ion detector

Abstract

An ion detector according to the present application includes: a microchannel plate for accepting incidence of ions to generate secondary electrons, multiplying the generated secondary electrons, and outputting; a plurality of electron-impact type diodes having narrower effective areas than an effective area of the microchannel plate, for accepting incidence of the secondary electrons output from the microchannel plate, multiplying the incident secondary electrons, and detecting; a focusing electrode disposed between the microchannel plate and the electron-impact type diodes, for focusing the secondary electrons toward the electron-impact type diodes; and a voltage supply portion for applying a driving voltage to each of the plurality of electron-impact type diodes.

Description

Technical Field

[0001] This disclosure relates to ion detectors. The ion detectors disclosed herein can be used, for example, for mass analysis. Background Technology

[0002] Patent document 1 (patent no. 4869526) discloses a mass analyzer. This mass analyzer includes: a pair of microchannel plates that generate secondary electrons due to an ion beam, a first anode that detects a portion of the secondary electrons generated in the microchannel plates, and a second anode disposed after the first anode that detects secondary electrons generated in the microchannel plates and passing through a perforation of the first anode.

[0003] Patent document 2 (patent no. 4848363) discloses a conventional ion detector. This conventional ion detector comprises: two overlapping microchannel plates, a first current collector anode that detects most of the secondary electrons emitted from the microchannel plates, and a second current collector anode that detects the remaining portion 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 collectors of different sizes. As described above, an expansion of the dynamic range is desirable in the aforementioned technical fields.

[0005] On the other hand, Patent Document 3 (Japanese Patent Application Publication No. 2017-16918) discloses a charged particle detector comprising: a microchannel plate that emits secondary electrons based on the incidence of charged particles; a focusing electrode for focusing the secondary electrons emitted from the microchannel plate; and an electron impact diode that receives the incident focused secondary electrons, multiplies the secondary electrons, and detects them. Even for a charged particle detector with this structure, as described above, it is desirable to expand the dynamic range.

[0006] Therefore, one aspect of this disclosure is to provide an ion detector capable of expanding the dynamic range.

[0007] One aspect of this disclosure relates to an ion detector comprising: a microchannel plate for receiving incident ions to generate secondary electrons, multiplying the generated secondary electrons, and outputting them; a plurality of electron impact diodes having an effective region narrower than the effective region of the microchannel plate for receiving incident secondary electrons output from the microchannel plate, multiplying the incident secondary electrons, and detecting them; a focusing electrode disposed between the microchannel plate and the electron impact diodes for focusing secondary electrons toward the electron impact diodes; and a voltage supply unit for applying a driving voltage to each of the plurality of electron impact diodes, wherein the voltage supply unit applies driving voltages of different values ​​to at least two of the plurality of electron impact diodes to make their gains different.

[0008] This ion detector comprises a microchannel plate, a focusing electrode, and electron impact diodes. As mentioned above, even with this structure, an expanded dynamic range is desirable for the ion detector. Therefore, in this ion detector, the voltage supply section that applies drive voltages to multiple electron impact diodes achieves different gains by applying different drive voltages to each of at least two electron impact diodes. Thus, for example, by using a relatively high-gain electron impact diode for detection when the number of incident ions is low, and using a relatively low-gain electron impact diode for detection when the number of incident ions is high, appropriate detection results can be obtained over a wide range of incident ion numbers. In other words, the dynamic range can be expanded according to this ion detector.

[0009] Alternatively, the effective regions of each of the multiple electron-impact diodes may be contained within the focusing range of the secondary electrons of the focusing electrode. In this case, secondary electrons can also be incident on the effective regions of the multiple electron-impact diodes.

[0010] Alternatively, viewed from the incident direction of secondary electrons in the electron-charge diode, the electron-charge diode includes an effective region and an ineffective region surrounding the effective region. When viewed from the incident direction, the effective region is offset in at least one direction relative to the center of the ineffective region, and at least two electron-charge diodes are arranged adjacent to each other on the side offset from the effective region. In this case, dead zones can be reduced by arranging the effective regions of the electron-charge diodes closer together.

