Process, system, and device for metal filling of a high temperature superconductor cable

Abstract

The technology described herein relates to systems and methods for obtaining high temperature superconducting (HTS) cable assemblies and filling the HTS cable assemblies with molten metal, such as solder.

Description

Technical Field

[0001] One embodiment of the present invention relates to a process, system, and device for metal filling of high temperature superconductor cables, for example.

Background Art

[0002]

[0001] High temperature superconductor (HTS) materials can carry large amounts of current with low losses.

[0002] Some known HTS cables and magnets can be fabricated in a manner similar to that used for low temperature superconductor (LTS) cables, i.e., without using any solder around the HTS material. For example, if the HTS material is an HTS tape or a stack of HTS tapes, the HTS cable or magnet is fabricated without any solder around the HTS tape or HTS tape stack.

[0003]

[0003] Other HTS cables and magnets can be fabricated using a soldering process. Takayasu, for example, describes a soldering process technique for a straight twisted stacked tape cable (TSTC). The HTS tape stack is encapsulated within a conductor, and the conductor is manually passed horizontally through a 60% Sn - 40% Pb molten bath in its straight configuration. In this technique, it is necessary to bend the cable after soldering. However, such bending after soldering results in degradation of the superconducting properties of the HTS material (i.e., degradation of the superconducting properties of the HTS tape stack).

[0004]

[0004] One technique for soldering a LTS cable having a so-called cable-in-conduit conductor (CICC) configuration is described by P. Bauer, P. Bruzzone et al. (Solder-Filling of a CICC cable For The EFDA Dipole Magnet, AIP Conference Proceedings 986, 151 (2008); see https: / / doi.org / 10.1063 / 1.2900339). In this technique, the CICC in which the low-temperature superconductor is disposed is evacuated, and the solder is pressurized with argon to initiate the flow of solder within the CICC.

Summary of the Invention

Problems to be Solved by the Invention

[0005] One embodiment of the present invention relates to a process, system, and device for metal filling of a high-temperature superconducting cable, for example.

Means for Solving the Problems

[0006]

[0005] According to one aspect of the concepts, processes, systems, devices, and techniques described herein, the method includes at least partially filling at least one channel of a high-temperature superconductor (HTS) cable assembly with molten metal, the HTS cable assembly comprising the HTS and at least one channel, and operating one or more cooling devices to cool the molten metal within the at least one channel.

[0007]

[0006] It should be understood that the individual elements of the different embodiments described herein can be combined to form other embodiments not specifically recited above. The various embodiments described in the context of a single embodiment can be provided separately or in any suitable sub-combination. It should also be understood that other embodiments not specifically described herein are also within the scope of the following claims.

[0008]

[0007] This method has the following features: The HTS cable assembly comprises a former in which at least one channel is disposed; the former comprises four channels each comprising HTS, and the method includes the step of at least partially filling the four channels of the former; the HTS cable assembly further comprises a jacket disposed around the former; completely filling at least one channel of the HTS cable assembly; the step of at least partially filling at least one channel of the HTS cable assembly with molten metal includes heating the HTS cable assembly and applying pressure to the molten metal to force it through at least one channel of the former; the molten metal is held by a container, and applying pressure to the molten metal includes applying pressure to the molten metal within the container; the HTS cable assembly comprises a tube having a wall defining at least one channel and at least partially filling at least one channel of the tube with molten metal; the HTS cable assembly comprises a stack of HTS tapes; the molten metal includes PbSn solder or a lead-tin solder alloy; depositing flux within at least one channel prior to at least partially filling the at least one channel with molten metal; the step of operating one or more cooling devices includes gradually cooling the HTS cable assembly towards the source of the molten metal, and may include one or more of the foregoing independently or in combination with one or more other features to be included.

[0009] According to further aspects of the concepts, processes, systems, devices, and techniques described herein, a vacuum impregnation (VPI) station for filling a cable assembly including a high temperature superconducting (HTS) material with molten metal, the VPI station comprising: (a) a can configured to hold a source of molten metal, (b) one or more heaters arranged to heat the HTS cable assembly, the HTS cable assembly comprising at least one of a tube or former in which at least one channel is formed or provided separately, and having an HTS material in which at least one of at least one channel of the tube or former is disposed, one or more heaters, and (c) pressure applying means coupled to the can for applying pressure to the molten metal in the can so as to push the molten metal through at least one channel of the tube or former from the can.

[0010]

[0009] The VPI station may include, independently or in combination with one or more other features to be included, one or more of the following features: a siphon coupled to the can and disposed at a height greater than the height of the molten metal in the can to inhibit flow of molten metal from the can when the pressure applying means is not operative; a plurality of contact sensors configured to monitor flow of metal into at least one channel of the tube or former from the can, the one or more heaters being disposed in contact with the can; an outlet tube coupled to the can, at least one of the one or more heaters being disposed adjacent to the outlet tube; a waste tank disposed to collect molten metal flowing through at least one channel of the tube or former and exiting from the at least one channel; and a U-bend coupled to the waste tank to inhibit molten metal from flowing from the waste tank and back into at least one channel of the tube or former.

[0011]

[0010] According to still further aspects of the concepts, processes, systems, devices, and techniques described herein, a dispenser for channeling molten metal into and / or out of an N-channel former, the dispenser comprising an elongated member having a mortar-shaped end, a smooth shank portion, and a twisted groove portion in which N grooves are provided, the twisted groove portion having a flare shape with a diameter that increases from a first end of the twisted groove portion to a second end of the twisted groove portion, the N grooves of the twisted groove portion being configured to direct molten metal into the channels of the N-channel former.

[0012]

[0011] In an embodiment, the dispenser may include one or more of the following features: the first end of the twisted groove portion has a diameter that substantially matches the diameter of one end of the smooth shank portion, and the second end of the twisted groove portion has a diameter that substantially matches the diameter of the N-channel former, either independently or in combination with one or more other features to be included.

[0013]

[0012] According to yet another aspect of the concepts, processes, systems, devices, and techniques described herein, a method includes obtaining a high temperature superconducting (HTS) cable assembly, bending the HTS cable assembly, heating the HTS cable assembly, and filling the HTS cable assembly with molten metal.

[0014]

[0013] In this particular arrangement, a method for manufacturing a high temperature superconducting (HTS) cable is provided. In an embodiment, the step of filling the HTS cable with molten metal includes using a vacuum impregnation (VPI) process to fill the HTS cable with molten metal.

[0015] According to yet another aspect of the concepts, processes, systems, devices, and technologies described herein, a method for filling a high temperature superconducting (HTS) cable with a molten metal includes the steps of bending or otherwise forming an HTS cable assembly into a desired shape and filling the HTS cable assembly with the molten metal.

[0016]

[0015] In this particular arrangement, a process for filling a cable containing a superconducting material with a molten metal is provided. With this technique, the cable can be bent, wound, molded, formed, or otherwise fabricated into a desired shape (e.g., the final shape of a magnet, current lead, or other structure) before or simultaneously with the soldering of the cable. In embodiments, the HTS cable may be provided as a tape-in-conduit cable.

[0017]

[0016] Since the cable can be shaped before or during the soldering process, a robust cable suitable for many applications is provided. Since the cable is shaped before or during the molten metal filling process, no cable deformation is required after the metal filling has cooled and solidified. Thus, cable degradation (and in particular, degradation of the HTS material within the cable) resulting from deforming the cable after the metal filling process does not occur. This results in a robust cable.

[0018]

[0017] In embodiments, the molten metal is solder. In embodiments, the solder may be provided as a tin-lead solder. In embodiments, the solder may be provided as Sn 60 Pb 40 solder.

[0019]

[0018] In embodiments, the superconducting material may be provided as a high temperature superconducting (HTS) tape. In embodiments, the HTS tape may be provided as a rare earth barium copper oxide (REBCO) tape. In embodiments, the HTS material may be provided as any of YBCO, BSCCO, or MgB2 tape.

[0020]

[0019] In an embodiment, the cable may comprise a former having one or more channels provided therein, and an HTS tape is disposed within the channel. In an embodiment, the channel may be provided having a helical shape (or helical pattern) along the length of the cable. In an embodiment, the cable may comprise one or more cooling channels.

[0021]

[0020] According to still further aspects of the concepts, processes, systems, devices, and techniques described herein, a vacuum impregnation (VPI) system for filling an HTS cable with molten metal, including a series of sensors for measuring temperature at multiple points, is described. Using these sensors for monitoring and control, the process has been developed with a time - temperature profile that enables filling of the HTS cable with molten metal without degrading the HTS material.

[0022]

[0021] According to still further aspects of the concepts, processes, systems, devices, and techniques described herein, a method for filling an HTS cable with molten metal includes bending a cable assembly in which an HTS material is disposed, and filling the cable assembly with molten metal. In an embodiment, the cable assembly may comprise a tube (or jacket) having one or more channels provided therein, and the HTS material may comprise an HTS tape. Thus, the cable assembly may have one or more HTS tapes disposed in corresponding ones of additional channels of the tube before filling the cable assembly with molten metal. In an embodiment, the cable assembly may comprise a former having one or more channels provided therein, and the HTS material may comprise an HTS tape disposed in the channels of the former. Thus, one or more HTS tapes (e.g., an HTS tape stack) may be disposed in corresponding ones of additional channels of the former.

[0023]

[0022] In an embodiment, the cable assembly can be bent before filling. In an embodiment where the cable assembly comprises one or more HTS tapes disposed in a channel, the size and / or shape of the channel is selected such that in the process of bending the cable assembly before filling it with molten metal, each HTS tape can twist and redistribute within the channel in which it is disposed. The twist and redistribution of the HTS tape within the channel in which it is disposed can be the result of the bending process. Thus, the manner in which the HTS tape twists and redistributes depends at least in part on the shape into which the cable is bent.

[0024]

[0023] Accordingly, in response to a small amount of bending of the cable assembly, the HTS tape may experience only a small amount (or even no) twist and redistribution within the channel. However, in response to a large amount of bending of the cable assembly or a portion of the cable assembly (e.g., into a substantially circular or loop shape), the HTS tape may experience a relatively large amount of twist and redistribution within the channel. Importantly, however, regardless of the amount of bending of the cable assembly, before initiating the metal filling process, the HTS tape is disposed in the channel with little or substantially no stress (e.g., the HTS tape is not subjected to forces from the molten metal during the bending operation, and thus the HTS tape is not deformed by liquid or solid metal during the bending operation). After the metal filling process and subsequent cooling process (during which the metal changes its phase from a liquid state to a solid state), the solid metal secures one or more HTS tapes within each of one or more channels of the former (i.e., the HTS tape is mechanically fixed within the channel by the solid metal).

[0025]

[0024] The foregoing features can be more fully understood from the following description of the drawings.

Brief Description of the Drawings

[0026]

Figure 1A

[0025] A cross-sectional view taken along line A-A of FIG. 1B of a cable formed from a tube, with a high-temperature superconducting (HTS) material disposed therein and filled with metal, according to the concepts described herein.

Figure 1B

[0026] An isometric view of a cable formed from a tube, with a high-temperature superconducting (HTS) material disposed therein and filled with metal, according to the concepts described herein.

Figure 2

[0027] A cross-sectional view of a cable comprising a 4-channel former with an HTS material disposed therein and a jacket disposed around the former.

Figure 3A

[0028] A cross-sectional view of a cable comprising a 4-channel former with an HTS material disposed therein and a jacket disposed around the former.

Figure 3B

[0029] A perspective view of a channeled former.

Figure 3C

[0030] A side view of an HTS cable.

Figure 4A

[0031] A flowchart illustrating a process for filling an HTS cable with metal.

Figure 4B

Figure 5

[0032] A schematic diagram of an exemplary processing station for performing a metal filling process that may be the same or similar to the process described in conjunction with FIGS. 4A and 4B.

Figure 6A

Figure 6B

[0034] A side view of the dispenser of FIG. 6A.

Figure 6C

[0035] An end view of the dispenser of FIG. 6A.

Figure 6D

[0022] A side view of a former with dispensers coupled to each end.

Figure 7

[0037] Schematic diagram of an exemplary processing station for performing a metal filling process of an HTS cable provided by forming a former having first and second dispensers coupled to opposite ends of the former.

Figure 8

[0038] Plot of former temperature versus time during a metal filling process using a system that can be the same as or similar to the processing station of FIG. 5 or FIG. 7.

