Ion detector

Abstract

An ion detector of the present invention comprises: a microchannel plate, which is used to receive the incidence of ions and generate secondary electrons, multiply the generated secondary electrons and output them; a plurality of electron impact diodes, which have an effective area narrower than the effective area of ​​the microchannel plate on the electron incident surface facing the microchannel plate, and are used to receive the incidence of the secondary electrons output from the microchannel plate, multiply and detect the incident secondary electrons; and a focusing electrode, which is arranged between the microchannel plate and the electron impact diodes, and is used to focus the secondary electrons toward the electron impact diodes. At least one pair of the electron impact diodes adjacent to each other among the plurality of electron impact diodes are arranged in such a manner that a corner protruding toward the microchannel plate side or the opposite side of the microchannel plate is formed through each other's electron incident surfaces.

Description

Technical Field

[0001] The present disclosure relates to an ion detector. The ion detector of the present disclosure can be used for mass analysis, for example. Background Art

[0002] Patent Document 1 (Patent No. 4869526) discloses a mass analyzer comprising: a pair of microchannel plates that generate secondary electrons from an ion beam; a first anode that detects a portion of the secondary electrons generated in the microchannel plates; and a second anode that is positioned downstream of the first anode and detects secondary electrons generated in the microchannel plates and that pass through a perforation in the first anode.

[0003] Patent Document 2 (Patent No. 4848363) discloses a conventional ion detector comprising two overlapping microchannel plates, a first collecting anode for detecting the majority of secondary electrons emitted from the microchannel plates, and a second collecting anode for detecting the remainder of the secondary electrons emitted from the microchannel plates. Summary of the Invention

[0004] In the mass analyzer described in Patent Document 1, the dynamic range is increased by selecting the ratio of the cross-sectional area of ​​the perforation to the total cross-sectional area of ​​the first anode in a manner that imparts a specific degree of attenuation to the incident secondary electron beam. Furthermore, in the ion detector described in Patent Document 2, the dynamic range is expanded by using two first and second current collecting anodes of different sizes. As described above, an increase in dynamic range is desired in the aforementioned technical field.

[0005] Meanwhile, Patent Document 3 (Japanese Patent Publication No. 2017-16918) describes a charged particle detector comprising: a microchannel plate that emits secondary electrons in response to incident charged particles; a focusing electrode that focuses the secondary electrons emitted from the microchannel plate; and an electron impact diode that receives the focused secondary electrons, multiplies them, and detects them. Even for charged particle detectors of this structure, it is desirable to expand the dynamic range. To this end, for example, the charged particle detector described in Patent Document 3 could utilize multiple electron impact diodes, similar to the use of multiple anodes described in Patent Documents 1 and 2.

[0006] In contrast, in Patent Document 2, two planar anodes are arranged side by side on the same plane. When this structure is applied to a charged particle detector in which secondary electrons are focused by a focusing electrode, as in Patent Document 3, and the active regions of the two electron impact diodes are arranged on the same plane, it can be difficult to reliably ensure total gain because it is difficult to reliably include the active region within the focusing diameter of the secondary electrons generated by the focusing electrode, or because the focusing diameter of the secondary electrons generated by the focusing electrode needs to be set larger to include the active region.

[0007] Therefore, an object of one aspect of the present disclosure is to provide an ion detector capable of reliably ensuring a total gain.

[0008] The ion detector involved in the present disclosure comprises: a microchannel plate, which is used to receive the incidence of ions and generate secondary electrons, multiply the generated secondary electrons and output them; a plurality of electron impact diodes, which have an effective area narrower than the effective area of ​​the microchannel plate on the electron incident surface facing the microchannel plate, and are used to receive the incidence of secondary electrons output from the microchannel plate, and multiply and detect the incident secondary electrons; and a focusing electrode, which is arranged between the microchannel plate and the electron impact diodes, and is used to focus the secondary electrons to the electron impact diodes. At least one pair of adjacent electron impact diodes among the plurality of electron impact diodes are arranged in such a manner that a corner protruding toward the microchannel plate side or the opposite side of the microchannel plate is formed through each other's electron incident surfaces.

[0009] The ion detector has a structure including a microchannel plate, a focusing electrode, and a plurality of electron impact diodes. In particular, in the ion detector, at least one pair of electron impact diodes adjacent to each other among the plurality of electron impact diodes are arranged in such a manner that a corner protruding toward the microchannel plate side or the opposite side of the microchannel plate is formed by each other's electron incident surfaces. Therefore, compared with the case where each other's electron incident surfaces are arranged on the same plane, each other's effective areas can be arranged closer. Therefore, by arranging the effective areas of the plurality of electron impact diodes closer, it becomes easy to include the effective area within the focusing diameter of the secondary electrons generated by the focusing electrode, or the secondary electrons can be focused in a narrower range by the focusing electrode, and thus, the total gain of the incident ions can be reliably ensured.

[0010] Alternatively, a cover may be provided, which is disposed between the focusing electrode and the electron-impact diodes and has an opening wider than the effective area of ​​the plurality of electron-impact diodes as viewed from the incident direction of the secondary electrons of the electron-impact diodes. In this case, the cover prevents charging.

