Soil moisture and air humidity dependence of the above-ground cosmic-ray neutron intensity
Investigations of neutron transport through air and soil by Monte Carlo simulations led to major advancements towards a precise interpretation of measurements, especially they improved the understanding of the cosmic-ray neutron footprint. Up to now, the conversion of soil moisture to a detectable n...
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| Main Authors: | , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
28 January 2021
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| In: |
Frontiers in water
Year: 2021, Volume: 2 |
| ISSN: | 2624-9375 |
| DOI: | 10.3389/frwa.2020.544847 |
| Online Access: | Verlag, kostenfrei, Volltext: https://doi.org/10.3389/frwa.2020.544847 Verlag, kostenfrei, Volltext: https://www.frontiersin.org/articles/10.3389/frwa.2020.544847/full 
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| Author Notes: | Markus Köhli, Jannis Weimar, Martin Schrön, Roland Baatz and Ulrich Schmidt |
| Summary: | Investigations of neutron transport through air and soil by Monte Carlo simulations led to major advancements towards a precise interpretation of measurements, especially they improved the understanding of the cosmic-ray neutron footprint. Up to now, the conversion of soil moisture to a detectable neutron count rate relies mainly on the equation presented by Desilets et al. (2010). While in general a hyperbolic expression can be derived from theoretical considerations, their empiric parameterisation needs to be revised for two reasons. Firstly, a rigorous mathematical treatment reveals that the values of the four parameters are ambiguous because their values are not independent. We find a 3-parameter equation with unambiguous values of the parameters which is equivalent in any other respect to the 4-parameter equation. Secondly, high-resolution Monte-Carlo simulations revealed a systematic deviation of the count rate to soil moisture relation especially for extremely dry conditions as well as very humid conditions. That is a hint, that a smaller contribution to the intensity was forgotten or not adequately treated by the conventional approach. Investigating the above-ground neutron flux by a broadly based Monte-Carlo simulation campaign revealed a more detailed understanding of different contributions to this signal, especially targeting air humidity corrections. The packages MCNP and URANOS were used to derive a function able to describe the respective dependencies including the effect of different hydrogen pools and the detector-specific response function. The new relationship has been tested at two exemplary measurement sites and its remarkable performance allows for a promising prospect of more comprehensive data quality in the future. |
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| Item Description: | Gesehen am 31.03.2021 |
| Physical Description: | Online Resource |
| ISSN: | 2624-9375 |
| DOI: | 10.3389/frwa.2020.544847 |