Diagnostic system and method for measuring low-wavenumber turbulence of magnetic confinement fusion device

Abstract

The invention discloses a diagnostic system and method for measuring low-wavenumber turbulence of a magnetic confinement fusion device, and the system comprises a gold film plane mirror which is used for changing the direction of mixed light formed by coupling main laser and scattered light; the zinc sulfide lens is used for changing the proportion of the main laser and the scattered light in the mixed light to realize light beam separation; the aluminum alloy baffle is used for shielding most of the emitted high-power main laser; the first circular diaphragm is used for selecting the mixed light in a low wave number range and controlling the power; the second circular diaphragm and the third circular diaphragm are used for shielding stray light, collimating a light path and matching mixed light into the detector; the focusing lens is used for focusing the mixed light which is emitted and propagated along a specific direction; and the tellurium-cadmium-mercury detector is used for receiving a plasma scattered light signal in a specific direction. According to the invention, the proportion of light reflection and transmission is controlled by using the zinc sulfide lens with a special coating film so as to separate the main laser and the scattered light, and the measurement of the low-wavenumber turbulence in the magnetic confinement fusion device can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of ion-scale turbulence measurement in a magnetic confinement fusion device, and in particular to a diagnostic system and method for measuring low-wavenumber turbulence in a magnetic confinement fusion device. Background Art

[0002] CO2 laser coherent Thomson scattering is one of the key technologies for measuring wide wave number turbulence in plasma. As of 2023, experimental techniques based on coherent scattering have been developed on two major tokamaks in China. The CO2 laser coherent Thomson scattering system on the EAST tokamak device in China can measure 10-30cm in the same area. -1 Turbulence information in the wavenumber range. The CO2 laser coherent Thomson scattering system on the Chinese HL-2A Tokamak device can measure 10-50cm -1 Turbulence information over a wide wavenumber range.

[0003] The shortcoming of the existing technology is that, under the condition of minimizing the aperture of the vacuum chamber of the tokamak device, the CO2 laser coherent Thomson scattering diagnosis has great potential in wide wave number turbulence measurement. However, the measurement scale of this diagnosis is not diverse enough, and the measurement scale of turbulence information in the same area is small. Currently, it can only monitor electron scale turbulence, and cannot measure ion scale turbulence, which requires lower wave number diagnosis.

[0004] For electron-scale measurements, the high-power main beam (~8W) will separate low-power local oscillator light (~1mW) with the corresponding scattering angle before entering the device. The power ratio between the two is about 1:0.0001. After the local oscillator light and the main beam enter the device together and are scattered by the plasma, the scattered light will couple with the local oscillator light and be collected by the detector to obtain turbulence information of the corresponding scale. However, for ion-scale monitoring, there are two main problems. The first is beam separation, with a wave number of 5cm -1 The measurement corresponds to an extremely small scattering angle of 0.05°. It is extremely difficult to separate the main beam and the local oscillator light, and the two are difficult to distinguish. The second is signal detection. The high-power main beam is easy to shift within a very small angle, causing the center of the Gaussian beam to deviate, thereby breaking through the detector probe. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art. To achieve the above purpose, a diagnostic system and method for measuring low-wavenumber turbulence in a magnetic confinement fusion device is used to solve the problems raised in the above background technology.

[0006] A diagnostic system for measuring low-wavenumber turbulence in a magnetic confinement fusion device, the diagnostic system comprising a gold film plane reflector, 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 plane 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 light beams;

[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 mixed light in a low wave number range and control the power;

[0011] The second circular aperture and the third circular aperture are used to shield stray light, collimate the light 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 in a specific direction.

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

[0015] As a further solution of the present invention: the zinc sulfide lens includes a first front surface coated with an anti-reflection film, a second front surface not coated with the film, and a back surface coated with an anti-reflection film.

[0016] As a further solution of the present invention: the anti-reflection film is set at an angle of 45°, that is, it can enhance the transmittance of 45° carbon dioxide laser.

[0017] As a further solution of the present invention: the shielding ratio of the aluminum alloy baffle is selected according to the measured wave number range.

[0018] As a further solution of the present invention: the first circular aperture selects the wave number range and controls the power of the mixed light by adjusting the three-dimensional position of the aperture and the aperture size.

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

[0020] A technical solution in another aspect: a diagnostic method using a diagnostic system for measuring low-wavenumber turbulence in a magnetic confinement fusion device as described in any one of the above items, comprising the following steps:

[0021] Step S1, after passing through the EAST fusion device, the carbon dioxide laser becomes a mixture of the main laser and the scattered light, which is first reflected by a gold film plane reflector to change the propagation direction of the beam;

[0022] Step S2, the mixed light is beam split through a zinc sulfide lens coated with an anti-reflection film, most of the main laser passes through the high transmittance area and is blocked by the aluminum alloy baffle, and the required mixed light passes through the low transmittance area to reach the first circular aperture. In the mixed light after beam splitting, the ratio of the main laser to the scattered light changes, and the proportion of the scattered light increases;

[0023] Step S3, after the split mixed light passes through the first circular aperture, the power is reduced, and the wave number range for turbulence measurement is selected by controlling the aperture position and aperture size;

[0024] Step S4, the selected mixed light reaches the center of the mirror surface of the focusing lens under the collimation of the second circular aperture and the third circular aperture; at the same time, the aperture can prevent stray light from entering the detector and causing damage to the detector;

[0025] Step S5: The focusing lens focuses the mixed light propagating in the specific direction and forms an image on the probe photosensitive area of ​​the mercury cadmium telluride detector.

