JPH0459763B2 - - 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, so they are housed inside a container that is insulated by a liquid nitrogen shield, a vacuum, or the like. The current lead supplies power from the room temperature part to the superconducting magnet kept at an extremely low temperature, and reduces the Joule heat that is generally generated in the conductor and the heat that invades from the outside room temperature part to the internal cryogenic part by conduction. For this purpose, 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 be large;
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 pass through a flange 5 provided on the top lid 4 of the container 1, and its 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 in FIG. 2, in which a gap 10 formed by densely inserting a plurality of conductors 9 into a hollow tube 8 is used as a flow path for helium gas. We are using. Further, the outer periphery of the hollow tube 8 is surrounded by an insulator 11 to insulate the lead body. 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 current, the number of conductors becomes large.
Therefore, there is a limit to reducing the diameter of the conductor due to the workability of inserting it into the hollow tube, and it has not been possible to sufficiently increase the cooling surface area of the conductor. As a result, the cooling effect is reduced, and heat intrusion from the normal temperature section to the cryogenic section increases, resulting in increased consumption of liquid helium, resulting in uneconomical operation.

[Purpose of the invention]

In view of the above-mentioned circumstances, it is an object of the present invention to improve the conductor structure of a current lead so as to improve the cooling effect of the current lead and reduce the amount of heat entering the superconducting electromagnet.

[Key points of the invention]

In the present invention, in order to achieve the above object, the conductor structure of the current lead is as follows. In other words, a round bar conductor is constructed by using a stainless steel rod with sufficient strength at extremely low temperatures and low thermal conductivity as a core, and surrounding the outer periphery of this stainless steel rod with a good conductor such as copper or copper alloy. A plurality of these round bar conductors were densely inserted into the hollow tube.

[Embodiments of the invention]

FIG. 1 is a cross-sectional view of a current lead showing an embodiment of the present invention. A plurality of round bar conductors 20 formed by surrounding the outer peripheral surface of a stainless steel bar 21 having sufficient strength at extremely low temperatures with a high quality conductor 22 such as steel or copper alloy are inserted into the hollow tube 8 in a dense manner. do.
The outer periphery of the hollow tube 8 is surrounded by an insulating material 11, and a space 10 within the hollow tube 8 is used as a flow path for helium gas. Note that the stainless steel rod can be replaced with another material having low thermal conductivity and high strength, such as a manganese steel rod or nichrome steel.

〔Effect of the invention〕

According to this invention, a round bar conductor is formed by surrounding the outer periphery of a stainless steel bar that has sufficient strength at extremely low temperatures with a good conductor, and a plurality of these round bar conductors are
Because they are densely inserted inside the hollow tube, it is possible to increase the number of conductors to correspond to the increase in the cross-sectional area of the stainless steel rod, and it is also possible to increase the diameter of the thin wire without changing the number of conductors. Therefore, the cooling surface area that comes into contact with the helium gas can be increased, and the cooling efficiency can be improved. In this case, to reduce conductive heat penetration,
Needless to say, the prerequisite is that the total cross-sectional area of the good conductor is constant. Therefore, the consumption of helium gas is reduced. Furthermore, since a stainless steel rod having high strength is inserted as the core of the round bar conductor, 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. Moreover, since a stainless steel rod with low thermal conductivity is inserted into the core of the round bar conductor, when the flow of helium gas in the hollow tube is stopped, the heat capacity of the lead body is increased by the heat capacity of the stainless steel rod. As a result, it is possible to slow down the temperature rise of the lead body.

[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. It is a front view. 1: Low temperature container, 3: Current lead, 8: Hollow tube,
9: Conductor, 10: Between, 20: Round bar conductor, 21:
SUS rod, 22: Good conductor, He: Helium.

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, multiple conductors are inserted into a hollow tube, and in the current lead for flowing helium gas between the holes in this hollow tube. A round bar conductor is made of a core made of stainless steel, manganese steel, nichrome steel, etc., which has sufficient strength even at extremely low temperatures and has low thermal conductivity, and the outer periphery is surrounded by a good conductor such as steel or copper alloy. A current lead for a superconducting electromagnet device, characterized in that a plurality of the round bar conductors are bundled and inserted densely into the hollow tube.