JPH0918062A - Superconducting magnet device - Google Patents

Abstract

PURPOSE: To prevent heat, which is generated with the operation of a permanent current switch, from intruding in the arrangement place of a superconducting coil as a thermal load. CONSTITUTION: A superconducting coil 2 is cooled at a first temperature level by a second-step cooling stage 6 of an air cooling refrigerator 4. The side of each one end of current lead elements 23a and 23b, which are formed of a superconductor of a superconducting transition temperature higher than that of the coil 2 and respectively constitute one part of a current lead 21, is connected with both ends of the coil 2. A permanent current switch element 32, which is formed of the same conductor as that forming the elements 23a and 23b, is connected between the sides of the other ends of the elements 23a and 23b and the element 32 and the sides of the other ends of the elements 23a and 23b are cooled at a second temperature level, which is higher than the first temperature level and is lower than the superconducting transition temperature of the elements, by a first-step cooling stage 5 of the refrigerator 4. An electric heatger 33 for making the element 32 transfer selectively to normal conductivity is arranged near the element 32.

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 having a permanent current switch.

[0002]

2. Description of the Related Art As is well known, most of the superconducting magnet devices currently in practical use employ an immersion cooling method in which a superconducting coil and a cryogenic refrigerant represented by liquid helium are housed together in a heat insulating container. In addition, the system uses a cryogenic refrigerator to cool the thermal shield provided in the heat insulating layer of the heat insulating container. Further, recently, with the advent of regenerator materials with excellent specific heat characteristics at cryogenic temperatures, a refrigerator direct cooling type superconducting magnet that directly cools the superconducting coil housed in a heat insulating container with a regenerator type refrigerator. The device is being put to practical use.

FIG. 4 shows a conventional refrigerator direct cooling type superconducting magnet device in which a superconducting coil is directly cooled by a regenerator type refrigerator. In this superconducting magnet device, the vacuum container 1 is used as a heat insulating container. Vacuum container 1
A superconducting coil 2 formed of an alloy superconductor such as Nb / Ti or a compound superconductor such as Nb ₃ Sn having a superconducting transition temperature of about 15 K is disposed inside the superconducting coil 2 so as to surround the superconducting coil 2. A thermal shield 3 made of a non-magnetic metal material is arranged.

A regenerator, for example, a Gifford-McMahon refrigerator (hereinafter abbreviated as GM refrigerator) 4 is arranged so that a part thereof is located inside the vacuum container 1 and the rest is located outside the vacuum container 1. Is provided, the first cooling stage 5 of the GM refrigerator 4 is thermally connected to the thermal shield 3, and the thermal shield 3 is cooled to about 50K. Further, the second cooling stage (final cooling stage) 6 of the GM refrigerator 4 is thermally connected to the superconducting coil 2 via the heat conducting members 7 and 8 formed of a copper material, etc. It is cooled to about 4K. In this figure, the means for holding the position of the superconducting coil 2 and the thermal shield 3 is omitted.

The structure and the refrigerating operation of the GM refrigerator 4 will be briefly described as follows. The GM refrigerator 4 shown in this figure is configured in a two-stage expansion type, and includes a first-stage refrigeration unit 10 and a second-stage refrigeration unit 11. Displacers 12 and 13 holding a regenerator are housed in the first-stage freezing unit 10 and the second-stage freezing unit 11, respectively, and these displacers 12 and 13 are integrally illustrated in synchronization with the rotation of the motor 14. It is driven to reciprocate up and down. Then, the first unit provided in the first-stage freezing unit 10
The stage cooling stage 5 is thermally connected to the thermal shield 3, and the second stage cooling stage 6 provided in the second stage freezing unit 11 is thermally connected to the heat conducting member 7.
A copper mesh or the like is used as the regenerator material of the regenerator held by the displacer 12, and a magnetic phase transition made of Er ₃ Ni or the like is used as the regenerator material of the regenerator held by the displacer 13. Magnetic regenerator materials, etc. that utilize the abnormal magnetic specific heat and the like are used.

