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The paper employs statistical methods to model low-frequency electromagnetic field fluctuations over printed circuit boards (PCBs) using near-field measurements within the frequency domain along the Coplanar Broadband Capacitance Wave (CBCPW) transmission line. The study characterizes electromagnetic noise profiles up to 15.2 MHz, assesses the impact of transmission lines (TL) on PCB environments, and explores the effects of signal interference. Advanced statistical methods, including the Hurst exponent and Ljung-Box tests, are integrated with traditional near-field measurements to quantify electromagnetic noise persistence and independence across frequencies. Additionally, 2-D autocovariance analysis provides a precise evaluation of electromagnetic field characteristics over the PCB surface. This research further develops a model for electromagnetic field fluctuations by incorporating theoretical frameworks aligned with stochastic Maxwell’s equations and addressing challenges such as measurement uncertainty and mechanical stepping of the probe head over the PCB surface. The autocovariance function enhances data analysis robustness, which is advantageous for the sparse data typically associated with PCBs and integrated circuits. Measurements extend up to 328.27 MHz, with a focus on significant fluctuations up to 15.2MHz due to their dominance over the measured noise. This study proposes a comprehensive statistical and modelling approach tailored for applications involving CBCPW transmission lines, especially relevant to microscale detectors and sensitive electronic devices.

Magnetic field sensors have extensive applications in various fields such as resource exploration, industrial production, and geomagnetic detection. Traditional electric magnetic field sensors have good stability, but they have disadvantages such as susceptibility to chemical corrosion, high cost, large size, and poor resistance to electromagnetic interference. In contrast, fiber optic magnetic field sensors have advantages such as compact structure, high precision, small size, and strong resistance to electromagnetic interference. Existing fiber optic magnetic field sensors mainly include the following four categories based on basic principles：based on magnetostrictive materials, based on magnetic fluid materials, based on Faraday effect, and based on fiber lasers. Among these, fiber optic magnetic field sensors based on magnetostriction have more advantages in manufacturing processes and applications. This article introduces the development of fiber optic sensing technology for magnetic field measurement, analyzes the principles, advantages and disadvantages, and research status of four different types of sensors. At the same time, the application of fiber optic magnetic field sensors in geomagnetic monitoring was also introduced. Finally, the challenges and future development trends faced by fiber optic magnetic field sensors were analyzed.

Abstract Incidents in extreme environments can bring unprecedented consequences that would endanger the lives of many humans. Real‐time and early detection of cracks and defects in the steel used for the construction of industrial sites can bring many benefits to remote operators and site managers. Although different methods and systems have been proposed in the past, they are not suitable for real‐time fault detection or long‐term operation in harsh environments. Therefore, this paper proposes a low‐power robotic platform with a magnetic actuator mechanism which is capable of wireless inspection of steel structures using the ultrasonic method. The proposed magnetic motion uses the inertia force generated by the piston vibration and the difference in frictional force during movement. The paper evaluates the performance of the steel structure defect detection system from four different perspectives: sensing principle, wireless communication network, driving part, and power supply.

Abstract The analysis of magnetic near‐field radiation emissions (MNRE) has recently raised more attention in device‐level electromagnetic compatibility testing. Pattern clustering of MNRE for integrated circuits manually is very time‐consuming because of the multi‐dimensional characteristics of MNRE, such as frequency, spatial position, emission intensity, etc. This paper proposes a novel pattern clustering method of MNRE, including strong emission frequency extraction, feature extraction, and density‐based clustering. Ring oscillator and five working states are designed on a Field Programmable Gate Array with 256 Ball Grid Array package, which are used to create a complex multi‐source emission case for verifying the effectiveness of the clustering method. The verification results show that the proposed method can correctly cluster the multi‐source emission patterns. Further, the method is also applied to a Microcontroller Unit with unknown operating states; the results show that the proposed method also can effectively distinguish the unknown emission patterns and locate the unknown interference source. The accuracy of the interference source location is proven by 3D X‐ray microscope inspection.

Abstract Simultaneous electromagnetic field probing system (SEMPS) has been popular in recent years. Herein, a simultaneous electromagnetic field probing system with Y‐shaped separation detection structure (SEMPS Y) is first proposed, in which the electric field probing region and the magnetic field probing region of the probe are separated by completely covering the shield along the loop and adding a pin‐shaped metal wire to capture the electric field, which are not the same as the classical dual probe structure. Combined with the non‐rotating asymmetric calibration method (NRACM), a 4‐port vector network analyser (VNA) and a highly symmetric grounded coplanar waveguide (GCPW) calibrator are used to solve the calibration matrix of the asymmetric SEMPS Y. The high symmetry GCPW calibrator is used to generate the standard electromagnetic field for calibration. The results of standing wave measurements show that the SEMPS Y can achieve ultrawideband electromagnetic field measurement of up to 20 GHz. Based on near‐field scanning measurements, SEMP Y can obtain results consistent with the calculation. In addition, when the probe is rotated 90° to invalidate the H‐field input, the decoupling curves of E‐field and H‐field are measured. Results show that the separation detection structure can effectively solve the cross‐coupling problem.

