Electron detectors and charged particle detectors

Abstract

The present invention provides an electron detector and a charged particle detector that can improve the quality of electrical signals. [Solution] The electron detector 5 comprises an electron detection unit 53 including a first electrode 52, a resin sheet 59, a second electrode 54 facing the first electrode 52 via the resin sheet 59, a third electrode 57 spaced apart from the first electrode 52 in the X direction, a fourth electrode 58 facing the third electrode 57 via the resin sheet 59, an insulating substrate 61 supporting the electron detection unit 53, the resin sheet 59, the second electrode 54, the third electrode 57 and the fourth electrode 58, and an output unit 55 that outputs an electrical signal. The output unit 55 includes an internal conductor 551 electrically connected to the second electrode 54 and an external conductor 552 electrically connected to the fourth electrode 58, wherein, when viewed from the Z direction, the area S2 in which the external conductor 552 overlaps with the fourth electrode 58 is larger than the area S1 in which the external conductor 552 overlaps with the second electrode 54.

Description

Technical Field

[0001] The present invention relates to an electron detector and a charged particle detector.

Background Art

[0002] As a charged particle detector applicable to a mass spectrometry device etc., Patent Document 1 describes an ion detector including a microchannel plate (hereinafter referred to as "MCP") that emits electrons upon incidence of ions, an anode electrode that detects electrons emitted from the MCP, a coaxial cable including an internal conductor electrically connected to the anode electrode, and a ground electrode electrically connected to an outer conductor of the coaxial cable. In the ion detector described in Patent Document 1, the anode electrode is configured by disposing a dielectric member between the collector electrode and the conductive plate. Thereby, the collector electrode and the conductive plate function as a capacitor, and a DC component is removed from an electrical signal output via the coaxial cable.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the ion detector described in Patent Document 1, since the conductive plate included in the anode electrode serving as the electron detection unit and the ground electrode face each other, a parasitic capacitance occurs between the anode electrode and the ground electrode, and as a result, ringing may occur in an electrical signal output via the coaxial cable. When the ion detector is applied to a mass spectrometry device, if ringing occurs in an electrical signal output from the ion detector, the accuracy of mass spectrometry may decrease.

[0005] The present invention aims to provide an electron detector and a charged particle detector that can improve the quality of electrical signals. [Means for solving the problem]

[0006] The electron detector of the present invention includes: [1] an electron detection unit that includes a first electrode and detects incident electrons; a resin sheet disposed on one side in a first direction relative to the first electrode; a second electrode disposed on the one side in a first direction relative to the resin sheet and facing the first electrode via the resin sheet; a third electrode disposed on the other side in a first direction relative to the resin sheet and spaced apart from the first electrode in a second direction intersecting the first direction; a fourth electrode disposed on one side in a first direction relative to the resin sheet and spaced apart from the second electrode in a second direction and facing the third electrode via the resin sheet; and an electron detection unit disposed on one side in a first direction relative to the second electrode. A charged particle detector comprising: a section, an insulating substrate supporting the resin sheet, the second electrode, the third electrode, and the fourth electrode; and an output section disposed on one side of the insulating substrate in a first direction and outputting an electrical signal, wherein the output section includes an internal conductor electrically connected to one of the second electrode and the fourth electrode, and an external conductor surrounding the internal conductor in a state of being electrically insulated from the internal conductor and electrically connected to the other electrode of the second electrode and the fourth electrode, wherein, when viewed from the first direction, the area in which the external conductor overlaps with the other electrode is greater than the area in which the external conductor overlaps with the one electrode, or, when viewed from the first direction, the external conductor does not overlap with the second electrode and the fourth electrode.

[0007] In the electron detector described in [1] above, the first and second electrodes, which face each other via a resin sheet, function as capacitors, as do the third and fourth electrodes, which face each other via a resin sheet. One of these capacitors functions as a capacitor that removes the DC component from the electrical signal detected in the electron detection unit. As a result, the electrical signal from which the DC component has been removed is output from the internal conductor of the output unit via the second or fourth electrode. On the other hand, the other of these capacitors functions as a return capacitor placed on the return path through which the return current from the external conductor flows. This suppresses the degradation of the electrical signal waveform due to ringing, etc. Furthermore, a resin sheet is used for these capacitors, and the electron detection unit, resin sheet, second electrode, third electrode, and fourth electrode are supported by an insulating substrate. This ensures sufficient voltage resistance for these capacitors and sufficient mechanical strength for the electron detector. Furthermore, when viewed from the first direction, the area in which the outer conductor overlaps with the other electrode of the second and fourth electrodes is greater than the area in which the outer conductor overlaps with the other electrode of the second and fourth electrodes, or when viewed from the first direction, the outer conductor does not overlap with the second and fourth electrodes. As a result, the parasitic capacitance caused by the outer conductor overlapping with the other electrode of the second and fourth electrodes is reduced, or the generation of such parasitic capacitance is suppressed, and as a result, ringing generated in the electrical signal due to parasitic capacitance is suppressed. Thus, the quality of the electrical signal can be improved with the above-described electron detector.

[0008] The electron detector of the present invention may also be [2] "the electron detector according to [1] above, wherein one electrode is the second electrode and the other electrode is the fourth electrode." According to the electron detector according to [2], an electrical signal from which the DC component has been removed is output from the internal conductor of the output section via the second electrode. In addition, the parasitic capacitance that occurs when the external conductor overlaps with the second electrode is reduced. As a result, ringing caused by parasitic capacitance in the electrical signal output via the second electrode can be suppressed.

