Electron and charged particle detectors

Abstract

An electron detector and a charged particle detector are provided that can improve the quality of an electrical signal. [Solution] The electron detector (5) includes 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), and when viewed from the Z direction, an area (S2) where the external conductor (552) overlaps with the fourth electrode (58) is larger than an area (S1) where the external conductor (552) overlaps with the second electrode (54).

Description

[Technical Field]

[0001] The present invention relates to electron and charged particle detectors. [Background technology]

[0002] As a charged particle detector applicable to mass spectrometry and the like, Patent Document 1 describes an ion detector including a microchannel plate (hereinafter referred to as "MCP") that emits electrons in response to incident ions, an anode electrode that detects the electrons emitted from the MCP, a coaxial cable including an inner conductor electrically connected to the anode electrode, and a ground electrode electrically connected to the 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 a conductive plate. This allows the collector electrode and the conductive plate to function as a capacitor, removing a DC component from the electrical signal output via the coaxial cable. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-273867 Summary of the Invention [Problem to be solved by the invention]

[0004] In the ion detector described in Patent Document 1, the conductive plate included in the anode electrode, which serves as the electron detector, and the ground electrode face each other, which generates parasitic capacitance between the anode electrode and the ground electrode, which can result in ringing in the electrical signal output via the coaxial cable.When the ion detector is applied to a mass spectrometer, if ringing occurs in the electrical signal output from the ion detector, the accuracy of mass analysis can be reduced.

[0005] An object of the present invention is to provide an electron detector and a charged particle detector that can improve the quality of an electric signal. [Means for solving the problem]

[0006] The electron detector of the present invention includes: [1] "an electron detection unit including a first electrode and detecting incident electrons; a resin sheet arranged on one side of the first electrode in a first direction; a second electrode arranged on the one side of the resin sheet in the first direction and facing the first electrode via the resin sheet; a third electrode arranged on the other side of the resin sheet in the first direction and spaced apart from the first electrode in a second direction intersecting the first direction; a fourth electrode arranged on the one side of the resin sheet in the first direction and spaced apart from the second electrode in the second direction and facing the third electrode via the resin sheet; and a fourth electrode arranged on the one side of the second electrode in the first direction and facing the electron detection unit. a resin sheet, an insulating substrate supporting the second electrode, the third electrode, and the fourth electrode; and an output section disposed on one side of the insulating substrate in the 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 while being electrically insulated from the internal conductor and electrically connected to the other of the second electrode and the fourth electrode, wherein, when viewed from the first direction, the area where the external conductor overlaps with the other electrode is larger than the area where 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 or 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, and the third and fourth electrodes, which face each other via a resin sheet, also function as capacitors. One of these capacitors functions as a capacitor that removes DC components from the electrical signal detected by the electron detection unit. As a result, the electrical signal from which the DC components have been removed is output from the internal conductor of the output unit via the second or fourth electrode. Meanwhile, the other of these capacitors functions as a return capacitor located on a return path through which a return current from the external conductor flows. This makes it possible to suppress deterioration of the waveform of the electrical signal 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 where the external conductor overlaps with the other of the second electrode and the fourth electrode is larger than the area where the external conductor overlaps with one of the second electrode and the fourth electrode, or when viewed from the first direction, the external conductor does not overlap with the second electrode or the fourth electrode. This reduces or suppresses the occurrence of parasitic capacitance caused by the external conductor overlapping with one of the second electrode and the fourth electrode, and as a result, ringing caused by the parasitic capacitance in the electrical signal is suppressed. As a result, the quality of the electrical signal can be improved with the above-mentioned electron detector.

[0008] The electron detector of the present invention may be [2] "the electron detector according to the above [1], in which the one electrode is the second electrode and the other electrode is the fourth electrode." According to the electron detector according to [2], an electric signal from which a DC component has been removed is output from the internal conductor of the output section via the second electrode. Furthermore, the overlap of the external conductor with the second electrode reduces parasitic capacitance. As a result, ringing caused by parasitic capacitance can be suppressed in the electric signal output via the second electrode.