When the motor 14 starts rotating, the displacers 12 and 13 start reciprocating motion. In synchronization with this, the high pressure valve 15 and the low pressure valve 16 are opened and closed to start the operation as a refrigerator. That is, the displacer 12,
When 13 reaches the top dead center (the lowest point in the figure), the high pressure valve 15
Opens, and the high-pressure helium gas sent from the compressor 17 flows into the first-stage freezing unit 10 and the second-stage freezing unit 11. When the displacers 12 and 13 move to the bottom dead center (uppermost point in the figure), the inflowing high-pressure helium gas comes into contact with the regenerator material of the regenerator held by the displacers 12 and 13 to be cooled. Displacer 12, 1
When 3 reaches the bottom dead center, the high pressure valve 15 closes and the low pressure valve 16
Opens. When the low-pressure valve 16 opens, the high-pressure helium gas in the first-stage expansion chamber 18 and the second-stage expansion chamber 19 adiabatically expands to generate cold. Due to this cold, the first cooling stage 5 absorbs heat from the outside, and the second cooling stage 6 also absorbs heat from the outside. Then, when the displacers 12 and 13 move to the top dead center again, the low temperature helium gas in the first-stage expansion chamber 18 and the second-stage expansion chamber 19 is stored in each regenerator. Contact the materials to cool them. The low temperature valve 16
It is discharged to the compressor 17 via. The above-described cycle is repeated to cool the thermal shield 3 to about 50K and the superconducting coil 2 to about 4K.

On the other hand, a current lead 21 for supplying a current to the superconducting coil 2 from outside the vacuum container 1 is connected to the superconducting coil 2. The current lead 21 is made of different materials depending on the temperature level range. That is, the current lead elements 22a, 22b made of copper such as phosphorous deoxidized copper are used in the range from room temperature to 50K level, and the superconducting transition temperature is higher than the temperature of the thermal shield 3 in the temperature range of 50K or less, for example, bismuth. Current lead elements 23a and 23b made of a system oxide superconductor (having a superconducting transition temperature of about 130K) are used. The portions of the current lead elements 22a and 22b that penetrate the thermal shield 3 and the portions that penetrate the wall of the vacuum container 1 are formed in a bushing configuration. In addition, the current lead element 23 in the current lead elements 22a and 22b
The portions near a and 23b are thermally connected to the thermal shield 3 through thermal anchors 24a and 24b whose surfaces are covered with a member having excellent thermal conductivity and electrical insulation such as aluminum nitride. With this configuration, the current lead elements 23a and 23b are entirely held below the superconducting transition temperature, that is, the upper end portion in the figure is about 50K and the lower end portion in the figure is about 4K.

A permanent current switch 25 is connected between both ends of the superconducting coil 2. The permanent current switch 25 is selected for the permanent current switch element 26, which is formed of the same superconductor as the superconductor forming the superconducting coil 2 and is connected between both ends of the superconducting coil 2, and the permanent current switch element 26. And an electric heater 27 that heats the material to bring it into a normal conduction transition state (off state).
Both ends of the electric heater 27 are guided to the outside of the vacuum container 1 via lead wires (not shown).

When the electric heater 27 is not energized, the permanent current switch element 26 is in the second cooling stage 6.
It is cooled down to about 4 K by and is kept in the superconducting transition state (ON state). Therefore, by turning on and off the electric heater 27, the permanent current switch 25 is turned on,
Can be turned off. That is, when exciting or demagnetizing the superconducting coil 2 via the current lead 21, the electric heater 27 may be energized to turn off the persistent current switch 25. In addition, by stopping the energization of the electric heater 27 in the excited state and turning on the permanent current switch 25, the superconducting coil 2 can be shifted to the persistent current mode.

However, the conventional superconducting magnet device constructed as described above has the following problems. That is, when the electric heater 27 is energized to turn off the permanent current switch 25, the surplus heat generated by the electric heater 27 consequently increases the heat load on the second cooling stage 6. The refrigeration capacity of the second cooling stage 6 is significantly smaller than that of the first cooling stage 5. Therefore, even if the amount of heat generated by the electric heater 27 is small, the temperature of the second cooling stage 6 is raised, and this may cause the superconducting coil 2 to undergo normal conduction transition (quenching). It was often there.

