Solenoid Research Articles

Fast time-varying current triggering flux jumps of multi-filamentary Nb3Sn wire exposed to oblique magnetic field

Due to the oblique magnetic field and rapid time-varying current, the electromagnetic response and thermomagnetic instabilities of high-field superconducting dipole magnets are quite different from the solenoid coils. In this work, we theoretically investigate the flux jump of composite multi-filamentary Nb3Sn wire with high critical current density exposed to an oblique magnetic field and fast transport current. The thermomagnetic stability/instability regions are obtained with respect to flux creep factor and oblique ratios of magnetic field. It is found that the parallel component of the oblique magnetic field can suppress the flux jump. Unlike slow current, it is interesting to find that the fast variations of self-field by high ramp current can trigger flux jumps in Nb3Sn wire. The fast current triggering flux jumps can be tuned by the static oblique magnetic field. Furthermore, we demonstrate that current-like distribution is more likely to trigger quenches, while the magnetic field-like distribution is more likely to trigger flux jumps. The findings of this work are helpful for the optimization of the superconducting coils exposed to oblique magnetic field and fast time-varying current.

Differential behavior of magnetic field and magnetic vector potential in an optically pumped Rb atomic magnetometer

Although vector potentials are more intrinsic physical quantities than magnetic and electric fields, measuring them macroscopically is difficult. A double-nested Helmholtz-type vector potential coil, consisting of an elongated solenoid coil wound around a cylinder, and producing a uniform magnetic vector potential, was developed in this study. The coil is carefully designed to reduce the influence of the leakage magnetic field and the scalar potential generated by the coil’s electrical resistance on the measurement. It has the ability to toggle between vector potential and magnetic field generation. We adapted the coil for use in an optically pumped atomic magnetometer. We also developed an optically pumping Rb atomic magnetometer that can calibrate in a zero magnetic field and applied a time-varying magnetic vector potential. We found that the output signal changed with the vector potential even when there was virtually no magnetic field. With increasing frequency, the output voltage decreases for the magnetic signal and increases for the magnetic vector potential signal. The results revealed that the atomic magnetometer is influenced not only by the magnetic field but also by the magnetic vector potential and that the frequency responses are opposite.

Miniaturized double transit magnetic field measurement probe using the Faraday rotation principle.

This paper presents the design and experimental results of a double transit magnetic field measurement probe based on the Faraday rotation principle using terbium doped borosilicate glass as a sensor element. When the magnetic field is applied in the direction of propagation of light through the glass, the Faraday effect produces non-reciprocal circular birefringence. This property of the Faraday effect adds rotations when the light beam is reflected using a mirror placed at the other end of the glass and passed through the glass, making double transit of light through the sensor element. Experiments were carried out to verify the characteristics of the designed probe by inserting it inside the solenoid load coil. The Verdet constant of the glass is determined using the slope of the linear least-squares fitted curve between the Faraday rotation angle and the applied magnetic field, obtained as 89.22r a d/(T⋅m) with a relative uncertainty of 2.43%. The magnetic field was measured with 0.28% accuracy. In the optics experiments, alignment of components is the major task. To the authors' knowledge, this is the first of its kind double transit miniaturized magnetic field measurement probe configuration in which components are aligned inside the single probe structure. The probe is easily portable and can be used in inaccessible locations in various applications such as accelerators, Z/θ pinch devices, or fusion reactors such as tokamaks, in which the magnetic field is one of the main parameters.

Design and Experiment of Discharge Control Methods for Three-Stage Coil Gun Experiments

The aim of this study was to design operation methods for three-stage coil gun experiments and to fabricate and compare prototypes of control systems using these methods. Two methods are proposed: (1) recognizing the position of a projectile using a photointerrupter and (2) operating a control circuit to supply power to a silicon-controlled rectifier when the projectile reaches an intended position by registering the delay time between coil gun operations. The distance between the projectile and the solenoid coil during a coil gun operation is a key design factor. For the multi-stage coil gun manufactured in this study, the discharge time must be determined according to the position of the projectile, which moves at high velocity. Therefore, the selected method should have minimal operation error and allow the circuit to be easily used according to the coil gun stage and configuration. This study compares the prototypes of coil gun discharge circuits that were fabricated based on the proposed methods by applying them to three-stage coil guns and measuring their velocities. The findings of this study could be used to suggest design methods for experimental models for coil guns with fewer stages according to the final velocity and coil gun stage to be manufactured.

