Ion Detector

Abstract

To provide an ion detector capable of detecting an ion having both poles while reducing a circuit scale.SOLUTION: An ion detector 1 comprises: an electron multiplying body 3 for detecting a positive ion; an electron multiplying body 4 for detecting a negative ion; an anode 5 for capturing an electron emitted by the electron multiplying body 3; an anode 6 for capturing an electron emitted by the electron multiplying body 4; and a changeover circuit 9 that includes an input terminal 9a electrically connected to the anode 5, an input terminal 9b electrically connected to the anode 6, and an output terminal 9c and selectively connects either the input terminal 9a or the input terminal 9b to the output terminal 9c.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to ion detectors. [Background technology]

[0002] Ion detectors that detect positive ions and negative ions are known. For example, Patent Document 1 describes an ion detector that includes an electron multiplier for detecting cations (positive ions) and an electron multiplier for detecting anions (negative ions). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 52-119290 Summary of the Invention [Problem to be solved by the invention]

[0004] In the ion detector described in Patent Document 1, a signal processing circuit such as a dedicated amplifier is provided for each output of an electron multiplier for detecting positive ions and an electron multiplier for detecting negative ions. Therefore, there is a risk that the circuit scale will increase. In this technical field, it is desired to detect ions of both polarities while reducing the circuit scale.

[0005] The present disclosure describes an ion detector capable of detecting ions of both polarities while reducing the circuit scale. [Means for solving the problem]

[0006] An ion detector according to one aspect of the present disclosure comprises 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, and selectively connecting either the first input terminal or the second input terminal to the output terminal.

[0007] In this ion detector, a first anode that captures electrons emitted from a first electron multiplier for detecting a first ion having a first polarity is electrically connected to a first input terminal of a switching circuit, and a second anode that captures electrons emitted from a second electron multiplier for detecting a second ion having a second polarity is electrically connected to a second input terminal of the switching circuit. The switching circuit selectively connects either the first input terminal or the second input terminal to the output terminal, so that a signal related to the first ion detection and a signal related to the second ion detection are selectively output from the output terminal. Therefore, a signal processing circuit commonly used for the first ion detection and the second ion detection can be provided in the rear stage of the ion detector, so there is no need to provide dedicated signal processing circuits for the first ion detection and the second ion detection, respectively. As a result, it is possible to detect ions of both polarities while reducing the circuit scale.

[0008] The ion detector may further include an ion introduction section provided with a through hole having a central axis extending in the first direction. The first electron multiplier may include a first multiplier section extending in the first direction, a first input electrode provided at one end of the first multiplier section in the first direction, and a first output electrode provided at the other end of the first multiplier section in the first direction. The second electron multiplier may include a second multiplier section extending in the first direction, a second input electrode provided at one end of the second multiplier section in the first direction, and a second output electrode provided at the other end of the second multiplier section in the first direction. The first input electrode may receive the first ion that has passed through the through hole. The second input electrode may receive the second ion that has passed through the through hole. The first electron multiplier and the second electron multiplier may 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 provided to extend in the first direction while being spaced apart from each other in the second direction. Both the first input electrode and the second input electrode face the ion introduction section in the first direction. Therefore, it is possible to reduce the possibility that the first input electrode and the second input electrode will receive noise derived from the charged particles generated in the other electron multiplier. As a result, it is possible to improve the detection accuracy of the first ions and the second ions.

[0009] The first input electrode may include a first main body portion facing 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 cover a portion of the first multiplication portion facing the second multiplication portion. For example, a negative voltage is applied to the first input electrode, and a positive voltage is applied to the second input electrode. The voltage of the first multiplication portion increases from the first input electrode toward the first output electrode, and the voltage of the second multiplication portion increases from the second input electrode toward the second output electrode. Therefore, even if the absolute value of the applied voltage of the first input electrode is equal to the absolute value of the applied voltage of the second input electrode, the difference between the absolute value of the voltage of the first multiplication portion and the absolute value of the voltage of the second multiplication portion increases toward the output electrode. In the above configuration, since the first extension portion of the first input electrode covers the portion of the first multiplication portion facing the second multiplication portion, the symmetry of the positive potential gradient and the negative potential gradient in the region where ions move can be improved. Therefore, it is possible to improve the detection accuracy of the first ions and the second ions.

[0010] The first extension may have a cylindrical shape. In this case, an end portion including one end of the first multiplication section is surrounded by the first extension. Compared to a configuration in which a part of an end portion including one end of the first multiplication section is covered by the first extension, the symmetry between the positive potential gradient and the negative potential gradient in the region where the ions move can be improved. Therefore, it is possible to further improve the detection accuracy of the first ion and the second ion.

[0011] The second input electrode may include a second main body portion facing 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 cover a portion of the second multiplication portion facing the first multiplication portion. Since the second extension portion of the second input electrode covers a portion of the second multiplication portion facing the first multiplication portion, the symmetry of the positive potential gradient and the negative potential gradient in the region where the ions move can be improved. Therefore, it is possible to improve the detection accuracy of the first ion and the second ion.

[0012] The second extension may have a cylindrical shape. In this case, an end portion including one end of the second multiplication section is surrounded by the second extension. Compared to a configuration in which a part of an end portion including one end of the second multiplication section is covered by the second extension, the symmetry between the positive potential gradient and the negative potential gradient in the region where the ions move can be improved. Therefore, it is possible to further improve the detection accuracy of the first ion and the second ion.

[0013] The distance in the second direction between the first electron multiplier and the central axis may be equal to the distance in the second direction between the second electron multiplier and the central axis, which can simplify the design of the arrangement of the first electron multiplier and the second electron multiplier.

