Ion optical elements and mass spectrometers

Abstract

We provide ion optical elements and mass spectrometers with high assembly precision. [Solution] The ion optical element comprises a plurality of rod electrodes 43, each having a protrusion 43a at one end; a plurality of electrode members 42 connected to each of the plurality of rod electrodes 43; and a non-conductive base member 41 having a window 41a through which ions pass, and fixing the plurality of electrode members 42 and the plurality of rod electrodes 43 in a position surrounding the window 41a. A through hole 42a is formed in each of the plurality of electrode members 42. A recess 41b corresponding to the protrusion 43a is formed in the base member 41. The plurality of electrode members 42 and the plurality of rod electrodes 43 are positioned relative to the base member 41 by fitting the protrusion 43a through the through hole 42a into the recess 41b.

Description

Technical Field

[0001] The present disclosure relates to an ion optical element used in a mass spectrometer and a mass spectrometer.

Background Art

[0002] A mass spectrometer that analyzes the mass of ions generated by an ion source is known. In a mass spectrometer, a configuration of a multi-stage operation exhaust system in which a plurality of intermediate vacuum chambers are arranged between an ionization chamber where an ion source is disposed and a high-vacuum analysis chamber where a mass separation device and an ion detector are disposed is adopted. In such a mass spectrometer, an ion optical element is used to efficiently converge ions in each intermediate vacuum chamber and send them to the next stage.

[0003] Japanese Unexamined Patent Application Publication No. 2023-28190 (Patent Document 1) discloses four rod electrodes having a function of an ion guide that converges ions and transports them to the subsequent stage as an ion optical element.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When the assembly accuracy of an ion optical element is low, the efficiency of converging ions to the center of the ion optical axis through which the ions pass deteriorates, and the amount of ions transported to the subsequent vacuum chamber decreases. Japanese Unexamined Patent Application Publication No. 2023-28190 discloses reducing the manufacturing cost by making the shape of the rod electrode a simple shape combining planes. However, improvement of the assembly accuracy of the ion optical element is not mentioned.

[0006] This disclosure was made to solve the aforementioned problems and aims to provide ion optical elements and mass spectrometers with high assembly precision. [Means for solving the problem]

[0007] This disclosure relates to an ion optical element used in a mass spectrometer. The ion optical element comprises a plurality of rod electrodes, each having a protrusion at one end; a plurality of electrode members connected to each of the plurality of rod electrodes; and a non-conductive base member having a window through which ions pass, and fixing the plurality of electrode members and the plurality of rod electrodes in a position surrounding the window. A first through hole is formed in each of the plurality of electrode members. A first recess corresponding to the protrusion is formed in the base member. The plurality of electrode members and the plurality of rod electrodes are positioned relative to the base member by fitting the protrusion through the first through hole into the first recess. [Effects of the Invention]

[0008] According to this disclosure, the base member has a first recess formed therein that corresponds to the protrusions of the multiple rod electrodes. The multiple electrode members and the multiple rod electrodes are positioned relative to the base member by fitting the protrusions into the first recess through first through holes formed in each of the electrode members. This makes positioning during assembly simple and accurate, and improves the assembly accuracy of the ion optical element. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram showing an example of the overall configuration of a mass spectrometer. [Figure 2] This is an exploded perspective view showing the ion optical element of the embodiment and the ion optical element of the comparative example. [Figure 3] This diagram illustrates the positional relationship between the rod electrode and the electrode member. [Figure 4] This is a cross-sectional view showing the ion optical element of the embodiment and the ion optical element of the comparative example. [Figure 5] This graph illustrates the relationship between the mass-to-charge ratio and the CV value. [Modes for carrying out the invention]

[0010] This embodiment will be described in detail with reference to the drawings. Note that identical or corresponding parts in the drawings are denoted by the same reference numerals, and their descriptions will not be repeated in principle.

[0011] Figure 1 is a schematic diagram showing an example of the overall configuration of the mass spectrometer 100. As shown in Figure 1, when the X, Y, and Z axes are defined, the X-axis direction is the front-to-back direction of the mass spectrometer 100, the Y-axis direction is the up-and-down direction of the mass spectrometer 100, and the Z-axis direction is the left-to-right direction of the mass spectrometer 100. The mass spectrometer 100 includes a chamber 1, an ESI (Electrospray ionization) probe 2, an ion detector 8, a voltage application unit 9, and a control device 20.

