Magnetic Shielding Research Articles

Analysis and Design of New Composite HTS Magnet With Active Magnetic Shield

The magnetic field modulated superconducting (SC) machines (FMSCMs) with advantages of stationary seal of coolant and brushless current transmission have become a research hotpot in the field of superconducting electrical machine. However, the complex airgap magnetic field in the FMSCM greatly affects the current-carrying capacity and AC losses of the HTS coils, further affecting the electromagnetic performance of the FMSCM. As a result, it is necessary to take measures to suppress the effect of the airgap magnetic field on the HTS coil. To overcome the problem faced by the FMSCM, a new composite HTS magnet with active magnetic shield is proposed and designed in this paper for a kind of distributed HTS armature winding permanent magnet machine (DHTSAW-PMM) belonging to FMSCM. In this paper, the topology of DHTSAW-PMM and the composite HTS magnet are illustrated in detail and their electromagnetic performances are comprehensively analyzed. The results show that the proposed composite HTS magnet can effectively suppress the effect of the complex airgap magnetic field on the HTS coil in the DHTSAW-PMM.

A New Correction Method of Distributed Magnetic Sensor System Based on Magnetic Shielding Room

Distributed Magnetic Sensor System (DMSS) can measure vector magnetic field and magnetic gradient tensor (MGT) and is widely used in magnetoencephalography, geological exploration, magnetic navigation, magnetic positioning, and other fields. The posture and position of the magnetic sensor are the key factors that affect measurement accuracy. For the first time, using a magnetic shielding room (MSR) and a composite coil that can switch between uniform and gradient fields in situ, a new correction method for various errors is proposed to reduce vector measurement errors. In addition, sensor position deviation can also lead to MGT calculation errors. This paper establishes a compensation model by using the magnetic field gradient formula. The simulation results show that the average calibration errors of the posture and position of the magnetic sensor are 0.08% and 0.53%, respectively, and the measurement error of the MGT is reduced by four times. Experimental results in the MSR show that the measurement error of the vector magnetic field is reduced by two orders of magnitude and that of the MGT by one order of magnitude. Therefore, the new calibration method can effectively enhance the measurement accuracy of the DMSS.

Performance Analysis of Distributed HTS Armature Winding Direct Drive Wind Generator With Active Magnetic Shielding Layer

High-temperature superconducting (HTS) electrical machine has higher torque density and higher efficiency than permanent magnet electrical machine, showing a great application prospect in the field of offshore wind power generation. However, if there is applied magnetic field acting on the wide plane of HTS tape perpendicularly, the current-carrying capacity of the HTS tape will be greatly reduced, resulting in the performance limitation of the HTS electrical machine. In order to reduce the negative effect of the applied magnetic field on the HTS tape, this paper proposes a new distributed HTS armature winding direct drive wind generator (DHTSAW-DDG) with active magnetic shielding layer. In this paper, the topology and working principle of the DHTSAW-DDG is clearly illustrated, meanwhile, the basic electromagnetic performances of the DHTSAW-DDG are carefully analyzed and compared with the counterpart with the copper armature winding. The results show that the active magnetic shielding layer made of HTS material can significantly weaken the negative effect of the applied magnetic field on the current-carrying capacity of the HTS tape. The electromagnetic performance of the HTS electrical machine can be significantly improved, if the distributed HTS armature winding and the active magnetic shielding layer are adopted. The torque density and the power factor of the proposed DHTSAW-DDG with active magnetic shielding layer can increase approximately 40% than the copper armature winding electrical machine with same topology.

Tubular Magnetic Shielding Scan (TMSS): A New Technique for Molecular Space Exploration. (i) The Case of Aromaticity of Benzene and [n]Paracyclophanes.

