ion detector

Abstract

The present application provides an ion detector capable of detecting bipolar ions while reducing the size of a circuit, the ion detector including: a first electron multiplier for detecting first ions having a first polarity; a second electron multiplier for detecting second ions having a second polarity different from the first polarity; a first anode for capturing electrons emitted from the first electron multiplier; a second anode for capturing electrons emitted from the second electron multiplier; and a switching circuit including a first input terminal electrically connected to the first anode, a second input terminal electrically connected to the second anode, and an output terminal, either of the first input terminal and the second input terminal being selectively connected to the output terminal.

Description

Technical Field

[0001] This invention relates to ion detectors. Background Technology

[0002] Ion detectors for detecting positive and negative ions are known. For example, Japanese Patent Application Publication No. 52-119290 describes an ion detector equipped with an electron multiplier tube for detecting cations (positive ions) and an electron multiplier tube for detecting anions (negative ions). Summary of the Invention

[0003] The ion detector described in Japanese Patent Application Publication No. 52-119290 includes signal processing circuits such as amplifiers dedicated to the outputs of electron multiplier tubes for positive ion detection and electron multiplier tubes for negative ion detection. This results in an increased circuit size. In this technical field, it is desirable to detect bipolar ions while reducing the circuit size.

[0004] This invention describes an ion detector capable of detecting bipolar ions while reducing circuit size.

[0005] An ion detector according to one aspect of the present invention includes: a first electron multiplier for detecting a first ion having a first polarity; a second electron multiplier for detecting a second ion having a second polarity different from the first polarity; a first anode for capturing electrons emitted from the first electron multiplier; a second anode for capturing electrons emitted from the second electron multiplier; and a switching circuit including a first input terminal electrically connected to the first anode, a second input terminal electrically connected to the second anode, and an output terminal, wherein either the first input terminal or the second input terminal is selectively connected to the output terminal.

[0006] In this ion detector, the first anode, which captures electrons emitted from a first electron multiplier used to detect a first ion of the first polarity, is electrically connected to the first input terminal of a switching circuit. The second anode, which captures electrons emitted from a second electron multiplier used to detect a second ion of the second polarity, is electrically connected to the second input terminal of the switching circuit. Because the switching circuit selectively connects either the first or second input terminal to the output terminal, signals related to the detection of the first ion and the detection of the second ion are selectively output from the output terminal. Therefore, a signal processing circuit shared by both the first and second ion detections can be provided in the subsequent stage of the ion detector, eliminating the need for separate dedicated signal processing circuits for each. As a result, bipolar ions can be detected while reducing the circuit size.

[0007] The aforementioned ion detector may further include an ion-introducing portion having a through-hole with a central axis extending along a first direction. The first electron multiplier may also include a first multiplier extending along the first direction, a first input electrode disposed at one end of the first multiplier in the first direction, and a first output electrode disposed at the other end of the first multiplier in the first direction. The second electron multiplier may also include a second multiplier extending along the first direction, a second input electrode disposed at one end of the second multiplier in the first direction, and a second output electrode disposed at the other end of the second multiplier in the first direction. The first input electrode may also receive a first ion passing through the through-hole. The second input electrode may also receive a second ion passing through the through-hole. The first electron multiplier and the second electron multiplier may also be spaced apart from each other in a second direction intersecting the first direction. In this case, the first electron multiplier and the second electron multiplier are spaced apart from each other in the second direction and are arranged extending along the first direction. Both the first input electrode and the second input electrode are opposite to the ion-introducing portion in the first direction. Therefore, the possibility of noise from charged particles generated in the second electron multiplier at the first input electrode can be reduced. Similarly, the possibility of noise from charged particles generated in the first electron multiplier at the second input electrode can be reduced. As a result, the detection accuracy of the first and second ions can be improved.

[0008] The first input electrode may also include a first main body portion opposite to the ion introduction portion in the first direction and a first extension portion extending toward the first output electrode in the first direction. The first extension portion may also cover the portion of the first multiplier portion opposite to the second multiplier portion. For example, a negative voltage is applied to the first input electrode and a positive voltage is applied to the second input electrode. As the voltage moves from the first input electrode to the first output electrode, the voltage of the first multiplier portion increases, and as the voltage moves from the second input electrode to the second output electrode, the voltage of the second multiplier portion increases. Therefore, even if the absolute value of the applied voltage at the first input electrode is equal to the absolute value of the applied voltage at the second input electrode, the difference between the absolute values ​​of the voltages of the first and second multiplier portions increases as the voltage moves toward the output electrode. In the above structure, the first extension portion of the first input electrode covers the portion of the first multiplier portion opposite to the second multiplier portion, thus improving the symmetry of the positive and negative potential gradients in the ion movement region. Therefore, the detection accuracy of the first and second ions can be improved.

[0009] The first extension can also have a cylindrical shape. In this case, the end containing the first multiplier is surrounded by the first extension around its axis. Compared to a structure where a portion of the end containing the first multiplier is covered by the first extension, the symmetry of the positive and negative potential gradients can be improved in the region where ions move. Therefore, the detection accuracy of the first and second ions can be further improved.

[0010] The second input electrode may also include a second main body portion opposite to the ion introduction portion in the first direction and a second extension portion extending toward the second output electrode in the first direction. The second extension portion may also cover the portion of the second multiplier portion opposite to the first multiplier portion. Because the second extension portion of the second input electrode covers the portion of the second multiplier portion opposite to the first multiplier portion, the symmetry of the positive and negative potential gradients in the region where ions move can be improved. Therefore, the detection accuracy of the first and second ions can be improved.

[0011] The second extension can also have a cylindrical shape. In this case, the end containing the second multiplier is surrounded by the second extension around its axis. Compared to a structure where a portion of the end containing the second multiplier is covered by the second extension, the symmetry of the positive and negative potential gradients in the region where ions move can be improved. Therefore, the detection accuracy of the first and second ions can be further improved.

[0012] The distance between the first electron multiplier and the central axis in the second direction can also be equal to the distance between the second electron multiplier and the central axis in the second direction. In this case, the design of the configuration of the first and second electron multipliers can be simplified.

