Quench Detection in Superconductors

Abstract

A method and system for detecting a quench in a high-temperature superconductor such as REBCO (rare earth-barium-copper oxide) before thermal runaway. The REBCO superconducting tape is excited as a transmission line forming a standing wave. Then, the quench can be detected in response to the detection of a disturbance in the standing wave. In this manner, the quench in a high-temperature superconductor such as REBCO is rapidly detected before thermal runaway.

Description

Technical Field

[0001] Rights of the government

[0001] This invention was made with government support under Award Number N00014 - 21 - 1 - 2429, awarded by the Office of Naval Research. The United States government has certain rights in this invention.

[0002] Technical field

[0002] The disclosure of the present invention generally relates to superconductors, and more particularly to detecting quenches in high - temperature superconductors (e.g., REBCO (rare - earth barium copper oxide)).

Background Art

[0003]

[0003] Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and the magnetic flux field is expelled from the material. Any material that exhibits these properties is a superconductor.

[0004]

[0004] Superconducting materials are expected to behave as superconductors in a region defined by the critical temperature of the superconductor (the highest temperature at which the material is a superconductor in zero applied magnetic field) and the critical magnetic field of the superconductor (the highest magnetic field at which the material is a superconductor at 0K). The temperature of the superconductor and the magnetic field present limit the current that can be carried by the superconductor without the superconductor becoming resistive or "normal". "Normal", as used herein, refers to "not superconducting".

[0005]

[0005] Superconducting materials are typically divided into "high-temperature superconductors" (HTS) and "low-temperature superconductors" (LTS). LTS materials such as Nb and NbTi are metals or metal alloys whose superconductivity can be explained by the BCS (Bardeen-Cooper-Schrieffer) theory. All low-temperature superconductors have a critical temperature of less than about 30 K (the temperature above which the material does not become superconducting even in zero magnetic field). The behavior of HTS materials is not explained by the BCS theory, but such materials may have a critical temperature above about 30 K (note, however, that what defines an HTS material is a physical difference in operation and composition in superconductivity rather than the critical temperature). The most commonly used HTS is the "cuprate superconductor", which corresponds to a ceramic based on cuprates (compounds containing a cuprate group) such as bismuth strontium calcium copper oxide (BSCCO) or rare earth element barium copper oxide (REBCO), and examples of rare earth elements can be Y or Gd. Other high-temperature superconductors include iron pnictides (e.g., FeAs and FeSe) and magnesium diboride (MgB 2 ).

[0006]

[0006] Among all superconductors, REBCO exhibits the best performance at high magnetic fields over a wide temperature range. Due to their stronger magnetic fields and relatively high superconducting critical temperature, these materials are proposed for future magnetic confinement fusion reactors, such as the affordable, robust, and compact (ARC) fusion reactor, which enable more compact and economical construction, and also for a new generation of magnets for use in particle accelerators such as the Large Hadron Collider (LHC) at CERN.

[0007]

[0007] In REBCO, any rare earth element can potentially be used. Some popular choices include yttrium (YBCO), dysprosium (DyBCO), samarium (Sm123), neodymium (Nd123), gadolinium (Gd123), and europium (Eu123), where the numbers in parentheses indicate the molar ratios of rare earth, barium, and copper.

[0008]

[0008] Since these types of materials are brittle, it was difficult to fabricate wires from them. Since 2005, industrial manufacturers have started producing tapes with various layers encapsulating REBCO materials, opening the way to commercial use. For example, REBCO tapes can be fabricated using an open reel process, in which the superconductor is coated as a thin film onto a flexible metal substrate with a dielectric buffer layer in between.

[0009]

[0009] The excellent current density of REBCO tapes enables highly efficient electromechanical devices with high power density. At such high current densities, the superconductor is prone to local heating at defective spots ("hot spots") that always exist in long tapes. Since the bent parts of each tape in a coil containing superconducting devices are usually insulated, the hot spots do not dissipate easily, thus causing thermal runaway (a process promoted by temperature rise, which in turn releases energy that further raises the temperature), leading to catastrophic failure (the end of operation in a normal resistive situation). The local heat accumulation leading to such thermal runaway can also be referred to as a "quench". That is, a quench refers to an abnormal termination of operation that occurs during the transition of a superconductor from the superconducting state to the normal resistive state. Therefore, a quench or a normal zone (i.e., a hot spot) needs to be detected quickly to protect superconducting devices.

