Subelement for a semi-finished wire for the production of an nb3sn superconductor wire

Abstract

The invention relates to a subelement (1) for a semi-finished wire for producing an Nb3Sn superconductor wire, the subelement (1) comprising: • - an Sn-containing core region (2); • - a Cu-containing inner intermediate region (3) that surrounds the Sn-containing core region (2); • - a ring region (4) that contains a multiplicity of Nb-containing reaction elements (5) and surrounds the inner intermediate region (3); • - a Cu-containing peripheral region (7) that surrounds the ring region (4); wherein the Nb-containing reaction elements (5) at least include: • - a tube structure which is at least partially made of an Nb alloy containing Nb and at least one other alloy component X; • - a filling region which lies within the tube structure and in which a multiplicity of particles is disposed, wherein the particles contain at least one partner component Pk, wherein the at least one alloy component X and the at least one partner component Pk are selected such that they form precipitates XPk during reaction annealing of the subelement (1). The subelement is characterized in that a metallic matrix is disposed in the filling region and in that the particles are distributed within the metallic matrix.

Description

[0001] Sub-element for a semi-rigid wire for the production of an NB3SN superconducting wire

[0002] The invention relates to a sub-element for a semi-finished wire for the production of an NbsSn superconducting wire, wherein the sub-element comprises a Sn-containing core region, a Cu-containing inner intermediate region surrounding the Sn-containing core region, a ring region containing a plurality of Nb-containing reaction elements, wherein the ring region surrounds the inner intermediate region, and a Cu-containing surrounding region surrounding the ring region.wherein the Nb-containing reaction elements at least have a tube structure which is at least partially made of an Nb alloy containing Nb and at least one further alloying component X, a filling region which lies within the tube structure and in which a plurality of particles are arranged, wherein the particles contain at least one partner component Pk, wherein the at least one alloying component X and the at least one partner component Pk are selected such that they form precipitates XPk upon reaction annealing of the subelement.

[0003] One such sub-element has been made known, for example, by T. Bagni et al., “Report of the activities at UNIGE in 2021”, Swiss Accelerator Research and Technology (CHART) Scientific Reports 2021, WireChar and WireDev, 02 / 2022, available on the internet at https: / / chart.ch / wp-content / uploads / 2022 / 02 / Senatore_UNIGE_CHART_report_2021_rev.pdf.

[0004] Superconducting materials can transport electric current without significant ohmic losses. For example, superconducting wires are wound to create magnetic coils that can generate very high magnetic field strengths, as required in NMR spectroscopy or for the magnetic confinement of plasma in fusion power plants.

[0005] Despite significant advances in high-temperature superconductor materials, low-temperature superconductor materials (with a transition temperature of 40 K or less) remain highly important in practical applications. In particular, NbsSn-containing superconducting wires are used in the manufacture of magnetic coils for high magnetic field strengths. These superconducting wires must exhibit both high current-carrying capacity and mechanical robustness to withstand the stresses encountered during application.

[0006] The production of NbsSn superconducting wires involves manufacturing an unreacted semi-finished wire containing Nb and Sn. This wire is then formed into a desired shape, for example, wound into a coil, and subjected to a reaction annealing (also known as reaction heat treatment). During this process, the Nb and Sn contained in the wire react to form the superconducting NbsSn phase, thus transforming the wire into a superconducting wire.

[0007] An important variant of NbsSn superconducting wires are the IT wires (IT = Internal Tin). Here, a large number of Nb-containing rods are arranged around a Sn-containing core, for example as bundles of hexagonal rods with a surrounding diffusion barrier according to the RRP® type (RR.p® = rod restack process), or inserted into a Cu block, where several subelements share a common diffusion barrier, according to the Global Barrier type.

[0008] The superconducting current-carrying capacity of an NbsSn superconducting wire is significantly influenced by its microstructure. High current-carrying capacity can be achieved, in particular, by minimizing the mobility of superconducting flux tubes ("flux pinning"). Specifically, superconducting flux tubes can be bound at the grain boundaries of the NbsSn; consequently, a finer NbsSn microstructure can result in improved superconducting current-carrying capacity.

[0009] In WO 2015 / 175064 A2 by Xu et al., NbsSn superconducting wires are proposed in which the superconducting layer contains a multitude of small-grain-size NbsSn grains stabilized by metal oxide particles (e.g., ZrO₂). In one variant, a subelement is proposed comprising a Sn-based core, a Cu-based layer surrounding the core, a multitude of bundled Nb alloy rods (containing, for example, Zr), each with a copper sheath and surrounding the Cu-based layer, a barrier layer surrounding the bundled Nb alloy rods, and a metal matrix surrounding the barrier layer. Within the stack of copper-sheathed Nb alloy rods, metal oxide regions made of a metal oxide powder (e.g., SnO₂ powder) are established. In other words, within the stack of copper-sheathed Nb alloy rods, some rods are replaced by metal oxide regions. Xu et al.It states that fine ZrO2 particles precipitated in the NbsSn matrix reduce the NbsSn grain size, thereby increasing current-carrying capacity. The underlying approach to increasing superconducting current-carrying capacity has become known as "internal oxidation".

[0010] In X. Xu, "A review and prospects for NbsSn superconductor development", Superconductor Science and Technology, Vol. 30, No. 9, 093001, August 3, 2017, it is proposed to replace a Sn rod in the center of the subelement for an RRP® superconductor with a mixture of a Sn source powder and an oxide powder, or to use Nb-Zr tubes filled with oxide powder in the bundle region.

[0011] The aforementioned "Report of the activities at UNIGE in 2021" specifically proposes a subelement in which twelve Nb alloy filaments made of Nb-7.5Ta-2Hf are arranged in a ring around a tin core. Each Nb alloy filament has a hole drilled and filled with a tin(II) nanopowder. A significant grain refinement was observed compared to control samples without an oxygen source.

[0012] In G. Bovone et al., “Effects of the oxygen source configuration on the superconducting properties of internally-oxidized internal-Sn NbsSn wires”, Superconductor Science and Technology 36 (2023), 095018, NbsSn wires were also fabricated, with twelve Nb alloy filaments arranged around an Sn core, and the Nb alloy rods filled with an SnC powder. Hf or Zr oxide precipitates would inhibit NbsSn grain growth during heat treatment and would apparently also act as effective pinning centers.

[0013] From DE 10 2018 126 760 B4, a monofilament for an NbsSn superconducting wire is known, which is constructed according to the powder-in-tube principle. The monofilament comprises a powder core containing tin-containing powder, a surrounding reaction tube made of an alloy containing Nb and at least one alloy component X, at least one source for at least one partner component Pk, and a moderation tube. The powder core is arranged in the moderation tube, and the moderation tube is arranged inside the reaction tube. Precipitations XPk are formed from the alloy component X and the partner component Pk during reaction annealing. Various oxide and non-oxide precipitates XPk are proposed.

[0014] The object of the invention is to provide an NbsSn superconducting wire with which the superconducting current-carrying capacity can be further improved.

[0015] This problem is solved according to the invention by a sub-element of the type mentioned above, which is characterized in that a metallic matrix is ​​arranged in the filling area and that the particles are arranged distributed in the metallic matrix.

[0016] Within the scope of the invention, the superconducting current-carrying capacity of an NbsSn superconducting wire can be improved by incorporating the inventive sub-elements into the semi-finished wire for the NbsSn superconducting wire. The invention utilizes the principle of internal oxidation, whereby the formation of the XPk precipitates is improved.

