Magnetic Shielding Research Articles

The correlation between structural attributes and magnetic shielding of some metal nanoparticles engineered polymeric surfaces

Polymeric structures for use in magnetic environments are of great importance for applications ranging from simple magnetic barriers to the design of high dimensions devices, or vehicles. The damage caused by magnetic radiations is invisible, slow, and accumulative. This can lead to genetic damage, reproductive defects, cancer, neurological degeneration and nervous system dysfunction. This research work has focused on the effects of magnetic radiations onto some polymeric supports coated with different molar ratios of Zn/Al oxides and their response to magnetic radiations. Of particular interest here was the adapting the coating conditions with the magnetic barrier of the coated polymeric supports.The engineered polymeric supports have been characterized using X-ray diffraction, UV–VIS spectroscopy, SEM techniques, and magnetic measurements. The XRD and SEM results are well correlated revealing the clustering of the Zn2+ cations and the forming of ZnO nanoparticles onto the surface of the polymeric support for all used cationic ratios. The magnetic measurements proved an average magnetic nature in ZnO/AlO NPs deposited onto polymeric supports.

Design of Highly Uniform Field Coils Based on the Magnetic Field Coupling Model and Improved PSO Algorithm in Atomic Sensors

The coupling between the coil and the cylindrical magnetic shield (CMS) in atomic sensors not only results in the inconsistency of the coil constant with the theory but also deteriorates the uniformity, which affects the sensor performance. To solve the above deficiencies, a design method of highly uniform field coils inside the CMS based on the coupling model with finite permeability and thickness and particle swarm optimization (PSO) with dynamic inertia weights is proposed for the first time. The coupling model of the coil inside the CMS is established by Green’s function method (GFM). Then it is combined with the nonlinear optimization method, and the coil configuration is optimized by the dynamic inertia weight PSO to obtain the optimal parameters. It not only reduces the calculation error of the model, but also improves the uniformity. Comparing this work with the Lee-Whiting coil inside a CMS, the theoretical uniformity is further improved by 2 orders of magnitude, and measured uniformity errors in the target region reach 1.404×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> , and 2.317×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> , respectively. The correctness and effectiveness are proved by finite element simulation and experimental results. The accuracy and uniformity of coils can be considerably improved, which is beneficial to further improve the measurement sensitivity of instruments related to magnetic field uniformity.

Measurement of noise of current source by pump-probe atomic magnetometer

&lt;sec&gt;The stable and reproducible magnetic field generated by a precision current source and a coil is usually used to calibrate the sensitivity of an atomic magnetometer. The noise of the current source directly determines the noise of the magnetic field. Therefore a highly sensitive atomic magnetometer can be used to measure the noise of the current source.&lt;/sec&gt;&lt;sec&gt;In this paper, a pump-probe atomic magnetometer is used to measure and estimate the noises of two current sources in a wide range. Firstly, in order to suppress the drift of magnetic field, which is caused by the drift of the current source or the gradual change of the magnetization of magnetic shielding materials, a method of implementing the magnetic compensation by using a precision source B2912A with small current is proposed and realized. The experimental results show that the magnetic compensation significantly suppresses the drift of magnetic field and reduces the amplitude of the power spectral density of magnetic field values to less than 0.1 Hz, but have little effect on the amplitude of the power spectral density of magnetic field values more than 0.1 Hz. Secondly, the relationship between the sensitivity of the pump-probe atomic magnetometer and the noises of two current sources in a wide range is respectively verified experimentally. When the magnetic field varies from 100 nT to 10000 nT, the sensitivity of the pump-probe atomic magnetometer increases stepwise from 0.2 pT/Hz&lt;sup&gt;1/2&lt;/sup&gt; to 15 pT/Hz&lt;sup&gt;1/2&lt;/sup&gt; by using a precision source B2912A to generate the magnetic field, while the magnetometer sensitivity is always about 20 pT/Hz&lt;sup&gt;1/2&lt;/sup&gt; by using a DC power analyzer N6705B to generate the magnetic field. When the magnetic field increases from 5000 nT to 6000 nT, the current resolution of B2912A changes from 100 nA to 1 μA, leading the peak to peak of the measured magnetic field to change from 23 pT to 230 pT. In the same transformation process of the magnetic field, the current resolution of N6705B is always about 2 μA, causing the peak to peak of the measured magnetic field to maintain at 300 pT. The experimental results show that the sensitivity of the pump-probe atomic magnetometer is limited by the noise of the magnetic field, thus the current noise can be estimated by the sensitivity of the pump-probe atomic magnetometer. When the magnetic field is set to 5000 nT, the current of B2912A or N6705B supplied to the coil is 94.8 mA, while the noise of B2912A or N6705B is 22.70 nA/Hz&lt;sup&gt;1/2&lt;/sup&gt; or 0.39 μA/Hz&lt;sup&gt;1/2&lt;/sup&gt;, respectively. The value of the current noise is about 20% of the value of the current resolution, which will be given a more reasonable explanation by combining the data processing process and the calibration details of current source in the future.&lt;/sec&gt;&lt;sec&gt;Our research is of great significance in calibrating the sensitivity of magnetic sensor, developing the high-precision current sources, and co-developing the magnetic induction metrology and current metrology.&lt;/sec&gt;

