Apparatus and method for increasing ion capacity of an ion trap mass analyzer

Abstract

The application provides a device and method for improving the ion capacity of an ion trap mass analyzer. In the ion storage stage, a high-frequency second auxiliary voltage is synchronously applied to the electrodes in the ion exit direction in addition to the main radio frequency field, so that the ion cloud is enlarged, small mass-to-charge ratio ions are distributed on the periphery of the cloud, spatial separation is achieved, and the space charge effect is inhibited. In the ion analysis stage, a first auxiliary voltage is applied to the electrodes in the ion exit direction, and the second auxiliary voltage is continuously applied, and the ions are ejected from the trap in order from small to large mass-to-charge ratio by scanning the main radio frequency voltage. The application can significantly improve the storage capacity, mass resolution and mass spectrum detection dynamic range of the ion trap without increasing the size of the device, and prevents the mass axis from drifting.

Description

Technical Field

[0001] This invention relates to the field of mass spectrometry analysis technology, and more specifically, to an apparatus and method for improving the ion capacity of an ion trap mass analyzer and suppressing the space charge effect. Background Technology

[0002] Mass spectrometry is an indispensable tool in modern analytical science, and its core component is the mass analyzer. Ion trap mass analyzers, especially three-dimensional ion traps (also known as Paul traps), are widely used due to their relatively simple structure, high sensitivity, and ability to perform multi-stage mass spectrometry analysis. In a mass spectrometry system, when analyzing high-concentration ion samples, a large number of ions are compressed within the limited space of the ion trap. These ions, carrying the same charge, generate a strong Coulomb repulsion force, known as the space charge effect. The space charge effect is a key bottleneck limiting the performance of mass spectrometry, especially the accuracy and dynamic range of quantitative analysis. During ion ejection and analysis, the interaction forces between ions disrupt their original trajectories, leading to deviations in the measured mass-to-charge ratio (m / z) and mass axis drift, thus reducing mass accuracy. Simultaneously, the strong signal generated by high-concentration ions suppresses the signal of low-concentration ions, making it difficult to detect low-abundance substances and severely limiting the instrument's dynamic range. When the number of ions in the trap exceeds a certain threshold, the space charge effect becomes dominant, leading to increased ion loss, decreased transmission efficiency, and ultimately a decrease in the detected signal strength, i.e., decreased sensitivity.

[0003] Invented by Wolfgang Paul in 1953, the three-dimensional ion trap is a classic device that uses a radio frequency electric field to trap charged particles. Compared to later-developed linear ion traps, the three-dimensional ion trap has a much greater depth, typically more than two orders of magnitude deeper than a linear trap of the same size. This makes it easier to load ions from room-temperature ion sources (such as electrospray ionization sources), and the ions within the trap are more resistant to background gas collisions, have a longer lifetime, and can operate stably even in environments with slightly lower vacuum levels. Furthermore, the three-dimensional ion trap has a higher trap frequency, stronger ion confinement, smaller ion movement amplitude, and lower cooling requirements. However, a significant drawback of the three-dimensional ion trap is its limited ion capacity. When the sample concentration is high, a large number of ions tend to accumulate within the trap, and the space charge effect becomes extremely severe, leading to reduced sensitivity, mass peak shift, and severely limiting its effective dynamic range and analytical performance.

[0004] To mitigate the space charge effect, several improvements have been proposed in existing technologies. For example, a rhombic ion excitation technique applies two pairs of dipole AC signals with the same frequency and amplitude but a 90-degree phase difference to the electrodes in the x and y directions of the ion trap. This selectively excites ions to approximately rhomboid orbits based on their mass, aiming to reduce the Coulomb forces between ion clouds. However, this technique is primarily applicable to linear ion traps and cannot be directly applied to three-dimensional ion traps, thus failing to effectively address the severe space charge effect problem faced by three-dimensional ion traps. Furthermore, this technique cannot solve a series of problems associated with axial emission from the ion trap, and the lack of a specific voltage applied in the initial ion emission direction may introduce peak broadening, affecting mass resolution. Therefore, a new method is urgently needed to effectively increase the ion capacity of three-dimensional ion traps, suppress the space charge effect, and thereby improve their analytical performance. Summary of the Invention