Both traditional and novel techniques were employed in this work for magnetic shielding evaluation to shed new light on the magnetic and aromaticity properties of benzene and 12 [n]paracyclophanes with n = 3-14. Density functional theory (DFT) with the B3LYP functional and all-electron Jorge-ATZP and x2c-TZVPPall-s basis sets was utilized for geometry optimization and magnetic shielding calculations, respectively. Additionally, the 6-311+G(d,p) basis set was incorporated for the purpose of comparing the magnetic shielding results. In addition to traditional evaluations such as NICS/NICSzz-Scan, and 2D-3D σiso(r)/σzz(r) maps, two new techniques were implemented: bendable grids (BGs) and cylindrical grids (CGs) of ghost atoms (Bqs). BGs allow for the recording of magnetic shielding from the bent ring levels of [n]pCPs, while CGs provide tubular magnetic shielding scan (TMSS) maps detailing the magnetic shielding from a cylindrical region above and below the ring frame. Our findings suggest that smaller [n]pCPs with n < 6 exhibit deviations in the magnetic shielding above and below the ring, indicating a broken electron delocalization under the ring. In contrast, larger [n]pCPs tend to behave similarly to benzene in terms of magnetic shielding. Moreover, we found that shorter polymethylene chains of [n]pCPs exhibit significantly higher magnetic shielding interactions with the ring. Both of the above techniques offer new and promising tools for characterizing nonplanar aromatic compounds, thereby contributing to a deeper understanding of their magnetic and electronic properties.

Flash sintering improves magnetic properties of spinel zinc ferrite

We report on a simple protocol for one step synthesis and sintering of single-phase magnetic spinel ZnFe2O4 zinc ferrite (ZFO) using an electric field assisted sintering. The resultant materials show improved saturation magnetization and higher coercivity compared to conventionally sintered ferrite. The changes in properties have been attributed to generation of non-thermal lattice defects when processed under electric field. Instead of using the high temperatures (>1000 °C) and extended dwell periods (> 4 h) required by the traditional sintering processes, this method permits sintering of ZFO at a furnace temperature of only 950 °C in just a minute by applying a minimal field of 25 Vcm−1. This magnetic material with decreased coercivity and increased saturation magnetization will improve the efficiency of solenoids, transformer/inductor cores, microwave devices and magnetic shields.

Demagnetization Parameters Evaluation of Magnetic Shields Based on Anhysteretic Magnetization Curve.

To achieve the nearly zero-field environment, demagnetization is an indispensable step for magnetic shields composed of high-permeability material, which adjusts the magnetization of the material to establish magnetic equilibrium with the environmental field and improve the shielding performance. The ideal demagnetization can make the high-permeability material on the anhysteretic magnetization curve to have a higher permeability than on the initial magnetization curve. However, inappropriate parameters of degaussing field cause the magnetization state to deviate from the anhysteretic magnetization curve. Therefore, this article proposes a new assessment criterion to analyze and evaluate the parameters of degaussing field based on the difference between the final magnetization state after demagnetization and theoretical anhysteretic state of the shielding material. By this way, the magnetization states after demagnetizations with different initial amplitude, frequency, period number and envelope attenuation function are calculated based on the dynamic Jiles-Atherton (J-A) model, and their magnetization curves under these demagnetization conditions are also measured and compared, respectively. The lower frequency, appropriate amplitude, sufficient period number and logarithmic envelope attenuation function can make the magnetization state after demagnetization closer to the ideal value, which is also consistent with the static magnetic-shielding performance of a booth-type magnetically shielded room (MSR) under different demagnetization condition.

Wide induction range analysis of DC magnetic properties and magnetization processes of Fe-based soft magnetic composites

The paper presents systematic analyses of a wide maximum induction range (0.001 T–1.4 T) DC magnetic properties of iron-based soft magnetic composite (SMC) materials by applying different methods to understand the specific features of magnetization reversal of this increasingly popular class of soft magnetic materials, including a hitherto less explored area of the Rayleigh region of very low magnetic fields, which has growing application potential in new, low-energy consuming electronic devices or ultra-low magnetic field shielding. The total permeability, coercive field and remanent magnetic induction were analysed in connection with the reciprocity factor and inner demagnetization factor and their relations to interparticle magnetic interaction, domain wall movability and predominance of individual magnetization processes. Their dependence on the magnetic induction and the properties of each sample were revealed and confirmed also by energy loss separation. The Rayleigh region analytical expressions for the coercive field, remanent magnetic induction, the ratio of irreversible to reversible magnetization changes and their percentages within the magnetizing cycle were used for SMCs for the first time.

