A method and device for real-time identification and positioning of low-order rational surface positions based on microwave reflection

Abstract

The application belongs to the technical field of magnetic confinement nuclear fusion, and discloses a method and device for identifying and positioning low-order rational surface position in real time based on microwave reflection. The technical scheme comprises the following method steps: S1, obtaining transmission delay time and signal amplitude of microwave in plasma at different detection frequencies; S2, obtaining mapping relationship between detection frequency and tokamak position and plasma electron density distribution through inversion; S3, obtaining transmission delay time and signal amplitude of different radial positions through spatial interpolation; and S4, obtaining spatial gradient of transmission delay time, and identifying radial coordinate value of low-order rational surface according to signal characteristics. The application can automatically identify and position low-order rational surface information of safety factor distribution in the tokamak in real time. Compared with the traditional inversion method based on magnetic measurement, the application is based on experimental measurement data of microwave reflection, has the advantages of more direct and local measurement, and improves the position accuracy.

Description

Technical Field

[0001] This invention belongs to the field of magnetic confinement nuclear fusion technology, specifically relating to a method and apparatus for real-time identification and positioning of low-order rational surfaces based on microwave reflection. Background Technology

[0002] In magnetically confined fusion devices like tokamaks, real-time diagnostic measurements of plasma safety factor distribution are crucial for achieving advanced operating modes with high performance and long-pulse stability. Due to the inaccessibility and complexity of the tokamak's internal components, the commonly used diagnostic tools for safety factor distribution are primarily spectral diagnostics, namely far-infrared polarization interferometry and kinematic Stark effect diagnostics. The former is an integral measurement diagnostic, requiring mathematical transformations and inversion models to obtain the safety factor distribution; while kinematic Stark effect diagnostics based on neutral atom beam injection heating can determine the internal safety factor distribution, but this diagnostic technique relies on neutral beam pulse injection, resulting in high system operating costs and low temporal resolution.

[0003] Therefore, this invention proposes a method and apparatus for real-time identification and positioning of low-order rational surfaces (i.e., the positions corresponding to rational numbers such as safety factors of 1, 2, or 3) of the safety factor distribution, which is of great significance for reducing the cost of spectral diagnostics and ensuring the safe operation of the apparatus in the future. Summary of the Invention

[0004] The purpose of this invention is to provide a method and apparatus for real-time identification and positioning of low-order rational surfaces in a tokamak based on microwave reflection. This method can achieve real-time measurement of plasma electron density distribution and, when a macroscopic magnetohydrodynamic mode is present, can quickly identify and accurately position the low-order rational surfaces.

[0005] Firstly, to achieve the above objectives, this invention proposes a method for real-time identification and positioning of low-order rational surfaces based on microwave reflection, comprising the following steps:

[0006] S1. Obtain the propagation delay time and signal amplitude of microwaves at different detection frequencies in the plasma;

[0007] S2. Obtain the mapping relationship between the detection frequency and the tokamak position and the plasma electron density distribution through inversion;

[0008] S3. The transmission delay time and signal amplitude at different radial positions are obtained through spatial interpolation;

[0009] S4. Obtain the spatial gradient of the transmission delay time and identify the radial coordinate set d1 of the low-order rational surface based on the signal characteristics; if the position of the low-order rational surface is determined to be a non-empty set, continue to the next step; otherwise, skip it and return to the initial step S1 for the signal and amplitude signal of the transmission delay time of the next time period.

[0010] S5. Determine the occurrence of the magnetohydrodynamic mode through the magnetic probe signal, and further calculate the characteristic frequency of the mode;

[0011] S6. Determine the ring m and poloidal modulus n of the magnetohydrodynamic mode;

[0012] S7. Analyze the filtered transmission delay time signal and its signal amplitude, and obtain the radial coordinate set d2 of the low-order rational surface based on the cross-correlation coefficient.

[0013] S8. Based on the results of radial coordinate set d1, radial coordinate set d2, and the ring m and poloidal modulus n of the magnetohydrodynamic mode, determine the values ​​of the lower-order rational surface and its corresponding radial position d3.

[0014] Optionally, in step S1, the propagation delay time of microwaves at different detection frequencies in the plasma is obtained, specifically as follows:

[0015] S11. Using a swept-frequency microwave source as the emission source, a series of microwaves with continuously changing frequency are emitted into the plasma;

[0016] S12. A directional coupler is used to split the microwave source output signal into a transmission channel and a receiving channel;

[0017] S13. Microwaves enter the plasma through the transmitting antenna, and are received by the receiving antenna after being cut off and reflected in the plasma.

[0018] S14. The reflected signal is then mixed with the intrinsic signal of the receiving channel. The phase change rate and frequency sweep speed are obtained through the mixed signal to obtain the microwave transmission delay time in the plasma.

[0019] Optionally, in step S14, the mixing signal is subjected to a time-frequency Fourier transform to obtain the signal amplitude corresponding to different detection frequencies.

