Multipole Coils Research Articles

Retraction Note: Comparison between Discrete Magnetic Coils and Multipole Coils for Measurement of Plasma Displacement in IR-T1 Tokamak

Retraction Note: Comparison between Discrete Magnetic Coils and Multipole Coils for Measurement of Plasma Displacement in IR-T1 Tokamak

Using a stepper motor as a low-power, low-rotation DC generator for renewable energy harvesting

Currently, the need for renewable energy is getting bigger; studying renewable energy generation requires a small-scale or miniature generator with a low rotation that can produce power for lamp loads. The selection of generators is not as appropriate as using DC motors with high rpm, as generators still produce a small voltage (<12V) and a small current. The use of DC motors equipped with gears requires a large torque to rotate the rotor. The solution offered to overcome this problem is the use of stepper motors as a DC generator with low rotation. The stepper motor has a multi-pole coil and permanent magnet that qualify it as a generator. This study uses the nema23 stepper motor as a DC generator. The stepper motor used is a 6-wire stepper motor (two pairs of coils), a half-wave rectifier, and a capacitor to buffer the voltage. The load is a 12VDC lamp. The results obtained indicate that the stepper motor generator can turn on the lights with a manual hand rotation.

Investigation of Gyroscopic Stabilization for Single-Stage Saddle Sextupole Field Electromagnetic Launcher

This paper presents a novel single-stage saddle multipole field electromagnetic launching mode for the realization of projectile linear acceleration with gyroscopic stabilization. The hollow cylindrical projectile with three symmetrical vertical slots can change the eddy current and magnetic field density distribution on the projectile surface. When twisted an angle relative to saddle multipole coils along the circumference, the projectile will be linear accelerated with spinning motion under the action of pulse current. In this paper, analytical calculations and simulation methods were used to analysis this mode, the simulation results indicated that the axial acceleration force and circumferential torque acting on the projectile were generated simultaneously, and an optimal initial twisted angle was existed to make the muzzle rotation speed reach peak. To verify the conceptual feasibility, a single-stage saddle sextupole field electromagnetic launcher was built and tested. The experiment demonstrate that the mode is indeed possible to realize the projectile linear acceleration moving with the gyroscopic stabilization, launching performance can be adjusted by changing the initial voltage or twisted angle, and the experimental results are accordant with the simulation results.

RETRACTED: A new perspective on remote Saddle Sine and Cosine coils technique for determination of tokamak plasma equilibrium status

In this contribution we have presented a new perspective for determination of tokamak plasma column shift based on remote multipole moments technique. First, we presented analytical details for using this technique. Then principle of different models based on this technique for design and fabrication of a six coils will be presented: four modified Rogowski coil (two Cosine coils and two Sine coils) and two Saddle coils (Saddle Sine coil (SSC) and Saddle Cosine coil (SCC)). Also, in order to comparison of results the flux loops technique is used. Because of continuous measurements of magnetic field distribution around the tokamak plasma using multipole coils, this technique give us more reliable information about the plasma current displacement.

Edgewise Bending Strain in Helical Coils With Geodesic Windings Based on Virial Theorem

Distributions of edgewise bending strain in helical coils with the geodesic winding based on virial theorem are analyzed theoretically and numerically. A force-balanced coil (FBC) is a multipole helical coil combining toroidal field (TF) coils and a solenoid helically wound on a torus. The combination reduces the net electromagnetic force in the direction of the major radius by canceling out the centering force due to the TF coil current and the hoop force due to the solenoid current. The FBC concept was extended using the virial theorem, which shows the theoretical lower limit of stress in the coils and their supporting structure. High-field coils should accordingly have the same averaged principal stresses in all directions, which is named the virial-limit condition. Since FBC winding is modulated to reduce the tilting force, the winding is slightly similar to but different from the shortest geodesic trajectory and has no tensile load. To apply FBC to high-temperature superconducting tapes, the degradation of superconducting properties originating from edgewise bending strain is an important problem. Since the geodesic trajectory is a kind of a straight line on a curved surface and curves only to the normal direction of the surface, it is expected that the tape with geodesic trajectories has a small residual stress. In this paper, we analyze the effect of the winding modulations including the geodesic modulation for the optimization of residual stress in helical windings.

