Solenoid Research Articles

Performances of the First Full-Length Module Prototype of the MgB$_\text{2}$ Round Coil Superferric Magnet at LASA

Developed within the INFN LASA and CERN collaboration agreement for the construction of the High Order Corrector Magnets for the High Luminosity-LHC project, the first half section of the Round Coil Superferric Magnet proved the feasibility of a new compact and modular corrector magnet type using MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> superconductor. Different from the classic superferric layout, its unconventional design exploits the iron permeability to shape, with an arbitrary number of poles, the solenoidal field created by a large bending radius coil suitable for strain-sensitive superconductors. After the design upgrade of the winding and impregnation process, in this paper, we describe the realization of the second superconducting coil for the full module length prototype of the sextupole corrector. The integration of the two half-sections of the magnet module is analyzed in detail and the performances of the newer one, during tests at cryogenic temperature, are compared with the older results. Finally, the powering test of the full module and its magnetic field characterization are described and compared with the electromagnetic simulations and expected performances.

Construction and Commissioning Status of the Superconducting Magnets for COMET Phase-I Experiment at J-PARC

A new muon beamline is under construction for the COMET Phase-I experiment at J-PARC. The experiment requires a negative muon beam with the world-highest intensity to search for muon-electron conversion processes. The muon beamline consists of a series of superconducting solenoid magnets to generate muons by 8 GeV pulsed proton beam from MR of J-PARC, to transport muons to the detectors. A radiation-tolerant superconducting solenoid, the Pion Capture Solenoid, is developed to generate a high magnetic field on a production target to trap pions and muons efficiently. A long curved solenoid, the Muon Transport Solenoid, with correction dipole coils is utilized not only to transport muons but also to select low-momentum muons against unnecessary particles. A large detector solenoid is planned to connect to the muon beamline with a gradually reduced solenoidal field tuned by additional small solenoids. This paper reports the status of the construction and commissioning of the superconducting magnet system.

ELECTRON BEAMS IN THE GRADIENT MAGNETIC FIELD: CONTROL FOR CONVERTING LONGITUDINAL MOTION INTO TRANSVERSAL

The motion of electrons in a cylindrical magnetic field with the gradient-type potential is considered. The motion of electrons in the cylindrical magnetic field with the gradient-type potential is considered. It is found that in the selected field, the initial motion of electrons along the longitudinal axis is converted into motion along the radius. It is determined that such the transformation is due to the action of a solenoidal magnetic field with large longitudinal gradient. The transformation of the longitudinal direction of motion into the transverse one turned out to be stable in the energy range of 20...55 keV of electrons and in the range of 5...50 mm of radial dimensions of the particle beam. The main dependences of the motion of the electron beam in the given solenoidal magnetic field are studied with the help of the software tool. The results of numerical simulation of electron trajectories in the gradient magnetic field with the circular secondary emission cathode located in the middle of the system are presented. To study the mechanism of stability with respect to magnetic field, two experimentally realized magnetic fields were used. Based on these two fields, arrays of additional 4 fields are numerically synthesized. For the set of 6 named fields, the operation of the gun, in which the particle undergoes the stable transformation of the direction of motion, is numerically studied. It is shown that for the given electron energy and the fixed magnetic field, the parameter that determines the rotation of the particles is the magnetic field gradient at the boundary of the entry region. It is found that the rotation effect takes place for the considered range of radial beam sizes, which leads to particle focusing. The possibility is shown to control the vertical coordinate of the focused beam on the basis of the field adjustment, thereby giving the interpretation of the pore dependence of the registration of electrons on the detector. The dependence of the formation of the final distribution of particles on the amplitude and gradient of the magnetic field along the axis of the system is studied. The results of numerical simulation on the motion of the electron beam are presented. Based on the model of electron flow motion, the characteristics of the resulting electron beam are considered. It is shown that the beam, having radial dimensions of 5...50 mm, is transformed and focused vertically on the area of 1 mm.

