JP2015220417A - Electrode structure of superconducting coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the electrode structure of a superconducting coil capable of maintaining the superconducting characteristics, by suppressing impairment of a superconducting wire rod at the joint of the superconducting wire rod and an electrode.SOLUTION: A superconducting coil 10 is formed by winding a tape-like superconducting wire rod 11, and an electrode 12 is bonded to the termination 11a thereof. Between at least one side of a superconducting wire rod 11 located at the termination 11a of the superconducting coil 10 and an outer electrode 12a and an inner electrode 12b constituting the electrode 12, an outer protective wire rod 15a and an inner protective wire rod 15b are interposed as a protective wire rod 15 for protecting the superconducting wire rod 11. Under this state, the superconducting wire rod 11 and the electrode 12 are joined by solder.

Description

  The present invention relates to an electrode structure of a superconducting coil formed by winding a tape-shaped superconducting wire and joining an electrode portion to a superconducting wire at a terminal portion of a superconducting coil used for power equipment or the like.

  As a tape-shaped superconducting wire forming a superconducting coil, for example, a superconducting layer of a rare earth oxide superconductor is formed on a substrate made of a nickel alloy via an intermediate layer, and a stabilizing layer such as silver or copper is formed thereon. Formed and configured. An electrode portion is joined to the superconducting wire at the terminal portion of the superconducting coil by solder.

  This type of superconducting coil is disclosed in Patent Document 1, for example. That is, a superconducting coil includes a coil body in which a superconducting wire having a base material, a superconducting layer on the base material, and a stabilizing layer on the superconducting layer is wound with the stabilizing layer side outward, and the coil body. And an electrode portion provided on the stabilization layer of the superconducting wire.

  The end portion of the superconducting wire and the electrode portion are integrally bent from the circumferential direction of the coil body toward the radially outer side, and the circumferential side portion along the circumferential surface of the coil body of the electrode portion and the outer side of the coil body of the electrode portion. Both the extended portion and the extended portion are electrically connected to the stabilization layer of the superconducting wire. A peripheral side portion of the electrode part is soldered to a stabilization layer of a superconducting wire on a coil body peripheral surface side, and an extension part of the electrode part is a stabilization layer of a superconducting wire extended radially outside the coil body. Soldered.

JP 2012-164859 A

  By the way, when the superconducting coil is cooled to a cryogenic temperature, thermal stress acts on the joint between the superconducting wire and the electrode portion based on the difference in thermal expansion coefficient between the superconducting wire and the electrode portion. In addition, the electromagnetic force generated when the superconducting coil is excited or demagnetized causes distortion in the superconducting coil, and stress acts on the joint between the superconducting wire and the electrode portion.

  For this reason, in the superconducting coil having the conventional configuration described in Patent Document 1, the soldering portion between the peripheral side portion of the superconducting wire and the electrode portion and the soldering portion between the extension portion and the electrode portion. There was a risk of stress concentration in the superconducting wire and the electrode part, resulting in poor connection or peeling. Therefore, there has been a problem that the characteristics of the superconducting coil deteriorate due to poor electrical connection between the superconducting wire and the electrode portion.

  Accordingly, an object of the present invention is to provide an electrode structure of a superconducting coil that can suppress the damage of the superconducting wire at the joint between the superconducting wire and the electrode portion and maintain the superconducting characteristics.

  In order to achieve the above object, an electrode structure of a superconducting coil according to claim 1 is a superconducting coil in which an electrode portion is joined to a terminal portion of a superconducting coil formed by winding a tape-like superconducting wire. In the electrode structure, the superconducting wire and the electrode part are joined between the superconducting wire located at the terminal part of the superconducting coil and the electrode part with a protective wire protecting the superconducting wire interposed therebetween. It is characterized by that.

  The electrode part is composed of an outer electrode part located on the outer peripheral side of the superconducting wire and an inner electrode part located on the inner peripheral side of the superconducting wire, and the protective wire is an outer peripheral surface of the superconducting wire located at the terminal part of the superconducting coil. It is preferably interposed between the outer electrode part and between the inner peripheral surface of the superconducting wire and the inner electrode part.

It is preferable that the protective wire is wound around the superconducting wire so as to make at least one turn along the superconducting coil.
The protective wire is preferably formed of a superconducting wire that forms a superconducting coil.

It is preferable that the superconducting wire is formed by forming a superconducting layer of a rare earth oxide superconductor through an intermediate layer on a substrate and forming a stabilizing layer on the superconducting layer.
The protective wire is preferably disposed on the superconducting layer side of the superconducting wire.