[0009] The electron detector of the present invention may also be [3] "the electron detector according to [1] or [2] above, wherein the outer conductor includes an enclosing portion that surrounds the inner conductor and a protruding portion that protrudes outward from the enclosing portion, the inner conductor faces the one electrode via the insulating substrate, and when viewed from the first direction, the area in which the protruding portion overlaps with the other electrode is greater than the area in which the protruding portion overlaps with the one electrode." According to the electron detector according to [3], the electrical connection between the other electrode and the outer conductor can be easily and reliably secured. In addition, since the parasitic capacitance generated by the overlap of the outer conductor with one electrode is further reduced, ringing caused by parasitic capacitance can be further suppressed.

[0010] The electron detector of the present invention may also be [4] "an electron detector according to any one of [1] to [3] above, further comprising a support portion that supports the output portion on one side in the first direction with respect to the insulating substrate, such that a space is formed between the output portion and the insulating substrate." According to the electron detector according to [4], the parasitic capacitance generated between the output portion and one electrode is further reduced by forming a space between the output portion and the insulating substrate, so that ringing generated in the electrical signal due to parasitic capacitance can be further suppressed.

[0011] The charged particle detector of the present invention may also be [5] "a charged particle detector comprising an electron detector according to any one of [1] to [4] above, and an electron emission unit that emits electrons upon the incidence of charged particles." According to the charged particle detector described in [5], the quality of the electrical signal can be improved in the electron detector.

[0012] The charged particle detector of the present invention may also be [6] "the charged particle detector described in [5] above, wherein the electron emission unit includes a microchannel plate." According to the charged particle detector described in [6], the electrons emitted from the electron emission unit are amplified as secondary electrons, thereby increasing the electrical signal output from the electron detector. Furthermore, emission of secondary electrons with a high amplification factor can be achieved.

[0013] The charged particle detector of the present invention may also be the charged particle detector described in [5] above, wherein the electron emission unit includes a plurality of dynodes. According to the charged particle detector described in [7], the electrons emitted from the electron emission unit are amplified as secondary electrons, thereby increasing the electrical signal output from the electron detector. Furthermore, emission of secondary electrons with a high amplification factor can be achieved. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide an electron detector and a charged particle detector that can improve the quality of electrical signals. [Brief explanation of the drawing]

[0015] [Figure 1] This figure shows the circuit configuration of a charged particle detector according to one embodiment. [Figure 2] Figure 1 is a cross-sectional view of the electron detector. [Figure 3] Figure 1 is a front view of the electron detector. [Figure 4] Figure 1 is a rear view of the electron detector. [Figure 5] This is a cross-sectional view of the electron detector of the first modified example. [Figure 6] It is a rear view of the electron detector of the first modification example. [Figure 7] It is a front view of the electron detector of the second modification example. [Figure 8] It is a rear view of the electron detector of the second modification example. [Figure 9] It is a front view of the electron detector of the third modification example. [Figure 10] It is a rear view of the electron detector of the third modification example. [Figure 11] It is a cross-sectional view of the electron detector of the fourth modification example. [Figure 12] It is a cross-sectional view of the electron detector of the fifth modification example. [Figure 13] It is a cross-sectional view of the charged particle detector of the modification example.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, embodiments 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 redundant descriptions are omitted. [Configuration of Charged Particle Detector]

[0017] The electron detector of the present invention outputs incident electrons as an electron signal. The electron detector of the present invention is applied to, for example, a charged particle detector, a photomultiplier tube, or a hybrid photodetector. In the present embodiment, an example in which the electron detector is applied to a charged particle detector will be described. As shown in FIG. 1, the charged particle detector 1 includes an electron emission unit 2, an acceleration electrode 3, a focus electrode 4, and an electron detector 5. In the charged particle detector 1, the electron emission unit 2, the acceleration electrode 3, the focus electrode 4, and the electron detection unit 53 of the electron detector 5 are arranged in this order. The charged particle detector 1 is, for example, an ion detector that detects bipolar ions. The charged particle detector 1 is applied to, for example, a mass spectrometer. Note that the charged particle detector 1 may detect charged particles other than ions (for example, electrons, etc.).

[0018] The electron emission unit 2 emits electrons upon incidence of ion IN. The polarity of ion IN may be negative or positive. The electron emission unit 2 includes a microchannel plate (hereinafter referred to as "MCP") 21. The MCP 21 is an electron multiplier element that emits electrons in response to incidence of ion IN. The MCP 21 has an input surface 21a and an output surface 21b. The sides of the MCP 21 are surrounded by an insulating ring made of an insulating material. When ion IN is incident on the input surface 21a of the MCP 21, it generates electrons in response to the incidence of ion IN, multiplies those electrons, and emits them from the output surface 21b. In other words, the MCP 21 also functions as an electron multiplier unit. The MCP 21 has a plurality of through holes (channels) formed along the thickness direction (the direction in which the input surface 21a and the output surface 21b face each other). Electrodes are formed on the outer edge of the input surface 21a and the outer edge of the output surface 21b. Furthermore, the electron emission unit 2 may independently include an electron emission unit that emits electrons upon incidence of ion IN, and an electron multiplication unit that emits electrons multiplied by multiples. For example, the electron emission unit 2 may include an ion-electron conversion unit provided upstream of the MCP21 as the electron emission unit, and the MCP21 as the electron multiplication unit.

[0019] The accelerating electrode 3 accelerates electrons emitted from the output surface 21b of the MCP 21. The focusing electrode 4 focuses the electrons accelerated by the accelerating electrode 3 onto the electron detection unit 53 of the electron detector 5.

[0020] The electron detector 5 outputs electrons emitted from the MCP 21 as an electrical signal. The electron detector 5 includes an electron detection unit 53 containing an avalanche diode (hereinafter referred to as "AD") 51 and a first electrode 52, a second electrode 54, an output unit 55, a signal output terminal 56, a third electrode 57, and a fourth electrode 58.

