Outer Coil Research Articles

Cubic coil system composed of three sets of cubic triple coils to produce wide area 0.66% uniform magnetic field in any direction.

A cubic coil system, which combines three sets of cubic triple square coils orthogonal to each other, is proposed, constructed, and tested. This coil system can generate a 0.66% (=±0.33%) uniform magnetic field in any direction over a large region of ∼2m, although there is some ripple. This system has the advantages of easy assembly, self-standing, and easy access to internal instruments. In one set of cubic triple square coils, the outer two square coils form a cube, and the middle square coil is located at the center of the cube. The number of turns in the center square coil is proposed to be 0.6 times that of the outer square coil.

Electromagnetic characteristics analysis of dual-frequency magnetic single negative metamaterials

Abstract With the development of multi-frequency wireless transmission technology, it is necessary to expand the research of single-frequency metamaterials in the multi-frequency field. The dual-frequency metamaterial studied adopts a nested square spiral structure, which can resonate at two frequencies, and the real part of the equivalent permeability of metamaterial changes dramatically at the resonance frequency, and the equivalent electromagnetic parameter exhibits anomalous characteristics in the two frequency bands. Firstly, the effects of the number of turns, the width of the copper wire, the spacing of the copper wire, and the length of the outermost edge of inner and outer helical coils are investigated, respectively, using the HFSS software on the resonance frequency of dual-frequency metamaterials, which improves the study of dual-frequency metamaterials with nested square spiral structure. Then, based on the results of the change rule of resonance frequency with the four types of influencing factors, the dual-frequency metamaterials with the real part of the equivalent permeability close to -1 at 6.78 MHz and 13.56 MHz are designed, which is of certain reference significance for the subsequent practical design of dual-frequency metamaterials to satisfy the needs of the project.

Optimization of transcutaneous energy transmission system suitable for implanted devices

Abstract Microdevices have been implanted in the body to diagnose diseases and treat functional disorders, such as an artificial sphincter for fecal incontinence. Since these devices are expected to work in the body as long as possible, the energy supply has become increasingly important. Wireless power transfer (WPT) systems are suitable for medically implanted devices. A transcutaneous energy transmission (TET) system, as one of the wireless power transfer systems, is discussed in this article. A TET system comprises two coils: a transmitter coil and a receiver coil. First, a serial-serial resonance circuit is adopted in the TET system by different resonance circuits’ efficiency analysis. In addition, coil features, such as magnetic field intensity, coil outer diameter, coil turns, and coil inner diameter, have been investigated in detail to improve the inductive coupling coefficient, leading to a high-power transmission efficiency. The proposed TET system with the optimal parameters is used in the in vivo experiments. Experiments using an optimized wireless power transfer system show a better performance than previous (before optimization) with a 38% increase in efficiency.

Conceptual design study of a large bore superconducting test facility magnet, SUCCEX

A 16 Tesla, large bore superconducting magnet for testing the superconducting Cable-in-Conduit Conductor (CICC) is being designed in parallel with the design of the steady state Korea fusion demonstration reactor (K-DEMO) magnet system. The test facility magnet, named SUperConducting Conductor Experiment (SUCCEX), was designed in 2014 and some design modifications of the magnet have been conducted since 2020. The peak magnetic field of the K-DEMO toroidal field coil is about 16 T, and thus the required background field of the conductor test magnet is expected to be over 15 T in a large bore of 600 mm diameter. The background field will be in addition to the K-DEMO conductor sample's self-field. To reach the target magnetic field, high current density Nb3Sn strands (Jc > 1100 A/mm2 at 4.2 K, 16 T) were employed in the design of the high field CICC. The modified SUCCEX magnet consists of concentric solenoids, with a high field inner coil (IC) and low field outer coil (OC). They are connected in series with each other, and the operating current is about 24 kA. In this study, the overall design concept is presented in relation to the results of electro-magnetic, structural analyses.

