A spatially resolved coherent scattering imaging system and method for plasma turbulence measurements

Abstract

The present application relates to the field of high-temperature plasma turbulence measurement, and particularly relates to a spatially resolved coherent scattering imaging system and method for plasma turbulence measurement. The system comprises a beam combining element for combining local oscillator light and probe light into an initial combined light coaxial and in the same path; a beam splitting and shaping assembly arranged on the light path of the initial combined light, for shaping the initial combined light into a wide parallel light beam covering a to-be-measured plasma region and a converging light beam incident to the to-be-measured plasma region at an adjustable angle; and an imaging receiving assembly for imaging a measurement line distributed along a one-dimensional direction in the to-be-measured plasma region to a detector array, and for causing each detection unit of the detector array to receive scattered light of a corresponding spatial point and local oscillator light components in the wide parallel light beam to perform optical mixing, and output a signal representing turbulence scattering intensity at the corresponding spatial point, so that intensity distribution of a specific turbulence scale on the entire plasma radial profile can be obtained, and the measurement effect is improved.

Description

Technical Field

[0001] This invention relates to the field of high-temperature plasma turbulence measurement, and more specifically to a spatially resolved coherent scattering imaging system and method for plasma turbulence measurement. Background Technology

[0002] In magnetically confined nuclear fusion plasma physics research, plasma turbulence (such as electron density fluctuations) is a key factor leading to anomalous energy and particle transport. Coherent scattering is one of the main methods for diagnosing microscopic plasma turbulence. Its principle involves using a probe laser to scatter the plasma density fluctuations that satisfy the Bragg condition, and then measuring the specific scattered wave vector k (k=k0). s -k i , where k s Let k be the wave vector of the scattered light. i The scattering power corresponding to the incident light wave vector is used to invert the intensity spectrum of turbulence at this spatial scale.

[0003] Traditional coherent scattering systems typically employ a point-detection mode. The standard configuration consists of a monochromatic probe beam (e.g., a short-wavelength microwave or near-infrared laser) incident at a specific angle onto the plasma; the scattered light is collected by an off-axis optical system and focused onto a single-point detector (e.g., a Schottky detector or a mercury cadmium telluride detector). This system achieves k-spectral scanning by rotating the incident and collected light paths to change the magnitude and direction of the scattered wave vector k.

[0004] However, this traditional approach suffers from poor spatial resolution. The signal received by the detector is the sum of all scattered light satisfying the angular conditions within the entire scattering and collecting optical path field of view (typically corresponding to a range of tens of centimeters along the optical path of the plasma). Therefore, the measured signal is essentially a spatial integration measurement. It cannot distinguish whether the turbulence signal originates from the plasma center, boundary, or a local region, which is particularly problematic at small-angle scattering. Due to the strong radial gradients in magnetically confined plasma parameters (such as density, temperature, and magnetic field), the driving mechanism and intensity of turbulence also change drastically. This spatial integration measurement can confuse the characteristics of different physical regions, lose crucial spatial distribution information, and affect the measurement results. Summary of the Invention

[0005] The purpose of this invention is to provide a spatially resolved coherent scattering imaging system and method for plasma turbulence measurement, which solves the problems in the prior art.

[0006] This invention is achieved through the following technical solution:

[0007] In a first aspect, embodiments of the present invention provide a spatially resolved coherent scattering imaging system for plasma turbulence measurement, comprising:

[0008] A beam combiner is used to combine the local oscillator beam and the probe beam into a single coaxial beam.

[0009] A beam splitting and shaping component is disposed on the optical path of the initial beam combining light, and is used to shape the initial beam combining light into a wide parallel beam covering the plasma region to be tested, and a converging beam incident on the plasma region to be tested at an adjustable angle, wherein the wide parallel beam and the converging beam are transmitted along the same path within the plasma region to be tested.

[0010] An imaging receiving component is used to image the measurement lines distributed along a one-dimensional direction in the plasma region to be measured onto a detector array, and to enable each detection unit of the detector array to receive the scattered light from the corresponding spatial point and perform optical mixing with the local oscillator component in the wide parallel beam, and output a signal characterizing the intensity of turbulent scattering at the corresponding spatial point; wherein the magnitude and direction of the scattered wave vector at the spatial point corresponding to each detection unit are consistent.

[0011] Preferably, the beam-splitting shaping component includes:

[0012] The first lens is used to expand the initial combined beam into expanded beam;

[0013] A beam splitting element is used to split the expanded beam into a first expanded beam and a second expanded beam, wherein both the first expanded beam and the second expanded beam simultaneously contain components of local oscillator light and probe light.

[0014] The second lens is used to focus the first expanded beam into a wide parallel beam.

[0015] The third lens is used to focus the second beam-expanding light into a converging beam;

[0016] The first reflection unit is used to adjust the wide parallel beam so that the wide parallel beam enters from the entrance window of the vacuum cavity and covers the plasma region to be measured.

[0017] The second reflection unit is used to adjust the converging beam so that the converging beam enters from the incident window and forms an angle with the wide parallel beam.

[0018] Preferably, the imaging receiving component includes:

[0019] An imaging optical unit is used to image the outgoing light corresponding to the wide parallel beam emitted from the exit window of the vacuum cavity onto the photosensitive surface of the detector array.

[0020] The detector array is a one-dimensional linear detector array arranged along the radial direction.

[0021] Preferably, the imaging optical unit includes:

[0022] The third reflection unit is disposed on the optical path after the wide parallel light passes through the plasma to be tested, and is used to reflect the outgoing light corresponding to the wide parallel beam emitted from the exit window of the vacuum cavity to the collecting lens group.

[0023] The collecting lens group is used to focus the emitted light onto the detector array.

[0024] Preferably, it further includes:

[0025] The first laser is used to emit local oscillator light;

[0026] The second laser is used to emit probe light;

[0027] When zero-difference measurement is required, the first laser and the second laser are configured to output beams with the same frequency; when heterodyne measurement is required, the first laser and the second laser are configured to output beams with similar frequencies.

[0028] Preferably, it also includes a spot monitoring unit for real-time monitoring and calibration of the spatial position of the probe light on the plasma under test.

[0029] Preferably, the light spot monitoring unit includes:

[0030] A beam splitter is placed in the optical path of the converging beam after it passes through the plasma to be tested, and is used to guide part of the light to the spot monitor.

[0031] A spot monitor is used to monitor and calibrate the spatial position of the probe light on the plasma under test in real time.

[0032] A beam absorber is positioned on the optical path of the converging beam after it passes through the plasma to be tested, and is used to absorb the probe light that has not been scattered.

[0033] Preferably, it further includes a vacuum cavity, in which the plasma to be tested is disposed. The vacuum cavity is spherical and includes an incident window for beam incidence and an exit window for beam emission.