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

[0027] As a further solution 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 to the probe photosensitive area of ​​the mercury cadmium telluride detector, and its field of view angle is 2°.

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

[0029] By adopting the above technical solution, a new splitter optical path is designed and the ratio of light reflection and transmission is controlled by using specially coated zinc sulfide lenses to separate the main laser and scattered light, which can realize the measurement of low wavenumber turbulence. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings:

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

[0032] Figure 2 It is a front schematic diagram of the diagnostic system of the disclosed embodiment of the present application measuring low wave number turbulence in the EAST device;

[0033] Figure 3 This is a diagram showing the zinc sulfide spectrometer lens with a special coating process according to an embodiment disclosed in the present application.

[0034] In the figure: 1. gold film plane reflector; 2. zinc sulfide lens; 21. first positive surface; 22. second positive 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 DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Please refer to Figure 1 and Figure 2 In an embodiment of the present invention, a diagnostic system for measuring low-wavenumber turbulence in a magnetic confinement fusion device comprises a gold film plane reflector 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 plane reflector 1, used to change the direction of mixed light formed by coupling of main laser and scattered light;

[0038] A zinc sulfide lens 2, used for changing the ratio of the main laser and the scattered light in the mixed light to separate the light beams;

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

[0040] A first circular aperture 4 is used to select mixed light in a low wave number range and control the power;

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

[0042] A focusing lens 7, used for focusing 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 in a specific direction.

[0044] In this embodiment, the gold film plane reflector 1 is a circular structure, and its surface is all gold-plated reflective film, and the reflectivity of the 10.6μm wavelength carbon dioxide laser is greater than 95%. By adjusting the circular plane reflector, the propagation direction of the main laser and scattered light in the measurement area can be changed. Due to the limited measurement area, there are other circular gold film plane reflectors 1 in the optical path to highlight the effective optical path, such as Figure 1 As shown, four gold film plane reflectors 1 of different sizes are omitted.

[0045] In this embodiment, the zinc sulfide lens 2 includes a first front surface 21 coated with an anti-reflection film, a second front surface 22 not coated with the film, and a rear surface 23 coated with an anti-reflection film.

[0046] In this embodiment, the antireflection film is arranged 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 shielding ratio of the aluminum alloy baffle 3 depends on the measured wave number range. The aluminum alloy baffle 3 shields most of the high-power main laser emitted from the EAST Tokamak device, and the specific shielding ratio depends on the measured wave number range. The high-power main laser can be terminated in time to avoid danger.

[0048] In this embodiment, the first circular aperture 4 selects the wave number range and controls the power of the mixed light by adjusting the three-dimensional position of the aperture and the aperture size. The entire surface is blackened to reduce harmful reflections.

[0049] The second circular aperture 5 and the third circular aperture 6 shield the stray light of the non-ideal Gaussian beam to prevent the stray light from entering the detector and causing damage to the detector. Figure 1 The light path shown is a straight line light path, and the actual light path is more complicated. The second circular aperture 5 and the third circular aperture 6 can collimate the light path and match the mixed light into the detector.

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

[0051] A technical solution in another aspect: a diagnostic method for measuring low-wavenumber turbulence in a magnetic confinement fusion device using a diagnostic system as described in any one of the above, comprising the following steps:

[0052] Step S1, after passing through the EAST fusion device, the carbon dioxide laser becomes a mixture of the main laser and the scattered light, which is first reflected by the gold film plane reflector 1 to change the propagation direction of the beam;

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

[0054] Step S3, after the split mixed light passes through the first circular aperture 4, the power is reduced, and the wave number range for turbulence measurement is selected by controlling the aperture position and aperture size;

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

[0056] Step S5 , the focusing lens 7 focuses the mixed light propagating in the specific direction and forms an image on the probe photosensitive area 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 the stray light of the non-ideal Gaussian light beam to prevent the stray light from entering the detector and causing damage to the detector.

[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 to the probe photosensitive area of ​​the mercury cadmium telluride detector 8, and its field of view angle is 2°.

[0059] like Figure 3 As shown, the figure shows the zinc sulfide spectroscopic lens with special coating process;

[0060] The zinc sulfide lens 2 coated with an anti-reflection film includes a first front surface 21 coated with a 45° anti-reflection film, and most of the main laser light is transmitted through this area. The uncoated second front surface 22 reflects a small portion of the mixed light of the main laser light and the scattered light. The back surface 23 coated with a 45° anti-reflection film, and most of the main laser light is transmitted through this area.

