A Study of the Gamma-Rays Associated with the Inelastic Scattering of Neutrons

Abstract

An experimental spectrometer, capable of measuring differential cross-sections for production of gamma-rays from neutron inelastic scattering, was available at the start of the project. 14 MeV neutrons were produced by the T(d,n)He4 reaction. The gamma-rays were detected by a heavily shielded NaI scintillator. Time of flight discrimination, using the associated particle technique, was used to eliminate background due to scattered neutrons. The performance of this system was improved, by achieving better time and energy resolution, resulting in an increase in sensitivity of the system by a factor of 10. The new system was then used to measure the differential cross sections for production of the 1:37 MeV gamma-ray from Mp24the 1°43 MeV gamma-ray from cr52, and the 0°84 MeV gamma-ray from Fe56, in the range of scattering angle 0° to 90°. The direct interaction theory, in the form of the coupled channels approximation, was used to predict these angular distributions. The programme INCH, written by A. D. Hill of Oxford, was used in this work. This programme predicts the neutron elastic and inelastic scattering differential cross-sections, and was modified by the addition of a subroutine GAMMA, to calculate the gamma-ray angular distributions. This was done by finding the correlation function between gamma-rays and scattered neutrons, and averaging over the neutron scattering angle. The theoretical predictions were then compared with the experimental results.