JPH05335145A - Superconducting current lead - Google Patents

Abstract

PURPOSE:To lessen an effect due to a leakage magnetic field and to reduce the amount of intrusion of heat by a method wherein at least one part of an oxide superconducting conductor constituting the conductor of a current lead is formed into a solenoid coil- shaped conductor and the direction of turn of this coil-shaped conductor is turned in the direction to nagate the leakage magnetic field. CONSTITUTION:A high-temperature part 1a is formed into a structure, wherein aggregate conductors 4 formed by laminating ten sheets of silver sheathed tape-shaped wires made using an oxide superconductor as their main component are respectively creeped vertically along the outer periphery of a pipe, such as a stainless steel pipe 3, as a reinforcing material. Moreover, a low-temperature part 1b is formed into a structure, wherein a silver sheathed wire 6 made using an oxide superconductor as its main component is spirally wound on the periphery of the pipe 3 at a prescribed pitch in a direction to negate a leakage magnetic field front a superconducting magnet and is made to interlock on the pipe 3 by a bonding means, such as a bonding agent. Thereby, the deterioration of a magnetic field in the conducting current density of a current lead can be prevented and at the same time, the amount of intrusion of heat due to heat conduction can be reduced as the effect of the length of a conductor of the current lead.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art A magnet or the like using superconductivity is used in a state of being cooled with liquid helium or the like, and a current is supplied to the magnet or the like through a current lead.

A copper material has been conventionally used for the current lead conductor, but recently, a current lead using an oxide superconductor has also been studied.

[0004]

The current lead is often used in an environment having a temperature gradient from cryogenic temperature such as liquid helium to about 150 K and a magnetic field gradient due to a leakage magnetic field from a superconducting magnet. Therefore, it is necessary to make the conductor suitable for a wide range of usage environment from low temperature part to high temperature part, but the oxide superconductor is weaker to the magnetic field as the temperature becomes higher, and the conductor cross-section area is increased in the design of the current lead. To be forced.

Further, when a current lead is designed by using an oxide superconductor, there is a problem that the optimum conductor length that minimizes the amount of heat penetration becomes longer than that when a copper material is used.

In view of the above points, the present invention is to provide a current lead using an oxide superconductor which is less affected by the leakage magnetic field and which can reduce the amount of heat penetration.

[0007]

SUMMARY OF THE INVENTION The gist of the present invention is to form at least a part of an oxide superconducting conductor forming a conductor of a current lead into a solenoid coil shape, and to wind a leakage magnetic field in the winding direction of the coiled conductor. By making the direction of canceling out, the magnetic field deterioration of the energization current density of the current lead is prevented, and the amount of heat penetration due to heat conduction is reduced as an effect of the length of the conductor. In this case, the oxide superconductor may be a Y-based material such as Y-Ba-Cu-O or Bi-Sr-C.
u-O, Bi-based such as Bi-Sr-Ca-Cu-O, Tl
-Ba-Cu-O, Tl-Ba-Ca-Cu-O, Tl
Tl system such as -Sr-Ca-Cu-O, La-Na-Cu
La-based materials such as -O, La-Ba-Cu-O and La-Sr-Cu-O can be used, and the shape thereof is a wire rod with a metal coating, a conductor having a superconductor layer on a base material. , There are aggregate conductors in which a plurality of such wire rods and conductors are aggregated,
They may have a structure in which the width becomes narrower toward the low temperature side or the width becomes narrower. By changing the conductor cross-sectional area, it is possible to prevent the conductor cross-sectional area from unnecessarily increasing.When a solenoid coil is formed using such a conductor, the winding density changes and the leakage magnetic field from the superconducting magnet is effective. Can be canceled.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of a current lead according to the present invention.

The illustrated current lead comprises a low temperature portion 1b immersed in liquid helium and a high temperature portion 1a exposed from the liquid helium. The current lead body is connected to a power source at the end portion on the high temperature portion 1a side. Connection terminal 2 for connecting the current lead and the superconducting magnet is connected to the end of the silver sheath wire 6 on the low temperature portion 1b side.

However, the high temperature portion 1a is made of an oxide superconductor such as (Bi / Pb) ₂ Sr ₂ Ca ₂ Cu ₃ O _x , and is a silver sheath tape-shaped wire, for example, a wire having a thickness of 0.1 mm and a width of 5 mm. As shown in FIG. 2, each of 12 assembly conductors 4 formed by stacking 10 is vertically arranged along the outer periphery of a pipe as a reinforcing material, for example, a stainless pipe 3 having an outer diameter of 40 mm and a wall thickness of 2 mm. Has become.