[0009] The electron detector of the present invention may be [3] "the electron detector according to the above [1] or [2], wherein the outer conductor includes a surrounding portion surrounding the inner conductor and a protruding portion protruding outward from the surrounding portion, the inner conductor faces the one electrode via the insulating substrate, and when viewed from the first direction, the area where the protruding portion overlaps with the other electrode is larger than the area where the protruding portion overlaps with the one electrode." The electron detector according to [3] can easily and reliably ensure electrical connection between the other electrode and the outer conductor. In addition, the parasitic capacitance generated by the outer conductor overlapping with the one electrode is further reduced, thereby further suppressing ringing caused by the parasitic capacitance.

[0010] The electron detector of the present invention may be [4] "the electron detector according to any one of the above [1] to [3], further comprising a support part supporting the output part on the one side in the first direction with respect to the insulating substrate so that a space is formed between the output part and the insulating substrate." According to the electron detector described in [4], the formation of a space between the output part and the insulating substrate further reduces the parasitic capacitance generated between the output part and one electrode, and therefore ringing generated in the electrical signal due to the parasitic capacitance can be further suppressed.

[0011] The charged particle detector of the present invention may be [5] "a charged particle detector comprising the electron detector according to any one of [1] to [4] above and an electron emitter that emits electrons in response to incidence of a charged particle." The charged particle detector according to [5] can improve the quality of the electrical signal in the electron detector.

[0012] The charged particle detector of the present invention may be [6] "the charged particle detector according to the above [5], wherein the electron emitter includes a microchannel plate." According to the charged particle detector according to [6], electrons emitted from the electron emitter are amplified as secondary electrons, so that the electrical signal output from the electron detector can be increased. Furthermore, secondary electrons can be emitted with a high amplification factor.

[0013] The charged particle detector of the present invention may be [7] "the charged particle detector according to the above [5], wherein the electron emitter includes a plurality of dynodes." According to the charged particle detector according to [7], electrons emitted from the electron emitter are amplified as secondary electrons, so that the electrical signal output from the electron detector can be increased. Furthermore, secondary electrons can be emitted with a high amplification factor. [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 an electric signal. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram illustrating a circuit configuration of a charged particle detector according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the electron detector shown in FIG. [Figure 3] FIG. 2 is a front view of the electron detector shown in FIG. 1. [Figure 4] FIG. 2 is a rear view of the electron detector shown in FIG. 1. [Figure 5] FIG. 10 is a cross-sectional view of an electron detector according to a first modified example. [Figure 6] FIG. 10 is a rear view of the electron detector of the first modified example. [Figure 7] FIG. 10 is a front view of an electron detector according to a second modified example. [Figure 8] FIG. 10 is a rear view of the electron detector of the second modified example. [Figure 9] FIG. 10 is a front view of an electron detector according to a third modified example. [Figure 10] FIG. 11 is a rear view of the electron detector of the third modified example. [Figure 11] FIG. 10 is a cross-sectional view of an electron detector according to a fourth modified example. [Figure 12] FIG. 10 is a cross-sectional view of an electron detector according to a fifth modified example. [Figure 13] FIG. 10 is a cross-sectional view of a modified charged particle detector. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are designated by the same reference numerals, and duplicated explanations will be omitted. [Charged particle detector configuration]

[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 this 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 emitter 2, an acceleration electrode 3, a focus electrode 4, and an electron detector 5. In the charged particle detector 1, the electron emitter 2, the acceleration electrode 3, the focus electrode 4, and the electron detection section 53 of the electron detector 5 are arranged in this order. The charged particle detector 1 is, for example, an ion detector that detects ions of both polarities. The charged particle detector 1 is applied to, for example, a mass spectrometer. Note that the charged particle detector 1 may also be one that detects charged particles other than ions (e.g., electrons, etc.).

