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Low-vibration high-cooling power 2-stage cryocoolers for ground-based astronomical instrumentation

This paper describes the outcome of a survey reviewing commercially available state-of-the-art high-cooling power 2- stage cryocooler systems for a potential use in powerful scientific instruments for ground-based astronomy. We present the development of a dedicated test-bed as well as vibration and performance measurements on different 2-stage refrigerator systems. As a result of this investigation program, one system was selected as ESO's new standard 20 K closed cycle cooler offering substantial advantages in flexibility and orientation insensitivity along with best compromise for a low vibration device with high cooling power. The new cryocooler type was integrated with VLT instrumentation. A concept for a comprehensive vibration test program at VLT is presented in order to define admissible vibration spectra for future instrumentation.