A system and method for measuring the tilt angle of magnetic field lines based on the principle of microwave scattering.

Abstract

This invention discloses a magnetic field line tilt angle measurement system and method based on the microwave scattering principle, relating to the field of nuclear fusion technology. The measurement system and method of this invention can be applied to the long-term stable monitoring of the magnetic field line deflection angle of magnetic confinement fusion devices, ensuring high performance of the magnetic confinement devices. This invention measures the magnetic field line tilt angle by combining microwave transceiver technology, the microwave scattering principle in plasma, and an adjustable polarizer. By rapidly adjusting the angle of the polarizer and simultaneously measuring the power intensity of the scattered signals at different receiving positions and with different polarization directions, the magnetic field line tilt angle is obtained through the dependence between the microwave scattered signals with different polarization directions and the adjustable polarizer.

Description

Technical Field

[0001] This invention relates to the field of nuclear fusion technology, and in particular to a magnetic field line tilt angle measurement system based on the principle of microwave scattering. Background Technology

[0002] The tilt angle of magnetic field lines in magnetic confinement fusion devices such as tokamas and stellarators is one of the most important parameters for evaluating the device's operational status. Precise measurement and control of the tilt angle of magnetic field lines are essential for achieving advanced operating modes and high performance in magnetic confinement fusion devices. Existing technologies mainly employ three methods for measuring the tilt angle of magnetic field lines: magnetic probe inversion, laser polarization interferometry, and kinematic Stark effect diagnosis. These methods, however, have at least the following limitations:

[0003] (1) Magnetic probe inversion is based on the EFIT model. Multiple calibrated magnetic probes are arranged in the device, and the magnetic field line tilt angle is inferred by calculating the signal of each probe. However, due to the inability of key components such as integrators to work stably for a long time, it cannot be used in magnetic confinement fusion devices that will operate for a long time in the future.

[0004] (2) The laser polarization interferometer is based on the Faraday effect. Its principle is that the polarization direction of linearly polarized light propagating in a medium will rotate due to the presence of a magnetic field. However, during the measurement process, the Faraday rotation angle is affected by the magnetic field and density along the path, and the magnetic field line tilt angle needs to be obtained through multi-channel measurement and complex inversion algorithms.

[0005] (2) The kinematic Stark effect diagnostic method utilizes the phenomenon of energy level splitting of particles under the action of an external electric field. By accurately measuring the radiation spectral lines in different polarization directions, the tilt angle of the magnetic field lines can be determined. However, it is strongly dependent on a high-energy neutral beam and cannot work without the injection of a neutral beam. In addition, optical measurement methods are usually complex, with difficult and expensive optical path adjustment and maintenance, and the optical devices are difficult to operate stably for a long time in the high-flux fusion neutron and complex radiation environment.

[0006] It is evident that current methods for measuring magnetic field lines either fail to meet the requirements for long-term stable measurement or involve complex measurement and inversion processes, thus failing to meet the need for long-term stable measurement of the tilt angle of magnetic field lines in magnetic confinement fusion devices. Summary of the Invention

[0007] This invention provides a magnetic field line tilt angle measurement system and method based on the microwave scattering principle, which simplifies the measurement and inversion processes to solve the problem that existing magnetic field line measurement methods cannot meet the requirements for long-term stable measurement.

[0008] This invention is achieved through the following technical solution:

[0009] In a first aspect, the present invention provides a magnetic field line tilt angle measurement system based on the principle of microwave scattering, for measuring the magnetic field line tilt angle of a magnetic confinement fusion device. The measurement system includes: a microwave transmitting and receiving device, an adjustable polarizer, and a signal processing module.

[0010] The microwave transmitting and receiving device includes an adjustable frequency source, a transmitting antenna, a first receiving antenna, and a second receiving antenna.

[0011] The adjustable polarizer is configured to rotate at a constant speed during measurement and to synchronize the rotation angle to the signal processing module;

[0012] The adjustable frequency source is used to output a microwave signal of a predetermined frequency. The microwave signal enters the uniformly rotating adjustable polarizer through the transmitting antenna, and then enters the plasma of the magnetic confinement fusion device after being transmitted through the adjustable polarizer. After being scattered in the plasma, it returns to the adjustable polarizer.

[0013] The polarization directions of the first receiving antenna and the second receiving antenna are perpendicular to each other. The first receiving antenna and the second receiving antenna are used to receive microwave signals that are scattered in the plasma and then return to the tunable polarizer.

[0014] The signal processing module is used to determine the tilt angle of the magnetic field lines of the magnetic confinement fusion device based on the microwave signals received by the first receiving antenna and the second receiving antenna and the rotation angle of the adjustable polarizer.

