Maximum Field Intensity Research Articles

Features of 2D mapping technique of non-uniform magnetic fields using self-biased magnetoelectric composites based on “bidomain LiNbO3/Ni/Metglas” structures

Magnetoelectric (ME) composites are extensively researched for their ability to detect magnetic fields but are typically characterized by their interactions with homogeneous magnetic fields. However, practical applications often involve non-uniform magnetic fields (NMFs). In this study, we developed and validated a technique for 2D mapping of NMFs using sensor based on ME composite. The primary focus was on mapping the magnetic field generated by a single wire carrying an alternating current (AC). The experimental setup included a “bidomain LiNbO3/Ni/Metglas” ME structure, which demonstrated a ME coefficient of 0.83 V/(cm⋅Oe) without external biasing at 117 Hz. The ME structure was characterized using both quasi-static and dynamic methods, with the mapping performed at a frequency of 232 Hz, chosen to ensure a linear response and minimize resonance effects. Our measurements revealed that the position of maximum magnitude of the ME signal was consistently shifted from the position of the maximum integral magnetic field intensity of the wire. This shift was attributed to the deformation of the ME structure and the redistribution of the magnetic flux along the sample due to the magnetic layers, as confirmed through modeling. Further, the measured 2D mapping of the NMF from the wire closely matched the theoretical distribution, displaying axial symmetry but with a persistent shift of 2–3 mm along the length of the ME structure. These effects were linked to the linear dimensions and clamping methods of the ME structure. Overall, our experimental results closely correlated with theoretical data and the FEM model, demonstrating that ME composites are effective for NMF detection and mapping. Future work will aim to reduce the dimensions of the ME structure using MEMS technology to minimize the observed shift effects in the measurements.

Design and construction of GaInSn experimental facility for studies of mixed-convection MHD flows

A multifunctional liquid metal loop named MaTHE-XJTU (Magneto-Thermo-Hydrodynamic Experiments-Xi'an Jiaotong University) that utilizes eutectic alloy GaInSn as a working fluid has been designed and constructed. The function of the MaTHE-XJTU facility is to study the magnetohydrodynamic (MHD) flow and mixed convection characteristics under the coupling effect. The main operating parameters of the loop are: the maximum magnetic field intensity is 3T, the effective magnetic field region is 300 mm × 800 mm × 1000 mm, the maximum flow rate of electromagnetic pump (EM pump) is 8 m3/h, the maximum pressure head of EM pump is 0.5 MPa. The paper describes the major components and basic operation procedures of the loop, the related flow diagnostics method, and near-future experiments. This loop could provide a high-parameter experimental platform (Ha∼104, Gr∼109, Re∼104) for investigations that improve the present understanding of magnetohydrodynamic and heat transfer performance in liquid metal blankets.

Analysis of Monte-Carlo collision method with argon and helium background gases at different RF-powers and pressures in ELTRAP device

The impact of confined excited electron with argon and helium background gases is systematically studied using Monte-Carlo particle-in-cell simulations for various low powers (1.0–8.0 V) and pressures (1.50 × 10−8 Torr and 3.75 × 10−9 Torr) in ELTRAP device. The results of these numerical studies showed that the heating effect of the excited confined electron plasma density of 5 × 1014 m−3 within the Brillouin limit (ne≤ε0B22me=31.086×1019m-3) resulted a higher temperature (eV) and increased collision time in argon as a background gas as compared to helium gas. The axial temperature (eV) has a higher value than the radial temperature (eV) and increases with the increase in RF-Powers and pressures. The maximum kinetic energy of excited confined electrons occurred in the range of 0.03–0.04 m radially due to the maximum self-electric field intensity in simulation time up to 20 µs. The electric field decreases when the collision frequency is increased. The secondary electron production and ionization are higher than expected at a background pressure of 1.50 × 10−8 Torr as compared to 3.75 × 10−9 Torr. The remaining secondary electrons were always ejected from the symmetry axis of the device. It was observed that the production of secondary electrons is proportional to the ionization rate.

