JP5675232B2 - Superconducting current lead - Google Patents

Description

  The present invention relates to a superconducting current lead having an oxide superconducting wire for supplying a current from a power source to a superconducting magnet, for example, a superconducting magnet.

  Conventionally, when operating a superconducting application device, for example, a superconducting magnet, it is necessary to cool the magnet to a cryogenic temperature in order to bring the magnet into a superconducting state, and two methods are known as this cooling method.

  That is, a method of immersing in a refrigerant such as liquid helium or liquid nitrogen (immersion cooling method) and a method of utilizing heat conduction from a refrigerator or a refrigerant (conduction cooling method). In order to excite the cooled magnet, a current must be passed through the superconducting coil, and a superconducting current lead for supplying current from the power source is required. In this case, the superconducting current lead needs to be a conductor. However, when a metal such as Cu or Al having a low electric resistance and a high thermal conductivity is used, in addition to the Joule heat generation of the superconducting current lead itself, The cooling efficiency of the superconducting magnet deteriorates due to heat penetration, and there is a problem that the cooling cost becomes enormous in order to maintain the superconducting state. In particular, this tendency is remarkable in the case of a conduction cooling system using a refrigerator, and cooling may be impossible.

  In order to solve this problem, it is necessary to achieve both conductivity and low thermal conductivity as the superconducting current lead used in the superconducting magnet. In the superconducting magnet, the superconducting current lead portion is also cooled to the liquid nitrogen temperature or lower. For this reason, by using an oxide superconductor having a small electric resistance and thermal conductivity as a superconducting current lead, it is possible to suppress the amount of heat penetration while supplying current.

  In this case, as a superconducting current lead, for example, as shown in Patent Document 1, an intermediate layer formed on a metal substrate, an oxide superconducting layer formed on the intermediate layer, and an oxide superconducting layer A superconducting current lead using a tape-shaped oxide superconducting wire having a formed stabilization layer is known.

  In this superconducting current lead, a plurality of oxide superconducting wires are electrically distributed in parallel on each of the grooves formed along the extending direction of the supporting member in parallel on the supporting member, The support member is bonded with a conductive resin. Moreover, both ends of the oxide superconducting wire are soldered to the electrodes on both ends of the support member.

JP 2009-21118A

  However, it is known that the superconducting layer in the conventional superconducting current lead is affected by the magnetic field depending on the arrangement state. In other words, the conventional superconducting current lead is arranged in a curved shape, so that the superconducting layer may generate heat due to the influence of magnetic flux perpendicular to the direction in which the current flows, impairing stable superconducting characteristics (current supply). is there.

  Also, in the conventional superconducting current lead configuration, when bent and installed in the superconducting device, the superconducting wire joined by the conductive resin and the support member are peeled off, and the superconducting resin is used for the mutual superconductivity. There is a problem that each layer of the wire rod or the support member is damaged. In the case of breakage, the superconducting lumber may not be able to obtain stable characteristics. In particular, due to the distortion of the superconducting wire due to cooling, that is, the difference in shrinkage between the support member and the metal terminal, not only the bonding by the conductive resin is released, but also the superconducting wire is detached from the support member or the metal terminal, Stable superconducting properties cannot be obtained as a lead.

  The present invention has been made in view of such points, and an object of the present invention is to provide a superconducting current lead that is less affected by a magnetic field even when used in a superconducting device in a curved state and can obtain stable superconducting characteristics. To do.

One aspect of the superconducting current lead of the present invention is a superconducting current lead that supplies power from a power source installed in a room temperature environment to a superconducting device installed in a cryogenic container. A plurality of superconducting wires that are arranged in parallel on at least one of the current lead support material to which the electrode terminals are joined and the front and back surfaces of the current lead support material, and whose both ends are connected to the electrode terminals, respectively. And the superconducting wire comprises ReBaCuO ( Re is one or more elements selected from Y, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb. And an oxide superconducting layer made of a system superconducting material. In the oxide superconducting layer, oxide particles of 50 nm or less containing at least one of Y, Zr, Sn, Ti, and Ce have a magnetic flux. Is dispersed as N'ningu point, the electrode terminal is provided with a notched cut-out portion in the same direction as the flowing direction, both end portions of the superconducting wire, in the notch, inserted together with the current lead support member In addition, a configuration is adopted in which the cutout portions are electrically connected .

  According to the present invention, even when installed in a superconducting device in a curved state, it is hardly affected by a magnetic field and can exhibit stable superconducting characteristics.

