宇宙射线缪子散射成像领域通常聚焦于提升成像区域的图像质量,对于其他区域的成像点及入射粒子各成分占比,尚缺乏系统的讨论。本文系统研究了海平面宇宙射线对缪子散射成像测量的影响。通过对PoCA(Point of Closest Approach)算法重建...宇宙射线缪子散射成像领域通常聚焦于提升成像区域的图像质量,对于其他区域的成像点及入射粒子各成分占比,尚缺乏系统的讨论。本文系统研究了海平面宇宙射线对缪子散射成像测量的影响。通过对PoCA(Point of Closest Approach)算法重建结果的分析,发现探测器区域内出现的PoCA点聚集并非单纯背景噪声,而是具有特定物理起源的系统性信号,主要源于宇宙射线在探测系统上方材料中相互作用产生的次级粒子,其在探测器中的记录会引发虚假位置信号,进而对散射重建产生显著影响。结合Geant4与CRY(Cosmicray Shower Generator)程序开展蒙特卡洛模拟,定量研究了该效应对覆盖材料种类与面密度的依赖性。在此基础上,进一步利用灵敏区内事例的散射角分布,通过多模板联合拟合方法对海平面宇宙射线粒子成分进行了测定。结果表明,缪子仍占主导地位,电子成分可被约束在百分之几的水平。因此,缪子散射探测系统不仅可用于目标成像,也可为海平面宇宙射线研究与本底扣除提供重要参考。展开更多
This paper studies the possibility of using the scattering of cosmic muons to identify threatening high-Z materials. Various scenarios of threat material detection are simulated with the Geant4 toolkit. PoCA （Point o...This paper studies the possibility of using the scattering of cosmic muons to identify threatening high-Z materials. Various scenarios of threat material detection are simulated with the Geant4 toolkit. PoCA （Point of Closest Approach） algorithm reconstructing muon track gives 3D radiography images of the target material. Z-discrimination capability, effects of the placement of high-Z materials, shielding materials inside the cargo, and spatial resolution of position sensitive detector for muon radiography are carefully studied. Our results show that a detector position resolution of 50 μm is good enough for shielded materials detection.展开更多
基金Supported by National Natural Science Foundation of China (10575046,10775062)Program for New Century Excellent Talents in University
文摘This paper studies the possibility of using the scattering of cosmic muons to identify threatening high-Z materials. Various scenarios of threat material detection are simulated with the Geant4 toolkit. PoCA （Point of Closest Approach） algorithm reconstructing muon track gives 3D radiography images of the target material. Z-discrimination capability, effects of the placement of high-Z materials, shielding materials inside the cargo, and spatial resolution of position sensitive detector for muon radiography are carefully studied. Our results show that a detector position resolution of 50 μm is good enough for shielded materials detection.
