A time-of-flight mass spectrometer detector for high-precision detection of isotope abundance

Abstract

The present invention discloses a time-of-flight mass spectrometer detector for high-precision detection of isotope abundance. The motion trajectory of high-abundance ions is instantaneously changed by introducing a pulse voltage electrode in an ion gate attenuator, and then the ion intensity is reduced by a grid attenuator. After the high-abundance ions are attenuated, a ring detector is used to detect the signal. When low-abundance ions pass through, the ion gate voltage remains unchanged, and the ions maintain their original motion trajectory and are detected by a central axis detector. High-abundance ions and low-abundance ions are detected using detectors with different magnifications, respectively. The error in concentration measurement caused by saturation of the acquisition system is reduced by combining the high-abundance ion attenuation system at the front end. The attenuation multiple can adjust the ion gate attenuator and the grid attenuator between 100 and 5, thereby achieving high-precision detection of isotopes with very different contents in a time-of-flight mass spectrometer.

Description

Technical Field

[0001] The invention relates to the technical field of isotope detection, and in particular to a time-of-flight mass spectrometer detector for high-precision detection of isotope abundance. Background Art

[0002] Time-of-Flight Mass Spectrometer (TOFMS) has a simple structure, a single spectrum analysis time of microseconds, high resolution and sensitivity, and one-time detection of the full mass range. It is widely used in environmental testing, life sciences and other fields. Usually, the detector of TOFMS consists of two to three microchannel plates (MCP) in series, and a Faraday disk is used as the electron receiving electrode. The high-speed data acquisition card can collect and record the current signal received by the Faraday disk, and finally form a mass spectrum. MCP is a flat electron multiplier made of many special hollow glass fibers. The inner wall of each hollow fiber channel is coated with secondary electron emission material. When a certain DC voltage (~1kV) is applied to both ends of the MCP, high-energy ions collide with the inner wall coating of the MCP channel to generate secondary electrons, which achieve electron multiplication through chain reactions. There are two types of high-speed data acquisition cards: analog-to-digital conversion (ADC) acquisition cards and time-to-digital conversion (TDC) acquisition cards. The ADC data acquisition card directly collects analog signals and converts them into digital signals. The dynamic range of ADC is determined by the number of bits of the AD chip. The higher the number of bits, the larger the dynamic range of ion flow can be detected. The TDC time-to-digital conversion card continuously records the triggering moment into a specific memory address. If the threshold is exceeded, it is recorded as "1" in the memory address (for flight time), otherwise it is recorded as "0". This means that when multiple ions arrive at the MCP in the same acquisition interval, the acquisition card can still only record one "1". Saturation problems are prone to occur when the ion flow is very strong. Moreover, in the mass spectrometry system, when the analyte concentration range varies greatly, the mass spectrometer detector will experience signal saturation, resulting in large measurement errors.

[0003] The determination of stable isotopes plays an important role in geochemical and cosmochemical dating studies. It is the most effective technical means in the study of fingerprint spectrum of drug production areas, rock and mineral deposit genesis, earth environment and climate change resources; it is also the most important means in studying the material composition of the moon and planets. The isotope abundance of high-abundance and low-abundance elements sometimes differ by three orders of magnitude. High-precision abundance measurement requires accuracy control at the level of 0.5 ten thousandths, which is very difficult for mass spectrometry systems using microchannel plates (MCPs) as detectors. The amplification efficiency of a single MCP is 10 3 The amplification efficiency of the double-chip MCP can be increased to 10 6However, the dynamic accuracy of MCP is only two orders of magnitude, and high-abundance signals can easily lead to saturation, making low-abundance signals difficult to detect.

[0004] Therefore, it is necessary to design a time-of-flight mass spectrometer detector with high-precision detection of isotope abundance to meet the measurement requirements. Summary of the invention

