Ion Temperature Diagnostic Method for Deuterium-Tritium Fusion Plasma

Abstract

The present invention discloses a method for diagnosing the ion temperature of a deuterium-tritium fusion plasma, comprising: irradiating an aluminum foil sample with a D-T neutron generator, measuring the activation product <supgt;26< / supgt;Al using an accelerator mass spectrometer, and obtaining the reaction cross section of the high-threshold <supgt;27< / supgt;Al(n,2n)<supgt;26< / supgt;Al reaction; fitting the obtained experimental data with a cubic polynomial to obtain the excitation function curve of the <supgt;27< / supgt;Al(n,2n)<supgt;26< / supgt>Al activation reaction cross section; calculating the D-T thermonuclear neutron energy spectrum under different ion temperature conditions in a fusion reactor using D-T as fuel; substituting the fitted reaction cross section excitation function and the calculated neutron energy spectrum into the integral yield ratio formula to obtain the plasma temperature diagnostic function. The threshold selected by this method is a high-threshold reaction close to 14 MeV, which will not be interfered during the diagnosis process, and this method can provide high-precision dynamic ion temperature and can dynamically diagnose the ion temperature of D-T fusion plasma below 20 keV.

Description

Technical Field

[0001] The present invention relates to the field of fusion plasma ion temperature diagnosis and neutron nuclear data measurement. More specifically, the present invention relates to a method for diagnosing the ion temperature of deuterium-tritium fusion plasma. Background Art

[0002] Before constructing a thermonuclear fusion reactor, various preliminary fusion devices need to be established to verify the plasma parameters that may be involved in thermonuclear reactions. At the current stage, the main task of the fusion device is to establish diagnostic means and methods for determining the basic parameters of the plasma and the entire device. The temperature of the ion component of the fusion plasma is one of the basic parameters of the plasma, and it is a prerequisite for achieving fusion ignition. Since it is very difficult to accurately measure the ion temperature of the fusion plasma, various technologies for diagnosing the temperature of the basic ion components need to be developed, and these technologies must be used after multiple cross-validations. Currently, there are mainly two categories of methods for diagnosing the ion temperature of fusion plasma: one is the non-nuclear diagnostic method, which mainly includes charge exchange recombination spectroscopy (CXRS), active neutral particle analysis (NPA), and Doppler broadening measurement of spectral lines; the other is the nuclear-related diagnostic method, which mainly includes neutron diagnosis and charged particle diagnosis.

[0003] Neutron diagnosis and charged particle diagnosis are relatively more applied in the case of lower ion temperatures, but new problems will be faced when realizing thermonuclear reactions: among them, the activation foils used for the absolute neutron yield generally have a low threshold and are easily affected by scattered neutrons and neutrons generated by photonuclear reactions. In addition, the selected nuclear reactions are based on evaluation databases, and there are large differences in data between different evaluation libraries, resulting in low accuracy; the neutron energy spectrum method will also be affected by scattered neutrons and photonuclear reaction neutrons. At the same time, the neutron yield per second after thermonuclear reactions will reach 10 18 Above, at this time, high-resolution neutron detectors will be interfered by a large dead time. In order to solve the problems of scattered neutrons, photonuclear neutrons, detector resolution ratio, dead time, etc., a new D-T fusion plasma ion temperature diagnostic method is urgently needed. Summary of the Invention

[0004] The present invention provides a method for diagnosing the ion temperature of deuterium-tritium fusion plasma, which can provide high-precision dynamic ion temperature, can dynamically diagnose the plasma temperature below 20 keV, and provides important reference and technical means for the construction of future fusion reactors using DT as fuel and the diagnosis application of ion temperature.

[0005] To achieve these objects and other advantages of the present invention, there is provided a method for diagnosing the ion temperature of deuterium-tritium fusion plasma, including:

[0006] Irradiating an aluminum foil sample with a D-T neutron generator and measuring the activation products using an accelerator mass spectrometer26 Al, obtaining a high threshold 27 Al(n,2n) 26 The reaction cross section of Al, specifically: Where σ is 27 Al(n,2n) 26 The reaction cross section of Al, N t is the target nucleus 27 The atomic number of Al, N p is the atomic number of the reaction product nucleus 26 The atomic number of Al, φ is the neutron fluence rate at the sample position, and t is the irradiation time;