Copyright of Progress in Earthquake Sciences is the property of China Earthquake Administration, Institute of Geophysics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Incidents in extreme environments can bring unprecedented consequences that would endanger the lives of many humans. Real‐time and early detection of cracks and defects in the steel used for the construction of industrial sites can bring many benefits to remote operators and site managers. Although different methods and systems have been proposed in the past, they are not suitable for real‐time fault detection or long‐term operation in harsh environments. Therefore, this paper proposes a low‐power robotic platform with a magnetic actuator mechanism which is capable of wireless inspection of steel structures using the ultrasonic method. The proposed magnetic motion uses the inertia force generated by the piston vibration and the difference in frictional force during movement. The paper evaluates the performance of the steel structure defect detection system from four different perspectives: sensing principle, wireless communication network, driving part, and power supply. [ABSTRACT FROM AUTHOR]

This paper reports the successful application of a self-developed, miniaturized, low-power nano-star tracker for precise attitude measurement of a 5-m-long satellite extension boom. Such extension booms are widely used in space science missions to extend and support payloads like magnetometers. The nano-star tracker, based on a CMOS image sensor, weighs 150 g (including the baffle), has a total power consumption of approximately 0.85 W, and achieves a pointing accuracy of about 5 arcseconds. It is paired with a low-cost, commercial lens and utilizes automated calibration techniques for measurement correction of the collected data. This system has been successfully applied to the precise attitude measurement of the 5-m magnetometer boom on the Chinese Advanced Space Technology Demonstration Satellite (SATech-01). Analysis of the in-orbit measurement data shows that within shadowed regions, the extension boom remains stable relative to the satellite, with a standard deviation of 30′′ (1σ). The average Euler angles for the "X-Y-Z" rotation sequence from the extension boom to the satellite are [−89.49°, 0.08°, 90.11°]. In the transition zone from shadow to sunlight, influenced by vibrations and thermal factors during satellite attitude adjustments, the maximum angular fluctuation of the extension boom relative to the satellite is approximately ±2°. These data and the accuracy of the measurements can effectively correct magnetic field vector measurements. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The analysis of magnetic near‐field radiation emissions (MNRE) has recently raised more attention in device‐level electromagnetic compatibility testing. Pattern clustering of MNRE for integrated circuits manually is very time‐consuming because of the multi‐dimensional characteristics of MNRE, such as frequency, spatial position, emission intensity, etc. This paper proposes a novel pattern clustering method of MNRE, including strong emission frequency extraction, feature extraction, and density‐based clustering. Ring oscillator and five working states are designed on a Field Programmable Gate Array with 256 Ball Grid Array package, which are used to create a complex multi‐source emission case for verifying the effectiveness of the clustering method. The verification results show that the proposed method can correctly cluster the multi‐source emission patterns. Further, the method is also applied to a Microcontroller Unit with unknown operating states; the results show that the proposed method also can effectively distinguish the unknown emission patterns and locate the unknown interference source. The accuracy of the interference source location is proven by 3D X‐ray microscope inspection. [ABSTRACT FROM AUTHOR]

Undergraduate courses in electrical machines often include an introduction to the air gap magnetic field as a basic element in the energy conversion process. The students must learn the main properties of the field produced by basic winding configurations and how they relate to the winding current and frequency. This paper describes a new test equipment design aimed at helping students achieve these learning goals. The test equipment is designed based on four main elements: a modified slip ring induction machine, a winding current driver board, the DAQ boards, and a PC-based virtual instrument. The virtual instrument provides the winding current drivers with suitable current references depending on the user selected machine operational status (single- or three-phase/winding with DC or AC current) and measures and displays the air gap magnetic field for that operational status. Students' laboratory work is organized into a series of experiments that guide their achievement of these air gap field-related abilities. Student learning, assessed based on pre- and post-lab exams and end-of-semester exams, has increased significantly. The students' opinions of the relevance, usefulness, and motivational effects of the laboratory were also positive. [ABSTRACT FROM AUTHOR]

Simultaneous electromagnetic field probing system (SEMPS) has been popular in recent years. Herein, a simultaneous electromagnetic field probing system with Y‐shaped separation detection structure (SEMPS Y) is first proposed, in which the electric field probing region and the magnetic field probing region of the probe are separated by completely covering the shield along the loop and adding a pin‐shaped metal wire to capture the electric field, which are not the same as the classical dual probe structure. Combined with the non‐rotating asymmetric calibration method (NRACM), a 4‐port vector network analyser (VNA) and a highly symmetric grounded coplanar waveguide (GCPW) calibrator are used to solve the calibration matrix of the asymmetric SEMPS Y. The high symmetry GCPW calibrator is used to generate the standard electromagnetic field for calibration. The results of standing wave measurements show that the SEMPS Y can achieve ultrawideband electromagnetic field measurement of up to 20 GHz. Based on near‐field scanning measurements, SEMP Y can obtain results consistent with the calculation. In addition, when the probe is rotated 90° to invalidate the H‐field input, the decoupling curves of E‐field and H‐field are measured. Results show that the separation detection structure can effectively solve the cross‐coupling problem. [ABSTRACT FROM AUTHOR]

Undergraduate courses in electrical machines often include an introduction to the air gap magnetic field as a basic element in the energy conversion process. The students must learn the main properties of the field produced by basic winding configurations and how they relate to the winding current and frequency. This paper describes a new test equipment design aimed at helping students achieve these learning goals. The test equipment is designed based on four main elements: a modified slip ring induction machine, a winding current driver board, the DAQ boards, and a PC-based virtual instrument. The virtual instrument provides the winding current drivers with suitable current references depending on the user selected machine operational status (single- or three-phase/winding with DC or AC current) and measures and displays the air gap magnetic field for that operational status. Students’ laboratory work is organized into a series of experiments that guide their achievement of these air gap field-related abilities. Student learning, assessed based on pre- and post-lab exams and end-of-semester exams, has increased significantly. The students’ opinions of the relevance, usefulness, and motivational effects of the laboratory were also positive.