[0020] Optionally, in step S4, the preliminary identification of the existence of low-order rational surfaces based on signal characteristics includes the following steps:

[0021] S41. When the distribution of transmission delay time changes from a monotonic distribution to a phenomenon where a peak "jumps" at a certain local location, and the detection frequency range corresponding to this local location is within a set frequency range, the radial coordinate set d of this local range is obtained. 11 ;

[0022] S42. During the transmission delay time, the signal amplitude exhibits a decrease in reflected signal power within the detection frequency range, and the power attenuation exceeds a set threshold. The radial coordinate set d of the corresponding cutoff layer is then obtained. 12 ;

[0023] S43. An extreme value phenomenon appears in the spatial gradient distribution of the transmission delay time, and the relative height of the extreme value exceeds a set threshold. The radial coordinate set d of the extreme value range is obtained. 13 ;

[0024] Take the radial coordinate set d from the above steps 11 d 12 d 13 The intersection of the two sets of points is obtained by finding the intersection d1=d. 11 ∩d 12 ∩d 13 ;

[0025] If conditions S41, S42, and S43 are met simultaneously, and the intersection d1 is a non-empty set, then it is preliminarily determined that the position of the low-order rational surface is identified by microwave reflection, and the next step is executed.

[0026] Optionally, in S5, the characteristic frequencies of the calculated pattern include:

[0027] A ring of probes is placed along the toroidal and poleal positions within the tokamak device to acquire magnetic field disturbance signals at different toroidal and poleal positions. These signals are then smoothed and subjected to spectral analysis. If a peak with a relative height exceeding a set threshold power appears in the spectrum of the magnetic probe signal, and the frequency of this peak falls within the frequency range of the magnetohydrodynamic (MHD) mode, and the transmission delay and amplitude signals correspond to the characteristics identified in step S4, then the MHD mode is confirmed to have occurred. The frequency at the point of maximum power is then identified as the characteristic frequency f of the MHD mode. MHD .

[0028] Optionally, in step S6, the phase difference between two adjacent magnetic probe data is analyzed, and the integer multiple relationship obtained by dividing the phase difference by the angle between the positions of the two magnetic probes in the circumferential or polar directions is the circumferential module m or the polar module n.

[0029] Optionally, in step S7, obtaining the existence of a lower-order rational surface based on its cross-correlation coefficient includes the following steps:

[0030] S71. Perform cross-correlation analysis between the relative propagation delay perturbation signals of each channel after bandpass filtering and a magnetic probe signal, and calculate the average cross-correlation coefficient of each channel within the characteristic frequency range. When it exceeds a set threshold, obtain the radial coordinate set d corresponding to that channel. 21 ;

[0031] S72. For the relative amplitude perturbation signals of each channel after bandpass filtering, perform correlation analysis with a magnetic probe signal, and calculate the average cross-correlation coefficient of each channel within the characteristic frequency range. When it exceeds a set threshold, obtain the radial coordinate set d corresponding to that channel. 22 ;

[0032] S73. Perform correlation analysis between the relative gradient perturbation signals of each channel after bandpass filtering and a magnetic probe signal to obtain the average cross-correlation coefficient of each channel within the characteristic frequency range. When it exceeds a set threshold, obtain the radial coordinate set d corresponding to that channel. 23 ;

[0033] The bandpass filtering range in steps S71, S72, and S73 above is [f MHD -df, f MHD +df], df is set to f MHD / 2; Using the magnetic probe signal with the maximum relative height peak near the characteristic frequency obtained in step S5 as the reference signal, and after the judgments in steps S71, S72, and S73, the union of the radial coordinate sets is obtained, that is, the intersection d2=d 21 d 22 d 23 .

[0034] Optionally, in step S8, the value q of the lower-order rational surface is determined by the ring and pole modulus, i.e., q = m / n; and the intersection of the radial coordinate sets d1 and d2 obtained in steps S4 and S7 is used as the radial coordinate position of the lower-order rational surface obtained by the final identification and positioning, i.e., d3 = d1∩d2.

[0035] Secondly, a device for real-time identification and positioning of low-order rational surfaces based on microwave reflection, applied to the method described in the first aspect, the device comprising:

[0036] The diagnostic system includes a microwave reflection diagnostic system and a magnetic diagnostic system. The magnetic diagnostic system places a ring of probes along the ring and pole positions inside the tokamak device to acquire magnetic field disturbance signals at different ring and pole positions. The microwave reflection diagnostic system uses receiving and transmitting antennas placed at the outer mid-plane of the tokamak to acquire the transmission delay time and signal amplitude of microwaves of different detection frequencies in the plasma.

[0037] The real-time acquisition system digitizes the diagnostic signals transmitted via coaxial cable, and includes a first data acquisition module and a second data module.

