JP2013065659A - Conduction cooling type superconductive magnet device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conduction cooling type superconductive magnet device including a structure which independently protects an oxide superconductive current lead even if failure occurs in a power source, a refrigerating machine, and the like.SOLUTION: A conduction cooling type superconductive magnet device 1 includes: a superconductive magnet 19; a radiation shield 4 for housing the superconductive magnet 19; a vacuum vessel 5 for housing the radiation shield 4; a refrigerating machine 3 attached to the vacuum vessel 5; and an oxide current lead 7 disposed in an area which is in the radiation shield 4 and between a first cooling end part 12a (a first cooling stage) and a second cooling end part 12b (a second cooling stage). A diode 13, which is used for protecting the oxide current lead 7 from burning, is parallely connected with the oxide current lead 7.

Description

  The present invention relates to a conduction cooling superconducting magnet apparatus including a two-stage refrigerator.

  A conduction-cooled superconducting magnet device that can cool and operate a superconducting magnet with a refrigerator without using liquid helium has been put into practical use. This conduction cooling type superconducting magnet device is described in, for example, Patent Document 1.

  As described in Patent Document 1, in a conduction-cooled superconducting magnet device, an oxide superconducting current lead is inserted into a current supply path to the superconducting magnet to block heat intrusion from the outside and accompany energization. It is possible to avoid self-heating.

JP 2009-277951 A

  In the conduction-cooling superconducting magnet device, when the refrigerator during the cooling operation stops, the temperature of each part in the device starts to rise, and the oxide superconducting current lead eventually ceases to be in the superconducting state and transitions to the high resistance state. If current continues to be supplied from the power source to the oxide superconducting current lead that has transitioned to the high resistance state, the oxide superconducting current lead generates heat and burns out.

  In addition, even if the superconducting magnet (main body coil) is quenched, if the power supply is delayed, and the current continues to be supplied from the power source to the oxide superconducting current lead, the oxide superconducting current lead changes to a high resistance state and generates heat. It will burn out.

  In addition, if a power supply interruption error occurs due to an incomplete system sequence, the oxide superconducting current lead is surely burned out.

  The present invention has been made in view of the above circumstances, and its purpose is conductive cooling provided with a structure capable of autonomously protecting an oxide superconducting current lead even if a failure occurs in a power supply, a refrigerator, or the like. Type superconducting magnet device.

  The present invention includes a superconducting magnet, a cooling container containing the superconducting magnet, a vacuum container containing the cooling container, a two-stage refrigerator attached to the vacuum container, and the inside of the cooling container. Introducing an electric current into the superconducting magnet disposed between the first cooling stage of the two-stage refrigerator and the second cooling stage of the two-stage refrigerator whose temperature is lower than that of the first cooling stage. A conductive cooling type superconducting magnet device comprising: an oxide superconducting current lead; and a diode for protecting the oxide superconducting current lead connected in parallel to the oxide superconducting current lead. To do.

  According to the conduction cooling type superconducting magnet apparatus of the present invention, even if a failure occurs in a power supply, a refrigerator, etc., the oxide superconducting current lead constituting the apparatus is independently protected.

1 is a partial cross-sectional view showing a conduction cooling superconducting magnet device according to an embodiment of the present invention. It is an electric circuit diagram of a conduction cooling type superconducting magnet device according to an embodiment of the present invention. It is a partial cross section figure which shows the modification of the conduction cooling superconducting magnet apparatus shown in FIG.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

(Configuration of superconducting magnet device)
FIG. 1 is a partial cross-sectional view showing a conduction-cooling superconducting magnet device 1 (hereinafter referred to as “superconducting magnet device 1”) according to an embodiment of the present invention. As shown in FIG. 1, the superconducting magnet device 1 includes a superconducting magnet 19, a radiation shield 4 (cooling container) that houses the superconducting magnet 19, and a vacuum container 5 that houses the radiation shield 4 in which the superconducting magnet 19 is housed. And the refrigerator 3 attached to the upper part of the vacuum vessel 5.

(Superconducting magnet)
The superconducting magnet 19 has a winding frame 9 and a superconducting coil 2 in which a superconducting wire is spirally wound around the winding frame 9. The reel 9 is made of a nonmagnetic material such as aluminum or stainless steel. Superconducting wires constituting the superconducting coil 2 are niobium tin (Nb ₃ Sn) superconducting wires, niobium titanium (NbTi) superconducting wires, and the like.

(Vacuum container)
The vacuum vessel 5 is a vessel whose inside is kept at a high vacuum and suppresses heat intrusion into the superconducting magnet 19 and the radiation shield 4. The vacuum vessel 5 has an end plate 5a that seals the upper part thereof. Examples of the material of the vacuum vessel 5 include an aluminum material and a stainless material. Moreover, the outer surface of the vacuum vessel 5 is exposed to normal temperature (about 300K).