[0017] The formation of XPk precipitates in an NbsSn superconducting wire manufactured with subelements according to the invention can, firstly, cause the direct binding of superconducting flux tubes (flux pinning) to the precipitates, and secondly, inhibit the grain growth of NbsSn grains. This latter effect can result in a finer microstructure of the NbsSn grains, and the numerous grain boundaries in this finer microstructure can, in turn, act as pinning centers. The inhibiting effect on NbsSn grain growth is greater the earlier the XPk precipitates are formed, particularly compared to the formation of NbsSn itself.

[0018] The arrangement of particles according to the invention, which places at least one partner component Pk (preferably with Pk=O) in the filling region of the Nb-containing reaction elements, ensures a short diffusion path of the partner component Pk to the alloy component X (preferably with X=Zr or Hf), particularly shorter than when the partner component is arranged in the Sn-containing core region. This inherently promotes the early formation of XPk. Furthermore, the diffusion of the partner component Pk is generally spatially separated from the diffusion of the Sn, so that the two diffusions relative to each other can be more easily controlled by the structure of the sub-element, and in particular, better control over the size of the XPk precipitates is possible.

[0019] However, another aspect is that before diffusion of the partner component Pk from the filling area into the tube structure towards the alloy partner X can begin, the partner component Pk must first be released from the particle. For this purpose, a bonding partner B of the partner component Pk in the particles is generally chosen to be more noble than the alloy component X. Typical bonding partners B of the partner component Pk in the particle are, for example, semi-precious metals (e.g., B=Sn or B=Cu), or even precious metals (e.g., B=Ag).

[0020] For the partner component Pk to efficiently detach from its previous bonding partner B within the particle, the inventors have determined that a highly electrically conductive connection between the particle and the alloy component X is still necessary. A kind of "local cell" must be formed to initiate the electrochemical reaction in which the partner component Pk exchanges its previous bonding partner B for the alloy component X. Only once the electrochemical reaction has begun is the partner component Pk released, and its diffusion to the alloy component X can commence.If, as in the prior art, the partner component Pk is present in an oxide powder that is simply filled into the bore of an Nb alloy filament, many powder particles of the oxide powder have only poor electrical contact with the Nb alloy filaments, especially in the radially inner part of the filling, because the surrounding oxide powder particles are poor electrical conductors. Even peripheral powder particles often only have contact with the Nb alloy filament over a small portion of their surface. In the prior art, this can significantly delay the release of the partner component Pk (usually oxygen). In the prior art, a considerable portion of the powder particles in the filling is initially not electrically accessible for the redox reaction, and the redox reaction must slowly work its way into the filling from the outside during the reaction annealing process.The release of the partner component Pk therefore begins only sparingly and then continues over a long period. Accordingly, in the prior art, the formation of the XPk precipitates largely occurs relatively late. If the XPk precipitates are formed late, they can no longer inhibit the growth of Nb3Sn grains that have already formed and grown.

[0021] In contrast, the invention provides for arranging the particles containing the partner components Pk in a distributed manner within a metallic matrix. Since the matrix in which the particles are distributed is metallic, it has good electrical conductivity, in particular higher (usually by several orders of magnitude) than the particles containing the at least one partner component (usually oxide particles with insulating, semiconducting, or at least poorly conducting characteristics such as SnÜ2 or CU2O).

[0022] The distribution of the particles within the metallic matrix allows for the establishment of a highly conductive current path between the particles containing at least one partner component Pk and the Nb-containing alloy within the tube structure, which contains at least one alloy component X. This facilitates the redox reaction necessary for the release of the partner component Pk from the particles and, consequently, the initiation of its diffusion to the alloy component X or the tube structure. The particles distributed within the metallic matrix are readily accessible from the outset, and the release of the partner component Pk can begin with a very large proportion of particles from the filling region. Accordingly, XPk precipitation can commence early in the reaction annealing process, thus effectively inhibiting the growth of NbsSn grains.

[0023] Overall, the formation of the XPk precipitates at the beginning of the reaction annealing process can be promoted and accelerated according to the invention. In particular, the XPk precipitates can be formed before NbsSn is formed, or at least in a relatively early stage of the formation of the NbsSn phase. Thus, according to the invention, the XPk precipitates can serve as nuclei for the formation of more NbsSn grains and very efficiently inhibit subsequent grain growth of NbsSn, resulting in a particularly fine microstructure of NbsSn grains. This leads to very good flux pinning of superconducting flux tubes, and a particularly high current-carrying capacity can be achieved in the superconducting wire.

[0024] Typically, within the scope of the invention, at least 50%, preferably at least 90%, and particularly preferably 100% of the particles in the filling area have direct contact (and thus good electrical contact) with the metallic matrix. The metallic matrix forms a continuous, electrically conductive structure; in other words, the metallic matrix percolates (regardless of any division into sub-areas). The metallic matrix, together with the particles distributed therein, at least partially fills the filling area, typically to at least 50%, preferably to at least 70%, particularly preferably to at least 95%, and most preferably to 100% (in each case based on volume).

[0025] The metallic matrix, in turn, maintains electrical contact with the tube structure and the Nb alloy contained therein, which includes at least one alloying component X. If the metallic matrix has spatially separated sub-regions, each of these can individually form an electrical contact with the tube structure.

[0026] Typically, there is (planar or quasi-planar) contact between the particles and the metallic matrix (on average) over at least 50% of the outer surface of the particles, preferably over at least 90% of the outer surface of the particles. Preferably, the particles are individually distributed within the metallic matrix, corresponding to (planar or quasi-planar) contact between the particles and the metallic matrix (on average) over practically 100% of the outer surface of the particles.

[0027] The metallic matrix can also help to maintain good forming behavior (especially in cross-section-reducing forming processes such as extrusion or drawing) of the sub-element, particularly so that cracking in the sub-element is minimized.

[0028] The metallic matrix preferably contains Ag and / or Cu. The alloying component X is preferably selected as Zr or Hf. Metals are preferred as alloying components X, but non-metals are also possible. The partner component Pk is preferably selected to O, but other elements are also possible as partner component Pk. Alloying components X and partner components Pk that can be used within the scope of the invention can also be found in DE 10 2018 126 760 B4. The particles can, for example, contain a metal oxide, in particular Cu₂O and / or Ag₂Ü and / or SnÜ₂. Preferably, the metallic matrix is ​​free of Sn or contains Sn only in a small proportion. If desired, the particles can be free of Sn. Preferably, the entire filling area is free of Sn.If the filling region contains tin (e.g., in the metallic matrix and / or the particles), the total proportion of tin in the filling region should be low, for example, 25 at% as a proportion of the sum of the metallic matrix phase and particles, or less, preferably 10 at% or less. Typically, the area fraction of the metallic matrix in the filling region, FMM = [A_matrix / (A_filling region)], is 25% or more, preferably FMM > 50%, and often FMM > 80%. The particles typically have a mean particle size (D50) of 100 nm or less, preferably 50 nm or less.

[0029] Note that the ring region may contain other elements besides the Nb-containing reaction elements described, such as additional elements for functional doping or mechanical stabilization / reinforcement, or simply Nb-containing elements of a different type (e.g., solid elements without tube structure and filling region).

[0030] The Nb-containing reaction elements and other elements in the ring region can each enclose a Cu-containing shell. The Nb-containing reaction elements and other elements in the ring region can have a hexagonal cross-section radially outward (especially when they are abutting each other in the ring region), or a circular cross-section (especially when they are inserted into recesses of a ring matrix).