[0011] Alternatively, the opening may be a long hole with the effective regions of the pair of electron impact diodes arranged in the longitudinal direction. In this case, secondary electrons can be appropriately incident on the pair of electron impact diodes arranged closer to the effective regions as described above through the long hole of the cover.

[0012] Alternatively, each of the plurality of electron impingement diodes may be provided with an output terminal for outputting a detection signal on the side opposite to the electron incident plane, and the output terminals of the pair of electron impingement diodes may be arranged so as to form a corner portion that protrudes toward the electron incident plane or toward the side opposite to the electron incident plane. This arrangement of the output terminals is suitable when the active regions of the pair of electron impingement diodes are arranged close to each other as described above.

[0013] Alternatively, the device may include a voltage supply unit that applies a driving voltage to each of the plurality of electron impingement diodes. The voltage supply unit applies driving voltages of different values ​​to at least two of the plurality of electron impingement diodes, thereby causing the gains of the two impingement diodes to differ. In this case, for example, by using electron impingement diodes with relatively high gain for detection when the number of incident ions is small, and using electron impingement diodes with relatively low gain for detection when the number of incident ions is large, appropriate detection results can be obtained over a wide range of incident ion numbers. In other words, in this case, the dynamic range can be expanded.

[0014] Alternatively, when viewed from the direction of incidence of secondary electrons, the electron impingement diode includes an active region and an inactive region surrounding the active region. When viewed from the incident direction, the active region is offset in at least one direction relative to the center of the inactive region, and the pair of electron impingement diodes are arranged adjacent to each other with the offset sides of the active region. In this case, by arranging the active regions of the pair of electron impingement diodes closer together, the dead zone can be reduced.

[0015] A mask may be provided, which is disposed between the focusing electrode and the electron impact diode and blocks a portion of the secondary electrons incident on at least one electron impact diode. As described above, the gain of the incident ions can be controlled by using the mask.

[0016] The mask may be formed on the electron incident surface of the electron impingement diode, or the mask may be arranged apart from the electron incident surface of the electron impingement diode.

[0017] According to the present disclosure, an ion detector capable of reliably ensuring a total gain can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1(a) is a diagram showing an ion detector according to one embodiment, and is an overall cross-sectional view.

[0019] Figure 1 (b) is Figure 1 (a) is a top view of an electron impact diode shown.

[0020] Figure 2 (a) is a partial enlargement showing Figure 1 The diagram of the ion detector shown in (a) is Figure 1 (a) is an enlarged view of the area AR.

[0021] Figure 2 (b) is a side view of a part of the region AR.

[0022] Figure 3 It shows Figure 1 (a), (b), and Figure 2 Schematic circuit diagrams of an example of an ion detector shown in (a) and (b).

[0023] Figure 4 (a) is used to illustrate Figure 1 (a), (b), Figure 2 (a), (b), and Figure 3 The graphs showing the operation and effects of the ion detector are examples of the case where one electron impact diode is used (or the case where a plurality of electron impact diodes are used with the same gain).

[0024] Figure 4 (b) is used to illustrate Figure 1 (a), (b), Figure 2 (a), (b), and Figure 3 The graphs showing the operation and effects of the ion detector shown relate to the ion detector according to the embodiment.

[0025] Figure 5 FIG. 1 is a schematic circuit diagram of an ion detector according to a modification example.

[0026] Figure 6 This is a schematic circuit diagram of an ion detector according to another modification.

[0027] Figure 7 (a) is a plan view of a modified example of an electron impact diode.

[0028] Figure 7 (b) is a top view of a modified example of an electron impact diode. DETAILED DESCRIPTION

[0029] Hereinafter, an ion detector according to one embodiment will be described. In the description of each figure, the same or corresponding elements are denoted by the same reference numerals, and overlapping descriptions may be omitted.

[0030] Figure 1 (a) is a diagram showing an ion detector according to one embodiment, and is an overall cross-sectional view. Figure 1 (b) is Figure 1 The top view of the electron impact diode shown in (a). Figure 1 As shown in (a) and (b) of FIG. 1 , the ion detector 1 includes a first unit 100 and a second unit 200. The first unit 100 includes a microchannel plate (MCP 110), an electron lens 120, and a mesh electrode 130. The ion detector 1 can be used for mass analysis, for example.

[0031] The MCP 110 is a circular plate with an input surface 110a and an output surface 110b opposite the input surface 110a. The MCP 110 is held by an input-side electrode 111 and an output-side electrode 112. For example, the MCP 110 comprises a thin, disc-shaped structure, or main body, primarily composed of lead glass. The main body has multiple through-holes, or channels, extending along the thickness direction (from the input surface 110a toward the output surface 110b), in addition to the annular outer periphery. Electrodes are also formed on the outer peripheries of the input surface 110a and the output surface 110b.

