Homogenous static magnetic field coils dedicated to portable nuclear magnetic resonance for agronomic studies

Nuclear magnetic resonance (NMR) experiments are usually carried out at very high and homogenous magnetic fields. However, portable systems have emerged in recent years at low fields, offering many advantages like easier maintenance and open design that permit us to imagine a variety of coil configurations in order to maximize the homogeneity of the static field B0 and the radio-frequency field B1. The wire winding distribution based on space harmonics suppression (SHS) of the cosine current density distribution offers new possibilities of producing homogenous static fields B0. In this work, an extension of the SHS method, allowing homogeneity enhancement and flexibility of the coil design, is presented. The efficiency of the method is demonstrated through the construction of homogenous magnetic field coils dedicated to a very low magnetic field (8 mT) 1H NMR spectrometer. The performance of these coils in terms of magnetic field intensity and homogeneity as well as self-heating behavior is compliant with in planta experiments for agronomic studies.