JP2010258376A - Superconducting magnet device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain the generation of eddy current, while miniaturizing a device, in a superconducting magnet device having a means blocking the radiation heat radiated from the outside of the device. <P>SOLUTION: The superconducting magnet device includes a superconducting coil 13 using a high temperature superconducting material, a superconductive current lead 19 for sending currents to the superconducting coil 13, a refrigerator 18 for performing cooling process so as to cool the superconducting coil 13 to a superconducting state, a thermally shielding means which thermally shields the superconducting coil 13 from the outside, and a load supporter 15 for supporting the superconducting coil 13. An MLI (multilayer heat insulating material) 16 as the thermally shielding means is arranged around the superconducting coil 13. A thermal anchor 20, which connects thermally the superconductive current lead 19 and the load supporter 15, and the refrigerator 18, is prepared. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a superconducting magnet device, and more particularly to a superconducting magnet device having means for blocking radiant heat from the outside of the device.

  A conventional superconducting magnet apparatus is shown in FIG. A superconducting magnet device 100A shown in FIG. 1 includes a vacuum vessel 102, a superconducting coil 103, a heat transfer member 104, a load support 105, a heat shield plate 107, a refrigerator 108, and the like.

  The vacuum container 102 is an airtight container, and has a configuration in which the inside can be evacuated. The superconducting coil 103 is formed of a low temperature superconducting wire, and is in a superconducting state at an ultralow temperature of about 4K, for example.

  The superconducting coil 103 is cooled by the refrigerator 108. The refrigerator 108 is a two-stage refrigerator, and the first stage 108 a is thermally connected to the heat shield plate 107, and the second stage 108 b is thermally connected to the superconducting coil 103 via the heat transfer member 104. It is connected.

  The heat shield plate 107 is cooled by the refrigerator 108 to block heat (radiant heat) transmitted from the outside of the apparatus to the superconducting coil 103. The heat transfer member 104 and the heat shield plate 107 use a material (copper or aluminum) having a high thermal conductivity in order to increase the cooling efficiency. In addition, these materials have a large electrical conductivity.

  On the other hand, the current line for energizing the superconducting coil 103 is made of a material having a high electrical conductivity (for example, copper, aluminum, etc.) between the vacuum vessel 102 and the heat shield plate 107 described later. On the other hand, between the heat shield plate 107 and the superconducting coil 103, there is used a superconducting current lead 109 that can suppress heat penetration and can carry a large current.

  The load support 105 is made of a high-strength insulating material (GFRP, CFRP, etc.). Since this load support 105 is directly connected to the superconducting coil 103 from the vacuum vessel 102 at room temperature, it becomes a source of heat Q1 entering the superconducting coil 103. Therefore, in order to suppress the heat intrusion into the superconducting coil 103, the load support 105 is installed between the vacuum vessel 102 and the superconducting coil 103 and is thermally connected to the heat shield plate 107 cooled by the refrigerator 108. Has been.

  A superconducting magnet device is also provided in which a multilayer heat insulating material is disposed on the outer periphery of the heat shield plate 107 in order to more reliably block heat (radiant heat) transmitted to the superconducting coil 103 from the outside of the device.

JP 2001-167923 A JP 2001-044018 A

  By the way, as is well known, in a region where a magnetic flux change occurs due to a magnetic change, if a metal member exists in the region, an eddy current is generated in the metal member. FIG. 4 is a schematic enlarged view showing the superconducting coil 103 and the heat shield plate 107.

  As shown in the figure, the heat shield plate 107 exists in a region where the magnetic flux generated in the superconducting coil 103 changes. Therefore, when the magnetic flux change dφ / dt per unit time (t) of the heat shield plate 107 increases due to the magnetic flux φ generated from the superconducting coil 103, an excessive eddy current I is generated in the heat shield plate 107.

  As described above, when an excessive eddy current I is generated in the heat shield plate 107, the heat shield plate 107 generates heat and causes a temperature rise. When the temperature of the heat shield plate 107 rises, the superconducting current lead 109 cannot be sufficiently cooled.

  Further, when the temperature of the heat shield plate 107 rises, the heat Q1 from the load support 105 toward the superconducting coil 103 increases, and the radiant heat from the heat shield plate 107 is also applied to the superconducting coil 103. The amount of heat penetration into 103 increases. In the worst case, the superconducting state of the superconducting current lead 109 and the superconducting coil 103 cannot be maintained, and there is a possibility that a magnetic field cannot be generated.

  As a method of avoiding this and ensuring the performance of the superconducting coil 103 and the superconducting current lead 109, it is conceivable to increase the number of cooling refrigerators 108 arranged. However, this method is not practical because the product cost is increased, the running cost is increased, and the apparatus is enlarged.

