One essential goal of ESO's VLT/ELT instrumentation programs is laboratory characterization of state-of-the-art mid-infrared detectors operated at temperatures as low as 4 Kelvin. Laboratory qualification of the 1k x 1k AQUARIUS detector array for applications in VISIR and MATISSE has been started some years ago and is still ongoing for the upcoming ELT instrument METIS. For this purpose the Thermal Infrared Multi-Mode Instrument TIMMI-2, which was formerly installed at ESO's La Silla 3.6-m telescope, was re-commissioned at ESO headquarters in Germany. This instrument provides a 150-liter volume vacuum vessel with an integrated cryogenic optics system optimized for the wavelength range of interest, five cryo-mechanisms for apertures, filters, and objectives, a polarimetric mode selection, a 4-Kelvin cryo-cooler and an IR-window with external calibration source feed-in option. After successful reproducibility measurements with the original optical and detector set-up, it was successively upgraded to a multi-purpose (mid-) infrared detector test facility.

Although working satisfactory for most of the applications, the current test facility has some shortcomings which are limiting potential future detector characterization programs. Previous measurements revealed that the thermal background is in fact too high for investigating the sensitivity limits of detectors, and it is therefore required to reduce the temperature levels of radiation shield and optical structure significantly. Despite of that, a larger detector temperature variation is desirable, covering an optional range from 4 up to 30 Kelvin. The scope of the offered master thesis is the next upgrade of the test facility which includes the mechanical design of implementing a second cryo-cooler and required modifications of vessel, shield, instrument structure, detector environment and temperature control, and integration and verification testing at nominal cryogenic operation temperature.

Supervisor: G. Jakob (Mechanical Engineering Department – Instrument & Cryo Systems Group)