Magnetic Shielding Effect Research Articles

Exact Closed-Form Shielding Effectiveness of Planar Screens With Small Parallel Loops

The magnetic shielding effectiveness of a single planar screen of infinite extent against a parallel current loop source is evaluated through an analytic closed-form expression which is valid for arbitrarily thick screens and for any source-observation distance. The only assumption in the formulation consists in considering small loops having a constant current. The resulting formula can be expressed in terms of only elementary functions and is believed to represent the most general closed-form expression for the magnetic shielding effectiveness of a planar screen in the presence of a parallel loop. Numerical results are provided to show the generality and the validity of the proposed formula.

Microstructure evolution and magnetic shielding effect of permalloy deposition on molybdenum substrate by electron beam freeform fabrication

In view of the excellent soft magnetic properties, 1J85 permalloy was deposited on molybdenum substrate by electron beam freeform fabrication to achieve magnetic shielding effect for molybdenum substrate. The magnetization of molybdenum substrate was increased from 0.04 emu/g to 8.96 emu/g after depositing permalloy layer, corresponding to the decrease in coercivity from 169.44 Oe to 7.33 Oe. The saturation magnetization was increased with the increased heat input. The cellular grain boundaries were demonstrated to be element segregation instead of the conventional dislocation-walls. A reaction layer consisting of numerous Mo-Ni binary phases was located at the interface between permalloy deposition and molybdenum substrate, indicating the maximum microhardness value. The shear strength of the interface between permalloy deposition and Mo substrate was firstly increased and then decreased with the increased heat input. The residual stress in permalloy deposition corresponded to local misorientation and dislocation, which was detrimental to soft magnetic properties. The decrease in residual stress was the main reason for the increased saturation magnetization with the increased heat input. • Magnetic shielding effect of permalloy deposition on Mo substrate was prominent. • Magnetic and mechanical properties and reasons for their change are analyzed. • Influence of residual stress, local misorientation and dislocation on properties are analyzed. • Solidified model of reaction layer in deposition was built.

Progress of antiaromatic ring-contracted porphyrinoids

<p indent="0mm">Antiaromatic ring-contracted porphyrinoids have fewer pyrrole units or <italic>meso</italic> carbons than standard 18π-conjugated aromatic porphyrins and exhibit a 4<italic>n</italic> π-conjugation system, with representative molecules including 16π-conjugated norcorrole, corrole, and triphyrin. Antiaromatic ring-contracted porphyrins exhibit great molecular rigidity, excellent stability, and simplicity of functionalization, as well as intense paratropic induced ring current, strong magnetic shielding effect, small highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gap, and high charge transfer capability. This review introduces recent advances in the synthesis and functionalization of antiaromatic ring-contracted porphyrins, and highlights their promising utility in electronic materials based on aromatic-antiaromatic conversion, rechargeable battery electrode materials, and supramolecular conductive materials.

FEA simulations for low-frequency multi-layer magnetically shielded rooms

This paper proposes using Finite Element Analysis (FEA) simulations to optimize the design structure for low-frequency Magnetically Shielded Rooms (MSRs). In constructing a multi-layer MSR, the different characteristics of the material and laminated structure will bring different levels of magnetic Shielding Effectiveness (SE). The theoretical SE of an MSR can be determined quickly. By using the method used in this paper, the ideal laminated material structure can be found without increasing the MSR construction cost. According to the simulation results and the actual MSR measurement results we built, the optimized MSR design structure can improve the SE by 13 dB. In the area where the external measurement magnetic field is 37 820 nT, the magnetic field in the MSR is as low as 28 nT, and the SE of the MSR is higher than 57.3 dB. The method proposed by this research can provide the theoretical basis for optimal design structure and the FEA simulation method for engineering practice, which can effectively improve the SE of shielded rooms and save the construction cost. The FEA simulations used in this paper can be obtained from the following URL: https://github.com/YuukiAsuna/-Finite-element-simulation-of-material-lamination-sequence.

Analysis of electromagnetic characteristics of the proposed composite four-rail electromagnetic launcher

Abstract In the existing composite four-rail electromagnetic launcher (CFREL), the armature and rail contact surface produces significant heat and bears considerable wear, thereby reducing the potential amount of electromagnetic thrust to be generated. To eliminate the damage caused by the thermal effect of the rail contact surface and to meet the electromagnetic thrust demand of the load, a CFREL is proposed. The proposed CFREL model is constructed, and the launcher’s electromagnetic characteristics are simulated and compared using the finite element method. The current density, distribution of magnetic flux density, and electromagnetic thrust characteristics are analysed. The results showed that the proposed CFREL reduced the maximum current density of the contact surface and effectively eliminated the current concentration of the armature and rail contact surfaces. Effective magnetic field shielding is realised with a larger range, which can better meet the requirements of the intelligent load’s magnetic field environment and provide stronger electromagnetic thrust for the load, hence solving the problem of insufficient thrust.

