Electrostatic ion trap

Abstract

The electrostatic ion trap comprises a pair of disc-shaped coaxial six-electrode structures which are arranged in a mirror symmetry mode, and each six-electrode structure is composed of six annular electrodes including a central circular electrode E1, a tangential kinetic energy focusing ring electrode E2, a plane ground electrode E3, an axial kinetic energy focusing ring electrode E4 and two radial reflection ring electrodes E5 and E6. E1 is at ground potential, E2, E4, E5 and E6 are loaded with stable direct current voltage, E2, E5 and E6 have the same polarity as trapped ions, E4 and trapped ions have opposite polarity, the electrostatic ion trap generates an electrostatic field between a pair of disc-shaped coaxial six-electrode structures, and the trapped ions can be trapped in the electrostatic field. And the ions are reflected back and forth in the imprisoned movement area and periodically move in a precession movement track. The ion adopts a pair of disc-shaped coaxial six-electrode structures which are arranged in a mirror symmetry mode, the electrode structures are simplified and firm, processing and assembling are easy, the number of power sources is saved, and tuning is easy.

Description

Technical Field

[0001] The invention relates to the technical field of mass spectrometry and ion storage, and in particular to an electrostatic ion trap. Background Art

[0002] Mass spectrometer (MS) is a common analytical instrument in modern science, which can be used for the detection and characterization of substances in many fields such as biology, material science, clinical research, space exploration, etc. Fourier transform mass spectrometry (FTMS) has many irreplaceable advantages, such as the ability to provide the highest mass resolution (such as baseline separation of ions with mass difference less than one electron mass), the highest mass accuracy (mass error as low as a few ppb), etc. In FTMS, the electric or magnetic field is designed to make the ions fly isochronously or at least energy synchronously along one of the directions of motion. The collected image charges reflect the motion frequency of the ion oscillations, and then the fast Fourier transform (FFT) algorithm is applied to convert the time domain charge signal into a frequency domain mass spectrum.

[0003] Fourier transform mass spectrometers are divided into two types: magnetic cyclotron resonance ion trap (FT ICR) and electrostatic ion trap. However, FT ICR is too expensive to be widely used; electrostatic ion traps only use electric fields, and the only products currently on the market are orbital traps (Orbitrap). It consists of an outer electrode and an inner electrode of a special shape. The generated logarithmic quadrupole field forces the ions to rotate around the inner electrode while oscillating along the central axis of the inner electrode. The frequency of this axial movement is mainly determined by the mass-to-charge ratio (m / z) of the ions, which allows the m / z to be determined directly by FFT. The resolution of Thermal Fisher Scientific's latest Orbitrap is 100,000-600,000, however, in order to maintain the stability of the axial oscillation harmonics, the center electrode and outer electrode of the Orbitrap must be processed very precisely. Other electrostatic traps have also been developed. A Cassinian trap was developed with a resolution of up to 53,000. Zajfman et al. pioneered the electrostatic ion beam trap (EIBT), in which ions are trapped along the central axis under the action of an electrostatic field. When a group of ions is injected into the EIBT, they are trapped and oscillated by applying a voltage between two sets of parallel electrode mirrors (WO2019030471A1). McLuckey et al. developed a series of electrostatic linear ion traps (ELITs) and demonstrated a mass resolution greater than 35,000 (WO2020117292A1). Ding Li et al. developed a series of planar electrostatic ion trap mass analyzers (CN110060918B, CN115763210A) and related image charge algorithms (CN112216596A, CN103493173A). The planar electrostatic ion trap mass analyzer includes a pair of disk-shaped coaxial electrode structures arranged in mirror symmetry. The area between the coaxial electrode structures is the movement area of ​​ions. The ion storage space is large, which effectively avoids the influence of space charge effects. Ion optical simulations show that within an acquisition time of 300 milliseconds, a mass resolution of 80k (T / 2ΔT) can be obtained, and the planar electrostatic trap provides a larger spatial charge capacity. However, this type of planar electrostatic ion trap has the following problems: 1) There are too many electrodes, requiring 8-10 pairs of circular ring electrodes, which are complex to process and assemble, and are costly; 2) Individual ring electrodes are relatively thin and lack rigidity, making them difficult to process to precise dimensions, and are prone to deformation during cleaning, assembly, and use, affecting mass spectrometry performance and stability; 3) The large number of electrodes also increases the number of power supplies required, which not only increases the cost of the instrument, but is also too complicated for voltage tuning. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide an electrostatic ion trap in view of the deficiencies of the prior art. The electrostatic ion trap adopts a pair of disc-shaped coaxial six-electrode structures arranged in mirror symmetry. The electrode structure is simplified and strong, easy to process and assemble, saves power and is easy to tune.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: an electrostatic ion trap, comprising a pair of disk-shaped coaxial six-electrode structures arranged in mirror symmetry, the area between the pair of disk-shaped coaxial six-electrode structures is the trapped motion area of ​​ions, each of the six-electrode structures is composed of six coaxial and radially spaced annular electrodes, namely: a central circular electrode E1 and a tangential kinetic energy focusing ring electrode E2, a planar ground electrode E3, an axial kinetic energy focusing ring electrode E4 and two radial reflection ring electrodes E1 are coaxially arranged in sequence with the central circular electrode E1 as the center. 5, E6; when the ions are trapped, E1 is at ground potential, and E2, E4, E5, and E6 are all loaded with stable DC voltages, wherein E2, E5, and E6 have the same polarity as the trapped ions, and E4 has an opposite polarity to the trapped ions. The electrostatic ion trap generates an electrostatic field between a pair of disk-shaped coaxial six-electrode structures, so that the ions are reflected back and forth in the trapped motion area and move periodically with a spiral motion trajectory, and the maximum radius of the mapping trajectory of the ion motion trajectory on the mirror symmetry plane of the pair of disk-shaped coaxial six-electrode structures is smaller than the outer radius of E6.

