High-temperature superconducting magnet stress detection method based on optical fiber interference

Abstract

The invention provides a high-temperature superconducting magnet stress detection method based on an optical fiber interference system. The core mechanism lies in the response of the refractive index of the optical fiber to the stress, two optical fibers with the same length are arranged in parallel, one optical fiber serves as a measuring optical fiber and forms a superconducting magnet structure together with a superconducting strip, and the other optical fiber serves as a reference optical fiber and is arranged in the same environment as a superconducting magnet but in an unstressed state. The light emitted by the light source is transmitted in the two optical fibers to form interference, and the optical path difference can be calculated by precisely analyzing the number change of light and shade stripes in an interference pattern, so that the strain condition of the superconducting magnet can be precisely measured. The optical fiber interference system is used for superconducting magnet stress detection, the method has the remarkable advantages of being high in precision and sensitivity, easy to operate and the like, and an efficient and reliable solution is provided for high-temperature superconducting magnet stress measurement.

Description

Technical Field

[0001] The invention belongs to the field of superconducting magnet applications and relates to a high-temperature superconducting magnet stress detection method based on an optical fiber interference system. Background Art

[0002] Superconducting magnets, with their excellent physical properties, such as excellent electromagnetic performance and energy-saving advantages, have opened up broad application prospects in high-tech fields such as power transmission, energy and medical equipment. However, the operating stability of high-temperature superconducting magnets is significantly affected by strain. Even a small stress fluctuation may cause changes in the state of the magnet or even quench, triggering a large amount of heat energy release and causing damage to the equipment. Therefore, accurate stress monitoring of high-temperature superconducting magnets is crucial to ensure their efficient and stable operation.

[0003] Traditional detection methods, such as magnetic measurement and mechanical methods, face limitations such as decreased measurement accuracy, high operation complexity and low detection efficiency in extreme environments such as strong magnetic fields and low temperatures. In view of this, the development of a superconducting magnet stress detection technology that combines high precision and high sensitivity has become the key to promoting the stable operation of high-temperature superconducting magnets. Summary of the invention

[0004] The present invention aims to propose a high-temperature superconducting magnet stress detection method based on an optical fiber interferometer system, which can measure the stress of a superconducting magnet during the operation of the high-temperature superconducting magnet and has the advantages of high detection accuracy, high sensitivity, and strong anti-interference ability.

[0005] The core idea of ​​the present invention is: based on the intrinsic relationship between the refractive index of optical fiber and strain, in the fiber optic interference system, the change in the optical path difference of the two optical fibers can accurately map the slight change in stress. By analyzing the change in the number of light and dark fringes in the interference image before and after the stress change, the subtle difference in the optical path difference can be captured, and then related to the stress state of the magnet. A 1×2 fiber coupler with a 1:1 splitting ratio is used to split a single light beam into two paths: measurement and reference. When the superconducting magnet is started or encounters an abnormality, the disturbance of the magnet directly causes the change in the stress of the measuring fiber, resulting in a difference in the refractive index of the two optical fibers. By focusing on the measurement of the number of fringes in the interference image, the precise change in the optical path difference can be obtained, thereby achieving accurate capture of the stress change of the magnet.

[0006] The technical solution of the present invention is as follows:

[0007] A stress detection method for a high-temperature superconducting magnet based on an optical fiber interference system is characterized in that stress detection is realized by using the principle of optical fiber interference. The specific structure is as follows: the transmitting end of the light source is connected to the receiving end of the first optical fiber coupler, and the two output ends of the coupler are respectively connected to two optical fibers, one of which is wound together with the superconducting tape and acts as a measuring optical fiber, and the other is wound into the same structure as a reference optical fiber, and the ends of the two optical fibers are respectively connected to the input end of the second optical fiber coupler. The coupled optical signal is transmitted to the photoelectric detector for conversion of the photoelectric signal, and then the electrical signal is enhanced by the amplifier and then sent to the data processor for analysis via the data acquisition card.

[0008] Among the two optical fibers of equal length, the measuring optical fiber and the superconducting tape jointly construct a superconducting magnet, while the reference optical fiber is wound with the same structure as the measuring optical fiber under the same environmental conditions, and the ambient temperature remains constant throughout the process.

