Butt splice for superconducting tapes and methods of producing the same

Abstract

According to an embodiment, an apparatus includes a first HTS tape and a second HTS tape, each having at least one axial end with a diagonal cut. The diagonal cut of the axial end of the first HTS tape is abutting the diagonal cut of the axial end of the second HTS tape at a junction. A first copper lap is disposed on a first outside surface of the first HTS tape and a first outside surface of the second HTS tape, covering the junction. A second copper lap is disposed on a second outside surface of the first HTS tape and a second outside surface of the second HTS tape, opposite to the first outside surface, also covering the junction.

Description

Agent’s File Ref. VEIR-012 / 01WO 338760-2061BUTT SPLICE FOR SUPERCONDUCTING TAPESAND METHODS OF PRODUCING THE SAMECROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to and the benefit of U.S. Provisional Application No. 63 / 730,224 filed on December 10, 2024, and entitled “Butt Splice for Superconducting Tapes and Methods of Producing the Same” the entire disclosure of which is hereby incorporated by reference herein.TECHNICAL FIELD

[0002] Embodiments described herein relate to apparatuses including spliced laminated high-temperature superconducting (HTS) tapes using copper laps, and methods of manufacturing the same.BACKGROUND

[0003] High-temperature superconducting (HTS) tapes, include a superconducting material layer integrated into a stack of conductive and / or non-conductive layers. Some applications for such tapes involve helically winding them around a cylindrical former and enclosing them in a tube cryostat. This method has enabled the development of power transmission cables capable of transmitting significantly higher currents compared to conventional cables, with some capable of carrying 1-10 kA or more. HTS cables can be utilized in both direct current (DC) and alternating current (AC) systems, offering the potential to transmit up to ten times more current than traditional cables and / or operate at much lower voltages. However, HTS tapes are usually supplied in fixed lengths, typically around 200-300 meters and up to about 1 km, which poses a challenge for applications requiring longer continuous lengths.

[0004] Known techniques for joining HTS tapes, such as soldering and ultrasonic welding may be suitable for configurations in which the tapes tend to maintain a linear configuration, such for superconducting magnets. When HTS tapes are wound under tension around a former to superconducting cable, however, existing techniques for joining HTS are unsatisfactory due to the increased mechanical stresses placed on the joint relative to linear configurations. Specifically, the intensity, size, and / or depth of the weld and / or size of the weld and / or solder1328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061 poses an unacceptable risk of damaging the superconducting portion of the HTS tape, degrading the electrical performance.SUMMARY

[0005] Provided herein is an apparatus including a first HTS tape and a second HTS tape, each tape having at least one axial end with a diagonal cut. The diagonal cut of the axial end of the first HTS tape is configured to abut the diagonal cut of the axial end of the second HTS tape at a junction. The apparatus includes a first copper lap disposed on a first outside surface of the first HTS tape and a first outside surface of the second HTS tape such that the first copper lap covers the junction of the first HTS tape and the second HTS tape. In some embodiments, the apparatus further includes an optional second copper lap disposed on a second outside surface of the first HTS tape and a second outside surface of the second HTS tape such that the second copper lap covers the junction of the first HTS tape and the second HTS tape. The second outside surface of the first HTS tape and the second HTS tape is opposite to the first outside surface of the first HTS tape and the second HTS tape. In some embodiments, the apparatus further includes a first solder disposed between the first copper lap and the first outside surface of the first HTS tape and the second HTS tape; and a second solder disposed between the second copper lap and the second outside surface of the first HTS tape and the second HTS tape.

[0006] In some embodiments, the first copper lap and the second copper lap have the same thickness. In some embodiments, the first copper lap and the second copper lap can have different thicknesses. In some embodiments, the first copper lap and the second copper lap are configured to generate no more than about 120 milliwatts of heat when carrying an electrical current of about 70 A RMS. In some embodiments, the apparatus further includes a first solder disposed between the first copper lap and the first outside surface of the first HTS tape and the second HTS tape, and a second solder disposed between the second copper lap and the second outside surface of the first HTS tape and the second HTS tape. In some embodiments, the first solder and the second solder have the same composition comprising indium. In other embodiments, the first solder has a first composition and the second solder has a second composition, the first composition being different from the second composition in terms of chemical element composition.

[0007] In some embodiments, at least one of the first HTS tape or the second HTS tape is laminated. In some embodiments, each of the first HTS tape and the second HTS tape has a2328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061 thickness between about 100 pm and about 500 pm. In some embodiments, the apparatus is disposed on and around a former at a winding angle ranging from about 10° to about 45°. In certain embodiments, the former has an outer diameter of at least about 10 mm, and in some embodiments, the outer diameter is between about 20 mm and about 50 mm. In some embodiments, the former defines a shape and has a hollow interior configured to allow passage of a cryogenic coolant therethrough. In some embodiments, the cryogenic coolant can include at least one of ethane, ethylene, krypton, methane, oxygen, argon, nitrogen, neon, hydrogen, xenon, or helium.

[0008] In some embodiments, the first copper lap has a thickness between about 20 pm and about 150 pm. In certain embodiments, the diagonal cut of the first HTS tape and the diagonal cut of the second HTS tape are each at an angle between about 15° and about 75° relative to the longitudinal axis of the respective HTS tape, and in some embodiments, each diagonal cut is at an angle of about 45° relative to the longitudinal axis of the respective HTS tape.

[0009] In some embodiments, the apparatus is configured such that local degradation of superconductivity at the junction between the first HTS tape and the second HTS tape is no more than about 10% when electrical current passes through the junction. In some embodiments, the apparatus is configured such that power loss at the junction between the first HTS tape and the second HTS tape is no more than about 120 milliwatts when carrying an electrical current of about 70 A RMS.{0010] Provided herein is a method including applying a first solder to a first copper lap, heating the first solder to adhere the first copper lap to a first outside surface of a first HTS tape and a first outside surface of a second HTS tape, such that the first copper lap covers a junction formed by a diagonal cut on at least one axial end of the first HTS tape and the second HTS tape. In some embodiments, the method can further include, optionally, applying a second solder to a second copper lap, and heating the second solder to adhere the second copper lap to a second outside surface of the first HTS tape and a second outside surface of the second HTS tape, such that the second copper lap covers the junction, thereby splicing the first HTS tape and the second HTS tape. The second outside surface of the first HTS tape and the second HTS tape is opposite to the first outside surface of the first HTS tape and the second HTS tape.

[0011] In some embodiments, applying the first solder includes using indium solder. In some embodiments, applying the second solder includes using a solder composition different3328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061 from the first solder composition in terms of chemical element composition, while in other embodiments, the second solder has the same chemical element composition as the first solder. In some embodiments, heating at least one of the first solder or the second solder includes using a technique selected from hot air reflow, infrared heating, or induction heating.

[0012] In some embodiments, the first copper lap and the second copper lap have the same thickness. In some embodiments, each of the first copper lap and the second copper lap has a thickness between about 20 pm and about 150 pm. In some embodiments, the method further includes winding the spliced first and second HTS tapes around a former. In some embodiments, winding includes winding at a winding angle between about 10° and about 45° under a tension between about 10 N and about 50 N. In some embodiments, the former defines a shape and has a hollow interior configured to allow passage of a cryogenic coolant therethrough. In some embodiments, the cryogenic coolant can include at least one of ethane, ethylene, krypton, methane, oxygen, argon, nitrogen, neon, hydrogen, xenon, or helium.

[0013] In some embodiments, the method further includes cutting the first HTS tape and the second HTS tape to form the diagonal cut on the first HTS tape and the corresponding diagonal cut on the second HTS tape at an angle between about 15° and about 75° relative to longitudinal axes of the respective HTS tapes. In some embodiments, the diagonal cuts are complementary in geometry and are positioned to abut at the junction.

