A high temperature plasma turbulence measurement system and method

Abstract

The present application relates to the field of high temperature plasma turbulence measurement, and particularly relates to a high temperature plasma turbulence measurement system and method, comprising: a transmitting module, used for transmitting a microwave detection signal to plasma; a receiving module, the receiving module comprising at least two receiving units, each receiving unit comprising a focusing element and a receiving antenna, the relative distance between the focusing element and the receiving antenna being adjustable to change the imaging focal point position of the receiving unit, so that the receiving unit is aligned with the radial area to be measured in the plasma, and the receiving module is used for processing the scattering signal obtained by each receiving unit to obtain an intermediate frequency signal; a signal processing module, connected with the receiving unit, used for obtaining the plasma density fluctuation wave spectrum and the turbulence power spectrum according to the received intermediate frequency signal. By adopting the mechanical zoom receiving design of the adjustable lens barrel, the focal point of the receiving system is no longer fixed, and the detection capability and the measurement precision of the weak scattering signal are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of high-temperature plasma turbulence measurement, and specifically to a high-temperature plasma turbulence measurement system and method. Background Technology

[0002] In high-temperature plasma research, such as magnetic confinement fusion, accurate diagnosis of plasma density, temperature fluctuations, and turbulence phenomena is crucial. Microwave scattering diagnostic technology is an important means of measuring microscopic turbulence in plasma, which inverts turbulence information by analyzing the scattering signal of incident microwaves by the plasma. Existing technologies mostly employ single-channel or multi-channel scatterers with fixed frequencies and fixed angles (especially perpendicular or small-angle incident). Such systems have significant shortcomings: First, the measurement geometry is fixed, making it difficult to flexibly select the optimal scattering angle and azimuth angle based on the plasma configuration and the expected wave vector spectrum characteristics of turbulence, resulting in limited sensitivity or information loss for turbulence in specific wave vector ranges. Second, the effective imaging area of ​​the receiving system is relatively fixed, unable to adapt to differences in the vacuum chamber window position and plasma profile in different experimental setups, and also difficult to perform focused measurements at different radial positions in a single discharge, leading to decreased spatial resolution and signal-to-noise ratio loss. In addition, traditional systems are mostly customized for specific experimental rigs, have poor reusability, and are difficult to perform systematic scanning measurements in wave vector space. Summary of the Invention

[0003] The purpose of this invention is to provide a high-temperature plasma turbulence measurement system and method, which solves the problems in the prior art.

[0004] This invention is achieved through the following technical solution:

[0005] In a first aspect, embodiments of the present invention provide a high-temperature plasma turbulence measurement system, comprising:

[0006] The transmitting module is used to transmit microwave detection signals into the plasma;

[0007] The receiving module includes at least two receiving units, each receiving unit including a focusing element and a receiving antenna. The relative distance between the focusing element and the receiving antenna is adjustable to change the imaging focal position of the receiving unit, so that the receiving unit is aligned with the radial region to be measured in the plasma. The receiving module is used to process the scattered signals acquired by each receiving unit to obtain an intermediate frequency signal.

[0008] The signal processing module, connected to the receiving unit, is used to obtain the plasma density fluctuation wavenumber spectrum and turbulent power spectrum based on the received intermediate frequency signal.

[0009] Preferably, each receiving unit further includes a cylindrical housing, the focusing element is installed inside the cylindrical housing, and the receiving antenna is installed at one end of the cylindrical housing away from the focusing element. The relative distance between the focusing element and the receiving antenna is changed by adjusting the axial position of the focusing element inside the cylindrical housing.

[0010] Preferably, the angles and / or focal positions of the plurality of receiving units are configured to simultaneously align with the same measurement region or different radial regions in the plasma.

[0011] Preferably, the receiving module further includes a distributor and a downconverter connected to each receiving unit;

[0012] The input terminal of the distributor is connected to the output terminal of the high-frequency source of the transmitting module, and the output terminal of the distributor is connected to each downconverter. The distributor is used to distribute the high-frequency signal output by the high-frequency source to each downconverter.

[0013] Each downconverter is used to downconvert the scattered signal output by the corresponding receiving unit and the high-frequency signal to output the corresponding intermediate frequency signal.

[0014] Preferably, the signal processing module includes:

[0015] The second frequency multiplier is connected to the intermediate frequency source of the transmitting module to obtain a reference signal;

[0016] A phase detector array, connected to the output of each receiving unit and the second frequency multiplier, is used to measure the amplitude and phase of each intermediate frequency signal relative to a reference signal;

[0017] The acquisition and data analysis system, connected to the phase detector array, is used to invert the wavenumber spectrum and turbulent power spectrum of plasma density fluctuations based on the amplitude and phase.

[0018] Preferably, the system further includes a mechanical adjustment mechanism, the mechanical adjustment mechanism comprising:

[0019] Fixed support base;

[0020] A guide rail is installed on the fixed support base;

[0021] Sliding seats corresponding to each receiving unit are installed on the guide rail. Each sliding seat is connected to the corresponding receiving unit. Each sliding seat can move along the guide rail and / or rotate about the axis to adjust the spatial position and receiving angle of the corresponding receiving unit.

[0022] An angle indicator scale is set on the guide rail or the sliding seat to indicate the angle between the axis of the receiving unit and a preset reference direction.

[0023] Preferably, the transmitting module includes a microwave source unit and an incident optical unit;

[0024] The microwave source unit includes a high-frequency source, an intermediate-frequency source, a sideband mixer, a first frequency multiplier, and an amplifier. The input terminal of the sideband mixer is connected to the output terminals of the high-frequency source and the intermediate-frequency source, respectively, and is used to process the high-frequency signal output by the high-frequency source and the intermediate-frequency signal output by the intermediate-frequency source to obtain a single-sideband signal. The input terminal of the first frequency multiplier is connected to the output terminal of the sideband mixer and is used to process the single-sideband signal to obtain a multiplied signal. The input terminal of the amplifier is connected to the output terminal of the first frequency multiplier and is used to process the multiplied signal to obtain a microwave detection signal.

[0025] The incident optical unit is used to adjust the beam direction and beam spot size of the microwave detection signal.

[0026] Preferably, there are one or more transmitting modules. When multiple transmitting modules are included, the transmission angle of each transmitting module can be adjusted independently to transmit microwave detection signals at different angles.

[0027] Preferably, it further includes a wave absorber, which is disposed in the transmission wave path of the plasma to absorb transmitted microwaves that pass through the plasma.

[0028] In a second aspect, embodiments of the present invention provide a method for measuring high-temperature plasma turbulence using the system described in the first aspect, comprising:

[0029] Microwave detection signals are transmitted into the plasma via the transmitting module;

[0030] Adjust the relative distance between the focusing element of each receiving unit and the receiving antenna so that the imaging focus of each receiving unit is aligned with the radial region to be measured in the plasma;

[0031] Each receiving unit receives the scattered signal generated by the plasma and processes the scattered signal into a corresponding intermediate frequency signal.

[0032] The intermediate frequency signal is sent to the signal processing module to obtain the plasma density fluctuation wavenumber spectrum and the turbulent power spectrum.

