JP2010262950A - Superconducting electromagnet and transport method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress increase in the temperature of a superconducting coil in transport and storage, and to reduce the amount of consumption of refrigerants, when reinjecting the refrigerants by also suppressing an increase in temperature of the superconducting coil when a refrigerating machine stops. <P>SOLUTION: A superconducting electromagnet includes the superconducting coil 7 that is provided in a vacuum vessel 15 and is arranged in a refrigerant vessel 2 for storing the refrigerant 8 for cooling; the refrigeration machine 1 provided at an upper portion of the refrigerant vessel 2 through the vacuum vessel 15; and a conductive cooling member 30 for thermally short-circuiting a low-temperature stage 6 of the refrigeration machine 1 and the superconducting coil 7. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a superconducting electromagnet that generates a strong magnetic field used in, for example, a medical magnetic resonance imaging apparatus and a method for transporting the same.

  The configuration of a conventional superconducting electromagnet is shown in FIG. As shown in this figure, the superconducting coil 7 for generating a magnetic field housed in the liquid helium container 2 disposed in the vacuum container 15, and the vacuum container 15 in the upper part of the liquid helium container 2 at a weak magnetic field portion. The refrigerator 1 is provided so as to pass through and cool the liquid helium container 2, and the liquid helium container 2 is cooled by the refrigerator 1 to reduce heat intrusion into the superconducting coil 7. It was. (For example, see Patent Document 1)

  In addition, without using liquid helium, the winding frame around which the superconducting coil is wound and a plurality of heat pipes are integrated, and each heat pipe is cooled by a refrigerator to reduce heat intrusion into the superconducting coil. Some of them are kept below a predetermined temperature. (For example, see Patent Document 2)

JP 2005-210015 (paragraph 0029, FIG. 1) Japanese Unexamined Patent Publication No. 7-57927 (paragraphs 0006, 0011-0012, FIG. 1)

  In addition to cooling the liquid helium container with a refrigerator, the one disclosed in Patent Document 1 often cannot be transported in a state in which liquid helium is stored during transportation on an aircraft or the like. Therefore, there is a problem that the temperature of the superconducting coil rises during transportation and storage, and a lot of liquid helium is required during recooling.

  Moreover, since the thing shown by patent document 2 does not use liquid helium, when a refrigerator stops, the temperature of a superconducting coil rises immediately and it is necessary to stop the magnetic field generated of a superconducting coil immediately. There was a problem.

  The present invention has been made to solve the above problems, and can suppress the temperature rise of the superconducting coil during transportation and storage, and can also suppress the temperature rise when the refrigerator is stopped. An object of the present invention is to provide a superconducting electromagnet that can be used and a method for transporting the same.

  A superconducting electromagnet according to the present invention is provided in a vacuum vessel, a superconducting coil provided in a refrigerant vessel containing a cooling refrigerant, and a refrigerator provided above the refrigerant vessel through the vacuum vessel And a conductive cooling member that thermally short-circuits the low-temperature stage of the refrigerator and the superconducting coil.

The superconducting electromagnet according to the present invention is configured as described above, and the superconducting coil disposed in the refrigerant container and the refrigerator are thermally short-circuited by the conductive cooling member. Therefore, even when there is no liquid helium as the refrigerant, the superconducting magnet is provided. The coil can be kept at a low temperature.

  In addition, since the refrigerator is operated during storage before and after the transport of the superconducting coil and the refrigerator is stopped during the transportation, the refrigerant is injected after the transportation for a short transportation such as air transportation. In this case, the initial cooling amount can be greatly reduced. In the case of transportation by ship, it takes a long time to transport, but since the refrigerator can be operated during transportation with the power supply or carry-in power supply in the ship, it can be kept cool even during transportation. It will be.

BRIEF DESCRIPTION OF THE DRAWINGS The structure of the superconducting electromagnet by Embodiment 1 of this invention is shown, (a) is a longitudinal cross-sectional view, (b) is sectional drawing along the AA line of (a). It is a longitudinal cross-sectional view which shows the structure of the superconducting electromagnet by Embodiment 2 of this invention. It is a longitudinal cross-sectional view which shows the structure of the conventional superconducting electromagnet.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to the drawings. 1A and 1B show a configuration of a superconducting electromagnet according to Embodiment 1, wherein FIG. 1A is a longitudinal sectional view, and FIG. 1B is a sectional view taken along line AA in FIG.

  As shown in these drawings, a refrigerant container 2 covered with a radiation shield 10 is provided in a vacuum container 15 for heat insulation from a normal temperature part by vacuum, and a superconducting coil 7 is arranged in the refrigerant container 2. It is installed. The refrigerant container 2 also contains liquid helium 8 as a refrigerant, and the space between the liquid surface and the refrigerant container 2 is filled with helium gas 16 to cool the superconducting coil 7.

  Further, in order to suppress evaporation of the liquid helium 8, the refrigerator 1 is provided above the vacuum container 15, and the first stage low temperature stage 3 and the second stage low temperature stage 6 are connected to the vacuum container 15 via the sleeve 4. The second low temperature stage 6 and the superconducting coil 7 are connected by the conductive cooling member 30 so as to be thermally short-circuited through the radiation shield 10 and the refrigerant container 2.

