First measurement of 222Rn activity with a CMOS active pixel sensor

Development of an integrated CMOS detector for radon activity measurement and neutron dosimetry

“…For this volumic activity A v , the measured surface counting rate (in a fully passive counting mode, e.g., without forced air circulation) is A s = 6.57 ± 0.40 α/h (figure 2). This reproducible figure, already twenty times higher than the previously published one [2], will be enhanced again with the next AlphaRad chip (with an active area of 0.5 cm 2 per chip). We define hereafter a Conversion factor to Volumic Activity (labelled F) through the relationship A v = F · A s .…”

“…The first application to dosimetry was performed with a true CMOS pixel sensor [2], leading to the development of a dedicated chip: the AlphaRad chip is manufactured with a 14 µm thick epitaxial layer on a standard silicon substrate, allowing efficient detection of all charged particles able to cross the SiO 2 passivation layer (6 µm thick). Charge collection is obtained by pure diffusion of carriers (in less than 500 ns) followed by detection on an array of micro-diodes distant of 80 µm.…”

“…The 222 Rn gas, injected from a standard 226 Ra source, has a mean activity of A v = 1100 Bq/m 3 (typical indoor critical level). As no filtration of the daughter elements of Rn is performed, the detected alpha activity is the sum of three emitters, 222 Rn plus the two shortlived 218 Po and 214 Po [2]. For this volumic activity A v , the measured surface counting rate (in a fully passive counting mode, e.g., without forced air circulation) is A s = 6.57 ± 0.40 α/h (figure 2).…”

“…Devoted especially to these applications, a new system-on-chip in 0.6 micron CMOS technology has also been designed at the IPHC. The AlphaRad chip [2], with an active area of 5 × 5 mm 2 and working up to 300 kHz, shows nearly 100% efficiency with alpha emitting sources and a remarkably high counting rate of 1.2 MBq/cm 2 . Both chips are used at room temperature.…”

R&D métrologie des rayonnements ionisants à l’IPHC : de l’application des détecteurs visuels aux mesures environnementales

“…Ce projet consiste à concevoir des capteurs CMOS pour la détection des neutrons et des particules alpha, pour en faire des dosimètres portatifs, notamment pour les mesures en continu de l'activité volumique du radon dans l'environnement atmosphérique. Des capteurs CMOS ont déjà été soumis à des tests de détection de particules α du radon et descendants (Nachab et al, 2004b ;Nourreddine et al, 2005 ;Husson et al, 2006) à l'aide d'une chaîne d'acquisition conçue pour cette application. Un nouveau dispositif pour la dosimétrie neutron multiplage est en cours de réalisation.…”