The absolute counting of 166mHo, 58Co and 88Y

In this study, absolute 4πβ–γ-coincidence counting was used to measure the mass activity of 166mHo, 58Co and 88Y. For 166mHo and 88Y, three gamma windows were set to study the systematic error caused by the different gamma window settings. To eliminate the effect arising from the large difference in counting efficiency of the 4πβ counter between electron capture events and β+ particles, the two-dimensional extrapolation method was used to measure 58Co. The measurement results for the three nuclides were linked with the BIPM SIR through two APMP regional comparisons, APMP.RI(II)-K2. Ho-166m and APMP.RI(II)K2. Co-58, Y-88. Results are presented.