"Wide-Area and Local-Area Water Characterization in Underlying Soil Using Cost-Effective, Directional Detectors and Novel Moderation Designs"

The Cosmic-ray Neutron Sensing (CRNS) method can measure the water content of soil with 2% accuracy (under optimal conditions) for agriculture-sized (ie., hectometers) scale. The method uses a neutron detector situated above ground in the center of the measurement area, monitoring in real-time the emission of cosmic-ray produced neutrons from the soil. The simple, non-invasive measurement can provide real-time data on the soil moisture content, leading to data-driven decisions on water use for irrigation.The objective of the proposed work is to develop a next-generation CRNS system using cost-effective lithium-based neutron detectors that enable the user to dial the CRNS to measure the moisture content of a user-defined footprint, from several meters away from the detector to the full range of up to 300 m. It is proposed that this can be accomplished by designing moderator configurations that focus the field of view of the detector, eliminating inbound neutrons from angles representing soil outside the area of interest.The proposed research has two components: (i) performing simulations to determine optimal moderator configurations for the lithium neutron detector to accomplish wide-area and local-area monitoring; (ii) building a prototype moderator/shielding system for the lithium neutron detector and testing the system in a moisture-controlled laboratory and field environments.The innovation will: create greater control of the detection footprint for a cost-effective CRNS system, and improve performance for large-scale measurements by reducing sensitivity to local area heterogeneities. These innovations are critical to the development and commercialization of next-generation CRNS systems.