Electron detector, charged particle detector, and mass spectrometer

Abstract

This electron detector comprises an electron detection unit that detects incident electrons and that outputs an electric signal, and a housing part that houses the electron detection unit. The electron detection unit includes an AD that detects electrons, a wiring board on which the AD is mounted, the wiring board disposed on one side of the AD in the Z direction, and an amplifier that amplifies a detection signal outputted from the AD. The housing part includes a first metal part that has an opening facing the AD on the other side of the AD in the Z direction and that faces the electron detection unit on the other side of the AD, and a second metal part surrounding the side surface of the wiring board.

Description

Electron detector, charged particle detector, and mass spectrometer

[0001] The present disclosure relates to an electron detector, a charged particle detector, and a mass spectrometer.

[0002] As a charged particle detector applicable to a mass spectrometer (mass spectrometry) or the like, Patent Document 1 describes an ion detector including a microchannel plate (hereinafter referred to as "MCP") that receives ions and outputs electrons, a photodiode array that detects electrons, and a time converter array that measures the arrival time of ions at the MCP. In the ion detector described in Patent Document 1, the time converter array is provided in an ASIC. The ASIC includes a plurality of channels to which signals output from the photodiode array are input, and an amplifier is incorporated in each channel in addition to the time converter array.

[0003] In such an amplifier, impedance matching may be performed between an electron detection element such as a photodiode and a transmission line that transmits an electrical signal output from the electron detection element. This suppresses the occurrence of noise peaks separately from the electrical signal due to signal reflection.

[0004] Japanese Patent No. 5632568

[0005] The electron detection element and the amplifier as described above may be affected by radiation noise in the mass spectrometer. For example, a transmission line that transmits an electrical signal output from the electron detection element may become a noise source. When the electron detection element and the amplifier are affected by radiation noise, noise may be superimposed on the electrical signal, and the accuracy of mass spectrometry may decrease.

[0006] An object of the present disclosure is to provide an electron detector, a charged particle detector, and a mass spectrometer that can improve the quality of an electrical signal.

[0007] One aspect of the present disclosure is an electron detector comprising: [1] an electron detection unit that detects incident electrons and outputs an electrical signal; and a housing that houses the electron detection unit, wherein the electron detection unit comprises an electron detection element that detects the electrons; a wiring board on which the electron detection element is mounted and is arranged on one side in a predetermined direction with respect to the electron detection element; and an amplifier that amplifies the detection signal output from the electron detection element, wherein the housing has an opening facing the electron detection element on the other side in the predetermined direction with respect to the electron detection element, a first metal part facing the electron detection unit on the other side with respect to the electron detection element, and a second metal part surrounding the side surface of the wiring board, the electron detector.

[0008] In the above-described electronic detector, the amplifier housed in the housing along with the electronic detection element performs impedance matching between, for example, the electronic detection element and the element connected to the subsequent stage, thereby suppressing the generation of peaks separate from the electrical signal due to signal reflection. Furthermore, since the first metal part faces the electronic detection unit on the other side, it is possible to suppress the incidence of radiated noise onto the electronic detection unit from the other side. In addition, since the second metal part surrounds the side of the wiring board, it is possible to suppress the incidence of radiated noise onto the wiring board from the side of the wiring board. As a result, the above-described electronic detector can suppress the superposition of noise on the electrical signal and improve the quality of the electrical signal.

[0009] An electron detector in one aspect of the present disclosure may be [2] "the electron detector according to [1], wherein the housing further has a third metal portion facing the electron detection unit on one side with respect to the wiring board." With this electron detector, it is possible to suppress the incidence of radiated noise onto the wiring board from one side, and it is possible to further suppress the superposition of noise on the electrical signal.

[0010] An electron detector in one aspect of the present disclosure may be [3] "the electron detector according to [2] above, wherein the first metal part is set to a potential for accelerating and focusing the electrons, the second metal part is integrally formed with the third metal part and is connected to a reference potential different from the potential, and the housing part further comprises an electrical insulating part disposed between the first metal part and the second metal part." According to this electron detector, the electrical insulating part disposed between the first metal part and the second metal part, which are set to different potentials, can suppress the occurrence of discharge between the first metal part and the second metal part.

[0011] One aspect of the present disclosure is an electron detector [4] "the electron detector described in [3] above, wherein the electrical insulating part is a resin sheet." With this electron detector, the dielectric strength between the first metal part and the second metal part can be ensured by the resin sheet. In addition, since the space between the first metal part and the second metal part is sealed by the resin sheet, the incidence of radiated noise from between the first metal part and the second metal part can be suppressed.

[0012] An electron detector in one aspect of the present disclosure may be [5] "the electron detector according to [4] above, wherein the electron detection unit further comprises a first electrode disposed on the other side of the resin sheet and a second electrode disposed on the one side of the resin sheet and facing the first electrode via the resin sheet, the first electrode being electrically connected to the electron detection element and the second electrode being electrically connected to the amplifier." According to this electron detector, the first electrode, the resin sheet, and the second electrode constitute a coupling capacitor. In other words, the electrical insulation part and the dielectric of the coupling capacitor can be made of a common resin sheet, and the structure can be simplified.

[0013] An electron detector in one aspect of this disclosure may be [6] "the electron detector described in [2] above, wherein a gap is formed between the first metal part and the second metal part." With this electron detector, sufficient dielectric strength between the first metal part and the second metal part can be ensured.

[0014] An electron detector in one aspect of the present disclosure may be [7] "the electron detector according to [2] above, wherein the first metal part is set to a potential for accelerating and focusing the electrons, is formed integrally with the second metal part, and is set to the same potential as the electrode, the third metal part is connected to a reference potential different from the potential, and the housing part further comprises an electrical insulating part disposed between the second metal part and the third metal part." According to this electron detector, the electrical insulating part disposed between the second metal part and the third metal part, which are set to different potentials, can suppress the occurrence of discharge between the second metal part and the third metal part.

[0015] One aspect of the present disclosure is an electron detector [8] "the electron detector according to [7] above, wherein the electrical insulating part is a resin sheet." With this electron detector, the dielectric strength between the second metal part and the third metal part can be ensured by the resin sheet. In addition, since the space between the second metal part and the third metal part is sealed by the resin sheet, the incidence of radiated noise from between the second metal part and the third metal part can be suppressed.

[0016] An electron detector in one aspect of the present disclosure may be the electron detector described in [8] above, wherein the third metal part faces the wiring board on one side with respect to the wiring board, the resin sheet extends from at least between the second metal part and the third metal part between the wiring board and the third metal part, an opening is formed in the resin sheet, and when viewed from the predetermined direction, the outer edge of the opening is located inside the outer edge of the wiring board, and the electron detection unit further has a metal pattern extending from the side of the opening between the resin sheet and the third metal part. With this electron detector, since the resin sheet extends from at least between the second metal part and the third metal part between the wiring board and the third metal part, a sufficient creepage distance between the second metal part and the third metal part can be secured. Furthermore, since the metal pattern functions as a shield to prevent radiated noise, it is possible to further prevent radiated noise from entering from between the second metal part and the third metal part.

[0017] An electron detector in one aspect of the present disclosure may be

[10] "an electron detector according to any one of [1] to [9] above, wherein the amplifier is located on one side of the wiring board and mounted on the wiring board." With this electron detector, since the electron detection element and the amplifier are supported on a common wiring board, the distance between the electron detection element and the amplifier becomes smaller, making it easier to suppress interference between reflected signals and electrical signals.

