A diagnostic system and method for measuring low-wavenumber turbulence in a magnetic confinement fusion device

Abstract

The application discloses a kind of diagnostic system and method for measuring low wave number turbulence of magnetic confinement fusion device, including gold film plane mirror, for changing the direction of mixed light formed by main laser and scattered light coupling;Zinc sulfide lens, for changing the proportion of main laser and scattered light in mixed light to beam separation;Aluminum alloy baffle, for shielding most of the high-power main laser emitted;First circular diaphragm, for selecting low wave number range mixed light and controlling power size;Second circular diaphragm and third circular diaphragm, for shielding stray light, collimating optical path and matching mixed light into detector;Focusing lens, for focusing mixed light emitted and propagated along a particular direction;Tellurium cadmium mercury detector, for receiving plasma scattered light signal in a particular direction.The application can realize the measurement of low wave number turbulence in magnetic confinement fusion device by using special coated zinc sulfide lens to control the ratio of light reflection and transmission to separate main laser and scattered light.

Description

Technical Field

[0001] This invention relates to the field of ion-scale turbulence measurement technology for magnetic confinement fusion devices, and particularly to a diagnostic system and method for measuring low wavenumber turbulence in magnetic confinement fusion devices. Background Technology

[0002] Coherent Thomson scattering using carbon dioxide lasers is one of the key techniques for measuring wide-wavenumber turbulence in plasmas. As of 2023, experimental techniques based on coherent scattering have been developed on two major tokamak facilities in China. The carbon dioxide laser coherent Thomson scattering system on the EAST tokamak facility in China can measure 10-30 cm⁻¹ regions in the same area. -1 Turbulence information within the wavenumber range can be measured using the CO2 laser coherent Thomson scattering system on the HL-2A Tokamaca facility in China, which can measure turbulence from 10 to 50 cm⁻¹. -1 Turbulence information within the wavenumber range.

[0003] The limitation of existing technologies is that, while carbon dioxide laser coherent Thomson scattering diagnostics has considerable potential for wide-wavenumber turbulence measurements under the condition of minimizing the aperture of the vacuum chamber in a tokamak device, its measurement scale is not diverse enough. Turbulence information in the same region is measured on a small scale, and currently it can only monitor electronic-scale turbulence, unable to measure ion-scale turbulence. Diagnostics with even lower wavenumbers are needed.

[0004] For electron-scale measurements, the high-power main beam (~8W) is separated into a low-power local oscillator beam (~1mW) with a corresponding scattering angle before entering the device, with a power ratio of approximately 1:0.0001. The local oscillator beam and the main beam enter the device together and are scattered by the plasma. The scattered light then couples with the local oscillator beam and is collected by a detector to obtain turbulence information at the corresponding scale. However, for ion-scale monitoring, two main challenges arise: firstly, beam separation at a wavenumber of 5 cm⁻¹. -1 The measurement corresponds to an extremely small scattering angle of 0.05°, making the separation of the main beam and the local oscillator extremely difficult, and the two are hard to distinguish. Secondly, in signal detection, the high-power main beam is prone to displacement within a very small angle, causing the center of the Gaussian beam to deviate, thereby breaking down the detector probe. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology. To achieve the above objective, a diagnostic system and method for measuring low wavenumber turbulence in a magnetic confinement fusion device are provided to solve the problems mentioned in the background art.

[0006] A diagnostic system for measuring low wavenumber turbulence in a magnetic confinement fusion device, the diagnostic system comprising a gold film plane mirror, a zinc sulfide lens, an aluminum alloy baffle, a first circular aperture, a second circular aperture, a third circular aperture, a focusing lens, and a mercury cadmium telluride detector.

[0007] The gold film planar reflector is used to change the direction of the mixed light formed by the coupling of the main laser and the scattered light;

[0008] The zinc sulfide lens is used to change the ratio of the main laser and the scattered light in the mixed light to separate the beam.

[0009] The aluminum alloy baffle is used to block most of the high-power main laser emitted from the EAST tokamak device.

[0010] The first circular aperture is used to select the mixed light in the low wavenumber range and control the power level;

[0011] The second and third circular apertures are used to shield stray light, collimate the optical path, and match the mixed light into the detector;

[0012] The focusing lens is used to focus the mixed light emitted from the EAST tokamak device and propagating in a specific direction;

[0013] The mercury cadmium telluride detector is used to receive plasma scattered light signals from a specific direction.

