URANOS v1.0 – the Ultra Rapid Adaptable Neutron-Only Simulation for Environmental Research

Abstract. The understanding of neutron transport by Monte-Carlo simulations led to major advancements towards precise interpretation of measurements. URANOS (Ultra Rapid Neutron-Only Simulation) is a free software package, which has been developed in the last years in a cooperation of Particle Physics and Environmental Sciences, specifically for the purposes of cosmic-ray neutron sensing (CRNS). Its versatile user interface and input/output scheme tailored for CRNS applications offers hydrologists a straightforward access to model individual scenarios and to directly perform advanced neutron transport calculations. The geometry can be modeled layerwise, whereas in each layer a voxel geometry is extruded using a two-dimensional map from pixel images representing predefined materials and allowing to construct objects on the basis of pixel graphics without a 3D editor. It furthermore features predefined cosmic-ray neutron spectra and detector configurations and allows also a replication of important site characteristics of study areas – from a small pond to the catchment scale. The simulation thereby gives precise answers to questions like: From which location do neutrons originate? How do they propagate to the sensor? What is the neutron response to certain environmental changes? In recent years, URANOS has been successfully employed by a number of studies, for example, to calculate the cosmic-ray neutron footprint, signals in complex geometries like mobile applications on roads, urban environments and snow patterns.