Nonlinear open mapping principles, with applications to the Jacobian equation and other scale-invariant PDEs

For a nonlinear operator T satisfying certain structural assumptions, our main theorem states that the following claims are equivalent: i) T is surjective, ii) T is open at zero, and iii) T has a bounded right inverse. The theorem applies to numerous scale-invariant PDEs in regularity regimes where the equations are stable under weak⁎ convergence. Two particular examples we explore are the Jacobian equation and the equations of incompressible fluid flow.For the Jacobian, it is a long standing open problem to decide whether it is onto between the critical Sobolev space and the Hardy space. Towards a negative answer, we show that, if the Jacobian is onto, then it suffices to rule out the existence of surprisingly well-behaved solutions.For the incompressible Euler equations, we show that, for any p<∞, the set of initial data for which there are dissipative weak solutions in LtpLx2 is meagre in the space of solenoidal L2 fields. Similar results hold for other equations of incompressible fluid dynamics.

The Green Tensor of the Nonstationary Stokes System in the Half Space

We prove the first ever pointwise estimates of the (unrestricted) Green tensor and the associated pressure tensor of the nonstationary Stokes system in the half-space, for every space dimension greater than one. The force field is not necessarily assumed to be solenoidal. The key is to find a suitable Green tensor formula which maximizes the tangential decay, showing in particular the integrability of Green tensor derivatives. With its pointwise estimates, we show the symmetry of the Green tensor, which in turn improves pointwise estimates. We also study how the solutions converge to the initial data, and the (infinitely many) restricted Green tensors acting on solenoidal vector fields. As applications, we give new proofs of existence of mild solutions of the Navier–Stokes equations in $$L^q$$ , pointwise decay, and uniformly local $$L^q$$ spaces in the half-space.

Quasi-periodic solutions to the incompressible Euler equations in dimensions two and higher

Building on the work of Crouseilles and Faou on the 2D case, we construct C∞ quasi-periodic solutions to the incompressible Euler equations with periodic boundary conditions in dimension 3 and in any even dimension. These solutions are genuinely high-dimensional, which is particularly interesting because there are extremely few examples of high-dimensional initial data for which global solutions are known to exist. These quasi-periodic solutions can be engineered so that they are dense on tori of arbitrary dimension embedded in the space of solenoidal vector fields. Furthermore, in the two-dimensional case we show that quasi-periodic solutions are dense in the phase space of the Euler equations. More precisely, for any integer N⩾1 we prove that any Lq initial stream function can be approximated in Lq (strongly when 1⩽q<∞ and weak-⁎ when q=∞) by smooth initial data whose solutions are dense on N-dimensional tori.

Power Transmission Characteristics in Commercial Frequency of Wireless Power Transfer System for Railway Vehicles Using High Temperature Superconducting Coil

This study investigated experimentally and analytically the power transmission characteristics of High Temperature Superconducting (HTS) coils at commercial power supply frequency (50 Hz) to realize highly efficient power transmission in wireless power transfer systems for railway vehicles. We proposed a solenoidal coil with a thin magnetic core as an HTS coil structure suitable for lower frequencies and investigated its effectiveness by finite element analysis. The analysis results showed that the proposed coil can significantly suppress the current increase due to the low frequency of the wireless power transfer system. We also investigated the core shape to reduce the losses of the proposed coil and found that the loss in the coil can be reduced by increasing the length and thickness of the magnetic core. Furthermore, we compared the power transmission characteristics between the proposed coil and the conventional spiral coil and showed that the proposed coil could improve the overall efficiency by about 10 %. The power transmission characteristics at 50 Hz were also measured using the scaled-down model coil. As a result, we demonstrated that highly efficient power transmission could be achieved at 50 Hz by using the proposed solenoidal coil with a magnetic core.

