On the synthesis of a highly homogeneous field of a permanent magnet in MR tomography

A procedure is developed for determining parameters of a permanent magnet of a MR tomograph, for which a highly homogeneous field is created in the air gap of the magnet. In this procedure, one uses an analogy between a magnet and a set of turns with current. This analogy permits one to use formulas for turns fields in calculating the magnet field. To enhance the field homogeneity, hollows and small pits are inserted into magnet pole pieces, i. e. the magnet of a complicated configuration is considered. The parameters of the magnet, hollows and small pits are determined starting from the condition of minimum deviation of a calculated field from a homogeneous one. The results of numerical modelling are shown. The recommendations for practical realization of the present procedure in MR tomography are given.