Ion guiding device and ion guiding method

Abstract

The present invention provides an ion guide device and an ion guide method for off-axis ion transmission, which can avoid or mitigate the ion heating problem caused by a radio frequency multipole field and improve the transmission efficiency of ions. The ion guide device comprises a plurality of parallel annular electrodes, each of which comprises at least four electrode units separated from each other, a channel for ion transmission is formed inside the plurality of annular electrodes, and the arrangement direction of the plurality of annular electrodes defines the axial direction of ion transmission; an RF voltage source, wherein the RF voltages applied to adjacent electrode units belonging to the same annular electrode have different phases, and the RF voltages applied to adjacent electrode units along the axial direction have the same phase, thereby forming an RF multipole field for confining ions in the ion guide device; and a DC voltage source, wherein the ions are transmitted off the axial direction and focused on the inner surface of the annular electrode under the combined action of the RF voltage and the DC voltage.

Description

Technical Field

[0001] The present invention relates to the technical field of ion guiding, and in particular to an ion guiding device and an ion guiding method. Background Art

[0002] In a mass spectrometer, the ion source region with a relatively high pressure (1 to 10 5 In order to achieve low-loss transmission of ions, an ion guide is usually required in addition to the necessary vacuum interface. The ion guide generally consists of a series of electrodes to which a radio frequency voltage is applied. The radio frequency voltage forms an effective barrier to bind ions around the central axis of the device, causing the ions to converge. At the same time, under the action of the airflow caused by differential pumping or the DC electric field attached along the axis, the converged ions are directed to move to the next level of vacuum and then analyzed by the mass spectrometer.

[0003] Earlier radio frequency guidance devices, such as the multipole guidance rod system invented by DJ Douglas (U.S. Patent 5179278) and the surface reflection multipole field guidance device proposed by J. Franzen (U.S. Patent 5572035), can focus ions at 0.1 torr. Later, the Q-array guide invented by N. Inatsugu and H. Waki, and the traveling wave guidance device proposed by Bateman et al. (U.S. Patent 7095013), can better guide and focus ions at pressures below 5 torr. In order to focus ions at higher pressures, RD Smith proposed an ion funnel device (U.S. Patent 6107628), which can effectively transmit and focus ions at pressures close to 30 torr, greatly improving the sensitivity of the device.

[0004] However, when the ion funnel is applied to the mass spectrometer, its front stage is generally a capillary structure connected to the atmospheric pressure or a sampling cone structure with a small hole, and the back stage is a cavity with a lower pressure than the inside of the ion funnel. Due to its funnel-shaped structure, there will be a strong airflow on the entire axis of the funnel. Even if a metal baffle (jet-disrupter) is added near the entrance of the funnel to reduce the airflow, there will still be a considerable airflow at the outlet. This airflow will not only increase the burden on the vacuum pump, but these neutral gas molecules will also bring noise to the final ion detection; in particular, when used with an electrospray ion source, the airflow will carry charged droplets that have not been completely desolvated into the next vacuum stage, thereby bringing more noise and affecting the sensitivity of the instrument.

[0005] K. Giles designed an off-axis transmission device in U.S. Patent US2011 / 0049357. The device is composed of a large and a small barrel electrode array similar to an ion funnel, with a certain potential barrier between the two arrays. Ions enter from one side of the large barrel electrode array, and then overcome the potential barrier between the arrays under the push of the DC electric field, enter the small barrel electrode array for transmission and extraction, while neutral molecules are extracted along the axis of the large barrel electrode array, thereby achieving off-axis transmission of ions. This device has two shortcomings. One is that it cannot achieve very effective focusing. The final focusing radius of the ion beam is determined by the radius of the small barrel electrode array, but if the radius of the small barrel electrode is too small, the radio frequency blocking barrier at the edge connected to the large barrel electrode will become stronger, making it difficult for ions to enter. Second, the structure of the device is relatively complex, so it is difficult to manufacture.

[0006] Zhang et al. disclosed an ion transmission device in patent CN103515183A, which adopts off-axis transmission and includes a plurality of annular electrodes arranged in parallel, each of which is surrounded by a plurality of discrete segmented electrodes. A power supply device applies a radio frequency voltage to the annular electrodes, and the radio frequency voltages applied to the adjacent segmented electrodes of the same annular electrode have different phases, and the radio frequency voltages applied to the adjacent segmented electrodes along the central axis also have different phases. Among them, the radio frequency voltage applied to the adjacent segmented electrodes along the central axis is used to focus ions. Specifically, the balance between the radio frequency voltage and the DC deflection voltage focuses the ions on the inner side of the ion transmission device. This device has a simple structure and is easy to process. However, the radio frequency voltages with different phases applied to the adjacent segmented electrodes along the central axis will cause the ions to oscillate on the inner side, causing the ions to be heated and dissociated, resulting in a reduction in the transmission efficiency of such ions. Summary of the invention

[0007] The present invention is proposed to solve the above-mentioned technical problems, and aims to provide an ion guiding device and an ion guiding method for off-axis ion transmission, so that when the ions are confined to the inner side of the ion guiding device, the ion heating problem caused by the radio frequency multipole field can be avoided or alleviated, thereby avoiding unexpected dissociation phenomena and improving the ion transmission efficiency.

