Using Additional Moderator to Control the Footprint of a COSMOS Rover for Soil Moisture Measurement
Using Additional Moderator to Control the Footprint of a COSMOS Rover for Soil Moisture Measurement
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DOI：
10.1029/2020wr028478
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发表时间：
2021-05
影响因子：
5.4
通讯作者：
A. Badiee;J. Wallbank;J. P. Fentanes;E. Trill;Pete Scarlet;Yongchao Zhu;Grzegorz Cielniak;Hollie M. Coop
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文献类型：
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作者：
A. Badiee;J. Wallbank;J. P. Fentanes;E. Trill;Pete Scarlet;Yongchao Zhu;Grzegorz Cielniak;Hollie M. Coop
宇宙射线中子探测器（CRNP）由于其方便的大（>100米）足迹而在土壤水分（SM）估计中得到了应用。在这里，我们探索了使用高密度聚乙烯（HDPE）减速剂来限制视场的可能性，因此，SM传感器的足迹由安装在移动的机器人平台（Thorvald）上的12个CRNP形成，以更好地现场定位水分变化。使用超快速自适应中子模拟中子散射模拟来表明，5 cm的附加HDPE慢化剂（用于屏蔽探测器的上表面和侧面）足以（a）显著减小探测器的覆盖区，（B）使从探测器的5 m内探测到的中子的百分比大约加倍，以及（c）不影响用于将中子计数转换成SM的曲线的形状。草与混凝土之间的横断面的模拟和流动站测量还表明，（d）SM变化可以在几十米或更短的长度尺度上被感知（大约比常用的覆盖区距离小一个数量级），以及（e）附加慢化剂不降低探测到的中子计数率（并因此增加噪声）尽可能多地考虑到附加减速剂的程度。探测器与额外的高密度聚乙烯减速器也被用来进行测量的残茬领域超过三个星期，以测试在测量空间和时间SM变化的流动站系统。
Cosmic‐Ray Neutron Probes (CRNP) have found application in soil moisture (SM) estimation due to their conveniently large (>100 m) footprints. Here, we explore the possibility of using high‐density polyethylene (HDPE) moderator to limit the field of view, and hence, the footprint of a SM sensor formed of 12 CRNP mounted on to a mobile robotic platform (Thorvald) for better in‐field localization of moisture variation. Ultra Rapid Adaptable Neutron‐Only Simulation neutron scattering simulations are used to show that 5 cm of additional HDPE moderator (used to shield the upper surface and sides of the detector) is sufficient to (a) reduce the footprint of the detector considerably, (b) approximately double the percentage of neutrons detected from within 5 m of the detector, and (c) does not affect the shape of the curve used to convert neutron counts into SM. Simulation and rover measurements for a transect crossing between grass and concrete additionally suggest that (d) SM changes can be sensed over a length scales of tens of meters or less (roughly an order of magnitude smaller than commonly used footprint distances), and (e) the additional moderator does not reduce the detected neutron count rate (and hence increase noise) as much as might be expected given the extent of the additional moderator. The detector with additional HDPE moderator was also used to conduct measurements on a stubble field over three weeks to test the rover system in measuring spatial and temporal SM variation.