Coaxial Solenoid Research Articles

Design and analysis of a HTS internally cooled cable for the Muon Collider target and capture solenoid magnets

The Muon Collider is one of the options considered as the next step in High Energy Physics. It bears many challenges, last not least in superconducting magnet technology. The target and capture solenoid is one of them, a channel of approximately 18 m length consisting of co-axial solenoid magnets with a 1.2 m free bore and peak field on axis of 20 T. One of the main concerns come from the nuclear radiation environment that may influence the stable operation of the coil, as well as its material integrity. Energetic photons cause large radiation heat load, of the order of several kW in the cold mass, and deposit a considerable dose, several tens of MGy. Neutrons cause material damage, at the level of 10-3 DPA. These values are at the present limit of superconducting coil technology. We describe here the conceptual design of the target and capture solenoid, focusing on the HTS cable design, which is largely inspired by the VIPER concept developed at MIT. We show how to address margin and protection, cooling and mechanics specific to the HTS cable selected.

High-speed two-stage Hall magnetometer with increased resolution

It is demonstrated that the use of two coaxial solenoids instead of one in the magnetic field sensor cell allows one to divide the dynamic range of the magnetometer into a wide range of support magnetic field and a narrow range of bias field. This makes it possible to design, on the basis of a Hall sensor, a two-stage magnetometer with resolution of about 8·10 –11 Т. An increase in the speed of the magnetometer is achieved due to the use of a weak bias field, which represents a decaying oscillating local magnetic field (DOLMF). The leading edge of the DOLMF is used to search for a signal to be measured by a servo-system, while its decaying part after switching off the magnetic field step does not lead to magnetic relaxation in the sensitive element made of a superconducting YBa 2 Cu 3 O 7– x epitaxial film due to the fast process of vortex–antivortex annihilation. The design of the proposed magnetometer provides a high-speed measurement of not only constant but also alternating magnetic fields in the range from 10 –11 to 10 –7 Т at a frequency of up to ∼1 kHz, while preserving the high performance of the magnetometer. With the use of high-frequency magnetic field transducers, the magnetometer can operate in the frequency range of up to ∼100 kHz and measure both alternating and pulsed magnetic fields. • The use of two coaxial solenoids allows the design of a two-stage magnetometer with high resolution. • A superconducting epitaxial YBCO film is used as the sensitive element of the magnetometer. • The magnetometer provides a high-speed measurement of both constant and alternating magnetic fields.

Frequency-selective signal enhancement by a passive dual coil resonator for magnetic particle imaging

Objective. Magnetic particle imaging (MPI) visualizes the spatial distribution of magnetic nanoparticles. MPI already provides excellent temporal and good spatial resolution, however, to achieve translation into clinics, further advances in the fields of sensitivity, image reconstruction and tracer performance are needed. In this work, we propose a novel concept to enhance the MPI signal and image resolution by a purely passive receive coil insert for a preclinical MPI system. Approach. The passive dual coil resonator (pDCR) provides frequency-selective signal enhancement. This is enabled by the adaptable resonance frequency of the pDCR network, which is galvanically isolated from the MPI system and composed of two coaxial solenoids connected via a capacitor. The pDCR aims to enhance frequency components related to high mixing orders, which are crucial to achieve high spatial resolution. Main Results. In this study, system matrix measurements and image acquisitions of a resolution phantom are carried out to evaluate the performance of the pDCR compared to the integrated receive unit of the preclinical MPI and a dedicated rat-sized receive coil. Frequency-selective signal increase and spatial resolution enhancement are demonstrated. Significance. Common dedicated receive coils come along with noise-matched receive networks, which makes them costly and difficult to reproduce. The presented pDCR is a purely passive coil insert that gets along without any additional receive electronics. Therefore, it is cost-efficient, easy-to-handle and adaptable to other MPI scanners and potentially other applications providing the basis for a new breed of passive MPI receiver systems.

К вопросу о коэффициенте взаимной индукции соленоида и кругового контура с параллельными осями

Object and purpose of research. Current recommendations on calculation of mutual inductance between solenoids and coiled circuits with parallel axes are shown and compared. Advisability of such verification for a limiting case when the axes are aligned is revealed. Materials and methods. Verification of these recommendations for cases of zero axial displacement is performed on the basis of well-tested expressions. For this purpose alternative expressions for the mutual inductance of the coaxial circuit and solenoid and two circuits. Main results. A number of significant discrepancies are identified between numerical values including difference in signs for the case of a solenoid and a circuit with parallel axes. For circuits with parallel axes, attention is focused on the necessity to use auxiliary tables, which confirms the complexity of numerical estimation in this case either. Conclusion. In terms of the identified flaws, the conclusion was drawn about the advisability of using computational methods for configurations with parallel axes. For circuits with parallel axes, as follows from the written expression, it is sufficient to apply a single numerical integration.

