JP2006093723A - Superconducting magnet device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a superconducting magnet device, wherein replacement of a multi-stage cooling storage type refrigerator facilitated and the thermal resistance between a superconducting coil and a final thermal stage of the multi-stage cooling storage type refrigerator is reduced. <P>SOLUTION: A refrigerator-attaching cylinder 30 is attached airtightly to a vacuum vessel 7, while first and second attaching thermal connection parts 33 and 35 are thermally connected to a thermal shield 5 and a superconducting coil cartridge 3. A two-stage regenerator type refrigerator 21A is attached airtightly to the refrigerator attaching cylinder 30, while first and second thermal stages 24 and 26 are thermally connected to the first and the second attaching thermal connection parts 33 and 35. Helium gas 60 is filled in between the 2-stage regenerator type refrigerator 21A and the refrigerator fitting cylinder 30 via a helium introduction pipe 40. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a superconducting magnet device that cools a superconducting coil with a multistage regenerative refrigerator.

The superconducting magnet device is a device for generating a strong magnetic field, and is used as a superconducting state in which a superconducting coil is cooled to a very low temperature and electric resistance is zero and current flows. For this reason, there is no Joule heat generation, and it is possible to generate a strong magnetic field with less power compared to a normal conducting magnet device.
In this type of superconducting magnet device, liquid helium has been conventionally used to cool the superconducting coil. However, liquid helium has a very small latent heat of vaporization, so that it is difficult to handle and expensive. Thus, a method of directly cooling the superconducting coil with a refrigerator has been proposed.

FIG. 9 is a cross-sectional view showing a conventional superconducting magnet device described in Patent Document 1, for example.
In the figure, a superconducting coil cartridge 3 is constructed by attaching a superconducting coil 2 made of Nb3Sn to a support 1 made of a metal such as aluminum. The superconducting coil cartridge 3 is accommodated in a heat shield 5 disposed in a vacuum vessel 7. The inside of the vacuum container 7 is maintained at a high vacuum to reduce heat intrusion into the superconducting coil cartridge 3 and the heat shield 5. The superconducting coil cartridge 3 is heat-insulated and supported by the heat shield 5 by the second heat-insulating support 4, and the heat shield 5 is heat-insulated and supported by the vacuum vessel 7 by the first heat-insulating support 6.
Here, the second and first heat insulating supports 4 and 6 are made of a material having low thermal conductivity and high strength, for example, GFRP (Glass Fiber Resinforced Plastic). The heat shield 5 is made of aluminum, copper, or an alloy thereof having a high thermal conductivity.

  The two-stage regenerative refrigerating machine 21 includes a drive unit 22, a first cylinder 23, a first heat stage 24, a second cylinder 25, a second heat stage 26, a gas pipe 27, and a compressor 28. The second heat stages 24 and 26 cool the heat shield 5 and the superconducting coil cartridge 3 to about 50K and about 8K, respectively. The refrigerator mounting cylinder 30 is for making the two-stage regenerative refrigerator 21 detachable and facilitating maintenance and replacement thereof. The mounting flange 31, the first mounting cylinder 32, and the first mounting heat connection. It is comprised from the part 33, the 2nd attachment cylinder 34, and the 2nd attachment heat connection part 35. As shown in FIG. The mounting cylinder 30 has its mounting flange 31 hermetically attached to the vacuum vessel 7 and is inserted through the vacuum vessel 7 and the heat shield 5 from the outside. The first attachment heat connection portion 33 is thermally connected to the heat shield 5, and the second attachment heat connection portion 35 is thermally connected to the superconducting coil cartridge 3. Further, in the two-stage regenerative refrigerator 21, the first heat stage 24 is thermally connected to the first attachment heat connection portion 33, and the second heat stage 26 is thermally connected to the second attachment heat connection portion 35. Are inserted into the mounting cylinder 30.

Next, the operation of the conventional superconducting magnet device will be described.
When the two-stage regenerative refrigerator 21 is operated, the heat energy of the superconducting coil cartridge 3 is absorbed by the second heat stage 26 via the second attachment heat connecting portion 35. Accordingly, the superconducting coil cartridge 3 has a temperature at which the amount of heat energy that can be absorbed by the second heat stage 26 of the two-stage regenerative refrigerator 21, that is, the refrigerating capacity and the heat energy entering from the outside by conduction or radiation. . At this time, in order to absorb the thermal energy, a temperature gradient corresponding to the thermal resistance is required, so that the thermal resistance between the superconducting coil cartridge 3 -the second attachment thermal connection portion 35 -the second thermal stage 26 is reduced. There is a need to. In particular, since the second attachment thermal connecting portion 35 and the second thermal stage 26 are configured to be detachable, there is a possibility that the thermal resistance is increased as compared with other portions, and caution is required. The operating temperature of the superconducting coil 2 is designed in consideration of the intensity of the generated magnetic field and the material of the superconducting wire so that the superconducting coil 2 can stably generate a strong magnetic field. In this conventional example, Sn3Nb is selected as the superconducting wire, so the operating temperature of the superconducting coil is about 12K, and a temperature gradient of about 1K is allowed from the refrigerating capacity characteristics.

