Safety factor profile measurement system and method based on magnetofluid instability

Abstract

The invention provides a safety factor profile measurement system and method based on magnetofluid instability, relates to the technical field of nuclear science, and solves the problem of measurement of safety factor distribution of a Tokamak device in the prior art. A magnetic probe array in the system is used for measuring a circumferential modulus and a polar modulus of magnetofluid instability in plasma, and an electron cyclotron radiometer is used for measuring a spatial position of magnetofluid instability; a central processing unit of the system is used for determining the numerical value of a corresponding safety factor according to the circumferential modulus and the polar modulus of the magnetofluid instability, determining the spatial position of the corresponding safety factor according to the spatial position of the magnetofluid instability, and determining the position of the corresponding safety factor based on the determined numerical value and spatial position of the safety factor. And performing numerical fitting in combination with the boundary safety factor to obtain the safety factor distribution of the plasma full profile in the device. According to the method, the safety factors of different space points can be determined, the distribution of the safety factors can be obtained, and the reliability and robustness of measurement are improved.

Description

Technical Field

[0001] This invention relates to the field of nuclear science and technology, and is applied to magnetic confinement plasma physics research. Specifically, it relates to a safety factor profile measurement system and method based on magnetohydrodynamic instability. Background Technology

[0002] The safety factor, a key parameter describing the magnetic surface structure of magnetically confined plasma, has a decisive influence on the equilibrium stability, energy confinement performance, and fusion power output of magnetically confined fusion devices. This parameter is directly related to the macroscopic instability behavior of the plasma, including the development of magnetohydrodynamic instabilities such as sawtooth oscillations and tearing modes, which in turn affect confinement time and fusion efficiency. Studies have shown that when the safety factor value in the plasma central region is greater than 1, sawtooth instability can be effectively suppressed. Meanwhile, the formation and evolution of the edge transport barriers are highly dependent on specific distribution conditions of the safety factor; only by meeting the corresponding threshold can high-quality confinement be achieved. Furthermore, a low safety factor operating mode may offer potential advantages for increasing fusion power, but an excessively high safety factor will reduce the plasma's specific pressure limit, impairing fusion economics. Therefore, precisely controlling the safety factor profile has become one of the core technical challenges in achieving steady-state, high-efficiency fusion reactions.

[0003] Currently, the measurement of safety factor distribution mainly relies on three diagnostic methods: magnetic probes, laser polarimeters, and dynamic Stark effect spectrometers. Magnetic probes are typically installed in the plasma boundary region, indirectly deriving the corresponding safety factor by detecting the boundary current distribution; however, their measurement range is limited to the boundary and cannot obtain information about the core. Laser polarimeters invert the current density distribution based on the physical relationship between the Faraday rotation angle and the plasma current and poloidal magnetic field; however, their accuracy is easily limited by fluctuations in laser source stability, mechanical vibration interference, and stray light noise. Dynamic Stark effect spectrometers derive the current density by analyzing the pitch angle of magnetic field lines, but under conditions of multiple neutral beam injections, mutual interference between spectral lines often leads to measurement distortion. While these diagnostic methods can provide boundary constraints for safety factor inversion, they all have significant technical bottlenecks, making the accurate measurement of safety factor distribution a long-standing major challenge in the field of magnetic confinement fusion.

[0004] During plasma operation, magnetohydrodynamic instabilities such as sawtooth, tearing modes, and antishear Alfvén eigenmodes are prevalent, and their spatial structure characteristics can provide indirect clues to the distribution of the safety factor. Sawtooth instability typically occurs in plasmas with a minimum safety factor below 1, and its occurrence often indicates the existence of a rational surface with q=1. Tearing modes, due to the flattening of the local temperature profile caused by the magnetic island structure, become a typical marker of this instability. The slow frequency variation of the antishear Alfvén eigenmode over time is closely related to the minimum safety factor. These instability modes share the common characteristic that their perturbation morphology is jointly determined by the circumferential and poloidal modes, with the circumferential mode... With polar modulus The ratio directly corresponds to the safety factor. Therefore, the distribution of safety factors can be indirectly inferred in experiments by observing the modulus characteristics and spatial location of instability. However, this method is limited by the complexity of instability itself and insufficient measurement accuracy, making it difficult to meet the requirements of high-precision control.