Figure 9A

[0023] Schematic diagram of a cooling system implemented with a single blower and heaters at both ends of an HTS cable.

Figure 9B

[0040] Plot of temperature versus axial position along the cable for the cooling system of FIG. 9A.

Figure 10A

[0041] Bar graph illustrating a comparison of void distributions in two cables, using a first cable produced using zone cooling as described above in conjunction with FIGS. 9A and 9B, and a second cable produced by cooling at least a portion of the cable uniformly (i.e., using a temperature gradient close to zero).

Figure 10B

Figure 11

[0042] Block diagram of a cooling system comprising one or more movable blowers and one or more heaters having a first heater configured to be in thermal contact with a first end of an HTS cable and a second heater configured to be in thermal contact with a second opposite end of the HTS cable.

Figure 12A

[0024] Schematic diagram of a zone cooling system with a movable baffle.

Figure 12B

[0025] Diagram of a zone cooling system with a movable baffle.

Figure 13

[0026] A wound HTS cable filled with metal and having a central channel, which utilizes one or more end heaters at a first end of the HTS cable and a cold fluid injection system configured to be coupled to a second end of the cable, is a top view of the wound HTS cable.

DETAILED DESCRIPTION

[0027]

[0027] Described herein are processes, systems, devices, and techniques for filling a high temperature superconducting (HTS) cable (i.e., a cable comprising an HTS material) with molten metal. As used herein, the expressions “HTS material” or “HTS superconductor” refer to a superconducting material having a critical temperature above 30°K in its self-field.

[0028]

[0047] For purposes of clarity in this description, it should be understood that reference is sometimes made herein to the use of a particular process, system, or device with a particular type of HTS cable. For example, the solder filling process is described as being applicable to a cable in which an HTS “tape” is disposed within a channel of a former. The HTS tape may comprise multiple layers, one of which comprises the HTS material. In one exemplary embodiment, the HTS tape may comprise a first stabilization layer (e.g., comprising copper), a first overlay layer (e.g., comprising silver), a substrate (e.g., having an electropolished surface), a buffer stack, an HTS material (e.g., comprising a rare earth barium copper oxide superconductor (REBCO) such as yttrium barium copper oxide (YBCO)), a second coating layer, and a second stabilization layer (e.g., comprising the same materials as the first overlay and first stabilization layers, respectively). Other embodiments of HTS tapes having more, fewer, or different layers than the example described above are, of course, possible.

[0029] However, after reading the description provided herein, one of ordinary skill in the art will understand that the concepts, systems, processes, devices, and techniques described herein are not limited to use with a cable having an HTS tape disposed within a former channel. Rather, the concepts, systems, processes, devices, and techniques described herein can be used to fill any molten metal into various different types of HTS cables.

[0030] [000299]That is, the concepts, systems, processes, devices, and techniques described herein can be used with various different types of HTS materials, different types of tubes and / or formers, and with different types or metals (e.g., including different types of solder). Generally, it should be understood that the concepts, systems, processes, devices, and techniques described herein are applicable to any vacuum impregnation (VPI) metal filling (e.g., solder filling of a tube having one or more HTS tapes disposed therein, as described below in conjunction with at least FIGS. 1-7, or solder filling of a channeled former having an HTS tape disposed therein, as described below in conjunction with at least FIGS. 2-7) of any tube in which an HTS material is disposed.

[0031]

[0050] Turning now to a description of some exemplary embodiments, and referring to FIGS. 1A and 1B in which like elements are provided with like reference numerals, cable 10 includes a tube 12 (sometimes referred to as a "jacket") in which a high temperature superconductor (HTS) material 14 is disposed. Tube 12 is filled with a metal (e.g., solder) 16 using a process that may be the same as or similar to the process described below in conjunction with at least FIGS. 4A, 4B, 5, and 7. Tube 12 may comprise or consist of any other material having electrical or mechanical properties that meet the needs / requirements of the application for which the cable is used. In an embodiment, the tube may comprise or consist of, for example, copper. Similarly, the HTS material may comprise or consist of any HTS material having electrical, mechanical, and superconducting properties that meet the needs / requirements of the application for which the cable is used.

[0032]

[0051] In the exemplary embodiment of FIG. 1, HTS material 14 is provided as an HTS tape stack 18 disposed within the tube. HTS tape stack 18 is formed from a plurality of individual tapes 20a - 20N (i.e., a layer of tapes, a plurality of N tape layers grouped, joined, or otherwise combined to form the tape stack, where N is an integer greater than 1). In an embodiment, each layer of HTS tape within HTS tape stack 18 may comprise or consist of a single HTS material, and thus, the HTS tape stack may be referred to as a single material HTS tape stack.

[0033]

[0052] Also, in this illustrative embodiment, the tube or jacket 12 (and thus the cable) is illustrated as having a circular cross-sectional shape. Of course, it should be understood that the tube (or cable) can be provided with any regular (e.g., rectangular, square, triangular) or irregular cross-sectional shape. Further, depending on the application, different tubes / jackets / cables used in the same application may not have the same cross-sectional shape. The particular cross-sectional shape of the tube / jacket / cable can be selected to conform to the needs of the particular application for which the tube / jacket / cable is to be used.

[0034]

[0030] Regardless of the configuration and / or composition of the HTS material, tube, and cable, the process described herein for filling the tube with a molten metal (e.g., solder) results in the metal being disposed around or substantially around all surfaces of the HTS material. In embodiments where the HTS material is provided as an HTS tape stack, it should also be noted that this process also enables the molten metal to fill any spaces (i.e., interstitial spaces) that may exist between the plurality of layers of HTS tape forming the HTS tape stack. Thus, in an embodiment, the metal can contact the interstitial surfaces of the HTS tape layers.

[0035]

[0031] The processes, systems, devices, and techniques described herein can thus be used to fabricate or otherwise produce a cable by, for example, placing the HTS material into conductive tubes of various sizes or disposing it separately (e.g., placing a stack of HTS tapes into a conductive tube as shown in FIG. 1A) for use as, for example, a current lead or for use in the fabrication of a magnet.

[0036]

[0032] In one embodiment, a 100 m long coil tube is filled with molten metal using the processes, systems, devices, and techniques described herein without any HTS tape disposed therein. This embodiment illustrates that the metal filling processes described herein can be used to provide field magnets (e.g., toroidal or poloidal field magnets) suitable for use in fusion applications such as, for example, low-cost, robust, and small (ARC) fusion reactors.

[0037]

[0033] It should be understood, of course, that the processes, systems, devices, and techniques described herein are utilized in fusion applications and any other applications that require HTS cables or magnets. Examples of such applications include, but are not limited to, nuclear magnetic resonance (NMR), magnetic resonance imaging (MRI), magnetic separation, accelerator / high energy physics (HEP) magnets, disposable mixing systems, generators and motors, fault current limiters, RF filtering, superconducting quantum interference device (SQUID) circuits, transmission lines, magnetic energy storage, transformers, and current leads for cryogenic superconducting cables.

[0038]

[0034] Referring now to FIG. 2, cable 30 includes a former 32 in which or separately provided with a plurality of channels 34, here four channels 34a - 34d, with a multi-stack HTS tape 36 disposed within each channel. A jacket 37 is disposed around the former. It should be understood that any number of channels can be used and the particular number of channels to be used is selected to suit the needs of the particular application for which cable 30 is to be used.

[0039]

[0058] In this exemplary embodiment, each of the channels 34a - 34d is provided with a substantially square cross - sectional shape. However, it should be understood that the channels can be provided with any regular (e.g., rectangular, circular, triangular) or irregular cross - sectional shape. Further, depending on the application, each channel may not have the same cross - sectional shape. The particular cross - sectional shape of the channel can be selected to conform to the needs of the particular application for which the cable is to be used.

[0040] [000359]Significantly, the metal filling process described herein can be used to fill a cable, and in particular, any channels provided within a former, with molten metal. Thus, regardless of the configuration and / or composition of the HTS material, the configuration of the former, and / or the configuration of any channels provided within the former, the metal filling process described herein results in the molten metal 38 being disposed around substantially all surfaces of the HTS material within the channel (and ideally, around all surfaces of the HTS material).

[0041]

[0060] Furthermore, when the HTS material is provided as a tape stack, the process also results in molten metal filling any spaces (i.e., interstitial spaces) that may exist between the multiple layers of HTS tapes that form the HTS tape stack. Thus, the molten metal can contact the interstitial surfaces of the HTS tape layers. That is, the metal filling process described herein can fill the space around each HTS tape stack, as well as any space between HTS tape layers comprising the stacked HTS tapes. The metal filling process described herein can also fill the space that may exist between the surface of the former and the surface of the jacket with metal (e.g., molten metal). The metal is then cooled (e.g., using techniques described hereinafter within this specification) to a solid state, resulting in an HTS cable.

[0042]

[0061] The metal filling process described herein can be applied to any cable that comprises a tube (e.g., as illustrated in FIG. 1) and / or a former (e.g., as illustrated in FIG. 2). Further, the metal filling process described herein can be readily used to fill tubes or channels having arbitrary or complex cross-sectional shapes as well as arbitrary or complex patterns with molten metal. Further, the metal filling process described herein can be used to provide cables of any length. In an embodiment, the metal filling process has been used to fill channels on a former greater than 11 meters (m) in length, although the process can be used with channeled formers or tubes having lengths of 100 m or greater.

[0043]

[0062] Referring now to FIGS. 3A - 3C, in which like elements are provided with like reference numerals throughout several views, cable 42 comprises a former 44 (and thus can be referred to as a "channeled former") having a plurality of channels provided therein (most clearly seen in FIG. 3B). In this exemplary embodiment, cable 42 comprises a former 44 having at least one channel 46 corresponding to a cooling channel. In this exemplary embodiment, former 44 comprises a single cooling channel 46 provided along its central longitudinal axis 43. In this example, the central longitudinal axis 43 of the former is aligned with the central longitudinal axis 43 of the cable (FIG. 3C). In an embodiment, the central longitudinal axis of the former may not be aligned with the central longitudinal axis of the cable. In an embodiment, the former may have a plurality of cooling channels provided therein. In an embodiment, one or more cooling channels may be disposed about the longitudinal central axis 43.

[0044]

[0036] The former 44 is also provided with a plurality of channels 48 in which the HTS material 50 can be disposed. In this exemplary embodiment (and as can be seen more clearly in FIG. 3B), the channels are provided in a helical or spiral pattern along the surface of the former along the length of the former with each channel having a generally square cross-sectional shape. In this exemplary embodiment, the HTS material 50 is disposed within each channel 48. In the exemplary embodiments of FIGS. 3A-3D, the HTS material 50 is shown as a multi-tape HTS stack disposed within each channel 48. Other configurations of the HTS material can, of course, also be used. The jacket 52 is disposed around the former.

[0045] [000374]As described above in conjunction with FIG. 2, the particular number of channels, as well as the cross-sectional shape of the channels within the former 44, are selected to conform to the needs of the particular application for which the cable is to be used. In this exemplary embodiment of FIGS. 3A-3C, each channel 50 is provided with a generally square cross-sectional shape and is formed or otherwise provided in a helical pattern along the length of the former (most clearly seen in FIG. 3B). However, as noted, the channels can be provided with any pattern along the length of the former and with any complex shape or geometry (e.g., any regular or irregular cross-sectional shape and pattern).

[0046] Significantly, the metal filling process described herein can be used to fill form channels (e.g., channels of a helical pattern) with a molten metal such as solder. Thus, regardless of the configuration and / or composition of the HTS material, the configuration of the former, the configuration of any channels provided within the former (including but not limited to the cross-sectional shape and pattern of the channels), and the configuration of the jacket, the metal filling process described herein results in the molten metal being disposed around substantially all surfaces of the HTS material within the channels. Further, when the HTS material is provided as a tape stack, the process can also result in a molten metal that fills any spaces (i.e., interstitial spaces) that may exist between the plurality of layers of HTS tape forming the HTS tape stack, such that the molten metal contacts the interstitial surfaces of the HTS tape layers.

[0047]

[0039] Figures 4A and 4B form a flow diagram constituting a series of processing operations that form an illustrative embodiment of the metal filling process according to the concepts described herein. It should be understood that, unless explicitly stated otherwise, the processing operations within the flow diagram are not ordered in the sense that the processing operations listed within the flow diagram can be performed in any convenient order.

