Parasitic Magnetic Fields Research Articles

Analysis of Parasitic Parameters and Winding Loss Characteristics of High-Frequency Transformer under Different Winding Structures

Abstract With the development of the smart grid and the increasing access of renewable energy to the distribution grid, the traditional AC power grid puts forward an urgent demand for power electronic transformer (PET). The high-frequency transformer (HFT) serves as the core equipment of PET, and its electromagnetic structure and parasitic parameters are the hot spot of study in the field of power electronics. In this paper, the parasitic parameters, winding loss, and leakage magnetic field characteristics of the 20 kHz, 20 kVA HFT are investigated under different winding structures. The results show that the higher the degree of crossover of HFT winding, the lower the leakage magnetic field. The cross winding reduces winding loss and leakage inductance, and also attenuates the impact of frequency variations. The higher the winding height, the lower the leakage inductance. As the insulation thickness increases, the leakage inductance rises. The distribution capacitance varies opposite to the leakage inductance. Based on the analysis of winding loss and parasitic parameters, as well as the consideration of insulation, the final winding layout, the height of winding and the thickness of insulation of the HFT are determined.

Current status of the Tohoku microbeam system at Tohoku University and other facilities

We developed two microbeam lines, MB-I and MB-II, which both have quadrupole lenses and slits on heavy, rigid, anti-vibration tables. The MB-I beam diameter of 400 nm was achieved by reducing the parasitic magnetic field. MB-II is a simpler version of MB-I; both beamlines have various applications, and both are controlled by LabVIEW-based software and a programable logic controller (PLC). The beam scanners are downstream of the quadrupole lenses and controlled by a CompactRIO system. An automatic beam-focusing and focal guidance system reduces the time required for experimental configuration; this system is in routine use by researchers at Tohoku University. Microbeam experiments can easily be performed using this system. To further expand the applications, we developed MB-II-AQUA, which is based on MB-II but has advanced modularization and packaging. MB-II-AQUA is commercially available and retains the performance of MB-II, but is easier to use. A control system for the quadrupole lens and slit has been installed at the Takasaki Advanced Radiation Research Institute, which is a leading microbeam research facility in Japan.

Trap-Induced ac Zeeman Shift of the Thorium-229 Nuclear Clock Frequency.

We examine the effect of a parasitic rf magnetic field, attributed to ion trapping, on the highly anticipated nuclear clock based on ^{229}Th^{3+} [C. J. Campbell etal., Phys. Rev. Lett. 108, 120802 (2012)PRLTAO0031-900710.1103/PhysRevLett.108.120802]. The rf magnetic field induces an ac Zeeman shift to the clock frequency. As we demonstrate, this shift threatens to be the dominant systematic frequency shift for the clock, exceeding other systematic frequency shifts and the projected systematic uncertainty of the clock by orders of magnitude. We propose practical means to suppress or eliminate this shift.

Application of bistable glass-coated microwire for monitoring and measuring the deformations of metal structural members

The paper presents some experimental results related to innovative research focused on contactless strain measurement and the possibility of substituting conventional electrical strain gauges with bistable glass-coated microwires for structural member monitoring. As a part of the aforementioned research, the results of strain measurements performed on samples made of metallic materials with ferromagnetic nature are shown. During the experimental tests, a strain gauge was used to verify and compare the results obtained from the bistable glass-coated microwire, which can be used as a passive element without the requirement of physical connection to the sensing unit. Moreover, an additional examination confirmed the possibility of separating the influence of the parasitic external magnetic field. The results presented in this paper proved that bistable glass-coated microwires could be considered suitable candidates for contactless strain measurements performed on metallic materials with ferromagnetic nature or in a changing magnetic environment.

Linear position sensor using magnetically bistable microwire

A linear position sensor based on the unique functionality of the magnetically bistable glass-coated microwire is presented. Despite the magnetic nature of the sensor, it is possible to separate the external magnetic field's contribution, thus providing independence from parasitic external magnetic fields. With the presented unique approach, it is possible to transfer the linear position of the piston into the switching time and obtain high sensitivity down to 1 µm. • Linear position sensor with down to 1 µm sensitivity based on bistable magnetic microwire • Linear position measuring is temperature and external magnetic field independent • 0.19% measurement error within the temperature range 15 – 50°C