[0013] The first ion can be a positive ion. The second ion can be a negative ion. The distance between the first electron multiplier and the central axis in the second direction can also be greater than the distance between the second electron multiplier and the central axis in the second direction. As described above, by breaking the symmetry between the positive and negative potential gradients in the region where the ion moves, the force causing the first ion to detach from the second electron multiplier in the second direction is greater than the force causing the second ion to detach from the first electron multiplier in the second direction. That is, the first ion moves further away from the central axis than the second ion. According to the above structure, the first electron multiplier is farther away from the central axis than the second electron multiplier, thus increasing the probability that the first ion will be incident on the first input electrode and the second ion will be incident on the second input electrode. Therefore, the detection accuracy of the first and second ions can be improved.

[0014] The aforementioned ion detector may also include a substrate having a main surface facing the ion introduction portion in a first direction. A first anode and a second anode may also be disposed on the main surface. A first electron multiplier is disposed on the main surface with its first output electrode facing the first anode in the first direction. A second electron multiplier may also be disposed on the main surface with its second output electrode facing the second anode in the first direction. In this case, the first electron multiplier and the second electron multiplier are disposed on a single substrate. Therefore, the distance between the first electron multiplier and the second electron multiplier is fixed, thereby improving the assembly accuracy of the ion detector.

[0015] The switching circuit can also be mounted on the substrate. In this case, the components of the ion detector can be mounted on a single substrate. Therefore, the number of components can be reduced.

[0016] A gap penetrating the substrate in the first direction may also be provided between the first anode and the second anode in the substrate. When the potential difference between the first anode and the second anode is large, surface discharge may sometimes occur between the first anode and the second anode along the main surface of the substrate. In the above structure, because a gap is provided between the first anode and the second anode, the surface distance between the first anode and the second anode becomes longer. As a result, the possibility of surface discharge occurring between the first anode and the second anode can be reduced.

[0017] The ion detector described above is mounted on the main surface and may further include a support member that supports the ion introduction section. In this case, because the ion introduction section is supported by the support member, the position of the central axis (through hole) is fixed. Therefore, the assembly accuracy of the ion detector can be improved.

[0018] The aforementioned ion detector may further include a first substrate having a first main surface opposite to the ion-introducing portion in a first direction and a second substrate having a second main surface opposite to the ion-introducing portion in the first direction. A first anode may also be disposed on the first main surface. A second anode may also be disposed on the second main surface. A first electron multiplier may also be disposed on the first main surface with a first output electrode opposite to the first anode in the first direction. A second electron multiplier may also be disposed on the second main surface with a second output electrode opposite to the second anode in the first direction. In this case, because the first anode and the second anode are disposed on different substrates, the possibility of surface discharge occurring between the first anode and the second anode can be reduced.

[0019] According to the present invention, it is possible to detect bipolar ions while reducing the circuit size. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating the structure of an ion detector according to one embodiment.

[0021] Figure 2 It means Figure 1 A cross-sectional view of an example installation of an ion detector.

[0022] Figure 3 yes Figure 2 The top view of the substrate shown.

[0023] Figure 4 It means Figure 2 The diagram shows the isopotential lines during positive ion detection by the ion detector.

[0024] Figure 5 It means Figure 2 The diagram shows the isopotential lines of the ion detector during negative ion detection.

[0025] Figure 6 This is a diagram showing the isopotential lines during positive ion detection in an ion detector of another installation example.

[0026] Figure 7 This is a diagram showing the isopotential lines during negative ion detection in an ion detector of another installation example.

[0027] Figure 8 It means Figure 1 A cross-sectional view of another installation example of the ion detector shown.

[0028] Figure 9 It means Figure 1 A cross-sectional view of another installation example of the ion detector shown. Detailed Implementation

[0029] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, in the description of the drawings, the same elements are labeled with the same reference numerals, and repeated descriptions are omitted.

[0030] Reference Figure 1 This describes the general structure of an ion detector according to one embodiment. Figure 1 Yes, this is a schematic diagram of the structure of an ion detector according to one embodiment. Figure 1 The ion detector 1 shown is a device capable of detecting bipolar ions. Ion detector 1 is, for example, suitable for a mass analysis apparatus. Ion detector 1 includes an ion introduction unit 2, an electron multiplier 3 (first electron multiplier), an electron multiplier 4 (second electron multiplier), an anode 5 (first anode), an anode 6 (second anode), a capacitor 7, a capacitor 8, and a switching circuit 9.

[0031] Ion introduction section 2 allows ions to pass from the outside of ion detector 1 through the internal space S of ion detector 1 (refer to...). Figure 2The ion-introducing part 2 can also be a perforated component that blocks external noise. The ion-introducing part 2 includes an ion lens 21 and an ion lens 22. The ion lens 21 is a plate-shaped conductive component. An opening 21a is provided in the ion lens 21, penetrating through it. The ion lens 21 is grounded, for example.

[0032] The ion lens 22 is a plate-shaped conductive component. An opening 22a is provided through the ion lens 22. The ion lens 22 is configured such that the central axis of the opening 21a coincides with the center of the opening 22a. That is, a through hole 2a with a central axis AX is provided in the ion introduction section 2. The through hole 2a is composed of the opening 21a and the opening 22a.

[0033] A positive or negative voltage is selectively applied to the ion lens 22. When the ion detector 1 detects a positive ion (a first ion with a first polarity), a negative voltage is applied to the ion lens 22. Through this structure, positive ions pass sequentially through openings 21a and 22a, thereby converging and being guided into the internal space S. When the ion detector 1 detects a negative ion (a second ion with a second polarity), a positive voltage is applied to the ion lens 22. Through this structure, negative ions pass sequentially through openings 21a and 22a, thereby converging and being guided into the internal space S. The positive voltage applied to the ion lens 22 is, for example, approximately 500V. The negative voltage applied to the ion lens 22 is, for example, approximately -500V.