[0034] In a second aspect, embodiments of the present invention provide a spatially resolved coherent scattering imaging method for plasma turbulence measurement, applied to the system of the first aspect, comprising:

[0035] The local oscillator beam and the probe beam are combined into a single coaxial beam;

[0036] The initial beam is shaped into a wide parallel beam covering the plasma region to be tested, and a converging beam incident on the plasma region to be tested at an adjustable angle, wherein the wide parallel beam and the converging beam are propagated in the same path within the plasma region to be tested.

[0037] The measurement lines distributed along a one-dimensional direction in the plasma region to be measured are imaged onto a detector array. Each detection unit of the detector array receives the scattered light from the corresponding spatial point and performs optical mixing with the local oscillator component in the wide parallel beam, outputting a signal characterizing the intensity of turbulent scattering at the corresponding spatial point. The magnitude and direction of the scattered wave vector at the spatial point corresponding to each detection unit are consistent.

[0038] By changing the incident angle of the converging beam, repeating the above steps of changing the incident angle of the converging beam, and repeating the above steps of imaging the measurement lines distributed along the one-dimensional direction in the plasma region to be measured onto the detector array, so that each detection unit of the detector array receives the scattered light from the corresponding spatial point and performs optical mixing with the local oscillator component in the wide parallel beam, and outputs a signal characterizing the turbulent scattering intensity at the corresponding spatial point, the spatial distribution of turbulent scattering intensity along the one-dimensional direction under different scattered wave vectors is obtained.

[0039] Preferably, shaping the initial combined beam into a wide parallel beam covering the region of the plasma to be tested, and a converging beam incident on the region of the plasma to be tested at an adjustable angle, includes:

[0040] The initial beam is divided into a first beam and a second beam, wherein both the first beam and the second beam contain components of local oscillator light and probe light.

[0041] The first beam is expanded to form a wide parallel beam covering the region of the plasma to be tested.

[0042] The second beam is focused to form a converging beam incident at an adjustable angle onto the plasma region to be tested.

[0043] Adjusting the incident angle of the converging beam changes the magnitude and direction of the scattered wave vector.

[0044] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0045] By using a beam-combining element, the local oscillator beam and the probe beam are combined into an initial beam that is coaxial and follows the same path. A beam-shaping component then simultaneously shapes this initial beam into a wide parallel beam covering the plasma region under test and a converging beam incident at an adjustable angle. This ensures that the local oscillator component in the wide parallel beam uniformly illuminates the entire radial cross-section of the plasma. An imaging receiving component images the measurement lines distributed along a one-dimensional direction in the plasma region onto a detector array. Each detector unit in the array receives the scattered light from its corresponding spatial point and the local oscillator component from the wide parallel beam, performing optical mixing. Since each detector unit only receives light signals from a tiny spatial region conjugate to it within the plasma, the system can distinguish the radial location of the scattered signal originating from within the plasma. This fundamentally overcomes the spatial integration measurement problem caused by the detector receiving the sum of all scattered light within the entire field of view in traditional coherent scattering techniques, achieving one-dimensional spatial distribution measurement of turbulence intensity along the plasma radial direction.

[0046] By combining the local oscillator beam and the probe beam into a coaxial initial beam, and ensuring that the wide parallel beam and the converging beam propagate in the same path within the plasma region, the phase relationship between the local oscillator beam and the converging beam is kept stable. The wavefront parallelism of the wide parallel beam ensures that its wave vector direction is consistent throughout the plasma region; the converging beam passes through the plasma at a fixed incident angle, and its wave vector direction remains consistent throughout the measurement line; the design of the imaging optics system in the imaging receiver ensures that the scattered light collection direction corresponding to each object point uniquely corresponds to its image point position, and that the geometric relationship between the scattered light collection direction and the incident light direction is the same at each point along the measurement line. Under the combined effect of the above conditions, at all spatial points corresponding to the probe units, the magnitude and direction of the vector difference between the incident light wave vector and the scattered light wave vector, i.e., the scattered wave vector, remain strictly consistent, solving the problem of measurement confusion caused by different scattered wave vectors corresponding to different spatial points in traditional coherent scattering techniques.

[0047] The detector array's individual detector units operate synchronously, simultaneously acquiring signals from all radial positions within a single measurement event. This directly yields the one-dimensional spatial distribution of turbulent scattering intensity along the plasma radial direction under the current scattered wave vector. By adjusting the incident angle of the converging beam to change the scattered wave vector, repeated measurements can be performed under different scattered wave vectors, rapidly acquiring radial distribution data of turbulence at different spatial scales. Compared to traditional coherent scattering techniques that use mechanical rotation of the incident and scattering collection light paths for point-by-point scanning, this system eliminates the need for point-by-point spatial scanning, reducing measurement time and facilitating the capture of the dynamic evolution of turbulence.

[0048] The system can obtain a three-dimensional dataset through a single measurement process. The scattered wave vector dimension corresponds to different turbulent spatial scales, the radial position dimension corresponds to the spatial distribution of plasma from the core to the boundary, and the scattered intensity dimension characterizes the relative intensity of turbulence at the corresponding location and scale. This multidimensional dataset provides complete experimental evidence for studying the driving mechanism, propagation characteristics, and suppression conditions of turbulence at different radial positions, and supports the verification and constraint of turbulent transport models. Attached Figure Description

[0049] 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:

[0050] Figure 1 A schematic diagram of the structure of the spatially resolved coherent scattering imaging system for plasma turbulence measurement provided by the present invention;

[0051] Figure 2 A schematic diagram showing the distribution of the two beams in plasma provided by the present invention;

[0052] Figure 3 A schematic flowchart of the spatially resolved coherent scattering imaging method for plasma turbulence measurement provided by the present invention;

[0053] The attached diagram shows the markings and corresponding component names:

[0054] 1-First laser, 2-Local oscillator, 3-Beam combiner, 4-First lens, 5-Beam splitter, 6-Second lens, 7-Wide parallel beam, 8-First reflecting unit, 9-Incident window, 10-Vacuum cavity, 10a-Plasma boundary, 10b-Plasma to be tested, 11-Outgoing window, 12-Reflector, 13-Collecting lens group, 14-Detector array, 15-Third lens, 16-First reflector, 17-Second reflector, 18-Beam splitter, 19-Beam swallower, 20-Spot monitor, 21-Second laser, 22-Detector beam, 23-Converging beam. Detailed Implementation

[0055] 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.

[0056] 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.

[0057] 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.

[0058] Example 1

[0059] Please see Figure 1 This invention provides a spatially resolved coherent scattering imaging system for plasma turbulence measurement, comprising:

[0060] The beam combiner 3 is used to combine the local oscillator light and the probe light into a coaxial initial beam.