[0005] In view of the deficiencies of the prior art, the present invention aims to provide a time-of-flight mass spectrometer detector for high-precision detection of isotope abundance.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A time-of-flight mass spectrometer detector for high-precision detection of isotope abundance comprises an ion gate attenuator, a grid attenuator, an annular detector and a central axis detector; the ion gate attenuator, the grid attenuator, the annular detector and the central axis detector are arranged in sequence, and the ion gate attenuator, the annular detector and the central axis detector are coaxial; the grid attenuator comprises dense metal grids arranged on both sides, and the central axis of the interval between the dense metal grids on both sides is coaxial with the ion gate attenuator; the annular detector has a central hole, and the central hole of the annular detector corresponds to the central axis detector; the dense metal grids on both sides correspond to the non-central hole parts of the annular detector respectively, and the interval between the dense metal grids on both sides is coaxial with the ion gate attenuator. The attenuator is composed of a Bradbury-Nielson ion gate, a pulse bias power supply and a time delay sequence generator; the Bradbury-Nielson ion gate includes two groups of metal wires spaced in a forked form and a pulse voltage electrode and a bias voltage electrode respectively connected to the two groups of metal wires; the pulse bias power supply includes a pulse voltage and a bias voltage, the bias voltage is connected to the bias voltage electrode, and the pulse voltage is connected to the pulse voltage electrode; the time delay sequence generator is used to output a pulse TTL signal to control the pulse bias power supply to output a pulse voltage to the pulse voltage electrode and output a bias voltage to the bias voltage electrode.

[0008] Furthermore, the annular detector comprises an ion post-acceleration electrode, a microchannel plate, an electron acceleration electrode, an annular receiving electrode and a uniform electric field grid, wherein the ion post-acceleration electrode, the microchannel plate, the electron acceleration electrode and the annular receiving electrode all have a central hole; the uniform electric field grid and the ion post-acceleration electrode are coaxial and fixed at the central hole of the ion post-acceleration electrode, and the uniform electric field grid and the ion post-acceleration electrode are applied with the same voltage; the electron acceleration electrode comprises a plurality of pieces and is placed in parallel, and a microchannel plate is sandwiched between two adjacent electron acceleration electrodes; the The rear end of the annular receiving electrode is connected to a high-voltage capacitor; the whole formed by a uniform electric field grid and an ion rear acceleration electrode, the whole formed by a microchannel plate and an electron acceleration electrode, and the annular receiving electrode are arranged in sequence along the direction away from the grid attenuator, and each center hole is coaxial with the ion gate attenuator; the dense metal grids on both sides correspond to the non-center hole part of the uniform electric field grid, the microchannel plate, and the non-center hole part of the annular receiving electrode, and the interval between the dense metal grids on both sides corresponds to the center hole of the uniform electric field grid, the microchannel plate, and the center hole of the annular receiving electrode.

[0009] Furthermore, the central axis detector comprises an ion rear accelerating electrode 2, a microchannel plate 2, an electron accelerating electrode 2, a central axis receiving electrode and a uniform electric field grid 2, neither the microchannel plate 2 nor the central axis receiving electrode has a central hole, and both the ion rear accelerating electrode 2 and the electron accelerating electrode 2 have a central hole; the uniform electric field grid 2 and the ion rear accelerating electrode 2 are coaxial and fixed at the central hole of the ion rear accelerating electrode 2, and the same voltage is applied to the uniform electric field grid 2 and the ion rear accelerating electrode 2; the electron accelerating electrode 2 comprises a plurality of pieces and is placed in parallel, and a microchannel plate 2 is sandwiched between two adjacent electron accelerating electrodes 2; the rear end of the central axis receiving electrode is connected to a high-voltage capacitor 2; the integral body formed by the uniform electric field grid 2 and the ion rear accelerating electrode 2, the integral body formed by the microchannel plate 2 and the electron accelerating electrode 2, and the central axis receiving electrode are arranged in sequence along the direction away from the annular detector and are coaxial with the ion gate attenuator; the interval between the dense metal grids on both sides corresponds to the uniform electric field grid 2, the microchannel plate 2 and the central axis receiving electrode.

[0010] The present invention also provides a working method of a time-of-flight mass spectrometer detector for high-precision detection of isotope abundance, the specific process of which is as follows:

[0011] When ions fly out of the field-free region of the time-of-flight mass spectrometer, the delay timing generator accurately records the ion flight time. When high-abundance ions enter the ion gate attenuator, the delay timing generator instantly outputs a pulse TTL signal to control the pulse bias power supply to apply a pulse voltage to the pulse voltage electrode and output a bias voltage to the bias voltage electrode. At this time, adjacent metal wires in the Bradbury-Nielson type ion gate have a certain potential difference. The electric field perpendicular to the axial direction generated by the potential difference causes the high-abundance ion movement direction to change and diffuse to both sides. The high-abundance ions pass through the dense metal grids on both sides. After being attenuated by the dense metal grids on both sides, the ions enter the non-central hole part of the annular detector and are received and detected by the annular detector.

