JP2008140900A - Superconductive coil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stable and high-performance superconductive coil that suppresses mechanical motion in a thin-film superconductive wire, keeps sufficient coil strength, and prevents strain due to the difference in a thermal shrinkage rate between the thin-film superconductive wire and a winding frame from occurring in the thin-film superconductive wire in a heat cycle of room temperature and liquid nitrogen temperature. <P>SOLUTION: In the pancake type superconductive coil, the thin-film superconductive wire is wound around the winding frame, and the thin-film superconductive wire in the innermost peripheral turn is stuck to the winding frame. In the superconductive coil, a thermal shrinkage rate A in the direction of the coil axis of the winding frame from the room temperature to the liquid nitrogen temperature (77K) is within a range of ±0.20% of the thermal shrinkage rate B in the direction of the coil axis of the thin-film superconductive wire from the room temperature to the liquid nitrogen temperature (77K). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a superconducting coil, and more specifically, in a pancake type superconducting coil formed by winding a thin-film superconducting wire having a multilayer structure around a winding frame, the thin-film superconducting wire is not distorted and is stable and has a high performance. It is what.

Conventionally, in Japanese Patent Application Laid-Open No. 2003-323822, a thin film superconducting wire having a multilayer structure having a substrate, an intermediate layer, a superconducting layer, and a stabilizing layer is provided.
This type of thin film superconducting wire is overlapped with an insulating tape and wound in a spiral shape on a winding frame to form a pancake type superconducting coil. To suppress the mechanical movement of the thin film superconducting wire when using the coil, to maintain the coil strength, to protect each other from the thin film superconducting wire, and to prevent "quenching", which is a state where the superconducting state of the superconducting coil is broken It is said that it is effective.

  As shown in FIG. 3, the conventional impregnated coil 100 includes an insulating tape 15 between the winding frame 22 and the innermost peripheral turn (T1) of the thin film superconducting wire 11, the outer peripheral surface of the innermost peripheral turn, and the next turn. It is integrated between the turns from (T2) to the outermost turn (TZ), and is adhered to each other on the outer peripheral surface of the outermost turn (TZ), and is heated and cured together with the reel 22 and the thin film superconducting wire 11. Is manufactured.

JP 2003-323822 A

However, when a thin film superconducting wire having a multilayer structure is distorted, delamination may occur between the substrate and the intermediate layer of the thin film superconducting wire made of different materials and between the superconducting layer and the stabilizing layer.
Therefore, when the winding frame and the thin film superconducting wire are bonded and fixed as in the impregnated coil, when cooled to below the liquid nitrogen temperature during use, or when the temperature is rapidly increased from the liquid nitrogen temperature to room temperature during inspection, There is a possibility that the thin film superconducting wire is distorted due to the difference in thermal contraction rate of the thin film superconducting wire, and the above delamination occurs.

  Specifically, in FIG. 3, the thermal contraction rate in the coil axial direction (arrow Y in the figure) of the thin film superconducting wire 11 when cooled from room temperature to liquid nitrogen temperature (77K) is approximately 0.30%. On the other hand, the thermal contraction rate in the coil axis direction of the winding frame 22 is approximately 0.75%. Due to the difference in thermal shrinkage rate, the thin film superconducting wire is dragged by the thermal contraction of the winding frame, and the thin film superconducting wire may be distorted.

  The present invention has been made in view of the above-described problem, and suppresses mechanical movement of a thin film superconducting wire to maintain a sufficient coil strength, and in a heat cycle of room temperature and liquid nitrogen temperature, a reel is formed on the thin film superconducting wire. It is an object of the present invention to provide a stable and high-performance superconducting coil that does not cause distortion due to the difference in thermal contraction rate.

In order to solve the above problems, the present invention is a pancake type superconducting coil in which a thin film superconducting wire is wound around a winding frame, and a thin film superconducting wire having an innermost turn is fixed to the winding frame.
The thermal contraction rate (A) between the room temperature in the coil axis direction of the winding frame and the liquid nitrogen temperature (77K) is the thermal contraction rate between the room temperature in the coil axis direction of the thin film superconducting wire and the liquid nitrogen temperature (77K). A superconducting coil characterized by being in the range of ± 0.20% of (B) is provided.

  The present inventor has intensively studied a superconducting coil that can surely suppress the mechanical movement of the thin film superconducting wire and does not cause the thin film superconducting wire to be distorted due to the difference in thermal shrinkage. As a result, even when the winding frame and the thin film superconducting wire are integrally fixed, the thermal contraction rate (A) between room temperature and liquid nitrogen temperature (77 K) in the coil axial direction of the winding frame, and the thin film superconductivity By making the thermal contraction rate (B) between room temperature in the coil axis direction of the wire rod and the liquid nitrogen temperature (77K) close to within ± 0.20%, the distortion generated in the thin film superconducting wire is suppressed, and a stable superconducting coil I found out that I can do it.

