Ion detector and analyzing device

Abstract

To provide an ion detector that can be compatibly made compact and improved in efficiency of ion detection.SOLUTION: An ion detector 1 comprises: a conversion diode 3 which has a conversion region 3a emitting an electron E in response to incidence of an ion P; an electron multiplication part 4 which has an electron incidence surface 42b on which the ion E impinges; and an aperture electrode 5 which has an aperture 5a allowing the electron E traveling from the conversion region 3a to the electron incidence surface 42b to pass through. The conversion region 3a is a region which is convex toward the space where the electron E is emitted.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an ion detector and an analysis device. [Background technology]

[0002] A known ion detector includes a conversion dynode that emits electrons when ions are incident on it, an electron multiplier section that multiplies the electrons emitted from the conversion dynode, and an aperture electrode that focuses the electrons emitted from the conversion dynode onto the electron entrance surface of the electron multiplier section (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-086403 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the ion detector described above, a potential with a large absolute value may be applied to the conversion dynode in order to increase the conversion efficiency from ions to electrons. In that case, it is difficult to reduce the distance between the conversion dynode and the aperture electrode due to the need to ensure voltage resistance. Therefore, it is possible to reduce the potential difference between the conversion dynode and the aperture electrode by bringing the potential applied to the aperture electrode closer to the potential applied to the conversion dynode, thereby reducing the distance between the conversion dynode and the aperture electrode. However, in that case, the electrons emitted from the conversion dynode are susceptible to the influence of not only the electric field formed by the potential difference between the conversion dynode and the aperture electrode, but also the electric field formed by the potential difference between the conversion dynode and the electron incident surface, and the electrons emitted from the conversion dynode may be focused in front of the electron incident surface and may be incident on the electron incident surface in a divergent state. As a result, the amount of electrons incident on the electron incident surface may decrease, and the detection efficiency of ions may decrease.

[0005] An object of the present invention is to provide an ion detector and an analyzer that can achieve both miniaturization and improved ion detection efficiency. [Means for solving the problem]

[0006] The ion detector of the present invention is [1] "an ion detector comprising: a conversion dynode having a conversion region that emits electrons in response to the incidence of ions; an electron multiplier section having an electron incident surface on which the electrons are incident; and an aperture electrode having an aperture that passes the electrons traveling from the conversion region to the electron incident surface, wherein the conversion region is a convex region toward the space side from which the electrons are emitted."

[0007] In the ion detector described in [1] above, the conversion dynode has a conversion region that is a convex region on the space side from which electrons are emitted. As a result, when electrons are incident on the conversion region, the electrons are emitted from the conversion region in a divergent manner. Therefore, even when a potential with a large absolute value is applied to the conversion dynode, the distance between the conversion dynode and the aperture electrode can be reduced, and an electric field can be formed that can appropriately focus the electrons emitted from the conversion region on the electron incidence surface. Therefore, the ion detector described in [1] above can achieve both miniaturization and improved ion detection efficiency.

[0008] The ion detector of the present invention may be [2] "the ion detector according to the above [1], in which the conversion region faces the electron incident surface of the electron multiplier section across the aperture of the aperture electrode." According to the ion detector according to [2], an electric field capable of focusing electrons emitted from the conversion region on the electron incident surface can be easily and reliably formed. Therefore, the electrons emitted from the conversion region can be reliably incident on the electron incident surface.

[0009] The ion detector of the present invention may be [3] "the ion detector according to the above [2], in which the conversion region is a convex region that is line-symmetrical with respect to the center line of the aperture when viewed from a direction perpendicular to the center line." According to the ion detector according to [3], an electric field capable of focusing electrons emitted from the conversion region on the electron incident surface can be more easily and reliably formed. Therefore, the electrons emitted from the conversion region can be more reliably incident on the electron incident surface.

[0010] The ion detector of the present invention may be [4] "the ion detector according to the above [3], in which the conversion region is formed so that the convex region extends in a direction intersecting with the center line of the aperture." According to the ion detector described in [4], the conversion region, which can more reliably cause emitted electrons to be incident on the electron incident surface, extends in a direction intersecting with the center line of the aperture, thereby further improving the ion detection efficiency.