[0032] The MCP 110 is used to receive ion incident from the input surface 110a to generate secondary electrons, and multiply the generated secondary electrons and output them from the output surface 110b. The gain of the MCP 110 is determined by the ratio of the channel length to the channel diameter corresponding to the thickness of the MCP 110 and the inherent secondary electron emission coefficient of the material, for example, 1 to 10 4 degree (e.g. 200).

[0033] An opening A1 is formed in the input-side electrode 111 and the output-side electrode 112. Opening A1 is perpendicular to the input surface 110a and the output surface 110b and is formed in a circular shape centered on a reference axis Ax passing through the center of the MCP 110. Opening A1 defines an active region 110P of the MCP 110. Specifically, the region of the MCP 110 exposed from opening A1, as viewed along the reference axis Ax, defines the active region 110P of the MCP 110.

[0034] Electron lens 120 is positioned on the output surface 110b side of MCP 110. Electron lens 120 includes a pair of focusing electrodes 121 and 122, each positioned to surround reference axis Ax. Focusing electrodes 121 and 122 are cylindrically centered on reference axis Ax. Focusing electrode 121 is secured to mesh electrode 130 via insulating spacers, while focusing electrode 122 is secured to focusing electrode 121 via insulating spacers. Specifically, mesh electrode 130 is positioned between MCP 110 and electron lens 120 (focusing electrode 121).

[0035] The potential of mesh electrode 130 is higher than that of output surface 110b of MCP 110. Mesh electrode 130 accelerates electrons and relatively reduces their angular component, thereby improving their convergence. Focusing electrodes 121 and 122 are located between MCP 110 and the electron impact diode (described later) and are used to focus secondary electrons output from MCP 110 toward the electron impact diode.

[0036] Figure 2 (a) is a partial enlargement showing Figure 1 The diagram of the ion detector shown in (a) is Figure 1 (a) is an enlarged view of the area AR. Figure 2 (b) is a side view of a part of the region AR. Figure 1 (a), (b), and Figure 2 As shown in (a) and (b) of FIG. 1 , the second unit 200 is provided on the side of the focusing electrode 122 opposite to the MCP 110. The second unit 200 includes a cover 210 and a plurality (two in this case) of electron impact diodes 220A and 220B.

[0037] The electron impact diodes 220A and 220B are single-channel components. The electron impact diodes 220A and 220B are respectively used to receive the incident secondary electrons output from the MCP 110 and focused by the focusing electrodes 121 and 122, and to multiply and detect the incident secondary electrons. The electron impact diodes 220A and 220B are, for example, avalanche diodes. In this case, the gains of the electron impact diodes 220A and 220B are, for example, 100 to 800 (e.g., 400) in the electron impact gain and 1 to 10 in the avalanche gain. 2 (e.g. 50). Thus, the total gain of the ion detector 1 is, for example, 10 6 degree (for example, 4×10 6 ).

[0038] The electron impact diode 220A is mounted on a substrate 203A. The substrate 203A is attached to the focusing electrode 122 via an insulating spacer 201 and fixed to the base 202 constituting the bottom of the ion detector 1. The electron impact diode 220B is similarly mounted on a substrate 203B fixed to the base 202.

[0039] Electron impact diode 220A includes an electron incident surface 200A that faces MCP 110 and focusing electrodes 121 and 122 and receives incident secondary electrons. Electron impact diode 220A includes an effective region 221A located at the center of electron incident surface 200A, as viewed from the incident direction of secondary electrons (along reference axis Ax), that detects electrons; and an inactive region 222A located around effective region 221A and covered by, for example, a mask, that does not detect electrons.

[0040] The electron impingement diode 220B includes an electron incident surface 200B that faces the MCP 110 and the focusing electrodes 121 and 122 and receives incident secondary electrons. The electron impingement diode 220B includes an effective region 221B located at the center of the electron incident surface 200B, as viewed from the incident direction of the secondary electrons (along the reference axis Ax), and that detects electrons; and an inactive region 222B located around the effective region 221B and covered, for example, by a mask, that does not detect electrons. The effective regions 221A and 221B of the electron impingement diodes 220A and 220B are narrower than the active region 110P of the MCP 110. The effective regions 221A and 221B of the electron impingement diodes 220A and 220B, respectively, are within the focusing range of the secondary electrons generated by the focusing electrodes 121 and 122 at the electron incident surfaces 200A and 200B.

[0041] Here, the electron impact diodes 220A and 220B are arranged symmetrically with reference axis Ax as the center. More specifically, the pair of electron impact diodes 220A and 220B are arranged so that a corner protruding toward the side opposite to MCP110 is formed by their respective electron incident surfaces 200A and 200B (or by extending the plane of the electron incident surfaces 200A and 200B), and are supported on base 202 via substrates 203A and 203B. Here, the corner formed by the electron incident surfaces 200A and 200B has reference axis Ax as its vertex. Furthermore, substrates 203A and 203B, on which the electron impact diodes 220A and 220B are mounted, are tilted so as to form a corner protruding toward the side opposite to MCP110.

