A multi-purpose cryogenic test facility for astronomical instrumentation

We present the design, capabilities and applications of a cryogenic test facility for astronomical instrumentation located at ETH Zurich, Switzerland. This facility was designed, built, and commissioned with the purpose to support opto-mechanical performance measurements of cryo-mechanisms for astronomical instruments. In particular, the facility was developed initially to test the opto-mechanical stability and repeatability of the wheel-mechanisms for the ERIS/VLT instrument that are developed in house. However, the facility has a generic application portfolio and can be used for other development projects as well. The unique setup allows optical access from the warm end with short working distance to the cold elements of only a few millimeters. Electrical, mechanical, and liquid feedthroughs provide a flexible infrastructure for a large variety of thermal, mechanical, electrical and optical tests. To provide maximum mechanical stability, the cooling is provided by a low vibration pulse tube cooler that cools the facility down to approximately 8 K.