Similarly, the heat energy of the heat shield 5 is absorbed by the first heat stage 24 through the first attachment heat connection portion 33. Therefore, the heat shield 5 has a temperature at which the amount of heat energy that can be absorbed by the first heat stage 24 of the two-stage regenerative refrigerating machine 21, that is, the refrigerating capacity and the heat energy entering from the outside by conduction or radiation is balanced. This temperature is usually designed to be about 50K.
Moreover, although not specified in the above-mentioned Patent Document 1, when the two-stage regenerative refrigerator 21 is installed and operated from the structure, the air between the mounting cylinder 30 and the two-stage regenerative refrigerator 21 is generated. Since it is thought that it is cooled and almost in a vacuum state, heat transfer is mainly conducted by heat transfer. When the two-stage regenerative refrigerator 21 is exchanged, a force is received in a vacuum state, so the temperatures of the superconducting coil cartridge 3 and the heat shield 5 need to be raised to room temperature.

  In this state, the conventional superconducting magnet device causes a current to flow through the superconducting coil 2 using a power lead (not shown) that supplies current from an external power source (not shown) to generate a strong magnetic field. A typical example in which this type of superconducting magnet apparatus is used is a medical MRI apparatus. In such an apparatus, since it is necessary to stably generate a magnetic field having the same strength, the apparatus is operated in a permanent current state using a superconducting switch. In such a device, since the safety of the device may affect human life, high reliability is required.

  In the conventional superconducting magnet device, a superconducting wire made of Nb3Sn is used as the superconducting coil 2. This is because the ultimate temperature of the two-stage regenerative refrigerator 21 using lead as the regenerator material is about 8K, and could not be cooled to 4K, which is the cooling temperature of the superconducting coil using the NbTi superconducting wire. However, the superconducting wire of Nb3Sn is a compound and is fragile, so that it is difficult to manufacture and expensive.

In recent years, a two-stage regenerative refrigerating machine capable of generating refrigeration at 4K using a magnetic regenerator material has been developed, and a superconducting coil using a superconducting wire of NbTi that is easier to manufacture and cheaper than Nb3Sn is directly cooled. A scheme has been proposed.
FIG. 10 is a cross-sectional view showing a main part of a conventional superconducting magnet device.
In the conventional superconducting magnet apparatus shown in FIG. 10, a heat transfer plate 50 is wound around a superconducting coil 2A using a NbTi superconducting wire, and a heat conducting member 51 is a second stage regenerative refrigerator 21A. The superconducting coil 2A is directly cooled by a two-stage regenerative refrigerator 21A that is installed between the two-heat stage 26 and the heat transfer plate 50 and uses a magnetic regenerator material.
In addition, a large amount of electric power is required to generate refrigeration at 4K. An example of the refrigerating capacity characteristic of the two-stage regenerative refrigerator 21A is shown in FIG. It can be understood from FIG. 11 that the refrigeration capacity changes greatly in the vicinity of 4K. When the thermal resistance is large and the temperature difference is 1K, the temperature of the second thermal stage 26 needs to be 3.2K in order to set the temperature of the superconducting coil 2A to 4.2K. From FIG. 11, it is understood that the refrigerating capacity is 0.5 W at 4.2K, but is drastically reduced to 0.1 W at 3.2K. As a result, if the temperature difference reaches 1K, a refrigerator that is five times larger is required, which is very disadvantageous in terms of power consumption and the like. Therefore, in the superconducting magnet device using the two-stage regenerative refrigerator 21A, compared with the superconducting magnet device using the two-stage regenerative refrigerator 21, the thermal resistance is extremely reduced, and the superconducting coil 2A and the second It is important to reduce the temperature gradient with the heat stage 26.

Therefore, conventionally, a method has been proposed in which the second heat stage 26 of the two-stage regenerative refrigerator 21A is directly attached to the superconducting coil cartridge 3. However, in this system, the two-stage regenerative refrigerator 21A is directly attached to the vacuum vessel 7, and it becomes difficult to replace the refrigerator. Further, the specific heat of the copper, aluminum, and NbTi wire constituting the superconducting coil cartridge 3 becomes very small at 4K. For this reason, the heat capacity at 4K of the support 1 and the superconducting coil 2A is small, and when the two-stage regenerative refrigerator 21A stops, the temperature of the superconducting coil 2A easily rises. Accordingly, the two-stage regenerative refrigerator 21A is required to have high reliability so as to stably generate the refrigerating capacity.
Further, when this type of superconducting magnet device is used in a small physical property measuring device or the like, it is necessary to greatly change the magnetic field, and it is used in a state where a power source is connected. In such a case, since the operation and the stop are frequently repeated, the requirement for reliability is small as compared with an MRI apparatus or the like, but ease of use and safety are required.

JP-A-5-59568

  In the conventional superconducting magnet apparatus shown in FIG. 9, a two-stage regenerative refrigerator 21 has a first and second heat stages 24 and 26 thermally connected to the heat shield 5 and the superconducting coil cartridge 3. And the second thermal connection portions 33 and 35 are inserted and attached in the mounting cylinder 30 so as to be thermally connected, the thermal resistance at the thermal connection portion is increased, and the two-stage regenerative refrigerating type refrigeration having a large refrigerating capacity. There is a problem that the machine 21 is necessary and disadvantageous in terms of power consumption. In the operation state, the mounting cylinder 30 and the two-stage regenerative refrigerator 21 are in a vacuum state, and the superconducting coil cartridge 3 and the heat are exchanged when the two-stage regenerative refrigerator 21 is replaced. There is also a problem that it is necessary to raise the temperature of the shield 5 to room temperature, and it takes time to replace the two-stage regenerative refrigerator 21.

