| The existence of the dark matter has been inferred from more and more astronomical observations, and the weakly interacting massive particles (WIMPs) because of its prominent advantages, have become the most popular ones among the numerous dark matter candidates.The orbital experiments are aiming at searching for evidences of the dark matter by measuring the spectra of photons, electrons and positrons produced by annihilation or decay of the WIMPs. The Dark Matter Particle Explorer, DAMPE is one of the first four scientific satellites of the Strategic Priority Research Program on Space Science of the Chinese Academy of Science, which will be launched by the end of this year (2015). Based on the studies and comprehensions of the similar experiments which had been finished (such as ATIC, PAMELA) or currently running (such as FERMI-LAT, AMS-02), the DAMPE will devote itself to measure the extreme high energy e* (up to 10 TeV), y and nuclides spectra, so that it will fill the blank of the high-energy section of the cosmic rays measurement with a high accuracy.This thesis will focus on the BGO electromagnetic calorimeter, which is one of the key sub-detector of the DAMPE. The evidences, candidates and detections of dark matter are introducted at the beginning, and the sub-detectors of DAMPE are discussed with their designed goals and structures.The high dynamic range for energy measurement (5GeV-10TeV) is one of the crucial techniques for the DAMPE project, and the PMT base board in the BGO ECAL, which is used for voltage dividing and signal readout of the PMT, is the key component for this technique, In the third chapter, the details of the design, test, improvement and vertification of a multi-dynode readout photomultiplier base board are presented. With the VA32 electronics, about 2×105 is achieved by that, the Dy8, Dy5 and Dy2 do provide a linear response in the whole dynamic range, which corresponds to BGO energy deposits of 0.5-1×102 MIPs,30-3.0×103 MIPs, and 1.0×103-1.0×105 MIPs, respectively (1 MIPs is about 23 MeV).The satellite based experiment requires much more stability and reliability for the payload. During the building of the BGO ECAL, the detection components are particularly studied, tested and selected, in order to make sure the most reliability. The fourth chapter is about the discussion on the whole processing including the performance testing of the components (BGO, PMT etc), unit matching etc with the time line of the building of the BGO ECAL. The details about the PMT aging, magnetic field shielding, dynode ratios, light yield of the BGO crystal and uniformity etc are presented.After the building of the BGO ECAL, the parameters calibration and performance estimating with the cosmic-rays and beam particles become the most important task on the ground. The chapter 5 focuses on the calibration of the parameters including the pedestal, MIPs response, dynode ratio, attenuation length of the crystal and the trigger threshold etc. And the roles of these parameters in the reconstruction and correction of the measured events are well considered. Then, a fast digitization for the Monte Carlo simulation of the BGO ECAL is carried out based on the calibrated parameters (chapter 6). Finally the energy reconstruction and correction (for electrons) of the beam data (tested at CERN) are finished with parameters from the cosmic-rays and high energy particle beams, and the results of reconstructed energy and energy resolution are compared with the simulation. The designed goal about the energy resolution of better than 1.5% at 800GeV is verified by the curve of the energy resolution changing with incident electron energy, which is obtained from both the MC and the beam data.Furthermore, a study on e/p identification of the BGO ECAL is presented in section 7.5. The primary results show that, a proton rejection rate better than 105 can be achieved for 200 GeV incident protons in the electron energy range of 86.1GeV to 103.3GeV. And the sources of errors are considered. |
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