Positronium decay research is one of the sensitive probes to discovernew physical phenomena. Because of the pairing system of electron (particle) and positron (antiparticle), we can study reactions which are forbiddenby the Standard Model. In this study, we designed a novel compact detector for precise measurement of ortho-positronium (o-Ps) decay. Due totheir compact size, silicon photomultipliers (SiPMs) are used for the photodetection in the detector. The SiPM is well-known as a photodetector thatcan replace photomultiplier tube (PMT). In general, the size of the PMTis relatively large, so an SiPM was used to make compact trigger part fordirect collection of scintillation light. In this research, the trigger partconsists of plastic scintillator coupled directly to a single-channel SiPM toobtain the positron signal from the center of the detector. The trigger partis surrounded by the gamma-detection part to detect decay gammas in alldirections. For dual readout, both sides of the Bismuth Germanate (BGO)scintillators are coupled with SiPMs. The designed frame and grid are usedto support BGO scintillators and SiPMs. We obtained pretest data of apositron trigger signal and gamma-energy spectrum of 22Na and 137Cs radioactive sources for the novel compact detector. The detector will be usedto study the C-parity violation, invisible, and rare decay search.
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