Experience with the UHV box coater and the evaporation procedure for VUV reflective coatings on the HADES RICH mirror

An UHV box coater was set up for the deposition of highly reflective layers in the vacuum ultraviolet (VUV) wavelength range on large-area mirror substrates. The VUV mirrors are needed for the ring imaging Cherenkov (RICH) detector of the high-acceptance di-electron spectrometer (HADES). The complete dry vacuum system is described. The spatial deposition distribution from the evaporation sources was measured. The reflectivity of the Al mirror layer was optimized for the wavelength range of 145–210 nm by varying the thickness of the MgF2 protective layer. The setup for measuring the reflectivity in the VUV range is described and reflectivity data are presented.