Szczegóły publikacji

Imaging atmospheric Cherenkov telescopes (IACTs) are often used for detection of high-energy gamma rays from the ground. The reflector of an IACT is typically tessellated into smaller mirror segments. The mirror segments are made of a glass or sandwich structure substrate with the front side coated typically with aluminum (Al) and a thin quartz protective layer. Direct exposure to harsh environmental conditions causes rapid degradation of optical performance of this type of mirrors and forces their regular replacement or re-coating that entails significant operational cost for the observatories. Mirrors with a thin front glass panel coated on a back surface, adjacent directly to the mirror substrate, can solve this problem. We report on our recent development of various technologies to build a reflective back-coated front glass surface with a composite mirror support structure manufactured with the cold glass slumping technique. We show that a decrease in optical efficiency due to the transmission of Cherenkov light reflected through the glass layer can be significantly compensated by selecting a special type of glass with appropriate thickness. We present full-size mirror prototypes that fit the specifications for the Medium-Sized Telescope mirrors for the Cherenkov Telescope Array. We also show first results of the laboratory tests of mechanical stability and focused reflectivity in the spectral range of the Cherenkov light.