Ion guide and mass spectrometer

Abstract

To improve robustness of an ion guide, the ion guide includes rod electrode (20) with a columnar shape which is arranged in a circle. The rod electrodes each include on a side surface thereof a cut-out portion (21) and a protruding portion (26). A cut-out portion (21) of a certain one of the rod electrodes (20) and a protruding portion (26) of another one of the rod electrodes (20) are fitted to each other without contact. The rod electrodes (20) are arranged such that an inscribed circle formed by the rod electrodes (20) on an inlet side is larger than an inscribed circle formed by the rod electrodes (20) on an outlet side.

Description

TECHNICAL FIELD

[0001] The present invention relates to a technology of an ion guide and a mass spectrometer.BACKGROUND ART

[0002] In a mass spectrometer, ions generated in an ion source are transported to a mass spectrometry unit via an ion transport unit. A mass spectrometer using an atmospheric-pressure ionization method is generally configured as a device of a differential exhaust system in which a vacuum chamber is segmented into a plurality of spaces in order to transport ions generated under an atmospheric pressure to a mass spectrometry unit in vacuum. In this case, it is often the case that the ion transport unit is at the preceding stage of the mass spectrometer and is disposed in the differential exhaust chamber which has low vacuum level and high pressure. In order to achieve a high sensitivity of a mass spectrometry device, the ion transport unit is demanded to have a high ion intake efficiency and a high ion convergence efficiency.

[0003] A general ion transport unit uses an ion guide system which causes ions to converge by using a high-frequency electric field which is formed by applying a high-frequency voltage. Ion guides employ an ion funnel system in which ring-shaped electrodes are stacked in an ion transport direction, a multipole ion guide system configured with a plurality of rod electrodes, and other systems.CITATION LIST Patent Literature

[0004] Patent Literature 1: US patent No. 10475633Non-Patent Literature

[0005] Non-Patent Literature 1: "Conical octopole ion guide: Design, focusing, and its application to the deposition of low energetic clusters", REVIEW OF SCIENTIFIC INSTRUMENTS, 77, 013302, 2006SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED

[0006] A multipole ion guide (hereinafter, referred to as an ion guide) is supported in a vacuum chamber by a holder made of an insulating material. Although liquid droplets are introduced into the ion guide besides ions, it is desirable that the liquid droplets be discharged from the ion guide. At this time, although the liquid droplets are discharged outside from a gap between rod electrodes included in the ion guide, some liquid droplets adhere to the inner side of the holder, causing the inner side of the holder to be contaminated. This contamination may highly cause the voltage applicable to the rod electrodes to decrease, or an electric discharge to occur inside the holder due to the adhered liquid droplets even when the same voltage as the voltage applied before the contamination is applied to the rod electrodes. This may result in deteriorating analytical performance or stability of the mass spectrometer.

[0007] Patent Literature 1 and Non-Patent Literature 1 state that the ion intake efficiency is improved by increasing the number of rod electrodes (the number of poles). In addition, Patent Literature 1 and Non-Patent Literature 1 state that the internal space of the ion guide is gradually narrowed toward the ion outlet side by arranging the rod electrodes obliquely along a longitudinal direction of the rod electrodes. In this way, the technologies described in Patent Literature 1 and Non-Patent Literature 1 improve the convergence efficiency of ions.

[0008] However, even these technologies do not describe a configuration of suppressing contamination of the inner side of a holder against the liquid droplets.

[0009] In view of such backgrounds, the present invention has been made, and an object of the present invention is to improve robustness of an ion guide.Solution to Problem

[0010] To solve the above-described problems, the present invention provides an ion guide comprising rod electrodes with a columnar shape which are arranged in a circle. The rod electrodes each include on a side surface thereof a recess portion and a protruding portion. A recess portion of a certain one of the rod electrodes and a protruding portion of another one of the rod electrodes are fitted to each other without contact. The other solutions are described in embodiments as appropriate.Advantageous Effects of Invention

[0011] According to the present invention, robustness of an ion guide can be improved.BRIEF DESCRIPTION OF DRAWINGS

[0012] [FIG. 1] FIG. 1 is a diagram showing a configuration of a mass spectrometer used in a first embodiment. [FIG. 2] FIG. 2 is a diagram showing a configuration of an ion guide including 12 cylindrical rod electrodes. [FIG. 3A] FIG. 3A is a diagram (No. 1) showing only one rod electrode among the rod electrodes included in the ion guide. [FIG. 3B] FIG. 3B is a diagram (No. 2) showing only one rod electrode among the rod electrodes included in the ion guide. [FIG. 4] FIG. 4 is a diagram showing a top view, a sectional view, and an arrow sectional view for one of the rod electrodes according to the present embodiment. [FIG. 5] FIG. 5 is a perspective view showing four rod electrodes among the twelve rod electrodes included in the ion guide. [FIG. 6] FIG. 6 is a diagram relating to a gap between adjacent rod electrodes. [FIG. 7] FIG. 7 is a diagram (No. 1) showing an example of the ion guide provided with holders. [FIG. 8] FIG. 8 is a diagram (No. 2) showing the example of the ion guide provided with the holders. [FIG. 9] FIG. 9 is a diagram showing another explanation relating to features of the ion guide according to the first embodiment. [FIG. 10] FIG. 10 is a diagram showing an ion guide according to a second embodiment. [FIG. 11] FIG. 11 is a diagram showing an ion guide of a third embodiment. [FIG. 12] FIG. 12 is a diagram showing an ion guide of a first modification. [FIG. 13A] FIG. 13A is a diagram (No. 3) showing only one rod electrode among rod electrodes included in the ion guide. [FIG. 13B] FIG. 13B is a diagram (No. 4) showing only one rod electrode among the rod electrodes included in the ion guide. [FIG. 14] FIG. 14 is a diagram showing an ion guide of a second modification. [FIG. 15A] FIG. 15A is a diagram (No. 5) showing only one rod electrode among rod electrodes included in the ion guide. [FIG. 15B] FIG. 15B is a diagram (No. 6) showing only one rod electrode among the rod electrodes included in the ion guide. [FIG. 16] FIG. 16 is a diagram showing an ion guide of a third modification. [FIG. 17A] FIG. 17A is a diagram (No. 7) showing only one rod electrode among rod electrodes included in the ion guide. [FIG. 17B] FIG. 17B is a diagram (No. 8) showing only one rod electrode among the rod electrodes included in the ion guide. [FIG. 18] FIG. 18 is a diagram showing a configuration of an ion guide of a fourth embodiment. [FIG. 19A] FIG. 19A is a diagram (No. 9) showing only one rod electrode among rod electrodes included in the ion guide. [FIG. 19B] FIG. 19B is a diagram (No. 10) showing only one rod electrode among the rod electrodes included in the ion guide. [FIG. 20] FIG. 20 is a perspective view showing two rod electrodes among four rod electrodes included in the ion guide. [FIG. 21] FIG. 21 is a diagram showing a configuration of a 12-pole ion guide of a fifth embodiment, in which twelve cylindrical rod electrodes are arranged in parallel. [FIG. 22] FIG. 22 is a diagram (No. 3) showing an example of the ion guide provided with holders. [FIG. 23] FIG. 23 is a sectional view showing an ion guide of a sixth embodiment. [FIG. 24] FIG. 24 is a diagram showing common features. [FIG. 25] FIG. 25 is a partially enlarged view of rod electrodes included in an ion guide. [FIG. 26] FIG. 26 is a diagram (No. 1) showing a configuration of an ion guide according to a comparative example. [FIG. 27] FIG. 27 is a diagram (No. 4) showing a configuration of the ion guide provided with holders. [FIG. 28] FIG. 28 is a diagram (No. 2) showing a configuration of an ion guide according to a comparative example. [FIG. 29] FIG. 29 is a diagram (No. 5) showing a configuration of the ion guide provided with holders. DESCRIPTION OF EMBODIMENTS

[0013] Next, configurations for carrying out the present invention (hereinafter, referred to as "embodiments") will be described in detail with reference to the drawings as appropriate.[First Embodiment]

[0014] In a first embodiment, a 12-pole ion guide 200 is used for a mass spectrometer 1. The 12-pole ion guide 200 includes twelve rod electrodes 20 (see FIG. 2) each provided with a cut-out portion 21 which is a recess portion having a recessed arc shape.[Mass Spectrometry Device 1]

[0015] FIG. 1 is a diagram showing a configuration of the mass spectrometer 1 used in the first embodiment. The mass spectrometer 1 mainly includes an ion source 100, an ion guide 200, an ion transport device 300, and a mass spectrometry unit 400. The ion guide 200, the ion transport device 300, and the mass spectrometry unit 400 are provided inside a vacuum container 130. Note that in FIG. 1, dashed lines indicate control lines for voltage, and dot-dashed lines indicate control lines through which information is transmitted.

[0016] The ion source 100 mainly includes an ion generation device 110 and an ion source chamber 120. For the ion source 100, any of various ionization systems such as electrospray ionization (ESI), atmospheric-pressure chemical ionization (APCI), and atmospheric-pressure photoionization (APPI) can be used. After generating ions from an introduced sample solution Q, the ion generation device 110 sprays the generated ions into the ion source chamber 120.

[0017] When the sample solution Q is ionized and the ions are sprayed, many liquid droplets are also sprayed besides the ions. Hence, removal of unnecessary liquid droplets is performed by discharging gas inside the ion source chamber 120 (symbol E). For example, in the case of the ESI system, in order to reduce unnecessary liquid droplets, electrostatic atomization and gas spray in the ion generation device 110 are used together. Thus, the vaporization of the sample solution Q is promoted, and the ionization efficiency is improved. Note that electrostatic atomization is performed by a power supply 500 applying high voltage to the ion generation device 110. A flow rate of the gas to be sprayed is around 0.5 to 10 L / min depending on a flow rate of the sample solution Q. In general, as the gas used in the ion generation device 110, an inert gas such as nitrogen or argon is used. The flow rate of the sample solution Q is generally in a range from around nL (nanoliter) / min order to mL (milliliter) / min order. In order to further improve the ionization efficiency, another system is also generally employed. The system involves heating the space inside the ion generation device 110 into which ions and liquid droplets are sprayed with a heating gas (around 800°C at most). The flow rate of the heating gas is around 0.5 to 50 L / min, and an inert gas such as nitrogen or argon is generally used.

[0018] In the configuration of FIG. 1, a counter electrode 121 having a hole H1 is disposed at a preceding stage of an introduction electrode 122. A gas G is introduced from a hole H11 into a space provided between the introduction electrode 122 and the counter electrode 121. Thus, the gas G is introduced between the introduction electrode 122 and the counter electrode 121. As a result, the introduction of noise components such as excessive liquid droplets sprayed by the ion source 100 into a hole H2 of the introduction electrode 122 can be suppressed. The flow rate of the gas G is around 0.5 to 50 L / min, and an inert gas such as nitrogen or argon is generally used. Although power supply 500 applies a voltage to both the counter electrode 121 and the introduction electrode 122, control lines for the voltage to be applied to the counter electrode 121 and the introduction electrode 122 are omitted in FIG. 1.

[0019] The ions having been introduced into the ion source chamber 120 are then introduced into the hole H2 provided in the introduction electrode 122 via the hole H1 provided in the counter electrode 121. At this time, the ions move from the ion generation device 110 to the ion source chamber 120, the hole H1, the hole H2 in this order, due to an electric field generated between the ion generation device 110 and the introduction electrode 122. In general, the diameters of the hole H1 provided in the counter electrode 121 and the hole H2 provided in the introduction electrode 122 are around several mm or less, and the voltage to be applied to the counter electrode 121 is around ± several kV at most. The polarities of the voltages to be applied to the counter electrode 121 and the introduction electrode 122 are the same.

[0020] Next, the ions are introduced into the mass spectrometry unit 400 from the hole H2 provided in the introduction electrode 122 via the ion guide 200 and the ion transport device 300, and are analyzed in the mass spectrometry unit 400. the power supply 500 applies different voltages to the ion source 100 (the ion generation device 110), the ion guide 200, the ion transport device 300, and the mass spectrometry unit 400. The timing in which a voltage is applied and its voltage value from the power supply 500 are controlled by a control device 600.[Ion Guide 200, Ion Transport Device 300]

[0021] As shown in FIG. 1, the inside of the vacuum container 130 can be partitioned into a plurality of vacuum chambers V1 to V3. The vacuum chamber V1 and the vacuum chamber V2 communicate with each other through a small-diameter hole H3. The vacuum chamber V2 and the vacuum chamber V3 communicate with each other through a small-diameter hole H4. The hole H2 provided in the introduction electrode 122 as well as the holes H3 and H4 are passages for the ions. In addition, a voltage may be applied to the members having the holes H3 and H4. When a voltage is applied to the members having the holes H3 and H4 (and the hole H2), housing portions such as the vacuum container 130 and the members having the holes H3 and H4 (and the hole H2) are insulated using insulators (not shown). The diameters of the holes H3 and H4 are generally around several mm or less.

[0022] In addition, the vacuum chambers V1 to V3 are exhausted by vacuum pumps P1 to P3. As a result of this, the vacuum chamber V1 is maintained at around several hundreds to several thousands Pa, the vacuum chamber V2 is maintained at around several Pa, and the vacuum chamber V3 is maintained at around 0.1 Pa or less, in general. The vacuum chamber V1 is provided with an ion guide 200 which allows ions to converge and penetrate therethrough. The vacuum chamber V2 is provided with an ion transport device 300 which allows ions to converge and penetrate therethrough like the ion guide 200. It is also possible to provide a multipole ion guide 200, an electrostatic lens, or an ion funnel in the ion transport device 300. The power supply 500 generates a high-frequency voltage, a direct-current voltage, an alternating-current voltage, and combinations thereof, which are applied to the ion guide 200 and the ion transport device 300. The number of the vacuum chambers V1 to V3 can be larger or smaller than the number shown in FIG. 1. For example, another vacuum chamber, which is maintained at around several hundreds Pa, can be provided between the vacuum chamber V1 and the vacuum chamber V2, and the vacuum chambers can include another ion transport device 300 different from the ion transport device 300 shown in FIG. 1.[Mass Spectrometry Unit 400]

[0023] The mass spectrometry unit 400 includes an ion separation device 401 and a detection device 402. The ion separation device 401, which separates or disassociates ions, can include an ion trap, a quadrupole filter electrode, a collision cell, and a time-of-flight mass spectrometer (TOF), or can include combinations thereof. The ions which have passed through the ion separation device 401 are detected by the detection device 402. The detection device 402 can include an electron multiplier tube and a multichannel plate (MCP). The ions detected by the detection device 402 are converted to an electrical signal, and information such as mass and intensity of the ions is analyzed by the control device 600. The control device 600 includes an input-output unit and a memory, which are not shown, for receiving an input of instructions from a user and controlling the voltage. The control device 600 further includes software necessary for operations of the power supply 500. The voltage supplied from the power supply 500 to the mass spectrometry unit 400 includes a high-frequency voltage, a direct-current voltage, an alternating-current voltage, and combinations thereof.

[0024] In the present embodiment, a longitudinal direction of the ion guide 200 is defined as an X axis. Axes, which are orthogonal to the X axis, pass a center C of the ion guide 200, and are orthogonal to each other, are defined as a Y axis and a Z axis. In particular, a direction from the ion source 100 to the mass spectrometry unit 400 is defined as the X axis, an upward direction of the mass spectrometer 1, which is orthogonal to the X axis, is defined as the Z axis, and a direction orthogonal to the X axis and the Z axis is defined as the Y axis.[Ion Guide 200] (12-pole, Cylindrical Rod Electrode 20)

[0025] Subsequently, the ion guide 200 according to the present embodiment will be described in detail with reference to FIGS. 2 to 9. FIG. 2 is a diagram showing a configuration of the ion guide 200 including twelve (12-pole) cylindrical rod electrodes 20 (20-1 to 20-12). Note that in the following description, the ion guide 200 including n pieces of rod electrodes 20 is referred to as an n-pole ion guide 200. FIG. 2 shows only the rod electrodes 20 for simplicity. In FIG. 2, a drawing Z1 on the left is a diagram as viewed from the ion inlet side. In the present embodiment, the ion inlet side (or simply, the inlet side) is the ion source 100 side shown in FIG. 1. A drawing Z2 in the center of FIG. 2 is a diagram of the ion guide 200 as viewed from its side. The drawing Z2 on the center of FIG. 2 only shows the rod electrodes 20-1 and 20-7 for simplicity. A drawing Z3 on the right of FIG. 2 is a diagram as viewed from the ion outlet side (the right side of FIG. 1). In the present embodiment, the ion outlet side (or simply, the outlet side) is the mass spectrometry unit 400 side shown in FIG. 1. As shown in FIG. 2, the plurality of rod electrodes 20 (20-1 to 20-12) each having a columnar shape are arranged in a circle (arranged annularly) about the center C of the ion guide 200. Each rod electrode 20 is arranged to have an angle "θ" to the longitudinal direction. The angle "θ" will be described later.