Three-dimensional fluid simulation of a planar coil inductively coupled argon plasma source for semiconductor processes

In this paper, the effect of the coil structure, as well as the gas pressure, on the spatial distribution of an inductively coupled argon plasma is numerically investigated based on our developed three-dimensional fluid model. The model is based on a modified ambipolar diffusion model, in which the electron density is solved under the quasi-neutral condition, the ion density and neutral particle density are obtained by solving continuity equations, and the ion flux is achieved by solving the full momentum balance equation. In addition, the inductive electric field is governed by the Maxwell equations, which are solved in the frequency domain. The results show that the electron density is nonuniform along the azimuthal direction due to the asymmetry of the coil structure, and the uniformity becomes better as gas pressure decreases. Besides, the plasma azimuthal uniformity can also be improved by reducing the opening of the coil. As the coil radius increases, the plasma density decreases, while the radial uniformity of the plasma improves, and the azimuthal uniformity deteriorates. In addition, the influence of the current amplitude ratio between the inner coil and outer coil on the plasma uniformity in dual-coil discharge is also investigated. It is found that the plasma radial uniformity becomes better by reducing the inter-to-outer coil current amplitude ratio. The results obtained in this work demonstrate that the plasma uniformity can be improved by optimizing the coil structure and adjusting the discharge parameters, which is of significant importance in etching and deposition processes.

Comprehensive analysis and design optimization of temperature distribution in radiant heaters for cooking applications

The temperature distribution inside a radiant heater for cooking purposes has not yet been fully investigated. A numerical methodology was developed to analyze the heat transfer inside a radiant heater. The numerical methodology was validated by experimental analysis, which showed close agreement for the temperature distributions of the heating coil and glass. Then, a parametric study was performed on the pitch of the heating coil, gaps in the inner coil (i.e., inner gap), and gaps in the outer coil (i.e., outer gap). The outer gap had an insignificant effect on the temperature distribution, but the coil and glass temperatures increased linearly as the pitch and inner gap were decreased. The design of the radiant heater was then optimized in terms of thermal stability. A heat loss analysis was carried out, and the numerical results showed close agreement with the experimental results in the case of 10 % heat loss. The results of this study can be used to predict the performance of a radiant heater and optimize its design.

Numerical study of heat transfer characteristics of organic heat carrier furnace chamber

The heat transfer oil in the organic heat carrier furnace (OHCF) is prone to deterioration and deterioration at higher operating temperatures, resulting in overheating of the furnace tube and bursting of the tube, resulting in safety accidents. Therefore, it is necessary to study and analyze the flowing heat transfer characteristics of organic heat carriers in the furnace tube. The paper takes YY(Q)W-180(15) OHCF as the research object, mainly through ANSYS CFX numerical simulation method, to analyze the influence of influencing factors: inner and outer spiral tube spacing R, oxygen content, air preheating degree T and excess air coefficient on the temperature field, velocity field and NOx concentration inside the OHCF, and found that the organic heat carrier in the oxygen concentration of 25%, air preheating The thermal efficiency of the furnace is higher and the pollutant content emitted at the exit of the furnace is lower when the oxygen concentration is 25%, the air preheating temperature is 498 K and the excess air coefficient is 1.10. Also, the smaller the inner coil spacing R1 and the outer coil spacing R2 from the furnace wall, the higher the overall furnace chamber temperature.

Numerical modeling and parametric study of the heat storage process of the 1.05 MW molten salt furnace

The implementation of thermal storage technology in the steel industry has the potential to reduce carbon emissions and contribute to a more sustainable future for the planet. Utilizing molten salt furnaces to convert waste heat from blast furnace gas into thermal energy from molten salt is an innovative approach. In this study, the heat flux density data calculated using ANSYS FLUENT were imported into a MATLAB calculation program developed based on the multi-section lumped parameter method to model the three-dimensional transient thermal performance calculations of the molten salt furnace. A benchmark energy storage experiment on a 1.05 MW furnace validated simulation results. The experimental molten salt outlet temperature is 566.5 °C, 13.92 °C higher than the simulation data with 2.46% deviation. The study investigates the dynamic characteristics of thermal energy storage in molten salt furnaces by disturbing external parameters. Results show that molten salt temperature rise is linearly related to heat flux density, molten salt inlet temperature, and mass flow rate. Notably, every 0.8 kg/s increase in molten salt mass flow rate reduces the outer coil temperature by 6.59%. The highly accurate model provides a reference for the design, control and commissioning of molten salt heating and thermal storage systems.