  The outer electrode portion and the inner electrode portion are provided with engaging portions, and are disposed between the outer electrode portion and the inner electrode portion in a state where protective wires are disposed on both surfaces of the superconducting wire, and in this state, the outer electrode portion It is preferable that the engaging portion and the engaging portion of the inner electrode portion are engaged and fastened integrally with a fastening member.

  According to the electrode structure of the superconducting coil of the present invention, it is possible to suppress the damage of the superconducting wire at the joint between the superconducting wire and the electrode and maintain the superconducting characteristics.

It is sectional drawing which shows the superconducting coil in 1st Embodiment, Comprising: Sectional drawing which shows the state which joined the electrode to the superconducting wire in the edge part of a superconducting coil. The partial expanded sectional view of FIG. Sectional drawing which shows a tape-shaped superconducting wire. The perspective view which shows the state which joined the electrode to the superconducting wire in the edge part of a single pancake coil. The perspective view which shows the state which joined the electrode to the superconducting wire in the edge part of a double pancake coil. The perspective view which shows the manufacturing method of a double pancake coil. The disassembled perspective view which shows the state which joins an electrode in the state which has arrange | positioned the superconducting wire for protection on the both sides of a superconducting wire. Sectional drawing which shows the state which joins an electrode in the state which has arrange | positioned the short superconducting wire on both sides of a superconducting wire by the method different from FIG. The principal part sectional drawing which shows the state which joined the electrode in the state which has arrange | positioned the superconducting wire for protection on both sides of the superconducting wire in 1st Embodiment and Example 1. FIG. The graph showing the characteristic of the superconducting coil in Example 1, and showing the relationship between the electric current and voltage of the 1st energization. The graph which represents the characteristic of the superconducting coil in Example 1, and shows the relationship between the electric current and voltage after the 5th cooling cycle. The principal part sectional drawing which shows the state which joined the electrode in the state which has arrange | positioned the superconducting wire for protection on both sides of the superconducting wire in 2nd Embodiment and Example 2. FIG. The graph which represents the characteristic of the superconducting coil in Example 2, and shows the relationship between the electric current of the 1st electricity supply, and a voltage. The graph showing the characteristic of the superconducting coil in Example 2, and showing the relationship between the electric current and voltage after the 5th cooling cycle. Sectional drawing which shows the state which joined the electrode to the both sides of the superconducting wire in the comparative example 1. The graph showing the characteristic of the superconducting coil in the comparative example 1, and showing the relationship between the electric current and the voltage of the first energization. The graph showing the characteristic of the superconducting coil in the comparative example 1, and showing the relationship between the electric current and voltage after the 3rd time of a cooling cycle. The graph showing the characteristic of the superconducting coil in the comparative example 1, and showing the relationship between the electric current and voltage after the 4th cooling cycle. Sectional drawing which shows the state which joined the electrode to the both sides of the superconducting wire in the comparative example 2. The graph showing the characteristic of the superconducting coil in the comparative example 2, and showing the relationship between the electric current and the voltage of the first energization. The graph which represents the characteristic of the superconducting coil in the comparative example 2, and shows the relationship between the electric current and voltage after the 2nd time of a cooling cycle. The graph showing the characteristic of the superconducting coil in the comparative example 2, and showing the relationship between the electric current and voltage after the 3rd time of a cooling cycle. The principal part sectional drawing which shows the state which joined the electrode in the state which has arrange | positioned the superconducting wire for protection in the one side of the superconducting wire in 3rd Embodiment and Example 3. FIG. The graph showing the characteristic of the superconducting coil in Example 3, and showing the relationship between the electric current and voltage of the 1st energization. The graph showing the characteristic of the superconducting coil in Example 3, and showing the relationship between the electric current and voltage after the 5th cooling cycle.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described in detail with reference to FIGS.
As shown in FIG. 1, the superconducting coil 10 is formed by winding a tape-shaped superconducting wire 11, and an electrode portion 12 is joined to the terminal end 11 a of the superconducting coil 10, that is, the terminal end 11 a of the superconducting wire 11. As shown in FIG. 4, a single pancake coil 10 </ b> A as the superconducting coil 10 is configured by winding a superconducting wire 11 in one stage, and an electrode portion is provided on the inner peripheral side terminal portion 11 a and the outer peripheral side terminal portion 11 a. 12 is joined.

  As shown in FIG. 5, the double pancake coil 10B as the superconducting coil 10 is configured by winding the superconducting wire 11 in two upper and lower stages through a partition frame member 13 formed of fiber reinforced resin (FRP). The electrode portion 12, that is, the upper electrode portion 12A and the lower electrode portion 12B are joined to the upper and lower end portions 11a on the outer peripheral side.