[0038] The real-time identification and positioning system and the human-computer interaction system are connected by a communication bus. The system is used to process the signals of the diagnostic system in real time, identify and locate low-order rational surfaces, and send the information to the human-computer interaction system. The real-time identification and positioning system includes a transmission delay time and amplitude signal extraction module, a magnetohydrodynamic mode time-frequency analysis module, a magnetohydrodynamic mode modulus analysis module, a density distribution inversion and mapping module, a first low-order rational surface identification module, a second low-order rational surface identification module, and a low-order rational surface positioning module.

[0039] Optionally, the transmission delay time and amplitude signal extraction module is used to obtain the transmission delay time and signal amplitude of microwaves at different detection frequencies in the plasma;

[0040] The density distribution inversion and mapping module is used to invert and obtain the mapping relationship between the detection frequency and the tokamak position and the plasma electron density distribution. After spatial interpolation, the transmission delay time and signal amplitude at different radial positions are obtained.

[0041] The first low-order rational surface identification module is used to obtain the spatial gradient of the transmission delay time and identify the radial coordinate set d1 of the low-order rational surface;

[0042] The magnetohydrodynamic mode time-frequency analysis module is used to determine the occurrence of a magnetohydrodynamic mode through magnetic probe signals and to calculate the characteristic frequency of the mode.

[0043] The magnetohydrodynamic mode modulus analysis module is used to determine the ring m and poloidal modulus n of the magnetohydrodynamic mode;

[0044] The second low-order rational surface identification module is used to analyze the filtered transmission delay time signal and its signal amplitude, and obtain the radial coordinate set d2 of the low-order rational surface according to the cross-correlation coefficient.

[0045] The low-order rational surface positioning module is used to determine the low-order rational surface value and its corresponding radial position d3 based on the results of the radial coordinate set d1, the radial coordinate set d2, the ring m and the poloidal modulus n of the magnetohydrodynamic mode.

[0046] Compared with the prior art, the beneficial effects of the present invention are:

[0047] This invention can automatically identify and locate low-order rational surface information of the safety factor distribution in a tokamak in real time. Compared with traditional magnetic measurement inversion methods, this invention is based on experimental measurement data from microwave reflection, which has the advantages of being more direct and localized, thus improving positional accuracy. Furthermore, compared with existing spectral diagnostic systems, the low-order rational surface real-time identification and location device built upon microwave reflection and magnetic diagnostics is simple, intuitive, and efficient, providing an important foundation for reducing the cost of spectral diagnostics and ensuring the safe operation of tokamas in the future. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the tokamak ring, poloidal section, and microwave reflection principle.

[0049] Figure 2 This is a comparison chart showing the electron density distribution and the corresponding propagation delay time distribution under two different conditions: with and without magnetohydrodynamic (MHD) modes.

[0050] Figure 3 (a) is the time evolution diagram of the magnetic probe signal, and (b) is the contour plot of the spatial gradient signal of the transmission delay time.

[0051] Figure 4 This is a schematic diagram of the structure of a real-time detection device for the position of a low-order rational surface based on microwave reflection recognition and positioning according to the present invention. Detailed Implementation

[0052] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] A tokamak is a toroidal device that confines plasma using a helical magnetic field. This helical field is composed of a superposition of a circumferential magnetic field and a poloidal magnetic field, such as... Figure 1 The direction of the magnetic field B is given in the figure. Here, r, θ, and ζ represent the radial, polar, and circumferential directions, respectively, o is the ring center of the tokamak device, and R... axis denoted as the magnetic axis position, and 'a' as the plasma radius.

[0054] Figure 1 The triangle in the diagram represents the measurement location of the microwave reflection diagnostic system, typically near the outer midplane of the device. This system, based on radar principles, measures the electron density distribution and density fluctuations in non-uniform plasmas and is a crucial routine diagnostic tool on tokamas. It obtains plasma information by measuring the propagation delay time after microwaves are emitted into the plasma; only microwaves returning along their original path can be received by the receiving antenna. When microwaves of a certain frequency are incident into the plasma, their refractive index varies with the plasma density, and reflection occurs at the location where the refractive index is 0; this location is the cutoff layer for the microwave of that detection frequency.

[0055] Figure 2The figure shows a comparison of the plasma electron density and the corresponding measured propagation delay time distribution under two conditions. The dashed and solid lines represent the cases under the non-magnetic hydrodynamic mode and the case under the magnetohydrodynamic mode, respectively. When a magnetohydrodynamic mode exists inside the tokamak, the density distribution changes from a monotonically increasing distribution to a locally flattened distribution. Consequently, through microwave reflection diagnostics, it can be observed that the corresponding propagation delay time distribution changes from a monotonically increasing distribution to a "jump" with a maximum value at the locally flattened location, and the microwave reflection power at the locally flattened location will show a significant decrease.