[0012] When low-abundance ions enter the ion gate attenuator, the delay timing generator does not output a pulse TTL signal, the pulse bias power supply does not apply a pulse voltage to the pulse voltage electrode and does not output a bias voltage to the bias voltage electrode. At this time, the pulse voltage electrode and the bias voltage electrode have the same potential, and the adjacent metal wires in the Bradbury-Nielson ion gate have the same voltage. The low-abundance ions maintain their original motion trajectory and directly reach the central axis detector after passing through the central hole of the annular detector, and are detected by the central axis detector.

[0013] The beneficial effects of the present invention are as follows: the present invention introduces a pulse voltage electrode into the ion gate attenuator to instantaneously change the motion trajectory of high-abundance ions, and then reduces the ion intensity by a certain proportion through a grid attenuator. After the high-abundance ions are attenuated, a ring detector is used to detect the signal. When low-abundance ions pass through, the ion gate voltage remains unchanged, and the ions maintain their original motion trajectory and are detected by the central axis detector. High-abundance ions and low-abundance ions are detected using detectors with different magnifications, respectively. The high-abundance ion attenuation system at the front end is combined to reduce the error in concentration measurement caused by the saturation of the acquisition system. The attenuation multiple can adjust the ion gate attenuator and the grid attenuator between 100 and 5, thereby achieving high-precision detection of isotopes with very different contents in a time-of-flight mass spectrometer. The present invention can also be used for the simultaneous detection of high-concentration and trace samples in a mixed sample. This technology can expand the detectable range of analyte concentrations. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the structure of a time-of-flight mass spectrometer detector for high-precision detection of isotope abundance in Example 1 of the present invention;

[0015] Figure 2 Schematic diagram of the structure of the ion gate attenuator in Example 1 of the present invention;

[0016] Figure 3 Schematic diagram of the structure of the central axis detector in Example 1 of the present invention;

[0017] Figure 4 Schematic diagram of the flow of low-abundance ions and high-abundance ions passing through the ion gate attenuator in Example 2 of the present invention. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to this embodiment.

[0019] Example 1

[0020] This embodiment provides a time-of-flight mass spectrometer detector for high-precision detection of isotope abundance, such as Figure 1 As shown, it includes an ion gate attenuator 1, a grid attenuator 2, an annular detector 3 and a central axis detector 9; the ion gate attenuator 1, the grid attenuator 2, the annular detector 3 and the central axis detector 9 are arranged in sequence, and the ion gate attenuator 1, the annular detector 3 and the central axis detector 9 are coaxial; the grid attenuator 2 includes dense metal grids arranged on both sides, and the central axis of the interval between the dense metal grids on both sides is coaxial with the ion gate attenuator; the annular detector 3 has a central hole, and the central hole of the annular detector 3 corresponds to the central axis detector 9; the dense metal grids on both sides correspond to the non-central hole parts of the annular detector 3 respectively, and the interval between the dense metal grids on both sides corresponds to the central hole of the annular detector 3.

[0021] It should be noted that high-abundance ions pass through the ion gate attenuator 1 and the dense metal grid in sequence and then reach the non-center hole part of the annular detector 3, and are detected by the annular detector 3; low-abundance ions pass through the ion gate attenuator 1, the gap between the dense metal grids on both sides, and the center hole of the annular detector 3 in sequence and then reach the central axis detector 9, and are detected by the central axis detector 9.

[0022] In this embodiment, if Figure 2 As shown, the ion gate attenuator 1 is composed of a Bradbury-Nielson type ion gate, a pulse bias power supply 14 and a delay timing generator 13; the Bradbury-Nielson type ion gate includes two groups of metal wires spaced apart in a forked form and a pulse voltage electrode 11 and a bias voltage electrode 12 respectively connecting the two groups of metal wires; the pulse bias power supply 14 is used to output a pulse voltage and a bias voltage, the bias voltage is output to the bias voltage electrode 12, and the pulse voltage is output to the pulse voltage electrode 11; the delay timing generator 13 is used to output a pulse TTL signal to control the pulse bias power supply 14 to output a pulse voltage to the pulse voltage electrode 11.

[0023] In this embodiment, if Figure 1As shown, the distance between the dense metal grids on both sides is 1-5 mm, and the dense metal grid is selected according to the designed signal attenuation multiples. For example, if the attenuation is required to be 10 times, a grid with a transmittance of 10% is selected.