Correlation between magnetic field and nuclear stopping in different rapidity segments during heavy ion collisions

The mid-rapidity zone is a region of crucial scientific interest during heavy ion collisions as it offers deep insight into the complex dynamics and properties of extremely dense nuclear matter. In the framework of the isospin-dependent quantum molecular dynamics model, the mid-rapidity zone (–0.6 ≤ Y c.m./Y beam ≤ 0.6) is segregated into three different regions to discover the intricate correlation between nuclear stopping (〈R p 〉) and the magnetic field eBy(0,0,0) generated due to the nucleons from these rapidity segments. Moreover, study of the time and space evolution of eBy(0,0,0) has been carried out for all the three rapidity bins. The maximum magnetic field intensity eBy(0,0,0)max is observed in the outwardmost region of the mid-rapidity zone due to less nuclear stopping and fewer nucleon–nucleon collisions. Additionally, a fruitful correlation has also been observed between eccentricity and nuclear stopping.

A Novel Antenna Design of Compact HF and UHF Passive RFID Tags with Interconnected Structure for Energy Harvesting and Tracking Systems

We propose a new dual-band passive RFID tag antenna design by combining a rectangular spiral coil and patch-meander-line dipole with an interconnected structure. This design enables operation in high-frequency (HF) and ultra-high-frequency (UHF) RFID systems, suitable for energy harvesting and tracking applications. The simulations by the CST full-wave software demonstrate conjugate impedance matching between the tag antenna and two RFID tag chips. At 13.56 MHz (HF), the tag antenna exhibits an inductive reactance of 422.79 Ω, while at 922.5 MHz (UHF), it presents an impedance of 9.41+j174.96 Ω. The antenna generates a maximum magnetic field intensity of 0.5 A/m and omnidirectional electromagnetic fields with an antenna realized gain of -4.26 dBi at 922.5 MHz. We also analyze the impact of the tag antenna combination using numerical software. Furthermore, we fabricate a prototype tag antenna and validate its performance with RFID readers. The proposed tag antenna achieves the maximum read ranges of 11 cm and 6.9 m for the HF (13.56 MHz) and UHF (920-925 MHz) bands, respectively, accompanied by the energy harvesting of 1.48 volts at the HF band by the coupling magnetic field received by the HF antenna to the chip ST25DV04K at the output voltage pin.

Mathematical modeling of the magnetic field in the vicinity of narrow capillaries

A mathematical model of the magnetic field, which is generated by negative charges located on the outer side of the red blood cell (RBC) membrane, has been constructed. When modeling, the geometric (area, volume) and physical (speed, number of revolutions per second, charge, number of charges on the membrane) characteristics of a red blood cell in a narrow capillary are taken into account. Computer calculations made it possible to find the magnetic field strength near a single RBC rolling along a narrow capillary. Calculations were also carried out to determine the magnetic field strength in the vicinity of a capillary through which several RBCs move. The dependence of the maximum magnetic field strength on the distances between RBCs (hematocrit) was found. In particular, it is shown that at distances from the capillary equal to 8 capillary diameters, the maximum magnetic field intensity changes on average by 1.3 times with an increase in hematocrit by 1.5 times (from 12.27% to 18.25%).

The optimization method with segmenting iteration strategy for a long-wavelength infrared metalens

Over the past several years, there has been a substantial surge in the utilization of metasurfaces in micro-electronics and micro-optical devices. As one of their applications, metalenses have aroused significant research interest. In this paper, a new optimization method based on micro co-fluctuation model is proposed to optimize the initial metalens for better focusing performance by adjusting the structural dimensions of nanopillars. A segmenting iteration strategy is used to legitimately reduce the computation space. Meanwhile, an improved Harris Hawks Optimizer (IHHO) is proposed to obtain the optimal solutions, in which a new formula for escape energy is defined to promote the diversity of solution space. The optimization results indicate that the proposed optimization method effectively enhances the focusing capability of the initial metalens with a numerical aperture (NA) of about 0.7 and an operating wavelength of 10.6 μm. The maximum field intensity of the central hot spot and the absolute efficiency have increased by approximately 59.02% and 71.13%, respectively, and the full width at half maximum (FWHM) remains nearly the same value, which provides the potential for achieving high-contrast imaging.