[0018] An electron detector in one aspect of the present disclosure may be

[11] "the electron detection unit further comprises an output unit disposed on one side of the wiring board and electrically connected to the amplifier, which outputs an electrical signal corresponding to the amplified detection signal, and a connector protruding from the surface of the one side of the wiring board, wherein the output unit includes an internal conductor that outputs the electrical signal, and an external conductor that surrounds the internal conductor in a state of being electrically insulated from the internal conductor, the external conductor being connected to the third metal part, and the internal conductor passing through the third metal part and electrically connected to the amplifier via the connector, as described in any one of [2] to [9] above." With this electron detector, since the external conductor is connected to the third metal part, fixing members for fixing the output unit and the third metal part are not required, and the structure can be simplified.

[0019] An electron detector in one aspect of the present disclosure may be

[12] "the electron detector according to any one of [2] to [9] above, wherein the electron detection unit is arranged on one side of the wiring board, is electrically connected to the amplifier, and further has an output unit that outputs an electrical signal corresponding to the amplified detection signal, the output unit penetrates the third metal part and is connected to the wiring board." With this electron detector, since the output unit is connected to the wiring board, fluctuations in the characteristic impedance of the output unit are easily suppressed, and an electrical signal can be output stably.

[0020] An electron detector in one aspect of the present disclosure may be

[13] "the electron detector according to

[12] above, wherein the output section includes an internal conductor that outputs the electrical signal and an external conductor that surrounds the internal conductor in a state of being electrically insulated from the internal conductor, and the housing section further includes a shielding ring that fixes and electrically connects the external conductor and the third metal part." With this electron detector, for example, by filling the gap between the external conductor and the third metal part with the shielding ring, it is possible to further suppress the incidence of radiated noise onto the wiring board from one side.

[0021] One aspect of the present disclosure is a charged particle detector comprising

[14] "an electron detector according to any one of [1] to

[13] above, and an electron emission unit that emits electrons upon incidence of charged particles." According to this charged particle detector, the quality of the electrical signal can be improved in the electron detector.

[0022] One aspect of the mass spectrometer of this disclosure is

[15] "a mass spectrometer comprising the charged particle detector described in

[14] above." According to this mass spectrometer, the quality of the electrical signal can be improved in the charged particle detector.

[0023] This disclosure makes it possible to provide an electron detector, a charged particle detector, and a mass spectrometer that can improve the quality of electrical signals.

[0024] Figure 1 is a diagram showing the circuit configuration of a charged particle detector according to one embodiment. Figure 2 is a graph showing an example of the behavior of the electrical signal output from the electron detector shown in Figure 1. Figure 3 is a cross-sectional view showing the structure of the charged particle detector shown in Figure 1. Figure 4 is a cross-sectional view showing the electron detector shown in Figure 1. Figure 5 is a cross-sectional view showing the first modified electron detector. Figure 6 is a cross-sectional view showing the second modified electron detector. Figure 7 is a cross-sectional view showing the third modified electron detector. Figure 8 is a cross-sectional view showing the fourth modified electron detector. Figure 9 is a cross-sectional view showing the fifth modified electron detector. Figure 10 is a cross-sectional view showing the sixth modified electron detector. Figure 11 is a cross-sectional view showing the seventh modified electron detector. Figure 12 is a schematic diagram showing the configuration of a mass spectrometer according to one embodiment.

[0025] Embodiments of this disclosure will be described in detail below with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions are omitted.

[0026] [Configuration of Charged Particle Detector] The electron detector of this disclosure outputs incident electrons as an electrical signal. The electron detector of this disclosure is applied to charged particle detectors such as ion detectors, or to electron tubes such as photomultiplier tubes and hybrid photodetectors. In this embodiment, an example in which the electron detector is applied to a charged particle detector will be described. As shown in Figure 1, the charged particle detector 100 includes an electron detector 1, an electron emission unit 5, an accelerating electrode 6, and a pair of focus electrodes 71 and 72. In the charged particle detector 100, the electron emission unit 5, the accelerating electrode 6, the focus electrode 71, the focus electrode 72, and the electron detector 1 are arranged in this order. The charged particle detector 100 is, for example, an ion detector that detects bipolar ions. The charged particle detector 100 is applied to, for example, a mass spectrometer. The charged particle detector 100 may also detect charged particles other than ions (for example, electrons).

[0027] The electron emission unit 5 emits electrons in response to the incidence of ions. The polarity of the ions may be negative or positive. The electron emission unit 5 includes a microchannel plate (hereinafter referred to as "MCP") 51. The MCP 51 is an electron multiplier element that emits electrons in response to the incidence of ions. The MCP 51 has an input surface 51a and an output surface 51b. The sides of the MCP 51 are surrounded by an insulating ring made of an insulating material. When an ion is incident on the input surface 51a of the MCP 51, it generates electrons in response to the incidence of the ion, multiplies those electrons, and emits them from the output surface 51b. In other words, the MCP 51 also functions as an electron multiplier unit. The MCP 51 has a plurality of through holes (channels) that extend along the thickness direction (the direction in which the input surface 51a and the output surface 51b face each other). Electrodes are formed on the outer edge of the input surface 51a and the outer edge of the output surface 51b. The electron emission unit 5 may independently include an electron emission unit that emits electrons upon ion incidence and an electron multiplication unit that emits electrons multiplied by multiples. For example, the electron emission unit 5 may include an ion-electron conversion unit provided upstream of the MCP 51 as the electron emission unit and the MCP 51 as the electron multiplication unit.

[0028] The accelerating electrode 6 accelerates electrons emitted from the output surface 51b of the MCP 51. The pair of focusing electrodes 71 and 72 focus the electrons accelerated by the accelerating electrode 6 onto the electron detection unit 2 of the electron detector 1.

[0029] The electron detector 1 outputs electrons emitted from the MCP 51 as an electrical signal. The electron detector 1 comprises an electron detection unit 2 and a housing 4. The electron detection unit 2 detects incident electrons, generates a detection signal, and outputs an electrical signal based on the detection signal. The electron detection unit 2 includes an electron detection element 20, a first electrode 22, a second electrode 23, an amplifier 24, an output unit 25, a third electrode 26, a fourth electrode 27, and a voltage input unit 28.

[0030] The electron detection element 20 receives electrons focused by a pair of focus electrodes 71 and 72 and outputs a detection signal. The electron detection element 20 includes an avalanche diode (hereinafter referred to as "AD") 21. The anode electrode 211 of the AD 21 faces the focus electrode 72. Electrons focused by the pair of focus electrodes 71 and 72 are incident on the anode electrode 211.

[0031] The first electrode 22 is electrically connected to the cathode electrode 212 of AD21. The first electrode 22 and the second electrode 23 constitute a signal capacitor C1. The signal capacitor C1 functions as a coupling capacitor that extracts the detection signal output from AD21 from the DC voltage of the power supply 82, which will be described later.

[0032] The input terminal of amplifier 24 is electrically connected to the second electrode 23. Amplifier 24 amplifies the detection signal output from AD 21 and after passing through signal capacitor C1. Amplifier 24 also performs impedance matching between, for example, AD 21 and an element connected downstream of AD 21. The element connected downstream of AD 21 may be the output unit 25, or it may be the electrical signal transmission line including the output unit 25. If impedance matching is not performed by amplifier 24, a peak due to signal reflection may occur in addition to the electrical signal output from the electronic detection unit 2. If, for example, a mass spectrometer is connected downstream of the electronic detector 1 via a transmission line, the occurrence of a peak due to signal reflection may result in the appearance of a false peak corresponding to the mass-to-charge ratio (time) that does not actually exist in the spectrum, potentially providing the mass spectrometer with incorrect mass information. Therefore, it is important to minimize the peak due to signal reflection and improve the quality of the electrical signal.

