Magnetic Coil Research Articles

Experimental characterization of the quasi-coherent mode in EDA H-Mode and QCE scenarios at ASDEX Upgrade

The quasi-coherent mode (QCM), appearing in enhanced D α high confinement mode (EDA H-mode) and quasi-continuous exhaust (QCE) plasmas has been analysed in detail at ASDEX Upgrade via thermal helium beam spectroscopy under various discharge parameters. In both scenarios the QCM appears to be localized close to the separatrix and to propagate in ion diamagnetic direction in the plasma frame. The poloidal wavenumber of the QCM is about 0.025<kθρs<0.075 and the radial wavenumber is kr≈0 cm−1 . It was found that the plasmas are generally below the ideal MHD limit at the separatrix. All the properties are consistent with ideal, resistive or kinetic ballooning modes. Simultaneous to the appearance of the QCM, higher harmonic modes can be observed in EDA H-modes, which are exclusively visible in magnetic pick-up coils and have toroidal mode numbers of up to n = 10. By performing a bicoherence analysis it was found that the higher harmonic modes and the QCM are coupling, but are disjoint phenomena. Qualitatively, the bandwidth of the QCM serves as a promising distinctive feature between QCE plasmas and EDA H-modes.

Magnetic field simulations of the GOLEM tokamak via the NICE code

In this paper, the direct and inverse equilibrium computation mode of the NICE code is put into operation for the case of the GOLEM tokamak. This enables, for the first time, simulations of GOLEM's magnetic field. The computation mode put into operation simulates the magnetohydrodynamic equilibrium of a tokamak plasma based on a given plasma position or given currents in poloidal magnetic field coils. In order to set up NICE, a virtual model of GOLEM is introduced that includes axially symmetrical approximations of GOLEM's iron core and primary transformer coils. The results of NICE simulations are compared with experimental measurements, and it is shown that NICE simulations produce plasma equilibrium configurations typical for GOLEM. Nevertheless, a more detailed validation of GOLEM's virtual model and of the results of NICE simulations is to be performed in the future.

Experimental observation of the vertical displacement between heating and levitation regions in an electromagnetic levitation coil

Scientific progress in the relevant fields of science and technology requires the production of crystals with quality beyond the current state of the art. Electro-magnetic levitation (EML) is a prospective method for the growth of high-purity crystals, allowing for avoidance of any contact between the crystal-melt and the crucible. Contactless crystal growth reduces the number of crystal defects commonly abundant in conventional crystal growth methods. The EML method also allows crystal growth of materials with very high melting points. In this article, we report detailed measurements of the EML method. The induction coil used in this study has three turns and one counterturn. We subject different metal material (Al, Cu, Sn, and Ni) samples to the induction coil’s electromagnetic field. For each sample, we measure the induced lift force, Joule heating, and components of magnetic induction as a function of position inside the coil. The results show that the maximum heating in an EML coil is emitted in the area below the levitation zone, a discrepancy not reported earlier. Our findings suggest that this shift should be considered in coil design to avoid instability of the levitated material. We hope this study will serve as a stepping stone for developing EML techniques. The experimental results we provide will be used to evaluate the accuracy of current and future theoretical models of EML coils. This, in turn, will facilitate progress in the application of EML to the growth of larger crystals of higher quality.

CORRECTION OF THE INHOMOGENEITY OF THE BRIGHTNESS OF MAGNETIC RESONANCE IMAGES

he article deals with the problem of correcting the uneven intensity in magnetic resonance images. This problem is related to the features of the visualization equipment, may be caused by the instability of the field registration by magnetic coils and other technical reasons. The displacement field makes it difficult to use digital methods for recognizing objects in images and making a correct diagnosis. In this paper, it is proposed to use high- frequency filtering (rho filter, or ramp filter) to remove the distorting low-frequency systematic component. The results are illustrated by a model example and real processing of biomedical MRI images.

