A method for measuring the concentration profile of impurity bare cores using active spectroscopy

Abstract

The present invention discloses a method for measuring the concentration profile of impurity bare nuclei using active spectroscopy, comprising: step 1, obtaining the beam density of a neutral beam during its travel; step 2, obtaining the ratio of the number density of particles in the excited state to the ground state in the neutral beam atoms; step 3, calculating the charge exchange recombination radiation rate coefficient of the neutral beam atoms and the impurity ions based on the obtained ratio of the number density of particles in the excited state to the ground state in the neutral beam atoms; step 4, measuring the active spectrum intensity of the impurity ions, and calculating the impurity ion concentration profile distribution in combination with the obtained beam density and charge exchange recombination radiation rate coefficient. This method calculates the profile distribution of the impurity bare nucleus concentration through the absolutely calibrated active spectrum intensity of the impurity ions, the neutral beam density, and the charge exchange recombination radiation rate coefficient, thereby improving the measurement of impurity concentration and providing the necessary physical parameters and experimental data support for further research on the control, transport, and internal physical mechanisms of plasma.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic confinement nuclear fusion, and in particular to a method for measuring the concentration profile of impurity bare nuclei by using active spectroscopy. Background Art

[0002] Magnetic confinement fusion is a type of controlled nuclear fusion, stemming from humanity's need for energy. It uses a specialized magnetic field to confine atomic nuclei, such as deuterium and tritium, and free electrons within a limited volume, where they undergo controlled thermonuclear fusion reactions, releasing significant amounts of energy that can be used as a large-scale energy source. The presence of impurities in magnetic confinement fusion plasma can lead to significant radiation losses and fuel dilution, and can even cause major plasma disruptions, severely damaging the fusion device. Therefore, diagnostics are essential to monitor impurity concentrations and control them to levels compatible with high-temperature plasmas.

[0003] Crucially, carbon and some low-Z impurities are very useful for studying particle transport. These low-Z impurities are essentially completely stripped away in high-temperature plasmas, simplifying atomic physics models for ion transport coefficients (involving ionization and recombination reactions). However, measuring impurity ion concentrations in magnetically confined high-temperature plasmas is difficult. Therefore, it is necessary to develop a new method for measuring the bare-core impurity concentration profile. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for measuring the impurity bare nucleus concentration profile using active spectroscopy to address the problem of difficulty in measuring the impurity ion concentration profile in magnetically confined high-temperature plasma. The method calculates the profile distribution of the impurity bare nucleus concentration through the absolutely calibrated impurity ion active spectrum intensity, neutral beam density and charge exchange recombination radiation rate coefficient.

[0005] The present invention is achieved through the following technical solutions:

[0006] The present invention provides a method for measuring the concentration profile of impurity bare nuclei using active spectroscopy, comprising:

[0007] Step 1: Obtain the beam density of the neutral beam during its travel;

[0008] Step 2: Obtain the ratio of the particle number density of the excited state to the ground state in the neutral beam atoms;

[0009] Step 3: Calculate the charge exchange recombination radiation rate coefficient of the neutral beam atoms and the impurity ions based on the obtained ratio of the excited state to the ground state particle number density in the neutral beam atoms;

[0010] Step 4: Measure the active spectrum intensity of the impurity ions, and calculate the impurity ion concentration profile distribution based on the obtained beam density and charge exchange recombination radiation rate coefficient.

[0011] Furthermore, in the step 1, the beam density distribution of each beam energy component is solved through a beam attenuation process.

[0012] Furthermore, the chord-integrated beam density of each beam energy component along the observation line of sight can be expressed as:

[0013]

[0014] Where P is the total power of the neutral beam, f is the ratio of each beam energy component, ζ is the beam attenuation factor, e is the charge constant, E is the energy of the beam atoms, v is the beam velocity, θ is the angle between the observation line and the neutral beam axis, and w ⊥ is the beam radius in the meridian plane.

