[论文解读] The Effect of Cosmic Ray Muon Momentum Measurement for Monitoring Shielded Special Nuclear Materials

Junghyun Bae, Stylianos Chatzidakis|arXiv (Cornell University)|Aug 20, 2021

Particle Detector Development and Performance参考文献 9被引用 11

一句话总结

本研究证明，测量宇宙射线μ子动量可显著提升对屏蔽特殊核材料（SNM），如高浓铀（HEU）、低浓铀（LEU）和钚（Pu）的探测与区分能力，即使在30厘米铅屏蔽后仍有效。通过蒙特卡洛模拟，作者表明动量测量可实现>3σ的识别准确度，与不依赖动量的方法相比，测量时间可减少3–4倍。

ABSTRACT

Recently, cosmic ray muons have been considered as a potential high energy radiation probe for monitoring and interrogation of dense, well-shielded special nuclear materials (SNM). Due to their high-penetrative nature, cosmic ray muons can easily penetrate shielded nuclear materials with minimal absorption and with leaving the target objects intact. However, despite the potential benefits from using cosmic ray muons for SNM monitoring, their widespread application has been limited for various reasons, including relatively low cosmic ray muon flux at sea level and the difficulty of measuring muon momentum in the field which can increase resolution and reduce measurement time. In this work, we explore in detail the effect of cosmic ray muon momentum measurement, focusing specifically on SNM monitoring applications. Three different types of SNMs (HEU, LEU, and Pu) surrounded by lead shielding with five different thicknesses (0, 5, 10, 20, and 30 cm), are analyzed using Monte Carlo simulation for three momentum measurement resolution levels (perfect, limited, and absent). 1000 muons were generated in the simulation which translates to 4 minutes of measurement time for a standard cargo container. We found that it is possible to identify and separate HEU, LEU, and Pu with high accuracy (> 3 s.d.) when using muon momentum measurement (perfect and limited) even when 30 cm-thick lead shielding was used. Currently, it is not possible to identify or separate the SNMs with 30 cm thick lead shielding without muon momentum knowledge. Our results show that the effect of measuring muon momentum can be significant and can result in reduced measurement times by a factor of 3 to 4 and/or improved monitoring and imaging resolution.

研究动机与目标

• 评估宇宙射线μ子动量测量对屏蔽特殊核材料（SNM）探测与识别的影响。
• 解决在货柜等场景中，传统辐射探测器对高度屏蔽SNM失效的挑战。
• 评估动量测量是否可克服现场应用中μ子通量低和分辨率差的限制。
• 确定在现实屏蔽条件下，实现可靠SNM区分所需的最小动量分辨率。

提出的方法

• 采用蒙特卡洛模拟，研究宇宙射线μ子与三种SNM（高浓铀（HEU）、低浓铀（LEU）和钚（Pu））的相互作用。
• 模拟了五种铅屏蔽厚度（0、5、10、20和30厘米），以评估在不同屏蔽条件下的性能表现。
• 评估了三种动量测量分辨率水平：理想、有限和缺失，以隔离动量分辨率的影响。
• 每次模拟运行生成1000个μ子，对应标准货柜约4分钟的测量时间。
• 模拟追踪μ子轨迹与能量损失，通过散射和吸收特性推断材料成分。
• 应用统计分析，确定在不同条件下SNM类型之间的分离置信水平（以标准差表示）。

实验结果

研究问题

• RQ1 在厚铅屏蔽后，μ子动量测量能否实现对HEU、LEU和Pu的可靠识别？
• RQ2 当μ子动量测量分辨率有限时，与完全不测量动量相比，SNM区分的准确性如何变化？
• RQ3 在测量动量的情况下，实现高置信度SNM识别所需的最短测量时间是多少？
• RQ4 动量测量在屏蔽SNM的μ子层析成像中，对成像分辨率的提升程度如何？
• RQ5 能否有效穿透并分析30厘米铅屏蔽的μ子动量数据，以实现SNM监测？

主要发现

• 即使在30厘米铅屏蔽下，μ子动量测量仍能以高精度（>3σ）实现对HEU、LEU和Pu的识别与区分。
• 若不测量动量，则无法在30厘米铅屏蔽后识别或区分SNM。
• 与不依赖动量的方法相比，采用动量测量可将所需测量时间减少3至4倍。
• 即使动量分辨率有限，厚屏蔽条件下的SNM区分仍可行且准确。
• 理想动量测量提供最高分辨率与置信度，但实际中有限分辨率系统仍能实现稳健性能。
• 结果表明，动量测量是实现现场可部署μ子基SNM监测系统的关键使能技术。