[0005] This invention aims to address the aforementioned problems in the prior art, namely, the limited ion capacity, mass axis shift, and restricted sensitivity and dynamic range of three-dimensional ion traps due to space charge effects. Therefore, this invention provides an apparatus and method that can effectively improve the ion capacity of an ion trap mass analyzer, suppress space charge effects, prevent peak drift, and improve mass resolution without increasing the physical size of the device.

[0006] To solve the above-mentioned technical problems, the technical solution proposed in this application is as follows:

[0007] This invention provides an apparatus for improving the ion capacity of an ion trap mass analyzer, comprising: Ion trap; A radio frequency power supply is used to apply a main radio frequency voltage to the ion trap to confine ions; A first auxiliary voltage source is used to generate a first auxiliary voltage; A second auxiliary voltage source is used to generate a second auxiliary voltage, the frequency of which is higher than the frequency of the first auxiliary voltage. At least one voltage application control unit is electrically connected to the first auxiliary voltage source, the second auxiliary voltage source, and the ion emission direction electrode of the ion trap, respectively, for synchronously applying the second auxiliary voltage to the ion emission direction electrode of the ion trap during the ion storage stage, and simultaneously applying the first auxiliary voltage and the second auxiliary voltage to the ion emission direction electrode of the ion trap during the ion analysis stage.

[0008] Furthermore, the first voltage application control unit includes an adder circuit or a coil resonant circuit, which is used to superimpose the first auxiliary voltage and the second auxiliary voltage and output them to the ion emission direction electrode.

[0009] Furthermore, the ion trap is a three-dimensional ion trap, and the ion emission direction electrode is an end cap electrode, which includes a left end cap electrode and a right end cap electrode; or the ion trap is a linear ion trap, and the ion emission direction electrode is an axial electrode.

[0010] Furthermore, the frequency of the second auxiliary voltage is set to avoid resonance with ions when the main radio frequency voltage increases.

[0011] Furthermore, it also includes an insulator disposed between the first voltage application control unit and the ion emission direction electrode or disposed in the electrode support structure.

[0012] On the other hand, this application also claims protection for a method for improving the ion capacity of an ion trap mass analyzer, comprising the following steps: Ion storage stage: During the process of ions being captured and stored in the ion trap, in addition to applying the main radio frequency field for ion confinement, a second auxiliary voltage is also synchronously applied to the ion emission direction electrode of the ion trap. Ion analysis stage: A first auxiliary voltage is applied to the ion emission direction electrode of the ion trap, and a second auxiliary voltage is applied simultaneously. By scanning the amplitude of the main radio frequency voltage, ions are ejected from the ion trap in order of increasing mass-to-charge ratio. The frequency of the second auxiliary voltage is higher than the frequency of the first auxiliary voltage.

[0013] Furthermore, in the ion analysis stage, the frequency of the first auxiliary voltage is equal to the secular movement frequency of the ion to be analyzed, and the amplitude of the second auxiliary voltage and the amplitude of the first auxiliary voltage both increase linearly with the increase of the amplitude of the main radio frequency voltage.

[0014] Furthermore, the amplitude of the second auxiliary voltage applied during the ion storage stage remains constant.

[0015] Furthermore, the ion trap is a three-dimensional ion trap, and the ion emission direction electrode is an end cap electrode, which includes a left end cap electrode and a right end cap electrode; or the ion trap is a linear ion trap, and the ion emission direction electrode is an axial electrode.

[0016] Furthermore, the first auxiliary voltage and the second auxiliary voltage are superimposed on the ion emission direction electrode through an adder circuit or coil resonance.

