JPH088165B2 - Current lead - Google Patents

Description

The present invention relates to a current lead for supplying a current to a superconducting magnet or the like.

<Problems to be Solved by Conventional Techniques and Inventions> Conventionally, in order to supply a current to a superconducting element such as a superconducting magnet, a current supply source and a current lead interposed between the superconducting element have a rod shape or a pipe shape. It is known to use a copper conductor formed in a strip shape.

However, since the copper conductor is a normal conductor and also a good conductor of heat, the heat generated by energization and the heat on the high temperature terminal side are conducted to the refrigerant such as liquid helium and liquid nitrogen in which the superconducting magnet is immersed. However, there is a problem that the refrigerant evaporates due to the conduction heat.

Therefore, in order to suppress the conduction heat to the liquid helium to a minimum, in the conventional current lead, as shown in FIG. 3, a spiral fin (110) is attached to the surface of the conventional current lead, which is made of stainless steel. The structure is such that it is housed inside the outer tube (120), and the helium gas (13
0) is taken into the lead from the superconducting magnet connection terminal (140) side, and current is supplied from the high temperature side terminal (150) to the superconducting magnet while cooling the current lead (100). In order to reduce the conduction heat to helium, various tests and researches have been conducted such as improving the structure of the current lead.
Heat conduction of 1W per 00A was said to be inevitable.

When liquid helium is used as the refrigerant of the superconducting magnet for heat conduction of 1 W, about 1.4 l / hr of helium gas evaporates.

<Object of the Invention> The present invention has been made in view of the problems of the conventional current leads described above, and it is an object of the present invention to provide a current lead capable of suppressing the evaporation amount of a refrigerant such as liquid helium or liquid nitrogen due to conduction heat to be low. To aim.

<Means for Solving the Problems> The current lead of the present invention for achieving the above object is a current lead interposed between a current supply source and a superconducting element, and includes a ceramic superconductor and an insulator. Alternatively, it is a composite with a support made of a non-magnetic metal body.

<Operation> Since the present invention forms the current lead by a composite of a ceramic superconductor and a support made of an insulator or a non-magnetic metal body, there is almost no heat generation due to energization below the critical temperature, and the high temperature part It is possible to reduce the heat conduction to the refrigerant due to the heat conduction from, and to reduce the evaporation amount of the refrigerant such as liquid helium and liquid nitrogen.

<Embodiment> An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view showing a case where two current leads (1) of the present invention are used as a pair, and FIG. 2 is II-II of FIG.
It is a line cutting sectional view.

The current lead (1) is a support made of a superconductor (1a) made of oxide ceramics, an insulator such as FRP supporting the superconductor (1a), or a non-magnetic metal body such as copper, aluminum or stainless steel. It is formed of a complex composed of the body (1b).

When a non-magnetic metal body is used as the support (1b), it serves not only as a support for supporting the superconductor (1a) but also as a stabilizer for the superconductor (1a). However, this is a suitable implementation.

The current lead (1) is formed, for example, by integrating the powder of the superconductor (1a) on a support (1b) made of a nonmagnetic metal body by a method such as powder compaction, adhesion, extrusion, electrodeposition, or superconductivity. Only the body (1a) is molded in advance, and the body (1a) is bonded to the support (1b) or bound to form a composite body. In the case where the both are combined and integrated by adhesion, it is easy to use an organic material such as an epoxy resin as an adhesive agent for adhesion to form a composite.

The current lead (1) can be used alone, but it is preferable to use it in a pair as it is more compact than that provided separately (see FIG. 1).

To describe in more detail below the implementation using a pair of current leads, a spacer (2) is longitudinally interposed between the current leads (1) and (1), and the periphery thereof is supported by a support (3) at appropriate intervals. To do.

The spacer (2) is made of an insulator such as GFRP when the support (1b) of the current lead (1) is made of a metal body, and is insulated when the support (1b) is an insulator. It may be a body or a metal body, and may be omitted. As the supporter (3), a disk-shaped one having an insulating property is fitted or an insulating tape for binding is wound.

In the case of the above example using a pair of positive and negative current leads (1), if current is applied with a magnetic field applied around the current leads (1), the current between the current leads (1) (1) and the external magnetic field The Lorentz forces acting between and act on the spacers (2) in such a direction that they push each other, and the spacer (2) acts on both current leads (1).
It is necessary that the supporter (3) has a strength capable of withstanding the compressive force between (1) and a sufficient insulation distance, but the supporter (3) does not have to be so rigid, and may be omitted or extremely Since it can be small in size, it can be implemented compactly, which is preferable.