[0014] The first ion may be a positive ion. The second ion may be a negative ion. The distance between the first electron multiplier and the central axis in the second direction may be greater than the distance between the second electron multiplier and the central axis in the second direction. As described above, the symmetry between the positive potential gradient and the negative potential gradient in the region in which the ions move is broken, so that the force that the first ion receives in the direction away from the second electron multiplier in the second direction is greater than the force that the second ion receives in the direction away from the first electron multiplier in the second direction. In other words, the first ion moves farther away from the central axis than the second ion. According to the above configuration, since the first electron multiplier is farther away from the central axis than the second electron multiplier, the possibility that the first ion enters the first input electrode and the second ion enters the second input electrode can be increased. Therefore, it is possible to improve the detection accuracy of the first ion and the second ion.

[0015] The ion detector may further include a substrate having a main surface facing the ion introduction section in the first direction. The first anode and the second anode may be provided on the main surface. The first electron multiplier may be disposed on the main surface such that the first output electrode faces the first anode in the first direction. The second electron multiplier may be disposed on the main surface such that the second output electrode faces the second anode in the first direction. In this case, the first electron multiplier and the second electron multiplier are disposed on one substrate. Therefore, the distance between the first electron multiplier and the second electron multiplier is constant, and therefore the assembly accuracy of the ion detector can be improved.

[0016] The switching circuit may be mounted on a substrate. In this case, the components of the ion detector are mounted on a single substrate, which makes it possible to reduce the number of components.

[0017] The substrate may be provided with a slit penetrating the substrate in the first direction between the first anode and the second anode. When the potential difference between the first anode and the second anode is large, a creeping discharge may occur between the first anode and the second anode along the main surface of the substrate. In the above configuration, since a slit is provided between the first anode and the second anode, the creeping distance between the first anode and the second anode is increased. This can reduce the possibility of a creeping discharge occurring between the first anode and the second anode.

[0018] The ion detector may further include a support member provided on the main surface and supporting the ion introduction section. In this case, the ion introduction section is supported by the support member, so that the position of the central axis (through hole) is determined. Therefore, the assembly accuracy of the ion detector can be improved.

[0019] The ion detector may further include a first substrate having a first main surface facing the ion introduction section in the first direction, and a second substrate having a second main surface facing the ion introduction section in the first direction. The first anode may be provided on the first main surface. The second anode may be provided on the second main surface. The first electron multiplier may be disposed on the first main surface such that the first output electrode faces the first anode in the first direction. The second electron multiplier may be disposed on the second main surface such that the second output electrode faces the second anode in the first direction. In this case, since the first anode and the second anode are disposed on different substrates, the possibility of creeping discharge occurring between the first anode and the second anode can be reduced. Effect of the Invention

[0020] According to the present disclosure, it is possible to detect ions of both polarities while reducing the circuit scale. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic diagram illustrating an ion detector according to an embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing an example of mounting the ion detector shown in FIG. [Diagram 3] FIG. 3 is a plan view of the substrate shown in FIG. [Figure 4] FIG. 4 is a diagram showing equipotential lines when the ion detector shown in FIG. 2 detects positive ions. [Diagram 5] FIG. 5 is a diagram showing equipotential lines when the ion detector shown in FIG. 2 detects negative ions. [Figure 6] FIG. 6 is a diagram showing equipotential lines when a positive ion is detected by an ion detector of another mounting example. [Figure 7] FIG. 7 is a diagram showing equipotential lines when an ion detector of another mounting example detects negative ions. [Figure 8] FIG. 8 is a cross-sectional view showing yet another implementation of the ion detector shown in FIG. [Figure 9]FIG. 9 is a cross-sectional view showing yet another implementation of the ion detector shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the description of the drawings, the same elements are given the same reference numerals, and duplicated description will be omitted.

[0023] A schematic configuration of an ion detector according to an embodiment will be described with reference to FIG. 1. FIG. 1 is a schematic configuration diagram of an ion detector according to an embodiment. The ion detector 1 shown in FIG. 1 is a device capable of detecting ions of both polarities. The ion detector 1 is applied to, for example, a mass spectrometer. The ion detector 1 includes an ion introduction section 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.

[0024] The ion introduction section 2 is a section that passes ions from the outside of the ion detector 1 into the internal space S (see FIG. 2) of the ion detector 1. The ion introduction section 2 may be an aperture member that blocks external noise. The ion introduction section 2 includes an ion lens 21 and an ion lens 22. The ion lens 21 is a plate-shaped conductive member. The ion lens 21 is provided with an opening 21a that penetrates the ion lens 21. The ion lens 21 is, for example, grounded.

[0025] The ion lens 22 is a plate-shaped conductive member. The ion lens 22 is provided with an opening 22a penetrating the ion lens 22. The ion lens 22 is disposed so that the central axis of the opening 21a coincides with the central axis of the opening 22a. That is, the ion introduction section 2 is provided with a through-hole 2a having a central axis AX. The through-hole 2a is composed of the opening 21a and the opening 22a.

[0026] Either a positive voltage or a negative voltage is selectively applied to the ion lens 22. When the ion detector 1 detects positive ions (first ions having a first polarity), a negative voltage is applied to the ion lens 22. With this configuration, the positive ions are focused and introduced into the internal space S by passing through the opening 21a and the opening 22a in this order. When the ion detector 1 detects negative ions (second ions having a second polarity), a positive voltage is applied to the ion lens 22. With this configuration, the negative ions are focused and introduced into the internal space S by passing through the opening 21a and the opening 22a in this order. The positive voltage applied to the ion lens 22 is, for example, about 500V. The negative voltage applied to the ion lens 22 is, for example, about -500V.

