  Recently CMOS (complementary metal-oxide semiconductor) sensors have
progressed to a point where they may offer improved performance in imaging
x-ray detection compared to the CCDs often used in x-ray satellites. We
demonstrate x-ray detection in the soft x-ray band (250-1700 eV) by a
commercially available back-illuminated Sony IMX290LLR CMOS sensor using the
Advanced Photon Source at the Argonne National Laboratory. While operating the
device at room temperature, we measure energy resolutions (FWHM) of 48 eV at
250 eV and 83 eV at 1700 eV which are comparable to the performance of the
Chandra ACIS and the Suzaku XIS. Furthermore, we demonstrate that the IMX290LLR
can withstand radiation up to 17.1 krad, making it suitable for use on
spacecraft in low earth orbit.
