阅读说明：本技术 离子检测器 (Ion detector ) 是由 小林浩之 高塚清香 于 2021-06-10 设计创作，主要内容包括：本发明的一种离子检测器具备：微通道板,其用于接受离子的入射而产生二次电子,将产生的所述二次电子倍增并输出；多个电子冲击型二极管,其在面向所述微通道板侧的电子入射面具有比所述微通道板的有效区域狭窄的有效区域,用于接受从所述微通道板输出的所述二次电子的入射,将入射的上述二次电子倍增并且检测；以及聚焦电极,其配置于所述微通道板与所述电子冲击型二极管之间,用于朝向所述电子冲击型二极管聚焦所述二次电子,所述多个电子冲击型二极管中的彼此相邻的至少一对上述电子冲击型二极管以通过彼此的所述电子入射面形成向所述微通道板侧或向与所述微通道板的相反侧凸出的角部的方式进行配置。(An ion detector according to the present invention includes: a microchannel plate for receiving an incident ion to generate a secondary electron, multiplying the generated secondary electron, and outputting the multiplied secondary electron; a plurality of electron impact diodes having an effective area narrower than an effective area of the microchannel plate on an electron incidence surface facing the microchannel plate side, for receiving incidence of the secondary electrons output from the microchannel plate, multiplying and detecting the incident secondary electrons; and a focusing electrode disposed between the microchannel plate and the electron impact diode for focusing the secondary electrons toward the electron impact diode, wherein at least one pair of the electron impact diodes adjacent to each other among the plurality of electron impact diodes is disposed so as to form a corner portion protruding toward the microchannel plate side or the opposite side to the microchannel plate by the electron incident surface of each other.)

1. An ion detector, wherein,

the disclosed device is provided with:

a microchannel plate for receiving an incident ion to generate a secondary electron, multiplying the generated secondary electron, and outputting the multiplied secondary electron;

a plurality of electron impact type diodes having an effective area narrower than an effective area of the microchannel plate on an electron incidence surface facing the microchannel plate side, for receiving incidence of the secondary electrons output from the microchannel plate, multiplying and detecting the incident secondary electrons; and

a focusing electrode disposed between the microchannel plate and the electron impact diode for focusing the secondary electrons toward the electron impact diode,

at least one pair of the electron impact diodes adjacent to each other among the plurality of electron impact diodes is disposed so that a corner portion protruding toward the microchannel plate side or the opposite side to the microchannel plate is formed by the electron incidence surfaces of the electron impact diodes.

2. The ion detector of claim 1,

the disclosed device is provided with: and a cover disposed between the focus electrode and the electron impact diode, and having an opening wider than an effective region of the electron impact diodes when viewed from an incident direction of secondary electrons of the electron impact diodes.

3. The ion detector of claim 2,

the opening is a long hole having a long side direction in which the effective regions of the pair of electron impact diodes are aligned.

4. The ion detector according to any one of claims 1 to 3,

an output terminal for outputting a detection signal is provided on each of the plurality of electron impact diodes on a side opposite to the electron incident surface,

the output terminals of the pair of electron impact diodes are arranged so as to form corner portions projecting toward the electron incident surface side or toward the opposite side to the electron incident surface.

5. The ion detector according to any one of claims 1 to 4,

the disclosed device is provided with: a voltage supply unit for applying a drive voltage to each of the plurality of electron impact diodes,

the voltage supply unit applies drive voltages having different values to at least two of the plurality of electron impact diodes, thereby making gains different from each other.

6. The ion detector according to any one of claims 1 to 5,

the electron impact type diode includes the active region and a non-active region located around the active region, as viewed from an incident direction of secondary electrons of the electron impact type diode,

the effective area is biased in at least one direction with respect to the center of the non-effective area when viewed from the incident direction,

the pair of electron impact diodes are disposed adjacent to each other on the deflection side of the effective region.

7. The ion detector according to any one of claims 1 to 6,

the disclosed device is provided with: a mask disposed between the focusing electrode and the electron impact diodes, for shielding a part of the secondary electrons incident on at least one of the electron impact diodes.

8. The ion detector of claim 7,

the mask is formed on the electron incident surface of the electron impact type diode.

9. The ion detector of claim 7,

the mask is disposed apart from the electron incident surface of the electron impact type diode.

Technical Field

The present disclosure relates to ion detectors. The ion detector to which the present disclosure relates may be used, for example, for mass analysis.

