Method for manufacturing termination

Abstract

A method for manufacturing a termination for a high temperature superconducting (HTS) tape by additive manufacturing using a moving sonotrode includes applying an end portion of a first HTS tape to a substrate and bonding the HTS tape to the substrate using ultrasonic welding. The method includes applying a first layer of metal foil to the HTS tape and bonding the first layer of metal foil to the HTS tape using ultrasonic welding.

Description

[Technical Field]

[0001] The present invention relates to preparing terminations for high temperature superconducting (HTS) tapes. [Background technology]

[0002] The primary use of HTS tapes is in the construction of magnets, for example to generate the strong magnetic fields required for fusion tokamaks. HTS tapes may also be used in MRI or power transmission.

[0003] HTS tapes and cables need to be terminated to carry current from a power supply or to connect to other tapes or cables. For example, in a fusion reactor, fusion magnets may need to be separated and reassembled, so reattachable terminations are needed to connect the magnet components together. Typically, HTS tapes are terminated to most metals using solder. However, creating reliable, repeatable, high-performance terminations for HTS tapes that are wrapped around cables presents challenges.

[0004] Rare-earth barium copper oxide (REBCO) HTS tapes are sensitive to high temperatures because the oxygen in the material is highly mobile. If REBCO is exposed to elevated temperatures for extended periods of time, this can result in oxygen diffusing from the tape, deteriorating its superconductivity, and forming a resistive oxide layer within the tape structure.

[0005] Soldering is a common method for single tape-to-tape connections. However, soldered REBCO tapes have problems with intermetallic phase formation, delamination, and void formation, resulting in undesirably high termination resistance and poor mechanical properties. These problems are exacerbated when multiple tape cables are terminated or when large terminations are required. REBCO is typically placed on a Hastelloy substrate, which has high electrical resistivity, meaning that current does not easily conduct through multiple tape layers. Cable terminations also tend to have greater thermal inertia, requiring extended heating to solder the cable. Summary of the Invention [Means for solving the problem]

[0006] According to the present invention there is provided an apparatus and method as set out in the accompanying claims. Further features of the invention will become apparent from the dependent claims and the following description.

[0007] According to an aspect of the invention, there is provided a method of fabricating a termination for a high temperature superconducting (HTS) tape by additive manufacturing using a moving sonotrode, the method including applying an end portion of a first HTS tape to a substrate, bonding the HTS tape to the substrate by ultrasonic welding, applying a first layer of metal foil to a top surface of the end portion of the HTS tape, and bonding the metal foil to the end portion using ultrasonic welding.

[0008] The method may include applying an additional layer of metal foil on top of the first layer of metal foil and bonding the additional layer to the first layer using ultrasonic welding. The method may include applying an additional HTS tape to the first layer of metal foil and bonding the additional HTS tape to the first layer of metal foil using ultrasonic welding. Alternatively, the method may include applying an additional HTS tape to the additional layer of metal foil and bonding the additional HTS tape to the additional layer or metal foil.

[0009] The method may include repeating the steps of applying additional layers of metal foil and / or additional HTS tape and bonding the additional layers to the underlying layers or metal foil using ultrasonic welding until a three-dimensional termination is built up, whereby the termination may be formed from metal foil layers built up on an end portion of the HTS tape.

[0010] Ultrasonic welding is a process that involves applying ultrasonic motion to two elements held together under pressure. The motion creates a solid-state bond between the elements without melting them. The ultrasonic weld bond can be as strong as the parent materials and does not lead to the creation of brittle intermetallic phases.

[0011] The moving sonotrode can be a rolling sonotrode. By way of example, the sonotrode can be configured to roll along the HTS tape in the longitudinal direction of the tape while applying ultrasonic motion to bond the first HTS tape to the substrate. The metal foil layer can include multiple strips of metal foil. The sonotrode can be configured to apply strips of metal foil to end portions of the first HTS tape and bond the strips of metal foil to the HTS tape by ultrasonic motion. The sonotrode can be configured to move laterally to apply additional strips of metal foil at locations beside the HTS tape.

[0012] The use of additive manufacturing in combination with ultrasonic welding allows for the fabrication of HTS tape terminations while keeping the HTS tape at a lower temperature and welding for a shorter period of time, thereby limiting oxygen migration from the HTS tape. This allows the HTS tape to maintain its low resistance in the termination without significant current degradation. Furthermore, the ultrasonic additive manufacturing method is highly controllable and repeatable, making it scalable for the fabrication of terminations for cables with large numbers of HTS tapes. The method is also quick, cost-effective, and more environmentally friendly, with minimal process waste and low energy requirements.

[0013] As the sonotrode rolls along the tape or foil, ultrasonic motion can be imparted through motion in a direction transverse to the rolling direction. The transverse motion can have an amplitude of 25 μm to 50 μm for joining to copper. The transverse motion can have an amplitude of 30 μm to 50 μm for joining to copper. By way of example, the transverse motion can have an amplitude of 36 μm to 42 μm for joining to copper.