[0026] FIG. 3A and FIG. 3B are diagrams showing only one rod electrode 20 (20-1) among the rod electrodes 20 included in the ion guide 200 shown in FIG. 2. FIG. 3A is a diagram of the rod electrode 20 as viewed from the ion inlet side, and FIG. 3B is a diagram of the rod electrode 20 as viewed from the ion outlet side.

[0027] As shown in FIG. 3A and FIG. 3B, the rod electrode 20 according to the present embodiment features that the cut-out portion 21, which is a recess portion having a recessed arc shape, is provided on a side surface of the cylindrical rod electrode 20. In addition, a protruding portion 26 is provided on a side surface of the rod electrode 20, which is positioned opposite to the side surface provided with the cut-out portion 21. In this way, the cut-out portion 21 (the recess portion) and the protruding portion 26 are provided on the side surfaces of the rod electrode 20. Note that in FIG. 3A, a shape without the cut-out portion 21 is indicated by a dot-dashed line. The present embodiment features that the rod electrodes 20-1 to 20-12 each having the cut-out portion 21 are arranged to be inclined at the angle "θ" to the X axis as shown in FIG. 2. That is, the ion guide 200 of the present embodiment is configured to be reduced in diameter on the mass spectrometer 1 side (the outlet side). The angle "θ" is desirably around 10° or less.

[0028] In FIG. 2, numerals of the cut-out portion 21 and the protruding portion 26 are omitted to avoid complication. As shown in FIGS. 2 to 3B, a cut-out portion 21 of a certain one of the rod electrodes 20 and a protruding portion 26 of another one of the rod electrodes 20 are fitted to each other without contact.

[0029] FIG. 4 is a diagram showing a top view, a sectional view, and an arrow sectional view of one of the rod electrodes 20 according to the present embodiment. When the direction in which the cut-out portion 21 is provided is considered as a sheet-surface upper side of the rod electrode 20, a drawing Z4 on the upper part of FIG. 4 is a diagram of the rod electrode 20 as viewed from the upper side (top view) . A drawing Z5 on the lower right part of FIG. 4 is an A-A sectional view of the rod electrode 20. A drawing Z6 (a Barrow sectional view) on the lower left part of FIG. 4 is a diagram of the rod electrode 20 as viewed from an arrow B (a direction inclined at α°) of the ion guide 200. As shown in FIG. 4, the rod electrode 20 features that the arc recessed cut-out portion 21 with a radius "RC" is formed across an entire length of cylinder having a diameter (φ) "D" and a length "L". The cut-out portion 21 is formed to be inclined at a predetermined angle "α°" (provided to have a predetermined angle) to the longitudinal direction of the rod electrode 20. This allows the cut-out portion 21 to be shallowly provided on the inlet side and deeply provided on the outlet side. This varies the thickness of the rod electrode 20 at the inlet side and the outlet side. Even when the twelve rod electrodes 20 are arranged to be inclined at the angle "θ" to the X axis as shown in FIG. 2, the ion guide 200 can be assembled without causing the rod electrodes 20 to come into contact with one another. That is, even when the rod electrodes 20 are arranged to be inclined, it is possible to maintain the state in which the cut-out portion 21 of a certain one of the rod electrodes 20 and the protruding portion 26 of another one of the rod electrodes are fitted to each other without contact. It is desirable that "D" is around 10 mm or less, "L" is around 100 to 300 mm, and "α°" is around 5° or less.

[0030] As shown in FIG. 4, in the present embodiment, the cut-out portion 21 is formed with an arc having a constant radius "RC" across the entire length of the rod electrode 20. However, any shape is acceptable for the cut-out portion 21 as long as a certain degree of a gap can be ensured without causing the adjacent rod electrodes 20 to come into contact with each other, and the shape of the cut-out portion 21 does not need to have the same shape across the entire length, as described later. Forming the cut-out portion 21 involves production of a ridge portion 22, which can be chamfered or arc chamfered for the purpose of discharge prevention.

[0031] In FIG. 2, the gap between the adjacent rod electrodes 20 is desirably around 0.1 mm to 5 mm depending on the voltage to be applied. The width of the gap may be configured to be substantially the same from the inlet side to the outlet side. Alternatively, the dimensions of the gap may vary from the inlet side to the outlet side. The same applies to the embodiments and modifications shown below.

[0032] FIG. 5 is a perspective view showing 4 rod electrodes 20-6 to 20-9 among the twelve rod electrodes 20 included in the ion guide 200. The rod electrode 20 featured in FIGS. 2 to 4 achieves the ion guide 200 which has a radius of an inscribed circle gradually decreasing from an inscribed circle 23 formed by the rod electrodes 20 on the inlet side to an inscribed circle 24 formed by the rod electrodes 20 on the outlet side. That is, the rod electrode 20 is arranged to be inclined at the angle "θ" (see FIG. 2) such that the inscribed circle 23 formed by the rod electrodes 20 on the inlet side is larger than the inscribed circle 24 formed by the rod electrodes 20 on the outlet side. This allows the space inside the ion guide 200 to be gradually narrower toward the outlet side. By gradually narrowing the space inside the ion guide 200 in this way, a force of convergence of the multipole electric field can be gradually intensified toward the outlet side, thereby gradually converging the ions on near the center C. In addition, while analyzing, an air flow containing liquid droplets, which would become a noise factor, is exhausted from the gap of the rod electrodes 20 (that is, the liquid droplets are discharged from the gap of the rod electrodes 20). This improves the separation efficiency between the air flow containing the liquid droplets and the ions.

[0033] Next, the gap between the adjacent rod electrodes 20 will be described with reference to FIG. 6. FIG. 6 is a diagram relating to the gap between the adjacent rod electrodes 20. FIG. 6 shows only the rod electrodes 20-1 and 20-2 for simplicity. A dot-dashed line S is line connecting centers GC1 to GCn of rod gaps GA1 to Gan at the same distances "R1" to "Rn" from the center C of the ion guide 200 (arcs indicated by dashed lines in FIG. 6). The ion guide 200 according to the present embodiment features that the dot-dashed line S is not on a straight line. This relation may be provided across the entire length of each rod electrode 20, or may be provided in part of each rod electrode 20 in the longitudinal direction.

[0034] FIG. 7 and FIG. 8 are diagrams showing an example of the ion guide 200 provided with holders 210. A drawing Z11 on the left of FIG. 7 is a diagram of the ion guide 200 provided with the holders 210 as viewed from the inlet side. A drawing Z12 on the right of FIG. 7 is a side view of the ion guide 200 provided with the holders 210. FIG. 8 is an enlarged view of the rod electrodes 20-1 and 20-2. In FIG. 7 and FIG. 8, the same configurations as those in FIGS. 2 to 6 are denoted by the same numerals, and descriptions thereof are omitted. In the actual ion guide 200, as shown in FIG. 7, the twelve rod electrodes 20 (20-1 to 20-12) are held by the holders 210 (210a, 210b) made of an insulating material, or an insulating member. As shown in FIG. 7, each holder 210 (210a, 210b) has a shape in contact with the corresponding rod electrode 20, and are made of an insulating member. The holder 210 may have any shape as long as the holder 210 is capable of supporting the rod electrodes 20. As described above, in the ion guide 200 according to the present embodiment, the rod electrodes 20-1 to 20-12 are each arranged to be inclined to the X axis. For this reason, the holder 210a and the holder 210b made of an insulating material have different inner diameters. That is, the inner diameter of the holder 210a disposed on the inlet side is larger than the inner diameter of the holder 210b disposed on the outlet side. As described above, the rod electrodes 20-1 to 20-12 each having the cut-out portion 21 with a recessed shape (see FIG. 3A, FIG. 3B, or other drawings) are arranged to be inclined to the X axis. This arrangement, as shown in FIG. 8, achieves a configuration in which when the ion guide 200 is viewed from the inlet side, contact portions 211a, 211b (dashed lines in the drawing Z11 on the left of FIG. 7) are invisible. The contact portions 211a, 211b are portions where the holders 210 (210a, 210b) and the rod electrodes 20 are in contact with each other. The contact portion 211a is a portion where the holder 210a is in contact with the rod electrodes 20. Similarly, the contact portion 211b is a portion where the holder 210b is in contact with the rod electrodes 20.

[0035] Each rod electrode 20 is held by the holders 210, allowing the ion guide 200 to be placed in the vacuum chamber V1 (see FIG. 1) without causing each rod electrode 20 to be dispersed.

[0036] In particular, as shown in FIG. 8, insulation creepage surface portions 212a, 212b are invisible when the ion guide 200 is viewed from the inlet side. The insulation creepage surface portion 212a is a portion corresponding to the gap between the rod electrodes 20 in the contact portion 211a. Similarly, the insulation creepage surface portion 212b is a portion corresponding to the gap between the rod electrodes 20 in the contact portion 211b. The insulation creepage surface portions 212a, 212b are invisible when the ion guide 200 is viewed from the inlet side, thereby preventing contamination and improving robustness. In actual configuration, the contact portions 211a, 211b (and the insulation creepage surface portions 212a, 212b) have a width but are shown in a linear form in FIG. 8.

[0037] FIG. 9 is a diagram showing another explanation of the features of the ion guide 200 according to the first embodiment. FIG. 9 shows only the rod electrodes 20-1 to 20-2 for simplicity. A line GL is defined as a line connecting the center C and a center GC of a rod gap GA at a certain distance "R" (an arc indicated by a dashed line in FIG. 9) from the center C of the ion guide 200 (see FIG. 2). The present embodiment features that near the line GL, the shapes of the adjacent rod electrodes 20 (the rod electrodes 20-1 and 20-2 in the example shown in FIG. 9) are asymmetrical with respect to the line GL. This relation may be provided across the entire length of each rod electrode 20, or may be provided in part of each rod electrode 20 in the longitudinal direction.

[0038] As shown in the first embodiment, the cut-out portion 21 of a certain one of the rod electrodes 20 and the protruding portion 26 of another one of the rod electrodes 20 are fitted to each other without contact. In the ion guide 200 having such a configuration, the liquid droplets discharged from the inside of the ion guide 200 to the outside are blocked by the protruding portions 26 of the rod electrodes 20. This causes the liquid droplets unlikely to reach the insulation creepage surface portion 212a.

[0039] With the configuration of the ion guide 200 according to the present embodiment as described above, it is possible to suppress contamination of the insulation creepage surface portions 212a, 212b of the holders 210 due to the liquid droplets. This improves the robustness of the ion guide 200. Moreover, the improvement in the robustness of the ion guide 200 allows the diameters of the holes H1 and H2 (see FIG. 1) to be enlarged and thus increases the amount of ions to be introduced. Hence, the analytical sensitivity of the mass spectrometer 1 (see FIG. 1) can be improved.

[0040] The ion guide 200 according to the present embodiment can be disposed in another vacuum chamber such as the vacuum chamber V2 besides the vacuum chamber V1 shown in FIG. 1.

[0041] Next, the other embodiments and modifications of the ion guide 200 of the present embodiment will be described with reference to FIGS. 10 to 23.[Second Embodiment] (Cylindrical Rod Electrodes 20a and 8-Pole Ion Guide 200a)

[0042] Next, a second embodiment will be described with reference to FIG. 10. FIG. 10 is a diagram showing an ion guide 200a according to the second embodiment. FIG. 10 describes only differences from the ion guide 200 shown in FIGS. 2 to 9 for simplicity. FIG. 10 shows only rod electrodes 20a for simplicity. A drawing Z21 on the left of FIG. 10 is a diagram as viewed from the inlet direction of ions. A drawing Z22 on the center of FIG. 10 is a diagram as viewed from a side of the ion guide 200a. The drawing Z22 on the center of FIG. 10 shows only rod electrodes 20a-1 and 20a-5 for simplicity. A drawing Z23 on the right of FIG. 10 is a diagram as viewed from the ion outlet side. FIG. 10 shows the ion guide 200a in which eight (8-pole) cylindrical rod electrodes 20a, each of which has a recessed arc-shaped cut-out portion 21, are arranged in a circle about a center C. The structure of each individual rod electrode 20a is the same as the rod electrode 20 shown in the first embodiment. In the ion guide 200a shown in FIG. 10 as well, a cut-out portion 21 of a certain one of the rod electrodes 20a and a protruding portion 26 of another one of the rod electrodes 20a are fitted to each other without contact. The ion guide 200a shown in FIG. 10 is different from the configuration of the ion guide 200 shown in FIGS. 2 to 9 in that the ion guide 200a includes eight cylindrical rod electrodes 20a-1 to 20a-8 (8-pole). The basic effects of the ion guide 200a shown in FIG. 10 are the same as the examples shown in FIGS. 2 to 9, while the ion convergence efficiency tends to be higher in eight poles than in twelve poles.[Third Embodiment] (Cylindrical Rod Electrodes 20b and 6-pole Ion Guide 200b)

[0043] Next, a third embodiment will be described with reference to FIG. 11. FIG. 11 is a diagram showing an ion guide 200b according to the third embodiment. FIG. 11 describes only differences from the ion guide 200 shown in FIGS. 2 to 9 for simplicity. FIG. 11 shows only rod electrodes 20b for simplicity. A drawing Z31 on the left of FIG. 11 is a diagram as viewed from the ion inlet side. A drawing Z32 on the center of FIG. 11 is a diagram as viewed from a side of the ion guide 200b. Note that the drawing Z32 on the center of FIG. 11 shows only the rod electrodes 20b-1 and 20b-4 for simplicity. A drawing Z33 on the right of FIG. 11 is a diagram as viewed from the ion outlet side. FIG. 11 shows the ion guide 200b in which six (6-pole) cylindrical rod electrodes 20b, each of which has a recessed arc-shaped cut-out portion 21, are arranged in a circle about a center C. The structure of each individual rod electrode 20b is the same as the rod electrode 20 shown in the first embodiment. In the ion guide 200b shown in FIG. 11 as well, a cut-out portion 21 of a certain one of the rod electrodes 20b and a protruding portion 26 of another one of the rod electrodes 20b are fitted to each other without contact. The ion guide 200b shown in FIG. 11 is different from the ion guide 200 shown in FIGS. 2 to 9 in that the ion guide 200b includes six cylindrical rod electrodes 20b-1 to 20b-6 (6-pole). The basic effects of the ion guide 200b are the same as that of the ion guide 200 shown in FIGS. 2 to 9 and the ion guide 200a shown in FIG. 10, while the ion convergence efficiency tends to be higher in six poles than in eight poles.

[0044] Next, modifications of the first embodiment (and the second and third embodiments) will be described with reference to FIGS. 12 to 17B.[First Modification] (Substantially Oval Cylindrical Rod Electrodes and 12-pole Ion Guide 200c)

[0045] Next, a first modification will be described with reference to FIG. 12, FIG. 13A, and FIG. 13B. FIG. 12 is a diagram showing an ion guide 200c of the first modification. FIG. 12 describes only differences from the ion guide 200 shown in FIGS. 2 to 9 for simplicity. FIG. 12 shows only the rod electrodes 20c for simplicity. A drawing Z41 on the left of FIG. 12 is a diagram as viewed in the inlet side direction of ions (the left side of FIG. 1). A drawing Z42 on the center of FIG. 12 is a diagram as viewed from a side of the ion guide 200c. Note that the drawing Z42 on the center of FIG. 12 shows only the rod electrodes 20c-1 and 20c-7 for simplicity. A drawing Z43 on the right of FIG. 12 is a diagram as viewed from the ion outlet side. In the ion guide 200c shown in FIG. 12, twelve substantially oval cylindrical rod electrodes 20c (20c-1 to 20c-12) (their sectional shapes are substantially oval) are arranged in a circle about a center C.

