JP7402620B2 - superconducting magnet - Google Patents

Description

The present invention relates to superconducting magnets.

Superconducting magnets using superconducting wires are used in MRI (Magnetic Resonance Imaging), NMR (Nuclear Magnetic Resonance), particle beam medical equipment, etc., and are also being used in new applications such as power generators. It is being considered on a daily basis. Superconducting magnets have the advantage of being compact and capable of producing high magnetic fields because they can handle a higher current density in their wires than normal conductor magnets. Furthermore, most superconducting magnets use a wire made of a superconductor such as NbTi or Nb3Sn, and liquid helium is used as a coolant. However, liquid helium is expensive and must be replenished as it evaporates and is lost during operation, which is a cost factor. Therefore, it is desirable to construct a superconducting magnet by a method in which the superconductor is cooled by conduction cooling without using liquid helium.

Conduction cooling is generally more difficult and technically difficult to cool than using liquid helium. In order to rationally realize a superconducting magnet using conduction cooling while reducing cooling costs, the heat generation within the superconducting magnet and heat intrusion from the outside must be reduced as much as possible, and the entire superconducting magnet must have a structure with high thermal conductivity. is desirable.
Heat generation within a superconducting magnet is generally caused mainly by hysteresis loss when the superconducting magnet current is varied during operation, such as during startup and shutdown. Hysteresis loss is caused by fluctuations in the magnetic field applied to the superconductor, and the greater the volume of the superconductor within the superconductor magnet, the greater the overall loss.
In terms of cooling, superconducting magnets generally use multilayer winding, in which superconducting wire is wound in the direction of the winding axis to form a layer of winding wire, and the winding direction is turned back at the end of the layer to wind the outer layer. It often takes the structure of In this case, it is desirable to improve thermal conductivity by winding the superconducting wire as tightly as possible. Furthermore, when a superconducting magnet is cooled via a winding bobbin, it is desirable to reduce the cooling cost by suppressing variations in thermal resistance between the ends of each layer and the winding bobbin and preventing the occurrence of hot spots.

In order to minimize the superconductor volume within a superconducting magnet in order to reduce the amount of heat generated within the superconducting magnet, it is effective to implement grading. Grading is a technology that changes the current density flowing through the superconducting wire in each layer of the superconducting magnet. Grading is based on the characteristic of superconducting wires that the current density that can be passed decreases as the magnetic field increases.The inner diameter side of the superconducting magnet has a higher magnetic field, so the current density is lower, and the outer diameter side has a lower magnetic field, so the current density is higher. shall be. This has the effect of maximizing the current of the entire superconducting magnet. This effect is equivalent to minimizing the amount of superconductor.

For grading, a method is often used in which a thick superconducting wire with a large strand cross-sectional area is used on the inner diameter side, and a thin superconducting wire with a small strand cross-sectional area is used on the outer diameter side. Alternatively, a method may be taken in which a superconducting material having a high critical current density in a magnetic field is applied to the inner diameter side. According to such a configuration, each layer of the superconducting magnet is composed of superconducting wires of different shapes, making it difficult to wind the magnets densely. Moreover, the dimensional variation of each layer becomes large. Therefore, when conduction cooling is applied, there is a problem that the cooling cost increases.

Patent Document 1 describes that the number of superconducting wires in each layer is increased inside the high-temperature superconducting coil, and the number of superconducting wires in each layer is decreased toward the outside of the high-temperature superconducting coil. A graded high-temperature superconducting coil is described, which is characterized in that it is configured to improve the conduction current of the coil and generate a high magnetic field while suppressing the amount of superconducting wire used. The graded high-temperature superconducting coil described in Patent Document 1 is a pancake-shaped superconducting coil in which a high-temperature superconducting tape wire is wound in the layer direction, and the inner layer is made by stacking a plurality of high-temperature superconducting wires of the same type in the layer direction. Grading is achieved by constructing parallel conductors, and the outer layer is composed of a single high-temperature superconducting wire. According to this configuration, grading can be achieved while using the same type of high-temperature superconducting wire.

In order to realize a superconducting magnet using conduction cooling, it is desirable to suppress variations in thermal resistance of each layer when winding a superconducting magnet in multiple layers, and to minimize the amount of superconductor input through grading.

JP2012-182265A

The high-temperature superconducting coil described in Patent Document 1 achieves grading by winding parallel-connected high-temperature superconducting wires on the inner diameter side and winding a single high-temperature superconducting wire on the outer diameter side, and reduces the amount of high-temperature superconductor input. has been reduced. On the other hand, since the wire is a high-temperature superconducting wire, it has a tape shape with a large aspect ratio. The tape shape is suitable for arranging and connecting in parallel in the layer direction. However, so-called low-temperature superconducting wires such as NbTi and Nb ₃ Sn have a wire cross section that is approximately circular or approximately rectangular (with an aspect ratio of less than 10). Therefore, arranging the low-temperature superconducting wires in parallel in the layer direction is a complicated work.
Further, the high-temperature superconducting coil described in Patent Document 1 has a pancake shape, and does not show a configuration in which the winding wire is wound in the winding axis direction like the superconducting magnet targeted by the present invention. Furthermore, conduction cooling is not considered.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a superconducting magnet that can realize grading while reducing cooling costs.

In order to solve the above problems, the superconducting magnet of the present invention configures a layer of the winding wire by winding the superconducting wire around a winding bobbin and advancing the winding in the direction of the winding axis, and at the end of the layer, the winding direction is The superconducting coil has a multilayer winding structure in which the outer layer is folded back and wound, and the superconducting coil has a cross-sectional external dimension of the superconducting wire in each layer having a predetermined value, and the strands of the superconducting wire are arranged in different layers. The superconducting coil has different current densities, and the number of the superconducting wires connected in parallel in the layer on the outer diameter side is smaller than the number of the superconducting wires connected in parallel in the layer on the inner diameter side, and The superconducting coil is characterized in that the number of turns obtained by multiplying the number of parallel superconducting wires in each layer by the number of turns is a common multiple of the number of parallel lines in each layer .