Analysis and Improvement of the Uniformity of Magnetic Field Coil Based on the Cylindrical Magnetic Shield in Atomic Magnetometers

Analysis and Improvement of the Uniformity of Magnetic Field Coil Based on the Cylindrical Magnetic Shield in Atomic Magnetometers

Magnetic shield effect for 8 MW high temperature superconducting synchronous motor

Magnetic shield effect for 8 MW high temperature superconducting synchronous motor

Suppression of Nonuniform Magnetic Fields in Magnetic Shielding System for SERF Co-Magnetometer

Suppression of Nonuniform Magnetic Fields in Magnetic Shielding System for SERF Co-Magnetometer

Contactless HVDC Overhead-Line Current Monitoring by a Magnetic Sensor Array With Sensing Parameter Correction Function

To improve the efficiency of power transmission, high-voltage direct current (HVDC) transmission systems are crucial power-related development in many countries. This study proposes a contactless DC current measurement method suitable for on-site measurements of HVDC overhead lines. In this method, a vertical magnetic field (MF) sensor array (three layers and one three-axis MF sensor installed in each layer) is designed to measure the spatial MFs on the ground. With the spatial MFs measured by the sensor array and the overhead-line specifications obtained from utilities, the core current algorithm of the proposed method can accurately calculate the current values. In addition, we design a magnetic shielding mechanism to correct a DC offset that is inevitably output from each MF sensor. The DC offset includes the quiescent voltage of the self-circuit of the MF sensor and the output voltage of the MF sensor caused by the earth&#x2019;s MF. Thus, this mechanism can effectively solve the problem in which the DC offset is misjudged as an MF formed by the measured current. The simulation results indicate that under arbitrary vertical sensor array placements, the core convergence condition (geomagnetic invariance) of the proposed current algorithm can improve the algorithm convergence. Finally, the experimental results verify the feasibility of the proposed method for the measurement of overhead-line current. Without conductor sags, all the current errors are less than 2 % in both the 500-kV and 800-kV overhead-line scenarios. Moreover, even with serious conductor sags, all the current errors are still within 9 %.

Measurement of coercivity of soft magnetic materials in open magnetic circuit by pump-probe rubidium atomic magnetometer