[0021] AD51 receives electrons focused by the focus electrode 4 and outputs them as an electrical signal. The anode electrode 511 of AD51 faces the focus electrode 4. That is, electrons focused by the focus electrode 4 are incident on the anode electrode 511.

[0022] The first electrode 52 is electrically connected to the cathode electrode 512 of AD51. The first electrode 52 and the second electrode 54 constitute a signal capacitor C1. The signal capacitor C1 functions as a coupling capacitor that removes the DC component from the electrical signal output from AD51.

[0023] The output section 55 is electrically connected to the second electrode 54 and outputs an electrical signal toward the signal output terminal 56. The output section 55 includes an inner conductor 551 and an outer conductor 552. The inner conductor 551 is electrically connected to the second electrode 54. The outer conductor 552 surrounds the inner conductor 551. There may be an air gap between the inner conductor 551 and the outer conductor 552, or an insulating member may be placed between them. The outer conductor 552 is connected to a reference potential GND. The output section 55 is, for example, an SMA connector. In this case, the inner conductor 551 is a signal line that transmits an electrical signal, and the outer conductor 552 is an outer conductor that covers the signal line.

[0024] The third electrode 57 is electrically connected to the anode electrode 511 of AD51. The fourth electrode 58 is electrically connected to the reference potential GND and the outer conductor 552. The third electrode 57 and the fourth electrode 58 are arranged on a return path formed from the outer conductor 552 to the anode electrode 511, and constitute a return capacitor C2. The arrangement of the return capacitor C2 suppresses the degradation of the electrical signal waveform due to ringing, etc. Ringing is a high-frequency component superimposed on an electrical signal when the magnitude of the electrical signal changes, such as during the rising or falling edge of the electrical signal.

[0025] Parasitic capacitance Cp may occur between the second electrode 54 and the outer conductor 552. Parasitic capacitance Cp is a parasitic component that arises when the second electrode 54 and the outer conductor 552 face each other. Parasitic capacitance Cp may cause ringing in the electrical signal output from the signal output terminal 56. If, for example, a mass spectrometer is connected downstream of the electron detector 5, ringing in the electrical signal may prevent the mass spectrometer from accurately reading the magnitude of the electrical signal, potentially affecting the accuracy of the mass spectrometry. Therefore, it is extremely important to minimize parasitic capacitance Cp as much as possible to suppress the effects of ringing.

[0026] The input surface 21a of the MCP21 is electrically connected to the power supply 71 and set to a potential Va (e.g., +10kV or -10kV). A potential difference Vb (e.g., 0V to 1kV) is supplied between the input surface 21a and the output surface 21b by the power supply 72. One end of resistor Ra is electrically connected to the node between the cathode electrode 512 and the first electrode 52. A potential difference Vc (e.g., 0V to 6kV) is supplied between the output surface 21b and the other end of resistor Ra by the power supply 73. The potential difference (voltage) Vc is divided by resistor Rb (e.g., 40MΩ), resistor Rc (e.g., 20MΩ), and Zener diode 74. The Zener diode 74 ensures a potential difference of 300V between resistor Rc and resistor Ra. The accelerating electrode 3 is electrically connected to the node located between resistor Ra and resistor Rb. The focus electrode 4 is set to the same potential as the output surface 21b. A resistor Rd is electrically connected between the node between resistor Rc and Zener diode 74 and the anode electrode 511.

[0027] When measuring negative ions IN, a potential Va of, for example, +10kV is applied. In this case, if the potential difference Vb is +1kV and the potential difference Vc is +6kV, the potential at the other end of resistor Ra will be +17kV. When measuring positive ions IN, a potential Va of, for example, -10kV is applied. In this case, if the potential difference Vb is +1kV and the potential difference Vc is +6kV, the potential at the other end of resistor Ra will be -3kV. In both the measurement of negative and positive ions IN, the potential increases as you move from the input surface 21a of MCP21 toward the anode electrode 511 of AD51. Furthermore, the potential applied to the cathode electrode 512 of AD51 is greater than the potential applied to the anode electrode 511. Therefore, a reverse bias voltage is applied between the anode electrode 511 and the cathode electrode 512 of AD51, causing AD51 to operate in a floating state. [Electron detector configuration]

[0028] As shown in Figures 2, 3, and 4, the electron detector 5 further comprises a resin sheet 59, an insulating substrate 61, a support portion 62, and an insulating layer 63. Hereinafter, the thickness direction of the insulating substrate 61 will be referred to as the Z direction (first direction), one direction perpendicular to the Z direction (a direction intersecting the Z direction) will be referred to as the X direction (second direction), and the direction perpendicular to both the Z and X directions will be referred to as the Y direction. In the electron detector 5, AD 51, the first electrode 52, the resin sheet 59, the second electrode 54, the insulating substrate 61, and the output unit 55 are arranged in this order in the Z direction. In the following description, "arranged on one side" means that each component is arranged on the opposite side of AD 51 (the output unit 55 side) from adjacent components on the AD 51 side. "Arranged on the other side" means that each component is arranged on the opposite side of the output unit 55 (the AD 51 side) from adjacent components on the output unit 55 side.

[0029] AD51 is positioned, for example, at the location where electrons emitted from MCP21 arrive. The first electrode 52 is positioned on the opposite side of AD51 from MCP21 and is electrically connected to AD51. In the electron detector 5, the first electrode 52 is in contact with the cathode electrode 512 of AD51.