[0010]

[0010] In particular, the thermal runaway leading to catastrophic failure in HTS materials such as REBCO is caused by the low normal zone propagation (NZP) speed (e.g., 0.01 - 0.1 m / s). Having such a low NZP speed causes the normal zone to spread slowly, thus slowly increasing the voltage induced by the fault. At the same time, the slow spread of heat brings about high temperatures before the voltage increases to a sufficient level for external detection. These two combined effects can cause thermal runaway and catastrophic failure of the coil before quench detection.

[0011]

[0011] Currently, numerous methods for quench detection are under development, including modifications to HTS coil designs for quench tolerance. Examples of these include acoustic emission detection, acoustic temperature measurement, Rayleigh scattering-based fiber optics, various quench antennas, ultrasonic-based detection, various laminations, non-insulated coils, various insulation materials, and epoxies. However, each solution has drawbacks such as being susceptible to vibrations, having a low signal-to-noise ratio, and external sensors wound together with the tape, which increase the complexity of coil fabrication or reduce the overall current density.

[0012]

[0012] As a result, there is currently no means for rapid quench detection in high-temperature superconductors such as REBCO before thermal runaway.

Summary of the Invention

Problems to be Solved by the Invention

[0013]

[0013] In one embodiment of the disclosure of the present invention, a method for quench detection in a superconductor includes exciting a REBCO (rare earth - barium - copper oxide) superconducting tape as a transmission line that forms a standing wave. The method further includes detecting a quench in response to detecting a disturbance of the standing wave.

[0014]

[0014] In another embodiment of the disclosure of the present invention, a system for quench detection in a superconductor includes a substrate, a buffer layer stack present on the substrate, the buffer layer stack including one or more dielectric layers, and a first REBCO layer on the buffer layer stack, the first REBCO layer including a REBCO (rare earth - barium - copper oxide) superconducting tape architecture that transports current and is used to form a transmission line with the substrate. The system further includes a first device for exciting the REBCO superconducting tape architecture to form a standing wave in the transmission line. The system also includes a first device or a second device for detecting a quench in response to detecting a disturbance of the standing wave.

[0015]

[0015] The foregoing has outlined rather generally the features and technical advantages of one or more embodiments of the disclosure of the present invention so as to enable a better understanding of the detailed description of the disclosure of the present invention that follows. Additional features and advantages of the disclosure of the present invention that may form the subject matter of the claims of the disclosure of the present invention are described below.

[0016]

[0016] A better understanding of the disclosure of the present invention can be obtained when the following detailed description is considered in conjunction with the following drawings. The drawings are as follows.

Brief Description of the Drawings

[0017]

Figure 1

[0017] FIG. 1 illustrates an embodiment of the disclosure of the present invention of a schematic layout of a REBCO superconducting tape.

Figure 2

[0018] FIG. 2 is a flowchart of a method for rapid quench detection in a high - temperature superconductor according to an embodiment of the disclosure of the present invention.

Figure 3A

[0019] FIG. 3A illustrates a system for quench detection in a REBCO superconducting tape having an integrated transmission line according to an embodiment of the disclosure of the present invention.

Figure 3B

[0020] Figure 3B illustrates an alternative system for quench detection in a REBCO superconducting tape having an integrated transmission line according to an embodiment of the disclosure of the present invention.

Figure 3C

[0021] Figure 3C illustrates a further alternative system for quench detection in a REBCO superconducting tape having an integrated transmission line according to an embodiment of the disclosure of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0018]

[0022] As described in the Background section, the excellent current density of the REBCO tape enables highly efficient electromechanical devices with high output density. At such a high current density, the superconductor is prone to local heating at defective spots ( "hot spots") that are always present in the long tape. Since the bent portions of each tape of the coil including the superconducting device are usually insulated, the hot spots do not dissipate easily, thus causing thermal runaway (a process promoted by temperature rise, which in turn releases energy that further raises the temperature), leading to catastrophic failure (the end of operation in a normal resistive situation). The local heat accumulation leading to such thermal runaway can also be referred to as a "quench". That is, a quench refers to an abnormal termination of operation that occurs during the transition of the superconductor from the superconducting state to the normal resistive state. Therefore, quenches or normal zones (i.e., hot spots) need to be detected quickly to protect the superconducting device.

