Compact low-energy carbon-14 special positive ion mass spectrometry system and detection method

Abstract

The invention discloses a compact low-energy carbon-14 special positive ion mass spectrometry system and a detection method, and the system comprises a gas sample injection unit which is used for injecting a CO2 gas sample; the positive ion unit is used for directly ionizing the CO2 gas sample to generate a C2 + ion beam; the fast alternate injection unit is used for carrying out preliminary quality analysis on the C2 + ion beam and realizing alternate injection of different carbon isotopes; the charge exchange unit adopts a differential pump type structure and a non-metal gas target, the center of the charge exchange unit is located at the waist-like position of the injection magnet, and the charge exchange unit is used for converting C2 + into C-ions; the beam analysis unit comprises an analysis magnet and an electrostatic analyzer, and the analysis magnet and the electrostatic analyzer form an energy achromatic system and are used for separating and screening the ions converted by the charge exchange unit to obtain < 14 > C-ions; the ion detection unit is used for counting and measuring < 14 > C <-> ions and finally obtaining the ratio of < 14 > C to < 12 > C or < 13 > C; and the high vacuum unit is used for keeping a vacuum state during the operation of the whole system.

Description

Technical Field

[0001] This invention relates to the field of accelerator mass spectrometry, specifically to a compact low-energy carbon-14 dedicated positive ion mass spectrometry system and detection method. Background Technology

[0002] Accelerator mass spectrometry (AMS) is a novel method based on accelerators and ion detection technology for analyzing trace nuclides and detecting rare particles. Compared with conventional analytical techniques and ordinary mass spectrometers, AMS has the ability to eliminate molecular background interference and identify isotopes, effectively improving the sensitivity of isotope measurement abundance to 10-1. -15 ~10 -16 Amphibious microscopy (AMS) is currently the most sensitive analytical technique for measuring long-lived radionuclides. It also offers advantages such as small sample volume and short measurement time, making it widely used in archaeology, geology, environmental science, biomedicine, nuclear physics, and astrophysics. In recent years, the main technological development trend of AMS devices has been towards miniaturization, simplification, and higher sensitivity, with significant research results achieved. For most nuclides measured by AMS, small AMS systems (accelerator terminal voltage below 1MV) not only possess the same measurement performance as large AMS systems (accelerator terminal voltage above 3MV), but also offer advantages such as system stability, ease of operation, small footprint, and lower cost. This has led to wider international acceptance of small AMS systems, making them a standard measurement device in an increasing number of laboratories.

[0003] The vast majority of existing AMS devices are used for 14 Specialized measurements of C account for over 90% of AMS-measured samples. Developed countries have already planned to implement [measures based on...]. 14 C-AMS measurements are used for environmental monitoring and rapid monitoring and response to radioactive contamination to prevent potential chemical, biological, and nuclear events (CBRN), providing governments with a scientific basis for decision-making. Simultaneously, with the rapid development of biomedicine, 14 C is widely used as a tracer. These applications highlight the need for rapid, large-scale basic data, but existing... 14 The graphite solid target sputtering method used in C-AMS analysis is no longer sufficient to meet the needs of rapid sample screening and analysis; furthermore, increasing research, such as in-depth studies on atmospheric particulate matter and DNA, focuses on trace samples (less than 1 mg C) and even ultra-trace samples (less than 0.1 mg C). 14 Accurate analysis of C isotopes has created an urgent need, while existing methods... 14 C-AMS measurement technology is insufficient for analyzing conventional solid samples with a concentration of around 1 mg C, which may not meet experimental requirements. Summary of the Invention

[0004] To achieve the above and other related objectives, this invention discloses a compact, low-energy carbon-14 dedicated positive ion mass spectrometry system, comprising:

[0005] The gas injection unit is used to inject CO2 gas samples;

[0006] The positive ion unit employs a 14.5 GHz high-current, high-charge-state, fully permanent magnet ECR ion source to directly ionize CO2 gas samples into C. 2+ Ion beam;

[0007] Fast alternating injection unit, used for C 2+ Ion beams are used for preliminary mass analysis and to achieve alternating implantation of different carbon isotopes;

[0008] The charge exchange unit employs a differential pump structure and a non-metallic gas target. The center of the charge exchange unit is connected to the waist of the injection unit, and it is used to transfer C... 2+ Convert to C - ion;

[0009] The beam analysis unit includes an analytical magnet and an electrostatic analyzer. These two components constitute an energy dedispersion system used to separate and screen ions converted by the charge exchange unit. 14 C - ion;

[0010] Ion detection unit, used for... 14 C - Ions are counted and measured.

