model for preequilibrium leads a better overall reproduction of the experimental data above E{sub n}=10 MeV, where preequilibrium processes are important. The FKK calculation predicts a strong reduction in the high-spin state population in {sup 48}Ti by inelastic scattering. Population of low-spin states was also affected, however the change in the low-lying 983.5-keV (2{sup +}) state production is small because almost all {gamma}-ray decay cascades feed this transition. In addition, the FKK calculation has a significant impact on the partial {gamma}-ray transition cross sections for the (n,2n) reaction above E{sub n}=15 MeV. The calculated cross sections for high-spin states in {sup 47}Timore » are reduced, and those from the low-spin states are enhanced, in agreement with the experimental cross section data.« less

Authors:
 [1];  [2];  [2]; ; ; ; ;  [3];  [4];  [5]; ; ; ;  [4];  [1];  [2]
  1. North Carolina State University, Raleigh, North Carolina 27695 (United States)
  2. (United States)
  3. Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
  4. Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)
  5. (Canada)
Publication Date:
OSTI Identifier:
20995298
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 75; Journal Issue: 5; Other Information: DOI: 10.1103/PhysRevC.75.054612; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; COMPARATIVE EVALUATIONS; CROSS SECTIONS; DISTRIBUTION; EXCITATION; GAMMA RADIATION; GERMANIUM; HIGH SPIN STATES; INELASTIC SCATTERING; KEV RANGE 100-1000; MEV RANGE; NEUTRONS; NUCLEAR MODELS; QUANTUM MECHANICS; SPIN; TITANIUM 47; TITANIUM 48

Citation Formats

Dashdorj, D., Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708, Lawrence Livermore National Laboratory, Livermore, California 94551, Kawano, T., Chadwick, M. B., Devlin, M., Fotiades, N., Nelson, R. O., Garrett, P. E., Department of Physics, University of Guelph, Guelph, Ontario N1G2W1, Becker, J. A., Agvaanluvsan, U., Bernstein, L. A., Younes, W., Mitchell, G. E., and Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708. Effect of preequilibrium spin distribution on {sup 48}Ti +n cross sections. United States: N. p., 2007. Web. doi:10.1103/PHYSREVC.75.054612.
Dashdorj, D., Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708, Lawrence Livermore National Laboratory, Livermore, California 94551, Kawano, T., Chadwick, M. B., Devlin, M., Fotiades, N., Nelson, R. O., Garrett, P. E., Department of Physics, University of Guelph, Guelph, Ontario N1G2W1, Becker, J. A., Agvaanluvsan, U., Bernstein, L. A., Younes, W., Mitchell, G. E., & Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708. Effect of preequilibrium spin distribution on {sup 48}Ti +n cross sections. United States. doi:10.1103/PHYSREVC.75.054612.
Dashdorj, D., Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708, Lawrence Livermore National Laboratory, Livermore, California 94551, Kawano, T., Chadwick, M. B., Devlin, M., Fotiades, N., Nelson, R. O., Garrett, P. E., Department of Physics, University of Guelph, Guelph, Ontario N1G2W1, Becker, J. A., Agvaanluvsan, U., Bernstein, L. A., Younes, W., Mitchell, G. E., and Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708. Tue . "Effect of preequilibrium spin distribution on {sup 48}Ti +n cross sections". United States. doi:10.1103/PHYSREVC.75.054612.
@article{osti_20995298,
title = {Effect of preequilibrium spin distribution on {sup 48}Ti +n cross sections},
author = {Dashdorj, D. and Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708 and Lawrence Livermore National Laboratory, Livermore, California 94551 and Kawano, T. and Chadwick, M. B. and Devlin, M. and Fotiades, N. and Nelson, R. O. and Garrett, P. E. and Department of Physics, University of Guelph, Guelph, Ontario N1G2W1 and Becker, J. A. and Agvaanluvsan, U. and Bernstein, L. A. and Younes, W. and Mitchell, G. E. and Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708},
abstractNote = {Nuclear model calculations of discrete {gamma}-ray production cross sections produced in {sup 48}Ti(n,n{sup '}{gamma}{sub i}){sup 48}Ti and {sup 48}Ti(n,2n{gamma}{sub i}){sup 47}Ti reactions were made as a function of incident neutron energy from E{sub n}=1 MeV to 35 MeV and compared with new experimental results using the large-scale Compton-suppressed germanium array for neutron induced excitations (GEANIE) at LANSCE. The Hauser-Feshbach reaction code GNASH, incorporating the spin distribution for the preequilibrium process calculated with the Feshbach-Kerman-Koonin (FKK) quantum-mechanical preequilibrium theory, was used to calculate partial {gamma}-ray transition cross sections. The comparisons of calculated and experimental data demonstrate that, the FKK model for preequilibrium leads a better overall reproduction of the experimental data above E{sub n}=10 MeV, where preequilibrium processes are important. The FKK calculation predicts a strong reduction in the high-spin state population in {sup 48}Ti by inelastic scattering. Population of low-spin states was also affected, however the change in the low-lying 983.5-keV (2{sup +}) state production is small because almost all {gamma}-ray decay cascades feed this transition. In addition, the FKK calculation has a significant impact on the partial {gamma}-ray transition cross sections for the (n,2n) reaction above E{sub n}=15 MeV. The calculated cross sections for high-spin states in {sup 47}Ti are reduced, and those from the low-spin states are enhanced, in agreement with the experimental cross section data.},
doi = {10.1103/PHYSREVC.75.054612},
journal = {Physical Review. C, Nuclear Physics},
number = 5,
volume = 75,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
  • Cross section measurements were made of prompt γ-ray production as a function of incident neutron energy on a 48Ti sample. Partial γ-ray cross sections for transitions in 45-48Ti, 44-48Sc, and 42-45Ca have been determined. Energetic neutrons were delivered by the Los Alamos National Laboratory spallation neutron source located at the LANSCE/WNR facility. The prompt-reaction γ rays were detected with the large-scale Compton-suppressed germanium array for neutron induced excitations (GEANIE). Neutron energies were determined by the time-of-flight technique. The γ-ray excitation functions were converted to partial γ-ray cross sections taking into account the dead-time correction, target thickness, detector efficiency and neutronmore » flux (monitored with an in-line fission chamber). The data are presented for neutron energies E n between 1 to 200 MeV. These results are compared with model calculations which include compound nuclear and pre-equilibrium emission. The model calculations are performed using the STAPRE reaction code for E n up to 20 MeV and the GNASH reaction code for E n up to 120 MeV. Using the GNASH reaction code the effect of the spin distribution in preequilibrium reactions has been investigated. The preequilibrium reaction spin distribution was calculated using the quantum mechanical theory of Feshbach, Kerman, and Koonin (FKK). The multistep direct (MSD) part of the FKK theory was calculated for a one-step process. The contribution from higher steps is estimated to be small. The spin distribution of the multistep compound (MSC) part of FKK theory is assumed to be the same as in the compound nucleus. The FKK preequilibrium spin distribution was incorporated into the GNASH calculations and the γ-ray production cross sections were calculated and compared with experimental data. The difference in the partial γ-ray cross sections using spin distributions with and without preequilibrium effects is found to be significant. Specifically, the probability of γ transitions from a high spin state is strongly suppressed because of the preequilibrium spin distribution. Preequilibrium reactions are found to be important for neutron energies above 10 MeV.« less
  • Activation techniques were used to determine the relative cross sections for the (n,p) reaction on /sup 46/Ti, /sup 48/Ti, and /sup 50/Ti at 14.7 plus or minus 0.7 Mev. (C.E.S.)