Measuring the Quantum Efficiency of X-Ray Hybrid CMOS Detectors

Next-generation X-ray observatories, such as the Lynx X-ray Observatory Mission Concept, will require detectors with high quantum efficiency (QE) across the soft X-ray band to observe the faint objects that drive their mission science cases. Hybrid CMOS Detectors (HCDs), a form of active-pixel sensor, are promising candidates for use on these missions because of their faster read-out, lower power consumption, and greater radiation hardness than detectors used in the current generation of X-ray telescopes. In this work, we present QE measurements of a Teledyne H2RG HCD. These measurements were performed using a gas-flow proportional counter as a reference detector to measure the absolute flux incident on the HCD. We find an effective QE of $95.0 \pm 1.1\%$ at the Mn K$\alpha$/K$\beta$ lines (at 5.9 and 6.5 keV), $98.5 \pm 1.8\%$ at the Al K$\alpha$ line (1.5 keV), and $85.0 \pm 2.8\%$ at the O K$\alpha$ line (0.52 keV).