Correlation effect in activity measurement of 59Fe

Correlation effects due to the cascade transition of gamma-rays with gates on the relevant peaks have been studied in activity measurement of 59Fe using the bi-dimensional coincidence counting method. Extrapolation curves were obtained at three gamma gates of 1099.2 keV, 1291.6 keV, and that covering both photo-peaks by a computer discrimination method. Of these extrapolation curves, only that obtained at (950–1350) keV gamma gate shows a linear variation, but those of two single gamma gates are not linearly varied in the high efficiency region. This non-linearity obtained at the gamma gate of 1099.2 keV photo-peak was caused by the correlation effects due to 1–3 coincidence relation via unobserved 192 keV gamma-ray transitions.