Techniques for quench detection in superconducting magnets

Abstract

Techniques for early detection of a local normal zone in superconducting magnets are provided. A superconducting magnet may include an insulated superconductor that is arranged along the primary non-insulated winding of the magnet. If a portion of the primary winding heats up, this may cause the insulated superconductor co-winding to also heat up. A quench may be detected by connecting ends of the co-winding to a voltage meter because heating of the co-winding may produce a measurable change in its resistance.

Description

TECHNIQUES FOR QUENCH DETECTION IN SUPERCONDUCTING MAGNETSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 63 / 617,689, filed January 4, 2024 under Attorney Docket No. C1599.70063US00 and entitled “TECHNIQUES FOR QUENCH DETECTION IN SUPERCONDUCTING MAGNETS,” which is hereby incorporated by reference herein in its entirety.

[0002] The present application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 63 / 624,685, filed January 24, 2024 under Attorney Docket No. C1599.70063US01 and entitled “TECHNIQUES FOR QUENCH DETECTION IN SUPERCONDUCTING MAGNETS,” which is hereby incorporated by reference herein in its entirety.

[0003] The present application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 63 / 688,398, filed August 29, 2024 under Attorney Docket No. C1599.70077US00 and entitled “QUENCH DETECTION FOR SUPERCONDUCTING MAGNETS AND SUPERCONDUCTING MAGNETS,” which is hereby incorporated by reference herein in its entirety.BACKGROUNDField

[0004] The present disclosure relates to techniques for quench detection in superconducting magnets.Related Art

[0005] Superconductors are materials that have no electrical resistance to current (are “superconducting”) below some critical temperature. For many superconductors, the criticaltemperature is below 30 Kelvin (K), such that operation of these materials in a superconducting state requires significant cooling, such as with liquid helium. A superconductor for which the critical temperature is above 30 K is referred to herein as a High Temperature Superconductor, or “HTS”. A superconductor that has a critical temperature at 30 K or below is in contrast referred to herein as a Low Temperature Superconductor, or “LTS”.

[0006] High-field magnets are often constructed from superconductors due to the capability of superconductors to carry a high current without resistance. Such magnets may, for instance, carry currents greater than 5 kilo Amperes (kA).BRIEF SUMMARY

[0007] According to some aspects of the present technology, a quench detection system comprising insulated back-to-back HTS co-windings, a current source, and a voltage detector is provided for a superconducting magnet having a primary winding. The insulated back-to-back HTS co-windings are arranged proximate to the primary winding of the superconducting magnet. The current source is coupled to the insulated back-to-back HTS co-windings and is configured to supply a quench detection current to the insulated back-to- back HTS co-windings. The voltage detector is coupled to the insulated back-to-back HTS co-windings and is configured to detect a voltage across the insulated back-to-back HTS cowindings.

[0008] According to some aspects of the present technology, a quench detection system comprising an insulated HTS co-winding, a current source, and a voltage detector is provided for a superconducting magnet having a primary winding. The insulated HTS cowinding is arranged proximate to the primary winding of the superconducting magnet and comprises a first portion and a second portion. The first portion is arranged alongside a plurality of turns of the primary winding, and the second portion is coupled in series to the first portion and is arranged alongside the first portion and alongside the plurality of turns of the primary winding. The current source is coupled to the insulated HTS co-winding and isconfigured to drive a current through the insulated HTS co-winding. The voltage detector is coupled to the insulated HTS co-winding and is configured to measure a voltage across the insulated HTS co-winding.

[0009] According to some aspects of the present technology, a method of quench detection for a superconducting magnet is provided. The method comprises measuring a voltage across terminals of an HTS co-winding arranged proximate to a primary winding of the superconducting magnet and detecting a quench of the superconducting magnet based on the voltage measured across the terminals of the insulated HTS co-winding.

[0010] The foregoing apparatus and method embodiments may be implemented with any suitable combination of aspects, features, and acts described above or in further detail below. These and other aspects, embodiments, and features of the present teachings can be more fully understood from the following description in conjunction with the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Various aspects and embodiments of the present technology will be described with reference to the following exemplary and non-limiting figures. It should be appreciated that the figures are not necessarily drawn to scale. Items appearing in multiple figures are indicated by the same reference number in all the figures in which they appear.