The low temperature portion 1b is mainly composed of an oxide superconductor, for example, Bi ₂ Sr ₂ CaCu ₂ O _X. For example, a silver sheath wire 6 having a diameter of 1 mm strikes a leakage magnetic field from the superconducting magnet around the pipe 3. It is spirally wound at a predetermined pitch in the erasing direction and is fixed on the pipe 3 by a fixing means such as an adhesive.

In this case, the collective conductor 4 and the silver sheath wire 6 are integrally connected via the connecting member 5 made of a good electric conductor. It is desirable to solder between the pipe 3 and the connecting member 5 using a flux for stainless steel so that a current also flows through the stainless steel pipe 3 as a reinforcing material, as in the connection terminal 2 side. The connecting member 5 does not necessarily have to be a normally conductive metal body, and may be made of an oxide superconductor.

In the current lead having such a structure,
Since the conductor on the low temperature portion 1b side is wound in a direction to cancel the leakage magnetic field from the superconducting magnet, the magnetic field applied to the current lead when the superconducting magnet is excited is reduced, and the operating current density of the superconductor can be improved. Not only that, but since it is coiled, the conductor length from the high temperature end to the low temperature end is substantially lengthened, and the amount of heat penetration into the low temperature side due to heat conduction can be reduced.

Regarding the reduction of the invasion heat, the sheath material of the wire 6 is mainly made of a material having a low thermal conductivity at a temperature lower than room temperature, for example, Ag or Au, and P is added thereto.
By using an alloy containing at least one of d, Pt, Mn, Mg, and Zr, it is possible to further reduce the heat of penetration due to heat transfer.

The magnetization loss of the superconducting conductor is proportional to the volume of the superconducting conductor, but in this example, the conductor on the low temperature side has one wire 6.
As a result, it is of course possible to reduce the loss as a current lead.

FIG. 3 shows a low temperature portion in another example of the current lead according to the present invention. In this current lead, the conductor on the low temperature side is constituted by the tape material 8 instead of the wire material 6 and the reinforcing material is used. The stainless steel pipe 3 is wound around a solenoid to be fixed.

In this case, the tape-shaped conductor 8 is the connecting member 5.
A layer of oxide superconductor, for example, Bi ₂ Sr ₂ CaCu ₂ O _X , is formed on a silver tape having a wide side and a narrow width on the connection terminal 7 side according to the width of the silver tape. By winding and fixing it on the pipe 3 at an interval of, the winding density on the side close to the superconducting coil has a structure.

In the current lead having such a structure,
The magnetic field received by the current leads can be reduced as compared with the case where the winding density is uniform.

[0019]

As is apparent from the above description, according to the current lead of the present invention, a part of the conductor is formed into a solenoid coil shape, and the winding direction of this coiled conductor is the direction to cancel the leakage magnetic field. Therefore, it is possible to prevent the magnetic field deterioration of the energization current density of the current lead, reduce the amount of heat intrusion due to heat conduction as an effect of the length of the conductor, and contribute to the reduction of energy loss during operation of the superconducting equipment.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline of one embodiment of a current lead according to the present invention.

FIG. 2 is an explanatory view showing a cross section perpendicular to the axis of a high temperature portion.

FIG. 3 is an explanatory view showing a low temperature part in another example of the current lead according to the present invention.

[Explanation of symbols]

 1a High temperature part 1b Low temperature part 2 and 7 Connection terminal 3 Stainless steel pipe 4 Assembly conductor of oxide superconducting conductor 5 Connection member 6 Wire material of oxide superconducting conductor 8 Tape material of oxide superconducting conductor

Claims (3)

[Claims] 1. A superconductor characterized in that at least a part of an oxide superconductor forming a conductor of a current lead is formed in a solenoid coil shape, and a winding direction of the coil conductor is a direction for canceling a leakage magnetic field. Current lead. 2. The superconducting current lead according to claim 1, wherein the conductor on the low temperature side is formed in a solenoid coil shape. 3. The superconducting current lead according to claim 1, wherein the coil on the side closer to the superconducting coil has a tight winding density.