Assessing the feasibility of a directional cosmic-ray neutron sensing sensor for estimating soil moisture

Abstract. Cosmic-ray neutron sensing (CRNS) is a non-invasive tool for measuring hydrogen pools such as soil moisture, snow or vegetation. The intrinsic integration over radial hectare-scale footprint clear advantage averaging out small-scale heterogeneity, but on the other hand data may become hard to interpret in complex terrain with patchy land use. This study presents directional shielding approach prevent neutrons from certain angles being counted while counting entering detector and explores its potential gain sharper horizontal view surrounding moisture distribution. Using Monte Carlo code URANOS (Ultra Rapid Neutron-Only Simulation), we modelled effect of additional polyethylene shields field assessed impact epithermal count rate, propagated uncertainties aggregation time. results demonstrate that CRNS measurements are strongly dominated by isotropic transport, which dilutes signal targeted direction especially far field. For typical rates customary stations, half-spaces could not lead acceptable precision at daily time resolution. However, mere statistical distinction two should be feasible.