[0015] This invention is based on the scattering characteristics of microwaves in plasma. When a microwave signal enters a plasma, due to density and magnetic field disturbances, microwaves of a specific frequency will be emitted and scattered near the plasma's cutoff layer. The scattered microwave signal returns to an adjustable polarizer, and the polarization direction and power intensity of the returned scattered signal differ from those of the incident microwave. The tilt angle of the magnetic field lines in a magnetic confinement fusion device mainly depends on the plasma's current density distribution. Therefore, the tilt angle of the magnetic field lines can be determined based on different polarizer angles and the power intensity of the microwave signal received by different receiving antennas. The measurement system of this invention can measure the tilt angle of the magnetic field lines simply by transmitting and receiving microwave signals, without relying on external conditions such as neutral beam injection. The measurement system is simple in construction, easy to adjust and maintain, and has low operating costs. The tilt angle of the magnetic field lines can be determined based on different polarizer angles and the power intensity of the microwave signal received by different receiving antennas. The measurement and inversion methods are simple, requiring no repeated measurements or complex inversions, enabling rapid real-time monitoring of the tilt angle of the magnetic field lines in plasma, and is suitable for long-term stable measurements.

[0016] In one embodiment, determining the magnetic field line tilt angle of the magnetic confinement fusion device based on the microwave signals received by the first and second receiving antennas and the rotation angle of the adjustable polarizer includes:

[0017] Obtain the first power curve of the microwave signal received by the first receiving antenna, and determine the first rotation angle of the adjustable polarizer corresponding to the minimum value of the first power curve.

[0018] Obtain the second power curve of the microwave signal received by the second receiving antenna, and determine the second rotation angle of the adjustable polarizer corresponding to the minimum value of the second power curve;

[0019] The magnetic field line tilt angle of the magnetic confinement fusion device is determined based on the difference between the first rotation angle and the second rotation angle.

[0020] In one embodiment, the microwave transmitting and receiving device further includes: a power divider, a first mixer, and a second mixer;

[0021] The power divider is connected to the output of the adjustable frequency source and is used to divide the microwave signal of the predetermined frequency into three paths. One microwave signal enters the transmitting antenna and then enters the adjustable polarizer that is rotating at a constant speed. The other two microwave signals enter the first mixer and the second mixer respectively, serving as the local oscillator reference signals of the first mixer and the second mixer.

[0022] The first mixer and the second mixer are respectively connected to the first receiving antenna and the second receiving antenna, and are used to receive the microwave signals that are scattered and return to the tunable polarizer.

[0023] The first mixer and the second mixer obtain mixing signals based on the received microwave signal and the local oscillator reference signal, respectively, and send the mixing signals to the signal processing module so that the signal processing module determines the magnetic field line tilt angle of the magnetic confinement fusion device based on the mixing signals of the first mixer and the second mixer and the rotation angle of the adjustable polarizer.

[0024] In one embodiment, the measurement system further includes a controller for controlling the adjustable polarizer to rotate at a predetermined rotation speed and in a predetermined rotation direction based on adjustment commands, and synchronizing the rotation angle to the signal processing module.

[0025] In one embodiment, the measurement system further includes a control module for issuing adjustment commands to the controller, the adjustment commands including rotation speed and rotation direction; the control module is also used to control the transmission frequency of the adjustable frequency source.

[0026] In one embodiment, the control module and the signal processing module are integrated in a host computer.

[0027] In one embodiment, the first receiving antenna and the second receiving antenna are two ports of a two-port antenna, the polarization directions of the two ports are perpendicular to each other, and the two ports are used to receive microwave signals that are scattered in the plasma and return to the tunable polarizer.

[0028] In one embodiment, the central optical axis of the adjustable polarizer forms a 45-degree angle with the central axis of the transmitting antenna, and the central optical axis of the adjustable polarizer forms a 45-degree angle with the central axis of the dual-port antenna.

[0029] In one embodiment, the transmitting antenna is a waveguide rotating antenna.

[0030] A second aspect of the present invention provides a method for measuring the tilt angle of magnetic field lines based on the principle of microwave scattering, used to measure the tilt angle of magnetic field lines in a magnetic confinement fusion device. The method utilizes the magnetic field line tilt angle measurement system based on the principle of microwave scattering described in any of the above embodiments, and includes:

[0031] The adjustable polarizer is made to rotate at a constant speed during measurement, and the rotation angle is synchronized to the signal processing module.

[0032] A microwave signal of a predetermined frequency is emitted by an adjustable frequency source. The microwave signal enters the adjustable polarizer, which is rotating at a constant speed, through the transmitting antenna. After being transmitted through the adjustable polarizer, it enters the plasma of the magnetic confinement fusion device and is scattered in the plasma before returning to the adjustable polarizer.

[0033] The microwave signals that are scattered in the plasma and return to the tunable polarizer are received by the first receiving antenna and the second receiving antenna, respectively.

[0034] The magnetic field line tilt angle of the magnetic confinement fusion device is determined by the signal processing module based on the microwave signals received by the first and second receiving antennas and the rotation angle of the adjustable polarizer.