Analytical Magnetic Shielding Calculation of a Slotted Conducting Plate Between Coplanar Circular Loops

This article proposes an analytic solution to calculate the magnetic shielding effectiveness (MSE) of a slotted conducting plate between coplanar circular loop antennas at a low-frequency range below 20 MHz. Mutual inductances of coplanar circular loops in the presence and absence of the slotted conducting plate are analytically derived by using the representation of an equivalent current loop and the analytic formulas presented in recent literature. Then, the MSE is defined by a ratio of two analytic mutual inductances. For the accuracy validation, the design of experiments (DOE) is performed using the difference between MSEs of the proposed solution and the numerical simulation in terms of the sizes of loop antenna and slot. Good agreement is achieved with an average error of 1.3 dB for the shielding measurement configuration of IEEE-Std-299. In addition, the proposed analytic solution requires negligible computation time.

Hall-Effect Thrusters for Deep-Space Missions: A Review

For several decades, Hall-effect thrusters (HETs) are being used in several applications, such as orbiting satellites, deep space missions, etc. This article studies the effect of several parameters, namely, thruster geometry, magnetic field, wall material, and different propellants that significantly influence thruster performance. It was reported that annular thrusters are preferred for deep space missions, whereas, cylindrical thrusters are widely used in low power applications, such as station keeping of satellites. The lifespan of HET is a crucial parameter that is decided by the erosion of the thruster wall. Magnetically shielded thrusters are preferred not only to reduce the erosion but also the secondary emission of electrons. The overall effect of magnetic shielding is the improvement in thruster performance and its lifespan. Boron nitride and mixture of boron nitride and silica (borosil) were found to be the most appropriate thruster wall materials due to their lowest electron emission and reduced ion–wall interaction. Over the years, Xenon has been the best choice among several propellants for the HET operation. Other potential propellants include Krypton, Bismuth, Iodine, etc.

Magnetic accumulation effect on the inner and outer surfaces of pipeline magnetic penetration in natural environment

In view of the detection requirements of pipeline internal and external surface defects and pipeline special regular structure detection, based on the magnetic shielding effect inside and outside the pipeline, the principle of magnetic field refraction at the interface between the pipe wall and air, and the principle of the magnetic field concentration on the pipe surface and the gap, this article focuses on the natural environment (geomagnetic background). The magnetic field distribution inside and outside the pipeline has been theoretically analyzed. After that, the finite element simulation software is used to model the finite length pipeline, and the internal and external magnetic fields are simulated and researched in combination with the finite element method. Finally, the tunnel magneto resistance (TMR) magnetic sensor is used to collect and process the internal magnetic field of the actual pipeline model, which verifies the correctness of the theoretical analysis. This paper analyzes the magnetic field inside and outside the pipeline by means of principle deduction, finite element simulation, and sensor measurement. The analysis results show that the distribution of the magnetic field in the pipeline under the excitation of the geomagnetic field has a very obvious regularity, which can meet the needs of pipeline defect detection. In addition, because the pipelines of different structures have different magnetic field distribution laws, they can also be used for the detection and analysis of pipelines with special structures.

Magnetic shield effect for 8 MW high temperature superconducting synchronous motor

Magnetic shield effect for 8 MW high temperature superconducting synchronous motor

개구면 크기에 따른 도전성 박막 소재의 자기장 차폐효과 분석

This study analyzes the effect of low-frequency (10 kHz-10 MHz) magnetic shielding effectiveness (SE) of a conductive sheet according to the aperture size used to measure its SE. To analyze the conductive sheet SE according to the size of the aperture, the analytical and numerical results of the aperture SE are compared and verified experimentally.

Electromagnetic Simulation of Low-Frequency Magnetic Shielding of a Welded Steel Plate

In this article, we experimentally evaluated the effectiveness of magnetic shielding for welded steel plates with the control of parameters such as a gap and a spot spacing for automobiles at frequencies below 1000 kHz, and predicted the shielding effectiveness by an electromagnetic analysis. It is shown that the shielding effectiveness of welded steel plates is reduced by more than 20 dB compared to that of a single plate above 10 kHz. Moreover, the shielding effectiveness of the welded steel plates strongly depended on the spacing between the spot welds, and the mechanism was studied by analyzing the eddy currents in the plates. These results provide important data for automotive design to reduce human exposure to electromagnetic waves.