[0014] As a further aspect of the present invention: the gold film plane mirror has a circular structure, and its surface is all plated with a gold reflective film, and its reflectivity to carbon dioxide laser with a wavelength of 10.6μm is greater than 95%.

[0015] As a further aspect of the present invention: the zinc sulfide lens includes a first front surface coated with an anti-reflective film, a second front surface without a film, and a back surface coated with an anti-reflective film.

[0016] As a further aspect of the present invention: the antireflection film is set at an angle of 45°, that is, it is used for antireflection of carbon dioxide laser at a 45° angle.

[0017] As a further aspect of the present invention, the shading ratio of the aluminum alloy baffle is selected according to the measured wavenumber range.

[0018] As a further aspect of the present invention: the first circular aperture selects the wavenumber range by adjusting the three-dimensional position of the aperture and the size of the aperture, while controlling the power of the mixed light.

[0019] As a further aspect of the present invention: the focal length of the focusing lens is F = 25cm and the aperture is Φ = 3cm.

[0020] Another technical solution: A diagnostic method using a diagnostic system for measuring low-wavenumber turbulence in a magnetically confined fusion device as described in any of the above claims, comprising the following steps:

[0021] Step S1: After passing through the EAST fusion device, the carbon dioxide laser becomes a mixture of main laser and scattered light. It is first reflected by a gold film plane mirror, which changes the direction of beam propagation.

[0022] Step S2: The mixed light is split by passing through a zinc sulfide lens coated with an anti-reflection film. Most of the main laser is blocked by an aluminum alloy baffle in the high transmittance region, and the required mixed light reaches the first circular aperture through the low transmittance region. In the mixed light after beam splitting, the ratio of the main laser and the scattered light changes, and the proportion of the scattered light increases.

[0023] Step S3: After the mixed light after beam splitting passes through the first circular aperture, the power decreases. By controlling the position and aperture size of the aperture, the selection of the wavenumber range for turbulence measurement is completed.

[0024] Step S4: The selected mixed light, collimated by the second and third circular apertures, reaches the center of the focusing lens; at the same time, the apertures can prevent stray light from entering the detector and causing damage to the probe.

[0025] Step S5: The focusing lens will focus the mixed light propagating in the above-mentioned specific direction and image it onto the photosensitive area of ​​the mercury cadmium telluride detector.

[0026] As a further aspect of the present invention: the second circular aperture and the third circular aperture are used to shield stray light from non-ideal Gaussian beams, so as to prevent stray light from entering the detector and causing damage to the probe.

[0027] As a further aspect of the present invention: the focusing lens focuses the mixed light emitted from the EAST tokamak device and propagating in a specific direction, and images it onto the photosensitive area of ​​the probe of the mercury cadmium telluride detector, with a field of view of 2°.

[0028] Compared with the prior art, the present invention has the following technical advantages:

[0029] By adopting the above technical solution, a new beam splitting optical path is designed, and a specially coated zinc sulfide lens is used to control the ratio of light reflection and transmission to separate the main laser and scattered light, which enables the measurement of low wavenumber turbulence. Attached Figure Description

[0030] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings:

[0031] Figure 1 This is a schematic diagram of the structure of the diagnostic system disclosed in this application measuring low wavenumber turbulence on an EAST device;

[0032] Figure 2 A frontal schematic diagram of the diagnostic system of this application measuring low wavenumber turbulence on an EAST device, according to an embodiment of this application.

[0033] Figure 3 This is a diagram illustrating a zinc sulfide beam splitter using a special coating process according to an embodiment of this application.

[0034] In the diagram: 1. Gold film plane mirror; 2. Zinc sulfide lens; 21. First front surface; 22. Second front surface; 23. Back surface; 3. Aluminum alloy baffle; 4. First circular aperture; 5. Second circular aperture; 6. Third circular aperture; 7. Focusing lens; 8. Mercury cadmium telluride detector. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Please refer to Figure 1 and Figure 2 In this embodiment of the invention, a diagnostic system for measuring low wavenumber turbulence in a magnetic confinement fusion device is provided. The diagnostic system includes a gold film plane mirror 1, a zinc sulfide lens 2, an aluminum alloy baffle 3, a first circular aperture 4, a second circular aperture 5, a third circular aperture 6, a focusing lens 7, and a mercury cadmium telluride detector 8.