[0008] According to one aspect of the present invention, an ion guide device is provided, comprising a plurality of annular electrodes placed in parallel, each annular electrode comprising at least four electrode units separated from each other, channels for ion transmission being formed inside the plurality of annular electrodes, and the arrangement direction of the plurality of annular electrodes defining the axial direction of ion transmission; an RF voltage source for applying an RF voltage to the plurality of annular electrodes, the RF voltages applied to adjacent electrode units belonging to the same annular electrode having different phases, and the RF voltages applied to adjacent electrode units along the axial direction having the same phase, thereby forming an RF multipole field for trapping ions in the ion guide device; a DC voltage source for applying a DC voltage to the plurality of annular electrodes, the DC voltage having a first DC component having an amplitude varying along the axial direction, and a second DC component having an amplitude varying along a specified direction on the plane where the annular electrodes are located; under the combined action of the RF voltage and the DC voltage, the ions are transmitted away from the axial direction and focused on the inner surface of the annular electrode.

[0009] As the number of electrode units on the same annular electrode increases, the distribution of the electrode units becomes denser, so that the distance between adjacent electrodes becomes shorter. The shorter the length of adjacent electrode units, the more the RF multipole field generated after adaptively applying the RF voltage can confine the ions in close proximity, which is convenient for focusing the ions.

[0010] When a radio frequency voltage is applied to adjacent electrode units belonging to the same annular electrode, ions can be more effectively confined in the channel for ion transmission. Furthermore, the balance between the radio frequency voltage and the second DC component of the DC voltage can be used to focus the ions on the inner surface of the annular electrode. Since the radio frequency voltage, which is a factor of the above-mentioned focusing balance, is the radio frequency voltage applied to adjacent electrode units of the same annular electrode, the application method of the radio frequency voltage can avoid or alleviate the oscillation heating problem during ion transmission, thereby avoiding unpredictable dissociation phenomena, and further improving the transmission efficiency of ions.

[0011] Herein, the term "ring electrode" is intended only to define the hollow structure of the electrode, and is not intended to define the overall contour shape of the electrode. Specifically, the outer ring contour of the ring electrode may be square, circular, polygonal, or any other suitable shape and combination of shapes. The inner ring contour of the ring electrode may be consistent with or correspond to the outer ring contour, or may be inconsistent with or not correspond to the outer ring contour. For example, the "ring electrode" may be a ring electrode with a circular outer ring contour and a square inner ring contour.

[0012] Herein, the term "prescribed direction" may be a pre-defined direction, such as a direction specified by the structure of the annular electrode. For example, in some technical solutions, the structure or segmentation of the annular electrode itself has a certain directionality, and the direction of application of the second DC component can be defined by the directionality. In addition, the term "prescribed direction" may also be a direction specified by a DC voltage source. For example, in some technical solutions, the structure or segmentation of the annular electrode is in a centrally symmetrical or rotationally symmetrical form, and it itself has no directionality in a radial plane, and the second DC component of the DC voltage source can be applied in any direction. In these technical solutions, the application direction of the second DC component pre-saved or temporarily generated by the DC voltage source defines the "prescribed direction".

[0013] In a preferred technical solution of the present invention, the shape of the annular electrode has at least one inner angle, and the prescribed direction points to the inner angle. Compared with the position of the edge or the position of the smooth curve, the electrodes at the two adjacent sides constituting the inner angle can provide a radio frequency multipole field that compresses the ion beam from both sides to the middle, thereby improving the focusing effect of the ion beam.

[0014] Furthermore, in a preferred technical solution of the present invention, the inner angle is a convex angle (inferior angle) of 30°-150°. The inner angle is a convex angle, which can effectively provide a radio frequency multipole field that compresses the ion beam from both sides to the middle. The size of the inner angle should not be too large or too small. If the inner angle is too large, it is easy to cause a decrease in the ion beam compression performance. If the inner angle is too small, it is not easy to stably transmit the ion beam off-axis to the pre-set ion outlet position. By setting the inner angle to 30°-150°, the above problems can be effectively taken into account.

[0015] In a preferred technical solution of the present invention, inside the plurality of annular electrodes, the radio frequency multipole field extends in the axial direction. "The radio frequency multipole field extends in the axial direction" means that the radio frequency multipole field as a whole basically extends in the axial direction. Since the radio frequency multipole field as a whole basically extends in the axial direction, the transmission process of ions in the axial direction is relatively smooth, which can more effectively alleviate the oscillation heating problem of ions during the transmission process.

[0016] In a preferred technical solution of the present invention, the annular electrode has a plurality of electrode units of the same length. Using electrode units of the same length to form an annular electrode can improve the versatility of production and assembly of the annular electrode assembly, and can also simplify the simulation or calculation of the electric field to be applied.