[0048]

[0067] Referring now to FIGS. 4A and 4B, an illustrative process for filling a HTS cable (e.g., any of the cables described herein) with a metal (e.g., solder) begins by cleaning the components (e.g., tubes, formers, HTS material, jackets, connectors, etc.) that will be used in the cable undergoing the metal filling process (62). In an embodiment, the cable components can be cleaned using a process involving flushing with an acidic solution and then rinsing with water or other liquid. Details of such a process related to one particular embodiment are described below.

[0049] As one non-limiting cleaning example, a reservoir containing a mixture of water and a cleaning solution (e.g., Citronox acid cleaner) can be coupled to the cable former, and this mixture is pumped or otherwise delivered from the reservoir through the cable former. Thereafter, a rinse fluid (e.g., clean water) can be pumped through the cable former to rinse the cleaning solution from the cable former. In some cases, the cleaning mixture and / or the rinse solution can be heated above room temperature (e.g., 60 °C (140 °F)).

[0050]

[0069] Once the components are cleaned, the HTS material is disposed within the tube (e.g., as shown in FIG. 1) or within the channels of a channeled former (e.g., as illustrated in FIGS. 2-3B) (64). In an embodiment, the HTS material can be provided as an HTS tape stack. In an embodiment, the HTS tape stack can be pre-tin plated to ensure good adhesion between the tapes (e.g., adhesion such that the tapes are firmly bonded to each other). In one embodiment, the HTS tape stack can be pre-tin plated with a metal to be used to fill the cable. In one embodiment, the HTS tape is pre-plated with a lead-tin (PbSn) solder (or a lead-tin solder alloy).

[0051]

[0070] Next, a "loose HTS cable assembly" (or more simply, an "HTS cable assembly") is formed (65). The HTS cable assembly is sometimes referred to as a "loose cable assembly" because at least the HTS material (and possibly other components) is not structurally fixed to a tube or a channeled former, or other structure that forms part of the HTS cable. As used herein, an "HTS cable assembly" or a "loose HTS cable assembly" can refer to any tube that includes an HTS material (e.g., an HTS tape), examples of which are provided herein. For example, one type of HTS cable assembly can be formed by disposing the HTS material in a tube (e.g., as shown in FIG. 1), and optionally adding additional components such as connectors as needed. In an actual embodiment, the tape can be disposed at the bottom of the tube. In this illustrative embodiment, the tube is shown as having a circular cross-sectional shape, but in other embodiments, the tube can be provided with a different cross-sectional shape (e.g., an elliptical cross-sectional shape, a rectangular cross-sectional shape, a square cross-sectional shape, or any regular or irregular geometric cross-sectional shape).

[0052]

[0071] As another example, an HTS cable assembly can comprise a channeled former in which the HTS material is disposed in a suitable one of the channels (e.g., as shown in FIGS. 2 - 3B), and optionally adding additional components such as connectors as needed. Other types of HTS cable assemblies can be envisioned, and techniques for filling the HTS cable assembly with metal, applicable to all such HTS cable assemblies, can be used. For example, it can be used with an HTS cross-conductor cable arrangement (CroCo HTS) in which tapes of different widths are arranged in a cross shape.

[0053]

[0072] Before or after the HTS material is disposed within the HTS cable assembly (e.g., after the HTS material is disposed in the opening of the tube, the channel of the tube, or the channel of the former or other structure), the HTS cable assembly can be bent into a desired shape (e.g., circular, loop, or multi-loop shape as illustrated in FIGS. 12A, 12B, 13).

[0054]

[0073] Returning now to FIG. 4A, as shown in processing element 66, flux can be applied to some or all of the HTS material and / or cable components forming the HTS cable, if desired, to remove any oxidation. The HTS cable assembly can then be evacuated (e.g., via a vacuum process) and purged with a gas that can be an inert gas (68). In embodiments, the liquid flux can be applied immediately prior to soldering. Ideally, the flux penetrates all surfaces of the cable components that will be exposed to the molten metal in a manner similar to the subsequent flow of the molten metal that will be described. In embodiments, it has been found that the application of the liquid flux enables good wetting of the tape and cable with solder. In embodiments, RMA-5 liquid flux (Indium Corp) can be used. However, it should be understood that other liquid fluxes having the same or similar properties as the RMA-5 liquid flux can also be used.

[0055] [000414]Excess flux (i.e., flux that does not adhere to the HTS material or component) is discharged from the assembly as a result of evacuation (68). However, it has been found that any remaining flux can be effectively washed away by the flow of the heavier molten metal solder (to be described in conjunction with 78). As such, an explicit step of discharging excess flux may not be required, depending on how much flux remains within the assembly. In embodiments having long and complex cable geometries, pressurization may be used to discharge excess flux. When flux application is used, after flux application, the cable assembly is evacuated again and purged with an inert gas to remove oxygen if oxygen is present, which would impede the effective action of the flux when it is heated.

[0056] [000425]The HTS cable assembly is heated to a temperature below the temperature at which the metal (e.g., solder) melts (74). In an embodiment, an oven, such as a convection oven, can be used to control the temperature of the cable as well as any associated connection fittings and tubing during the metal filling process. This provides evenness with the required reduced (and ideally minimal) external temperature control and, importantly, reduces (and ideally avoids) the risk of degradation to that portion of the HTS tape (and thus that portion of the cable) due to the HTS tape temperature exceeding the oven set point and being exposed to undesired temperatures.

[0057] [000436]Before, after, or simultaneously with the heating of the cable assembly (74), the metal to be filled into the HTS cable assembly is melted (75) into a liquid state. The metal can be melted, for example, using a temperature-controlled heater in a container (sometimes also referred to herein as a can or crucible). Thermocouples on the inside and / or outside of the can can be used to determine when melting is complete and the temperature of the molten metal before outflow. In some embodiments, the metal can be melted inside the oven in which the cable is located, while in other embodiments, the metal can be melted separately (i.e., outside the oven). The HTS cable assembly is then heated (76) to the temperature at which the metal flows.

[0058] [000447]One aspect of the metal filling process that has been found to be important was to obtain the desired time-temperature profile. The temperature needs to be high enough for the metal to become a low-viscosity fluid, but result in low enough exposure to avoid thermal degradation and degradation due to the chemical effect of the metal on the HTS material (e.g., REBCO tape stacks).

[0059]

[0078] For solder filling of an HTS cable comprising an HTS tape stack with REBCO tape layers and for using a tin - lead (PbSn) solder, in one embodiment, two steps can be used. First, the oven can be set to a temperature that warms the HTS cable assembly but does not degrade the HTS tape. In an embodiment, the oven can be set to a temperature lower than the melting point of the solder on the HTS tape (e.g., 185 °C for PbSn solder), whereby the degradation of the HTS tape stack is greatly reduced and ideally avoided, and the temperature of the entire cable (or more appropriately, the cable assembly) is equilibrated. The cable assembly is held at this temperature until the solder supply (e.g., the supply of solder in a can) is completely melted and equilibrated to a process temperature of about 200 °C. Second, the oven temperature can then be set to a temperature that achieves the desired flow temperature of the solder. In an embodiment using PbSn solder, the oven temperature can be set to a temperature of about 205 °C, and a waiting period occurs until all points on the cable and any associated tubes, as described in conjunction with FIG. 5, reach the desired flow temperature (e.g., a flow temperature of about 200 °C for PbSn solder), and temperature monitoring is performed to ensure that there are no points exceeding a temperature of about 202 °C. This approach reduces and ideally avoids the degradation of the superconducting properties of the HTS tape stack. When these temperature conditions are met, the metal flow process (78) can begin (and preferably begins immediately so as to reduce and ideally minimize the amount of time the HTS tape stack is exposed to such relatively high temperatures (e.g., temperatures above 200 °C or about 200 °C)).

[0060] [000459]The application and monitoring of multiple temperature monitoring devices (e.g., thermocouples) at multiple points within the metal filling treatment station (an example of which is described below in conjunction with FIG. 5) and on the cable can be important for this process because the degradation of some HTS materials (e.g., REBCO) increases exponentially at temperatures above 200 °C. The location of the temperature monitoring devices is selected for each cable geometry. Considerations include the size of the cable and the predicted thermal uniformity, as well as the local measurements required to guide the planned cooling process. The temperature can be adjusted for different solders or different types of HTS materials. Such an optimized time-temperature profile for the solder filling (or more generally, metal filling) of the HTS cable is specific to the process described herein, and Sn 60 Pb 40 even when solders such as are used, is one factor leading to the success of the described technique.

[0061]

[0080] Alternative solder alloys that reduce degradation can also be used. The selection of a suitable solder for a given application will depend on the properties required for the use of the cable, including but not limited to mechanical, thermal, and electrical properties.

[0062]

[0081] The processing elements 78, 80 implement loops to ensure that the molten metal flows (78) through the entire cable assembly. In embodiments, the flow of molten metal through the entire cable assembly can be achieved at least in part by gravity (i.e., air pressure), by a positive displacement pump, or using vacuum pressure techniques. One example of a vacuum pressure technique is described below in conjunction with FIG. 5.

[0063]

[0082] In decision block 80, if it is determined that sufficient molten metal has flowed through a part (or portion) of the cable assembly where the HTS material is disposed, the flow of the molten metal is stopped (82), the molten metal and the HTS cable assembly are cooled (84), and after the cooling is completed, a soldered (or more generally, metal-filled) HTS cable is obtained. Note that in an embodiment, it is noted that the flow of the molten metal (e.g., solder in a liquid state) does not immediately stop when the metal passes through the cable. Rather, the metal flow is not stopped until a predetermined amount of metal has passed through the cable and reached the waste section. Flowing additional metal beyond simply filling the cable can be beneficial in removing flux from the cable and / or reducing the porosity within the metal-filled cable when the metal returns to a solid state.

[0064]

[0083] In the illustrative method shown in FIGS. 4A and 4B, it should be understood that the HTS cable can be formed without performing all of the processes shown in FIGS. 4A and 4B and / or in the specific order presented. Furthermore, in at least some cases, some parts of the method can be performed simultaneously. As one non-limiting example, in some cases, the application of flux in (68) can be performed after the evacuation of the HTS cable assembly in (66). As another non-limiting example, in some cases, the melting of the HTS cable assembly (74) and the metal (75) can be performed simultaneously, or either step can be started before or even completed before the other. In some cases, the steps (and / or portions of steps) of the illustrative method shown in FIGS. 4A and 4B can be completely omitted. For example, in some embodiments, the step (68) where flux is applied to and discharged from the HTS material can be omitted. In some embodiments, the purge mode of step (66) can be omitted, but the evacuation mode of step (66) can be performed.

[0065]

[0084] Referring now to FIG. 5, a processing station 90 that can be used to perform a metal filling process that can be the same as or similar to the process described in conjunction with FIGS. 4A and 4B includes an oven sized to accommodate an HTS cable assembly 94, the resulting HTS cable (not shown in FIG. 5), and optionally a container 96 (e.g., a crucible) for holding a molten metal and associated inlet and outlet tubes generally designated 97. A gas source 95 is coupled to an input portion 96a of the container 96 through one or more valves V4, V5, and a flow controller 99 that limits the gas flow rate and thus the initial viscosity of the solder flow.

[0066]

[0085] The container 96 (sometimes also referred to herein as a “can”) is arranged to hold an amount of metal (e.g., solder) sufficient to fill the cable assembly 94 and can be located inside or outside the oven 92. In an embodiment, the container can be provided with a cylindrical shape having a length and diameter sufficient to hold the metal (e.g., solder). In an embodiment, the container can comprise a cylindrical stainless steel (SS) tube having an outer diameter of about 8.89 cm (3.5 inches) configured to hold up to 13.606 kg (30 pounds) of metal (e.g., a solder bar of up to 13.606 kg (30 pounds)). Of course, other shapes can be used. However, generally, the container 90, the crucible, should be sized to hold at least an amount of molten metal sufficient to fill a known size HTS cable according to the concepts and processes described herein, and ideally, some additional metal to flow through the cable, fill all voids, and wash out any impurities. After reading the description provided herein, one of ordinary skill in the art will understand how to select the appropriate amount of metal and thus the container shape and size (e.g., volume) for a particular application.

