JP2003022907A - Superconducting magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a superconducting magnet which makes simple the connecting constitution of a refrigerator with a superconductor coil and the assembling work thereof, improves the maintainability of the refrigerator, effectively removes heat resulting from the AC loss and stably operates it, without causing the conductive dislocation. SOLUTION: The magnet comprises a superconducting coil 1 composed of a superconducting wire wound around a bobbin in layers and cooling flanges 4A for supporting it, and a vacuum container 3 for heat-insulating and housing the coil 1. Using an attached refrigerator, the coil 1 is cooled to hold it at cryogenic temperatures. The refrigerator is disposed outside the container 3 and a cooling plate 12 disposed well heat conductively with the cooling flange 4A of the coil 1 is cooled at specified temperatures with a refrigerant gas produced by the refrigerator at cryogenic temperatures to cool the coil 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting magnet used for component analysis and energy storage utilizing a strong magnetic field, and more particularly to a superconducting magnet for cooling a superconducting coil using a refrigerator.

[0002]

2. Description of the Related Art A conventional superconducting magnet is mainly a system in which a superconducting coil is cooled by liquid helium, and the running cost for maintaining the superconducting coil at an extremely low temperature of liquid helium (about 4K) is extremely high and practically used. Although it was a big problem, in recent years, with the improvement of the critical temperature of the superconducting wire and the improvement of the refrigerating capacity of the refrigerator, a superconducting magnet of the type in which a refrigerator is attached to the superconducting coil and the superconducting coil is cooled by heat conduction Has been actively developed and patent proposals have been made (for example, JP-A-63-186403, JP-A-64-76706, JP-A-11-13).
5318).

FIG. 7 is a sectional view schematically showing the basic structure of a conventional refrigerator-cooling type superconducting magnet disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 11-135318, which has a room temperature high magnetic field space. 2 is a cross section of the superconducting magnet passing through the central axis.

In FIG. 7, reference numeral 1 is a superconducting coil formed by winding a superconducting wire in a solenoid shape, 2 is a radiation shield which is arranged around the superconducting coil 1, and which shields heat radiation from the outside and insulates it. Is a vacuum container that surrounds these and keeps the inside of the vacuum state to insulate them. Further, 7 is a refrigerator that cools the superconducting coil 1, 8 is a compressor that supplies compressed helium gas to the refrigerator 7 and has a refrigeration cycle operation control system, and 9 is a current that is supplied to the superconducting coil 1 from a power source (not shown). It is a current lead that is excited by.

As shown in FIG. 7, the refrigerator 7 is connected to one of the cooling flanges 4 and the radiation shield 2 for supporting the superconducting coil 1 wound in layers on the cooling bobbin 5 from above and below. 1 to a predetermined cryogenic temperature (about 20-80
K) and the radiation shield 2 at a predetermined cryogenic temperature (about 80-
Cool to 100K).

The cooling flange 4 on the lower side of the drawing by the refrigerator 7
The cooling bobbin 5, the cooling outer cylinder plate 6, and the upper cooling flange 4 connected to the cooling bobbin 5 are cooled by heat conduction by cooling one end of the superconducting coil 1, and the superconducting coil 1 surrounded by these is superconducting by heat conduction. It is cooled to a temperature below its critical temperature and kept in a superconducting state. When current is supplied to the superconducting coil 1 using the current lead 9 in the superconducting state, a strong magnetic field is generated, and at the same time, magnetic energy proportional to the inductance is accumulated in the superconducting coil 1.

When the superconducting coil 1 is operated so as to generate AC loss, the internal temperature of the coil rises due to heat generation due to AC loss. If this heat generation cannot be removed, the superconducting coil 1 will be transferred from the superconducting state to the normal conducting state by exceeding the critical temperature, stable energization will not be possible, and the coil may be damaged by the normal conducting transition (quenching). is there.

An example of the structure of the superconducting coil for suppressing the risk of the normal conducting dislocation as described above is described in the above-mentioned JP-A-11-135318. In the structure described in the above publication, a conductive cooling plate made of a good heat conductive material such as copper or copper alloy is incorporated between the layers of the superconducting wire wound in layers on the cooling bobbin 5 for conduction. Both ends of the cooling plate are inserted into the grooves provided in the upper and lower cooling flanges 4 in FIG. According to this configuration, the inside of the superconducting coil is cooled to a predetermined temperature below the critical current by heat transfer through the conduction cooling plate, so that the superconducting coil can be operated without causing a normal conduction dislocation.

