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 a conversion unit 2A that emits electrons e to the other side of direction D when ions i are incident from one side in direction D, and an output unit 3 that outputs an electrical signal in response to the incidence of electrons e emitted from the conversion unit 2A. The conversion unit 2A includes a support having a support surface perpendicular to direction D, and an electron generation layer disposed on the support surface that generates electrons e in response to the incidence of ions i. The support has a plurality of passages through which ions i or electrons e pass. The plurality of passages are arranged two-dimensionally along the support surface.

Description

Technical Field

[0001] The present invention relates to an ion detector and a mass spectrometer.

Background Art

[0002] As an ion detector used in a time-of-flight mass spectrometer, there is known one including a microchannel plate that generates electrons in response to the incidence of ions and multiplies and emits the electrons, and an anode that collects the electrons emitted from the microchannel plate and outputs an electrical signal (see, for example, Patent Document 1).

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In ion detectors as described above, the holes in the microchannel plate are sometimes tilted with respect to the direction of ion incidence to ensure that ions are reliably converted into electrons. In such cases, even ions with the same mass-to-charge ratio may vary in the time it takes for an ion to reach the inner surface of each hole after it has reached the incident opening of that hole (i.e., the incident surface of the microchannel plate). More specifically, even if ions with the same mass-to-charge ratio reach the incident opening of each hole simultaneously, there will be ions incident in regions of the inner surface relatively close to the opening, ions incident in regions of the inner surface relatively far from the opening, and ions incident in intermediate regions of the inner surface, and the timing of ion conversion to electrons will differ in each case. Furthermore, since the velocity of ions is slower than, for example, the velocity of electrons, the "difference in the timing of ion conversion to electrons" (time difference) due to the difference in incident position will be large. As a result, even ions with the same mass-to-charge ratio may vary in the time it takes for an ion to reach the incident surface of the microchannel plate and for the electrons generated by that ion's incidence to reach the anode (i.e., the time from when an ion is incident until an electron is detected in the ion detector). In ion detectors, variations in the time it takes from the incidence of ions with the same mass-to-charge ratio to the detection of electrons (hereinafter referred to as "ion detection time") can reduce the resolution of mass spectrometry.

[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 [1] "an ion detector comprising: a conversion unit that emits electrons to the other side in a predetermined direction when ions are incident from one side in a predetermined direction; and an output unit that outputs an electrical signal in response to the incidence of the electrons emitted from the conversion unit, wherein the conversion unit includes a support having a support surface perpendicular to the predetermined direction; and an electron generation layer disposed on the support surface and generating electrons in response to the incidence of ions, wherein the support has a plurality of passages through which the ions or electrons pass, and the plurality of passages are arranged two-dimensionally along the support surface."

[0007] In the above-described ion detector, an electron generation layer that generates electrons in response to ion incidence is arranged on the support surface of a support perpendicular to a predetermined direction, and multiple passages for ions or electrons to pass through are arranged two-dimensionally along the support surface of the support. This ensures the flatness of the electron generation layer, so that when ions with the same mass-to-charge ratio are incident from one side in a predetermined direction, the time it takes for ions to reach the electron generation layer does not vary depending on the incident position of the ions in the electron generation layer. Therefore, the above-described ion detector can 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 described in [1] above, wherein the support is formed of a conductive material." According to this ion detector, it is possible to reliably apply a predetermined potential to an electron generation layer disposed on the support surface of the support and to supply electrons.

[0009] The ion detector of the present invention may also be the ion detector according to [1] or [2] above, wherein each of the plurality of passages is a hole penetrating the support along the predetermined direction. According to the ion detector, ions or electrons can be reliably passed through each of the plurality of passages.

[0010] The ion detector of the present invention may also be [4] "an ion detector according to any one of [1] to [3] above, wherein the electron generation layer is formed of a carbon-containing material." According to this ion detector, electrons can be efficiently generated and the electron generation layer can be easily placed on the support surface of the support.

[0011] The ion detector of the present invention may also be [5] "the ion detector according to any one of [1] to [4] above, wherein the conversion unit further includes an electron emission layer disposed on the surface of the electron generation layer and on the other side of the surface in the predetermined direction, and the electron emission layer is formed of a material with a lower work function than the material of the electron generation layer." With this ion detector, electrons generated in the electron generation layer in response to the incidence of ions are more easily emitted to the other side in the predetermined direction, thereby further improving the electron extraction efficiency in the conversion unit.

