Measuring the soft x-ray quantum efficiency of a hybrid CMOS detector

Next-generation x-ray observatories, such as the Lynx X-ray Observatory Mission Concept or other similar concepts in the coming decade, will require detectors with high quantum efficiency (QE) across the soft x-ray band to observe the faint objects that drive their mission science objectives. Hybrid CMOS detectors (HCDs), a form of active-pixel sensor, are promising candidates for use on these missions because of their fast read-out, low power consumption, and intrinsic radiation hardness. We present QE measurements of a Teledyne H2RG HCD, performed using a gas-flow proportional counter as a reference detector. We find that this detector achieves high QE across the soft x-ray band, with an effective QE of 94.6 +/- 1.1% at the Mn K alpha/K beta energies (5.90/6.49 keV), 98.3 +/- 1.9% at the Al K alpha energy (1.49 keV), 85.6 +/- 2.8% at the O K alpha energy (0.52 keV), and 61.3 +/- 1.1% at the C K alpha energy (0.28 keV). These values are in good agreement with our model, based on the absorption of detector layers. We find similar results in a more restrictive analysis considering only high-quality events, with only somewhat reduced QE at lower energies. (C) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 International License.