Ion guide, and mass spectrometer including the same

Abstract

To provide an ion guide with a wide ion m / z range, which is ion transparent therethrough and resistant to pollution with a simple structure.SOLUTION: A disclosed ion guide guides ions and converges and emits the ions. The ion guide has multipolar electrodes to form multipolar electric fields and an axial electric field electrode for forming the axial electric field. The ion guide changes the cross-sectional area perpendicular to the central axis of the ion guide of at least one of the multiple electrodes or axial electric field electrodes from the entrance to the exit of the ion guide.SELECTED DRAWING: Figure 2A

Description

[Technical field]

[0001] The present disclosure relates to an ion guide and a mass spectrometer including the same. [Background technology]

[0002] Ion guides are widely used to transport ions in mass spectrometers. In particular, in ion guides used in collision cells of tandem mass spectrometers, it is necessary to generate an axial electric field on the central axis to prevent crosstalk. Regarding the axial electric field, for example, Patent Document 1 discloses the generation of an axial electric field for accelerating ions in a multipole ion guide composed of parallel rod electrodes of a multipole (such as a quadrupole). In addition, for example, Patent Document 2 discloses the generation of an axial electric field by inserting a resistive electrode to which a radio frequency voltage is applied into the gap between multipole electrodes to which a radio frequency voltage is applied. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 5,847,386 [Patent Document 2] U.S. Patent No. 8,785,847 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in an ion guide in which an axial electric field is applied by tilting a pair of rod electrodes as shown in Patent Document 1, there is a problem that the m / z range of ions that can pass through the ion guide is narrow. In addition, in an ion guide in which an electrode is inserted into a gap between rod electrodes as shown in Patent Document 2, there is a problem that the configuration of the ion guide is complicated, the gap between the electrodes is narrow, and the surface area of ​​the electrodes is also narrow, so that the electrodes are easily contaminated by impurities such as neutral droplets introduced into the ion guide, and the performance is easily degraded. In addition, the ion guide shown in Patent Document 2 has a complicated configuration, the gap between the electrodes is narrow, and the surface area of ​​the electrodes that form the axial electric field is also small. Therefore, there is also a problem that the electrode surface is easily contaminated by impurities such as neutral droplets introduced into the ion guide, and the performance is easily degraded. In view of the above circumstances, the present disclosure proposes a technique for realizing an ion guide that can transmit ions in a wide m / z range, has a simple structure, and is resistant to contamination. [Means for solving the problem]

[0005] In order to solve the above problems, the present disclosure proposes an ion guide into which ions are introduced and which focuses and ejects the ions, the ion guide having a multipole electrode for forming a multipole electric field and an axial electric field electrode for forming an axial electric field, in which the cross-sectional area perpendicular to the central axis of the ion guide of at least one of the multipole electrode or the axial electric field electrode changes from the entrance to the exit of the ion guide.

[0006] Further features related to the present disclosure will be apparent from the description of the present specification and the accompanying drawings. Also, the aspects of the present disclosure are achieved and realized by the elements and combinations of various elements and the following detailed description and the appended claims. The description of the present specification is merely exemplary and does not limit the scope or application of the present disclosure in any way. Effect of the Invention