[0014] The sonotrode can provide a downward force to the foil or tape. The force applied can depend on the material properties or width of the foil or tape and the size of the sonotrode.

[0015] The termination can be for a cable comprising a plurality of HTS tapes. The method can include applying a layer of metal foil to the plurality of HTS tapes and joining the foil to the tape by ultrasonic welding.

[0016] At least a portion of the surface of the end portion of the HTS tape may be exposed at the termination for attachment to another termination by the exposed HTS tape. Thus, the method may include applying a layer of metal foil to an upper surface of the end portion of the HTS tape while leaving a lower surface of the HTS tape exposed, and joining the layers together to the HTS tape by ultrasonic welding.

[0017] The metal foil layer at the termination can encapsulate the end portion of the HTS tape such that the distal end of the tape and the top and bottom surfaces of the end portion are covered by the metal foil layer. Thus, the method can include applying a metal foil to the bottom surface of the end portion of the HTS tape, and joining the HTS tape to the metal foil by ultrasonic welding before applying the metal foil layer to the top surface of the end portion of the HTS tape.

[0018] The termination can connect the first HTS tape to the second HTS tape. According to an example, the first HTS tape and the second HTS tape can be in direct contact with each other. The method can include applying a lower surface of an end portion of the second HTS tape to an upper surface of the end portion of the first HTS tape and joining the end portions of the first HTS tape and the second HTS tape together using ultrasonic welding before applying a first layer of metal foil to the upper surfaces of the end portions of the first HTS tape and the second HTS tape. According to another example, the first HTS tape and the second HTS tape can be connected by one or more layers of metal foil. The method can include applying an end portion of the second HTS tape to a layer of metal foil after the one or more layers of metal foil have been joined to the first HTS tape, and then joining the second HTS tape to the layer of metal foil by ultrasonic welding.

[0019] According to another example, a first HTS tape ultrasonically welded to a first layer of metal foil and a second HTS tape ultrasonically welded to a second layer of metal foil may be connected by pressure welding, which may be through direct bonding of the first and second HTS tapes or through a metal foil layer being bonded to the first and second HTS tapes.

[0020] A layer of metal foil can form the termination resistive element. The metal foil can be copper. In another example, the metal foil can be aluminum. The metal foil can have a thickness of 100 μm to 150 μm. The HTS tape can be a rare earth barium copper oxide HTS tape.

[0021] By way of example, an HTS tape may be formed from an HTS layer, a buffer layer, a metal stabilizer layer, and a substrate. The HTS layer in the tape may have a thickness of up to 5 μm, e.g., 1 μm to 5 μm, e.g., 1.6 μm. The metal stabilizer layer in the tape may have a thickness of up to 50 μm, e.g., 10 μm to 30 μm. The substrate in the tape may have a thickness of 15 μm to 100 μm, e.g., 50 μm, preferably 40 μm to 60 μm.

[0022] The use of additive manufacturing in creating the terminations allows the terminations to have complex shapes and geometries. The method may include creating passages in a metal foil layer of the termination. For example, the method may include creating passages that extend across the HTS tape. The passages may be cooling passages. The cooling passages may be configured to channel a cooling fluid through the cooling passages to cool the HTS tape. Forming cooling passages in the terminations can improve the thermal stability of the terminations.

[0023] The passages can be created by an additive method, where creating the passages can include placing metal foil in selected areas and leaving other areas free of metal foil, thereby creating passages between the stacked metal foils.

[0024] According to another example, the passages may be created by a subtractive process. Creating the passages may include removing a portion of a built-up metal layer to create features in the metal before applying a further successive layer of foil. Removing a portion of the metal may include using a computer numerically controlled (CNC) milling process to create features in the metal layer.

[0025] The terminations are formed from multiple metal foils built up on or around the HTS tape. The multiple metal foils can be the same metal or different metals. Using different metals can create composite terminations.

[0026] The use of different metal foils in the terminations allows the terminations to comprise metals that may typically be more difficult to adhere to HTS tape. For example, aluminum may be a preferred metal for terminations, but soldering HTS tape to aluminum has typically been more difficult than soldering HTS tape to copper.

[0027] The first layer of metal foil that contacts the HTS tape can be a metal with increased bonding to the HTS tape, and subsequent layers of metal foil can be different metals. For example, the metal foil in the first layer can be copper and the metal foil in subsequent layers can be aluminum. As another example, the terminations can be formed from foils of different grades of aluminum, where a first grade of aluminum with increased bonding to the HTS tape can be bonded to the HTS tape, while foils of other grades of aluminum can be used in subsequent layers and bonded to the first grade of aluminum foil.

[0028] The termination can be formed from a plurality of first metal foils and a plurality of second metal foils. The second metal foils can have different properties than the first metal foils. The first metal foils can form the majority of the termination. The first metal foils can be copper or aluminum. The second metal foils can provide functional properties of the termination, thereby optimizing the material properties of the termination.

