A device and method for measuring the absolute yield of long-range alpha particles and tritons in ternary fission of fissile nuclei

Abstract

The application relates to a kind of measuring device and method of fission nuclear ternary fission medium long-range alpha particle and tritium absolute yield, belong to nuclear data measurement technical field, solve the technical problem of low measurement efficiency and low precision of light charged particle in fission nuclear ternary fission, its measuring device includes screen grid ionization chamber, cathode, grid, anode, shielding electrode, aluminum film, four-component alpha source for calibration, data acquisition and processing system.Aluminum film covers sample well with fission target material, for shielding part of binary fission fragment and decay alpha particle.The measurement method includes the steps of measuring binary fission fragment under the condition of no aluminum film and low pressure working gas, simulating the measurement process of binary fission fragment, measuring light charged particle in ternary fission under the condition of aluminum film and high pressure working gas, simulating the measurement process of light charged particle in ternary fission, obtaining the absolute yield of medium long-range alpha particle in ternary fission, and obtaining the absolute yield of tritium in ternary fission.

Description

Technical Field

[0001] This invention belongs to the field of nuclear data measurement technology, specifically relating to a device and method for measuring the absolute yield of long-range alpha particles and tritium in fission nuclear ternary fission. Background Technology

[0002] The ternary fission phenomenon has a unique probe function in studying the characteristics of the fracture point during fission, because the charged particles of the third fission are emitted at the fracture point simultaneously with the fragments of the other two binary fissions, and their absolute yield data helps to further understand the fission process.

[0003] In common ternary fission, the measurement methods for light charged particles are based on detector-telescope methods or low-pressure ionization chamber methods. However, due to the low detection efficiency or lack of particle resolution of existing measurement methods, it is impossible to obtain experimental data on the absolute yield of the most light charged particles (long-range alpha particles and tritium) in ternary fission of fast neutron-induced fission nuclei above 1 MeV. Summary of the Invention

[0004] To overcome the shortcomings of low efficiency and low accuracy in the measurement of light charged particles in nuclear fission ternary fission, this invention proposes a device and method for measuring the absolute yield of long-range alpha particles and tritium in nuclear fission ternary fission.

[0005] The technical solution adopted by this invention to solve its technical problem is:

[0006] A measuring device for the absolute yield of long-range alpha particles and tritium in fission nuclear ternary fission includes a screened ionization chamber, a cathode, a grid, an anode, a shielding electrode, an aluminum film, a four-component alpha source for calibration, and a data acquisition and processing system.

[0007] The ionization chamber is a sealed cylindrical shape, equipped with a sealed door for installing and removing fission target materials. The interior is filled with a working gas, which is a mixture of argon and methane.

[0008] The cathode, grid, anode, and shield are all rectangular flat plates. There is one cathode, and two grids, anodes, and shields. The grids are symmetrically distributed with respect to the cathode, the anodes are symmetrically distributed with respect to the cathode, and the shields are symmetrically distributed with respect to the cathode. From the inside out, the cathode, grid, anode, and shield are arranged in parallel and are installed in the grid ionization chamber.

[0009] The cathode is a rectangular plate installed on the center line of the grid ionization chamber. A sample well is set up, and the fission target material is placed in the sample well. The aluminum film and the four-component α source for calibration are located on both sides of the fission target material.

[0010] The data acquisition and processing system is used to measure the two-dimensional spectrum of cathode signal amplitude vs. anode signal amplitude and the two-dimensional spectrum of anode signal amplitude vs. anode signal rise time.

[0011] In the aforementioned measuring device, the aluminum film is located on the plane of the cathode plate and covers the sample well containing the fission target material, thereby shielding some of the binary fission fragments and decay alpha particles.

[0012] The aluminum film thickness in the above-mentioned measuring device is 30 μm or 10 μm.

[0013] The working gas pressure of the aforementioned measuring device is 0.5 atmospheres or more than 6 atmospheres.

[0014] The working gas in the above-mentioned measuring device is a 90% Ar + 10% CH4 mixture at 0.5 atm, or a 90% Ar + 10% CH4 mixture at 7.0 atm, or a 90% Ar + 10% CH4 mixture at 7.5 atm.

