High-precision high-temperature superconducting magnet temperature detection method based on optical fiber interference principle

Abstract

The invention relates to a high-precision high-temperature superconducting magnet temperature detection method based on an optical fiber interference principle. The core idea of the method is that the relation between the refractive index and the temperature of optical fibers is utilized, a measuring system comprises two optical fibers with the same length, one measuring optical fiber is wound along with a superconducting strip to form a superconducting magnet, and the other reference optical fiber is wound in the same structure and is located at the same environment temperature as the superconducting magnet. Light passes through the two optical fibers and then interferes in the optical coupler, light and shade stripes are generated, and the corresponding optical path difference is obtained by detecting the number change of the light and shade stripes in an interference image, so that the temperature of the superconducting magnet can be obtained. The temperature of the superconducting magnet is detected by using the optical fiber interference system, the system has the advantages of high detection precision, high sensitivity, high reliability, high anti-interference capability and the like, and a solution is provided for temperature detection of the high-temperature superconducting magnet.

Description

Technical Field

[0001] The invention belongs to the field of superconducting magnet applications, and in particular relates to a high-precision high-temperature superconducting magnet temperature detection method based on the optical fiber interference principle. Background Art

[0002] The magnetic field generated by magnets, especially high-intensity magnetic fields, plays a vital role in the development of science and technology. It can promote the emergence of many major scientific discoveries and technological breakthroughs. Compared with ordinary magnets, high-temperature superconducting magnets have the advantages of high magnetic field intensity, low energy consumption, and small size. They show broad application potential in many cutting-edge fields such as efficient power transmission, magnetic levitation transportation systems, and advanced nuclear fusion tokamaks. However, the operating stability of high-temperature superconducting magnets is subject to temperature conditions. Even a small temperature change may significantly affect the excitation performance of the magnet, and even cause the superconducting magnet to quench, while generating a lot of heat, which will greatly reduce the working life of the equipment. Therefore, accurate temperature detection of high-temperature superconducting magnets is the key to ensure their efficient and stable operation.

[0003] Given that traditional temperature detection technologies, such as thermocouples and infrared temperature measurement, often encounter problems such as reduced measurement accuracy, slow response, or susceptibility to external interference when facing strong magnetic field environments, extreme low temperature conditions, or harsh working conditions, it is particularly urgent and important to develop a temperature detection technology designed specifically for high-temperature superconducting magnets with high accuracy and high sensitivity. This technology can not only overcome the limitations of existing methods, but also provide solid technical support and guarantee for the long-term stable operation of high-temperature superconducting magnets. Summary of the invention

[0004] The purpose of the present invention is to provide a high-precision high-temperature superconducting magnet temperature detection method based on the principle of optical fiber interference. This method can measure the temperature of a high-temperature superconducting magnet in operation and has the advantages of high detection accuracy, high sensitivity, and strong anti-interference ability.

[0005] The core idea of ​​the present invention is that when the temperature of the optical fiber changes, its refractive index will also change, thereby causing the optical path of the light in the optical fiber to change. In the optical fiber interference system, the optical path difference of the two optical fibers is quantitatively related to the temperature. The optical path difference is obtained by detecting the change in the number of light and dark fringes in the interference image before and after the temperature of the magnet changes, thereby obtaining the temperature of the superconducting magnet. A 1×2 type optical fiber coupler with a splitting ratio of 1:1 is used to split the incident light into two beams and inject them into the measuring optical fiber and the reference optical fiber. When the magnet starts to run or fails, the heat generated will increase the temperature of the measuring optical fiber, resulting in different refractive indices of the two optical fibers and an optical path difference, and the interference image will also change accordingly. Therefore, it is only necessary to detect the change in the number of light and dark fringes of the two optical fibers in the interference image to obtain the corresponding optical path difference, and the temperature of the superconducting magnet can be accurately obtained.

