JPS6260771B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to hollow superconductors.

As is well known, various hollow superconductors have been proposed that include a hollow conductor in which a refrigerant passage is formed and a superconducting wire fixed to the hollow conductor. A frequently used hollow superconductor has a structure as shown in Fig. 1, which includes a hollow conductor 2 such as oxygen-free copper with a coolant passage 1 formed inside, and a conductor 2 formed on the outer surface of the hollow conductor 2. A superconducting wire 4 is fixed in a groove 3 with solder or the like. When a superconducting magnet is manufactured by winding this hollow superconductor into a coil, the following advantages can be obtained.

(1) Compared to cooling by natural convection, forced circulation of liquid helium or supercritical pressure helium inside a hollow conductor cools each part evenly.

(2) A helium dewar to cool the entire magnet is not required; a vacuum container is sufficient.

(3) Unlike the conventional immersion method, there is no need for helium channels between turns or layers, making it possible to produce compact and mechanically strong magnets. Also,
The shape of the coil can be complex, and there is a high degree of selectivity in the shape.

In addition, a hollow superconductor in which a groove 5 is formed on the inner peripheral surface of a hollow conductor 2 as shown in Fig. 2 has also been proposed, and a magnet using this hollow superconductor has the advantages (1) to (3) above. In addition to this, it also has advantages such as increased cooling area and improved cooling efficiency.

However, when a conventional hollow superconductor is used, the following disadvantages occur.

(a) Not only is a device for pumping the refrigerant required, but there is also loss due to pressure drop during pumping.

(b) If a normal conducting part occurs in a part of the hollow conductor, the normal conducting part will propagate as the refrigerant is pumped.
Then, the stability of the magnet is lost.

Therefore, in order to prevent the propagation of the normal conducting part, the amount of copper in the hollow superconductor may be increased, the flow rate of the refrigerant may be increased, or a heat exchanger may be inserted at an intermediate position to absorb the normal conducting part. Methods such as providing a heat sink at a predetermined position have been proposed, but each has advantages and disadvantages, and there remains room for improvement.

In view of the above circumstances, the present inventors conducted intensive research and found that by arranging a separator in the refrigerant passage of a hollow conductor to divide it into two regions, a fast region and a slow region, two refrigerants with different flow velocities can be separated. It was found that the normal conductive part almost disappeared due to cooling by the flow, and the propagation of the normal conductive part was substantially prevented. The present invention was completed based on this knowledge.

The present invention will be described in detail below with reference to FIGS. 3 and 4.

FIG. 3 shows an embodiment of the hollow superconductor of the present invention. Hollow superconductor 10 of this example
includes a hollow conductor 12 in which a refrigerant passage 11 having a rectangular cross section is formed, a superconducting wire 14 fixed with solder or the like in a groove 13 formed on the outer peripheral surface of the hollow conductor 12, and the hollow conductor 12. a separator 15 provided at a predetermined distance on the inner circumferential surface 12a of the
A holding member 16 that fixes and holds this separator 15
It is composed of. The separator 15 is
For example, a metal mesh with good thermal conductivity such as copper or a stainless steel metal mesh is used. When a separator is installed, the flow of refrigerant is resisted by the separator and the inner surface of the hollow conductor, and only the slow area A where the refrigerant flows at a slow flow rate and the outer part of the flow of refrigerant are resisted by the separator and the refrigerant flows at a high flow rate. It is divided into basin B. Therefore, when the refrigerant is poured from the inlet at the same speed, two refrigerant flows with different flow speeds are formed in the slow region A outside the separator and the fast region B in the center. Then, the following effects are produced. In other words, even if the temperature of the refrigerant in a part of the slow region A rises due to the normal conductivity generated in a part of the hollow conductor, the speed at which the refrigerant propagates to the fast region B due to the obstruction of the separator 15 will be lower than that of the conventional hollow superconductor without a separator. much slower than the speed at which it propagates throughout the body's refrigerant passages. Then, the refrigerant having sufficient cooling capacity flowing into the fast region B in the center can cool the refrigerant in the slow region A whose temperature has increased, and the refrigerant in the fast region B flows into the slow region A through the separator, so that the synergistic effect of these refrigerants is As a result of this effect, the normal conductive portion disappears and propagation of the normal conductive portion is substantially prevented. Therefore, it can be efficiently cooled without impairing superconductivity.