[0027] The electron multiplier 3 is a structure for detecting positive ions. The electron multiplier 4 is a structure for detecting negative ions. Examples of the 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 a combination of two of these. The CEM, the EM tube, and the AD may further be provided with a conversion dynode (CD). In this embodiment, the electron multipliers 3 and 4 are exemplified by a CEM.

[0028] 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 rectangular parallelepiped shape. The multiplier section 31 has end faces 31a and 31b. The end face 31a (one end) is one end face in the longitudinal direction of the multiplier section 31 and faces the ion introduction section 2. The end face 31b (the other end) is the end face opposite to the end face 31a in the longitudinal direction of the multiplier section 31. The multiplier section 31 includes, for example, an insulating material such as a ceramic material. The multiplier section 31 has a plurality of channels extending from the end face 31a to the end face 31b.

[0029] The input electrode 32 receives the positive ions that have passed through the through hole 2a and converts the positive ions into electrons. The input electrode 32 is provided on the end face 31a. The input electrode 32 is made of a conductive metal material. A negative high voltage is applied to the input electrode 32. For example, a voltage of about -10 kV is applied to the input electrode 32.

[0030] The output electrode 33 is provided on the end face 31b. The output electrode 33 is made of a conductive metal material. A negative high voltage higher 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 so 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 higher than the voltage applied to the input electrode 32. The input electrode 32 and the output electrode 33 generate a potential gradient in the multiplication section 31 along the longitudinal direction of the multiplication section 31 so that the potential becomes higher from the end face 31a toward the end face 31b.

[0031] 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 rectangular parallelepiped shape. The multiplier section 41 has end faces 41a and 41b. The end face 41a (one end) is one end face in the longitudinal direction of the multiplier section 41 and faces the ion introduction section 2. The end face 41b (the other end) is the end face opposite to the end face 41a in the longitudinal direction of the multiplier section 41. The multiplier section 41 includes, for example, an insulating material such as a ceramic material. The multiplier section 41 has a plurality of channels extending from the end face 41a to the end face 41b.

[0032] The input electrode 42 receives the negative ions that have passed through the through hole 2a and converts the negative ions into electrons. The input electrode 42 is provided on the end surface 41a. The input electrode 42 is made of a conductive metal material. A positive high voltage is applied to the input electrode 42. For example, a voltage of about +10 kV is applied to the input electrode 42.

[0033] The output electrode 43 is provided on the end face 41b. The output electrode 43 is made of a conductive metal material. A positive high voltage higher 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 so 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 higher than the voltage applied to the input electrode 42. The input electrode 42 and the output electrode 43 generate a potential gradient in the multiplication section 41 along the longitudinal direction of the multiplication section 41 so that the potential becomes higher from the end face 41a toward the end face 41b.

[0034] The anode 5 is an electrode that captures electrons emitted from the electron multiplier 3. The anode 5 outputs an electrical signal corresponding to the captured electrons. The anode 5 outputs an electrical signal to a switching circuit 9 via a capacitor 7. The anode 6 is an electrode that captures electrons emitted from the electron multiplier 4. The anode 6 outputs an electrical signal corresponding to the captured electrons. The anode 6 outputs an electrical signal to a switching circuit 9 via a capacitor 8.

[0035] The capacitors 7 and 8 are AC (Alternating Current) coupling capacitors. The capacitor 7 removes a DC (Direct Current) offset voltage from the electrical signal output from the anode 5. The capacitor 8 removes a DC offset voltage from the electrical signal output from the anode 6.

[0036] The switching circuit 9 is a circuit for selectively connecting either the anode 5 or the anode 6 to a signal processing circuit such as a downstream amplifier. Examples of the switching circuit 9 include an RF (Radio Frequency) switch IC (Integrated Circuit) and a contactless relay. Examples of the contactless relay include a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The switching circuit 9 selects the anode to be measured from the anode 5 and the anode 6 in response to a switching signal from the outside. The switching circuit 9 has an input terminal 9a (first input terminal), an input terminal 9b (second input terminal), and an output terminal 9c. The input terminal 9a is electrically connected to the anode 5. In this embodiment, the input terminal 9a is electrically connected to the anode 5 via the capacitor 7. The input terminal 9b is electrically connected to the anode 6. In this embodiment, the input terminal 9b is electrically connected to the anode 6 via the capacitor 8. The output terminal 9c is electrically connected to a downstream signal processing circuit.

[0037] The switching circuit 9 selectively connects either the input terminal 9a or the input terminal 9b to the output terminal 9c. The switching circuit 9 is switched between a first state and a second state by an external switching signal. The first state is a state in which the input terminal 9a and the output terminal 9c are electrically connected and the input terminal 9b and the output terminal 9c are electrically disconnected. The second state is a state in which the input terminal 9a and the output terminal 9c are electrically disconnected and the input terminal 9b and the output terminal 9c are electrically connected.

[0038] The switching circuit 9 includes a switch 91 and a switch 92. The switch 91 is provided between an input terminal 9a and an output terminal 9c. The switch 91 is configured to be switchable between an ON state in which the input terminal 9a and the output terminal 9c are electrically connected and an OFF state in which the input terminal 9a and the output terminal 9c are electrically disconnected. The switch 92 is provided between the input terminal 9b and the output terminal 9c. The switch 92 is configured to be switchable between an ON state in which the input terminal 9b and the output terminal 9c are electrically connected and an OFF state in which the input terminal 9b and the output terminal 9c are electrically disconnected. The switch 91 and the switch 92 are set to opposite states by a switching signal. That is, when the switch 91 is set to an ON state, the switch 92 is set to an OFF state (first state), and when the switch 91 is set to an OFF state, the switch 92 is set to an ON state (second state).