Background

Patent document 1 (patent No. 4869526) discloses a mass spectrometer. The mass analyzer includes: the ion source includes a pair of microchannel plates that generate secondary electrons due to an ion beam, a first anode that detects a part of the secondary electrons generated at the microchannel plates, and a second anode that is disposed at a subsequent stage of the first anode and detects the secondary electrons generated at the microchannel plates and passing through the through-holes of the first anode.

A conventional ion detector is disclosed in patent document 2 (patent No. 4848363). This conventional ion detector includes: the electron-collecting device comprises two superposed microchannel plates, a first current-collecting anode for detecting most of secondary electrons emitted from the microchannel plates, and a second current-collecting anode for detecting the rest of the secondary electrons emitted from the microchannel plates.

Disclosure of Invention

The mass analyzer described in patent document 1 achieves an increase in the dynamic range by selecting the ratio of the cross-sectional area of the perforations to the total cross-sectional area of the first anode so as to provide a certain degree of attenuation to the incident secondary electron beam. In the ion detector described in patent document 2, the dynamic range is expanded by using two first and second current collecting anodes having different sizes. As described above, expansion of the dynamic range is desired in the above-described technical fields.

On the other hand, patent document 3 (japanese patent application laid-open No. 2017-16949) discloses a charged particle detector including: the electron impact type electron impact detector includes a microchannel plate that emits secondary electrons in response to incidence of charged particles, a focusing electrode that focuses the secondary electrons emitted from the microchannel plate, and an electron impact type diode that receives incidence of the focused secondary electrons, multiplies the secondary electrons, and detects the multiplied secondary electrons. Even for a charged particle detector of such a structure, it is desirable to expand the dynamic range. For this reason, for example, in the charged particle detector described in patent document 3, it is conceivable to use a plurality of electron impact diodes in a manner of using a plurality of anodes described in patent documents 1 and 2.

In contrast, in patent document 2, two flat plate-shaped anodes are provided on the same plane. When such a configuration is applied to a configuration in which secondary electrons are focused by a focusing electrode as in the charged particle detector of patent document 3 and the effective regions of the two electron impact diodes are made to be the same plane, it is difficult to reliably include the effective regions in the focusing diameter of the secondary electrons generated by the focusing electrode, or it is necessary to set the focusing diameter of the secondary electrons generated by the focusing electrode to be large in order to include the effective regions, and thus it may be difficult to reliably secure the total gain.

Accordingly, an object of one aspect of the present disclosure is to provide an ion detector capable of reliably ensuring an overall gain.

An ion detector according to the present disclosure includes: a microchannel plate for receiving the incident ions to generate secondary electrons, multiplying the generated secondary electrons, and outputting the multiplied secondary electrons; a plurality of electron impact type diodes having an effective area narrower than an effective area of the microchannel plate on an electron incidence surface facing the microchannel plate side, for receiving incidence of secondary electrons output from the microchannel plate, multiplying the incident secondary electrons, and detecting the multiplied secondary electrons; and a focusing electrode disposed between the microchannel plate and the electron impact diode for focusing secondary electrons on the electron impact diode, wherein at least one pair of electron impact diodes adjacent to each other among the plurality of electron impact diodes are disposed so as to form a corner portion protruding toward the microchannel plate side or toward the opposite side to the microchannel plate by electron incident surfaces of the pair of electron impact diodes.

The ion detector is a structure comprising a microchannel plate, a focusing electrode, and a plurality of electron impact diodes. In particular, in the ion detector, at least one pair of electron impact diodes adjacent to each other among the plurality of electron impact diodes are arranged so as to form a corner portion protruding toward the microchannel plate side or the opposite side to the microchannel plate by the electron incidence surfaces of each other. Therefore, the effective regions can be arranged closer to each other than in the case where the electron incidence surfaces are arranged on the same plane. Therefore, by disposing the effective regions of the plurality of electron impact diodes closer to each other, it becomes easy to include the effective regions in the focal diameter of the secondary electrons generated by the focusing electrode, or the secondary electrons can be focused in a narrower range by the focusing electrode, and further, the total gain of the incident ions can be ensured reliably.

The present invention may further include: and a cover disposed between the focusing electrode and the electron impact diode, wherein an opening wider than the effective regions of the plurality of electron impact diodes is formed when viewed from the incident direction of the secondary electrons of the electron impact diode. In this case, the prevention of charging is achieved by the cover.

The opening may be a long hole having a longitudinal direction in which the effective regions of the pair of electron impact diodes are aligned. In this case, secondary electrons can be appropriately incident on the pair of electron impact diodes in which the effective regions are arranged closer to each other through the long holes of the cover.