[0006] Preferably, during the ion trapping motion, E3 is at ground potential.

[0007] Preferably, three annular electrodes are coaxially arranged in sequence on the periphery of each of the six-electrode structures, which are respectively denoted as E7, E8, and E9. Electrodes E7 to E9 form a quadrupole annular guide, thereby forming a quadrupole electric field. The potentials on E7, E8, and E9 are denoted as V7, V8, and V9, respectively. During the movement of ions in the quadrupole annular guide composed of E7 to E9, a stable square wave radio frequency voltage with a certain frequency and amplitude is applied to E7, E8, and E9 to transmit ions, and after the ions are injected into the six-electrode structure, the square wave radio frequency voltage is stopped from being applied to E7, E8, and E9.

[0008] When the electrostatic ion trap is working, the foreign ions first enter the annular quadrupole field formed by E7~E9, and are guided and distributed along the arc center axis of the quadrupole field. During this period, E7, E8 and E9 must load a stable square wave radio frequency voltage with a certain frequency and amplitude. When ions are injected into the six-electrode structure ion trap, V7, V8 and V9 must form a radial potential gradient to push the ions into the middle of the two six-electrode structures. After the ions are injected into the six-electrode structure, V7, V8 and V9 stop loading the square wave radio frequency voltage, and load a DC voltage on a pair of disc-shaped coaxial six-electrode structures, namely V1, V2, V3, V4, V5, V6, thereby generating an electrostatic field, which traps the ions in the motion area and performs periodic motion in an approximately elliptical and continuously rotating ion motion orbit.