[0046] FIG. 13A and FIG. 13B are diagrams showing only one rod electrode 20c-1 among the rod electrodes 20c included in the ion guide 200c. FIG. 13A is a diagram of the rod electrode 20c-1 as viewed from the inlet side, and FIG. 13B is a diagram of the rod electrode 20c-1 as viewed from the outlet side. The rod electrode 20c of the first modification features that a recessed arc-shaped cut-out portion 21 is provided in the substantially oval cylindrical rod electrode 20c (the rod electrode 20c-1 in FIG. 13A and FIG. 13B). In addition, a protruding portion 26 is provided on a side surface of the rod electrode 20c, which is positioned opposite to a side surface provided with the cut-out portion 21. In FIG. 13A, a shape without the cut-out portion 21 is indicated by a dot-dashed line. The basic effects of the ion guide 200c according to the first modification are the same as that of the ion guide 200 shown in FIGS. 2 to 9.

[0047] Note that in FIG. 12, numerals of the cut-out portion 21 and the protruding portion 26 are omitted to avoid complication. As shown in FIG. 12, the cut-out portion 21 of a certain one of the rod electrodes 20c and the protruding portion 26 of another one of the rod electrodes 20c are fitted to each other without contact.[Second Modification] (12-pole Ion Guide 200d Having V-shaped Cut-out Portions 21)

[0048] Next, a second modification will be described with reference to FIG. 14, FIG. 15A, and FIG. 15B. FIG. 14 is a diagram showing an ion guide 200d of the second modification. FIG. 14 describes only differences from the ion guide 200 shown in FIGS. 2 to 9 for simplicity. FIG. 14 shows only rod electrodes 20d for simplicity. A drawing Z51 on the left of the FIG. 14 is a diagram as viewed from the ion inlet side. A drawing Z52 on the center of FIG. 14 is a diagram as viewed from a side of the ion guide 200d. Note that the diagram Z52 on the center of FIG. 14 shows only the rod electrodes 20d-1 and 20d-7 for simplicity. A drawing Z53 on the right of FIG. 14 is a diagram as viewed from the ion outlet side. FIG. 14 shows a configuration of a 12-pole ion guide 200d including the cylindrical rod electrodes 20d (20d-1 to 20d-12). FIG. 14 shows only the rod electrodes 20d for simplicity.

[0049] FIG. 15A and FIG. 15B are diagrams showing only one rod electrode 20d-1 among the rod electrodes 20d included in the ion guide 200d. FIG. 15A is a diagram of the rod electrode 20d-1 as viewed from the inlet side. FIG. 15B is a diagram of the rod electrode 20d-1 as viewed from the outlet side. As shown in FIG. 14, the rod electrodes 20d are arranged in a circle about a center C. The rod electrode 20d (the rod electrode 20d-1 in FIG. 15A and FIG. 15B) of the second modification shown in FIGS. 14 to 15B features that a recessed V-shaped cut-out portion 21 is provided in the cylindrical rod electrode 20d. In addition, a protruding portion 26 is provided on a side surface of the rod electrode 20d, which is positioned opposite to a side surface with the cut-out portion 21. In FIG. 14A, a shape without the cut-out portion 21 is indicated by a dot-dashed line. The basic effects of the ion guide 200d are the same as that of the ion guide 200 shown in FIGs. 2 to 9.

[0050] In FIG. 14, numerals of the cut-out portion 21 and the protruding portion 26 are omitted to avoid complication. As shown in FIG. 14, the cut-out portion 21 of a certain one of the rod electrodes 20d and the protruding portion 26 of another one of the rod electrodes 20d are fitted to each other without contact.[Third Modification] (12-pole Ion Guide 200e Having V-shaped Cut-out Portions 21 and Rectangular Columnar Rod Electrodes 20e)

[0051] Next, a third modification will be described with reference to FIG. 16, FIG. 17A, and FIG. 17B. FIG. 16 is a diagram showing an ion guide 200e of the third modification. FIG. 16 describes only differences from the ion guide 200 shown in FIGS. 2 to 9 for simplicity. FIG. 16 shows only rod electrodes 20e for simplicity. A drawing Z61 on the left of FIG. 16 is a diagram as viewed from the ion inlet side. A drawing Z62 on the center of FIG. 16 is a diagram of the ion guide 200e as viewed from a side thereof. Note that the drawing Z62 on the center of FIG. 16 shows only the rod electrodes 20e-1 and 20e-7 for simplicity. A drawing Z63 on the right of FIG. 16 is a diagram of the ion guide 200e as viewed from the ion outlet side. FIG. 16 shows the 12-pole ion guide 200e including twelve rectangular columnar rod electrodes 20e (20e-1 to 20e-12).

[0052] FIG. 17A and FIG. 17B are diagrams showing only one rod electrode 20e-1 among the rod electrodes 20e included in the ion guide 200e. FIG. 17A is a diagram of the rod electrode 20e-1 as viewed from the inlet side, and FIG. 17B is a diagram of the rod electrode 20e-1 as viewed from the outlet side. As shown in FIG. 16, the rod electrodes 20e are arranged in a circle about a center C. The rod electrode 20e (the rod electrode 20e-1 in FIG. 17A and FIG. 17B) of the third modification shown in FIGS. 16 to FIG. 17B features that a recessed V-shaped cut-out portion 21 is provided to each rod electrode 20e having a rectangular columnar shape. In addition, a protruding portion 26 is provided on a side surface of the rod electrode 20e, which is positioned opposite to a side surface with the cut-out portion 21. In FIG. 17A, a shape without the cut-out portion 21 is indicated by a dot-dashed line. The basic effects of the ion guide 200e are the same as that of the ion guide 200 shown in FIG. 2 to FIG. 9.

[0053] In FIG. 16, numerals of the cut-out portion 21 and the protruding portion 26 are omitted to avoid complication. As shown in FIG. 16, the cut-out portion 21 of a certain one of the rod electrodes 20e and the protruding portion 26 of another one of the rod electrodes 20e are fitted to each other without contact.[Fourth Embodiment] (Cut-out Portion 21 Provided from Middle of Rod Electrode.)

[0054] Next, a fourth embodiment will be described with reference to FIGS. 18 to 20. In the fourth embodiment, a configuration of a 4-pole ion guide 200f including cylindrical rod electrodes 20f will be described. The cylindrical rod electrodes 20f have a recessed arc-shaped cut-out portion 21 provided from a middle thereof in a longitudinal direction. FIG. 18 is a diagram showing the configuration of the ion guide 200f of the fourth embodiment. FIG. 18 describes only differences from the ion guide 200 shown in FIGS. 2 to 9 for simplicity. FIG. 18 shows only the rod electrodes 20f for simplicity. A drawing Z71 on the left of FIG. 18 is a diagram of the ion guide 200f as viewed from the ion inlet side. A drawing Z72 on the center of FIG. 18 is a diagram of the ion guide 200f as viewed from a side thereof. Note that the drawing Z72 on the center of FIG. 18 shows only the rod electrodes 20f-1 and 20f-3 for simplicity. A drawing Z73 on the right is a diagram of the ion guide 200f as viewed from the ion outlet side. FIG. 18 shows the configuration of the 4-pole ion guide 200f in which four cylindrical rod electrodes 20f (20f-1 to 20f-4) are arranged in a circle about a center C. As shown in FIG. 18, the ion guide 200f has the recessed arc-shaped cut-out portion 21 provided in the rod electrode 20f from the middle thereof in the longitudinal direction.

[0055] FIG. 19A and FIG. 19B are diagrams showing only one rod electrode 20f-1 among the rod electrodes 20f included in the ion guide 200f. FIG. 19A is a diagram of the rod electrode 20f-1 as viewed from the inlet side. FIG. 19B is a diagram of the rod electrode 20f-1 as viewed from the outlet side. The rod electrode 20f (the rod electrode 20f-1 in the examples shown in FIG. 19A and FIG. 19B) of the fourth embodiment features that the recessed arc-shaped cut-out portion 21 is provided in the rod electrode 20f from the middle thereof in the longitudinal direction. In addition, a protruding portion 26 is provided on a side surface of the rod electrode 20f, which is positioned opposite to a side surface provided with the cut-out portion 21.

[0056] FIG. 20 is a perspective view showing two rod electrodes 20f-3 and 20f-4 among the four rod electrodes 20f included in the ion guide 200f. In the example shown in FIG. 20, an inscribed circle radius gradually decreases from an inscribed circle 23f formed by the rod electrodes 20f on the inlet side to an inscribed circle 24f formed by the rod electrodes 20f on the outlet side as in the ion guide 200 shown in FIGS. 2 to 9. In the fourth embodiment, the cut-out portion 21 is provided from a starting point 25, which is provided in the middle of the rod electrode 20f in the longitudinal direction, toward the outlet side. That is, the cut-out portion 21 of the rod electrode 20f is provided from the middle of the rod electrode 20f toward the ion outlet side (in the direction to the inscribed circle 24f) in the longitudinal direction of the rod electrode 20f.

[0057] In FIG. 18, numerals of the cut-out portion 21 and the protruding portion 26 are omitted to avoid complication. As shown in FIGS. 18 to 20, the cut-out portion 21 of a certain one of the rod electrodes 20f and the protruding portion 26 of another one of the rod electrodes 20f are fitted to each other without contact.

[0058] In the rod electrode 20f, the holder 210 (see FIG. 7) is not placed on a portion where the cut-out portion 21 is not provided. Hence, in a portion where the cut-out portion 21 is not provided, contamination of the insulation creepage surface portions 212a, 212b does not occur.

[0059] The basic effects of the ion guide 200f are the same as that of the ion guide 200, while the ion convergence efficiency tends to be higher in four poles than in six poles of the third embodiment. In particular, the configuration, in which the number of rod electrodes 20f (the number of poles) is small, is capable of having a sufficient gap between the adjacent rod electrodes 20f even without the cut-out portion 21 on the inlet side. Hence, there is no problem even when the cut-out portion 21 is formed from the middle in the longitudinal direction of the rod electrode 20f like the fourth embodiment.

[0060] According to the fourth embodiment, the portions to be cut for the cut-out portions 21 can be reduced as compared with the ion guides 200 and 200a to 200e and thus improves a cost.[Fifth Embodiment] (Rod Electrodes 20g Placed in Parallel)

[0061] An ion guide 200g of a fifth embodiment will be described in detail with reference to FIG. 21. FIG. 21 is a diagram showing a configuration of a 12-pole ion guide 200g in which twelve cylindrical rod electrodes 20g (20g-1 to 20g-12) are arranged in parallel in a longitudinal direction. FIG. 21 describes only differences from the ion guide 200 for simplicity. In FIG. 21, a drawing Z81 on the left is a diagram of the ion guide 200g as viewed from the ion inlet side. A drawing Z82 on the center of FIG. 21 shows only the rod electrodes 20g-1 and 20g-7 for simplicity. The drawing Z82 on the center of FIG. 21 is a diagram of the ion guide 200g as viewed from a side thereof. A drawing Z83 on the right of FIG. 21 is a diagram of the ion guide 200g as viewed from the ion outlet side. In the ion guide 200g shown in FIG. 21, the cylindrical rod electrodes 20g-1 to 20g-12 each provided with a recessed arc-shaped cut-out portion 21 are arranged in parallel. Thus, the drawing Z81 on the left and the drawing Z83 on the right of FIG. 21 are simply reversed to each other relative to the Z axis. The rod electrodes 20g are arranged in a circle about a center C.

[0062] As shown in FIG. 21, a protruding portion 26 is provided on a side surface of the rod electrode 20g, which is positioned opposite to a side surface provided with the cut-out portion 21. The cut-out portion 21 of a certain one of the rod electrodes 20g and the protruding portion 26 of another one of the rod electrodes 20g are fitted to each other without contact.

[0063] The features of the ion guide 200g shown in the fifth embodiment are the same as that of the ion guide 200 in terms of the features shown in FIG. 6 and the features shown in FIG. 9. Note that the feature shown in FIG. 6 is that the dot-dashed line S, which connects the centers GC1 to GCn of the rod gaps GA1 to GAn at the same distances R1 to Rn from the center C, is not on a straight line. In addition, as shown in FIG. 9, the line GL is defined as a line connecting the center C and the center GC of the rod gap GA at a predetermined distance "R" from the center C of the ion guide 200g. The feature shown in FIG. 9 is that, near the line GL, the shapes of the rod electrodes 20g are asymmetrical with respect to the line GL.

[0064] FIG. 22 is a diagram showing an example of the ion guide 200g provided with holders 210c. A drawing Z91 on the left of FIG. 22 is a diagram of the ion guide 200g provided with the holders 210c as viewed from the inlet side. A drawing Z92 on the right of FIG. 22 is a side view of the ion guide 200g provided with the holders 210c. As shown in FIG. 22, the actual ion guide 200g may include the holders 210c made of an insulating material in order to hold the twelve rod electrodes 20g (20g-1 to 20g-12). In the fifth embodiment, since the rod electrodes 20g (20g-1 to 20g-12) are arranged in parallel with the X axis, the holders 210c on the inlet side and the outlet side may have the same shape as shown in FIG. 22.

[0065] The ion guide 200g has the same effects as the ion guide 200 shown in FIGS. 2 to 9. Since the rod electrodes 20g are not placed to be inclined, the ion guide 200g can be placed more simply and easily than the ion guides 200 and 200a to 200f.[Sixth Embodiment] (Ion Guide 200h in which Cut-out Portions 21 are Provided on Both Side Surfaces of Rod Electrode 20h)

[0066] FIG. 23 is a sectional view showing an ion guide 200h of the sixth embodiment. FIG. 23 describes only differences from the ion guide 200 for simplicity. The above embodiments show the configurations in which the cut-out portion 21 is provided on one of the rod electrodes 20 and 20a to 20g near the gap formed between the adjacent rod electrodes 20 and 20a to 20g. That is, in the above embodiments, the cut-out portion 21 is provided only on one side surface of the rod electrodes 20 and 20a to 20g. In contrast, the ion guide 200h shown in sixth embodiment includes rod electrodes 20h (20h-1 to 20h-12). The rod electrodes 20h are configured such that near a gap formed between the adjacent rod electrodes 20h, recessed arc-shaped cut-out portions 21 are provided on both side surfaces of the rod electrode 20h. The ion guide 200h includes twelve (12-pole), cylindrical rod electrodes 20h. In the sixth embodiment, the cut-out portions 21 are provided on both side surfaces of each rod electrode 20h included in the ion guide 200h. Note that the configuration in which the cut-out portions 21 are provided in both surfaces represents that the cut-out portion 21 and the protruding portion 26 are provided on one surface of the rod electrode 20h, while the cut-out portion 21 and the protruding portion 26 are also provided on the other surface of the rod electrode 20h.

[0067] The example in FIG. 23 shows the ion guide 200h in which twelve (12-pole) cylindrical rod electrodes 20h (20h-1 to 20h-12) are arranged in a circle about a center C. FIG. 23 is a sectional view of the ion guide 200h on the YZ-plane (see FIG. 1 and FIG. 5). As described above, the arc-shaped cut-out portion 21 is provided on the rod electrodes 20h located on both sides of the gap between the adjacent rod electrodes 20h near the gap between adjacent rod electrodes 20h. That is, in the ion guide 200h shown in FIG. 23, the cut-out portion 21 and the protruding portion 26 are provided on both side surfaces of the rod electrode 20h. The cut-out portion 21 of a certain one of the rod electrodes 20h and the protruding portion 26 of another one of the rod electrodes 20h are fitted to each other without contact.

