Active Fast Neutron Multiplicity Counting with DT Neutron Generator

The active fast neutron multiplicity counting (AFNMC) apparatus was consisted of an array with 36 pieces of liquid scintillator detectors in three rings cylindrical layout, multi-modules 500M14bit digitizers based on PXIe platform, the DT neutron generator, shielding cone and mechanical structure. Its center cavity was 35 cm in radius and 50 cm in height for assaying the standard container of plutonium item. The DT neutron generator was the type of alpha-associated to make the neutron injecting into the assay area being tagged and located on the bottom of detector array. The shielding cone was fixed between the DT generator and the lower ring detector with a hole to let the tagged neutron injecting to the sample assay area. The alpha signal was used as gating signal when doing neutron mutiplicity analysis. The experiments were performed with iron, lead, HEU metal in standard container for technical verification. The SDT values from both conventional and gating FNMC were obtained for comparison. The experimental results indicated this method dramatically reduced the random or non-correlated neutron signal noise and substantially promoted the D and T values sensitivity when the alpha signal gating was enabled.