[0039] Next, the operation of the ion detector 1 will be described. When the ion detector 1 detects positive ions, the switch 91 is set to an ON state, and the switch 92 is set to an OFF state, and then a negative voltage is applied to the ion lens 22. The positive ions are attracted to the negative voltage of the ion lens 22, pass through the opening 21a and the opening 22a in order, and are introduced into the internal space S of the ion detector 1. Then, since a negative high voltage is applied to the input electrode 32, the positive ions move toward the input electrode 32 and are incident on the input electrode 32. Electrons generated in response to the positive ions incident on the input electrode 32 are multiplied in the multiplier section 31 and emitted from the output electrode 33. Then, the electrons emitted from the output electrode 33 are captured by the anode 5, and an electric signal corresponding to the electrons is output to the input terminal 9a via the capacitor 7. Since the input terminal 9a and the output terminal 9c are electrically connected in the switching circuit 9, the electric signal is output from the output terminal 9c to a signal processing circuit in the subsequent stage.

[0040] When the ion detector 1 detects negative ions, the switch 91 is set to an OFF state, and the switch 92 is set to an ON state, and then a positive voltage is applied to the ion lens 22. The negative ions are attracted to the positive voltage of the ion lens 22, pass through the opening 21a and the opening 22a in order, and are introduced into the internal space S of the ion detector 1. Since a positive high voltage is applied to the input electrode 42, the negative ions move toward the input electrode 42 and are incident on the input electrode 42. Electrons generated in response to the negative ions incident on the input electrode 42 are multiplied in the multiplier section 41 and emitted from the output electrode 43. The electrons emitted from the output electrode 43 are captured by the anode 6, and an electric signal corresponding to the electrons is output to the input terminal 9b via the capacitor 8. Since the input terminal 9b and the output terminal 9c are electrically connected in the switching circuit 9, the electric signal is output from the output terminal 9c to a signal processing circuit in the subsequent stage.

[0041] In the ion detector 1 described above, the anode 5 that captures electrons emitted from the electron multiplier 3 for detecting positive ions is electrically connected to the input terminal 9a of the switching circuit 9, and the anode 6 that captures electrons emitted from the electron multiplier 4 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, so that the output terminal 9c selectively outputs an electric signal related to positive ion detection and an electric signal related to negative ion detection. Therefore, a signal processing circuit that is commonly used for positive ion detection and negative ion detection is provided in the rear stage of the ion detector 1, so there is no need to provide dedicated signal processing circuits for positive ion detection and negative ion detection, respectively. As a result, it is possible to detect ions of both polarities while reducing the circuit scale.

[0042] In the ion detector 1, ions of both polarities are directly converted into electrons, so that it is possible to improve the detection efficiency of ions of both polarities. Since an electron multiplier 3 for detecting positive ions and an electron multiplier 4 for detecting negative ions are provided, the life of the ion detector 1 can be extended by about twice as long as a configuration in which one electron multiplier is used for detecting ions of both polarities. Since the switching circuit 9 electrically separates the anode 5 and the anode 6, it is possible to reduce the dark count of the other anode and eliminate the effect of the capacitance of the other anode as compared to a configuration in which the anode 5 and the anode 6 are directly connected to a signal processing circuit in the subsequent stage. As a result, it is possible to suppress deterioration of the output waveform.

[0043] Next, an implementation example of the ion detector 1 shown in Fig. 1 will be described with reference to Fig. 2 and Fig. 3. Fig. 2 is a cross-sectional view showing an implementation example of the ion detector shown in Fig. 1. Fig. 3 is a plan view of the substrate shown in Fig. 2. As shown in Fig. 2, the ion detector 1 further includes a substrate 51, a spacer 52, and a spacer 53.

[0044] The substrate 51 is a plate-like member on which the components of the ion detector 1 are mounted. The substrate 51 is, for example, a printed circuit board 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 (here, perpendicular to) direction D1 (first direction).

[0045] The spacers 52 and 53 are support members for supporting the ion introduction section 2. The spacers 52 and 53 are provided on the main surface 51a and extend in the direction D1. The ion lenses 21 and 22 are fixed so that the central axis AX extends in the direction D1. Specifically, the base ends of the spacers 52 and 53 are fixed to the substrate 51 by a fixing member such as a screw. The ion introduction section 2 is attached to the tip of the spacers 52 and 53 so that the main surface 51a faces the ion introduction section 2 in the direction D1. More specifically, the ion lens 21 is placed on the tip of the spacers 52 and 53, and the ion lens 22 is sandwiched between the spacers 52 and 53. The ion lens 21 and the ion lens 22 are fixed to the spacers 52 and 53 by a fixing member such as a screw. In this manner, the ion introduction section 2 is fixed to the substrate 51 by the spacers 52 and 53.

[0046] The anodes 5 and 6 are provided on the main surface 51a. The anodes 5 and 6 may be formed on the main surface 51a as a wiring pattern. The anodes 5 and 6 are arranged in a direction D2 (a second direction). The direction D2 is a direction intersecting (here, perpendicular to) the direction D1 and extending along the main surface 51a. The anodes 5 and 6 are arranged substantially symmetrically with respect to a virtual plane that is perpendicular to the direction D2 and extends along the central axis AX.