[0005] In summary, existing safety factor measurement technologies have significant shortcomings in terms of coverage, anti-interference capability, and reliability, while methods that indirectly rely on instability cannot provide continuous and accurate profile information. This poses a severe challenge to the real-time and precise control of safety factor distribution, seriously hindering the progress of magnetic confinement fusion devices towards steady-state and efficient operation. There is an urgent need to develop novel diagnostic strategies to overcome current technological bottlenecks and lay the foundation for the commercial application of fusion energy. Summary of the Invention

[0006] The purpose of this invention is to solve the problem of measuring the safety factor distribution of tokamak devices in the prior art. Therefore, a safety factor profile measurement system and method based on magnetohydrodynamic instability is proposed. This invention utilizes mature plasma diagnostic technology to measure the modulus and spatial location of magnetohydrodynamic instability, thereby determining the safety factor at different spatial points and obtaining the safety factor distribution.

[0007] The present invention employs the following technical solutions to achieve its objective: A safety factor profile measurement system based on magnetohydrodynamic instability includes a plasma, a magnetic probe array, an electron cyclotron radiometer, and a central processing unit; the output terminal of the plasma is connected to the input terminal of the magnetic probe array and the input terminal of the electron cyclotron radiometer, respectively, and the output terminals of the magnetic probe array and the electron cyclotron radiometer are both connected to the input terminal of the central processing unit. The magnetic probe array is used to measure the circumferential and poloidal modes of magnetohydrodynamic instability in the plasma; the electron cyclotron radiometer is used to measure the spatial location of the magnetohydrodynamic instability. The central processing unit is used to determine the value of the corresponding safety factor based on the circumferential and poloidal moduli of the magnetohydrodynamic instability, determine the spatial position of the corresponding safety factor based on the spatial position of the magnetohydrodynamic instability, and obtain the safety factor distribution of the full plasma profile in the tokamak device by numerical fitting based on the determined value and spatial position of the safety factor and the boundary safety factor.

[0008] Preferably, the system further includes a display, the output of the central processing unit is connected to the input of the display, and the display is used to present the distribution of security factors measured by the central processing unit to the outside world.

[0009] Specifically, the magnetic probe array includes a circumferential probe group and a poloidal probe group, and both the circumferential probe group and the poloidal probe group consist of at least two probes; the circumferential probe group is used to measure the circumferential modulus of magnetohydrodynamic instability in the plasma. The poloidal probe array is used to measure the poloidal modulus of magnetohydrodynamic instability in the plasma. .

[0010] Specifically, the spatial position measured by the electron cyclotron radiometer By plasma magnetic field strength and operating frequency The decision is as follows:

[0011] In the formula, The large radius of the tokamak device; the operating frequency of the electron cyclotron radiometer. As determined by its design specifications, measurements are performed using a given plasma magnetic field strength. The corresponding spatial location is obtained in this way. .

[0012] Specifically, the plasma is a highly ionized quasi-neutral gas, and various magnetohydrodynamic instabilities exist within the plasma, including serrated, tearing, and anti-shear Alfvén eigenmodes.

[0013] Preferably, the electron cyclotron radiometer is used to measure the spatial position corresponding to the sawtooth, thereby enabling the central processing unit to obtain the spatial position of the rational surface of the first safety factor; the electron cyclotron radiometer is also used to measure the spatial position corresponding to the tearing mode, thereby enabling the central processing unit to obtain the spatial position of the rational surface of the second safety factor; the electron cyclotron radiometer is also used to determine its spatial position by measuring the frequency change of the anti-shear Alfvén eigenmode, thereby enabling the central processing unit to obtain the spatial position of the minimum safety factor; the central processing unit is used to obtain the safety factor distribution of the entire plasma profile by numerical fitting based on the obtained spatial positions of the multiple safety factors and the spatial positions of the boundary safety factors.