[0012] FIG. 1 depicts a general schematic of a quench detection (QD) circuit for a non-insulated magnet comprising three non-insulated primary windings disposed in a Cryostat.

[0013] FIG. 2A illustrates a schematic diagram of a QD circuit of the type illustrated in FIG. 1.

[0014] FIG. 2B illustrates a schematic diagram of an alternative QD circuit in which the primary winding and co-winding are shorted together.

[0015] FIGs. 3A-3C illustrate sawtooth quench detection current signals applied to a co- winding according to non-limiting embodiments of the present technology.

[0016] FIGs. 4A, 4B, and 4C illustrate examples of high-temperature superconductor (HTS) tape that may be used as a co-winding in aspects of the present technology.

[0017] FIG. 5 is a cross-section of an example of a superconducting magnet according to non-limiting embodiments of the present technology.

[0018] FIG. 6A depicts an insulated superconducting quench detection co-winding (“QD Wires”) arranged between turns of a stack of HTS tapes according to a non-limiting embodiment of the present technology.

[0019] FIG. 6B depicts an insulated superconducting quench detection co-winding (“QD Wires”) arranged within a stack of HTS tapes according to a non-limiting embodiment of the present technology.

[0020] FIGs. 7A, 7B, and 7C illustrate cross-sectional views of three non-limiting examples of superconducting cables comprising superconducting co- windings.

[0021] FIGs. 8 A and 8B illustrate non-limiting examples of a quench detection apparatus in superconducting magnets having a grooved radial plate, according to nonlimiting embodiments of the present technology.

[0022] FIG. 9 is a perspective view of a non-limiting example of a superconducting cable such as those shown in FIGs. 7A-7C.

[0023] FIG. 10 is a flow chart illustrating a method of quench detection for a superconducting magnet.DETAILED DESCRIPTION

[0024] A high-field superconducting magnet often comprises multiple turns of a superconducting material. When the temperature of the superconducting material is below its critical temperature (the temperature below which the electrical resistivity of the materialdrops to zero), current is allowed to pass through the superconducting path formed by the superconducting material without resistive losses. However, for various reasons some or all of the superconducting material may be heated to above its critical temperature and therefore lose its superconducting characteristics. If uncontrolled, such heating can lead to the superconducting magnet losing its superconducting abilities, often referred to as a “quench.” Moreover, if the quench is not properly addressed by the system of which the superconducting magnet is a part (e.g., by nullifying the current in the magnet), components of the superconducting magnet and / or the larger system can be damaged by the heating.

[0025] Some superconducting magnet systems handle quench events via a system of active alarms and detection mechanisms. Some superconducting magnet systems actively shut down the magnet when quench is detected. Alternatively, or additionally, some superconducting magnet systems handle quenches passively through design of the superconducting magnet itself. An example of the latter approach is a non-insulated (NI) magnet (also referred to as a no-insulation (NI) magnet), in which adjacent superconducting turns of the magnet are not insulated from one another but are instead separated by a conventional conductor (i.e., not a superconductor). It is understood that “non-insulated” is a general term in the art, and its usage herein is intended to cover partially-insulated magnets as well as magnets with no insulation. When the magnet is operating below the superconductor’s critical temperature, current flows through the superconductor and not across turns because the superconductor has zero resistance compared with the finite resistance of the conductor that lies between the turns.

[0026] Non-insulated magnets have quench protection properties because the formation of a local normal zone (NZ) - that is, a non-superconducting zone - results in a change of the current path from the spiral HTS winding to a transverse path (e.g. through the conventional conductor separating the turns of the superconductor) that bypasses the normal zone. Since current can flow across the turns, it need not flow through a normal zone, and therefore contributes to heating of the normal zone much less than would occur if the current continued to flow through the normal zone. Transverse current during a quench reduces heating of the normal zone by instead heating a larger volume within the magnet andspreading the normal zone wider and eventually quenching the whole magnet safely, without critically overheating it such as would damage the magnet and / or system.

[0027] Quenches in NI magnets typically happen in two stages. First, in a resistive stage lasting around 10-100 seconds, the temperature in the vicinity of the initial normal zone increases due to resistive losses in the current path around the normal zone. Second, in an inductive stage lasting a short time (a fraction of a second to several seconds), flux lost by redirection of current around the normal zone is compensated by currents induced in superconducting portions of the winding according to Maxwell’s Law. As a result, the total transport and induced currents in the superconductor may exceed the critical current (the maximum current which a superconducting material can maintain, above which the material will cease to superconduct) of portions of the winding, thereby causing those portions to turn normal and so on, quenching the magnet in an avalanche manner.