[0012] Chamber 1 includes an ionization chamber 11, a first intermediate vacuum chamber 12, a second intermediate vacuum chamber 13, and an analysis chamber 14. The ionization chamber 11 is at approximately atmospheric pressure. The first intermediate vacuum chamber 12, the second intermediate vacuum chamber 13, and the analysis chamber 14 are each evacuated by vacuum pumps (not shown). The mass spectrometer 100 has a multi-stage differential pumping system in which the vacuum level increases sequentially from the ionization chamber 11 to the first intermediate vacuum chamber 12, the second intermediate vacuum chamber 13, and the analysis chamber 14.

[0013] The ESI probe 2 is placed in the ionization chamber 11. The ESI probe 2 functions as an ion source that ionizes various components contained in the sample solution by spraying the sample solution into the ionization chamber 11 as tiny charged droplets. The ionization chamber 11 and the first intermediate vacuum chamber 12 are connected through a small-diameter desolvation tube 3. Ions generated in the ionization chamber 11 are drawn into the desolvation tube 3 by the gas flow formed by the differential pressure between its ends. The desolvation tube 3 is heated to a predetermined temperature, and when charged droplets in which the solvent has not sufficiently vaporized are drawn into the desolvation tube 3, the vaporization of the solvent is accelerated as the droplets pass through the tube 3, generating ions.

[0014] Ion guides 4 and 6, which are ion optical elements, are placed in the first intermediate vacuum chamber 12 and the second intermediate vacuum chamber 13, respectively. A predetermined voltage is applied to each of the multiple electrodes constituting the ion guides 4 and 6 from the voltage application unit 9. As a result, an electric field is formed in the space surrounded by the multiple electrodes, which focuses and transports ions. Ions from the sample components introduced into the first intermediate vacuum chamber 12 are focused by the ion guide 4 and sent to the second intermediate vacuum chamber 13 through a small hole provided at the top of the skimmer 5. Ions introduced into the second intermediate vacuum chamber 13 are focused by the ion guide 6 and sent to the analysis chamber 14.

[0015] In the analysis chamber 14, a quadrupole mass filter 7 and an ion detector 8 are arranged along the ion optical axis C through which the ions pass. The quadrupole mass filter 7 includes a main rod electrode and pre-rod electrodes and post-rod electrodes positioned before and after it, respectively. A predetermined voltage is applied to the multiple rod electrodes constituting the quadrupole mass filter 7 from a voltage application unit 9. This creates an electric field in the analysis chamber 14 that selectively allows ions having a specific mass-to-charge ratio (hereinafter also referred to as "m / z") (or being within a specific mass-to-charge ratio range) to pass through, while diverting other ions. Of the various ions introduced into the analysis chamber 14, only ions having, for example, a specific mass-to-charge ratio pass through the quadrupole mass filter 7 and reach the ion detector 8.

[0016] The ion detector 8 outputs an ion intensity signal corresponding to the amount of incident ions. The ion intensity signal is input to the data processing unit (not shown) of the control device 20, where data processing is performed. For example, by scanning the voltage applied to the electrodes constituting the quadrupole mass filter 7 within a predetermined range, the mass-to-charge ratio of ions that can pass through the quadrupole mass filter 7 changes. The data processing unit can create a mass spectrum showing the change in ion intensity over a predetermined mass-to-charge ratio range.

[0017] The control device 20 includes a processor 21, a memory 22, an input device 23, and a display device 24. The processor 21 includes, for example, a CPU (Central Processing Unit). The processor 21 functions as an arithmetic unit that controls the operations of each part of the mass spectrometer 100 by reading and executing a program stored in the memory 22. For example, the processor 21 controls the voltage application unit 9 to control the voltage applied to each part by executing the program. In the example of FIG. 1, a configuration in which the processor 21 is singular is illustrated, but the mass spectrometer 100 may have a configuration including a plurality of processors.

[0018] The memory 22 is realized by a non-volatile storage device such as a ROM (Read Only Memory) or a hard disk. The memory 22 stores a program executed by the processor 21, data used by the processor 21, and the like. The program may be stored in a non-temporary computer-readable medium.

[0019] The input device 23 is typically a mouse, a keyboard, various buttons, a touch panel, or the like. The input device 23 receives information necessary for controlling the operation of the mass spectrometer 100 and information necessary for the processing performed by the control device 20 through the user's operation.