[0033] The output unit 25 is electrically connected to the output terminal of the amplifier 24 and outputs an electrical signal corresponding to the amplified detection signal toward the signal output terminal P1. In the example in Figure 1, a capacitor C3 is connected between the output terminal of the amplifier 24 and the output unit 25. The capacitor C3 may function, for example, as a coupling capacitor that extracts the detection signal output from the amplifier 24 from the DC component of the signal input terminal P2, which will be described later. The electronic detection unit 2 may further have signal processing elements between the amplifier 24 and the output unit 25, such as the capacitor C3, to improve the accuracy of the detection signal or adjust the level of the detection signal. For example, the electronic detection unit 2 may have a buffer, a filter, etc., as a signal processing element instead of or together with the capacitor C3. The output unit 25 outputs the detection signal that has passed through such signal processing elements as an electrical signal.

[0034] The output section 25 includes an inner conductor 251 and an outer conductor 252. The inner conductor 251 is electrically connected to the output terminal of the amplifier 24. The outer conductor 252 surrounds the inner conductor 251. There may be an air gap between the inner conductor 251 and the outer conductor 252, or an insulating member may be placed between them. The outer conductor 252 is connected to a reference potential GND. The reference potential GND is, for example, the earth potential, and in this embodiment, the reference potential GND will be described as the earth potential. The output section 25 is, for example, an SMA connector. In this case, the inner conductor 251 is a signal line that transmits electrical signals, and the outer conductor 252 is an outer conductor that covers the signal line. The inner conductor 251 may be connected to a transmission line for transmitting electrical signals.

[0035] The third electrode 26 is electrically connected to the anode electrode 211 of AD21 via a resistor R7. The fourth electrode 27 is electrically connected to the reference potential GND and the outer conductor 252. The third electrode 26 and the fourth electrode 27 are arranged on a return path formed from the outer conductor 252 to the anode electrode 211, 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.

[0036] A bias signal supplied to the amplifier 24 via the signal input terminal P2 is input to the voltage input section 28 from an external source. The voltage input section 28 is connected to a power supply (not shown) provided in the electronic detector 1, for example. The voltage input section 28, like the output section 25, includes an internal conductor 281 and an external conductor 282. The internal conductor 281 is electrically connected to the output terminal of the amplifier 24 via a resistor R8 and an inductor L1. Furthermore, the internal conductor 281 is connected to a reference potential GND via a capacitor C4. Capacitor C4 may function as a bypass capacitor to remove high-frequency noise superimposed on the internal conductor 281. The external conductor 282 surrounds the internal conductor 281. The external conductor 282 is connected to a reference potential GND. By supplying a bias voltage to the output terminal of the amplifier 24, for example, the detection signal output from the amplifier 24 is biased, and the detection signal can be output accurately. Accurate output may mean that the detection signal is output without clipping.

[0037] The input surface 51a of the MCP 51 is electrically connected to the power supply 81 and set to a potential Va (e.g., +10kV or -10kV). One end of resistor R6 is electrically connected to the node between the cathode electrode 212 and the first electrode 22. A potential difference Vb (e.g., 0V to 7kV) is supplied between the input surface 51a and the other end of resistor R6 by the power supply 82. The potential difference (voltage) Vb can be divided by resistors R1, R2, R3, R4 and Zener diode 83. Zener diode 83 ensures a potential difference Vc (e.g., 300V) between resistors R4 and R6. An accelerating electrode 6 is electrically connected to the node located between resistors R2 and R3. The focus electrode 71 is set to the same potential as the output surface 51b. The focus electrode 72 is electrically connected to Zener diode 83 via resistor R4. A resistor R5 is electrically connected between the node between resistor R4 and Zener diode 83 and the anode electrode 211.

[0038] When measuring negative ions, a potential Va of, for example, +10kV is applied. In this case, if the potential difference Vb becomes +7kV, the potential at the other end of resistor R6 becomes +17kV. When measuring positive ions, a potential Va of, for example, -10kV is applied. In this case, if the potential difference Vb becomes +7kV, the potential at the other end of resistor R6 becomes -3kV. In both negative and positive ion measurements, the potential increases as you move from the input surface 51a of MCP51 toward the anode electrode 211 of AD21. Furthermore, the potential applied to the cathode electrode 212 of AD21 is greater than the potential applied to the anode electrode 211. Therefore, a reverse bias voltage is applied between the anode electrode 211 and the cathode electrode 212 of AD21, causing AD21 to float.

[0039] The housing 4 functions as a shield to prevent radiated noise from entering the electronic detection unit 2 from outside. The electronic detection unit 2 may be exposed to radiated noise from, for example, a charged particle detector 100 or a mass spectrometer connected downstream of the electronic detector 1. For example, a transmission line that transmits electrical signals can be a noise source. If the electronic detection unit 2 is affected by radiated noise, noise may be superimposed on the electrical signal, potentially reducing the accuracy of mass spectrometry. Therefore, it is extremely important to minimize the effects of radiated noise and improve the quality of the electrical signal.

[0040] The housing section 4 houses the electron detection unit 2. The housing section 4 is conductive and made of metal. The housing section 4 has a first metal section, a second metal section, and a third metal section. In the example shown in Figure 1, the first metal section 41 and the third metal section 43 are shown. The first metal section 41 is positioned between the focus electrode 72 and the electron detection unit 2 and is set to a potential for accelerating and focusing electrons. Specifically, the first metal section 41 is set to the same potential as the focus electrode 72. As a result, a positive high voltage is applied to the first metal section 41 when measuring negative ions, and a negative high voltage is applied to the first metal section 41 when measuring positive ions. The first metal section 41 has an opening 41a formed therein for injecting electrons focused by the focus electrode 72 into AD21. The third metal section 43 is electrically connected to the output section 25 and is also connected to the reference potential GND.

[0041] In the electron detector 1, high-speed response to electrical signals is sometimes required. High-speed response can be evaluated, for example, by the pulse width of the electrical signal. The pulse width may be the full width at half maximum. By reducing the pulse width of the electrical signal, the resolution of the mass spectrometer connected downstream of the electron detector 1 can be improved. Figure 2 is a graph showing an example of the output voltage when the capacitance of the signal capacitor C1 is 1 nF or 3 pF. The horizontal axis of Figure 2 represents time, and the vertical axis of Figure 2 represents the normalized value of the output voltage. The output voltage is, for example, the voltage measured at the signal output terminal P1. As shown in Figure 2, the pulse width when the capacitance of the signal capacitor C1 is 3 pF is smaller than the pulse width when the capacitance of the signal capacitor C1 is 1 nF. That is, the responsiveness of the electrical signal can be improved by adjusting the capacitance of the signal capacitor C1.

[0042] Figure 3 is a cross-sectional view showing the structure of the charged particle detector 100. The charged particle detector 100 comprises an electron emission unit 5, a mesh-shaped accelerating electrode 6, a pair of focus electrodes 71 and 72, and an electron detector 1, which are stacked in this order and fixed to each other. Hereinafter, the direction in which the electron emission unit 5, the accelerating electrode 6, the pair of focus electrodes 71 and 72, and the electron detector 1 overlap is referred to as the Z direction (a predetermined direction). Electrons emitted from the electron emission unit 5 are accelerated and focused in the Z direction and incident on AD21 in the electron detection unit 2 of the electron detector 1. One direction perpendicular to the Z direction is called the X direction, and the direction perpendicular to both the Z direction and the X direction is called the Y direction. In the following explanation, "one side in the Z direction" refers to the side opposite to the electron emission unit 5. "The other side in the Z direction" refers to the side of the electron emission unit 5.