Study on a Novel Peeling of Nano-Particle (PNP) Process for Localized Material Removal on a 4H-SiC Surface by Controllable Magnetic Field

This study proposes a novel process called peeling of nano-particle (PNP) to remove material locally on a hard material surface, such as silicon carbide (SiC), diamond, and gallium nitride (GaN), using the magnetic nano-particles in an aqueous solution controlled by magnetic fields. By the concept of the PNP process, magnetic fields are generated by two solenoid coils, which are sandwiched between the hard material sample, to pull the magnetic nano-particles to adhere to and then peel the material from the sample surface. In this experiment, iron (II, III) oxide (Fe3O4) particles with a diameter size in the range of 50–100 nm were dispersed in water, and the pH value was adjusted to 10 by potassium hydroxide (KOH). The particles were magnetically controlled on the silicon carbide (4H-SiC) surface by the magnetic fields at approximately 17 mT. To confirm the contact phenomenon of the Fe3O4 particles on the 4H-SiC surface during the PNP process, an optical system was developed by applying evanescent field microscopy to limit the observation range to approximately 300 nm from the 4H-SiC surface. According to the experimental observed results, the control phenomenon of two examples of Fe3O4 particles could be observed through their scattering light, which relates to the magnetic field generating sequence wherein the particles were magnetically pulled in and out of the 4H-SiC surface in the limit range of the evanescent field. During the particle pull to the surface, particles were able to be tracked in the X–Y directions during the approach to the 4H-SiC surface. The Brownian motion ranges in all directions of the particles decreased when the particles approached close to the surface due to the pulling magnetic field. Moreover, the magnetic field enforced the magnetic moment of the particle and limited their rotation.

Stable operation characteristics and perspectives of the large-current HTS STARS conductor

The High-Temperature Superconducting (HTS) magnet option has been explored for fusion reactors as well as for next-generation fusion experimental devices. The Stacked Tapes Assembled in Rigid Structure (STARS) conductor uses HTS tapes with simple stacking without twisting and transposition. A practically applicable STARS conductor is presently being developed with an operating current of 18 kA at 20 K temperature and ~15 T magnetic field. The conductor is required to have a high current density of 80 A/mm2. For the second stage of the conductor development, internal electrical insulation is applied between the copper stabilizer casing and the outer stainless-steel jacket, and a 6-m conductor sample was fabricated in a solenoid coil shape with a 600-mm diameter and three turns. The coiled sample was tested in 8 T, 20 K using a facility equipped with a maximum 13-T, 700-mm bore solenoid coil. Excitation up to the rated current of 18 kA was successfully attained with stable operation. The characteristics of the conductor observed during the excitation test are discussed.

High-Speed Spin Testing of Bi-2212 Superconducting Wires for High-Field NMR Magnet Qualification: Final Progress Report

This paper summarizes an NIH-funded research project designed to study the strength of high temperature superconductors under high circumferential hoop stress, in order to qualify these materials for high-field (> 1 GHz-class) NMR magnets. The unique approach presented here is to spin test coils at high rotational speeds, approaching 50,000 rpm, in order to induce mechanical hoop stresses which are equivalent to the magnetic Lorentz stresses experienced by a high-field solenoid insert coil. Bi-2212 wires and coils were tested in sub-cooled nitrogen to determine if any mechanical damage was imparted by each spin test. These preliminary experimental results demonstrate that, with further development, this test could prove to be a simple method for qualifying superconducting wires for high-field insert magnets.

The effect of coating concentration of curcumin: H2O on copper winding characteristics

