JP2016134418A - Superconducting coil and superconducting wire rod - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique that properly prevents damage of a superconducting layer due to shrinkage of an epoxy resin layer under cooling, thereby achieving a superconducting coil which is difficult to be reduced in Ic.SOLUTION: A tape-like superconducting wire rod 1 having a superconducting layer 3 formed on the surface of a metal substrate 2 is wound, and impregnated in an epoxy resin composition to achieve a superconducting coil having an epoxy resin layer 5 between the wound superconducting wire rods 1. A carbon layer 4 which is broken with weaker force than the breaking strength of the superconducting layer 3 is formed on at least one surface of the superconducting wire rod 1. The tape-like superconducting wire rod 1 is used for a superconducting coil, the superconducting layer 3 is formed on the surface of the metal substrate 2, and the carbon layer 4 which is broken with weaker force than the breaking strength of the superconducting layer 3 is provided to the at least one surface of the front and back surfaces.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a superconducting coil and a superconducting wire widely used in superconducting equipment such as a superconducting magnet.

  In recent years, a superconducting coil wound with a thin film superconducting wire (hereinafter also simply referred to as “superconducting wire”) has attracted attention from the viewpoint of excellent current-carrying characteristics.

  As shown in FIG. 2, such a superconducting coil is manufactured by winding a long superconducting wire 1 having a superconducting layer formed on a metal substrate around a winding frame.

  When disturbance occurs in the wound superconducting wire 1, there is a risk of magnetic field uniformity, magnetic field distribution disturbance, and the like. Particularly, when such disturbance occurs in an MRI (Magnetic Resonance Imaging) device, Accurate inspection becomes difficult.

  Therefore, normally, the superconducting wire 1 is fixed by forming the epoxy resin layer 5 by impregnating the epoxy resin composition between the superconducting wires 1 which are wound and adjacent to each other and curing. Yes.

JP 2013-065816 A

  However, when the above-described superconducting coil is used by being immersed in a refrigerant such as liquid nitrogen, the superconducting layer may be damaged, resulting in a decrease in Ic of the superconducting coil.

  Specifically, as shown in FIG. 3A, the thermal contraction rate (thermal expansion rate) of the epoxy resin layer 5 is 1%, and the metal substrate 2 (0.3%) and the superconducting layer 3 (0.3). Therefore, the epoxy resin layer 5 contracts greatly in the direction of the arrow as shown in FIG. 3B during cooling, and a tensile stress is applied to the metal substrate 2 and the superconducting layer 3. As a result, breakage occurs in the portion C of the superconducting layer 3 that is the weakest to the tensile stress, and the Ic of the superconducting coil is reduced. Note that FIG. 3 is a diagram schematically showing an enlarged view of the portion denoted by reference sign X in FIG.

  Accordingly, an object of the present invention is to provide a technique capable of obtaining a superconducting coil in which Ic is hardly lowered by appropriately preventing damage to the superconducting layer due to shrinkage of the epoxy resin layer during cooling.

A superconducting coil according to one aspect of the present invention is provided.
Superconducting in which an epoxy resin layer is formed between the wound superconducting wires by winding a tape-shaped superconducting wire having a superconducting layer formed on the surface of a metal substrate and then impregnating with an epoxy resin composition A coil,
In the superconducting coil, a carbon layer that is broken by a force weaker than a breaking strength of the superconducting layer is provided on at least one surface of the superconducting wire.

In addition, the superconducting wire according to one aspect of the present invention,
A tape-like superconducting wire used for a superconducting coil,
A superconducting layer is formed on the surface of the metal substrate,
It is a superconducting wire in which a carbon layer that breaks with a force weaker than the breaking strength of the superconducting layer is provided on at least one of the front surface and the back surface.

  ADVANTAGE OF THE INVENTION According to this invention, the technique which can obtain the superconducting coil which Ic cannot fall easily can be provided by preventing appropriately the damage of the superconducting layer by the shrinkage | contraction of the epoxy resin layer at the time of cooling.

