Plutonium isotope accelerator mass spectrometry measuring device and method based on positive ion ionization

Abstract

The invention belongs to the technical field of isotope detection, and particularly relates to a plutonium isotope accelerator mass spectrometry measuring device based on positive ion ionization, which comprises a positive ion source for ionizing plutonium isotope to generate positive ions, the positive monovalent ions of the plutonium isotope accelerated by the accelerating tube enter the stripping system and then are stripped into multi-charge state positive ions, 3 + charge state plutonium isotope ions are selected by the analysis magnet for analysis, and after interference of various analysis fragments is eliminated by the electrostatic analyzer, the 3 + charge state plutonium isotope ions are measured by the detector. The ionization efficiency of the plutonium isotope is improved, the sample preparation process is simplified, and the in-situ analysis of the sample can be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of isotope detection, and in particular relates to a plutonium isotope accelerator mass spectrometry measurement device and method based on positive ion ionization. Background Art

[0002] The detection of plutonium isotopes in the environment is of great significance in the nuclear industry and environmental analysis. 239 Pu, 240 Pu, etc.) content is extremely low, and the traditional α spectrometer and other methods cannot meet the requirements due to sensitivity reasons. Therefore, the plutonium isotopes in the environment are generally measured by mass spectrometry, among which accelerator mass spectrometry (AMS) is the most sensitive analytical technology for measuring plutonium isotopes. When measuring plutonium isotopes, AMS extracts the negative ion form of plutonium isotopes and uses the AMS device of the traditional tandem accelerator to achieve the determination of plutonium isotopes. However, since the electron affinity of plutonium isotopes is very small, it is difficult for them to form atomic negative ions. Therefore, in order to improve the negative ion ionization efficiency of plutonium isotopes, the oxide negative ion form of plutonium isotopes is extracted to improve the ionization efficiency of its negative ions. Even so, the ionization efficiency of the oxide negative ions of plutonium isotopes is still very low, and only about 1% of plutonium isotopes will form the oxide negative ions of plutonium isotopes, thus greatly limiting the efficiency and sensitivity of AMS measurement. On the other hand, plutonium isotopes are easily ionized to form positive ions, and their positive ion ionization efficiency can reach 10-20%, which is more than one order of magnitude higher than the negative ion ionization efficiency. Therefore, the present invention realizes efficient and sensitive determination of plutonium isotopes by adopting a plutonium isotope positive ion ionization method and using a special monopolar accelerated AMS device. Summary of the invention

[0003] In view of the problems existing in the prior art, the purpose of the present invention is to provide a plutonium isotope accelerator mass spectrometry device and method based on positive ion ionization. Based on the characteristic that the positive ion ionization efficiency of plutonium isotopes is much higher than the negative ion ionization efficiency, a small low-energy (acceleration energy 0.3MeV) monopolar AMS device and method based on positive ion ionization is adopted; the traditional AMS technical method of tandem accelerator is not adopted; the measurement efficiency and sensitivity of plutonium isotopes are greatly improved, and high-sensitivity analysis of ultra-trace plutonium isotopes is achieved, providing high-quality analysis devices and technologies for applications in the nuclear industry and the environment.

[0004] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows:

[0005] A plutonium isotope accelerator mass spectrometry device based on positive ion ionization comprises a positive ion source for ionizing plutonium isotopes to generate positive ions, wherein positive monovalent ions of plutonium isotopes are selected by an injection magnet and sent into an accelerating tube, wherein the positive monovalent ions of plutonium isotopes accelerated by the accelerating tube enter a stripping system and are stripped into multi-charged positive ions, wherein 3+ charged plutonium isotope ions are selected by an analysis magnet for analysis, and after interference from various analysis fragments is eliminated by an electrostatic analyzer, the 3+ charged plutonium isotope ions are measured by a detector.

[0006] Furthermore, the positive ion source and the injection magnet are placed on a 0.3MV high voltage stand and connected to the ground potential through an accelerating tube.

[0007] Furthermore, the positive ion source is a microwave ion source or a laser positive ion source.

