Ion detectors and mass spectrometers

Abstract

The present invention provides an ion detector that can suppress variations in ion detection time for ions with the same mass-to-charge ratio, and a mass spectrometer that can improve the resolution of mass spectrometry. [Solution] The ion detector 1A includes an incident electrode 20 that includes an incident section 21 through which ions i pass; a conversion electrode 30 that faces the incident electrode 20 in the Z direction and emits electrons e in response to the incidence of ions i that have passed through the incident section 21; an exit electrode 40 that is located on the incident electrode 20 side in the Z direction relative to the conversion electrode 30 and on one side in the X direction intersecting the Z direction relative to the conversion electrode 30 and includes an exit section 41 through which electrons e emitted from the conversion electrode 30 pass; an ion control electrode 50 that is located on the incident electrode 20 side in the Z direction relative to the exit electrode 40 and on one side in the X direction relative to the conversion electrode 30; and an output unit 100 that outputs an electrical signal in response to the incidence of electrons e that have passed through the exit section 41.

Description

[Technical Field]

[0001] This invention relates to an ion detector and a mass spectrometer. [Background technology]

[0002] As an ion detector used in time-of-flight mass spectrometers, one is known that comprises a converter plate, which is a conversion electrode that generates electrons in response to the incidence of ions, and a microchannel plate that multiplies and emits the electrons generated by the converter plate (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 62-40148 [Overview of the project] [Problems that the invention aims to solve]

[0004] The ion detector described above further comprises an ion injection electrode for injecting ions into the ion detector and an ion emission electrode for ejecting electrons converted from ions by the conversion electrode. Since a potential is applied to each electrode, an electric field is formed in the space between the ion injection electrode and the conversion electrode. Such an electric field may be affected by the potential of the ion emission electrode. For example, in the ion detector described in Patent Document 1, the electric field formed in the space between the first mesh, which is the ion injection electrode, and the converter plate, which is the conversion electrode, may be affected by the potential of the ion emission electrode. The velocity of ions moving from the ion injection electrode to the conversion electrode may change due to the influence of the electric field. Even ions with the same mass-to-charge ratio may have variations in ion velocity due to the influence of the electric field, resulting in differences in the timing (time difference) of their conversion into electrons. In this case, there is a risk of variation in the time it takes for electrons generated at the conversion electrode due to ion incidence to reach the electron detection unit downstream of the microchannel plate (i.e., the time from when ions are incident to when electrons are detected in the ion detector). Furthermore, if there is variation in the time it takes for electrons to be detected after ions with the same mass-to-charge ratio are incident on an ion detector (hereinafter referred to as "ion detection time"), the resolution of the mass spectrometry may decrease.

[0005] The present invention aims to provide an ion detector that can suppress variations in ion detection time for ions with the same mass-to-charge ratio, and a mass spectrometer that can improve the resolution of mass spectrometry. [Means for solving the problem]

[0006] The ion detector of the present invention is an ion detector comprising: [1] an incident electrode including an incident portion through which ions pass; a conversion electrode facing the incident electrode in a first direction and emitting electrons in response to the incidence of ions that have passed through the incident portion; an exit electrode located on the incident electrode side in the first direction with respect to the conversion electrode and on one side in a second direction intersecting the first direction with respect to the conversion electrode, and including an exit portion through which the electrons emitted from the conversion electrode pass; an ion control electrode located on the incident electrode side in the first direction with respect to the exit electrode and on one side in the second direction with respect to the conversion electrode; and an output unit that outputs an electrical signal in response to the incidence of electrons that have passed through the exit portion.

[0007] In the above-described ion detector, ions passing through the incident portion of the incident electrode travel along a first direction and are incident on the conversion electrode, and electrons emitted from the conversion electrode pass through the output portion of the output electrode and are incident on the output portion. Here, for ions traveling from the incident portion to the conversion electrode, ions traveling in a region closer to the output electrode are more greatly affected by the potential of the output electrode. In the above-described ion detector, for example, by applying different potentials to the ion control electrode and the output electrode, the influence of the electric field due to the potential of the output electrode on the velocity of ions traveling from the incident portion to the conversion electrode can be canceled out by the influence of the electric field due to the potential of the ion control electrode. As a result, for ions with the same mass-to-charge ratio, the time it takes for ions traveling in a region close to the output electrode and ions traveling in a region far from the output electrode to reach the conversion electrode can be made uniform. Therefore, with the above-described ion detector, it is possible to suppress variations in ion detection time for ions with the same mass-to-charge ratio.

[0008] The ion detector of the present invention may also be [2] "the ion detector according to [1] above, wherein the ion control electrode is given a negative potential with respect to the conversion electrode, and the output electrode is given a positive potential with respect to the conversion electrode." With this ion detector, the influence of the electric field due to the potential of the output electrode on the velocity of ions traveling in a region close to the output electrode can be reliably canceled out by the influence of the electric field due to the potential of the ion control electrode.

[0009] The ion detector of the present invention may also be [3] "an ion detector according to [1] or [2] above, further comprising: a first counter electrode located on the other side in the second direction with respect to the conversion electrode and facing the output electrode in the second direction; and a second counter electrode located on the other side in the second direction with respect to the conversion electrode and facing the ion control electrode in the second direction." With this ion detector, an electric field due to the potential of the ion control electrode can be stably formed in the space corresponding to the ion control electrode, and an electric field due to the potential of the output electrode can be stably formed in the space corresponding to the output electrode.

[0010] The ion detector of the present invention may also be [4] "an ion detector according to [3] above, further comprising: a pair of first peripheral electrodes located on both sides in a third direction intersecting both the first and second directions with respect to the conversion electrode, and facing each other through the space between the output electrode and the first counter electrode; and a pair of second peripheral electrodes located on both sides in the third direction with respect to the conversion electrode, and facing each other through the space between the ion control electrode and the second counter electrode." According to this ion detector, an electric field due to the potential of the ion control electrode can be formed more stably in the space corresponding to the ion control electrode, and an electric field due to the potential of the output electrode can be formed more stably in the space corresponding to the output electrode.

[0011] The ion detector of the present invention may also be [5] "an ion detector according to any one of [1] to [4] above, further comprising a separation electrode positioned between the incident electrode and the conversion electrode so as to separate the space between the incident electrode and the conversion electrode into a space corresponding to the ion control electrode and a space corresponding to the output electrode, and including a passage portion for passing the ions through." According to this ion detector, an electric field due to the potential of the ion control electrode can be stably formed in the space corresponding to the ion control electrode, and an electric field due to the potential of the output electrode can be stably formed in the space corresponding to the output electrode.

[0012] The ion detector of the present invention may also be [6] "an ion detector according to any one of [1] to [5] above, wherein the output electrode has a first surface facing the other side in the second direction, the ion control electrode has a second surface facing the other side in the second direction, the position of the second surface in the second direction is substantially the same as the position of the first surface in the second direction, and the area of ​​the second surface is substantially the same as the area of ​​the first surface." With this ion detector, the potentials applied to the ion control electrode and the output electrode can be easily set in order to cancel out the effect of the electric field due to the potential of the output electrode with the effect of the electric field due to the potential of the ion control electrode on the velocity of ions traveling in a region close to the output electrode.

[0013] The ion detector of the present invention may also be [7] "an ion detector according to any one of [1] to [6] above, wherein the output unit includes an electron multiplier unit that multiplies the electrons that have passed through the emission unit, and an electron detection unit that detects electrons emitted from the electron multiplier unit." The ion detector can improve the detection sensitivity of ions.

[0014] The ion detector of the present invention may also be [8] "the ion detector according to [7] above, wherein the electron multiplication unit includes a dynode located on one side in the second direction with respect to the output unit, and a microchannel plate located on one side in the second direction with respect to the output unit and on the opposite side of the dynode from the incident electrode, and the dynode is arranged to face the incident surface of the output unit and the microchannel plate." With this ion detector, the flight distance of electrons from the conversion electrode to the incident surface of the microchannel plate via the dynode can be made uniform regardless of the incident position of the ion at the conversion electrode. Therefore, for ions with the same mass-to-charge ratio, electrons can be reliably multiplied while suppressing variations in the time from when the ion is incident on the conversion electrode until the electron reaches the incident surface of the microchannel plate.

