Coincidence–based High-resolution Analysis for On–site–inspection Spectrometry (CHAOS) development

Abstract A ruggedised, γ – γ based system for in–field, real–time measurements of environmental samples has been developed. This is specifically designed to enable measurement restrictions (if required), such that it can support On Site Inspection (OSI) activities envisaged under the Comprehensive Nuclear–Test–Ban Treaty. In restricted mode, only the 17 OSI relevant radionuclides are measured, with zero information recorded regarding other radionuclides. All data acquisition, analysis, and reporting is automated, and implemented within a CAEN S.p.A. HEXAGON dual–input Multi–Channel Analyser (MCA). Multiple analysis streams are utilised, including traditional analysis for each detector channel and coincidence analysis based upon real–time sorting of time–stamped, list–mode events stored in the buffer of the MCA. This multi–faceted approach allows for far greater confidence in the reported results, as all data streams report fully quantified radionuclide activities and uncertainties. Outputs are also configurable, ranging from fully analysed histograms to a simple yes/no traffic light system to denote the presence or absence of a relevant radionuclide.