JPS63250020A - Refrigerant self-holding superconductor - Google Patents

Abstract

PURPOSE:To keep a superconductor at the critical temperature or lower even if part of it is exposed from a refrigerant liquid by providing voids holding a refrigerant in the superconductor showing a superconductive state when cooled by the refrigerant liquid. CONSTITUTION:A superconductive coil 6 and a refrigerant 2 are stored in a cooling container 3. The coil 6 contains voids in response to the refrigerant and made of a porous sintered body. When the refrigerant liquid level 5a is lowered by evaporation during the operation of the coil 6 for a long time, the coil 6 itself holds the refrigerant liquid via the capillary tube force even if the upper section of the coil 6 is exposed from the liquid level 5a, and it is cooled by the refrigerant liquid and can be kept at the critical temperature or lower.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to a superconductor used in superconducting equipment, and relates to a refrigerant self-retaining superconductor that has the ability to retain its own refrigerant and has more effective cooling properties. It's about the body.

[Prior Art] FIG. 3 is a block diagram of a cooling device in a conventional superconducting device disclosed in, for example, Japanese Unexamined Patent Publication No. 61-217658.

In the figure, (1) is a superconducting coil made of a superconductor, (
2) is a refrigerant for cooling the superconducting coil (1);
) is a low-temperature container containing a superconducting coil (1) and a refrigerant (2). (4) is a condenser for recondensing refrigerant gas that has evaporated due to heat intrusion from the outside or minute internal heat generation. The other components are omitted because they are not directly related to this invention, but they are a refrigeration system for supplying cold heat to the condenser.

Next, the operation will be explained. Normally, superconducting coil (1)
is used to obtain a higher magnetic field or a highly uniform magnetic field, but in order to achieve a superconducting state, it is necessary to cool the material to a certain temperature (hereinafter, this temperature will be referred to as the critical temperature).

According to FIG. 3, a refrigerant (for example, liquid helium) is first poured into the low temperature container (3) to cool the superconducting coil (1).

In order to constantly maintain the superconducting state, it is immersed in the refrigerant liquid (2a) as shown in the figure, and then the excitation power source (
(not shown) to supply electricity and use it as a magnet. In addition, a refrigerator and a condenser (
A refrigeration system such as 4) is added.

Superconducting coil (1) and refrigerant here? ! A schematic cross-sectional view is shown in FIG. 4 to make the relationship with (2a) easier to understand. According to FIG. 4, in order to maintain the superconducting coil (1) in a superconducting state during the operation of the superconducting equipment, it is necessary to maintain the liquid level position of the refrigerant liquid (2a) in a state as shown in (5a). If the liquid level position of refrigerant liquid (2a) is like (5b),
When the upper part of the superconducting coil (1) comes out of the refrigerant liquid (2a) and comes into contact with the refrigerant gas (2b), the part that is in contact with the refrigerant gas (2b) is slightly thermally disturbed and the superconducting coil (1)
cannot be maintained in a superconducting state, leading to superconducting breakdown (hereinafter referred to as quench), and the possibility of transition to normal conductivity.

This is because liquid and gas have different heat transfer characteristics, and the latter is worse than the former.

In the unlikely event that quenching occurs, the superconducting coil (1) will be damaged and may lose its function as a coil. This could lead to the superconducting equipment losing its functionality, and could even lead to a major accident. Therefore, to prevent these situations from occurring, the superconducting coil (1) is usually heated with a refrigerant liquid (
It will be operated under conditions that are fully immersed in 2a). To achieve this, the cryogenic container (3) should be made larger or placed in the upper tank so that there is more room for the refrigerant liquid (2a), and if the refrigerant liquid (2a) decreases, it must be refilled each time. Either apply the liquid or use cold Va(
In order not to reduce 2a), a reliquefaction system is added.

[Intervertical point to be solved by the invention] Since the superconducting coil (1) made of a conventional superconductor is cooled and maintained in a superconducting state using the method described above, the amount of stored refrigerant (2) is Due to the necessity of increasing the size, there was a problem in that the cryogenic container (3) became large. As the low-temperature container (3) becomes larger, the amount of heat intrusion due to thermal radiation increases (proportional to the outer surface area of the low-temperature container (2)), and the refrigerant becomes more likely to evaporate.

This invention was made in order to eliminate the above-mentioned conventional problems.For example, as a superconductor used in a superconducting coil, instead of the conventional dense one, the refrigerant liquid is sucked up and held inside by capillary action. By using a refrigerant that has voids that can
It is an object of the present invention to provide a superconductor that can reduce the size of the device and maintain the superconducting state even when a part of the superconducting coil is exposed from the refrigerant liquid. □ [Means for solving the problem] The refrigerant self-retaining superconductor according to the present invention is a superconductor whose electrical resistance becomes zero and becomes superconducting when cooled to a predetermined temperature or below, and which retains the refrigerant. It has voids that can be removed.

[Operation] The refrigerant self-retaining superconductor in this invention has a void that retains the refrigerant liquid within the superconductor, so even if a part of the superconductor is exposed from the refrigerant, the refrigerant retained within the void remains. It is possible to maintain a state similar to that in a refrigerant and maintain a superconducting state. In addition, when initial cooling is performed below the critical temperature, cooling can be performed quickly. Therefore, the amount of refrigerant used can be reduced, and the low-temperature container and apparatus can be made more compact.

