Detectors for detecting charged particles or light

Abstract

One embodiment of the present disclosure relates to a detector that includes an AD and detects charged particles or light. Without changing the structure of the AD that limits the response of the detector, it is possible to achieve a faster response of the detector. The driving circuit of the AD includes a first capacitor and a first resistor. The first capacitor and the first resistor are connected in series with the AD, with both terminals set to the same potential. Through this structure, the apparent electrostatic capacitance of the AD is reduced, which speeds up the overall response of the detector including the driving circuit.

Description

Technical Field

[0001] The present disclosure relates to detectors for detecting charged particles such as ions and electrons, or light.

[0002] This application claims the benefit of Japanese Patent Application No. 2020-193255, filed on November 20, 2020, which is hereby incorporated by reference in its entirety into this specification based on the contents thereof. Background Art

[0003] As a charged particle detector for time-of-flight mass spectrometry, such as an ion detector, a detector comprising a microchannel plate (hereinafter referred to as "MCP") and an avalanche diode (hereinafter referred to as "AD") is known (Patent Document 1). The MCP is an electron multiplying element that releases electrons in response to the incidence of charged particles such as ions and electrons. The AD is an electronic device that captures the released electrons and outputs them as an electrical signal.

[0004] In such detectors, it is desirable to increase the speed of the ion detector's response characteristics. For example, the mass resolution of mass analysis depends on the response characteristics of the ion detector. Therefore, to improve the mass resolution of mass analysis, it is necessary to improve the response characteristics of the ion detector. Specifically, it is necessary to increase the speed of the ion detector's response.

[0005] The response speed of an ion detector, which includes both an MCP and an AD, is limited by the response speed of the AD. In other words, the response speed of the AD is the primary factor determining the response speed of the ion detector. Therefore, to improve the response characteristics of the ion detector, attempts are being made to increase the speed of the AD response.

[0006] To speed up AD response, it is known to reduce the AD's capacitance. The AD's capacitance is proportional to the area of ​​the AD's active layer and inversely proportional to its thickness. Therefore, increasing the thickness of the AD's active layer can reduce the AD's capacitance, resulting in faster response (Patent Document 2).

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-16918

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2007-250585 Summary of the Invention

[0009] The inventors studied the above-mentioned prior art and discovered the following problem. Specifically, increasing the thickness of the active layer of an AD can reduce the electrostatic capacitance of the AD. However, increasing the thickness of the active layer increases the distance traveled by carriers (electrons and holes) generated within the AD, and this travel time also increases. As a result, the temporal waveform of the induced current broadens, leading to a decrease in response speed. Therefore, there is a limit to how fast the response of the AD itself can be increased.

[0010] The present disclosure has been developed to solve the above-mentioned problems, and its purpose is to achieve a faster response of a detector for detecting charged particles or light using AD.

[0011] The detector disclosed herein is an electronic device suitable for use in mass spectrometry, for example, and is used to detect charged particles or light. The detector comprises an AD having an electron incident surface upon which electrons generated by charged particles, photoelectrons generated by light, or electrons generated by multiplying photoelectrons are incident; and a drive circuit that drives the AD. The drive circuit comprises a first capacitor and a first resistor. The first capacitor and the first resistor are both connected in series to the AD and are substantially connected in parallel to the wiring on which the first capacitor is located and the wiring on which the first resistor is located. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a diagram showing an example of the circuit configuration of the ion detector according to the first embodiment.

[0013] Figure 2 This is a cutaway perspective view showing an example of the structure of the ion detector according to the first embodiment.

[0014] Figure 3 It is a cross-sectional view schematically showing an example of the structure of AD of the ion detector according to the first embodiment.

[0015] Figure 4 This is a circuit diagram showing an example of an AD drive circuit of the ion detector according to the first embodiment.

[0016] Figure 5 : is a circuit diagram showing an equivalent circuit of an AD driving circuit of a comparative example.

[0017] Figure 6 This is a circuit diagram showing an equivalent circuit of an example of an AD drive circuit of the ion detector according to the first embodiment.

[0018] Figure 7 This is a waveform diagram showing an example of an AD response waveform.

[0019] Figure 8This is a diagram showing an example of the result of simulating the response waveform of AD when the effective diameter of the electron incident surface is 1 mm.

[0020] Figure 9 This is a diagram showing an example of the result of simulating the response waveform of AD when the effective diameter of the electron incident surface is 3 mm.

[0021] Figure 10 This is a diagram showing an example of the result of simulating the temporal change in the potential difference between electrodes of an AD having an effective diameter of 3 mm on the electron incident surface.

[0022] Figure 11 This is a diagram showing an example of the result of simulating the response waveform of AD when the effective diameter of the electron incident surface is 3 mm.

[0023] Figure 12 This is a diagram showing an example of the result of simulating the temporal change in the potential difference between electrodes of an AD having an effective diameter of 5 mm on the electron incident surface.

[0024] Figure 13 This is a diagram showing an example of the result of simulating the response waveform of AD when the effective diameter of the electron incident surface is 5 mm.

[0025] Figure 14 This is a circuit diagram showing an example of an AD drive circuit of an ion detector according to a first modification of the first embodiment.

[0026] Figure 15 This is a circuit diagram showing an example of an AD drive circuit of an ion detector according to a second modification of the first embodiment.

[0027] Figure 16 This is a circuit diagram showing an example of a circuit configuration of an ion detector according to the second embodiment.

[0028] Figure 17 This is a diagram showing an example of the appearance of an ion detector according to the second embodiment.

[0029] Figure 18 This is a circuit diagram showing an example of an AD driving circuit of the ion detector according to the second embodiment.

[0030] Figure 19 This is a circuit diagram showing an example of a circuit configuration of a photodetector according to the third embodiment. DETAILED DESCRIPTION

[0031] [Description of Embodiments of the Present Disclosure]

[0032] First, the contents of the embodiments of the present disclosure will be individually listed and described.

