JP2016131231A - Permanent current switch and superconducting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a permanent current switch capable of suppressing increase in the load of refrigeration means when turning the switch OFF, while cooling a superconducting wire effectively when turning the switch ON.SOLUTION: In a permanent current switch (1) including a reel (12), a superconducting wire (25), a first heater (21), a housing (30), an operation medium (50), and a second heater (42), the housing (30) has a bottom wall (32), and a support wall (34) for supporting the reel (12) at a position where an interruption space is formed between a lower end (18) of the reel and the bottom wall (32). The amount of the operation medium (50) is set sufficiently so that the operation medium (50) accumulates in the interruption space in the state of liquid phase, when the temperature thereof goes below the condensation temperature, and a solid layer having a shape for filling the interruption space is formed so as to thermally connect the lower end (18) of the reel and the bottom wall (32), when the temperature of the operation medium (50) goes below the solidification temperature.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a permanent current switch that forms a closed circuit through which a permanent current caused by superconducting flows, and a superconducting device including the permanent current switch.

  In general, in an apparatus that needs to generate a static magnetic field, such as an MRI (magnetic resonance imaging) apparatus or an NMR (nuclear magnetic resonance) apparatus, a superconducting magnet (superconducting magnet) is operated in a permanent current mode to generate a static magnetic field. . The permanent current mode means exciting the superconducting magnet with a permanent current. In order to operate a superconducting magnet in the permanent current mode, it is necessary to pass a permanent current through a closed circuit composed of a superconducting wire and incorporating the superconducting magnet.

  In order to pass a permanent current through a closed circuit in which a superconducting magnet is incorporated, first, the closed circuit is disconnected, and a current is supplied from an external power source to the superconducting magnet constituting a part of the closed circuit. Then, the current supplied to the superconducting magnet is confined in the closed circuit constituted by the superconducting wire by connecting the closed circuit again after the value of the current flowing through the superconducting magnet reaches the rating. This confined current flows through the closed circuit as a permanent current. The closing of the closed circuit and the switching of the connection are performed by a permanent current switch connected to the superconducting magnet in the closed circuit. This permanent current switch is a member necessary for constituting a closed circuit including a superconducting magnet. As the permanent current switch, methods such as a thermal type, a magnetic type, and a mechanical type are known. However, since the production is relatively easy, a thermal type permanent current switch is often adopted. In particular, when the uniformity of the magnetic field generated by the superconducting magnet determines the performance of the apparatus, such as an MRI apparatus or NMR apparatus, the thermal type is used frequently instead of the magnetic type.

  Specifically, the thermal permanent current switch includes a superconducting wire and a heater capable of heating the superconducting wire, and by controlling energization to the heater, the superconducting wire is switched to a superconducting state (switch ON state). Switch between normal conducting state (switch off state). For example, if the superconducting wire is brought into a superconducting state (switch ON state) by stopping energization to the heater, a closed circuit incorporating a superconducting magnet is formed, so that a current supplied from an external power source is closed circuit By continuing to flow, the superconducting magnet is excited in the permanent current mode. On the contrary, if the superconducting wire is brought into a normal conducting state (switch OFF state) by energizing the heater, the closed circuit is disconnected, so that the permanent current mode is canceled.

  As such a permanent current switch, for example, the one shown in Patent Document 1 is known. The permanent current switch includes a winding frame, a superconducting wire wound around the winding frame, and a heater wire that is wound around the superconducting wire and heats the superconducting wire. The superconducting wire is connected to a superconducting coil that forms a closed circuit together with the superconducting wire. The superconducting coil and the winding frame are conductively cooled by refrigeration means (a refrigerator and a cooling plate). In the permanent current switch, when the energization to the heater wire is cut off, the superconducting wire is cooled by the refrigeration means via the winding frame, and enters a superconducting state (switch ON state). On the other hand, when the heater wire is energized, the superconducting wire is heated and the superconducting wire enters a normal conducting state (switch OFF state). At this time, there is a concern that the heat generated by the heater wire is transmitted to the refrigeration means via the winding frame, and the load on the refrigeration means is increased. For this reason, in the permanent current switch described in Patent Document 1, a heat insulating material is wound between the winding frame and the superconducting wire. Thereby, the increase in the load of the freezing means resulting from the heat of the heater wire wound around the superconducting wire being transmitted to the freezing means via the winding frame is suppressed.

JP-A-10-189324

  In the permanent current switch described in Patent Document 1, since a heat insulating material is provided between the winding frame and the superconducting wire, an increase in the load of the refrigeration unit when the switch is turned off is suppressed, but the heat insulation is performed. The material inhibits heat conduction from the superconducting wire to the winding frame and the refrigeration means when the switch is turned on, that is, cooling of the superconducting wire. For this reason, the time required from the switch OFF state to the switch ON state becomes longer.

  An object of the present invention is to provide a permanent current switch that can suppress an increase in the load of the refrigeration means when the switch is turned off and can effectively cool the superconducting wire when the switch is turned on. is there.

  As means for solving the above-mentioned problems, the present invention is a permanent current switch that constitutes a closed circuit through which a permanent current flows together with a superconducting coil and is capable of interrupting the closed circuit, and is wound around the winding frame and the winding frame. A superconducting wire connectable to the superconducting coil; and a first heater capable of heating the superconducting wire so that the temperature of the superconducting wire is equal to or higher than a critical temperature at which the superconducting wire changes from a superconducting state to a normal conducting state. And a refrigeration means for cooling the superconducting wire so that the reel, the superconducting wire, and the first heater can be accommodated in a sealed state, and the temperature of the superconducting wire is equal to or lower than the critical temperature. A housing to be connected, a working medium enclosed in the housing, having a solidification temperature higher than a critical temperature of the superconducting wire, and a temperature of the working medium equal to or higher than the solidification temperature A second heater capable of heating the working medium, wherein the casing is thermally connected to the refrigeration means, and the winding is connected to the bottom wall together with the bottom wall. A cut-off space having a shape that accommodates the frame, the superconducting wire, and the first heater in a sealed state and capable of blocking a thermal connection between the lower end portion of the winding frame and the bottom wall is a lower end portion of the winding frame. And a support wall that supports the reel at a position formed between the bottom wall and the bottom wall, and the amount of the working medium is determined when the temperature of the working medium is equal to or lower than the condensation temperature. The medium is accumulated in the shut-off space in a liquid phase state, and the lower end of the reel and the bottom wall are thermally connected when the temperature of the working medium becomes equal to or lower than the solidification temperature. It is set to an amount sufficient to form a solid layer having a shape that fills the blocking space. , To provide a permanent current switch.