[0018] The electron emitter 2 emits electrons in response to the incidence of ions IN. The polarity of the ions IN may be negative or positive. The electron emitter 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 the incidence of ions IN. The MCP 21 has an input surface 21a and an output surface 21b. The side surfaces of the MCP 21 are surrounded by an insulating ring made of an insulating material. When ions IN are incident on the input surface 21a, the MCP 21 generates electrons in response to the incidence of the ions IN, multiplies the electrons, and emits them from the output surface 21b. In other words, the MCP 21 also functions as an electron multiplier. The MCP 21 has a plurality of through-holes (channels) formed therein, each extending 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 portions of the input surface 21a and the output surface 21b, respectively. The electron emitter 2 may independently include an electron emitter that emits electrons in response to incident ions IN and an electron multiplier that multiplies and emits the electrons. For example, the electron emitter 2 may include an ion-electron converter provided in front of the MCP 21 as the electron emitter, and the MCP 21 as the electron multiplier.

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

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

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

[0022] The first electrode 52 is electrically connected to the cathode electrode 512 of the AD 51. The first electrode 52 and the second electrode 54 form a signal capacitor C1. The signal capacitor C1 functions as a coupling capacitor that removes DC components from the electrical signal output from the AD 51.

[0023] The output unit 55 is electrically connected to the second electrode 54 and outputs an electrical signal toward the signal output terminal 56. The output unit 55 includes an internal conductor 551 and an external conductor 552. The internal conductor 551 is electrically connected to the second electrode 54. The external conductor 552 surrounds the internal conductor 551. A gap may be provided between the internal conductor 551 and the external conductor 552, or an insulating member may be disposed therebetween. The external conductor 552 is connected to a reference potential GND. The output unit 55 is, for example, an SMA connector. In this case, the internal conductor 551 is a signal line that transmits an electrical signal, and the external 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 the AD 51. The fourth electrode 58 is electrically connected to the reference potential GND and the external conductor 552. The third electrode 57 and the fourth electrode 58 are arranged on a return path formed from the external conductor 552 to the anode electrode 511, and form a return capacitor C2. By providing the return capacitor C2, deterioration of the waveform of the electrical signal due to ringing and the like is suppressed. Ringing is a high-frequency component that is superimposed on the electrical signal when the magnitude of the electrical signal changes, for example, when the electrical signal rises or falls.

[0025] A parasitic capacitance Cp may occur between the second electrode 54 and the external conductor 552. The parasitic capacitance Cp is a parasitic component that occurs when the second electrode 54 and the external conductor 552 face each other. The 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 and ringing occurs in the electrical signal, the mass spectrometer may not be able to accurately read the magnitude of the electrical signal, which may affect the accuracy of mass analysis. For this reason, it is extremely important to minimize the parasitic capacitance Cp and suppress the effects of ringing.

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

[0027] When measuring negative ions IN, for example, +10 kV is applied as the potential Va. In this case, if the potential difference Vb becomes +1 kV and the potential difference Vc becomes +6 kV, the potential at the other end of the resistor Ra becomes +17 kV. When measuring positive ions IN, for example, -10 kV is applied as the potential Va. In this case, if the potential difference Vb becomes +1 kV and the potential difference Vc becomes +6 kV, the potential at the other end of the resistor Ra becomes -3 kV. In both measurements of negative ions IN and positive ions IN, the potential increases from the input surface 21 a of the MCP 21 toward the anode electrode 511 of the AD51. Furthermore, the potential applied to the cathode electrode 512 of the 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 the AD51, and the AD51 operates in a floating state. [Electron detector configuration]

[0028] As shown in FIGS. 2, 3, and 4, the electron detector 5 further includes 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 is referred to as the Z direction (first direction), a direction perpendicular to the Z direction (a direction intersecting the Z direction) is referred to as the X direction (second direction), and a direction perpendicular to the Z direction and the X direction is referred to as the Y direction. In the electron detector 5, the AD 51, the first electrode 52, the resin sheet 59, the second electrode 54, the insulating substrate 61, and the output portion 55 are arranged in this order in the Z direction. In the following description, "disposed on one side" means that each component is disposed on the opposite side of the AD 51 (the output portion 55 side) from the adjacent component on the AD 51 side. "disposed on the other side" means that each component is disposed on the opposite side of the output portion 55 (the AD 51 side) from the adjacent component on the output portion 55 side.

