JP5448988B2 - Superconducting magnet - Google Patents

Description

  The present invention relates to a superconducting magnet in which a superconducting wire is wound.

  In an MRI apparatus or the like used in medical treatment, it is necessary to downsize the entire apparatus while ensuring a large bore diameter. In order to downsize the entire apparatus, it is necessary to realize (1) downsizing of the superconducting magnet, (2) downsizing of the helium tank, and (3) downsizing of the cryostat.

  Here, as a technique capable of realizing (2) miniaturization of the helium tank, for example, there is a technique described in Patent Document 1. Patent Document 1 describes a double-structured winding frame that includes an outer diameter side winding frame in contact with a superconducting coil and an inner diameter side winding frame that supports the outer diameter side winding frame. The material of the outer diameter side reel is, for example, aluminum having a high thermal conductivity, and the material of the inner diameter side reel is, for example, stainless steel having a low thermal contraction rate. Patent Document 1 states that quenching hardly occurs even when the replenishment interval of liquid helium is increased by bringing the outer diameter side winding frame having high thermal conductivity into contact with the superconducting coil.

JP-A-6-5419

  The technique described in Patent Document 1 is suitable for reducing the filling amount of liquid helium. That is, if the technique described in Patent Document 1 is used, (2) downsizing of the helium tank can be realized. However, from the viewpoint of realizing (1) miniaturization of the superconducting magnet, the superconducting magnet is inevitably enlarged in the double structure winding frame. Also, from the viewpoint of realizing (3) miniaturization of the cryostat, the double-structured reel has a large weight and has disadvantages such as an increase in the size of the support member. Furthermore, the double-structured reel is more complicated in structure than the general single-layer reel, and the manufacturing cost increases.

  The present invention has been made in view of the above circumstances, and its purpose is to realize (1) miniaturization of a superconducting magnet, (2) miniaturization of a helium tank, and (3) miniaturization of a cryostat. It is to provide a superconducting magnet having a simple structure.

  The present invention provides a winding frame comprising a cylindrical body portion and at least a pair of flange portions provided on an outer periphery of the body portion with a predetermined interval, and the space between the pair of flange portions. A superconducting coil made of a superconducting wire wound around the body, and a winding member made of a metal material wound around the outer periphery of the superconducting coil, the winding member comprising a plate-like body, a belt-like body, Alternatively, the cross-sectional shape is a linear body having a circular or rectangular shape, and the thickness or diameter of the winding member is smaller than the thickness of the body portion, and the winding frame, the superconducting coil, and the winding member are liquid helium. It is a superconducting magnet that is immersed and cooled.

  In addition, "the thickness or diameter of the winding member is smaller than the thickness of the body part" means the following. When the winding member is a plate-like body or a strip-like body, it means that the thickness of one of the members is smaller than the thickness of the body portion. When the winding member is a linear body having a circular cross-sectional shape, it means that one diameter (diameter of the cross-section) is smaller than the thickness of the body portion. In the case where the winding member is a linear body having a rectangular cross-sectional shape, the thickness of one of the linear members (the thickness of the cross section, and further when the linear body is wound around the outer periphery of the superconducting coil) (Thickness in the coil radial direction) means smaller than the thickness of the body portion.

  According to this configuration, the winding member made of a metal material wound around the outer periphery of the superconducting coil has a role of a so-called thermal anchor (a role of transmitting the cold heat of liquid helium to the superconducting coil) and a role of a heat shield (outside For example, even if the amount of liquid helium is reduced, quenching can hardly occur. That is, (2) downsizing of the helium tank can be realized. In addition, as described above, the winding member plays the role of a so-called thermal anchor and the role of heat shielding, so there is no need to make the winding frame a double structure or the like. That is, (1) downsizing of the superconducting magnet can be realized. Further, in addition to the weight reduction effect due to the fact that the winding frame does not need to have a double structure, the increase in weight due to the addition of the winding member is small due to the small thickness or diameter of the winding member. That is, the support member of the cryostat is not increased in size, and (3) the cryostat can be reduced in size.

  Further, the above three problems can be solved with a simple structure in which the winding member made of a metal material is wound around the outer periphery of the superconducting coil.

  Moreover, in this invention, it is preferable that the said winding member is a plate-shaped body or strip | belt-shaped body which has the width | variety substantially equal to the length between a pair of said flange parts.

  According to this configuration, the entire outer peripheral surface of the superconducting coil can be reliably covered with the winding member, so that the function of the so-called thermal anchor and the heat shielding property of the winding member are improved.

  Furthermore, in this invention, it is preferable that the said winding member is wound with the linear or strip | belt-shaped metal material with respect to the said superconducting coil.