[0034] Electron multiplier 3 is a structure used for detecting positive ions. Electron multiplier 4 is a structure used for detecting negative ions. Examples of electron multipliers 3 and 4 include a channel electron multiplier (CEM), an electron multiplier tube (EM tube), a combination of a microchannel plate (MCP) and an avalanche diode (AD), an MSP (including an MCP, a scintillator, and a photomultiplier tube (PMT)), and combinations of two of these. Conversion nodes (CDs) can also be further provided in the CEM, EM tube, and AD. In this embodiment, CEM is used as an example of electron multipliers 3 and 4.

[0035] The electron multiplier 3 includes a multiplier section 31 (first multiplier section), an input electrode 32 (first input electrode), and an output electrode 33 (first output electrode). The multiplier section 31 extends in one direction and has, for example, a cuboid shape. The multiplier section 31 has end faces 31a and 31b. End face 31a (one end) is an end face of the multiplier section 31 in the longitudinal direction, opposite to the ion-introducing section 2. End face 31b (the other end) is an end face of the multiplier section 31 in the longitudinal direction opposite to end face 31a. The multiplier section 31 contains, for example, an insulating material such as ceramic. The multiplier section 31 has multiple channels extending from end face 31a to end face 31b.

[0036] The input electrode 32 receives positive ions passing through the through-hole 2a and converts them into electrons. The input electrode 32 is disposed on the end face 31a. The input electrode 32 is made of a conductive metallic material. A negative high voltage is applied to the input electrode 32. For example, a voltage of approximately -10 kV is applied to the input electrode 32.

[0037] An output electrode 33 is disposed on end face 31b. The output electrode 33 is made of a conductive metallic material. A negative high voltage, greater than the voltage applied to the input electrode 32, is applied to the output electrode 33. That is, a negative high voltage is applied to the output electrode 33 such that the potential of the output electrode 33 is higher than the potential of the input electrode 32. The voltage applied to the output electrode 33 is about 2 to 4 kV greater than the voltage applied to the input electrode 32. Through the input electrode 32 and the output electrode 33, a potential gradient is generated in the multiplier section 31 along its length direction, such that the potential becomes higher as it moves from end face 31a to end face 31b.

[0038] The electron multiplier 4 includes a multiplier section 41 (second multiplier section), an input electrode 42 (second input electrode), and an output electrode 43 (second output electrode). The multiplier section 41 extends in one direction and has, for example, a cuboid shape. The multiplier section 41 has end faces 41a and 41b. End face 41a (one end) is an end face of the multiplier section 41 in the longitudinal direction, opposite to the ion introduction section 2. End face 41b (the other end) is an end face of the multiplier section 41 in the longitudinal direction opposite to end face 41a. The multiplier section 41 contains, for example, an insulating material such as ceramic. The multiplier section 41 has multiple channels extending from end face 41a to end face 41b.

[0039] The input electrode 42 receives negative ions passing through the through-hole 2a and converts the negative ions into electrons. The input electrode 42 is disposed on the end face 41a. The input electrode 42 is made of a conductive metallic material. A positive high voltage is applied to the input electrode 42. For example, a voltage of approximately +10 kV is applied to the input electrode 42.

[0040] An output electrode 43 is disposed on end face 41b. The output electrode 43 is made of a conductive metallic material. A positive high voltage, greater than the voltage applied to the input electrode 42, is applied to the output electrode 43. That is, a positive high voltage is applied to the output electrode 43 such that the potential of the output electrode 43 is higher than the potential of the input electrode 42. The voltage applied to the output electrode 43 is about 2 to 4 kV greater than the voltage applied to the input electrode 42. Through the input electrode 42 and the output electrode 43, a potential gradient is generated in the multiplier section 41 along the length direction of the multiplier section 41, such that the potential becomes higher as it moves from end face 41a to end face 41b.

[0041] Anode 5 is the electrode that captures electrons emitted from electron multiplier 3. Anode 5 outputs an electrical signal corresponding to the captured electron. Anode 5 outputs an electrical signal to switching circuit 9 via capacitor 7. Anode 6 is the electrode that captures electrons emitted from electron multiplier 4. Anode 6 outputs an electrical signal corresponding to the captured electron. Anode 6 outputs an electrical signal to switching circuit 9 via capacitor 8.

[0042] Capacitors 7 and 8 are AC (Alternating Current) coupling capacitors. Capacitor 7 removes the DC (Direct Current) offset voltage from the electrical signal output from anode 5. Capacitor 8 removes the DC offset voltage from the electrical signal output from anode 6.

[0043] The switching circuit 9 is a circuit used to selectively connect anode 5 or anode 6 to a subsequent signal processing circuit such as an amplifier. Examples of switching circuits 9 include RF (Radio Frequency) switching ICs (Integrated Circuits) and contactless relays. Examples of contactless relays include MOSFETs (Metal-Oxide Semiconductor Field-Effect Transistors). The switching circuit 9 selects the anode of the target object from anode 5 and anode 6 based on a switching signal from an external source. The switching circuit 9 includes an input terminal 9a (first input terminal), an input terminal 9b (second input terminal), and an output terminal 9c. Input terminal 9a is electrically connected to anode 5. In this embodiment, input terminal 9a is electrically connected to anode 5 via capacitor 7. Input terminal 9b is electrically connected to anode 6. In this embodiment, input terminal 9b is electrically connected to anode 6 via capacitor 8. Output terminal 9c is electrically connected to a subsequent signal processing circuit.

[0044] The switching circuit 9 selectively connects either input terminal 9a or input terminal 9b to output terminal 9c. The switching circuit 9 switches between a first state and a second state based on an external switching signal. The first state is a state where input terminal 9a is electrically connected to output terminal 9c and the resistance between input terminal 9b and output terminal 9c is disconnected. The second state is a state where the resistance between input terminal 9a and output terminal 9c is disconnected and input terminal 9b is electrically connected to output terminal 9c.

