3D nonlinear magnetostatic analysis of a double-walled cylindrical shield

The performance of a double-walled cylindrical shield for magnetostatic field has been optimized using a 3-D numerical code. The shielding factor of the double-walled screen has been evaluated by varying the geometrical parameters. The optimization of the screen and the design criteria are reported. The influence on the shielding factor of the presence of a hole perpendicular to the cylindrical shield has been evaluated by calculating the field penetration into the internal region of the screen. Finally, the FEM (finite-element method) results have been tested by means of measurements performed on a shield prototype. The comparison between the numerical and experimental data shows good agreement, especially in the region where the finite-element model has been refined with more elements