缪子能量测量及其在缪子散射成像中的应用研究

发布时间：2018-08-25 19:35

【摘要】：天然宇宙线缪子散射成像技术具有无需人工放射源,穿透力强,对高Z材料敏感等特点,适用于探测隐藏的高Z材料,成为近年来一个研究热点。但由于天然宇宙线缪子通量低,该方法实现材料鉴别所需的检测时间长。本论文围绕基于飞行时间法的宇宙线缪子能量测量,能量信息在缪子散射成像中的应用及高Z材料快速鉴别等问题开展了理论和实验研究。为了将能量信息有效地引入缪子散射成像,并缩短材料鉴别所需时间,首先基于缪子散射成像理论,研究了引入精确缪子能量信息条件下,缪子散射成像方法在材料鉴别性能方面的物理极限。针对实际缪子能量测量技术精度有限的问题,建立了引入缪子能量分段的材料鉴别方法。通过蒙卡模拟研究了能量测量不确定度对散射成像方法中缪子能量信息的引入方式和材料鉴别性能的影响。分析了缪子散射成像方法对缪子能量测量的要求,采用了不显著改变缪子物理性质的飞行时间法来测量缪子能量,并提出了在有限飞行空间内提升能量测量精度的多层飞行时间法,建立了相应的能量分段方法,讨论了能量分段性能与缪子事例数、时间分辨率和飞行时间探测器层数的关系。采用时间分辨率约100ps的MRPC探测器,搭建了飞行时间法缪子能量测量实验平台,修正了飞行时间测量系统延迟,实现了基于飞行时间法的缪子能量测量与分段。在清华大学缪子散射成像原理性实验装置的基础上,搭建了首套具有飞行时间法能量测量功能的缪子散射成像实验系统,实现了宇宙线缪子径迹和能量的同步测量。参照此实验系统,建立了相应的蒙卡模拟方案,给出了基于飞行时间法能量测量与分段的材料鉴别方法的理论预期,实验结果基本符合预期。在高Z材料鉴别方面,采用假设检验和ROC分析方法给出了高Z材料检出率以及误判率随缪子事例数的变化规律,并通过性能对比论证了采用飞行时间法能量测量与分段,与不引入能量信息相比,ROC曲线的AUC值提升了大约25%。
[Abstract]:The natural cosmic ray mouton scattering imaging technology has many advantages, such as no artificial radiation source, strong penetration, sensitive to high Z material, etc. It is suitable for detecting hidden high Z material, and has become a research hotspot in recent years. However, due to the low flux of natural cosmic rays, it takes a long time to realize material identification. In this paper, theoretical and experimental studies have been carried out on energy measurement of cosmic ray moutons based on time-of-flight method, application of energy information in moutons scattering imaging and rapid identification of high-Z materials. In order to effectively introduce energy information into Miao scattering imaging and shorten the time required for material identification, firstly, based on Miuron scattering imaging theory, the condition of introducing accurate mouton energy information is studied. The physical limit of Miao scattering imaging method in material identification. In order to solve the problem of limited precision of practical meatus energy measurement technique, a material identification method with the introduction of muzzle energy segment is established. The influence of uncertainty of energy measurement on the introduction of energy information and material identification in scattering imaging is studied by Monka simulation. The requirements of Miurus scattering imaging method for energy measurement are analyzed. The time-of-flight method, which does not significantly change the physical properties of the moutons, is used to measure the moutons energy. A multi-layer time-of-flight method is proposed to improve the accuracy of energy measurement in a limited flight space. The corresponding energy segmentation method is established. The relationship between the performance of energy segmentation and the number of examples, time resolution and the number of layers of time-of-flight detector is discussed. Based on the MRPC detector with time resolution about 100ps, the experimental platform of time-of-flight energy measurement is built, and the delay of time-of-flight measurement system is corrected, and the energy measurement and segmentation based on time-of-flight method are realized. On the basis of the principle experimental device of Mius scattering imaging in Tsinghua University, the first experimental system of Miu scattering imaging with the function of time-of-flight energy measurement is set up, and the simultaneous measurement of track and energy of cosmic ray moutons is realized. With reference to the experimental system, the corresponding Monka simulation scheme is established, and the theoretical expectation of the material identification method based on the energy measurement and segmentation of the time-of-flight method is given. The experimental results are basically in line with the expectation. In the aspect of high Z material identification, the rule of the detection rate and misjudgment rate of high Z material with the number of cases is given by using hypothesis test and ROC analysis, and the energy measurement and segmentation by time-of-flight method are demonstrated through the performance comparison. The AUC value of the ROC curve is about 25% higher than that without energy information.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O572.1

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