Superconducting coil quenching detection method by using leakage current

Abstract

The invention provides a superconducting coil quench detection method using leakage current, comprising the following steps: step 1, a first detection connection point is determined at a position adjacent to a first current connection point on a main superconducting strip part, and the first detection connection point and the first current connection point are equipotential points; 2, determining a second detection connection point on the sampling superconducting strip part, wherein the second detection connection point and a second current connection point are equipotential points; and step 3, connecting a leakage current sampling circuit to the first detection connection point and the second detection connection point, and if the leakage current sampling circuit detects leakage current, determining that quenching exists in the main superconducting strip part. The detection mode of the leakage current sampling circuit is adopted, and the problem that the superconducting magnet quench voltage is difficult to sample is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of superconducting detection, and in particular to a method for detecting a quench of a superconducting coil by utilizing leakage current. Background Art

[0002] When a superconducting magnet is working, local heating may cause a vicious cycle of temperature increase, resistance increase, heat generation power increase, and temperature further increase, resulting in a sharp quench response, causing the entire superconducting magnet to stop working. Quench detection of high-temperature superconducting magnets is a difficult problem that needs to be solved in the application of high-temperature superconducting magnets. Conventional quench detection methods include Figure 1 As shown in the figure, the voltmeter in the figure 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 be quenched. Since the resistive voltage is too small, the signal-to-noise ratio of the test is low. A longer sampling time is required to reduce the noise, and a higher judgment voltage has to be accepted.

[0003] Patent document with publication number US11353555B2 discloses a circuit for quenching an avalanche photodiode (APD) detector. The circuit may include a discrete transistor configured to draw a quench current so as to reduce a reverse bias voltage applied to the APD detector, and an integrated circuit connected to the discrete transistor, the integrated circuit including a circuit for controlling the reverse bias voltage. However, the patent document still has the defect of requiring a longer sampling time to reduce noise. Summary of the invention

[0004] In view of the defects in the prior art, an object of the present invention is to provide a superconducting coil quench detection method using leakage current.

[0005] According to a superconducting coil quench detection method using leakage current provided by the present invention, 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 a first current connection point is formed; the other end of the main superconducting tape portion is connected to the other end of the sampling superconducting tape portion, and a second current connection point is formed;

[0006] The steps include:

[0007] Step 1: determining a first detection connection point on the main superconducting tape portion adjacent to the first current connection point, wherein the first detection connection point and the first current connection point are equipotential points;

[0008] Step 2: determining a second detection connection point on the sampled superconducting tape portion, wherein the second detection connection point and the second current connection point are equipotential points;

[0009] Step 3: Connect a leakage current sampling circuit to the first detection connection point and the second detection connection point. If the leakage current sampling circuit detects a leakage current, it is determined that a quench exists in the main superconducting tape portion.

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

[0011] When a quench occurs in the main superconducting tape portion between the first current connection point and the second current connection point, 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 a quench occurs in the main superconducting tape portion between the first current connection point and the second current connection point, 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 a leakage current, and determines that a quench occurs in the main superconducting tape portion;

[0013] When the main superconducting tape between the first current connection point and the second current connection point does not quench, 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 portion does not quench.

[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 arranged adjacent to the first detection connection point.

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

[0017] A superconducting tape is pattern-etched along its length to form two parts of the superconducting tape connected only at the current output end, which serve as a main superconducting tape part and a sampling superconducting tape part respectively, and the etched superconducting tape is wound into a superconducting coil.

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

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

[0020] Take two superconducting tapes, respectively serving as a main superconducting tape portion and a sampling superconducting tape portion, place the two superconducting tapes side by side in parallel with an interval, connect the current output end of the main superconducting tape portion to one end of the sampling superconducting tape portion through a superconducting joint, and wind the two superconducting tapes 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 a connection terminal for connecting the first detection connection point and the second detection connection point is formed through the sampling connection line.

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

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

[0025] 1. The present invention solves the problem of low signal-to-noise ratio of voltage sampling and difficulty in quench detection by adopting leakage current instead of voltage sampling structure.

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

[0027] 3. The present invention is to detect leakage current. In electromagnetic measurement, the voltage accuracy of conventional detection methods can reach 1μV, and the current accuracy can reach 0.1nA. Using weak signal detection methods, the voltage accuracy can reach 0.1nV, and the current accuracy can reach 10 -5 nA, the detection method of the present invention can achieve higher accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0029] Figure 1 It is a schematic diagram of a conventional quench voltage detection method;

[0030] Figure 2 It is a schematic diagram of the structure 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 It is a schematic diagram of the development of a superconducting coil quench detection method using leakage current;

[0033] Figure 5 This is the leakage current measurement principle diagram;

[0034] Figure 6 It is a schematic diagram of the structure of a superconducting tape with a straight-line etching pattern;

[0035] Figure 7 Schematic diagram of the quench detection method for a superconducting coil with two tapes wound in parallel.