  Electrode pins 8 (electrodes) made of a copper material are attached to the end plate 5a of the vacuum vessel 5. The electrode pin 8 includes an anode pin and a cathode pin, and an excitation power source 50 (see FIG. 2) for exciting the superconducting coil 2 is connected to the electrode pin 8. A part of the electrode pin 8 protrudes outside and is exposed to the atmosphere (outside air).

(Radiation shield)
The radiation shield 4 has a shield body 4a and a plate 4b attached to the upper opening of the shield body 4a. Examples of the material of the radiation shield 4 (plate 4b) include an aluminum material and a copper material.

(refrigerator)
The refrigerator 3 is a two-stage regenerative refrigerator (two-stage refrigerator), and includes a drive unit 12 and a cylinder 11 disposed below the drive unit 12. The cylinder 11 has an upper first cylinder 11a and a lower second cylinder 11b. A first cooling end 12a (first cooling stage) is provided at the lower end of the first cylinder 11a, and a second cooling end at which the temperature is lower than the first cooling end 12a at the lower end of the second cylinder 11b. A portion 12b (second cooling stage) is provided. The first cooling end portion 12a and the second cooling end portion 12b are both in the form of a flange. The first cooling end 12a is attached to the plate 4b of the radiation shield 4 by fixing means such as bolts, and the second cooling end 12b is fixed to the heat transfer member 16 (heat transfer plate) such as bolts. It is attached by means. The heat transfer member 16 is thermally connected to the outer periphery of the superconducting magnet 19. Helium gas is supplied to the drive unit 12, and the supplied helium gas is ejected to the lower part of the first cylinder 11a and the lower part of the second cylinder 11b. The refrigerator 3 cools the radiation shield 4 and the superconducting magnet 19 to about 40K and about 4K through the first cooling end 12a and the second cooling end 12b, respectively. Note that “thermally connected” means that heat is conducted but electricity is connected in an insulated state (a state where electricity does not flow).

(Current lead)
The electrode pin 8 and the superconducting coil 2 are connected by conducting wires 10, 14, 15, 6 through a cylindrical or flat oxide superconducting current lead 7 (hereinafter referred to as “oxide current lead 7”). Yes. Conductive wires 10, 14, and 15 are high-temperature current lead wires that connect the electrode pins 8 and the oxide current leads 7. The conductive wires 10 are disposed outside the radiation shield 4, and the conductive wires are disposed inside the radiation shield 4. 14 and 15 are arranged. The conducting wire 6 is a low-temperature current lead wire connecting the oxide current lead 7 and the superconducting coil 2, and is usually an extension of the superconducting wire constituting the superconducting coil 2. Conductive wires 10 and 15 are copper wires, and conductive wire 14 is an HTS wire made of a high-temperature superconducting material (oxide superconducting material). The sum of the cross-sectional area of the metal portion of the lead wire 14 (HTS wire) and the cross-sectional area of the metal portion of the lead wire 15 is smaller than the cross-sectional area of the metal portion of the lead wire 10.

  The oxide current lead 7 is a current lead body for introducing a current into the superconducting magnet 19 while suppressing heat intrusion into the superconducting magnet 19, and is a high temperature such as Bi (bismuth) or Y (yttrium). It consists of a superconducting material (oxide superconducting material). A current flows from the exciting power source 50 to the superconducting magnet 19 via one oxide current lead 7, and the current returns from the superconducting magnet 19 to the exciting power source 50 via the other oxide current lead 7. The oxide current lead 7 is disposed inside the radiation shield 4 and between the first cooling end 12a (first cooling stage) and the second cooling end 12b (second cooling stage) of the refrigerator 3. Has been.

  The conducting wires 10, 14, and 15, which are high-temperature side current leads, are thermally connected to the first cooling end 12a (first cooling stage) via the plate 4b. Only the lead wire 10 is provided between the electrode pin 8 and the plate 4b, and two lead wires 14 and 15 are provided between the plate 4b and the oxide current lead 7. Moreover, the conducting wire 14 (HTS wire) is along the conducting wire 15 (copper wire). Further, the lead wire 6 (extension of the superconducting wire constituting the superconducting coil 2), which is a current lead wire on the low temperature side, is thermally applied to the second cooling end portion 12b (second cooling stage) via the heat transfer member 16. It is connected to the.