Additively manufactured high permeability Fe-Ni alloys and novel bi-metallic magnetic shields

The sensitivity and sophistication of spacecraft for Earth Science and Planetary Science missions are increasing with each successive mission. Advances in instrumentation, robotics, remote sensing, avionics and controls are allowing un-crewed missions to be incredibly sophisticated. Effective electromagnetic shielding is critical for high fidelity functioning of the spacecraft and onboard instrumentation. Moreover, the geometrical complexity of the shielding arrangement and the constraints of size and shape, make additive manufacturing (AM) a critical, enabling technology for current and future missions. Two AM approaches - directed energy deposition (DED) and laser powder bed fusion (LPBF) - were used to produce Fe-80Ni-5Mo alloy rings and shields. The microstructure and magnetic properties of the materials produced through these processes are reported in this paper. A mechanism relating the microstructure to the soft magnetic performance of the material is proposed. The AM material produced in this work demonstrated the highest reported magnetic permeability and lowest reported coercivity of any additively manufactured soft magnetic material. Two different combinations of bi-metallic shields, Fe-80Ni-5Mo/FeCo-2V and Fe-80Ni-5Mo/Fe-49Ni, were fabricated using the DED process. The creation of these shields as monoliths in general, and for space-related applications in particular, is a novel aspect of this work. These multi-alloy, multi-layer shields showed a nearly 10 dB increase in shielding performance over Fe-80Ni-5Mo single alloy shielding, a significant improvement. For the DED builds, the coercivity decreases and permeability increases (better soft magnetic performance) with increasing build power. With increasing build power in the DED process, the grain size in the printed part increases. The corresponding reduction in the grain boundary area results in fewer obstacles to the movement of magnetic domain walls.

Design of uniform field coils coupled with a magnetic shield cylinder

Active magnetic field coils and magnetic shields are widely employed to achieve uniform and low magnetic fields, and the coil generating magnetic field would be influenced as a result of the coupling with the shields. It turns out to increase the magnetic field strength and shrink the uniform area, which is detrimental to atomic devices. An analytical solution that takes into account the coupling effect of shields and coils is established by using the magnetic vector potential. Analyses for three different configurations are first performed, including mu-metals, 2K-MnZn ferrites and 10K-MnZn ferrites. Analytical calculations reveal that the optimal radii of the standard Lee-Whiting coils with high uniformity are all around 0.81 of shield radii. Additionally, adopting the Whale Optimization Algorithm (WOA), a modified coil with improved uniformity and comparable size is proposed. Experimental results show that a better uniformity of 2.68e−5 and a 34% longer uniform area is obtained when compared with the standard coil. The accuracy of the internal magnetic field distributions is compared and tested by simulations and experiments. Situations utilizing shields and coils will be facilitated by this effective application of WOA in uniform field coil design.

Crystal structure refinement, optical, magnetic, and X-band microwave shielding properties of Dy3+ doped Ni2Y-type strontium hexagonal ferrites

Ni2Y-type strontium hexaferrites having chemical dddof Sr1·8Ba0·2Ni2Fe12-xDyxO22 (x = 0.0, 0.1, 0.2) were made utilizing the sol-gel combustion technique. All samples' XRD patterns demonstrate the production of NiFe2O4 and Fe3O4 which are a phase that is intermediate in the synthesis of the required Ni2Y-type strontium hexaferrites. The FTIR indicates the presence of absorption peaks at about 557 and 432 cm−1, this shows the possibility of the formation of Y-type hexaferrites. UV-vis NIR spectroscopy analysis indicates that the energy band-gap of Y-type hexaferrites is affected by the increase in Dy3+ concentration. The values of the band-gap were found to be between 1.66 and 1.78 eV. According to the FESEM analysis, platelet-structure is formed with particles that range in size from 3.665 to 3.927 μm. The observed coercivity, saturation, and remnant magnetization first decreased with an increase in the concentration of Dy3+ for the sample having x = 0.1 and then increases for the sample with x = 0.2. The sample with the greatest amount of Dy3+ (i.e.x = 0.2) has a value of total shielding effectiveness of 27.5 dB. The prepared Ni2Y-type hexaferrites sample could be use for efficient shielding of microwaves in X-band.