[0043] The electron emission unit 5 includes an MCP 51, an input-side electrode 52, an output-side electrode 53, and an insulating ring 54. As described above, the side surface of the MCP 51 is surrounded by the insulating ring 54. The annular outer peripheral portion of the MCP 51 and the insulating ring 54 are sandwiched between the input-side electrode 52 and the output-side electrode 53. The input-side electrode 52 has an opening for allowing charged particles incident on the input surface 51a of the MCP 51 to pass through. Similarly, the output-side electrode 53 has an opening for allowing electrons emitted from the output surface 51b of the MCP 51 to pass through. The central axis of the opening of the input-side electrode 52 and the central axis of the opening of the output-side electrode 53 coincide with the central axis of the MCP 51.

[0044] The acceleration electrode 6 is sandwiched between an insulating spacer 101 and an insulating spacer 102. The input-side electrode 52, the insulating ring 54, the output-side electrode 53, the insulating spacer 101, the insulating spacer 102, and the focus electrode 71 are fixed to each other by fixing screws 103. The fixing screws 103 are insulating and are made of, for example, resin.

[0045] The focus electrode 71 is an annular conductive member, and its central axis coincides with the central axis of the MCP 51. In the following description, the annular member may be an annular member or a cylindrical member. The end portion on the other side of the focus electrode 71 is in contact with the insulating spacer 102. The male screw of the insulating spacer 104 is inserted into the end portion on one side of the focus electrode 71. For example, the end portion on the other side of the insulating spacer 104 is a male screw, and the end portion on one side of the insulating spacer 104 is a female screw. The end portion on one side of the focus electrode 71 faces the end portion on the other side of the focus electrode 72.

[0046] The focus electrode 72 is an annular conductive member, and its central axis coincides with the central axis of the MCP 51. The other end of the focus electrode 72 is a flange 721. The flange 721 is sandwiched in the Z direction by an insulating spacer 104 and a conductive spacer 106. For example, the other end of the conductive spacer 106 is a male thread, and the one end of the conductive spacer 106 is a female thread. The male thread of the conductive spacer 106 passes through the flange 721 and is inserted into the female thread of the insulating spacer 104. The focus electrode 71 and the focus electrode 72 are fixed by the insulating spacer 104 and the conductive spacer 106.

[0047] [Configuration of the Electron Detector] As described above, the electron detector 1 comprises an electron detection unit 2 and a housing section 4. The housing section 4 has a first metal part 41, a second metal part 42, and a third metal part 43. The first metal part 41 is, for example, a disc-shaped conductive member. One end of the first metal part 41 is a flange 411. The flange 411 is annular in shape. The flange 411 is fixed to the conductive spacer 106 via an insulating spacer 107 by a conductive fixing screw 108. The fixing screw 108 penetrates the flange 411 and the insulating spacer 107 and is inserted into the female thread of the conductive spacer 106. As a result, the first metal part 41 is electrically connected to the focus electrode 72 via the conductive spacer 106 and the fixing screw 108.

[0048] The first metal part 41 faces the electron detection unit 2 on the other side in the Z direction with respect to AD21. For example, a protruding part 412 protruding from the flange 411 to the other side is formed on the first metal part 41. The protruding part 412 is formed so as to close the opening on the other side of the flange 411. An opening 41a is formed in the protruding part 412. When viewed from the Z direction, the outer edge of the opening 41a is smaller than the outer edge of the opening on the other side of the flange 411. The opening 41a faces AD21 on the other side with respect to AD21. When viewed from the Z direction, the opening 41a overlaps AD21. The center of the opening 41a may be offset from the central axis of the MCP51 or may coincide with it.

[0049] The electron detection unit 2 further has a wiring board 31. The wiring board 31 is arranged on one side in the Z direction with respect to AD21. The wiring board 31 has a plate-shaped rectangular parallelepiped shape composed of a surface 31a on the other side in the Z direction, a back surface 31b (a surface on one side) opposite to the surface 31a, and a side surface 31c connecting the surface 31a and the back surface 31b. AD21 is mounted on the surface 31a. The amplifier 24 is arranged on one side with respect to the wiring board 31 and is mounted on the back surface 31b of the wiring board 31. That the AD21 and the amplifier 24 are mounted means that the AD21 and the amplifier 24 are electrically connected to the wiring board 31, and more preferably, the AD21 and the amplifier 24 are supported by the wiring board 31 and are physically connected.

[0050] The second metal part 42 is an annular conductive member. The second metal part 42 surrounds the side surface 31c of the wiring board 31. For example, the inner surface of the second metal part 42 is in contact with the side surface 31c. The width (height in the Z direction) of the inner surface of the second metal part 42 may be the same as the width of the wiring board 31. In this case, the surface 42a on the other side of the second metal part 42 may be flush with the surface 31a of the wiring board 31.

[0051] The second metal portion 42 is formed integrally with the third metal portion 43. Therefore, the second metal portion 42, like the third metal portion 43, is connected to the reference potential GND. That is, the potentials of the second metal portion 42 and the third metal portion 43 are different from the potential of the first metal portion 41. For example, when measuring negative ions, the potentials of the second metal portion 42 and the third metal portion 43 are lower than the potential of the first metal portion 41. On the other hand, when measuring positive ions, the potentials of the second metal portion 42 and the third metal portion 43 are higher than the potential of the first metal portion 41. The third metal portion 43 faces the wiring board 31 on one side in the Z direction relative to the wiring board 31. In the example of Figure 3, the third metal portion 43 includes a metal portion 431 and a metal portion 432. The metal portion 431 has a frame shape. The metal portion 431 is in contact with the outer edge of the back surface 31b of the wiring board 31. The metal portion 432 is integrally formed with the metal portion 431 such that it closes the opening of the metal portion 431 at one end in the Z direction. As a result, the space SP1 is defined by the back surface 31b, the inner surface of the metal portion 431, and the metal portion 432.

[0052] When viewed from the Z direction, the outer edge of the second metal part 42 coincides with the outer edge of the third metal part 43. The outer edge of the second metal part 42 is larger than the outer edge of the flange 411 of the first metal part 41.

[0053] The housing section 4 further includes an electrical insulating section positioned between the first metal section 41 and the second metal section 42. The electrical insulating section is, for example, a resin sheet 44. The material of the resin sheet 44 is a resin such as liquid crystal polymer (LCP), polyester film, polyimide, or polyamide. The resin sheet 44 covers the surface 42a of the second metal section 42 and the surface 31a of the wiring board 31. When viewed from the Z direction, the outer edge of the resin sheet 44 coincides with the outer edges of the second metal section 42 and the third metal section 43. The outer edge of the resin sheet 44 is larger than the outer edge of the flange 411 of the first metal section 41. The space SP2 is defined by the resin sheet 44, the inner surface of the flange 411 of the first metal section 41, and the protruding portion 412 of the first metal section 41. AD21 is mounted, for example, on the surface 31a within the space SP2.

[0054] The second metal part 42, the third metal part 43, and the insulating spacer 107 are fixed to each other by fixing screws 109. The fixing screws 109 are insulating and are made of, for example, resin. The fixing screws 109 may penetrate the resin sheet 44.