[0014] This invention also provides a method for measuring safety factor profiles based on magnetohydrodynamic instability, the hardware basis of which is the aforementioned safety factor profile measurement system; the method includes the following steps: S1. Use a magnetic probe array to measure the circumferential and poloidal moduli of magnetohydrodynamic instability in plasma and determine the corresponding safety factor values; S2. Use an electron cyclotron radiometer to measure the spatial location of magnetohydrodynamic instabilities in the plasma and determine the spatial location of the corresponding safety factor. S3. Based on the determined values ​​and spatial locations of the safety factors, and combined with the boundary safety factors, numerical fitting is performed to obtain the safety factor distribution of the entire plasma profile.

[0015] Furthermore, the magnetohydrodynamic instabilities include sawtooth, tearing mode, and antishear Alfvén eigenmode; in step S2, based on the characteristic performance of multiple adjacent channels, the spatial positions of the rational surface of the first safety factor characterized by sawtooth and the rational surface of the second safety factor characterized by tearing mode are determined from the output data of the electron cyclotron radiometer; at the same time, the spectrum corresponding to the output data of the electron cyclotron radiometer is obtained, and based on the spectrum and the frequency change data of the antishear Alfvén eigenmode, the spatial position of the corresponding minimum safety factor is determined.

[0016] Preferably, for multiple adjacent channels of the output data of the electron cyclotron radiometer, when any one channel exhibits a periodically rising positive sawtooth pattern, while another channel has a corresponding periodically falling anti-sawtooth pattern, and there is a channel between these two channels that does not have typical sawtooth features, the spatial position of the rational surface of the first safety factor is determined to be the corresponding position of the channel that does not have typical sawtooth features. When determining the spatial location of the rational surface of the second safety factor, low-frequency oscillation data of multiple adjacent channels are acquired. When any one channel presents a waveform that meets the preset requirements, and another channel has a corresponding waveform that is 180 degrees out of phase with the waveform, and there is another channel between these two channels whose waveforms have different amplitudes in their two half-cycles, the spatial location of the rational surface of the second safety factor is determined to be the corresponding location of the channel with waveforms that have different amplitudes in their two half-cycles. To determine the spatial location of the minimum safety factor, a fast Fourier transform is first performed on the output data of the electron cyclotron radiometer to obtain a spectrum, which determines the frequency variation of the anti-shear Alfvén eigenmode over time. The spectrum data is then filtered, with the filtering range determined by the frequency of the anti-shear Alfvén eigenmode. After filtering, the amplitude of temperature disturbances at different spatial locations is obtained. The spatial location with the largest temperature disturbance amplitude is the spatial location of the anti-shear Alfvén eigenmode, corresponding to the spatial location of the minimum safety factor. The value of the minimum safety factor is obtained by measuring the poloidal modulus of the anti-shear Alfvén eigenmode using a magnetic probe array and then performing numerical fitting, including the minimum safety factor values ​​corresponding to different times during its existence.

[0017] Specifically, in step S3, the boundary security factor is determined using the correspondence formula of the boundary security factors. ,as follows:

[0018] In the formula, For the small radius of the tokamak device, For the large radius of the tokamak device, The strength of the plasma magnetic field. To correspond to the current, the determined safety factor values ​​and spatial locations, along with the boundary safety factor, are placed together in the same coordinate system for numerical fitting, thus obtaining the safety factor distribution of the entire plasma profile.