An output terminal for outputting a detection signal may be provided on the opposite side of the electron incidence surface in each of the plurality of electron impact diodes, and the output terminals of the pair of electron impact diodes may be arranged so as to form corner portions projecting toward the electron incidence surface side or toward the opposite side of the electron incidence surface. In the case where the effective regions of the pair of electron impact type diodes are arranged close to each other as described above, the output terminals may be arranged in this manner.

The present invention may further include: and a voltage supply unit that applies a drive voltage to each of the plurality of electron impact diodes, wherein the voltage supply unit applies drive voltages having different values to at least two of the plurality of electron impact diodes, thereby making gains different from each other. In this case, for example, when the number of incident ions is small, detection by an electron impact diode having a relatively high gain is employed, and when the number of incident ions is large, detection by an electron impact diode having a relatively low gain is employed, whereby an appropriate detection result can be obtained in a wide range of the number of incident ions. That is, in this case, the dynamic range can be expanded.

The electron impact diode may include an effective region and an ineffective region located around the effective region as viewed from an incident direction of secondary electrons of the electron impact diode, the effective region may be biased in at least one direction with respect to a center of the ineffective region as viewed from the incident direction, and the pair of electron impact diodes may be arranged so that biased sides of the effective regions are adjacent to each other. In this case, by disposing the effective regions of the pair of electron impact type diodes closer, the dead zone can be reduced.

The present invention may further include: and a mask which is arranged between the focusing electrode and the electron impact type diode and shields a part of the secondary electrons incident on at least one electron impact type diode. As described above, by using the mask, the gain of the incident ions can be controlled.

The mask may be formed on the electron incidence surface of the electron impact diode, or the mask may be disposed separately from the electron incidence surface of the electron impact diode.

According to the present disclosure, an ion detector capable of reliably ensuring the total gain can be provided.

Drawings

Fig. 1(a) is a view showing an ion detector according to an embodiment, and is a cross-sectional view of the whole.

Fig. 1(b) is a plan view of the electron impact diode shown in fig. 1 (a).

Fig. 2(a) is a partially enlarged view of the ion detector shown in fig. 1(a), and is an enlarged view of the region AR of fig. 1 (a).

Fig. 2(b) is a partial side view of the area AR.

Fig. 3 is a schematic circuit diagram showing an example of the ion detector shown in fig. 1(a) and (b) and fig. 2(a) and (b).

Fig. 4(a) is a graph for explaining the operation and effect of the ion detector shown in fig. 1(a) and (b), fig. 2(a) and (b), and fig. 3, and is an example of a case where one electron impact diode is used (or a case where a plurality of electron impact diodes are used with the same gain).

Fig. 4(b) is a graph for explaining the operation and effect of the ion detector shown in fig. 1(a) and (b), fig. 2(a) and (b), and fig. 3, and relates to the ion detector according to the embodiment.

Fig. 5 is a schematic circuit diagram of an ion detector according to a modification.

Fig. 6 is a schematic circuit diagram of an ion detector according to another modification.

Fig. 7(a) is a plan view of a modification of the electron impact diode.

Fig. 7(b) is a plan view of a modification of the electron impact diode.

Detailed Description

An ion detector according to an embodiment will be described below. In the description of the drawings, the same or corresponding elements are denoted by the same reference numerals, and redundant description may be omitted.

Fig. 1(a) is a view showing an ion detector according to an embodiment, and is a cross-sectional view of the whole. Fig. 1(b) is a plan view of the electron impact diode shown in fig. 1 (a). As shown in fig. 1(a) and (b), the ion detector 1 includes a first cell 100 and a second cell 200. The first unit 100 has a microchannel plate (MCP110), an electron lens 120, and a mesh electrode 130. The ion detector 1 may be used for mass analysis, for example.

The MCP110 has a circular plate shape having an input surface 110a and an output surface 110b opposite to the input surface 110 a. The MCP110 is held by an input-side electrode 111 and an output-side electrode 112. For example, the MCP110 includes a main body, which is a thin disk-shaped structure mainly composed of lead glass, and a plurality of through holes, i.e., channels, extending in the thickness direction (the direction from the input surface 110a to the output surface 110 b) are formed in the main body except for an annular outer peripheral portion. Further, electrodes are formed on the outer peripheral portion of the input surface 110a and the outer peripheral portion of the output surface 110 b.

The MCP110 is configured to receive incident ions from the input surface 110a to generate secondary electrons, multiply the generated secondary electrons, and output the multiplied secondary electrons from the output surface 110 b. The gain of the MCP110 is determined by the ratio of the channel length to the channel diameter corresponding to the thickness of the MCP110 and the secondary electron emission coefficient inherent to the material, and is, for example, 1 to 10⁴The degree (e.g., 200).