According to the present invention, it is possible to provide a superconducting magnet that can realize grading while reducing cooling costs.

1 is a cross-sectional view of a superconducting coil of a superconducting magnet according to a first embodiment of the present invention. FIG. 3 is a diagram showing an example of a connection structure between layers in which the number of parallel superconducting coils of the superconducting magnet according to the first embodiment changes. FIG. 3 is a cross-sectional view taken along the line AA in FIG. It is a figure showing an example of spacer arrangement in a paragraph of three parallel superconducting wires of a superconducting magnet concerning a 1st embodiment of the above. It is a figure which shows another structural example of the connection part of the connection structure between layers in which the number of parallel superconducting coils of the superconducting magnet according to the first embodiment is changed. It is a figure which shows another structural example of the connection part of the connection structure between layers in which the number of parallel superconducting coils of the superconducting magnet according to the first embodiment is changed. It is a figure which shows the example of the connection structure between layers in which the number of parallel superconducting coils of the modification of the superconducting magnet based on the said 1st Embodiment changes. It is a figure which shows the example of the connection structure between layers in which the number of parallel superconducting coils of the modification of the superconducting magnet based on the said 1st Embodiment changes. FIG. 2 is a cross-sectional view of a superconducting coil in which the number of parallel superconducting magnets is three types according to the first embodiment. FIG. 2 is a sectional view of a superconducting coil in which the outer diameter side (outermost diameter side) of the superconducting magnet according to the first embodiment is not connected in parallel. FIG. 3 is a diagram showing an example of dislocation positions of three parallel superconducting wires of the superconducting magnet according to the first embodiment. It is a figure which shows the example of the transposition method of 3 parallel superconducting wires of the superconducting magnet based on the said 1st Embodiment. It is a figure which shows the example of the transposition method of the 4 parallel superconducting wire of the superconducting magnet based on the said 1st Embodiment. It is a sectional view of the superconducting coil of the modification of the superconducting magnet concerning the above-mentioned 1st embodiment. FIG. 3 is a cross-sectional view of a superconducting coil of a superconducting magnet according to a second embodiment of the present invention. It is a figure which shows the example of the connection structure between layers in which the number of strands of the superconducting magnet according to the second embodiment changes. 1 is a cross-sectional view schematically showing the structure of a superconducting magnet according to an application example of the present invention.

Embodiments of the present invention will be described in detail below with reference to the drawings.
(First embodiment)
FIG. 1 is a sectional view of a superconducting coil of a superconducting magnet according to a first embodiment of the present invention. FIG. 1 shows a detailed cross-section of the right side of the superconducting coil with line symmetry about the coil winding axis center.
This embodiment is an example in which the present invention is applied to a conduction-cooled superconducting magnet.
As shown in FIG. 1, the superconducting magnet 1 includes a superconducting coil 10.
The superconducting coil 10 is constructed by winding a superconducting wire 20 having a rectangular cross section around a winding bobbin 11 from the inner circumferential side in a stacked manner in the direction of the winding axis to form a layer of the winding wire. It has a multi-layered structure in which the outer layer is rolled up by folding it back. The superconducting wire 20 wound around the winding bobbin 11 is fixed by injecting a resin (not shown), typically epoxy, to form a coil.

The superconducting wire 20 includes a superconducting wire 21 in which niobium titanium (NbTi) is coated with metal, for example, and an insulating coating 22 that covers the wire 21. For the superconducting wire 21, metal superconductors such as the above-mentioned niobium titanium (NbTi), niobium tritin (Nb ₃ Sn), and magnesium diboride (MgB ₂ ) can be selected.

In this embodiment, the number of wire rods 21 (hereinafter referred to as the number of strands) of the superconducting wire 20 on the outer diameter side is the same as the number of strands of the superconducting wire 20 on the inner diameter side.

The superconducting coil 20 is characterized in that the external dimensions (shape) of the cross section of the superconducting wire in each layer are predetermined numerical values. Ideally, it is desirable that the predetermined values be the same, but a sufficient effect can be obtained if, for example, the external dimensions are within an error range of ±0.05 mm (more preferably ±0.02 mm). . Here, it is assumed that the identity of the external shape is also included in the predetermined numerical value. For example, when the cross-sectional shape of a superconducting wire is a rectangular cross-sectional shape, there is a shape of parallel sides (a straight shape, a curved shape, a radius of a corner, etc.). In the following description, for convenience of explanation, the same external dimensions refer to the same dimensions within the above error range.

The cross-sectional shape of the superconducting wire 20 is not particularly limited, but in this embodiment, it is a rectangular cross-sectional shape. Since the cross-sectional shape of the superconducting wire 20 is rectangular, there is an advantage that it is easy to wind the superconducting wire 20 around the winding bobbin 11 when manufacturing the superconducting coil 10. Since the superconducting coil 20 can be tightly wound (no gaps are formed), the thermal resistance within the superconducting magnet 1 can be reduced.

<Detailed structure of parallel connection of superconducting coils 10>
As shown in FIG. 1, a superconducting coil 10 is constructed by winding a superconducting wire 20 while winding it in the direction of the winding axis to form a layer of the winding wire, and then folding back the winding direction at the end of the layer to form an outer layer. It has a multi-layered structure.
In this embodiment, the superconducting coil 10 includes a plurality of superconducting wires 20 connected in parallel, the superconducting wires 20 connected in parallel being arranged side by side in the winding axis direction, and superconducting wires 20 connected in parallel on the outer diameter side of the superconducting coil 10. The number of wires 20 in parallel is smaller than the number of superconducting wires 20 connected in parallel on the inner diameter side.