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

[0007] A high-precision high-temperature superconducting magnet temperature detection method based on the principle of optical fiber interference is characterized in that its measurement system includes a light source, the output port of the light source is connected to the input port of a first optical fiber coupler, the two output ports of the first optical fiber coupler are respectively connected to the input ports of two optical fibers, one of which is used as a measuring optical fiber and is wound together with a superconducting tape to form a superconducting magnet, and the other optical fiber of the same length is used as a reference optical fiber and is placed in the same ambient temperature as the superconducting magnet, the output ports of the two optical fibers are respectively connected to the two input ports of a second optical coupler, one output port of the second optical coupler is connected to a photoelectric detector to convert an optical signal into an electrical signal, and is connected to a data processor via an amplifier and a data acquisition card.

[0008] The two optical fibers have the same length. One optical fiber is used as a measuring optical fiber and is wound together with the superconducting tape to form a superconducting magnet. The other optical fiber is used as a reference optical fiber and is wound into the same structure as the measuring optical fiber and is placed in the same ambient temperature as the superconducting magnet.

[0009] Among them, the light emitted by the light source is divided into two beams of outgoing light through the optical fiber coupler, which meet and interfere in the interference device and produce alternating light and dark interference fringes. By detecting the change in the number of light and dark fringes in the interference image, the optical path difference of the outgoing light of the two optical fibers can be obtained. There is a definite relationship between the optical path difference and the temperature of the optical fiber, thereby obtaining the temperature of the superconducting magnet.

[0010] Wherein, the light source is other light-emitting devices such as a fiber laser, a distributed feedback laser or a light emitting diode.

[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] The superconducting magnet is wound from superconducting tape and is cooled by immersion cooling, gas cooling, conduction cooling or the like.

[0013] The high-precision high-temperature superconducting magnet temperature detection method using the above-mentioned optical fiber interference system comprises the following steps:

[0014] ① Start the light source, and the light it emits is divided into two beams through the first fiber coupler and enters the measuring fiber and the reference fiber respectively. Then the outgoing light intersects at the second fiber coupler and interferes to produce light and dark interference fringes. The light signal is converted into an electrical signal by the photodetector to obtain the interference image of the two light beams and input into the data processor. At this time, the initial optical path difference is set to 0.

[0015] ② Start the superconducting magnet and make it run in the superconducting state for a long time. The heat generated at this time will cause the local temperature of the measuring fiber to rise, while the temperature of the reference fiber remains unchanged, resulting in the difference in the refractive index of the measuring fiber and the reference fiber. Therefore, the optical path of the light in them also changes, resulting in a change in the number of light and dark fringes in the interference image. The detailed principle is as follows:

[0016] When the optical path difference satisfies △x=sλ, the interference image presents bright fringes; when the optical path difference satisfies △x=(s+1 / 2)λ, the interference image presents dark fringes; where s is a positive integer and λ is the wavelength of the refracted light.

[0017] In the interference system, the optical path difference can be expressed as △x=x1-x0=n1(T1)L1-n0(T0)L0=△n△L, wherein n1(T1) represents the refractive index of the measuring optical fiber at temperature T1, n0(T0) represents the refractive index of the reference optical fiber at the cooling environment temperature T0, 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 temperature change portion of the measuring optical fiber.

[0018] At the beginning, the temperature of the measuring fiber and the reference fiber is equal, T1 = T0, and the lengths of the two fibers are the same, L1 = L0, so △x = 0. When the superconducting magnet is running or fails, the heat will cause the temperature T1 of a certain length △L of the measuring fiber to change, causing the refractive index n1 to change. At this time, the change in the optical path difference △x causes the change of light and dark fringes in the interference image. By recording the number of changes in light and dark fringes to obtain the s value, the corresponding optical path difference △x can be obtained.

[0019] ③Use the data processor to process the data, and obtain the temperature change △T through the following formula to obtain the magnet temperature T:

[0020]

[0021] Where: L(T0) represents the length of the measured optical fiber at temperature T0, n(T0) represents the refractive index of the measured optical fiber at temperature T0, α T Indicates the thermal expansion coefficient of the measured optical fiber, C T It indicates the temperature coefficient of the measured optical fiber. The above data can be obtained through calibration measurement or from the manufacturer. T0 indicates the temperature of the environment where the superconducting magnet is located.