[0015] The fission target material in the above-mentioned measuring device is... 252 Cf, or for 235 U, or for 239 Pu fissile materials.

[0016] A method for measuring the absolute yield of long-range alpha particles and tritium in fission nuclear ternary fission includes the following steps:

[0017] Step 1: Measuring binary fission fragments using a grid ionization chamber under conditions of no aluminum film and low working gas pressure.

[0018] The fission target material is placed in the sample well of the measuring device for the absolute yield of long-range alpha particles and tritium in the ternary fission of fission nuclei. No aluminum film is placed, and the working gas pressure is 0.5 atmospheres.

[0019] When the fission target material undergoes spontaneous or neutron-induced binary fission, a data acquisition and processing system is used to collect the amplitude spectrum of the anode signal when measuring the binary fission fragments in a screen ionization chamber.

[0020] Step 2: Simulate the measurement process of binary fission fragments.

[0021] The Monte Carlo method was used to simulate the measurement process of fission nuclei ejecting binary fission fragments in a grid-connected ionization chamber. The mass, independent yield, and total energy released by the binary fission fragments were calculated using GEF 2020 / 1.1 software. Then, the energy of the binary fission fragments was calculated based on the conservation of momentum and energy. Considering the energy of the binary fission fragments, the mass, independent yield, energy, and ejection angle of the binary fission fragments were discretely sampled from the fission nuclei. Taking into account sample thickness, sample inhomogeneity, and the PHD effect, the anode signal amplitude spectrum during the measurement of binary fission fragments in the grid-connected ionization chamber was simulated.

[0022] The simulated anode signal amplitude spectrum is compared with the anode signal amplitude spectrum measured in step 1. The two are consistent, thus determining the detection efficiency of the grid ionization chamber for binary fission fragments. The subthreshold fraction of binary fission is corrected to obtain the total binary fission count rate.

[0023] Step 3: Measure the light charged particles in the three-part splitting reaction using a screened ionization chamber under conditions of aluminum film and high-pressure working gas.

[0024] Place aluminum films of different thicknesses and adjust the working gas pressure to more than 6 atmospheres.

[0025] When the fission target material undergoes spontaneous or neutron-induced ternary fission, a data acquisition and processing system is used to acquire the two-dimensional spectrum of cathode signal amplitude vs. anode signal amplitude, the two-dimensional spectrum of anode signal amplitude vs. anode signal rise time, and the anode signal amplitude spectrum when measuring light charged particles in the ternary fission in the screen grid ionization chamber.

[0026] Step 4: Simulate the measurement process of light charged particles in the three-phase splitting process.

[0027] Using the Monte Carlo method, the measurement process of light charged particles in the ternary fission of fission nuclei in a grid-screened ionization chamber was simulated. The charge number, mass number, energy distribution, and emission angle of the light charged particles in the ternary fission were sampled. Considering the sample thickness, sample inhomogeneity, and the influence of the aluminum film, the deposition energy of these charged particles in the grid-screened ionization chamber was calculated, and the track length, emission angle, and deposition energy information of the charged particles were obtained. Based on the above information, the corresponding two-dimensional spectrum of cathode signal amplitude vs. anode signal amplitude, two-dimensional spectrum of anode signal amplitude vs. anode signal rise time, and anode signal amplitude spectrum were obtained.

[0028] Step 5: Obtain the absolute yield of long-range alpha particles in the three-fission transition.

[0029] For long-range alpha particles in the ternary fission, the event region of long-range alpha particles is delineated in the two-dimensional spectrum of cathode signal amplitude vs. anode signal amplitude obtained by measurement in step 3 and simulation calculation in step 4, respectively. The corresponding experimental measurement and simulation calculation anode signal amplitude spectrum are obtained. The two are consistent with each other, thereby determining the detection efficiency of the grating ionization chamber for long-range alpha particles in the ternary fission. The subthreshold fraction of long-range alpha particles is corrected to obtain the total long-range alpha particle count rate. Dividing it by the total binary fission count rate obtained in step 2, the absolute yield of long-range alpha particles in the ternary fission is obtained.