[0033] (1) The detector disclosed in the present invention is a detector for detecting charged particles or light, and is provided with an AD (avalanche diode) and a driving circuit. The AD has a first electrode, a second electrode, and an electron incident surface. The first electrode is electrically connected to a power supply terminal set to a first reference potential different from the ground potential. The second electrode is electrically connected to a signal output terminal. Electrons generated by charged particles, photoelectrons generated by light, or electrons generated by multiplication of the photoelectrons are incident on the electron incident surface. The driving circuit (avalanche diode driving circuit) drives the AD. The driving circuit includes a first capacitor and a first resistor, and the driving circuit has a first circuit structure in which the first capacitor and the first resistor are arranged on the first electrode side of the AD, or a second circuit structure in which the first capacitor and the first resistor are arranged on the second electrode side of the AD.

[0034] In a drive circuit having a first circuit structure, a first capacitor is disposed on a wiring between a power supply terminal and a first electrode of an AD. Furthermore, the first capacitor has a first terminal electrically connected to the power supply terminal and a second terminal electrically connected to the first electrode of the AD. A first resistor has a first terminal electrically connected to the power supply terminal and a second terminal electrically connected to the first electrode of the AD. Furthermore, the first terminal of the first capacitor and the first terminal of the first resistor are set to the same potential, and the second terminal of the first capacitor and the second terminal of the first resistor are set to the same potential.

[0035] On the other hand, in a driving circuit having a second circuit structure, a first capacitor is arranged on a wiring having a branch structure having a signal output terminal and located between the second electrode of the AD and a node set to a second reference potential different from the first reference potential (e.g., a ground potential). In addition, the first capacitor has a first terminal electrically connected to the second electrode of the AD and a second terminal electrically connected to the signal output terminal. The first resistor has a first terminal and a second terminal electrically connected to the second electrode of the AD. The first terminal of the first resistor is set to the same potential as the first terminal of the first capacitor. The second terminal of the first resistor is electrically connected to the second terminal of the first capacitor in a manner set to the same potential as the second terminal of the first capacitor, or the second terminal of the first resistor is set to the same potential as the above-mentioned node (the second reference potential).

[0036] Both the first and second circuit structures described above can achieve faster response times for the detector as a whole, including the AD and the drive circuit. Furthermore, because the drive circuit driving the AD includes a first capacitor connected in series with the AD, this detector is apparently connected to the AD with a small capacitance. Furthermore, the first resistor is connected in parallel with the first capacitor, or with the series connection between the first capacitor and the voltage drop element. Therefore, even when the first capacitor is connected in series with the AD, a voltage can be applied to the AD. As a result, faster response times can be achieved for the detector as a whole, including the AD and the drive circuit.

[0037] (2) As one aspect of the present disclosure, the capacitance of the first capacitor is preferably 10 times or less the capacitance of the AD. In this case, the effect of increasing the speed of response of the entire detector including the AD and the drive circuit can be enhanced.

[0038] (3) As one embodiment of the present disclosure, the capacitance of the first capacitor may be equal to or smaller than that of the AD. In this case, the effect of increasing the speed of response of the entire detector including the AD and the drive circuit can be further enhanced.

[0039] (4) As one aspect of the present disclosure, the resistance value of the first resistor is preferably 30 kΩ or more and 500 kΩ or less. In this case, the variation in the potential difference between the AD electrodes can be suppressed, and the symmetry of the response waveform can be maintained.

[0040] (5) As one embodiment of the present disclosure, the driving circuit may further include a second capacitor. In the first circuit structure, the signal output terminal is electrically connected to the wiring between the second electrode of the AD and the node set to a second reference potential different from the first reference potential. On the other hand, the second capacitor has a first terminal electrically connected to both the first terminal of the first capacitor and the first terminal of the first resistor, and a second terminal set to the same potential as the above-mentioned node (second reference potential). That is, the first terminal of the second capacitor is set to the same potential as both the first terminal of the first capacitor and the first terminal of the first resistor. On the other hand, in the second circuit structure, the second capacitor has a first terminal electrically connected to the first electrode of the AD (set to the same potential as the first electrode of the AD), and a second terminal set to the second reference potential like the above-mentioned node. In any case, a return path is formed between the electron incident surface of the AD and the ground potential, which can eliminate the fluctuation of the DC component of the output voltage caused by the voltage drop on the electron incident surface caused by the continuous incidence of electrons to the AD. In addition, the high-speed signal output from the AD can be returned to the AD with low resistance via the return path.

[0041] (6) As one embodiment of the present disclosure, a driving circuit having a first circuit configuration (a circuit configuration in which both the first capacitor and the first resistor are arranged on the first electrode side of the AD) may further include a third capacitor serving as an AC coupler, arranged on a wiring line between the signal output terminal and the second electrode of the AD. The third capacitor has a first terminal electrically connected to the second electrode of the AD and a second terminal electrically connected to the signal output terminal. In this case, the AC component can be extracted as a signal, and thus, for example, the detector can be applied to mass spectrometry in which ions of both polarities can be detected.

[0042] (7) As one embodiment of the present disclosure, the detector may further include an MCP (microchannel plate) and a focusing electrode. The MCP has an input surface for incident charged particles and an output surface for emitting electrons generated by the charged particles. The electrons emitted from the output surface of the MCP are focused by the focusing electrode and then incident on the electron incident surface of the AD. In this case, the electrons generated by the charged particles incident on the input surface of the MCP are multiplied by the MCP and then emitted from the output surface. In addition, the relevant electrons are focused by the focusing electrode and then incident on the electron incident surface of the AD. Therefore, high-sensitivity and high-resolution detection of charged particles can be achieved.

[0043] (8) As one embodiment of the present disclosure, the detector may further include a photoelectric conversion unit. The photoelectric conversion unit is an optical device that converts light into photoelectrons, and the photoelectrons or electrons generated by multiplication of the photoelectrons are incident on the electron incident surface of the AD. In this case, since the photoelectrons generated by light incident on the photoelectric conversion unit or the electrons generated by multiplication of the photoelectrons are incident on the electron incident surface of the AD, high-sensitivity and high-resolution detection of light can be achieved.

[0044] Each embodiment listed in the above section “Description of the embodiment of the present disclosure” is applicable to each of all the remaining embodiments or all combinations of the remaining embodiments.

[0045] [Details of the embodiment of the present disclosure]

[0046] The specific structure of the detector involved in the present disclosure is described in detail below with reference to the accompanying drawings. The present invention is not limited to these examples but is defined by the scope of the claims, which are intended to encompass all modifications equivalent to and within the scope of the claims. In the description of the drawings, identical elements are denoted by identical reference numerals, and duplicate descriptions are omitted.

