JP4414617B2 - Low resistance conductor, its manufacturing method, current lead, power supply cable, coil, magnetic field generator, transformer and AC power supply - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a substantially low-resistance electrical conductor, a method for producing the same, and applied equipment using the same.
[0002]
[Prior art]
Currently, copper is most frequently used as a conductor for conducting electricity. This is because the specific resistance at room temperature is almost the same as that of silver, the lowest relative to other materials, and relatively inexpensive. As a method of reducing the specific resistance of the conductor, there is a method of cooling the conductor. In the case of copper, when cooled to liquid nitrogen temperature (77K), the specific resistance is about 1/7, about 2.5 x 10^-9Ωm.
[0003]
Although a superconducting wire needs to be cooled below the superconducting transition temperature, it has an almost zero electrical resistance and is an ideal conductor. Metal-based superconducting wires have a high degree of completeness as wires, and have been put into practical use as magnets such as MRI. However, they have not been widely used due to the necessity of cooling to cryogenic temperatures. On the other hand, there are roughly two types of oxide-based superconducting materials that become superconducting at liquid nitrogen temperature: Bi-based and Y-based. Development of tape wires with a silver sheath as the Bi type is mainly in progress, and tape wires with a superconducting thin film formed on the Y tape as a buffer layer on the metal tape surface are being developed. These wires have high expectations because they can be cooled with liquid nitrogen that is easy to handle when high characteristics are obtained. And the development and spread of electrical equipment using these wires are expected.
[0004]
[Problems to be solved by the invention]
However, Bi-based wires do not have a sufficient critical current density at 77K, and are particularly expensive due to their characteristic deterioration in a magnetic field and the use of silver as a sheath material. There's a problem. Y-based wires are under development due to problems such as film formation speed and uniformity of properties in vacuum.
[0005]
On the other hand, as long as the specific resistance is sufficiently low, and an inexpensive and easy-to-handle conductor can be manufactured, it is not always necessary to use a superconducting wire having zero electrical resistance. Therefore, an object of the present invention is to provide a conductor having such a sufficiently small specific resistance. Another object of the present invention is to provide an electric device that uses such a conductor and has low power loss and is easy to handle.
[0006]
Further, techniques for superconducting connection of a plurality of bulk superconductors are disclosed in JP-A-5-279028, JP-A-6-40775, and JP-A-7-17774. The present invention provides a conductor joined relatively easily via a normal conductor having a finite electrical resistance and a method for producing the conductor.
[0007]
[Means for Solving the Problems]
  As an example, a high critical current density has already been obtained at 77K, mainly for Y-based oxide superconducting bulk materials. It has been found that a substantially low resistance conductor and its applied electrical equipment can be obtained by electrically connecting superconductors represented by such materials to each other. That is,
  (1)Have a thickness of 100 μm or moreBulk superconductor3 or moreA conductor formed by normal conduction, wherein the apparent specific resistance of the conductor below the superconducting transition temperature of the superconductor is lower than the specific resistance of copper at the temperature. Was a low resistance conductor.
  (2)Have a thickness of 100 μm or moreBulk superconductor3 or moreA low-resistance conductor using a superconductor, wherein the conductor has a normal conductive connection, and the apparent specific resistance of the conductor at 77K is lower than the specific resistance of copper at 77K.
  (3)A thickness of the bulk superconductor is 200 μm or more and 10 mm or less, The low resistance conductor using the superconductor according to (1) or (2).
  (4)Above3 or moreA part or all of the bulk superconductor has a rod-like or plate-like shape (1)~(3)EitherA low-resistance conductor using the superconductor described in 1.
  (5)3 or moreA part of the bulk superconductor of (1) to (1) is characterized by having a rod-like or plate-like shape that is at least one of curved and bent states.4A low-resistance conductor using the superconductor according to any one of the above.
  (6)3 or moreSome or all of the bulk superconductor of REBa₂Cu_ThreeO_7-x(1) to (1) characterized by being a superconductor (where RE is one or a combination of rare earth elements including Y)5A low-resistance conductor using the superconductor according to any one of the above.
  (7) A part or all of the three or more bulk superconductors are single crystal oxide bulk superconductors obtained by growing from a seed crystal (1) to (1) 6) A low-resistance conductor using the superconductor according to any one of
  (8)3 or moreA longitudinal direction of a part or all of the bulk superconductor is characterized by being perpendicular to the c-axis in the crystallographic orientation of the superconductor (6)Or (7)Low resistance conductor using the described superconductor.
  (9)3 or moreThat part or all of the normal conduction connections of the bulk superconductors are bonded to at least one of the planes substantially perpendicular to the longitudinal direction of the adjacent superconductors and the planes substantially parallel to each other. A low-resistance conductor using the superconductor described in (1) or (2).
