A visible light bremsstrahlung diagnostic device and a method for measuring electron density profiles in fusion plasma

Abstract

This invention discloses a visible light bremsstrahlung diagnostic device and a method for measuring the electron density profile of fusion plasma. The visible light bremsstrahlung diagnostic device includes a vacuum chamber, an objective lens, an optical fiber, a spectrometer, and a spectral detector. The vacuum chamber is used to generate plasma and has an observation window. The objective lens, optical fiber, spectrometer, and spectral detector are sequentially connected to form an optical diagnostic system for observation. Accordingly, the front end of the objective lens faces the observation window, and the visible light bremsstrahlung of the plasma is observed through the observation window. The method for measuring the electron density profile of fusion plasma includes the following steps: S100 Measurement: Measuring the radiation of the plasma using the visible light bremsstrahlung diagnostic device; S200 Calculation: Calculating the plasma electron density profile using a formula. Compared with existing contact measurement methods, the visible light bremsstrahlung diagnostic device and the method for measuring the electron density profile of fusion plasma provide a non-contact, interference-free measurement method.

Description

Technical Field

[0001] This invention relates to the field of plasma measurement methods, specifically to a visible light bremsstrahlung diagnostic device and a method for measuring the electron density profile of fusion plasma. Background Technology

[0002] The measurement of fundamental parameter profiles of magnetically confined fusion plasma, such as electron density and temperature, ion temperature and rotational velocity, current density, and safety factor, provides important data support for the control of high-temperature plasma parameters and the safe operation of the device, and also provides important data assurance for the physical analysis of plasma confinement and transport.

[0003] The measurement of electron density profile in the main plasma region is generally based on laser diagnostic technology. It introduces plasma from outside the device and detects relevant parameters of the plasma (such as electron and ion density, temperature, magnetic field, etc.) through the interaction between the laser probe and the plasma, and has high spatiotemporal resolution.

[0004] Under certain conditions, the interaction between laser and high-temperature plasma is weak, thus not causing serious interference to the high-temperature plasma. Generally, the plasma electron density profile is measured using laser scattering and laser interferometry. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that the existing technology measures the electron density profile of plasma through contact measurement methods. The purpose of the present invention is to provide a visible light bremsstrahlung diagnostic device and a method for measuring the electron density profile of fusion plasma by utilizing the spontaneous emission of high-temperature plasma. This is a non-contact, interference-free measurement method, which can serve as another effective means of measuring electron density.

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

[0007] In a first aspect, the present invention provides a visible light bremsstrahlung diagnostic device, comprising a vacuum chamber, an objective lens, an optical fiber, a spectrometer, and a spectral detector;

[0008] The vacuum chamber is used to generate plasma, and it has an observation window.

[0009] The objective lens, optical fiber, spectrometer, and spectral detector are connected in sequence to form an optical diagnostic system for observation. Accordingly, the front end of the objective lens faces the observation window and the plasma is observed through the observation window.

[0010] In one possible design, the observation chamber is equipped with an extinction plate located on the opposite side of the observation window, with the extinction plate facing the front of the objective lens.

[0011] In one possible design, the matte panel can be made of graphite or carbon fiber.

[0012] In one possible design, the objective lens's field of view covers at least the poloidal section of the plasma.

[0013] In one possible design, there are several optical fibers arranged vertically in one dimension, with each fiber forming a transmission channel.

[0014] In one possible design, a portion of the optical fiber is connected to the spectrometer, wherein the number of optical fibers connected to the spectrometer is equal to the target height of the spectrometer / the vertical magnification of the spectrometer / the core diameter of the optical fiber.

[0015] In one possible design, the spectrometer has an entrance slit end for connecting an optical fiber.