[0042] Thus, for example, compared to the case where the electron impingement diodes 220A and 220B are arranged with the electron incident surfaces 200A and 200B on the same plane, the distance DA between the effective regions 221A and 221B of the electron impingement diodes 220A and 220B is shortened.

[0043] On the other hand, the electron impingement diode 220A is provided with an output terminal 223A (output port (coaxial connector)) for outputting the detection signal of secondary electrons. Output terminal 223A protrudes and extends from the surface of the substrate 203A opposite to the surface on which the electron impingement diode 220A is provided. Furthermore, the electron impingement diode 220B is provided with an output terminal 223B (output port (coaxial connector)) for the same purpose. Output terminal 223B protrudes and extends from the surface of the substrate 203B opposite to the surface on which the electron impingement diode 220B is provided.

[0044] Furthermore, the output terminals 223A and 223B (the extension lines of the output terminals 223A and 223B) are arranged so as to form corners that protrude toward the electron incident surfaces 200A and 200B and the MCP 110. Here, the corners formed by the electron incident surfaces 200A and 200B and the corners formed by the output terminals 223A and 223B protrude in opposite directions.

[0045] The cover 210 is disposed between the focusing electrode 122 and the electron-impact diodes 220A and 220B, and is clamped between the focusing electrode 122 and the substrate 202, for example, via an insulating spacer 201 or the like. An opening A2 centered on the reference axis Ax is formed in the cover 210. When viewed from the direction of incidence of secondary electrons from the electron-impact diodes 220A and 220B, the opening A2 is wider than the effective regions 221A and 221B of the electron-impact diodes 220A and 220B. In particular, the opening A2 is an elongated hole with the direction in which the effective regions 221A and 221B are arranged as the longitudinal direction. Thus, when viewed from the direction in which secondary electrons from the electron-impact diodes 220A and 220B are incident, the effective regions 221A and 221B are exposed through the opening A2. Furthermore, the opening A2 is narrower than the opening A1. The cover 210 is made of, for example, stainless steel.

[0046] Next, the electrical connection relationship of the ion detector 1 will be described. Figure 3 It shows Figure 1 (a), (b), and Figure 2 Schematic circuit diagram of an example of an ion detector shown in (a) and (b). Figure 3As shown, the ion detector 1 includes a main unit and a voltage supply circuit. The main unit is composed of the first unit 100 and the second unit 200 described above. In the first unit 100, the resistance between the input surface 110a and the output surface 110b of the MCP 110 is, for example, 30 MΩ. The mesh electrode 130 is connected between the resistor R1 and the resistor R2 and is connected to the ground potential GND via the resistor R2. The focusing electrode 121 is set to the same potential as the output surface 110b of the MCP 110. The focusing electrode 122 is connected to a negative potential via the resistor R3.

[0047] In the second unit 200, the electron impinger diode 220A has one terminal connected to a negative potential via a resistor R4 and the other terminal connected to the ground potential GND via a capacitor C1. The detection signal of the electron impinger diode 220A is obtained from a signal line 500A connected to an output terminal 223A. The electron impinger diode 220B has one terminal connected to a negative potential via a resistor R5 and the other terminal connected to the ground potential GND via a capacitor C2. The detection signal of the electron impinger diode 220B is obtained from a signal line 500B connected to an output terminal 223B.

[0048] The voltage supply circuit includes a power supply unit 300 and a power supply unit (voltage supply unit) 400. The power supply unit 300 includes a power supply V1 for setting the potential of the input surface 110a of the MCP 110 via terminal T1, and a power supply V2 for ensuring a predetermined potential difference between terminal T1 and terminal T2, which is connected to the output surface 110b of the MCP 110. Power supply V1 is disposed between ground GND and terminal T1 and generates an electromotive force (EMF) for setting the potential of terminal T1 to, for example, -7 kV. Power supply V2 generates an electromotive force (EMF) to ensure a potential difference of, for example, 0 to 3.5 kV between the input surface 110a and the output surface 110b.

[0049] The power supply unit 400 includes a power supply V3 connected to one terminal of the electron impact diode 220A via a terminal T3 and a resistor R4, and a power supply V4 connected to one terminal of the electron impact diode 220B via a terminal T4 and a resistor R5. Power supply V3 is disposed between the ground potential GND and terminal T3 and generates an electromotive force for setting the potential of terminal T3 to, for example, 350 V. Power supply V4 is disposed between the ground potential GND and terminal T4 and generates an electromotive force for setting the potential of terminal T4 to, for example, 250 V, a potential different from the potential of terminal T3.

[0050] Specifically, power supply unit 400 is used to apply a driving voltage to each of electron impingement diodes 220A and 220B. By applying driving voltages of different values ​​to each of electron impingement diodes 220A and 220B, the gains of the respective impingement diodes 220A and 220B are varied. The difference in gain between the impingement diodes 220A and 220B is, for example, approximately 10 times. As described above, in ion detector 1, secondary electrons emitted from MCP 110 are focused by focusing electrodes 121 and 122 and fed into multiple (here, two) electron impingement diodes 220A and 220B having different gains.