[0007] According to the technique of the present disclosure, it is possible to realize an ion guide that is simple in structure, resistant to contamination, and transmits a wide range of masses, and a mass spectrometer equipped with the same. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view showing a schematic configuration example of a mass spectrometer 10 including a curved ion guide 20 according to the first embodiment. [Figure 2A] 1 is a diagram showing an example of the external configuration of an ion guide 20 according to a first embodiment. [Figure 2B] 2 is a diagram showing an example of a cross-sectional configuration of an ion guide 20 according to the first embodiment, taken along a central axis 23. FIG. [Figure 2C] 2 is a diagram showing an example of the cross-sectional configuration of an entrance 1A and an exit 1B of an ion guide 20 according to the first embodiment. FIG. [Diagram 3] FIG. 3 is a diagram showing an example of the configuration of an ion guide power supply 300 used in each embodiment. [Figure 4] FIG. 2 shows pseudopotentials in the ry plane at the entrance 1A and the exit 1B of the ion guide 20 according to the first embodiment. [Diagram 5] 2 is a diagram showing a DC potential in the xz plane including the central axis 23 of the ion guide 20 according to the first embodiment. FIG. [Figure 6] 2 and 5 ) on the central axis 23 of the ion guide 20 according to the first embodiment. FIG. [Figure 7] FIG. 2 shows DC potentials in the yr plane at the entrance 1A and exit 1B of the ion guide 20 according to the first embodiment. [Figure 8] FIG. 13 is a diagram showing the distribution of transmission times of 200 ions under the conditions of potential differences of 6 V, 3 V, 1.5 V, and 1 V between the axial electric field electrode 22 and the multipole electrode 21. [Figure 9] FIG. 13 is a diagram showing the transmittance of ions of m / z 150 to m / z 4000 under conditions where the potential difference between the axial electric field electrode 22 and the multipole electrode 21 is 3V and 6V. [Figure 10]FIG. 2 is a diagram showing a schematic configuration example of an ion guide 201 according to a second embodiment. [Figure 11] 13 shows a schematic configuration example of an ion guide 202 according to a third embodiment. [Figure 12] FIG. 13 is a diagram showing an example of the configuration of an ion guide 203 according to a fourth embodiment. [Figure 13] FIG. 13 is a diagram showing an example of the configuration of an ion guide 204 according to a fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] This embodiment discloses an ion guide in which at least one of the cross-sectional area of ​​the multipole electrode relative to the central axis (the area of ​​the surface perpendicular to the ion traveling direction) and the cross-sectional area of ​​the axial electric field electrode relative to the central axis is changed from the inlet to the outlet of the ion guide, thereby realizing an ion guide that has a wide m / z range of ions that can transmit through the ion guide, has a simple structure, and is resistant to contamination.

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the accompanying drawings, functionally identical elements may be indicated by the same numbers. Note that the accompanying drawings show specific embodiments and implementation examples according to the principles of the present disclosure, but these are for understanding the present disclosure and are by no means used to interpret the present disclosure in a limiting manner.

[0011] In the present embodiment, the description is given in sufficient detail for a person skilled in the art to implement the present disclosure, but it should be understood that other implementations and forms are possible, and that changes in configuration and structure and substitutions of various elements are possible without departing from the scope and spirit of the technical ideas of the present disclosure. Therefore, the following description should not be interpreted as being limited thereto.

[0012] (1) First embodiment <Configuration Example of Mass Spectrometer 10> FIG. 1 is a cross-sectional view showing a schematic configuration example of a mass spectrometer 10 including a curved ion guide 20 according to the first embodiment.

[0013] As an example, the mass spectrometer 10 includes an ion source 101, a first differential pumping section 102 including an ion guide 121 for ion transport as necessary, a vacuum pump 131 that evacuates the air in the first differential pumping section 102 to create a vacuum, a second differential pumping section 103 including an ion guide (curved ion guide) 20, a vacuum pump 132 that evacuates the air in the second differential pumping section 103 to create a vacuum, an ion guide power supply 300 that applies a voltage to the ion guide, a mass analysis chamber 104 having a mass filter 125, a collision cell 126, and a detector 127, and a vacuum pump 133 that evacuates the air in the mass analysis chamber 104 to create a vacuum.

[0014] The ion source 101 may be an electrospray ion source, an atmospheric pressure chemical ion source, an atmospheric pressure photoion source, or an atmospheric pressure matrix-assisted laser desorption ion source.

[0015] Ions generated in the ion source 101 pass through an aperture 111 provided in the first differential pumping section 102 together with an airflow, and are introduced into the first differential pumping section 102 (vacuum chamber). The ions that have passed through the differential pumping section 102 pass through an aperture 112 provided in the connection section (wall) between the first differential pumping section 102 and the second differential pumping section 103, and are introduced into the ion guide 20 according to the technology of the present disclosure.

[0016] A voltage is applied to the ion guide 20 by an ion guide power supply 300. The pressure at which the ion guide 20 operates is 1000 Pa to 10 -3 The pressure is about 1000 Pa to 0.1 Pa. In particular, at 1000 Pa to 0.1 Pa, the kinetic energy of the ions is cooled by collisions with neutral gas molecules, so that the ions can be focused efficiently. The ions discharged from the ion guide 20 pass through a fine hole 113 provided in the connection (wall) between the second differential pumping section 103 and the mass spectrometry chamber 104, and are introduced into the mass spectrometry chamber 104.

