Design And Research Of 3-inch PMT Voltage Divider For JUNO

Research on neutrinos in recent years has become a hot topic in basic scientific field.After the Daya Bay neutrino experiment,another major scientific project on the research of neutrino-JUNO is under construction in China.The main physical goal of the JUNO experiment is to accurately measure the mass order of neutrinos and other oscillation parameters.In the JUNO experiment,the 3-inch PMT detection system is a relatively independent system that undertakes important tasks such as independent physical measurement and mutual inspection with the 20-inch PMT detection system.In addition,the 3-inch PMT detection system has its own physical target,which can independently measure θ₁₂ and △m₂₁²;it can improve the accuracy of time measurement,accurately reconstruct the cosmic ray muon,and reduce the cosmic ray isotopic background;measure the rate and energy spectrum of supernova neutrinos;increase the dynamic range of the detector’s energy measurement and improve the detection ability of high-energy particles.In this paper,a 3-inch PMT low-current voltage divider is designed.Three versions of the voltage divider are designed.The structure and function of the voltage divider are optimized one by one.In order to reduce the total power of the high-voltage supply system and improve the system reliability,the JUNO experiment requires that the single-channel current of each 3-inch PMT does not exceed 9uA.The final designed voltage divider has met the JUNO experimental project and 3 Inch PMT detection performance requirements.This article tested the performance of two 3-inch PMT tubes,HainanZhanchuang XP72B20 and Hamamatsu R12199,including quantum efficiency and dark count.The test results show that the maximum quantum efficiency of the two sample tubes is 26.98% and 27.61%,which can meet the requirements of the JUNO experiment for 3-inch PMT performance.However,dark counts are 16.20 Hz and 35.77 Hz when the threshold is 3pe,which is much greater than the requirements of the JUNO experiment.In this paper,an independently designed voltage divider was used to study the influence of different divider currents on the detection performance of the3-inch PMT.Three kinds of voltage dividers with current of 347.0uA,11.6uA,and 7.8uA were used to test the performance of the XP72B20 and R12199 sample tubes.Performances,including gain,Single photoelectron resolution,peak-to-valley ratio,anode nonlinearity and transit time spread were studied.The results show that different divider currents do not have significant effect on these detection performances for the 3-inch PMT.The voltage distribution ratio is a key factor to the 3-inch PMT detection performance.This article uses the independently designed 7 voltage distribution ratio of voltage dividers to test the gain,Single photoelectron resolution,peak-to-valley ratio and transit time spread of the XP72B22 sample tube.The comparison test results show that the 3:2:1… voltage distribution ratio of these7 voltage distribution ratios is the best working partial pressure ratio for this 3inch PMT.The above test results will provide an important experimental basis for the3-inch PMT to use a voltage divider with a small voltage divider in the JUNO detector and to determine the voltage distribution ratio of the voltage divider.