  In such a configuration, by operating the refrigerator 1, the superconducting coil 7 is maintained at a temperature of, for example, 4.2K. Therefore, in this state, even if the superconducting coil 7 transitions (quenches) from the superconducting state to the normal conducting state for some reason, the temperature of the superconducting coil rises due to the stored energy in the superconducting coil, and the liquid helium 8 disappears. Since the refrigerator 1 and the superconducting coil 7 are thermally short-circuited by the conductive cooling member 30, the cooling is continued in the refrigerator 1 even if the temperature of the superconducting coil 7 increases, and liquid helium 8 is injected again. Since the superconducting coil 7 can be sufficiently cooled until this time, the required amount of liquid helium required for the initial cooling to the liquid storage when the liquid helium 8 is injected can be reduced.

  Further, when transporting the superconducting electromagnet, the liquid helium, which is a refrigerant, is often extracted, and when the refrigerant is extracted, the temperature of the superconducting coil 7 rises. According to this embodiment, the temperature of the refrigerator 1 is increased. Since the second low-temperature stage 6 and the superconducting coil 7 are thermally short-circuited by the conductive cooling member 30, if the refrigerator 1 is operated during transportation or storage before and after transportation, the temperature rise of the superconducting coil 7 can be suppressed. This makes it possible to suppress helium consumption for cooling the superconducting coil 7 to the liquid helium temperature when liquid helium is reinjected.

For example, in a superconducting electromagnet in which the superconducting coil 7 and the refrigerant container 2 have a weight to be cooled of 2500 kg and there is no conductive cooling member 30 that directly cools the superconducting coil 7 as in the prior art, the liquid helium 8 that is the refrigerant is removed and frozen. When the machine 1 is stopped, the temperature of the superconducting coil 7 rises to about 100K in about one week. If liquid helium is to be injected from this state, about 1000 liters will be consumed before the liquid storage starts, and even if the refrigerator 1 is operated, it takes 30 days or more to reach about 50K.

On the other hand, in the superconducting electromagnet having the configuration in which the second low temperature stage 6 of the refrigerator 1 and the superconducting coil 7 are thermally short-circuited by the conductive cooling member 30 as in the first embodiment, the thermal conductance is configured at 5 W / K. In this case, the 100K superconducting coil can be cooled for 3.9 days to reach 40K, 4.5 days to reach 20K, and cooled to liquid helium temperature within 5 days. Even if the period is about one week, the consumption of liquid helium can be significantly reduced by operating the refrigerator 1 for 4 or 5 days.

In addition, the consumption of liquid helium is 50 liters when it is cooled to 20K, and it is 200 liters when it is cooled to 1/20 as described above and 40K, which can be significantly suppressed to 1/5 as described above. .
As described above, the superconducting coil 7 and the refrigerator 1 are thermally short-circuited by the conductive cooling member 30 so that the cooling can be performed in any temperature state.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a cross-sectional view showing the configuration of the superconducting electromagnet according to the second embodiment. In this figure, the same or corresponding parts as in FIG.

The difference from FIG. 1 is that the conductive cooling member is formed by a so-called heat pipe 32 formed by pressurizing and sealing helium gas in a thin stainless steel tube. By using the heat pipe 32, the temperature rise of the superconducting coil 7 can be suppressed if the refrigerator 1 is operated during transportation or storage before and after transportation as in the first embodiment. Regardless, when the refrigerator 1 stops, the temperature of the refrigerator 1 rises due to heat intrusion and becomes higher than the temperature of the superconducting coil 7, resulting in a heat load. Therefore, it is difficult for heat intrusion from the refrigerator 1 to be transmitted to the superconducting coil 7, and temperature rise can be suppressed.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described. Embodiment 3 provides a method for transporting a superconducting electromagnet.
When the superconducting electromagnet having the configuration of the first or second embodiment is transported by air or ship, the liquid gas of the refrigerant 8 is extracted, so that the temperature of the superconducting coil 7 rises as it is.

  For this reason, for example, at the time of waiting for unloading during transportation, power is supplied to the refrigerator 1 and the gas compressor and the superconducting coil 7 is cooled to the minimum temperature. In the case of air transportation, since it is difficult to supply power during that time, the refrigerator 1 is stopped. In this case, although the temperature of the superconducting coil 7 rises, in the case of air transportation, since the transportation time is relatively short, it is possible to maintain the low temperature by operating the refrigerator 1 again after arrival and starting cooling. In the case of ship transportation, although the transportation time is long, the power supply of the refrigerator can be supplied by ship power supply or generator operation, so that it can be kept cooled during transportation.

DESCRIPTION OF SYMBOLS 1 Refrigerator, 2 Refrigerant container, 3 1st stage low temperature stage, 4 Sleeve, 6 2nd stage low temperature stage, 7 Superconducting coil, 8 Liquid helium, 10 Radiation shield,
15 vacuum vessel, 16 helium gas, 30 conduction cooling member, 32 heat pipe.

Claims (3)

  A superconducting coil disposed in a refrigerant container provided in a vacuum container and containing a cooling refrigerant, a refrigerator provided on the refrigerant container through the vacuum container, and a low-temperature stage of the refrigerator And a conductive cooling member that thermally short-circuits the superconducting coil.   The superconducting electromagnet according to claim 1, wherein the conductive cooling member is a heat pipe.   The refrigerator is stopped when the superconducting electromagnet according to claim 1 or 2 is transported, and the superconducting coil is kept at a low temperature by operating the refrigerator during storage of the superconducting magnet before and after transporting. A method for transporting a superconducting electromagnet.

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