[0030] The resin sheet 59 is positioned on one side of the first electrode 52 in the Z direction. The resin sheet 59 is in contact with the first electrode 52. The material of the resin sheet 59 is a resin such as liquid crystal polymer (LCP), polyester film, polyimide, or polyamide. The second electrode 54 is positioned on one side of the resin sheet 59 in the Z direction. The second electrode 54 is in contact with the resin sheet 59. The second electrode 54 faces the first electrode 52 through the resin sheet 59. The area of ​​the first electrode 52 and the area of ​​the second electrode 54 may be the same, and the outer edges of the first electrode 52 and the outer edges of the second electrode 54 may coincide when viewed from the Z direction.

[0031] The first electrode 52, the resin sheet 59, and the second electrode 54 constitute a signal capacitor C1. The first electrode 52 and the second electrode 54 are a pair of electrode plates of the signal capacitor C1, and the resin sheet 59 is the dielectric of the signal capacitor C1. The capacitance required for the signal capacitor C1 to function as a coupling capacitor is, for example, 50 pF or more. In addition, the resin sheet 59 is required to withstand high voltages with an absolute value of 10 kV or more. Based on the above, the thickness of the resin sheet 59 is preferably 25 μm or more and 200 μm or less, and the area of ​​the first electrode 52 and the second electrode 54 is preferably 5 mm × 5 mm or more and 30 mm × 30 mm or less.

[0032] The third electrode 57 is positioned on the other side of the resin sheet 59 in the Z direction. The third electrode 57 is spaced apart from the first electrode 52 in the X direction. When viewed from the Z direction, the third electrode 57 is spaced apart from the first electrode 52 and is aligned with the first electrode 52 in the X direction. The third electrode 57 is in contact with the resin sheet 59. In the electron detector 5, the third electrode 57 is electrically connected to the anode electrode 511 via wiring WR.

[0033] The fourth electrode 58 is positioned on one side of the resin sheet 59 in the Z direction. The fourth electrode 58 is spaced apart from the second electrode 54 in the X direction. When viewed from the Z direction, the fourth electrode 58 is spaced apart from the second electrode 54 and is aligned with the second electrode 54 in the X direction. The fourth electrode 58 is in contact with the resin sheet 59. The fourth electrode 58 faces the third electrode 57 through the resin sheet 59. The area of ​​the third electrode 57 and the area of ​​the fourth electrode 58 may be the same, and when viewed from the Z direction, the outer edges of the third electrode 57 and the outer edges of the fourth electrode 58 may coincide.

[0034] The third electrode 57, the resin sheet 59, and the fourth electrode 58 constitute the return capacitor C2. The third electrode 57 and the fourth electrode 58 are a pair of electrode plates of the return capacitor C2, and the resin sheet 59 is the dielectric of the return capacitor C2. That is, the dielectric of the return capacitor C2 is the same as the dielectric of the signal capacitor C1. The capacitance of the return capacitor C2 is the same as that of the signal capacitor C1, for example, 50 pF or less. The thickness of the resin sheet 59 is preferably 25 μm or more and 200 μm or less, and the area of ​​the first electrode 52 and the second electrode 54 is preferably 5 mm × 5 mm or more and 30 mm × 30 mm or less.

[0035] The insulating substrate 61 is positioned on one side in the Z direction relative to the second electrode 54 and the fourth electrode 58. The insulating substrate 61 supports AD 51, the first electrode 52, the resin sheet 59, the second electrode 54, the third electrode 57, and the fourth electrode 58.

[0036] The insulating substrate 61 includes an insulating substrate body 613. The material of the insulating substrate body 613 is, for example, an insulating material such as FR-4. FR-4 is a composite material based on a glass fiber-reinforced epoxy resin. The thickness of the insulating substrate body 613 is, for example, 0.5 mm to 3 mm. The signal capacitor C1 and the return capacitor C2 are, for example, sheet-like structures with a thickness of several hundred μm. Therefore, the insulating substrate 61 functions as a reinforcing plate that reinforces the first electrode 52, the resin sheet 59 and the second electrode 54, as well as the third electrode 57, the resin sheet 59 and the fourth electrode 58.

[0037] The insulating substrate 61 further includes wiring (first wiring) 611 and wiring (first wiring) 612. Wiring 611 and wiring 612 are wirings that pass through the insulating substrate body 613. Wiring 611 is electrically connected to the second electrode 54. One end of wiring 611 is physically connected to the second electrode 54, and the other end of wiring 611 is exposed on one side in the Z direction relative to the insulating substrate body 613. In the electron detector 5, the other end of wiring 611 constitutes an electrode pad 611a on the surface of the insulating substrate body 613 opposite to the second electrode 54. Wiring 612 is electrically connected to the fourth electrode 58. One end of wiring 612 is physically connected to the fourth electrode 58, and the other end of wiring 612 is exposed on one side in the Z direction relative to the insulating substrate body 613. In the electron detector 5, the other end of the wiring 611 forms an electrode pad 612a on the surface of the insulating substrate body 613 opposite to the fourth electrode 58. When viewed from the Z direction, the electrode pad 612a is spaced apart from the electrode pad 611a, and in the X direction, it is aligned with the electrode pad 611a.

[0038] The insulating substrate 61 is circular when viewed from the Z direction, for example. For example, if the MCP210 is circular, the circular shape of the insulating substrate 61 facilitates alignment between the MCP210 and the AD51 in the X and Y directions. The first electrode 52, second electrode 54, third electrode 57, and fourth electrode 58 may be circular in shape to match the shape of the insulating substrate 61. However, the shapes of the insulating substrate 61 and each electrode are not limited to circular; they may be rectangular, elliptical, or polygonal. Also, when viewed from the Z direction, the first electrode 52 and the third electrode 57 may be positioned with the center of the insulating substrate 61 in between. That is, the first electrode 52 and the third electrode 57 may be positioned point-symmetrically from the center of the insulating substrate 61. Similarly, when viewed from the Z direction, the second electrode 54 and the fourth electrode 58 may be positioned with the center of the insulating substrate 61 in between. In other words, the second electrode 54 and the fourth electrode 58 may be arranged point-symmetrically with respect to the center of the insulating substrate 61.

