Optimization Design of Portable NMR Probe Main Magnet

Theoretically, a permanent magnetic ring can produce a uniform and perfect unilateral magnetic field, which is a suitable option for the main magnet of a portable NMR probe. However, two main problems exist in an actual permanent magnetic ring: first, the uniformity difference is inevitable in the radial direction; second, the axial direction inevitably produces the end effect. These two problems affect the magnetic field uniformity of the main magnet of the probe. This paper focuses on these two main problems. Based on the radial optimization structure, a compensation structure for the end of the permanent magnetic ring is proposed, which achieves axial compensation of the magnetic field of the permanent magnetic ring. This structure serves as the main magnet for a new portable NMR probe, offering a technological methodology for reducing the manufacturing cost, weight, and volume of existing nuclear magnetic resonance instrument (including MRI) probes.