Pre-clinical Magic Angle Field Spinning MRI magnet for localized NMR spectroscopy

Magic Angle Sample spinning is one of the cornerstones of solid-state NMR. Most of anisotropic interactions can be eliminated upon rapid sample rotation, leading to narrow high-resolution NMR spectra. There are however many situations where the sample cannot, or should not be spun rapidly, for example in living tissues, in porous media, in heterogeneous reactors and in energy materials. In these cases the equivalent option (1) of Magic Angle Field Spinning seems very appealing. Many efforts (2,3,4) have been made to produce a sufficiently strong and homogeneous magnetic field, rotating at the magic angle, without for the moment reaching the required homogeneity and stability for resolving 1H resonances.

We have recently shown that pure permanent magnets can provide solenoidal fields having sub-ppm high spectral resolution. Furthermore, we have demonstrated high-resolution Magic Angle sample spinning at 0.9T, resolving the resonances from small mobile molecules in various heterogeneous samples such as seeds and rock cores (5).

Here we present the first wide-bore (76mm diameter), preclinical pure permanent magnet for magic angle field spinning imaging and spectroscopy experiments. The structure of the magnet is inspired by a hybrid, interleaved design (6). The field strength is 1.0T and the vertical spinning frequency is limited for safety reasons to 6Hz. Additional instrumentation (shims and pulsed field gradients) are spinning together with the magnet.