Visible light bremsstrahlung diagnostic device and fusion plasma electron density profile measurement method

Abstract

The invention discloses a visible light bremsstrahlung diagnostic device and a fusion plasma electron density profile measurement method. The visible light bremsstrahlung diagnostic device comprises a vacuum chamber, an objective lens, an optical fiber, a spectrograph and a spectrum detector. The vacuum chamber is used for generating plasma and is provided with an observation window; the objective lens, the optical fiber, the spectrograph and the spectrum detector are sequentially connected to form an optical diagnosis system for observation, and correspondingly, the front end of the objective lens faces the observation window, and visible light bremsstrahlung radiation of the plasma is observed through the observation window. The fusion plasma electron density profile measurement method comprises the following steps: S100, measurement: measuring plasma radiation through the visible light bremsstrahlung radiation diagnosis device; and S200, calculation: calculating the electron density profile of the plasma through a formula. Compared with an existing contact type measurement method, the visible light bremsstrahlung radiation diagnosis device and the fusion plasma electron density profile measurement method are a non-contact and interference-free measurement method.

Description

Technical Field

[0001] The invention relates to the technical field of plasma measurement methods, and in particular to a visible light bremsstrahlung diagnostic device and a fusion plasma electron density profile measurement method. Background Art

[0002] The measurement of basic parameter profiles of magnetic confinement fusion plasma, such as electron density and temperature, ion temperature and rotation speed, current density, safety factor, etc., provides important data support for high-temperature plasma parameter control and safe operation of the device, and provides important data guarantee for the physical analysis of plasma confinement and transport.

[0003] The measurement of the electron density profile in the main plasma region is generally based on laser diagnostic technology, which is sent into the 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 time and space resolution.

[0004] Under certain conditions, the interaction between laser and high temperature plasma is weak, so it will not cause serious interference to high temperature plasma. Generally, the plasma electron density profile is measured by 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 plasma electron density profile by a contact measurement method. The purpose of the present invention is to use the spontaneous radiation of high-temperature plasma to provide a visible light bremsstrahlung radiation diagnostic device and a method for measuring the electron density profile of fusion plasma. This is a non-contact, non-interference measurement method and can serve as another effective means of measuring electron density.

[0006] The present invention is achieved through the following technical solutions:

[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 spectrum detector;

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

[0009] The objective lens, the optical fiber, the spectrometer and the spectrum 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 observes the plasma through the observation window.

[0010] In a possible design, a matte plate is provided on the observation chamber and is located on the opposite side of the observation window. Accordingly, the matte plate faces the front end of the objective lens.

[0011] In a possible design, the matte plate is a graphite plate or a carbon fiber plate.

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

[0013] In a possible design, a plurality of optical fibers are provided and arranged vertically in one dimension, and accordingly, each optical fiber forms a transmission channel.

[0014] In a possible design, some optical fibers are connected to the spectrometer, wherein the number of optical fibers connected to the spectrometer = the target height of the spectral detector / the vertical axis magnification of the spectrometer / the core diameter of the optical fiber.

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

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

[0017] S100 measurement: measuring the radiation of the plasma by the visible light bremsstrahlung diagnostic device;

[0018] S200 calculation: The plasma electron density is calculated by the following formula:

[0019]

[0020] in, is the chord-integrated electron density in the plasma core, is the central chord-integrated bremsstrahlung brightness, T eo is the core electron temperature, C is a constant coefficient, η is the shape factor and is constant along different lines of sight, is the average effective charge of the central chord, a is the plasma small radius, n e is the local electron density, r is the line of sight chord height, '-' represents below the midplane, ε ff is the local bremsstrahlung rate.

[0021] In a possible design, in S200, the middle temperature on each line of sight is measured by electron cyclotron radiation diagnosis, and the middle temperature is the highest electron temperature T of each line of sight passing through the plasma. e (r), by T e (r) = T e0 (1-(r / a) 2 ) α Fitting obtained;

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

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

[0024] Compared with the existing contact measurement method, the visible light bremsstrahlung diagnostic device and the fusion plasma electron density profile measurement method provide a non-contact, non-interference measurement method, which uses the radiation spectrum of the high-temperature plasma itself to measure the electron density profile. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0026] Figure 1 The figure is a schematic diagram of the structure of a visible light bremsstrahlung diagnostic device.