ESTIMATION OF THE TOLERANCE AREA FOR CORRECTION PARAMETERS IN INDUCTION ACCELERATION SYSTEMS

he issues of formalization and numerical solution of the problems of calculating tolerances for the parameters of corrective elements for a linear induction acceleration system, which are directly related to the performance of a real object, are considered. The key moments of the dynamics of the transverse motion of particles for a specific structure of a linear induction system of acceleration are studied for given values of energy for each of the periods of the resonator. The presence of parasitic electric and magnetic fields, which arise as a result of particle displacement relative to the accelerator axis and change the transverse components of the pulses, is taken into account. The original difference model of the induction system has been transformed into a linear form. To formulate the problem statements for calculating tolerances, the scatter vectors of phase coordinates and tolerances for the correction parameters are introduced. In order to apply the methods of practical stability, the set of tolerances for the parameters of the corrective elements is given in the form of an ellipsoid. Provided that the initial displacements of the transverse coordinates relative to the axis of the accelerator are known constant values, the structured tolerance region was estimated under known linear restrictions on the spread of the phase coordinate vectors. Due to the developed algorithms of practical stability, the original problem of calculating tolerances is reduced to the problem of finding the maximum of a linear form on an ellipsoid. Some important types of restrictions on deviations of phase coordinates concerning the estimation of tolerances on the parameters of the first correction element and the number of particles are investigated. For the case of non-linear dynamic constraints on the spread of the phase coordinate vector, it is proposed to approximate the convex closed set by tangent hyperplanes. From the standpoint of practical stability, the problem of estimating tolerances for the case of given restrictions on the spread of the quality criterion is considered. With the help of practical directional stability algorithms, it is proposed to estimate the maximum tolerance ranges for parameters in terms of volume in the presence of dynamic restrictions on the spread of phase coordinates or a quality criterion.

Розрахунок оптимальних параметрів коректувальних елементів в індукційних системах прискорення

The formulations of a number of optimization problems for a linear induction acceleration system with respect to the adjustment parameters are considered. The dynamics of the transverse motion of electrons in the horizontal plane is investigated in the presence of given energy values for each resonator period: the particles at the initial moment of time are somewhat displaced relative to the accelerator axis (we neglect the displacements of the ends of the solenoids and the centers of the accelerating gaps relative to the accelerator axis). A connection is established between the initial and final coordinates and the components of the momentum. The presence of parasitic electric and magnetic fields arising as a result of the displacement of particles relative to the axis of the accelerator, which change the transverse components of the pulses, is taken into account. For the mathematical formulation of problems, in order to apply algorithms of practical stability, the original difference model of the induction system was converted to a linear form. By introducing into consideration the vector of parameters, the scatter of phase coordinates, and tolerances on the parameters, the problem of calculating the tolerances for given linear constraints on the scatter of phase coordinates for the corresponding inhomogeneous system is formulated. For the case of nonlinear dynamic constraints on the spread of the vector of phase coordinates, it is proposed to approximate a convex closed set by tangent hyperplanes. Numerical estimation of the range of tolerances for the parameters of correcting elements is reduced to the problems of practical stability of discrete parametric systems. In this case, the region of the initial conditions on the state vector, the tolerances on the parameters, are given structurally in the form of an ellipsoid, which makes it possible to numerically solve the original problem as an extremal one. From the standpoint of practical stability in the corresponding space of functions, the problem of assessing the range of tolerances for the parameters of correcting elements in the presence of specified restrictions on the spread of the quality criterion is considered. Attention is focused on an important class of problems of numerical modelling of a linear induction acceleration system − problems of practical stability. Numerical estimation of the region of initial displacements of the transverse coordinates of the linear induction acceleration system in the given structures in the presence of linear constraints on the vector of phase coordinates in dynamics is carried out. Key words: modeling, induction system of acceleration, solenoid, parameters, elements of correction, optimization, stability

Imaging non-collinear antiferromagnetic textures via single spin relaxometry

Antiferromagnetic materials are promising platforms for next-generation spintronics owing to their fast dynamics and high robustness against parasitic magnetic fields. However, nanoscale imaging of the magnetic order in such materials with zero net magnetization remains a major experimental challenge. Here we show that non-collinear antiferromagnetic spin textures can be imaged by probing the magnetic noise they locally produce via thermal populations of magnons. To this end, we perform nanoscale, all-optical relaxometry with a scanning quantum sensor based on a single nitrogen-vacancy (NV) defect in diamond. Magnetic noise is detected through an increase of the spin relaxation rate of the NV defect, which results in an overall reduction of its photoluminescence signal under continuous laser illumination. As a proof-of-concept, the efficiency of the method is demonstrated by imaging various spin textures in synthetic antiferromagnets, including domain walls, spin spirals and antiferromagnetic skyrmions. This imaging procedure could be extended to a large class of intrinsic antiferromagnets and opens up new opportunities for studying the physics of localized spin wave modes for magnonics.