[0033] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0034] This invention introduces a graduated, independent mechanical adjustment mechanism, enabling the continuous, precise, and independent setting of the microwave beam incident angle and position for each transmission channel over a wide range. This allows researchers to flexibly configure the scattering geometry based on turbulence theory predictions or diagnostic needs, and systematically measure the scattering power under different wave vectors (k), thereby obtaining more complete and accurate plasma turbulence wavenumber spectrum information.

[0035] By employing a mechanical zoom receiver design with an adjustable lens tube, the focal point of the receiving system is no longer fixed. The operator can precisely align the receiver focus with the radial location of interest in the plasma (such as the boundary region during LH mode transition, or the internal transport barrier) based on the position of the experimental setup's vacuum window and the real-time profile of the plasma discharge. This not only significantly improves the longitudinal (along the line-of-sight) spatial resolution of the diagnostics but also ensures the maximization of the intensity of the scattered signal collected from the target region, effectively enhancing the detection capability and measurement accuracy of weak scattered signals.

[0036] The combination of these two core design features enables the system to achieve coordinated adjustability of the detection wave vector (angle) and the measurement position (focal point). The system exhibits excellent modularity and versatility, allowing for easy adaptation to the detection requirements of plasma experimental devices. It provides a powerful and advanced diagnostic tool for in-depth research into the generation mechanism, transmission, and confinement effects of high-temperature plasma turbulence. Attached Figure Description

[0037] 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:

[0038] Figure 1 This is a schematic diagram of the high-temperature plasma turbulence measurement system provided by the present invention;

[0039] The attached diagram shows the markings and corresponding component names:

[0040] 1-High frequency source, 2-Intermediate frequency source, 3-Sideband mixer, 4-First frequency multiplier, 5-Amplifier, 6-Incident optical unit, 7-Plasma, 8-Wave absorber, 9-Focusing element, 10-Cylindrical housing, 11-Receiving antenna, 12-Fixed support base, 13-Guide rail, 14-Adjustable fixing hole, 15-Scaled support frame, 16-Downconverter, 17-Distributor, 18-Second frequency multiplier, 19-Phase detector array, 20-Acquisition and data analysis system, 21-Scattered wave vector. Detailed Implementation

[0041] 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.

[0042] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0043] It should be noted that all actions involving the acquisition of signals, information, or data in this invention are carried out in compliance with the relevant data protection laws and regulations of the locality and with authorization from the owner of the relevant device.

[0044] Example 1

[0045] Please see Figure 1 This invention provides a high-temperature plasma turbulence measurement system, comprising:

[0046] The transmitting module is used to transmit microwave detection signals to plasma 7;

[0047] The receiving module includes at least two receiving units, each receiving unit including a focusing element 9 and a receiving antenna 11. The relative distance between the focusing element 9 and the receiving antenna 11 is adjustable to change the imaging focal position of the receiving unit, so that the receiving unit is aligned with the radial region to be measured in the plasma 7. The receiving module is used to process the scattered signals acquired by each receiving unit to obtain an intermediate frequency signal.

[0048] The signal processing module, connected to the receiving unit, is used to obtain the plasma density fluctuation wavenumber spectrum and turbulent power spectrum based on the received intermediate frequency signal.

[0049] The transmitting module refers to a collection of units used to generate and transmit microwave detection signals to plasma 7. Its core function is to provide a microwave beam with stable frequency and sufficient power as a probe to detect the turbulence of plasma 7.

[0050] The transmitting module operates based on the interaction between microwaves and plasma 7. When microwaves are incident on plasma 7, if density fluctuations (turbulence) exist within the plasma 7, the microwaves will be scattered. The intensity of the scattered signal is related to the amplitude of the fluctuation, and the scattering direction is related to the wave vector of the fluctuation. The transmitting module provides a frequency-stable and phase-coherent probe wave, which is the foundation for subsequent coherent detection. The core function of the transmitting module is to provide a high-quality signal source, laying the foundation for the entire measurement system. Its frequency stability and phase coherence directly affect the accuracy of subsequent signal processing.

[0051] The receiving module is a collection of units used to collect and preliminarily process the plasma 7 scattered signal 21. The receiving module includes at least two receiving units, each of which includes a focusing element 9 and a receiving antenna 11, and the relative distance between the focusing element 9 and the receiving antenna 11 is adjustable.

[0052] The focusing element 9 refers to a device capable of focusing microwaves. In the microwave band, the focusing element 9 includes dielectric lenses, Fresnel zone lenses, parabolic mirrors, etc. Its function is to concentrate microwave energy from a specific direction onto the receiving antenna 11, thereby improving reception efficiency and spatial resolution.

[0053] A receiving antenna 11 is a device that converts microwaves propagating in space into guided waves (i.e., electromagnetic waves transmitted in waveguides or cables). In microwave scattering measurements, the receiving antenna 11 includes feed horn antennas, open waveguides, microstrip antennas, etc. Its function is to efficiently couple the converged microwave energy into the receiving link.

[0054] The axial distance between the focusing element 9 and the receiving antenna 11 can be adjusted continuously or in increments, thereby changing the equivalent focal length and imaging focal point position of the receiving system. When this distance changes, the receiving system has different sensitivity responses to point sources at different locations in space, with the position of highest sensitivity being the focal point of the system. By adjusting this distance, the focal point can be precisely aligned with the specific radial region to be measured in the plasma 7 (such as the core, boundary, or sump region).

[0055] The signal processing module refers to the set of units that perform subsequent processing on the intermediate frequency signal output by the receiving module, and finally extract the plasma density fluctuation information.

[0056] Intermediate frequency (IF) signals refer to signals that have undergone down-conversion, resulting in a lower frequency but retaining the amplitude and phase information of the original scattered signal. In microwave receiving systems, directly processing high-frequency signals (e.g., 90 GHz) is technically challenging and costly. Down-converting these signals to a lower frequency IF signal (e.g., 100 MHz) facilitates amplification, filtering, and analog-to-digital conversion while fully preserving the physical information carried by the original signal.

[0057] Wavenumber spectrum refers to the intensity of density fluctuations as a function of wavenumber. Distribution, wavenumber Spatial scale of turbulent eddies Inversely proportional. By measuring the scattering signals corresponding to different scattering angles, the energy distribution of turbulence at different wavenumbers can be inverted, thereby studying the scale cascade characteristics of turbulence.

[0058] Turbulent power spectrum refers to the intensity of turbulent fluctuations as a function of frequency. The distribution of energy reflects the temporal evolution characteristics of turbulence. By performing spectral analysis on the time series of the scattered signal, the energy distribution of turbulence at different frequencies can be obtained, thereby enabling the study of turbulence wave patterns and propagation characteristics.

[0059] In this embodiment, the transmitting module provides a stable probe wave to irradiate the plasma 7; in the receiving module, multiple receiving units adjust the distance between the focusing element 9 and the receiving antenna 11 so that their respective focal points are aligned with the radial region to be measured, and receive the scattered signal from the region and process it into an intermediate frequency signal; the signal processing module performs synchronous amplitude and phase detection on the multi-channel intermediate frequency signal and inverts to obtain the density fluctuation wavenumber spectrum and turbulent power spectrum of the plasma 7.

[0060] Multiple receiving units can be configured with different receiving angles to achieve selective measurement of turbulence with different wave vectors. This is because the scattering angle and the turbulent wave vector satisfy the wave vector matching condition. (in Let be the incident wave vector. For the scattered wave vector 21, (This refers to the turbulent wavenumber vector). By changing the receiving angle, the turbulent component of a specific wavenumber can be selected for measurement, thereby obtaining more complete information about the turbulent wavenumber spectrum.