[0055] Figure 4 is an enlarged cross-sectional view of the electron detector 1 shown in Figure 3. In the electron detection unit 2, the AD21, first electrode 22, resin sheet 44, second electrode 23, wiring board 31, and output unit 25 are arranged in this order in the Z direction.

[0056] AD21 is positioned, for example, at the location where electrons incident from aperture 41a reach. The first electrode 22 is positioned on the opposite side of AD21 from aperture 41a and is electrically connected to AD21. In the electron detector 1, the first electrode 22 is in contact with the cathode electrode 212 of AD21. The third electrode 26 is electrically connected to the anode electrode 211 of AD21 via wire WR.

[0057] The first electrode 22 is positioned on the other side of the resin sheet 44 in the Z direction. The second electrode 23 is positioned on one side of the resin sheet 44 in the Z direction and faces the first electrode 22 via the resin sheet 44. The first electrode 22 and the second electrode 23 are in contact with the resin sheet 44. The first electrode 22, the resin sheet 44 and the second electrode 23 constitute a signal capacitor C1. The first electrode 22 and the second electrode 23 are a pair of electrode plates of the signal capacitor C1, and the resin sheet 44 is the dielectric of the signal capacitor C1.

[0058] The third electrode 26 is positioned on the other side of the resin sheet 44 in the Z direction. The third electrode 26 is spaced apart from the first electrode 22 in the X direction. When viewed from the Z direction, the third electrode 26 is spaced apart from the first electrode 22 and aligned with the first electrode 22 in the X direction. The fourth electrode 27 is positioned on one side of the resin sheet 44 and faces the third electrode 26 through the resin sheet 44. The fourth electrode 27 is spaced apart from the second electrode 23 in the X direction. When viewed from the Z direction, the fourth electrode 27 is spaced apart from the second electrode 23 and aligned with the second electrode 23 in the X direction. The third electrode 26 and the fourth electrode 27 are in contact with the resin sheet 44. The third electrode 26, the resin sheet 44 and the fourth electrode 27 constitute a return capacitor C2. The third electrode 26 and the fourth electrode 27 are a pair of electrode plates of the return capacitor C2, and the resin sheet 44 is the dielectric of the return capacitor C2. In other words, the electrical insulating portion positioned between the first metal portion 41 and the second metal portion 42, the dielectric of the signal capacitor C1, and the dielectric of the return capacitor C2 are all made of a common resin sheet 44.

[0059] The wiring board 31 includes a wiring board body 311 and a plurality of wirings. The material of the wiring board body 311 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 plurality of wirings may include wiring 312 that passes through the wiring board body 311 from the front surface 31a to the back surface 31b, wiring 313 that passes through the wiring board body 311 parallel to wiring 312, wiring 314 formed along the back surface 31b, and wiring 315 that extends in the opposite direction to wiring 314. The second electrode 23 is electrically connected to the input terminal of the amplifier 24 via wiring 312.

[0060] The output unit 25 is located on one side of the wiring board 31 in the Z direction. The voltage input unit 28 is located on one side of the wiring board 31 in the Z direction. The output unit 25 is spaced apart from the voltage input unit 28 in the X direction. When viewed from the Z direction, the output unit 25 is spaced apart from the voltage input unit 28 and is aligned with the voltage input unit 28 in the X direction. The internal conductor 251 of the output unit 25 is electrically connected to the output terminal of the amplifier 24 via wiring 314. The internal conductor 281 of the voltage input unit 28 is electrically connected to the output terminal of the amplifier 24 via wiring 315.

[0061] The electronic detection unit 2 further has a connector 29. The connector 29 protrudes to one side from the back surface 31b of the wiring board 31. The connector 29 is a conductive connector, for example, a spring connector. The other end of the connector 29 is electrically connected to the fourth electrode 27 via the wiring 313. The other end of the connector 29 is physically connected to the metal portion 432 of the third metal portion 43. Thus, the connector 29 electrically connects the third metal portion 43 and the fourth electrode 27, and connects the fourth electrode 27 to the reference potential GND.

[0062] The output section 25 penetrates the third metal section 43 and is physically connected to the back surface 31b of the wiring board 31. Specifically, the output section 25 passes through a through hole 432a formed in the metal section 432 and is physically connected to the back surface 31b via space SP1. Similarly, the voltage input section 28 penetrates the third metal section 43 and is physically connected to the back surface 31b of the wiring board 31. The voltage input section 28 passes through a through hole 432b formed in the metal section 432 and is physically connected to the back surface 31b via space SP1. The housing section 4 further includes shielding rings 45 and 46. The shielding ring 45 fixes and electrically connects the outer conductor 252 of the output section 25 to the third metal section 43. This electrically connects the outer conductor 252 to the reference potential GND and fills the gap between the through hole 432a and the outer conductor 252. Similarly, the shield ring 46 fixes and electrically connects the outer conductor 282 of the voltage input section 28 to the third metal section 43. This electrically connects the outer conductor 282 to the reference potential GND and fills the gap between the through hole 432b and the outer conductor 282.

[0063] [Operation and Effects] In the electron detector 1 described above, the amplifier 24 housed in the housing 4 together with the AD 21 performs impedance matching between the AD 21 and the element connected to the subsequent stage, thereby suppressing the generation of peaks separate from the electrical signal due to signal reflection. Furthermore, since the first metal part 41 faces the electron detection unit 2 on the other side, it is possible to suppress the incidence of radiated noise on the electron detection unit 2 from the other side. In addition, since the second metal part 42 surrounds the side surface 31c of the wiring board 31, it is possible to suppress the incidence of radiated noise on the wiring board 31 from the side of the wiring board 31. As a result, the electron detector 1 can suppress the superposition of noise on the electrical signal and improve the quality of the electrical signal.

[0064] The housing section 4 further has a third metal section 43 that faces the electronic detection unit 2 on one side relative to the wiring board 31. This makes it possible to suppress the incidence of radiated noise onto the wiring board 31 from one side, and to further suppress the superposition of noise on electrical signals.

[0065] The first metal part 41 is set to a potential for accelerating and focusing electrons, and the second metal part 42 is formed integrally with the third metal part 43 and is connected to a reference potential GND that is different from the potential of the first metal part 41. The housing part 4 further has an electrical insulating part disposed between the first metal part 41 and the second metal part 42. With this, the electrical insulating part disposed between the first metal part 41 and the second metal part 42, which are set to different potentials, can suppress the occurrence of discharge between the first metal part 41 and the second metal part 42.

[0066] The electrical insulating part is a resin sheet 44. This ensures that the dielectric strength between the first metal part 41 and the second metal part 42 is maintained by the resin sheet 44. Furthermore, since the space between the first metal part 41 and the second metal part 42 is sealed by the resin sheet 44, the gap between the first metal part 41 and the second metal part 42 is reduced, thereby suppressing the incidence of radiated noise from between the first metal part 41 and the second metal part 42.

[0067] The electron detection unit 2 further includes a first electrode 22 positioned on the other side of the resin sheet 44, and a second electrode 23 positioned on one side of the resin sheet 44 and facing the first electrode 22 via the resin sheet 44. The first electrode 22 is electrically connected to AD 21, and the second electrode 23 is electrically connected to amplifier 24. In this configuration, the first electrode 22, the resin sheet 44, and the second electrode 23 constitute a coupling capacitor (signal capacitor C1). In other words, the electrical insulation part and the dielectric of the signal capacitor C1 can be made of the same resin sheet 44, and the structure of the electron detector can be simplified.