In the example of FIG. 1, the superconducting coil 10 is constructed by winding three parallel superconducting wires 20-3 in the winding axis direction, in which three superconducting wires 20 lined up in the winding axis direction are connected in parallel in the two layers on the inner diameter side. In the two layers on the outer diameter side, two parallel superconducting wires 20-2, which are two superconducting wires 20 lined up in the direction of the winding axis and connected in parallel, are wound in the direction of the winding axis. As shown in the thick broken line box in FIG. 1, the three-parallel superconducting wire 20-3, in which three superconducting wires 20 are connected in parallel in a set of three, is wound four times per layer, and the two layers on the inner diameter side Configure. Further, a two-parallel superconducting wire 20-2, which is a set of two superconducting wires 20 connected in parallel, is wound six times per layer to form two layers on the outer diameter side.
The ends of each layer are aligned at the flange 11a of the winding bobbin 11.

As mentioned above, the 3-parallel superconducting wire 20-3, in which three superconducting wires 20 are connected in parallel in a set of three, is wound four times per layer, and two superconducting wires 20 are connected in parallel in a set of two. The connected two parallel superconducting wires 20-2 are wound six times per layer. Therefore, the number of turns (parallel number x number of turns) of the superconducting wire 20 in each layer is 12, and the number of turns of the superconducting wire 20 "12" is equal to the number of parallel superconducting wires "3" on the inner diameter side and the superconducting wire on the outer diameter side. It is assumed to be a common multiple of the number of parallel lines "2".

<Connection structure between layers of superconducting coil 10>
FIG. 2 is a diagram showing an example of a connection structure between layers in which the number of parallel connections changes in the superconducting coil 10 of the superconducting magnet 1 according to the first embodiment. FIG. 3 is a cross-sectional view taken along the line AA in FIG. In addition, in FIG. 3, the coil winding center axis direction is O.
As shown in FIGS. 2 and 3, the 3-parallel superconducting wire 20-3 and the 2-parallel superconducting wire 20-2 are arranged at the end of the layer of the 3-parallel superconducting wire 20-3 and the beginning of the layer of the 2-parallel superconducting wire 20-2. The connection is made using the connecting portion 12 at the position of the flange 11a of the winding bobbin 11 (the position in contact with the flange 11a).
The connecting portion 12 makes a lap connection (described later) between the end of the three-parallel superconducting wire 20-3 and the end of the two-parallel superconducting wire 20-2 by using the gap between the layered sections 14.

The connecting portion 12 is a sintered body containing niobium titanium (NbTi) or the like. The connecting portion 12 connects the end faces of the 3-parallel superconducting wire 20-3 and the 2-parallel superconducting wire 20-2, including end faces where niobium titanium (NbTi) or the like is exposed, via a sintered body containing niobium titanium (NbTi) or the like. (fix).

The superconducting coil 10 has a stepped portion 14 at the end of the layer on the inner diameter side or the start end of the layer on the outer diameter side of adjacent layers with different numbers of parallel connections, and a connection of parallel superconducting wires with different numbers of parallel connections in the stepped portion 14. and a connecting portion 12. The connecting portion 12 can be connected using the space where the layers are rolled up, and the external dimensions of the superconducting coil 10 can be reduced.

FIG. 4 is a diagram showing an example of spacer arrangement in a row of three parallel superconducting wires in the superconducting magnet 1 according to the first embodiment.
As shown in FIGS. 3 and 4, in the empty gap defined by the end of the 3-parallel superconducting wire 20-3, the connecting portion 12, and the inner peripheral surface of the winding start of the 2-parallel superconducting wire 20-2. The spacer 13 is provided to support the winding and reduce the gap.
The superconducting coil 10 may be impregnated with a resin, but in this case, the spacer 13 limits the amount of resin in the gap, thereby suppressing quenching caused by resin cracks. FRP (Fiber-Reinforced Plastics) can be selected for the spacer. The material for the spacer 13 is preferably one with good thermal conductivity.

In this way, by filling and alleviating the quench source where the impregnated resin accumulates with the spacer 13, the spacer 13 can limit the amount of resin in the gap as described above, and prevent quenching due to resin cracking. can.

<Another structural example of the connection portion 12 of the interlayer connection structure of the superconducting coil 10>
5 and 6 are diagrams showing another structural example of the connection portion 12 of the connection structure between layers in which the number of parallel connections changes in the superconducting coil 10 of the superconducting magnet 1 according to the first embodiment.
The connecting portion 12A shown in FIG. 5 connects the 3-parallel superconducting wire 20-3 and the 2-parallel superconducting wire 20-2 from the notch 11b provided in the flange 11a of the winding bobbin 11 to the winding bobbin 11 along the coil winding center axis. It has a structure that allows it to be drawn outside. The connecting portion 12A has an appearance in which the ends of the 3-parallel superconducting wire 20-3 and the end of the 2-parallel superconducting wire 20-2 are pulled out in parallel in the radial direction and connected in a lap manner, so that they look like they are bundled together. The connecting portion 12A is surrounded by an electrical insulator such as a polyimide film.

The connecting portion 12B shown in FIG. 6 connects the 3-parallel superconducting wire 20-3 and the 2-parallel superconducting wire 20-2 from the notch 11b provided in the flange 11a of the winding bobbin 11 to the winding bobbin 11 along the coil winding center axis. It has a structure that allows it to be drawn outside. The connecting portion 12B has an appearance in which the ends of the 3-parallel superconducting wire 20-3 and the end of the 2-parallel superconducting wire 20-2 are drawn out in parallel in the circumferential direction and connected by lap, so that they are bundled together. The connecting portion 12B is surrounded by an electrical insulator such as a polyimide film.