[0061] In coherent scattering measurements, the local oscillator beam and the probe beam are generated by different light sources. Before entering the subsequent optical system, the two beams need to have a defined spatial and phase relationship. The beam combiner 3 can be any of a beam splitter, dichroic mirror, or polarizing beam combiner. It transmits one beam and reflects the other, allowing the two beams to propagate along the same optical axis. For example, when a beam splitter is used as the beam combiner 3, the local oscillator beam 2 is transmitted through the beam splitter, and the probe beam 22 is reflected by the beam splitter. The two beams then overlap behind the beam splitter, forming a coaxial beam. After passing through the beam combiner 3, the local oscillator beam 2 and the probe beam 22 are completely spatially overlapped and experience the same optical elements and environmental disturbances in their subsequent propagation paths. Therefore, the relative phase relationship between the two beams remains stable. This coaxial configuration provides a phase reference for subsequent heterodyne detection, avoiding the influence of relative phase jitter introduced by independent optical paths on the measurement results. Furthermore, the coaxial common path structure simplifies the alignment process of the optical system, eliminating the need to recalibrate the spatial overlap between the local oscillator and the probe light each time the incident angle of the probe light is adjusted.

[0062] The beam splitting and shaping component is disposed on the optical path of the initial beam combining light and is used to shape the initial beam combining light into a wide parallel beam 7 covering the region of the plasma to be tested and a converging beam 23 incident on the region of the plasma to be tested 10b at an adjustable angle, wherein the wide parallel beam 7 and the converging beam 23 are transmitted along the same path within the region of the plasma to be tested 10b.

[0063] The initial beam combines two components: local oscillator light 2 and probe light 22. The beam splitting and shaping component can divide the initial beam into a first beam and a second beam, both of which retain the components of local oscillator light 2 and probe light 22.

[0064] The first beam is expanded to form a wide parallel beam 7. The beam expanding optical system can use a Keplerian beam expander or a Galilean beam expander. The beam diameter is expanded to cover the entire incident window 9 through the lens group before entering the cross section of the plasma to be measured 10b. At the same time, the wavefront of the output beam is kept parallel. The beam width is determined by the local oscillator 2, the probe 22, the incident window 9, the exit window 11 and the region of the plasma to be measured 10b.

[0065] The second beam is processed by a focusing optical system to form a converging beam 23. The focusing optical system can be a single lens or a combination of lenses, which compresses the beam waist of the converging beam 23 to a size smaller than the cross-sectional size of the wide parallel beam 7, and controls the incident direction of the converging beam 23 through an angle adjustment mechanism.

[0066] The angle adjustment mechanism can employ a rotating mirror assembly or a rotating prism assembly, adjusting the incident angle of the converging beam 23 by changing the orientation of the mirrors or prisms. At the output end of the beam splitting and shaping assembly, the wide parallel beam 7 and the converging beam 23 maintain a coaxial or intersecting geometric relationship, jointly passing through the region of the plasma to be measured 10b. The local oscillator component in the wide parallel beam 7 does not undergo scattering or the scattering is negligible in the plasma, mainly serving as the reference light for heterodyne detection; the probe light component in the converging beam 23 interacts with the density fluctuations in the plasma to generate scattered light, the magnitude of which is determined by the incident angle of the converging beam 23.

[0067] Since the two beams originate from the same initial combined beam, their spatial correspondence in the plasma is determined by the optical design of the beam-shaping assembly, eliminating the need for additional alignment steps. The wide parallel beam 7 covers the entire radial cross-section, ensuring the presence of local oscillator light at all radial positions; the converging beam 23 penetrates the plasma with a narrow cross-section, defining the spatial region where scattered light is generated, but every spatial point within this region is simultaneously illuminated by the local oscillator light in the wide parallel beam 7, thus satisfying the conditions for heterodyne detection.

[0068] An imaging receiving component is used to image the measurement lines distributed along a one-dimensional direction in the region of the plasma under test 10b onto the detector array 14. Each detection unit of the detector array 14 receives the scattered light from the corresponding spatial point and performs optical mixing with the local oscillator component of the wide parallel beam 7, outputting a signal characterizing the intensity of turbulent scattering at the corresponding spatial point. The imaging receiving component includes an imaging optical system and a detector array 14. The imaging optical system can employ a transmission-type imaging lens group or a reflection-type imaging mirror group to image the radially distributed measurement lines inside the plasma onto the photosensitive surface of the detector array 14 at a certain magnification. The detector array 14 contains multiple independent detection units, which can be photovoltaic detectors or photoconductive detectors, arranged in a one-dimensional linear array along the direction corresponding to the measurement lines.

[0069] During imaging, the mixed light emitted from the plasma contains two components: scattered light generated by the interaction between the probe light in the converging beam 23 and the plasma, and local oscillator light in the wide parallel beam 7 that passes through the plasma without being scattered. The imaging optical system focuses the light emitted from each object point in this mixed light onto the corresponding image point position, i.e., the corresponding detection unit on the detector array 14. Therefore, the light signal received by each detection unit comes only from a tiny spatial region conjugate to it within the plasma. Within this spatial region, the local oscillator light component and the scattered light component undergo optical mixing on the photosensitive surface of the detection unit. When the local oscillator light and the probe light have the same frequency, the mixing output is a DC signal, the amplitude of which is linearly related to the amplitude of the scattered light; when there is a slight difference in frequency between the two beams, the mixing output is an intermediate frequency AC signal, the amplitude of which is proportional to the amplitude of the scattered light, and the frequency is equal to the frequency difference between the two beams. Because the wavefront of the wide parallel beam 7 is parallel, its wave vector direction is consistent throughout the plasma region; the incident angle of the converging beam 23 is fixed, and its wave vector direction is also consistent throughout the measurement line; the design of the imaging optical system ensures that the scattered light collection direction corresponding to each object point uniquely corresponds to its image point position, and the geometric relationship between the scattered light collection direction and the incident light direction is the same at each point along the measurement line. Therefore, at all spatial points corresponding to all detection units, the magnitude and direction of the vector difference between the incident light wave vector and the scattered light wave vector, i.e., the scattered wave vector, remain strictly consistent. The detector array 14 synchronously acquires the output signals of all detection units, thus obtaining the one-dimensional spatial distribution of the turbulent scattering intensity along the plasma radial direction under the current scattered wave vector.

[0070] In some embodiments, the beam-splitting shaping component includes:

[0071] The first lens 4 is used to expand the initial combined beam into an expanded beam. After being combined by the combining element 3, the initial combined beam usually has a small beam diameter, requiring expansion to meet the requirements of subsequent optical processing. The first lens 4 can be a negative lens in a Galilean beam expander structure or a positive lens in a Keplerian beam expander structure. The beam diameter is increased through the divergence effect of the negative lens or the focusing and collimation combination of the positive lens. The expanded beam output after processing by the first lens 4 still maintains the coaxial and common-path characteristics, that is, the local oscillator beam 2 and the probe beam 22 are completely overlapped in the expanded beam. The beam diameter after expansion determines the coverage range of the subsequent wide parallel beam 7. An appropriate beam diameter helps the subsequent optical elements to effectively process the beam, and at the same time provides a basis for the wide parallel beam 7 to cover the entire region of the plasma under test 10b. The beam expansion process does not change the relative phase relationship between the two beams, so the phase difference between the local oscillator beam 2 and the probe beam 22 is maintained after beam expansion.