[0047] (First embodiment)

[0048] Figure 1 This diagram shows an example of the circuit configuration of an ion detector 1A according to the first embodiment of the detector disclosed herein. The ion detector 1A according to the first embodiment includes an MCP unit 100 serving as an electron multiplier, a mesh-shaped accelerating electrode 150, a pair of focusing electrodes (electron lenses) 160 and 170, an AD cover 180, an AD 220 serving as a signal output unit 200, and a signal output terminal 110.

[0049] The MCP unit 100 includes an MCP 102 having an input surface 102a and an output surface 102b, and the side of the MCP 102 is surrounded by an insulating ring made of an insulating material. When charged particles are incident on the input surface 102a, the MCP 102 generates electrons in response to the charged particles, multiplies the electrons, and then emits the multiplied electrons from the output surface 102b. As an example, the MCP 102 includes a thin disk-shaped structure, i.e., a main body, mainly composed of lead glass. In addition to the annular outer periphery, the main body is provided with a plurality of through holes, i.e., channels, extending in the thickness direction (from the input surface 102a toward the output surface 102b). In addition, electrodes are formed on the outer periphery of the input surface 102a and the outer periphery of the output surface 102b.

[0050] The accelerating electrode 150 is disposed between the MCP 102 and the AD 220 , for example, between the MCP 102 and the focusing electrode 160 , and accelerates electrons emitted from the output surface 102 b of the MCP 102 .

[0051] A pair of focusing electrodes 160 and 170 are disposed between the MCP 102 and the AD 220 , for example, between the accelerating electrode 150 and the AD 220 , so as to focus the electrons accelerated by the accelerating electrode 150 toward the AD 220 .

[0052] The AD cover 180 prevents electrons focused toward the AD 220 from colliding with the printed wiring substrate 221 on which the AD 220 is mounted and from charging the printed wiring substrate 221 .

[0053] AD220 is mounted on the top surface (the surface facing output surface 102b) of printed wiring board 221, facing output surface 102b of MCP 102 via accelerating electrode 150 and a pair of focusing electrodes 160 and 170. An SMA jack 120A is attached to the bottom surface (the surface facing signal output terminal 110) of printed wiring board 221. AD220 captures electrons focused by the pair of focusing electrodes 160 and 170 and outputs them as electrical signals.

[0054] The input surface 102a of the MCP unit 100 is connected to the power supply 910 and is set to a potential Va (e.g., -7 kV). A potential difference Vb (e.g., 500 V to 1 kV) is ensured between the input surface 102a and the output surface 102b by the power supply 920. The output surface 102b is grounded via a resistor Ra (e.g., 40 MΩ) and a resistor Rb (e.g., 20 MΩ) connected in series between the output surface 102b and the ground wiring. The potential of the output surface 102b (i.e., the potential difference between the output surface 102b and the ground potential) is divided by the resistors Ra and Rb. An accelerating electrode 150 is connected to a node N1 located between the resistors Ra and Rb. The focusing electrode 160 located on the output surface 102b side of the pair of focusing electrodes is set to the same potential as the output surface 102b of the MCP 102.

[0055] Of the pair of focusing electrodes, the focusing electrode 170 located on the AD 220 side is connected to a power supply 940 set to a potential Vd (eg, 0 to 400 V) via a resistor Rc (eg, 1 kΩ).

[0056] The power supply 940 is connected to the P-side electrode (first electrode) of AD220 via a resistor Rd (e.g., 1 kΩ), a capacitor C1 as a first capacitor, and a resistor R1 as a first resistor. Capacitor C1 and resistor R1 are connected in series to the P-side electrode of AD220 and resistor Rd and are connected in parallel to each other. In addition, the P-side electrode of AD220 is connected to the P-side electrode of AD220. + The AD220 has an electron incident surface on the P side. Details will be described later.

[0057] Node N2, located between capacitor C1 and resistors R1 and Rd, is connected to the side of the SMA socket 120A via capacitor C2 (e.g., 10nF), which serves as a second capacitor. The side of the SMA socket 120A is grounded. The signal output terminal 110 is also grounded via a terminal resistor Re (e.g., 50Ω). Therefore, a return path is formed between the electron incident surface of AD220 and the grounded side of the SMA socket 120A. When electrons continue to be incident on AD220, a voltage drop occurs on the electron incident surface of AD220. In this case, the signal (output voltage) output from AD220 to the signal output terminal 110 reflects the fluctuation of the DC component caused by this voltage drop. Therefore, by configuring capacitor C2 between the electron incident surface of AD220 and the side of the SMA socket 120A, the fluctuation of the DC component reflected in the output signal is eliminated. Furthermore, the capacitor C2 enables a high-speed signal output from the AD 220 to the signal output terminal 110 to return to the AD 220 via a return path with low resistance.

[0058] Figure 2 This is a cutaway perspective view showing an example of the structure of an ion detector 1A according to the first embodiment. The ion detector 1A includes an MCP unit 100, a mesh-shaped accelerating electrode 150 (not shown), a pair of focusing electrodes 160 and 170, and a printed wiring board 221 carrying an AD 220, which are fixed to each other.

[0059] The MCP unit 100 includes: an MCP 102, an input-side electrode 103, and an output-side electrode 104. As described above, the side surface of the MCP 102 is surrounded by an insulating ring. The annular outer periphery of the MCP 102 and the insulating ring are clamped by the input-side electrode 103 and the output-side electrode 104. The input-side electrode 103 has an opening 103a for allowing charged particles incident on the input surface 102a of the MCP 102 to pass through. Similarly, the output-side electrode 104 has an opening for allowing electrons emitted from the output surface 102b of the MCP 102 to pass through. The central axis of the opening 103a of the input-side electrode 103 and the central axis of the opening of the output-side electrode 104 are consistent with the central axis of the MCP 102.

[0060] The accelerating electrode 150 (not shown) is sandwiched between a first insulating spacer 151 and a second insulating spacer 152 .

[0061] The input side electrode 103, the insulating ring surrounding the side surface of the MCP 102, the output side electrode 104, and the first insulating spacer 151 are fixed to each other by fixing screws 130. Thus, the MCP unit 100 and the accelerating electrode 150 are fixed to each other.