[0028] In terms of quench detection, insulated magnets (in which the adjacent superconducting turns of the magnet are separated from one another by an electrical insulator and not by a conventional conductor), as opposed to non-insulated magnets, measure the resistive voltages of the normal zone. These methods work well for insulated LTS magnets due to small temperature margins, fast normal zone propagation speed and the fact that resistances that develop in the normal zone may be large enough to be detected by voltage measurements early enough to safely discharge the magnet.

[0029] However, in non-insulated magnets the resistance experienced by transverse currents bypassing the normal zone during the resistive stage of a quench is small, and as a result any voltage changes across the terminals of the magnet are practically undetectable. Thus, even though in theory a NI magnet may safely quench due to the operation explained above in which current flows between turns of the magnet winding, detection of the quench may be difficult and therefore complicate efforts to take corrective action at the onset of a quench event. As a result of the voltage changes across the terminals being practically undetectable, the first indicators of a coming quench come too late or perhaps do not come at all, depending on the coil design, diagnostics, and instrumentation. Detecting the formation of a local normal zone in a non-insulated magnet is therefore problematic becausetemperature rise is local and can happen anywhere inside the magnet. In addition, temperature sensors are limited in number and are usually located on the surface of the cold mass (the cooled magnet), so that when the temperature rise reaches those sensors the temperature of the normal zone can be already too high (e.g. damage to the magnet and / or system may be unavoidable).

[0030] The inventors have recognized and appreciated techniques for early detection of a local normal zone in non-insulated magnets, and particularly in non-insulated HTS magnets, although the techniques may also be applied in non-insulated LTS magnets, as well as in insulated HTS or LTS magnets.

[0031] A non-insulated magnet having a primary non-insulated winding may include an insulated superconductor that is arranged along the primary non-insulated winding of the magnet, thus defining an insulated path referred to herein as the “co-winding.”. The primary winding and co-winding may be configured to receive separate current, for example by connecting the co-winding to a separate source of current from the primary non-insulated winding. It is understood that “winding,” as used herein, includes any suitable type of winding used in the construction of superconducting magnets, such as a “pancake” winding or a layer winding, and that the techniques disclosed herein are not limited in this respect. If a portion of the primary winding heats up, this may cause the co-winding to also heat up. Since the co-winding carries the same current over its entire length and does not produce transverse currents because it is insulated, a quench may be detected by connecting ends of the co-winding to a voltage meter because the heating of the co-winding may produce a measurable change in its resistance. At the same time, however, any changes in the terminal voltage of the primary winding may remain undetectably small (e.g. due to transverse currents as discussed above).

[0032] According to some embodiments, the co-winding may comprise two back-to- back insulated wires. A single insulated co-winding may, in at least some magnets, generate or experience an inductive voltage due to the changing magnetic field (e.g., dB / dt) produced by the primary winding during charge and / or discharge (for DC magnets), from transients (for AC magnets), or by other AC magnets in its vicinity. Such an induced voltage wouldincrease the difficulty of measuring any resistive changes in the co-windings as a means to detect a quench. By co-winding two back-to-back insulated wires, any induced voltage may be significantly reduced, or cancelled entirely, such that the measurable change in resistance produced during a quench may be reduced. This means a smaller change in resistance due to quench will be detectable compared to if induced voltages were present. That is, the sensitivity to resistive voltage changes may be increased. Accordingly, techniques presented herein enable a quench detection system which exhibits high sensitivity to a resistive signal; this high sensitivity is beneficial for the timely detection of quench events such as may facilitate the implementation of quench protection measures which, for example, prevent damage to the magnet and / or system.

[0033] In some cases, the back-to-back insulated wires may be electrically connected to either side of a current source and arranged to form a spiral path inward and then outward along turns of the primary winding so that the inward and outward paths are arranged next to one another.

