Analytical model for calculation of the magnetic field of triaxial uniform coils in magnetically shielded cylinder

An analytical model to calculate the magnetic field of triaxial uniform coils inside magnetically shielded cylinders (MSCs) composed of high-permeability materials is proposed. The proposed model offers two major advantages over existing methods. First, the model is not limited to the research on coaxial circular coils, but also can be used to analyze the magnetic field characteristics of saddle coils inside MSCs. Second, based on Green’s function expansion and the ferromagnetic boundary conditions, the image method is introduced to consider the reflection effect of the MSC end cap on the coil, thus enabling the coupling effect between the coil and the MSC to be analyzed. To verify the model’s correctness, simulations and experiments are performed separately. With regard to the magnetic field distributions of the saddle coil and the Lee-Whiting coil within a range of ± 80 mm along their axes, the results show that the maximum relative error between the analytical method and the finite element method results is 0.08% and 0.06%, respectively; the maximum relative error between the experimental values and the analytical values is 0.29% and 0.13%, respectively, thus confirming the validity of the analytical model. The results of this research have far-reaching implications for the research of quantum precision measurement devices and triaxial uniform field coils.