  (10)3 or moreA plurality of layers of superconductors are arranged so as to cover a part or all of the normal connection portion in the longitudinal direction of the bulk superconductor (9A low-resistance conductor using the superconductor described in 1.).
[0008]
  (11A part or all of the normal conduction connection is formed by joining adjacent superconductors through a metal (9Or (10A low-resistance conductor using the superconductor described in 1.).
  (12The metal is one or more selected from the group consisting of copper, copper alloy, silver, silver alloy, gold, gold alloy, aluminum, and aluminum alloy (11) A low resistance conductor using the described superconductor.
  (13The metal has a thickness of 100 μm or less (11Or (12A low-resistance conductor using the superconductor described in 1.).
  (14) A part or all of the bulk superconductor in the longitudinal direction is the energizing direction (1) to (13A low-resistance conductor using the superconductor according to any one of the above.
  (15The distance between the bulk superconductors is 10 mm or less (1) to (14The low resistance conductor according to any one of the above.
  (16The apparent specific resistance is RS / nL (1) to (1)15The low resistance conductor according to any one of the above. Where R is the resistance value of the conductor, S is the cross-sectional area of the conductor, n is the number of the bulk superconductors, and L is the length of one bulk superconductor.
  (17) A gap L between two bulk superconductors disposed through one of the bulk superconductors. ₁ Is 50% or less of the length L of the bulk superconductor. The low-resistance conductor according to any one of (1) to (16),
[0009]
  (18)Have a thickness of 100 μm or moreBulk superconductor3 or moreA method for producing a low-resistance conductor, characterized in that the low-resistance conductor is disposed through a normal conductor and pressed to perform connection processing.
  (19The bulk superconductor is connected using solder (18The manufacturing method of the low resistance conductor of description.
  (20)Have a thickness of 100 μm or moreBulk superconductor3 or moreA method for producing a low-resistance conductor, which is disposed through a normal conductor, pressurized, and then heat-treated in a reduced-pressure atmosphere or vacuum.
  (21The bulk superconductor is connected using a paste or foil of copper, copper alloy, silver, silver alloy, gold, gold alloy, aluminum or aluminum alloy, and then heat-treated (18Or (20The manufacturing method of the low resistance conductor as described in).
  (22The surface of the bulk superconductor has one or more coatings selected from the group consisting of copper, copper alloy, silver, silver alloy, gold, gold alloy, aluminum, and aluminum alloy. Do (18) ~ (21The manufacturing method of the low resistance conductor in any one of.
[0010]
  (23(1) to (17A current lead comprising at least a portion of the low resistance conductor according to any one of the above.
  (24) An electrode made of copper, aluminum, gold, silver, or an alloy thereof is connected to both ends of the low-resistance conductor (23) Current leads as described.
  (25()23Or (24The power supply cable according to claim 1 is provided at least partially.
  (26) The current lead is arranged at the center of one space of a multi-pipe more than a double tube, and the other space has a space through which the refrigerant flows around the center of the space, and has a heat insulating layer on the outer periphery. Do (25Power supply cable as described in).
  (27) The electrodes connected to the current leads are electrically connected to each other, and the connection electrode portions are covered with a vacuum heat insulating layer (25Power supply cable as described in).
[0011]
  (28(1) to (17A coil obtained by winding the low-resistance conductor according to any one of the above.
  (29The cross-sectional area of the surface perpendicular to the energizing direction of the low-resistance conductor of the coil is larger in the inner peripheral portion than in the outer peripheral portion (28) Coil.
  (30The low-resistance conductor used for the low-resistance conductor of the coil is characterized by combining superconductors having different rare earth compositions (28) Coil.
  (31The gap between the wound low resistance conductors is used as a refrigerant flow path (28) ~ (30The coil according to any one of the above.
  (32The low-resistance conductor is reinforced with at least one of resin and fiber reinforced plastic (28) ~ (31The coil according to any one of the above.
  (33()28) ~ (32A magnetic field generator using the coil according to any one of the above.
  (34()28) ~ (32) Is used at least on the secondary side.
  (35()28) ~ (32An AC power source characterized in that the coil according to any one of the above is used on at least the secondary side.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is a conductor joined relatively easily through a normal conductor having a finite electrical resistance, and a method for manufacturing the conductor. Techniques for superconducting connection of a plurality of bulk superconductors are disclosed in JP-A-5-279028, JP-A-6-40775, and JP-A-7-17774. The crystal itself is connected without grain boundaries or weak bonds, and it is necessary to align the crystal orientation three-dimensionally. On the other hand, according to the present invention, the orientation of the crystal that is a superconducting phase is three-dimensional. There is no need to align. For this reason, manufacture of a conductor is very easy and industrial utility is very large.