The figure which shows the typical structure of an example of the superconducting magnet apparatus using the superconducting current | flow lead which concerns on one embodiment of this invention. Perspective view showing low temperature side superconducting part in superconducting current lead 1 is a cross-sectional view taken along line P-P in FIG. Diagram showing the structure of superconducting wire Diagram showing configuration of superconducting layer The figure which uses for the explanation of the critical current value with respect to the applied magnetic field of the superconductor manufactured by the adoption example which is an example of the superconducting wire employ | adopted with the superconducting current lead of this invention, and the non-adoption example The figure which uses for the description of the magnetic field application angle dependence of the superconductor manufactured by the adoption example which is an example of the superconducting wire employ | adopted with the superconducting electric current lead of this invention, and the non-adoption example. The perspective view which shows the edge part of the lead main body which has a superconducting wire.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an example of a superconducting magnet device using a superconducting current lead according to an embodiment of the present invention.

  A superconducting current lead 100 shown in FIG. 1 energizes a superconducting magnet 12 disposed in a cryogenic container 11. In the superconducting current lead 100, the connection terminal 100 a at one end is connected to the superconducting magnet 12 through the connection terminal 12 a of the superconducting magnet 12 in the cryogenic container 11, and the connection terminal 100 b at the other end is connected to the cryogenic container 11. Connected to a power source installed outside the room at room temperature. As a result, the superconducting current lead 100 supplies power to the superconducting magnet 12 in the cryogenic container 11 from the power supply outside the cryogenic container 11.

  The superconducting current lead 100 shown in FIG. 1 includes a high-temperature side copper lead portion 110 connected to a connection terminal 100b located outside the cryogenic vessel 11 and a low-temperature side connected to the connection terminal 100a located inside the cryogenic vessel 11. And a superconducting portion 120.

  FIG. 2 is a perspective view showing the low temperature side superconducting portion 120 in the superconducting current lead 100.

  As shown in FIG. 2, the low temperature side superconducting portion 120 includes a pair of electrodes (electrode terminals) 131 and 133 and a lead body 150 in which the pair of electrodes 131 and 133 are joined to both end portions 151 and 153.

  The pair of electrodes 131 and 133 is made of a metal such as copper or copper alloy, and a recess (notch) 135 into which the end portions 151 and 153 of the lead body 150 are inserted is formed by notching one end surface of each. ing.

  The recesses 135 are formed so as to face each other end surfaces of the pair of electrodes 131 and 133, that is, open to each other in the energization direction. Ends 151 and 153 of the lead main body 150 are inserted and fitted into the recesses 135 of the electrodes 131 and 133 so as to be orthogonal to the end surfaces, respectively.

  The lead body 150 includes a long current lead support member (hereinafter referred to as “support member”) 152 and a plurality of tapes arranged on the support member (current lead support member) 152 along the extending direction of the support member 152. High-temperature superconducting wire (hereinafter referred to as “superconducting wire”) 160.

  3 is a cross-sectional view taken along the line PP in FIG.

  As shown in FIG. 3, in the lead main body 150, a plurality of tape-shaped superconducting wires 160 are arranged on the front and back surfaces 152 a and 152 b of the support member 152 in parallel with each other along the axial direction of the support member 152. The plurality of superconducting wires 160 may be arranged in parallel with each other only on one of the front and back surfaces of the support member 152. Here, the plurality of tape-shaped superconducting wires 160 are disposed on the front and back surfaces 152a and 152b of the support member 152, respectively, but are not limited thereto, and are formed on the front and back surfaces 152a and 152b of the support member 152, respectively. It is good also as a structure arrange | positioned in the groove | channel made. Note that the grooves in this configuration have a width and depth equivalent to the width and thickness of the superconducting wire 160 on the front and back surfaces 152a and 152b of the support member 152 in parallel with the longitudinal direction (energization direction). Preferably, it is formed as a recess.

  The support member 152 is made of a low heat conductive metal material in order to reduce heat intrusion from the normal temperature portion, and for example, stainless steel, nickel alloy, titanium alloy, FRP or the like is used as the low heat conductive metal material. .

  As shown in FIG. 2, a plurality of superconducting wires 160 arranged side by side on the front and back surfaces 152a, 152b (see FIG. 3) of the support member 152 are arranged so that both ends 152c, 152d of the support member 152 are recessed portions of the electrodes 131, 133. Joined at 135 via solder.

  That is, the plurality of superconducting wires 160 are fixed to the support member 152 only in the recesses 135 of the electrodes 131 and 133. Here, the plurality of superconducting wires 160 are fixed to the support member 152 by solder only in the recesses 135 of the electrodes 131 and 133, but may be fixed by an adhesive. The superconducting wire 160 is electrically joined to the electrodes 131 and 133 in the recess 135 via solder. Here, the stabilization layer of superconducting wire 160 is electrically connected to electrodes 131 and 133 via solder.

  FIG. 4 is a view showing the structure of the superconducting wire 160. As shown in FIG. 4, the superconducting wire 160 is formed by sequentially laminating an intermediate layer 162, an oxide superconducting layer (hereinafter referred to as “superconducting layer”) 163, and a stabilization layer 164 on a tape-shaped metal substrate 161. It is formed.