  According to this configuration, the adhesion between the superconducting coil and the winding member is increased, and the function of the so-called thermal anchor of the winding member is further improved.

  Furthermore, in the present invention, it is preferable that the winding frame, the superconducting coil, and the winding member are fixed by a vacuum impregnation treatment.

  According to this configuration, the adhesion between the superconducting coil and the winding member is further increased, and the function of a so-called thermal anchor of the winding member is further improved.

  According to the present invention, by the winding member wound around the outer periphery of the superconducting coil, which is made of a metal material and has a thickness or diameter smaller than the thickness of the body of the winding frame, (1 It is possible to easily realize a reduction in the size of the superconducting magnet, (2) a reduction in the size of the helium tank, and (3) a reduction in the size of the cryostat.

It is a side cross-sectional schematic diagram which shows the superconducting magnet which concerns on 1st Embodiment of this invention. It is AA sectional drawing of Fig.1 (a), and a figure which shows the modification of a winding member. It is a cross-sectional schematic diagram which shows the superconducting magnet which concerns on 2nd Embodiment of this invention. It is a side cross-sectional schematic diagram of the superconducting magnet for showing the modification of 3rd Embodiment.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The superconducting magnet of the present invention is suitable as a superconducting magnet for an MRI apparatus used in medicine. However, the superconducting magnet of the present invention may be applied to apparatuses other than the MRI apparatus.

(First embodiment)
FIG. 1 is a schematic side sectional view showing a superconducting magnet 1 according to a first embodiment of the present invention. FIG. 1A is a schematic side sectional view of the entire superconducting magnet 1, and FIG. 1B is an enlarged view of a portion B in FIG.

  As shown in FIG. 1A, the superconducting magnet 1 includes four superconducting coils 3 a to 3 d and a winding frame 2. In the case of an MRI apparatus, a superconducting magnet is usually composed of an inner winding frame (main coil) and an outer winding frame (shield coil) having a plurality of superconducting coils. The superconducting magnet 1 shown in FIG. 1A is an example of a shield coil (outer coil) of an MRI apparatus. Note that the present invention can also be applied to a superconducting magnet other than the one for the MRI apparatus including one superconducting coil and one winding frame.

(Reel)
As shown in detail in FIG. 1B, the winding frame 2 includes a cylindrical body portion 11 and a pair of flange portions 12 a and 12 b provided on the outer periphery of the body portion 11 at a predetermined interval. Is provided. In the present embodiment, as shown in FIG. 1A, five flange portions 12 a to 12 c are provided on the outer periphery of the trunk portion 11 so as to correspond to the four superconducting coils 3 a to 3 d. The five flange portions 12a to 12c form a total of four pairs of flange portions.

  Since the four superconducting coils 3a to 3d and the configurations around the respective coils are the same, the configuration of the superconducting coils and the surroundings of the coils will be described with reference to FIG.

(Superconducting coil)
Superconducting coil 3a is made of a superconducting wire wound tightly around body 11 between a pair of flange portions 12a and 12b. The superconducting wire is, for example, a wire material in which a niobium-titanium (NbTi) alloy-based ultrafine multi-core wire is embedded in a copper base material.

  An insulating sheet 5 is disposed between the body 11 of the winding frame 2 and the superconducting coil 3a. Moreover, the insulating member 6 is arrange | positioned between the flange part 12a and the superconducting coil 3a, and between the flange part 12b and the superconducting coil 3a.

(Wound material)
A linear body 4a having a circular cross-sectional shape is wound around the outer periphery of the superconducting coil 3a. The linear body 4a is, for example, a copper wire, and the diameter thereof is smaller than the thickness T of the body portion 11 (the same applies to winding members such as a plate-like body and a belt-like body described later). Here, the linear body 4a is made of a metal material having a higher thermal conductivity than the stainless material (the same applies to winding members such as a plate-shaped body and a belt-shaped body described later). Specific examples of the material of the linear body 4a include high-purity copper and aluminum. A winding member made of a copper alloy such as an aluminum alloy or brass may be used.

  After winding the superconducting coil 3a and the linear body 4a around the body 11 of the winding frame 2, the winding frame 2, the superconducting coil 3a, and the linear body 4a are vacuum impregnated using an impregnating agent such as epoxy resin or wax. It is preferable to be fixed by treatment (the same applies to winding members such as plate-like bodies and strip-like bodies described later). The linear body 4a may be fixed by wrapping the linear body 4a around the body 11 while spraying or applying an adhesive to the linear body 4a. Furthermore, the linear body 4a may be fixed to the outer peripheral surface of the superconducting coil 3a only by winding the linear body 4a around the body portion 11 of the winding frame 2 without using an impregnating agent or an adhesive.