[0020] The display device 24 is typically a liquid crystal monitor or the like, and displays information input by the user via the input device 23, analysis results, analysis conditions, and the like. Note that the display device 24 may be composed of a printer and paper, and display analysis conditions and the like by printing analysis results and the like on the paper. <A

[0021] FIG. 2 is an exploded perspective view showing the ion optical element of the embodiment and the ion optical element of the comparative example. FIG. 2(A) shows the ion guide 4 which is the ion optical element of the embodiment, and FIG. 2(B) shows the ion guide 40 which is the ion optical element of the comparative example. The ion guide 40 which is the comparative example is an ion optical element having a structure assembled using a jig 440 as will be described later.

[0022] As shown in FIG. 2(B), the ion guide 40 includes a base member 410, four electrode members 420, and four rod electrodes 430. A window portion 410a through which ions pass is formed in the base member 410. Through holes 420a and screw holes 420b at positions outside the center from the through holes 420a are formed in the electrode members 420. A screw hole 430a is formed at the end in the positive direction of the Z-axis, which is one end of the cylindrical tube portion 430b, of the rod electrode 430. The ion guide 40 is assembled using a cylindrical jig 440. A hole portion 440b for fitting the tube portion 430b of the rod electrode 430 is formed in the jig 440.

[0023] The plurality of rod electrodes 430 are positioned with respect to the jig 440 by fitting the hole portion 440b with a bottom provided in the jig 440 and the tube portion 430b. The electrode member 420 and the rod electrode 430 are fixed at the screw hole 430a at the end of the rod electrode 430 by a screw 460 passing through the through hole 420a of the base member 410 and the electrode member 420. The electrode member 420 is fixed to the base member 410 at the screw hole 420b of the electrode member 420 by a screw 450. The base member 410 is a non-conductive member. The plurality of electrode members 420 and the plurality of rod electrodes 43 are conductive members. The jig 440 is removed after the four electrode members 420 and the four rod electrodes 430 are fixed to the base member 410.

[0024] For the ion guide 40, which is an ion optical element shown in FIG. 2(B), since there is inevitably a gap formed between the hole portion 440b of the jig 440 and the tube portion 430b of the rod electrode 430 when assembling using the jig 440, there may be an error during assembly. On the other hand, for the ion guide 4, which is an ion optical element of the embodiment, since no jig is used, the error during assembly can be reduced. The ion guide 4 will be specifically described.

[0025] As shown in Figure 2(A), the ion guide 4 includes a base member 41, four electrode members 42, and four rod electrodes 43. The base member 41 has a window portion 41a through which ions pass. The electrode members 42 have through holes 42a and screw holes 42b located outside the center of the ion optical axis relative to the through holes 42a. The rod electrodes 43 have a convex portion 43a at one end of the cylindrical tube portion 43b, which is the end in the positive direction of the Z axis.

[0026] The base member 41 is a non-conductive member that fixes a plurality of electrode members 42 and a plurality of rod electrodes 43 in positions surrounding the window portion 41a. The plurality of electrode members 42 are connected to each of the plurality of rod electrodes 43. The electrode members 42 and rod electrodes 43 are conductive members and are fixed to the base member 41 at predetermined intervals. The electrode members 42 are fixed to the base member 41 by screws 45.

[0027] The ions ionized in the ionization chamber 11 are focused by the electric field generated by the four rod electrodes 43 and four electrode members 42 located in the first intermediate vacuum chamber 12, and guided to the second intermediate vacuum chamber 13, which is located after the base member 41. The configuration of the ion guide 4 as an ion optical element may also be applied to the ion guide 6 in the second intermediate vacuum chamber 13.

[0028] Figure 3 is a diagram illustrating the positional relationship between the rod electrode 43 and the electrode member 42. As shown in Figure 3, the rod electrode 43 and electrode member 42, which are ion optical elements, are arranged at 90-degree intervals around the ion optical axis C in the Z-axis direction through which ions pass. Note that the shape and arrangement of the rod electrode 43 and electrode member 42 may be changed within a range that does not affect the electric field formed in the space surrounded by the four rod electrodes 43.

[0029] Let A1 be a circle tangent to the inner circumference of the electrode member 42, with the ion optical axis C as the center. Let A2 be a circle tangent to the inner circumference of the side surface of the rod electrode 43, with the ion optical axis C as the center. It is desirable that circles A1 and A2 be perfect circles with minimal error from the ion optical axis C. This is because distortion of the circle's shape will worsen the efficiency of ion focusing. Therefore, in an ion optical element, accurate positioning from the ion optical axis C to the electrode member 42 and the rod electrode 43 is important.

