Development of a Calibration Stand for Photosensors for Extremely High-Energy Cosmic Ray Research

This work is about the development of a single photon calibration stand for photosensors that are used for the detection of cosmic rays of highest energies via UV-light from extensive air showers. The calibration stand was designed, built & improved during this work. Single photons and ~10,000 photons, with different wavelengths, can be sent onto a photodetector with up to 64 channels. Calibration measurements were done under comparable systematics and are shown for two different detector types.