[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 electron generation layer is located on the other side in the predetermined direction with respect to the support." With this ion detector, ions are incident on the electron generation layer through each of the multiple passages, and electrons are emitted on the side opposite to the support, so that electrons are not trapped in the support, and the electron extraction efficiency in the conversion unit (i.e., the number of electrons emitted by the incidence of one ion) can be improved.

[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 emitted from the conversion unit, and an electron detection unit that detects the 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 the ion detector described in [7] above, wherein the electron multiplication unit includes a microchannel plate. With this ion detector, electrons can be reliably multiplied while suppressing variations in the time from when electrons enter the electron multiplication unit to when electrons exit the electron multiplication unit for ions with the same mass-to-charge ratio.

[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."

[0017] According to the above-described mass spectrometer, variations in ion detection time for ions with the same mass-to-charge ratio are suppressed in the ion detector, thereby improving the resolution of the mass spectrometer. [Effects of the Invention]

[0018] 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 explanation of the drawing]

[0019] [Figure 1] This is a diagram illustrating the configuration of an example mass spectrometer. [Figure 2] Figure 1 is a diagram showing the configuration of the ion detector. [Figure 3]It is a perspective view of the holes of the microchannel plate shown in FIG. 2. [Figure 4] It is a cross-sectional view of the conversion part shown in FIG. 2. [Figure 5] It is a diagram showing the manufacturing process of the conversion part shown in FIG. 4. [Figure 6] It is a diagram showing the manufacturing process of the conversion part shown in FIG. 4. [Figure 7] It is a diagram showing the manufacturing process of the conversion part shown in FIG. 4. [Figure 8] It is a graph showing the relationship between the ion detection time and the count number for the comparative example. [Figure 9] It is a graph showing the relationship between the electron arrival time and the count number for the example. [Figure 10] It is a graph showing the relationship between the mass-to-charge ratio and the jitter at the time of ion incidence. [Figure 11] It is a graph showing the relationship between the mass-to-charge ratio and the electron extraction efficiency. [Figure 12] It is a cross-sectional view of the conversion part of the modified example. [Figure 13] It is a configuration diagram of the ion detector of the modified example. [Figure 14] It is a configuration diagram of the ion detector of the modified example. [Figure 15] It is a configuration diagram of the ion detector of the modified example. [Embodiments for Carrying Out the Invention]

[0020] 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]

[0021] 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 molecules contained in the sample (mass spectrometry) based on the detection timing of ion i. [Ion detector configuration]

[0022] As shown in Figure 2, the ion detector 1A comprises a conversion unit 2A and an output unit 3. The conversion unit 2A emits electrons e on the other side of direction D (the lower side in Figure 2) when ions i are incident on one side of direction D (the upper side in Figure 2). In this example, direction D is the direction along the directional axis when ions i that have flown through the ion separation unit 12 are incident on the ion detector 1A. The output unit 3 outputs an electrical signal to an external device in response to the incidence of electrons e emitted from the conversion unit 2A. The output unit 3 includes an electron multiplication unit 4 and an electron detection unit 5. The electron multiplication unit 4 multiplies the electrons e emitted from the conversion unit 2A. The electron detection unit 5 detects the electrons e emitted from the electron multiplication unit 4.

[0023] The electron multiplication unit 4 includes an MCP (microchannel plate) 41. The MCP 41 has an incident surface 41a and an exit surface 41b. The incident surface 41a is a surface facing one side in direction D. The exit surface 41b is a surface facing the other side in direction D. In this example, both the incident surface 41a and the exit surface 41b are surfaces perpendicular to direction D. The incident surface 41a of the MCP 41 faces the conversion unit 2A in direction D. As shown in Figure 3, the electron multiplication region of the MCP 41 is provided with a plurality of holes 41c that penetrate between the incident surface 41a and the exit surface 41b and are arranged two-dimensionally along a surface perpendicular to direction D. For the sake of simplicity in the drawing, only one hole 41c is shown in Figure 3. One end of each hole 41c opens to the incident surface 41a. The other end of each hole 41c opens to the exit surface 41b. Each hole 41c is inclined with respect to direction D. The angle between the center line of each hole 41c and direction D is, for example, 4 to 20 degrees. A secondary electron surface is formed on the inner wall surface of each hole 41c, enabling secondary electron multiplication in each hole 41c.

