Method for measuring impurity bare nucleus concentration profile by using active spectrum

Abstract

The invention discloses a method for measuring an impurity bare nucleus concentration profile by using an active spectrum. The method comprises the following steps: step 1, acquiring the beam density of a neutral beam in the advancing process; 2, obtaining the particle number density ratio of the excited state to the ground state in the neutral beam atoms; 3, calculating a charge exchange composite radiation rate coefficient of the neutral beam atoms and foreign ions according to the obtained particle number density ratio of the excited state to the ground state in the neutral beam atoms; and 4, measuring the active spectral intensity of the impurity ions, and calculating the concentration profile distribution of the impurity ions by combining the obtained beam density and the charge exchange composite radiation rate coefficient. According to the method, the profile distribution of the impurity bare nucleus concentration is calculated through absolutely calibrated impurity ion active spectrum intensity, neutral beam density and charge exchange recombination radiation rate coefficient, so that the measurement of the impurity concentration is perfected; necessary physical parameters and experimental data support are provided for further research on control, transportation, internal physical mechanisms and the like of the plasma.

Description

Technical Field

[0001] The 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 that originates from human demand for energy. It uses a special form of magnetic field to confine deuterium, tritium and other atomic nuclei and free electrons in a limited volume, and controllably produces thermonuclear fusion reactions, releasing a large amount of energy, which can be used as a large-scale energy source. The presence of impurities in magnetic confinement fusion plasma can lead to strong radiation loss and fuel dilution, and even cause a large rupture of the plasma, seriously damaging the fusion device. Therefore, it is necessary to detect the impurity concentration through diagnosis and control the impurity content to a level compatible with high-temperature plasma.

[0003] Crucially, carbon and some low-Z impurities are very useful for studying particle transport. These low-Z impurities are basically completely stripped in the high-temperature plasma region, which simplifies the atomic physics model for solving the ion transport coefficient (involving ionization and recombination reaction processes). However, in magnetically confined high-temperature plasma, it is difficult to measure the impurity ion concentration. For this reason, it is necessary to study a new method to measure the impurity bare core 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 a magnetically confined high-temperature plasma. The method calculates the profile distribution of the impurity bare nucleus concentration through 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 cores using active spectroscopy, comprising:

[0007] Step 1, obtaining the beam density of the neutral beam during its travel;

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

[0009] Step 3, calculating the charge exchange recombination radiation rate coefficient of the neutral beam atoms and the impurity ions according to the obtained particle number density ratio of the excited state to the ground state 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 in combination with the acquired 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 attenuation factor. ⊥ is the beam radius in the meridian plane.

[0015] Furthermore, in the 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 beam pumping probability of the neutral beam 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 the 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 charge exchange recombination radiation rate coefficient between the ground state beam atoms and the 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 by 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 through 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 plasma so as to calculate the impurity transport coefficient of the entire plasma region. At the same time, the effective charge number profile calculated from the impurity concentration can be cross-checked with the effective charge number profile calculated by 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 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:

[0031] Figure 1 It is a flow chart 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] Marks and corresponding parts names in the attached drawings:

[0034] 1- objective lens, 2- fiber 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 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.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field 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" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof 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] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood 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 the present application, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists, A and B exist at the same time, and B exists. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0040] In the embodiments of the present application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width and other dimensions of various components in the embodiments of the present application shown in the drawings, as well as the overall thickness, length, width and other dimensions of the integrated device are only exemplary descriptions and should not constitute any limitation to the present 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. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which 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 referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not 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 clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0044] Deuterium and tritium are used as nuclear fusion fuels in magnetic confinement fusion devices. Particles other than hydrogen isotope fuel particles in plasma are called impurities. The presence of impurities will seriously affect the confinement quality and macroscopic stability of high-temperature plasma, because impurity radiation is the main cause of tokamak plasma power loss.

[0045] The impurity spectrum information in plasma can reflect many important plasma parameters, such as ion temperature, rotation speed, etc. By using the impurity spectrum to diagnose the impurity concentration, it will provide necessary physical parameters and experimental data support for further research on 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 have conducted in-depth research and 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 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 number Z calculated by the cross section and visible light bremsstrahlung eff The profiles 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 strong, which is convenient for observation and measurement. Therefore, the following takes the bare core concentration measurement of carbon impurity ions as an example to explain the concentration profile measurement method in this embodiment.

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

[0050] Step 1, obtaining the beam density of the neutral beam during its travel;

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

[0052] Step 3, calculating the charge exchange recombination radiation rate coefficient of the neutral beam atoms and the impurity ions according to the obtained particle number density ratio of the excited state to the ground state 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 in combination with the acquired 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 solved by a beam attenuation process. Neutral beam attenuation refers to the attenuation of beam intensity caused by collision ionization or charge exchange reaction between high-energy neutral particles and electrons and ions in the plasma after they are injected into the plasma. The beam density distribution of the neutral beam during its travel is solved by the beam attenuation process, and the purpose of the beam attenuation calculation is to solve the neutral beam density.

[0055] It should be noted that in magnetic confinement fusion devices, neutral beam (NBI) is usually used to measure important plasma parameters such as ion temperature and its distribution, plasma rotation speed, etc. The neutral beam mainly includes three energy components: E, E / 2 and E / 3, and the spectral method can be used to analyze the share 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 according to the beam pumping process. Both the ground state and excited state of the beam atoms participate in the charge exchange recombination reaction of the plasma ions, and the fraction of excited-state beam atoms is first evaluated, that is, the ratio of the number density of H* (n = 2) excited states to that of H (1s) ground states.

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

[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 beam pumping probability of the neutral beam 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 of 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 spectral diagnostic system (CXRS) and obtained by absolute calibration using an integrating sphere. The charge exchange composite spectral 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 flux sphere, etc. One or more window holes are opened on the sphere wall, which are used as light inlet holes and receiving holes for placing light receiving devices. In order to obtain higher measurement accuracy, the opening 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 of which has a core diameter of 400um and is arranged in one dimension on 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 by 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 the 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 calculation: an initial, hypothetical impurity ion density profile is substituted into the program, and when the input 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 in the same way.

[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, obtaining the beam density of the neutral beam during its travel; Step 2, obtaining the particle number density ratio of 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 according to the obtained particle number density ratio of the excited state to the ground state in the neutral beam atoms; Step 4: Measure the active spectrum intensity of the impurity ions, and calculate the impurity ion concentration profile distribution in combination with the acquired beam density and charge exchange recombination radiation rate coefficient.

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 attenuation factor. ⊥ 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 step 2, 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 beam pumping probability of the neutral beam 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 impurity bare core concentration profile using active spectroscopy according to claim 1, characterized in that: In the step three, for each beam energy component, the charge exchange recombination radiation rate coefficients of the neutral beam atoms and the impurity ions in the ground state and the excited state are calculated respectively.

7. The method for measuring the concentration profile of impurity bare cores 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 charge exchange recombination radiation rate coefficient between the ground state beam atoms and the 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 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.

9. The method for measuring the impurity bare core concentration profile using active spectroscopy according to claim 8, characterized in that: 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.

10. The method for measuring the concentration profile of impurity bare cores using active spectroscopy according to claim 9, characterized in that: The impurity ion concentration profile in step 4 is obtained through self-consistent calculation.

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