  Here, of the high-temperature side conductors 10, 14, and 15 connected to the oxide current lead 7, the end portion of the conductor 10 is spirally wound (rounded), and the plate 4 b Is placed in an electrically insulated state. That is, a part of the conducting wire 10 is thermally connected to the first cooling end 12a (first cooling stage) of the refrigerator 3 through the plate 4b in a wound state. Note that it is not always necessary to thermally connect the first cooling end portion 12a (first cooling stage) in a state where a part of the conductive wire 10 is wound, and a conductive wire is provided between the electrode pin 8 and the plate 4b. 10 may simply be connected. In addition, the conducting wire 10 and the plate 4b are connected in an electrically insulated state.

  As a modification, the end portions (on the side opposite to the oxide current lead 7) of the conductors 14 and 15 disposed in the radiation shield 4 are spirally wound (rounded) and fixed to the mask surface of the plate 4b. Good. The conducting wires 14 and 15 and the plate 4b are fixed in an electrically insulated state.

  Further, a diode 13 for protecting the oxide current lead 7 from burning or the like is connected to the oxide current lead 7 in parallel with the oxide current lead 7. It is preferable that the diode 13 has a conduction voltage set to a low voltage of 0.2 V or less. Note that the lower limit of the energization voltage is, for example, about 0.02 V (20 mV).

  Further, the oxide current lead 7 and the diode 13 are disposed at a position that is thermally closer to the second cooling end 12b (second cooling stage) than the first cooling end 12a (first cooling stage) of the refrigerator 3. Has been. Specifically, the oxide current lead 7 and the diode 13 are connected to the heat transfer member 16 by contacting the low temperature side end portion of the oxide current lead 7 to which the diode 13 is connected in parallel with the heat transfer member 16. Is thermally connected to the second cooling end 12b (second cooling stage). The high-temperature side end of the oxide current lead 7 and the plate 4b of the radiation shield 4 are spaced apart by a certain distance.

  In this embodiment, the diode 13 is connected in parallel to the oxide current lead 7 by connecting both ends of the diode 13 to the high temperature side end and the low temperature side end of the oxide current lead 7. The diode 13 may be connected in parallel to the oxide current lead 7 by directly connecting one end of 13 to the conductors 14 and 15 and directly connecting the other end to the conductor 6. With this connection, only the diode 13 is disposed at a position that is closer to the second cooling end portion 12b (second cooling stage) than the first cooling end portion 12a (first cooling stage) of the refrigerator 3. can do. In this way, only the diode 13 is disposed at a position thermally closer to the second cooling end 12b (second cooling stage) than the first cooling end 12a (first cooling stage) of the refrigerator 3, The oxide current lead 7 that itself has a heat intrusion preventing function may be disposed, for example, at an intermediate position between the first cooling end 12a and the second cooling end 12b.

  It should be noted that the arrangement of the first cooling end 12a (first cooling stage) at a position "thermally closer" to the second cooling end 12b (second cooling stage) than the first cooling end 12a (first cooling stage). This means that the heat transfer efficiency from the second cooling end portion 12b (second cooling stage) is higher than the heat transfer efficiency from the first cooling stage. For example, the diode 13 is disposed at a position “thermally closer” to the second cooling end 12b (second cooling stage) than the first cooling end 12a (first cooling stage). This means that the diode 13 is arranged in a state in which the heat transfer efficiency from the second cooling end portion 12b (second cooling stage) is higher than the heat transfer efficiency from the end portion 12a (first cooling stage).

  In the present embodiment, the diode 13 is thermally connected to the second cooling end portion 12b (second cooling stage) via the low temperature side end portion / heat transfer member 16 of the oxide current lead 7, and the diode 13 The distance between 13 and the second cooling stage is shorter than the distance between the diode 13 and the first cooling stage. The diode 13 is disposed at a position "thermally closer" to the second cooling end 12b (second cooling stage) than the first cooling end 12a (first cooling stage). It is not determined only by the fact that the distance is closer to the second cooling end 12b (second cooling stage) than the first cooling end 12a (first cooling stage).

  FIG. 2 shows an electrical circuit diagram around the oxide current lead 7. In FIG. 2, the three superconducting coils 2 a to 2 c are shown, but the three superconducting coils 2 a to 2 c are not necessarily required. A state in which the diode 17 is connected in parallel to the superconducting coils 2a to 2c and the diode 13 is also connected in parallel to the oxide current lead 7 is shown in the electric circuit diagram of FIG. ing.

(Action / Effect)
It is assumed that a failure occurs in the power source (excitation power source 50), the refrigerator 3, etc., the temperature of each part in the superconducting magnet device 1 rises, and the superconducting state of the oxide current lead 7 disappears. At this time, since the diode 13 as the protective element is connected in parallel to the oxide current lead 7, when the oxide current lead 7 transitions to the high resistance state due to a temperature rise, the current flowing in the oxide current lead 7 Is bypassed to the diode 13 to prevent the oxide current lead 7 from being burned out. That is, even if a failure occurs in the power source, the refrigerator, etc., the oxide current lead 7 is protected independently.

