JP2014049570A - Spool of superconducting magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a superconducting magnet and a spool which can suppress occurrence of quench due to Lorentz force effectively.SOLUTION: A superconducting magnet includes a superconducting coil 50 and a spool. The spool includes shanks 12, 20 having cylindrical outer peripheral surface on which a superconducting wire rod 52 composing the superconducting coil 50 is wound, and flanges 14A, 30A, 14B, 30B located at both ends of the shanks 12, 20 in the axial direction. At least one of the shanks and flanges include magnetizable parts 20, 30A, 30B composed of a ferromagnetic material, and the magnetizable parts are arranged to be magnetized by a magnetic field formed by the superconducting coil 50 and to exert an attractive force for cancelling the Lorentz force acting on the superconducting coil 50.

Description

  The present invention relates to a superconducting magnet winding frame and a superconducting magnet used for NMR, MRI and the like.

  Conventionally, as a superconducting magnet used for NMR, MRI, etc., what is described in Patent Document 1 is known. The superconducting magnet includes a winding frame 1 as shown in FIG. 6 and a superconducting coil 2, and the superconducting coil 2 is constituted by a superconducting wire wound around the winding frame 1. The winding frame 1 includes a barrel portion having a cylindrical outer peripheral surface, and a pair of flange portions that are respectively located at both axial ends of the barrel portion and project radially outward from the outer peripheral surface of the barrel portion. And the superconducting wire is wound around the outer peripheral surface of the body portion between the flange portions.

JP-A-10-41123

  In such a superconducting magnet, a large current flows through the superconducting wire in the superconducting state, and a strong magnetic field is thereby formed. Therefore, a very large electromagnetic force (on the superconducting wire due to the interaction between the magnetic field and the current ( Lorentz force). Specifically, an axial compressive force and a radially outward force act on the superconducting coil 2. This Lorentz force may cause a so-called quench phenomenon in which the entire superconducting magnet is dislocated to a normal state. Specifically, the Lorentz force promotes the generation of a so-called wire motion in which the superconducting wire is displaced from the initial winding state, and the frictional heat accompanying this wire motion causes the temperature of a part of the superconducting wire to exceed a critical temperature. There is a risk of increasing the temperature to generate electrical resistance. Self-heating is induced by the current flowing through the part having such electric resistance, that is, the normal conduction part, and this causes an irreversible temperature rise process, and finally the entire superconducting magnet is shifted to the normal conduction state. That is, quenching may occur. In order to return the superconducting magnet to a normal operating state after such a quench occurs, it is necessary to reinject liquid helium for cooling, and a substantial increase in cost is inevitable.

  As means for suppressing the occurrence of quenching due to the Lorentz force, in Patent Document 1, a binding wire 3 made of stainless steel, copper or the like is wound around the outer periphery of the superconducting coil 2 as shown in FIG. It is described that the superconducting coil 2 is restrained from the outside. However, the restraint by the binding line 3 does not eliminate the fundamental cause of the occurrence of quenching. The winding of the bind wire 3 may cause stress concentration at the interface between the bind wire 3 and the outermost layer of the superconducting coil 2, and may cause a new cause of friction at the interface. Further, in addition to the superconducting coil 2, a large amount of labor and a large device are required to wind the bind wire 3 around the periphery of the superconducting coil 2 with a force sufficient to restrain the superconducting coil 2 against the Lorentz force. On the other hand, there is a risk of increasing costs.

  In view of such circumstances, an object of the present invention is to provide a superconducting magnet winding frame capable of effectively suppressing the occurrence of quenching due to Lorentz force and a superconducting magnet including the winding frame.

