JPH11329823A - Magnetic system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a compact configuration and a large electromagnetic power by using a pancake coil. SOLUTION: In the magnetic system, two conductor rings 2 are coupled to a pancake coil 1, wherein oxide superconducting tape wire material is wound in the pancake pattern. The conductor ring 2 is formed in the closed loop pattern by using, e.g. copper, stainless steel, hastelloy, copper-silver alloy, nickel alloy, silver magnesium and the like. The inner diameter of the conductor ring 2 is equal to the outer diameter of the pancake coil 1, the width (height) is equal to the width of the oxide superconducting tape wiring material and the thickness is the thickness satisfying the required yield stress. The final end of the pancake coil 1 and the conductor ring 2 are electrically connected. The conductor ring 2 supports the final end of the winding part of the pancake coil 1 by the tensile force in the circumferentail direction, reinforces the outermost surface of the pancake 1 and also functions as the current connecting part of the magnetic system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnet system using a pancake coil.

[0002]

2. Description of the Related Art With respect to formation and reinforcement of a current terminal at a winding end portion of a pancake coil, after a current lead for current connection is drawn from the winding end, a reinforcing tape such as a stainless steel tape or glass fiber is further wound. The method of reinforcing by using is used. The electrical connection between the pancake coils is integrated with the whole coil by soldering or the like.

JP-A-56-133803 describes that an outer peripheral surface of a pancake coil is surrounded by an annular reinforcing member having a notch.

JP-A-6-290933 describes a double pancake coil in which an oxide superconductor tape wire is wound around a conductive bobbin.

[0005]

With an electromagnet that generates a high magnetic field or a large-diameter electromagnet, a strong electromagnetic force acts on the coil to expand the coil in a radially outward direction, and can withstand this electromagnetic force. It must be designed into a structure.

Particularly, in the case of an electromagnet using a superconducting wire, if the electromagnet is deformed by an electromagnetic force, the superconducting characteristics of the superconducting wire are deteriorated and a sufficient superconducting current does not flow. Of Nb ₃ Sn and an oxide superconducting wire of metallic superconductor Bi2
Since the 212-silver sheathed wire has a small allowable strain, electromagnets using these wires must be sufficiently reinforced so that the distortion of the wire due to the electromagnetic force is less than the allowable strain.

Further, in a metal-based superconducting conductor having a small temperature margin, the superconducting wire is slightly moved by electromagnetic force to generate frictional heat, or heat is generated by releasing elastic energy, so that the superconducting wire is brought out of the superconducting state. A quenching phenomenon that transitions to a normal conducting state may occur.

In general, electromagnetic stress, which is a stress caused by an electromagnetic force, tends to concentrate on a place where the structure is not symmetrical or a place where the structure is changing rapidly compared with the surroundings. The middle part of the pancake coil can resist electromagnetic force due to the tension of the wound wire. However, the end of the winding of the pancake coil where electromagnetic stress tends to concentrate is not affected by the tension of the wire, so that it is necessary to use a reinforcing structure having a sufficient electromagnetic resistance.

Further, in an electromagnet that generates a high magnetic field, in order to increase the space current density, the number of wire portions through which current flows among components is increased as much as possible. Therefore, it is necessary to reduce the reinforcement structure as much as possible.
Further, the reinforcing structure needs to be a spatially efficient structure in order to improve the cooling efficiency of the electromagnet.
Further, a magnet system configured by laminating a plurality of pancake coils is required to have excellent maintainability such as repair and replacement of the pancake coils. But,
If the connection between the pancake coils is made by soldering, the maintainability is poor.

An object of the present invention is to provide a magnet system which is compact and has high electromagnetic resistance using a pancake coil, and a method of manufacturing the same.

[0011]

A feature of the present invention to achieve the above object is that a conductive ring covering the outer periphery of a pancake coil is electrically connected to a winding end of the pancake coil. Since the conductive ring supports the end of the winding portion of the pancake coil with circumferential tension, the outer periphery of the pancake coil is reinforced, and the end of the pancake coil and the conductor ring are electrically connected. So
Also functions as a current connection for the magnet system. Therefore, according to the magnet system of the present invention, since the conductive ring functions as a current connection terminal and reinforces the outer periphery of the double pancake coil, it is compact, has excellent electromagnetic stress resistance, and suppresses the occurrence of quench. As a result, a stable generated magnetic field with a small current loss can be obtained.

