JP5154512B2 - Superconducting magnet device - Google Patents

Description

  The present invention relates to a superconducting magnet device, and more particularly to a superconducting magnet device having a load support for supporting a superconducting coil.

  A conventional superconducting magnet apparatus is shown in FIG. A superconducting magnet device 100 shown in FIG. 1 includes an iron core 102, a superconducting coil 103, a heat transfer member 104, a load support 105, a heat shield plate 107, a refrigerator 108, a coil frame 109, and the like.

  The iron core 102 also functions as a vacuum container, and thus has a configuration in which the inside can be evacuated. The superconducting coil 103 is made of a superconducting wire, and is in a superconducting state at an extremely low temperature of about 4K, for example.

  The superconducting coil 103 is cooled by the refrigerator 108. The refrigerator 108 is a two-stage refrigerator, and the first stage 108 a is thermally connected to the heat shield plate 107, and the second stage 108 b is thermally connected to the superconducting coil 103 via the heat transfer member 104. It is connected. Further, the heat shield plate 107 is cooled by the refrigerator 108 to block heat (radiant heat) transmitted from the outside of the apparatus to the superconducting coil 103.

  On the other hand, the current line for energizing the superconducting coil 103 is made of a material having a high electrical conductivity (for example, copper, aluminum, etc.) between the iron core 102 and the heat shield plate 107 described later. On the other hand, between the heat shield plate 107 and the superconducting coil 103 is used a superconducting current lead (not shown) that can suppress heat intrusion and can carry a large current.

  The load support 105 is made of a high-strength insulating material (GFRP, CFRP, etc.). The load support 105 supports loads such as an attractive force generated between the superconducting coil 103 and the iron core 102 when a magnetic field is generated and a sudden fluctuation electromagnetic force generated when the superconducting coil 103 is quenched. The coil 103 is prevented from being damaged.

  Since this load support 105 is directly connected to the superconducting coil 103 from the iron core 102 at room temperature, it becomes an intrusion source of external heat to the superconducting coil 103. Therefore, in order to suppress the heat intrusion into the superconducting coil 103, the load support 105 is thermally connected to the heat shield plate 107 cooled by the refrigerator 108.

  In addition, when the load applied to the superconducting coil 103 is large, a coil frame 109 is provided separately from the load support 105. The coil frame 109 is made of a metal such as stainless steel and accommodates the superconducting coil 103 and the heat transfer member 104 therein.

  Thus, when the coil frame 109 is provided so as to cover the entire circumference of the superconducting coil 103, the coil frame 109 forms a loop. Therefore, when the magnetic flux change rate (dφ / dt) per unit time t of the magnetic flux φ generated by the superconducting coil 103 increases, an eddy current i is generated in the coil frame 109 as shown in FIG. When the eddy current i is generated in the heat conducting member in this manner, the superconducting coil 103 cannot be sufficiently cooled by Joule heat, and the temperature of the superconducting coil 103 may rise and cause quenching.

  Since the coil frame 109 reinforces the superconducting coil 103, it cannot be provided apart from the superconducting coil 103. In addition, the total amount of heat generated by the eddy current increases as the electrical resistance of the material forming the loop (the material of the heat conducting member) decreases. Therefore, as shown in FIG. 6B, it has been proposed to suppress the generation of eddy currents by forming slits 110 in the coil frame 109, thereby blocking the loop of the coil frame 109 (Patent Document). 1).

JP 2000-269021 A

  By forming the slit 110 in the coil frame 109 as described above, generation of eddy current can be effectively suppressed. However, if the slit 110 is formed in the coil frame 109, the mechanical strength of the coil frame 109 is greatly reduced, and thus the original function of reinforcing the superconducting coil 103 cannot be achieved.

  Therefore, as shown in FIG. 6C, the slit 110 is filled with a high-strength insulating material (GFRP, CFRP, etc.) or an insulating material such as epoxy resin as a filler 111, thereby increasing the strength of the coil frame 109. Improvements have also been proposed. However, the mechanical strength differs greatly between the stainless steel coil frame 109 and the filler 111 made of GFRP or the like. For this reason, depending on the direction of the load applied to the coil frame 109, a large stress (indicated by an arrow ST in FIG. 6C) may be generated in the superconducting coil 103, which may cause distortion.