[0051] Next, the operation and effects of the ion detector 1 will be described. Figure 4 (a) is used to illustrate Figure 1 (a), (b), Figure 2 (a), (b), and Figure 3 The graphs showing the operation and effects of the ion detector are for examples of the case where one electron impact diode is used (or the case where a plurality of electron impact diodes are used with the same gain).

[0052] Figure 4 (b) is used to illustrate Figure 1 (a), (b), Figure 2 (a), (b), and Figure 3 The graph showing the effects of an ion detector is for an ion detector according to an embodiment. In this case, when the gain is relatively high (line L1), a large number of ions enter the ion detector (when the number of incident ions increases), detector saturation or over-range of the digitizer occurs. On the other hand, in this case, when the gain is relatively low (line L2), single ion detection becomes difficult. Therefore, multiple measurements are required while varying the gain.

[0053] In contrast, Figure 4 As shown in (b), the ion detector 1 according to this embodiment can appropriately detect single ions when the number of incident ions is small, using the detection signal of the electron impact diode with a relatively high gain (line L3). Furthermore, when the number of incident ions is large, the detection signal of the electron impact diode with a relatively low gain and a large upper limit of the saturated number of incident ions (line L4) is used, thereby reducing the influence of detector saturation. In other words, the ion detector 1 achieves an expanded dynamic range. Figure 4 (b) is used to illustrate Figure 1 (a), (b), Figure 2 (a), (b), and Figure 3 The graphs showing the operation and effects of the ion detector shown relate to the ion detector according to the embodiment.

[0054] In addition, in the ion detector 1, the power supply unit 400 applies a driving voltage to the electron impact diodes 220A and 220B in such a manner that the detection range of the electron impact diode with relatively high gain (here, the range of the number of incident ions is about 1 to 1000) and the detection range of the electron impact diode with relatively low gain (here, the range of the number of incident ions is about 10 to 10000) have a repetition range S that partially overlap with each other.

[0055] The repetition range S is the range between the lower limit of the number of incident ions detectable by an electron impact diode with relatively low gain (here, approximately 10) and the upper limit of the number of incident ions detectable by an electron impact diode with relatively high gain (here, approximately 1000). By setting this repetition range S, it is possible to utilize this repetition range S to calibrate electron impact diodes with different gains.

[0056] As described above, the ion detector 1 includes the MCP 110, focusing electrodes 121 and 122, and electron impact diodes 220A and 220B. In particular, in the ion detector 1, a pair of adjacent electron impact diodes 220A and 220B are arranged so that their electron incident surfaces 200A and 200B form a corner that protrudes toward the side opposite to the MCP 110. Consequently, compared to a case where the electron incident surfaces 200A and 200B are arranged on the same plane, the effective regions 221A and 221B can be positioned closer together.

[0057] Therefore, by arranging the effective areas 221A and 221B of the electron impact diodes 220A and 220B more closely, the effective areas 221A and 221B can be included in the focusing diameter of the secondary electrons generated by the focusing electrodes 121 and 122, or the secondary electrons can be focused within a narrower range by the focusing electrodes 121 and 122, thereby reliably ensuring the total gain of the incident ions.

[0058] In addition, even in the ion detector 1 of the above structure, it is desired to expand the dynamic range. Therefore, in the ion detector 1, the power supply unit 400 applies driving voltages of different values ​​to each of the two electron impact diodes 220A and 220B, so that the gains of each other are different. Thus, for example, by adopting detection by an electron impact diode with a relatively high gain when the number of incident ions is small, and adopting detection by an electron impact diode with a relatively low gain when the number of incident ions is large, appropriate detection results can be obtained over a wide range of the number of incident ions. That is, according to the ion detector 1, the dynamic range can be expanded. In addition, in the ion detector 1, when a plurality of electron impact diodes with different gains are used as described above, crosstalk can be suppressed by using a plurality of single-channel elements, compared with the case of using multi-channel elements.

[0059] In the ion detector 1, effective regions 221A and 221B of the electron impact diodes 220A and 220B are included in the focusing range of secondary electrons generated by the focusing electrodes 121 and 122. Therefore, the secondary electrons can be incident on the effective regions 221A and 221B of the electron impact diodes 220A and 220B in the same manner.

[0060] Ion detector 1 is disposed between focusing electrodes 121 and 122 and electron impact diodes 220A and 220B, and includes a cover 210 having an opening A2 that is wider than effective areas 221A and 221B when viewed from the direction of incidence of secondary electrons from electron impact diodes 220A and 220B. Therefore, cover 210 prevents charging.

[0061] In the ion detector 1, the opening A2 is an elongated hole with the effective regions 221A and 221B of the electron impact diodes 220A and 220B arranged in the longitudinal direction. Therefore, secondary electrons can be appropriately incident through the elongated hole of the cover 210 onto the pair of electron impact diodes 220A and 220B arranged closer to the effective regions 221A and 221B as described above.

