LHAASO-KM2A阵列模拟及LHAASO实验物理预期的研究
发布时间：2018-11-01 10:34
【摘要】：自上世纪初发现宇宙线以来,宇宙线之起源、加速和传播等问题一直是宇宙线研究的基本问题。高能伽马射线携带天体源的信息,是探索宇宙线起源的重要探针。随着探测技术的发展,卫星实验已经发现3000多个GeV伽马射线源,地面切伦科夫望远镜阵列发现了200多个TeV伽马射线源,标志着伽马射线天文发展到了一个新阶段。高能伽马射线既可以由轻子加速产生也可以通过强子加速产生。现有实验对伽马射线测量局限于1OTeV以下,对几十TeV以上乃至IPeV的伽马射线能谱尚无观测结果,因此不足以认证宇宙线源。由于受到Klein-Nishina效应影响的轻子加速很难产生能量在100TeV以上的伽马射线,而强子加速则可以产生100TeV以上伽马射线,因此精确测量几十TeV到PeV的伽马射线有助于人们对宇宙线的加速机制和起源做出有效判断。高海拔宇宙线观测站(LHAASO)是我国科学家自主提出的下一代宇宙线探测器阵列,位于海拔4410米的四川稻城海子山。LHAASO实验是一个复合型EAS阵列,主要由KM2A、WCDA和WFCTA这三个子阵列组成。KM2A作为LHAASO实验的主体阵列,占地面积一平方公里,观测能量范围为10TeV-20PeV。本文以KM2A阵列为分析对象,优化其阵列性能。从研究结果中看到KM2A阵列是世界上在超高能区灵敏度最高的探测器阵列,其能量分辨率、本底排除能力及灵敏度在50TeV以上分别为23%、10-4和1%Icrab。LHAASO的主要科学目标之一是精确测量300GeV到20PeV的伽马射线能谱及探索高能宇宙线起源。本文针对LHAASO实验的科学目标,选取超新星遗迹、超级泡、弥散伽马射线及活动星系核进行研究,利用不同加速模型给出LHAASO实验观测预期,这一结果尤其是对30TeV以上能谱的预期将为我们评判超高能伽马辐射机制提供重要依据,为研究宇宙线起源奠定基础。LHAASO-KM2A的全模拟程序以Geant4为基础,细致模拟了广延大气簇射粒子进入KM2A后探测器的响应,其缺点在于产生模拟事例会消耗太多时间,因而无法满足实验对海量模拟数据的需求。本文以KM2A阵列全模拟为基础,开发出一套提高程序运行速度的简化模拟方法,并且简化模拟结果与全模拟结果有较好的符合,验证了简化模拟的可靠性和可行性。这一研究将为LHAASO阵列模拟的大数据产生做好准备,进而为实验数据的理解提供重要依据。此外,KM2A简化模拟在LHAASO软件框架中的成功运行,为LHAASO实验中三个子阵列共同分析实验数据打下坚实的基础。
[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.
【学位授予单位】：山东大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O572.212
本文编号：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.
【学位授予单位】：山东大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O572.212
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