[0022] The beneficial effects of the present invention are:

[0023] The present invention discloses a high-precision high-temperature superconducting magnet temperature detection method based on the principle of optical fiber interference, which realizes accurate measurement of the temperature of the superconducting magnet. Compared with the traditional temperature detection method, this method uses the relationship between the refractive index of the optical fiber and its temperature, and uses one optical fiber as the measuring optical fiber to be wound into a superconducting magnet with a superconducting tape, and the other optical fiber as the reference optical fiber. The optical path difference is obtained by analyzing the interference image of the two beams of light to reflect the temperature change of the magnet. The temperature of the superconducting magnet can be measured during the operation of the high-temperature superconducting magnet, and has the advantages of simple operation, high detection accuracy, high sensitivity, strong anti-interference ability, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Attached Figure 1 Schematic diagram of the superconducting magnet structure prepared by winding optical fiber and superconducting tape together for measurement;

[0025] Description of reference numerals: 101 - measuring optical fiber; 102 - superconducting tape;

[0026] Attached Figure 2 is a schematic diagram of the reference optical fiber structure;

[0027] Description of reference numerals: 201 - reference optical fiber;

[0028] Attached Figure 3 This is a system connection block diagram of a high-precision high-temperature superconducting magnet temperature detection method based on the principle of optical fiber interference;

[0029] 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

[0030] 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.

[0031] The present invention provides a high-precision high-temperature superconducting magnet temperature detection method based on the optical fiber interference principle. The present invention is further described below in conjunction with embodiments and drawings.

[0032] 1. As attached Figure 1 , the measuring optical fiber and the superconducting tape are wound together to prepare the superconducting magnet 1, and the specific process is as follows:

[0033] The measuring optical fiber is fixed to the middle of the superconducting tape using a low-temperature adhesive, and then the superconducting tape and the measuring optical fiber are wound together into a solenoid shape, so as to obtain the following Figure 1 The solenoid-shaped high-temperature superconducting magnet 1 is shown.

[0034] 2. As attached Figure 2 , prepare reference fiber 2: wind the reference fiber into the same helical structure as the measurement fiber to obtain the following Figure 2 Reference fiber 2 is shown.

[0035] 3. As attached Figure 3 , is a connection block diagram of the fiber interference system of the present invention, which comprises a light source 301, the output port of the light source 301 is connected to the input port of the first fiber coupler 302, the two output ports of the first fiber coupler 302 are respectively connected to the input ports of two optical fibers, one of which is used as a measuring optical fiber 303 and is wound together with the superconducting tape to form a superconducting magnet, and the other reference optical fiber 304 is wound into the same structure as the measuring optical fiber, the output ports of the two optical fibers are respectively connected to the two input ports of the second optical coupler 305, and one output port of the second optical coupler 305 is connected to a photodetector 306 to convert the optical signal into an electrical signal, which is then connected to a data processor 309 via an amplifier 307 and a data acquisition card 308.

[0036] The two optical fibers have the same length. One optical fiber is wound into a superconducting magnet 310 together with the superconducting tape as the measuring optical fiber 303, and the other optical fiber is wound into a reference optical fiber 304 with the same structure as the measuring optical fiber 303 and is placed in the same ambient temperature as the superconducting magnet.

[0037] The light source 301 is a fiber laser, a distributed feedback laser or other light emitting device, such as a light emitting diode.

[0038] The first optical fiber coupler 302 is of 1×2 type, and the splitting ratio is 1:1. The second optical fiber coupler 305 is of 2×1 type.

[0039] The following are the functions of the relevant devices in the embodiment:

[0040] The light source 301 is a self-made 1550nm band fiber laser with an output light intensity of 50mW and a line width of 8kHz. Other distributed feedback lasers or other light-emitting devices may also be used.

[0041] The optical fiber coupler 302 is a 1x2 common single-mode optical fiber coupler with a splitting ratio of 1:1.

[0042] The photodetector 306 is a high-speed detector that converts optical signals into electrical signals. The bandwidth of the photodetector used in the example of the present invention is 900 MHz, which can realize high-speed optical pulse signal detection. Other types of high-speed photodetectors can also be used.

[0043] The amplifier 307 is a device for amplifying electrical signals, and other types of microwave amplifying elements may also be used.

[0044] The data acquisition card 308 is a device for triggering data acquisition, and the sampling rate is 5 GS / s. Other types of high-speed acquisition cards can also be used.

