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

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 n1 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 n1 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.