LHAASO-KM2A Array's Sensitivity To Gamma Ray Sources Above 30TeV

YBJ International Cosmic Ray Observatory is located in Yangbajing (YBJ) valley of Tibetan highland with altitude of 4300 meters.There is the well-known geothermal energy, the Qinghai-Tibet Railway pass through, there is also communication cable here. It has a wide flat terrain, and climate advantages of on snow in winter ,and good power supply by geothermal power plant nearby,and good communication,living facilities,which make it the world's best ground base to detect cosmic rays in the mountains.ARGO experiment and Asγexperiment,which located in YBJ,as the ground base array of cosmic ray detection on the run in the world , has been running for 20 years.As its effective area is small,and it can not exclude the background events,its sensitivity on theγ-ray detection is always slightly lower than the Cherenkov telescope in the same period, failed to give full play to the high-altitude advantage ,and the large field of view, and the advantage of nearly 100% duty cycle.LHAASO is a large compound of ground base detector array plans to bulit in YBJ, covering an area of 1 square kilometer. It exclude the background events by the different between theμcontents of the extensive air shower induced by photons and hadrons. It is expected to greatly increase the sensitivity, change the passive situation. In this paper, only electronic detector array andμdetector array were simulated, this combined array called KM2A. This paper is based on the prophase research of LHAASO ,we estimate the performance of KM2A by simulating the sensitivity toγsource with energy above 30TeV. This paper can be roughly divided into several sections:The first chapter introduce the knowledge of cosmic rays, including the research history of cosmic ray ,the cosmic ray composition and energy spectrum, several methods to detect cosmic rays and modern comsic ray astronomy.The second chapter introduce LHAASO, scientific aim that LHAASO want to achieve and infrastructure. Including the limitation of the current ground base array and the essentiality of LHAASO. The third chapter introduce simulation method to simulate the sensitivity to theγray sources with energy above 30TeV, and the results of simulation. Including CORSIKA software package used to simulate extensive air shower, two kinds of detectors: electronic detectors andμdetectors and the layout of two kinds of detector array, methods to calculate effective area and angular resolution ,the select conditions ,the result of effective area, angular resolution, sensitivity of KM2A . the method to identify photon and proton, then the sensitivity curve of KM2A is given.The forth chapter has carry on the summary to this article and forecast the contribution that LHAASO may make toγastronomy and cosmic ray physics.