JPH06132124A - Current lead for superconducting device - Google Patents

Abstract

PURPOSE:To make a hollow tube resist quench without enlarging a diameter and a plate thickness thereof by restraining gas pressure inside the hollow tube from rising which is caused by quench caused by an oxide superconductor passing through an inside of the hollow tube of a low temperature side lead of a current lead. CONSTITUTION:A bursting mechanism 7 is provided to a hollow tube of a low temperature side lead 5A. It operates to discharge helium gas 12 inside a hollow tube to the outside when a pressure of the helium gas 12 inside the hollow tube exceeds a specified value, and stops discharge when the pressure is the specified value or less; thereby, the pressure inside the hollow tube can be restrained from rising not to exceed the specified value. Furthermore, when the pressure stops rising, the mechanism returns to a normal state and the operation of a superconducting device can be continued. Since just mechanical strength which is high enough to resist the specified value is required for the hollow tube, it is possible to reduce a diameter and a plate thickness thereof and to reduce the penetration of heat transmitted through a current lead.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting device for supplying electric power by connecting a superconducting coil housed inside a cryocontainer and an exciting power source provided outside the cryocontainer. For current lead.

[0002]

2. Description of the Related Art Since a superconducting coil of a superconducting device is cooled by a cryogenic refrigerant such as liquid helium gas to maintain a superconducting state, it is housed in a vacuum heat insulation container having a radiation shield using liquid nitrogen and a multilayer heat insulation layer. It is stored in a state in which it is immersed in liquid helium sealed in a cryogenic container. Further, the current lead electrically connecting between the superconducting coil excitation power supply provided outside the superconducting device and the superconducting coil is cooled by the low temperature helium gas in which liquid helium is vaporized, and the conduction heat from the normal temperature side and It is configured to prevent Joule heat (collectively referred to as penetration heat) generated in the current lead from entering the cryogenic container.

FIG. 3 is a simplified sectional view of a conventional superconducting device. In this figure, a superconducting coil 10 is stored in a low temperature container 1 inside a vacuum heat insulating container 2 in a state of being immersed in liquid helium 11 and cooled to the evaporation temperature (4.2 K) of liquid helium 11 so that the superconducting state is changed. Retained. The space between the cryogenic container 1 and the vacuum heat insulating container 2 is maintained in a high vacuum, and the cryogenic container 1 is placed in this high vacuum space.
A liquid nitrogen shield (not shown), a radiation shield, or a multilayer heat insulating layer (not shown) is provided in a manner surrounding the above, and the consumption of expensive liquid helium 11 is reduced by blocking the heat entering from the outside.

The current lead 3 inserted in the low temperature container 1 has a high temperature side lead 4 and a low temperature side lead 5 connected in series. The helium gas 12 generated by vaporization of the liquid helium 11 passes through the through hole (not shown) provided in the low temperature terminal 50 to which the extraction lead 6 connecting the current lead 3 and the superconducting coil 10 is connected, and the current lead 3 Enters the inside of the chamber, rises therein, and is discharged from the room temperature terminal 40.
While the helium gas 12 passes through the current leads 3, it cools the conductors that pass therethrough.

FIG. 4 is a sectional view taken along line AA of FIG. 3, and is a sectional view of the high temperature side lead 4. The high temperature side lead 4 is a hollow tube 41.
And a good electric conductor 42 passing through it. The helium gas 12 passes through the gap between the good electric conductors 42 to cool the good electric conductors 42. The good electric conductors 42 are made of copper or copper alloy to increase the surface area. In order to improve the cooling effect of the helium gas 12, a combination of fine conductors is used. In this figure, the cross-sectional area of one conductor is drawn thicker than the actual one.

FIG. 5 is a sectional view taken along line BB of FIG. 3, and is a sectional view of the low temperature side lead 5. In this figure, the low temperature side lead 5 comprises a hollow tube 51 and an oxide superconductor 52 passing through the hollow tube 51. In this case also, the oxide superconductor 52 is cooled by the helium gas 12 flowing in the hollow tube 51. It
The oxide superconductor 52 is made of an yttrium-based, bismuth-based or thallium-based oxide superconductor. Since the oxide superconductor 52 is a high-temperature superconductor that maintains the superconducting state even at the evaporation temperature of liquid nitrogen (about 77 K), the oxide superconductor 52 is kept in the superconducting state by cooling with the helium gas 12 lower than this temperature. Maintained. Therefore, the resistance loss in the low temperature side lead 5 becomes zero, and the heat entering the low temperature terminal 50 is reduced. As a result, the liquid helium 1
The consumption of 1 is reduced.

[0007]

[Problems to be Solved by the Invention] Oxide superconductor 5
As is well known, it is rare that a stable superconducting state is obtained from the beginning of energization, and in most cases, a so-called quench occurs in which the superconducting state is locally broken and the state changes to the normal conducting state when energizing for the first time. By repeating such quenching several times, the current value at which current can be supplied increases, and finally it becomes possible to stably supply a predetermined current. Further, even if the stable superconducting state is maintained, it is considered that the quench occurs due to an unexpected factor such as a failure of the cooling system.