[0011] Alternatively, a mask may be provided, positioned between the focusing electrode and the electron-impact diode, to block a portion of the secondary electrons incident on at least one electron-impact diode. This allows the mask to be used when controlling the gain of the incident ions.

[0012] Alternatively, the mask can be formed on the electron incident surface of the electron-impact diode, or the mask can be configured separately from the electron incident surface of the electron-impact diode.

[0013] Alternatively, a cover may be provided, disposed between the focusing electrode and the electron-impact diode, forming an opening wider than the effective area of ​​multiple electron-impact diodes when viewed from the incident direction of the secondary electrons of the electron-impact diode, with the mask disposed at the opening. In this case, the cover has the function of preventing charging and can also constitute a mask.

[0014] Alternatively, the voltage supply unit applies a driving voltage to at least two electronic impulse diodes such that the detection range of the higher-gain electronic impulse diode and the lower-gain electronic impulse diode have a repetition range that overlaps with each other. In this case, the two electronic impulse diodes can be calibrated using the repetition range.

[0015] According to this disclosure, an ion detector capable of expanding the dynamic range can be provided. Attached Figure Description

[0016] Figure 1 (a) is a diagram showing an ion detector according to one embodiment, and is a cross-sectional view of the whole.

[0017] Figure 1 (b) is Figure 1 (a) is a top view of an electronically impacted diode.

[0018] Figure 2 (a) is a magnified view of a portion. Figure 1 The diagram of the ion detector shown in (a) is Figure 1 A magnified view of region AR in area (a).

[0019] Figure 2 (b) is a partial side view of region AR.

[0020] Figure 3 It is shown Figure 1 (a), (b), and Figure 2 Schematic circuit diagrams of an example of an ion detector shown in (a) and (b).

[0021] Figure 4 (a) is used to explain Figure 1 (a), (b) Figure 2 (a), (b), and Figure 3 The diagram shows the function and effect of the ion detector, with examples of cases using a single electron-impact diode (or multiple electron-impact diodes with the same gain).

[0022] Figure 4 (b) is used to explain Figure 1 (a), (b) Figure 2 (a), (b), and Figure 3 The diagram shows the function and effect of the ion detector, and the ion detector involved in the implementation method.

[0023] Figure 5 This is a schematic circuit diagram of the ion detector involved in the modified example.

[0024] Figure 6 This is a schematic circuit diagram of an ion detector involved in another variation.

[0025] Figure 7 (a) is a top view of a modified example of an electronically impacted diode.

[0026] Figure 7 (b) is a top view of a variation of an electronically impacted diode.

[0027] Symbol Explanation

[0028] 1…Ion detector, 110…MCP (microchannel plate), 110a…Input surface, 110b…Output surface, 110P…Effective area, 121, 122…Focusing electrode, 200A, 200B…Electron incident surface, 210…Mask, 220A, 220B…Electron impact diode, 221A, 221B…Effective area, 222A, 222B…Ineffective area, 223A, 223B…Output terminal, 400, 400A…Power supply section (voltage supply section), A2…Opening, M…Mask. Detailed Implementation

[0029] The following describes an ion detector according to one embodiment. In the description of the figures, the same or equivalent elements are labeled with the same symbols, and repeated descriptions are sometimes omitted.

[0030] Figure 1 (a) is a diagram showing an ion detector according to one embodiment, and is a cross-sectional view of the whole. Figure 1 (b) is Figure 1 (a) shows a top view of an electron-impact diode. Figure 1 As shown in (a) and (b), 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 example, for mass analysis.

[0031] The MCP110 is a circular plate having an input surface 110a and an output surface 110b opposite to the input surface 110a. The MCP110 is held by an input-side electrode 111 and an output-side electrode 112. As an example, the MCP110 includes a thin, disk-shaped structure, i.e., a main body, primarily composed of lead glass. In the main body, multiple through-holes, i.e., channels, extending along the thickness direction (from the input surface 110a to the output surface 110b), are formed, except for an annular outer periphery. Furthermore, electrodes are formed on the outer periphery of the input surface 110a and the outer periphery of the output surface 110b.