[0035] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0036] Based on the scattering characteristics of microwave signals in plasma, the angle of magnetic field lines can be inverted by receiving the scattered microwave signal and the polarizer angle. The main equipment of the measurement system only needs to realize microwave transmission and reception, control of the adjustable polarizer, and back-end signal processing. It has a simple structure, is easy to maintain, and has low cost.

[0037] The measurement principle and inversion method are simple, eliminating the need for repeated measurements and complex inversions. It can quickly monitor the tilt angle of the magnetic field lines of plasma in real time, meeting the needs of long-term stable measurements. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0039] Figure 1 This is a schematic diagram of a magnetic field line tilt angle measurement system based on the microwave scattering principle according to an embodiment of the present invention;

[0040] Figure 2 This is a second schematic diagram of a magnetic field line tilt angle measurement system based on the microwave scattering principle according to an embodiment of the present invention;

[0041] Figure 3 This is a schematic diagram illustrating the principle of measuring the tilt angle of magnetic field lines according to the present invention;

[0042] Figure 4 This is the third schematic diagram of a magnetic field line tilt angle measurement system based on the microwave scattering principle according to an embodiment of the present invention;

[0043] Figure 5 This is a diagram showing the distribution of scattered microwave power received at different receiving ports under different polarization angles;

[0044] Figure 6 This is the fourth schematic diagram of a magnetic field line tilt angle measurement system based on the microwave scattering principle according to an embodiment of the present invention.

[0045] The explanations of the reference numerals in the above figures are as follows:

[0046] 1-Microwave transmitting and receiving device, 2-Adjustable polarizer, 3-Signal processing module, 4-Adjustable frequency source, 5-Transmitting antenna, 6-Receiving antenna, 7-Receiving antenna, 8-Plasma, 9-Power divider, 10-Mixer, 11-Mixer, 12-Mixer, 13-Controller. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0048] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims, and accompanying drawings of this invention are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to other steps or units inherent in the device.

[0049] The terminology used in the various embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the various embodiments of this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which the various embodiments of this application pertain. The terms (such as those defined in a generally used dictionary) are to be interpreted as having the same meaning as in the context of the relevant technical field and are not to be interpreted as having an idealized or overly formal meaning, unless clearly defined in the various embodiments of this application.

[0050] The embodiments of the present invention provide a magnetic field line tilt angle measurement system based on the microwave scattering principle, which is applicable to the measurement of the magnetic field line tilt angle of magnetic confinement fusion devices. Its advantages are that it can quickly determine the magnetic field line tilt angle, and it has the characteristics of low cost, stable operation and strong robustness. It can meet the requirements of magnetic field line tilt angle monitoring in the long-term operation and complex radiation environment of magnetic confinement fusion devices.

[0051] like Figure 1 As shown, Figure 1 This is a schematic diagram of a magnetic field line tilt angle measurement system based on the microwave scattering principle according to an embodiment of the present invention. The measurement system includes: a microwave transmitting and receiving device 1, an adjustable polarizer 2, and a signal processing module 3.

[0052] The microwave transmitting and receiving device 1 includes an adjustable frequency source 4, a transmitting antenna 5, a first receiving antenna 6, and a second receiving antenna 7.

[0053] The adjustable polarizer 2 is configured to rotate at a constant speed during measurement and synchronize the rotation angle to the signal processing module;

[0054] The adjustable frequency source 4 is used to output a microwave signal of a predetermined frequency. The microwave signal enters the uniformly rotating adjustable polarizer 2 through the transmitting antenna 5, and then enters the plasma 8 of the magnetic confinement fusion device after being transmitted through the adjustable polarizer 2. After being scattered in the plasma 8, it returns to the adjustable polarizer 2.

[0055] The polarization directions of the first receiving antenna 6 and the second receiving antenna 7 are perpendicular to each other. The first receiving antenna 6 and the second receiving antenna 7 are used to receive microwave signals that are scattered in the plasma and return to the tunable polarizer, respectively.

[0056] The signal processing module 3 is used to determine the tilt angle of the magnetic field lines of the magnetic confinement fusion device based on the microwave signals received by the first receiving antenna 6 and the second receiving antenna 7 and the rotation angle of the adjustable polarizer.

[0057] Device connection relationship as follows Figure 1 As shown, the output of the adjustable frequency source 4 is connected to the transmitting antenna 5, which transmits a microwave signal of a predetermined frequency. The microwave signal enters the adjustable polarizer 2 via the transmitting antenna 5 and is subsequently emitted into the plasma 8. The adjustable polarizer 2 rotates at a constant speed under the control of an electrical signal, and the rotation angle and rotation mode are adjustable. During the measurement process, the adjustable polarizer 2 performs an angle scan at a uniform speed. Therefore, when the microwave signal enters the adjustable polarizer 2 from the polarization direction of the transmitting antenna 5, the relative angle of incidence on the adjustable polarizer also changes accordingly. In this embodiment, the movement of the adjustable polarizer is controlled using conventional automated control technology in the art. All aspects not described in detail in this invention can be implemented using existing or general technologies.