[0068] The amplifier 24 is positioned on one side of the wiring board 31 and is mounted on the wiring board 31. As a result, since the AD 21 and the amplifier 24 are supported by a common wiring board 31, the distance between the AD 21 and the amplifier 24 is reduced, making it easier to suppress interference between reflected signals and electrical signals.

[0069] The electronic detection unit 2 is positioned on one side of the wiring board 31, is electrically connected to the amplifier 24, and further has an output unit 25 that outputs an electrical signal corresponding to the amplified detection signal. The output unit 25 penetrates the third metal part 43 and is physically connected to the wiring board 31. As a result, since the output unit 25 is physically connected to the wiring board 31, fluctuations in the characteristic impedance of the output unit 25 are easily suppressed, and an electrical signal can be output stably.

[0070] The output section 25 includes an internal conductor 251 that outputs an electrical signal, and an external conductor 252 that surrounds the internal conductor 251 while being electrically insulated from the internal conductor 251. The housing section 4 further includes a shielding ring 45 that fixes and electrically connects the external conductor 252 and the third metal part 43. With this configuration, for example, by filling the gap between the external conductor 252 and the third metal part 43 with the shielding ring 45, it is possible to further suppress the incidence of radiated noise onto the wiring board 31 from one side.

[0071] The charged particle detector 100 comprises an electron detector 1 and an electron emission unit 5 that emits electrons upon the incidence of charged particles. The charged particle detector 100 makes it possible to improve the quality of the electrical signal in the electron detector 1.

[0072] [Modifications] This disclosure is not limited to the embodiments described above. As shown in Figure 5, the first modified electron detector 1A differs from the electron detector 1 in that the first metal part 41 is integrally formed with the second metal part 42. The first metal part 41 and the second metal part 42 are set to the same potential as the focus electrode 72. For example, a fixing screw 108 may be inserted through the second metal part 42, the flange 411 and the insulating spacer 107 into the female thread of the conductive spacer 106, thereby electrically connecting the first metal part 41 and the second metal part 42 to the focus electrode 72 via the conductive spacer 106 and the fixing screw 108. In the electron detector 1A, the third metal part 43 is electrically connected to the reference potential GND. That is, the potential of the third metal part 43 is different from the potentials of the first metal part 41 and the second metal part 42. For example, when measuring negative ions, the potential of the third metal part 43 is lower than the potentials of the first metal part 41 and the second metal part 42. On the other hand, when measuring positive ions, the potential of the third metal part 43 is higher than the potentials of the first metal part 41 and the second metal part 42.

[0073] The electron detector 1A differs from the electron detector 1 in that the housing 4 has an electrically insulating portion positioned between the second metal portion 42 and the third metal portion 43 instead of the resin sheet 44. The electrically insulating portion is, for example, a resin sheet 47. The resin sheet 47 extends from between the second metal portion 42 and the third metal portion 43 to between the wiring board 31 and the third metal portion 43. In the example of Figure 5, when viewed from the Z direction, the outer edge of the resin sheet 47 coincides with the outer edge of the third metal portion 43. The resin sheet 47 only needs to extend at least from between the second metal portion 42 and the third metal portion 43 to between the wiring board 31 and the third metal portion 43. For example, the outer edge of the resin sheet 47 may be located inside the outer edge of the third metal portion 43 (on the space SP1 side). The resin sheet 47 may be bonded to the wiring board 31 by adhesive between the wiring board 31 and the third metal portion 43. Adhesives include, for example, bonding sheets and thermosetting adhesives.

[0074] An opening 47a is formed in the resin sheet 47. When viewed from the Z direction, the outer edge of the opening 47a is located inside the outer edge of the wiring board 31. When viewed from the Z direction, the outer edge of the opening 47a may coincide with the inner edge of the metal portion 431. The electron detection unit 2A of the electron detector 1A further has an electrode pattern (metal pattern) 316 extending from the side surface of the opening 47a between the resin sheet 47 and the third metal portion 43. In the example of Figure 5, the electrode pattern 316 extends from the back surface 31b of the wiring board 31 along the side surface of the opening 47a in the Z direction, and also extends in the X direction on the opposite side of the space SP1 along the boundary line between the resin sheet 47 and the third metal portion 43. When viewed from the Z direction, the electrode pattern 316 may have an annular shape surrounding the outer edge of the opening 47a.

[0075] The electron detector 1A also differs from the electron detector 1 in that it further includes a resin sheet 48. The resin sheet 48 covers the surface 31a of the wiring board 31. The resin sheet 48 constitutes the dielectric of the signal capacitor C1 and the dielectric of the return capacitor C2, instead of the resin sheet 44. That is, in the electron detector 1A, the electrical insulating portion placed between the second metal part 42 and the third metal part 43 is made of a resin sheet different from the dielectric of the signal capacitor C1 and the dielectric of the return capacitor C2. In the example of Figure 5, when viewed from the Z direction, the outer edge of the resin sheet 48 coincides with the outer edge of the wiring board 31. The second metal part 42 may surround the side surface of the resin sheet 48 together with the side surface 31c of the wiring board 31. When viewed from the Z direction, the area of ​​the portion where the second metal part 42 surrounds the side surface and side surface 31c of the resin sheet 48 may be larger than the area of ​​the portion where the flange 411 defines the space SP2.

[0076] According to the electron detector 1A, the first metal part 41, the second metal part 42, and the third metal part 43 are each set to different potentials. However, the electrical insulating part placed between the second metal part 42 and the third metal part 43 can suppress the occurrence of discharge between the second metal part 42 and the third metal part 43. Furthermore, the withstand voltage between the second metal part 42 and the third metal part 43 can be ensured by the resin sheet 47. In addition, since the space between the second metal part 42 and the third metal part 43 is sealed by the resin sheet 47, reducing the gap between the second metal part 42 and the third metal part 43 can suppress the incidence of radiated noise from between the second metal part 42 and the third metal part 43.

[0077] According to the electron detector 1A, since the resin sheet 47 extends from at least between the second metal part 42 and the third metal part 43 to between the wiring board 31 and the third metal part 43, a sufficient creepage distance can be secured between the second metal part 42 and the third metal part 43. Furthermore, since the electrode pattern 316 functions as a shield to prevent radiated noise, it is possible to further prevent radiated noise from entering from between the second metal part 42 and the third metal part 43.

[0078] As shown in Figure 6, the electron detection unit 2 of the second modified electron detector 1B differs from the first modified electron detector 1A in that it does not have a first electrode 22, a second electrode 23, a third electrode 26, a fourth electrode 27, and a resin sheet 48. That is, the electron detector 1B does not have a signal capacitor C1 composed of the first electrode 22, the second electrode 23, and the resin sheet 48, and a return capacitor C2 composed of the third electrode 26, the fourth electrode 27, and the resin sheet 48. Note that the electron detector 1B may include, for example, a chip capacitor as the return capacitor C2 instead of the return capacitor C2 composed of the third electrode 26, the fourth electrode 27, and the resin sheet 48.

[0079] In the electronic detector 1B, the input terminal of the amplifier 24 is electrically connected to the cathode electrode 212 of AD21 via wiring 312, without going through the signal capacitor C1. The wiring board 31 may further include an electrode pattern 317 formed on its surface 31a. The electrode pattern 317 is electrically connected to the connector 29 via wiring 313. The electrode pattern 317 is also electrically connected to the anode electrode 211 of AD21 via wire WR. In the electronic detector 1B, a return capacitor C2 is mounted on the electrode pattern 317 and is electrically connected to the electrode pattern 317. In the electronic detector 1B, a return path is formed from the outer conductor 252 to the anode electrode 211 via the return capacitor C2.