[0007] For 27 Al(n,2n) 26 The experimental data of the reaction cross section of Al at different positions relative to the D-T reaction target center are fitted with a cubic polynomial to obtain the excitation function curve of the activation reaction cross section;

[0008] Calculate the D-T thermonuclear neutron energy spectrum under different ion temperature conditions in a fusion reactor using DT as fuel. The formula used is:

[0009]

[0010] Where f(E n ) is the D-T neutron energy spectrum, E n is the neutron energy, <E n > is the average neutron energy of the D-T neutron energy spectrum, m n is the neutron mass, m a is the mass of the accompanying α particle generated by the D-T reaction, θ i is the plasma temperature;

[0011] Substitute the fitted activation reaction cross section excitation function and the calculated neutron energy spectrum into the following formula

[0012]

[0013] Obtain the plasma temperature diagnostic function of the relationship between the integral yield ratio and the plasma temperature. Where η is the integral yield ratio of the high threshold sensitive reaction cross section to the reference reaction cross section, σ s (E n ) represents the high threshold sensitive activation reaction cross section, σ b (E n ) represents the reference activation reaction cross section, F(E n ) represents the neutron flux at the irradiated location.

[0014] Preferably, in the method for diagnosing the temperature of a fusion plasma based on high threshold neutron activation reaction, the process of irradiating an aluminum foil sample with the D-T neutron generator is as follows:

[0015] The aluminum foil sample includes aluminum foil, niobium foil and zirconium foil with the same size. The aluminum foil is sandwiched between the niobium foil and the zirconium foil, and the niobium foil is used as the neutron flux monitor for the aluminum foil sample.

[0016] On the D-T neutron generator, aluminum foil samples to be irradiated are arranged at multiple angular positions such as 0°, 20°, 60° and 100° relative to the incident d + beam direction respectively.

[0017] Quasi-monochromatic neutrons with an energy of 13 - 15 MeV are selected to irradiate the arranged aluminum foil samples to obtain the irradiated aluminum samples.

[0018] Preferably, in the deuterium-tritium fusion plasma ion temperature diagnostic method, the use of accelerator mass spectrometry to measure the high-threshold 27 Al(n,2n) 26 Al reaction cross section specifically includes:

[0019] Each irradiated aluminum sample is made into an Al2O3 target sample.

[0020] The 26 Al / 27 Al ratio in each Al2O3 target sample is measured on a tandem accelerator mass spectrometer.

[0021] 93 Nb(n,2n) 92m The Nb reaction cross section is used as the neutron flux monitor for the aluminum foil sample to calculate the neutron fluence rate at the position of the aluminum foil sample, specifically:

[0022]

[0023] where σ1 is the cross section of the monitored reaction for nuclear reaction, I γ is the characteristic gamma ray intensity of the neutron nucleus in the monitored reaction, F is the total correction factor of the characteristic gamma ray in the monitored reaction, C is the full energy peak count of the characteristic gamma ray, M is the mass of the parent nucleus, A is the atomic weight of the parent nucleus, ξ is the isotopic abundance of the parent nucleus, λ is the decay constant of the daughter nucleus, N A is the Avogadro constant, ε is the detection efficiency of the high-purity germanium detector for the characteristic gamma ray of the daughter nucleus, S is the generation factor, D is the measurement collection factor, and K is the neutron fluence rate fluctuation correction factor.

[0024] Preferably, in the deuterium-tritium fusion plasma ion temperature diagnostic method, the process of making the irradiated aluminum sample into an Al2O3 target sample is as follows:

[0025] Dissolve the irradiated aluminum target sample with hydrochloric acid to obtain an aluminum chloride solution. Drop dilute ammonia water into the aluminum chloride solution to obtain aluminum hydroxide. Centrifuge the precipitate and wash the surface with dilute ammonia water;

[0026] Dissolve, precipitate, and wash again;

[0027] Transfer the precipitate to a quartz crucible, dry it at low temperature, and calcine it in a muffle furnace to obtain an Al2O3 powder sample;

[0028] After cooling, add Cu powder with the same mass as Al2O3 to the quartz crucible. Grind and mix evenly, and then press to obtain an Al2O3 target sample.