[0058] The tunable polarizer 2 is composed of fine metal wire grids with a diameter of 5 micrometers that are parallel to each other and a spacing of 10 micrometers. It can reflect microwave signals with polarization direction parallel to the metal wires and transmit only microwaves with polarization direction perpendicular to the metal wires. The cross isolation of the tunable polarizer needs to reach 30dB or 50dB or more.

[0059] Cross-isolation refers to the selectivity of a polarizer for electromagnetic waves parallel to and perpendicular to the direction of the metal wires. Ideally, only electromagnetic waves with electric fields perpendicular to the metal wires can penetrate the polarizer, while those with parallel electric fields will be reflected. However, the actual isolation is determined by the conductivity of the polarizer, the spacing and thickness of the metal wires, and represents the magnitude of the perpendicular power / parallel power, dB = 10log10(N). Therefore, 10dB corresponds to a factor of 10, and 30dB corresponds to a factor of 1000.

[0060] During measurement, the microwave signal is scattered after entering plasma 8. The scattered microwave signal returns to the tunable polarizer 2, and the polarization direction and power intensity of the returned scattered signal differ from those of the incident microwave. The tilt angle of the magnetic field lines can be determined based on different polarizer angles and the signal power intensity received by different receiving antennas.

[0061] Microwave transceiver technology primarily employs fixed-frequency transmission and reception techniques, mainly for microwave backscatter diagnosis. Alternatively, frequency-modulated continuous wave (FM) sweep technology, multi-frequency transceiver technology, or pulse radar technology can be used. The frequency range depends on the characteristics of the measured object, such as magnetic field strength, density, and plasma current. The microwave scattering principle primarily utilizes backscattering, where the scattered microwaves follow essentially the same path as the incident microwaves. This allows the receiving and transmitting antennas to be placed adjacent to each other, or the receiving antenna to be positioned in different locations to measure scattered signals from other directions. Figure 1 The diagram illustrates a scheme where receiving antenna 6 and transmitting antenna 5 are placed in adjacent spatial locations, while another receiving antenna 7 is placed in a different location. It is understood that, provided the basic principles are met, the positions of the transmitting and receiving antennas are adjustable, and this invention does not impose limitations. Furthermore, the first and second receiving antennas are only distinguished by their names; they are essentially the same and can be used interchangeably.

[0062] The key point of this invention lies in measuring the tilt angle of magnetic field lines through a combination of microwave transceiver technology, the principle of microwave scattering in plasma, and an adjustable polarizer. By rapidly adjusting the angle of the polarizer and simultaneously measuring the power intensity of scattered signals at different receiving positions and with different polarization directions, the tilt angle of the magnetic field lines is obtained by finding the angle difference at which the power of microwave scattered signals with two different polarization directions reaches its minimum. This invention can be applied to magnetic confinement fusion devices and other magnetic confinement plasma fields, such as magnetic mirrors, plasma thrusters, and plasma beams.

[0063] In some embodiments of the present invention, receiving antenna 6 and receiving antenna 7 are replaced by the two ports of a dual-port antenna, such as... Figure 2 As shown, Figure 2 This is the second schematic diagram of the magnetic field line tilt angle measurement system based on the microwave scattering principle of the present invention. The first and second receiving antennas are replaced with the two ports of a dual-port antenna. The polarization directions of ports 6 and 7 of the dual-port antenna are perpendicular to each other. The two ports are used to receive the microwave signals that are scattered in the plasma and return to the tunable polarizer.

[0064] Furthermore, the dual-port receiving antenna in the above embodiment is a dual-polarized antenna, or it can be replaced by any two independent linearly polarized antennas with their polarization directions arranged perpendicular to each other.

[0065] In some embodiments of the present invention, the adjustable polarizer technology can be replaced by replacing the transmitting antenna with a waveguide rotating antenna or other solutions with adjustable polarization.

[0066] In one embodiment of the present invention, determining the magnetic field line tilt angle of the magnetic confinement fusion device based on the microwave signals received by the first receiving antenna 6 and the second receiving antenna 7 and the rotation angle of the adjustable polarizer includes:

[0067] Obtain the first power curve of the microwave signal received by the first receiving antenna 6, and determine the first rotation angle of the adjustable polarizer corresponding to the minimum value of the first power curve.

[0068] Obtain the second power curve of the microwave signal received by the second receiving antenna 7, and determine the second rotation angle of the adjustable polarizer corresponding to the minimum value of the second power curve.

[0069] The tilt angle of the magnetic field lines of the magnetic confinement fusion device is determined based on the difference between the first rotation angle and the second rotation angle.