[0029] The second metal foil can be a structural foil and can be a stronger metal than the first metal foil. For example, the second metal foil can be a steel foil. A stronger second metal foil can increase the strength of the termination.

[0030] The second metal foil may be a metal having a different coefficient of thermal expansion than the first metal foil, and may be selected to adjust the coefficient of thermal expansion of the termination.

[0031] The second metal foil can be a metal having a different conductivity than the first metal foil. The second metal foil may be selected to tailor the conductivity of the termination. In some examples, the second metal foil can form an insulating or partially insulating layer in the termination. In other examples, the second metal foil can provide a highly conductive path to reduce termination resistance. In other examples, the second metal foil can provide a means to reduce AC losses in the termination.

[0032] The second metal foil can be a metal that can prevent radiation, so that the termination can prevent radiation to protect the HTS tape.

[0033] The method may include integrating additional components in the termination. The additional components may be integrated into the termination by applying the component to a layer of foil, applying an additional layer of foil over the component, and joining the metal foil to the component by ultrasonic welding or by joining the metal foil to the layer of metal foil around the component to secure the component in place. The component may be a fiber optic cable. According to another example, the component may be a sensor. Integration of one or more sensors in the termination may enable monitoring of the termination. Multiple components may be integrated into the termination.

[0034] The method may include applying a coating to one or more of the HTS tape and / or metal foil. The coating may be applied to a surface of an end portion of the HTS tape. The coating may improve the interface between the HTS tape and a first layer of metal foil. The coating may be between the HTS tape and a terminating second HTS tape. The coating may also be provided on an exposed surface of the HTS tape. The coating may be a metal nanoparticle paste. For example, the coating may be a silver nanoparticle paste. According to other examples, the coating may be a copper nanoparticle paste or a gold nanoparticle paste.

[0035] According to another example, a metal foil layer can be applied along the length of an HTS tape or along the length of multiple HTS tapes, thereby forming a cable in which one or more HTS tapes are coated with a metal.

[0036] According to another example, a method for manufacturing a termination for a high temperature superconducting (HTS) tape by additive manufacturing using a moving sonotrode is provided, the method including the steps of building up a first metal layer from a plurality of metal foils bonded together, forming a first passage in the first metal layer, providing the first HTS tape within the passage, providing an upper metal foil over the first HTS tape, and bonding the first HTS tape and the upper metal foil within the first passage using ultrasonic welding.

[0037] The passages may be shallow passages. The passages may be formed by CNC milling.

[0038] The upper foil may be wider than the passageway.

[0039] The method may include bonding an additional metal foil onto the top foil to form a second metal layer. The method may include forming a second passage in the second metal layer to receive a second HTS tape. The second HTS tape may be provided in the second passage, and the method may further include providing an additional metal foil to the second HTS tape and bonding the second HTS tape and the additional metal foil in the second passage using ultrasonic welding.

[0040] These steps can be repeated to form a third, fourth, fifth, etc. layer. That is, the method can include bonding an additional metal foil onto the top foil to form an additional metal layer. The method can include forming additional vias in the additional metal layer to receive an additional HTS tape. An additional HTS tape may be provided in the additional vias, and the method can further include providing an additional metal foil to the additional HTS tape and joining the additional HTS tape and the additional metal foil in the additional vias using ultrasonic welding.

[0041] The first metal layer and / or the second metal layer may be a copper layer, and the top metal foil and / or the further metal foil may be a copper foil.

[0042] The moving sonotrode can be a rolling sonotrode. The sonotrode can be configured to roll along the upper metal foil in the lengthwise direction of the tape while imparting ultrasonic motion to bond the upper metal foil and the first HTS tape into the passages. Bonding of the tape into the passages can be achieved by multiple passes of the sonotrode over the metal foil covering the HTS tape in the passages.

[0043] As the sonotrode rolls along the tape or foil, ultrasonic motion can be imparted through motion in a direction transverse to the rolling direction. The transverse motion can have an amplitude of 25 μm to 50 μm for joining to copper. The transverse motion can have an amplitude of 30 μm to 50 μm for joining to copper. By way of example, the transverse motion can have an amplitude of 36 μm to 42 μm for joining to copper.

[0044] The sonotrode can provide a downward force to the foil or tape. The force applied can depend on the material properties or width of the foil or tape and the size of the sonotrode.

[0045] The metal foil can have a thickness of 100 μm to 150 μm. The HTS tape can be a rare earth barium copper oxide HTS tape.

[0046] By way of example, an HTS tape may be formed from an HTS layer, a metal stabilizer layer, and a substrate. The HTS layer in the tape may have a thickness of up to 5 μm, for example, from 1 μm to 5 μm, such as 1.6 μm. The metal stabilizer layer in the tape may have a thickness of up to 50 μm, for example, from 10 μm to 30 μm. The substrate in the tape may have a thickness of 15 μm to 100 μm, for example, 50 μm, preferably from 40 μm to 60 μm.