[0037] Gold film planar reflector 1 is used to change the direction of the mixed light formed by the coupling of the main laser and the scattered light;

[0038] Zinc sulfide lens 2 is used to change the ratio of the main laser and the scattered light in the mixed light to separate the beam;

[0039] Aluminum alloy baffle 3 is used to block most of the high-power main laser emitted from the EAST tokamak device;

[0040] The first circular aperture 4 is used to select the mixed light in the low wavenumber range and control the power.

[0041] The second circular stop 5 and the third circular stop 6 are used to shield stray light, collimate the optical path, and match the mixed light into the detector.

[0042] Focusing lens 7 is used to focus the mixed light emitted from the EAST tokamak device and propagating in a specific direction;

[0043] The mercury cadmium telluride detector 8 is used to receive plasma scattered light signals from a specific direction.

[0044] In this embodiment, the gold-coated plane mirror 1 is a circular structure, with its surface entirely coated with a gold reflective film. It exhibits a reflectivity greater than 95% for 10.6μm wavelength carbon dioxide laser light. By adjusting the circular plane mirror, the propagation directions of the main laser and scattered light within the measurement area can be changed. Due to the limited measurement area, other circular gold-coated plane mirrors 1 exist in the optical path. To highlight the effective optical path, such as... Figure 1 As shown, four gold-coated planar mirrors of different sizes are omitted.

[0045] In this embodiment, the zinc sulfide lens 2 includes a first front surface 21 coated with an anti-reflective film, a second front surface 22 without a coating, and a back surface 23 coated with an anti-reflective film.

[0046] In this embodiment, the antireflective coating is set at an angle of 45°. When the lens is placed at an angle of 45°, the transmittance of the coating area to the carbon dioxide laser is 99%.

[0047] In this embodiment, the blocking ratio of the aluminum alloy baffle 3 depends on the measured wavenumber range. The aluminum alloy baffle 3 blocks most of the high-power main laser emitted from the EAST tokamak device, with the specific blocking ratio depending on the measured wavenumber range. This allows for timely termination of the high-power main laser, preventing potential hazards.

[0048] In this embodiment, the first circular aperture 4 selects the wavenumber range and controls the power of the mixed light by adjusting the three-dimensional position and aperture size of the aperture. The overall black surface treatment reduces harmful reflections.

[0049] The second circular stop 5 and the third circular stop 6 shield stray light from non-ideal Gaussian beams, preventing stray light from entering the detector and causing damage. For example... Figure 1 The diagram shows a linearized optical path; the actual optical path is more complex. The second circular stop 5 and the third circular stop 6 collimate the optical path, matching the mixed light into the detector.

[0050] In this embodiment, the focal length of the focusing lens 7 is F = 25cm and the aperture is Φ = 3cm.

[0051] Another technical solution: A diagnostic method for a diagnostic system for measuring low-wavenumber turbulence in a magnetically confined fusion device, applying any of the above methods, includes the following steps:

[0052] Step S1: After passing through the EAST fusion device, the carbon dioxide laser becomes a mixture of main laser and scattered light. It is first reflected by the gold film plane mirror 1, which changes the direction of beam propagation.

[0053] Step S2: The mixed light is split by the zinc sulfide lens 2 coated with an anti-reflection film. Most of the main laser is blocked by the aluminum alloy baffle 3 through the high transmittance area. The required mixed light reaches the first circular aperture through the low transmittance area. In the mixed light after beam splitting, the ratio of the main laser and the scattered light changes and the proportion of the scattered light increases.

[0054] Step S3: After the mixed light after beam splitting passes through the first circular aperture 4, the power decreases. By controlling the position and aperture size of the aperture, the selection of the wavenumber range for turbulence measurement is completed.

[0055] Step S4: The selected mixed light, collimated by the second circular aperture 5 and the third circular aperture 6, reaches the center of the mirror surface of the focusing lens 7; at the same time, the aperture can prevent stray light from entering the detector and causing damage to the probe.