[0009] The movement of ions in an electrostatic ion trap can be simplified as repeated half-turn movement. In order to improve the performance of the electrostatic ion trap, the half-turn movement time of the ions is made independent of spatial divergence and energy divergence, and is only related to mass. Since (1) the ions have tangential kinetic energy before entering the planar orbital trap, the ions will not pass through the center of the trap. Although this is beneficial to reducing the density of the central ion cloud, it will cause time errors caused by tangential energy dispersion and time errors caused by spatial divergence. It is necessary to use a tangential kinetic energy focusing ring electrode E2 to focus the time difference caused by the initial tangential kinetic energy difference. Since (2) the ions have axial kinetic energy and axial position differences before entering the planar orbital trap, in order to prevent the ions from continuously diverging in the axial direction, an axial kinetic energy focusing ring electrode E4 is required. Due to (3) the position difference of the ions before being pushed into the planar orbital trap, the radial kinetic energy of the ions after entering the trap will be very different, affecting the isochronism of the ion half-turn movement. Therefore, it is necessary to use two radial reflection ring electrodes E5 and E6. By optimizing their voltages, the ions can achieve more than two levels of kinetic energy focusing in reflection. The electrostatic ion trap of the present invention adopts a pair of disk-shaped coaxial six-electrode structures arranged in mirror symmetry, and can achieve the above three necessary functions with the simplest structure.

[0010] In order to conveniently describe the motion of ions in an electrostatic ion trap, cylindrical coordinates are usually used to describe the motion trajectory of ions in the trap. In order to accurately calculate the time error, a Cartesian coordinate system is also used, that is, the longitudinal direction is the y-axis, the transverse direction is the x-axis, and the direction perpendicular to the xy plane is the z-axis. Each annular electrode is cylindrically symmetrical with the z-axis as the central axis. At the same time, a pair of disc-shaped coaxial six-electrode structures with mirror symmetry in the xy plane are the upper and lower regions of the electrostatic ion trap. In use, the annular electrodes in the upper and lower regions are provided with the same voltage mode, so that the ions are focused and transmitted in the middle region between the upper and lower regions of the electrostatic ion trap (i.e., the trapped motion region of the ions), thereby realizing periodic oscillation motion in the middle position.

[0011] Furthermore, the trapped motion area includes a central electric field zone, a field-free zone, an axial focusing zone and a reflection zone which are coaxially arranged in sequence with the axis of the central circular electrode E1 as the center, wherein the central electric field zone is opposite to E1 and E2, the field-free zone is opposite to E3, the axial focusing zone is opposite to E4, and the reflection zone is opposite to E5, E6 and E7.

[0012] Preferably, the central circular electrode E1 is used as a signal collection electrode, connected to an amplifier circuit, and used to detect the image current. The electrostatic ion trap of the present invention can analyze the movement frequency of ions of different masses by collecting the image charge on the electrode, thereby performing mass spectrometry analysis. The electrostatic ion trap of the present invention can be used in analytical testing fields such as mass spectrometry analysis. When used for mass spectrometry analysis, ions are distributed on the movement area of ​​the electrostatic ion trap, and the storage space is large, which effectively avoids the influence of the space charge effect, increases the capacity of ion storage, and can improve the signal-to-noise ratio.

[0013] Preferably, the radius of the electrostatic ion trap is greater than 90 mm, the radial thicknesses of E1, E2, E3, E4, and E5 are greater than 6 mm, and the radial thickness of E6 is greater than 3.6 mm. In terms of the ratio of the radial thickness of each ring (i.e., the difference between the inner and outer radii) to the radius, the ratio of the radial thickness of E1, E2, E3, E4, and E5 to the radius is greater than 6.6%, and the ratio of the radial thickness of E6 to the radius is greater than 4%, thereby improving the rigidity of the ring electrode.

[0014] Preferably, the radial thickness of E3 exceeds 45% of the outer radius of E6, and the radial thickness of E3 exceeds 70% of the outer radius of E3. The above-mentioned size limitation, on the one hand, solves the engineering problem that the electrostatic ion trap is difficult to accurately process, and at the same time is conducive to isolating the negative high voltage V4 and the positive voltage V2 and the image charge detection circuit connected to E1, thereby reducing the risk of electric field breakdown and damage to the image charge detection circuit, and on the other hand, it can ensure the mass resolution of the electrostatic ion trap of the present invention, reaching 161k.

