JPH04369875A - Superconductive device current lead - Google Patents

Abstract

PURPOSE:To protect a current lead formed of high temperature superconductor against damage caused by thermal shrinkage difference between the component parts of a superconductive device and the current lead. CONSTITUTION:A current lead of this design is composed of a low temperature side lead 5 which is formed of high temperature superconductor that stays in a superconductive state at a temperature of liquid nitrogen and connected to a superconductive equipment 1 in a cryostat, an intermediate lead 7 formed of flexible, good conductor connected to the low temperature side lead 5, and a normal temperature side lead 8 connected to the intermediate lead 7.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention applies to superconducting coils etc. immersed in liquid helium contained in a liquid helium container.
This invention relates to an improvement in a current lead for supplying current from a power source placed in a normal temperature environment.

0002

[Prior Art] A current lead is used as a means for supplying current from an excitation power supply placed at room temperature to a superconducting coil that is immersed and cooled in liquid helium contained in a liquid helium container. . In superconducting devices, very expensive liquid helium evaporates due to external heat conduction, radiation, and heat intrusion from current leads. Of this, in a normal superconducting device, the heat that enters from the current leads accounts for most of the total heat.

[0003] Therefore, it has been considered to construct a current lead using a high-temperature superconductor that exhibits a superconducting state above the liquid nitrogen temperature to reduce the intrusion heat (Japanese Patent Laid-Open No. 63-2926).
Publication No. 10). The high-temperature end of the high-temperature superconductor is cooled to around 80 K using liquid nitrogen contained in a liquid nitrogen container to bring it into a superconducting state. A lead made of copper or the like is used from the high temperature end of the high temperature superconductor to room temperature. High-temperature superconductors have low thermal conductivity, so the amount of heat that enters the liquid helium container is small, and since the electrical resistance is zero, there is no Joule heat generation when energized. Therefore, current leads using high-temperature superconductors can be expected to be highly effective in reducing the amount of evaporation of liquid helium.

0004

[Problems to be Solved by the Invention] Since high-temperature superconductors are ceramic-based, they experience a difference in thermal contraction from liquid helium containers made of stainless steel, liquid nitrogen containers, gas piping, and leads made of copper, etc., which constitute the superconducting device. Ceramic high-temperature superconductors are mechanically fragile and may break due to differential thermal contraction, making it impossible to conduct electricity. An object of the present invention is to provide a current lead for a superconducting device in which a high temperature superconductor is not damaged due to differential thermal contraction.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the current lead of the present invention is a low-temperature side lead that is made of a high-temperature superconductor that exhibits a superconducting state above the liquid nitrogen temperature and is connected to a superconducting device in a cryogenic container. , an intermediate lead made of a flexible good conductor connected to this low temperature side lead, and a normal temperature side lead connected to this intermediate lead.

[0006]

[Operation] In such a current lead for a superconducting device, the flexibility of the intermediate lead can absorb the difference in thermal contraction caused by cooling. Moreover, since materials with good conductivity generally have high thermal conductivity, high-temperature superconductors are efficiently cooled.

[0007]

【Example】

(Configuration of Example)

An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, 1 is a superconducting coil formed by winding a superconducting wire, and this superconducting coil 1 is immersed in liquid helium 3 contained in a liquid helium container 2 made of stainless steel or the like. The liquid helium container 2 is housed in a heat insulating vacuum container 4 made of stainless steel or the like. 5 is a low-temperature side lead made of a ceramic-based high-temperature superconductor that exhibits a superconducting state above the liquid nitrogen temperature; its low-temperature end is connected to a superconducting coil terminal 6, and the high-temperature end is an intermediate lead 7 made of a plain braided wire of copper or the like. connected to. Reference numeral 8 denotes a normal temperature side lead made of a copper rod, the low temperature end of which passes through a liquid nitrogen container 10 containing liquid nitrogen 9 and is connected to the intermediate lead 7, and the high temperature end is provided with a normal temperature terminal 11. This room temperature terminal 11 is connected to an excitation power source (not shown) placed in a room temperature environment. Reference numeral 12 denotes a gas flow pipe made of stainless steel or the like provided around the outer periphery of the high temperature superconductor 5, and serves as a flow path for the helium gas 13 evaporated within the liquid helium container 2. FIG. 2 is a diagram showing details of the connecting portions of the low temperature side lead 5, the intermediate lead 7, and the normal temperature side lead 8. Each is connected by soldering. (Effect of Example)

Liquid helium container 2 made of stainless steel or the like
, the difference in thermal contraction caused by cooling between the liquid nitrogen container 10, the gas flow pipe 12, the room temperature side lead 8, and the low temperature side lead 5 is as follows.
This is absorbed because the intermediate lead 7 has flexibility. Furthermore, since the low temperature end of the normal temperature side lead 8 passes through the liquid nitrogen container 10 containing liquid nitrogen 9, it reaches the temperature of liquid nitrogen. Therefore, the low temperature end of the room temperature side lead 8 and the high temperature end of the low temperature side lead 5 which are connected via the intermediate lead 7 are connected because the intermediate lead 7 is made of copper or the like and is a good conductor, which generally has a high thermal conductivity. Efficiently cooled to liquid nitrogen temperature,
The entire low temperature side lead 5 becomes superconducting. (Effects of the Embodiment) Therefore, there is no possibility that the low-temperature side lead made of a mechanically fragile high-temperature superconductor is damaged due to the difference in thermal shrinkage and becomes unable to conduct electricity. (Other Embodiments) A conductor made of stacked thin copper plates may be used as the intermediate lead. Further, the flexible good conductor may be connected to both ends of the low temperature side lead.

0010

As explained above, according to the present invention, a flexible and highly conductive intermediate lead is connected to the low-temperature lead made of a high-temperature superconductor, so that the difference in thermal contraction caused by cooling can be reduced. It can be absorbed and the low temperature side lead will not be damaged. Moreover, the low temperature side lead can be efficiently cooled.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a current lead for a superconducting device according to an embodiment of the present invention.

FIG. 2 is a detailed diagram showing the main parts of FIG. 1;

[Explanation of symbols]

1...Superconducting coil
2...Liquid helium container 3...Liquid helium
4...Insulated vacuum container 5...Low temperature side lead
6...Superconducting coil terminal 7...Intermediate lead
8...Normal temperature side lead 9...Liquid nitrogen
10...Liquid nitrogen container 11...Normal temperature terminal
12...Gas flow pipe 13...Helium gas

Claims (1)

[Claims] Claim 1: A current lead for supplying current from a power source placed in a normal temperature environment to a superconducting device housed in a cryogenic container, which is made of a high-temperature superconductor that exhibits a superconducting state at a temperature higher than liquid nitrogen temperature. A current lead for a superconducting device, comprising a low temperature side lead connected to the low temperature side lead, an intermediate lead made of a flexible good conductor connected to the low temperature side lead, and a normal temperature side lead connected to the intermediate lead. .