[0008] Furthermore, a pre-acceleration tube is provided between the positive ion source and the injection magnet.

[0009] Furthermore, the pre-acceleration tube accelerates the positive ions of plutonium isotopes to an energy of about 30 KeV.

[0010] Furthermore, the accelerating voltage of the accelerating tube is set to be less than 0.3 MV.

[0011] Furthermore, the stripping system is a circulating gas system that can accurately control the helium flow rate and can decompose molecular ions.

[0012] Furthermore, the detector is a proportional gas ionization chamber or a microchannel plate.

[0013] Furthermore, by changing the magnetic fields of the injection magnet and the analysis magnet, the determination of different plutonium isotope ions can be achieved, and the determination of the plutonium isotope ratio can also be achieved.

[0014] Furthermore, the above device is used to perform a plutonium isotope accelerator mass spectrometry method based on positive ion ionization, comprising the following steps:

[0015] Step 1, using a positive ion source to ionize plutonium isotopes in the sample into positive ions;

[0016] Step 2, using a pre-acceleration tube to accelerate the positive ions of plutonium isotopes to an appropriate energy;

[0017] Step 3, using an injection magnet to select positive monovalent ions of plutonium isotopes and send them into an accelerating tube;

[0018] Step 4, the positive monovalent ions of the plutonium isotope accelerated by the accelerating tube enter the stripping system and are stripped into multi-charged positive ions;

[0019] Step 5, selecting 3+ charged plutonium isotope ions for analysis by an analysis magnet;

[0020] Step 6, using an electrostatic analyzer to eliminate interference from various analytical debris;

[0021] Step 7, using a detector to measure the plutonium isotope ions in the 3+ charge state.

[0022] Furthermore, in step 1, the positive ion source is a microwave ion source or a laser positive ion source.

[0023] Furthermore, in step 2, the pre-acceleration tube accelerates the positive ions of the plutonium isotope to an energy of about 30 KeV.

[0024] Further, in step 4, the stripping system uses helium as the stripping gas.

[0025] The beneficial effects of the present invention are as follows:

[0026] 1. Improved ionization efficiency of plutonium isotopes: Compared with negative ion ionization technology, the positive ion (positive monovalent) ionization technology can increase the ionization efficiency of plutonium isotopes by more than 10 times;

[0027] 2. Simplified sample preparation process: In order to improve the ionization efficiency in the technical method of negative ion ionization, it is necessary to prepare the sample into an oxide form through a complex chemical process, while the positive ion ionization does not require a complex chemical preparation process. For some samples, even the chemical purification process can be omitted and direct ionization can be performed, which greatly simplifies the sample preparation process;

[0028] 3. In-situ analysis of samples can be realized: This technology combined with laser ionization technology can realize the in-situ determination of plutonium isotopes by micro-area scanning, providing technical support for some special applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the structure of a plutonium isotope accelerator mass spectrometry device based on positive ion ionization. DETAILED DESCRIPTION

[0030] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0031] The present invention discloses a plutonium isotope accelerator mass spectrometry device based on positive ion ionization, comprising a positive ion source for ionizing plutonium isotopes to generate positive ions, selecting positive monovalent ions of plutonium isotopes through an injection magnet and sending them into an accelerating tube, the positive monovalent ions of plutonium isotopes accelerated by the accelerating tube enter a stripping system and are stripped into multi-charged positive ions, selecting ions of plutonium isotopes in a 3+ charge state through an analysis magnet for analysis, and using a detector to measure ions of plutonium isotopes in a 3+ charge state after eliminating interference from various analysis fragments through an electrostatic analyzer. The specific technical scheme is as follows:

[0032] The plutonium isotope accelerator mass spectrometry device based on positive ion ionization of the present invention adopts the following method: Figure 1 The AMS structure shown in the figure is composed of a positive ion source, an injection magnet, an accelerating tube, a stripping system, an analysis magnet, an electrostatic analyzer, and a detector. The positive ion source and the injection magnet are placed on a 0.3MV high voltage stand and connected to the ground potential through the accelerating tube.

