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Measurement of Secondary Cosmic Rays Lithium, Beryllium, and Boron

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Measurement of Secondary Cosmic Rays Lithium, Beryllium, and Boron Measurement of Secondary Cosmic Rays Lithium, Beryllium, and Boron by the Alpha Magnetic Spectrometer by Yi Jia B.S., Xi’an Jiaotong University, China (2016) Submitted to the Department of Physics in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY September 2018 c Massachusetts Institute of Technology 2018. All rights reserved. ○ Author................................................................ Department of Physics August 8th, 2018 Certified by. Samuel C. C. Ting Thomas Dudley Cabot Professor of Physics Thesis Supervisor Accepted by . Nergis Mavalvala Associate Department Head, Physics 2 Measurement of Secondary Cosmic Rays Lithium, Beryllium, and Boron by the Alpha Magnetic Spectrometer by Yi Jia Submitted to the Department of Physics on August 8th, 2018, in partial fulfillment of the requirements for the degree of Doctor of Philosophy Abstract Secondary cosmic rays are mainly produced by the collisions of nuclei with the in- terstellar medium. The precise knowledge of secondary cosmic rays is important to understand the origin and propagation of cosmic rays in the Galaxy. In this thesis, my work on the precision measurement of secondary cosmic rays Li, Be, and B in the rigidity (momentum/charge) range 1.9 GV to 3.3 TV with a total of 5.4 million nuclei collected by AMS is presented. The total error on each of the fluxes is 3%-4% at 100 GV, which is an improvement of more than a factor of 10 compared to previ- ous measurements. Unexpectedly, the results show above 30 GV, these three fluxes have identical rigidity dependence and harden identically above 200 GV. In addition, my work on a new method of the tracker charge measurement leads to significant improvements in the AMS charge resolution, thus paving the way for the unexplored flux measurements of high Z cosmic rays. Thesis Supervisor: Samuel C. C. Ting Title: Thomas Dudley Cabot Professor of Physics 3 4 Acknowledgments I’ve imagined a lot of possibilities of what it would be like to be a graduate student at MIT, but what I truly experienced is ultimately out of my imagination. I have many people to thank throughout this unusual journey. First of all, I want to particularly thank Dr. Vitaly Choutko, Dr. Mike Capell, and Professor Anna Frebel for constructive suggestions in preparing this thesis. I’d like to thank my research advisor Professor Samuel Ting, who changed my entire track of Ph.D. study and had tremendous influence on my attitudes towards research. Although he might be one of the busiest persons in the world, he paid great attention to the academic progress and life quality of students. It was his trust in me that supported me to pass through the hardest period in my Ph.D. journey. On the first day I was in his office, he said “We only live once, so weneedtofind something that really interesting and devoted all the life to it.” I remember a lot of such conversations, and they always encouraged me to become a better scientist. I also thank Dr. Susan Ting for generous support both at MIT and CERN. I’d like to thank Professor Paolo Zuccon who introduced the basic structure of the AMS detectors when I decided to be a member of the collaboration. He settled me down at the office in MIT building 44, and kindly got me started with theAMS software. I cherish those good memories with my friends I met in the first year at MIT. Thank Field Rogers for inviting me to her home for Thanksgiving. It was a wonderful experience to spend a few days with such a great family. I was always impressed by the enthusiasm from Field Rogers, not only physics, but also life. Thank Sangbaek Lee and Patrick Moran for teaming up with me to survive at Course 8.711. I was really amazed to meet Patrick as my classmate at MIT since we used to work on the same floor of the same building at Notre Dame University in 2014 summer. Although sometimes our group study on the problem sets could be very intense and stressful, I have to say when I look back I somehow really enjoyed the time we spent at the graduate lounge. I also thank Afroditi Papadopoulou, Alex Diaz, Efain Segarra, Joe 5 Johnston, Lauren Yates, and Zhaozhong Shi for creating such a lovely atmosphere in the Laboratory for Nuclear Science (LNS). I’m also very fortunate to have a Chinese student community around at MIT. I’d like to thank Jinghui Liu, Junang Li and all others for sharing their experiences with me. I learnt a lot from Quantum Field Theory and String theory with Linghang Kong, Champ Somboonpanyakul, and