[0034] FIG. 1 depicts a general schematic of a quench detection (QD) circuit 100 for a non-insulated magnet comprising three non-insulated primary windings- although the primary windings are not shown in FIG. 1 for clarity - disposed in a cryostat 102. A quench detection current IQD is supplied by a current source 104 to the insulated co-winding 106 via leads 108 (e.g., copper leads), and instrumentation wires 110 are connected (e.g. via voltage taps 112) to the superconducting part of the co-winding 106 and to a voltage detector 114 which measures a voltage VQD across the co-winding, as shown in FIG. 1 and as step 1002 of FIG. 10. The current source may be a variable current source in at least some embodiments, configured to vary the quench detection current.

[0035] The insulated co-winding 106 follows the turns of each of the three primary non-insulated windings of the magnet, comprising each of three pancakes 122, with the cowinding 106 forming a spiral 116 inward along the turn of the primary winding in direction 118, then doubling back along itself outward along the turn of the primary winding in direction 120. In some embodiments, the insulated co-winding 106 may be inserted adjacentto the primary winding, for example adjacent the radially outer side of the turns of the primary winding.

[0036] During normal operation of the magnet in which the primary winding is superconducting and the insulated co- winding 106 is superconducting, the voltage detector 114 detects a zero (or close to zero) voltage. Once somewhere within the pancakes 122 the primary winding forms a normal zone, this zone heats up a portion of the superconducting insulated co-winding 106 forming a normal zone 124 (shown by dashing in FIG. 1). As a result, at least part of the insulated co-winding 106 becomes normal with finite resistance, RNZ. A resistive voltage VQD=RNZ X IQD is then measured by the voltage detector 114.

[0037] According to some embodiments, at least part of the co-winding 106 arranged outside of the pancakes 122 is arranged in a twisted pair to minimize pickup of inductive voltage during transients.

[0038] According to some embodiments, processor 128 receives the output of voltage detector 114 and processes it to determine whether a quench event has occurred or is about to occur, shown also as step 1004 of FIG. 10. If processor 128, upon detecting a resistive signal, determines that such a quench event has occurred or is about to occur, processor 128 may send a command to a quench protection system 126 to take action to protect the magnet against a quench, one embodiment of which is shown as step 1006 of FIG. 10. For instance, the quench protection system 126 may comprise one or more heaters embedded within the magnet to safely warm up the magnet upon activation. Quench protection system 126 may be a system to offload energy from the superconducting magnet.

[0039] According to some embodiments, once the existence of a normal zone in the primary winding is detected and one or more quench protection actions taken, the current source 104 may be deactivated to prevent the co-winding 106 from overheating or burning.

[0040] The system of FIG. 1 may also be depicted schematically as shown in FIG. 2A. In the quench detection system 200 of FIG. 2A, the primary winding 202 is represented by the upper-right circuit having an operating current IOP and the co-winding 210 is represented by the lower-right circuit having a quench detection current IQD. In the case of an HTSmagnet, the division between the portions of each winding (the primary winding and the cowinding) that are formed from copper (Cu) or some other conventional conductor, and the portions that are formed from, or comprise, HTS, is shown by the dotted line. A normal zone 208 is represented by the letters NZ and shown in dashed lines.

[0041] In some embodiments utilizing insulated magnets, the co-winding may be grounded to the primary winding. FIG. 2B illustrates an example in which the co-winding and primary winding are coupled by short 212. Any suitable electrical coupling may be used to ground the co-winding to the primary winding. This grounding may mitigate the risk of the development of a high voltage between the co-winding and primary winding during current dump or other AC operations of the primary winding.

[0042] According to some embodiments, the quench detection current IQD may be varied over time (e.g., by a variable current source such as when current source 104 is implemented as a variable current source) to obtain additional information regarding a quench. The quench detection current IQD(I may be varied over part or all of the time the magnet is in operation, including, in particular, during the time interval between an initial detection of a normal zone 208 in the primary winding 202 and initiating quench protection operations in the magnet. For instance, in some cases, the quench detection current IQD(I may be varied with a sawtooth pattern, as shown in FIGs. 3A-3C. Such variation in the quench detection current may be realized using a variable current source.

