Project Details
Projekt
Neutron Simulation; Developing a theoretical framework for CRNS
Applicant
Professor Dr. Ulrich Schmidt
Subject Area
Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management
Term
since 2018
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 357874777
Based on Monte-Carlo transport studies in phase I of Cosmic Sense we developed analytical solutions for the cosmic-ray neutron flux to a variety of environmental conditions and topologies. The main finding is a revised model of the above-ground neutron intensity as a function of soil moisture and air humidity. The understanding of the detection process led to substantial improvements in the design of neutron probes with respect to their capability to detect environmental water. Furthermore, we improved the code basis and versatility of the neutron simulation URANOS, benchmarked it against state-of-the-art software and acquired new users in the CRNS community.So far mostly homogeneous environments have been considered and the currently applied intensity conversion assumes soil moisture to be evenly distributed within the footprint. It was however shown that, due to the complex nature of neutron transport and detection, the horizontal and vertical distribution of different water pools have non-linear effects on the overall signal. This is a crucial issue, because the research modules (RMs) of Cosmic Sense investigate different hydrogen pools. We hypothesize that these different components could be disentangled from each other using comprehensive neutron simulations. Gradients within the footprint, horizontally or likewise vertically, as well as combinations of both have been identified as relevant influence factors, which require an independent analysis and theoretical understanding of the corresponding neutron response. The scope of this RM is also set to understand more in detail the processes involved in atmospheric cascades, which generate not only cosmic-ray neutrons, but also other particles, like muons, which eventually contribute to the ground-albedo neutron flux. A better understanding of particle reactions in the atmosphere is crucial to refine correction factors air pressure, air humidity, and incoming radiation at different latitudes and altitudes. The latter could be approached by better theoretical understanding or on-board muon detectors to facilitate real-time data correction (RM “Detector Development”). The URANOS model will be also used to extend and recalibrate the 1D forward operator COSMIC, which will be extensively used for the data assimilation in RM “Hydrological Modeling”, the simulation of dynamic vertical water profiles in RM “Root Zone” and RM “Snow Dynamics”, and also for the spatial inversion techniques investigated in RM “Smart Coverage”. NS will further establish a “virtual neutron laboratory” based on URANOS, which will allow users of various disciplines to easily conduct their own research on the spatiotemporal neutron response to specific model entities. This virtual environment would extend the usability of simulation toolkits in environmental sciences and boosts the field of CRNS and their interfaces to hydrological applications.
DFG Programme
Research Units
Co-Investigator
Dr. Martin Schrön
