A Compact Continuous Analyzer of Particulate Matter Radioactivity

We present a microcontroller-based in-flow airborne spectrometer to quantify the presence and activity of radioactive isotopes in particulate matter (PM). It is based on a hollow CsI(Tl) scintillator inside which air flows, thanks to a fan, and PM is captured by a micrometric filter placed in the middle, thus allowing full solid angle capture of gamma rays. The instrument is very compact, fitting in a 10 cm cube and thus being compatible with several unmanned flying vehicles, including an experimental rocket inside which it will be launched as scientific payload to evaluate the robustness of its design during flight. Here we report the mechanical and electronics (for SiPM readout) design, as well as a preliminary characterization. Simulations have allowed to find the optimal compromise in the number and position of SiPMs with an expected energy resolution better than 7% at 662 keV.