[0017] In a preferred technical solution of the present invention, the length of each electrode unit of each annular electrode gradually decreases in a specified direction.

[0018] In addition to the electrode units at the corners, by configuring the length of each electrode unit of the annular electrode to gradually decrease in a specified direction, the compression performance of the electrode unit on the ion beam can be adaptively set. The electrode unit that is closer to the beginning in the specified direction has a longer length, which can produce a medium- and long-range repulsion effect. By repelling ions from both sides to the middle, the ions are kept close to the central axis, which is convenient for further compression and focusing of the ion beam; and the electrode unit that is closer to the end in the specified direction is shorter. The shorter electrode unit can bind ions in a close position. By repelling ions from both sides to the middle, the ion beam can be compressed to a smaller diameter, thereby improving the transmission performance of the ion beam. In some more preferred technical solutions, the compression capacity of the annular electrode on the ion beam can be further improved by configuring the end of the annular electrode in the specified direction as the inner angle of the annular electrode.

[0019] In a preferred technical solution of the present invention, the shapes and sizes of the multiple annular electrodes are the same. Unifying the structures and sizes of the annular electrodes can facilitate the manufacture of the annular electrodes and the application of voltage.

[0020] In a preferred technical solution of the present invention, the annular electrode is a metal part made on a circuit board. On the one hand, the use of a circuit board structure to make and assemble the ion guide device can conveniently and neatly reserve wiring for each electrode unit; on the other hand, the circuit board process or gold finger process is mature, and a more uniform and smooth electrode unit can be obtained, thereby improving the uniformity of the formed electric field.

[0021] In a preferred technical solution of the present invention, each annular electrode is made on one or more circuit boards. Optionally, the annular electrode is obtained by assembling multiple circuit boards, and the circuit board structure at some positions can be omitted, saving the use of materials.

[0022] In a preferred technical solution of the present invention, the circuit board includes at least one notch for gas circulation. When manufacturing or assembling the circuit board, the notch is reserved to provide a path for gas circulation. This configuration can make the structure of the ion guide device more compact and neat. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic structural diagram of an ion guide device in a first embodiment of the present invention;

[0024] Figure 2 is a schematic structural diagram of each annular electrode in the first embodiment of the present invention;

[0025] Figure 3 is a schematic diagram of the structure and distribution of the annular electrodes of the ion guide device according to the second embodiment of the present invention;

[0026] Figure 4 yes Figure 3 A schematic diagram of the cross-sectional structure of the annular electrode of the ion guide device;

[0027] Figure 5 is the distribution of the radio frequency multipole field formed by the radio frequency voltage source in the second embodiment around the annular electrode of the ion guide device (simulation result);

[0028] Figure 6 is the distribution of the radio frequency multipole field formed by the radio frequency voltage source in the second embodiment along the axial direction of the ion guide device (simulation result);

[0029] Figure 7 is the distribution of the DC electric field formed by the DC voltage source in the second embodiment around the annular electrode of the ion guide device (simulation result);

[0030] Figure 8 is the distribution of the DC electric field formed by the DC voltage source in the second embodiment along the axial direction of the ion guide device (simulation result);

[0031] Fig. 9 is a schematic diagram of the trajectory of ions in the ion guide device in the second embodiment (simulation result);

[0032] Fig.10 is the kinetic energy distribution of ions when moving along the axial direction in the second implementation mode (simulation result);

[0033] Fig.11 is a schematic structural diagram of a circuit board provided with an annular electrode in the third embodiment;

[0034] Fig.12 is a schematic structural diagram of an annular electrode according to a fourth embodiment;

[0035] Fig.13 is a flow chart of an ion guiding method according to an embodiment of the present invention.

[0036] Description of reference numerals:

[0037] 1- ion guide device; 10, 11, 12, 20- annular electrodes; 101, 102, 103, 104, 105- electrode units; 2- ion guide device; 21- ion inlet; 22- ion outlet; 201- first side; 202- second side; 203- third side; 204- fourth side; 205, 206, 207, 208, 209, 210, 211- electrode units; 212- inner corner; 3- circuit board; 302- notch; 402- second side; 404- fourth side; 405- electrode unit; RF- radio frequency voltage source; DC- direct current voltage source. DETAILED DESCRIPTION

[0038] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0039] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0040] Implementation Method 1

[0041] This embodiment provides an ion guide device 1, referring to Figure 1 The ion guide device 1 includes a plurality of annular electrodes 10, 11, 12, and the plurality of annular electrodes 10, 11, 12 are placed parallel to each other.

[0042] Each annular electrode 10, 11, 12 comprises four electrode units 101, 102, 103 and 104 separated from each other. Channels for ion transmission are formed inside the multiple annular electrodes 10, 11, 12. The arrangement direction of the multiple annular electrodes 10, 11, 12 defines the axial direction of ion transmission.