This phenomenon is caused by applying a magnetic field higher than the critical magnetic field to the permanent current switch element using a coil, or stopping the application of the magnetic field to turn off and on the superconducting magnet incorporating a superconducting magnet. The same applies to the device. That is, when a current is applied to the coil to apply a magnetic field, the coil generates heat, and this heat generation increases the heat load on the second cooling stage. The same applies to a superconducting magnet device adopting an immersion cooling method in which a superconducting coil is immersed in an extremely low temperature liquid represented by liquid helium and cooled. In this case,
Since the superconducting coil is surrounded by the cryogenic liquid, the heat generated when the permanent current switch is turned off hardly quenches the superconducting coil, but the heat generated when the persistent current switch is turned off causes the cryogenic temperature to decrease. This leads to an increase in the amount of liquid evaporation.

[0012]

As described above, in the conventional superconducting magnet device having the permanent current switch, the heat generated when the permanent current switch is turned off causes the heat load in the placement field of the superconducting coil. Acts to increase, which causes quenching of the superconducting coil,
There are problems such as increasing the evaporation amount of the cryogenic liquid that cools the superconducting coil.

Therefore, the present invention can prevent the heat generated when the permanent current switch is operated from invading the placement field of the superconducting coil as a heat load, thereby improving the economical efficiency and reliability of the device. It is intended to provide a magnet device.

[0014]

In order to achieve the above object, a superconducting magnet device according to the present invention comprises a superconducting coil,
A first cooling means for cooling the superconducting coil to a first temperature level equal to or lower than a superconducting transition temperature; and a superconductor having a superconducting transition temperature higher than the superconducting transition temperature of the superconducting coil. A pair of current lead elements connected to a superconducting coil to form a part of a current lead for supplying a current to the superconducting coil, and a superconductor having a superconducting transition temperature higher than the superconducting transition temperature of the superconducting coil, A permanent current switch element connected between the other end sides of the current lead elements and the other end sides of the permanent current switch element and the pair of current lead elements are higher than the first temperature level, and the pair of currents. Second cooling means for cooling to a second temperature level below the superconducting transition temperature of the lead element and the persistent current switch element; And means for selectively normal conducting transition of Hisashi current switching element.

When the superconducting coil is formed of an alloy superconductor or a compound superconductor, that is, a superconductor that must be cooled to a temperature close to liquid helium temperature for the superconducting transition, the liquid nitrogen temperature It is preferable that the pair of current lead elements and the permanent current switch element are formed of an oxide superconductor that can be transformed into a superconducting state by cooling.

Further, the first cooling means has a liquid or gas refrigerant having the first temperature level, and a cooling system for directly or indirectly cooling the superconducting coil with the liquid or gas refrigerant. It may be composed of. Similarly, the second cooling means has a liquid or gas refrigerant of the second temperature level, and the liquid or gas refrigerant is used for the other end side of the permanent current switch element and the pair of current lead elements. May be configured by a cooling system that directly or indirectly cools.

Further, the first cooling means cools the superconducting coil by using a final stage cooling stage of a multi-stage expansion regenerator having a regenerator as a heat absorption source.
The second cooling means may be constituted by a second heat absorption system having a cooling stage other than the final stage of the regenerator as a heat absorption source.

Here, the first endothermic system may be provided with a heat conducting member for thermally connecting the final stage cooling stage and the superconducting coil to directly cool the superconducting coil. Further, the second cooling means may also be configured to also cool the thermal shield that blocks heat from entering the placement field of the superconducting coil.

[0019]

The superconducting coil is cooled to the first temperature level below the superconducting transition temperature by the first cooling means. on the other hand,
The pair of current lead elements and the permanent current switch element are formed of a superconductor having a superconducting transition temperature higher than the superconducting transition temperature of the superconducting coil. The other end side of the pair of current lead elements and the permanent current switch element are higher than the first temperature level by the second cooling means, and the superconducting transition of the pair of current lead elements and the permanent current switch element. Cooled to a second temperature level below the temperature.

Now, assuming that the first temperature level is 4K and the second temperature level is 50K, the superconducting coil is cooled to 4K by the first cooling means, and the permanent current switch element is 50K by the second cooling means. Will be cooled to. Generally, the refrigerating capacity of the cooling means depends on the temperature, and the higher the temperature, the greater the refrigerating capacity. In the case of the above temperature relationship, the refrigerating capacity of the second cooling means is much larger than the refrigerating capacity of the first cooling means. Therefore, even if heat is generated when the means for selectively changing the superconducting switch element to the normal conduction is operated, this heat is quickly absorbed by the second cooling means having a large refrigerating capacity, and the first cooling means. Is less likely to be a heat load. Therefore, it is possible to prevent heat generated when the permanent current switch is operated from entering the placement field of the superconducting coil as a heat load.