[0015] The ion detector of the present invention may also be the ion detector described in [7] or [8] above, wherein the electron detection unit includes an avalanche diode. According to this ion detector, electrons can be reliably detected while increasing their number.

[0016] The mass spectrometer of the present invention is

[10] "a mass spectrometer comprising an ionization unit that generates ions, an ion separation unit that separates the ions generated in the ionization unit according to the mass-charge ratio of the ions, and an ion detector according to any one of [1] to [9] above that detects the ions separated in the ion separation unit." In the above mass spectrometer, the ion detector suppresses variations in ion detection time for ions with the same mass-charge ratio, thereby improving the resolution of the mass spectrometer. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide an ion detector that can suppress variations in ion detection time for ions with the same mass-to-charge ratio, and a mass spectrometer that can improve the resolution of mass spectrometry.

Brief Description of the Drawings

[0018] [Figure 1] It is a configuration diagram of a mass spectrometer of an example. [Figure 2] It is a configuration diagram of the ion detector shown in FIG. 1. [Figure 3] FIG. 3(a) is a cross-sectional view along the a-a line shown in FIG. 2, and FIG. 3(b) is a cross-sectional view along the b-b line shown in FIG. 2. [Figure 4] It is a diagram for explaining the control of the ion velocity in the ion detector shown in FIG. 1. [Figure 5] It is a diagram showing the electron orbit in the ion detector shown in FIG. 1. [Figure 6] It is a configuration diagram of the ion detector of the first modification example. [Figure 7] It is a configuration diagram of the ion detector of the second modification example. [Figure 8] It is a configuration diagram of the ion detector of the third modification example. [Figure 9] It is a configuration diagram of the ion detector of the fourth modification example.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, an example of the present invention will be described in detail with reference to the drawings. In each figure, the same or corresponding parts are denoted by the same reference numerals, and duplicate explanations are omitted. [Configuration of Mass Spectrometer]

[0020] As shown in Figure 1, the mass spectrometer 10 comprises an ionization unit 11, an ion separation unit 12, and an ion detector 1A. The mass spectrometer 10 is, for example, a time-of-flight mass spectrometer (TOF-MS). The ionization unit 11 generates ions i by ionizing molecules contained in the sample. For example, matrix-assisted laser desorption ionization (MALDI) and electrospray ionization (ESI) are used for ionizing molecules. The ion separation unit 12 separates the ions i generated in the ionization unit 11 according to their mass-to-charge ratio. In the ion separation unit 12, the ions i are accelerated by an electric field and then fly at a constant velocity from the ionization unit 11 towards the ion detector 1A. At this time, the time of flight of the ions i (i.e., the time it takes for the ions i to fly from the ionization unit 11 to the ion detector 1A) is determined according to the mass-to-charge ratio of the ions i, and therefore the ions i are separated according to their mass-to-charge ratio. The ion detector 1A detects the ions i separated in the ion separation unit 12. The mass spectrometer 10 can analyze the atoms and molecules contained in the sample (mass spectrometry) based on the detection timing of ion i. [Ion detector configuration]

[0021] As shown in Figures 2 and 3, the ion detector 1A comprises an ion conversion unit IC, an output unit 100, and a potential application unit 200. The ion conversion unit IC comprises an incident electrode 20, a conversion electrode 30, an output electrode 40, an ion control electrode 50, a first counter electrode 61, a second counter electrode 62, a pair of first lateral electrodes 71, a pair of second lateral electrodes 72, a separation electrode 80, and an electronic control electrode 90.

[0022] The incident electrode 20 has an ion incident surface 20a and an ion exit surface 20b. The ion incident surface 20a is a surface facing one side (upper side in Figure 2) in the Z direction (first direction). The ion exit surface 20b is a surface facing the other side (lower side in Figure 2) in the Z direction. For example, the ion incident surface 20a and the ion exit surface 20b are each surfaces perpendicular to the Z direction. The incident electrode 20 includes an incident section 21. Ions i that have flown from the ion separation unit 12 to the ion detector 1A pass through the incident section 21 and are incident into the ion detector 1A. For example, the incident electrode 20 is constructed by stretching a mesh on the inside of a frame along the ion incident surface 20a and the ion exit surface 20b. In that case, the inner part of the frame (i.e., the part with the mesh) corresponds to the incident section 21. The incident electrode 20 may also be constructed of a frame without a mesh stretched on the inside. In that case, the inner part of the frame (i.e., the part where the mesh is not stretched) corresponds to the injection section 21.

[0023] The conversion electrode 30 faces the incident electrode 20 in the Z direction. The conversion electrode 30 emits electrons e in response to the incidence of ions i that have passed through the incident portion 21. The conversion electrode 30 has an electron emission surface 30a. The electron emission surface 30a is a surface facing one side in the Z direction. For example, the electron emission surface 30a is a surface perpendicular to the Z direction. The electron emission surface 30a is the surface to which ions i are incident, and also the surface from which electrons e are emitted. The electron emission surface 30a faces the ion emission surface 20b of the incident electrode 20 in the Z direction.

[0024] The exit electrode 40 is located on the side of the input electrode 20 in the Z direction relative to the conversion electrode 30, and on one side of the X direction relative to the conversion electrode 30 (the side of the output unit 100, which will be described later, and is the right side in Figure 2). The X direction is perpendicular to the Z direction (the second direction intersecting the first direction). The exit electrode 40 has an electron input surface (first surface) 40a and an electron output surface 40b. The electron input surface 40a is the surface facing the other side in the X direction (the left side in Figure 2). The electron output surface 40b is the surface facing one side in the X direction. As an example, both the electron input surface 40a and the electron output surface 40b are surfaces perpendicular to the X direction. The exit electrode 40 includes an output section 41. Electrons e emitted from the conversion electrode 30 pass through the output section 41 and are incident on the output unit 100. As an example, the ejection electrode 40 is constructed by stretching a mesh on the inside of a frame along the electron incident surface 40a and the electron ejection surface 40b. In this case, the inner part of the frame (i.e., the part with the mesh) corresponds to the ejection section 41. Alternatively, the ejection electrode 40 may be constructed from a frame without a mesh stretched on the inside. In this case, the inner part of the frame (i.e., the part without the mesh) corresponds to the ejection section 41.

[0025] The ion control electrode 50 is located on the incident electrode 20 side in the Z direction relative to the output electrode 40 and on one side in the X direction relative to the conversion electrode 30 (the output unit 100 side, which will be described later, and is on the right side in Figure 2). In this example, the ion control electrode 50 is located between the incident electrode 20 and the output electrode 40 in the Z direction. The ion control electrode 50 is aligned with the output electrode 40 in the Z direction. The ion control electrode 50 has an inner surface (second surface) 50a. The inner surface 50a is the surface facing the other side in the X direction (the left side in Figure 2). For example, the inner surface 50a is the surface perpendicular to the X direction. The position of the inner surface 50a in the X direction is substantially the same as the position of the electron incident surface 40a of the output electrode 40 in the X direction. In other words, the position of the inner surface 50a in the X direction may perfectly coincide with the position of the electron incident surface 40a in the X direction, or it may be located within ±0.5 mm of the position of the electron incident surface 40a in the X direction. Furthermore, the area of ​​the inner surface 50a is substantially the same as the area of ​​the electron incident surface 40a. In other words, the area of ​​the inner surface 50a may be exactly equal to the area of ​​the electron incident surface 40a, or it may be within ±20% of the area of ​​the electron incident surface 40a.

[0026] The first counter electrode 61 is located on the other side of the conversion electrode 30 in the X direction (left side in Figure 2) and faces the exit electrode 40 in the X direction. The first counter electrode 61 has an inner surface 61a. The inner surface 61a is a surface facing one side in the X direction. For example, the inner surface 61a is a surface perpendicular to the X direction. The inner surface 61a faces the electron incident surface 40a of the exit electrode 40 in the X direction.

[0027] The second opposing electrode 62 is located on the other side in the X direction relative to the conversion electrode 30 and faces the ion control electrode 50 in the X direction. The second opposing electrode 62 has an inner surface 62a. The inner surface 62a is a surface facing one side in the X direction. For example, the inner surface 62a is a surface perpendicular to the X direction. The inner surface 62a faces the inner surface 50a of the ion control electrode 50 in the X direction.