Numerical Analysis of the Effect of Converter Transformer Combined Magnetic Shielding on Stray Load Losses Considering DC Bias

In order to accurately analyze the effect of combined magnetic shielding on stray load losses of converter transformer, a three-dimensional (3D) finite-element analysis (FEA) model is established. The total losses can be gotten by summing the simulated losses of each harmonic. The effectiveness of the presented simulation method is verified by comparing the simulated and tested stray load losses of the converter transformer in the case of rated operation without lobe-type magnetic shielding structure. Afterwards, the installation position of lobe-type magnetic shielding is optimized by considering its effect on stray load losses. Finally, the stray load losses under different DC bias currents are simulated and analyzed.

Possible External Factors Determining Ultradian (4-20-min) Rhythms of Body Temperature.

The study examined the effect of passive magnetic shielding on the magnitude of rhythmic oscillations of body temperature (BT) with 4-20 min periods in mice and their correlation with similar oscillations in unshielded control group. A magnetic permalloy screen that 35-fold attenuates the total geomagnetic field and decreased the undulations of magnetic field with the periods of few minutes by 5 times, produced no effect on the mean amplitude of BT oscillations within the same period range, their spectral power, and the cross-spectral density of examined rhythms in comparison with the control (unshielded) mice. Thus, either the mice possess a very sensitive magnetic sensory system or there exists an external non-magnetic factor affecting rhythmicity of BT. The study advanced intensity of thermal neutron radiation near the Earth's surface known to reflect the flow of accelerated particles generated by the secondary cosmic rays as the external factor, which strongly correlates with BT rhythms revealed by cross-spectrum analysis.

Low-Temperature Baking Effect of the Radio-Frequency Nb3Sn Thin Film Superconducting CavitySupported by the Youth Innovation Promotion Association of Chinese Academy of Sciences (Grant No. 2020410), the Major Research Plan of National Natural Science Foundation of China (Grant No. 91426303), the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB25000000), and the National Postdoctoral Program for Innovative Talents

The Nb3Sn thin film cavity, having the potential to be operated at a higher temperature and higher gradient compared to the cavity made from bulk niobium, is one of the most promising key technologies for the next-generation radio-frequency superconducting accelerators. In our work, several 1.3 GHz single-cell TESLA-shaped Nb3Sn thin film cavities, coated by the vapor diffusion method, were tested at Peking University and Institute of Modern Physics, Chinese Academy of Sciences. It was observed that the performance of the Nb3Sn thin film cavities in the tests without the slow cooling down procedure and the effective magnetic field shielding was significantly improved by using a low temperature baking at 100 °C for 48 hours. Although the peak electric field of the cavity remained unchanged, the rapid drop of the unloaded Q value (Q 0) with the increasing accelerating field (Q-slope) was effectively eliminated, resulting in an improvement of the Q 0 in the intermediate field region by ∼ 8 times. Furthermore, under better test conditions with the shielded magnetic field less than 5 mG and the slow cooling down procedure in the temperature range of 25–15 K, the Q 0 was still improved by about 20%. Our study shows that the low temperature baking can be an effective supplement to the effective post-treatment for the Nb3Sn thin film cavity.

Study on Magnetic Field Shielding Effectiveness of Slotted Conductor Plate

In this paper, the magnetic field shielding effectiveness of slotted conductor plate is tested. According to the dominant effect of magnetic shielding at different measuring points, the slotted conductor plate is divided into edge effect area, platform area and aperture leakage area, and the change law of magnetic field shielding effectiveness in different regions is analyzed. The magnetic field shielding effectiveness of slotted conductor plates at different frequencies is tested. The results show that the shielding effectiveness increases with the increase of frequency.

Research on Influencing Factors of Magnetic Shielding Effectiveness of Finite Length Cylinder

The article mainly studies the shielding effectiveness (SE) inside a cylinder with a finite-length metal shell. Since the SE inside an infinite-length cylinder is equal everywhere, this article focuses on exploring the SE of a finite-length metal shell cylinder. The article simulates the influence of the cylindrical shape factor (the ratio of the height to the inner diameter of the cylinder) on the SE at different frequencies; the influence of the frequency of the external magnetic field on the SE of the cylinder; the change of the SE on the central axis of the cylinder; the change in the SE on the central axis of the cylinder when a small hole is opened at the centre of the bottom of the cylinder; the change in the SE on the central axis of the cylinder when small holes are opened at the centre of the upper and lower surfaces of the cylinder.

Research on shell magnetic shielding based on finite element method

In this paper, several different magnetic shielding schemes are proposed, the finite element static magnetic field analysis method is introduced, and the finite element method is used to simulate these methods. According to the calculation results, we analysed different magnetic shielding schemes, the results show that the opening will significantly reduce the magnetic shielding efficiency; under the same materials, the multi-layer magnetic shielding effect is significantly improved; when the opening is parallel to the direction of the magnetic induction intensity, the magnetic shielding has a better effect; when the direction of the magnetic field is unknown, the two-layer magnetic shielding opening direction can be orthogonal to improve the magnetic shielding effect.

