Coincidence counting of I-129; some remarks on the efficiency extrapolation technique in coincidence counting; a determination of the efficiency of a methane 4π-counter to 32 keV photons

Several methods of coincidence counting of 129I are examined. Efficiency functions are estimated for these different methods and compared with the results of experiments leading to the indication of the most suitable conditions of measurements. It was also found that the γ-efficiency of the 4πβ methane flow counter for photons near 32 keV was 0.024 +- 0.005. Finally some general remarks are made on the extrapolation technique as used for coincidence counting. (author)