An opening a1 is formed in the input side electrode 111 and the output side electrode 112. The opening a1 is orthogonal to the input surface 110a and the output surface 110b, and is formed in a circular shape centered on a reference axis Ax passing through the center of the MCP 110. The opening a1 defines an active area 110P of the MCP 110. That is, a region of the MCP110 exposed from the opening a1 is defined as an effective region 110P of the MCP110 as viewed in a direction along the reference axis Ax.

The electron lens 120 is disposed on the output surface 110b side of the MCP 110. The electron lens 120 includes a pair of focus electrodes 121 and 122 each disposed so as to surround the reference axis Ax. The focusing electrodes 121 and 122 are formed in a cylindrical shape with the reference axis Ax as the center. The focus electrode 121 is fixed to the mesh electrode 130 via an insulating spacer, and the focus electrode 122 is fixed to the focus electrode 121 via an insulating spacer. That is, the mesh electrode 130 is disposed between the MCP110 and the electron lens 120 (the focus electrode 121).

The mesh electrode 130 is at a higher potential than the output face 110b of the MCP 110. The mesh electrode 130 has a function of accelerating electrons and relatively reducing an angular component to improve convergence of electrons. The focusing electrodes 121 and 122 are disposed between the MCP110 and an electron impact diode, which will be described later, and focus secondary electrons output from the MCP110 on the electron impact diode.

Fig. 2(a) is a partially enlarged view of the ion detector shown in fig. 1(a), and is an enlarged view of the region AR of fig. 1 (a). Fig. 2(b) is a partial side view of the area AR. As shown in fig. 1(a) and (b) and fig. 2(a) and (b), the second cell 200 is disposed on the opposite side of the focus electrode 122 from the MCP 110. The second cell 200 has a cap 210 and a plurality of (here two) electron impact diodes 220A, 220B.

The electron impact diodes 220A and 220B are single-channel elements. The electron impact type diodes 220A, 220B are used to receive incidence of secondary electrons output from the MCP110 and focused by the focusing electrodes 121, 122, respectively, and multiply and detect the incident secondary electrons. The electron impact diodes 220A and 220B are avalanche diodes, for example. In this case, the gains of the electron impact diodes 220A, 220B are, for example, 100 to 800 (e.g., 400) in electron impact gain and 1 to 10 in avalanche gain²(e.g., 50). Thereby, ionsThe total gain of the detector 1 is for example 10⁶Degree (for example, 4 × 10)⁶)。

The electron impact diode 220A is mounted on the substrate 203A. The substrate 203A is attached to the focusing electrode 122 via an insulating spacer 201, and is fixed to a base 202 constituting the bottom of the ion detector 1. The electron impact diode 220B is similarly mounted on the substrate 203B fixed to the base 202.

The electron impact diode 220A includes an electron incident surface 200A facing the MCP110 and the focusing electrodes 121 and 122 and receiving incidence of secondary electrons. The electron impact diode 220A includes: an effective region 221A that is located at the center of the electron incidence plane 200A as viewed from the incidence direction of the secondary electrons (the direction along the reference axis Ax) and detects electrons; and a non-active area 222A which is located around the active area 221A and is covered with, for example, a mask without detecting electrons.

The electron impact diode 220B includes an electron incident surface 200B facing the MCP110 and the focusing electrodes 121 and 122 and receiving incidence of secondary electrons. The electron impact diode 220B includes: an effective region 221B that is located at the center of the electron incidence plane 200B as viewed from the incidence direction of the secondary electrons (the direction along the reference axis Ax) and detects electrons; and a non-active area 222B which is located around the active area 221B and is covered with, for example, a mask without detecting electrons. The effective regions 221A, 221B of the electron impact diodes 220A, 220B are narrower than the effective region 110P of the MC P110. The effective regions 221A and 221B of the electron impact diodes 220A and 220B are included in the focusing ranges of the secondary electrons generated by the focusing electrodes 121 and 122 on the electron incidence surfaces 200A and 200B.

Here, the electron impact diodes 220A and 220B are arranged symmetrically about the reference axis Ax. More specifically, the pair of electron impact diodes 220A and 220B are arranged so that the electron incidence surfaces 200A and 200B (or the planes of the electron incidence surfaces 200A and 200B) form corners projecting toward the opposite side of the MCP110, and are supported by the base 202 via the substrates 203A and 203B. Here, the corner formed by the electron incident surfaces 200A and 200B has the reference axis Ax as a vertex. Here, the substrates 203A and 203B on which the electron impact diodes 220A and 220B are mounted are inclined so as to form corners projecting toward the opposite side of the MCP 110.