Определение взаимных индуктивностей и электро- динамических сил между катушкой и соосным соленоидом при симметричном расположении

Object and purpose of research. Mutual inductances are among the main parameters of electrical circuits, and their determination is the most important task for studying the physical processes occurring in them, including the occurrence of electrodynamic forces. Coaxial coils and solenoids are very common part of electrical devices, and finding mutual inductances and electrodynamic forces in them has a great practical importance. Materials and methods. Methods of theoretical electrical engineering are used. Main results. Expressions for mutual inductance are obtained, and they are based on the decomposition of the solenoid into its external and internal parts relative to the end planes of the coil. Conclusion. On the basis of the undertaken analysis, alternative expressions for mutual inductances are obtained.

Mutual Inductance Modeling of Two Coaxial Solenoid Antennas With Large Ferrite Core for Underground RFID Applications

Mutual inductance is a crucial parameter in the design and optimization of coupled antennas in underground radio frequency identification (RFID) systems. In this article, a simple and accurate modeling method for determining the mutual inductance between two coaxial solenoid antennas with a large ferrite core is proposed. This proposed model is verified by comparing the results obtained from the commonly used method for small ferrite core antennas, high-precision filament method, and finite element method (FEM). An experimental setup has also been built to validate the proposed method. This new method for predicting mutual inductance has greater adaptability and higher accuracy, and is much better suitable to optimize the performance of RFID antennas with a large ferrite core.

ЕЛЕКТРОМАГНІТНІ ПОЛЯ В ЦИЛІНДРИЧНІЙ ІНДУКТОРНІЙ СИСТЕМІ ІЗ ЗОВНІШНІМ КОАКСІАЛЬНИМ БІФІЛЯРНИМ СОЛЕНОЇДОМ

Purpose. Bifilar structures are widely used in modern electrical devices for various purposes. The specific interest is the using of inductor systems with external bifilar coils in the elements of modern metalworking equipment. In particular, it is very important to study the possibility of using such devices as elements of equipment for magnetic-pulse processing of metals. The aim of this research is a derivation of design expressions for theoretical analysis and numerical estimates of the characteristics of electromagnetic processes in a cylindrical inductor system. The case when the inductor is located inside a coaxial solenoid, the winding of which is made in the form of a bifilar with oppositely directed currents is considered. Methodology. Maxwell’s equations with appropriate boundary conditions and Laplace transforms are used to solve this problem. This made it possible to determine the expression for the z-th component of the magnetic field intensity excited in the considered inductor system. Results. It was found that the excited magnetic fluxes are subtracted outside the bifilar coil windings, which leads to a decrease in the resulting field compared to the magnetic field of each of the currents separately. Thus, it is possible to reduce the inductance of the coil as an element of the electrical circuit. It is shown that the formulas obtained for the fields and currents remain valid for the case of unidirectional currents when the sign of the corresponding algebraic term changes. Numerical estimates for the experimental model of the inductor system showed that the induced current as a percentage of the value of the exciting current does not exceed ~ 6.3 %. Originality. The novelty of this work lies in proposing the idea of constructive execution of the inductor system itself, as well as in considering its physical and mathematical model and obtaining calculated expressions for analyzing the ongoing electromagnetic processes with numerical estimates of the characteristics of the excited fields. Practical value. The obtained time dependences for voltages and currents induced in the bifilar winding are applicable depending on the design conditions for various specific designs of the inductor system

A geometrically decoupled, twisted solenoid single-axis gradient coil set for TRASE.