As described above, the connecting portion 12A and the connecting portion 12B may be superconductingly connected using a sintered body containing niobium titanium (NbTi) or the like, or may be connected by a connecting method such as soldering. When soldering, for cooling purposes, the loss of the connecting parts 12A and 12B is specified to be less than 0.01W, and when the current is 300A, it is constructed (specified) to be less than 0.1μΩ. Ru.

The superconducting coil 10 is constructed by pulling each parallel superconducting wire out of the winding bobbin 11 at the end of the layer on the inner diameter side or the start end of the layer on the outer diameter side of a layer composed of adjacent superconducting wires 20 having different numbers of parallel parallels. It has connecting portions 12A and 12B that are connected to each other. By providing the connecting portions 12A and 12B at positions where they are pulled out from the flange 11a of the winding bobbin 11, the connecting work can be facilitated.

<Transition of layers without connection part 12 in interlayer connection structure of superconducting coil 10>
2 and 3 show the transition of layers without connecting parts of the superconducting wire 20, such as from the first layer to the second layer and from the third layer to the fourth layer from the inner diameter side of the superconducting coil 10 shown in FIG. This is the same as the interlayer connection structure of the superconducting coil 10 shown, except that the connection portion 12 is removed.

As explained above, in the superconducting coil 10 of the superconducting magnet 1 according to the present embodiment, the superconducting wire 20 is wound around the winding bobbin 11 and wound in the direction of the winding axis to form a layer of the winding wire. It has a multi-layered structure in which the winding direction is turned back at the end and the outer layer is wound.

In the superconducting coil 10, the cross-sectional dimensions of the superconducting wire 20 in each layer are the same, and the wire current density of the superconducting wire 20 differs depending on the layer. Specifically, in the superconducting coil 10, the number of superconducting wires 20 connected in parallel in the outer layer is smaller than the number of superconducting wires 20 connected in parallel in the inner layer.

With this configuration, the superconducting coil 10 has the same cross-sectional external dimensions of the superconducting wire 20 in each layer, so it is possible to realize grading in which the wire current density is changed using wires with the same cross-sectional dimensions, and the entire superconducting coil current density can be maximized.

That is, even if the superconducting coil 10 is composed of one type of superconducting wire 20, the current density of the two-parallel superconducting wire 20-2 on the outer diameter side is 1.5 times higher than the current density of the three-parallel superconducting wire 20-3 on the inner diameter side. It becomes 5 times. This allows the inner diameter side of the superconducting coil 10 to have a low current density and the outer diameter side to have a high current density, and has the effect of maximizing the current of the entire superconducting magnet 1, in other words, reducing the amount of superconductor input. can be minimized. Furthermore, since the superconducting wires 20 of each layer can be tightly wound, the thermal resistance within the superconducting coil 10 can be reduced. As a result, it is possible to realize a conduction-cooled superconducting magnet 1 in which the hysteresis loss (AC loss) is small and the cooling efficiency is uniform for each layer, thereby minimizing the cooling cost.

In addition, in this embodiment, as shown in FIG. 1, the number of turns (parallel number x number of turns) of the superconducting wire in each layer is set to 12 turns, which is a common multiple of the number of parallel superconducting wires (2, 3) in each layer. This makes it possible to suppress dimensional variations in each layer. Therefore, variations in thermal resistance between the layer ends and the flange 11a of the winding bobbin 11 are reduced, and cooling costs can be further reduced.

[Modified example]
<Number of parallel superconducting wires>
In this embodiment, the number of parallel superconducting wires on the inner diameter side is "3" and the number on the outer diameter side is "2", but the number of parallel superconducting wires is not limited as long as the outer diameter side is smaller than the inner diameter side. For example, the number of parallel superconducting wires on the inner diameter side may be "4", the number on the outer diameter side may be "2", the number of parallel superconducting wires on the inner diameter side may be "4", and the number of parallel superconducting wires on the outer diameter side may be "3".
FIGS. 7 and 8 are diagrams showing examples of connection structures between layers in which the number of parallel connections changes in a modified superconducting coil 10. The superconducting coil 10 shown in FIGS. 7 and 8 is applicable to the superconducting magnet 1 shown in FIG. 17.
FIG. 7 is an example in which the number of parallel superconducting wires on the inner diameter side is "4" and the number on the outer diameter side is "2".
As shown in FIG. 7, the 4-parallel superconducting wire 20-4 and the 2-parallel superconducting wire 20-2 are connected to the winding bobbin at the end of the layer of the 4-parallel superconducting wire 20-4 and the beginning of the winding of the 2-parallel superconducting wire 20-2. The connection is made using the connecting portion 12 at the flange 11a position of No. 11.
The connecting portion 12 connects the end of the four-parallel superconducting wire 20-4 and the end of the two-parallel superconducting wire 20-2 by lap, using the gaps between the layers.

FIG. 8 is an example in which the number of parallel superconducting wires on the inner diameter side is "4" and the number on the outer diameter side is "3".
As shown in FIG. 8, the 4-parallel superconducting wire 20-4 and the 3-parallel superconducting wire 20-3 are connected to the winding bobbin at the end of the layer of the 4-parallel superconducting wire 20-4 and the beginning of the winding of the 3-parallel superconducting wire 20-3. The connection is made using the connecting portion 12 at the flange 11a position of No. 11.
The connection portion 12 connects the ends of the 4-parallel superconducting wire 20-4 and the end of the 3-parallel superconducting wire 20-3 by lap, using gaps between the layers.

