Design and operation of FACT – the first G-APD Cherenkov telescope

Abstract

The First G-APD Cherenkov Telescope (FACT) is designed to detect cosmic\ngamma-rays with energies from several hundred GeV up to about 10 TeV using the\nImaging Atmospheric Cherenkov Technique. In contrast to former or existing\ntelescopes, the camera of the FACT telescope is comprised of solid-state\nGeiger-mode Avalanche Photodiodes (G-APD) instead of photomultiplier tubes for\nphoto detection. It is the first full-scale device of its kind employing this\nnew technology. The telescope is operated at the Observatorio del Roque de los\nMuchachos (La Palma, Canary Islands, Spain) since fall 2011. This paper\ndescribes in detail the design, construction and operation of the system,\nincluding hardware and software aspects. Technical experiences gained after one\nyear of operation are discussed and conclusions with regard to future projects\nare drawn.\n