[0024] As shown in Figure 2, the electron detection unit 5 includes an AD (avalanche diode) 51. The AD 51 is mounted on a wiring board 6. The AD 51 has an incident surface 51a. The incident surface 51a is a surface facing one side in direction D. In this example, the incident surface 51a is a surface perpendicular to direction D. The incident surface 51a of the AD 51 faces the exit surface 41b of the MCP 41 in direction D. As an example, the AD 51 is a semiconductor electron detection element including a semiconductor substrate (e.g., a silicon substrate), which detects electrons emitted from the exit surface 41b of the MCP 41 and incident on the incident surface 51a by avalanche multiplication.

[0025] In the ion detector 1A configured as described above, a positive potential is applied to the incident surface 41a of the MCP41 with respect to the conversion unit 2A, a positive potential is applied to the exit surface 41b of the MCP41 with respect to the incident surface 41a of the MCP41, and a positive potential is applied to the incident surface 51a of the AD51 with respect to the exit surface 41b of the MCP41. A reverse bias voltage is then applied to the AD51. In this state, when an ion i is incident on the conversion unit 2A from one side in direction D, electrons e are emitted from the conversion unit 2A to the other side in direction D. The electrons e emitted from the conversion unit 2A are incident on each hole 41c of the MCP41 from one side in direction D, and the electrons e multiplied at each hole 41c are emitted from each hole 41c to the other side in direction D. Electrons e emitted from MCP41 are focused by electron lens 7 and incident on the incident surface 51a of AD51. The electrons e, multiplied by the avalanche effect in AD51, are output as an electrical signal from the wiring board 6 to an external device. The space from the conversion unit 2A through MCP41 to AD51 is formed within a vacuum-sealed housing (not shown). [Configuration of the conversion unit]

[0026] As shown in Figure 4, the conversion unit 2A includes a support 21, an electron generation layer 22, and an electron emission layer 23. The support 21 has a first surface 21a and a second surface (support surface) 21b. The first surface 21a is a surface facing one side in direction D (upper side in Figure 4). The second surface 21b is a surface facing the other side in direction D (lower side in Figure 4). In this example, each of the first surface 21a and the second surface 21b is a surface perpendicular to direction D. The support 21 has a plurality of holes (through-holes) 21c. The plurality of holes 21c are arranged two-dimensionally along a surface perpendicular to direction D. That is, the plurality of holes 21c are arranged two-dimensionally along the second surface 21b. One end of each hole 21c opens to the first surface 21a. The other end of each hole 21c opens to the second surface 21b. Each pore 21c penetrates the support 21 along direction D, allowing ions i to pass from one side in direction D to the other side in direction D.

[0027] The support 21 is conductive. In this example, the support 21 is formed of a conductive material. As an example, the support 21 is formed of a metallic material (e.g., stainless steel). The thickness of the support 21 is, for example, 20 to 500 μm. The inner diameter of each hole 21c is, for example, 20 to 500 μm. The distance between the centers of adjacent holes 21c is, for example, 25 to 550 μm. The arrangement of the multiple holes 21c when viewed from direction D may be matrix-like or staggered. The shape of each hole 21c when viewed from direction D may be circular or polygonal. The formation of the multiple holes 21c in the support 21 is carried out, for example, by etching.

[0028] The electron generation layer 22 is located on the second surface 21b of the support 21 and covers the other end of each pore 21c of the support 21. In other words, in this example, the electron generation layer 22 is located on the other side in direction D relative to the support 21. The electron generation layer 22 generates electrons e in response to the incidence of ions i passing through each pore 21c. The electron generation layer 22 is formed of a layered material that converts ions into electrons and is self-supporting. In this example, the electron generation layer 22 is formed of a carbon-containing material. As an example of this, the electron generation layer 22 is formed of a film made of graphene, a film made of graphite, etc. The thickness of the electron generation layer 22 is, for example, 0.3 to 30 nm. The electron generation layer 22 may also be formed of, for example, SiN, MoS2, BN, metallic materials, etc.