[0031] Preferred embodiments of the invention

[0032] A preferred embodiment of a sub-element according to the invention is one in which the metallic matrix is ​​at least partially formed by a metallic powder mixed with the particles. This allows a metallic matrix for the particles in the filling area to be established in a very simple manner. It should be noted that cross-sectional reduction deformations typically achieve intimate contact between the particles of the metallic powder and the particles containing the at least one partner component Pk, particularly where the particles of the metallic powder can also be plastically deformed.

[0033] An advantageous embodiment is one in which the metallic matrix is ​​at least partially formed by a metal body in which the particles are dispersed. This achieves particularly good contact between the particles and the metallic matrix, typically with contact over virtually 100% of the particles' outer surface. A high degree of filling of the matrix can also be achieved. In particular, the particles can be stirred into a liquid metallic melt, and the solidification of the melt forms the metal body in which the particles are dispersed (regardless of any forming processes). The metal body can, for example, be a wire, rod, or foil.

[0034] A preferred further development of this embodiment is in which the metal body is designed as a wire or rod that is inserted into the filling area. This approach is particularly simple. Furthermore, a particularly high fill level of the filling area can be achieved.

[0035] In an advantageous embodiment, the Nb-containing reaction elements further comprise a core structure, with the filling region located between the tube structure and the core structure. The core structure improves the forming behavior of the sub-element. Furthermore, if the core structure contains Nb, a higher proportion of the NbsSn phase in the finished superconducting wire can be achieved.

[0036] Advantageously, the core structure is designed to be at least partially made of an Nb alloy containing Nb and at least one other alloying component X. Within the core structure, additional Nb can be stored for the formation of NbsSn, and further alloying component X for the formation of XPk precipitates, thereby shortening the average diffusion path of the partner component Pk. This further accelerates the formation of the XPk precipitates.

[0037] A further development is advantageous in which the metallic matrix is ​​formed by a metal foil, and the metal foil is at least partially wrapped around the core structure. This is particularly easy to manufacture. The particles containing the partner components Pk can be dispersed within the metal foil. Alternatively, the particles containing the partner component Pk can also be arranged on the surface of the metal foil. To generate the particles, the foil can be subjected to surface oxidation (typically before winding); the partner component Pk is then oxygen. Similarly, the foil can be coated, for example, by dip-coating. By rolling the foil (typically in 5 or more layers) onto the core structure (and typically followed by a reduction in cross-section, e.g., by extrusion or drawing), the metallic matrix with the particles dispersed within it is then effectively created.The metal foil can have a width equal to the axial length of the core structure; in this case, the metal foil can be wound on without any slope. Alternatively, the metal foil can have a width smaller than the axial length of the core structure; in this case, the metal foil (which is then also referred to as a metal strip) can be wound helically around the core structure, possibly multiple times back and forth along the axial direction. Typically, the foil is completely wrapped around the core structure. If desired, the metal foil can be wound around the core structure with only one part (i.e., one end) and folded with the remaining part (i.e., the other end) stored in the filling area.

[0038] A preferred embodiment is one in which the metallic matrix contains silver (Ag). Silver possesses very good electrical conductivity. Furthermore, silver has a low tendency to surface oxidation, which could impair good electrical contact with the particles containing the partner component. Accordingly, particularly good electrical contact with the particles can be achieved with silver.

[0039] In a preferred embodiment, a moderation tube is formed on the inner side of the tube structure, within which the filling area is located. In particular, the moderation tube and an adjacent part of the tube structure are made of different materials. The moderation tube can improve the drawing properties of the sub-element and / or allow for pre-compaction of powder in the filling area and / or control the diffusion of the partner component Pk. Furthermore, the moderation tube enables a more uniform introduction of the partner component Pk from the filling area into the tube structure; in particular, it prevents direct contact between the particles (or the metallic matrix in which the particles are distributed) and the tube structure.When the particles (containing the partner component Pk bound to the bonding partner B) begin to decompose during reaction annealing, a very high partial pressure of the partner component (or also of the bonding partner B) can be reached on the inside of the tube structure if the particles are in direct contact with it. This can lead to the formation (at least temporarily) of one or more phases on the inside of the tube structure, particularly as closed layers, which block or at least delay the diffusion of the partner component Pk into the tube structure. Such phases can be oxide phases, for example, consisting of NbO or NbzOs (with Pk=O). The moderation tube can prevent the formation of these phases, and the XPk precipitates can form unhindered and at an early stage. The material of the moderation tube should not be less noble than Nb and X.The moderation tube and at least an adjacent part of the tube structure are typically made of different materials. Preferably, the moderation tube is made of silver (Ag) or copper (Cu). The moderation tube should have a certain permeability to the partner component (e.g., oxygen) to allow diffusion of the partner component through it for the formation of the XPk precipitates. This can be ensured both by selecting the appropriate material and by using suitable dimensions / wall thicknesses for the moderation tube.

[0040] A preferred embodiment also provides that at least some of the Nb-containing reaction elements are designed as doping reaction elements, wherein the doping reaction elements contain at least one element of the fourth subgroup of the periodic table in at least one contained phase, and / or that additional doping elements are also arranged in the ring region, wherein the additional doping elements contain at least one element of the fourth subgroup of the periodic table in at least one contained phase, in particular wherein the at least one element of the fourth subgroup of the periodic table comprises titanium, and / or that at least some of the Nb-containing reaction elements are designed as reinforcing reaction elements, wherein the reinforcing reaction elements contain at least one element of the fifth subgroup of the periodic table in at least one contained phase, and / or that reinforcing additional elements are also arranged in the ring region.wherein the reinforcing additive elements in at least one contained phase include at least one element of the fifth transition group of the periodic table, in particular wherein the at least one element of the fifth transition group of the periodic table comprises tantalum.

[0041] The formation of the NbsSn phase can be easily accelerated by doping with dopant elements and doping additives. The forming behavior, particularly the drawing behavior, of the subelement can be easily improved by reinforcement with reinforcing elements or reinforcing additives. Preferably, only a small fraction, e.g., 20% or less, of the Nb-containing reaction elements is configured as dopant elements and / or reinforcing elements, so that a further large fraction of the Nb-containing reaction elements, e.g., more than 80%, can be manufactured from a cost-effective standard alloy (e.g., NblZr).

[0042] A preferred embodiment is one in which the Nb-containing reaction elements are in contact with one another in the ring region, and in which the sub-element further comprises a diffusion barrier surrounding the ring region. Such sub-elements are inexpensive to produce and flexible in their design, particularly with regard to the size of the ring region. The Nb-containing reaction elements can have a hexagonal cross-section, which facilitates defined bundling. The diffusion barrier is typically arranged between the ring region and the surrounding area. The diffusion barrier ensures that the surrounding Cu retains high conductivity (and is not contaminated by Sn during reaction annealing and thus becomes less conductive), which electrically stabilizes the superconducting wire.Local diffusion barriers at each sub-element allow the pure, stabilizing copper in the superconducting wire to be positioned relatively close to the superconducting zones. Such sub-elements can be used for RRP®-type superconducting wires.