[0056] Since the magnetohydrodynamic modes within the tokamak occur near low-order rational surfaces, especially where the safety factor q equals 1, 2, or 3, this principle allows for the mapping, interpolation, and spatial differentiation of the transmission delay time signal measured by the microwave reflection diagnostic system. This yields a high-spatiotemporal resolution image of the spatiotemporal evolution of the transmission delay time and its spatial derivative. Further combining magnetic diagnostics and correlation analysis, the evolution of the radial coordinates of the low-order rational surfaces can be clearly identified and located from the image.

[0057] Furthermore, this embodiment provides a method for real-time identification and positioning of low-order rational surfaces based on microwave reflection. This method is implemented sequentially through the following steps:

[0058] Step 1: Obtain the propagation delay time τ(f) of microwaves at different detection frequencies in the plasma. q , t p This method utilizes microwaves with a frequency sweep range of 33-110 GHz as the transmitter, emitting a series of continuously varying frequency microwaves into the plasma. A directional coupler is used to split the microwave source output signal into a transmitter channel and a receiver channel. The microwaves enter the plasma through the transmitting antenna, are then cut off and reflected within the plasma, and are received by the receiving antenna. The reflected signal is then mixed with the intrinsic signal of the receiver channel, and the phase change rate d is obtained from the mixed signal. The propagation delay time τ(f) of microwaves in plasma is obtained by using / dt and the sweep frequency speed dfq / dt. q , t p The calculation formula is as follows:

[0059] (1)

[0060] Perform a time-frequency Fourier transform on the mixed signal to obtain the signal amplitude P(fq,tp) corresponding to different detection frequencies.

[0061] Where τ is the group delay time between the transmitted and reflected signals; f q For microwave detection frequencies, q = 1,...,M; t pFor each detection time, p = 1, ..., N; M is the number of detection frequency points, and N is the number of time points.

[0062] Step 2: Invert the plasma electron density distribution n from the propagation delay time signal obtained in Step 1. e (R q , t p ), to obtain the mapping relationship R between the detection frequency and the tokamak position. q (f q ), τ(R) q , t p ) and P(R q , t p For the transmission delay time signal of a single frequency sweep cycle, the plasma density distribution is calculated numerically using the electromagnetic wave propagation formula in plasma, thereby obtaining the mapping relationship between the microwave frequency and the cutoff layer position, and further substituting into the formula to obtain τ(R). q , t p ) and P(R q , t p ).

[0063] Where, n e R is the electron density; q Let q be the radial position coordinates corresponding to the qth detection frequency.

[0064] Step 3: After performing spatial linear interpolation on the transmission delay time signal and its amplitude signal obtained in Step 2, the transmission delay time τ(R) at different radial positions is obtained. k ,t p ) and its signal amplitude P(R) k ,t p The calculation formula is as follows:

[0065] (2)

[0066] Among them, R k Let be the radially interpolated coordinate value of the k-th channel, where k = 1, …, L. The interpolation range is from the tokamak magnetic axis position to the smallest radius of its plane, i.e., R. axis ≤R k ≤R axis +a. Where R axis denoted as the position of the plasma magnetic axis, and 'a' as the small radius of the device.

[0067] Step 4: Take the spatial derivative of the transmission delay time signal obtained in Step 3 to obtain the spatial gradient dτ(R) of the transmission delay time. k , t pThe position coordinates d1(R) of the lower-order rational surface are determined based on signal characteristics: if the magnetohydrodynamic mode exists, there are peaks in the spatial characteristics of the transmission delay time signal and amplitude signal, thus allowing the determination of the lower-order rational surface's position coordinates d1(R). k , t p Conversely, it is impossible to determine the location of lower-order rational surfaces based on the following three signal characteristics:

[0068] 1) Feature 1: such as Figure 2 The solid black line in the figure represents the transmission delay time distribution, which changes from a monotonic distribution to a peak "jump" at a certain local location, and the detection frequency f corresponding to this local location range. peak Located within the set frequency range [f p1 , f p2 The radial coordinate set d of this local area is obtained through the peak-finding algorithm. 11 (R k , t p Its coordinate range is the peak coordinate ±2 times the half-width of the extreme peak, i.e., d 11 =R max_peak +2*w peak .

[0069] 2) Feature 2: Signal amplitude P(R) during transmission delay k , t p A phenomenon of decreased reflected power signal occurs at a local location. When the power attenuation of the reflected power exceeds a set threshold, the radial coordinate set d of the corresponding cutoff layer is obtained. 12 (R k , t p ).