[0015] Preferably, the voltage setting is obtained according to an artificial intelligence optimization algorithm to automatically control the voltage on the electrodes, with the goal of using the voltages on E1 to E6 to make the motion period of the moving ions in the trap tend to be isochronous with respect to the initial spatial divergence and energy divergence.

[0016] Compared with the prior art, the present invention has the following advantages: the electrostatic ion trap of the present invention adopts a pair of disk-shaped coaxial six-electrode structures arranged in mirror symmetry, has a simplified appearance and structure, and the overall structure is strong and stable, avoiding the engineering problem that thin ring electrodes are difficult to accurately process, and has a moderate resolution compared to other Fourier transform mass spectrometers, and has a more simplified structure compared to existing electrostatic orbital traps, and the electrode structure is simplified and strong, easy to process and assemble, saves power and is easy to tune. The electrostatic ion trap of the present invention can be used in analytical testing fields such as mass spectrometry analysis. When used for mass spectrometry analysis, ions are distributed in the trapped motion area of ​​the electrostatic ion trap, and the storage space is large, which effectively avoids the influence of space charge effect, increases the capacity of ion storage, and can improve the signal-to-noise ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram of the xz cross-sectional structure of the electrostatic ion trap in the embodiment;

[0018] Figure 2 The motion trajectory and regional position correspondence diagram of the xz cross section of the electrostatic ion trap in the embodiment;

[0019] Figure 3 is a quarter isometric view of an electrostatic ion trap of an embodiment;

[0020] Figure 4 It is a working timing diagram of the electrostatic ion trap of the embodiment;

[0021] Figure 5 is an xy plane view of an electrostatic ion trap of an embodiment;

[0022] Figure 6 An xz plane view of an electrostatic ion trap of an embodiment;

[0023] Figure 7 The half-turn time deviation caused by the spatial divergence and energy divergence of the electrostatic ion trap of the embodiment;

[0024] Figure 8 is a single precession trajectory of the electrostatic ion trap of the embodiment;

[0025] Fig. 9 is a potential distribution diagram of the electrostatic ion trap xz plane of the embodiment;

[0026] Fig.10 is the stable motion trajectory of the ion in the xy plane in the trap;

[0027] Fig.11 : is the mass spectrum of the electrostatic ion trap of the embodiment. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below with reference to the accompanying drawings.

[0029] The electrostatic ion trap implemented, such as Figure 1As shown, it includes a pair of disk-shaped coaxial six-electrode structures arranged in mirror symmetry, the area between the pair of disk-shaped coaxial six-electrode structures is the trapped motion area of ​​ions, and each six-electrode structure is composed of six coaxial and radially spaced annular electrodes, namely: a central circular electrode E1 and a tangential kinetic energy focusing ring electrode E2, a plane ground electrode E3, an axial kinetic energy focusing ring electrode E4 and two radial reflection ring electrodes E5 and E6 that are coaxially arranged in sequence with the central circular electrode E1 as the center, and the potentials on E1, E2, E3, E4, E5, and E6 are recorded as V1, V2, and V3, respectively. , V4, V5, V6. When the ions are trapped, E1 and E3 are at ground potential, and E2, E4, E5, and E6 are loaded with stable DC voltages, wherein E2, E5, and E6 have the same polarity as the trapped ions, and E4 has an opposite polarity to the trapped ions. The electrostatic ion trap generates an electrostatic field between a pair of disk-shaped coaxial six-electrode structures, so that the ions are reflected back and forth in the trapped motion area and move periodically with a precession motion trajectory, and the maximum radius of the mapping trajectory of the ion motion trajectory on the mirror symmetry plane of the pair of disk-shaped coaxial six-electrode structures is smaller than the outer radius of E6.

