Calibration of 55Fe activity with a lithium-drifted silicon detector

NMIJ participated in the CCRI (II) key comparison of 55Fe activity measurement. A planar-type Si(Li) detector and a liquid-scintillation counter were used to calibrate the activity. The calibration result obtained by the Si(Li) detector agreed with that obtained by the liquid-scintillation counter using the CIEMAT/NIST method within uncertainty. The result was reported to the BIPM in 2006. The activity of 55Fe was also measured by using a 2π pressurized proportional counter. The result obtained by the 2π pressurized proportional counter agreed with the above results within uncertainty. The measurement by the Si(Li) detector was very simple and its procedure was a combination of conventional methods. The measurement by the liquid-scintillation counter is most popular to calibrate the activity of 55Fe. However the Si(Li) detector is also useful.