[0047] As shown in FIG. 3, the substrate 51 is provided with a slit 51s between the anode 5 and the anode 6, penetrating the substrate 51 in the direction D1. The slit 51s is provided to extend the creepage distance between the anode 5 and the anode 6. In the example shown in FIG. 3, the slit 51s extends in the direction D3 between the anode 5 and the anode 6. The direction D3 intersects (here, is perpendicular to) the directions D1 and D2, and is along the main surface 51a. The slit 51s extends to near both ends of the substrate 51 in the direction D3. The slit 51s extends not only between the anode 5 and the anode 6, but also between the anode 5 and the switching circuit 9 and between the anode 6 and the switching circuit 9.

[0048] The electron multiplier 3 is disposed on the main surface 51a such that the output electrode 33 faces the anode 5 in the direction D1. The electron multiplier 4 is disposed on the main surface 51a such that the output electrode 43 faces the anode 6 in the direction D1. The electron multipliers 3 and 4 (multiplier sections 31 and 41) all extend in the direction D1. The electron multipliers 3 and 4 are spaced apart from each other in the direction D2. The distance L1 between the electron multiplier 3 and the central axis AX in the direction D2 is substantially equal to the distance L2 between the electron multiplier 4 and the central axis AX in the direction D2. In other words, the electron multipliers 3 and 4 are disposed substantially symmetrically with respect to the virtual plane. The electron multiplier 3 and the anode 5 are disposed in the space S1, and the electron multiplier 4 and the anode 6 are disposed in the space S2. The space S1 and the space S2 are spaces obtained by dividing the internal space S by the virtual plane.

[0049] In this implementation 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 provided 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 slightly larger than the end face 31a when viewed from the direction D1. The main body portion 32a faces the ion introduction unit 2 in the direction D1.

[0050] The extension 32b is a portion that extends toward the output electrode 33 in the direction D1. The extension 32b covers at least a portion of the side surface of the multiplier 31 that faces the multiplier 41. In this implementation example, the extension 32b has a cylindrical shape and covers the entire periphery of the end portion including the end surface 31a of the multiplier 31. The extension 32b is provided along the periphery of the main body 32a and extends toward the output electrode 33. The extension 32b extends to a position closer to the end surface 31b than half the length of the multiplier 31 in the direction D1. The extension 32b is spaced apart from the side surface of the multiplier 31.

[0051] In this implementation example, the output electrode 33 includes a main body portion 33a and a support portion 33b. The main body portion 33a is provided on the end surface 31b and covers the entire surface of the end surface 31b. The main body portion 33a has, for example, a rectangular plate shape and is slightly larger than the end surface 31b when viewed from the direction D1. The main body portion 33a is supported by the support portion 33b. The support portion 33b has a cylindrical shape. One end of the support portion 33b is connected to the main body portion 33a, and the other end of the support portion 33b is fixed to the main surface 51a of the substrate 51 by screws, welding, or the like. The anode 5 is surrounded by the support portion 33b.

[0052] In this implementation 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 slightly larger than the end face 41a when viewed from the direction D1. The main body portion 42a faces the ion introduction unit 2 in the direction D1.

[0053] The extension 42b is a portion that extends toward the output electrode 43 in the direction D1. The extension 42b covers at least a portion of the side surface of the multiplier unit 41 that faces the multiplier unit 31. In this implementation example, the extension 42b has a cylindrical shape and covers the entire end of the multiplier unit 41, including the end surface 41a. The extension 42b is provided along the periphery of the main body 42a and extends toward the output electrode 43. The extension 42b extends to a position closer to the end surface 41b than half the length of the multiplier unit 41 in the direction D1. The extension 42b is spaced apart from the side surface of the multiplier unit 41.

[0054] In this implementation example, the output electrode 43 includes a main body portion 43a and a support portion 43b. The main body portion 43a is provided on the end surface 41b and covers the entire surface of the end surface 41b. The main body portion 43a has, for example, a rectangular plate shape and is slightly larger than the end surface 41b when viewed from the direction D1. The main body portion 43a is supported by the support portion 43b. The support portion 43b has a cylindrical shape. One end of the support portion 43b is connected to the main body portion 43a, and the other end of the support portion 43b is fixed to the main surface 51a of the substrate 51 by screws, welding, or the like. The anode 6 is surrounded by the support portion 43b.

[0055] The switching circuit 9 is mounted on the main surface 51a. The switching circuit 9 may be mounted on the back surface 51b. Although not shown in FIG. 2, the capacitors 7 and 8 are mounted on the substrate 51. The capacitors 7 and 8 may be mounted on the main surface 51a or on the back surface 51b. Furthermore, an output terminal for connecting to a signal processing circuit in a subsequent stage may be mounted on the substrate 51. As the output terminal, an SMA (Sub Miniature Type A) connector or the like is used.

[0056] Next, the effects of the ion detector 1 according to the above mounting example will be described with reference to Figs. 4 to 7. Fig. 4 is a diagram showing equipotential lines when the ion detector shown in Fig. 2 detects positive ions. Fig. 5 is a diagram showing equipotential lines when the ion detector shown in Fig. 2 detects negative ions. Fig. 6 is a diagram showing equipotential lines when the ion detector of another mounting example detects positive ions. Fig. 7 is a diagram showing equipotential lines when the ion detector of another mounting example detects negative ions. The ion detector of another mounting example shown in Figs. 6 and 7 differs from the ion detector shown in Figs. 4 and 5 in that the input electrode 32 does not include the extension 32b and the input electrode 42 does not include the extension 42b.

