JP2980097B2 - Superconducting coil - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting coil, and more particularly to a superconducting coil which can generate a large magnetic field with a small electric power, and can be applied to various uses such as magnetic separation and crystal pulling. The present invention relates to an oxide high-temperature superconducting coil that can be used at high temperatures.

[0002]

2. Description of the Related Art Conventionally, coils wound with a normal conductor such as copper and coils wound with a metal-based superconductor exhibiting a superconducting phenomenon at liquid helium temperature have been used.

However, when a high magnetic field is generated by a coil wound with a copper wire, heat is generated so much that it is necessary to cool the coil by forcibly flowing water or the like. Therefore, a coil wound with a normal conductor consumes large power,
There are problems such as lack of compactness and difficulty in maintenance.

[0004] A coil wound with a metal-based superconductor is:
It is necessary to cool down to extremely low temperature (temperature around 4K), which not only raises the cost of cooling, but also uses coils at very low temperature where the specific heat is small, so the stability is poor and quench is likely to occur. Had properties.

However, since the oxide high-temperature superconducting coil can be used at a relatively high temperature as compared with the metal-based superconducting coil, it can be used in a region where the specific heat is large, and the stability is excellent. It has been found that there is a practical use as a superconducting coil for a superconducting magnet which is easier to use.

An oxide high-temperature superconducting wire exhibits a superconducting phenomenon at liquid nitrogen temperature, but at liquid nitrogen temperature, the critical current density and its magnetic field characteristics are relatively poor. Therefore, at present, the oxide high-temperature superconducting coil is used as a coil for generating a low magnetic field at the temperature of liquid nitrogen.

[0007] The oxide high-temperature superconducting coil can be used as a higher-performance coil at a temperature lower than the liquid nitrogen temperature, but liquid helium as a refrigerant suitable for practical use is expensive and complicated to handle. For this reason, attempts have been made to cool and use the oxide high-temperature superconducting coil at a very low temperature using a refrigerator whose operating cost is low and which is easy to handle.

Conventionally, in the operation of a metal-based superconducting coil of the immersion cooling type, in order to prevent quenching, the coil is operated at a current considerably smaller than the critical current, and the superconducting coil is used with little heat generation, or The superconducting coil has been used in a state where a superconducting coil is cooled by forcibly flowing a refrigerant into the inside of the container or by providing a gap so that the refrigerant can sufficiently pass around the superconducting wire.

On the other hand, recent conduction cooling type superconducting coils are used in a state where conduction cooling is performed from around the coil and heat is hardly generated in the coil.

It is possible to cool an oxide high-temperature superconducting coil in the same manner as a metal-based superconducting coil. However, an oxide high-temperature superconducting wire has a high critical temperature and a moderate normal-conductivity transition, so that it has high stability and is hardly quenched. Therefore, it is expected that the oxide high-temperature superconducting coil is operated at a high current near the critical current. In order to operate the superconducting coil at a current near the critical current, it is necessary to sufficiently cool the superconducting coil.In particular, in a conduction cooling method using a refrigerator, the temperature is not increased by a minute heat generation, The superconducting coil needs to be cooled.

[0011]

In the case of conduction cooling by a refrigerator, efficient cooling is difficult because the cooling capacity and the cooling path are limited.

In the conventional method, conduction cooling is performed only from around the coil. The superconducting wire is electrically insulated between the turns in the coil, but the material used for the insulation has very poor heat conduction, so conduction cooling from around the coil causes low heat to the inside of the coil. It is difficult to cool by resistance. That is, when a small amount of heat is generated inside the coil, the temperature rise of the coil becomes extremely large.
Therefore, in the conventional cooling method, the heat generated in the coil is very small, and the operating current is much smaller than the critical current.

The oxide high-temperature superconducting coil is expected to operate at a current closer to the critical current because of the high stability of the oxide high-temperature superconducting wire. Further, in the oxide high-temperature superconducting coil, since the n value (how the current-voltage characteristic rises) is small, the coil tends to gradually generate heat when the current is smaller than the critical current. From the above, in order to operate the oxide high-temperature superconducting coil, more efficient cooling than before is required.

The n value is used in the following relational expression.