[0017] When the mass spectrometer 10 is, for example, a tandem mass spectrometer, in the mass analysis chamber 104, precursor ions of a specific m / z are selected by a mass filter 125 and dissociated in a collision cell 126. Fragment ions generated in the collision cell 126 are detected by a detector 127. An electron multiplier or the like can be used as the detector 127. It is to be noted that the ion guide 20 can also be used as the collision cell 126.

[0018] <Example of ion guide 20 configuration> Fig. 2 is a diagram showing a configuration example of an ion guide according to the first embodiment. Fig. 2A is a diagram showing an external configuration example of an ion guide 20. Fig. 2B is a diagram showing a cross-sectional configuration example of the ion guide 20 along a central axis 23. Fig. 2C is a diagram showing a cross-sectional configuration example of an inlet 1A and an outlet 1B of the ion guide 20.

[0019] As shown in FIG. 2A, the ion guide 20 has a curved shape (curved ion guide) and includes two upper and two lower plate-like multipole electrodes 21 and two upper and two upper axial field electrodes 22 sandwiched between the upper and lower multipole electrodes. Ions enter from an entrance 1A and accelerated ions exit from an exit 1B.

[0020] The ion guide 20 is configured so that the central axis 23 is a quarter arc having an arc center (Ion guide arc center) 29. As can be seen from FIG. 2A, the cross section of the entrance 1A of the ion guide 20 is on the x-axis, and the cross section of the exit 1B is on the z-axis. In this case, if the angle between the radius r of the quarter arc and the x-axis when the radius r is moved along the central axis 23 is θ, the length of the axial electric field electrode 22 in the direction of the distance r from the arc center (r-axis direction) in the cross section perpendicular to the ion guide central axis 23 changes as a function of the angle θ from the arc center 29 of the ion guide 20. In other words, the axial electric field electrode 22 is configured so that its cross-sectional area increases from the entrance 1A to the exit 1B. It can also be seen from FIG. 2B that the size (on the xz plane) of the axial electric field electrode 22 decreases from the entrance 1A to the exit 1B.

[0021] The potential formed by the axial electric field electrode 22 on the central axis (ion guide central axis) 23 of the ion guide 20 depends on the area of ​​the axial electric field electrode 22 seen from the ion guide central axis 23, so an axial electric field is formed on the ion guide central axis 23 according to the potential difference between the potential of the multipole electrode 21 and the potential of the axial electric field electrode 22. In FIG. 2C, the signs "+" and "-" indicate the phase of the RF voltage applied from the ion guide power supply 300 to the multipole electrode 21 and the axial electric field electrode 22. RF voltages of the same phase and frequency are applied to electrodes with the same sign. To generate a multipole electric field that confines ions, an RF voltage of opposite phase to that of the adjacent multipole electrode 21 is applied to the multipole electrode 21. In addition, an RF voltage of approximately the same amplitude and in the same phase as that of the adjacent multipole electrode 21 is applied to the axial electric field electrode 22. By applying the voltage in this manner, no potential difference in the RF voltage is generated between the multipole electrode 21 and the axial electric field electrode 22, which are narrowly spaced from each other, and discharge can be prevented. Furthermore, different offset DC voltages are applied to the set (pair) of multipole electrodes 21 and the set (pair) of axial electric field electrodes 22. Ions pass through the central axis 23 of the ion guide 20, but the area of ​​the cross section of the axial electric field electrodes 22 perpendicular to the central axis 23 as seen from the central axis 23 changes according to the distance on the central axis 23, so that the strength of the DC voltage of the axial electric field electrodes 22 that ions on the central axis 23 receive changes. This causes the ions to be accelerated.

[0022] <Example of the ion guide power supply 300 configuration> Fig. 3 is a diagram showing an example of the configuration of the ion guide power supply 300 used in each embodiment. In Fig. 3, two types of example configurations of the ion guide power supply 300 are shown.

[0023] The ion guide power supply 300 in any of the configuration examples includes an axial electric field electrode DC power supply 301, a multipole electrode DC power supply 302, and an RF power supply 303, and supplies a DC voltage to the multipole electrode 21 and the axial electric field electrode 22 from the axial electric field electrode DC power supply 301 or the multipole electrode DC power supply 302. The RF power supply 303 includes an AC power supply and multiple coils, and applies RF voltages of the same phase and amplitude to the multipole electrode 21 and the axial electric field electrode 22 using each coil.

