Gamma spectroscopy with automated efficiency optimization for nuclear safeguards applications

In all applications of gamma-ray spectroscopy, one of the important parts of the data analysis is to measure the detection efficiency which depends on the geometrical conditions of the source-detector arrangement. As the samples commonly measured can vary greatly in volume and shape, it is impractical to manufacture standard sources for large and complex measurement items and packaging's for the purpose of efficiency calibration. Canberra Industries developed the mathematical efficiency software called In Situ Object Calibration Software (ISOCS) to overcome the difficulties presented above. Recently, Canberra has extended the capability of ISOCS and has developed a software package for the International Atomic Energy Agency (IAEA) that simplifies, automates, and optimizes mathematical efficiency analysis for a given set of experimental parameters. The new optimization software called the 'Advanced-ISOCS' varies the 'not well known' parameters of the source geometry within user specified intervals and determines the optimal efficiency. The efficiency optimization capability is carried out using either a random search based on standard probability distributions or using numerical technique that carry out more directed search. The radionuclide mass is determined using the optimum efficiency and compared against the known mass. Results of optimizations carried out using the numerical technique are presented in this paper.