[0029] The electron emission layer 23 is located on the surface 22a of the electron generation layer 22 opposite to the support 21. In other words, in this example, the electron emission layer 23 is located on the other side in direction D relative to the electron generation layer 22. The electron emission layer 23 is formed of a material with a lower work function than the material of the electron generation layer 22. If the material of the electron generation layer 22 is graphene, the material of the electron emission layer 23 is, for example, an alkali metal (Cs, etc.), a metal fluoride (NaF, MgF2, etc.), or a metal oxide (BaO, SrO, Al2O3, MgO, etc.). The electron emission layer 23 has the function of lowering the work function of the surface 22a of the electron generation layer 22. The contact of the electron emission layer 23 with the surface 22a of the electron generation layer 22 improves the electron emission performance from the electron generation layer 22 to the other side in direction D. The thickness of the electron emission layer 23 is, for example, 0.1 to 10 nm.

[0030] In the conversion unit 2A configured as described above, when a predetermined potential is applied to the support 21 and the electron generation layer 22, and ions i are incident on the electron generation layer 22 from one side in direction D through each pore 21c of the support 21, electrons e are generated in the electron generation layer 22. The electrons e generated in the electron generation layer 22 are emitted to the other side in direction D through the electron emission layer 23. [Manufacturing method for the conversion unit]

[0031] An example of a manufacturing method for the above-mentioned conversion unit 2A will now be described. In this example, the material of the support 21 is stainless steel, the material of the electron generation layer 22 is graphene, and the material of the electron emission layer 23 is Cs.

[0032] First, as shown in Figure 5(a), a graphene film 220 is formed on a first support film 101 made of Cu, and a "graphene film 220 formed on the first support film 101" is prepared. Next, as shown in Figure 5(b), a second support film 102 made of resin (e.g., PMMA) is formed on the graphene film 220 of the "graphene film 220 formed on the first support film 101". Then, as shown in Figure 5(c), the first support film 101 is removed from the graphene film 220 by etching, and a "graphene film 220 formed on the second support film 102" is prepared.

[0033] Next, as shown in Figures 6(a) and (b), the graphene film 220 formed on the second support film 102 is joined to the graphene film 220 formed on the first support film 101. Subsequently, as shown in Figure 6(c), the first support film 101 is removed from the graphene film 220 by etching. Thereafter, the manufacturing process shown in Figures 6(a) to (c) is repeated to form a structure in which multiple layers of graphene films 220 are stacked on the second support film 102.

[0034] Next, as shown in Figure 7(a), the multiple layers of graphene film 220, which are "multiple layers of graphene film 220 stacked on the second support film 102," are bonded to the support 21. Subsequently, as shown in Figure 7(b), the second support film 102 is removed from the multiple layers of graphene film 220 by baking, forming "multiple layers of graphene film 220 stacked on the support 21." This multiple layers of graphene film 220 corresponds to the electron generation layer 22. Subsequently, as shown in Figure 7(c), an electron emission layer 23 made of Cs is formed on the electron generation layer 22 from the side opposite to the support 21, and the conversion section 2A is obtained. [Mechanism of Action and Effects]

[0035] In the ion detector 1A, an electron generation layer 22 that generates electrons e in response to the incidence of ions i is arranged on the second surface 21b of a support 21 perpendicular to the direction D, and multiple pores 21c that allow ions i to pass through are arranged two-dimensionally along the second surface 21b. This ensures the flatness of the electron generation layer 22, so that when ions i with the same mass-to-charge ratio are incident from one side in the direction D, the time it takes for ions i to reach the electron generation layer 22 does not vary depending on the incident position of ions i in the electron generation layer 22. Therefore, the ion detector 1A can suppress variations in ion detection time for ions i with the same mass-to-charge ratio.

[0036] In the ion detector 1A, the support 21 is formed of a conductive material so that it is conductive. This ensures that a predetermined potential is applied to the electron generation layer 22 located on the second surface 21b of the support 21 and that electrons e are supplied to it.

[0037] In the ion detector 1A, each of the multiple holes 21c arranged two-dimensionally along the second surface 21b penetrates the support 21 along direction D. This ensures that ions i can reliably pass through each hole 21c. Furthermore, because collisions between ions i and each hole 21c are suppressed, differences in the timing (time lag) of ions i being converted into electrons e can be suppressed.