[0011] The ion detector of the present invention may be [5] "the ion detector according to the above [4], further comprising a partition having an ion entrance port for introducing the ions incident on the conversion dynode, the ion entrance port being arranged such that a center line of the ion entrance port intersects with a center line of the aperture and the extension direction of the conversion region, and the electron entrance surface of the electron multiplier section extends along the extension direction of the conversion region." According to the ion detector described in [5], the incidence condition of the electrons emitted from the conversion region onto the electron entrance surface is made uniform in the extension direction, and the electron multiplication condition on the electron entrance surface of the electron multiplier section is made uniform in the extension direction, thereby improving the detection accuracy of ions.

[0012] The ion detector of the present invention may be [6] "the ion detector according to the above [5], wherein the partition portion, together with the aperture electrode, forms an enclosed space surrounding the conversion dynode." According to the ion detector according to [6], the electric field around the conversion dynode can be stabilized, and the conversion of ions to electrons in the conversion dynode can be stably performed.

[0013] The ion detector of the present invention may be [7] "the ion detector according to any one of the above [1] to [6], wherein the conversion region is a curved region." According to the ion detector according to [7], the divergence state of electrons emitted from the conversion region can be made to be a desired divergence state. Therefore, the electrons emitted from the conversion region can be reliably incident on the electron incident surface.

[0014] The ion detector of the present invention may be [8] "the ion detector according to any one of the above [1] to [7], in which an angle formed between a first imaginary plane tangent to a vertex of the conversion region and a second imaginary plane tangent to a point other than the vertex in the conversion region is greater than 0 degrees and less than or equal to 60 degrees." According to the ion detector according to [8], it is possible to suppress excessive divergence of electrons emitted from the conversion region. Therefore, it is possible to reliably make the electrons emitted from the conversion region incident on the electron incident surface.

[0015] The ion detector of the present invention may be [9] "the ion detector according to any one of the above [1] to [8], further comprising a potential applying unit that applies a first potential to the conversion dynode, applies a second potential to the electron incident surface of the electron multiplier, and applies a third potential to the aperture electrode, wherein the second potential is higher than the first potential, and the third potential is equal to or higher than the first potential and lower than the second potential." According to the ion detector described in [9], by using the potential applying unit, it is possible to reduce the distance between the conversion dynode and the aperture electrode, and to specifically form an electric field that can appropriately focus electrons emitted from the conversion region on the electron incident surface.

[0016] The ion detector of the present invention may be

[10] "the ion detector described in [9] above, in which the difference between the first potential and the third potential is smaller than the difference between the second potential and the third potential." According to the ion detector described in

[10] , the potential difference between the conversion dynode and the aperture electrode can be further reduced, and the distance between the conversion dynode and the aperture electrode can be further reduced.

[0017] The analytical device of the present invention may be

[11] "an analytical device using the ion detector according to any one of the above [1] to

[10] ." The analytical device according to

[11] can achieve both miniaturization and improved ion detection efficiency. Effect of the Invention

[0018] According to the present invention, it is possible to provide an ion detector and an analyzer that can achieve both miniaturization and improved ion detection efficiency. [Brief description of the drawings]

[0019] [Figure 1] FIG. 2 is a configuration diagram of an ion detector according to an embodiment. [Diagram 2] FIG. 2 is a perspective view of a conversion dynode included in the ion detector shown in FIG. [Diagram 3] FIG. 4 is a diagram showing an example of an electric field distribution formed in an ion detector. [Figure 4] FIG. 13 is a perspective view of a modified conversion dynode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and duplicated explanations will be omitted.