[0019]

[0023] In particular, thermal runaway leading to catastrophic failure in HTS materials such as REBCO is caused by the low normal zone propagation (NZP) speed (e.g., 0.01 - 0.1 m / s). Having such a low NZP speed causes the normal zone to spread slowly, thus slowly increasing the voltage induced by the fault. At the same time, the slow spread of heat results in high temperatures before the voltage increases to a sufficient level for external detection. The combination of these two effects can cause thermal runaway and catastrophic failure of the coil before quench detection.

[0020]

[0024] Currently, numerous methods for quench detection are under development, including modifications to HTS coil designs for quench tolerance. Examples of these include acoustic emission detection, acoustic temperature measurement, Rayleigh scattering-based fiber optics, various quench antennas, ultrasonic-based detection, various laminations, non-insulated coils, various insulating materials, and epoxies. However, each solution has drawbacks such as being susceptible to vibrations, having a low signal-to-noise ratio, and external sensors wound together with the tape, which increase the complexity of coil fabrication or reduce the overall current density.

[0021]

[0012] As a result, there is currently no means for rapid quench detection in high-temperature superconductors such as REBCO before thermal runaway.

[0025] As a result, there is currently no means for rapid quench detection in high-temperature superconductors such as REBCO before thermal runaway.

[0022]

[0026] Embodiments of the present disclosure provide a means for rapid quench detection in high-temperature superconductors such as REBCO before thermal runaway by utilizing a high-temperature superconductor (e.g., REBCO) tape architecture as a transmission line at high frequencies for rapid quench detection as discussed herein.

[0023]

[0027] The following discusses the use of REBCO tape architecture as a transmission line at high frequencies for rapid quench detection, but the principles of the disclosure of the present invention are not limited to such a method, and it should be noted that any high-temperature superconductor tape architecture can be used as a transmission line at high frequencies for rapid quench detection. Those skilled in the art will be able to apply the principles of the disclosure of the present invention to such implementations. Furthermore, embodiments applying the principles of the disclosure of the present invention to such implementations are expected to be within the scope of the disclosure of the present invention.

[0024]

[0028] In some embodiments of the disclosure of the present invention, the disclosure of the present invention includes methods and systems for quench detection in high-temperature superconductors such as REBCO before thermal runaway. In one embodiment, the REBCO superconducting tape is excited as a transmission line forming a standing wave. The quench can then be detected in response to the detection of a disturbance in the standing wave. In this way, the principles of the disclosure of the present invention provide a means for rapid quench detection in high-temperature superconductors such as REBCO before thermal runaway.

[0025]

[0029] Referring now to the drawings in detail, FIG. 1 illustrates an embodiment of the disclosure of the present invention of a schematic layout of a REBCO superconducting tape 100.

[0030] As shown in FIG. 1, the REBCO (rare earth element - barium - copper oxide) superconducting tape 100 includes a substrate 101 of a structural material (e.g., Hastelloy (registered trademark), stainless steel or nickel alloy). In one embodiment, a layer of metal oxide (buffer layer stack 102) and a superconducting REBCO layer 103 are deposited on the substrate 101 together with a two-dimensional texture by chemical or physical means. In one embodiment, silver for stabilization (e.g., Ag cap layer 104) is deposited on the superconducting REBCO layer 103. In one embodiment, the tape 100 is copper stabilized with surrounding copper layers (e.g., Cu stabilization layers 105', 105"). In one embodiment, the copper stabilization layers 105', 105" are optional.

[0026]

[0031] In one embodiment, the thickness of the copper stabilization layer 105' is approximately 20 μm. In one embodiment, the thickness of the substrate 101 is approximately 50 μm. In one embodiment, the thickness of the buffer layer stack is less than 0.2 μm. In one embodiment, the thickness of the REBCO layer 103 is approximately 1 μm. In one embodiment, the thickness of the Ag cap layer 104 is approximately 2 μm. In one embodiment, the thickness of the copper stabilization layer 105" is approximately 20 μm. In one embodiment, the overall thickness of the REBCO superconducting tape 100 is less than 0.1 mm. In one embodiment, the overall thickness of the REBCO superconducting tape 100 without the copper stabilization layers 105', 105" is less than 0.06 mm.

[0027]

[0032] In one embodiment, the REBCO superconducting tape 100 is a high-temperature superconducting tape that can operate as a superconductor at temperatures above 77K. In one embodiment, the REBCO superconducting tape 100 conducts electricity with zero electrical resistance.

