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

Abstract

Abstract. 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.

Multiscale NMR investigations of two anatomically contrasted genotypes of sorghum under watered conditions and during drought stress

“…The magnetic field is produced by a homemade homogenous resistive magnet based on the SHS method. The design of the prototype is detailed in Sidi‐Boulenouar et al This choice is a compromise between generation of a homogeneous magnetic field on one side and self‐heating to avoid the thermal stress around the plant on the other side (less than 6°C).…”

“…Unfortunately, these MRI scanners are not transportable, require a considerable amount of electric power, and are not suitable for large‐scale studies in the fields . On the contrary, low‐field portable NMR devices have a great potential for studying plants in their natural environment, and their development is still at beginning …”

“…[27,40] On the contrary, low-field portable NMR devices have a great potential for studying plants in their natural environment, and their development is still at beginning. [25,26,[28][29][30][31][32][33][34] In this context, this work reports on the feasibility to study drought stress in sorghum plants with the help of an original homemade, portable, and noninvasive NMR device coupled with a high-impedance low-noise amplifier as receiver and power radio frequency amplifier as transmitter. This device presents several innovations such as the improvement of the homogeneity of the space harmonics suppression (SHS) static magnetic field, the gain in signal-to-noise ratio, and the attenuation of the acoustic ringing thanks to switching and blanking the coil between the emission and detection periods, the weight that is less than 10 kg easy to move outside the laboratory and the total cost of production.…”

“…This device presents several innovations such as the improvement of the homogeneity of the space harmonics suppression (SHS) static magnetic field, the gain in signal-to-noise ratio, and the attenuation of the acoustic ringing thanks to switching and blanking the coil between the emission and detection periods, the weight that is less than 10 kg easy to move outside the laboratory and the total cost of production. [32,35] The originality of our work is also related to the nature of the studied sorghum plant, which is a candidate species with high economic potential because of its immense biodiversity, its rapid growth, its large amount of generated biomass, and its incredible genotypic and phenotypic panels. [36] In addition, its resistance to drought and high temperature make it possible to adapt to real climatic constraints.…”

Homogenous nuclear magnetic resonance probe using the space harmonics suppression method

“…The efficiency of the SHS method was demonstrated thanks to numerical finite element method analysis. SHS method was then extended to enhance the homogeneity of the coils by adjusting both the angular position of the wires (distributed along the circle circumference) and the current magnitude flowing through the wires (Sidi-Boulenouar et al, 2018). The extended method efficiency was illustrated through the realization of a spherical shape distributed coils creating a highly homogenous static magnetic field for NMR device.…”