Quench detection method for superconducting coils using a leakage current

Abstract

This invention provides a method for detecting quench in a superconducting coil using leakage current, comprising the following steps: Step 1: Determine a first detection connection point on the main superconducting tape adjacent to a first current connection point, wherein the first detection connection point and the first current connection point are equipotential points; Step 2: Determine a second detection connection point on the sampling superconducting tape, wherein the second detection connection point and the second current connection point are equipotential points; Step 3: Connect a leakage current sampling circuit to the first and second detection connection points. If the leakage current sampling circuit detects leakage current, it is determined that quench exists in the main superconducting tape. This invention uses a leakage current sampling circuit to solve the problem of difficulty in sampling the quench voltage of superconducting magnets.

Description

Technical Field

[0001] This invention relates to the field of superconducting detection technology, and more specifically, to a method for detecting quenching in a superconducting coil using leakage current. Background Technology

[0002] Superconducting magnets, during operation, may experience a vicious cycle due to localized heating, leading to increased temperature, increased resistance, increased heating power, and further increased temperature, ultimately resulting in a rapid quench response and causing the entire superconducting magnet to cease operation. Queue detection in high-temperature superconducting magnets is a challenging problem that needs to be solved in their applications. Conventional quench detection methods include... Figure 1 As shown in the figure, the voltmeter continuously monitors the resistive voltage of the superconducting wire from beginning to end. When the resistive voltage is higher than a certain threshold, the magnet is judged to have lost quench. This method results in a low signal-to-noise ratio due to the small resistive voltage, requiring a longer sampling time to reduce noise and having to accept a higher criterion voltage.

[0003] US Patent Publication No. 11353555B2 discloses a circuit for quenching an avalanche photodiode (APD) detector. This circuit may include a discrete transistor configured to draw quench current to reduce the reverse bias voltage applied to the APD detector, and an integrated circuit connected to the discrete transistor, the integrated circuit including features for controlling the reverse bias voltage. However, this patent still suffers from the drawback of requiring a longer sampling time to reduce noise. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for detecting quenching in superconducting coils using leakage current.

[0005] According to the present invention, a method for detecting quenching of a superconducting coil using leakage current is provided. The superconducting coil includes a main superconducting tape portion and a sampling superconducting tape portion. One end of the main superconducting tape portion is isolated from one end of the sampling superconducting tape portion and forms a first current connection point. The other end of the main superconducting tape portion is connected to the other end of the sampling superconducting tape portion and forms a second current connection point.

[0006] Includes the following steps:

[0007] Step 1: Determine a first detection connection point on the main superconducting tape near the first current connection point. The first detection connection point and the first current connection point are equipotential points.

[0008] Step 2: Determine a second detection connection point on the sampling superconducting tape section. The second detection connection point and the second current connection point are equipotential points.

[0009] Step 3: Connect the leakage current sampling circuit to the first detection connection point and the second detection connection point. If the leakage current sampling circuit detects leakage current, it is determined that the main superconducting tape has lost superelevation.

[0010] Preferably, the first detection connection point is not located in the area between the first current connection point and the second current connection point;

[0011] When the main superconducting tape section between the first current connection point and the second current connection point loses its quench, the first detection connection point and the first current connection point are equipotential points, and the second detection connection point and the second current connection point are equipotential points.

[0012] Preferably, when the main superconducting tape portion between the first current connection point and the second current connection point loses quench, there is a voltage difference between the first current connection point and the second current connection point, there is a voltage difference between the first detection connection point and the second detection connection point, the leakage current sampling circuit detects the leakage current, and determines that the main superconducting tape portion has lost quench;

[0013] When the main superconducting tape between the first current connection point and the second current connection point does not experience quenching, there is no voltage difference between the first current connection point and the second current connection point, there is no voltage difference between the first detection connection point and the second detection connection point, the leakage current sampling circuit cannot detect leakage current, and it is determined that the main superconducting tape does not experience quenching.

[0014] Preferably, the main superconducting tape portion and the sampling superconducting tape portion have the same length direction and are two parts wound in parallel.

[0015] Preferably, the second detection connection point is located adjacent to the first detection connection point.

[0016] Preferably, the superconducting coil is prepared by the following method:

[0017] Patterns are etched along the length of a superconducting tape to form two parts of the superconducting tape that are connected only at the current output end. These parts serve as the main superconducting tape and the sampling superconducting tape, respectively. The etched superconducting tape is then wound into a superconducting coil.

[0018] Preferably, the etching pattern is L-shaped or linear.