[0030] Figure 4 is a cross-sectional view showing the ion optical element of the embodiment and the ion optical element of the comparative example. Figure 4(A) shows a cross-sectional view of the ion optical element of the embodiment, and Figure 4(B) shows a cross-sectional view of the ion optical element of the comparative example. The cross-sectional view in Figure 4 shows a cross-section cut in the YZ plane, which includes the ion optical axis C and the two rod electrodes 43 (rod electrodes 430).

[0031] As shown in Figure 4(B), the base member 410 has through holes 410b and 410c. The electrode member 420 has a through hole 420a and a screw hole 420b. The rod electrode 430 has a screw hole 430a at the end in the positive direction of the Z axis. The jig 440 has a hole 440b with a bottom. The multiple rod electrodes 430 are fixed to the jig 440 and then screwed to the base member. After that, the jig 440 is removed from the multiple rod electrodes 430.

[0032] The electrode member 420 and the rod electrode 430 are fixed to the base member 41 by screwing the screw 460 through the through hole 410b of the base member 410 and the through hole 420a of the electrode member 420 into the screw hole 430a of the rod electrode 430. The cylindrical portion 430b of the rod electrode 430 fits into the hole 440b of the jig 440 and is positioned at position S3.

[0033] The screw 450 fastens the base member 410 and the electrode member 420 by screwing it through the through hole 410c of the base member 410 into the screw hole 420b of the electrode member 420. In this way, the multiple electrode members 420 are positioned relative to the base member 410 at position S4 by the screw 450. The comparative example skimmer 5 is arranged to cover the outer circumference of the base member 410.

[0034] In Figure 4(B), the ion optical element uses a jig 440 to position multiple rod electrodes 430. The jig 440 requires a gap to be removed after the multiple rod electrodes 430 have been fitted, which can lead to assembly errors. In particular, the ion optical element used as the ion guide 4 has a structure that allows it to be disassembled, cleaned, and reassembled by the user. Therefore, assembly using the jig 440 is likely to result in larger assembly errors.

[0035] Specifically, when using the jig 440, assembly errors may occur in the distance from the ion optical axis C to the cylindrical portion 430b of the rod electrode 430. This can lead to assembly errors between the rod electrode 430 and the electrode member 420, and consequently, assembly errors in the distance from the ion optical axis C to the inner circumference of the electrode member 420. In other words, using the jig 440 may reduce the overall assembly accuracy of the ion optical element. Furthermore, the cylindrical portions 430b, which are the sides of multiple rod electrodes 430, may be damaged by contact with the jig 440 during assembly. Thus, when using the jig 440, the impact of damage to the rod electrodes 430 must be considered, and the tolerance, which is the difference between the maximum and minimum dimensions of the allowable error, cannot be made too strict.

[0036] On the other hand, the ion optical element of the embodiment is not assembled using a jig. As shown in Figure 4(A), the base member 41 has a recess 41b, a through hole 41c, and a recess 41d. The through hole 41c is provided as a hole for a screw 45 to pass through between the recess 41b and the recess 41d. The electrode member 42 has a through hole 42a, a screw hole 42b, and a recess 42c. The rod electrode 43 has a protrusion 43a formed at the end in the positive direction of the Z axis. The recess 41b of the base member 41 is formed in a shape corresponding to the protrusion 43a of the rod electrode 43.

[0037] The electrode member 42 and the rod electrode 43 are positioned relative to the base member 41 by fitting the protrusion 43a of the rod electrode 43 into the recess 41b of the base member 41 through the through hole 42a of the electrode member 42. In this way, the multiple electrode members 42 and the multiple rod electrodes 43 are positioned at position S1.

[0038] The screw 45 fastens the base member 41 and the electrode member 42 by screwing it through the through hole 41c of the base member 41 into the screw hole 42b of the electrode member 42. A pin 46 is positioned between the recess 41d of the base member 41 and the recess 42c of the electrode member 42. The pin 46, while fixed in the recess 42c of the electrode member 42, fits into the recess 41d of the base member 41, thereby positioning the base member 41 and the electrode member 42. In this way, the multiple electrode members 42 are positioned relative to the base member 41 even at position S2 by the fitting of the pin 46 into the recess 41d.

[0039] The skimmer 5 is positioned to cover the outer circumference of the base member 41. The skimmer 5 is provided with a small hole 5a centered on the ion optical axis C. Each of the multiple electrode members 42 is positioned opposite to the other electrode member 42, centered on the ion optical axis C. On the opposing surfaces of each of the multiple electrode members 42, an inclined portion 41e is formed, extending from the side surfaces of the multiple rod electrodes 43 toward the ion optical axis C.