Global optimal design of longitudinal gradient magnetic field coils based on a modified PSO algorithm in micro atomic sensors

Global optimal design of longitudinal gradient magnetic field coils based on a modified PSO algorithm in micro atomic sensors

Research on Transient Electromagnetic Positioning Method of Underwater Towed Array Source for Moving Small Target on the Seabed

Different from the large-scale delineation and exploration of oil and gas resources and deep-sea hydrothermal sulfide deposits, small targets moving on the seabed require fine and accurate trace detection and higher positioning accuracy. Although the towed single source transient electromagnetic (TEM) device can detect the poisition of the static target body, but cannot determine the poisition of the moving target, the array source TEM device can effectively solve the problem of fine detection and accurate positioning of moving small targets on the seabed, and improve the signal-to-noise ratio and resolution. In this paper, an array source transient electromagnetic positioning method based on underwater towed platform is proposed for moving small targets on the seabed. At the same time, in view of the underwater towed body and array source transient electromagnetic coil, its attitude changes cause the problem of target body positioning error. Through the simulation calculation and error analysis, the results show that the calculation error of attitude angle had a great influence on positioning accuracy. In practical engineering application, attitude correction is necessary to eliminate positioning error.

Health assessment for low-voltage electromagnetic coils based on fusion of creep degradation mechanism and transformed MD

Low-voltage electromagnetic coils play ever-increasing roles in safety-critical systems, like electromechanical actuators in more electric aircraft and tractors in zero emission vehicles. Identifying insulation degradation prior to the formation of turn-to-turn short can effectively avoid accidental shutdown and enable predictive maintenance for these systems. High-frequency electrical response analysis is currently a promising technique for electromagnetic coil insulation health assessment. However, the correlation between high-frequency electrical response parameters (HFERP) and actual insulation degradation status (AIDS) is still not clear, which brings challenges in insulation health assessment and remaining useful life prediction. Therefore, in this paper, a fusion method based on creep degradation mechanism and transformed mahalanobis distance (MD) for insulation health assessment is proposed. First, correlation analysis between the coil HFERP and the AIDS is performed from coil insulation coating creep degradation point of view. Second, a coil on-line monitoring parameter (OLMP) for monitoring insulation degradation status on-site is constructed based on transformed MD. A correlation model between OLMP and AIDS is consequently built to assist in determining OLMP failure threshold for coil insulation health assessment. Coil accelerated testing shows that the fusion method can be used to assess insulation status prior to the formation of harmful shorts, enabling condition-based maintenance for components or systems that incorporate electromagnetic coils.

Identifying Locations for Transcranial Magnetic Stimulation Coil Placement For Deep Brain Structures

Stimulation of deep brain structures with transcranial magnetic stimulation (TMS) is the premier mode of non-invasive brain stimulation (NIBS). Currently, there is little support for the application of TMS in modulating deeper brain structures. This study validates the use of TMS for a set of 8 deep brain structures shown to alleviate symptoms of certain conditions when stimulated. 200 sets of T1-weighted and T2-weighted MRIs were processed using the SimNIBS headreco pipeline. Then, 200 TMS optimization simulations were run for each brain structure, which generated 200 3D coordinates for each structure representing the best TMS coil placement locations on the scalp for stimulation. This data was analyzed using K-means and agglomerative clustering methods to find the overall best coil placement locations. Overall, this study validates the use of TMS to stimulate these brain structures and finds the optimal parameters for stimulation.

Comprehensive analysis of the influence of magnetic field gradients on single-beam SERF atomic magnetometer

Magnetic field gradients interfere with the coherence of the atomic ensemble and degrade the performance of the spin-exchange relaxation-free (SERF) atomic magnetometer. In this paper, the influence of magnetic field gradients is incorporated into the response model of single-beam atomic magnetometer, and the theoretical models of transverse relaxation rate, spin polarization and scale factor are established. Based on this model, we find that magnetic field gradients in different directions can cause varying degrees of degradation in the performance parameters of the magnetometer. The magnetic linewidths under different light power and magnetic field gradients are measured using the designed dedicated magnetic field gradients coils, and the spin polarization and magnetic field gradients relaxation rate are obtained through fitting. An unevenness and deviation of the curve are also observed in the experiments, indicating the presence of the magnetic field gradient of approximately 2 nT/cm in the magnetic shields. Furthermore, in a magnetic field gradient environment of 20 nT/cm, the mean of the long-term sensitivity decreased by 3.5 times and the standard deviation increased by 11 times. It shows that the magnetic field gradients will not only affect the signal-to-noise ratio, but also make the magnetometer more vulnerable to external interference when working. The sensitivity and stability of magnetometer will be greatly reduced. The research in this article provides a theoretical and experimental basis for eliminating the influence of magnetic field gradients and improving the accuracy of magnetic field measurements.

