Evaluating the GeoSnap 13−μ \mu m cutoff HgCdTe detector for mid−IR ground−based astronomy
October 2023 • 2023AN....34430103L
Abstract • New mid−infrared HgCdTe (MCT) detector arrays developed in collaboration with Teledyne Imaging Sensors (TIS) have paved the way for improved 10−m sensors for space− and ground−based observatories. Building on the successful development of longwave HAWAII−2RGs for space missions such as NEO Surveyor, we characterize the first 13−m GeoSnap detector manufactured to overcome the challenges of high−background rates inherent in ground−based mid−IR astronomy. This test device merges the longwave HgCdTe photosensitive material with Teledyne's GeoSnap−18 (18−m pixel) focal plane module, which is equipped with a capacitive transimpedance amplifier (CTIA) readout circuit paired with an onboard 14−bit analog−to−digital converter (ADC). The final assembly yields a mid−IR detector with high QE, fast readout (>85 Hz), large well depth (>1.2 million electrons), and linear readout. Longwave GeoSnap arrays would ideally be deployed on existing ground−based telescopes as well as the next generation of extremely large telescopes. While employing advanced adaptive optics (AO) along with state−of−the−art diffraction suppression techniques, instruments utilizing these detectors could attain background− and diffraction−limited imaging at inner working angles <10 /D, providing improved contrast−limited performance compared with JWST MIRI while operating at comparable wavelengths. We describe the performance characteristics of the 13−m GeoSnap array operating between 38 45 K, including quantum efficiency, well depth, linearity, gain, dark current, and frequency−dependent () noise profile.
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