[0061] By adjusting the focal position of each receiving unit, focused measurements can be performed on different radial regions of the plasma. Traditional fixed-focal-point systems can only maintain optimal focus at a specific radial position, while other positions are out of focus, resulting in decreased spatial resolution. This system, through its adjustable-focal-point design, ensures that the receiving units are in optimal focus regardless of whether the core or the boundary is being measured, thereby obtaining a refined radial distribution of the turbulent structure.

[0062] Focusing on the target area means that the scattered signal from that area is received to the maximum extent, while stray signals from other areas are suppressed, effectively improving the signal-to-noise ratio. Simultaneously, the signal processing module employs multi-channel coherent detection technology, which can extract weak scattered signals from strong background noise, further enhancing the detection capability of weak scattered signals.

[0063] Ultimately, this embodiment effectively solves the problems of fixed measurement angle, non-adjustable receiving focus, and insufficient spatial resolution and wave vector detection flexibility in existing microwave scattering diagnostic systems, providing a powerful and advanced measurement tool for in-depth research on the generation mechanism, transport process, and confinement performance of high-temperature plasma 7 turbulence.

[0064] Furthermore, each receiving unit also includes a cylindrical housing 10, the focusing element 9 is installed inside the cylindrical housing 10, and the receiving antenna 11 is installed at one end of the cylindrical housing 10 away from the focusing element 9. By adjusting the axial position of the focusing element 9 inside the cylindrical housing 10, the relative distance between the focusing element 9 and the receiving antenna 11 is changed.

[0065] The cylindrical housing 10 refers to the mechanical structure used to install and support the focusing element 9 and the receiving antenna 11. It has a cylindrical shape, is hollow inside, and has the focusing element 9 and the receiving antenna 11 installed at its two ends, respectively.

[0066] In practical implementation, the cylindrical housing 10 can be made of metal or composite materials, possessing sufficient structural strength and dimensional stability. The inner wall of the cylindrical housing 10 can be equipped with threaded guide rails or linear sliding guide rails to guide the focusing element 9 to move axially. The outer wall of the cylindrical housing 10 can be equipped with an adjustment handle, scale markings, or a drive interface, facilitating manual or automatic adjustment of the focusing element's position by the operator. The core function of the cylindrical housing 10 is to provide a stable mounting base and a precise guiding mechanism, ensuring coaxiality between the focusing element 9 and the receiving antenna 11, while simultaneously enabling the focusing element 9 to move smoothly along the axial direction.

[0067] The focusing element 9 is installed inside the cylindrical housing 10, specifically at the front end of the cylindrical housing 10 (the end closest to the plasma 7). The focusing element 9 engages with the inner wall of the cylindrical housing 10 via a guide rail or threaded structure, allowing it to move axially along the cylindrical housing 10. By adjusting the axial position of the focusing element 9 within the cylindrical housing 10, the relative distance between the focusing element 9 and the receiving antenna 11 can be changed. This adjustment can be continuous (e.g., stepless adjustment via threaded rotation) or stepped (e.g., multi-stage adjustment via positioning holes). In a preferred embodiment, the cylindrical housing 10 employs a threaded sleeve structure, with the focusing element 9 installed at the front end of the threaded sleeve. By rotating the sleeve, the focusing element 9 moves axially, achieving continuous and precise distance adjustment.

[0068] The receiving antenna 11 is installed at the end of the cylindrical housing 10 furthest from the focusing element 9, i.e., at the rear end of the cylindrical housing 10. The receiving antenna 11 is fixedly installed within the cylindrical housing 10, and its axial position remains unchanged. The receiving antenna 11 is a device that converts microwaves propagating in space into guided waves, such as a feed horn antenna, an open waveguide, or a microstrip antenna. Its function is to efficiently couple the microwave energy focused by the focusing element 9 into a transmission line (such as a waveguide or coaxial cable) and send it to the subsequent downconverter 16 for processing.

[0069] The relative distance between the focusing element 9 and the receiving antenna 11 is adjustable, and its adjustment principle is based on geometric optics and microwave quasi-optics theory. For the lens antenna system, its focal position F, the lens focal length f_lens, and the distance L between the lens and the antenna satisfy the imaging formula:

[0070] 1 / F = 1 / f_lens - 1 / L

[0071] Where f_lens is the inherent focal length of the focusing element 9, and L is the axial distance between the focusing element 9 and the receiving antenna 11. When L changes, the equivalent focal position F of the system changes accordingly.

[0072] During operation, the operator or automatic control system moves the focusing element 9 axially to a predetermined position by rotating or pushing / pulling the cylindrical housing 10, based on the location of the radial region to be measured. When the focusing element 9 approaches the receiving antenna 11, the system's focus moves towards the near field; when the focusing element 9 moves away from the receiving antenna 11, the system's focus moves towards the far field. By designing a suitable focal length and adjustment range for the focusing element, the focus can cover the entire radial range of the plasma 7 from the core to the boundary.

[0073] During the system calibration phase, the operator can place a point source at the equivalent position of plasma 7, rotate the cylindrical shell 10, and monitor the output signal strength of the receiving antenna 11. When the signal strength is at its maximum, it indicates that the focus has been aligned to that position. At this time, the position of the focusing element 9 is recorded, thus establishing the correspondence between the position and the radial position of the focus for subsequent experiments.

[0074] Furthermore, the angles and / or focal positions of the plurality of receiving units are configured to simultaneously align with the same measurement region or different radial regions in the plasma.

[0075] The angle refers to the receiving direction of the receiving unit, that is, the angle between the axis of the receiving unit and the preset reference direction. This angle determines the direction of the scattered wave vector 21 that the receiving unit is sensitive to, and thus determines the measured turbulence wave vector.

[0076] The focal position refers to the spatial location in the plasma 7 where the receiving unit has the highest sensitivity, determined by the relative distance between the focusing element 9 and the receiving antenna 11. This position corresponds to the radial region to be measured, such as the core, boundary, or pedestal region in the plasma 7.

[0077] The same measurement area means that the focal positions of multiple receiving units are all aligned with the same spatial position in plasma 7, while the receiving angles can be the same or different.

[0078] Different radial regions refer to the fact that the focal positions of multiple receiving units are respectively aligned with different spatial positions along the radial direction in plasma 7, such as one receiving unit aligned with the core and another receiving unit aligned with the boundary.

[0079] Being configured means that the receiving unit is put into a specific working state through pre-adjustment or automatic control in order to perform the corresponding measurement task.

[0080] Specifically, the situation where both are aligned with the same measurement area is as follows:

[0081] In this mode, the focal positions of multiple receiving units are all adjusted to the same radial position in plasma 7, for example, all aligned with the boundary region of normalized radius ρ=0.8. Simultaneously, the receiving angle of each receiving unit can be independently configured to different angle values.

[0082] This configuration is based on the following principle: according to the wave vector matching condition of microwave scattering, the scattering angle θ and the turbulent wave vector k satisfy a specific relationship. By setting up multiple receiving units with different receiving angles at the same spatial location, the turbulent components of different wave vectors at the same location can be measured simultaneously, thereby obtaining the turbulent wavenumber spectrum S(k) at that location.