We present a theoretical study on the magnetic signals of structural surface defects like cracks or indents combined with inhomogeneities on the surface or subsurface inclusions of soft ferromagnetic metals like body-centred cubic Fe or amorphous CoFeB. We discuss limits of early detection of small surface defects on the basis of calculated magnetic stray fields few tens of nm above the surface. The considered surface imperfections have extensions of a few nm which correspond to low multiples of the magnetic exchange lengths of Fe or CoFeB. The detection of such small inhomogeneities requires that the sensor is about as close to the surface as the size of the inhomogeneity is. Furthermore, the step width of a scanning sensor must be of the same size as well. Both these requirements may be fulfilled for instance by scanning microscopy with diamond nitrogen-vacancy-centre quantum sensors. [ABSTRACT FROM AUTHOR]

Abstract The asymmetric calibration method is a very interesting technology for differential output probes. It has been proven that the asymmetric calibration method (ACM) can broaden the application scenarios of the electromagnetic field dual probe. However, ACM is not verified on a back‐to‐back double‐loop differential magnetic field probing system. This paper calibrates a back‐to‐back double‐loop differential magnetic field probing system by inserting a connector for creating an asymmetry using ACM. The calibration results show that ACM can be used to calibrate an asymmetric back‐to‐back double‐loop differential magnetic field probing system. The calibration results are further verified by measuring the standing wave magnetic field, and the verification results show that the asymmetric calibration method is effective in eliminating the asymmetry of the back‐to‐back double‐loop differential magnetic field probing system and the work frequency band reaches up to 12 GHz.

Superconducting undulators (SCUs) can offer a much higher on-axis undulator field than state-of-the-art cryogenic permanent-magnet undulators with the same period and vacuum gap. The development of shorter-period and high-field SCUs would allow the free-electron laser and synchrotron radiation source community to reduce both the length of undulators and the dimensions of the accelerator. Magnetic measurements are essential for characterizing the magnetic field quality of undulators for operation in a modern light source. Hall probe scanning is so far the most mature technique for local field characterization of undulators. This article focuses on the systematic error caused by thermal contraction that influences Hall probe measurements carried out in a liquid helium cryostat. A novel procedure, based on the redundant measurement of the magnetic field using multiple Hall probes at known relative distance, is introduced for the correction of such systematic error.

High-dynamic-range integrated magnetometers demonstrate extensive potential applications in fields involving complex and changing magnetic fields. Among them, Diamond Nitrogen Vacancy Color Core Magnetometer has outstanding performance in wide-range and high-precision magnetic field measurement based on its inherent high spatial resolution, high sensitivity and other characteristics. Therefore, an innovative frequency-tracking scheme is proposed in this study, which continuously monitors the resonant frequency shift of the NV color center induced by a time-varying magnetic field and feeds it back to the microwave source. This scheme successfully expands the dynamic range to 6.4 mT, approximately 34 times the intrinsic dynamic range of the diamond nitrogen-vacancy (NV) center. Additionally, it achieves efficient detection of rapidly changing magnetic field signals at a rate of 0.038 T/s. [ABSTRACT FROM AUTHOR]

The asymmetric calibration method is a very interesting technology for differential output probes. It has been proven that the asymmetric calibration method (ACM) can broaden the application scenarios of the electromagnetic field dual probe. However, ACM is not verified on a back‐to‐back double‐loop differential magnetic field probing system. This paper calibrates a back‐to‐back double‐loop differential magnetic field probing system by inserting a connector for creating an asymmetry using ACM. The calibration results show that ACM can be used to calibrate an asymmetric back‐to‐back double‐loop differential magnetic field probing system. The calibration results are further verified by measuring the standing wave magnetic field, and the verification results show that the asymmetric calibration method is effective in eliminating the asymmetry of the back‐to‐back double‐loop differential magnetic field probing system and the work frequency band reaches up to 12 GHz. [ABSTRACT FROM AUTHOR]

It is important to measure the global and/or local velocity of an in-pipe metallic flow to control its running state in applications such as a Tokamak fusion reactor. The magnetic field outside the pipe wall will be perturbed by the motion induced eddy current when the liquid metal flows across an applied static magnetic field. This phenomenon gives a possibility to evaluate the in-pipe velocity from the measured magnetic field perturbation signals. In this paper, a non-intrusive velocity evaluation method is proposed accordingly for measuring the velocity of liquid metal through measurement and inversion of the magnetic field surrounding the pipe. An efficient forward simulation method to calculate the magnetic field near a metallic flow in a static environmental magnetic field is developed at first. An inversion scheme based on the singular value decomposition and the L-curve method is then proposed to reconstruct the velocity distribution at a pipe cross-section with the linear equations correlating the flow velocity and the magnetic field regulated using the Tikhonov method. The reconstruction results of pipe flows of different velocity modes verified the feasibility and efficiency of the proposed velocity measurement method for in-pipe metallic flows. [ABSTRACT FROM AUTHOR]