[0028] The second counter electrode 62 is located between the first counter electrode 61 and the incident electrode 20 in the Z direction. The second counter electrode 62 is aligned with the first counter electrode 61 in the Z direction. The first counter electrode 61 and the second counter electrode 62 are formed separately, for example. In this case, a gap exists between the first counter electrode 61 and the second counter electrode 62 in the Z direction. In this example, a separation electrode 80 is placed in the gap between the first counter electrode 61 and the second counter electrode 62.

[0029] As shown in Figure 3(a), the pair of first lateral electrodes 71 are located on both sides of the conversion electrode 30 in the Y direction. The Y direction is perpendicular to both the Z and X directions (a third direction intersecting both the first and second directions). For example, one of the pair of first lateral electrodes 71 is located on one side of the conversion electrode 30 in the Y direction (the upper side in Figure 3(a)), and the other of the pair of first lateral electrodes 71 is located on the other side of the conversion electrode 30 in the Y direction (the lower side in Figure 3(a)). The pair of first lateral electrodes 71 face each other with a space S1 between the output electrode 40 and the first counter electrode 61. The space S1 is sandwiched between the pair of first lateral electrodes 71 in the Y direction and sandwiched between the output electrode 40 and the first counter electrode 61 in the X direction. The pair of first lateral electrodes 71 and the first counter electrode 61 are formed integrally, for example. In this case, there is no gap between each of the pair of first lateral electrodes 71 and the first opposing electrode 61. The pair of first lateral electrodes 71 and the first opposing electrode 61 may be formed continuously from one of the pair of first lateral electrodes 71 through the first opposing electrode 61 to the other of the pair of first lateral electrodes 71.

[0030] As shown in Figure 3(b), the pair of second lateral electrodes 72 are located on both sides of the conversion electrode 30 in the Y direction. For example, one of the pair of second lateral electrodes 72 is located on one side of the conversion electrode 30 in the Y direction (upper side in Figure 3(b)), and the other of the pair of second lateral electrodes 72 is located on the other side of the conversion electrode 30 in the Y direction (lower side in Figure 3(b)). The pair of second lateral electrodes 72 face each other with a space S2 between the ion control electrode 50 and the second opposing electrode 62. The space S2 is sandwiched between the pair of second lateral electrodes 72 in the Y direction and sandwiched between the ion control electrode 50 and the second opposing electrode 62 in the X direction. The pair of second lateral electrodes 72 and the second opposing electrode 62 are formed as a single unit, for example. In this case, there is no gap between each of the pair of second lateral electrodes 72 and the second opposing electrode 62. The pair of second lateral electrodes 72 and second opposing electrodes 62 may be formed continuously from one of the pair of second lateral electrodes 72 through the second opposing electrode 62 to the other of the pair of second lateral electrodes 72.

[0031] As shown in Figure 2, the separation electrode 80 is positioned between the incident electrode 20 and the conversion electrode 30 so as to separate the space between the incident electrode 20 and the conversion electrode 30 into a space S1 corresponding to the exit electrode 40 and a space S2 corresponding to the ion control electrode 50. In other words, the internal space of the ion conversion unit IC consists of space S1 and space S2 separated by the separation electrode 80. Space S1 corresponding to the exit electrode 40 is the same as space S1 between the exit electrode 40 and the first counter electrode 61. That is, space S1 is sandwiched between a pair of first lateral electrodes 71 in the Y direction, sandwiched between the exit electrode 40 and the first counter electrode 61 in the X direction, and further sandwiched between the conversion electrode 30 and the separation electrode 80 in the Z direction. Space S1 is a space that is closed on six sides by these electrodes. Similarly, space S2 corresponding to the ion control electrode 50 is the same as space S2 between the ion control electrode 50 and the second counter electrode 62. In other words, space S2 is sandwiched between a pair of second lateral electrodes 72 in the Y direction, between the ion control electrode 50 and the second counter electrode 62 in the X direction, and further sandwiched between the incident electrode 20 and the separation electrode 80 in the Z direction. Space S2 is a space enclosed on six sides by these electrodes.

[0032] The separation electrode 80 faces the incident electrode 20 on one side in the Z direction (upper side in Figure 2) and faces the conversion electrode 30 on the other side in the Z direction (lower side in Figure 2). The incident electrode 20, separation electrode 80, and conversion electrode 30 are arranged in this order in the Z direction. The separation electrode 80 has an ion incident surface 80a and an ion exit surface 80b. The ion incident surface 80a is a surface facing one side in the Z direction. The ion exit surface 80b is a surface facing the other side in the Z direction. For example, the ion incident surface 80a and the ion exit surface 80b are surfaces perpendicular to the Z direction. The ion incident surface 80a faces the ion exit surface 20b of the incident electrode 20 in the Z direction. The ion exit surface 80b faces the electron exit surface 30a of the conversion electrode 30 in the Z direction. The separation electrode 80 includes a passage section 81. Ions i that have passed through the inlet section 21 pass through the through section 81 and are incident on the conversion electrode 30. For example, the separation electrode 80 is constructed by stretching a mesh on the inside of a frame along the ion inlet surface 80a and the ion outlet surface 80b. In this case, the inside part of the frame (i.e., the part with the mesh) corresponds to the through section 81. The separation electrode 80 may also be constructed of a frame without a mesh stretched on the inside. In this case, the inside part of the frame (i.e., the part without the mesh) corresponds to the through section 81.

[0033] The electronic control electrode 90 is located on the incident electrode 20 side in the Z direction relative to the conversion electrode 30. The electronic control electrode 90 is located between the discharge section 41 and the conversion electrode 30 in the Z direction. The electronic control electrode 90 is in close proximity to the conversion electrode 30. In other words, the distance between the electronic control electrode 90 and the conversion electrode 30 (length in the Z direction) is smaller than the distance between the electronic control electrode 90 and the separation electrode 80. Furthermore, the distance between the electronic control electrode 90 and the conversion electrode 30 (length in the Z direction) is, for example, 5% or less of the distance between the conversion electrode 30 and the incident electrode 20. As an example, consider the case where the distance between the incident electrode 20 and the separation electrode 80 is 21.5 mm, and the distance between the separation electrode 80 and the conversion electrode 30 is 21 mm. In this case, the distance between the electronic control electrode 90 and the conversion electrode 30 is between 0.1 mm and 1 mm. The distance between the electronic control electrode 90 and the conversion electrode 30 is such that the electronic control electrode 90 is in close proximity to the conversion electrode 30 while ensuring sufficient dielectric strength between the two electrodes.

[0034] The electronic control electrode 90 faces the separation electrode 80 on one side in the Z direction (upper side in Figure 2) and faces the conversion electrode 30 on the other side in the Z direction (lower side in Figure 2). The separation electrode 80, the electronic control electrode 90, and the conversion electrode 30 are arranged in this order in the Z direction. The electronic control electrode 90 has an electron emission surface 90a and an electron incidence surface 90b. The electron emission surface 90a is a surface facing one side in the Z direction. The electron incidence surface 90b is a surface facing the other side in the Z direction. For example, the electron emission surface 90a and the electron incidence surface 90b are surfaces perpendicular to the Z direction. The electron emission surface 90a faces the ion emission surface 80b of the separation electrode 80 in the Z direction. The electron incidence surface 90b faces the electron emission surface 30a of the conversion electrode 30 in the Z direction.

[0035] The electronic control electrode 90 includes a passage section 91. The passage section 91 allows ions i that are incident from the incident electrode 20, pass through the separation electrode 80, and proceed to the conversion electrode 30 to pass through. At the same time, the passage section 91 also allows electrons e that proceed from the conversion electrode 30 to the output electrode 40 to pass through. After passing through the passage section 91, the electrons e proceed towards the output electrode 40. As an example, the electronic control electrode 90 is constructed by stretching a mesh on the inside of a frame along the electron output surface 90a and the electron incident surface 90b. In this case, the inside part of the frame (i.e., the part with the mesh) corresponds to the passage section 91. The electronic control electrode 90 may also be constructed of a frame without a mesh stretched on the inside. In this case, the inside part of the frame (i.e., the part without the mesh) corresponds to the passage section 91.

