JP3172893B2 - Superconducting current lead - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting current lead used for supplying a current to a superconducting magnet.

[0002]

2. Description of the Related Art In general, superconducting electromagnets are cooled to extremely low temperatures using helium. For this reason, oxide ceramics are used for superconducting current leads for supplying current to the superconducting magnet.

Here, the configuration of the superconducting electromagnet will be outlined with reference to FIG.

[0004] A coil winding frame 12 is provided in the vacuum vessel 11, and a so-called superconducting coil 13 is wound around the coil winding frame 12. As shown, an outer peripheral cooling copper block 14 is mounted on the outer peripheral surface of the coil 12, and the outer peripheral cooling copper block 14 is mounted on the cooling stage 15 together with the bobbin 12. The cooling stage 15 is supported by a refrigerant (for example, helium) passage tube 16.

Further, a pair of electrodes (hereinafter referred to as low-temperature side electrodes) 17a and 17b
Are supported via an insulator (not shown). Although not shown, these low-temperature electrodes 17 a and 17 b are connected to the coil 13. Below the cooling stage 15, another cooling stage 18 is supported by the refrigerant passage tube portion 16, and a pair of electrodes (hereinafter, this electrode is referred to as a high-temperature side electrode) 19a and 19b are insulated on the cooling stage 18. Body (not shown)
Is supported through. A current lead bulk 20a is mounted between the low-temperature side electrode 17a and the high-temperature side electrode 19a, and these low-temperature side electrode 17a, high-temperature side electrode 19a,
A superconducting current lead is constituted by the current lead bulk 20a. Similarly, a current lead bulk 20b is mounted between the low-temperature side electrode 17b and the high-temperature side electrode 19b, and the low-temperature side electrode 17b, the high-temperature side electrode 19b, and the current lead bulk 20b constitute a superconducting current lead. You.

As shown, the superconducting coil 13 is covered by a heat shield plate 21 supported on the outer peripheral end of the cooling stage 18. Copper current leads 22 are connected to the high-temperature electrodes 19a and 19b (FIG. 5 shows the high-temperature electrodes 19a and 19b).
Only the copper current lead 22 connected to a is shown), and this copper current lead 22 is drawn out of the vacuum vessel 11. The so-called GM refrigerator 23 is located below the vacuum vessel 11.
The refrigerator 23 is connected to the refrigerant passage tube 16.

[0007]

By the way, oxide ceramics are generally used for a current lead bulk used for a superconducting current lead. For this reason, the current lead bulk is brittle, and the strength of oxide ceramics is about several tenths to one-tenth that of structural ceramics, for example, alumina, zirconia, or silicon nitride. Therefore, when actually using the current lead bulk,
It is necessary to sufficiently reduce the thermal stress.

However, it is impossible to completely eliminate the thermal stress from the viewpoint of design, and there is a problem that the superconducting current lead is likely to be damaged when an external force is applied during transportation or the like.

In order to prevent the above-mentioned problems, there has been proposed a method in which Ag or ZrO ₂ is added to the calcined powder, followed by molding and sintering to obtain a bulk body.
When Ag is added, the thermal conductivity of the bulk body itself increases due to the high thermal conductivity of Ag,
It becomes unsuitable for use as a current lead.
On the other hand, when ZrO ₂ is added, the critical current density Jc
Is reduced.

In order to solve this problem, a material having a low thermal conductivity, for example, stainless steel (SUS) or glass fiber plastic (FRP) may be disposed as a reinforcing material on the outer peripheral surface of the bulk material (bulk material). If the body is cylindrical, place the FRP on its inner peripheral surface). However, there is a problem that thermal stress is generated due to a difference in thermal expansion between the reinforcing member and the bulk body because the coefficient of thermal expansion is large. In addition, the bulk body deforms slightly during sintering. In consideration of this point, the reinforcing material must be manufactured for each bulk body, and there is a problem that the manufacturing is extremely troublesome.

It is an object of the present invention to provide a superconducting current lead that is extremely unlikely to be damaged or the like.

[0012]

According to the present invention, there is provided a superconducting current lead used for supplying a current to a superconducting magnet, comprising a hollow ceramic conductor having electrodes formed at both ends thereof. the ceramic conductor portion except for a portion of the electrode is resin-molded together with the electrode, the tree
The fat mold superconducting current lead body characterized in that the ceramic powder is added is obtained.

