Development of cryogenic detectors for radioactivity metrology

Low temperature detectors are expected to improve radioactivity measurements as they offer two major advantages compared to classical semiconductor detectors: excellent energy resolution (10 eV for 6 keV X-rays) and 100% detection efficiency for low energy X-rays (i.e. 1–10 keV). The main difficulties encountered in the development of such detectors are their high sensitivity to electromagnetic noise and acoustic vibrations. These difficulties are due to the low energy threshold and the very low temperature required to perform those devices (typically 50 mK). An inverted 3He/4He dilution refrigerator has been characterized for the development of these detectors for radioactivity metrology applications. Temperature, thermal stability and noise analysis are presented. An energy spectrum was obtained with a sapphire bolometer for the first time in our laboratory.