[0015]

(Equation 1)

The oxide superconductor has magnetic field anisotropy. A superconducting wire formed so as to orient the oxide superconductor exhibits magnetic field anisotropy, is weak against a magnetic field parallel to the C axis, and has a larger decrease in critical current density. When the oxide superconductor is formed into a tape shape, the C axis is usually oriented perpendicular to the tape surface.

Japanese Unexamined Patent Publication No. Hei 8-316022 discloses a structure of a superconducting coil which suppresses frictional heat between insulated conductors and enhances cooling performance between the superconducting wire and the refrigerator. ing. In the disclosed structure,
After applying a heat treatment at 400 ° C. or higher, a superconducting wire which becomes a predetermined material is coated with an inorganic insulating layer or an insulating layer to be mineralized to form an insulated conducting wire, and the insulated conducting wire is wound to form a winding portion. In a superconducting coil configured by adding a material, a fixing material such as aluminum or an aluminum alloy that softens or melts at a heat treatment temperature is wound around a winding portion when winding an insulated conductive wire. This superconducting coil is manufactured by a so-called wind-and-react method (a method of producing a superconductor by reactive heat treatment after coil winding).

However, this superconducting coil has the following problems. First, it is necessary to heat-treat the superconducting coil at 400 ° C. or higher. Therefore, the material constituting the insulating layer is limited, and the degree of freedom is reduced. Usually, a material having a large thickness is used as a material of the insulating layer. As a result, the ratio of the wire constituting the superconducting coil is reduced, and the performance of the superconducting coil is reduced.

In the above-described superconducting coil, the heat treatment must be performed in an inert gas or a reducing gas. When heat treatment is performed in an oxygen atmosphere, aluminum or an aluminum alloy used as a fixing material is oxidized. As a result, heat conduction characteristics deteriorate. On the other hand, when a superconducting wire made of an oxide high-temperature superconductor is used, if heat treatment is performed in an inert gas or a reducing gas, superconducting characteristics such as a critical temperature and a critical current density deteriorate.

Further, in the above superconducting coil structure,
The bonding material is thermally connected to the superconducting wire via the insulating layer. The insulating layer has a lower thermal conductivity than metal. Therefore, the cooling characteristics deteriorate.

An object of the present invention is to solve the above-mentioned problems and to provide a structure of a superconducting coil capable of improving cooling efficiency.

Another object of the present invention is to further improve the cooling efficiency in a superconducting coil manufactured by a method of coil winding a superconducting wire after a superconductor is generated by a reaction heat treatment (react and wind method). It is possible to provide a superconducting coil structure.

[0023]

SUMMARY OF THE INVENTION A superconducting coil according to the present invention is a superconducting coil having a structure in which a plurality of pancake coils are laminated, wherein a first pancake coil around which a superconducting conductor is wound is provided. Between the first pancake coil and the second pancake coil, the second pancake coil having a superconducting conductor wound thereon and stacked on the first pancake coil in the coil axis direction. And a cooling plate disposed so as to be interposed.

In the superconducting coil configured as described above, since the cooling plate is disposed so as to be interposed between the first and second pancake coils, it is possible to directly cool the heat generated by the coil. it can. Thereby, the thermal resistance of the coil can be reduced, and the temperature rise of the coil can be reduced. The material of the cooling plate is preferably a material having good heat conductivity, but is not particularly limited.

In the superconducting coil of the present invention, preferably, the cooling plate is disposed at a portion where a magnetic field is generated in a direction perpendicular to the coil axis.

By arranging the cooling plate in this manner,
The cooling plate will be placed in the part where the magnetic field is likely to be applied from the outside in the direction perpendicular to the coil axis direction or in the part where the magnetic field is likely to be generated, and the cooling plate can be placed in the part of the coil that generates a large amount of heat. it can. Therefore, the heat generation of the coil can be efficiently suppressed in a state where the reduction of the coil packing rate due to the arrangement of the cooling plate is minimized. Here, the coil packing ratio refers to the ratio of the volume occupied by the superconducting conductor itself constituting the superconducting coil to the external volume occupied by the entire superconducting coil.

In the superconducting coil of the present invention, preferably, the cooling plate is disposed at an end of the superconducting coil in the coil axial direction.

By arranging the cooling plate in this manner,
In a superconducting coil using a bismuth-based superconducting wire, heat generation at the coil end is large, so that a rise in coil temperature can be suppressed efficiently.

