PASSIVE SHIMMING OF THE SUPERCONDUCTING MAGNET FOR MRI

The method of passive shimming of homogeneous magnets is presented. Th e simple regular configuration of the thin iron strips is used. Positi ons of the strips are optimized by computer simulation and independent of the held distribution, i.e. remain the same despite magnet modific ation. The variable parameter for field correction is the number of st rips on each position. Contribution of shims to the field distribution is defined by computer simulation. Number of strips is calculated by regularizated least square method taking into account points field mea surements in the working volume. This method was successfully used for correction of the field of the 0.3T superconducting magnet for MRI wi th large initial unhomogeneities. The results are presented.