[0080] As shown in Figure 7, the third modified electron detector 1C differs from the first modified electron detector 1A in that the second metal part 42 includes a metal part 421 and a metal part 422, and the third metal part 43 does not include a metal part 431. The metal part 421 has a frame shape. The metal part 421 surrounds the side surface 31c of the wiring board 31 and the side surface of the resin sheet 48. For example, the inner surface of the metal part 421 is in contact with the side surface 31c and the side surface of the resin sheet 48. The metal part 422 is formed integrally with the metal part 421 so as to connect one end of the metal part 421 and the metal part 432 of the third metal part 43 in the Z direction. When viewed from the Z direction, the metal part 422 has a frame shape. The inner surface of the metal part 422, in place of the metal part 431, defines the space SP1 together with the back surface 31b and the metal part 432.

[0081] The electron detector 1C differs from the electron detector 1A in that, instead of opening 47a, openings 47b and 47c are formed in the resin sheet 47. Opening 47b is spaced apart from opening 47c in the X direction. When viewed from the Z direction, opening 47b is spaced apart from opening 47c and is aligned with opening 47c in the X direction. When viewed from the Z direction, the outer edge of opening 47b includes the outer edge of the through hole 432a. Opening 47b includes a portion that overlaps with the through hole 432a and a portion that does not overlap with the through hole 432a. In the portion that overlaps with the through hole 432a, the output section 25 passes through the through hole 432a and opening 47b and is physically connected to the back surface 31b via space SP1. In the portion that does not overlap with the through hole 432a, the connector 29 passes through opening 47b and physically and electrically connects the fourth electrode 27 and the metal portion 432. When viewed from the Z direction, the outer edge of the opening 47c overlaps with the outer edge of the through hole 432b. The voltage input section 28 passes through the through hole 432b and the opening 47c, and is physically connected to the back surface 31b via space SP1.

[0082] As shown in Figure 8, the electron detector 1D according to the fourth modification differs from the electron detector 1C of the third modification in that it does not have a resin sheet 47 and a gap GP is formed between the second metal part 42 and the third metal part 43. In the electron detector 1D, instead of a resin sheet 47, the gap GP ensures the dielectric strength between the second metal part 42 and the third metal part 43. The width of the gap GP (length in the Z direction) should be such that sufficient dielectric strength is ensured between the second metal part 42 and the third metal part 43, for example, 50 μm or more. The gap GP spatially connects the space SP1 and the space outside the second metal part 42. The second metal part 42 and the third metal part 43 may also be fixed to each other by fixing screws 109 so that a gap GP is created. According to the electron detector 1D, a gap GP is formed between the second metal part 42 and the third metal part 43, so sufficient dielectric strength can be ensured between the second metal part 42 and the third metal part 43.

[0083] As shown in Figure 9, the fifth modified electron detector 1E differs from the fourth modified electron detector 1D in that the third metal portion 43 further includes a metal portion 433. The metal portion 433 extends from the other side surface of the third metal portion 43 toward the wiring board 31. A gap may be formed between the other end of the metal portion 433 and the back surface 31b of the wiring board 31. When viewed from the Z direction, the metal portion 433 may have an annular shape surrounding the connector 29, the output section 25, and the voltage input section 28. When viewed from the Z direction, the outer edge of the metal portion 433 may be located inward from the outer edge of the wiring board 31. The metal portion 433 can function, for example, to suppress radiated noise incident from the gap GP from affecting the output section 25 and the amplifier 24, etc.

[0084] As shown in Figure 10, the sixth modified electron detector 1F differs from the fourth modified electron detector 1D in the structure of the output section 25, the structure of the voltage input section 28, and the fact that the electron detection unit 2F further has connectors 32 and 33. Connectors 32 and 33 are conductive connectors, for example, spring connectors. The other end of connector 32 is electrically connected to the output terminal of amplifier 24 via wiring 314. One end of connector 32 is physically and electrically connected to the internal conductor 251. The internal conductor 251 penetrates the third metal section 43 and is electrically connected to the output terminal of amplifier 24 via connector 32. The external conductor 252 is physically connected to the third metal section 43. The external conductor 252 does not penetrate the third metal section 43. The other end of the external conductor 252 is physically connected to one side surface of the third metal section 43.

[0085] The other end of the connector 33 is electrically connected to the output terminal of the amplifier 24 via the wiring 315. The other end of the connector 33 is physically and electrically connected to the internal conductor 281. The internal conductor 281 passes through the third metal part 43 and is electrically connected to the output terminal of the amplifier 24 via the connector 33. The external conductor 282 is physically connected to the third metal part 43. The external conductor 282 does not pass through the third metal part 43. The other end of the external conductor 282 is physically connected to the surface of one side of the third metal part 43. In the electron detector 1F, since the external conductor 252 is physically connected to the third metal part 43, fixing members for fixing the output part 25 and the third metal part 43 are unnecessary. Similarly, since the external conductor 282 is physically connected to the third metal part 43, fixing members for fixing the voltage input part 28 and the third metal part 43 are unnecessary. Therefore, the structure of the electron detector can be simplified.

[0086] As shown in Figure 11, the seventh modified electron detector 1G differs from electron detector 1 in that the second metal part 42 includes a metal part 421 and a metal part 422, and the third metal part 43 does not include a metal part 431. The metal part 421 has a frame shape. The metal part 421 surrounds the side surface of the flange 411 together with the side surface 31c of the wiring board 31 and the side surface of the resin sheet 48. A gap GP is formed between the first metal part 41 and the second metal part 42. Specifically, a gap GP is formed between the side surface of the flange 411 and the inner surface of the metal part 421. In electron detector 1G, the gap GP is used instead of the resin sheet 44 to ensure the dielectric strength between the first metal part 41 and the second metal part 42. The width of the gap GP (length in the X or Y direction) should be such that sufficient dielectric strength can be ensured between the second metal part 42 and the third metal part 43, for example, 50 μm or more.

[0087] The metal portion 422 is formed integrally with the metal portion 421 so as to connect one end of the metal portion 421 and the metal portion 432 of the third metal portion 43 in the Z direction. When viewed from the Z direction, the metal portion 422 has a frame shape. In the example of Figure 11, a space is formed between the inner surface of the metal portion 421, the side surface 31c, and the side surface of the resin sheet 48. This space constitutes space SP1. Therefore, in the electron detector 1G, the inner surface of the metal portion 421, the inner surface of the metal portion 422, the back surface 31b, and the metal portion 432 define space SP1. The gap GP spatially connects space SP1 and the external space of the second metal portion 42. The second metal portion 42 and the third metal portion 43 may also be fixed to each other by fixing screws 109 so as to create a gap GP. According to the electron detector 1G, a gap GP is formed between the first metal part 41 and the second metal part 42, so sufficient dielectric strength can be ensured between the first metal part 41 and the second metal part 42.

[0088] In the first to seventh modified electron detectors described above, the first metal part 41 faces the electron detection unit 2 on the other side, so that radiated noise can be prevented from entering the electron detection unit 2 from the other side. In addition, since the second metal part 42 surrounds the side surface 31c of the wiring board 31, radiated noise can be prevented from entering the wiring board 31 from the side. Furthermore, since the third metal part 43 faces the electron detection unit 2 on one side of the wiring board 31, radiated noise can be prevented from entering the wiring board 31 from the one side, making it easier to prevent noise from being superimposed on the electrical signal.