[0083] In practice, the operator first adjusts the focal position of each receiving unit to the target radial area using a manual or mechanical adjustment mechanism, and then independently adjusts the receiving angle of each receiving unit to a predetermined value. The angle value can be accurately read from the graduated support frame 15. After adjustment, the position of each receiving unit is locked through the adjustable fixing hole 14.

[0084] This mode solves the problem of difficulty in simultaneously measuring multiple wave vector components at the same location in existing technologies, enabling the system to synchronously acquire complete wavenumber spectrum information at that location, thus greatly improving measurement efficiency and data consistency.

[0085] The following are the cases where different radial regions are aligned simultaneously:

[0086] In this mode, the focal positions of multiple receiving units are aligned with different locations along the radial direction in plasma 7. For example, one receiving unit is aligned with the core at ρ=0.2, and another receiving unit is aligned with the boundary at ρ=0.9. The receiving angle of each receiving unit can be configured independently as needed.

[0087] This configuration is based on the following principle: by setting up receiving units at different radial positions, the radial distribution of turbulence parameters can be measured simultaneously. When the receiving angles of each receiving unit are the same, the fluctuation intensity of the same wave vector at different radial positions can be obtained, i.e., the radial distribution S(f,ρ) of the turbulence power spectrum; when the receiving angles are also different, richer multidimensional turbulence information can be obtained.

[0088] In practice, the operator first adjusts the distance between the focusing element 9 and the receiving antenna 11 in each receiving unit, based on the radial position to be measured, so that the focal point of each unit is aligned with a predetermined radial region. The focal point position can be determined through a pre-calibrated distance-position correspondence. Subsequently, the receiving angle of each receiving unit is adjusted independently as needed. After adjustment, the system can simultaneously acquire turbulence information at multiple radial positions during a single discharge process.

[0089] This approach solves the problem in existing technologies that require multiple discharges or moving the entire system to obtain radial distribution, significantly improving diagnostic efficiency and the reliability of radial comparison.

[0090] Furthermore, the receiving module also includes a distributor 17 and a downconverter 16 connected to each receiving unit. The input terminal of the distributor 17 is connected to the output terminal of the high-frequency source 1 of the transmitting module, and the output terminal of the distributor 17 is connected to each downconverter 16. Each downconverter 16 is used to downconvert the scattered signal output by the corresponding receiving unit and the high-frequency signal provided by the distributor 17 to output the corresponding intermediate frequency signal.

[0091] The distributor 17 is a microwave device that distributes one input signal into multiple output signals. Its input terminal is connected to the output terminal of the high-frequency source 1, and its output terminal is connected to the downconverter 16 of each receiving unit.

[0092] The core function of distributor 17 is to replicate the high-frequency signal generated by high-frequency source 1 into multiple phase-consistent signals, which are then supplied as local oscillator signals to each downconverter 16. In the microwave frequency band, distributor 17 can be implemented using structures such as Wilkinson power dividers, resistive power dividers, or directional couplers, which have the characteristics of low insertion loss, high port isolation, and good phase consistency.

[0093] The specific role of distributor 17 in the system is reflected in:

[0094] Distributor 17 ensures that the local oscillator signals received by all downconverters 16 originate from the same high-frequency source 1 and that their phase relationships are determined. This is the basis for realizing multi-channel coherent measurement, enabling the subsequent phase detector array 19 to accurately measure the phase difference between the scattered signals of each channel, and thus retrieve the turbulence wave vector information.

[0095] If each receiving channel is configured with an independent local oscillator, not only will the system complexity and cost increase, but it will also be difficult to guarantee phase synchronization between multiple sources. By using distributor 17 to distribute the signal from a single high-frequency source 1 to multiple downconverters 16, both signal quality is guaranteed and system design is simplified.

[0096] The output signals of distributor 17 all have the same frequency, which is the output frequency of high-frequency source 1. This ensures that the down-conversion processing of all receiving channels has a unified frequency reference, avoiding measurement errors caused by frequency drift in multi-source schemes.

[0097] Downconverter 16 refers to a mixer device that converts high-frequency signals into intermediate-frequency signals. The input terminal of each downconverter 16 is connected to the corresponding receiving antenna 11 and distributor 17, and the output terminal is connected to the signal processing module.

[0098] The downconverter 16 can be composed of a mixer, a local oscillator port, an intermediate frequency filter, and an amplifier. In this embodiment, the downconverter 16 receives two input signals: one is a high-frequency scattered signal (frequency f_RF) output from the receiving antenna 11, and the other is a high-frequency signal (frequency f_LO) provided by the distributor 17. The two signals are multiplied in the mixer to generate a sum frequency f_RF + f_LO and a difference frequency |f_RF - f_LO|. The difference frequency component is extracted by the intermediate frequency filter to obtain the intermediate frequency signal f_IF = |f_RF - f_LO|.

[0099] The core function of the downconverter 16 is frequency conversion. The frequency of plasma scattering signals is usually in the microwave or even millimeter wave band (such as 90GHz in the W band), and direct amplification, filtering and analog-to-digital conversion are technically difficult and costly. By converting them into a lower frequency intermediate frequency signal (such as 100MHz) through the downconverter 16, it is easy to process them using mature low-frequency electronic technology.

[0100] The down-conversion process is a linear transformation, and the amplitude information A(t) and phase information φ(t) carried by the scattered signal are completely preserved in the intermediate frequency signal during the transformation. Let the high-frequency scattered signal be A(t)cos[ω_RF t+φ(t)] and the local oscillator signal be cos(ω_LO t), then the intermediate frequency signal after down-conversion is A(t)cos[(ω_RF-ω_LO)t+φ(t)], and neither amplitude nor phase information is lost.

[0101] By selecting an appropriate local oscillator frequency f_LO, scattered signals of different frequencies can be flexibly converted to the same intermediate frequency, facilitating subsequent fixed-frequency processing. Simultaneously, the built-in filter in the downconverter 16 can suppress image frequencies and spurious interference, improving signal purity.

[0102] Each receiving unit is equipped with an independent downconverter 16, which operates in parallel without interfering with each other. The distributor 17 ensures that the local oscillator signals of all downconverters 16 are from the same source, so that the intermediate frequency signals output by each channel maintain a certain phase relationship, creating conditions for the subsequent phase detector array 19 to perform multi-channel synchronous amplitude and phase detection.

[0103] Combining the two components mentioned above, the specific signal processing flow within the receiving module is as follows:

[0104] In the first step, the high-frequency signal output from high-frequency source 1 enters distributor 17. Distributor 17 divides the signal into multiple paths, and each path is sent as a local oscillator signal to a downconverter 16.

[0105] In the second step, the receiving antenna 11 of each receiving unit captures the scattered signal 21 generated by the plasma 7 and sends it to the corresponding downconverter 16.

[0106] Third, each downconverter 16 simultaneously receives two signals: a scattered signal from the receiving antenna 11 and a local oscillator signal from the distributor 17. The two signals are mixed internally within the downconverter 16 to generate sum and difference frequency components.

[0107] In the fourth step, the filter built into the downconverter 16 extracts the difference frequency component, thus obtaining the intermediate frequency signal. The frequency of this intermediate frequency signal is |f_RF-f_LO|, and its amplitude and phase are exactly the same as the original scattered signal.