[0014] In some embodiments, the splice formed by the first copper lap and the second copper lap is configured such that power loss at the junction is no more than about 120 milliwatts when carrying an electrical current of about 70 A RMS. In some embodiments, the junction between the first HTS tape and the second HTS tape is configured such that local degradation of superconductivity is no more than about 10% when electrical current passes through the junction.BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1 illustrates a first schematic block diagram of an apparatus including spliced HTS tapes, according to an embodiment.

[0016] FIGS. 2A-2D illustrate the apparatus including spliced HTS tapes, from top, side, inside, and exploded perspective views, respectively, according to an embodiment.4328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061

[0017] FIGS. 3A-3B are pictures of an apparatus including spliced HTS tapes, according to an embodiment. FIG. 3C illustrates picture of the apparatus from FIGS. 3A-3B wrapped around a former, according to an embodiment.|0018| FIG. 4 illustrates a flow chart illustrating a method for splicing HTS tapes, according to an embodiment.DETAILED DESCRIPTION

[0019] High-temperature superconducting (HTS) cables are designed to carry substantially higher currents than conventional copper cables, often several times greater, and in some applications can enable delivery of up to ten times or more power within the same right-of- way, while reducing energy losses. These cables typically include HTS tapes, which are wound around a central former, which serves as a support structure, to enhance mechanical and electrical stability and obtain desired current flow.

[0020] In some embodiments, an HTS tape can include a layered structure with a flexible substrate, often stainless steel or Hastelloy, ranging from 30 to 100 microns in thickness. The substrate is then coated with several buffer layers, typically a few microns thick, onto which the HTS layer is applied. The HTS layer, often composed of rare-earth barium copper oxide (ReBCO) or other high-temperature superconducting materials, exhibits high-temperature superconducting properties above the critical temperature of 77 Kelvin (-196°C). The HTS layer itself is very thin, typically around 1 micron, yet it enables the tape to achieve superconductivity at temperatures around the critical temperature when cooled with a cryogen, e.g., liquid nitrogen, liquid helium, and / or the like. This layered structure allows HTS cables to achieve high current densities, often exceeding 42000 amps per square millimeter, making them ideal for high-demand applications such as power grids and high-capacity industrial systems.

[0021] However, HTS tapes are usually supplied in fixed lengths by manufacturers, typically around 200-300 meters and up to about 1 km, which poses a challenge for applications requiring longer continuous lengths of HTS tapes. Accordingly, some practical applications of high-temperature superconducting (HTS) transmission cables require that cable sections be periodically spliced together. For longer-distance field installations, joints (e.g., lap solder or bridge solder joints) have been implemented to connect superconducting cable segments, but they often introduce several technical and engineering challenges. The bulkiness of these joints can increase the thermal load, making it more challenging to maintain the low temperatures5328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061 required for superconductivity, and also increasing the heat load that must be removed by the cryogens and the cooling system. Additionally, the mechanical integrity of the system can be compromised due to the added weight and complexity, potentially leading to mechanical failures or inefficiencies.[0022| Alternative to joining segments of HTS cables, splicing techniques such as welding have been employed to join shorter segments of HTS tapes. However, these methods often result in mechanical instability and increased electrical resistance, leading to power losses and potential degradation of superconductivity. The welding process can introduce microstructural defects, which may compromise the superconducting properties at the joint. Localized heating during welding can cause thermal stresses that weaken the tape and lead to delamination or cracking, reducing the critical current density of the splice. Additionally, achieving precise alignment between the tapes is challenging, especially given the thin and fragile nature of HTS materials, and any misalignment can further degrade current flow across the weld.

[0023] Ultrasonic welding has been used to join HTS tapes by placing a third section of tape on top to bridge a gap between two HTS tapes. While this method can be implemented for certain applications, it is not suitable for laminated HTS tapes that need to be bent to small radii at an angle, as required, for example, in helically wound cables. Additionally, ultrasonic welding equipment is expensive, and the process can introduce unnecessary complexity.

[0024] Splicing of laminated HTS tapes, which are relatively thick at about 200 microns or more, presents several challenges due to the intricate mechanical and electrical specifications required to ensure performance standards are met. To illustrate, according to some embodiments described herein, formers having small diameters, such as around 5 cm or below, typically necessitates winding of the superconducting tapes under controlled tension, generally above 10 N. However, applying this level of tension adds to the complexity of the process, as it requires precise handling to avoid damage to the tape or issues during winding. In addition, splicing of HTS tapes can create power losses due to resistive connections at the splice points. These losses generate heat that compromises the efficiency of the system and must be mitigated to preserve superconductivity. Consequently, reducing power losses is crucial, as any increase introduces additional heat into the system, requiring removal by the cryogen to maintain the low operating temperatures necessary for desired superconducting properties.

[0025] A diagonal butt splice with copper laps, described herein, can address one or more inefficiencies of conventional splicing methods. The diagonal cut can increase the splice's6328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061 surface area, reducing electrical resistance and enhancing mechanical stability. The copper laps offer additional support, providing the splice can endure the winding and bending stresses typical in cable manufacturing. By utilizing readily available materials and techniques, this splicing method can be integrated into existing manufacturing processes, making it a practical solution for large-scale production of superconducting cables.

[0026] While using the diagonal butt splice, the HTS tapes remain mechanically stable and maintain their superconducting properties under high tension and tight bending radii. According to some embodiments, the butt splice provided herein remain mechanically intact without signs of unsoldering, even when wound under tension around a 2 cm diameter pipe at angles between 10-45 degrees. In some embodiments, the butt splice described herein is configured to withstand mechanical stresses encountered during winding, including but not limited to, torsional, bending, and tensile forces. These stresses can arise when HTS tapes are wound under tension around small-diameter formers, which can exceed 10 N of applied force. Conventional butt splices using a straight-cut often fail under such conditions due to stress concentration at the junction, leading to delamination or solder fatigue. By implementing diagonal cuts, the butt splice distributes mechanical loads over an increased contact area, reducing localized stress and enhancing structural integrity during winding and operation.

[0027] Described herein is a method involving making diagonal cuts at the axial ends of the HTS tapes, aligning the cuts to form a junction, and then soldering copper laps on both tapes to cover the junction. The use of diagonal cuts prevents the splice from splitting open during winding, while the copper laps provide robust electrical and mechanical support. Compared to conventional splicing techniques such as ultrasonic welding or straight-cut solder joints (e.g., solder lap splices), diagonal butt splices described herein offer superior mechanical performance under bending stresses encountered during cable winding. While solder lap splices can demonstrate good electrical performance), their relatively thick structure tends to delaminate when bent around small-diameter formers. In contrast, the diagonal butt splice maintains structural integrity under tight bending radii and high winding tensions, which enables better electrical performance in wound cable configurations. Additionally, the diagonal cut increases the contact area at the junction, which can help reduce electrical resistance relative to straight-cut solder joints.

[0028] The described splicing technique also allows for flexibility in the design and manufacturing of superconducting cables. By enabling the creation of longer continuous7328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061 lengths of HTS tapes, it reduces the need for bulky joints and connectors, which can be sources of electrical resistance and mechanical failure.

[0029] By enabling the use of longer HTS tapes, the described embodiments can enhance the practicality and efficiency of using HTS tapes in various applications, including power transmission and other high-current electrical systems. This advancement addresses the limitations of traditional splicing methods and provides a solution for creating continuous lengths of HTS tapes that meet stringent electrical, heating, and mechanical requirements.

[0030] The apparatuses and methods described herein can be suitable for use with HTS tapes including rare-earth barium copper oxide (ReBCO) superconducting materials, which exhibit high-temperature superconducting properties at temperatures of 77 K which is below the critical temperature. ReBCO materials typically have the general formula REBa2Cu3O?-x, where RE represents a rare earth element such as yttrium (Y), samarium (Sm), neodymium (Nd), europium (Eu), or gadolinium (Gd). Among these, yttrium barium copper oxide (YBCO) is one of the most well-known and widely used ReBCO materials. The structure of ReBCO is characterized by layers of copper-oxygen planes separated by layers containing the rare earth and barium atoms, which is crucial for their superconducting properties. ReBCO materials exhibit superconductivity at temperatures significantly higher than conventional superconductors, with a critical temperature Tc typically around 90 K. This higher Tc makes ReBCO materials more cost-effective and easier to handle in practical applications. However, the embodiments are not limited to ReBCO and may be applicable to other high-temperature superconductors, such as YBa2Cu3O7-x (YBCO), Bi2Sr2Ca2Cu30io+y, ThBa2Ca2Cu30io+y, and HgBa2Ca2Cu30s+y.