  In the conventional superconducting magnet apparatus shown in FIG. 10, the second heat stage 26 of the two-stage regenerative refrigerator 21A is thermally connected to the superconducting coil 2A via the heat conducting member 51 and the heat transfer plate 50. Therefore, there is a problem that the thermal resistance at the heat connecting portion is increased, the two-stage regenerative refrigerator 21A having a large refrigerating capacity is required, and disadvantageous in terms of power consumption. Further, since the two-stage regenerative refrigerator 21A is directly attached to the vacuum vessel 7, when replacing the two-stage regenerative refrigerator 21A, a cylinder or the like is used so as not to break the vacuum state in the vacuum vessel 7. There was also a problem that it was difficult to replace the two-stage regenerative refrigerator 21A because the internal components were pulled out while leaving the outer cylinder part. Furthermore, since the heat capacity at 4K of the superconducting coil cartridge 3 is small, when the two-stage regenerative refrigerator 21A stops, the temperature of the superconducting coil 2A rises in a short time, and the superconducting state is easily broken. There were also challenges.

  Further, in the improved apparatus for the conventional superconducting magnet apparatus shown in FIG. 10, the second heat stage 26 of the two-stage regenerative refrigerator 21A is directly thermally connected to the superconducting coil cartridge 3, so that the superconducting coil cartridge 3 When the heat capacity at 4K is small and the two-stage regenerative refrigerator 21A is stopped, the temperature of the superconducting coil 2A rises in a short time, and the superconducting state is easily broken. Further, since the two-stage regenerative refrigerator 21A is directly attached to the vacuum vessel 7, when replacing the two-stage regenerative refrigerator 21A, a cylinder or the like is used so as not to break the vacuum state in the vacuum vessel 7. There was also a problem that it was difficult to replace the two-stage regenerative refrigerator 21A because the internal components were pulled out while leaving the outer cylinder part.

The present invention has been made to solve the above-described problems, facilitates the exchangeability of the multistage regenerative refrigerator, and between the superconducting coil and the final stage heat stage of the multistage regenerative refrigerator. An object is to obtain a superconducting magnet device capable of reducing thermal resistance.
It is another object of the present invention to provide a superconducting magnet device that can suppress a temperature rise of a superconducting coil and maintain a superconducting state for a long time even when a multistage regenerative refrigerator is stopped.

  The present invention includes a vacuum container, a superconducting coil cartridge having a superconducting coil disposed in the vacuum container, a heat shield disposed in the vacuum container so as to surround the superconducting coil cartridge, and a plurality of The mounting cylinder is connected via the mounting heat connection portion of each stage, and the mounting heat connection portion of each stage is thermally connected to the heat shield and the superconducting coil cartridge, respectively, and attached to the vacuum vessel in an airtight manner. The chiller mounting cylinder and the thermal stage of each stage are thermally connected to the mounting heat connection portions of the respective stages of the chiller mounting cylinder and attached to the chiller mounting cylinder, and the superconducting coil cartridge is interposed therebetween. A superconducting magnet apparatus comprising a multi-stage regenerative refrigerator for cooling approximately 4K for conducting and cooling the superconducting coil to approximately 4K. The space between the freezing machine mounting cylinder and the multi-stage regenerative refrigerator, the helium gas introduction pipe that allows supplying the helium gas from the cold section but on the aforementioned cylinder for fastening the refrigerator.

  According to the present invention, the multistage regenerative refrigerator can be easily replaced, the thermal resistance between the superconducting coil and the final stage heat stage of the multistage regenerative refrigerator can be reduced, and the multistage regenerative refrigerator can be reduced. Even when is stopped, it is possible to obtain a superconducting magnet device capable of suppressing the temperature rise of the superconducting coil and maintaining the superconducting state for a long time.

Embodiments of the present invention will be described below with reference to the drawings.
Embodiment 1 FIG.
1 is a cross-sectional view showing a superconducting magnet device according to Embodiment 1 of the present invention.
In the figure, a superconducting coil cartridge 3 is constructed by attaching a superconducting coil 2A made of NbTi to a support 1 made of a metal such as aluminum. The superconducting coil cartridge 3 is accommodated in a heat shield 5 disposed in a vacuum vessel 7. The inside of the vacuum container 7 is maintained at a high vacuum to reduce heat intrusion into the superconducting coil cartridge 3 and the heat shield 5. The superconducting coil cartridge 3 is heat-insulated and supported by the heat shield 5 by the second heat-insulating support 4, and the heat shield 5 is heat-insulated and supported by the vacuum vessel 7 by the first heat-insulating support 6.
Here, the second and first heat insulating supports 4 and 6 are made of a material having low thermal conductivity and high strength, for example, GFRP (Glass Fiber Resinforced Plastic). The heat shield 5 is made of aluminum, copper, or an alloy thereof having a high thermal conductivity.