In addition, in the modified superconducting coil 10 shown in FIGS. 7 and 8, as shown in FIGS. 5 and 6, the superconducting wire on the inner diameter side and the outer diameter side A superconducting wire may also be used as a structure.

<Types of number of parallel superconducting wires>
The above is an example in which the number of parallels is two, but the number of parallels does not have to be two. For example, three or more types may be selected in order from the inner diameter side, such as 4 parallels, 3 parallels, and 2 parallels. .
FIG. 9 is a cross-sectional view of superconducting coils 10 with three types of parallel connections. Components that are the same as those in FIG. 1 are given the same numbers. The superconducting coil 10 shown in FIG. 9 is applicable to the superconducting magnet 1 shown in FIG. 17, which will be described later.

As shown in the thick broken line box in FIG. 9, the 4-parallel superconducting wire 20-4, in which four superconducting wires 20 are connected in parallel in a set of three on the innermost diameter side, is wound three times per layer, and the three A 3-parallel superconducting wire 20-3 in which three superconducting wires 20 are connected in parallel in a set is wound four times per layer, and a 2-parallel superconducting wire 20-3 in which two superconducting wires 20 are connected in parallel in a set of two is wound four times per layer. 2 is wound 6 times per layer. The number of turns (parallel number x number of turns) of the superconducting wire 20 in each layer is 12, and the number of turns of the superconducting wire 20 "12" is the number of parallel superconducting wires on the innermost side "4" and the superconducting wire on the inner diameter side. It is a common multiple of the number of parallel superconducting wires "3" and the number of parallel superconducting wires "2" on the outer diameter side.

FIG. 10 is a cross-sectional view of a superconducting coil 10 whose outer diameter side (outermost diameter side) is not connected in parallel. Components that are the same as those in FIG. 1 are given the same numbers. The superconducting coil 10 shown in FIG. 10 is applicable to the superconducting magnet 1 shown in FIG. 17.
The superconducting coil 10 shown in FIG. 10 includes a 3-parallel superconducting wire 20-3 in which three superconducting wires 20 are connected in parallel, a 2-parallel superconducting wire 20-2 in which two superconducting wires 20 are connected in parallel, and an outer diameter side and a superconducting wire 20 that is not connected in parallel. The superconducting coil 10 shown in FIG. 10 further includes a layer around which one superconducting wire 20 is wound. That is, the superconducting coil 10 shown in FIG. 10 is composed of a single superconducting wire 20 without parallel connection on the outermost diameter side. In this case as well, the number of turns of each layer (number of parallel layers x number of turns) is a common multiple of the number of parallel layers.

In this way, in the superconducting coil 10, the number of turns obtained by multiplying the number of parallel superconducting wires 20 in each layer by the number of windings is a common multiple of the number of parallel superconducting wires 20 in each layer, so that dimensional variations in each layer can be suppressed. Therefore, variations in thermal resistance between the layer end portion and the flange 11a of the winding bobbin 11 are reduced, and cooling costs can be further reduced.

<Dislocations at the layer ends of parallel superconducting wires>
FIG. 11 is a diagram showing an example of the transposition positions of three parallel superconducting wires in the superconducting coil 10 of the superconducting magnet 1. FIG. 12 is a diagram showing an example of a method for transposing three parallel superconducting wires. FIG. 13 is a diagram showing an example of a method for transposing four parallel superconducting wires. In addition, in the notation of FIG. 12 and FIG. 13, the rectangle in a figure shows a parallel superconducting wire, and the number in it shows the number of rows of parallel superconducting wires.

If the coupling loss due to the inductance difference between parallel superconducting wires is large, the coupling loss can be reduced by applying dislocations 25 to the parallel superconducting wires (here, three parallel superconducting wires 20-3) at the layer ends, as shown in FIG. Can be reduced.

The method of transposition 25 of the 3-parallel superconducting wire 20-3 is as shown by the broken line arrow in FIG. , the second column is transposed to the first column, and the third column is left unchanged. Then, at the end of winding the next layer (the next layer on the outside when viewed from the inner diameter side), the first row of the three-parallel superconducting wire 20-3 is left as is, the second row is transposed to the third row, and the third row is Transpose the eyes to the second row. For example, as shown by the broken line arrow a in FIG. 12, at the beginning of winding, the first row "1" of the innermost layer is lowered (translocated) by one in the innermost layer as a paragraph. It becomes a column and is wound downward as it is (see the ↓ arrow in Figure 12), and at the end of the winding, it becomes a paragraph and is further lowered (translocated) by one position as shown by the broken line arrow b in Figure 12. This is the last column of the layer (the 12th column in the example of FIG. 1). Then, it is wound upward (see the ↑ arrow in FIG. 12), and as shown by the dashed arrow c in FIG. 12, it becomes the third row of the next layer without being dislocated at the beginning of winding. Thereafter, similarly, two dislocations and no dislocations are repeated at the beginning and end of winding. The same applies to other rows of parallel superconducting wires.

The method of dislocation 25 of the 4-parallel superconducting wire 20-4 is to form a plurality of (three in this case) patterns 1 to 3 at both ends of the parallel superconducting wire in the direction of the coil winding center axis, as shown by the broken line arrows in FIG. Use repeatedly.
Pattern 1:
At the beginning of winding a certain layer, the first row of the four-parallel superconducting wire 20-4 is transposed to the second row, the second row is transposed to the first row, and the third and fourth rows are left as they are. Then, at the end of winding the next layer (the next layer on the outside when viewed from the inner diameter side), the first and fourth rows of the 4-parallel superconducting wire 20-4 are left as they are, and the second row is transposed to the third row. At the same time, the third column is transferred to the second column.