Effect of Metal Ions and Suspended Particles on Streamer Propagation

Metal contamination in insulating oil is one of the main threats to the safe and reliable operation of oil-immersed equipment such as on-load tap changers. The mechanism analysis of metal ions’ influence on the discharge process of insulating oil is rarely involved in previous studies. Herein, the generation mechanism of metal ions and suspended particles is summarized first for subsequent modeling. Numerical models are constructed to simulate the streamer propagation in oil, considering the effect of two forms of metal contaminant. The dissociation source term of ionic compounds is introduced into the charge continuity equation to elucidate the impact of metal ions on streamer propagation. The results reveal that adding metal ions increases the overall speed of the streamer and decreases the maximum field intensity at the head of the steamer compared to pure oil conditions. Excessive ion concentration hinders the streamer’s development by creating the space charge shielding effect. Charge accumulation on the surface of suspended metal particles is the leading cause for the branching or turning of the streamer channel. The size, quantity of the metal particles, and the landing location will significantly affect the streamer propagation characteristics, e.g., the landing location on the surface of the metal particle will determine whether the subsequent branching streamer head can further develop. The results contribute to a better understanding of the influence of ionic and particulate metal contaminants on the microscopic discharge process in insulating oil.

Separation of iron from converter dust by superconducting HGMS: A simulation analysis and experimental study

Converter dust (LT dust) is an important solid waste from steelmaking, in which iron oxides are the preferred raw material for preparing high value-added α-Fe2O3. Since LT dust contains many impurities, the iron oxides in the LT dust must be enriched and purified before the preparation of α-Fe2O3. Particle trapping behaviors of the matrices as well as the magnetic flocculation of LT dust particles in superconducting high gradient magnetic separation (S-HGMS) were investigated with numerical simulations and experiments. The geometric shape, aspect ratio a:b, and angle α between the axis and the magnetic field direction of the matrices affected the maximum magnetic field intensity (Hmax) and effective capture area (Seca). Diamond matrices had better particle-capture capacity than elliptic and circular matrices because the diamond matrices produced a tip effect and increased the magnetic field force. When the cross section of the matrices was parallel to the direction of the particle velocity, magnetic/weakly magnetic particles were more easily captured by the upper and lower ends of the matrices compared with that of two sides because the particle velocity at the upper and lower ends of the matrices was smaller than that of two sides, making the magnetic force greater than the drag force. Fe2MgO4 and Fe2O3 particles were more prone to magnetic flocculation than other particles because of their higher magnetic susceptibility. The dispersant changed the pH of the solution and the charges on the surface of LT dust particles, and the particles were effectively dispersed because of the action of electrostatic forces. When the magnetic induction was 1.8 T, the dispersant dosage was 20 mg/L, the pulp concentration was 1.5%, and the total Fe content increased by 8.72%, corresponding to an Fe recovery of 91.65%. Finally, a method was developed for extracting iron oxides from LT dust using S-HGMS, to prepare high value-added α-Fe2O3.

KoBRA Wien filter for low-energy RI beam production and recoil separation

The Wien filter is one of the key components in ion optics to improve the mass separation performance. The KoBRA Wien filter will be installed at the low-energy beamline KoBRA of RAON in Korea. The specifications of the KoBRA Wien filter were determined based on the ion beams expected in the KoBRA beamline, especially, beam energies less than about 5 MeV/nucleon suitable for nuclear astrophysics experiments. The Wien filter is designed to have the maximum field intensities of 0.2 T for the magnetic field and 2.0 kV/mm for the electric field in the ±75(H)×±50(V)×2500(L)mm3 good-field region. Performance of the Wien filter was estimated by the ion optics calculations of the KoBRA beamline for 40Ar beams at 18.5 MeV/nucleon and 14O beams at 2.5 MeV/nucleon. The mass resolving powers are 42.65 and 517, respectively. Currently, the KoBRA Wien filter is being manufactured, and will perform a factory acceptance test.

