Activity determination of 67Ga using 4πβ‒γ coincidence counting

The activity of a 67Ga solution was measured by means of the 4πβ-γ coincidence counting technique. A setup with a proportional counter and non-extending dead-time modules in the two detector channels was used. The influence of the delayed state affecting the measured count rates was taken into account by using appropriate correction formulae. The analysis requires a variation of the dead time and a subsequent extrapolation to infinite dead time. An uncertainty of about 0.5% was obtained and the result was used to make an intercomparison with the SIR of the BIPM.