Identification of background isotopes to reduce false-positives in active interrogation systems

Active interrogation systems must overcome the problem of interfering signals due to the activation and decay of environmental background isotopes. Identifying specific reactions that cause conflicting signatures allows for the filtering of such signals and reducing the probability of false-positives; however, investigations by computational modeling to this level of depth is often limited by time, computer resources and insufficient cross section data. By filtering cross section data from existing nuclear data libraries, it is possible to identify, filter, and thus reduce such signals. Several reactions were identified that have significant probabilities of interaction that can cause background interference, including ¹⁸O(γ,P)¹⁷Nand ²⁸Si(γ,N)²⁷Si, which each have high gamma decay energies or delayed neutron emissions (¹⁷N) and decay on a time scale of several seconds, similar to signatures of target materials of interest.