[0070] During the measurement process, the adjustable polarizer 2 rotates around a predetermined rotation axis. The angle at which microwaves enter the plasma through the adjustable polarizer is different at different times. Therefore, there is a corresponding relationship between the received scattered microwaves and the incident angle, which is also the rotation angle of the adjustable polarizer. By analyzing the microwave signal power curves received by the receiving antennas in different directions, the magnetic field line tilt angle can be quickly obtained by measuring the scattered microwaves.

[0071] The principle of this invention for measuring magnetic field lines is as follows:

[0072] like Figure 3 The diagram illustrates the principle of measuring the tilt angle of magnetic field lines according to this invention. Based on the scattering characteristics of microwaves in plasma, it is assumed that the polarization direction of the transmitting antenna (the electric field direction of the microwave) is parallel to the E direction and perpendicular to the H direction. After the frequency source passes through the polarizer, the polarization direction will rotate by an angle θ. If the angle of the magnetic field line B is α, the angular relationship satisfies: α = θ + δ. Microwaves incident on the plasma can be divided into two types according to their angular relationship with the magnetic field lines: the O mode parallel to the magnetic field lines and the X mode perpendicular to the magnetic field lines. Due to density and magnetic field disturbances in the plasma, microwaves of specific frequencies will be emitted and scattered near its cutoff layer. The scattered signal consists of four parts: First, the O-mode transforms into O and the X-mode transforms into X due to density perturbations. O-mode incident electromagnetic waves interact with small-scale density perturbations, resulting in scattering. The electric field direction of the scattered signal is the same as that of the incident signal, hence O->O, X->X. Second, the O-mode transforms into X and the X-mode transforms into O due to magnetic field perturbations. Magnetic field perturbations cause a 90-degree deflection of the electric field direction of the scattered electromagnetic wave, i.e., O->X or X->O. The scattered microwaves return to the polarizer along the path of the incident microwaves and undergo transmission and reflection depending on their angular relationship with the polarizer.

[0073] like Figure 4 The diagram shown is a third schematic diagram of a magnetic field line tilt angle measurement system based on the microwave scattering principle of the present invention. The measurement system includes: a signal processing and control module 1, an adjustable frequency source 4, a power divider 9, an adjustable polarizer 2, a dual-polarized antenna 6, a dual-polarized antenna 7, a controller 13, and mixers 10-12.

[0074] Signal processing and control module 1 integrates the signal processing unit and the control unit into one module, implemented through a host computer. The signal processing and control module mainly provides the following three functions:

[0075] 1. Used to set parameters such as the microwave frequency and power emitted by the frequency source;

[0076] 2. Used to send adjustment commands to the controller 13 to set parameters such as the rotation period, rotation speed, rotation direction and rotation mode of the adjustable polarizer 2. After receiving the command, the controller 13 controls the polarizer to perform the corresponding movement.

[0077] The rotation methods include parameters that control the rotation shape of the adjustable polarizer, such as continuous rotation, rotation at intervals, continuous rotation at a fixed angle (e.g., 20° to 360°), rotation at intervals at a fixed angle (e.g., 20° to 360°), and rotation at intervals with the angle decreasing sequentially.

[0078] 3. Used to receive the signal after downconversion by mixer 10-12, and to collect, process, analyze and store the signal power. Combined with the angle of polarizer 2 and the power of microwaves scattered in different directions, the magnetic field line tilt angle is extracted and uploaded to the central control system.

[0079] After receiving relevant parameters from the control unit of the signal processing and control module 1, the adjustable frequency source 4 transmits a microwave signal of a specific frequency. The power divider 9 divides the microwave signal into four paths. One microwave signal enters the adjustable polarizer through the vertical polarization port of the dual-polarized antenna 6 and is then transmitted into the plasma. The other three signals enter mixers 10, 11, and 12 respectively, providing local oscillator reference signal inputs for mixers 10-12.

[0080] After receiving instructions from the control unit, the controller 13 controls the adjustable polarizer 2 to perform an angle scan. The microwave signal, after being transmitted through the adjustable polarizer 2, enters the plasma 8 and is scattered. The scattered signal returns to the adjustable polarizer 2 along the original path of the incident microwave. The central optical axis of the adjustable polarizer 2 forms a 45° angle with both the dual-polarized antenna 6 and the dual-polarized antenna 7. That is, the optical axis directions of the receiving antennas of the dual-polarized antenna 6 (determined by the antenna opening direction) and the receiving antenna optical axes of the dual-polarized antenna 7 are perpendicular to each other and coplanar. The central optical axis of the polarizer forms a 45° angle with the optical axes of the two antennas and is coplanar. Thus, the scattered microwaves are transmitted and reflected according to their polarization angle with the polarizer. The polarization angle of the transmitted microwave is θ. The transmitted microwave enters the horizontal port of the dual-polarized antenna 6, and the reflected microwave enters both the horizontal and vertical ports of the dual-polarized antenna 7.

