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The Vernier machine can utilize magnetic-gear effect, which conspicuously improves the torque production over other type of synchronous machines. However, a dual-rotor/dual-stator structure enabled high torque density Vernier design is often unfavorable for industrial applications, due to manufacturing complexity and thermal management challenges. This article successfully addresses this problem, by building magnetic-gear effect into a consequent pole enabled alternating flux barrier structure with single-rotor single-stator (SRSS). In this way, the proposed machine can achieve a superior torque density as a Vernier machine does, while maintaining an equivalent manufacturing complexity as a conventional SRSS synchronous machine. This article begins with elaborating generic analytical equations, which can transform into a Vernier machine or an SRSS synchronous machine. More specifically, the magnetic-gear effect is manifested in the equations, via stator teeth originating flux modulation concept and resulting multiharmonic field coupling effects. An SRSS Vernier topology with consequent pole and V-shape magnet is then proposed. A considerable 52.6% improvement on the torque production with comparable efficiency is validated by experiments, where the comparison is made over that of a benchmark rare earth PM machine. Power factor would fall behind with increasing current load. Overall, this new design achieves an outstanding torque density, showing solid potential and feasibility for industry adoption. [ABSTRACT FROM AUTHOR]

In this article, we deal with design considerations of a new ac hybrid-excitation permanent-magnet machine with axial stator. Due to the presence of an axial stator, the machine features a typical three-dimensional geometric structure and field distribution. A simplified reluctance-based network is developed to capture the main design features of the machine. The analytical equations are deduced relating the main geometric dimensions to the machine design criteria: speed, power, and flux regulation capability. The influence of key machine geometric parameters, i.e., radial/axial air-gap length, stack length, and bore diameter, on output power, flux density, and flux regulation capability is investigated. It is found that there is a design tradeoff between the machine power density and flux regulation capability. The d/q-axis inductance and its ratio, which has an influence on flux weakening capability and operation performance, is examined. Finally, a 6-pole/36-slot prototype is built. Intensive experimental tests are carried out to verify the machine characteristics. [ABSTRACT FROM AUTHOR]

In this article, an axial-flux permanent-magnet (PM) Vernier machine with the triple-stator, spoke-type PM rotor, and toroidal winding wound on the innerstator is proposed. Benefited from the flux focusing spoke-type PM rotor and short end length toroidal winding, the proposed machine has a high torque density and the improved power factor. Based on the air-gap permeance function, the analytical expression of the proposed machine is derived to qualitatively analyze the machine's performance. The quasi-three-dimensional (3-D) finite element analysis (FEA) is adopted to optimize the design parameters, such as innerstator diameter, PM thickness, and slot opening width. The quasi-3-D FEA results match well with the 3-D FEA. The 3-D FEA results show the torque densities of the proposed machine reach 49.4 Nm/L and 11.4 Nm/kg, respectively, under the 232 A/cm average electrical loading. The performances, such as overload capacity, PM demagnetization, and PM and core losses, are also analyzed by 3-D FEA. The comparison with the other axial-flux PM Vernier machine is conducted, and the results reveal that the proposed machine has the great advantages of the torque density and power factor. Since the prototype is not built, in this article, the assembly scheme and thermal behavior of the proposed machine are discussed. [ABSTRACT FROM AUTHOR]

The Darwin model, which simultaneously incorporates resistive, capacitive, and inductive effects but neglects the radiation one, has recently attracted more and more attention in the research area. For our industrial application needs, the finite-element (FE) system to solve derived from the Darwin model generally has a large size, which is beyond the capabilities of the direct solvers due to the memory limitation. In this work, a specially designed formulation amenable to an iterative solver is proposed for industrial applications. Moreover, a detailed comparison of different cases is carried out on two different examples. [ABSTRACT FROM AUTHOR]

Planar electromagnetic vibration energy harvester (EVEH) is a promising technology for compact, low form factor self-powered wireless devices. However, planar EVEH has the limitation of non-fully utilized magnetic flux gradient and low output power due to its structure constraint and weak magnetic flux gradient capturing capability. Planar coil is the key component in harvesting magnetic flux gradient and determining the output electromotive force (EMF) voltage and output power. A novel non-uniform distributed planar (NUDP) coil is proposed to break the current limitation of output power for the planar coil. The boost in output power is realized with tight inner windings and loose outer windings. The breakpoint is determined based on power increasing rate for each winding. The optimal winding radius for both inner and outer coils is investigated using discrete non-linear constraint heuristic optimization method. The designed NUDP coil-based EVEH achieves peak-to-peak output voltage of 305 mV and output power of 1.163 mW at 64.3 Hz resonant frequency and 0.05 g acceleration. It realizes 16.3% higher output power and 19.4% higher output voltage than uniform distributed planar (UDP) coil under the same spring and magnet. The power density of the proposed prototype reaches 9.616 mW/cm3g2, which is 15.025 times higher than the state-of-the-art EVEHs with the planar coil. [ABSTRACT FROM AUTHOR]

The use of interlocks often represents an affordable stacking solution for soft magnetic cores in mass production of electrical machines. However, due to the process itself, the material behavior and thus the resulting electrical machine performance is negatively impacted. On the one hand, this is due to additional conductive paths, which increase the eddy current losses. On the other hand, locally introduced mechanical stresses occur. These lead to nonnegligible degradation of the magnetic material properties inside and around the interlock area, following higher hysteresis losses. This article investigates and develops a reliable and accurate three-dimensional finite-element method model that considers the contact resistance between interlocks and laminations, as well as layered regions for the material degradation around the interlock area. Examples of flux and eddy current density distributions are provided, together with the computation of the total iron losses for a variable number of rectangular dowels in the yoke of stator core samples. The numerical analyses are validated by several interlaboratory measurements conducted on multiple stator core samples made of two different grades of electrical steels and with different numbers of interlocks. Results reveal impact of some percent on the core losses and well evident degradation on the material BH curve. [ABSTRACT FROM AUTHOR]