[0067] [000466] A plurality of heaters 98 are disposed around the container 96 (e.g., on the inner or outer surface of the container 96) and are configured to heat the container in a desired manner. The heater can be coupled to one or more controllers 100 that control the heater. In one embodiment, three 650W, 120VAC heaters are thermally coupled to the container and are controlled by one or more proportional-integral-derivative (PID) processors (not shown in FIG. 5). In an embodiment, the controller can be provided as a Solo SL4848-VV series controller from Automation Direct. In this embodiment, the output of the controller 100 is a voltage pulse that operates a relay, and this relay then gates 120VAC power with a duty cycle control to the heater. Other means for heating the container 90 (or other means for melting the metal inside the container) can of course also be used.

[0068]

[0087] A plurality of thermocouples 102 outside the container 96 and two thermocouples 103 at different levels inside the container 96 (e.g., disposed within a tube such as a stainless steel tube having a known thickness selected so as not to interfere with the operation of the thermocouple) can be used to control the melting process and establish when the melting of the metal inside the container is complete. A plurality of heaters 99 (two heaters 99 are shown in FIG. 5) proximate to the outlet of the container 90 are cooperatively controlled using a single external thermocouple (TC) 101, and the upper heater 98 (up to 650W) is controlled separately from the heaters 99. The details of the thermocouples and other equipment can vary depending on the size and geometry of the cable being processed (i.e., the cable to be filled).

[0069]

[0088] After reading the description provided herein, those skilled in the art will understand how to select the appropriate number, size (watts), and placement (i.e., physical location) of the heaters, as well as the number, characteristics, and placement (i.e., physical location) of the thermocouples to suit the needs for a particular application.

[0070]

[0089] The siphon 104 has a first end coupled to the output portion 96b of the container 96. The siphon is provided with a height greater than the height of the molten metal in the container so that flow cannot occur without pressure. In an embodiment, the siphon 104 may comprise a tube having an inner diameter of 1.27 cm (0.5 inches).

[0071]

[0090] A plurality of contact sensors 108 are disposed at various points within the processing station 90 to monitor both the melting and flow of the metal. In an embodiment, the contact sensor may be provided as a commercially available single-conductor vacuum feedthrough sensor. In an embodiment, the contact sensor has pins. In an embodiment, the pins may be part of a coaxial structure with a center pin, a ceramic insulator, and a stainless steel outer housing. In one embodiment, the feedthrough may be soldered or otherwise fixed to a connector fitting (e.g., a threaded end cap) that can be connected to mating fixtures on various devices (e.g., siphons, connecting pipes, and waste tanks) that are part of the processing station. Some sensors 108 may be disposed near the predicted level of the liquid solder in the container, and sensors 109 may be disposed at different levels or heights (either inside or outside) within or on the waste tank 110. In this example embodiment of FIG. 5, a set of three sensors are disposed at different heights within the waste tank. Such a sensor arrangement may be useful in monitoring the metal filling process and stopping at the desired amount of solder or other metal.

[0072]

[0091] In one embodiment, to detect the presence of solder, the center pin of the sensor is connected to a DC power source (e.g., 5 - 24 volts DC) through a light emitting diode (LED) lamp and a current limiting resistor. The tank and pipes are connected to a reference potential (e.g., electrical ground or 0 VDC), and the voltage with respect to the center pin is recorded.

[0073]

[0092] In this embodiment, in the absence of solder, there is no connection between the center pin of the sensor and the reference potential (e.g., no connection between the center pin of the sensor and ground). The LED is off, and the recorded voltage is HIGH (e.g., a voltage level corresponding to a logical HIGH value). In the presence of solder, the center pin is connected to ground. The LED is excited, and the recorded voltage is LOW (e.g., a voltage level corresponding to a logical LOW value). Such an electronic device provides both a visual indication of solder flow that is very useful for immediate manual control of the process, as well as electronic recording and inlets that are useful for post-process interpretation and can be used for process automation (e.g., using a programmable logic controller).

[0074]

[0093] In an embodiment where the HTS cable assembly 94 is provided with a jacket (such as shown in FIG. 3A) that abuts against the former and the former, the jacket extends beyond the ends of the HTS cable assembly 94, as indicated by reference numerals 112a, 112b in FIG. 5. The extensions 112a, 112b enable a smooth transition at the inlet tube 114 of the metal flow (e.g., solder flow) to the cable assembly (e.g., former and jacket) and at the outlet tube 115 leading to the waste tank 110. If it is desired or necessary to bend the extensions, the extensions are preferably provided with smooth bends.

[0075]

[0094] The heaters 116a, 116b are disposed adjacent to or separately coupled to the extensions 112a, 112b and the thermal extensions so as to maintain liquid solder within these extensions until the solder within the cable assembly 94 solidifies. In an embodiment, the heaters can also be placed on either side of each bend in the inlet and outlet tubes 114, 115, or at each end of the cable assembly. As will be described below, the heaters serve to avoid the generation of voids that could occur in the absence of heaters as a result of the cooling of the molten metal within the cable assembly.

[0076]

[0095] The tube 115 at the inlet 110a of the waste tank 110 is provided with a second "U bend" 140. This prevents the first solder and flux that has flowed through the cable to be filled and into the waste tank from flowing back into the cable assembly.

[0077]

[0096] The waste tank holds excess molten metal after it has flowed through the cable assembly. As noted, contact sensors 109 at various heights indicate how much molten metal has reached the waste tank. The variable flow valve (99) adjusts the amount of gas flow (e.g., inert gas flow) and the pressure rise. In embodiments, an inert gas such as argon may be used, although another inert gas may be used. In embodiments, the waste tank may comprise a stainless steel tube with a diameter of about 10.16 cm (4 inches) with an inlet from the top and may be sized to hold about 4.5359 kg (10 pounds) of excess molten metal (e.g., excess solder). Those skilled in the art will understand how to size the waste tank to meet the needs of a particular application.

[0078]

[0097] The container and the waste tank are coupled to (i.e., in fluid communication with) a vacuum system 122 and a gas system 124 that allow either of them to be evacuated (typically to 250 mTorr) or pressurized with an inert gas such as argon. The variable flow valve 99 can be used to adjust the gas flow rate and the pressure rise. Valve V4 is an on / off valve and valve 99 is a flow regulator / valve.

[0079]

[0098] Thermocouples can be disposed at various multiple points within the system (e.g., on cans, pipes, above ovens), including thermocouple 130a along cable 94 to be filled, and can be monitored in real time (e.g., by a monitor). In an embodiment, in a cable assembly having a length of about 10 meters, up to 18 thermocouples can be monitored in real time by two 16-channel Agilent 34972A scanners typically at a rate of 1 second. Such a monitor can also store and display the contact sensor status (converted to a DC voltage as described above) and the pressure gauge analog output. The spacing of the thermocouples will depend on the cable length, geometry, predicted thermal uniformity, and the planned cooling method.

[0080]

[0099] The processing station also includes a vacuum and pressurization system 131 with a vacuum pump 133, a plurality of valves 134, and tubes 136 that enable the inlet area of the cable assembly and the solder can, as well as the outlet area of the cable assembly 94 and the solder discard section 110, to be independently evacuated, pumped, or pressurized. Thus, it should be understood that the cable assembly 94 is coupled to the associated tubes, fixtures, sensors, heaters, thermocouples in a manner that forms a closed system, such that various components (including the cable assembly) can be evacuated and / or pressurized.

[0081]

[0100] Before filling the HTS cable with metal, the bypass valve V2 remains open to equalize the pressure at each end of the cable assembly 94. This, along with the siphon area 104 between the container 104 and the cable assembly 94, prevents early solder flow before all components reach the target temperature. When both the metal in the container and the cable reach their respective target temperatures, the metal flow is initiated. In one embodiment, the metal flow can be initiated by setting the gas pressure to the target pressure with respect to the gas source 95.

[0082]

[0101] To flow the metal, bypass valve V2 is closed, allowing the differential pressure between cable assembly ends 94a, 94b. At this point, the outlet 96b of container 96 is blocked by the molten metal, and the pressure from gas source 95 pushes the metal into cable assembly 94 from container 96 through the tube and siphon 104 via extension 112a.

[0083]

[0102] In an embodiment, pressurized inert gas from source 95 is applied to the container (e.g., by opening valves V4, V5), thereby pushing the molten metal down and through the inlet siphon 104 into the cable assembly. The molten metal flow continues through the cable assembly and penetrates all vacuum gaps including any space between and around the HTS materials. Since the molten metal is heavier than the flux, the molten metal pushes any remaining light flux in front of it. In this manner, a vacuum impregnation (VPI) process is provided for filling a cable assembly (e.g., one with a tube or jacketed former) containing high temperature superconducting material with molten metal.

[0084]

[0103] A second reverse tube (“siphon”) 139 is used between the cable assembly outlet 94b and the waste tank inlet 110a at a similar height to the inlet siphon 104. This prevents the molten metal from flowing out under gravity. The molten metal remaining in each vertical section 104a, 104b, 139a provides pressure to the metal-filled cable assembly after flowing.

[0085]

[0104] In an embodiment, the contact sensors 108, 109 can be used at multiple points within the system to monitor and help control the molten metal flow. For example, the contact sensors can be placed inside and / or outside of the can, at the outlet of the vessel, inside the inlet siphon, at the cable inlet and / or outlet, and at multiple heights within the waste tank. In an embodiment, the contact sensor comprises a pin, and the pin of the sensor is inside the can and must contact the solder. In an embodiment, one or more sensors can be disposed on the wall of the can using a fixture that penetrates the wall on which the pin of the sensor is disposed such that the pin can contact the solder (or another molten metal) when the solder (or another molten metal) reaches the level of the sensor pin. In an embodiment, one or more sensors can be disposed within a tube that is an internal tube of the can. The contact sensors at the cable outlet and inside the waste section can be used to monitor the flow of the molten metal. The use of sensors at multiple levels inside the waste tank makes it possible to set a predetermined amount of molten metal flowing through the cable to optimize filling and flushing of the flux.

[0086]

[0105] In one embodiment, typically 2.2680 to 4.5359 kg (5 to 10 pounds) of molten metal is present in the outlet tube and the waste tank, which is sufficient for a cable having a length of about 3 meters. When the target level is reached, the bypass valve V2 is opened, thereby equalizing the pressure between the first and second ends of the cable assembly again, stopping the flow, and ensuring that the inlet tube of the cable assembly does not empty.

[0087]

[0047] In an embodiment, the contact sensors 108, 109 can be provided as a commercially available single-conductor vacuum feedthrough having a coaxial structure with a center pin, a ceramic insulator, and a stainless steel outer housing. In this application, the feedthrough can be brazed to a threaded end cap that can be coupled to a mating fixture on the equipment.

[0088]

[0487] In embodiments, all tanks, pipes, and fittings may comprise or consist of electrically conductive copper or stainless steel and may be disposed within the oven to ensure a uniform temperature. In embodiments, a vacuum level of typically several hundred mTorr is achieved prior to flux application and typically 1 to several Torr is achieved after flux application. After reading the disclosure provided herein, one of ordinary skill in the art will understand how to select the vacuum level for a particular application. The vacuum ensures an oxygen-free environment prior to heating and ensures good impregnation of the metal (e.g., solder) even within all parts of the cable, between and around the tapes, and within the gaps between the surface of the former and the jacket.

[0089]

[0049] Following the solder flow, one or more air movers (e.g., blowers) may be used to preferentially direct air at selected zones on the cable so as to control the cooling profile of the cable. Specific techniques for cooling the metal-filled cable are selected according to the geometry of the cable as discussed below in conjunction with FIGS. 7-11. For HTS cables bent in a substantially circular or loop shape, movable baffles may be utilized to confine the cooling to specific portions of the loop. One illustrative embodiment is described below in conjunction with FIGS. 10A and 10B.

[0090]

[0509] A process enabling metal filling of an HTS cable that may be implemented using a system the same as or similar to the system of FIG. 5 is next described. The following process is described for an HTS cable comprising a channeled former in which one or more HTS tape stacks are disposed within channels and a jacket is disposed over the former. The process begins with cable fabrication and preparation prior to the actual metal filling process. Cable Preparation and Handling

[0110] In an embodiment, one or more HTS tape stacks are inserted into a channeled former, and the former and jacket (e.g., a copper or steel or stainless steel jacket, and / or, in some cases, an outer stainless steel jacket) can be cleaned with a solution of an acid cleaner. In an embodiment, a cleaner provided by Citronox can be used.

