Space Radiation Damage To PSD And Measurements Of Ultra-heavy Cosmic Rays (Z=30-40) Based On DAMPE

The era of experimental observation and theoretical study of cosmic rays has been opened since Hess first observed radiation from outer space using balloon experiment.After a century of development,cosmic rays physics has made great progress in both experimental equipment and theoretical research,which is a powerful tool for people to explore the universe from a new perspective.However the fundamental questions such as the origin,acceleration and propagation of cosmic rays have not been studied clearly up to now,this is also driving force for people in this field.PAMELA satellite first observed the deviation between its own measurements and traditional single power law on proton spectrum at energies of 300 GeV,and DAMPE satellite observed hardening phenomena on proton spectrum at higher energies of 14 TeV.That’s very important and meaningful for revealing the mystery of cosmic rays.DAMPE has discovered the fine structure of electrons and protons energy spectrum in high energy range with excellent energy resolution and low error,which made a significant breakthrough.Except for measuring the energy spectrum of high abundance nuclei,measuring the abundance of rare ultra-heavy nuclei is new route for studying the origin and accelaration of cosmic rays.It is very important for finding the fine structure of cosmic ray energy spectrum and measuring the abundance of ultra-heavy nuclei to accumulate more statistics.The geometry factor and acquisition rate of electronics has been decided in design stage and are unchanged,longer working lifetime of DAMPE satellite is only route to increase statistics.Thus it is meaningful that evaluating the working lifetime of DAMPE in space radiation environment.Due to the location at the outside of DAMPE,PSD will face the worst harshest radiation environment without any other shielding,so it is reasonable to take PSD as an example to survey the space radiation damage to detector.In thesis,PSD is taken as example to survey the space radiation damage to detection part,namely plastic scintillator and photomultiplier tube(PMT).The evaluation method of indirect space radiation damage to PMT is established,which offers reference technical notes for other similar space projects;Though the measurement of Ultra-heavy nuclei is not in DAMPE’s plan at the beginning of design,the large dynamic range of PSD can cover the measurement of Zr(Z=40)according to the beam calibration results,and it is feasible that measuring the abundance of Ultra-heavy nuclei based on DAMPE.Some characteristics of Ultra-heavy nuclei is presented in thesis: rare,high energy deposited in ΔE detector and the problem of energy threshold.And then the pre-selected method has developed based on the characteristics of Ultra-heavy nuclei.The events passed pre-selection condition is reconstructed according to the charge reconstruction algorithm to obtain the measured charge spectrum.The quenching behavior of Ultra-heavy nuclei is not verified by beam experiments,so different models have been used to describe the quenching effect of Ultra-heavy nuclei in PSD.Finally the linear function is adopted to fit the relationship between the measured charge and standard charge of Ultra-heavy nuclei.The thesis also discusses the energy threshold selection of DAMPE in detail,and finally gives the results of the abundance of Ultra-heavy nuclei with BGO energy greater than 20 GeV and makes comparision with SuperTiger.The measuments of the abundance of ultra-heavy nuclei in DAMPE and SuperTiger are consistent within uncertainty,which demonstrates that the analysis method of ultra-heavy nuclei based on DAMPE is credible.The next step is to solve the problem of energy threshold,research the selection efficiency of ultra-heavy nuclei based on simulation data,optimize the algorithm of track selection and give the final abundance of Ultra-heavy nuclei.And then deduce the result of Ultra-heavy nuclei abundance of cosmic ray source according to the leaky box model.Finally carry out physical analysis based on Ultra-heavy nuclei abundance at source.