[0021] As shown in FIG. 1, the ion detector 1 includes a partition section 2, a conversion dynode 3, an electron multiplier section 4, an aperture electrode 5, and a potential applying section 6. The ion detector 1 is accommodated in an ion detector housing (not shown) in a mass spectrometer (analysis device) 200, and is disposed in a vacuum space. The material of the partition section 2 is a metal such as stainless steel. The partition section 2 is a plate-shaped member whose thickness direction is in the X-axis direction. An ion entrance port 21a is formed in a wall section 21 of the partition section 2. The ion entrance port 21a has a center line A1 parallel to the X-axis direction. The shape of the ion entrance port 21a when viewed from the X-axis direction is, for example, circular. Hereinafter, one direction perpendicular to the X-axis direction is referred to as the Y-axis direction, and a direction perpendicular to both the X-axis direction and the Y-axis direction is referred to as the Z-axis direction. The ion entrance port 21a is positioned so that the center line A1 of the ion entrance port 21a intersects with the center line A2 of the aperture 5a described later and the extension direction of the conversion region 3a described later. In this embodiment, the center line A1 of the ion entrance port 21a, the center line A2 of the aperture 5a, and the extension direction of the conversion region 3a all intersect perpendicularly and correspond to the X-axis direction, Y-axis direction, and Z-axis direction, respectively.

[0022] In this embodiment, the ion detector 1 is used as a part of a mass spectrometer 200. In the mass spectrometer 200, a sample is ionized by being irradiated with, for example, a deuterium lamp for photoionization. The mass spectrometer 200 selects ions P to be measured from the generated ions, for example, by using a quadrupole. The ions P to be measured are introduced into the ion detector 1 through an ion entrance port 21a. The ion detector 1 detects the incident ions P. The ion detector 1 can detect both positive ions and negative ions, but in this embodiment, the ions P are described as positive ions. The potential of an ion detector housing (not shown) is described as a ground potential.

[0023] The conversion dynode 3 has a surface including a conversion region 3a. The conversion region 3a emits electrons E when ions P are incident on the conversion dynode 3. The conversion dynode 3 is made of a metal such as stainless steel. The conversion dynode 3 is supported by a support member (not shown). The conversion dynode 3 is disposed on one side in the Y-axis direction with respect to the center line A1. The conversion region 3a faces the other side in the Y-axis direction (the center line A1 side) on a plane α that includes the center line A1 and is perpendicular to the Z-axis direction. The conversion region 3a has a center line that coincides with a center line A2 (a center line A2 that is included in the plane α and is parallel to the Y-axis direction) of an aperture 5a described later. When viewed from the X-axis direction, the conversion region 3a does not overlap with the ion entrance port 21a, but overlaps with the wall portion 21. This makes it possible to suppress stray light that is generated in the mass spectrometer 200 and may become noise from entering the conversion dynode 3.

[0024] A first potential is applied to the conversion dynode 3 by the potential applying unit 6. The first potential is a potential of the opposite polarity to the polarity of the ions P, and is a negative potential in this embodiment. As an example, the first potential is -10 kV. As a result, the incident ions P move gradually away from the center line A1 of the ion entrance port 21a to one side in the Y-axis direction and proceed toward the conversion region 3a. Then, the ions P are incident on the conversion region 3a with an energy of, for example, 10 keV, and electrons E are emitted from the conversion region 3a. The amount of emitted electrons E increases as the energy of the ions P incident on the conversion region 3a increases. In other words, the higher the absolute value of the first potential, the higher the conversion efficiency from the ions P to the electrons E can be.

[0025] The electron multiplier section 4 is disposed on the other side in the Y-axis direction (opposite the conversion dynode 3) with respect to the center line A1. In this embodiment, the electron multiplier section 4 has a metal wall section 41, a plurality of dynodes 42, and an anode 43. The electron multiplier section 4 is supported by a support member (not shown). An electron passing port 41a that passes electrons E is formed in the wall section 41. The electron passing port 41a faces the conversion region 3a in the Y-axis direction and has a center line that coincides with the center line A2. The shape of the electron passing port 41a when viewed from the Y-axis direction is, for example, circular. The plurality of dynodes 42 and the anode 43 are arranged on a plane α. The material of each dynode 42 and the anode 43 is, for example, a metal such as stainless steel. Of the plurality of dynodes 42, the first stage dynode 42a faces the electron passing port 41a in the Y-axis direction and has an electron incident surface 42b. The electron incident surface 42b in the electron multiplier 4 is the portion of the electron multiplier 4 where the electrons E emitted from the conversion region 3a of the conversion dynode 3 first enter. In the electron multiplier 4, the electrons E that have passed through the electron passage port 41a enter the electron incident surface 42b of the first dynode 42a, causing secondary electrons (not shown) to be emitted from the first dynode 42a. The secondary electrons are multiplied by each dynode 42 in the subsequent stage and enter the anode 43. The anode 43 is configured to output the secondary electrons as a pulse signal. The electron incident surface 42b of the first dynode 42a extends in the extension direction of the conversion region 3a described later, that is, along the Z-axis direction in this embodiment. In other words, the electron incident surface 42b of the first dynode 42a extends so as to face the conversion region 3a, and is formed to have a concave region with respect to the convex region of the conversion region 3a.

