Observation Of 10-100 TeV Gamma-rays Emission From The Region Of G65.0+0.1 With LHAASO-KM2A And The Performance Test Of ED-PMT

Since Hess's discovery in 1912,cosmic rays have been studied for more than 110 years,but the three fundamental questions of their origin,acceleration,and propagation remain unanswered.With the development of detection technology,it becomes an important method to search cosmic ray sources and study their acceleration by means of y astronomy.At present,the main gamma ray experiments are the space Fermi satellite experiment,the Pavel Cherenkov Telescope Array H.E.S.S.The Tibet-as gammaand HAWC arrays have so far found a large number of gamma-ray sources,but the observed energy ranges of these experiments are all below tens of TeV and can not effectively distinguish the radiation mechanisms of gamma rays.It is expected that ultra-high-energy gamma-ray observations above 100 TeV will provide key information for the study of the radiation mechanism of celestial sources and hopefully resolve the origin of cosmic rays from within the Milky Way up to PeV.The High Altitude Air Shower Observatory(LHAASO)proposed and built by Chinese scientists is the largest and most sensitive complex cosmic ray detector in the world at present.LHAASO consists of three sub-arrays:the one-square-kilometer array(KM2A),the WCDA.and the Wide Cherenkov telescope array(WFCTA).As one of the main arrays of LHAASO.KM2A is composed of 5195 electromagnetic particle detector and 1188 muon detectors(MD).The observation energy range of KM2A is from 10 TeV to 10 PeV.The main objective of KM2A is to survey the northern sky region for y source observations,thanks to the powerful ability of the large area muon detector to eliminate cosmic ray background,its sensitivity to gamma rays above 100 TeV is more than 10 times that of all previous experiments.The main work of this thesis is to measure and study the gamma ray source with KM2A array data.KM2A operates on a build-and-run basis,with the 1/2 array running at the end of 2019,the 3/4 array starting in December 2020,and the full array starting July 20 at the 2021.Using the experimental data of the KM2A array from December 27,2019,to July 19,2019,we first measured the radiation of the Crab Nebula,the "Standard candle"in gamma-ray astronomy,based on this,the performance of KM2A array is tested.This paper studies the pointing longitude of the array using the position measurement of Crab Nebula,which shows that the pointing accuracy of the array is better than 0.1°,and the extended measurement of the Crab Nebula orientation case shows that the angular resolution of the KM2A array is better than 0.3° at 100 TeV.Longterm monitoring of the Crab Nebula indicates that the KM2A array operated steadily during this period.In addition,the angular resolution,core position resolution,energy resolution and gamma proton discrimination of KM2A are analyzed by using the gamma ray simulation data.The predicted results are in good agreement with the measured results,the results of KM2A's measurement of Crab Nebula Energy Spectrum below 300 TeV are in good agreement with the previous experimental results.These results show that KM2A array is reliable for the measurement of gamma ray source,and it lays a solid foundation for the measurement of other gamma ray sources based on KM2A array data.Based on the KM2A data,this paper further studies the gamma radiation above 10 tev in G65.1+0.1 region.This region,located near the galactic disk,contains pulsars,pulsar wind clouds,Supernova Remnant,and molecular clouds.Magci,HAWC,Fermi,Veritas and others have observed this region and the results are not the same.Using the KM2A data,we observed two significant outliers of gammaradiation in one region,namely LHAASO J1954+2834 and LHAASO J1959+2846.When the energy is greater than 63 TeV,the significance of the two sources is 10.01 sigmaand 9.02 sigmarespectively.LHAASO J1959 + 2846 has no known counterpart of the very high energy gamma-ray source.It is a new very high energy gamma-source.In this paper,the position,extension and energy spectrum of these two sources are given by using the Likelihood method.We give the energ spectrum distribution between 10 TeV to 300 TeV,LHAASO J1954+2834:(1.85 ± 0.15stat±0.13sys)×10-15 ×(E/20Te V)(-2.95±0.07stat±0.02sys)?J1959+2846:(1.32±0.15stat±0.09sys)×10-15×(E/20Te V)-2 78±0.09stat=0.02sys(cm-2 Te V-1 s-1).This paper also analyzes the molecular cloud data in this region,and makes a model fitting and discussion on the radiation generation mechanism in this region.The present measurement results can not give a definite conclusion,the future needs to accumulate more experimental data and the combination of X-ray,radio and other bands of data.The orientation,core position,and energy reconstruction of the KM2A case is based on the particle number density and particle arrival time detected by the ED detector,one of the core components of which is the Photomultiplier tubes,its performance will directly account for the reconstruction accuracy of the case.Another important aspect of this paper is the detection and calibration of the Photomultiplier tubes used in Ed.For the XP3960 type PMT used by ED,a dual-read-out voltage divider is designed in this paper.The anode and the 6th dynode signal of the PMT are read out at the same time.The dynamic range is more than 10000 particles to meet the requirement that the gamma energy detected by KM2A is up to 10 PeV.We have tested the nonlinearity of more than 5000 PMT.The maximum linear current(defined as nonlinearity of 5%)is greater than 990 mA(corresponding to 10000 particles).In addition,the noise count rate of each PMT was tested,and the average noise level was 2.1 Hz,which was much better than the target requirement of 200 Hz.The temperature difference of ED working environment was 50?,in order to make the change of single particle signal detected by ED less than 10%,we tested the temperature coefficient of each PMT to meet the requirement of 0.2%/°;ED transmits the scintillation light generated by the scintillator to the PMT end face through 12 optical fibers,so we also checked the photocathode surface uniformity of the PMT,in order to meet the time resolution requirement of ED,the TTS of 5000 PMT used for ED was sampled at the ratio of 5%,and all PMTs meet the requirement of 4.5 ns.We also study the performance characteristics of PMT under high count rate.The gain and maximum linear current of PMT will increase with the increase of count rate,but the count rate of KM2A experiment is 1-2 kHz,in this case the linear current and gain of the PMT are essentially unaffected.