OPTIMAL-DESIGN METHOD FOR MRI SUPERCONDUCTING MAGNETS WITH FERROMAGNETIC SHIELD

This paper describes an optimal design method for highly homogeneous s uperconducting magnet systems with ferromagnetic shield. The presented design technique is a combination of the equivalent magnetization cur rent method for the computation of the magnetic field problem, which i ncludes nonlinear and saturated iron, and the simulated annealing for solving the corresponding optimization problem. The equivalent magneti zation current method is superior in estimating the field homogeneity of the center of the magnet systems. By using the simulated annealing, the positions of each solenoid coil are optimized as continuous desig n variables, while the number of turns and layers of the coil windings are treated as discrete design variables. The details of the algorith m and some examples of its application to 1.5-tesla magnet systems wit h three types of magnetic shielding are shown.