  In the present invention, when the first heater is energized, the superconducting wire is changed from the superconducting state (switch ON state) to the normal conducting state (switch OFF state), and at this time, the heat generated in the first heater is cut off via the reel. Since the solid layer is vaporized by being transmitted to the solid layer (solid phase working medium) filling the space and heat generated in the second heater by conduction to the second heater, the lower end of the reel A blocking space is formed between the bottom wall and the bottom wall (thermal connection between the lower end of the reel and the bottom wall is blocked). Therefore, when the superconducting wire is changed from the superconducting state to the normal conducting state, an increase in the load of the refrigeration unit due to the heat of the first heater being transmitted to the refrigeration unit through the lower end portion and the bottom wall of the winding frame is suppressed. . On the other hand, by stopping energization of the first heater and energization of the second heater, the temperature of the working medium is condensed before the superconducting wire reaches the superconducting state (before the temperature of the superconducting wire reaches the critical temperature). When the temperature reaches the temperature, the working medium accumulates in a liquid state in the shut-off space, and then the liquid-phase working medium is cooled by the refrigeration means through the bottom wall, so that the temperature of the working medium reaches the solidification temperature. Since the working medium forms a solid layer that fills the blocking space, the lower end of the reel and the bottom wall are thermally connected (the heat conduction between the lower end and the bottom wall of the reel through the solid layer). Is possible). Therefore, when the superconducting wire is changed from the normal conducting state to the superconducting state, the heat of the superconducting wire is effectively transmitted to the refrigeration means through the lower end portion, the solid layer and the bottom wall of the winding frame. Since it is cooled effectively by the means, the superconducting wire reaches the superconducting state at an early stage. That is, in the present invention, when the superconducting wire is changed from the superconducting state to the normal conducting state, the thermal connection between the lower end portion of the winding frame and the bottom wall is cut off by the cut-off space. On the contrary, when the superconducting wire is changed from the normal conducting state to the superconducting state, the lower end portion and the bottom wall of the reel are thermally connected by the solid layer filling the blocking space. The heat conduction from the superconducting wire to the refrigeration means (cooling of the superconducting wire) is promoted.

  Specifically, the thermal conductivity of the support wall is preferably set lower than the thermal conductivity of the solid layer.

  In this way, the superconducting wire is effectively cooled when the superconducting wire is brought into the superconducting state while suppressing the increase in the load of the refrigeration means (heat input to the refrigeration means) when the superconducting wire is brought into the normal conducting state. Is more reliably achieved. Specifically, when the superconducting wire is brought into a normal conducting state, a cut-off space is formed, so that the heat generated by the first heater is transferred to the refrigeration means through the winding frame, the support wall and the bottom wall, while the superconducting wire is When the superconducting state is established, since the blocking space is filled with the solid layer, the heat of the superconducting wire is transmitted to the refrigeration means through the winding frame, the solid layer and the bottom wall. In the present invention, since the thermal conductivity of the support wall is set lower than that of the solid layer, the heat conduction from the first heater to the refrigeration means when the superconducting wire is in the normal conducting state is effectively suppressed, In addition, heat conduction from the superconducting wire to the refrigeration means when the superconducting wire is brought into a superconducting state (cooling of the superconducting wire) is effectively performed.

  In this case, it is preferable that the support wall has a shape that makes an area of a contact portion between the support wall and the bottom wall smaller than an area surrounded by the contact portion.

  In this way, the above effect can be further enhanced. Specifically, since the area of the contact portion between the support wall and the bottom wall is smaller than the area surrounded by the contact portion (the contact area between the working medium and the bottom wall), the support when placing the superconducting wire in the normal conduction state While reducing the amount of heat input from the wall to the bottom wall, it is possible to ensure a large amount of heat input from the solid layer to the bottom wall when the superconducting wire is brought into a superconducting state. Therefore, while ensuring effective cooling of the superconducting wire through the solid layer when the superconducting wire is brought into the superconducting state, an increase in the load of the refrigeration means when the superconducting wire is brought into the normal conducting state can be further reduced.

  In the present invention, the support wall supports the reel in a state where a lower end of the reel is separated from the support wall and an upper end of the reel is in contact with the support wall. It is preferable.

  In this way, heat conduction from the first heater to the refrigeration means when the superconducting wire is brought into the normal conducting state is suppressed as compared with the case where the lower end portion of the reel is in contact with the support wall. Specifically, since the lower end of the reel is separated from the support wall and the upper end of the reel is in contact with the support wall, the heat generated by the first heater is generated by the upper end of the reel and the support wall. It is transmitted to the bottom wall through. That is, compared to the case where the lower end of the reel is in contact with the support wall, the distance (heat transfer path) through which the heat generated by the first heater is transmitted through the support wall becomes longer. Heat conduction is suppressed.

  The present invention further includes an adsorbent capable of adsorbing and releasing the working medium and a third heater for heating the adsorbent, and the adsorbent has a lower temperature of the adsorbent. Accordingly, it is preferable that the working medium is formed of a material having a property of increasing the amount of adsorption of the working medium.

  In this way, it is possible to more reliably form the cut-off space when the superconducting wire is brought into the normal conduction state while effectively filling the cut-off space with the solid layer when the superconducting wire is put into the superconducting state. Specifically, by lowering the temperature of the adsorbent when the superconducting wire is placed in the normal conducting state, the working medium retreated from the shut-off space by vaporizing when the first heater and the second heater are energized becomes the adsorbent. Since it is adsorbed, the formation of the blocking space becomes more reliable. On the other hand, when the superconducting wire is brought into the superconducting state, the operating medium released from the adsorbent fills the blocking space by increasing the temperature of the adsorbent by energizing the third heater, so that the solid layer is effectively formed. It is formed.

  In this case, the third heater is further provided with an adsorbent container that is disposed outside the housing and accommodates the adsorbent, and a communication pipe that communicates the blocking space and the inside of the adsorbent container. The coil is preferably wound around the adsorbent container.

  In this way, since the heat generated by the third heater is suppressed from being transmitted to the casing when the superconducting wire is brought into the superconducting state, the working medium that has flowed into the casing from the adsorbent container through the communication pipe is solid. The time required to form the layer is reduced.

  Furthermore, in this case, it is preferable to further include a cooling unit that cools the working medium flowing into the housing from the adsorbent through the communication pipe.

  In this way, the working medium flowing from the adsorbent into the housing through the communication pipe is cooled, so that the time required for forming the solid layer in the blocking space is shortened.

  Further, the present invention is a superconducting device comprising the permanent current switch, the superconducting coil, a storage container for housing the permanent current switch and the superconducting coil, and the refrigeration means, wherein the refrigeration means comprises: A cooling member that supports the bottom wall and the superconducting coil in the storage container; and a refrigerator that cools the cooling member and the storage container. The refrigerator cools the storage container. A cooling stage; and a second cooling stage capable of cooling the cooling plate, wherein the first cooling stage has a refrigerating capacity larger than that of the second cooling stage, and the bottom of the casing The wall is connected to the cooling member, and the adsorbent container is provided with the superconducting device connected to the containing container.

  In the present superconducting device, the adsorbent container is connected to the receiving container, and the receiving container is cooled by the first cooling stage having a relatively large refrigerating capacity, so that the adsorbent can be effectively cooled. Therefore, the working medium vaporized in the housing when the superconducting wire is brought into the normal conducting state can be effectively adsorbed.

  In this case, a thermal resistance member provided between the bottom wall and the cooling member is further provided, and the thermal conductivity of the thermal resistance member is set lower than the thermal conductivity of the bottom wall. Is preferred.

  If it does in this way, since it will be suppressed that the heat | fever generate | occur | produced with the 1st heater at the time of making a superconducting wire into a normal conduction state is transmitted to a cooling member through a support wall and a bottom wall, a superconducting wire is made into a normal conduction state. The increase in the load of the refrigerator at that time (heat input to the refrigerator) is suppressed.