FFC NMR Relaxometer with Magnetic Flux Density Control

This paper describes an innovative solution for the power supply of a fast field cycling (FFC) nuclear magnetic resonance (NMR) spectrometer considering its low power consumption, portability and low cost. In FFC cores, the magnetic flux density must be controlled in order to perform magnetic flux density cycles with short transients, while maintaining the magnetic flux density levels with high accuracy and homogeneity. Typical solutions in the FFC NMR literature use current control to get the required magnetic flux density cycles, which correspond to an indirect magnetic flux density control. The main feature of this new relaxometer is the direct control of the magnetic flux density instead of the magnet current, in contrast with other equipment available in the market. This feature is a great progress because it improves the performance. With this solution it is possible to compensate magnetic field disturbances and parasitic magnetic fields guaranteeing, among other possibilities, a field control below the earth magnetic field. Experimental results validating the developed solution and illustrating the real operation of this type of equipment are shown.

Broadband dual phase energy harvester: Vibration and magnetic field

Broadband mechanical energy harvesting implies stable output power over a wide range of source frequency. Here we present a cost-effective solution towards achieving broadband response by designing a magnetically coupled piezoelectric energy harvester array that exhibits a large power density of 243 μW/cm3 g2 at natural frequency and bandwidth of more than 30 Hz under 1 g acceleration. The magnetically coupled piezoelectric energy harvester array exhibits dual modes of energy harvesting, responding to both stray magnetic field as well as ambient vibrations, and is found to exhibit the output power density of 36.5 μW/cm3 Oe2 at 79.5 Hz under the ambient magnetic field while maintaining the broadband nature. The magnetically coupled piezoelectric energy harvester array was demonstrated to harvest continuous power from a rotary pump vibration, an automobile engine vibration and a parasitic magnetic field surrounding a cable of an electric kettle. These demonstrations suggest that the magnetically coupled piezoelectric energy harvester array could serve the role of a standalone power source for wireless sensor nodes and small electronic devices.

Materials, Devices and Spin Transfer Torque in Antiferromagnetic Spintronics: A Concise Review

From historical obscurity, antiferromagnets are recently enjoying revived interest, as antiferromagnetic (AFM) materials may allow the continued reduction in size of spintronic devices. They have the benefit of being insensitive to parasitic external magnetic fields, while displaying high read/write speeds, and thus poised to become an integral part of the next generation of logical devices and memory. They are currently employed to preserve the magnetoresistive qualities of some ferromagnetic based giant or tunnel magnetoresistance systems. However, the question remains how the magnetic states of an antiferromagnet can be efficiently manipulated and detected. Here, we reflect on AFM materials for their use in spintronics, in particular, newly recognized antiferromagnet Mn2Au with its in-plane anisotropy and tetragonal structure and high Néel temperature. These attributes make it one of the most promising candidates for AFM spintronics thus far with the possibility of architectures freed from the need for ferromagnetic (FM) elements. Here, we discuss its potential for use in ferromagnet-free spintronic devices.

Empirical Analysis of the Effects of Parasitic Magnetic Stray Field on Force Output of Electromagnetic Actuators

Electromagnetic actuators are used in a variety of technical applications especially in the automotive industry. In-line process control methods are an essential component of the Lean and Six Sigma methodology to ensure process quality. However, the current state of the art in process and quality control is largely limited to end-of-line measurements of the force output. Analysing the magnetic stray field is a promising method that can be used to draw conclusions on the properties and defects of the flux-conducting magnetic materials. This phenomenon can potentially be used to identify defects in magnetic actuators thus allowing inline quality-monitoring. In order to realize this feature, patterns in the magnetic stray field of an actuator have to be identified and linked to a specific defect. The resulting challenge is the analysis of large datasets in order to characterize the stray field anomalies. This paper summarizes the results of a study on linear magnetic actuators trying to prove a relationship between parasitic magnetic stray field and the overall force output of an actuator by analysing the data with statistical methods. The findings of this study suggest that certain statistical methods, like regression, are not well suited to build a prediction model for defects in actuators using a similar approach of measuring stray field outside the actuator. This is mainly due to the fact that prerequisites for model building are difficult to full fill within the context of stray field analysis. Nevertheless, the findings also suggest that methods of exploratory data analysis can be used to derive quality relevant information from data of stray field measurements. The paper elaborates on the problem of defining a population, choosing variables for model building, as well as model error.