The two-stage regenerative refrigerator 21A includes a drive unit 22, a first cylinder 23, a first heat stage 24, a second cylinder 25, a second heat stage 26, and a gas pipe and a compressor (not shown). A magnetic regenerator material such as GdRh, Gd0.5Er0.5Rh or the like is used as the regenerator material in the second cylinder 25, and the heat shield 5 and the superconducting coil cartridge 3 are about 50K by the first and second heat stages 24 and 26, respectively. It cools to about 4K. The refrigerator mounting cylinder 30 is for making the two-stage regenerative refrigerator 21A detachable and facilitating its maintenance and replacement. The mounting flange 31, the first mounting cylinder 32, and the first mounting heat connection It is comprised from the part 33, the 2nd attachment cylinder 34, and the 2nd attachment heat connection part 35. As shown in FIG. The mounting cylinder 30 has its mounting flange 31 hermetically attached to the vacuum vessel 7 and is inserted through the vacuum vessel 7 and the heat shield 5 from the outside. The first attachment heat connection portion 33 is thermally connected to the heat shield 5, and the second attachment heat connection portion 35 is thermally connected to the superconducting coil cartridge 3. Further, in the two-stage regenerative refrigerator 21 </ b> A, the first heat stage 24 is thermally connected to the first attachment heat connection portion 33, and the second heat stage 26 is thermally connected to the second attachment heat connection portion 35. , Inserted into the mounting cylinder 30 and attached in an airtight manner.
Here, for example, stainless steel is used for each cylinder, and for example, copper or aluminum is used for each heat stage and each mounting heat connecting portion.

Further, the helium introduction tube 40 is attached to the attachment flange 31 so that one end thereof faces the inside of the attachment cylinder 30. A first joint 42 is attached to the other end of the helium introduction pipe 40. Further, a cutoff valve 41, a safety valve 47 and a pressure gauge 48 are attached to the helium introduction pipe 40.
Further, the pipe 44 is connected to the helium container 46, and the second joint 43 is attached to the other end of the pipe 44. A pressure reducing valve 45 is attached to the pipe 44.

When operating the superconducting magnet apparatus configured as described above, first the first joint 42 and the second joint 43 are connected, the helium introduction pipe 40 and the pipe 44 are connected, and the cutoff valve 41 is opened. Then, the helium gas 60 decompressed to about atmospheric pressure by the pressure reducing valve 45 is introduced into the mounting cylinder 30 from the helium container 46 through the pipe 44, the shutoff valve 41 and the helium introducing pipe 40.
When the two-stage regenerative refrigerator 21A is operated and the initial cooling proceeds, when the helium gas 60 introduced into the mounting cylinder 30 is cooled to a pressure equal to or lower than the set value of the pressure reducing valve 45, a new helium gas 60 is obtained. Is introduced through the above-mentioned path, and the pressure in the mounting cylinder 30 is controlled to be almost atmospheric pressure. Finally, when the temperature of the second heat stage 26 becomes approximately 4K, a part of the helium gas 60 in the mounting cylinder 30 is liquefied and becomes liquid helium 61 at the bottom of the second cylinder 25 of the mounting cylinder 30. Accumulate. When the predetermined amount of liquid helium 61 is generated and the initial cooling is completed, the helium container 46 is no longer needed, so the cutoff valve 41 is closed and the helium container 46 is separated from the second joint 43.

Here, the thermal connection between the second thermal stage 26 and the second attachment thermal connection portion 35 is obtained by adding a good thermal connection accompanying the boiling and condensation of the liquid helium 61 to the solid contact, and similarly, the first thermal stage. The thermal connection between the first mounting thermal connection portion 33 and the first attachment thermal connection portion 33 is obtained by adding a good thermal connection associated with the convection and conduction of the helium gas 60 to the solid contact.
Therefore, the heat energy of the superconducting coil cartridge 3 is absorbed by the second heat stage 26 via the second attachment heat connection portion 35 and the liquid helium 61 and cooled to about 4K. Further, the heat energy of the heat shield 5 is absorbed by the first heat stage 24 via the first attachment heat connecting portion 33 and the helium gas 60 and cooled to about 50K.
In this state, a current is passed through the superconducting coil 2A using a power lead (not shown) that supplies current from an external power source (not shown) to generate a strong magnetic field.

As described above, according to the first embodiment, the thermal connection between the second thermal stage 26 and the second attachment thermal connection portion 35 is not only in contact with the solid but also in good heat accompanying the boiling and condensation of the liquid helium 61. A connection is added, and the thermal resistance of the thermal connection between the two is greatly reduced. Similarly, the thermal connection between the first thermal stage 24 and the first attachment thermal connection portion 33 is not only a solid contact, but also a good thermal connection associated with the convection and conduction of the helium gas 60, and the thermal connection portion between the two. The thermal resistance of is greatly reduced. Therefore, the temperature gradient between the superconducting coil 2A and the second heat stage 26 and the temperature gradient between the heat shield 5 and the first heat stage 24 are extremely reduced, and it is necessary to use a refrigerator having a large refrigerating capacity. This is very advantageous in terms of power consumption.
Further, since the liquid helium 61 is stored at the bottom of the mounting cylinder 30, even if the two-stage regenerative refrigerator 21A stops, the superconducting coil 2A can be maintained at approximately 4K until the liquid helium 61 has completely evaporated, The superconducting state can be maintained for a long time.
Further, since the space between the mounting cylinder 30 and the two-stage regenerative refrigerator 21A is filled with the helium gas 60 at atmospheric pressure, no force is applied when replacing the two-stage regenerator refrigerator 21A. It is not necessary to raise the temperature of the superconducting coil cartridge 3 and the heat shield 5 to room temperature as in the above apparatus, and the replacement time can be shortened and the replacement workability can be improved.