[0045] The switching circuit 9 includes switches 91 and 92. Switch 91 is disposed between input terminal 9a and output terminal 9c. Switch 91 is configured to switch between an "on" state, which electrically connects input terminal 9a and output terminal 9c, and an "off" state, which disconnects the resistance between input terminal 9a and output terminal 9c. Switch 92 is disposed between input terminal 9b and output terminal 9c. Switch 92 is configured to switch between an "on" state, which electrically connects input terminal 9b and output terminal 9c, and an "off" state, which disconnects the resistance between input terminal 9b and output terminal 9c. According to a switching signal, switches 91 and 92 are set to opposite states. That is, when switch 91 is set to the "on" state, switch 92 is set to the "off" state (first state), and when switch 91 is set to the "off" state, switch 92 is set to the "on" state (second state).

[0046] Next, the operation of ion detector 1 will be explained. When ion detector 1 detects positive ions, switch 91 is set to the on state and switch 92 is set to the off state. Then, a negative voltage is applied to ion lens 22. Positive ions are attracted by the negative voltage of ion lens 22 and are introduced into the internal space S of ion detector 1 through openings 21a and 22a in sequence. Then, because a negative high voltage is being applied to input electrode 32, positive ions move towards input electrode 32 and are injected into input electrode 32. Electrons generated corresponding to the positive ions injected into input electrode 32 are multiplied in multiplier 31 and emitted from output electrode 33. Then, the electrons emitted from output electrode 33 are captured by anode 5, and the electrical signal generated by these electrons is output to input terminal 9a via capacitor 7. In switching circuit 9, because input terminal 9a and output terminal 9c are electrically connected, the electrical signal is output from output terminal 9c to the subsequent signal processing circuit.

[0047] When ion detector 1 detects negative ions, switch 91 is set to the off state and switch 92 is set to the on state, and then a positive voltage is applied to ion lens 22. Negative ions are attracted by the positive voltage of ion lens 22 and sequentially pass through openings 21a and 22a, entering the internal space S of ion detector 1. Then, because a high positive voltage is applied to input electrode 42, negative ions move towards input electrode 42 and are incident on it. Electrons generated by the negative ions incident on input electrode 42 are multiplied in multiplier 41 and emitted from output electrode 43. Then, the electrons emitted from output electrode 43 are captured by anode 6, and the electrical signal generated by these electrons is output to input terminal 9b via capacitor 8. In switching circuit 9, because input terminal 9b and output terminal 9c are electrically connected, the electrical signal is output from output terminal 9c to the subsequent signal processing circuit.

[0048] In the ion detector 1 described above, the anode 5, which captures electrons emitted from the electron multiplier 3 used for detecting positive ions, is electrically connected to the input terminal 9a of the switching circuit 9, and the anode 6, which captures electrons emitted from the electron multiplier 4 used for detecting negative ions, is electrically connected to the input terminal 9b of the switching circuit 9. The switching circuit 9 selectively connects either the input terminal 9a or the input terminal 9b to the output terminal 9c, thus selectively outputting electrical signals related to positive ion detection and negative ion detection from the output terminal 9c. Therefore, a signal processing circuit shared by both positive and negative ion detection is provided in the subsequent stage of the ion detector 1, eliminating the need for separate dedicated signal processing circuits for positive and negative ion detection. As a result, bipolar ions can be detected while reducing the circuit size.

[0049] In ion detector 1, because bipolar ions are directly converted into electrons, the detection efficiency of bipolar ions can be improved. Because an electron multiplier 3 for positive ion detection and an electron multiplier 4 for negative ion detection are provided, the lifetime of ion detector 1 can be extended by up to twice compared to a structure using only one electron multiplier for bipolar ion detection. Because the switching circuit 9 electrically separates anodes 5 and 6, compared to a structure directly connecting anodes 5 and 6 to subsequent signal processing circuits, the dark count of the other anode can be reduced, and the effect of the capacitance of the other anode can be eliminated. As a result, degradation of the output waveform can be suppressed.

[0050] Next, refer to Figure 2 and Figure 3 ,illustrate Figure 1 An example installation of ion detector 1 is shown. Figure 2 It means Figure 1 A cross-sectional view of an example installation of an ion detector. Figure 3 yes Figure 2 The top view of the substrate shown. Figure 2 As shown, the ion detector 1 further includes a substrate 51, a spacer 52, and a spacer 53.

[0051] The substrate 51 is a plate-shaped component for mounting the ion detector 1. The substrate 51 is, for example, a printed substrate such as a glass epoxy board. The substrate 51 has a main surface 51a and a back surface 51b opposite to the main surface 51a. The main surface 51a intersects (orthogonally) the direction D1 (first direction).

[0052] Spacers 52 and 53 are support members for supporting the ion-introducing portion 2. Spacers 52 and 53 are provided on the main surface 51a and extend along direction D1. Ion lenses 21 and 22 are fixed such that they extend along direction D1 with a central axis AX. Specifically, the base ends of spacers 52 and 53 are fixed to the substrate 51 by screws or other fixing members. The ion-introducing portion 2 is mounted at the front ends of spacers 52 and 53 such that the main surface 51a faces the ion-introducing portion 2 in direction D1. More specifically, the ion lens 21 is placed at the front ends of spacers 52 and 53, and the ion lens 22 is held between spacers 52 and 53. The ion lens 21 and ion lens 22 are fixed to spacers 52 and 53 by screws or other fixing members. In this way, the ion-introducing portion 2 is fixed to the substrate 51 using spacers 52 and 53.

[0053] Anodes 5 and 6 are disposed on the main surface 51a. Anodes 5 and 6 may also be formed on the main surface 51a as a wiring pattern. Anodes 5 and 6 are arranged in direction D2 (the second direction). Direction D2 is a direction that intersects (is orthogonal to) direction D1 along the main surface 51a. Anodes 5 and 6 are substantially surface-symmetrically arranged with respect to an imaginary surface orthogonal to direction D2 and along the central axis AX.