[0017] Compared with the prior art, the present invention achieves the following beneficial technical effects: This invention introduces a high-frequency auxiliary voltage during the ion storage stage without increasing the device size, effectively expanding the ion cloud and achieving spatial separation of ions with different mass-to-charge ratios. This significantly suppresses the space charge effect, prevents mass axis drift, and greatly improves the system capacity, mass resolution, and dynamic range of mass spectrometry detection of the ion trap. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The diagram shows the formula for the Mathieu equation.

[0020] Figure 2 This is a schematic diagram of the voltage application timing in one embodiment of the present invention.

[0021] Figure 3 This is a schematic diagram of the structure and voltage application of a three-dimensional ion trap device in one embodiment of the present invention.

[0022] Figure 4 This is a three-dimensional structural diagram of a three-dimensional ion trap device in another embodiment of the present invention.

[0023] Figure 5 This is a cross-sectional structural diagram of a three-dimensional ion trap device in another embodiment of the present invention.

[0024] Figure 6 This is a simulation diagram of the spatial distribution of ion clouds in a three-dimensional ion trap when a second auxiliary voltage is applied, according to one embodiment of the present invention.

[0025] Figure 7 This is a simulation diagram of the spatial distribution of ion clouds in a three-dimensional ion trap under comparative conditions without the application of a second auxiliary voltage.

[0026] Figure 8 This is a three-dimensional structural diagram of a linear ion trap according to another embodiment of the present invention.

[0027] Figure 9 This is a schematic diagram of the electrode structure of a linear ion trap in another embodiment of the present invention.

[0028] Figure 10 This is a schematic diagram of voltage application to a linear ion trap in another embodiment of the present invention.

[0029] In the attached diagram, 100 represents the ion trap, 101 represents the annular electrode, 102 represents the left end cap electrode, 103 represents the right end cap electrode, 200 represents the radio frequency power supply, 300 represents the first voltage application control unit, 400 represents the insulator, 500 represents the second voltage application control unit, 3001 represents the third voltage application control unit, 3002 represents the fourth voltage application control unit, 5001 represents the fifth voltage application control unit, 5002 represents the sixth voltage application control unit, AC1 represents the first auxiliary voltage, and AC2 represents the second auxiliary voltage. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, 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.

[0031] In one embodiment of this application, an apparatus for increasing the ion capacity of an ion trap mass analyzer is provided. For example... Figure 4 and Figure 5As shown, the device includes: an ion trap 100, a radio frequency (RF) power supply 200, a first auxiliary voltage source, a second auxiliary voltage source, a first voltage application control unit 300, and a second voltage application control unit 500. The ion trap 100 can be a three-dimensional ion trap or a linear ion trap, having an internal space for confining and storing ions and an exit direction electrode for ion ejection. The RF power supply 200 is electrically connected to the annular electrode 101 (for a three-dimensional trap) or rod electrode (for a linear trap) of the ion trap to apply a main RF voltage to the ion trap to confine ions. The first auxiliary voltage source generates a first auxiliary voltage AC1, which is a dipole AC signal with a frequency set equal to or close to the secular motion frequency of the target ion to be analyzed, for resonant excitation of ions during the analysis phase. The second auxiliary voltage source generates a second auxiliary voltage AC2, which is a high-frequency AC signal with a frequency higher than that of the first auxiliary voltage AC1. The selection of this frequency ensures that, when the main RF voltage scan increases, it does not resonate with the secular motion frequency of any ions within the trap, thereby avoiding unintended ion excitation or heating. The first voltage application control unit 300 controls the positive-phase superposition signal +AC1+AC2, and the second voltage application control unit 500 controls the negative-phase superposition signal -AC1-AC2. The first voltage application control unit 300 and the second voltage application control unit 500 are electrically connected to the first auxiliary voltage source, the second auxiliary voltage source, and the ion emission direction electrode of the ion trap, respectively. The device is configured such that: during the ion storage stage, the second auxiliary voltage AC2 is synchronously applied to the ion emission direction electrode of the ion trap; during the ion analysis stage, the first auxiliary voltage AC1 and the second auxiliary voltage AC2 are simultaneously applied to the ion emission direction electrode of the ion trap. Through timing control, this device achieves the function of pre-dispersing ion clouds during the storage stage and maintaining dispersion and achieving resonant excitation during the analysis stage, thereby effectively improving the ion capacity of the ion trap and suppressing the space charge effect. Specifically, during the ion storage stage, sample molecules are first ionized by the ionization source to generate gaseous sample ions, which then enter the ion trap through the ion optical system. Before or simultaneously with ion entry, the radio frequency power supply 200 applies a main radio frequency voltage with a fixed amplitude to the annular electrode 101 to form a potential well. The voltage application control unit applies a second auxiliary voltage AC2 to the emission direction electrode. This high-frequency voltage significantly expands the volume of the ion cloud and promotes the distribution of low mass-to-charge ratio ions on the periphery of the cloud, thereby reducing the number of ions per unit volume and weakening the space charge effect.During the ion analysis stage, the voltage application control unit applies the first auxiliary voltage AC1 and the second auxiliary voltage AC2 to the emission direction electrode simultaneously. The radio frequency power supply 200 begins a linear scan to increase the amplitude of the main radio frequency voltage. Ions are ejected in sequence with the first auxiliary voltage AC1 according to their mass-to-charge ratio from small to large. The second auxiliary voltage AC2 maintains the expansion and spatial separation of the ion cloud throughout the process.

