JPH07142241A - Superconducting magnet device - Google Patents

Abstract

PURPOSE:To provide a superconducting magnet device which can ensure the safety of a superconducting coil, which can contribute toward the effective utilization of the bore diameter of the superconducting coil and which is coupled directly to a refrigerator. CONSTITUTION:The superconducting magnet device is provided with a superconducting coil 6, with a heat-absorbing member 7 which is formed of a good heat-conducting member and which is connected thermally to the outer circumferential face of the superconducting coil 6, with a cooling stage 11 and with a GM refrigerator 9 which cools the heat-absorbing member 7 through thermal conduction by the cooling stage 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting magnet device, and more particularly to a superconducting magnet device in which a superconducting coil is directly conductively cooled by a cryogenic refrigerator.

[0002]

2. Description of the Related Art As is well known, most of the superconducting magnet devices currently in practical use are immersed in a cryogenic liquid typified by liquid helium as a means for cooling the superconducting coil below a critical temperature. The method to do is adopted.
However, in this method, it is difficult to handle liquid helium or liquid nitrogen, and it is necessary to take an expensive refrigerant in and out of the cryostat, so that a large amount of refrigerant is wasted.
There is no avoiding an increase in running costs.

By the way, in recent years, with the discovery of new regenerator materials, the performance of cryogenic refrigerators typified by Gifode-McMahon type refrigerators has been dramatically improved. Under these circumstances, recently, a superconducting magnet device has been proposed in which the superconducting coil is directly conductively cooled by a cryogenic refrigerator. In this superconducting magnet device, without using a refrigerant,
Alternatively, since the waste of the refrigerant can be eliminated, the running cost can be significantly reduced.

However, the so-called direct-cooling type superconducting magnet device in which the superconducting coil is directly conductively cooled by the cryogenic refrigerator has the following problems. That is, in the conventional superconducting magnet device directly connected to the refrigerator, the superconducting coil is cooled by conduction through the winding frame of the superconducting coil. Specifically, a superconducting wire is wound around a winding frame made of a good heat conducting material to form a coil body, and then a resin such as an epoxy resin is impregnated into the gap between the wires and the winding frame. The superconducting coil and the bobbin are integrated. Then, this is arranged in a vacuum container, and the reel is thermally connected to the cooling stage of the cryogenic refrigerator via a good heat conducting member.

However, with the above structure, the following phenomenon occurs when the superconducting coil is actually cooled to a cryogenic temperature by conduction and when the superconducting coil is energized in this state. That is, when the superconducting coil is cooled to a cryogenic temperature via the winding frame, both the winding frame and the superconducting coil thermally contract in the radial direction. When the superconducting coil is energized in this state, the superconducting coil is deformed by the electromagnetic force so as to expand outward in the radial direction. Therefore, tensile stress acts on the interface between the superconducting coil and the winding frame, the tensile stress causes the resin to peel, and the frictional heat generated during the peeling may quench the superconducting coil (normal conduction transition). There was a problem of lack of stability.

Further, with the above structure, since the winding frame exists inside the superconducting coil, the effective bore diameter of the superconducting coil is limited by the winding frame, and there is a problem of lack of applicability as a device.

[0007]

As described above, in the conventional superconducting magnet device directly connected to the refrigerator, it is essentially difficult to ensure the stability of the superconducting coil, and the superconducting coil is Since the effective bore diameter is limited, there is a problem of lack of applicability as a device. Therefore, an object of the present invention is to provide a superconducting magnet device of a refrigerator direct connection type capable of solving the above-mentioned problems.

[0008]

In order to achieve the above object, a superconducting magnet device according to the present invention comprises a superconducting coil,
A heat absorbing member formed of a good heat conducting member and thermally connected to the outer circumferential surface of the superconducting coil, a cooling stage, and a refrigerator for conducting and cooling the heat absorbing member by the cooling stage are provided.