[0011] The high-vacuum unit is used to maintain a vacuum state during the operation of the overall system.

[0012] Furthermore, the positive ion unit also includes:

[0013] An accelerating tube, detachably connected to the outlet of the ECR ion source, is used to process the extracted C2 ions. 2+ The ion beam is pre-accelerated;

[0014] The first and third unit electrostatic quadrupole lenses are located at the exit of the accelerating tube and are used to focus the ion beam to form a real image waist.

[0015] An adjustable beam-limiting aperture, positioned at the image point of the ECR ion source, serves as the object slit for the injection magnet and is used to limit the C0... 2+ Ion beam emittance, elimination of beam corona, and collimation of the beam.

[0016] Furthermore, the fast alternating injection unit includes an insulating electrostatic vacuum box and an injection magnet. The insulating electrostatic vacuum box is fitted over the injection magnet and is electrically insulated from the system's pipes and supports. The injection magnet is a 90° double-focused diode magnet. By applying a pulse offset voltage through the insulating electrostatic vacuum box, fast alternating injection of different mass isotopes is achieved.

[0017] Furthermore, the non-metallic gas target material in the differential pump type non-metallic gas target is a mixture of one or more of the following gases: methane, ethane, propane, acetylene, or ethylene.

[0018] The center of the differential pump type non-metallic gas target is located at the waist of the injection magnet, and the outlet is equipped with a second and third unit electrostatic quadrupole lens for reshaping the beam phase space.

[0019] Furthermore, the analytical magnet is a sector-shaped uniform field secondary magnet, used for analyzing C. - The ion beam is deflected by 90° to select and separate ions of different masses;

[0020] The electrostatic analyzer selects the energy of the analyzed magnetic ions, eliminating interference from adjacent isotopes, neutral ions, and molecular fragments.

[0021] Furthermore, the electrostatic analyzer has a front slit at its inlet and a rear slit at its outlet. The front and rear slits are used to shield the edge electric field, collimate the beam, and limit the beam width.

[0022] Furthermore, the outlet of the analytical magnet is equipped with a detection device. 12 C - The second bias Faraday cup for ion beam current intensity and for detection 13 C - The third bias Faraday cup for ion beam current intensity.

[0023] Secondly, the present invention provides a method for detecting carbon-14 positive ions, which employs the aforementioned positive ion mass spectrometry system and performs the following steps:

[0024] The gas injection unit injects CO2 gas samples into the system;

[0025] The positive ion unit directly ionizes the CO2 gas sample to generate C 2+ Ion beam;

[0026] Fast alternating injection unit for C 2+ Ion beams are used for preliminary mass analysis and to achieve alternating injection of different isotopes;

[0027] The charge exchange unit will convert C 2+ Ion beam converted to C -Ion beam;

[0028] The beam analysis unit separates and screens the ions converted by the charge exchange unit to obtain... 14 C - ion;

[0029] Ion detection unit 14 C - Ions are counted and measured.

[0030] Furthermore, the method also includes:

[0031] According to the detection of the second biased Faraday cup 12 C - The ion beam current intensity and the detection results of the ion detection unit are used to obtain... 14 C and 12 The ratio of C;

[0032] Based on the detection of the third bias Faraday cup 13 C - The ion beam current intensity and the detection results of the ion detection unit are used to obtain... 14 C and 13 The ratio of C.

[0033] By adopting the above technical solutions, improving core components and redesigning the beam transmission system, accelerators are no longer used, vacuum insulation is adopted, and SF6 or other insulating gases are not required; the magnet system is air-cooled, eliminating the need for cooling water devices, which can greatly reduce manufacturing and operation and maintenance costs.

[0034] The high-current, high-charge state all-permanent magnet ECR ion source features high beam intensity, good beam stability, low ion energy dispersion, weak memory effect, low sample consumption, and high ionization efficiency, which is beneficial for improving beam transmission efficiency. The all-permanent magnet ECR ion source has a compact magnet structure, does not require cooling water or a high-power excitation power supply, has low cost, is simple to operate, and can greatly reduce manufacturing and operating costs. It also avoids complex alkali metal vapor operation and maintenance, as well as alkali metal contamination and corrosion of the vacuum system.