[0029] The AD 51 is disposed, for example, at a position where electrons emitted from the MCP 21 reach. The first electrode 52 is disposed on the opposite side of the AD 51 from the MCP 21 and is electrically connected to the AD 51. In the electron detector 5, the first electrode 52 is in contact with the cathode electrode 512 of the AD 51.

[0030] The resin sheet 59 is disposed on one side in the Z direction of the first electrode 52. The resin sheet 59 is in contact with the first electrode 52. The resin sheet 59 is made of a resin such as a liquid crystal polymer (LCP), a polyester film, a polyimide, or a polyamide. The second electrode 54 is disposed on one side in the Z direction of the resin sheet 59. The second electrode 54 is in contact with the resin sheet 59. The second electrode 54 faces the first electrode 52 with the resin sheet 59 interposed therebetween. The area of ​​the first electrode 52 and the area of ​​the second electrode 54 may be the same, and the outer edge of the first electrode 52 and the outer edge 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 the 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 be able to withstand a high voltage with an absolute value of 10 kV or more. In light of the above, the thickness of the resin sheet 59 is preferably 25 μm or more and 200 μm or less, and the area of ​​each 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 disposed on the other side in the Z direction with respect to the resin sheet 59. 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 aligned with the first electrode 52 in the X direction while being spaced apart from the first electrode 52. 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 a wiring WR.

[0033] The fourth electrode 58 is disposed on one side in the Z direction with respect to the resin sheet 59. 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 with the resin sheet 59 interposed therebetween. The area of ​​the third electrode 57 and the area of ​​the fourth electrode 58 may be the same, and the outer edge of the third electrode 57 and the outer edge of the fourth electrode 58 may coincide when viewed from the Z direction.

[0034] The third electrode 57, resin sheet 59, and fourth electrode 58 constitute the return capacitor C2. The third electrode 57 and 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. In other words, 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 ​​each 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 disposed on one side in the Z direction with respect to the second electrode 54 and the fourth electrode 58. The insulating substrate 61 supports the 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 (Frequency Reduction Four). FR-4 is a composite material based on epoxy resin reinforced with glass fiber. 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 sheet-like structures with a thickness of, for example, several hundred μm. Therefore, the insulating substrate 61 reinforces the first electrode 52, the resin sheet 59, and the second electrode 54, and also functions as a reinforcing plate that reinforces the third electrode 57, the resin sheet 59, and the fourth electrode 58.

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

[0038] The insulating substrate 61 has a circular shape when viewed from the Z direction, for example. For example, if the MCP 210 is circular, the circular insulating substrate 61 facilitates alignment between the MCP 210 and the AD 51 in the X and Y directions. The first electrode 52, the second electrode 54, the third electrode 57, and the fourth electrode 58 may have a circular 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 a circular shape and may be rectangular, elliptical, or polygonal. Furthermore, when viewed from the Z direction, the first electrode 52 and the third electrode 57 may be disposed with the center of the insulating substrate 61 sandwiched therebetween. That is, the first electrode 52 and the third electrode 57 may be disposed point-symmetrically with respect to each other with respect to 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 disposed with the center of the insulating substrate 61 sandwiched therebetween. That is, 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 disposed 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 through the insulating substrate 61, and also faces the fourth electrode 58 through the insulating substrate 61. The outer conductor 552 of the output unit 55 includes an enclosing portion 552A that encloses the internal conductor 551 and a protruding portion 552B that protrudes outward from the enclosing portion 552A. The protruding portion 552B surrounds the enclosing portion 552A so as to be in direct contact with the enclosing portion 552A. The output unit 55 is fixed to the insulating substrate 61. As shown in FIG. 2, the tip of the internal conductor 551 is physically connected to the electrode pad 611a. As a result, an electrical signal from the AD 51 is transmitted from the second electrode 54 to the internal 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 FIG. 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 across the second electrode 54 and the fourth electrode 58. As a result, the first protruding portion 553B overlaps with the second electrode 54 at a portion closer to the second electrode 54 than the internal conductor 551, and overlaps with the fourth electrode 58 at a portion closer to the fourth electrode 58 than the internal conductor 551. The second protruding portion 554B is electrically connected to the first protruding portion 553B, and in this embodiment, physically connected to the first protruding portion 553B, in a region where the fourth electrode 58 and the insulating substrate 61 overlap, and extends in the Y direction. 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 aligned on the same line in the X direction. When viewed from the Z direction, the protruding portion 552B has a T-shape.