  Furthermore, when the shape of the superconducting coil 103 is an asymmetrical complex formation as shown in FIG. 7, not only a compressive load but also a bending load indicated by an arrow M in the figure is applied to the load support 105 that supports this. Is done. At this time, if the length of the load support 105 is long, the moment due to the bending load M increases, and the load support 105 may be damaged.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a superconducting magnet device that can suppress the generation of eddy currents and can reliably support a superconducting coil.

From the first point of view, the above problem is
A vacuum vessel;
A superconducting coil mounted in the vacuum vessel;
A metal coil frame equipped with a slit that cuts off eddy current while mounting the superconducting coil inside,
A refrigerator that cools the superconducting coil to be in a superconducting state;
A reinforcing member that is disposed so as to surround the coil frame to reinforce the coil frame,
A first load support disposed between the vacuum vessel and the reinforcing member and supporting the reinforcing member with respect to the vacuum vessel;
And a plurality of arranged, the second load bearing member for supporting the coil form from a plurality of directions with respect to the reinforcement member between the reinforcing member and the coil frame,
This can be solved by a superconducting magnet device characterized by comprising:

  In the disclosed superconducting magnet device, since the superconducting coil is reinforced by both the reinforcing member and the coil frame, it is possible to effectively prevent the superconducting coil from being damaged even when a load is applied when a magnetic field is generated. Further, since the load support is separated into the first load support and the second load support with the reinforcing member interposed therebetween, the heat transfer path from the first load support to the superconducting coil becomes longer. , It is possible to suppress the invading heat from reaching the superconducting coil.

FIG. 1 is a cross-sectional view of a main part of a superconducting magnet device according to an embodiment of the present invention. 2 is a cross-sectional view taken along line AA in FIG. FIG. 3 is an enlarged perspective view showing the coil frame 22. FIG. 4 is a diagram showing various superconducting coils having an asymmetric shape. FIG. 5 is a cross-sectional view of a conventional superconducting magnet device. FIG. 6 is a diagram for explaining countermeasures for eddy current that have been conventionally performed. FIG. 7 is a diagram for explaining a problem that occurs in a conventional superconducting magnet device.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG.1 and FIG.2 is a figure for demonstrating the superconducting magnet apparatus 10 which is one Embodiment of this invention. FIG. 1 is a transverse sectional view of the superconducting magnet device 10, and FIG. 2 is a sectional view taken along the line AA in FIG. The superconducting magnet device 10 is applied to, for example, a deflection electromagnet for a proton beam therapy apparatus gantry.

  The superconducting magnet device 10 is a conduction-cooling superconducting magnet device, which roughly includes an iron core 12, a superconducting coil 13A, load supports 15A and 15B, a heat shield plate 17, a refrigerator 18, a coil frame 22, a reinforcing ring 24, and the like. Have.

  The iron core 12 is an airtight container and is connected to a vacuum pump (not shown). By operating this vacuum pump, the inside of the iron core 12 is in a vacuum state. The iron core 12 functions as a yoke for guiding the magnetic flux generated by the superconducting coil 13A. Therefore, by providing the iron core 12, the magnetic flux generated by the superconducting coil 13A can be focused and the magnetic flux density can be made uniform.

  The superconducting coil 13 </ b> A is disposed in the coil frame 22 together with the heat conducting member 20. The superconducting coil 13A has a structure in which a superconducting wire is wound. In this embodiment, a high-temperature superconducting wire is used as the superconducting wire. As this high-temperature superconducting wire, for example, Bi2223, Bi2212, Y123, MgB2, an oxide superconductor or the like can be used. In the present embodiment, a high-temperature superconducting wire is used as the superconducting wire, but a configuration using a low-temperature superconducting wire can also be used.

  The superconducting coil 13A is fed using a current line (not shown). In this current line, a material having high electrical conductivity (for example, copper, aluminum, etc.) is used between the iron core 12 and the heat shield plate 17, and a superconducting current lead is used between the heat shield plate 17 and the superconducting coil 13A. It is done.

  Moreover, the superconducting magnet apparatus 10 according to the present embodiment is applied to the deflection electromagnet for the proton beam therapy apparatus gantry as described above. For this reason, the shape of the superconducting coil 13A is a complicated shape corresponding to the deflection direction of the proton beam.

  FIG. 4A shows a superconducting coil 13A used in this embodiment. The superconducting coil 13A is called a D-type coil, and has a shape that is substantially D-shaped when viewed in plan. Thus, the superconducting coil 13A used in the present embodiment has an asymmetric shape with respect to the center thereof.