Pattern 2:
At the start of winding the next layer, the first and second rows of the four-parallel superconducting wire 20-4 are left as they are, the third row is transposed into the fourth row, and the fourth row is transposed into the third row. Furthermore, at the end of the winding of the next layer, the first row of the four-parallel superconducting wire 20-4 is transposed to the second row, the second row is transposed to the first row, and the third and fourth rows are left as they are. do.
Pattern 3:
At the start of winding the next layer, the first and fourth rows of the four-parallel superconducting wire 20-4 are left as they are, the second row is transposed to the third row, and the third row is transposed to the second row. Furthermore, at the end of the winding of the next layer, the first and second rows of the four-parallel superconducting wire 20-4 are left as they are, the third row is transposed into the fourth row, and the fourth row is transposed into the third row. .
After pattern 3, the process returns to pattern 1 and repeats the transposition 25 of the four parallel superconducting wires 20-4.
Note that the present invention is not limited to the dislocation methods shown in FIGS. 12 and 13.

<Cross-sectional shape of superconducting wire>
Although the configuration using the superconducting wire 20 having a rectangular cross section has been described above, a superconducting wire having a cross-sectional shape other than the rectangular cross section may be used.
FIG. 14 is a sectional view of a modified superconducting coil 10A. Components that are the same as those in FIG. 1 are given the same numbers. The superconducting coil 10A shown in FIG. 14 is applicable to the superconducting magnet 1 shown in FIG. 17, which will be described later.
As shown in FIG. 14, in the superconducting coil 10A, superconducting wires 20A having a circular cross section are connected in parallel to a winding bobbin 11, and the superconducting wires 20A connected in parallel are arranged side by side in the direction of the winding axis, and The number of superconducting wires 20A connected in parallel is smaller than the number of superconducting wires 20A connected in parallel on the inner diameter side.

In the example of FIG. 14, the superconducting coil 10A has three parallel superconducting wires 20A-3 in which three superconducting wires 20A lined up in the winding axis direction are connected in parallel in the inner two layers, and the layers are wound in the winding axis direction. The two layers on the outer diameter side are constructed by winding two parallel superconducting wires 20A-2, which are two parallel superconducting wires 20A arranged in the winding axis direction and connected in parallel, in the winding axis direction. As shown in the thick broken line box in FIG. 1, the three-parallel superconducting wire 20A-3, in which three superconducting wires 20A are connected in parallel in a set of three, is wound four times per layer, and the two layers on the inner diameter side Configure. Further, a two-parallel superconducting wire 20A-2, which is a set of two superconducting wires 20A connected in parallel, is wound six times per layer to form two layers on the outer diameter side.
The ends of each layer are aligned at the flange 11a of the winding bobbin 11.

<Other variations>
This embodiment (FIGS. 17 to 6) and each modification example (FIGS. 7 to 14) may be combined. For example, it is possible to partially use different types of wire in the main body of the superconducting magnet 1 shown in FIG. 17, or to include locations where the number of turns of the layers (number of parallel lines x number of turns) is not a common multiple of the number of parallel lines of each layer. .

(Second embodiment)
FIG. 15 is a sectional view of a superconducting coil 10B of a superconducting magnet according to a second embodiment of the present invention. Components that are the same as those in FIG. 1 are given the same numbers. The superconducting coil 10B shown in FIG. 15 is applicable to the superconducting magnet 1 shown in FIG. 17.
As shown in FIG. 15, the superconducting coil 10B is constructed by winding a superconducting wire 30 having a rectangular cross section around a winding bobbin 11 from the inner circumference side in a stacked manner while winding it in the direction of the winding axis to form a layer of the winding wire. It has a multi-layered structure in which the winding direction is turned back at the end and the outer layer is wound. The superconducting wire 30 wound around the winding bobbin 11 is fixed by injecting a resin (not shown), typically epoxy, to form a coil.
The ends of each layer are aligned at the flange 11a of the winding bobbin 11.

The superconducting wire 30 includes a superconducting wire 30a consisting of a superconducting wire 31 ₁₀₀ having 100 strands and an insulating coating 32 covering the superconducting wire 31 ₁₀₀ , a superconducting wire 31 50 having 50 strands, and a superconducting wire 31 ₅₀ having 50 strands. The superconducting wire 30b includes an insulating coating 32 that covers the wire ₃₁₅₀ . The cross sections of the superconducting wire 31 ₁₀₀ and the superconducting wire 31 ₅₀ have approximately the same size. That is, the cross-sectional area per strand is the same, but the number of strands is different. As the superconducting wire 31 ₁₀₀ and the superconducting wire 31 ₅₀ , a metal superconductor such as niobium titanium (NbTi) or niobium tritin (Nb ₃ Sn) can be selected.

In this embodiment, the superconducting coil 10B is characterized in that the number of strands of the superconducting wire 30 on the outer diameter side is smaller than the number of strands of the superconducting wire 30 on the inner diameter side.

The superconducting coil 30 has the same feature as the superconducting coil 20 of the first embodiment (see FIG. 1) in that the cross-sectional dimensions (shapes) of the superconducting wires in each layer are the same. Similar to the superconducting coil 20, since the superconducting coil 30 can be wound closely (no gaps are formed), the thermal resistance within the superconducting magnet 1 can be reduced.