[0030] Three annular electrodes are coaxially arranged in sequence on the periphery of each six-electrode structure, which are respectively denoted as E7, E8, and E9. Electrodes E7 to E9 form a quadrupole annular guide, thereby forming a quadrupole electric field. The potentials on E7, E8, and E9 are denoted as V7, V8, and V9, respectively. During the movement of ions in the middle of the quadrupole annular guide formed by E7 to E9, a stable square wave radio frequency voltage with a certain frequency and amplitude is loaded on E7, E8, and E9 to transmit ions. After the ions are injected into the six-electrode structure, the square wave radio frequency voltage is stopped from being loaded on E7, E8, and E9. When the electrostatic ion trap is working, the foreign ions first enter the annular quadrupole field formed by E7 to E9, are guided by it, and are distributed along the arc center axis of the quadrupole field. During this period, E7, E8, and E9 are loaded with a stable square wave radio frequency voltage with a certain frequency and amplitude. When ions are injected into the six-electrode structure ion trap, V7, V8, and V9 are required to form a radial potential gradient to push the ions into the middle of the two six-electrode structures. After the ions are injected into the six-electrode structure, V7, V8 and V9 stop loading the square wave RF voltage, and a pair of disc-shaped coaxial six-electrode structures are loaded with DC voltage, namely V1, V2, V3, V4, V5 and V6, thereby generating an electrostatic field, which traps the ions in the motion region and causes them to move periodically in an elliptical and continuously precessing ion motion orbit. Figure 2 As shown, the trapped motion region of ions includes a central electric field region, a field-free region, an axial focusing region and a reflection region which are coaxially arranged in sequence with the axis of the central circular electrode E1 as the center, wherein the central electric field region is opposite to E1 and E2, the field-free region is opposite to E3, the axial focusing region is opposite to E4, and the reflection region is opposite to E5, E6 and E7.

[0031] Figure 3 This is a quarter isometric view of a six-electrode electrostatic ion trap of an embodiment. The diameter of the entire electrostatic ion trap is greater than 200 mm, and the axial thickness z is greater than 30 mm; the maximum trajectory radius of the ion motion trajectory is greater than 80 mm, and the axial thickness is less than 2 mm; the radial thickness of E3 exceeds 45% of the outer radius of E6, and the radial thickness of E3 exceeds 70% of the outer radius of E3. The electrostatic ion trap has a simplified shape and structure, a compact overall structure, can be precisely processed, and reduces the risk of electric field breakdown.

[0032] like Figure 4 As shown, the working sequence of the electrostatic ion trap is:

[0033] (I) In the initial stage, ions move stably around the central axis in the quadrupole annular guide outside the six-electrode structure under the action of the radio frequency voltage on the electrode;

[0034] (II) the voltage on the quadrupole ring guide electrode is switched to a dipole mode, that is, V8 and V9 become high level, V7 becomes low level, and at the same time, V6 drops to a low level, so that the ions moving in the quadrupole ring guide are injected into the six-electrode structure;

[0035] (III) Introducing ions into V6 through pulses, the width of the pulse depends on the mass of the ions, and is 1 to 2 microseconds for a small mass range, that is: after a time delay of 1 to 2 microseconds, V6 is rapidly raised, thereby establishing a potential barrier to reflect the ions, and the ions will present a high aspect ratio in the motion area, and perform periodic elliptical precession motion with an elliptical precession ion motion trajectory, while on E1, the periodic time domain charge signal is collected and amplified, and the time series charge signal is converted into a frequency domain mass spectrum through a known fast Fourier transform algorithm;

[0036] (IV) Before the next ion injection, the level of E6 is lowered, the ions in the six-electrode electrostatic ion trap are emptied, and then the next sequence begins.

[0037] like Figure 5 and Figure 6 As shown, in order to conveniently describe the motion of ions in an electrostatic ion trap, cylindrical coordinates are usually used to describe the motion trajectory of ions in the trap. In order to accurately calculate the time error, a Cartesian coordinate system is also used, that is, the longitudinal direction is the y-axis, the transverse direction is the x-axis, and the direction perpendicular to the xy plane is the z-axis. Each annular electrode is cylindrically symmetrical with the z-axis as the central axis. At the same time, a pair of disc-shaped coaxial six-electrode structures with mirror symmetry in the xy plane are the upper and lower regions of the electrostatic ion trap.