[0072] Beam splitter 5 is used to split the expanded beam into a first expanded beam and a second expanded beam, both of which contain components of the local oscillator beam 2 and the probe beam 22. Beam splitter 5 can be any of a beam splitter or a beam splitter prism, splitting the incident light into two paths through partial transmission and partial reflection. When the expanded beam is incident on beam splitter 5, a portion of the energy is transmitted to form the first expanded beam, and the remaining energy is reflected to form the second expanded beam. Because beam splitter 5 is insensitive to wavelength and polarization or is specially designed, the ratio of the local oscillator beam 2 to the probe beam 22 in the two output beams remains consistent with the incident light. This beam splitting method ensures that both beams retain complete information about the local oscillator beam 2 and the probe beam 22, providing a basis for subsequent shaping into a wide parallel beam 7 and a converging beam 23, respectively. After beam splitting, the two beams still maintain the phase relationship between the local oscillator beam 2 and the probe beam 22. However, due to the difference in transmission and reflection paths introduced by the beam splitting element 5, the relative phase between the two beams may be fixedly shifted. This shift can be compensated or calibrated through the design of the subsequent optical system.

[0073] The second lens 6 is used to focus the first beam-expanding light into a wide parallel beam 7. After being split by the beam-splitting element 5, the first beam-expanding light needs further processing to form a wide parallel beam 7 covering the region of the plasma to be measured 10b. The second lens 6 can be a positive lens or a lens group, which expands the beam by focusing and then collimating the first beam-expanding light, or directly uses a beam-expanding mirror structure to expand the beam diameter to the required size. In actual configuration, the second lens 6 and the first lens 4 cooperate to form a beam-expanding system. The first lens 4 pre-expands the initial combined beam, and the second lens 6 expands and collimates the first beam-expanding light again. The diameter of the final output beam can reach tens to hundreds of millimeters, which is sufficient to cover the entire cross section of the plasma to be measured 10b. The wavefront parallelism of the output beam is achieved by the collimation function of the second lens 6, ensuring that the beam does not diverge or converge during propagation. The local oscillator component in the wide parallel beam 7 serves as the reference light for heterodyne detection in subsequent measurements, and its uniform spatial distribution helps to ensure consistent heterodyne efficiency at different radial positions.

[0074] The third lens 15 is used to focus the second expanded beam into a converging beam 23. After the second expanded beam is split by the beam splitter 5, it needs to form a converging beam 23 with a small cross-sectional size to serve as the probe light for excitation scattering. The third lens 15 can be a positive lens or a combination of lenses, which focuses the energy of the second expanded beam to a smaller beam waist size through focusing. The beam waist position of the converging beam 23 can be designed inside the region of the plasma to be measured 10b to ensure that the beam has a small cross-sectional size within the measurement range, thereby improving the spatial positioning accuracy. The focal length and position of the third lens 15 determine the convergence angle and beam waist diameter of the converging beam 23. By selecting appropriate lens parameters, the converging beam 23 can maintain a cross-sectional size smaller than the coverage area of ​​the wide parallel beam 7 during its passage through the plasma. The converging beam 23 contains both probe light and local oscillator light components. The probe light component interacts with the density fluctuations in the plasma to generate scattered light, while the local oscillator light component enters the plasma along with the probe light and ultimately participates in heterodyne detection together with the local oscillator light in the wide parallel beam 7.

[0075] The first reflecting unit 8 is used to adjust the wide parallel beam 7 so that it enters through the incident window 9 of the vacuum cavity 10 and covers the region of the plasma 10b to be measured. The first reflecting unit 8 can be either a plane mirror or a prism mirror. By changing the propagation direction of the beam, the wide parallel beam 7 passes through the incident window 9 in a direction parallel to the axis of the vacuum cavity 10. Under the action of the first reflecting unit 8, the optical axis of the wide parallel beam 7 is aligned with the geometric axis of the vacuum cavity 10, ensuring that the beam can uniformly cover the entire radial section from the center of the plasma to the boundary. The mounting base of the first reflecting unit 8 can be configured with an adjustment mechanism for fine-tuning the beam direction during system installation and commissioning to compensate for positional errors of optical components or installation deviations of the vacuum cavity 10. After adjustment by the first reflecting unit 8, the wide parallel beam 7 enters the vacuum cavity 10 in a defined incident direction, providing uniform local oscillator illumination to the entire measurement area.

[0076] The second reflecting unit is used to adjust the converging beam 23 so that it enters through the incident window 9 and forms an angle with the wide parallel beam 7. The second reflecting unit can employ two independently adjustable plane mirrors or a two-dimensional adjustable mirror group. The incident direction and angle of the converging beam 23 are adjusted by changing the orientation of the mirrors. The second reflecting unit may include a first reflecting mirror 16 and a second reflecting mirror 17 forming an angle adjustment mechanism. After the converging beam 23 is reflected sequentially by the two mirrors, its propagation direction changes, and it ultimately passes through the incident window 9 at a specific angle θ with the wide parallel beam 7. The angle can be continuously changed by rotating one or both mirrors. The magnitude of this changes the scattered wave vector. The value. Please see [the relevant information]. Figure 2 Scattered light collection direction According to the scattered wave vector and included angle get, .

[0077] The adjustment range of the second reflection unit should cover the required scattered wave vector scanning range, while ensuring that the converging beam 23 maintains a common or intersecting relationship with the wide parallel beam 7 during its passage through the plasma. After adjustment by the second reflection unit, the converging beam 23 enters the vacuum cavity 10 at a determined incident angle and spatial position, forming the optical field distribution of heterodyne detection together with the wide parallel beam 7.