[0035] The measurement method using direct CO2 gas injection eliminates the need for graphite solidification of the sample or external GIS gas processing systems, simplifying the sample preparation process, minimizing contamination risk, reducing sample preparation time, and enabling rapid measurement of ultra-micro quantities. 14 Real-time online processing and measurement of sample C;

[0036] The differential pump type non-metallic gas charge exchange target has the advantages of easy target thickness control, low ionization energy, and long service life. While ensuring charge exchange efficiency, it can reduce the complexity of the charge exchange unit and the continuity and reliability of operation and maintenance.

[0037] entire 14 The C-PIMS system has a simple and compact structure, small footprint, low cost, and is easy to operate and maintain; while ensuring... 14 While improving measurement accuracy, it also makes it easier to achieve the specialization, miniaturization, lightweighting, and commercialization of AMS devices. Attached Figure Description

[0038] The above and other features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. The drawings are provided for a better understanding of the invention and are not intended to limit the scope of this disclosure. In the drawings, the same or similar reference numerals denote the same or similar elements, wherein:

[0039] Figure 1 The overall system layout provided by this invention;

[0040] Figure 2 This refers to the beam transmission trajectory in the first half of the system in this embodiment of the invention;

[0041] Figure 3 This is the beam transmission trajectory for the latter half of the system in this embodiment of the invention.

[0042] Reference numerals: 1. ECR ion source; 2. Accelerator tube; 31. First three-element electrostatic quadrature lens; 32. Second three-element electrostatic quadrature lens; 41. Adjustable beam-limiting aperture; 42. Image slit; 43. Front slit; 44. Rear slit; 51. First movable Faraday cup; 52. First bias Faraday cup; 53. Second bias Faraday cup; 54. Third bias Faraday cup; 55. Second movable Faraday cup; 56. Third movable Faraday cup; 6. Insulating electrostatic vacuum box; 7. Injection magnet; 8. Charge exchange unit; 9. Analytical magnet; 10. Electrostatic analyzer; 11. Ion detection unit. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] Reference Figure 1 This invention provides a compact, low-energy carbon-14 dedicated positive ion mass spectrometry system, comprising:

[0045] The gas injection unit is used to inject CO2 gas samples;

[0046] The positive ion unit employs a 14.5 GHz high-current, high-charge-state, fully permanent magnet ECR ion source 1 to directly ionize CO2 gas samples into C. 2+ Ion beam;

[0047] The rapid alternating injection unit includes an insulating electrostatic vacuum box 6 and an injection magnet 7. The insulating electrostatic vacuum box is fitted outside the injection magnet and is used for C 2+ Ion beams are used for preliminary mass analysis and to achieve alternating injection of different isotopes;

[0048] Charge exchange unit 8 employs a differential pump structure and a non-metallic gas target. The center of the charge exchange unit is connected to the waist of the injection unit, and is used to transfer C... 2+ Convert to C - ion;

[0049] The beam analysis unit includes an analytical magnet 9 and an electrostatic analyzer 10. The analytical magnet 9 and the electrostatic analyzer 10 constitute an energy dedispersion system, used to separate and screen the ions converted by the charge exchange unit 8, obtaining... 14 C - ion;

[0050] Ion detection unit 11, used for detecting 14 C - Ions are counted and measured.

[0051] The high-vacuum unit is used to maintain the vacuum state during the operation of the entire system;

[0052] The control unit is used to control the above-mentioned units to achieve automatic operation.

[0053] Reference Figure 1 The positive ion source uses a 14.5GHz high-current, high-charge-state, fully permanent magnet ECR ion source 1. After directly injecting the CO2 gas sample, it is ionized to produce C. 2+ Ions are extracted and bundled; accelerator tube 2, detachably connected to the outlet of the ECR ion source, is used to process the extracted C ions. 2+ The ion beam is pre-accelerated. The extracted C... 2+ The ion beam is first pre-accelerated to a set energy by the front-end accelerating tube 2 before being transported to the injection system. As mentioned above, the maximum microwave feed power of the 14.5GHz high-current, high-charge state all-permanent magnet ECR ion source 1 is 200W. The working medium is a mixture of CO2 and Ar in a certain proportion; the inert gas Ar can eliminate impurities in the extracted ion beam. Ions are beneficial for improving the ionization efficiency of CO2 gas samples and C 2+ The generation efficiency is improved, and the formation of hydrocarbon molecular ions is suppressed, thereby generating the desired high current (1 eMA) of low-charge C. 2+Ion beam; the ECR plasma generated by ionization is extracted into a beam through a three-electrode extraction system (extraction voltage 35kV), and then pre-accelerated in accelerating tube 2 (accelerating voltage 35kV), C 2+ Ions can reach energies of up to 140 keV.

