The Taishan Antineutrino Observatory Simulation And Related Experimental Studies

The phenomenon of neutrino oscillation indicates that neutrinos possess mass,which is a phenomenon beyond the standard model.In-depth research on neutrinos is the key to opening up new fields of physics.The main purpose of the Jiangmen Underground Neutrino Observatory(JUNO)is to use the phenomenon of neutrino oscillation to measure the energy spectrum of reactor neutrino oscillation,so as to determine the mass hierarchy(MH)of the three eigenstates of neutrino mass.The Taishan Antineutrino Observatory(TAO)measures the energy spectrum of reactor neutrino as the input spectrum of JUNO.The JUNO and TAO detectors are expected to be put into operation in 2022.TAO is designed as a 2.8-ton liquid scintillator detector.The silicon photomultiplier(Si PM)with high detection efficiency is used to detect the light emitted by the liquid scintillator,enabling the TAO detector to achieve unprecedented energy resolution,which is less than 2%at1Me V.This paper mainly introduces the simulation of TAO detector performance and the research of light detection system,including:TAO detector design and performance simulation,Si PM reflectivity measurement in linear linear alkylbenzene-LAB,test and comparison of KLau S5 ASIC(Si PM readout chip)at room temperature and low temperature.This paper also introduce another kind of neutrino energy spectrum detector-gas TPC research.In order to develop the TAO detector,we built TAO simulation software;compare the detector geometry(spherical,cylindrical)and the influence of the dielectric ma-terials(alkylbenzene,mineral oil,silicone oil)on detector performance.The detector simulation shows that:the existing liquid scintillator recipe(LAB+PPO+bis-MSB)and Si PM with a detection efficiency greater than 50%,with a Si PM coverage rate of94%,TAO can detect approximately about 4500 photoelectrons,when one Me V energy deposited in the liquid scintillator.There is less energy leakage in the fiducial volume within a radius of 650 mm,and the non-uniformity of energy is better than 4%.The deviation of the position reconstruction within this range is less than 5 cm,and there is sufficient event rate(inverse beta decay(IBD)detection efficiency is about 46%;It can detect 2000 antineutrino events every day.).In addition,the simulation verified the beta-alpha decay of the radioactive background²³²Th can be used as the energy calibration of the detector.As a light-sensitive sensor of TAO,Si PM needs to be immersed in an alkyl benzene medium(LAB).In order to understand the reflectance of Si PM in LAB,we designed and constructed corresponding experimental setup,and used two Si PMs,FBK Si PM(NUV-HDlow CT)and HPK Si PM(S14160-6050HS),interested by TAO experiment,as measurement samples.Their reflectivity was measured in LAB for the first time.The reflectivity of the two Si PMs in the air is 14%to 23%and 8%to 14%,respectively.In LAB,the reflectivity of the two Si PMs is about 10%lower than in the air.This will help improve Si PM detection efficiency.The measurement verified the feasibility of Si PM for TAO detector and expanded the application of Si PM in LAB medium.The KLau S ASIC chip,as an optional readout chip for Si PM,needs to work with Si PM in a low temperature environment of-50 degrees.To this end,we need to measure the fifth version of the KLau S chip,that is,the performance of KLau S5 at low temperatures.Measurement result show that at-50 degrees,the chip still maintains good linearity,can distinguish IBD fast and slow signals with a time interval greater than 600 nanoseconds;can distinguish single photon,and the dynamic range can meet TAO‘s requirements that single readout channel can detect 10 photoelectrons at one time.The properties of the chip meet the experimental requirements of TAO.Gas TPC is a different experiment from TAO.TPC uses the elastic scattering of neutrinos and electrons to measure the scattering angle and scattering kinetic energy of the scattered electrons to obtain the neutrino energy spectrum.By simulating the scattering angle distribution of different candidate gases,Ne gas,Ar gas and CF₄gas can be used as candidate working gases.Build a prototype detector and conduct a preliminary detector signal test.