Note that the low resistance conductor in the present invention does not exhibit the properties of a good conductor at a temperature above the superconducting transition temperature, but in this case, it is referred to as a low resistance conductor in the present invention.
[0013]
A normal superconducting material with a thickness d (m) that is sufficiently thinner than t is obtained by using a plate-like superconducting wire of length L (m), thickness t (m), and width w (m) as shown in FIG. Consider a sufficiently long conductor connected through. Connection resistance R between superconductor 1 (S1) and superconductor 2 (S2)_j(Ω) is the contact resistance R between S1 and the normal conductor_c1 Resistance R between S2 and normal conductor_c2And normal conductor resistance R_nBecause it is the sum of
R_j= R_c1+ R_c2+ R_n
Indicated by
The contact resistivity between each superconductor and normal conductor is ρ_c(Ωm²)
R_c1+ R_c2= 4ρ_c/ Lw
Indicated by
R_nIs the specific resistance of the normal conductor ρ_n(Ωm)
R_n= Ρ_n2d / Lw
Indicated by
[0014]
Assuming that the conduction current is sufficiently small compared to the critical current of the superconductor, that is, the voltage drop in the superconductor is zero, the resistance R of the conductor of length nL is
R = 2nR_j
Therefore, the apparent resistivity ρ in the longitudinal direction of such a conductor below the superconducting transition temperature of the superconductor^*(Ωm) is
ρ^*= 2nR_jS / nL
Because the apparent cross-sectional area (S) is 2tw,
ρ^*= 4R_jtw / L
                         = 8t (2ρ_c+ ρ_nd) / L²
It becomes. Here, however, it is assumed that the length-wise butted portions shown in FIG. 1 are not electrically connected.
[0015]
Next, as shown in FIG. 2, a conductor in which three plate-like superconductors are connected in parallel is considered in the same manner. Under the same conditions as in the case of two in parallel, ρ of such a conductor^*(Ωm) is
ρ^*= 27 (2ρ_c+ ρ_nd) t / 4L²
It becomes.
From these calculations, the apparent ρ^*IstProportional to and inversely proportional to the square of L, and the smaller d, ρ^*It turns out that becomes small.
[0016]
Furthermore, as shown in FIG.₁Similarly, consider the case where the conductor is constructed while leaving a gap. Ρ in this case^*Is
ρ^*= 8 (2ρ_c+ ρ_nd) t / (L²-L₁ ²)
Thus, it can be seen that although the length can be increased with the same number of conductors, the specific resistance increases. It can also be seen that the same tendency is found in the conductor as shown in FIG.
[0017]
In practice, to maintain mechanical strength, L₁Is preferably 50% or less of L, more preferably 10% or less. The most desirable form is substantially L₁Is zero, and is joined with a low electrical resistance. The expression that multiple layers of superconductors are arranged so as to cover the normal conducting connection in the longitudinal direction of the superconducting conductor is₁Means an arrangement of conductors sufficiently small with respect to L. In FIG. 1 to FIG. 3, a rod-shaped superconducting conductor having a rectangular cross section is taken as an example, but the cross sectional shape is not necessarily rectangular.
[0018]
  L₁It is desirable to further dispose a superconductor in the gap and to make electrical connection, since this improves mechanical strength and energization characteristics near the critical current. As described above, it can be understood that, in order to make the apparent specific resistance smaller, in principle, the thickness (t) of the superconductor should be made smaller. The actual thickness of the superconductor is 20 μm or more of the thickness level of the flaky Y-type single crystal superconducting sample, preferably 100 μm or more that can be manufactured by grinding, more preferably, easy slice cutting. 200 μm or more is possible.Among the thicknesses of the superconductors, in the present invention, the thickness of the bulk superconductor is set to 100 μm or more.The upper limit of the thickness is not particularly limited, but is preferably 10 mm or less in view of the apparent specific resistance.
[0019]
  Various combinations of the cross-sectional shapes of such conductors are conceivable. A specific example is shown in FIG. Also, if there are many parallel lines,BulkWhen the superconductor has defects such as a portion having a low critical current density (Jc), the degree of deterioration of the characteristics on the entire conductor is reduced. In addition, the continuity is also given to the mating part,RatioNeedless to say, the resistance can be further reduced.
[0020]
  in this wayBulkA superconductor is normally connected, and the conductor is viewed at a cooling temperature below the superconducting transition temperature.KenoIf the specific resistance is smaller than the specific resistance of copper at the cooling temperature, such a conductor will have various advantages as a low resistance conductor. In particular, ρ * in the vicinity of 77K obtained from liquid nitrogen as a refrigerant for the convenience of cooling is an important parameter indicating the usefulness of the conductor.