&lt;sec&gt;We report an experimental device and method of measuring the coercivity of soft magnetic material in an open magnetic circuit by using a pump-probe rubidium atomic magnetometer. The experimental device consists of a background magnetic field generation module, a pump-probe atomic magnetometer, a soft magnetic material magnetization and demagnetization module, and a software in a computer. The uniform background magnetic field ranging from 200 nT to 20000 nT along the &lt;i&gt;z&lt;/i&gt;-axis at the rubidium bubble’s position is generated by a current carrying coil which is placed in a five-layer magnetic shielding cylinder. The saturation magnetization and demagnetization of soft magnetic material are realized by the soft magnetic sample magnetization and demagnetization module, respectively, which consists of a sample chamber, a soft magnetic sample, a magnetizing coil, a precision current source and a sample transfer rod. The sample chamber is placed in the magnetic field uniform area of the magnetizing coil which is placed in the magnetic shielding cylinder, and the sample transfer rod is used to transfer the soft magnetic sample into the center of the magnetizing coil. Both the rubidium bubble and the soft magnetic sample are placed on the &lt;i&gt;z&lt;/i&gt;-axis of the magnetic shielding cylinder, and their distance is greater than or equal to 10 cm. The axis of the magnetizing coil coincides with the axis of the magnetic shielding cylinder, which ensures that the background magnetic field, the magnetic field generated by the magnetizing coil, and the magnetic field generated by the soft magnetic sample at the rubidium bubble’s position are all parallel to the axis direction of the magnetic shielding cylinder. The software in the computer realizes the magnetization and demagnetization of the soft magnetic sample by controlling the current output by the precision current source to the magnetizing coil, and also controls the pump-probe atomic magnetometer to measure the magnetic field at the rubidium bubble’s position. When the soft magnetic sample is magnetized or demagnetized in cycles, the magnetic field generated by the soft magnetic sample at the rubidium bubble’s position is obtained by subtracting the magnetic field value measured in advance when the sample is not placed in the sample chamber from the magnetic field value measured at same current value when the sample is placed in the sample chamber. Note that the sample does not move during the hysteresis loop measurement. When the magnetization of the soft magnetic sample decreases from the saturation value to zero, the magnetic field generated by the soft magnetic sample at the rubidium bubble’s position is zero, and the average coercivity of the sample can be calculated from the hysteresis loop.&lt;/sec&gt;&lt;sec&gt;We use a superconducting quantum interference device (SQUID), a pump-detection rubidium atomic magnetometer and a Hall probe to measure the coercivity of the same permalloy strip sample, the average coercivities are 42.15 A/m, 40.632 A/m and 38.64 A/m, the biases of the hysteresis loops are 229.74 A/m, –0.95 A/m and –52.88 A/m, and the times of each measurement cycle are 9639 s, 1144 s, and 1630 s, respectively. The reproducibility of ten repeated measurements by using the pump-probe atomic magnetometer, expressed as relative standard deviation, is 0.16%, which is an order of magnitude higher than the counterparts from the methods described in China’s national standards GB/T 3656-2008 and GB/T 13888-2009. The accumulated drift of the biases of ten hysteresis loops measured by the pump-probe atomic magnetometer is 0.3 A/m. Based on the above experimental results, the coercivity measurement method by using the pump-probe atomic magnetometer has the advantages of no zero-point drift, good repeatability, fast measurement speed, and &lt;i&gt;in-situ&lt;/i&gt; measurement, and has the potential applications in the basic research field and industrial field of magnetism.&lt;/sec&gt;

Absolute 13C nuclear magnetic shielding of simple isolated molecules from gas phase measurements.

The new experimental value of 13C absolute shielding constant in an isolated 13CO molecule was evaluated from the 13C and 3He gas phase NMR measurements performed for 3He/13CO mixtures. An absolute shielding constant σ0(13CO)300 K= 0.80(90) ppm was previously formally established for this reference molecule with uncertainty but much higher precision than ever before. This result serves as a reference value for the 13C NMR absolute shielding scale. Several earlier used shielding values were noted and then discussed. Taking this estimate into account, we also report the gas-phase 13C shielding constants obtained by extrapolation to the zero density limit for 57 carbon containing molecules and 86 different atom positions in the molecules. Our results are very precise experimental absolute shielding values which are a benchmark set of data suitable for comparison with the sophisticated theoretical calculations. They fully correlate with the experimental and advanced theoretical values reported earlier in the literature. The shielding constant of tetramethylsilane (TMS) of neat liquid used as an external standard is established as σ(13C)300 K(TMS) = 186.43(90) ppm. For TMS used as internal standard, σ(13C)300 K(0.05% TMS in CDCl3) = 186.43 + 0.048(%) ppm and this value can be recommended as a secondary reference. With more than 20 years of achievements in this field, we report a large collection of carbon shielding constants and second virial coefficients from the gas phase experiments.