In-vivo verified anatomically aware deep learning for real-time electric field simulation

Objective. Transcranial magnetic stimulation (TMS) has emerged as a prominent non-invasive technique for modulating brain function and treating mental disorders. By generating a high-precision magnetically evoked electric field (E-field) using a TMS coil, it enables targeted stimulation of specific brain regions. However, current computational methods employed for E-field simulations necessitate extensive preprocessing and simulation time, limiting their fast applications in the determining the optimal coil placement. Approach. We present an attentional deep learning network to simulate E-fields. This network takes individual magnetic resonance images and coil configurations as inputs, firstly transforming the images into explicit brain tissues and subsequently generating the local E-field distribution near the target brain region. Main results. Relative to the previous deep-learning simulation method, the presented method reduced the mean relative error in simulated E-field strength of gray matter by 21.1%, and increased the correlation between regional E-field strengths and corresponding electrophysiological responses by 35.0% when applied into another dataset. In-vivo TMS experiments further revealed that the optimal coil placements derived from presented method exhibit comparable stimulation performance on motor evoked potentials to those obtained using computational methods. The simplified preprocessing and increased simulation efficiency result in a significant reduction in the overall time cost of traditional TMS coil placement optimization, from several hours to mere minutes. Significance. The precision and efficiency of presented simulation method hold promise for its application in determining individualized coil placements in clinical practice, paving the way for personalized TMS treatments.

The Conceptual Design of An Electro-Magnetic Power Generator

Nowadays, magnetic field induction is a dependable renewable energy source that can convert magnetic fields into electrical power. In this study, our objective is to propose a low-cost free energy generator design based on neodymium. The main problems with existing generators were air pollution, noise pollution, and even fuel price volatility. To begin addressing this issue, we compared 6 currently used generators. We concentrated on 5 criteria in light of this outcome. Our top considerations in this study are cost and maintenance. Then comes the size, weight, and noise. The best electromagnetic power generators for satisfying all the criterion domains are determined using Pugh's matrix. It demonstrates that electromagnetic power generators have a high score of 95 compared to natural gas, portable, and diesel power generators. We have also calculated the resulting voltage from the selected number of permanent magnet coils. This calculation shows 60V resulting in 9600 turns. As a result, we draw the conclusion that the reduction of problems like noise and air pollution makes this power generator look like a very appealing alternative.

Vertical stray field measurements using an electron beam in the MEPhIST-0 tokamak

In the MEPhIST-0 tokamak, toroidal magnetic coil system is implemented as a single continuous toroidal solenoid. This design ensures synchronized operation of each segment of the solenoid and requires only one power supply line to operate. However, this configuration has the downside of introducing stray vertical and radial magnetic field components, which result from the inclination of the solenoid segments. Such stray fields can be measured using an electron beam, as previously demonstrated in experiments on T-15, TEXTOR, KSTAR, and SST-1. This paper describes the parameters of the experiment and presents the main results obtained from the MEPhIST-0 tokamak. Two experimental techniques for measuring the vertical magnetic field are discussed: one with a change in the current direction in the toroidal solenoid and one without. The ratio of the stray vertical field to the toroidal field was found to be approximately 0.5%. The conducted experiments highlight the necessity of compensating for the stray vertical field using additional poloidal coils.

Influence of process parameters including the confining magnetic field of a plasma beam source on the deposition of N‐doped hydrogenated carbon films

Electrically conductive nitrogen‐doped hydrogenated carbon films (a‐C:H:N) were deposited using a nitrogenacetylene gas mixture by plasma‐assisted chemical vapor deposition (PACVD). A capacitively coupled plasma beam source was used for the depositions. The plasma is excited by a radio‐frequency (RF) discharge and confined by Helmholtz magnetic coils, resulting in an increase in plasma density. The ion energy, as well as the deposition rate, can be controlled by the choice of the size of the coupling electrode, i.e. the ratio of cathode-to‐anode area, the electric current at the Helmholtz magnet coils, the total gas pressure and the RF power. The interdependence of these process parameters on the ion energy and the deposition rate has been studied in detail in this work. Hardness and electrical resistivity were measured on the deposited a‐C:H:N films.