[0062] Focusing electrode 160 is a cylindrical conductive component whose central axis is aligned with the central axis of MCP 102. One end of focusing electrode 160 is fixed to second insulating spacer 152. The other end of focusing electrode 160 is provided with an annular portion 161 that protrudes inwardly from the tube. The other end of focusing electrode 160 faces one end of focusing electrode 170.

[0063] The focusing electrode 170 is a cylindrical conductive member, and its central axis coincides with the central axis of the MCP 102. A flange portion 171 is provided at one end of the focusing electrode 170.

[0064] AD cover 180 is a disc-shaped conductive component, positioned to block the other end of focusing electrode 170. AD cover 180 has a circular protrusion 181 that protrudes toward MCP unit 100. Protrusion 181 has an opening 182 for allowing electrons SE, emitted from output surface 102b of MCP 102 and focused by a pair of focusing electrodes 160 and 170, to pass through. The central axis of protrusion 181 coincides with the central axis of MCP 102. The central axis of opening 182 is offset from the central axis of MCP 102 in the offset direction of MCP 102.

[0065] The printed wiring board 221 on which the AD 220 is mounted is mounted on the AD cover 180 and is covered by the AD cover 180 .

[0066] Figure 3 This is a cross-sectional view schematically showing an example of the structure of the AD220 of the ion detector 1A according to the first embodiment. The AD220 includes an N-side electrode 222 (second electrode), an N + Type semiconductor layer 223, N － Type semiconductor layer 224, P type semiconductor layer (avalanche photomultiplier layer) 225, P + The N-side electrode 222 is provided on the N-side semiconductor layer 226, the P-side electrode 227 (first electrode), the insulating film 228, and the passivation film 229. + The back side of the semiconductor layer 223. － The N-type semiconductor layer 224 and the P-type semiconductor layer 225 are + The surface side of the N-type semiconductor layer 223 is formed by, for example, ion implantation. + In the thickness direction of the type semiconductor layer 223, N － The N-type semiconductor layer 224 is located + Between the N-type semiconductor layer 223 and the P-type semiconductor layer 225. － The P-type semiconductor layer 224 and the P-type semiconductor layer (avalanche photomultiplier layer) 225 constitute the active layer. + The N-type semiconductor layer 226 is provided on the surface of the P-type semiconductor layer 225 and functions as a P-type contact layer. + Type semiconductor layer 223, N － Type semiconductor layer 224, P type semiconductor layer 225, and P + The surface of the semiconductor structure composed of the type semiconductor layer 226. The insulating film 228 has an opening for electrons to pass through. The P-side electrode 227 is arranged on the insulating film 228 in a manner surrounding the opening of the insulating film 228. The P-side electrode 227 is connected to the P-side electrode through another opening formed in the insulating film 228. +The passivation film 229 is an insulating film and covers the P-side electrode 227 and the insulating film 228. + The AD 220 is mounted on the upper surface of the printed wiring board 221 so that the AD 220 faces the output surface 102b of the MCP 102 (on the P-type semiconductor layer 226 side). That is, the AD 220 has an electron incident surface on the P side.

[0067] Figure 4 1A is a circuit diagram showing an example of an AD drive circuit of the ion detector 1A according to the first embodiment. Figure 4 The circuit symbol of AD220 shown is represented by the circuit symbol of a general diode in order to distinguish it from the Zener diode 250 described later. In the circuit described later, AD220 is also represented by the circuit symbol of a general diode. Figure 4 The driving circuit has a first circuit structure (a circuit structure in which the first capacitor and the first resistor are arranged on the P-side electrode side of AD220). As described above, the P-side electrode (first electrode) of AD220 is connected to the power supply terminal (first reference potential different from the ground potential) of the power supply 940 via the resistor Rd, the capacitor C1 as the first capacitor, and the resistor R1 as the first resistor. The other power supply terminal of the power supply 940 is grounded. The capacitor C1 and the resistor R1 are both connected in series with the AD220 and the resistor Rd and are connected in parallel with each other. In order to form a return path, the node N2 located between the capacitor C1, the resistor R1 and the resistor Rd is grounded via the capacitor C2 as the second capacitor and the side of the SMA jack 120A. The N-side electrode (second electrode) of AD220 is connected to the signal output terminal 110, and the signal output terminal 110 is connected to the node N set to the ground potential (second reference potential) from the N-side electrode. F Wiring branches between.

[0068] Reference Figures 5 to 7 The operation of the AD drive circuit of the ion detector 1A according to the first embodiment will be described. Figure 5 : is a circuit diagram showing an equivalent circuit of an AD driving circuit of a comparative example. Figure 6 This is a circuit diagram showing an equivalent circuit of an example of an AD drive circuit of the ion detector 1A according to the first embodiment. Figure 7 This is a waveform diagram showing an example of the response waveform of AD220. Figure 5 and Figure 6 In the equivalent circuit, AD220 has an electrostatic capacitance C AD A circuit in which a capacitor C4 and a current source S1 are connected in parallel with each other is represented.

[0069] In the AD driving circuit of the comparative example ( Figure 5), the P-side electrode of AD220 is connected to the power supply 940 for applying the AD bias only via resistor Rd, and the N-side electrode of AD220 is connected to the signal output terminal 110. In this AD driving circuit, assuming that the induced current of AD220 is constant u0 when 0 ≤ t ≤ T (t: time, T: duration of the induced current), the response waveform v of AD220 is expressed by the following equations (1) and (2). Here, R represents the resistance of the load, and C represents the effective electrostatic capacitance of the circuit including AD220 and through which the induced current flows.

[0070]

[0071]

[0072] The response waveform of AD220 expressed by the above equations (1) and (2) is Figure 7 Shown in. Figure 7 The white circle shown corresponds to formula (1), and the black circle corresponds to formula (2). Figure 7 As can be seen from the response waveform shown, in order to reduce the half-value width of the response waveform and increase the response speed, it is necessary to reduce the electrostatic capacitance C or shorten the duration T of the induced current.