[0019] In summary, due to the adoption of this technical solution, the beneficial effects of this invention are as follows: This invention effectively circumvents the inherent limitations of traditional safety factor measurement techniques by utilizing magnetohydrodynamic instabilities. It abandons reliance on complex dedicated diagnostic systems, instead integrating mature conventional diagnostic methods from tokamak devices, such as magnetic probes and electron cyclotron radiometers, to capture in real-time the circumferential and poloidal modal characteristics and their spatial evolution of magnetohydrodynamic instabilities such as sawtooth, tearing modes, and anti-shear Alfvén eigenmodes. Based on the physical relationship between the safety factor and the modulus ratio, i.e. Equal to the ratio of the poloidal modulus to the circumferential modulus, the system can directly invert the safety factor values ​​at different radial positions of the plasma, thereby constructing a continuous and high-resolution safety factor profile distribution.

[0020] Compared to existing technologies, this invention significantly reduces measurement complexity and implementation costs, avoids the limitations of laser polarimeters due to laser source stability, mechanical vibration, and stray light interference, and addresses the distortion problems caused by spectral line interference in dynamic Stark effect spectrometers under multi-neutral beam injection conditions. By fully utilizing magnetohydrodynamic instabilities as natural diagnostic probes, this technology achieves high-precision, real-time acquisition of safety factor distribution, greatly improving measurement reliability and robustness, and providing a solid data foundation for predicting macroscopic instabilities in plasma and optimizing confinement performance.

[0021] This invention makes precise control of the safety factor profile possible, directly promoting enhanced equilibrium stability, extended energy confinement time, and increased fusion power output in magnetic confinement fusion devices. Its application not only solves a key bottleneck that has long constrained the steady-state operation of tokamaks, but also lays important technical support for the efficient and economical commercialization of nuclear fusion energy, possessing significant engineering practical value and scientific significance. Attached Figure Description

[0022] The present invention further illustrates its embodiments and technical solutions in detail with reference to the following figures, specifically including 5 figures as follows: Figure 1 This is a schematic diagram of the composition and structure of the safety factor profile measurement system of the present invention; Figure 2 This is a schematic diagram of the overall process of the safety factor profile measurement method of the present invention; Figure 3 This is a multi-channel schematic diagram of the sawtooth characteristics of magnetohydrodynamic instability data in the method of the present invention; Figure 4 This is a multi-channel schematic diagram of the tearing mode characteristics of magnetohydrodynamic instability data in the method of the present invention; Figure 5 This is a schematic diagram of the safety factor distribution curve obtained after fitting in the method of the present invention.

[0023] Figure 1 The meanings of the reference numerals in the attached figures are as follows: 1-Plasma; 2-Magnetic probe array; 3-Electron cyclotron radiometer; 4-Central processing unit; 5-Display. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0025] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0026] Example 1 like Figure 1 As shown, a safety factor profile measurement system based on magnetohydrodynamic instability includes a plasma 1, a magnetic probe array 2, an electron cyclotron radiometer 3, and a central processing unit 4. The output terminal of the plasma 1 is connected to the input terminal of the magnetic probe array 2 and the input terminal of the electron cyclotron radiometer 3, respectively. The output terminals of the magnetic probe array 2 and the electron cyclotron radiometer 3 are both connected to the input terminal of the central processing unit 4.

[0027] Magnetic probe array 2 is used to measure the circumferential modulus of magnetohydrodynamic instability in plasma 1. and polar modulus The electron cyclotron radiometer 3 is used to measure the spatial location of magnetohydrodynamic instabilities.

[0028] Central Processing Unit 4 is used for the circumferential modulus based on magnetohydrodynamic instability. and polar modulus The corresponding safety factor values ​​are determined, and the spatial locations of the corresponding safety factors are determined based on the spatial locations of the magnetohydrodynamic instabilities. Based on the determined safety factor values ​​and spatial locations, the safety factor distribution of the plasma 1 full profile in the tokamak device is obtained by numerical fitting in combination with the boundary safety factor.