[0040] As shown in Figure 4(A), the distance between the electrode members 42 on the side closer to the skimmer 5 is d1, and the distance between the rod electrodes 43 is d2. As shown in Figure 4(B), the distance between the electrode members 420 on the side closer to the skimmer 5 is d3, and the distance between the rod electrodes 430 is d4. The diameter of circle A1 shown in Figure 3 corresponds to distance d1, and the diameter of circle A2 corresponds to distance d2. As shown in Figure 3, it is desirable that circles A1 and A2 are perfect circles. For this reason, it is desirable that the diameter of the circles (corresponding to distances d1 to d4) on the XY plane passing through the ion optical axis C does not have an error due to the angle from the center of the circle. The ion optical element of this embodiment does not use a jig, so it is possible to reduce errors due to differences in assembly and reduce errors in the diameter of the circles.

[0041] Specifically, as shown in Figure 4(A), the ion optical element of the embodiment has a structure in which the electrode member 42 and the rod electrode 43 are positioned relative to the base member 41 by fitting the protrusion 43a of the rod electrode 43 into the recess 41b of the base member 41 through the through hole 42a of the electrode member 42. In this way, the ion optical element of the embodiment without a jig, compared to the ion optical element shown in Figure 4(b) which uses a jig 440, can prevent damage to the rod electrode 43, simplify and make positioning during assembly easier and more accurate, and improve the assembly accuracy of the ion optical element.

[0042] Figure 5 is a graph illustrating the relationship between the mass-to-charge ratio and the coefficient of variation (CV). The horizontal axis represents the mass-to-charge ratio [m / z], and the vertical axis represents the CV, a dimensionless quantity that is the coefficient of variation. The coefficient of variation is the standard deviation divided by the mean, and is used as an indicator of data variability. Figure 5(A) shows a graph comparing the comparative example and the example for positive ions. Figure 5(B) shows a graph comparing the comparative example and the example for negative ions.

[0043] As shown in Figure 5(A), for positive ions, when the CV value of the comparative example at each mass-to-charge ratio is set to 1, the CV value of the corresponding example was lower than that of the comparative example at every mass-to-charge ratio. Similarly, as shown in Figure 5(B), for negative ions, when the CV value of the comparative example at each mass-to-charge ratio is set to 1, the CV value of the corresponding example was lower than that of the comparative example at every mass-to-charge ratio.

[0044] Thus, when using the ion optical element of the example, the data variability is smaller than when using the ion optical element of the comparative example, indicating improved assembly accuracy of the ion optical element. As a result, it can be said that ions can be focused more efficiently when using the ion optical element of the example than when using the ion optical element of the comparative example.

[0045] [Differentiation] In the ion optical element of the above-described embodiment, the pin 46 may be fixed to the base member 41 instead of the electrode member 42. Alternatively, a projection may be formed from either the electrode member 42 or the base member 41 instead of the pin 46. Furthermore, the pin 46 may be omitted.

[0046] [Pattern] Those skilled in the art will understand that the exemplary embodiments described above are specific examples of the following embodiments.

[0047] (Section 1) An ion optical element according to one embodiment relates to an ion optical element used in a mass spectrometer. The ion optical element comprises a plurality of rod electrodes, each having a protrusion formed at one end; a plurality of electrode members connected to each of the plurality of rod electrodes; and a non-conductive base member having a window through which ions pass, and fixing the plurality of electrode members and the plurality of rod electrodes in a position surrounding the window. A first through hole is formed in each of the plurality of electrode members. A first recess corresponding to the protrusion is formed in the base member. The plurality of electrode members and the plurality of rod electrodes are positioned relative to the base member by fitting the protrusion through the first through hole into the first recess.

[0048] According to the ion optical element described in paragraph 1, a first recess is formed in the base member, corresponding to the protrusions of the multiple rod electrodes. The multiple electrode members and the multiple rod electrodes are positioned relative to the base member by fitting their protrusions into the first recess through first through holes formed in each of the electrode members. This makes positioning during assembly simple and accurate, and improves the assembly accuracy of the ion optical element.

[0049] (Section 2) In the ion optical element described in Section 1, a second recess is formed in the base member. A pin is provided on each of the plurality of electrode members. The plurality of electrode members are positioned relative to the base member by the fitting of the pins into the second recess.

[0050] According to the ion optical element described in paragraph 2, the positioning of multiple electrode members can be performed using pins, making positioning during assembly simple and accurate, and improving the assembly accuracy of the ion optical element.