[0054] To limit the beam transmission envelope and facilitate the arrangement of beam measurement elements, a first three-element electrostatic quadrupole lens 31 is installed at a certain position at the exit of the ECR ion source 1. This lens is used to focus the extracted ion beam to form a solid image waist, thereby improving beam transmission efficiency. This position is determined by those skilled in the art based on actual conditions and will not be elaborated here. Simultaneously, an adjustable beam-limiting aperture 41 is installed at the ion source image point. The adjustable beam-limiting aperture 41 also serves as the object slit for the injected magnet 7, used to limit beam emissivity, eliminate beam corona, and collimate the beam. A first movable Faraday cup 51 is placed after the adjustable beam-limiting aperture 41 to measure the total beam intensity extracted from the ion source. When beam intensity measurement is required, the movable Faraday cup 51 is moved onto the beam axis; otherwise, it is removed.

[0055] To achieve rapid alternating injection, the insulated electrostatic vacuum box 6 is electrically insulated from the beam lines and support structure. The momentum of the ions is adjusted by applying a high-frequency pulsed offset voltage, allowing carbon isotope ions of different masses to be injected. 12 C- 13 C- 14 C can be sequentially and alternately injected into the charge exchange unit 8. The pulse width of the insulating electrostatic vacuum box 6 is typically set to around 100 μs to keep the voltage drop due to the load sufficiently small; the pulse duration follows... 12 C- 13 C- 14 The C-sequence is used to minimize time loss due to pulsed system discharge; the pulse frequency is set between 10 and 100 Hz to eliminate the influence of ion source output instability on isotope ratio measurement; the pulse period is set to approximately 0.1 s to rapidly achieve periodic changes in pulse voltage, and the system injects at a frequency of 10 times per second. 12 C 2 +、 13 C 2 + and 14 C 2 + Beam, with injection times of 0.3ms, 1ms, and 100ms respectively.

[0056] Reference Figure 1 and Figure 2The injection magnet 7 is a sector-shaped uniform field dipole magnet with a magnetic stiffness of 0.1 T·m, a deflection angle of 90°, a deflection radius of 250 mm, and incident and exit edge angles of 28.5°. It utilizes the edge effect to achieve dual focusing, with drift distances of L1 = 570 mm and L2 = 473 mm. A first bias Faraday cup 52 is installed at the corresponding deflection position at the exit of the injection magnet 7 (L3 = 323 mm, H1 = 189 mm @ 26.7°) to monitor high-abundance isotopes of the nuclide being tested during injection. 12 C is located in the same vacuum chamber as charge exchange unit 8. Charge exchange unit 8 employs a differential pump structure to improve beam transmission efficiency and charge conversion efficiency. Since the first ionization energy of C is 11.26 eV, a non-metallic gas with low ionization energy needs to be selected as the target material. Suitable targets include methane (first ionization energy 12.6 eV), ethane (first ionization energy 11.5 eV), propane (first ionization energy 10.9 eV), acetylene (first ionization energy 11.4 eV), and ethylene (first ionization energy 10.5 eV), or a mixture of several of these. A corresponding gas mass flow controller is configured to accurately control or measure the flow rate of the injected non-metallic gas; simultaneously, appropriate flow-limiting orifices are provided to better control the gas pressure in the vacuum chamber.

[0057] Reference Figure 3 Since the center of the charge exchange unit 8 is located at the waist of the injection magnet 7, i.e., position L2, no additional focusing lens is needed. However, before the ions generated after charge exchange enter the beam analysis unit, a second and third unit electrostatic quadrupole lens 32 needs to be installed at the exit of the charge exchange unit 8 to reshape the beam phase space. The total effective length of the second and third unit electrostatic quadrupole lens 32 is 580 mm (L5), the lens spacing is 20 mm, the air gap diameter is 80 mm, and the drift distance is 220 mm (L4).