[0013]

According to the present invention, since the ceramic conductor is resin-molded together with the electrode except for a part of the electrode, the strength against stress is increased, and the thermal expansion coefficient of the resin mold is increased by adding ceramic powder to the resin mold. The coefficient of thermal expansion of the ceramic conductor can be almost the same,
As a result, almost no thermal stress is generated.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

First, referring to FIG. 1, a superconducting current lead according to the present invention includes a current lead bulk (superconductor) 30 having a cylindrical shape. 31 are formed. In forming the silver electrode portion 31, in order to reduce the contact resistance with the superconductor 30, a silver tape is wound around the superconductor 30 or silver spraying is performed, and then heat treatment is performed to form the silver electrode portion 31. A copper electrode 32 is attached to each silver electrode part 31. The copper electrode 32 includes an annular portion 32a and a connection portion 32.
b, and the silver electrode portion 3 is formed by the annular portion 32a.
1 is pinched. One of the copper electrodes 32 is connected to the superconducting coil shown in FIG. 5 at a connection portion 32b, and the other of the copper electrodes 32 is connected to a copper current lead shown in FIG. 5 at a connection portion 32b. Used up to 77K).

Here, referring to FIG. 2, the superconducting current lead obtained as described above is immersed in the molten resin for a predetermined time while leaving a part of the connection portion 32b, and then pulled up to cure the resin. Will be By performing such an operation at least once, the resin mold layer 33 is formed as shown by a thick line in FIG. Ceramic powder is appropriately added to the above resin,
Thereby, the coefficient of thermal expansion of the superconductor 30 and the coefficient of thermal expansion of the resin mold layer 33 are approximated.

By the way, in the superconducting current lead in the state shown in FIG. 1, stress is generally concentrated at point A, and as a result, the lead often breaks. On the other hand, in the superconducting current lead in the state shown in FIG. 2, since the entire superconductor 30 including the electrodes is reinforced by the resin mold layer 33, stress concentration at the point A is alleviated, and breakage is extremely small. further,
Since the thermal expansion coefficient of the superconductor 30 and the thermal expansion <br/> of the resin molded layer 33 is substantially the same, never thermal stress occurs. Furthermore, since the superconductor 30 is hollow, it has a cylindrical shape.
Of high current flow compared to the shape
There is also. This is the central axis of a cylindrical superconductor.
In the region close to, the orientation of the crystal is
However, if the superconductor 30 is hollow,
Does orientation improve when crystals are arranged in one direction?
It is.

Here, the attachment of the superconducting current lead shown in FIG. 2 will be specifically described with reference to FIG. In FIG. 2, the same components as those in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted.

The low-temperature side electrode 17a is supported on the cooling stage 15 via an insulator 17c, and the low-temperature side electrode 17a is connected to a superconducting coil. Similarly, cooling stage 1
8, a high-temperature side electrode 19a is supported via an insulator 19c. Then, the low-temperature side electrode 17a and the high-temperature side electrode 19
A superconducting current lead 40 shown in FIG.

The superconducting current lead 40 is connected to the low-temperature side electrode 17a.
When attaching to the high-temperature side electrode 19a, a ring-shaped electrode 41 is separately prepared as shown in FIG. The ring electrode 41 is provided with a connection portion 41b and the annular portion 41a, connecting portions 41b are manually fixed to the connecting portion 32b and the bolt 42 of the copper electrode 32. Then, after inserting the low-temperature side electrode 17a and the high-temperature side electrode 19a into the annular portion 41a of the ring-shaped electrode 41, respectively, they are fixed with solder.

[0021]

As described above, in the present invention, since the ceramic conductor (current lead bulk) is resin-molded together with the electrodes except for a part of the electrodes, the strength against stress is increased, and the ceramic powder is added to the resin mold. It can be substantially the same thermal expansion coefficient of the thermal expansion coefficient of the ceramic Seishirube collector of the resin mold by adding, as a result, there is an effect that occurrence of thermal stress is hardly. Ma
In addition, since the superconductor is hollow, it becomes cylindrical.
The effect that a higher current can be flowed is obtained.
You.

[Brief description of the drawings]

FIG. 1 is a diagram showing a superconducting current lead according to the present invention in a state before resin molding.

FIG. 2 is a diagram showing a superconducting current lead according to the present invention in a state after resin molding.

FIG. 3 is a diagram for explaining attachment of a superconducting current lead according to the present invention.

FIG. 4 is a diagram for explaining a ring-shaped electrode used when attaching a superconducting current lead according to the present invention.

FIG. 5 is a diagram schematically showing a superconducting electromagnet device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Vacuum container 12 Coil winding frame 13 Superconducting coil 14 Peripheral cooling copper block 15 Cooling stage 16 Refrigerant passage tube part 17a, 17b Low-temperature side electrode 18 Cooling stage 19a, 19b High-temperature side electrode 20a, 20b Current lead bulk 21 Heat shield plate 22 Copper current lead 23 GM refrigerator 23 30 Current lead bulk (superconductor) 31 Silver electrode part 32 Copper electrode 32a Annular part 32b Connection part 33 Resin mold layer

Claims (1)

(57) [Claims] 1. A superconducting current lead for use in supplying a current to a superconducting magnet, comprising: a hollow ceramic conductor portion having electrodes formed at both ends; The conductor is resin-molded together with the electrodes, and the resin mold contains ceramic powder.
A superconducting current lead, wherein the lead is added .