JP5980651B2 - Superconducting magnet - Google Patents

Description

  The present invention relates to a superconducting magnet connected to a cooling means.

  Conventionally, for example, Patent Document 1 is known as a technique in such a field. The superconducting magnet described in Patent Document 1 includes a cylindrical vacuum vessel, and a space penetrating in the vertical direction is formed at the center of the vacuum vessel. A superconducting coil for generating a high magnetic field in the space is disposed in the vacuum vessel. A winding frame around which the superconducting coil is wound is composed of a cylindrical inner frame and a pair of flanges formed at both ends of the inner frame. Above the superconducting coil, cooling means integrated with a GM (Gifford McMahon) refrigerator is provided. The cold head of the cooling means is connected to the upper flange through a cooling stage. A high magnetic field can be generated by cooling the superconducting coil by the cooling means.

  The superconducting magnet described in Patent Document 1 is applied to a silicon single crystal pulling apparatus, and is used as a high magnetic field source in a so-called MCZ (magnetic field application Czochralski) method. As a silicon single crystal pulling apparatus using the MCZ method, for example, an apparatus described in Patent Document 2 is known. This apparatus includes a crucible for containing a single crystal silicon raw material, and a magnet as a high magnetic field source is provided on the side of the crucible. The magnet described in Patent Document 2 includes an air-core coil that does not have an inner frame.

JP 2004-319777 A JP-A 63-297292

  By the way, when a superconducting magnet is used, the superconducting state may be suddenly destroyed for some reason. This destruction of the superconducting state is called quenching. Quenching tends to occur in the vicinity of the inner frame in the superconducting coil. Therefore, the cause of quenching can be reduced by eliminating the inner frame and employing an air-core coil.

  However, the present inventors have found a problem that the cooling temperature of the superconducting coil becomes unstable due to the absence of the inner frame. That is, since the inner frame has a function as a cooling path to the superconducting coil, the cooling path is also lost by adopting the air-core coil. Thus, there is a problem that the cooling efficiency of the superconducting coil is reduced due to the absence of the inner frame.

  An object of the present invention is to provide a superconducting magnet that can prevent a decrease in cooling efficiency of a superconducting coil even when there is no inner frame.

The superconducting magnet of the present invention is a superconducting magnet connected to a cooling means, and is disposed at one end and the other end in the central axis direction of the superconducting coil as an air-core coil, and at least one of them is a cooling means. A first frame body and a second frame body to be connected; and an adhesive mixed with a heat conductive material to cover the inner periphery of the superconducting coil . The heat conductivity of the heat conductive material is an adhesive. The adhesive in which the heat conductivity is higher and the heat conductive material is mixed is in contact with the first frame and the second frame .

  According to this superconducting magnet, the cooling means is connected to at least one of the first frame and the second frame. Since the superconducting coil is an air-core coil, there is no inner frame on the inner peripheral side of the superconducting coil. Here, a heat conductive material is mixed in the adhesive applied to the inner periphery of the superconducting coil. Therefore, the heat conductive material contained in the adhesive becomes a heat medium, and the superconducting coil can be cooled by the cooling means. That is, a cooling path is formed by the heat conductive material contained in the adhesive. Therefore, even if there is no inner frame, it is possible to prevent a decrease in the cooling efficiency of the superconducting coil.

  In the superconducting magnet, the thermally conductive material is a nonmagnetic material. According to this configuration, the thermally conductive material is hardly affected by the superconducting coil, and the thermal conductivity of the thermally conductive material is effectively exhibited.

  Moreover, said superconducting magnet is provided in the inner peripheral side of a superconducting coil, and is provided with the band which connects a 1st frame and a 2nd frame. According to this configuration, since the first frame and the second frame are connected by the band, the band contributes to heat transfer. That is, a cooling path is formed by the band. Therefore, a decrease in cooling efficiency can be further suppressed by the cooperation between the adhesive mixed with the heat conductive material and the band.

  In the superconducting magnet, the band and the adhesive are in contact with each other. According to this configuration, since the adhesive contacts both the band and the superconducting coil, heat exchange can be performed between the band and the superconducting coil via the adhesive. Therefore, the cooling efficiency can be increased.

  According to the present invention, it is possible to prevent the cooling efficiency of the superconducting coil from being lowered even when there is no inner frame.