  Moreover, in this invention, it further comprises the other heat resistance member provided between the said adsorption body container and the storage container, The heat conductivity of the said other heat resistance member is from the heat conductivity of the said adsorption body container. Is preferably set to be low.

  If it does in this way, since it will be suppressed that an adsorbent container is cooled by the 1st cooling stage via an accommodation container at the time of energization of the 3rd heater, an adsorbent will be heated up earlier.

  The working medium is preferably any one of parahydrogen, neon, and nitrogen.

  As described above, according to the present invention, a permanent current switch that can suppress an increase in the load of the refrigeration means when the switch is turned off and can effectively cool the superconducting wire when the switch is turned on. Can be provided.

It is a figure which shows the outline of a structure of the superconducting apparatus of one Embodiment of this invention. It is sectional drawing of a permanent current switch. It is a graph which shows the relationship between the temperature and thermal conductivity in various substances. It is a graph which shows the relationship between the equilibrium pressure of an adsorbent, and adsorption amount. It is a graph which shows the relationship between the pressure of the inflow side of a communicating pipe, and conductance.

  A superconducting device 10 according to an embodiment of the present invention will be described with reference to FIGS. The superconducting device 10 is a device used for an MRI (magnetic resonance imaging) device, an NMR (nuclear magnetic resonance) device, or the like, and generates a static magnetic field.

  As shown in FIG. 1, the superconducting device 10 includes a permanent current switch 1, a superconducting coil 3, a container 2, a vacuum container 4, and a refrigeration unit 5.

  The permanent current switch 1 and the superconducting coil 3 constitute a closed circuit (a circuit through which a permanent current flows). The permanent current switch 1 performs switching of the closed circuit intermittently. Details of the permanent current switch 1 will be described later.

  The superconducting coil 3 is a coil obtained by winding a wire made of a superconductor (superconducting substance). The superconducting coil 3 is connected to the permanent current switch 1 via a wire made of a superconductor, thereby forming the closed circuit. The superconducting coil 3 is configured to be connectable to an external power supply (not shown) that supplies current to the superconducting coil 3. When a current is supplied to the superconducting coil 3 when the temperature of the superconducting coil 3 is equal to or lower than the superconducting transition temperature (critical temperature), the current is a superconducting current whose electric resistance is almost zero as a so-called permanent current. Continue to flow through the coil 3. The superconducting coil 3 generates a magnetic field by electromagnetic induction caused by this permanent current.

  The container 2 houses the permanent current switch 1 and the superconducting coil 3. In the present embodiment, the storage container 2 is formed of a material having high thermal conductivity such as aluminum.

  The vacuum container 4 is a container that stores the storage container 2, and has a shape that is slightly larger than the storage container 2. The vacuum container 4 has such a strength that the inside of the vacuum container 4 can be evacuated under atmospheric pressure. In the present embodiment, the vacuum vessel 4 is made of stainless steel. The inside of the vacuum vessel 4 is maintained in a vacuum state. Thereby, the contact of the storage container 2 with the atmosphere, that is, the heat of the atmosphere outside the storage container 2 entering the storage container 2 is avoided.

  The refrigeration means 5 is means for cooling the container 2 and the superconducting coil 3. In the present embodiment, the refrigeration unit 5 includes a refrigerator 6, a flexible heat conducting member 7, and a cooling member 8.

  In the present embodiment, a cryogenic refrigerator such as a GM (Gifford McMahon) refrigerator is used as the refrigerator 6. The refrigerator 6 includes a driving unit 60 including a rotary valve, a first cooling stage 61 connected to the driving unit 60, and a second cooling stage 62 connected to the first cooling stage 61.

  The drive unit 60 is connected to the vacuum vessel 4. Specifically, the drive unit 60 is held by the vacuum vessel 4 in a state of penetrating the vacuum vessel 4.

  The first cooling stage 61 is connected to the container 2 and cools the container 2. The first cooling stage 61 has a refrigerating capacity capable of cooling the receiving container 2 until the temperature of the receiving container 2 reaches about 40K.

  The second cooling stage 62 is disposed in the storage container 2. The second cooling stage 62 is connected to the cooling member 8 via the flexible heat conducting member 7 and cools the cooling member 8. The flexible heat conducting member 7 is made of a material having high heat conductivity such as copper. The second cooling stage 62 has a refrigerating capacity capable of cooling the cooling member 8 until the temperature of the cooling member 8 reaches about 4K. In the present embodiment, the first cooling stage 61 has a cooling capacity larger than that of the second cooling stage 62.

  The cooling member 8 is made of a material having high thermal conductivity such as copper. In the present embodiment, the cooling member 8 is formed in a flat plate shape. The superconducting coil 3 is connected to one surface of the cooling member 8 (downward in FIG. 1). For this reason, the superconducting coil 3 is cooled by the second cooling stage 62 via the cooling member 8 and the flexible heat conducting member 7. For this reason, by driving the refrigerator 6, the temperature of the superconducting coil 3 becomes equal to or lower than the superconducting transition temperature (for example, 4K).

  Here, details of the permanent current switch 1 will be described. As shown in FIGS. 1 and 2, the permanent current switch 1 includes a main body 1 </ b> A, an adsorption tank 1 </ b> B, and a communication pipe 1 </ b> C. The main body 1 </ b> A is connected to the cooling member 8. The adsorption tank 1B is connected to the container 2. The communication pipe 1C communicates the main body 1A and the adsorption tank 1B.

  As shown in FIG. 2, the main body 1 </ b> A includes a winding frame 12, a first heater 21, a superconducting wire 25, a housing 30, a second heater 42, and a working medium 50.

  The reel 12 includes a cylindrical body portion 14, an upper flange 16 connected to the upper end of the body portion 14, and a lower flange 18 connected to the lower end of the body portion 14. In the present embodiment, the winding frame 12 is made of copper. Moreover, the outer diameter of the trunk | drum 14 is set to 15 mm.

  The upper flange 16 has a shape that protrudes outward in the radial direction of the body 14 from the upper end of the body 14. In the present embodiment, the upper flange 16 has a cylindrical outer peripheral surface.

  The lower flange 18 has a shape that protrudes outward in the radial direction of the body 14 from the lower end of the body 14. In the present embodiment, the lower flange 18 has a cylindrical outer peripheral surface. The outer diameter of the lower flange 18 is set smaller than that of the upper flange 16.

  The first heater 21 is formed of a conductive wire material that generates heat when energized, such as a constantan wire. The first heater 21 is wound around the body portion 14 in a coil shape with a non-dielectric winding. The first heater 21 is connected to an external power source. The first heater 21 has such a length that the superconducting wire 25 can be heated so that the temperature of the superconducting wire 25 becomes equal to or higher than a critical temperature (the temperature at which the superconducting wire 25 changes from the superconducting state to the normal conducting state). In the present embodiment, the first heater 21 has a resistance corresponding to both ends of 100Ω.

  The superconducting wire 25 is formed of a superconductor wire such as CuNi / NbTi. The superconducting wire 25 is wound in a coil shape by non-inductive winding so as to overlap the first heater 21 wound around the body portion 14. However, the first heater 21 may be wound around the body portion 14 so that the superconducting wire 25 is wound around the superconducting wire 25. The superconducting wire 25 is connected to the superconducting coil 3 through a superconductor wire. The superconducting wire 25 has an electric resistance of almost zero (superconducting state) at a critical temperature (about 9K) or lower. In the present embodiment, the superconducting wire 25 is set to such a length that the resistance at both ends at room temperature is 100Ω.

