利用宇宙射线 μ 子评估地下地质特征
Using Cosmic Ray Muons to Assess Geological Characteristics in the Subsurface
AI总结：
本文提出基于塑料闪烁体的低功耗 μ 子探测系统，结合 Geant4 模拟与重建算法，通过测量地下 μ 子通量和天顶角反演上覆层、岩石密度及孔隙度等地质特征。
摘要：
宇宙射线是源自恒星和星系际事件的高能原子核与基本粒子。这些粒子与高层大气相互作用，产生一系列到达地球表面的次级粒子，其中 μ 子最为显著。凭借足够高的能量，μ 子在被完全阻止之前，可穿行至地球表面以下数公里深处。地面 μ 子通量分布及其相关的天顶角可用于确定某一地点的地质特征，而无需采用传统方法。本工作旨在将一种基于塑料闪烁体的低功耗 μ 子探测系统用于这种无损地质分析方法。系统采用 4 块定制设计的塑料闪烁体面板，构成两个相互正交的探测平面。来自两个平面的探测器之间同时触发即表示一次符合事件，并由费米国家加速器实验室（FNAL）的数据采集系统记录。为量化与探测器相关的系统不确定性，例如该探测器设计的能量沉积和角分辨率，正在开发一种使用 Geant4 的蒙特卡洛模拟。模拟数据和实验数据将推动重建算法的开发与验证；该算法完成后，预计能够预测平均上覆层厚度和岩石密度。延长探测器对 μ 子的曝光时间，可作为了解周围环境变化（如岩石孔隙度）的一种手段。在实验方面，测得的通量数据将用于对独立且成熟的模型进行基准测试。该技术成功的概念验证展示可为长期非侵入式地质监测打开大门。本文详细介绍了探测器设计和实验方法。
英文摘要：
Cosmic rays are energetic nuclei and elementary particles that originate from stars and intergalactic events. The interaction of these particles with the upper atmosphere produces a range of secondary particles that reach the surface of the earth, of which muons are the most prominent. With enough energy, muons can travel up to a few kilometers beneath the surface of the earth before being stopped completely. The terrestrial muon flux profile and associated zenith angle can be utilized to determine geological characteristics of a location without having to use conventional methods. This work intends to use a low-power plastic scintillator-based muon detection system for this non-destructive geological assay methodology. 4 custom designed plastic scintillation panels are used to realize two orthogonal detection planes. Simultaneous triggers between detectors from two planes indicate a coincidence event which is recorded using a data acquisition system from FNAL. In order to quantify the systematic uncertainties associated with the detector, such as energy depositions and angular resolution of the detector design, a Monte Carlo simulation using Geant4 is being developed. Simulated and experimental data will drive the development and validation of a reconstruction algorithm that, upon completion, is expected to predict average overburden and rock density. Extended detector exposure to muons can be used as a means to understand changes in the surrounding environment like rock porosity. On the experimental front, the measured flux data will be used to benchmark independent and established models. Successful proof-of-concept demonstration of this technology can open doors for long term non-invasive geological monitoring. The detector design, and experimental methodology are detailed in this work.
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