As described above, the difference between the thermal shrinkage rates (A) and (B) of the winding frame and the thin film superconducting wire is within ± 0.20% because the difference between the thermal shrinkage rates (A) and (B) is ± 0. This is because if it exceeds 20%, the thin film superconducting wire may be distorted (tensile or compressed). The difference between the heat shrinkage rates (A) and (B) is preferably within ± 0.10%.
The thermal shrinkage rate (A) (B) is measured by the rate of dimensional change from room temperature when a strain gauge is attached to the outer peripheral surface of the reel and the thin film superconducting wire and cooled to liquid nitrogen temperature (77 K). .

  In the superconducting coil, it is preferable that the thermal contraction rate (A) of the winding frame is close to the thermal contraction rate (B) of the thin film superconducting wire. In general, since it is difficult to change the material of the thin film superconducting wire, in the present invention, this is dealt with by changing the material of the reel.

The material of the reel used in the present invention may be any material as long as the difference between the thermal shrinkage rates (A) and (B) is within ± 0.20%. For example, metals such as stainless steel and aluminum, ceramics, and glass And fiber reinforced plastics.
Among these, it is preferable to use a fiber reinforced plastic because it is excellent in insulation, can secure mechanical characteristics at a liquid nitrogen temperature, and has high stability.
The fiber reinforced plastic includes those produced by various methods, but it is preferable to use a prepreg sheet laminated and heat-integrated and vacuum formed.

As the prepreg sheet constituting the winding frame, a fabric (cross) prepreg in which a fabric or a fiber material such as glass fiber, carbon fiber, or aramid fiber is impregnated with a thermosetting resin such as an uncured epoxy resin or a phenol resin, Unidirectional prepregs can be used.
Among these, a fabric prepreg sheet in which a glass fiber fabric is impregnated with an uncured epoxy resin is preferably used. The woven prepreg sheet preferably has a resin amount of 60 ± 10% by mass and a thickness of 100 μm or less.

  Further, among the fiber reinforced plastic winding frames, the heat shrinkage rate (A) is less than 0.35%, which is formed from a laminate of prepreg sheets arranged in parallel with the coil axis direction. preferable.

Conventionally, a fiber reinforced plastic winding frame used in the past is a process in which a required number of prepreg sheets are stacked and heated in the thickness direction (that is, the direction perpendicular to the axial direction of the winding frame) to form a vacuum-formed flat plate. It was made. Therefore, as shown in FIG. 3 (B), the prepreg sheet and the reinforcing fiber cloth 20 constituting the prepreg sheet are laminated in the winding frame 22 in a direction perpendicular to the axial direction of the superconducting coil.
In this case, the thermal contraction rate of the winding frame 22 decreases in the circumferential direction of the coil reinforced with fibers (approximately 0.23%) and increases in the axial direction of the coil not reinforced with fibers (approximately 0.75). %).

Therefore, in the present invention, as described above, it is preferable that the winding frame is formed from a laminate of prepreg sheets arranged in parallel to the coil axis direction to reduce the thermal shrinkage rate in the coil axis direction.
Specifically, it is preferable that the thermal contraction rate between the room temperature in the coil axis direction and the liquid nitrogen temperature (77 K) is less than 0.35%. More preferably, it is less than 0.30%. If the thermal contraction rate of the winding frame in the temperature range is less than 0.35%, the thermal contraction rate in the coil axis direction can be significantly reduced as compared with the conventional fiber-reinforced plastic winding frame, and the thin film superconducting wire The thermal contraction rate (approximately 0.30%) can be close.

  The laminate of prepreg sheets arranged in parallel with the coil axis direction is prepared in a pipe shape by a method such as winding the prepreg sheet around a mold, thermosetting the core, and separating from the mold. It can be produced by cutting a pipe.

  An insulating adhesive layer is provided between the winding frame and the thin film superconducting wire and between each turn of the thin film superconducting wire, with a prepreg tape interposed, and from the room temperature in the coil axial direction of the insulating adhesive layer to the liquid nitrogen temperature (77K). ) Is preferably 0.30% or less.