  The superconducting coil applicable to the present invention is not limited to the D-type superconducting coil 13A. For example, a superconducting coil 13B called a racetrack coil as shown in FIG. 4B is shown in FIG. 4C. The present invention can also be applied to various types of coils that are asymmetric with respect to the center, such as a superconducting coil 13C called a trapezoidal coil as shown.

  The heat conductive member 20 is formed of a material having high heat conductivity (for example, copper, aluminum, or an alloy thereof). The heat conducting member 20 is thermally connected to the superconducting coil 13 </ b> A and is connected to the two-stage portion 18 b of the refrigerator 18. Therefore, the superconducting coil 13A is cooled by the refrigerator 18 through the heat conducting member 20, thereby realizing a superconducting state.

  As shown in an enlarged view in FIG. 3, the coil frame 22 is provided with superconducting coils 13 </ b> A at the upper and lower portions. Further, a heat conducting member 20 is provided on the back side of the superconducting coil 13 </ b> A in the coil frame 22. The coil frame 22 is formed of a metal such as stainless steel and has a function of reinforcing the superconducting coil 13A. The coil frame 22 is provided so as to cover the entire circumference of the superconducting coil 13A.

  Therefore, since the coil frame 22 also forms a loop in this embodiment, an eddy current i may be generated when the rate of change in magnetic flux (dφ / dt) per unit time t generated by the superconducting coil 13A increases. Concerned. Therefore, in this embodiment, the slit 21 is formed in the coil frame 22 and the loop of the coil frame 22 is interrupted to suppress the generation of eddy current.

  In the present embodiment, an example in which one slit 21 is formed in the coil frame 22 has been described, but a plurality of slits 21 may be formed in the coil frame 22. Further, the width of the slit 21 is preferably as narrow as possible. This is because, in order to uniformly cool the superconducting wire and suppress the occurrence of quenching, it is desirable that the heat conducting member 20 be in close contact with the superconducting coil 13A as wide as possible.

  However, the width of the slit 21 needs to be a dimension that leaves a margin that does not cause contact between the cut ends due to thermal contraction when cooled to a low temperature and that does not cause dielectric breakdown due to a voltage generated during quenching. . The slit 21 may be filled with a high-strength insulating material (GFRP, CFRP, etc.) that is an electrical insulator and has mechanical strength as a filler.

  The heat shield plate 17 is provided so as to surround the superconducting coil 13A (coil frame 22). In addition, a second load support 15 </ b> B, which will be described later, is also disposed inside the heat shield plate 17.

  The heat shield plate 17 is thermally connected to the first stage portion 18a of the refrigerator 18 (see FIG. 2). The heat shield plate 17 is formed of a material having excellent heat transfer characteristics such as copper or aluminum. Therefore, by providing the heat shield plate 17, the radiant heat entering the superconducting coil 13A can be reduced.

  The refrigerator 18 is fixed to the iron core 12. In the present embodiment, a Gifford McMahon type (GM type) refrigerator is used as the refrigerator 18. This GM type refrigerator 18 is configured such that a displacer reciprocates in a cylinder by driving an internal motor. And by the reciprocating movement of this displacer, it is set as the structure which carries out adiabatic expansion of the high-pressure refrigerant | coolant supplied from the refrigerator compressor which is not shown in figure, and this generates cold.

  The GM refrigerator 18 is a two-stage refrigerator, and the first stage portion 18 a is connected to the heat shield plate 17, and the second stage portion 18 b is connected to the superconducting coil 13 </ b> A via the heat conducting member 20. Therefore, the heat shield plate 17 is cooled to about 40K to 110K by the first stage portion 18a of the refrigerator 18. Further, the heat conducting member 20 thermally connected to the coil body 19 is cooled to about 4K to 40K by the two-step portion 18b. Thus, when the heat conductive member 20 is cooled by the refrigerator 18, the coil body 19 is cooled and a superconducting state is realized.

  The reinforcing ring 24 is provided so as to surround the entire outer periphery of the coil frame 22 (superconducting coil 13A) as shown in FIG. Specifically, the reinforcing ring 24 is disposed on the surface of the heat shield plate 17 facing the iron core 12. The reinforcing ring 24 has a function of preventing deformation (distortion) generated in the coil body 19 due to electromagnetic force (hoop force).