When quenching occurs in the oxide superconductor 52, the oxide superconductor 52 is locally heated due to its small thermal conductivity, and the temperature of the helium gas 12 in the hollow tube 51 rapidly rises. As a result, the phenomenon that the gas pressure also rises occurs. In order to reduce this pressure increase, it is necessary to increase the diameter of the hollow tube 51 or increase the plate thickness of the hollow tube 51 to increase the mechanical strength. However, this causes a problem that intrusion heat increases. Occurs.

An object of the present invention is to solve such a problem and to suppress an increase in gas pressure in the hollow tube caused by quenching of the oxide superconductor of the low temperature side lead, thereby reducing the diameter of the hollow tube. An object of the present invention is to provide a current lead for a superconducting device that can withstand quenching without increasing the plate thickness.

[0010]

In order to solve the above-mentioned problems, according to the present invention, a hollow tube and an oxide superconductor passing through the hollow tube are used, and an oxide is formed by a low temperature helium gas flowing in the hollow tube. The low temperature side lead for cooling the superconductor, the hollow tube and the good electric conductor passing through the hollow pipe, and the high temperature side lead for cooling the good electric conductor by the helium gas flowing in the hollow pipe are connected in series. In the current lead for the superconducting device, the hollow tube of the low temperature side lead is operated when the pressure in the hollow tube exceeds a predetermined value to release the helium gas in the hollow tube to the outside, which is below a predetermined value. Sometimes a pressure release mechanism is provided to stop the release of helium gas, and the pressure release mechanism is a frame that closes the through hole provided in the hollow tube, and a valve that is provided on the wall that partitions the center of this frame. Hole Valves for closing the valve hole, consisted of discharge holes for releasing gas discharged from the spring and the valve hole is pressed against the said wall of the valve at a predetermined pressure to the outside,
Further, it is assumed that the gas release destination of the gas by the pressure release mechanism is in the low temperature container, or the release pipe for guiding the gas released from the release hole to the outside of the vacuum heat insulating container is provided.

[0011]

In the structure of the present invention, a pressure releasing mechanism is provided in the hollow tube of the low temperature side lead and operates when the pressure of the helium gas in the hollow tube exceeds a predetermined value to release the helium gas in the hollow tube to the outside. Thus, the pressure rise is suppressed, and when the pressure becomes equal to or lower than a predetermined value, the discharge is stopped, so that the normal state is restored and the operation of the superconducting device can be continued.

Further, a through hole is provided in the hollow tube, the through hole is closed by a frame of a pressure release mechanism, a valve hole is provided in a wall partitioning the central portion of the frame, and the valve hole is pressed against the wall by a spring. By closing the valve with a valve, the valve hole is normally closed so that the helium gas flowing in the hollow tube does not leak to the outside, and if the pressure inside the hollow tube rises above the force that pushes the valve of the spring, the valve will be closed. Since it separates from the valve hole, helium gas is discharged through the discharge hole through the valve hole. When the pressure in the hollow tube drops, the valve closes the valve hole with the force of the spring, and the valve returns to its normal state.

The destination of the gas released by the pressure release mechanism may be inside the cryogenic container provided with the pressure release mechanism, or a release pipe for guiding the gas released from the release hole may be provided outside the vacuum heat insulating container. May be released to Even if released into the cryogenic container, there is no problem because the cryogenic container itself has a pressure release mechanism for quenching the superconducting coil.

[0014]

EXAMPLES The present invention will be described below based on examples.
FIG. 1 is a cross-sectional view showing a simplified superconducting device showing an embodiment of the present invention. The same members as those in FIG. 3 are designated by common reference numerals and their detailed description will be omitted. The difference from FIG. 3 in this figure is that the pressure release mechanism 7 is provided in the low temperature side lead 5A. The pressure release mechanism 7 is, as described later, a low temperature side lead 5A.
The helium gas inside the low temperature side lead 5A is released to the outside when the internal pressure of the battery rises and exceeds a preset constant value. Also, when the gas pressure drops, the gas release stops. ing.

FIG. 2 is a sectional view taken along the line CC in FIG. 1, showing the details of the pressure release mechanism 7. In this figure, the hollow tube 51A of the low temperature side lead 5A is provided with a through hole 53, and the pressure release mechanism 7 is provided so as to cover the through hole 53.
The pressure release mechanism 7 includes a frame 70 as an outer frame attached to the hollow tube 51A, a valve hole 72 provided in a wall 71 partitioning the inside of the frame 70, a valve 73 for closing the valve hole 72, and a valve 73 for the wall 71. It comprises a pressing spring 74 and a discharge hole 75 for discharging the helium gas discharged from the valve hole 72 to the outside. By adjusting the force of the spring 74, the gas pressure at which the valve 73 moves and the valve hole 72 opens can be set to a predetermined value.