[0041] When viewed from the Z direction, the area S2 over which the external conductor 552 overlaps with the fourth electrode 58 is larger than the area S1 over which the external conductor 552 overlaps with the second electrode 54. Specifically, the internal conductor 551 faces the second electrode 54 via the insulating substrate 61, and the area over which the protruding portion 552B overlaps with the fourth electrode 58 is larger than the area over which the protruding portion 552B overlaps with the second electrode 54. In the example of FIG. 4 , the length over which the first protruding portion 553B extends in the X direction from the internal conductor 551 toward the fourth electrode 58 is longer than the length over which the first protruding portion 553B extends in the X direction from the internal conductor 551 toward the second electrode 54. In addition, the second protruding portion 554B is provided in the region over which the fourth electrode 58 and the insulating substrate 61 overlap. As described above, the facing of the second electrode 54 and the external conductor 552 generates parasitic capacitance Cp. 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 of the parasitic capacitance Cp. In this case, the dielectric 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 of FIG. 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. Therefore, the parasitic capacitance Cp generated in the electron detector 5 is smaller than when, for example, 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) of the resin sheet 59 in the Z direction. The first insulating layer 631 is in contact with the resin sheet 59 except for the portions of the resin sheet 59 that are in contact with the first electrode 52 and the third electrode 57. However, the first insulating layer 631 does not cover the connection portions of the anode electrode 511 and the third electrode 57 of the AD 51 with the wiring WR. The connection portions of the anode electrode 511 and the third electrode 57 with 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) of the resin sheet 59 in the Z direction. The second insulating layer 632 is in contact with the resin sheet 59 except for the portions of the resin sheet 59 that are in contact with the second electrode 54 and the fourth electrode 58. The second insulating layer 632 is in contact with the surface of the insulating substrate 61 on the AD 51 side. The material of the insulating layer 63 is, for example, an insulating material such as an insulating resin. [Action and effect]

[0043] In the charged particle detector 1, the first electrode 52 and the second electrode 54, which face each other via the resin sheet 59, function as capacitors. Similarly, the third electrode 57 and the fourth electrode 58, which face each other via the resin sheet 59, also function as capacitors. The first electrode 52 and the second electrode 54 function as a signal capacitor C1 that removes DC components from the electrical signal detected by the electron detection unit 53. As a result, the electrical signal from which the DC components have been removed is output from the internal conductor 551 of the output unit 55 via the second electrode 54. Meanwhile, the third electrode 57 and the fourth electrode 58 function as a return capacitor C2 located on a return path through which a return current from the external conductor 552 flows. This makes it possible to suppress deterioration of the waveform of the electrical signal due to ringing and the like. Furthermore, the resin sheet 59 is used for these capacitors, and the electron 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 electron detector 5. Furthermore, when viewed from the Z direction, the area S2 where the external conductor 552 overlaps with the fourth electrode 58 is larger than the area S1 where the external conductor 552 overlaps with the second electrode 54. This reduces the parasitic capacitance Cp generated by the overlap of the external conductor 552 with the second electrode 54, and as a result, ringing generated in the electrical signal due to the parasitic capacitance Cp is suppressed. As described above, 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 surrounding the inner conductor 551 and a protruding portion 552B protruding outward from the surrounding portion 552A, the inner conductor 551 faces the second electrode 54 via the insulating substrate 61, and when viewed from the Z direction, an area S2 over which the protruding portion 552B overlaps with the fourth electrode 58 is larger than an area S1 over which the protruding portion 552B overlaps with the second electrode 54. This makes it possible to easily and reliably ensure electrical connection between the fourth electrode 58 and the outer conductor 552. In addition, the parasitic capacitance Cp generated by the outer conductor 552 overlapping with the second electrode 54 is further reduced, thereby further suppressing ringing caused by the parasitic capacitance Cp.