  Here, Fig.2 (a) is a figure which shows the cooling state of the superconducting coil 3a. Reference numeral 7 indicates liquid helium. As shown in FIG. 2A, about a quarter of the superconducting coil 3a is immersed in liquid helium 7 and cooled. The liquid helium 7 is filled in a helium tank (not shown).

  According to the superconducting magnet 1 of this embodiment, since the superconducting coil 3a is surrounded by the linear body 4a made of a metal material having high thermal conductivity, the portion of the superconducting coil 3a that is not immersed in the liquid helium 7 is liquid helium. 7 is cooled by the cold heat transmitted from the linear body 4a. Further, when the linear body 4a is not provided, if helium tank is additionally replenished with liquid helium while the magnet is excited, the evaporated helium gas may come into contact with the coil to increase the temperature and quench it. However, in the superconducting magnet 1 of this embodiment, since the superconducting coil 3a is surrounded by the linear body 4a, the linear body 4a shields the heat of the warm helium gas and can prevent the temperature of the superconducting coil 3a from rising. That is, quenching can be suppressed.

  As described above, according to the present invention, even if the superconducting coil 3a is immersed in the liquid helium 7 only about 1/4, for example, the linear body with high thermal conductivity wound around the outer periphery of the superconducting coil 3a. The layer 4a plays the role of so-called thermal anchor (the role of transmitting the cold heat of the liquid helium 7 to the superconducting coil 3a) and the role of heat shielding (the role of shielding the superconducting coil 3a from the outside heat source). Can be difficult to cause. That is, a sufficient cooling effect of the superconducting coil 3a is obtained by the layer of the linear body 4a, and there is a problem even if the liquid helium 7 is stored in a small helium tank (helium can) and the liquid level 7a is lowered. Absent. Therefore, “miniaturization of the helium tank” can be realized.

  During excitation of the superconducting magnet, even if a refrigerator is attached to the apparatus, cooling cannot catch up, and the liquid level 7a of liquid helium may decrease. The layer of the linear body 4a having a high thermal conductivity is particularly effective in reducing the liquid level 7a during such excitation.

  Further, as described above, since the linear body 4a plays the role of so-called thermal anchor and the role of heat shielding, the reel 2 need not have a double structure. That is, it is possible to realize “miniaturization of a superconducting magnet”. Moreover, in addition to the weight reduction effect by not having to make the winding frame 2 into a double structure, since the diameter of the linear body 4a which is a winding member is smaller than the thickness T of the trunk | drum 11, the winding member Small increase in weight due to addition. That is, the size of the cryostat support member is not increased, and the “miniaturization of the cryostat” can be realized.

  In addition, the above three effects are obtained with a simple structure in which the linear body 4a made of a metal material having high thermal conductivity is wound around the outer periphery of the superconducting coil 3a.

  Furthermore, not only the linear body 4a is wound around the superconducting coil 3a, but the superconducting coil 3a and the linear body 4a are fixed by vacuum impregnation treatment, whereby the adhesion between the superconducting coil 3a and the linear body 4a is improved. This further increases the function of a so-called thermal anchor of the linear body 4a.

(Modification of linear body 4a)
FIG. 2B is a diagram showing a modification of the linear body 4a. As shown in FIG. 2B, the cross-sectional shape may be a linear body 8a, or the cross-sectional shape may be a rectangular (flat angle) linear body 8b. Moreover, it is good also as a winding member of the strip | belt-shaped body 8c (tape shape). Note that the shape of the winding member is not limited to these shapes.

(Second Embodiment)
FIG. 3 is a schematic cross-sectional view showing a superconducting magnet 102 according to the second embodiment of the present invention. FIG. 3A is a partially enlarged cross-sectional view of the superconducting magnet 102 corresponding to FIG. FIG.3 (b) is C sectional drawing of FIG.1 (b) (only the plate-shaped object 9 is shown).

  As shown in FIG. 3, in this embodiment, the 4 plate-shaped bodies 9a-9d of the same shape curved are used as a winding member. As shown to Fig.3 (a), the width | variety of the plate-shaped body 9 (9a-9d) is made into the width | variety substantially equal to the length between flange part 12a * 12b. (The width of the plate-like body 9 (9a to 9d) is smaller than the length between the flange portions 12a and 12b by the thickness of the two insulating members 6.) The thickness of the plate-like body 9 (9a to 9d) is It is smaller than the thickness T of the body part 11.