Next, an outline of the superconducting magnet described in the above-mentioned Japanese Patent Laid-Open Nos. 63-186403 and 64-76706 will be described below.

In FIG. 1 of Japanese Patent Application Laid-Open No. 63-186403, as in the case of FIG.
A configuration is disclosed in which one low temperature end of the multistage refrigerator is connected to a superconducting coil cooling pipe and the other low temperature end having a high temperature level is connected to a radiation shield cooling pipe. The superconducting coil cooling pipe is wound around the outer periphery of the cylindrical superconducting coil, and a cryogenic refrigerant gas is passed through the pipe to cool the superconducting coil.

Further, in Japanese Patent Laid-Open No. 64-76706, a heat exchanger and an adiabatic expansion valve, which are main components of a refrigerator, are built in a vacuum container, and a cryogenic refrigerant gas is used for a winding portion of a superconducting coil. There is disclosed a structure in which the superconducting coil is cooled by flowing the gas through the.

[0012]

The conventional superconducting magnet, which has a refrigerator and cools the superconducting coil by heat conduction, has the following problems.

When the refrigerator or the main components of the refrigerator are built in the vacuum container, the connecting structure and assembling work between the refrigerator and the superconducting coil become complicated.
In addition, it is necessary to break the vacuum in the vacuum container to normal pressure when the refrigerator is regularly maintained or fails, which causes a problem of poor maintainability. Further, in the case of a superconducting coil in which AC loss occurs, there are the following problems due to the lack of built-in capacity of the refrigerator.

The refrigerating capacity of a small refrigerator is generally about 20 W at 20 K, and in the case of a superconducting coil having a large AC loss, the refrigerating capacity is insufficient and the superconducting coil cannot be kept at a predetermined temperature. There is also a method of increasing the number of refrigerators to deal with it, but it is difficult to arrange a large number of refrigerators in a vacuum container due to the limitation of the installation space. In particular, the refrigerator needs to be installed in a low magnetic field, and it is not desirable to place it in the vicinity of the superconducting coil. If the distance from the refrigerator to the superconducting coil becomes long, effective cooling cannot be expected. Therefore, installation of a large number of refrigerators becomes even more difficult.

When the capacity of the refrigerator is insufficient, the operation of the superconducting coil is restricted, and not only the prescribed performance cannot be exhibited, but also there is a possibility that the superconducting coil is transferred to normal conduction and stable energization cannot be performed.

The present invention has been made to solve the above problems, and an object of the present invention is to simplify the connection construction and assembling work of a refrigerator and a superconducting coil, and to maintain the refrigerator. Another object of the present invention is to provide a superconducting magnet which has good properties and which can effectively remove heat generated by AC loss and can be stably operated without causing a normal conduction transition.

[0017]

In order to solve the above-mentioned problems, the present invention has a superconducting coil in which layers are wound around a superconducting wire and supported by a cooling flange, and the superconducting coil is heat-insulated and accommodated. A superconducting magnet comprising a vacuum container, cooling the superconducting coil using an attached refrigerator, and maintaining the cryogenic temperature in the superconducting magnet, the refrigerator is installed outside the vacuum container, and a cooling flange of the superconducting coil. The superconducting coil is cooled by cooling the cooling plate arranged in good heat conduction to a predetermined temperature with the cryogenic refrigerant gas generated in the refrigerator (invention of claim 1).

According to the invention of claim 1, since the refrigerator is installed outside the vacuum container and the refrigerant gas pipe of the refrigerator is connected to the cooling plate of the superconducting coil, the refrigerator and the superconducting coil are connected. The connection configuration with and becomes simple, and the maintainability of the refrigerator is improved. Further, when the AC loss of the superconducting coil increases, the temperature inside the superconducting coil can be kept below a predetermined temperature by appropriately selecting the refrigerant gas temperature and the flow rate.