[0091]

[0111] In one exemplary embodiment for cleaning the cable, the cleaning solution reservoir is filled with approximately 26.50 liters (7 gallons) of hot water (60 °C (140 °F)) to 283.50 grams (10 ounces) of acid cleaner. The channeled former or the channeled former with jacket (i.e., the channeled former having the jacket under discussion) is inserted into a pipe (e.g., a PVC pipe) and connected to a pump and reservoir. The diameter of the pipe is selected to accommodate the channeled former (or the channeled former with jacket).

[0092]

[0112] The cleaning solution is pumped onto the cable to be filled at 124.1 kPa (18 psi) and 75.7 liters / minute (20 gpm) for 30 minutes. This is followed by a 2-minute rinse cycle in clean hot water. The cable to be filled is drained of moisture and dried (ideally, immediately drained of moisture and dried). Ideally, the cable to be filled should have a shiny appearance and be free of oil and light scale. This process is repeated for the jacket, adding scrubbing the holes with Scotch Brite or other suitable cleaner and wiping with ethanol and a cloth until the wipe is clean. Regardless of the particular cleaning method, the cable to be filled must be cleaned.

[0093]

[0113] In one embodiment, the REBCO tape (e.g., pre-plated with solder) is disposed within the former's channel. Preferably, the pre-plated solder is of the same type used to fill the cable. HTS tapes from several different manufacturers (e.g., SuperPower, Super Ox, Shanghai) can be used.

[0094]

[0514] The dispenser, which will be discussed in conjunction with FIGS. 6A - 6D, can optionally be added to the former prior to jacket application.

[0525] The cable jacket can optionally be provided with a length that is longer than the cable length (e.g., longer than the former so as to form a so-called extension) to provide a smooth flow of the molten metal as it flows in and out of the former. In embodiments, a cable without an extension can be soldered. In such embodiments, the tube can be directly coupled to the cable jacket such that the tube serves the same purpose / function as the extension. It should also be understood that the jacket need not be highly conductive.

[0095]

[0116] The cable can be bent into a desired shape after jacket application and before, or simultaneously with, the metal filling process. The ability to bend the cable before the metal filling process is one advantage of the solder filling processes and structures described herein for making complex cables or multi-turn magnets. That is, the metal filling processes described herein allow the cable to be bent before, or during, the metal filling process.

[0096]

[0537] Cable components (e.g., connectors) and cable assemblies are kept in an inert gas until soldering to reduce (ideally, minimize) the amount of oxidation that occurs. In embodiments, the gas can be nitrogen (N2) or argon (Ar). Flux Application

[0118] In an embodiment, prior to soldering, a flux is applied to the cable to remove oxides and ensure good wetting and adhesion. In an embodiment, the cable is flux-coated using Indium Corp. 5RMA-RC flux. Other types of commercially available flux may of course also be used. When a liquid flux is used (e.g., Indium Corp. 5RMA-RC flux), the flux is provided on the surface of the former and / or the surface of the HTS material, or applied separately, and left for an appropriate amount of time (e.g., for Indium Corp. 5RMA-RC flux, several minutes to several tens of minutes), and then drained. In the case of a substantially straight cable, the draining process can be achieved by gravity. In the case of long, helical, or other complex-shaped cables or formers, pressurization with an inert gas can be used to fill and drain the flux. Vacuum pump and purge

[0549] In an embodiment, after completing the flux application process (and ideally, immediately after flux application), the HTS cable can be coupled to a soldering station and a vacuum can be drawn on the cable (i.e., the HTS cable is evacuated (or "pumped down") to remove O2). The vacuum can extend to a container that is pre-filled with a solid metal (e.g., a solder bar) that will ultimately be melted and used for the solder filling process.

[0097]

[0120] In an embodiment, it may be desirable to utilize multiple pump and purge cycles with an inert gas. In an embodiment, argon (Ar) can be used.

[0098] [0012155]Depending on the process timing, the cable can either be purged for about 2 hours or backfilled with an inert gas and left for a time period sufficient to remove much of the O2 from the cable atmosphere and the alcohol in the flux (e.g., within the range of about 8 to about 24 hours).

[0099]

[0122] A processing system that may be the same as or similar to the processing system described above in conjunction with FIG. 5 is placed under vacuum before starting the metal filling process. A bypass valve (e.g., valve V2 in FIG. 5) ensures substantially equal pressure at both ends of the cable assembly to be filled with metal (i.e., the HTS cable assembly) and remains open to prevent premature solder flow. Solder melting

[0123] In an embodiment, a heater on the container (e.g., heater 98 in FIG. 5) may be controlled using a PID algorithm via a thermocouple outside the container (e.g., thermocouple 102 in FIG. 5) to melt the metal and may be used to bring it to a target temperature T. The specific target temperature depends on the metal. In one embodiment where the metal is lead - tin solder (e.g., Sn 60 Pb 40 ), the heater on the container may be controlled using a PID algorithm via a thermocouple outside the container, and the heater is controlled to melt the solder and bring it to a target temperature T of 200 °C. In other embodiments, a slightly lower temperature may be used as long as it exceeds the solder liquidus temperature. A heater in the outlet tube of the container (e.g., heater 112 in FIG. 5) may be used to ensure that the solder remains in the liquid phase within the inlet siphon. Internal thermocouples and contact sensors inside the container (e.g., thermocouple 103 and sensor 108 in FIG. 5), and contact sensors in the inlet siphon (e.g., sensor 109) may be used to determine when the solder is completely melted. One indication that the metal is completely melted is a rapid rise above the liquidus temperature of the metal used to fill the HTS cable. Cable temperature rise

[0124] In an embodiment, oven convection can be used to heat the cable to a target temperature T. The target temperature for the cable is lower than the melting point of the metal being used to fill the cable, but is a temperature that speeds up the overall metal filling process. Also, if the process is being used to fill an HTS cable, the target temperature is also selected to reduce (and ideally avoid) the risk of HTS degradation due to exposure of the HTS material to relatively high temperatures over a relatively long time period. The specific temperatures and time periods that can result in HTS degradation depend on the particular HTS material.

[0100]

[0125] For example, if the HTS material is a REBCO multilayer tape stack and Sn 60 Pb 40 is used, the oven convection can be used to heat the cable to a temperature below the solder melt (e.g., about 182 °C) while raising the temperature inside the can to a temperature above the solder melt so that the solder inside the can melts. This approach not only speeds up the overall process but also avoids the risk of HTS degradation.

[0101]

[0126] Once the metal inside the container is melted, the cable temperature can be raised and carefully monitored by a plurality of thermocouples to ensure uniformity and avoid either cold spots that can impede the metal flow or hot spots that can degrade the HTS. For an HTS cable comprising a REBCO multilayer tape stack and Sn 60 Pb 40 solder being used, a typical oven set point is about 205 °C and the process temperature can be about 200 °C ± 2 °C. Of course, other heating methods can also be used as long as the heating method achieves the same or similar heating uniformity as can be achieved by convective heating. Embodiments can include covering with a resistive heater tape, a jacket having a heating liquid, or Joule heating where current passes through the cable. Solder flow

[0127] In an embodiment, when both the metal (e.g., solder) and the cable within the container reach their respective target temperatures, solder flow can be initiated. In one embodiment, solder flow can be initiated by setting the gas pressure to a target pressure (e.g., via gas source 140).

[0102]

[0128] In one embodiment, the system utilizes argon gas and the pressure is set to a target pressure typically in the range of about 34.5 to about 206.8 kPa (gauge pressure) (about 5 to about 30 psig). The appropriate pressure can be calculated based on the pressure drop of the liquid metal for the length and diameter of the empty cable channel and the target fill time.

[0103]

[0129] Higher pressures can be used as needed to reduce the fill time in the cable assembly with appropriate design of the components. This approach may be desirable when filling a cable assembly having a length that can result in a flow-down time that can damage the HTS (e.g., due to exposure of the HTS to combinations of temperature and time that can result in damage / deterioration of the superconducting and / or mechanical properties of the HTS).

[0104]

[0130] The bypass valve (e.g., bypass valve V2 in FIG. 5) can then be closed and the inert gas valve (e.g., valve V4 in FIG. 5) can then be opened so that the pressure is applied to the container while the waste tank (e.g., waste tank 110 in FIG. 5) and the cable assembly (e.g., cable assembly 94 in FIG. 5) remain under vacuum.

[0105]

[0131] In an embodiment, a contact sensor can be used to monitor the flow of solder. During solder flow, the solder can quickly reach the cable inlet sensor and then the outlet sensor. The time is typically 10 to 30 seconds for a cable having a length of about several meters (e.g., 2 to 3 meters).

[0106]

[0132] The flow is allowed to continue to a predetermined level within the waste tank (which may be indicated by multiple internal contact sensors), thereby effecting a flushing of any remaining flux and filling of voids.

[0107]

[0133] To stop the flow, the pump valve (e.g., pump valve V1 in FIG. 5) is closed and the bypass valve is opened. When the system pressure becomes equal at 1 atmosphere or more, the gas valve (e.g., inert gas valve V4 in FIG. 5) is closed. This, in combination with the weight of the solder at the inlet and outlet siphons, keeps both ends of the cable under pressure during cooling to reduce voids. Cooling

[0134] According to the concepts described herein, one solder (i.e., Sn 60 Pb 40 solder) used for this cable filling process is known to have a shrinkage of about 4% during solidification. If not properly controlled, this can result in large voids, especially in the areas that cool last. Such large voids can impair the mechanical, electrical, and thermal properties of the HTS cable. Therefore, the following general methods and principles can be used to reduce and ideally minimize voids during solidification.

[0108] 1. Ensure that the supply of molten metal (e.g., liquid solder) is maintained at one or both ends of the cable until the metal within the cable becomes solid. In embodiments, the cable can be provided with an extended region (“extension”), and heaters can be used on the cable extension at the inlet and / or outlet. Such heaters can be activated before being cooled and temperature controlled (e.g., raised, lowered, held, maintained, managed, or otherwise controlled) to a temperature that ensures the supply of molten metal fills the shrinking voids.

[0109] 2. Maintain the molten metal under pressure (e.g., both ends of the cable can be pressurized during cooling to reduce and ideally minimize voids). 3. Cool gradually towards the metal source so that the voids can always be filled by the supply of molten metal. (For example, start cooling the cable at the end of the cable furthest from the source of liquid metal, or start in the middle and proceed towards the two ends).

[0135] The cooling principles and methods described above result in controlled gradual cooling to reduce and ideally avoid shrinkage voids that can occur within the cable. In the case of a substantially straight cable, it may be desirable to first cool the cable from the middle (e.g., using a blower), while simultaneously heating both ends. Temperature measurement devices (e.g., thermocouples disposed thereon) on or near the cable can be used to monitor when the molten metal in each section of the cable, at which point the cooling device (e.g., blower) is moved or otherwise directed to another section of the cable, solidifies. This prevents having a section with molten metal between two solid sections that could result in shrinkage voids when it cools. The method of actively controlling cooling spatially while providing a strong temperature gradient is unique, and its usefulness is evident from fewer and larger voids compared to uniform cooling (see FIGS. 8A and 8B).

[0110]

[0136] In a longer helical cable with a former that may be most useful for fusion and other magnets, only one end of the cable is heated, and channels (or holes) within the cable for cryogenic cooling can be used to gradually cool the cable from the other end.

[0111]

[0137] The cooling methods have been developed and demonstrated to optimize for different cable lengths and geometries to practice these principles, and examples illustrating these general concepts are described herein in conjunction with at least FIGS. 7 - 11. Of course, it should be understood that variations of these methods can be used for different cable geometries and / or lengths.

[0112]

[0138] However, while the cooling methods described herein may be preferred, it is also possible to cool by filling the cable and using a more uniform cooling (e.g., simply by allowing the oven to be stopped and cables to be disposed therein (i.e., HTS cables filled with metal)), and the results can be acceptable for at least some (and perhaps many) applications and HTS cables utilized. Cable removal

[0139] Once the metal filling process and the cooling process are completed, the jacket of the HTS cable (i.e., the extended region of the cable assembly) can simply be cut past the former having HTS, and the cable is removed. The connecting pipes (e.g., between the can, the siphon, the cable to be filled, and the waste tank) can be replaced for subsequent processes. Also, the metal (e.g., solder) can be removed from the container and the waste tank (e.g., by melting the metal outside the container and the waste tank) so that the container and the waste tank can be reused in subsequent metal filling processes.

