The experimental determination of the fraction of neutrons below 1.5 MeV for the Chinese-made Am–Be neutron source

Abstract A practical method for experimentally determining the fraction of neutrons below 1.5 MeV for the Am–Be neutron source is described. The partial neutron spectrum (the n 1 group) was measured by time-of-flight accompanied with the 4.438-MeV gamma ray. The fraction of neutrons below 1.5 MeV was derived from the 4.438-MeV gamma ray to total neutron ratio and the ratio of the area of the n 1 group spectrum to the measured total spectrum above 1.5 MeV normalized at the peak near 3.2 MeV. The fraction of neutrons with energies below 1.5 MeV amounts to (19.1±1.9)% for the Chinese-made Am–Be neutron source.