[0033] The positive ion source ionizes the plutonium isotopes in the sample into positive ions. The positive ion source can be any form of ion source that can achieve positive ion ionization, such as a microwave ion source, a laser positive ion source, etc.

[0034] The plutonium isotopes ionized into positive ions are accelerated to an energy of about 30 KeV by an electric field in a pre-acceleration tube arranged between the positive ion source and the injection magnet, and then the plutonium isotopes (such as 239 Pu, 240 Pu, etc.) and send them into the accelerator tube; the reason for choosing plutonium isotope positive monovalent ions is, on the one hand, its high ionization efficiency, and on the other hand, it can reduce the interference of accompanying particles.

[0035] The positive monovalent ions of plutonium isotopes are accelerated by the accelerating tube and enter the stripping system. In order to achieve effective stripping of the positive monovalent ions of plutonium isotopes and take into account factors such as the safe operation of the equipment, the accelerating voltage of the accelerating tube is set to below 0.3MV. The stripping system is a circulating gas system that can accurately control the helium flow rate. In order to increase the stripping probability of 3+ charged plutonium isotope ions and improve the transmission efficiency of plutonium isotope ions in the stripping system, helium is used as the stripping gas. After the acceleration, the positive monovalent ions of plutonium isotopes enter the stripping system and are further stripped into multi-charged positive ions, while the molecular ions are disintegrated.

[0036] The 3+ charged plutonium isotope ions with the highest stripping probability are selected for analysis by the analysis magnet. The 3+ charged plutonium isotope ions are selected because the stripping system can effectively eliminate the molecular ion background. After eliminating the interference of various analytical fragments by the electrostatic analyzer, the 3+ charged plutonium isotope ions are sent to the detector.

[0037] The detector can use a proportional gas ionization chamber, a microchannel plate and other types of detectors to measure the 3+ charged state plutonium isotope ions. By changing the magnetic field of the injection magnet and the analysis magnet, the measurement of different plutonium isotope ions can be achieved, and the measurement of the plutonium isotope ratio can also be achieved.

[0038] The plutonium isotope accelerator mass spectrometry method based on positive ion ionization comprises the following steps:

[0039] Step 1, using a positive ion source to ionize plutonium isotopes in the sample into positive ions;

[0040] Step 2, using a pre-acceleration tube to accelerate the positive ions of plutonium isotopes to an appropriate energy;

[0041] Step 3, using an injection magnet to select positive monovalent ions of plutonium isotopes and send them into an accelerating tube;

[0042] Step 4, the positive monovalent ions of the plutonium isotope accelerated by the accelerating tube enter the stripping system and are stripped into multi-charged positive ions;

[0043] Step 5, selecting 3+ charged plutonium isotope ions for analysis by an analysis magnet;

[0044] Step 6, using an electrostatic analyzer to eliminate interference from various analytical debris;

[0045] Step 7, using a detector to measure the plutonium isotope ions in the 3+ charge state.

[0046] Take the plutonium isotope accelerator mass spectrometry device based on positive ion ionization as an example:

[0047] Embodiment 1

[0048] The plutonium isotope accelerator mass spectrometry device based on positive ion ionization in this embodiment adopts the following method: Figure 1 The AMS structure shown in the figure is composed of a positive ion source, a pre-acceleration tube, an injection magnet, an acceleration tube, a stripping system, an analysis magnet, an electrostatic analyzer and a detector.

[0049] A positive ion source, which uses a laser ion source as a positive ion source to ionize plutonium isotopes in the sample into positive ions;

[0050] A pre-acceleration tube, wherein the positive ions of the plutonium isotope generated by ionization are accelerated to an energy of about 30 KeV by a pre-acceleration tube arranged between the positive ion source and the injection magnet, and then sent to the injection magnet;

[0051] Injection magnet, in order to improve the measurement efficiency and eliminate the interference of other charge state accompanying ions, the injection magnet is used to select the positive monovalent plutonium isotope ions to enter the acceleration tube;

[0052] In order to achieve effective stripping of plutonium isotope ions and taking into account factors such as the safe operation of the equipment, the accelerating voltage of the accelerating tube is set to below 0.3MV;