[0057] The equipotential lines shown in Figs. 4 to 7 were calculated by simulation. In Figs. 4 to 7, equipotential lines are shown at intervals of 1000V in the range of -5000V to +5000V. A simulation model in which the main body 32a, the multiplier 31, the output electrode 33, and the anode 5 are integrated was used as the electron multiplier 3 and the anode 5. A simulation model in which the main body 42a, the multiplier 41, the output electrode 43, and the anode 6 are integrated was used as the electron multiplier 4 and the anode 6. A voltage of -10 kV was applied to the input electrode 32, and a voltage of -6.5 kV was applied to the anode 5. A voltage of +10 kV was applied to the input electrode 42, and a voltage of +13.5 kV was applied to the anode 6. The ion lens 21 was set to a ground potential. In the calculation of the equipotential lines in Figs. 4 and 6, a voltage of -500 V was applied to the ion lens 22. In the calculation of the equipotential lines in FIG. 5 and FIG.

[0058] As shown in Figs. 4 to 7, in the space S1, a negative potential is dominant due to the voltage applied to the electron multiplier 3, and the potential becomes lower as the space approaches the electron multiplier 3. In the space S2, a positive potential is dominant due to the voltage applied to the electron multiplier 4, and the potential becomes higher as the space approaches the electron multiplier 4. Positive ions move from the through-hole 2a toward the input electrode 32, and negative ions move from the through-hole 2a toward the input electrode 42. For this reason, the potential gradient in the space between the ion introduction unit 2 and the input electrode 32 and the input electrode 42 (ion movement region) can affect the trajectory of the ions.

[0059] As shown in FIG. 6 and FIG. 7, when the input electrode 32 does not include the extension 32b, the multiplier 31 is exposed, and the voltage (potential) of the multiplier 31 affects the potential in the internal space S. Similarly, when the input electrode 42 does not include the extension 42b, the multiplier 41 is exposed, and the voltage (potential) of the multiplier 41 affects the potential in the internal space S. Although the absolute value of the applied voltage of the input electrode 32 and the absolute value of the applied voltage of the input electrode 42 are equal, the absolute value of the voltage of the multiplier 41 is larger than the absolute value of the voltage of the multiplier 31, and the difference between them increases toward the output electrodes 33, 43. Therefore, since a negative voltage has a larger effect on the potential in the internal space S than a positive voltage, the symmetry between the positive potential gradient and the negative potential gradient with respect to the virtual plane is greatly broken. As a result, a positive potential is also generated in the space S1 in the ion migration region.

[0060] Therefore, when a positive ion is detected, the repulsive component due to the positive potential is greater than the attractive component due to the negative potential, so that a force is applied to the positive ion in the direction D2 away from the electron multiplier 4. Similarly, when a negative ion is detected, the attractive component due to the positive potential is greater than the attractive component due to the negative potential, so that a force is applied to the negative ion in the direction D2 away from the electron multiplier 3. When the distances L1 and L2 are set based on an ideal state in which the positive potential gradient and the negative potential gradient are highly symmetrical, the distances L1 and L2 are equal to each other. In this case, in the example shown in FIG. 6 and FIG. 7, the possibility that the positive ion reaches the input electrode 32 is reduced, and the detection accuracy of the positive ion may be reduced. Similarly, the possibility that the negative ion reaches the input electrode 42 is reduced, and the detection accuracy of the negative ion may be reduced.

[0061] On the other hand, as shown in FIG. 4 and FIG. 5, when the input electrode 32 includes the extension 32b, the end including the end face 31a of the multiplier 31 is covered by the extension 32b. Therefore, the influence of the voltage of the multiplier 31 on the potential in the internal space S is reduced, and the influence of the applied voltage of the input electrode 32 on the potential in the internal space S is increased. Similarly, when the input electrode 42 includes the extension 42b, the end including the end face 41a of the multiplier 41 is covered by the extension 42b. Therefore, the influence of the voltage of the multiplier 41 on the potential in the internal space S is reduced, and the influence of the applied voltage of the input electrode 42 on the potential in the internal space S is increased. As a result, compared with FIG. 6 and FIG. 7, the symmetry between the positive potential gradient and the negative potential gradient is improved in the ion migration region. Therefore, when detecting positive ions, the repulsive component and the attractive component are balanced, and the possibility that the positive ions reach the input electrode 32 is increased, so that it is possible to improve the detection accuracy of the positive ions. Similarly, when detecting negative ions, the repulsive and attractive components are balanced, increasing the possibility that negative ions will reach the input electrode 42, thereby improving the detection accuracy of negative ions.

[0062] Since the extension 32b has a cylindrical shape, the end of the multiplier 31 including the end face 31a is surrounded by the extension 32b. Similarly, since the extension 42b has a cylindrical shape, the end of the multiplier 41 including the end face 41a is surrounded by the extension 42b. Therefore, compared to a configuration in which a part of the end including the end face 31a is covered by the extension 32b and a part of the end including the end face 41a is covered by the extension 42b, the symmetry between the positive potential gradient and the negative potential gradient in the ion migration region is further improved. As a result, it is possible to improve the detection accuracy of positive ions and negative ions.

[0063] A distance L1 in the direction D2 between the electron multiplier 3 and the central axis AX is equal to a distance L2 in the direction D2 between the electron multiplier 4 and the central axis AX. Therefore, since it is not necessary to individually adjust the arrangement of the electron multiplier 3 and the arrangement of the electron multiplier 4, the design of the arrangement of the electron multiplier 3 and the electron multiplier 4 can be simplified.

[0064] The electron multiplier 3 and the electron multiplier 4 are provided to extend in the direction D1 while being spaced apart from each other in the direction D2. The input electrode 32 and the input electrode 42 both face the ion introduction unit 2 in the direction D1. In other words, the main body 32a and the main body 42a face the same direction, and the input electrode 32 and the input electrode 42 do not face each other. Therefore, it is possible to reduce the possibility that the input electrode 32 receives noise derived from the charged particles generated by the electron multiplier 4. Similarly, it is possible to reduce the possibility that the input electrode 42 receives noise derived from the charged particles generated by the electron multiplier 3. As a result, it is possible to improve the detection accuracy of positive ions and negative ions.

