Mobile sensor for high resolution NMR spectroscopy and imaging

In this work we describe the construction of a mobile NMR tomograph with a highly homogeneous magnetic field. Fast MRI techniques as well as NMR spectroscopy measurements were carried out. The magnet is based on a Halbach array built from identical permanent magnet blocks generating a magnetic field of 0.22 T. To shim the field inhomogeneities inherent to magnet arrays constructed from these materials, a shim strategy based on the use of movable magnet blocks is employed. With this approach a reduction of the line-width from ∼20 kHz to less than 0.1 kHz was achieved, that is by more than two orders of magnitude, in a volume of 21 cm 3. Implementing a RARE sequence, 3D images of different objects placed in this volume were obtained in short experimental times. Moreover, by reducing the sample size to 1 cm 3, sub ppm resolution is obtained in 1H NMR spectra.