[0032] In one embodiment of this application, the voltage application control unit in the above-described device is specifically defined. Specifically, the first voltage application control unit 300 or the second voltage application control unit 500 includes an adder circuit or a coil resonant circuit. The adder circuit is used to linearly superimpose the first auxiliary voltage AC1 and the second auxiliary voltage AC2, and output the superimposed composite voltage to the ion emission direction electrode. The input terminal of the adder circuit receives signals from the first auxiliary voltage source and the second auxiliary voltage source, and its output terminal is connected to the emission direction electrode of the ion trap, linearly superimposing the two AC voltage signals and synchronously applying the superimposed composite voltage signal to the electrode. The coil resonant circuit couples and superimposes the two AC voltage signals through the resonance principle and outputs them to the ion emission direction electrode. Specifically, in the circuit connected to the emission direction electrode, a coil with a specific inductance is provided. This coil and the distributed capacitance of the electrode together form a resonant circuit. By adjusting the frequencies of the first auxiliary voltage AC1 and the second auxiliary voltage AC2 respectively, they are matched with two different resonant frequencies of the resonant circuit, thereby efficiently coupling and superimposing the two AC voltage signals onto the electrode. The advantages of the coil resonance method are high energy efficiency and a natural filtering effect, reducing signal interference. Both circuit structures can reliably achieve synchronous application of two auxiliary voltages and have the advantages of simple circuitry and ease of implementation.

[0033] In one embodiment of this application, the type of ion trap in the above-described device is specifically defined. Specifically, the ion trap 100 can be a three-dimensional ion trap, in which case the ion emission direction electrode is an end cap electrode, including a left end cap electrode 102 and a right end cap electrode 103. Alternatively, the ion trap 100 can be a linear ion trap, in which case the ion emission direction electrode is an axial electrode. This design makes the device of the present invention highly versatile, allowing the selection of a suitable ion trap type according to actual application requirements without changing the core voltage application control strategy. For a three-dimensional ion trap, both the second auxiliary voltage AC2 and the first auxiliary voltage AC1 are applied to the left end cap electrode 102 and the right end cap electrode 103; for a linear ion trap, both the second auxiliary voltage AC2 and the first auxiliary voltage AC1 are applied to the axial electrodes at both ends of the linear ion trap. For linear ion trap applications, during the ion storage stage, a constant high-frequency second auxiliary voltage AC2 is applied to the axial electrode to expand the radially confined ion cloud by axial perturbation and to promote the diffusion of ions with low mass-to-charge ratio to both ends. During the analysis stage, a first auxiliary voltage AC1 and a linearly increasing second auxiliary voltage AC2 are applied to the axial electrode simultaneously, while the main radio frequency voltage is scanned. The first auxiliary voltage AC1 is used to resonate and excite ions, causing them to pop out along the axial direction, while the second auxiliary voltage AC2 continuously suppresses the space charge effect.

