Fast Neutron Cross Sections Of Oxygen And Nitrogen

Results of research toward measuring the neutron cross sections for nitrogen and oxygen in the neutron energy range from 4 to 12 Mev are presented. New techniques for the use of low-yield and multiple-group neutron source reactions, which were developed to perform these measurements, are shown, along with additional data obtained for the neutron source reactions Be-9 (alpha, n)C-12 and N-15 (d, n)O-16. In addition to the N-14(n, d sub O)C-13 reaction measurements, the C-13 (d, n)N-14 reaction was investigated to provide additional deuteron stripping data for evaluating the spins and parities of the lowlying states of N-14, and to provide additional information on the reaction mechanism for deuteron induced reactions. Measurements and results are given for the differential elastic, total, and nonelastic neutron cross sections for nitrogen and oxygen at several neutron energies. (Author).

Neutron cross sections for nitrogen and oxygen that are of primary interest in shielding and transport calculations are compiled in this report. Cross sections for the following processes are compiled for both oxygen and nitrogen: total, elastic scattering, nonelastic collisions, inelastic scattering, differential elastic scattering, (n, alpha) reactions, (n, p) reaction, and (n, d) reaction. The following cross sections are compiled for nitrogen only: gamma-ray production, (n, t) reaction, (n,2n) reaction, and (n,2 alpha) reaction. Cross sec tions of nitrogen for excitation of the various levels of the residual nucleus in the (n, alpha j), and (n, n'j) reactions are also compiled.thor).

Neutron cross-section sets were prepared for N, O, Al, Si, Fe, D, and Be for neutron energies from 0.037 eV to 18 MeV. The cross sections tabulated include the total, elastic, inelastic, (n,2n), and cross sections for charged particle emission. Information is also given on the angular distribution of elastically scattered neutrons and on the energy distribution of neutrons and gamma-rays following nonelastic reactions. (Author).

Absolute differential cross sections for the elastic scattering of neutrons in the angular range from 2.5 degrees to 16 degrees have been determined for nitrogen at neutron energies of 7.65, 7.88, 8.11, 10.95, and 14.00 MeV and for oxygen at neutron energies of 10.25, 10.75, 10.95, 11.25 and 14.10 MeV. The measured cross sections are in good agreement with the most recent evaluations by Young and Foster except for oxygen around 11 MeV where the measured differential cross sections are significantly lower than the evaluated ones.