The range of the pressure gauge 48 is preferably about 2 × 10 5 Pa (2 bar) from vacuum. By using the vacuum gauge in such a range, a gas thermometer can be configured, and the temperature of the second thermal stage 26 can be measured at a low cost.
Further, in the event of an accident such as a power failure, the liquid helium 61 may evaporate and the pressure in the mounting cylinder 30 may increase significantly. However, since the safety valve 47 is used, if the internal pressure increases excessively, The safety valve 47 is actuated to control the internal pressure so as not to exceed a predetermined value, thereby ensuring safety.

Embodiment 2. FIG.
FIG. 2 is a cross-sectional view showing the main part of the superconducting magnet device according to Embodiment 2 of the present invention.
In the second embodiment, as shown in FIG. 2, the liquid helium storage container 70 is provided in the second mounting heat connection portion 35 of the mounting cylinder 30, and the liquid helium introduction path 71 is connected to the liquid helium storage container 70. The second attachment heat connection portion 35 is drilled so as to communicate with the inside of the refrigerator attachment cylinder 30. Here, the liquid helium storage container 70 is made of copper or aluminum having a large thermal conductivity, like the second attachment heat connecting portion 35.
Other configurations are the same as those in the first embodiment.

In the superconducting magnet apparatus configured as described above, when the two-stage regenerative refrigerator 21A is operated and the initial cooling proceeds, the helium gas 60 introduced into the mounting cylinder 30 is cooled and the set value of the pressure reducing valve 45 is reached. When the following pressure is reached, new helium gas 60 is introduced through the above path, and the pressure in the mounting cylinder 30 is controlled to substantially atmospheric pressure. Finally, when the temperature of the second heat stage 26 becomes approximately 4K, a part of the helium gas 60 in the mounting cylinder 30 is liquefied and becomes liquid helium 61 from the bottom of the second cylinder 25 of the mounting cylinder 30. It accumulates in the liquid helium storage container 70 through the liquid helium introduction path 71.
Therefore, also in the second embodiment, the same effect as in the first embodiment can be obtained.

Even in the second embodiment, even when the two-stage regenerative refrigerator 21A is stopped, 4.2K can be maintained while the liquid helium 61 evaporates.
For example, the amount of heat penetration into 4K of a superconducting magnet device used in a medical MRI apparatus that requires high reliability is about 0.5 W. When calculated from the latent heat of vaporization of liquid helium, the amount of helium vaporization when the heat input is 1 W is 1.4 l / h. Therefore, for example, when a 20 l liquid helium storage container 70 is used,
It becomes possible to maintain the superconducting state for 20 / (0.5 × 1.4) = 29 hours. On the other hand, if the temperature rise is calculated only by the heat capacity of the superconducting coil cartridge 3, the superconducting state may be broken within 30 minutes, and it can be seen that the effect of liquid helium is great.
Therefore, the superconducting magnet device according to the second embodiment is sufficiently applicable to a medical superconducting magnet device that is used in the permanent current mode and requires high reliability. In this case, a permanent current switch (not shown) is installed in series with the superconducting coil 2A.

Embodiment 3 FIG.
In the third embodiment, as shown in FIG. 3, a thermal connection part 72 is provided in a part of the liquid helium storage container 70, and the liquid helium storage container 70 is connected to the superconducting coil cartridge via the thermal connection part 72. 3 is connected to the support 1 by heat.
Other configurations are the same as those in the second embodiment.

  In the third embodiment, the liquid helium storage container 70 held at approximately 4K is firmly thermally connected to the superconducting coil cartridge 3 via the thermal connection portion 72. Therefore, when cooling is performed only by heat conduction of the superconducting coil cartridge 3, a temperature gradient is likely to be generated in the superconducting coil cartridge 3, but the temperature gradient is obtained by thermally connecting the liquid helium storage container 70 held at approximately 4K. Can be reduced.

Embodiment 4 FIG.
In the fourth embodiment, as shown in FIG. 4, two superconducting coil cartridges 3 are arranged apart from each other in the vertical direction, and two liquid helium storage containers 70 are thermally connected to each of the superconducting coil cartridges 3. The two liquid helium storage containers 70 are connected by a helium communication pipe 73.
Other configurations are the same as those in the third embodiment.

