Optimal design of closed multilayer magnetic shields

The present paper deals with the optimisation of closed shield for the attenuation of magnetic fields produced by direct and alternating currents. A multilayer shield made of different concentric layers is proposed. The optimisation procedure defines the best thicknesses and the distances between layers. The shield performance is required in a wide range of frequencies and magnetic field strengths (from 50-100 nT to 10000-50000 nT). In a first step the optimisation procedure has been applied to a simplified structure as a 2D cylinder immersed in a uniform magnetic field. In a second step the procedure has been applied to a 3D case, with cubic shape, which simulates an actual situation that can be found in the so called Magnetically Shielded Rooms.