Detection of Cherenkov light from air showers with Geigermode-APDs

Abstract We have detected Cherenkov light from air showers with Geigermode-APDs (G-APDs). G-APDs are novel semiconductor photon detectors, which offer several advantages compared to conventional photomultiplier tubes in the field of ground-based very high energy (VHE) γ -ray astronomy. In a field test with the MAGIC telescope we have tested the efficiency of a G-APD/light catcher setup to detect coinciding Cherenkov light from air showers. From our test we estimate a detection efficiency of our G-APD/light catcher setup to be ≥ 60 % higher than the efficiency of a MAGIC camera pixel. The dark count rates of the tested G-APD at ambient temperature are 10 times lower than the rates of detected photons from the night sky light background (NSB). This relaxes the need for cooling the G-APD to the level where the noise rate is sufficiently low. According to this recent test, G-APDs promise a major progress in ground-based VHE γ-ray astronomy.