[0032] The MCP110 is used to receive incident ions from the input surface 110a to generate secondary electrons, multiplies the generated secondary electrons, and outputs them from the output surface 110b. The gain of the MCP110 is determined by the ratio of the channel length to the channel diameter corresponding to the thickness of the MCP110 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 on the input-side electrode 111 and the output-side electrode 112. The opening A1 is orthogonal to the input surface 110a and the output surface 110b, and is formed as a circle centered on a reference axis Ax passing through the center of the MCP 110. The opening A1 defines the effective region 110P of the MCP 110. That is, the area of ​​the MCP 110 exposed from the opening A1 when viewed along the reference axis Ax is defined as the effective region 110P of the MCP 110.

[0034] An electron lens 120 is disposed on the output surface 110b side of the MCP 110. The electron lens 120 includes a pair of focusing electrodes 121 and 122, each arranged to surround a reference axis Ax. The focusing electrodes 121 and 122 are formed into a cylindrical shape centered on the reference axis Ax. The focusing electrode 121 is fixed to the mesh electrode 130 via an insulating spacer, and the focusing electrode 122 is fixed to the focusing electrode 121 via an insulating spacer. That is, the mesh electrode 130 is disposed between the MCP 110 and the electron lens 120 (focusing electrode 121).

[0035] The potential of the mesh electrode 130 is higher than the potential of the output surface 110b of the MCP110. The mesh electrode 130 has the function of accelerating electrons and relatively reducing the angular component, thereby improving the electron convergence. Focusing electrodes 121 and 122 are disposed between the MCP110 and the electron impact diode described later, for focusing the secondary electrons output from the MCP110 onto the electron impact diode.

[0036] Figure 2 (a) is a magnified view of a portion. Figure 1 The diagram of the ion detector shown in (a) is Figure 1A magnified view of region AR in area (a). Figure 2 (b) is a partial side view of region AR. Figure 1 (a), (b), and Figure 2 As shown in (a) and (b), the second unit 200 is disposed on the opposite side of the focusing electrode 122 from the MCP 110. The second unit 200 has a cover 210 and a plurality of (two in this case) electron-impact type diodes 220A and 220B.

[0037] Electron-impact diodes 220A and 220B are single-channel devices. They are used to receive incident secondary electrons from the MCP110, focused by focusing electrodes 121 and 122, and to multiply and detect these incident secondary electrons. Electron-impact diodes 220A and 220B are, for example, avalanche diodes. In this case, the gain of electron-impact diodes 220A and 220B is, for example, 100–800 (e.g., 400) in electron collision gain and 1–10 in avalanche gain. 2 (e.g., 50). Therefore, the total gain of ion detector 1 is, for example, 10. 6 Degree (as an example, 4 × 10) 6 ).

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

[0039] The electron-impact diode 220A includes an electron incident surface 200A facing the MCP110 and the focusing electrodes 121 and 122, and receiving secondary electrons. The electron-impact diode 220A includes: an effective region 221A located at the center of the electron incident surface 200A when viewed from the incident direction of the secondary electrons (along the reference axis Ax), and which detects electrons; and a non-effective region 222A located around the effective region 221A, and which is covered, for example, by a mask and does not detect electrons.

[0040] Electron-charge type diode 220B includes an electron incident surface 200B facing the MCP110 and focusing electrodes 121, 122 and receiving secondary electrons. Electron-charge type diode 220B includes: an effective region 221B located at the center of the electron incident surface 200B and detecting electrons when viewed from the incident direction of the secondary electrons (along the reference axis Ax); and a non-effective region 222B located around the effective region 221B and covered, for example, by a mask, and not detecting electrons. The effective regions 221A, 221B of electron-charge type diodes 220A, 220B are narrower than the effective region 110P of the MCP110. The respective effective regions 221A, 221B of electron-charge type diodes 220A, 220B are included within the focusing range of secondary electrons generated by the focusing electrodes 121, 122 on the electron incident surfaces 200A, 200B.

