Materia Oscura: Instrumentation Development to Observe the Invisible

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This project aims to draw on an area of expertise supported by the STFC core science programme, ultra-precise radioactivity measurement and calorimetry developed for dark matter and neutrino physics, and develop application of these techniques to the problem of measuring lead contamination in water and food.The motivation for growing capacity for and developing new lead measurement techniques is that lead pollution is the #1 cause of loss of life expectancy in the world, and currently 2 of the top 10 worst pollution problems in the world are associated with lead [PureEarth2016]. This is a problem both in LMICs and in high income countries- recent examples like the Flint, Michigan, USA, water safety breaches demonstrate that water quality in violation of WHO guidelines can happen anywhere, and information about water quality, and its variation in time, is not widespread. Even 'clean' techologies, like electric cars, employ traditional lead-based batteries; the disposal of these batteries is a leading contributor to lead pollution, particularly in LMICs.The work in this proposal aims to make lead water contamination measurements accessible to anyone with a mobile phone. Currently, such measurements require expensive, specialized equipment or 6-month measurements to reach relevant sensitivity levels for human health- even 0.1 parts per million contamination with lead produces devastating biological impacts. Developing mobile-phone assay capability makes widely-distributed metrology and real-time, crowd-sourced monitoring possible, and therefore would have transformative impact on the public health problems associated with lead pollution. While mobile-phone based radioassay has been prototyped for higher-energy and higher-rate radioactive decays, nothing exists currently to assay lead. Reaching the sensitivity levels required for lead is an incredibly challenging problem, which we propose to address by leveraging the precision calorimetry techniques in silicon (Si) detectors developed by the DAMIC and DMTPC dark matter experiments, together with the lead assay coincidence methodology developed by the DEAP-3600 dark matter experiment that gives a factor of up to 10,000 in background suppression beyond conventional techniques. Our ultimate goal is to to develop a mobile phone application to measure the presence of lead in water samples. The app will employ the phone Si sensor (the camera) to perform radio-assay, with the goal of reaching the 10 parts per billion (ppb) sensitivity level, which is the World Health Organization limit on lead contamination in drinking water.