[0062] In the ion detector 1, output terminals 223A and 223B for outputting detection signals are provided on the sides of the electron impact diodes 220A and 220B, respectively, opposite to the electron incident surfaces 200A and 200B. Furthermore, the output terminals 223A and 223B are arranged so as to form corners that protrude toward the electron incident surfaces 200A and 200B. When the active regions 221A and 221B of the pair of electron impact diodes 220A and 220B are arranged close to each other as described above, the output terminals 223A and 223B can be arranged as described above.

[0063] The above embodiment is an example of the ion detector according to the present disclosure. Therefore, the ion detector according to the present disclosure can be arbitrarily modified from the above ion detector. Next, a modification example will be described.

[0064] Figure 5 : is a schematic circuit diagram of an ion detector according to a modification example. Figure 5 As shown, ion detector 1A differs from ion detector 1 in that it includes power supply 400A in place of power supply 400. It is identical to ion detector 1 in all other respects. Power supply (voltage supply) 400A includes a single power supply V5 connected to one terminal of electron impact diode 220A via resistor R6, terminal T3, and resistor R4, and to one terminal of electron impact diode 220B via resistor R7, terminal T4, and resistor R5. Power supply 400A also includes a Zener diode D1 interposed between resistor R6 and ground potential GND, and a Zener diode D2 interposed between resistor R7 and ground potential GND.

[0065] This power supply unit 400A can also apply different drive voltages to the two electron impactor diodes 220A and 220B, for example, by adjusting the relative resistance values ​​of resistors R6 and R7, thereby varying their gains. Furthermore, in the ion detector 1, by using Zener diodes D1 and D2, a single power supply V5 can be used to supply voltage to both electron impactor diodes 220A and 220B.

[0066] Figure 6 FIG. 1 is a schematic circuit diagram of an ion detector according to another modification. Figure 6 As shown, the ion detector 1B includes a power supply unit 600 as a voltage supply circuit. In the power supply unit 600, a power supply V1 is connected to the input surface 110a of the MCP 110 via the terminal T1. The power supply V1 has a function for floating the ion detector 1B. The power supply unit 600 includes a power supply V6 and a power supply V7. The power supply V6 is provided between the terminal T1 connected to the input surface 110a and the terminal T2 connected to the output surface 110b. The power supply V6 is used to apply a voltage (e.g., 0V to 1000V) to the MCP 110. The power supply V7 is provided between the terminal T2 and the terminal T3. The power supply V7 is used to supply a voltage (e.g., 3kV to 7kV) to the focusing electrodes 121 and 122 and the electron impact diodes 220A and 220B that are further downstream than the MCP 110.

[0067] Resistors R1 and R2 serve as bleeder resistors for supplying potential to mesh electrode 130 and focus electrodes 121 and 122. Capacitors C1 and C2 form a loop that allows high-speed signals to return to the other terminals of electron-shock diodes 220A and 220B via ground potential GND with low impedance. Capacitors C1 and C2, along with resistors R4 and R5, form a low-pass filter that removes power supply noise. Resistor R3 prevents coupling between focus electrode 122 and ground potential GND.

[0068] Capacitor C3 is provided on signal line 500A connected to output terminal 223A of electron impingement diode 220A, and capacitor C4 is provided on signal line 500B connected to output terminal 223B of electron impingement diode 220B. Capacitors C3 and C4 function as coupling capacitors, maintaining the potential of the other terminals of electron impingement diodes 220A and 220B while allowing high-frequency signals to pass through. Resistor R9 is connected to the upstream of capacitor C3 on signal line 500A. Furthermore, resistor R10 is provided to the upstream of capacitor C4 on signal line 500B.

[0069] Resistors R9 and R10 are blocking resistors that apply a potential to one terminal of electron-shock diodes 220A and 220B, preventing the signal from returning to power supply unit 600. A circuit for Zener diode D3 and a circuit for resistor R8 and Zener diode D4 are formed between resistor R2 and resistors R9 and R10, respectively. Resistor R8 absorbs the potential difference between Zener diodes D3 and D4.

[0070] The ion detector floats when detecting positive and negative ions. In this case, using Zener diodes D3 and D4 allows voltage to be supplied to electron impact diodes 220A and 220B without increasing the power supply. For example, using a 350V diode for Zener diode D3 and a 250V diode for Zener diode D4 allows different voltages to be applied to electron impact diodes 220A and 220B.

[0071] Here, Figure 7 (a) is a top view of a modified example of an electron impact diode. Figure 7 As shown in (a), in ion detectors 1 to 1B, by partially removing electron impact diodes 220A and 220B, effective regions 221A and 221B can be arranged closer together. Here, a portion of ineffective regions 222A and 222B is removed to shorten the length of a pair of opposing sides of electron impact diodes 220A and 220B when viewed from the incident direction of secondary electrons.

[0072] Thus, in electron-impact diodes 220A and 220B, when viewed from the incident direction of secondary electrons, effective regions 221A and 221B are offset in one direction (the cut-off side) relative to the center of inactive regions 222A and 222B. Therefore, by arranging the two electron-impact diodes 220A and 220B so that the offset sides of effective regions 221A and 221B are adjacent, it is possible to arrange effective regions 221A and 221B closer together.