  As shown in FIG. 6, when manufacturing the double pancake coil 10 </ b> B, the central portion of the superconducting wire 11 that forms a single tape is centered on the inner peripheral frame 14 to which the partition frame member 13 is connected. Wrap in the opposite direction on the top and bottom two steps. That is, the upper coil is wound counterclockwise when viewed from above, and the lower coil is wound clockwise when viewed from above. The partition frame member 13 is provided with a through-hole (not shown) through which the superconducting wire 11 passes. Further, the winding direction of the superconducting wire 11 around the inner peripheral frame 14 may be opposite to the above.

  As shown in FIGS. 1 and 2, the superconducting wire 11 is provided between the inner and outer peripheral surfaces of the superconducting wire 11 located at the terminal end 11a and the outer electrode portion 12a and the inner electrode portion 12b as the electrode portion 12, respectively. An outer protective wire 15a and an inner protective wire 15b are interposed as protective wire 15 for mechanically protecting the wire. The electrode part 12 is branched into an outer electrode part 12a and an inner electrode part 12b, and both electrode parts 12a and 12b are connected to each other and connected to a lead wire (not shown).

  The superconducting wire 11 is joined to the outer electrode portion 12a and the inner electrode portion 12b by solder via the outer protective wire 15a and the inner protective wire 15b, respectively. The protective wire 15 is configured to circulate substantially along the superconducting coil 10, and an outer peripheral end thereof serves as an outer protective wire 15 a and an inner peripheral end serves as an inner protective wire 15 b. The protective wire 15 is formed of the same superconducting wire as the superconducting wire 11, and is formed in a short length that is sufficient for one round.

  As shown in FIG. 3, in the superconducting wire 11, a superconducting layer 18 is formed on a substrate 16 via an intermediate layer 17, and a stabilization layer 19 is provided on the superconducting layer 18. The stabilization layer 19 includes a first stabilization layer 19a on the superconducting layer 18 and a second stabilization layer 19b covering the outer periphery.

  The substrate 16 is made of a metal such as nickel alloy (Hastelloy), silver, or silver alloy, and has a thickness of 100 μm and a width of 10 mm, for example. The intermediate layer 17 is made of a compound such as gadolinium / zirconium oxide (Gd / Zr oxide), magnesium oxide (MgO), yttrium-stabilized zirconium (YSZ), barium / zirconium oxide (Ba / Zr oxide), for example. It has a thickness of 500 nm and a width of 10 mm.

  The superconducting layer 18 is formed, for example, to a thickness of about 1 μm and a width of 10 mm by a rare earth oxide superconductor CVD method (chemical vapor deposition method). As rare earth elements, lanthanum (La), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), dysprosium (Dy), holmium (Ho), erbium (Er), yttrium (Y), And ytterbium (Yb). Examples of rare earth oxides include RE, Ba, Cu, and O. However, RE represents a rare earth element. Specific examples of the superconducting layer 18 include yttrium / barium / copper oxide and lanthanum / barium / copper oxide (La / Ba / Cu oxide).

  The first stabilization layer 19a is formed to have a thickness of about 15 μm and a width of 10 mm, for example, by sputtering of a metal such as silver. The second stabilization layer 19b is formed to a thickness of about 50 μm, for example, by plating with a metal such as copper.

The electrode portion 12 is formed of a highly conductive metal material such as silver, copper, gold, platinum, or an alloy containing these metals.
As shown in FIG. 9, the superconducting wire 11 is disposed such that the substrate 16 is located on the inner peripheral side and the superconducting layer 18 is located on the outer peripheral side. The outer protective wire 15a is arranged such that the superconducting layer 18 is located on the inner peripheral side, and the superconducting layer 18 faces the superconducting layer 18 of the superconducting wire 11. For this reason, the electrical continuity between the outer protective wire 15a and the superconducting wire 11 is enhanced. Further, the inner protective wire 15b is disposed such that the superconducting layer 18 is located on the inner peripheral side, and the superconducting layer 18 faces the inner electrode portion 12b. For this reason, electrical continuity between the inner protective wire 15b and the inner electrode portion 12b is enhanced.

  Thus, since the protective wire 15 is interposed on both inner and outer peripheral surfaces of the superconducting wire 11 and joined to the outer electrode portion 12a and the inner electrode portion 12b with solder, the superconducting wire 11 is attached to the outer electrode portion 12a and the inner electrode portion 12b. There is no direct contact and it is shielded and protected by the protective wire 15.