It is a figure which shows typically the cross-sectional structure of the superconducting coil which concerns on one Embodiment of this invention, (a) is a state before cooling, (b) is a figure which shows the state after cooling. It is a side view which shows notionally the winding structure of the conventional superconducting coil. It is a figure which expands and shows typically the part of the code | symbol X in FIG. 2, (a) is a state before cooling, (b) is a figure which shows the state after cooling.

[Description of Embodiment of the Present Invention]
First, embodiments of the present invention will be listed and described.

(1) A superconducting coil according to an aspect of the present invention includes:
Superconducting in which an epoxy resin layer is formed between the wound superconducting wires by winding a tape-shaped superconducting wire having a superconducting layer formed on the surface of a metal substrate and then impregnating with an epoxy resin composition A coil,
In the superconducting coil, a carbon layer that is broken by a force weaker than a breaking strength of the superconducting layer is provided on at least one surface of the superconducting wire.

  In the superconducting coil according to this aspect, the carbon layer that breaks with a force weaker than the breaking strength of the superconducting layer is formed on at least one surface of the superconducting wire. As a result, when the epoxy resin layer shrinks greatly due to cooling, the carbon layer breaks before the superconducting layer breaks. Therefore, even if tensile stress occurs due to shrinkage of the epoxy resin layer during cooling, this tensile stress Is not applied to the metal substrate or the superconducting layer, the damage to the superconducting layer can be appropriately prevented, and the decrease in Ic of the superconducting coil is prevented.

(2) Moreover, it is preferable that the said carbon layer is formed in both surfaces of the said superconducting wire.

  By forming carbon layers on both surfaces of the superconducting wire, the number of carbon layers that break when the epoxy resin layer shrinks increases, so that damage to the superconducting layer can be prevented more reliably.

(3) Moreover, the superconducting wire according to an aspect of the present invention is
A tape-like superconducting wire used for a superconducting coil,
A superconducting layer is formed on the surface of the metal substrate,
It is a superconducting wire in which a carbon layer that breaks with a force weaker than the breaking strength of the superconducting layer is provided on at least one of the front surface and the back surface.

  When such a superconducting wire is wound and impregnated with an epoxy resin composition to form a superconducting coil, even if tensile stress is generated due to shrinkage of the epoxy resin layer during cooling, the tensile stress is applied to the metal substrate or Without being applied to the superconducting layer, breakage of the superconducting layer is appropriately prevented, and a decrease in Ic can be prevented.

[Details of the embodiment of the present invention]
Specific examples of the superconducting coil according to the embodiment of the present invention will be described below with reference to the drawings. In addition, this invention is not limited to these illustrations, is shown by the claim, and intends that all the changes within the meaning and range equivalent to a claim are included.

1. 1 is a cross-sectional view schematically showing a superconducting coil according to the present embodiment, in which FIG. 1 (a) shows a state before cooling, and FIG. 1 (b) shows a state after cooling. It is.

(1) Superconducting wire The superconducting coil according to the present embodiment is formed by winding a long superconducting wire around a winding frame in the same manner as a conventional superconducting coil, and the outer periphery of the wound superconducting wire is It is fixed to an outer frame such as a C-shaped ring.

  The superconducting wire 1 in this embodiment includes a metal substrate 2 and a superconducting layer 3 formed on the metal substrate 2 as shown in FIG. Although not shown, a stabilization layer made of a highly conductive metal material such as copper is formed around the superconducting wire 1.

As the metal substrate 2, for example, CeO ₂ , YSZ, and CeO ₂ are provided as an intermediate layer on a biaxially oriented metal base material such as a clad material in which a Cu layer and a Ni layer are formed on SUS. An oriented metal substrate or the like is used.

The superconducting layer 3 is composed of a rare earth oxide superconductor. Examples of the rare earth oxide superconductor include an oxide superconductor represented by REBCO (REBa ₂ Cu ₃ O _7-δ : RE is a rare earth). As RE, yttrium (Y) may be used. , Praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), holmium (Ho), ytterbium (Yb), and the like.