[0081] Mixer 10-12 is used to mix the microwave scattered signal collected by the receiving antenna with the local oscillator reference signal given by the frequency source. After mixing, the microwave frequency is reduced, and the real part (I) and imaginary part (Q) signals after down-conversion are input to the signal processing module and the control module. The microwave power information is extracted by the signal processing unit and compared with the polarizer angle.

[0082] Based on the characteristics of plasma, the scattering efficiency caused by density fluctuations is S. n The scattering efficiency caused by magnetic field fluctuations is S B And S n Typically much higher than S B (At least 100 times), therefore, the signal strength received at the horizontal port of polarized antenna 1, and at the horizontal and vertical ports of polarized antenna 2, is determined by parameters such as the polarizer angle and the tilt angle of the magnetic field lines. If the microwave power output by the frequency source through the transmitting antenna is Pin, the received power of the several antennas can be calculated according to the following formula:

[0083] (1) Received power at the horizontal port of antenna 1:

[0084] P 1-H =(S B cos 2 δsin 2 δ+S n cos 4 δ+S n sin 4 δ+S B sin 2 δcos 2 δ)P in cos 2 θsin 2 θ

[0085] (2) Received power at the horizontal port of antenna 2:

[0086] P 2-H =(S B cos 4 δ+2S n cos 2 δsin 2 δ+S B sin 4 δ)P in cos 4 θ

[0087] (3) Received power at the vertical port of antenna 2:

[0088] P 2-V =(S B cos 4 δ+2S n cos 2 δsin 2 δ+S B sin 4 δ)P in cos 2 θsin 2 θ

[0089] like Figure 5 As shown, Figure 5 This is a distribution diagram of scattered microwave power received at different receiving ports under different polarization angles. When the polarizer angle is 0°, the received power at the horizontal port of polarized antenna 1 and the vertical port of polarized antenna 2 has a minimum value. When the polarizer angle is equal to the tilt angle of the magnetic field lines (θ = 6°), the microwave power measured at the horizontal port of polarized antenna 2 will also have a minimum value, i.e. Figure 5 The angle is shown by the vertical line. Therefore, when measuring magnetic field lines, the tilt angle of the magnetic field lines can be obtained by comparing the polarizer angle corresponding to the minimum microwave power at the horizontal port of the polarized antenna 7 with the angle corresponding to the minimum microwave power measured at the horizontal port of the polarized antenna 6 or the vertical port of the polarized antenna 7.

[0090] Based on the above principle, it can be deduced that in the actual measurement process, only two antennas with mutually perpendicular polarization directions are needed to receive the scattered microwave signals. The tilt angle of the magnetic field lines can be easily obtained based on the scattered microwave power in different directions and the corresponding polarizer deflection angle.

[0091] In some embodiments of the present invention, the measurement system further includes: a power divider 9, a first mixer 10, and a second mixer 11. For example... Figure 6 As shown, Figure 6 This is the fourth schematic diagram of a magnetic field line tilt angle measurement system based on the microwave scattering principle of the present invention.

[0092] The power divider 9 is connected to the output of the adjustable frequency source 4 and is used to divide a microwave signal of a predetermined frequency into three paths. One microwave signal enters the uniformly rotating adjustable polarizer 2 through the transmitting antenna 5, and the other two microwave signals enter the first mixer 10 and the second mixer 11 respectively, serving as the local oscillator reference signals for the first mixer 10 and the second mixer 11.

[0093] The first mixer 10 and the second mixer 11 are respectively connected to the first receiving antenna 6 and the second receiving antenna 7, and are used to receive microwave signals that are scattered and returned to the tunable polarizer 2.

[0094] The first mixer 10 and the second mixer 11 obtain mixing signals based on the received microwave signal and the local oscillator reference signal, respectively, and send the mixing signals to the signal processing module 1 so that the signal processing module 1 can determine the magnetic field line tilt angle of the magnetic confinement fusion device based on the mixing signals of the first mixer 10 and the second mixer 11 and the rotation angle of the adjustable polarizer 2.

[0095] In this embodiment, when the measurement system starts working, a microwave signal with a specific frequency and power is generated by the adjustable frequency source 4 and divided into 3 paths by the power divider. One of the signals is transmitted to the transmitting port of the transmitting antenna 5 and transmitted outward. The microwave power is Pin. The other two signals are transmitted to the mixer 10 and mixer 11 respectively as local oscillator reference signals.

[0096] Initially, the polarization direction of the adjustable polarizer 2 is at an initial angle, such as -90° in the horizontal direction, and it rotates at a constant speed according to the control signal, such as 180° per second. As the polarizer angle θ changes, the polarization direction of the microwave incident on the plasma 8 is modulated to θ, with a power of P. in cos 2 θ.

