Development Of An Automated Test System For The Readout Unit Of CEPC Electromagnetic Calorimeter

With the discovery of the Higgs at the Large Hadron Collider(LHC),the Circular Electron Positron Collider(CEPC)scheme has been proposed by Chinese high-energy physicists.Electromagnetic calorimeter(ECAL)is an important part of CEPC spectrometer.Studying the readout unit,which includes the SiPM and the plastic scintillator,has become a hotspot as one of the main options of ECAL.Based on the pre-study,the electromagnetic calorimeter of CEPC will need about 8 million detection units.So we need to deeply study the performance of the readout unit and have an optimal design of the calorimeter.Due to the individual differences of the plastic scintillators,an auto test platform is need to high-efficiency finish the test work of the plastic scintillator.The platform need to help us select the plastic scintillator with a good consistency.In order to realize the fast test of readout unit,we designed an automated test system based on Lab VIEW virtual instrument to test the readout unit,analyze.With the DT5751,SiPM driver circuit board,stepper motor,low-voltage power supply,relays and so on,we has completed the hardware development based on the Lab VIEW and the software interface communication with the automatic control device.At the same time,we also completed the readout unit Automated testing with the simple online data processing,the data storage for offline processing and analysis.Based on the platform,we have finished the main experiment measurement,including the calibration of SiPM,the uniformity test of the scintillator luminescence,light output of SiPM scintillation units coupled with the different pixels,the influence of the reflective material on the light output and the dark noise of SiPM with the different methods.When testing the readout unit in the laboratory,we use the 90Sr source to replace the cosmic rays to study the detector performance because the event rate is too low for the cosmic rays signal with the small area detector.Finally,we also do some test with the electron beam current to verify the feasibility of the laboratory test system and the performance of the readout unit.