[0015] Furthermore, in step 2, the fraction of excited atoms in each beam energy component is evaluated according to the beam pumping process.

[0016] Furthermore, the beam pumping probability in high-temperature plasma can be expressed as:

[0017]

[0018] in, is the probability of neutral beam pumping in a single impurity plasma, C i is the local concentration of the ion species, and Z is the ion charge number.

[0019] Furthermore, in step three, for each beam energy component, the charge exchange recombination radiation rate coefficients of the ground state and excited state neutral beam atoms and impurity ions are calculated respectively.

[0020] Furthermore, the charge exchange recombination radiation rate coefficient of each beam energy component can be expressed as:

[0021]

[0022] Among them, P n＝2 is the fraction of excited-state atoms, is the charge exchange recombination radiation rate coefficient between excited state beam atoms and impurity ions, 1-P n＝2 is the ground state atomic fraction, is the radiation rate coefficient of charge exchange recombination between ground state beam atoms and impurity ions.

[0023] Furthermore, the active spectrum intensity of the impurity ions in step 4 can be measured by a charge exchange composite spectrum diagnostic system and obtained by absolute calibration using an integrating sphere.

[0024] Furthermore, the impurity ion concentration profile can be calculated using the following formula:

[0025]

[0026] Among them, Φ CVI is the active spectrum photon flux, is the charge exchange recombination radiation rate coefficient corresponding to each beam energy component, N b,k is the chord-integrated beam density of the kth energy component, n Z (ρ) is the impurity ion concentration profile to be calculated.

[0027] Furthermore, the impurity ion concentration profile in step 4 is obtained through self-consistent calculation.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] The present invention calculates the profile distribution of impurity bare core concentration using absolutely calibrated impurity ion active spectrum intensity, neutral beam density, and charge exchange recombination radiation rate coefficient. This method improves the measurement of impurity ion density in different ionization states in high-temperature plasmas to facilitate the calculation of the impurity transport coefficient in the entire plasma region. Furthermore, the effective charge number profile calculated from the impurity concentration can be cross-checked with the effective charge number profile calculated using visible light bremsstrahlung to verify the effectiveness of the diagnosis. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] 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 examples. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be considered as limiting the scope. A person of ordinary skill in the art can also derive other relevant drawings based on these drawings without inventive effort. In the drawings:

[0031] Figure 1 Flowchart of the method for measuring the concentration profile of bare impurity cores using active spectroscopy in the present invention;

[0032] Figure 2 Schematic diagram of the charge exchange composite spectroscopy diagnostic system used in the present invention.

[0033] Markings and corresponding parts names in the accompanying drawings:

[0034] 1-Objective lens, 2-Fiber optic bundle, 3-Spectrometer. DETAILED DESCRIPTION

[0035] 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 examples and drawings. The exemplary embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0037] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0038] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0039] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists, A and B exist at the same time, and B exists. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0040] In the embodiments of this application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components in different embodiments are omitted. It should be understood that the thickness, length, width, and other dimensions of the various components in the embodiments of this application, as well as the overall thickness, length, width, and other dimensions of the integrated device shown in the drawings are merely illustrative and should not constitute any limitation on this application.

[0041] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces), unless otherwise clearly and specifically defined.

[0042] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0043] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0044] In magnetic confinement fusion devices, deuterium and tritium are used as nuclear fusion fuel. Particles other than hydrogen isotope fuel particles in the plasma are called impurities. The presence of impurities can severely affect the confinement quality and macroscopic stability of the high-temperature plasma, as impurity radiation is the primary cause of power loss in tokamak plasmas.

[0045] Impurity spectra in plasma can reveal many important plasma parameters, such as ion temperature and rotational speed. Using impurity spectra to diagnose impurity concentrations will provide the necessary physical parameters and experimental data to support further research into plasma control, transport, and internal physical mechanisms.