[0068] For the ion guides 200 and 200a to 200h of the respective embodiments described above, the above-described effects can be achieved even with configurations obtained by combining the elements of features of the respective ion guides 200 and 200a to 200h.

[0069] Hereinafter, it is assumed that the ion guide 200 represents the ion guides 200 and 200 to 200h, and that the rod electrode 20 represents the rod electrodes 20 and 20a to 20h. There is a tendency that depending on the number of the rod electrodes 20 (the number of poles), different performances such as the ion intake efficiency (which is higher when the number of poles is larger) and the ion convergence efficiency (which is higher when the number of poles is smaller) may be shown. However, since the optimal configuration of the ion guide 200 may vary depending on the subject sample, the configuration of any number of poles is important. Note that the configuration of the ion guide 200 may have any configuration of any number of rods, other than four poles, six poles, eight poles, or twelve poles. However, the number of the rod electrodes 20 is limited only to an even number because voltages of opposite phases are applied to adjacent rod electrodes 20.

[0070] In addition, the implementation of the ion guide 200 including a plurality of rod electrodes 20 includes a form in which the holders 210 made of an insulating material and the rod electrodes 20 are screwed to each other, for example. Besides, fixing means such as bonding the holders 210 and the rod electrodes 20 can be used. Alternatively, members such as pins which determine the positional relation may be used between the holders 210 and the rod electrodes 20.

[0071] The rod electrode 20 may have a shape other than a cylindrical shape, a rectangular columnar shape, or a substantially oval shape shown in the embodiments (for example, a hexagonal columnar shape). In addition, for the machining of the cut-out portion 21, various methods can be used, such as a cutting process (including machining using a multi-axis machining tool), an electric discharge machining (including a wire-cut electric discharge machining), a casting, a three-dimensional printer, and a plastic molding (adding a metal layer on a surface).[Common Features]

[0072] FIG. 24 is a diagram showing common features of the embodiments described above (particularly, the cylindrical rod electrodes 20). In FIG. 24, the diameter of the rod electrode 20 (the maximum-diameter portion in the direction in which the cut-out portion 21 (see FIG. 3A, and FIG. 3B) is not provided) is defined as "D", and the distance between the centers of the adjacent rod electrodes 20 is defined as "P". As shown in FIG. 24, the feature of the ion guide 200 is in a relation of D>P. That is, since "D" is larger than "P", a portion where the rod electrodes 20 overlap each other (a shaded area DL) is generated as shown in FIG. 24. The present embodiment features that the cut-out portion 21 is formed in this overlapping portion (the shaded area DL) to provide the gap between the rod electrodes 20. This relational expression may be included across the entire length of the rod electrode 20, or may be included in part in the longitudinal direction as shown in FIGS. 18 to 20.[Summary of Effects]

[0073] Next, the effects in the ion guides 200 and 200a to 200h shown in FIGS. 2 to 23 will be summarized with reference to FIG. 25. In FIG. 25, the ion guide 200 is mainly referred to as a representative of the ion guides 200 and 200a to 200h. FIG. 25 is a partially enlarged view of the rod electrodes 20-1 and 20-2 among the rod electrodes 20 included in the ion guide 200. In the ion guide 200 of the present embodiment, the cut-out portion 21 of a certain one of the rod electrodes 20 and the protruding portion 26 of another one of the rod electrodes 20 are fitted to each other without contact. In the ion guide 200 having such a configuration, a configuration in which the contact portion 211a and the insulation creepage surface portion 212a are invisible from the center C can be achieved. An angle between straight lines L1 and L2 connecting respectively both ends of a range of the insulation creepage surface portion 212a and the center C is defined as "β". The obstruction (the rod electrode 20-1) is present within a range of "β". Therefore, the present embodiment features that the insulation creepage surface portion 212a is invisible from the center C.

[0074] In addition, as shown in FIG. 2, the rod electrode 20 are disposed to be inclined. This allows the insulation creepage surface portions 212a, 212b (see FIG. 8) not to be seen when the ion guide 200 is viewed from the inlet side. In the present embodiment, a configuration of the ion guide 200g in which the rod electrodes 20g are arranged in parallel as shown in FIG. 21 is also possible other than the configuration in which the rod electrodes 20 are arranged to be inclined as shown in FIG. 2.

[0075] In addition, even when the rod electrodes 20g are arranged in parallel like the ion guide 200g shown in FIG. 21, a configuration in which the insulation creepage surface portion 212a (FIG. 25) is invisible from the center C can be achieved as shown in FIG. 25. In other words, such a configuration allows the protruding portions 26 of the rod electrodes 20 to block liquid droplets to be discharged from the inside of the ion guide 200g to the outside. This makes the liquid droplets unlikely to reach the insulation creepage surface portion 212a. Thus, contamination of the insulation creepage surface portion 212a due to the liquid droplets can be suppressed. This improves the robustness of the ion guide 200g as well like the ion guide 200 and improves the long-term analytical performance and stability.[Comparative Examples]

[0076] Next, a comparative example of the present embodiment will be described with reference to FIGS. 26 to 29. FIG. 26 is a diagram showing a configuration of an ion guide 200j according to the comparative example. A drawing Z101 on the left of FIG. 26 is a diagram of the ion guide 200j as viewed from the ion inlet side, and a drawing Z102 on the right of FIG. 26 shows a sectional view of the ion guide 200j on the Z axis. FIG. 26 shows only rod electrodes 20j for simplicity. FIG. 26 shows the multipole (4-pole in FIG. 26) ion guide 200j including cylindrical rod electrodes 20j (20j-1 to 20j-4). FIG. 27 is a diagram showing a configuration of the ion guide 200j provided with a holder 210. A drawing Z111 on the left of FIG. 27 is a diagram of the ion guide 200j as viewed from the ion inlet side, and a drawing Z112 on the right of FIG. 27 shows a sectional view of the ion guide 200j on the Z axis.

[0077] In FIG. 26, high-frequency voltages of opposite phases need to be applied to the adjacent rod electrodes 20j. For this reason, it is often the case that the rod electrodes 20j are held by the holders 210 made of an insulating material as shown in FIG. 27. In the YZ-plane, a line SA is defined as a line connecting centers GC1 to GCn of rod gaps GA1 to GAn at the same distances "R1" to "Rn" (circles indicated by dashed lines of FIG. 26) from the center C of the ion guide 200j. The ion guide 200j having multiple poles as shown in FIG. 26 features that the line SA is on a straight line.

[0078] In addition, in the configuration of the ion guide 200j shown in FIG. 26, the rod electrodes 20j are arranged in parallel along the X axis direction. Therefore, the relation in which the line SA connecting the centers GC1 to GCn of the rod gaps GA1 to GAn is on a straight line becomes constant across the longitudinal direction of the rod electrodes 20j. In such a configuration, as shown in the drawing Z111 on the left of FIG. 27, the insulation creepage surface portion 212 of the holder 103 is visible through the rod gaps GA1 to GAn when the ion guide 200j is viewed from the inlet side. The ions generated in the ion source 100 (see FIG. 1) and the liquid droplets are introduced into the ion guide 200j. The ion guide 200j plays a role of discharging the liquid droplets, which would be a noise factor in analysis, from the rod gaps GA1 to GAn (see FIG. 26) and converging only the ions on near the center C by a multipole electric field. That is, the ion guide 200j plays a role of separating an air flow containing the liquid droplets and the ions.

[0079] Therefore, in the configuration in which the insulation creepage surface portion 212 of the holder 210 is visible through the rod gaps GA1 to GAn (see FIG. 26) as shown in FIG. 27, the insulation creepage surface portion 212 can be highly contaminated by the liquid droplets. When the insulation creepage surface portion 212 for insulating adjacent rod electrodes 20j is contaminated by the liquid droplets, the insulating performance generally deteriorates. Along with this, a voltage applicable to the rod electrodes 20j decreases. As a result, even when the same voltage as a voltage applied before the contamination is applied to the rod electrodes 20j, discharge can highly occur on the insulation creepage surface portion 212. Consequently, the analytical performance or stability may deteriorate.

[0080] FIG. 28 is a diagram showing a configuration of an ion guide 200k according to a comparative example. A drawing Z121 on the left of FIG. 28 is a diagram of the ion guide 200k as viewed from the ion inlet side, and a drawing Z122 on the right of FIG. 28 shows a sectional view of the ion guide 200k on the Z axis. FIG. 28 shows only rod electrodes 20k for simplicity. As shown in FIG. 28, the rod electrodes 20k included in the ion guide 200k have a rectangular columnar shape.

[0081] FIG. 29 is a diagram showing a configuration of the ion guide 200k provided with the holders 210. A drawing Z131 on the left of FIG. 29 is a diagram of the ion guide 200k as viewed from the ion inlet side, and the drawing Z132 on the right of FIG. 29 shows a sectional view of the ion guide 200k on the Z axis. Note that in FIG. 28 and FIG. 29, the same configurations as those in FIG. 26 and FIG. 27 are denoted by the same numerals, and descriptions thereof are omitted. Even in the ion guide 200k including the rod electrodes 20k (20k-1 to 20k-4) having a rectangular columnar shape as shown in FIG. 28 and FIG. 29, the features and problems are the same as those of the ion guide 200j shown in FIG. 26 and FIG. 27.

[0082] For improving the sensitivity of the mass spectrometer 1, there are technologies of improving the ion intake efficiency by increasing the number of rod electrodes 20j, 20k (the number of poles) as in Non-Patent Literature 1 and Patent Literature 1. In these technologies, the rod electrodes 20j and 20k are arranged obliquely (to be inclined) along a longitudinal direction of the rod electrodes 20j, 20k. That is, the internal space of the ion guide 200k is gradually narrowed toward the outlet side. This improves the convergence efficiency of the ions. However, even these technologies are employed, they have the same configuration in which the line SA connecting the centers GC1 to GCn of the rod gaps GA1 to GAn shown in FIG. 26 and FIG. 28 is on a straight line, which has the problem as described above. Therefore, it is considered that the problem of contamination of the holder 210 cannot be solved. In addition, for improving the sensitivity, the diameter of the hole H2 (see FIG. 1) of the introduction electrode 122 (see FIG. 1) can be enlarged to increase the amount of the ions themselves to be introduced from the atmosphere. This causes the amount of the liquid droplets to be introduced to the ion guide 200j and 200k to further increase. Hence, the problem of contamination of the holders 210 may become further significant.

[0083] As described above, the ion guides 200 and 200a to 200h shown in the present embodiment prevents the holders 210 (the insulation creepage surface portions 212a and 212b) from contamination.

[0084] The present invention is not limited to the above-described embodiments, and encompasses various modifications. For example, the embodiments are described in detail to facilitate understanding the present invention, and are not necessarily limited to those having all the configurations described above. In addition, the configuration of a certain embodiment can be partly replaced with the configuration of another embodiment, or the configuration of a certain embodiment can be combined with the configuration of the other embodiment. Furthermore, the configurations of the embodiments can be partly removed, partly replaced with other configurations, or partly incorporated with other configurations.

[0085] In addition, the above-described control device 600 and other devices may be achieved by replacing part of or all of their configurations with hardware such as integrated circuits designed. Further, each configuration and function described above may be replaced with software with which a processor such as CPU interprets and executes programs for implementing the respective functions. Information such as programs, tables, and files for implementing the functions can be stored in a storage device such as a memory and an SSD (Solid-State Drive), or in a storage medium such as an IC (Integrated Circuit) card, an SD (Secure Digital) card, and a DVD (Digital Versatile Disc), besides in a HD (Hard Disk).

[0086] In addition, in the present embodiments, only control lines and information lines assumed necessary for the explanation are shown, and not all control lines and information lines in a product are necessarily shown. It can be considered that almost all of the configurations are actually connected to one another.Reference Signs List

[0087] 1 mass spectrometer 20, 20a to 20h, 20-1 to 20-12, 20a-1 to 20a-8, 20b-1 to 20b-6, 20c-1 to 20c-12, 20e-1 to 20e-12, 20f-1 to 20f-4, 20h-1 to 20h-12, 20g-1 to 20g-12 rod electrode 21 cut-out portion (recess portion) 23 inscribed circle (inscribed circle formed by a rod electrodes on an inlet side) 23f inscribed circle 24 inscribed circle (inscribed circle formed by a rod electrodes on an outlet side) 24f inscribed circle 26 protruding portion 200, 200a to 200h ion guide 210, 210a to 210c holder 211a, 211b contact portion 212, 212a, 212b insulation creepage surface portion 300 ion transport device C center

Examples

first embodiment

[First Embodiment]

[0014]In a first embodiment, a 12-pole ion guide 200 is used for a mass spectrometer 1. The 12-pole ion guide 200 includes twelve rod electrodes 20 (see FIG. 2) each provided with a cut-out portion 21 which is a recess portion having a recessed arc shape.

[Mass Spectrometry Device 1]

[0015]FIG. 1 is a diagram showing a configuration of the mass spectrometer 1 used in the first embodiment. The mass spectrometer 1 mainly includes an ion source 100, an ion guide 200, an ion transport device 300, and a mass spectrometry unit 400. The ion guide 200, the ion transport device 300, and the mass spectrometry unit 400 are provided inside a vacuum container 130. Note that in FIG. 1, dashed lines indicate control lines for voltage, and dot-dashed lines indicate control lines through which information is transmitted.

[0016]The ion source 100 mainly includes an ion generation device 110 and an ion source chamber 120. For the ion source 100, any of various ionization systems such as...

second embodiment

[Second Embodiment] (Cylindrical Rod Electrodes 20a and 8-Pole Ion Guide 200a)

[0042]Next, a second embodiment will be described with reference to FIG. 10. FIG. 10 is a diagram showing an ion guide 200a according to the second embodiment. FIG. 10 describes only differences from the ion guide 200 shown in FIGS. 2 to 9 for simplicity. FIG. 10 shows only rod electrodes 20a for simplicity. A drawing Z21 on the left of FIG. 10 is a diagram as viewed from the inlet direction of ions. A drawing Z22 on the center of FIG. 10 is a diagram as viewed from a side of the ion guide 200a. The drawing Z22 on the center of FIG. 10 shows only rod electrodes 20a-1 and 20a-5 for simplicity. A drawing Z23 on the right of FIG. 10 is a diagram as viewed from the ion outlet side. FIG. 10 shows the ion guide 200a in which eight (8-pole) cylindrical rod electrodes 20a, each of which has a recessed arc-shaped cut-out portion 21, are arranged in a circle about a center C. The structure of each individual rod ele...

third embodiment

[Third Embodiment] (Cylindrical Rod Electrodes 20b and 6-pole Ion Guide 200b)

[0043]Next, a third embodiment will be described with reference to FIG. 11. FIG. 11 is a diagram showing an ion guide 200b according to the third embodiment. FIG. 11 describes only differences from the ion guide 200 shown in FIGS. 2 to 9 for simplicity. FIG. 11 shows only rod electrodes 20b for simplicity. A drawing Z31 on the left of FIG. 11 is a diagram as viewed from the ion inlet side. A drawing Z32 on the center of FIG. 11 is a diagram as viewed from a side of the ion guide 200b. Note that the drawing Z32 on the center of FIG. 11 shows only the rod electrodes 20b-1 and 20b-4 for simplicity. A drawing Z33 on the right of FIG. 11 is a diagram as viewed from the ion outlet side. FIG. 11 shows the ion guide 200b in which six (6-pole) cylindrical rod electrodes 20b, each of which has a recessed arc-shaped cut-out portion 21, are arranged in a circle about a center C. The structure of each individual rod ele...

TECHNICAL FIELD

[0001] The present invention relates to a technology of an ion guide and a mass spectrometer.BACKGROUND ART

[0002] In a mass spectrometer, ions generated in an ion source are transported to a mass spectrometry unit via an ion transport unit. A mass spectrometer using an atmospheric-pressure ionization method is generally configured as a device of a differential exhaust system in which a vacuum chamber is segmented into a plurality of spaces in order to transport ions generated under an atmospheric pressure to a mass spectrometry unit in vacuum. In this case, it is often the case that the ion transport unit is at the preceding stage of the mass spectrometer and is disposed in the differential exhaust chamber which has low vacuum level and high pressure. In order to achieve a high sensitivity of a mass spectrometry device, the ion transport unit is demanded to have a high ion intake efficiency and a high ion convergence efficiency.

