Application of avalanche photodiodes as a readout for scintillator tile–fiber systems

The application of reach-through avalanche photodiodes (RʹAPD) as a photodetector for scintillator tiles has been investigated. The light collected by WLS fibers (0.84 and 1 mm diameter) embedded in the scintillator has been transmitted to the 0.5 mm2 active surface of APD by clear optical fibers and optical connectors. A low noise charge sensitive preamplifier (≈400e− equivalent noise charge) has been used to amplify the photodiode signal. Various configurations of tile–fiber systems, suitable for CMS and LHCb experiments at LHC have been studied using cosmic muons and muon beam at SPS at CERN. In order to optimize the performance of APD, measurements in the temperature range from −10°C to +25°C have been made. The MIP detection efficiency and e−/MIP separation have been estimated in order to determine applicability of the readout for LHCb preshower.