Superconducting undulators (SCUs) can offer a much higher on-axis undulator field than state-of-the-art cryogenic permanent-magnet undulators with the same period and vacuum gap. The development of shorter-period and high-field SCUs would allow the free-electron laser and synchrotron radiation source community to reduce both the length of undulators and the dimensions of the accelerator. Magnetic measurements are essential for characterizing the magnetic field quality of undulators for operation in a modern light source. Hall probe scanning is so far the most mature technique for local field characterization of undulators. This article focuses on the systematic error caused by thermal contraction that influences Hall probe measurements carried out in a liquid helium cryostat. A novel procedure, based on the redundant measurement of the magnetic field using multiple Hall probes at known relative distance, is introduced for the correction of such systematic error. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Measurement Science & Instrumentation is the property of Journal of Measurement Science & Instrumentation and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In Intelligent Transportation Systems the identification and tracking of vehicles play an important role in enhancing traffic management, security, and overall road safety. Traditional means for vehicle re-identification rely solely on video-based systems which are not resilient to harsh environment conditions, suffer from visual obstructions, and are facing other challenges. To address these shortcomings and provide a more robust solution, alternative methods can be employed. This study addresses the gap in vehicle re-identification accuracy under harsh environmental conditions and visual obstructions faced by traditional video-based systems by integrating magnetic sensors into the road surface. The essence of this study revolves around a comprehensive comparison of various algorithms employed for feature extraction from registered magnetic field distortions. These distortions are treated as transient time series and various distance metrics are applied to calculate their similarity. Useful features are extracted and their classification performance is compared using a single neighbor classifier also taking into account calculation time. The validation experiments demonstrate the efficacy of presented approach in extracting critical features that hold the potential for successfully re-identifying same vehicles. For tested subset up to 90 % re-identification accuracy can be reached. The main contribution of this work involves determining which magnetic sensor axis to use—whether single or in combination—and identifying the most effective methods for feature extraction from the registered magnetic field distortions.

Abstract The de‐embedding calibration method has been proposed to achieve high‐precision calibration for a single port electric field or magnetic field probe, which can effectively eliminate the calibration ripple. However, the method's effectiveness for a four‐port calibration system has not been verified yet. In this paper, a four‐port de‐embedding calibration method with a differential magnetic field probe is proposed, and its effectiveness is proved. Two symmetric grounded coplanar waveguide transmission lines are applied in the proposed method to solve the ABCD‐matrix of the embedded part of the calibrator. The de‐embedded S‐parameter model of the four‐port calibration system for differential magnetic field probe can be obtained. The calibration results indicate that the proposed method can also reduce the calibration ripple and compensate for the attenuation caused by the calibrator. Compared with the traditional calibration method using a microstrip line calibrator, the ripples of the proposed method can be reduced by 34%. The analysis results of the frequency interval of the ripple (FIR) in different methods show that the de‐embedding method can reduce the FIRs (except around 1.2 GHz) caused by the reflection of the calibrator and retain the FIR (about 1.2 GHz) caused by the reflection of the probe itself.

Accurate measuring magnetic induction intensity is important for some scientific research. In the paper, the conventional nuclear magnetic resonance (NMR) experiment under static magnetic field has been extended to longitudinal time-varying magnetic field (TVMF), and the time domain transient solution of the Bloch equations for spin nuclei exhibits the so-called non-steady state nuclear magnetic resonance (NSS-NMR) phenomenon. Based on the above effect and the precise gyromagnetic ratio of spin nucleus, a new magnetic field measurement method and corresponding experimental apparatus have been developed in longitudinal TVMF environment. The orthogonal dual-coil probe, radio frequency (RF) exciting and receiving hardware, key signal processing algorithms, host computer controlling and analysis software are deeply studied. In order to improve the signal-to-noise ratio of the NSS-NMR signal, the RF signal envelope shaping and the low-frequency pre-emphasis probe matching techniques are designed and verified by the invented circuit-field-nuclear multi-domain joint simulation subassembly (CFN-MDJS) which is integrated in the host computer software. Furthermore, the multi-tone RF excitation signal substituting the bandpass continuous spectrum signal for NSS-NMR experiment is also verified by the CFN-MDJS. The experimental results under longitudinal 50Hz TVMF environment has demonstrated the authentic existence of the NSS-NMR effect and simultaneously verified the effectiveness of the experimental scheme and signal processing algorithms proposed in the paper.

Modern electric railway vehicles are faced with the challenge of achieving electromagnetic compatibility (EMC) compliance with railway signaling systems. Currently, no established countermeasures or design methods that guarantee passing the EMC compliance test are available. Therefore, the enhancement of EMC management during vehicle manufacturing processes is imperative. This study devised a pre-accreditation method to be implemented at the vehicle completion stage, prior to the EMC compliance test. The proposed method entails the substitution of real ground signaling devices, whose parameters are difficult to obtain, with unified coils. The effectiveness of this approach is validated by observing whether the gain difference remains consistent when using both an exciting coil and a test train. To illustrate this method, we selected the platform screen door (PSD) balise as a representative signaling device, which is widely utilized in various railway stations. The unified coil employed in this study can be easily fabricated. First, we measured the gain difference (the ratio between the induced voltage of coils and the exciting coil current) between the PSD balise and unified coil. Next, we measured the unknown magnetic flux induced by an 8-car electric multiple unit test train by utilizing the PSD balise and unified coil. Finally, we calculated the measured difference between them. The gain and measured differences properly agreed (within 6 dB) across a wide frequency range of 200 kHz to 4 MHz.

