Mobile Magnetic Ressonance Sensor utilizing a superconductive coil for prepolarisation in the near subsurface (MORE SPIN)

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The aim of the proposed project is the development of a highly mobile NMR sensor to detect lateral and vertical changes in the soil moisture content down to about 2 m depth.Soil moisture is important for numerous processes. As soil is the interface between the atmosphere and the subsurface it is relevant for fluid and mass transport processes. However, up to now, there are no adequate methods that can directly map the soil moisture content at all demanded time and spatial scales. Either the methods are direct but cannot be used on a large scale or they can be used on the large scale such as common geophysical methods but are indirect and therefore suffer from ambiguities.As a non-destructive direct method nuclear-magnetic-resonance (NMR) and its application from the surface of the Earth (SNMR) has gained increasing interest in the geophysical community to target hydrological questions. Unfortunately, SNMR is not capable to deliver soil parameters for the very near surface (dm) due to insufficiently low sensitivity at that depth range and furthermore SNMR measurement are too time consuming to map large (km) areas. Recently, theoretical concepts were presented lately that suggest the development of a new NMR-based sensor to overcome these restrictions of measurement progress and sensitivity.The proposed concept of a proper, highly mobile NMR sensor is based on prepolarisation using a superconducting coil together with adiabatic pulses and small point-like receivers. While prepolarisation is used to increase the macroscopic magnetisation, adiabatic pulses ensure a more homogeneous excitation of the subsurface. Both features combined promise an increase in signal amplitude of at least a decade whereas point-like receivers will help to increase lateral resolution.The full-functional new sensor enables to access the soil moisture distribution at a large scale and at selected depths (e.g., top soil, root zone, subsoil) down to 2 m. Therefore, it has the potential to become a ground-breaking tool to obtain information on mass transport (in connection with permafrost or climate change modelling), groundwater recharge, soil protection or even precision agriculture. Consequently, soil scientists from the Leibniz University Hanover, the Berlin Technical University, the Federal Institute for Geosciences and Natural Resources and the RWTH Aachen support the proposal as they have great interest to use the developed instrument for their own research.