姜山, 刘国睿, 刘军涛, 李晓鹏, 钱湘萍, 付治强, 王宝祥, 刘志毅. 基于宇宙射线缪子的土壤含水率监测[J]. 农业工程学报, 2022, 38(6): 330-336. DOI: 10.11975/j.issn.1002-6819.2022.06.037
    引用本文: 姜山, 刘国睿, 刘军涛, 李晓鹏, 钱湘萍, 付治强, 王宝祥, 刘志毅. 基于宇宙射线缪子的土壤含水率监测[J]. 农业工程学报, 2022, 38(6): 330-336. DOI: 10.11975/j.issn.1002-6819.2022.06.037
    Jiang Shan, Liu Guorui, Liu Juntao, Li Xiaopeng, Qian Xiangping, Fu Zhiqiang, Wang Baoxiang, Liu Zhiyi. Soil moisture monitoring using cosmic ray muons[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2022, 38(6): 330-336. DOI: 10.11975/j.issn.1002-6819.2022.06.037
    Citation: Jiang Shan, Liu Guorui, Liu Juntao, Li Xiaopeng, Qian Xiangping, Fu Zhiqiang, Wang Baoxiang, Liu Zhiyi. Soil moisture monitoring using cosmic ray muons[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2022, 38(6): 330-336. DOI: 10.11975/j.issn.1002-6819.2022.06.037

    基于宇宙射线缪子的土壤含水率监测

    Soil moisture monitoring using cosmic ray muons

    • 摘要: 为了丰富土壤含水率的测量手段,拓展宇宙射线缪子技术在农业工程领域的应用,该研究提出了利用宇宙射线缪子监测土壤含水率的方法,即通过放置在土壤中的缪子探测器测得的宇宙射线缪子计数来反推出土壤含水率。利用蒙特卡罗程序FLUKA对不同含水率的土壤建模并进行数值模拟,得出土壤含水率的探测分辨率,进一步得到最佳的缪子探测器放置深度。结果表明,探测半径与探测器放置深度相关,将探测器放置在地表下方80 cm深度处时,探测半径为6.2 m,此时当探测时长为2 h时,对土壤含水率的探测分辨率可以达到0.1 cm3/cm3;当探测时长达到8 h时,探测分辨率可以达到0.05 cm3/cm3。相较于60、70、80、100、110、120 cm等不同深度,探测器放置在地表下方90 cm处时,在相同探测时长条件下,土壤含水率的探测分辨精度最高,达到0.038 cm3/cm3。验证试验结果表明,缪子计数值的变化可以反映出待测物质质量厚度的较小变化。相较于传统的点测量方法和宇宙射线中子法,该方法的探测范围适中(探测半径为6~8 m),且测量结果不易受土壤密度之外的因素影响,可以作为其他监测技术的重要补充,具有广阔的应用前景。

       

      Abstract: Abstract: Cosmic ray neutron flux measurements have emerged for the soil water content in many fields in recent years. According to the count of the cosmic ray neutrons above the ground scattered by the soil, the detection depth is very sensitive to the soil water content, atmospheric pressure, and hydrogen-containing substances on the surface. In this study, a novel approach was proposed to monitor the soil moisture using cosmic ray muons with a higher average energy (about 3GeV). The water content of the soil was inferred from the muon count of the detector. The depth of detection was improved to minimize the influence of surface environmental factors on the measurement, compared with the cosmic ray fast neutron. A CRY program was used to generate the energy and angular distributions of cosmic ray muons at sea level. A Monte-Carlo program (FLUKA) was selected to construct the soil model with the different moisture. The transportation process of cosmic ray muons in soil was simulated to determine the relationship between the muon count of the detector in the soil and the average water content of the soil above the detector. The soil was equally divided into the upper and lower layers with a total thickness of 80 cm in the model. The moisture of the upper layer of soil varied from 0.05 to 0.5 cm3/cm3, while the water content of the lower layer was maintained at 0.5 cm3/cm3. The variation of the upper layer's moisture was simulated with the FLUKA program. The results showed that the count of the detector was a linear function of the soil water content. The detection resolution of the soil moisture was inversely proportional to the square root of detecting time, which reached 0.1 and 0.05 cm3/cm3, when the detection time was 2 and 8 h, respectively, particularly with the placement depth of the detector of 80 cm. Furthermore, the situations of the water content of the upper soil varied from 0.1 to 0.5 with the placement depth of the detector (from 60 to 120 cm), and the sensitive radius of the soil model (from 5 to 8.5 m) were simulated with FLUKA, indicating that the detection resolution also varied in the detection time at various placement depths. The highest resolution accuracy (0.038 cm3/cm3) of soil water content was achieved at the placement depth of 90 cm under the same duration. Another identical detector was required on the soil surface to monitor the cosmic ray muon flux reaching the surface in practical measurements, in order to correct for the effect of atmospheric factors on the muon count of the detector placed in the soil. Correspondingly, an experiment was performed which suggested that the muon event count can be an indicator of the mass thickness, and the soil density. In summary, the cosmic ray muons can be widely expected to monitor the soil moisture with a moderate and flexible detection range without radioactive hazards.

       

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