Realization of a Multishell Magnetically Shielded Cylinder for SERF Magnetometer Via Hybrid Design Method

Magnetically shielded cylinder (MSC) is an efficient way to construct a proper working environment for spin-exchange relaxation-free (SERF) magnetometers. In this article, we propose a modified hybrid method combining analytical solutions with finite element analysis (FEA) to improve the design efficiency and validity of an MSC. Focusing on the radial and axial shielding factors, the number of Permalloy-shell can be fast determined as 4 via analytical solutions. Then based on a carefully built FEA model in COMSOL, shielding factors together with uniformity factors extracted from magnetic distribution maps, are employed to optimize the distance of air gaps and the size and shape of access holes. The shielding performance is well tested after the realization of MSC with optimal structural parameters. It shows that the static residual field can reach as low as 0.50 and 1.39 nT in radial and axial directions, and the field uniformity are superior to 5% in most of the target region. The measurement results are well in coincidence with the simulation ones, indicating the validity of this hybrid design method.