Each coil of copper produces a magnetic field and the total field inside the solenoid will be the sum of the fields caused by each coil of current. If the solenoid coils are very closely spaced, the internal field will be essentially parallel to the axis except at the very ends. To find out the magnitude of the magnetic field inside the solenoid, you can use Ampere’s law, namely B=μo∙N∙I, where B is the magnetic field strength (T), µo is air permeability (4×10‒7 T m/A), N is the number of turns and I is an electric current. The value of B depends on the number of turns per unit length, N, and current I. The field is independent of the position inside the solenoid, so the value of B is uniform. This only applies to infinite solenoids, but is a good approximation for actual points that are not near the ends of the solenoid. The research object is 4 identical copper coils with a length of 3 cm, a coil diameter of 2 cm, a cross section of 1.5 mm2 with an inductance value of 2.17 µH. Before coating curcumin on the copper winding, the initial value of the magnetic field strength was 2.54 µTesla. After the coating process of curcumin:H2O concentration, the value of the magnetic field strength increased. The method used was immersing 4 copper coils with an inductance value of 2.17 µH in curcumin:H2O concentration in a 100 ml volume measuring cup, with the respective concentrations: (20 %:80 %), (40 %:60 %), (60 %:40 %), (80 %:20 %) in a certain time. Then the copper coil conductor is supplied with a 5-volt DC voltage source. Then the value of the magnetic field strength (B) and electric current is measured, the results are compared with the system before immersing the copper coil. The measurement results showed that the values of electric current and magnetic field strength increased after curcumin coating compared to before treatment. To see the bonding performance of curcumin and copper, the FTIR test and simulation of the curcumin: copper bond were carried out using Avogadro software. In the IR test, there is a strong absorption of aromatic C-C from 1,650 cm-1 to 1,500 cm-1. Whereas in the simulation, the bond between copper and curcumin produces a bond energy of 164.532 kJ/mol or equivalent to 171.12×10-2 eV

Direct Steady-State Calculation of Electromagnetic Devices Using Field-Circuit Models

Field-circuit models are very often used to model electromagnetic devices with conductive and non-linear magnetic materials. The numerical calculations of the field in the magnetic material must be combined with an equation of an external coil placed in the magnetic circuit. This means that the partial differential equations of the electromagnetic field in non-linear conductive materials and the non-linear ordinary differential equations must be solved together. Effective algorithms for solving such problems are still being developed. The article presents an algorithm directly providing the steady state solution without the simulation of transients. The basic assumption is that the solution can be predicted as a periodic time and space function, which is represented by appropriate Fourier series. The developed algorithm uses discrete partial differential operators for time and space derivatives. It allows us to create finite difference equations directly from the field and circuit equations, which take the form of algebraic equations, generally non-linear. This is a unique approach developed by us, which till now did not exist (and is not mentioned) in the literature. That algorithm is tested on a simple case of a solenoid coil with a ferromagnetic and conductive cylindrical core, in 2D space of radius and time. The calculation results confirm the effectiveness of the proposed approach both qualitatively, with regard to physical phenomena in ferromagnetic and conductive material, and quantitatively, in comparison with the results from specialized commercial software.

The magnetic field design of a solenoid for the cold-cathode Penning ion source of a miniature neutron tube

A high-yield and beam-stable neutron tube can be applied in many fields. It is of great significance to the optimal external magnetic field intensity of the cold-cathode Penning ion source (PIS) and precisely controls the movement of deuterium (D), tritium (T) ions and electrons in the source of the neutron tubes. A cold-cathode PIS is designed based on the solenoidal magnetic field to obtain better uniformity of the magnetic field and higher yield of the neutron tube. The degree of magnetic field uniformity among the magnetic block, double magnetic rings and solenoidal ion sources is compared using finite element simulation methods. Using drift diffusion approximation and a magnetic field coupling method, the plasma distribution of hydrogen and the relationship between plasma density and magnetic field intensity at 0.06 Pa pressure and a solenoid magnetic field are obtained. The results show that the solenoidal ion source has the most uniform magnetic field distribution. The optimum magnetic field strength of about 0.1 T is obtained in the ion source at an excitation voltage of 1 V. The maximum average number density of monatomic hydrogen ions (H+) is 1 × 108 m−3, and an ion-beam current of about 14.51 μA is formed under the −5000 V extraction field. The study of the solenoidal magnetic field contributes to the understanding of the particle dynamics within the PIS and provides a reference for the further improvement of the source performance of the neutron tube in the future.

Design of superconducting tokamak magnet systems and applications to HTS

In this paper we illustrate a self-consistent procedure to design the superconducting Toroidal Field (TF) and Central Solenoid (CS) magnet systems starting from the basic plasma dimensioning parameters. By defining the plasma major radius and minor radii, as well as the inboard TF coil neutron shielding radial built, we proceed by sizing the TF Winding Pack (WP), its case and the CS modules. The ITER magnets design philosophy and criteria are adopted throughout the study. A key outcome of this work is to illustrate the inter-play between machine size, magnetic field and availability of inductive flux for burn. In doing so we investigate the advantages brought by high field tokamak design compared the more conventional (ITER-like) Nb3Sn based magnet design solutions.