  A winding frame provided by the present invention constitutes a superconducting magnet together with a superconducting coil, and has a cylindrical outer peripheral surface on which a superconducting wire constituting the superconducting coil is wound on the outer peripheral surface; And a flange portion that is located at both ends in the axial direction of the body portion and protrudes radially outward from the outer peripheral surface of the body portion. Further, as a feature thereof, at least one of the body portion and the flange portion includes a magnetizable portion made of a ferromagnetic material, and the magnetizable portion is magnetized by a magnetic field formed by energization of the superconducting coil, and the superconducting coil. The superconducting coil is arranged so as to exert an attractive force that cancels out the Lorentz force acting on the superconducting coil.

  A superconducting magnet provided by the present invention includes the above-described winding frame and a superconducting coil formed of a superconducting wire wound around the outer peripheral surface of the body portion of the winding frame.

  In the winding frame and the superconducting magnet provided with the winding frame, the magnetizable components included in the flange portion and the trunk portion of the winding frame using a magnetic field formed by energization of a superconducting coil provided around the trunk portion of the winding frame. By magnetizing the part, it is possible to generate a magnetic force that cancels out the Lorentz force generated in the superconducting coil, that is, an attractive force by the magnetizable part. Therefore, the Lorentz force itself that becomes a cause of quenching can be reduced without adding a special restraining member, and a drastic solution for quench prevention can be achieved.

  Specifically, at least one of the flange portions, preferably both flange portions have the magnetizable portion, and the magnetizable portion of the flange portion is magnetized to attract the superconducting coil from the outside in the axial direction. Those that generate attractive forces are preferred. The magnetizable portion included in the flange portion can effectively reduce the axial compressive force of the Lorentz force generated in the superconducting coil.

  The flange portion may include the magnetizable portion by forming the entire flange portion from a ferromagnetic material, or the flange portion may incorporate a ferromagnetic material constituting the magnetizable portion. However, preferably, the reel according to the present invention is made of a non-magnetic material, and has a main body body having the cylindrical outer peripheral surface and axially opposite ends of the main body body from the cylindrical outer peripheral surface. A reel body having a main body flange portion projecting radially outward, and a magnetizable plate made of the ferromagnetic material, and the magnetizable plate is on at least one outer surface of the two main body flange portions; It is preferable that the flange portion be configured together with the main body flange portion by being fixed on the outer surfaces of both the main body flange portions. In this structure, the winding area of the superconducting wire constituting the superconducting coil is accurately defined by the cylindrical outer peripheral surface of the main body of the reel body and the inner surface of both main body flanges with a high degree of freedom in selecting the material. In addition, it is possible to include a magnetizable portion effective in reducing the Lorentz force in the flange portion with a simple structure in which the magnetizable plate is fixed to one or both of the main body flange portions.

  In the present invention, it is also preferable that the barrel portion has the magnetizable portion, and the magnetizable portion of the barrel portion is magnetized to generate an attractive force that attracts the superconducting coil from the inside in the radial direction. The magnetizable portion included in the flange portion can effectively reduce the radially outward force of the Lorentz force generated in the superconducting coil.

  The body portion may include the magnetizable portion by forming the entire body portion from a ferromagnetic material, or the body portion may incorporate a ferromagnetic material constituting the magnetizable portion. Preferably, however, the reel according to the present invention is made of a non-magnetic material and has a cylindrical main body having the cylindrical outer peripheral surface and the cylindrical inner peripheral surface, and axial ends of the main body. A reel body having a main body flange portion positioned and projecting radially outward from the cylindrical outer peripheral surface, and made of the ferromagnetic material, and fixed on the inner side surface of the main body torso together with the main body torso What has the magnetizable cylinder which comprises the said trunk | drum is suitable. In this structure, the winding area of the superconducting wire constituting the superconducting coil is accurately defined by the cylindrical outer peripheral surface of the main body of the reel body and the inner surface of both main body flanges with a high degree of freedom in selecting the material. In addition, it is possible to include a magnetizable portion effective for reducing the Lorentz force in the barrel portion with a simple structure in which the magnetizable cylinder is simply fixed on the inner surface of the body barrel portion.