Thus, for example, the distance DA between the effective regions 221A and 221B of the electron impact diodes 220A and 220B is shortened as compared with the case where the electron impact diodes 220A and 220B are arranged such that the electron incidence surfaces 200A and 200B are on the same plane. That is, the effective regions 221A and 221B are arranged close to each other.

On the other hand, the electron impact diode 220A is provided with an output terminal 223A (output port (coaxial connector)) for outputting a detection signal of the secondary electrons. The output terminal 223A protrudes and extends from the surface of the substrate 203A opposite to the surface on which the electron impact diode 220A is provided. In addition, an output terminal 223B (output port (coaxial connector)) for the same purpose is provided in the electron impact diode 220B. Output terminal 223B protrudes and extends from the surface of substrate 203B opposite to the surface on which electron impact diode 220B is provided.

The output terminals 223A and 223B (extensions of the extending directions of the output terminals 223A and 223B) are arranged so as to form corners protruding toward the electron incident surfaces 200A and 200B and the MCP 110. Here, the corner formed by the electron incident surfaces 200A and 200B and the corner formed by the output terminals 223A and 223B project in opposite directions to each other.

The cover 210 is disposed between the focus electrode 122 and the electron impact diodes 220A and 220B, and is sandwiched between the focus electrode 122 and the base 202 via, for example, an insulating spacer 201. An opening a2 centered on the reference axis Ax is formed in the cover 210. The opening a2 is wider than the effective regions 221A, 221B of the electron impact diodes 220A, 220B, as viewed from the incident direction of the secondary electrons of the electron impact diodes 220A, 220B. In particular, the opening a2 is a long hole whose longitudinal direction is the direction in which the effective regions 221A and 221B are aligned. As a result, the effective regions 221A and 221B are exposed from the opening a2 when viewed from the incident direction of the secondary electrons of the electron impact diodes 220A and 220B. In addition, opening a2 is narrower than opening a 1. The cover 210 is made of, for example, stainless steel.

Next, the electrical connection relationship of the ion detector 1 will be described. Fig. 3 is a schematic circuit diagram showing an example of the ion detector shown in fig. 1(a) and (b) and fig. 2(a) and (b). As shown in fig. 3, the ion detector 1 includes a main part and a voltage supply circuit. The main portion is composed of the first cell 100 and the second cell 200 described above. In the first unit 100, the resistance value between the input surface 110a and the output surface 110b of the MCP110 is, for example, 30M Ω. The mesh electrode 130 is connected between the resistor R1 and the resistor R2, and is connected to the ground potential GND via the resistor R2. The focus electrode 121 is set to the same potential as the output face 110b of the MCP 110. The focusing electrode 122 is connected to a negative potential via a resistor R3.

In the second cell 200, the electron impact diode 220A includes one terminal connected to the negative potential via the resistor R4 and the other terminal connected to the ground potential GND via the capacitor C1. A detection signal of the electron impact diode 220A is taken out from the signal line 500A connected to the output terminal 223A. The electron impact diode 220B includes one terminal connected to the negative potential via a resistor R5 and the other terminal connected to the ground potential GND via a capacitor C2. A detection signal of the electron impact diode 220B is taken out from the signal line 500B connected to the output terminal 223B.

The voltage supply circuit includes a power supply unit 300 and a power supply unit (voltage supply unit) 400. The power supply unit 300 includes a power supply V1 for setting the potential of the input surface 110a of the MCP110 via the terminal T1, and a power supply V2 for securing a predetermined potential difference between the terminal T2 connected to the output surface 110b of the MCP110 and the terminal T1. The power source V1 is disposed between the ground potential GND and the terminal T1, and generates an electromotive force for setting the potential of the terminal T1 to, for example, -7 kV. The power supply V2 generates electromotive force so as to secure a potential difference of, for example, about 0 to 3.5kV as a potential difference between the input surface 110a and the output surface 110 b.

The power supply unit 400 includes a power supply V3 connected to one terminal of the electronic impact diode 220A via a terminal T3 and a resistor R4, and a power supply V4 connected to one terminal of the electronic impact diode 220B via a terminal T4 and a resistor R5. The power source V3 is disposed between the ground potential GN D and the terminal T3, and generates an electromotive force for setting the potential of the terminal T3 to 350V, for example. The power source V4 is disposed between the ground potential GND and the terminal T4, and generates an electromotive force of, for example, 250V for setting the potential of the terminal T4 to a potential different from the potential of the terminal T3.