  The tape-shaped metal substrate 161 is, for example, nickel (Ni), nickel alloy, stainless steel, or silver (Ag). Here, the metal substrate 161 is a non-oriented metal substrate, and is Ni-Cr-based (specifically, Ni-Cr-Fe-Mo-based Hastelloy (registered trademark) B, C, X, etc.), W-Mo. Cubic Hv = 150 or more nonmagnetic alloys represented by materials such as Fe-Cr (for example, austenitic stainless steel), Fe-Ni (for example, nonmagnetic compositions), etc. is there. The thickness of the metal substrate 161 is, for example, 50 to 200 [μm].

The intermediate layer 162 includes a first intermediate layer 162-1 formed by depositing Gd ₂ Zr ₂ O ₇ (GZO) or yttrium stabilized zirconia (YSZ) on the tape-shaped metal substrate 161 by the IBAD method, and a second intermediate layer 162-2 which is formed by depositing a CeO ₂ on the intermediate layer 162-1 by RF-Sputtering method.

  The first intermediate layer 162-1 functions as a diffusion preventing layer that prevents deterioration of superconducting characteristics by diffusing elements from the tape-shaped metal substrate 161 into the superconducting layer 163 laminated thereon. The first intermediate layer 162-1 functions as a ceramic layer formed by biaxial orientation on the tape-shaped metal substrate 161.

The second intermediate layer 162-2 improves lattice matching with the superconducting layer 163 and suppresses diffusion of elements (such as Zr) constituting the first intermediate layer 162-1. The second intermediate layer 162-2 includes a CeO ₂ film, a Ce—Gd—O film in which a predetermined amount of Gd is added to CeO ₂ , and a Ce-M in which part of Ce is partially substituted with another metal atom or metal ion. An acid-resistant thin film such as an -O-based oxide film. The second intermediate layer 162-2 can be formed by any of a MOD method (Metal Organic Deposition Processes), a pulsed laser deposition method, a sputtering method, or a CVD method. When the second intermediate layer 162-2 is a Ce—Gd—O film in which Gd is added to a CeO ₂ film, in order to obtain good orientation when a YBCO superconducting layer is formed as the superconducting layer 163, The amount of Gd added in the film is preferably 50 at% or less.

  In the second intermediate layer 162-2, the crystal grain orientation greatly affects the crystal orientation and the critical current value (Ic) of the superconducting layer 163, which is the upper layer. The second intermediate layer 162-2 is formed on the first intermediate layer 162-1 by an RTR type RF-magnetron sputtering method. This RTR-type RF-magnetron sputtering method, like the PLD method, has less compositional deviation between the target and the produced film, and enables accurate film formation, but is less expensive to maintain than the PLD method. . The intermediate layer 162 has a thickness of, for example, 1 [μm], and the superconducting layer 163 is formed on the intermediate layer 162.

  On this superconducting layer 163, a stabilizing layer (also referred to as a cap layer) 164, which is a noble metal such as silver, gold, platinum, or an alloy thereof and is a low-resistance metal, is provided. Since the superconducting layer 163 is made of an active material that easily reacts with other metals, it directly reacts with materials other than noble metals such as gold and silver, or alloys thereof, causing a decrease in performance. Therefore, the stabilization layer 164 prevents performance degradation of the superconducting layer 163 by being formed immediately above the superconducting layer 163. In addition, the stabilization layer 164 serves as a bypass circuit when a normal conduction transition occurs when a current flows through the superconducting layer 163.

  Note that the second stabilization layer may be formed on the stabilization layer 164 using a low-resistance metal tape having a low resistance such as copper. The second stabilization layer may be a high-resistance metal tape such as brass, Ni, Ni—Cu alloy, or stainless steel. If the second stabilizing layer is Cu, Ni, or an alloy thereof, it is difficult to dissolve in the solder material, so that the performance deterioration as the superconducting wire 160 can be prevented. When the second stabilization layer is a high-resistance metal tape such as a Ni-Cu alloy, the superconducting wire 160 itself can be reinforced to improve the strength, and the superconducting wire 160 is used for alternating current. Loss can be reduced. As described above, the second stabilizing layer, together with the stabilizing layer 164, can ensure the mechanical, chemical, electromagnetic and thermal stability of the superconducting layer 163, that is, the superconducting wire 160. The thickness of the tape serving as the second stabilization layer is not particularly limited as long as it is a thickness that can be used as a bypass circuit when the superconducting layer 163 undergoes normal conduction transition, but is preferably about 50 μm to 200 μm. When the second stabilization layer is provided, the electrical connection of the superconducting wire 160 to the electrodes 131 and 133 is performed by joining the second stabilization layer and the electrodes 131 and 133 with solder.

  FIG. 5 is a diagram showing the configuration of the superconducting layer 163.

Superconducting layer 163 shown in FIG. _5, ReBa y _Cu 3 _{O z} system (Re is, Y, Nd, Sm, Eu , Gd, Tb, Dy, Ho, Er, 1 or 2 or more selected from Tm and Yb Wherein y ≦ 2 and z = 6.2 to 7.). Here, the superconducting layer 163 is an yttrium oxide superconductor (RE123). In the superconducting layer 163, oxide particles of 50 nm or less containing at least one of Y, Zr, Sn, Ti, and Ce are dispersed as the magnetic flux pinning points 165.