[0031] While the foregoing description references a layered architecture commonly associated with rare-earth barium copper oxide (ReBCO) tapes, the embodiments disclosed herein are not limited to any particular high-temperature superconductor (HTS) architecture. Other HTS tape configurations, including those based on different superconducting materials or structural designs, may also be suitable for use with the splicing techniques described herein. For example, tapes incorporating alternative substrates, buffer layers, or stabilizing layers, as well as tapes formed from superconductors such as Bi-based, Tl-based, or Hg-based compounds, can be implemented without departing from the scope of the present disclosure. Accordingly, the spliced HTS tapes described herein should be understood as encompassing any tape structure capable of exhibiting high-temperature superconductivity and meeting the mechanical and electrical requirements for splice formation.8328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061

[0032] The apparatuses and methods described herein generally offer multiple benefits by all combinations of the foregoing concepts and additional concepts discussed herein (provided such concepts are not mutually inconsistent) are contemplated as being part of the subject matter disclosed herein. The terminology explicitly employed herein that also may appear in any disclosure incorporated by reference should be accorded a meaning most consistent with the particular concepts disclosed herein.

[0033] The terminology used herein is for the purpose of describing particular embodiments, implementations, and / or concepts (including any feature(s) or aspect(s) thereof) and is not intended to be limiting. Unless defined otherwise, all technical and / or scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. Any explanation or discussion of or using particular terms is intended to provide context and to facilitate understanding and is not necessarily intended to replace or supersede commonly used or known definitions understood by one skilled in the art unless explicitly stated otherwise. Moreover, various terms may be used to describe similar or substantially the same embodiments, implementations, and / or concepts (including any feature(s) or aspect(s) thereof) and thus, the use of particular terms is not intended to be limiting and / or to the exclusion of other terms unless the terms are mutually exclusive, or the context clearly states otherwise.

[0034] As used herein, the term “a” or “an” refers to one or more of that entity; for example, “an element” refers to one or more element or at least one element. As such, the terms “a” (or “an”), “one or more” and “at least one” are used interchangeably herein. In addition, reference to “an element” by the indefinite article “a” or “an” does not exclude the possibility that more than one of the elements is present, unless the context clearly requires that there be one and only one of the elements.

[0035] As used herein, the terms “about” and “approximately” when preceding a numerical value mean a range (e.g., plus or minus 10% of that value). For example, “about 50” can mean 45 to 55, “about 25,000” can mean 22,500 to 27,500, etc., unless such an interpretation would result in a value above or below range of possible values, such as below 0% or above 100% of a possible value. Furthermore, the phrases “less than about / approximately” a value or “greater than about / approximately” a value should be understood in view of the definition of the term “about / approximately” provided herein, as applied to any recited endpoint. Similarly, the term “about / approximately” when preceding a series of numerical values or a range of values (e.g.,9328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061“about 10, 20, 30” or “about 10-30”) refers to and / or modifies, respectively, all values in the series, and / or the endpoints of the range.

[0036] Where a range of values is provided, it is to be understood that each intervening value (e.g., to the tenth of the unit of the lower limit unless the context clearly dictates otherwise) between the upper and lower limit of that range and any other stated or intervening value in that stated range is encompassed within the disclosure. That the upper and lower limits of these smaller ranges can independently be included in the smaller ranges is also encompassed within the disclosure, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the disclosure. All ranges described herein include each individual member or value of the listed range, including the end members or values. Any listed ranges are intended to encompass any and all possible subranges and / or combinations of subranges thereof unless expressly stated otherwise. Any listed range should be recognized as sufficiently describing and enabling the same range being broken down into at least equal subparts unless expressly stated otherwise.

[0037] As used herein, the phrase “and / or” as used herein, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and / or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and / or” clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to “A and / or B”, when used in conjunction with open- ended language such as “comprising” can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.10038] As used herein, the term “or” should be understood to have the same meaning as “and / or” as defined above. For example, when separating items in a list, “or” or “and / or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of’ or “exactly one of,” “not more than one of,” and / or the like will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating10328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061 exclusive alternatives (i.e., “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the embodiments, shall have its ordinary meaning as used in the field of patent law.

[0039] As used herein, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and / or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.

[0040] It should be noted that the term “for example” or “exemplary” as used herein to describe various embodiments is intended to indicate that such embodiments are possible examples, representations, and / or illustrations of possible embodiments (and such term is not intended to connote that such embodiments are necessarily extraordinary or superlative examples).

[0041] As used herein, the term “set” and “plurality” can refer to multiple features or a singular feature with multiple parts. For example, when referring to a set of electrodes, the set of electrodes can be considered as one electrode with multiple portions, or the set of electrodes can be considered as multiple, distinct electrodes. Additionally, for example, when referring to a plurality of electrochemical cells, the plurality of electrochemical cells can be considered as multiple, distinct electrochemical cells or as one electrochemical cell with multiple portions. Thus, a set of portions or a plurality of portions may include multiple portions that are either continuous or discontinuous from each other. A plurality of particles or a plurality of materials can also be fabricated from multiple items that are produced separately and are later joined together (e.g., via mixing, an adhesive, or any suitable method).11328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061

[0042] The phrase “based on” does not mean “based only on,” unless expressly specified otherwise. In other words, the phrase “based on” describes both “based only on” and “based at least on.

[0043] In the embodiments, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of’ and “consisting essentially of’ shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

[0044] As used herein, the terms “high temperature superconductor (HTS) tape” and “high temperature superconductor (HTS) layer” as used herein refer to a tape or layer in which at least a portion of the respective tape or layer contains a high temperature superconductor material. Thus, a “HTS tape” may include one or more regions of superconductor material and optionally one or more regions of non-superconductor material.

[0045] As used herein, the term “junction” refers to a specific point or area where edges of the HTS tapes meet or come closest to each other along the former. The junction can involve direct physical contact between the tapes or a small gap (i.e., a gap less than about 100 pm) between them. Accordingly, in some embodiments, the HTS tapes are nearly touching but not necessarily in direct contact, allowing for a narrow separation with a gap being less than 100 pm. In some embodiments, the HTS tapes are in physical contact with each other.

[0046] As used herein, the term “abutting at a junction” refers to the condition where the HTS tapes are positioned next to each other and make physical contact or are extremely close at a specific meeting point. At this junction, the edges of the tapes are aligned with either direct physical contact or a very minimal gap, defined as less than 100 pm. The abutting may or may not include physical contact of superconducting materials disposed within a stack of conductive and / or non-conductive layers that form the HTS tape(s).

[0047] As used herein, the term “fluid” refers to gases, liquids, supercritical fluids and materials that flow.

[0048] As used herein, the term “cryogen” refers to a substance used to achieve and maintain temperatures below -123 °C (150K). These substances have very low boiling points. For example, liquid nitrogen has a boiling point of -196°C (77K), and liquid helium has a boiling point of -269°C (4K). Exemplary cryogens include liquid nitrogen, liquid nitrous oxide,12328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061 liquid methane, liquid natural gas, or liquid or solid carbon dioxide, chlorodifluoromethane, or Freon®, or any number of other fluids with a high thermal energy transfer capacity and low boiling point, as are commonly known to those skilled in the art. Cryogens can readily induce a temperature differential when applied to an object.