Application of multipole moments and magnetic techniques for determination of tokamak plasma shift

AbstractIn this contribution, we presented approaches for the determination of tokamak plasma column shift based on multipole moments and magnetic techniques. First, we presented analytical details for using this technique. Then, the principle of different models based on this technique for the design and fabrication of six coils will be presented: four modified Rogowski coils (two cosine coils and two sine coils) and two saddle coils (saddle sine coil and saddle cosine coil). Also, to compare the results, the flux loops technique is used. Because of continuous measurements of magnetic field distribution around the tokamak plasma using multipole coils, this technique gives us more reliable information about the plasma current displacement. Moreover, we deduced the plasma current and plasma boundary centers shift using the two semi-empirical techniques in the IR-T1 tokamak. First, the plasma current center is calculated from the vertical field coil characteristics. The calculation is made focusing on the vertical field coil current and voltage changes due to a horizontal displacement of the plasma column. Also, the plasma boundary center shift was measured from the external magnetic coils. The results from these two techniques are compared and discussed.

In-Plane Electromagnetic Generator Fabricated on Printed Circuit Board Technology

Small and efficient energy harvesters, as a renewable power supply, draw lots of attention in the last few years. This paper presents a planar rotary electromagnetic generator with copper coils fabricated by using printed circuit board (PCB) as inductance and Nd-Fe-B magnets as magnetic element. Coils are fabricated on PCB, which is presumably cost-effective and promising methods. 28-pole Nd-Fe-B magnets with outer diameter of 50 mm and thickness of 2 mm was sintered and magnetized, which can provide magnetic field of 1.44 Tesla. This harvester consists of planar multilayer with multi-pole coils and multi-pole permanent magnet, and the volume of this harvester is about 50x50x2.5 mm3. Finite element analysis is used to design energy harvesting system, and simulation model of the energy harvester is established. In order to verify the simulation, experiment data are compared with simulation result. The PCB energy harvester prototype can generate induced voltage 0.61 V and 13.29mW output power at rotary speed of 4,000 rpm.

Beam optical design of in-flight fragment separator for high-power heavy ion beam

An in-flight fragment separator has been designed for the rare isotope science project (RISP) in Korea. A beam used for the design is 238U in the energy of 200MeV/u with the maximum beam power of 400kW. The use of high-power beam requires careful removal of the primary beam by pre-separator, for which its configuration was revised to employ four dipole magnets instead of two. Different configurations of the separator have been tested in search of optimal design in non-linear optics, which was complicated by the space needed for the target, beam dump and radiation shielding. Non-linear optical calculations have been carried out using GICOSY and COSY Infinity including the fringe fields of large-aperture quadrupole magnets. Correction of non-linear terms is made with multipole coils located inside the superconducting quadrupole magnets and by external multipole magnets. Beam simulations using LISE++ and MOCADI have been performed to consider the effects of multiple charge states of the primary and isotope beams produced at the target. Layout of the separator is being finalized, and detailed optics simulation will continue to refine its design.

Coil-dominated combined function magnet design

Most coil-dominated combined function magnets are built by stacking multipole coils around the beam aperture, which result in unnecessary cancellations of currents. This article suggests that conductor positions can be computed analytically based upon the combined potentials, so that significant ampere-turns can be reduced. The two dimensional complex potential theory is the base of this method. Examples are demonstrated. Detailed formulas are laid out and ready for various applications.

