Optimal Design of the Self-shielded Shim Coil Combined with Target Points

This research proposes a self-shielded saddle shim coil design technique, based on the magnetic field data of the target field points, to counterbalance the coupling effect of the magnetic shield on the coil in the utilization of atomic sensors. This coil is composed of two nested saddle coils: the main coil and the shielding coil. The optimization function, which characterizes the internal homogeneity of the magnetic field and attenuation of the external field, is determined by the magnitude of magnetic induction at both internal and external points of the coil. The NSGA-II optimization algorithm was then used to solve the geometrical parameters of the coil, with the optimization function serving as the optimization criterion to attain the parametric solution. Based on the proposed optimized method, a self-shielded coil was designed and tested in a cylindrical ferrite shield barrel. Results from both simulation and experimentation demonstrate a decrease in the coil constant due to the coupling effect of magnetic shield and coil from 58.96% to 0.54%, while the coil designed preserves the magnetic field uniformity in the central region in comparison to the classic saddle coil. This method is suitable for applications where the magnetic shield is combined with coils.