  As shown in FIG. 7, a plurality of engaging protrusions 20 are provided at the upper and lower ends of the inner surface of the outer electrode portion 12a, and the engaging protrusions are provided at the upper and lower ends of the outer surface of the inner electrode portion 12b. A plurality of engaging recesses 21 with which 20 is engaged are provided. A female screw hole 22 as a fastening member is formed in the engaging convex portion 20 of the outer electrode portion 12a, and a through hole 23 penetrating the inner electrode portion 12b is formed in the engaging concave portion 21 of the inner electrode portion 12b. The male screw 24 is threaded into the female screw hole 22 of the outer electrode portion 12a through the through hole 23 of the inner electrode portion 12b.

  In addition, a plurality of notches 25 are formed at the upper end and the lower end of the superconducting wire 11, the outer protective wire 15a, and the inner protective wire 15b, respectively, and the engaging convex portion 20 of the outer electrode portion 12a and the engaging concave portion of the inner electrode portion 12b. 21 is formed at a position corresponding to 21. Then, in a state where the outer protective wire 15a and the inner protective wire 15b are arranged on both surfaces of the superconducting wire 11, the engaging convex portion 20 is engaged with the engaging concave portion 21, the male screw 24 is passed through the through hole 23, and the female screw hole 22 is inserted. The superconducting wire 11 can be connected to the electrode portion 12 by being screwed to the electrode portion 12.

  In this way, by connecting the superconducting wire 11 to the electrode portion 12, the bonding state of the solder joint portion between the superconducting wire 11 and the electrode portion 12 can be firmly maintained. Furthermore, the adhesion between the superconducting wire 11 and the electrode part 12 can be increased, the contact resistance can be suppressed, and the electrical conductivity can be improved.

  The connection structure between the superconducting wire 11 and the electrode portion 12 can adopt other forms. For example, as shown in FIG. 8, the engaging groove 26 is formed on the inner surface of the outer electrode portion 12a, and the engaging protrusion 27 is engaged with the engaging groove 26 on the outer surface of the inner electrode portion 12b. To form. The engaging recess 26 of the outer electrode portion 12a is configured such that the outer protective wire 15a and the inner protective wire 15b can be accommodated on both surfaces of the superconducting wire 11 in an overlapping manner. The inner electrode portion 12b, the inner protective wire 15b, the superconducting wire 11 and the outer protective wire 15a are formed with insertion holes 28, and the outer electrode portion 12a is formed with a female screw hole portion 29 as a fastening member. Then, the superconducting wire 11 can be connected to the electrode portion 12 by passing a screw 30 as a fastening member through the insertion hole 28 and screwing it into the female screw hole portion 29.

Next, an effect | action is demonstrated about the electrode structure of the superconducting coil 10 of 1st Embodiment.
Now, as shown in FIG. 1, a protective wire 15 is wound around the superconducting wire 11 located at the terminal end portion 11a almost once. As shown in FIG. 2, in the electrode portion 12, the outer electrode portion 12 a is joined to the outer peripheral surface of the superconducting wire 11 via the outer protective wire 15 a by soldering to achieve electrical connection. The inner electrode portion 12b is joined to the peripheral surface by soldering via the inner protective wire 15b to achieve electrical connection.

  When the superconducting coil 10 is cooled to 77K with, for example, liquid nitrogen, the superconducting coil 10 contracts and the superconducting wire 11 receives an inward force. Further, when the superconducting coil 10 is energized and excited, an electromagnetic force (hoop force) acts on the superconducting coil 10, and the superconducting wire 11 receives an outward force, and when the energization is stopped and demagnetized, the electromagnetic force is applied. The force is suddenly released, and the superconducting wire 11 receives an impact force. For this reason, the stress which tries to separate both acts on the junction part of the superconducting wire 11, the outer electrode part 12a, and the inner electrode part 12b.

  However, in the superconducting coil 10 of the first embodiment, the outer protective wire 15a is interposed between the superconducting wire 11 and the outer electrode portion 12a, and the inner protective wire 15b is interposed between the superconducting wire 11 and the inner electrode portion 12b. Has been. Therefore, the stress mainly acts on the outer protective wire 15a and the inner protective wire 15b, and avoids acting directly on the superconducting wire 11 sandwiched between the protective wires 15. For this reason, the superconducting wire 11 at the end portion 11a is mechanically protected and wear and the like are alleviated. Further, the stress that the superconducting wire 11 receives from the protective wire 15 is also limited to one round of the terminal portion of the superconducting coil 10, and hardly affects the superconducting wire 11 when viewed from the whole superconducting coil 10. Therefore, the superconducting coil 10 can maintain superconducting characteristics.