The internal pressure rises, the valve 73 moves, and the valve hole 72
When the quench is eliminated and the oxide superconductor 52 is restored to the superconducting state again in a state in which the helium gas is released to the outside through the opening, the gas pressure in the hollow tube 51A also decreases, When the gas pressure at the time when the valve hole 72 is opened becomes equal to or lower than the gas pressure when the valve hole 72 is opened, the valve hole 72 is closed by the valve 73 as described above, and the normal state before the quench is restored, so that the normal operation can be continued as it is.

The released helium gas raises the pressure of the cryocontainer 1, but since the volume of the cryocontainer 1 is large, it is unlikely that the pressure value will cause a problem.
Moreover, since a pressure release device (not shown) is provided in consideration of the rapid evaporation of the liquid helium 11 due to the quenching of the superconducting coil 10 and the accompanying pressure rise, there is no practical problem.

As described above, the release destination of the helium gas whose pressure is increased is in the cryogenic container 1. However, the tip of the pressure release mechanism 7 is lengthened to provide a pipe for guiding the released gas to the outside of the vacuum heat insulating container 2. It is also possible to adopt a configuration in which the pressure is released directly to the outside air. It should be noted that the pressure release mechanism 7 shown in FIG. 2 is merely an example, and various configurations of the pressure release mechanism are commercially available and used. Therefore, an appropriate one may be selected from these. The contents of the present invention are not limited by the configuration of 2.

[0019]

As described above, the present invention is provided with a pressure release mechanism in the hollow tube of the low temperature side lead, and operates when the pressure of the helium gas in the hollow tube exceeds a predetermined value to remove the helium gas in the hollow tube. By releasing to the outside and stopping the release when the pressure falls below a predetermined value, the pressure rise inside the hollow tube can be suppressed below the above-mentioned predetermined value, and when the pressure rise stops, it returns to normal and the superconductivity increases. The operation of the device can be continued. Since the mechanical strength of the hollow tube can withstand the above-mentioned predetermined value, the diameter of the hollow tube can be made small and the plate thickness thereof can be made small, so that the heat entering through the current leads is reduced. And as a result,
The effect of reducing the consumption of expensive liquid helium and the operating cost can be obtained.

Further, a through hole is provided in the hollow tube, the through hole is closed by a frame of the pressure release mechanism, a valve hole is provided in a wall partitioning the central part of the frame, and this is closed by a valve pressed against the wall by a spring. As a result, the valve hole is normally closed and the helium gas flowing through the hollow tube does not leak outside. The valve in which the pressure in the hollow pipe has risen above the force pushing the valve of the spring separates from the valve hole, passes through the valve hole, and helium gas is discharged from the discharge hole. When the pressure in the hollow pipe is lowered, the valve closes the valve hole, so that the original normal state is restored, which is an effect that a pressure release mechanism having a required function can be configured.

Further, since the cryogenic container accommodating the superconducting coil is equipped with a pressure releasing mechanism when the superconducting coil is quenched and the internal pressure rises, the gas release destination of the current lead is directed to the cryogenic container. There is no problem even if it is inside. Further, a gas discharge pipe for guiding the gas discharged from the discharge hole may be provided to discharge the gas outside the vacuum heat insulating container.

[Brief description of drawings]

FIG. 1 is a sectional view showing a simplified superconducting device showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along line CC of FIG.

FIG. 3 is a simplified cross-sectional view showing a conventional superconducting device.

4 is a sectional view taken along line AA of FIG.

5 is a sectional view taken along line BB of FIG.

[Explanation of symbols]

 1 Low Temperature Container 10 Superconducting Coil 11 Liquid Helium 12 Helium Gas 3 Current Lead 4 High Temperature Side Lead 5A Low Temperature Side Lead 51A Hollow Tube 52 Oxide Superconductor 53 Through Hole 7 Pressure Release Mechanism 71 Wall 72 Valve Hole 73 Valve 74 Spring 75 75 Release Hole

Claims (4)

[Claims] 1. A low temperature side lead comprising a hollow tube and an oxide superconductor passing through the hollow tube, wherein the low temperature helium gas flowing in the hollow tube cools the oxide superconductor, and the hollow tube and the inside thereof. In a current conductor for a superconducting device, which is made of a good electric conductor that passes through, and is connected in series with a high temperature side lead in which the good electric conductor is cooled by helium gas flowing in the hollow tube, in the hollow tube of the low temperature side lead, A pressure release mechanism that operates when the pressure in the hollow tube exceeds a predetermined value to release the helium gas in the hollow tube to the outside and stops the release of the helium gas when the pressure falls below the predetermined value is provided. Characteristic current lead for superconducting device. 2. A pressure relief mechanism, a frame for closing a through hole provided in a hollow pipe, a valve hole provided in a wall for partitioning a central portion of the frame, a valve for closing the valve hole, and a predetermined pressure for the valve. The current lead for a superconducting device according to claim 1, comprising a spring that is pressed against the wall and a discharge hole that discharges gas discharged from the valve hole to the outside. 3. The current lead for a superconducting device according to claim 1 or 2, wherein the gas is released by the pressure releasing mechanism into a cryogenic container. 4. The current lead for a superconducting device according to claim 1, further comprising a discharge pipe for guiding the gas discharged from the discharge hole to the outside of the vacuum heat insulating container.