With the above-mentioned configuration, the turns of the thin film superconducting wire can be reliably insulated and fixed to prevent quenching, and the thermal contraction rate between the room temperature in the coil axial direction of the insulating adhesive layer and the liquid nitrogen temperature (77K). Since the thermal contraction rate of the thin film superconducting wire and the winding frame can be made extremely close to each other, the distortion generated in the thin film superconducting wire can be further reduced.
When the prepreg tape that forms the insulating adhesive layer is wound around a winding frame together with the thin film superconducting wire, the coil axis direction is reinforced with the orientation direction of the reinforcing fibers, so that the prepreg tape is reinforced between room temperature and liquid nitrogen temperature (77K). The heat shrinkage rate can be 0.30% or less.

  That is, with the above configuration, both the orientation direction of the reinforcing fibers of the prepreg sheet forming the winding frame and the orientation direction of the reinforcing fibers of the prepreg tape forming the insulating adhesive layer can be the coil axis direction. The thermal contraction rate of the winding frame, the insulating adhesive layer, and the thin film superconducting wire can be made extremely close to each other. Therefore, it is possible to obtain a superconducting coil that hardly causes distortion in the thin film superconducting wire.

  The thin film superconducting wire of the present invention is not limited as long as it has a multilayer structure. For example, a ceramic intermediate layer made of YSZ (yttrium stabilized zirconia), a holmium type on a metal substrate made of Hastelloy (registered trademark) tape. Examples thereof include a thin film superconducting wire having a structure in which a superconducting layer made of an oxide superconducting layer such as an oxide superconductor and a stabilizing layer made of silver or the like are laminated. Furthermore, the entire periphery of the laminate may be covered with the metal protective film made of copper by electroless plating.

As described above, according to the present invention, the thermal contraction rate (A) between the room temperature in the coil axis direction of the winding frame and the liquid nitrogen temperature (77K) is reduced from the room temperature in the coil axis direction of the thin film superconducting wire. Since the thermal contraction rate (B) between the nitrogen temperature (77K) is within a range of ± 0.20% and the thermal contraction rate (A) and (B) of the winding frame and the thin film superconducting wire are very close to each other, Almost no distortion caused by the difference in thermal shrinkage with the reel.
Further, since the winding frame and the thin film superconducting wire are fixed, the mechanical movement of the thin film superconducting wire can be suppressed, and quenching can be effectively prevented.

  Also, the winding frame and the thin film superconducting wire are fixed by an insulating adhesive layer, and the thermal contraction rate between the room temperature in the coil axial direction of the insulating adhesive layer and the liquid nitrogen temperature (77K) is 0.30% or less. Then, since it can be made close to the thermal contraction rate of a winding frame and a thin film superconducting wire, it can be set as an extremely stable and high performance superconducting coil.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a superconducting coil 10 according to an embodiment of the present invention.
The superconducting coil 10 is a single pancake-type coil formed by winding a thin film superconducting wire 11 having a multilayer structure around a winding frame 12 together with a prepreg tape (not shown), and heat-treating and solidifying it integrally.
The superconducting coil 10 uses an oxide superconductor as the thin film superconducting wire 11 and is cooled to a liquid nitrogen temperature (77 K).

  In the superconducting coil 10, the inner electrode 13 is attached to and electrically connected to the inner peripheral surface of the innermost turn (T 1) of the thin film superconducting wire 11, and the inner electrode 13 is attached to the winding frame 12. It is fixed to. On the other hand, an outer electrode 14 is attached to the outer peripheral surface of the outermost turn (TZ) of the thin film superconducting wire 11 for electrical connection, and the outer electrode 14 is insulated by wrapping five prepreg tapes around the outer electrode 14. Layer 17 is provided.

  FIG. 2A is a cross-sectional view of the superconducting coil 10 cut along the line AA in parallel with the coil axis direction (arrow Y in the figure).

The winding frame 12 is prepared by winding a prepreg sheet (not shown) around a mold and thermosetting it, and then cutting and cutting a pipe separated from the mold.
That is, the winding frame 12 is formed of a laminated body in which the prepreg sheet is arranged in parallel with the coil axis direction (Y). Therefore, as shown in FIG. 2 (B), the reinforcing fiber cloth 20 of the prepreg sheet is connected to the coil axis. It is oriented and strengthened in the direction (Y). Therefore, the thermal contraction rate between the room temperature and the liquid nitrogen temperature (77 K) of the winding frame 12 in the coil axis direction (Y) is small, 0.23%.
As the prepreg sheet constituting the winding frame 12, an epoxy resin impregnated with a reinforcing fiber cloth 20 made of glass fiber as a reinforcing fiber is used, and the ratio of the resin to the entire formed winding frame 12 is 40 ±. 5% by mass.

