Development And Application Of Cosmic Ray Reference System (CoRaRs)-A General Purpose Detector Testing System

The history of human’s understanding and study of cosmic rays is more than100years. In the early20th century, cosmic rays, as natural sources of high energy particles, made important contributions to discoveries of many new par-ticles. Then, because of the invention and development of particle accelerators, the research direction of cosmic rays turned from particle physics to astrophysics and kept progressing along with the development of detection technologies. The fundamental questions about cosmic rays are it’s origin:Where do they come from, how are they accelerated, and how do they propagate? To answer these questions, scientists from all over the word have been carrying out many spa-cial and ground-based experiments for measurements of the energy spectrum, composition and direction of cosmic particles.Large High Altitude Air Shower Observatory (LHAASO) is a new genera-tion of large all-sky survey system for gamma astronomy proposed by Chinese scientists. The central scientific goal of LHAASO project is to explore for the origin of high energy cosmic rays and the evolution of the universe and high ener-gy celestial bodies, and to push forward the research of dark matter. LHAASO, covering an area of1km2, consisting of arrays of different kind of detectors, is planed to centre at Shangri-La, who has an altitude of over four kilometers. As the main array of LHAASO, Kilometer-square Array (KM2A) aims for two main field of cosmic ray research:7astronomy with energy beyond30TeV and physics about the "knee" of cosmic rays.KM2A consists of over5600electron detectors (ED). To fulfil the scientific goals of LHAASO, the ED’s are needed to satisfy some indicators:sensitive detection area should be no less than1m×1m, time resolution better than2ns, detection efficiency greater than95%, and single-electron resolution better than0.25. As a member of LHAASO collaboration, Shandong University has undertaken the task of testing and characterization of all the over5600ED’s. For this purpose, a Cosmic Ray Reference System (CoRaRS) was developed in SDU, and the first ED prototype was tested using it.The history of human’s discovery and research of cosmic ray, the method-s and the frontier of cosmic ray study, and the new generation of cosmic ray experiments——LHAASO are stated in the first two chapters of this thesis.In chapter3, the indicators and structure of ED are described firstly. Then the CoRaRS is introduced, which is the main content of this thesis, and the design goals, the whole structure and main functions of CoRaRS are described.The three functional system are discussed in the4th,5th and6th chapters, detector system, electronics system and data acquisition system respectively.Chapter7is about the calibration of CoRaRS, including system trigger, position resolution and time resolution. The analysis and simulation indicate that the system trigger rate should be12/s, and after the adjustment of the high voltage and threshold, a trigger rate of10/s was obtained, which roughly agrees with the simulated value. Then the reconstruction method of the hit position of cosmic muon is discussed, and the analysis shows that the degree of accuracy of reconstructed positions is about2cm, and the resolution better than lcm. And the procedure of timing calibration of scintillator is introduced. The distribution of calibration values of the whole area of all the8scintillation detectors are obtained, and thanks to these values, the time resolution of single scintillator turns out to be640ps, and time resolution of the reconstructed time is about500ps.The methods and results of the test of the ED prototype using CoRaRS are discussed in chapter8. The results shows that the time resolution of this prototype is1.73ns, the detection efficiency when threshold is-15mV is93.7%, single-particle resolution is0.23. The results roughly meet the requirement of design. And using CoRaRS’s ability of reconstructing the hit position of incident muons, the whole area of this prototype is scanned and the degrees of uniformities of these performances are obtained.The last chapter is a summary, and the upgrade plan of CoRaRS is proposed here.