[0036] The electrical connection relationships of each electrode described above are as follows, for example: The ion control electrode 50 is electrically isolated from the discharge electrode 40. In this example, a gap exists between the ion control electrode 50 and the discharge electrode 40 in the Z direction. This gap enables electrical isolation between the ion control electrode 50 and the discharge electrode 40. The electronic control electrode 90 is electrically isolated from the conversion electrode 30 and the discharge electrode 40. In this example, a gap exists between the electronic control electrode 90 and the discharge electrode 40 in the X direction. This gap enables electrical isolation between the electronic control electrode 90 and the discharge electrode 40. Note that the electrical isolation between electrodes described above is not limited to electrical isolation by gaps, but may also be achieved through an insulating member.

[0037] The ion control electrode 50 is electrically isolated from the incident electrode 20, the separation electrode 80, and the pair of second lateral electrodes 72. There are gaps between the ion control electrode 50 and the incident electrode 20, between the ion control electrode 50 and the separation electrode 80, and between the ion control electrode 50 and the pair of second lateral electrodes 72, for example, in the X direction. The output electrode 40 is electrically isolated from the conversion electrode 30, the separation electrode 80, and the pair of first lateral electrodes 71. There are gaps between the output electrode 40 and the conversion electrode 30, between the output electrode 40 and the separation electrode 80, and between the output electrode 40 and the pair of first lateral electrodes 71, for example, in the X direction. The electronic control electrode 90 is electrically isolated from the first opposing electrode 61 and the pair of first lateral electrodes 71. There is a gap between the electronic control electrode 90 and the first opposing electrode 61, for example, in the X direction. A gap exists between the electronic control electrode 90 and the pair of first lateral electrodes 71, for example, in the Y direction. Note that the electrical isolation between the electrodes described above is not limited to electrical isolation through the gap, but may also be achieved through an insulating member.

[0038] The incident electrode 20, the conversion electrode 30, the first counter electrode 61, the second counter electrode 62, the separation electrode 80, the pair of first lateral electrodes 71, and the pair of second lateral electrodes 72 are electrically connected to each other. The incident electrode 20 is, for example, physically connected to the second counter electrode 62 and the pair of second lateral electrodes 72. The separation electrode 80 is, for example, physically connected to the second counter electrode 62 and the pair of second lateral electrodes 72 on one side in the Z direction, and physically connected to the first counter electrode 61 and the pair of first lateral electrodes 71 on the other side in the Z direction. The conversion electrode 30 is, for example, physically connected to the first counter electrode 61 and the pair of first lateral electrodes 71. Note that the electrical connections between the electrodes described above are not limited to electrical connections by physical connections, but may also be electrical connections via conductive members.

[0039] The output unit 100 outputs an electrical signal in response to the incidence of electrons e that have passed through the emission portion 41 of the emission electrode 40. The output unit 100 includes an electron multiplication unit 110, an electron lens 120, and an electron detection unit 130.

[0040] The electron multiplication unit 110 multiplies the electrons e that have passed through the emission unit 41. The electron multiplication unit 110 includes a dynode 111, which is a first electron multiplication unit, and an MCP (microchannel plate) 112, which is a second electron multiplication unit. The dynode 111 is located on one side in the X direction (right side in Figure 2) relative to the emission unit 41. The dynode 111 has a secondary electron emission surface 111a. The secondary electron emission surface 111a faces the other side in the X direction and the other side in the Z direction. The secondary electron emission surface 111a faces the electron emission surface 40b of the emission electrode 40 in the X direction. In this example, the secondary electron emission surface 111a is a concave surface and is inclined so that the one side in the X direction (right side in Figure 2) is located further to the other side in the Z direction (lower side in Figure 2). Electrons e that pass through the emission section 41 are incident on the secondary electron emission surface 111a, where they are amplified and emitted as secondary electrons. Because the secondary electron emission surface 111a faces the other side in the Z direction, electrons e emitted on the secondary electron emission surface 111a can travel to the other side in the Z direction.

[0041] The MCP112 is located on one side in the X direction relative to the output section 41 and on the opposite side of the dynode 111 from the incident electrode 20. The MCP112 has an electron incident surface (incident surface) 112a and an electron exit surface 112b. The electron incident surface 112a is a surface facing one side in the Z direction (upper side in Figure 2). The electron incident surface 112a faces the secondary electron emission surface 111a of the dynode 111 in the Z direction. The electron exit surface 112b is a surface facing the other side in the Z direction (lower side in Figure 2). For example, the electron incident surface 112a and the electron exit surface 112b are surfaces perpendicular to the Z direction. The electron incident surface 112a of the MCP112 faces the secondary electron emission surface 111a of the dynode 111 in the Z direction. The electron multiplication region of the MCP112 is provided with a plurality of holes (not shown) that penetrate between the electron input surface 112a and the electron output surface 112b and are arranged two-dimensionally along a plane perpendicular to the Z direction. One end of each hole opens to the electron input surface 112a. The other end of each hole opens to the electron output surface 112b. Each hole is inclined with respect to the Z direction. The angle that the center line of each hole makes with the Z direction is, for example, 4 to 20 degrees. A secondary electron emission structure is formed on the inner wall surface of each hole, enabling secondary electron multiplication at each hole. Electrons e emitted from the dynode 111 are incident on the electron input surface 112a, reflected as they pass through the plurality of holes, and can be multiplied. The multiplied electrons e are then emitted from the electron output surface 112b.

[0042] The electron lens 120 is located on one side in the X direction relative to the emission section 41 and on the opposite side of the MCP 112 from the incident electrode 20. The electron lens 120 has, for example, an annular shape. The electron lens 120 focuses the electrons e emitted from the MCP 112 towards the electron detection section 130.

[0043] The electron detection unit 130 includes an AD (avalanche diode) 131. The AD 131 is mounted on a wiring board 132. The AD 131 has an electron incidence surface 131a. The electron incidence surface 131a is a surface facing one side in the Z direction. For example, the electron incidence surface 131a is a surface perpendicular to the Z direction. The electron incidence surface 131a of the AD 131 faces the electron emission surface 112b of the MCP 112 in the Z direction. For example, the AD 131 is a semiconductor electron detection element including a semiconductor substrate (e.g., a silicon substrate), which detects electrons emitted from the electron emission surface 112b of the MCP 112 and incident on the electron incidence surface 131a by avalanche multiplication. In other words, the electron detection unit 130 is both a third electron multiplication unit and an electron detection unit. The AD131 receives incoming electrons e focused by the electron lens 120, generates an electrical signal, and outputs the electrical signal to, for example, an analyzer connected to a subsequent stage.

[0044] In the ion detector 1A configured as described above, the potential application unit 200 is, for example, a power supply, and applies potential to each electrode and output unit 100 included in the ion detector 1A. The potential application unit 200 applies a negative potential to the ion control electrode 50 with the potential of the conversion electrode 30 as a reference, and applies a positive potential to the output electrode 40 with the potential of the conversion electrode 30 as a reference. The potential application unit 200 applies the same potential as the conversion electrode 30 to the incident electrode 20, the first counter electrode 61, the second counter electrode 62, the separation electrode 80, the pair of first lateral electrodes 71, and the pair of second lateral electrodes 72. Furthermore, the potential application unit 200 applies a positive first potential to the electronic control electrode 90 with the conversion electrode 30 as a reference, and applies a positive second potential to the output electrode 40 with the electronic control electrode 90 as a reference. Furthermore, the positive potential applied to the output electrode 40, with reference to the potential of the conversion electrode 30, is the sum of the positive first potential and the positive second potential. The potential application unit 200 applies a positive potential to the secondary electron emission surface 111a of the dynode 111 with reference to the output electrode 40, applies a positive potential to the electron incidence surface 112a of the MCP 112 with reference to the secondary electron emission surface 111a of the dynode 111, applies a positive potential to the electron output surface 112b of the MCP 112 with reference to the electron incidence surface 112a of the MCP 112, and applies a positive potential to the electron incidence surface 131a of the AD 131 with reference to the electron output surface 112b of the MCP 112. The potential application unit 200 then applies a reverse bias voltage to the AD 131. [Operation of the ion detector]

[0045] As described above, the ion detector 1A operates with a predetermined potential applied to each part of the ion detector 1A by the potential application unit 200. Ions i are separated in the ion separation unit 12 according to their mass-to-charge ratio before being incident on the incident electrode 20. Therefore, ions i with the same mass-to-charge ratio can be incident on the incident electrode 20 at the same time. Ions i that have passed through the incident section 21 of the incident electrode 20 travel along the Z direction, pass through the passage section 81 of the separation electrode 80, and then pass through the passage section 91 of the electronic control electrode 90 before being incident on the conversion electrode 30. Electrons e emitted from the conversion electrode 30 pass through the passage section 91 of the electronic control electrode 90, and then pass through the emission section 41 of the emission electrode 40 before traveling towards the output unit 100. Electrons that have passed through the emission section 41 are incident on the secondary electron emission surface 111a of the dynode 111, where they are amplified and emitted. The emitted electrons e enter each hole of the MCP112 from one side in the Z direction, and the electrons e multiplied at each hole are emitted from each hole to the other side in the Z direction. The electrons e emitted from the MCP112 are focused by the electron lens 120 and enter the electron incident surface 131a of the AD131, and the electrons e multiplied by the avalanche effect at the AD131 are output as an electrical signal from the wiring board 132 to an external device. The space from each electrode to the AD131 via the dynode 111 and MCP112 is formed within a vacuum-sealed housing (not shown).

