LHAASO-KM2A陣列模擬及LHAASO實驗物理預期的研究
發(fā)布時間：2018-11-01 10:34
【摘要】：自上世紀初發(fā)現(xiàn)宇宙線以來,宇宙線之起源、加速和傳播等問題一直是宇宙線研究的基本問題。高能伽馬射線攜帶天體源的信息,是探索宇宙線起源的重要探針。隨著探測技術(shù)的發(fā)展,衛(wèi)星實驗已經(jīng)發(fā)現(xiàn)3000多個GeV伽馬射線源,地面切倫科夫望遠鏡陣列發(fā)現(xiàn)了200多個TeV伽馬射線源,標志著伽馬射線天文發(fā)展到了一個新階段。高能伽馬射線既可以由輕子加速產(chǎn)生也可以通過強子加速產(chǎn)生。現(xiàn)有實驗對伽馬射線測量局限于1OTeV以下,對幾十TeV以上乃至IPeV的伽馬射線能譜尚無觀測結(jié)果,因此不足以認證宇宙線源。由于受到Klein-Nishina效應影響的輕子加速很難產(chǎn)生能量在100TeV以上的伽馬射線,而強子加速則可以產(chǎn)生100TeV以上伽馬射線,因此精確測量幾十TeV到PeV的伽馬射線有助于人們對宇宙線的加速機制和起源做出有效判斷。高海拔宇宙線觀測站(LHAASO)是我國科學家自主提出的下一代宇宙線探測器陣列,位于海拔4410米的四川稻城海子山。LHAASO實驗是一個復合型EAS陣列,主要由KM2A、WCDA和WFCTA這三個子陣列組成。KM2A作為LHAASO實驗的主體陣列,占地面積一平方公里,觀測能量范圍為10TeV-20PeV。本文以KM2A陣列為分析對象,優(yōu)化其陣列性能。從研究結(jié)果中看到KM2A陣列是世界上在超高能區(qū)靈敏度最高的探測器陣列,其能量分辨率、本底排除能力及靈敏度在50TeV以上分別為23%、10-4和1%Icrab。LHAASO的主要科學目標之一是精確測量300GeV到20PeV的伽馬射線能譜及探索高能宇宙線起源。本文針對LHAASO實驗的科學目標,選取超新星遺跡、超級泡、彌散伽馬射線及活動星系核進行研究,利用不同加速模型給出LHAASO實驗觀測預期,這一結(jié)果尤其是對30TeV以上能譜的預期將為我們評判超高能伽馬輻射機制提供重要依據(jù),為研究宇宙線起源奠定基礎(chǔ)。LHAASO-KM2A的全模擬程序以Geant4為基礎(chǔ),細致模擬了廣延大氣簇射粒子進入KM2A后探測器的響應,其缺點在于產(chǎn)生模擬事例會消耗太多時間,因而無法滿足實驗對海量模擬數(shù)據(jù)的需求。本文以KM2A陣列全模擬為基礎(chǔ),開發(fā)出一套提高程序運行速度的簡化模擬方法,并且簡化模擬結(jié)果與全模擬結(jié)果有較好的符合,驗證了簡化模擬的可靠性和可行性。這一研究將為LHAASO陣列模擬的大數(shù)據(jù)產(chǎn)生做好準備,進而為實驗數(shù)據(jù)的理解提供重要依據(jù)。此外,KM2A簡化模擬在LHAASO軟件框架中的成功運行,為LHAASO實驗中三個子陣列共同分析實驗數(shù)據(jù)打下堅實的基礎(chǔ)。
[Abstract]:Since the discovery of cosmic rays at the beginning of the last century, the origin, acceleration and propagation of cosmic rays have been the basic problems in the study of cosmic rays. High-energy gamma rays carry information about celestial sources and are important probes for exploring the origin of cosmic rays. With the development of detection technology, more than 3000 GeV gamma ray sources have been found in satellite experiments, and more than 200 TeV gamma ray sources have been discovered in the ground Cherenkov telescope array, which marks a new stage in the development of gamma ray astronomy. High energy gamma rays can be produced both by lepton acceleration and by hadron acceleration. The existing experiments are limited to 1OTeV, and no observations have been made on the gamma ray spectra of dozens of TeV or even IPeV, so it is not sufficient to verify the cosmic ray source. It is very difficult for lepton acceleration affected by Klein-Nishina effect to produce gamma rays with energy above 100TeV, while hadron acceleration can produce gamma rays above 100TeV. Therefore, the accurate measurement of dozens of TeV to PeV gamma rays is helpful to judge the accelerating mechanism and origin of cosmic rays. High altitude cosmic ray observation station (LHAASO) is the next generation cosmic ray detector array proposed by Chinese scientists. It is located in Haizi Mountain, Daocheng, Sichuan Province, 4410 meters above sea level. The LHAASO experiment is a composite EAS array, mainly composed of KM2A,. As the main array of LHAASO experiments, KM2A covers an area of one square kilometre, and the observed energy range is 10TeV-20 PeV. In this paper, KM2A array is used as an analysis object to optimize its array performance. The results show that KM2A array is the most sensitive detector array in the ultra-high energy region in the world. Its energy resolution, background exclusion ability and sensitivity are 23.3% above 50TeV, respectively. One of the main scientific objectives of 10-4 and 1%Icrab.LHAASO is to accurately measure the gamma-ray spectra from 300GeV to 20PeV and to explore the origin of high-energy cosmic rays. In this paper, we select supernova remnants, superbubbles, diffuse gamma rays and active galactic nuclei to study the scientific target of LHAASO experiment, and give the observation expectation of LHAASO experiment by using different accelerated models. This result, especially for the energy spectrum above 30TeV, will provide an important basis for us to judge the mechanism of ultra-high energy gamma radiation and lay a foundation for studying the origin of cosmic ray. The whole simulation program of LHAASO-KM2A is based on Geant4. The response of the detector after the wide-range atmospheric shower particle enters the KM2A is simulated in detail. The disadvantage of the detector is that it takes too much time to produce the simulation case, so it can not meet the needs of the experiment for the massive simulation data. Based on the full simulation of KM2A array, a simplified simulation method is developed to improve the running speed of the program. The simplified simulation results are in good agreement with the full simulation results. The reliability and feasibility of the simplified simulation are verified. This study will prepare big data for LHAASO array simulation and provide important basis for the understanding of experimental data. In addition, KM2A simplifies the successful operation of the simulation in the framework of LHAASO software, and lays a solid foundation for the three sub-arrays in the LHAASO experiment to analyze the experimental data together.