[0034] In one embodiment of this application, the second auxiliary voltage in the aforementioned device is further parameterized. Specifically, the frequency of the second auxiliary voltage AC2 is set to avoid resonance with ions when the main radio frequency voltage increases. This is because the function of the second auxiliary voltage AC2 is to expand the ion cloud and achieve spatial separation, not to resonate and excite ejection. If its frequency coincides with the secular motion frequency of a certain mass-to-charge ratio ion during the main radio frequency scan, it will cause the ion to be unexpectedly resonantly excited, resulting in premature ejection or abnormal heating, thereby interfering with the normal mass analysis process. Therefore, by reasonably selecting the frequency of the second auxiliary voltage AC2 (usually much higher than the frequency of the first auxiliary voltage AC1, and higher than the upper limit of the secular motion frequency of all ions within the main radio frequency voltage scan range), it can be ensured that it only plays a "dispersing" role and does not produce an "excitation" role throughout the analysis process.

[0035] In one embodiment of this application, the above-described device further includes an insulator 400. For example... Figure 4As shown, the insulator 400 is disposed between the first voltage application control unit 300 and the ion emission direction electrode, or disposed in the electrode support structure, to electrically isolate components at different potentials and prevent high-voltage breakdown or signal crosstalk. The insulator 400 can be made of high-insulation materials such as ceramics or polytetrafluoroethylene. When voltage is superimposed using a coil resonance method, the insulator 400 can also serve as the coil frame, providing mechanical support and electrical insulation. By incorporating the insulator 400, the stability and reliability of the device of the present invention under high-voltage operating conditions are further improved.

[0036] In one embodiment of this application, a method for improving the ion capacity of an ion trap mass analyzer is provided. This method specifically includes an ion storage stage and an ion analysis stage. In a Paul trap, ion stability is described by the Mathieu equation, such as... Figure 1As shown. During the ion storage stage, sample molecules are first ionized by an ionization source (such as an electrospray ionization source) to generate gaseous sample ions. These ions are guided into the internal space of the three-dimensional ion trap by an ion optical system (such as an ion lens). Before or simultaneously with the entry of the ions, the radio frequency power supply 200 applies a main radio frequency voltage with a fixed amplitude to the ring electrode 101, forming a three-dimensional potential well inside the ion trap to confine the ions. At the same time, in addition to applying this main radio frequency field for ion confinement, a second auxiliary voltage AC2 is simultaneously applied to the ion emission direction electrodes of the ion trap. Specifically, for the three-dimensional ion trap, the ion emission direction electrodes are end cap electrodes (left end cap electrode 102 and right end cap electrode 103), and the second auxiliary voltage AC2 is applied to the left and right end cap electrodes. This second auxiliary voltage AC2 is a high-frequency AC signal with a frequency higher than that of the first auxiliary voltage AC1 to be applied in the subsequent analysis stage. The ions entering the trap are confined and converged under the action of the main radio frequency field, forming an initial ion cloud. However, due to the effect of the high-frequency second auxiliary voltage AC2, the volume of this ion cloud is significantly expanded. The mechanism is as follows: the high-frequency second auxiliary voltage AC2 generates an alternating perturbation field between the end cap electrodes 102, 103 and the ring electrode 101. This perturbation field has different effects on ions with different mass-to-charge ratios—ions with smaller mass-to-charge ratios are more sensitive to the high-frequency electric field, and their forced motion amplitude is greater, thus tending to be distributed in the outer layer of the ion cloud. This effect of "ion cloud expansion" and "spatial mass-to-charge ratio separation" greatly reduces the number of ions per unit volume, thereby fundamentally weakening the Coulomb repulsion force between ions, i.e., the space charge effect. The ion analysis stage then begins. In the ion analysis stage, the first auxiliary voltage AC1 continues to be applied to the ion exit direction electrode of the ion trap, while the second auxiliary voltage AC2 is still applied. The first auxiliary voltage AC1 is a dipole AC signal whose frequency is set to be equal to or close to the secular motion frequency of the target ion to be analyzed, used for resonant excitation of the ions. Simultaneously, the RF power supply 200 begins a linear scan upwards from its initial value, increasing the amplitude of the main RF voltage applied to the annular electrode 101. As the main RF voltage scans, the ions within the ion trap resonate with the first auxiliary voltage AC1 in ascending order of their mass-to-charge ratio, causing a sharp increase in their motion amplitude. Ultimately, they are ejected from the ion trap through a small hole on the emission direction electrode. Throughout the analysis phase, the second auxiliary voltage AC2 remains applied, thus maintaining the expansion and spatial separation of the ion cloud during the entire mass scan, effectively suppressing interference from the space charge effect. Finally, the ejected ions can be received by the ion detector, generating an electrical signal and producing a mass spectrum.After completing an analysis, a zeroing phase may also be included: all voltages applied to the ion trap (including the main RF voltage, the first auxiliary voltage AC1, and the second auxiliary voltage AC2) are set to zero, so that there are no ion residues in the ion trap, preparing for the next analysis cycle.

