  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 to 20 degree at high gain mode (7.5 times),
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*10^10 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 degree. However, after the exposure the dark
current has increased by hundreds of times, and for every 20 degree 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 4k * 4k 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 degree. 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 degree, 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.