(2) Carbon Layer In the superconducting coil according to this embodiment, carbon layers 4 are formed on both the front and back surfaces of the superconducting wire 1. The thickness of the carbon layer 4 is preferably 200 nm to 50 μm, and more preferably 200 nm to 5 μm.

  The carbon layers 4 formed on the front and back surfaces of the superconducting wire 1 are configured to break with a force weaker than the breaking strength of the superconducting layer 3. Thereby, as shown by the symbol A in FIG. 1B, when the epoxy resin layer 5 contracts, the carbon layer 4 breaks and the metal substrate 2 or the superconducting layer 3 and the epoxy resin layer 5 are separated, It is possible to prevent a tensile stress from being applied to the metal substrate 2 and the superconducting layer 3.

  Such a carbon layer can be formed using, for example, a vapor phase method such as CVD (Chemical Vapor Deposition) or PVD (Physical Vapor Deposition). Moreover, you may form using a commercially available graphite spray etc.

(3) Epoxy resin layer The epoxy resin layer 5 in the superconducting coil according to the present embodiment is wound in layers by impregnating the epoxy resin composition with the superconducting wire 1 wound in a coil shape, as in the prior art. It is formed between the superconducting wires 1 formed.

2. Production of Superconducting Coil The superconducting coil according to this embodiment can be produced, for example, as follows.

  The superconducting coil according to the present embodiment is a so-called reel-to-reel system in which a superconducting layer and a stabilizing layer are formed after a tape-shaped metal substrate is unwound from the unwinding reel and wound on the take-up reel. After producing a superconducting wire using a wire, the superconducting wire is wound around a winding frame and impregnated in an epoxy resin composition, and the superconducting wire is fixed by an epoxy resin layer, as in the prior art. It is.

  However, in the superconducting coil manufacturing process as described above, the superconducting coil is manufactured by winding the superconducting wire and impregnating the epoxy resin composition with carbon layers on both sides of the superconducting wire. It is different from the conventional one.

  For example, in the manufacture of the above-described reel-to-reel superconducting wire, the carbon layer is formed on the both surfaces of the superconducting wire after being formed on the take-up reel after the superconducting layer and the stabilizing layer are formed. Can be formed.

  As a method for forming the superconducting layer, a vapor phase method (evaporation method, sputtering method, PLD method, etc.) or a liquid phase method (MOD method) can be employed. Further, vacuum impregnation can be employed as a method for forming the epoxy resin layer.

3. Effects of the present embodiment As described above, according to the superconducting coil according to the present embodiment, the carbon layer that breaks with a force weaker than the fracture strength of the superconducting layer is formed. When contracted, the carbon layer breaks before the superconducting layer breaks. As a result, since the superconducting layer and the metal substrate are separated from the epoxy resin layer, tensile stress is not applied to the metal substrate and the superconducting layer, and the damage of the superconducting layer due to the shrinkage of the epoxy resin layer is appropriately prevented. It is possible to obtain a superconducting coil that does not easily decrease.

  Moreover, in this Embodiment, since the carbon layer is formed on both surfaces of the superconducting wire, it is possible to more reliably prevent a decrease in Ic due to breakage of the superconducting layer. Even if the carbon layer is formed on at least one surface of the superconducting wire, the superconducting layer can be sufficiently prevented from being damaged.

  In addition, from the viewpoint of reliably preventing adjacent superconducting wires from short-circuiting, when the superconducting wire having a carbon layer formed on the surface is wound around a winding frame in the superconducting coil manufacturing process, the superconducting wire is used. It is preferable to interpose an insulating tape between them.

  In the present embodiment, the carbon layers are provided on both the front and back surfaces of the superconducting wire, but the carbon layers may be selectively provided only on either the front or back surface of the superconducting wire. Thereby, the surface of the superconducting wire separated from the epoxy resin layer can be controlled.

[Experimental example]
Hereinafter, the present invention will be described more specifically based on experimental examples.