  The housing 30 has a shape that can accommodate the winding frame 12, the superconducting wire 25, and the first heater 21 in a sealed state. The housing 30 includes a bottom wall 32 and a support wall 34 that supports the winding frame 12.

  The bottom wall 32 is connected to the cooling member 8. In the present embodiment, the bottom wall 32 is connected to the upper surface of the cooling member 8 via a thermal resistance member Ri1. The bottom wall 32 is formed in a disk shape. The bottom wall 32 is made of copper. The thermal conductivity of the thermal resistance member Ri <b> 1 is set lower than the thermal conductivity of the bottom wall 32.

  The support wall 34 is connected to the upper surface of the bottom wall 32, and has a shape that accommodates the winding frame 12, the superconducting wire 25, and the first heater 21 together with the bottom wall 32 in a sealed state. The support wall 34 is positioned at a position where a blocking space capable of blocking the thermal connection between the lower flange 18 and the bottom wall 32 of the winding frame 12 is formed between the lower flange 18 and the bottom wall 32. Support. Specifically, the support wall 34 includes a cylindrical side wall 35 and an upper wall 36 that closes an opening on the upper side of the side wall 35. The support wall 34 is formed of a material having lower thermal conductivity than copper (in this embodiment, stainless steel).

  The side wall 35 has a shape that makes the area of the contact portion between the lower end portion of the side wall 35 and the upper surface of the bottom wall 32 smaller than the area surrounded by the contact portion. In the present embodiment, the outer diameter of the side wall 35 is set to be the same as that of the bottom wall 32. The inner diameter of the side wall 35 is set to be the same as the outer diameter of the upper flange 16, and the outer peripheral surface of the upper flange 16 is connected to the inner peripheral surface of the side wall 35. Further, the upper surface of the upper flange 16 is connected to the lower surface of the upper wall 36. Since the outer diameter of the lower flange 18 is smaller than that of the upper flange 16, the support wall 34 has the outer peripheral surface of the upper flange 16 in contact with the inner peripheral surface of the side wall 35 and the upper surface of the upper flange 16 is the lower surface of the upper wall 36. And the outer peripheral surface of the lower flange 18 is separated from the inner peripheral surface of the side wall 35, and the lower surface of the lower flange 18 is supported upwardly from the upper surface of the bottom wall 32.

  Similar to the first heater 21, the second heater 42 is formed of a conductive wire material that generates heat when energized, such as a constantan wire. The second heater 42 is provided on the bottom wall 32. The second heater 42 has a length capable of heating the working medium 50 such that the temperature of the liquid or solid working medium 50 existing in the shut-off space is equal to or higher than the condensation temperature of the working medium 50. Yes.

  The working medium 50 is a medium having a solidification temperature higher than the critical temperature (about 9 K) of the superconducting wire 25. The working medium 50 exhibits high thermal conductivity in a state where the temperature is equal to or lower than the solidification temperature (solid state). In the present embodiment, parahydrogen is used as the working medium 50. However, neon or nitrogen may be used as the operating medium 50. The operating medium 50 is enclosed in the housing 30.

  Here, the physical properties of the working medium 50 will be described with reference to FIG. FIG. 3 shows the relationship between the temperature and the thermal conductivity of various substances at very low temperatures. In FIG. 3, the physical properties of para-hydrogen, which is the working medium 50 of the present embodiment, are indicated by thick lines compared to other substances. The thermal conductivity of this parahydrogen shows a maximum value in the vicinity of 4K, which is lower than the critical temperature of the superconducting coil 3 (a temperature lower than the solidification temperature of parahydrogen), which is almost equal to the thermal conductivity of copper at the same temperature. It is the same size. This value (the thermal conductivity of the solid-phase working medium 50) is larger than the thermal conductivity of the support wall 34.

  Most of the working medium 50 is retracted from the shut-off space (a space formed between the lower flange 18 and the bottom wall 32) in a gas phase state, while the working medium 50 enters the shut-off space in a liquid phase state. The blocking space is filled in a solid phase state. Specifically, the amount of the working medium 50 is such that when the temperature of the working medium 50 becomes equal to or lower than the condensation temperature, the working medium 50 accumulates in the shut-off space in a liquid state and the temperature of the working medium 50 Is set to an amount sufficient to form a solid layer having a shape that fills the blocking space so as to thermally connect the lower flange 18 and the bottom wall 32 when the temperature becomes equal to or lower than the solidification temperature. That is, when the temperature of the working medium 50 becomes equal to or lower than its solidification temperature (about 6K in the present embodiment), the superconducting wire 25 is firmly and thermally connected to the second cooling stage 62 via the solid-phase working medium 50. Connected. On the other hand, when the temperature of the working medium 50 becomes equal to or higher than the vaporization temperature, a shut-off space is formed between the lower flange 18 and the bottom wall 32, so that the lower flange 18 and the bottom wall 32 are thermally connected. Blocked.

  As shown in FIG. 2, the adsorption tank 1 </ b> B includes an adsorbent 71, an adsorbent container 72, and a third heater 73.

  The adsorbent 71 is made of a material that can adsorb and release the working medium 50. Furthermore, this material has a property that the adsorption capacity (the mass of the working medium 50 that can be adsorbed per unit mass of the material) gradually increases as the temperature decreases. Specifically, as such a material, a porous material (zeolite or the like) having very fine pores having a size of several inches is suitable. This porous material can adsorb molecules smaller than the size of the pores in the pores.

  FIG. 4 shows an example of an isothermal adsorption diagram of the adsorbent 71. In FIG. 4, the horizontal axis indicates the pressure (equilibrium) of the working medium 50 when the adsorption speed and the desorption speed reach equilibrium (equilibrium state) in a state where the adsorbent 71 and the gas-phase working medium 50 are in contact with each other. The vertical axis represents the mass of the gas phase working medium 50 adsorbed per unit weight of the adsorbent 71 in the equilibrium state. As shown in FIG. 4, when the equilibrium pressure is equal, the amount of the gas-phase working medium 50 that can be adsorbed by the adsorbent 71 increases as the temperature decreases. FIG. 4 shows the relationship between the pressure of the gas-phase working medium 50 in the equilibrium state and the amount of adsorption of the working medium 50 by the adsorbent 71. The state in which the working medium 50 is being adsorbed or released is shown. Not shown.

  The adsorbent container 72 is disposed outside the housing 30 and has a shape for accommodating the adsorbent 71. Specifically, the adsorbent container 72 has a cylindrical body that surrounds the adsorbent 71 from the side. The adsorbent container 72 is made of copper. As shown in FIG. 2, the adsorbent container 72 is thermally connected to the inner surface of the storage container 2. For this reason, when the refrigerator 6 is driven, the adsorbent container 72 is cooled to about 40 K by the first cooling stage 61 via the storage container 2. In the present embodiment, the adsorbent container 72 is connected to the inner surface of the storage container 2 via the heat resistance member Ri2. The thermal conductivity of the thermal resistance member Ri2 is set to be lower than the thermal conductivity of the adsorbent container 72.