When the cooling is performed only by the heat conduction of the two superconducting coil cartridges 3 arranged apart from each other, the temperature gradient becomes large, and the temperature of the superconducting coil cartridge 3 rises.
In the fourth embodiment, since the two liquid helium storage containers 70 are connected by the helium communication pipe 73, the liquid helium 61 can be freely introduced into each liquid helium storage container 70, and each liquid helium storage container 70 can be introduced. The container 70 can be held at approximately 4K. Therefore, even if the two superconducting coil cartridges 3 are separated from each other, each superconducting coil cartridge 3 is thermally connected to the liquid helium storage container 70 held at approximately 4K through the thermal connection portion 72. The temperature rise is suppressed and the temperature is kept low.

Embodiment 5. FIG.
In the fifth embodiment, as shown in FIG. 5, the container 49 is provided in the path of the helium introduction pipe 40, and the cutoff valve 41 is provided between the container 49 and the first joint 42.
Other configurations are the same as those in the first embodiment.

In the superconducting magnet device according to the first embodiment, when the operation is stopped, the liquid helium 61 evaporates and increases in volume, and the helium gas 60 in the mounting cylinder 30 expands as the temperature rises, so the pressure increases. . And if the pressure in the attachment cylinder 30 rises too much, the safety valve 47 will act | operate and helium gas 60 will be discharge | released outside.
However, in the fifth embodiment, the helium gas 60 expanded as the temperature rises in the mounting cylinder 30 is pushed out into the container 49 provided in the normal temperature section through the helium introduction pipe 40, and in the mounting cylinder 30. Increase in pressure is suppressed. Therefore, even if the superconducting coil cartridge 3 returns to normal temperature, the safety valve 47 does not operate, the amount of helium in the mounting cylinder 30 is maintained, and it is not necessary to replenish the helium gas 60 from the helium container 46, which is advantageous in terms of cost. Become.
As described above, according to the fifth embodiment, a superconducting magnet device that can be sufficiently applied to an experimental superconducting magnet device that is often repeatedly operated and stopped is obtained.
Although the pressure increase is smaller as the volume of the container 49 is larger, it is desirable that the container 49 is appropriately sized so that the safety valve 47 does not operate.

Embodiment 6 FIG.
In the sixth embodiment, as shown in FIG. 6, the two-stage regenerative refrigerator 21 </ b> A has the outer diameter of the first cylinder 23 and the outer diameter of the first heat stage 24 substantially equal, and further the second cylinder 25. The outer diameter of the second heat stage 26 is substantially equal to the outer diameter of the second heat stage 26, and the refrigerator mounting cylinder 30 has the inner diameter of the first mounting cylinder 32 substantially equal to the outer diameter of the first heat stage 24. The inner diameter of 34 is configured to be approximately equal to the outer diameter of the second heat stage 26.
Other configurations are the same as those in the first embodiment.

In the superconducting magnet device according to the first embodiment, when the operation is stopped, the liquid helium 61 evaporates and increases in volume, and the helium gas 60 in the mounting cylinder 30 expands as the temperature rises, so the pressure increases. . This increase in pressure increases as the amount of liquid helium 61 increases and the volume of the low temperature portion increases.
However, in the sixth embodiment, the outer diameter of the first cylinder 23 and the inner diameter of the first mounting cylinder 32 are substantially equal to the outer diameter of the first thermal stage 24, and the outer diameter of the second cylinder 25 and the second mounting cylinder 34. Is smaller than the outer diameter of the second thermal stage 26, so that the gap between the first cylinder 23 and the first mounting cylinder 32 and the gap between the second cylinder 25 and the second mounting cylinder 34 are small. The volume of the space between the two-stage regenerative refrigerator 21A and the refrigerator mounting cylinder 30 can be reduced.
Therefore, an increase in pressure in the mounting cylinder 30 when the operation is stopped can be suppressed, and the same effect as in the fifth embodiment can be obtained.

Embodiment 7 FIG.
In the seventh embodiment, as shown in FIG. 7, the fillings 80 and 81 are inserted into the gap between the first cylinder 23 and the first mounting cylinder 32 and the gap between the second cylinder 25 and the second mounting cylinder 34, respectively. Has been. The fillings 80 and 81 are formed by molding a low thermal conductivity material, for example, a natural rubber foam into a cylindrical shape.
Other configurations are the same as those in the first embodiment.

  Also in the seventh embodiment, the filling 80, 81 reduces the volume of the space between the two-stage regenerative refrigerator 21A and the refrigerator mounting cylinder 30, and the same effect as in the sixth embodiment can be obtained. .

Embodiment 8 FIG.
In the eighth embodiment, as shown in FIG. 8, the first mounting cylinder 32 and the second mounting cylinder 34 of the refrigerator mounting cylinder 30 are made of fiber reinforced resin, for example, GFRP. Then, both ends of the first mounting cylinder 32 are joined to the outer periphery of the mounting flange 31 and the first mounting heat connecting portion 33, and both ends of the second mounting cylinder 34 are connected to the first mounting heat connecting portion 33 and the second mounting heat connecting portion. It is joined to the outer periphery of 35.
Other configurations are the same as those in the first embodiment.

