JPH03248580A - Cooling method of oxide superconductor - Google Patents

Abstract

PURPOSE:To eliminate the need for a cryogenic refrigerator and a pressure vessel by using a refrigerant, which is brought to the state of a solid at approximately 10K and to the state of a liquid at approximately 300K, as a refrigerant for cooling an oxide group superconductor. CONSTITUTION:Since a refrigerant vessel 14 is kept at 10K under the state of normal operation, water 15 as a refrigerant is brought into ice, i.e., solid state. The thermal conductivity of water under solid state, i.e., ice, is improved, and a superconducting coil 11 is cooled efficiently. Ice melts and is changed into water by a temperature rise in a device when heat penetrates from the outside or when a quenching phenomenon is volumetric generated, but no pressure rise as a gas is generated because of the comparatively small coefficient of volumetric expansion of water. Accordingly, a thick firm pressure vessel need not be used and a normal vessel may be employed as the refrigerant vessel 14, a special refrigerator for recondensation need not also be used as a refrigerator 20, and cold heads 21, 22 at 10K and 80K can be utilized as cooling sources as they are.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for cooling a superconducting device, and particularly to a method for cooling an oxide-based high temperature superconductor.

(Prior Art) In conventional superconducting devices, superconductors such as coils are operated while being cooled to an extremely low temperature using a coolant such as liquid helium. In a superconducting device equipped with such a cooling means, during operation, heat may enter from outside the device or due to quenching of the superconducting coil, etc.
When the temperature inside the device increases by 4.2, which is the boiling point of liquid helium, the liquid helium evaporates. At this time, the evaporated liquid helium was discharged to the outside of the system through piping, or the evaporated helium was condensed and reused using a refrigerator with a J-T valve.

(Problems to be Solved by the Invention) In such conventional superconducting devices, when liquid helium evaporates during operation, it is necessary to replenish liquid helium when discharging it outside the system, and when reusing it by condensation. had drawbacks such as the installation of a cryogenic refrigerator and the high power consumption of this refrigerator. Furthermore, in both cases,
When a so-called quench phenomenon occurs in a superconducting coil, a large amount of liquid helium evaporates due to a sudden rise in temperature within the device, so it is necessary to use a pressure vessel as a container for storing liquid helium.

By the way, oxide-based high-temperature superconductors such as YBaCuO have a temperature of 10K higher than the boiling point of liquid helium, which is 4,2.
Since it can be used both before and after, when liquid helium is used as a refrigerant, a gas refrigerant is used instead of a liquid refrigerant. However, compared to liquid refrigerants, gaseous refrigerants have the disadvantage that their thermal conductivity with the coil device to be cooled is lower, resulting in poorer cooling effects.

The present invention aims to improve the drawbacks of such conventional cooling methods in superconducting devices, and to provide a cooling method particularly suitable for oxide-based high-temperature superconductors.

(Means for Solving the Problems) According to the present invention, in a system where an oxide superconductor is used at a temperature of around 10K where the critical magnetic field increases, the refrigerant for cooling the oxide superconductor can be used at around 10K. solid state, 3
The above-mentioned drawbacks have been solved by a method for cooling an oxide-based superconductor, which is characterized by using a refrigerant that becomes liquid at around 0.00C.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing the configuration of a superconducting device to which the cooling method of the present invention is applied. The oxide superconducting coil 11 is wound around a coil winding frame 12, and is suspended from the upper part of a refrigerant container 14 by a coil support member 13 made of a heat insulating material such as FRP resin. Water 15 is stored in this refrigerant container 14 as a refrigerant. The refrigerant container 14 is suspended from the upper part of the vacuum container 17 by a container supporting material 16 made of a heat insulating material such as FRP resin. The refrigerant in the container 14 is arranged to be led out to the outside of the vacuum container 17. Furthermore, a heat shield plate 19 made of copper, for example, is provided in the vacuum container 17 so as to surround the refrigerant container 14. This heat shield plate 19 is supported by a container support member 16 that supports the refrigerant container 14. A refrigerator main body 20 is attached to the upper part of the vacuum container 17.

The refrigerator body 20 includes first and second cold heads 21 and 22 that contact the refrigerant container 14 and the heat shield plate 19, respectively. These first and second cold heads 21,22 are maintained at a temperature of 10K and 80K, respectively.

In the superconducting device configured in this way, in its normal operating state, the refrigerant container 14 is maintained at 10K.
Water 15, which is a refrigerant, is in ice, that is, in a solid state. Water in a solid state, that is, ice, has a good thermal conductivity (2.2 w/km at 0" C) and efficiently cools the superconducting coil 11. Next, when heat enters from the outside or the quench phenomenon When this happens, ice melts into water due to the rise in temperature inside the equipment, but since water has a relatively small volumetric expansion coefficient,
There is no pressure increase like in gases.

(Effects of the Invention) According to the method for cooling a superconductor of the present invention described above, the superconductor is cooled using a refrigerant such as water, which is solid under normal use and becomes liquid when the temperature rises. Therefore, unlike liquid helium, there is no need for strict leakage countermeasures when it is liquid or a high pressure rise when it evaporates. Therefore, it is not necessary to use a thick and strong pressure vessel as the refrigerant container, and an ordinary container may be used. Further, there is no need to use a special recondensing refrigerator, and the cold head of 10K and 80K can be used as it is as a cooling source.

Furthermore, when water is used as a refrigerant, the volume expands when the water solidifies at a low temperature, so that sufficient thermal contact with a superconductor such as a coil can be ensured and the cooling effect can be enhanced.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a superconducting device showing an embodiment of the method for cooling an oxide-based superconductor of the present invention. ...Oxide-based superconducting coil, 2.. Coil winding frame, 13.. coil support material, 14.. refrigerant container, 15.
... Water, 16 ... Container support material, 17 ... Vacuum container,
18...Exhaust pipe, 19...Heat shield plate, 20...
- Refrigerator main body, 21...first cold head, 22
...Second cold head. Figure 1

Claims (2)

[Claims] (1) At 10K, the critical magnetic field increases for oxide-based superconductors.
A method for cooling an oxide superconductor, characterized in that in the system used before and after the oxide superconductor, a refrigerant that becomes a solid state at around 10 K and a liquid state at around 300 K is used as a refrigerant for cooling the oxide superconductor. . (2) The method for cooling an oxide superconductor according to claim (1), wherein the coolant is water.