In this paper, a new portable, low-cost magnet with a good homogeneity is presented. The single-layer central magnet structure based on Halbach-type array has been designed, simulated which can generate a magnetic field of 1 T under the weight of 2 kg. Magnetic strips placed at the ends of the central magnet are presented to improve the central homogeneity. In order to counteract the inhomogeneity resulting from manufacturing tolerances, a new compact shimming structure designed for miniature Halbach magnet is applied. With this structure a reduction of the full width at half maximum (FWHM) from 21 kHz to less than only 0.7 kHz, which is adequate for achieving a good NMR relaxation signal. This novel miniature magnet structure has achieved an excellent balance between cost and homogeneity for portable time domain NMR.
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