[0078] In some embodiments, the imaging receiving component includes:

[0079] An imaging optical unit is used to image the outgoing light corresponding to the wide parallel beam 7 emitted from the exit window 11 of the vacuum cavity 10 onto the photosensitive surface of the detector array 14. The beam emitted from the exit window 11 of the vacuum cavity 10 contains two components: one is the local oscillator light in the wide parallel beam 7 that passes through the plasma without being scattered, and the other is the scattered light generated by the interaction between the probe light in the converging beam 23 and the plasma. The imaging optical unit can employ either a transmissive imaging lens group or a reflective imaging lens group, and through a combination of optical elements, it images the radially distributed measurement lines inside the plasma onto the photosensitive surface of the detector array 14 at a determined magnification. Specifically, the imaging optical unit may include a reflector 12 and a collecting lens group 13. The reflector 12 is used to change the propagation direction of the outgoing light so that the beam enters the collecting lens group 13 at an appropriate angle; the collecting lens group 13 consists of one or more lenses and is used to focus and image the beam. The optical parameters of the imaging optical unit should be designed according to the measurement requirements, including that the imaging field of view should cover the entire radial range from the plasma center to the boundary, and the imaging magnification should match the pixel size of the detector array 14 to ensure optimized spatial resolution. The depth of focus of the imaging optical unit should be sufficient to cover the thickness of the plasma along the optical path, so that all object points within the entire measurement line range can be clearly imaged. Through the processing of the imaging optical unit, light emitted from different radial positions inside the plasma is guided to the corresponding different detection units on the detector array 14, realizing the mapping of spatial position information to detector pixel positions.

[0080] Detector array 14 is a radially arranged one-dimensional linear detector array. Multiple independent detector units receive scattered light from corresponding spatial points in the image formed by the imaging optical unit and perform optical mixing with the local oscillator light, outputting a signal characterizing the turbulent scattering intensity at the corresponding spatial point. Detector array 14 can be either a photovoltaic detector or a photoconductive detector, arranged in a one-dimensional linear array along a direction corresponding to the plasma's radial direction. Each detector unit corresponds to a specific radial position. The spacing and number of detector units determine the system's spatial sampling interval and the number of measurement points, and should be selected based on the plasma size and the spatial distribution characteristics of the turbulence. On the photosensitive surface of the detector unit, the local oscillator light component and the scattered light component from the same spatial point are simultaneously incident, resulting in optical mixing. When the local oscillator light and the detector light have the same frequency, the mixing output is a DC signal, whose amplitude is linearly related to the amplitude of the scattered light. When there is a slight difference in the frequencies of the two beams, the mixing output is a mid-frequency AC signal, whose amplitude is proportional to the amplitude of the scattered light, and whose frequency is equal to the frequency difference between the two beams. Each detector unit in detector array 14 operates synchronously, simultaneously acquiring signals from all radial positions in a single measurement, thereby obtaining a one-dimensional spatial distribution of turbulent scattering intensity along the plasma radial direction under the current scattered wave vector. Due to the combined effects of the wavefront parallelism of the wide parallel beam 7, the fixed incident angle of the converging beam 23, and the imaging relationship of the imaging optical unit, the magnitude and direction of the scattered wave vector at the corresponding spatial point of each detector unit remain strictly consistent.

[0081] In some implementations, the system further includes:

[0082] The first laser 1 emits a local oscillator beam 2. In coherent scattering measurements, the local oscillator beam 2 serves as the reference beam for heterodyne detection and requires stable frequency and phase characteristics. The first laser 1 can be any of a gas laser, a solid-state laser, or a semiconductor laser, with the appropriate operating wavelength and output power selected based on the parameters of the plasma 10b under test and the measurement requirements. The local oscillator beam 2 output by the first laser 1 is shaped into a wide parallel beam 7 by a subsequent optical system, covering the entire region of the plasma 10b under test and providing a phase reference for each spatial point. The wavefront parallelism of the local oscillator beam 2 ensures that its wave vector direction is consistent throughout the plasma region, which is one of the prerequisites for all spatial points to correspond to the same scattered wave vector.

[0083] The second laser 21 is used to emit a probe beam 22. In coherent scattering measurements, the probe beam 22 acts as a probe beam to excite scattering, interacting with density fluctuations in the plasma to generate scattered light. The second laser 21 can be the same type as the first laser 1, or a different type can be selected as needed, but its output beam must have good coherence with the output beam of the first laser 1. The probe beam 22 output by the second laser 21 is shaped into a converging beam 23 by a subsequent optical system, passing through the plasma region 10b under test at a specific incident angle, and exciting a scattering signal during its co-path propagation with the wide parallel beam 7. The incident angle of the probe beam 22 determines the magnitude and direction of the scattered wave vector; by changing the incident angle, measurements of turbulence at different scales can be achieved.

[0084] When zero-difference measurement is required, the first laser 1 and the second laser 21 are configured to output beams with the same frequency; when heterodyne measurement is required, the first laser 1 and the second laser 21 are configured to output beams with similar frequencies. The laser frequency configuration can be selected and adjusted according to measurement requirements. In zero-difference measurement mode, the two beams have the same frequency, and the output of detector array 14 is a DC signal with a linear relationship between the signal amplitude and the amplitude of the scattered light, suitable for direct measurement of the intensity of the scattered light. In heterodyne measurement mode, the two beams have a slight frequency difference, and the output of detector array 14 is a mid-frequency AC signal with a signal amplitude proportional to the amplitude of the scattered light, and the frequency equal to the frequency difference between the two beams. Heterodyne measurement can effectively suppress background noise, improve the signal-to-noise ratio, and extract the phase information of the scattered light. Two beams with similar frequencies can be obtained from different branches of the same laser or generated by two independent lasers with locked frequencies. The selection of the laser operating mode does not affect the structure and function of other components in the system, and the same system can switch between zero-difference mode and heterodyne mode according to measurement requirements.

[0085] In some implementations, the system further includes:

[0086] The spot monitoring unit is used to monitor and calibrate the spatial position of the probe light 22 on the plasma to be tested 10b in real time.

[0087] During the scattered wave vector scanning process, the incident angle of the converging beam 23 is adjusted by the second reflection unit. Changes in the incident angle may cause the penetration position of the converging beam 23 in the plasma to shift, thereby changing the source region of the scattered signal. The spot monitoring unit can use either a beam splitter combined with a position-sensitive detector or an imaging camera combined with an image processing module to detect the spatial position of the converging beam 23 after passing through the plasma.

[0088] The beam spot monitoring unit may include a beam splitter 18 and a beam spot monitor 20. The beam splitter 18 is positioned on the optical path of the converging beam 23 after it passes through the plasma, guiding a portion of the beam to the beam spot monitor 20. The beam spot monitor 20 determines the spatial coordinates of the converging beam 23 on the plasma exit side by detecting the position, shape, or intensity distribution of the incident beam spot. Since the propagation path of the converging beam 23 in the plasma can be calculated from the incident angle and the geometric parameters of the vacuum cavity 10, by monitoring the spatial position of the exit beam, the spatial distribution of the converging beam 23 within the plasma can be deduced, thereby achieving real-time calibration of the spatial position of the probe light 22. The output signal of the beam spot monitoring unit can be used for spatial coordinate correction in data post-processing, and can also be used as a feedback signal input to the control system of the second reflection unit to perform closed-loop adjustment of the incident direction of the converging beam 23, ensuring that the probe light 22 can accurately pass through the radial position to be measured at different incident angles. Through real-time monitoring and calibration by the spot monitoring unit, the system can accurately correlate the scattered signal with the spatial position in the plasma, avoiding spatial positioning deviations caused by beam pointing drift or mechanical adjustment errors, and improving the reliability of spatial resolution measurement.