[0021]

Embodiments will be described below with reference to the drawings. FIG. 1 shows a superconducting magnet device according to an embodiment of the present invention.
Here, an example in which the present invention is applied to a refrigerator direct cooling type superconducting magnet device is shown. In this figure, the same functional parts as those in FIG. 4 are indicated by the same reference numerals. Therefore, detailed description of the overlapping portions will be omitted.

The superconducting coil 2 arranged in the vacuum container 1 has a superconducting transition temperature of about 8 to 15 K Nb.
It is formed of an alloy superconductor such as Ti or a compound superconductor such as Nb ₃ Sn. The thermal shield 3 is cooled to about 50 K (second temperature level) using the first cooling stage 5 of the GM refrigerator 4 as an endothermic source, and the second cooling stage of the GM refrigerator 4 (final cooling stage). ) 6 as a heat-absorbing source, the superconducting coil 2 is about 4K (first
Temperature level).

On the other hand, to the superconducting coil 2, a current lead 21 for supplying a current to the superconducting coil 2 from outside the vacuum container 1 is connected. The current lead 21 is made of different materials depending on the temperature level range. That is, the current lead elements 22a, 22b made of copper such as phosphorous deoxidized copper are used in the range from room temperature to 50K level, and the superconducting transition temperature is higher than the temperature of the thermal shield 3 in the temperature range of 50K or less, for example, bismuth. Current lead elements 23a and 23b made of a system oxide superconductor (having a superconducting transition temperature of about 130K) are used. Thermal shield 3 in the current lead elements 22a, 22b
The portion penetrating through and the portion penetrating the wall of the vacuum container 1 are formed in a bushing configuration. Current lead element 22
The portions of a and 22b close to the current lead elements 23a and 23b are heated to the thermal shield 3 via thermal anchors 24a and 24b whose surfaces are covered with a member having excellent thermal conductivity and electrical insulation such as aluminum nitride. Connected to each other. With this configuration, the current lead element 23
All of a and 23b are maintained at or below the superconducting transition temperature, that is, the upper end in the figure is maintained at about 50K (second temperature level) and the lower end in the figure is maintained at about 4K (first temperature level).

In the case of this embodiment, the current lead element 23
The other end side of a, 23b, that is, the current leads 22a, 22b
The permanent current switch 31 is connected to a portion close to the boundary between and. The permanent current switch 31 is formed of the same bismuth-based oxide superconductor as the superconductor forming the current lead elements 23a and 23b.
It is composed of a permanent current switch element 32 connected between the other ends of a and 23b, and an electric heater 33 for selectively applying heat to the permanent current switch element 32 to bring it into a normal conduction transition state (off state). ing. Both ends of the electric heater 33 are guided to the outside of the vacuum container 1 via lead wires (not shown).

As described above, since the boundary between the current leads 22a and 22b and the current leads 23a and 23b is thermally connected to the thermal shield 3 via the thermal anchors 24a and 24b, the permanent current switch element 32 is also. The electric heater 3 is cooled to 50K, which is the same as the thermal shield 3.
When 3 is not energized, the superconducting transition state (ON state) is maintained. Then, when the electric heater 33 is energized and the temperature rises to a level exceeding the superconducting transition temperature,
The permanent current switch element 32 is in the normal conduction transition state (off state).

As can be seen from the above construction, the cold storage type refrigerator 4
Second stage (final stage) cooling stage 6 and heat conducting members 7 and 8
In order to cool the superconducting coil 2 to 4K (first temperature level) using the second cooling stage 6 as a heat absorption source,
Cooling means is configured. Further, with the first-stage cooling stage 5, the thermal shield 3, and the thermal anchors 24a, 24b of the regenerator 4, the permanent-current switch element 32 and the current lead elements 23a, 23b of the first-stage cooling stage 5 as a heat absorption source. A second cooling means is provided for cooling the other end side to 50K (second temperature level).

