Sorption-based vibration-free coolerfor the METIS instrument on E-ELT

摘要

METIS is the 'Mid-infrared ELT Imager and Spectrograph' for the European Extremely Large Telescope. This E-ELTinstrument will cover the thermal/mid-infrared wavelength range from 3 to 14 μm and will require cryogenic cooling ofdetectors and optics. We present a vibration-free cooling technology for this instrument based on sorption coolersdeveloped at the University of Twente in collaboration with Dutch Space. In the baseline design, the instrument has fourtemperature levels: N-band: detector at 8 K and optics at 25 K; L/M-band: detector at 40K and optics at 77 K. The lattertemperature is established by a liquid nitrogen supply with adequate cooling power. The cooling powers required at thelower three levels are 0.4 W, 1.1 W, and 1.4 W, respectively. The cryogenic cooling technology that we propose uses acompressor based on the cyclic adsorption and desorption of a working gas on a sorber material such as activated carbon.Under desorption, a high pressure can be established. When expanding the high-pressure fluid over a flow restriction,cooling is obtained. The big advantage of this cooling technology is that, apart from passive valves, it contains nomoving parts and, therefore, generates no vibrations. This, obviously, is highly attractive in sensitive, high-performanceoptical systems. A further advantage is the high temperature stability down to the mK level. In a Dutch national researchprogram we aim to develop a cooler demonstrator for METIS. In the paper we will describe our cooler technology anddiscuss the developments towards the METIS cooler demonstrator.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.