[0056] In step S5, the focusing lens 7 will focus the mixed light propagating in the above-mentioned specific direction and image it onto the photosensitive area of ​​the probe of the mercury cadmium telluride detector 8.

[0057] In this embodiment, the second circular aperture 5 and the third circular aperture 6 are used to shield stray light from non-ideal Gaussian beams, preventing stray light from entering the detector and causing damage to the probe.

[0058] In this embodiment, the focusing lens 7 focuses the mixed light emitted from the EAST tokamak device and propagating in a specific direction, and images it onto the photosensitive area of ​​the probe of the mercury cadmium telluride detector 8, with a field of view of 2°.

[0059] like Figure 3 The image shown is a display diagram of a zinc sulfide beam splitter with a special coating process.

[0060] The zinc sulfide lens 2 coated with an anti-reflective coating includes a first front surface 21 coated with a 45° anti-reflective coating, through which most of the main laser light passes. A second front surface 22, without coating, reflects a small portion of the mixed light from the main laser and scattered light. A back surface 23 coated with a 45° anti-reflective coating, through which most of the main laser light passes.

[0061] The carbon dioxide laser has a reflectivity of 13.9% and a refractive index of 2.192 on the zinc sulfide lens. The elliptical portion of the front surface of the zinc sulfide lens is coated with an anti-reflection film; when the lens is placed at a 45° angle, the transmittance of the uncoated area to the carbon dioxide laser is 86%. The first front surface 21 and the back surface 23, both coated with a 45° anti-reflection film, have a transmittance of 99% to the carbon dioxide laser when the lens is placed at a 45° angle. Most of the main laser beam passes through this elliptical region and is subsequently blocked by the aluminum alloy baffle 3.

[0062] The uncoated second positive surface 22 reflects a small portion of the mixed light of the main laser and scattered light. This mixed light is the target of the diagnostic system and will enter the detector. The entire process will change the ratio of the main laser to the scattered light in the mixed light to achieve precise beam separation.

[0063] Working principle:

[0064] For a carbon dioxide laser coherent scattering diagnostic system applied to a tokamak device, the spectrum and angular distribution of the scattered light reveal the density turbulence spectrum, |n e (k,ω) 2 .

[0065] After integrating the differential scattering power, the total scattering power is:

[0066] Wherein, the probe optical power is P i The classical radius of the electron is r e The scattering volume length is L, and the probe light wavelength is λ. i =2π / k i Electron density fluctuation is

[0067] According to the law of conservation of energy and momentum, the relationship between the frequency w of electron density fluctuations and the wave vector k is ω = ω s -ω i and k = k s -k i The subscripts s and i represent the scattered wave and the incident wave, respectively.

[0068] In the EAST tokamak device's carbon dioxide laser coherent scattering diagnostic system, the carbon dioxide laser can maintain a stable wavenumber (k). i ~5927cm -1 ), frequency (ω) i ~28THz).

[0069] In the geometry of an isosceles triangle Inner scattering angle θ s Satisfying the Bragg condition k = 2k i sin(θ s / 2).

[0070] Therefore, in practical optical device configurations, the scattering angle θ can be adjusted. s The Bragg condition is satisfied to measure the fluctuation of a certain wave number k.

[0071] The angle θ of the low wavenumber turbulence measurement method of the present invention s ~0.05°, corresponding to a wavenumber k ~5cm -1 .

[0072] When a carbon dioxide laser passes through plasma, the light within a very small scattering angle is composed of scattered light and a portion of the main laser beam. The main laser beam has a Gaussian beam shape, and its intensity distribution follows...

[0073] As the scattering angle decreases with k, the turbulence scale increases. When the scale increases to k... θ ρ s When the value is ≤0.5, the measured turbulence scale is ion scale, and the mixed light contains information about low-k turbulence.

[0074] When the intensity of the scattered light is comparable to that of the main laser, their mixing can achieve interference of turbulence information.

[0075] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention. The scope of the invention is defined by the appended claims and their equivalents, all of which should be included within the scope of protection of the invention.