The Re-based superconducting wire 160 using such a superconducting layer 163 is obtained by applying a raw material solution on a substrate via an intermediate layer 162, performing a calcination heat treatment, and then performing a heat treatment for generating a superconductor. producing ReBa _y Cu ₃ O _z based superconductor. In this method, an organometallic complex solution containing Re (represents one kind of metal element selected from Re = Y, Nd, Sm, Gd, or Eu), Ba, and Cu as a raw material solution; Using a mixed solution consisting of an organometallic complex solution containing at least one metal selected from large Zr, Ce, Sn, or Ti, the molar ratio of Ba is in the range of y <2, and in the superconductor It can be manufactured by dispersing 50 nm or less oxide particles containing Zr, Ce, Sn or Ti as magnetic flux pinning points 165.

Further, in ReBa _y Cu ₃ O _z superconductor formed via an intermediate layer on a substrate, the Re and a composition of _{Re = A 1-x B x} , A and B, Y respectively, Nd, Sm, Gd Alternatively, it is made of any one or more different elements selected from Eu, the molar ratio of Ba is in the range of y <2, and oxide particles of 50 nm or less containing Zr in the superconductor are flux pinning points 165 And may be formed as dispersed. In this _case, a process for the preparation of ReBa y _Cu 3 _{O z} superconductor, as a raw material solution has a composition of _{Re (Re = A 1-x} B x, A and B, Y respectively, Nd, Sm, One or more different elements selected from Gd and Eu are represented.), An organometallic complex solution containing Ba and Cu and at least one selected from Zr, Ce, Sn or Ti having a high affinity with Ba An oxide of 50 nm or less containing Zr, Ce, Sn, or Ti containing a molar ratio of Ba in the range of y <2 using a mixed solution composed of an organometallic complex solution containing the above metal It can be produced by dispersing the particles as flux pinning points 165.

Further, in the Re-based superconducting layer having a composition of _{Re = A 1-x B x} , suitably be a composition of _{Re = Y 1-x Sm x} . In this case, the oxide particles containing Sm and the oxide particles of 50 nm or less containing Zr in the superconductor can be dispersed as the magnetic flux pinning points 165.

In such a Re-based superconducting layer 163 and its manufacturing method, it is preferable that the molar ratio of Ba is in the range of 1.3 <y <1.8. By making the molar ratio of Ba smaller than the standard molar ratio, segregation of Ba is suppressed, and precipitation of Ba-based impurities at the crystal grain boundaries is suppressed. Thus, the electrical coupling between them is improved, and Jc defined by the energization current is improved. By reducing the molar ratio of Ba, Y ₂ Cu ₂ O ₅ and CuO which are magnetic flux pinning points 165 are formed, and the magnetic field characteristics are improved.

  Further, the oxide particles containing Zr, Ce, Sn, or Ti dispersed as the magnetic flux pinning points 165 artificially introduced into the superconducting layer 163 are 50 nm or less, and particularly contain 5 to 30 nm of Zr. Oxide particles are preferred.

In this case, when the composition of Y _1-x Sm _x is used, a particulate Sm-rich phase (Sm _{1 + x} Ba _2−x Cu ₃ O _z ) which is a low-Tc phase is present in the superconducting layer 163 as a magnetic flux. Formed as a pinning point 165. In the superconducting layer 163, the magnetic flux pinning point 165 is formed of oxide particles containing Sm and oxide particles containing 5 to 30 nm of Zr. As a result, the pinning force is remarkably improved.

  The amount of Zr added to form the artificially introduced magnetic flux pinning point 165 is preferably 0.5 to 10 mol% in terms of metal concentration, and the amount of Zr added is 0.5 mol%. If it is less than 1, the density of the oxide particles is not sufficient, so that a sufficient pinning force cannot be obtained in a high magnetic field. On the other hand, if it exceeds 10 mol%, the precipitate becomes coarse and crystallinity is lowered. In particular, the metal concentration is preferably in the range of 0.5 to 5 mol%.

  The superconducting layer 163 in the superconducting wire 160 is formed on the intermediate layer 162 by any one of the MOD method, the pulse laser deposition method, the sputtering method, and the CVD method. Here, the superconducting layer 163 is formed by the TFA-MOD method, and as a technique for introducing the magnetic flux pinning point 165 into the Re-based superconducting layer by the TFA-MOD method, Zr having a high affinity for Ba in a solution containing TFA. A technique of mixing naphthenic acid salt and the like is employed.