A nonlinear transformer model is used for describing the tokamak discharge with fraction of noninductive current. The nonlinear model accurately identifies the tokamak as a toroidal transformer by a voltage balance equation. In order to verify the feasibility of the application of the nonlinear model in the experimental advanced superconducting tokamak (EAST), the voltage balance equation is checked for the different scenarios and applied to calculate and analyze the noninductive current in shots #73999 and #66740, respectively. Calculation results indicate that the #73999 shot H-mode plasma discharge is full noninductive current drive and occupies approximately 99% of plasma current. It is a good agreement with the simulation result (98%) by the integrated modeling under the framework OMFIT with equilibrium code EAST equilibrium fitting (EFIT), and transport codes TGYRO and ONETWO in EAST. For the #66740 shot, it is nearly full noninductive current drive. [ABSTRACT FROM AUTHOR]

In this article, we suggest and study a novel omnidirectional wireless power transfer (WPT) system based on unusual double-toroidal helix coils. The suggested antenna is a double-helix coil wounded around a torus. It creates two mutually orthogonal magnetic fields. One is toroidal and confined inside the torus, and another one is poloidal and is distributed outside it. The intensities of these two fields can be independently tuned via the geometry of the turns. The coupling coefficients are tailored to ensure high efficiency regardless of the receiver position and orientation, without active circuitry for tuning or control. This topology provides self-tuning functionality which is achieved when the coupling between the transmitter and receiver is minimized while the coupling in the pairs transmitter–repeater and repeater–receiver is strong. The system consists of three transmitter–repeater pairs orthogonal to each other, ensuring omnidirectional functionality. Experimental results confirm self-tunability and high efficiency for any position and orientation of receivers. The proposed double-helix antenna is applicable to different WPT applications where the coupling/decoupling between coils can be freely controlled. [ABSTRACT FROM AUTHOR]

This paper proposes a toroidal plasmons resonator composed of a slotted circle and a ring fed by a microstrip line. Multi-modes Mie resonances are well excited by the feed of the microstrip line. A toroidal magnetic field is demonstrated and analyzed by CST simulation at 14.318 GHz. The higher-order resonance shows higher sensitivity for permittivity sensing. By reconstructing the structure, the excited octupole has a high sensitivity of 3.68 GHz/RIU and quality factors of 340.6 with a ${Q}$ -factor of 340.6. The high sensitivity, high Q-factor, and compact size make it a good choice for sensing applications. [ABSTRACT FROM AUTHOR]

As part of the European Strategy for Particle Physics there is an ongoing development towards a Future Circular Collider (FCC-ee) where electron-positron collisions could be used to study the entire electro-weak sector in a low background environment. Particle detectors are used to study these collisions and a strong magnetic field is required to measure the particles’ momenta. Currently, two detector concepts are being studied: the Innovative Detector for Electron-positron Accelerators (IDEA) and the CLIC-Like Detector (CLD). Both these detectors include a superconducting solenoid magnet with a central field of $2 \,\mathrm{T}$ of which the designs are presented here. The IDEA magnet has an stored magnetic energy density of 14 kJ/kg and in CLD this is 12 kJ/kg. Taking into account their respective free-bore diameters of $4.2 \,\mathrm{m}$ for IDEA and $7.2 \,\mathrm{m}$ for CLD this results in very challenging designs for which the mechanical and quench studies are presented. Their results are promising, but extensive R&D on these magnets would be needed in the future to reach the goals set out in the Conceptual Design Report (CDR). [ABSTRACT FROM AUTHOR]

The electron cooling technology is applied in the spectrometer ring (SRing) to improve the luminosity of ion beam for the High Intensity heavy-ion Accelerator Facility (HIAF). The electron cooler consists of a gun section, two 90-degree toroids, a cooling section and a collector section. There are four kinds of main coils used to provide longitudinal magnetic fields along the path of the electron beam. In this paper, we present the modeling and analyzing of the electron cooler magnets by three-dimension software. The optimizing of the magnetic field of cooling section is completed to achieve the required effective cooling length. The magnetic fields along the electron beam path and ion beam path are calculated and the beam trajectory of typical ion is also simulated to offer data for correcting the orbit. [ABSTRACT FROM AUTHOR]

As signified by the well-known Aharanov–Bohm effect, the fields only under-describe electromagnetics and are thus not sufficient, while the potentials over-describe electromagnetics and are more than necessary with gauge redundancy. In lieu of the traditional fields and potentials, this article presents new formulations that introduce from the outset the concept and utilization of field-impulses for the fundamental equations of electromagnetics. Unlike the potentials that may or may not be real or causal depending on the gauge, the field-impulses as physical field-integrators (time-integrals) are like fields being physically real, causal, and gauge-independent. Furthermore, the single electric field-impulse/integrator alone through its second-order (wave) equation is capable of aptly describing electromagnetics in all cases of electrostatics, magnetostatics, and electrodynamics. Upon close scrutiny and comparison, the optional static–dynamic decomposition of electric field-impulse can be related to the potentials with source-incorporated gauge condition. Such source-incorporated condition is unlike other popular gauge conditions that are source-free or incorporating the source implicitly. The electric field-impulse as physical field-integrator is necessary and sufficient for many aspects of electromagnetics including field derivation, Lorentz force, momentum, interaction energy, quantum particle–electromagnetic interactions, etc. [ABSTRACT FROM AUTHOR]

Ferromagnetic materials may be affected by the presence of local losses due to defects or magnetic anomalies caused by machining processes. To highlight such anomalies is not easy; a noninvasive thermographic method has been refined to allow a proper comparison of different machining processes’ impact on the iron losses. Specimens obtained with punching, wire erosion, and laser cut have been analyzed using a high-speed IR camera when subjected to alternate magnetization at different frequencies. Also, the same technique has been adopted to the assembled stacks to investigate more simultaneous phenomena. The possibility to point out localized anomalies should be exploited to foresee and avoid electrical machines core faults. [ABSTRACT FROM AUTHOR]

