True coincidence-summing corrections for the coincident γ-rays measured with coplanar grid CdZnTe detectors

In this study, true coincidence-summing (TCS) correction factors have been measured for the sources 22Na, 60Co, 133Ba and 152Eu by use of three large volume coplanar grid CdZnTe (acronym: CZT) detectors. In case of a close-in detection geometry, two different TCS calculation algorithms were used to compute the required TCS correction factors. Both of the algorithms are based on the measured total-to-peak (TTP) ratio and full-energy peak (FEP) efficiency values that were obtained using almost “single” energy and coincidence-free nuclides. The results for TCS correction factors obtained by two different algorithms were agreeable to each other. The obtained TCS factors were ranged from about 7% to 30.5% in a 2250 mm3 CZT detector when a close counting geometry was used. For other two detectors with a volume of 1000 and 1687.5 mm3, the resulted TCS correction factors were relatively smaller and varied between about 0.1% and 20% at the close counting geometry condition. Therefore, the results indicate that there is a need for the estimation of TCS corrections in CZT detectors, especially when their crystal volumes are greater than 1 cm3 and these detectors are used in the case of a close-in detection geometry.