[0030] Step 6: Obtain the absolute yield of tritium in the ternary fission variant.

[0031] For tritium in the ternary fission, the event region of tritium is delineated in the two-dimensional spectrum of anode signal amplitude vs. anode signal rise time obtained from the measurement in step 3 and the simulation calculation in step 4, respectively. The corresponding experimental measurement and simulation calculation anode signal amplitude spectrum are obtained. The two are consistent with each other, thereby determining the detection efficiency of the grating ionization chamber for tritium in the ternary fission. The subthreshold fraction of tritium and the influence of long-range α particles are corrected to obtain the total tritium count rate. Dividing the total binary fission count rate obtained in step 2, the absolute yield of tritium in the ternary fission is obtained.

[0032] The beneficial effects of this invention are:

[0033] A device for measuring the absolute yield of long-range alpha particles and tritium in fission ternary nuclei is proposed. Based on a screened ionization chamber with a certain particle resolution capability, the device measures long-range alpha particles and tritium in fission ternary nuclei under low-pressure unshielded aluminum film conditions and high-pressure shielded aluminum film conditions. The results include experimental spectra of the anode amplitude in the screened ionization chamber when measuring fission fragments, two-dimensional experimental spectra of the cathode signal amplitude vs. anode signal amplitude in the screened ionization chamber when measuring ternary nuclei, two-dimensional experimental spectra of the anode signal amplitude vs. anode signal rise time, and the anode signal amplitude spectrum. These are then combined with high-fidelity simulations to provide the corresponding absolute yield data. Since alpha particles and tritium have significantly different stopping abilities in the same working gas, these two lightly charged particles with the same energy and angle will have different ranges in the gas. Therefore, their rise times and cathode signal amplitudes will differ. The long-range alpha particles and tritium are easily distinguished in the two two-dimensional experimental spectra mentioned above.

[0034] A measuring device for the absolute yield of long-range alpha particles and tritium in fission ternary processes is disclosed. This device utilizes a screened ionization chamber to measure the absolute yield of long-range alpha particles and tritium in fission ternary processes. It has high detection efficiency and can be applied to the measurement of data on the absolute yield of long-range alpha particles and tritium in fast neutron-induced fission ternary processes above 1 MeV.

[0035] A method for measuring the absolute yield of long-range alpha particles and tritium in fission nuclear ternary fission can significantly reduce the uncertainty of measurement results and obtain more accurate absolute yield data under the same fission target material and neutron source conditions.

[0036] A method for measuring the absolute yield of long-range alpha particles and tritium in fission nuclear ternary fission is proposed, which uses Monte Carlo simulation of the ionization chamber measurement process. The simulation method is simple and easy to implement. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the measuring device of the present invention;

[0038] Figure 2 This is a flowchart of the high-fidelity simulation process;

[0039] Figure 3 The measurements of the grating ionization chamber are obtained through experimental measurements and simulation calculations. 252 Anode signal amplitude spectrum during Cf binary splitting and fragmentation;

[0040] Figure 4 The measurements of the grating ionization chamber are obtained through experimental measurements and simulation calculations. 252 The two-dimensional spectrum of cathode signal amplitude vs. anode signal amplitude during light charged particles in the Cf ternary splitting process, and the anode signal amplitude spectrum in the selected alpha particle event region. Figure 4 (a) is the experimentally measured ionization chamber measurement. 252 Two-dimensional spectrum of cathode signal amplitude vs. anode signal amplitude in Cf ternary splitting of light charged particles. Figure 4 (b) is the measurement of the screen ionization chamber obtained from simulation calculation. 252 Two-dimensional spectrum of cathode signal amplitude vs. anode signal amplitude in Cf ternary splitting of light charged particles. Figure 4 (c) is the anode signal amplitude spectrum of the selected α-particle event region obtained by experimental measurement and simulation calculation;

