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The shielding property of cylinder with circular, square, and equilateral triangle holes was investigated by finite element analysis (FEA). The hole area (S hole) plays an important role in magnetic circuit on the surface of cylinder. When S hole is less than the critical area (S H), cylinder with three shapes of holes obtained the same remanent magnetization inside, indicating that the shielding property is unaffected by the shape of the hole. Hence, high-permeability material is the major path of the magnetic field. On the condition of S hole > S H, the sequence of the shielding property is equilateral triangle > square > circular, resulting from magnetoresistance of leakage flux in air dielectric. Besides, the anisotropy of shielding property caused by hole structural differences of the cylinder is evaluated. We find that a good shielding effectiveness is gained in the radial direction, compared with the axis direction. This research focuses on providing a theoretical support for the design of magnetic shield and improvement on the magnetic shielding ability.

In this paper, the influence of rectangular holes with different aspect ratios in a cylinder on shielding properties is investigated using the finite element method. The two indicators used to assess the shielding properties of the cylinder are its internal residual magnetic field and its outer-surface magnetic field map. The internal residual magnetic field ( B) of a cylinder as a function of the aspect ratio of a rectangular hole and its area is simulated, and the conclusions are as follows: with increasing length of the hole, the value of B increases first and then decreases. A cylindrical shield with square holes (the hole aspect ratio is equal to 1) delivers the worst shielding performance. A cylinder with a smaller hole area has better shielding properties, resulting from a less flux leakage from the environmental magnetic field. The anisotropy of the shielding properties is evaluated, and the magnetic shielding in the radial direction is better than that in the axial direction. This research provides a theoretical guide for the application and optimization of magnetic shields.

The spin exchange relaxation free (SERF) atomic magnetometer plays an important role in ultrahigh sensitive magnetic measurements. With the improvement of signal response and the reduction of sensor noise, the sensitivity of the SERF atomic magnetometer is limited mainly by environmental magnetic noise. In order to improve the performance of magnetic shielding, the models of a magnetic shielding cylinder with triangular holes were established in this paper, and the effect of aperture angle ( θ) on the efficiency of shielding by a permalloy cylinder was investigated by the finite element analysis. The results showed that the shielding effectiveness decreases first and then increases with the augment of θ. The cylinder showed that the worst shielding effect at θ equals 60°, resulting from the magnetoresistance of leakage flux in the air dielectric. This research focuses on providing theoretical support for the design of magnetic shields and improvement of the magnetic shielding ability.

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