[0045] The charged particle detector 1 includes an electron detector 5 and an electron emitter 2 that emits electrons in response to incident charged particles. This makes it possible to improve the quality of the electrical signal in the electron detector 5. [Variations]

[0046] The present invention is not limited to the above-described embodiment. As shown in Figures 5 and 6, the electron detector 5A of the first modified example differs from the 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 the electron detector 5A may not include the second protruding portion 554B and may be composed of only the first protruding portion 553B. Even in this case, the area S2 where the external conductor 552 overlaps with the fourth electrode 58 is larger than the area S1 where the external conductor 552 overlaps with the second electrode 54.

[0047] The support portion 62 supports the output portion 55 on one side in the Z direction relative to the insulating substrate 61 so that a space SP1 is formed between the output portion 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 portion 55 to the insulating substrate 61. The fixing portions 621 and 622 are connectors with their longitudinal direction in the Z 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 the protruding portion 552B. The support portion 62 adjusts the width L1 of the space SP1 between the insulating substrate 61 and the output portion 55 by adjusting the width of the fixing portions 621 and 622. Furthermore, the internal conductor 551 protrudes more toward the insulating substrate 61 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 ensured. Therefore, based on the above-mentioned formula 1, the parasitic capacitance Cp generated in the electron detector 5 can be smaller than the parasitic capacitance Cp generated in the electron detector 5. In the electron detector 5A, the space SP1 is formed between the output section 55 and the insulating substrate 61, which further reduces the parasitic capacitance Cp generated between the output section 55 and the second electrode 54, thereby further suppressing ringing that occurs in the electrical signal due to the parasitic capacitance Cp.

[0049] As shown in FIGS. 7 and 8 , the electron detector 5B of the second modification differs from the 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 farther away from the external conductor 552 in the Y direction. This may further reduce the area S1 compared to the electron detectors 5 and 5A. The first electrode 52A and the second electrode 54A are L-shaped when viewed from the Z direction. The second electrode 54A extends in the Y direction from the connection point with the internal conductor 551, bends in the X direction midway to move away from the fourth electrode 58, and continues to extend in the X direction. The first electrode 52A extends in the Y direction from the connection point with the AD51, bends in the X direction midway to move away from the third electrode 57, and continues to extend in the X direction. In this case as well, the first electrode 52A and the second electrode 54A face each other with the insulating substrate 61 interposed therebetween.

[0050] As shown in FIGS. 9 and 10 , the electron detector 5C of the third modification differs from the electron detector 5 in that, when viewed from the Z direction, the external conductor 552 does not overlap the second electrode 54B and the fourth electrode 58B. As shown in FIG. 9 , the second electrode 54B and the fourth electrode 58B may be positioned offset in the Y direction from the output section 55. For example, the second electrode 54B is electrically connected to the internal conductor 551 by a wiring electrode 65 extending from the internal conductor 551 in the Y direction. The fourth electrode 58B is electrically connected to the electrode pad 612a by a wiring electrode 66 extending from the electrode pad 612a in the Y direction. The first electrode 52B, the second electrode 54B, the third electrode 57B, and the fourth electrode 58B each have a rectangular shape when viewed from the Z direction. Even in this case, 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 occurrence of parasitic capacitance Cp caused by the external conductor 552 overlapping with the second electrode 54 is suppressed, and as a result, ringing occurring in the electrical signal due to the parasitic capacitance Cp is suppressed.