[0019] Preferably, the superconducting coil is prepared by the following method:

[0020] Two superconducting tapes are taken and designated as the main superconducting tape section and the sampling superconducting tape section, respectively. The two superconducting tapes are placed side by side with a gap between them. The current output terminal of the main superconducting tape section is connected to one end of the sampling superconducting tape section through a superconducting connector. The two superconducting tapes are wound in parallel to form a superconducting coil.

[0021] Preferably, the leakage current sampling circuit includes a sampling resistor, a sampling connection line, and a leakage current sensor;

[0022] The sampling resistor and the leakage current sensor are connected in series through the sampling connection line, and the sampling connection line forms a connection terminal for connecting the first detection connection point and the second detection connection point.

[0023] Preferably, the sampling resistor is less than or equal to 10mΩ.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. This invention solves the problems of low signal-to-noise ratio and difficulty in quench detection by using leakage current instead of voltage sampling.

[0026] 2. This invention solves the problem of excessive resistance on the sampling wire, thereby reducing leakage current, by using superconducting tape pattern etching or superconducting wire winding.

[0027] 3. This invention is for detecting leakage current. In electromagnetic measurements, conventional detection methods can achieve a voltage accuracy of 1μV and a current accuracy of 0.1nA. Using a weak signal detection method, the voltage accuracy can reach 0.1nV and the current accuracy can reach 10nA. -5 nA, the detection method of the present invention can achieve high accuracy. Attached Figure Description

[0028] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0029] Figure 1 This is a schematic diagram of a conventional overvoltage detection method;

[0030] Figure 2 This is a schematic diagram of a superconducting tape with an L-shaped etching pattern.

[0031] Figure 3 A schematic diagram of a superconducting coil quench detection method using leakage current;

[0032] Figure 4 A schematic diagram illustrating the superconducting coil quench detection method utilizing leakage current;

[0033] Figure 5 Schematic diagram of leakage current measurement principle;

[0034] Figure 6 This is a schematic diagram of a superconducting tape with a linear etching pattern.

[0035] Figure 7 This is a schematic diagram illustrating the quench detection method for a superconducting coil wound with two strips in parallel.

[0036] The diagram shows:

[0037] Superconducting coil 100, superconducting tape 200

[0038] Etching pattern 300 on main superconducting tape section 101

[0039] First current connection point 1011 Superconducting connector 400

[0040] Second current connection point 1012 Leakage current sampling circuit 500

[0041] First detection connection point 1013, sampling resistor 501

[0042] Sampling superconducting tape section 102, sampling connection line 502

[0043] Second detection connection point 1021 Leakage current sensor 503 Detailed Implementation

[0044] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0045] Example 1:

[0046] like Figure 2-7 As shown, this embodiment provides a method for detecting quench failure of a superconducting coil using leakage current, including the following steps:

[0047] Step 1: Determine the first detection connection point 1013 on the main superconducting tape section 101, near the first current connection point 1011. The first detection connection point 1013 and the first current connection point 1011 are equipotential points.

[0048] Step 2: Determine the second detection connection point 1021 on the sampling superconducting tape section 102. The second detection connection point 1021 and the second current connection point 1012 are equipotential points.

[0049] Step 3: Connect the leakage current sampling circuit to the first detection connection point 1013 and the second detection connection point 1021. If the leakage current sampling circuit detects leakage current, it is determined that the main superconducting tape section 101 has lost superelevation.

[0050] The superconducting coil 100 includes a main superconducting tape portion 101 and a sampling superconducting tape portion 102. One end of the main superconducting tape portion 101 is isolated from one end of the sampling superconducting tape portion 102, and a first current connection point 1011 is formed thereon. The other end of the main superconducting tape portion 101 is connected to the other end of the sampling superconducting tape portion 102, and a second current connection point 1012 is formed thereon. The main superconducting tape portion 101 and the sampling superconducting tape portion 102 have the same length direction and are two parts wound in parallel. The first detection connection point 1013 and the first current connection point 1011 are located on the same straight line parallel to the width direction of the main superconducting tape portion 101. The second detection connection point 1021 is disposed adjacent to the first detection connection point 1013.

[0051] The first detection connection point 1013 is not located in the region between the first current connection point 1011 and the second current connection point 1012; when the main superconducting tape portion 101 between the first current connection point 1011 and the second current connection point 1012 experiences quenching, the first detection connection point 1013 and the first current connection point 1011 are equipotential points, and the second detection connection point 1021 and the second current connection point 1012 are equipotential points. For example... Figure 5 As shown, the first detection connection point 1013 and the first current connection point 1011 are on the same vertical line, or the first detection connection point 1013 is located in the right region of the vertical line, but not in the left region of the vertical line.

