Long-term operation of a multi-channel cosmic muon system based on scintillation counters with MRS APD light readout

Abstract A Cosmic Ray Test Facility (CRTF) is the first large-scale implementation of a scintillation triggering system based on a new technique, scintillation tile with MRS APD light readout (START). In START, the scintillation light is collected and transported by WLS optical fibers, while light detection is performed by pairs of avalanche photodiodes with the Metal–Resistor–Semiconductor structure (MRS APD) operated in the Geiger mode. START delivers 100% efficiency of cosmic muon detection, while its intrinsic noise level is less than 10 - 2 Hz . CRTF, consisting of 160 START channels, has been continuously operated by the ALICE TOF collaboration for more than 25 000 h, and has demonstrated a high level of stability. Fewer than 10% of MRS APDs had to be replaced during this period.