Design and fabrication of LTCC electro-magnetic energy harvester for low rotary speed

This study focuses on the design and fabrication of a planar rotary electromagnetic energy harvester with a low rotary speed for bicycle dynamos. The primary components of a dynamo system include planar multilayer and multipole coils, a soft magnet (iron) used to enhance magnetic efficiency, and a multipole Nd/Fe/B (neodymium, iron, and boron) permanent magnet. Finite element analysis and the Taguchi method were used to design this dynamo system. The optimal parameters of the magnet, coil, and soft magnet were determined by using the Taguchi method. Low temperature co-fired ceramics (LTCC) technology was applied to fabricate silver planar multilayer coils with 10 and 20 layers, respectively. Nd/Fe/B was sintered to obtain the desired characteristics of a permanent magnet. A 28-pole magnet Nd/Fe/B with an outer diameter of 50mm and a thickness of 2mm was also sintered and magnetized, creating a magnetic field of 1.4T. Simulation results show that a harvester with 20-layer and 22 poles coils, a linewidth of 200μm, an interspace of 100μm, and a layer thickness of 40μm can generate voltages of 1.796V at a rotary speeds of 300rpm. This harvester system was approximately 50mm×50mm×3mm in volume (including 20-layer micro-coils+magnet+spacing between the coil and magnet surface). The experimentally induced voltages of 20-layer coils were 1.539V. Measurements show a similar trend with finite element simulations. The power output was 0.788mW with an external resistance load of 737Ω. This harvester is capable of powering 200 LEDs (forward voltage (VF)<2.2V and 20mA) using a rotary speed of 250rpm, and could be used for bicycle dynamo lighting.

Design of a Novel Damping-Controllable Damper for Suspension Systems

Conventional oil dampers are non-controllable passive dampers because the viscosity of the fluid used is not wide-range variable. By using magneto-rheological fluid (MRF), MRF damper has excellent performance for variable-damping applications. Due to the single-coil design in the general MRF damper, the obtained damping from MR effect is not quite large. This research provides a high-damping MRF damper by adopting multi-pole coil and special polarization configuration. The simulated results show that the new MRF damper has good performance in the magnetic field and damping. Compared with a similar-size general single-coil MRF damper, this new MRF damper can get 47% higher performance under the same operating conditions.

Magnetic field and structure analysis of a superconducting dipole magnet for a rotating gantry

The conceptual design of a superconducting dipole magnet for a rotating gantry has been conducted. The dipole magnet is composed of a saddle shaped (cosine theta) multi-pole coil, which is wound with a NbTi superconducting wire, surrounded by an iron collar. In terms of a design parameter, a magnetic field strength of not only 1.5T but also 3.0T at the magnet center is required within the field quality of 1.0×10−3. In this study, the magnetic field analysis and structural analysis of the superconducting dipole magnet are described.

Numerical Study on AC Loss Reduction of Multi-Pole HTS Coil by Optimal Design of Winding Cross Section of Element Coil

We study the optimal design of 2- and 4-pole coils wound by YBCO tapes as the case studies of the optimal design of the multiple-coil system based on the AC loss minimization. The winding cross sections of the element coils of the 2- and 4-pole coils were optimized starting from the conventional rectangular cross section to minimize the AC loss. The result shows that the AC loss in the optimized coil is significantly reduced and the critical current of the optimized coil is increased compared with the base coil. According to the results, the validity of our optimal design method is verified to effectively reduce the AC loss in the multi-pole coils wound by the YBCO tapes. Some disadvantageous points of the optimized coil are also discussed.

Comparison Between Discrete Magnetic Coils and Multipole Coils for Measurement of Plasma Displacement in IR-T1 Tokamak

We have expressed two different methods to determine the plasma positions in the IR-T1 tokamak. An array of magnetic probes are placed polidally outside the chamber surface and their signals are plugged in the displacement equation and horizontal displacement of plasma column is obtained. The results of this measurement are compared with the experimental data obtained from sensors of multipole moment. It was detected a fluctuation in plasma displacement obtained with discrete magnetic coils, so the method of multiple moments is better than the discrete magnetic coils for the determination plasma displacement that used for feed back control.