[0070] 3) Feature 3: Spatial gradient distribution of transmission delay time dτ(R) k ,t p The extreme value phenomenon () / dR occurred at a local location. When the relative height of the extreme value exceeds a set empirical threshold, the radial coordinate set d of the extreme value range is obtained. 13 (R k , t p );

[0071] After judging through steps 1 to 3 above, the intersection of the radial coordinate sets that meet features 1-3 is obtained, i.e., d1=d 11 ∩d 12 ∩d 13 If d1(R) k , t p If d1(R) is a non-empty set, it can be preliminarily determined that the position of the lower-order rational surface can be identified by microwave reflection, and steps 5 to 8 are continued; otherwise, if the obtained d1(R) is not empty, it can be determined that the position of the lower-order rational surface can be identified by microwave reflection, and steps 5 to 8 are continued.k , t p If ) is an empty set, then skip the next step and proceed with the transmission delay signal τ(f) for the next time period. q , t p+1 ) and its amplitude signal P(f q , t p+1 Repeat steps 1 through 4.

[0072] Step 5: Determine the presence of macroscopic magnetohydrodynamic modes using magnetic probe signals, and further calculate the characteristic frequency f of the modes. MHD (t p The magnetic field disturbance signal δB, measured by magnetic probes distributed along the tokamak rings and poloidal direction, is acquired, smoothed, and subjected to spectral analysis. If a peak with a relative height greater than a set threshold power appears in the spectrum of the magnetic probe signal, and the frequency of the peak is within the frequency range of the magnetohydrodynamic mode, while the transmission delay time signal and amplitude signal meet the characteristics listed in step 4, then the occurrence of the magnetohydrodynamic mode is confirmed, and the frequency at the maximum power is identified as the characteristic frequency f of the magnetohydrodynamic mode. MHD (t p ).

[0073] Step 6: Determine the loop and poloidal moduli m(t) of the magnetohydrodynamic mode. p ), n(t) p The magnetic probe signal obtained in step 5 is filtered. The filtering range is [f...]. MHD (t p )-df, f MHD (t p )+df], where df is set to f MHD (t p The relative magnetic disturbance signal δB2 is obtained by dividing the phase difference between two adjacent magnetic probe data by 2. The integer multiple of this phase difference obtained is the circumferential modulus m(t). p ) or the polar modulus n(t) p ).

[0074] For the same polar angle, through two adjacent circumferential directions The angular magnetic probe calculates the circumferential modulus of this mode. .in The phase difference between the two magnetic probes is obtained through correlation analysis. Similarly, the calculation of the poloidal modulus follows a similar principle.

[0075] Step 7: Convert the transmission delay time signal τ(R) obtained in Step 3 into a signal that is τ(R). k ,t p ) and its amplitude signal P(R) k , tp ) and the spatial gradient signal dτ(R) obtained in step 4 k ,t p Bandpass filtering is performed on ) / dR respectively to obtain the relative disturbance signal δτ(R) k , t p ), δP(R) q , t p ) and δD(R q , t p The location of the lower-order rational surface is further determined based on relevant characteristics: if the magnetohydrodynamic modulus exists, the time characteristics of the transmission delay time signal and amplitude signal are periodic, and this periodic time is the reciprocal of the characteristic frequency of the magnetohydrodynamic mode; otherwise, it cannot be determined. Correlation analysis is performed on the filtered relative disturbance signals and the magnetic probe signal respectively, and the radial coordinate set d2(R) of the lower-order rational surface is obtained based on their cross-correlation coefficient characteristics. k ,t p The approximate location of the lower-order rational surface can be determined based on the following specific cross-correlation coefficient characteristics:

[0076] 1) Feature 1: The relative propagation delay perturbation signal δτ(R) of each channel after bandpass filtering k , t p Cross-correlation analysis was performed between the signal and a magnetic probe signal δB to obtain the δτ(R) of each channel. q , t p cross-correlation coefficients The calculation formula is as follows:

[0077] (3)

[0078] Calculate δτ(R) for each channel q , t p The average cross-correlation coefficient of cross-correlation coefficients over the characteristic frequency range. When it exceeds a set threshold, obtain the radial coordinate set d corresponding to that channel. 21 (R k , t p );

[0079] 2) Feature 2: For the relative amplitude perturbation signals δP(R) of each channel after bandpass filtering q , t p Correlation analysis was performed between the signal and a magnetic probe signal δB to obtain the δτ(R) of each channel. q , t p cross-correlation coefficients When the average cross-correlation coefficient of that channel... If the value is greater than a set threshold, obtain the radial coordinate set d corresponding to that channel. 22 (R k, t p );

[0080] 3) Feature 3: For the relative gradient perturbation signals δD(R) of each channel after bandpass filtering q , t p Correlation analysis was performed between the signal and a magnetic probe signal δB to obtain the δD(R) of each channel. q , t p cross-correlation coefficients When the average cross-correlation coefficient of that channel... If the value is greater than a set threshold, obtain the radial coordinate set d corresponding to that channel. 23 (R k , t p ).