The effects obtained by the first embodiment described in detail above are collectively described below.
(1) In the superconducting coil 10 of the first embodiment, the superconducting wire 11 and the electrode with the protective wire 15 interposed between both surfaces of the superconducting wire 11 located at the terminal end 11a and the electrode portion 12 are provided. The part 12 is soldered. For this reason, the thermal stress at the time of cooling and the electromagnetic force at the time of energization mainly act on the protective wire 15 and the influence on the superconducting wire 11 is mitigated.

  Therefore, according to the electrode structure of the superconducting coil 10 in the first embodiment, it is possible to suppress the damage of the superconducting wire 11 at the joint portion between the superconducting wire 11 and the electrode portion 12 and maintain the superconducting characteristics. Play.

  (2) The protective wire 15 is wound around the superconducting wire 11 so as to make at least one turn along the superconducting coil 10. For this reason, while being able to arrange | position the protection wire 15 easily on both surfaces of the superconducting wire 11 in the termination | terminus part 11a, the protection of the superconducting wire 11 can be performed effectively.

  (3) The protective wire 15 is formed of a superconducting wire 11 that forms the superconducting coil 10. Therefore, the protective wire 15 can be easily prepared, and the thermal expansion coefficient can be made the same as that of the superconducting wire 11 to maintain the adhesion between the superconducting wire 11 and the electrical connection between the superconducting wire 11 and the protective wire 15 can be maintained. Continuity can be improved.

  (4) The superconducting wire 11 has a superconducting layer 18 of a rare earth oxide superconductor formed on a substrate 16 via an intermediate layer 17 and a stabilization layer 19 formed on the superconducting layer 18. Yes. Therefore, the superconducting properties of the superconducting coil 10 can be satisfactorily exhibited by the superconducting wire 11 having a high critical temperature and being usable for liquid nitrogen cooling and having a high critical current density.

  (5) The protective wire 15 is disposed so that the superconducting layer 18 of the superconducting wire 11 and the superconducting layer 18 of the outer protective wire 15a face each other. For this reason, the electrical continuity between the superconducting wire 11 and the protective wire 15 can be enhanced, and the superconducting characteristics of the superconducting coil 10 can be exhibited stably.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. In the second embodiment and the third embodiment to be described later, portions different from the first embodiment will be mainly described.

  As shown in FIG. 12, the superconducting wire 11 is disposed such that the substrate 16 is located on the outer peripheral side and the superconducting layer 18 is located on the inner peripheral side. The outer protective wire 15a is arranged so that the superconducting layer 18 is positioned on the outer peripheral side, and the superconducting layer 18 faces the outer electrode portion 12a. For this reason, the electrical continuity between the outer protective wire 15a and the outer electrode portion 12a is good. Further, the inner protective wire 15b is arranged so that the superconducting layer 18 is located on the outer peripheral side, and the superconducting layer 18 faces the superconducting layer 18 of the superconducting wire 11. For this reason, the electrical continuity between the inner protective wire 15b and the superconducting wire 11 is good.

  Now, with respect to thermal stress during cooling and electromagnetic force during energization, both surfaces of the superconducting wire 11 are mechanically protected by the outer protective wire 15a and the inner protective wire 15b at the terminal portion 11a. In addition, since the superconducting layer 18 of the superconducting wire 11 is disposed on the inner peripheral side, the influence of thermal stress and electromagnetic force can be reduced compared to the case of the first embodiment.

Therefore, according to the second embodiment, the superconducting characteristics of the superconducting coil 10 can be further improved.
(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 23, the superconducting wire 11 is disposed such that the substrate 16 is located on the outer peripheral side and the superconducting layer 18 is located on the inner peripheral side, and the superconducting layer 18 is hardly affected by electromagnetic force or the like. An inner protective wire 15b is disposed on the inner peripheral side of the superconducting wire 11, and the inner protective wire 15b is disposed such that the superconducting layer 18 is positioned on the outer peripheral side. For this reason, the superconducting layer 18 of the inner protective wire 15b faces the superconducting layer 18 of the superconducting wire 11, and the electrical continuity between the inner protective wire 15b and the superconducting wire 11 is good. In the third embodiment, the outer protective wire 15 a is not disposed on the outer peripheral side of the superconducting wire 11.