[0029] In this embodiment, plasma 1, as the object of measurement, refers to the high-temperature plasma in the tokamak device. Its "output" does not refer to a physical interface, but rather symbolically represents the physical phenomena generated by plasma 1 itself, such as magnetic field fluctuations or electromagnetic radiation caused by magnetohydrodynamic instability. These phenomena serve as "data sources" captured and measured by downstream devices. For example, when plasma 1 experiences magnetohydrodynamic instability, it radiates electromagnetic waves of a specific frequency or generates local magnetic field disturbances. These signals are naturally "output" into the environment and received by the "input" of the magnetic probe array 2 and the electron cyclotron radiometer 3, i.e., the detection area of ​​the sensor. Similarly, the "output" of the magnetic probe array 2 refers to its process of converting the measured raw magnetic field data into electrical signals and transmitting them to the central processing unit 4, while the "output" of the electron cyclotron radiometer 3 represents its digital processing result of the radiation intensity.

[0030] As a preferred embodiment, such as Figure 1As shown, the system also includes a display 5. The output of the central processing unit 4 is connected to the input of the display 5. The display 5 is used to present the distribution of safety factors measured by the central processing unit 4 to the outside world.

[0031] In this embodiment, the magnetic probe array 2 includes a circumferential probe group and a poloidal probe group, and both the circumferential probe group and the poloidal probe group consist of at least two probes; the circumferential probe group is used to measure the circumferential modulus of the magnetohydrodynamic instability in plasma 1. The poloidal probe array is used to measure the poloidal modulus of magnetohydrodynamic instability in plasma 1. A specific measurement method can be exemplified as follows: First, determine the spatial angle between two circumferential or poloidal probes. Then, filter the data based on the frequency of the magnetohydrodynamic instability and obtain the phase difference between the two probes. Finally, determine the circumferential or poloidal modulus based on the ratio of the phase difference to the intrinsic phase. This process is a relatively mature technology and will not be elaborated upon here.

[0032] In this embodiment, the electron cyclotron radiometer 3 is typically used to measure electron temperature and temperature disturbances, and its measurement spatial location... By plasma magnetic field strength and operating frequency The decision is as follows:

[0033] In the formula, The large radius and small radius are two important parameters of the tokamak device. The large radius refers to the distance from the geometric center of the tokamak to the center line of the toroidal plasma 1 region, which essentially defines the size of the entire device. The small radius refers to the distance from the inner center line of the toroidal plasma 1 to the edge of plasma 1, which determines the thickness of the plasma 1 cross-section. Due to the operating frequency of the electron cyclotron radiometer 3... It has been determined during the research and development process that, under a given magnetic field In such cases, the specific measurement location for this diagnosis can be easily obtained. Therefore, in this embodiment, it can be used to measure the spatial location of magnetohydrodynamic instability as a basis for determining the spatial location of the safety factor.

[0034] In this embodiment, plasma 1 is a highly ionized quasi-neutral gas. Numerous magnetohydrodynamic instabilities exist within plasma 1, providing the fundamental conditions for measuring the magnetohydrodynamic instability modes and spatial locations. The various magnetohydrodynamic instabilities present within the plasma include serrated, tearing, and anti-shear Alfvén eigenmodes.

[0035] Therefore, considering these three types of magnetohydrodynamic instabilities, the key to this embodiment lies in: measuring the spatial position corresponding to the sawtooth using the electron cyclotron radiometer 3, thereby enabling the central processing unit 4 to derive the safety factor. The spatial position of the tear modulus is determined by the electron cyclotron radiometer 3, which measures the corresponding spatial position, thereby enabling the central processing unit 4 to derive the safety factor. or The spatial location of the surface is determined by the measurement of the frequency variation of the anti-shear Alfvén eigenmode. Simultaneously, the electron cyclotron radiometer 3 is also used to determine its spatial location by measuring the frequency variation of the anti-shear Alfvén eigenmode, thereby enabling the central processing unit 4 to derive the minimum safety factor. Spatial location.