[0043] The multiple annular electrodes 10, 11, 12 may be coaxial or non-coaxial. The arrangement direction of the multiple annular electrodes 10, 11, 12 is the direction of the line between the centers of the annular electrodes 10, 11, 12. For the case of non-coaxiality, the axial direction of ion transmission may be inclined to the axial direction of the annular electrodes 10, 11, 12.

[0044] like Figure 1 , Figure 2 As shown, the lengths of the two axisymmetric electrode units 102 and 104 at the ends of the prescribed direction in the annular electrodes 10, 11, 12 gradually decrease along the axial direction of the device. In other words, along the axial direction, the lengths of the electrode units 102, 104 near the downstream position are less than or equal to the lengths of the electrode units 102, 104 near the upstream position. At the same time, the lengths of the electrode units 101 and 103 at the beginning of the prescribed direction gradually increase along the axial direction of the device. The electrode units 102 and 104 form an inner angle 105 of the annular electrodes 10, 11, 12. Preferably, the inner angle 105 is a convex angle with an angle size within 30°-150°.

[0045] The ion guide device 1 includes a radio frequency voltage source RF and a direct current voltage source DC. Radio frequency voltages with different phases are applied to adjacent electrode units in each annular electrode 10, 11, 12, so that a radio frequency quadrupole field for trapping ions is formed inside the annular electrode by utilizing the radio frequency voltages applied to the adjacent electrode units, and the center of the quadrupole field gradually approaches the end of a specified direction along the axial direction of the device, so that the ions are focused near the inner corner 105 of the annular electrode 10, 11, 12.

[0046] The DC voltage source DC applies a DC voltage to the annular electrodes 10, 11, 12, and the DC voltage includes a first DC component distributed along the axial direction, which is used to drive the ions to move along the axial direction. In addition, the DC voltage also includes a second DC voltage whose amplitude changes along a specified direction on the plane where the annular electrodes 10, 11, 12 are located, so as to make the ions move away from the axis.

[0047] Specifically, the radio frequency voltage source RF and the direct current voltage source DC can work together in a patterned manner. In this working mode, the radio frequency voltages applied to adjacent electrode units belonging to the same annular electrode 10, 11, 12 have different phases, and the function of confining ions inside the channel is mainly provided by these radio frequency voltages with different phases. The radio frequency voltages applied to the adjacent electrode units in the axial direction have the same phase, so that the direction of the equipotential lines of the radio frequency quadrupole field is basically parallel to the axial direction of ion transmission, and the movement of ions in the axial direction is smoother. By applying the above-mentioned form of radio frequency voltage, a radio frequency quadrupole field capable of confining ions can be formed in the ion guide device 1, so that the ions can stably pass through the ion guide device 1 without leaking from the annular electrodes 10, 11, 12 themselves or the gaps between them.

[0048] The DC voltage source DC is used to apply a DC voltage to the plurality of annular electrodes 10, 11, 12. The DC voltage has a first DC component whose amplitude varies along the axial direction, and the first DC component is used to drive the movement of ions along the axial direction.

[0049] The DC voltage also includes a second DC component whose amplitude changes along a specified direction on the plane where the annular electrodes 10, 11, and 12 are located (i.e., in the driving electric field formed by the second DC component, the direction from the high potential side to the low potential side), and the second DC component is used to drive the deflection of ions, especially the deflection movement pointing to the specified direction. By using the off-axis transmission method, it is possible to avoid forming an airflow channel that directly passes through the ion guide device 1 in the axial direction, thereby avoiding the ion guide device 1 from making excessively high requirements on the performance of the vacuum system.

[0050] Since the RF quadrupole field is mainly distributed on the inner surface of the annular electrodes 10, 11, 12, and the closer to the inner surface, the higher the pseudopotential barrier, the balance between the DC electric field formed by the second DC component and the pseudopotential barrier formed by the RF quadrupole field can be used to effectively focus the ions on the inner surface of the annular electrodes 10, 11, 12, and the first DC component can be used to stably transmit the ions in the axial direction. In the above manner, under the combined action of the RF voltage and the DC voltage, the ions are transmitted away from the axial direction and focused on the inner surface of the annular electrodes 10, 11, 12.

[0051] In this embodiment, the DC voltage source DC and the radio frequency voltage source RF may be separate voltage sources that are independently provided, or may be different modules provided in the same housing, or may be power supply components integrated in the same circuit. In other embodiments of the present invention, any other suitable form of power supply may also be used, as long as it can form an electric field having the above form, it shall also be regarded as an equivalent implementation of the embodiment of the present invention.