[Embodiment □ Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view schematically showing a superconducting device to which an embodiment of the present invention is applied. In the figure, (2・) is a refrigerant for cooling the superconducting coil, (3)' is a cold container for storing the superconducting coil and refrigerant (2), (5a) is the liquid level of the refrigerant, and (6) is the refrigerant. An embodiment of the present invention is a superconductor containing voids depending on the refrigerant, in this case a superconducting coil made of a porous sintered body. FIG. 2 is a cross-sectional view schematically showing the superconducting device shown in FIG. 1 when the refrigerant liquid (2) decreases and the superconducting coil (6) is exposed from the refrigerant liquid level, ) is the liquid level of the refrigerant liquid at that time. Note that (6b) is the refrigerant reaching surface, which is of course the case in Fig. 1, but also in the case of Fig. 2, where the superconducting coil (6),
The coolant is held inside up to the upper end (6b), that is, throughout the void in the superconductor.

Next, the operation will be explained. The method of operating the superconducting coil (6) is the same as that of the conventional device, and is illustrated in FIG. By the way, during long-term operation, the refrigerant liquid level (5a) gradually decreases as the liquid evaporates due to heat intrusion from the outside. In the case of a superconducting coil (6) made of a superconductor containing voids depending on the refrigerant as in the present invention, even if the upper part of the superconducting coil (1) is exposed from the refrigerant liquid level (5b) as shown in FIG. Since the superconducting coil (1) itself retains the refrigerant liquid by capillary force, it is cooled by the captured refrigerant liquid and maintains a state as if it were in the refrigerant liquid, so that the superconducting state can be maintained. Therefore, it is possible to drive without worrying about quenching.

In addition, since it has the ability to suck up the refrigerant liquid by capillary force, even when the superconducting coil (6) is initially cooled down to below the critical temperature, it can be cooled more quickly. Even when the initial cooling is completed and the refrigerant liquid is stored, the entire part does not necessarily need to be immersed in the refrigerant liquid, so the amount of refrigerant used can be reduced. As a result, the low-temperature container can be made more compact, and the amount of heat intrusion due to heat flux can be reduced accordingly.

On the other hand, even when reliquefaction is performed by adding a refrigerator and a condenser, the amount of heat intrusion can be reduced, so the capacity can be smaller than before, which also leads to a more compact reliquefaction system.

As the superconductor according to the present invention, for example, an NbT1 alloy superconducting material, a Nb3Sn compound superconducting material, and an oxide superconducting material consisting of La and S are used.

An example of a method for producing a superconductor according to the present invention is a method of baking and solidifying powder. This is a so-called sintered body.

The size of the void may be arbitrary as long as capillary force is generated and the refrigerant is sucked up or retained, but in general, capillary force is maximized depending on the size of the void depending on the surface tension of the refrigerant. It is more preferable that the average void size be close to that.

In any case, any superconductor is suitable as long as it is manufactured by a manufacturing method that includes appropriate voids and has a refrigerant self-suction function or a refrigerant self-retention function. In other words, even if the material itself is a superconductor with voids, a superconductor formed with voids between the materials, such as a metal superconducting wire wound with voids, Anything is fine.

Furthermore, as long as the refrigerant is dropped from above, replenishment of the refrigerant into the voids within the superconductor does not need to rely on capillary action.

[Effects of the Invention] As described above, according to the present invention, a superconductor that exhibits a superconducting state with zero electrical resistance when cooled to a predetermined temperature or below has voids capable of holding a refrigerant. Even if a part of the superconductor is exposed to the refrigerant liquid, the temperature can be maintained below the critical temperature, and as a synergistic effect, a self-retaining superconductor can be obtained that can reduce heat intrusion into equipment, save space, and save energy. There is.

[Brief explanation of drawings]

Figures 1 and 2 are schematic cross-sectional views of a superconducting device according to an embodiment of the present invention. Figure 1 shows a steady state, and Figure 2 shows a state in which the refrigerant has decreased and the superconducting coil is exposed above the liquid level. represents. FIG. 3 is a block diagram of a cooling device in a conventional superconducting device, and FIG. 4 is a schematic cross-sectional view of the superconducting device in the device in FIG. (2) Refrigerant (5aX5b) Refrigerant liquid level (6) Superconducting coil (6b) Refrigerant reaching surface Note that the same reference numerals in the drawings indicate the same or equivalent parts.

Claims (4)

[Claims] (1) A refrigerant self-retaining superconductor characterized in that the superconductor exhibits a superconducting state with zero electrical resistance when cooled to a predetermined temperature or below, and has voids capable of retaining a refrigerant. (2) A refrigerant self-holding superconductor according to claim 1, characterized in that the refrigerant self-retaining superconductor has a void capable of sucking up and retaining refrigerant by capillary action. (3) A refrigerant self-retaining superconductor according to claim 1 or 2, wherein the voids are distributed within the superconductor main body. (4) The refrigerant self-retaining superconductor according to any one of claims 1 to 3, wherein the superconductor is a porous body.