  As the material of the reinforcing ring 24, it is desirable to use a non-magnetic high-strength alloy or the like (for example, a non-magnetic austenite or the like that maintains strength even at low temperatures and has a relatively high Young's modulus). In the present embodiment, stainless steel is adopted as the material of the reinforcing ring 24.

  Further, since the reinforcing ring 24 is disposed so as to surround the entire outer periphery of the coil frame 22 (superconducting coil 13A), a loop is formed. However, the arrangement position of the reinforcing ring 24 is a position away from the arrangement position of the superconducting coil 13A. For this reason, even if a magnetic flux change occurs in the superconducting coil 13A, since the eddy current generated in the reinforcing ring 24 is small, it is not necessary to provide the reinforcing ring 24 with a slit for interrupting the eddy current.

  The reinforcing ring 24 is formed with a convex portion 24A and a concave portion 24B. In this specification, a portion where the reinforcing ring 24 protrudes toward the coil frame 22 in the direction of the arrow X1 in the drawing is referred to as a convex portion 24A, and a portion where the reinforcing ring 24 is recessed toward the iron core 12 in the direction of the arrow X2 in the drawing is a concave portion 24B. Let's say.

  The load supports 15A and 15B (referred to as the first load supports 15A-1 and 15A-2 and the second load supports 15B-1, 15B-2, and 15B-3, respectively) In contrast, the superconducting coil 13A is supported. Conventionally, a single load support 105 is provided and supported from the iron core 102 to the coil frame 109 (superconducting coil 103) at each support position by a plurality of load supports 105 (see FIG. 5).

  On the other hand, in this embodiment, it arrange | positions between the 1st load support body 15A arrange | positioned between the iron core 12 and the reinforcement ring 24, and the reinforcement ring 24 and the coil frame 22 (superconducting coil 13A). The second load support 15B is provided.

  The first load support 15 </ b> A supports the reinforcing ring 24 with respect to the iron core 12. The second load support 15 </ b> B supports the coil frame 22 (superconducting coil 13 </ b> A) with respect to the reinforcing ring 24.

  Therefore, in the superconducting magnet device 10 according to the present embodiment, the superconducting coil 13A is reinforced by the coil frame 22 and the reinforcing ring 24 via the first and second load supports 15A and 15B. As described above, since the coil frame 22 has a configuration in which the slit 21 is formed, the mechanical strength is lower than the configuration in which the slit 21 is not provided.

  However, since the coil frame 22 is connected to the reinforcing ring 24 via the second load support 15B, the superconducting coil 13A is also reinforced by the reinforcing ring 24. Further, since the eddy current does not occur in the reinforcing ring 24 as described above, no slit for reducing the mechanical strength is provided. Therefore, according to the superconducting magnet device 10 according to the present embodiment, the generation of eddy current in the coil frame 22 can be suppressed, and the superconducting coil 13A can be reliably supported.

  In addition, since the first load support 15A is fixed to the iron core 12 at room temperature, this external heat may enter the superconducting coil 13A via the first load support 15A. However, since the first and second load supports 15A and 15B are separated as described above, the first load support 15A-1 and the second load support 15B-1 are not necessarily aligned. There is no need to dispose the first and second load supports 15A-2 and 15B-3.

  Assuming that external heat has entered from the first load support 15A-1, this external heat is indicated by the arrows in the figure, and the first load support 15A, the reinforcing ring 24, the second load support 15B, heat is transferred to the superconducting coil 13A via the coil frame 22. At this time, the heat transfer path can be lengthened by biasing the first load support 15A-2 and the second load support 15B-3.

  Therefore, the heat transfer path of the external heat can be lengthened as compared with the conventional configuration in which the iron core 102 and the coil frame 109 are supported by the single load support 105. Thereby, the thermal resistance reaching the superconducting coil 13A of external heat can be increased, and the temperature of the superconducting coil 13A can be prevented from rising due to external heat.

  On the other hand, when considering the mechanical strength, it is desirable to arrange them in a straight line like the first load support 15A-1 and the second load support 15B-1. Therefore, the first load support 15A and the first load support 15A and the first load support 15A and the first load support 15A and the first load support 15A and the second load support 15A and the second load support 15A and the first load support 15A and the second load support 15 The position of the second load support 15B may be selected.