[0045] The data processor 309 is mainly used to process and display in real time the data collected by the data acquisition card 308. The system software written in the example of the present invention is based on the data acquisition card for processing.

[0046] The high-precision high-temperature superconducting magnet temperature detection method using the above-mentioned optical fiber interference system comprises the following steps:

[0047] ① Start the light source, and the light it emits is divided into two beams through the first fiber coupler and enters the measuring fiber and the reference fiber respectively. Then the outgoing light intersects at the second fiber coupler and interferes to produce light and dark interference fringes. The light signal is converted into an electrical signal by the photodetector to obtain the interference image of the two light beams and input into the data processor. At this time, the initial optical path difference is set to 0.

[0048] ② Start the superconducting magnet and make it run in the superconducting state for a long time. The heat generated at this time will cause the local temperature of the measuring fiber to rise, while the temperature of the reference fiber remains unchanged, resulting in the difference in the refractive index of the measuring fiber and the reference fiber. Therefore, the optical path of the light in them also changes, resulting in a change in the number of light and dark fringes in the interference image. The detailed principle is as follows:

[0049] When the optical path difference satisfies △x=sλ, the interference image presents bright fringes; when the optical path difference satisfies △x=(s+1 / 2)λ, the interference image presents dark fringes; where s is a positive integer and λ is the wavelength of the refracted light.

[0050] In the interference system, the optical path difference can be expressed as △x=x1-x0=n1(T1)L1-n0(T0)L0=△n△L, wherein n1(T1) represents the refractive index of the measuring optical fiber at temperature T1, n0(T0) represents the refractive index of the reference optical fiber at the cooling environment temperature T0, 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 temperature change portion of the measuring optical fiber.

[0051] At the beginning, the temperature of the measuring fiber and the reference fiber is equal, T1 = T0, and the lengths of the two fibers are the same, L1 = L0, so △x = 0. When the superconducting magnet is running or fails, the heat will cause the temperature T1 of a certain length △L of the measuring fiber to change, causing the refractive index n1 to change. At this time, the change in the optical path difference △x causes the change of light and dark fringes in the interference image. By recording the number of changes in light and dark fringes to obtain the s value, the corresponding optical path difference △x can be obtained.

[0052] ③Use the data processor to process the data, and obtain the temperature change △T through the following formula to obtain the magnet temperature T:

[0053]

[0054] Where: L(T0) represents the length of the measured optical fiber at temperature T0, n(T0) represents the refractive index of the measured optical fiber at temperature T0, α T Indicates the thermal expansion coefficient of the measured optical fiber, C T It indicates the temperature coefficient of the measured optical fiber. The above data can be obtained through calibration measurement or from the manufacturer. T0 indicates the temperature of the environment where the superconducting magnet is located.

[0055] 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 high-precision high-temperature superconducting magnet temperature detection method based on the principle of optical fiber interference, characterized in that its measurement system includes a light source, the output port of the light source is connected to the input port of a first optical fiber coupler, the two output ports of the first optical fiber coupler are respectively connected to the input ports of two optical fibers, one of which is used as a measuring optical fiber and is wound together with a superconducting tape to form a superconducting magnet, and the other optical fiber of the same length is used as a reference optical fiber and is placed in the same ambient temperature as the superconducting magnet, the output ports of the two optical fibers are respectively connected to the two input ports of a second optical coupler, and one output port of the second optical coupler is connected to a photodetector to convert an optical signal into an electrical signal, which is then connected to a data processor via an amplifier and a data acquisition card. The two optical fibers have the same length. One optical fiber is used as a measuring optical fiber and is wound together with the superconducting tape to form a superconducting magnet. The other optical fiber is used as a reference optical fiber and is wound into the same structure as the measuring optical fiber and is placed in the same ambient temperature as the superconducting magnet. The light emitted by the light source is divided into two beams through the fiber coupler. The two beams meet and interfere in the interference device to produce alternating light and dark interference fringes. By detecting the change in the number of light and dark fringes in the interference image, the optical path difference of the two optical fiber output lights can be obtained. There is a definite relationship between the optical path difference and the fiber temperature, and thus the temperature of the superconducting magnet can be obtained.

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

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: The superconducting magnet is wound by superconducting tape and is cooled by immersion cooling, gas cooling, conduction cooling or the like.

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