In this article we want to give an overview about the GERDA experiment and then present in more detail the liquid argon veto system in the scope of photosensor developments. We give special emphasis on the SiPM-Fiber-System produced at Technische Universität München.
The GERmanium Detector Array, GERDA, aims to measure the neutrinoless double beta (0νββ) decay. A very good background reduction and understanding is essential due to the extremely low rate of double beta decays. To reduce the background from cosmic rays the GERDA experiment is located below a rock overburden of about 3500m water equivalent in the Gran Sasso National Institute (LNGS) of the Italian National Institute for Nuclear Physics (INFN). The detector is located within a cryostat filled with liquid argon which is used for cooling and acts as a distinguished veto system.