[0003] A general ion transport unit uses an ion guide system which causes ions to converge by using a high-frequency electric field which is formed by applying a high-frequency voltage. Ion guides employ an ion funnel system in which ring-shaped electrodes are stacked in an ion transport direction, a multipole ion guide system configured with a plurality of rod electrodes, and other systems.CITATION LIST Patent Literature

[0004] Patent Literature 1: US patent No. 10475633Non-Patent Literature

[0005] Non-Patent Literature 1: "Conical octopole ion guide: Design, focusing, and its application to the deposition of low energetic clusters", REVIEW OF SCIENTIFIC INSTRUMENTS, 77, 013302, 2006SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED

[0006] A multipole ion guide (hereinafter, referred to as an ion guide) is supported in a vacuum chamber by a holder made of an insulating material. Although liquid droplets are introduced into the ion guide besides ions, it is desirable that the liquid droplets be discharged from the ion guide. At this time, although the liquid droplets are discharged outside from a gap between rod electrodes included in the ion guide, some liquid droplets adhere to the inner side of the holder, causing the inner side of the holder to be contaminated. This contamination may highly cause the voltage applicable to the rod electrodes to decrease, or an electric discharge to occur inside the holder due to the adhered liquid droplets even when the same voltage as the voltage applied before the contamination is applied to the rod electrodes. This may result in deteriorating analytical performance or stability of the mass spectrometer.

[0007] Patent Literature 1 and Non-Patent Literature 1 state that the ion intake efficiency is improved by increasing the number of rod electrodes (the number of poles). In addition, Patent Literature 1 and Non-Patent Literature 1 state that the internal space of the ion guide is gradually narrowed toward the ion outlet side by arranging the rod electrodes obliquely along a longitudinal direction of the rod electrodes. In this way, the technologies described in Patent Literature 1 and Non-Patent Literature 1 improve the convergence efficiency of ions.

[0008] However, even these technologies do not describe a configuration of suppressing contamination of the inner side of a holder against the liquid droplets.

[0009] In view of such backgrounds, the present invention has been made, and an object of the present invention is to improve robustness of an ion guide.Solution to Problem

[0010] To solve the above-described problems, the present invention provides an ion guide comprising rod electrodes with a columnar shape which are arranged in a circle. The rod electrodes each include on a side surface thereof a recess portion and a protruding portion. A recess portion of a certain one of the rod electrodes and a protruding portion of another one of the rod electrodes are fitted to each other without contact. The other solutions are described in embodiments as appropriate.Advantageous Effects of Invention

[0011] According to the present invention, robustness of an ion guide can be improved.BRIEF DESCRIPTION OF DRAWINGS

[0012] [FIG. 1] FIG. 1 is a diagram showing a configuration of a mass spectrometer used in a first embodiment. [FIG. 2] FIG. 2 is a diagram showing a configuration of an ion guide including 12 cylindrical rod electrodes. [FIG. 3A] FIG. 3A is a diagram (No. 1) showing only one rod electrode among the rod electrodes included in the ion guide. [FIG. 3B] FIG. 3B is a diagram (No. 2) showing only one rod electrode among the rod electrodes included in the ion guide. [FIG. 4] FIG. 4 is a diagram showing a top view, a sectional view, and an arrow sectional view for one of the rod electrodes according to the present embodiment. [FIG. 5] FIG. 5 is a perspective view showing four rod electrodes among the twelve rod electrodes included in the ion guide. [FIG. 6] FIG. 6 is a diagram relating to a gap between adjacent rod electrodes. [FIG. 7] FIG. 7 is a diagram (No. 1) showing an example of the ion guide provided with holders. [FIG. 8] FIG. 8 is a diagram (No. 2) showing the example of the ion guide provided with the holders. [FIG. 9] FIG. 9 is a diagram showing another explanation relating to features of the ion guide according to the first embodiment. [FIG. 10] FIG. 10 is a diagram showing an ion guide according to a second embodiment. [FIG. 11] FIG. 11 is a diagram showing an ion guide of a third embodiment. [FIG. 12] FIG. 12 is a diagram showing an ion guide of a first modification. [FIG. 13A] FIG. 13A is a diagram (No. 3) showing only one rod electrode among rod electrodes included in the ion guide. [FIG. 13B] FIG. 13B is a diagram (No. 4) showing only one rod electrode among the rod electrodes included in the ion guide. [FIG. 14] FIG. 14 is a diagram showing an ion guide of a second modification. [FIG. 15A] FIG. 15A is a diagram (No. 5) showing only one rod electrode among rod electrodes included in the ion guide. [FIG. 15B] FIG. 15B is a diagram (No. 6) showing only one rod electrode among the rod electrodes included in the ion guide. [FIG. 16] FIG. 16 is a diagram showing an ion guide of a third modification. [FIG. 17A] FIG. 17A is a diagram (No. 7) showing only one rod electrode among rod electrodes included in the ion guide. [FIG. 17B] FIG. 17B is a diagram (No. 8) showing only one rod electrode among the rod electrodes included in the ion guide. [FIG. 18] FIG. 18 is a diagram showing a configuration of an ion guide of a fourth embodiment. [FIG. 19A] FIG. 19A is a diagram (No. 9) showing only one rod electrode among rod electrodes included in the ion guide. [FIG. 19B] FIG. 19B is a diagram (No. 10) showing only one rod electrode among the rod electrodes included in the ion guide. [FIG. 20] FIG. 20 is a perspective view showing two rod electrodes among four rod electrodes included in the ion guide. [FIG. 21] FIG. 21 is a diagram showing a configuration of a 12-pole ion guide of a fifth embodiment, in which twelve cylindrical rod electrodes are arranged in parallel. [FIG. 22] FIG. 22 is a diagram (No. 3) showing an example of the ion guide provided with holders. [FIG. 23] FIG. 23 is a sectional view showing an ion guide of a sixth embodiment. [FIG. 24] FIG. 24 is a diagram showing common features. [FIG. 25] FIG. 25 is a partially enlarged view of rod electrodes included in an ion guide. [FIG. 26] FIG. 26 is a diagram (No. 1) showing a configuration of an ion guide according to a comparative example. [FIG. 27] FIG. 27 is a diagram (No. 4) showing a configuration of the ion guide provided with holders. [FIG. 28] FIG. 28 is a diagram (No. 2) showing a configuration of an ion guide according to a comparative example. [FIG. 29] FIG. 29 is a diagram (No. 5) showing a configuration of the ion guide provided with holders. DESCRIPTION OF EMBODIMENTS

[0013] Next, configurations for carrying out the present invention (hereinafter, referred to as "embodiments") will be described in detail with reference to the drawings as appropriate.[First Embodiment]

[0014] In a first embodiment, a 12-pole ion guide 200 is used for a mass spectrometer 1. The 12-pole ion guide 200 includes twelve rod electrodes 20 (see FIG. 2) each provided with a cut-out portion 21 which is a recess portion having a recessed arc shape.[Mass Spectrometry Device 1]

[0015] FIG. 1 is a diagram showing a configuration of the mass spectrometer 1 used in the first embodiment. The mass spectrometer 1 mainly includes an ion source 100, an ion guide 200, an ion transport device 300, and a mass spectrometry unit 400. The ion guide 200, the ion transport device 300, and the mass spectrometry unit 400 are provided inside a vacuum container 130. Note that in FIG. 1, dashed lines indicate control lines for voltage, and dot-dashed lines indicate control lines through which information is transmitted.

[0016] The ion source 100 mainly includes an ion generation device 110 and an ion source chamber 120. For the ion source 100, any of various ionization systems such as electrospray ionization (ESI), atmospheric-pressure chemical ionization (APCI), and atmospheric-pressure photoionization (APPI) can be used. After generating ions from an introduced sample solution Q, the ion generation device 110 sprays the generated ions into the ion source chamber 120.

[0017] When the sample solution Q is ionized and the ions are sprayed, many liquid droplets are also sprayed besides the ions. Hence, removal of unnecessary liquid droplets is performed by discharging gas inside the ion source chamber 120 (symbol E). For example, in the case of the ESI system, in order to reduce unnecessary liquid droplets, electrostatic atomization and gas spray in the ion generation device 110 are used together. Thus, the vaporization of the sample solution Q is promoted, and the ionization efficiency is improved. Note that electrostatic atomization is performed by a power supply 500 applying high voltage to the ion generation device 110. A flow rate of the gas to be sprayed is around 0.5 to 10 L / min depending on a flow rate of the sample solution Q. In general, as the gas used in the ion generation device 110, an inert gas such as nitrogen or argon is used. The flow rate of the sample solution Q is generally in a range from around nL (nanoliter) / min order to mL (milliliter) / min order. In order to further improve the ionization efficiency, another system is also generally employed. The system involves heating the space inside the ion generation device 110 into which ions and liquid droplets are sprayed with a heating gas (around 800°C at most). The flow rate of the heating gas is around 0.5 to 50 L / min, and an inert gas such as nitrogen or argon is generally used.

[0018] In the configuration of FIG. 1, a counter electrode 121 having a hole H1 is disposed at a preceding stage of an introduction electrode 122. A gas G is introduced from a hole H11 into a space provided between the introduction electrode 122 and the counter electrode 121. Thus, the gas G is introduced between the introduction electrode 122 and the counter electrode 121. As a result, the introduction of noise components such as excessive liquid droplets sprayed by the ion source 100 into a hole H2 of the introduction electrode 122 can be suppressed. The flow rate of the gas G is around 0.5 to 50 L / min, and an inert gas such as nitrogen or argon is generally used. Although power supply 500 applies a voltage to both the counter electrode 121 and the introduction electrode 122, control lines for the voltage to be applied to the counter electrode 121 and the introduction electrode 122 are omitted in FIG. 1.

[0019] The ions having been introduced into the ion source chamber 120 are then introduced into the hole H2 provided in the introduction electrode 122 via the hole H1 provided in the counter electrode 121. At this time, the ions move from the ion generation device 110 to the ion source chamber 120, the hole H1, the hole H2 in this order, due to an electric field generated between the ion generation device 110 and the introduction electrode 122. In general, the diameters of the hole H1 provided in the counter electrode 121 and the hole H2 provided in the introduction electrode 122 are around several mm or less, and the voltage to be applied to the counter electrode 121 is around ± several kV at most. The polarities of the voltages to be applied to the counter electrode 121 and the introduction electrode 122 are the same.

[0020] Next, the ions are introduced into the mass spectrometry unit 400 from the hole H2 provided in the introduction electrode 122 via the ion guide 200 and the ion transport device 300, and are analyzed in the mass spectrometry unit 400. the power supply 500 applies different voltages to the ion source 100 (the ion generation device 110), the ion guide 200, the ion transport device 300, and the mass spectrometry unit 400. The timing in which a voltage is applied and its voltage value from the power supply 500 are controlled by a control device 600.[Ion Guide 200, Ion Transport Device 300]

[0021] As shown in FIG. 1, the inside of the vacuum container 130 can be partitioned into a plurality of vacuum chambers V1 to V3. The vacuum chamber V1 and the vacuum chamber V2 communicate with each other through a small-diameter hole H3. The vacuum chamber V2 and the vacuum chamber V3 communicate with each other through a small-diameter hole H4. The hole H2 provided in the introduction electrode 122 as well as the holes H3 and H4 are passages for the ions. In addition, a voltage may be applied to the members having the holes H3 and H4. When a voltage is applied to the members having the holes H3 and H4 (and the hole H2), housing portions such as the vacuum container 130 and the members having the holes H3 and H4 (and the hole H2) are insulated using insulators (not shown). The diameters of the holes H3 and H4 are generally around several mm or less.

[0022] In addition, the vacuum chambers V1 to V3 are exhausted by vacuum pumps P1 to P3. As a result of this, the vacuum chamber V1 is maintained at around several hundreds to several thousands Pa, the vacuum chamber V2 is maintained at around several Pa, and the vacuum chamber V3 is maintained at around 0.1 Pa or less, in general. The vacuum chamber V1 is provided with an ion guide 200 which allows ions to converge and penetrate therethrough. The vacuum chamber V2 is provided with an ion transport device 300 which allows ions to converge and penetrate therethrough like the ion guide 200. It is also possible to provide a multipole ion guide 200, an electrostatic lens, or an ion funnel in the ion transport device 300. The power supply 500 generates a high-frequency voltage, a direct-current voltage, an alternating-current voltage, and combinations thereof, which are applied to the ion guide 200 and the ion transport device 300. The number of the vacuum chambers V1 to V3 can be larger or smaller than the number shown in FIG. 1. For example, another vacuum chamber, which is maintained at around several hundreds Pa, can be provided between the vacuum chamber V1 and the vacuum chamber V2, and the vacuum chambers can include another ion transport device 300 different from the ion transport device 300 shown in FIG. 1.[Mass Spectrometry Unit 400]

[0023] The mass spectrometry unit 400 includes an ion separation device 401 and a detection device 402. The ion separation device 401, which separates or disassociates ions, can include an ion trap, a quadrupole filter electrode, a collision cell, and a time-of-flight mass spectrometer (TOF), or can include combinations thereof. The ions which have passed through the ion separation device 401 are detected by the detection device 402. The detection device 402 can include an electron multiplier tube and a multichannel plate (MCP). The ions detected by the detection device 402 are converted to an electrical signal, and information such as mass and intensity of the ions is analyzed by the control device 600. The control device 600 includes an input-output unit and a memory, which are not shown, for receiving an input of instructions from a user and controlling the voltage. The control device 600 further includes software necessary for operations of the power supply 500. The voltage supplied from the power supply 500 to the mass spectrometry unit 400 includes a high-frequency voltage, a direct-current voltage, an alternating-current voltage, and combinations thereof.

[0024] In the present embodiment, a longitudinal direction of the ion guide 200 is defined as an X axis. Axes, which are orthogonal to the X axis, pass a center C of the ion guide 200, and are orthogonal to each other, are defined as a Y axis and a Z axis. In particular, a direction from the ion source 100 to the mass spectrometry unit 400 is defined as the X axis, an upward direction of the mass spectrometer 1, which is orthogonal to the X axis, is defined as the Z axis, and a direction orthogonal to the X axis and the Z axis is defined as the Y axis.[Ion Guide 200] (12-pole, Cylindrical Rod Electrode 20)

[0025] Subsequently, the ion guide 200 according to the present embodiment will be described in detail with reference to FIGS. 2 to 9. FIG. 2 is a diagram showing a configuration of the ion guide 200 including twelve (12-pole) cylindrical rod electrodes 20 (20-1 to 20-12). Note that in the following description, the ion guide 200 including n pieces of rod electrodes 20 is referred to as an n-pole ion guide 200. FIG. 2 shows only the rod electrodes 20 for simplicity. In FIG. 2, a drawing Z1 on the left is a diagram as viewed from the ion inlet side. In the present embodiment, the ion inlet side (or simply, the inlet side) is the ion source 100 side shown in FIG. 1. A drawing Z2 in the center of FIG. 2 is a diagram of the ion guide 200 as viewed from its side. The drawing Z2 on the center of FIG. 2 only shows the rod electrodes 20-1 and 20-7 for simplicity. A drawing Z3 on the right of FIG. 2 is a diagram as viewed from the ion outlet side (the right side of FIG. 1). In the present embodiment, the ion outlet side (or simply, the outlet side) is the mass spectrometry unit 400 side shown in FIG. 1. As shown in FIG. 2, the plurality of rod electrodes 20 (20-1 to 20-12) each having a columnar shape are arranged in a circle (arranged annularly) about the center C of the ion guide 200. Each rod electrode 20 is arranged to have an angle "θ" to the longitudinal direction. The angle "θ" will be described later.

[0026] FIG. 3A and FIG. 3B are diagrams showing only one rod electrode 20 (20-1) among the rod electrodes 20 included in the ion guide 200 shown in FIG. 2. FIG. 3A is a diagram of the rod electrode 20 as viewed from the ion inlet side, and FIG. 3B is a diagram of the rod electrode 20 as viewed from the ion outlet side.