Further, in the invention of claim 1, the cooling plate is made of a nonmagnetic material having good heat conductivity, and a flow passage for the cryogenic refrigerant gas is formed therein ( The invention of claim 2). As described above, by using the material having good heat conductivity, the temperature difference between the heat transfer peripheral surface in contact with the refrigerant gas and the heat transfer portion between the superconducting coil is suppressed,
The superconducting coil can be cooled effectively. Further, in the cooling plate, for example, by configuring the flow path of the refrigerant gas so that the refrigerant gas flows in zigzag, the cooling plate itself can be downsized while ensuring the heat transfer length, and the cooling plate itself. The temperature distribution can be made uniform. Therefore, the superconducting coil can be effectively cooled with a simple structure. Furthermore, since the cooling plate is made of a non-magnetic material, it can be arranged in the vicinity of the superconducting coil, so that the length required for heat conduction can be shortened as much as possible and effective cooling can be achieved.

From the viewpoint of improving the cooling performance of the superconducting coil, the coolant gas flow passage may be provided directly on the cooling flange, and the cooling plate in the invention of claim 1 or 2 may be omitted. Further, from the viewpoint of further improving the cooling performance, it is preferable to configure as the invention of claim 3 below. That is, in the superconducting magnet according to any one of claims 1 to 3, the cooling plates are provided on the cooling flanges on the upper and lower sides of the superconducting coil. Also in this case, the cooling performance can be further improved by directly providing the cooling gas flow passage on the cooling flange.

Further, in the superconducting magnet according to any one of claims 1 to 3, after the refrigerant gas that has cooled the cooling plate is passed through a current lead for supplying a current to the superconducting coil to cool the current lead. It is configured to flow back to the refrigerator (the invention of claim 4).

As a result, not only the superconducting coil but also the current lead is cooled by the refrigerant gas, so that the amount of heat penetrating through the current lead is significantly reduced, which is negligible compared to the heat loss in the superconducting coil. Become. Therefore, the temperature inside the superconducting coil can be easily kept below a predetermined temperature without being affected by the amount of heat entering through the current lead.

Furthermore, in the superconducting magnet according to any one of claims 1 to 4, a radiation shield is provided in the vacuum container to block heat radiation to the superconducting coil from the outside. The radiation shield is cooled by a small single-stage refrigerator provided separately from the refrigerator (the invention of claim 5).

As a result, the radiation shield can be effectively cooled to 80 to 100K by the dedicated small single-stage refrigerator.
The cooling efficiency of the superconducting coil is improved. From the viewpoint of improving maintainability, it is desirable to provide the refrigerator dedicated to the radiation shield also outside the vacuum container, but it is easier to work as compared to connecting the refrigerator to the superconducting coil, and also in terms of temperature. It can also be provided in a vacuum vessel, since at a high level the thermal coupling level may be relatively simple.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an enlarged sectional view showing a superconducting coil portion of an embodiment of a superconducting magnet according to the present invention, which is partially simplified as compared with the conventional example of FIG. Also,
In FIG. 1, members having the same functions as those of the constituent members in FIG. 7 are designated by the same reference numerals and the description thereof is partially omitted.

In this embodiment, the superconducting wire is wound around the cooling bobbin 5 to form the superconducting coil 1, and the upper and lower cooling flanges 4A and 4B and the cooling outer cylinder plate 6 are arranged around the superconducting coil 1. The cooling flange 4A is thermally conductively connected to the cooling plate 12. The cooling plate 12 is thermally connected to the cooling pipe 20, and these both constitute a heat exchanger. These are arranged in the vacuum container 3.

The cooling pipe 20 is connected to a refrigerator (not shown) capable of supplying a cryogenic refrigerant gas outside the vacuum container 3, and the cryogenic refrigerant gas is passed through the cooling pipe 20. By doing so, the superconducting coil 1 is cooled by heat conduction via the cooling plate 12 and the cooling flange 4A, and is maintained at an extremely low temperature.

When the superconducting coil is operated with AC loss, the superconducting coil 1 generates heat, but this heat is removed by the refrigerant gas flowing through the cooling pipe 20 through the heat conduction path. Therefore, even when AC loss is involved, the heat generation of the superconducting coil is removed, so that the temperature rise of the superconducting coil can be suppressed low. The amount of heat transfer capable of heat exchange can be set by the refrigerant flow rate and the refrigerant temperature. By setting the heat transfer amount corresponding to the heat generation of the superconducting coil, the superconducting coil can be maintained at a predetermined temperature and stable energization becomes possible.