  Similar to the first heater 21 and the second heater 42, the third heater 73 is formed of a conductive wire material that generates heat when energized, such as a constantan wire. The third heater 73 is wound around the trunk portion of the adsorbent container 72. The third heater 73 has a length capable of heating the adsorbent 71 such that the temperature of the adsorbent 71 is equal to or higher than a temperature (about 100 K) that significantly reduces the adsorption capability of the adsorbent 71.

  The communication pipe 1 </ b> C communicates the inside of the housing 30 and the adsorbent container 72. Specifically, one end of the communication pipe 1 </ b> C is connected to the approximate center of the upper wall 36 of the support wall 34, and the other end of the communication pipe 1 </ b> C is connected to the approximate center of the lower part of the adsorbent container 72. As a result, the blocking space and the adsorbent 71 communicate with each other through the space formed inside the winding frame 12 and the communication pipe 1C. That is, the movement of the working medium 50 between the blocking space and the adsorbent 71 is possible. The communication pipe 1C is made of stainless steel.

  In the present embodiment, the cooling unit 55 is disposed in a space formed inside the winding frame 12. The cooling unit 55 cools (condenses) the vapor-phase working medium 50 flowing from the adsorbent 71 into the housing 30 through the communication pipe 1C. The cooling unit 55 is made of a porous material having high thermal conductivity such as copper. The cooling part 55 is formed in a cylindrical shape having the same outer diameter as the inner diameters of the body part 14 and the upper flange 16. The cooling unit 55 is held in the winding frame 12 with an outer peripheral surface thereof in contact with the winding frame 12 and an upper surface thereof in contact with a lower surface of the upper wall 36.

  Here, the conductance of the communication pipe 1C (ease of flow when fluid passes through the inside) will be described.

  In general, the conductance of a linear flow path having a circular cross section is divided into a viscous flow area and a molecular flow area, depending on the relationship between the pressure of the fluid passing through the flow path and the inner diameter of the flow path. The conductance in each region is expressed by Equation (1) and Equation (2).

  Here, a is the inner diameter of the flow path, L is the length of the flow path, (p bar) is the average pressure of the gas phase fluid in the flow path, η is the viscosity of the fluid, and T is the absolute temperature of the gas phase fluid , R is the gas constant, and M is the molecular weight of the gas phase fluid. Further, (v bar) is an average flow velocity of gas phase fluid molecules, and is determined from the molecular weight and temperature.

  Expression (1) is a calculation expression in the viscous flow region, and Expression (2) is a calculation expression in the molecular flow region. Actually, there is an intermediate area between the two areas, but the description is omitted here for simplicity. From both equations, it can be seen that the conductance in the viscous flow region is proportional to the average pressure, whereas the conductance in the molecular flow region is characterized only by the inner diameter and temperature of the flow path.

The boundary between the viscous flow region and the molecular flow region is generally determined by the reference pressure p _c of the formula (3). While the case where the pressure of the fluid in the vapor phase is larger than the reference pressure p _c is applied has the formula (1), if the pressure of the fluid in the vapor phase is less than the reference pressure p _c is applied the formula (2) .

  Since the actual communication pipe 1C has pressure distribution and temperature distribution along the longitudinal direction, the conductance of the flow path is simply calculated by applying the above formulas (1) to (3). Is difficult and requires an integral calculation considering the temperature distribution.

FIG. 5 shows an example of a conductance calculation result when the inner diameter of the communication pipe 1C is 1 mm and the length of the communication pipe 1C is 0.3 m. FIG. 5 shows two examples of case (1) and case (2). Case (1) corresponds to the case where the gas phase working medium 50 flows from the adsorption tank 1B to the main body 1A. The case (2) corresponds to the case where the gas phase working medium 50 flows from the main body 1A to the adsorption tank 1B. In the case (1), the inlet temperature of the communication pipe 1C is 100K, the inlet pressure is 2.1 × 10 ⁴ (hereinafter, “× 10 ⁿ ” is expressed as “en”) Pa, the outlet temperature is 14K, and the outlet pressure. Is set to 6.94e3Pa. In the case (2), the inlet temperature of the communication pipe 1C is set to 14K, the inlet pressure is set to 6.94e3Pa, the outlet temperature is set to 40K, and the outlet pressure is set to 3.1e-3Pa.

  Here, the relationship between the inlet pressure (Inlet Pressure) of the gas phase working medium 50 and the conductance (Total Flow Conductance) in the communication pipe 1C will be described with reference to FIG.

For example, in case (1), the internal pressure of the adsorption tank 1B, which is the inlet pressure, is 2.1e4 Pa (the internal pressure of the adsorbent container 72 when the operating medium 50 is adsorbed to the adsorbent 71), and the housing is the outlet pressure. When the internal pressure of the body 30 is 4.16e-5 Pa (saturated vapor pressure of the working medium 50 when the temperature of the main body 1A is 4.2K), the conductance is 5.3e-3m ³ / sec from FIG. It becomes. Although the outlet pressure is different from the setting of FIG. 5, it is a very small difference with respect to the inlet pressure, and the influence can be ignored. On the other hand, for example, if the inlet pressure is about 1e-2 Pa, the gas phase working medium 50 is in the molecular flow region, and its conductance is about 6.6e-6 m ³ / sec.

As estimated above, the difference in conductance between the above two examples is three digits. However, since the mass transfer rate of the gas phase working medium 50 is the product of the inlet pressure and the conductance, the mass transfer of the previous example (when the inlet pressure is 2.1e4 Pa) in the standard state (273.15K). The speed is 1.1e2 Pa · m ³ / sec, and the mass transfer speed in the later example (when the inlet pressure is 1e-2 Pa) is 6.6e-8 Pa · m ³ / sec. That is, the difference in mass movement speed in the above example is 9 digits. In other words, the conductance and the mass transfer rate rapidly decrease as the inlet pressure decreases. The relationship between the inlet pressure and the mass transfer speed is closely related to the operation of the permanent current switch 1.

  Next, the operation of the permanent current switch 1 will be described. Hereinafter, when the temperature of the superconducting coil 3 is room temperature, the operation when the refrigerator 6 is driven (initial precooling), the switch OFF operation for switching the permanent current switch 1 from the switch ON state to the switch OFF state, and the permanent current switch 1 The switch ON operation for switching from the switch OFF state to the switch ON state will be described in this order.

<Initial precooling>
First, a gas phase working medium 50 is introduced into the main body 1A, the adsorption tank 1B, and the communication pipe 1C and sealed.

  Next, the refrigerator 6 is driven. Then, the container 2 is cooled by the first cooling stage 61, and the flexible heat conducting member 7 and the cooling member 8 are cooled by the second cooling stage 62. At this time, as cooling of the adsorption tank 1B through the storage container 2 proceeds, the gas-phase working medium 50 in the housing 30 continues to flow into the adsorbent container 72 through the communication pipe 1C, and the operation by the adsorbent 71 is performed. The adsorption amount of the medium 50 increases. When the temperature of the first cooling stage 61 reaches the lowest temperature (about 40K), substantially the entire amount of the gas-phase working medium 50 is adsorbed on the adsorbent 71. The amount of adsorption of the working medium 50 of the adsorbent 71 is determined by the area and temperature of the inner surface of each of the main body 1A and the adsorption tank 1B.