[0047] The method may further include creating cooling passages in the termination foil layer. For example, the method may include creating cooling passages that extend across the HTS tape. The cooling passages may be configured to pass a cooling fluid through them to cool the HTS tape.

[0048] The cooling passages can be created by an additive method, which can include placing metal foil in selected areas and leaving other areas free of metal foil, thereby creating passages between the stacked metal foils.

[0049] According to another example, the cooling passages may be created by a subtractive process. Creating the cooling passages may include removing a portion of a built-up metal layer to create features in the metal before applying additional successive layers of foil. Removing a portion of the metal may include using a computer numerically controlled (CNC) milling process to create features in the metal layer.

[0050] The metal foils can be the same metal or different metals. By using different metals, composite terminations can be created.

[0051] The upper metal foil in contact with the HTS tape can be a metal with increased bonding to the HTS tape, and the subsequent metal foil forming the second metal layer can be a different metal. For example, the upper metal foil can be copper, and the metal foil forming the second metal layer can be aluminum. According to another example, the terminations can be formed from foils of different grades of aluminum, where the upper metal foil can be a first grade of aluminum with increased bonding to the HTS tape, and the metal foil forming the second metal layer can be formed from another grade of aluminum.

[0052] The plurality of metal foils forming the first and second metal layers can be formed from a plurality of first metal foils and a plurality of second metal foils. The second metal foil can have different properties than the first metal foil. The first metal foil can form the majority of the termination. The first metal foil can be copper or aluminum. The second metal foil can provide functional properties of the termination, thereby optimizing the material properties of the termination.

[0053] The second metal foil can be a structural foil and can be a stronger metal than the first metal foil. For example, the second metal foil can be a steel foil. A stronger second metal foil can increase the strength of the termination.

[0054] The second metal foil may be a metal having a different coefficient of thermal expansion than the first metal foil, and may be selected to adjust the coefficient of thermal expansion of the termination.

[0055] The second metal foil can be a metal having a different conductivity than the first metal foil. The second metal foil may be selected to tailor the conductivity of the termination. In some examples, the second metal foil can form an insulating or partially insulating layer in the termination. In other examples, the second metal foil can provide a highly conductive path to reduce termination resistance. In other examples, the second metal foil can provide a means to reduce AC losses in the termination.

[0056] The second metal foil can be a metal that can prevent radiation, so that the termination can prevent radiation to protect the HTS tape.

[0057] The method may include integrating an additional component in the termination. The additional component can be integrated into the termination by applying the component to one of the foils forming the first or second metal layer, applying an additional layer of foil over the component, and joining the metal foil to the component by ultrasonic welding or joining the metal foil to the layer of metal foil around the component to secure the component in place. The component can be a fiber optic cable. According to another example, the component can be a sensor. The integration of one or more sensors in the termination can enable monitoring of the termination. Multiple components can be integrated into the termination.

[0058] The method may include applying a coating to one or more of the HTS tape and / or metal foil. The coating may be applied to a surface of an end portion of the HTS tape. The coating may improve the interface between the HTS tape and a first layer of metal foil. The coating may be between the HTS tape and a terminating second HTS tape. The coating may also be provided on an exposed surface of the HTS tape. The coating may be a metal nanoparticle paste. For example, the coating may be a silver nanoparticle paste. According to other examples, the coating may be a copper nanoparticle paste or a gold nanoparticle paste.

[0059] According to another aspect, a termination for an HTS tape is provided, the termination comprising multiple layers of metal foil bonded to an end portion of the HTS tape, the multiple layers being bonded to one another.

[0060] While several preferred embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims.

[0061] For a better understanding of the present invention, and to show how embodiments thereof may be carried into effect, reference will now be made, by way of example only, to the accompanying diagrammatic drawings in which: [Brief explanation of the drawings]

[0062] [Figure 1] FIG. 10 is a diagram of an example method for fabricating terminations for HTS tapes by additive manufacturing. [Figure 2A] 1 is a diagram of a termination at a stage of manufacture. [Figure 2B] 1 is a view of the termination at a stage of manufacture. [Figure 2C] 1 is a view of the termination at a stage of manufacture. [Figure 3] FIG. 1 is a perspective view of an example termination. [Figure 4] 1 is a cross-sectional view of an example termination for a cable. [Figure 5] FIG. 10 is a cross-sectional view of another example end where two tapes are connected. [Figure 6] FIG. 10 is a cross-sectional view of another example termination in which two different metal foils are used. [Figure 7] FIG. 10 is a cross-sectional view of another example termination with embedded components. [Figure 8] FIG. 1 is a cross-sectional view of an example cable with HTS tape. [Figure 9] FIG. 1 is a diagram of layers of an example HTS tape. [Figure 10A] FIG. 10 is a diagram of an example setup for measuring critical current and resistance in an example termination tie. [Figure 10B] FIG. 10 is a diagram of an example setup for measuring critical current and resistance in an example termination connection. [Figure 11A] 10 is a graph of measured current and resistance for an example termination connection. [Figure 11B] 10 is a graph of measured current and resistance for an example termination connection. DETAILED DESCRIPTION OF THE INVENTION