[0038] In the ion detector 1A, the electron generation layer 22 is located on the other side of direction D relative to the support 21. As a result, ions i are incident on the electron generation layer 22 through each pore 21c, and electrons e are emitted on the opposite side from the support 21. This suppresses the trapping of electrons e in the support 21 and improves the electron extraction efficiency in the conversion unit 2A (i.e., the number of electrons emitted by the incidence of one ion).

[0039] In the ion detector 1A, an electron emission layer 23 is positioned on the surface of the electron generation layer 22, on the other side in direction D, that is, on the surface 22a opposite to the support 21, and is made of a material with a lower work function than the material of the electron generation layer 22. As a result, electrons e generated in the electron generation layer 22 in response to the incidence of ions i are more easily emitted to the other side in direction D, that is, the side opposite to the support 21, thereby further improving the electron extraction efficiency in the conversion unit 2A.

[0040] In the ion detector 1A, electrons e emitted from the conversion unit 2A are multiplied by the electron multiplier unit 4, and the electrons e emitted from the electron multiplier unit 4 are detected by the electron detection unit 5. This improves the detection sensitivity of ions i.

[0041] In the ion detector 1A, the electron multiplier unit 4 includes an MCP41. This allows for reliable multiplication of electrons e while suppressing variations in the time it takes for electrons e to enter the electron multiplier unit 4 and to exit the unit for ions i with the same mass-to-charge ratio.

[0042] In the ion detector 1A, the electron detection unit 5 includes AD51. This allows for reliable detection of electrons e while simultaneously amplifying them.

[0043] The mass spectrometer 10 comprises an ionization unit 11 that generates ions i, an ion separation unit 12 that separates the ions i generated in the ionization unit 11 according to their mass-to-charge ratio, and an ion detector 1A that detects the ions i separated in the ion separation unit 12. With the mass spectrometer 10, variations in ion detection time for ions i with the same mass-to-charge ratio are suppressed by the ion detector 1A, thereby improving the resolution of the mass spectrometry.

[0044] Figure 8 is a graph showing the relationship between ion detection time (i.e., the time from when an ion enters the ion detector until an electron is detected in the ion detector for ions with the same mass-to-charge ratio) and count for the comparative example. The comparative example corresponds to the detection of ion i in a configuration in which the conversion unit 2A is removed from the ion detector 1A shown in Figure 2, that is, in a configuration in which ion i is converted to electron e on the inner wall of each hole 41c on the incident surface 41a side of the MCP41. As shown in Figure 8, for ions with a mass-to-charge ratio (m / z) of 1000, the ion detection time varied in a time width of approximately 650 ps. For ions with a mass-to-charge ratio of 5000, the ion detection time varied in a time width of approximately 1440 ps. For ions with a mass-to-charge ratio of 10000, the ion detection time varied in a time width of approximately 2040 ps.

[0045] Figure 9 is a graph showing the relationship between electron arrival time and count for the embodiment. Electron arrival time is the time from when ion i is converted to electron e by the conversion unit 2A until the electron e reaches the inner wall of each pore 41c of the MCP41. As shown in Figure 9, in the embodiment, the variation in electron arrival time was suppressed to a time width of approximately 3 ps. In the embodiment, by converting ion i to electron e by the conversion unit 2A, the variation in ion detection time that occurs when the conversion unit 2A is not present can be suppressed. However, variation may occur in the electron arrival time from when ion i is converted to electron e by the conversion unit 2A until the electron e reaches the inner wall of each pore 41c of the MCP41. However, from the results shown in Figures 8 and 9, it was found that the variation in electron arrival time is significantly smaller than the variation in ion detection time when the conversion unit 2A is not present. In other words, it can be said that the embodiment can sufficiently suppress the occurrence of variation in ion detection time.