Further, in the superconducting coil of the present invention,
The cooling plate is preferably arranged to be cooled by conduction from the refrigerator.

The method of cooling a coil by arranging a cooling plate between a plurality of pancake coils according to the present invention is also effective in a form in which a coil is immersed in a cooling medium to cool the coil, but cooling has conventionally been difficult. If the present invention is applied to a cooling mode based on conduction from a refrigerator, it becomes possible to more effectively suppress the temperature rise of the coil.

Preferably, the superconducting coil of the present invention is placed in a vacuum. Placing the superconducting coil in a vacuum facilitates thermal insulation and makes the cryostat compact, but the superconducting coil is cooled only by heat conduction. In such a case, if the structure of the superconducting coil of the present invention is applied, the superconducting coil can be cooled more effectively.

The superconducting conductor constituting the superconducting coil of the present invention is preferably formed of a tape-shaped superconducting wire.

Although the shape of the wire used for the superconducting coil of the present invention is not limited, the use of a tape-shaped superconducting wire facilitates the manufacture of a pancake coil, and a cooling plate is provided between a plurality of coils. It is also easy to arrange them.

The superconducting conductor constituting the superconducting coil of the present invention preferably contains an oxide superconductor.

Although the structure of the superconducting coil of the present invention is not limited with respect to the type of superconductor, it is more effective if applied to a coil using a highly stable oxide high-temperature superconductor.

The material used as the composite material of the oxide high-temperature superconductor is preferably silver or silver alloy having good thermal conductivity, but is not particularly limited.

The oxide superconductor is preferably a bismuth-based superconductor. Since the bismuth-based superconductor has particularly high stability among oxide high-temperature superconductors, the above-described efficient cooling can be more effectively exerted by applying the bismuth-based superconductor to the superconducting coil of the present invention.

In order to further improve the cooling characteristics of the superconducting coil of the present invention, it is necessary to use a good heat conductor as the cooling plate. However, good thermal conductors are generally electrically low resistance. An electric low-resistance element is used to excite and demagnetize a coil (hereinafter referred to as “excitation demagnetization”).
Eddy current loss occurs when the magnetic field changes as shown in FIG. In a conduction cooling type superconducting coil, it is necessary to use a cooling plate having a structure that does not generate heat when the coil is excited and demagnetized although heat is well transmitted.

Therefore, in the superconducting coil of the present invention, preferably, a slit is formed in the cooling plate.

By forming a slit in the cooling plate,
During excitation and demagnetization of the coil, AC loss, particularly heat generation due to eddy current loss, can be minimized. as a result,
The superconducting coil can always be efficiently cooled.

More preferably, the slit formed in the cooling plate is formed along a circumferential direction around the coil axis.

By forming the slit in the circumferential direction around the coil axis, the heat conduction direction along the circumferential direction of the coil axis, that is, the cooling characteristic of the cooling plate along the circumferential direction is not reduced. Since the heat generation due to the eddy current loss can be suppressed, the superconducting coil can be more effectively cooled.

The superconducting coil is cooled mainly in the coil axis direction. However, if the compressive force in the coil axis direction is weak, the contact thermal resistance increases, and the cooling efficiency of the superconducting coil deteriorates. Therefore, it is preferable to configure the superconducting coil so that a constant compressive force is always applied to the coil in the coil axis direction.

Preferably, in the superconducting coil of the present invention, 0.05 kg / mm ² or more and 3 kg in the coil axial direction.
/ Mm ² or less. More preferably, 0.2 kg / mm ² or more and 3 kg / m ^{2 in the} coil axis direction.
A compressive force of m ² or less is applied. By applying a certain range of compressive force in the coil axial direction, the contact thermal resistance can be reduced. However, if a large compressive force is used, the coil itself cannot withstand the compressive force and deteriorates.

As a means for applying a compressive force in the coil axis direction as described above, it is effective to use a spring. Since a superconducting coil is usually manufactured at room temperature and used at a very low temperature, a force due to thermal strain is also applied to the coil. Therefore, it is difficult to control the compressive force without using a spring. That is, by applying a compressive force in the coil axial direction using a spring, a predetermined compressive force can be applied in the coil axial direction without being affected by cooling strain.