In addition, by controlling the amount of introduction, the grain boundary characteristics are improved by forming BaZrO ₃ by combining with Ba, which is one of the causes of Jc lowering due to grain boundary segregation, and dispersing it in the grains. Furthermore, BaZrO ₃ and ZrO ₂ formed in the superconductor are present not only in the film surface direction but also in the film thickness direction at nano-size and nano-interval, and these effectively pin the magnetic flux, and the difference in Jc with respect to the magnetic field application angle. It is possible to significantly improve the directivity. In order to control the size, density and dispersion of BaZrO ₃ and ZrO ₂ , not only the amount of Zr-containing naphthenate and the like introduced, but also the oxygen partial pressure and water vapor partial pressure during calcination heat treatment and crystallization heat treatment It becomes possible by controlling the firing temperature, and effective flux pinning point 165 can be introduced by optimizing these.

  In the Re-based superconducting layer with a reduced Ba concentration, the Zr-containing magnetic flux pinning points 165 can be finely dispersed artificially in the superconductor.

Therefore, the magnetic field application angle dependency of Jc is small, and the magnetic field characteristic has a high Jc at a high magnetic field, and the magnetic field application angle dependency (Jc _{, min} / Jc _{, max} ) of Jc is remarkably improved. Therefore, the magnetic flux can be effectively pinned in any magnetic field application angle direction to improve the Jc-B-θ characteristic (see FIG. 6), and an isotropic Jc characteristic can be obtained.

  Here, the characteristics of a superconducting wire having a magnetic flux pinning point, in particular, a Zr-containing magnetic flux pinning point, in the superconducting layer will be described.

<Characteristics of superconducting layer including magnetic flux pinning point>
<Example of Superconducting Wire Adopted in Superconducting Conductive Lead 100 and Adopting Superconducting Layer Including Superconducting Pinning Point>
In the adopted example, as a substrate on which a superconducting layer including a magnetic flux pinning point is provided, a first intermediate layer made of Gd ₂ Zr ₂ O ₇ by an IBAD method and a second intermediate layer made of CeO ₂ by a PLD method are sequentially formed on a Hastelloy tape. The formed composite substrate was used. In this case, Δφ of the first intermediate layer and the second intermediate layer is 14 deg. And 4.5 deg. Met.

  On the other hand, the Y: TFA salt, Sm-TFA salt, Ba-TFA salt, and Cu naphthenate salt have a Y: Sm: Ba: Cu molar ratio of 0.77: 0.23: 1.5: 3. Was mixed in an organic solvent, and 1% of the Zr-containing naphthenate was mixed at a metal molar ratio in this mixed solution to prepare a raw material solution.

  The raw material solution was applied onto the second intermediate layer of the composite substrate, and then calcined heat treatment was performed. The calcination heat treatment was performed by heating to a maximum heating temperature (Tmax) of 500 ° C. in an oxygen gas atmosphere with a water vapor partial pressure of 16 Torr and then cooling the furnace.

  After the above calcining heat treatment, heat treatment for generating a superconductor (crystallization heat treatment) was performed to form a superconducting film on the composite substrate. This heat treatment was performed by holding the furnace at 760 ° C. in an argon gas atmosphere having a water vapor partial pressure of 76 Torr and an oxygen partial pressure of 0.23 Torr, and then cooling the furnace.

  The film thickness of the tape-shaped Re-based superconductor (YSmBCO + BZO) produced by the above method was 0.8 μm.

With respect to the superconducting film thus obtained, its magnetic field application angle dependency, that is, Jc (77 K) when an external magnetic field is applied in a direction parallel to the c-axis (perpendicular to the ab plane) and the value is changed. ) Was measured. The result is shown in FIG. Further, the magnetic field application angle dependency of this superconducting film, that is, Jc (77K) when an external magnetic field of 1T was applied and the angle with respect to the ab plane was changed, was measured. The result is shown in FIG. In FIG. 7, the dependence of Jc on the magnetic field application angle was Jc _{, min} / Jc _{, max} = 0.91.

Flux pinning centers at this _{time, Sm 1 + x Ba y =} 2-x Cu 3 O z (low-Tc phase), a BaZrO ₃ and ZrO _2, the BaZrO ₃ and ZrO ₂ of about 20 nm (5 to 25 nm) In the cross section (parallel to the c-axis) of the superconducting film, it was confirmed that it was uniformly dispersed in the film thickness direction at intervals of approximately 50 nm.

<Non-adoption example 1>
Using the same composite substrate as that used in the example, the Y: TFA salt, Sm-TFA salt, Ba-TFA salt and Cu naphthenate were mixed at a molar ratio of Y: Sm: Ba: Cu of 0.77: 0.23: It mixed in the organic solvent so that it might be set to 1.5: 3, and the raw material solution was produced. A raw material solution is applied onto the second intermediate layer of the composite substrate, and then a calcination heat treatment and a heat treatment for generating a superconductor (crystallization heat treatment) are performed in the same manner as in the adopted example to form a superconducting film on the composite substrate. did. The film thickness of the tape-shaped Re-based superconductor (YSmBCO) manufactured by the above method was 0.8 μm.