[0029] Preferably, in the deuterium-tritium fusion plasma ion temperature diagnostic method, measure the 26 Al / 27 Al ratio in each Al2O3 target sample on a tandem accelerator mass spectrometer, specifically including:

[0030] Place the samples: Place the standard sample, the process blank sample, and the Al2O3 target sample to be measured on the target disk in sequence;

[0031] Ionize the sample: The ionized Cs + is accelerated in an electric field provided by a voltage of several thousand volts, bombards the surface of the Al2O3 target sample, and sputters out 26 Al - and 27 Al - negative ions;

[0032] Primary injection system screening: 26 Al - and 27 Al - After the negative ions of Al enter the electrostatic analyzer for the same energy selection, they become negative ions with different momenta. Under the modulation of the jump magnet, momentum compensation is performed so that 27 Al- and 26 Al- are alternately injected into the tandem accelerator with the same momentum;

[0033] Accelerator acceleration: 27 Al- and 26 The Al- negative ions are preliminarily accelerated to a high energy in the tandem accelerator, and then the negative ions enter the gas stripper and interact with the thin stripping gas. The negative ions are stripped into positive ions with different positive charges (n = 1+, 2+, 3+...). The positive ions are continuously accelerated at the other end of the tandem accelerator and enter the high-energy analysis system;

[0034] High-energy analysis system screening: The beam is first momentum-screened in the first high-energy analysis magnet, 26 Al n+Transmit along the beam center line, 27 Al n+ After passing through the first analyzing magnet, it deviates from the beam center line and enters the offset Faraday cup outside the beam center line to complete the beam measurement; 26 Al n+ Further, after completing the screening of energy and momentum in the electrostatic analyzer and the second analyzing magnet respectively, it enters the gas ionization chamber detector to complete 26 the measurement of Al counting;

[0035] Ratio calculation: By calculating the number of 26 Al in the gas ionization chamber detector and the number of 27 Al in the Faraday cup, the 26 Al / 27 Al ratio in the Al2O3 target sample is obtained;

[0036] The obtained ratio is deducted from the process blank and calibrated with the standard sample to obtain the final ratio of the Al2O3 target sample.

[0037] Preferably, in the method for diagnosing the ion temperature of deuterium-tritium fusion plasma, the relationship between the neutron flux F(E n ) and the neutron energy spectrum f(E n ) is F(E n ) = n D n T f(E n )<σ(v) v >, where n D and n T respectively represent the deuterium-tritium ion density, <σ (v) v> represents the average value of σ (v) v of deuterium-tritium two particles over the entire velocity distribution, which is called the average thermonuclear reaction rate, v is the magnitude of the relative velocity of deuterium-tritium two particles, and σ (v) is the fusion reaction cross section of deuterium-tritium two types of particles at a relative velocity of v.

[0038] Preferably, in the method for diagnosing the ion temperature of deuterium-tritium fusion plasma, the excitation function for obtaining the activation reaction cross section is specifically: y = -5882.34 + 1412.37x - 113.07x 2 + 3.02x 3 , R 2 = 0.999, where the x-axis is the neutron energy, the y-axis is the activation reaction cross section, and R 2 is the fitting curve determination coefficient.

[0039] Preferably, in the method for diagnosing the ion temperature of deuterium-tritium fusion plasma, the obtained plasma temperature diagnostic function is: Among them, the y-axis is the normalized integral yield ratio, the x-axis is the plasma temperature, and R 2 is the coefficient of determination of the fitting curve.

[0040] Preferably, in the method for diagnosing the ion temperature of deuterium-tritium fusion plasma, the high-threshold neutron activation reaction 27 Al(n,2n) 26 The threshold of Al is 13.5 MeV.

[0041] The present invention has at least the following beneficial effects:

[0042] First, when the D-T fusion neutrons irradiate the sample, the threshold selected in the present invention is a high-threshold activation reaction close to 14 MeV (far higher than the energies of scattered neutrons and photonuclear reaction neutrons in the fusion reactor), and it will not be interfered during the diagnosis process. And because the high-threshold reaction selected in the present invention is in the energy region near the threshold, the general reaction cross-section is relatively small, and it can accept long-term neutron irradiation in the case of high neutron yield.

[0043] Second, the present invention uses a high-sensitivity analytical instrument - accelerator mass spectrometer (AMS) to re-measure the reaction cross-section data, and derives a temperature measurement function for diagnosing the fusion plasma temperature based on the experimental measurement data, greatly improving the diagnostic accuracy of the temperature measurement function, and also solving the problem of large differences in different evaluation values in the selected activation reaction cross-section database.