[0009] In the interference device, two beams of light interfere with each other, and the changes in the light and dark fringes in the generated interference image are accurately collected. By analyzing the changes in the fringes, the optical path difference after strain is calculated. Based on the deterministic relationship between the optical path difference and the stress of the superconducting magnet, the stress of the superconducting magnet can be accurately calculated.

[0010] Wherein, the light source is a fiber laser or other light-emitting device.

[0011] The first optical fiber coupler is of 1×2 type with a splitting ratio of 1:1. The second optical fiber coupler is of 2×1 type.

[0012] Among them, superconducting magnets adopt cooling methods such as immersion cooling, gas cooling, and conduction cooling.

[0013] The method for detecting stress of a high temperature superconducting magnet using the above-mentioned optical fiber interference system comprises the following steps:

[0014] ① Fiber optic interference system initialization and signal conversion: After the system is started, the light source is activated and first enters the first fiber optic coupler. The light beam is then accurately distributed to form two independent optical paths for the measurement light and the reference light. The measurement light and the reference light propagate along the measurement fiber and the reference fiber respectively, and then intersect at the second fiber optic coupler to achieve interference fusion of the optical paths. At this time, the two light waves meet in a completely synchronized state, and the optical path difference returns to zero. Subsequently, the interference light pattern is efficiently converted by the photodetector, converting the optical signal into an electrical signal to generate an initial interference image. The signal is then sent to the data processor, laying the foundation for subsequent precision analysis and real-time monitoring, ensuring the precise startup and stable operation of the system.

[0015] ② When the superconducting magnet is started and continues to operate in the superconducting state, if the magnet experiences strain, this physical change will be directly transmitted to the measuring optical fiber, causing its structural strain. As a result, the effective length of the light propagation path in the measuring optical fiber changes, that is, the optical path changes significantly. The specific principles are as follows:

[0016] In the interference image, if the optical path difference OPD = kλ, the interference image is bright fringes; if the optical path difference OPD = (k+1 / 2)λ, the interference image is dark fringes; where k is a positive integer and λ is the wavelength of light.

[0017] In the interference system, OPD=OPL1-OPL0=n1(ε1)L1-n0(ε0)L0=△n△L, wherein n1(ε1) represents the refractive index of the measuring optical fiber under stress ε1, n0(ε0) represents the refractive index of the reference optical fiber under initial stress ε0, L1 represents the length of the measuring optical fiber, L0 represents the length of the reference optical fiber, and △L represents the length of the stress change section of the measuring optical fiber.

[0018] At the beginning, the length and stress of the measuring fiber and the reference fiber are equal, L1 = L0, ε1 = ε0, so OPD = 0. When the superconducting magnet continues to operate, the strain of the superconducting magnet causes the stress ε1 of a certain length △L of the measuring fiber to change, which causes the refractive index n1 to change. At this time, the optical path difference OPD causes the change of light and dark fringes in the interference image. The corresponding optical path difference OPD can be obtained by recording the number of changes in light and dark fringes to obtain the k value.

[0019] ③ The data processor performs data processing, assuming that the optical fiber is initially in a zero stress state, that is, ε0=0, and uses the following formula to obtain the magnet stress ε after the change:

[0020]

[0021] Where: L represents the length of the measured optical fiber, n(ε0) represents the refractive index of the measured optical fiber under the initial stress ε0, C ε Indicates the strain coefficient of the measured optical fiber. The above data can be obtained through calibration measurement or from the manufacturer.

[0023] The beneficial effects of the present invention are:

[0024] The present invention innovatively uses fiber interferometry technology to propose a precise detection method for high-temperature superconducting magnet stress. This scheme achieves precise detection of superconducting magnet stress by measuring the optical path difference between the optical fiber and the reference optical fiber.

[0025] Compared with traditional detection methods, the core advantages of this method are: simplified operation, using the direct correlation between the optical fiber refractive index and stress to simplify the stress detection process; high-precision detection, accurately reflecting the stress changes of the superconducting magnet to ensure the accuracy of the measurement; high sensitivity, sensitive to tiny stress changes, and achieving fine monitoring; strong anti-interference performance, still maintaining measurement stability and reliability in complex electromagnetic environments.

