JPH0750207A - Current lead of superconducting device - Google Patents

Abstract

PURPOSE:To prevent the characteristics of an oxide superconductor from being deteriorated by making water content adhere on the superconductor. CONSTITUTION:The interior of a cylindrical container 221A, in which an oxide superconductor 222 is housed, of a low-temperature side lead 22A is held in a vacuum state, whereby when a superconducting device is stopped its operation after being operated, the normal-temperature air flows in the container 221A and waterdrops are not generated on the surface of the superconductor 222 of a cryogenic temperature of 100 deg.K or lower. As a result, the characteristics of the superconductor 222 are never deteriorated. Moreover, an intermediate connection fitment 20A is provided with a refrigerant piping 202 for injecting a refrigerant from the outside and circulating holes 201A for connecting this piping 202 with a hollow part 233 of a high-temperature side lead 23, whereby the fitment 20A can be cooled at a temperature, which is required for maintaining the superconductor 222 in a superconductive state, and a circulating path, through which helium gas 41 required for cooling the lead 23 is made to pass, can be secured.

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 passing an exciting current from an external power source to a superconducting coil which is housed in a liquid helium container in a vacuum insulation container of a superconducting device and immersed in liquid helium. In particular, the present invention relates to a current lead of a superconducting device in which an oxide superconductor such as a bismuth-based oxide is used to reduce the amount of heat penetration.

[0002]

2. Description of the Related Art A superconducting coil uses expensive liquid helium as a refrigerant to maintain a superconducting state. Therefore, the evaporation amount of this liquid helium is suppressed to a small amount to reduce the consumption of liquid helium and the operating cost of the superconducting device. Therefore, it is necessary to reduce the amount of heat penetration from the current lead to the superconducting coil.

Usually, a current lead for supplying an exciting current from an external power source at room temperature to a superconducting coil kept at a cryogenic temperature is
It is composed of a good conductive metal such as copper or a copper alloy, and such a good conductive metal simultaneously has the characteristics of a good thermal conductor. Therefore, conduction heat penetrates from the room temperature part to the cryogenic part. In order to reduce Joule heat generated in the conductor and heat invasion due to heat conduction from room temperature, low temperature helium gas generated by evaporation of liquid helium is introduced from the low temperature terminal to cool the conductor part. .

Since most of the heat load of the entire superconducting device is occupied by the current leads, lowering the heat penetration of the current leads is an important issue for realizing economical operation of the superconducting device. When an oxide superconductor was discovered, the superconducting phenomenon can be maintained even in the liquid nitrogen temperature state, so that it has no Joule heat generation and has a low thermal conductivity characteristic of 1/100 or less that of copper at low temperature. It is effective in reducing the heat load of the equipment and enables economical operation of the equipment.

FIG. 2 is an elevational view including a rotating sectional view showing a current lead of a conventional superconducting device using an oxide superconductor. In this figure, the current lead 2 is from the bottom, the low temperature terminal 2
1, a low temperature side lead 22, a high temperature side lead 23, and a room temperature terminal 24. The low temperature side lead 22 and the high temperature side lead 23 are electrically and mechanically connected by an intermediate connection fitting 20, and the low temperature terminal 21 is housed in the liquid helium container 10 via the lead lead 11 and immersed in the liquid helium 4. The normal temperature terminal 24 is connected to the superconducting coil 1 and is connected to an external power source (not shown) through the terminal metal fitting 242 in the atmosphere outside the vacuum container 3 which is shown only partially. The outlet pipe 241 is an outlet for helium gas that has flowed up while cooling the conductor in the current lead 2 as described later.

As shown in the rotational cross-sectional view, the low temperature side lead 22 includes a cylindrical container 221 and a rod-shaped oxide superconductor 222 arranged concentrically with the cylindrical container 221, and a hollow portion 22 between them.
3, and the helium gas 41 flows through the hollow portion 223, so that the oxide superconductor 222 is maintained at a temperature below the superconductivity. The helium gas 41 flows into the current lead 2 through the flow hole provided in the low temperature terminal 21, as described later.

As shown in the rotational cross-sectional view, the high temperature side lead 23 comprises a cylindrical container 231 and a conductor wire bundle 232 passing through the cylindrical container 231, and helium gas for cooling flows through the hollow portion 233. FIG. 3 is a vertical sectional view showing a part of the current lead. In this figure, the oxide superconductor 222 has a lower part inserted into the hole of the connection fitting 212 of the low temperature terminal 21, and an upper part inserted into the hole of the intermediate connection fitting 20 and is electrically and mechanically connected by soldering or the like. There is. The cylindrical container 221 is also hermetically connected to the connection fitting 212 and the intermediate connection fitting 20, respectively. The connecting fitting 212 is provided with a through hole 213, which communicates the liquid helium container 10 shown in FIG. 2 in which the terminal fitting 211 is arranged with the hollow portion 223, and the intermediate connecting fitting 20 has a through hole 201. And the hollow portion 223 of the low temperature side lead 22 and the high temperature side lead 23 are provided.
To communicate with the hollow portion 233, and the helium gas 41 can flow therethrough.