Another feature of the present invention is that the electrical connection means electrically connects a conductive ring that covers the outer periphery of an adjacent pancake coil of the plurality of stacked pancake coils, The electrically conductive ring that covers the outer periphery of the cake coil and the winding end of the pancake coil are electrically connected, so that the conductive ring functions as a current connection terminal and reinforces the outer periphery of the double pancake coil Therefore, it is compact, has excellent electromagnetic resistance, suppresses the occurrence of quench, reduces current loss, and can generate a stable generated magnetic field, and the electrical connection means is integrated by soldering etc. Instead, it is electrically connected to an adjacent magnet system, so that maintenance such as repair and replacement is significantly improved.

Further, since the electric connection means covers one surface of the pancake coil, the heat of the pancake coil can be released to the outside, so that the cooling efficiency of the magnet system is improved.

Further, when the electric connection means is annular and the inner peripheral surface of the electric connection means and the outer peripheral surface of the ring are in contact with each other, the pancake coil fitted into the ring is sandwiched between the electric connection means. When the force is applied from above and below, the adjacent rings are electrically connected via the electrical connection means by the pressing force from above and below, and at the same time,
The pressing force can be a radial compression force, and the entire pancake coil can be reinforced.

[0015]

(Embodiment 1) FIG. 1 shows a magnet system according to a first embodiment of the present invention. In the magnet system of this embodiment, two conductor rings 2 are fitted to a pancake coil 1 in which an oxide superconducting tape wire is pancake-wrapped.

The oxide superconducting tape wire is made of a Bi-based, Y
System, Tl system, Hg system, etc.
It is made by metal coating, chemical vapor deposition (CVD), physical vapor deposition (PVD), or the like. When the oxide superconducting tape wire is wound with pancake, an insulating tape or a reinforcing tape may be wound together as necessary. The pancake coil 1 may be impregnated with a resin.

The conductor ring 2 is formed in a closed loop using, for example, copper, stainless steel, Hastelloy, copper-silver alloy, nickel alloy, silver magnesium, or the like. The inner diameter of the conductor ring 2 is equal to the outer diameter of the pancake coil 1, the width (height) is equal to the width of the oxide superconducting tape wire, and the thickness is such that the required yield stress is satisfied. When fitting the conductor ring 2 to the conductor ring 2 by shrink fitting,
The inner diameter of the conductor ring 2 may be smaller than the outer diameter of the pancake coil 1. It is desirable that the conductor ring 2 has good (large) mechanical properties such as Young's modulus and yield stress and electrical properties such as conductivity.

The end of the pancake coil 1 and the conductor ring 2
And are electrically connected. The electrical connection is performed by soldering, crimping, welding, or the like. Also, pancake coil 1
And the conductor ring 2 may be heated to cause a chemical reaction at the interface between the pancake coil 1 and the conductor ring 2 to integrate the pancake coil 1 and the conductor ring 2. The pancake coil 1 and the conductor ring 2 may be alloyed and integrated.

As described above, the conductor ring 2 supports the end of the winding portion of the pancake coil 1 with the circumferential tension, so that the outermost periphery of the pancake coil 1 is reinforced and
Since the end of the pancake coil 1 is electrically connected to the conductor ring 2, the conductor ring 2 also functions as a current connection part of the magnet system.

Further, a pancake coil 1 and a conductor ring 2
If these are designed in consideration of the difference in thermal shrinkage between them, the conductor ring 2 shrinks at the temperature during operation of the magnet system and tightens the pancake coil 1, so that the entire pancake coil 1 can be reinforced. .

Next, the current-voltage characteristics of the magnet system A of this embodiment and the magnet system B of the prior art will be described more specifically. In both magnet systems A and B, a double pancake coil 1 in which a Bi2212 silver sheath wire and a copper-silver alloy tape as a reinforcing tape are co-wound.
Is used. The double pancake coil 1 is provided with a voltage terminal for measuring the voltage at the center of the coil.

In the magnet system A, after a copper conductor ring 2 is fitted to the double pancake coil 1, a solder is poured between the double pancake coil 1 and the conductor ring 2 to perform integration and electrical connection. , And further impregnated with resin.