[0046] In magnetically confined high-temperature plasma, it is relatively difficult to measure the concentration of impurity ions. For this reason, the inventors, after in-depth research, proposed a new method for measuring the impurity bare nucleus concentration profile using active spectroscopy. The profile distribution of the impurity bare nucleus concentration is calculated by the absolutely calibrated impurity ion active spectrum intensity, neutral beam density and charge exchange recombination radiation rate coefficient.

[0047] This method improves the measurement of impurity ion density in different ionization states in high-temperature plasma, so as to calculate the impurity transport coefficient of the entire plasma region; at the same time, the effective charge number Z calculated from the impurity concentration eff The effective charge Z calculated by the cross section and visible light bremsstrahlung eff The sections are cross-checked to verify the effectiveness of the diagnosis.

[0048] Since carbon impurities are one of the main impurities in the HL-2A / HL-3 tokamak plasma, the visible light intensity of carbon ion CVI radiation is relatively strong, making it easy to observe and measure. Therefore, the following uses the bare core concentration measurement of carbon impurity ions as an example to illustrate the concentration profile measurement method in this embodiment.

[0049] Please refer to Figure 1 and Figure 2 In an embodiment of the present application, a method for measuring the concentration profile of an impurity bare core using active spectroscopy is provided, comprising:

[0050] Step 1: Obtain the beam density of the neutral beam during its travel;

[0051] Step 2: Obtain the ratio of the particle number density of the excited state to the ground state in the neutral beam atoms;

[0052] Step 3: Calculate the charge exchange recombination radiation rate coefficient of the neutral beam atoms and the impurity ions based on the obtained ratio of the excited state to the ground state particle number density in the neutral beam atoms;

[0053] Step 4: Measure the active spectrum intensity of the impurity ions, and calculate the impurity ion concentration profile distribution based on the obtained beam density and charge exchange recombination radiation rate coefficient.

[0054] According to some embodiments of the present application, in step 1, the beam density distribution of each beam energy component is calculated through a beam decay process. Neutral beam decay refers to the attenuation of beam intensity caused by high-energy neutral particles injected into a plasma, undergoing collision ionization or charge exchange reactions with electrons and ions in the plasma. The beam density distribution of the neutral beam during its propagation is calculated through the beam decay process. The purpose of the beam decay calculation is to determine the neutral beam density.

[0055] It's important to note that in magnetic confinement fusion devices, neutral beam irradiation (NBI) is commonly used to measure key plasma parameters such as ion temperature and distribution, and plasma rotation speed. The neutral beam consists of three energy components: E, E / 2, and E / 3. Spectroscopy can be used to analyze the contribution of each energy component.

[0056] According to some embodiments of the present application, the chord-integrated beam density of each beam energy component along the observation line of sight can be expressed as:

[0057]

[0058] Where P is the total power of the neutral beam in W, f is the ratio of each beam energy component, ζ is the beam attenuation factor, e is the charge constant, E is the beam atomic energy in keV / amu, v is the beam velocity in m / s, θ is the angle between the observation line and the neutral beam axis, and w ⊥ is the beam radius in the meridian plane (beam half-width at 1 / e height).

[0059] According to some embodiments of the present application, in step 2, the fraction of excited-state atoms in each beam energy component is evaluated based on the beam pumping process. Both the ground state and excited state of beam atoms participate in charge exchange recombination reactions of plasma ions. First, the fraction of excited-state beam atoms is evaluated, i.e., the ratio of the number density of H*(n=2) excited-state atoms to the number density of H(1s) ground-state atoms.

[0060] It should be noted that pumping is the process of raising (or "pumping") electrons from lower energy levels in atoms or molecules to higher energy levels through collisions. Determining the ratio of the number density of excited-state H* (n = 2) to ground-state H (1s) atoms in the neutral beam is the process of beam pumping, as the excited-state H* (n = 2) in the low-energy component of the neutral beam accounts for a large proportion of the charge exchange reaction with bare carbon nuclei.

