Gamma-ray irradiation tests of CMOS sensors used in imaging techniques

Abstract

Technologically-enhanced electronic image sensors are used in various fields as diagnostic techniques in medicine or space applications. In the latter case the devices can be exposed to intense radiation fluxes over time which may impair the functioning of the same equipment. In this paper we report the results of gamma-ray irradiation tests on CMOS image sensors simulating the space radiation over a long time period. Gamma-ray irradiation tests were car ried out by means of IGS-3 gamma irradiation facility of Palermo Uni ver sity, based on 60Co sources with dif fer ent ac tiv i ties. To re duce the dose rate and re al ize a nar row gamma-ray beam, a lead-collimation sys tem was pur posely built. It per - mits to have dose rate val ues less than 10 mGy/s and to ir ra di ate CMOS Im age Sen sors dur ing op er a tion. The to tal ion iz ing dose to CMOS im age sen sors was mon i tored in-situ, dur ing ir - ra di a tion, up to 1000 Gy and im ages were ac quired ev ery 25 Gy. At the end of the tests, the sen sors con tin ued to op er ate de spite a back ground noise and some pix els were com pletely sat u rated. These ef fects, how ever, in volve iso lated pix els and there - fore, should not af fect the im age qual ity.