[0036] The figure shows:

[0037] Superconducting coil 100 Superconducting tape 200

[0038] Main superconducting tape portion 101 Etching pattern 300

[0039] First current connection point 1011 Superconducting joint 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 portion 102 Sampling connecting line 502

[0043] Second detection connection point 1021 Leakage current sensor 503 DETAILED DESCRIPTION

[0044] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0045] Embodiment 1:

[0046] like Figure 2-7 As shown, this embodiment provides a superconducting coil quench detection method using leakage current, comprising the following steps:

[0047] Step 1: determining a first detection connection point 1013 at a position adjacent to the first current connection point 1011 on the main superconducting tape portion 101, wherein the first detection connection point 1013 and the first current connection point 1011 are equipotential points;

[0048] Step 2: determining a second detection connection point 1021 on the sampled superconducting tape portion 102, wherein 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 portion 101 has a quench.

[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; 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; 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 arranged adjacent to the first detection connection point 1013.

[0051] The first detection connection point 1013 is not in the area 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 is quenched, 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. 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 area of ​​the vertical line, but not in the left area of ​​the vertical line.

[0052] When the main superconducting tape portion 101 between the first current connection point 1011 and the second current connection point 1012 quenches, there is a voltage difference between the first current connection point 1011 and the second current connection point 1012, there is a voltage difference between the first current connection point 1011 and the second current connection point 1012, 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 it is determined that the main superconducting tape portion 101 has a quench; when the main superconducting tape between the first current connection point 1011 and the second current connection point 1012 does not quench, 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 current connection point 1013 and the second detection connection point 1021, the leakage current sampling circuit cannot detect the leakage current, and it is determined that the main superconducting tape portion 101 does not 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 end 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 10 mΩ.

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

[0055] In another embodiment, if Figure 7 As shown, the superconducting coil 100 is prepared by the following method: two superconducting tapes are taken, respectively serving as a main superconducting tape portion 101 and a sampling superconducting tape portion 102, the two superconducting tapes are placed side by side in parallel with an interval, the current output end of the main superconducting tape portion 101 is connected to one end of the sampling superconducting tape portion 102 through a superconducting joint 400, and the two superconducting tapes are wound in parallel to form the superconducting coil 100.

[0056] Embodiment 2:

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

[0058] This embodiment provides a quench detection method using leakage current, using a superconducting tape 200 for pattern etching, and winding a superconducting coil 100, and bypassing a leakage current sampling circuit 300, 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 is formed with a first detection connection point 1013 and a second detection connection point 1021 for connecting the leakage current sampling circuit 500 as bypass lead-out contacts. The superconducting coil 100 is also formed with 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 may be wound together to replace the low-resistance sampling loop formed by pattern-etching the superconducting tape, and the two may be connected by the superconducting joint 400 or a low-resistance joint.

[0060] This embodiment uses a low-resistance or zero-resistance non-inductive voltage sampling circuit formed by etching a superconducting tape pattern or winding a superconducting wire, a leakage current quench sampling circuit and a magnet quench detection method formed by using a low-resistance or zero-resistance non-inductive sampling circuit and a leakage current measurement principle, and a superconducting magnet quench detection method formed by using a high-precision fluxgate principle current sensor and a leakage current sampling circuit.

[0061] This embodiment utilizes the unique scenario of large current (tens to hundreds of amperes) and small voltage (microvolts) during the operation of superconducting magnets, and adopts a bypass leakage current detection method to solve the problem of difficulty in sampling the superconducting magnet's overvoltage. In order to apply the leakage current method in the magnet scenario, a low-resistance or zero-resistance non-inductive sampling loop is formed by strip pattern etching or wire winding.

[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 . 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 may be formed by winding a main superconducting wire and a sampling superconducting wire in parallel, instead of a superconducting magnet wound by etching a 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, and its voltage drop is much smaller than that of conventional circuits. A bypass is constructed to draw out the leakage current when superconducting magnets are quenched, and the leakage current is monitored by a current sensor. In principle, the accuracy and speed are much higher than those of voltage detection. This principle can be used to develop a leakage current method to measure superconducting magnets.

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

[0067] The typical quench voltage of a superconducting magnet is 1μV, which is comparable to the limit of conventional detection methods. Considering the establishment of a leakage current loop in a superconductor, assuming that its typical resistance is 50μΩ, the leakage current is 20mA, which is more than 8 orders of magnitude higher than the limit of conventional detection methods. It can be seen that the detection of bypass current is much less difficult than the detection of resistive voltage in principle. In the operation of actual equipment, the reduction in detection difficulty not only means the improvement of detection accuracy, but also means that the detection can be completed quickly, so as to respond in time at the early stage of quenching; at the same time, the high signal-to-noise ratio also means that misjudgment can be greatly reduced.