[0041] Here, the electron-impact diodes 220A and 220B are arranged symmetrically about the reference axis Ax. More specifically, the pair of electron-impact diodes 220A and 220B are arranged such that corners protruding toward the opposite side of the MCP110 are formed by their respective electron incident surfaces 200A and 200B (or by extending the planes of the electron incident surfaces 200A and 200B), and they are supported on the substrate 202 via substrates 203A and 203B. Here, the corners formed by the electron incident surfaces 200A and 200B have the reference axis Ax as their vertices. Furthermore, the substrates 203A and 203B on which the electron-impact diodes 220A and 220B are mounted are inclined such that corners protruding toward the opposite side of the MCP110 are formed.

[0042] Therefore, for example, compared to the case where the electron-impact diodes 220A and 220B are arranged with their electron incident surfaces 200A and 200B on the same plane, the distance DA between the effective regions 221A and 221B of the electron-impact diodes 220A and 220B is shortened. That is, the effective regions 221A and 221B are arranged close to each other.

[0043] On the other hand, the electron-type diode 220A is provided with an output terminal 223A (output port (coaxial connector)) for outputting a detection signal of secondary electrons. The output terminal 223A protrudes and extends from the side of the substrate 203A opposite to the side where the electron-type diode 220A is provided. Similarly, the electron-type diode 220B is provided with an output terminal 223B (output port (coaxial connector)) for the same purpose. The output terminal 223B protrudes and extends from the side of the substrate 203B opposite to the side where the electron-type diode 220B is provided.

[0044] Furthermore, the output terminals 223A and 223B (extension lines of the extension direction of output terminals 223A and 223B) are arranged to form corners that protrude toward the electron incident surfaces 200A and 200B and the MCP110 side. 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 to each other.

[0045] A cover 210 is disposed between the focusing electrode 122 and the electron-impact diodes 220A and 220B, and is held between the focusing electrode 122 and the substrate 202, for example, via an insulating spacer 201. An opening A2 centered on a reference axis Ax is formed in the cover 210. Viewed from the incident direction 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 orientation of the effective regions 221A and 221B along their longer sides. Therefore, viewed from the incident direction of secondary electrons from the electron-impact diodes 220A and 220B, 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 connections of ion detector 1 will be explained. Figure 3 It is shown Figure 1 (a), (b), and Figure 2 Schematic circuit diagrams of an example of an ion detector shown in (a) and (b). Figure 3 As 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 resistors R1 and R2, and is connected to ground potential GND via 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 resistor R3.

[0047] In the second unit 200, the electronic impulse diode 220A has one terminal connected to a negative potential via resistor R4 and another terminal connected to ground potential GND via capacitor C1. The detection signal of the electronic impulse diode 220A is taken from signal line 500A connected to output terminal 223A. The electronic impulse diode 220B has one terminal connected to a negative potential via resistor R5 and another terminal connected to ground potential GND via capacitor C2. The detection signal of the electronic impulse diode 220B is taken from signal line 500B connected to 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 MCP110 via terminal T1, and a power supply V2 for ensuring a predetermined potential difference between terminal T2 connected to the output surface 110b of the MCP110 and terminal T1. Power supply V1 is positioned between ground potential GND and terminal T1, generating an electromotive force (EMF) to set the potential of terminal T1 to, for example, -7kV. Power supply V2 generates the EMF in a manner that ensures a potential difference of, for example, 0 to 3.5kV 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 an electronically driven diode 220A via terminal T3 and resistor R4, and a power supply V4 connected to one terminal of an electronically driven diode 220B via terminal T4 and resistor R5. Power supply V3 is positioned between ground potential GND and terminal T3, generating an electromotive force (EMF) to set the potential of terminal T3 to, for example, 350V. Power supply V4 is positioned between ground potential GND and terminal T4, generating an EMF to set the potential of terminal T4 to a different potential than that of terminal T3, for example, 250V.