[0036] Finally, the central processing unit 4 can determine the spatial location of the various security factors and combine them with the boundary security factors. The spatial location was used to obtain the safety factor distribution of the entire plasma profile after numerical fitting.

[0037] Example 2 Building upon Example 1, this example introduces a method for measuring the safety factor profile based on magnetohydrodynamic instability. The hardware foundation of this method is the safety factor profile measurement system described in Example 1. (See also...) Figure 2 The process can be summarized as follows: S1. Use a magnetic probe array to measure the circumferential and poloidal moduli of magnetohydrodynamic instability in plasma and determine the corresponding safety factor values; S2. Use an electron cyclotron radiometer to measure the spatial location of magnetohydrodynamic instabilities in the plasma and determine the spatial location of the corresponding safety factor. S3. Based on the determined values ​​and spatial locations of the safety factors, and combined with the boundary safety factors, numerical fitting is performed to obtain the safety factor distribution of the entire plasma profile.

[0038] In this embodiment, similarly, magnetohydrodynamic instabilities include sawtooth, tearing modes, and anti-shear Alfvén eigenmodes. Step S1 can be implemented using existing mature technologies in the field, and will not be elaborated further here; while in step S2, the safety factor characterized by sawtooth is determined based on the characteristic performance of multiple adjacent channels in the output data of the electron cyclotron radiometer. The spatial location of the rational surface, and the safety factor characterized by the tear modulus. or The spatial location of the rational surface is determined; simultaneously, the spectrum corresponding to the output data of the electron cyclotron radiometer is acquired. Based on this spectrum, combined with the frequency variation data of the back-sheared Alfvén eigenmode, the corresponding minimum safety factor is determined. Spatial location.

[0039] Firstly, regarding safety factors At that time, look for signal data with sawtooth characteristics on the electron cyclotron radiometer, such as Figure 3 As shown, the three adjacent channels in the example exhibit distinctly different characteristics: the upper channel displays periodically rising positive zigzags, the middle channel lacks typical zigzag features, and the lower channel displays periodically falling negative zigzags. Therefore, it can be determined that the zigzag reversal surface is located in the middle channel, i.e., the safety factor. The spatial position of the rational surface is the same as the position of the channel in the electron cyclotron radiometer.

[0040] For safety factors or At that time, signal data with tearing mode characteristics are searched on the electron cyclotron radiometer, such as... Figure 4 As shown, low-frequency oscillations appear in all three adjacent channels of the example, but their characteristics are significantly different. The upper channel exhibits a relatively regular sine wave, while the middle channel... and The two half-cycles have different amplitudes, and the lower channel exhibits a 180-degree phase reversal compared to the upper channel. This confirms that the center of the tearing mode is located in the middle channel. In most cases, the poloidal mode of the tearing mode... With circumferential module ratio The ratio is 2 / 1 or 3 / 2; therefore, by determining the spatial location of the tear mold, the safety factor can be determined accordingly. or The spatial position of the surface.

[0041] Determine the minimum safety factor When the spatial location is determined, a fast Fourier transform is performed on the signal from an electron cyclotron radiometer to obtain a spectrum. The variation of the inverse-sheared Alfvén eigenmode frequency with time is observed. Simultaneously, the poloidal mode number of this mode is obtained using a magnetic probe array, and the following formula is applied:

[0042] In the formula, For the large radius of the tokamak device; The angular frequency of the anti-sheared Alfvén eigenmode; Let be the Alfvén velocity. This formula reveals an approximately linear relationship between the time-varying rate of change of the anti-shear Alfvén eigenmode frequency and the time-varying rate of change of the minimum safety factor. This change can be observed using the fast Fourier transform of the electron cyclotron radiometer signal and verified by measuring the poloidal mode using a magnetic probe array. Numerical fitting based on this formula yields the minimum safety factor at different times during the existence of the anti-shear Alfvén eigenmode. Simultaneously, signals from different channels of the electron cyclotron radiometer are filtered. The filtering range depends on the frequency of the back-shear Alfvén eigenmode. Temperature perturbation amplitudes at different spatial locations are obtained; the location with the largest temperature perturbation amplitude is the spatial location of the back-shear Alfvén eigenmode, i.e., the minimum safety factor. Spatial location.

