Abstract: Background: In the proposal of the circular electron positron collider (CEPC) scheme, readout unit consisting of a silicon photomultiplier (SiPM) and a plastic scintillator has become a research hotspot as one of the main options of electromagnetic calorimeter (ECAL). Purpose: This study aims to optimize the detector prototype by setup an automated testing system to test, analyze and improve the performance of each readout unit of CEPC ECAL. Methods: Based on the DT5751 waveform sampling plug-in module, SiPM drive circuit, stepper motor, low-voltage power supply (LVPS), relay, etc., the hardware of CEPC ECAL readout unit was built up whilst the software was developed with the LabVIEW. Repeated measurements were carried out to find the optimized parameters, and the SiPM calibration was performed. Results: Experimental results show that proposed automated testing system satisfied basic requirements of CEPC ECAL readout unit. Setup of the testing platform of scintillator readout unit based on waveform sampling is option for CEPC ECAL and be used for SiPM calibration, scintillator uniformity of light output and reflective material study. Conclusion: The experiment rwsult shows that the plastic scintillator strip with the ESR has the highest light yeild and the light yeild of 25 μm coupled with SiPM 3 times than 10 μm.

Key words: SiPM, Plastic scintillator, Electromagnetic calorimeter, CEPC