[0061] According to some embodiments of the present application, the beam pumping probability in high temperature plasma can be calculated by the following formula:

[0062]

[0063] in, is the probability of neutral beam pumping in a single impurity plasma, C i is the local concentration of the ion species, and Z is the ion charge number.

[0064] According to some embodiments of the present application, in step 3, for each beam energy component, the H(1s) ground state and H*(n=2) excited state neutral beam atoms and C 6+ The charge exchange recombination radiation rate coefficient of the impurity ions. This rate coefficient depends on the beam atom collision energy, electron density, ion temperature and effective charge number Z eff The collision cross section of excited state beam atoms is much larger than that of ground state atoms. For example, the reaction rate of H*(n=2) excited state beam atoms is three orders of magnitude higher than that of H(1s) ground state beam atoms.

[0065] According to some embodiments of the present application, considering the pumping probability of excited state beam atoms, the charge exchange recombination radiation rate coefficient of each beam energy component can be expressed as:

[0066]

[0067] Among them, P n＝2 is the fraction of excited-state atoms, is the charge exchange recombination radiation rate coefficient between excited state beam atoms and impurity ions, 1-P n＝2 is the ground state atomic fraction, is the charge exchange recombination radiation rate coefficient between the ground state beam atoms and the impurity ions. In this calculation, the contribution of excited state beam atoms at n=3 and above energy levels is not considered, however, their contribution should be one order of magnitude lower than that of beam atoms at n=2.

[0068] According to some embodiments of the present application, the active spectrum intensity of the impurity ions in step 4 can be measured by a charge exchange composite spectroscopy diagnostic system (CXRS) and obtained by absolute calibration using an integrating sphere. The charge exchange composite spectroscopy diagnostic system mainly includes an objective lens 1, an optical fiber bundle 2, and a spectrometer 3. The integrating sphere is a hollow sphere with an inner wall coated with a white diffuse reflective material, also known as a photometric sphere, a light-passing sphere, etc. One or more window holes are opened on the wall of the sphere, which are used as light inlets and receiving holes for placing light receiving devices. In order to obtain higher measurement accuracy, the aperture ratio of the integrating sphere should be as small as possible.

[0069] At the end of the tokamak device, the objective lens 1 collects the light emitted by the reaction between the neutral beam and the impurity ions and images it to the end face of the fiber bundle 2. The fiber bundle 2 is composed of 32 optical fiber filaments, each with a core diameter of 400um, and is arranged in one dimension at the end face of the fiber bundle 2. Therefore, the CXRS diagnosis has a total of 32 spatial measurement channels, and the field of view covers the plasma core to the edge along the neutral beam. The tail end of the fiber bundle 2 is connected to a high spectral resolution spectrometer 3 to collect the plasma emission spectrum. In fact, the impurity ion spectrum collected by the diagnostic observation line of sight includes three parts, namely the active spectrum, the passive spectrum and the edge spectrum. The active spectrum needs to be obtained by spectrum decomposition. The CVI (n = 8-7,529.1nm) active spectrum photon flux measured by the toroidal charge exchange recombination radiation spectrum diagnosis is expressed as Φ CVI .

[0070] According to some embodiments of the present application, the impurity ion concentration profile may be calculated using the following formula:

[0071]

[0072] Among them, n Z (ρ) is the local C that needs to be calculated 6+ Ion density, Φ CVI is the active spectrum photon flux, is the charge exchange recombination radiation rate coefficient corresponding to each beam energy component, N b,k is the chord-integrated beam density of the kth energy component. The measured charge exchange composite spectral signal comes from the contribution of the three energy components of the neutral beam. Since the line of sight of CXRS diagnosis is almost tangent to the magnetic surface along the intersection of the line of sight and the neutral beam, plasma parameters such as ion temperature T i , electron density n e and ion density n zIt is assumed to be a constant on the intersection line. The density and concentration profile of carbon impurity ions can be calculated using this equation. Z (ρ).