[0027] As shown in FIG. 3A and FIG. 3B, the rod electrode 20 according to the present embodiment features that the cut-out portion 21, which is a recess portion having a recessed arc shape, is provided on a side surface of the cylindrical rod electrode 20. In addition, a protruding portion 26 is provided on a side surface of the rod electrode 20, which is positioned opposite to the side surface provided with the cut-out portion 21. In this way, the cut-out portion 21 (the recess portion) and the protruding portion 26 are provided on the side surfaces of the rod electrode 20. Note that in FIG. 3A, a shape without the cut-out portion 21 is indicated by a dot-dashed line. The present embodiment features that the rod electrodes 20-1 to 20-12 each having the cut-out portion 21 are arranged to be inclined at the angle "θ" to the X axis as shown in FIG. 2. That is, the ion guide 200 of the present embodiment is configured to be reduced in diameter on the mass spectrometer 1 side (the outlet side). The angle "θ" is desirably around 10° or less.

[0028] In FIG. 2, numerals of the cut-out portion 21 and the protruding portion 26 are omitted to avoid complication. As shown in FIGS. 2 to 3B, a cut-out portion 21 of a certain one of the rod electrodes 20 and a protruding portion 26 of another one of the rod electrodes 20 are fitted to each other without contact.

[0029] FIG. 4 is a diagram showing a top view, a sectional view, and an arrow sectional view of one of the rod electrodes 20 according to the present embodiment. When the direction in which the cut-out portion 21 is provided is considered as a sheet-surface upper side of the rod electrode 20, a drawing Z4 on the upper part of FIG. 4 is a diagram of the rod electrode 20 as viewed from the upper side (top view) . A drawing Z5 on the lower right part of FIG. 4 is an A-A sectional view of the rod electrode 20. A drawing Z6 (a Barrow sectional view) on the lower left part of FIG. 4 is a diagram of the rod electrode 20 as viewed from an arrow B (a direction inclined at α°) of the ion guide 200. As shown in FIG. 4, the rod electrode 20 features that the arc recessed cut-out portion 21 with a radius "RC" is formed across an entire length of cylinder having a diameter (φ) "D" and a length "L". The cut-out portion 21 is formed to be inclined at a predetermined angle "α°" (provided to have a predetermined angle) to the longitudinal direction of the rod electrode 20. This allows the cut-out portion 21 to be shallowly provided on the inlet side and deeply provided on the outlet side. This varies the thickness of the rod electrode 20 at the inlet side and the outlet side. Even when the twelve rod electrodes 20 are arranged to be inclined at the angle "θ" to the X axis as shown in FIG. 2, the ion guide 200 can be assembled without causing the rod electrodes 20 to come into contact with one another. That is, even when the rod electrodes 20 are arranged to be inclined, it is possible to maintain the state in which the cut-out portion 21 of a certain one of the rod electrodes 20 and the protruding portion 26 of another one of the rod electrodes are fitted to each other without contact. It is desirable that "D" is around 10 mm or less, "L" is around 100 to 300 mm, and "α°" is around 5° or less.

[0030] As shown in FIG. 4, in the present embodiment, the cut-out portion 21 is formed with an arc having a constant radius "RC" across the entire length of the rod electrode 20. However, any shape is acceptable for the cut-out portion 21 as long as a certain degree of a gap can be ensured without causing the adjacent rod electrodes 20 to come into contact with each other, and the shape of the cut-out portion 21 does not need to have the same shape across the entire length, as described later. Forming the cut-out portion 21 involves production of a ridge portion 22, which can be chamfered or arc chamfered for the purpose of discharge prevention.

[0031] In FIG. 2, the gap between the adjacent rod electrodes 20 is desirably around 0.1 mm to 5 mm depending on the voltage to be applied. The width of the gap may be configured to be substantially the same from the inlet side to the outlet side. Alternatively, the dimensions of the gap may vary from the inlet side to the outlet side. The same applies to the embodiments and modifications shown below.

[0032] FIG. 5 is a perspective view showing 4 rod electrodes 20-6 to 20-9 among the twelve rod electrodes 20 included in the ion guide 200. The rod electrode 20 featured in FIGS. 2 to 4 achieves the ion guide 200 which has a radius of an inscribed circle gradually decreasing from an inscribed circle 23 formed by the rod electrodes 20 on the inlet side to an inscribed circle 24 formed by the rod electrodes 20 on the outlet side. That is, the rod electrode 20 is arranged to be inclined at the angle "θ" (see FIG. 2) such that the inscribed circle 23 formed by the rod electrodes 20 on the inlet side is larger than the inscribed circle 24 formed by the rod electrodes 20 on the outlet side. This allows the space inside the ion guide 200 to be gradually narrower toward the outlet side. By gradually narrowing the space inside the ion guide 200 in this way, a force of convergence of the multipole electric field can be gradually intensified toward the outlet side, thereby gradually converging the ions on near the center C. In addition, while analyzing, an air flow containing liquid droplets, which would become a noise factor, is exhausted from the gap of the rod electrodes 20 (that is, the liquid droplets are discharged from the gap of the rod electrodes 20). This improves the separation efficiency between the air flow containing the liquid droplets and the ions.

[0033] Next, the gap between the adjacent rod electrodes 20 will be described with reference to FIG. 6. FIG. 6 is a diagram relating to the gap between the adjacent rod electrodes 20. FIG. 6 shows only the rod electrodes 20-1 and 20-2 for simplicity. A dot-dashed line S is line connecting centers GC1 to GCn of rod gaps GA1 to Gan at the same distances "R1" to "Rn" from the center C of the ion guide 200 (arcs indicated by dashed lines in FIG. 6). The ion guide 200 according to the present embodiment features that the dot-dashed line S is not on a straight line. This relation may be provided across the entire length of each rod electrode 20, or may be provided in part of each rod electrode 20 in the longitudinal direction.

[0034] FIG. 7 and FIG. 8 are diagrams showing an example of the ion guide 200 provided with holders 210. A drawing Z11 on the left of FIG. 7 is a diagram of the ion guide 200 provided with the holders 210 as viewed from the inlet side. A drawing Z12 on the right of FIG. 7 is a side view of the ion guide 200 provided with the holders 210. FIG. 8 is an enlarged view of the rod electrodes 20-1 and 20-2. In FIG. 7 and FIG. 8, the same configurations as those in FIGS. 2 to 6 are denoted by the same numerals, and descriptions thereof are omitted. In the actual ion guide 200, as shown in FIG. 7, the twelve rod electrodes 20 (20-1 to 20-12) are held by the holders 210 (210a, 210b) made of an insulating material, or an insulating member. As shown in FIG. 7, each holder 210 (210a, 210b) has a shape in contact with the corresponding rod electrode 20, and are made of an insulating member. The holder 210 may have any shape as long as the holder 210 is capable of supporting the rod electrodes 20. As described above, in the ion guide 200 according to the present embodiment, the rod electrodes 20-1 to 20-12 are each arranged to be inclined to the X axis. For this reason, the holder 210a and the holder 210b made of an insulating material have different inner diameters. That is, the inner diameter of the holder 210a disposed on the inlet side is larger than the inner diameter of the holder 210b disposed on the outlet side. As described above, the rod electrodes 20-1 to 20-12 each having the cut-out portion 21 with a recessed shape (see FIG. 3A, FIG. 3B, or other drawings) are arranged to be inclined to the X axis. This arrangement, as shown in FIG. 8, achieves a configuration in which when the ion guide 200 is viewed from the inlet side, contact portions 211a, 211b (dashed lines in the drawing Z11 on the left of FIG. 7) are invisible. The contact portions 211a, 211b are portions where the holders 210 (210a, 210b) and the rod electrodes 20 are in contact with each other. The contact portion 211a is a portion where the holder 210a is in contact with the rod electrodes 20. Similarly, the contact portion 211b is a portion where the holder 210b is in contact with the rod electrodes 20.

[0035] Each rod electrode 20 is held by the holders 210, allowing the ion guide 200 to be placed in the vacuum chamber V1 (see FIG. 1) without causing each rod electrode 20 to be dispersed.

[0036] In particular, as shown in FIG. 8, insulation creepage surface portions 212a, 212b are invisible when the ion guide 200 is viewed from the inlet side. The insulation creepage surface portion 212a is a portion corresponding to the gap between the rod electrodes 20 in the contact portion 211a. Similarly, the insulation creepage surface portion 212b is a portion corresponding to the gap between the rod electrodes 20 in the contact portion 211b. The insulation creepage surface portions 212a, 212b are invisible when the ion guide 200 is viewed from the inlet side, thereby preventing contamination and improving robustness. In actual configuration, the contact portions 211a, 211b (and the insulation creepage surface portions 212a, 212b) have a width but are shown in a linear form in FIG. 8.

[0037] FIG. 9 is a diagram showing another explanation of the features of the ion guide 200 according to the first embodiment. FIG. 9 shows only the rod electrodes 20-1 to 20-2 for simplicity. A line GL is defined as a line connecting the center C and a center GC of a rod gap GA at a certain distance "R" (an arc indicated by a dashed line in FIG. 9) from the center C of the ion guide 200 (see FIG. 2). The present embodiment features that near the line GL, the shapes of the adjacent rod electrodes 20 (the rod electrodes 20-1 and 20-2 in the example shown in FIG. 9) are asymmetrical with respect to the line GL. This relation may be provided across the entire length of each rod electrode 20, or may be provided in part of each rod electrode 20 in the longitudinal direction.

[0038] As shown in the first embodiment, the cut-out portion 21 of a certain one of the rod electrodes 20 and the protruding portion 26 of another one of the rod electrodes 20 are fitted to each other without contact. In the ion guide 200 having such a configuration, the liquid droplets discharged from the inside of the ion guide 200 to the outside are blocked by the protruding portions 26 of the rod electrodes 20. This causes the liquid droplets unlikely to reach the insulation creepage surface portion 212a.

[0039] With the configuration of the ion guide 200 according to the present embodiment as described above, it is possible to suppress contamination of the insulation creepage surface portions 212a, 212b of the holders 210 due to the liquid droplets. This improves the robustness of the ion guide 200. Moreover, the improvement in the robustness of the ion guide 200 allows the diameters of the holes H1 and H2 (see FIG. 1) to be enlarged and thus increases the amount of ions to be introduced. Hence, the analytical sensitivity of the mass spectrometer 1 (see FIG. 1) can be improved.

[0040] The ion guide 200 according to the present embodiment can be disposed in another vacuum chamber such as the vacuum chamber V2 besides the vacuum chamber V1 shown in FIG. 1.

[0041] Next, the other embodiments and modifications of the ion guide 200 of the present embodiment will be described with reference to FIGS. 10 to 23.[Second Embodiment] (Cylindrical Rod Electrodes 20a and 8-Pole Ion Guide 200a)

[0042] Next, a second embodiment will be described with reference to FIG. 10. FIG. 10 is a diagram showing an ion guide 200a according to the second embodiment. FIG. 10 describes only differences from the ion guide 200 shown in FIGS. 2 to 9 for simplicity. FIG. 10 shows only rod electrodes 20a for simplicity. A drawing Z21 on the left of FIG. 10 is a diagram as viewed from the inlet direction of ions. A drawing Z22 on the center of FIG. 10 is a diagram as viewed from a side of the ion guide 200a. The drawing Z22 on the center of FIG. 10 shows only rod electrodes 20a-1 and 20a-5 for simplicity. A drawing Z23 on the right of FIG. 10 is a diagram as viewed from the ion outlet side. FIG. 10 shows the ion guide 200a in which eight (8-pole) cylindrical rod electrodes 20a, each of which has a recessed arc-shaped cut-out portion 21, are arranged in a circle about a center C. The structure of each individual rod electrode 20a is the same as the rod electrode 20 shown in the first embodiment. In the ion guide 200a shown in FIG. 10 as well, a cut-out portion 21 of a certain one of the rod electrodes 20a and a protruding portion 26 of another one of the rod electrodes 20a are fitted to each other without contact. The ion guide 200a shown in FIG. 10 is different from the configuration of the ion guide 200 shown in FIGS. 2 to 9 in that the ion guide 200a includes eight cylindrical rod electrodes 20a-1 to 20a-8 (8-pole). The basic effects of the ion guide 200a shown in FIG. 10 are the same as the examples shown in FIGS. 2 to 9, while the ion convergence efficiency tends to be higher in eight poles than in twelve poles.[Third Embodiment] (Cylindrical Rod Electrodes 20b and 6-pole Ion Guide 200b)

[0043] Next, a third embodiment will be described with reference to FIG. 11. FIG. 11 is a diagram showing an ion guide 200b according to the third embodiment. FIG. 11 describes only differences from the ion guide 200 shown in FIGS. 2 to 9 for simplicity. FIG. 11 shows only rod electrodes 20b for simplicity. A drawing Z31 on the left of FIG. 11 is a diagram as viewed from the ion inlet side. A drawing Z32 on the center of FIG. 11 is a diagram as viewed from a side of the ion guide 200b. Note that the drawing Z32 on the center of FIG. 11 shows only the rod electrodes 20b-1 and 20b-4 for simplicity. A drawing Z33 on the right of FIG. 11 is a diagram as viewed from the ion outlet side. FIG. 11 shows the ion guide 200b in which six (6-pole) cylindrical rod electrodes 20b, each of which has a recessed arc-shaped cut-out portion 21, are arranged in a circle about a center C. The structure of each individual rod electrode 20b is the same as the rod electrode 20 shown in the first embodiment. In the ion guide 200b shown in FIG. 11 as well, a cut-out portion 21 of a certain one of the rod electrodes 20b and a protruding portion 26 of another one of the rod electrodes 20b are fitted to each other without contact. The ion guide 200b shown in FIG. 11 is different from the ion guide 200 shown in FIGS. 2 to 9 in that the ion guide 200b includes six cylindrical rod electrodes 20b-1 to 20b-6 (6-pole). The basic effects of the ion guide 200b are the same as that of the ion guide 200 shown in FIGS. 2 to 9 and the ion guide 200a shown in FIG. 10, while the ion convergence efficiency tends to be higher in six poles than in eight poles.

[0044] Next, modifications of the first embodiment (and the second and third embodiments) will be described with reference to FIGS. 12 to 17B.[First Modification] (Substantially Oval Cylindrical Rod Electrodes and 12-pole Ion Guide 200c)

[0045] Next, a first modification will be described with reference to FIG. 12, FIG. 13A, and FIG. 13B. FIG. 12 is a diagram showing an ion guide 200c of the first modification. FIG. 12 describes only differences from the ion guide 200 shown in FIGS. 2 to 9 for simplicity. FIG. 12 shows only the rod electrodes 20c for simplicity. A drawing Z41 on the left of FIG. 12 is a diagram as viewed in the inlet side direction of ions (the left side of FIG. 1). A drawing Z42 on the center of FIG. 12 is a diagram as viewed from a side of the ion guide 200c. Note that the drawing Z42 on the center of FIG. 12 shows only the rod electrodes 20c-1 and 20c-7 for simplicity. A drawing Z43 on the right of FIG. 12 is a diagram as viewed from the ion outlet side. In the ion guide 200c shown in FIG. 12, twelve substantially oval cylindrical rod electrodes 20c (20c-1 to 20c-12) (their sectional shapes are substantially oval) are arranged in a circle about a center C.

[0046] FIG. 13A and FIG. 13B are diagrams showing only one rod electrode 20c-1 among the rod electrodes 20c included in the ion guide 200c. FIG. 13A is a diagram of the rod electrode 20c-1 as viewed from the inlet side, and FIG. 13B is a diagram of the rod electrode 20c-1 as viewed from the outlet side. The rod electrode 20c of the first modification features that a recessed arc-shaped cut-out portion 21 is provided in the substantially oval cylindrical rod electrode 20c (the rod electrode 20c-1 in FIG. 13A and FIG. 13B). In addition, a protruding portion 26 is provided on a side surface of the rod electrode 20c, which is positioned opposite to a side surface provided with the cut-out portion 21. In FIG. 13A, a shape without the cut-out portion 21 is indicated by a dot-dashed line. The basic effects of the ion guide 200c according to the first modification are the same as that of the ion guide 200 shown in FIGS. 2 to 9.

