A high-performance multilayer cylindrical magnetic shielding with a varying layer spacing for NMR sensors

Abstract

A stable inner working environment is essential for NMR sensors, which requires the absence of remnant magnetic fields and fluctuations caused by the surrounding magnetic fields. In this study, we utilized analytical formulations to derive transverse and longitudinal magnetic shielding factors for multilayer cylindrical magnetic shielding. Subsequently, we proposed a novel method for designing and improving the shielding factor by optimizing the spacing of every pair of adjacent layers within a limited volume. The final design result of the multilayer cylindrical magnetic shielding features optimally designed varying layer spacing, which are associated with a specific length and diameter. After optimization, the transverse shielding factor increased by 5.53%, 8.99%, and 13.51% for the three-, four-, and five-layer shields, respectively, compared to traditional magnetic shielding. The opening in the axial center of the magnetic shielding barrel may cause leakage of the magnetic flux and inhomogeneous remnant magnetic induction. We introduced a stovepipe to the end cap of the axial shield based on the finite element method, resulting in an improvement in the homogeneity of remnant magnetic induction. This modification widened the axial uniform region of the innermost shielding layer by approximately 9 cm within 52.5 cm in our simulation. To implement our proposed optimization method, we established and manufactured a four-layer cylindrical magnetic shielding with stovepipes and varying layer spacing. Moreover, the results indicate that this optimal method works for other applications in which multilayer magnetic shielding is required.

A combined magnetic field stabilization system for improving the stability of 40Ca+ optical clock

“…Future improvements in magnetic shields can be achieved by increasing the number of layers and optimizing the spacing of each pair of adjacent layers within a limited volume. [27] 3. Active magnetic shielding system For practical applications of portable 40 Ca + optical clocks, a passive magnetic field shielding system alone is usually not sufficient to reduce the transition spectral linewidth to the Hertz level in complex external magnetic field environments.…”