[0046] Figure 10 is a graph showing the relationship between the mass-to-charge ratio and the jitter during ion incidence. In Figure 10, d corresponds to the maximum height difference of the surface of the electron generation layer 22 when it is assumed that the surface of the electron generation layer 22 into which ion i is incident is bent. In the configuration of the ion detector 1A shown in Figure 2, the electron generation layer 22 is located on the second surface 21b of the support 21 and covers the other end of each hole 21c of the support 21. Therefore, the surface of the electron generation layer 22 located on the holes 21c may bend slightly, but the maximum height difference d of the surface of the electron generation layer 22 in that case is considered to be 2 μm or less. In contrast, as shown in Figure 10, even if the surface of the electron generation layer 22 bends with a maximum height difference of 2 μm, the jitter generated during ion incidence is approximately 500 ps even for ions with a mass-to-charge ratio of 120,000. Therefore, based on the results shown in Figures 8 and 10, it can be said that the configuration of the ion detector 1A shown in Figure 2 is capable of sufficiently suppressing the jitter generated during ion incidence and sufficiently suppressing variations in ion detection time.

[0047] Figure 11 is a graph showing the relationship between the mass-to-charge ratio and the electron extraction efficiency. Example 1 is the electron extraction efficiency in the configuration of the ion detector 1A shown in Figure 2, where the material of the electron generation layer 22 is graphene and the material of the electron emission layer 23 is Cs. Example 2 is the electron extraction efficiency in the configuration of the ion detector 1A shown in Figure 2, where the material of the electron generation layer 22 is graphene and the electron emission layer 23 is not provided. From the results shown in Figure 11, it was found that sufficient electron extraction efficiency can be obtained in both Examples 1 and 2. In particular, it was found that more sufficient electron extraction efficiency can be obtained in Example 1. [Differentiation]

[0048] The present invention is not limited to the example described above. As shown in Figure 12, the electron generation layer 22 may be located on the first surface (support surface) 21a of the support 21. The conversion unit 2B shown in Figure 12 differs from the conversion unit 2A described above, at least in this respect. In the conversion unit 2B, the electron generation layer 22 covers one end of each hole 21c of the support 21. The electron emission layer 23 is located on the region of the support 21-side surface 22b of the electron generation layer 22 corresponding to each hole 21c, and on the second surface 21b of the support 21. The electron emission layer 23 does not have to be located on the second surface 21b of the support 21. In the conversion unit 2B, when an ion i is incident on the electron generation layer 22 from one side in direction D (the upper side in Figure 12) with a predetermined potential applied to the support 21 and the electron generation layer 22, electrons e are generated in the electron generation layer 22. The electrons e generated in the electron generation layer 22 are emitted through the electron emission layer 23 and the holes 21c of the support 21 to the other side in direction D (the lower side in Figure 12). In the manufacturing method of the conversion unit 2B, in the step shown in Figure 7(c) described above, the electron emission layer 23 made of Cs is formed from the support 21 side on the region of the surface 22b of the electron generation layer 22 on the support 21 side that corresponds to each hole 21c.

[0049] As shown in Figure 13, the electron detection unit 5 may include an anode electrode 52 instead of AD 51. The ion detector 1B shown in Figure 13 differs from the ion detector 1A described above in at least this respect. In the ion detector 1B, the incident surface 52a of the anode electrode 52 faces the exit surface 41b of the MCP 41. The anode electrode 52 outputs an electrical signal to an external device in response to the incidence of electrons e on the incident surface 52a. The ion detector 1B may also include a converter 2B instead of a converter 2A.

[0050] As shown in Figure 14, the electron generation layer 22 may be arranged on the incident surface 41a of the MCP 41. The ion detector 1C shown in Figure 14 differs from the ion detector 1B described above in at least this respect. In the ion detector 1C, the conversion unit 2C is configured by forming the electron generation layer 22 on the incident surface 41a of the MCP 41, which functions as a support 21. The ion detector 1C may also be equipped with an AD 51 instead of an anode electrode 52.

[0051] As shown in Figure 15, the electron detection unit 5 may include a photomultiplier tube 53, a light guide 54, and a scintillator layer 55 instead of AD 51. The ion detector 1D shown in Figure 15 differs from the ion detector 1A described above in at least this respect. In the ion detector 1D, the light guide 54 is located on the photomultiplier tube 53, and the scintillator layer 55 is located on the light guide 54. In the ion detector 1D, when electrons e focused by the electron lens 7 enter the scintillator layer 55, light is emitted in the scintillator layer 55. The light emitted in the scintillator layer 55 is guided to the photomultiplier tube 53 by the light guide 54 and detected in the photomultiplier tube 53. The ion detector 1D may also include a converter 2B instead of a converter 2A.