[0050] That is, the power supply unit 400 applies a driving voltage to each of the electron impact diodes 220A and 220B. By applying different driving voltages to each of the electron impact diodes 220A and 220B, their gains are made different. The difference in gain between the electron impact diodes 220A and 220B is, for example, a factor of 10. As described above, in the ion detector 1, secondary electrons emitted from the MCP 110 are focused by the focusing electrodes 121 and 122, and multiple (in this case, two) electron impact diodes 220A and 220B with different gains are input.

[0051] Next, the function and effect of ion detector 1 will be explained. Figure 4 (a) is used to explain Figure 1 (a), (b) Figure 2 (a), (b), and Figure 3 The diagram shows the function and effect of the ion detector, with examples of cases using a single electron impact diode (or, cases using multiple electron impact diodes with the same gain).

[0052] Figure 4 (b) is used to explain Figure 1 (a), (b) Figure 2 (a), (b), and Figure 3The diagram illustrates the function and effect of the ion detector, relating to the ion detector involved in the implementation method. In this case, when the gain is relatively high (line L1), when a large number of ions are incident on the ion detector (when the number of incident ions increases), detector saturation or out-of-range operation of the digital converter occurs. On the other hand, in this case, when the gain is relatively low (line L2), single-ion detection becomes difficult. Therefore, it is necessary to perform multiple measurements while changing the gain.

[0053] In contrast, such as Figure 4 As shown in (b), the ion detector 1 of this embodiment can appropriately detect single ions using the detection signal (line L3) of an electron impact diode with relatively high gain when the number of incident ions is small, and can reduce the effect of detector saturation by using the detection signal (line L4) of an electron impact diode with relatively low gain and a large upper limit of the saturated number of incident ions when the number of incident ions is large. That is, the dynamic range is expanded according to the ion detector 1. Figure 4 (b) is used to explain Figure 1 (a), (b) Figure 2 (a), (b), and Figure 3 The diagram shows the function and effect of the ion detector, and the ion detector involved in the implementation method.

[0054] Furthermore, in the ion detector 1 and the power supply unit 400, a driving voltage is applied to the electron impact type diodes 220A and 220B in such a way that the detection range of the electron impact type diode with relatively high gain (in this case, the range of incident ion number from 1 to 1000) and the detection range of the electron impact type diode with relatively low gain (in this case, the range of incident ion number from 10 to 10000) partially overlap with each other.

[0055] The repeatability range S is the range between the lower limit of the detectable incident ion number of a relatively low-gain electron-impact diode (in this case, around 10) and the upper limit of the detectable incident ion number of a relatively high-gain electron-impact diode (in this case, around 1000). By setting such a repeatability range S, it is possible to calibrate electron-impact diodes with different gains.

[0056] As explained above, the ion detector 1 has a structure including an MCP 110, focusing electrodes 121 and 122, and electron impact diodes 220A and 220B. Even with this structure, an expanded dynamic range is desirable for the ion detector 1. Therefore, in this ion detector 1, different driving voltages are applied to each of the two electron impact diodes 220A and 220B via the power supply unit 400, resulting in different gains for each. Thus, for example, by using a detection diode with relatively high gain when the number of incident ions is low, and using a detection diode with relatively low gain when the number of incident ions is high, appropriate detection results can be obtained over a wide range of incident ion numbers. That is, the dynamic range can be expanded according to this ion detector 1. Furthermore, in the ion detector 1, when multiple electron impact diodes with different gains are used as described above, crosstalk can be suppressed compared to the case of using multiple single-channel elements.

[0057] Furthermore, in the ion detector 1, the effective regions 221A and 221B of the electron impact diodes 220A and 220B are contained within the focusing range of secondary electrons generated by the focusing electrodes 121 and 122. Therefore, secondary electrons can be incident on the effective regions 221A and 221B of the electron impact diodes 220A and 220B in the same way.