Computational Numerical Analysis of a Magnetic Flux Permanent Magnet with Different Shape for The Development of a Hybrid Generator

A hybrid generator is one of the attempts to reduce carbon emissions in electricity generation, as it could replace the combustion system currently used in generator sets to generate electricity while increasing carbon emissions. In the hybrid generator system, Lenz's rule of electromagnetic induction is applied in reverse by using a relay to change the polarity of the solenoid coil's electric current. The permanent magnet in the solenoid coil generates mechanical energy (motion) and thereby moves the generator engine, since the permanent magnet is connected to the generator engine via the crankshaft. The objective of this study is to determine and compare the behaviour of N55, N52, N42, N42SH, and samarium-cobalt permanent magnets for the magnet system. The objective of this study is also to find a suitable permanent magnet for use in the magnet system to increase the power generation efficiency. A simple model is simulated to achieve the desired result, including magnetic flux density inside and around the magnets, magnetic field strength calculation, and applied force. The simulations and analysis are performed using ANSYS R19 software and finally all the data are recorded and compared to select the best magnet and develop a prototype. The permanent magnet inside the solenoid plays an important role in the hybrid generator and it is crucial to choose the suitable permanent magnet to increase the efficiency of power generation. From the data, Alliance N-55 permanent magnet has the highestmagnetic force of 131.57 N for 1 mm because it has significantly higher magnetic flux density, magnetic flux intensity and magnetic force.

Sharp Uncertainty Principle inequality for solenoidal fields

This paper solves the L2 version of Maz'ya's open problem [1, Section 3.9] on the sharp uncertainty principle inequality∫RN|∇u|2dx∫RN|u|2|x|2dx≥CN(∫RN|u|2dx)2 for solenoidal (namely divergence-free) vector fields u=u(x) on RN. The best value of the constant for N≥3 turns out to be CN=14(N2−4(N−3)+2)2 which exceeds the original value N2/4 for unconstrained fields. Moreover, we show the attainability of CN and specify the profiles of the extremal solenoidal fields: for N≥4, the extremals are proportional to a poloidal field that is axisymmetric and unique up to the axis of symmetry; for N=3, there exist extremal toroidal fields, in addition to extremal poloidal fields; for N=2, the extremal fields are all toroidal.

Inertial Tracking System for Monitoring Dual Mobility Hip Implants In Vitro.

Dual mobility (DM) implants are being increasingly used for total hip arthroplasties due to the additional range of motion and joint stability they afford over more traditional implant types. Currently, there are no reported methods for monitoring their motions under realistic operating conditions while in vitro and, therefore, it is challenging to predict how they will function under clinically relevant conditions and what failure modes may exist. This study reports the development, calibration, and validation of a novel inertial tracking system that directly mounts to the mobile liner of DM implants. The tracker was custom built and based on a miniaturized, off-the-shelf inertial measurement unit (IMU) and employed a gradient-decent sensor fusion algorithm for amalgamating nine degree-of-freedom IMU readings into three-axis orientation estimates. Additionally, a novel approach to magnetic interference mitigation using a fixed solenoid and magnetic field simulation was evaluated. The system produced orientation measurements to within 1.0° of the true value under ideal conditions and 3.9° with a negligible drift while in vitro, submerged in lubricant, and without a line of sight.

NO2 Sensor Based on Faraday Rotation Spectroscopy Using Ring Array Permanent Magnets.

Faraday rotation spectroscopy (FRS) exploits the magneto-optical effect to achieve highly selective and sensitive detection of paramagnetic molecules. Usually, a solenoid coil is used to provide a longitudinal magnetic field to produce the magneto-optical effect. However, such a method has the disadvantages of excessive power consumption and susceptibility to electromagnetic interference. In the present work, a novel FRS approach based on a combination of a neodymium iron boron permanent magnet ring array and a Herriott multipass absorption cell is proposed. A longitudinal magnetic field was generated by using 14 identical neodymium iron boron permanent magnet rings combined in a non-equidistant form according to their magnetic field's spatial distribution characteristics. The average magnetic field strength within a length of 380 mm was 346 gauss. A quantum cascade laser was used to target the optimum 441 ← 440 Q-branch nitrogen dioxide transition at 1613.25 cm-1 (6.2 μm) with an optical power of 40 mW. Coupling to a Herriott multipass absorption cell, a minimum detection limit of 0.4 ppb was achieved with an integration time of 70 s. The low-power FRS nitrogen dioxide sensor proposed in this work is expected to be developed into a robust field-deployable environment monitoring system.