[0027] Figure 2 Figure 2 shows the visible light bremsstrahlung profiles at two times (a) 580 ms and (c) 1280 ms in the HL-2A plasma 29738 cannon. The blue asterisks in (b) and (d) represent the electron density profiles inferred by the fusion plasma electron density profile measurement method. The red squares in (b) and (d) represent the four-channel chord-integrated electron density obtained by laser interferometer FIR diagnostic measurement.

[0028] Marks and corresponding parts names in the attached drawings:

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

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0031] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is apparent to one of ordinary skill in the art that these specific details are not necessarily employed to practice the present invention. In other embodiments, in order to avoid obscuring the present invention, well-known structures, circuits, materials, or methods are not specifically described.

[0032] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment," "an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. In addition, it will be appreciated by those of ordinary skill in the art that the figures provided herein are for illustrative purposes and that the figures 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 the present invention, the directions or positional relationships indicated by terms such as “front”, “rear”, “left”, “right”, “up”, “down”, “vertical”, “horizontal”, “high”, “low”, “inside” and “outside” are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limiting the scope of protection of the present invention.

[0034] Embodiment 1:

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

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

[0037] The objective lens 2 , the optical fiber 3 , the spectrometer 4 and the spectrum detector 5 are sequentially connected to form an optical diagnostic system for observation. Accordingly, the front end of the 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 in the vacuum chamber 1, and the vacuum chamber 1 is provided with an observation window 6 so that the radiation light of the plasma can be transmitted and then collected by the objective lens 2. It is easy to understand that the tokamak fusion device is provided with a plate for reducing wall reflection in the divertor area, thereby reducing the interference of wall reflection on the optical signal and improving the measurement accuracy of the optical diagnostic system.

[0039] For the optical diagnostic system, the radiation light of the plasma is collected through the objective lens 2, and the optical fiber 3 is used to transmit energy to the spectrometer 4. The spectrometer 4 and the spectrum detector 5 cooperate with each other to realize the spectrum analysis of the radiation light. It can not only be used to measure the linear radiation spectrum of hydrogen isotopes and impurities in the plasma with low ionization states, such as HeI, HeⅡ, CII, CIII, Dα and NeI, but also can flexibly select the range of continuous spectrum to measure visible light bremsstrahlung. Based on this, the optical diagnostic system has various functions, a wide range of applications, and good practicality.

[0040] Furthermore, the chord-integrated electron density passing through the plasma core can be estimated by visible light bremsstrahlung, thereby obtaining the electron density profile of the plasma, that is, the optical diagnostic system realizes non-contact measurement of the plasma electron density profile. Compared with the existing weak interference laser measurement method based on the interaction between laser and matter, the visible light bremsstrahlung diagnostic device realizes non-interference measurement.

[0041] When working, the optical diagnostic system observes the plasma in the vacuum chamber 1 and records relevant data, and the data is provided for processing, analysis and use by the staff.

[0042] In a possible implementation, the vacuum chamber 1 is provided with a matt plate 7 located on the opposite side of the observation window 6, and accordingly, the matt plate 7 is directly opposite to the front end of the objective lens 2. Based on the above design, the matt plate 7 reduces the interference of the wall reflection on the optical signal, thereby improving the accuracy of the optical diagnosis system measurement. In combination with the plate on the divertor, the wall reflection in the vacuum chamber 1 can be greatly reduced, thereby ensuring the accuracy of the measurement results of the optical diagnosis system.

[0043] Optionally, the matte plate 7 is a graphite plate or a carbon fiber plate. Based on this, the graphite plate or the carbon fiber plate can absorb the radiated light, thereby reducing the wall reflection.