[0108] Fifth, the intermediate frequency signals output by each downconverter 16 are sent to the phase detector array 19 of the signal processing module for subsequent amplitude and phase detection and data analysis.

[0109] Furthermore, the signal processing module includes a second frequency multiplier 18, a phase detector array 19, and an acquisition and data analysis system 20. The second frequency multiplier 18 is connected to the intermediate frequency source 2 of the transmitting module to obtain a reference signal; the phase detector array 19 is connected to the output of each receiving unit and the second frequency multiplier 18 to measure the amplitude and phase of each intermediate frequency signal relative to the reference signal; the acquisition and data analysis system 20 is connected to the phase detector array 19 to invert the wavenumber spectrum and turbulent power spectrum of plasma density fluctuations based on the amplitude and phase.

[0110] The second frequency multiplier 18 refers to a frequency conversion device connected to the output terminal of the intermediate frequency source 2. It is used to process the original intermediate frequency signal output by the intermediate frequency source 2 and generate a reference signal that matches the frequency of the down-converted intermediate frequency signal.

[0111] The second frequency multiplier 18 operates based on the frequency multiplication effect of nonlinear devices. When the original intermediate frequency signal (frequency f_IF) output from the intermediate frequency source 2 enters the second frequency multiplier 18, it generates harmonic components through nonlinear elements. The required Nth harmonic (frequency N·f_IF) is then extracted by an internal filter and output as a reference signal. In specific implementations, the multiplication order N is chosen based on the frequency of the intermediate frequency signal output from the downconverter 16, ensuring that the reference signal frequency matches the intermediate frequency frequency of each channel.

[0112] The reference signal output by the second frequency multiplier 18 is from the same source as the original signal of the intermediate frequency source 2 and has the same phase stability. This reference signal serves as the reference for the phase detector array 19 and is used for phase comparison with the intermediate frequency signals of each receiving channel.

[0113] The intermediate frequency (IF) signal output by downconverter 16 has a frequency of |f_RF - f_LO|, where f_RF is determined by both high-frequency source 1 and IF source 2, and f_LO originates from high-frequency source 1. It can be deduced that the frequency of the downconverted IF signal has a definite relationship with the frequency of IF source 2. The second frequency multiplier 18, through appropriate frequency multiplication, ensures that the reference signal frequency accurately matches the frequency of the IF signal in each channel, creating conditions for subsequent coherent detection.

[0114] The input of the second frequency multiplier 18 is directly taken from the intermediate frequency source 2, which is the same source as the intermediate frequency signal used to generate the probe wave in the transmitting module. This design ensures the phase coherence of the entire system: the transmitting probe wave, the receiving local oscillator signal, and the phase detection reference signal all originate from the same set of high frequency source 1 and intermediate frequency source 2, eliminating the phase drift problem that is difficult to avoid in multi-source schemes.

[0115] The phase detector array 19 refers to a signal processing unit connected to the output of each receiving unit (i.e., the output of each downconverter 16) and the output of the second frequency multiplier 18, used to simultaneously measure the amplitude and phase of the intermediate frequency signals of multiple receiving channels relative to a reference signal.

[0116] The phase detector array 19 can integrate multiple parallel high-precision phase detectors, each corresponding to one receiving channel. Each phase detector receives two input signals: one is the intermediate frequency signal S_i(t) from the corresponding downconverter 16, and the other is the reference signal R(t) from the second frequency multiplier 18. The phase detectors simultaneously output the in-phase component I_i and the quadrature component Q_i through quadrature demodulation (I / Q demodulation) technology.

[0117] The working principle of quadrature demodulation is as follows: Let the intermediate frequency signal of the i-th channel be S_i(t) = A_i(t)cos[ωt + φ_i(t)], and the reference signal be R(t) = cos(ωt). The phase detector internally multiplies S_i(t) by R(t) and the phase-shifted R(t) by 90°, respectively, and after low-pass filtering, obtains:

[0118] In-phase component: I_i=A_i(t)cos[φ_i(t)];

[0119] Orthogonal component: Q_i=A_i(t)sin[φ_i(t)].

[0120] Therefore, it can be calculated that:

[0121] Amplitude: A_i=√(I_i²+Q_i²);

[0122] Phase: φ_i=arctan(Q_i / I_i).

[0123] The phase detector array 19 can simultaneously process the intermediate frequency signals from all receiving channels, acquiring amplitude and phase data for each channel at the same time. This ensures the temporal consistency of multi-channel data, which is crucial for studying the instantaneous spatial structure of turbulence.

[0124] Employing orthogonal demodulation technology, the phase detector array 19 can simultaneously extract amplitude and phase information from a single intermediate frequency signal, avoiding errors caused by time-division measurement. The accuracy of orthogonal demodulation can reach the sub-degree level, meeting the requirements for turbulent phase measurement.

[0125] Since all channels share a single reference signal R(t), and the phase values ​​φ_i(t) output by each channel are all referenced to the same standard, the phase difference Δφ_ij=φ_i-φ_j between channels directly reflects the true phase difference between the original scattered signals and is the basic data for subsequent wavenumber spectrum inversion.

[0126] The I_i and Q_i components output by the phase detector array 19 are analog voltage signals, which can be sent to the acquisition and data analysis system 20 for high-speed analog-to-digital conversion to meet the high time resolution measurement requirements of turbulent fluctuation signals.

[0127] The data acquisition and analysis system 20 refers to a computer or embedded processing platform connected to the output of the phase detector array 19. It is used to acquire the amplitude and phase data output by the phase detector array 19 and calculate the plasma density fluctuation wavenumber spectrum and turbulent power spectrum through a preset inversion algorithm.

[0128] A data acquisition and analysis system typically includes a high-speed analog-to-digital conversion module, a data storage module, a data processing module, and a human-computer interaction interface. Its workflow is as follows:

[0129] The first step is data acquisition. The system synchronously acquires amplitude data A_i(t) and phase data φ_i(t) of each channel at a set sampling rate to form multidimensional time series data.

[0130] The second step is preprocessing. Preprocessing operations such as filtering, denoising, and correction are performed on the raw data to eliminate systematic errors and random noise.

[0131] The third step is spectrum analysis. Fourier transform is performed on the amplitude time series of each channel to obtain the turbulent power spectrum S_i(f)=|FFT[A_i(t)]|², which reflects the energy distribution of turbulence at different frequencies.

[0132] The fourth step is wavenumber spectrum inversion. Based on the receiving angle of each channel and the measured phase difference Δφ_ij, combined with the wave vector matching condition k_s=k_i-k (where k_i is the incident wave vector and k_s is the scattered wave vector), the density fluctuation wavenumber spectrum S(k) at a specific location in the plasma is inverted. When multiple receiving units are aligned with the same location at different angles, the wavenumber spectrum at that location can be obtained; when the receiving units are aligned with different radial positions, the radial distribution of the wavenumber spectrum S(k,ρ) can be obtained.

[0133] The fifth step is result visualization and output. The processed wavenumber spectrum and power spectrum are displayed in a graphical interface, and the data files can be exported for further physical analysis.

[0134] Combining the above three components, the workflow within the signal processing module is as follows:

[0135] In the first step, the original intermediate frequency signal output from intermediate frequency source 2 enters the second frequency multiplier 18, and after frequency multiplication, a reference signal R(t) matching the frequency of the intermediate frequency signal of each channel is generated.