[0052] In this embodiment, since the same annular electrode 10, 11, 12 has 4 electrode units, compared with the existing ion guide device 1, the distribution of the electrode units 101, 102, 103, 104 becomes more dense, and the spacing between adjacent electrode units becomes shorter. Specifically, the central angles corresponding to the electrode units 102, 104 at the ends of the specified direction are all less than or equal to π / 8, preferably less than π / 16. By applying a radio frequency quadrupole field to the shorter electrode units 102, 104, a radio frequency quadrupole field that is closer to the surface of the electrode units 102, 104 can be generated, so that ions can be focused at positions close to the electrode units 102, 104. For example, the balance between the radio frequency quadrupole field and the second DC component can be used to focus the ions on the inner surface of the annular electrode 12. More importantly, since the RF voltages with different phases that mainly play a role in focusing balance are applied to adjacent electrode units of the same annular electrode, compared to applying RF voltages with different phases to adjacent electrode units in the axial direction, this method of applying the RF quadrupole field can reduce the oscillations generated by ions during the transmission process, thereby avoiding unpredictable dissociation phenomena and improving ion transmission efficiency.

[0053] Implementation Method 2

[0054] Figure 3 The structure and distribution diagram of the annular electrode 20 of the ion guide device 2 of the second embodiment is shown. Figure 4 It is a cross-sectional structure of the annular electrode of the ion guide device 2. The second embodiment includes further improvements on the first embodiment, and the main improvements include: in the second embodiment, the shape and segmented structure of the annular electrode 20 are different from those in the first embodiment.

[0055] refer to Figure 3 , Figure 4 , each annular electrode 20 is square (or rhombus) as a whole, and the segmented structure of the annular electrode 20 is axisymmetric along the diagonal of the square. The diagonal as the axis of symmetry is a diagonal extending in a specified direction. On one side of the axis of symmetry, the annular electrode includes a first side 201 and a second side 202, and on the other side of the axis of symmetry, the annular electrode includes a third side 203 and a fourth side 204. The segmented structures of the first side 201 and the third side 203 are symmetrical to each other, and the segmented structures of the second side 202 and the fourth side 204 are symmetrical to each other. The first side 201 and the third side 203 are each divided into two separate electrode segments that basically occupy 1 / 2 of the side length (basically corresponding to π / 8 of the central angle of a circle), and an electrode segment of the first side 201 and an electrode segment of the third side 203 are connected to each other at the corner to form an integrated electrode unit 205 with a corner.

[0056] The second side 202 and the fourth side 204 are both segmented in a non-uniform manner, and the segmented structures are symmetrical along the specified symmetry axis. The second side 202 and the fourth side 204 each include an electrode unit 207 that occupies 1 / 2 of the side length (basically corresponding to π / 8 of the central angle of a circle), and the electrode unit 207 and the electrode unit 206 that are substantially the same length as those set on the first side 201 and the third side 203 can effectively form a medium- and long-range binding effect on ions by applying radio frequency voltages with different (especially opposite) phases, and drive the ions to focus to a position close to the symmetry axis.

[0057] The second side 202 and the fourth side 204 also include electrode units 208, 209, and 210 whose lengths gradually decrease along the specified direction. These electrode units, such as electrode units 208, 209, and 210, are all arranged at the bottom of the annular electrode 20, that is, the end of the annular electrode 20 along the specified direction. Because the lengths of the electrode units 208, 209, and 210 are short and the spacings are small, the radio frequency voltage applied to the electrode units 208, 209, and 210 with short lengths and small spacings can generate a radio frequency multipole field that binds ions to the inner surface of the annular electrode 20 in close proximity. In this embodiment, as the lengths of the electrode units 208, 209, and 210 are shortened, the second side 202 and the fourth side 204 are gradually tightened in the specified direction, so that the ion beam is always confined to a position close to the symmetry axis, and the ions are moved and focused on the inner surface of the annular electrode 20 basically along the path where the symmetry axis is located.

[0058] In this embodiment, except for the electrode unit 211 at the corner, by configuring the length of each electrode unit (including electrode units 206-210) of the annular electrode 20 to gradually decrease in a specified direction, the compression performance of the electrode units 206-210 on the ion beam can be adaptively set. The electrode units 206 and 207 that are closer to the beginning in the specified direction have longer lengths, which can produce medium- and long-range repulsion. By repelling ions from both sides to the middle, the ions are kept in a position close to the symmetry axis of the annular electrode 20, which is convenient for further compression and focusing of the ion beam; and the electrode units 209 and 210 that are closer to the end in the specified direction are shorter. The shorter electrode units 209 and 210 can bind ions in a more adjacent position. By repelling ions from both sides to the middle, the ion beam is compressed to a smaller diameter, thereby improving the transmission performance of the ion beam.

[0059] In this embodiment, the end of the annular electrode 20 in a specified direction is configured as the inner corner 212 of the annular electrode 20. By focusing the ion beam toward the inner corner 212, the radio frequency multipole field formed by the two side edges of the inner corner 212 or the electrode units 210 on both sides of the inner corner can be used to further compress the ion beam, thereby improving the focusing effect of the ion beam.

[0060] In some embodiments, in order to further prevent the ion beam from leaking out of the gap between adjacent electrode units, the specified direction can be specified to point to the electrode unit rather than to the gap between the electrode units. In this embodiment, the specified direction is parallel to the symmetry axis of the square (or diamond) annular electrode 20. Specifically, in this embodiment, in the specified direction, the electrode unit directly pointed to by the second DC component is the electrode unit 211. The electrode unit 211 is the electrode unit 211 located at the inner corner 212 of the annular electrode 20.

