Study Of The Scintillator Module For CEPC Scintillator-Tungsten Electro-Magnetic Calorimeter

The study of the particle properties of Higgs is the most advanced scientific research in the field of high-energy physics.It is of great significance for human beings to further understand the world.The Circular Electron Positron Collider(CEPC)is a large international scientific facility proposed by the Chinese particle physics community in 2012.It is designed with a circumference of 100 km to be as a Z,and Higgs factory.A Particle Flow Algorithm(PFA)oriented calorimetry system is considered in the CEPC detectors to provide hermetic coverage for high-resolution energy measurements of electrons,photons,taus and hadronic jets.A sampling calorimeter with scintillator-tungsten sandwich structure(ScW),derived from the CALICE scintillator ECAL developments,is selected as one of the ECAL detector options.It can be built in a compact and cost effective way.Major design parameters for the scintillator-tungsten ECAL were studied and optimized.The active layers of the scintillator-tungsten ECAL consists of 2 mm thick and 5 × 45 mm2 large scintillator strips.Plastic scintillator is a robust material which has been used in many high energy physics experiments.Production of the scintillator strips can be performed at low cost by the extrusion method.Moreover,the number of readout channels can also be significantly reduced due to the strip structure.The scintillator strips in adjacent layers are perpendicular to each other to achieve a small effective transverse readout cell size.Each strip is covered by a reflector film to increase light collection efficiency and improve the uniformity of scintillation light yield.Photons from each scintillator strip are read out by a very compact photo-sensor,silicon photomultiplier(SiPM),attached to the strip.The SiPM and highly integrated readout electronics make the dead area in the scintillator-tungsten ECAL almost negligible.The light output has non-uniformity along the length of the scintillator,which has an effect on the resolution of the ScW ECAL.In order to achieve good uniformity along the entire scintillator strip,it is necessary to optimize the scintillator unit,including the coupling mode of the SiPM and scintillator strips.This thesis mainly introduces the experimental research and optimization of the scintillator unit design,and obtains the coupling mode with good light output uniformity.In addition,the simulation results of the scintillator unit based on Geant4 are also introduced.The simulation results are basically consistent with the actual test results.At last,the assembly and cosmic-ray test of a single layer prototype was introduced.The test results show that the performance of the ScW ECAL scintillator unit can basically meet the requirements.