TRASE uses phase gradients in the RF transmit field to encode MRI data. A highly efficient twisted solenoid coil was proposed recently for TRASE imaging for transverse geometries. This novel coil can be rotated to generate a phase gradient in any transverse direction, therefore, combining two such coils would double k-space coverage for single-axis encoding, resulting in higher spatial resolution. However, the strong inductive coupling between a pair of coaxial twisted solenoids must be overcome. Here, we demonstrate that two concentric twisted solenoids, designed using previously described Biot-Savart calculations, can be geometrically decoupled by attaching to each a regular solenoid in series. The regular solenoid geometry resulting in minimization of mutual inductance was determined from simulations using the FastHenry2 tool. The effects on TRASE encoding performance due to the regular solenoids were assessed from simulations and experiments. The maximum resulting magnitude and phase distortions were 3.7% and , while a good isolation dB between the coil pair was obtained. TRASE experiments confirmed the double k-space coverage, and achieved a rapid spin echo train with 128 k-space points collected within 80 ms, allowing short samples to be accurately imaged. This study demonstrates that a pair of twisted solenoid phase gradient RF coils can be geometrically decoupled. Advantages over active PIN diode decoupling include faster switching, lower hardware complexity, and scalability.

Solenoid antenna of radio engineering system of metal identification

The detection of metallic objects hidden in a dielectric medium is carried out with the aid of metal detectors constructed on a vortical current principle. Then detected metal is identified. For identification of metals, as usual, chemical, optoelectric, X-ray methods are used. But detection and identification can be done simultaneously using the graphic-digital image method. In such devices a coaxial solenoid antenna of the frame type is used. But it has low sensitivity, uneven depth sensitivity and a significant parasitic connection between the receiving and transmitting antennas. From such shortcomings, a free antenna is a DD type system, but it does not allow the use of a graphical-digital signal processing method. Therefore, a new design of the antenna system is proposed, which allows us to take advantage of the considered signal processing method and DD antennas. It is characterized in that one of the antennas, for example, a transmitter, consists of two parts that are symmetrically placed relative to the second and creates two active radiation zones, such as a coaxial antenna, but are similar to the radiation zones of the DD type antenna.

Циліндрична індукторна система з внутрішнім біфілярним соленоїдом. Аналіз електромагнітних характеристик

A cylindrical inductor system with an internal coaxial solenoid, the winding of which is made in the form of a bifilar, is considered. The physical and mathematical model of the proposed system assumes the working conditions when the external inductor is turned off, its turns are made of metal with high electrical conductivity; sufficiently close to each other, so that their inner surface can be considered a continuous surface of the ideal conductor. The coils of the bifilar winding are made of metal tape and do not affect the occurring electromagnetic processes. A harmonic current flows in the bifilar. Based on the calculated ratios for the strengths of the fields excited in the system, numerical estimates of the characteristics of the electromagnetic processes are obtained. The case when the currents in each of the branches of the bifilar which directed in opposite directions is analyzed. Various cases of the transverse and longitudinal dimensions of the system are considered, as well as options for connecting one or two bifilar coils. It is shown that the integral magnetic flux in the internal cavity of the system under consideration, regardless of its design features, is zero and, accordingly, the inductance of the entire system as a whole is zero. The concentration of the magnetic flux in the system with a bifilar takes place in the cavity between its windings, which is explained by the positive superposition of the unidirectional induction vectors of the excited fields. Changes in the geometry and number of components allow varying the indices of the radial distributions of electro-magnetic fields in the inductor system considered. The obtained numerical estimates for the characteristics of magnetic fields excited in inductor system, real design first proposed by the authors, excited by directed in opposite directions currents in the windings of the bifilar, will be useful in choosing working design solutions for the corresponding elements of magnetic pulse metal processing equipment. The proposed method of analysis will also allow appropriate experimental studies, as well as calculation and analysis of electromagnetic processes in inductor systems, where bifilar coils are placed on top of cylindrical solenoids, which is very interesting for the formation for new equipment magnetic-pulse processing of metal.

Basic Design and Progress of Central Solenoid Model Coil for CFETR

The central solenoid model coil (CSMC) project of China fusion engineering test reactor (CFETR) began in 2014 and the purpose is to develop and verify the manufacture technology of the large-scale superconducting magnet. The Nb 3Sn cable-in-conduit-conductor (CICC) is chosen for CFETR CSMC as the best conductor type because of 12 T field and 1.5 m inner diameter design requirement. The CFETR CSMC consists of two coaxial solenoid coils named Nb3 Sn coil in the high field region and NbTi coil in the low field region to optimize the manufacture cost effectively. The maximum field of the Nb3Sn and NbTi coil can reach to 12 T and 6.1 T, respectively, when the operating current is 47.65 kA. In this paper, first, the basic design aim and operation requirements of CFETR CSMC are summarized. Second, the characteristics of Nb3Sn superconducting strands and CICCs are described in detailed. Subsequently, the basic structure design of CFETR CSMC is presented in the third part. The current sharing temperature and coupling loss measurement of Nb3Sn CICC sample, as the most important stage assessment, are performed in SUTLAN test facility and some meaningful conclusions are.