[0028]

[0033] As discussed above, the principles of the disclosure of the present invention provide means for rapid quench detection in high-temperature superconductors such as REBCO prior to thermal runaway. In one embodiment, a quench can be rapidly detected in REBCO (e.g., the REBCO layer 103) by utilizing the REBCO tape architecture (e.g., the REBCO superconducting tape 100) as a transmission line at a high frequency for rapid quench detection, as discussed below in connection with FIG. 2.

[0029]

[0034] FIG. 2 is a flowchart of a method 200 for rapid quench detection in a high-temperature superconductor according to an embodiment of the disclosure of the present invention.

[0035] Referring to FIG. 2 in conjunction with FIG. 1, in step 201, the REBCO superconducting tape, e.g., the REBCO superconducting tape 100, is excited as a transmission line forming a standing wave.

[0030]

[0036] In one embodiment, the tape 100 is treated as a microstrip-like transmission line in which the TEM (transverse electromagnetic mode) is excited. In one embodiment, the excitation of such a tape 100 forms a standing wave of a specific Q (quality) factor, which is a characteristic of the elements included in the circuit.

[0031]

[0037] In step 202, the quench is detected in response to the detection of a standing wave perturbation.

[0038] It should be noted that the transmission line is susceptible to any change in uniformity, dimensional change, or property change along its length, such as a change in the dielectric constant of the dielectric layer or the conductivity of the conductive layer. Since the REBCO film (e.g., the REBCO layer 103) is a non-linear device at the transition between the superconducting state and the normal state, a large change in resistivity is expected when a quench occurs locally. Unlike the voltage detection where the signal is proportional to the length of the normal conduction zone, a 100 m long transmission line is expected to effectively become two 50 m transmission lines when a quench occurs in the middle of the tape and is coupled by a resistive transmission segment. The standing wave formed in the transmission line is immediately perturbed, which can be easily detected in a sweep mode by a frequency analyzer as the source of excitation and the detection circuit (used to detect the standing wave perturbation) in one embodiment. Therefore, the standing wave perturbation is due to a change in the resistivity of the REBCO superconducting tape 100. Further, in one embodiment, the dual mode can be achieved when two excitation circuits are connected at each end of the tape 100 (or coil), or when the tape 100 is used as a transmitter (whereby the excitation is performed at one end, but the signal is detected at both ends). Such a change in the signal is expected to be detected almost instantaneously.

[0032]

[0039] In one embodiment, the standing wave perturbation is a standing wave that occurs at multiple wavelengths of a partial characteristic length in a transmission line (e.g., the length of the transmission line itself, or the length of a segment of the transmission line from one end to the quenched location), and is detected by detecting multiple reflections in a frequency sweep.

[0033]

[0040] In another embodiment, the standing wave perturbation is detected by detecting a change in the frequency of reflection, for example, when the perturbation along the transmission line changes the characteristic length or introduces a new characteristic length.

[0034]

[0041] In a further embodiment, the standing wave perturbation is detected by detecting a change in the line quality factor, for example, a change in the line quality factor of a resonance peak.

[0042] In one embodiment, the standing wave perturbation is detected by detecting a change in the line quality factor when a part of the superconductor becomes a normal conductor (quenching).

[0035]

[0043] In a further embodiment, the standing wave perturbation is detected by detecting a change in the scale of the resonance peak.

[0044] Note that the standing wave perturbation may be detected using a combination of the embodiments discussed above.

[0036]

[0045] Since the REBCO film, e.g., REBCO layer 103, and the metal substrate, e.g., substrate 101, are separated by a thin dielectric layer, e.g., the dielectric layer of buffer layer stack 102, the REBCO superconducting tape 100 can be excited by an alternating current (AC) source that produces a signal that is a function of the total capacitance or transmission line characteristics at high frequencies.

[0037]

[0046] In one embodiment, a high-temperature superconductor (HTS) tape, such as a REBCO superconducting tape 100, used in a transmission line mode, is excited in a non-contact manner. For example, capacitor plates in the vicinity of the REBCO superconducting tape 100 introduce electromagnetic waves (EM) expected to propagate along the entire length of the REBCO superconducting tape 100 (e.g., the entire length of the REBCO layer 103).

[0038]

[0047] In another embodiment, the REBCO superconducting tape 100 is excited by an induction loop and forms an EM wave again when the frequency and coupling are appropriately selected.