[0046] When ion i is a positive ion, the potential application unit 200 applies -10kV to each of the following: the incident electrode 20, the conversion electrode 30, the first counter electrode 61, the second counter electrode 62, the separation electrode 80, the pair of first lateral electrodes 71, and the pair of second lateral electrodes 72, as an example; -10.45kV to the ion control electrode 50; -9.5kV to the output electrode 40; and -9.95kV to the electronic control electrode 90. In this case, as shown in Figure 4, an electric field E1 is formed in space S1, and an electric field E2 is formed in space S2. The shape of the equipotential lines of electric field E2 is almost the same as the shape of the equipotential lines of electric field E1. On the other hand, the polarity of the potential indicated by the equipotential lines of electric field E2 is inverted with respect to the polarity of the potential indicated by the equipotential lines of electric field E1, with reference to the potential of the conversion electrode 30. In other words, in space S2, an electric field is formed consisting of equipotential lines that are almost the same shape as space S1 but have different polarities when the reference potential is -10kV. More specifically, for example, electric field E2 may be an electric field in which the potential decreases as it approaches the ion control electrode 50 (an electric field formed by equipotential lines that are negative when the potential of the conversion electrode 30 is taken as the reference potential), and electric field E1 may be an electric field in which the potential increases as it approaches the output electrode 40 (an electric field formed by equipotential lines that are positive when the potential of the conversion electrode 30 is taken as the reference potential). Note that some of the equipotential lines of electric field E1 may be formed toward the electronic control electrode 90.

[0047] The electric fields E1 and E2 can affect the velocity of ions i traveling from the incident electrode 20 to the conversion electrode 30. For example, for positive ions i of the same mass, space S2 becomes a space that accelerates ions i due to electric field E2, and space S1 becomes a space that decelerates ions i due to electric field E1. In this case, in the region of electric field E2 formed in space S2 that is close to the ion control electrode 50, the magnitude of the absolute value of the negative potential relative to the conversion electrode 30 becomes large (the potential difference relative to the conversion electrode 30 becomes large), so the velocity of the traveling positive ions i increases. On the other hand, in the region of electric field E2 formed in space S2 that is far from the ion control electrode 50, the magnitude of the absolute value of the negative potential relative to the conversion electrode 30 becomes small (the potential difference relative to the conversion electrode 30 becomes small), so the velocity of the traveling positive ions i does not increase easily. In contrast, in the region close to the exit electrode 40 in the electric field E1 formed in space S1, the magnitude of the absolute value of the positive potential relative to the conversion electrode 30 increases (the potential difference relative to the conversion electrode 30 increases), so the velocity of positive ions i traveling in the region close to the exit electrode 40 decreases. On the other hand, in the region far from the exit electrode 40 in the electric field E1 formed in space S1, the magnitude of the absolute value of the positive potential relative to the conversion electrode 30 decreases (the potential difference relative to the conversion electrode 30 decreases), so the velocity of positive ions i traveling in the region far from the exit electrode 40 does not decrease as easily. Therefore, in the ion detector 1A, the effect of electric field E1 on the velocity of ions i is canceled out by the effect of electric field E2.

[0048] When ion i is a negative ion, the potential application unit 200 applies +10kV to each of the incident electrode 20, conversion electrode 30, first counter electrode 61, second counter electrode 62, separation electrode 80, a pair of first lateral electrodes 71, and a pair of second lateral electrodes 72, as an example, applies +9.55kV to the ion control electrode 50, and applies +10.5kV to the output electrode 40. In this case as well, for example, the electric field E2 may become an electric field whose potential decreases as it approaches the ion control electrode 50 (an electric field formed by equipotential lines that are negative when the potential of the conversion electrode 30 is taken as the reference potential), and the electric field E1 may become an electric field whose potential increases as it approaches the output electrode 40 (an electric field formed by equipotential lines that are positive when the potential of the conversion electrode 30 is taken as the reference potential).

[0049] For example, for a negative ion i of the same mass, space S2 becomes a space that decelerates the ion i due to the electric field E2, and space S1 becomes a space that accelerates the ion i due to the electric field E1. In this case, in the region close to the ion control electrode 50 in the electric field E2 formed in space S2, the magnitude of the absolute value of the negative potential relative to the conversion electrode 30 becomes large (the potential difference relative to the conversion electrode 30 becomes large), so the velocity of the moving negative ion i decreases. On the other hand, in the region far from the ion control electrode 50, the magnitude of the absolute value of the negative potential relative to the conversion electrode 30 becomes small (the potential difference relative to the conversion electrode 30 becomes small), so the velocity of the negative ion i moving in the region far from the ion control electrode 50 does not decrease as easily. In contrast, in the region close to the output electrode 40 in the electric field E1 formed in space S1, the magnitude of the absolute value of the positive potential relative to the conversion electrode 30 becomes large (the potential difference relative to the conversion electrode 30 becomes large), so the velocity of the negative ion i moving in the region close to the output electrode 40 increases. On the other hand, in the region far from the output electrode 40 in the electric field E1 formed in space S1, the magnitude of the absolute value of the positive potential relative to the conversion electrode 30 becomes smaller (the potential difference relative to the conversion electrode 30 becomes smaller), so the velocity of negative ions i traveling in the region far from the output electrode 40 does not increase easily. Therefore, in the ion detector 1A, even if ions i are negative ions, the effect of electric field E1 on the velocity of ions i is canceled out by the effect of electric field E2.

[0050] For ions i traveling from the incident electrode 20 to the conversion electrode 30, the closer the ions i travel to the exit electrode 40, the greater the influence of the potential of the exit electrode 40. Even for ions i with the same mass-to-charge ratio, the influence of the potential applied to the exit electrode 40 changes depending on the incident position to the ion detector 1A, causing variations in the incident timing to the conversion electrode 30 (i.e., the timing at which ions i are converted to electrons e). As a result, variations occur in the ion detection time for ions i with the same mass-to-charge ratio, which may lead to a decrease in the resolution of the mass spectrometry. In the ion detector 1A, for example, by applying different potentials to the ion control electrode 50 and the exit electrode 40 (in this embodiment, potentials with different polarities, with the potential of the conversion electrode 30 as the reference potential), the influence of the electric field E1 due to the potential of the exit electrode 40 on the velocity of ions i traveling from the incident electrode 20 to the conversion electrode 30 can be canceled out by the influence of the electric field E2 due to the potential of the ion control electrode 50. This makes it possible to equalize the time it takes for ions i with the same mass-to-charge ratio to travel from the incident portion 21 of the incident electrode 20 to the conversion electrode 30, for ions i traveling in the region close to the exit electrode 40 and ions i traveling in the region far from the exit electrode 40. Therefore, the ion detector 1A can suppress variations in ion detection time for ions i with the same mass-to-charge ratio.