[0046]

(Example 1) Bismuth-based oxide superconductor, mainly
2223 phase (Bi_xPb_1-x)_Two Sr_Two Ca _Two Cu_Three 
O_YSuperconducting wire composed of silver-coated superconductor
Materials were prepared. The width of the tape-shaped superconducting wire is 3.6 ±
0.4 mm and a thickness of 0.23 ± 0.02 mm.
Three tape-shaped superconducting wires are superimposed, and the superimposed
The thickness of about 0.1 mm
Stainless steel tape of SUS316, about 15μm thick
The polyimide tape was overlaid. Configured in this way
Wrapped tape-shaped composite around the bobbin,
Double of 65mm in diameter, 250mm in outer diameter and 8mm in height
A pancake coil was made. Bismuth coated with silver
Based superconducting wire is a cross section of silver with bismuth based superconductor.
When the product ratio is 2.4, the critical current is about 30A (77K)
Some were used.

Twelve double pancake coils manufactured as described above were laminated, and each coil was joined. The double pancake coils were electrically insulated by interposing a 0.1 mm thick FRP sheet.

The superconducting coil 10 thus obtained is
Has a structure in which twelve double pancake coils 1 are stacked in the coil axis direction as shown in FIG. The copper plate 3 was arranged on the upper side of the superconducting coil 10, and the copper plate 4 was arranged on the lower side. Thus, the superconducting coil 10 was fixed so as to be sandwiched between the disk-shaped copper plates 3 and 4.
An approximately disk-shaped cooling plate 2 made of copper was arranged between the double pancake coils 1. At this time, the coil packing ratio was 71%.

Example 2 A superconducting coil 10 was manufactured in the same manner as in Example 1 as shown in FIG. A substantially disk-shaped cooling plate 2 made of copper was disposed only at the end of the superconducting coil 10 in the coil axis direction. At this time, the coil packing ratio was 77%.

Comparative Example A superconducting coil 10 was manufactured in the same manner as in Example 1 as shown in FIG. At this time, no cooling plate was arranged between the double pancake coils 1. The coil packing ratio was 80%.

The superconducting coils 10 manufactured in Examples 1, 2 and Comparative Examples were fixed so as to be sandwiched between copper plates 3 and 4. The cooling plate 2 and the copper plates 3 and 4 were fixed to a heat conducting bar 5 connected to a cold head of a refrigerator.

Further, as shown in FIG. 4, the bar 5 for heat conduction is connected to the second stage 2 of the cold head of the refrigerator 20.
2 was thermally connected. The cold head second stage 22 extends from the refrigerator 20 via the cold head first stage 21.

A current lead 11 made of an oxide high-temperature superconducting wire was connected to the superconducting coil 10. Current lead 11
Further includes a current lead 12 made of an oxide high-temperature superconducting wire.
Was connected. A current lead 13 made of a copper wire was connected to the current lead 12. In this manner, the current lead suppresses heat intrusion from the superconducting coil 10 to the temperature anchor portion of the first stage 21 using the oxide high-temperature superconducting wire, and the current lead extends from the temperature anchor portion of the first stage 21 to a portion at room temperature. Copper wire was used. Superconducting coil 10
Was housed in a vacuum vessel 30. The vacuum vessel 30 was provided with a heat shield plate 31. Thereby, superconducting coil 10 was shielded from radiant heat. Further, a vacuum container 40 was provided to accommodate the vacuum container 30.

Using the cooling device thus configured, a current was applied to the superconducting coils of Examples 1, 2 and Comparative Example, and the temperature of each part of the coils was measured.

Table 1 shows the initial cooling characteristics (when the energizing current is 0 A).

[0056]

[Table 1]

As shown in Table 1, the temperature of each part of the superconducting coil of the comparative example, the example 1 and the example 2 was the same as the initial cooling characteristic.

As an energizing test, 10 at each energizing current value
Table 2 (Example 1), Table 3 (Example 2), and Table 4 (Comparative Example) show the temperature measured at each part of the superconducting coil after holding for one minute.