[0009]

In the superconducting magnet device according to the present invention, the bobbin used when manufacturing the superconducting coil is removed. now,
If the heat-absorbing member is formed in a tubular shape that almost covers the outer peripheral surface of the superconducting coil and the superconducting coil and the heat-absorbing member are integrated by resin impregnation, the superconducting coil is cryogenic by conduction through the heat-absorbing member. The following phenomenon occurs when the superconducting coil is energized in this state when it is cooled down. That is, when the superconducting coil is cooled to an extremely low temperature via the heat absorbing member, the superconducting coil changes to the superconducting state. At this time, both the heat absorbing member and the superconducting coil thermally contract in the radial direction. When the superconducting coil is energized in this state, the superconducting coil is deformed by the electromagnetic force so as to expand outward in the radial direction. For this reason, compressive stress acts on the interface between the superconducting coil and the heat absorbing member, and the resin is unlikely to peel off at the interface. Therefore, it is possible to effectively prevent the quenching that tends to occur when the superconducting coil is energized.

Further, since there is no winding frame inside the superconducting coil, the effective bore diameter of the superconducting coil is not limited, and the applicability as a device can be expanded.

[0011]

Embodiments will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a superconducting magnet device according to an embodiment of the present invention. This superconducting magnet device is roughly provided with a vacuum container 1 that is evacuated so that the inside is in a vacuum atmosphere. The vacuum container 1 is formed of a non-magnetic material such as stainless steel. Holes 4a and 4b are provided in the upper wall 2 and the lower wall 3 of the vacuum container 1 so as to face each other, and a cylinder made of a non-magnetic material such as stainless steel so as to communicate these holes 4a and 4b. Body 5
Both ends of the are connected airtightly to the inner surfaces of the upper wall 2 and the lower wall 3. Therefore, the inside of the cylindrical body 5 is kept at atmospheric pressure and the outside is kept in a vacuum atmosphere.

In the vacuum atmosphere around the cylindrical body 5, the cylindrical body 5
A superconducting coil 6 is arranged in a non-contact manner with and concentrically with the tubular body 5, and the superconducting coil 6 is thermally connected to the heat conducting member 8 via the heat absorbing member 7. The heat conducting member 8 is a cryogenic refrigerator, in this example, a Gifode-McMahon type refrigerator (hereinafter abbreviated as GM refrigerator) 9.
Connected to the cooling stage.

The GM refrigerator 9 has a first-stage cooling stage 10 cooled to about 30K and a second-stage cooling stage 1 cooled to about 4K or less (below the superconducting transition temperature of a superconducting wire).
1, and each cooling stage is attached to the vacuum container 1 using a mounting hole (not shown) provided on the upper wall 2 of the vacuum container 1 so that each cooling stage is located in the vacuum container 1. The heat conducting member 8 is thermally and mechanically connected to the second cooling stage 11.

The superconducting coil 6, the heat absorbing member 7 and the heat conducting member 8 are specifically constructed as shown in FIGS. 2 and 3. That is, in this example, the superconducting coil 6 is made of a metal superconducting wire such as NbTi alloy coated with an electrical insulating material, a compound superconducting wire such as Nb ₃ Sn coated with an electrical insulating material, or an oxide superconducting wire. Has been formed. Specifically, after winding these superconducting wires around the outer circumference of the reel a predetermined number of times, the resin is impregnated with a resin having a relatively high thermal conductivity such as epoxy resin and cured, and then the reel is entirely removed. , Is formed into a cylindrical shape with a predetermined accuracy.

The heat absorbing member 7 is made of a good heat conductive metal material such as copper or aluminum and has a cylindrical shape whose inner diameter is larger than the outer diameter of the superconducting coil 6 by a predetermined amount and whose axial length is slightly longer than that of the superconducting coil 6. The tubular portion 12 and the annular portion 13 integrally formed with the tubular portion 12 so as to project inward from the inner surface of the tubular portion 12 at one end side. The tubular portion 12 and the annular portion 13 are provided with notches 14 extending in the axial direction so as to prevent circumferential eddy current passages from being formed therein. In addition, the annular portion 13
Is a fraction of the radial thickness t of the superconducting coil 6.
Is set to.