[0061] The electrode units at the inner corner 212 are arranged such that the electrode units 207, 208, 209, and 210 on both sides of the path approaching the inner corner 212 along the specified direction are gradually narrowed. This gradually narrowed shape can gradually compress the ion beam. In other words, the cross-sectional aperture of the ion beam is gradually reduced, thereby improving the transmission performance of the ion beam. Preferably, the inner corner 212 is a convex angle with an angle size within a range of 30°-150°.

[0062] The angle of the inner angle 212 as the focusing target should not be too large or too small. If the inner angle 212 is too large, it will easily lead to a decrease in the ion beam compression performance. If the inner angle 212 is too small, it will not be easy to stably transmit the ion beam off-axis to the preset ion outlet position. By setting the inner angle 212 to 30°-150°, the above problems can be effectively taken into account.

[0063] In addition, in order to apply radio frequency voltages with different phases between adjacent electrode units of the annular electrode 20, the number of electrode units separated from a single annular electrode 20 is preferably an even number. Preferably, the annular electrode 20 is an axisymmetric structure, and its axis of symmetry is parallel to the straight line where the vector of the specified direction is located. The annular electrode 20 with an axisymmetric structure is convenient for generating a radio frequency multipole field that causes the ion beam to converge toward the axis of symmetry, and the complexity of the simulation and calculation of the electric field is also reduced.

[0064] In this embodiment, the shapes and sizes of the plurality of annular electrodes 20 are the same. Unifying the structures and sizes of the annular electrodes 20 can facilitate the manufacture of the annular electrodes 20 and the application of voltage.

[0065] (Simulation results)

[0066] Figure 5 It is the distribution of the radio frequency multipole field formed by the radio frequency voltage source RF around the annular electrode of the ion guide device 2. Figure 6 It is the distribution of the radio frequency multipole field formed by the radio frequency voltage source RF along the axial direction of the ion guide device 2.

[0067] Depend on Figure 5 It can be seen that the RF electrode field is weak in the center of the annular electrode 20, and when the ions move to a position close to the electrode unit, the ions will be affected by the repulsive force generated by the RF multipole field on the surface of the electrode unit and will be retained inside the ion guide device 2. Specifically, the distribution of the RF multipole field applied to the axisymmetric annular electrode 20 is also axisymmetric, and the ion beam can gradually approach the electrode unit 211 downward in a manner that is basically maintained on the axis of the symmetry axis, and finally focused between the electrode unit 211 and the two electrode units 210, and finally stably focused on the inner side of the ion guide device 2 through the balance between the repulsive force formed by the electrode unit 211, the two electrode units 210 and the second DC component.

[0068] It should be noted that the reference Figure 6 In this embodiment, the ion inlet 21 of the ion guide device 2 is located on the central axis of the arrangement of the plurality of annular electrodes 20, while the ion outlet 22 of the ion guide device 2 is arranged away from the central axis of the annular electrode 20. Specifically, the setting position of the ion outlet 22 corresponds to the inner surface of the end of the annular electrode 20 along a specified direction. In some other embodiments of the present invention, the positions of the ion inlet 21 and the ion outlet 22 on the radial plane can also be adjusted according to actual needs.

[0069] refer to Figure 6It can be seen from the distribution of the RF multipole field that in this embodiment, the RF multipole field extends in the axial direction inside the multiple annular electrodes 20. With this arrangement, the transmission process of ions in the axial direction is relatively smooth, which can more effectively alleviate the oscillation heating problem of ions during the transmission process.

[0070] Figure 7 It is the distribution of the DC electric field formed by the DC voltage source DC around the annular electrode 20 of the ion guide device 2. Figure 8 It is the distribution of the DC electric field formed by the DC voltage source DC along the axial direction of the ion guide device 2.

[0071] refer to Figure 7 The DC electric field formed by the second DC component is distributed along the plane where the annular electrode 20 is located. The distribution of the DC electric field in the specified direction is basically uniform. Figure 7 The top of the middle annular electrode 20 is the high potential side, and the bottom is the low potential side. The ions in the ion guide device 2 will be acted upon by the substantially uniform electric field force of the second DC component toward the bottom, and thus move toward the inner side of the bottom of the annular electrode 20 driven by the electric field force.

[0072] refer to Figure 8 The DC electric field formed by the first DC component is distributed in the axial direction, forming an electric potential gradient in the axial direction. The equipotential lines of the DC electric field formed by the first DC component are substantially uniformly distributed in the axial direction, wherein the ion inlet 21 of the ion guide device 2 is located on the high potential side, and the ion outlet 22 is located on the low potential side. The ions in the ion guide device 2 will be acted upon by the substantially uniform electric field force of the first DC component toward the ion outlet, and thus, driven by the electric field force, will move toward the ion outlet in the axial direction, and will be deflected toward the ion outlet 22 disposed off-axis under the action of the second DC component.