  Now, against the thermal stress during cooling and the electromagnetic force during energization, the inner peripheral surface of the superconducting wire 11 is mechanically protected by the inner protective wire 15b at the end portion 11a. For this reason, the electrical conductivity between the superconducting layer 18 of the superconducting wire 11 and the inner electrode portion 12b is maintained well.

  Therefore, according to the third embodiment, the superconducting characteristics of the superconducting coil 10 can be maintained.

Next, the embodiment will be described more specifically with reference to examples and comparative examples.
Example 1
The electrode structure of the superconducting coil 10 of Example 1 is the electrode structure of the superconducting coil 10 shown in the first embodiment. That is, the double pancake coil 10B was produced using the superconducting wire 11 having a length of about 100 m. In order to prepare the superconducting wire 11, a 1 μm-thickness is formed on a nickel alloy (Hastelloy) substrate 16 having a width of 4 mm and a thickness of 100 μm through an intermediate layer 17 of a magnesium / lanthanum / manganese-based oxide having a thickness of 500 nm. A superconducting layer 18 made of an yttrium-based superconducting material was formed. Subsequently, a first stabilization layer 19a by sputtering of silver having a thickness of 8 μm is formed on the superconducting layer 18, and a second stabilization layer 19b by copper plating having a thickness of 20 μm is formed on the outer periphery thereof. (Critical current 140A in self-magnetic field in liquid nitrogen) was prepared.

  Next, the FRP partition frame member 13 is used, the superconducting wire 11 is wound around the inner peripheral frame 14, the insulating tape is wound together, and wound in two stages according to a conventional method, and a double having an inner diameter of 50 mm and an outer diameter of 112 mm. A pancake coil 10B was produced. At this time, as shown in FIG. 1 and FIG. 2, the outer electrode portion 12a and the inner electrode portion 12b were joined together by soldering the protective wire 15 around one turn of the superconducting wire 11 at the end portion 11a. As a result, as shown in FIG. 9, the outer electrode portion 12 a is joined to the outer peripheral surface of the superconducting wire 11 at the terminal portion of the superconducting coil 10 via the outer protective wire 15 a, and the inner peripheral surface of the superconducting wire 11 is inner. The inner electrode part 12b was joined via the protective wire 15b.

  Then, the double pancake coil 10B of Example 1 is transferred into a vacuum chamber containing liquid nitrogen, cooled to 77K by conduction cooling, and at that temperature, the double pancake coil 10B is energized without an external magnetic field, and further The cooling cycle was repeated several times between liquid nitrogen and room temperature, and the current (A) -voltage (μV) characteristics were measured according to a conventional method. The current-voltage characteristics at the first energization are shown in FIG. 10, and the current-voltage characteristics after 5 cooling cycles are shown in FIG.

When measuring the current-voltage characteristics, the voltage between the upper electrode portion 12A and the coil winding, the voltage between the coil winding itself and the lower electrode portion 12B and the coil winding were measured.
From the results shown in FIG. 10, in the superconducting coil 10 of Example 1, the superconducting state was maintained until a voltage was generated in the coil winding at a current value of about 45 A, and good superconducting characteristics were exhibited. Furthermore, from the result of FIG. 11, even when the cooling cycle was repeated five times, the current-voltage characteristics were hardly changed and the superconducting characteristics were maintained.

(Example 2)
The electrode structure of the superconducting coil 10 of Example 2 is the electrode structure of the superconducting coil 10 shown in the second embodiment. That is, using the same superconducting wire 11 as in Example 1, a double pancake coil 10B was produced in the same manner as in Example 1. As a result, as shown in FIG. 12, the outer electrode portion 12a is joined to the outer peripheral surface of the superconducting wire 11 at the terminal portion 11a via the outer protective wire 15a, and the inner protective wire 15b is connected to the inner peripheral surface of the superconducting wire 11. The inner electrode part 12b was joined via

  Then, the current (A) -voltage (μV) characteristics of the double pancake coil 10B were measured in the same manner as in Example 1. FIG. 13 shows the current-voltage characteristics at the first energization, and FIG. 14 shows the current-voltage characteristics after 5 cooling cycles.

  From the results of FIG. 13, in the superconducting coil 10 of Example 2, the superconducting state was maintained until the voltage was generated in the coil winding at a current value of about 45 A, and good superconducting characteristics were exhibited. Furthermore, from the result of FIG. 14, even when the cooling cycle was repeated five times, the current-voltage characteristics were hardly changed, and the superconducting characteristics were maintained.