A Compact Dual-Channel WPT System With Power Boosting Function Based on Dual-Sided Decoupling Coils

Traditional high-power WPT systems have problems such as low semiconductor power rating, insufficient system compactness, and difficulty in system design due to complex cross-coupling in the magnetic coupler. Based on this, a compact dual-channel WPT system with power boosting function based on dual-sided decoupling coils is proposed in this manuscript. Two pairs of independent solenoid coils are respectively integrated on the transmitter-side and the receiver-side ferrite plates in the mutually perpendicular manner. In the proposed magnetic coupler, the mutually perpendicular solenoid coils are naturally decoupled under the conditions of alignment, horizontal misalignment and vertical misalignment. Therefore, the essence of the proposed system is the superposition of two independent WPT systems without cross-coupling interference, which enables the system to boost power while ensuring compactness. Firstly, a comprehensive theoretical analysis of the negligible cross-coupling of the proposed magnetic coupler is performed. Then, a detailed output power comparison with a traditional single-channel WPT system is conducted to demonstrate the practicability of the proposed dual-channel WPT system in terms of power boosting function. Thirdly, the magnetic decoupling characteristic of the proposed magnetic coupler is verified under different conditions. Finally, a confirmatory experimental prototype is built, and the experimental results agree well with the theoretical analysis.

Analysis of Electromagnetic Characteristics of 6.5 MVA/25 kV HTS Traction Transformer Using T–A Formulation

Low AC loss of the winding of high-capacity high temperature superconducting (HTS) traction transformer is a very important link to introduce large capacity traction transformer into commercialization. A new winding structure is proposed for the transformer. The HV windings are made of double pancake coils (DPCs), which are wound by 4.8 mm-wide tapes, and the LV windings, which are wound by 12 mm-wide tapes, are solenoid coils. The electromagnetic characteristics of the new winding structure of the traction transformer are analyzed by <i>H</i>-formulation homogenization method and <i>T</i>-<i>A</i> formulation homogenization method respectively. Significant HTS tape cost reduction could be achieved without compromising AC loss by using hybrid windings into the new winding structure. We report that the <i>H</i>-formulation homogenization model and <i>T</i>-<i>A</i> formulation homogenization model are used to calculate the AC loss of the new winding structure with flux diverters (FDs) at the end. The results meet the design requirements of less than 2 kW, which shows the feasibility of the new winding structure. Due to the good convergence of <i>H</i>-formulation and poor convergence of <i>T</i>-<i>A</i> formulation under the homogenization model of the transformer, no one has used <i>T</i>-<i>A</i> formulation to calculate the electromagnetic characteristics of the transformer before. Due to the simplicity of <i>T</i>-<i>A</i> formulation applied to large-scale superconducting system, a new form of mesh generation is proposed to improve the convergence and accuracy of <i>T</i>-<i>A</i> formulation homogenization model calculation of the transformer in this paper. This paper verifies the correctness of the calculation of HTS transformer by <i>T</i>-<i>A</i> formulation, and provides a reference for the application of <i>T</i>-<i>A</i> formulation in more superconducting fields

Temperature-variable apparatus for measuring Barnett field.

We have developed experimental equipment for observing the Barnett effect, in which mechanical rotation magnetizes an object, at low temperatures. A sample in a rotor is rotated bidirectionally using a temperature-controlled high-pressure gas. The stray field generated from the sample due to the Barnett effect was detected using a fluxgate magnetic sensor with a sensitivity on the order of several picoteslas, even at low temperatures. By replacing the rotor with a solenoid coil, the magnetic susceptibility of the sample was estimated from the stray field to be of the same order of magnitude as that due to the Barnett effect. The Barnett field was estimated using the dipole model. To assess the performance of the setup at low temperatures, measurements were performed on commercial magnetite (Fe3O4) nanogranules. We confirmed the accordance of the g' factor between the experimental results using the present setup and those of our previous study performed at room temperature.