FIG. 4 shows another embodiment of the hollow superconductor of the present invention, and the same members as in the previous embodiment are given the same numbers and their explanations will be omitted. In the hollow superconductor 10 of FIG. 4, a groove 17 is formed in the inner circumferential surface of the hollow conductor 12, and a separator 15 is disposed in the crest 17a of the groove 17.
Forming grooves on the inner circumferential surface of the hollow conductor 12 not only increases the cooling perimeter but also increases the resistance of the coolant flowing near the inner circumferential surface and slows down the flow rate. In addition, as in the case of the previous embodiment, it is divided into a slow region A and a fast region B by a separator such as a metal mesh, and the same effects as in the above embodiment are achieved in this embodiment as well.

Note that the present invention is not limited to the above two embodiments, and of course includes hollow superconductors having other structures or shapes. For example, (1)
A hollow superconductor comprising a hollow conductor having a rectangular refrigerant passage, a superconducting wire wound around the outer peripheral surface of the hollow conductor, and a separator arranged at a predetermined distance on the inner peripheral surface of the hollow conductor. , (2) a hollow conductor having a groove and a refrigerant passage formed on its inner peripheral surface, a separator disposed at the peak of the groove, and a superconducting wire wound around the outer peripheral surface of the hollow conductor. There are hollow superconductors etc.

As explained above, in the present invention, a separator such as a metal mesh is provided in the refrigerant passage of a hollow superconductor to divide the refrigerant passage into a fast region and a slow region.
It is divided into two basins. Since the area is divided into two areas, even if a part of the conductor has a normal conduction area, it will not propagate to the entire refrigerant path, and the low-temperature refrigerant flowing in the fast area will always The conductive part is eliminated. For this reason,
It is possible to provide a superconducting magnet that can be efficiently and reliably cooled, can reliably impart superconductivity, and has excellent stability.

Hereinafter, the present invention will be specifically explained with reference to specific examples.

Specific Example 1 The hollow superconductor 10 of this specific example has the structure shown in FIG. 3, and has an inner diameter of 3.4 mm x 2.4 mm and an outer diameter of 6 mm.
×5mm hollow conductor 12 and 4 of this hollow conductor 12
Superconducting wire (braided with 216 Nb ₃ Sn wires with a diameter of 0.1 mm) fixed with solder in the groove 13 formed on the surface
14, and a separator (0.1 mm holes formed in a 0.1 mm thick Al tape at 0.2 mm intervals) 15 arranged at a distance of 0.5 mm on the inner peripheral surface of the hollow conductor 12.
and a plurality of 0.2 mmφ oxygen-free copper wires 16 provided along the longitudinal direction to securely hold the separator 15.

A magnet was manufactured using 150 m of the hollow superconductor with the above configuration, supercritical pressure helium was flowed into the coolant passage 11 at a flow rate of 2 m/sec, and a heat pulse (10 W x 1 sec, 5 cm long) was applied at the magnet inlet. The propagation situation to the magnet outlet was investigated. Furthermore, for comparison, a similar experiment was conducted without providing a separator.
In the case of the conventional one without a separator, the temperature rose by 0.5〓 at the inlet, while it still rose by 0.3 to 0.35〓 at the exit, but in the case of the hollow superconductor of the present invention with a separator, the temperature rise at the exit was 0.1 〓It was below. From this, it can be seen that in the case of the present invention, the normal conductive portion generated at the inlet substantially disappears at the outlet.