(Comparative Example 1)
As shown in FIG. 15, the electrode structure of the superconducting coil 10 of Comparative Example 1 is a structure in which the outer protective wire 15a and the inner protective wire 15b are omitted from the first embodiment. And the double pancake coil 10B was produced like Example 1. FIG. As a result, as shown in FIG. 15, the outer electrode portion 12a is directly joined to the outer peripheral surface of the superconducting wire 11 at the terminal end portion 11a, and the inner electrode portion 12b is directly joined to the inner peripheral surface of the superconducting wire 11. .

  For the double pancake coil 10B of Comparative Example 1, the current (A) -voltage (μV) characteristics were measured in the same manner as in Example 1. FIG. 16 shows current-voltage characteristics at the first energization, FIG. 17 shows current-voltage characteristics after three cooling cycles, and FIG. 18 shows current-voltage characteristics after four cooling cycles.

  From the result of FIG. 16, also in the double pancake coil 10B of Comparative Example 1, the superconducting state was maintained until a voltage was generated in the coil winding at a current value of about 40 A, and good superconducting characteristics were exhibited. However, when the cooling cycle was repeated three times thereafter, the generated voltage of the upper electrode portion 12A suddenly increased from the result shown in FIG. 17, and the junction between the superconducting wire 11 and the outer electrode portion 12a was damaged. It is thought that the contact resistance increased.

  Furthermore, after the cooling cycle was repeated four times, the voltage of the coil winding part also increased rapidly from the result shown in FIG. When the junction between the superconducting wire 11 and the outer electrode portion 12a was observed after the current-voltage characteristics were measured, a portion where the superconducting wire 11 and the outer electrode portion 12a were separated was seen, and the superconducting wire 11 and the outer electrode portion were observed. 12a was only joined at several points.

(Comparative Example 2)
As shown in FIG. 19, the electrode structure of the superconducting coil 10 of Comparative Example 2 is a structure in which the superconducting layer 18 of the superconducting wire 11 is arranged on the inner peripheral side in Comparative Example 1. And the double pancake coil 10B was produced like Example 1. FIG. As a result, as shown in FIG. 19, the outer electrode portion 12 a was directly joined to the outer peripheral surface of the superconducting wire 11 at the terminal portion 11 a, and the inner electrode portion 12 b was directly joined to the inner peripheral surface of the superconducting wire 11.

  With respect to the double pancake coil 10B of Comparative Example 2, the current (A) -voltage (μV) characteristics were measured in the same manner as in Example 1. FIG. 20 shows current-voltage characteristics at the first energization, FIG. 21 shows current-voltage characteristics after two cooling cycles, and FIG. 22 shows current-voltage characteristics after three cooling cycles.

  From the result of FIG. 20, in the superconducting coil 10 of the comparative example 2, the generated voltage of the upper electrode part 12A and the lower electrode part 12B tended to be high. Thereafter, when the cooling cycle was repeated twice, the generated voltage of the upper electrode portion 12A and the lower electrode portion 12B further increased from the result of FIG. Furthermore, after the cooling cycle was repeated three times, a voltage increase in the coil winding portion was also observed from the result shown in FIG. After measurement of the current-voltage characteristics, the superconducting wire 11 and the outer electrode portion 12a and the inner electrode portion 12b were observed to be bonded, and the superconducting wire 11 was damaged in the vicinity of the outer electrode portion 12a and the inner electrode portion 12b. It is considered that the superconducting wire 11 was damaged due to shrinkage of the superconducting wire 11 during cooling.

(Example 3)
The electrode structure of the superconducting coil 10 of Example 3 is the electrode structure of the superconducting coil 10 shown in the third embodiment. That is, using the same superconducting wire 11 as in Example 1, a double pancake coil 10B was produced in the same manner as in Example 1. As a result, as shown in FIG. 23, the inner electrode portion 12b was joined to the inner peripheral surface of the superconducting wire 11 at the end portion 11a via the inner protective wire 15b. The inner protective wire 15b was formed longer than the superconducting wire 11 so as to be in sufficient contact with the superconducting wire 11.

  Then, the current (A) -voltage (μV) characteristics of the double pancake coil 10B were measured in the same manner as in Example 1. The current-voltage characteristics at the first energization are shown in FIG. 24, and the current-voltage characteristics after 5 cooling cycles are shown in FIG.

