V. Thomas¹ , O. Delaune¹ , S. Topin¹

¹CEA/DAM Ile de France

Abstract:

An ultra-compact lightweight unshielded spectrometer for detection and analysis of atmospheric radioxenons has been developped. This system works at ambient temperature and has a 58 cm3 inner active volume. Atmospheric radioxenon activities are determined with beta/gamma coincidence technique using both NaI(Tl) detectors and large pixellized Si-PIN detectors. The concept of this detection system, especially the gas cell, is partially inspired by the PIPSBox detector integrated into the SPALAX-NG (SPALAX New Generation). Carbon window suppression allows to operate over atmospheric pressure (~2 bar) in order to enhance the detection sensivity at the price of a slight decrease of the energy resolution. The performances of the detection system in terms of Minimal Detectable Activities are below 20 mBq (12h acquisition, unshielded), for all radioxenon of interest (131m-Xe,133-Xe,133m-Xe and 135-Xe). Coupled with the SPALAX-NG gas enrichment system, Minimal Detectable Concentrations of this spectrometer are lower than 1 mBq/m3 for the four radioxenon of interest (12h acquisition, 60 m3 sampled volume). This new system and its performances will be presented.