The magnet system B is obtained by winding a copper-silver alloy tape around the outer periphery of the double pancake coil 1 for several turns after drawing out the current lead, and further impregnating the resin with the resin.

With the magnet systems A and B both kept at liquid helium temperature, current-voltage characteristics are measured under a bias magnetic flux density of 10T.

In the range where the electromagnetic stress was small, the entire coil showed a good superconducting state in both the magnet systems A and B.

In the magnet system A, the conductor ring 2
In the outer peripheral portion of the double pancake coil 1 including the above, voltage was generated by copper and solder, but the value was not a problem in practical use. In the magnet system A, BJR = 218
No difference in current-voltage characteristics between the center and the outer periphery of the double pancake coil 1 was observed up to [MPa].

In the magnet system B, as the current increases, a voltage is generated at the outer peripheral portion of the double pancake coil 1 including the current lead draw-out portion, and the current further increases, and the electromagnetic stress reaches BJR = 188 [MPa]. Then, a voltage was generated in all portions of the double pancake coil 1 except the central portion.

In the double pancake coil 1 of the magnet system A, Hastelloy X was used instead of the copper-silver alloy tape.
Even when the tape was used, there was no difference in current-voltage characteristics between the central portion and the outer peripheral portion of the double pancake coil 1 until the coil was short-circuited due to heat generation.

According to the magnet system of this embodiment,
Since the conductor ring 2 functions as a current connection terminal and reinforces the outer periphery of the double pancake coil 1, it is compact, has excellent electromagnetic resistance, suppresses quench, suppresses current loss, and generates a stable magnetic field. Can be obtained.

In place of the conductor ring 2, a reinforcing tape of a conductor may be wound around the double pancake coil 1 with the number of turns required for reinforcement, and a terminal portion may be formed by soldering or welding. . In addition to connecting only the end portions, the entire reinforcing tape may be integrated.

(Embodiment 2) FIG. 2 shows a magnet system according to a second embodiment of the present invention. The magnet system of the present embodiment is such that the pancake coil 1 used in the first embodiment is sandwiched between two conductor disks 3.

The conductor disk 3 is provided on the circular plane portion 4 having the same outer diameter as the pancake coil 1 on the conductor ring 2 of the first embodiment.
This is a shape with an edge 5 having the same function as that of FIG. As long as the conductor disk 3 is electrically connected to the edge portion 5 and the plane portion 4,
It does not need to be made entirely of a single material.

When the magnet systems of the present invention are laminated and a force is applied from above and below, the flat portions 4 of the adjacent conductor disks 3 are pressed together, and the adjacent magnet systems can be electrically connected. The contact resistance of the adjacent conductor disks 3 is sufficiently large as the area of the connecting plane is larger than the side surface of the pancake coil 1, so that there is no problem in operating the magnet system.

In the magnet system of the present embodiment, the conductor disk 3 is electrically connected to the adjacent magnet system without performing integration by soldering or the like, so that maintenance such as repair and replacement is remarkably improved. I do.

Further, since the heat of the pancake coil 1 can be released to the outside by the conductor disk 3, the cooling efficiency of the magnet system is improved.

According to the magnet system of this embodiment,
Since the conductor disk 3 functions as a current connection terminal and reinforces the outer periphery of the double pancake coil 1, it is compact, has excellent electromagnetic resistance, suppresses quench, suppresses current loss, and generates a stable magnetic field. And it is electrically connected to the adjacent magnet system without performing integration by soldering or the like, so that maintenance such as repair and replacement is significantly improved, and the heat of the pancake coil 1 is reduced. Since it can escape to the outside, the cooling efficiency of the magnet system is improved.

(Embodiment 3) FIG. 2 shows a magnet system according to a second embodiment of the present invention. The magnet system of the present embodiment is different from the conductor ring 2 of the first embodiment in that
Conductor ring 6 provided with an outer taper as shown in FIG.
The pancake coil 1 fitted into the coil is laminated using a connection ring 7 that connects the conductor rings 2 of adjacent magnet systems.

The inside of the connection ring 7 is tapered in accordance with the outer periphery of the conductor ring 6 so that the inside surface of the connection ring 7 and the outside surface of the conductor ring 6 are in close contact with each other. The connection ring 7 does not need to be entirely made of a single material as long as the adjacent conductor rings 6 can be electrically connected to each other. For example, a portion in contact with the conductor ring 6 is made of metal, The outside may be made of metal having high mechanical strength or glass fiber reinforced resin.
Further, the inner surface of the connection ring 7 and the outer surface of the conductor ring 6 may be connected by screwing.