LQXFA/B production series cryogenic assemblies are being built for the LHC upgrade by the HL-LHC Accelerator Upgrade Project (AUP). These contain a pair of MQXFA quadrupole magnets combined as a cold mass within a vacuum vessel, and are to be installed in the IR regions of the LHC. The LQXFA/B are being tested at 1.9 K to assess alignment and magnetic performance at Fermilab's horizontal test facility. The ∼10 m long assembly must meet stringent specifications for quadrupole strength and harmonic field integrals determination, magnetic axis location, and for variations in axis position and local field profiles. A multi-probe, PCB-based rotating coil and a Single Stretched Wire system are employed for these measurements. To accurately determine rotating coil location and angles within the cold mass, a laser tracker is utilized to record multiple targets at one end of the probe. This paper describes the measurements, probes/equipment, and techniques used to perform the necessary characterization of the cold mass.

The magnetoencephalogram (MEG) based on array optically pumped magnetometers (OPMs) has the potential of replacing conventional cryogenic superconducting quantum interference device. Phase synchronization is a common method for measuring brain oscillations and functional connectivity. Verifying the feasibility and fidelity of OPM-MEG in measuring phase synchronization will help its widespread application in the study of aforementioned neural mechanisms. The analysis method on source-level time series can weaken the influence of instantaneous field spread effect. In this paper, the OPM-MEG was used for measuring the evoked responses of 20Hz rhythmic and arrhythmic median nerve stimulation, and the inter-trial phase synchronization (ITPS) and inter-reginal phase synchronization (IRPS) of primary somatosensory cortex (SI) and secondary somatosensory cortex (SII) were analysed. The results find that under rhythmic condition, the evoked responses of SI and SII show continuous oscillations and the effect of resetting phase. The values of ITPS and IRPS significantly increase at the stimulation frequency of 20Hz and its harmonic of 40Hz, whereas the arrhythmic stimulation does not exhibit this phenomenon. Moreover, in the initial stage of stimulation, the ITPS and IRPS values are significantly higher at Mu rhythm in the rhythmic condition compared to arrhythmic. In conclusion, the results demonstrate the ability of OPM-MEG in measuring phase pattern and functional connectivity on source-level, and may also prove beneficial for the study on the mechanism of rhythmic stimulation therapy for rehabilitation. [ABSTRACT FROM AUTHOR]

The de‐embedding calibration method has been proposed to achieve high‐precision calibration for a single port electric field or magnetic field probe, which can effectively eliminate the calibration ripple. However, the method's effectiveness for a four‐port calibration system has not been verified yet. In this paper, a four‐port de‐embedding calibration method with a differential magnetic field probe is proposed, and its effectiveness is proved. Two symmetric grounded coplanar waveguide transmission lines are applied in the proposed method to solve the ABCD‐matrix of the embedded part of the calibrator. The de‐embedded S‐parameter model of the four‐port calibration system for differential magnetic field probe can be obtained. The calibration results indicate that the proposed method can also reduce the calibration ripple and compensate for the attenuation caused by the calibrator. Compared with the traditional calibration method using a microstrip line calibrator, the ripples of the proposed method can be reduced by 34%. The analysis results of the frequency interval of the ripple (FIR) in different methods show that the de‐embedding method can reduce the FIRs (except around 1.2 GHz) caused by the reflection of the calibrator and retain the FIR (about 1.2 GHz) caused by the reflection of the probe itself. [ABSTRACT FROM AUTHOR]

A high-accuracy magnetic field measurement device based on a cyclotron is being developed for accelerator mass spectrometry (AMS). In this study, a magnetic field measurement device consisting of a Hall probe sensor, piezo-motor, and step motor was developed to measure the magnetic field of the AMS cyclotron magnet. The Hall probe sensor was calibrated to achieve positional accuracy by using polar coordinates. The measurement results between the ratchet gear and piezo-motor, which are the instruments used for driving the measurement device, were analyzed. The measurement result of the device with a piezo-motor exhibits a difference of 5 Gauss (0.04%) as compared with the simulation result.

To improve the understanding and monitoring the impacts of geomagnetic disturbances (GMDs) on power grids globally, the presented software, Global-GMDs, uses magnetic field measurements from geomagnetic observatories worldwide and Kriging method to generate global maps of GMDs. It provides better observational information during a solar storm to power grid operations and other crucial infrastructures. It can also help researchers to assess the GMDs prediction model by comparing with Global-GMDs maps and to get better understanding of physics mechanisms.

