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., , producing -emissions with energies ranging from 10 to several 100 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 -rays and assess its sensitivity relative to the World Health Organization upper limit on lead in drinking water. Energies from 6 to 60 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 . The smallest detectable rate is , corresponding to an incident activity on the chip of . 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 ( ). Taking calorimetric information into account we measure a minimal detectable rate of ( ) for ( ) -rays, which corresponds to an incident activity of ( ). Toy Monte Carlo and Geant4 simulations agree with these results. These results show this CMOS sensor is well-suited as a - and X-ray detector with sensitivity at the few to 100 ppb level for in a sample.
Highlights
Ingesting lead can have acute and chronic health effects and it is especially harmful to infants and children
For this paper we study a CMOS sensor, which has been designed for imaging optical wavelengths
We examine the general performance of the Neo sCMOS when exposed to X-rays and γ-rays
Summary
Ingesting lead can have acute and chronic health effects and it is especially harmful to infants and children. There is no safe threshold for the onset of lead’s negative effects on the human condition and damages are permanent—for example, a child loses three IQ points on average when it consumes as much lead as 25 μg kg−1 body weight per week over a longer period [1]. It is estimated that globally million people in low- and middle-income countries are at risk of lead exposure [2] as for example, people living in rural areas in Mexico [3]. The main source of lead pollution is from improper recycling of lead-acid batteries. The trend towards clean technologies, such as electric cars, will likely increase the demand on lead-acid battery recycling, the corresponding pollution can be expected to increase
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