[0054] like Figure 3 As shown, a gap 51s is provided on substrate 51, extending through substrate 51 in direction D1 between anode 5 and anode 6. The gap 51s is provided to extend the surface distance between anode 5 and anode 6. Figure 3 In the example shown, the slot 51s extends along direction D3 between anodes 5 and 6. Direction D3 is a direction that intersects (is orthogonal to) directions D1 and D2, along the main surface 51a. The slot 51s extends to near both ends of the substrate 51 in direction D3. The slot 51s extends not only between anodes 5 and 6, but also between anode 5 and switching circuit 9 and between anode 6 and switching circuit 9.

[0055] Electron multiplier 3 is disposed on main surface 51a with output electrode 33 facing anode 5 in direction D1. Electron multiplier 4 is disposed on main surface 51a with output electrode 43 facing anode 6 in direction D1. Electron multipliers 3 and 4 (multiplying parts 31 and 41) both extend along direction D1. Electron multipliers 3 and 4 are spaced apart from each other in direction D2. The distance L1 between electron multiplier 3 and central axis AX in direction D2 is substantially equal to the distance L2 between electron multiplier 4 and central axis AX in direction D2. In other words, electron multipliers 3 and 4 are substantially symmetrically arranged with respect to the aforementioned imaginary surface. Electron multiplier 3 and anode 5 are disposed in space S1, and electron multiplier 4 and anode 6 are disposed in space S2. Spaces S1 and S2 are spaces obtained by dividing the internal space S by the aforementioned imaginary surface.

[0056] In this installation example, the input electrode 32 includes a main body portion 32a (first main body portion) and an extension portion 32b (first extension portion). The main body portion 32a is disposed on the end face 31a and covers the entire surface of the end face 31a. The main body portion 32a has, for example, a rectangular plate shape, and is larger than the end face 31a when viewed from direction D1, and is opposite to the ion-introducing portion 2 in direction D1.

[0057] The extension portion 32b is the portion that extends toward the output electrode 33 in the direction D1. The extension portion 32b covers at least the portion of the side surface of the multiplier portion 31 opposite to the multiplier portion 41. In this mounting example, the extension portion 32b has a cylindrical shape and covers the end portion of the multiplier portion 31, including the end face 31a, throughout its entire circumference. The extension portion 32b is disposed along the periphery of the main body portion 32a and extends toward the output electrode 33. The extension portion 32b extends to a position closer to the end face 31b than half the length of the multiplier portion 31 in the direction D1. The extension portion 32b is spaced apart from the side surface of the multiplier portion 31.

[0058] In this mounting example, the output electrode 33 includes a main body 33a and a support 33b. The main body 33a is disposed on the end face 31b and covers the entire surface of the end face 31b. The main body 33a has, for example, a rectangular plate shape and is larger than the end face 31b when viewed from direction D1. The main body 33a is supported by the support 33b. The support 33b has a cylindrical shape. One end of the support 33b is connected to the main body 33a, and the other end of the support 33b is fixed to the main surface 51a of the substrate 51 by screws or welding. The anode 5 is surrounded by the support 33b around its axis.

[0059] In this installation example, the input electrode 42 includes a main body portion 42a (second main body portion) and an extension portion 42b (second extension portion). The main body portion 42a is provided on the end face 41a and covers the entire surface of the end face 41a. The main body portion 42a has, for example, a rectangular plate shape and is larger than the end face 41a when viewed from direction D1. The main body portion 42a is opposite to the ion-introducing portion 2 in direction D1.

[0060] The extension portion 42b is the portion that extends toward the output electrode 43 in the direction D1. The extension portion 42b covers at least the portion of the side surface of the multiplier portion 41 opposite to the multiplier portion 31. In this mounting example, the extension portion 42b has a cylindrical shape and covers the end portion of the multiplier portion 41, including the end face 41a, throughout its entire circumference. The extension portion 42b is disposed along the periphery of the main body portion 42a and extends toward the output electrode 43. The extension portion 42b extends to a position closer to the end face 41b than half the length of the multiplier portion 41 in the direction D1. The extension portion 42b is spaced apart from the side surface of the multiplier portion 41.

[0061] In this mounting example, the output electrode 43 includes a main body 43a and a support 43b. The main body 43a is disposed on the end face 41b and covers the entire surface of the end face 41b. The main body 43a has, for example, a rectangular plate shape and is larger than the end face 41b when viewed from direction D1. The main body 43a is supported by the support 43b. The support 43b has a cylindrical shape. One end of the support 43b is connected to the main body 43a, and the other end of the support 43b is fixed to the main surface 51a of the substrate 51 by screws or welding. The anode 6 is surrounded by the support 43b around its axis.

[0062] The switching circuit 9 is mounted on the main surface 51a. The switching circuit 9 can also be mounted on the rear surface 51b. Although... Figure 2 Although not shown in the diagram, capacitors 7 and 8 are mounted on substrate 51. Capacitors 7 and 8 can be mounted on either the main surface 51a or the back surface 51b. Furthermore, output terminals for connection to subsequent signal processing circuitry can also be mounted on substrate 51. SMA (Sub Miniature Type A) connectors, etc., are used as output terminals.

[0063] Next, refer to Figures 4-7 This illustrates the effect of the ion detector 1 in the above installation example. Figure 4 It means Figure 2 The diagram shows the isopotential lines during positive ion detection by the ion detector. Figure 5 It means Figure 2 The diagram shows the isopotential lines of the ion detector during negative ion detection. Figure 6 This is a diagram showing the isopotential lines during positive ion detection in an ion detector of another installation example. Figure 7This is a diagram showing the isopotential lines during negative ion detection in an ion detector of another installation example. Figure 6 and Figure 7 The ion detector in the other installation example shown is similar to the one in that the input electrode 32 does not have an extension 32b and the input electrode 42 does not have an extension 42b. Figure 4 and Figure 5 The ion detectors shown are different.