The size of magnetic components can be reduced with novel designs, but the intricate structures are difficult to make due to the limited sets of conventional magnetic core geometries and materials. Magnetic pastes have the flexibility of forming complicated structures with a pressure-less and low-temperature molding process, and are ideal for making the novel magnetic designs. The conventional approach of developing magnetic pastes involves time-consuming experimental iterations to determine the optimal composition parameters. Instead of relying on the trial-and-error efforts, we explored a computer-aided approach to guiding the magnetic paste development by creating material’s microstructure by discrete element method (DEM) and studying the property by finite element method (FEM). From a starting formula with two different-sized spherical powders, we improved the composition guided by DEM and FEM, and studied the magnetic permeability versus two variables: powder mixing ratio and magnetic volume fraction. The simulated permeability agreed well with the experimental data with an average error of only 10%. With the computer-aided formulation methodology demonstrated in this work, one can develop magnetic pastes with minimum experimental efforts and explore different compositions to meet various magnetic design needs. [ABSTRACT FROM AUTHOR]

High-temperature superconducting (HTS) magnets offer a novel pathway to magnetically confined fusion energy generation. Reactor-scale fusion devices require tens of kA of current to generate large toroidal fields for magnetic confinement. Operating HTS magnets at kA-current levels is difficult due to unavoidable joint resistances that require active driving of current. The large footprint and energy demand of a solid-state power supply and multi-kA current leads present significant constraints on the size, cost and efficiency of a fusion tokamak. An alternative approach is to use an HTS flux pump, which can generate and sustain persistent currents in HTS coils at the kA-levels required by fusion magnet systems. Here, we outline the design of a 60 kA transformer-rectifier flux pump for energizing and sustaining an 80 mH HTS fusion magnet. The flux pump is driven by an iron-core transformer with copper primary and HTS secondary windings. This is rectified by switching elements in the superconducting circuit into a uni-directional dc voltage output which charges the inductive load. To charge the load coil to 60 kA in 24 hours, an output dc voltage of 55 mV is needed. However, only 6 mV is required to maintain a long-term steady current of 60 kA. Such a device can significantly reduce the cost and footprint of future fusion reactor designs. [ABSTRACT FROM AUTHOR]

On the basis of prior research, a conceptual three-dimensional (3-D) configuration of a non-destructive two-layer magnet capable of generating megagauss-level magnetic field was developed. The design is based on the concept of quasi-force-free coils, in which conductors have a special shape tailored to minimize mechanical stresses caused by electromagnetic forces. Multivariate multi-physical finite element simulations were used as the main tool for developing the presented configuration. The magnetic system was analyzed for its ability to withstand Lorentz forces, and calculations demonstrate that the design ensures maximum stresses in the windings significantly less than the magnetic pressure of the generated field. That reveals a possibility of achieving a megagauss field in the system, provided that certain requirements are met for the used materials. Such requirements were formulated and are realistic (e.g., ultimate strength about 1 GPa for the conductors). Estimation of the possible pulse duration limited by the admissible temperature of the conductors allowed us to perform a transient electromagnetic analysis. Results highlight the importance of mitigating the skin effect in the system, and possible ways for that are proposed. The energy of the magnetic field in the proposed system is estimated to be about 1 MJ, which is significantly less than the energy in magnets of more conventional configurations with similar bore diameters. [ABSTRACT FROM AUTHOR]

Encapsulated payload pellet injection (EPPI) has been demonstrated to be an effective method of disruption mitigation system (DMS) through a number of experiments and simulations in DIII-D and JET. This article investigates the effects of plasma rotation on impurity spreading under neon EPPI. Our analysis of simulations shows that the magnetic surface stochastization has a decisive influence on the core-oriented spread of impurity. The MHD instabilities increase with impurity ionization, especially of the $n = 1$ component, leading to the enhancement of the local transport of impurities along the stochastic field lines. In the rotating plasma, the toroidal rotation can suppress the magnetic perturbation, and then, the boundary-oriented spreading of impurities is reduced. When the pellet source is toroidally localized at the magnetic axis, the rotation can quickly flatten the toroidal distribution of impurities, resulting in a smaller maximum radiated power and a lower toroidal peek factor (TPF). [ABSTRACT FROM AUTHOR]

A dual-output magnetoelectric (ME) energy harvester consisting of strictly concentric toroidal Ni0.8Zn0.2Tb0.02Fe1.98O4/(Pb0.70Ba0.26Sr0.04)(Zr0.52Ti0.48)O3 (PbaS-4)/Ni0.8Zn0.2Tb0.02Fe1.98O4 composite with solenoid wound around it is presented and developed. In this case, spatial electromagnetic energy from power lines can be scavenged by ME element and the solenoid simultaneously, and then, the output power density was improved due to electromagnetic induction involved. Experimental results show that the maximum induced voltage can reach 15 mV (port I) and 1.2 mV (port II) for open-circuit conditions under the amplitude of 70 mA current driving of 50 Hz. Correspondingly, generated output power for ports I and II reaches 0.4285 and 30.1476 nW at optimum load resistances of 250 and $140~\Omega $ , respectively. Through these study results, new research paths to move forward with enhanced flexibility for device design of magnetic energy harvester in application in power line autonomous monitoring systems. Through these study results, new research paths to move forward with enhanced flexibility for device design of magnetic energy harvester were achieved in application of power line autonomous monitoring systems. [ABSTRACT FROM AUTHOR]

Electric vehicles (EVs) are increasingly connected to the power grid using the charging connectors based on the charging connector standards, such as SAE J1772, SAE Combo, or CHAdeMO, which are mainly intended for single directional charging for grid-to-vehicle application. However, with the development of a smart grid, EVs should play a role as active distributed resources, that can transfer their energy into the grid and can charge or be charged by another EV. Therefore, the concept of vehicle-to-X (V2X), where X can be the grid, the local load, or another EV, has been proposed. Unfortunately, the current standard of the charging connector does not support all possible connections of the V2X. This article proposes a new universal power connector (UPC), which can support all possible connections of the V2X configuration including vehicle-to-vehicle, so that, if needed, EV owners can trade their EVs’ stored energy independently among themselves. The proposed connector transfers the power through a magnetic link formed by two magnetic parts (one in the EV and another in the charging plug). To validate the proposed new power plug/connector, a scaled-down prototype of an EV charger that utilizes the proposed UPC has been designed, analyzed, implemented, and validated in the laboratory. [ABSTRACT FROM AUTHOR]