[0049] As used herein, the term “cryogenic liquid” refers to a cryogen in liquid phase. In some instances, cryogenic liquids are liquefied gases that have a normal boiling point below -150° C. For example, liquid argon has a boiling point of-185.9° C and liquid nitrogen has a boiling point of -196° C.10050] FIG. 1 is a block diagram of an apparatus 100 for splicing HTS tapes, according to an embodiment. The apparatus 100 includes a first HTS tape 110 and a second HTS tape 120, each tape having at least one axial end with a diagonal cut (not shown). The diagonal cut of the axial end of the first HTS tape 110 is configured to abut the diagonal cut of the axial end of the second HTS tape 120 at a junction. The apparatus 100 further includes a first electrically conductive splice 130. The first electrically conductive splice 130 is disposed on a first outside surface of the first HTS tape 110 and a first outside surface of the second HTS tape 120 such that the first electrically conductive splice 130 covers the junction of the first HTS tape 110 and the second HTS tape 120. In some embodiments, a second electrically conductive splice 140 can be disposed on a second outside surface of the first HTS tape 110 and a second outside surface of the second HTS tape 120 such that the second electrically conductive splice 140 covers the junction of the first HTS tape 110 and the second HTS tape 120. The second outside surface of the first HTS tape 110 and the second HTS tape 120 is opposite to the first outside surface of the first HTS tape 110 and the second HTS tape 120. The apparatus 100 may further include a first solder 150 disposed between the first electrically conductive splice 130 and the first outside surface of the first HTS tape 110 and the second HTS tape 120. The apparatus 100 may further include a second solder 160 disposed between the second electrically conductive splice 140 and the second outside surface of the first HTS tape 110 and the second HTS tape 120. In some embodiments, the apparatus 100 may be disposed on a former, which serves as a base structure for the HTS tapes.

[0051] In some embodiments, at least one of the first HTS tape 110 or the second HTS tape 120 is laminated. Splicing the first 110 and second 120 HTS tapes can involve positioning the first 110 and second 120 HTS tapes as close together as possible, which can result in the splice having advantageous mechanical and electrical properties. Reducing the distance between the first 110 and second 120 HTS tapes reduces the section of the gap supported only by the13328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061 electrically conductive splices 130, 140, which enhances both electrical conductivity and mechanical stability. This approach lowers resistance in the splice, thereby reducing power loss and improving the structural integrity of the connection. Accordingly, it can be desirable for at least a portion of the first HTS tape 110 to be in direct physical contact with the second HTS tape 120. Alternatively, in some embodiments, the minimum gap between the first HTS tape 110 and the second HTS tape 120 can be less than 100 pm.

[0052] In some embodiments, the apparatus 100 includes a first HTS tape 110 and a second HTS tape 120 (collectively referred to as “the HTS tapes 110, 120”), each have at least one axial end with a diagonal cut, which can improve alignment and linear contact length (i.e., length along the diagonal cut(s)) and / or contact area at splice junctions. The diagonal cut at each end may serve to reduce the electrical resistance at the junction and increase the mechanical stability of the splice. For instance, in certain embodiments, the first HTS tape 110 includes a single diagonal cut at one axial end, allowing it to abut the second HTS tape 120 at a junction. Alternatively, the first HTS tape 110 may have diagonal cuts at both axial ends: one end can form a junction with a correspondingly cut axial end of the second HTS tape 120, while the opposite end can connect with a third HTS tape (not shown), also featuring a diagonal cut. Similarly, the second HTS tape 120 may, in some embodiments, have diagonal cuts on both ends, allowing for a connection with the third HTS tape at one end and a fourth HTS tape (not shown) at the other end. In some embodiments, the diagonal cut may be at a 45-degree angle, or any other suitable diagonal, such as between 15 and 75 degrees. The diagonal cut is particularly advantageous for preventing the splice from splitting open during the winding process, an issue encountered when using a straight-across cut.

[0053] In some embodiments, the HTS tapes described herein can include a substrate and a high temperature superconducting (HTS) material disposed on the substrate. In some embodiments, the substrate is a flexible substrate that provides mechanical support to the HTS material. In some embodiments, the HTS tapes can include a plurality of layers stacked on top of each other. In some embodiments, one or more layer(s) from the plurality of layers can include a HTS layer. The plurality of layers can further include at least one of a buffer layer, a stabilizing layer, a capping layer, or any other layer to obtain desired performance of the HTS tapes. For example, the stabilizer layer and / or capping layer can be implemented to provide a low resistance interface for electrical stabilization to aid in prevention of superconductor burnout in practical use. In some embodiments, the HTS tape can further include one or more14328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061 additional laminate layers configured to provide enhanced electrical and / or mechanical strength.

[0054] The substrate can be a material that withstands a pre-determined mechanical stress and strain and may also provide mechanical integrity for the HTS in a variety of applications. Further, the substrate may be operable to withstand high processing temperatures and aggressive processing environments (e.g., highly oxidative) that are utilized during fabrication of the HTS tape. In some embodiments, the substrate can be a metal-based substrate. In some embodiments, the substrate can be an alloy of at least two metallic elements. Moreover, the substrate may be treated so as to have desirable surface properties for subsequent deposition of the constituent layers of the HTS tape. For example, the surface may be lightly polished to a desired flatness and surface roughness.

[0055] The substrate is in a form for a tape, having a high dimension ratio. For example, the width of the substrate can range approximately from 2 mm - 12 mm and the length of the substrate is typically greater than about 100 m, greater than about 500 m, greater than 1 km. In some embodiments, the substrate can have a length of about 1 km. Accordingly, the substrate may have a dimension ratio that is fairly high, on the order of not less than 10, not less than about 100, not less than about 103, not less than about 104.

[0056] The buffer layer may be a single layer, or more commonly, be made up of several films. In some embodiments, the buffer layer can include a biaxially textured film, having a crystalline texture that is generally aligned along crystal axes both in-plane and out-of-plane of the film. Any suitable manufacturing (e.g., deposition) technique that may be advantageously utilized to form a suitably textured buffer layer for subsequent formation of a HTS layer having desirable crystallographic orientation for superior superconducting properties.

[0057] The HTS layer can include any one of the high-temperature superconducting materials that exhibit superconducting properties above the temperature of liquid nitrogen, 77 K. In some embodiments, the HTS layer can include any one of the high-temperature superconducting materials of the rare earth barium copper oxide (ReBCO) family. Such materials may include REBa2Cu3O?-x, wherein RE is a rare earth element, and x denotes the oxygen deficiency in the crystal structure (typically ranging from about 0 to 1, inclusive all values). The rare earth element can include at least one of yttrium (Y), gadolinium (Gd), samarium (Sm), or europium (Eu). In some embodiments, the HTS layer can include at least one of YBa2Cu3O(YBCO), GdBa2Cu3O?-x (GdBCO), or EuBa2Cu3O?-x (EuBCO), wherein x15328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061 represents an oxygen deficiency ranging from about 0 to 1, inclusive all values. In some embodiments, the HTS layer can include mixed rare-earth formulations such as GdYBa2Cu3O?- x (GdYBCO). The specific elemental composition is typically determined by the manufacturer, and the splicing process described herein is compatible with all such formulations.

[0058] In some embodiments, the superconducting layer may be formed by any thin film deposition processes, including but not limited to metalo-organic chemical vapor deposition (MOCVD), pulsed laser deposition (PLD), dc / rf sputtering, vapor deposition, metal organic deposition, molecular beam epitaxy, and sol gel processing. Typically, the HTS layer has a thickness on the order of about 1 to about 10 microns, most typically about 1 to about 5 microns, such as about 1 to about 2 microns, in order to get desirable amperage ratings associated with the superconducting layer.