Cooled ferromagnetic shield as a part hybrid system for isolation of a flux qubit from electromagnetic environment

Currently, circuits for quantum informatics, communications and measuring equipment containing superconducting flux qubits in a planar design are being created by quantum engineering techniques. To function, such structures must be cooled in a refrigerator down to about 10 mK. The flux qubits have linear size of superconducting circuit of some tens of micrometers and are very sensitive to external magnetic fields and their variations. The qubit built in the gradiometer-like design has reduced sensitivity to external uniform magnetic fields, but remains quite sensitive to their variations. To protect the qubit from unwanted external magnetic fields, which include the Earth's field, man-made fields, and residual magnetic fields of the cryostat parts, it is necessary to create efficient magnetic shields. Earlier, we proposed a scheme for a single-photon microwave counter, in which a planar flux qubit in a gradiometer version serves as the receiving element. To let it function properly, a 3-layer hybrid magnetic shield composed of two superconducting and one ferromagnetic cylinders, has been designed for installation in a dilution refrigerator at 10 mK temperature. The effectiveness of such a shield depends on the correct design of all three shells. This paper presents the results of calculation and magnetic measurements of a cylindrical ferromagnetic screen made of low-temperature permalloy Cryoperm 10 in dc and low-frequency alternating magnetic fields. Cryoperm 10 keeps high magnetic permeability at liquid helium temperatures and below. It is shown that this shield is able of reducing the absolute value of the magnetic field and its variations by 55-70 dB. Together with superconducting lead magnetic shields, this design will reduce the absolute value of the field by 70 dB, and the field variation by 200 dB, which will provide the necessary conditions for the operation of a single-photon counter based on a flux qubit.

QED Effect on the Nuclear Magnetic Shielding of ^{3}He.

The leading quantum electrodynamic corrections to the nuclear magnetic shielding in one- and two-electron atomic systems are obtained in a complete form, and the shielding constants of ^{1}H, ^{3}He^{+}, and ^{3}He are calculated to be 17.735 436(3)×10^{-6}, 35.507 434(9)×10^{-6}, and 59.967 029(23)×10^{-6}, respectively. These results are orders of magnitude more accurate than previous ones, and, with the ongoing measurement of the nuclear magnetic moment of ^{3}He^{+} and planned ^{3}He^{2+}, they open the window for high-precision absolute magnetometry using ^{3}He NMR probes. The presented theoretical approach is applicable to all other light atomic and molecular systems, which facilitates the improved determination of magnetic moments of any light nuclei.

Metal Additive Manufacturing for Satellites and Rockets

The emerging technology of 3D printing can not only be used for rapid prototyping, but will also play an important role in space exploration. Additive manufactured parts can be used in diverse space applications, such as magnetic shields, heat pipes, thrusters, etc. Three-dimensional printed parts offer reduced mass, high possible complexity, and fast printability of custom-made objects. On the other hand, materials which are not excessively damaged by the harsh conditions in space and are also printable by available technologies are not abundantly available. This review gives an overview of recent metal additive manufacturing technologies and their possible applications in space, with a focus on satellites and rockets, highlighting already applied technologies and materials and gives an outlook on possible future applications and challenges.

Synthesis, Properties, and Packing Structures of Wing-Shaped N-Doped Nanographene in Various Oxidation States.

A rigid wing-shaped bicyclo[2.2.2]octadiene-fused bis-hexapyrrolohexaazacoronene (HPHAC) is synthesized, and subsequent chemical oxidation affords a stable biradical dication and an aromatic tetracation. The physicochemical properties and single-crystal structures in various oxidation states are characterized. The face-to-face π-stacked dimeric structures are observed in the neutral and dicationic states. The HPHAC flakes can act as aromatic walls in a tetracation state, producing enlarged induced magnetic shielding space through the superimposition effect.

Predicting Catalytic Activity from 13CCH Alkylidene Chemical Shift in Cationic Tungsten Oxo Alkylidene N‐Heterocyclic Carbene Complexes

AbstractA series of cationic tungsten oxo alkylidene N‐heterocyclic carbene (NHC) complexes was synthesized and structurally characterized by single crystal X‐ray diffraction. The 13C NMR chemical shifts of the alkylidene C atoms of these complexes were correlated with the diamagnetic, paramagnetic and spin‐orbit chemical shifts calculated by DFT. A good correlation (R2=0.90) between the DFT isotropic chemical shifts and the experimental chemical shift as well as a strong correlation between the DFT isotropic chemical shifts and the TOF1min for the RCM of 1,7‐octadiene was found. Further, a comparison of the catalyst geometries allowed for assigning tetracoordinate pseudotetrahedral catalysts to the most deshielded alkylidenes and to the highest TOF1min, pentacoordinate square‐planar catalysts to the intermediate deshielded alkylidenes and intermediate TOF1min, and hexacoordinate and octahedral catalyst to the most shielded alkylidene and lowest TOF1min. Analysis of the magnetic shielding tensors allowed for ascribing variations in the chemical shifts to electronic transitions between occupied molecular orbitals corresponding to the alkylidene‐C and alkylidene‐H σ‐bonds and the empty molecular orbital corresponding to the W‐alkylidene σ*‐bond.