[0024] <Pseudopotential> Fig. 4 is a diagram showing pseudopotentials in the ry plane at the entrance 1A and the exit 1B of the ion guide 20. In Fig. 4, the pseudopotentials were measured with the ion m / z set to 600 and the RF voltage amplitude set to 300 V0-peak.

[0025] An RF voltage of approximately the same amplitude and in phase with the adjacent multipole electrode 21 is applied to the axial electric field electrode 22, and a multipole pole is formed by a pair of the multipole electrode 21 and the adjacent axial electric field electrode 22. Therefore, the axial electric field electrode 22 does not block the multipole electrode 21, and distortion of the pseudopotential is unlikely to occur.

[0026] At the ion guide entrance 1A, the length in the r-axis direction of the axial electric field electrode 22 is shorter (the electrode width is smaller) than at the ion guide exit 1B, and the distance from the ion guide central axis 23 is greater, so the pseudopotential becomes shallower. For this reason, the pseudopotential becomes deeper as it approaches the ion guide exit 1B, resulting in a funnel-shaped potential. This allows the ion distribution to be efficiently converged.

[0027] In the mass spectrometer 10, charged droplets and neutral impurities are introduced into the vacuum chamber together with ions, causing contamination inside the device. In this regard, ions travel straight in the z-axis direction in Fig. 2 from the aperture 112 just before the entrance 1A of the ion guide 20, because charged droplets and neutral impurities, which have a large mass, are less susceptible to the electric field. On the other hand, ions introduced from the entrance 1A of the ion guide 20 are converged near the minimum point of the pseudopotential on the central axis 23, move along the central axis 23, and are discharged from the exit 1B of the ion guide 20.

[0028] In the ion guide 20 of FIG. 2, since the inlet 1A is in the xy plane and the outlet 1B is in the yz plane, charged droplets and neutral contaminants go straight in the z-axis direction from the inlet 1A of the ion guide 20 and are excluded from the ion guide 20, and only ions pass through the ion guide 20. Thereby, noise can be reduced.

[0029] The charged droplets and neutral contaminants introduced from the pores 112 spread in a range of about several millimeters as shown in FIG. 2 and go straight in the z-axis direction. On the other hand, in the ion guide 20, there are no electrodes in the range through which the charged droplets and neutral contaminants in front of the inlet 1A (in the z-axis direction) pass, and a wide gap (space) is formed. For this reason, the ion guide 20 has a low possibility that neutral contaminants and charged droplets collide with the electrodes (the multipole electrode 21 and the axial electric field electrode 22) and the electrodes get dirty, and is also resistant to contamination.

[0030] <State of DC potential> FIG. 5 is a diagram showing the DC potential of the xz plane including the central axis 23 of the ion guide 20. FIG. 6 is a diagram showing the potential on the central axis 23 of the ion guide 20 (a function of θ in FIGS. 2 and 5). The DC potential is calculated with the potential difference between the axial electric field electrode 22 and the multipole electrode 21 being 10V.

[0031] As can be seen from FIG. 5, the DC potential of the xz plane is dense near the inlet 1A and sparse near the outlet 1B, so it is the highest at the inlet 1A of the ion guide 20 and gradually decreases toward the outlet 1B of the ion guide 20. Also, as can be seen from FIG. 6, the potential decreases almost in proportion to the angle θ from the center of curvature along the central axis 23 of the ion guide 20. The ions can always be accelerated at a constant acceleration by the potential on this central axis 23.

[0032] FIG. 7 shows the DC potentials in the yr plane at the entrance 1A and exit 1B of the ion guide 20. From FIG. 7, it can be seen that the potential at the entrance 1A of the ion guide 20 includes higher-order multipole components such as octopoles in addition to the quadrupole. Therefore, compared to the case where a quadrupole DC potential is applied due to the effect of the higher-order terms, it is possible to efficiently transmit ions in a wide m / z range. On the other hand, it can be seen that the DC potential in the yr plane at the exit 1B of the ion guide 20 is almost uniform because the multipole electrodes are covered with axial electric field electrodes. Therefore, the spatial distribution of ions does not spread due to the DC potential, and the spatial distribution of ions can be converged.

