Advanced surface coil layout with intrinsic noise cancellation properties for surface-NMR applications

Abstract

A recent study demonstrated that in small-scale prepolarized surface nuclear magnetic resonance (SNMR-PP) measurements with a footprint of a few square meters, customized PP switch-off ramps can serve as an efficient excitation mechanism, eliminating the requirement for a conventional oscillating excitation pulse. This approach enables the detection of short relaxation signals from the unsaturated soil zone and can, therefore, be used to directly provide soil moisture and pore geometry information. Because ultimately such small-scale SNMR-PP setups are intended for a mobile application, it is necessary to develop strategies that allow for speedy measurement progress and do not require noise cancellation protocols based on reference stations. Hence, we developed a new concentric figure-of-eight (cFOE) loop layout that combines the direction independence of a circular loop with the intrinsic noise cancellation properties of a classical FOE-loop. This approach significantly decreases the measurement time because suitable signal-to-noise ratios are reached much faster compared to a classical circular loop and will bring us one step further toward fast and non-invasive soil moisture mapping applications.