[0043] In another, equally preferred embodiment, the ring region comprises a copper-containing ring matrix forming a plurality of recesses into which the nitrogen-containing reaction elements are inserted. This approach is particularly simple. The ring matrix is ​​typically formed by a copper block or a copper-containing block with bores. The nitrogen-containing reaction elements (and optionally other elements) can be easily arranged in the ring region using the ring matrix. Corresponding sub-elements can be used for global barrier-type superconducting wires; in this case, several such sub-elements are surrounded by a common diffusion barrier within the semi-finished wire.

[0044] The present invention also encompasses a semi-finished wire for the production of an NbsSn superconducting wire, comprising several bundled sub-elements as described above according to the invention. The number of bundled sub-elements can be selected according to the desired application. Typically, seven or more sub-elements are bundled to form a semi-finished wire.

[0045] In a preferred embodiment of the semi-finished wire according to the invention, the sub-elements are formed as described above with a ring matrix into the recesses of which the Nb-containing reaction elements are inserted, and an overall diffusion barrier is present which surrounds all the bundled sub-elements on the outside. This overall diffusion barrier protects the surrounding pure Cu from the diffusion of Sn during the reaction annealing, thus ensuring high electrical conductivity of the surrounding Cu.

[0046] Furthermore, the present invention also includes a method for producing an NbsSn superconducting wire, characterized by the following steps:

[0047] Step a): Manufacturing a large number of sub-elements according to the invention, as described above,

[0048] Step b): Bundling of the sub-elements to form a semi-finished wire according to the invention, as described above,

[0049] Step c): Reaction annealing of the semi-finished wire to form NbsSn superconducting wire, whereby Sn and Nb react to form NbsSn. In step c), XPk precipitates are initially formed in the tube structures and / or the core structures, and only subsequently is at least the majority of the NbsSn formed. In this way, an NbsSn superconducting wire with particularly high current-carrying capacity can be obtained. The XPk precipitates are formed before at least the majority (more than 50%) of the total NbsSn formed (by volume), so that the grain growth of said majority can be inhibited by the precipitates. Accordingly, a particularly fine microstructure of the NbsSn in the superconducting wire can be obtained, and correspondingly strong flux pinning.Typically, at a point during the reaction annealing process when at least 50%, preferably at least 75%, of the total XPk precipitates formed have already been formed, only a maximum of 50%, preferably a maximum of 25%, of the total NbsSn formed has been formed (based on volume). The fabrication of the sub-elements typically includes a cross-sectional reduction forming process (e.g., extrusion or drawing) at the end. The bundling in step b) can be carried out in a single stage or in multiple stages. The bundling in step b) typically includes a cross-sectional reduction forming process (e.g., extrusion or drawing) at the end. Typically, at the end of step b), the semi-finished wire is also deformed into a desired shape for the intended application, e.g., winding the semi-finished wire onto a spool carrier. The invention further comprises an NbsSn superconducting wire produced according to the inventive process described above.This NbsSn superconducting wire can achieve a particularly high superconducting current-carrying capacity.

[0050] Also within the scope of the present invention is the use of an NbsSn superconducting wire according to the invention, as described above, in a nuclear fusion device, particularly wherein the nuclear fusion device is a fusion power plant. Typically, the NbsSn superconducting wire is installed in one or more magnetic coils, which generate a magnetic field with which the fusion plasma is confined. The superconducting wire is typically arranged in a cable which, in addition to the superconducting wire, also includes copper and / or auxiliary wires (particularly as structures providing mechanical stability to the cable). Due to the high current-carrying capacity of the superconducting wire, the cable can be designed very freely and thus optimally adapted to the application.

[0051] The NbsSn superconducting wire according to the invention can alternatively also be used in NMR magnets, in particular to obtain a particularly compact NMR apparatus.

[0052] The NbsSn superconducting wire according to the invention can alternatively also be used in high-energy physics applications, particularly in particle accelerators, especially to generate a maximum magnetic field strength in the available installation space.

[0053] Further advantages of the invention will become apparent from the description and the drawing. Likewise, the features mentioned above and those described in more detail below can each be used individually or in any combination according to the invention. The embodiments shown and described are not to be understood as an exhaustive list, but rather serve as examples for illustrating the invention.

[0054] Detailed description of the invention and drawing Fig. 1 shows a schematic cross-sectional view of an embodiment of a sub-element according to the invention;

[0055] Fig. 2 shows a schematic cross-sectional view of an Nb-containing reaction element for a sub-element according to the invention;

[0056] Fig. 3 shows a schematic cross-sectional view of an Nb-containing reaction element, wherein a metallic powder mixed with particles is arranged in the filling area, for the invention;

[0057] Fig. 4 shows a schematic cross-sectional view of an Nb-containing reaction element, wherein a metal body with particles dispersed therein is arranged in the filling area, for the invention;

[0058] Fig. 5 shows a schematic perspective view of the Nb-containing reaction element of Fig. 4;

[0059] Fig. 6 shows a schematic cross-sectional view of an Nb-containing reaction element, wherein the filling area lies radially between a tube structure and a core structure, for the invention;

[0060] Fig. 7 shows a schematic cross-sectional view of an Nb-containing reaction element, wherein a metal foil is wrapped in several layers around the core structure, for the invention;

[0061] Fig. 8 shows a schematic perspective view of an Nb-containing reaction element, wherein a metal strip containing dispersed particles is wound helically around a core structure, for the invention; Fig. 9 shows a schematic cross-sectional view of an Nb-containing reaction element, wherein a metal foil is wound in several layers around the core structure and particles are arranged on one side of the metal foil, for the invention;

[0062] Fig. 10 shows a schematic cross-sectional view of an Nb-containing reaction element with a moderation tube, for the invention;

[0063] Fig. 11 shows a schematic cross-sectional view of a further embodiment of a sub-element according to the invention, wherein some Nb-containing reaction elements are designed as doping reaction elements and strengthening reaction elements;

[0064] Fig. 12 shows a schematic cross-sectional view of a further embodiment of a sub-element according to the invention, wherein Nb-containing reaction elements, doping additive elements and reinforcing additive elements are arranged mixed together in the ring region;

[0065] Fig. 13 shows a schematic cross-sectional representation of a further embodiment of a sub-element according to the invention, wherein Nb-containing reaction elements and additive elements from an Nb alloy containing Nb and at least one further alloying element X are arranged mixed together in the ring region;

[0066] Fig. 14 shows a schematic cross-sectional view of a further embodiment of a sub-element according to the invention, wherein the Nb-containing reaction elements in the ring region have a hexagonal outer cross-section and a diffusion barrier is present;

[0067] Fig. 15 shows a schematic cross-sectional view of a further embodiment of a sub-element according to the invention, wherein the ring region comprises a Cu-containing ring matrix with recesses into which the Nb-containing reaction elements are inserted; Fig. 16 shows a schematic cross-sectional view of an embodiment of a semi-finished wire according to the invention, which comprises bundled, hexagonal sub-elements, each with its own diffusion barrier;

[0068] Fig. 17 shows a schematic cross-sectional view of a further embodiment of a semi-finished wire according to the invention, comprising bundled, round sub-elements and an overall diffusion barrier;

[0069] Fig. 18 shows a schematic flow chart for an exemplary variant of a method according to the invention for the production of an NbsSn superconductor wire.

[0070] Fig. 1 schematically shows an exemplary embodiment of a sub-element 1 according to the invention in cross-section.

