JPH04359406A - Superconducting coil - Google Patents

Abstract

PURPOSE:To reduce an axial compressive force which results in a degraded critical current density. CONSTITUTION:A superconducting coil is comprised of: outer windings 2 which are made of a superconductor being wrapped like a coil; inner windings 1 which are shorter, in axial length, than the outer winding and which are disposed adjacent to the inner end of the outer windings; and rings 3 of a magnetic substance, each surrounding the inner winding 1.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to superconducting coils that generate high magnetic fields.

0002

[Prior Art] A superconducting coil that generates a high magnetic field exceeding about 8 T (Tesla) uses an inner winding made of a compound-based superconducting material such as Nb3Sn, which has an excellent critical current density in a high magnetic field, as shown in Figure 3. 1 and an outer winding 2 made of an alloy superconducting material such as NbTi are arranged concentrically. In this case, in order to generate a higher magnetic field with a smaller winding volume, the inner winding 1 is often designed to have a shorter shaft height than the outer winding 2.

0003

In such a coil, an axial compressive force F based on the vector product of the radial component of the magnetic field line B5 and the coil current acts. Due to this axial compressive force F, the conductor of the inner winding 1 has its critical current density (hereinafter referred to as J
(abbreviated as c) deteriorates significantly. Conventionally, this axial compressive force F increases as the coil becomes larger and the magnetic field becomes stronger, and the degree of deterioration becomes more noticeable. An object of the present invention is to provide a coil structure that can reduce as much as possible the axial compressive force that causes Jc deterioration. [Structure of the invention]

0004

[Means for solving the problem] In order to achieve the above object, there is an outer winding in which a superconducting conductor is wound in a cylindrical shape, and an outer winding in which a superconducting conductor is wound in a cylindrical shape and whose axial length is shorter than the outer winding. The structure includes an inner winding disposed inside the winding and a magnetic ring provided at an axial end of the inner winding.

[0005]

[Effect] In this way, the radial component of the magnetic field lines is reduced, the axial compressive force is reduced, and therefore the Jc of the conductor of the inner winding is reduced.
It becomes possible to suppress deterioration.

[0006]

[Embodiment] An embodiment of the present invention will be described below with reference to FIG. In Fig. 1, the coil has an inner winding 1 made of a compound superconducting material and an outer winding 2 made of an alloy superconducting material arranged concentrically, and a magnetic material such as iron or permalloy is placed at the axial difference between the two. The configuration is such that a ring 3 is inserted.

In this configuration, due to the presence of the magnetic ring 3, the magnetic force line B5 in FIG. 3 changes into a shape with less radial component, like the magnetic force line A4 in FIG. 1. Therefore, the axial compressive force F
is also reduced, making it possible to suppress Jc deterioration of the inner winding 1. (Other examples)

The coil shown in FIG. 3 has a magnetic ring 3 on top,
It is fixed to the lower flange 6, and in this case, since the axial compressive force as a mutual attraction force between the upper and lower magnetic rings 3 is not applied to the inner winding 1, it has the effect of further suppressing Jc deterioration.

[0009]

Effects of the Invention According to the present invention, the axial compression force can be reduced even in a solenoid type coil in which a winding made of a compound superconducting material is provided on the inside. Jc deterioration can be suppressed.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of a superconducting coil of the present invention.

FIG. 2 is a cross-sectional view of a superconducting coil showing another embodiment.

FIG. 3 is a cross-sectional view showing a conventional superconducting coil.

[Explanation of symbols]

1...Inner winding
2...Outer winding 3...Magnetic ring
4... Lines of magnetic force A5... Lines of magnetic force B
6...Flange F...axial compression force

Claims (3)

[Claims] Claim 1: An outer winding in which a superconducting conductor is wound into a cylindrical shape, and an inner winding in which the superconducting conductor is wound in a cylindrical shape and whose axial length is shorter than that of the outer winding and is disposed inside the outer winding. and a magnetic ring provided at the axial end of the inner winding. 2. The superconducting coil according to claim 1, wherein the conductor material of the inner winding is a compound superconducting material, and the conductor material of the outer winding is an alloy superconducting material. [Claim 3] In claim (1) or (2),
A superconducting coil characterized by a magnetic ring fixed to a winding flange.