A low-frequency ferrohydrodynamic pump for a magneto-caloric refrigerator

Ferrohydrodynamic or magnetic pumping enables the design of a magnetocaloric refrigerator with no moving parts. Existing magnetic pumps utilize travelling wave magnetic fields with frequencies in the range of 100 to 1000 Hz. Such high frequencies when utilized in the proposed refrigerator could cause heating which is detrimental to its performance. Hence, a magnetic pump that works with low magnetic field frequencies (¡ 1 Hz) is designed and its performance is experimentally characterized and compared against an one-dimensional model. The design of the magnetic pump consists of a rising and falling pipe, circumscribed by an electromagnetic coil. On application of a magnetic field, due to the inward acting force on either end of the pipes, the ferrofluid progresses in the rising pipe and reaches the falling pipe. On removal of the magnetic field, the portion of the fluid in the falling pipe falls down due to gravity, thereby achieving a net pumping action. Thus on continuously cycling the magnetic field, an intermittent motion of the ferrofluid is obtained. The maximum cross-sectional area and time-averaged mass flow rate of the proposed design is 1.8 g s-1 cm-2 at 0.74 Hz and 35.7 mT. This mass flow rate is comparable to pump designs that work on travelling wave magnetic fields, whose operational frequency is three orders of magnitude higher.

The effect of magnetic field variations on the spectral properties of tornado plasma

At atmospheric pressure and at a frequency of 9.1 kHz, a constructed magnetically stabilized tornado gliding arc discharge (MSGAD) system was utilized in this study to generate a non-thermal plasma with an alternating voltage source from 2,4,6,8 to 10 kV. Argon gas was used to generate the arc plasma with an adjustable flow rate using a flow meter regulator to stabilize the gas flow rate to 2 L/min. A gliding plasma discharge is achieved by a magnetic field for the purpose of a planned investigation. The influence of the magnetically stabilized tornado gliding arc discharge parameters such as magnetic field and applied voltage on microscopic tornado plasma parameters was studied. The electron temperature1was measured using a Boltzmann plot and the electron1density was1determined by the Stark1broadening method. The electron temperature ranged from 0.818 eV to 1.495 eV, and the electron density varied from 1.37 × 1018 cm−3 to 2.49 × 10 18 cm−3 at a magnetic coil with 350 turns. Subsequently, the electron temperature increased to a range of 1.029 eV–1.794 eV, and the electron density reached a range of 1.53 × 1018 cm−3 to 2.89 × 1018 cm−3 at a magnetic coil with 500 turns. It can be observed that the plasma properties exhibit a rise as the number of turns of the coil and the applied voltage increase.

Parametric study of the axial force and negative stiffness of an electromagnetic mechanism for vibration isolation applications

Nonlinear vibration isolators that take advantage of negative stiffness elements can provide high static stiffness to bear high static loads and quasi-zero dynamic stiffness to widen the isolation frequency band and hence are desirable for vibration isolation. Electromagnetic negative stiffness elements can be used to design and fabricate quasi-zero-stiffness vibration isolators. Different combinations of permanent magnets and electromagnetic coils in attractive or repulsive configurations can lead to negative stiffness. The magnitude of the electromagnetic restoring force and negative stiffness is dependent upon many geometric and electromagnetic parameters and is controllable by adjusting the current in the electromagnetic coils. The present work compares the negative stiffness properties of three different configurations and provides a general guideline for selecting the appropriate configuration. The finite element method is used to simulate the magnetic fields and electromagnetic force acting on the permanent magnet. Numerical results are presented, and findings are validated by analytical solutions.

Self‐Powered Smart Proximity‐Detection System Based on a Hybrid Magneto‐Mechano‐Electric Generator