In this article, a multiload wireless power transfer (WPT) system is proposed for the power supply of autonomous underwater vehicle (AUV) cluster system. The segmented arc solenoid transmitter coil is designed to generate the concentrated magnetic field. The adjacent transmitter coils are reversely wound to form the strengthened magnetic field, which can improve the coupling between the transmitter and the receiver. The proposed coil structure is verified via finite element analysis based on ANSYS Maxwell. The transfer performance is analyzed and it is found that the transfer efficiency can be maximized against the voltage gain under the two-receiver case, which can also be extended to multiple-receiver case. An LCC–LCC compensated multiload WPT prototype was established and the experimental results verified the theoretical analysis and simulations. The output power of each receiver and the system efficiency can reach 500 W and 90% under the different angles between any two receivers. [ABSTRACT FROM AUTHOR]

Gaussian analysis of neutral hydrogen $\lambda 21$ -cm line (HI) profiles associated with an $\text{H}\alpha $ filament reveal a broad-line underlying component similar to the $\text{H}\alpha $ structure as well as a narrow-line thread along the backbone of the filament. Both the $\text{H}\alpha $ and the broad-line HI have a linewidth of about 25 km s−1. The narrow-line components are of order 7 and 9 km s−1. The filament appears to be part a complex gas structure flowing out of the Perseus arm and is located at an order of 1 kpc from the Galactic plane. Neither traditional photoionization nor shocks seem to be responsible for the energy required to explain the presence of $\text{H}\alpha $ at this location. We investigate two other possibilities. The first is similar to the solar wind-ionized material that is created near the large numbers of O associations in the Perseus arm, and then streams out into the halo where far lower densities limit recombination. The other is the critical ionization velocity (CIV) where the kinetic energy of the neutral particles relative to the plasma equals the ionization potential of the atoms. This velocity for hydrogen atoms in the $n=2$ level, the state after the emission of an $\text{H}\alpha $ photon, is 25 km s−1, the measured linewidth for both the $\text{H}\alpha $ and the broad-line HI. Marklund convection may be responsible for the formation of interstellar filaments. In other astrophysical regimes filaments with thread-like substructure appear to be common. Although different jargon—strands, spines, tendrils, threads, etc.—is used in different disciplines, these may be revealing the same underlying physics. [ABSTRACT FROM AUTHOR]

In this article, coupled electromagnetic-thermal simulations of inductive power transfer (IPT) pads using finite-element simulations are discussed. Derivation of each electrical and thermal parameters required for the modeling process is outlined. Simulation models are used to predict the power loss and the temperature rise of an IPT pad at different ambient temperatures at steady state. Using these simulation methods, the power loss within an IPT pad operating at 50 ${^\circ }$ C ambient temperature is predicted. A 10-KW IPT system is set up within an environmental chamber to validate the predicted losses within the system. [ABSTRACT FROM AUTHOR]

Using recent observational data, we here test the theory, first proposed by Carlqvist and Gahm, that astrophysical filaments are formed by the Bennett pinch process. In this process, current flowing along the axis of the filament creates a toroidal magnetic field, which in turn creates an inward electromagnetic pressure that draws plasma toward the axis of the filament. In such filaments, the inward pinching force and outwards kinetic forces are approximately equal–the Bennett pinch condition. We find that the Bennett pinch condition does in fact hold, as predicted by the theory, for a sample of interstellar filaments, including molecular clouds, such as Taurus, IC5146, the pipe nebula, the infrared dark cloud G035.39–00.33, as well as $H\text{I}$ fibers at high galactic latitudes, supernova remnant SN1006. The currents are estimated to be about 1012–1014 A. These values are similar to that estimated by Carlqvist and Gahm for Lynds204. The Bennett pinch relation is also applied to intergalactic filaments, such as the ridge between Abell 0399 and 0401. This filament is almost in equilibrium. These results reinforce the validity of the theory. [ABSTRACT FROM AUTHOR]

HL-2M is a middle-sized copper conductor tokamak, which aims to operate close-burning and high-performance plasma for experimental magnetic fusion researches. The magnetic field coil system is an important part of HL-2M machine, consisting of a toroidal field (TF) coil system and a poloidal field (PF) coil system. In the operation of HL-2M, the TF coils operate in the environment of high current, strong magnetic field, and high stress. The structure, electromagnetic, electrical and thermal issues of TF coils were solved in design and construction phase. In this paper, the structure design principle of the demountable TF coils including some key components, was introduced, and then the construction of the TF coils, especially the industry processing, was established. [ABSTRACT FROM AUTHOR]

In this work, the mechanical lap joint of commercial ReBCO tape from SHSC is prepared. The tape is reinforced with stainless steel bar in both side to reduce the effect of bending moment in the joint tensile test. We use Indium and GaInSn as interlayer material, respectively, and different pressures are applied on the joint by jig during testing. The relationship between joint resistance and applied tensile stress was measured at 77 K. The results shows that for all measured joints under pressure, the voltage rise duo to tensile stress is small at first and then sharply grows until a certain value of stress is reached. The maximum tensile stress is higher for the joint which has lower resistance. Comparing two types of mechanical lap joints with Indium and GaInSn, the former joint shows smaller dispersion on joint resistance than the latter under pressure above 40 Mpa. It is also shown that the joint with Indium can tolerate higher tensile stress than the joint with GaInSn by using the Weibull distribution function analysis. [ABSTRACT FROM AUTHOR]