[0051] As shown in Figures 2 and 5, electrons e emitted from the conversion electrode 30 first travel to the electron control electrode 90. Electrons e possess energy (initial energy) at the time of emission from the conversion electrode 30. This initial energy varies within a certain range. For example, the initial energy of electrons e is thought to follow the Maxwell-Boltzmann distribution shown in equation (1). Assuming a peak of 3 eV in the initial energy distribution, approximately 85% of the electrons e emitted from the conversion electrode 30 have initial energies distributed in the range of 0 eV to 10 eV. P(E0) = C(E0 / E p ) × exp(-(E0 / E p ))···(1) C represents the normalization coefficient, E p This shows the peak energy of the initial energy distribution, E p =3eV. In equation (1), the distribution of initial energy P(E0) starts from initial energy E0=0eV, and initial energy E0=E p The distribution peaks at a certain energy level, and then tends to decrease exponentially in higher energy ranges. Since the velocity of electrons e follows the kinetic energy formula shown in equation (2), the larger the initial energy E0, the larger the initial velocity v0. In other words, variations in the initial energy E0 lead to variations in the initial velocity v0. E0 = (1 / 2)mv0 2 ...(2) Variations in the initial velocity v0 of electrons e can cause variations in the movement of electrons e converted from ions i within a predetermined region (same region) of the conversion electrode 30 and heading toward the output unit 100 (dynode 111 in this embodiment), potentially resulting in variations in the ion detection time. Furthermore, electrons e have an initial emission angle shown in equation (3). Similar to variations in the initial velocity v0, variations in the initial emission angle can cause variations in the movement of electrons e, potentially resulting in variations in the ion detection time. P(θ)∝cos(θ)···(3) θ represents the angle of the conversion electrode 30 with respect to the normal to the electron emission surface 30a. In order to suppress variations in ion detection time, it is necessary to suppress the effects of variations in electron behavior, particularly variations in the initial velocity v0 and the initial emission angle.

[0052] As described above, the potential application unit 200 applies a positive first potential to the electronic control electrode 90 with the conversion electrode 30 as the reference (using the potential of the conversion electrode 30 as the reference potential). Specifically, the potential application unit 200 applies the energy E of the electron e at the time it passes through the passage unit 91. 15The first potential is applied to the electron control electrode 90 such that the minimum value of 15 is greater than the maximum value of the initial energy E0 of the electrons e when they are emitted from the conversion electrode 30. For example, the potential application unit 200 applies a potential of +50 V as the first potential to the electron control electrode 90 with reference to the conversion electrode 30. When the potential of the conversion electrode 30 is -10 kV, the potential of the electron control electrode 90 becomes -9.95 kV. Thereby, the electrons e emitted from the conversion electrode 30 move toward the electron control electrode 90 according to the potential difference (+50 V) between the conversion electrode 30 and the electron control electrode 90. At this time, the energy E 15 of the electrons e becomes a value obtained by adding the potential difference between the conversion electrode 30 and the electron control electrode 90 to the initial energy E0 of the electrons e. Therefore, the variation in the energy E 15 of the electrons e is in the range of 50 eV to 60 eV, and the minimum value of the energy E

[0053] is greater than 10 eV, which is the maximum value of the initial energy E0 of the electrons e. The potential application unit 200 may apply a potential of +50 V or more to the electron control electrode 90 with reference to the conversion electrode 30, for example, a potential of +100 V.

[0054] By applying a positive potential to the electron control electrode 90 with reference to the conversion electrode 30, the moving speed of the electrons e at the time of passing through the passing portion 91 increases. As a result, regarding the moving speed of the electrons e passing through the emitting portion 41 of the emitting electrode 40, the relative variation becomes small, so that the variation in the movement tendency of the electrons e from the conversion electrode 30 toward the output unit 100 is suppressed, and the variation in the ion detection time for ions i having the same mass-to-charge ratio can be suppressed.The arrangement of the dynode 111 and MCP 112 described above adjusts the length of the orbit from when the electron e is emitted from the conversion electrode 30 until it is incident on the MCP 112, thereby suppressing variations in orbital length. As shown in Figure 5, for example, suppose electrons e1, e2, and e3 are emitted from the conversion electrode 30. The positions of electrons e1, e2, and e3 in the X direction are different. This is due to the different incident positions of ions i on the conversion electrode 30 in the X direction. Electron e1 is located on the electron emission surface 30a of the conversion electrode 30, furthest towards the emission electrode 40 in the X direction. Electron e3 is located on the electron emission surface 30a, furthest towards the first opposing electrode 61 in the X direction. Electron e2 is located between electrons e1 and e3 on the electron emission surface 30a in the X direction. The length of the orbits from the conversion electrode 30 to the electronic control electrode 90 for electrons e1, e2, and e3 is the same for electrons e1, e2, and e3.

[0055] Let ep1 be the trajectory of electron e1 from passing through the passage 91 of the electronic control electrode 90 to passing through the discharge portion 41 of the discharge electrode 40 and reaching the dynode 111. Let ep2 be the trajectory of electron e2 from passing through the passage 91 of the electronic control electrode 90 to passing through the discharge portion 41 of the discharge electrode 40 and reaching the dynode 111. Let ep3 be the trajectory of electron e3 from passing through the passage 91 of the electronic control electrode 90 to passing through the discharge portion 41 of the discharge electrode 40 and reaching the dynode 111. As described above, the secondary electron emission surface 111a is inclined such that one side in the X direction (right side in Figure 2) is located further to the other side in the Z direction (lower side in Figure 2). Therefore, the incident position of electron e1 on the secondary electron emission surface 111a is the position on the secondary electron emission surface 111a closest to the discharge electrode 40 in the X direction. The incident position of electron e3 on the secondary electron emission surface 111a is the position on the secondary electron emission surface 111a furthest from the exit electrode 40 in the X direction. The incident position of electron e2 on the secondary electron emission surface 111a is the position on the secondary electron emission surface 111a between electrons e1 and e3 in the X direction. Therefore, the lengths of orbitals ep1, ep2, and ep3 decrease in this order.

[0056] Next, let ep4 be the typical trajectory of electron e1 from when it is amplified and emitted on the secondary electron emission surface 111a until it reaches the MCP112. Let ep5 be the typical trajectory of electron e2 from when it is amplified and emitted on the secondary electron emission surface 111a until it reaches the MCP112. Let ep6 be the typical trajectory of electron e3 from when it is amplified and emitted on the secondary electron emission surface 111a until it reaches the MCP112. As mentioned above, the electron incident surface 112a of the MCP112 faces the secondary electron emission surface 111a of the dynode 111 in the Z direction and is a plane perpendicular to the Z direction. Therefore, the distance between the incident position (emission position) of electron e1, electron e2, and electron e3 on the secondary electron emission surface 111a and the electron incident surface 112a of the MCP112 increases in the order of electron e1, electron e2, and electron e3. Thus, the lengths of trajectories ep4, ep5, and ep6 increase in this order.

[0057] As a result, the differences between the sum of orbital ep1 and orbital ep4, the sum of orbital ep2 and orbital ep5, and the sum of orbital ep3 and orbital ep6 become smaller. Therefore, variations in the orbital length between electrons e1 and e3, from the time they are emitted from the conversion electrode 30 until they are incident on the MCP112, can be suppressed. [Mechanism of Action and Effects]

[0058] In the ion detector 1 described above, ions i that pass through the incident portion 21 of the incident electrode 20 travel along the Z direction and are incident on the conversion electrode 30, and electrons e emitted from the conversion electrode 30 pass through the exit portion 41 of the exit electrode 40 and are incident on the output portion 100. Here, for ions i traveling from the incident electrode 20 to the conversion electrode 30, the closer the ions i travel to the exit electrode 40, the greater the influence of the potential of the output portion 100. In the ion detector 1A, for example, by applying different potentials to the ion control electrode 50 and the exit electrode 40, the influence of the electric field E1 due to the potential of the output portion 100 on the velocity of ions i traveling from the incident electrode 20 to the conversion electrode 30 can be canceled out by the influence of the electric field E2 due to the potential of the ion control electrode 50. This makes it possible to equalize the time it takes for ions i with the same mass-to-charge ratio to travel from the incident portion 21 of the incident electrode 20 to the conversion electrode 30, for ions i traveling in the region close to the exit electrode 40 and ions i traveling in the region far from the exit electrode 40. Therefore, the ion detector 1A can suppress variations in ion detection time for ions i with the same mass-to-charge ratio.

[0059] In the ion detector 1A described above, a negative potential is applied to the ion control electrode 50 with respect to the conversion electrode 30, and a positive potential is applied to the output electrode 40 with respect to the conversion electrode 30. With this configuration, the effect of the electric field E1 due to the potential of the output electrode 40 on the velocity of ions i traveling in a region close to the output electrode 40 can be reliably canceled out by the effect of the electric field E2 due to the potential of the ion control electrode 50.