[0073] Fig. 9 Schematic diagram of the trajectory of ions in the ion guide device 2. Fig. 9 In the embodiment, the ions are driven by the electric field force to move axially from the ion inlet toward the ion outlet, and are deflected toward the ion outlet 22 set off the axis under the action of the second DC component, and are finally focused on the inner side of the bottom of the ion guide device 2, and flow out from the ion outlet 22. The trajectory of the ions can be adjusted by using the parameters of the DC voltage source and the radio frequency voltage source (such as amplitude, phase and other parameters). In some embodiments, the amplitude can be adjusted to ensure that substantially all types of ions can be effectively focused on the inner side of the bottom of the ion guide device 2. In other embodiments, the amplitude can also be adjusted to screen out some ions to be focused and flow out.

[0074] Fig.10The kinetic energy distribution of ions when moving in the axial direction is further shown. Fig.10 The X axis is the position of the ion along the axial direction. Fig.10 The Y axis is the kinetic energy of the ions. Fig.10 It can be seen that during the entire axial movement of the ions, the kinetic energy changes slightly, basically below 2 eV. The simulation results further verify that the ion guide device 2 effectively solves the problem of oscillation heating of the ions in the axial direction.

[0075] Implementation Method 3

[0076] Fig.11 The schematic diagram of the structure of the circuit board 3 provided with the annular electrode 20 of the third embodiment is shown. The third embodiment includes further improvements on the second embodiment, and the main improvements include: in the third embodiment, the annular electrode 20 is a metal part made on the circuit board.

[0077] The use of a circuit board structure to manufacture and assemble an ion guide device can conveniently and neatly reserve wiring for each electrode unit; in addition, the circuit board process or gold finger process is mature, and a thinner, smoother electrode unit can be obtained, thereby improving the uniformity of the electric field formed.

[0078] In this embodiment, each annular electrode 20 is made on one or more circuit boards 3, specifically two circuit boards 3. By assembling multiple circuit boards 3 to obtain the annular electrode 20, the circuit board structure at some positions can be omitted to save materials. When the annular electrode is assembled from two circuit boards 3, a gap is left between the two circuit boards, and the gap is constituted as a notch 302 for gas circulation. When manufacturing or assembling the circuit board, a path is provided for gas circulation by reserving the notch 302. This configuration can make the structure of the ion guide device 2 more compact and neat.

[0079] Implementation Method 4

[0080] Fig.12 The schematic diagram of the structure of the annular electrode 40 of the fourth embodiment is shown. The fourth embodiment provides a modified example of the annular electrode 40. The main improvements include: in the fourth embodiment, the second side 402 and the fourth side 404 of the annular electrode 40 are composed of electrode units 405 of equal length. The other parts are the same as those in the second embodiment, and the parts with the same figure marks are exactly the same.

[0081] refer to Fig.12The second side 402 and the fourth side 404 of the annular electrode 40 both have a plurality of electrode units 405 of equal length, and the number of electrode units 405 of the second side 402 is the same as the number of electrode units 405 of the fourth side 404, and the segmented structures of the second side 402 and the fourth side 404 are mirror images of each other about the symmetry axis. The use of electrode units 405 of the same length to form an annular electrode can improve the versatility of the production and assembly of the annular electrode assembly on the one hand, and simplify the simulation or calculation of the electric field to be applied on the other hand.

[0082] The annular electrodes 20 and 40 in embodiments 2 to 4 all adopt a polygonal (e.g., square, rhombus) outer ring profile, but the structure of the annular electrode in the embodiments of the present invention is not limited to this. In some embodiments, circular, elliptical or other suitable curved types of annular electrodes may also be used, or annular electrodes may be used in combination with curves and straight lines. For example, the annular electrode may be configured as a structure in which a circular ring is used on the upper part and a straight electrode is used on the lower part.

[0083] Based on the first to fourth embodiments, the present invention further provides an ion guiding method. Fig.13 The ion guiding method provided in this embodiment includes the following steps:

[0084] S1. Providing a plurality of annular electrodes placed in parallel, each annular electrode comprising at least 4 electrode units separated from each other, a channel for ion transmission is formed inside the plurality of annular electrodes, and an arrangement direction of the plurality of annular electrodes defines an axial direction of ion transmission;

[0085] S2. applying radio frequency voltages to the plurality of annular electrodes, wherein the radio frequency voltages applied to adjacent electrode units belonging to the same annular electrode have different phases, and the radio frequency voltages applied to adjacent electrode units in the axial direction have the same phase, so as to form an axially distributed radio frequency multipole field in the device;

[0086] S3. applying a DC voltage to a plurality of annular electrodes, the DC voltage having a first DC component whose amplitude varies in the axial direction, and a second DC component whose amplitude varies in a prescribed direction on the plane where the annular electrodes are located;

[0087] S4. Under the combined action of RF voltage and DC voltage, ions deviate from the axial direction and are transmitted and focused on the inner surface of the annular electrode.