[0051] The internal conductor 551 may be electrically connected to one of the second electrode 54 and the fourth electrode 58, and the external conductor 552 may be electrically connected to the other of the second electrode 54 and the fourth electrode 58. In the above-described embodiment and modified examples, an example in which one electrode is the second electrode 54, i.e., an example in which the internal conductor 551 is electrically connected to the second electrode 54, has been described. However, the internal conductor 551 may be electrically connected to the fourth electrode 58. In addition, in the above-described embodiment and modified examples, an example in which the other electrode is the fourth electrode 58, i.e., an example in which the external conductor 552 is electrically connected to the fourth electrode 58, has been described. However, the external conductor 552 may be electrically connected to the second electrode 54. As shown in FIG. 11 , an electron detector 5D of the fourth modified example 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 FIG. 11, the tip of the internal conductor 551 is physically connected to the electrode pad 612a. As a result, an electrical signal from the AD 51 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. That is, in the electron detector 5D, the third electrode 57, the resin sheet 59, and the fourth electrode 58 form a 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. That is, in the electron detector 5D, the first electrode 52, the resin sheet 59, and the second electrode 54 form a return capacitor C2.

[0052] When viewed from the Z direction, the area over which the external conductor 552 overlaps with the other of the second electrode 54 and the fourth electrode 58 (the electrode electrically connected to the external conductor 552) may be larger than the area over which the external conductor 552 overlaps with one of the second electrode 54 and the fourth electrode 58 (the electrode electrically connected to the internal conductor 551). In the electron detector 5D, when viewed from the Z direction, the area S1 over which the external conductor 552 overlaps with the second electrode 54 is larger than the area S2 over which the external conductor 552 overlaps with the fourth electrode 58. Because an electrical signal is transmitted from the fourth electrode 58 to the internal conductor 551, the parasitic capacitance Cp that contributes to ringing occurring in the electrical signal is capacitance generated when the fourth electrode 58 and the external conductor 552 face each other. Therefore, since the area S2 is small, the parasitic capacitance Cp generated when the external conductor 552 overlaps with the fourth electrode 58 is smaller. As a result, ringing occurring in the electrical signal due to the parasitic capacitance Cp is suppressed.

[0053] The electron detection unit 53 may not include the AD51. In this case, for example, the electron detection unit 53 is composed of a first electrode 52. The first electrode 52 may serve as both the electron detection unit 53 and the signal capacitor C1. As shown in FIG. 12, an electron detector 5E of a fifth modified example differs from the electron detector 5 in that it does not include the AD51. In addition, in a charged particle detector 1A including the electron detector 5E, the electron emitter 2 may include an MCP unit 2A composed of two MCPs. In the charged particle detector 1A, a wiring WR electrically connects the third electrode 57 and the MCP unit 2A. This forms a return path from the external 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 the AD51, the first electrode 52 does not have an amplification function. The electron incident surface of the first electrode 52 is not covered with the first insulating layer 631 and is exposed to the outside.

[0054] The electron emitter 2 may include another electron multiplier element instead of or in addition to the MCP 21. As shown in FIG. 13 , a modified charged particle detector 1B differs from the charged particle detector 1A in that the electron emitter 2 includes a dynode unit 23 instead of the MCP 21. The dynode unit 23 includes multiple dynodes. In the dynode unit 23, each dynode emits secondary electrons and passes them on to the next dynode, gradually increasing the number of electrons. FIG. 13 shows only the final dynode. In the charged particle detector 1B, a 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. According to the charged particle detector 1B, electrons emitted from the electron emitter 2 are multiplied as secondary electrons, thereby increasing the electrical signal output from the electron detector 5. Furthermore, secondary electrons can be emitted with a high amplification factor.

[0055] The above-described multiple modified examples may be combined in any manner. For example, in the electron detector 5A shown in Fig. 5, the internal conductor 551 may be electrically connected to the fourth electrode 58, and the external conductor 552 may be electrically connected to the second electrode 54. Furthermore, in the electron detector 5E shown in Figs. 12 and 13, the internal conductor 551 may be electrically connected to the fourth electrode 58, and the external conductor 552 may be electrically connected to the second electrode 54.

