Development of a β-spectrometer using PIPS technology

Various anthropogenic sources contribute to the inventory of long live β-emitters in the environment. Studies have been carried out to obtain the 90Sr distribution in environment in order to estimate its impact in terms of radiation exposure to humans. The Laboratory routinely measures 90Sr by proportional counter after radiochemistry. An incomplete radiochemical separation leads to a deposit submitted to count polluted by natural β-emitters. In order to confirm the result, 90Y (daughter of 90Sr), is extracted from the final radiochemical fraction and counted. The 90Y decreasing (T1/2 = 2.67 days) is checked by successive counts over 64 h. The delay between the end of radiochemistry and the counting is imposed by 15 days to allow radioactive equilibrium between 90Sr and 90Y to be established. In order to remove this delay the purity of the 90Sr fraction source can be verified by β-spectrometry. Thus, a β-spectrometer is under development in collaboration with Canberra Semi-Conductor and Canberra Electronic. It consists in a PIPS detector where several silicon layers are combined. Initial results will be presented in this paper.