Multilayer Cylindrical Magnetic Shield for SERF Atomic Co-Magnetometer Application

Abstract

This paper presents the development of a spin-exchange relaxation-free atomic co-magnetometer with a magnetic shielding system. The shielding system includes multiple cylindrical passive magnetic shield and active magnetic compensation coils. The multilayer shield, which adopts a structural style comprising a barrel body and end cover, is applied to attenuate the external magnetic field to less than 10 nT or ideally close to 0. For the purpose of degaussing, pumping, and probing light paths, several openings must be made on the magnetic shield. A hybrid approach combining theoretical calculations and the finite element method is proposed to analyze the shielding properties, considering the influence of openings. To evaluate the shielding properties of the magnetic shield, two different simplified finite element models are established and analyzed. The simulation results are compared with theoretical and experimental data, and the results are in good agreement. The modeled results show that the openings bear a considerable influence on the shielding performance, and thus, their effect cannot be ignored. The axial magnetic shielding factor with several openings is roughly $4.4\times 10^{4}$ , which is about 2 orders of magnitude lower than that without openings. Furthermore, a rotation sensitivity of $5.86\times 10^{-7}$ rad $\cdot \,\,\text{s}^{-1}\,\,\cdot $ Hz−1/2 is obtained with the open-hole magnetic shield. This sensitivity corresponds to a magnetic sensitivity of 27.8 fT/Hz1/2. Based on the results, possible improvements are suggested for future designs.