The pancake coils 1 fitted in the conductor ring 6 are stacked with the connection ring 7 interposed therebetween, and when a force is applied from above and below, the conductor rings adjacent to each other via the connection ring 7 are pressed by the pressing force from above and below. At the same time as 6 is electrically conducted, the pressing force can be changed to a radial compressive force, and the entire pancake coil 1 can be reinforced.

According to the magnet system of this embodiment,
Since the conductor ring 6 functions as a current connection terminal and reinforces the outer periphery of the pancake coil 1, the conductor ring 6 is compact, has excellent anti-electromagnetic stress, and the connection ring 7 makes the adjacent conductor ring 6 electrically conductive. At the same time, the pressing force is set to a radial compressive force to reinforce the entire pancake coil 1, so that the occurrence of quench can be further suppressed, a current loss is reduced, and a more stable generated magnetic field can be obtained.

Further, since the connection ring 7 is electrically connected to an adjacent magnet system without performing integration by soldering or the like, maintenance properties such as repair and replacement are remarkably improved.

The pancake coil 1 described in the first to third embodiments includes a double pancake coil including a single pancake coil and a joint in addition to a normal double pancake coil. It can also be used. When a single pancake coil or a double pancake coil including a joint is wound, a conductive bobbin is used as the bobbin, and the beginning of the oxide superconducting tape wire is connected to the conductor bobbin by soldering or welding. As the material of the conductor bobbin, copper, a copper-silver alloy, a copper-magnesium alloy, stainless steel, or the like is used, but is not limited thereto. The pancake coil can be reinforced from the inner peripheral side by giving the conductor bobbin a mechanical property such as a large Young's modulus and a yield stress. Especially,
Oxide superconducting wires such as Bi-based silver sheath wires easily deteriorate their superconducting properties due to strain.
By connecting with a conductor bobbin, double pancake winding without distortion can be performed.

[0043]

According to the magnet system of the present invention,
The conductive ring functions as a current connection terminal and reinforces the outer periphery of the double pancake coil, so it is compact, has excellent electromagnetic resistance, suppresses quench, reduces current loss, and generates a stable magnetic field. Can be obtained.

Further, since the conductive ring functions as a current connection terminal and reinforces the outer periphery of the double pancake coil, it is compact and has excellent electromagnetic stress resistance.
Suppress the occurrence of quench, reduce current loss and obtain a stable generated magnetic field.Electrical connection means are electrically connected to adjacent magnet systems without integration by soldering or the like. Therefore, maintainability such as repair and replacement is remarkably improved.

Further, since the electric connection means covers one surface of the pancake coil, the heat of the pancake coil can be released to the outside, so that the cooling efficiency of the magnet system is improved.

Further, when the electric connection means is annular and the inner peripheral surface of the electric connection means and the outer peripheral surface of the ring are in contact with each other, the adjacent rings are electrically connected via the electric connection means. At the same time, the pressing force can be reduced to a radial compression force, and the entire pancake coil can be reinforced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a magnet system according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a magnet system according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a magnet system according to a third embodiment of the present invention.

FIG. 4 is a diagram in which the pancake coil 1 of the third embodiment is stacked with a connection ring 7 interposed therebetween.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pancake coil, 2 ... Conductor ring, 3 ... Conductor disk, 4 ... Plane part, 5 ... Edge part, 6 ... Conductor ring, 7 ... Connection ring.

Continued on the front page (72) Inventor Michiya Okada 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd.

Claims (4)

[Claims] 1. A magnet system, comprising: a conductive ring that covers an outer periphery of a pancake coil, wherein the ring is electrically connected to a winding end of the pancake coil. 2. An electric connection for electrically connecting a plurality of stacked pancake coils, a conductive ring covering the outer periphery of the pancake coil, and the ring covering the outer periphery of an adjacent pancake coil. Means, wherein the ring is electrically connected to a winding end of the pancake coil. 3. The magnet system according to claim 2, wherein said electric connection means covers one surface of said pancake coil. 4. The magnet system according to claim 2, wherein said electric connection means is annular, and an inner peripheral surface of said electric connection means contacts an outer peripheral surface of said ring.