The Michigan Infrared Test Thermal ELT N-band (MITTEN) Cryostat

TL;DR

The MITTEN Cryostat is a new facility designed for testing mid-infrared detectors, especially for upcoming large telescopes, by providing a controlled, low-temperature environment to measure detector performance metrics.

Contribution

This paper introduces the MITTEN Cryostat, a novel test facility optimized for characterizing advanced MIR detectors like GeoSnap for ELT applications.

Findings

Cryostat maintains < 40 K temperature.

No measurable background radiation detected.

Capability to measure various detector parameters.

Abstract

We introduce the Michigan Infrared Test Thermal ELT N-band (MITTEN) Cryostat, a new facility for testing infrared detectors with a focus on mid-infrared (MIR) wavelengths (8-13 microns). New generations of large format, deep well, fast readout MIR detectors are now becoming available to the astronomical community. As one example, Teledyne Imaging Sensors (TIS) has introduced a long-wave Mercury-Cadmium-Telluride (MCT) array, GeoSnap, with high quantum efficiency (> 65 %) and improved noise properties compared to previous generation Si:As blocked impurity band (BIB) detectors. GeoSnap promises improved sensitivities, and efficiencies, for future background-limited MIR instruments, in particular with future extremely large telescopes (ELTs). We describe our new test facility suitable for measuring characteristics of these detectors, such as read noise, dark current, linearity, gain, pixel operability, quantum efficiency, and point source imaging performance relative to a background scene, as well as multiple point sources of differing contrast. MITTEN has an internal light source, and soon an accompanying filter wheel and aperture plate, reimaged onto the detector using an Offner relay. The baseline temperature of the cryostat interior is maintained < 40 K and the optical bench maintains a temperature of 16 K using a two-stage pulse-tube cryocooler package from Cryomech. No measurable background radiation from the cryostat interior has yet been detected.