[0037] In one embodiment of this application, the above method is further optimized. Specifically, during the ion analysis stage, the frequency of the applied first auxiliary voltage AC1 is precisely set to be equal to the secular motion frequency of the ion to be analyzed, to ensure the high efficiency of resonant excitation. Simultaneously, the amplitudes of both the second auxiliary voltage AC2 and the first auxiliary voltage AC1 increase linearly with the increase of the main radio frequency voltage. This is because, as the main radio frequency voltage scan increases, high mass-to-charge ratio ions begin to be excited. If the amplitude of the second auxiliary voltage AC2 does not increase, its effect on expanding the ion cloud may be weakened for high mass-to-charge ratio ions. By synchronously and linearly increasing the second auxiliary voltage AC2, it can be ensured that the ion cloud remains in a relatively expanded and spatially separated state throughout the entire mass scan range, thereby minimizing mutual interference between ions with different mass-to-charge ratios during ejection and ensuring the accuracy and high resolution of the mass axis. Furthermore, since the frequency of the second auxiliary voltage AC2 is much higher than the frequency of the first auxiliary voltage AC1, it will not interfere with the resonant excitation process of the first auxiliary voltage for specific ions.

[0038] In one embodiment of this application, the ion storage stage of the above method is further defined. Specifically, the amplitude of the second auxiliary voltage AC2 applied during the ion storage stage remains constant. The purpose of this is to ensure that the ion cloud remains in a stable, expanded state during the storage stage to accommodate as many ions as possible and reduce the space charge effect. A constant amplitude avoids ion cloud oscillations or instability caused by voltage fluctuations, thus preparing for high-capacity storage and low space charge effects in subsequent analysis stages. Of course, this constant amplitude can be adaptively adjusted according to the actual ion concentration introduced; a higher concentration requires a larger amplitude to achieve better dispersion, but this does not affect its consistency during a single analysis.

[0039] In one embodiment of this application, the above method can be applied to different types of ion traps. Specifically, when the ion trap is a three-dimensional ion trap (Paul trap), the ion emission direction electrode is the end cap electrode, that is, both the second auxiliary voltage AC2 and the first auxiliary voltage AC1 are applied to the left end cap electrode 102 and the right end cap electrode 103. When the ion trap is a linear ion trap, the ion emission direction electrode is the axial electrode, that is, both the second auxiliary voltage AC2 and the first auxiliary voltage AC1 are applied to the axial electrodes at both ends of the linear ion trap. This cross-type applicability makes the present invention have broad industrial application value. For the application scenario of linear ion traps, in the ion storage stage, only a constant high-frequency second auxiliary voltage AC2 is applied to the axial electrode to expand the radially confined ion cloud in a axial perturbation manner and promote the diffusion of ions with low mass-to-charge ratio to both ends; in the analysis stage, the first auxiliary voltage AC1 and the linearly increasing second auxiliary voltage AC2 are applied to the axial electrode at the same time, while the main radio frequency voltage is scanned. The first auxiliary voltage AC1 is used to resonantly excite ions, causing them to eject along the axial direction, while the second auxiliary voltage AC2 continuously suppresses the space charge effect.