[0051] (Section 3) In the ion optical element described in Section 1 or Section 2, the plurality of rod electrodes consists of four rod electrodes. The plurality of electrode members consists of four electrode members corresponding to the four rod electrodes. The four rod electrodes and the four electrode members are arranged at 90-degree intervals with respect to the ion optical axis through which the ions pass.

[0052] According to the ion optical element described in Section 3, the four rod electrodes and four electrode members are arranged at 90-degree intervals around the ion optical axis through which the ions pass. This allows for efficient focusing of the ions.

[0053] (Section 4) In the ion optical element described in any one of Sections 1 to 3, each of the multiple electrode members is arranged opposite to the ion optical axis. On the surfaces of each of the multiple electrode members facing each other, an inclined portion is formed that extends from the side surfaces of the multiple rod electrodes toward the ion optical axis.

[0054] According to the ion optical element described in Section 4, each of the multiple electrode members has a sloping portion formed on the opposing surface, extending from the side of the multiple rod electrodes toward the ion optical axis. This allows for efficient focusing of ions.

[0055] (Clause 5) An ion optical element according to any one of Clauses 2 to 5 further comprises screws for fixing a base member and a plurality of electrode members. The base member has a second through hole formed between a first recess and a second recess for the screws to pass through.

[0056] According to the ion optical element described in Section 5, the base member and the multiple electrode members can be properly fixed between the first recess and the second recess.

[0057] (Clause 6) A mass spectrometer according to one embodiment comprises an ion source, an ion optical element according to any one of Clauses 1 to 5 for focusing ions generated by the ion source, and an ion detector for detecting ions focused by the ion optical element.

[0058] The mass spectrometer described in paragraph 6 can be equipped with an ion optical element that allows for easy and accurate positioning during assembly, thereby improving assembly accuracy.

[0059] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0060] 1 Chamber, 2 ESI probe, 3 Desolvation tube, 4,6,40 Ion guide, 5 Skimmer, 5a Small hole, 7 Quadrupole mass filter, 8 Ion detector, 9 Voltage application section, 11 Ionization chamber, 12 First intermediate vacuum chamber, 13 Second intermediate vacuum chamber, 14 Analysis chamber, 20 Control device, 21 Processor, 22 Memory, 23 Input device, 24 Display device, 41,410 Base member, 41a,410a Window section, 41b,41d,42c Recess, 41c,42a,410b,410c,420a Through hole, 41e Inclined section, 42,420 Electrode member, 42b,420b,430a Screw hole, 43,430 Rod electrode, 43a Protrusion, 43b,430b Cylinder section, 45,450,460 Screw, 100 Mass spectrometer, 440 Fixture, 440b Hole, C Ion optical axis.

Claims

1. An ion optical element used in a mass spectrometer, The aforementioned ion optical element is Multiple rod electrodes, each having a protrusion at one end, A plurality of electrode members connected to each of the plurality of rod electrodes, It has a window portion through which ions pass, and comprises a non-conductive base member that fixes the plurality of electrode members and the plurality of rod electrodes in a position surrounding the window portion, A first through-hole is formed in each of the plurality of electrode members. The base member has a first recess that corresponds to the protrusion, An ion optical element in which the plurality of electrode members and the plurality of rod electrodes are positioned relative to the base member by fitting the protrusions into the first recesses through the first through holes.

2. The base member has a second recess formed therein. Each of the aforementioned plurality of electrode members is provided with a pin. The ion optical element according to claim 1, wherein the plurality of electrode members are positioned relative to the base member by the pins fitting into the second recesses.

3. The aforementioned plurality of rod electrodes are composed of four rod electrodes, The plurality of electrode members consist of four electrode members corresponding to the four rod electrodes. The ion optical element according to claim 1 or claim 2, wherein the four rod electrodes and the four electrode members are arranged at 90-degree intervals with respect to the ion optical axis through which the ions pass.

4. Each of the plurality of electrode members is arranged opposite to the ion optical axis, The ion optical element according to claim 3, wherein each of the plurality of electrode members has an inclined portion formed on the opposing surface of the plurality of rod electrodes toward the ion optical axis, extending from the side surface of the plurality of rod electrodes.

5. The system further includes screws for fixing the base member and the plurality of electrode members, The ion optical element according to claim 2, wherein the base member has a second through-hole formed between the first recess and the second recess for the screw to pass through.

6. Ion source and, An ion optical element according to claim 1 that focuses ions generated by the ion source, A mass spectrometer comprising an ion detector for detecting ions focused by the aforementioned ion optical element.

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