[0016] Secondly, the present invention provides a method for measuring the electron density profile of fusion plasma based on the aforementioned visible light bremsstrahlung diagnostic device, comprising the following steps:

[0017] S100 Measurement: The radiation of the plasma is measured by the visible light bremsstrahlung diagnostic device;

[0018] S200 Calculation: The plasma electron density is calculated using the following formula:

[0019]

[0020] in, It is the string integral electron density of the plasma core. It is the central chord integral bremsstrahlung radiance, T eo It represents the core electron temperature, C is a constant, and η is the form factor, which is represented as a constant along different lines of sight. Let n be the average effective charge number of the center chord, a be the plasma small radius, and n be the average effective charge number. e It represents the local electron density, r is the line-of-sight chord height, '-' indicates below the mid-plane, and ε ff It is the local bremsstrahlung emissivity.

[0021] In one possible design, in S200, the intermediate temperature along each line of sight is measured via electron cyclotron radiation diagnostics. This intermediate temperature is the highest electron temperature T that passes through the plasma in each line of sight. e (r), by T e (r)=T e0 (1-(r / a) 2 ) α Obtained through fitting;

[0022] In one possible design, in the S200, T is measured via Thomson laser scattering diagnostics. eo .

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] Compared with existing contact measurement methods, the visible light bremsstrahlung diagnostic device and fusion plasma electron density profile measurement method provide a non-contact, interference-free measurement method that uses the radiation spectrum of the high-temperature plasma itself to measure the electron density profile. Attached Figure Description

[0025] 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:

[0026] Figure 1 This is a schematic diagram of a visible light bremsstrahlung diagnostic device.

[0027] Figure 2 The visible light bremsstrahlung profiles at two times (a) 580 ms and (c) 1280 ms in the HL-2A plasma 29738 gun are shown. The blue asterisks in (b) and (d) represent the electron density profiles calculated by the fusion plasma electron density profile measurement method. The red squares in (b) and (d) represent the four-string integral electron density obtained by laser interferometry (FIR) diagnostic measurement.

[0028] The attached diagram shows the markings and corresponding component names:

[0029] 1. Vacuum chamber; 2. Objective lens; 3. Optical fiber; 4. Spectrometer; 5. Spectrometer detector; 6. Observation window; 7. Extinction plate. Detailed Implementation

[0030] 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.

[0031] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other embodiments, well-known structures, circuits, materials, or methods have not been specifically described in order to avoid obscuring the invention.

[0032] Throughout this specification, references to "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment of the invention. Therefore, the phrases "an embodiment," "an example," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. Moreover, those skilled in the art will understand that the illustrations provided herein are for illustrative purposes and are not necessarily drawn to scale. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0033] In the description of this invention, the terms "front", "rear", "left", "right", "up", "down", "vertical", "horizontal", "high", "low", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this invention.

[0034] Example 1:

[0035] like Figure 1 As shown, a visible light bremsstrahlung diagnostic device includes a vacuum chamber 1, an objective lens 2, an optical fiber 3, a spectrometer 4, and a spectrometer detector 5.

[0036] Vacuum chamber 1 is used to generate plasma, and vacuum chamber 1 has an observation window 6;

[0037] Objective lens 2, optical fiber 3, spectrometer 4 and spectrometer detector 5 are connected in sequence to form an optical diagnostic system for observation. Accordingly, the front end of objective lens 2 faces the observation window 6 and observes the plasma through the observation window 6.

[0038] In the visible light bremsstrahlung diagnostic device, fusion plasma is generated inside the vacuum chamber 1. The vacuum chamber 1 is equipped with an observation window 6 to allow the plasma's radiation light to pass through and be collected by the objective lens 2. It is easy to understand that the tokamak fusion device has a plate in the divertor region to reduce wall reflections, thereby reducing the interference of wall reflections on the optical signal and improving the measurement accuracy of the optical diagnostic system.