It is a schematic sectional drawing which shows one Embodiment of the superconducting magnet which concerns on this invention. It is a perspective view which shows the superconducting magnet of FIG. (A) is sectional drawing which follows the IIIA-IIIA line | wire of FIG. 2, (b) is sectional drawing which follows the IIIB-IIIB line | wire of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, a case where the superconducting magnet according to the present invention is applied to a cyclotron will be described.

  As shown in FIG. 1, the cyclotron A is a circular accelerator that accelerates charged particles supplied from an ion source (not shown) and outputs a charged particle beam (charged particle beam). Examples of the charged particles include protons and heavy particles (heavy ions). The cyclotron A has a superconducting magnet 1.

  The cyclotron A includes an annular vacuum vessel 3, a superconducting coil body 2 having two superconducting coils 8 and 9 disposed in the vacuum vessel 3, and air core portions 8 a and 9 a of the superconducting coils 8 and 9, respectively. An upper pole (upper magnetic pole) 4 and a lower pole (lower magnetic pole) 5, a refrigerator (cooling means) 6 for cooling the superconducting coils 8 and 9, and a yoke 7 are provided. The yoke 7 is a hollow disk-shaped block, and the vacuum vessel 3, the upper pole 4 and the lower pole 5 are disposed therein.

  The superconducting magnet 1 includes a superconducting coil body 2, an upper pole 4 and a lower pole 5. The superconducting magnet 1 generates a strong magnetic field by causing a current to flow through the superconducting coils 8 and 9 which are cooled by the refrigerator 6 and brought into a superconducting state. The superconducting coil body 2 includes annular superconducting coils 8 and 9 disposed around the central axis C, an annular plate-shaped upper flange 10a disposed at the upper end of the superconducting coil 8 in the direction of the central axis C, and superconducting. An annular intermediate frame 10b interposed between the coil 8 and the superconducting coil 9 and an annular plate-like lower flange 10c disposed at the lower end of the superconducting coil 9 in the central axis C direction are provided. As shown in FIG. 2, the intermediate frame 10b includes a flange portion 10d located at the upper end thereof, a flange portion 10f located at the lower end thereof, and a cylindrical portion 10e connecting the flange portion 10d and the flange portion 10f. Have. The upper flange 10a, the intermediate frame 10b, and the lower flange 10c are made of metal, and can be made of, for example, iron, stainless steel, or copper.

  As shown in FIGS. 1 and 2, superconducting coil 8 and superconducting coil 9 are air-core coils and do not have an inner frame (or inner winding frame). Superconducting coil 8 and superconducting coil 9 are arranged side by side in the central axis C direction. The superconducting coil 8 and the superconducting coil 9 are formed by inserting an inner frame when winding a wire, fixing the wire with an adhesive such as an epoxy resin, and then removing the inner frame. Superconducting coil 8 is fixed to upper flange 10a and flange 10d of intermediate frame 10b. Superconducting coil 9 is fixed to flange portion 10f and lower flange 10c of intermediate frame 10b.

  The upper flange 10 a corresponds to the first frame of the superconducting coil 8, and the flange portion 10 d corresponds to the second frame of the superconducting coil 8. The flange portion 10 f corresponds to the first frame body of the superconducting coil 9, and the lower flange 10 c corresponds to the second frame body of the superconducting coil 9. The upper flange 10a, the intermediate frame 10b, and the lower flange 10c are support members that support the superconducting coils 8 and 9.

  A part of the refrigerator 6 is connected to the lower flange 10c (the connection part is not shown), and the superconducting coils 8 and 9 are cooled to an extremely low temperature of about 4.2K. As the refrigerator 6, for example, a small GM refrigerator can be adopted. The refrigerator 6 as a cooling means may be connected to the upper flange 10a, or may be connected to both the upper flange 10a and the lower flange 10c. The refrigerator 6 may be connected to at least one of the upper flange 10a, the intermediate frame 10b, and the lower flange 10c.

  In the present embodiment, the case where the cyclotron A is arranged in a posture (horizontal posture) in which the central axis C extends in the vertical direction will be described. However, the cyclotron A has, for example, the central axis C extending in the horizontal direction. It is also possible to arrange in an existing posture (vertical posture). That is, “up / down / left / right” in the description does not limit the arrangement direction of members, and “up / down” and “left / right” can be replaced. For example, the upper pole 4 and the lower pole 5 can be expressed as a left pole or a right pole in the case of a cyclotron in a vertical position.