[0047] Note that in FIG. 12, numerals of the cut-out portion 21 and the protruding portion 26 are omitted to avoid complication. As shown in FIG. 12, the cut-out portion 21 of a certain one of the rod electrodes 20c and the protruding portion 26 of another one of the rod electrodes 20c are fitted to each other without contact.[Second Modification] (12-pole Ion Guide 200d Having V-shaped Cut-out Portions 21)

[0048] Next, a second modification will be described with reference to FIG. 14, FIG. 15A, and FIG. 15B. FIG. 14 is a diagram showing an ion guide 200d of the second modification. FIG. 14 describes only differences from the ion guide 200 shown in FIGS. 2 to 9 for simplicity. FIG. 14 shows only rod electrodes 20d for simplicity. A drawing Z51 on the left of the FIG. 14 is a diagram as viewed from the ion inlet side. A drawing Z52 on the center of FIG. 14 is a diagram as viewed from a side of the ion guide 200d. Note that the diagram Z52 on the center of FIG. 14 shows only the rod electrodes 20d-1 and 20d-7 for simplicity. A drawing Z53 on the right of FIG. 14 is a diagram as viewed from the ion outlet side. FIG. 14 shows a configuration of a 12-pole ion guide 200d including the cylindrical rod electrodes 20d (20d-1 to 20d-12). FIG. 14 shows only the rod electrodes 20d for simplicity.

[0049] FIG. 15A and FIG. 15B are diagrams showing only one rod electrode 20d-1 among the rod electrodes 20d included in the ion guide 200d. FIG. 15A is a diagram of the rod electrode 20d-1 as viewed from the inlet side. FIG. 15B is a diagram of the rod electrode 20d-1 as viewed from the outlet side. As shown in FIG. 14, the rod electrodes 20d are arranged in a circle about a center C. The rod electrode 20d (the rod electrode 20d-1 in FIG. 15A and FIG. 15B) of the second modification shown in FIGS. 14 to 15B features that a recessed V-shaped cut-out portion 21 is provided in the cylindrical rod electrode 20d. In addition, a protruding portion 26 is provided on a side surface of the rod electrode 20d, which is positioned opposite to a side surface with the cut-out portion 21. In FIG. 14A, a shape without the cut-out portion 21 is indicated by a dot-dashed line. The basic effects of the ion guide 200d are the same as that of the ion guide 200 shown in FIGs. 2 to 9.

[0050] In FIG. 14, numerals of the cut-out portion 21 and the protruding portion 26 are omitted to avoid complication. As shown in FIG. 14, the cut-out portion 21 of a certain one of the rod electrodes 20d and the protruding portion 26 of another one of the rod electrodes 20d are fitted to each other without contact.[Third Modification] (12-pole Ion Guide 200e Having V-shaped Cut-out Portions 21 and Rectangular Columnar Rod Electrodes 20e)

[0051] Next, a third modification will be described with reference to FIG. 16, FIG. 17A, and FIG. 17B. FIG. 16 is a diagram showing an ion guide 200e of the third modification. FIG. 16 describes only differences from the ion guide 200 shown in FIGS. 2 to 9 for simplicity. FIG. 16 shows only rod electrodes 20e for simplicity. A drawing Z61 on the left of FIG. 16 is a diagram as viewed from the ion inlet side. A drawing Z62 on the center of FIG. 16 is a diagram of the ion guide 200e as viewed from a side thereof. Note that the drawing Z62 on the center of FIG. 16 shows only the rod electrodes 20e-1 and 20e-7 for simplicity. A drawing Z63 on the right of FIG. 16 is a diagram of the ion guide 200e as viewed from the ion outlet side. FIG. 16 shows the 12-pole ion guide 200e including twelve rectangular columnar rod electrodes 20e (20e-1 to 20e-12).

[0052] FIG. 17A and FIG. 17B are diagrams showing only one rod electrode 20e-1 among the rod electrodes 20e included in the ion guide 200e. FIG. 17A is a diagram of the rod electrode 20e-1 as viewed from the inlet side, and FIG. 17B is a diagram of the rod electrode 20e-1 as viewed from the outlet side. As shown in FIG. 16, the rod electrodes 20e are arranged in a circle about a center C. The rod electrode 20e (the rod electrode 20e-1 in FIG. 17A and FIG. 17B) of the third modification shown in FIGS. 16 to FIG. 17B features that a recessed V-shaped cut-out portion 21 is provided to each rod electrode 20e having a rectangular columnar shape. In addition, a protruding portion 26 is provided on a side surface of the rod electrode 20e, which is positioned opposite to a side surface with the cut-out portion 21. In FIG. 17A, a shape without the cut-out portion 21 is indicated by a dot-dashed line. The basic effects of the ion guide 200e are the same as that of the ion guide 200 shown in FIG. 2 to FIG. 9.

[0053] In FIG. 16, numerals of the cut-out portion 21 and the protruding portion 26 are omitted to avoid complication. As shown in FIG. 16, the cut-out portion 21 of a certain one of the rod electrodes 20e and the protruding portion 26 of another one of the rod electrodes 20e are fitted to each other without contact.[Fourth Embodiment] (Cut-out Portion 21 Provided from Middle of Rod Electrode.)

[0054] Next, a fourth embodiment will be described with reference to FIGS. 18 to 20. In the fourth embodiment, a configuration of a 4-pole ion guide 200f including cylindrical rod electrodes 20f will be described. The cylindrical rod electrodes 20f have a recessed arc-shaped cut-out portion 21 provided from a middle thereof in a longitudinal direction. FIG. 18 is a diagram showing the configuration of the ion guide 200f of the fourth embodiment. FIG. 18 describes only differences from the ion guide 200 shown in FIGS. 2 to 9 for simplicity. FIG. 18 shows only the rod electrodes 20f for simplicity. A drawing Z71 on the left of FIG. 18 is a diagram of the ion guide 200f as viewed from the ion inlet side. A drawing Z72 on the center of FIG. 18 is a diagram of the ion guide 200f as viewed from a side thereof. Note that the drawing Z72 on the center of FIG. 18 shows only the rod electrodes 20f-1 and 20f-3 for simplicity. A drawing Z73 on the right is a diagram of the ion guide 200f as viewed from the ion outlet side. FIG. 18 shows the configuration of the 4-pole ion guide 200f in which four cylindrical rod electrodes 20f (20f-1 to 20f-4) are arranged in a circle about a center C. As shown in FIG. 18, the ion guide 200f has the recessed arc-shaped cut-out portion 21 provided in the rod electrode 20f from the middle thereof in the longitudinal direction.

[0055] FIG. 19A and FIG. 19B are diagrams showing only one rod electrode 20f-1 among the rod electrodes 20f included in the ion guide 200f. FIG. 19A is a diagram of the rod electrode 20f-1 as viewed from the inlet side. FIG. 19B is a diagram of the rod electrode 20f-1 as viewed from the outlet side. The rod electrode 20f (the rod electrode 20f-1 in the examples shown in FIG. 19A and FIG. 19B) of the fourth embodiment features that the recessed arc-shaped cut-out portion 21 is provided in the rod electrode 20f from the middle thereof in the longitudinal direction. In addition, a protruding portion 26 is provided on a side surface of the rod electrode 20f, which is positioned opposite to a side surface provided with the cut-out portion 21.

[0056] FIG. 20 is a perspective view showing two rod electrodes 20f-3 and 20f-4 among the four rod electrodes 20f included in the ion guide 200f. In the example shown in FIG. 20, an inscribed circle radius gradually decreases from an inscribed circle 23f formed by the rod electrodes 20f on the inlet side to an inscribed circle 24f formed by the rod electrodes 20f on the outlet side as in the ion guide 200 shown in FIGS. 2 to 9. In the fourth embodiment, the cut-out portion 21 is provided from a starting point 25, which is provided in the middle of the rod electrode 20f in the longitudinal direction, toward the outlet side. That is, the cut-out portion 21 of the rod electrode 20f is provided from the middle of the rod electrode 20f toward the ion outlet side (in the direction to the inscribed circle 24f) in the longitudinal direction of the rod electrode 20f.

[0057] In FIG. 18, numerals of the cut-out portion 21 and the protruding portion 26 are omitted to avoid complication. As shown in FIGS. 18 to 20, the cut-out portion 21 of a certain one of the rod electrodes 20f and the protruding portion 26 of another one of the rod electrodes 20f are fitted to each other without contact.

[0058] In the rod electrode 20f, the holder 210 (see FIG. 7) is not placed on a portion where the cut-out portion 21 is not provided. Hence, in a portion where the cut-out portion 21 is not provided, contamination of the insulation creepage surface portions 212a, 212b does not occur.

[0059] The basic effects of the ion guide 200f are the same as that of the ion guide 200, while the ion convergence efficiency tends to be higher in four poles than in six poles of the third embodiment. In particular, the configuration, in which the number of rod electrodes 20f (the number of poles) is small, is capable of having a sufficient gap between the adjacent rod electrodes 20f even without the cut-out portion 21 on the inlet side. Hence, there is no problem even when the cut-out portion 21 is formed from the middle in the longitudinal direction of the rod electrode 20f like the fourth embodiment.

[0060] According to the fourth embodiment, the portions to be cut for the cut-out portions 21 can be reduced as compared with the ion guides 200 and 200a to 200e and thus improves a cost.[Fifth Embodiment] (Rod Electrodes 20g Placed in Parallel)

[0061] An ion guide 200g of a fifth embodiment will be described in detail with reference to FIG. 21. FIG. 21 is a diagram showing a configuration of a 12-pole ion guide 200g in which twelve cylindrical rod electrodes 20g (20g-1 to 20g-12) are arranged in parallel in a longitudinal direction. FIG. 21 describes only differences from the ion guide 200 for simplicity. In FIG. 21, a drawing Z81 on the left is a diagram of the ion guide 200g as viewed from the ion inlet side. A drawing Z82 on the center of FIG. 21 shows only the rod electrodes 20g-1 and 20g-7 for simplicity. The drawing Z82 on the center of FIG. 21 is a diagram of the ion guide 200g as viewed from a side thereof. A drawing Z83 on the right of FIG. 21 is a diagram of the ion guide 200g as viewed from the ion outlet side. In the ion guide 200g shown in FIG. 21, the cylindrical rod electrodes 20g-1 to 20g-12 each provided with a recessed arc-shaped cut-out portion 21 are arranged in parallel. Thus, the drawing Z81 on the left and the drawing Z83 on the right of FIG. 21 are simply reversed to each other relative to the Z axis. The rod electrodes 20g are arranged in a circle about a center C.

[0062] As shown in FIG. 21, a protruding portion 26 is provided on a side surface of the rod electrode 20g, which is positioned opposite to a side surface provided with the cut-out portion 21. The cut-out portion 21 of a certain one of the rod electrodes 20g and the protruding portion 26 of another one of the rod electrodes 20g are fitted to each other without contact.

[0063] The features of the ion guide 200g shown in the fifth embodiment are the same as that of the ion guide 200 in terms of the features shown in FIG. 6 and the features shown in FIG. 9. Note that the feature shown in FIG. 6 is that the dot-dashed line S, which connects the centers GC1 to GCn of the rod gaps GA1 to GAn at the same distances R1 to Rn from the center C, is not on a straight line. In addition, as shown in FIG. 9, the line GL is defined as a line connecting the center C and the center GC of the rod gap GA at a predetermined distance "R" from the center C of the ion guide 200g. The feature shown in FIG. 9 is that, near the line GL, the shapes of the rod electrodes 20g are asymmetrical with respect to the line GL.

[0064] FIG. 22 is a diagram showing an example of the ion guide 200g provided with holders 210c. A drawing Z91 on the left of FIG. 22 is a diagram of the ion guide 200g provided with the holders 210c as viewed from the inlet side. A drawing Z92 on the right of FIG. 22 is a side view of the ion guide 200g provided with the holders 210c. As shown in FIG. 22, the actual ion guide 200g may include the holders 210c made of an insulating material in order to hold the twelve rod electrodes 20g (20g-1 to 20g-12). In the fifth embodiment, since the rod electrodes 20g (20g-1 to 20g-12) are arranged in parallel with the X axis, the holders 210c on the inlet side and the outlet side may have the same shape as shown in FIG. 22.

[0065] The ion guide 200g has the same effects as the ion guide 200 shown in FIGS. 2 to 9. Since the rod electrodes 20g are not placed to be inclined, the ion guide 200g can be placed more simply and easily than the ion guides 200 and 200a to 200f.[Sixth Embodiment] (Ion Guide 200h in which Cut-out Portions 21 are Provided on Both Side Surfaces of Rod Electrode 20h)

[0066] FIG. 23 is a sectional view showing an ion guide 200h of the sixth embodiment. FIG. 23 describes only differences from the ion guide 200 for simplicity. The above embodiments show the configurations in which the cut-out portion 21 is provided on one of the rod electrodes 20 and 20a to 20g near the gap formed between the adjacent rod electrodes 20 and 20a to 20g. That is, in the above embodiments, the cut-out portion 21 is provided only on one side surface of the rod electrodes 20 and 20a to 20g. In contrast, the ion guide 200h shown in sixth embodiment includes rod electrodes 20h (20h-1 to 20h-12). The rod electrodes 20h are configured such that near a gap formed between the adjacent rod electrodes 20h, recessed arc-shaped cut-out portions 21 are provided on both side surfaces of the rod electrode 20h. The ion guide 200h includes twelve (12-pole), cylindrical rod electrodes 20h. In the sixth embodiment, the cut-out portions 21 are provided on both side surfaces of each rod electrode 20h included in the ion guide 200h. Note that the configuration in which the cut-out portions 21 are provided in both surfaces represents that the cut-out portion 21 and the protruding portion 26 are provided on one surface of the rod electrode 20h, while the cut-out portion 21 and the protruding portion 26 are also provided on the other surface of the rod electrode 20h.

[0067] The example in FIG. 23 shows the ion guide 200h in which twelve (12-pole) cylindrical rod electrodes 20h (20h-1 to 20h-12) are arranged in a circle about a center C. FIG. 23 is a sectional view of the ion guide 200h on the YZ-plane (see FIG. 1 and FIG. 5). As described above, the arc-shaped cut-out portion 21 is provided on the rod electrodes 20h located on both sides of the gap between the adjacent rod electrodes 20h near the gap between adjacent rod electrodes 20h. That is, in the ion guide 200h shown in FIG. 23, the cut-out portion 21 and the protruding portion 26 are provided on both side surfaces of the rod electrode 20h. The cut-out portion 21 of a certain one of the rod electrodes 20h and the protruding portion 26 of another one of the rod electrodes 20h are fitted to each other without contact.

[0068] For the ion guides 200 and 200a to 200h of the respective embodiments described above, the above-described effects can be achieved even with configurations obtained by combining the elements of features of the respective ion guides 200 and 200a to 200h.

[0069] Hereinafter, it is assumed that the ion guide 200 represents the ion guides 200 and 200 to 200h, and that the rod electrode 20 represents the rod electrodes 20 and 20a to 20h. There is a tendency that depending on the number of the rod electrodes 20 (the number of poles), different performances such as the ion intake efficiency (which is higher when the number of poles is larger) and the ion convergence efficiency (which is higher when the number of poles is smaller) may be shown. However, since the optimal configuration of the ion guide 200 may vary depending on the subject sample, the configuration of any number of poles is important. Note that the configuration of the ion guide 200 may have any configuration of any number of rods, other than four poles, six poles, eight poles, or twelve poles. However, the number of the rod electrodes 20 is limited only to an even number because voltages of opposite phases are applied to adjacent rod electrodes 20.

[0070] In addition, the implementation of the ion guide 200 including a plurality of rod electrodes 20 includes a form in which the holders 210 made of an insulating material and the rod electrodes 20 are screwed to each other, for example. Besides, fixing means such as bonding the holders 210 and the rod electrodes 20 can be used. Alternatively, members such as pins which determine the positional relation may be used between the holders 210 and the rod electrodes 20.