[0052] When the main superconducting tape section 101 between the first current connection point 1011 and the second current connection point 1012 experiences a quench, there is a voltage difference between the first current connection point 1011 and the second current connection point 1012, and there is a voltage difference between the first detection connection point 1013 and the second detection connection point 1021. The leakage current sampling circuit detects the leakage current and determines that the main superconducting tape section 101 has experienced a quench. When the main superconducting tape section between the first current connection point 1011 and the second current connection point 1012 does not experience a quench, there is no voltage difference between the first current connection point 1011 and the second current connection point 1012, and there is no voltage difference between the first detection connection point 1013 and the second detection connection point 1021. The leakage current sampling circuit does not detect the leakage current and determines that the main superconducting tape section 101 has not experienced a quench.

[0053] The leakage current sampling circuit 500 includes a sampling resistor 501, a sampling connection line 502, and a leakage current sensor 503. The sampling resistor 501 and the leakage current sensor 503 are connected in series through the sampling connection line 502, and the sampling connection line 502 forms a connection terminal for connecting the first detection connection point 1013 and the second detection connection point 1021. The sampling resistor 501 is less than or equal to 10mΩ.

[0054] In this embodiment, as Figure 2 and Figure 6 As shown, the superconducting coil 100 is prepared by the following method: a pattern is etched along the length of a superconducting tape 200 to form two parts of the superconducting tape connected only at the current output end, which serve as the main superconducting tape part 101 and the sampling superconducting tape part 102, respectively. The etched superconducting tape 200 is then wound into a superconducting coil 100. The etching pattern 300 is L-shaped or linear, such as... Figure 2 As shown, the etched pattern 300 is L-shaped, as... Figure 6 As shown, the etching pattern 300 is a straight line.

[0055] In another embodiment, such as Figure 7 As shown, the superconducting coil 100 is prepared by the following method: two superconducting tapes are taken and used as the main superconducting tape section 101 and the sampling superconducting tape section 102, respectively. The two superconducting tapes are placed side by side in parallel with intervals. The current output terminal of the main superconducting tape section 101 is connected to one end of the sampling superconducting tape section 102 through a superconducting connector 400. The two superconducting tapes are wound in parallel to form the superconducting coil 100.

[0056] Example 2:

[0057] Those skilled in the art can understand this embodiment as a more specific description of Embodiment 1.

[0058] This embodiment provides a quench detection method using leakage current. A superconducting coil 100 is wound using a superconducting tape 200 with a pattern etched onto it, and a leakage current sampling circuit 300 is connected in parallel. The leakage current sampling circuit 500 includes a sampling resistor 501, a sampling connection line 502, and a leakage current sensor 503. The superconducting coil 100 has a first detection connection point 1013 and a second detection connection point 1021 formed on it for connecting to the leakage current sampling circuit 500, serving as bypass lead-out contacts. The superconducting coil 100 also has two coil current injection points, namely a first current connection point 1011 and a second current connection point 1012.

[0059] In other embodiments, the main superconducting tape / wire and the sampling superconducting tape / wire can be wound together to replace the low-resistance sampling circuit formed by pattern etching of the superconducting tape, and the two can be connected by a superconducting connector 400 or a low-resistance connector.

[0060] This embodiment utilizes a low-resistance or zero-resistance non-inductive voltage sampling circuit formed by etching superconducting tape patterns or winding superconducting wires; a leakage current quench sampling circuit and a magnet quench detection method constructed using the low-resistance or zero-resistance non-inductive sampling circuit and the leakage current measurement principle; and a superconducting magnet quench detection method constructed using a high-precision fluxgate current sensor and a leakage current sampling circuit.

[0061] This embodiment utilizes the unique scenario of high current (tens to hundreds of amperes) and low voltage (microvolts) during the operation of superconducting magnets. It adopts a bypass leakage current detection method to solve the problem of difficulty in sampling superconducting magnets when they lose overvoltage. In order to apply the leakage current method in the magnet scenario, a low-resistance or zero-resistance non-inductive sampling circuit is formed by etching strip patterns or winding wires.

[0062] like Figure 2 As shown, taking pattern etching of superconducting tape as an example, the system includes a superconducting coil 100 or a superconducting magnet and a leakage current sampling circuit 500. A current injection point is formed on the superconducting coil 100, and the leakage current sampling circuit 500 includes a sampling resistor 501 and a leakage current sensor 503.