[0068] Coil quench detection device:

[0069] In order to explain the working principle of the quench detection device, Figure 3 The magnet structure in the Figure 4 The main components include superconducting tape, current injection point, and leakage current detection bypass.

[0070] A loop with a sampling resistor 501 is established, and the loop is connected to the superconducting tape at two contacts, the two contacts being the first detection connection point 1013 and the second detection connection point 1021. The working principle is as follows: Figure 5 As shown, when the superconducting magnet works normally, due to the zero resistance characteristic of the superconductor, the first current connection point 1011 and the first detection connection point 1013 are equipotential, and the second current connection point 1012 and the second detection connection point 1021 are equipotential. If the superconducting magnet works 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 causes the measured leakage current to be zero.

[0071] When a certain section of the superconducting magnet, such as point C, quenches, the voltage drop from the first current connection point 1011 to the second current connection point 1012 is not zero. At this time, since 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 are still equipotential points. At this time, a leakage current will occur on 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 using a sensor to detect the leakage current, the voltage drop from the first current connection point 1011 to the second current connection point 1012 can be obtained with higher accuracy.

[0072] Superconducting tape etching pattern / superconducting tape circuit:

[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 causes the leakage current to be too small, making it more difficult to detect the leakage current, and failing to fully demonstrate the advantages of the leakage current method. To address this problem, a superconducting sampling wire is used to reduce the bypass resistance.

[0074] Figure 7 The most basic superconducting wire sampling scheme is demonstrated, that is, using the sampling superconducting tape portion 102 as the superconducting wire, connecting it to the superconducting wire through a superconducting joint 400 at one end of the superconducting magnet, and leading out a leakage current sampling circuit 500 at the measuring end. At this time, the resistance of the entire sampling loop is still very small, and the required accuracy can be achieved.

[0075] A further solution is to directly use laser, chemical or other etching methods on the main superconducting tape to produce Figure 2 or Figure 6 The etching pattern shown in the figure, under this etching pattern, the second detection connection point 1021 is directly connected to the second current connection point 1012 through a superconducting path to form an equipotential, and is not equipotential with the first detection connection point 1013 in the case of a quench. Figure 7 Similar, but the structure is simpler and more compact, and the mechanical properties are more guaranteed.

[0076] This embodiment solves the problem of low voltage sampling signal-to-noise ratio and difficult quench detection by adopting leakage current instead of voltage sampling structure. This embodiment solves the problem of excessive resistance on the sampling wire and reduces leakage current by adopting superconducting tape pattern etching or superconducting wire winding.

[0077] The present invention adopts a detection method of a leakage current sampling circuit to solve the problem of difficulty in sampling the quench voltage of a superconducting magnet.

[0078] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0079] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A method for detecting superconducting coil quench using leakage current, characterized in that: The superconducting coil (100) comprises 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; 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; The steps include: Step 1: determining a first detection connection point (1013) at a position adjacent to the first current connection point (1011) on the main superconducting tape portion (101), wherein the first detection connection point (1013) and the first current connection point (1011) are equipotential points; Step 2: determining a second detection connection point (1021) on the sampled superconducting tape portion (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), and if the leakage current sampling circuit detects leakage current, it is determined that the main superconducting tape portion (101) has a quench.

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 in a region between the first current connection point (1011) and the second current connection point (1012); When a quench occurs in the main superconducting tape portion (101) between the first current connection point (1011) and the second current connection point (1012), 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 portion (101) between the first current connection point (1011) and the second current connection point (1012) is quenched, a voltage difference exists between the first current connection point (1011) and the second current connection point (1012), a voltage difference exists 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 portion (101) is quenched; When the main superconducting tape between the first current connection point (1011) and the second current connection point (1012) does not quench, 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 portion (101) does not quench.

4. The superconducting coil quench detection method using leakage current according to claim 1, characterized in that: 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.

5. The superconducting coil quench detection method using leakage current according to claim 4, characterized in that: The second detection connection point (1021) is arranged 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: A superconducting tape (200) is pattern-etched along its length direction to form two parts of the superconducting tape connected only at the current output end, which are respectively used as a main superconducting tape part (101) and a sampling superconducting tape part (102), and the etched superconducting tape (200) is 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 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, respectively serving as a main superconducting tape portion (101) and a sampling superconducting tape portion (102), and the two superconducting tapes are placed side by side in parallel and spaced apart, and the current output end of the main superconducting tape portion (101) is connected to one end of the sampling superconducting tape portion (102) through a superconducting joint (400), and the two superconducting tapes are wound in parallel to form a superconducting coil (100).

9. The superconducting coil quench detection method using leakage current according to claim 1, characterized in that: The leakage current sampling circuit (500) comprises 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 via the sampling connection line (502), and a connection terminal for connecting the first detection connection point (1013) and the second detection connection point (1021) is formed via the sampling connection line (502).

10. The superconducting coil quench detection method using leakage current according to claim 9, characterized in that: The sampling resistor (501) is less than or equal to 10 mΩ.

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