[0041] Figure 5 The measurements of the grating ionization chamber are obtained through experimental measurements and simulation calculations. 252 The two-dimensional spectrum of the anode signal amplitude vs. the rise time of the anode signal in the Cf ternary splitting process involving light charged particles, and the anode signal amplitude spectrum in the selected tritium event region. Figure 5 (a) shows the experimentally obtained measurements of the ionization chamber with a screen. 252 Two-dimensional spectrum of anodic signal amplitude vs. anodic signal rise time for light charged particles in Cf ternary splitting. Figure 5 (b) is the measurement of the screen ionization chamber obtained from simulation calculation. 252 Two-dimensional spectrum of anodic signal amplitude vs. anodic signal rise time for light charged particles in Cf ternary splitting. Figure 5(c) is the anode signal amplitude spectrum of the selected tritium event region obtained from experimental measurements and simulation calculations;

[0042] Figure 6 This is a comparison chart of the absolute yields of long-range alpha particles and tritium obtained from our experimental measurements with the results from five other studies. Figure 6 (a) is a comparison graph of the absolute yield of long-range alpha particles obtained by our experimental measurements and the results of measurements in five other papers. Figure 6 (b) is a comparison graph of the absolute tritium yield measured in this work and the measurement results of five literatures.

[0043] Figure reference numerals: 1. Grid ionization chamber, 2. Fission target material, 3. Aluminum film, 4. Four-component α source for calibration, 5. Cathode, 6. Grid, 7. Anode, 8. Shielding electrode, 9. Working gas. Detailed Implementation

[0044] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0045] Example 1

[0046] 252 Cf is the most commonly used spontaneous fission source because it is a spontaneous fission process that does not require an additional neutron source, making experiments convenient. Meanwhile, for 252 There is considerable research on the ternary fission phenomenon of Cf, which contains a large number of... 252 Experimental data on the absolute yields of long-range alpha particles and tritium in Cf triple fission; therefore, in this example, the research object is a spontaneous fission source. 252 Cf.

[0047] A schematic diagram of a device for measuring the absolute yield of long-range alpha particles and tritium in nuclear ternary fission is shown below. Figure 1 As shown.

[0048] A method for measuring the absolute yield of long-range alpha particles and tritium in fission nuclear ternary fission is as follows:

[0049] Will 252 A Cf fission target is placed inside the cathode sample well. The Monte Carlo method is used to simulate the measurement process of lightly charged particles in the binary and ternary fission fragments emitted from the fission nucleus in a screened ionization chamber. A flowchart of the high-fidelity simulation process is shown below. Figure 2 As shown. First, without setting a shielding aluminum film and using 0.5 atm of 90% Ar + 10% CH4 as the working gas, the experiment obtained the measurement of the grid ionization chamber. 252 The experimental spectrum of the anode signal amplitude during spontaneous binary fission and fragmentation of Cf is compared with the amplitude spectrum calculated in the simulation above. The experimental spectrum and the simulation spectrum of the anode signal amplitude are as follows: Figure 3As shown. The two conditions are consistent, thus determining the detection efficiency of the grid ionization chamber for binary fission fragments, correcting the subthreshold fraction of binary fission, and obtaining the total binary fission rate. Secondly, a 30μm shielding aluminum film was set up, and 90% Ar + 10% CH4 at 7 atm was used as the working gas. Experiments showed that the grid ionization chamber measurement... 252 The two-dimensional spectrum of cathode signal amplitude vs. anode signal amplitude during spontaneous Cf ternary fission is used to delineate the event region of long-range α particles in the experimental and simulated two-dimensional spectra, yielding the corresponding experimental and simulated anode signal amplitude spectra. The experimental and simulated cathode signal amplitude vs. anode signal amplitude two-dimensional spectra and the anode signal amplitude spectrum for the selected long-range α particle event region are shown below. Figure 4 (a) Figure 4 (b) Figure 4 As shown in (c), the amplitude spectra of the experimental and simulated anode signals are consistent, thus determining the detection efficiency of the screened ionization chamber for long-range alpha particles in ternary fission. The subthreshold fraction of long-range alpha particles is corrected to obtain the total long-range alpha particle count rate. Dividing this by the total binary fission count rate yields the absolute yield of long-range alpha particles in ternary fission. Finally, a 10 μm aluminum shielding film is used, and 90% Ar + 10% CH4 at 7.5 atm is used as the working gas. The experimental results of the screened ionization chamber measurement... 252 The two-dimensional spectrum of cathode signal amplitude vs. anode signal amplitude during spontaneous trifleic splitting of Cf particles is obtained by delineating the tritium event region in experimental and simulated two-dimensional spectra, and obtaining the corresponding experimental and simulated anode signal amplitude spectra. The experimental and simulated anode signal amplitude vs. anode signal rise time two-dimensional spectra and the anode signal amplitude spectrum of the selected tritium event region are shown below. Figure 5 (a) Figure 5 (b) Figure 5 As shown in (c). The amplitude spectra of the experimental and simulated anode signals are consistent, thus determining the detection efficiency of the grating ionization chamber for tritium in the ternary fission. The influence of the subthreshold fraction of tritium and long-range α particles is corrected to obtain the total tritium count rate. Dividing this by the total binary fission count rate obtained above, the absolute yield of tritium in the ternary fission is obtained. This invention measures... 252 The Cf spontaneous three-split variable-range alpha particle and tritium absolute yield data are consistent with the measurement results from five literature studies, such as... Figure 6 (a) Figure 6 (b) shows. The five references are: [1] SW Cosper, J. Cerny and R.C. Gatti, Long-Range Particles of Z=1 to 4 Emitted During the Spontaneous Fission of 252Cf[J].Phys.Rev,1967,154:1193-1206.[2]SLWhetstone,TDThomas,LightChargedParticles fromSpontaneousFissionof 252 Cf[J].Phys.Rev,1967,154:1174-1181.[3]GM Raisbeck,TDThomas,LightNucleiEmittedintheFissionof 252 Cf[J].Phys.Rev,1968,172:1272-1282.[4]JFWild,PABaisden,RJDouganetal.,Light-charged-particle EmissionintheSpontaneousFissionof 250 Cf, 256 Fm, and 257 Fm[J].Phys.Rev.C,1985,32:488-495.[5]S.Vermote,C.Wagemans,O.Serotetal.,TernaryParticleEmissionin SpontaneousFissionof 250 Cfand 252 CfandinNeutronInducedFissionof 249 Cfand 251 Cf[J].Nucl.Phys.A,2010,837:176-194.

[0050] The above examples illustrate the accuracy of the simulation results obtained in this invention, and the methods of this invention were experimentally measured. 252 The absolute yields of long-range alpha particles and tritium from Cf were obtained with reliable absolute yield results, which fully demonstrates the feasibility of using this method to measure absolute yield.

[0051] Example 2

[0052] A measuring device for the absolute yield of long-range alpha particles and tritium in fission ternary fission mainly includes a fission target material 2, a screened ionization chamber 1, aluminum films 3 of different thicknesses, working gases 9 of different pressures, and a data acquisition and processing system. The fission target material 2 is placed in the sample well of the cathode plate 5 of the screened ionization chamber. The fission target material 2 generates binary fission fragments, long-range alpha particles from ternary fission, and tritium from ternary fission through spontaneous fission or neutron-induced fission. The screened ionization chamber 1 is used to measure the light charged particles (i.e., long-range alpha particles and tritium) in binary fission fragments and ternary fission. The aluminum films 3 of different thicknesses are used to shield most of the binary fission fragments and decay alpha particles. The working gases 9 of different pressures are used to prevent long-range alpha particles and high-energy tritium from entering the working gas. The data acquisition and processing system is used to measure and obtain the corresponding two-dimensional spectrum of cathode signal amplitude vs. anode signal amplitude and two-dimensional spectrum of anode signal amplitude vs. anode signal rise time.

[0053] The grid ionization chamber 1 is a sealed cylindrical shape, with a sealed door for the installation and removal of the fission target material 2, and the interior is filled with working gas 9.

[0054] Cathode 5, grid 6, anode 7, and shield 8 are all rectangular flat plates. There is one cathode 5, and two grids, anode 7, and shield 8. Grid 6, anode 7, and shield 8 are symmetrically distributed with respect to the cathode. From the inside out, the cathode 5, grid 6, anode 7, and shield 8 are arranged in sequence. Cathode 5, grid 6, anode 7, and shield 8 are parallel to each other and installed in the grid ionization chamber 1.