[0026] A second potential is applied to the first-stage dynode 42a by the potential application unit 6. That is, the second potential is applied to the electron incident surface 42b by the potential application unit 6. The second potential is higher than the first potential of the conversion dynode 3. As an example, the second potential is -2 kV. A predetermined potential is applied to each dynode 42 other than the first-stage dynode 42a by the potential application unit 6 so that secondary electrons emitted from the first-stage dynode 42a proceed sequentially to each dynode 42 in the subsequent stage. The anode 43 is set to ground potential. In the ion detector 1, a second potential is applied to the wall portion 41 of the electron multiplier unit 4 by the potential application unit 6.

[0027] The aperture electrode 5 is disposed between the conversion dynode 3 and the electron multiplier section 4. More specifically, the aperture electrode 5 is disposed on the other side in the Y-axis direction (opposite the conversion dynode 3) with respect to the center line A1. In this embodiment, the aperture electrode 5 is a plate-shaped electrode whose thickness direction is in the Y-axis direction, and extends along a plane perpendicular to the Y-axis direction so as to separate the space in which the conversion dynode 3 is disposed from the space in which the electron multiplier section 4 is disposed. The material of the aperture electrode 5 is a metal such as stainless steel. The aperture electrode 5 is formed with an aperture 5a that passes electrons E traveling from the conversion region 3a to the first stage dynode 42a. The aperture 5a faces each of the conversion region 3a and the first stage dynode 42a on the plane α, and has a center line A2 that is included in the plane α and is parallel to the Y-axis direction. The shape of the aperture 5a when viewed from the Y-axis direction is, for example, circular.

[0028] A third potential is applied to the aperture electrode 5 by the potential application unit 6. The third potential is equal to or higher than the first potential of the conversion dynode 3 and is lower than the second potential of the first stage dynode 42a. As an example, the third potential is −9.5 kV.

[0029] The potential application unit 6 applies a predetermined potential to each of the conversion dynode 3, the electron multiplier unit 4, and the aperture electrode 5. The potential application unit 6 is electrically connected to each of the conversion dynode 3, the electron multiplier unit 4, and the aperture electrode 5 by wiring or the like. As described above, the potential application unit 6 applies a first potential (e.g., −10 kV) to the conversion dynode 3, applies a second potential (e.g., −2 kV) higher than the first potential to the first stage dynode 42a of the electron multiplier unit 4, and applies a third potential (e.g., −9.5 kV) that is equal to or greater than the first potential and less than the second potential to the aperture electrode 5. In this embodiment, the potential applying unit 6 applies a predetermined potential to each of the conversion dynode 3, the electron multiplier unit 4, and the aperture electrode 5 so that the difference between the first potential (e.g., −10 kV) and the third potential (e.g., −9.5 kV) is smaller than the difference between the second potential (e.g., −2 kV) and the third potential (e.g., −9.5 kV). The potential applying unit 6 may be disposed inside the ion detector housing case (not shown), or may be disposed outside the ion detector housing case (not shown). As an example, the potential applying unit 6 is a power supply unit capable of supplying a plurality of potentials, and may be, for example, a power supply unit having a plurality of high voltage generating units and their control units, or may be configured by a power supply unit having a high voltage generating unit consisting of a single boost unit and resistance division and its control unit.

