A low-noise multilayer mu-metal thin shell magnetic shield for ultra-highly sensitive atomic sensors

Magnetic shields are essential in various high-sensitivity measurements to ensure a stable and weak magnetic field. Multilayer mu-metal shields have wide applications owing to their high shielding factors. However, the magnetic noise generated by their innermost layers limits the performance of high-sensitive atomic devices, and thus it should be suppressed as much as possible. A multilayer mu-metal thin-shell structure is proposed to replace the conventional single-layer mu-metal structure with the same thickness. The proposed structure reduces the magnetic noise by decreasing eddy current loss and while simultaneously improving the shielding factors. The calculation models of this structure are established by the finite element method, and its magnetic noise and shielding factors are compared with those of the conventional single-layer mu-metal structure. Furthermore, the influence of insulating layers between the thin shells on the performance of the proposed structure in the low-frequency range was quantitatively analyzed. Finally, the magnetic noise and shielding factors of the two structures are experimentally measured. Compared with the single-layer mu-metal structure, the magnetic noise of the multilayer mu-metal thin-shell magnetic structure is reduced by 46%, and the radial shielding factor is increased by 280%, which confirming the superiority of the novel structure. This study has applications in precision measurements, which require low-noise magnetic shields.