[0043] FIGs. 3A-3C are graphs with IQD on the y-axis and time on the x-axis. In the system represented by the graphs, the quench detection current IQD(I is configured to increase until VQD, given by VQD=RNZ X IQD, reaches a given value Vgiven, at which point IQD(I dumps to zero and the pulse is repeated. Because RNZ is dependent on the possible presence and characteristics of a normal zone, this technique yields information concerning the absence of, presence of, and change in a normal zone. It should be noted that determining VQD by varying IQD rather than applying a constant current and depending solely on a change in RNZ may be desirable for reasons including reducing heat generated. The example pattern of FIG. 3A demonstrates a situation in which the required magnitude 302 of IQD to obtain Vgiven decreases over time, reflecting an increasing RNZ. This ischaracteristic of a normal zone which is increasing in size and / or temperature and may indicate a quench in the HTS magnet. FIG. 3B shows an example pattern in which over time the required magnitude 302 of IQD to obtain Vgiven remains constant, reflecting the absence of a normal zone or a stable normal zone. This may indicate safe operation of the HTS magnet. FIG. 3C shows an example pattern in which the required magnitude 302 of IQD to obtain Vgiven increases over time, reflecting a decreasing RNZ. This is characteristic of a normal zone which is decreasing in size and / or temperature and may indicate a recovery (e.g. from possible quench) in the HTS magnet.

[0044] While the foregoing discussion describes one method of varying the quench detection current, not all embodiments are limited in this respect. In some embodiments, the quench detection current may not vary but may be a generally constant value. The quench detection current may be determined not just by the design and characteristics of the magnet comprising a quench detection system, but may also be set at different values, or to vary in different ways, from one usage of a superconducting magnet to the next. For example, because the quench detection current is not necessarily determined by the physical characteristics of the co-winding, the same magnet comprising a quench detection system may at one time operate with a constant quench detection current and at a different time operating with a varying quench detection current.

[0045] Additionally, the quench detection current may be set with reference to a current through the primary winding(s) of a magnet comprising a quench detection system. This may be particularly the case given that the superconducting material in the co-winding may be the same superconducting material as is in the primary windings, and as such the cowinding may have superconductive properties aligned with those of the primary winding across the whole “critical surface” (that is, for all values of magnetic field strength, temperature, currents, stresses, and strains at which the winding exhibits superconductivity). Thus, the same degree of heating, or other phenomenon, which would cause a normal zone in the primary winding would cause a normal zone in the co-winding being used for quench detection.

[0046] Accordingly, in some instances the quench detection current through the cowinding to be equal to or approximately equal to the current magnitude through the primary windings (e.g. equal to the average current per tape of a primary winding comprising a plurality of tapes, as will be discussed below) because, in such a configuration, the quench detection system would be highly sensitive to the emergence of a normal zone in a primary winding. This can be contrasted with a system in which the quench detection current through the co-winding is only a small fraction (e.g. 5%) of the average current through the HTS tapes of the primary winding — in such a system, although a certain change in temperature of the primary winding may give rise to a normal zone in the primary winding, for example, the lower current through the co-winding may mean that the same change in temperature would not create a normal zone in the co-winding, thus creating no detectable change in resistivity and failing to detect a quench either altogether or early enough to protect the magnet from significant (e.g., unrecoverable) damage resulting from the quench.

[0047] However, considerations such as manufacturing tolerances and the desire to avoid false positives (e.g. the detection of a normal zone through increased resistivity in the co-winding when no normal zone exists in the primary winding) may dictate that the quench detection current be less than the average current through the primary winding. Imperfections in manufacturing may yield co-windings which exhibit “dropout,” or localized decreases in critical current, and it may be advantageous to characterize individual co-windings before integration into a quench detection system. Thereafter in operating a magnet comprising a quench detection system, it may be advantageous to provide for a quench detection current which is some fraction of the current (e.g. between 25% and 90%, between 30% and 80%, between 40% and 70%, or any value within such ranges)) in the primary windings (the average current through the tapes of the primary winding(s)) to balance sensitivity and false positives.

[0048] It should also be understood that, depending on the application and the characteristics of a superconducting magnet being utilized — including whether such a magnet comprises LTS or HTS — the current through the primary windings may be any current within a large range of values. For example, magnets at a temperature of 77 K maybe operated at a maximum per-tape average current of tens of amperes, whereas magnets at a temperature of 4 K may be operated at more than 1 kA. Accordingly, the quench detection current applied by quench detection systems according to aspects of the present technology may be between tens of Amperes and more than 1 kA, as examples. For instance, the quench detection current may be several kAmps in some embodiments.