This letter proposed a novel high-current planar inductor with cooling fins based on 3-D printing and its copper winding is 3-D printed by using selective laser melting technology. The 3-D-printed winding is designed for high-current applications based on 3-D space and can work as both winding and cooling fins. Compared with conventional printed circuit board (PCB) planar inductor, the proposed planar inductor not only has better performance, such as low dc resistance (DCR), ac resistance, and temperature rise, without volume increasing, but also has the superiorities of conventional PCB planar magnetics, such as ease of manufacture and controllability. To verify its performance, a 100-A-output buck converter using the proposed inductor was fabricated and compared with another identical buck converter using a conventional PCB inductor with the same size. The DCR of the proposed inductor is almost one-fifth of the PCB inductor. Besides, the efficiency of the buck converter with the proposed inductor is always over 0.5% higher than that with PCB inductor under different loads and its maximum efficiency is nearly 1% higher at light load. Furthermore, the maximum temperature rise of the proposed inductor is 26.8 $^{\circ }$ C under full load, only one-third of the PCB planar inductor. In other words, the proposed inductor can work well under 100-A current, whereas the traditional PCB inductor cannot due to too high temperature (103.8 $^{\circ }$ C). [ABSTRACT FROM AUTHOR]

A key component in superconducting magnetic energy storage (SMES) system design is the cooling system. A well-designed cooling apparatus allows a SMES to work with higher critical currents, have less AC losses and work in a stable way. Acknowledging the importance of cooling systems in a SMES and that there have been many different designs presented in the bibliography, we hereby analyze various thermal designs that utilize cryocoolers, and we estimate the total volume of the superconducting coils used in their experiments. This review article focuses on recent high temperature superconducting (HTS) materials, and presents the cooling methods employed to cool the coil in conjunction with other important characteristics, such as the coil geometry, the operating temperature of the magnet, the thermal insulation temperature and the cooling power of the cryocoolers. From the presented analysis, the authors propose a procedure to devise a proper cooling scheme for a SMES design. Additionally, a qualitative comparative assessment of the analyzed designs in literature, in eight assessment criteria, is presented. [ABSTRACT FROM AUTHOR]

The sharp increase of pressure at the edge of a high confinement mode (H-mode) plasma, the pedestal, strongly impacts overall plasma performance. Predicting the pedestal is a necessity to control and optimize tokamak operations. An experimental data-driven machine learning (ML) approach is presented, which predicts the pedestal heights and widths of electron density ($n_{\mathrm {e}}$) and electron temperature ($T_{\mathrm {e}}$) profiles as well as the separatrix $n_{\mathrm {e}}$ from externally controllable parameters such as the plasma shape, heating method and power, and gas puff rate and integrated gas puff. The one modeling framework for integrated tasks (OMFIT) framework was used with DIII-D data to efficiently, robustly, and automatically build a database of pedestal parameters to train ML models. Database creation was enabled by the search engine tool for DIII-D data, TokSearch, which parallelizes data fetching, enabling fast searches through basic signals of thousands of DIII-D shots and selection of relevant time intervals. Principal component analysis (PCA) separated the database into three clusters that represent classes of plasma shapes that are regularly used in DIII-D. The most important parameters for setting the pedestal structure were plasma current ($I_{\mathrm {p}}$), toroidal magnetic field ($B_{\phi }$), neutral beam heating power ($P_{{\mathrm {NBI}}}$), and shaping quantities. The deep jointly informed neural networks (DJINNs) algorithm was applied to identify suitable neural network (NN) architectures that appropriately capture the features of the pedestal database. Separate NNs were implemented for each pedestal parameter, and ensembling methods were used to improve the prediction accuracy and allowed estimation of the prediction uncertainty. The pedestal predictions of the test dataset lie within the measurement uncertainties of the pedestal parameters. The NN outperformed simple linear regression (LR) analysis, indicating nonlinear dependencies in the pedestal structure. The presented achievements illustrate a promising path for future research, using feature extraction to infer experimental trends and thereby improve pedestal models as well as deploying NN for a fast pedestal prediction in DIII-D scenario development. [ABSTRACT FROM AUTHOR]

The article presents the investigation results on the main angular divergence sources of a high-current relativistic electron beam when it passes through a real 12° bend magnet of the transport system in the linear induction accelerator (LIA), being developed by collaboration of Budker Institute of Nuclear Physics (BINP), Novosibirsk, Russia, and Russian Federal Nuclear Center—Zababakhin All-Russia Research Institute of Technical Physics (RFNC-VNIITF). The main results of the work are the calculated trajectories of the beam electrons, the shape of its cross section, as well as the change in the normalized emittance of the beam as it passes through the region of the bend magnet. It was shown that at typical beam parameters—electron energy of 20 MeV, beam current of 2 kA, and beam radius of 2 cm—the emittance of a high-current relativistic electron beam with uniform current and charge densities after the bend element is determined mostly by the magnet aberrations and much less by the beam self-fields. Optimization of the dipole magnet geometry made it possible to achieve a substantial decrease in the beam emittance with geometric expansion of the magnet in the median plane of the beam. [ABSTRACT FROM AUTHOR]

In this article, we present two methods for calculation of the inductance of toroidal inductor wound by rectangular cross-sectional wire, considering that the current density is inversely proportional to the circular coil radius. The first method is to simplify the helical toroidal coil into a thick-walled toroidal, and based on Grover’s toroidal inductor formula, the inductance is obtained by calculation the magnetic flux and the calculation method is simple, but the applicability is poor. The second method is to simplify the helical toroidal coil into a collection of self-closing circular coils, the calculation method is complex but has high accuracy, and the mutual inductance between the circular coils is calculated by the filament method based on the adjusted Grover’s mutual inductance of circular coils with inclined axes. We verify the adjusted Grover’s mutual inductance of filamentary circular coils with inclined axes and the mutual inductance between inclined circular coils with a rectangular cross section. Finally, we compared and analyzed the results calculated by the two methods proposed in this article and the results calculated by the finite element method. [ABSTRACT FROM AUTHOR]