[0059] In some embodiments, at least one of the first HTS tape 110 or the second HTS tape 120 has a thickness of about 100 pm to about 300 pm. In some embodiments, at least one of the first HTS tape 110 or the second HTS tape 120 has a thickness of at least about 100 pm, at least about 110 pm, at least about 120 pm, at least about 130 pm, at least about 140 pm, at least about 150 pm, at least about 160 pm, at least about 170 pm, at least about 180 pm, at least about 190 pm, at least about 200 pm, at least about 210 pm, at least about 220 pm, at least about 230 pm, or at least about 240 pm. In some embodiments, the thickness of at least one of the HTS tapes may be no more than about 300 pm, no more than about 290 pm, no more than about 280 pm, no more than about 270 pm, no more than about 260 pm, no more than about 250 pm, no more than about 240 pm, no more than about 230 pm, no more than about 220 pm, or no more than about 210 pm. Combinations and / or ranges of the above-referenced thicknesses are also possible (e.g., at least about 150 pm and no more than about 300 pm, or at least about 170 pm and no more than about 250 pm), inclusive of all values and ranges therebetween. In some embodiments, the thickness of at least one of the HTS tapes may be about 150 pm to about 300 pm, inclusive of all values (or fractions thereof) and / or all ranges (or subranges thereof) therebetween.

[0060] In some embodiments, the first electrically conductive splice 130 and the second electrically conductive splice 140 (collectively referred to as “the conductive splices 130, 140”) can be independently made of at least one of copper, aluminum, silver, gold, brass, bronze, nickel-copper alloy (e.g., Monel), or steel. In some embodiments, the conductive splices 130, 140, collectively, can result in a local degradation of superconductivity of about 10 percent or less, and in embodiments, of about 5 percent or less.16328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061

[0061] In some embodiments, at least one of the first electrically conductive splice 130 and the second electrically conductive splice 140 can include a copper lap (or lap constructed of other suitable conductive material). In some embodiments, the conductive splices 130, 140 include copper laps. That is, in some embodiments, the first electrically conductive splice 130 can be a first copper lap (e.g., a first copper bridge), and the second electrically conductive splice 140 can be a second copper lap (e.g. a second copper bridge).

[0062] Relatively thick splices 130, 140 can reduce resistance and enhance mechanical stability when wound onto a former. A drawback of relatively thick splices 130, 140, however, it is that they may interfere with the winding process tolerances, cause kinking of the HTS tape 110, 120 soldered onto the splices 130, 140, and lead to unsoldering during bending. Accordingly, it may be advantageous to balance the benefit of reduced resistance against the drawbacks associated with winding difficulty. In some embodiments, thicknesses of each of the splices 130, 140 can be between 20 pm and 150 pm. In some embodiments, thicknesses of each of the splices 130, 140 can be between 20 pm and 60 pm, or between 30 pm and 50 pm, inclusive of all values and ranges therebetween.

[0063] In some embodiments, a thickness of the first splice 130 is the same as that of the second splice 140. In other embodiments, a thickness of the first splice 130 may differ from that of the second splice 140, which can be implemented to obtain the desired splice performance for specific applications. This variation in thickness allows for tailored mechanical support and electrical conductivity, enabling the splice to meet varying operational requirements. For instance, a thicker splice may be used where greater mechanical stability is required, while a thinner splice may be applied to enhance flexibility or to fit within space constraints. In some embodiments, each of the first and second splices 130, 140 can have a length between 15cm or 4 cm between 4 cm and 8 cm, or between at least about 5 cm and 7 cm, inclusive of all values and ranges therebetween.

[0064] The splices 130, 140 can provide both electrical and mechanical support to the splice. In some embodiments, particularly when the apparatus is wound on a former, it may be advantageous to apply a copper lap to each side of the junction between the HTS tapes 110, 120. This configuration can enhance mechanical stability on both sides of the splice during the winding process.

[0065] In some embodiments, a single copper lap may be applied to cover the junction where the HTS tapes abut. In such cases, the single copper lap may have a greater thickness17328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061 than individual laps applied to each side. The selection between a single lap and dual laps may depend on various operational and mechanical requirements, such as the compression forces exerted on the lap, the amount of heat generation that can be tolerated by the copper lap, the current-carrying capacity of the copper lap, and the manner in which the lap is applied, including whether the structure is mounted on a former.

[0066] In some embodiments, where the apparatus is wound on a former, a single copper lap may cover the junction between the first and second HTS tapes 110 and 120, while the uncovered portion of the junction may face downward toward the former. Additionally, typically HTS tapes are wound on formers with the substrate facing up, as this provides superior mechanical resiliency and / or lower risk of superconductor degradation by decreasing the bending stresses on the inner superconducting portions of the HTS tapes. However, when a single copper lap is used, the HTS tapes have superior mechanical performance when the substrate within each tape faces upward when wound on the former.[00671 To secure the splice, solder 150, 160 is applied to each splice 130, 140, for example on a copper lap. In some embodiments, the first solder 150 and the second solder 160 may have the same composition. In other embodiments, the first solder 150 and the second solder 160 may have different compositions to optimize specific properties for each splice. In some embodiments, the solder used can include various compositions tailored to specific application requirements. In some embodiments, the first solder 150 and / or the second solder 160 may include indium. Indium is particularly advantageous due to its high ductility, low melting point (which minimizes thermal stress on the HTS tapes during the soldering process), and ability to form strong, ductile joints that can withstand mechanical stresses. The first solder 150 and / or the second solder 160 may comprise a combination of indium and other metals to balance conductivity and mechanical properties, or it may include specialized alloys designed to enhance performance under particular environmental conditions. For example, in some embodiments, the first solder 150 and / or the second solder 160 may include at least one of indium, tin, silver, or lead-free alloys to enhance mechanical strength, adjust melting points, or improve compatibility with different HTS tape materials.

[0068] In some embodiments, the first solder 150 and the second solder 160 are configured to secure the respective electrically conductive splices 130, 140 to the HTS tapes 110. 120, ensuring a robust connection. Specifically, the first solder 150 secures the first electrically conductive splice 130 to the first outside surface of the first HTS tape 110 and the first outside surface of the second HTS tape 120. Similarly, the second solder 160 secures the second18328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061 electrically conductive splice 140 to the second outside surface of the first HTS tape 110 and second outside surface of the second HTS tape 120.

[0069] In some embodiments, the apparatus 100 can be wound around a former (e.g., a central structural member resembling a bar, tube, and / or pipe defining a shape and providing a mechanical support for the HTS tapes 110, 120). In some embodiments, the apparatus 100 can be wound around the former in a spiral pattern. In some embodiments, the apparatus 100 can be wound around the former in a non-spiral pattern. In some embodiments, the apparatus 100 can be wrapped around a former at a winding angle ranging from 10 degrees to 45 degrees around a former having a diameter between 5 cm and 1 cm under about 10-50 N of tension. Accordingly, in some embodiments, the HTS tapes 110, 120 can be wound around a former (e.g., a central structural member resembling a bar, tube, and / or pipe defining a shape and providing a mechanical support for the HTS tapes 110, 120). In some embodiments, the HTS tapes can be wound around the former in a spiral pattern. In some embodiments, the HTS tapes can be wound around the former in a non-spiral pattern. In some embodiments, the HTS tapes 110, 120 can be wrapped around a former at a winding angle ranging from 10 degrees to 45 degrees around a former having a diameter between 5 cm and 1 cm under about 10-50 N of tension.[0 70| In some embodiments, having both the first electrically conductive splice 130 and the second electrically conductive splice 140 can enhance mechanical stability of the apparatus 100 under winding tensions exceeding 10 N, while maintaining a compact profile suitable for small-diameter formers (e.g., formers having diameters of 100 mm or less).[00711 The apparatus 100 described herein can be flexible designed to withstand significant bending stresses without failure. For example, the apparatus 100 can endure a two-way bending strain of more than about 0. 1%, more than about 0.2%, more than about 0.3%, more than about 0.4% , more than about 0.5% , more than about 1% with a bend diameter of more than 10 mm for a tape thickness of more than 20 pm. The HTS tapes provided herein can be suitable for applications requiring high flexibility and durability in constrained bending conditions.

