Gamma Radiation from Inelastic Scattering of 14-Mev Neutrons by the Common Earth Elements

Abstract

Gamma rays in the energy range 2 to 11 Mev produced by inelastic scattering of 14-Mev neutrons by nine elements were measured at a mean angle of 90 deg. Excluding carbon and oxygen, the maximum energy gamma rays varied from about 8 Mev for phosphorus to about 10.5 Mev for magnesium and 11 Mev for silicon. Resolved gamma rays were observed from carbon (4.43 Mev), oxygen (6.1 and 7 Mev), silicon (1.78 Mev), aluminum (2.2 Mev), phosphorus (2.2 Mev), sulfur (2.2 Mev), and calcium (3.7 Mev). In the energy range 4–6 Mev there are indications of individual gamma rays in silicon; no resolved gamma-ray peaks above 2 Mev were observed for iron and magnesium. Except for carbon and oxygen, the intensity of gamma rays decreases with increase in energy and varies from about 3 to 9 times higher at 2–3 Mev than at 5–6 Mev. Gamma-ray production cross sections are given for each element, relative to the known cross section for carbon. The ratio of the integrated cross section for gamma-ray production above 2 Mev to the nonelastic neutron cross section varies from 0.59 for sulfur to 0.99 for iron.