[0081] The bandpass filtering range in features 1)-3) above is [f MHD (t p )-df, f MHD (t p )+df], where df is set to f MHD (t p ) / 2. The magnetic probe signal with the maximum relative height peak near the characteristic frequency obtained in step 5 is used as the reference signal in features 1)-3) above. After judging in steps 1 to 3 above, the union of the radial coordinate sets of features 1)-3) above is obtained, that is, d2=d 21 d 22 d 23 .

[0082] Step 8: Determine the numerical value q=m / n of the lower-order rational surface, i.e., through the multiple relationship between the toroidal and polar moduli; and take the intersection of the radial coordinate sets obtained in Steps 4 and 7 as the radial coordinate position corresponding to the rational surface, such as... Figure 3 The position of the black square in (b) is shown, i.e., d3 = d1 ∩ d2.

[0083] The technical effects of the present invention will be further explained below with reference to experimental results. The background of this example is as follows: In a certain tokamak device, during a long pulse discharge, a periodic m / n=1 / 1 magnetohydrodynamic mode was observed at time 6.603 seconds. The characteristic frequency of this mode is f. MHD =2kHz, magnetic field strength is 2.3 T, plasma current is 450 kA. For example... Figure 3 As shown in (a), when this mode occurs, the relative height of the peak of the magnetic probe perturbation δB signal at the characteristic frequency exceeds a set threshold; as Figure 3As shown by the black square in (b), the collected transmission delay time signal and magnetic probe signal are processed through the above steps 1-8 to finally obtain the spatiotemporal evolution result of the radial position of the low-order q=1 rational surface.

[0084] Furthermore, based on the aforementioned conditions and in conjunction with the appendix... Figure 4 The diagram illustrates the device for real-time identification and localization of low-order rational surfaces based on microwave reflection, as proposed in this invention. The device comprises four parts: a diagnostic system, a real-time acquisition system, a real-time identification and localization system, and a human-computer interaction system. The diagnostic system consists of a microwave reflection diagnostic system and a magnetic diagnostic system. The magnetic diagnostic system places a ring of probes along the toroidal and poleal positions within the tokamak device to acquire magnetic field disturbance signals at different toroidal and poleal positions. The receiving and transmitting antennas of the microwave reflection diagnostic system are placed at the outer midplane of the tokamak to acquire the propagation delay time and signal amplitude of microwaves at different detection frequencies in the plasma.

[0085] The real-time acquisition system digitizes the diagnostic signals transmitted via coaxial cable and consists of a first data acquisition module and a second data acquisition module. The first data acquisition module is responsible for digitizing the output signals of the magnetic diagnostic system, while the second data acquisition module is responsible for digitizing the output signals of the microwave reflection diagnostic system.

[0086] The real-time identification and positioning system is connected to the real-time acquisition system via a high-speed digital communication bus. It is used to process the signals from the diagnostic system in real time using the method proposed in this invention, identify and locate low-order rational surfaces, and send the information to the human-computer interaction system. The real-time identification and positioning system is the core component of the device proposed in this invention. This component can be implemented using software algorithms deployed on a general-purpose central processing unit, or it can be implemented using hardware algorithms deployed on a programmable logic array or a dedicated chip.

[0087] The real-time identification and positioning system consists of a transmission delay time and amplitude signal extraction module, a magnetohydrodynamic (MHD) mode time-frequency analysis module, a MHD mode modulus analysis module, a density distribution inversion and mapping module, a first low-order rational surface identification module, a second low-order rational surface identification module, and a low-order rational surface positioning module. The transmission delay time and amplitude signal extraction module primarily performs step 1 of the method proposed in this invention to obtain the transmission delay time and signal amplitude of microwaves at different detection frequencies in the plasma. The density distribution inversion and mapping module primarily performs steps 2-3 of the method proposed in this invention to invert and obtain the mapping relationship between the detection frequency and the tokamak position and the plasma electron density distribution, and obtains the transmission delay time and signal amplitude at different radial positions through spatial interpolation. The first low-order rational surface identification module primarily performs step 4 of the method proposed in this invention to obtain the spatial gradient of the transmission delay time and identify the radial coordinate set d1 of the low-order rational surface. The magnetohydrodynamic (MHD) mode time-frequency analysis module primarily performs the following steps: Step 5 of the proposed method is used to determine the occurrence of the magnetohydrodynamic mode and calculate the characteristic frequency of the mode; the main function of the magnetohydrodynamic modulus analysis module is to execute step 6 of the proposed method, which is used to determine the ring m and poloidal modulus n of the magnetohydrodynamic mode; the main function of the second low-order rational surface identification module is to execute step 7 of the proposed method, which is used to analyze the filtered transmission delay time signal and its signal amplitude, and obtain the radial coordinate set d2 of the low-order rational surface according to the cross-correlation coefficient; the main function of the low-order rational surface positioning module is to execute step 8 of the proposed method, which is used to determine the value of the low-order rational surface and its corresponding radial position d3 based on the results of the radial coordinate set d1, the radial coordinate set d2 and the ring m and poloidal modulus n of the magnetohydrodynamic mode.