[0008]

As described above, the flow of the helium gas 41 in the current lead 2 is such that the liquid helium evaporates and passes through the through hole 213 of the low temperature terminal 21 and the hollow portion in the low temperature side lead 22. 223 and the hollow portion 233 of the high temperature side lead 23 through the through hole 201 of the intermediate connection fitting 20.
Flowing in, further rising, passing through the internal space of the room temperature terminal 24, and discharged from the outlet pipe 241 to the outside. Therefore, as long as the liquid helium 4 is evaporated and the helium gas 41 is generated while the superconducting device is in operation, the space inside the current lead 2 is filled with the helium gas. On the other hand, the air is discharged from the outlet pipe 24 during pre-cooling in a state before a current is passed through the superconducting coil 1 or in a post-treatment such as a post-treatment after energization.
It will flow through 1 into the current lead 2 in reverse.

By the way, it has been found from experiments and the like that the characteristics generally deteriorate when water adheres to oxide superconductors. As described above, when air enters the hollow portion 223, water may be attached to the surface of the oxide superconductor 222 which is kept in a superconducting state by being kept at a cryogenic temperature of 100 K or less, and therefore the oxide is The problem arises that the superconductor 222 deteriorates and becomes unusable, and the current lead 2 needs to be replaced or repaired. For replacing or repairing the current lead 2, it is necessary to remove it from the superconducting device, but for that purpose it is necessary to disassemble the superconducting device, which requires a great deal of cost, and during replacement and repair, the entire superconducting device is required. There is also the problem that it becomes impossible to drive.

An object of the present invention is to solve such a problem and to provide a highly reliable current lead for a superconducting device in which there is no possibility of characteristic deterioration due to adhesion of water to an oxide superconductor.

[0011]

In order to solve the above problems, according to the present invention, a high temperature side lead having a room temperature terminal connected to an external power source, and a low temperature terminal connected to a superconducting coil via a coil lead. A low temperature side lead and an intermediate connecting metal fitting for electrically and mechanically connecting the high temperature side lead and the low temperature side lead, and the low temperature side lead is composed of a rod-shaped oxide superconductor and a cylindrical container for housing the same. In the current lead of the superconducting device, the inside of the cylindrical container accommodating the oxide superconductor is held in vacuum, and
It is assumed that the intermediate connection fitting is provided with a refrigerant pipe for injecting a refrigerant and a circulation hole that communicates between the refrigerant pipe and the inside of the high temperature side lead, and the refrigerant at this time is helium gas even if it is liquid nitrogen. It may be. In the case of the helium gas, it may be supplied from the outside, or may be generated by the liquid helium being vaporized in the liquid helium container and introduced to the refrigerant pipe.

[0012]

In the structure of the present invention, by keeping the inside of the tubular container of the low temperature side lead in which the oxide superconductor is housed in a vacuum, even if the superconducting device is stopped after the operation, the oxidation was at a low temperature of 100K or less. Since no water droplets are generated on the surface of the superconductor, its characteristics are not deteriorated. Further, by providing a refrigerant pipe for injecting a refrigerant from the outside to the intermediate connection fitting and a through hole communicating between the refrigerant piping and the hollow portion of the high temperature side lead, the intermediate connection fitting maintains the oxide superconductor in a superconducting state. It is possible to cool to a temperature necessary for cooling and to secure a flow hole through which the coolant necessary for cooling the high temperature side lead passes. Further, the refrigerant may be liquid nitrogen or helium gas, and in the case of helium gas, it may be supplied from outside the superconducting device, but the helium gas generated by the evaporation of liquid helium in the liquid helium container is guided to the refrigerant pipe. It may be configured as follows.

[0013]

EXAMPLES The present invention will be described below based on examples.
FIG. 1 is a partial vertical cross-sectional view of a current lead showing an embodiment of the present invention. The same members as those in FIG. 3 are designated by the same reference numerals and the similar members are denoted by a suffix A to omit the explanation of common matters. In this figure, the low temperature side lead 22A is provided with a vacuum suction sealing pipe 224, and the low temperature terminal 21A is eliminated with the flow hole 213 provided in the low temperature terminal 21 of FIG.
The intermediate connection fitting 20A also eliminates the flow hole 201 provided in the intermediate connection fitting 20 of FIG. 3, and instead, the hollow portion 233 of the high temperature side lead 23 is provided with a flow hole 201A communicating with the outside and connected to the refrigerant pipe 202. Has been adopted. Therefore, the hollow portion 223 of the low temperature side lead 22A does not communicate with anything other than the vacuum sealing pipe 224.

In the hollow portion 223A, the vacuum suction sealing pipe 224 is connected to a vacuum pump to evacuate it to a vacuum state, and then the vacuum suction sealing pipe 224 is completely sealed. Therefore, the oxide superconductor 222 is in the hollow portion 223A in a vacuum state while the superconducting device in which a current flows through the current lead 2A is in operation or stopped, and water droplets are attached to the oxide superconductor 222 as in the conventional current lead 2. A factor that deteriorates the characteristics of the oxide superconductor 222 such as contact with air with high humidity is eliminated.