[0033] <Ion transmission time distribution: Simulation results> In order to verify the technical effect of the ion guide 20, the transmission time was confirmed by a simulation. Figure 8 shows the distribution of the transmission time of 200 ions for each condition of the potential difference between the axial electric field electrode 22 and the multipole electrode 21 being 6 V, 3 V, 1.5 V, and 1 V. Table 1 shows parameter values ​​other than the potential difference between the axial electric field electrode 22 and the multipole electrode 21.

[0034] [Table 1]

[0035] 8, the transmission time became shorter and the half-width of the time distribution became narrower as the potential difference between the axial electric field electrode 22 and the multipole electrode 21 became larger. In other words, according to the simulation, when the potential difference between the axial electric field electrode 22 and the multipole electrode 21 was 3 V or more, the transmission time was 1 ms or less, and the transmission time was the shortest when the potential difference was 6 V.

[0036] As described above, according to the ion guide 20, the ions are accelerated by the electric field formed on the central axis 23, thereby shortening the transmission time and preventing signal crosstalk.

[0037] <Ion m / z range: Simulation results> In order to verify the technical effect of the ion guide 20, a simulation was performed to confirm the m / z range of ions that can stably transmit through the ion guide 20. The lower limit of the m / z of ions that can stably transmit through the ion guide 20 is determined by the low mass cut off value (LMCO), which is the lower limit of the stability region of the Mathieu equation. For example, when a quadrupole electrode is used, the LMCO of a singly charged ion is given by the following equation (1).

[0038]

number

[0039] where V is the RF voltage amplitude, m is the mass of the ion, and q LMCO is the q value of the Mathieu equation in LMCO, e is the elementary charge, Ω is the RF voltage frequency, r 0 represents the radius of the quadrupole inscribed circle. From this formula (1), it can be seen that the higher the RF voltage amplitude, the higher the lower limit of the m / z of ions that can stably transmit through the ion guide 20 becomes. On the other hand, the upper limit of the m / z of ions that can transmit through the ion guide is determined by the relationship between the pseudopotential (Ψ) of singly charged ions shown in equation (2) and the effect of ion exclusion by the DC potential.

[0040]

number

[0041] Here, E represents the electric field. From equation (1), we can see that the pseudopotential is inversely proportional to the m / z of the ion, so the pseudopotential is low for ions with high m / z, and the ions are rejected by the DC potential. In addition, the higher the RF voltage amplitude, the higher the pseudopotential becomes, and so the upper limit of the m / z of the ions that can be transmitted becomes higher.

[0042] 9 is a diagram showing the transmittance of ions of m / z 150 to m / z 4000 under the conditions that the potential difference between the axial electric field electrode 22 and the multipole electrode 21 is 3 V and 6 V. When the potential difference between the axial electric field electrode 22 and the multipole electrode 21 is 3 V, an average transmittance of 97% was obtained for ions of m / z 175 to m / z 2500, i.e., LMCO to LMCO×14.3. When the potential difference between the axial electric field electrode 22 and the multipole electrode 21 is 6 V, an average transmittance of 97% was obtained for ions of m / z 175 to m / z 1500, i.e., LMCO to LMCO×8.6.

[0043] As described above, the ion guide 20 according to this embodiment can transmit ions in a wide m / z range. In addition, since the multipole electrode 21 and the axial electric field electrode 22 are both plate electrodes, the ion guide 20 has a degree of freedom in terms of ease of manufacture, and can accommodate a 1 / 2 circular arc or a more complicated flow channel shape with the same design concept. Therefore, it can be flexibly implemented in the future according to the footprint (bottom area) and shape of the mass spectrometer 10.

[0044] (2) Second embodiment FIG. 10 is a diagram showing a schematic configuration example of an ion guide 201 according to the second embodiment. The ion guide 201 has a linear shape and includes a multipole electrode 21 and an axial electric field electrode 22. The length of the axial electric field electrode 22 forming the axial electric field in the x direction is short at the entrance 10A (the cross-sectional area of ​​the electrode is small) and long at the exit 10B (the cross-sectional area of ​​the electrode is large). The configuration of the radial cross section of the ion guide 201, the pseudopotential, the DC potential, and the potential on the central axis 23 are the same as those of the first embodiment. Since the ion guide 201 is linear, the structure is simpler and can be implemented more inexpensively than the ion guide 20 according to the first embodiment. On the other hand, since the direction in which ions enter the ion guide 201 and the direction in which they exit the ion guide 201 are the same, the effect of reducing noise is smaller than that of the first embodiment.