[0063] like Figure 7 As shown, a superconducting magnet can also be formed by winding the main superconducting wire and the sampling superconducting wire together, instead of a superconducting magnet formed by etching the tape.

[0064] Leakage current generation and measurement accuracy:

[0065] For superconducting magnets, the current during normal operation is much larger than that of conventional circuits, while the voltage drop is much smaller. By constructing a bypass to draw out the leakage current when quench is lost, and monitoring the magnitude of the leakage current through a current sensor, the accuracy and speed are far superior to voltage detection. Based on this principle, a leakage current method for measuring quench can be developed.

[0066] In electromagnetic measurements, conventional detection methods can achieve a voltage accuracy of 1 μV and a current accuracy of 0.1 nA. Using weak signal detection methods, voltage accuracy can reach 0.1 nV and current accuracy can reach 10 nA. -5 nA.

[0067] The typical quench voltage of a superconducting magnet is 1 μV, comparable to the limit of conventional detection methods. Considering a leakage circuit within the superconductor, assuming a typical resistance of 50 μΩ, the leakage current would be 20 mA, exceeding the limit of conventional detection methods by more than eight orders of magnitude. Therefore, detecting bypass current is, in principle, far less difficult than detecting resistive voltage. In practical equipment operation, reduced detection difficulty not only translates to improved detection accuracy but also allows for rapid detection, enabling timely responses in the early stages of quench occurrence. Furthermore, a high signal-to-noise ratio significantly reduces false alarms.

[0068] Coil quench detection device:

[0069] To explain the working principle of the quench detection device, Figure 3 The magnet structure unfolds into Figure 4 This mainly includes superconducting tape, current injection point, and leakage current detection bypass.

[0070] A circuit with sampling resistor 501 is established, and this circuit is connected to the superconducting tape at two contact points, namely the first detection connection point 1013 and the second detection connection point 1021. Its working principle is as follows: Figure 5 As shown, when the superconducting magnet is operating normally, due to the zero-resistance characteristic of the superconductor, the first current connection point 1011 and the first detection connection point 1013 are at the same potential, as are the second current connection point 1012 and the second detection connection point 1021. If the superconducting magnet is operating normally, the voltage drop from the first current connection point 1011 to the second current connection point 1012 is zero, and the finite resistance between the first detection connection point 1013 and the second detection connection point 1021 results in zero measured leakage current.

[0071] When a section of the superconducting magnet, such as point C, experiences quenching failure, the voltage drop from the first current connection point 1011 to the second current connection point 1012 is not zero. At this time, because the superconductor on the sampling wire is still in a superconducting state, the second detection connection point 1021 and the second current connection point 1012 remain equipotential points. Meanwhile, a leakage current will occur in the bypass between the first detection connection point 1013 and the second detection connection point 1021 due to the finite voltage appearing at point C. By detecting this leakage current using a sensor, the voltage drop from the first current connection point 1011 to the second current connection point 1012 can be determined with higher accuracy.

[0072] Superconducting tape etching patterns / superconducting tape circuits:

[0073] The problem that cannot be solved by using a conventional structure to construct a leakage current loop is that the resistance from the second current connection point 1012 to the first detection connection point 1013 is too high, much greater than 50μΩ, which results in a small leakage current and increases the difficulty of detecting the leakage current, thus failing to fully demonstrate the advantages of the leakage current method. To address this issue, a superconducting sampling wire is used to reduce the bypass resistance.

[0074] Figure 7 The most basic superconducting wire sampling scheme is shown, which uses the sampling superconducting tape 102 as the superconducting wire, connects one end of the superconducting magnet to the superconducting wire through the superconducting connector 400, and leads out the leakage current sampling circuit 500 at the measurement end. At this time, the resistance of the entire sampling circuit is still very small, which can achieve the required accuracy.

[0075] A further approach involves directly fabricating, using laser, chemical, or other etching methods on the main superconducting tape, such as... Figure 2 or Figure 6 The etched pattern shown has a second detection connection point 1021 directly connected to the second current connection point 1012 through a superconducting path, forming an equipotential relationship. However, in the event of quench loss, it is not at the same potential as the first detection connection point 1013. Its working effect is similar to... Figure 7 Similar to other materials, but with a simpler and more compact structure and more reliable mechanical properties.

[0076] This embodiment solves the problems of low signal-to-noise ratio and difficulty in quench detection caused by using leakage current instead of voltage sampling. This embodiment also solves the problem of excessive resistance on the sampling wire, which reduces leakage current, by using superconducting tape pattern etching or superconducting wire winding.