[0060] The ion detector 1A further comprises a first counter electrode 61 located on the other side in the X direction relative to the conversion electrode 30 and facing the output electrode 40 in the X direction, and a second counter electrode 62 located on the other side in the X direction relative to the conversion electrode 30 and facing the ion control electrode 50 in the X direction. With this configuration, an electric field E2 due to the potential of the ion control electrode 50 can be stably formed in the space S2 corresponding to the ion control electrode 50, and an electric field E1 due to the potential of the output electrode 40 can be stably formed in the space S1 corresponding to the output electrode 40.

[0061] The ion detector 1A further comprises a pair of first lateral electrodes 71 positioned on both sides of the conversion electrode 30 in the Y direction, which intersects both the Z and X directions, and facing each other via a space S1 between the output electrode 40 and the first counter electrode 61, and a pair of second lateral electrodes 72 positioned on both sides of the conversion electrode 30 in the Y direction and facing each other via a space S2 between the ion control electrode 50 and the second counter electrode 62. This configuration allows for a more stable formation of an electric field due to the potential of the ion control electrode 50 in the space S2 corresponding to the ion control electrode 50, and also allows for a more stable formation of an electric field due to the potential of the output electrode 40 in the space S1 corresponding to the output electrode 40.

[0062] The ion detector 1A is positioned between the incident electrode 20 and the conversion electrode 30 so as to separate the space between the incident electrode 20 and the conversion electrode 30 into a space S1 corresponding to the ion control electrode 50 and a space S2 corresponding to the output electrode 40, and further comprises a separation electrode 80 including a passage portion 81 for passing ions i through. With this configuration, an electric field E2 due to the potential of the ion control electrode 50 can be stably formed in the space S2 corresponding to the ion control electrode 50, and an electric field E1 due to the potential of the output electrode 40 can be stably formed in the space S1 corresponding to the output electrode 40.

[0063] The exit electrode 40 has an electron incident surface 40a facing the other side in the X direction, and the ion control electrode 50 has an inner surface 50a facing the other side in the X direction. The position of the inner surface 50a in the X direction is substantially the same as the position of the electron incident surface 40a in the X direction, and the area of ​​the inner surface 50a is substantially the same as the area of ​​the electron incident surface 40a. With this arrangement, the potentials applied to the ion control electrode 50 and the exit electrode 40 can be easily set in order to cancel out the effect of the electric field E1 due to the potential of the exit electrode 40 with the effect of the electric field E2 due to the potential of the ion control electrode 50 on the velocity of ions i traveling in a region close to the exit electrode 40.

[0064] The output unit 100 includes an electron multiplier unit 110 that multiplies the electrons e that have passed through the emission unit 41, and an electron detection unit 130 that detects the electrons e emitted from the electron multiplier unit 110. This makes it possible to improve the detection sensitivity of ions i.

[0065] The electron multiplication unit 110 includes a dynode 111 located on one side in the X direction relative to the output unit 41, and an MCP 112 located on one side in the X direction relative to the output unit 41 and on the opposite side of the dynode 111 from the incident electrode 20. The dynode 111 is positioned to face the output unit 41 and the electron incident surface 112a of the MCP 112. This arrangement makes it possible to make the flight distance of electrons e from the conversion electrode 30 through the dynode 111 to the electron incident surface 112a of the MCP 112 uniform regardless of the incident position of ions i in the conversion electrode 30. Therefore, for ions i with the same mass-to-charge ratio, it is possible to reliably multiply electrons e while suppressing variations in the time from when ions i are incident on the conversion electrode 30 until electrons e reach the electron incident surface 112a of the MCP 112.

[0066] The electron detection unit 130 includes AD131. This allows for reliable detection of electrons e while increasing their magnitude.

[0067] In the mass spectrometer 10 described above, the ion detector 1A suppresses variations in ion detection time for ions i with the same mass-to-charge ratio, thereby improving the resolution of the mass spectrometer. [Differentiation]

[0068] The present invention is not limited to the embodiments described above. The first counter electrode 61 and the second counter electrode 62 may be formed integrally. In this case, the first counter electrode 61 and the second counter electrode 62 may be formed from a single electrode, where the portion of the single electrode facing the output electrode 40 in the X direction is the first counter electrode 61, and the portion facing the ion control electrode 50 in the X direction is the second counter electrode 62. Alternatively, each of the pair of first lateral electrodes 71 and the first counter electrode 61 may be formed separately. In this case, gaps may exist between the pair of first lateral electrodes 71 and the first counter electrode 61, and between the other of the pair of first lateral electrodes 71 and the first counter electrode 61. Similarly, each of the pair of second lateral electrodes 72 and the second counter electrode 62 may be formed separately. In this case, gaps may exist between one of the pair of second lateral electrodes 72 and the second counter electrode 62, and between the other of the pair of second lateral electrodes 72 and the second counter electrode 62. Furthermore, the ion control electrode 50 only needs to be electrically isolated from the output electrode 40, and does not necessarily need to be physically isolated. The ion control electrode 50 may be physically connected to the output electrode 40 via an insulating material. Similarly, the electronic control electrode 90 only needs to be electrically isolated from the output electrode 40, and does not necessarily need to be physically isolated. The electronic control electrode 90 may be physically connected to the output electrode 40 via an insulating material.

[0069] As shown in Figure 6, the first modified ion detector 1B differs from ion detector 1A in that it includes a first counter electrode 61A instead of the first counter electrode 61, and a second counter electrode 62A instead of the second counter electrode 62. The first counter electrode 61A is electrically isolated from the conversion electrode 30, the separation electrode 80, and the pair of first lateral electrodes 71. There may be gaps between the first counter electrode 61A and the conversion electrode 30, the separation electrode 80, and the pair of first lateral electrodes 71. Alternatively, the first counter electrode 61A and the conversion electrode 30, the separation electrode 80, and the pair of first lateral electrodes 71 may be physically connected via an insulating member. The second counter electrode 62A is electrically isolated from the incident electrode 20, the separation electrode 80, and the pair of second lateral electrodes 72. A gap may exist between the second counter electrode 62A and each of the incident electrode 20, the separation electrode 80, and the pair of second lateral electrodes 72. Alternatively, the second counter electrode 62A may be physically connected to each of the incident electrode 20, the separation electrode 80, and the pair of second lateral electrodes 72 via an insulating member.

[0070] In the ion detector 1B, the potential application unit 200 may apply a potential different from the potential of the conversion electrode 30 to the first counter electrode 61A and the second counter electrode 62A. The potential application unit 200 applies a positive potential to the second counter electrode 62A with the potential of the conversion electrode 30 as a reference, and applies a negative potential to the first counter electrode 61A with the potential of the conversion electrode 30 as a reference. When ion i is a positive ion, the potential application unit 200 applies -10.3kV to the first counter electrode 61A and -9.7kV to the second counter electrode 62A, as an example. The potential application unit 200 also applies -10kV to each of the incident electrode 20, the conversion electrode 30, the separation electrode 80, the pair of first lateral electrodes 71, and the pair of second lateral electrodes 72, applies -10.3kV to the ion control electrode 50, and applies -9.7kV to the output electrode 40. In this case, as shown in Figure 6, an electric field E3 is formed in space S1 and an electric field E4 is formed in space S2. The equipotential lines of electric field E3 can be equipotential lines such that an equipotential line with respect to the output electrode 40 and an equipotential line with respect to the first counter electrode 61A face each other. The equipotential lines of electric field E4 can be equipotential lines such that an equipotential line with respect to the ion control electrode 50 and an equipotential line with respect to the second counter electrode 62A face each other. Similar to the relationship between electric fields E1 and E2 shown in Figure 4, the shape of the equipotential lines of electric field E4 is almost the same as the shape of the equipotential lines of electric field E3. On the other hand, the polarity of the potential shown by the equipotential lines of electric field E4 is inverted with respect to the potential shown by the equipotential lines of electric field E3, with respect to the potential of the conversion electrode 30. For example, electric field E4 may be such that its potential decreases as it approaches the ion control electrode 50 (an electric field formed by equipotential lines that result in a negative potential when the potential of the conversion electrode 30 is taken as the reference potential), and electric field E3 may be such that its potential increases as it approaches the discharge electrode 40 (an electric field formed by equipotential lines that result in a positive potential when the potential of the conversion electrode 30 is taken as the reference potential). The effect of electric fields E3 and E4 on the velocity of ion i is the same as the effect of electric fields E1 and E2 on the velocity of ion i.

