Research On The Time Calibration System Of LHAASO-WCDA And The Performance Of The PMT

The Large High Altitude Air Shower Observatory(LHAASO)is one of the national major science and technology infrastructure projects in the 12 th Five-Year Plan,with the main observation targets of high energy gamma ray and cosmic rays.The core scientific goals of the LHAASO experiment are to explore the origin of high-energy cosmic rays and related cosmic evolution,high-energy celestial body movements,and research on new frontiers of physics.LHAASO experiment includes a square kilometer array(KM2A),water Cherenkov detector array(WCDA),and wide field Cherenkov telescope array(WFCTA).The water Cherenkov Detector Array(WCDA)is an important part of the Large High Altitude Air Shower Observatory(LHAASO)project.It is located at the center of the LHAASO site,and its main physical goal is to achieve a sky survey of the gamma source in the entire north sky region at very high energy(100 GeV ~ 30 TeV).Cosmic rays enter the earth through the atmosphere and interact with the air nucleus to produce air showers.Secondary particles of air showers pass through the medium to produce Cherenkov light.The WCDA detector is mainly used to detect the water Cherenkov light generated by the air shower secondary particles entering the water,and to realize the direction and energy reconstruction of the radiation source.This thesis mainly works in two aspects of the water cherenkov detector array: the study on the performance of the photoelectric conversion system,and the development of the time calibration system.The detector consists of photomultiplier tubes(PMT),and its function is to realize the detection of water Cherenkov light and convert it into the electrical signals.The performance of the installed detector should be relatively consistent.It can receive signals more conveniently and efficiently.The performance of PMT should be tested before installation to meet the detection requirements.The relative consistency of the performance of each detector unit is beneficial to the data analysis of the detector.The error caused by the test results will affect the data analysis of the detector,so it is necessary to ensure the accuracy of the test results.In order to ensure the pointing accuracy of the radiation source detection,the detector array needs the time calibration system.The paper gives the time calibration method of the WCDA detector,completes the construction of the calibration system,and conducts batch test of the key component-spectral fiber bundle.The data quality monitoring of the detection system and the location of the Moon Shadow and Crab Nebula Crab Nebula are performed.The detection verifies the accuracy and reliability of the photoelectric conversion system and time calibration system.