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Neutron cross section measurements using the ORELA: /sup 40/Ar(n,x), /sup 40/Ca(n,x), /sup 22/Ne(n,. gamma. ), /sup 187/Os(n,n') /sup 186/ /sup 187/ /sup 188/Os(n,nn'. gamma. ), the stable tellurium isotopes (n,. gamma. ), and /sup 205/Tl(n,n. gamma. ). Progress report, September 1, 1982-August 31, 1983

Description: The research performed during this reporting period consisted primarily of (1) measurement, analysis, and publication of the /sup 187/Os(n,n') cross section near 30 keV, (2) measurement and analysis of the /sup 148/ /sup 149/ /sup 159/Sm(n,..gamma..) cross sections, (3) development and publication of a significantly better approximation to the average neutron scattering function as determined by total cross section measurements at the Oak Ridge Electron Linear Accelerator (ORELA), and (4) providing support for the neutron capture facility at ORELA as in the corrections made to the /sup 60/Ni(n,..gamma..) data discussed in a paper included with this report. The major result of the /sup 187/Os(n,n') cross section measurement was the 30 keV average value for that cross section anti sigma/sub nn'/ approx. = 1.5 +- 0.2 b and the implication that the duration of stellar nucleosynthesis, as derived from the /sup 187/Re ..-->.. /sup 187/Os beta decay, is estimated to be (8.9 +- 2.0) x 10/sup 9/ year consistent with an earlier estimate reported by Winters and Macklin. The Sm(n,..gamma..) measurement has already resulted in an estimate of the importance of branching in the s-process in the samarium mass region. We estimate the average neutron density during s-process nucleosynthesis in the vicinity of the solar system to be between less than or equal to (1.1 + 0.7) and (1.1 - 0.6) x 10/sup 8/ neutrons/cm/sup 3/. In the optical model analysis of neutron total cross sections we continue to find that orbital angular momentum dependent well depths are required if the spherical optical model is used to describe the neutron-nucleus interaction at low neutron energies.
Date: September 1, 1983
Creator: Winters, R.R.
Partner: UNT Libraries Government Documents Department

Influence of nuclear structure on heavy-ion fusion at subbarrier energies

Description: Measurements of the cross section for fusion of projectiles of /sup 16/O and /sup 40/Ar with isotopes of Sm were made at energies below the fusion barrier. The experimental identification of the evaporation residues proceeds through the off-line detection of x-rays from radioactive product nuclei. Large differences are observed in the thresholds for fusion with vibrational and rotational target nuclei. 18 figures
Date: January 1, 1980
Creator: Stokstad, R.G.
Partner: UNT Libraries Government Documents Department

Entry state distributions of discrete yrast transitions in heavy ion induced fusion reactions

Description: Gamma rays emitted during yrast transitions from compound nuclei are detected with a 4..pi.. multielement gamma ray detector system. Both total pulse height (H) and coincidence fold data (k) are obtained for each event. Results presented include entry state distribution states, k and H projections for some of these distributions, and k and H as a function of spin of the yrast transition. 5 figs. (DWL)
Date: May 28, 1985
Creator: Lee, I.Y.; Baktash, C.; Beene, J.R.; Fewell, M.P.; Halbert, M.L.; Johnson, N.R. et al.
Partner: UNT Libraries Government Documents Department

Few-nucleon transfer reactions on deformed nuclei

Description: Recent developments discussed include: alpha-transfer reactions on deformed nuclei, quasi-elastic neutron transfer reactions induced by /sup 58/Ni beams on spherical and deformed samarium nuclei, and the population of low-lying states in neutron rich nuclei using (particle,..gamma..) or (particle,e) coincidence methods. 37 refs., 10 figs. (LEW)
Date: January 1, 1985
Creator: van den Berg, A.M.
Partner: UNT Libraries Government Documents Department

Neodymium, samarium and europium capture cross-section adjustments based on EBR-II integral measurements

Description: Integral capture measurements were made for highly enriched isotopes of neodymium, samarium, and europium irradiated in a row 8 position of EBR-II with samples located both at mid-plane and in the axial reflector. Broad response, resonance, and threshold dosimeters were included to characterize the neutron spectra at the sample locations. The saturation reaction rates for the rare-earth samples were determined by post-irradiation mass-spectrometric analyses and for the dosimeter materials by the gamma-spectrometric method. The HEDL maximum-likelihood analysis code, FERRET, was used to make a least-squares adjustment of the ENDF/B-IV rare-earth cross sections based on the measured dosimeter and fission-product reaction rates. Preliminary results to date indicate a need for a significant upward adjustment of the capture cross sections for /sup 143/Nd, /sup 145/Nd, /sup 147/Sm, and /sup 148/Sm. 8 figures, 2 tables.
Date: January 1, 1979
Creator: Anderl, R.A.; Harker, Y.D. & Schmittroth, F.
Partner: UNT Libraries Government Documents Department