[0072] In some embodiments, the apparatus 100 (e.g., the splice) is designed to maintain performance under operational conditions including vibration, thermal cycling, electromagnetic forces, and / or the like encountered in power transmission systems. In some embodiments, the first and second electrically conductive splices 120, 140, along with the associated solders 150, 160, can provide enhanced mechanical resilience against repeated thermal expansion and contraction during cryogenic cooling cycles. Additionally, the splice19328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061 configuration (e.g., diagonal cuts) can reduce susceptibility to forces , reducing the risk of fatigue or displacement over extended service life

[0073] In some embodiments, the apparatus 100 is configured to limit power loss at the junction between the first HTS tape and the second HTS tape to no more than about 120 milliwatts when carrying an electrical current of about 70 A RMS. In some embodiments, the power loss can be no more than about 115 milliwatts, no more than about 110 milliwatts, no more than about 105 milliwatts, no more than about 100 milliwatts, no more than about 95 milliwatts, no more than about 90 milliwatts, no more than about 85 milliwatts, or no more than about 80 milliwatts under the same current conditions. Excess heat generated at splice locations can increase the thermal load on the cooling system, resulting in higher cryogen consumption and reduced overall system efficiency. To mitigate this, the first electrically conductive splice 130 and / or the second electrically conductive splice 140 may be configured to provide high thermal conductivity to facilitate rapid heat removal, while low-resistance solder materials, such as indium-based solders, further reduce Joule heating at the junction. By limiting power dissipation and promoting efficient heat transfer, the splice maintains stable superconducting properties under cryogenic operating conditions and supports reliable performance in high-current applications.

[0074] FIGS. 2A-2D show top view, side view, an inside view, and exploded perspective view, respectively, of an apparatus 200 including spliced HTS tapes, according to an embodiment. The apparatus 200 includes a first HTS tape 210 and a second HTS tape 220, each having at least one axial end with a diagonal cut. These diagonal cuts are configured to abut each other at a junction. The apparatus 200 also includes a first electrically conductive splice 230 (e.g., a copper lap) and a second electrically conductive splice 240 (not shown in FIG. 2A and 2C), which cover the junction on the first and second outside surfaces of the HTS tapes 210, 220, respectively. Additionally, the apparatus 200 may include a first solder and a second solder, disposed between the electrically conductive splices and the outside surfaces of the HTS tapes. In some embodiments, the first HTS tape 210, the second HTS tape 220, the first electrically conductive splice 230, and second electrically conductive splice 240 are structurally and / or functionally similar to the first HTS tape 110, the second HTS tape 120, the first electrically conductive splice 130, and the second electrically conductive splice 140 described above with respect to the apparatus 100.

[0075] FIG. 2D illustrates an exploded perspective view of the apparatus 200, according to an embodiment. In this view, the relative positioning of the first electrically conductive splice20328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061230 and the second electrically conductive splice 240 with respect to the first HTS tape 210 and the second HTS tape 220 is shown prior to assembly. This configuration shows the diagonal cuts on the axial ends of the HTS tapes, which increase the contact area at the junction to reduce electrical resistance and / or improve mechanical stability. In some embodiments, solder layers or solder materials can be disposed between the splices and the HTS tapes, and the splices 230, 240 can be adhered by heating either sequentially or in a single step after stacking the components to minimize thermal stress. The splices 230, 240 can have thicknesses tailored to balance electrical robustness with flexibility, for example between about 20 pm and about 150 pm, and lengths sufficient to cover the junction, for example up to about 15 cm. This arrangement provides a compact splice architecture capable of withstanding winding angles between about 10° and about 45° and tensions up to about 50 N without delamination or loss of superconductivity.|0076| FIGS. 3A-3B are pictures of an apparatus 300 including spliced HTS tapes, according to an embodiment. The apparatus 300 includes a first HTS tape 310 and a second HTS tape 320, each having at least one axial end with a diagonal cut (not shown). These diagonal cuts are configured to abut each other at a junction. The apparatus also includes a first copper lap 330 and a second copper lap (not shown), which cover the junction on the first and second outside surfaces of the HTS tapes, 310, 320, respectively. FIG. 3B shows how the apparatus 300 can conform to a spiral shape without the copper laps splitting open. FIG. 3C illustrates a picture of the apparatus from FIGS. 3A-3B wrapped around a former F, according to an embodiment. This view demonstrates how the spliced HTS tapes are positioned on the former, which serves as a base structure. The former helps maintain the alignment and stability of the HTS tapes, providing the splices remain intact and functional during operation. In some embodiments, the first HTS tape 310, the second HTS tape 320, the first copper lap 330 and the second copper lap, are structurally and / or functionally similar to the first HTS tape 110, the second HTS tape 120, the first copper lap and the second copper lap described above with respect to apparatus 100. FIG. 4 shows a flow chart of a method 10 for splicing HTS tapes, according to an embodiment. Two HTS tapes can have corresponding diagonal cuts. Method 10 can involve splicing the first HTS tape and the second HTS tape using first copper lap and second copper laps, which can be structurally and / or functionally similar to HTS tapes 110, 120 and splices 130, 140, respectively, as described above with reference to FIG. 1. In some instances, the apparatus 100 can be produced and / or obtained by performing method 10.21328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061

[0077] At step 11, the method 10 can optionally include cutting the HTS tapes to have corresponding diagonal cuts. In some embodiments, cutting methods, such as laser cutting, wire electrical discharge machining (wire EDM), or mechanical tools, which can be chosen based on the material characteristics of the HTS tapes and the angle needed for the splice.

[0078] The diagonal cuts on the HTS tapes may be made at angles ranging from about 15° to 75°. In some embodiments, the cut can be at 45 degrees. The angle selection can help obtain desired splice length, mechanical strength, and current-carrying capacity. In some embodiments, the first HTS tape may include a diagonal cut on one axial end to form a splice with the second HTS tape, while in other embodiments, both axial ends of the first HTS tape may be diagonally cut to permit connection to the second HTS tape on one side and another HTS tape on the opposite side, optionally using additional copper laps. Similarly, the second HTS tape may include a diagonal cut on one axial end to form a splice with the second HTS tape, while in other embodiments, both axial ends of the second HTS tape may be diagonally cut to permit connection to the second HTS tape on one side and another HTS tape on the opposite side, optionally using additional copper laps. In some embodiments, these configurations can facilitate continuous splicing of multiple HTS tapes in sequence to form extended lengths suitable for cable manufacturing, with the diagonal cuts being complementary in geometry and positioned to abut at each junction to provide mechanical stability, low electrical resistance, and / or the like.

[0079] At step 12, the method 10 includes positioning the diagonal cuts of the HTS tapes so that they abut at a junction. In some embodiments, the diagonal cuts can be aligned such that the edges of the HTS tapes physically touch each other.[00801 In some embodiments, the positioning of the diagonal cuts of the HTS tapes can be performed using techniques such as alignment fixtures or jigs that securely hold the tapes in place during the positioning and / or splicing process. In some embodiments, visual inspection methods or measurement techniques, such as calipers or specialized alignment tools, can be employed to verify that the cuts are properly aligned at the junction. In some embodiments, optical inspection techniques may be utilized to confirm that the edges of the HTS tapes are in contact, eliminating any gaps that could lead to increased electrical resistance or mechanical failure. Proper positioning is critical for achieving continuous current flow through the junction and enhancing the overall performance of the spliced HTS tapes.22328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061

[0081] At step 13, the method 10 includes applying a first solder to a first copper lap via any suitable technique. The first copper lap is then positioned to cover the junction formed by a diagonal cut on at least one axial end of the first HTS tape and the second HTS tape. This diagonal cut can help prevent the splice from splitting open during the winding process.

[0082] In some embodiments, soldering can be applied using various techniques, including manual soldering with a soldering iron, automated soldering machines, or reflow soldering. The choice of technique may depend on the specific requirements of the application and the available equipment. The solder composition can include indium, which is known for its superior electrical and thermal conductivity, or other materials such as tin, silver, or lead-free alloys. The solder should be chosen based on its melting point, mechanical properties, and compatibility with the HTS tapes and copper laps. The first solder can be provided in any suitable form, including, but not limited to, a sheet, foil, paste, or other forms of solder. In some embodiments, applying the first solder to the first copper lap may include positioning the first solder (e.g., a thin foil, preform, and / or paste) between the first and second HTS tapes and the first copper lap such that the first solder is sandwiched between the HTS tapes and the first copper lap. When heated at step 14, the first solder melts and adheres the first copper lap to the HTS tapes, forming a robust electrical and mechanical bond. In some embodiments, the first solder can be applied directly onto the surface of the first copper lap prior to heating.