As shown in FIG. 3, the superconducting coil 6 is inserted into the heat absorbing member 7 having the above-mentioned structure. In this state, the superconducting coil 6 and the tubular portion 12 and the annular portion 13 are made of epoxy resin or the like. It is adhered and fixed by the impregnated resin layer 15.

On the other hand, as shown in FIG. 2, the heat conducting member 8 is made of a good heat conducting metal material such as copper or aluminum and has an outer diameter of the same as the outer diameter of the cylindrical portion 12 and an inner diameter of the annular portion 13. It is composed of an annular portion 16 that is larger than the inner diameter by a predetermined amount, and a portion 17 that integrally extends from this portion 16.
A cut 18 is formed in the portion 16 in order to prevent a circumferential eddy current passage from being formed in this portion.

In the heat conducting member 8 thus formed, the portion 16 is applied to the outer surface of the annular portion 13 so that the notch 18 is aligned with the notch 14 provided in the heat absorbing member 7,
In this state, the portion 16 is screwed to the annular portion 13. That is, the portion 16 and the annular portion 13 are thermally and mechanically connected by the screwing. The portion 17 is thermally and mechanically connected to the second cooling stage 11 of the GM refrigerator 9 described above.

As can be seen from the above structure, the superconducting coil 6
Is thermally connected to the second stage cooling stage 11 of the GM refrigerator 9 via the heat absorbing member 7 and the heat conducting member 8, and its load is passed through the heat absorbing member 7 and the heat conducting member 8 to the GM refrigerator 9 Supported by.

Note that, in FIG. 1, a current lead system for energizing the superconducting coil 6 from the outside, a heat shield plate for preventing heat intrusion due to radiation from the vacuum chamber constituent wall, a vacuum exhaust system, etc. are directly applied to the present invention. Irrelevant elements are omitted.

With this structure, when the GM refrigerator 9 is started, the temperatures of the first and second cooling stages 10 and 11 of the GM refrigerator 9 are lowered. As a result, the sensible heat of the superconducting coil 6, the heat absorbing member 7 and the heat conducting member 8 is transmitted to the second cooling stage 11 by conduction,
It is absorbed by the GM refrigerator 9 through the second cooling stage 11. Therefore, these are gradually cooled. Then, finally, the superconducting coil 6, the heat absorbing member 7, and the heat conducting member 8 are cooled to a temperature close to the minimum reached temperature of the second stage cooling stage 11, that is, 4K or less.

When the superconducting coil 6 and the heat absorbing member 7 are cooled to an extremely low temperature in this way, they contract heat. Further, at this temperature, the wire material forming the superconducting coil 6 transitions to the superconducting state.

When excitation of the superconducting coil 6 is started in this state and the current value is gradually increased toward the target level, the electromagnetic force generated between the lines also gradually increases. This electromagnetic force acts as a force for expanding the superconducting coil 6 outward in the radial direction.

In this case, the force for expanding the superconducting coil 6 outward in the radial direction acts as a compressive force on the interface between the superconducting coil 6 and the heat absorbing member 7. Therefore, the resin is unlikely to peel off at the interface. Further, even if peeling occurs, the peeling position is near the outer peripheral surface of the superconducting coil 6, that is, a place where the magnetic field is weaker than the inner periphery (the critical current of the superconducting wire is usually higher at higher temperature and stronger magnetic field). Quench is unlikely to occur. Further, although an eddy current tends to flow through the heat absorbing member 7 and the heat conducting member 8 at the time of excitation (demagnetization), the cylindrical portion 12 and the annular portion 13 and the heat conducting member 8 constituting the heat absorbing member 7 are constituted. The portion 16 is located near the outer peripheral surface of the superconducting coil 6 in a place where the magnetic field is weak, and a cut 1 for preventing an eddy current passage in the circumferential direction from being formed in these portions.
Since Nos. 4 and 18 are provided, the eddy current can be suppressed to a small value, and quenching due to heat generation due to the eddy current can be prevented. Therefore, it is possible to effectively prevent the quenching that tends to occur when the superconducting coil 6 is energized.

Further, with the above structure, the superconducting coil 6
Since there is no winding frame inside, the effective bore diameter of the superconducting coil 6 is not limited, and the applicability as a device can be expanded.