Lift-Off Effect Evaluation by Using Eddy Current Testing Technique on Copper (C101)

This study aims to develop an eddy current testing (ECT) probe that generates eddy current signals when a coil is placed above copper101 metal testing with and without nonconductive coating and the presence of lift-off height, i.e., 0, 2.5, 5.0, 7.5, and 10.0 0.5 mm. Then, the metal test with a variety of thicknesses, i.e., 1.5, 3.0, and 5.0 0.5 mm, and with varies of surface defects, i.e., 10, 20, and 30  0.5 mm, engraved on the metal testing. The coil probe is a rodshaped solenoid coil designed with an iron core with 65 mm length, 5 mm area, and 200 N turns. It demonstrates how the rod-shaped solenoid coil may be used to detect various surface defects on copper101 (C101). The optimal frequencies for C101 are 7.850 MHz. In conclusion, the output voltage signals for larger surface defect sizes increase but decrease as the thickness becomes thicker. Furthermore, as the lift-off height increases, the output voltage for both coated and non-coated metal decreases accordingly. Therefore, besides comparing the output voltage for coated and non-coated metals, there are minor differences which shows that the ECT technique in this studyis capableto detect surface defects appropriately.

Direct Measurement of the Electric Field Induced by a Transcranial Magnetic Stimulator

This work proposes a simple method to carry out in lab a direct measurement of the primary solenoidal electric field that transcranial magnetic stimulation coils generate in the brain. This method avoids indirect estimation of this electric field from measurements of magnetic fields, and at the same time, overcomes the difficulty posed by the presence of a dominant conservative electric field, also produced by the coil. This conservative electric field, which is removed in practice by human tissue, is eliminated in the proposed measurement method by using a simple setup that does not require the introduction of the measurement probe inside a conducting solution resembling the human tissue. The proposed measurement method allows for measuring the primary solenoidal electric field in front of the coil in the air. This method has been validated by comparing the results of electromagnetic simulation with the measurement of the magnetic field and the non-conservative electric field produced by a commercial transcranial magnetic stimulation coil.

The Effect of Low-Frequency Pulsed Electromagnetic Fields on the Differentiation of Permanent Dental Pulp Stem Cells into Odontoblasts.

Exposure to pulsed electromagnetic field (PEMF) has been revealed to affect the differentiation and proliferation of human mesenchymal stem cells derived from dental pulp multipotent stromal stem cells (DP-MSCs). This study aimed to investigate the differentiation effect of electromagnetic fields (EMFs) on the DP-MSC. PEMF was produced by a system comprising a multi-meter autotransformer, solenoid coils, and teslameter. This study included 10 groups of DP-MSCs which underwent different electromagnetic radiation time and beam intensity. Three samples tested for each group. The effect of PEMF with the intensity of 0.5 and 1 mT (mili Tesla) and 50 Hz on the proliferation rate of DP-MSC was evaluated at 20 and 40 minutes per day for seven days. MTT assay was applied to determine the growth and proliferation of DP-MSC. Gene expression of DMP1 for differentiation of DPSCs to odontoblasts was confirmed by Real Time PCR., ANOVA statistical analysis and Kruskal-Wallis test were used to analyze the data. The survival in all exposure groups was significantly higher than that in control except in the group of 40 minutes, 1 mT (P<0.05). In 20 minutes, 0.5 mT exposure, the survival intensity is significantly more than others (P<0.05). In general, the intensity of survival was recorded, 20, 0.5 mT≥20, 1 mT≥40, 0.5 mT≥40, 1 mT respectively. Therefore, according to the obtained results, ELF-EMF increases the survival of cells except for one case (40 minutes, 1 mT), even though the effective underlying mechanisms in this process are still unclear. The results obtained promise that in the future, by placing an important part of the pulp next to the electromagnetic field, the lost part of the pulp can be reconstructed and the dentin barrier can be created.

Statistical Temporal Variations in the Auroral Electrojet Estimated With Ground Magnetometers in Fennoscandia

