A. Ebersoldt

Ground Calibration of MAPMT and SiPM for JEM-EUSO

In order to unveil the mystery of ultra-high energy cosmic rays (UHECRs), JEM-EUSO (Extreme Universe Space Observatory on-board Japanese Experiment Module) will observe extensive air showers induced by UHECRs from the International Space Station (ISS) orbit with a huge acceptance. To discuss the origin of UHECRs precisely with the observed results, it is essential to calibrate the detector pre-flight with utmost precision. The technical readiness level of JEM-EUSO is demonstrated with several pathfinder missions, e. g. EUSO-Balloon, EUSO-TA, and Mini-EUSO. These pathfinder missions also provide the perfect environment to investigate the capability of new state of the art photo sensors based on Geiger mode avalanche photodiodes (G-APDs), so called silicon photomultipliers (SiPMs). A first concept design for a JEM-EUSO elementary cell based on SiPMs is presented to be used with one of the pathfinder experiments. For the case of EUSO-TA comparison studies have been performed for MAPMTand SiPM-response to fluorescence light. To absolutely calibrate and characterize different types of photo sensors, an universal calibration and test setup is built at the Karlsruhe Institute of Technology (KIT). It consists of a photon shielding dark box (1.5 m×1 m×1 m), a diffuse uniform light source with a calibrated optical output and several readout electronics for MAPMTs and SiPMs. The light source can be used in singlephoton mode (pulsed light) and other modes, ranging from a few tens of photons to continuous light. The spectral output is around (377±6) nm. Further wavelengths will be implemented with respect to the emission lines of the nitrogen fluorescence spectrum. Former measurements with SiPMs have shown a temperature dependence of dark count and gain. Therefore, a temperature control has been implemented into the setup. With this the photo detection efficiency of various photo sensors can be measured for different wavelengths and temperatures. The present status of the calibration and test setup as well as of the design and comparison studies with SiPMs will be reported.