[0030] In this embodiment, the conversion region 3a faces the electron entrance surface 42b of the first stage dynode 42a across the aperture 5a and the electron passing port 41a. The conversion region 3a, the aperture 5a, the electron passing port 41a, the multiple dynodes 42, and the anode 43 are arranged on a plane α. The center line A2 of the aperture 5a intersects with the center line A1 of the ion entrance port 21a, and is perpendicular to the center line A1 in this embodiment. The center line of the conversion region 3a and the center line of the electron passing port 41a each coincide with the center line A2 of the aperture 5a. In other words, the aperture 5a, the conversion region 3a, and the electron passing port 41a have the same center line A2. When viewed from the Y-axis direction, the outer edge of the aperture 5a is located inside the outer edge of the conversion region 3a. When viewed from the Y-axis direction, the outer edge of the electron passing port 41a is located inside the outer edge of the aperture 5a.

[0031] In the ion detector 1 configured as above, a predetermined potential is applied to each of the conversion dynode 3, the electron multiplier section 4, and the aperture electrode 5 by the potential application section 6. In this state, ions P are incident from the ion incident port 21a, and the ions P proceed toward the conversion region 3a of the conversion dynode 3 due to the formed electric field. When the ions P are incident on the conversion region 3a, electrons E are emitted from the conversion region 3a. The electrons E emitted from the conversion region 3a pass through the aperture 5a of the aperture electrode 5 and the electron passing port 41a of the electron multiplier section 4, and are incident on the electron incident surface 42b of the first-stage dynode 42a. When the electrons E are incident on the electron incident surface 42b of the first-stage dynode 42a, secondary electrons (not shown) are emitted from the electron incident surface 42b of the first-stage dynode 42a. The secondary electrons are multiplied by each dynode 42 in the subsequent stage, and are incident on the anode 43. The anode 43 then outputs the secondary electrons as a pulse signal, causing the ion detector 1 to detect the ions P. The aperture electrode 5 prevents electrons or ions that could become noise from entering the electron multiplier section 4.

[0032] As shown in FIG. 1 and FIG. 2, the conversion region 3a is a convex region toward the space side from which the electrons E are emitted. In the ion detector 1, the conversion region 3a is a convex region that is symmetrical with respect to the center line A2 when viewed from the Z-axis direction perpendicular to the plane α (direction perpendicular to the center line A2 of the aperture 5a). That is, the apex of the conversion region 3a is located on the center line A2 when viewed from the Z-axis direction. In addition, the conversion region 3a is formed so that the convex region extends in the Z-axis direction perpendicular to the plane α (direction intersecting the center line A2 of the aperture 5a, in this embodiment, direction intersecting perpendicularly). The conversion region 3a is a smoothly curved region, and maintains the same cross-sectional shape along the Z-axis direction. That is, in the conversion dynode 3 of this embodiment, the conversion region 3a has a shape in which a circular arc-shaped portion that gently protrudes toward the space side from which electrons E are emitted is continuously extended in a direction perpendicular to the center line A1 of the ion entrance port 21a and the center line A2 of the aperture 5a. The conversion dynode 3 is an electrode having an end face formed from a flat surface that connects the surface opposite the conversion region 3a to the conversion region 3a, and has an electrical connection part with the potential application part 6 on one of the end faces. The angle formed by the first imaginary plane K1 that contacts the vertex of the conversion region 3a and the second imaginary plane K2 that contacts a point on the conversion region 3a other than the vertex is, for example, greater than 0 degrees and less than or equal to 60 degrees.

[0033] As described above, in the ion detector 1, the conversion dynode 3 has the conversion region 3a which is a region convex toward the space side from which the electrons E are emitted. As a result, when the electrons E are incident on the conversion region 3a, the electrons E are emitted from the conversion region 3a in a divergent manner. Therefore, even when a potential with a large absolute value is applied to the conversion dynode 3, the distance between the conversion dynode 3 and the aperture electrode 5 can be reduced, and an electric field can be formed that can focus the electrons E emitted from the conversion region 3a on the electron incident surface 42b. Therefore, the ion detector 1 can achieve both miniaturization and improved ion detection efficiency.

[0034] In the ion detector 1, the conversion region 3a faces the electron incident surface 42b of the electron multiplier section 4 across the aperture 5a of the aperture electrode 5. This makes it possible to easily and reliably form an electric field capable of focusing the electrons E emitted from the conversion region 3a onto the electron incident surface 42b. Therefore, the electrons E emitted from the conversion region 3a can be reliably made incident on the electron incident surface 42b.

