LHAASO-WCDA Detector Experiment And Pre Study On High Precision Scintillation Fiber Detector

With the development of the study on cosmic rays,the combination of various detection methods has been the main research orientation on high-energy cosmic rays and high-energy gamma rays.Large High Altitude Air Shower Observatory(LHAASO)is a major research facilities of the "twelfth five-year" scientific plan of China,which was granted and at the end of 2015 and started construction.So far,the scientific observation has been conducted for a long time and a series of important research results have been obtained.LHAASO consists of the Square Kilometer Array(KM2A),the Water Cherenkov Array(WCDA),and the Wide-angle Cherenkov Telescope Array(WFCTA).It studies the original case by detecting the cosmic ray/gamma ray shower secondary particles in the atmosphere.The LHAASO experiment is of great significance to the exploration of the origin of high-energy cosmic rays and the related cosmic evolution,the motion of high-energy celestial bodies and the study of new physical frontiers.The thesis consists of two parts: The LHAASO-WCDA detector experiment and the pre study on high precision scintillation fiber detector.In the LHAASO-WCDA detector experiment,we carry out the performance research on the large size photomultiplier and the development of time calibration system.Photomultiplier is the main photoelectric conversion device of the detector,the accurate test on its performance is an important step to ensure the completion of the detection task.The cold resistance,compression resistance,air leak detection,magnetic shielding and its Q-T effect of the Photomultiplier tubes were systematically studied and tested.In order to reconstruct the original direction of the shower accurately with the arrival time of the secondary particles of cosmic rays,the detector array needs to be calibrated systematically.We established and developed a set of time calibration system based on LED and plastic fiber beam division,the relative time difference between each unit of the detector array was obtained through the testing and installation of the calibration system,which provides a guarantee for the scientific operation and data quality in the further research work.With the continuous development of the experimental project of LHAASO,a new kind of high-precision radiation detector based on plastic scintillation fiber and Si PM array is proposed.As a potential advanced detector,it can give more accurate measurements in spatial resolution in the future.In this part of the work,the selection and the performance testing of the components of the new kind of detector are carried out and the construction and optimization of the detector test platform are also completed.The research results will be applied to the measure the secondary component energy spectrum and current intensity of cosmic rays in high-altitude areas,which is of great significance for verifying the particle interaction model,the low-energy radiation monitoring in the environment and the solar activity detection.