[0021]
As described above, the present invention relates to a conductor joined relatively easily via a normal conductor having a finite electrical resistance and a method for manufacturing the same. On the other hand, the technology for superconducting connection of multiple bulk superconductors is a single crystal structure in which a plurality of superconductors are aligned in crystal orientation via a solder, and the solder portion is crystal-grown from the superconductor by heat treatment. It is basically necessary to align the crystal orientation of the superconductor three-dimensionally. On the other hand, in the present invention, it is not necessary to three-dimensionally align the crystal orientation as the superconducting phase. Ρ^*By making this sufficiently small, it is intended to obtain substantially the same effect as a perfect superconductor.
[0022]
Ρ of such a low resistance body^*In order to reduce this, it is necessary to increase the substantial contact area between each superconductor. For that purpose, it is desirable that the shape of the superconductor is a rod or plate, and the surfaces perpendicular to the longitudinal direction and / or parallel surfaces of adjacent superconductors are in contact with each other. Further, in order to change the energization direction, it is necessary to have a curved or bent rod shape or plate shape.
[0023]
  Configure low resistance conductorBulkSuperconducting materials,MoneyLinear or tape-like with a genus sheathBulkEven a superconductorTheSingle crystal material that does not contain grain boundaries etc. that reduce critical currentIs. In particular, RE₂BaCuO_FiveREBa with high critical current density with finely dispersed phases₂Cu_ThreeO_7-xA superconductor is desirable. In such a superconductor, since microcracks are likely to occur perpendicular to the c-axis, it is desirable that the longitudinal direction as the energization direction is perpendicular to the c-axis. Also, by making the longitudinal direction the energizing direction, ρ^*Is reduced by the aforementioned ρ^*It is clear from the formula for
[0024]
As the metal in direct contact with the superconductor, one or more of copper, copper alloy, silver, silver alloy, gold, or gold alloy, aluminum, or aluminum alloy can be used. It is desirable to use one or more of silver, silver alloy, gold or gold alloy, which has low properties, good electrical compatibility with superconductors, and low contact resistance.
In addition, it is advantageous in the manufacturing process that the superconductor is coated with the metal coating having a relatively low contact resistance and then connected by an appropriate method. In this case, as a material for joining the metal-coated superconductor, there are a solder mainly composed of tin and lead and a metal paste such as a silver paste. Solder is excellent in that it can be easily processed by local heating at room temperature, such as easy bonding. In the case of solder connection, the thickness of the metal layer in the connection portion is usually about 100 to 50 μm. Further, an adhesive such as silver paste is also excellent in the following points. When silver paste is used as an adhesive and sintered by heat treatment, a thin metal layer of 25 μm or less is obtained due to the small specific resistance of silver itself and the shrinkage of the metal layer at the joint due to sintering. Therefore, the connection resistance can be reduced compared to the solder connection. In this sintering step, heat treatment in a reduced pressure atmosphere or vacuum is desirable from the viewpoint of void removal.
[0025]
Although it is desirable that the thickness of the normal connection portion between the superconductors is thinner, when the superconductors are in direct contact with each other, the contact resistance is increased. 10 mm or less is preferable, and 1 mm or less is more preferable. In practice, it is related to the surface roughness of the superconductor, but an average value of 100 to 2 μm is desirable. More desirably, the thickness is 50 to 2 μm. More preferably, it is 25-2 μm.
The low resistance conductor functions as a current lead by attaching electrodes or the like to both ends. As the electrode material, copper, aluminum, silver or the like having a small specific resistance is desirable.
[0026]
By arranging the cooled low resistance conductor in the heat insulating layer, a power supply cable can be configured. Here, the cable means a conductor in which a heat insulating layer surrounds a low-resistance conductor, and a conductor having electrodes at least at both ends of the low-resistance conductor is called a current lead.
[0027]
In addition, when a coil is manufactured using a low-resistance conductor, a cylindrical coil similar to a conventional wire can be made by connecting arc-shaped superconductors, but a linear superconductor. It is extremely efficient in the manufacturing process to produce a coil with a small number of members (at least two members) having a certain angle of bend and 360 degrees. FIG. 5 shows an example of a coil using a member having a bending angle of 45 degrees (n = 8). In this case, it is comprised by the member which consists of three types of superconductors except one bending member. In general, since Jc decreases in a strong magnetic field, it is efficient to use a relatively thick conductor inside the coil and a relatively thin conductor at the outer periphery. In addition, since the Jc characteristics in the magnetic field differ depending on the composition of rare earth elements, the outer peripheral part uses a material having a high critical current density in a low magnetic field, and the inner peripheral part has a high critical current density in a high magnetic field. It is desirable to select the composition of the rare earth element according to the characteristics of the superconductor.