【學位授予單位】：山東大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：O572.212
本文編號：2303647
[Abstract]:Since the discovery of cosmic rays at the beginning of the last century, the origin, acceleration and propagation of cosmic rays have been the basic problems in the study of cosmic rays. High-energy gamma rays carry information about celestial sources and are important probes for exploring the origin of cosmic rays. With the development of detection technology, more than 3000 GeV gamma ray sources have been found in satellite experiments, and more than 200 TeV gamma ray sources have been discovered in the ground Cherenkov telescope array, which marks a new stage in the development of gamma ray astronomy. High energy gamma rays can be produced both by lepton acceleration and by hadron acceleration. The existing experiments are limited to 1OTeV, and no observations have been made on the gamma ray spectra of dozens of TeV or even IPeV, so it is not sufficient to verify the cosmic ray source. It is very difficult for lepton acceleration affected by Klein-Nishina effect to produce gamma rays with energy above 100TeV, while hadron acceleration can produce gamma rays above 100TeV. Therefore, the accurate measurement of dozens of TeV to PeV gamma rays is helpful to judge the accelerating mechanism and origin of cosmic rays. High altitude cosmic ray observation station (LHAASO) is the next generation cosmic ray detector array proposed by Chinese scientists. It is located in Haizi Mountain, Daocheng, Sichuan Province, 4410 meters above sea level. The LHAASO experiment is a composite EAS array, mainly composed of KM2A,. As the main array of LHAASO experiments, KM2A covers an area of one square kilometre, and the observed energy range is 10TeV-20 PeV. In this paper, KM2A array is used as an analysis object to optimize its array performance. The results show that KM2A array is the most sensitive detector array in the ultra-high energy region in the world. Its energy resolution, background exclusion ability and sensitivity are 23.3% above 50TeV, respectively. One of the main scientific objectives of 10-4 and 1%Icrab.LHAASO is to accurately measure the gamma-ray spectra from 300GeV to 20PeV and to explore the origin of high-energy cosmic rays. In this paper, we select supernova remnants, superbubbles, diffuse gamma rays and active galactic nuclei to study the scientific target of LHAASO experiment, and give the observation expectation of LHAASO experiment by using different accelerated models. This result, especially for the energy spectrum above 30TeV, will provide an important basis for us to judge the mechanism of ultra-high energy gamma radiation and lay a foundation for studying the origin of cosmic ray. The whole simulation program of LHAASO-KM2A is based on Geant4. The response of the detector after the wide-range atmospheric shower particle enters the KM2A is simulated in detail. The disadvantage of the detector is that it takes too much time to produce the simulation case, so it can not meet the needs of the experiment for the massive simulation data. Based on the full simulation of KM2A array, a simplified simulation method is developed to improve the running speed of the program. The simplified simulation results are in good agreement with the full simulation results. The reliability and feasibility of the simplified simulation are verified. This study will prepare big data for LHAASO array simulation and provide important basis for the understanding of experimental data. In addition, KM2A simplifies the successful operation of the simulation in the framework of LHAASO software, and lays a solid foundation for the three sub-arrays in the LHAASO experiment to analyze the experimental data together.
【學位授予單位】：山東大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：O572.212
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