  Thereafter, the third heater 73 is energized when the temperature of the superconducting coil 3 reaches a critical temperature (about 9K) as the second cooling stage 62 is cooled. Thereby, the temperature of the adsorbent container 72 and the adsorbent 71 rises, and the adsorbing capacity of the adsorbent 71 starts to decrease. For example, the adsorption capacity of the adsorbent 71 is significantly reduced by heating the adsorbent container 72 and the adsorbent 71 until the temperature reaches about 100K. As a result, most of the working medium 50 adsorbed on the adsorbent 71 is released from the adsorbent 71 (released as gas). The energization of the third heater 73 is controlled based on the detection value of the temperature sensor T3 attached to the adsorbent container 72.

  Here, in this embodiment, since the heat resistance member Ri2 is interposed between the adsorbent container 72 and the storage container 2, the first cooling stage 61 is interposed via the storage container 2 when the third heater 73 is energized. This suppresses cooling of the adsorbent container 72 and the adsorbent 71. Therefore, the temperature of the adsorbent 71 rises quickly. In addition, a rapid increase in the thermal load of the first cooling stage 61 due to the heat generated by the third heater 73 is suppressed. Furthermore, since the third heater 73 is disposed outside the housing 30, heat conduction from the third heater 73 to the housing 30 is suppressed.

  The gas phase working medium 50 released from the adsorption tank 1B flows into the housing 30 of the main body 1A through the communication pipe 1C.

  On the other hand, in the main body 1A, due to energization of the first heater 21 and the second heater 42, the temperature of the reel 12 and the temperature of the bottom wall 32 are slightly higher than the temperature of the triple point of the operating medium 50 (this embodiment). In the form, it is maintained at around 14K). When the gas phase working medium 50 flows into the housing 30 through the communication pipe 1C in this state, the gas phase working medium 50 is condensed by being cooled by the cooling unit 55. That is, the cooling unit 55 shortens the cooling time of the working medium 50. The working medium 50 that has become a liquid phase in this manner flows down the space inside the winding frame 12 and accumulates in the blocking space. The energization of the first heater 21 is controlled based on the detection value of the temperature sensor T1 attached to the upper wall 36. However, the temperature sensor T1 may be attached to the lower flange 18. The energization of the second heater 42 is controlled based on the detection value of the temperature sensor T2 attached to the bottom wall 32.

  Thereafter, when the blocking space is filled with the liquid-phase working medium 50, in other words, when the liquid-phase working medium 50 contacts the entire upper surface of the bottom wall 32 and the entire lower surface of the lower flange 18. Energization to the first heater 21 and the second heater 42 is stopped. Then, the temperature of the liquid-phase working medium 50 is lowered to the solidification temperature (about 14K) or less by the liquid-phase working medium 50 being cooled by the second cooling stage 62 through the bottom wall 32 and the cooling member 8. . As a result, the working medium 50 is solidified to form a solid layer (solid phase working medium 50) having a shape that fills the blocking space. Since the solid-phase working medium 50 has a very high thermal conductivity as described above, the lower flange 18 and the bottom wall 32 are thermally connected via the solid layer (the lower part via the solid layer). Heat conduction between the flange 18 and the bottom wall 32 is possible). Therefore, the superconducting wire 25 is effectively cooled by the second cooling stage 62 through the winding frame 12, the solid layer (solid phase working medium 50), and the bottom wall 32, and the temperature is the lowest of the second cooling stage 62. It reaches the ultimate temperature (about 4.2K). Thereby, the superconducting wire 25 is in a superconducting state. That is, the permanent current switch 1 is switched on. At this time, since substantially the entire amount of the working medium 50 forms a solid layer in the casing 30, the internal pressure of the casing 30 is about 4.16e-5 Pa.

  On the other hand, the power supply to the third heater 73 is also stopped when the power supply to the first heater 21 and the second heater 42 is stopped. For this reason, the temperature of the adsorption tank 1B changes from the temperature (about 100K) when the third heater 73 is energized to the lowest temperature reached (about 40K) of the first cooling stage 61. Thereby, since the temperature of the adsorbing body 71 is lowered, the adsorbing capacity of the adsorbing body 71 is increased. Since the mass of the working medium 50 adsorbed on the adsorbent 71 is decreasing, the equilibrium pressure at this time is lower than that when the third heater 73 is energized. For example, it becomes about 3.97e-5Pa. This pressure is lower than the internal pressure of the casing 30 (about 4.16e-5 Pa), but as described above, the conductance of the communication pipe 1C is significantly reduced due to the decrease in the inlet pressure (internal pressure of the casing 30). Therefore, the inflow (backflow) of the working medium 50 from the main body 1A to the adsorption tank 1B is substantially negligible. That is, the working medium 50 that has flowed into the main body 1A from the adsorption tank 1B is fixed to the main body 1A.

<Switch OFF operation>
In the state where the initial pre-cooling is completed, the blocking space is filled with a solid layer (solid phase working medium 50). In this state, the first heater 21 is energized. If it does so, the temperature of the superconducting wire 25 will begin to rise and the said temperature will become more than critical temperature. Thereby, the superconducting wire 25 changes from the superconducting state (switch ON state) to the normal conducting state (switch OFF state). That is, the closed circuit formed by the superconducting coil 3 and the superconducting wire 25 is interrupted.

On the other hand, the second heater 42 is energized simultaneously with the energization of the first heater 21, and the temperature of the bottom wall 32 is slightly higher than the temperature of the triple point of the working medium 50 (in this embodiment, around 14 K). Maintained. As a result, the solid-phase working medium 50 evaporates after being dissolved. The gas-phase working medium 50 flows into the adsorption tank 1B through the cooling unit 55 and the communication pipe 1C. The conductance of the communication pipe 1C at this time is 3.0e-3m ³ / sec from FIG. 5 because the saturated vapor pressure of the working medium 50 at 14K (temperature in the housing 30 on the inlet side) is 6.94e3Pa. It becomes. For example, if the mass of the working medium 50 moving from the main body 1A to the adsorption tank 1B is 7.78e-6 kg, the movement is completed in 0.42 seconds.

  The vapor-phase working medium 50 that has flowed into the adsorption tank 1B via the communication pipe 1C is adsorbed by the adsorbent 71. At this time, the pressure in the adsorbent container 72 is an equilibrium pressure determined by the temperature of the adsorbent 71 and the amount of adsorption of the working medium 50 by the adsorbent 71. For example, when the mass of the adsorbent 71 is 5.13e-6 kg and the final adsorption amount is 1.2e-5 kg, the equilibrium pressure is 3.13e-3 Pa. Since this value is lower than the internal pressure of the housing 30 of the main body 1A, the movement of the working medium 50 from the main body 1A to the adsorption tank 1B is continued without any problem while the second heater 42 is energized.

  Subsequently, the second heater 42 is energized when the movement of the working medium 50 from the main body 1A to the adsorption tank 1B is completed (when the working medium 50 is hardly left in the housing 30). Stopped. Then, the temperature of the bottom wall 32 quickly reaches the temperature of the second cooling stage 62 (about 4.2K). When the temperature of the bottom wall 32 is lowered to about 4.2K, the internal pressure of the housing 30 is lowered to about 4.16e-5 Pa which is the saturated vapor pressure of the working medium 50 at 4.2K. This value is lower than the equilibrium pressure of 3.13e-3 Pa in the adsorbent vessel 72. That is, the working medium 50 that has flowed into the adsorption tank 1B from the main body 1A seems to flow backward, but the conductance of the communication pipe 1C is reduced due to the decrease in the internal pressure of the housing 30 and the internal pressure of the adsorbent container 72 as described above. Since it is remarkably lowered, the inflow (reverse flow) of the working medium 50 from the adsorption tank 1B to the main body 1A is substantially negligible. That is, the working medium 50 that has flowed into the adsorption tank 1B from the main body 1A is fixed to the adsorption tank 1B.