[0073] In the AD driving circuit ( Figure 6 ), a capacitor C1 with an electrostatic capacitance C1 and a resistor R1 are added. The capacitor C1 and the resistor R1 are connected in series with AD220 and in parallel with each other. Therefore, the electrostatic capacitance C1 of AD220 AD The combined capacitance C is the capacitance of capacitor C4 included in the equivalent circuit of AD220 and the capacitance of capacitor C1. T As shown in the following formula (3), the capacitance C of AD220 is smaller than AD .

[0074]

[0075] This is Figure 6 In the AD driver circuit shown, Figure 5 Compared to the AD driving circuit of the comparative example shown, it appears that the AD220 with smaller electrostatic capacitance is connected. On the other hand, if the AD220 used in both AD driving circuits is the same, the thickness of the active layer of AD220, the travel distance and travel time of the carriers generated in AD220, and the induced current of AD220 are also the same in both driving circuits. Therefore, even if the AD220 is used, the AD220 is the same. Figure 6 The AD driver circuit shown is replaced by Figure 5The AD driving circuit shown does not increase the induced current and does not cause a decrease in response speed. In addition, the resistor R1 is connected in parallel with the capacitor C1, so even if the capacitor C1 is connected in series with the AD220, a voltage can be applied to the AD220.

[0076] Therefore, according to the ion detector 1A according to the first embodiment, the response speed of the entire ion detector including the AD 220 and the AD drive circuit can be increased.

[0077] As the electrostatic capacitance of capacitor C1 becomes larger than the electrostatic capacitance of AD220 AD , synthetic electrostatic capacitance C T Close to the electrostatic capacitance C of AD220 AD Therefore, the effect of reducing the apparent electrostatic capacitance of AD220 is reduced. In addition, when the resistance value of resistor R1 becomes equal to or greater than the resistance value of AD220, a large voltage drop occurs across resistor R1. The voltage applied to AD220 from power supply 940 decreases by the amount of the voltage drop, and therefore, the voltage required to drive AD220 may not be applied.

[0078] Figure 8 and Figure 9 This is a diagram showing an example of the result of simulation of the response waveform of the AD220 when the resistance value of the resistor R1 is set to 100 kΩ and the electrostatic capacitance C1 of the capacitor C1 is set to various values. Figure 8 The effective diameter of the electron incident surface is 1 mm. AD =5.8pF) related results, Figure 9 The effective diameter of the electron incident surface is 3 mm. AD =24pF) related results. In addition, Figure 8 and Figure 9 The graph also shows the response waveform when there is no capacitor C1 and resistor R1. The curve G1 in the figure shows that C1=C AD In the case of C1=2C, curve G2 shows AD In the case of C1=5C, curve G3 shows AD In the case of C1=10C, curve G4 shows AD Curve G5 shows the case where there is no capacitor C1 and resistor R1.

[0079] The effective diameter of the electron incident surface is 1mm AD220 ( Figure 8 ), the half-value width of the response waveform (full width at half value FWHM), when C1=C AD The case (curve G1) is 420ps (picoseconds), when C1 = 2C ADThe case (curve G2) is 460ps, when C1 = 5C AD The case (curve G3) is 480ps, when C1 = 10C AD The case with the capacitor C1 and the resistor R1 (curve G4) is 490 ps, ​​and the case without the capacitor C1 and the resistor R1 (curve G5) is 510 ps.

[0080] The effective diameter of the electron incident surface is 3mm AD220 ( Figure 9 ), the half-value width of the response waveform, when C1=C AD The case (curve G1) is 840ps, when C1 = 2C AD The case (curve G2) is 1130ps, when C1 = 5C AD The case (curve G3) is 1220ps, when C1 = 10C AD The case with the capacitor C1 and the resistor R1 (curve G4) is 1300 ps, ​​and the case without the capacitor C1 and the resistor R1 (curve G5) is 1400 ps.

[0081] from Figure 8 and Figure 9 As can be seen from the response waveform shown, at least when the capacitance of capacitor C1 is equal to the capacitance of AD, AD When the speed is less than 10 times, the response is accelerated.

[0082] Figures 10 to 13 This is a diagram showing an example of the results of simulating the time change of the potential difference between the electrodes of AD220 and the response waveform of AD220 when the electrostatic capacitance C1 of capacitor C1 is set to 2pF and the resistance value R1 of resistor R1 is set to various values ​​under the condition that an induced current with a wave height of 10mV is generated at a frequency of 10MHz.

[0083] Figure 10 The effective diameter of the electron incident surface is 3 mm. AD = 24pF) of the potential difference between the electrodes, Figure 11 The results are shown in relation to the response waveform of the same AD220. Figure 12 The effective diameter of the electron incident surface is 5 mm. AD =85pF) of the potential difference between the electrodes, Figure 13 The results are shown in relation to the response waveform of the same AD220.

[0084] Figure 10 and Figure 12Curve L1 in FIG. 1 shows the case where R1 = 10 kΩ, curve L2 shows the case where R1 = 100 kΩ, curve L3 shows the case where R1 = 500 kΩ, curve L4 shows the case where R1 = 1 MΩ, and curve L5 shows the case where R1 = 10 MΩ.

[0085] Figure 11 and Figure 13 The curve M1 in FIG. 1 shows the case where R1 = 100 kΩ, the curve M2 shows the case where R1 = 30 kΩ, the curve M3 shows the case where R1 = 10 kΩ, and the curve M4 shows the case where R1 = 1 kΩ.

[0086] From actual measurements, it is known that in order to suppress the fluctuation of AD gain to less than 10%, the fluctuation of the potential difference between the electrodes of AD220 needs to be suppressed to less than 5V. Figure 10 and Figure 12 As shown in the time variation of the potential difference between the electrodes of AD220, if the resistance value of the resistor R1 is set to 500 kΩ or less, the decrease of the potential difference between the electrodes of AD220 from the initial value (300 V) can be suppressed to less than 5 V. Therefore, in order to suppress the fluctuation of the potential difference between the electrodes of AD220, the resistance value of the resistor R1 is set to 500 kΩ or less. Figure 11 and Figure 13 As shown in the response waveform of AD220, if the resistance value of resistor R1 is greater than 30 kΩ, the symmetry of the response waveform is guaranteed. Therefore, in order to ensure the symmetry of the response waveform, the resistance value of resistor R1 is, for example, greater than 30 kΩ.