A Design Study on HTS Halbach Array for Field Coil of 40 MW Ship Propulsion Motor

A 40 MW ship propulsion motor was designed with a high temperature superconductor coil Halbach array. The Halbach array was applied to the field coil of the motor for further performance improvement. We performed our design study on two different motor types: Halbach array inner positioned field coil motor (HIFM) and Halbach array outer positioned field coil motor (HOFM). The design for the field coil was optimized with NSGA-II. Final models were selected for HIFM and HOFM, respectively, and to estimate the effect of the HTS coil Halbach array, they were compared with reference motors with a conventional field coil. Both HIFM and HOFM showed a 7% increase in the flux to the air-gap. As the shielding effect of the Halbach array in HOFM reduced by 70% the weight of the iron shield, HOFM showed comparable weight compared to the conventional inner field coil motor. This overcomes the problem of the low power density of the outer field coil motor. With the Halbach array field coil, a design topology having the stationary field coil on the outer side of the motor would be realized with a simplified cooling structure while maintaining the light shield weight.

Sudden-Discharging Quench Dynamics in a No-Insulation Superconducting Coil.

It is generally agreed that no-insulation (NI) high-temperature superconducting (HTS) magnets do not quench because of the turn-to-turn energy-releasing bypass unique to NI. However, these magnets, especially with high operating current and low ambient thermal capacity, still occur unexpected quenches when the current through the magnets suddenly drops to zero (i.e., the sudden-discharging quench). Here, we report this kind of quench, which is different from that widely-reported quench happening during charging (i.e., the energizing quench). Here, a demonstrative coil with 655-turns, 350 A operating current, and 4 K conduction cooling, is used to prove this sudden-discharging quench, and a simulation model is built to reveal the quench dynamics. Results show the turn-to-turn heat triggers the initial partial quench in the inner coil turns and then the induced overcurrent spreads out the quench like an avalanche to the outer coil turns.

Modulation of the plasma radial uniformity in pulsed dual-antenna inductively coupled plasmas

Pulse modulation in inductively coupled plasmas (ICPs) has been proven as an effective method not only to restrain the charging effect in etching trenches but also as a potential approach to ameliorate the plasma uniformity. In this paper, a two-dimensional fluid model is employed to systematically study the modulation of the radial uniformity in pulsed dual-antenna Ar ICPs. The inner four-turn coils are connected to a continuous wave at the current of 5.0 A, and the outer three-turn coils are pulse modulated at various duty cycles and currents. The results indicate that when the outer coil current is fixed at 7.0 A, the electron density always shows an off-center distribution during the active-glow period when the duty cycle increases from 20% to 60%, due to the stronger electric field induced by the higher outer coil current. Although the ionization mainly happens at the reactor center during the after-glow period, the electron density distribution evolves from a center-high profile to a rather uniform distribution as duty cycle increases. Under the combined influence, the time-averaged electron density over one pulse period shifts from center-high over uniform to edge-high. When the pulse duty cycle is fixed at 50%, the time-averaged electron density distribution shifts from a center-high profile over uniform to an edge-high profile, as the outer coil current increases from 5.7 to 7.7 A. The results obtained in this work could help to optimize the plasma radial uniformity, which plays a significant role in improving the large-area plasma processing.

Field Study of Novel Storage Tank of Solar Water Heating System

In this paper thermo-hydrodynamic characteristics were investigated experimentally for a new type shell-helical coiled tube heat exchanger used as a storage tank of closed loop solar water heater system. Triple concentric helical coils were made of copper tubes of (12.5mm OD and 10mm ID) with coils diameter of (207, 152.2, 97mm) for outer, middle and inner coils respectively. The experiments were carried out during a clear sky days of (March and April 2012). The parameters studied in this work are: history of average temperature of shell side of the storage tank, collector heat gain, heat rejected from coils to shell side of the storage tank, collector efficiency, thermal effectiveness of the heat exchanger (storage tank), and pressure drop. These parameters were studied at four different circulating mass flow rates of (1.8, 3, 6, 9 l/min) and for two consuming modes of supply water namely no withdrawal, and continuous withdrawal of (1 l/min). The results show that stratification temperature in the storage tank is increased for no withdrawal compared with water withdrawal, also the shell side average temperature increases with increased solar time. Collector efficiency is increased with increasing circulation flow rates, also increases with water withdrawn from storage tank. The pressure drop decreases with the increase of solar radiation .