[0048] In one embodiment, the arrangement of the excitation of the capacitor and / or inductor is modified to introduce different wave modes (e.g., transverse waves, longitudinal waves having different polarization states, etc.). These features provide great flexibility and numerous options for circuit optimization to form a quench detection system that is most sensitive to disturbances.

[0039]

[0049] Discussions regarding various embodiments of a quench detection system using method 200 are provided below. Specifically, such embodiments utilize quench detection integrated within the REBCO superconducting tape 100.

[0040]

[0050] Referring now to FIG. 3A, FIG. 3A illustrates a system 300 for quench detection in a REBCO superconducting tape having an integrated transmission line according to an embodiment of the disclosure of the present invention.

[0041]

[0051] As shown in FIG. 3A, system 300 includes a substrate 101 corresponding to a metal substrate (conductor) having a thickness of approximately 50 μm. Further, as shown in FIG. 3A, system 300 includes a buffer layer stack 102 present on substrate 101, and buffer layer stack 102 includes a plurality of dielectric layers, such as dielectric layer 301 (e.g., alumina) and dielectric layer 302 (e.g., magnesium oxide (MgO) and lanthanum manganite (LMO)). In one embodiment, the thickness of dielectric layer 301 is approximately 80 nm. In one embodiment, the thickness of dielectric layer 302 is approximately 80 nm.

[0042]

[0052] In addition, as shown in FIG. 3A, system 300 includes a REBCO layer 103 present on buffer layer stack 102. In one embodiment, the thickness of REBCO layer 103 is approximately 1 μm.

[0043]

[0053] Further, as shown in FIG. 3A, system 300 includes an excitation device 303 configured to excite REBCO layer 103 as a transmission line that forms a standing wave. In one embodiment, excitation device 303 corresponds to an alternating current (AC) source having terminals between substrate 101 and REBCO layer 103. In one embodiment, the AC source produces a signal that is a function of the transmission line characteristics.

[0044]

[0054] In one embodiment, excitation device 303 excites REBCO layer 103 in a non-contact manner. In such an embodiment, excitation device 303 corresponds to a capacitor plate or an inductor loop. Further, in such an embodiment, such excitation introduces an electromagnetic wave that propagates along REBCO superconducting tape 100, such as REBCO layer 103.

[0045]

[0055] In addition, as shown in FIG. 3A, system 300 includes a detection device 304 configured to detect a quench in response to detecting a disturbance of the standing wave.

[0056] In one embodiment, the excitation device 303 and the detection device 304 are the same device, for example, a frequency analyzer, in which the frequency analyzer functions as both a source of excitation for detecting standing wave disturbances in a sweep mode and a sensing circuit.

[0046]

[0057] In one embodiment, the detection device 304, as discussed previously, detects standing wave disturbances via one or more of the following means: detecting multiple reflections in a frequency sweep, detecting a change in the frequency of the reflection, detecting a change in the quality factor, and detecting a change in the magnitude of the resonance peak.

[0047]

[0058] Furthermore, the detection device 304 is configured to detect standing wave disturbances via one or more of the following techniques.

[0059] For example, in one embodiment, the detection device 304 uses capacitance measurement to detect standing wave disturbances. For example, when a section of a superconducting coil quenches, the capacitance of an HTS tape, such as tape 100, changes from a superconducting capacitor of length L to two segments of lengths (1 - f)L - s / 2 and fL + s / 2 coupled by a normal capacitor of length s, where f indicates the location of the quench. Both the amplitude and phase of the AC signal are affected.

[0048]

[0060] In one embodiment, the detection device 304 uses a single - ended radio frequency sweep using contact coupling to detect standing wave disturbances. For example, in the case of using a single - ended sweep, a transmission line study of RF / microwave resonance in a tape structure such as tape structure 100 is expected to use a contact or capacitive coupling implemented above such a finite - length transmission line. Furthermore, in the case of using a single - ended sweep, the Q - factor and resonance frequency values of the resonance generated in the reflection (s11) mode are monitored.

[0049]

[0061] In one embodiment, the detection device 304 detects standing wave perturbations using a double-ended radio frequency (RF) sweep. For example, the double-ended RF sweep provides the advantage of obtaining both reflection (s11) and transmission (s12) signals and superimposing them as a function of time. Thus, reflection and propagation are correlated by the location and size of the quenched section of the coil. Phase displacement and Q factor are also correlated, which provides an increase in the spatial resolution of the quenched region. Further, the correlation between the detected modes provides an additional level of information not available in single-ended modes, so that more detailed information about the nature of the perturbation can be obtained.