[0045] (3) Third embodiment FIG. 11 shows a schematic configuration example of an ion guide 202 according to the third embodiment. In the ion guide 202, the multipole electrode 21 and the axial electric field electrode 22 are present in the same xz plane. That is, in the first and second embodiments, the multipole electrode 21 and the axial electric field electrode 22 are arranged so as to overlap spatially in the z-axis direction to configure the ion guide 20 or 201 (see FIGS. 2A and B and FIG. 10). In the third embodiment, the ion guide 202 is configured using four nearly rectangular flat plate electrodes (upper and lower pairs) configured by bonding the sides of the multipole electrode 21 forming a trapezoidal or triangular plate and the axial electric field electrode 22 forming a trapezoid or triangular plate (by bonding the short side (apex) side and the long side (base) side together). Alternatively, the ion guide 202 may be configured using four seemingly nearly rectangular flat plate electrodes (upper and lower pairs) by arranging the sides of the two electrodes facing each other without bonding them together.

[0046] 11, in the ion guide 202, the length in the x direction (electrode width in the x direction) of the multipole electrode 21 is long at the entrance 11A of the ion guide 202 and short at the exit 11B. Also, the length in the x direction (electrode width in the x direction) of the axial electric field electrode 22 is short at the entrance 11A of the ion guide 202 and long at the exit 11B. An axial electric field is formed by such an electrode configuration.

[0047] According to the ion guide 202 of the third embodiment, the multipole electrode 21 and the axial electric field electrode 22 exist on the same plane (xz plane), so the distance between the electrodes in the y-axis direction is wider than that of the ion guide 20 of the first embodiment. Therefore, the incident charged droplets and neutral impurities are less likely to collide with the electrodes, and the ion guide 202 has the characteristic of being resistant to contamination. On the other hand, the depth of the pseudopotential along the central axis 23 is constant, and the efficiency of focusing ions is relatively low (compared to the first embodiment).

[0048] (4) Fourth embodiment 12 is a diagram showing an example of the configuration of an ion guide 203 according to the fourth embodiment. The ion guide 203 is configured so that the width of the axial electric field electrode 22 in the r-axis direction (xz plane) is constant, and the width of the multipole electrode 21 in the r-axis direction (xz plane) changes depending on the position on the central axis of the ion guide.

[0049] The potential that the multipole electrode 21 forms on the central axis 23 of the ion guide 203 depends on the area of ​​the multipole electrode 21 seen from the central axis 23 of the ion guide 203. Therefore, an axial electric field is formed on the central axis 23 of the ion guide 203 according to the potential difference between the multipole electrode 21 and the axial electric field electrode 22.

[0050] (5) Fifth embodiment 13 is a diagram showing a configuration example of an ion guide 204 according to the fifth embodiment. In addition to the components of the ion guide 20 according to the first embodiment, the ion guide 204 includes a second multipole electrode (an additional multipole electrode) at a position closer to the central axis 23 than the axial electric field electrode 22. The same voltage is applied to the first multipole electrode 22 and the second multipole electrode 28.

[0051] The ion guide 204 has a somewhat more complicated configuration than the ion guide 20 according to the first embodiment, but the DC potential at the inlet 13A of the ion guide 204 approaches a higher-order multipole. Therefore, the ion guide 204 has an advantage that the m / z range of ions transmitted therethrough is wider than that of the ion guide 20 according to the first embodiment.

[0052] (6) Summary of the embodiment The features of each embodiment, when summarized, are that in the ion guide according to the present disclosure, the cross-sectional area perpendicular to the central axis of at least one of the ion guides (20, and 201 to 204) of the multipole electrode 21 or the axial electric field electrode 22 varies from the entrance (1A, 10A, 11A, 12A, 13A) to the exit (1B, 10B, 11B, 12B, 13B) of the ion guide.

