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High-Resolution Measurements and Calculations of Photon-Production Cross Sections for 16O(n,x) Reactions Induced by Neutrons with Energies Between 4 and 200 MeV

R. O. Nelson, M. B. Chadwick, A. Michaudon, P. G. Young

Nuclear Science and Engineering / Volume 138 / Number 2 / June 2001 / Pages 105-144

Technical Paper /

Photon-production data from neutron-induced reactions with oxygen are important over a wide range of neutron energies for many applied purposes. The quality of existing data is not sufficient for many applications as evident from the lack of agreement between various data sets, the rather large uncertainties quoted, and the dearth of angular-distribution data. Moreover, measurements of these reactions were rarely made above 15 MeV. To address these data needs, the high-energy pulsed neutron source at the Weapons Neutron Research Facility at the Los Alamos Neutron Science Center was used to measure photon-production data over a wide neutron-energy range. The gamma rays were detected with two high-resolution germanium detectors. Several measurements were made with these detectors at different locations to obtain data at seven angles. Excitation functions and angular-distribution data have been extracted for 24 gamma rays produced in neutron-induced reactions on oxygen. The data are presented and compared with previous measurements and with cross-section calculations. The data reported here are the basis for a new evaluation of neutron-induced reactions with oxygen; furthermore, the photon-production results have been validated through comparison with independent measurements of emitted-neutron spectra in inelastic 16O(n,n') reactions at 14 MeV.

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