Dosimetry and calorimetry performance of a scientific CMOS camera for environmental monitoring

• Main Authors: Aguilar-Arevalo, Alexis, Bertou, Xavier, Canet, Carles, Cruz-Perez, Miguel Angel, Deisting, Alexander, Dias, Adriana, D'Olivo, Juan Carlos, Favela-Perez, Francisco, Garces, Estela A, Munoz, Adiv Gonzalez, Guerra-Pulido, Jaime Octavio, Mancera-Alejandrez, Javier, Marin-Lambarri, Daniel Jose, Montero, Mauricio Martinez, Monroe, Jocelyn, Paling, Sean, Peeters, Simon J. M, Scovell, Paul, Turkoglu, Cenk, Vazquez-Jauregui, Eric, Walding, Joseph
• Format: Journal Article
• Language: English
• Published: 23.09.2020
• Subjects: Physics - Applied Physics; Physics - Instrumentation and Detectors
• DOI: 10.48550/arxiv.2009.11227

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. Lead-210, producing $\gamma$-emissions with energies ranging from 10 keV to several 100 keV 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 $\gamma$-rays and assess its sensitivity relative to the World Health Organization upper limit on lead in drinking water. Energies from 6 keV to 60 keV 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 $\sim\!\!10 keV$. The smallest detectable rate is 40$\pm$3 mHz, corresponding to an incident activity on the chip of 7$\pm$4 Bq. The estimation of the incident activity sensitivity from the detected activity relies on geometric acceptance and the measured efficiency vs. energy. We report the efficiency measurement, which is 0.08$\pm$0.02 % (0.0011$\pm$0.0002 %) at 26.3 keV (59.5 keV). Taking calorimetric information into account we measure a minimal detectable rate of 4$\pm$1 mHz (1.5$\pm$0.1 mHz) for 26.3 keV (59.5 keV) $\gamma$-rays, which corresponds to an incident activity of 1.0$\pm$0.6 Bq (57$\pm$33 Bq). Toy Monte Carlo and Geant4 simulations agree with these results. These results show this CMOS sensor is well-suited as a $\gamma$- and x-ray detector with sensitivity at the few to 100 ppb level for Lead-210 in a sample.