[0026] This scheme involves tightly winding one optical fiber in a superconducting tape as a measurement optical fiber and the other as a reference optical fiber. The interference of the two beams of light clearly reveals the stress state, providing strong technical support for real-time monitoring of high-temperature superconducting magnets and significantly improving the stability and safety of superconducting magnet operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Attached Figure 1 Schematic diagram of the superconducting magnet structure prepared by winding optical fiber and superconducting tape together for measurement;

[0028] Description of reference numerals: 101 - measuring optical fiber; 102 - superconducting tape;

[0029] Attached Figure 2 is a schematic diagram of the reference optical fiber structure;

[0030] Description of reference numerals: 201 - reference optical fiber;

[0031] Attached Figure 3 The system connection block diagram of a high-temperature superconducting magnet temperature detection method based on optical fiber interferometry;

[0032] Description of reference numerals: 301 - light source; 302 - first optical fiber coupler; 303 - measuring optical fiber; 304 - reference optical fiber; 305 - second optical fiber coupler; 306 - photodetector; 307 - amplifier; 308 - data acquisition card; 309 - data processor; 310 - high temperature superconducting magnet; DETAILED DESCRIPTION

[0033] The following will be combined with the accompanying drawings in the examples of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. It is obvious that the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] The present invention provides a high-temperature superconducting magnet stress detection method based on an optical fiber interference system, which is further described below in conjunction with embodiments and drawings.

[0035] 1. As attached Figure 1, the measuring optical fiber and the superconducting tape are wound together to form a superconducting magnet 1, and the specific process is as follows:

[0036] The measuring optical fiber is fixed to the middle of the superconducting tape using a low-temperature adhesive, and the superconducting tape and the measuring optical fiber are wound together into a solenoid shape to obtain an attached Figure 1 The solenoid-shaped high-temperature superconducting magnet 1 is shown.

[0037] 2. As attached Figure 2 , prepare reference fiber 2: wind the reference fiber into the same shape as the measurement fiber to obtain the attached Figure 2 Reference fiber 2 is shown.

[0038] 3. As attached Figure 3 , is the structural layout of the fiber interference system of the present invention. The construction of the system revolves around the core components, and the specific composition is as follows:

[0039] Light source module (301): At the beginning of the system, it is responsible for providing a stable light source. In the embodiment, it is a 632.8nm band helium-neon laser with an output light intensity of 35mW and a line width of 1MHz. Other fiber lasers or other light-emitting devices may also be used.

[0040] The first optical fiber coupler (302): 1×2 type, with a splitting ratio of 1:1, is connected to the light source outlet and evenly distributes the light beam to the two optical fibers.

[0041] Measuring optical fiber (303): tightly wound with the superconducting tape, directly sensing stress changes.

[0042] Reference optical fiber (304): wound similarly to the measurement optical fiber, used to provide a reference signal.

[0043] The second optical fiber coupler (305): a 2×1 type, where two optical fiber signals meet to produce an interference effect.

[0044] Photoelectric detector (306): captures interference light and converts optical signals into electrical signals. The bandwidth of the photoelectric detector used in the embodiment of the present invention is 25 GHz, which can realize high-speed optical pulse signal detection. Other types of high-speed photoelectric detectors can also be used.

[0045] Amplifier (307): enhances the electrical signal and improves the accuracy of subsequent processing.

[0046] Data acquisition card (308): A device for triggering data acquisition, with a sampling rate of 3GS / s. High-speed acquisition cards from other companies can also be used. Responsible for signal digitization and preparing data processing.

[0047] Data processor (309): core analysis unit, analyzes stress change information, processes and displays the data collected by the data acquisition card 308 in real time. The system processing software written in the example of the present invention is based on the data acquisition card.

[0048] The entire system achieves seamless connection from light source to signal analysis through precise optical fiber layout and photoelectric conversion technology, ensuring efficient and accurate stress detection.

[0049] The stress detection of a high temperature superconducting magnet using the above-mentioned optical fiber interferometry system includes the following steps:

[0050] ① Fiber optic interference system initialization and signal conversion: After the system is started, the light source is activated and first enters the first fiber optic coupler. The light beam is then accurately distributed to form two independent optical paths for the measurement light and the reference light. The measurement light and the reference light propagate along the measurement fiber and the reference fiber respectively, and then intersect at the second fiber optic coupler to achieve interference fusion of the optical paths. At this time, the two light waves meet in a completely synchronized state, and the optical path difference returns to zero. Subsequently, the interference light pattern is efficiently converted by the photodetector, converting the optical signal into an electrical signal to generate an initial interference image. The signal is then sent to the data processor, laying the foundation for subsequent precision analysis and real-time monitoring, ensuring the precise startup and stable operation of the system.