[0055] The cathode 5 is a rectangular plate, installed on the center line of the grid ionization chamber 1, with a sample well set up. The fission target material 2 is placed in the sample well, and the aluminum film 3 and the four-component α source 4 for calibration are located on both sides of the fission target material 2.

[0056] Fission target material 2 adopts 252 Cf、 235 U and 239 Fissionable materials such as Pu.

[0057] For two-stage splitting rate measurement, the working gas 9 is at a low pressure (approximately 0.5 atmospheres); for three-stage splitting rate measurement, the working gas 9 is at a high pressure (more than 6 atmospheres).

[0058] Aluminum films 3 of different thicknesses are placed on the plane of cathode plate 5 to cover the sample well containing fission target material 2.

[0059] A method for measuring the absolute yield of long-range alpha particles and tritium in fission nuclear ternary fission includes the following steps:

[0060] Step 1: Under the conditions of not placing an aluminum film and low-pressure (approximately 0.5 atmospheres) working gas, the amplitude spectrum of the anode signal was obtained in the screen grid ionization chamber when measuring the spontaneous or neutron-induced binary fission fragments of fission nuclei.

[0061] Step 2: The Monte Carlo method is used to simulate the measurement process of fission nucleus ejected binary fission fragments in a grid ionization chamber. The mass, independent yield, and total energy released by the fission fragments are calculated using GEF 2020 / 1.1 software. Then, the energy of the binary fission fragments is calculated based on the conservation of momentum and energy. Considering the energy of the binary fission fragments, the mass, independent yield, energy, and ejection angle of the fission nucleus binary fission fragments are discretized, and factors such as sample thickness, sample inhomogeneity, and PHD effects are taken into account to obtain the anode signal amplitude spectrum when measuring binary fission fragments in the grid ionization chamber. By comparing this spectrum with the experimental amplitude spectrum obtained in Step 1, the two are found to be consistent, thus determining the detection efficiency of the grid ionization chamber for binary fission fragments. The subthreshold fraction of binary fission is corrected to obtain the total binary fission count rate.

[0062] Step 3: Under the conditions of placing aluminum films of different thicknesses and working gas at high pressure (more than 6 atmospheres), the experiment obtained the two-dimensional spectrum of cathode signal amplitude vs. anode signal amplitude, the two-dimensional spectrum of anode signal amplitude vs. anode signal rise time, and the anode signal amplitude spectrum when measuring light charged particles in spontaneous or neutron-induced ternary fission of fission nuclei in the screen grid ionization chamber.

[0063] Step 4: The Monte Carlo method is used to simulate the measurement process of light charged particles in the ternary fission of fission nuclei in the grating ionization chamber. The charge number, mass number, energy distribution and emission angle of the light charged particles in the ternary fission are sampled. Considering the influence of sample thickness, sample inhomogeneity and aluminum film, the deposition energy of these charged particles in the grating ionization chamber is calculated, and information such as the track length, emission angle and deposition energy of charged particles are obtained. Based on the above information, the corresponding two-dimensional spectrum of cathode signal amplitude vs anode signal amplitude, two-dimensional spectrum of anode signal amplitude vs anode signal rise time and anode signal amplitude spectrum are calculated.

[0064] Step 5: For long-range α particles in the ternary fission, the event region of long-range α particles is delineated in the two-dimensional spectrum of cathode signal amplitude vs. anode signal amplitude obtained from the experimental measurement in Step 3 and the simulation calculation in Step 4, respectively. The corresponding experimental measurement and simulation calculation anode signal amplitude spectrum are obtained. The two are consistent with each other, thereby determining the detection efficiency of the grating ionization chamber for long-range α particles in the ternary fission. The subthreshold fraction of long-range α particles is corrected to obtain the total long-range α particle count rate. Divide it by the total binary fission count rate obtained in Step 2 to obtain the absolute yield of long-range α particles in the ternary fission.