[0087] In the AD driving circuit of the ion detector 1A according to the first embodiment, the capacitor C1 and the resistor R1 are connected to the P side of the AD 220 . However, the capacitor C1 and the resistor R1 may be connected to the N side of the AD 220 .

[0088] (First Modification)

[0089] Figure 14 This is a circuit diagram showing an example of an AD drive circuit of an ion detector according to a first modification of the first embodiment. The AD drive circuit of the ion detector according to the first modification differs from the AD drive circuit of the ion detector according to the first embodiment in that it has a second circuit structure in which a capacitor C1 as a first capacitor and a resistor R1 as a first resistor are connected to the N-side electrode of AD220. Figure 14 In the circuit symbol of AD220, a general diode circuit symbol is also used. In the AD driving circuit of the ion detector according to the first modification, the first capacitor C1 and the first resistor R1 are both connected in series with AD220 and in parallel with each other.

[0090] Specifically, the capacitor C1 is disposed between the N-side electrode of the AD220 and the node N set to the ground potential (second reference potential). F The wiring between has a first terminal electrically connected to the N-side electrode of AD220 and a second terminal electrically connected to the signal output terminal 110 branching from the wiring. Resistor R1 has a first terminal electrically connected to the N-side electrode of AD220 and a second terminal electrically connected to the signal output terminal 110. In addition, the first terminal of capacitor C1 and the first terminal of resistor R1 are set to the same potential, and the second terminal of capacitor C1 and the second terminal of resistor R1 are set to the same potential. In addition, one power supply terminal of power supply 940 electrically connected to node N2 is set to the first reference potential, and the other power supply terminal is set to the ground potential (second reference potential).

[0091] In the above structure, the electrostatic capacitance of AD220 connected to the AD driver circuit is, on the surface, smaller than Figure 5 The capacitance of the AD220 connected to the AD drive circuit in the comparative example shown is 0. Therefore, the response speed of the entire ion detector including the AD220 and the AD drive circuit can be increased.

[0092] (Second Modification)

[0093] Figure 15 This is a circuit diagram showing an example of an AD drive circuit of an ion detector according to a second variant of the first embodiment. The AD drive circuit of the ion detector according to the second variant has a second circuit structure similar to the AD drive circuit of the ion detector according to the first variant, in which a capacitor C1 as a first capacitor and a resistor R1 as a first resistor are connected to the N-side electrode of AD220. However, this circuit structure differs from the AD drive circuit of the ion detector according to the first variant in that the resistor R1 is directly grounded. Figure 15 In the circuit symbol of AD220, the circuit symbol of a general diode is also represented. In the AD driving circuit of the ion detector involved in the second modification, the capacitor C1 and the resistor R1 are connected in series with the AD220, and the terminal resistor Re and the ground wiring (with a node N F wiring) are connected in parallel with each other.

[0094] Specifically, the capacitor C1 is disposed between the N-side electrode of the AD220 and the node N set to the ground potential (second reference potential). FThe first terminal of the resistor R1 is electrically connected to the N-side electrode of the AD220 and the second terminal of the resistor R1 is electrically connected to the N-side electrode of the AD220. The first terminal of the resistor R1 is electrically connected to the N-side electrode of the AD220 and the second terminal of the resistor R1 is set to the ground potential (the second reference potential). In addition, the first terminal of the capacitor C1 and the first terminal of the resistor R1 are set to the same potential. On the other hand, a voltage drop element (in Figure 15 In the example shown in FIG. 1 , the other terminal of the resistor R1 and the second terminal of the resistor R2 are set to the same potential. With the above configuration, the overall response speed of the ion detector, which includes the AD220 and the AD drive circuit, can be increased. Furthermore, one power supply terminal of the power supply 940 electrically connected to the node N2 is set to the first reference potential, and the other power supply terminal is set to the ground potential (the second reference potential).

[0095] (Second embodiment)

[0096] Figure 16 This circuit diagram shows an example of the circuit configuration of an ion detector 1B according to the second embodiment of the detector disclosed herein. The driving circuit has the first circuit configuration. The ion detector 1B according to the second embodiment is used for mass analysis in which ions of both polarities can be detected. The ion detector 1B according to the second embodiment includes an AC coupler (AC coupling circuit composed of capacitors, etc.) 500 between the AD 220 and the signal output terminal 110 for extracting the AC component as a signal.

[0097] Specifically, the ion detector 1B according to the second embodiment includes an MCP unit 100 as an electron multiplying unit, a mesh accelerating electrode 150 , a pair of focusing electrodes 160 and 170 , an AD 220 as a signal output unit 200 , an AC coupler 500 , and a signal output terminal 110 .

[0098] The MCP unit 100 includes an MCP 102 having an input surface 102a and an output surface 102b. The MCP 102 is similar to the MCP 102 of the ion detector 1A according to the first embodiment, and therefore detailed description thereof will be omitted.

[0099] The accelerating electrode 150 is disposed between the MCP 102 and the AD 220 , for example, between the MCP 102 and the focusing electrode 160 , and accelerates electrons emitted from the output surface 102 b of the MCP 102 .

[0100] A pair of focusing electrodes 160 and 170 are disposed between the MCP 102 and the AD 220 , for example, between the accelerating electrode 150 and the AD 220 , so as to focus the electrons accelerated by the accelerating electrode 150 toward the AD 220 .

[0101] AD220 is mounted on the top surface (the surface facing output surface 102b) of printed wiring board 221, facing output surface 102b of MCP 102 via accelerating electrode 150 and a pair of focusing electrodes 160 and 170. An SMA socket 120A is attached to the bottom surface (the surface facing signal output terminal 110) of printed wiring board 221. AD220 captures electrons focused by the pair of focusing electrodes 160 and 170 and outputs them as electrical signals.

[0102] An SMA plug 120B is attached to one side (AD220 side) of the AC coupler 500. An SMA jack 120C is attached to the other side (signal output terminal 110 side) of the AC coupler 500.