[0039] For optical diagnostic systems, the objective lens 2 collects the radiation light from the plasma, and the optical fiber 3 transmits the energy to the spectrometer 4. The spectrometer 4 and the spectral detector 5 work together to perform spectral analysis of the radiation light. This allows for the measurement of the line radiation spectra of hydrogen isotopes and low-ionization states of impurities in the plasma, such as HeI, HeII, CII, CIII, Dα, and NeI. Furthermore, it allows for flexible selection of continuous spectral ranges to measure visible bremsstrahlung. Therefore, optical diagnostic systems are versatile, widely applicable, and highly practical.

[0040] Furthermore, the string integral electron density passing through the plasma core can be estimated using visible light bremsstrahlung, thereby obtaining the plasma's electron density profile. This optical diagnostic system enables non-contact measurement of the plasma's electron density profile. Compared to existing weakly interfering laser measurement methods based on laser-matter interaction, the visible light bremsstrahlung diagnostic device achieves interference-free measurement.

[0041] During operation, the optical diagnostic system observes the plasma inside vacuum chamber 1 and records relevant data, which is then processed, analyzed, and used by staff.

[0042] In one possible implementation, an extinction plate 7 is provided on the vacuum chamber 1, located opposite the observation window 6, with the extinction plate 7 facing the front end of the objective lens 2. Based on the above design, the extinction plate 7 reduces the interference of wall reflections on the light signal, improving the accuracy of the optical diagnostic system measurements. Combined with the plate material on the divertor, wall reflections in the vacuum chamber 1 can be significantly reduced, ensuring the accuracy of the optical diagnostic system measurement results.

[0043] Optionally, the matting panel 7 can be made of graphite or carbon fiber. Based on this, the graphite or carbon fiber panel absorbs radiated light, thereby reducing wall reflection.

[0044] In one possible implementation, the field of view of objective lens 2 covers the poloidal cross-section of the plasma. Based on the above design, objective lens 2 has a large field of view to cover the poloidal cross-section of the plasma, thereby collecting the radiation light from the entire plasma cross-section. Combined with optical fiber 3 for spatial resolution adjustment, the requirements for field of view and resolution selection can be met.

[0045] Optionally, objective lens 2 can be constructed as a reverse telephoto objective lens structure, which consists of a negative front group and a positive rear group. It is readily understood that, provided the field of view meets the requirements, those skilled in the art can also choose any other suitable objective lens structure for objective lens 2.

[0046] In one possible implementation, several optical fibers 3 are arranged vertically in one dimension, with each optical fiber 3 forming a transmission channel. Based on the above design, multiple optical fibers 3 are arranged to form multiple transmission channels. By selecting the transmission channel, the line-of-sight coverage and spatial resolution of the objective lens 2 can be controlled, achieving adjustable spatial resolution and making measurements more flexible.

[0047] Alternatively, fiber 3 can be selected from silica fiber, glass fiber, or any other suitable type of fiber.

[0048] In one possible implementation, a portion of the optical fiber 3 is connected to the spectrometer 4, wherein the number of optical fibers connected to the spectrometer 4 is equal to the target surface height of the spectrometer detector 5 / the vertical magnification of the spectrometer 4 / the core diameter of the optical fiber.

[0049] Based on the above design scheme, by selecting the optical fiber connected to the spectrometer 4, the measurement channel can be flexibly selected so that the line of sight and spatial resolution of the optical diagnostic system can be adapted to the observed plasma.

[0050] Furthermore, considering that once the fiber core diameter of fiber 3 is determined, the number of fibers connected to spectrometer 4 can be adjusted by adjusting the target height of spectrometer 5 and the vertical magnification of spectrometer 4, making it more flexible and offering more diverse options.

[0051] In order to perform quantitative analysis, absolute intensity calibration of visible light bremsstrahlung diagnostics is required. Therefore, during device maintenance, the integrating sphere is placed at the front of objective lens 2 to achieve absolute intensity calibration.