[0088] Furthermore, the human-computer interaction system communicates with the real-time identification and positioning system via a network cable to initialize the real-time acquisition system and the real-time identification and positioning system, and uploads, stores and displays the acquired data from the real-time acquisition system and the data processing results from the real-time identification and positioning system to the human-computer interaction system in the form of network streams.

[0089] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for real-time identification and localization of low-order rational surfaces based on microwave reflection, characterized in that, The methods and steps include the following: S1. Obtain the propagation delay time and signal amplitude of microwaves at different detection frequencies in the plasma; S2. Obtain the mapping relationship between the detection frequency and the location of the tokamak device, as well as the plasma electron density distribution, through inversion; S3. The transmission delay time and signal amplitude at different radial positions are obtained through spatial interpolation; S4. Obtain the spatial gradient of the transmission delay time and identify the radial coordinate set d1 of the low-order rational surface based on the signal characteristics; if the position of the low-order rational surface is determined to be a non-empty set, continue to the next step; otherwise, skip it and return to the initial step S1 for the signal and amplitude signal of the transmission delay time of the next time period. S5. Determine the occurrence of the magnetohydrodynamic mode through the magnetic probe signal, and further calculate the characteristic frequency of the mode; S6. Determine the ring m and poloidal modulus n of the magnetohydrodynamic mode; S7. Analyze the filtered transmission delay time signal and its signal amplitude, and obtain the radial coordinate set d2 of the low-order rational surface based on the cross-correlation coefficient. S8. Based on the results of radial coordinate set d1, radial coordinate set d2, and the ring m and poloidal modulus n of the magnetohydrodynamic mode, determine the values ​​of the lower-order rational surface and its corresponding radial position d3.

2. The method for real-time identification and positioning of low-order rational surfaces based on microwave reflection according to claim 1, characterized in that, In step S1, the propagation delay time of microwaves at different detection frequencies in the plasma is obtained as follows: S11. Using a swept-frequency microwave source as the emission source, a series of microwaves with continuously changing frequency are emitted into the plasma; S12. A directional coupler is used to split the microwave source output signal into a transmission channel and a receiving channel; S13. Microwaves enter the plasma through the transmitting antenna, and are received by the receiving antenna after being cut off and reflected in the plasma. S14. The reflected signal is then mixed with the intrinsic signal of the receiving channel. The phase change rate and frequency sweep speed are obtained through the mixed signal to obtain the microwave transmission delay time in the plasma.

3. The method for real-time identification and positioning of low-order rational surfaces based on microwave reflection according to claim 2, characterized in that, In step S14, the mixed signal is subjected to a time-frequency Fourier transform to obtain the signal amplitude corresponding to different detection frequencies.

4. The method for real-time identification and positioning of low-order rational surfaces based on microwave reflection according to claim 1, characterized in that, In step S4, the existence of low-order rational surfaces is initially identified based on signal characteristics, which includes the following steps: S41. When the distribution of transmission delay time changes from a monotonic distribution to a phenomenon where a peak "jumps" at a certain local location, and the detection frequency range corresponding to this local location range is within a set frequency range, the radial coordinate set d of this local location range is obtained. 11 ; S42. During the transmission delay time, the signal amplitude exhibits a decrease in reflected signal power within the detection frequency range, and the power attenuation exceeds a set threshold. The radial coordinate set d of the corresponding cutoff layer is then obtained. 12 ; S43. An extreme value phenomenon appears in the spatial gradient distribution of the transmission delay time, and the relative height of the extreme value exceeds a set threshold. The radial coordinate set d of the extreme value range is obtained. 13 ; Take the radial coordinate set d from the above steps 11 d 12 d 13 The intersection of the two sets of points is obtained by finding the intersection d1=d. 11 ∩d 12 ∩d 13 ; If conditions S41, S42, and S43 are met simultaneously, and the intersection d1 is a non-empty set, then it is preliminarily determined that the position of the low-order rational surface is identified by microwave reflection, and the next step is executed.

5. The method for real-time identification and positioning of low-order rational surfaces based on microwave reflection according to claim 1, characterized in that, In step S5, the characteristic frequencies of the calculated mode include: A ring of probes is placed along the toroidal and poleal positions within the tokamak device to acquire magnetic field disturbance signals at different toroidal and poleal positions. These signals are then smoothed and subjected to spectral analysis. If a peak with a relative height exceeding a set threshold power appears in the spectrum of the magnetic probe signal, and the frequency of this peak falls within the frequency range of the magnetohydrodynamic (MHD) mode, and the transmission delay and amplitude signals correspond to the characteristics identified in step S4, then the MHD mode is confirmed to have occurred. The frequency at the point of maximum power is then identified as the characteristic frequency f of the MHD mode. MHD .

