Atmospheric Model And Relarted Work In LHAASO-WFCTA Calibration

The cosmic rays were discovered in 1912.Since the discovery,many researchers have conducted detailed research on them,but there are still many unresolved problems.For these problems,high-altitude cosmic ray observatories came into being.The Large High Altitude Air Shower Observatory(LHAASO),located at 4,400 meters above sea level in Daocheng County,Sichuan Province,is a large cosmic ray observation array.The main scientific target is the measurement of cosmic ray spectrum and the resolution of high-energy cosmic rays.The origin of this century is a problem.The Wide Field-of-view Cherenkov Telescope Array(WFCTA)is one of the three main detectors of the LHAASO.It is used to measure the cosmic ray spectrum from 30 TeV to several EeV.In order to explain the phenomenon of changes in the cosmic ray spectrum and the acceleration mechanism of the cosmic ray origin.Before entering the Earth,the cosmic rays will have a wide-spread air shower with the atmosphere and emit Cerenkov light.WFCTA is also based on this principle to capture and observe cosmic rays.The LHAASO station area is located at Haizi Mountain,Daocheng County at an altitude of 4,300 meters.The current atmospheric physical data in the area has not yet been obtained,so a pre-simulation is required.Simulate the vertical distribution profile of atmospheric depth over the LHAASO station area as an atmospheric basis for the calibration of the WFCTA telescope.In this paper,the atmospheric data of the existing Yangbajing Observatory and the MSISE90 atmospheric model data are compared.It is found that the MSISE90 atmospheric model is basically consistent with the atmospheric depth variation of the high altitude mountain climate.Therefore,based on this model,the atmospheric depth distribution over the Daocheng of LHAASO station area is simulated,and the vertical profile of atmospheric distribution is given.The test system was designed according to the preamplifier circuit version of WFCTA.Detection is performed by the test system to detect whether the WFCTA's dynamic range,resolution,and gain stability requirements are met.A stable LED circuit module that satisfies the absolute calibration of the WFCTA telescope array is also studied to perform calibration during WFCTA operation.At the same time,the calibration of the mirror surface of the Cherenkov telescope was carried out,and the transmittance of the mirror surface was designed and tested.