As shown in FIG. 3, since the helium gas 41 for cooling the high temperature side lead 23 was supplied through the low temperature side lead 22, as described above, the low temperature side lead 22.
Since the supply passage of the helium gas 41 to the high temperature side lead 23 is eliminated by adopting the structure of keeping the inside of A in vacuum, as shown in FIG. 1, the intermediate connection fitting 20A has a through hole 201A communicating with the outside. Is provided and the helium gas 41 is supplied through the refrigerant pipe 202.

The helium gas 41 is actually used as a coolant for cooling the high temperature side lead 23.
Even when using a liquid helium 4 generated by vaporization as in the conventional case, since the position where the intermediate connection fitting 20A is provided is outside the liquid helium container 10, the helium gas is supplied to the refrigerant pipe 202 by some method. Need to be introduced. Further, the temperature of the intermediate connection fitting 20A cooled by the refrigerant may be equal to or lower than the temperature at which the oxide superconductor 222 becomes the superconducting state, and thus may be cooled to 100K or lower. Therefore, cheap liquid nitrogen (77K) can also be used as the refrigerant. However, in this case, there is a risk that the liquid nitrogen will be solidified due to overcooling, so in order to prevent this, it is necessary to consider attaching a heating element to the intermediate connection fitting 20A.

Since the hollow portion 223A has to maintain a vacuum state, the connection of the cylindrical container 221A, the intermediate connecting metal fitting 20A and the low temperature terminal 212A constituting the hollow portion 223A is airtight enough to hold the vacuum for a long period of time. Since the outside of the cylindrical container 221A is at normal pressure, it is also necessary to have mechanical strength capable of withstanding a pressure difference corresponding to 1 atm. However, such a requirement is easily satisfied within the scope of conventional techniques.

As long as the oxide superconductor 222 is in the superconducting state, no loss due to current will occur, so the intermediate connecting fitting 20
There is no problem as long as A is cooled and the temperature thereof is maintained at 100 K or less, and it is not necessary to cool the oxide superconductor 222 itself.
It is not necessary to flow helium gas into 23A, and there is no problem in cooling even if the vacuum is maintained.

[0019]

As described above, according to the present invention, the inside of the cylindrical container in which the oxide superconductor is housed is kept in vacuum, so that the oxide superconductor maintains a cryogenic temperature of 100 K or less. Even if the operation is stopped after the operation state of (1), normal temperature air does not flow into the cylindrical container, so that water droplets do not occur on the surface of the oxide superconductor. Therefore, the characteristics of the oxide superconductor are not deteriorated by moisture, and the current lead having high reliability can be obtained. Further, a refrigerant pipe for injecting a refrigerant from the outside to the intermediate connection fitting and a flow hole for guiding the refrigerant injected from this refrigerant pipe to the hollow portion of the high temperature side lead are provided to cool the intermediate connection fitting to cool the oxide superconductor. Can maintain both the superconducting state and the circulation hole through which the refrigerant passes in the high temperature side lead. The refrigerant at this time may be liquid nitrogen or helium gas, and in the case of helium gas, it may be supplied from the outside of the superconducting device, but the helium gas generated by evaporation of liquid helium in the liquid helium container is used as a refrigerant pipe. You may comprise so that it may lead to.

[Brief description of drawings]

FIG. 1 is a partial vertical sectional view of a current lead of a superconducting device showing an embodiment of the present invention.

FIG. 2 is an elevation view including a rotating cross-sectional view showing a current lead of a conventional superconducting device.

FIG. 3 is a partial vertical sectional view of the current lead shown in FIG.

[Explanation of symbols]

 1 superconducting coil 2A current lead 21A low temperature terminal 211 terminal metal fitting 212A connection metal fitting 22 low temperature side lead 221 cylindrical container 222 oxide superconductor 223 hollow part 224 vacuum suction sealing pipe 23 high temperature side lead 231 cylindrical container 233 hollow part 20A middle Connection fitting 201A Circulation hole 202 Refrigerant pipe 10 Liquid helium container 4 Liquid helium 41 Helium gas

Claims (5)

[Claims] 1. A high temperature side lead having a room temperature terminal connected to an external power source, a low temperature side lead having a low temperature terminal connected to a superconducting coil via a coil lead, and these high temperature side lead and low temperature side lead are electrically connected. In the current lead of a superconducting device consisting of an intermediate connecting metal fitting that mechanically connects and the low temperature side lead consisting of a rod-shaped oxide superconductor and a cylindrical container accommodating this, a tubular shape in which the oxide superconductor is accommodated. A current lead of a superconducting device, characterized in that the inside of the container is held in vacuum. 2. The electric current of the superconducting device according to claim 1, wherein the intermediate connection fitting is provided with a refrigerant pipe for injecting a refrigerant and a flow hole communicating the refrigerant pipe with the inside of the high temperature side lead. Reed. 3. The current lead for a superconducting device according to claim 2, wherein the refrigerant is liquid nitrogen. 4. The current lead for a superconducting device according to claim 2, wherein the refrigerant is helium gas. 5. The current lead of a superconducting device according to claim 4, wherein the helium gas is generated by the evaporation of liquid helium in the liquid helium container and is led to the refrigerant pipe.