[0083] At step 14, the method 10 includes heating the first solder to adhere the first copper lap to the first outside surface of the first HTS tape and the first outside surface of the second HTS tape. The heating process can be controlled to ensure that the solder melts and flows evenly, creating a strong bond between the copper lap and the HTS tapes. The first copper lap covers the junction, providing both electrical and mechanical support. This step provides that the splice remains intact and functional under the mechanical stresses encountered during the winding process.

[0084] In some embodiments, the heating process can be performed using various methods such as hot air reflow, infrared heating, or induction heating. The temperature range for heating the solder typically depends on the solder composition. For example, indium solder may melt at temperatures around 150°C to 160°C, while tin-silver solders may melt at higher temperatures, typically between 210°C and 230°C. It can be important to monitor the temperature closely to avoid overheating, which can damage the HTS tapes or cause the solder to flow unevenly. Accordingly, the heating, at step 14, can be maintained within a range suitable for the selected solder composition, for example, between about 150°C and 230°C, to23328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061 prevent thermal degradation of the HTS layer. Controlled heating duration and uniform temperature distribution across the copper laps can prevent localized overheating, which could otherwise compromise the superconducting properties of the HTS tapes.

[0085] At step 15, the method 10 includes applying a second solder to a second copper lap. In some embodiments, the first copper lap has the same thickness as the second copper lap. Similar to the first solder, the second solder is applied to the second copper lap. The second copper lap is then positioned to cover the junction on the opposite side of the HTS tapes, ensuring that both sides of the splice are reinforced. This dual-sided reinforcement may be beneficial for the mechanical stability of the splice, especially when the tapes are wound around a former having a small diameters (e.g., less than 10 cm, less than 5 cm) at angles between 10- 45 degrees under tension.

[0086] In some embodiments, the application of the second solder can be done using similar techniques as the first solder. The solder composition for the second solder can be the same as the first solder or different, depending on the specific requirements. For instance, if the first solder includes indium, the second solder can include a tin-silver alloy to provide different mechanical properties or melting points, enhancing the overall performance of the splice. The second solder can be provided in any suitable form, including, but not limited to, a sheet, foil, paste, or other forms of solder. In some embodiments, applying the second solder to the second copper lap may include inserting the second solder (e.g., a thin foil, preform, and / or paste) between the first and second HTS tapes and the second copper lap such that the second solder is sandwiched between the HTS tapes and the second copper lap. When heated at step 16, the second solder melts and adheres the second copper lap to the HTS tapes, forming a robust electrical and mechanical bond. In some embodiments, the second solder can be applied directly onto the surface of the second copper lap prior to heating.

[0087] At step 16, the method 10 includes heating the second solder to adhere the second copper lap to the second outside surface of the first HTS tape and the second outside surface of the second HTS tape. The heating process for the second solder is similar to that of the first solder, ensuring a strong and uniform bond. The second copper lap covers the junction, thereby splicing the first HTS tape and the second HTS tape. The second outside surface of the first HTS tape and the second HTS tape is opposite to the first outside surface, providing a robust connection that doesn’t split open during winding. In some embodiments, the heating techniques for the second solder can include hot air reflow, infrared heating, or induction heating, similar to the first solder.24328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061

[0088] In some embodiments, steps 14 and 16 can be performed simultaneously. That is, in some embodiments, steps 14 and 16 can be carried out in a single heating operation. After completing steps 13 and 15, where the first solder is applied to the first copper lap and the second solder is applied to the second copper lap, the entire splice assembly can be stacked and heated in a single heating step. In some embodiments, both the first solder and the second solder can melt simultaneously, securing the first and second copper laps to the respective outside surfaces of the first HTS tape and the second HTS tape. Performing the heating in one step can reduce thermal cycling, minimize the risk of superconductor degradation, and / or promote uniform bonding across both sides of the splice. In other embodiments, the heating may be performed sequentially, first heating the first solder and then heating the second solder, based on process requirements, the type of solder compositions used for the first and second copper laps, and / or equipment limitations.|0089| In some embodiments, the spliced HTS tapes described herein are configured to maintain performance under the mechanical stresses associated with winding onto a former during cable fabrication. Winding HTS tapes onto a former typically involves bending the tapes at controlled angles and applying tension, which can introduce significant strain on splice regions. The splice provided herein is configured to withstand these conditions without compromising electrical or mechanical integrity. For example, the splice can maintain structural stability and / or electrical performance when wound around a former having diameters as low as about 20 mm. In some embodiments, winding can occur at angles between about 10° and about 45° under tensions up to about 50 N, with less than about 10% degradation in performance compared to an HTS cable without a splice.

[0090] In some embodiments, the method can include verifying splice integrity prior to winding (e.g., using quality assurance techniques). Non-destructive inspection methods such as X-ray imaging and / or ultrasonic testing can be used to detect voids or misalignment within the solder joint. For example, electrical resistance measurements can confirm that the splice achieves a resistance below a predetermined threshold, for example, less than 1 p . These inspection steps can ensure that the splice meets mechanical and / or electrical performance criteria before forming into a HTS cable.

[0091] In some embodiments, the winding process can be automated using specialized winding machines that control the tension and angle of the HTS tapes. These machines ensure that the tapes are wound with consistent tension, which is crucial for maintaining the mechanical stability and electrical performance of the cable. The tension applied during25328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061 winding can range from 10 to 50 N, depending on the thickness and material properties of the HTS tapes.

[0092] The method can further include securing the wound HTS tapes to the former to prevent any movement or slippage during subsequent handling and operation. In some embodiments, this can be achieved using adhesive materials, mechanical fasteners, or additional soldering. The securing process provides that the HTS tapes remain in place, maintaining the alignment and contact necessary for optimal electrical performance.

[0093] All combinations of the foregoing concepts and additional concepts discussed herewithin (provided such concepts are not mutually inconsistent) are contemplated as being part of the subject matter disclosed herein. The terminology explicitly employed herein that also may appear in any disclosure incorporated by reference should be accorded a meaning most consistent with the particular concepts disclosed herein.

[0094] The drawings are primarily for illustrative purposes and are not intended to limit the scope of the subject matter described herein. The drawings are not necessarily to scale; in some instances, various aspects of the subject matter disclosed herein may be shown exaggerated or enlarged in the drawings to facilitate an understanding of different features. In the drawings, like reference characters generally refer to like features (e.g., functionally similar and / or structurally similar elements).10095] The entirety of this application (including the Cover Page, Title, Headings, Background, Summary, Brief Description of the Drawings, Detailed Description, Embodiments, Abstract, Figures, Appendices, and otherwise) shows, by way of illustration, various embodiments in which the embodiments may be practiced. The advantages and features of the application are of a representative sample of embodiments only and are not exhaustive and / or exclusive. Rather, they are presented to assist in understanding and teach the embodiments and are not representative of all embodiments. As such, certain aspects of the disclosure have not been discussed herein. That alternate embodiments may not have been presented for a specific portion of the innovations or that further undescribed alternate embodiments may be available for a portion is not to be considered to exclude such alternate embodiments from the scope of the disclosure. It will be appreciated that many of those undescribed embodiments incorporate the same principles of the innovations and others are equivalent. Thus, it is to be understood that other embodiments may be utilized and functional, logical, operational, organizational, structural and / or topological modifications may be made26328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061 without departing from the scope and / or spirit of the disclosure. As such, all examples and / or embodiments are deemed to be non-limiting throughout this disclosure.