[0103] The input surface 102a of the MCP unit 100 is connected to a power supply 910 and set to a potential Va (e.g., +10 kV). A potential difference Vb (e.g., 0 V to 1 kV) is maintained between the input surface 102a and the output surface 102b by a power supply 920. A potential difference Vc (e.g., 0 V to 4 kV) is maintained between the output surface 102b and the side surface of the SMA plug 120B by a power supply 930. This potential difference Vc is divided by a resistor Ra (e.g., 40 MΩ), a resistor Rb (e.g., 20 MΩ), and a Zener diode (hereinafter, "ZD") 250, which are connected in series between the output surface 102b and the side surface of the SMA plug 120B and in parallel with the power supply 930. The ZD 250 maintains a potential difference of, for example, 200 to 400 V between the resistor Rb and the side surface of the SMA plug 120B. An accelerating electrode 150 is connected to a node N1 between resistors Ra and Rb. Of the pair of focusing electrodes, focusing electrode 160, located on the output surface 102b side, is set to the same potential as the output surface 102b of the MCP. Focusing electrode 170, located on the AD 220 side, is connected to a node N3 between resistor Rb and ZD 250 via a resistor Rc (e.g., 1 kΩ).

[0104] Node N3, located between resistor Rb and ZD250, is connected to the P-side electrode of AD220 via resistor Rd (e.g., 1 kΩ), capacitor C1 (a first capacitor), and resistor R1 (a first resistor). Capacitor C1 and resistor R1 are connected in series with the P-side electrode of AD220 and resistor Rd, and in parallel with each other.

[0105] Node N2, located between capacitor C1 and resistors R1 and Rd, is connected to the side of the SMA socket 120C via capacitor C2 (e.g., 10 nF), which serves as a second capacitor. The side of the SMA socket 120C is grounded. The signal output terminal 110 is also grounded via a terminal resistor Re (e.g., 50 Ω). Therefore, a return path is formed between the electron incident surface of AD220 and the grounded side of the SMA socket 120C. When electrons continue to be incident on AD220, a voltage drop occurs at the electron incident surface of AD220. In this case, the signal (output voltage) output from AD220 to the signal output terminal 110 reflects the fluctuation of the DC component caused by this voltage drop. Therefore, by configuring capacitor C2 between the electron incident surface of AD220 and the side of the SMA socket 120C, the fluctuation of the DC component reflected in the output signal is eliminated. Furthermore, the capacitor C2 enables a high-speed signal output from the AD 220 to the signal output terminal 110 to return to the AD 220 via a return path with low resistance.

[0106] AC coupler 500 includes a signal capacitor PC1 (e.g., 150 pF) as a third capacitor, connected between the N-side electrode of AD220 and signal output terminal 110, for extracting the AC component as a signal. Node N4, located between the N-side electrode of AD220 and signal capacitor PC1, is connected to the side surface of SMA plug 120B via resistor 520 (e.g., 1 kΩ to 10 MΩ) to maintain the potential of the N-side electrode of AD220.

[0107] Figure 17 This figure shows an example of the appearance of the ion detector 1B according to the second embodiment. The MCP unit 100, a pair of focusing electrodes 160, 170, a printed wiring board 221 constituting a part of the signal output unit, and the AC coupler 500 are fixed via spacers.

[0108] Figure 18 1B is a circuit diagram showing an example of an AD driving circuit of the ion detector 1B according to the second embodiment. The driving circuit has a first circuit configuration. Figure 18 In FIG, the circuit symbol of AD220 is also represented by the circuit symbol of a general diode. As described above, the P-side electrode of AD220 is connected to the node N3 ( located between the resistor Rb and ZD250 ) via the resistor Rd, the capacitor C1 as the first capacitor, and the resistor R1 as the first resistor. Figure 16), AD bias is applied. Capacitor C1 and resistor R1 are connected in series with AD220 and resistor Rd and are connected in parallel with each other. In order to form a return path, the node N2 located between capacitor C1, resistor R1 and resistor Rd is grounded via capacitor C2 as the second capacitor and the side of the SMA jack 120C. The N-side electrode of AD220 is connected to the signal output terminal 110 via the signal capacitor PC1 as the third capacitor of the AC coupler 500. That is, the signal capacitor PC1 is configured between the N-side electrode of AD220 and the node N set to the ground potential (second reference potential). F On the wiring between, one terminal is electrically connected to the N-side electrode of AD220, and the other terminal is electrically connected to the signal output terminal 110. In addition, the N-side electrode of AD220 is connected to the power supply 930 ( Figure 16 The node N3 is electrically connected to a power supply terminal of the power supply 930 set to a first reference potential via the resistors Rd, Rb, and Ra.

[0109] The AD drive circuit of the ion detector 1B according to the second embodiment also includes a capacitor C1 and a resistor R1. Furthermore, capacitor C1 and resistor R1 are both connected in series with AD 220 and in parallel with each other. Therefore, the apparent electrostatic capacitance of AD 220 connected to the AD drive circuit is small. Therefore, the ion detector 1B according to the second embodiment can achieve faster response times for the entire ion detector, including AD 220 and the AD drive circuit.

[0110] Although an ion detector is described as the first and second embodiments of the detector of the present disclosure, an embodiment of the detector of the present disclosure may also be a photodetector.

[0111] (Third embodiment)

[0112] Figure 19 This is a circuit diagram showing an example of the circuit configuration of a photodetector 1C according to the third embodiment of the detector disclosed herein. The photodetector 1C according to the third embodiment includes the MCP unit 100, the accelerating electrode 150, the focusing electrode 160 of the ion detector 1A according to the first embodiment, and a photoelectric converter 300, which replaces the power supply and resistors for setting the potentials of these components. The photoelectric converter 300 has a light-receiving surface 302a and an output surface 302b. When light is incident on the light-receiving surface 302a, photoelectrons are generated in response to the light and are emitted from the output surface 302b. The AD 220 captures these photoelectrons and outputs them as electrical signals, thereby detecting light.

[0113] The AD drive circuit of the photodetector 1C according to the third embodiment also includes the capacitor C1 and the resistor R1 that constitute the first circuit configuration. Furthermore, the capacitor C1 and the resistor R1 are both connected in series with the AD 220 and in parallel with each other, so the apparent electrostatic capacitance of the AD connected to the AD drive circuit is small. The signal output terminal 110 is connected from the N-side electrode of the AD 220 to the node N set to the ground potential (second reference potential). F One terminal of capacitor C2 is electrically connected to the terminals of capacitor C1 and resistor R1 on the power supply 940 side, and the other terminal is set to be connected to node N F Therefore, according to the photodetector 1C according to the third embodiment, the response speed of the entire photodetector including the AD 220 and the AD driving circuit can be increased.