[0038] Figure 7The electrode voltage is obtained by the optimization algorithm, and then the time divergence of the ion half-turn motion caused by the z spatial divergence and tangential energy divergence is obtained by theoretical calculation. The so-called half-turn motion refers to the characteristic motion trajectory of the ion in the electrostatic ion trap, that is, the time taken to start from the closest distance to the center of the electrostatic ion trap (this point is also called the "perihelion"), after E6 reflection, and reach the closest distance to the center of the electrostatic ion trap again (that is, the second perihelion). The so-called half-turn time deviation is the half-turn time deviation of each ion relative to the reference ion. The reference ion has a fixed spatial position and energy. For a group of ions, they have energy divergence and spatial divergence, which will cause the divergence of the half-turn time. Figure 7 The spatial divergence range of the z-axis is 0-0.5 mm, and the energy divergence range is 3700-3800 eV. Using certain optimization algorithms, such as genetic algorithms, particle swarm algorithms and other artificial intelligence algorithms, the voltage on the electrodes can be automatically controlled. The goal is to use the voltages on E1-E6 to make the motion period of the moving ions in the trap tend to be isochronous with respect to the initial spatial divergence and energy divergence, thereby minimizing the half-turn time divergence. In addition, as the half-turn time divergence decreases, the resolution of the electrostatic ion trap will also increase.

[0039] Figure 8 is the single precession trajectory of a split single ion.

[0040] Fig. 9 The potential distribution in the trap is shown. In use, the annular electrodes in the upper and lower regions are provided with the same voltage pattern, so that the ions are focused and transmitted in the middle region (i.e., the movement region of the ions) between the upper and lower regions of the electrostatic ion trap, thereby realizing the periodic oscillation motion of the middle position. In addition, the central circular electrode is used as a signal collection electrode, connected to an amplifier circuit, for detecting the image current, which has a frequency component related to the mass-to-charge ratio of the ions undergoing periodic oscillation motion in the region space between the upper and lower regions.

[0041] Fig.10 The stable and repetitive precession trajectory of the ion in the trap is shown. The ions moving in the motion region exhibit characteristic motion trajectories, in which the ions follow orbital trajectories close to the diameter, with axial precession in the z-axis, and the motion trajectory mapped in the xz direction extends in the x-direction, with voltage barriers at the beginning and the end of the ion turning point for reflecting the ions in the x-direction.

[0042] The electrostatic ion trap of the present invention can analyze the movement frequencies of ions of different masses by collecting the image charges on the electrodes, thereby performing mass spectrometry analysis. Fig.11The mass spectrometry performance of the six-electrode electrostatic ion trap of the present invention was verified. Six groups of ions were used in the study, including m / z=117.000Th, 117.002Th, 117.004Th, 117.006Th, 117.008Th and 117.010Th (50 each). The initial position was set to the center of the Gaussian distributed quadrupole annular guide. According to the experimental settings, the image charge collection time was 300 milliseconds and the sampling step was 0.5ns (the sampling frequency was 2000MHz). After the image charge collection was completed, the corresponding mass spectrum could be generated by applying FFT to the recorded image charge signal. Fig.11 a shows a simulated mass spectrum (without mass calibration) from 1 MHz to 8 MHz, where there are many harmonic frequencies. Fig.11 The mass spectrum peaks in the three intervals in a are shown in Fig.11 b~ Fig.11 d. It can be found that the mass resolution increases gradually from i to iii, which means that the ions are gradually separated in frequency. Fig.11 Harmonic peaks up to the 17th order are shown in a, although their intensities vary with the harmonic order. The mass resolution is calculated using equation (1)

[0043]