[0058] Furthermore, referring to Figure 3 The analytical magnet 9 is used to select and separate ions of different masses. Because the system uses a continuous beam, the displacement of ions along the beam axis is independent; therefore, carbon isotopes of different masses are separated into three distinct image waists by the analytical magnet. 12 A second offset Faraday cup 53 is set near the waist point of C. 13 A third bias Faraday cup 54 is set near the image waist of C to measure the beam intensity of stable isotopes, while at the beam axis 14A slit 42 is installed near the waist of the image of C to reduce scattering from background ions, and a second movable Faraday cup 55 is set up to measure the intensity of the negative ion beam generated by charge exchange. Since the energy of interfering ions differs from that of the analyte, an electrostatic analyzer 10 is placed at a certain position after the analyzing magnet 9 to reselect the ion energy, further eliminating background interference from adjacent isotopes, neutral ions, and molecular fragments. This position is determined by those skilled in the art based on actual conditions and will not be elaborated here. The analyzing magnet 9 and the electrostatic analyzer 10 constitute an energy dedispersion system, which is beneficial for improving the system's quality resolution and beam transmission efficiency. The deflection radius of both the analyzing magnet 9 and the electrostatic analyzer 10 is 250 mm, and the deflection angle is 90° to reduce the overall system size. Similar to the injection magnet 7, the analyzing magnet 9 is also a fan-shaped uniform field dipole magnet, with incident and exit edge angles of 28.5° to achieve double focusing. The forward and backward drift lengths are both L6 = 570 mm, at which point the magnetic stiffness is 0.2 T·m, used for measurement. 12 The second offset Faraday cup C is positioned at L7 = 390 mm and H2 = 195 mm at 27.4°, and is used for measurement. 13 The third bias Faraday cup 54 of C is positioned at L8 = 410 mm and H3 = 90 mm @ 12.7°. The electrodes of the electrostatic analyzer 10 are made into concentric spherical surfaces to generate a non-uniform electric field to achieve dual focusing. The drift distances L9 and L12 are 252 mm and 164 mm, respectively. A front slit 43 is provided at the entrance of the electrostatic analyzer 10, and a rear slit 44 is provided at the exit of the electrostatic analyzer 10. The distances L10 and L11 from the electrode edges of the front slit 43 and rear slit 44 are both 8 mm. In addition to shielding the edge electric field, these slits can also collimate the beam and limit the beam width.

[0059] Reference Figure 1 The aperture at the inlet of the ion detection unit 11 is matched to the beam size at that location to further reduce background scattering. A third movable Faraday cup 56 is also provided to measure the beam intensity transmitted to the ion detection unit 11 to evaluate beam transmission efficiency. The ion detection unit 11 is mounted on a linear feedthrough so that its position can be precisely adjusted to the image waist of the electrostatic analyzer 10. Given the low energy, short range, and lack of need to identify isotope interference of carbon ions, a PIPS-type semiconductor detector is selected for the ion detection unit 11. 14 High-sensitivity determination of C. The analyte is 14C. - Measurements are taken within the ion detection unit 11, based on the values ​​detected by the second biased Faraday cup. 12 C - The ion beam current intensity and the detection results of the ion detection unit 11 are used to obtain... 14 C and 12The ratio of C, as detected by the third bias Faraday cup. 13 C - The ion beam current intensity and the detection results of the ion detection unit 11 are used to obtain... 14 C and 13 The ratio of C.

[0060] In a preferred embodiment, the present invention provides a method for detecting carbon-14 positive ions, comprising:

[0061] The gas injection unit injects CO2 gas samples into the system;

[0062] The positive ion unit directly ionizes the CO2 gas sample to generate C 2+ Ion beam;

[0063] Fast alternating injection unit for C 2+ Ion beams are used for preliminary mass analysis and to achieve alternating injection of different isotopes;

[0064] Charge exchange unit 8 will transfer C 2+ Ion beam converted to C - Ion beam;

[0065] The beam analysis unit separates and screens the ions converted by the charge exchange unit to obtain... 14 C - ion;

[0066] 11 pairs of ion detection units 14 C - Ions are counted and measured.

[0067] Based on the detection of the second biased Faraday cup 53 12 C - The ion beam current intensity and the detection results of the ion detection unit 11 are used to obtain... 14 C and 12 The ratio of C;

[0068] Based on the detection of the third bias Faraday cup 54 13 C - The ion beam current intensity and the detection results of the ion detection unit 11 are used to obtain... 14 C and 13 The ratio of C.

[0069] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined.

[0070] For the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should understand that the embodiments of the present invention are not limited to the described order of actions, because according to the embodiments of the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions involved are not necessarily essential to the embodiments of the present invention.