[0028]
When the coil is energized, an electromagnetic force acts on the low resistance conductor, so it is necessary to reinforce it with resin or fiber reinforced plastic. Further, it is desirable to provide a cooling path through which a refrigerant or the like flows in order to efficiently remove heat.
By using a coil made of such a low-resistance conductor on the secondary side with a small winding ratio, a transformer capable of passing a large current on the secondary side can be obtained. Moreover, such a transformer functions as an AC power source capable of energizing a large current.
[0029]
【Example】
Example 1
Y₂O_Three, BaO₂, CuO raw powders are mixed so that the molar ratio of each metal element (Y: Ba: Cu) is (13:17:24), and 0.5% by mass of Pt is added to the mixed powder and mixed. A raw material powder was prepared. This raw material powder was calcined at 900 ° C. in an oxygen stream. This calcined powder is 2 ton / cm using a rubber press.²Was formed into a disk-shaped molded body having a diameter of 55 mm and a thickness of 20 mm.
[0030]
This was heated up to 1150 ° C. in the atmosphere over 8 hours and held for 1 hour. After that, using a Sm-based seed crystal, the seed crystal was arranged at 1040 ° C. so that the normal of the board surface substantially coincided with the c-axis. Thereafter, the temperature was lowered to 1005 ° C. over 30 minutes, and further cooled gradually to 970 ° C. over 220 hours for crystal growth. Subsequently, it was cooled to room temperature in 20 hours. The obtained cylindrical Y-type bulk material having a diameter of about 46 mm was sliced to a thickness of 0.6 mm, and further processed to a width of 2.0 mm and a length of 40 mm to prepare a rod-shaped sample. The material thus obtained is a single crystal YBa₂Cu_ThreeO_7-xAbout 1μm Y in the phase₂BaCuO_FiveThe phase had a finely dispersed structure. YBa₂Cu_ThreeO_7-xThe relationship with the crystal orientation of the phase is shown in FIG.
[0031]
Silver was deposited on these rod-shaped sample surfaces by sputtering of about 2 μm, and then annealed in an oxygen stream. The annealing heat treatment pattern was raised from room temperature to 600 ° C in 6 hours, held for 1 hour, then lowered to 450 ° C in 2 hours, further lowered to 380 ° C in 60 hours, and cooled to room temperature in 12 hours .
[0032]
These rod-shaped samples are electrically connected to the low resistance conductor having the cross section shown in FIGS. 7A to 7C using the silver-containing solder in the arrangement shown in FIG. Was made. At this time, the thickness of the metal layer was about 100 μm in normal soldering, but the thickness of the metal layer could be reduced to about 50 μm by solidifying the solder while applying pressure. And after attaching the electric current introduction terminal and the voltage terminal to the conductor produced by each connection method, it was immersed in liquid nitrogen, and the superconductor was made into the superconducting state.
[0033]
When the resistance was measured by energizing 500A to the above three types of low resistance conductors, each of them was 1.25 × 10^-FiveΩ, 0.69 × 10^-FiveΩ, 0.75 × 10^-FiveΩ, apparent resistivity is 3.0 × 10^-11 Ωm, 2.5 × 10^-11Ωm, 2.7 × 10^-11Ωm, copper resistivity at liquid nitrogen temperature (77K) (2.5 × 10^-9It was found that the resistivity is about two orders of magnitude lower than that of (Ωm).
[0034]
(Example 2)
Raw material powder Y₂O_ThreeTo Dy₂O_ThreeA Dy-based bulk material was produced in the same manner as described in Example 1 only by changing to This was sliced and cut to a thickness of 0.6 mm, and then processed into a rod-shaped material having a curved and bent shape as shown in FIGS. 8 (a) and 8 (b) together with the rod-shaped material of FIG. After forming silver on the surface in the same manner as in Example 1, each member was combined to produce an L-shaped low-resistance conductor having a total length of about 1 m. At this time, the connection between the superconductors was performed in the same manner as in Example 1 using solder in the manner shown in FIG.
In this connection, the silver coating layer was 5 μm and the solder layer was about 50 μm.
[0035]
When the resistance was measured by applying 500A to the above two types of low resistance conductors, each was about 1.3 × 10^-FiveΩ, apparent resistivity is about 3.0 × 10^-11It was found that the resistivity was about two orders of magnitude lower than the resistance of copper at liquid nitrogen temperature (77K).
In addition, such a cable or conductor functions as a current lead.