[0065] In a configuration in which the electron multiplier 3 and the electron multiplier 4 are mounted on different substrates, the positions of the electron multiplier 3 and the electron multiplier 4 need to be individually aligned. On the other hand, in the ion detector 1 according to the above mounting example, the electron multiplier 3 and the electron multiplier 4 are arranged on a single substrate 51, so that the distance between the electron multiplier 3 and the electron multiplier 4 is constant. Therefore, the positions of the electron multiplier 3 and the electron multiplier 4 in the direction D2 are determined simply by aligning the center point between the electron multiplier 3 and the electron multiplier 4 on the central axis AX. As a result, the assembly accuracy of the ion detector 1 can be improved.

[0066] Not only the electron multipliers 3, 4 and the anodes 5, 6, but also the capacitors 7, 8 and the switching circuit 9 are mounted on the substrate 51. In this configuration, the components of the ion detector 1 are mounted on a single substrate 51, so there is no need to prepare a separate substrate for mounting the capacitors 7, 8 and the switching circuit 9. This makes it possible to reduce the number of components.

[0067] When the potential difference between the anode 5 and the anode 6 is large, a creeping discharge may occur between the anode 5 and the anode 6 along the main surface 51a or the back surface 51b of the substrate 51. In response to this, the substrate 51 is provided with a slit penetrating the substrate 51 in the direction D1 between the anode 5 and the anode 6. Therefore, the creeping distance between the anode 5 and the anode 6 is increased. This can reduce the possibility of a creeping discharge occurring between the anode 5 and the anode 6.

[0068] Since the ion introduction portion 2 is supported by the spacers 52 and 53, the position of the central axis AX (through hole 2a) is determined. Therefore, the assembly precision of the ion detector 1 can be improved.

[0069] The ion detector according to the present disclosure is not limited to the above embodiment.

[0070] Either one of the input electrodes 32, 42 may not include an extension. In this case, the symmetry between the positive potential gradient and the negative potential gradient in the ion migration region can be improved compared to a configuration in which neither of the input electrodes 32, 42 includes an extension. As a result, it is possible to improve the detection accuracy of positive ions and negative ions.

[0071] The arrangement of the electron multiplier 3 and the electron multiplier 4 is not limited to the arrangement in the implementation example shown in Fig. 2. For example, the electron multiplier 3 and the electron multiplier 4 may be arranged such that the input electrode 32 and the input electrode 42 face each other in the direction D2 across the central axis AX. In this case, the symmetry of the positive potential gradient and the negative potential gradient with respect to the virtual plane can be maintained. One of the electron multiplier 3 and the electron multiplier 4 may be arranged to extend in the direction D1, and the other may be arranged to extend in the direction D2.

[0072] The absolute value of the voltage applied to the input electrode 32 and the absolute value of the voltage applied to the input electrode 42 do not have to be equal.

[0073] Next, with reference to Fig. 8, a further implementation example of the ion detector 1 shown in Fig. 1 will be described. Fig. 8 is a cross-sectional view showing a further implementation example of the ion detector shown in Fig. 1. As shown in Fig. 8, the ion detector 1 of this implementation example differs from the ion detector 1 of the implementation example shown in Fig. 2 mainly in that it includes a substrate 61 (first substrate) and a substrate 62 (second substrate) instead of the substrate 51, and in the implementation of the capacitors 7, 8 and the switching circuit 9.

[0074] The substrate 61 is a plate-like member on which the electron multiplier 3 is mounted. The substrate 61 is, for example, a printed circuit board such as a glass epoxy substrate. The 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 (here, perpendicular to) the direction D1. The main surface 61a faces the ion introduction section 2 in the direction D1. The substrate 62 is a plate-like member on which the electron multiplier 4 is mounted. The substrate 62 is, for example, a printed circuit board such as a glass epoxy substrate. The 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 (here, perpendicular to) the direction D1. The main surface 62a faces the ion introduction section 2 in the direction D1. The substrate 61 and the substrate 62 are arranged in the direction D2. The substrate 61 and the substrate 62 are disposed substantially symmetrically with respect to an imaginary plane that is perpendicular to the direction D2 and that is along the central axis AX.

[0075] The anode 5 is provided on the main surface 61a. The anode 5 may be formed on the main surface 61a as a wiring pattern. The anode 6 is provided on the main surface 62a. The anode 6 may be formed on the main surface 62a as a wiring pattern. The anode 5 and the anode 6 are disposed substantially symmetrically with respect to the virtual plane.

[0076] The electron multiplier 3 is disposed on the main surface 61a such that the output electrode 33 faces the anode 5 in the direction D1. In this implementation example, the other end of the support portion 33b is fixed to the main surface 61a of the substrate 61 by screws, welding, or the like. The electron multiplier 4 is disposed on the main surface 62a such that the output electrode 43 faces the anode 6 in the direction D1. In this implementation example, the other end of the support portion 43b is fixed to the main surface 62a of the substrate 62 by screws, welding, or the like.

[0077] The capacitors 7 and 8 and the switching circuit 9 are mounted on a substrate (not shown) separate from the substrates 61 and 62. The capacitor 7 may be mounted on the substrate 61, and the capacitor 8 may be mounted on the substrate 62.

[0078] In this implementation example, the anode 5 and the anode 6 are arranged on different substrates, which reduces the possibility of creeping discharge occurring between the anode 5 and the anode 6. Furthermore, the electron multiplier 3 and the electron multiplier 4 are arranged on different substrates, which improves the freedom of arrangement of the electron multiplier 3 and the electron multiplier 4.