  As the ferromagnetic material constituting each of the magnetizable portions, for example, a material selected from iron, cobalt, nickel, and alloys thereof is preferable.

  As described above, according to the present invention, a winding frame of a superconducting magnet capable of effectively suppressing the occurrence of quenching due to Lorentz force and a superconducting magnet provided with the winding frame are provided.

1 is an exploded cross-sectional perspective view of a superconducting magnet according to an embodiment of the present invention. It is a cross-sectional perspective view which shows the winding frame main body of the winding frame in the said superconducting magnet, and the magnetizable board fixed to the main body flange part. It is a cross-sectional perspective view which shows the winding frame main body of the winding frame in the said superconducting magnet, and the magnetizable cylinder fixed to the main body trunk | drum. It is a cross-sectional perspective view showing the magnetic field formed by the superconducting coil of the superconducting magnet and the direction in which the magnetizable plate is magnetized by this magnetic field. It is a cross-sectional perspective view showing the magnetic field formed by the superconducting coil of the superconducting magnet and the direction in which the magnetizable cylinder is magnetized by this magnetic field. It is a cross-sectional front view of a conventional superconducting magnet.

  An embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 shows a superconducting magnet according to an embodiment of the present invention. This superconducting magnet is composed of a winding frame and a superconducting coil 50. The winding frame includes a winding body 10, a magnetizable tube 20, and a pair of upper and lower magnetizable plates 30 </ b> A and 30 </ b> B, and the superconducting coil 50 is formed by a superconducting wire 52 wound around the winding frame. Composed.

  The reel body 10 is formed of a normal nonmagnetic material such as an aluminum alloy, stainless steel, or FRP, and integrally includes a main body barrel 12 and a pair of upper and lower main body flange portions 14A and 14B. The main body trunk 12 has a cylindrical shape, that is, a shape having a cylindrical outer peripheral surface and a cylindrical inner peripheral surface. The main body flange portions 14A and 14B are located at both ends in the axial direction of the main body barrel portion 12 (both ends in the vertical direction in FIG. 1), and project radially outward from the cylindrical outer peripheral surface of the main body barrel portion 12. . In this embodiment, the protrusion amount of the main body flange portions 14A and 14B from the cylindrical outer peripheral surface is constant regardless of the circumferential position. That is, the main body flange portions 14A and 14B have a donut plate shape.

  The superconducting wire 52 is formed in the region between the inner side surfaces of the main body flange portions 14A and 14B (the lower surface of the upper main body flange portion 14A and the upper surface of the lower main body flange portion 14B in the posture of FIG. 1). Thus, the superconducting coil 50 is formed. In this embodiment, the superconducting wire 52 is wound and energized in the direction shown in FIG. In FIG. 1, among the marks shown in each cross section of the superconducting wire 52, the mark “·” indicates that current flows through the same cross section, and the mark “×” indicates that the current passes through the cross section and the current is on the back side. Indicates flowing. Accordingly, the superconducting coil 50 arranged in the posture shown in FIG. 1 forms an upward magnetic field inside the main body trunk portion 12 by energization thereof.

  As shown in FIGS. 1 and 2, the magnetizable plates 30A and 30B are formed on the outer surfaces of the main body flange portions 14A and 14B (in the posture shown in FIG. 1, the upper surface and the lower main body flange portion of the upper main body flange portion 14A). 14B on the lower surface). The magnetizable plate 30A constitutes the upper flange portion of the winding frame together with the upper body flange portion 14A, and the magnetizable plate 30B constitutes the lower flange portion of the winding frame together with the lower body flange portion 14B.

