Measuring the Soft X-Ray Quantum Efficiency of a Hybrid CMOS Detector

Abstract

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 Xray 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. In this work, 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 Kα/Kβ energies (5.90/6.49 keV), 98.3 ± 1.9% at the Al Kα energy (1.49 keV), 85.6 ± 2.8% at the O Kα energy (0.52 keV), and 61.3 ± 1.1% at the C Kα 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.