[0089] In some embodiments, the spot monitoring unit includes:

[0090] Beam splitter 18, positioned on the optical path of the converging beam 23 after it passes through the plasma 10b to be measured, guides a portion of the light to spot monitor 20. After passing through the plasma, the main energy of the converging beam 23 continues to propagate in its original direction, consisting mostly of unscattered probe light 22, and possibly containing a small amount of scattered light. Beam splitter 18 can be either a beam splitter or a beam splitting prism, splitting the incident beam into two paths through partial transmission and partial reflection. In a typical configuration, beam splitter 18 reflects or transmits a small portion of the energy (e.g., a few percent to a dozen percent) towards spot monitor 20, while most of the energy continues to propagate along the original path to beam swallower 19. The reflectivity and transmittance of beam splitter 18 should be selected based on the sensitivity requirements of spot monitor 20 and the energy level of the main beam, ensuring that spot monitor 20 obtains a sufficiently strong signal for position detection while avoiding excessive energy loss that could affect the absorption efficiency of beam swallower 19. The beam splitter 18 should be positioned behind the exit window 11 to ensure that it does not interfere with the operation of the incident beam or the imaging receiving components.

[0091] A beam spot monitor 20 is used to monitor and calibrate the spatial position of the probe beam 22 on the plasma 10b under test in real time. The beam spot monitor 20 can be either a position-sensitive detector or an imaging camera. By detecting the intensity distribution center, shape, or boundary of the incident beam spot, it determines the spatial coordinates of the converging beam 23 on the receiver surface of the monitor. When a position-sensitive detector is used, the detector outputs an electrical signal proportional to the beam spot position, which, after processing, yields the center coordinates of the beam spot. When an imaging camera is used, more detailed spatial distribution information of the beam spot can be obtained by processing the image data. Since the propagation path of the converging beam 23 in the plasma is determined by the incident angle and the geometric parameters of the vacuum cavity 10, by monitoring the spatial position of the emitted beam and combining it with the system optical model, the spatial distribution of the converging beam 23 within the plasma can be deduced, thereby achieving real-time calibration of the spatial position of the probe beam 22. The output signal of the spot monitor 20 can be used for spatial coordinate correction in data post-processing, and can also be used as a feedback signal input to the control system of the second reflection unit to perform closed-loop adjustment of the incident direction of the converging beam 23, ensuring that the probe light 22 can accurately pass through the radial position to be measured under different incident angles. Through real-time monitoring and calibration of the spot monitor 20, the system can accurately correlate the scattering signal with the spatial position in the plasma, avoiding spatial positioning deviations caused by beam pointing drift or mechanical adjustment errors.

[0092] A beam absorber 19 is positioned on the optical path of the converging beam 23 after it passes through the plasma 10b to be tested, and is used to absorb the unscattered probe light 22. After passing through the plasma, most of the energy of the converging beam 23 remains in its original beam form. If this portion of light is not processed, it may generate stray light reflections inside the vacuum cavity 10 or on the optical platform, interfering with the normal operation of other optical components and even posing safety hazards to personnel and equipment. The beam absorber 19 can be either a light absorption trap or a beam collector, converting the energy of the incident beam into heat energy through multiple reflections or direct absorption. In a typical configuration, the beam absorber 19 has a conical or wedge-shaped internal structure and a high-absorption coating on its surface, so that the incident light is almost completely absorbed after multiple reflections inside. The beam absorber 19 should be placed on the main beam path after the beam splitter 18 to ensure that most of the energy of the probe light 22 after passing through the beam splitter 18 is effectively absorbed. The position and orientation of the beam absorber 19 should ensure that it can stably receive the beam, and that the receiving port of the beam absorber 19 can still cover the propagation range of the beam even when the incident angle of the converging beam 23 changes. By absorbing the unscattered probe light 22 through the beam absorber 19, interference from stray light on the measurement results is avoided, thereby improving the signal-to-noise ratio and safety of the system.

[0093] In some implementations, the system further includes:

[0094] A vacuum cavity 10 is used to contain the plasma to be tested 10b, providing the necessary vacuum environment for plasma generation and confinement. The vacuum cavity 10 can be either a spherical or annular cavity, selected according to the overall design of the magnetic confinement fusion device. In a typical configuration, the vacuum cavity 10 is a spherical structure, forming a closed vacuum space inside, confining the plasma to be tested 10b to the central region of the cavity, with the plasma boundary 10a maintaining a certain distance from the inner wall of the cavity. The vacuum cavity 10 includes an entrance window 9 for beam incidence and an exit window 11 for beam exit. The two windows are arranged opposite each other, their positions and orientations designed according to the propagation paths of the wide parallel beam 7 and the converging beam 23. The entrance window 9 is located on one side of the vacuum cavity 10, used to introduce the wide parallel beam 7 and the converging beam 23 into the cavity; the exit window 11 is located on the other side of the vacuum cavity 10, used to guide the mixed light after passing through the plasma out of the cavity to the imaging receiving assembly. The window material of the vacuum cavity 10 should be selected according to the beam wavelength, and can be any one of fused silica, calcium fluoride, or zinc selenide. Anti-reflective coatings should be deposited on both sides of the window to improve beam transmittance. The window size should be large enough to ensure that the wide parallel beam 7 covers the entire cross-section of the plasma under test 10b, while providing sufficient space for the converging beam 23 to pass through at different incident angles. The spherical structure of the vacuum cavity 10 helps maintain a uniform magnetic field distribution and vacuum pressure, while also providing flexible geometric position selection for the optical window arrangement. Through the arrangement of the incident window 9 and the exit window 11, the wide parallel beam 7 and the converging beam 23 can maintain common path transmission while interacting with the plasma in a non-contact manner through the vacuum environment, avoiding obstruction or interference of the beam by the cavity structure.

[0095] Example 2

[0096] Please see Figure 2 This invention provides a spatially resolved coherent scattering imaging method for plasma turbulence measurement, applied to the system of Embodiment 1, comprising:

[0097] S1. Combine the local oscillator beam and the probe beam into a coaxial initial beam;

[0098] Specifically, this step combines the local oscillator light and the probe light from different light sources into a combined beam propagating along the same optical axis. In coherent scattering measurements, the two beams perform different functions, but a definite relative phase relationship is required for effective heterodyne detection. By combining the two beams using a beam combiner, they are made to completely overlap in space, experiencing the same optical medium and environmental disturbances in their subsequent propagation path. The beam combiner can be a beam splitter, allowing one beam to be transmitted while the other is reflected, with both beams propagating in the same direction behind the beam combiner; a dichroic mirror can be used, utilizing wavelength differences to combine the two beams; or a polarization beam combiner can be used, utilizing polarization characteristics to achieve beam combining. After beam combining, the relative phase difference between the two beams remains stable during propagation, providing a phase reference for subsequent heterodyne detection. Simultaneously, the coaxial, common-path structure avoids the need to recalibrate the spatial overlap of the two beams each time the probe light's incident angle is adjusted, simplifying the measurement process.