[0071] Subelement 1 comprises a tin-containing core region 2. Here, this core region is formed by a rod made of a tin-containing alloy. The core region 2 may also contain a certain proportion of copper. A tubular, copper-containing inner intermediate region 3 surrounds the core region 2. The inner intermediate region 3 is formed by a copper tube in which the rod made of the tin-containing alloy is arranged. Alternatively, the core region 2 could also be formed, for example, by a tin-containing powder or a tin-containing powder mixture arranged within the surrounding tubular inner intermediate region (not shown in detail).

[0072] A ring-shaped region 4 is formed around the inner intermediate region 3, in which a plurality of Nb-containing reaction elements 5 are arranged; the Nb-containing reaction elements 5 are explained in more detail in Fig. 2. In the design shown in Fig. 1, only Nb-containing reaction elements 5 are arranged as elements in the ring-shaped region 4; however, alternatively, other types of elements can also be present besides Nb-containing reaction elements (e.g., dopant reaction elements, see below in Figs. 12 and 13). The spaces 6 between the elements contained in the ring-shaped region 4 (here the Nb-containing reaction elements 5) are preferably filled with solid material, e.g., elemental Cu or a Cu alloy.

[0073] A copper-containing surrounding area 7 is arranged around the ring area 4, which here is designed as a copper tube.

[0074] In Fig. 2, a schematic cross-section of an Nb-containing reaction element 5 from Fig. 1 is explained in more detail.

[0075] The Nb-containing reaction element 5 comprises a tube structure 8, which is at least partially, and in the illustrated configuration completely, made of an alloy containing Nb and at least one further alloying component X. The further alloying component is chosen here as Zr (zirconium). The tube structure 8 is made of NblZr; thus, the alloy contains 1 wt% Zr, and the remainder consists of Nb.

[0076] Inside the tube structure 8, a filling region 9 is formed. Within the filling region 9, a plurality of particles (not shown in detail in Fig. 2, but see, for example, Fig. 3 and Fig. 4 below) are arranged, each containing at least one partner component Pk. Here, the partner component Pk is selected as O (oxygen). The partner component Pk is bound to a bonding partner B. Here, the bonding partner B is selected as Cu (copper). The particles consist of Cu₂O. According to the invention, the filling region 9 also contains a metallic matrix (not shown in detail in Fig. 2, but see, for example, Fig. 3 and Fig. 4 below) in which the particles are distributed. Here, the metallic matrix is ​​made of Ag (silver).

[0077] During reaction annealing (also called reaction heat treatment), precipitates XPk can form early on from the alloy component X in the tube structure 8 and the partner component Pk in the filling region 9, typically in the region of the tube structure 8. These precipitates consist of ZrÜ2. These XPk precipitates can inhibit grain growth of NbsSn grains, which are formed from the Nb in the tube structure 8 and the Sn from the core region of the subelement (see Fig. 1). The electrically conductive metallic matrix in the filling region 9 provides a highly conductive current path between the individual particles containing the partner components Pk in the filling region 9 and the alloy component X in the tube structure 8.The redox reaction, in which the partner component Pk is released from the bonding partner B, diffuses to alloy component X, and finally forms the precipitate XPk, can begin early and involve a large proportion of the particles present, typically practically all of them, from the outset. Accordingly, the XPk precipitates (or at least the majority of them) can be formed before the NbsSn (or at least the majority of it) is formed (in each case, relative to mass). This results in a particularly fine microstructure of the NbsSn grains in the finished NbsSn superconducting wire, and the NbsSn superconducting wire achieves a particularly high superconducting current-carrying capacity.

[0078] Note that the Nb-containing reaction element 5 is typically first manufactured with a larger cross-section, then subjected to a cross-section-reducing deformation (e.g. drawing or extrusion), and then installed in a sub-element (assembly not shown in detail here, but see Fig. 15 for an example).

[0079] In the following, some different designs of Nb-containing reaction elements and sub-elements for the invention are presented; only the respective special features and, if applicable, deviations from the designs of Fig. 1 and Fig. 2 are explained.

[0080] Figure 3 illustrates in schematic cross-section a preferred design of an Nb-containing reaction element 5 for the invention. The filling region 9 is formed here by a bore 14 in an NbZr rod 10. The drilled NbZr rod 10 accordingly forms the tubular structure 8; the alloying element X is therefore X = Zr. The filling region 9 contains a metallic matrix 11, which in the design shown is formed by a metallic powder 12. The metallic powder 12 is an Ag powder. The metallic powder 12 is mixed with particles 13, which contain 0 as the partner component Pk, i.e., Pk = 0. The particles 13 are formed by SnC particles.

[0081] Note that in the schematic representation of Fig. 3 only a few particles 13 are shown as examples, and the particles 13 are depicted as exaggeratedly large (this also applies to the following figures).

[0082] In the illustrated design, the metallic matrix 11 occupies approximately 60% of the surface area of ​​the filling region 9, i.e., 60% of the cross-sectional area of ​​the filling region 9 is occupied by the metallic matrix 11; generally preferred are FMM > 5%, or even FMM > 50% or more, or even FMM > 80%. The remaining 40% of the cross-sectional area is comprised of voids and the particles 13; the surface area of ​​the particles 13 in relation to the total cross-sectional area of ​​the filling region 9 is approximately 10%. The proportion of Sn (here due to the particles 13) in the filling region 9, measured in atomic percent (at%) and based on the sum of all phases in the filling region 9 (here metallic matrix 11 and particles 13), is less than 10%; generally preferred are 25 at% or less, or even 10 at% or less.

[0083] Further powder components can easily be mixed into the metallic powder 12, for example for doping purposes. In addition, the proportion (or quantity and size) of particles 13 in the filling area 9 is easily adjustable.

[0084] Figure 4, a schematic cross-section, and Figure 5, a schematic perspective view (with the tube structure partially removed), illustrate another preferred design of an Nb-containing reaction element 5 for the invention. The tube structure 8 is again formed by a drilled NbZr rod 10. Its bore 14 forms the filling region 9. A metal body 15 is arranged in the bore 14, which here is designed as a wire (metal wire) 16 and inserted into the bore 14. Alternatively, the metal body 15 can also be designed as a rod (not shown in detail). The metal body 15 here forms the metallic matrix 11. The wire 16 is made of elemental silver. The particles 13, which contain the partner component Pk, are dispersed in the metal body 15 or in the wire 16. In the design shown, the particles 13 are made of SnÜ2.

[0085] With this design, the filling area 9 can be practically completely fulfilled in a simple way by selecting the diameter of the wire 16 according to the diameter of the bore 14 (with sufficient clearance for insertion).

[0086] In the illustrated configuration, the metallic matrix 11 occupies approximately 90% of the surface area of ​​the filling region 9, meaning that 90% of the cross-sectional area of ​​the filling region 9 is occupied by the metallic matrix 11. The remaining 10% of the cross-sectional area is comprised of the particles 13. Here too, the proportion of Sn (due to the particles 13) in the filling region 9, measured in atomic percent (at%) and relative to the sum of all phases in the filling region 9 (here, the metallic matrix 11 and the particles 13), is less than 10%.

[0087] Fig. 6 shows another advantageous design of an Nb-containing reaction element 5 in a schematic cross-section.

[0088] The Nb-containing reaction element 5 comprises the tube structure 8, here made from a tube of the alloy Nb7.5Hf, furthermore a core structure 17, also made from the alloy Nb7.5Hf, and a filling area 9. The alloy component X is therefore chosen here to be X=Hf.

