JPH0459764B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a conductor configuration of a current lead for a superconducting electromagnet for supplying power from an external power source to a superconducting electromagnet in a low-temperature container.

[Prior art and its problems]

Generally, superconducting electromagnets are cooled by a cryogenic coolant such as liquid helium, and therefore are housed inside a container that is insulated by a liquid nitrogen shield, a vacuum, or the like. The current lead supplies power from room temperature to the superconducting magnet kept at an extremely low temperature.
Generally, in order to reduce the Joule heat generated in the conductor and the heat that invades from the outside room temperature part to the internal cryogenic part by conduction, a cooling method is used that uses low-temperature helium gas that is evaporated from liquid helium. . Therefore, if the intrusion heat is too large, not only will the consumption of expensive liquid helium become large, but there is also a possibility that the characteristics of the superconducting electromagnet will be adversely affected.

Figure 2 shows the general configuration of a superconducting electromagnet device. Liquid helium He is contained inside the low temperature container 1, and a superconducting electromagnet 2 is immersed therein. The current lead 3 is attached to the container 1 by passing through a flange 5 provided on the upper lid 4, and the lower end inside the container 1 is connected to the superconducting electromagnet 2 via a connection lead 6. A liquid nitrogen shield N is provided outside the liquid helium He storage tank to block heat from entering from the outside. Further, a bus bar 7 for connecting to an external power source (not shown) is provided at the upper end of the current lead 3 outside the container. In the configuration shown in FIG. 2, the helium gas evaporated in the container 1 is guided between the interiors of the current leads 3 and exchanged with heat within the current leads 3, thereby reducing the amount of heat entering the cryogenic part.

FIG. 3 shows a cross section of the current lead 3 shown in FIG. It is used as. Also hollow tube 8
The outer periphery of the lead body is covered with an insulator 11 to insulate the lead body.
is surrounded by. According to this configuration, the cooling surface area of the conductor is increased by dividing the conductor through which current flows into a plurality of pieces, thereby improving the cooling efficiency. However, when using the current lead with this configuration for large currents, a large number of conductors are required, so there is a limit to reducing the diameter of the conductor due to the workability of inserting it into a hollow tube. It was not possible to make the cooling surface area sufficiently large. As a result, the cooling effect is reduced, and the amount of heat entering from the room temperature section to the cryogenic section increases, which increases the amount of liquid helium consumed, resulting in uneconomical operation.

FIG. 4 is a partially exploded perspective view of a current lead 3 with a different conductor configuration, in which a conductor 19 is placed inside a hollow tube 8 whose outer periphery is surrounded by an insulating material, similar to the current lead shown in FIG.
This is a configuration that accommodates. The conductor 19 is a round bar made of a good conductor such as copper or copper alloy, and has a shape on the outer periphery.
Disc-shaped fins 2 having slits 21 at two symmetrical positions on the circumference are thermally connected. This conductor 19 is inserted into a hollow tube 8 forming a flow path for helium gas to constitute a current lead body. The slits 21 of the disk-shaped fins 20 are each angled at 90° and maintain a predetermined pitch in the axial direction around the outer periphery of the conductor 19, forming a flow path for helium gas. The reason for arranging the fins 20 on the conductor 19 is to increase the cooling surface area to improve cooling efficiency, and to prevent the temperature rise of the conductor 19 from increasing when the helium gas is stopped for some reason by increasing the heat capacity due to the installation of the fins. This is to slow down the process. However, while having these advantages, these configurations have the following drawbacks when used for large currents. In other words, since the conductor requires a large number of disk-shaped fins with slits, it takes a lot of time to cut and install the fins.
There is a problem of high cost and uneconomical current leads.

That is, all of the conductor configurations described above have problems when used for large current applications.

[Purpose of the invention]

In view of the above-mentioned circumstances, the present invention aims to improve the conductor structure so as to improve the cooling effect of the current lead and reduce the amount of heat entering the superconducting electromagnet, especially when using a large current, thereby providing an economical current lead. With the goal.

[Key points of the invention]

In this invention, in order to achieve the above object, the conductor structure of the current lead is as follows. In other words, inside the hollow tube that forms the helium gas flow path, there is a round wire conductor made of a highly conductive material such as copper or copper alloy, and a conductor made of a material with low thermal conductivity such as stainless steel, manganese steel, or nichrome steel that can be used at low temperatures. A plurality of round wire rods made of a material having high strength were mixed and inserted densely.

[Embodiments of the invention]

FIG. 1 is a cross-sectional view of a current lead showing an embodiment of the present invention. The conductor structure of this current lead includes a plurality of round wire conductors 29a made of a good conductive material such as copper or copper alloy inside a hollow tube 8 whose outer periphery is covered with an insulator 11, and a plurality of round wire conductors 29a made of a good conductive material such as copper or copper alloy, and stainless steel or manganese steel. - A plurality of round wire rods 29b made of a material having low thermal conductivity and high strength even at low temperatures, such as nichrome steel, were mixed and inserted densely. Then, there are many small gaps 10 surrounded by the inner wall of the hollow tube 8, the round wire conductor 29a, and the round wire rod 29b.
According to this configuration, in which the helium gas is used as a flow path for helium gas, it is possible to improve the cooling efficiency and provide an economical current lead with excellent manufacturability.

〔Effect of the invention〕

According to this invention, a plurality of round wire conductors with good electrical conductivity and a plurality of round wires with low thermal conductivity are mixed and inserted densely into the hollow tube that forms the helium gas flow path. The cooling surface area of the current lead body can be increased compared to
Even when the helium gas is stopped, the heat capacity of the current lead body can be increased due to the heat capacity of the round wire with low thermal conductivity, which has the advantage of slowing down the temperature rise. Furthermore, since this round wire material has high strength even at low temperatures, the rigidity of the lead body can be increased, and a structure that can sufficiently withstand electromagnetic force acting on the lead body can be obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a current lead for a superconducting electromagnet device according to an embodiment of the present invention, FIG. 2 is a longitudinal cross-sectional view of the superconducting electromagnet device, and FIG. 3 is a cross-sectional view of a current lead for a superconducting electromagnet device having a conventional configuration. Front view, 4th
The figure is a partially exploded perspective view of another example of a current lead for a superconducting electromagnet device having a conventional configuration. 1: Low temperature container, 3: Current lead, 8: Hollow tube,
9: Conductor, 10: Between, 29a: Round bar conductor, 29
b: Round wire rod.

Claims (1)

[Claims] 1 In order to supply power from an external power supply to a superconducting electromagnet kept at an extremely low temperature in a cryogenic container, a conductor is inserted into a hollow tube, and in a current lead for flowing helium gas between the holes in this hollow tube;
Inside the hollow tube, there is a round wire conductor made of a highly conductive material such as copper or copper alloy, and a material with low thermal conductivity and high strength even at low temperatures such as stainless steel, manganese steel, or nichrome steel. A current lead for a superconducting electromagnet device, characterized in that a plurality of formed round wires are mixed and inserted densely.