1. Experimental example 1, 2, 3
(1) Experimental example 1
A superconducting layer made of YBCO was formed on the surface of a tape-like metal substrate having a width of 10 mm and a thickness of 100 μm to produce a superconducting wire (width 4 mm, length 200 m). And the carbon layer (10 micrometers) was formed in the back surface of the produced superconducting wire using CVD method.

  Next, a superconducting wire having a carbon layer formed on the back surface is wound around a winding frame (metal bobbin), and a single pancake coil having an inner diameter of 80 mm, an outer diameter of about 270 mm, and a height of about 4.3 mm. Was made.

  Next, by impregnating an epoxy resin composition in which an epoxy resin and a curing agent are mixed between the wound superconducting wires by vacuum impregnation, the epoxy resin composition is cured by holding at room temperature. An epoxy resin layer was formed, and the superconducting coil of Experimental Example 1 was produced.

(2) Experimental example 2
A superconducting coil of Experimental Example 2 was produced in the same procedure as Experimental Example 1 except that a superconducting wire wrapped with a polyimide insulating tape was used instead of the superconducting wire having a carbon layer formed on the back surface.

(3) Experimental example 3
A carbon layer is formed on the back surface in the same procedure as in Experimental Example 1, and then a superconducting wire wrapped with a polyimide insulating tape is used in the same manner as in Experimental Example 2, and the same procedure as in Experimental Example 1 is used. A superconducting coil was produced.

2. Evaluation The critical current (Ic) was measured in a state where the produced superconducting coil was immersed in liquid nitrogen and cooled (77K). After the measurement, the superconducting coil was lifted from liquid nitrogen and allowed to stand at room temperature until it returned to room temperature, and the temperature was raised naturally.

  For each of the superconducting coils of Experimental Examples 1, 2, and 3, the above-described operation (immersion in liquid nitrogen, pulling up from liquid nitrogen, temperature rise) was performed nine times, and Ic at the tenth immersion in liquid nitrogen Was measured again. Table 1 shows the first and tenth measurement results of Ic.

  From Table 1, in Experimental Example 2 in which no carbon layer was formed, Ic was remarkably low in the first Ic measurement, and Ic was further reduced in the tenth Ic measurement. Then, after the 10th Ic measurement, the superconducting coil was disassembled and the superconducting layer was observed with an optical microscope, and many breaks were observed.

  On the other hand, in Experimental Example 1 and Experimental Example 3, almost no decrease in Ic was observed between the first Ic measurement and the tenth Ic measurement, and it was confirmed that the decrease in Ic was sufficiently suppressed. It was. In the observation by the decomposition after the 10th Ic measurement, damage to the superconducting layer was not confirmed.

  From this, by providing a carbon layer that breaks with a force weaker than the superconducting layer's breaking strength, it is possible to appropriately prevent breakage of the superconducting layer due to shrinkage of the epoxy resin layer during cooling, and to prevent the superconducting coil from being reduced in Ic. It was confirmed that it could be manufactured.

  While the present invention has been described based on the embodiments, the present invention is not limited to the above embodiments. Various modifications can be made to the above-described embodiments within the same and equivalent scope as the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the technique which can obtain the superconducting coil which Ic cannot fall easily can be provided by preventing appropriately the damage of the superconducting layer by the shrinkage | contraction of the epoxy resin layer at the time of cooling.

1 Superconducting wire 2 Metal substrate 3 Superconducting layer 4 Carbon layer 5 Epoxy resin layer

Claims (3)

Superconducting in which an epoxy resin layer is formed between the wound superconducting wires by winding a tape-shaped superconducting wire having a superconducting layer formed on the surface of a metal substrate and then impregnating with an epoxy resin composition A coil,
A superconducting coil in which a carbon layer that is broken by a force weaker than the breaking strength of the superconducting layer is provided on at least one surface of the superconducting wire.   The superconducting coil according to claim 1, wherein the carbon layer is formed on both surfaces of the superconducting wire. A tape-like superconducting wire used for a superconducting coil,
A superconducting layer is formed on the surface of the metal substrate,
A superconducting wire in which a carbon layer that breaks with a force weaker than the breaking strength of the superconducting layer is provided on at least one of the front surface and the back surface.

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