Analysis of the National Nuclear Array Performance for the Primary Standardisation of 88Y using γ - γ Coincidence Counting Technique

Abstract

The updated version of the National Nuclear Array (NANA) γ-ray spectrometer, consisting of 12 CeBr3 scintillator detectors, was analysed and utilised to determine the absolute activity of 88Y source through applying γ - γ coincidence counting technique which is one of the absolute standardisation techniques. Experimental data were analysed and compared with the Monte Carlo simulations for the detector response. Through measuring 60Co source the absolute FEP efficiency was 0.069 ± 0.010% at 1.33 MeV, and by analysing 152Eu source there was a good agreement between the experimental and simulation findings. The absolute standardisation of radionuclides is one of the core missions of National Metrology Institutes, such as National Physical Laboratory NPL. The activity of the 88Y source was determined to be 111.9 ± 0.4 kBq via an independent measurement using ionisation chamber with a calibration coefficient obtained from a primary standardisation. This compared with the activity value obtained using the γ - γ coincidence counting method of 114.1 ± 2.7 kBq. The γ - γ coincidence counting method was based on the 898.05 and 1836.1 keV gamma cascade which directly follows the beta decay of 88Y. The final activity value was determined after applying a correction for the angular correlation assuming a spin/parity cascade of 3- → 2+ (898.05 keV) followed by 2+ → 0+ pure E2 transition of the 88Sr.