[0053] (i) According to the first embodiment, the cross-sectional area of ​​the axial electric field electrode 22 perpendicular to the central axis 23 of the ion guide changes (becomes larger) from the entrance 1A to the exit 1B of the ion guide 20. This allows a funnel-shaped potential in which the pseudopotential becomes deeper as it approaches the ion guide exit 1B, and the ion distribution can be efficiently converged. Also, as shown in FIG. 2C, the multipole electrode 21 and the axial electric field electrode 22 are each installed as two pairs of plate-shaped electrodes. Furthermore, both the multipole electrode and the axial electric field electrode are shaped like an arc from the entrance to the exit (curved electrodes). Specifically, since the entrance 1A is on the xy plane and the exit 1B is on the yz plane, charged droplets and neutral impurities travel straight from the entrance 1A of the ion guide 20 in the z-axis direction and are expelled from the ion guide 20, and only ions pass through the ion guide 20. This allows noise to be reduced. Then, the ion guide power supply 300 applies RF voltages of the same phase and amplitude to the multipole electrode 21, and applies different DC voltages so as to generate a potential difference between the multipole electrode 21 and the axial electric field electrode 22. By applying voltages in this manner, no potential difference in the RF voltage is generated between the multipole electrode 21 and the axial electric field electrode 22, which have a narrow gap between the electrodes, and discharge can be prevented.

[0054] Furthermore, as can be seen from FIG. 6, the potential decreases along the central axis 23 of the ion guide 20 in approximately proportion to the angle θ from the center of curvature. This potential on the central axis 23 allows ions to be accelerated at a constant acceleration. On the other hand, at the exit 1B of the ion guide 20, the multipole electrodes are covered with axial electric field electrodes, so the DC potential on the yr plane is approximately uniform. Therefore, the spatial distribution of ions does not spread due to the DC potential, and the spatial distribution of ions can be converged. In this way, by using the ion guide 20, ions in a wide m / z range can be transmitted.

[0055] (ii) According to the second embodiment, as in the first embodiment, the cross-sectional area of ​​the axial electric field electrode 22 perpendicular to the central axis 23 of the ion guide increases from the entrance 10A to the exit 10B of the ion guide 201, and the shapes of the multipole electrode 21 and the axial electric field electrode 22 are both linear. Even when the ion guide 201 according to the second embodiment is used, the same technical effects as those of the first embodiment can be expected (voltage application is the same as in the first embodiment).

[0056] (iii) According to the third embodiment, the plate-shaped axial electric field electrode 22 is configured so that the cross-sectional area perpendicular to the central axis 23 increases from the inlet 11A to the outlet 11B, and the plate-shaped multipole electrode 21 is configured so that the cross-sectional area decreases from the inlet 11A to the outlet 11B (see FIG. 11). The axial electric field electrode 22 and the multipole electrode 21 are arranged on the same plane so that their respective side surfaces face each other (they are attached at their side surfaces, or arranged in parallel in the same plane (xz plane)). Even in this case, the same technical effects as in the first embodiment can be expected (voltage application is the same as in the first embodiment).

[0057] (iv) According to the fourth embodiment, the axial electric field electrode 22 is configured so that the cross-sectional area perpendicular to the central axis 23 of the ion guide is the same from the entrance 12A to the exit 12B, and the multipole electrode 21 is configured so that the cross-sectional area increases from the entrance 12A to the exit 12B (see FIG. 12). In this way, by configuring the multipole electrode 21 to be relatively larger than the axial electric field electrode 22 (configuring the multipole electrode 21 to cover the axial electric field electrode 22), the same technical effect as in the first embodiment can be expected (voltage application is the same as in the first embodiment).

[0058] (v) According to the fifth embodiment, the cross-sectional area perpendicular to the central axis 23 of the ion guide of the axial electric field electrode 22, which is disposed closer to the central axis 23 than the multipole electrode 21, becomes larger from the entrance 1A to the exit 1B of the ion guide 20, and the multipole electrode 21 is disposed so as to cover the axial electric field electrode 22 (the configuration up to this point is the same as in the first embodiment). Furthermore, an additional multipole electrode 28 is provided at a position closer to the central axis 23 than the axial electric field electrode 22. This makes it possible to further widen the m / z range of the transmitted ions.

[0059] (vi) Note that the above description of each embodiment is merely an example, does not limit the technology of the present disclosure, and various modifications are possible. The description of each embodiment is detailed to clearly explain the technology of the present disclosure, and is not necessarily limited to those having all of the configurations described. In addition, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration. [Explanation of symbols]

[0060] 20, 201, 202, 203, 204 Ion Guide 21 Multipole electrode 22-axis electric field electrode 23 Central axis of ion guide 28 Second multipole electrode (additional multipole electrode) 29 Arc center of central axis of ion guide 101 Ion source 102 First differential pumping section 103 Second differential pumping section 104 Mass spectrometry room 111, 112, 113 Pore 121 Ion guide (for ion transport) 125 Mass Filter 126 Collision Cell 131, 132, 133 Vacuum pump 300 Ion Guide Power Supply 301 Axial electric field electrode DC power supply 302 Multipole electrode DC power supply 303 RF power supply