[0050]

[0062] In one embodiment, the detection device 304 detects standing wave perturbations using intermodulation detection. For example, an HTS tape, such as a YBCO tape, is driven with a signal containing two frequencies f 1 and f 2 to detect the presence of non-linearity, i.e., intermodulation distortion (IMD) peaks, in the output signal. In such an embodiment, the YBCO tape acts as an RCL resonator. In one embodiment, such frequencies are generated by a two-tone generator.

[0051]

[0063] Typically, in the case of non-linearity, the IMD spectrum contains many higher-order peaks; however, in one embodiment, to conserve bandwidth, only the fundamental (f 1 and f 2 ) and third-order IMD peaks (2f 1 -f 2 and 2f 2 -f 1 ) are measured as a function of the input power, for example via a spectrum analyzer.

[0052]

[0064] Furthermore, an additional advantage of the IMD technique is its ability to investigate non-linearity at extremely low power levels with respect to its sensitivity, thereby avoiding any thermal effects.

[0053]

[0065] Referring back to FIG. 3A, the REBCO layer 103 is used to transport current (such REBCO layers are referred to herein as "T-REBCO") and forms a transmission line with the substrate 101. In one embodiment, a small-scale high-frequency signal is superimposed on the transport current via the T-REBCO 103. Since the transmission line is very sensitive only to high-frequency signals, an effective detection circuit is formed. Different from the voltage detection method where the signal during quenching is proportional to the length of the normal conducting zone (which is small in REBCO), a 100 m long transmission line is expected to effectively become two 50 m lines when a quench occurs in the middle along the tape. The standing wave formed in the transmission line is immediately disturbed, which can be easily detected by the detection device 304 as a change in the frequency of reflection and a change in the Q factor of the resonance peak.

[0054]

[0066] Referring to FIG. 3B, FIG. 3B illustrates an alternative system 300' for quench detection in an REBCO superconducting tape having an integrated transmission line according to an embodiment of the disclosure of the present invention.

[0055]

[0067] As shown in FIG. 3B, the system 300' is different from the system 300 in that a second REBCO layer 305 is present on the buffer layer stack 102. In one embodiment, the REBCO layer 305 has a thickness of approximately 100 nm. In one embodiment, the REBCO layer 305 has a thickness of 10 - 100 nm. Such a layer is referred to herein as "S-REBCO" and is used solely for detection as part of the transmission line. In one embodiment, the S-REBCO layer 305 is electrically floating with respect to all other layers and can be separately excited to serve as a detection circuit.

[0056]

[0068] Furthermore, as shown in FIG. 3B, the system 300' includes a dielectric layer 306 (e.g., LMO) present on the REBCO layer 305. In one embodiment, the thickness of the dielectric layer 306 is approximately 40 nm.

[0057]

[0069] In addition, as shown in FIG. 3B, the system 300' includes a REBCO layer 103 present on the dielectric layer 306.

[0070] In one embodiment, the excitation device 303 corresponds to a plurality of AC sources, for example, a first AC source having terminals connected between the substrate 101 and the REBCO layer 305, and a second AC source having terminals connected between the REBCO layer 305 and the REBCO layer 103, etc.

[0058]

[0071] Referring now to FIG. 3C, FIG. 3C illustrates a further alternative system 300” for quench detection in a REBCO superconducting tape having an integrated transmission line according to an embodiment of the disclosure of the present invention.

[0059]

[0072] As shown in FIG. 3C, the system 300” differs from the system 300' in that a third REBCO layer 307 is present on the dielectric layer 306. In one embodiment, the REBCO layer 307 has a thickness of approximately 100 nm. In one embodiment, the REBCO layer 307 has a thickness of 10 - 100 nm. In one embodiment, the REBCO layer 307 corresponds to an “S-REBCO” layer.

[0060]

[0073] Furthermore, in one embodiment, the REBCO layer 305 has a thickness of approximately 100 nm. In one embodiment, the REBCO layer 305 has a thickness of 10 - 100 nm. In one embodiment, the REBCO layer 305 corresponds to an “S-REBCO” layer. Alternatively, in another embodiment, the REBCO layer 305 corresponds to an S-normal conductor (e.g., TiN).