[0056] In the above-described embodiment and modified examples, 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 including a photocathode that converts photons into photoelectrons. The electron detector 5 may also be applied to, for example, a photomultiplier tube or a hybrid photodetector (HPD). A photomultiplier tube includes an electron multiplier section that multiplies photoelectrons emitted from the photocathode and emits secondary electrons. This electron multiplier section corresponds to the electron emitter section 2 in the charged particle detector 1. An HPD does not include a component corresponding to the electron emitter section 2. In an HPD, photoelectrons emitted from the photocathode directly enter the electron detector 5.

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

[0058] The charged particle detector of the present invention is [1] "comprised of an electron emitter that emits electrons in response to incidence of a charged particle, and an electron detector that outputs the electrons emitted from the electron emitter as an electric signal, wherein the electron detector includes an electron detector that includes a first electrode and detects the electrons emitted from the electron emitter, a resin sheet that is arranged on one side of the first electrode in a first direction, a second electrode that is arranged on the one side of the resin sheet in the first direction and faces the first electrode via the resin sheet, a third electrode that is arranged on the other side of the resin sheet in the first direction and is spaced from the first electrode in a second direction intersecting the first direction, and a fourth electrode that is arranged on the one side of the resin sheet in the first direction and is spaced from the second electrode in the second direction and faces the third electrode via the resin sheet." a first electrode, an insulating substrate disposed on one side in the first direction with respect to the second electrode and supporting the electron detection unit, the resin sheet, the second electrode, the third electrode, and the fourth electrode; and an output unit disposed on the one side in the first direction with respect 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 while being electrically insulated from the internal conductor and electrically connected to the other of the second electrode and the fourth electrode, wherein an overlapping area of ​​the external conductor with the other electrode is larger than an overlapping area of ​​the external conductor with the one electrode when viewed from the first direction, or the external conductor does not overlap with the second electrode or the fourth electrode when viewed from the first direction.

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

[0060] The charged particle detector of the present invention may be [3] "the charged particle detector according to the above [1] or [2], wherein the outer conductor includes an enclosing portion that encloses 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 where the protruding portion overlaps with the other electrode is larger than the area where the protruding portion overlaps with the one electrode."

[0061] The charged particle detector of the present invention may be [4] "the charged particle detector according to any one of the above [1] to [3], wherein the electron detector further has a support portion that supports the output portion on the one side in the first direction relative to the insulating substrate so that a space is formed between the output portion and 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... surrounding portion, 552B... protruding portion, S1, S2... area, SP1... space.

Claims

1. an electron detection unit including a first electrode and detecting incident electrons; a resin sheet disposed on one side of the first electrode in a first direction; a second electrode disposed on the one side of the resin sheet in the first direction and facing the first electrode with the resin sheet interposed therebetween; a third electrode disposed on the other side of the resin sheet in the first direction and spaced apart from the first electrode in a second direction intersecting the first direction; a fourth electrode disposed on the 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 with the resin sheet interposed therebetween; an insulating substrate disposed on the one side of the second electrode in the first direction and supporting the electron detection unit, the resin sheet, the second electrode, the third electrode, and the fourth electrode; an output unit that is disposed on the one side of the insulating substrate in the first direction and outputs an electrical signal, The output unit an internal conductor electrically connected to one of the second electrode and the fourth electrode; an outer conductor surrounding the internal conductor in a state of being electrically insulated from the internal conductor, and electrically connected to the other of the second electrode and the fourth electrode; An electron detector, wherein when viewed from the first direction, the area where the external conductor overlaps with the other electrode is larger than the area where 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.

2. the 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 surrounding the inner conductor and a protruding portion protruding outward from the surrounding portion, the internal conductor faces the one electrode via the insulating substrate, The electron detector according to claim 1 , wherein an area where the protruding portion overlaps with the other electrode is larger than an area where the protruding portion overlaps with the one electrode when viewed from the first direction.

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

5. The electron detector according to claim 1 or 2; an electron emitting portion that emits electrons in response to incidence of a charged particle;

6. The charged particle detector of claim 5 , wherein the electron emitter comprises a microchannel plate.

7. The charged particle detector of claim 5 , wherein the electron emitter includes a plurality of dynodes.

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