[0089] The filling region 9 is annular in shape and lies radially between the tube structure 8 and the core structure 17. Within the filling region 9, a metallic matrix is ​​arranged in which the particles containing the partner component Pk are distributed (not shown in detail). For example, a metal powder can also be arranged within the filling region 9, into which the particles are mixed (not shown in detail, but see Fig. 3 for an analogous example); other possible configurations are illustrated by way of example in Figures 7 to 9.

[0090] By arranging the core structure 17, which also contains the alloy component X, radially within the filling area 9, diffusion paths for the partner component Pk to the alloy component X can be shortened, and the formation of precipitates XPk can thereby be accelerated.

[0091] Figure 7 shows a schematic cross-section of a structure of an Nb-containing reaction element 5 with core structure 17, wherein the metallic matrix 11 is formed by a metal foil 18. The metal foil 18 is wound in several layers onto the core structure 17 and arranged accordingly in the filling region 9. The metal foil 18 contains the particles (not shown in detail) dispersed within it.

[0092] Figure 8 shows a schematic perspective view (with the tube structure 8 partially removed) of a design of an Nb-containing reaction element 5 with a core structure 17. The metal foil 18 is wound onto the core structure 17.

[0093] The metal foil 18 here has the form of a metal strip 19, which is wound helically on the core structure 17. In the configuration shown, only one layer of the metal strip 19 is wound helically, but alternatively, several layers can also be wound helically (not shown in detail, but see, for example, Fig. 7). The particles 13 are dispersed in the metal strip 19.

[0094] Figure 9 shows a schematic cross-section of a structure of an Nb-containing reaction element 5 with a core structure 17, wherein the metallic matrix 11 is formed by a metal foil 18. The metal foil 18 is wound in several layers onto the core structure 17. Particles 13 containing the partner component Pk are arranged on a radially outward-facing side of the metal foil 18. A corresponding metal foil 18 can be produced, for example, by subjecting one side of the metal foil 19 to surface oxidation. The metal foil 19 can, for example, be a copper foil, and the particles 13 consist of Cu₂O. By winding the metal foil 18 in several layers, a metallic matrix 11 is obtained in which the particles 13 are distributed.

[0095] After a cross-sectional reduction of the Nb-containing reaction element 5, for example by drawing or extrusion, any remaining cavities are essentially eliminated after the core structure 17 wrapped with the metal foil 18 is inserted into the bore 10 of the tube structure 8.

[0096] Fig. 10 shows another design of an Nb-containing reaction element 5 in schematic cross-section, for the invention.

[0097] In this design, a moderation tube 20 is arranged radially between the tube structure 8 and the filling area 9. The moderation tube 20 is typically made of a different material than the radially adjacent tube structure 8. In the exemplary design shown, the tube structure is made of NbZr (here with an NblZr alloy), and the moderation tube 20 is made of Cu. The moderation tube 20 is fundamentally made of a metallic material and is therefore electrically conductive.

[0098] The moderation tube 20 allows the diffusion of the partner component Pk from the filling area 9 into the tube structure 8, i.e., to the alloy component X located there, to be influenced and adjusted. In particular, the formation and / or growth of precipitates XPk can be delayed or accelerated compared to the case without a moderation tube 20, if desired; for this purpose, suitable combinations, especially of the partner component Pk in the particles in the filling area 9 and the material of the moderation tube 20, can be selected. The size of the XPk precipitates can also be influenced by the moderation tube. A moderation tube 20 made of, for example, pure Ta can significantly slow down the diffusion of O from the filling area 9 into the tube structure 8; in this case, the wall thickness of the moderation tube 20 must not be chosen to be too thick so that the formation of the XPk precipitates is not excessively delayed.In general, a more uniform introduction of the partner component Pk into the tube structure 8 can also be achieved. Furthermore, by reducing the cross-section of the filled moderation tube 20 beforehand (i.e., before insertion into the tube structure 8), the metallic matrix and the particles distributed within it can be compacted. This can increase the current-carrying cross-section in the finished NbsSn superconductor wire.

[0099] Fig. 11 shows a schematic cross-section of another embodiment of a sub-element 1 according to the invention, similar to that shown in Fig. 1. In contrast, in the embodiment shown, different types 21, 22, 23 of Nb-containing reaction elements 5 are provided in the ring region 4.

[0100] A first, largest part of the Nb-containing reaction elements 5 in the ring region 4 is formed here as regular Nb-containing reaction elements 21, wherein in the described design the tube structure (shown with cross hatching) consists of an NblZr alloy, and the filling area is filled with an Ag powder mixed with SnO2 particles.

[0101] A second, smaller portion of the Nb-containing reaction elements 5 in the ring region 4 is configured as doping reaction elements 22, where the tube structure (shown horizontally striped) consists of an Nb₄H₄TilZr alloy. The titanium contained, from the fourth transition group of the periodic table, catalyzes the formation of NbsSn during reaction annealing. The filling region is again filled with an Ag powder mixed with SnO₂ particles.

[0102] A third, also smaller, portion of the Nb-containing reaction elements 5 in the ring region 4 is configured as reinforcing reaction elements 23, where the tube structure (shown vertically striped) consists of an Nb7,5TalZr alloy. The tantalum contained, from the fifth transition group of the periodic table, mechanically reinforces the subelement 1. The filling region is again filled with an Ag powder mixed with SnO2 particles.

[0103] Note that in other embodiments only doping reaction elements 22 or only strengthening reaction elements 23 may be arranged distributed in the regular Nb-containing reaction elements 21 (not shown in detail).

[0104] Fig. 12 shows a schematic cross-section of another embodiment of a sub-element 1 according to the invention, similar to that shown in Fig. 1. In contrast, the embodiment shown provides different elements 24 in the ring region 4.

[0105] A first, largest part of the elements 24 in the ring region 4 is formed here as Nb-containing reaction elements 5, wherein the tube structure (shown with cross hatching) consists of an NblZr alloy, and the filling region is filled with an Ag powder mixed with SnO2 particles.

[0106] A second, smaller portion of the elements 24 in ring region 4 is formed as dopant elements 25 (shown as horizontal stripes). These dopant elements 25 each consist entirely of an Nb₄H₄Ti alloy. The titanium contained within, from group 4 of the periodic table, catalyzes the formation of NbsSn during annealing. The dopant elements 25 do not have a filling region.

[0107] A third, also smaller, portion of the elements 24 in the ring region 4 is configured as reinforcing additive elements 26 (shown as vertical stripes). Here, the reinforcing additive elements 26 consist entirely of pure tantalum. The tantalum contained within, from group 5 of the periodic table, mechanically reinforces the subelement 1. The reinforcing additive elements 25 have no filling region and do not form NbsSn during heat treatment. Note that in other embodiments, only doping additive elements 25 or only reinforcing additive elements 26 may be distributed within the Nb-containing reaction elements 5 (not shown in detail).

[0108] Fig. 13 shows a schematic cross-section of another embodiment of a sub-element 1 according to the invention, similar to that shown in Fig. 1. In contrast, the embodiment shown again provides different elements 24 in the ring region 4.

[0109] A first part of the elements 24 in the ring region 4 is formed here as Nb-containing reaction elements 5, wherein the tube structure (shown with cross hatching) consists of an NblZr alloy, and the filling region is filled with an Ag powder mixed with SnO2 particles.