[0044] Third, the diagnostic method of the present invention is applicable to the measurement of data of long-lived radionuclides, and measures 27 Al(n,2n) 26 the reaction cross-section of Al, and the derived plasma temperature diagnostic function can provide a high-precision dynamic ion temperature, and can dynamically diagnose the ion temperature below 20 keV, providing an important reference for the construction of future fusion reactors using DT as fuel and the diagnostic application of ion temperature. When only considering the systematic uncertainty during the measurement process, the ion temperature uncertainty is about 10%-12%, because the selected sensitive reaction and reference reaction thresholds are both relatively high, and the influence of scattered neutrons can be ignored.

[0045] Other advantages, objectives and features of the present invention will be partially reflected by the following description, and partially will be understood by those skilled in the art through the research and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is a schematic flow chart of the method for diagnosing the ion temperature of deuterium-tritium fusion plasma according to the present invention;

[0047] Figure 2 is a schematic diagram of the irradiation layout according to the present invention;

[0048] Figure 3 For the normalized deuterium-tritium neutron spectrum in the embodiments of the present invention and 27 Al(n,2n) 26 The fitting excitation function graph of the Al reaction;

[0049] Figure 4 It is the function graph of the relationship between the normalized integral yield ratio and the plasma temperature in the embodiments of the present invention. Specific embodiments

[0050] The following further elaborates on the present invention in conjunction with the attached drawings, enabling those skilled in the art to implement it with reference to the written description.

[0051] It should be understood that terms such as "having", "comprising", and "including" as used herein do not exclude the presence or addition of one or more other elements or their combinations.

[0052] It should be noted that the experimental methods described in the following embodiments are all conventional methods unless otherwise specified, and the reagents and materials can all be obtained commercially unless otherwise specified; in the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected", and "set" should be understood in a broad sense. For example, it can be fixedly connected and set, or detachably connected and set, or integrally connected and set. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. The orientation or positional relationships indicated by terms such as "lateral", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0053] As Figure 1 shown, the embodiments of the present invention provide a method for diagnosing the ion temperature of deuterium-tritium fusion plasma, including the following steps:

[0054] S10. Irradiate an aluminum foil sample with a D-T neutron generator, and use an accelerator mass spectrometer to measure the activation product 26 Al, to obtain the high-threshold 27 Al(n,2n) 26 Al reaction cross-section, and the threshold of the high threshold is 13.5 MeV. Specifically: Among them, σ is 27 Al(n,2n) 26 Al reaction cross-section, N t is the target nucleus 27The number of Al atoms, N p is the reaction-generated nucleus 26 where N is the number of Al atoms, φ is the neutron fluence rate at the sample position, and t is the irradiation time.

[0055] It should be noted that the D-T fusion reaction is: D+T→ 4 He+n+17.586MeV, where 17.586MeV is the Q value of the D-T reaction, D is the deuteron, and T is the triton. When the reaction nuclei are in thermal equilibrium, their velocity distribution is Maxwell distribution. After derivation, the energy distribution of neutrons generated by the D-T reaction shows a Gaussian distribution. The principle of the diagnostic method in the embodiments of the present invention is: on the premise that the fusion plasma shows a Maxwell distribution, at the effective plasma temperature θ i the D-T neutron spectrum f(E n ) generated is a symmetric Gaussian distribution. The shape of the D-T neutron spectrum is determined by the thermal motion of the interacting ions. It will have a certain broadening as the ion temperature increases, and the symmetry center of the neutron energy spectrum will shift a certain amount to the right as the temperature increases. Thus, the high-threshold reaction whose reaction threshold is close to the symmetry center of the D-T neutron spectrum is particularly sensitive to the high-energy neutrons with a certain broadening during the fusion neutron irradiation, while being insensitive to the low-energy neutrons. Therefore, by measuring the integral yield ratio of the high-threshold sensitive reaction to the reference reaction with a relatively stable cross-section value, the relationship between the broadening width of the neutron energy spectrum and the plasma temperature can be obtained, and then a temperature measurement function curve can be obtained.