  As another method for avoiding heat generation of the heat shield plate 107 due to eddy current, it is conceivable to arrange the heat shield plate 107 in a place where the magnetic flux change dφ / dt is small. However, the superconducting magnet device 100A is desired to be reduced in size, and if the heat shield plate 107 is disposed in a place where the magnetic flux change dφ / dt is small in the vacuum vessel 102, a so-called dead space is generated and the device is enlarged. .

  In particular, in the superconducting magnet device 100B provided with the iron core 110 so as to surround the superconducting coil 103 as shown in FIG. 5, in order to reduce the weight and size of the device, the iron core 110 which is inevitably heavy is used. In this case, the internal space 112 formed in the iron core 110 needs to be small (narrow). In this case, it is inevitably necessary to reduce the heat shield plate 107 provided in the internal space 112, and the heat shield plate 107 must be disposed in a place where the magnetic flux change dφ / dt is large.

  On the other hand, when the heat shield plate 107 is completely removed, the superconducting current lead 109 cannot be cooled and cannot be used, and the amount of heat Q1 entering the superconducting coil 103 from the load support 105 increases, which is also not realistic. .

  The present invention has been made in view of the above points, and an object of the present invention is to provide a superconducting magnet device that suppresses the generation of eddy currents while reducing the size of the device.

From the first point of view, the above problem is
A superconducting coil using a high-temperature superconducting material;
A current lead for energizing the superconducting coil;
A cooling device that performs a cooling process so that the superconducting coil is in a superconducting state;
Heat shield means for heat-shielding the superconducting coil to the outside;
A superconducting magnet device having a load support for supporting the superconducting coil,
The heat shield means is a multilayer heat insulating material disposed around the superconducting coil,
In addition, this can be solved by a superconducting magnet device provided with a thermal anchor that thermally connects the current lead and the load support to the cooling device.

  According to the disclosed superconducting magnet device, heat penetration from the outside into the superconducting coil is suppressed by disposing a multilayer heat insulating material around the superconducting coil. Further, since the current lead and the load support are cooled by the cooling device via the thermal anchor, it is possible to prevent external heat from entering the superconducting coil via the current lead and the load support. Therefore, it is not necessary to provide a large heat shield as in the prior art, and the apparatus can be downsized.

FIG. 1 is a configuration diagram of a superconducting magnet apparatus according to a first embodiment of the present invention. FIG. 2 is a configuration diagram of a superconducting magnet device according to the second embodiment of the present invention. FIG. 3 is a block diagram of a superconducting magnet device as a first conventional example. FIG. 4 is a diagram for explaining the generation of eddy currents. FIG. 5 is a configuration diagram of a superconducting magnet device as a second conventional example.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a superconducting magnet apparatus 10A according to the first embodiment of the present invention. A superconducting magnet apparatus 10A shown in the figure is a refrigerator-cooled superconducting magnet apparatus, and is applied to, for example, a deflection electromagnet for a proton beam therapy apparatus gantry.

  The superconducting magnet device 10A generally includes a vacuum vessel 12, a superconducting coil 13, a multilayer heat insulating material 16 (hereinafter referred to as MLI 16), a refrigerator 18, a thermal anchor 20, and the like.

  The vacuum container 12 is an airtight container and is connected to a vacuum pump (not shown). By operating this vacuum pump, the inside of the vacuum vessel 12 is configured to be in a vacuum state. The superconducting coil 13 is disposed inside the vacuum vessel 12.

  The superconducting coil 13 is made of a high-temperature superconducting wire, and a material having a critical temperature of 10K or more and 110K or less is selected. Specifically, Bi2223, Bi2212, Y123, MgB2, iron pnictide-based materials, oxide superconductors, etc. can be used as the high-temperature superconducting wire used as the material of the superconducting coil 13, and Bi2223 is particularly desirable. . The superconducting coil 13 is wound around a coil winding frame 17.

  Here, the low temperature superconducting wire means a superconducting wire that is normally used at liquid helium and lower temperature (4.2K or lower), and the low temperature superconducting magnet is commonly used at liquid helium and lower temperature (4.2K or lower). It shall be a superconducting magnet. The high-temperature superconducting wire means a superconducting wire that is used at a higher temperature than the low-temperature superconducting wire. Similarly, the high-temperature superconducting magnet means a superconducting magnet that is used at a higher temperature than the low-temperature superconducting wire magnet. And

  The current line for supplying power to the superconducting coil 13 is made of a material having a high electrical conductivity (for example, copper, aluminum, etc.) between the vacuum vessel 12 and the thermal anchor 20. On the other hand, between the thermal anchor 20 and the superconducting coil 13 is used a superconducting current lead 19 that can suppress heat intrusion and can carry a large current.