  From the result of FIG. 24, in the superconducting coil 10 of Example 3, the generated voltage of the upper electrode part 12A and the lower electrode part 12B was slightly higher than that of Examples 1 and 2, but the current value was about 45 A and coil winding was performed. Until the voltage was generated on the wire, the superconducting state was maintained and good superconducting properties were exhibited. Further, even when the cooling cycle was repeated five times, the generated voltage of the upper electrode portion 12A and the lower electrode portion 12B increased from the result of FIG. 25, but the voltage of the coil winding did not increase, and the current-voltage characteristics were almost unchanged. No change was observed and the superconducting properties were maintained.

It should be noted that the embodiment described above can be modified and embodied as follows.
The tape-shaped superconducting wire 11 may be formed of a bismuth oxide superconductor or the like. The superconductor of this bismuth-based oxide is a superconducting material formed of an oxide containing bismuth (Bi). For example, Bi2223, that is, Bi ₂ Sr ₂ Ca ₂ Cu ₃ O _10-α (α is 0 to 0. 15), Bi2212, that is, Bi ₂ Sr ₂ CaCu ₂ O _8-α (α is 0 to 0.15) or the like is used. A superconductor of a bismuth oxide is dispersed in a sheath layer of a metal material having stretchability.

  In the first embodiment and the second embodiment, the protective wire 15 may be configured only by the outer protective wire 15a interposed between the superconducting wire 11 and the outer electrode portion 12a. Or you may comprise the protective wire 15 only with the inner side protective wire 15b interposed between the superconducting wire 11 and the inner side electrode part 12b.

The protective wire 15 may be disposed only in a portion facing the electrode portion 12 without being wound once around the terminal portion 11 a of the superconducting wire 11.
-You may comprise the said electrode part 12 in either the outer side electrode part 12a or the inner side electrode part 12b. In that case, a protective wire 15 is interposed between any one of the electrode portions 12 and the superconducting wire 11.

  The engagement recess 21 may be provided on the outer electrode portion 12a, and the engagement protrusion 20 may be provided on the inner electrode portion 12b. Moreover, you may change the notch 25 of the superconducting wire 11, the outer side protection wire 15a, and the inner side protection wire 15b into the hole for penetration.

  DESCRIPTION OF SYMBOLS 10 ... Superconducting coil, 10A ... Single pancake coil, 10B ... Double pancake coil, 11 ... Superconducting wire, 11a ... Terminal part, 12 ... Electrode part, 12a ... Outer electrode part, 12b ... Inner electrode part, 15 ... Protective wire 15a ... outer protective wire, 15b ... inner protective wire, 16 ... substrate, 17 ... intermediate layer, 18 ... superconducting layer, 19 ... stabilizing layer, 19a ... first stabilizing layer, 19b ... second stabilizing layer, 20 ... Engaging convex portion as an engaging portion, 21... Engaging concave portion as an engaging portion, 22... Female screw hole as a fastening member, 24... Male screw as a fastening member, 29. ... Screws as fastening members.

Claims (7)

An electrode structure of a superconducting coil in which an electrode portion is joined to a terminal portion of a superconducting coil formed by winding a tape-shaped superconducting wire,
A superconducting wire and an electrode part are joined between a superconducting wire located at a terminal part of the superconducting coil and the electrode part with a protective wire protecting the superconducting wire interposed therebetween. Coil electrode structure. The electrode part is composed of an outer electrode part located on the outer peripheral side of the superconducting wire and an inner electrode part located on the inner peripheral side of the superconducting wire, and the protective wire is an outer peripheral surface of the superconducting wire located at the terminal part of the superconducting coil. 2. The superconducting coil electrode structure according to claim 1, wherein the electrode structure is interposed between the outer electrode portion and between the inner peripheral surface of the superconducting wire and the inner electrode portion. The electrode structure for a superconducting coil according to claim 1 or 2, wherein the protective wire is wound around the superconducting wire so as to make at least one turn along the superconducting coil. The superconducting coil electrode structure according to any one of claims 1 to 3, wherein the protective wire is formed of a superconducting wire that forms a superconducting coil. 2. The superconducting wire comprises a superconducting layer of a rare earth oxide superconductor formed on a substrate via an intermediate layer, and a stabilization layer formed on the superconducting layer. The electrode structure of the superconducting coil according to claim 1. The superconducting coil electrode structure according to claim 5, wherein the protective wire is disposed on a superconducting layer side of the superconducting wire. The outer electrode portion and the inner electrode portion are provided with engaging portions, and are disposed between the outer electrode portion and the inner electrode portion in a state where protective wires are disposed on both surfaces of the superconducting wire, and in this state, the outer electrode portion The electrode structure for a superconducting coil according to any one of claims 2 to 6, wherein the engaging portion and the engaging portion of the inner electrode portion are engaged and integrally fastened by a fastening member.