Dosimetry and Calorimetry Performance of a Scientific CMOS Camera for Environmental Monitoring

This paper explores the prospect of CMOS devices to assay lead in drinking water, using calorimetry. Lead occurs together with traces of radioisotopes, e.g., [Formula: see text] , producing [Formula: see text]-emissions with energies ranging from 10 [Formula: see text] [Formula: see text] to several 100 [Formula: see text] [Formula: see text] when they decay; this range is detectable in silicon sensors. In this paper we test a CMOS camera (Oxford Instruments Neo 5.5) for its general performance as a detector of X-rays and low energy [Formula: see text]-rays and assess its sensitivity relative to the World Health Organization upper limit on lead in drinking water. Energies from 6 [Formula: see text] [Formula: see text] to 60 [Formula: see text] [Formula: see text] are examined. The CMOS camera has a linear energy response over this range and its energy resolution is for the most part slightly better than 2%. The Neo sCMOS is not sensitive to X-rays with energies below [Formula: see text]. The smallest detectable rate is [Formula: see text] [Formula: see text] [Formula: see text] , corresponding to an incident activity on the chip of [Formula: see text] [Formula: see text]. The estimation of the incident activity sensitivity from the detected activity relies on geometric acceptance and the measured efficiency vs. energy. We report the efficiency measurement, which is 0.08(2)% (0.0011(2)%) at [Formula: see text] [Formula: see text] [Formula: see text] ([Formula: see text] [Formula: see text] [Formula: see text]). Taking calorimetric information into account we measure a minimal detectable rate of [Formula: see text] [Formula: see text] [Formula: see text] ([Formula: see text] [Formula: see text] [Formula: see text]) for [Formula: see text] [Formula: see text] [Formula: see text] ([Formula: see text] [Formula: see text] [Formula: see text]) [Formula: see text]-rays, which corresponds to an incident activity of [Formula: see text] [Formula: see text] ([Formula: see text] [Formula: see text]). Toy Monte Carlo and Geant4 simulations agree with these results. These results show this CMOS sensor is well-suited as a [Formula: see text]- and X-ray detector with sensitivity at the few to 100 ppb level for [Formula: see text] in a sample.