In the eighth embodiment, since the first and second mounting cylinders 32 and 34 are made of GFRP having a lower thermal conductivity than stainless steel, the amount of heat penetration can be kept small.
Further, GFRP has a large thermal contraction rate. When helium gas is introduced from the outside through the helium introduction pipe 40 and initial cooling is performed, the first and second mounting cylinders 32 and 34 are thermally contracted. Since the first and second mounting cylinders 32 and 34 are joined to the outer periphery of the mounting flange 31 and the first and second mounting heat connection portions 33 and 35, the airtightness of the refrigerator mounting cylinder 30 is ensured, and helium gas Leakage can be prevented.

In the eighth embodiment, the first and second mounting cylinders 32 and 34 are made of GFRP which is a fiber reinforced resin, but may be made of CFRP (C-arbon Fiber Resinforced Plastic) instead of GFRP. Good.
In this case, CFRP is a material having a low thermal conductivity like GFRP. However, since CFRP has a characteristic of transferring heat relatively in a high temperature region, it has a large refrigerating capacity when performing initial cooling. Part of the refrigeration capacity of the one heat stage 24 can be used, and an initial cooling time can be proposed.

In each of the above embodiments, a two-stage regenerative refrigerator is used. However, the regenerative refrigerator is not limited to a two-stage refrigerator, and can be selected according to the number of installed heat shields. Well, for example, if the heat shields are arranged so as to surround the superconducting coil cartridge, a three-stage regenerative refrigerator is used.
Moreover, this invention is applied also to the superconducting magnet apparatus which combined the characteristic part of said each embodiment.

  According to the present invention, a vacuum container, a superconducting coil cartridge having a superconducting coil disposed in the vacuum container, a heat shield disposed in the vacuum container so as to surround the superconducting coil cartridge, A plurality of mounting cylinders are connected via mounting heat connection portions at each stage, and the mounting heat connection portions at each stage are thermally connected to the heat shield and the superconducting coil cartridge, respectively, and airtight to the vacuum vessel. The superconducting coil cartridge is mounted on the refrigerator mounting cylinder by thermally connecting the refrigerator mounting cylinder mounted on the refrigerator and the heat stage of each stage to the mounting heat connecting portion of each stage of the refrigerator mounting cylinder. A superconducting magnet apparatus comprising a multi-stage regenerative refrigerator for cooling of approximately 4K that conducts and cools the superconducting coil to approximately 4K via Since the helium gas introduction pipe that enables the supply of helium gas from the room temperature portion is provided in the refrigerator mounting cylinder in the space between the refrigerator mounting cylinder and the multistage cool storage type refrigerator, the multistage cool storage type This makes it easy to replace the refrigerator, reduce the thermal resistance between the superconducting coil and the final stage heat stage of the multistage regenerative refrigerator, and even when the multistage regenerative refrigerator stops, It is possible to obtain a superconducting magnet device that can suppress the temperature rise and can maintain the superconducting state for a long time.

  In addition, since helium gas supplied at room temperature is liquefied at least partially in the space between the final stage heat stage of the multistage regenerative refrigerator and the refrigerator mounting cylinder, the multistage regenerative regenerator In addition to the solid contact, the thermal connection between the final stage heat stage of the type refrigerator and the refrigerator mounting cylinder adds a good thermal connection due to the boiling and condensation of liquid helium, and the thermal resistance of the thermal connection between them is reduced. It is greatly reduced.

  Further, since the cutoff valve is provided in the helium gas introduction pipe of the refrigerator mounting cylinder, it is easy to introduce helium gas into the refrigerator mounting cylinder.

  In addition, a liquid helium storage container is disposed on the outer peripheral portion of the mounting heat connection portion at the final stage of the refrigerator mounting cylinder, and a liquid helium introduction path communicates the refrigerator mounting cylinder and the liquid helium storage container. As described above, the superheated state can be maintained for a long time even when the multistage regenerative refrigerator is stopped.

  Further, a thermal connection part is provided in a part of the liquid helium storage container, and the superconducting coil cartridge is thermally connected to the liquid helium storage container via the thermal connection part. Can be reduced.

  In addition, a plurality of superconducting coil cartridges are dispersedly arranged, and the plurality of superconducting coil cartridges are thermally connected to the liquid helium storage container through the thermal connection portion, respectively. The temperature of each can be kept low.

  In addition, since a container that alleviates the pressure increase associated with the expansion of the helium gas in the refrigerator mounting cylinder is provided in the room temperature portion of the helium gas introduction pipe, the refrigerator when the multistage regenerative refrigerator is stopped An increase in pressure in the mounting cylinder can be suppressed.

Further, since the outer diameter of the cylinder of the multistage regenerative refrigerating machine and the inner diameter of the mounting cylinder of the refrigerating machine mounting cylinder are substantially the same as the outer diameter of the heat stage, the multistage regenerative refrigerating machine The pressure rise in the refrigerator mounting cylinder when the machine stops can be suppressed.

  In addition, since the padding made of low thermal conductivity material is inserted into the gap between the mounting cylinder of the refrigerator mounting cylinder and the cylinder of the multistage regenerative refrigerating machine, the refrigeration when the multistage regenerative refrigerating machine stops The pressure rise in the machine mounting cylinder can be suppressed.

  Further, since the mounting cylinder of the refrigerator mounting cylinder is made of fiber reinforced resin, the amount of heat penetration can be suppressed.