  Each of the magnetizable plates 30A and 30B is made of a ferromagnetic material. In this embodiment, each of the magnetizable plates 30A and 30B has a shape that matches the planar shape of the main body flange portions 14A and 14B, that is, a donut plate shape. And it fixes in the state piled up on the outer surface of each said main body flange part 14A, 14B. The fixing means is not particularly limited. For example, welding may be used, but in this embodiment, fastening by a plurality of bolts 40 is performed. Specifically, each of the magnetizable plates 30A and 30B is provided with a plurality of bolt insertion holes 32 penetrating the magnetizable plates 30A and 30B in the thickness direction, and positions corresponding to the bolt insertion holes 32 in the main body flange portions 14A and 14B. Are provided with screw holes 18 that open outwardly. The bolts 40 are inserted into the corresponding bolt insertion holes 32 and screwed into the corresponding screw holes 18 to fix the magnetizable plates 30A and 30B on the outer surfaces of the main body flange portions 14A and 14B.

  As shown in FIGS. 1 and 3, the magnetizable cylinder 20 is disposed on the inner side of the main body barrel 12 and fixed on the inner side surface (inner peripheral surface) of the main body barrel 12, thereby A body part of the winding frame is configured together with the body body part 12. The magnetizable cylinder 20 is made of a ferromagnetic material. In this embodiment, the magnetizable cylinder 20 has a cylindrical shape that covers the entire inner surface of the main body barrel 12 and is fixed in a state of being overlapped with the inner surface of the main body barrel 12. . The fixing means is not particularly limited. For example, welding may be used, but in this embodiment, fastening with a plurality of bolts 40 is performed in the same manner as the two magnetizable plates 12. Specifically, the magnetizable cylinder 20 is provided with a plurality of bolt insertion holes 22 penetrating the magnetizable cylinder 20 in the radial direction, and radially inward at positions corresponding to the bolt insertion holes 22 in the main body trunk portion 12. A screw hole 16 is provided in the opening. Each of the bolts 40 is inserted into the corresponding bolt insertion hole 22 and screwed into the corresponding screw hole 16, thereby fixing the magnetizable cylinder 20 on the inner surface of the main body barrel 12.

  The ferromagnetic material constituting the magnetizable plates 30A and 30B and the magnetizable cylinder 20 is not particularly limited as long as it has a degree of ferromagnetism that can be magnetized by the magnetic field in which the superconducting coil 50 is formed. Good. Specifically, those selected from iron, cobalt, nickel, and alloys thereof, or those exhibiting ferromagnetism equivalent to these are preferable.

  Next, the action of this superconducting magnet is configured.

  When a large current is passed through the superconducting wire 52 constituting the superconducting coil 50 in the superconducting state, a strong magnetic field is formed inside the body of the winding frame, but the large current is strong against the superconducting wire 52. Generate Lorentz force. Specifically, between the elements of the superconducting wire 52 that overlap each other in the reel axis direction, an attractive force is generated such that the elements are attracted by currents flowing in the same direction in these elements, and therefore the superconducting coil 50 as a whole. A compressive force in the axial direction is generated. On the other hand, between the elements disposed at positions opposite to each other (left and right positions in FIG. 1) of the superconducting wire 52 across the body of the winding frame, currents flowing in these elements in opposite directions are caused by A repulsive force that causes the elements to separate from each other is generated, and as a result, a radially outward force is generated in the entire superconducting coil 50. As these forces increase, displacement of the superconducting wire 52 that can cause quenching, so-called wire motion, is more likely to occur.

  However, in this superconducting magnet, the magnetic field formed by the superconducting coil 50 magnetizes the upper and lower magnetizable plates 30A and 30B and the magnetizable cylinder 20 made of a ferromagnetic material, thereby reducing the Lorentz force. To effectively suppress quenching caused by the Lorentz force. Specifically, when a current having a direction as shown by the “•” mark and the “x” mark in FIG. 1 is passed through the superconducting coil 50, the superconducting coil 50 forms a magnetic field as shown in FIGS. To do. Due to this magnetic field, the upper and lower magnetizable plates 30A, 30B are magnetized radially outward as shown in FIG. 4, thereby generating an attractive force that attracts the superconducting coil 50 from the outside along its axial direction. This attractive force is offset by the Lorentz force in the axial direction to reduce the Lorentz force. On the other hand, the magnetizable tube 20 is magnetized upward as shown in FIG. 5, thereby generating an attractive force that attracts the superconducting coil 50 from the inside along its radial direction. This attractive force is offset by the Lorentz force in the radial direction and reduces the Lorentz force.

