DESIGN AND CONSTRUCTION OF LIGHT WEIGHT PORTABLE NMR HALBACH MAGNET

Abstract

A light weight, simple design NMR apparatus consists of 24 identical magnets arranged in Halbach array was designed and built. The homogeneity of the magnetic field B0 can be improved by dividing a long magnets into several rings. The size of the useful volume depends on both the gap between each ring and some others shim magnets. Our aim is to enhance the sensitive volume and to maintain the highest magnetic static field (B0). This apparatus generates a B0 field strength of about 0.1 T. This work focuses on the magneto-static simulation of NdFeB magnets arrangement and on the comparison with the measurement of the magnetic field strength and homogeneity in three dimensions (3D). The homogeneity of the magnetic field B0 is optimized with the help of CAD and mathematical software. Our results were also validated with a Finite Element Method (FEM). The simulation results of the strength and of the homogeneity of B0 field were compared to those obtained with a digital gaussmeter. The homogeneity in the magnet longitudinal axis and the field B0 strength are similar. However, the homogeneity in transverse plane differs from simulation and measurement because of the quality of the magnets. In order to improve the homogeneity, we propose a new shim method.