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Abstract

We developed three prototype detector modules using silicon photomultipliers (SiPMs) instead of conventional photomultiplier tubes (PMTs) at the Max Planck Institute for Physics. These prototypes are being used to compare the performance of SiPMs and PMTs during operation in the imaging cameras of the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes. The detector modules use either Hamamatsu, SensL or Excelitas devices. To achieve an active area comparable to a 1 inch PMT, we used a matrix of up to nine 6 × 6 mm 2 SiPMs, actively summing the individual signals while maintaining their fast signal response. The installation of the three prototype modules was completed in 2017. Since then they have been operated alongside the PMT based camera on nightly basis. The resulting data, comprised of Cherenkov light generated in extensive air showers (EAS) and artificial light pulses, is collected during telescope operation and used for performance comparisons. The MAGIC camera structure is suitable for the installation of up to six prototype detector modules next to the PMTs for parallel operation. The outer camera rim, where we installed the SiPM based detector modules, is not included in the trigger. In order to gather data on operation in the trigger area one prototype module was installed to the camera centre for a single night in 2018. The two MAGIC telescopes utilized in this study are located on the Canary Island of La Palma. Each telescope consists of a 17 m diameter mirror dish and a camera composed of 1039 PMTs.