In the configuration of the embodiment of FIG. 1 described above (the same applies to the configurations of the following embodiments), particularly when the superconducting coil 1 is operated so as to generate AC loss, As described in Japanese Patent Laid-Open No. 11-135318, as a means for enhancing the conduction cooling inside the superconducting coil 1, for example, a conduction cooling plate (not shown) is provided between layers of the superconducting wire wound in layers on the cooling bobbin 5. It is desirable that the inside of the winding can be effectively cooled from the axial end portion by incorporating the above structure into the groove (not shown) in which both ends are provided in the upper and lower cooling flanges 4A and 4B. .

FIG. 2 shows a plan view of an embodiment in which a part of the cooling pipe 20 of FIG. 1 is integrated with the cooling plate 12. Cooling plate 1
A coolant gas passage 24 is provided inside the coolant 2, and the coolant gas passage 24 is connected to the cooling pipe 20. The coolant gas flow path 24 is formed in a zigzag pattern on the cooling plate 12, and has a length that allows the coolant gas to sufficiently transfer heat to the cooling plate.
Thereby, heat exchange can be effectively performed between the refrigerant gas and the cooling plate 12, and as a result, the superconducting coil can be cooled well. Further, as the material of the cooling plate 12, a non-magnetic material having good thermal conductivity is suitable, and copper, aluminum nitride or the like is preferable.

Next, FIGS. 3 and 4 are schematic enlarged sectional views of a superconducting coil portion of a superconducting magnet according to an embodiment different from that shown in FIG. According to FIG. 3, the cooling pipe 20 is in thermal contact with the cooling plate 12A and then in thermal contact with the cooling plate 12B. The cryogenic refrigerant gas first flows into the cooling plate 12
A, the superconducting coil 1 is cooled via the cooling flange 4A. Here, although the temperature of the refrigerant gas rises slightly, it has the ability to further cool, so that the superconducting coil 1 can be cooled via the cooling plate 12A and the cooling flange 4B. As a result, the inside can be cooled from both ends of the superconducting coil.

FIG. 4 shows an embodiment in which the flow passage for the refrigerant gas is provided directly on the cooling flange. In the embodiment shown in FIG. 4, the cooling pipe 20 is in thermal contact with the cooling flange 4A and then with the cooling flange 4B. Since the cooling pipe 20 directly contacts the cooling flange, the contact thermal resistance can be reduced and the temperature difference between the refrigerant and the superconducting coil can be reduced.

Next, FIG. 5 shows a configuration in which the refrigerant gas flowing through the cooling plate 12 is used for cooling the current leads. After the cooling pipe 20 is connected to the cooling plate 12,
It branches into a bypass pipe 25 and a connection pipe 26. The bypass bus pipe 25 is provided to adjust the amount of refrigerant gas supplied to the current lead 9. The connection pipe 26 has a structure in which it is electrically insulated from the current lead by an insulating pipe (not shown) and is connected to the current lead 9.

According to this structure, since the current lead is cooled by using the refrigerant gas, the amount of heat intrusion of the current lead is, for example, about 1.2 W / kA, which is a conduction cooling method (not cooled by the refrigerant gas. It can be significantly reduced compared to the method). Since the lower end of the current lead 9 is cooled to almost the same temperature as the superconducting coil 1, the current lead 9 and the superconducting coil 1 are electrically connected using the high temperature superconducting conductor 13.
The high-temperature superconducting conductor 13 has an electric resistance of almost zero, does not generate Joule heat, has a thermal conductivity of about 1/100 of that of metal, and the amount of heat entering the superconducting coil can be suppressed to a negligible level. Therefore, most of the cooling capacity of the refrigerant gas can be used for the superconducting coil, which is suitable for removing heat from the large coil.

Further, the cooling pipe 20 and the bypass pipe 25
The atmosphere side pipe 27 is connected to an externally installed refrigerator having a refrigerant gas circulation function. Atmosphere side pipe 27
The temperature of the refrigerant flowing through is approximately room temperature, and after cooling to a predetermined temperature by the refrigerator, the superconducting coil is cooled by supplying it to the cooling pipe 20.