Claims

1. A diagnostic system for measuring low-wavenumber turbulence in a magnetic confinement fusion device, characterized in that, The diagnostic system includes a gold-film plane mirror, a zinc sulfide lens, an aluminum alloy baffle, a first circular aperture, a second circular aperture, a third circular aperture, a focusing lens, and a mercury cadmium telluride detector. The gold film planar reflector is used to change the direction of the mixed light formed by the coupling of the main laser and the scattered light; The zinc sulfide lens is used to change the ratio of the main laser and the scattered light in the mixed light to separate the beam. The zinc sulfide lens includes a first front surface coated with an anti-reflection film, a second front surface without a film, and a back surface coated with an anti-reflection film, so that most of the main laser is transmitted through the coated area and blocked by the aluminum alloy baffle, while a small part of the main laser and the scattered light are reflected through the uncoated area and enter the first circular aperture. The aluminum alloy baffle is used to block most of the high-power main laser emitted from the EAST tokamak device. The first circular aperture is used to select the mixed light in the low wavenumber range and control the power level; The second and third circular apertures are used to shield stray light, collimate the optical path, and match the mixed light into the detector; The focusing lens is used to focus the mixed light emitted from the EAST tokamak device and propagating in a specific direction; The mercury cadmium telluride detector is used to receive plasma scattered light signals from a specific direction.

2. The diagnostic system for measuring low-wavenumber turbulence in a magnetic confinement fusion device according to claim 1, characterized in that, The gold-coated planar reflector has a circular structure, and its surface is covered with a gold-coated reflective film. It has a reflectivity of more than 95% for carbon dioxide laser with a wavelength of 10.6 μm.

3. The diagnostic system for measuring low-wavenumber turbulence in a magnetic confinement fusion device according to claim 1, characterized in that, The antireflective coating is set at an angle of 45°, which means it is effective against carbon dioxide lasers at a 45° angle.

4. The diagnostic system for measuring low-wavenumber turbulence in a magnetic confinement fusion device according to claim 1, characterized in that, The shading ratio of the aluminum alloy baffle is selected according to the measured wavenumber range.

5. The diagnostic system for measuring low-wavenumber turbulence in a magnetic confinement fusion device according to claim 1, characterized in that, The first circular aperture selects the wavenumber range by adjusting the three-dimensional position of the aperture and the size of the aperture, while controlling the power of the mixed light.

6. The diagnostic system for measuring low-wavenumber turbulence in a magnetic confinement fusion device according to claim 1, characterized in that, The focal length of the focusing lens is F=25±0.2cm, and the aperture is Φ=3±0.1cm.

7. A diagnostic method for using a diagnostic system for measuring low-wavenumber turbulence in a magnetically confined fusion device as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Step S1: After passing through the EAST fusion device, the carbon dioxide laser becomes a mixture of main laser and scattered light. It is first reflected by a gold film plane mirror, which changes the direction of beam propagation. Step S2: The mixed light is split by passing through a zinc sulfide lens coated with an anti-reflection film. Most of the main laser is blocked by an aluminum alloy baffle in the high transmittance region, and the required mixed light reaches the first circular aperture through the low transmittance region. In the mixed light after beam splitting, the ratio of the main laser and the scattered light changes, and the proportion of the scattered light increases. Step S3: After the mixed light after beam splitting passes through the first circular aperture, the power decreases. By controlling the position and aperture size of the aperture, the selection of the wavenumber range for turbulence measurement is completed. Step S4: The selected mixed light, collimated by the second and third circular apertures, reaches the center of the focusing lens; at the same time, the apertures can prevent stray light from entering the detector and causing damage to the probe. Step S5: The focusing lens will focus the mixed light propagating in the above-mentioned specific direction and image it onto the photosensitive area of ​​the mercury cadmium telluride detector.

8. The diagnostic method for a diagnostic system for measuring low-wavenumber turbulence in a magnetic confinement fusion device according to claim 7, characterized in that, The second and third circular apertures are used to shield stray light from non-ideal Gaussian beams, preventing stray light from entering the detector and causing damage to the probe.

9. The diagnostic method for a diagnostic system for measuring low-wavenumber turbulence in a magnetic confinement fusion device according to claim 7, characterized in that, The focusing lens focuses the mixed light emitted from the EAST tokamak device and propagating in a specific direction, and images it onto the photosensitive area of ​​the mercury cadmium telluride detector, with a field of view of 2°.

Images