[0063] Ultrasonic welding additive manufacturing, also referred to herein as ultrasonic additive manufacturing, involves building three-dimensional shapes by sequentially applying layers of metal foil and bonding the layers to the layers below using ultrasonic welding. An ultrasonic welding additive manufacturing machine typically includes a print head, also referred to as a rolling sonotrode, configured to apply a layer of metal foil to a surface and apply ultrasonic motion to the layer of metal foil to bond the metal foil to the surface. The surface can be the layer below the metal foil. The rolling sonotrode can be configured to apply additional layers of metal foil, bonding each additional layer to the layer below. This process is repeated until a three-dimensional object is built up from multiple metal layers. An example method described herein uses ultrasonic additive manufacturing to create terminations for HTS tape by bonding metal foil to the HTS tape and then building up additional layers of metal foil to create a three-dimensional termination. This allows for fabrication of the termination while the HTS tape is kept at a lower temperature and welded for a shorter period of time, thereby limiting oxygen migration from the HTS tape. Thereby, terminations can be prepared by a highly controllable and repeatable method that is scalable for the manufacture of terminations for cables with large numbers of HTS tapes.

[0064] 1 , an example method 10 for manufacturing a termination for an HTS tape includes applying an end portion of the HTS tape to a substrate in step S12. The method includes bonding the HTS tape to the substrate using ultrasonic welding in step S14. The method further includes applying a first layer of metal foil to the top surface of the HTS tape in step S16 and bonding the first layer of metal foil to the HTS tape using ultrasonic welding in step S18. The method may further include applying and welding additional layers of metal tape and / or HTS tape until the termination is built up to the appropriate size.

[0065] 2A-2D show cross-sectional views of a termination as method 10 of FIG. 1 is performed. FIG. 2A shows an end portion 22 of HTS tape 24 applied to a substrate. FIG. 2B shows the configuration after HTS tape 24 has been bonded to substrate 23, with the bond between end portion 22 and substrate 23 indicated by a dashed line. FIG. 2C shows a first metal foil layer 26 applied to the top surface of HTS tape 24. FIG. 2D shows termination 20 when layer 26 has been bonded to HTS tape 24 by ultrasonic welding, with the bond between layer 26 and HTS tape 24 indicated by a dashed line. While termination 20 in FIG. 2D shows only one HTS tape and one layer of metal foil, it will be understood that many more layers of metal foil and / or HTS tape can be applied and welded together to build up the layers into a three-dimensional termination.

[0066] Although only one foil is shown in Figure 2A, according to another example, each layer is formed from multiple metal foils, such as metal foil strips, as shown in Figure 3. The metal foil layers have an area that is larger than the area of ​​the end portion 22 of the HTS tape 24, such that the length and width of the terminations are larger than the end portion 22 of the HTS tape.

[0067] During manufacture of the termination, the rolling sonotrode is configured to apply strips of metal foil to the HTS tape 24 in the longitudinal direction of the HTS tape 24, indicated as the x-direction in Figure 3. The rolling sonotrode is configured to roll in the x-direction over the metal foil strip 26A to bond the metal foil strip to the HTS tape 24. The rolling sonotrode is configured to apply additional metal strips 26B, 26C beside the first strip of metal foil in the z-direction, indicated in Figure 3, to bond the additional strips to the substrate 23. The rolling sonotrode can then apply and bond additional metal foil strips and / or tapes to the first layer 26 such that the termination is built up in the y-direction.

[0068] According to an example, the method 10 further includes creating cooling passages in the terminal metal foil layer, the cooling passages extending across the HTS tape. The passages are created by an additive method by placing pieces or strips of metal foil in selected areas to create passages between stacked metal foils and leaving other areas free of metal foil. In another example, the passages are created by a subtractive method by removing portions of the stacked metal layers to create passages in the metal before applying additional successive layers of metal foil. The portions of the metal layers are removed using computer numerically controlled milling.

[0069] According to an example, the method further includes applying a coating to the top and / or bottom surfaces of the HTS tape to improve the interface between the HTS tape and the first layer of metal foil and / or the interface between the HTS tape and the substrate. The coating can be a metal nanoparticle paste. For example, the coating can be a silver nanoparticle paste. In another example, the coating can be a gold nanoparticle paste or a copper nanoparticle paste.

[0070] According to an example, method 10 also includes embedding one or more additional tapes within termination 20 by applying additional tapes to the foil layer and joining the additional tapes to the foil layer by ultrasonic welding. As shown in FIG. 4 , according to an example, termination 120 includes multiple HTS tapes 124, 130, 132 embedded within termination 20, with one or more layers of foil 126, 128, 134 joined to HTS tapes 124, 130, 132 between the layers of HTS tape by ultrasonic welding. A foil layer 136 is also provided at the distal ends of tapes 124, 130, 132 such that the distal ends of the HTS tapes are embedded within termination 20. While not shown, the distal end of tape 24 shown in FIG. 2 may also be embedded within termination 20.