[0064] Figures 4-7 The equipotential lines shown are obtained through simulation calculations. Figures 4-7 In this model, equipotential lines are represented in 1000V increments within the range of -5000V to +5000V. A simulation model integrating the main body 32a, multiplier 31, output electrode 33, and anode 5 is used as the electron multiplier 3 and anode 5. A simulation model integrating the main body 42a, multiplier 41, output electrode 43, and anode 6 is used as the electron multiplier 4 and anode 6. A voltage of -10kV is applied to the input electrode 32, and a voltage of -6.5kV is applied to the anode 5. A voltage of +10kV is applied to the input electrode 42, and a voltage of +13.5kV is applied to the anode 6. A ground potential is applied to the ion lens 21. Figure 4 and Figure 6 In the calculation of the equipotential lines, a voltage of -500V is applied to the ion lens 22. Figure 5 and Figure 7 In the calculation of the equipotential line, a voltage of +500V is applied to the ion lens 22.

[0065] like Figures 4-7 As shown, in space S1, due to the voltage applied to the electron multiplier 3, the negative potential becomes the dominant potential, and the potential decreases as it approaches the electron multiplier 3. In space S2, due to the voltage applied to the electron multiplier 4, the positive potential becomes the dominant potential, and the potential increases as it approaches the electron multiplier 4. Positive ions move from the through-hole 2a towards the input electrode 32, and negative ions move from the through-hole 2a towards the input electrode 42. Therefore, the potential gradient in the space (ion movement region) between the ion introduction section 2 and the input electrodes 32 and 42 can influence the ion orbital.

[0066] like Figure 6 and Figure 7As shown, when the input electrode 32 does not have the extension portion 32b, the multiplication portion 31 is exposed, and therefore the voltage (potential) of the multiplication portion 31 affects the potential of the internal space S. Similarly, when the input electrode 42 does not have the extension portion 42b, the multiplication portion 41 is exposed, and therefore the voltage (potential) of the multiplication portion 41 affects the potential of the internal space S. Although the absolute value of the applied voltage of the input electrode 32 is equal to the absolute value of the applied voltage of the input electrode 42, the absolute value of the voltage of the multiplication portion 41 is larger than the absolute value of the voltage of the multiplication portion 31, and their difference increases as it moves toward the output electrodes 33 and 43. Therefore, compared with a negative voltage, a positive voltage has a greater influence on the potential of the internal space S, and thus the symmetry of the positive and negative potential gradients relative to the aforementioned imaginary surface is severely disrupted. As a result, a positive potential is also generated in the space S1 in the ion movement region.

[0067] Therefore, during positive ion detection, the repulsive component caused by the positive potential is greater than the adsorption component caused by the negative potential, thus a force is applied to the positive ion in direction D2 to attract the positive ion away from the electron multiplier 4. Similarly, during negative ion detection, the adsorption component caused by the positive potential is greater than the repulsive component caused by the negative potential, thus a force is applied to the negative ion in direction D2 to attract the negative ion away from the electron multiplier 3. In an ideal state based on the high symmetry of the positive and negative potential gradients, when distances L1 and L2 are set, distances L1 and L2 are equal. In this case, Figure 6 and Figure 7 In the example shown, the probability of positive ions reaching input electrode 32 decreases, resulting in a decrease in the detection accuracy of positive ions. Similarly, the probability of negative ions reaching input electrode 42 decreases, resulting in a decrease in the detection accuracy of negative ions.

[0068] On the other hand, such as Figure 4 and Figure 5 As shown, when the input electrode 32 includes an extension portion 32b, the end of the multiplier portion 31 containing the end face 31a is covered by the extension portion 32b. Therefore, the effect of the voltage of the multiplier portion 31 on the potential of the internal space S is reduced, while the effect of the applied voltage of the input electrode 32 on the potential of the internal space S is increased. Similarly, when the input electrode 42 includes an extension portion 42b, the end of the multiplier portion 41 containing the end face 41a is covered by the extension portion 42b. Therefore, the effect of the voltage of the multiplier portion 41 on the potential of the internal space S is reduced, while the effect of the applied voltage of the input electrode 42 on the potential of the internal space S is increased. As a result, compared with... Figure 6 and Figure 7In comparison, the symmetry of the positive and negative potential gradients is improved in the ion migration region. Therefore, in positive ion detection, a balance between repulsive and adsorption components is achieved, increasing the likelihood of positive ions reaching the input electrode 32, thus improving the detection accuracy of positive ions. Similarly, in negative ion detection, a balance between repulsive and adsorption components is achieved, increasing the likelihood of negative ions reaching the input electrode 42, thus improving the detection accuracy of negative ions.

[0069] Because the extension portion 32b has a cylindrical shape, the end portion containing the end face 31a of the multiplier portion 31 is surrounded by the extension portion 32b around its axis. Similarly, because the extension portion 42b has a cylindrical shape, the end portion containing the end face 41a of the multiplier portion 41 is surrounded by the extension portion 42b around its axis. Therefore, compared to the structure where a portion of the end portion containing the end face 31a is covered by the extension portion 32b, and a portion of the end portion containing the end face 41a is covered by the extension portion 42b, the symmetry of the positive and negative potential gradients is further improved in the ion movement region. As a result, the detection accuracy of both positive and negative ions can be improved.

[0070] The distance L1 between electron multiplier 3 and the central axis AX in direction D2 is equal to the distance L2 between electron multiplier 4 and the central axis AX in direction D2. Therefore, it is not necessary to individually adjust the configuration of electron multiplier 3 and electron multiplier 4, thus simplifying the design of the configuration of electron multiplier 3 and electron multiplier 4.

[0071] Electron multipliers 3 and 4 are spaced apart from each other in direction D2 and extend along direction D1. Input electrodes 32 and 42 are both opposite to the ion introduction section 2 in direction D1. In other words, the main body 32a and main body 42a face the same direction, and the input electrodes 32 and 42 are not face-to-face. Therefore, the possibility of noise from charged particles generated in the electron multiplier 4 affecting the input electrode 32 can be reduced. Similarly, the possibility of noise from charged particles generated in the electron multiplier 3 affecting the input electrode 42 can be reduced. As a result, the detection accuracy of positive and negative ions can be improved.

[0072] In a structure where electron multipliers 3 and 4 are mounted on different substrates, the positions of electron multipliers 3 and 4 need to be individually aligned. However, in the ion detector 1 of the above mounting example, since electron multipliers 3 and 4 are arranged on a single substrate 51, the distance between them is fixed. Therefore, the positions of electron multipliers 3 and 4 in direction D2 can be determined by aligning only the center points along the central axis AX in the direction between them. As a result, the assembly accuracy of the ion detector 1 can be improved.