[0039] The output unit 55 is positioned on one side of the insulating substrate 61 in the Z direction. When viewed from the Z direction, the output unit 55 faces the second electrode 54 via the insulating substrate 61 and also faces the fourth electrode 58 via the insulating substrate 61. The outer conductor 552 of the output unit 55 includes a surrounding portion 552A that encloses the inner conductor 551 and a protruding portion 552B that protrudes outward from the surrounding portion 552A. The protruding portion 552B encloses the surrounding portion 552A so as to be in direct contact with it. The output unit 55 is fixed to the insulating substrate 61. As shown in Figure 2, the tip of the inner conductor 551 is physically connected to the electrode pad 611a. This allows electrical signals from AD 51 to be transmitted from the second electrode 54 to the inner conductor 551 via the wiring 611. The protruding portion 552B is physically connected to the electrode pad 612a. As a result, the current flowing through the return path is transmitted from the protruding portion 552B to the fourth electrode 58 via the wiring 612.

[0040] As shown in Figure 4, the protruding portion 552B includes a first protruding portion 553B and a second protruding portion 554B. The first protruding portion 553B extends in the X direction, straddling the space between the second electrode 54 and the fourth electrode 58. As a result, the first protruding portion 553B overlaps with the second electrode 54 in the portion closer to the second electrode 54 than the internal conductor 551, and overlaps with the fourth electrode 58 in the portion closer to the fourth electrode 58 than the internal conductor 551. The second protruding portion 554B extends in the Y direction and is electrically, and in this embodiment, physically, connected to the first protruding portion 553B in the region where the fourth electrode 58 and the insulating substrate 61 overlap. The centers of the first protruding portion 553B in the Y direction and the centers of the second protruding portion 554B in the Y direction are collinear in the X direction. The protruding portion 552B has a T-shape when viewed from the Z direction.

[0041] When viewed from the Z direction, the area S2 in which the outer conductor 552 overlaps with the fourth electrode 58 is larger than the area S1 in which the outer conductor 552 overlaps with the second electrode 54. Specifically, the inner conductor 551 faces the second electrode 54 via the insulating substrate 61, and the area in which the protruding portion 552B overlaps with the fourth electrode 58 is larger than the area in which the protruding portion 552B overlaps with the second electrode 54. In the example of Figure 4, the length of the first protruding portion 553B extending in the X direction from the inner conductor 551 toward the fourth electrode 58 is longer than the length of the first protruding portion 553B extending in the X direction from the inner conductor 551 toward the second electrode 54. In addition, the second protruding portion 554B is provided on the region in which the fourth electrode 58 and the insulating substrate 61 overlap. As mentioned above, parasitic capacitance Cp is generated when the second electrode 54 and the outer conductor 552 face each other. The parasitic capacitance Cp can be expressed, for example, by "Cp = ε × (S / L1)". Here, the dielectric constant ε represents the dielectric constant of the dielectric material of the parasitic capacitance Cp. In this case, the dielectric material is, for example, the insulating substrate 61 interposed between the second electrode 54 and the output unit 55. The width L1 is, for example, the width of the space between the insulating substrate 61 and the output unit 55. In the example in Figure 2, since the output unit 55 is fixed to the insulating substrate 61, the width L1 is assumed to be infinitesimally small. As shown in Equation 1, it can be seen that the smaller the area S1, the smaller the parasitic capacitance Cp becomes. Therefore, the parasitic capacitance Cp generated in the electron detector 5 is smaller than, for example, the case when the area S1 is equal to or greater than the area S2.

[0042] The insulating layer 63 includes a first insulating layer 631 and a second insulating layer 632. The first insulating layer 631 covers the first electrode 52 and the third electrode 57 on the other side (output section 55 side) in the Z direction relative to the resin sheet 59. The first insulating layer 631 is in contact with the resin sheet 59 except for the areas where it is in contact with the first electrode 52 and the third electrode 57 on the resin sheet 59. However, the first insulating layer 631 does not cover the connection points between the anode electrode 511 and the third electrode 57 of AD 51 and the wiring WR. The connection points between the anode electrode 511 and the third electrode 57 and the wiring WR are exposed to the outside. The second insulating layer 632 covers the second electrode 54 and the fourth electrode 58 on one side (AD 51 side) in the Z direction relative to the resin sheet 59. The second insulating layer 632 is in contact with the resin sheet 59 except for the areas where it is in contact with the second electrode 54 and the fourth electrode 58 on the resin sheet 59. Furthermore, the second insulating layer 632 is in contact with the AD51 side surface of the insulating substrate 61. The material of the insulating layer 63 is, for example, an insulating material such as an insulating resin. [Mechanism of Action and Effects]