[0056] Among them, the process of irradiating the aluminum foil sample with the D-T neutron generator is as follows:

[0057] S110. The aluminum foil sample includes aluminum foil, niobium foil and zirconium foil with the same size. The aluminum foil is sandwiched between the niobium foil and the zirconium foil, and the niobium foil is used as the neutron flux monitor for the aluminum foil sample. Specifically, when implemented, the diameter of the aluminum foil sample can be selected as 20mm;

[0058] S111. On the D-T neutron generator, at the angular positions of 0°, 20°, 60° and 100° relative to the incident d + beam direction, the aluminum foil samples to be irradiated are respectively arranged, as Figure 2 shown;

[0059] S112. Quasi-monochromatic neutrons with an energy of 13-15MeV are selected to irradiate the arranged aluminum foil samples, and the irradiated aluminum samples are obtained. Since aluminum foil samples are arranged at multiple angular positions such as 0°, 20°, 60° and 100°, 4 aluminum samples at different positions can be obtained after irradiation. The neutron energy in the 14MeV energy region is determined by the outgoing neutron angle relative to the d + beam and 90Zr(n,2n) 89 Zr, 93 Nb(n,2n) 92m Calculated by the Nb cross-section ratio, the D-T neutron generator can measure the reaction cross-section data at multiple neutron energy points in the range of 13 MeV to 15 MeV.

[0060] Furthermore, the use of accelerator mass spectrometry to measure high thresholds 27 Al(n,2n) 26 Al reaction cross-section, specifically including:

[0061] S120. Each irradiated aluminum sample is made into an Al2O3 target sample;

[0062] S121. Measure the 26 Al / 27 Al ratio in each Al2O3 target sample on the tandem accelerator mass spectrometry;

[0063] S122. 93 Nb(n,2n) 92m The Nb(n,2n) Nb reaction cross-section is used as a neutron flux monitor for the aluminum foil sample to calculate the neutron fluence rate at the position of the aluminum foil sample, specifically:

[0064]

[0065] Among them, σ1 is the cross-section of the monitored reaction for nuclear reaction, I γ is the characteristic gamma-ray intensity of the monitored reaction neutron nucleus, F is the total correction factor of the characteristic gamma-ray in the monitored reaction, C is the full-energy peak count of the characteristic gamma-ray, M is the mass of the parent nucleus, A is the atomic weight of the parent nucleus, ξ is the isotopic abundance of the parent nucleus, λ is the decay constant of the daughter nucleus, N A is the Avogadro constant, ε is the detection efficiency of the high-purity germanium detector for the characteristic gamma-ray of the daughter nucleus, S is the generation factor, D is the measurement collection factor, and K is the neutron fluence rate fluctuation correction factor.

[0066] For the irradiation time t, it can be calculated according to the background value of the accelerator mass spectrometer, the neutron fluence rate at the position to be irradiated, and the theoretical cross-section value corresponding to the position to be irradiated.

[0067] S20. Cubic polynomial fitting is performed on the experimental data of the 27 Al(n,2n) 26 Al reaction cross-section at different positions to obtain the excitation function of the activation reaction cross-section.

[0068] Due to the significant differences in the sensitivity of the ion temperature diagnostic function obtained from the scattered experimental data measured in experiments under different fitting methods. The measured experimental data were calculated respectively in the ways of linear fitting, quadratic polynomial fitting, and cubic polynomial fitting. By comparing the ratios when the ion temperature is 20 keV and 1 keV, it can be found that under the condition of determining the threshold of the sensitive reaction, the cubic polynomial fitting method has the highest sensitivity. Therefore, in this embodiment, the experimental data at four positions are fitted by the cubic polynomial, and the fitted 27 Al(n,2n) 26 excitation function of the Al reaction is specifically: y = -5882.34 + 1412.37x - 113.07x 2 + 3.02x 3 ,R 2 = 0.999, where the x-axis is the neutron energy and the y-axis is the activation reaction cross section (unit: mb), and R 2 is the determination coefficient of the fitting curve.

[0069] S30. Calculate the D-T thermonuclear neutron energy spectra under different ion temperature conditions in a fusion reactor with DT as fuel. The formula used is:

[0070]

[0071] where f(E n ) is the D-T neutron energy spectrum, E n is the neutron energy, <E n > is the average neutron energy of the D-T neutron energy spectrum, m n is the neutron mass, m a is the mass of the accompanying α particle generated by the D-T reaction, and θ i is the plasma temperature.

