Initial evaluation for a combined neutron and gamma ray multiplicity counter

Multiplicity counters for neutron assay have been extensively used in materials control and accountability for nonproliferation and nuclear safeguards. Typically, neutron coincidence counters are utilized in these fields. In this paper we present a measurement system that makes use not only of neutron (n) multiplicity counting but also of gamma ray (γ) multiplicity counting and the combined higher-order multiplets containing both neutrons and gamma rays. The benefit of this approach is in using both particle types available from the sample, leading to a reduction in measurement time when using more measurables. We present measurement results of n, γ, nn, nγ,γγ, nnn, nnγ,nγγ and γγ γ multiplets emitted by a ²⁵²Cf source and a ²³⁹PuBe source. A dual radiation measuring system proposed here could use extra measurables either to improve the statistics when compared to a neutron-only system, or alternatively be used for extended analysis and interpretation of sample parameters. The study presented here provides an answer to the questions regarding the ability to measure both neutron and gamma ray coincidences at once. The results show that the measurements system proposed in this study has a potential to be valuable in the area of nuclear nonproliferation and homeland security.