A Conduction-Cooled Superconducting Magnet System - Design, Fabrication and Thermal Tests

A conduction-cooled superconducting magnet system with an operating current of 105.5 A was designed, fabricated and tested for material processing applications. The magnet consists of two coaxial NbTi solenoid coils with an identical vertical height of 300 mm and is installed in a high-vacuumed cryostat. A two-stage GM cryocooler with a cooling power of 1.5 W at 4.2 K in the second stage is used to cool the system from room temperature to 4.2 K. In this paper, the detailed design, fabrication, thermal analysis and tests of the system are presented.

Analysis of inductance calculation of coaxial circular filamentary coils, thin‐wall solenoids, and disk coils using inverse hyperbolic functions

This study presents a method using inverse hyperbolic functions to calculate the mutual and self-inductance inductance of coaxial circular filamentary coils, thin-wall solenoids, disk coils, and coils with rectangular cross-section in air. A generalised expression is given for any combination of these coils, which only requires numerical integration with one variable. Singularities are fully analysed and methods to resolve the singularities are presented in this study. When calculating the self-inductance of a disk coil or a thin-wall solenoid, the proposed method involves an improper integral, and the accuracy of the proposed method is limited unless a quadrature rule applicable to improper integrals is applied. For other situations, results by the proposed method were compared with those in the literature, and they were in excellent agreement.

Wireless Power Transmission Model Using Coaxial Helical Solenoid Coils for Powering Utility Equipment

Mid-range low-power wireless power transmission systems using resonant–inductive coupling have recently been in use for powering a variety of household gadgets. A modified resonantly coupled system for a wireless power transmission system using coaxial helical solenoid coils is presented, using distributed parameters predominantly at high frequency. The proposed system is reduced using circuit transformations, and the operating power transfer efficiency under varying conditions of source and load are derived. The model is tested with an experiment consisting of a home lighting utility load for the resonant frequency of 1.2 MHz. The experimental results are in close agreement with the proposed analytical model for varying distances between the transmitter and receiver. A comparison of the operating power transfer efficiency of the proposed model with resonantly and inductively coupled models for varying distances between the transmitter and receiver is presented. Maximum power transfer efficiency by matching source and load resistances is simulated using the RF Toolbox (http://www.mathworks.in/products/rftoolbox) on the proposed, resonantly coupled, and inductively coupled models. The simultaneous conjugate-matching technique for increasing the power transfer efficiency to near 100% is also presented.

Biot-Savart law as a tool to calculate the matrix of inductances and the coupling coefficient of two coaxial solenoids with arbitrary cross sections

The Biot-Savart law is a basic topic in teaching of electromagnetism in undergraduate courses. However, its applicability in textbooks is reduced, focused on a very specific set of problems. Generally, the student considers that this law does not completely solve some major problems in electromagnetism. One of them is the determination of the magnetic field inside and outside of an ideal solenoid of arbitrary cross section. In this article, we carry out the calculation of this field in a didactic and simple way by employing the Biot-Savart law. We obtain that the magnetic field inside of the solenoid is uniform and independent of its cross section. Besides, we directly determine that the outer field is equal to zero. These results allow us to introduce the expression of the matrix of inductances and the coupling coefficient of two coaxial solenoids with arbitrary cross sections.

Improved Method for Elastomagnetic Effect Based Tension Measurement Using Harmonic Analysis Techniques

An improved method for elastomagnetic(EM) effect-based tension measurement is presented using harmonic analysis technique(HAT). The magnitudes of odd harmonics of EM signals are extracted to calculate the total harmonic distortion(THD), which is commonly used in electrical engineering area to represent the extent of the distortion of sinusoidal signals. The value of THD is applied for tension characterization. The EM signals are acquired by a EM sensor which is made of two coaxial solenoid coils, and then are alternatively processed in time and frequency domain. The advantages of the two signal processing methods are compared to find that the HAT is much more succinct. The determined characteristic parameters of calibration equation, such as linear regression and slope, tend to be stable as the number of orders for statistics increases. Moreover, the obtained calibration equation has better parameters, for example, the linear regression is larger than 0.996. The mentioned techniques are then applied for measuring the tension of high voltage transmission line, the experimental results testify that there is a significant linear relationship between THD and the applied tension. When the value of THD is equal to 1, the relative errors of estimated forces, which are calculated from calibration equations corresponding to various statistical harmonic orders, are less than 3%(a maximum of 2.4%for seven-wire steel strand and a maximum of 2.9% for high voltage transmission line). This study provides a new characterization and data processing method for EM-based tension measurement technology.