[0072] S40. Substitute the fitted activation reaction cross section excitation function and the calculated neutron energy spectrum into the following formula

[0073]

[0074] to obtain the plasma temperature diagnostic function of the relationship between the integral yield ratio and the plasma temperature, as Figure 4 shown. The obtained plasma temperature diagnostic function is: where the y-axis is the normalized integral yield ratio, the x-axis is the plasma temperature, and R 2 is the determination coefficient of the fitting curve. Among them, η is the integral yield ratio of the high-threshold sensitive reaction cross section to the reference reaction cross section, and σ s (E n ) represents the high-threshold sensitive activation reaction cross section, and σ b (E n) represents the reference activation reaction cross-section, F(E n ) represents the neutron flux at the irradiated location. The neutron flux F(E n ) at the irradiated location and the neutron energy spectrum f(E n ) are related as follows: F(E n ) = n D n T f(E n )<σ (v) v>, where n D and n T respectively represent the deuterium-tritium ion densities. <σ (v) v> is the average value of σ (v) v for the entire velocity distribution of deuterium and tritium particles, which is called the average thermonuclear reaction rate. v is the magnitude of the relative velocity of deuterium and tritium particles, and σ (v) is the fusion reaction cross-section of deuterium and tritium particles with a relative velocity of v.

[0075] It should be noted that for the reference activation reaction cross-section, niobium is generally selected as the standard activation reaction cross-section.

[0076] In one specific embodiment, for the method for diagnosing the ion temperature of deuterium-tritium fusion plasma, the process of making the irradiated aluminum sample into an Al2O3 target sample is as follows:

[0077] A. Dissolve the irradiated aluminum target sample with an appropriate amount of 4.5M HCL to obtain an aluminum chloride solution. Then, drop dilute ammonia water into the aluminum chloride solution to obtain aluminum hydroxide. Centrifuge to remove the supernatant and wash the surface with dilute ammonia water.

[0078] B. Dissolve, precipitate, and wash again.

[0079] C. Transfer the precipitate to a quartz crucible, dry it at a low temperature, and then calcine it in a muffle furnace at 900 °C for 3 hours to obtain an Al2O3 powder sample.

[0080] D. After cooling, add copper powder with the same mass as Al2O3 to the quartz crucible, grind and mix evenly, and then press to obtain the Al2O3 target sample for measurement.

[0081] In one specific embodiment, for the method for diagnosing the ion temperature of deuterium-tritium fusion plasma, the measurement of the 26 Al / 27 Al ratio in each Al2O3 target sample on a tandem accelerator mass spectrometer specifically includes:

[0082] A. Place the samples: Place the standard sample, the process blank sample, and the Al2O3 target sample on the target disk in sequence.

[0083] B. Sample ionization: At the ion source, Cs vapor generated by high-temperature heating loses its outer electrons on the metal surface at a high temperature (1100 °C) and is ionized into Cs + ions. The ionized Cs + is accelerated in the electric field provided by a voltage of several thousand volts and bombards the surface of the Al2O3 target sample, sputtering out 26 Al - and 27 Al - negative ions.

[0084] C. Primary injection system screening: 26 Al - and 27 Al - negative ions are accelerated by the extraction electrode voltage and enter the electrostatic analyzer at the low-energy end for energy screening. Since magnesium metal cannot form stable negative ions in the cesium sputtering negative ion source, 26 isotopes of Al 26 Mg are effectively suppressed at the ion source; negative molecular ions with the same energy and different momenta are momentum-screened under the modulation of the jump magnet, and 27 Al- with a mass number of 27 and 26 Al- with a mass number of 26 are alternately injected into the tandem accelerator.

[0085] D. Accelerator acceleration: 27 Al- and 26 Al- negative ions are initially accelerated to high energy in the tandem accelerator, and then the negative ions enter the gas stripper and interact with the rarefied stripping gas. The negative ions are stripped into positive ions with different positive charges (n = 1+, 2+, 3+...), and these positive ions are secondarily accelerated at the other end of the tandem accelerator and enter the high-energy analysis system.

[0086] E. High-energy analysis system screening: The high-energy analysis system includes two magnets and an electrostatic analyzer. 26 Al n+ positive ions are transported along the midline in the first high-energy analysis magnet. 27 Al n+ positive ions enter the biased Faraday cup after passing through the first high-energy analysis magnet to complete the beam current measurement (in nA, the unit of current, the amount of 27 Al charge received per unit time per unit area); 26 Al n+ positive ions further complete energy and momentum screening in the electrostatic analyzer and the second analysis magnet respectively and then enter the gas ionization chamber detector to complete 26 Al counting measurement (in units of number, that is, the number of 26 Al detected per unit time);

[0087] F. Ratio calculation: By recording the number of 26 Al atoms in the gas ionization chamber detector and the number of 27 Al atoms in the Faraday cup, the 26 Al / 27 Al ratio in the Al2O3 target sample is obtained;

[0088] G. Subtract the process blank from the obtained ratio, and after calibration with standard samples, the final ratio of the Al2O3 target sample is obtained.