[0024] In this embodiment, if Figure 1 As shown, the annular detector 3 includes an ion post-acceleration electrode 4, a microchannel plate 5, an electron acceleration electrode 6, an annular receiving electrode 7 and a uniform electric field grid 8, and the ion post-acceleration electrode 4, the microchannel plate 5, the electron acceleration electrode 6, and the annular receiving electrode 7 all have a central hole; the uniform electric field grid 8 and the ion post-acceleration electrode 4 are coaxial and fixed at the central hole of the ion post-acceleration electrode 4, and the uniform electric field grid 8 and the ion post-acceleration electrode 4 are applied with the same voltage; the electron acceleration electrode 6 includes a plurality of pieces and is placed in parallel, and a microchannel plate 5 is sandwiched between two adjacent electron acceleration electrodes 6; The rear end of the annular receiving electrode 7 is connected to a high-voltage capacitor; the whole composed of a uniform electric field grid 8 and an ion rear acceleration electrode 4, the whole composed of a microchannel plate 5 and an electron acceleration electrode 6, and the annular receiving electrode 7 are arranged in sequence along the direction away from the grid attenuator 2, and each center hole is coaxial with the ion gate attenuator 1; the dense metal grids on both sides correspond to the uniform electric field grid 8, the non-center hole part of the microchannel plate 5, and the non-center hole part of the annular receiving electrode 7, and the interval between the dense metal grids on both sides corresponds to the center hole of the uniform electric field grid 8, the microchannel plate 5, and the center hole of the annular receiving electrode 7.

[0025] It should be noted that if the ions pass through the dense metal grids on both sides, they will then pass through the uniform electric field grid-8, the non-center hole part of the microchannel plate-5 and the non-center hole part of the annular receiving electrode-7 in turn. The annular receiving electrode-7 receives the electrons amplified by the microchannel plate-5, and the signal is output from the high-voltage capacitor-1 and collected using a data acquisition card.

[0026] In this embodiment, if Figure 3As shown, the central axis detector 9 includes an ion rear acceleration electrode 11, a microchannel plate 12, an electron acceleration electrode 13, a central axis receiving electrode 10 and a uniform electric field grid 14. The microchannel plate 12 and the central axis receiving electrode 10 do not have a central hole, and the ion rear acceleration electrode 11 and the electron acceleration electrode 13 both have a central hole; the uniform electric field grid 14 and the ion rear acceleration electrode 11 are coaxial and fixed at the central hole of the ion rear acceleration electrode 11, and the uniform electric field grid 14 and the ion rear acceleration electrode 11 are applied with the same voltage; the electron acceleration electrode 11 3 includes multiple pieces and placed in parallel, a microchannel plate 12 is sandwiched between two adjacent electron acceleration electrodes 13; the rear end of the central axis receiving electrode 10 is connected to a high-voltage capacitor 2; the uniform electric field grid 14 and the ion rear acceleration electrode 11 constitute a whole, the microchannel plate 12 and the electron acceleration electrode 13 constitute a whole, and the central axis receiving electrode 10 are arranged in sequence along the direction away from the annular detector 3, and are coaxial with the ion gate attenuator 1; the interval between the dense metal grids on both sides corresponds to the uniform electric field grid 14, the microchannel plate 12 and the central axis receiving electrode 10.

[0027] It should be noted that if the ions pass through the gap between the dense metal grids on both sides, they will then pass through the uniform electric field grid 14 and the microchannel plate 12 in turn after passing through the central hole of the annular detector 3, and finally reach the central axis receiving electrode 10; the central axis receiving electrode 10 receives the electrons amplified by the microchannel plate 12, and the signal is output from the high-voltage capacitor 2 and collected using a data acquisition card.

[0028] It should be noted that, in the present embodiment, the detector includes an annular detector 3 and a central axis detector 9. The annular detector 3 adopts a microchannel plate with a central hole. Low-abundance ions pass through the central hole (non-detection part) of the annular detector 3 to reach the central axis detector 9 and are detected by the central axis detector 9, while high-abundance ions pass through the dense metal grids on both sides to reach the detection part of the annular detector 3 and are detected by the annular detector 3.