[0059]

[Table 2]

[0060]

[Table 3]

[0061]

[Table 4]

From the results of Tables 2 to 4, it can be seen that the temperature of each portion of the superconducting coil is lower when the cooling plate is disposed between the double pancake coils, and the entire superconducting coil is efficiently cooled. Recognize. In particular, it can be seen that when the value of the energizing current is increased, the heat generated by the superconducting coil is increased, so that the effect is significantly exhibited. Since the superconducting wire of the present embodiment is weak to the magnetic field in the direction perpendicular to the tape surface, thereby increasing the heat generation at the coil axial end of the superconducting coil, the cooling plate is disposed only at the end of the superconducting coil. In Example 2 in which the cooling plate was arranged between the double pancake coils, there was not much difference in the cooling effect. In Example 2, the operating current was 20
At 0 A, about 1 W, when the operating current is 240 A, about 8 W
The calorific value of W was measured in the superconducting coil.

Example 3 Bismuth-based oxide superconductor
Mainly 2223 phase (Bi_XPb_1-X)_Two Sr_Two Ca _Two Cu
_Three O_YSuperconductor composed of silver covered with silver
A wire rod was prepared. The width of the tape-shaped superconducting wire is 3.6 ±
0.4 mm and a thickness of 0.23 ± 0.02 mm.
Three tape-shaped superconducting wires are superimposed, and the superimposed
The thickness of the superconducting wire is about 0.05mm.
SUS316 stainless tape, about 15μm thick
The polyimide tape was overlaid. Configuration in this way
Wound the tape-like composite around the bobbin,
Dub with inner diameter 80mm, outer diameter about 250mm, height about 8mm
Lupine cake coil was made. Bisma coated with silver
-Based superconducting wires are used to cut silver from bismuth-based superconductors.
When the area ratio is 2.4, the critical current is 30 to 40 A (77
K) was used.

Twelve double pancake coils manufactured as described above were laminated, and each coil was joined. The double pancake coils were electrically insulated by interposing a 0.1 mm thick FRP sheet.

The superconducting coil 10 thus obtained
Has a structure in which twelve double pancake coils 1 are stacked in the coil axis direction as shown in FIG. The copper plate 3 was arranged on the upper side of the superconducting coil 10, and the copper plate 4 was arranged on the lower side. Thus, the superconducting coil 10 was fixed so as to be sandwiched between the disk-shaped copper plates 3 and 4.
An approximately disk-shaped cooling plate 2 made of copper was arranged between the double pancake coils 1. The cooling plate 2 and the copper plates 3 and 4 were fixed to a heat conducting bar 5 connected to a cold head of a refrigerator. At this time, the coil packing ratio was 80%.

Further, as shown in FIG. 4, the bar 5 for heat conduction is connected to the second stage 2 of the cold head of the refrigerator 20.
2 was thermally connected. The cold head second stage 22 extends from the refrigerator 20 via the cold head first stage 21.

A current lead 11 made of an oxide high-temperature superconducting wire was connected to the superconducting coil 10. Current lead 11
Further includes a current lead 12 made of an oxide high-temperature superconducting wire.
Was connected. A current lead 13 made of a copper wire was connected to the current lead 12. In this way, the current lead suppresses heat intrusion from the superconducting coil 10 to the temperature anchor portion of the first stage 21 using the oxide high-temperature superconducting wire, and the current lead extends from the temperature anchor portion of the first stage 21 to a portion at room temperature. Copper wire was used. Superconducting coil 10
Was housed in a vacuum vessel 30. The vacuum vessel 30 was provided with a heat shield plate 31. Thereby, superconducting coil 10 was shielded from radiant heat. Further, a vacuum container 40 was provided to accommodate the vacuum container 30.

A current was applied to the superconducting coil using the cooling device thus configured, and the coil temperature at the time of excitation and demagnetization of the coil was measured. At this time, three types of cooling plates 2 were disposed between the double pancake coils 1 in FIG. FIG. 5 to FIG.
It is a top view which shows the structure 1, the structure 2, and the structure 3 of a cooling plate.

In the structure 1 shown in FIG. 5, the cooling plate 2 comprises a donut-shaped portion 201 and a portion 203 on the side of the heat conducting bar, and a hole 202 is formed in the center of the donut-shaped portion 201.

In the structure 2 shown in FIG. 6, the cooling plate 2 comprises a donut-shaped portion 201 and a portion 203 on the side of the heat conducting bar, and a hole 202 is formed in the center of the donut-shaped portion 201 and a donut-shaped portion is formed. A radial slit 204 is formed from the outer periphery to the inner periphery of the portion 201. In FIG. 6, one dividing slit 205 extends vertically from the outer periphery to the inner periphery of the donut-shaped portion 201 and is formed so as to divide the circumferential direction.