[0043] In the charged particle detector 1, the first electrode 52 and the second electrode 54, which face each other via a resin sheet 59, function as capacitors, as do the third electrode 57 and the fourth electrode 58, which also face each other via the resin sheet 59. The first electrode 52 and the second electrode 54 function as signal capacitors C1 that remove the DC component from the electrical signal detected by the electronic detection unit 53. As a result, the electrical signal from which the DC component has been removed is output from the internal conductor 551 of the output unit 55 via the second electrode 54. On the other hand, the third electrode 57 and the fourth electrode 58 function as return capacitors C2 that are placed on the return path through which the return current from the external conductor 552 flows. This suppresses the degradation of the electrical signal waveform due to ringing and the like. Furthermore, a resin sheet 59 is used for these capacitors, and the electronic detection unit 53, the resin sheet 59, the second electrode 54, the third electrode 57, and the fourth electrode 58 are supported by an insulating substrate 61. This ensures sufficient voltage resistance for these capacitors and sufficient mechanical strength for the electronic detector 5. Furthermore, when viewed from the Z direction, the area S2 in which the outer conductor 552 overlaps with the fourth electrode 58 is larger than the area S1 in which the outer conductor 552 overlaps with the second electrode 54. As a result, the parasitic capacitance Cp generated by the overlap of the outer conductor 552 with the second electrode 54 is reduced, and consequently, ringing generated in the electrical signal due to the parasitic capacitance Cp is suppressed. Thus, the charged particle detector 1 can improve the quality of the electrical signal.

[0044] In the charged particle detector 1, the outer conductor 552 includes a surrounding portion 552A that encloses the inner conductor 551 and a protruding portion 552B that protrudes outward from the surrounding portion 552A. The inner conductor 551 faces the second electrode 54 via an insulating substrate 61. When viewed from the Z direction, the area S2 in which the protruding portion 552B overlaps with the fourth electrode 58 is larger than the area S1 in which the protruding portion 552B overlaps with the second electrode 54. This makes it easy and reliable to ensure an electrical connection between the fourth electrode 58 and the outer conductor 552. In addition, the parasitic capacitance Cp generated by the overlap of the outer conductor 552 with the second electrode 54 is further reduced, thus further suppressing ringing caused by the parasitic capacitance Cp.

[0045] The charged particle detector 1 comprises an electron detector 5 and an electron emission unit 2 that emits electrons upon the incidence of charged particles. This configuration allows for improved electrical signal quality in the electron detector 5. [Differentiation]

[0046] The present invention is not limited to the embodiments described above. As shown in Figures 5 and 6, the first modified electron detector 5A differs from electron detector 5 in that it has a support portion 62 and in the shape of the protruding portion 552B. As shown in Figure 6, the protruding portion 552B of electron detector 5A may not include the second protruding portion 554B and may consist only of the first protruding portion 553B. In this case as well, the area S2 in which the outer conductor 552 overlaps with the fourth electrode 58 is larger than the area S1 in which the outer conductor 552 overlaps with the second electrode 54.

[0047] The support portion 62 supports the output unit 55 on one side of the insulating substrate 61 in the Z direction such that a space SP1 is formed between the output unit 55 and the insulating substrate 61. The support portion 62 includes fixing portions 621 and 622. The fixing portions 621 and 622 fix the output unit 55 to the insulating substrate 61. The fixing portions 621 and 622 are connectors with the Z direction as their longitudinal direction. One end of the fixing portions 621 and 622 is physically connected to an electrode pad on the insulating substrate 61. Of these, the fixing portion 622 is physically connected to the electrode pad 612a. The other end of the fixing portions 621 and 622 is physically connected to a protruding portion 552B. The support portion 62 adjusts the width L1 of the space SP1 between the insulating substrate 61 and the output unit 55 by the width of the fixing portions 621 and 622. In addition, the internal conductor 551 protrudes toward the insulating substrate 61 side than the external conductor 552 in the Z direction. The length of the protruding portion of the internal conductor 551 is, for example, the same as the width of the fixing portions 627 and 628. The tip of the internal conductor 551 is physically connected to the electrode pad 611a.

[0048] In the electron detector 5A, the area S1 is smaller than the area S2, and the width L1 of the space SP1 is secured. Therefore, based on the aforementioned equation 1, the parasitic capacitance Cp generated in the electron detector 5 may be smaller than the parasitic capacitance Cp generated in the electron detector 5. In the electron detector 5A, the parasitic capacitance Cp generated between the output unit 55 and the second electrode 54 is further reduced by the formation of space SP1 between the output unit 55 and the insulating substrate 61, so that ringing generated in the electrical signal due to parasitic capacitance Cp can be further suppressed.

[0049] As shown in Figures 7 and 8, the second modified electron detector 5B differs from electron detector 5 in the configuration of the first electrode 52A and the second electrode 54A. The first electrode 52A and the second electrode 54A may be arranged so as to be away from the outer conductor 552 in the Y direction. This can make the area S1 even smaller compared to electron detectors 5 and 5A. The first electrode 52A and the second electrode 54A have an L-shape when viewed from the Z direction. The second electrode 54A extends in the Y direction from the connection point with the inner conductor 551, bends in the X direction so as to be away from the fourth electrode 58 along the way, and extends in the X direction. The first electrode 52A extends in the Y direction from the connection point with AD 51, bends in the X direction so as to be away from the third electrode 57 along the way, and extends in the X direction. In this case as well, the first electrode 52A and the second electrode 54A face each other via the insulating substrate 61.

[0050] As shown in Figures 9 and 10, the third modified electron detector 5C differs from electron detector 5 in that, when viewed from the Z direction, the outer conductor 552 does not overlap with the second electrode 54B and the fourth electrode 58B. As shown in Figure 9, the second electrode 54B and the fourth electrode 58B may be positioned offset in the Y direction from the output unit 55. For example, the second electrode 54B is electrically connected to the inner conductor 551 by a wiring electrode 65 extending in the Y direction from the inner conductor 551. The fourth electrode 58B is electrically connected to the electrode pad 612a by a wiring electrode 66 extending in the Y direction from the electrode pad 612a. The first electrode 52B, the second electrode 54B, the third electrode 57B, and the fourth electrode 58B have a rectangular shape when viewed from the Z direction. In this case as well, the first electrode 52B and the second electrode 54B face each other via the insulating substrate 61. Similarly, the third electrode 57B and the fourth electrode 58B face each other via the insulating substrate 61. In the electron detector 5C, the generation of parasitic capacitance Cp caused by the overlap of the outer conductor 552 with the second electrode 54 is suppressed, and as a result, ringing generated in the electrical signal due to parasitic capacitance Cp is suppressed.