Essure removal surgery: Are preoperative transvaginal ultrasound and pelvic X-ray necessary?

ObjectiveThe objective of this study was twofold. (1) To investigate the predictive characteristics of transvaginal ultrasonography for hysteroscopy necessity in Essure removal surgery. (2) To investigate the additional predictive value of a preoperative pelvic radiograph to transvaginal ultrasonography for hysteroscopy necessity. Study DesignRetrospective cohort study, performed in an academic and a non-academic teaching hospital in the Netherlands. 71 women who underwent Essure removal surgery with a perioperative hysteroscopy and who had a preoperative pelvic X-ray and transvaginal ultrasound were included. Four experts first predicted hysteroscopy necessity based on transvaginal ultrasound description and secondly based on transvaginal ultrasound combined with the preoperative pelvic radiograph. Sensitivity, specificity, positive predictive value and negative predictive value of the predictive tests were calculated. ResultsBased on transvaginal ultrasound, the mean predictive characteristics for experts were: sensitivity 89.7% (range 66.7%–100%), specificity 37.4% (range 17.6%–67.7%), positive predictive value 18.8% (range 13.2%–29.5%) and negative predictive value 95.1% (range 86.1%–100%). After adding the pelvic radiograph to the transvaginal ultrasound descriptions, the results were: sensitivity 66.7% (range 53.3%–80%), specificity 72.6% (range 56%–97.3%), positive predictive value 23% (range 14.3%–26.9%) and negative predictive value 94.1 % (range 90.3%–98.4%). For three experts sensitivity decreased after adding the pelvic radiograph. For all experts specificity increased. ConclusionIt is difficult to preoperatively decide if the fourth marker of the Essure outer coil can be excised during hysteroscopy. The addition of pelvic radiography to transvaginal ultrasound is not beneficial. It is recommended to perform a hysteroscopy during Essure removal surgery.

Direct stellarator coil optimization for nested magnetic surfaces with precise quasi-symmetry

We present a robust optimization algorithm for the design of electromagnetic coils that generate vacuum magnetic fields with nested flux surfaces and precise quasi-symmetry. The method is based on a bilevel optimization problem, where the outer coil optimization is constrained by a set of inner least squares optimization problems whose solutions describe magnetic surfaces. The outer optimization objective targets coils that generate a field with nested magnetic surfaces and good quasi-symmetry. The inner optimization problems identify magnetic surfaces when they exist, and approximate surfaces in the presence of magnetic islands or chaos. We show that this formulation can be used to heal islands and chaos, thus producing coils that result in magnetic fields with precise quasi-symmetry. We show that the method can be initialized with coils from the traditional two-stage coil design process, as well as coils from a near-axis expansion optimization. We present a numerical example where island chains are healed and quasi-symmetry is optimized up to surfaces with aspect ratio 6. Another numerical example illustrates that the aspect ratio of nested flux surfaces with optimized quasi-symmetry can be decreased from 6 to approximately 4. The last example shows that our approach is robust and a cold-start using coils from a near-axis expansion optimization.

Cage-Embedded Crown-Type Dual Coil Wireless Power Transfer Based Microwave Brain Stimulation System for Untethered and Moving Mice.