[0071] The rod electrode 20 may have a shape other than a cylindrical shape, a rectangular columnar shape, or a substantially oval shape shown in the embodiments (for example, a hexagonal columnar shape). In addition, for the machining of the cut-out portion 21, various methods can be used, such as a cutting process (including machining using a multi-axis machining tool), an electric discharge machining (including a wire-cut electric discharge machining), a casting, a three-dimensional printer, and a plastic molding (adding a metal layer on a surface).[Common Features]

[0072] FIG. 24 is a diagram showing common features of the embodiments described above (particularly, the cylindrical rod electrodes 20). In FIG. 24, the diameter of the rod electrode 20 (the maximum-diameter portion in the direction in which the cut-out portion 21 (see FIG. 3A, and FIG. 3B) is not provided) is defined as "D", and the distance between the centers of the adjacent rod electrodes 20 is defined as "P". As shown in FIG. 24, the feature of the ion guide 200 is in a relation of D>P. That is, since "D" is larger than "P", a portion where the rod electrodes 20 overlap each other (a shaded area DL) is generated as shown in FIG. 24. The present embodiment features that the cut-out portion 21 is formed in this overlapping portion (the shaded area DL) to provide the gap between the rod electrodes 20. This relational expression may be included across the entire length of the rod electrode 20, or may be included in part in the longitudinal direction as shown in FIGS. 18 to 20.[Summary of Effects]

[0073] Next, the effects in the ion guides 200 and 200a to 200h shown in FIGS. 2 to 23 will be summarized with reference to FIG. 25. In FIG. 25, the ion guide 200 is mainly referred to as a representative of the ion guides 200 and 200a to 200h. FIG. 25 is a partially enlarged view of the rod electrodes 20-1 and 20-2 among the rod electrodes 20 included in the ion guide 200. In the ion guide 200 of the present embodiment, the cut-out portion 21 of a certain one of the rod electrodes 20 and the protruding portion 26 of another one of the rod electrodes 20 are fitted to each other without contact. In the ion guide 200 having such a configuration, a configuration in which the contact portion 211a and the insulation creepage surface portion 212a are invisible from the center C can be achieved. An angle between straight lines L1 and L2 connecting respectively both ends of a range of the insulation creepage surface portion 212a and the center C is defined as "β". The obstruction (the rod electrode 20-1) is present within a range of "β". Therefore, the present embodiment features that the insulation creepage surface portion 212a is invisible from the center C.

[0074] In addition, as shown in FIG. 2, the rod electrode 20 are disposed to be inclined. This allows the insulation creepage surface portions 212a, 212b (see FIG. 8) not to be seen when the ion guide 200 is viewed from the inlet side. In the present embodiment, a configuration of the ion guide 200g in which the rod electrodes 20g are arranged in parallel as shown in FIG. 21 is also possible other than the configuration in which the rod electrodes 20 are arranged to be inclined as shown in FIG. 2.

[0075] In addition, even when the rod electrodes 20g are arranged in parallel like the ion guide 200g shown in FIG. 21, a configuration in which the insulation creepage surface portion 212a (FIG. 25) is invisible from the center C can be achieved as shown in FIG. 25. In other words, such a configuration allows the protruding portions 26 of the rod electrodes 20 to block liquid droplets to be discharged from the inside of the ion guide 200g to the outside. This makes the liquid droplets unlikely to reach the insulation creepage surface portion 212a. Thus, contamination of the insulation creepage surface portion 212a due to the liquid droplets can be suppressed. This improves the robustness of the ion guide 200g as well like the ion guide 200 and improves the long-term analytical performance and stability.[Comparative Examples]

[0076] Next, a comparative example of the present embodiment will be described with reference to FIGS. 26 to 29. FIG. 26 is a diagram showing a configuration of an ion guide 200j according to the comparative example. A drawing Z101 on the left of FIG. 26 is a diagram of the ion guide 200j as viewed from the ion inlet side, and a drawing Z102 on the right of FIG. 26 shows a sectional view of the ion guide 200j on the Z axis. FIG. 26 shows only rod electrodes 20j for simplicity. FIG. 26 shows the multipole (4-pole in FIG. 26) ion guide 200j including cylindrical rod electrodes 20j (20j-1 to 20j-4). FIG. 27 is a diagram showing a configuration of the ion guide 200j provided with a holder 210. A drawing Z111 on the left of FIG. 27 is a diagram of the ion guide 200j as viewed from the ion inlet side, and a drawing Z112 on the right of FIG. 27 shows a sectional view of the ion guide 200j on the Z axis.

[0077] In FIG. 26, high-frequency voltages of opposite phases need to be applied to the adjacent rod electrodes 20j. For this reason, it is often the case that the rod electrodes 20j are held by the holders 210 made of an insulating material as shown in FIG. 27. In the YZ-plane, a line SA is defined as a line connecting centers GC1 to GCn of rod gaps GA1 to GAn at the same distances "R1" to "Rn" (circles indicated by dashed lines of FIG. 26) from the center C of the ion guide 200j. The ion guide 200j having multiple poles as shown in FIG. 26 features that the line SA is on a straight line.

[0078] In addition, in the configuration of the ion guide 200j shown in FIG. 26, the rod electrodes 20j are arranged in parallel along the X axis direction. Therefore, the relation in which the line SA connecting the centers GC1 to GCn of the rod gaps GA1 to GAn is on a straight line becomes constant across the longitudinal direction of the rod electrodes 20j. In such a configuration, as shown in the drawing Z111 on the left of FIG. 27, the insulation creepage surface portion 212 of the holder 103 is visible through the rod gaps GA1 to GAn when the ion guide 200j is viewed from the inlet side. The ions generated in the ion source 100 (see FIG. 1) and the liquid droplets are introduced into the ion guide 200j. The ion guide 200j plays a role of discharging the liquid droplets, which would be a noise factor in analysis, from the rod gaps GA1 to GAn (see FIG. 26) and converging only the ions on near the center C by a multipole electric field. That is, the ion guide 200j plays a role of separating an air flow containing the liquid droplets and the ions.

[0079] Therefore, in the configuration in which the insulation creepage surface portion 212 of the holder 210 is visible through the rod gaps GA1 to GAn (see FIG. 26) as shown in FIG. 27, the insulation creepage surface portion 212 can be highly contaminated by the liquid droplets. When the insulation creepage surface portion 212 for insulating adjacent rod electrodes 20j is contaminated by the liquid droplets, the insulating performance generally deteriorates. Along with this, a voltage applicable to the rod electrodes 20j decreases. As a result, even when the same voltage as a voltage applied before the contamination is applied to the rod electrodes 20j, discharge can highly occur on the insulation creepage surface portion 212. Consequently, the analytical performance or stability may deteriorate.

[0080] FIG. 28 is a diagram showing a configuration of an ion guide 200k according to a comparative example. A drawing Z121 on the left of FIG. 28 is a diagram of the ion guide 200k as viewed from the ion inlet side, and a drawing Z122 on the right of FIG. 28 shows a sectional view of the ion guide 200k on the Z axis. FIG. 28 shows only rod electrodes 20k for simplicity. As shown in FIG. 28, the rod electrodes 20k included in the ion guide 200k have a rectangular columnar shape.

[0081] FIG. 29 is a diagram showing a configuration of the ion guide 200k provided with the holders 210. A drawing Z131 on the left of FIG. 29 is a diagram of the ion guide 200k as viewed from the ion inlet side, and the drawing Z132 on the right of FIG. 29 shows a sectional view of the ion guide 200k on the Z axis. Note that in FIG. 28 and FIG. 29, the same configurations as those in FIG. 26 and FIG. 27 are denoted by the same numerals, and descriptions thereof are omitted. Even in the ion guide 200k including the rod electrodes 20k (20k-1 to 20k-4) having a rectangular columnar shape as shown in FIG. 28 and FIG. 29, the features and problems are the same as those of the ion guide 200j shown in FIG. 26 and FIG. 27.

[0082] For improving the sensitivity of the mass spectrometer 1, there are technologies of improving the ion intake efficiency by increasing the number of rod electrodes 20j, 20k (the number of poles) as in Non-Patent Literature 1 and Patent Literature 1. In these technologies, the rod electrodes 20j and 20k are arranged obliquely (to be inclined) along a longitudinal direction of the rod electrodes 20j, 20k. That is, the internal space of the ion guide 200k is gradually narrowed toward the outlet side. This improves the convergence efficiency of the ions. However, even these technologies are employed, they have the same configuration in which the line SA connecting the centers GC1 to GCn of the rod gaps GA1 to GAn shown in FIG. 26 and FIG. 28 is on a straight line, which has the problem as described above. Therefore, it is considered that the problem of contamination of the holder 210 cannot be solved. In addition, for improving the sensitivity, the diameter of the hole H2 (see FIG. 1) of the introduction electrode 122 (see FIG. 1) can be enlarged to increase the amount of the ions themselves to be introduced from the atmosphere. This causes the amount of the liquid droplets to be introduced to the ion guide 200j and 200k to further increase. Hence, the problem of contamination of the holders 210 may become further significant.

[0083] As described above, the ion guides 200 and 200a to 200h shown in the present embodiment prevents the holders 210 (the insulation creepage surface portions 212a and 212b) from contamination.

[0084] The present invention is not limited to the above-described embodiments, and encompasses various modifications. For example, the embodiments are described in detail to facilitate understanding the present invention, and are not necessarily limited to those having all the configurations described above. In addition, the configuration of a certain embodiment can be partly replaced with the configuration of another embodiment, or the configuration of a certain embodiment can be combined with the configuration of the other embodiment. Furthermore, the configurations of the embodiments can be partly removed, partly replaced with other configurations, or partly incorporated with other configurations.

[0085] In addition, the above-described control device 600 and other devices may be achieved by replacing part of or all of their configurations with hardware such as integrated circuits designed. Further, each configuration and function described above may be replaced with software with which a processor such as CPU interprets and executes programs for implementing the respective functions. Information such as programs, tables, and files for implementing the functions can be stored in a storage device such as a memory and an SSD (Solid-State Drive), or in a storage medium such as an IC (Integrated Circuit) card, an SD (Secure Digital) card, and a DVD (Digital Versatile Disc), besides in a HD (Hard Disk).

[0086] In addition, in the present embodiments, only control lines and information lines assumed necessary for the explanation are shown, and not all control lines and information lines in a product are necessarily shown. It can be considered that almost all of the configurations are actually connected to one another.Reference Signs List

[0087] 1 mass spectrometer 20, 20a to 20h, 20-1 to 20-12, 20a-1 to 20a-8, 20b-1 to 20b-6, 20c-1 to 20c-12, 20e-1 to 20e-12, 20f-1 to 20f-4, 20h-1 to 20h-12, 20g-1 to 20g-12 rod electrode 21 cut-out portion (recess portion) 23 inscribed circle (inscribed circle formed by a rod electrodes on an inlet side) 23f inscribed circle 24 inscribed circle (inscribed circle formed by a rod electrodes on an outlet side) 24f inscribed circle 26 protruding portion 200, 200a to 200h ion guide 210, 210a to 210c holder 211a, 211b contact portion 212, 212a, 212b insulation creepage surface portion 300 ion transport device C center

Examples

first embodiment

[First Embodiment]

[0014]In a first embodiment, a 12-pole ion guide 200 is used for a mass spectrometer 1. The 12-pole ion guide 200 includes twelve rod electrodes 20 (see FIG. 2) each provided with a cut-out portion 21 which is a recess portion having a recessed arc shape.

[Mass Spectrometry Device 1]

[0015]FIG. 1 is a diagram showing a configuration of the mass spectrometer 1 used in the first embodiment. The mass spectrometer 1 mainly includes an ion source 100, an ion guide 200, an ion transport device 300, and a mass spectrometry unit 400. The ion guide 200, the ion transport device 300, and the mass spectrometry unit 400 are provided inside a vacuum container 130. Note that in FIG. 1, dashed lines indicate control lines for voltage, and dot-dashed lines indicate control lines through which information is transmitted.

[0016]The ion source 100 mainly includes an ion generation device 110 and an ion source chamber 120. For the ion source 100, any of various ionization systems such as...

second embodiment

[Second Embodiment] (Cylindrical Rod Electrodes 20a and 8-Pole Ion Guide 200a)

[0042]Next, a second embodiment will be described with reference to FIG. 10. FIG. 10 is a diagram showing an ion guide 200a according to the second embodiment. FIG. 10 describes only differences from the ion guide 200 shown in FIGS. 2 to 9 for simplicity. FIG. 10 shows only rod electrodes 20a for simplicity. A drawing Z21 on the left of FIG. 10 is a diagram as viewed from the inlet direction of ions. A drawing Z22 on the center of FIG. 10 is a diagram as viewed from a side of the ion guide 200a. The drawing Z22 on the center of FIG. 10 shows only rod electrodes 20a-1 and 20a-5 for simplicity. A drawing Z23 on the right of FIG. 10 is a diagram as viewed from the ion outlet side. FIG. 10 shows the ion guide 200a in which eight (8-pole) cylindrical rod electrodes 20a, each of which has a recessed arc-shaped cut-out portion 21, are arranged in a circle about a center C. The structure of each individual rod ele...

third embodiment

[Third Embodiment] (Cylindrical Rod Electrodes 20b and 6-pole Ion Guide 200b)

[0043]Next, a third embodiment will be described with reference to FIG. 11. FIG. 11 is a diagram showing an ion guide 200b according to the third embodiment. FIG. 11 describes only differences from the ion guide 200 shown in FIGS. 2 to 9 for simplicity. FIG. 11 shows only rod electrodes 20b for simplicity. A drawing Z31 on the left of FIG. 11 is a diagram as viewed from the ion inlet side. A drawing Z32 on the center of FIG. 11 is a diagram as viewed from a side of the ion guide 200b. Note that the drawing Z32 on the center of FIG. 11 shows only the rod electrodes 20b-1 and 20b-4 for simplicity. A drawing Z33 on the right of FIG. 11 is a diagram as viewed from the ion outlet side. FIG. 11 shows the ion guide 200b in which six (6-pole) cylindrical rod electrodes 20b, each of which has a recessed arc-shaped cut-out portion 21, are arranged in a circle about a center C. The structure of each individual rod ele...

Claims

1. An ion guide comprising rod electrodes with a columnar shape which are arranged in a circle, wherein the rod electrodes each include on a side surface thereof a recess portion and a protruding portion, and a recess portion of a certain one of the rod electrodes and a protruding portion of another one of the rod electrodes are fitted to each other without contact.

2. The ion guide according to claim 1, wherein the rod electrodes are arranged such that an inscribed circle formed by the rod electrodes on an inlet side is larger than an inscribed circle formed by the rod electrodes on an outlet side, and the recess portion is provided at a predetermined angle to a longitudinal direction of each rod electrode.

3. The ion guide according to claim 2, wherein the recess portion is provided from a middle of each rod electrode toward the ion outlet side in the longitudinal direction of the rod electrode.

4. The ion guide according to claim 1, wherein the recess portion and the protruding portion are provided on opposite side surfaces of each rod electrode.

5. The ion guide according to claim 1, wherein the rod electrodes are held by a holder which has a shape in contact with each of the rod electrodes, and which is made of an insulating member.

6. The ion guide according to claim 1, wherein the number of the rod electrodes is twelve.

7. The ion guide according to claim 1, wherein the number of the rod electrodes is eight.

8. The ion guide according to claim 1, wherein the number of the rod electrodes is six.

9. The ion guide according to claim 1, wherein each rod electrode has a cylindrical shape.

10. The ion guide according to claim 1, wherein the recess portion has an arc shape.

11. A mass spectrometer comprising an ion guide including rod electrodes with a columnar shape which are arranged in a circle, wherein in the ion guide, the rod electrodes each include on a side surface thereof a recess portion and a protruding portion, and a recess portion of a certain one of the rod electrodes and a protruding portion of another one of the rod electrodes are fitted to each other without contact.

Images