[0099] S2. The initial beam-combining beam is shaped into a wide parallel beam covering the plasma region to be tested, and a converging beam incident on the plasma region to be tested at an adjustable angle, wherein the wide parallel beam and the converging beam are propagated in the same path within the plasma region to be tested.

[0100] Specifically, this step processes the initial combined beam to generate two beams with different spatial shapes. The initial combined beam is first split into two paths, each retaining components of both the local oscillator and probe beams. The first path is processed by a beam-expanding optical system to form a wide parallel beam with a diameter expanded to cover the entire cross-section of the plasma under test. The beam-expanding optical system can employ a Keplerian or Galilean beam expander, which expands and collimates the beam diameter through a lens group, keeping the wavefront of the output beam parallel. The second path is processed by a focusing optical system to form a converging beam with a cross-sectional size compressed to be smaller than the wide parallel beam. The focusing optical system can employ a single lens or a lens combination, which focuses the beam energy to a smaller beam waist size. The incident direction of the converging beam is controlled by an angle adjustment mechanism, which can employ a rotating mirror group or a rotating prism group. The incident angle of the beam is adjusted by changing the orientation of the mirrors or prisms. At the output end, the wide parallel beam and the converging beam maintain a coaxial or intersecting geometric relationship, passing together through the plasma region under test. The local oscillator component in the wide parallel beam undergoes no or negligible scattering in the plasma, serving as the reference light for heterodyne detection and uniformly illuminating the entire measurement area. The probe component in the converging beam interacts with density fluctuations in the plasma to generate scattered light, the magnitude of which is determined by the incident angle of the converging beam. Since the two beams originate from the same initial combined beam, their spatial positional correspondence in the plasma is determined by the optical design, requiring no additional alignment steps. The wide parallel beam covers the entire radial cross-section, ensuring the presence of local oscillator light at all radial positions; the converging beam penetrates the plasma with a narrow cross-section, defining the spatial region where scattered light is generated. Every spatial point within this region is simultaneously illuminated by the local oscillator light from the wide parallel beam, satisfying the conditions for heterodyne detection.

[0101] S3. Image the measurement lines distributed along a one-dimensional direction in the plasma region to be measured onto a detector array, so that each detection unit of the detector array receives the scattered light from the corresponding spatial point and performs optical mixing with the local oscillator light component in the wide parallel beam, and outputs a signal characterizing the turbulent scattering intensity at the corresponding spatial point. The magnitude and direction of the scattered wave vector at the spatial point corresponding to each detection unit are consistent.

[0102] Specifically, this step involves imaging and receiving the mixed light emitted from the plasma and extracting its signal. The mixed light emitted from the plasma contains two components: scattered light generated by the interaction of the probe light in the converging beam with the plasma, and local oscillator light that passes through the plasma without scattering in the wide parallel beam. The imaging optical system images the measurement lines distributed radially along the plasma in this mixed light onto the photosensitive surface of the detector array at a certain magnification. The imaging optical system can employ a transmissive imaging lens group or a reflective imaging mirror group, using a combination of optical elements to guide light emitted from different spatial locations to the corresponding detection units on the detector array. The detector array is a radially arranged one-dimensional linear array containing multiple independent detection units. Each detection unit receives only the light signal from a small spatial region conjugate to itself within the plasma. Within this spatial region, the local oscillator light component and the scattered light component are simultaneously incident on the photosensitive surface of the detection unit, resulting in optical mixing. When the local oscillator and the probe light have the same frequency, the mixing output is a DC signal, and its amplitude is linearly related to the amplitude of the scattered light. When there is a slight difference in frequency between the two beams, the mixing output is a mid-frequency AC signal, and its amplitude is proportional to the amplitude of the scattered light, with a frequency equal to the frequency difference between the two beams. Because the wavefronts of the wide parallel beams are parallel, their wave vector directions are consistent throughout the plasma region. The incident angle of the converging beam is fixed, and its wave vector direction remains consistent throughout the measurement line. The design of the imaging optical system ensures that the scattered light collection direction corresponding to each object point uniquely corresponds to its image point position, and the geometric relationship between the scattered light collection direction and the incident light direction is the same at each point along the measurement line. Therefore, at all spatial points corresponding to the detector units, the magnitude and direction of the scattered wave vector (i.e., the vector difference between the incident and scattered light wave vectors) remain strictly consistent. By synchronously acquiring the output signals of all detector units, the one-dimensional spatial distribution of turbulent scattering intensity along the plasma radial direction under the current scattered wave vector can be obtained.

[0103] S4. Change the incident angle of the converging beam, repeat the above steps of changing the incident angle of the converging beam, repeat the above steps of imaging the measurement lines distributed along the one-dimensional direction in the plasma region to be measured onto the detector array, so that each detection unit of the detector array receives the scattered light from the corresponding spatial point and performs optical mixing with the local oscillator light component in the wide parallel beam, and outputs a signal characterizing the turbulent scattering intensity at the corresponding spatial point, thereby obtaining the spatial distribution of turbulent scattering intensity along the one-dimensional direction under different scattered wave vectors.

[0104] Specifically, this step achieves the scanning measurement of the scattered wave vector by changing the incident angle of the converging beam, thereby obtaining radial distribution information of turbulence at different spatial scales. The incident angle of the converging beam determines the direction of the probe wave vector, while the magnitude and direction of the scattered wave vector are determined by the vector difference between the incident and scattered wave vectors. When the incident angle of the converging beam changes, the spatial scale of turbulence satisfying the Bragg scattering condition also changes. The incident angle is adjusted by an angle adjustment mechanism, which can be a rotating mirror group or a rotating prism group. The incident direction of the converging beam is continuously adjusted by changing the orientation of the mirrors or prisms. Each time the incident angle is changed, a new scattered wave vector value is set. The system repeats the imaging and mixing steps, synchronously acquiring the output signals of all detection units on the detector array, and obtaining the one-dimensional spatial distribution of turbulent scattering intensity along the radial direction under the current scattered wave vector. By sequentially setting multiple incident angles within one scanning cycle, the system sequentially acquires radial distribution data corresponding to different scattered wave vectors. Finally, all measurement data were organized according to three dimensions: scattered wave vector, radial position, and scattered intensity, forming a three-dimensional dataset. The scattered wave vector dimension corresponds to different turbulent spatial scales, the radial position dimension corresponds to the spatial distribution of plasma from the core to the boundary, and the scattered intensity dimension characterizes the relative intensity of turbulence at the corresponding location and scale. Through this step, the system fully realizes spatially resolved measurements of the wavenumber spectrum of plasma micro-turbulence.