The temperature of the first cooling stage 5 is much higher than that of the second cooling stage 6. Therefore, the first
The refrigerating capacity of the stage cooling stage 5 is equal to that of the second stage cooling stage 6.
Much larger than the freezing capacity of. The other ends of the permanent current switch element 32 and the current lead elements 23a and 23b are cooled to 50K (second temperature level) by using the first cooling stage 5 having a large refrigerating capacity as a heat absorption source. Therefore, when the electric heater 33 is energized to turn off the permanent current switch 31, the surplus heat generated by the electric heater 33 passes through the thermal anchors 24a, 24b and the thermal shield 3 and has a large refrigerating capacity. It is rarely absorbed by the stage cooling stage 5 and becomes a heat load on the second stage cooling stage 6. Therefore, it becomes possible to prevent the superconducting coil 2 from being quenched due to the heat generated when the permanent current switch 31 is operated.

FIG. 2 shows a superconducting magnet device according to another embodiment of the present invention, which is also an example in which the present invention is applied to a refrigerator direct cooling type superconducting magnet device. In this figure, the same functional parts as those in FIG. 1 are indicated by the same reference numerals. Therefore, detailed description of the overlapping portions will be omitted.

This embodiment differs from the embodiment shown in FIG. 1 in the configuration of the permanent current switch 31a. The permanent current switch 31a is of a magnetic field application type that is turned off by applying a magnetic field above the critical magnetic field to the superconductor.

That is, the permanent current switch 31a is made of the same bismuth oxide superconductor as the superconductor forming the current lead elements 23a and 23b, and is connected between the other end sides of the current lead elements 23a and 23b. And the permanent current switch element 32 is disposed concentrically around the permanent current switch element 32 to selectively apply a magnetic field higher than the critical magnetic field to the permanent current switch element 32 to cause a normal conduction transition (off state). And the coil 34. In addition,
The coil 34 is formed of the same bismuth oxide superconductor as the superconductor forming the current lead elements 23a and 23b, and is thermally connected to the thermal shield 3 via the thermal anchor 35. Both ends of the coil 34 are guided to the outside of the vacuum container 1 via lead wires (not shown).

With such a structure, the coil 34 is always maintained at the superconducting transition temperature or lower through the thermal shield 3 and the thermal anchor 35. That is, the coil 34 is also kept in the superconducting state. And the coil 34
The permanent current switch element 32 can be brought into the normal conduction transition (off state) by selectively energizing the switch. In this case, even if the coil 34 is energized, there is no heat generation in the coil 34. Therefore, it is possible to prevent the superconducting coil 2 from being quenched due to the heat generated when the permanent current switch 31a is operated. it can.

FIG. 3 shows a superconducting magnet device according to still another embodiment of the present invention, in which the present invention is applied to a dipping cooling type superconducting magnet device. In the figure, 41 indicates a heat insulating container. The heat insulating container 41 includes an inner tank 42 made of a non-magnetic metal material, an outer tank 43 made of a non-magnetic material, and a vacuum heat insulating layer 44 formed between the inner and outer tanks.
The vacuum heat insulating layer 44 includes a thermal shield 45 made of a non-magnetic metal material provided so as to surround the inner tank 42.

Liquid helium 46 which is a cryogenic refrigerant is accommodated in the inner tank 2, and a superconducting coil 47 is arranged so as to be submerged in the liquid helium 46. The superconducting coil 47 has a superconducting transition temperature of about 8 to 15 K Nb.
It is formed of an alloy superconductor such as Ti or a compound superconductor such as Nb ₃ Sn. In this figure, the inner tank 4
A liquid injection pipe for injecting liquid helium 46 into the second chamber, an exhaust pipe for collecting helium gas generated in the inner tank 42, a means for holding the position of the superconducting coil 47, etc. are omitted.

On the other hand, there is provided a regenerator refrigerator 49 for absorbing the heat which tends to enter the inner tank 42 due to radiation or the like to maintain the temperature environment of the superconducting coil 47. The cold storage refrigerator 49 is provided in a relationship that extends inside and outside the heat insulating container 41, and has a first-stage freezing unit 50 and a second-stage freezing unit 51.
And

The first stage refrigerating section 50 adopts the Gifford-McMahon refrigerating cycle and has a displacer 52 holding a regenerator therein. The displacer 52 is reciprocally driven in the vertical direction in the figure in synchronization with the rotation of the motor 53. Then, when the displacer 52 reaches the top dead center (the lowest point in the figure), the high pressure valve 54 opens, and the high pressure helium gas sent from the compressor 55 becomes the first
It flows into the stage freezing section 50. In addition, the displacer 52
When it reaches the bottom dead center (uppermost point in the figure), the low-pressure valve 56 opens, and the high-pressure helium gas in the first-stage freezing section 50 is adiabatically expanded to generate cold in the first-stage cooling stage 57. That is, the first-stage freezing unit 50 constitutes a single-stage GM refrigerator, and the first-stage cooling stage 57 includes the thermal shield 4.
5 is cooled to about 50K.