Design and optimization of superconducting CUSP electromagnetic field structure based on a COMSOL-GMDH-MOSO hybrid strategy

As the semiconductor industry gains momentum, there is a significant focus on producing high-quality silicon wafers with larger diameters. However, the preparation of major-diameter, high-quality silicon single-crystal has encountered challenges such as intense convection inside the melt and high oxygen impurity concentration at the interface between the fluid and solid phases. To tackle these problems, the external superconducting CUSP electromagnetic field structure was designed to optimize the crystal growth parameters. A hybrid strategy of the multiphysics field coupling method, Group Method of Data Handling (GMDH) type neural network identification, and the Multiple Objective Snake Optimizer (MOSO) algorithm was proposed to optimize the superconducting CUSP electromagnetic field structure. A two-dimensional axisymmetric model was established for 18-inch silicon single-crystal preparation using the Magnet system Applied Czochralski (MCZ) method. The amount of longitudinal plies of superconducting CUSP electromagnetic field coils, coil spacing, and the thickness of magnetic shields were selected as design variables, and the radial electromagnetic induction intensity at the graphite crucible inner wall and the superconducting magnet volume were used as dual objective functions. The required samples for GMDH training were provided by COMSOL Multiphysics (COMSOL) numerical calculations, and polynomial mathematical equations were established with the radial electromagnetic induction intensity at the graphite crucible inner wall and the superconducting magnet volume as the dual objective functions. Then the Pareto optimal solution for the electromagnetic field structure design variables was obtained using the dual objective function optimized by MOSO. With the hybrid strategy, numerical simulations and theoretical analysis of the crystal preparation process parameters under the effect of the superconducting electromagnetic field with the optimal structure were carried out. The results displayed that the added superconducting CUSP electromagnetic field reduced the crystal radial and axial thermal gradients and greatly suppressed the melt convection. As a result, the heat distribution inside the hot fused silicon was more even, the thermal gradient at the solid–liquid interface was reduced by 68.4%, and the oxygen impurity content was reduced by 82.1%, which effectively improved the crystal quality. The thermal field simulation results verified that the proposed hybrid strategy provided a new numerical calculation method for obtaining the optimal superconducting electromagnetic field structure.

Electromagnetic Characteristics of Dual-Air-Gap Surface Permanent Magnet Synchronous Motor

This paper introduces a novel dual-air-gap surface permanent magnet synchronous motor (DAG-SPMSM) and investigates its electromagnetic characteristics. The motor comprises two stators (inner and outer) and a single rotor with permanent magnets on both sides (inner and outer). The magnets are arranged in a zig-zag configuration to isolate the inner and outer stator and rotor magnets. Additionally, a magnetic shield is incorporated into the rotor to further isolate the rotor magnetic flux, which results in a localized short flux path that can reduce core loss. The insertion of the magnetic shield also affects the flux path, reducing torque ripple. The electromagnetic characteristics, such as flux path, flux density, and torque, are analyzed using finite element analysis. The effectiveness of using a magnetic screen is also evaluated, and simple experiments are conducted to validate the observed characteristics of the proposed motor.

