Comparison of the precision and accuracy of digital versus analogue gamma-ray spectrometric systems used in INAA for evaluation of homogeneity and certification of reference materials of the IAEA

Performance of three commercial gamma-ray spectrometric systems was evaluat ed for precision and accuracy prior to use in characterization of reference materials. Two of the systems were based on fast processing of the analogu e signal from the amplifier (EGG Ortec model 672) using a toss free countin g module (Canberra model LFC 599) interfaced to one of two analog-to-digita l converters (Canberra models 8713 or 8715). The third system was based on a digital signal processor (Canberra model DSP 9660). Performance of the sy stems was tested over a range of count rates up to a maximum of 70,000 coun ts per second (dead time up to 90%) using Co-60 and Cs-137 sources. Best re solution was achieved with an analogue system with ADC 8713. The analytical results obtained with the digital system show the lowest and well-quantifi ed uncertainty.