[0113]

[0140] Referring now to FIGS. 6A - 6C, a flow diffuser 150 (or, more simply, a "diffuser") having first and second ends 150a, 150b includes a central member 152 having a first tapered end 152a that transitions to a smooth shank region 152b and then to a channel region 152c in which a channel 154 is formed.

[0114]

[0141] In the illustrative embodiment of FIGS. 6A - 6C where like elements are provided with like reference numerals, the diffuser is designed to interface with a cable having four angled channels. One example of such a cable was described above in conjunction with FIGS. 3A and 3B. Thus, the diffuser 150 includes four channels 154 configured to channel solder into and out of a cable having four channels, such as a cable having a four - channel former (e.g., as illustrated in FIGS. 3A and 3B).

[0115]

[0142] Of course, it should be understood that the size and number of channels within the spreader 150 can be readily adapted to other cable or former geometries. That is, the spreader channel area comprises four angled square channels having a configuration (e.g., size, shape, and pattern) selected to mate with channels within the cable or former.

[0116]

[0143] The flow spreader 150 is configured to channel the flow of molten metal into and out of channels provided within the cable. Thus, it should be understood that the mechanical characteristics of the spreader (including, but not limited to, the number of spreader channels, the shape of the spreader channels, the pattern of the spreader channels, and other channel characteristics) are selected for operation with a particular former or a particular tube.

[0117]

[0144] As demonstrated, the spreader has a tapered end 152a and is shaped to gradually transition the molten metal flow from a single circular channel (such as may be present in tube 114 in the system of FIG. 5) to a plurality of angled channels of the former or tube, in order to reduce turbulence and thus reduce (and ideally eliminate) the number of voids that can occur within the metal at the inlet and outlet of the former or tube. In the exemplary embodiments of FIGS. 6A-6C, the spreader region 152a tapers towards the tip to reduce turbulence and thus reduce (and ideally eliminate) the number of voids that can occur within the metal at the inlet and outlet of a 4-channel former such as those shown in FIGS. 2-3B, gradually transitioning the molten metal flow from a single circular channel to the four angled channels of the former. The channels of the former have a rectangular cross-sectional shape, and thus the channels of the spreader also have a rectangular cross-sectional shape. The spreader end 150 is configured to couple or join to a channeled former or channeled tube. Thus, ideally, the channels at the spreader end 150b are selected to have dimensions, shape, and configuration that substantially match the dimensions, shape, and configuration of the former (including the channels within the former) to which the spreader is coupled (i.e., the dimensions and configuration of the channels at the spreader end 150b substantially match the dimensions and configuration of the former at the interface between the spreader and the former).

[0118]

[0145] Referring now to FIG. 6D, a first conical twisted dispenser 158a, which may be the same as or similar to the dispenser 150 described above in conjunction with FIGS. 6A-6C, is coupled to the first end of the former 160, and a second conical twisted dispenser 158b, which may be the same as or similar to the dispenser 158a, is coupled to the second opposite end of the former 160. The former 160 has a plurality of channels 48' arranged in a helical configuration, and thus the former is sometimes referred to herein as a "twisted" former. The dispenser 150 likewise has channels in a helical configuration. As described above, the size (i.e., dimensions), shape (e.g., cross-sectional shape), and configuration of the dispenser channels are selected to substantially match the size, shape, and configuration of the former channels.

[0119]

[0146] The dispenser smoothly directs the solder flow into and out of the channels of the twisted former. As described above, the dispenser geometry may be adapted to substantially match the former geometry. The dispenser reduces the amount of turbulence in the flow of molten metal (compared to the amount of turbulence that would occur in the absence of the dispenser), and thus reduces the risk of voids present near the inlet and outlet of the molten metal to and from the former.

[0120]

[0147] Referring now to FIG. 7, in which like elements of FIG. 5 are provided with like reference numerals, a processing station 90, which may be the same as or similar to the processing station of FIG. 5, operates to metal-fill a cable assembly 94' (which may be the same as or similar to the cable assembly 94 described above in conjunction with FIG. 5) that includes a channeled former 170 having dispensers 172 disposed at each end.

[0121]

[0148] The former 170 and the HTS material disposed within its channels (not visible in FIG. 7) can be the same as or similar to the exemplary HTS material and former described above in conjunction with FIGS. 1-6D. The filling process can be the same as or similar to the filling process described above in conjunction with at least FIGS. 1-5 (e.g., using SnPb solder), and the system for heating and filling the former can be the same as or similar to that described in the processing station of FIG. 5. The temperature of the former illustrated in FIG. 8 can be measured or otherwise determined using one or more thermocouples, as described in conjunction with FIG. 5, for example.

[0122]

[0149] Significantly, the exemplary time-temperature exposure profile illustrated in FIG. 8 results in a metal-filled HTS cable while reducing (and ideally minimizing) HTS tape degradation (e.g., the superconducting properties of the HTS tape are not degraded as a result of exposure to temperature during the metal filling process). Ideally, the superconducting properties of the HTS tape are not degraded at all, or at most, the superconducting properties of the HTS tape are degraded by an amount that does not prevent the HTS tape from maintaining its superconducting properties.

[0123]

[0150] Referring now to FIG. 9A, a cable assembly 180 comprising a former 170, with dispensers 172 coupled to its first and second opposing ends, is cooled using a cooling system 182 and zone cooling techniques. Zone cooling begins in the central region 184 of the metal-filled cable 180 (and ideally, the center of the metal-filled cable). One or more temperature measurement devices (e.g., thermocouples) TC8, TC10, TC11, TC13, TC14, TC16 are coupled to various regions of the cable assembly 180 and optionally to extended regions.

[0124]

[0151] The metal source 190 is coupled to the first end of the cable assembly 180 through a first siphon 192. The second end of the cable assembly 180 is coupled to the waste tank 194 through a second siphon area 196. In embodiments, the cooling system may comprise one or more fans or blowers. In other embodiments, the cooling system may comprise a jacket disposed around (or wound around) one, some, or all of the smallest portions of the solder-filled cable, and this jacket has a coolant therein such that the application of the jacket cools the solder-filled cable in a controlled and desired manner. Alternatively, still, the solder-filled cable may be cooled by the direct application of a liquid (e.g., coolant) to one, some, or all of the portions of the solder-filled cable.

[0125]

[0056] In one method suitable for a substantially straight cable, both ends 180a, 180b of the cable 180 are kept in a liquid state using heaters 186 attached to or directed towards a slightly extended portion of the cable assembly 180 (e.g., a jacket extension). If the ends (and in fact, the solder-filled cable portions up to the solidified regions) are not kept in a liquid state, the molten metal may not be able to reach and fill the voids. The oven (not shown in FIG. 9A) is turned off and opened to ambient room temperature air after the metal flow. Convection is directed towards the central portion of the cable through the cooling system 182 (FIG. 9A). This forms a temperature gradient along the cable, as illustrated in FIG. 9B. After the molten metal regions near the ends of the cable have solidified, the end heaters 186 (e.g., heaters within or around the extension) are turned off, and the cable assembly 180 is cooled to ambient room temperature.

[0126]

[0153] Figures 10A and 10B are bar graphs illustrating a comparison of the void distribution of a cable produced using a zone cooling method (e.g., as described above in conjunction with FIGS. 7A and 7B), including the use of end heaters, with that of a cable produced by a very similar process that cools the remainder of the cable uniformly, i.e., near zero temperature gradient. The voids were determined from computerized tomography (CT) scans of the central region of each cable.

[0127]

[0154] The bar graph of FIG. 10A, based on all voids, reveals that both cables (i.e., the cable produced using the zone cooling method and the cable produced using the uniform cooling method) have a similar number of small voids (i.e., voids with a volume less than 1 mm 3 . These small voids are likely due to processes other than shrinkage, such as minor flux inclusions, and did not affect cable performance.

[0128]

[0155] However, the bar graph of FIG. 10B reveals that a higher number of large voids (i.e., voids greater than about 2 mm 3 in size) are present in the cable produced using the uniform cooling process compared to the number of large voids present in the cable produced using the zone cooling method. Such large voids are likely due to shrinkage. Thus, FIGS. 10A and 10B confirm the effectiveness of the zone cooling method in reducing the number of large voids (compared to the number that occur when the uniform cooling method is used or compared to large voids).

[0129]

[0156] The zone cooling method described above has been demonstrated to be effective for cables with a length of at least about 2 m at most, but can also be applied to cables with lengths greater than 2 m. The length of the cable that can be cooled using this technique is determined by how quickly the cable cools by natural convection. To obtain the advantages provided by this technique, it is preferred that the entire cable does not cool by natural convection before the effect of the cooling system.

[0130]

[0157] In embodiments, different cooling methods comparable to an oven or other cable heating device that is still on can be used, which enables cooling of cables longer than 2 m. Of course, there is a trade-off between cable length and oven temperature, so the longer the cable, the slower the cooling process.

[0131]

[0158] It has been recognized that the cooling zone desirably reaches all regions of the cable before they (i.e., the cable regions) are solidified by natural convection. Thus, a variant of the above method has been developed using a cooling system that can cool multiple cable sections simultaneously, as will be described below in conjunction with FIG. 11.

[0132]

[0159] Referring now to FIG. 11, the cooling system 200 includes one or more movable cooling units (e.g., blowers or fans or other air moving devices) and one or more movable heating units (e.g., heaters). In the illustrative embodiment of FIG. 11, the cooling system 200 comprises two movable blowers (or fans) and a pair of heaters. The cooling system is thermally coupled to a cable assembly 206 that may or may not include an extension. One or more end heaters 204 may be thermally coupled to opposite ends of the HTS cable, while the two blowers 204 are thermally coupled to the HTS cable 106 but are movable with respect to the HTS cable.

[0133]

[0160] Cooling begins with first and second cooling elements directed towards a first region 208a or zone of the HTS cable (identified by reference number "1" in FIG. 11 and hereinafter referred to as "zone 1" or "region 1"). Thermocouples (shown as TC11 in FIG. 11) are disposed within or in proximity to zone 1 of the cable. Thermocouples (shown as TC10 or TC12 in FIG. 11) are disposed within or in proximity to zone 2 of the cable. When thermocouples TC10, TC11, and TC12 indicate that the liquid metal within and adjacent to this region (i.e., zones 1 and 2) has solidified, the cooling elements are moved or otherwise directed to one or more regions of the cable assembly adjacent to zone 1. In this example, the cooling elements are moved to two regions adjacent to zone 1, each shown as zone 2 (identified by reference number "2" in FIG. 11 and hereinafter referred to as "zone 2" or region 2). The minimum zone width is set by the length affected by the cooling elements. When thermocouples TC9 and TC13 indicate that the molten metal in the next region (i.e., zone 3) is solid, the cooling elements are moved to zone 3 and then zone 4, and so on, and the process is repeated for each zone. In some embodiments, it may be preferable to position the thermocouples substantially in the middle of the zone. However, the thermocouples may be placed in other parts of the zone.

[0134]

[0161] During operation, the cooling elements initially target the central portion of the cable (and ideally the center of the cable), and the temperature along the cable is monitored (e.g., via a thermocouple or any other suitable means for monitoring temperature). When each region of the cable solidifies (certainly, for example, from a temperature drop following a certain period of constant temperature), the cooling element is moved to that area (or region) to cool that area more rapidly and then create a gradient towards the next. Thus, as illustrated in FIG. 11, both cooling elements 201a, 201b are initially directed towards region 1 (i.e., TC11), then towards region 2 (e.g., one cooling element is moved to zone 2 208b and the other to zone 2 208c), and then to zone 3 208d, 208d, etc., and are moved in a similar manner until each cable region is cooled. The number of regions used in this process can be adapted to the length of the cable. In this approach, by waiting for a region to become solid before cooling the adjacent region, the risk of "trapping" the liquid is avoided.

[0135]

[0162] The cooling system and process described in conjunction with FIG. 11 may be suitable for cables having a length greater than about 2 m. This method has been successfully applied to cables up to a length of approximately 3 m, and suitable mechanical and electrical performance has been demonstrated in tests at high magnetic fields. The upper limit on the cable length for this method can be set by cooling via natural convection and can be increased by increasing the ambient temperature around the cable 206.

[0136]

[0163] Referring now to FIGS. 12A and 12B, another cooling method is described, referred to as zone cooling from the center using a single blower with a movable baffle.