[0040] In one embodiment of this application, the superposition method of the first auxiliary voltage and the second auxiliary voltage in the above method is specifically defined. Specifically, the first auxiliary voltage AC1 and the second auxiliary voltage AC2 are superimposed by an adder circuit and applied to the ion emission direction electrode. The input terminal of the adder circuit receives signals from the first auxiliary voltage source and the second auxiliary voltage source, and its output terminal is connected to the emission direction electrode of the ion trap, linearly superimposing the two AC voltage signals and synchronously applying the superimposed composite voltage signal to the electrode. Alternatively, the first auxiliary voltage AC1 and the second auxiliary voltage AC2 are superimposed by a coil resonance method and applied to the ion emission direction electrode. Specifically, in the circuit connected to the emission direction electrode, a coil with a specific inductance is provided. This coil and the distributed capacitance of the electrode together form a resonant circuit. By adjusting the frequencies of the first auxiliary voltage AC1 and the second auxiliary voltage AC2 respectively to match the two different resonant frequencies of the resonant circuit, the two AC voltage signals are efficiently coupled and superimposed on the electrode. The advantage of the coil resonance method is its high energy efficiency and natural filtering effect, reducing signal interference. Both superposition methods can reliably achieve the voltage application required by the present invention.

[0041] The invention will now be described in more detail with reference to its specific device structure and operating sequence. For example... Figure 3As shown, in one specific embodiment, the ion trap 100 is a three-dimensional ion trap, having an annular electrode 101 and a pair of end cap electrodes (left end cap electrode 102 and right end cap electrode 103). A main radio frequency voltage is applied to the annular electrode 101. The end cap electrodes 102 and 103 receive a superimposed first auxiliary voltage AC1 and a second auxiliary voltage AC2 through a first voltage application control unit 300 (such as an adder circuit), and the output is labeled "+AC1+AC2". The radio frequency power supply 200 and the first voltage application control unit 300 are both time-controlled by a central controller. Figure 2 As shown, the entire working process is divided into three stages: ion storage, ion analysis, and zeroing. In the ion storage stage, the main RF voltage rises to a preset amplitude and remains constant, while the second auxiliary voltage AC2 is simultaneously turned on and maintained at a constant amplitude, and the first auxiliary voltage AC1 is turned off. Ions are introduced and stored in this stage, and the ion cloud expands and achieves spatial separation under the action of the second auxiliary voltage AC2. In the ion analysis stage, the main RF voltage begins to rise linearly, the first auxiliary voltage AC1 is turned on, and its amplitude increases linearly with the main RF voltage. The second auxiliary voltage AC2 remains constant, and its amplitude also increases linearly with the main RF voltage. Ions are ejected resonantly in order of increasing mass-to-charge ratio. In the zeroing stage, all voltages are set to zero, and the ions in the trap are emptied.

[0042] In another embodiment, such as Figure 8 and Figure 9 As shown, for a linear ion trap, the device can include multiple voltage application control units to achieve different phase combinations. Specifically, a third voltage application control unit 3001 is used to control the positive phase superposition signal +AC1+AC2, a fourth voltage application control unit 3002 is used to control another positive combination; a fifth voltage application control unit 5001 is used to generate the -RF+AC2 signal, and a sixth voltage application control unit 5002 is used to generate the -RF-AC2 or -AC1-AC2 signal. These control units are respectively connected to different axial electrodes or rod electrodes of the linear ion trap to achieve flexible ion cloud manipulation and mass analysis. By setting multiple voltage application control units, the device of the present invention can independently adjust the voltage phase and amplitude on each electrode as needed, thereby optimizing the ion storage, spatial separation, and mass analysis processes.