[0029] It should be noted that, in this embodiment, the magnification of the annular detector 3 and the central axis detector 9 can be adjusted by the voltage U applied to the microchannel plate. The annular detector 3 is set to a low magnification (10 5 times), reduce the signal intensity of high-abundance ions, and set the central axis detector 9 to a high magnification (10 6 times), increasing the signal intensity of low-abundance ions.

[0030] Example 2

[0031] This embodiment provides a working method of the time-of-flight mass spectrometer detector for high-precision detection of isotope abundance described in Embodiment 1, and the specific process is as follows:

[0032] When ions fly out of the field-free region of the time-of-flight mass spectrometer, the delay timing generator 13 accurately records the ion flight time. When high-abundance ions enter the ion gate attenuator 1, the delay timing generator 13 instantly outputs a pulse TTL signal to control the pulse bias power supply 14 to apply a pulse voltage to the pulse voltage electrode 11 and output a bias voltage to the bias voltage electrode 12. At this time, adjacent metal wires in the Bradbury-Nielson type ion gate have a certain potential difference. The electric field perpendicular to the axial direction generated by the potential difference causes the high-abundance ion movement direction to change and diffuse to both sides. The high-abundance ions pass through the dense metal grids on both sides. After being attenuated by the dense metal grids on both sides, the ions enter the non-central hole part of the annular detector, are received by the annular detector and detected. Figure 4 As shown in B;

[0033] like Figure 4 As shown in A, when low-abundance ions enter the ion gate attenuator 1, the delay timing generator 13 does not output a pulse TTL signal, the pulse bias power supply 14 does not apply a pulse voltage to the pulse voltage electrode 11 and does not output a bias voltage to the bias voltage electrode 12. At this time, the pulse voltage electrode 11 and the bias voltage electrode 12 have the same potential, and the adjacent metal wires in the Bradbury-Nielson type ion gate have the same voltage. The low-abundance ions maintain their original motion trajectory, and they pass through the central hole of the annular detector 3 and directly reach the central axis detector 9, and are detected by the central axis detector 9.

[0034] It should be noted that before conducting precise isotope analysis, a full spectrum analysis is required to lock in a certain mass-to-charge ratio compound that needs to be analyzed. After entering the mass-to-charge ratio compound, the flight time of the high-abundance ion can be calculated based on the mass-to-charge ratio, and then the corresponding pulse voltage can be applied through the delay timing generator.

[0035] For those skilled in the art, various corresponding changes and modifications can be made according to the above technical solutions and concepts, and all of these changes and modifications should be included in the protection scope of the claims of the present invention.

Claims

1. A time-of-flight mass spectrometer detector for high-precision detection of isotope abundance, characterized in that: It includes an ion gate attenuator, a grid attenuator, a ring detector and a central axis detector; the ion gate attenuator, the grid attenuator, the ring detector and the central axis detector are arranged in sequence, and the ion gate attenuator, the ring detector and the central axis detector are coaxial; the grid attenuator includes dense metal grids arranged on both sides, and the central axis of the interval between the dense metal grids on both sides is coaxial with the ion gate attenuator; the ring detector has a central hole, and the central hole of the ring detector corresponds to the central axis detector; the dense metal grids on both sides correspond to the non-central hole parts of the ring detector respectively, and the interval between the dense metal grids on both sides corresponds to the central hole of the ring detector; the ion gate attenuator is composed of a Bradbury-Nielson type ion gate, a pulse bias power supply and a delay timing generator; the Bradbury-Nielson type ion gate includes two groups of metal wires spaced in a forked finger form and a pulse voltage electrode and a bias voltage electrode respectively connected to the two groups of metal wires; the pulse bias power supply includes a pulse voltage and a bias voltage, the bias voltage is connected to the bias voltage electrode, and the pulse voltage is connected to the pulse voltage electrode; The delay timing generator is used to output a pulse TTL signal to control the pulse bias power supply to output a pulse voltage to the pulse voltage electrode and to output a bias voltage to the bias voltage electrode.