  In the cyclotron A, the inside of the vacuum vessel 3 is evacuated and then a current is passed through the superconducting coils 8 and 9 which are cooled by the refrigerator 6 and brought into a superconducting state, thereby forming a strong magnetic field. In a space G between the upper pole 4 and the lower pole 5, a pair of dee electrodes (acceleration electrodes) (not shown) are arranged, and charged particles supplied from the ion source are the upper pole 4, the lower pole 5, and It is accelerated by the action of the Dee electrode and output as a charged particle beam.

  The superconducting coil body 2 is supported by tensile support members 11 and 12. The support member 11 is provided between the inner surface of the vacuum vessel 3 and the upper flange 10a. The support member 12 is provided between the inner surface of the vacuum vessel 3 and the lower flange 10c. The support member 11 and the support member 12 are arranged as a pair of upper and lower sides so as to sandwich the superconducting coil body 2 and hold the position of the superconducting coil body 2 by pulling the superconducting coil body 2 in opposite directions. The number, arrangement, structure, and the like of the support member 11 and the support member 12 are not particularly limited, and are appropriately selected according to the size of the cyclotron A and other design items.

  A block body 7a constituting a part of the yoke 7 is disposed on the back side of the surface to which the support members 11 and 12 are fixed in the vacuum vessel 3 (that is, the outer surface side in the direction of the central axis C). The block body 7 a is disposed so as to suppress the outside of the vacuum vessel 3 and reinforces the portion of the vacuum vessel 3 to which the support members 11 and 12 are fixed.

  Next, the configuration of the superconducting coil body 2 in the superconducting magnet 1 will be described in more detail. As shown in FIGS. 1 to 3, an adhesive 20 is applied to the inner circumference 8 b of the superconducting coil 8 over substantially the entire surface. An adhesive 21 is applied to the inner circumference 9b of the superconducting coil 9 over substantially the entire surface thereof. The adhesives 20 and 21 maintain adhesion to the superconducting coils 8 and 9 even when the superconducting coils 8 and 9 are expanded or contracted. The adhesives 20 and 21 are, for example, cryogenic epoxy resin adhesives. The adhesives 20 and 21 are not limited to epoxy resin adhesives, and may be other adhesives. For example, the adhesives 20 and 21 may be phenol resin adhesives, acrylic resin adhesives, urethane resin adhesives, and the like. The material of the adhesives 20 and 21 is not limited. The adhesives 20 and 21 may be the same as the adhesive that fixes the wires of the superconducting coils 8 and 9, or may be different from the adhesive that fixes the wires.

  Furthermore, the adhesives 20 and 21 are mixed with high thermal conductive powder as a thermal conductive material. In other words, the adhesive layer L formed by the adhesives 20 and 21 contains high thermal conductive powder. A heat conductive material is a thing whose heat conductivity is higher than the heat conductivity of an adhesive agent. The high heat conductive powder functions as a heat exchange medium between the refrigerator 6 and the superconducting coils 8 and 9. The adhesives 20 and 21 have a function of holding high heat conductive powder as a heat medium. As the high thermal conductive powder, for example, aluminum nitride powder can be used. The high thermal conductive powder is a nonmagnetic material. As the high thermal conductive powder, those having high affinity for the adhesives 20 and 21 are suitable. Moreover, an electrically insulating material is suitable as the high thermal conductive powder.

The thermal conductivity of the high thermal conductive powder is not particularly limited, but is, for example, 10 W · m ⁻¹ · K ⁻¹ or more. The thermal conductivity of the high thermal conductive powder is desirably 200 W · m ⁻¹ · K ⁻¹ or more. The heat conductivity of the high heat conductive powder is preferably equal to or higher than that of a metal such as iron, stainless steel, or copper. The average particle size of the high thermal conductive powder is not particularly limited, but is, for example, 0.1 to 10 μm. When aluminum nitride powder is used as the high thermal conductive powder, the average particle diameter is, for example, 1 to 3 μm.

