11 T liquid helium-free superconducting magnet

An 11 T liquid helium-free superconducting magnet designed at 6 K in vacuum using high temperature superconducting current leads was developed. The coil was conductively cooled down from room temperature to 4.1 K in 40 h by two 4 K GM-cryocoolers. In a performance test, the coil temperature rose to 6.8 K for the inner Nb₃Sn coil and 5.9 K for the outer NbTi coil, while sweeping the field at 5 A min⁻¹. A central field of 10.7 T in a 52 mm room temperature bore was generated at an operating current of 149 A. Holding the field at 10.5 T was achieved continuously for 24 h at a constant coil temperature of 4.8 K.     

A flying superconducting magnet and cryostat for magnetic suspension of wind-tunnel models

The quality of aerodynamic tests on aircraft or missile models in wind tunnels is improved by magnetically suspending these models, thus avoiding the intrusion of mechanical supports. The size of the electromagnet array required for this task may be prohibitive at large scales but can be reduced by increasing the magnetic moment of the model's internal magnetic core. This article describes a new approach, in which a superconducting solenoid is carried within the model in place of the conventional ferromagnetic core. The potential advantages, the philosophy and details of the design of a prototype, and some experiences in its use are outlined.     

Sweeping a persisting superconducting magnet with a transformer

A method for sweeping a persisting superconducting magnet is described. The field sweep is achieved by including in the superconducting loop of the magnet a coil which acts as the secondary coil of a transformer. Variation of the current in the primary coil of the transformer, controlled from outside the cryostat, causes the field-sweeping action through flux-linking with the superconducting loop. Compared by the ratio of the magnet's inductance to the transformer's inductance. The advantages of using an all-metal vacuum-tight superconducting feedthrough are discussed.     

Minimum heat pulse to quench a superconducting magnet

The minimum energy required to quench a fully impregnated superconducting winding has been measured at a constant field of 5 T for various currents. Great care has been taken to match the experimental conditions with those presumed in the minimum propagating zone (MPZ) treatments of the situation. In particular the winding has been designed so that the MPZ is smaller than the heat source thus satisfying the requirement for a point disturbance. The adiabatic requirement has been met with an inductive heating technique in place of the usual resistive heating. As a consequence of these features the minimum quench energies are much smaller than those obtained in previous experiments and agree well with Wilson's theoretical treatment for a point disturbance.     

On the testing of large superconducting magnet systems

A new approach to the testing of large superconducting magnet system is proposed.     

Coupling losses in superconducting,torus-shaped wires due to applied magnetic field changes

The stationary electric field, current pattern and coupling losses in a multfilamentary, superconducting, twisted, torus-shaped wire are calculated for a torus placed in a homogeneous magnetic field increasing in time at a constant rate and parallel to the torus plane. The radius of the wire is considered to be small compared to the mean radius of the torus. An important parameter for the problem is the ratio between the twist length of the superconducting filaments and the mean radius of the torus. In the configuration considered this parameter is small. The coupling losses are approximately inversely proportional to the square of this ratio. Furthermore, for the wire to have unsaturated parts, the analysis shows that the rate of change of the magnetic field must decrease when this ratio increases.Deceased.     

Design of an energy storage flywheel system using permanent magnet bearing (PMB) and superconducting magnetic bearing (SMB)

We propose a new energy storage flywheel system using a superconducting magnetic bearing (SMB) and a permanent magnet bearing (PMB). The superconducting magnetic bearing (SMB) suppresses the vibrations of the flywheel rotor. And the permanent magnet bearing (PMB) passively controls the rotor position. The energy storage flywheel system is characterized by using the two different type magnetic bearings of permanent magnet bearing (PMB) and superconducting magnetic bearing (SMB). This paper, discusses the design of the permanent magnet bearing (PMB) and the dynamics of the new energy storage flywheel system.     

Experiences on high current leads for superconducting magnets; seven types from 1 kA to 30 kA

In order to extend the current lead techniques to higher currents, the operational minimum flow rates of leads from 1 to 30 kA were measured and compared with the design value.     

A 1.5 t superconducting magnet with closed cooling system for spin-imaging: an outline

In the field of NMR-imaging superconducting magnets will become important. At higher field strengths proton-imaging can be achieved faster and with better resolution.In this paper a 1.5 T superconducting magnet system based on a double pair coil configuration is described. Some details are given on the construction of the coils. Also the use of a small cryogenerator for cooling radiation shields and precooling the magnet system is described.     

Finite element model of training in the superconducting quadrupole magnet SQ02

This paper describes the use of 3D finite element models to study training in superconducting magnets. The simulations are used to examine coil displacements when the electromagnetic forces are cycled, and compute the frictional energy released during conductor motion with the resulting temperature rise. A computed training curve is then presented and discussed. The results from the numerical computations are compared with test results of the Nb₃Sn racetrack quadrupole magnet SQ02.     

