Radiation effects on scientific CMOS sensors for X-ray astronomy: I. Proton irradiation

Complementary metal-oxide-semiconductor (CMOS) sensors are a competitive choice for future X-ray astronomy missions. Typically, CMOS sensors on space astronomical telescopes are exposed to a high dose of irradiation. We investigate the impact of irradiation on the performance of two scientific CMOS (sCMOS) sensors between -^{30 °} C and 20 ^° C at high gain mode (7.5 × ), including the bias map, readout noise, dark current, conversion gain, and energy resolution. The two sensors are irradiated with 50 MeV protons with a total dose of 5.3 × 10¹⁰ p · cm ^{- 2}. After the exposure, the bias map, readout noise, and conversion gain at various temperatures are not significantly degraded, nor is the energy resolution at -^{30 °} C. However, after the exposure the dark current has increased by hundreds of times, and for every ^{20 °} C increase in temperature, the dark current also increases by an order of magnitude. Therefore, at room temperature, the fluctuations of the dark currents dominate the noise and lead to a serious degradation of the energy resolution. Moreover, among the 4 k × 4 k pixels, there are about 100 pixels whose bias at 50 ms has changed by more than 10 DN ( ∼ 18 e ^- ), and about 10 pixels whose readout noise has increased by over 15 e ^- at -^{30 °} C. Fortunately, the influence of the dark current can be reduced by decreasing the integration time, and the degraded pixels can be masked by regular analysis of the dark images. Some future X-ray missions will likely operate at -30 ^° C, under which the dark current is too small to significantly affect the X-ray performance. Our investigations show the high tolerance of the sCMOS sensors for proton radiation and prove their suitability for X-ray astronomy applications.