Efficiency Optimization Employing Random and Smart Search Using Multiple Counts and Line Activity Consistency Benchmarks - 11398

The ISOCS mathematical method developed by Canberra Industries is a well established technique for computing High Purity Germanium (HPGe) detector efficiencies for a wide variety of source shapes and sizes. In the ISOCS method, the user inputs the source dimensions, matrix composition and density, along with the source-to-detector distance. In many applications, the source dimensions, the matrix material and density may not be well known. Under such circumstances, the efficiencies may not be very accurate since the modeled source geometry may not be very representative of the measured geometry. Canberra is developing a customized efficiency optimization software, which is an extension of the ISOCS, known as “Advanced ISOCS” that varies the uncertain parameters and determines the optimal efficiency shape and magnitude based on available benchmarks in the measured spectra. The benchmarks could be results from isotopic codes such as MGAU, MGA, or FRAM, activities from multi-line nuclides, and multiple counts of the same item taken in different geometries (from the side, bottom, top etc). The efficiency optimization is carried out using either a random search based on standard probability distributions, or using numerical techniques that carry out a more directed (smart) search. Measurements were carried out using representative source geometries and radionuclide distributions. Benchmark data from multiple geometry counts of the same item, and activities from multi-line nuclides was used in efficiency optimization. Results of optimizations carried out using the random search method are presented in this paper. The radionuclide activities were determined using the optimized efficiency and compared against the true activities.