AN INVESTIGATION INTO THE USEFULNESS OF THE ISOCS MATHEMATICAL EFFICIENCY CALIBRATION FOR LARGE RECTANGULAR 3”x5”x16” NAI DETECTORS

Large NaI detectors are commonly used in gamma measurement systems where nuclide identification and quantification is desired. These systems are used to measure people, soil, drums, boxes, animals, and other things. For quantification, an efficiency calibration must be performed, which becomes increasingly difficult as the sources become large and complicated. Mathematical techniques can be quite useful here, if they are easy enough to use, and accurate enough for the application. A series of experiments was performed to show how accurately the efficiency of large (3”x5”x16”) rectangular NaI detectors can be computed with techniques that could be implemented within the commercially available ISOCS mathematical efficiency calibration software. This software assumes that the detector response function is cylindrically symmetric, which certainly isn’t the case here. But, perhaps it is good enough for the applications for which these large rectangular detectors are commonly used.