[0071] As can be seen from the above description of the embodiments, those skilled in the art can clearly understand that this application can be implemented by means of software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments of this application.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A compact, low-energy carbon-14 dedicated positive ion mass spectrometry system, characterized in that, include: The gas injection unit is used to inject CO2 gas samples; The positive ion unit employs a 14.5 GHz high-current, high-charge-state, fully permanent magnet ECR ion source to directly ionize CO2 gas samples into C. 2+ Ion beam; Fast alternating injection unit, used for C 2+ Ion beams are used for preliminary mass analysis and to achieve alternating implantation of different carbon isotopes; The charge exchange unit employs a differential pump structure and a non-metallic gas target. The center of the charge exchange unit is located at the waist of the injection unit image, and it is used to transfer C... 2+ Convert to C - ion; The beam analysis unit includes an analytical magnet and an electrostatic analyzer. These two components constitute an energy dedispersion system used to separate and screen ions converted by the charge exchange unit. 14 C - ion; Ion detection unit, used for... 14 C - Ions are counted and measured. The high-vacuum unit is used to maintain a vacuum state during the operation of the overall system.

2. The compact low-energy carbon-14 dedicated positive ion mass spectrometry system according to claim 1, characterized in that, The fast alternating injection unit includes an insulating electrostatic vacuum box and an injection magnet. The insulating electrostatic vacuum box is fitted outside the injection magnet and is electrically insulated from the system's pipes and supports. The injection magnet is a 90° double-focused diode magnet. A pulse offset voltage is applied through the insulating electrostatic vacuum box to achieve fast alternating injection of different mass isotopes.

3. A compact, low-energy carbon-14 dedicated positive ion mass spectrometry system according to claim 2, characterized in that, The positive ion unit further includes: An accelerating tube, detachably connected to the outlet of the ECR ion source, is used to process the extracted C2 ions. 2+ The ion beam is pre-accelerated; The first and third unit electrostatic quadrupole lenses are located at the exit of the accelerating tube and are used to focus the ion beam to form a real image waist. An adjustable beam-limiting aperture, positioned at the image point of the ECR ion source, serves as the object slit for the injection magnet and is used to limit the C0... 2+ Ion beam emittance, elimination of beam corona, and collimation of the beam.

4. A compact, low-energy carbon-14 dedicated positive ion mass spectrometry system according to claim 1, characterized in that, The non-metallic gas target material in the differential pump type non-metallic gas target is a mixture of one or more of the following gases: methane, ethane, propane, acetylene, or ethylene. The center of the differential pump type non-metallic gas target is located at the waist of the injection magnet, and the outlet is equipped with a second and third unit electrostatic quadrupole lens for reshaping the beam phase space.

5. A compact, low-energy carbon-14 dedicated positive ion mass spectrometry system according to claim 1, characterized in that, The analytical magnet is a sector-shaped uniform field secondary magnet, used for C - The ion beam is deflected by 90° to select and separate ions of different masses; The electrostatic analyzer selects the energy of the analyzed magnetic ions, eliminating interference from adjacent isotopes, neutral ions, and molecular fragments.

6. A compact, low-energy carbon-14 dedicated positive ion mass spectrometry system according to claim 1, characterized in that, The electrostatic analyzer has a front slit at its entrance and a rear slit at its exit. The front and rear slits are used to shield the edge electric field, collimate the beam, and limit the beam width.

7. A compact, low-energy carbon-14 dedicated positive ion mass spectrometry system according to claim 1, characterized in that, The outlet of the analytical magnet is equipped with a detection device. 12 C - The second bias Faraday cup for ion beam current intensity and for detection 13 C - The third bias Faraday cup for ion beam current intensity.

8. A method for detecting carbon-14 positive ions, characterized in that, Using the positive ion mass spectrometry system according to any one of claims 1 to 7, perform the following steps: The gas injection unit injects CO2 gas samples into the system; The positive ion unit directly ionizes the CO2 gas sample to generate C 2+ Ion beam; Fast alternating injection unit for C 2+ Ion beams are used for preliminary mass analysis and to achieve alternating injection of different isotopes; The charge exchange unit will convert C 2+ Ion beam converted to C - Ion beam; The beam analysis unit separates and screens the ions converted by the charge exchange unit to obtain... 14 C - ion; Ion detection unit 14 C - Ions are counted and measured.

9. The method according to claim 8, characterized in that, The method further includes: According to the detection of the second biased Faraday cup 12 C - The ion beam current intensity and the detection results of the ion detection unit are used to obtain... 14 C and 12 The ratio of C; Based on the detection of the third bias Faraday cup 13 C - The ion beam current intensity and the detection results of the ion detection unit are used to obtain... 14 C and 13 The ratio of C.

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