First H- beam extracted from the non-caesiated external RF-coil ion source at ISIS

A high power, high duty-cycle, non-caesiated negative hydrogen ion source is in development at the ISIS pulsed spallation neutron and muon facility. Stable operation of an inductively-coupled plasma pulsing at 50 Hz, 1 ms, 70 kW has been perfected with no apparent lifetime issues. Novel features compared to similar H- sources include a very low power microwave ignition gun, an adjustable permanent magnet filter field and multiple large 3D-printed components. This paper details the initial commissioning efforts required to generate a beam. An H- beam current of 10 mA was extracted on the first try in pure volume-production mode. Parameter sweeps and optimisation to reach the required 35 mA were put on hold to address ancillary equipment problems. Mitigation of RF pickup required major mechanical changes such as additional screening and magnetic shielding. Extraction voltage holding capabilities were investigated to cope with co-extracted electron current loading in excess of 0.7 A. Preliminary studies of the biased plasma electrode current showed that co-extracted electrons could be suppressed by increasing the magnetic filter field and gas flow.

Magnetic Model Calibration and Distortion Compensation for Electromagnetic Tracking in a Clinical Environment

Electromagnetic tracking (EMT) of surgical tools is used for image-guided navigation in minimally invasive interventions. Calibration of the tracker position and orientation is a fundamental task to correct systematic errors. This article explores the effect of metallic distortion on the open hardware Anser EMT system and describes a newly developed approach for volume calibration of the magnetic field model. The technique is also applied to effectively map the field in the presence of magnetic shields that can be used to reduce electromagnetic distortions passively. Unlike calibration techniques commonly found in literature, which aim to correct the tracking position error, our method can reconstruct an analytical magnetic field model starting from a reduced amount of scattered data. This way, a faster convergence of the solver algorithm is obtained, and EMT position and orientation errors are inherently corrected. The new modelling technique was applied to generate a new, undistorted magnetic field model for Anser EMT, to demonstrate the effectiveness of passive shielding, and to compensate for the distortion introduced by a commercial fluoroscopy C-arm. Furthermore, the concept of a real-time distortion compensation technique is expressed based on the modelling method presented in this article. For all the experiments, sub-millimeter errors were obtained after calibration, which may meet the needs of most endoscopic and surgical navigation tasks.

Predicting a New Δ-Proton Sponge-Base of 4,12-Dihydrogen-4,8,12-triazatriangulene through Proton Affinity, Aromatic Stabilization Energy, and Aromatic Magnetism.

Herein, we report designing a new Δ (delta-shaped) proton sponge base of 4,12-dihydrogen-4,8,12-triazatriangulene (compound 1) and calculating its proton affinity (PA), aromatic stabilization, natural bond orbital (NBO), electron density ρ(r), Laplacian of electron density ∇2 ρ(r), (2D-3D) multidimensional off-nucleus magnetic shielding (σzz (r) and σiso (r)), and scanning nucleus-independent chemical shift (NICSzz and NICS). Density functional theory (DFT) at B3LYP/6-311+G(d,p), ωB97XD/6-311+G(d,p), and PW91/def2TZVP were used to compute the magnetic shielding variables. In addition, relevant bases like pyridine, quinoline, and acridine were also studied and compared. The protonation of compound 1 yields a highly symmetric carbocation of three Hückel benzenic rings. Comparing our findings of the studied molecules showed that compound 1 precedes others in PA, aromatic isomerization stabilization energy, and basicity. Therefore, the basicity may be enhanced when a conjugate acid gains higher aromatic features than its unprotonated base. Both multidimensional σzz (r) and σiso (r) off-nucleus magnetic shieldings outperformed electron-based techniques and can visually monitor changes in aromaticity that occur by protonation. The B3LYP/6-311+G(d,p), ωB97XD/6-311+G(d,p), and PW91/def2TZVP levels showed no significant differences in detailing isochemical shielding surfaces.