  That is, in this superconducting magnet, the upper and lower magnetizable plates 30A and 30B and the magnetizable cylinder 20 are magnetized using the magnetic field formed by the superconducting coil 50, thereby adding a special magnetism generating device, a restraining member, and the like. In addition, the Lorentz force acting on the superconducting coil 50 can be reduced. Therefore, a drastic solution for the occurrence of quenching due to the Lorentz force is achieved. Moreover, this effect can be obtained with a very simple structure in which the upper and lower flange portions and the body portion of the winding frame only include a magnetizable portion made of a ferromagnetic material.

  The structure in which the upper and lower flange portions and the body portion each include the magnetizable portion is, for example, that the entire upper and lower flange portions and the entire body portion are formed of a magnetizable material, or the upper and lower flange portions and the body portion. It is also possible to form a magnetizable material by incorporating (eg, mixing) a magnetizable material into the material constituting the material. However, in the structure in which the upper and lower magnetizable plates 30A and 30B and the magnetizable cylinder 20 are added to the reel body 10 made of the non-magnetic material as described above, the main body body of the reel body 10 having a high degree of freedom in selecting the material. The upper and lower magnetizable plates on the reel body 10 while accurately defining the winding area of the superconducting wire 52 constituting the superconducting coil 50 by the cylindrical outer peripheral surface of the portion 12 and the inner side surfaces of both body flange portions 14A and 14B. There is an advantage that a magnetizable portion effective for reducing the Lorentz force can be included in the flange portion with a simple structure in which 30A, 30B and the magnetizable cylinder 20 are simply added.

  The magnetizable portion according to the present invention may be included in at least a part of the body portion and both flange portions of the winding frame. For example, as shown in Example 1 described later, the axial component of the Lorentz force can be reduced even if the magnetizable part is included only in one of both flange portions of the winding frame. As shown, the radial component of the Lorentz force can be reduced even if the magnetizable portion is included only in the body portion of the winding frame. In the present invention, a plurality of magnetizable portions may be dispersedly arranged in at least one of the body portion and both flange portions of the winding frame.

  A structure obtained by adding the upper and lower magnetizable plates 30A and 30B shown in FIG. 2 to the winding body 10 shown in FIG. 1 is used as a winding frame, and a superconducting wire 52 is wound around the superconducting coil 50. Is formed. The inner diameter and axial length of the superconducting coil 50 are both 200 mm, the outer diameter is 296 mm, the superconducting wire 52 constituting the superconducting coil 50 is made of copper matrix NbTi, the covered wire diameter is 0.55 mm, and the upper and lower magnetizable plates 30A and 30B are made of materials. Is 10 mm thick, and the magnetizable plates 30 </ b> A and 30 </ b> B are arranged 5 mm apart from the upper and lower end surfaces of the superconducting coil 50.

In this superconducting magnet, when the superconducting coil 50 is energized at a current density of 670 A / mm ² , an upward magnetic field of 3.8 T is formed at the center of the magnet, and Lorentz force acts on the superconducting coil 50. Without the upper and lower magnetizable plates 30A and 30B, the axial maximum compressive stress generated in the superconducting coil 50 by the axial component of the Lorentz force is 8.1 MPa. Due to the presence of 30B, the maximum compressive stress can be reduced to 7.6 MPa. That is, the maximum compressive stress is reduced by 0.5 MPa.