[0164] In a cable assembly 220 filled with molten metal and having a non-linear geometry, a cooling system comprising an air moving device (e.g., a fan, a blower, or other device capable of generating an air flow, all such devices being collectively referred to as an air mover) that directs air to only one cable assembly region can prematurely solidify the leading region along the cable assembly, thereby trapping liquid and creating voids.

[0137]

[0165] Thus, for cooling a cable assembly filled with molten metal and having a non-linear geometry (e.g., a cable assembly 220 having a circular or loop geometry as shown in FIG. 12A), an air flow directing device capable of generating a directed air flow 221 (e.g., using a specific air directing structure) can be used to confine convection (i.e., confine the air flow to a specific portion or region of the cable assembly). In the case of the circular (or loop) cable assembly configuration of FIG. 12A, region 222 is first cooled, then region 224, and then region 226 is cooled.

[0138]

[0166] An example of a device for gradually cooling a cable having a single loop is shown in FIG. 12B. The air moving device 230 (illustrated as a blower in FIG. 12B) directs air towards a specific region or zone 232a - 232c of the metal-filled cable assembly 234. In the illustrative embodiment of FIG. 12B, three regions are shown (labeled as zone 1 232a, zone 2 232b, and zone 3 232c). Those skilled in the art will understand that in other embodiments, more or fewer than three regions may be used.

[0139]

[0167] In an embodiment, the air mover 230 can be movable (e.g., tilted in an elevational plane) so as to direct the air flow towards different zones.

[0168] In an embodiment, one or more air directing devices (or baffles) 240 may be disposed within the air flow path between the air mover 230 and the cable 234 (for clarity, only one baffle 240 is illustrated in FIG. 12B). The one or more baffles are configured to direct air towards different zones.

[0140]

[0169] In an embodiment, the baffle 240 may be provided as a movable baffle that can move between a plurality of different positions 242a - 242N. During operation, the baffle 240 first aims to direct cooling towards the lower part of the cable (including the lower part of the loop), i.e., is directed to cool zone 1 232a, and is gradually raised to cool the zones including the ends of the cable loop. That is, zone 1 is first cooled, then zone 2, and then zone 3. The baffle may help concentrate the air flow such that the cable loop 234 is cooled in a progressive manner (i.e., rather than the entire cable loop being cooled simultaneously, different parts of the cable loop in each of the aforementioned zones are cooled over time).

[0141]

[0170] In an embodiment, the baffle 240 may be approximately the same width as the cable loop diameter D1 so as to direct the air flow across the portion of the cable within each desired cooling zone.

[0142]

[0171] Other air flow directing structures may, of course, be used. Any structure or device that can cool different parts of the coil (and ideally, local regions of the cable) over time may be used. In an embodiment, the blower may be coupled to a movable frame and tilted slightly downward in height, and the baffle may be movably coupled (e.g., by a hinge) to the movable frame.

[0143]

[0172] Referring now to FIG. 13, there is shown a cable 250 wound in a helical shape which is a general configuration of the fusion and other magnets. In this example, the helix lies in a single plane. Cooling such a cable configuration by a fan is not practical since such an approach is likely to cool multiple turns and thus trap liquid volume. Therefore, for cables having a central cooling hole (e.g., used for cryogenic cooling during HTS cable operation) and wound in a helical shape, a cooling method utilizing the central cooling hole within the cable has been developed and demonstrated. Thus, this method applies to cooling a wound cable having a cooling channel (e.g., a central cooling channel such as channel 46 described above in conjunction with at least FIGS. 3A - 3C).

[0144]

[0173] This technique excludes the use of a dispenser at the inlet and outlet. Thus, in this approach, the jacket area is relied upon to smooth the metal flow (e.g., solder flow) and direct it into the channel.

[0145]

[0174] This method utilizes an end heater only at one end of the cable. The cable is disposed in an oven maintained at a temperature above the liquid phase of the metal (e.g., solder). A fluid at a temperature lower than the liquid phase of the metal is injected from the end of the cable away from the heater. This gradually cools and solidifies the solder along the cable from the first end (where the cold fluid is injected) to the second end (where the heater is located).

[0146]

[0175] Once it is determined that the molten metal within the cable has solidified (e.g., by a thermocouple closest to the distal end but not on the heater), the end heater is turned off and the oven temperature is lowered to completely cool the cable.

[0147]

[0176] In the demonstration of the principle embodiments, this technology has been demonstrated on an 11-meter cable with six windings using room temperature air cooling. For faster cooling (which may be desirable for cables longer than two meters), a closed loop fluid cooling system can be used. In such a system, the fluid can be at any temperature lower than the solder liquid phase. In embodiments (e.g., during the manufacture of magnets), a liquid cooling system can be used.

[0148]

[0177] For cables without a central cooling channel, or for faster cooling, an alternative method is to add a cooling jacket outside the cable (i.e., a method for cooling the cable using an external jacket). The cold fluid is then applied to the end of the cable on the opposite side of the heater with a similar effect on the central fluid.

[0149]

[0178] In the foregoing detailed description, various features of the concepts, systems, devices, and technologies may be grouped into one or more individual embodiments for the purpose of streamlining the disclosure. The present method of disclosure should not be construed as reflecting an intention that the claimed concepts require more features than are expressly recited in each claim. Rather, aspects of the invention may be less than all of the features of each disclosed embodiment.

[0150]

[0179] Although implementations have been described that serve to illustrate the various concepts, structures, and technologies that are the subject of this disclosure, it will be apparent to those skilled in the art that other implementations incorporating these concepts, structures, and technologies may be used.

[0151]

[0180] For example, in an alternative embodiment, instead of zoned cooling, zoned external heating or Joule heating may be used. This implies the use of alternative heating means for the oven, which may be more realistic in the case of very large magnets. Drawbacks or concerns include the need for more active control and monitoring and the risk of temperature non-uniformities. Also, the fluid jacket described in the method for using an external jacket to cool the cable may also be used to heat the cable instead of, or in addition to, the oven. Further, it should be noted that it may be possible to fill with HTS cables at ambient pressure rather than solder at vacuum and high pressure. Such an approach is recognized to result in an increase in the trapping of air or flux in the narrow space and, thus, may result in more voids. Further, in such an approach, oxidation may occur during heating.

[0152]

[0181] Still further, the metal crucible described above within this specification may be placed outside the oven and the solder is melted prior to heating the cable. This can reduce (and ideally minimize) the time-temperature exposure of the cable and, thus, reduce (and ideally minimize) the risk of waiting for the HTS to reach temperature such that the metal melting is completed or the cable cools in the case of excessive temperature after melting. The drawback of this approach may be that a larger heater output is required in an ambient room temperature environment compared to a hot oven and that all tubing between the can and the cable needs to be at a temperature controlled to the process temperature.

[0153]

[0182] As used herein, "filling" of an HTS cable, HTS cable assembly, or open channel with a molten material refers to the introduction of the material into the cable, cable assembly, or channel, and does not necessarily imply that all available space within the cable, cable assembly, or channel is replaced with the material. For example, "filling" a channel such as that described above may involve directing molten metal into the channel and subsequently cooling the metal with the goal of preventing the formation of any voids within the channel. Nevertheless, in some cases, the channel may not consist solely of metal due to at least one void formed within the channel. In such a case, it is fully consistent with this disclosure that the channel is nevertheless "filled" with molten metal. In some embodiments, "filling" a cable, cable assembly, or channel with molten metal may involve depositing the metal such that at least 90%, at least 95%, at least 98%, at least 99%, or at least 99.9% of the initially open volume of the cable, cable assembly, or channel contains metal. It should be noted that in HTS cable embodiments with channeled formers, it may also be the case that much (or most) of the cable is composed of the former and tape, and the void volume to be filled with molten metal (e.g., solder) may be relatively small compared to the total volume of the cable.

[0154]

[0183] The various embodiments of the concepts, systems, devices, structures, and technologies that are sought to be protected are described herein with reference to the accompanying drawings. Alternative embodiments may be devised without departing from the scope of the concepts, systems, devices, structures, and technologies described herein. Note that the various connections and positional relationships (e.g., above, below, adjacent, etc.) are specified between elements in the above description and drawings. These connections and / or positional relationships can be direct or indirect, and the concepts, systems, devices, structures, and technologies described are not intended to be limited in this regard. Thus, a physical connection can refer to either a direct or an indirect connection, and the positional relationship between physical objects can be a direct or an indirect positional relationship.

[0155]

[0184] As an example of an indirect positional relationship, a reference in this description to disposing or otherwise positioning element "A" relative to element "B" includes a situation where one or more intermediate elements (e.g., element "C") are between element "A" and element "B", provided that the relevant characteristics and functionality of elements "A" and "B" are not substantially changed by the intermediate element.

[0156]

[0185] Also, the following definitions and abbreviations are to be used for the interpretation of the claims and the specification. As used herein, the terms "comprise", "comprises", "comprising", "include", "includes", "including", "has", "having", "contains", "containing", or any variant thereof are intended to cover non-exclusive inclusion. For example, an apparatus, method, composition, mixture, or article that includes a list of elements is not necessarily limited to only those elements and may include other elements not explicitly listed or that are inherent to such apparatus, method, composition, mixture, or article.

[0157]

[0186] In addition, the term "exemplarily" is used in this specification to mean serving as an example, instance, or illustration. Any embodiment or design described as "exemplarily" in this specification should not necessarily be construed as being more preferred or advantageous than other embodiments or designs. The terms "one or more" and "one or plurality of" are understood to include any integer greater than or equal to 1, i.e., 1, 2, 3, 4, etc. The term "plurality" is understood to include any integer greater than or equal to 2, i.e., 2, 3, 4, 5, etc. The term "connection" may include indirect "connection" and direct "connection".

[0158]

[0577] References in this specification to "embodiment", "one embodiment", "an embodiment", "example embodiment", etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may or may not include that particular feature, structure, or characteristic. Furthermore, such expressions do not necessarily refer to the same embodiment. Moreover, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is within the knowledge of those skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly described.

[0159]

[0588] For the purposes of the following description, without limitation, relative or positional terms including the terms "above", "below", "right", "left", "vertical", "horizontal", "up", "down", and their derivatives shall relate to the described structures and methods as oriented in the drawings. The terms "overlay", "uppermost", "on top", "positioned above", or "positioned uppermost" mean that a first element such as a first structure is present above a second element such as a second structure, and intervening elements such as an interface structure may be present between the first and second elements. The term "direct contact" means that a first element such as a first structure and a second element such as a second structure are connected without any intermediate element.

[0160]

[0189] The use of terms such as "first," "second," "third," etc. within a claim to indicate an order for modifying claim elements does not, in itself, imply any priority, precedence, or order of one claim element over another, or the temporal order in which acts of a method are performed, and is used only as a label to distinguish one claim element having a particular name from another element having the same name (however, due to the use of the terms indicating order).

[0161]

[0190] The terms "about" and "approximately" may be used in some embodiments to mean within ±20% of a target value, in some embodiments within ±10% of a target value, in some embodiments within ±5% of a target value, and further, in some embodiments within ±2% of a target value. The terms "about" and "approximately" may include the target value. The term "substantially equal" may be used in some embodiments to refer to values that are within ±20% of each other, in some embodiments within ±10% of each other, in some embodiments within ±5% of each other, and further, in some embodiments within ±2% of each other.

[0162]

[0191] The term "substantially" may be used in some embodiments to refer to values that are within ±20% of a comparative measurement, in some embodiments within ±10% of a comparative measurement, in some embodiments within ±5% of a comparative measurement, and further, in some embodiments within ±2% of a comparative measurement. For example, a first direction that is "substantially" perpendicular to a second direction may, in some embodiments, refer to a first direction that is within ±20% of forming a 90° angle with the second direction, in some embodiments within ±10% of forming a 90° angle with the second direction, in some embodiments within ±5% of forming a 90° angle with the second direction, and further, in some embodiments within ±2% of forming a 90° angle with the second direction.

[0163]

[0192] It should be understood that the disclosed subject matter is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The disclosed subject matter has other embodiments and can be practiced and carried out in various ways.

[0164]

[0193] Also, it should be understood that the expressions and terms used herein are for the purpose of description and should not be regarded as limiting. As such, those skilled in the art will understand that the concepts on which this disclosure is based can be readily utilized as a basis for the design of other structures, methods, and systems for carrying out some of the purposes of the disclosed subject matter. Accordingly, the claims should be regarded as including such equivalent structures insofar as they do not depart from the spirit and scope of the disclosed subject matter.