This study proposes a novel brain-stimulated mouse experiment system which is insensitive to the variations in the position and orientation of a mouse. This is achieved by the proposed novel crown-type dual coil system for magnetically coupled resonant wireless power transfer (MCR-WPT). In the detailed system architecture, the transmitter coil consists of a crown-type outer coil and a solenoid-type inner coil. The crown-type coil was constructed by repeating the rising and falling at an angle of 15 ° for each side which creates the H-field diverse direction. The solenoid-type inner coil creates a magnetic field distributed uniformly along the location. Therefore, despite using two coils for the Tx system, the system generates the H-field insensitive to the variations in the position and angle of the receiver system. The receiver is comprised of the receiving coil, rectifier, divider, LED indicator, and the MMIC that generates the microwave signal for stimulating the brain of the mouse. The system resonating at 2.84 MHz was simplified to easy fabrication by constructing 2 transmitter coils and 1 receiver coil. A peak PTE of 19.6% and a PDL of 1.93 W were achieved, and the system also achieved an operation time ratio of 89.55% in vivo experiments. As a result, it is confirmed that experiments could proceed for approximately 7 times longer through the proposed system compared to the conventional dual coil system.

Utility of a multipurpose catheter for transvenous extraction of old broken leads: A novel technique for fragile leads

Transvenous lead extraction has been possible since the 1980s. However, complications during lead extraction, such as the distal end fragment of the lead remaining in the myocardium or venous system and injury to the veins or heart, have been reported. The purpose of this study was to examine our method for complete removal of a separated lead, as extraction of long-term implanted devices is difficult using standard methods and may require additional procedures. The removal of leads with inner conductor coil and lead tip separated from outer insulation, conductor coil, and proximal ring electrode using a multipurpose catheter is reported. In total, 345 consecutive patients who underwent transvenous lead extraction (TLE) from April 2014 to March 2021 were retrospectively analyzed. Lead characteristics, device type, and indications for extraction were further analyzed in 20 patients who developed separation of the proximal ring electrode and outer conductor coil from the inner conductor and distal tip at the time of extraction. Extractions were performed using an excimer laser sheath laser and a Byrd polypropylene telescoping sheath (n = 15); laser, Byrd polypropylene telescoping sheath, and Evolution RL (n = 2); laser and Evolution RL (n = 3); Byrd polypropylene telescoping sheath and Evolution RL (n = 1); Byrd polypropylene telescoping sheath only (n = 4); and Evolution RL only (n = 2). Twenty-seven leads implanted for more than 10 years had lead separation. A multipurpose catheter was used to protect the fragile leads from further damage. All leads were completely extracted. All distal tip-to-proximal ring electrode separated leads were successfully removed using laser and other sheaths with the assistance of a multipurpose catheter, without any part of the leads remaining in the heart.

ST-40 HALL TRUSTER TESTING WITH LaB6 HOLLOW CATHODE


 
 
 The results of experimental investigation of the ST-40 Hall thruster operating with a heating hexaboride cathode are presented. The readiness of the heating hollow cathode to the thruster start was assessed by reducing the cathode keeper voltage from the start value of 100 V to 15 ... 17 V, when an internal discharge in the hollow cathode occurred. Various cyclograms of the thruster start are considered with the definition of the purpose of the cyclogram, which ensures reliable thruster start. Three cyclograms of the thruster start are investigated: with the thruster’s electromagnet coils switched on; with the coils off; without switching off the voltage at the hollow cathode keeper, which made it possible to restart the thruster without preheating the hollow cathode. The obtained cyclograms make it possible to ensure a reliable start of the ST-40 thruster when operating with a heating hexaboride hollow cathode. In the course of laboratory research, the PPU-300 power processing unit was used. It ensured the stabilization of the discharge power in the thruster’s accelerating channel and stabilization of the currents supplied to the central and external coils of the thruster. The main operating characteristics and parameters of the ST-40 thruster were obtained for three fixed values of the discharge power: 265, 281, 300 W and a change in the mass flow rate of the working substance (Xenon) through the anode unit of the thruster 0.7 ... 1.3 mg/sec. Experimental investigation of the ST-40 thruster in a wide range of parameters made it possible to determine the optimal thruster’s parameters that provide the maximum values of thrust and specific impulse for the given values of the discharge power in the accelerating channel of the thruster and the minimum discharge current. The process of the thruster’s parameters optimizing was carried out by changing the currents flowing through the internal and external coils of the thruster. In the course of experimental research, it was found that the inner coil and the serially connected outer coils can be connected in parallel and powered by a single power supply. Experimental studies have confirmed the correctness of the adopted technical solutions in the development of the ST-40 Hall thruster and the heating hexaboride hollow cathode.
 