Further, in this embodiment, the superconducting coil 6
Since the load of (1) is supported by the GM refrigerator 9 via the heat absorbing member 7 and the heat conducting member 8, there is also an advantage that the structure can be simplified.

The superconducting magnet device configured as described above is
It is suitable as a magnetic field source for an NMR spectrometer for physicochemical analysis or a semiconductor single crystal pulling apparatus, but of course it can be used for other purposes. The thickness of each part of the heat absorbing member 7 and the thickness of the heat conducting member 8 are optimal in consideration of the material used, the heat capacity of the superconducting coil 6, the amount of heat intrusion due to radiation, the weight of the superconducting coil 6 and the like. Set to the value.

The present invention is not limited to the above-mentioned embodiments, but can be modified in various ways. For example, in the above-described embodiment, the resin-impregnated superconducting coil 6 is prepared in advance, and this is inserted into the tubular portion 12 of the heat absorbing member 7. In this state, the superconducting coil 6 and the heat absorbing member 7 are made of resin. It is impregnated and adhered, but
The superconducting coil not impregnated with the resin may be housed in the tubular portion of the heat absorbing member, and in this state, the resin may be impregnated to simultaneously impregnate the superconducting coil and bond the impregnating member to the heat absorbing member. By doing so, the number of manufacturing steps can be reduced. Also, the impregnation method is not limited to impregnation after winding,
A semi-cured fiber reinforced plastic (FRP) such as prepreg glass may be sandwiched between winding layers and wound, and then the winding may be heated to form an impregnated body. The resin-impregnated superconducting coil and the tubular portion of the heat absorbing member may be fitted together by a so-called shrink fit method, or the resin may be impregnated after the shrink fitting to impregnate the superconducting coil and the heat absorbing member. You may make it adhere | attach.

Further, as shown in FIG. 4, contact heat resistance can be reduced by using an indium ribbon or an indium sheet between the resin-impregnated superconducting coil 6 and the heat absorbing member 7, or beryllium or grease instead of indium. You may make it interpose the inclusion 19 which does not exist. By doing so, the thermal resistance between the superconducting coil 6 and the heat absorbing member 7 can be reduced.

Further, as shown in FIG. 5, the resin-impregnated superconducting coil 6 and the heat absorbing member 7 are impregnated and bonded, or an inclusion 19 such as an indium ribbon or an indium sheet is interposed between the superconducting coil 6 and the heat absorbing member 7. After this, the winding 20 may be provided on the outer circumference of the heat absorbing member 7 at room temperature, and the impregnating resin layer and the inclusions 19 may be prestressed by the tightening force of the winding 20. By doing so, it is possible to prevent an increase in the thermal resistance between the superconducting coil 6 and the heat absorbing member 7 due to the difference in the amount of heat shrinkage at extremely low temperatures.

Further, as shown in FIG. 6, the winding is carried out by using a winding frame made of FRP having good adhesiveness with the epoxy resin, and then impregnation with the epoxy resin is carried out to form the flange portions 21a and 21b of the winding frame. Is formed, the superconducting coil 6a is formed, and the superconducting coil 6a is connected to the tubular portion 12 of the heat absorbing member 7.
Then, the superconducting coil 6a and the heat absorbing member 7 may be impregnated and bonded with an epoxy resin or the like. By doing this, FR
Since the flange portions 21a and 21b made of P have low mechanical strength, even if peeling occurs at the interface between the superconducting coil 6a and the flange portions 21a and 21b, the amount of heat generated is small and quenching does not occur. In addition, the flange portion 21a,
Due to the presence of 21b, the superconducting coil 6a can be mechanically protected.