That is, the power supply unit 400 applies a drive voltage to each of the electron impact diodes 220A and 220B, and applies drive voltages having different values to each of the electron impact diodes 220A and 220B, thereby making the gains different from each other. The difference in gain between the electron impact diodes 220A and 220B is, for example, about 10 times. As described above, in the ion detector 1, the secondary electrons emitted from the MCP110 are focused by the focusing electrodes 121 and 122, and a plurality of (here, two) electron impact diodes 220A and 220B having different gains are input.

Next, the operation and effect of the ion detector 1 will be described. Fig. 4(a) is a graph for explaining the operation and effect of the ion detector shown in fig. 1(a) and (b), fig. 2(a) and (b), and fig. 3, and shows an example of a case where one electron impact diode is used (or a case where a plurality of electron impact diodes are used with the same gain).

Fig. 4(b) is a graph for explaining the operation and effect of the ion detector shown in fig. 1(a) and (b), fig. 2(a) and (b), and fig. 3, and relates to the ion detector according to the embodiment. In this case, in the case where the gain is relatively high (line L1), when a large number of ions are incident on the ion detector (when the number of incident ions becomes large), saturation of the detector or an over range in the digitizer occurs. On the other hand, in this case, in the case where the gain is relatively low (line L2), the detection of a single ion is difficult. Therefore, it is necessary to perform measurement a plurality of times while changing the gain.

In contrast, as shown in fig. 4 b, in the ion detector 1 according to the present embodiment, when the number of incident ions is small, single ions can be appropriately detected by the detection signal (line L3) of the electron impact diode having a relatively high gain, and when the number of incident ions is large, the gain is relatively low, and the influence of saturation of the detector can be reduced by the detection signal (line L4) of the electron impact diode having a large upper limit of the number of saturated incident ions. That is, according to the ion detector 1, the dynamic range is expanded. Fig. 4(b) is a graph for explaining the operation and effect of the ion detector shown in fig. 1(a) and (b), fig. 2(a) and (b), and fig. 3, and relates to the ion detector according to the embodiment.

In the ion detector 1, the power supply unit 400 applies a driving voltage to the electron impact diodes 220A and 220B so that the detection range of the electron impact diodes having relatively high gains (here, the range of about 1 to 1000 incident ions) and the detection range of the electron impact diodes having relatively low gains (here, the range of about 10 to 10000 incident ions) have overlapping ranges S that partially overlap each other.

The repetition range S is a range between the lower limit of the number of detectable incident ions of the electron impact type diode having a relatively low gain (here, 10 degrees) and the upper limit of the number of detectable incident ions of the electron impact type diode having a relatively high gain (here, 1000 degrees). By providing such a repetition range S, it is possible to calibrate the electron impact diodes having different gains from each other by using the repetition range S.

As described above, the ion detector 1 includes the MCP110, the focusing electrodes 121 and 122, and the electron impact diodes 220A and 220B. In particular, in the ion detector 1, a pair of electron impact diodes 220A and 220B adjacent to each other are disposed so that the electron incidence surfaces 200A and 200B form corners projecting toward the opposite side of the MCP 110. Therefore, the effective regions 221A and 221B can be arranged closer to each other than when the electron incidence surfaces 200A and 200B are arranged on the same plane.

Therefore, by disposing the effective regions 221A and 221B of the electron impact diodes 220A and 220B closer to each other, the effective regions 221A and 221B can be included in the focal diameters of the secondary electrons generated by the focusing electrodes 121 and 122, or the secondary electrons can be focused in a narrower range by the focusing electrodes 121 and 122, and further, the total gain of the incident ions can be ensured reliably.

In addition, even in the ion detector 1 having the above structure, an expansion of the dynamic range is desired. Therefore, in the ion detector 1, the power supply unit 400 applies the drive voltages having different values to the two electron impact diodes 220A and 220B, respectively, so that the gains are different from each other. Thus, for example, when the number of incident ions is small, detection by an electron impact diode having a relatively high gain is employed, and when the number of incident ions is large, detection by an electron impact diode having a relatively low gain is employed, whereby an appropriate detection result can be obtained over a wide range of the number of incident ions. That is, according to the ion detector 1, the dynamic range can be expanded. In the ion detector 1, when a plurality of electron impact diodes having different gains are used as described above, crosstalk can be suppressed by using a plurality of single-channel elements as compared with the case of using a multi-channel element.

In the ion detector 1, the effective regions 221A and 221B of the electron impact diodes 220A and 220B are included in the focusing range of the secondary electrons generated by the focusing electrodes 121 and 122. Therefore, secondary electrons can be made to enter the effective regions 221A and 221B of the electron impact diodes 220A and 220B in the same manner.