In the structure 3 shown in FIG. 7, the cooling plate 2 is composed of a donut-shaped portion 201 and a portion 203 on the side of the heat conducting bar. A plurality of different circumferential slits 206 are formed between the outer periphery and the inner periphery of the donut-shaped portion 201. 7, one dividing slit 205 extends from the outer periphery of the donut-shaped portion 201 toward the inner periphery thereof, and is formed so as to divide the circumferential direction of the donut-shaped portion 201.

The excitation and demagnetization of the superconducting coil is performed when the current flowing through the coil is small, and the heat generated by the electric resistance is small.
The sweep speed was 1 minute. Table 5 shows the measurement results of the temperature characteristics of the coil during the excitation demagnetization.

[0073]

[Table 5]

As shown in Table 5, in the structure 1 using the cooling plate having no slit, the coil temperature was 20 K, while in the structure 2 having a plurality of slits formed in the radial direction.
Showed a low value of 19K, and the structure 3 in which a plurality of slits were formed in the circumferential direction showed a lower coil temperature of 17K. From this, it is understood that by forming the dividing slit 205 in the cooling plate 2, the eddy current loss in the cooling plate 2 can be reduced, and the heat generated thereby can be suppressed to a minimum. In addition, the fact that the cooling efficiency of the coil is better in the structure 3 than in the structure 2 is that the heat conduction in the circumferential direction is slightly reduced in the structure 2 due to the formation of the plurality of radial slits 204. While
It is considered that in the structure 3, the heat generation due to the eddy current loss can be suppressed in a state where the circumferential slit 206 holds the heat conduction in the circumferential direction, that is, without lowering the cooling characteristics.

The temperature of the superconducting coil after holding the current at a current of 200 A for one hour is almost the same, regardless of the cooling plate of any of the structures 1 to 3, is 12K, and the excitation demagnetization is performed. When the cooling was not performed, there was no change in the cooling characteristics.

Example 4 A superconducting coil 10 as shown in FIG. 9 was manufactured in the same manner as in Example 3. In the superconducting coil shown in FIG. 9, a spring 101 is arranged on the copper plate 3 to apply a compressive force to the superconducting coil shown in FIG. Although not shown, a plurality of springs 101 are circumferentially arranged on the copper plate 3. Spring 101 is bolt 1
02 and nuts 103 and 104. A substantially disk-shaped cooling plate 2 made of copper was disposed only at the end of the superconducting coil 10 in the coil axis direction. At this time, the structure of the cooling plate used was that of structure 1 shown in FIG. A refrigerator was configured as shown in FIG. 4 as in Example 3, and the coil temperature was measured. As the coil temperature, the compressive force applied in the coil axial direction was changed, and the temperature at each compressive force was measured. The current value was 295 A, and 1 W of heat was generated in the entire superconducting coil. Table 6 shows the temperature of each part of the superconducting coil measured at each compression force applied to the coil shaft.

[0077]

[Table 6]

[0078] From the results of Table 6, also appears cooling effect at the coil center as long as the compression force of the coil axis direction 0.05 kg / mm ² or more, each portion of the superconducting coil becomes to 0.2 kg / mm ² or more It can be seen that the temperature of the coil was kept low, and the entire coil was efficiently cooled.

Example 5 Bismuth-based oxide superconductor
Mainly 2223 phase (Bi_XPb_1-X)_Two Sr_Two Ca _Two Cu
_Three O_YSuperconductor composed of silver covered with silver
A wire rod was prepared. The width of the tape-shaped superconducting wire is 3.6 ±
0.4 mm and a thickness of 0.23 ± 0.02 mm.
Four tape-shaped superconducting wires are superimposed, and the superimposed
The width of the superconducting wire is about 3.5mm and the thickness is
Only about 0.2mm SUS316 stainless tape, thickness
A polyimide tape having a thickness of about 100 μm was overlaid. This
The tape-shaped composite configured as
Instead, wrap it around 940mm inside diameter and about 1010m outside diameter
m, make a double pancake coil about 8mm high
Was. Bismuth-based superconducting wire coated with silver is bismuth
Critical when the cross-sectional area ratio of silver to the system superconductor is 2.2
Those having a current of 30 to 40 A (77 K) were used.

