Absolute calibration of 60Co by using sum-peak method and an HPGe detector

The sum-peak method was applied to calibrate four Co-60 sources in the range of 25-350kBq. An HPGe-based gamma-ray spectroscopy system was used, and the effects of the angular correlation and pulse pile-up were corrected, and are discussed. The correction for the angular correlation was obtained from a theoretical calculation, while the pulse pile-up effect was corrected using a new extrapolation technique based on the pile-up measurements by varying the shaping time of the amplifier. The determined radioactivities were within 2% deviation from the values reported by the supplier and the associated uncertainties were less than 2%. The observed consistency was obtained under the experimental condition of keeping the total counting rate less than or equal to 15 kcps. (C) 2003 Elsevier Science Ltd. All rights reserved.