[0136] In the second step, the intermediate frequency signal S_i(t) and the reference signal R(t) output by each downconverter 16 are simultaneously sent to the phase detector array 19.

[0137] The third step involves the phase detector array 19 performing quadrature demodulation on each intermediate frequency signal and synchronously outputting the amplitude data A_i and phase data φ_i of each channel (in the form of analog voltage or digital signal).

[0138] The fourth step involves the acquisition and data analysis system 20 simultaneously acquiring amplitude and phase data from all channels, performing spectral analysis and wavenumber spectrum inversion, and finally outputting the plasma density fluctuation wavenumber spectrum and turbulent power spectrum.

[0139] Furthermore, the system also includes a mechanical adjustment mechanism, which comprises a fixed support base 12, a guide rail 13, a sliding seat corresponding to each receiving unit, and an angle indicator scale 15. The guide rail 13 is mounted on the fixed support base 12; the sliding seats are mounted on the guide rail 13, each sliding seat is connected to a corresponding receiving unit, and can move along the guide rail 13 and / or rotate around its axis to adjust the spatial position and receiving angle of the corresponding receiving unit; the angle indicator scale 15 is disposed on the guide rail 13 or the sliding seat to indicate the angle between the axis of the receiving unit and a preset reference direction.

[0140] Among them, the fixed support base 12 refers to the base component of the mechanical adjustment mechanism, which is installed on the optical platform outside the experimental platform or diagnostic window to provide a stable support foundation for the entire adjustment mechanism.

[0141] The guide rail 13 refers to the linear guide component installed on the fixed support base 12, which is used to guide the sliding seat to move in a specific direction and provide rotational support for the sliding seat.

[0142] The guide rail 13 can be a precision linear guide, a dovetail guide, or a graduated straight groove structure. In a preferred embodiment, the guide rail 13 is a straight groove with length graduations, serving both as a guide for the movement of the sliding seat and facilitating the reading of the sliding seat's position information. The length of the guide rail 13 is determined according to the required adjustment range and should cover all positions from the minimum to the maximum receiving angle.

[0143] The installation direction of the guide rail 13 is determined according to the window position of the experimental device and the geometry of the plasma 7. It can be along the horizontal direction or at a certain angle to the horizontal plane, so that the adjustment range of the receiving unit can cover the required detection area.

[0144] The sliding seat refers to a movable component installed on the guide rail 13. Each receiving unit corresponds to one sliding seat. The sliding seat is connected to the corresponding receiving unit and can move along the guide rail 13 and / or rotate about the axis.

[0145] The sliding seat can be made of metal, and its bottom mates with the guide rail 13, allowing it to move smoothly along the rail. Its upper part is provided with an interface for mounting the receiving unit, such as a threaded hole or a clamping device, for fixing the receiving unit. A locking mechanism (such as an adjustable fixing hole 14 or a locking screw) can be provided inside or on the side of the sliding seat to lock its position after adjustment.

[0146] The sliding block has two degrees of freedom for adjustment:

[0147] First, the receiving unit moves linearly along guide rail 13. By pushing the sliding block along guide rail 13, the linear position of the receiving unit in space can be changed, thereby adjusting the distance or lateral offset between the receiving unit and the plasma 7. This adjustment is mainly used to coarsely adjust the spatial position of the receiving unit so that it is roughly aligned with the area to be measured.

[0148] Second, rotation about the axis. The sliding seat can rotate about its own vertical or horizontal axis, causing the receiving unit to rotate synchronously, thereby changing the receiving angle of the receiving unit (i.e., the azimuth angle of the receiving unit's axis relative to a preset reference direction). This adjustment is used to precisely set the detection direction of the receiving unit, aligning it with a specific scattering angle.

[0149] The core function of the sliding mount is to enable independent and continuous adjustment of the spatial position and receiving angle of the receiving unit, providing a mechanical basis for optimizing the detection geometry.

[0150] Angle indicator scale 15 refers to the scale mark set on the guide rail 13 or the sliding seat, which is used to indicate the angle between the receiving unit axis and the preset reference direction.

[0151] The angle indicator scale 15 can be implemented in several ways: one is to set a pointer on the rotating part of the slide base and set an angle scale on the guide rail 13 or the fixed support base 12; another is to install an encoder or angle sensor on the rotating shaft of the slide base to display the angle value in digital form. In a preferred embodiment, the angle indicator scale 15 is an angle scale directly engraved on the guide rail 13 or the fixed support base 12, which, together with the reference line or pointer on the slide base, allows for intuitive reading of the current received angle.

[0152] The working process of the mechanical adjustment mechanism is as follows:

[0153] The first step is initial installation. Securely install each receiving unit onto its corresponding sliding base, ensuring a firm and reliable connection between the receiving unit and the sliding base.

[0154] The second step is to roughly adjust the spatial position. Move each sliding seat along the guide rail 13 so that each receiving unit is roughly aligned with the area to be measured in the plasma 7. During the movement, the length scale on the guide rail 13 can be referenced as needed.

[0155] The third step is to fine-tune the receiving angle. Rotate the sliding base to make the receiving unit rotate around the axis, observe the angle indicator scale 15, and adjust the axis of the receiving unit to the preset angle value. During the adjustment process, you can refer to the angle marks on the scale support 15.

[0156] Fourth step, locking and fixing. After adjustment, lock the sliding seat in the current position through the adjustable fixing hole 14 or the locking screw to prevent position displacement due to vibration or external force during measurement.

[0157] Fifth step, record parameters. Record the spatial position and receiving angle of each receiving unit for use in subsequent data analysis.

[0158] When it is necessary to change the measurement geometry, the locking mechanism can be loosened, the above adjustment steps can be repeated, and the position and angle of each receiving unit can be reset.

[0159] Furthermore, the angle indicator scale, when placed on the guide rail, can form a scaled support frame 15. The scaled support frame 15 is fixedly installed on the fixed support base 12, and angle values ​​are engraved on its arc-shaped edge, increasing towards both sides with a preset reference direction as the zero point. The sliding seat is provided with a pointer or reference line that cooperates with the scaled support frame 15. When the sliding seat moves along the guide rail 13 or rotates around the axis, the pointer points to the corresponding scale on the scaled support frame 15, thereby indicating the angle between the current receiving unit axis and the preset reference direction.

[0160] Furthermore, the transmitting module includes a microwave source unit and an incident optical unit 6. The microwave source unit includes a high-frequency source 1, an intermediate-frequency source 2, a sideband mixer 3, a first frequency multiplier 4, and an amplifier 5. The input of the sideband mixer 3 is connected to the outputs of the high-frequency source 1 and the intermediate-frequency source 2, respectively, to process the high-frequency signal output from the high-frequency source 1 and the intermediate-frequency signal output from the intermediate-frequency source 2 to obtain a single-sideband signal. The input of the first frequency multiplier 4 is connected to the output of the sideband mixer 3, to process the single-sideband signal to obtain a multiplied signal. The input of the amplifier 5 is connected to the output of the first frequency multiplier 4, to process the multiplied signal to obtain a microwave detection signal. The incident optical unit 6 is used to adjust the beam direction and beam size of the microwave detection signal and to emit it into the plasma 7.