[0071] By way of example, the top surface of the HTS tape may be exposed, and the termination may be used as a remountable connection, where the exposed surface of the HTS tape can interface with the exposed surface of the HTS tape of the other termination.

[0072] As shown in Figures 2 and 4, according to some examples, terminations are formed at the distal ends of one or more HTS tapes. According to other examples, terminations link the distal ends of two HTS tapes or cables so that the HTS tapes can be spliced ​​together. As shown in Figure 5, according to examples, the method includes joining the second end portion 244 of the second HTS tape 246 to the top surface of the first end portion 222 of the first HTS tape 224 by ultrasonic welding before laying up an additional layer 228 of metal foil to form termination 220. This allows the first HTS tape 224 and the second HTS tape 246 to be in direct contact at termination 220. In another example, one or more layers of metal foil may be provided between the first HTS tape 224 and the second HTS tape 246, which are ultrasonically welded to each other and to the first HTS tape 224 and the second HTS tape 246 so that the first tape and the second tape are not in direct contact with each other.

[0073] 2-5, the metal foil layers making up the terminations can be the same metal, such as copper or aluminum, or can comprise different metals. In FIG. 6, a first metal is used in a first metal foil layer 326 that is applied to and bonded to HTS tape 324, and a second, different metal is used in a further metal foil layer 328 that is applied to and bonded to first metal foil layer 326. By way of example, first metal foil layer 326 can comprise a first grade of aluminum, and the second metal foil layer can comprise a second grade of aluminum.

[0074] In other examples, the second metal foil may form another layer of the termination or may be interspersed within one or more layers of the first metal foil. For example, the second metal foil may be a structural foil formed from a metal stronger than the first metal foil. In other examples, the second metal foil may be formed from a metal having a different thermal expansion coefficient than the first metal foil. In other examples, the second metal foil may be formed from a metal having a different electrical conductivity than the first metal foil. In other examples, the second metal foil may be a metal capable of blocking radiation. In other examples, terminations may be formed that include a combination of two or more structural foils, a blocking foil, a foil for adjusting the thermal expansion coefficient of the termination, and a foil for adjusting the electrical conductivity of the termination.

[0075] 7, termination 420 further includes a component 448 embedded therein. The component may be a sensor or a fiber optic cable. The method may include applying component 448 directly to HTS tape 424, applying additional metal foil layers 426, 428, 430 around and over component 448, and joining the metal foil layers together by ultrasonic welding.

[0076] FIG. 8 shows a cross-sectional view of an example cable 500 manufactured using additive manufacturing and ultrasonic welding. The cable 500 shows multiple HTS tapes 502, 504, 506 with metal foil layers 508, 510, 512, 514 provided between and around the tapes, and the metal foil layers 508, 510, 512, 514 are bonded to the HTS tapes 502, 504, 506 by ultrasonic welding. While FIG. 8 shows only one layer of metal foil between the HTS tapes, in other examples, multiple layers of metal foil may be provided between the HTS tapes and bonded together by ultrasonic welding. In other examples, there may be no metal foil layer between the HTS tapes, such that the HTS tapes are directly bonded together.

[0077] Figure 9 shows an example of layers of an HTS tape that may be used in the method of claim 1. In the configuration shown in Figure 9, the underlayer 602 is a copper layer having a thickness of approximately 20 μm, a silver layer 604 having a thickness of approximately 2 μm is provided on the copper layer 602, a Hastelloy substrate 606 having a thickness of approximately 50 μm is provided on the silver layer 604, a buffer stack 608 having a thickness of 0.2 μm is provided on the Hastelloy substrate 606, a REBCO HTS layer 610 is bonded to the buffer stack 608, a further silver layer 612 having a thickness of approximately 2 μm is provided on the HTS layer 610, and a further copper layer 614 having a thickness of approximately 20 μm is provided on the silver layer 612. The tape has a width of approximately 4 mm and a thickness of approximately 90 μm. [Example]

[0078] Multiple samples of termination joints were fabricated by additive manufacturing ultrasonic welding using the method of FIG. 1. In the configuration shown in FIGS. 10A and 10B, each HTS tape comprises an HTS layer 702, 704 and a Hastelloy substrate 706, 708. The HTS tape may comprise additional layers as described throughout this description. The two HTS tapes in the joint are joined together via a copper layer 710. The length of the joint for each of the samples is 3 cm.