A reflection photonic jet induced by light interaction with a partially gilded hollow micro-fiber in liquid

Reflection photonic jet (r-PJ) is a new type of photonic jet (PJ), formed in reflection mode, which has the potential to revolutionize mesoscale photonics in many applications, e.g. optical nanoparticle trapping, liquids and gas refractive index sensing, signal switching, etc. In this paper, we present a microfluidic channel based on a hollow micro-fiber structure with partially coated optically thick gold film to produce r-PJs for biofluid application. The proposed scheme is studied by the full-wave simulations using the finite element method. The key r-PJ parameters, such as the maximum field intensity, focus position and full width at half-maximum (FWHM) are studied for different size of the microchannel and coated area. The proposed design allows a wide range of flexible control of the r-PJ parameters and can be easily integrated into microchannel systems.

Electric field analysis for hybrid high voltage DC circuit breaker

The structure and potential distribution of the 535kV HVDC circuit breaker are complex. In order to improve the reliability of insulation design in valve tower, this paper takes the forced commutation hybrid HVDC circuit breaker as the research object. Firstly, its topology and working principle are explained. Then, based on the insulation performance requirements of a flexible DC power grid demonstration project, and the electrostatic field analysis method, the electric field distribution and electrical shielding design of the HVDC circuit breaker are carried out. The results show that the reasonable electrical shielding design and application can effectively improve the electric field distribution of the DC circuit breaker. The maximum field intensity of the valve tower is 1.74kV/mm, located at the arc part of the U-shaped tubular shielding, and is lower than the corona inception gradient 3kV/mm. The field intensity of the valve unit in transfer branch generally shows a law of decreasing first and then increasing with the increase of the valve layer. Finally, the reliability of the insulation design is verified by experiments, which provides a reference for the insulation design of HVDC circuit breakers.

Calculation of Magnetic Fields Generated by Traction Transformers and Busbars in Electric Locomotive Systems by Finite Element Method

Güç sistemi ekipmanlarının etrafında oluşturduğu manyetik alan yoğunluğunun insan sağlığı üzerine olan etkileri çeşitli kuruluşlar tarafından incelenmektedir. İnsanların güç sistemi ekipmanlarının şebeke frekansında oluşturduğu manyetik alan yoğunluğuna maruz kalması durumunda izin verilen sınır değerler International Commission on Non‐Ionizing Radiation Protection (ICNIRP) tarafından belirlenmiştir. Buna göre kamuya açık alanlar ve çalışma ortamları için izin verilen en yüksek manyetik alan yoğunluğu değerleri sırası ile 0,2mT ve 1mT olarak belirtilmiştir. Bu kapsamda lokomotiflerde cer gücünü sağlamak için kullanılan cer transformatörü, bara, sürücü ve motor gibi elemanların oluşturduğu manyetik alan yoğunluklarının önemli bir parametre olduğu görülmektedir. Bu bileşenlerin etrafında oluşan manyetik alan yoğunluklarının yolcuların ve personelin sağlığı için belirlenen sınırların altında kalması önerilmektedir. Bu sebepten dolayı lokomotif sistemlerinin tasarımı aşamasında bileşenlerin etrafında oluşan manyetik alan yoğunluklarının belirlenmesi gerekmektedir. Bu çalışma kapsamında lokomotiflerde kullanılmakta olan bir cer transformatörünün ve örnek bir bara yapısının oluşturduğu manyetik alan yoğunluklarının hesaplanması hedeflenmiştir. Bu amaç ile cer transformatörü, basit bir lokomotif kasası ve bara yapısının geometrik modeli üç boyutlu koordinat sisteminde oluşturulmuş ve Ansys Electronics Suite sonlu elemanlar analizi yazılımına aktarılıp analiz çalışmaları gerçekleştirilmiştir. Analiz sonuçlarına göre belirlenen ölçüm düzlemlerinde manyetik alan yoğunluklarının sınır değerlerin altında kaldığı görülmektedir. Manyetik alan yoğunluğu değerleri modelin geometrik yapısına, malzeme parametrelerine ve işletme durumuna bağlı olarak değiştiğinden dolayı bu analizlerin tasarım aşamasında değerlendirilmesinin gerekliliği çalışma kapsamında vurgulanmıştır.