[0161] High-frequency source 1 refers to the oscillator that generates the initial high-frequency microwave signal, outputting a high-frequency signal with stable frequency and low phase noise. This signal serves as the frequency reference for the entire system, providing the basis for subsequent frequency conversion and coherent detection.

[0162] The high-frequency source 1 can be implemented using a dielectric oscillator, a synthesized signal source, or a phase-locked oscillator, and the output frequency can be selected according to the detection requirements, such as 15 GHz. Its core indicators include frequency stability, phase noise, and output power, which directly affect the measurement accuracy of the entire system.

[0163] Intermediate frequency source 2 refers to an oscillator that generates an intermediate frequency modulation signal, outputting a stable and adjustable intermediate frequency signal. This signal is used to mix with the signal from high frequency source 1 to generate a probe signal carrying a frequency offset.

[0164] Intermediate frequency source 2 is typically implemented using a direct digital frequency synthesizer or a phase-locked oscillator, and its output frequency can be selected and adjusted according to detection requirements, such as 100MHz. The frequency adjustability of intermediate frequency source 2 provides the system with the ability to flexibly select the detection frequency.

[0165] The sideband mixer 3 is a microwave device that mixes high-frequency signals with intermediate-frequency signals. Its input is connected to the output of high-frequency source 1 and intermediate-frequency source 2, respectively, and is used to mix high-frequency signals and intermediate-frequency signals to output a single-sideband signal.

[0166] The sideband mixer 3 operates on the principle of nonlinear mixing. When the high-frequency signal f0 and the intermediate-frequency signal f_IF are simultaneously input to the mixer, due to nonlinear effects, multiple frequency components are generated at the output, mainly including: the sum frequency f0+f_IF, the difference frequency f0-f_IF, and the f0 component of the high-frequency signal itself. The sideband mixer 3 uses an internally integrated filter or a mirror-rejection mixing structure to suppress unwanted sideband and carrier components, retaining only one sideband (usually the upper sideband f0+f_IF or the lower sideband f0-f_IF) as the output.

[0167] The first frequency multiplier 4 refers to a microwave device that performs frequency multiplication on a single-sideband signal. Its input is connected to the output of the sideband mixer 3, and it is used to multiply the single-sideband signal and output a multiplied signal.

[0168] The first frequency multiplier 4 operates based on the frequency multiplication effect of nonlinear devices. When a single-sideband signal (frequency f0 ± f_IF) enters the frequency multiplier, it generates abundant harmonic components through nonlinear elements. The required Nth harmonic is extracted by an internal filter, and a multiplied signal with a frequency of N·(f0 ± f_IF) is output. The multiplication order N is determined according to the target detection frequency band; for example, multiplying 15.1 GHz by 6 yields a W-band signal of 90.6 GHz.

[0169] Amplifier 5 refers to a microwave device that amplifies the power of the frequency multiplier signal. Its input terminal is connected to the output terminal of the first frequency multiplier 4, and it is used to amplify the power of the frequency multiplier signal and output a high-power microwave detection signal.

[0170] Amplifier 5 is typically implemented using a solid-state power amplifier or a traveling wave tube amplifier, providing sufficient output power according to the detection requirements, so that the probe wave can penetrate the plasma and generate a detectable scattered signal.

[0171] Incident optical unit 6 refers to the quasi-optical system connected to the output of amplifier 5, used to adjust the beam direction and beam spot size of microwave detection signals and to emit them into plasma 7.

[0172] The incident optical unit 6 may include various quasi-optical elements such as lenses, mirrors, polarizers, and phase shifters, designed and combined according to detection requirements. Its specific functions include:

[0173] First, adjust the beam direction. By using adjustable mirrors or lens groups, the exit angle of the detection beam can be changed, allowing the beam to be incident on the target region in plasma 7 in a specific direction. The beam direction can be adjusted within a wide range according to experimental requirements.

[0174] Second, adjust the beam size. By using lens groups or beamforming elements, the beam size of the probe beam at plasma 7 can be changed to optimize the balance between spatial resolution and signal strength. A smaller beam provides higher spatial resolution, while a larger beam provides a stronger scattered signal.

[0175] Third, control beam polarization. By using a polarizer or grid, the polarization direction of the probe wave (such as ordinary or extraordinary wave) can be set to meet different physical measurement requirements.

[0176] Fourth, beam focusing is achieved. By using focusing elements, the probe beam is focused on a specific radial position in plasma 7, improving local power density and spatial resolution.

[0177] The core function of the incident optical unit 6 is to shape the high-power detection signal output by the amplifier 5 into a beam that meets the measurement requirements and accurately project it onto the area to be measured in the plasma 7, thus creating conditions for subsequent scattering measurements.

[0178] Based on the above components, the complete process of signal generation and transmission within the transmitting module is as follows:

[0179] The first step is to output a high-frequency signal f0 from high-frequency source 1 and an intermediate-frequency signal f_IF from intermediate-frequency source 2.

[0180] The second step involves simultaneously feeding both signals into the sideband mixer 3. The sideband mixer 3 mixes the high-frequency signal with the intermediate-frequency signal, and after filtering, outputs a single-sideband signal with a frequency of f0+f_IF or f0-f_IF.

[0181] Third, the single-sideband signal enters the first frequency multiplier 4. The first frequency multiplier 4 multiplies the signal N times and outputs a multiplied signal with a frequency of N·(f0±f_IF).

[0182] Fourth, the frequency-doubled signal enters amplifier 5. Amplifier 5 amplifies its power to the required level and outputs a high-power microwave detection signal.

[0183] Fifth, the high-power detection signal enters the incident optical unit 6. The incident optical unit 6 adjusts the beam direction, beam spot size, and polarization state according to experimental requirements, and finally emits the formed detection beam into the plasma 7.

[0184] Furthermore, the transmitting module may be one or more. When multiple transmitting modules are included, the transmitting angle of each transmitting module can be adjusted independently to transmit microwave detection signals at different angles.

[0185] Furthermore, it also includes a wave absorber, which is disposed in the transmission wave path of the plasma to absorb transmitted microwaves that pass through the plasma.

[0186] Example 2

[0187] This invention provides a method for measuring high-temperature plasma turbulence, comprising:

[0188] Microwave detection signals are transmitted into the plasma via the transmitting module;

[0189] Adjust the relative distance between the focusing element of each receiving unit and the receiving antenna so that the imaging focus of each receiving unit is aligned with the radial region to be measured in the plasma;

[0190] Each receiving unit receives the scattered signal generated by the plasma and processes the scattered signal into a corresponding intermediate frequency signal.

[0191] The intermediate frequency signal is sent to the signal processing module to obtain the plasma density fluctuation wavenumber spectrum and the turbulent power spectrum.

[0192] For example, Example 1: Combining Figure 1 This illustrates boundary turbulence measurements performed on a tokamak device. Taking the study of the boundary local mode (ELM) of a tokamak device as an example, high-frequency source 1 generates a signal with f0 = 15 GHz, and intermediate-frequency source 2 generates a signal with f0 = 15 GHz. IF A 100MHz signal, after passing through sideband mixer 3 and first frequency multiplier 4 (N=6), generates a probe wave with a center frequency of 90.6GHz. Amplifier 5 amplifies the probe wave, which is then split into 4 channels by distributor 17 (taking 4 channels as an example).