Claims

1. An ion guide into which ions are introduced and which focuses and ejects the ions, comprising: A multipole electrode for forming a multipole electric field; an axial electric field electrode for forming an axial electric field; a cross-sectional area perpendicular to a central axis of the ion guide of at least one of the multipole electrodes or the axial electric field electrodes varies from the entrance to the exit of the ion guide; The ion guide wherein the axial electric field electrode is configured such that the cross-sectional area increases from the entrance to the exit.

2. An ion guide into which ions are introduced and which focuses and ejects the ions, comprising: A multipole electrode for forming a multipole electric field; an axial electric field electrode for forming an axial electric field; a cross-sectional area perpendicular to a central axis of the ion guide of at least one of the multipole electrodes or the axial electric field electrodes varies from the entrance to the exit of the ion guide; The multipole electrodes and the axial electric field electrodes are provided in two pairs, The multipole electrode and the axial electric field electrode are both shaped like a plate.

3. In claim 2, An ion guide, wherein the multipole electrode and the axial electric field electrode are both shaped like a circular arc from the entrance to the exit.

4. In claim 2, An ion guide, wherein the multipole electrode and the axial electric field electrode are both linear in shape.

5. An ion guide into which ions are introduced and which focuses and emits the ions, comprising: A multipole electrode for forming a multipole electric field; an axial electric field electrode for forming an axial electric field; a cross-sectional area perpendicular to a central axis of the ion guide of at least one of the multipole electrodes or the axial electric field electrodes varies from the entrance to the exit of the ion guide; the axial electric field electrode is configured such that the cross-sectional area is the same from the inlet to the outlet; The multipole electrodes are configured such that the cross-sectional area increases from the entrance to the exit.

6. In claim 2, The multipole electrode is positioned over the axial electric field electrode.

7. An ion guide into which ions are introduced and which focuses and emits the ions, comprising: A multipole electrode for forming a multipole electric field; an axial electric field electrode for forming an axial electric field; a cross-sectional area perpendicular to a central axis of the ion guide of at least one of the multipole electrodes or the axial electric field electrodes varies from the entrance to the exit of the ion guide; The axial electric field electrode is plate-shaped and configured such that the cross-sectional area increases from the inlet to the outlet, The multipole electrode is plate-shaped and configured such that the cross-sectional area decreases from the inlet to the outlet; An ion guide, wherein the axial electric field electrode and the multipole electrode are arranged on the same plane so that their respective sides face each other.

8. An ion guide into which ions are introduced and which focuses and emits the ions, comprising: A multipole electrode for forming a multipole electric field; an axial electric field electrode for forming an axial electric field; a cross-sectional area perpendicular to a central axis of the ion guide of at least one of the multipole electrodes or the axial electric field electrodes varies from the entrance to the exit of the ion guide; the axial electric field electrode is disposed closer to the central axis than the multipole electrode; The ion guide further comprises an additional multipole electrode separate from the multipole electrode, the additional multipole electrode being disposed at a position closer to the central axis than the axial electric field electrode.

9. An ion source that generates ions; an ion guide disposed downstream of the ion source, into which the ions are introduced and which converges and emits the ions, the ion guide having a multipole electrode for forming a multipole electric field and an axial electric field electrode for forming an axial electric field, wherein a cross-sectional area perpendicular to a central axis of the ion guide of at least one of the multipole electrode and the axial electric field electrode varies from an inlet to an outlet of the ion guide; an ion guide power supply for applying a voltage to the ion guide; a detector for detecting ions focused by the ion guide, A mass spectrometer, wherein the ion guide power supply applies RF voltages of the same phase and amplitude to the axial electric field electrode and the multipole electrode, and applies different DC voltages so that a potential difference is generated between the multipole electrode and the axial electric field electrode.

10. An ion source that generates ions; The ion guide according to claim 8 , which is disposed downstream of the ion source and focuses the ions; an ion guide power supply for applying a voltage to the ion guide; a detector for detecting ions focused by the ion guide, a multipole electrode and an axial electric field electrode, and a second multipole electrode and a second multipole electrode, the ...

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