[0052] Example 2:

[0053] This embodiment, based on Embodiment 1, introduces a practically feasible solution, specifically:

[0054] In vacuum chamber 1, the plasma used for observation is HL-2A plasma. The poloidal cross section of the HL-2A plasma ranges from r = -36.5 cm to 35.6 cm, where r is the line-of-sight chord height and '-' represents below the mid-plane. A graphite plate is installed in the area directly opposite objective lens 2 (i.e., the first wall on the strong field side) in vacuum chamber 1, and the protective plates of the upper and lower divertor areas are also covered with carbon fiber plates.

[0055] In the optical diagnostic system, objective lens 2 adopts a reverse telephoto objective lens structure, which consists of a negative front group and a positive rear group. This lens structure can provide a large field of view, which covers the poloidal section range of the HL-2A plasma.

[0056] Fiber 3 consists of 80 fibers arranged in a fiber bundle, with the front ends of the fiber bundle arranged in a one-dimensional vertical direction. Each fiber 3 is 50m long, with a core diameter of 400µm and a numerical aperture of 0.22. Thus, visible light bremsstrahlung diagnostics offers 80 selectable transmission channels, achieving a spatial resolution of up to 1cm.

[0057] Spectrometer 4 utilizes a Czerny-Turner structure long-focal-length high-resolution spectrometer with a spectral measurement range of 185 nm to 860 nm. The target surface of the spectrometer detector 5 has dimensions of 13.3 × 13.3 mm. Based on the target surface size of the spectrometer detector 5 and the transverse magnification (1X) of the spectrometer 4, 30 optical fibers 3 from the fiber bundle are connected to the slit end of the spectrometer 4. Furthermore, any 30 of the 80 optical fibers 3 are selected as transmission channels to flexibly control the line-of-sight coverage and spatial resolution, thereby achieving an adjustable spatial resolution of 1-2.4 cm.

[0058] For quantitative analysis, absolute intensity calibration of the visible light bremsstrahlung diagnostics is required. This is achieved by placing the integrating sphere at the front of objective lens 2 during device maintenance, ensuring the diagnostic system operates in the same manner as during physical experiments. Furthermore, the relative response rates between different spatial measurement channels are also calibrated using the integrating sphere.

[0059] Example 3:

[0060] Based on Examples 1 and 2, this embodiment introduces a method for measuring the electron density profile of fusion plasma using the aforementioned visible light bremsstrahlung diagnostic device. The method includes the following steps:

[0061] S100 Measurement: The radiation of the plasma is measured by the visible light bremsstrahlung diagnostic device;

[0062] S200 Calculation: The plasma electron density profile is calculated using the following formula:

[0063]

[0064] in, It is the string integral electron density of the plasma core. It is the central chord integral bremsstrahlung radiance, T eo It represents the core electron temperature, C is a constant, and η is the form factor, which is represented as a constant along different lines of sight. Let n be the average effective charge number of the center chord, a be the plasma small radius, and n be the average effective charge number. e It represents the local electron density, r is the line-of-sight chord height, '-' indicates below the mid-plane, and ε ff It is the local bremsstrahlung emissivity.

[0065] In S100, visible light bremsstrahlung is measured and relevant data is obtained using a visible light bremsstrahlung diagnostic device.

[0066] In S200, the data obtained from S100 is used as a basis, combined with other measured data, such as the core electronic temperature T. eo Simply substitute the values ​​into the formula to perform the calculation.

[0067] For the core electronic temperature T eo In S200, the intermediate temperature along each line of sight is measured using electron cyclotron radiation diagnostics. The intermediate temperature is the highest electron temperature T that passes through the plasma in each line of sight. e (r), by T e (r)=T e0 (1-(r / a) 2 ) α Obtained through fitting.

[0068] In S200, T is measured by Thomson laser scattering diagnostics. eo .