  Here, if the energization voltage of the diode 13 is set to a low voltage of 0.2 V or less, the burning of the oxide current lead 7 can be more reliably prevented.

  In addition, the diode 13 which is a protective element is disposed at a position thermally closer to the second cooling end 12b (second cooling stage) than the first cooling end 12a (first cooling stage) of the refrigerator 3. Therefore, even if the diode 13 is connected in parallel to the oxide current lead 7, the temperature difference between both ends of the diode is reduced, and heat intrusion to the superconducting coil 2 through the diode 13 can be suppressed. It is possible to suppress malfunctions and quenching of the superconducting magnet 19.

  Furthermore, in this embodiment, a part of the conducting wire 10 is thermally connected to the first cooling end 12a (first cooling stage) via the plate 4b in a wound state. Since a part of the conducting wire 10 is thermally connected to the first cooling stage, the conducting wire 10 is cooled by the first cooling stage. Moreover, since the part thermally connected to the 1st cooling stage is wound, the thermal contact area with the 1st cooling stage via the plate 4b becomes large, and the conducting wire 10 is cooled more. As a result, heat penetration into the superconducting coil 2 can be further suppressed.

(Modification)
FIG. 3 is a partial cross-sectional view showing a modification of the superconducting magnet device 1 shown in FIG. The superconducting magnet device 1 shown in FIG. 1 is different from the superconducting magnet device 101 shown in FIG. 3 in that the superconducting magnet device 101 has a single conducting wire between the plate 4b and the oxide current lead 7. That is, one conductive wire 14 (HTS wire) is provided for the oxide current lead 7.

  When the conducting wire 14 is made of a Bi-based (bismuth-based) high-temperature superconducting material (oxide superconducting material), for example, as in the present modification, one oxide current lead 7 has 1 It is possible to connect with two lead wires 14 (HTS wires). This is because, in the case of Bi, since the high temperature superconducting material is wrapped inside the silver coating, the silver coating can serve as a current bypass when the internal superconducting state disappears. On the other hand, when the Y-system is used for the conductive wire 14, since it does not have a bypass function in structure, it is necessary to attach 15 copper wires (see FIG. 1). In general, since the oxide superconductor carries almost all of the energization current, the sum of the cross-sectional areas of the metal portions 14 and 15 can be made significantly smaller than that of a normal copper wire alone. (10% or less). Therefore, heat penetration via the conductive wire 14 (HTS wire) and the conductive wire 15 can be suppressed. That is, at least a part of the high-temperature-side conductors connected to the oxide current lead 7 is made of an oxide superconducting material (by being made an HTS wire), so that heat to the superconducting coil 2 can be obtained. Intrusion can be further suppressed.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims. .

1: Conduction-cooled superconducting magnet device 2: Superconducting coil 3: Refrigerator (two-stage refrigerator)
4: Radiation shield (cooling container)
5: Vacuum container 7: Oxide superconducting current lead 12a: First cooling end (first cooling stage)
12b: second cooling end (second cooling stage)
13: Diode 19: Superconducting magnet

Claims (5)

A superconducting magnet,
A cooling container containing the superconducting magnet;
A vacuum vessel that houses the cooling vessel;
A two-stage refrigerator attached to the vacuum vessel;
The cooling vessel is disposed between the first cooling stage of the two-stage refrigerator and the second cooling stage of the two-stage refrigerator having a temperature lower than that of the first cooling stage. An oxide superconducting current lead for introducing current into the superconducting magnet;
In a conduction cooling type superconducting magnet device comprising:
A conduction cooled superconducting magnet device, wherein a diode for protecting the oxide superconducting current lead is connected in parallel to the oxide superconducting current lead. In the conduction cooling type superconducting magnet device according to claim 1,
The conduction-cooling superconducting magnet apparatus, wherein the diode is disposed at a position that is closer to the second cooling stage than the first cooling stage. In the conduction cooling type superconducting magnet apparatus according to claim 1 or 2,
A conduction cooling type superconducting magnet apparatus, wherein a part of a high temperature side conductor connected to the oxide superconducting current lead is thermally connected to the first cooling stage in a wound state. In the conduction cooling type superconducting magnet device according to any one of claims 1 to 3,
A conduction cooled superconducting magnet device, wherein at least a part of the high-temperature-side conducting wire connected to the oxide superconducting current lead is made of an oxide superconducting material. In the conduction cooling type superconducting magnet device according to any one of claims 1 to 4,
The diode is a conduction-cooling superconducting magnet device, wherein an energization voltage is 0.2 V or less.

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