[0089] It should be noted that when measuring a sample, it is necessary to know whether the test instrument is contaminated. Therefore, a blank sample, that is, a process blank sample, is required for testing. The above test was completed on the three-million-volt tandem accelerator mass spectrometer at the Xi'an Accelerator Mass Spectrometry Center. It can also be completed in other accelerator mass spectrometry laboratories with the ability to measure 26 Al.

[0090] The ion temperature diagnostic function obtained in the embodiments of the present invention can dynamically diagnose the ion temperature of D-T fusion plasmas below 20 keV. Considering only the systematic uncertainties in the measurement process, the ion temperature uncertainty is about 10%-12%. Since the selected sensitive reaction and reference reaction thresholds are both relatively high, the influence of scattered neutrons can be ignored. It should also be noted that the diagnostic method described in the present invention can be used to measure data not only for aluminum foils but also for other long-lived radionuclides such as iron foils.

[0091] The equipment quantities and processing scales described here are used to simplify the description of the present invention. Applications, modifications, and variations of the present invention will be apparent to those skilled in the art.

[0092] Although the embodiments of the present invention have been disclosed above, it is not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and the illustrated examples described herein.

Claims

1. A method for diagnosing the ion temperature of a deuterium-tritium fusion plasma, characterized in that, Including: Irradiate an aluminum foil sample with a D-T neutron generator and measure the activation products using an accelerator mass spectrometer 26 Al to obtain a high threshold 27 Al(n,2n) 26 Al reaction cross-section, specifically: , where is 27 Al(n,2n) 26 Al reaction cross-section, is the number of atoms of the target nucleus 27 Al, is the number of atoms of the reaction-produced nucleus 26 Al, is the neutron fluence rate at the sample position, is the irradiation time; For the 27 Al(n,2n) 26 experimental data of the reaction cross section at different positions of the D-T neutron generator target center are fitted by a cubic polynomial to obtain the excitation function curve of the neutron activation reaction cross section in the 14 MeV energy region. Among them, the excitation function of the obtained activation reaction cross section is specifically: , where the x-axis is the neutron energy and the y-axis is the activation reaction cross section, is the determination coefficient of the fitting curve; Calculating the D-T thermonuclear fusion neutron energy spectrum under different ion temperature conditions in a D-T fuel fusion reactor, and the formula used is: ， wherein, is the D-T neutron energy spectrum, is the neutron energy, is the average neutron energy of the D-T neutron energy spectrum, is the neutron mass, is the associated particle generated by the D-T reaction mass of, is the plasma temperature; Substituting the fitted activation reaction cross-section excitation function and the calculated neutron energy spectrum into the following formula ， Obtain a plasma temperature diagnostic function for the relationship between the integral yield ratio and the plasma temperature, where is the integral yield ratio of the high-threshold sensitive reaction cross-section to the reference reaction cross-section, represents the high-threshold sensitive activation reaction cross-section, represents the reference activation reaction cross-section, represents the neutron flux at the irradiated location; among them, the obtained plasma temperature diagnostic function is: , where the y-axis is the normalized integral yield ratio and the x-axis is the plasma temperature, is the determination coefficient of the fitting curve; Wherein, the D-T neutron generator irradiates an aluminum foil sample, and the specific process is: The aluminum foil sample includes aluminum foil, niobium foil and zirconium foil with the same size. The aluminum foil is sandwiched between the niobium foil and the zirconium foil, and the niobium foil is used as the neutron flux monitoring sheet for the aluminum foil sample; On the D-T neutron generator, aluminum foil samples to be irradiated are respectively arranged at the angular positions of 0°, 20°, 60° and 100° relative to the incident d + beam direction; Selecting quasi-monochromatic neutrons with an energy of 13-15 MeV to irradiate the arranged aluminum foil sample to obtain the irradiated aluminum sample.

