Simulations of Dual Electrical Source-Based SNMR for Deep Water in Urban Environments

Recently, surface nuclear magnetic resonance (SNMR) detection work for groundwater has been performed in complex and noisy urban environments as this method directly provides quantitative water content distribution information. However, the weak signal, the high noise, and the inconvenience of the large size magnetic source (MS) restrict the development of this work. The application of electrical source (ES) with low topographic requirement enables SNMR measurements in obstacle areas. To further improve the signal strength and depth resolution, we propose configurations based on dual ESs. Three long wires are laid side by side on the surface, and all the ends of each wire are grounded by electrodes. The middle one is used for signal acquisition, and the two on either side are used as dual ESs to implement NMR excitation of groundwater. We have simulated 3-D magnetic field, kernel, and signal with an expanded range of effective actions. It has been proved by simulations that the signal amplitude can be increased to more than ten times that of MS by dual ESs with the coincident current flows (CF-ESs) in deep water modeling over 100 m. Its theoretically determinable depth is 50 m deeper than MS. The CF-ESs consume only half the pulse intensity to achieve the same amplitude as previous single ES. The new approach shows great potential to expand SNMR measurements in challenging urban settings.