  The compounding ratio of the adhesives 20 and 21 and the high thermal conductive powder is, for example, adhesive: high thermal conductive powder = 50 to 20:50 to 80 by weight ratio. In other words, the weight ratio of the high thermal conductive powder in the adhesive layer L is 50 to 80%. If the blending ratio of the high thermal conductive powder is high, high thermal conductivity can be obtained, but if the amount of the adhesive is too small, sufficient adhesive strength cannot be obtained. From this viewpoint, an appropriate blending ratio of the high thermal conductive powder is being sought. If it is in said ratio, thermal conductivity can be improved, making adhesion | attachment suitable.

  When the adhesives 20 and 21 are applied, the high thermal conductive powder is mixed in advance. The high adhesives 20 and 21 mixed with the high thermal conductive powder are applied to the inner peripheries 8b and 9b after the wires are fixed by the adhesive and the superconducting coils 8 and 9 are formed. The application thickness of the adhesives 20 and 21 (layer thickness of the adhesive layer L) is not particularly limited, but is, for example, 0.3 to 0.5 mm.

  As shown in FIG. 3A, the adhesive 20 is applied to the entire inner circumference 8 b of the superconducting coil 8. The adhesive 20 is in contact with the upper flange 10a and the flange portion 10d. The adhesive 20 is mixed with high thermal conductive powder uniformly. That is, the high heat conductive powder is uniformly dispersed in the adhesive layer L. In the adhesive 20, the surface of the adhesive layer L formed by the adhesive 20 is substantially flush with the inner peripheral surface 16 of the upper flange 10a and the inner peripheral surface 17 of the flange portion 10d.

  The adhesive layer L may slightly protrude from the inner peripheral surfaces 16 and 17 to the central axis C side (the right side in the drawing), or is recessed radially outward (the left side in the drawing) from the inner peripheral surfaces 16 and 17. Also good. The inner periphery 8 b of the superconducting coil 8 may be substantially flush with the inner peripheral surfaces 16 and 17, or may be recessed more radially outward than the inner peripheral surfaces 16 and 17. The configuration of the adhesive 21 provided for the superconducting coil 9 is the same as the configuration of the superconducting coil 8 described above.

  The adhesives 20 and 21 (adhesive layer L) form a cooling path between the refrigerator 6 and the superconducting coils 8 and 9.

  2 and 3B, the superconducting coil body 2 is provided with a plurality of metal bands 22 that connect the upper flange 10a and the flange portion 10d. The superconducting coil body 2 is provided with a plurality of metal bands 23 that connect the flange portion 10f and the lower flange 10c. The band 22 and the band 23 have an elongated thin plate shape extending in the central axis C direction. The band 22 and the band 23 are arranged at equal intervals in the circumferential direction. The band 22 is in contact with the surface of the adhesive 20 (adhesive layer L). The band 23 is in contact with the surface of the adhesive 21 (adhesive layer L). The bands 22 and 23 are not limited to the case where the adhesives 20 and 21 are contacted in a planar shape, and may be partially contacted (for example, linearly or dottedly). The bands 22 and 23 may be separated from the adhesives 20 and 21.

  The upper end 22a of the band 22 is fixed to the inner peripheral side of the upper flange 10a. The lower end portion 22b of the band 22 is fixed to the inner peripheral side of the flange portion 10d. The upper end portion 23a of the band 23 is fixed to the inner peripheral side of the flange portion 10f. The lower end 23b of the band 23 is fixed to the inner peripheral side of the lower flange 10c.

  The bands 22 and 23 have a function of integrally restraining the superconducting coil body 2 including the upper flange 10a, the superconducting coil 8, the intermediate frame 10b, the superconducting coil 9, and the lower flange 10c. That is, the bands 22 and 23 mechanically restrain the inner peripheral side of the superconducting coil body 2. In addition, the outer periphery of the upper flange 10a, the intermediate frame 10b, and the lower flange 10c (for example, the outer edge 18 of the upper flange 10a and the outer edge 19 of the flange 10d shown in FIGS. 3A and 3B) are bolted to each other. Etc. (not shown).

  The bands 22 and 23 function as a mechanical restraining member as described above, and at the same time form a cooling path between the refrigerator 6 and the superconducting coils 8 and 9. The thermal conductivity of the bands 22 and 23 is higher than the thermal conductivity of the adhesives 20 and 21. The bands 22 and 23 assist the heat transfer function by the adhesives 20 and 21. The bands 22 and 23 can be omitted.