A hybrid magneto‐mechano‐electric (H‐MME) generator that combines a Mn‐doped Pb(Mg1/3Nb2/3)O3‐Pb(Zr,Ti)O3 piezoelectric single crystal and an electromagnetic induction coil is demonstrated to convert stray magnetic noise of 60 Hz into useful electrical energy. The authors optimize the design of the piezoelectric cantilever, the weight of the magnetic mass, and the distance between the magnet and coil through theoretical simulation and experiments to maximize each contribution for the H‐MME generator. The total root mean square output power of the H‐MME generator is 28.35 mW with a power density of 0.042 mW cm−3 Oe2 in a 5 Oe magnetic field of 60 Hz, which is sufficient for driving multiple functional Internet of Things sensors that detect temperature, humidity, light, UV radiation, air pressure, and sound. In addition, a self‐powered smart proximity‐detection system (including a microcontroller unit, an ultrasonic sensor module, a piezo speaker, and a Bluetooth module) is demonstrated by rectifying the output of the H‐MME generator and controlling it using a power management circuit. The superior output power of the H‐MME generator exceeds simple sensing functions and presents the possibility of achieving battery‐free self‐powered smart devices and systems.

Magnetic field properties in non-axisymmetric divertors

Stellarator power plants require a plan for the removal of the particles and the heat that are exhausted across the plasma edge. Unless a flowing liquid metal can be used to carry the helium exhaust to places where it can be removed from the plasma chamber, the particle exhaust must be magnetically diverted into pumping chambers. Studies are required to determine how magnetic features relate to the required divertor properties, how these magnetic features can be produced, and how they can be controlled. General studies are clarified and simplified by the use of the magnetic field line Hamiltonian ψp(ψ,θ,φ) and a vector x→(ψ,θ,φ) that gives the point in space associated with each point in the (ψ,θ,φ) canonical coordinates, a flux and two angles. The non-resonant Fourier terms in ψp can be removed by a canonical transformation, so only resonant Fourier terms can determine the field line properties in the plasma edge and divertor. This paper discusses the important divertor properties and explains how ψp(ψ,θ,φ) and x→(ψ,θ,φ) can be obtained numerically in a special form for any stellarator magnetic field, B→(x→). This form holds between an arbitrary magnetic surface and the chamber walls with the non-resonant terms eliminated. Studies based on variations in the terms in such derived field-line Hamiltonians can determine what magnetic features are mathematically possible and how they could be produced and controlled by the external magnetic field coils.

Proton Therapy Equipment Installation, Upgrades, and Building Design

This work aims at reviewing challenges and pitfalls in proton facility design related to equipment upgrade or replacement. Proton therapy was initially developed at research institutions in the 1950s which ushered in the use of hospital-based machines in 1990s. We are approaching an era where older commercial machines are reaching the end of their life and require replacement. The future widespread application of proton therapy depends on cost reduction; customized building design and installation are significant expenses. We take this opportunity to discuss how commercial proton machines have been installed and how buildings housing the equipment have been designed. Data on dimensions and weights of the larger components of proton systems (cyclotron main magnet and gantries) are presented and innovative, nongantry-based, patient positioning systems are discussed. We argue that careful consideration of the building design to include larger elevators, hoistways from above, wide corridors and access slopes to below grade installations, generic vault and treatment room layouts to accommodate multiple vendor's equipment, and modular system design can provide specific benefits during planning, installation, maintenance, and replacement phases of the project. Room temperature magnet coils can be constructed in a more modular manner: potential configurations are presented. There is scope for constructing gantries and magnet yokes from smaller modular sub-units. These considerations would allow a hospital to replace a commercial machine at its end of life in a manner similar to a linac.

A solution using only electromagnetic coils for relative pose control in satellite docking

This paper proposes an electromagnetic coil topology and its control strategy, which can be incorporated into the electromagnetic docking device to achieve relative pose control in satellite docking. The target satellite has a main coil; the chaser satellite possesses a main coil of the same size accompanied by six and four evenly arranged secondary coils inside and outside the main coil, respectively. The coil on the target satellite is DC energized, while the currents in the coils of the chaser satellite are regulated. To remove the coupling between the pitch/yaw torque and translational force, the internal and external secondary coils of the chaser satellite interact with the main coil of the target satellite to perform the control of relative pitch/yaw and relative translation, respectively, so relative pose control can be achieved. The torque and force vectors exerted by the secondary coils of the chaser satellite are synthesized onto the pitch and yaw axes of the body frame. According to their spatial composition relationship, the formulas are proposed, which obtain the magnetic moment vectors of the coils from the set torques and forces. The controllers regulating pitch/yaw, translation, and distance utilize a three-loop cascaded structure that consists of an outer position loop, a middle velocity loop and an inner current loop. The control strategy is verified by dynamics simulation.