Plastic Scintillator Detector

The primary goal of the PSD is to trigger in real time gamma rays from 0.5 to 10 GeV by rejecting low energy charged particles which are mainly protons and electrons. A SiPM, instead of a traditional PMT, is coupled to the plastic scintillator to get a full coverage of CALO and avoid false triggers. A gamma ray trigger efficiency of 80% at low energy and a gamma ray identification efficiency of 80% up to TeV can be realized by both a long bar segmentation with a width of 3 cm and a square tile segmentation with a width of 20 cm. Thanks to the fast decay time of plastic scintillator and rapid response of SiPM, the total delay of trigger signals from PSD is within 100 ns.