[0079] The ultrasonic additive manufacturing machine was a 9 kW SonicLayer® 4000 at 20 kHz with a sonotrode made from maraging 350 steel, with a diameter of 98 mm and a width of 27 mm. The REBCO HTS tape was Superpower SCS4050-AP tape with a minimum critical current of 82 A at a self-field of 77 K. The metal foil was C101 copper foil with a thickness of 127 μm. The sonotrode welding amplitude and downforce varied for the samples, as shown in Table 1. Samples S1 and S2 underwent two welding passes, while the remaining samples underwent one welding pass. All samples had two welding passes applied to the sample when joining the tape to the passageway: one at half downforce and the other at full downforce.

[0080] [Table 1]

[0081] The critical current was measured for each of the samples using the configuration shown in FIG. 10A. Measurements were taken at 77 K with a self-field ramp rate of 5 A / s. Two current leads were attached to the junction area, and an additional removable voltage tap was attached directly to the junction between the current leads to measure the voltage. A 300 A-50 μV shunt was connected in series with the sample and used to measure the current in the sample.

[0082] The resistance of the junction was measured using the setup shown in Figure 10B. Measurements were taken at 77 K with a self-field ramp rate of 5 A / s. Current was applied to the brass terminals of the sample holder at the distal end of the HTS tape. The voltage between the soldered voltage taps was measured. A shunt 300 A-50 μV was connected in series with the sample and used to measure the current in the sample.

[0083] FIG. 11A is a graph of current versus electric field for sample S1. Result 802 is the critical current measurement using the configuration of FIG. 10A with the inner voltage tap. Result 804 is the measurement used to determine resistance with the configuration of FIG. 10B with the outer voltage tap. As shown in FIG. 11A, a sharp transition in the sample's electric field current occurs at 90 A, indicating the critical current value for the HTS tape at joint S1.

[0084] 11B is a graph of resistance versus current for sample S1. As shown in result 806 in FIG. 11B, at currents below 90 A, the resistance was small, approximately 0.1 μΩ. At higher currents, the resistance increased.

[0085] 11A and 11B show that the use of ultrasonic additive manufacturing allows for the fabrication of HTS tape terminations that maintain the low resistance of the HTS tape at the terminations without significant current degradation.

[0086] Table 2 shows the measured critical current Ic and resistance values ​​for various samples. Resistance R1 is the resistance value at the critical current measured at the inner current tap shown in Figure 10A, resistance R2 is the resistance value at 200 A measured at the inner current tap shown in Figure 10B, and resistance R3 is the resistance value at 60 A measured at the outer current tap shown in Figure 10B.

[0087] [Table 2]

[0088] Each of samples S1, S2, S3, and S4 shows that the critical current is not significantly reduced from the value of the tape prior to the 90 A joint measurement. Furthermore, samples S1, S2, S3, and S4 indicate that the low resistance of the tape at the joint is maintained. The higher resistance value for R3 is believed to be due to the presence of some non-superconducting parts of the joint between the outer taps.

[0089] As shown in Table 2, the critical current was found to not vary significantly between the different welding amplitudes used in producing the samples. More consistent resistance and critical current values ​​were found across samples with larger downforces.

[0090] It is to be understood that various combinations of optional features are described herein, and that the described features can be combined in any suitable combination. In particular, the features of any one example embodiment can be combined with the features of any other embodiment as appropriate, except where mutually exclusive. Throughout this specification, the terms "comprising" or "comprises" mean the inclusion of the specified elements, but do not exclude the presence of other elements.

[0091] In connection with this application, attention is directed to all documents and literature filed contemporaneously herewith or previously filed herewith and which are hereby open to public inspection, and the contents of all such documents and literature are incorporated herein by reference.

[0092] All of the features disclosed in this specification (including any accompanying claims, abstract, and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations in which at least some of such features and / or steps are mutually exclusive.

[0093] Each feature disclosed in this specification (including any accompanying claims, abstract, and drawings), unless expressly stated otherwise, may be replaced by alternative features serving the same, equivalent, or similar purpose. Thus, unless expressly stated otherwise, each feature disclosed is merely one example of a generic series of equivalent or similar features.

[0094] The invention is not limited to the details of the foregoing embodiments, but extends to any novel or any novel combination of features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel or any novel combination of method or process steps so disclosed. [Explanation of symbols]

[0095] 20 Termination 22 End part 23 Circuit Board 24 HTS Tape 26 First metal foil layer 26A, 26B, 26C Metal foil strips 120 Termination 124, 130, 132 HTS tapes 126, 128, 134, 136 foil layer 220 Termination 222 first end portion 224 First HTS Tape 228 Further Layers of Metal Foil 244 Second end portion 246 Second HTS Tape 324 HTS tape 326 First metal foil layer 328 Further Metal Foil Layers 420 Termination 424 HTS Tape 426, 428, 430 Additional metal foil layers 448 Components 500 Cable 502, 504, 506 HTS tapes 508, 510, 512, 514 Metal foil layer 602 Lower layer, copper layer 604 Silver layer 606 Hastelloy substrate 608 Buffer Stack 610 REBCO HTS layer 612 More Silver Layers 614 More copper layers 702, 704 HTS layer 706, 708 Hastelloy substrate 710 copper layer

Claims

1. 1. A method of manufacturing a termination for a high temperature superconducting (HTS) tape by additive manufacturing using a moving sonotrode, the method comprising: applying an end portion of a first HTS tape to a substrate; bonding the HTS tape to the substrate using ultrasonic welding; applying a first layer of metal foil to the HTS tape; bonding the first layer of metal foil to the HTS tape using ultrasonic welding; A method comprising:

2. 10. The method of claim 1, comprising applying one or more further layers of metal foil and / or one or more HTS tapes to the first layer of metal foil, and joining the further layers and / or the HTS tapes to the first layer by ultrasonic welding.