The ion detector 1 is disposed between the focusing electrodes 121 and 122 and the electron impact diodes 220A and 220B, and includes: and a cover 210 having an opening a2 wider than the effective regions 221A, 221B when viewed from the incident direction of the secondary electrons of the electron impact diodes 220A, 220B. Therefore, the prevention of charging can be achieved by the cover 210.

In the ion detector 1, the opening a2 is a long hole having the direction in which the effective regions 221A and 221B of the electron impact diodes 220A and 220B are aligned as the longitudinal direction. Therefore, secondary electrons can be appropriately incident on the pair of electron impact diodes 220A and 220B in which the effective regions 221A and 221B are disposed closer to each other as described above, via the long hole of the cover 210.

In the ion detector 1, output terminals 223A and 223B for outputting detection signals are provided on the electron impact diodes 220A and 220B, respectively, on the opposite side to the electron incidence surfaces 200A and 200B. The output terminals 223A and 223B are arranged so as to form corner portions projecting toward the electron incident surfaces 200A and 200B. When the effective regions 221A and 221B of the pair of electron impact diodes 220A and 220B are arranged close to each other as described above, the output terminals 223A and 223B may be arranged as described above.

The above embodiments are examples of the ion detector according to the present disclosure. Therefore, the ion detector according to the present disclosure can arbitrarily modify the above-described ion detector. Next, a modified example will be explained.

Fig. 5 is a schematic circuit diagram of an ion detector according to a modification. As shown in fig. 5, the ion detector 1A is different from the ion detector 1 in that the power supply unit 400 is provided instead of the power supply unit 400, and is matched with the ion detector 1 at other points, as compared with the ion detector 1. The power supply unit (voltage supply unit) 400A includes a single power supply V5 connected to one terminal of the electronic impact diode 220A via a resistor R6, a terminal T3, and a resistor R4, and connected to one terminal of the electronic impact diode 220B via a resistor R7, a terminal T4, and a resistor R5. The power supply unit 400A includes a zener diode D1 interposed between the resistor R6 and the ground potential GND, and a zener diode D2 interposed between the resistor R7 and the ground potential GND.

By adjusting the relative relationship between the resistance values of the resistor R6 and the resistor R7, the power supply unit 400A can apply different drive voltages to the two electron impact diodes 220A and 220B, thereby making the gains different from each other. In addition, in the ion detector 1, by using the zener diodes D1, D2, it is possible to supply a voltage to the two electron impact diodes 220A, 220B by one power supply V5.

Fig. 6 is a schematic circuit diagram of an ion detector according to another modification. As shown in fig. 6, the ion detector 1B includes a power supply unit 600 as a voltage supply circuit. In the power supply unit 600, a power supply V1 is connected to the input surface 110a of the MCP110 via a terminal T1. The power supply V1 has a function for the floating ion detector 1B. The power supply unit 600 includes a power supply V6 and a power supply V7. The power source V6 is interposed between the terminal T1 connected to the input surface 110a and the terminal T2 connected to the output surface 110 b. The power supply V6 is used to apply a voltage (e.g., 0V to 1000V) to the MCP 110. The power source V7 is interposed between the terminal T2 and the terminal T3. The power supply V7 is used to supply a voltage (for example, 3kV to 7kV) to the focusing electrodes 121 and 122 and the electron impact diodes 220A and 220B at a later stage than the MCP 110.

The resistors R1 and R2 are discharge resistors for supplying electric potentials to the mesh electrode 130 and the focus electrodes 121 and 122. The capacitors C1, C2 form a loop through which a high-speed signal can return to the other terminal of the electron impact diodes 220A, 220B with low impedance via the ground potential GND. The capacitors C1 and C2 and the resistors R4 and R5 constitute a low-pass filter, and have a function of removing power supply noise. The resistor R3 has a function for preventing coupling of the focus electrode 122 with the ground potential GND.

The capacitor C3 is provided on the signal line 500A connected to the output terminal 223A of the electron impact diode 220A, and the capacitor C4 is provided on the signal line 500B connected to the output terminal 223B of the electron impact diode 220B. The capacitors C3 and C4 are coupling capacitors, and pass high-frequency signals while maintaining the potential of the other terminal of the electron impact diodes 220A and 220B. A resistor R9 is connected to the front stage of the capacitor C3 of the signal line 500A. Further, a resistor R10 is provided in the front stage of the capacitor C4 of the signal line 500B.