[0071] In ion detector 1B, the potential on the first counter electrode 61A side is lower compared to ion detector 1A (the electric field E3 on the first counter electrode 61A side in space S1 becomes stronger). As a result, the potential difference between the first counter electrode 61A and the output electrode 40 becomes larger, making it easier to accelerate electrons e converted from ions i to the output electrode 40 side in the region of the conversion electrode 30 on the first counter electrode 61A side and guide them to the output electrode 40. This improves the delay in electron travel time. Furthermore, by forming an electric field that more actively controls ions i and electrons e, spaces S1 and S2 can be miniaturized. Also, similar to ion detector 1A, for ions i of the same mass, the time from passing through the incident portion 21 of the incident electrode 20 to reaching the conversion electrode 30 can be made uniform for ions i traveling in the region close to the output electrode 40 and ions i traveling in the region far from the output electrode 40.

[0072] As shown in Figure 7, the second modified ion detector 1C differs from ion detector 1A in that it has an output unit 100A instead of an output unit 100. The output unit 100A differs from the output unit 100 in that it does not include an MCP 112. The electron lens 120 is located on one side in the X direction relative to the output portion 41 of the output electrode 40 and on the opposite side of the dynode 111 from the incident electrode 20. The electron incident surface 131a of AD 131 directly faces the secondary electron emission surface 111a of the dynode 111 in the Z direction. Electrons e reflected from the dynode 111 are focused by the electron lens 120 and incident on the electron incident surface 131a. In ion detector 1C as well, the detection sensitivity of ions can be improved by multiplying the electrons e in the dynode 111.

[0073] As shown in Figure 8, the third modified ion detector 1D differs from the ion detector 1A in that it includes an output unit 100B instead of an output unit 100. The output unit 100B differs from the output unit 100 in that it includes a dynode unit 111A instead of a dynode 111. The dynode unit 111A includes multiple dynodes 111. In the dynode unit 111A, each stage dynode 111 emits electrons e as secondary electrons, which are incident on the next stage, thereby increasing the number of electrons stepwise. In the dynode unit 111A, each stage dynode 111 is positioned to receive electrons e from the preceding dynode 111 and to be able to incident electrons e on the next stage dynode 111. As an example, in the dynode unit 111A, multiple dynodes 111 are arranged sequentially away from the output electrode 40 in the X direction. The secondary electron emission surface 111a of the final stage dynode 111 faces the electron incidence surface 112a of the MCP 112 in the Z direction. In the ion detector 1C, secondary electron emission with a high amplification factor can be achieved by repeatedly multiplying electrons e by the dynode unit 111A.

[0074] As shown in Figure 9, the ion detector 1E of the fourth modification differs from the ion detector 1A in that it includes an output unit 100C instead of an output unit 100. The output unit 100C differs from the output unit 100 in that it does not include an electron lens 120 and includes an electron detection unit 140 instead of an electron detection unit 130. The electron detection unit 140 includes a scintillator 141, a light guide 142, and a PMT (photomultiplier tube) 143. The scintillator 141 faces the electron emission surface 112b of the MCP 112 in the Z direction. The light guide 142 is positioned on the opposite side of the MCP 112 in the Z direction from the scintillator 141. The PMT 143 is positioned on the opposite side of the MCP 112 in the Z direction from the light guide 142.

[0075] Electrons e emitted from the electron emission surface 112b of the MCP 112 of the ion detector 1E are incident on the scintillator 141. The scintillator 141 converts the electrons e into scintillation light. The converted scintillation light is transmitted to the PMT 143 by the light guide 142. The PMT 143 converts the scintillation light back into electrons and multiplies them. The PMT 143 then generates an electrical signal corresponding to the multiplied electrons and outputs the electrical signal to, for example, an analyzer connected to a subsequent stage. Thus, the electron detection unit 140 can also be called an optical detection unit because it converts electrons e into light and detects the light. Furthermore, since the electron detection unit 140 performs electron multiplication in the PMT 143, it also functions as an electron multiplication unit.

[0076] In the ion detector 1E, the output unit 100C does not necessarily include the MCP 112. The scintillator 141 may be directly facing the secondary electron emission surface 111a of the dynode 111 in the Z direction. In this case, electrons e reflected from the secondary electron emission surface 111a are directly incident on the scintillator 141. [Explanation of symbols]

[0077] 1A, 1B, 1C, 1D, 1E…Ion detector, 10…Mass spectrometer, 11…Ionization unit, 12…Ion separation unit, 20…Injection electrode, 21…Injection unit, 30…Conversion electrode, 40…Output electrode, 40a…Electron injection surface (first surface), 41…Output unit, 50…Ion control electrode, 50a…Inner surface (second surface), 61, 61A…First counter electrode, 62, 62A…Second counter electrode, 71…First side electrode Electrode, 72...Second lateral electrode, 80...Separation electrode, 81...Pass section, 100, 100A, 100B, 100C...Output section, 110...Electron multiplication section, 111...Dynode, 112...MCP (Microchannel plate), 112a...Electron incident surface (incident surface), 130...Electron detection section, 131...AD (Avalanche diode), e, e1, e2, e3...Electrons, i...Ions, S1, S2...Space.

Claims

1. An incident electrode including an incident portion through which ions pass, A conversion electrode facing the incident electrode in the first direction, which emits electrons in response to the incident ions that have passed through the incident portion, An ejection electrode is located on the input electrode side in the first direction with respect to the conversion electrode and on one side in the second direction intersecting the first direction with respect to the conversion electrode, and includes an ejection portion through which the electrons ejected from the conversion electrode pass, An ion control electrode located on the input electrode side in the first direction relative to the output electrode and on one side in the second direction relative to the conversion electrode, An ion detector comprising: an output unit that outputs an electrical signal in response to the incident electrons that have passed through the emission unit.

2. The ion detector according to claim 1, wherein a negative potential is applied to the ion control electrode with reference to the conversion electrode, and a positive potential is applied to the output electrode with reference to the conversion electrode.

3. A first opposing electrode is located on the other side in the second direction with respect to the conversion electrode and faces the output electrode in the second direction, The ion detector according to claim 1, further comprising: a second opposing electrode located on the other side in the second direction with respect to the conversion electrode, and facing the ion control electrode in the second direction.

4. A pair of first lateral electrodes are located on both sides of the conversion electrode in a third direction that intersects both the first and second directions, and face each other across the space between the output electrode and the first opposing electrode, The ion detector according to claim 3, further comprising: a pair of second lateral electrodes located on both sides in the third direction with respect to the conversion electrode, and facing each other across the space between the ion control electrode and the second counter electrode.

5. The ion detector according to claim 1, further comprising a separation electrode positioned between the incident electrode and the conversion electrode so as to separate the space between the incident electrode and the conversion electrode into a space corresponding to the ion control electrode and a space corresponding to the output electrode, and including a passage portion for passing ions.

6. The ejection electrode has a first surface facing the other side in the second direction, The ion control electrode has a second surface facing the other side in the second direction, The position of the second surface in the second direction is substantially the same as the position of the first surface in the second direction. The ion detector according to claim 1, wherein the area of ​​the second surface is substantially the same as the area of ​​the first surface.

7. The output unit is, An electron multiplier unit that multiplies the electrons that have passed through the emission unit, The ion detector according to claim 1, further comprising an electron detection unit for detecting electrons emitted from the electron multiplication unit.

8. The aforementioned electron multiplier unit is A dynode located on one side in the second direction with respect to the ejection section, The microchannel plate is located on one side in the second direction relative to the ejection portion and on the opposite side of the dynode from the incident electrode, The ion detector according to claim 7, wherein the dynode is arranged to face the emission surface and the incident surface of the microchannel plate.

9. The ion detector according to claim 7, wherein the electron detection unit includes an avalanche diode.

10. An ionization unit that generates ions, An ion separation unit separates the ions generated in the ionization unit according to the mass-charge ratio of the ions, A mass spectrometer comprising an ion detector according to any one of claims 1 to 9 for detecting the ions separated in the ion separation unit.

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