Detachable electromagnetic actuation system for inverted microscope and its function in motion control of microrobots

In recent years, magnetic microrobots have shown unique advantages and exciting prospects in many application fields. However, the motion mechanism, driving force and imaging effect of magnetic microrobots still need to be further studied and improved. These factors are related to the design of magnetic actuation systems and the manufacturing of microrobots. This paper presents a new structural design involving detachable electromagnetic coils for developing a combinable magnetic actuation system that can be integrated with inverted microscopes for microrobot research. A maximum magnetic field intensity of 20 mT and uniform working space of 10 mm × 10 mm are achieved by applying coil parameter optimization and the yoke design. Furthermore, a dumbbell microrobot, which is symmetrical along its length axis, and a moon microrobot, which is asymmetric along its length axis, are fabricated and their motion characteristics are compared. The dumbbell microrobot exhibits reversible switching of three motion modes, whereas the motion of the moon microrobot exhibits the obvious drift. These dumbbell and moon microrobots are successfully controlled to move along a square path and a labyrinth path respectively, thus verifying the control performance of the magnetic actuation system.

Micro-dimensional oscillation-based optimization for a dielectric metalens in the mid-infrared.

In the past few decades, there has been significant progress made in metasurfaces and integrated and miniaturized optical devices. As one of the most prominent applications of metasurfaces, the metalens is the subject of significant research. In this paper, for achieving better focusing performance of the initial metalens designed by the Pancharatnam-Berry (PB) phase, a concept of micro-dimensional oscillation is proposed to optimize the geometric parameters of nanopillars. A strategy of grouping iteration is proposed to reduce the loss rate and computational effort in a holistic way. Its essence is to divide an extremely large-scale optimization space into many overlapping groups. Meanwhile, an improved genetic-simulated annealing (IGSA) algorithm is presented for the optimal solution of each group. By introducing the adaptive crossover and mutation probabilities in traditional genetic algorithms, the IGSA algorithm has both strong global searching capability and excellent local searching capability. After optimization, the maximum field intensity of the central hot spot can be increased by about 8% compared to the initial metalens. Moreover, the field intensity of the side lobes around the hot spot is almost constant, and the central hot spot increases, which provides a potential for the realization of high imaging contrast.

Measurement of electromagnetic environment of hybrid DC circuit breaker during bipolar short circuit fault

Hybrid DC circuit breakers (DCBs) have recently been used to break short-circuit fault currents to ensure safety in flexible DC transmission projects. However, electromagnetic transients from DCB operation can interfere with the secondary equipment and cause malfunctions. In this paper, the bipolar short-circuit test, which is the first short-circuit test for DC transmission line in flexible DC project in the world, has been carried out in the 200 kV HVDC converter station equipped with two hybrid DCBs. The transient magnetic field near the secondary equipment in the DCB hall were measured, and its characteristics were discussed. Furthermore, the relationships among the space magnetic field, the short-circuit current and the action of the power electronic equipment in the DCB were also analyzed The main findings are as follows. During the bipolar short-circuit process, the maximum space magnetic field intensity near the secondary device is 109 A/m, and the maximum rising rate of the magnetic field waveform is about 350 A/m/ms. The magnetic field strength reached its peak value at the moment when the DCB was blocked, as well as the short-circuit current. It can be indicated that the DCB can cut off the short-circuit fault current accurately and reliably. The results can provide reference for the immunity evaluation and anti-interference protection of secondary equipment, and its optimal arrangement in the DCB hall.

Automobile Laminated Glass Window Embedded Transmitarray and Ray Tracing Validation for Enhanced 5G Connectivity

This article presents a 38.5 GHz transmitarray, for the first time, embedded into laminated car glass, and indoor 5G connectivity enhanced by this transmitarray laminated glass has also been validated using a ray-tracing simulator. The transmitarray structure reduces the penetration loss and realizes a desired beam shaping function. Metallic layers of the transmitarray structure adopt the Jerusalem cross shape that minimizes opacity. A ray-tracing simulator was used to analyze electromagnetic fields in a massive space, such as the interior of a car. The proposed transmitarray laminated glass was applied to the passenger side window in the simulation, and the variation in the communication performance with and without the transmitarray was compared. This comparison confirmed that field intensity increases of up to approximately 5 dB are realized at the target area, where communication is mainly performed. In addition, the proposed transmitarray laminated glass increases the field intensity by more than 3 dB, from approximately 36 to 40 GHz. The transmitarray laminated glass has also been fabricated. The maximum field intensity increase of approximately 5 dB, which is similar to the simulation results, was successfully measured at the target area.

