Soil moisture and air humidity dependence of the above-ground cosmic-ray neutron intensity

• Verfasst von: Köhli, Markus [VerfasserIn]
• Verfasst von: Weimar, Jannis [VerfasserIn]
• Verfasst von: Schmidt, Ulrich [VerfasserIn]
• Titel: Soil moisture and air humidity dependence of the above-ground cosmic-ray neutron intensity
• Verf.angabe: Markus Köhli, Jannis Weimar, Martin Schrön, Roland Baatz and Ulrich Schmidt
• E-Jahr: 2021
• Jahr: 28 January 2021
• Umfang: 15 S.
• Teil: volume:2
• Teil: year:2021
• Teil: day:28
• Teil: month:01
• Teil: elocationid:544847
• Teil: extent:15
• Fussnoten: Gesehen am 31.03.2021
• Titel Quelle: Enthalten in: Frontiers in water
• Ort Quelle: Lausanne : Frontiers Media, 2019
• Jahr Quelle: 2021
• Band/Heft Quelle: 2(2021) vom: 28. Jan., Artikel-ID 544847
• ISSN Quelle: 2624-9375
• DOI: doi:10.3389/frwa.2020.544847
• Datenträger: Online-Ressource
• Sprache: eng
• Sach-SW: Air humidity
• Sach-SW: Cosmic-ray neutron sensing
• Sach-SW: MCNP
• Sach-SW: monte carlo
• Sach-SW: neutron
• Sach-SW: soil moisture
• Sach-SW: URANOS
• K10plus-PPN: 1752980514
• K10plus-PPN:
  Universitätsbibliothek
• Lokale URL UB: Zum Volltext

Abstract

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.