[0073] Not only electron multipliers 3 and 4 and anodes 5 and 6, but also capacitors 7 and 8 and switching circuit 9 are mounted on substrate 51. In this structure, since the components of ion detector 1 are mounted on a single substrate 51, it is not necessary to prepare additional substrates for mounting capacitors 7 and 8 and switching circuit 9. Therefore, the number of components can be reduced.

[0074] When the potential difference between anodes 5 and 6 is large, surface discharge may sometimes occur between anodes 5 and 6 along the main surface 51a or back surface 51b of substrate 51. To address this, a gap 51s is provided in substrate 51, penetrating the substrate 51 in direction D1, between anodes 5 and 6. This increases the surface distance between anodes 5 and 6, thereby reducing the likelihood of surface discharge occurring between anodes 5 and 6.

[0075] Because the ion-introducing part 2 is supported by spacers 52 and 53, the position of the central axis AX (through hole 2a) is fixed. Therefore, the assembly accuracy of the ion detector 1 can be improved.

[0076] Furthermore, the ion detector of the present invention is not limited to the embodiments described above.

[0077] Either input electrode 32 or 42 may be without an extension portion. In this case, compared to a structure where neither input electrode 32 nor 42 has an extension portion, the symmetry of the positive and negative potential gradients in the ion movement region can be improved. As a result, the detection accuracy of both positive and negative ions can be improved.

[0078] The configuration of electron multipliers 3 and 4 is not limited to Figure 2The installation example shown illustrates the configuration. For instance, electron multipliers 3 and 4 can also be configured such that the input electrodes 32 and 42 clamp the central axis AX opposite each other in direction D2. In this case, the symmetry of the positive and negative potential gradients with respect to the aforementioned imaginary surface can be maintained. Alternatively, one electron multiplier of electron multipliers 3 and 4 can be configured to extend along direction D1, and the other electron multiplier can be configured to extend along direction D2.

[0079] The absolute values ​​of the voltage applied to the input electrode 32 and the absolute values ​​of the voltage applied to the input electrode 42 may not be equal.

[0080] Next, refer to Figure 8 ,illustrate Figure 1 Another installation example of ion detector 1 shown. Figure 8 It means Figure 1 A cross-sectional view of another installation example of the ion detector is shown. (See figure) Figure 8 As shown, the ion detector 1 in this mounting example mainly replaces the substrate 51, including substrate 61 (first substrate) and substrate 62 (second substrate), and is mounted with capacitors 7 and 8 and switching circuit 9. Figure 2 The ion detector 1 shown in the installation example is different.

[0081] Substrate 61 is a plate-shaped component for mounting the electron multiplier 3. Substrate 61 is, for example, a printed circuit board such as a glass epoxy resin substrate. Substrate 61 has a main surface 61a (first main surface) and a back surface 61b opposite to the main surface 61a. The main surface 61a and the back surface 61b intersect (orthogonally) direction D1. The main surface 61a faces the ion-introducing portion 2 in direction D1. Substrate 62 is a plate-shaped component for mounting the electron multiplier 4. Substrate 62 is, for example, a printed circuit board such as a glass epoxy resin substrate. Substrate 62 has a main surface 62a (second main surface) and a back surface 62b opposite to the main surface 62a. The main surface 62a and the back surface 62b intersect (orthogonally) direction D1. The main surface 62a faces the ion-introducing portion 2 in direction D1. Substrate 61 and substrate 62 are arranged in direction D2. Substrate 61 and substrate 62 are orthogonal to direction D2 and substantially symmetrically arranged with respect to an imaginary surface along the central axis AX.

[0082] Anode 5 is disposed on main surface 61a. Anode 5 may also be formed on main surface 61a as a wiring pattern. Anode 6 is disposed on main surface 62a. Anode 6 may also be formed on main surface 62a as a wiring pattern. Anodes 5 and 6 are substantially symmetrically arranged with respect to the aforementioned imaginary surface.

[0083] Electron multiplier 3 is disposed on main surface 61a with output electrode 33 facing anode 5 in direction D1. In this mounting example, the other end of support portion 33b is fixed to main surface 61a of substrate 61 by screws or welding. Electron multiplier 4 is disposed on main surface 62a with output electrode 43 facing anode 6 in direction D1. In this mounting example, the other end of support portion 43b is fixed to main surface 62a of substrate 62 by screws or welding.

[0084] Capacitors 7 and 8 and switching circuit 9 are mounted on substrates other than substrates 61 and 62 (not shown). Alternatively, capacitor 7 may also be mounted on substrate 61 and capacitor 8 may also be mounted on substrate 62.

[0085] In this mounting example, because anode 5 and anode 6 are disposed on different substrates, the possibility of surface discharge occurring between anode 5 and anode 6 can be reduced. Furthermore, because electron multiplier 3 and electron multiplier 4 are disposed on different substrates, the degree of freedom in the arrangement of electron multiplier 3 and electron multiplier 4 can be increased.

[0086] Next, refer to Figure 9 ,illustrate Figure 1 Another installation example of ion detector 1 shown. Figure 9 It means Figure 1 A cross-sectional view of another installation example of the ion detector is shown. (See figure) Figure 9 As shown, input electrode 32 does not include extension portion 32b. Input electrode 42 does not include extension portion 42b. In this structure, as described above, during positive ion detection, positive ions are repelled due to the positive potential, and a force is applied to the positive ions in direction D2 to draw them away from electron multiplier 4. Similarly, during negative ion detection, negative ions are attracted due to the positive potential, and a force is applied to the negative ions in direction D2 to draw them away from electron multiplier 3.