[0073] in addition, Figure 7 (b) is a top view of a modified example of an electron impact diode. Figure 7 As shown in (b), the ion detectors 1 to 1B may include a mask M that shields a portion of the secondary electrons incident on at least one electron impact diode (here, the electron impact diode 220B) among the multiple electron impact diodes. The mask M can be arranged at any position between the focusing electrode 122 and the electron impact diode 220B. As an example, the mask M can be formed on the electron incident surface 200B of the electron impact diode 220B. In this case, the mask M can be formed by, for example, forming a film by evaporating Al on the surface that becomes the electron incident surface 200B after the process of the electron impact diode 220B, or forming a film by ion implantation from the surface side of the electron impact diode 220 that becomes the electron incident surface 200B during the process.

[0074] Alternatively, the mask M may be disposed separately from the electron incident surface 200B. In this case, the mask M may be formed by, for example, placing a mesh on the trajectory of the secondary electrons focused by the focusing electrodes 121 and 122 as they travel toward the electron impact diode 220B. Furthermore, in this case, the mask M may be disposed in the opening A2 of the cover 210.

[0075] Alternatively, the amount of secondary electrons incident on at least one of the plurality of electron-impact diodes may be controlled by disposing the diode offset so that a portion of its effective region is located outside the focal diameter of the secondary electrons.

[0076] As described above, in ion detectors 1 to 1B, as methods for making the gains of at least two of the multiple impinger diodes different from each other, any combination of methods can be used: a method of varying the driving voltage, a method of shielding secondary electrons with a mask, and a method of adjusting the amount of incident secondary electrons by shifting the effective region. That is, as an example, one of the above methods can be applied to a certain pair of impinger diodes, and another of the above methods can be applied to another pair of impinger diodes. Furthermore, any of the above methods can be applied to make the gains of three or more impinger diodes different from each other.

[0077] In addition, in the ion detectors 1 to 1B, from the viewpoint of making the gains of at least two of the plurality of electron impact diodes different from each other, as shown in FIG. Figure 2 The configuration shown in (b) of FIG. 1 , in which a pair of electron impact diodes 220A and 220B are arranged so that their electron incident surfaces 200A and 200B form a corner protruding toward the side opposite to MCP 110, is not essential. Furthermore, in ion detectors 1 to 1B, from the perspective of arranging effective regions 210A and 210B closer together, a configuration in which the gains of at least two electron impact diodes are different from each other is not essential.

[0078] Alternatively, you can: Figure 2 In contrast to the example shown in (b), the pair of electron impact diodes 220A and 220B are arranged so that their respective electron incident surfaces 200A and 200B (or the planes extending the electron incident surfaces 200A and 200B) form a corner portion protruding toward the MCP 110. In this case, the output terminals 223A and 223B (the extension of the output terminals 223A and 223B) may also be arranged so that a corner portion protrudes toward the side opposite to the electron incident surfaces 200A and 200B and the MCP 110.

[0079] Furthermore, in the above embodiment, an example in which two electron impact diodes 220A and 220B are provided is described. However, the ion detectors 1 to 1B may include three or more electron impact diodes.

Claims

1. An ion detector, wherein: have: A microchannel plate, which is used to receive incident ions to generate secondary electrons, multiply the generated secondary electrons and output them; a plurality of electron impact diodes, each having an effective area narrower than an effective area of ​​the microchannel plate on an electron incident surface facing the microchannel plate, for receiving the secondary electrons output from the microchannel plate, multiplying the incident secondary electrons, and detecting the incident secondary electrons; as well as a focusing electrode disposed between the microchannel plate and the electron impact diode, for focusing the secondary electrons toward the electron impact diode, At least one pair of adjacent electron impingement diodes among the plurality of electron impingement diodes are arranged such that their electron incident surfaces form a corner portion protruding toward the microchannel plate or the side opposite to the microchannel plate.

2. The ion detector according to claim 1, wherein The invention further comprises a cover disposed between the focusing electrode and the electron impingement diodes and having an opening wider than an effective area of ​​the plurality of electron impingement diodes when viewed from an incident direction of secondary electrons of the electron impingement diodes.

3. The ion detector according to claim 2, wherein The opening is a long hole whose longitudinal direction is the direction in which the effective regions of the pair of electron impact diodes are arranged.

4. The ion detector according to any one of claims 1 to 3, wherein Each of the plurality of electron impact diodes is provided with an output terminal for outputting a detection signal on the side opposite to the electron incident surface. The output terminals of the pair of electron impact diodes are arranged so as to form corner portions that protrude toward the electron incident surface or toward the side opposite to the electron incident surface.

5. The ion detector according to any one of claims 1 to 3, wherein The device comprises: a voltage supply unit for applying a driving voltage to each of the plurality of electron impact diodes; The voltage supply unit applies drive voltages of different values ​​to at least two of the plurality of electron impingement diodes, thereby making the gains of the at least two electron impingement diodes different from each other. The ion detector according to claim 4 , wherein: The device comprises: a voltage supply unit for applying a driving voltage to each of the plurality of electron impact diodes; The voltage supply unit applies drive voltages of different values ​​to at least two of the plurality of electron impingement diodes, thereby making the gains of the at least two electron impingement diodes different from each other.