This paper discusses the manufacturing process of magnetic-field-assisted abrasive sensing for electroplated diamond cutting wires. The study uses a magnetization device to partially magnetize the piano wire and coat diamond abrasives around it. A magnetic field sensing coil is used to measure the magnetized area and a pair of needle-type vertical coil electromagnets are used for partial magnetization. The magnetic field that can be measured ranges between 9.44 and 375 mT. The study found that the distribution of diamond abrasives on the diamond cutting wire and its rigidity are crucial factors that affect the cutting performance and service life. [ABSTRACT FROM AUTHOR]

Rubidium laser optically pumped magnetometers (OPMs) are widely used magnetic sensors based on the Zeeman effect, laser pumping, and magnetic resonance principles. They measure the magnetic field by measuring the magnetic resonance signal passing through a rubidium atomic gas cell. The quality of the magnetic resonance signal is a necessary condition for a magnetometer to achieve high sensitivity. In this research, to obtain the best magnetic resonance signal of rubidium laser OPMs in the Earth's magnetic field intensity, the experiment system of rubidium laser OPMs is built with a rubidium atomic gas cell as the core component. The linewidth and amplitude ratio (LAR) of magnetic resonance signals is utilized as the optimization objective function. The magnetic resonance signals of the magnetometer experiment system are experimentally measured for different laser frequencies, radio frequency (RF) intensities, laser powers, and atomic gas cell temperatures in a background magnetic field of 50,765 nT. The experimental results indicate that optimizing these parameters can reduce the LAR by one order of magnitude. This shows that the optimal parameter combination can effectively improve the sensitivity of the magnetometer. The sensitivity defined using the noise spectral density measured under optimal experimental parameters is 1.5 pT/Hz1/2@1 Hz. This work will provide key technical support for rubidium laser OPMs' product development. [ABSTRACT FROM AUTHOR]

We describe a weak magnetic field sensor operating at room temperature based on the magnonic crystal (MC). MC consisting of periodic stripes of cobalt (Co) and permalloy (Py) in one dimension is studied. The magnonic bandgaps are calculated by solving the eigenvalue problem of the Landau–Lifshitz equation using the finite element method. Magnonic bandgap frequency shifts depend upon the external magnetic field and this phenomenon is utilized for magnetic field sensing. The sensitivity characteristics of MCs with dispersion spectra in the gigahertz (GHz) frequency range are studied. It is found that the sensor's performance gets enhanced for smaller thickness and larger periodicity. The sensitivity reaches a magnitude as large as 66.0 GHz T−1 for 10 nm thickness and 1 μ m periodicity. Our analysis indicates that a limit of detection (LOD) of the order of 10−11 T can be achieved for all the geometric configurations considered in the 0–1 T range. The results are explained in terms of corresponding fundamental concepts and phenomena. Further, our simulation results show that the typical gap (e.g. 1 nm) between Co and Py stripes does not significantly affect the sensitivity of the sensor. The results also indicate that any small variation (e.g. 1 nm) in MC thickness may lead to reasonable variation in sensitivity magnitudes. Moreover, the proposed sensor's performance is significantly superior (in terms of sensitivity, LOD, miniaturization, and material, etc) to the currently available state-of-the-art magnetometers. [ABSTRACT FROM AUTHOR]

A radio frequency (RF)-assisted Sagnac interferometer based on a dual-loop optoelectronic oscillator (OEO) is experimentally demonstrated for high-precision magnetic field measurement, in which the tapered fiber covered with the magnetic fluid (MF) as the magnetic field sensing head is embedded in the Sagnac interferometer. The evanescent field of the tapered fiber can interact with the MF under the external magnetic field to cause the birefringence variation of the fundamental mode, leading to the change in the free spectral range (FSR) of the interferometer, which can be mapped to the oscillation frequency shift of the OEO in the microwave domain. By the above converting, the magnetic field measurement with high interrogation speed and resolution can be realized. In addition, the designed device shows a certain measurement directionality of the magnetic field due to two orthogonally polarized fundamental modes asymmetric to the magnetic field, obtaining a good conformity with the constructed theoretical models. The experimental results show the maximum magnetic field sensitivities of 159.4 Hz/mT in the range of 8.48-27.83 mT, and 350.8 Hz/mT in the range of 0-5.14 mT, corresponding to the light wave vector parallel and perpendicular to the magnetic field, respectively.

The increasing presence of vehicles on roads necessitates intelligent traffic management solutions in areas where video cameras cannot be utilized. Currently, there are limited choices for depersonalized vehicle reidentification systems. This paper introduces a system that later will be used for vehicle reidentification. The system uses anisotropic magnetoresistive sensors and is based on the hypothesis that each vehicle leaves unique magnetic signatures which can be used for comparison and matching. Vehicle location on the road perpendicular to sensor array detection methodology is presented in this work. An array of magnetic sensors is installed in asphalt across the vehicle’s driving direction. The system continuously measures Earth’s natural magnetic field and detects distortions when vehicles pass an array of a sensors and then logs magnetic signatures. Useful parameters from raw sensor axes are calculated– modules and derivatives. Applying signal-to-noise ratio calculation for module derivatives between ambient noise and signal gives important features for neural network input. Different types of neural network architectures and output result interpretation techniques are investigated. Further, after evaluating network output it is possible to label sensor nodes that are directly beneath the vehicle. Experiment results show that implemented algorithm is highly sufficient for valid sensors under the vehicle selection. Correct sensor selection is important for further re-identification algorithms.