  The four plate-like bodies 9a to 9d are arranged along the outer peripheral surface of the superconducting coil 3a so as to be in close contact with the outer peripheral surface of the superconducting coil 3a.

  As shown in FIG. 3B, the plate-like body 9 has a slit 14 every 90 degrees in a state fixed (wrapped) around the outer periphery of the superconducting coil 3a. It is not limited to this. For example, it may be a two-part plate having a slit every 180, or a plate having a slit only in one place.

  By arranging the four plate-like bodies 9a to 9d on the outer periphery of the superconducting coil 3a, the substantially entire outer peripheral surface of the superconducting coil 3a can be reliably covered with the winding member, and the so-called thermal anchor of the winding member can be covered. Function and heat shielding are improved.

  In the present embodiment, the plate-like body 9 (9a to 9d) is wound around the superconducting coil 3a by the linear body 10 having a circular cross-sectional shape made of a metal material. The reason why the plate-like body 9 (9a to 9d) is wound with the linear body 10 is to increase the adhesion between the superconducting coil 3a and the plate-like body 9 (9a to 9d) without a special fastening structure. By tightening the plate-like body 9 (9a to 9d), the adhesion is enhanced, and the function of the so-called thermal anchor of the plate-like body 9 (9a to 9d) is further improved. The cross-sectional shape of the linear body 10 is not limited to a circle.

  There are two options for the material of the linear body 10. The first selection is to select a metal material having high tensile strength such as stainless steel. Thereby, the plate-shaped body 9 (9a-9d) can be wound up with the thin linear body 10, As a result, the outer diameter of the superconducting magnet 102 can be made small as a whole. The second selection is to select a metal material having a high thermal conductivity such as copper / aluminum. Thereby, the cooling effect of the superconducting coil 3a can be further enhanced.

(Modification)
FIG. 4 is a schematic side sectional view of the superconducting magnet 103 for showing a modification of the third embodiment. Note that only a part of the superconducting magnet 103 is shown enlarged.

  As shown in FIG. 4, in this embodiment, the plate-like body 9 is wound around the superconducting coil 3a with an extremely thin sheet 13 (one of strip-shaped metal materials). The sheet 13 is made of, for example, a copper material, and the plate-like body 9 is wound around the sheet 13 multiple times. By tightening the plate-like body 9 with the sheet 13 having high thermal conductivity, the adhesion between the superconducting coil 3a and the plate-like body 9 can be enhanced. And the sheet | seat 13 also plays the role of what is called a thermal anchor (the role which transmits the cold heat of the liquid helium 7 to the superconducting coil 3a).

  Further, the width of the sheet 13 is substantially equal to the length between the flange portions 12a and 12b. (The width of the sheet 13 is smaller than the length between the flange portions 12a and 12b by the thickness of the two insulating members 6.) Thereby, the entire outer peripheral surface of the plate-like body 9 can be covered with the sheet 13, The function of 13 so-called thermal anchors is improved. Note that it is not always necessary to cover the entire outer peripheral surface of the plate-like body 9 with the sheet 13, and even if the plate-like body 9 is wound with a tape-like metal material (for example, copper tape) having a smaller width than the sheet 13. Good.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims. .

1: Superconducting magnet 2: Winding frames 3a to 3d: Superconducting coils 4a to 4d: Linear bodies (winding members)
11: trunk | drum 12a-12c: flange part

Claims (4)

A winding frame comprising a cylindrical body part and at least a pair of flange parts provided on the outer periphery of the body part at a predetermined interval;
A superconducting coil made of a superconducting wire wound around the body portion between the pair of flange portions;
A wound member made of a metal material having a higher thermal conductivity than stainless steel such as copper, copper alloy, aluminum, or aluminum alloy , wound around the outer periphery of the superconducting coil;
With
The winding member is a plate-like body, a belt-like body, or a linear body having a circular or rectangular cross-sectional shape, and the thickness or diameter of the winding member is smaller than the thickness of the body portion,
It said winding frame, wherein the superconducting coil, and the winding member, from one end of the barrel up to the other end, at least a portion of the circumferential direction, characterized in Tei Rukoto immersed cooled with liquid helium , Superconducting magnet. In the superconducting magnet according to claim 1,
The superconducting magnet according to claim 1, wherein the winding member is a plate-like body or a belt-like body having a width substantially equal to a length between the pair of flange portions. The superconducting magnet according to claim 2,
A superconducting magnet, wherein the winding member is wound around the superconducting coil with a linear or belt-shaped metal material. In the superconducting magnet according to any one of claims 1 to 3,
The superconducting magnet, wherein the winding frame, the superconducting coil, and the winding member are fixed by a vacuum impregnation process.

Images