FIG. 6 shows an embodiment in which the low temperature end of a dedicated single-stage refrigerator is connected to the radiation shield. The radiation shield 2 is connected to the small single-stage refrigerator 7a and cooled. With this configuration, the radiation shield is cooled by the dedicated refrigerator regardless of the supply of the refrigerant gas for cooling the superconducting coil.
Generally, when the superconducting coil 1 is out of operation, the supply of the refrigerant gas is also stopped, but at this time, the temperature of the superconducting coil rises. According to the configuration shown in FIG. 6, the radiation shield 2 can be continuously cooled by continuously operating the refrigerator 7a, so that the superconducting coil can be cooled through the superconducting coil support member (not shown). At this time, the temperature cannot be cooled to the temperature during operation, but the cooling time from the restart of the supply of the refrigerant gas for cooling the superconducting coil to the start of operation can be shortened. In this case, since the operation can be restarted promptly, the superconducting coil can be operated efficiently.

[0038]

According to the present invention, as described above, the superconducting wire is wound around the winding frame in layers and supported by the cooling flange, and the vacuum container for insulating and housing the superconducting coil is provided. , In a superconducting magnet that cools a superconducting coil using an attached refrigerator, and holds it at a cryogenic temperature, the refrigerator is installed outside the vacuum container, and the cooling flange of the superconducting coil and heat conduction Since the arranged cooling plate is configured to cool the superconducting coil by cooling it to a predetermined temperature with the cryogenic refrigerant gas generated in the refrigerator, the connecting configuration and assembling work of the refrigerator and the superconducting coil are performed. Is simple, and the maintainability of the refrigerator is improved. Further, since heat generation due to AC loss in the superconducting coil is effectively removed, the superconducting coil can be stably operated without causing a normal conduction transition.

[Brief description of drawings]

FIG. 1 is a schematic enlarged sectional view of a superconducting coil portion of a superconducting magnet according to an embodiment of the present invention.

FIG. 2 is a plan view of an embodiment of a cooling plate according to the present invention.

FIG. 3 is a schematic enlarged cross-sectional view of a superconducting coil portion of a superconducting magnet of an embodiment different from FIG.

FIG. 4 is a schematic enlarged cross-sectional view of a superconducting coil portion of a superconducting magnet of an embodiment different from FIG.

FIG. 5 is a schematic sectional view of a superconducting magnet according to another embodiment of the present invention.

FIG. 6 is a schematic cross-sectional view of a superconducting magnet of still another embodiment of the present invention.

FIG. 7 is a cross-sectional view schematically showing the basic configuration of a conventional refrigerator-cooled superconducting magnet.

[Explanation of symbols]

1: superconducting coil, 2: radiation shield, 3: vacuum container,
4A, 4B: Cooling flange, 5: Cooling bobbin, 6: Cooling outer cylinder plate, 7a: Refrigerator, 9: Current lead, 12, 12
A, 12B: cooling plate, 20: piping for cooling.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Katsuya Tsutsumi             2-47 Shiobara 2-chome, Minami-ku, Fukuoka City, Fukuoka Prefecture             State Electric Power Co., Inc. (72) Inventor Akira Tomioka             1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa             Within Fuji Electric Co., Ltd. (72) Inventor Yujiro Yagi             1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa             Within Fuji Electric Co., Ltd.

Claims (5)

[Claims] 1. A superconducting coil comprising a superconducting wire wound around a winding frame in layers and supported by a cooling flange, and a vacuum container for accommodating and insulating the superconducting coil. In a superconducting magnet that is cooled and kept at an extremely low temperature, the refrigerator is installed outside the vacuum container, and a cooling flange of the superconducting coil and a cooling plate arranged in good heat conduction are provided in the refrigerator. A superconducting magnet, which is configured to cool a superconducting coil by cooling it to a predetermined temperature with a cryogenic refrigerant gas generated. 2. The superconducting magnet according to claim 1, wherein the cooling plate is made of a non-magnetic material having good heat conductivity, and a flow passage for the cryogenic refrigerant gas is formed therein. And a superconducting magnet. 3. The superconducting magnet according to claim 1, wherein the cooling plate is provided on cooling flanges on both upper and lower sides of the superconducting coil. 4. The superconducting magnet according to claim 1, wherein the refrigerant gas that has cooled the cooling plate is
A superconducting magnet, which is configured to flow through a current lead for supplying a current to a superconducting coil, cool the current lead, and then return the current to the refrigerator. 5. The superconducting magnet according to any one of claims 1 to 4, wherein a radiation shield is arranged in the vacuum container to block heat radiation to the superconducting coil from the outside. A superconducting magnet, characterized in that the radiation shield is cooled by a small single-stage refrigerator provided separately from the refrigerator.