The demonstrated performance and cost-effectiveness of complementary metal–oxide–semiconductor (CMOS) sensors make them a potentially attractive option for low-cost space-based X-ray observatories. We have previously reported on the performance of a commercially available backside-illuminated Sony IMX290LLR-C CMOS sensor and found it to offer X-ray spectral resolutions comparable to the charged coupled devices (CCDs) aboard Suzaku and Chandra and to have a sufficient radiation hardness for use in low Earth orbit. In this work, we report on the quantum efficiency (QE) of this sensor, an essential metric for modeling the sensitivity of an instrument as an X-ray detector. Using the Advanced Photon Source at Argonne National Laboratory, we measure the soft X-ray QE of this CMOS sensor to be 0.28±0.02 at a photon energy of 490.5 eV. This energy was chosen for its proximity to the astrophysically important O VII triplet emission lines (∼574 eV) studied by the HaloSat mission. Although not surpassing that of the back-illuminated CCDs aboard Suzaku and Chandra, this QE compares favorably to that of the front-illuminated CCDs aboard the same observatories and is competitive with that of the silicon drift detectors used aboard HaloSat, making it a strong candidate for use on future X-ray small satellite (SmallSat) missions.
Commercially manufactured complementary metal–oxide–semiconductor (CMOS) sensors have demonstrated competitive x-ray spectral imaging performance to the charge-coupled devices flown on the Suzaku and Chandra missions without the cooling demands required of these sensors. This performance, in combination with their reduced costs, warrants regarding CMOS sensors as promising candidates for low-Earth orbit (LEO) x-ray small satellites. We investigate the radiation tolerance of these devices to the anticipated total ionizing dose (TID) radiation expected in LEO. We expose a backside-illuminated Sony IMX290LLR CMOS sensor to up to 12 krad of TID from Cs137 gamma-ray radiation. We find an increase in the abundance of noisy pixels with increasing dosage, but no discernible increase in the average dark signal or RMS noise. Measurements of the x-ray spectrum from a Fe55 source indicate no change in spectral resolution and only minor gain degradation with TID.
Complementary metal–oxide–semiconductor (CMOS) sensors may offer improved performance compared to the charge-coupled devices common in X-ray satellites. We demonstrate x-ray detection in the soft x-ray band (250 to 1700 eV) by a commercially available back-illuminated CMOS sensor using the Advanced Photon Source at Argonne National Laboratory. While operating the device at room temperature, we measure energy resolutions (FWHM) of 48 eV at 250 eV and of 83 eV at 1700 eV, which are comparable to the performance of the CCD on Chandra and Suzaku.
Recently, complementary metal–oxide–semiconductor (CMOS) sensors have progressed to a point where they may offer improved performance in imaging x-ray detection compared to the charge-coupled devices often used in x-ray satellites. We demonstrate x-ray detection in the soft x-ray band (250 to 1700 eV) by a commercially available back-illuminated Sony IMX290LLR CMOS sensor using the Advanced Photon Source at Argonne National Laboratory. While operating the device at room temperature, we measure energy resolutions (full width at half maximum) of 48 eV at 250 eV and of 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.
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