[0058] Furthermore, in the ion detector 1, a pair of electron impact diodes 220A and 220B are arranged such that their respective electron incident surfaces 200A and 200B form corners that bulge toward the opposite side of the MCP110. Therefore, compared to the case where their respective electron incident surfaces 200A and 200B are arranged on the same plane, their effective regions 221A and 221B can be arranged closer together.

[0059] Furthermore, by arranging the effective regions 221A and 221B of the electron-impact diodes 220A and 220B closer together, the effective regions 221A and 221B can be included within the focusing path 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.

[0060] Furthermore, the ion detector 1 is disposed between the focusing electrodes 121, 122 and the electron impact diodes 220A, 220B, and includes a cover 210 having an opening A2 wider than the effective regions 221A, 221B when viewed from the incident direction of secondary electrons from the electron impact diodes 220A, 220B. Therefore, charging can be prevented by the cover 210.

[0061] Furthermore, in the ion detector 1, the opening A2 is an elongated hole in which the effective regions 221A and 221B of the electron impact diodes 220A and 220B are arranged along their long sides. Therefore, secondary electrons can be appropriately incident through the elongated hole of the cover 210 onto a pair of electron impact diodes 220A and 220B that are arranged closer together to the effective regions 221A and 221B as described above.

[0062] Furthermore, in the ion detector 1, each of the electron impact diodes 220A and 220B has an output terminal 223A and 223B for outputting a detection signal on the side opposite to the electron incident surfaces 200A and 200B. Moreover, the output terminals 223A and 223B are arranged such that they form corners protruding towards the electron incident surfaces 200A and 200B. The output terminals 223A and 223B can be arranged in this way when they are close to the effective regions 221A and 221B of the pair of electron impact diodes 220A and 220B as described above.

[0063] The above embodiments illustrate one example of the ion detector involved in this disclosure. Therefore, the ion detector involved in this disclosure can be arbitrarily modified from the above-described ion detector. Next, modified examples will be described.

[0064] Figure 5 This is a schematic circuit diagram of the ion detector involved in the modified example. For example... Figure 5 As shown, compared to ion detector 1, ion detector 1A differs from ion detector 1 in that it has a power supply unit 400A instead of a power supply unit 400; otherwise, it is identical to ion detector 1. The power supply unit (voltage supply unit) 400A includes a single power supply V5 connected to one terminal of the electronic impulse diode 220A via resistor R6, terminal T3, and resistor R4, and connected to one terminal of the electronic impulse diode 220B via resistor R7, terminal T4, and resistor R5. Additionally, the power supply unit 400A includes a Zener diode D1 between resistor R6 and ground potential GND, and a Zener diode D2 between resistor R7 and ground potential GND.

[0065] By adjusting the relative values ​​of resistors R6 and R7 using this power supply section 400A, different driving voltages can be applied to each of the two electron-impact diodes 220A and 220B, resulting in different gains. Furthermore, in the ion detector 1, voltage can be supplied to the two electron-impact diodes 220A and 220B through a single power supply V5 using Zener diodes D1 and D2.

[0066] Figure 6 This is a schematic circuit diagram of an ion detector involved in another variation. For example... Figure 6 As shown, the ion detector 1B includes a power supply section 600 as a voltage supply circuit. In the power supply section 600, a power supply V1 is connected to the input surface 110a of the MCP 110 via terminal T1. The power supply V1 functions for the floating ion detector 1B. The power supply section 600 includes a power supply V6 and a power supply V7. Power supply V6 is disposed between terminal T1 connected to the input surface 110a and terminal T2 connected to the output surface 110b. Power supply V6 is used to apply a voltage (e.g., 0V to 1000V) to the MCP 110. Power supply V7 is disposed between terminal T2 and terminal T3. Power supply V7 is used to supply voltage (e.g., 3kV to 7kV) to the focusing electrodes 121 and 122 and the electron-impact diodes 220A and 220B, which are located after the MCP 110.

