Shape optimization of ferromagnetic pole of a superconducting MRI magnet with niching genetic algorithm

The magnetic field inhomogeneity and the Lorentz force of a superconducting magnet for magnetic resonance image are optimized by changing the shape of the ferromagnetic poles. The two objectives are calculated by a commercial software Opera3D-TOSCA based on the finite element method. The genetic algorithm improved by adding niching and adaptive algorithms is developed on the computation platform MATLAB and is applied to the optimization problem. Twice calculations with progressive discretization are performed and satisfactory results with low magnetic field inhomogeneity and very small Lorenz force are obtained.