Processing–Microstructure–Property Relationships in a Laser‐Deposited Fe‐Co‐V Alloy

The microstructure and magnetic performance of Fe49Co2V (Hiperco50) manufactured via laser‐directed energy deposition are determined. In the as‐printed form, the material displays a fine, equiaxed microstructure and magnetically “hard” behavior. With a customized post‐process annealing treatment, significant grain growth occurs, resulting in soft magnetic performance comparable to traditionally manufactured materials. An inverse correlation between laser power and post‐anneal grain size is observed, with lower laser powers resulting in samples with larger grain sizes after annealing. Samples printed with lower laser powers also display improvements in soft magnetic performance. This is consistent with the expected relationships between grain size, magnetic permeability, and magnetic coercivity, i.e., as grain size increases, magnetic permeability increases and magnetic coercivity decreases. A prototype magnetic shield for a Hall‐effect thruster is successfully printed. The magnetic performance of the printed and annealed shield is comparable to one that is traditionally manufactured.

Halbach-Type Coupler WPT System With Flux-Shielding Function for Linear Motor

In order to solve the problem of increased system weight and cost of current wireless power transfer (WPT) systems with ferrite, a Halbach-type coupler WPT system with flux-shielding function for linear motor has been proposed in this article. It is characterized by high transmitting efficiency, better shielding ability, and antioffset ability. First, the topology and working mechanism of the proposed coupler have been analyzed. Second, considering the coupling ability and magnetic flux density, the parameters of the proposed Halbach-type coupler have been optimized. Third, the prototype of the proposed system has been built and tested, compared with the current DD-type coupler WPT system. Fourth, the magnetic field shielding ability and antioffset ability of the proposed Halbach-type coupler and DD-type coupler have been analyzed, respectively. The experimental results have verified that the WPT system based on the Halbach-type coupler has more promising magnetic field shielding ability and better resistance to the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$z$ </tex-math></inline-formula> -axis offset, compared with the WPT system based on the DD-type coupler. The efficiency of the WPT system based on the proposed Halbach coupler can achieve 80.5% and the maximum output power reaches 69.5 W at 11 mm.

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.

Iron loss estimation of soft magnetic materials for power transformers considering hysteretic properties

AbstractThis paper investigates an efficient iron loss calculation method for soft magnetic materials of power transformers. To accurately estimate iron losses in the materials such as structural steels and magnetic shielding, the magnetic field analysis taking account of the nonlinear magnetic properties is considered to be effective. In this paper, quasi‐DC magnetic properties of the soft magnetic materials are measured and the iron losses are calculated by using a three‐dimensional finite element method. Furthermore, the effect of considering hysteretic properties on the accuracy of the iron loss calculation is discussed based on a theoretical representation of eddy current loss in a conductive rectangular plate.

A low-cost and shielding-free ultra-low-field brain MRI scanner

Magnetic resonance imaging is a key diagnostic tool in modern healthcare, yet it can be cost-prohibitive given the high installation, maintenance and operation costs of the machinery. There are approximately seven scanners per million inhabitants and over 90% are concentrated in high-income countries. We describe an ultra-low-field brain MRI scanner that operates using a standard AC power outlet and is low cost to build. Using a permanent 0.055 Tesla Samarium-cobalt magnet and deep learning for cancellation of electromagnetic interference, it requires neither magnetic nor radiofrequency shielding cages. The scanner is compact, mobile, and acoustically quiet during scanning. We implement four standard clinical neuroimaging protocols (T1- and T2-weighted, fluid-attenuated inversion recovery like, and diffusion-weighted imaging) on this system, and demonstrate preliminary feasibility in diagnosing brain tumor and stroke. Such technology has the potential to meet clinical needs at point of care or in low and middle income countries.

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.