[0077] This invention employs a leakage current sampling circuit to solve the problem of difficulty in sampling the overvoltage of superconducting magnets.

[0078] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0079] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for detecting quenching in a superconducting coil using leakage current, characterized in that, The superconducting coil (100) includes a main superconducting tape portion (101) and a sampling superconducting tape portion (102); one end of the main superconducting tape portion (101) is isolated from one end of the sampling superconducting tape portion (102) and forms a first current connection point (1011); the other end of the main superconducting tape portion (101) is connected to the other end of the sampling superconducting tape portion (102) and forms a second current connection point (1012); Includes the following steps: Step 1: Determine a first detection connection point (1013) on the main superconducting tape (101) near the first current connection point (1011), where the first detection connection point (1013) and the first current connection point (1011) are equipotential points; Step 2: Determine a second detection connection point (1021) on the sampling superconducting tape section (102), wherein the second detection connection point (1021) and the second current connection point (1012) are equipotential points; Step 3: Connect the leakage current sampling circuit to the first detection connection point (1013) and the second detection connection point (1021). If the leakage current sampling circuit detects leakage current, it is determined that the main superconducting tape section (101) has lost superelevation.

2. The superconducting coil quench detection method using leakage current according to claim 1, characterized in that, The first detection connection point (1013) is not located in the area between the first current connection point (1011) and the second current connection point (1012); When the main superconducting tape section (101) between the first current connection point (1011) and the second current connection point (1012) loses quench, the first detection connection point (1013) and the first current connection point (1011) are equipotential points, and the second detection connection point (1021) and the second current connection point (1012) are equipotential points.

3. The superconducting coil quench detection method using leakage current according to claim 2, characterized in that, When the main superconducting tape section (101) between the first current connection point (1011) and the second current connection point (1012) loses quench, there is a voltage difference between the first current connection point (1011) and the second current connection point (1012), and there is a voltage difference between the first detection connection point (1013) and the second detection connection point (1021). The leakage current sampling circuit detects the leakage current and determines that the main superconducting tape section (101) has lost quench. When the main superconducting tape between the first current connection point (1011) and the second current connection point (1012) does not experience quenching, there is no voltage difference between the first current connection point (1011) and the second current connection point (1012), there is no voltage difference between the first detection connection point (1013) and the second detection connection point (1021), the leakage current sampling circuit cannot detect leakage current, and it is determined that the main superconducting tape section (101) does not experience quenching.

4. The superconducting coil quench detection method using leakage current according to claim 1, characterized in that, The main superconducting tape section (101) and the sampling superconducting tape section (102) have the same length direction and are two parts wound in parallel.

5. The superconducting coil quench detection method using leakage current according to claim 4, characterized in that, The second detection connection point (1021) is located adjacent to the first detection connection point (1013).

6. The superconducting coil quench detection method using leakage current according to claim 4, characterized in that, The superconducting coil (100) is prepared by the following method: Pattern etching is performed along the length of a superconducting tape (200) to form two superconducting tape parts connected only at the current output end, which serve as the main superconducting tape part (101) and the sampling superconducting tape part (102), respectively. The etched superconducting tape (200) is then wound into a superconducting coil (100).

7. The superconducting coil quench detection method using leakage current according to claim 6, characterized in that, The etching pattern (300) is either L-shaped or straight-line shaped.

8. The superconducting coil quench detection method using leakage current according to claim 4, characterized in that, The superconducting coil (100) is prepared by the following method: Two superconducting tapes are taken and used as the main superconducting tape section (101) and the sampling superconducting tape section (102) respectively. The two superconducting tapes are placed side by side in parallel with intervals. The current output end of the main superconducting tape section (101) is connected to one end of the sampling superconducting tape section (102) through a superconducting connector (400). The two superconducting tapes are wound in parallel to form a superconducting coil (100).

9. The method for detecting quenching of a superconducting coil using leakage current according to claim 1, characterized in that, The leakage current sampling circuit (500) includes a sampling resistor (501), a sampling connection line (502), and a leakage current sensor (503); The sampling resistor (501) and the leakage current sensor (503) are connected in series through the sampling connection line (502), and the sampling connection line (502) forms a connection terminal for connecting the first detection connection point (1013) and the second detection connection point (1021).

10. The method for detecting quenching of a superconducting coil using leakage current according to claim 9, characterized in that, The sampling resistor (501) is less than or equal to 10mΩ.

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