The superconducting film thus obtained was measured for the magnetic field dependence of Jc in the same manner as in the adopted example. The results are shown in Figure 6. For this superconducting film, the magnetic field application angle dependence of Jc was measured in the same manner as in the adopted example. The magnetic field application angle dependence of Jc was Jc _{, min} / Jc _{, max} = 0.6. The magnetic flux pinning point at this time was Sm _{1 + x} Bay _{= 2−x} Cu ₃ O _z (low-Tc phase), which was about 100 nm.

<Non-employment example 2>
Using the same composite substrate as in the example, Y-TFA salt, Ba-TFA salt, and Cu naphthenate salt were added in an organic solvent so that the molar ratio of Y: Ba: Cu was 1: 1.5: 3. A raw material solution was prepared by mixing.

  A raw material solution is applied onto the second intermediate layer of the composite substrate, and then a calcination heat treatment and a heat treatment for generating a superconductor (crystallization heat treatment) are performed in the same manner as in the adopted example to form a superconducting film on the composite substrate. did. The film thickness of the tape-shaped Re-based superconductor (YBCO) manufactured by the above method was 0.8 μm.

The superconducting film thus obtained was measured for the magnetic field dependence of Jc in the same manner as in the adopted example. The results are shown in FIG. For this superconducting film, the magnetic field application angle dependence of Jc was measured in the same manner as in the adopted example. The results are shown in FIG. In FIG. 7, the magnetic field application angle dependency of Jc was Jc _{, min} / Jc _{, max} = 0.47.

  As is apparent from the results of the adoption examples and non-adoption examples shown in FIGS. 6 and 7, the tape-shaped Re-based superconductor (YSmBCO + Zr-containing oxide particles) which is a superconducting layer including a magnetic flux pinning point is Y In comparison with the tape-shaped Re-based superconductor (YSmBCO) of the non-adopted example 1 in which a part of is replaced with Sm and the tape-shaped Re-based superconductor (YBCO) of the non-adopted example 2 in which the Ba concentration is reduced from the standard composition The magnetic field characteristics of Jc having a small magnetic field dependency and having a high Jc at a high magnetic field are shown.

Also, when a 1T external magnetic field is applied in a direction parallel to the c-axis (perpendicular to the ab plane) (77K), (YSmBCO) in non-adopted example 1 is 1. Although it has 3 times Jc, the adopted example (YSmBCO + Zr-containing oxide grains) has 2.2 times Jc compared to (YBCO) in the non-adopted example 2. Further, the magnetic field application angle dependency (Jc _{, min} / Jc _{, max} ) of the adopted example (YSmBCO + Zr-containing oxide grains) is 0.47 and YBCO of the non-adopted example 2 and YSmBCO of the non-adopted example 1, respectively. While 0.6 shows anisotropy, it is significantly improved to 0.91.

  Therefore, as shown in FIG. 5, the superconducting layer 163 including the magnetic flux pinning point is perpendicular to the superconducting layer 163 (in the ab plane) in addition to the generation of the magnetic field IA parallel to the superconducting layer 163 (parallel to the c-axis). Even if a vertical magnetic field IB is generated, stable characteristics can be obtained that are hardly affected by the pinning point 165. Note that it is preferable to add 3 wt% of Zr in the superconducting layer 163.

  FIG. 8 is a perspective view showing an end portion of the lead body 150 having the superconducting wire 160.

  As shown in FIG. 8, the superconducting current lead 100 has a plurality of superconducting wires 160 formed on the front and back surfaces of the support member 152 to form a lead body 150.

  The both ends 151 (153) of the lead body 150 configured as described above are inserted into the recesses 135 of the electrodes 131 (133), respectively. Before inserting the end portion 151 (153) of the lead main body 150 into the recess 135, the end portion 152c (152d) of the support member 152 and both ends of the superconducting wire 160 are joined together with solder or an adhesive. Keep it.

  Next, the superconducting wire 160 is electrically connected to the electrodes 131 and 133 by flowing solder between the inner wall of the recess 135 and both ends 151 (153) of the lead body 150 in the recess 135 into which the lead body 150 is inserted. The electrodes 131 (133) are connected to the support member 152 while being connected.

  In the superconducting current lead 100 configured as described above, the superconducting wire 160 disposed on the front and back surfaces of the support member 152 along the extending direction of the support member 152 is bonded to the support member 152 only at both ends thereof. Has been. Furthermore, the superconducting wire 160 is connected to the electrodes 131 and 133 only in the recess 135 through solder. That is, in the superconducting current lead 100, the electrodes 131 and 133, the support member 152, and the superconducting wire 160 are joined only at the fitting portion 152 e between the recess 135 and the lead body 150.

  Thus, even if the superconducting current lead 100 is curved, the support member 152 and the superconducting wire 160 can be independently deformed independently in the lead body 150 interposed between the electrodes 131 and 133. Therefore, even when the superconducting current lead 100 is bent and installed in the superconducting device, unlike the conventional case, the connecting portion of the support member 152 and the superconducting wire 160 does not peel off due to the bending.