[0065] Step 6: For tritium in the ternary fission, the event region of tritium is delineated in the two-dimensional spectrum of anode signal amplitude vs. anode signal rise time obtained from the experimental measurement in Step 3 and the simulation calculation in Step 4, respectively. The corresponding experimental measurement and simulation calculation anode signal amplitude spectrum are obtained. The two are consistent with each other, thereby determining the detection efficiency of the grating ionization chamber for tritium in the ternary fission. The subthreshold fraction of tritium and the influence of long-range α particles are corrected to obtain the total tritium count rate. Divide the total binary fission count rate obtained in Step 2 to obtain the absolute yield of tritium in the ternary fission.

Claims

1. A method for measuring the absolute yield of long-range alpha particles and tritium in fission nuclear ternary fission, characterized in that, Includes the following steps: Step 1, measure the anodic signal of the binary splitting fragments under the condition of aluminum film (3) screen grid: The fission target material (2) is placed in the sample well of the measuring device for the absolute yield of long-range α particles and tritium in the three-fission of fission nuclei, without placing the aluminum film (3), and the working gas (9) is at a pressure of 0.5 atmospheres. When the fission target material (2) undergoes spontaneous or neutron-induced binary fission, the anode signal amplitude spectrum of the binary fission fragments in the screen grid ionization chamber (1) is collected by a data acquisition and processing system to obtain the anode signal amplitude spectrum of the binary fission fragments without aluminum film (3), which is the measured anode signal amplitude spectrum of the binary fission fragments without aluminum film (3). Step 2, simulating the measurement process of binary fission fragments: The measurement process of fission nuclei ejecting binary fission fragments in the grating ionization chamber (1) was simulated using the Monte Carlo method. The mass, independent yield, and total energy released by fission of the binary fission fragments were calculated using GEF 2020 / 1.1 software. The energy of the binary fission fragments was then calculated based on the conservation of momentum and energy. The energy of the binary fission fragments was discretely sampled, and the mass, independent yield, energy, and ejection angle of the binary fission fragments were calculated. The sample thickness, sample inhomogeneity, and PHD effect were also considered to simulate the anode signal amplitude spectrum of the binary fission fragments. The amplitude spectrum of the anode signal of the simulated binary fission fragments is compared with the amplitude spectrum of the anode signal measured in step 1. The two are consistent, and the detection efficiency of the screen grid ionization chamber (1) for the binary fission fragments is determined. The subthreshold fraction of the binary fission is corrected to obtain the total binary fission count rate. Step 3, measure the cathode and anode signals of light charged particles in the three-split transformation under the aluminum film (3) screen grid condition: Place aluminum films (3) of different thicknesses respectively, and adjust the pressure of the working gas (9) to more than 6 atmospheres; When the fission target material (2) undergoes spontaneous or neutron-induced ternary fission, a data acquisition and processing system is used to acquire the cathode signal amplitude vs. anode signal amplitude two-dimensional spectrum, anode signal amplitude vs. anode signal rise time two-dimensional spectrum, and anode signal amplitude spectrum of the light charged particles in the ternary fission of the screen grid ionization chamber (1). The measured cathode signal amplitude vs. anode signal amplitude two-dimensional spectrum, anode signal amplitude vs. anode signal rise time two-dimensional spectrum, and anode signal amplitude spectrum of the light charged particles in the ternary fission of the screen grid ionization chamber (1) are obtained. Step 4, Simulate the measurement process of light charged particles in the ternary splitting process: Using the Monte Carlo method, the measurement process of light charged particles in the ternary fission of fission nuclei in a grid-screened ionization chamber was simulated. The charge number, mass number, energy distribution, and emission angle of the light charged particles in the ternary fission were sampled. Considering the sample thickness, sample inhomogeneity, and the influence of the aluminum film, the deposition energy of these charged particles in the grid-screened ionization chamber was calculated, and the track length, emission angle, and deposition energy information of the charged particles were obtained. Based on the track length, emission angle, and deposition energy information of the charged particles, the corresponding two-dimensional spectrum of cathode signal amplitude vs. anode signal amplitude, two-dimensional spectrum of anode signal amplitude vs. anode signal rise time, and anode signal amplitude spectrum were calculated. Step 5: Calculate the absolute yield of long-range alpha particles in the three-fission transition: For long-range α particles in the ternary fission, the event region of long-range α particles is delineated in the two-dimensional spectrum of cathode signal amplitude vs. anode signal amplitude obtained by measurement in step 3 and simulation calculation in step 4, respectively. The corresponding experimental measurement and simulation calculation anode signal amplitude spectrum are obtained. The two are consistent with each other, thereby determining the detection efficiency of the grating ionization chamber for long-range α particles in the ternary fission. The subthreshold fraction of long-range α particles is corrected to obtain the total long-range α particle count rate. Dividing it by the total binary fission count rate obtained in step 2, the absolute yield of long-range α particles in the ternary fission is obtained. Step 6, calculate the absolute yield of tritium in the ternary fission: For tritium in the ternary fission, the event region of tritium is delineated in the two-dimensional spectrum of anode signal amplitude vs. anode signal rise time obtained from the measurement in step 3 and the simulation calculation in step 4, respectively. The corresponding experimental measurement and simulation calculation anode signal amplitude spectrum are obtained. The two are consistent with each other, thereby determining the detection efficiency of the grating ionization chamber for tritium in the ternary fission. The subthreshold fraction of tritium and the influence of long-range α particles are corrected to obtain the total tritium count rate. Dividing the total binary fission count rate obtained in step 2, the absolute yield of tritium in the ternary fission is obtained.