Specific Example 2 A pipe-shaped hollow conductor with an inner diameter of 3.4 mm x 2.4 mm and an outer diameter of 5 mm x 4 mm and a rectangular cross section was used. Twenty-eight 0.3 mmφ multicore NbTi wires and 14 0.3 mmφ oxygen-free copper wires were wound around the outer peripheral surface of this oxygen-free copper hollow conductor and fixed with solder. In addition, a 60-mesh separator made of oxygen-free copper wire was placed 0.2 mm apart from the inner peripheral surface of the hollow conductor.

The propagation state was investigated in the same manner as in Example 1 above.
Furthermore, for comparison, a similar experiment was conducted without providing a separator. In the case of the conventional wire without a separator, the temperature increased by 0.5〓 at the inlet, but it still rose by 0.3〓 at the exit, but in the case of the hollow superconducting wire of the present invention with a separator, the temperature at the exit did not increase.
It was less than 0.1〓.

Specific Example 3 The hollow superconductor 10 of this specific example has the structure shown in FIG. 4, and has an inner diameter of 3.4 mm x 2.4 mm and an outer diameter of 6 mm.
x 5mm, groove 1 with a width of 0.2mm and a depth of 0.2mm on the inner circumferential surface
A hollow conductor 12 in which 7 is formed, and this hollow conductor 1
A superconducting wire (braided of 216 Nb ₃ Sn wires with a diameter of 0.1 mm) 14 is fixed with solder in a groove 13 formed on the outer peripheral surface of the hollow conductor 12, and The separator 15 (0.1 mm holes formed at 0.3 mm intervals in a 0.08 mm thick stainless steel tape) 15 is provided.

A magnet was manufactured using 150 m of the hollow superconductor with the above configuration, supercritical pressure helium was flowed into the coolant passage 11 at a flow rate of 2 m/s, and a heat pulse (0.6 W x 15 seconds, 5 cm length) was applied at the magnet inlet. We investigated the propagation situation to the magnet outlet. Furthermore, for comparison, a similar experiment was conducted without providing a separator. In the case of the conventional type without a separator, it increases by 0.5〓 at the entrance, but it still rises by 0.3~ at the exit.
0.35〓, but in the case of the hollow superconductor of the present invention equipped with a separator, the temperature rise at the outlet is
It was less than 0.1〓. From this, it can be seen that in the case of the present invention, the normal conduction portion generated at the inlet substantially disappears at the outlet.

Specific example 4 It is a pipe with an inner diameter of 3.4 mm x 2.4 mm, an outer diameter of 5 mm x 4 mm, and a rectangular cross section, and a 0.3 mm width on the inner circumference.
A hollow conductor with a groove 0.3 mm deep was used.
Twenty-eight 0.3 mmφ multicore NbTi wires and 14 0.3 mmφ oxygen-free copper wires were wound around the outer peripheral surface of this oxygen-free copper hollow conductor and fixed with solder. In addition, a 60-mesh separator made of oxygen-free copper wire was placed in contact with the peaks of the groove. Furthermore, for comparison, a similar experiment was conducted without providing a separator. In the case of the conventional model without a separator, there was a rise of 0.6〓 at the entrance, but there was still a rise of 0.3 to 0.4〓 at the exit.
In the case of the hollow superconductor of the present invention provided with a separator, the temperature rise at the outlet was less than 0.1〓.

[Brief explanation of the drawing]

1 and 2 are schematic cross-sectional views of conventional hollow superconductors, FIG. 3 is a schematic cross-sectional view of a hollow superconductor according to an embodiment of the present invention, and FIG. 4 is a schematic cross-sectional view of a hollow superconductor according to another embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of the body. 10...Hollow superconductor, 11...Refrigerant passage, 1
2...Hollow conductor, 14...Superconducting wire, 15...Separator.

Claims (1)

[Claims] 1. In a hollow superconductor comprising a hollow conductor in which a refrigerant passage is formed and a superconducting wire fixed to the hollow conductor, the refrigerant passage of the hollow conductor is divided into two regions, a fast region and a slow region. A hollow superconductor characterized in that a separator is disposed within the refrigerant passage.