7. The ion detector according to any one of claims 1 to 3, wherein When viewed from the incident direction of the secondary electrons of the electron-impact diode, the electron-impact diode includes the effective region and an ineffective region located around the effective region. When viewed from the incident direction, the effective area is offset in at least one direction relative to the center of the ineffective area. The pair of electron impact diodes are arranged so that the deflected sides of the active region are adjacent to each other.

8. The ion detector according to claim 4, wherein When viewed from the incident direction of the secondary electrons of the electron-impact diode, the electron-impact diode includes the effective region and an ineffective region located around the effective region. When viewed from the incident direction, the effective area is offset in at least one direction relative to the center of the ineffective area. The pair of electron impact diodes are arranged so that the deflected sides of the active region are adjacent to each other.

9. The ion detector according to claim 5, wherein When viewed from the incident direction of the secondary electrons of the electron-impact diode, the electron-impact diode includes the effective region and an ineffective region located around the effective region. When viewed from the incident direction, the effective area is offset in at least one direction relative to the center of the ineffective area. The pair of electron impact diodes are arranged so that the deflected sides of the active region are adjacent to each other.

10. The ion detector according to claim 6, wherein When viewed from the incident direction of the secondary electrons of the electron-impact diode, the electron-impact diode includes the effective region and an ineffective region located around the effective region. When viewed from the incident direction, the effective area is offset in at least one direction relative to the center of the ineffective area. The pair of electron impact diodes are arranged so that the deflected sides of the active region are adjacent to each other.

11. The ion detector according to any one of claims 1 to 3, wherein A mask is provided, which is arranged between the focusing electrode and the electron-impact diodes and shields a portion of the secondary electrons incident on at least one of the electron-impact diodes.

12. The ion detector according to claim 4, wherein A mask is provided, which is arranged between the focusing electrode and the electron-impact diodes and shields a portion of the secondary electrons incident on at least one of the electron-impact diodes.

13. The ion detector according to claim 5, wherein A mask is provided, which is arranged between the focusing electrode and the electron-impact diodes and shields a portion of the secondary electrons incident on at least one of the electron-impact diodes.

14. The ion detector according to claim 6, wherein A mask is provided, which is arranged between the focusing electrode and the electron-impact diodes and shields a portion of the secondary electrons incident on at least one of the electron-impact diodes.

15. The ion detector according to claim 7, wherein A mask is provided, which is arranged between the focusing electrode and the electron-impact diodes and shields a portion of the secondary electrons incident on at least one of the electron-impact diodes.

16. The ion detector according to claim 8, wherein A mask is provided, which is arranged between the focusing electrode and the electron-impact diodes and shields a portion of the secondary electrons incident on at least one of the electron-impact diodes.

17. The ion detector according to claim 9, wherein A mask is provided, which is arranged between the focusing electrode and the electron-impact diodes and shields a portion of the secondary electrons incident on at least one of the electron-impact diodes.

18. The ion detector according to claim 10, wherein A mask is provided, which is arranged between the focusing electrode and the electron-impact diodes and shields a portion of the secondary electrons incident on at least one of the electron-impact diodes.

19. The ion detector according to claim 11, wherein The mask is formed on the electron incident surface of the electron impact diode.

20. The ion detector according to claim 12, wherein The mask is formed on the electron incident surface of the electron impact diode.

21. The ion detector according to claim 13, wherein The mask is formed on the electron incident surface of the electron impact diode.

22. The ion detector according to claim 14, wherein The mask is formed on the electron incident surface of the electron impact diode.

23. The ion detector according to claim 15, wherein The mask is formed on the electron incident surface of the electron impact diode.

24. The ion detector according to claim 16, wherein The mask is formed on the electron incident surface of the electron impact diode.

25. The ion detector according to claim 17, wherein The mask is formed on the electron incident surface of the electron impact diode.

26. The ion detector according to claim 18, wherein The mask is formed on the electron incident surface of the electron impact diode.

27. The ion detector according to claim 11, wherein The mask is arranged to be separated from the electron incident surface of the electron impact diode.

28. The ion detector according to claim 12, wherein The mask is arranged to be separated from the electron incident surface of the electron impact diode.

29. The ion detector according to claim 13, wherein The mask is arranged to be separated from the electron incident surface of the electron impact diode.

30. The ion detector according to claim 14, wherein The mask is arranged to be separated from the electron incident surface of the electron impact diode.

31. The ion detector according to claim 15, wherein The mask is arranged to be separated from the electron incident surface of the electron impact diode.

32. The ion detector according to claim 16, wherein The mask is arranged to be separated from the electron incident surface of the electron impact diode.

33. The ion detector according to claim 17, wherein The mask is arranged to be separated from the electron incident surface of the electron impact diode.

34. The ion detector according to claim 18, wherein The mask is arranged to be separated from the electron incident surface of the electron impact diode.

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