Standardization of 152Eu and 88Y.

The activities of 152Eu and 88Y have been measured by the digital coincidence counting (DCC) technique and compared with those of the conventional coincidence counting technique. In the DCC, the pulse amplitudes from both beta and gamma channels are digitized in commercial ADCs and the pulse input times are simultaneously determined by 10 MHz oscillation clock installed in the coincidence module. The activity of the measured source is determined from the information of pulse height and input time for each pulse by off-line analysis. The activity of 152Eu was determined from extrapolations of efficiency functions obtained at 3gamma gates and the result showed a good agreement with that of the conventional method with 0.2% of uncertainty. The activity of 88Y was also determined by the DCC technique, and the reliability of the result was proved through Asia Pacific Metrology Program (APMP) inter-comparison of 88Y.