2. A measuring apparatus for the absolute yield of long-range alpha particles and tritium in fission ternary processes, used to implement the measuring method for the absolute yield of long-range alpha particles and tritium in fission ternary processes as described in claim 1, characterized in that, It includes a grid ionization chamber (1), cathode (5), grid (6), anode (7), shielding electrode (8), aluminum film (3), a four-component α source for calibration (4), and a data acquisition and processing system; The ionization chamber (1) is a closed cylindrical shape, with a sealing door for the installation and removal of the fission target material (2), and the interior is filled with working gas (9), which is a mixture of argon and methane. The cathode (5), grid (6), anode (7) and shield (8) are all rectangular flat plates. There is one cathode (5), and two grids (6), anode (7) and shield (8). The grid (6) is symmetrically distributed with respect to the cathode (5), the anode (7) is symmetrically distributed with respect to the cathode (5), and the shield (8) is symmetrically distributed with respect to the cathode (5). From the inside out, the order is cathode (5), grid (6), anode (7) and shield (8). The cathode (5), grid (6), anode (7) and shield (8) are parallel to each other and installed in the grid ionization chamber (1). The cathode (5) is installed on the center line of the grid ionization chamber (1), a sample well is set up, the fission target material (2) is placed in the sample well, and the aluminum film (3) and the four-component α source (4) for calibration are located on both sides of the fission target material (2). The data acquisition and processing system is used to measure the two-dimensional spectrum of cathode signal amplitude vs. anode signal amplitude and the two-dimensional spectrum of anode signal amplitude vs. anode signal rise time.

3. The measuring device for the absolute yield of long-range alpha particles and tritium in fission ternary fission according to claim 2, characterized in that, The aluminum film (3) is located on the plane of the cathode (5) plate, covering the sample well containing the fission target material (2) to shield some of the binary fission fragments and decay α particles.

4. The measuring device for the absolute yield of long-range alpha particles and tritium in fission ternary fission according to claim 3, characterized in that, The aluminum film (3) has a thickness of 30 μm or 10 μm.

5. The measuring device for the absolute yield of long-range alpha particles and tritium in fission ternary fission according to claim 2, characterized in that, The working gas (9) has a pressure of 0.5 atmospheres or more than 6 atmospheres.

6. The measuring device for the absolute yield of long-range alpha particles and tritium in fission ternary fission according to claim 5, characterized in that, The working gas (9) is a 0.5 atm mixture of 90% Ar and 10% CH4, or a 7.0 atm mixture of 90% Ar and 10% CH4, or a 7.5 atm mixture of 90% Ar and 10% CH4.

7. The measuring device for the absolute yield of long-range alpha particles and tritium in fission ternary fission according to claim 2, characterized in that, The fission target material (2) is 252 Cf, or for 235 U, or for 239 Pu fissile materials.

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