Radiation damage studies of multipixel Geiger-mode avalanche photodiodes

Results on the radiation hardness of multipixel Geiger-mode avalanche photodiodes (G-APDs) are presented. Recently developed G-APDs from three manufacturers (Hamamatsu (Japan), CPTA(Russia) and Mikron/Dubna(Russia)) were exposed to 28 MeV positrons with fluences up to 8×1010positrons/cm2 at the Paul Scherrer Institute. The effects of this radiation on many G-APD parameters such as gain, photon detection efficiency, dark current and count rate for these devices are shown and discussed.