  When the gas-phase working medium 50 is adsorbed on the adsorbent 71, the adsorption heat is released in the adsorbent 71. The adsorbent container 72 is thermally transferred to the first cooling stage 61 via the storage container 2. Since it is connected, the heat of adsorption is quickly removed, and the temperature of the adsorption tank 1B is kept substantially constant.

  Even after the movement of the working medium 50 from the main body 1A to the adsorption tank 1B is completed, energization to the first heater 21 is continued, and the temperature of the superconducting wire 25 is maintained at a critical temperature or higher. Thereby, the switch OFF operation is completed. By energizing the superconducting coil 3 while maintaining this state, the excitation operation can be performed stably.

  Here, in the switch OFF state, although the thermal connection between the lower flange 18 and the bottom wall 32 is cut off by the shut-off space, the first heater 21 is energized, and thus is generated in the first heater 21. The heat continues to flow to the cooling member 8 and the second cooling stage 62 via the winding frame 12, the support wall 34 and the bottom wall 32. However, in this embodiment, since the lower flange 18 is separated from the support wall 34, in other words, the support wall 34 is separated from the side wall 35 and the upper flange 16 is separated from the side wall 35 and the upper wall. Since the winding frame 12 is supported in contact with the wall 36, heat conduction from the first heater 21 to the cooling member 8 is suppressed as compared with the case where the lower flange 18 is in contact with the side wall 35. Specifically, the heat generated by the first heater 21 is transmitted to the cooling member 8 through the trunk portion 14, the upper flange 16, the side wall 35, and the bottom wall 32. That is, compared to the case where the lower flange 18 is in contact with the side wall 35, the distance (heat transfer path) through which the heat generated in the first heater 21 is transmitted through the support wall 34 becomes longer. Heat conduction to the second cooling stage 62 via 8 is suppressed. Furthermore, since the thermal resistance member Ri1 is interposed between the bottom wall 32 and the cooling member 8, heat conduction from the first heater 21 to the second cooling stage 62 (second) when the first heater 21 is energized. The increase in the thermal load of the cooling stage 62 is further suppressed. For example, when the height H1 of the side wall 35 is 0.1 m, the thickness t1 of the side wall 35 is 1 mm, and the thermal resistance of the thermal resistance member Ri1 is 100 K / W, the first heater 21 to the second cooling stage. The steady heat flow flowing into 62 is 9 mW.

<Switch ON operation>
In the switch-off state, a blocking space is formed, the working medium 50 is adsorbed by the adsorbent 71, and energization to the first heater 21 is maintained. In this state, the third heater 73 is energized. This energization is performed until the adsorbent 71 releases almost the entire amount of the working medium 50. The gas phase working medium 50 released from the adsorption tank 1B flows into the main body 1A through the communication pipe 1C. At this time, the second heater 42 is energized, and the temperature of the bottom wall 32 is maintained at a temperature slightly higher than the triple point temperature of the working medium 50 (around 14K). The subsequent operation or behavior of the working medium 50 is the same as that of the initial precooling.

  As described above, in the permanent current switch 1 of the present embodiment, the superconducting wire 25 changes from the superconducting state (switch ON state) to the normal conducting state (switch OFF state) by energizing the first heater 21, and at this time, The heat generated in the first heater 21 is transmitted to the solid layer (solid phase working medium 50) filling the blocking space via the winding frame 12, and the heat generated in the second heater 42 by energization of the second heater 42. Since the solid layer is vaporized by being transmitted to the solid layer, a blocking space is formed between the lower flange 18 and the bottom wall 32 (the thermal connection between the lower flange 18 and the bottom wall 32 is blocked). Therefore, when the superconducting wire 25 is changed from the superconducting state to the normal conducting state, the load of the refrigerator 6 is increased due to the heat of the first heater 21 being transmitted to the second cooling stage 62 through the lower flange 18 and the bottom wall 32. Is suppressed. On the other hand, by stopping the energization of the first heater 21 and the energization of the second heater 42, the working medium 50 before the superconducting wire 25 reaches the superconducting state (before the temperature of the superconducting wire 25 reaches the critical temperature). The operating medium 50 reaches its condensing temperature and the working medium 50 accumulates in the liquid phase in the shut-off space, and then the liquid working medium is cooled by the second cooling stage 62 through the bottom wall 32. Since the temperature of the medium 50 reaches the solidification temperature and the working medium 50 forms a solid layer that fills the blocking space, the lower flange 18 and the bottom wall 32 are thermally connected (the lower part through the solid layer). Heat conduction between the flange 18 and the bottom wall 32 is possible). Therefore, when the superconducting wire 25 is changed from the normal conducting state to the superconducting state, the heat of the superconducting wire 25 is effectively transmitted to the second cooling stage 62 through the lower flange 18, the solid layer and the bottom wall 32, in other words, Since the superconducting wire 25 is effectively cooled by the second cooling stage 62, the superconducting wire 25 quickly reaches the superconducting state. That is, in this embodiment, when the superconducting wire 25 is changed from the superconducting state to the normal conducting state, the thermal connection between the lower flange 18 and the bottom wall 32 is cut off by the cut-off space. When heat conduction to the machine 6 is suppressed and, conversely, when the superconducting wire 25 is changed from the normal conducting state to the superconducting state, the lower flange 18 and the bottom wall 32 are thermally connected by the solid layer filling the blocking space. Thus, heat conduction from the superconducting wire 25 to the refrigerator 6 (cooling of the superconducting wire 25) is promoted.

  In the present embodiment, since the thermal conductivity of the support wall 34 is set lower than that of the solid layer (solid phase working medium 50), the refrigerator when the superconducting wire 25 is brought into the normal conducting state. When the superconducting wire 25 is brought into a superconducting state while suppressing an increase in the load of 6 (heat input to the refrigerator 6), the superconducting wire 25 is effectively cooled more reliably. Specifically, when the superconducting wire 25 is brought into the normal conducting state, a cut-off space is formed, so that the heat generated by the first heater 21 is transferred to the refrigerator 6 through the winding frame 12, the support wall 34 and the bottom wall 32. On the other hand, when the superconducting wire 25 is brought into the superconducting state, since the blocking space is filled with the solid layer, the heat of the superconducting wire 25 is transmitted to the refrigerator 6 through the winding frame 12, the solid layer and the bottom wall 32. In this embodiment, since the thermal conductivity of the support wall 34 is set lower than that of the solid layer, the heat conduction from the first heater 21 to the refrigerator 6 when the superconducting wire 25 is in the normal conducting state is performed. The heat conduction (cooling of the superconducting wire 25) from the superconducting wire 25 to the refrigerator 6 when the superconducting wire 25 is brought into the superconducting state is effectively suppressed.