[0049] It is understood that the choice of fraction of primary winding current to run through the co-winding may be impacted by the magnitude of current in the primary winding. Additionally, it is understood that, as described above, the current through the cowinding is not necessarily determined by physical characteristics of the co-winding or the primary winding, and that as such, the quench detection current may be adjusted from operation to operation or even from moment to moment within the same period of operation of a magnet system.

[0050] Returning now to a discussion of the figures, note that according to some embodiments, the co-winding may comprise an insulated HTS. FIG. 4A’s insulated QD wire 402 and FIG. 4B’s two back-to-back QD wires 404 are examples of such an arrangement, comprising a stack of HTS tapes 406 with insulation 408 arranged around the stack of HTS tapes 406.

[0051] FIG. 5 shows a cross-sectional view of a portion of an example magnet according to some embodiments. A superconducting magnet 500, which may be a toroidal magnet comprising a central void 512 (not necessarily drawn to scale), may comprise a pancake 502 comprising an upper plate 504, a lower plate 506, and a gap 510 between these plates. In the gap 510 may be disposed a single continuous piece of HTS tape (or continuous stack of HTS tapes) wound around an inner side 508 spiraling outward between the upper plates 504 and lower plates 506. The superconducting magnet 500 as shown comprises a stack of such pancakes 502. It is understood that the structure of the pancake 502 shown is merely exemplary, and that any other suitable (e.g., capable of containing superconducting cables) structure may be used.

[0052] In FIG. 5, the HTS tape is not shown, but would be arranged within the gaps 510 in each of the four pancakes 502 shown, with the windings arranged in a spiral outward from the inner side 508. As may be evident from the cross-section shown, the pancakes 502 may be circular or form some other closed contour to, for example, accommodate spiral windings like shown in FIG. 1. Accordingly, it is understood that the dashed lines shown connecting the left and right sides of the superconducting magnet 500 in the cross-sectional view of FIG. 5 are shown serve to indicate the central void 512 and to signify that the two sections shown may be connected outside the cross-sectional plane of the drawing.

[0053] In such a magnet as shown in FIG. 5, an insulated superconducting co-winding may be disposed between turns of the HTS tape or may be arranged within a stack of HTS tapes used to form the primary winding. These two approaches are shown in FIGs. 6A and 6B, respectively, with FIG. 6A depicting the insulated superconducting co-winding (“QD Wires”) 602 arranged between turns (demarcated by dashed lines representing divisions 606) of the stack of HTS tapes (which may also include copper and / or steel co-wind tapes) 604, and FIG. 6B depicting the insulated superconducting co-winding (“QD Wires”) arranged within the stack of HTS tapes (which may also include copper and / or steel co-wind tapes).

[0054] Arranging insulated co-windings between turns of HTS tapes may prevent transverse current from flowing between the turns of the primary winding upon formation of a normal zone within the primary winding. This may change the above-discussed dynamics of quench in a non-insulated primary winding and can lead to overheating. Thus, to create a low-resistance transverse path around the insulated co-windings, the insulated co-windings 602 may be coated with a conductive material such as copper, for example on top of the insulation 408 shown in FIGs. 4A and 4B. An example of this is shown as the conductive coating 410 of FIG. 4C, which may be copper in at least some embodiments.

[0055] According to some embodiments, a superconducting magnet may comprise a plurality of windings of a cable comprising HTS material. Cross-sectional views of two such illustrative superconducting cables are shown in FIGs. 7A-7B. A superconducting cable 700 (FIG. 7A) and 720 (FIG. 7B) may be formed from a conductive structure (e.g., a copperformer) 702 comprising channels 704 in which HTS tape 706 is arranged. In some embodiments the conductive structure 702 may be segmented, for example into four segments, with an electrically insulating material such as insulation 718 disposed between segments of the conductive structure 702. The conductive structure 702 may be disposed in an outer jacket 714 covered by an insulative layer 716. In some embodiments, an insulated superconducting co-winding 708 may be disposed within the cable 700, such as within an additional channel in the conductive structure.

[0056] In each of these examples, multiple superconducting co-windings 708 are inserted into the cable 700 adjacent to a respective stack of HTS tapes 706; the difference between examples is in the particular location chosen for the superconducting co-windings 708. In some embodiments, a vacuum pressure impregnation process may be performed to fill gaps in the cable 700 with a molten metal, which is then cooled to solid (e.g., a solder). The black portions of each of FIGs. 7A-7C depict such a material 722, which may be arranged around and in contact with the wires of the co-winding 708.