 

Analysis of Coil-Thickness-Variation Technique for Q-Factor Enhancement of Rectangular Planar Coils

For wireless power transfer (WPT) applications, such as battery charging, the attainment of a high coil quality factor ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> ) becomes prudent to ensure a high-power transfer efficiency (PTE). In this article, we demonstrate an effective method to enhance <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> by employing different thicknesses for each trace of the coil. The thickness of the inner turns of the coil, where high alternating current (ac) losses are concentrated, is relatively smaller compared to the outer coil turns. This technique realizes a reduction in the ohmic resistance, thereby increasing <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> of the coil. Furthermore, we present the analysis on the performance of the conventional coils with the same turn thicknesses compared to the proposed coil. To validate this technique, the prototypes of both the proposed and conventional coil structures are fabricated, where good agreement is achieved between the simulation and measurement results. The proposed coil realizes an increment of about 11.54% in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> compared to the conventional coil.

Tooth whorl structure, growth and function in a helicoprionid chondrichthyan Karpinskiprion (nom. nov.) (Eugeneodontiformes) with a revision of the family composition

ABSTRACTRestudy of Campyloprion annectans Eastman, 1902 from North America demonstrated that neither specimen included is diagnostic at the species level; thus, the species name is a nomen dubium. Since this species was designated as the type species of the genus, this requires suppression of the generic name also. Another species earlier assigned to Campyloprion, Campyloprion ivanovi Karpinsky, 1924 is used as a type for a newly established genus Karpinskiprion Lebedev et Itano gen. nov. The composition of the family Helicoprionidae Karpinsky, 1911 is reviewed, and a new family Helicampodontidae Itano et Lebedev fam. nov. is erected. A new specimen of Karpinskiprion ivanovi (Karpinsky, 1924) recently discovered in the Volgograd Region of Russia is the most complete Karpinskiprion specimen ever found. It unambiguously demonstrates the coiled nature of these tooth whorls and presents information on their developmental stages. During organogeny, cutting blades of the crown became reshaped, and basal spurs progressively elongated, forming a grater. Whorl growth occurred by addition of new crowns to the earlier mineralised base followed by later spur growth. In contrast to consistently uniform cutting blades, spurs are often malformed and bear traces of growth interruption. Both sides of the outer coil of the tooth whorl bear lifetime wear facets. The youngest (lingual) crowns are as yet unaffected by wear. The best-preserved facets show parallel radially directed scratch marks. The upper jaw dentition of Karpinskiprion is unknown, but we suggest that the faceted areas resulted from interaction with the antagonistic dental structures here. Three possible hypotheses for this interaction are suggested: (a) two opposing whorls acted as scissor blades, moving alternately from one side to another; (b) the lower tooth whorl fitted between paired parasymphyseal tooth whorls of the opposing jaw; or (c) the lower tooth whorl fitted into a dental pavement in the upper jaw.

A New Magnetic Coupler With High Rotational Misalignment Tolerance for Unmanned Aerial Vehicles Wireless Charging

In this letter, a novel magnetic coupler with high rotational misalignment tolerance is proposed for unmanned aerial vehicles (UAVs) wireless charging. The transmitting coil consists of an inner coil and an outer circular coil connected in series, which generates a horizontal magnetic field from the center to all periphery directions within the charging range. Then, to receive the flux effectively and to adapt to UAV's structure, a vertical square air-core coil is designed and attached to the landing gear. The proposed magnetic coupler can reduce significantly the magnetic fluxes penetrating through the body of the UAV, therefore mitigating electromagnetic interference with onboard devices. Simulation based on ANSYS Maxwell and experiments based on a laboratory prototype are carried out to validate the proposal. The results show that, the proposed magnetic coupler can transmit power in all 360° of rotational misalignments, and the output voltage of the wireless charging system fluctuates only 2% around the 48 V reference.