[0043] Finally, in step S3, the boundary security factor is determined using the correspondence formula of the boundary security factors. ,as follows:

[0044] In the formula, For the small radius of the tokamak device, For the large radius of the tokamak device, The strength of the plasma magnetic field. To correspond to the current; the determined safety factor value and spatial location, along with the boundary safety factor, are placed together in the same coordinate system for numerical fitting, resulting in the following: Figure 5 The safety factor distribution of the full plasma profile is shown. Figure 5 In the diagram, the vertical axis represents the safety factor. The numerical value; x-axis This is the normalized radius of the device, used to describe the positional distribution from the plasma center to the boundary. Figure 5 x-coordinate in It is expressed as a dimensionless parameter, ranging from 0 (plasma center) to 1 (plasma boundary).

Claims

1. A safety factor profile measurement system based on magnetohydrodynamic instability, characterized by, The system comprises a plasma, a magnetic probe array, an electron cyclotron radiation meter and a central processing unit; the output end of the plasma is connected to the input end of the magnetic probe array and the input end of the electron cyclotron radiation meter respectively, and the output end of the magnetic probe array and the output end of the electron cyclotron radiation meter are both connected to the input end of the central processing unit; The magnetic probe array is used for measuring the toroidal mode number and the poloidal mode number of the magnetohydrodynamic instability in the plasma; and the electron cyclotron radiation meter is used for measuring the spatial position of the magnetohydrodynamic instability. The central processing unit is used for determining the numerical value of the corresponding safety factor according to the toroidal mode number and the poloidal mode number of the magnetohydrodynamic instability, determining the spatial position of the corresponding safety factor according to the spatial position of the magnetohydrodynamic instability, and obtaining the safety factor distribution of the whole cross section of the plasma in the tokamak device after numerical fitting based on the determined numerical value and spatial position of the safety factor and the boundary safety factor.

2. The safety factor profile measurement system of claim 1, wherein: The system further comprises a display, and the output end of the central processing unit is connected to the input end of the display; the display is used for presenting the safety factor distribution measured by the central processing unit.

3. The safety factor profile measurement system of claim 1, wherein: The magnetic probe array comprises a poloidal probe group and a toroidal probe group, and the poloidal probe group and the toroidal probe group each consist of at least two probes; the poloidal probe group is used for measuring a poloidal mode number of a magnetohydrodynamic instability in the plasma , and the toroidal probe group is used for measuring a toroidal mode number of the magnetohydrodynamic instability in the plasma .

4. The safety factor profile measurement system of claim 1, wherein: The spatial position of the electron cyclotron radiation measurements By the plasma magnetic field strength And the operating frequency Is determined as follows: wherein is the major radius of the tokamak device; the operating frequency of the electron cyclotron The measurement is performed in such a way that the given plasma magnetic field strength is obtained in a corresponding spatial position .

5. The safety factor profile measurement system of claim 1, wherein: The plasma is a highly ionized quasi-neutral gas, and a plurality of magnetohydrodynamic instabilities exist in the plasma, including sawteeth, tearing modes and inverse shear Alfven eigenmodes.

6. The safety factor profile measuring system of claim 5, wherein: The electron cyclotron radiation meter is used for measuring the spatial position corresponding to the sawteeth, so that the central processing unit obtains the spatial position of the first safety factor rational surface; the electron cyclotron radiation meter is also used for measuring the spatial position corresponding to the tearing modes, so that the central processing unit obtains the spatial position of the second safety factor rational surface; the electron cyclotron radiation meter is also used for determining the spatial position of the inverse shear Alfven eigenmodes by measuring the frequency change of the inverse shear Alfven eigenmodes, so that the central processing unit obtains the spatial position of the minimum safety factor; and the central processing unit is used for obtaining the safety factor distribution of the whole cross section of the plasma after numerical fitting based on the spatial positions of the plurality of types of safety factors and the spatial position of the boundary safety factor.