In the example of FIG. 15, the superconducting coil 10B is constructed by winding the superconducting wire 30 around the winding bobbin 11, and in the two layers on the inner diameter side, the superconducting wire 30a having 100 strands is wound in the winding axis direction. The two layers on the outer diameter side are constructed by winding superconducting wires 30b having 50 strands in the winding axis direction.
The superconducting wire 30a having 100 strands and the superconducting wire 30a having 50 strands are connected at the flange 11a of the winding bobbin 11, similarly to the superconducting coil 10 of the first embodiment.
Further, similarly to FIGS. 5 and 6 of the first embodiment, the superconducting wire 30a and the ends of the superconducting wire 30a may be pulled out from the notch 11b of the flange 11a of the winding bobbin 11 and connected to the connecting portion 12A.

FIG. 16 is a diagram showing an example of a connection structure between layers of a superconducting magnet in which the number of wires changes. As shown in FIG. 16, the superconducting wire 30a having 100 strands and the superconducting wire 30a having 50 strands are connected at the flange 11a of the winding bobbin 11, as in the first embodiment. .
In addition, similarly to FIG. 5 and FIG. 6 of 1st Embodiment, you may pull out and connect from the notch 11b of the flange 11a of a winding bobbin.

The operation of the superconducting magnet 1 configured as described above will be described below.
Due to the characteristic of superconducting wires that the current density that can be passed becomes smaller as the magnetic field is higher, the inner diameter side of the superconducting magnet 1 has a higher magnetic field and therefore has a lower current density, and the outer diameter side has a lower magnetic field and therefore has a higher current density. . In this embodiment, the superconducting coil 10B has 50 strands of strands on the outer diameter side by making the number of strands of the superconducting wire 30 on the outer diameter side smaller than the number of strands of the superconducting wire 30 on the inner diameter side. The current density of the superconducting wire 30b is twice that of the superconducting wire 30a in which the number of strands on the inner diameter side is 100. Thereby, the current of the entire superconducting magnet 1 can be maximized, in other words, the amount of superconductor can be minimized, and the amount of superconductor input can be reduced.

In addition, since each layer of the superconducting coil 10B is composed of superconducting wires 30 of the same shape, winding work is easy, and the superconducting wires 30 can be tightly wound in each layer, so that can reduce the thermal resistance of Moreover, since the cross sections of the superconducting wires 30 in each layer have approximately the same size, it is possible to suppress dimensional variations in the layers by winding each layer by the same number of turns. Therefore, variations in thermal resistance between the layer ends and the flanges of the winding bobbin 11 are reduced, and cooling costs can be reduced when conduction cooling is applied.

Further, in this embodiment, the wire rod 31 ₁₀₀ and the wire rod 31 ₅₀ are combined into one superconducting wire 30. Since the superconducting wires 20 are not connected in parallel as in the first embodiment, the winding work is facilitated.

Furthermore, in this embodiment, since the ratio of the current density on the inner diameter side and the outer diameter side can be designed more precisely, the amount of superconducting wire input can be further reduced.

In this embodiment, the number of strands on the inner diameter side is 100 and the number of strands on the outer diameter side is 50, but the number of strands on the outer diameter side may be smaller than the number of strands on the inner diameter side.

The present invention is not limited to the embodiments and modifications described above, and includes various modifications. For example, the embodiments described above are described in detail in order to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to having all the configurations described. Furthermore, it is possible to replace a part of the configuration of one embodiment with a part of the configuration of another embodiment, and furthermore, it is possible to add part or all of the configuration of another embodiment to the configuration of one embodiment. is also possible. For example, the following application examples (1) and (2) are also possible.

(1)
FIG. 17 is a cross-sectional view schematically showing the structure of a superconducting magnet according to an application example of the present invention. This application example is an example in which the present invention is applied to a conduction-cooled permanent electric superconducting magnet that operates with persistent current.
As shown in FIG. 17, the superconducting magnet 1A includes a superconducting coil 10 (10A, 10B), a persistent current switch 2 that switches between a power supply drive mode and a persistent current mode, an end-to-end connection part 3, a DC power supply, and a superconducting coil. 10, a support plate 5 (heat transfer path) that thermally connects the superconducting coil 10, the persistent current switch 2, and the refrigerator 7, the cooling container 6, the superconducting coil 10, and the persistent current switch A refrigerator 7 that cools the refrigerator 2 is provided.
However, for persistent current operation, superconducting connections between wires are essential. For this reason, it is necessary to use a superconducting connection structure to connect the wires to each other instead of using solder, which causes electrical resistance.

(2)
The superconducting magnets according to each of the above embodiments have been described as conduction-cooled superconducting magnets that are cooled, for example, by a refrigerator, but they can also be applied to immersion-cooled superconducting magnets that cool superconducting coils and persistent current switches with a coolant such as liquid helium. It is also possible to do so.

1,1A superconducting magnet 2 Persistent current switch 3 End-to-end connection 4 Current lead 5 Support plate (heat transfer path)
6 Cooling container 7 Freezer 10, 10A, 10B Superconducting coil 11 Winding bobbin 12, 12A, 12B Connection section 13 Spacer 14 Parallel section 20, 20A, 30, 30a, 30b Superconducting wire 20-2, 20A-2 2 parallel superconducting Wire 20-3, 20A-3 3-parallel superconducting wire 20-4 4-parallel superconducting wire 21, 31 ₁₀₀ , 31 ₅₀ superconducting wire 22, 32 Insulating coating 25 Dislocation

Claims (14)