[0051] The internal conductor 551 is electrically connected to one of the second electrode 54 and the fourth electrode 58, and the external conductor 552 is electrically connected to the other electrode of the second electrode 54 and the fourth electrode 58. In the embodiments and modifications described above, an example was given in which one electrode is the second electrode 54, that is, an example in which the internal conductor 551 is electrically connected to the second electrode 54, but the internal conductor 551 may also be electrically connected to the fourth electrode 58. Also, in the embodiments and modifications described above, an example was given in which the other electrode is the fourth electrode 58, that is, an example in which the external conductor 552 is electrically connected to the fourth electrode 58, but the external conductor 552 may also be electrically connected to the second electrode 54. As shown in Figure 11, the electron detector 5D of the fourth modification differs from the electron detector 5 in that the internal conductor 551 is electrically connected to the fourth electrode 58 and the external conductor 552 is electrically connected to the second electrode 54. As shown in Figure 11, the tip of the internal conductor 551 is physically connected to the electrode pad 612a. As a result, the electrical signal from AD51 flows through the wiring WR and is transmitted to the third electrode 57. The electrical signal is then transmitted from the fourth electrode 58 to the internal conductor 551 via the wiring 612. In other words, in the electron detector 5D, the third electrode 57, the resin sheet 59, and the fourth electrode 58 constitute the signal capacitor C1. The protruding portion 552B is physically connected to the electrode pad 611a. As a result, the current flowing through the return path is transmitted from the protruding portion 552B to the second electrode 54 via the wiring 611. In other words, in the electron detector 5D, the first electrode 52, the resin sheet 59, and the second electrode 54 constitute the return capacitor C2.

[0052] When viewed from the Z direction, the area in which the outer conductor 552 overlaps with the second electrode 54 and the other electrode of the fourth electrode 58 (the electrode electrically connected to the outer conductor 552) may be larger than the area in which the outer conductor 552 overlaps with one of the electrodes of the second electrode 54 and the fourth electrode 58 (the electrode electrically connected to the inner conductor 551). In the electron detector 5D, when viewed from the Z direction, the area S1 in which the outer conductor 552 overlaps with the second electrode 54 is larger than the area S2 in which the outer conductor 552 overlaps with the fourth electrode 58. Since the electrical signal is transmitted from the fourth electrode 58 to the inner conductor 551, the parasitic capacitance Cp that contributes to ringing in the electrical signal is the capacitance generated by the facing of the fourth electrode 58 and the outer conductor 552. Therefore, a smaller area S2 reduces the parasitic capacitance Cp generated by the overlap of the outer conductor 552 with the fourth electrode 58. As a result, ringing generated in the electrical signal due to parasitic capacitance Cp is suppressed.

[0053] The electron detection unit 53 does not necessarily have to include AD51. In this case, for example, the electron detection unit 53 is composed of a first electrode 52. The first electrode 52 may also serve as the signal capacitor C1. As shown in Figure 12, the electron detector 5E of the fifth modified example differs from the electron detector 5 in that it does not have AD51. In the charged particle detector 1A including the electron detector 5E, the electron emission unit 2 may also include an MCP unit 2A composed of two MCPs. In the charged particle detector 1A, the wiring WR electrically connects the third electrode 57 and the MCP unit 2A. This forms a return path from the outer conductor 552 to the MCP unit 2A. The first electrode 52 functions as an anode electrode, which is an electron capture electrode. For example, the first electrode 52 detects electrons emitted from the MCP unit 2A. In this case, unlike AD51, the first electrode 52 does not have an amplification function. The electron incident surface of the first electrode 52 is not covered by the first insulating layer 631 and is exposed to the outside.

[0054] The electron emission unit 2 may include other electron multiplier elements in place of or together with the MCP21. As shown in Figure 13, the modified charged particle detector 1B differs from the charged particle detector 1A in that the electron emission unit 2 includes a dynode unit 23 instead of the MCP21. The dynode unit 23 includes multiple dynodes. In the dynode unit 23, each stage of dynodes emits electrons as secondary electrons and passes them to the next stage, thereby increasing the number of electrons in steps. In Figure 13, only the final stage dynode is shown. In the charged particle detector 1B, the wiring WR electrically connects the third electrode 57 and the dynode unit 23. This forms a return path from the external conductor 552 to the dynode unit 23. With the charged particle detector 1B, since the electrons emitted from the electron emission unit 2 are multiplied as secondary electrons, the electrical signal output from the electron detector 5 can be made larger. In addition, secondary electron emission with a high amplification factor can be achieved.

[0055] Any combination is possible in the various modifications described above. For example, in the electron detector 5A shown in Figure 5, the internal conductor 551 may be electrically connected to the fourth electrode 58, or the external conductor 552 may be electrically connected to the second electrode 54. Also, for example, in the electron detector 5E shown in Figures 12 and 13, the internal conductor 551 may be electrically connected to the fourth electrode 58, or the external conductor 552 may be electrically connected to the second electrode 54.

[0056] In the embodiments and modifications described above, an example was given in which the electron detector 5 is applied to the charged particle detector 1. However, the electron detector 5 may also be applied to an electron tube that includes a photocathode that converts photons into photoelectrons. The electron detector 5 may be applied to, for example, a photomultiplier tube or a hybrid photodetector (HPD). A photomultiplier tube includes an electron multiplier unit that multiplies photoelectrons emitted from the photocathode to emit secondary electrons. This electron multiplier unit corresponds to the electron emission unit 2 in the charged particle detector 1. An HPD does not include a configuration corresponding to the electron emission unit 2. In an HPD, photoelectrons emitted from the photocathode directly enter the electron detector 5.