7. A method of measuring a safety factor profile based on magnetohydrodynamic instability, characterized by, The hardware basis of the method is the safety factor cross section measurement system of claim 1; and the method comprises the following steps: S1, measuring the toroidal mode number and the poloidal mode number of the magnetohydrodynamic instability in the plasma by using the magnetic probe array, and determining the numerical value of the corresponding safety factor; S2, measuring the spatial position of the magnetohydrodynamic instability in the plasma by using the electron cyclotron radiation meter, and determining the spatial position of the corresponding safety factor; S3, obtaining the safety factor distribution of the whole cross section of the plasma after numerical fitting based on the determined numerical value and spatial position of the safety factor and the boundary safety factor.

8. The safety factor profile measurement method according to claim 7, characterized by: The MHD instabilities include sawteeth, tearing modes and inverse shear Alfven eigenmodes; in step S2, according to the characteristic performance of the multiple adjacent channels in the output data of the electron cyclotron radiometer, the spatial position of the first safety factor rational surface characterized by sawteeth and the spatial position of the second safety factor rational surface characterized by tearing modes are determined; meanwhile, the frequency spectrum corresponding to the output data of the electron cyclotron radiometer is obtained, and according to the frequency spectrum, the spatial position of the minimum safety factor is determined in combination with the frequency variation data of the inverse shear Alfven eigenmodes.

9. The safety factor profile measurement method according to claim 8, characterized by: For the multiple adjacent channels of the output data of the electron cyclotron radiometer, when any one channel presents a periodic rising positive sawtooth, and another channel has a corresponding periodic descending inverse sawtooth, and there is a channel between the two channels without typical sawtooth characteristics, the spatial position of the first safety factor rational surface is determined as the corresponding position of the channel without typical sawtooth characteristics; When determining the spatial position of the second safety factor rational surface, the low-frequency oscillation data of the multiple adjacent channels are obtained, when any one channel presents a waveform satisfying the preset requirement, and another channel has a corresponding waveform with a phase inversion of 180 degrees, and there is a channel between the two channels with a waveform with different amplitudes in two half periods, the spatial position of the second safety factor rational surface is determined as the corresponding position of the channel with the waveform with different amplitudes in two half periods; When determining the spatial position of the minimum safety factor, the output data of the electron cyclotron radiometer is first subjected to fast Fourier transform to obtain a frequency spectrum, and the variation law of the frequency of the inverse shear Alfven eigenmodes with time is determined; the data of the frequency spectrum are subjected to filtering, and the filtering range is determined by the frequency of the inverse shear Alfven eigenmodes, and the temperature disturbance amplitude at different spatial positions is obtained after filtering, and the spatial position with the maximum temperature disturbance amplitude is the spatial position of the inverse shear Alfven eigenmodes, corresponding to the spatial position of the minimum safety factor; the value of the minimum safety factor is obtained by numerical fitting after the poloidal mode number of the inverse shear Alfven eigenmodes is measured by the magnetic probe array, including the minimum safety factor values corresponding to different time periods during the existence of the inverse shear Alfven eigenmodes.

10. The safety factor profile measurement method according to claim 7, wherein, In step S3, the corresponding relation formula of the boundary security factor is used to determine the boundary security factor As follows: wherein R is a small radius of the tokamak device, R is a large radius of the tokamak device, B is a magnetic field strength of the plasma, I is a corresponding current; the determined values of the safety factor and the spatial position, and the boundary safety factor are collectively put in the same coordinate system for numerical fitting, so as to obtain the safety factor distribution of the whole profile of the plasma.

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