[0043] The above process was simulated using SIMION software, and the results are as follows: Figure 6 and Figure 7 As shown. Figure 5 The spatial distribution of ions at 50 m / z (green), 100 m / z (red), and 200 m / z (blue) is shown after applying the second auxiliary voltage AC2. It can be clearly seen that the green ions with a low mass-to-charge ratio are distributed at the outermost edge of the cloud, followed by the red ions, and the blue ions are closest to the center. The entire cloud has a relatively large volume. Figure 6 The simulation results show a comparison without the application of a second auxiliary voltage, where all ions are tightly aggregated at the center of the trap, resulting in a small, high-density cloud. This simulation result visually demonstrates the effectiveness of the invention.

[0044] 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 of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for increasing the ion capacity of an ion trap mass analyzer, characterized in that, include: Ion trap (100); Radio frequency power supply (200) is used to apply a main radio frequency voltage to the ion trap to confine ions; A first auxiliary voltage source is used to generate a first auxiliary voltage (AC1). A second auxiliary voltage source is used to generate a second auxiliary voltage (AC2), the frequency of which is higher than the frequency of the first auxiliary voltage; At least one voltage application control unit (300, 500) is electrically connected to the first auxiliary voltage source, the second auxiliary voltage source, and the ion emission direction electrode of the ion trap, respectively, for synchronously applying the second auxiliary voltage to the ion emission direction electrode of the ion trap during the ion storage stage, and simultaneously applying the first auxiliary voltage and the second auxiliary voltage to the ion emission direction electrode of the ion trap during the ion analysis stage.

2. The apparatus according to claim 1, characterized in that, The first voltage application control unit includes an adder circuit or a coil resonant circuit, which is used to superimpose the first auxiliary voltage and the second auxiliary voltage and output them to the ion emission direction electrode.

3. The apparatus according to claim 1, characterized in that, The ion trap is a three-dimensional ion trap, and the ion emission direction electrode is an end cap electrode, which includes a left end cap electrode (102) and a right end cap electrode (103); or the ion trap is a linear ion trap, and the ion emission direction electrode is an axial electrode.

4. The apparatus according to claim 1, characterized in that, The frequency of the second auxiliary voltage is set to avoid resonance with ions when the main radio frequency voltage increases.

5. The apparatus according to claim 1, characterized in that, It also includes an insulator (400) disposed between the first voltage application control unit and the ion emission direction electrode or disposed in the electrode support structure.

6. A method for improving the ion capacity of an ion trap mass analyzer, characterized in that, Includes the following steps: Ion storage stage: During the process of ions being captured and stored in the ion trap, in addition to applying the main radio frequency field for ion confinement, a second auxiliary voltage (AC2) is also synchronously applied to the ion emission direction electrode of the ion trap. Ion analysis stage: A first auxiliary voltage (AC1) is applied to the ion emission direction electrode of the ion trap, while the second auxiliary voltage is applied simultaneously. By scanning the amplitude of the main radio frequency voltage, ions are ejected from the ion trap in order of increasing mass-to-charge ratio. The frequency of the second auxiliary voltage is higher than the frequency of the first auxiliary voltage.

7. The method according to claim 6, characterized in that, During the ion analysis stage, the frequency of the first auxiliary voltage is equal to the secular movement frequency of the ion to be analyzed, and the amplitudes of the second auxiliary voltage and the first auxiliary voltage both increase linearly with the increase of the amplitude of the main radio frequency voltage.

8. The method according to claim 6, characterized in that, The amplitude of the second auxiliary voltage applied during the ion storage stage remains constant.

9. The method according to claim 6, characterized in that, The ion trap is a three-dimensional ion trap, and the ion emission direction electrode is an end cap electrode, which includes a left end cap electrode and a right end cap electrode; or the ion trap is a linear ion trap, and the ion emission direction electrode is an axial electrode.

10. The method according to claim 6, characterized in that, The first auxiliary voltage and the second auxiliary voltage are superimposed by an adder circuit or a coil resonance method and then applied to the ion emission direction electrode.

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