The as-manufactured design of the cryostat for ELT/METIS

We present the final design of the cryostat of the Mid-infrared ELT Imager and Spectrograph (METIS) instrument to be operated at ESO’s Extremely Large Telescope (ELT). The cryostat provides the cold optics of the instrument with the required cryo-vacuum environment. The radiation shields of the cryostat are cooled with liquid nitrogen and the cold optics is cooled via pulse-tube coolers down to temperatures between 35 K and 70 K. The cold-warm interface is provided with G10 blades that build together with the top part of the cryostat vessel the structural interface to the cold optics, the warm support structure, and the warm calibration source. The cryostat design is now finalized with most of the parts already produced and final integration almost complete. We present in this paper the final design as manufactured, the key design considerations, and highlights from the integration phase.