Objectives In order to obtain the plane magnetic field data at different heights above a ship and solve the problem of calculating the plane magnetic field from the vaulted magnetic field above the ship, this paper proposes a method for calculating the magnetic field above the ship using the equivalent surface magnetic charge.MethodsBased on the theory of equivalent source, the magnetic field data of the vault is used for inversion modeling. As the ship's magnetic field is equivalent to that generated by the surface magnetic charge, it is calculated accordingly to simulate the magnetic field above the ship. The magnetic field calculated by the surface magnetic charge method is then compared with the ship's actual magnetic field to verify the feasibility of the surface magnetic charge method.ResultsThrough numerical simulation, the relative root mean square error of the vertical component of the ship's magnetic field calculation is 0.44%. Using the magnetic field ship model, the relative root mean square error of the vertical component calculation is 7.64%.ConclusionsThe simulation and ship model experiment analysis herein show that the calculated value of the magnetic field using the surface magnetic charge method is consistent with the measured value. Moreover, the relative root mean square error of the calculated value is small and has high precision, which makes it feasible for use in practical engineering calculation.

This paper proposes a novel design of shielded two-turn near-field probe with focus on high sensitivity and high electric field suppression. A comparison of different two-turn loop topologies and their influence on the probe sensitivity in the frequency range up to 3 GHz is presented. Furthermore, a comparison between a single loop probe and a two-turn probe is given and different topologies of the two-turn probe are analyzed and evaluated. The proposed probes were simulated using Ansys HFSS and manufactured on a standard FR4 substrate four-layer printed circuit board (PCB). A measurement setup for determining probe sensitivity and electric field suppression ratio using an in-house made PCB probe stand, vector network analyzer, microstrip line (MSL) and the manufactured probe is presented. It is shown that using a two-turn probe design it is possible to increase the probe sensitivity while minimizing the influence on the probe spatial resolution. The average sensitivity of the proposed two-turn probe compared to the conventional design is increased by 10.1 dB in the frequency range from 10 MHz up to 1 GHz. [ABSTRACT FROM AUTHOR]

Autonomous underwater vehicle (AUV) with towed magnetic anomaly detection (MAD) system is a reliable technique for detecting underwater magnetic targets. However, arranging too many magnetometers in the towed MAD system is not suitable, and the key lies in their reasonable arrangement. As a result, this letter proposes a new MAD system equipped with two scalar and one vector magnetometers, along with the corresponding multiparameter magnetic target localization method. By using two scalar magnetometers and the geometric relationship with vector magnetometer, the time when the vector magnetometer reaches the closest point approach (CPA) on the trajectory and the value range of the shortest distance are obtained. The value range of the shortest distance is cleverly set as the search boundary for the improved particle swarm optimization algorithm in this dimension, which greatly mitigates the randomness of the optimization algorithm and enhances the accuracy of the solution. Subsequently, the unique solution for the magnetic target parameters can be easily obtained by using the vector magnetometer. The combination of scalar and vector magnetometers proves to be both economical and effective. Numerical simulation and field experiments show that this method provides a new idea for static magnetic target detection. [ABSTRACT FROM AUTHOR]

In the field of magnetic anomaly detection (MAD), the anomaly signal is easily submerged by ambient electromagnetic interference. Though the existing noise suppression methods can effectively improve the signal-to-noise ratio (SNR), there are still some intractable problems, such as signal distortion and boundary blur. To solve these problems, a novel MAD method based on structured low rank (SLR) and total variation (TV) regularization constraints is proposed in this letter. The noise suppression performance is improved by leveraging the structured low rankness of the signal. To preserve clean boundaries of the anomalies, an anisotropic TV regularization constraint is employed in the approach. Comparing the SLR-TV method with four state-of-the-art methods with extensive field tests, the results demonstrate that the proposed SLR-TV method achieves the greatest SNR improvement by about 63.24% and the best structural similarity (SSIM) improvement by about 53.02% over other methods in the range from −40 to 0 dB, showing the utility and high fidelity of the proposed framework in low SNR. [ABSTRACT FROM AUTHOR]

Current-driven spin-orbit-torque (SOT)-induced device is a promising candidate with nonvolatility, low energy consumption, and ultrafast speed for the next-generation storage and computing technique. However, the requirement of the assistant magnetic field hinders its application. Besides, the switching current density in SOT-induced devices still needs to be further reduced. Here, we prepared devices with stacks of Ta/Pt100-xWx/Co/AlOy/Pt and systematically investigated changes in the switching efficiency with W content. A high damping-like effective field per unit current density ηDL up to 40.57 ± 3.32 (Oe/(106 A/cm2)) was observed in the device with a Pt74W26 layer, which is one order of magnitude higher than that in the typical spin-orbit devices with pure heavy metal layer reported in the previous articles. In addition, field-free switching is observed in devices with a wide range of W content using the competing spin currents generated from the Pt100-xWx layer. Zero-field switching (ZFS) critical current densities of them are less than 1.09 ± 0.05 (107 A/cm2) with the minimum of 1.58 ± 0.13 (106 A/cm2), indicating the highly efficient field-free spin-orbit switching in the PtW system. Our findings pave the way to high-energy-efficiency spin-orbit devices. [ABSTRACT FROM AUTHOR]