  On the other hand, in the conventional superconducting current lead, since the superconducting wire is connected to the support member by soldering, if the conventional superconducting current lead is bent, the supporting member and the superconducting wire are peeled off, and the joint portion is separated. The solder may damage each layer of the support member or the superconducting wire and may damage the characteristics.

  In particular, even if the installed superconducting current lead is distorted by cooling, unlike the conventional case, in the superconducting current lead 100 according to the present embodiment, the joining by soldering is released and the superconducting wire 160 is peeled off from the support member 152. In other words, the lead body 150 cannot be detached from the support member 152 or the electrodes 131 and 133.

  That is, in the superconducting current lead 100, the solder is poured into the recess 135 only by the fitting portion between the both ends 151 and 153 of the lead body 150 and the recess 135 that are fitted by inserting the electrodes 131 and 133 into the recess 135. As a result, the electrodes 131 and 133 are joined to the support member 152 and the superconducting wire 160 in the lead main body 150.

  Therefore, the superconducting wire 160 can reduce the amount of solder that joins the support member and the high-temperature superconducting wire as compared with the conventional high-temperature superconducting wire, and can reduce the manufacturing cost.

  Further, even if the superconducting wire 160 is distorted, the support member 152 and the superconducting wire 160 are not entirely joined via solder, and therefore, the possibility that both the joined members are peeled off is small. As such, it can maintain stable characteristics.

  Further, unlike the conventional case, the superconducting current lead 100 does not have the superconducting wire 160 attached to the support member 152 entirely by solder. For this reason, it is hard to receive the influence of the heat at the time of soldering, and deterioration of the performance (specifically, the performance of superconducting layer 163) of superconducting wire 160 by heat does not occur easily.

  Further, the deformed superconducting wire 160 has a pinning point 165 (see FIG. 5) in the superconducting layer 163, so that it is not affected by the magnetic field even when it is installed in a magnetic field and obtains stable characteristics. Can do.

  Furthermore, since the joining portion of the support member 152 and the superconducting wire 160 by solder is only at both end portions, the connection resistance (thickness of the entire solder) can be reduced as compared with the conventional configuration in which the entire surface is joined.

  As described above, even if the superconducting current lead 100 is installed in the superconducting device in a curved state, the superconducting current lead 100 is hardly affected by the magnetic field, and can obtain characteristics equivalent to those of the superconducting current lead 100 in a non-curved state.

<Example 1>
In Example 1, the superconducting wire 160 manufactured by the TFA-MOD method includes a YBCO superconducting layer 163 having a width of 4.5 mm and a thickness of 1.0 μm, and a first intermediate layer 162-1 as Gd ₂ Zr ₂ O _7. A (GZO) layer, an intermediate layer 162 having a thickness of 1.5 μm in which the second intermediate layer 162-2 is a CeO ₂ layer, and a tape-shaped metal substrate 161 that is 100 μm thick Hastelloy (registered trademark). A silver layer (first stabilizing layer) 164 having a thickness of about 20 μm is deposited on the surface of the superconducting layer 163 for the purpose of improving thermal stability, electrical contact stability, mechanical strength, and the like. ing. Transport current is supplied through this silver first stabilization layer 164.

  The support member 152 was an austenitic stainless steel plate having a width of 36 mm, a length of 220 mm, and a plate thickness of 3.0 mm. The lead main body 150 was configured by arranging superconducting wires 160 having 12 YBCO superconducting layers 163 on both sides of the stainless steel plate material, that is, arranging 6 superconductors on one side.

  Both ends of the lead body 150 are covered with electrodes 131 and 133 that are cap-shaped voltage terminals made of copper, and then the electrodes 131 and 133 and a superconducting wire (YBCO wire) using a commercially available Pb-Sn solder. 160 was soldered. The electrodes 131 and 133 had a length of 105 mm, a width of 46 mm, a plate thickness of 30 mm, and a recess depth of 35 mm, and a superconducting current lead total length of 360 mm using these electrodes 131 and 133.

  The metal substrate 161 made of stainless steel plays a role of a shunt in overcurrent energization and plays a role of relaxing thermal contraction in the thin tape-like YBCO wire (superconducting wire 160). The pair of electrodes 131 and 133 was installed at 12 sets for each YBCO wire (superconducting wire 160), with the distance between the electrodes being 150 mm.

  That is, the superconducting current lead of Example 1 is a superconducting wire 160 having the superconducting layer 163 shown in FIG. 5, that is, the superconducting wire 160 having the superconducting layer 163 including the magnetic flux pinning point 165, and the electrodes 131 and 133 and the support. Member 152. The electrodes 131 and 133 and the support member 152 are joined to each other only in the recess 135.