[0096] Also, no inference should be drawn regarding those embodiments discussed herein relative to those not discussed herein other than it is as such for purposes of reducing space and repetition. For instance, it is to be understood that the logical and / or topological structure of any combination of any program components (a component collection), other components and / or any present feature sets as described in the figures and / or throughout are not limited to a fixed operating order and / or arrangement, but rather, any disclosed order is exemplary and all equivalents, regardless of order, are contemplated by the disclosure.

[0097] Various concepts may be embodied as one or more methods, of which at least one example has been provided. The acts performed as part of the method may be ordered in any suitable way. For example and with reference to FIG. 4, in some embodiments, the first solder can be applied to a first copper lap, at 11, then a second solder can be applied to a second copper lap, at 13, before the first solder is heated, at 12. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments. For example and with reference to FIG. 4, in some embodiments, the first soldier and the second soldier may be heated simultaneously, at 12 and 14. As such, some of these features may be mutually contradictory, in that they cannot be simultaneously present in a single embodiment. Similarly, some features are applicable to one aspect of the innovations, and inapplicable to others.

[0098] In addition, the disclosure may include other innovations not presently described. Applicant reserves all rights in such innovations, including the right to embodiment such innovations, file additional applications, continuations, continuations-in-part, divisionals, and / or the like thereof. As such, it should be understood that advantages, embodiments, examples, functional, features, logical, operational, organizational, structural, topological, and / or other aspects of the disclosure are not to be considered limitations on the disclosure as defined by the embodiments or limitations on equivalents to the embodiments.27328531013

Claims

Agent’s File Ref. VEIR-012 / 01WO 338760-2061CLAIMS1. An apparatus comprising: a first HTS tape and a second HTS tape, each tape having at least one axial end with a diagonal cut, the diagonal cut of the axial end of the first HTS tape abutting the diagonal cut of the axial end of the second HTS tape at a junction; a first copper lap disposed on a first outside surface of the first HTS tape and a first outside surface of the second HTS tape such that the first copper lap covers the junction of the first HTS tape and the second HTS tape.

2. The apparatus of claim 1, further comprising: a second copper lap disposed on a second outside surface of the first HTS tape and a second outside surface of the second HTS tape such that the second copper lap covers the junction of the first HTS tape and the second HTS tape, the second outside surface of the first HTS tape and the second HTS tape being opposite to the first outside surface of the first HTS tape and the second HTS tape.

3. The apparatus of claim 2, wherein the first copper lap and the second copper lap have same thickness.

4. The apparatus of claims 2 or 3, wherein the first copper lap and the second copper lap are configured to generate no more than about 120 milliwatts of heat when carrying an electrical current of about 70 A RMS.

5. The apparatus of any one of claims 2-4, further comprising: a first solder disposed between the first copper lap and the first outside surface of the first HTS tape and the second HTS tape; and a second solder disposed between the second copper lap and the second outside surface of the first HTS tape and the second HTS tape.

6. The apparatus of claim 5, wherein the first solder and the second solder have same composition comprising indium.28328531013Agent’s File Ref. VEIR-012 / 01WO 338760-20617. The apparatus of claim 5, wherein the first solder has a first composition, and the second solder has a second composition, the first composition being different from the second composition in terms of chemical element composition.

8. The apparatus of any one of the preceding claims, wherein at least of the first HTS tape or the second HTS tape is laminated.

9. The apparatus of any one of the preceding claims, wherein each of the first HTS tape and the second HTS tape has a thickness between about 100 pm and about 500 pm.

10. The apparatus of any one of the preceding claims, wherein the apparatus is disposed on and around a former at a winding angle ranging from 10 degrees to 45 degrees.

11. The apparatus of claim 10, wherein the former has an outer diameter of at least about 10 mm.

12. The apparatus of claims 10 or 11, wherein the former has an outer diameter between about 20 mm and about 50 mm.

13. The apparatus of any one of claims 10-12, wherein the former defines a shape, and has a hollow interior configured to allow passage of a cryogenic coolant therethrough.

14. The apparatus of any one of the preceding claims, wherein the first copper lap has a thickness between about 20 pm and about 150 pm.

15. The apparatus of any one of the preceding claims, wherein the diagonal cut of the first HTS tape and the diagonal cut of the second HTS tape are each at an angle between about 15° and about 75° relative to the longitudinal axis of the respective HTS tape.

16. The apparatus of claim 15, wherein each diagonal cut of the first HTS tape and the second HTS tape is at an angle of about 45° relative to longitudinal axis of the respective HTS tape.

17. The apparatus of any one of the preceding claims, the apparatus is configured such that local degradation of superconductivity at the junction between the first HTS tape and the29328531013Agent’s File Ref. VEIR-012 / 01WO 338760-2061 second HTS tape is no more than about 10% when electrical current passes through the junction.

18. The apparatus of any one of the preceding claims, wherein the apparatus is configured such that power loss at the junction between the first HTS tape and the second HTS tape is no more than about 120 milliwatts when carrying an electrical current of about 70 A RMS.

19. A method comprising: applying a first solder to a first copper lap; and heating the first solder to adhere the first copper lap to a first outside surface of a first HTS tape and a first outside surface of a second HTS tape, such that the first copper lap covers a junction formed by a diagonal cut formed on at least one axial end of the first HTS tape and a corresponding diagonal cut formed on at least one axial end of the second HTS tape, thereby splicing the first HTS tape and the second HTS tape.

20. The method of claim 19, further comprising: applying a second solder to a second copper lap; heating the second solder to adhere the second copper lap to a second outside surface of the first HTS tape and a second outside surface of the second HTS tape, such that the second copper lap covers the junction, the second outside surface of the first HTS tape and the second HTS tape being opposite to the first outside surface of the first HTS tape and the second HTS tape.

21. The method of claims 19 or 20, wherein applying the first solder comprises using indium solder.

22. The method of claims 20 or 21, wherein applying the second solder comprises using a solder composition different from the first solder composition in terms of chemical element composition.

23. The method of claims 20 or 21, wherein applying the second solder comprises using a solder composition having same chemical element composition as the first solder.30328531013Agent’s File Ref. VEIR-012 / 01WO 338760-206124. The method of any one of claims 20-23, wherein heating at least one of the first solder or the second solder comprises using a technique selected from hot air reflow, infrared heating, or induction heating.

25. The method of any one of claims 20-24, wherein the first copper lap and the second copper lap have same thickness.

26. The method of any one of claims 20-25, wherein each of the first copper lap and the second copper lap has a thickness between about 20 pm and about 150 pm.

27. The method of any one of claims 20-26, wherein the heating of the first solder and the heating of the second solder are performed simultaneously.

28. The method of any one of claims 19-26, further comprising: winding the spliced first and second HTS tapes around a former.

29. The method of claim 28, wherein winding the spliced first and second HTS tapes comprises winding at a winding angle between about 10° and about 45° under a tension between about 10 N and about 50 N.

30. The method of claims 28 or 29, wherein the former defines a shape, and has a hollow interior configured to allow passage of a cryogenic coolant therethrough.

31. The method of any one of claims 19-30, further comprising: cutting the first HTS tape and the second HTS tape to form the diagonal cut on the first HTS tape and the corresponding diagonal cut on the second HTS tape at an angle between about 15° and about 75° relative to longitudinal axes of the respective HTS tapes.

32. The method of claim 31, further comprising: forming the corresponding diagonal cuts on the first HTS tape and the second HTS tape such that the diagonal cuts are complementary in geometry.

33. The method of claims 31 or 32, further comprising: positioning the corresponding diagonal cuts of the first HTS tape and the second HTS tape to abut at the junction.31328531013Agent’s File Ref. VEIR-012 / 01WO 338760-206134. The method of any one of claims 20-33, wherein the splice formed by the first copper lap and the second copper lap is configured such that power loss at the junction is no more than about 120 milliwatts when carrying an electrical current of about 70 A RMS.

35. The method of any one of claims 20-34, wherein the junction between the first HTS tape and the second HTS tape is configured such that local degradation of superconductivity is no more than about 10% when electrical current passes through the junction.328531013

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