[0036]
(Example 3)
A copper electrode was connected to the end of the low resistance conductor produced in Example 1, and then an insulating coating was applied. Then, it was inserted into the center of the triple tube as shown in FIG. 9 (a). In addition, the end of the triple tube that can be connected in series has the structure shown in FIG. 9 (b). There is a copper electrode that is insulated from the surroundings, and a structure that covers the liquid nitrogen channel with a vacuum heat insulating layer. It has become. By connecting five such cables in series and further connecting a load and a DC power source, a power transmission experiment circuit shown in FIG. 10 was produced. When this load is energized with 500A, the power transmission loss generated in one cable is about 3.2W, and the loss at room temperature (about 120W) of the copper wire with the cable thickness (outer diameter of the triple tube) In comparison, it could be reduced to about 1/40.
[0037]
Example 4
By the method described in Example 1 and Example 2, Y-type and Dy-type columnar bulk materials having a diameter of about 46 mm were prepared. After slicing and cutting these pieces to 1.0 mm, a straight rod-shaped material having a width of 1.9 mm from the Y-based material and a 2.2-mm straight rod-shaped material from the Dy-based material and a rod-shaped material having a bending angle of 45 degrees are prepared, and these are coated with silver After the application, oxygen addition treatment was performed by the annealing method described in Example 1. They were electrically connected by solder. At this time, the thickness of the solder layer was about 60 μm, and the thickness of each silver coating was 5 μm. An eight-turn pancake coil (outer diameter 62 mm, outermost diameter 138 mm) using a conductor with a width of 2.2 mm on the inside and 5 turns on the outside and a conductor with a width of 1.9 mm on the outside, and a 0.4 mm thick glass Fabricated on a fiber reinforced plastic (FRP) as shown in FIGS. 5 (a) and 5 (b). In this FRP, holes with a diameter of 2 mm are formed in a lattice shape, and these holes serve as a liquid nitrogen channel. For bonding the FRP and the conductor, a resin containing about 20% by volume of a filler of several μm was used.
Thirty-one such pancake coils were stacked and electrically connected in the direction in which the magnetic fields generated by each pancake coil were strengthened to produce a stacked coil having a height of about 80 mm. At this time, it connected so that the direction of a vortex might be reversed for every layer so that the terminal inside and outside of each pancake coil might be connected.
[0038]
After connecting the current introduction terminal to the laminated coil, it was immersed in liquid nitrogen and cooled. When 500A was energized, the generated voltage in the coil was 1.5V and a magnetic field of about 2.0T was generated in the center. At this time, there was no voltage increase due to heat generation, and the coil did not burn out even when energized for a long time.
Thus, it was found that a strong magnetic field can be easily generated by using a low resistance conductor.
[0039]
(Example 5)
By the method described in Example 1, a cylindrical bulk material having a Y-system diameter of about 46 mm was produced. After slicing and cutting this to 1.5 mm, a linear rod-shaped material having a width of 3.0 mm and a rod-shaped material having a bending angle of 45 degrees were prepared, and after these were coated with silver, the annealing method described in Example 1 was used. Then, oxygen addition treatment was performed. As shown in FIGS. 11 (a) and 11 (b), they were electrically connected by soldering to produce a solenoid coil (the innermost diameter 20 mm, the outermost diameter 26 mm) with 5 turns per layer. At this time, the thickness of the solder layer was about 45 μm, and the thickness of each silver coating was 3 μm. As shown in FIG. 12, this was linked with an iron core having a regular octagonal cross section to form a secondary winding of a transformer, and a coated copper wire was wound 500 times on the primary side. This transformer was immersed in liquid nitrogen, and a sine wave current of 15 A peak was applied to the primary side, and it was confirmed that a sine wave of about 1500 A was flowing on the secondary side. As a result, it has been clarified that such a transformer functions as a power supply capable of supplying a large current.
[0040]
(Example 6)
Single-crystal YBa produced in Example 1₂Cu_ThreeO_7-xAbout 1μm Y in the phase₂BaCuO_FiveAfter silver is deposited on the surface of a rod-shaped material having a structure in which phases are finely dispersed by sputtering of about 2 μm, these rod-shaped samples are formed as low-resistance conductors having cross sections shown in FIGS. 7 (a) to (c). In the arrangement shown in Fig. 1, a silver paste was used for connection to produce a conductor of about 1 m. About 1.3 × 10 this conductor²Heating was performed at about 900 ° C. for about 1 hour under reduced pressure of Pa to sinter the silver particles of the silver paste and the silver film on the surface of the rod-shaped material. At this time, the total thickness of the silver layer was about 25 μm.