[0044] In formula (1), ω is the frequency, Δω is 50％ is the half-height width of the spectrum peak. Fig.11 In b, use Fig.11 The fifth harmonic peak in a shows six mass spectrum peaks, which means that these six groups of ions are resolved and the calculated mass resolution is 56k. Fig.11 In c, use Fig.11 The eighth harmonic peak in a and six mass spectrum peaks can also be seen, and the mass resolution can be further reduced to about 101k. Fig.11 d) uses the 11th harmonic for the ion m / z = 117.010Th, and the mass resolution reaches about 161k. The calculation process is shown in Fig.11 d. It is reported that mass resolution increases with the increase of harmonic order N. If we can ensure that the ion cloud does not diverge after a long flight, then the mass spectrum peaks with higher harmonic orders can provide higher mass resolution.

Claims

1. An electrostatic ion trap, characterized in that: The invention comprises a pair of disk-shaped coaxial six-electrode structures arranged in mirror symmetry, wherein the area between the pair of disk-shaped coaxial six-electrode structures is the trapped motion area of ​​ions, and each of the six-electrode structures is composed of six coaxial and radially spaced annular electrodes, namely: a central circular electrode E1 and a tangential kinetic energy focusing ring electrode E2, a plane ground electrode E3, an axial kinetic energy focusing ring electrode E4 and two radial reflection ring electrodes E5 and E6 which are coaxially arranged in sequence with the central circular electrode E1 as the center; when the ions are trapped, E1 is at ground potential, and stable DC voltages are loaded on E2, E4, E5 and E6, wherein E2, E5 and E6 have the same polarity as the trapped ions, and E4 has the opposite polarity to the trapped ions; the electrostatic ion trap generates an electrostatic field between the pair of disk-shaped coaxial six-electrode structures, so that the ions are reflected back and forth in the trapped motion area and move periodically with a precession motion trajectory, and the maximum radius of the mapping trajectory of the ion motion trajectory on the mirror symmetry plane of the pair of disk-shaped coaxial six-electrode structures is smaller than the outer radius of E6.

2. An electrostatic ion trap according to claim 1, characterized in that: During the ion trapping motion, E3 is at ground potential.

3. An electrostatic ion trap according to claim 1, characterized in that: Each of the six-electrode structures is coaxially provided with three annular electrodes, which are respectively denoted as E7, E8, and E9, and the electrodes E7 to E9 form a quadrupole annular guide. During the movement of ions in the quadrupole annular guide formed by E7 to E9, a stable square wave radio frequency voltage with a certain frequency and amplitude is applied to E7, E8, and E9 to transmit ions, and after the ions are injected into the six-electrode structure, the square wave radio frequency voltage is stopped from being applied to E7, E8, and E9.

4. An electrostatic ion trap according to claim 3, characterized in that: The trapped motion area includes a central electric field zone, a field-free zone, an axial focusing zone and a reflection zone which are coaxially arranged in sequence with the axis of the central circular electrode E1 as the center, wherein the central electric field zone is opposite to E1 and E2, the field-free zone is opposite to E3, the axial focusing zone is opposite to E4, and the reflection zone is opposite to E5, E6 and E7.

5. The electrostatic ion trap according to claim 1, characterized in that: The central circular electrode E1 is used as a signal collection electrode and is connected to an amplifier circuit for detecting the image current.

6. The electrostatic ion trap according to claim 1, characterized in that: The radius of the electrostatic ion trap is greater than 90 mm, the radial thicknesses of E1, E2, E3, E4 and E5 are respectively greater than 6 mm, and the radial thickness of E6 is greater than 3.6 mm.

7. The electrostatic ion trap according to claim 1, characterized in that: The radial thickness of E3 exceeds 45% of the outer radius of E6, and the radial thickness of E3 exceeds 70% of the outer radius of E3.

8. The electrostatic ion trap according to claim 1, characterized in that: The voltage setting is obtained according to an artificial intelligence optimization algorithm, thereby automatically controlling the voltage on the electrodes. The goal is to use the voltages on E1 to E6 to make the motion period of the moving ions in the trap tend to be isochronous with respect to the initial spatial divergence and energy divergence.

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