[0035] In the ion detector 1, the conversion region 3a is a convex region that is line-symmetrical with respect to the center line A2 of the aperture 5a when viewed from the Z-axis direction perpendicular to the center line A2. This makes it possible to more easily and reliably form an electric field that can focus the electrons E emitted from the conversion region 3a on the electron incident surface 42b. Therefore, the electrons E emitted from the conversion region 3a can be more reliably incident on the electron incident surface 42b.

[0036] In the ion detector 1, the conversion region 3a is formed such that the convex region extends in a direction intersecting with the center line A2 of the aperture 5a. As a result, the conversion region 3a, which can more reliably cause the emitted electrons E to be incident on the electron incident surface 42b, extends in a direction intersecting with the center line A2 of the aperture 5a. In other words, the area of ​​the conversion region 3a along the direction intersecting with the center line A2 of the aperture 5a becomes large. Therefore, the detection efficiency of ions can be further improved.

[0037] The ion detector 1 includes a partition section 2 having an ion entrance port 21a for introducing ions P incident on the conversion dynode 3, the ion entrance port 21a being disposed such that a center line A1 of the ion entrance port 21a intersects with a center line A2 of the aperture 5a and the extension direction of the conversion region 3a, and the electron entrance surface 42b of the electron multiplier section 4 extends along the extension direction of the conversion region 3a. This makes it possible to uniformize the incidence conditions of electrons E emitted from the conversion region 3a onto the electron entrance surface 42b in the extension direction, and to uniformize the electron multiplication conditions on the electron entrance surface 42b of the electron multiplier section 4 in the extension direction, thereby improving the detection accuracy of ions.

[0038] In the ion detector 1, the conversion region 3a is a region having a smooth curved surface. This allows the electrons E emitted from the conversion region 3a to have a desired divergence state. Therefore, the electrons E emitted from the conversion region 3a can be reliably incident on the electron incident surface 42b.

[0039] In the ion detector 1, the angle formed by the first imaginary plane K1 tangent to the vertex of the conversion region 3a and the second imaginary plane K2 tangent to a point other than the vertex in the conversion region 3a is greater than 0 degrees and equal to or less than 60 degrees. This makes it possible to prevent the electrons E emitted from the conversion region 3a from diverging excessively. Therefore, the electrons E emitted from the conversion region 3a can be reliably incident on the electron incident surface 42b.

[0040] The ion detector 1 includes a potential applying unit 6 that applies a first potential to the conversion dynode 3, applies a second potential to the electron incident surface 42b of the electron multiplier unit 4, and applies a third potential to the aperture electrode 5, where the second potential is higher than the first potential, and the third potential is equal to or greater than the first potential and less than the second potential. By using the potential applying unit 6, it is possible to reduce the distance between the conversion dynode 3 and the aperture electrode 5, and to specifically form an electric field that can appropriately focus the electrons E emitted from the conversion region 3a onto the electron incident surface 42b.

[0041] In the ion detector 1, the difference between the first potential and the third potential is smaller than the difference between the second potential and the third potential, which makes it possible to further reduce the potential difference between the conversion dynode 3 and the aperture electrode 5 and further reduce the distance between the conversion dynode 3 and the aperture electrode 5.

[0042] In the ion detector 1, the conversion region 3a, the aperture 5a, and the multiple dynodes 42 are arranged on a plane α, and the conversion region 3a is a convex region when viewed from the Z-axis direction perpendicular to the plane α. This allows the trajectory of the electrons E to be formed along the plane α, making it possible to simplify the design of each part of the ion detector 1.