In the future, superconducting magnetic energy storage (SMES) technology will be developed toward large capacity. Among them, a single magnet is expensive and technically challenging. The integration of multiple SMES (M-SMES) is a feasible technical route. But there is coordination among multimodule energy storage magnets, so the formulation of its control strategy is very important. In this article, based on the toroidal magnet, a state evaluation method of toroidal magnet considering the withstand voltage and temperature of the magnet is proposed. To solve the problem of power distribution caused by the difference in initial capacity, initial temperature, and maximum output power during the cooperative control of multiple SMES, a temperature equilibrium control strategy for energy storage magnets combined with state assessment is proposed. System simulation results showed that this strategy could effectively balance the working state of each module and maximize the power output capability of the energy storage magnet by ensuring the safety of the magnet. [ABSTRACT FROM AUTHOR]

This paper presents a detailed design methodology for a DC-DC converter based on the recent Quasi-Y Source impedance network, which has interesting characteristics for applications related to renewable energy sources. Despite the advantages of this particular impedance network, there is a lack in the current literature, of details regarding the design of the diode and coupled inductors, and a description of its leakage inductance impact on the performance of the Quasi-Y-Source based converter. Therefore, this work presents design guidelines for the coupled inductors including core material choice criteria and optimization of windings combinations. Several analyses are conducted, through computational simulation, with respect to voltage stresses on the converter switches. The simulations results are compared with experimental implementation considering different voltage gain B operational scenarios. The obtained results shows that the proposed approach is useful to design: (a) Quasi-Y Source DC-DC converter components; (b) Evaluate the best coupled inductors configuration; (c) Implement closed loop controllers and snubbers circuits. A discussion evaluating the converter characteristics is made, exploring possible solutions to problems related to real operation scenarios. [ABSTRACT FROM AUTHOR]

The large Hadron collider (LHC) is expected to increase its center-of-mass energy from 13 to 14 TeV for Run 3 scheduled from 2022 to 2024. After Run 3, upgrades for the high-luminosity-LHC (HL-LHC) program are planned and the operation will start in 2027, increasing the instantaneous luminosity to 5.0–7.5 times its nominal luminosity. Continuous upgrades of the ATLAS trigger system are planned to cope with the high event rate and to keep the physics acceptance. During the long shutdown period before Run 3, new detectors will be installed to improve the trigger performance. A new trigger logic, combining information from detectors located outside of the magnetic field and new detectors installed inside the magnetic field, will be introduced for Run 3 to reduce the trigger rate. In order to handle data from the various detectors, a new trigger processor board has been developed and the design is presented. During the upgrade for HL-LHC, the trigger and readout systems of the first level hardware-based part are planned to be upgraded. Full-granularity information will be transferred to the trigger processor board which enables more OFF-line like track reconstruction in the hardware-based system. To handle the full-granularity information and perform the hardware-based track reconstruction, the trigger processor board will be equipped with a field programmable gate array (FPGA) with hundreds of transceivers and a large memory. Expected performance for the hardware-based endcap muon trigger in Run 3 and HL-LHC will also be presented. [ABSTRACT FROM AUTHOR]

For a miniature toroidal single-turn magnetic probe the spatial distribution of a harmonically time-varying uniform external magnetic field, B0 = Bm sin(ωt), is investigated theoretically. Based on the solution obtained, in this article, a method is proposed for increasing the accuracy of measuring pulsed magnetic fields with a miniature probe. The analysis takes into account the effects of skinning of the external field. The magnetic flux Φ measured by the probe is characterized by a “separation radius” R*, which corresponds to the relation Φ = B0πR*2. The dependence of the separation radius on the governing parameters, namely, the wire radius Rw, the coil radius Ra, and the thickness of the skin layer δs is found. The problem has an analytical solution for the limiting case of a stationary field ω → 0). For arbitrary values of ω, the problem has been solved numerically. The limiting case of high-frequency fields has been analyzed in the approximation of a “surface current.” The numerical solution results are consistent with the analytical solutions. The total set of calculated data on the separation radius is fitted by an analytical function R*( Ra, Rw,δs). Using this function, we constructed a level chart that can serve as a convenient tool for quick engineering assessments to accurately determine the amplitude Bm of a measured magnetic pulse. [ABSTRACT FROM AUTHOR]

This paper presents a MEMS based electrochemical angular accelerometer with feedback where the relative movement between the liquid inertial mass and the sensitive microelectrodes was counter balanced by the feedback force. Theoretical analysis was conducted to model the response of the angular accelerometer with feedback. Both sensitive and feedback electrodes were made based on microfabrication and assembled to form MEMS based electrochemical angular accelerometer with feedback. Device characterization was conducted, locating a sensitivity of 8 V/(rad/s2), a bandwidth of 0.0083-8 Hz and a noise level of $6.31\times 10 ^{-7}$ (rad/ $\text{s}^{2})/\surd $ Hz. In comparison to previously reported MEMS based electrochemical angular accelerometer without feedback, a significant improvement at low frequencies in 3dB bandwidth (0.0083-8 Hz vs. 0.02-10 Hz) was achieved due to the inclusion of the feedback part. This study can provide a new perspective for the development of electrochemical angular accelerometer, which may be further used in seismic monitoring. [ABSTRACT FROM AUTHOR]

We describe efficient four-coil inductive power transfer (IPT) systems that operate at 100 MHz. The magnetically coupled transmitter and receiver were made from electrically small and high- ${Q}$ loop-gap resonators (LGRs). In contrast to the commonly used helical and spiral resonators, the LGR design has the distinct advantage that electric fields are strongly confined to the capacitive gap of the resonator. With negligible fringing electric fields in the surrounding space, the IPT system is immune to interference from nearby dielectric objects, even when they are in close proximity to the transmitter and/or receiver. We experimented with both cylindrical and split-toroidal LGR (TLGR) geometries. Although both systems performed well under laboratory conditions, the toroidal geometry has the additional advantage that the magnetic flux is weak everywhere except within the bore of the LGR and in the space directly between the transmitter and the receiver. Furthermore, we show that the TLGR system can be operated efficiently at a fixed frequency for a wide range of transmitter–receiver distances. The experimental results are complimented by 3-D finite-element simulations that were used to investigate the electromagnetic field profiles and surface current density distributions. Finally, we demonstrate the use of our IPT system at powers up to 32 W and discuss possible applications. [ABSTRACT FROM AUTHOR]