[0051] ② When the superconducting magnet is started and continues to operate in the superconducting state, if the magnet experiences strain, this physical change will be directly transmitted to the measuring optical fiber, causing its structural strain. As a result, the effective length of the light propagation path in the measuring optical fiber changes, that is, the optical path changes significantly. The specific principles are as follows:

[0052] In the interference image, if the optical path difference OPD = kλ, the interference image is bright fringes; if the optical path difference OPD = (k+1 / 2)λ, the interference image is dark fringes; where k is a positive integer and λ is the wavelength of light.

[0053] In the interference system, OPD=OPD1-OPD0=n1(ε1)L1-n0(ε0)L0=△n△L, wherein n1(ε1) represents the refractive index of the measuring optical fiber under stress ε1, n0(ε0) represents the refractive index of the reference optical fiber under initial stress ε0, L1 represents the length of the measuring optical fiber, L0 represents the length of the reference optical fiber, and △L represents the length of the stress change section of the measuring optical fiber.

[0054] At the beginning, the length and stress of the measuring fiber and the reference fiber are equal, L1 = L0, ε1 = ε0, so OPD = 0. When the superconducting magnet continues to operate, the strain of the superconducting magnet causes the stress ε1 of a certain length △L of the measuring fiber to change, which causes the refractive index n1 to change. At this time, the optical path difference OPD causes the change of light and dark fringes in the interference image. The corresponding optical path difference OPD can be obtained by recording the number of changes in light and dark fringes to obtain the k value.

[0055] ③ The data processor performs data processing, assuming that the optical fiber is initially in a zero stress state, that is, ε0=0, and uses the following formula to obtain the magnet stress ε after the change:

[0056]

[0057] Where: L represents the length of the measured optical fiber, n(ε0) represents the refractive index of the measured optical fiber under the initial stress ε0, C ε Indicates the strain coefficient of the measured optical fiber. The above data can be obtained through calibration measurement or from the manufacturer.

[0059] The above description is only an example of the implementation of the solenoid-shaped superconducting magnet of the present invention, and is not intended to limit the protection scope of the present invention. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention. For example, the light source can be natural single-shot light, lasers of other wavelengths, infrared lasers, etc.; other shapes of high-temperature superconducting magnets such as D-type, racetrack type, etc., and the superconducting materials can be wires, strips or composite conductors, etc., all of which are covered within the protection scope of the present invention.

Claims

1. A stress detection method for a high-temperature superconducting magnet based on an optical fiber interference system, characterized in that stress detection is achieved by using the principle of optical fiber interference. The specific structure is as follows: the transmitting end of the light source is connected to the receiving end of the first optical fiber coupler, and the two output ends of the coupler are respectively connected to two optical fibers, one of which is wound together with the superconducting tape and acts as a measuring optical fiber, and the other is wound into the same structure as a reference optical fiber, and the ends of the two optical fibers are respectively connected to the input end of the second optical fiber coupler. The coupled optical signal is transmitted to the photoelectric detector for conversion of the photoelectric signal, and then the electrical signal is enhanced by the amplifier and then sent to the data processor for analysis via the data acquisition card. Of the two optical fibers of equal length, the measurement fiber and the superconducting tape together construct a superconducting magnet, while the reference fiber is wound with the same structure as the measurement fiber under the same environmental conditions, and the ambient temperature remains constant throughout the process. In the interference device, two beams of light interfere with each other, and the changes in the light and dark fringes in the generated interference image are accurately collected. By analyzing the changes in the fringes, the optical path difference after strain is calculated. Based on the deterministic relationship between the optical path difference and the stress of the superconducting magnet, the stress of the superconducting magnet can be accurately calculated.

2. The method according to claim 1, characterized in that The light source is a fiber laser or other light emitting device.

3. The method according to claim 1, characterized in that The first optical fiber coupler is of 1×2 type, and the splitting ratio is 1:

1. The second optical fiber coupler is of 2×1 type.

4. The method according to claim 1, characterized in that: Superconducting magnets are cooled by immersion cooling, gas cooling, and conduction cooling.

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