[0088] By adopting the above-mentioned ion guiding method, the oscillation of ions during the transmission process can be reduced, thereby avoiding unpredictable dissociation phenomena and improving the ion transmission efficiency.

[0089] Those skilled in the art will appreciate that, in the above-mentioned embodiments, many technical details are provided in order to enable readers to better understand the present application. However, even without these technical details and various changes and modifications based on the above-mentioned embodiments, the technical solutions claimed for protection in the claims of the present application can be basically realized. Therefore, in practical applications, various changes can be made to the above-mentioned embodiments in form and detail without departing from the spirit and scope of the present invention.

Claims

1. An ion guide device, It is characterized in that include A plurality of annular electrodes placed in parallel, each of the annular electrodes comprising at least four electrode units separated from each other, a channel for ion transmission being formed inside the plurality of annular electrodes, and an arrangement direction of the plurality of annular electrodes defining an axial direction of ion transmission; A radio frequency voltage source, used for applying radio frequency voltage to the plurality of annular electrodes, wherein the radio frequency voltages applied to adjacent electrode units belonging to the same annular electrode have different phases, and the radio frequency voltages applied to adjacent electrode units along the axial direction have the same phase, thereby forming a radio frequency multipole field for trapping ions in the ion guide device; a DC voltage source, used for applying a DC voltage to the plurality of annular electrodes, the DC voltage having a first DC component whose amplitude varies along the axial direction, and a second DC component whose amplitude varies along a specified direction on the plane where the annular electrodes are located; Under the combined effect of the radio frequency voltage and the direct current voltage, the ions deviate from the axial direction and are transmitted and focused on the inner surface of the annular electrode. The end of the annular electrode pointing in the prescribed direction has at least one inner angle.

2. The ion guide device according to claim 1, It is characterized in that The inner angle is a convex angle of 30°-150°.

3. The ion guide device according to claim 1, It is characterized in that Inside the plurality of annular electrodes, the radio frequency multipole field extends along an axial direction.

4. The ion guide device according to claim 1, It is characterized in that The annular electrode has a plurality of electrode units with the same length.

5. The ion guide device according to claim 1, It is characterized in that The length of each of the electrode units of each of the annular electrodes gradually decreases in the prescribed direction.

6. The ion guide device according to claim 1, It is characterized in that The plurality of annular electrodes have the same shape and size.

7. The ion guide device according to claim 1, It is characterized in that The annular electrode is a metal part made on a circuit board.

8. The ion guide device according to claim 7, It is characterized in that Each of the annular electrodes is made on one or more circuit boards.

9. The ion guide device according to claim 7, It is characterized in that The circuit board comprises at least one notch, and the notch is used for gas circulation.

10. An ion guiding method, It is characterized in that The following steps are involved: Providing a plurality of annular electrodes placed in parallel, each of the annular electrodes comprising at least four electrode units separated from each other, a channel for ion transmission being formed inside the plurality of annular electrodes, and an arrangement direction of the plurality of annular electrodes defining an axial direction of ion transmission; Applying radio frequency voltages to the plurality of annular electrodes, wherein the radio frequency voltages applied to adjacent electrode units belonging to the same annular electrode have different phases, and the radio frequency voltages applied to adjacent electrode units along the axial direction have the same phase, so as to form a radio frequency multipole field distributed along the axial direction in the device; Applying a DC voltage to the plurality of annular electrodes, the DC voltage having a first DC component whose amplitude varies along the axial direction, and a second DC component whose amplitude varies along a specified direction on the plane where the annular electrodes are located; Under the combined effect of the radio frequency voltage and the direct current voltage, the ions deviate from the axial direction and are transmitted and focused on the inner surface of the annular electrode. The end of the annular electrode pointing in the prescribed direction has at least one inner angle.

11. An ion guide device, It is characterized in that include A plurality of annular electrodes placed in parallel, each of the annular electrodes comprising at least four electrode units separated from each other, a channel for ion transmission being formed inside the plurality of annular electrodes, and an arrangement direction of the plurality of annular electrodes defining an axial direction of ion transmission; A radio frequency voltage source, used for applying radio frequency voltage to the plurality of annular electrodes, wherein the radio frequency voltages applied to adjacent electrode units belonging to the same annular electrode have different phases, and the radio frequency voltages applied to adjacent electrode units along the axial direction have the same phase, thereby forming a radio frequency multipole field for trapping ions in the ion guide device; A DC voltage source, used for applying a DC voltage to the plurality of annular electrodes, wherein the DC voltage has a second DC component whose amplitude varies along a specified direction on the plane where the annular electrodes are located, so as to deflect ions toward the electrode unit pointing in the specified direction; The central angles of the electrode unit pointed to by the specified direction and the electrode unit adjacent to it are both less than or equal to π / 8, The end of the annular electrode pointing in the prescribed direction has at least one inner angle.

12. The ion guide device according to claim 11, It is characterized in that The central angles of the electrode unit pointed to by the specified direction and the electrode units adjacent to the electrode unit are both smaller than or equal to π / 16.

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