[0087] In contrast, electron multipliers 3 and 4 are arranged asymmetrically with respect to an imaginary plane along the central axis AX. Specifically, electron multipliers 3 and 4 are arranged such that distance L1 is greater than distance L2. It is set such that the greater the difference between the voltage applied to output electrode 33 and the voltage applied to output electrode 43, the greater the distance L1 is compared to distance L2. Distance L1 can also be determined by pre-calculating the orbits of positive ions through simulation. Similarly, distance L2 can be determined by pre-calculating the orbits of negative ions through simulation.

[0088] According to this structure, electron multiplier 3 is farther from the central axis AX in direction D2 than electron multiplier 4, thus increasing the likelihood of positive ions entering the input electrode 32. Similarly, because electron multiplier 4 is closer to the central axis AX in direction D2 than electron multiplier 3, it increases the likelihood of negative ions entering the input electrode 42. Therefore, the detection accuracy of both positive and negative ions can be improved.

Claims

1. An ion detector, characterized in that, include: The first electron multiplier used to detect the first ion with the first polarity; A second electron multiplier used to detect a second ion having a second polarity different from the first polarity; The first anode that captures electrons emitted from the first electron multiplier; A second anode that captures electrons emitted from the second electron multiplier; A switching circuit includes a first input terminal electrically connected to the first anode, a second input terminal electrically connected to the second anode, and an output terminal, wherein either the first input terminal or the second input terminal is selectively connected to the output terminal; and An ion-introducing portion is provided with a through-hole having a central axis extending along a first direction. The first electron multiplier includes a first multiplication section extending along the first direction, a first input electrode disposed at one end of the first multiplication section in the first direction, and a first output electrode disposed at the other end of the first multiplication section in the first direction. The second electron multiplier includes a second multiplying portion extending along the first direction, a second input electrode disposed at one end of the second multiplying portion in the first direction, and a second output electrode disposed at the other end of the second multiplying portion in the first direction. The first input electrode receives the first ion passing through the through hole. The second input electrode receives the second ions passing through the through-hole. The first electron multiplier and the second electron multiplier are spaced apart from each other in a second direction that intersects the first direction. The first input electrode includes a first main body portion opposite to the ion-introducing portion in the first direction and a first extension portion extending toward the first output electrode in the first direction. The first extension covers the portion of the first multiplier that is opposite to the second multiplier.

2. The ion detector as described in claim 1, characterized in that: The first extension has a cylindrical shape.

3. The ion detector as described in claim 1, characterized in that: The second input electrode includes a second main body portion opposite to the ion-introducing portion in the first direction and a second extension portion extending toward the second output electrode in the first direction. The second extension covers the portion of the second multiplier that is opposite to the first multiplier.

4. The ion detector as described in claim 2, characterized in that: The second input electrode includes a second main body portion opposite to the ion-introducing portion in the first direction and a second extension portion extending toward the second output electrode in the first direction. The second extension covers the portion of the second multiplier that is opposite to the first multiplier.

5. The ion detector as described in claim 3, characterized in that: The second extension has a cylindrical shape.

6. The ion detector as described in claim 4, characterized in that: The second extension has a cylindrical shape.

7. The ion detector according to any one of claims 1 to 6, characterized in that: The distance between the first electron multiplier and the central axis in the second direction is equal to the distance between the second electron multiplier and the central axis in the second direction.

8. The ion detector as described in claim 1, characterized in that: The first ion is a positive ion. The second ion is a negative ion. The distance between the first electron multiplier and the central axis in the second direction is greater than the distance between the second electron multiplier and the central axis in the second direction.

9. The ion detector according to any one of claims 1 to 6 and 8, characterized in that: It also includes a substrate having a main surface opposite to the ion-introducing portion in the first direction. The first anode and the second anode are disposed on the main surface. The first electron multiplier is disposed on the main surface such that the first output electrode and the first anode are opposite each other in the first direction. The second electron multiplier is disposed on the main surface such that the second output electrode and the second anode are opposite each other in the first direction.

10. The ion detector as described in claim 7, characterized in that: It also includes a substrate having a main surface opposite to the ion-introducing portion in the first direction. The first anode and the second anode are disposed on the main surface. The first electron multiplier is disposed on the main surface such that the first output electrode and the first anode are opposite each other in the first direction. The second electron multiplier is disposed on the main surface such that the second output electrode and the second anode are opposite each other in the first direction.

11. The ion detector as described in claim 9, characterized in that: The switching circuit is mounted on the substrate.

12. The ion detector as described in claim 10, characterized in that: The switching circuit is mounted on the substrate.

13. The ion detector as described in claim 9, characterized in that: In the substrate, a gap penetrating the substrate in the first direction is provided between the first anode and the second anode.

14. The ion detector according to any one of claims 10 to 12, characterized in that: In the substrate, a gap penetrating the substrate in the first direction is provided between the first anode and the second anode.

15. The ion detector as described in claim 9, characterized in that: It also includes a support member disposed on the main surface to support the ion-introducing portion.

16. The ion detector according to any one of claims 10 to 13, characterized in that: It also includes a support member disposed on the main surface to support the ion-introducing portion.

17. The ion detector as claimed in claim 14, characterized in that: It also includes a support member disposed on the main surface to support the ion-introducing portion.

18. The ion detector according to any one of claims 1 to 6 and 8, characterized in that, Also includes: A first substrate having a first main surface opposite to the ion-introducing portion in the first direction; and A second substrate having a second main surface opposite to the ion-introducing portion in the first direction. The first anode is disposed on the first main surface. The second anode is disposed on the second main surface. The first electron multiplier is disposed on the first main surface such that the first output electrode and the first anode are opposite each other in the first direction. The second electron multiplier is disposed on the second main surface such that the second output electrode and the second anode are opposite each other in the first direction.

19. The ion detector as claimed in claim 7, characterized in that, Also includes: A first substrate having a first main surface opposite to the ion-introducing portion in the first direction; and A second substrate having a second main surface opposite to the ion-introducing portion in the first direction. The first anode is disposed on the first main surface. The second anode is disposed on the second main surface. The first electron multiplier is disposed on the first main surface such that the first output electrode and the first anode are opposite each other in the first direction. The second electron multiplier is disposed on the second main surface such that the second output electrode and the second anode are opposite each other in the first direction.

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