[0110] A second part of the elements 24 in the ring region 4 is configured as Nb-containing additive elements 27 (shown completely hatched). Here, the Nb-containing additive elements 27 each consist entirely of an alloy containing Nb and at least one further alloying element X. The alloy of the Nb-containing additive elements 27 is again NblZr. The alloy of the Nb-containing additive elements 27 is thus chosen according to the alloy of the tube structures of the Nb-containing reaction elements 5, which is a preferred case. The Nb-containing additive elements 27 do not have a filling region.

[0111] The first part and the second part are approximately the same size here, i.e., they comprise approximately the same number of elements 24 in the ring region 4 of the subelement 1.

[0112] The quantity of particles containing the partner component Pk in the filling regions of the Nb-containing reaction elements 5 is dimensioned such that a sufficient amount of partner component Pk, here with Pk=O, is available for the amount of alloying component X, here with X=Zr, in the Nb-containing reaction elements 5 and the Nb-containing additive elements 27 to form all intended precipitates XPk in the ring region 4. The production of the Nb-containing additive elements 27 is significantly cheaper than the production of the Nb-containing reaction elements 5. Accordingly, sub-element 1 of Fig. 13 is particularly cost-effective to manufacture.

[0113] Fig. 14 shows a schematic cross-section of a particularly preferred embodiment of a sub-element 1 according to the invention. The sub-element 1 is provided for an NbsSn superconductor wire of the RRP® type.

[0114] Subelement 1 comprises a tin-containing core region 2, which is surrounded by the copper-containing inner intermediate region 3. The inner intermediate region 3 is profiled on its radial outer surface, corresponding to a profile of the adjacent hexagonal elements 24 in the ring region 4. The hexagonal elements 24 in the ring region 4 are all configured here as nitrate-containing reaction elements 5 (see also the enlargement on the right in Fig. 14).

[0115] Each Nb-containing reaction element 5 comprises here an outer Cu-containing shell 30 with a hexagonal outer cross-section, here made of elemental copper, furthermore a tube structure 8 and a filling area 9.

[0116] The Nb-containing reaction elements 5 are abutting each other in the ring region 4. An outer intermediate region 28, which here contains Cu, for example elemental copper, is arranged around the Nb-containing reaction elements 5 of the ring region 4. The outer intermediate region 28 has a radially inward profile corresponding to a profile of the adjacent hexagonal elements 24 in the ring region 4.

[0117] A diffusion barrier 29, made of, for example, Nb, is arranged around the outer intermediate region 28 and is annular in the configuration shown. The diffusion barrier 29 prevents the diffusion of Sn from the Sn-containing core region 2 (or other Sn sources inside the diffusion barrier 29) into the Cu-containing surrounding region 7, which is arranged around the diffusion barrier 29. This allows the Cu-containing surrounding region 7 to retain high electrical conductivity after reaction annealing. The Cu-containing surrounding region 7 is typically made of elemental Cu and, in the configuration shown, has a circular outer surface.

[0118] Note that in one variant of sub-element 1 the Cu-containing surrounding area 7 may have a hexagonal outer cross-section, and the diffusion barrier 29 may also be hexagonal-ring-shaped (instead of circular-ring-shaped) (not shown in Fig. 14, but see Fig. 16, right-hand side).

[0119] Fig. 15 illustrates a further, particularly preferred embodiment of a sub-element 1 according to the invention in a schematic perspective view, at an intermediate stage of its manufacture. A corresponding schematic cross-sectional view of the finished sub-element 1 is shown in Fig. 17, right-hand side. The sub-element 1 is designed for an NbsSn superconducting wire of the global barrier type.

[0120] The subelement 1 is based here on a drilled Cu block 31, which is essentially cylindrical in shape.

[0121] In a central, large bore 32 of the Cu block 31, the Sn-containing core area 2 is formed, here by filling an Sn-containing powder (e.g. a mixture of Sn powder and NbSn2 powder) into the central bore 32.

[0122] A subsequent, radially inner part of the Cu block 31 forms the Cu-containing inner intermediate region 3. Radially outwards, the ring region 4 adjoins, in which the Cu block 31 forms a plurality of recesses 33 or small bores.

[0123] Nb-containing reaction elements 5 are inserted into these recesses 33, each of which is formed with a tube structure 8 and a filling area 9, see also the enlargement on the right in Fig. 15. As a result, the Cu block 31 forms a Cu-containing ring matrix 34 for the Nb-containing reaction elements 5 in the ring area 4.

[0124] A subsequent, radially outer part of the Cu block 31 finally forms the Cu-containing surrounding area 7.

[0125] The sub-elements 1 of the RRP® type can be used to manufacture a semi-finished wire 35 as shown in the schematic cross-sectional view of Fig. 16. Here, the sub-elements 1 are designed in the variant with a hexagonal outer cross-section and a hexagonal-ring-shaped diffusion barrier 29; see the enlargement in Fig. 16 on the right and also Fig. 14 for further details of the sub-element 1.

[0126] Several hexagonal sub-elements 1 are placed next to each other and bundled, and arranged in a copper-containing sheathing tube 36. The sheathing tube 36 is made of elemental copper.

[0127] The diffusion barriers 29 of the subelements 1 prevent the Cu-containing surrounding areas 7 of the subelements 1 and the Cu-containing casing tube 36 from being contaminated by Sn from the interior of the subelements 1 during reaction annealing.

[0128] The sub-elements 1 of the Global Barrier type can be used to manufacture a semi-finished wire 35 as shown in the schematic cross-sectional view of Fig. 17. The sub-elements 1 are formed with a round outer surface and a copper block 31; see the enlargement in Fig. 17 on the right and also Fig. 15 for further details of the sub-element 1.

[0129] Several round sub-elements 1 are arranged in corresponding bores of a copper-containing wire matrix 37. The wire matrix 37 can, for example, be made of copper. A total diffusion barrier (or global diffusion barrier) 38, which here has an annular cross-section, is arranged around the wire matrix 37. The total diffusion barrier 38 can, for example, be made of elemental niobium. A copper-containing sheathing tube 39 is formed around the total diffusion barrier 38. The copper-containing sheathing tube 39 is here made of elemental copper.

[0130] The overall diffusion barrier 38 prevents the Cu-containing jacket tube 39 from being contaminated by Sn from the interior of the sub-elements 1 during reaction annealing.

[0131] Figure 18 illustrates the sequence of steps in the manufacture of an NbsSn superconducting wire 40 within the scope of the invention. Schematic partial diagrams of the various manufacturing steps are shown in chronological order from 11 to 126.

[0132] In step tl, a large number of sub-elements 1 are manufactured; typical sub-elements 1 for the invention are explained in the preceding figures.

[0133] In step t2, the sub-elements 1 are then subjected to a cross-section-reducing forming process, for example a drawing process or an extrusion process. This results in a tapered sub-element 1'.

[0134] In step t3, several tapered sub-elements 1' are bundled and arranged in a sheathing tube 36. This yields a semi-finished wire 35.

[0135] In the subsequent step t4, the semi-finished wire 35 undergoes a cross-sectional reduction forming process, for example, a drawing or extrusion process. This results in a tapered semi-finished wire 35'. If desired, the tapered semi-finished wire can undergo a further bundling and tapering iteration (not shown in detail). At the end of step t4, the tapered semi-finished wire 35' has the diameter required for the application.

[0136] The tapered semi-finished wire 35' is now formed into the desired shape for the application in step t5. In the example shown, the tapered semi-finished wire 35' is wound onto a coil former 41 to form a coil. Note that the tapered semi-finished wire 35' is still highly elastic and plastically deformable before the reaction annealing (the reaction heat treatment).