[0053] Stripping system, in order to improve the stripping probability of 3+ charged plutonium isotope ions and improve the transmission efficiency of plutonium isotope ions in the stripping system, helium is used as the stripping gas; at the same time, the selection of 3+ charged plutonium isotope ions can effectively exclude molecular ion background;

[0054] An analytical magnet is used to select the 3+ charged plutonium isotope ions with the highest stripping probability for analysis;

[0055] Electrostatic analyzer, which uses the electrostatic analyzer to eliminate interference from various analytical fragments and then send 3+ charged plutonium isotope ions into the detector;

[0056] The detector uses a proportional gas ionization chamber to measure the 3+ charged state plutonium isotope ions.

[0057] Embodiment 2

[0058] The plutonium isotope accelerator mass spectrometry device based on positive ion ionization in this embodiment adopts the following method: Figure 1 The AMS structure shown in the figure is composed of a positive ion source, a pre-acceleration tube, an injection magnet, an acceleration tube, a stripping system, an analysis magnet, an electrostatic analyzer and a detector.

[0059] A positive ion source, which uses a microwave ion source as a positive ion source to ionize plutonium isotopes in the sample into positive ions;

[0060] A pre-acceleration tube, wherein the positive ions of the plutonium isotope generated by ionization are accelerated to an energy of about 30 KeV by a pre-acceleration tube arranged between the positive ion source and the injection magnet, and then sent to the injection magnet;

[0061] Injection magnet, in order to improve the measurement efficiency and eliminate the interference of other charge state accompanying ions, the injection magnet is used to select the positive monovalent plutonium isotope ions to enter the acceleration tube;

[0062] In order to achieve effective stripping of plutonium isotope ions and taking into account factors such as the safe operation of the equipment, the accelerating voltage of the accelerating tube is set to below 0.3MV;

[0063] Stripping system, in order to improve the stripping probability of 3+ charged plutonium isotope ions and improve the transmission efficiency of plutonium isotope ions in the stripping system, helium is used as the stripping gas; at the same time, the selection of 3+ charged plutonium isotope ions can effectively exclude molecular ion background;

[0064] An analytical magnet is used to select the 3+ charged plutonium isotope ions with the highest stripping probability for analysis;

[0065] Electrostatic analyzer, which uses the electrostatic analyzer to eliminate interference from various analytical fragments and then send 3+ charged plutonium isotope ions into the detector;

[0066] The detector uses a microchannel plate to measure plutonium isotope ions in the 3+ charge state.

[0067] Take the plutonium isotope accelerator mass spectrometry method based on positive ion ionization as an example:

[0068] Embodiment 3

[0069] Step 1, using a laser ion source to ionize plutonium isotopes in the sample into positive ions;

[0070] Step 2, using a pre-acceleration tube to accelerate the positive ions of plutonium isotopes to an energy of about 30 KeV;

[0071] Step 3, using an injection magnet to select positive monovalent ions of plutonium isotopes and send them into an accelerating tube, wherein the accelerating voltage of the accelerating tube is set to be less than 0.3 MV;

[0072] Step 4, the positive monovalent ions of the plutonium isotope accelerated by the accelerating tube enter the stripping system and are stripped into multi-charged positive ions;

[0073] Step 5, selecting 3+ charged plutonium isotope ions for analysis by an analysis magnet;

[0074] Step 6, using an electrostatic analyzer to eliminate interference from various analytical debris;

[0075] Step 7, using a proportional gas ionization chamber as a detector to measure the 3+ charged state plutonium isotope ions.

[0076] Embodiment 4

[0077] Step 1, using a microwave ion source to ionize plutonium isotopes in the sample into positive ions;

[0078] Step 2, using a pre-acceleration tube to accelerate the positive ions of plutonium isotopes to an energy of about 30 KeV;

[0079] Step 3, using an injection magnet to select positive monovalent ions of plutonium isotopes and send them into an accelerating tube, wherein the accelerating voltage of the accelerating tube is set to be less than 0.3 MV;

[0080] Step 4, the positive monovalent ions of the plutonium isotope accelerated by the accelerating tube enter the stripping system and are stripped into multi-charged positive ions;

[0081] Step 5, selecting 3+ charged plutonium isotope ions for analysis by an analysis magnet;

[0082] Step 6, using an electrostatic analyzer to eliminate interference from various analytical debris;

[0083] Step 7, using the microchannel plate as a detector to measure the 3+ charged state plutonium isotope ions.