Analytical and experimental approaches in plasma displacement measurement in IR-T1 tokamak

AbstractIn this paper two methods for determining plasma position in the IR-T1 tokamak are presented: a multipole moments method and an analytical solution of the equilibrium problem using the Grad–Shafranov equation. Based on the multipole moments method, modified Rogowski and saddle coils were designed and constructed for measuring plasma column displacement. Good agreement in comparison between the analytical and experimental approaches in determining plasma displacement in the IR-T1 tokamak is achieved.

Study on Axially Distributed Divertor Magnetic Field Configuration in a Mirror Cell

A mirror magnetic field configuration (MFC) is studied in which a divertor is distributed axially using multipole coils. Both configurations of divertor and minimum-B are obtained in a mirror cell. Magnetohydrodynamic (MHD) instability of a mirror cell can be eliminated in this way. Concept of the design and properties of the MFC are discussed.

SMES coil configurations with reduced stray field

The stray field of SMES restricts its site location, although SMES has an attractive potential for power management and quality control. The stray field outside a solenoid is analyzed by a series of Legendre polynomials and the result is applied to the stray fields of various SMES coil configurations. As long as the summation of magnetic moments from all coils is zero, the term of a stray field decreasing as r/sub p//sup -3/ can be cancelled out. The higher order of the stray field can vanish if the coil arrangement is optimized. In this paper, the authors consider a single solenoid as a reference, active shield coils, axially displaced coils and multipole coils to reduce the stray field. The multipole coil configuration has high potential to drop the stray field, since the stray field behaves like r/sub p//sup (3+n/2)/, where n is the coil number.

Study of quench propagation with quench antennas

A quench antenna consists of four multipole coils whose signals give us information about the position of a quench origin and current redistribution. In this paper, we report a simulation and test results of the quench antenna developed for the TRISTAN insertion quadrupole magnets (QCS magnets). Heater quench tests were performed, and it was confirmed that the quench start locations evaluated from quench antenna signals were consistent with those from the voltage tap signals and the heater position. The amplitude and the direction of the current redistribution were calculated, and they did not conflict with what was expected from a simulation.

2D coupled structural/magnetic analysis of SSC CQM

The deformation of a collider quadrupole magnet (CQM) coil under pre-compression, cool down and Lorentz forces may cause some significant changes in magnetic multipoles. The magnetic measurements of the CQM short model magnets at 4.2 K showed an average b/sub 5/ of -2.866 units compared to a numerical prediction of -0.162 units. Out of these -2.866 units, -1.5 units are due to a shim placed at the mid-plane to increase coil precompression. We also suspect that the permeability of the stainless steel collar may contribute some of the missing b/sub 5/. For example, a permeability of 1.004 for the collar adds -0.5 units of b/sub 5/. Including the collar, we are still missing -0.8 to -1.0 units. We believe that the mechanical deformation due to pre-compression of the coil is responsible for the remaining units. This study builds a 2D magneto-structural coupled model, calculates the magnetic multipoles under different loading conditions and establishes a correlation between multipole changes and coil pre-compression and Lorentz force stresses. >

Superconducting Coil Manufacturing Method for Low Current DC Beam Line Magnets

A method of manufacturing superconducting multipole coils for 40 to 50 kG DC beam line magnets with low current is described. We built small coils and tested them successfully to short sample characteristics. The coils did not train after the first cooldown. The coils are porous and well cooled to cope with mechanical instability and energy deposited in the coil from the beam particles. The coils are wound with insulated strand cable. The cable is shaped rectangularly for winding simplicity and good tolerances. After the coil is wound, the insulated strands are electrically connected in series. This reduces the operating current and, most important, improves the coil quench propagation due to heat conduction of one strand adjacent to the other. A well distributed quench allows the magnet energy to distribute more uniformly to the copper in the superconductor wire, giving self-protected coils. We are now fabricating a one-meter long, 43 kG. 6-inch bore tube superconducting dipole. The porous coil design and coil winding methods are discussed.