2. The isotope abundance high-precision detection time-of-flight mass spectrometer detector according to claim 1, characterized in that: The annular detector comprises an ion post-acceleration electrode, a microchannel plate, an electron acceleration electrode, an annular receiving electrode and a uniform electric field grid, wherein the ion post-acceleration electrode, the microchannel plate, the electron acceleration electrode and the annular receiving electrode all have a central hole; the uniform electric field grid and the ion post-acceleration electrode are coaxial and fixed at the central hole of the ion post-acceleration electrode, and the uniform electric field grid and the ion post-acceleration electrode are applied with the same voltage; the electron acceleration electrode comprises a plurality of pieces and is placed in parallel, and a microchannel plate is sandwiched between two adjacent electron acceleration electrodes; the annular receiving electrode comprises a plurality of pieces and is placed in parallel, and a microchannel plate is sandwiched between two adjacent electron acceleration electrodes; the annular receiving electrode comprises a plurality of pieces and is fixed at the central hole of the ion post-acceleration electrode, and the uniform electric field grid and the ion post-acceleration electrode are applied with the same voltage; the electron acceleration electrode comprises a plurality of pieces and is placed in parallel, and a microchannel plate is sandwiched between two adjacent electron acceleration electrodes; the annular receiving electrode comprises a plurality of pieces and is disposed in parallel, and a microchannel plate is sandwiched between two adjacent electron acceleration electrodes; the annular receiving electrode comprises a plurality of pieces and is disposed in parallel, and the ... The rear end of the receiving electrode is connected to a high-voltage capacitor; the whole composed of a uniform electric field grid and an ion rear acceleration electrode, the whole composed of a microchannel plate and an electron acceleration electrode, and an annular receiving electrode are arranged in sequence along the direction away from the grid attenuator, and each center hole is coaxial with the ion gate attenuator; the dense metal grids on both sides correspond to the uniform electric field grid, the non-center hole part of the microchannel plate, and the non-center hole part of the annular receiving electrode, and the interval between the dense metal grids on both sides corresponds to the center hole of the uniform electric field grid, the microchannel plate, and the center hole of the annular receiving electrode.

3. The isotope abundance high-precision detection time-of-flight mass spectrometer detector according to claim 1, characterized in that: The central axis detector comprises a second ion rear acceleration electrode, a second microchannel plate, a second electron acceleration electrode, a central axis receiving electrode and a second uniform electric field grid, wherein the second microchannel plate and the second central axis receiving electrode do not have a central hole, and the second ion rear acceleration electrode and the second electron acceleration electrode both have a central hole; the second uniform electric field grid and the second ion rear acceleration electrode are coaxial and fixed at the central hole of the second ion rear acceleration electrode, and the same voltage is applied to the second uniform electric field grid and the second ion rear acceleration electrode; the second electron acceleration electrode comprises a plurality of pieces and is placed in parallel, and a second microchannel plate is sandwiched between two adjacent second electron acceleration electrodes; the rear end of the central axis receiving electrode is connected to a second high-voltage capacitor; the integral body formed by the second uniform electric field grid and the second ion rear acceleration electrode, the integral body formed by the second microchannel plate and the second electron acceleration electrode, and the central axis receiving electrode are sequentially arranged in a direction away from the annular detector and are coaxial with the ion gate attenuator; the interval between the dense metal grids on both sides corresponds to the second uniform electric field grid, the second microchannel plate, and the central axis receiving electrode.

4. A method for operating the time-of-flight mass spectrometer detector for high-precision detection of isotope abundance according to any one of claims 1 to 3, characterized in that: The specific process is: When ions fly out of the field-free region of the time-of-flight mass spectrometer, the delay sequence generator accurately records the ion flight time. When high-abundance ions enter the ion gate attenuator, the delay sequence generator instantly outputs a pulse TTL signal to control the pulse bias power supply to apply a pulse voltage to the pulse voltage electrode and output a bias voltage to the bias voltage electrode. At this time, the adjacent metal wires in the Bradbury-Nielson type ion gate have a certain potential difference. The electric field perpendicular to the axial direction generated by the potential difference changes the movement direction of the high-abundance ions and diffuses to both sides. The high-abundance ions pass through the dense metal grids on both sides; the ions attenuated by the dense metal grids on both sides enter the non-central hole part of the annular detector, and are received and detected by the annular detector; When low-abundance ions enter the ion gate attenuator, the delay timing generator does not output a pulse TTL signal, the pulse bias power supply does not apply a pulse voltage to the pulse voltage electrode and does not output a bias voltage to the bias voltage electrode. At this time, the pulse voltage electrode and the bias voltage electrode have the same potential, and the adjacent metal wires in the Bradbury-Nielson ion gate have the same voltage. The low-abundance ions maintain their original motion trajectory and directly reach the central axis detector after passing through the central hole of the annular detector, and are detected by the central axis detector.

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