  The refrigerator 18 is fixed to the vacuum container 12. In the present embodiment, a Gifford McMahon type (GM type) refrigerator is used as the refrigerator 18. This GM type refrigerator 18 is configured such that a displacer reciprocates in a cylinder by driving an internal motor. And by the reciprocating movement of this displacer, it is set as the structure which carries out adiabatic expansion of the high-pressure refrigerant | coolant supplied from the refrigerator compressor which is not shown in figure, and this generates cold.

  The GM refrigerator 18 has a first stage cooling cylinder and a second stage cooling cylinder. The first stage cooling cylinder has a first stage 18a, and the second stage cooling cylinder has a second stage 18b. The first stage 18 a is thermally connected to the thermal anchor 20, and the second stage 18 b is thermally connected to the superconducting coil 13 via the heat transfer member 14.

  The thermal anchor 20 is cooled to about 20K to 110K by the first stage 18a. The heat transfer member 14 is cooled to about 10K to 110K by the second stage 18b. Therefore, the superconducting current lead 19 thermally connected to the thermal anchor 20 and the superconducting coil 13 connected to the heat transfer member 14 are cooled by the refrigerator 18 to realize a superconducting state.

  The thermal anchor 20 is thermally connected to the superconducting current lead 19 as described above, and is also thermally connected to the load support 15. The load support 15 is made of a high-strength insulating material (GFRP, CFRP, etc.).

  Since the load support 15 is directly connected to the superconducting coil 13 from the vacuum container 12 at room temperature, it becomes a heat intrusion source to the superconducting coil 13. Therefore, the load support 15 is thermally connected to the thermal anchor 20 cooled by the refrigerator 18 in order to suppress heat intrusion into the superconducting coil 13.

  The thermal anchor 20 is disposed so as to surround the outer peripheral position of the superconducting coil 13. That is, the thermal anchor 20 has a substantially annular shape and is disposed between the vacuum vessel 12 and the superconducting coil 13.

  Here, since FIG. 1 is a cross-sectional view, the thermal anchor 20 connected to the first stage 18a and the thermal anchor 20 connected to the load support 15 are separately illustrated on the left and right. However, the thermal anchor 20 has an integral structure, and thus the thermal anchors 20 illustrated on the left and right are cooled together by the refrigerator 18. The thermal anchor 20 and the above-described heat transfer member 14 use materials (copper, aluminum) having a high thermal conductivity in order to increase the cooling efficiency.

  Next, the MLI 16 will be described. This embodiment is characterized in that this MLI 16 is used as a heat shield means for heat-shielding the superconducting coil 13 to the outside. The MLI 16 is disposed so as to cover the upper MLI 16 a disposed so as to cover the upper portion of the superconducting coil 13, the side MLI 16 b disposed so as to cover the side portion of the superconducting coil 13, and the lower portion of the superconducting coil 13. The lower MLI 16c is formed. By providing each of the upper, side, and lower MLIs 16a to 16c, the superconducting coil 13 is configured so that the periphery thereof is covered with the MLI 16.

  The MLI 16 has a structure in which, for example, an aluminum vapor-deposited film whose emissivity is reduced by vapor-depositing aluminum on a polyester film and spacers such as nylon nets are alternately laminated. Since this MLI 16 has a low emissivity and is lightweight, it has good usability. The number and thickness of the MLI 16 disposed in the superconducting coil 13 are appropriately set based on the size of the superconducting coil 13 and the volume of the vacuum vessel 12.

  Conventionally, as described above, the MLI is disposed on the outer periphery of the heat shield plate 107 in the superconducting magnet device 100A (see FIG. 3) using the low-temperature superconducting coil 103 that realizes criticality at an extremely low temperature of about 4K. It was broken. In some cases, the MLI is disposed directly on the superconducting coil 103 and the heat shield plate 107 is also disposed.

  However, in the low-temperature superconducting coil 103, when the MLI is arranged on the superconducting coil 103 to cut off the radiant heat from the outside at room temperature, it is necessary to arrange a large number of MLIs, which increases the size of the apparatus. It became the target.

  In contrast, the present embodiment is characterized in that the MLI 16 is directly disposed around the superconducting coil 13, the shield plate 107 is removed, and the thermal anchor 20 is disposed. As mentioned above, it is usually difficult to envisage winding MLI around a superconducting coil, but in this embodiment, focusing on the use of a high-temperature superconducting wire having a higher critical temperature than the low-temperature superconducting wire as the superconducting coil 13, It is conceived that the MLI 16 and the thermal anchor 20 are arranged directly on the superconducting coil 13.

  Thus, by covering the superconducting coil 13 with the MLI 16 and thermally insulating the outside, it is possible to suppress radiant heat from the outside from entering the superconducting coil 13. The superconducting current lead 19 that needs to be in a superconducting state and the load support 15 that needs to prevent heat from entering from the outside are thermally connected to a thermal anchor 20, and the thermal anchor 20 is a refrigerator. 18 is configured to be cooled.