[0057] Based on the embodiments and modifications described above, the charged particle detector of the present invention can also be described as follows.

[0058] The charged particle detector of the present invention comprises: [1] an electron emission unit that emits electrons upon incidence of charged particles; and an electron detector that outputs the electrons emitted from the electron emission unit as an electrical signal, wherein the electron detector includes a first electrode and an electron detection unit that detects the electrons emitted from the electron emission unit; a resin sheet disposed on one side in a first direction relative to the first electrode; a second electrode disposed on the one side in a first direction relative to the resin sheet and facing the first electrode via the resin sheet; a third electrode disposed on the other side in a first direction relative to the resin sheet and spaced apart from the first electrode in a second direction intersecting the first direction; and a fourth electrode disposed on one side in a first direction relative to the resin sheet and spaced apart from the second electrode in a second direction and facing the third electrode via the resin sheet. A charged particle detector comprising: an electrode; an insulating substrate positioned on one side in the first direction relative to the second electrode and supporting the electronic detection unit, the resin sheet, the second electrode, the third electrode, and the fourth electrode; and an output unit positioned on one side in the first direction relative to the insulating substrate and outputting the electrical signal, wherein the output unit includes an internal conductor electrically connected to one of the second electrode and the fourth electrode, and an external conductor surrounding the internal conductor in an electrically insulated state and electrically connected to the other electrode of the second electrode and the fourth electrode, wherein, when viewed from the first direction, the area in which the external conductor overlaps with the other electrode is greater than the area in which the external conductor overlaps with the one electrode, or, when viewed from the first direction, the external conductor does not overlap with the second electrode and the fourth electrode.

[0059] The charged particle detector of the present invention may also be [2] "the charged particle detector according to [1] above, wherein one electrode is the second electrode and the other electrode is the fourth electrode."

[0060] The charged particle detector of the present invention may also be [3] "the charged particle detector according to [1] or [2] above, wherein the outer conductor includes an enclosing portion that surrounds the inner conductor and a protruding portion that protrudes outward from the enclosing portion, the inner conductor faces the one electrode via the insulating substrate, and when viewed from the first direction, the area in which the protruding portion overlaps with the other electrode is greater than the area in which the protruding portion overlaps with the one electrode."

[0061] The charged particle detector of the present invention may also be [4] "the charged particle detector according to any one of [1] to [3] above, wherein the electron detector further has a support portion that supports the output portion such that a space is formed between the output portion and the insulating substrate on one side in the first direction with respect to the insulating substrate." [Explanation of symbols]

[0062] 1, 1A, 1B... Charged particle detector, 5, 5A, 5B, 5C, 5D, 5E... Electron detector, 55... Output section, 52, 52A, 52B... First electrode, 53... Electron detection section, 54, 54A, 54B... Second electrode, 57, 57B... Third electrode, 58, 58B... Fourth electrode, 59... Resin sheet, 61... Insulating substrate, 62... Support section, 551... Internal conductor, 552... External conductor, 552A... Enclosing section, 552B... Protruding section, S1, S2... Area, SP1... Space.

Claims

1. An electron detection unit including a first electrode for detecting incident electrons, A resin sheet disposed on one side in the first direction relative to the first electrode, A second electrode is positioned on one side in the first direction relative to the resin sheet and faces the first electrode via the resin sheet, A third electrode is positioned on the other side in the first direction relative to the resin sheet, and is spaced apart from the first electrode in a second direction intersecting the first direction, A fourth electrode is positioned on one side of the resin sheet in the first direction, spaced apart from the second electrode in the second direction, and facing the third electrode via the resin sheet, An insulating substrate is positioned on one side in the first direction relative to the second electrode and supports the electron detection unit, the resin sheet, the second electrode, the third electrode, and the fourth electrode, The insulating substrate is positioned on one side in the first direction and comprises an output unit that outputs an electrical signal, The output unit is, An internal conductor electrically connected to one of the second electrode and the fourth electrode, It includes an outer conductor that surrounds the inner conductor in a state of being electrically insulated from the inner conductor and is electrically connected to the other electrode of the second electrode and the fourth electrode, An electron detector in which, when viewed from the first direction, the area in which the outer conductor overlaps with the other electrode is greater than the area in which the outer conductor overlaps with the one electrode, or, when viewed from the first direction, the outer conductor does not overlap with the second electrode and the fourth electrode.

2. The aforementioned one electrode is the second electrode, The electron detector according to claim 1, wherein the other electrode is the fourth electrode.

3. The outer conductor includes a surrounding portion that encloses the inner conductor and a protruding portion that protrudes outward from the surrounding portion. The internal conductor faces the one electrode via the insulating substrate. The electron detector according to claim 1 or 2, wherein, when viewed from the first direction, the area in which the protruding portion overlaps with the other electrode is larger than the area in which the protruding portion overlaps with the one electrode.

4. The electron detector according to claim 1 or 2, further comprising a support portion that supports the output portion such that a space is formed between the output portion and the insulating substrate on one side in the first direction with respect to the insulating substrate.

5. The electron detector according to claim 1 or 2, A charged particle detector comprising an electron emission unit that emits electrons upon the incidence of charged particles.

6. The charged particle detector according to claim 5, wherein the electron emission unit includes a microchannel plate.

7. The charged particle detector according to claim 5, wherein the electron emission unit includes a plurality of dynodes.

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