[0193] The incident optical unit 6 emits the probe wave at a certain angle toward the plasma to be tested 7. The incident optical unit 6 can be a phased antenna (here, W-band) or a combination of a horn antenna and a microwave quasi-optical structure with a rotatable angle.

[0194] The receiving unit and mechanical adjustment mechanism are fixed on an optical platform outside the tokamak diagnostic window. The four receiving antennas are aligned with the same measurement position in the plasma, and the optimal focusing position is obtained by adjusting the variable-focus receiving unit. Based on the magnetic surface geometry and the expected wavenumber of turbulence, the scattered wave vector k is perpendicular to the magnetic field lines. The position of the variable-focus receiving unit on the scaled support frame 15 and guide rail 13 is adjusted by sliding the variable-focus receiving unit and rotating its angle. After fine adjustment to the predetermined value by the scale, it is locked. The angle between each channel and the probe wave in the plasma, i.e., the scattering angles θ1, θ2, θ3, and θ4, is calculated.

[0195] During table calibration, place a point source or a grooved rotating roller in the measurement area, rotate the cylindrical housing 10, and adjust the position of the focusing element 9 until the receiving antenna 11 (open waveguide) receives the maximum signal strength, indicating that the focus has been aligned with the target area.

[0196] During plasma discharge, turbulence in the plasma scatters the probe wave. The scattered signal is received by the receiving unit. The phase detector array 19 simultaneously measures the amplitude (A1, A2, A3, A4) and phase (φ1, φ2, φ3, φ4) of the scattered channel relative to the reference signal. The acquisition and data analysis system 20, combined with preset geometric parameters and focal position, retrieves the turbulent power spectrum and its temporal evolution of the density fluctuations in the boundary region within a certain wavenumber range, which is used to analyze the changes in turbulent characteristics at different scales before and after the ELM eruption.

[0197] Example 2: This embodiment demonstrates the application of this system for radial scanning measurement.

[0198] In the same tokamak discharge, it is desirable to compare the turbulence spectrum from the core to the boundary (taking four channels as an example, normalized radii ρ=r / a=0.15, 0.4, 0.65, 0.9). First, the emission angle is set to be fixed as in Example 1. During the pre-discharge preparation stage, the correspondence between the adjustment knob scale of the cylindrical shell 10 and the radial position of the focal point is pre-calibrated. The positions of the four measurement channels are adjusted to the corresponding positions, and their scattering angles are made equal. During the first discharge, the scattered signal and turbulence spectrum at this position are measured and recorded. During the second discharge with different constraints, all emission and reception parameters are kept unchanged, and the measurement is performed again. By comparing the two measurement results, the radial distribution difference of the turbulence power spectrum can be directly obtained. This method avoids the trouble of traditionally needing to move the entire diagnostic system or use multiple fixed-focus receivers, significantly improving diagnostic efficiency and the reliability of radial comparison, highlighting the great advantages of the variable-focus design of this invention.

[0199] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0200] 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 high-temperature plasma turbulence measurement system, characterized in that, include: The transmitting module is used to transmit microwave detection signals into the plasma; The receiving module includes at least two receiving units, each receiving unit including a focusing element and a receiving antenna. The relative distance between the focusing element and the receiving antenna is adjustable to change the imaging focal position of the receiving unit, so that the receiving unit is aligned with the radial region to be measured in the plasma. The receiving module is used to process the scattered signals acquired by each receiving unit to obtain an intermediate frequency signal. The signal processing module, connected to the receiving unit, is used to obtain the plasma density fluctuation wavenumber spectrum and turbulent power spectrum based on the received intermediate frequency signal.

2. The system according to claim 1, characterized in that, Each receiving unit also includes a cylindrical housing, the focusing element is installed inside the cylindrical housing, and the receiving antenna is installed at one end of the cylindrical housing away from the focusing element. The relative distance between the focusing element and the receiving antenna is changed by adjusting the axial position of the focusing element inside the cylindrical housing.

3. The system of claim 2, wherein, The angles and / or focal positions of the multiple receiving units are configured to simultaneously align with the same measurement region or different radial regions in the plasma.

4. The system of claim 1, wherein, The receiving module also includes a distributor and a downconverter connected to each receiving unit; The input terminal of the distributor is connected to the output terminal of the high-frequency source of the transmitting module, and the output terminal of the distributor is connected to each downconverter. The distributor is used to distribute the high-frequency signal output by the high-frequency source to each downconverter. Each downconverter is used to downconvert the scattered signal output by the corresponding receiving unit and the high-frequency signal to output the corresponding intermediate frequency signal.

5. The system of claim 1, wherein, The signal processing module includes: The second frequency multiplier is connected to the intermediate frequency source of the transmitting module to obtain a reference signal; A phase detector array, connected to the output of each receiving unit and the second frequency multiplier, is used to measure the amplitude and phase of each intermediate frequency signal relative to a reference signal; The acquisition and data analysis system, connected to the phase detector array, is used to invert the wavenumber spectrum and turbulent power spectrum of plasma density fluctuations based on the amplitude and phase.

6. The system of claim 1, wherein, The system further includes a mechanical adjustment mechanism, which comprises: Fixed support base; A guide rail is installed on the fixed support base; Sliding seats corresponding to each receiving unit are installed on the guide rail. Each sliding seat is connected to the corresponding receiving unit. Each sliding seat can move along the guide rail and / or rotate about the axis to adjust the spatial position and receiving angle of the corresponding receiving unit. An angle indicator scale is set on the guide rail or the sliding seat to indicate the angle between the axis of the receiving unit and a preset reference direction.

7. The system of claim 1, wherein, The transmitting module includes a microwave source unit and an incident optical unit; The microwave source unit includes a high-frequency source, an intermediate-frequency source, a sideband mixer, a first frequency multiplier, and an amplifier. The input terminal of the sideband mixer is connected to the output terminals of the high-frequency source and the intermediate-frequency source, respectively, and is used to process the high-frequency signal output by the high-frequency source and the intermediate-frequency signal output by the intermediate-frequency source to obtain a single-sideband signal. The input terminal of the first frequency multiplier is connected to the output terminal of the sideband mixer and is used to process the single-sideband signal to obtain a multiplied signal. The input terminal of the amplifier is connected to the output terminal of the first frequency multiplier and is used to process the multiplied signal to obtain a microwave detection signal. The incident optical unit is used to adjust the beam direction and beam spot size of the microwave detection signal.

8. The system of claim 1, wherein, The transmitting module may be one or more. When multiple transmitting modules are included, the transmitting angle of each transmitting module can be adjusted independently to transmit microwave detection signals at different angles.

9. The system of claim 1, wherein, It also includes a wave absorber, which is disposed in the transmission wave path of the plasma to absorb transmitted microwaves that pass through the plasma.

10. A method for high temperature plasma turbulence measurement using the system of any one of claims 1-9, characterized in that, include: Microwave detection signals are transmitted into the plasma via the transmitting module; Adjust the relative distance between the focusing element of each receiving unit and the receiving antenna so that the imaging focus of each receiving unit is aligned with the radial region to be measured in the plasma; Each receiving unit receives the scattered signal generated by the plasma and processes the scattered signal into a corresponding intermediate frequency signal. The intermediate frequency signal is sent to the signal processing module to obtain the plasma density fluctuation wavenumber spectrum and the turbulent power spectrum.

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