A 12 T 80 mm bore superconducting V3Ga NbTi magnet system

A V₃Ga-NbTi magnet system for a field of 12 T in 80 mm clear bore is described. The V₃Ga and NbTi magnets are connected in series to one power supply. The differences in the materials (NbTi multifilamentary wire and V₃Ga bronze processed stranded cable) require special measures for protection during a quench. In the V₃Ga magnet no training or degradation was observed. The short sample critical current value was reached in the V₃Ga magnet with a reversible active voltage which made it possible to reduce the current without quench.     

Fabrication experiences and performance tests of the coal-fired flow facility superconducting dipole magnet

The Argonne National Laboratory has designed, constructed and tested a large aperture superconducting MHD magnet for use in the coal-fired flow facility at Tullahoma, Tennessee. The magnet generates a peak on-axis field of 6 T in a MHD warm bore of 80 cm diameter at inlet, 100 cm diameter at outlet, and 300 cm effective length. The stored energy of the magnet is 210 MJ, the cold mass (4.2 K) is 131 metric tons and the ampere-turns, 13.7 × 10⁶. The final design of the magnet will be briefly introduced. Described in detail are the experiences of coil winding and coil assembly, the assembly of force-containment superstructure, assembly of magnet cryostat and results of magnet performance tests.     

传导冷却超导磁体系统真空问题的试验研究

成功研制了6T NbTi 传导冷却超导磁体系统,制冷机为二级GM-制冷机.磁体冷却到4 K需用74 h左右,目前磁体系统已分别完成了115 A(6T),45 h和95 A,264 h的无间断运行实验.制冷机可在长达15天(359 h)的时间里,对系统抽真空并维持系统真空在1.5×10-2 Pa左右,其间不再使用扩散泵对超导磁体系统抽真空.     

Bottom-coverage simulation for magnetron-sputtering apparatus activated with superconducting bulk magnet

The bottom coverage in circular via holes for magnetron sputtering apparatus equipped with a superconducting bulk magnet was analyzed using computer simulation. Owing to the high magnetic field, the apparatus allowed film deposition under low pressure. In the simulation, the transport of sputtered atoms was treated by the Monte Carlo method and the film deposition was calculated using a string model. The simulated results qualitatively reproduced the behavior of the measured bottom coverage. However, considerable deviation was observed depending on the geometry. It was ascribed to factors such as resputtering, reflection, and surface diffusion.     

35 kJ高温超导磁储能(SMES)的热输运实验研究

研制了中国首台高温超导磁储能直接冷却系统,该系统不使用低温液体(液氦、液氮).在10-3Pa的真空度下,高温超导磁体线圈由1台单级GM制冷机从室温293 K冷却到19 K,Bi2223电流引线由另一台制冷机冷却到77 K以下.整个系统在通140 A直流电流的时候产生了4.5 T的磁场.系统连续运行480 h(20 d),磁体和低温系统各参数动态特性良好.实验研究表明,控制系统的漏热,优化磁体内部导冷结构,有效减少热传导部件的接触界面热阻是制冷机直接冷却高温超导磁体的关键技术.     

Study of flow fractionation characteristics of magnetic chromatography utilizing high-temperature superconducting bulk magnet

Abstract

We present numerical simulation of separating magnetic particles with different magnetic susceptibilities by magnetic chromatography using a high-temperature superconducting bulk magnet. The transient transport is numerically simulated for two kinds of particles having different magnetic susceptibilities. The time evolutions were calculated for the particle concentration in the narrow channel of the spiral arrangement placed in the magnetic field. The field is produced by the highly magnetized high-temperature superconducting bulk magnet. The numerical results show the flow velocity difference of the particle transport corresponding to the difference in the magnetic susceptibility, as well as the possible separation of paramagnetic particles of 20 nm diameter.     

Study of flow fractionation characteristics of magnetic chromatography utilizing high-temperature superconducting bulk magnet

We present numerical simulation of separating magnetic particles with different magnetic susceptibilities by magnetic chromatography using a high-temperature superconducting bulk magnet. The transient transport is numerically simulated for two kinds of particles having different magnetic susceptibilities. The time evolutions were calculated for the particle concentration in the narrow channel of the spiral arrangement placed in the magnetic field. The field is produced by the highly magnetized high-temperature superconducting bulk magnet. The numerical results show the flow velocity difference of the particle transport corresponding to the difference in the magnetic susceptibility, as well as the possible separation of paramagnetic particles of 20 nm diameter.     

A capacitance-graded cryogenic high voltage bushing for vertical or horizontal mounting

The cryogenic high voltage bushing for the terminations of the 138 kV, 4100 A superconducting cable prototype at the Brookhaven National Laboratory (BNL) is described. The bushing is energized with the line-to-ground voltage between the coaxial centre and outer surrounding conductors, in the axial direction there is a temperature difference from ambient to about 6 K.The capacitively graded bushing can be mounted in any position. It is vacuum tight and withstands pressures of more than 20 bar. The heat leak of the insulation body in axial direction is only 8.5 W.The electrical specifications of the bushing are: 825 kV, 1.2 × 50 μs impulse voltage; 240 kV rms ac 2h test voltage: and > 160 kVs partial discharge inception voltage.This bushing concept may easily be modified to meet most conceivable thermal, mechanical and electrical requirements of cryogenic high voltage engineering.