[0041]
Then, the temperature was raised from room temperature to 600 ° C in 6 hours, held for 1 hour, then lowered to 450 ° C in 2 hours, further lowered to 380 ° C in 60 hours, cooled to room temperature in 12 hours, oxygen annealed Processed.
After the current introduction terminal and the voltage terminal were attached to the conductors produced by the respective connection methods, they were immersed in liquid nitrogen to bring the superconductor into a superconducting state.
[0042]
When the above three types of low-resistance conductors were energized with 500A and the resistance was measured, each 1.25 × 10^-6Ω, 0.76 × 10^-6Ω, 0.72 × 10^-6Ω, apparent resistivity is 3.0 × 10^-12Ωm, 2.8 × 10^-12Ωm, 2.7 × 10^-12Ωm, copper resistivity at liquid nitrogen temperature (77K) (2.5 × 10^-9It was found that the resistivity was about 3 orders of magnitude lower than (Ωm).
[0045]
【The invention's effect】
As described above, the present invention provides a low-resistance conductor that is substantially smaller than the specific resistance of copper, a method for manufacturing the same, and various electrical devices using the conductor, and has a significant industrial effect. is there.
[Brief description of the drawings]
FIG. 1 shows an example of a low-resistance conductor in which two superconductors are alternately connected in parallel.
FIG. 2 shows an example of a low resistance conductor in which three superconductors are alternately connected in parallel.
[Fig. 3] Alternately superconductor L₁Of low resistance conductors connected with a gap of
(a) Example of arrangement above and below (b) Example of arrangement above
[Fig. 4] (a) to (e) are cross-sectional schematic diagrams of a low-resistance conductor in which a plurality of superconductors are connected.
FIG. 5 shows an example of a coil in which a bent member and a rod-like member are connected in combination.
(a) Viewed from the surface. The black part shows two types (long and short) of rod-shaped superconducting members.
(b) Viewed from the back. The black part is bent. It is made of one type except for the hatched members.
6 is a rod-shaped superconductor produced in Example 1. FIG.
[Fig. 7] (a) Cross-sectional shape of a low-resistance conductor in which two superconductors are alternately connected in parallel.
(b) Cross section of low resistance conductor with three superconductors connected in parallel
(c) Cross section of low-resistance conductor with three superconductors connected in parallel
[Fig.8] (a) Example of bent member
(b) Example of curved member
[Fig. 9] (a) Cross section of triple tube and conductor arranged in triple tube
(b) Connectable triple tube end structure
Fig. 10 Circuit diagram of power transmission experiment
[Fig. 11] (a) Secondary low-resistance coil used in the transformer seen from the surface
(You can see the bent parts)
(b) Secondary side low resistance coil used in the transformer viewed from the back side
(Bar-shaped member is visible)
FIG. 12 shows a structure of a transformer using a low resistance conductor.
[Explanation of symbols]
1 Butting part
2 Short rod-shaped member
3 Long rod-shaped member
4 Bent material
5 Insulation coating
6 Liquid nitrogen channel
7 Vacuum insulation layer
8 Low resistance conductor
9 Flange
10 O-ring
11 Copper lead
12 Liquid nitrogen channel
13 Cable
14 Power supply
15 Load
16 Bent material
17 Bar-shaped member
18 Primary winding
19 Iron core with regular octagonal cross section
20 Secondary winding made of low resistance conductor
21 Joints between coils made of low-resistance conductors

Claims (35)

A conductor formed by normal conduction connection of three or more bulk superconductors having a thickness of 100 μm or more , wherein an apparent specific resistance of the conductor at a temperature equal to or lower than a superconducting transition temperature of the bulk superconductor is A low-resistance conductor using a superconductor characterized by being lower than the specific resistance of copper. A conductor formed by normal conduction connection of three or more bulk superconductors having a thickness of 100 μm or more, characterized in that the apparent specific resistance of the conductor at 77K is lower than the specific resistance of copper at 77K Low resistance conductor using superconductor. The low resistance conductor using the superconductor according to claim 1 or 2, wherein the bulk superconductor has a thickness of 200 µm or more and 10 mm or less. The superconductor according to any one of claims 1 to 3, wherein a part or all of the three or more bulk superconductors have a rod-like or plate-like shape. Was a low resistance conductor. Some of the three or more bulk superconductor, of curved and bent, according to claim 1-4, characterized by comprising a rod-like or plate-like shape which is one state of at least one A low-resistance conductor using the superconductor according to any one of the items. Part or all of the three or more bulk superconductors are REBa ₂ Cu ₃ O _7-x based superconductors (where RE is one of rare earth elements including Y or a combination thereof). A low resistance conductor using the superconductor according to any one of claims 1 to 5 . The part or all of the three or more bulk superconductors are single-crystal oxide bulk superconductors obtained by growing from a seed crystal. A low-resistance conductor using the superconductor according to item 1. The super direction according to claim 6 or 7 , wherein a part or all of the longitudinal directions of the three or more bulk superconductors are