  Further, the side wall 35 has a shape that makes the area of the contact portion between the side wall 35 and the bottom wall 32 smaller than the area surrounded by the contact portion. For this reason, the said effect increases more. Specifically, since the area of the contact portion between the side wall 35 and the bottom wall 32 is smaller than the area surrounded by the contact portion (the contact area between the working medium 50 and the bottom wall 32), the superconducting wire 25 is brought into a normal conducting state. While the amount of heat input from the side wall 35 to the bottom wall 32 is reduced, a large amount of heat input from the solid layer to the bottom wall 32 when the superconducting wire 25 is brought into a superconducting state can be secured. Therefore, while ensuring effective cooling of the superconducting wire 25 through the solid layer when the superconducting wire 25 is brought into the superconducting state, an increase in the load on the refrigerator 6 when the superconducting wire 25 is brought into the normal conducting state is further reduced. be able to.

  In the superconducting device 10, the adsorbent container 72 is connected to the storage container 2, and the storage container 2 is cooled by the first cooling stage 61 having a relatively large refrigerating capacity. It is possible to effectively cool. Therefore, the working medium 50 vaporized in the housing 30 when the superconducting wire 25 is in the normal conducting state is effectively adsorbed by the adsorbent 71.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

  For example, the adsorption tank 1B and the communication pipe 1C may be omitted. However, by providing the adsorption tank 1B and the communication pipe 1C, when the superconducting wire 25 is brought into the superconducting state, the shielding space is more effectively filled with the solid layer while the superconducting wire 25 is put into the normal conducting state more effectively. Can be formed. Specifically, when the superconducting wire 25 is placed in the normal conducting state, the temperature of the adsorbent 71 is lowered, so that the working medium 50 retreated from the shut-off space by being vaporized in the housing 30 passes through the communication pipe 1C. Since it is adsorbed by the adsorbent 71 in the container 72, the formation of the blocking space becomes more reliable. On the other hand, when the superconducting wire 25 is brought into the superconducting state, the temperature of the adsorbent 71 is increased by energizing the third heater 73, so that the vapor-phase working medium 50 released from the adsorbent 71 is connected to the communication pipe 1C. Since it flows into the housing | casing 30 through and fills the interruption | blocking space, a solid layer is formed effectively.

  Further, the connection location between the communication pipe 1 </ b> C and the support wall 34 is not limited to the substantially central portion of the upper wall 36. The communication pipe 1 </ b> C may be connected to the side wall 35. In this case, the body 14 of the winding frame 12 may be formed in a columnar shape.

DESCRIPTION OF SYMBOLS 1 Permanent current switch 2 Containment container 3 Superconducting coil 4 Vacuum container 5 Refrigeration means 6 Refrigerator 8 Cooling member 10 Superconducting device 12 Winding frame 14 Body part 16 Upper flange 18 Lower flange 21 1st heater 25 Superconducting wire 30 Case 32 Bottom wall 34 Support Wall 42 Second Heater 50 Operating Medium 55 Cooling Unit 61 First Cooling Stage 62 Second Cooling Stage 71 Adsorbent 72 Adsorbent Container 73 Third Heater 1A Main Body 1B Adsorption Tank 1C Communication Pipe Ri1 Thermal Resistance Member R12 Thermal Resistance Element

Claims (12)

A permanent current switch that constitutes a closed circuit through which a permanent current flows together with a superconducting coil, and that can interrupt the closed circuit,
A reel,
A superconducting wire wound around the winding frame and connectable to the superconducting coil;
A first heater capable of heating the superconducting wire so that the temperature of the superconducting wire is equal to or higher than a critical temperature at which the superconducting wire changes from a superconducting state to a normal conducting state;
The reel, the superconducting wire, and the first heater have a shape that can be accommodated in a sealed state, and are connected to refrigeration means for cooling the superconducting wire so that the temperature of the superconducting wire is equal to or lower than the critical temperature. A housing to be
A working medium enclosed in the housing and having a solidification temperature higher than a critical temperature of the superconducting wire;
A second heater capable of heating the working medium so that the temperature of the working medium is equal to or higher than the solidification temperature;
The housing includes a bottom wall that is thermally connected to the refrigeration means, and is connected to the bottom wall and accommodates the winding frame, the superconducting wire, and the first heater together with the bottom wall in a sealed state. And a winding space is formed between the lower end portion of the winding frame and the bottom wall so that a shut-off space capable of blocking the thermal connection between the lower end portion of the winding frame and the bottom wall is formed. A support wall for supporting the frame,
The amount of the working medium is such that when the working medium accumulates in the shut-off space in a liquid phase and the temperature of the working medium becomes equal to or lower than the solidification temperature, the lower end of the reel and the bottom wall A permanent current switch set to an amount sufficient to form a solid layer having a shape that fills the blocking space so as to be thermally connected. The permanent current switch according to claim 1,
The permanent current switch, wherein the thermal conductivity of the support wall is set lower than the thermal conductivity of the solid layer. The permanent current switch according to claim 2, wherein
The said support wall is a permanent current switch which has a shape which makes the area of the contact part of the said support wall and the said bottom wall smaller than the area surrounded by the said contact part. The permanent current switch according to claim 2 or 3,
The said support wall is a permanent current switch which is supporting the said reel in the state in which the lower end part of the said reel was spaced apart from the said support wall, and the upper end part of the said reel contacted the said support wall. The permanent current switch according to any one of claims 1 to 4,
An adsorbent capable of adsorbing and releasing the working medium;
A third heater for heating the adsorbent,
The adsorbent is a permanent current switch formed of a material having a property that the amount of adsorption of the working medium increases as the temperature of the adsorbent decreases. The permanent current switch according to claim 5,
An adsorbent container disposed outside the housing and containing the adsorbent;
A communication pipe that communicates between the blocking space and the adsorbent container; and
The third heater is a permanent current switch wound around the adsorbent container. The permanent current switch according to claim 6.
The permanent current switch further comprising a cooling unit that cools the working medium flowing into the casing from the adsorbent through the communication pipe. A permanent current switch according to claim 6 or 7,
The superconducting coil;
A container for housing the permanent current switch and the superconducting coil;
The refrigeration means;
A superconducting device comprising:
The refrigeration means includes a cooling member that supports the bottom wall and the superconducting coil in the storage container, and a refrigerator that cools the cooling member and the storage container.
The refrigerator has a first cooling stage that cools the storage container, and a second cooling stage that can cool the cooling plate,
The first cooling stage has a refrigerating capacity larger than that of the second cooling stage,
A bottom wall of the housing is connected to the cooling member;
The adsorbent container is a superconducting device connected to the storage container. The superconducting device according to claim 8, wherein
A heat resistance member provided between the bottom wall and the cooling member;
The superconducting device, wherein the thermal resistance of the thermal resistance member is set lower than the thermal conductivity of the bottom wall. The superconducting device according to claim 8 or 9,
Further comprising another heat resistance member provided between the adsorbent container and the storage container,
The superconducting device, wherein the thermal conductivity of the other thermal resistance member is set lower than the thermal conductivity of the adsorbent container. The permanent current switch according to any one of claims 1 to 7,
The working medium is a permanent current switch which is any one of parahydrogen, neon and nitrogen. The superconducting device according to any one of claims 8 to 10,
The superconducting device, wherein the working medium is any one of parahydrogen, neon, and nitrogen.

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