3. The method of claim 2 further comprising creating cooling passages in one or more of the foil layers of the termination.

4. 4. The method of claim 3, wherein creating the cooling passages includes placing metal foil in selected areas and leaving other areas free of metal foil, the passages being formed between stacked metal foils in the areas where no metal foil is applied.

5. 4. The method of claim 3, wherein creating the cooling passages comprises removing a portion of the metal foil layer to create the passages in the metal prior to applying a further successive layer of foil, and wherein removing the portion of the metal comprises using a computer numerically controlled milling process.

6. 6. The method of claim 2, wherein the layer of metal foil comprises a first metal foil and at least one further metal foil, the at least one further metal foil having different material properties than the first metal foil.

7. The method of claim 6 , wherein the at least one additional metal foil is a structural foil and is a stronger metal than the first metal foil.

8. 8. The method according to claim 6 or 7, wherein the at least one further metal foil has a different coefficient of thermal expansion and / or a different electrical conductivity than the first metal foil.

9. 9. The method of claim 6, wherein the at least one further metal foil is a metal configured to block radiation.

10. 10. The method of any one of claims 2 to 9, wherein the first layer of metal foil is formed from a first metal and the further layer of metal foil is formed from a second metal, the first metal being different from the second metal and capable of increased bonding with the HTS tape compared to the second metal.

11. 11. The method of claim 1, further comprising the steps of: integrating at least one component at the termination by applying the component to the layer of foil; applying a further layer of foil over the component; and joining the metal foil to the component by ultrasonic welding.

12. The method of claim 11 , wherein the at least one component is a fiber optic cable and / or a sensor.

13. 13. The method of claim 1, further comprising applying a coating to the HTS tape and / or the first layer of metal foil before bonding the first layer of metal foil to the HTS tape.

14. The method of claim 12 , wherein the coating is a silver nanoparticle paste, a gold nanoparticle paste, or a copper nanoparticle paste.

15. 15. The method of claim 1, wherein bonding the metal foil to the HTS tape comprises rolling the sonotrode along the foil and applying an ultrasonic motion in a direction transverse to the rolling direction, the foil being a copper foil, and the transverse motion having an amplitude of 25 μm to 50 μm.

16. 16. The method of any one of claims 1 to 15, wherein the foil is a copper foil, the foil having a thickness of from 100 μm to 150 μm.

17. 1. A method of manufacturing a termination for a high temperature superconducting (HTS) tape by additive manufacturing using a moving sonotrode, the method comprising: building up a metal layer from a plurality of metal foils bonded together; forming a via in the metal layer; providing an HTS tape into the passage; providing a top metal foil over the HTS tape; bonding the HTS tape and the top metal foil into the vias using ultrasonic welding; A method comprising:

18. The method of claim 17, wherein the passages are formed by computer numerically controlled CNC milling.

19. 19. The method of claim 17 or 18, wherein the top layer of metal foil is wider than the passages.

20. bonding a further metal foil onto the top metal foil to form a top metal layer; forming additional vias in the top metal layer to receive additional HTS tapes; providing the further HTS tape in the further passage; providing a further metal foil to the further HTS tape and joining the further HTS tape and the further metal foil at the further passage by ultrasonic welding; 20. The method of any one of claims 17 to 19, further comprising:

21. A termination comprising a high temperature superconducting (HTS) tape bonded to a substrate, the termination comprising multiple layers of metal foil bonded together and to the HTS tape.

22. The termination of claim 21 further comprising a cooling passage.

23. 23. The termination of claim 21 or 22, wherein the plurality of metal foil layers are formed from two or more different types of metal.

24. 24. The termination of any one of claims 21 to 23, further comprising at least one fiber optic cable and a sensor embedded within the metal.

25. 1. A method for producing a cable of HTS tapes by additive manufacturing, said method comprising: joining a plurality of HTS tapes together by ultrasonic welding; The method wherein the plurality of HTS tapes are directly bonded together or one or more layers of metal foil are provided between the plurality of HTS tapes and bonded to the HTS tapes.

26. 1. A cable comprising a plurality of HTS tapes, said HTS tapes being either directly bonded together or separated by one or more layers of metal foil, said layers of metal foil being bonded together and to said HTS tapes.

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