On the contrary, when energized in the non-magnetized state, the magnetic field is generated by the current lead (1) itself, and moreover, the direction of the current flowing through each current lead (1) is in the opposite direction, so the Lorentz force is It acts to repel each other. Therefore, unlike the case where the current is applied in the state where a magnetic field is applied around the current lead (1), in this case, the supporter (3) needs to have a firm structure rather than the spacer (2). Further, (4) is a flange for attaching the current lead (1) to the top flange of the cryostart, and keeps the function of insulating the cryostart top flange and the current lead (1). (5) is a high temperature side connecting terminal, and (6) is a superconducting magnet side connecting terminal.

The ceramic superconductor is manufactured by sintering a raw material for a ceramic superconductor, and the raw material may be either a simple substance or a compound as long as it contains an element constituting the superconductor. Examples of the above-mentioned elements include oxygen in the groups I, II and III of the periodic table,
An example is fluorine.

More specifically, among the group I elements of the periodic table, examples of the group Ia elements include Li, Na, K, Rb, and Cs, and the group Ib elements include Cu, Ag, and Au. Also, the periodic table
Of the II group elements, the IIa group elements include Be, Mg, Ca, S
r, Ba, and Ra, and the IIb group elements include Zn and Cd.
Etc. Of the III group elements of the periodic table, IIIa group elements include Sc, Y and lanthanoid series elements such as La and C.
Actinides such as e, Gd, Lu, etc. Ac, Th, Pa, C
f and the like. Further, as the group IIIb element, Al, G
a, In, Tl and the like.

Of the above elements, a ceramic superconductor composed of an element selected from the group Ib, particularly an element selected from the group IIa composed of oxides, a group IIIa and a lanthanoid series element, and an element selected from oxygen and fluorine. Is preferred. Note that Cu and Ag are preferable as the Group Ib element.

In addition, in the case of the current lead (1) using the oxide ceramics superconductor (1a), as a result of measuring the amount of heat conduction to the refrigerant due to heat transfer from the high temperature part, for example, in the case of 4.2K to 300K, Conduction integral value Superconductivity ▲ ∫ ^300k _4.2k λ ▼ dT (λ is thermal conductivity) was about 1990 × 10 ^-3 (W / cm).

This is approximately similar to glass and quartz, and is 1620 of electrolytic copper.
(W / cm), compared with 461 (W / cm) of phosphorous deoxidized copper, it was reduced by 1/800 or 1/230, and it was revealed that the heat of conduction to the refrigerant could be extremely reduced. .

Further, when the support (1b) to be combined with the superconductor (1a) is, for example, tetrafluoroethylene resin, GFRP, etc., the heat conduction is 700 × 10 ^{−3 to} 1000 × 10 ⁻³ (W / cm 2 ) Is very small and good. Furthermore, even when a metal body is used, it does not pass an electric current through the metal body as in the conventional one, but it functions as a stabilizer or a support. Therefore, it is not necessary to make the cross-sectional area and the like particularly large in order to secure the current carrying capacity unlike the conventional ones, and a size that acts as a stabilizing material and a support is sufficient, and a refrigerant such as liquid helium is sufficient. The amount of heat transferred to can be greatly reduced.

<Effects of the Invention> As described above, according to the present invention, the current lead is formed of a composite of a ceramics superconductor and a support made of an insulating material or a non-magnetic metal material. The heat generated by the heat is almost eliminated, and the amount of heat transferred to the refrigerant due to heat conduction from the high temperature part is greatly reduced, so that the evaporation amount of the refrigerant can be minimized and the structure is much simpler than that of the normal conducting type. Therefore, it has a unique effect that it can be formed with a compact structure.

[Brief description of drawings]

FIG. 1 is a sectional view showing one embodiment of a current lead, FIG. 2 is a sectional view taken along the line II-II of the front surface, and FIG. 3 is a sectional view showing a conventional example. (1) ... Current lead, (1a) ... Superconductor, (1b) ...
... support,

Claims (1)

[Claims] 1. A current lead interposed between a current supply source and a superconducting element, comprising a composite of a ceramics superconductor and a support made of an insulating material or a non-magnetic metal material. Current lead.