Development of the CMS Magnetic Field Map

This article focuses on pioneering work on the performance of the three-dimensional (3D) magnetic field map in the entire volume of the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider at CERN. In the CMS heterogeneous magnetic system, the magnetic flux is created by a superconducting solenoid coil enclosed in a steel flux-return yoke. To describe the CMS magnetic flux distribution, a system of the primitive 3D volumes containing the values of the magnetic flux density measured inside the superconducting coil inner volume and modelled outside the coil across a special mesh of reference nodes was developed. This system, called the CMS magnetic field map, follows the geometric features of the yoke and allows the interpolation of the magnetic flux density between the nodes to obtain the magnetic field values at any spatial point inside a cylinder of 18 m in diameter and 48 m in length, where all the CMS sub-detectors are located. The geometry of the volumes is described inside one 30° azimuthal sector of the CMS magnet. To obtain the values of the magnetic flux density components across the entire azimuth angle of the CMS detector, rotational symmetry is applied.

VIBRATION ISOLATION SCHEME BASED ON ELECTROMAGNETIC SPRING

Sensitive measurements require a vibration isolation system to safeguard against detrimental tremble. Two types of vibration isolation systems - passive and active - are currently implemented. The spring-based passive designs usually accompany with ineffective low-frequency response. Therefore, the active designs, consisting of sensors, feedback control systems, and actuators, are consolidated to improve the total effectiveness of the cancellation performance. In this work, we focus on developing the actuator founded on electromagnetic spring to be incorporated into our compact quantum gravimeter. Each spring-actuated part comprises two repelling Nd magnets positioned face to face inside a solenoid. With this configuration, the spring can also work in the passive mode via repulsive magnetic force. In the active mode, the exerted force is a result of magnetic fields formed by the magnets and the current-controlled solenoid coils. By changing the coil current, the stiffness of the spring can be modified, and thus the displacement can be controlled. Different sizes of magnets are explored, and their force behaviors in passive and active modes are characterized. The implementation scheme of the actuator in the quantum gravimeter is also discussed.

Quadruple-U Auxiliary Structure-Based Receiving Coil Positioning System for Electric Vehicle Wireless Charger

In order to strike a balance between economic development and green travel, electric vehicles with wireless charging have become one of the first choices for future transportation. Misalignment between the transmitting coil and receiving coil in wireless charging systems decreases power capacity and efficiency to a great extent. Hence, the detection of whether the electric vehicle enters the effective charging area is a hot issue in the current research. In this paper, a receiving coil positioning approach integrated with a quadruple-U auxiliary structure is proposed. The designed quadruple-U auxiliary structure with cruciform distribution consists of four U-shaped coils, which are inspired by the solenoid coil. Based on the symmetry of the auxiliary structure, a receiving coil positioning method is proposed by measuring the load voltages of each U-shaped coil working independently. Coordinates can be obtained by retrieving the measured results with the database established in advance. The positioning method has the advantages of wider positioning ranges, higher positioning accuracy, and not changing the structure of the receiving coil. Furthermore, the specific magnetic coupler is simulated by a three-dimensional finite element modeling tool and was verified by an experiment on a prototype. During the positioning process, the positions distributed throughout the ΔX ∈ [−300 mm, 0 mm]∩ΔY ∈ [−300 mm, 300 mm] positioning range were tested. The experimental results indicate that all of the tested positions are accurate to within 10 mm, with a 160 mm transfer distance. Meanwhile, combined with the symmetry of the auxiliary structure and the test results, it can be indicated that the positioning range can reach ΔX ∈ [−300 mm, 300 mm]∩ΔY ∈ [−300 mm, 300 mm].

Numerical analysis of self-driven temperature-sensitive magnetic fluid heat flow around two side-by-side heating cylinders under a solenoidal magnetic field

A temperature-sensitive magnetic fluid (TSMF) is a functional fluid that enables heat transfer due to the temperature difference and magnetic field. Using this property, we can increase the driving force while promoting heat transfer by increasing the heat transfer area, in the same manner as a heat sink. However, when multiple cylinders are juxtaposed, the interference between the cylinders will greatly affect the heat transfer. In the present study, we used the hybrid lattice Boltzmann method to investigate the flow and heat transfer characteristics of a TSMF around two side-by-side heating circular cylinders under a solenoidal magnetic field. As the magnetic field increases, the heat transfer effect increases. Moreover, when the distance between the cylinders is close enough, the heat flow becomes unstable. Under the same magnetic field conditions, the unstable flow can promote heat transfer.