  With the superconducting current lead configured in this way as a sample, with the liquid nitrogen of the cryostat as a cryogen, in a curved state, specifically, in a state in which the sample is curved along the outer periphery of a cylindrical body having a radius R = 10 mm Immersion cooled. The results are shown in Table 1 as examples.

In addition, in the superconducting current lead of Example 1 described above, a superconducting wire having a superconducting wire not including a pinning point was used as Reference Example 1. That is, in the reference example 1, the superconducting current lead 100 is the same as in the embodiment, but the superconducting wires that do not include the electrodes 131, 133, the support member 152, and the magnetic flux pinning point 165 are other than the part in the recess 135, that is, other than the fitting part. Is a superconducting current lead that is not bonded. Further, Comparative Example 1 has the same electrode and supporting member as in Example 1, and a superconducting wire that does not include a magnetic flux pinning point in the superconducting wire of Example 1, and the supporting member and the superconducting wire are entirely soldered. It is a superconducting current lead attached. The critical current value (I _C ) of the wire was evaluated using a normal four-terminal resistance method and defined using a voltage reference of 1 μV / cm.

Electrode as shown in Table 1, the supporting member, only the junction portion of the superconducting wire, the support member and the superconducting wire between soldering has been that of the superconducting current lead in Example 1, superconducting properties I _C in the curved state 2400A Thus, no disconnection between the support member and the superconducting wire was found.

The superconducting current lead Comparative Example 1, the superconducting characteristic I _C in a state where the curved is 600A, was found joined out of the support member and the superconducting wire.

  Thus, as seen in the comparison between Example 1 and Comparative Example 1, the superconducting current lead of this embodiment can obtain stable superconducting characteristics even if it is installed in a superconducting device in a curved state. Can do.

Further, in the superconducting current lead in Reference Example 1, superconducting properties I _C in the curved state is 1200A, the junction off the support member and the superconducting wire was found.

  In the superconducting current lead of the present embodiment, the degree of addition of Zr that forms magnetic flux pinning points in a plurality of superconducting wires may be different for each superconducting wire.

  For example, in a configuration in which a plurality of superconducting wires are arranged along the longitudinal direction on at least one of the front and back surfaces of the support member, the Zr content in the superconducting wire close to both ends of the support member may be maximized. Good.

  For example, in the superconducting current lead 100 of the present embodiment, among the six superconducting wires, the Zr contained in the superconducting layer in the wire disposed on both ends extending in the longitudinal direction in the support member is 3 wt%, and these The Zr of the superconducting layer of the wire adjacent to is 1 wt%. Further, there is a configuration in which the Zr in the superconducting layer of the wire adjacent inside 1 wt% Zr is set to 0 wt%.

  Even if the superconducting current lead according to the present invention is installed in a superconducting device in a curved state, it has an effect of being able to exhibit stable superconducting characteristics, being hardly affected by a magnetic field, and useful as a lead for supplying current to the superconducting device. is there.

11 Cryogenic container 12 Superconducting magnet 100 Superconducting current lead 120 Low temperature side superconducting part 131, 133 Electrode 135 Recess 150 Lead body (current lead support material)
151, 153 End portion 152 Support member 152a Front surface 152b Back surface 152c, 152d End portion 152e Fitting portion 160 Superconducting wire 161 Metal substrate 162 Intermediate layer 163 Superconducting layer 164 Stabilization layer 165 Magnetic flux pinning point

Claims (5)

In a superconducting current lead that supplies power from a power source installed in a room temperature environment to a superconducting device installed in a cryogenic container,
A current lead support in which a pair of electrode terminals are joined to each of both ends;
A plurality of superconducting wires arranged in parallel on each of at least one of the front and back surfaces of the current lead support material, and both ends connected to the electrode terminals, respectively,
Have
The superconducting wire is a ReBaCu 2 O ( Re represents one or more elements selected from Y, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb) series superconducting material Comprising an oxide superconducting layer consisting of
Said in the oxide superconducting layer, Y, Zr, Sn, Ti , is dispersed as magnetic flux pinning points following oxide particles 50nm comprising at least one of Ce,
The electrode terminal includes a cutout portion cut out in the same direction as the energization direction,
Both ends of the superconducting wire are inserted into the notch together with the current lead support material, and are electrically connected at the notch.
Superconducting current lead. The superconducting wire is fixed to the current lead support only at both ends connected to the electrode terminal,
The superconducting current lead according to claim 1. The magnetic flux pinning point is an oxide particle containing Zr.
The superconducting current lead according to claim 1 or 2 . Said oxide superconducting _{layer, ReBa y Cu 3 O z (} RE is, Y, Nd, Sm, Eu , Gd, Tb, Dy, Ho, Er, the one or more elements selected from Tm and Yb Y ≦ 2 and z = 6.2-7) based on a superconducting material,
The superconducting current lead according to any one of claims 1 to 3 . The oxide superconducting layer is a YBCO-based superconductor formed by a TFA-MOD method.
The superconducting current lead according to any one of claims 1 to 4 .

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