[0105] In some embodiments, shaping the initial combined beam into a wide parallel beam covering the region of the plasma under test, and a converging beam incident on the region of the plasma under test at an adjustable angle, includes:

[0106] The initial beam is divided into a first beam and a second beam, wherein both the first beam and the second beam contain components of local oscillator light and probe light.

[0107] The first beam is expanded to form a wide parallel beam covering the region of the plasma to be tested.

[0108] The second beam is focused to form a converging beam incident at an adjustable angle onto the plasma region to be tested.

[0109] Adjusting the incident angle of the converging beam changes the magnitude and direction of the scattered wave vector.

[0110] Specifically, this step divides the initial combined beam into a first beam and a second beam, both of which retain components of the local oscillator and the probe beam. The first beam is expanded to form a wide parallel beam covering the entire cross-section of the plasma to be tested. The second beam is focused to form a converging beam with a smaller cross-sectional size. The incident direction of the converging beam is controlled by an angle adjustment mechanism so that the converging beam is incident on the plasma region to be tested at an adjustable angle. The magnitude and direction of the scattered wave vector are determined by the incident angle of the converging beam.

[0111] 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.

[0112] 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 spatially resolved coherent scattering imaging system for plasma turbulence measurement, characterized in that, include: A beam combiner is used to combine the local oscillator beam and the probe beam into a single coaxial beam. A beam splitting and shaping component is disposed on the optical path of the initial beam combining light, and is used to shape the initial beam combining light into a wide parallel beam covering the plasma region to be tested, and a converging beam incident on the plasma region to be tested at an adjustable angle, wherein the wide parallel beam and the converging beam are transmitted along the same path within the plasma region to be tested. An imaging receiving component is used to image the measurement lines distributed along a one-dimensional direction in the plasma region to be measured onto a detector array, and to enable each detection unit of the detector array to receive the scattered light from the corresponding spatial point and perform optical mixing with the local oscillator component in the wide parallel beam, and output a signal characterizing the intensity of turbulent scattering at the corresponding spatial point; wherein the magnitude and direction of the scattered wave vector at the spatial point corresponding to each detection unit are consistent.

2. The system according to claim 1, characterized in that, The beam-splitting and shaping component includes: The first lens is used to expand the initial combined beam into expanded beam; A beam splitting element is used to split the expanded beam into a first expanded beam and a second expanded beam, wherein both the first expanded beam and the second expanded beam simultaneously contain components of local oscillator light and probe light. The second lens is used to focus the first expanded beam into a wide parallel beam. The third lens is used to focus the second beam-expanding light into a converging beam; The first reflection unit is used to adjust the wide parallel beam so that the wide parallel beam enters from the entrance window of the vacuum cavity and covers the plasma region to be measured. The second reflection unit is used to adjust the converging beam so that the converging beam enters from the incident window and forms an angle with the wide parallel beam.

3. The system according to claim 1, characterized in that, The imaging receiving component includes: An imaging optical unit is used to image the outgoing light corresponding to the wide parallel beam emitted from the exit window of the vacuum cavity onto the photosensitive surface of the detector array. The detector array is a one-dimensional linear detector array arranged radially.

4. The system according to claim 3, characterized in that, The imaging optical unit includes: The third reflection unit is disposed on the optical path after the wide parallel light passes through the plasma to be tested, and is used to reflect the outgoing light corresponding to the wide parallel beam emitted from the exit window of the vacuum cavity to the collecting lens group. The collecting lens group is used to focus the emitted light onto the detector array.

5. The system according to claim 1, characterized in that, Also includes: The first laser is used to emit local oscillator light; The second laser is used to emit probe light; When zero-difference measurement is required, the first laser and the second laser are configured to output beams with the same frequency; When heterodyne measurements are required, the first laser and the second laser are configured to output beams with similar frequencies.

6. The system according to claim 1, characterized in that, It also includes a spot monitoring unit for real-time monitoring and calibration of the spatial position of the probe light on the plasma under test.

7. The system according to claim 6, characterized in that, The light spot monitoring unit includes: A beam splitter is placed in the optical path of the converging beam after it passes through the plasma to be tested, and is used to guide part of the light to the spot monitor. A spot monitor is used to monitor and calibrate the spatial position of the probe light on the plasma under test in real time. A beam absorber is positioned on the optical path of the converging beam after it passes through the plasma to be tested, and is used to absorb the probe light that has not been scattered.

8. The system according to claim 1, characterized in that, It also includes a vacuum cavity, in which the plasma to be tested is disposed. The vacuum cavity is spherical and includes an incident window for the light beam to enter and an exit window for the light beam to exit.

9. A spatially resolved coherent scattering imaging method for plasma turbulence measurement, characterized in that, Applied to the system according to any one of claims 1-8, comprising: The local oscillator beam and the probe beam are combined into a single coaxial beam; The initial beam is shaped into a wide parallel beam covering the plasma region to be tested, and a converging beam incident on the plasma region to be tested at an adjustable angle, wherein the wide parallel beam and the converging beam are propagated in the same path within the plasma region to be tested. The measurement lines distributed along a one-dimensional direction in the plasma region to be measured are imaged onto a detector array. Each detection unit of the detector array receives the scattered light from the corresponding spatial point and performs optical mixing with the local oscillator component in the wide parallel beam, outputting a signal characterizing the intensity of turbulent scattering at the corresponding spatial point. The magnitude and direction of the scattered wave vector at the spatial point corresponding to each detection unit are consistent. By changing the incident angle of the converging beam, the above steps are repeated to image the measurement lines distributed along the one-dimensional direction in the plasma region to be measured onto the detector array, so that each detection unit of the detector array receives the scattered light from the corresponding spatial point and performs optical mixing with the local oscillator component in the wide parallel beam, and outputs a signal characterizing the turbulent scattering intensity at the corresponding spatial point, thereby obtaining the spatial distribution of turbulent scattering intensity along the one-dimensional direction under different scattered wave vectors.

10. The method according to claim 9, characterized in that, Shaping the initial combined beam into a wide parallel beam covering the region of the plasma under test, and a converging beam incident on the region of the plasma under test at an adjustable angle, includes: The initial beam is divided into a first beam and a second beam, wherein both the first beam and the second beam contain components of local oscillator light and probe light. The first beam is expanded to form a wide parallel beam covering the region of the plasma to be tested. The second beam is focused to form a converging beam incident at an adjustable angle onto the plasma region to be tested. Adjusting the incident angle of the converging beam changes the magnitude and direction of the scattered wave vector.

Images