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

[0045] Optionally, the objective lens 2 can be constructed as a reverse telephoto objective lens structure, which is composed of a negative front group and a positive rear group. It is easy to understand that on the basis of ensuring that the field of view meets the requirements, those skilled in the art can also select the objective lens 2 of any other suitable structure.

[0046] In a possible implementation, a plurality of optical fibers 3 are provided and arranged vertically in one dimension, and accordingly, each optical fiber 3 forms a transmission channel. Based on the above design, a plurality of optical fibers 3 are provided to form a plurality of transmission channels, and the visual coverage and spatial resolution of the objective lens 2 can be controlled by selecting the transmission channel, thereby achieving adjustable spatial resolution and more flexible measurement.

[0047] Optionally, the optical fiber 3 may be quartz optical fiber, glass optical fiber or any other suitable type of optical fiber.

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

[0049] Based on the above design, by selecting the optical fiber connected to the spectrometer 4, the measurement channel is flexibly selected so that the visual range and spatial resolution of the optical diagnostic system are adapted to the observed plasma.

[0050] Furthermore, after determining the core diameter of the optical fiber 3, the number of optical fibers connected to the spectrometer 4 can be adjusted by adjusting the target height of the spectrum detector 5 and the vertical axis magnification of the spectrometer 4, which is more flexible to use and more diverse to choose from.

[0051] In order to perform quantitative analysis, it is necessary to perform absolute intensity calibration on the visible light bremsstrahlung diagnosis. Therefore, during the maintenance of the device, an integrating sphere is placed in front of the objective lens 2 to achieve absolute intensity calibration.

[0052] Embodiment 2:

[0053] This embodiment introduces a practical solution based on Embodiment 1. Specifically:

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

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

[0056] There are 80 optical fibers 3 and they are constructed into an optical fiber bundle, and the front end of the optical fiber bundle is arranged vertically in one dimension; a single optical fiber 3 is 50m long, the core diameter of the single fiber is 400um, and the numerical aperture is 0.22. Therefore, the visible light bremsstrahlung diagnosis has 80 transmission channels to choose from, and its spatial resolution can reach 1cm.

[0057] The spectrometer 4 uses a Czerny-Turner structure telephoto high-resolution spectrometer, and the spectral measurement range of the spectrometer 4 is between 185nm-860nm. The target surface size of the spectral detector 5 is 13.3×13.3mm. According to the target surface size of the spectral detector 5 and the vertical axis magnification (1X) of the spectrometer 4, 30 optical fibers 3 in the optical fiber bundle are connected to the slit end of the spectrometer 4. Further, 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 1-2.4cm.

[0058] In order to perform quantitative analysis, it is necessary to calibrate the absolute intensity of visible light bremsstrahlung diagnosis, that is, during the maintenance of the device, the integrating sphere is placed in front of the objective lens 2, so that the operating state of the diagnostic system is consistent with that during the physical experiment of the device. Furthermore, the relative response rate between different spatial measurement channels is also calibrated using the integrating sphere.

[0059] Embodiment 3:

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

[0061] S100 measurement: measuring the radiation of the plasma by the visible light bremsstrahlung diagnostic device;

[0062] S200 calculation: The plasma electron density profile is calculated by the following formula:

[0063]

[0064] in, is the chord-integrated electron density in the plasma core, is the central chord-integrated bremsstrahlung brightness, T eo is the core electron temperature, C is a constant coefficient, η is the shape factor and is constant along different lines of sight, is the average effective charge of the central chord, a is the plasma small radius, n e is the local electron density, r is the line of sight chord height, '-' represents below the midplane, ε ff is the local bremsstrahlung rate.

[0065] Among them, in S100, the visible light bremsstrahlung radiation is measured by a visible light bremsstrahlung radiation diagnostic device and relevant data is obtained.

[0066] In S200, the data obtained in S100 are combined with other measured data, such as the core electron temperature T eo , substitute it into the calculation formula and perform the calculation.

[0067] For the core electron temperature T eo In S200, the middle temperature on each line of sight is measured by electron cyclotron radiation diagnosis. The middle temperature is the highest electron temperature T of each line of sight passing through the plasma. e (r), by T e (r) = T e0 (1-(r / a) 2 ) α Fitting obtained.

