Precise determination of photon emission probabilities for the main X- and γ-rays of 226Ra in equilibrium with daughters

Within the context of a joint project between VNIIM (D.I. Mendeleyev Institute for Metrology) and LNHB (Laboratoire National Henri Becquerel), special 226Ra sources were prepared by VNIIM in order to determine as accurately as possible the absolute photon emission probabilities for the main X- and γ-rays following the decay of 226Ra and daughters. The main purpose of this work was to supplement a previous joint study by Laboratorio Nacional de Metrologia das Radiaçoes Ionizantes (LNMRI) and LNHB to determine their relative values. Some specific point sources were produced for α-spectrometry measurements that were undertaken at VNIIM and also for γ-ray spectrometry studies at VNIIM and LNHB. The 226Ra activity for the γ-spectrometric sources was measured relative to the α-spectrometric sources by comparing the counts of the main γ-rays. The total uncertainty of the activity for these sources was 0.2% (k=1). Using calibrated germanium detectors, several X- and γ-ray spectra were analyzed to determine the absolute photon emission probabilities of 226Ra in radioactive equilibrium with daughters. The results are presented and compared to other published values.