Critical Current and Cooling Favored Structure Design and Electromagnetic Analysis of 1 MVA HTS Power Transformer

This paper presents a conceptual design of a 1 MVA / 10 kV / 0.4 kV high temperature superconducting power transformer by using Dynamically Innovative BSCCO (DI- BSCCO) tapes. The three-phase three-limb iron core is formed by laminated silicon steel sheets at room temperature. The high- voltage (HV) windings take the form of five solenoid groups per phase, where the five solenoids are coaxially placed and connected in series. The preliminary design of the low-voltage (LV) windings includes two winding schemes. One is with the form of five coaxial solenoids in parallel; the other is to use the ten-stacked tapes directly to wind one solenoid with 17 axial turns. The structural designs and electromagnetic analyses are presented with critical current and uniformity of current distribution discussed. The designed 1 MVA HTS transformer has the advantages of smaller volume, lighter weight and less operation loss as compared to a 1 MVA conventional transformer.

Quench protection design of a 9.4 T whole-body MRI superconducting magnet

A 9.4 T MRI superconducting magnet with a 800mm clear warm bore in diameter is designed and fabricated for bioscience research. The superconducting magnet consisting of five coaxial solenoid coils is fabricated with NbTi Wire-in-Channel (WIC) conductor where the ratios of copper to non-copper are from 5 to 10. The four compensation solenoid coils are with rectangular NbTi/Cu strand wires. The magnet will be operated in a relative low nominal current of 224.5A with a high level of stored energy, about 138MJ. A protection method with the cold diodes and resistors in series across the subdivided sections and active trigger heater to accelerate quench is adopted to avoid the damage of the magnet. In the paper, the quench simulation results of currents, voltages and hot-spot temperatures based on the protection scheme are analyzed in details.

Effect of Enhanced Plasma Density on the Properties of Aluminium Doped Zinc Oxide Thin Films Produced by DC Magnetron Sputtering

Aluminum doped zinc oxide (AZO) thin films were prepared by DC magnetron sputtering at low substrate temperature. A coaxial solenoid coil was placed near the magnetron target to enhance the plasma density (J(i)). The enhanced plasma density improved significantly the bulk resistivity (p) and its homogeneity in spatial distribution of AZO films. X-ray diffraction (XRD) analysis revealed that the increased J(i) had influenced the crystallinity, stress relaxation and other material properties. The AZO films deposited in low plasma density (LPD) mode showed marked variation in rho (ranging from similar to 6.5x10(-2) to 1.9x10(-3) Omega.cm), whereas those deposited in high plasma density (LPD) mode showed a better homogeneity of films resistivity (ranging from similar to 1.3x10(-3) to 3.3x10(-3) Omega.cm) at different substrate positions. The average visible transmittance in the wavelength range of 500-800 nm was over 80%, irrespective of the deposition conditions. The atomic force microscopy (AFM) surface morphology showed that AZO films deposited in HPD mode were smoother than that in LPD mode. The high plasma density produced by the coaxial solenoid coil improved the electrical property, surface morphology and the homogeneity in spatial distribution of AZO films deposited at low substrate temperature.

Radio-frequency plasma transducer for use in harsh environments

We describe a compact transducer used to generate and modulate low-intensity radio-frequency atmospheric pressure plasma (RF-APP) for high temperature gap measurement and generation of air-coupled ultrasound. The new transducer consists of a quarter-wave transmission line where the ground return path is a coaxial solenoid winding. The RF-APP is initiated at the open end of the transmission line and stabilized by passive negative feedback between the electrical impedance of the plasma and the energy stored in the solenoid. The electrical impedance of the plasma was measured at the lower-voltage source end of the transducer, eliminating the need to measure kilovolt-level voltages near the discharge. We describe the use of a 7 MHz RF-APP prototype as a harsh-environment clearance sensor to demonstrate the suitability of plasma discharges for a common nondestructive inspection application. Clearance measurements of 0-5 mm were performed on a rotating calibration target with a measurement precision of 0.1 mm and a 20 kHz sampling rate.