[0114] The photodetector 1C according to the third embodiment includes the MCP unit 100, the accelerating electrode 150, and the focusing electrode 160 of the ion detector 1A according to the first embodiment, and a photoelectric converter 300 in place of the power supply and resistor for setting the potentials of these components. However, by adding the photoelectric converter 300 to the ion detector 1A according to the first embodiment, a photodetector can be constructed. Specifically, photoelectrons emitted from the output surface 302b of the photoelectric converter 300 can be incident on the input surface 102a of the MCP 102. When photoelectrons emitted from the output surface 302b of the photoelectric converter 300 are incident on the input surface 102a, the MCP 102 multiplies the electrons in response to the photoelectrons and emits the multiplied electrons from the output surface 102b. Electrons emitted from the output surface 102b of the MCP 102 are accelerated by the accelerating electrode 150 and focused by the focusing electrode 160. The AD 220 captures the electrons focused by the focusing electrode 160 and outputs them as an electrical signal, thereby detecting light.

[0115] Similarly, by adding the photoelectric conversion unit 300 to the ion detector 1B according to the second embodiment, a photodetector can be configured.

[0116] The AD drive circuit of each photodetector includes a capacitor C1 and a resistor R1. Furthermore, capacitor C1 and resistor R1 are connected in series with AD220 and in parallel with each other. This allows for faster response times for the entire photodetector, including AD220 and the AD drive circuit.

[0117] As described above, according to the detector according to the present disclosure, it is possible to increase the speed of response of the detector that detects charged particles or light using AD.

[0118] It is apparent from the above description of the present invention that various modifications can be made to the present invention. Such modifications should not be considered as departing from the spirit and scope of the present invention, and modifications obvious to all those skilled in the art are encompassed by the following claims.

Claims

1. A detector for detecting charged particles or light, the detector comprising: An avalanche diode comprising: a first electrode electrically connected to a power supply terminal having a first reference potential different from a ground potential; a second electrode electrically connected to a signal output terminal; an electron incident surface on which electrons generated by the charged particles, photoelectrons generated by the light, or electrons generated by multiplication of the photoelectrons are incident; and a driving circuit that drives the avalanche diode, The driving circuit comprises: a first capacitor disposed on a wiring between the power supply terminal and the first electrode of the avalanche diode and having a first terminal electrically connected to the power supply terminal and a second terminal electrically connected to the first electrode of the avalanche diode; and a first resistor having a first terminal electrically connected to the power supply terminal and a second terminal electrically connected to the first electrode of the avalanche diode; The first terminal of the first capacitor and the first terminal of the first resistor have the same potential, and the second terminal of the first capacitor and the second terminal of the first resistor have the same potential.

2. The detector according to claim 1, wherein The electrostatic capacitance of the first capacitor is 10 times or less than the electrostatic capacitance of the avalanche diode.

3. The detector according to claim 2, wherein The electrostatic capacitance of the first capacitor is less than or equal to the electrostatic capacitance of the avalanche diode.

4. The detector according to claim 1, wherein The resistance value of the first resistor is greater than or equal to 30 kΩ and less than or equal to 500 kΩ.

5. The detector according to claim 1, wherein The signal output terminal is electrically connected to a wiring between the second electrode of the avalanche diode and a node having a second reference potential different from the first reference potential. The driving circuit further includes a second capacitor having a first terminal electrically connected to both the first terminal of the first capacitor and the first terminal of the first resistor, and a second terminal having the same potential as the node. The detector according to claim 1 , wherein: The driving circuit also has a third capacitor as an AC coupler arranged on the wiring between the signal output terminal and the second electrode of the avalanche diode, and the third capacitor has a first terminal electrically connected to the second electrode of the avalanche diode and a second terminal electrically connected to the signal output terminal.

7. A detector for detecting charged particles or light, the detector comprising: An avalanche diode comprising: a first electrode electrically connected to a power supply terminal having a first reference potential different from a ground potential; a second electrode electrically connected to a signal output terminal; an electron incident surface on which electrons generated by the charged particles, photoelectrons generated by the light, or electrons generated by multiplication of the photoelectrons are incident; and a driving circuit that drives the avalanche diode, The driving circuit comprises: a first capacitor disposed on a wiring line located between the second electrode of the avalanche diode and a node having a second reference potential different from the first reference potential and electrically connected to the signal output terminal, the capacitor having a first terminal electrically connected to the second electrode of the avalanche diode and a second terminal electrically connected to the signal output terminal; and a first resistor having a first terminal electrically connected to the second electrode of the avalanche diode and a second terminal, The first terminal of the first resistor and the first terminal of the first capacitor have the same potential, The second terminal of the first resistor is electrically connected to the second terminal of the first capacitor so as to have the same potential as the second terminal of the first capacitor, or the second terminal of the first resistor has the same potential as the node.

8. The detector according to claim 7, wherein The electrostatic capacitance of the first capacitor is 10 times or less than the electrostatic capacitance of the avalanche diode.

9. The detector according to claim 8, wherein The electrostatic capacitance of the first capacitor is less than or equal to the electrostatic capacitance of the avalanche diode.

10. The detector according to claim 7, wherein The resistance value of the first resistor is greater than or equal to 30 kΩ and less than or equal to 500 kΩ.

11. The detector according to claim 7, wherein The drive circuit further includes a second capacitor having a first terminal electrically connected to the first electrode of the avalanche diode and a second terminal having the same potential as the node.

12. The detector according to any one of claims 1 to 11, wherein Also features: a microchannel plate having an input surface for the charged particles to be incident upon and an output surface for emitting the electrons generated by the charged particles; and Focusing electrode, The electrons emitted from the output surface of the microchannel plate are focused by the focusing electrode and then incident on the electron incident surface of the avalanche diode.

13. The detector according to any one of claims 1 to 11, wherein further comprising: a photoelectric conversion unit that converts the light into the photoelectrons; The photoelectrons or the electrons generated by multiplication of the photoelectrons are incident on the electron incident surface of the avalanche diode.

Images