Passive shimming of the superconducting magnet for MRI

The method of passive shimming of homogeneous magnets is presented. The simple regular configuration of the thin iron strips is used. Positions of the strips are optimized by computer simulation and independent of the field distribution, i.e. remain the same despite magnet modification. The variable parameter for field correction is the number of strips on each position. Contribution of shims to the field distribution is defined by computer simulation. The number of strips is calculated by a regularized least square method taking into account point field measurements in the working volume. This method was successfully used for correction of the field of the 0.3 T superconducting magnet for MRI with large initial unhomogeneities. The results are presented. >