In this study, a new field-programmable gate array (FPGA)-based electromagnetic stirrer system was developed allowing mixing on a single axis, and the energy efficiency of the system was increased with fuzzy logic control. The electromagnetic stirrer system was designed with three phases and each phase is fed with pulsewidth modulation (PWM) voltage with 120° phase difference. Ranked control of phases in the system used the FPGA structure in the myRIO® embedded system to determine the PWM signal production, increase intervals for phase frequencies, and rotation rate of the magnetic stir bar. In the system, to increase the energy efficiency with fuzzy logic control, the ARM® microcontroller structure in the myRIO® embedded system was used. Programming of the myRIO® embedded system was provided through the graphic-based LabVIEW® software. In situations where the system is operated with 100% duty cycle, the force affecting the magnetic stir bar should be continuous and have fixed value until the next phase change. As a result, the magnetic stir bar performs more than 120° rotation and a braking effect of the force is observed. To resolve this situation, fuzzy logic control ensured operation of a different duty cycle without loss of speed of the stir bar. Thus, the energy efficiency of the system was increased with lower current and lower stimulation duration. Within the scope of this article, the experimental results obtained about the structure, control, and energy efficiency of the electromagnetic stirrer system are discussed in detail. [ABSTRACT FROM AUTHOR]

In inductive pulsed power supplies (IPPSs), the toroidal circular disk-type inductors have the advantages of high energy density, good symmetry, and slight magnetic field interference. However, the inductance calculation of the toroidal coils with a different geometric structure and electrical connection is very complicated, let alone the overall optimization of the IPPS system using structure parameters as variables. In this article, a systematic quick calculation method for the toroidal circular disk-type inductor with any geometric structure and electrical connection has been summarized and elaborated. Some improvements in accelerating the calculation speed have been proposed and verified. The error between the proposed calculation method and measurement is less than 1.1%. Finally, with the quick calculation methods, the genetic algorithm (GA) is used to optimize a 20-stage inductor for an XRAM generator with a total energy of 1.25 MJ. After 12 400 calculations, the energy density of the obtained optimal toroidal coil reaches 14.54 MJ/m3. [ABSTRACT FROM AUTHOR]

The power industry is changing rapidly. One approach to accommodate a part of the change is the use of energy storage, in particular superconducting magnetic storage systems (SMES). Both solenoidal and toroidal magnets storing a few megajoules have been designed and valuated for this application. Solenoidal magnets have extensive stray fields, which are one of the serious limitations. Toroidal magnets require more conductor and are more complicated in terms of construction and insulation. The existing power systems require 100 s of megawatts of power from energy storage systems, whereas the power capacity of a single SMES installation will be quite limited. Modular SMES may provide a solution to this limitation. This article describes a 3 MJ/2 MW modular toroidal SMES using YBCO tape. The design approach is aimed at the reduction of the insulation requirement; and a slit structure of the cooling plate is designed to reduce the eddy current loss. The cooling process and losses of the magnet are analyzed. [ABSTRACT FROM AUTHOR]

BabyIAXO, a 20 m-long telescope aiming at the search for solar axions, is planned since late 2017 as a smaller scale but fully functional demonstrator of the International Axion Observatory (IAXO). It essentially comprises a superconducting magnet, optics and X-ray detectors, installed on a Sun-tracking drive system providing rotation and tilting of the detector. The preliminary design of the BabyIAXO magnet has been developed with time and the most recent modifications are reported. The magnet concept is based on using Al-stabilized NbTi conductor in a common-coil winding layout, fully resembling the baseline IAXO design and providing two free bores of 700 mm diameter and 10 m length with a magnetic field of about 2 T. The key challenges for construction and operation of the conduction cooled 40 MJ BabyIAXO magnet are addressed, such as procurement of the conductor, quench protection of the magnet components and magnetic shielding of vacuum and cryogenic equipment. Following the lab-scale experiments carried out to verify the magnet concept, their relevance and main results are further discussed before taking up the construction of the full project anticipated in 2020. [ABSTRACT FROM AUTHOR]

AC losses deposited in the magnets during JT-60SA commissioning and operation will both affect the local stability of the conductor and act as a load on the cryogenic system. Our objective is thus to establish a detailed modeling of AC losses generated in the magnets by different current scenarios. Since the TF coils have been tested in the Cold Test Facility (CTF) and will be the first ones to be fully energized during the commissioning, we have focused our work on the AC losses deposited in the TF; this enables us to assess the relevancy of our modeling against the CTF data. We also present thermohydraulic simulations conducted with TACTICS (a CEA tool coupling THEA and Cast3m) to both have a view on heat load propagation inside TF winding pack and estimate the impact on the helium temperature of the AC losses generated by the TF fast discharge during the cold tests and the commissioning. [ABSTRACT FROM AUTHOR]

The aim of this article is to describe and model a sawtooth crash in RFX-mod2 and compute the eddy currents induced in the stabilizing shell surrounding the plasma for two alternative gap concepts and the subsequent error field. The sawtooth crash displacement of the plasma column is represented by a vacuum model coupled with a suitable magneto-quasi-static (MQS) volume integral (VI) formulation. [ABSTRACT FROM AUTHOR]

Toroidal multipoles, together with electric and magnetic multipoles, provide a complete description of electromagnetic responses of matter. The fundamental toroidal resonance has been extensively achieved and investigated in nanooptics, showing great ability to increase light absorption and light force. In this paper, we obtained plasmonic toroidal dipole resonance in core-shell (dielectric-core/gold-shell) nanodisk and demonstrated an enhanced second harmonic generation (SHG) from this resonance. It was shown that the toroidal dipole resonance based SHG depends on the refractive index of dielectric-core. For large refractive index cases, head-to-tail magnetic dipole pairs form a close loop, which is a signature of toroidal dipole and results in the enhancement of SHG. In addition, the frequency of this SHG red shifts as the refractive index of dielectric-core increases. We also investigated the cases in which the dielectric-core is filled with several common materials. Moreover, the toroidal resonance based SHG depends on both inner and outer radius of the core-shell nanodisk. Such results may serve for the developments of nonlinear nanooptics and their applications. [ABSTRACT FROM AUTHOR]

