Categorization of the main techniques of neutron coincidence/multiplicity analysis

Reactor noise analysis and neutron coincidence/multiplicity analysis for safeguards both examine the non‑random clustering of neutrons in time, caused by the simultaneous emission of multiple neutrons from each fission event and by the correlation of successive fissions in the same fission chain. Despite these same physical origins, the various kinds of techniques are not often compared with each other on an intuitive level. This paper makes this comparison, primarily by examining whether a given technique relies on the joint probability of detecting neutrons or on the conditional probability. The techniques are compared in other ways, too, such as how they deal with fission chains. Subtleties are also addressed, such as the time origin of the Rossi‑α diagram and the taking of moments. Specific instruments are not described in detail; the focus is the understanding of the physics and counting principles.