[0097] At this point, if the angle of the magnetic field lines in the plasma is α, the microwave can be decomposed in the plasma into an o-mode component parallel to the tilt angle of the magnetic field lines and an X-mode component perpendicular to the tilt angle of the magnetic field lines, where the power of the o-mode is P. in cos 2 θsin 2 The power of the δ, X mode is P in cos 2 θcos 2 δ. The scattering efficiency caused by density fluctuations is S. n The scattering efficiency caused by magnetic field fluctuations is S B .

[0098] The scattered microwaves will return to the tunable polarizer 2 along the same path as the incident microwaves. The scattered microwaves are transmitted and reflected according to their polarization angle with the tunable polarizer 2. The polarization angle of the transmitted microwaves is θ. These microwaves enter the first receiving antenna 6 and are led out by the first receiving antenna 6 to the mixer 10.

[0099] The polarization angle of the reflected microwave is θ±90°. The microwave enters the second receiving antenna 7 and is led out to the mixer 11 through the second receiving antenna 7.

[0100] Mixer 10 and mixer 11 output the real part (I) and imaginary part (Q) of the mixed low-frequency signal and send them to the signal processing module. The signal processing module performs high-speed acquisition of the signal and extracts information such as the signal power intensity through short-time Fourier transform. Based on the measurement principle and Figure 5 The signal processing module compares the angle θ1 of the minimum power of the second receiving antenna 7 with the angle θ2 corresponding to the minimum power of the first receiving antenna 6 to obtain the tilt angle of the magnetic field lines as: α = θ1 - θ2.

[0101] In some embodiments of the present invention, reference is made to Figure 4 The measurement system also includes a controller, which controls the adjustable polarizer to rotate at a predetermined speed and direction based on adjustment commands, and synchronizes the rotation angle to the signal processing module.

[0102] In some embodiments of the present invention, the measurement system further includes a control module, which is used to issue adjustment commands to the controller, the adjustment commands including rotation speed and rotation direction; the control module is also used to control the transmission frequency of the adjustable frequency source.

[0103] The control module and controller can be used to control the adjustable polarizer and the adjustable frequency source. For ease of operation, in one embodiment, the control module and the signal processing module are integrated in the host computer.

[0104] In a second aspect, the present invention provides a method for measuring the tilt angle of magnetic field lines based on the principle of microwave scattering, wherein the measurement system measures the tilt angle of magnetic field lines in a magnetic confinement fusion device.

[0105] The measurement method applies the magnetic field line tilt angle measurement system based on the microwave scattering principle of any of the above embodiments of the present invention, as shown in the appendix. Figure 1 The measurement system, the method comprising:

[0106] The adjustable polarizer 2 is made to rotate at a constant speed during measurement, and the rotation angle is synchronized to the signal processing module 1.

[0107] A microwave signal of a predetermined frequency is emitted by an adjustable frequency source 4. The microwave signal enters the uniformly rotating adjustable polarizer 2 through the transmitting antenna, and then enters the plasma 8 of the magnetic confinement fusion device after being transmitted through the adjustable polarizer 2. After being scattered in the plasma 8, it returns to the adjustable polarizer 2.

[0108] The microwave signals that are scattered in the plasma and return to the tunable polarizer 2 are received by the first receiving antenna 6 and the second receiving antenna 7, respectively.

[0109] The signal processing module 1 determines the tilt angle of the magnetic field lines of the magnetic confinement fusion device based on the microwave signals received by the first receiving antenna 6 and the second receiving antenna 7 and the rotation angle of the adjustable polarizer.

[0110] The measurement method of the present invention is used in conjunction with a measurement system based on the scattering principle. It is simple to operate, and the operation method corresponds to the function of each device, so it will not be described in detail here.

[0111] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A magnetic field line tilt angle measurement system based on microwave scattering principle, characterized in that, The measurement system is used to measure the tilt angle of the magnetic field lines in a magnetic confinement fusion device. The measurement system includes: a microwave transmitting and receiving device, an adjustable polarizer, and a signal processing module. The microwave transmitting and receiving device includes an adjustable frequency source, a transmitting antenna, a first receiving antenna, and a second receiving antenna. The adjustable polarizer is configured to rotate at a constant speed during measurement and to synchronize the rotation angle to the signal processing module; The adjustable frequency source is used to output a microwave signal of a predetermined frequency. The microwave signal enters the uniformly rotating adjustable polarizer through the transmitting antenna, and then enters the plasma of the magnetic confinement fusion device after being transmitted through the adjustable polarizer. After being scattered in the plasma, it returns to the adjustable polarizer. The polarization directions of the first receiving antenna and the second receiving antenna are perpendicular to each other. The first receiving antenna and the second receiving antenna are used to receive microwave signals that are scattered in the plasma and then return to the tunable polarizer. The signal processing module is used to determine the magnetic field line tilt angle of the magnetic confinement fusion device based on the microwave signals received by the first receiving antenna and the second receiving antenna and the rotation angle of the adjustable polarizer. The determination of the magnetic field line tilt angle of the magnetic confinement fusion device based on the microwave signals received by the first and second receiving antennas and the rotation angle of the adjustable polarizer includes: Obtain the first power curve of the microwave signal received by the first receiving antenna, and determine the first rotation angle of the adjustable polarizer corresponding to the minimum value of the first power curve. Obtain the second power curve of the microwave signal received by the second receiving antenna, and determine the second rotation angle of the adjustable polarizer corresponding to the minimum value of the second power curve; The magnetic field line tilt angle of the magnetic confinement fusion device is determined based on the difference between the first rotation angle and the second rotation angle.