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

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

[0070] like Figure 2 As shown, Figure 2 (a) and Figure 2 (c) shows the chord-integrated bremsstrahlung profiles at two times: t1 = 580 ms and t2 = 1280 ms (exposure time 20 ms) in the HL-2A plasma #29738 cannon.

[0071] The electron density profiles at these two moments are measured by the laser interferometer FIR diagnostic system, as shown in Figure 2 (b) and Figure 2 The electron density profiles at these two moments are calculated by the fusion plasma electron density profile measurement method, as shown in FIG. Figure 2 (b) and Figure 2 Indicated by blue asterisk in (d).

[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 interferometer FIR diagnostic system (red square) are in good agreement. This shows that the fusion plasma electron density profile measurement method can be used as another effective measurement method to measure the electron density profile.

[0073] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method 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 in the scope of protection of the present invention.

Claims

1. A visible light bremsstrahlung diagnostic device, characterized in that: It comprises a vacuum chamber (1), an objective lens (2), an optical fiber (3), a spectrometer (4) and a spectrum detector (5); The vacuum chamber (1) is used to generate plasma, and the vacuum chamber (1) has an observation window (6); The objective lens (2), the optical fiber (3), the spectrometer (4) and the spectrum detector (5) are connected in sequence to form an optical diagnostic system for observation. Accordingly, the front end of the objective lens (2) faces the observation window (6) and observes the plasma through the observation window (6).

2. The visible light bremsstrahlung diagnostic device according to claim 1, characterized in that: The vacuum chamber (1) is provided with a matte plate (7) located on the opposite side of the observation window (6); correspondingly, the matte plate (7) faces the objective lens (2).

3. The visible light bremsstrahlung diagnostic device according to claim 2, characterized in that: The matte plate (7) is selected from graphite plates or carbon fiber plates.

4. The visible light bremsstrahlung diagnostic device according to any one of claims 1 to 3, characterized in that: The field of view of the objective lens (2) at least covers the poloidal cross section of the plasma.

5. The visible light bremsstrahlung diagnostic device according to claim 4, characterized in that: A plurality of optical fibers (3) are provided and arranged vertically in one dimension, and accordingly, each optical fiber (3) forms a transmission channel.

6. The visible light bremsstrahlung diagnostic device according to claim 5, characterized in that: Part of the optical fiber (3) is connected to the spectrometer (4), wherein the number of optical fibers connected to the spectrometer (4) = the target surface height of the spectrum detector (5) / the vertical axis magnification of the spectrometer (4) / the optical fiber core diameter.

7. The visible light bremsstrahlung diagnostic device according to claim 6, characterized in that: The spectrometer (4) has an incident slit end for connecting to the optical fiber (3).

8. A method for measuring the electron density profile of a fusion plasma based on the visible light bremsstrahlung diagnostic device according to any one of claims 1 to 7, characterized in that: The following steps are involved: S100 measurement: measuring the radiation of the plasma by the visible light bremsstrahlung diagnostic device; S200 calculation: The plasma electron density is calculated by the following formula: in, is the chord-integrated electron density in the plasma core, is the central chord-integrated bremsstrahlung brightness, T eo is the core electron temperature, C is a constant coefficient, η is the shape factor and is constant along different lines of sight, is the average effective charge of the central chord, a is the plasma small radius, n e is the local electron density, r is the line of sight chord height, '-' represents below the midplane, ε ff is the local bremsstrahlung rate.

9. The method for measuring the fusion plasma electron density profile according to claim 8, characterized in that: In S200, the middle temperature on each line of sight is measured by electron cyclotron radiation diagnosis. The middle temperature is the highest electron temperature T of each line of sight passing through the plasma. e (r), by T e (r) = T e0 (1-(r / a) 2 ) α Fitting obtained.

10. The method for measuring the fusion plasma electron density profile according to claim 8, characterized in that: In S200, T was measured by Thomson laser scattering diagnostics. eo .

Images