  Furthermore, in the present embodiment, the reinforcing ring 24 is formed with convex portions 24A and concave portions 24B. As shown in FIG. 2, the first load support 15A-2 is inserted deeply into the convex portion 24A formed on the reinforcing ring 24, and the second load support 15B-2 is reinforced. It is configured to be inserted into a recess 24 </ b> B formed in the ring 24.

  In this way, the convex portion 24A and the concave portion 24B are formed in the reinforcing ring 24, and the first and second load supports 15A and 15B are mounted at the formation positions, thereby adjusting the heat transfer path of the external heat. Is possible. Therefore, it is possible to prevent the temperature of the superconducting coil 13A from rising due to external heat by appropriately setting the protruding amount and the recessed amount of the convex portion 24A and the concave portion 24B.

  In addition, by providing the convex portion 24A and the concave portion 24B in the reinforcing ring 24, the reinforcing ring 24 has increased shape rigidity and can also increase mechanical strength. Further, in order to provide the convex portion 24A and the concave portion 24B in the reinforcing ring 24, the heat shield plate 17 in which the reinforcing ring 24 is closely attached is appropriately formed with an opening into which the convex portion 24A and the concave portion 24B are fitted. .

  Further, the second load support 15 </ b> B disposed inside the heat shield plate 17 is configured to be connected to the heat shield plate 17 connected to the refrigerator 18. The second load support 15B-1 and the second load support 15B-2 are thermally connected directly to the heat shield plate 17, so that the refrigerator 18 performs cooling.

  Further, the reinforcing ring 24 is positioned inside the heat shield plate 17 at the position where the second load support 15B-3 is formed, and cannot be directly connected to the heat shield plate 17. Therefore, a thermal anchor 26 is provided between the second load support 15B-2 and the heat shield plate 17, so that the second load support 15B-3 is cooled by the refrigerator 18. It is configured to do. With this configuration, it is possible to more reliably prevent external heat from entering the superconducting coil 13A via the second load support 15B.

  Further, in the present embodiment, conventionally, one load support 105 (see FIG. 5) is divided into a first load support 15A and a second load support 15B. Therefore, the length of each of the first and second load supports 15A and 15B is shorter than that of the conventional load support 105. Therefore, the superconducting coil 13A has an asymmetric and complicated shape, and even when a bending load is applied to the first and second load supports 15A and 15B, the moment generated thereby is small. Therefore, it is possible to prevent the first and second load supports 15A and 15B from being damaged by this bending load.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific embodiments described above, and various modifications can be made within the scope of the present invention described in the claims. It can be modified and changed.

  Specifically, in this embodiment, an example in which the present invention is applied to a deflecting electromagnet for a proton beam therapy apparatus gantry has been described. However, the application of the present invention is not limited to this, and the superconducting coil is relatively large. In addition, the present invention can be widely applied to superconducting magnet devices having a configuration in which conductive cooling is performed by a refrigerator.

DESCRIPTION OF SYMBOLS 10 Superconducting magnet apparatus 12 Iron core 13A, 13B, 13C Superconducting coil 15A 1st load support body 15B 2nd load support body 17 Heat shield board 18 Refrigerator 20 Thermal conduction member 21 Slit 22 Coil frame 24 Reinforcement ring 24A Convex part 24B Recess 26 heat anchor

Claims (4)

A vacuum vessel;
A superconducting coil mounted in the vacuum vessel;
A metal coil frame equipped with a slit that cuts off eddy current while mounting the superconducting coil inside,
A refrigerator that cools the superconducting coil to be in a superconducting state;
A reinforcing member that is disposed so as to surround the coil frame to reinforce the coil frame,
A first load support disposed between the vacuum vessel and the reinforcing member and supporting the reinforcing member with respect to the vacuum vessel;
And a plurality of arranged, the second load bearing member for supporting the coil form from a plurality of directions with respect to the reinforcement member between the reinforcing member and the coil frame,
A superconducting magnet device comprising: The reinforcing member includes a heat shield plate and a reinforcing ring,
The heat shield plate is configured to be cooled by the refrigerator,
The superconducting magnet apparatus according to claim 1, wherein a thermal anchor is provided between the second load support and the heat shield plate . The superconducting magnet apparatus according to claim 1 or 2, wherein the first load support and the second load support are arranged at positions deviated across the reinforcing member. 4. The superconducting magnet device according to claim 3, wherein the reinforcing member is provided with a concave portion or a convex portion, and the first load support and the second load support are joined to the concave or convex portion. .

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