On the other hand, the second-stage freezing section 51 employs a double-inlet type pulse tube refrigeration cycle. That is, the low temperature space in the first-stage freezing unit 50 is connected to the pipe 58, the regenerator 59, the heat absorbing pipe 60, the pulse tube 6
1. Connect the high temperature end space of the pulse tube 61 to the buffer tank 63 while connecting to the pipe 58 via the capillary tube 62, and generate cold about 4K with the heat absorption tube 60 that constitutes the second cooling stage 81. There is.
Then, the heat sink tube 60 directly cools the inner tank 42.

To the superconducting coil 47, a current lead 64 for supplying a current to the superconducting coil 47 from outside the heat insulating container 41 is connected. The current lead 64 is made of different materials depending on the temperature level range. That is, the current lead elements 65a and 65b made of copper such as phosphorous deoxidized copper are used in the range from room temperature to 50K level, and the superconducting transition temperature is higher than the temperature of the thermal shield 45 in the temperature range of 50K or less. Current lead elements 66a, 66b made of a system oxide superconductor (having a superconducting transition temperature of about 130K) are used. The portions of the current lead elements 65a and 65b that penetrate the outer tank 43 and the thermal shield 45 are formed into a bushing structure. Similarly, a portion extending from the superconducting coil 47 and penetrating the upper wall of the inner tank 42 is also formed in a bushing structure. In addition, the current lead elements 65a, 65
The portion near the current lead elements 66a and 66b in b is a thermal anchor 67 whose surface is covered with a member having excellent thermal conductivity and electrical insulation such as aluminum nitride.
It is thermally connected to the thermal shield 45 via a and 67b.

With this configuration, the current lead element 66
All of a and 66b are maintained at or below the superconducting transition temperature, that is, the upper end in the figure is maintained at about 50K (second temperature level) and the lower end in the figure is maintained at about 4K (first temperature level).

The other ends of the current lead elements 66a and 66b,
That is, the permanent current switch 70 is connected to a portion near the boundary between the current leads 65a and 65b. The persistent current switch 70 is made of the same bismuth oxide superconductor as the superconductor forming the current lead elements 66a and 66b, and is connected between the other ends of the current lead elements 66a and 66b. It is composed of a switch element 71 and an electric heater 72 for selectively applying heat to the permanent current switch element 71 to bring it into a normal conduction transition state (off state). Both ends of the electric heater 72 are guided to the outside of the heat insulating container 41 via lead wires (not shown).

As can be seen from the above configuration, the cold storage refrigerator 4
The first cooling stage 57, the thermal shield 45, and the thermal anchors 67a, 67b of 9 use the first cooling stage 57 as a heat-absorbing source, and the other end side of the permanent current switch element 71 and the current lead elements 66a, 66b is 50K ( Second
Second cooling means for cooling to a temperature level of 1).

The temperature of the first cooling stage 57 is much higher than that of the endothermic tube 60 forming the second cooling stage 81. Therefore, the refrigerating capacity of the first cooling stage 57 is much larger than the refrigerating capacity of the second cooling stage 81. The other ends of the permanent current switch element 71 and the current lead elements 66a and 66b are cooled to 50K (second temperature level) by using the first cooling stage 57 having a large refrigerating capacity as a heat absorption source. Therefore, when the electric heater 72 is energized to turn off the permanent current switch 70, the surplus heat generated by the electric heater 72 is generated by the thermal anchors 67a and 67b and the thermal shield 4.
It is unlikely that the liquid helium 46 is quickly absorbed by the first-stage cooling stage 57 having a large refrigerating capacity via 5 and becomes a heat load on the liquid helium 46. Therefore, it is possible to prevent the evaporation amount of the liquid helium 46 from increasing due to the heat generated when the permanent current switch 70 is operated.