Ali Fahimniya. One of the most thrilling experiences for me towards Ph.D. is to take Oral exam very early. I’d like to thank my Oral exam committee, especially Professor Boleslaw Wyslouch. I remember he settled me down at LNS when I first came to MIT and was in anxiety with the new environment. His generous encouragements make me feel like home at LNS. I also thank Thomas Boettcher, Yunjie Yang, Stephanie Brandt and others for helps in the practice sessions. Thank my academic advisor Professor Gunther Roland for helping me with course selections. It’s my great pleasure to work at CERN, with the most brilliant scientists in the world. I’m very grateful to Dr. Vitaly Choutko for carefully watching my progress towards my Ph.D. degree. He was the first one to get me started with research at CERN, and kindly guide me to contribute to the AMS publications. He made me feel I was truly part of the collaboration, and I’m very lucky to have him as my mentor. Qi Yan inspired me with his dedicated attitude towards research. I remember the “AMS spirit” he told me on the first day we met. I could have given up without his encouragement of this spirit. I’d like to thank Melanie Heil, Alberto Oliva, and Zhili Weng for insightful conversations and advice, and thank Joseph Burger for help on taking thermal shifts. Thank Andrew Ian Chen, Huy Phan, Matthew Behlmann, Zijian Liu, Jian Zhang, Xiaoting Qin, Hu Liu, Cheng Zhang, Jie Feng, who settled me down with the new environment and made life at CERN less boring. Thank Ms. Laurence Barrin and Ms. Christine Titus for always being willing to help me. Thank Miao Hu for occasionally inviting me to dinner with her friends. Thank Ming Guo, Xi Jiang and Ziqiu Wang for constant supports and warm friendships. I’m very grateful to Professor John M. LoSecco from Notre Dame University 6 and Professor Clark McGrew from Stony Brook University, who guided me into the exciting field of experimental particle physics. Thank my previous advisors Liangjian Wen and Yufeng Li from the Institute of High Energy Physics (IHEP) in Beijing for inspiring and encouraging me with their warm hearts. I couldn’t have survived without these people mentioned above. The most valuable thing I learn from these experiences is to stick to why you start in the very beginning, and no matter what happens, never give up and believe all efforts will pay off in the end. Last but not the least, thank my parents for unconditional love and support in my life. 7 8 Contents 1 Introduction 23 1.1 History of Cosmic Rays . 24 1.1.1 Discovery of Cosmic Rays . 24 1.1.2 Progress of Physics using Cosmic Rays . 26 1.2 Cosmic Ray Physics . 26 1.2.1 Energy Spectrum and Composition of Cosmic Rays . 27 1.2.2 Acceleration and Propagation of Cosmic Rays . 29 1.3 Primary and Secondary Cosmic Rays.................. 30 2 The Alpha Magnetic Spectrometer 35 2.1 The AMS Detector . 35 2.1.1 The Transition Radiation Detector (TRD) . 37 2.1.2 The Silicon Tracker . 38 2.1.3 The Electromagnetic Calorimeter (ECAL) . 39 2.1.4 The Time of Flight (TOF) . 42 2.1.5 The Ring Image Cherenkov (RICH) Detector . 44 2.2 Operation in Space . 46 2.2.1 Trigger . 46 2.2.2 The Geomagnetic Cutoff . 47 2.2.3 South Atlantic Anomaly . 48 3 The Silicon Tracker Charge Measurement 51 3.1 Silicon Detector . 51 9 3.1.1 Principle of Charge Measurement . 52 3.1.2 Silicon Sensors . 52 3.2 New Tracker Charge Measurement Method............... 54 3.3 New Charge Correction Procedures . 56 3.3.1 Energy Loss Correction . 57 3.3.2 Readout Element Correction . 62 3.3.3 Velocity Correction . 63 3.4 Results and Improvements . 64 3.4.1 Results of the Performance of the Silicon Tracker . 64 3.4.2 Improvements by this Work . 66 4 Data Analysis 69 4.1 Collection Time Ti ............................ 69 4.2 Event Selection Ni ............................ 71 4.3 Effective Acceptance Ai ......................... 75 4.3.1 Inner Tracker Reconstruction Efficiency . 76 4.3.2 L1 Hit Reconstruction Efficiency . 77 4.3.3 TOF Reconstruction Efficiency . 78 4.3.4 Inelastic Interactions of Nuclei in the AMS Materials . 79 4.4 Trigger Efficiency 휖i ............................ 81 4.5 Systematic Errors . 82 4.6 Results of Flux Measurements of Li, Be, and B . 85 5 Summary 93 5.1 Thesis Results . 93 5.2 Theoretical Interpretations of the Results................ 94 5.3 Outlook for Future Nuclei Flux Measurements . 96 A List of Publications 103 B S, K5, and K7 Routing Schemes 109 10 C Software Implementation 111 11 12 List of Figures 1-1 The variation of ionization with altitude. Left panel: Final ascent by Hess (1912), carrying two ion chambers (chamber 2 was shielded with thicker walls).
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