2. The magnetic field line tilt angle measuring system according to claim 1, characterized in that, The microwave transmitting and receiving device further includes: a power divider, a first mixer, and a second mixer; The power divider is connected to the output of the adjustable frequency source and is used to divide the microwave signal of the predetermined frequency into three paths. One microwave signal enters the transmitting antenna and then enters the adjustable polarizer that is rotating at a constant speed. The other two microwave signals enter the first mixer and the second mixer respectively, serving as the local oscillator reference signals of the first mixer and the second mixer. The first mixer and the second mixer are respectively connected to the first receiving antenna and the second receiving antenna, and are used to receive the microwave signals that are scattered and returned to the tunable polarizer. The first mixer and the second mixer obtain mixing signals based on the received microwave signal and the local oscillator reference signal, respectively, and send the mixing signals to the signal processing module so that the signal processing module determines the magnetic field line tilt angle of the magnetic confinement fusion device based on the mixing signals of the first mixer and the second mixer and the rotation angle of the adjustable polarizer.

3. The magnetic field line tilt angle measuring system according to claim 1, characterized in that, The measurement system also includes a controller, which controls the adjustable polarizer to rotate at a predetermined speed and direction based on adjustment commands, and synchronizes the rotation angle to the signal processing module.

4. The magnetic field line tilt angle measuring system according to claim 3, characterized in that, The measurement system also includes a control module, which is used to send adjustment commands to the controller, the adjustment commands including rotation speed and rotation direction; the control module is also used to control the transmission frequency of the adjustable frequency source.

5. The magnetic field line tilt angle measuring system according to claim 4, characterized in that, The control module and the signal processing module are integrated in the host computer.

6. The magnetic field line tilt angle measuring system according to claim 1, characterized in that, The first receiving antenna and the second receiving antenna are two ports of a two-port antenna. The polarization directions of the two ports are perpendicular to each other. The two ports are used to receive microwave signals that are scattered in the plasma and return to the tunable polarizer.

7. The magnetic field line tilt angle measuring system according to claim 6, characterized in that, The central optical axis of the adjustable polarizer forms a 45-degree angle with the central axis of the transmitting antenna, and the central optical axis of the adjustable polarizer forms a 45-degree angle with the central axis of the dual-port antenna.

8. The magnetic field line tilt angle measuring system according to any one of claims 1-7, characterized in that, The transmitting antenna is a waveguide rotating antenna.

9. A method for measuring the tilt angle of magnetic field lines based on the principle of microwave scattering, characterized in that, For measuring the tilt angle of magnetic field lines in a magnetic confinement fusion device, the magnetic field line tilt angle measurement system based on the microwave scattering principle as described in any one of claims 1-8 is used, and the method includes: The adjustable polarizer is rotated at a constant speed during measurement, and the rotation angle is synchronized to the signal processing module. A microwave signal of a predetermined frequency is emitted through an adjustable frequency source, and the microwave signal enters the uniformly rotating adjustable polarizer through the transmitting antenna, then enters the plasma of the magnetic confinement fusion device after being transmitted through the adjustable polarizer, and returns to the adjustable polarizer after being scattered in the plasma. The microwave signals that are scattered in the plasma and return to the tunable polarizer are received by the first receiving antenna and the second receiving antenna, respectively. The magnetic field line tilt angle of the magnetic confinement fusion device is determined by the signal processing module based on the microwave signals received by the first and second receiving antennas and the rotation angle of the adjustable polarizer. The determination of the magnetic field line tilt angle of the magnetic confinement fusion device based on the microwave signals received by the first and second receiving antennas and the rotation angle of the adjustable polarizer includes: Obtain the first power curve of the microwave signal received by the first receiving antenna, and determine the first rotation angle of the adjustable polarizer corresponding to the minimum value of the first power curve. Obtain the second power curve of the microwave signal received by the second receiving antenna, and determine the second rotation angle of the adjustable polarizer corresponding to the minimum value of the second power curve; The magnetic field line tilt angle of the magnetic confinement fusion device is determined based on the difference between the first rotation angle and the second rotation angle.

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