Dependence of transverse magnetothermoelectric effects on inhomogeneous magnetic fields

Transverse magneto-thermoelectric effects are studied in permalloy thin films grown on MgO substrates. We find that small parasitic magnetic fields below 1 Oe can produce artifacts of the order of 1 % of the amplitude of the anisotropic magneto-thermopower which is also detected in the experiments. The measured artifacts reveal a new source of uncertainties for the detection of the transverse spin Seebeck effect. Taking these results into account we conclude that the contribution of the transverse spin Seebeck effect to the detected voltages is below the noise level of 20 nV.

Some features of bulk melt-textured high-temperature superconductors subjected to alternating magnetic fields

Monolithic, large grain, (RE)Ba2Cu3O7 high-temperature superconductors (where RE denotes a rare-earth ion) are known to be able to trap fields in excess of several teslas and represent thus an extremely promising competing technology for permanent magnet in several applications, e.g. in motors and generators. In any rotating machine, however, the superconducting permanent magnet is subjected to variable (transient, or alternating) parasitic magnetic fields. These magnetic fields interact with the superconductor, which yields a reduction of the remnant magnetization. In the present work we quantify these effects by analysing selected experimental data on bulk melt-textured superconductors subjected to AC fields. Our results indicate that the non-uniformity of superconducting properties in rather large samples might lead to unusual features and need to be taken into account to analyse the experimental data. We also investigate the evolution of the DC remnant magnetization of the bulk sample when it is subjected to a large number of AC magnetic field cycles, and investigate the experimental errors that result from a misorientation of the sample or a mispositioning of the Hall probe. The time-dependence of the remnant magnetization over 100000 cycles of the AC field is shown to display distinct regimes which all differ strongly from the usual decay due to magnetic relaxation.

Calibration of SQUID vector magnetometers in full tensor gradiometry systems

Measurement of magnetic vector or tensor quantities, namely of field or field gradient, delivers more details of the underlying geological setting in geomagnetic prospection than a scalar measurement of a single component or of the scalar total magnetic intensity. Currently, highest measurement resolutions are achievable with superconducting quantum interference device (SQUID)-based systems.Due to technological limitations, it is necessary to suppress the parasitic magnetic field response from the SQUID gradiometer signals, which are a superposition of one tensor component and all three orthogonal magnetic field components. This in turn requires an accurate estimation of the local magnetic field. Such a measurement can itself be achieved via three additional orthogonal SQUID reference magnetometers. It is the calibration of such a SQUID reference vector magnetometer system that is the subject of this paper.A number of vector magnetometer calibration methods are described in the literature. We present two methods that we have implemented and compared, for their suitability of rapid data processing and integration into a full tensor magnetic gradiometry, SQUID-based, system.We conclude that the calibration routines must necessarily model fabrication misalignments, field offset and scale factors, and include comparison with a reference magnetic field. In order to enable fast processing on site, the software must be able to function as a stand-alone toolbox.

Erratum: Effects of rf breakdown on the beam in the Compact Linear Collider prototype accelerator structure [Phys. Rev. ST Accel. Beams16, 081004 (2013)

Understanding the effects of RF breakdown in high-gradient accelerator structures on the accelerated beam is an extremely relevant aspect in the development of the Compact Linear Collider (CLIC) and is one of the main issues addressed at the Two-beam Test Stand at the CLIC Test Facility 3 at CERN. During a RF breakdown large electro-magnetic fields are generated and produce parasitic magnetic fields which interact with the accelerated beam affecting its orbit and energy. We discuss here measurements of such effects observed on an electron beam accelerated in a CLIC prototype structure. Measurements of the trajectory of bunch-trains on a nanosecond time-scale showed fast changes in correspondence of breakdown which we compare with measurements of the relative beam spots on a scintillating screen. We identify different breakdown scenarios for which we offer an explanation based also on measurements of the power at the input and output ports of the accelerator structure. Finally we present the distribution of the magnitude of the observed changes in the beam orbit and we discuss its correlation with RF power and breakdown location in the accelerator structure.

