Determining the “doubles” count rate for AmLi sources

A simple calculation model for AmLi neutron sources is considered: the primary neutrons from Li ( α , n ) reaction are assumed to be randomly emitted from the centre of a spherical source, and to induce the time-correlated secondary neutrons via fission process. The effect of Am 241 (n, fission) was calculated and found to be very small. However, it largely contributes to the “doubles” count rate of AmLi determined by neutron counting technique.