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

Abstract

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., 210Pb, producing g-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 g-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 ~10 keV. The smallest detectable rate is 40 ± 3 mHz, corresponding to an incident activity on the chip of 7 ± 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(2)% (0.0011(2)%) at 26.3 keV (59.5 keV). Taking calorimetric information into account we measure a minimal detectable rate of 4 ± 1 mHz (1.5 ± 0.1 mHz) for 26.3 keV (59.5 keV) g-rays, which corresponds to an incident activity of 1.0 ± 0.6 Bq (57 ± 33 Bq). Toy Monte Carlo and Geant4 simulations agree with these results. These results show this CMOS sensor is well-suited as a g- and X-ray detector with sensitivity at the few to 100 ppb level for 210Pb in a sample.

Residential Environment Pollution Monitoring System Based on Cloud Computing and Internet of Things

“…Aguilar-arevalo et al believed that environment monitoring technology in various countries started early and became increasingly mature through advanced scientific and technological means. The whole development process mainly included three important stages of special monitoring of environment pollution accidents, pollution sources, and environment quality [ 11 ]. Saoutieff et al believed that, in the 1950s, after several serious pollution accidents caused by toxic chemical leakage, the developed countries began to analyze collected environment samples by chemical means to determine the composition and content of pollution, assisting the subsequent treatment [ 12 ].…”

Volume reduction of water samples to increase sensitivity for radioassay of lead contamination

“…210 Pb was observed in sample C (which had a reduction factor of 633±4), with a calculated specific activity of 730 ± 150 mBq kg −1 . Using a similar calculation as shown in Aguilar-Arevalo et al (2020b), this specific activity is equal to 2.55 ± 0.58 × 10 −7 ppb. To determine the concentration of stable Pb corresponding to the 210 Pb concentration of sample C, a ratio of 34 ppb of 210 Pb/Pb for rainwater in London was used (Yanga and Appleby 2016).…”

“…3.1.1. This work demonstrates that the volume reduction technique retains >99% of 210 Pb whilst increasing the 210 Pb concentration to a level measurable via calorimetry in Si detectors (Aguilar-Arevalo et al 2020b).…”

“…210 Pb decays via − decay to 210 Bi , with the most probable − decay (84%) resulting in an excited state of 210 Bi , emitting an electron with an average decay energy of 4.16 keV. De-excitation of the nucleus results in the emission of a of 46.5 keV with a 4% yield per decay (Aguilar-Arevalo et al 2020b). This constitutes the low energy band, for which HPGe detectors are optimised, therefore justifying the use of these detectors for the radioassay of the water samples.…”

“…With the aim of developing lowcost, widely available metrology for lead in drinking water, we recently explored the potential of leveraging the precision calorimetry techniques of silicon (Si) detectors. This work demonstrated the capability of identifying Lead-210 210 Pb at the 100 ppb level in a sample (Aguilar-Arevalo et al 2020b), through calorimetry and identification of characteristic gamma energies in a Si detector. While this technique is promising for dosimetry applications, it is not able to reach the WHO level in sensitivity.…”