AbstractWe present the implementation of an improved technique to coherently model the high‐latitude ionospheric equivalent current. Using a fixed selection of 20 ground magnetometers in Fennoscandia, we present a method based on Spherical Elementary Current Systems (SECS) to model the currents coherently during 2000–2020. Due to the north‐south extent of the magnetometers, we focus on the model output along the 105° magnetic meridian. Our improvements involve fixed data locations and SECS analysis grid and using a priori knowledge of the large‐scale currents improving the robustness of the inverse problem solution. We account for contributions from ground induced currents assuming so‐called mirror currents. This study produces a new data set of divergence‐free (DF) currents and magnetic field perturbations along the 105° magnetic meridian with 1‐min resolution. By comparing averages of the data set with an empirical model of the ionosphere we demonstrate the validity of the data set. We show how our data set, in particular its temporal nature, is distinct from empirical models and other studies. Not only can the temporal evolution of the DF currents and magnetic field perturbations be investigated, but the time derivative of said quantities can be analyzed. For application in ground induced currents, we present the statistical properties of where (in magnetic latitude and local time) and at what rate (∂Br/∂t) the radial magnetic field component fluctuates, a temporal derivative that has received very little attention. We show that ∂Br/∂t is dependent on latitude, local time, and solar cycle. We present other applications such as Ultra Low Frequency Waves monitoring.

Comparison of the Measurement Results of PIV with Different Tracer

Particle Image Velocimetry (PIV) was used to measure the solenoidal vector field of the Taylor-Couette flow with different tracers. It can be seen that both of them, the polyamide and flocs can be a suitable performance tracer particles for PIV in flow field measurement. The results indicated that the instantaneous velocity vector maps obtained with different tracer particles which could denote the characteristics of the flow structure, the size and the vortex centers of the vortex. At the meantime, the experimental results demonstrated that the velocity vector obtained by the flocs generated in real-time as tracer particles was similar with suitable performance to those obtained by polyamide.

Improvement of Moving RFID Microtag Detection in Different Angular Orientations Using Multiple Tubular Coils

Directionality problem caused by the rolling of microtag with flowing fluid seriously affects the reliability of oilwell downhole radio frequency identification (RFID) system. In this paper, we propose a novel RFID reader antenna structure using multiple tubular coils for reduced orientation sensitivity. The conventional solenoid coil and saddle-coil pairs are combined to overcome the respective defects of the two coils and develop their advantages to form a complementary structure at the same time. Then, a series of coil parameters are designed in detailed to provide strong magnetic field distribution both in the x-axis, y-axis and z-axis directions. To verify the design, the proposed multiple tubular coils have been fabricated and measured. Experimental results demonstrate more potential than the conventional solenoid coil for microtag detection in different angular orientations, which is very important to improve the reliability and applicability of current oilwell downhole RFID system.

Research on Push-Pull Energy Storage PWM Power Drive of High-Power High-Response Proportional Solenoid

As the traditional power drive circuit is difficult to meet the requests of high-power high-frequency proportional solenoid fast drive, this paper proposes a push-pull energy storage PWM power drive circuit. The circuit is equipped with an energy storage module, which releases energy when the proportional solenoid coil is charged, supplements the output of the power supply current, and shortens the arrival time of the steady-state current. When the coil is discharged, it recovers energy and shortens the time for the coil current to return to zero. In this paper, a theoretical model of push-pull energy storage power drive circuit is established, and simulation analysis and experimental verification are carried out for a proportional solenoid coil with rated current of 3.3A and power of 79W. The results show that the push-pull storage PWM power drive has excellent input-output linearity, minimal ripple, and good steady-state current output performance. Compared with the traditional single switch and reverse discharging power drives, the coil charging speed under the push-pull energy storage type power drive is increased by 25%, and the discharge speed is increased by 95% and 45% respectively.

Low-Cost Instrument for the Versatile Measurement of Spin Caloritronic Phenomena: Spin Seebeck Effect, Anisotropic Magnetoresistance, Anomalous Hall Effect, and Anomalous Nernst Effect

In this article, we report on a low-cost instrument for the versatile measurement of spin Caloritronics phenomena such as the spin Seebeck effect (SSE), anomalous Nernst effect (ANE) anisotropic magnetoresistance (AMR) and anomalous Hall effect (AHE). Solenoid coils provide a uniform variable magnetic field while the sample was sandwiched between thermal baths and measured in a vacuum chamber. Our results show excellent magnetic field uniformity (± 0.37 mT) within the magnet gap and high stability of the generated temperature difference (± 0.07 K). For verifying the effectiveness of our instrument, YIG/Co structure was used to measure the SSE, AMR, and AHE, while a SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Co structure was used for measuring the ANE. Our SSE measurements of the YIG/Co structure were found to be comparable with that of a commercially available instrument. We can therefore conclude that our low-cost and versatile instrument can be used to effectively observe spin Caloritronics phenomena.