2. The method for diagnosing the ion temperature of a deuterium-tritium fusion plasma according to claim 1, wherein Measuring a high threshold using an accelerator mass spectrometer 27 Al(n,2n) 26 Al reaction cross section, specifically including: Each irradiated aluminum sample is made into an Al2O3 target sample; Measure the 26 Al / 27 Al ratio in each Al2O3 target sample on a tandem accelerator mass spectrometer; 93 Nb(n,2n) 92m The Nb reaction cross section is used as a neutron flux monitor for the aluminum foil sample to calculate the neutron fluence rate at the position of the aluminum foil sample, specifically: Among them, is the supervision reaction 93 Nb(n,2n) 92m the cross section of the nuclear reaction of Nb, is the characteristic gamma-ray intensity of the neutron nucleus of the supervision reaction, is the total correction factor of the characteristic gamma rays in the supervision reaction, is the full-energy peak count of the characteristic gamma rays, is the mass of the parent nucleus, is the atomic weight of the parent nucleus, is the isotope abundance of the parent nucleus, is the decay constant of the daughter nucleus, is the Avogadro constant, is the detection efficiency of the high-purity germanium detector for the characteristic gamma rays of the daughter nucleus, is the generation factor, is the measurement collection factor, is the neutron fluence rate fluctuation correction factor.

3. The deuterium-tritium fusion plasma ion temperature diagnostic method according to claim 2, characterized in that, The process of making the irradiated aluminum sample into an Al2O3 target sample is as follows: Dissolving the irradiated aluminum target sample with hydrochloric acid to obtain an aluminum chloride solution, dropping dilute ammonia water into the aluminum chloride solution to obtain aluminum hydroxide, centrifuging the precipitate, and washing the surface with dilute ammonia water; Dissolving, precipitating and washing again; Transferring the precipitate to a quartz crucible, drying at low temperature, and calcining in a muffle furnace to obtain an Al2O3 powder sample; After cooling, adding Cu powder with the same mass as Al2O3 to the quartz crucible, grinding and mixing evenly, and pressing to obtain an Al2O3 target sample.

4. The method for diagnosing the ion temperature of a deuterium-tritium fusion plasma according to claim 2, wherein Measuring the 26 Al / 27 Al ratio in each Al2O3 target sample on the tandem accelerator mass spectrometer specifically includes: Placing the samples: Placing the standard sample, the process blank sample and the Al2O3 target sample to be measured on the target plate in sequence; Sample ionization: Ionized Cs + Accelerated in an electric field provided by a voltage of several thousand volts, bombarding the surface of the Al2O3 target sample, sputtering out 26 Al - and 27 Al - negative ions; Primary injection system screening: 26 Al - and 27 Al - After the negative ions enter the electrostatic analyzer for the same energy selection, they become negative ions with different momenta and are momentum-complemented under the modulation of the jumping magnet, so that 27 Al - and 26 Al - are alternately injected into the tandem accelerator with the same momentum; Accelerator acceleration: 27 Al - and 26 Al - Negative ions are preliminarily accelerated to high energy in a tandem accelerator. Then the negative ions enter a gas stripper and interact with a thin stripping gas. The negative ions are stripped into positive ions with different positive charges. The positive ions are continuously accelerated at the other end of the tandem accelerator and enter a high-energy analysis system; High-energy analysis system screening: The beam first undergoes momentum screening in the first high-energy analysis magnet. 26 Al n+ It is transmitted along the beam center line. 27 Al n+ After passing through the first analysis magnet, it deviates from the beam center line and enters the offset Faraday cup outside the beam center line to complete the beam measurement. 26 Al n+ After further completing energy and momentum screening in the electrostatic analyzer and the second analysis magnet respectively, it enters the gas ionization chamber detector to complete 26 the measurement of Al counting. Ratio calculation: By calculating the number of 26 Al atoms in the gas ionization chamber detector and the number of 27 Al atoms in the Faraday cup, the 26 Al / 27 Al ratio in the Al2O3 target sample is obtained; Subtracting the process blank from the obtained ratio, and obtaining the final ratio of the Al2O3 target sample after calibration with the standard sample.

5. The method for diagnosing the ion temperature of a deuterium-tritium fusion plasma according to claim 1, wherein Relationship between neutron flux and neutron energy spectrum at the irradiated location , where and represent the deuterium-tritium ion density respectively, is the average value of the deuterium-tritium particles over the entire velocity distribution, called the average thermonuclear reaction rate, is the magnitude of the relative velocity of the deuterium-tritium particles, is the T(d,n)α fusion reaction cross section of the deuterium-tritium particles at the relative velocity of .

6. The method for diagnosing the ion temperature of a deuterium-tritium fusion plasma according to claim 1, wherein High-threshold neutron activation reaction 27 Al(n,2n) 26 The threshold of Al is 13.5 MeV.

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