NMR Magnetic Shielding in Transition Metal Compounds Containing Cadmium, Platinum, and Mercury

In this article, we delve into the intricate behavior of electronic mechanisms underlying NMR magnetic shieldings σ in molecules containing heavy atoms, such as cadmium, platinum, and mercury. Specifically, we explore PtXn−2 (X = F, Cl, Br, I; n = 4, 6) and XCl2Te2Y2H6 (X = Cd, Hg; Y = N, P) molecular systems. It is known that the leading electronic mechanisms responsible for the relativistic effects on σ are well characterized by the linear response with elimination of small components model (LRESC). In this study, we present the results obtained from the innovative LRESC-Loc model, which offers the same outcomes as the LRESC model but employs localized molecular orbitals (LMOs) instead of canonical MOs. These LMOs provide a chemist’s representation of atomic core, lone pairs, and bonds. The whole set of electronic mechanisms responsible of the relativistic effects can be expressed in terms of both non-ligand-dependent and ligand-dependent contributions. We elucidate the electronic origins of trends and behaviors exhibited by these diverse mechanisms in the aforementioned molecular systems. In PtX4−2 molecules, the predominant relativistic mechanism is the well-established one-body spin–orbit (σSO(1)) mechanism, while the paramagnetic mass–velocity (σMv) and Darwin (σDw) contributing mechanisms also demand consideration. However, in PtX6−2 molecules, the σ(Mv/Dw) contribution surpasses that of the SO(1) mechanism, thus influencing the overall ligand-dependent contributions. As for complexes containing Cd and Hg, the ligand-dependent contributions exhibit similar magnitudes when nitrogen is substituted with phosphorus. The only discrepancy arises from the σSO(1) contribution, which changes sign between the two molecules due to the contribution of bond orbitals between the metal and tellurium atoms.

Effectiveness of a dual solenoid magnetic shield at reducing x-ray-like background in silicon-based x-ray detectors

Effectiveness of a dual solenoid magnetic shield at reducing x-ray-like background in silicon-based x-ray detectors

Measurement and analysis of an optimized Jiles–Atherton model considering the influence of temperature applied in magnetic shielding devices

Magnetic shielding devices work at different temperatures due to the influence of gas chamber and environmental temperature in the application of ultra-highly sensitive spin exchange relaxation free (SERF) magnetometers. To accurately evaluate the residual magnetic field (MF) of a magnetic shielding device at different temperatures, it is necessary to build a magnetization model considering temperature. However, the modeling of permalloy’s magnetization properties and the measurement of residual MF in magnetic shielding devices at different temperatures have not been considered. In this paper, an optimized Jiles–Atherton (JA) model of permalloy considering temperature is constructed, in which parameters are extracted using a particle swarm optimization algorithm. To further verify the effectiveness of the model in the magnetic shielding device, it is applied to the residual MF simulation of magnetic shielding devices and verified by measurement. The optimized JA model considering temperature improves the calculation accuracy of magnetic shielding devices, which is of great significance for the application of ultra-highly sensitive SERF magnetometers.

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

A stable inner working environment is essential for nuclear magnetic resonance 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 spacings, 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 spacings. Moreover, the results indicate that this optimal method works for other applications in which multilayer magnetic shielding is required.

Soft Magnetic Properties and Electromagnetic Shielding Performance of Fe40Ni40B20 Microfibers

AbstractFe40Ni40B20 metallic glass is a key material among the many amorphous systems investigated thus far, owing to its high strength and appealing soft magnetic properties that make it suitable for use as transformer cores. In this study, Fe40Ni40B20 microfibers are fabricated down to 5 µm diameter. Three different melt–spinning wheel velocities: ≈51 m s−1, ≈59 m s−1, and ≈63 m s−1 (MG1, MG2, MG3) are used. Their fully amorphous structure is confirmed using X–ray diffraction, and differential scanning calorimetry (DSC) traces reveal a larger relaxation profile for the higher–quenched microfiber. Vibrating sample magnetometer measurements showed a higher saturation magnetization of 136 emug−1 for annealed metallic glass microfibers with a wheel velocity of 59.66 ms−1. Cylindrical magnetic field shields are obtained by aligning and wrapping the fibers around a cast. The observed anisotropic static field shielding behavior is in accordance with the microfibers' anisotropic nature. Composite samples are also produced by embedding the microfibers in an epoxy matrix to investigate their electromagnetic properties at GHz frequencies. Inclusion of the microfibers increase the composite's attenuation constant by 20 to 25 times, making it an ideal candidate for applications in the communications frequency range.