ANALIZA UNUI ECRAN MAGNETIC POZIțIONAT ÎN SPAȚIUL DINTRE ÎNFĂȘURĂRILE UNUI TRANSFORMATOR MONOFAZAT, DE MICĂ PUTERE

"This paper aims to analyze the impact of using a thin magnetic shield placed in the space between the primary and secondary winding of a simplified, low power, single-phase transformer used in energy harvesting applications that demand power transformers not only in the energy conditioning stage but also in the energy harvesting stage. By using magnetic shields, the saturation of the ferromagnetic core and, in some particular cases, the destruction of electronic devices is avoided. For this purpose two scenarios are studied: one which doesn't take into account the magnetic shield, as it considers only the air space between the primary and secondary windings, respectively, and the second case study which considers a magnetic screen placed in the centre of the air space domain. The size of the air space domain, d, is varied as the secondary winding distance itself from the primary one until it reaches the core. The number of turns in the primary and secondary winding is equal, N1 = N2 = 300 turns. By moving the secondary winding away from the primary winding, the variation of the distance d between the coils is achieved, thus keeping the same cross-section of the secondary winding. The thickness of the magnetic shield is chosen arbitrarily, as thin as possible, with a dimension of 400 µm. The idealy, 1:1, simplified, low-power, single-phase transformer powered by a harmonic voltage supply at V1 = 20 V and at a frequency, f = 50 Hz, with load resistance of Rs = 100 Ω, is analyzed in a time-dependent study and its computational domain is taken from literature [4]. Different materials can be used for realizing this magnetic shieling, even copper and aluminum, but in this paper a magnetic sheet metal material is considered because of its small, almost nonexistent electrical conductivity. Our goal is to analyze the effect of magnetic shielding on the saturation of the ferromagnetic core, and the reactance and resistance values of the primary and secondary winding, respectively, for different dimensions of the air space, d. For comparison purposes, the second model, the one in which we have the magnetic sheet metal, an analysis is performed in the permanent harmonic regime, in addition to the one performed in the dynamic one."

Feasibility Study of High-Efficiency Cooling of High-Temperature Superconducting Coils by Magnetic Refrigeration

As a high-efficiency cooling technology for high-temperature superconducting coils, we have begun research and development to examine the feasibility of a cooling assist technology that maintains a cryogenic state by combining the magnetic force generated by the superconducting coil with magnetic refrigeration technology. Magnetic refrigeration requires the magneto caloric material to change the magnetic field. In many cases, the magnetic field change is obtained by moving the magnetic source, but moving the superconducting coil is not a good idea. Although it is possible to generate a change in the magnetic field by turning on and off the power supply of the high-temperature superconducting coil, it is unlikely to be established as a system that assists cooling of the superconducting coil because the coil generates heat due to AC loss. Therefore, it was considered that the magnetic field change can be obtained if the magnetic force generated from the superconducting coil can be controlled by the magnetic shield. As a verification of the principle, it was clarified experimentally that a magnetic field change can be obtained by repeatedly inserting and removing the magnetic shield into and from the gap between the magnetic field generation source and the magneto caloric material, and the temperature change can be extracted by the magneto caloric effect. In the experiment, the temperature change obtained when a magnetic shield was inserted into the air gap was measured by a simple test device using an iron-based magneto caloric material having high magneto caloric effect performance at room temperature and a permanent magnet. The principle verification confirmation test was performed using several types of magnetic shielding materials such as Permalloy bulks and the electrical steel sheets. In addition, numerical analysis is performed on the magnetic shielding effect, and the shielding effect is improved by increasing the thickness of the shielding material and the possibility of using high temperature superconductors as magnetic shielding materials were also analyzed. In this study, we report the possibility of cooling the high-temperature superconducting coil with high efficiency by combining the magnetic field created by the superconducting coil and magnetic refrigeration.

Prediction of magnetic shield plate performance using permeability in alternating micromagnetic fields

Magnetoencephalographs (MEGs) are highly sensitive to magnetic noises, and thus, a high performance magnetically shielded room (MSR) is essential. The shielding effect of a novel MSR should predicted to verify if it satisfies the required specifications of the MEG at the design stage. Therefore, an accurate prediction method based on the properties of shielding materials and shape of the MSR is necessary. We focused on the initial permeability μi of mu-metals which are generally used for MEGs; further, we proposed an estimation method for μi and a prediction method for the shielding effect using μi. To verify the prediction accuracy, we estimated μi of mu-metals and predicted the shielding effect of a plate, as simple examples, and compared the obtained result with experimental results. The comparison indicated that the prediction method can predict the shielding effect within approximate deviation of 8.2% for the plate even in a small magnetic field fluctuation region with a magnetic field as low as ΔH = 0.001 A/m. This result provided an important step necessary for predicting the magnetic shield effect of MSRs.