Twenty double pancake coils manufactured as described above were laminated, and each coil was joined by soldering. 0.1mm thick F between double pancake coils
Electrical insulation was achieved by interposing an RP sheet.

The superconducting coil 10 thus obtained
Has a structure in which 20 double pancake coils 1 are stacked in the coil axis direction as shown in FIG. A stainless steel plate 7 was arranged above the superconducting coil 10, and a stainless steel plate 8 was arranged below the superconducting coil 10. Thus, the superconducting coil 10 was fixed so as to be sandwiched between the disc-shaped stainless steel plates 7 and 8. Each double pancake coil 1
Between them, an approximately disc-shaped aluminum alloy has a thickness of 0.1 mm.
An 8 mm cooling plate 2 was arranged. The cooling plate 2 and the stainless plates 7 and 8 were fixed to a heat conducting bar 5 connected to a cold head of a refrigerator. In the case of this embodiment, two refrigerators were used because the superconducting coil was large. The manufacturing process of the superconducting coil was performed at room temperature.

The current lead used was a high-temperature oxide superconducting wire to suppress heat penetration from the superconducting coil to the first stage temperature anchor, and a copper wire was used from the first stage temperature anchor to the room temperature state. . The superconducting coil shielded radiant heat with a heat shield.

After the superconducting coil was cooled down to about 15K by a refrigerator, it was operated by passing an exciting current. As a result, although the exciting current was increased to 290 A, the superconducting coil exhibited stable operation characteristics.

Next, the superconducting coil was returned to room temperature, and the resin was impregnated into the superconducting coil. After the epoxy resin was sufficiently penetrated into the superconducting coil, the epoxy resin was cured by performing a heat treatment in an air atmosphere at 120 ° C. for about 1.5 hours. After impregnation with the resin, the superconducting coil was cooled by a refrigerator, and an exciting current was applied to examine the coil conduction characteristics. As a result, the superconducting coil showed the same performance as before the impregnation with the epoxy resin. From this, it can be seen that even when heat treatment is performed at 120 ° C. to impregnate the resin, the cooling characteristics of the superconducting coil by the cooling plate do not change.

In the structure of the superconducting coil of the present invention,
As the cooling plate, it is preferable to use a metal material such as gold, silver, copper, aluminum, or an alloy thereof that does not recrystallize by heat treatment up to 130 ° C. during resin impregnation.
Further, it is preferable to use a cooling plate having a thickness in the range of 0.3 to 3.0 mm. If the thickness of the cooling plate is small, the effect of improving the cooling characteristics is not seen, and if the thickness of the cooling plate is large, the coil packing factor (the occupied volume ratio of the superconducting wire in the coil) decreases. Further, it is preferable that the cooling plate is electrically and thermally connected directly to the refrigerator without any intervening insulator. When the cooling plate is connected to the refrigerator through an insulator, the cooling characteristics are deteriorated.

The structure of the superconducting coil of the present invention is as follows.
It is preferably applied to a coil manufactured by a react-and-wind method.

The above-described embodiment is shown by way of example only, and should not be construed as limiting in any way. The scope of the present invention is not limited by the above description of the embodiments, but is defined by the appended claims, and includes all modifications within the scope equivalent to the appended claims. Should be interpreted as

[0088]

As described above, according to the present invention, the cooling characteristics of the entire superconducting coil are improved by disposing the cooling plate between the pancake coils, and the superconducting coil is provided even when the heating value of the superconducting coil is large. Can be driven. Therefore, by employing the structure of the present invention, the performance of the superconducting coil can be maximized.

Further, by disposing a cooling plate at a portion where a magnetic field is generated in a direction perpendicular to the coil axis direction or at an end in the coil axis direction, the operating current can be increased without lowering the coil packing ratio. Can be.

Further, by forming a slit in the cooling plate, it is possible to suppress AC loss, particularly heat generation due to eddy current loss during excitation and demagnetization of the superconducting coil, and preferably along the circumferential direction of the coil axis. By forming the slit, heat generation due to eddy current loss can be suppressed without lowering the coil conduction cooling characteristics of the cooling plate. Therefore, even when the coil is excited and demagnetized, the performance of the superconducting coil can be maximized.