One of the key challenges in the industrialisation of Voltage Controlled Magnetic Anisotropy-Magnetic Random Access Memory (VCMA-MRAM) is the reliability of the writing process. As VCMA is a non-deterministic write process, it is more sensitive to any offset of the Free Layer (FL) ($\mu _{0}H_{off}$) due to stray fields generated by the Hard Layer (HL)/Reference Layer (RL), as compared to alternative MRAM technologies. In this work, a simple method for the control of $\mu _{0}H_{off}$ is demonstrated. The relative moments of the HL and RL can be tuned by varying the Co concentration, and number of repeats, in a typical Co/Pt HL. The effect of this is demonstrated at thin film and device level where a FL offset of $\mu _{0}H_{off}=0$  mT is obtained, with minimal change in any other device properties. Furthermore, the switching probability distribution, with respect to VCMA pulse width, is shown to be symmetric in the optimised device. This result shows that with simple tuning, one of the key challenges to VCMA-MRAM can be solved. [ABSTRACT FROM AUTHOR]

After eons of evolution, biological systems have developed excellent actuating methodology in micro-nano scale, which inspired the design and development of advanced microrobots. Cardiomyocytes have received extensive attention following the development of bio-syncretic robots in terms of its spontaneous contraction and high energy efficiency. However, the multipoint, high-precision synchronized, and comprehensive acquisition of the axial motion parameters of cardiomyocytes still constitutes the major factor hindering the development of quantitative control methods for bio-syncretic robots. Herein, off-focus imaging method was proposed to quantify the axial beating of cardiomyocyte. The spontaneously beating of cardiomyocytes were quantitative analyzed based on the combination of cross-correlation and off-focusing imaging. We also validated the use of the proposed SiO2 microspheres in cardiotoxicity test. Following the administration of isoproterenol, cardiomyocytes exhibited positive inotropic and chronotropic effects. Finally, we analyzed the beating responses of individual cardiomyocytes at different locations, and we validated the feasibility of multipoint, synchronized measurements. In the future, this study can also be extended to the analysis of the motion coupling relationship between individual cardiomyocytes and cardiomyocyte clusters, thus providing a data acquisition platform for the dynamic analysis and modeling of bio-syncretic robot actuators. [ABSTRACT FROM AUTHOR]

High-dynamic-range integrated magnetometers demonstrate extensive potential applications in fields involving complex and changing magnetic fields. Among them, Diamond Nitrogen Vacancy Color Core Magnetometer has outstanding performance in wide-range and high-precision magnetic field measurement based on its inherent high spatial resolution, high sensitivity and other characteristics. Therefore, an innovative frequency-tracking scheme is proposed in this study, which continuously monitors the resonant frequency shift of the NV color center induced by a time-varying magnetic field and feeds it back to the microwave source. This scheme successfully expands the dynamic range to 6.4 mT, approximately 34 times the intrinsic dynamic range of the diamond nitrogen-vacancy (NV) center. Additionally, it achieves efficient detection of rapidly changing magnetic field signals at a rate of 0.038 T/s.

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.

This paper investigates the magnetic filed interference problem when the ROV equipped with a three-axis magnetometer measures the magnetic field of underwater magnetic targets within a short range, and a magnetic field compensation method based on an improved mayfly algorithm is proposed to improve the measurement accuracy of underwater magnetic field information. Firstly, a compensation model is established based on the installation error of the three-axis magnetometer and the interference magnetic field of the ROV. Then, in view of the problem that the original mayfly algorithm is easy to fall into local optimal and the convergence accuracy is poor, the Tent chaotic sequence and the Levy flight mutation strategy are introduced to improve the original mayfly algorithm. Finally, a series of magnetic field information is obtained through the three-axis magnetometer, and the original mayfly algorithm, particle swarm algorithm and improved mayfly algorithm are used to estimate the compensation parameters. The experimental results show that the improved mayfly algorithm has obtained faster convergence speed and higher compensation accuracy than others.

Designing of the vehicle magnetic signature generator is presented in this paper. The basic concept used in designing is distortion of the Earth's magnetic field that occurs in the presence of ferromagnetic materials. The experimental setup for measuring the magnetic field distortion caused by a vehicle is presented, and based on the obtained values of the magnetic field, input data for signature generator are obtained. The magnetic signature generator consists of a solenoid with a copper wire wound on the bobbin made by the three-dimensional (3D) printer, and an arbitrary function generator RIGOL DG1022Z. Determination of the solenoid parameters and a voltage level of a generator are described thoroughly. In order to demonstrate performances of the generator, magnetic signatures of four different vehicles are generated by proposed design and compared with measured ones by Pearson's correlation coefficient, indicating a greater correlation than 0.993. [ABSTRACT FROM AUTHOR]

A magnetic field measurement system for an undulator has been developed at the Plasma and Beam Physics (PBP) Research Facility, Chiang Mai University (CMU), as a part of the mid-infrared (MIR) and terahertz (THz) radiation free-electron laser (FEL) project. The measurement system consists of a motorized linear translation stage, a Hall magnetic probe, a teslameter, a motor control unit, and control software. The system is designed to precisely control the position of the probe, which can move up to 1.8m with a minimum step of 25 μm, with high repeatability and at low cost. The system is able to record transverse magnetic field intensities as a function of the probe's position in real time and has been used to measure the magnetic field of the MIR and THz undulator. Herein, the components, construction, and test results of the system are described. [ABSTRACT FROM AUTHOR]