[0057] FIG. 7C illustrates a third non-limiting example of a manner of positioning a HTS co-winding alongside a primary winding of a superconducting magnet. In some embodiments, a quench detection co-winding (e.g., an insulated superconducting cowinding) 710, which is an implementation of co-winding 708, may be co-wound with one or more, for redundancy, primary superconducting windings 712, which is an implementation of HTS tapes 706.

[0058] FIG. 9 is a perspective view of a portion of a superconducting cable such as those shown in FIGs. 7A-C. FIG. 9 demonstrates that in some embodiments of a superconducting cable 700, the conductive structure 702 may be twisted around a central axis 906 of superconducting cable 700. Accordingly, HTS 706 may follow a helical path about the central axis 906.

[0059] FIGs. 8A and 8B show cross-sections of portions of non-insulated superconducting magnets 800 and 801 comprising a quench detection apparatus according to non-limiting embodiments of the present technology in which HTS 810 is wound in agroove (e.g., a spiral groove) 804 of a grooved radial plate 802 that withstands the Lorentz forces produced by the magnet. The plate 802 may include any suitable material such as steel, for example. The groove 804 including the HTS 810 may be capped by a suitable cap (e.g., a copper cap) 806. The HTS 810 may be held in the groove with solder 808. In some embodiments, a quench detection co-winding 812 as described above may be positioned within the groove 804 with the HTS tape 810. For example, the quench-detection cowinding 812 may be positioned within a solder groove flow channel 814. FIG. 8B shows an embodiment wherein the quench-detection co-winding 812 is positioned within a side-cut groove 816 within the solder flow channel 814.

[0060] As described above, the co-winding in various embodiments may comprise two back-to-back insulated wires, which may be seen in the above cross-sectional views. In this approach the insulated wires may be joined at one end of the cable so that when the cable is arranged into a plurality of windings the co-winding is arranged as two windings with opposite winding directions to cancel out inductive couplings, as described above.

[0061] In some embodiments, the co-winding may be formed from insulated round MgB HTS, or other such wire.

[0062] While the techniques described herein may be of particular application to noninsulated HTS magnets, they may be applied in non-insulated LTS magnets as well as in insulated HTS or LTS magnets. For clarity, these techniques may be applied in embodiments where the primary winding comprises HTS and the co-winding comprises HTS or LTS as well as in embodiments where the primary winding comprises LTS and the co-winding comprises HTS or LTS; additionally, these techniques may be applied in both insulated and non-insulated magnets of any of the foregoing embodiments.

[0063] Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated that various alterations, modifications, and improvements will readily occur to those skilled in the art.

[0064] Such alterations, modifications, and improvements are intended to be part of this disclosure and are intended to be within the spirit and scope of the invention. Further,though advantages of the present invention are indicated, it should be appreciated that not every embodiment of the technology described herein will include every described advantage. Some embodiments may not implement any features described as advantageous herein and in some instances one or more of the described features may be implemented to achieve further embodiments. Accordingly, the foregoing description and drawings are by way of example only.

[0065] Various aspects of the present invention may be used alone, in combination, or in a variety of arrangements not specifically described in the embodiments described in the foregoing and is therefore not limited in its application to the details and arrangement of components set forth in the foregoing description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments.

[0066] Also, aspects of the invention may be embodied as a method, of which an example has been provided. The acts performed as part of the method may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments.

[0067] Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having,” “containing,” “involving,” and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

Claims

CLAIMSWhat is claimed is:

1. A quench detection system for a superconducting magnet having a primary winding, the quench detection system comprising: insulated back-to-back high temperature superconductor (HTS) co-windings arranged proximate to the primary winding of the superconducting magnet; a current source coupled to the insulated back-to-back HTS co-windings and configured to supply a quench detection current to the insulated back-to-back HTS cowindings; and a voltage detector coupled to the insulated back-to-back HTS co-windings and configured to detect a voltage across the insulated back-to-back HTS co-windings.

2. The quench detection system of claim 1 or any other preceding claim, wherein the superconducting magnet is a non-insulated superconducting magnet, and wherein the primary winding is a non-insulated winding.

3. The quench detection system of claim 1 or any other preceding claim, wherein the superconducting magnet is an insulated superconducting magnet, and wherein the primary winding is an insulated primary winding.