perpendicular to the c-axis in the crystallographic orientation of the bulk superconductor. A low-resistance conductor using a conductor. Part or all of the normal conduction connections of the three or more bulk superconductors are joined to at least one of the surfaces substantially perpendicular to the longitudinal direction of the adjacent superconductors and the surfaces substantially parallel to each other. A low resistance conductor using the superconductor according to claim 1 or 2. The superconductor according to claim 9 , wherein a plurality of layers of bulk superconductors are arranged so as to cover a part or all of the normal conducting connection portions in the longitudinal direction of the three or more bulk superconducting conductors. A low-resistance conductor using a conductor. The low resistance conductor using a superconductor according to claim 9 or 10 , wherein a part or all of the normal conduction connection is formed by joining adjacent bulk superconductors through a metal. The superconductivity according to claim 11 , wherein the metal is one or more selected from the group consisting of copper, copper alloy, silver, silver alloy, gold, gold alloy, aluminum, and aluminum alloy. Low resistance conductor using the body. The low resistance conductor using the superconductor according to claim 11 or 12 , wherein the metal has a thickness of 100 µm or less. The low resistance conductor using the superconductor according to any one of claims 1 to 13 , wherein a part or all of the bulk superconductor in a longitudinal direction is a conduction direction. The low resistance conductor according to any one of claims 1 to 14 , wherein a distance between the bulk superconductors is 10 mm or less. The low-resistance conductor according to any one of claims 1 to 15 , wherein the apparent specific resistance is RS / nL. Where R is the resistance value of the conductor, S is the cross-sectional area of the conductor, n is the number of the bulk superconductors, and L is the length of one bulk superconductor. A gap L between two of the bulk superconductors disposed through one of the bulk superconductors ₁ The low resistance conductor according to any one of claims 1 to 16, wherein is less than 50% of a length L of the bulk superconductor. A method for producing a low-resistance conductor, comprising arranging three or more bulk superconductors having a thickness of 100 μm or more via normal conductors and pressurizing and connecting them. The method of manufacturing a low resistance conductor according to claim 18 , wherein the bulk superconductor is connected using solder. A method for producing a low-resistance conductor, comprising placing three or more bulk superconductors having a thickness of 100 μm or more through normal conductors, pressurizing them, and then heat-treating them in a reduced-pressure atmosphere or vacuum. Copper said bulk superconductor, copper alloy, silver, silver alloy, gold, gold alloy, using a paste or foil of aluminum or an aluminum alloy connecting claim 18 or 20, characterized in that heat treatment thereafter A method for producing a low-resistance conductor according to 1. The surface of the bulk superconductor has one or more coatings selected from the group consisting of copper, copper alloy, silver, silver alloy, gold, gold alloy, aluminum or aluminum alloy. Item 22. The method for producing a low-resistance conductor according to any one of Items 18 to 21 . A current lead comprising the low resistance conductor according to any one of claims 1 to 17 at least partially. The current lead according to claim 23 , wherein electrodes made of copper, aluminum, gold, silver, or an alloy thereof are connected to both ends of the low-resistance conductor. 25. A power supply cable comprising the current lead according to claim 23 or 24 disposed at least in part. The current lead is arranged in the center of one space of a multiple tube more than a double tube, and has a space in which the refrigerant flows around the space center as another space, and has a heat insulating layer on the outer periphery thereof. The power supply cable according to claim 25 . 26. The power supply cable according to claim 25 , wherein the electrodes connected to the current leads are electrically connected to each other, and the connection electrode portions are covered with a vacuum heat insulating layer. A coil formed by winding the low-resistance conductor according to any one of claims 1 to 17 . The coil according to claim 28 , wherein a cross-sectional area of a surface perpendicular to the energizing direction of the low-resistance conductor of the coil is larger in the inner peripheral portion than in the outer peripheral portion. The coil according to claim 28 , wherein the low-resistance conductor used for the low-resistance conductor of the coil is a combination of superconductors having different rare earth compositions. The coil according to any one of claims 28 to 30 , wherein a gap between the wound low resistance conductors is used as a refrigerant flow path. The coil according to any one of claims 28 to 31 , wherein the low-resistance conductor is reinforced by at least one of resin and fiber reinforced plastic. A magnetic field generator using the coil according to any one of claims 28 to 32 . A transformer using the coil according to any one of claims 28 to 32 on at least a secondary side. An AC power supply comprising the coil according to any one of claims 28 to 32 on at least a secondary side.

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