Evaluation of magnetic properties of two kinds of permendurs by vector magnetic measurement

Vector magnetic properties of various electrical steel sheets have been investigated by using a vector magnetic property measurement apparatus to select a magnetic material suitable as a motor core material. However, a magnetic material with a higher saturation magnetization than an electrical steel sheet is useful for increasing torque of a motor. Therefore, a permendur with higher saturation magnetization than an electrical steel sheet is selected as a measurement sample. It is known that a permendur does not have magnetic anisotropy. In this paper, vector magnetic properties of two kinds of permendurs made by VACUUMSCHMELZE (VAC) and Hitachi Metals are measured. Moreover, maximum magnetic field intensities and core losses of two kinds of permendurs to an inclination angle of magnetic flux density vector locus from rolling direction are evaluated for investigation of those magnetic anisotropies. As a result, differences of vector magnetic properties of two kinds of permendurs are revealed.

Magnetic Field Sensing Based on Whispering Gallery Mode with Nanostructured Magnetic Fluid-Infiltrated Photonic Crystal Fiber.

A kind of novel and compact magnetic field sensor has been proposed and investigated experimentally. The proposed sensor consists of a tapered single mode fiber coupled with a nanostructured magnetic fluid-infiltrated photonic crystal fiber, which is easy to be fabricated. The response of magnetic fluid to magnetic field is used to measure the intensity of magnetic field via whispering gallery mode. The magnetic field-dependent shift in resonance wavelength is observed. The maximum magnetic field intensity sensitivity is 53 pm/mT. The sensor sensitivity is inversely proportional to the thickness of the photonic crystal fiber cladding.

CONTROL OVER HIGHER-ORDER TRANSVERSE MODES IN A WAVEGUIDE-BASED QUASI-OPTICAL RESONATOR

Subject and Purpose. The problems under consideration concern selection and focusing of higher-order modes in a waveguide-based dielectric laser. The purpose is to clarify the physics underlying the behavior of, and permitting control over, continuous terahertz-frequency laser beams of various spatial polarizations. Methods and Methodology. The mode parameters of the waveguide-based laser resonator involving an inhomogeneous phase-stepped mirror were calculated in a matrix technique. To analyze the propagation and focusing of the laser beams that can be excited in a variety of diffraction zones by the wave modes of a waveguide-based quasi-optical resonator, a vectorial Rayleigh–Sommerfeld theory was used. The pertinent experimental studies were performed with the use of known measurement methods suitable for the terahertz frequency range. Results. A method for selecting the higher-order EH12q-mode of a terahertz-range laser resonator has been suggested, substantiated theoretically and approbated in experiment. It envisages placing an additional element to perform control over the system’s modal structure, namely a (2.3…2.8) λ-wide groove on the surface of one of the resonator mirrors. This measure can significantly increase losses for all undesirable modes. At the same time, the losses for the higher EH12q-mode remain practically unchanged, which creates conditions for its predominant excitation. Theoretical and experimental studies of moderate and ‘sharp’ focusing in free space of higher-order modes with different spatial polarizations of a dielectric waveguide-based resonator have been carried out. Conclusion. As has been shown, the proposed phase-stepped mirror with a groove can effectively select the higher-order transverse modes that may be required. The linearly polarized EH12q-mode has maximum field intensity in the focal region of the lens employed. For azimuthally polarized TE02q- and TE03q-modes the central lobes, noticeably shifted from the focus of the lens, have a field maximum. An increase in the axial intensity is observed upon ‘sharp’ focusing in the field distribution of the radially polarized TM02q- and TM03q-modes. In this case their central lobes, like those of the higher TE0nq-modes, are noticeably shifted from the lens focus.