[0052] The ion detector 1A shown in Figure 2 and the ion detector 1D shown in Figure 15 do not necessarily have an MCP41. This allows for stable gain in electron multiplication e. Also, the ion detector 1A shown in Figure 2 and the ion detector 1D shown in Figure 15 do not necessarily have an electron lens 7. This allows for structural simplification. Furthermore, in any of the ion detectors 1A, 1B, 1C, and 1D, the electron multiplication unit 4 may include other electron multiplication units instead of the MCP41. Also, in any of the ion detectors 1A, 1B, and 1C, the electron detection unit 5 may include other electron detection units instead of the AD51 or anode electrode 52.

[0053] Both conversion units 2A and 2B do not need to include an electron emission layer 23, as long as they include a support 21 and an electron generation layer 22. In conversion unit 2A, the second surface 21b of the support 21 on which the electron generation layer 22 is located may be a plane perpendicular to direction D. In conversion unit 2B, the first surface 21a of the support 21 on which the electron generation layer 22 is located may be a plane perpendicular to direction D. In conversion unit 2C, the incident surface 41a of the MCP 41 on which the electron generation layer 22 is located may be a plane perpendicular to direction D. In conversion unit 2A, a member for passing ions i may be located in each hole 21c of the support 21. In conversion unit 2B, a member for passing electrons e may be located in each hole 21c of the support 21. In other words, the support 21 may be provided with multiple passages for passing ions i or electrons e.

[0054] The support 21 may be made of an insulating material, for example, as long as the surface layer including the first surface 21a or the second surface 21b on which the electron generation layer 22 is located is conductive. Alternatively, if the electron generation layer 22 itself can ensure conductivity, the entire support 21 may be made of an insulating material.

[0055] When the material of the main body of the support 21 is a material other than Cu, and the material of the electron generation layer 22 is graphene, in either manufacturing method of the conversion unit 2A or 2B, when joining the multiple layers of graphene film 220, which is "a plurality of layers of graphene film 220 laminated on the second support film 102," to the support 21 (see Figure 7(a)), it is preferable to form a Cu film or Ni film on the surface of the main body of the support 21, for example by plating, to a thickness of 500 nm or more. This improves the adhesion of the electron generation layer 22 to the support 21. From this viewpoint, the support 21 may be a Cu mesh, a stainless steel mesh coated with Cu on its surface, etc. Stainless steel is advantageous in that it has excellent processability. [Explanation of Symbols]

[0056] 1A, 1B, 1C, 1D... Ion detector, 2A, 2B, 2C... Conversion unit, 3... Output unit, 4... Electron multiplication unit, 5... Electron detection unit, 10... Mass spectrometer, 11... Ionization unit, 12... Ion separation unit, 21... Support, 21a... First surface (support surface), 21b... Second surface (support surface), 21c... Hole (pass-through part), 22... Electron generation layer, 22a... Surface, 23... Electron emission layer, 41... MCP (microchannel plate), 51... AD (avalanche diode), D... Direction (predetermined direction), e... Electron, i... Ion.

Claims

1. A conversion unit that emits electrons to the other side in a predetermined direction when ions are incident from one side in a predetermined direction, The system comprises an output unit that outputs an electrical signal in response to the incident electrons emitted from the conversion unit, The conversion unit is A support having a support surface perpendicular to the predetermined direction, It includes an electron generation layer disposed on the support surface and generating electrons in response to the incidence of ions, The support has a plurality of passages that allow the ions or electrons to pass through, The plurality of passages are arranged two-dimensionally along the support surface in an ion detector.

2. The ion detector according to claim 1, wherein the support is conductive.

3. The ion detector according to claim 1, wherein each of the plurality of passage portions is a hole penetrating the support along the predetermined direction.

4. The ion detector according to claim 1, wherein the electron generation layer is formed of a carbon-containing material.

5. The conversion unit further includes an electron emission layer disposed on the surface of the electron generation layer, on the other side of the surface in the predetermined direction, The ion detector according to claim 1, wherein the electron emission layer is formed of a material with a lower work function than the material of the electron generation layer.

6. The ion detector according to claim 1, wherein the electron generation layer is located on the other side in the predetermined direction with respect to the support.

7. The output unit is, An electron multiplier unit that multiplies the electrons emitted from the conversion 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 ion detector according to claim 7, wherein the electron multiplication unit includes a 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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