[0069] Furthermore, the accuracy of the fusion plasma electron density profile measurement method was calculated, specifically:

[0070] like Figure 2 As shown, where, Figure 2 (a) and Figure 2 (c) Shows the string integral bremsstrahlung profiles at two times, t1 = 580 ms and t2 = 1280 ms (exposure time 20 ms), in the HL-2A plasma #29738 gun.

[0071] The electron density profiles at these two moments were measured using a laser interferometry (FIR) diagnostic system, such as... Figure 2 (b) and Figure 2 (d) is indicated by a red asterisk. The electron density profiles at these two moments were calculated using the fusion plasma electron density profile measurement method, as shown below. Figure 2 (b) and Figure 2 (d) is indicated by the blue asterisk.

[0072] It can be seen that the electron density profile calculated by the fusion plasma electron density profile measurement method (blue asterisk) and the profile measured by the laser interferometry (FIR) diagnostic system (red square) show good consistency. This indicates that the fusion plasma electron density profile measurement method can be used as another effective measurement tool for electron density profile measurement.

[0073] 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 method of measuring the electron density profile of a fusion plasma, characterized in that, The method comprises the following steps: S100 measurement: measuring the radiation of the plasma by a visible light bremsstrahlung diagnostic device; S200 calculation: calculating the electron density of the plasma by the following formula: where is the chord-integrated electron density of the plasma core, is the chord-integrated bremsstrahlung brightness of the core, T eo is the core electron temperature, C is a constant, η is a shape factor and is constant along different lines of sight, is the chord-averaged effective charge number of the core, a is the minor radius of the plasma, e is the local electron density, r is the line-of-sight chord height, ‘-’ stands for below the midplane, ε ff is the local bremsstrahlung emissivity; The visible light bremsstrahlung diagnostic device for the fusion plasma electron density profile measurement method comprises a vacuum chamber (1), an objective lens (2), optical fibers (3), a spectrometer (4) and a spectral detector (5); The vacuum chamber (1) is used for generating plasma, and the vacuum chamber (1) has an observation window (6); The objective lens (2), the optical fibers (3), the spectrometer (4) and the spectral detector (5) are sequentially connected and constitute an optical diagnostic system for observation, and correspondingly, the front end of the objective lens (2) faces the observation window (6) and observes the plasma through the observation window (6).

2. The fusion plasma electron density profile measurement method according to claim 1, characterized by, The vacuum chamber (1) is provided with an extinction plate (7) located on the opposite side of the observation window (6), and correspondingly, the extinction plate (7) faces the objective lens (2).

3. The fusion plasma electron density profile measurement method according to claim 2, characterized by, The extinction plate (7) is selected from a graphite plate or a carbon fiber plate.

4. The fusion plasma electron density profile measurement method according to any one of claims 1 to 3, characterized by, The field of view of the objective lens (2) covers at least the poloidal cross-sectional range of the plasma.

5. The fusion plasma electron density profile measurement method according to claim 4, wherein, The optical fibers (3) are arranged in a one-dimensional vertical arrangement, and correspondingly, each optical fiber (3) forms a transmission channel.

6. The fusion plasma electron density profile measurement method according to claim 5, wherein, Part of the optical fibers (3) are connected to the spectrometer (4), and the number of the optical fibers connected to the spectrometer (4) is equal to the height of the target surface of the spectral detector (5) divided by the vertical magnification of the spectrometer (4) divided by the core diameter of the optical fiber.

7. The fusion plasma electron density profile measurement method according to claim 6, wherein, The spectrometer (4) has an entrance slit end for connecting the optical fibers (3).

8. The fusion plasma electron density profile measurement method according to claim 1, wherein, In S200, the intermediate temperature on each line of sight is measured by electron cyclotron emission diagnostics, the intermediate temperature is the highest electron temperature T e (r) = T e (r) = T e0 (1-(r / a) 2 ) α is obtained by fitting.

9. The fusion plasma electron density profile measurement method according to claim 1, wherein, In S200, T is measured by Thomson laser scattering diagnostics eo .

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