[0067] Additionally, resistors R1 and R2 serve as bleeder resistors to supply potential to the mesh electrode 130 and focusing electrodes 121 and 122. Capacitors C1 and C2 form a loop through which high-speed signals can return with low impedance to the other terminal of the electronic impulse diodes 220A and 220B via the ground potential GND. Capacitors C1 and C2, along with resistors R4 and R5, constitute a low-pass filter, which removes power supply noise. Resistor R3 prevents coupling between the focusing electrode 122 and the ground potential GND.

[0068] Capacitor C3 is connected to signal line 500A, which is connected to the output terminal 223A of the electronic impulse diode 220A. Capacitor C4 is connected to signal line 500B, which is connected to the output terminal 223B of the electronic impulse diode 220B. Capacitors C3 and C4 are coupling capacitors, maintaining the potential of the other terminal of the electronic impulse diodes 220A and 220B while allowing high-frequency signals to pass through. A resistor R9 is connected before capacitor C3 on signal line 500A. Additionally, a resistor R10 is connected before capacitor C4 on signal line 500B.

[0069] Resistors R9 and R10 are blocking resistors, which function to apply a potential to one terminal of the electronic impulse diodes 220A and 220B while preventing the signal from returning to the power supply section 600. Between resistors R2 and R9 / R10, there are lines for setting Zener diode D3 and for setting resistor R8 and Zener diode D4, respectively. Resistor R8 functions to absorb the potential difference between Zener diodes D3 and D4.

[0070] The ion detector floats while detecting both positive and negative ions. In this case, voltages can be supplied to the electron-charge diodes 220A and 220B without increasing the power supply by using Zener diodes D3 and D4. For example, if a 350V diode is used as Zener diode D3 and a 250V diode is used as Zener diode D4, different voltages can be applied to the electron-charge diodes 220A and 220B.

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

[0072] Therefore, when viewed from the incident direction of secondary electrons, the effective regions 221A and 221B of the electron-impact diodes 220A and 220B are biased in one direction (cut-off side) relative to the centers of the ineffective regions 222A and 222B. Thus, by arranging the two electron-impact diodes 220A and 220B adjacent to each other on the biased sides of the effective regions 221A and 221B, it is possible to arrange the effective regions 221A and 221B more closely.

[0073] in addition, Figure 7 (b) is a top view of a variation of the electronically impacted diode. Figure 7 As shown in (b), the ion detectors 1-1B may include a mask M that blocks a portion of the secondary electrons incident on at least one of the plurality of electron-impact diodes (here, electron-impact diode 220B). The mask M may be disposed at any position between the focusing electrode 122 and the electron-impact diode 220B. As an example, the mask M may be formed on the electron incident surface 200B of the electron-impact diode 220B. In this case, the mask M may be formed, for example, by depositing Al on the surface of the electron incident surface 200B after the process of the electron-impact diode 220B, or by ion implantation from the surface side of the electron incident surface 200B of the electron-impact diode 220 during the process.

[0074] On the other hand, the mask M can also be arranged separately from the electron incident surface 200B. In this case, the mask M can also be formed, for example, by providing a mesh on the track of the secondary electrons focused by the focusing electrodes 121, 122 toward the electron impact diode 220B. Alternatively, in this case, the mask M can also be provided in the opening A2 of the cover 210.

[0075] Alternatively, the amount of secondary electrons incident on the electron-impact diode can be controlled by offsetting at least one of a plurality of electron-impact diodes such that a portion of its effective region is located outside the focusing path of the secondary electrons.

[0076] As described above, in ion detectors 1-1B, as a method to make the gains of at least two of the multiple electron impact diodes different from each other, methods such as different driving voltages, using masks to block secondary electrons, and adjusting the amount of incident secondary electrons by shifting the effective region can be arbitrarily combined and employed. That is, as an example, one of the above methods can be applied to one pair of electron impact diodes, and other methods of the above methods can be applied to another pair of electron impact diodes. In addition, the above methods can be arbitrarily applied to make the gains of three or more electron impact diodes different from each other.