[0084] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A plutonium isotope accelerator mass spectrometry device based on positive ion ionization, Features: It includes a positive ion source for ionizing plutonium isotopes to produce positive ions, which selects the positive monovalent ions of plutonium isotopes through an injection magnet and sends them into an acceleration tube. The positive monovalent ions of plutonium isotopes accelerated by the acceleration tube enter a stripping system and are stripped into multi-charged positive ions, and 3+ charged plutonium isotope ions are selected for analysis by an analysis magnet. After various analysis fragments are eliminated by an electrostatic analyzer, the 3+ charged plutonium isotope ions are measured by a detector.

2. The plutonium isotope accelerator mass spectrometry device based on positive ion ionization according to claim 1, Features: The positive ion source and the injection magnet are placed on a 0.3MV high voltage stand and connected to the ground potential through an accelerating tube.

3. The plutonium isotope accelerator mass spectrometry device based on positive ion ionization according to claim 1, Features: The positive ion source is a microwave ion source or a laser positive ion source.

4. The plutonium isotope accelerator mass spectrometry device based on positive ion ionization according to claim 1, Features: A pre-acceleration tube is provided between the positive ion source and the injection magnet.

5. The plutonium isotope accelerator mass spectrometry device based on positive ion ionization according to claim 4, Features: The pre-acceleration tube accelerates the positive ions of plutonium isotopes to an energy of about 30 KeV.

6. The plutonium isotope accelerator mass spectrometry device based on positive ion ionization according to claim 1, Features: The accelerating voltage of the accelerating tube is set to be below 0.3 MV.

7. The plutonium isotope accelerator mass spectrometry device based on positive ion ionization according to claim 1, Features: The stripping system is a circulating gas system that can precisely control the helium flow rate and can disintegrate molecular ions.

8. The plutonium isotope accelerator mass spectrometry device based on positive ion ionization according to claim 1, Features: The detector is a proportional gas ionization chamber or a microchannel plate.

9. The plutonium isotope accelerator mass spectrometry device based on positive ion ionization according to claim 1, Features: By changing the magnetic fields of the injection magnet and the analysis magnet, the determination of different plutonium isotope ions can be achieved, and the determination of the plutonium isotope ratio can also be achieved.

10. A method for measuring plutonium isotope accelerator mass spectrometry based on positive ion ionization using the device according to any one of claims 1 to 9, Features: The following steps are involved: Step 1, using a positive ion source to ionize plutonium isotopes in the sample into positive ions; Step 2, using a pre-acceleration tube to accelerate the positive ions of plutonium isotopes to an appropriate energy; Step 3, using an injection magnet to select positive monovalent ions of plutonium isotopes and send them into an accelerating tube; Step 4, the positive monovalent ions of the plutonium isotope accelerated by the accelerating tube enter the stripping system and are stripped into multi-charged positive ions; Step 5, selecting 3+ charged plutonium isotope ions for analysis by an analysis magnet; Step 6, using an electrostatic analyzer to eliminate interference from various analytical debris; Step 7, using a detector to measure the plutonium isotope ions in the 3+ charge state.

11. The plutonium isotope accelerator mass spectrometry method based on positive ion ionization according to claim 10, Features: In step 1, the positive ion source is a microwave ion source or a laser positive ion source.

12. The plutonium isotope accelerator mass spectrometry method based on positive ion ionization according to claim 10, Features: In step 2, the pre-acceleration tube accelerates the positive ions of plutonium isotopes to an energy of about 30 KeV.

13. The plutonium isotope accelerator mass spectrometry method based on positive ion ionization according to claim 10, Features: In step 4, the stripping system uses helium as the stripping gas.

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