[0079] Next, referring to FIG. 9, another implementation example of the ion detector 1 shown in FIG. 1 will be described. FIG. 9 is a cross-sectional view showing another implementation example of the ion detector shown in FIG. 1. As shown in FIG. 9, the input electrode 32 does not include the extension 32b. The input electrode 42 does not include the extension 42b. In this configuration, as described above, when positive ions are detected, the positive potential repels the positive ions, and a force is applied to the positive ions in a direction away from the electron multiplier 4 in the direction D2. Similarly, when negative ions are detected, the positive potential attracts the negative ions, and a force is applied to the negative ions in a direction away from the electron multiplier 3 in the direction D2.

[0080] In contrast, the electron multiplier 3 and the electron multiplier 4 are arranged asymmetrically with respect to a virtual plane along the central axis AX. Specifically, the electron multiplier 3 and the electron multiplier 4 are arranged such that the distance L1 is greater than the distance L2. The greater the difference between the voltage applied to the output electrode 33 and the voltage applied to the output electrode 43, the greater the value to which the distance L1 is set than the distance L2. The distance L1 may be determined by calculating the trajectory of the positive ions in advance by simulation. The distance L2 may be determined by calculating the trajectory of the negative ions in advance by simulation.

[0081] According to this configuration, since the electron multiplier 3 is farther from the central axis AX in the direction D2 than the electron multiplier 4, it is possible to increase the possibility that positive ions are incident on the input electrode 32. Similarly, since the electron multiplier 4 is closer to the central axis AX in the direction D2 than the electron multiplier 3, it is possible to increase the possibility that negative ions are incident on the input electrode 42. Therefore, it is possible to improve the detection accuracy of positive ions and negative ions. [Explanation of symbols]

[0082] 1... ion detector, 2... ion introduction section, 2a... through hole, 3... electron multiplier (first electron multiplier), 4... electron multiplier (second electron multiplier), 5... anode (first anode), 6... anode (second anode), 9... switching circuit, 9a... input terminal (first input terminal), 9b... input terminal (second input terminal), 9c... output terminal, 31... multiplier section (first multiplier section), 32... input electrode (first input electrode), 32a... main body section (first main body section), 32b... extension section (first extension section), 33... output electrode ( 41...multiplication section (second multiplication section), 42...input electrode (second input electrode), 42a...main body section (first main body section), 42b...extension section (first extension section), 43...output electrode (second output electrode), 51...substrate, 51a...main surface, 51s...slit, 52, 53...spacer (support member), 61...substrate (first substrate), 62...substrate (second substrate), 61a...main surface (first main surface), 62a...main surface (second main surface), AX...central axis, D1...direction (first direction), D2...direction (second direction).

Claims

1. a first electron multiplier for detecting a first ion having a first polarity; a second electron multiplier for detecting second ions having a second polarity different from the first polarity; a 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 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, the switching circuit selectively connecting either the first input terminal or the second input terminal to the output terminal; an iontophoresis unit provided with a through hole having a central axis extending in a first direction; Equipped with the first electron multiplier includes a first multiplication section extending in the first direction, a first input electrode provided at one end of the first multiplication section in the first direction, and a first output electrode provided at the other end of the first multiplication section in the first direction, the second electron multiplier includes a second multiplier section extending in the first direction, a second input electrode provided at one end of the second multiplier section in the first direction, and a second output electrode provided at the other end of the second multiplier section in the first direction, the first input electrode receives the first ions that have passed through the through hole; the second input electrode receives the second ions that have passed through the through hole; the first electron multiplier and the second electron multiplier are spaced apart from each other in a second direction intersecting the first direction; the first input electrode includes a first main body portion facing the iontophoresis portion in the first direction and a first extension portion extending toward the first output electrode in the first direction, The first extension portion covers a portion of the first multiplication portion facing the second multiplication portion.

2. The ion detector according to claim 1 , wherein the first extension portion has a cylindrical shape.

3. the second input electrode includes a second main body portion facing the iontophoresis portion in the first direction and a second extension portion extending toward the second output electrode in the first direction, The second extension portion covers a portion of the second multiplication portion facing the first multiplication portion. The ion detector according to claim 1 or 2.

4. The ion detector according to claim 3 , wherein the second extension portion has a cylindrical shape.

5. 5. The ion detector according to claim 1, wherein a distance between the first electron multiplier and the central axis in the second direction is equal to a distance between the second electron multiplier and the central axis in the second direction.

6. Further comprising a substrate having a main surface facing the ion introduction unit in the first direction, the first anode and the second anode are provided on the main surface, the first electron multiplier is disposed on the main surface such that the first output electrode faces the first anode in the first direction; 6. The ion detector according to claim 1, wherein the second electron multiplier is disposed on the main surface such that the second output electrode faces the second anode in the first direction.

7. The ion detector of claim 6 , wherein the switching circuitry is mounted on the substrate.

8. 8. The ion detector according to claim 6, wherein the substrate is provided with a slit between the first anode and the second anode, the slit penetrating the substrate in the first direction.

9. 9. The ion detector according to claim 6, further comprising a support member provided on the main surface and supporting the ion introduction section.

10. a first substrate having a first main surface facing the ion introduction portion in the first direction; a second substrate having a second main surface facing the ion introduction portion in the first direction; Further comprising: The first anode is provided on the first main surface, The second anode is provided on the second main surface, the first electron multiplier is disposed on the first main surface such that the first output electrode faces the first anode in the first direction; 6. The ion detector according to claim 1, wherein the second electron multiplier is disposed on the second main surface such that the second output electrode faces the second anode in the first direction.

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