6. The method for real-time identification and positioning of low-order rational surfaces based on microwave reflection according to claim 5, characterized in that, In step S6, the phase difference between two adjacent magnetic probe data is analyzed and obtained. The integer multiple relationship obtained by dividing the phase difference by the angle between the positions of the two magnetic probes in the circumferential or polar directions is the circumferential module m or the polar module n.

7. The method for real-time identification and positioning of low-order rational surfaces based on microwave reflection according to claim 1, characterized in that, In step S7, obtaining the existence of a low-order rational surface based on the cross-correlation coefficient includes the following steps: S71. Perform cross-correlation analysis between the relative propagation delay perturbation signals of each channel after bandpass filtering and a magnetic probe signal, and calculate the average cross-correlation coefficient of each channel within the characteristic frequency range. When it exceeds a set threshold, obtain the radial coordinate set d corresponding to that channel. 21 ; S72. For the relative amplitude perturbation signals of each channel after bandpass filtering, perform correlation analysis with a magnetic probe signal, and calculate the average cross-correlation coefficient of each channel within the characteristic frequency range. When it exceeds a set threshold, obtain the radial coordinate set d corresponding to that channel. 22 ; S73. Perform correlation analysis between the relative gradient perturbation signals of each channel after bandpass filtering and a magnetic probe signal to obtain the average cross-correlation coefficient of each channel within the characteristic frequency range. When it exceeds a set threshold, obtain the radial coordinate set d corresponding to that channel. 23 ; The bandpass filtering range in steps S71, S72, and S73 above is [f MHD -df, f MHD +df], df is set to f MHD / 2; Using the magnetic probe signal with the maximum relative height peak near the characteristic frequency obtained in step S5 as the reference signal, and after the judgments in steps S71, S72, and S73, the union of the radial coordinate sets is obtained, that is, the intersection d2=d 21 d 22 d 23 .

8. The method for real-time identification and positioning of low-order rational surfaces based on microwave reflection according to claim 1, characterized in that, In step S8, the value q of the low-order rational surface is determined by the ring and polar modulus, i.e., q = m / n; and the intersection of the radial coordinate sets d1 and d2 obtained in steps S4 and S7 is used as the radial coordinate position of the low-order rational surface obtained by final identification and positioning, i.e., d3 = d1∩d2.

9. A device for real-time identification and positioning of low-order rational surfaces based on microwave reflection, characterized in that, The apparatus, used in the method of any one of claims 1-8, comprises: The diagnostic system includes a microwave reflection diagnostic system and a magnetic diagnostic system. The magnetic diagnostic system places a ring of probes along the ring and pole positions inside the tokamak device to acquire magnetic field disturbance signals at different ring and pole positions. The microwave reflection diagnostic system uses receiving and transmitting antennas placed at the outer mid-plane of the tokamak to acquire the transmission delay time and signal amplitude of microwaves of different detection frequencies in the plasma. The real-time acquisition system digitizes the diagnostic signals transmitted via coaxial cable, and includes a first data acquisition module and a second data module. The real-time identification and positioning system and the human-computer interaction system are connected by a communication bus. The system is used to process the signals of the diagnostic system in real time, identify and locate low-order rational surfaces, and send the information to the human-computer interaction system. The real-time identification and positioning system includes a transmission delay time and amplitude signal extraction module, a magnetohydrodynamic mode time-frequency analysis module, a magnetohydrodynamic mode modulus analysis module, a density distribution inversion and mapping module, a first low-order rational surface identification module, a second low-order rational surface identification module, and a low-order rational surface positioning module.

10. The device for real-time identification and positioning of low-order rational surfaces based on microwave reflection according to claim 9, characterized in that: The transmission delay time and amplitude signal extraction module is used to obtain the transmission delay time and signal amplitude of microwaves of different detection frequencies in the plasma. The density distribution inversion and mapping module is used to invert and obtain the mapping relationship between the detection frequency and the tokamak position and the plasma electron density distribution. After spatial interpolation, the transmission delay time and signal amplitude at different radial positions are obtained. The first low-order rational surface identification module is used to obtain the spatial gradient of the transmission delay time and identify the radial coordinate set d1 of the low-order rational surface; The magnetohydrodynamic mode time-frequency analysis module is used to determine the occurrence of a magnetohydrodynamic mode through magnetic probe signals and to calculate the characteristic frequency of the mode. The magnetohydrodynamic mode modulus analysis module is used to determine the ring m and poloidal modulus n of the magnetohydrodynamic mode; The second low-order rational surface identification module is used to analyze the filtered transmission delay time signal and its signal amplitude, and obtain the radial coordinate set d2 of the low-order rational surface according to the cross-correlation coefficient. The low-order rational surface positioning module is used to determine the low-order rational surface value and its corresponding radial position d3 based on the results of the radial coordinate set d1, the radial coordinate set d2, the ring m and the poloidal modulus n of the magnetohydrodynamic mode.

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