[0061]

[0074] Furthermore, as shown in FIG. 3C, the system 300” includes a dielectric layer 308 (e.g., LMO) present on the REBCO layer 307. In one embodiment, the thickness of the dielectric layer 308 is approximately 40 nm.

[0062]

[0075] In addition, as shown in FIG. 3C, system 300” includes a REBCO layer 103 that exists on the dielectric layer 308.

[0076] In one embodiment, system 300” includes two floating layers (layers 305, 307) grown for sense / transmission lines (e.g., S-REBCO / S-REBCO or S-REBCO / S normal conductor). In one embodiment, multiple couplings are expected to form characteristic peaks of different Q factors in a frequency sweep. During a quench, new reflections are formed and existing reflections are expected to change frequency, Q factor, and intensity. The spread of heat from a quench in the T-REBCO film (layer 103) to the S-REBCO film (layer 307) is expected to be almost instantaneous, easily transitioning the S-REBCO layer (layer 307) to the normal state and forming a signal change in the transmission line.

[0063]

[0077] Note that the sense layers 305, 307 form a floating circuit independent of the transport REBCO layer 103. Thus, the sense circuit is completely separated / floating and forms a very high Q line.

[0064]

[0078] As a result of the foregoing, embodiments of the present disclosure provide a means for rapidly detecting a quench in a high-temperature superconductor (HTS) by utilizing the HTS tape architecture itself as a transmission line at high frequencies. For example, in one embodiment, the HTS tape is treated as a microstrip-like transmission line, in which case the TEM mode is excited and a standing wave that is not affected by noise is formed. A quench can be rapidly detected in response to the detection of a perturbation in such a standing wave.

[0065]

[0079] For example, even in the case of a 10 km long REBCO tape in the form of a coil having an unrealistically high dielectric constant of the dielectric layer (e.g., 500 F / m), the signal propagation speed in the transmission line can be 10,000 km / s, which results in a quench response time of 0.5 ms. In another example, by using the principles disclosed in the present invention, a quenched zone size of 10 cm over a 1 km tape length is detected that has no noise interference with the measured signal. As a result, the principles disclosed in the present invention provide a rapid quench detection system.

[0066]

[0080] Furthermore, by utilizing such an embodiment, significant modifications to the HTS coil construction are avoided. For example, additional co-wound sensors for quench detection are avoided. In another example, there is no need to modify the coil design to address insulation, stability, effective current density, or lateral heat transfer.

[0067]

[0081] For purposes of illustration, various embodiments of the disclosure of the present invention have been shown, but it is not intended to be exhaustive or to be limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art that depart from the scope and spirit of the described embodiments. The terms used herein are chosen in order to best explain the principles of the embodiments, the practical application to technologies found in the marketplace, or the technological improvement thereof, or to enable those skilled in the art to understand the embodiments disclosed herein.

Description of the Reference Numerals

[0068] 100 REBCO superconducting tape 102 Buffer layer stack 103 Superconducting REBCO layer 104 Ag cap layer 105’, 105 Copper stabilization layer 300 System 301 Dielectric layer 302 Dielectric layer 303 Excitation device 304 Detection Device 305 Second REBCO Layer 306 Dielectric Layer 307 Third REBCO Layer 308 Dielectric Layer

Claims

1. A method for detecting a quench in a superconductor including a transition between a superconducting state and a resistive normal state, comprising: exciting a REBCO (rare earth - barium - copper oxide) superconducting tape as a transmission line forming a standing wave; and detecting a quench in response to detection of a disturbance of the standing wave. The method as described above.

2. The method according to claim 1, wherein the disturbance of the standing wave is caused by a change in the resistivity of the REBCO superconducting tape.

3. The disturbance of the standing wave is detected through one or more of the following: detecting a plurality of reflections in a frequency sweep, detecting a change in the frequency of the reflections, detecting a change in the quality factor, and detecting a change in the scale of the resonance peak. The method according to claim 1 or 2.

4. The disturbance of the standing wave is detected through one or more of the following techniques: capacitance measurement, single - ended radio - frequency sweep using a contact junction, single - ended radio - frequency sweep using a capacitive coupling, single - ended radio - frequency sweep using an electromagnetic coupling, double - ended radio - frequency sweep, and intermodulation detection. The method according to claim 1 or 2.