The superconducting wire is wound around a winding bobbin and wound in the direction of the winding axis to form a layer of winding wire, and at the end of the layer, the winding direction is turned back and the outer layer is wound, creating a multilayer winding structure. Equipped with a superconducting coil,
The superconducting coil is
The external dimensions of the cross section of the superconducting wire in each layer are predetermined numerical values, and the strand current density of the superconducting wire differs depending on the layer,
In the superconducting coil, the number of the superconducting wires connected in parallel in the layer on the outer diameter side is smaller than the number of the superconducting wires connected in parallel in the layer on the inner diameter side,
The superconducting coil is characterized in that the number of turns obtained by multiplying the number of parallel lines of the superconducting wires in each layer by the number of turns is a common multiple of the number of parallel lines in each layer. The superconducting wire is wound around a winding bobbin and wound in the direction of the winding axis to form a layer of winding wire, and at the end of the layer, the winding direction is turned back and the outer layer is wound, creating a multilayer winding structure. Equipped with a superconducting coil,
The superconducting coil is
The external dimensions of the cross section of the superconducting wire in each layer are predetermined numerical values, and the strand current density of the superconducting wire differs depending on the layer,
In the superconducting coil, the number of the superconducting wires connected in parallel in the layer on the outer diameter side is smaller than the number of the superconducting wires connected in parallel in the layer on the inner diameter side,
The superconducting coil has a stepped portion at the end of the layer on the inner diameter side or a starting end of the layer on the outer diameter side of adjacent layers having different numbers of parallel connections, and a connection of parallel superconducting wires with different numbers of parallel lines in the stepped portion. A superconducting magnet characterized by having a connecting portion that includes: The superconducting wire is wound around a winding bobbin and wound in the direction of the winding axis to form a layer of winding wire, and at the end of the layer, the winding direction is turned back and the outer layer is wound, creating a multilayer winding structure. Equipped with a superconducting coil,
The superconducting coil is
The external dimensions of the cross section of the superconducting wire in each layer are predetermined numerical values, and the strand current density of the superconducting wire differs depending on the layer,
In the superconducting coil, the number of the superconducting wires connected in parallel in the layer on the outer diameter side is smaller than the number of the superconducting wires connected in parallel in the layer on the inner diameter side,
The superconducting coil is configured such that each parallel superconducting wire is pulled out of the winding bobbin at the end of the layer on the inner diameter side or the start end of the layer on the outer diameter side of the layer composed of the superconducting wires having different numbers of adjacent parallel superconducting wires. A superconducting magnet characterized in that it has a connecting part that is connected by The superconducting wire is wound around a winding bobbin and wound in the direction of the winding axis to form a layer of winding wire, and at the end of the layer, the winding direction is turned back and the outer layer is wound, creating a multilayer winding structure. Equipped with a superconducting coil,
The superconducting coil is
The external dimensions of the cross section of the superconducting wire in each layer are predetermined numerical values, and the strand current density of the superconducting wire differs depending on the layer,
The superconducting wire has one or more superconducting wires as strands,
The superconducting coil is
layers in which the number of strands of the superconducting wire on the outer diameter side is smaller than the number of strands of the superconducting wire on the inner diameter side;
a stepped portion at the end of the layer on the inner diameter side or the start end of the layer on the outer diameter side of the layers having different numbers of adjacent strands;
A superconducting magnet, comprising: a connection part where different numbers of the superconducting wires are connected in the paragraphed part. The superconducting wire is wound around a winding bobbin and wound in the direction of the winding axis to form a layer of winding wire, and at the end of the layer, the winding direction is turned back and the outer layer is wound, creating a multilayer winding structure. Equipped with a superconducting coil,
The superconducting coil is
The external dimensions of the cross section of the superconducting wire in each layer are predetermined numerical values, and the strand current density of the superconducting wire differs depending on the layer,
The superconducting wire has one or more superconducting wires as strands,
The superconducting coil has layers in which the number of the strands of the superconducting wire is different,
In the superconducting coil, the number of strands of the superconducting wire on the outer diameter side is smaller than the number of strands of the superconducting wire on the inner diameter side,
The superconducting coil is configured such that each of the superconducting wires is pulled out of the winding bobbin at the end of the layer on the inner diameter side or the start end of the layer on the outer diameter side of the layers of the superconducting wires having different numbers of adjacent wires. A superconducting magnet characterized in that it has a connecting part that is connected by The superconducting coil includes a layer in which a plurality of the superconducting wires are wound as parallel superconducting wires arranged in a winding axis direction;
The superconducting magnet according to claim 1, further comprising a layer in which the superconducting wires arranged in a winding axis direction and having a different number of parallel superconducting wires are wound as parallel superconducting wires. The superconducting magnet according to claim 6, wherein the superconducting coil further includes a layer around which one of the superconducting wires is wound. 2. The superconducting magnet according to claim 1, wherein the number of turns of the superconducting coil multiplied by the number of parallel turns of the superconducting wire in each layer is a common multiple of the number of parallel turns in each layer. The superconducting coil has a stepped portion at the end of the layer on the inner diameter side or a starting end of the layer on the outer diameter side of adjacent layers having different numbers of parallel connections, and a connection of parallel superconducting wires with different numbers of parallel lines in the stepped portion. The superconducting magnet according to claim 1, further comprising: a connecting portion comprising: a connecting portion; The superconducting coil is configured such that each parallel superconducting wire is pulled out of the winding bobbin at the end of the layer on the inner diameter side or the start end of the layer on the outer diameter side of the layer composed of the superconducting wires having different numbers of adjacent parallel superconducting wires. The superconducting magnet according to claim 1, further comprising a connecting portion for connection. The superconducting magnet according to claim 9, wherein the parallel superconducting wires are transposed in the superconducting coil. The superconducting magnet according to claim 11, wherein the position where the parallel superconducting wire is transposed is the stepped portion at the folded end of the layer. The superconducting magnet according to claim 4 or 5, wherein the superconducting coil is wound with one superconducting wire, and the number of the strands on the outer diameter side is smaller than on the inner diameter side. The superconducting magnet according to any one of claims 1 to 13, wherein the superconducting coil has a superconductor cooled by conduction cooling.

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