  Therefore, the superconducting coil 13 and the superconducting current lead 19 can be brought into a superconducting state without providing the heat shield plate 107, and the heat can be prevented from entering the superconducting coil 13 from the load support 15. Further, since the heat shield plate 107 is not necessary, the number of parts of the superconducting magnet device 10A can be reduced and the size can be reduced.

  Regarding the eddy current due to the magnetic flux change of the magnetic flux φ generated from the superconducting coil 13, the MLI 16 is disposed in the region where the magnetic flux change of the superconducting coil 13 is generated. As described above, the MLI 16 is made of an aluminum vapor deposited film and nylon. It is a structure in which spacers such as nets are alternately stacked, and thus it is difficult to generate eddy currents. For this reason, even if the magnetic flux change dφ / dt per unit time in the superconducting coil 13 increases, the eddy current loss generated in the MLI 16 is negligible, and thus heat generation due to the eddy current can be reduced.

  Further, by reducing the heat generation due to the eddy current in this way, it becomes possible to cool the superconducting coil 13 and the superconducting current lead 19 to a temperature at which the performance can be maintained with a small number of refrigerators 18, and the superconducting magnet device. The running cost of 10A can be reduced. In addition, since the number of the refrigerators 18 can be reduced, the size of the superconducting magnet device 10A can be reduced.

  FIG. 2 shows a superconducting magnet device 10B according to the second embodiment of the present invention. In FIG. 2, components corresponding to those shown in FIG.

  The superconducting magnet device 10A according to the first embodiment described above has a configuration in which a vacuum container 12 is provided in order to prevent the heat from entering from the outside by making the inside of the device a vacuum. On the other hand, the superconducting magnet device 10B according to the present embodiment has a configuration in which an iron core 30 is provided instead of the vacuum vessel 12. The iron core 30 functions as a yoke for guiding the magnetic flux generated in the superconducting coil 13. Therefore, the provision of the iron core 30 can make the magnetic flux φ generated in the superconducting coil 13 uniform.

  As described above, the superconducting magnet device 10B provided with the iron core 30 so as to surround the superconducting coil 13 as in the present embodiment is necessarily a heavy iron core 30 in order to reduce the weight and size of the device. Therefore, the internal space 31 formed in the iron core 30 also needs to be small (narrow).

  On the other hand, also in the superconducting magnet device 10B according to the present embodiment, the MLI 16 is disposed in the superconducting coil 13, and the MLI 16 prevents the radiant heat from entering the superconducting coil 13. In addition, the superconducting current lead 19 that needs to be cooled in order to maintain the performance and the load support 15 that needs to be cooled in order to suppress external heat intrusion are both the thermal anchor 20 that is cooled by the refrigerator 18. Is thermally connected to.

  Therefore, the heat shield plate 107 (see FIG. 5) that is conventionally disposed in the internal space 112 of the iron core 110 can be made unnecessary in the superconducting magnet device 10B according to the present embodiment, and the internal space 31 is reduced ( Narrow). Thereby, size reduction of the iron core 30 can be achieved, and also weight reduction and size reduction of the superconducting magnet apparatus 10B can be achieved.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific embodiments described above, and various modifications are possible within the scope of the gist of the present invention described in the claims. It can be modified and changed.

10A, 10B Superconducting magnet device 12 Vacuum container 13 Superconducting coil 14 Heat transfer member 15 Load support 16 MLI (multilayer insulation)
18 Refrigerator 19 Superconducting current lead 20 Thermal anchor 20A Lead thermal anchor 20B Support thermal anchor 30 Iron core 31 Internal space

Claims (5)

A superconducting coil using a high-temperature superconducting material;
A current lead for energizing the superconducting coil;
A cooling device that performs a cooling process so that the superconducting coil is in a superconducting state;
Heat shield means for heat-shielding the superconducting coil to the outside;
A superconducting magnet device having a load support for supporting the superconducting coil,
The heat shield means is a multilayer heat insulating material disposed around the superconducting coil,
A superconducting magnet device comprising a thermal anchor that thermally connects the current lead and the load support to the cooling device.   The superconducting magnet device according to claim 1, wherein the superconducting material is a material having a critical temperature of 10K to 110K.   The superconductor according to claim 1 or 2, wherein the cooling device is a two-stage refrigerator, wherein a first stage portion is thermally connected to the thermal anchor and a second stage portion is thermally connected to the superconducting coil. Magnet device.   The superconducting magnet device according to any one of claims 1 to 3, wherein an iron core for homogenizing a magnetic field generated in the superconducting coil is disposed so as to surround at least the superconducting coil.   The superconducting magnet device according to any one of claims 1 to 4, wherein the superconducting material is Bi2223.

Images