Testing of magnetic shielding system exceeding 10 ¹⁰ damping based on ultrasensitive atomic magnetometer

Abstract High-performance magnetic shielding systems require accurate shielding factor (SF) evaluation, yet testing ultra-high-performance systems (SF > 10 8 ) remains challenging due to the need for impractically large external excitation fields. We developed a testing system specifically designed for this task, based on a portable atomic magnetometer, achieving a sensitivity better than 1 fT/Hz 1/2 . By applying an order of 10 4 nT external field via uniform coils and extracting signals via noise spectrum analysis, we achieved the capability to test SFs up to the order of 10 10 at a signal-to-noise ratio (SNR) of 2. Testing of 10‑layer magnetic shielding cylinders revealed a pronounced frequency dependence of the SF within the 1-100 Hz band. The radial SF ranges from 1.7 × 10 9 to 5.0 × 10 10 , while the axial SF varies between 4.8 × 10 7 and 1.3 × 10 10 , exhibiting the characteristic of an initial increase followed by a decrease with frequency. Furthermore, the phase-frequency characteristics, which are often overlooked in previous studies, were also tested. The results revealed pronounced hysteresis, which is of great significance for practical applications involving real-time magnetic field closed-loop systems.