Joint TEXT (J-TEXT) is an iron-core tokamak. The iron core can reduce the requirement of heating power supplies, and it also has a significant effect on the poloidal magnetic field during J-TEXT discharge. However, it is difficult to simulate an iron-core tokamak discharge process for many tokamak simulation codes (TSCs), such as TSC and DINA. Thus, the influence of the iron core on the J-TEXT magnetic field is analyzed by the theoretical model and the ANSYS model and compared with experimental results. ANSYS simulation shows that the influence of the iron core on the toroidal magnetic field can be ignored, but it has a significant impact on the poloidal magnetic field. By the comparison of ANSYS simulation and experimental results, the correction coefficient of the poloidal field with and without iron core is obtained, which can be used in some non iron-core TSC. [ABSTRACT FROM AUTHOR]

We report the construction of Polaris, a new linear plasma device with an axial magnetic field dedicated to research and education at the American University of Beirut in Lebanon. The goal is to initiate the investigation of topics related to basic magnetized plasma physics and nuclear fusion. We discuss the novel technical solutions found to set up various components of the device. We start with the magnetic coils where we use power cables to generate the required axial magnetic field. They are included in a stainless steel case for water-cooling. Then, we present the vacuum and the gas inlet systems with which we control the neutral pressure. The way we manufacture the water-cooled radio frequency (RF) antenna allows the production of a variety of designs. Polaris is thus built to operate in a steady state. Using a reciprocating Langmuir probe, we determine the plasma properties as a function of the various control parameters. As the plasma remains in the “blue mode,” we show that the increase in the main magnetic field leads to an increase in the density but a decrease in the plasma temperature. The increase in neutral pressure yields the same effects. However, the increase in RF power leads to an increase in both density and temperature. Finally, plans for future investigations are briefly described. [ABSTRACT FROM AUTHOR]

This article presents the design and characterization of a direct current (dc) sensor utilizing the Hall effect in AlGaN/GaN 2-D electron gas (2DEG) four-terminal devices and a flux concentrator. The sensor was fabricated from an AlGaN/GaN/Si wafer grown by metal-organic chemical vapor deposition. The sensor exhibited excellent linearity and repeatability with a high Hall voltage under the primary current ranging from −5 to 5 A. The sensitivity of the sensor was measured to be 0.26 (V/A)/A at 20 °C and independent of ambient temperature up to 200 °C. The obtained result is greater than that of other reported Hall effect-based current sensors. The high sensitivity and thermal stability at varying temperatures are attributed to the high electron mobility, wide bandgap, and stability of carrier density in 2DEG. Combining these factors with the excellent mechanical strength, electrical conductivity, and chemical inertness of GaN, the proposed sensor is promising for current monitoring in a wide range of operation temperatures. [ABSTRACT FROM AUTHOR]

The toroidal field (TF) coil is a crucial system in the tokamak, which provides the main magnetic field to confine the plasma. One TF coil of the China Fusion Engineering Test Reactor (CFETR) will be constructed with the support of the Chinese government in the next five years. In order to study the quench behavior of the CFETR TF coil, the assumed quench initiation at the maximum and minimum temperature margin position of the TF coil is analyzed, and the effect of the quench detection threshold on the hot spot temperature is studied. It is found that 0.5 V quench detection voltage leads to hot spot temperature above 250 K in the low-field region. In order to meet the design criteria of the hot spot temperature, the quench detection voltage should be less than 0.2 V. [ABSTRACT FROM AUTHOR]

This article presents a novel toroidal metasurface that is able to support a toroidal response at almost all incident angles for a transverse magnetic (TM) wave at the microwave range. A flat band is observed from the calculated band structure where the radiation power of the toroidal response is highest around 7.51 GHz. A high transmission at a resonant frequency is observed from the simulated and measured transmission coefficients with different incident angles, whereas the transmission is lower at the rest frequency range. The resonance frequency at a high sensitivity of 0.78 GHz/refraction index unit (RIU) is experimentally demonstrated, which is very sensitive to the thickness and the refraction index of the surrounding materials such that the proposed toroidal metasurface could be used for a tunable highly efficient filters. [ABSTRACT FROM AUTHOR]

In tokamak operation, the control of dangerous MHD instabilities, possibly in real-time scenarios, must rely on prompt robust diagnostics of the state and stability of the system. The set of magnetic signals measured on the outside of the plasma boundary, based on the Zakharov–Shafranov, Shkarowsky, Wootton (ZSSW) current moments, has been always used for reliable monitoring of key characteristics of the instantaneous equilibrium condition, such as the quantities $\Delta _{\mathrm{ Sh}}$ , the Shafranov centroid shift, $\beta _{p} $ related to the thermal energy content, and $l_{i}$ related to the current profile peakedness. In addition, the fast pickup coils monitor the external magnetic field fluctuations due to internal MHD activity, however, without the possibility of radial localization of the source. Here, we explore the potential usefulness of more complete use of ZSSW moments in association with the information from fast B perturbation signals to detect tearing stability conditions. For clarity, we set up an analysis of the measurable response to tearing perturbations based on an exact equilibrium model, which is an extension of the Solov’ev case with the addition of an equilibrium, nonuniform plasma rotation $\Omega (\psi)$. The relation of the selected (externally measurable) ZSSW moments to the calculated stability index is mapped for different rotation values. The footprint of the stability condition $\Delta '< 0$ on some current moments on the outer surface can then identify stability boundaries for different rotation conditions. This first discussion on an idealized exact model is proposed for testing the concept for application to realistic equilibria since it relies on a few externally monitorable quantities and very basic assumptions on the tearing modes physics. [ABSTRACT FROM AUTHOR]