Further, as shown in FIG. 7, a good heat conducting wire 23 such as a copper wire, an aluminum wire or another superconducting wire is provided on the outside of the winding portion 22 formed by winding the superconducting wire, and the adjusting winding 24 is provided.
Winding, and impregnating them with resin, and then adjusting winding 24
A superconducting coil 6b having a good heat conducting wire 23 exposed by cutting the outer peripheral portion of is prepared, and the superconducting coil 6b and the tubular portion 12 of the heat absorbing member 7 are fitted by so-called shrink fitting. Alternatively, the resin may be impregnated after shrink fitting, and the superconducting coil 6b and the heat absorbing member 7 may be impregnated and bonded. The superconducting coil 6b and the heat absorbing member 7 may be directly impregnated and adhered, a soft metal such as indium may be interposed therebetween, or a SUS band may be adhered.

In the embodiment shown in FIG. 1, the load of the superconducting coil 6 and the force applied thereto are supported by the GM refrigerator 9 via the heat absorbing member 7 and the heat conducting member 8. As shown in FIG.
Between the upper wall 2 of the vacuum container 1 and the vacuum vessel 1
5 may be provided and supported by the suspension bolt 25 and the GM refrigerator 9. In this case, part 1
It is possible to use the heat conducting member 8a provided with only 7.

Further, in the embodiment shown in FIG. 1, the heat absorbing member 7
A notch 14 extending in the axial direction is provided in the tubular portion 12 and the annular portion 13 that form the above, and the notch 14 cuts the circumferential eddy current passage. As shown in FIG. 9 (a), In the notch 14, a non-magnetic member having a high resistivity such as stainless steel or aluminum nitride is used as the filler 26.
Alternatively, the mechanical strength of the heat absorbing member 7a may be ensured in a state where the eddy current passage is blocked by welding or brazing this to the tubular portion 12 and the annular portion 13.

Further, as shown in FIG. 9 (b), the cylindrical portion 12
And the annular portion 13 are made of stainless steel having high resistivity, non-magnetism, and high mechanical strength.
A good heat conducting layer 27 made of aluminum, copper or the like is provided on the inner surface of the annular portion 13 so as to form at least one separating portion 28 in the circumferential direction by plating, vapor deposition, bonding or the like. Alternatively, the heat absorbing member 7b configured to cool the superconducting coil via may be used. That is, in this case, conduction cooling is performed by the good heat conduction layer 27, and mechanical strength is maintained by the tubular portion 12 and the annular portion 13. In this case, it is not necessary to make a cut in the cylindrical portion 12 and the annular portion 13, and the separation portion 28 blocks the eddy current passage.

In each of the above-mentioned embodiments, only one superconducting coil is provided. However, when two superconducting coils 6 are provided, for example, as shown in FIG. A flange portion 29 projecting outward is integrally provided on the heat absorbing member 7c for conducting and cooling, and a heat absorbing member 7d for conducting and cooling the outer superconducting coil 6 is thermally and mechanically connected to the flange portion 29 to form a heat absorbing member 7d. May be thermally connected to a cooling stage of a refrigerator (not shown). In this case, heat generation due to eddy current can be suppressed by providing a plurality of notches extending in the radial direction in the flange portion 29 in the circumferential direction.

Further, in each of the above-mentioned embodiments, the superconducting coil is conductively cooled through the outer peripheral surface of the superconducting coil. However, as shown in FIG. Heat guide member 3 formed in a foil shape, a ribbon shape, a net shape, or the like
Superconducting coil 6c obtained by impregnating 0 in which resin is impregnated
The heat guide member 30 is connected to the annular portion 1 of the heat absorbing member 7e.
The superconducting coil 6c may be cooled by conduction through the tubular portion 12a and the heat guide member 30 by making thermal contact with the 3a. In this case, since the cooling performance is improved as compared with the case of cooling from only the outer peripheral surface, the axial length of the tubular portion 12a can be shortened and the weight can be reduced. Although the wire forming the superconducting coil is provided with an insulating coating, this wire and the heat guide member 3
An insulating coating may be provided on the surface of the heat guide member 30 in order to secure the electrical insulation between the heat guide member 30 and the heat guide member 30.