  Further, since the fiber reinforced resin is a carbon fiber reinforced resin, the initial cooling time can be shortened.

It is sectional drawing which shows the superconducting magnet apparatus which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the principal part of the superconducting magnet apparatus which concerns on Embodiment 2 of this invention. It is sectional drawing which shows the principal part of the superconducting magnet apparatus which concerns on Embodiment 3 of this invention. It is sectional drawing which shows the principal part of the superconducting magnet apparatus which concerns on Embodiment 4 of this invention. It is sectional drawing which shows the superconducting magnet apparatus which concerns on Embodiment 5 of this invention. It is sectional drawing which shows the principal part of the superconducting magnet apparatus which concerns on Embodiment 6 of this invention. It is sectional drawing which shows the principal part of the superconducting magnet apparatus which concerns on Embodiment 7 of this invention. It is sectional drawing which shows the refrigerator attachment cylinder applied to the superconducting magnet apparatus which concerns on Embodiment 8 of this invention. It is sectional drawing which shows the conventional superconducting magnet apparatus. It is sectional drawing which shows the principal part of the other example of the conventional superconducting magnet apparatus. It is a figure which shows the freezing characteristic of a two-stage type cool storage type refrigerator.

Explanation of symbols

  2A superconducting coil, 3 superconducting coil cartridge, 5 heat shield, 7 vacuum vessel, 21A two-stage regenerative refrigerator, 23 first cylinder, 24 first heat stage, 25 second cylinder, 26 second heat stage, 30 freezing Machine mounting cylinder, 32 1st mounting cylinder, 33 1st mounting thermal connection, 34 2nd mounting cylinder, 35 2nd mounting thermal connection, 40 helium inlet tube, 41 shutoff valve, 49 container, 60 helium gas, 61 liquid Helium, 70 liquid helium reservoir, 71 liquid helium inlet, 72 thermal connection, 80, 81 padding.

Claims (11)

A vacuum container, a superconducting coil cartridge having a superconducting coil disposed in the vacuum container, a heat shield disposed in the vacuum container so as to surround the superconducting coil cartridge, and a plurality of mounting cylinders are provided. Refrigerator configured to be connected via a stage mounting heat connection portion, wherein each stage mounting heat connection portion is thermally connected to the heat shield and the superconducting coil cartridge, and is hermetically attached to the vacuum vessel. The mounting cylinder and the thermal stage of each stage are thermally connected to the mounting heat connection portion of each stage of the refrigerator mounting cylinder and mounted on the refrigerator mounting cylinder, and the superconducting coil is connected to the refrigerator mounting cylinder via the superconducting coil cartridge. In a superconducting magnet apparatus provided with a multi-stage regenerative refrigerator for approximately 4K cooling that conducts and cools to approximately 4K.
A superconductivity characterized in that a helium gas introduction pipe that enables supply of helium gas from a normal temperature part is provided in the space between the refrigerator mounting cylinder and the multistage regenerator type refrigerator. Magnet device.   By liquefying at least part of the helium gas supplied at normal temperature in the space between the final stage heat stage of the multistage regenerative refrigerator and the refrigerator mounting cylinder, the multistage regenerative refrigerator 2. The superconducting magnet device according to claim 1, wherein a thermal resistance of a thermal connection portion between a final stage heat stage and the refrigerator mounting cylinder is reduced.   The superconducting magnet apparatus according to claim 1 or 2, wherein a cutoff valve is provided in the helium introduction pipe of the refrigerator mounting cylinder.   A liquid helium storage container is disposed on the outer peripheral portion of the mounting heat connection portion at the final stage of the refrigerator mounting cylinder, and a liquid helium introduction path communicates with the refrigerator mounting cylinder and the liquid helium storage container. The superconducting magnet device according to any one of claims 1 to 3, wherein the superconducting magnet device is formed in the attachment heat connecting portion in the final stage.   5. The thermal connection part is provided in a part of the liquid helium storage container, and the superconducting coil cartridge is thermally connected to the liquid helium storage container via the thermal connection part. Superconducting magnet device.   6. The superconducting device according to claim 5, wherein a plurality of superconducting coil cartridges are arranged in a distributed manner, and the plurality of superconducting coil cartridges are thermally connected to the liquid helium storage container through the thermal connecting portion. Magnet device.   4. A superconducting magnet apparatus according to claim 3, wherein a container for relieving a pressure increase caused by expansion of helium gas in the refrigerator mounting cylinder is provided at a normal temperature portion of the helium gas introduction pipe.   The outer diameter of the cylinder of the multistage regenerative refrigerator and the inner diameter of the mounting cylinder of the refrigerator mounting cylinder are configured so as to substantially coincide with the outer diameter of the thermal stage. The superconducting magnet device according to claim 7.   The padding made of a low thermal conductivity material is inserted into a gap between the mounting cylinder of the refrigerator mounting cylinder and the cylinder of the multistage regenerative refrigerator. The superconducting magnet device described.   The superconducting magnet device according to any one of claims 1 to 9, wherein a mounting cylinder of the refrigerator mounting cylinder is made of fiber reinforced resin.   The superconducting magnet device according to claim 10, wherein the fiber reinforced resin is a carbon fiber reinforced resin.

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