|Description:|| This image shows X-shooter NIR Spectrograph Mirror 6, just before integration into the Collimator box.|
M6 is made of polished aluminium, just like the other X-shooter mirrors in the Cold Optics box. Polishing the bare aluminium blank is a unique process - performed only at ASTRON - and produces high-performance mirrors that keep their shape at cryogenic temperatures. The backside of M6 is light-weighted, but this is not visible from this angle. The mirror is gold-coated and accurately baffled in order to reduce stray light.
Also visible in this pictures is the torque-less clamping system that is specially designed to securely mount the X-shooter mirrors without the need of a rotational force (for tightening a bolt) that could impact the quality of the optical surface. The clamps are loaded in the clamping tools on the table.
Due to large temperature variations during cool-down and warm-up, thermal expansion can build up excessive force that could damage the optical surface. This force is absorbed by spring leaves integrated in the collimator box. The collimator box and a spring leaf are reflected nicely in the mirror.