When sufficient cooling performance can be obtained by the heat guide member 30, as shown in FIG. 11 (b), it is possible to use the heat absorbing member 7f with the tubular portion omitted. Further, in the example shown in FIG. 1, the heat absorbing member 7 including the tubular portion 12 and the annular portion 13 is used, but as shown in FIG. 12, it is formed of a good heat conductive metal material in a gutter shape. The heat absorbing member 7g including the portion 31 and the heat conducting member 32 whose one end side is thermally and mechanically connected to the portion 31 may be used. In this case, the superconducting coil 6 is impregnated and bonded to the concave surface of the portion 31 with resin or the like. When actually arranging the superconducting coil 6 in a vacuum container (not shown), the superconducting coil 6 is placed downward, the axis 31 of the superconducting coil 6 is set horizontally, and the conduction cooling of the superconducting coil 6 and the superconducting coil 6 are performed. The load supporting may be performed by the heat absorbing member 7g. Further, when a relatively low magnetic field is generated, the superconducting coil can be formed of an oxide-based superconducting wire.

[0039]

As described above, according to the present invention,
It is possible to ensure the stability of the superconducting coil and contribute to effective use of the bore diameter of the superconducting coil.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a superconducting magnet device according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view showing a superconducting coil, a heat absorbing member, and a heat conducting member in the same device.

FIG. 3 is a sectional view for explaining a thermal coupling configuration between a superconducting coil and a heat absorbing member in the same device.

FIG. 4 is a cross-sectional view for explaining another example of the thermal coupling structure between the superconducting coil and the heat absorbing member.

FIG. 5 is a sectional view for explaining still another example of the thermal coupling configuration between the superconducting coil and the heat absorbing member.

FIG. 6 is a sectional view for explaining an example of a different thermal coupling configuration between the superconducting coil and the heat absorbing member.

FIG. 7 is a cross-sectional view for explaining a further different example of the thermal coupling configuration between the superconducting coil and the heat absorbing member.

FIG. 8 is a cross-sectional view showing another example of load supporting means for a superconducting coil.

FIG. 9 is a top view showing a modified example of the heat absorbing member.

FIG. 10 is a cross-sectional view locally showing a configuration example of a heat absorbing member when two superconducting coils are arranged in a concentric circle shape.

FIG. 11 is a local cross-sectional view for explaining respective modified examples of the thermal coupling configuration of the superconducting coil and the heat absorbing member.

FIG. 12 is a local perspective view for explaining another modified example of the thermal coupling structure between the superconducting coil and the heat absorbing member.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Vacuum container 2 ... Upper wall 3 ... Lower wall 4a, 4b ... Hole 5 ... Cylindrical body 6, 6a, 6
b, 6c ... Superconducting coil 7, 7a, 7b, 7c, 7d, 7e, 7f, 7g ... Heat absorption member 8, 8a, 32 ... Heat conduction member 9 ... GM refrigerator 10 ... First stage cooling stage 11 ... Second stage Cooling stage 12, 12a ... Cylindrical part 13, 13a ...
Annular portion 14, 18 ... Notch 15 ... Impregnated resin layer 16, 17 ... Part 19 ... Inclusion 20 ... Winding 24 ... Adjusting winding 25 ... Suspension bolt 26 ... Filler 27 ... Good heat conduction layer 28 ... Separation part 29 ... Collar part 30 ... Heat guide member 31 ... Gutter-shaped part

Front page continuation (72) Hideaki Maeda, 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Inside Toshiba Research & Development Center, Inc. (72) Hideki Nakagome 1 Komukai-shiba, Kawasaki, Kanagawa Incorporated company Toshiba Research and Development Center (72) Inventor Masami Urata No. 1 Komukai Toshiba-cho, Kouki-ku, Kawasaki-shi, Kanagawa Incorporated company Toshiba Research and Development Center

Claims (3)

[Claims] 1. A superconducting coil, a heat absorbing member formed of a good heat conducting member and thermally connected to an outer peripheral surface of the superconducting coil, and a cooling stage. The cooling stage conductively cools the heat absorbing member. A superconducting magnet device comprising a refrigerator. 2. The superconducting magnet device according to claim 1, wherein the heat absorbing member includes a cylindrical portion that substantially covers an outer peripheral surface of the superconducting coil. 3. The superconducting magnet device according to claim 1, wherein the heat absorbing member also serves as a supporting member for supporting the superconducting coil.