The resistors R9 and R10 are blocking resistors (blocking resistors), and have a function of preventing a signal from returning to the power supply unit 600 while applying a potential to one terminal of the electronic impact diodes 220A and 220B. A line provided with the zener diode D3 and a line provided with the resistor R8 and the zener diode D4 are formed between the resistor R2 and the resistors R9 and R10, respectively. The resistor R8 has a function for absorbing the potential difference between the zener diodes D3, D4.

The ion detector floats while detecting positive and negative ions. At this time, by using the zener diodes D3 and D4, the voltage can be supplied to the electronic surge diodes 220A and 220B without increasing the power supply. For example, if a diode of 350V is used as the zener diode D3 and a diode of 250V is used as the zener diode D4, voltages different from each other can be applied to the electron impact diodes 220A and 220B.

Here, fig. 7(a) is a plan view of a modification of the electron impact diode. As shown in fig. 7(a), in the ion detectors 1 to 1B, the effective regions 221A and 221B can be disposed closer to each other by cutting off a part of the electron impact diodes 220A and 220B. Here, the non-effective regions 222A and 222B are partially cut out so as to shorten the lengths of a pair of sides of the electron impact diodes 220A and 220B facing each other when viewed from the incident direction of the secondary electrons.

Thus, when the electron impact diodes 220A and 220B are viewed from the incident direction of the secondary electrons, the effective regions 221A and 221B are shifted in one direction (cut-off side) with respect to the centers of the ineffective regions 222A and 222B. Therefore, by disposing the two electron impact diodes 220A and 220B so that the deflection sides of the effective regions 221A and 221B are adjacent to each other, the effective regions 221A and 221B can be disposed closer to each other.

Fig. 7(b) is a plan view of a modification of the electron impact diode. As shown in fig. 7B, the ion detectors 1 to 1B may include a mask M for shielding a part of the secondary electrons incident on at least one electron impact diode (here, the electron impact diode 220B) of the plurality of electron impact diodes. The mask M may be disposed at any position between the focusing electrode 122 and the electron impact type diode 220B. For example, the mask M may be formed on the electron incident surface 200B of the electron impact diode 220B. In this case, the mask M may be formed by, for example, a film formed by depositing Al on the surface to be the electron incident surface 200B after the process of the electron impact diode 220B, or a film formed by ion implantation from the surface side to be the electron incident surface 200B of the electron impact diode 220 in the process.

On the other hand, the mask M may be disposed separately from the electron incident surface 200B. In this case, the mask M may be formed by, for example, providing a mesh on the trajectories of the secondary electrons focused by the focusing electrodes 121 and 122 toward the electron impact type diode 220B. In this case, the mask M may be provided in the opening a2 of the cover 210.

Further, at least one of the plurality of electron impact diodes may be arranged offset so that a part of an effective region thereof is located outside a focal path of the secondary electrons, thereby controlling an amount of incidence of the secondary electrons to the electron impact diode.

As described above, in the ion detectors 1 to 1B, as a method of making the gains of at least two electron impact diodes of the plurality of electron impact diodes different from each other, a method of making the driving voltages different from each other, a method of shielding the secondary electrons using a mask, and a method of adjusting the amount of incident secondary electrons by shifting the effective region may be arbitrarily combined and used. That is, as an example, one of the above-described methods may be applied to a pair of electron impact diodes, and the other of the above-described methods may be applied to the other pair of electron impact diodes. The above-described method may be arbitrarily applied, and the gains of 3 or more electron impact diodes may be different from each other.

In the ion detectors 1 to 1B, the configuration in which the pair of electron impact diodes 220A and 220B are arranged so as to form the corner portions protruding to the opposite side from the MCP110 by the electron incident surfaces 200A and 200B as shown in fig. 2(B) is not essential from the viewpoint of making the gains of at least two of the plurality of electron impact diodes different from each other. In the ion detectors 1 to 1B, it is not necessary to have a structure in which the gains of at least two electron impact diodes are different from each other in view of disposing the effective regions 210A and 210B closer to each other.

In addition, it is also possible: contrary to the example shown in fig. 2(B), the pair of electron impact diodes 220A, 220B are arranged so that the corners protruding toward the MCP110 side are formed by the electron incident surfaces 200A, 200B (or by extending the planes of the electron incident surfaces 200A, 200B). In this case, the output terminals 223A and 223B (extensions of the extending directions of the output terminals 223A and 223B) may be arranged to form corner portions projecting toward the opposite side of the electron incidence surfaces 200A and 200B and the MCP 110.

In the above embodiment, the example in which two electron impact diodes 220A and 220B are provided has been described, but the ion detectors 1 to 1B may be provided with 3 or more electron impact diodes.