5. The method according to any one of claims 1 to 4, wherein the standing wave is formed with a specific quality factor.

6. The method according to any one of claims 1 to 5, wherein the REBCO superconducting tape is a high - temperature superconducting tape that can operate as a superconductor at a temperature above 77K.

7. The method according to claim 1 or 2, wherein the disturbance of the standing wave is detected by a frequency analyzer in a sweep mode that functions as both a source of excitation and a detection circuit.

8. The method according to any one of claims 1 to 7, wherein the excitation is performed by an AC source.

9. The method according to claim 8, wherein the AC source produces a signal that is a function of the transmission line characteristics.

10. The method according to any one of claims 1 to 7, wherein the REBCO superconducting tape is excited in a non - contact manner.

11. The method according to any one of claims 1 to 7, wherein the excitation is performed through a capacitor plate or an induction loop.

12. The method according to any one of claims 1 to 7, wherein the excitation introduces an electromagnetic wave propagating along the REBCO superconducting tape.

13. A system for detecting a quench in a superconductor including a transition between a superconducting state and a resistive normal state using the method according to claim 1, the system comprising: the REBCO superconducting tape architecture that conducts electricity with zero electrical resistance; a first device in the transmission line for exciting the REBCO superconducting tape architecture to form the standing wave; wherein the REBCO superconducting tape architecture comprises: a substrate; a buffer layer stack present on the substrate, the buffer layer stack including one or more dielectric layers; and a first REBCO layer on the buffer layer stack, the first REBCO layer being used to transport current to form the substrate and the transmission line; wherein the first device or the second device is for detecting the quench in response to detection of the disturbance of the standing wave. The above system.

14. wherein the REBCO superconducting tape architecture further comprises: a second REBCO layer present on the buffer layer stack; a first dielectric layer present on the second REBCO layer; and the first REBCO layer present on the first dielectric layer; The system according to claim 13, further comprising.

15. The system according to claim 14, wherein the second REBCO layer is used for detection as part of the transmission line.

16. The system according to claim 14 or 15, wherein the second REBCO layer is electrically floating with respect to other layers of the REBCO superconducting tape architecture.

17. wherein the REBCO superconducting tape architecture further comprises: a second REBCO layer present on the buffer layer stack; a first dielectric layer present on the second REBCO layer; a third REBCO layer present on the first dielectric layer; a second dielectric layer present on the third REBCO layer; and the first REBCO layer present on the second dielectric layer; The system according to claim 13, further comprising.

18. The system according to claim 17, wherein the second and third REBCO layers include two sensing layers forming a floating circuit independent of the first REBCO layer.

19. The system according to any one of claims 13 to 18, wherein the perturbation of the standing wave is caused by a change in the resistivity of the REBCO superconducting tape architecture.

20. The first device or the second device is as follows: Detecting a plurality of reflections in a frequency sweep; Detecting a change in the frequency of the reflection; Detecting a change in the quality factor; and Detecting a change in the scale of the resonance peak, The system according to any one of claims 13 to 18, wherein the perturbation of the standing wave is detected through one or more of the above.

21. The first device or the second device is the following technology: Capacitance measurement, single-ended radio frequency sweep using contact coupling, single-ended radio frequency sweep using capacitive coupling, single-ended radio frequency sweep using electromagnetic coupling, double-ended radio frequency sweep, and intermodulation detection, The system according to any one of claims 13 to 18, wherein the perturbation of the standing wave is detected through one or more of the above.

22. The system according to any one of claims 13 to 18, wherein the standing wave is formed with a specific quality factor.

23. The system according to any one of claims 13 to 18, wherein the first device includes a frequency analyzer configured for both exciting the REBCO superconducting tape architecture and detecting the perturbation of the standing wave.

24. The system according to any one of claims 13 to 18, wherein the first device includes an AC source configured to excite the REBCO superconducting tape architecture.

25. The system according to claim 24, wherein the AC source produces a signal that is a function of the transmission line characteristics.

26. The system according to any one of claims 13 to 18, wherein the first device excites the REBCO superconducting tape architecture in a non-contact manner.

27. The system according to any one of claims 13 to 18, wherein the first device excites the REBCO superconducting tape architecture via a capacitor plate or an induction loop.

28. The system according to any one of claims 13 to 18 and 27, wherein the excitation introduces an electromagnetic wave propagating along the first REBCO layer.

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