[0165]

[0194] The disclosed subject matter is described and illustrated in the foregoing exemplary embodiments, but the present disclosure is for illustrative purposes only, and it should be understood that numerous changes in the details of the implementation forms of the disclosed subject matter can be made without departing from the spirit and scope of the disclosed subject matter.

[0166]

[0195] Therefore, the scope of this patent should not be limited to the described implementation forms but should be limited only by the spirit and scope of the following claims.

[0059] All publications and references listed herein are hereby expressly incorporated by reference in their entirety. Some embodiments of the invention related to the present invention are shown below. [Embodiment 1] A step of at least partially filling at least one channel of a high temperature superconductor (HTS) cable assembly with a molten metal, wherein the HTS cable assembly comprises an HTS and the at least one channel, and Operating one or more cooling devices to cool the molten metal in the at least one channel A method comprising. [Embodiment 2] The method according to Embodiment 1, wherein the HTS cable assembly comprises a former in which the at least one channel is disposed. [Embodiment 3] The former comprises four channels each comprising an HTS, and the method comprises the step of at least partially filling the four channels of the former. The method according to Embodiment 2. [Embodiment 4] The method according to Embodiment 3, wherein the HTS cable assembly further comprises a jacket disposed around the former. [Embodiment 5] The method according to Embodiment 1, comprising the step of completely filling the at least one channel of the HTS cable assembly. [Embodiment 6] The step of at least partially filling the at least one channel of the HTS cable assembly with a molten metal comprises Heating the HTS cable assembly, and Applying pressure to the molten metal to force the molten metal through the at least one channel of the former. The method according to Embodiment 1. [Embodiment 7] The method according to Embodiment 6, wherein the molten metal is held by a container, and applying pressure to the molten metal comprises applying pressure to the molten metal in the container. [Embodiment 8] The HTS cable assembly A tube having a wall defining the at least one channel, and At least partially filling the at least one channel of the tube with the molten metal. The method according to Embodiment 1. [Embodiment 9] The method according to Embodiment 1, wherein the HTS cable assembly comprises a stack of HTS tapes. [Embodiment 10] The molten metal is the method according to Embodiment 1, including PbSn solder. [Embodiment 11] The method according to Embodiment 1, further including the step of depositing flux in the at least one channel before at least partially filling the at least one channel with the molten metal. [Embodiment 12] The step of operating the one or more cooling devices includes gradually cooling the HTS cable assembly towards the source of the molten metal, according to the method of Embodiment 1. [Embodiment 13] A vacuum impregnation (VPI) station for filling a cable assembly containing high-temperature superconducting (HTS) material with molten metal, a) a can configured to hold a source of molten metal, b) one or more heaters arranged to heat the HTS cable assembly, the HTS cable assembly comprising at least one of a tube or a former in which at least one channel is formed or provided separately, and having HTS material disposed in at least one of the at least one channel of the tube or the former, one or more heaters, and c) a pressure application means coupled to the can for applying pressure to the molten metal in the can so as to push the molten metal from the can through at least one channel of the tube or former, a vacuum impregnation (VPI) station. [Embodiment 14] The VPI station according to Embodiment 13, further comprising a siphon coupled to the can and disposed at a height greater than the height of the molten metal in the can to suppress the flow of the molten metal from the can when the pressure application means is not operating. [Embodiment 15] The VPI station according to Embodiment 13, further comprising a plurality of contact sensors configured to monitor the flow of the metal from the can into at least one channel of the tube or former. [Embodiment 16] The VPI station according to Embodiment 13, wherein the one or more heaters are disposed in contact with the can. [Embodiment 17] The VPI station according to Embodiment 13, further comprising an outlet tube coupled to the can, and at least one of the one or more heaters is disposed adjacent to the outlet tube. [Embodiment 18] The VPI station according to Embodiment 13, further comprising a waste tank arranged to collect the molten metal flowing through at least one channel of the tube or former and emerging from the at least one channel. [Embodiment 19] The VPI station according to Embodiment 18, further comprising a U-bend coupled to the waste tank to prevent the molten metal from flowing from the waste tank back into the at least one channel of the tube or former. [Embodiment 20] A dispenser for channeling molten metal into and / or out of an N-channel former, comprising an elongated member having a mortar-shaped end, a smooth shank portion, and a twisted groove portion with N grooves provided therein, the twisted groove portion having a flare shape with a diameter increasing from a first end of the twisted groove portion to a second end of the twisted groove portion, the N grooves of the twisted groove portion being configured to direct the molten metal into the channels of the N-channel former. [Embodiment 21] The device according to Embodiment 20, wherein the first end of the twisted groove portion has a diameter substantially matching the diameter of one end of the smooth shank portion, and the second end of the twisted groove portion has a diameter substantially matching the diameter of the N-channel former. [Embodiment 22] Obtaining a HTS cable assembly; Bending the HTS cable assembly; Filling the bent HTS cable assembly with molten metal and a method including the above steps. [Embodiment 23] The step of obtaining a high temperature superconductor (HTS) cable assembly includes obtaining a former having at least one channel and at least partially filling the at least one channel of the former with the molten metal, according to the method of Embodiment 22. [Embodiment 24] The step of obtaining a high temperature superconductor (HTS) cable assembly includes obtaining a former having at least one channel and completely filling the at least one channel of the former with the molten metal, according to the method of Embodiment 23. [Embodiment 25] At least partially filling the at least one channel of the former with molten metal includes obtaining a source of the molten metal, heating the HTS cable assembly to a temperature that enables the molten metal to flow through at least one channel of the former, and applying pressure to the molten metal to force the molten metal from the source through at least one channel of the former, the method of embodiment 23. [Embodiment 26] The step of obtaining a high temperature superconductor (HTS) cable assembly comprises obtaining a tube having walls defining at least one channel, and at least partially filling the at least one channel of the tube with the molten metal, the method of embodiment 22. [Embodiment 27] The step of obtaining a high temperature superconductor (HTS) cable assembly comprises obtaining a tube having walls defining at least one channel, and completely filling the at least one channel of the tube with the molten metal, the method of embodiment 26. [Embodiment 28] At least partially filling the at least one channel of the tube with molten metal comprises obtaining a source of the molten metal, heating the HTS cable assembly to a temperature that enables the molten metal to flow through at least one channel of the tube, and applying pressure to the molten metal to force the molten metal from the source through at least one channel of the tube, the method of embodiment 26. [Embodiment 29] A vacuum impregnation (VPI) station for filling a cable assembly containing a high temperature superconducting (HTS) material with molten metal, comprising a) a can configured to hold a source of molten metal, b) means for heating the HTS cable assembly, the HTS cable assembly comprising at least one of a tube or a former in which at least one channel is formed or provided separately, and having an HTS material disposed in at least one of the at least one channel of the tube or the former, means, and c) A vacuum impregnation (VPI) station comprising pressure applying means coupled to the can for applying pressure to the molten metal within the can so as to push the molten metal through the can into at least one channel of the tube or former. [Embodiment 30] An exit siphon and a waste section configured to couple to one end of an HTS cable assembly, wherein excess solder flows through the HTS cable assembly to wash away flux and completely fill the HTS cable assembly with molten metal from the can such that the end of the cable remains pressurized by the molten metal and impurities cannot return to the HTS cable assembly, the VPI station according to Embodiment 29, further comprising an exit siphon and a waste section. [Embodiment 31] A method comprising the step of at least partially filling at least one channel of a high temperature superconductor (HTS) cable assembly with molten metal, the HTS cable assembly comprising HTS and the at least one channel. [Embodiment 32] The method according to Embodiment 31, wherein the HTS cable assembly comprises a former in which the at least one channel is disposed. [Embodiment 33] The former comprises four channels each comprising HTS, and the method according to Embodiment 32 comprises the step of at least partially filling the four channels of the former. [Embodiment 34] The method according to Embodiment 33, wherein the HTS cable assembly further comprises a jacket disposed around the former. [Embodiment 35] The method according to Embodiment 31, comprising the step of completely filling the at least one channel of the HTS cable assembly. [Embodiment 36] The step of at least partially filling at least one channel of the HTS cable assembly with molten metal comprises heating the HTS cable assembly, and applying pressure to the molten metal so as to push the molten metal through the at least one channel of the former, the method according to Embodiment 32. [Embodiment 37] The method according to Embodiment 36, wherein the molten metal is held by a container, and applying pressure to the molten metal comprises applying pressure to the molten metal within the container. [Embodiment 38] The HTS cable assembly comprises a tube having a wall defining the at least one channel, and filling at least partially the at least one channel of the tube with the molten metal, the method according to Embodiment 31. [Embodiment 39] The HTS cable assembly comprises a stack of HTS tapes, the method according to Embodiment 31. [Embodiment 40] The molten metal comprises PbSn solder, the method according to Embodiment 31. [Embodiment 41] The method according to Embodiment 31, further comprising depositing a flux in the at least one channel before at least partially filling the at least one channel with the molten metal. [Embodiment 42] The method according to Embodiment 31, further comprising gradually cooling the HTS cable assembly towards the source of the molten metal following the step of at least partially filling the at least one channel with the molten metal. [Embodiment 43] A method for filling an HTS cable with a molten metal, the method comprising heating at least a portion of the HTS cable comprising an HTS tape using a time-temperature exposure profile that does not degrade the HTS tape properties by more than 5%. [Embodiment 44] A method for filling an HTS cable, the method comprising: bending a cable assembly in which an HTS material is disposed; and filling the cable assembly with a molten metal after bending the cable assembly. [Embodiment 45] The method according to Embodiment 44, wherein the step of bending a cable assembly in which an HTS material is disposed comprises bending the cable assembly to form at least one partial loop. [Embodiment 46] The step of filling the cable assembly with a molten metal comprises: heating the HTS cable assembly comprising the HTS material, and heating the HTS cable assembly; and applying pressure to the molten metal to force the molten metal through the cable assembly to form at least one partial loop, the method according to Embodiment 45. [Embodiment 47] ​ The step of bending a cable assembly in which an HTS material is disposed therein includes bending the cable assembly to form at least one loop, the method according to Embodiment 45. [Embodiment 48] The HTS material comprises at least an HTS tape, and the step of bending the HTS cable assembly includes twisting the HTS tape and allowing the HTS tape to redistribute during bending such that the HTS tape is substantially stress-free before filling the cable assembly with molten metal, the method according to Embodiment 47. [Embodiment 49] The method according to Embodiment 48 further includes the step of cooling the molten metal in the cable assembly to fix the position of the HTS tape in the cable assembly.

Claims

**Claim 1** A step of at least partially filling at least one channel of a high temperature superconductor (HTS) cable assembly with a molten metal, wherein the HTS cable assembly comprises an HTS and the at least one channel; A step of operating one or more cooling devices to cool the molten metal within the at least one channel; A method comprising the steps. **Claim 2** The method according to claim 1, wherein the HTS cable assembly comprises a former in which the at least one channel is disposed. **Claim 3** The method according to claim 2, wherein the former comprises four channels each comprising an HTS, and the method comprises a step of at least partially filling the four channels of the former. **Claim 4** The method according to claim 3, wherein the HTS cable assembly further comprises a jacket disposed around the former. **Claim 5** The method according to claim 1, comprising a step of completely filling the at least one channel of the HTS cable assembly. **Claim 6** The step of at least partially filling the at least one channel of the HTS cable assembly with a molten metal comprises: Heating the HTS cable assembly; and Applying pressure to the molten metal to force the molten metal through the at least one channel of the former. The method according to claim 2. **Claim 7** The method according to claim 6, wherein the molten metal is held by a container, and applying pressure to the molten metal comprises applying pressure to the molten metal within the container. **Claim 8** The HTS cable assembly comprises: A tube having a wall defining the at least one channel; and At least partially filling the at least one channel of the tube with the molten metal. The method according to claim 1. **Claim 9** The method according to claim 1, wherein the HTS cable assembly comprises a stack of HTS tapes. **Claim 10** The method according to claim 1, wherein the molten metal comprises a PbSn solder. **Claim 11** The method according to claim 1, further comprising a step of depositing a flux within the at least one channel prior to at least partially filling the at least one channel with the molten metal. **Claim 12** The method of claim 1, wherein the step of operating the one or more cooling devices comprises gradually cooling the HTS cable assembly towards the source of the molten metal.

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