Revealing the properties of Mn2Au for antiferromagnetic spintronics

The continuous reduction in size of spintronic devices requires the development of structures, which are insensitive to parasitic external magnetic fields, while preserving the magnetoresistive signals of existing systems based on giant or tunnel magnetoresistance. This could be obtained in tunnel anisotropic magnetoresistance structures incorporating an antiferromagnetic, instead of a ferromagnetic, material. To turn this promising concept into real devices, new magnetic materials with large spin-orbit effects must be identified. Here we demonstrate that Mn2Au is not a Pauli paramagnet as hitherto believed but an antiferromagnet with Mn moments of ~4 μB. The particularly large strength of the exchange interactions leads to an extrapolated Néel temperature well above 1,000 K, so that ground-state magnetic properties are essentially preserved up to room temperature and above. Combined with the existence of a significant in-plane anisotropy, this makes Mn2Au the most promising material for antiferromagnetic spintronics identified so far.

Effects of rf breakdown on the beam in the Compact Linear Collider prototype accelerator structure

Understanding the effects of rf breakdown in high-gradient accelerator structures on the accelerated beam is an extremely relevant aspect in the development of the Compact Linear Collider (CLIC) and is one of the main issues addressed at the Two-beam Test Stand at the CLIC Test Facility 3 at CERN. During a rf breakdown high currents are generated causing parasitic magnetic fields that interact with the accelerated beam affecting its orbit. The beam energy is also affected because the power is partly reflected and partly absorbed thus reducing the available energy to accelerate the beam. We discuss here measurements of such effects observed on an electron beam accelerated in a CLIC prototype structure. Measurements of the trajectory of bunch trains on a nanosecond time scale showed fast changes in correspondence of breakdown that we compare with measurements of the relative beam spots on a scintillating screen. We identify different breakdown scenarios for which we offer an explanation based also on measurements of the power at the input and output ports of the accelerator structure. Finally we present the distribution of the magnitude of the observed changes in the beam position and we discuss its correlation with rf power and breakdown location in the accelerator structure.

CIRCULAR RIBBON FLARES AND HOMOLOGOUS JETS

Solar flare emissions in the chromosphere often appear as elongated ribbons on both sides of the magnetic polarity inversion line (PIL), which has been regarded as evidence of a typical configuration of magnetic reconnection. However, flares having a circular ribbon have rarely been reported, although it is expected in the fan--spine magnetic topology involving reconnection at a three-dimensional (3D) coronal null point. We present five circular ribbon flares with associated surges, using high-resolution and high-cadence halpha blue wing observations obtained from the recently digitized films of Big Bear Solar Observatory. In all the events, a central parasitic magnetic field is encompassed by the opposite polarity, forming a circular PIL traced by filament material. Consequently, a flare kernel at the center is surrounded by a circular flare ribbon. The four homologous jet-related flares on 1991 March 17 and 18 are of particular interest, as (1) the circular ribbons brighten sequentially, with co-spatial surges, rather than simultaneously, (2) the central flare kernels show an intriguing "round-trip" motion and become elongated, and (3) remote brightenings occur at a region with the same magnetic polarity as the central parasitic field and are co-temporal with a separate phase of flare emissions. In another flare on 1991 February 25, the circular flare emission and surge activity occur successively, and the event could be associated with magnetic flux cancellation across the circular PIL. We discuss the implications of these observations combining circular flare ribbons, homologous jets, and remote brightenings for understanding the dynamics of 3D magnetic restructuring.

On the Amplitude and Phase Errors of Quadrature LC-Tank CMOS Oscillators

An analytic approach for the estimation of the phase and amplitude imbalances caused by component mismatches and parasitic magnetic fields in two popular quadrature LC oscillators is presented. Very simple and closed-form equations are derived, proving that, although the two topologies share the same small signal circuit, they display very different sensitivities to the mentioned sources of imbalance. Moreover, it is shown that parasitic inductors coupling, overlooked up to date, plays a key role ultimately limiting the achievable phase accuracy. The theoretical results are verified through extensive simulations and measurements on a 1.7-GHz quadrature oscillator and frequency up-converter implemented in a 0.18-/spl mu/m CMOS process.