4. The quench detection system of claim 1 or any other preceding claim, wherein the primary winding comprises an HTS tape.

5. The quench detection system of claim 1 or any other preceding claim, wherein the primary winding is configured to carry a primary current, and wherein the current source is configured to set the quench detection current to be a fraction of the primary current.

6. A quench detection system for a superconducting magnet having a primary winding, the quench detection system comprising:an insulated high temperature superconductor (HTS) co-winding arranged proximate to the primary winding of the superconducting magnet, the insulated HTS co-winding comprising: a first portion arranged alongside a plurality of turns of the primary winding; and a second portion coupled in series to the first portion and arranged alongside the first portion and alongside the plurality of turns of the primary winding; a current source coupled to the insulated HTS co-winding and configured to drive a current through the insulated HTS co-winding; and a voltage detector coupled to the insulated HTS co-winding and configured to measure a voltage across the insulated HTS co-winding.

7. The quench detection system of claim 6 or any other preceding claim, further comprising at least one processor configured to detect a quench of the superconducting magnet based on the voltage measured across the insulated HTS co-winding.

8. The quench detection system of claim 6 or any other preceding claim, wherein the superconducting magnet comprises a plurality of plates each comprising a spiral groove, and wherein the primary winding is arranged within the spiral grooves of the plurality of plates.

9. The quench detection system of claim 8 or any other preceding claim, wherein the insulated HTS co-winding comprises a plurality of spiral portions that are arranged within or proximate to the spiral grooves of the plurality of plates.

10. The quench detection system of claim 9 or any other preceding claim, wherein the first portion and the second portion of the insulated HTS co-winding are each spiral portions of the plurality of spiral portions, and wherein the first portion and the second portion of the insulated HTS co-winding are each arranged within or proximate to the spiral groove of a first plate of the plurality of plates.

11. The quench detection system of claim 6 or any other preceding claim, wherein the superconducting magnet comprises a plurality of windings of a cable, the cable comprising: an electrically conductive structure extending along the cable and comprising a channel; a stack of high temperature superconductor (HTS) tapes arranged within the channel, comprising at least part of the primary winding of the superconducting magnet; the first portion of the insulated HTS co-winding arranged within the electrically conductive structure and proximate to the stack of HTS tapes; and the second portion of the insulated HTS co-winding arranged within the electrically conductive structure and proximate to the stack of HTS tapes.

12. The quench detection system of claim 11 or any other preceding claim, wherein the electrically conductive structure of the cable is one of a plurality of electrically conductive segments that extend along the cable and that each comprise a respective channel in which a stack of HTS tapes is arranged.

13. The quench detection system of claim 12 or any other preceding claim, wherein none of the plurality of electrically conductive segments directly contacts any other of the plurality of electrically conductive segments.

14. The quench detection system of claim 12 or any other preceding claim, wherein the plurality of electrically conductive segments are twisted around a central axis of the cable, and wherein the stack of HTS tapes follows a helical path around the central axis.

15. The quench detection system of claim 12 or any other preceding claim, wherein the cable further comprises an electrically insulating material arranged between adjacent electrically conductive segments of the plurality of electrically conductive segments that electrically insulates the plurality of electrically conductive segments from one another.

16. A method of quench detection for a superconducting magnet, the method comprising: measuring a voltage across terminals of an insulated high temperature superconductor (HTS) co-winding arranged proximate to a primary winding of the superconducting magnet; and detecting a quench of the superconducting magnet based on the voltage measured across the terminals of the insulated HTS co-winding.

17. The method of claim 16 or any other preceding claim, wherein the insulated HTS cowinding comprises: a first portion arranged alongside a plurality of turns of the primary winding of the superconducting magnet; and a second portion coupled in series to the first portion and arranged alongside the first portion and alongside the plurality of turns of the primary winding.

18. The method of claim 17 or any other preceding claim, wherein a first terminal of the terminals is a terminal of the first portion, and wherein a second terminal of the terminals is a terminal of the second portion.

19. The method of claim 16 or any other preceding claim, wherein the method further comprises, in response to detecting a quench, activating a system to offload energy from the superconducting magnet.

20. The system or method of any preceding claim, wherein the primary winding of the superconducting magnet comprises a plurality of HTS tapes.

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