[0137] In step t6, the tapered semi-finished wire is subjected to reaction annealing in a furnace 42. During this process, the Nb contained reacts with the Sn contained to form NbsSn, with XPk precipitates inhibiting the grain growth of NbsSn grains. The previously tapered semi-finished wire thus becomes the finished NbsSn superconducting wire 40. In the example shown, this completes a superconducting magnet coil 43. Note that the NbsSn in the finished semi-finished wire is relatively brittle and should therefore not be deformed further.

[0138] The finished superconducting magnetic coil 43 can be used, for example, in a nuclear fusion facility (e.g., a fusion power plant) to generate a magnetic field that confines the plasma (not shown in detail).

[0139]

[0140] 1 subelement

[0141] 1' tapered subelement

[0142] 2 Sn-containing core area

[0143] 3 inner intermediate area

[0144] 4 ring area

[0145] 5 Nb-containing reaction element

[0146] 6 spaces

[0147] 7 Cu-containing environment

[0148] 8-pipe structure

[0149] 9 Filling area

[0150] 10 NbZr rod

[0151] 11 metallic matrix

[0152] 12 metallic powder

[0153] 13 particles

[0154] 14 bore

[0155] 15 metal bodies

[0156] 16 wire (metal wire)

[0157] 17 Core Structure

[0158] 18 metal foil

[0159] 19 metal band

[0160] 20 Moderation tube

[0161] 21 regular Nb-containing reaction element

[0162] 22 Doping reaction element

[0163] 23 Amplification reaction element

[0164] 24 elements (in the ring area in general)

[0165] 25 Doping additive element

[0166] 26 Reinforcement add-on element

[0167] 27 Nb-containing additive element

[0168] 28 outer intermediate area

[0169] 29 Diffusion barrier (of the subelement)

[0170] 30 Cu-containing shell (of the Nb-containing reaction element) 31 Cu block

[0171] 32 central large bore

[0172] 33 cutouts (in the ring area)

[0173] 34 Ring matrix 35 Semi-finished wire

[0174] 35' tapered semi-finished wire

[0175] 36 Cu-containing sheathing tube (of the semi-finished wire)

[0176] 37 wire matrix

[0177] 38 Total diffusion barrier (of the semi-finished wire) 39 Cu-containing sheathing tube (of the semi-finished wire)

[0178] 40 NbsSn superconducting wire

[0179] 41 coil formers

[0180] 42 Oven

[0181] 43 superconducting magnetic coil

Claims

Patent claims 1. Sub-element (1) for a semi-finished wire (35) for the production of an NbsSn superconducting wire (40), wherein the sub-element (1) comprises - a tin-containing core area (2), - a Cu-containing, inner intermediate region (3) surrounding the Sn-containing core region (2), - a ring region (4) containing a plurality of Nb-containing reaction elements (5), wherein the ring region (4) surrounds the inner intermediate region (3), - a Cu-containing surrounding region (7) surrounding the ring region (4); wherein the Nb-containing reaction elements (5) have at least - a tube structure (8) which is at least partially made of an Nb alloy containing Nb and at least one further alloying component X, - a filling region (9) located within the tube structure (8) in which a plurality of particles (13) are arranged, wherein the particles (13) contain at least one partner component Pk, wherein the at least one alloy component X and the at least one partner component Pk are selected such that they form precipitates XPk upon reaction annealing of the sub-element (1), characterized in that a metallic matrix (11) is arranged in the filling region (9), and that the particles (13) are distributed in the metallic matrix (11).

2. Subelement (1) according to claim 1, characterized in that the metallic matrix (11) is at least partially formed by a metallic powder (12) which is mixed with the particles (13).

3. Subelement (1) according to claim 1 or 2, characterized in that the metallic matrix (11) is at least partially formed by a metal body (15) in which the particles (13) are dispersed.

4. Subelement (1) according to claim 3, characterized in that the metal body (15) is designed as a wire (16) or rod which is inserted into the filling area (9).

5. Subelement (1) according to one of the preceding claims, characterized in that the Nb-containing reaction elements (5) further comprise - a core structure (17), wherein the filling area (9) lies between the tube structure (8) and the core structure (17).

6. Subelement (1) according to claim 5, characterized in that the core structure (17) is at least partially made of an Nb alloy containing Nb and at least one further alloying component X.

7. Subelement (1) according to claim 5 or 6, characterized in that the metallic matrix (11) is formed by a metal foil (18) and that the metal foil (18) is at least partially wrapped around the core structure (17).

8. Subelement (1) according to one of the preceding claims, characterized in that the metallic matrix (11) contains Ag.

9. Subelement (1) according to one of the preceding claims, wherein a moderation tube (20) is formed on an inside of the tube structure (8), within which the filling area (9) is located, in particular wherein the moderation tube (20) and an adjacent part of the tube structure (8) are made of different materials.

10. Subelement (1) according to one of the preceding claims, characterized in that at least a part of the Nb-containing reaction elements (5) are configured as doping reaction elements (22), wherein the doping reaction elements (22) contain at least one element of the fourth subgroup of the periodic table in at least one contained phase, and / or that doping addition elements (25) are also arranged in the ring region (4), wherein the doping addition elements (25) contain at least one element of the fourth subgroup of the periodic table in at least one contained phase, in particular wherein the at least one element of the fourth subgroup of the periodic table comprises titanium, and / or that at least a part of the Nb-containing reaction elements (5) are configured as reinforcing reaction elements (23), wherein the reinforcing reaction elements (23) contain at least one element of the fifth subgroup of the periodic table in at least one contained phase.and / or that reinforcing elements (26) are also arranged in the ring region (4), wherein the reinforcing elements (26) contain at least one element of the fifth subgroup of the periodic table in at least one contained phase, in particular wherein the at least one element of the fifth subgroup of the periodic table comprises tantalum.

11. Subelement (1) according to one of claims 1 to 10, characterized in that the Nb-containing reaction elements (5) are adjacent to each other in the ring region (4), and that the subelement (1) further comprises a diffusion barrier (29) which surrounds the ring region (4).

12. Subelement (1) according to one of claims 1 to 10, characterized in that the ring region (4) has a Cu-containing ring matrix (34) which forms a plurality of recesses (33) into which the Nb-containing reaction elements (5) are inserted.

13. Semi-finished wire (35) for the production of an NbsSn superconducting wire (40) comprising several bundled sub-elements (1) according to one of the preceding claims.

14. Semi-finished wire (35) according to claim 13, characterized in that the sub-elements (1) are formed according to claim 12, and that an overall diffusion barrier (38) is present which surrounds the entirety of the bundled sub-elements (1) on the outside.

15. Method for producing an NbsSn superconducting wire (40), characterized by the following steps: Step a): Manufacturing a plurality of sub-elements (1) according to any one of claims 1 to 12, Step b): Bundling of the sub-elements (1) to form a semi-finished wire (35) according to one of claims 13 or 14, Step c): Reaction annealing of the semi-finished wire (35) to the NbsSn superconducting wire (40), wherein Sn and Nb react to form NbsSn, wherein in step c) precipitates XPk are first formed in the tube structures (8) and / or the core structures (17), and only subsequently is at least the largest part of the NbsSn formed.

16. NbsSn superconducting wire (40), produced according to a method according to claim 15.

17. Use of an NbsSn superconducting wire (40) according to claim 16 in a nuclear fusion device, in particular wherein the nuclear fusion device is a fusion power plant.

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