[0077] Furthermore, in ion detectors 1-1B, from the viewpoint that at least two of the multiple electron-impact diodes have different gains, such as Figure 2 The configuration shown in (b), in which a pair of electron-impact diodes 220A and 220B are arranged such that their electron incident surfaces 200A and 200B protrude to the opposite side of the MCP110, is not necessary. Furthermore, in the ion detectors 1-1B, from the viewpoint of being closer to the effective regions 210A and 210B, a configuration where the gains of at least two electron-impact diodes are different is not necessary.

[0078] Alternatively, it can also be: with Figure 2 In contrast to the example shown in (b), a pair of electron-impact diodes 220A and 220B are configured such that their electron incident surfaces 200A and 200B (or by extending the planes of the electron incident surfaces 200A and 200B) form corners protruding toward the MCP110 side. In this case, the output terminals 223A and 223B (extensions of the extension directions of the output terminals 223A and 223B) can also be configured such that they form corners protruding toward the opposite side of the electron incident surfaces 200A and 200B and the MCP110.

[0079] Furthermore, in the above embodiments, an example with two electron impact type diodes 220A and 220B has been described, but the ion detectors 1 to 1B may also have three or more electron impact type diodes.

Claims

1. An ion detector, wherein, have: Microchannel plates are used to receive incident ions to generate secondary electrons, multiply the generated secondary electrons, and output them. Multiple electron-impact diodes, each having an effective region narrower than the effective region of the microchannel plate, are used to receive incident secondary electrons output from the microchannel plate, multiply the incident secondary electrons, and detect them. A focusing electrode, disposed between the microchannel plate and the electron-impact diode, is used to focus the secondary electrons toward the electron-impact diode; and The voltage supply unit applies a driving voltage to each of the plurality of electronically driven diodes. The voltage supply unit achieves different gains by applying different driving voltages to at least two of the plurality of electronic impulse diodes. Viewed from the incident direction of secondary electrons in the electron-impact diode, the electron-impact diode includes the effective region and an ineffective region surrounding the effective region. When viewed from the incident direction, the effective region is offset in at least one direction relative to the center of the ineffective region. At least two of the aforementioned electronically driven diodes are configured to be adjacent to each other on the side biased towards the effective region.

2. The ion detector according to claim 1, wherein, The effective region of each of the plurality of electron-impact diodes is contained within the focusing range of the secondary electrons of the focusing electrode.

3. The ion detector according to claim 1, wherein, It includes: a mask disposed between the focusing electrode and the electron-impact diode, which blocks a portion of the secondary electrons incident on at least one of the electron-impact diodes.

4. The ion detector according to claim 2, wherein, It includes: a mask disposed between the focusing electrode and the electron-impact diode, which blocks a portion of the secondary electrons incident on at least one of the electron-impact diodes.

5. The ion detector according to claim 3, wherein, The mask is formed on the electron incident surface of the electron-impact diode.

6. The ion detector according to claim 4, wherein, The mask is formed on the electron incident surface of the electron-impact diode.

7. The ion detector according to claim 3, wherein, The mask is configured separately from the electron incident surface of the electron-impact diode.

8. The ion detector according to claim 4, wherein, The mask is configured separately from the electron incident surface of the electron-impact diode.

9. The ion detector according to claim 7, wherein, It includes: a cover disposed between the focusing electrode and the electron-impact diode, having an opening wider than the effective area of ​​the plurality of electron-impact diodes when viewed from the incident direction of secondary electrons from the electron-impact diode. The mask is disposed at the opening.

10. The ion detector according to claim 8, wherein, It includes: a cover disposed between the focusing electrode and the electron-impact diode, having an opening wider than the effective area of ​​the plurality of electron-impact diodes when viewed from the incident direction of secondary electrons from the electron-impact diode. The mask is disposed at the opening.

11. The ion detector according to any one of claims 1 to 10, wherein, The voltage supply unit applies the driving voltage to at least two of the electronic impulse diodes in such a manner that the detection range of the electronic impulse diode with relatively high gain has a repetition range that overlaps with the detection range of the electronic impulse diode with relatively low gain.

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