  According to the superconducting magnet 1 of the cyclotron A described above, the refrigerator 6 is connected to the lower flange 10 c of the superconducting coil body 2. Since the superconducting coils 8 and 9 are air-core coils, there is no inner frame. However, the adhesives 20 and 21 applied to the inner peripheries 8b and 9b of the superconducting coils 8 and 9 are mixed with high thermal conductive powder. Yes. Therefore, the high heat conductive powder contained in the adhesives 20 and 21 becomes a heat medium, and the superconducting coils 8 and 9 can be cooled by the refrigerator 6. That is, the cooling path is formed by the high thermal conductive powder contained in the adhesives 20 and 21. Therefore, even if there is no inner frame, it is possible to prevent the cooling efficiency of the superconducting coils 8 and 9 from being lowered.

  Conventionally, in a superconducting magnet without an inner frame, the cooling temperature to be secured has been unstable due to the loss of the cooling path. According to the superconducting magnet 1, a stable cooling temperature can be obtained. Furthermore, since there is no inner frame, the occurrence of quenching is also suppressed.

  Since the high thermal conductive powder is a non-magnetic material, the high thermal conductive powder is hardly affected by the superconducting coils 8 and 9, and the thermal conductivity of the high thermal conductive powder is effectively exhibited.

  Since the upper flange 10a and the flange portion 10d are connected by the band 22, and the flange portion 10f and the lower flange 10c are connected by the band 23, the bands 22 and 23 contribute to heat transfer. That is, a cooling path is formed by the bands 22 and 23. Therefore, a reduction in cooling efficiency can be further suppressed by the cooperation of the adhesives 20 and 21 mixed with the high thermal conductive powder and the bands 22 and 23. In addition, the bands 22 and 23 provide a restraining effect for the upper flange 10a, the intermediate frame 10b, and the lower flange 10c.

  Since the adhesive 20 contacts both the band 22 and the superconducting coil 8, and the adhesive 21 contacts both the band 23 and the superconducting coil 9, the bands 22, 23 and the superconducting coil 8 are interposed via the adhesives 20, 21. , 9 can perform heat exchange. Therefore, the cooling efficiency can be increased.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. For example, the high thermal conductive powder is not limited to aluminum nitride powder. Boron nitride powder can also be employed as the high thermal conductive powder. Further, the high thermal conductive powder may be a powder made of a metal such as copper. The high thermal conductive powder is not limited to a non-magnetic material, and may have magnetism.

  The thermally conductive material is not limited to powder, and may be granular having a predetermined particle size. The thermally conductive material may be in the form of pellets. The thermally conductive material may be spherical or fibrous. The heat conductive material is not limited to non-magnetic high heat conductive powder. The thermally conductive material may have magnetism.

  The superconducting coil body 2 of the superconducting magnet 1 is not limited to having two superconducting coils 8 and 9 and may have one or three or more superconducting coils.

  Further, the superconducting magnet according to the present invention is not limited to the cyclotron, but can be applied to a silicon single crystal pulling apparatus by the MCZ method. The superconducting magnet can be applied to any device that requires a high magnetic field.

  DESCRIPTION OF SYMBOLS 1 ... Superconducting magnet, 2 ... Superconducting coil body, 6 ... Refrigerator (cooling means), 8, 9 ... Superconducting coil, 8a, 9a ... Air core part, 8b ... Inner periphery, 10a ... Upper flange (1st frame) ) 10c ... lower flange (second frame), 10f ... flange part (first frame), 10d ... flange part (second frame), 20, 21 ... adhesive, 22, 23 ... band A ... cyclotron, C ... central axis.

Claims (4)

A superconducting magnet connected to the cooling means,
A superconducting coil that is an air-core coil;
A first frame and a second frame which are disposed at one end and the other end in the central axis direction of the superconducting coil and at least one of which is connected to the cooling means;
A heat conductive material is mixed, and an adhesive covering the inner periphery of the superconducting coil ,
The thermal conductivity of the thermally conductive material is higher than the thermal conductivity of the adhesive,
The superconducting magnet in which the adhesive mixed with the thermally conductive material is in contact with the first frame and the second frame .   The superconducting magnet according to claim 1, wherein the thermally conductive material is a nonmagnetic material.   The superconducting magnet according to claim 1, further comprising a band that is disposed on an inner peripheral side of the superconducting coil and connects the first frame body and the second frame body.   The superconducting magnet according to claim 3, wherein the band and the adhesive are in contact with each other.

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