[0073] According to some embodiments of the present application, during the entire calculation process, the impurity ion concentration profile is obtained through self-consistent calculations: an initial, hypothetical impurity ion density profile is substituted into the program, and when the substituted value and the output value are very close (i.e., converged) through continuous iterative calculations, it indicates that the calculation of the impurity ion density profile is completed.

[0074] Similarly, the concentrations of impurities such as helium, oxygen, neon and argon in magnetically confined high-temperature plasma are calculated using the same method.

[0075] 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 method for measuring the concentration profile of impurity bare cores using active spectroscopy, characterized in that: include: Step 1: Obtain the beam density of the neutral beam during its travel; Step 2: Obtain the ratio of the particle number density of the excited state to the ground state in the neutral beam atoms; Step 3: Calculate the charge exchange recombination radiation rate coefficient of the neutral beam atoms and the impurity ions based on the obtained ratio of the excited state to the ground state particle number density in the neutral beam atoms; Step 4: Measure the active spectrum intensity of the impurity ions and calculate the impurity ion concentration profile distribution based on the acquired beam density and charge exchange recombination radiation rate coefficient; The active spectrum intensity of the impurity ions in step 4 can be measured by a charge exchange composite spectrum diagnostic system and obtained by absolute calibration using an integrating sphere. The impurity ion concentration profile can be calculated by the following formula: Among them, Φ CVI is the active spectrum photon flux, is the charge exchange recombination radiation rate coefficient corresponding to each beam energy component, N b,k is the chord-integrated beam density of the kth energy component, n Z (ρ) is the impurity ion concentration profile to be calculated.

2. The method for measuring the concentration profile of impurity bare cores using active spectroscopy according to claim 1, characterized in that: In the step 1, the beam density distribution of each beam energy component is solved through the beam attenuation process.

3. The method for measuring the concentration profile of impurity bare cores using active spectroscopy according to claim 2, characterized in that: The chord-integrated beam density of each beam energy component along the observation line of sight can be expressed as: Where P is the total power of the neutral beam, f is the ratio of each beam energy component, ζ is the beam attenuation factor, e is the charge constant, E is the energy of the beam atoms, v is the beam velocity, θ is the angle between the observation line and the neutral beam axis, and w ⊥ is the beam radius in the meridian plane.

4. The method for measuring the concentration profile of impurity bare cores using active spectroscopy according to claim 1, characterized in that: In the second step, the fraction of excited atoms in each beam energy component is evaluated according to the beam pumping process.

5. The method for measuring the concentration profile of impurity bare cores using active spectroscopy according to claim 4, characterized in that: The beam pumping probability in high-temperature plasma can be expressed as: in, is the probability of neutral beam pumping in a single impurity plasma, C i is the local concentration of the ion species, and Z is the ion charge number.

6. The method for measuring the concentration profile of impurity bare cores using active spectroscopy according to claim 1, characterized in that: In the step 3, for each beam energy component, the charge exchange recombination radiation rate coefficients of the ground state and excited state neutral beam atoms and impurity ions are calculated respectively.

7. The method for measuring the concentration profile of impurity bare nuclei using active spectroscopy according to claim 6, characterized in that: The charge exchange recombination radiation rate coefficient for each beam energy component can be expressed as: Among them, P n＝2 is the fraction of excited-state atoms, is the charge exchange recombination radiation rate coefficient between excited state beam atoms and impurity ions, 1-P n＝2 is the ground state atomic fraction, is the radiation rate coefficient of charge exchange recombination between ground state beam atoms and impurity ions.

8. The method for measuring the concentration profile of impurity bare cores using active spectroscopy according to claim 1, characterized in that: The impurity ion concentration profile in step 4 is obtained through self-consistent calculation.

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