The Measurement Of Charge And Helium Spectrum With DAMPE And Study Of High Energy Astrophysics

The research of cosmic rays have been started since late in 1890s and lasted more than 100 years,people have done many works extensively and deeply.In recent years,some experiment found the hardening features at a few hundred Ge V compared with the conventional scenario,just power law model.The obvious inconsistency between new discovery and conventional one may indicate some hints of acceleration,propagation and some other topics of cosmic rays.However,the recent experiment on orbit mea-sured spectra up to several TeV as high as possible,the upper bound of energy range is lower than the one of ground-based.For the range from?TeV to a few hundred TeV,which is almost unobserved and also limited by low particle number density of high en-ergetic cosmic ray,as well the relative small observation area of detector.Intriguingly,this range could act as the bridge between direct observation(ballon-borne or onboard satellite and international space station)and indirect observation(ground-based),which is meaningful and important in astroparticle physics over a wide energy range.We introduce the PSD position alignment,fluorescence attenuation and charge re-construction in chapter 2.The precise position of scintillator in the frame of DAMPE is essential to path length within its volume as particle passes through,which plays an im-portant role in charge measurement.We have finished position calibration of all plastic scintillators by using flight data.For all of scintillators,the movements along the width are relative small.The movements along height are dominated,the average are-2mm,-1mm for the first layer and second layer,respectively.As a whole,the rotation of PSD detector is?0.0015rad.All of the movement and rotation are stable over operation time,we found the alignment of position is meaningful to improve the charge resolu-tion at least by 4%We also corrected attenuation of fluorescence within scintillator and found that the attenuation would reduce the intensity of ionization energy by twice as much as possible when one particle passes through a scintillator at different position along its length.On the other hand,we developed methods to correct the quenching effect and non-equalization of PSD bar.After applying these corrections,the charge resolution of proton and helium are 0.137 and 0.238 charge unit,respectively.In the third chapter,firstly,we introduce the correction to saturation at a few ten TeV.Secondly,the data analysis and helium spectrum are presented.The BGO calorimeter of DAMPE could measure helium spectra from dozens of GeV to a few hundreds TeV over nearly four orders of magnitude.There are some saturated read-outs within calorimeter as the deposited energy as high as a few ten TeV.We developed a method to correct the saturation based on Monte Carlo data effectively.We obtained the spectrum of helium with DAMPE by using flight data with period from January in 2016 to September in 2019.The preliminary spectrum shows the hardening feature at a few hundreds GeV,which is consistent with AMS02.DAMPE also found the signifi-cant softening feature at?10 TeV/n.DAMPE found the softening with high confidence level for the first time,which are consistent with results from previous experiment ATIC,CREAM and NUCLEON.The softening also favors the breaking of proton and helium mixed spectrum by ground-based experiment.At the current stage,there are relative large uncertainties from a few TeV to a few hundreds TeV in ground-based experiment,DAMPE's high precision spectrum could be essential and crucial to measurement of keen energies of each kind of nucleus.In chapter 4,we report our theoretical works on high energy astrophysics.We have studied the softening of DAMPE's proton spectrum at?14 TeV by combination with spectra of AMS02,ATIC,CREAM and ground-based experiment,i.e.YBJ-ARGO.We found the single power law could not fit the softening feature and spectra measured by air shower experiment simultaneously.Based on the multiple components spectrum,we discussed the multi sources model and nearby source with background model.All of the two model could fit the spectra from TeV to PeV.the nearby source model could be more concrete as we took into account progress of anisotropy in recent years.We also discussed the fate of remnants by binary neutron stars(NS)merge based on the first event,GW179817 and estimated the maximum gravitational mass of NS.We found that the maximum gravitational mass of NS would be less than 2.32M? if the central engine of GRB170817A was a black hole.In chapter 5,there are our summary based on the thesis and prospect for the near future.