  The thin film superconducting wire 11 used in this embodiment has a multilayer structure in which a substrate layer made of metal, an intermediate layer made of ceramics, a superconducting layer made of an oxide superconductor, and a stabilizing layer made of silver are laminated, starting from room temperature. A heat shrinkage ratio between liquid nitrogen temperatures (77 K) of 0.30% is used.

  That is, in this embodiment, the thermal contraction rate (A) between the room temperature in the coil axis direction (Y) of the winding frame 12 and the liquid nitrogen temperature (77 K) is changed from the room temperature in the coil axis direction of the thin film superconducting wire 11 to the liquid. The thermal contraction rate (B) between the nitrogen temperature (77K) is set to -0.07%, and the thermal contraction rate of the winding frame 12 and the thin film superconducting wire 11 is very close. Therefore, the thin film superconducting wire 11 is not distorted by the thermal contraction of the winding frame 12, and a stable superconducting coil can be obtained.

Furthermore, the superconducting coil 10 is insulated and bonded by heat-curing the prepreg tape 15 between the winding frame 12 and the thin-film superconducting wire 11 and between the turns of the thin-film superconducting wire 11 and then winding it. Layer 16 is provided. As the prepreg tape 15 for forming the insulating adhesive layer 16, a prepreg tape made of glass fiber reinforced fiber impregnated with a reinforcing fiber cloth 21 (epoxy resin amount: 55 ± 5 mass%) is used. Since the insulating adhesive layer 16 can bond and fix the winding frame 12, the thin film superconducting wire 11 and the thin film superconducting wire, the mechanical movement of the thin film superconducting wire 11 is suppressed and the coil strength is maintained. Can do.
The thermal contraction rate (C) between the room temperature in the coil axial direction (Y) of the insulating adhesive layer 16 and the liquid nitrogen temperature (77K) is 0.23 to 0.30%.

  Further, with this configuration, the orientation directions of the reinforcing fiber cloth 21 of the prepreg sheet 15 that forms the insulating adhesive layer 16 and the reinforcing fiber cloth 20 that forms the winding frame 12 are both the same as the coil axis direction (Y). Therefore, the thermal shrinkage rate (C) of the insulating adhesive layer 16 can be made very close to the thermal shrinkage rates (A) and (B) of the winding frame 12 and the thin film superconducting wire 11. Therefore, it is possible to obtain a very stable superconducting coil in which the thin film superconducting wire is not distorted.

  As the thin film superconducting wire 11 and the winding frame 12 used in the present invention, if the thermal contraction rate (A) of the winding frame is within ± 0.20% of the thermal contraction rate (B) of the thin film superconducting wire, The present invention is not limited to the materials and structures described in the embodiments, and includes modifications within the scope equivalent to the scope of claims.

  In the embodiment, the single pancake type superconducting coil has been described. However, the present invention can be similarly applied to a double pancake type superconducting coil.

It is a schematic perspective view of the superconducting coil of the embodiment of the present invention. (A) It is a schematic diagram which shows the AA cross section of the superconducting coil of FIG. 1, (B) is an enlarged view which shows the principal part of (A). (A) is a cross-sectional schematic diagram of a conventional superconducting coil, and (B) is an enlarged view showing the main part of (A).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Superconducting coil 11 Thin film superconducting wire T1 Innermost turn TZ Outermost turn 12, 22 Winding frame 13 Inner electrode 14 Outer electrode 15 Prepreg tape 16 Insulating adhesive layer 17 Insulating protective layer 20, 21 Reinforcing fiber cloth

Claims (3)

In a pancake type superconducting coil in which a thin film superconducting wire is wound around a winding frame, and a thin film superconducting wire having an innermost turn is fixed to the winding frame,
The thermal contraction rate (A) between the room temperature in the coil axis direction of the winding frame and the liquid nitrogen temperature (77K) is the thermal contraction rate between the room temperature in the coil axis direction of the thin film superconducting wire and the liquid nitrogen temperature (77K). A superconducting coil which is within a range of ± 0.20% of (B).   The superconducting coil according to claim 1, wherein the winding frame is formed of a laminate of prepreg sheets arranged in parallel with the coil axis direction, and the thermal shrinkage rate (A) is less than 0.35%.   An insulating adhesive layer is provided between the winding frame and the thin film superconducting wire and between each turn of the thin film superconducting wire, with a prepreg tape interposed, and from the room temperature in the coil axial direction of the insulating adhesive layer to the liquid nitrogen temperature (77K). The superconducting coil according to claim 1 or 2, wherein a thermal contraction rate (C) during () is 0.30% or less.

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