[0089] Any combination is possible in the above-described modifications. For example, the electron detector 1 shown in Figure 4 may have connectors 32 and 33 shown in Figure 10. In this case, the internal conductor 251 may pass through the third metal part 43 and be electrically connected to the output terminal of the amplifier 24 via the connector 32. The external conductor 252 may be physically connected to the third metal part 43. Alternatively, in the first modified electron detector 1A shown in Figure 5, the third metal part 43 may further include the metal part 433 shown in Figure 9. In this case, in addition to the fact that the space between the second metal part 42 and the third metal part 43 is sealed by the resin sheet 47, the metal part 433 can further suppress the radiated noise from affecting the output unit 25 and the amplifier 24, etc.

[0090] Furthermore, in the first to seventh modified electron detectors described above, the wiring board 31 is arranged such that its surface 31a, that is, the larger surface of the wiring board 31, faces the opening 41a, but the configuration is not limited to this. The wiring board 31 may be arranged such that its side surface 31c, that is, its end face, faces the opening 41a. In this case, the surface 31a of the wiring board 31 may extend along the Z direction and be arranged to face the second metal part 42. In this case as well, AD21 is mounted on the wiring board 31 facing the opening 41a, and at least a part of the side surface 31c is surrounded by the second metal part 42.

[0091] In the embodiments and modifications described above, examples were given in which the electron detectors 1 to 1G are applied to a charged particle detector 100. However, the electron detectors 1 to 1G may also be applied to electron tubes that include a photocathode that converts photons into photoelectrons. The electron detectors 1 to 1G 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 5 in the charged particle detector 100. An HPD does not include a configuration corresponding to the electron emission unit 5. In an HPD, photoelectrons emitted from the photocathode directly enter the electron detectors 1 to 1G.

[0092] The charged particle detector 100 to which electron detectors 1 to 1G are applied may also be applied to a mass spectrometer. In this case, the charged particle detector 100 functions as an ion detector. As shown in Figure 12, the mass spectrometer 200 comprises a sample introduction unit 201, an ionization unit 202, a mass spectrometry unit 203, a charged particle detector 100, and a signal processing unit 204. The sample introduction unit 201 introduces the sample SM1 into the ionization unit 202. The ionization unit 202 ionizes the sample SM1 introduced from the sample introduction unit 201. The ionization unit 202 introduces the ionized sample SM2 into the mass spectrometry unit 203. The mass spectrometry unit 203 has, for example, a quadrupole analyzer and allows only the ions SM3 to be detected to pass through. The ions SM3 to be detected are incident on the charged particle detector 100. The charged particle detector 100 detects the incident ions SM3. The signal processing unit 204 processes the detection signal SG1 from the charged particle detector 100.

[0093] The mass spectrometer 200 includes a housing 205. The housing 205 houses an ionization unit 202, a mass spectrometry unit 203, and a charged particle detector 100. In this embodiment, the housing 205 is a vacuum chamber. The mass spectrometer 200 also includes a power supply unit 206. The power supply unit 206 supplies power EP1 to the charged particle detector 100. The power supply unit 206 is, for example, an assembly of multiple power supplies.

[0094] 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G... Electron detector, 2... Electron detection unit, 4... Housing section, 5... Electron emission section, 20... Electron detection element, 22... First electrode, 23... Second electrode, 24... Amplifier, 25... Output section, 31... Wiring board, 31b... Back side (front side of one side), 31c... Side view, 32... Connector, 41... First metal part, 41a... Opening, 42... Second metal part, 43... Third metal part, 44, 47... Resin sheet, 45... Shielding ring, 47a, 47b, 47c... Opening, 100... Charged particle detector, 200... Mass spectrometer, 251... Internal conductor, 252... External conductor, 316... Electrode pattern (metal pattern), GND... Reference potential, GP... Gap.

Claims

1. An electron detector comprising: an electron detection unit that detects incident electrons and outputs an electrical signal; and a housing that houses the electron detection unit, wherein the electron detection unit comprises: an electron detection element that detects the electrons; a wiring board on which the electron detection element is mounted, which is arranged on one side in a predetermined direction with respect to the electron detection element; and an amplifier that amplifies the detection signal output from the electron detection element, wherein the housing has an opening on the other side in the predetermined direction with respect to the electron detection element that faces the electron detection element, and a first metal part that faces the electron detection unit on the other side with respect to the electron detection element, and a second metal part that surrounds the side surface of the wiring board.

2. The electron detector according to claim 1, wherein the housing portion further has a third metal portion facing the electron detection unit on one side with respect to the wiring board.

3. The electron detector according to claim 2, wherein the first metal part is set to a potential for accelerating and focusing the electrons, the second metal part is formed integrally with the third metal part and is connected to a reference potential different from the aforementioned potential, and the housing part further comprises an electrically insulating part disposed between the first metal part and the second metal part.

4. The electronic detector according to claim 3, wherein the electrical insulating part is a resin sheet.

5. The electron detector according to claim 4, wherein the electron detection unit further comprises a first electrode disposed on the other side of the resin sheet and a second electrode disposed on the one side of the resin sheet and facing the first electrode via the resin sheet, the first electrode being electrically connected to the electron detection element and the second electrode being electrically connected to the amplifier.

6. The electron detector according to claim 2, wherein a gap is formed between the first metal part and the second metal part.

7. The electron detector according to claim 2, wherein the first metal part is set to a potential for accelerating and focusing the electrons and is formed integrally with the second metal part, the third metal part is connected to a reference potential different from the aforementioned potential, and the housing part further comprises an electrically insulating part disposed between the second metal part and the third metal part.

8. The electronic detector according to claim 7, wherein the electrical insulating part is a resin sheet.

9. The electron detector according to claim 8, wherein the third metal portion faces the wiring board on one side with respect to the wiring board, the resin sheet extends from at least between the second metal portion and the third metal portion to between the wiring board and the third metal portion, an opening is formed in the resin sheet, the outer edge of the opening is located inside the outer edge of the wiring board when viewed from the predetermined direction, and the electron detection unit further has a metal pattern extending from the side of the opening to between the resin sheet and the third metal portion.

10. The electron detector according to any one of claims 1 to 9, wherein the amplifier is located on one side of the wiring board and is mounted on the wiring board.

11. The electronic detection unit further comprises: an output unit disposed on one side of the wiring board and electrically connected to the amplifier, which outputs an electrical signal corresponding to the amplified detection signal; and a connector protruding from the surface of the one side of the wiring board, wherein the output unit includes an internal conductor that outputs the electrical signal; and an external conductor that surrounds the internal conductor in a state of being electrically insulated from the internal conductor, the external conductor being connected to the third metal part, and the internal conductor passing through the third metal part and electrically connected to the amplifier via the connector, the electronic detector according to any one of claims 2 to 9.

12. The electronic detection unit is located on one side of the wiring board, is electrically connected to the amplifier, and further has an output unit that outputs an electrical signal corresponding to the amplified detection signal, the output unit passing through the third metal part and connected to the wiring board, the electronic detector according to any one of claims 2 to 9.

13. The electron detector according to claim 12, wherein the output section includes an internal conductor that outputs the electrical signal and an external conductor that surrounds the internal conductor in a state of being electrically insulated from the internal conductor, and the housing section further includes a shielding ring that fixes and electrically connects the external conductor and the third metal section.

14. A charged particle detector comprising: an electron detector according to any one of claims 1 to 13; and an electron emission unit that emits electrons upon the incidence of charged particles.

15. A mass spectrometer comprising the charged particle detector described in claim 14.

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