[0061] The reflectivity of the carbon dioxide laser on the zinc sulfide lens is 13.9%, and the refractive index is 2.192. The elliptical part of the front surface of the zinc sulfide lens is coated with an anti-reflection film. When the lens is placed at an angle of 45°, the transmittance of the non-coated area to the carbon dioxide laser is 86%. The first front surface 21 coated with a 45° anti-reflection film and the back surface 23 coated with a 45° anti-reflection film, when the lens is placed at an angle of 45°, the transmittance of the coated area to the carbon dioxide laser is 99%. Most of the main laser is transmitted from the elliptical area and then blocked by the aluminum alloy baffle 3.

[0062] The uncoated second front surface 22 reflects a small portion of the mixed light of the main laser and the scattered light, which is the detection object of the diagnostic system and will enter the detector. The whole process will change the ratio of the main laser and the scattered light in the mixed light to achieve accurate beam separation.

[0063] Working principle:

[0064] For the CO2 laser coherent scattering diagnostic system used in the 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 scattered power, the total scattered power is

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

[0067] According to the conservation of energy and momentum, the relationship between the frequency w of electron density fluctuation 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 CO2 laser coherent scattering diagnostic system, the CO2 laser can maintain a stable wave number (k i ~5927cm -1 ), frequency (ω i ~28THz).

[0069] In isosceles triangle geometric shape Internal, scattering angle θ s Meeting the Prague condition k = 2k i sin(θ s / 2).

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

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

[0072] When the CO2 laser passes through the plasma, the light in a very small scattering angle is a mixture of the scattered light and a portion of the main laser. The main laser has the form of a Gaussian beam, and its intensity distribution follows

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

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

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

Claims

1. A diagnostic system for measuring low-wavenumber turbulence in a magnetic confinement fusion device, characterized in that: The diagnostic system comprises a gold film plane reflector, 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 plane 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 light beams; 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 mixed light in a low wave number range and control the power; The second circular aperture and the third circular aperture are used to shield stray light, collimate the light 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 in a specific direction.

2. A diagnostic system for measuring low-wavenumber turbulence in a magnetic confinement fusion device according to claim 1, characterized in that: The gold film plane reflector is a circular structure, the surface of which is all coated with a gold reflective film, and the reflectivity of the carbon dioxide laser with a wavelength of 10.6 μm is greater than 95%.

3. A diagnostic system for measuring low-wavenumber turbulence in a magnetic confinement fusion device according to claim 1, characterized in that: The zinc sulfide lens comprises a first front surface coated with an anti-reflection film, a second front surface not coated with the film, and a back surface coated with an anti-reflection film.

4. A diagnostic system for measuring low-wavenumber turbulence in a magnetic confinement fusion device according to claim 1, characterized in that: The anti-reflection film is set at an angle of 45°, that is, it can enhance the transmittance of 45° carbon dioxide laser.

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

6. A 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 wave number range and controls the power of the mixed light by adjusting the three-dimensional position of the aperture and the aperture size.

7. A 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±0.2 cm, and the aperture Φ is 3±0.1 cm.

8. A diagnostic method using a diagnostic system for measuring low-wavenumber turbulence in a magnetic confinement fusion device as claimed in any one of claims 1 to 7, characterized in that: The following steps are involved: Step S1, after passing through the EAST fusion device, the carbon dioxide laser becomes a mixture of the main laser and the scattered light, which is first reflected by a gold film plane reflector to change the propagation direction of the beam; Step S2, the mixed light is beam split through a zinc sulfide lens coated with an anti-reflection film, most of the main laser passes through the high transmittance area and is blocked by the aluminum alloy baffle, and the required mixed light passes through the low transmittance area to reach the first circular aperture. In the mixed light after beam splitting, the ratio of the main laser to the scattered light changes, and the proportion of the scattered light increases; Step S3, after the split mixed light passes through the first circular aperture, the power is reduced, and the wave number range for turbulence measurement is selected by controlling the aperture position and aperture size; Step S4, the selected mixed light reaches the center of the mirror surface of the focusing lens under the collimation of the second circular aperture and the third circular aperture; at the same time, the aperture can prevent stray light from entering the detector and causing damage to the detector; Step S5: The focusing lens focuses the mixed light propagating in the specific direction and forms an image on the probe photosensitive area of ​​the mercury cadmium telluride detector.

9. A diagnostic system for measuring low-wavenumber turbulence in a magnetic confinement fusion device according to claim 8, characterized in that: The second circular aperture and the third circular aperture are used to shield the stray light of the non-ideal Gaussian light beam to prevent the stray light from entering the detector and causing damage to the detector.

10. A diagnostic system for measuring low-wavenumber turbulence in a magnetic confinement fusion device according to claim 8, 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 probe photosensitive area of ​​the mercury cadmium telluride detector, and its field of view angle is 2°.

Images