Dual mid-infrared wavelength Faraday rotation spectroscopy NOx sensor based on NdFeB ring magnet array

Faraday rotation spectroscopy (FRS) exploits the magneto-optical Faraday rotation effect to achieve highly sensitive detection of paramagnetic molecules. Most of the currently reported FRS sensors suffer from high power consumption, while enabling detection of only a single component. In this work, a novel dual mid-infrared wavelength FRS sensor is proposed that enables the simultaneous detection of two paramagnetic molecules (nitrogen oxides, NOx = NO + NO2) in a single absorption cell. A neodymium-iron-boron (NdFeB) ring magnet array was designed to replace the solenoid coil to provide a stable, power-free magnetic field. The magnetic induction line distribution characteristics around the permanent magnets were analyzed based on the finite element method. Two mid-infrared quantum cascade lasers were used to detect the strongest fundamental ν2 rotational-vibrational band of NO (1875.81 cm−1) and the ν3 fundamental band of NO2 (1613.25 cm−1), respectively. A dual-wavelength Herriott cell (DWHC) is coaxially combined with a NdFeB ring magnet array to amplify the interaction of the laser beam with paramagnetic NOx molecules in an axial magnetic field. This low-power FRS NOx sensor achieves minimum detection limits of 0.58 ppb and 0.95 ppb for NO2 and NO, respectively, over an optical length of 23.7 m.

On the Magnetic Field of a Finite Solenoid

The magnetostatic field of a finite solenoid with infinitely thin walls carrying a dc current oriented in the azimuthal direction is calculated everywhere in space in terms of complete elliptic integrals by direct integration of the Biot–Savart law. The solution is particularized near the solenoid axis and in the midplane perpendicular to the axis obtaining expressions that agree with some typical approximations that are made in introductory courses of electromagnetism or in the technical literature. The range of validity of these approximations has been studied comparing them with the obtained general expression.

Investigating the Manufacturing Process of Heat-Treated Nb3Sn-CICC Conductor for CFETR CSMC Modules

The center solenoid model coil (CSMC) of the China fusion engineering test reactor (CFETR) requires a high heat treatment temperature of 650 °C, which would destroy the insulation layer by carbonization and cause coil failure. To avoid this, using the manufacturing technology and routine process of the ITER center solenoid coil as a reference, in this article, a solution is introduced that is applied for manufacturing the CFETR CSMC module. The coil is heat treated before insulation and after winding. A single turn of the heat-treated coil is separated and the wrapping turn insulation is applied, and then the separated layers are reversed back into the integrated coil. To manufacture the integrated coils, the heat-treated coils are molded. After heat treatment, the interlayer separation distance of the Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn cable-in-conduit conductor in the coil should satisfy the allowable strain range of the superconductor, which is crucial for designing the rotational support structure of the interlayer separation. In addition, to achieve the accurate final shape of the coil and meet the design requirements, as well as to ensure coil contour accuracy after layer by layer separation, the antideformation ability of the coil mold is a key research topic. Herein, mechanical properties of the key components were optimized and numerical calculations and ANSYS simulations were used for statistical analyses. Results from the analyses indicated that the equivalent stress on the device is less than the maximum permissible stress of the raw material. The device was manufactured and compared with a design mold. The overall deformation error was <5%, movement error of the electric frame was <2%, rotation error of rotating was less than ±1° per 360°, levelness between the upper and lower platform was <1 mm, and motion error was less than ±1 mm per 100 mm. These results demonstrated the optimized structure design of the device. In the as-obtained device, the coil could separate a single turn and wrapping turn insulation could be applied. Parameters of the manufactured coil satisfied all the CSMC design requirements; these results indicate that the proposed device is suitable for manufacturing the CFETR CSMC module coil.