  A magnet body 20 shown in FIG. 3 to which the magnetizable cylinder 20 shown in FIG. 3 is added is used as a reel, and a superconducting coil 50 is formed by winding a superconducting wire 52 on the reel. The Both the inner diameter and axial length of the superconducting coil 50 are 400 mm, the outer diameter is 440 mm, the material of the superconducting wire 52 constituting the superconducting coil 50 is copper matrix NbTi, the covered wire diameter is 0.55 mm, the material of the magnetizable tube 20 is iron, The thickness in the radial direction is 20 mm, and the magnetizable tube 20 is disposed so as to be separated from the inner surface of the superconducting coil 50 by 5 mm.

In this superconducting magnet, when the superconducting coil 50 is energized at a current density of 670 A / mm ² , an upward magnetic field of 4.0 T is formed at the center of the magnet, and Lorentz force acts on the superconducting coil 50. In the absence of the magnetizable cylinder 20, the maximum radial stress generated in the superconducting coil 50 by the radial component of the Lorentz force is 52.3 MPa. The stress can be reduced to 51.5 MPa. That is, the maximum stress is reduced by 0.8 MPa.

DESCRIPTION OF SYMBOLS 10 Reel body 12 Main body trunk part 14A Upper body flange part 14B Lower main body flange part 20 Magnetizable cylinder 30A, 30B Magnetizable plate 50 Superconducting coil 52 Superconducting wire

Claims (8)

A winding frame constituting a superconducting magnet together with a superconducting coil,
A body portion having a cylindrical outer peripheral surface, on which the superconducting wire constituting the superconducting coil is wound,
A flange portion located at both ends in the axial direction of the barrel portion and projecting radially outward from the outer peripheral surface of the barrel portion;
Further, at least one of the body part and the flange part includes a magnetizable part made of a ferromagnetic material, and the magnetizable part is magnetized by a magnetic field formed by energization of the superconducting coil and acts on the superconducting coil. A reel arranged to exert an attractive force on the superconducting coil so as to cancel out the Lorentz force.   The winding frame of the superconducting magnet according to claim 1, wherein at least one flange portion of the two flange portions has the magnetizable portion, and the magnetizable portion of the flange portion is magnetized to thereby form the superconducting coil. A reel that generates an attractive force that attracts from the outside in the axial direction.   The winding frame of the superconducting magnet according to claim 2, wherein each of the flange portions has the magnetizable portion, and the magnetizable portion of the flange portion is magnetized to attract the superconducting coil from the outside in the axial direction. A reel that generates attraction.   The superconducting magnet winding frame according to claim 2 or 3, wherein the winding frame is made of a non-magnetic material and has a main body body having the cylindrical outer peripheral surface and axial ends of the main body body. A reel body having a main body flange portion projecting radially outward from the cylindrical outer peripheral surface; and a magnetizable plate made of the ferromagnetic material, and the magnetizable plate is at least of the two main body flange portions. A winding frame of a superconducting magnet fixed on one outer surface and constituting the flange portion together with the main body flange portion.   The winding frame of the superconducting magnet according to any one of claims 1 to 4, wherein the body portion has the magnetizable portion, and the magnetizable portion of the body portion is magnetized so that the superconducting coil has a diameter. A superconducting magnet reel that generates attractive force from the inside.   The winding frame of the superconducting magnet according to claim 5, wherein the winding frame is made of a nonmagnetic material, and has a cylindrical main body portion having the cylindrical outer peripheral surface and the cylindrical inner peripheral surface, and the main body main body portion. A winding body having a main body flange portion located at both ends in the axial direction and projecting radially outward from the cylindrical outer peripheral surface; and a magnetizable tube made of the ferromagnetic material. A winding frame of a superconducting magnet, which is fixed on an inner side surface of the main body barrel portion and constitutes the trunk portion together with the main body barrel portion.   The superconducting magnet winding frame according to claim 6, wherein the ferromagnetic material constituting each of the magnetizable portions is selected from iron, cobalt, nickel, and alloys thereof. frame. A reel according to any one of claims 1 to 7,
A superconducting magnet comprising: a superconducting coil composed of a superconducting wire wound around the outer peripheral surface of the body of the winding frame.

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