The present invention is not limited to the above embodiment. That is, in the superconducting magnet device,
There is a type in which the superconducting coil is directly or indirectly cooled with liquid helium and the thermal shield is directly or indirectly cooled with liquid nitrogen, but the present invention can be applied to such a type.

Further, by using a refrigerator and a refrigerant gas circulation system for circulating helium gas or nitrogen gas in combination, the first and second cooling stages of the refrigerator, the superconducting coil and the thermal shield are connected to the refrigerant gas. The present invention can also be applied to a superconducting magnet device of a system that is thermally connected by a circulation system and is cooled by circulating a refrigerant gas.

[0044]

As described above, according to the present invention,
It is possible to prevent heat generated when the permanent current switch is operated from entering the placement field of the superconducting coil as a heat load.

[Brief description of the drawings]

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

FIG. 2 is a schematic configuration diagram of a superconducting magnet device according to another embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a superconducting magnet device according to still another embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a conventional typical superconducting magnet device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Vacuum container 2, 47 ... Superconducting coil 3, 45 ... Armal shield 4, 49 ... Regenerative refrigerator 5, 57 ... 1st stage cooling stage 6, 81 ... 2nd stage cooling stage 7, 8 ... Heat conduction member 21, 64 ... Current leads 22a, 22b, 65a, 65b ... Copper current lead elements 23a, 23b, 66a, 66b ... Superconductor current lead elements 24a, 24b, 67a, 67b ... Thermal anchors 30, 31a, 70 ... Superconducting switch 32, 71 ... Superconducting switch element 33, 72 ... Electric heater 34 ... Coil

Claims (9)

[Claims] 1. A superconducting coil, first cooling means for cooling the superconducting coil to a first temperature level below the superconducting transition temperature, and a superconductor each having a superconducting transition temperature higher than the superconducting transition temperature of the superconducting coil. And a pair of current lead elements each of which is connected to the superconducting coil and constitutes a part of a current lead for supplying a current to the superconducting coil, and a superconducting transition temperature higher than the superconducting transition temperature of the superconducting coil. Made of superconductor of
The permanent current switch element connected between the other end sides of the pair of current lead elements, the permanent current switch element and the other end side of the pair of current lead elements are higher than the first temperature level, and Second lower than the superconducting transition temperature of the current lead element of
A superconducting magnet device comprising: second cooling means for cooling to the temperature level of 1) and means for selectively causing the persistent current switching element to transition to the normal conduction state. 2. The superconducting coil is formed of an alloy superconductor or a compound superconductor, and the pair of current lead elements and the permanent current switch element are formed of an oxide superconductor. The superconducting magnet device according to claim 1. 3. The first cooling means is constituted by a first endothermic system for cooling the superconducting coil by using a final stage cooling stage in a multistage expansion regenerator having a regenerator as an endothermic source. The superconducting magnet according to claim 1, wherein the second cooling means is constituted by a second endothermic system having a cooling stage other than the final stage of the regenerative refrigerator as an endothermic source. apparatus. 4. The first cooling means has a liquid or gas refrigerant of the first temperature level, and the first or second cooling means directly or indirectly cools the superconducting coil with the liquid or gas refrigerant. The second cooling means has a liquid or gas refrigerant of the second temperature level, and the permanent current switch element and the pair of current lead elements are constituted by the liquid or gas refrigerant. 2. The superconducting magnet device according to claim 1, wherein the superconducting magnet device is configured by a second cooling system that directly or indirectly cools the other end side of the. 5. The superconducting magnet device according to claim 3, wherein the first endothermic system includes a heat conducting member that thermally connects the final cooling stage and the superconducting coil. . 6. The second cooling means also functions as a cooling for a thermal shield for preventing heat from entering the placement field of the superconducting coil. The superconducting magnet device as described in the paragraph. 7. The superconducting device according to claim 1, wherein the means for selectively changing the permanent current switch element to the normal conduction state comprises heat generating means for applying heat to the permanent current switch element. Magnet device. 8. The magnetic field generating means for selectively applying a magnetic field to the permanent current switch element, wherein the means for selectively causing the permanent current switch element to undergo a normal conduction transition is constituted by a magnetic field generating means. Superconducting magnet device. 9. The superconducting magnet device according to claim 8, wherein the magnetic field generating means includes a coil made of an oxide superconductor.