Further, by applying a predetermined range of compressive force in the coil axis direction of the superconducting coil, the thermal resistance in the coil can be reduced, and the cooling characteristics of the conduction cooling coil can be maximized. .

[Brief description of the drawings]

FIG. 1 is a side view schematically showing a configuration of a superconducting coil employed in Embodiments 1 and 3 of the present invention.

FIG. 2 is a side view schematically showing a configuration of a superconducting coil employed in Embodiment 2 of the present invention.

FIG. 3 is a schematic side view showing a configuration of a superconducting coil as a comparative example of the present invention.

FIG. 4 is a diagram showing a schematic configuration of a refrigerator used for cooling a superconducting coil of the present invention.

FIG. 5 is a plan view showing a structure 1 of a cooling plate used in a third embodiment.

FIG. 6 is a plan view illustrating a structure 2 of a cooling plate used in a third embodiment.

FIG. 7 is a plan view showing a structure 3 of a cooling plate used in Embodiment 3.

FIG. 8 is a side view schematically showing a configuration of a superconducting coil employed in Embodiment 5 of the present invention.

FIG. 9 is a side view schematically showing a configuration of a superconducting coil employed in Embodiment 4 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Double pancake coil 2 Cooling plate 10 Superconducting coil 101 Spring 204 Radial slit 205 Dividing slit 206 Circumferential slit

Claims (15)

(57) [Claims] 1. A superconducting coil having a structure in which a plurality of pancake coils are stacked, a first pancake coil on which a superconducting conductor is wound, and a coil shaft on the first pancake coil. stacked in a direction, it is arranged so as to be interposed between the second pancake coils superconducting conductor is wound, and the first pancake coil and the second pancake coil, wherein the first and
A cooling plate for directly cooling the heat generated by the second pancake coil. 2. A plurality of pancake coils are stacked.
A conduction cooling type superconducting coil having a structure, A first pancake coil wound with a superconducting conductor, Stacking in the coil axis direction on the first pancake coil
The second pancake carp with the superconducting conductor wound
And The first pancake coil and the second pancake coil
And a cooling plate arranged to be interposed between
e, The cooling plate is cooled by conduction from the refrigerator.
Superconducting coil. 3. A plurality of pancake coils are stacked.
A superconducting coil having a structure, A first pancake coil wound with a superconducting conductor, Stacking in the coil axis direction on the first pancake coil
The second pancake carp with the superconducting conductor wound
And The first pancake coil and the second pancake coil
And a cooling plate arranged to be interposed between
e, The cooling plate is arranged in a coil axial direction in the superconducting coil.
Superconducting coil placed at the end of the Wherein said cooling plate portions the magnetic field is generated in the direction perpendicular to the coil axis direction are arranged, according to claim 1 to 3
The superconducting coil according to any one of the above. Wherein said cooling plate is disposed on the end of the coil axis direction in the superconducting coil, according to claim 1 or 2
3. The superconducting coil according to claim 1. Wherein said cooling plate is superconducting coil according to, is arranged to be cooled by conduction from the refrigerator according to claim 1 or 3. 7. The superconducting coils are disposed in a vacuum, the superconducting coil according to any one of claims 1-3. Wherein said superconducting conductor is composed of a superconducting wire having a tape-like form, according to claim 1-3 noise
2. The superconducting coil according to claim 1 . 9. The superconducting coil according to claim 1, wherein said superconducting conductor includes an oxide superconductor. Wherein said oxide superconductor is a bismuth-based superconductor, the superconducting coil according to claim 9. 11. The superconducting coil according to claim 1, wherein a slit is formed in the cooling plate. 12. The method of claim 11, wherein the slits are formed along a circumferential direction around the coil axis, superconducting coil according to claim 11. 13. A 0.05 kg / m direction in the coil axis direction.
a compressive force of not less than m ^{2 and not} more than 3 kg / mm ² is applied,
The superconducting coil according to any one of claims 1 to 3 . 14. A pressure of 0.2 kg / mm in the coil axis direction.
² or 3 kg / mm ² or less compressive force is applied, the superconducting coil according to claim 1 3. 15. The compressive force is applied by a spring, the superconducting coil according to claim 1 3 or 1 4.