[0043] 3(a) and (b), the advantages of the shape of the conversion region 3a described above will be described. In FIG. 3(a), the electric field distribution formed in an ion detector 101 different from the above-mentioned ion detector 1 is shown by equipotential lines. The ion detector 101 differs from the ion detector 1 in that the shape of the conversion region 103a of the conversion dynode 103 is different from the shape of the conversion region 3a. The conversion region 103a is a concave region on the opposite side to the space that emits electrons E, and has a shape that is adopted for conventional general conversion dynodes. In the ion detector 101, the conversion region 103a is a concave region that is line-symmetrical with respect to the center line A2 (see FIG. 1) when viewed from the Z-axis direction perpendicular to the plane α (direction perpendicular to the center line A2 of the aperture 5a). In FIG. 3(b), the electric field distribution formed in the above-mentioned ion detector 1 is shown by equipotential lines. As described above, the first potential of the conversion dynode 3 and the conversion dynode 103 is -10 kV, the second potential of the first stage dynode 42a is -2 kV, and the third potential of the aperture electrode 5 is -9.5 kV. By applying such potentials to each component, an electric field is formed in the ion detector 1 such that electrons E emitted from the conversion region 3a travel to the first stage dynode 42a, and in the ion detector 101, an electric field is formed such that electrons E emitted from the conversion region 103a travel to the first stage dynode 42a.

[0044] As shown in FIG. 3A, the electrons E emitted from the conversion region 103a first proceed to the aperture 5a under the influence of an electric field EF1 formed near the conversion region 103a. Next, the electrons E are focused under the influence of an electric field EF2 formed near the aperture 5a and spreading from the aperture 5a toward the conversion region 103a. That is, when viewed from the Z-axis direction, the electrons E are focused on the center line A2 (see FIG. 1) of the aperture 5a. When the distance between the conversion region 103a and the aperture electrode 5 is small, the effect of the electric field EF2 on the electrons E is large, so that the electrons E are easily focused. As a result, in the ion detector 101, the electrons E are focused in front of the first dynode 42a and enter the electron incident surface 42b of the first dynode 42a in a divergent state.

[0045] As shown in FIG. 3B, in the ion detector 1, the electrons E are first emitted from the conversion region 3a in a diverging direction. This is because the conversion region 3a is a convex region, and the electrons E are likely to be emitted along a direction perpendicular to the conversion region 3a. In addition, the emitted electrons E are further diverged by the effect of the electric field EF3 formed in the vicinity of the conversion region 3a. That is, in the ion detector 1, the electrons E diverge due to the shape of the conversion region 3a, and are also diverged by the effect of the electric field EF3. Next, the electrons E are focused by the effect of the electric field EF4 formed in the vicinity of the aperture 5a, which spreads from the aperture 5a toward the conversion region 3a. In the ion detector 1, since the electrons E diverge, the focusing point F2 of the electrons E can be brought closer to the first dynode 42a even when the effect of the electric field EF4 on the electrons E is large. As a result, in the ion detector 1, the focal point F2 of the electrons E is closer to the first dynode 42a than the focal point F1 in the ion detector 101. As a result, in the ion detector 1, the electrons E are incident on the electron incident surface 42b of the first dynode 42a in a focused state, so that the amount of electrons E incident on the electron incident surface 42b of the first dynode 42a increases compared to the case of the ion detector 101. Note that the focal point F2 may be located on the electron incident surface 42b of the first dynode 42a.

[0046] The present invention is not limited to the above-described embodiment. In the ion detector 1, the conversion region 3a of the conversion dynode 3 is a smoothly curved region and maintains the same cross-sectional shape along the Z-axis direction, but the conversion region 3a may be a convex region toward the space side from which the electrons E are emitted. As an example, the conversion region 3a may be polygonal instead of smoothly curved, or may be a hemispherical region as shown in FIG. 4. As another example, the conversion dynode 3 may include a pyramidal portion, and the conversion region 3a may be the surface of the pyramidal portion.

[0047] In the ion detector 1, the partition 2, together with the aperture electrode 5, may form an enclosed space surrounding the conversion dynode 3. As an example, the partition 2 may be shaped like a box. In this case, the electric field around the conversion dynode 3 can be stabilized, and the conversion of ions to electrons in the conversion dynode 3 can be stably performed.

[0048] In the ion detector 1, one potential application section 6 applies a predetermined potential to each of the conversion dynode 3, the electron multiplier section 4, and the aperture electrode 5, but each of multiple potential application sections 6 may apply a predetermined potential to at least one of the conversion dynode 3, the electron multiplier section 4, and the aperture electrode 5.

[0049] In the ion detector 1, the angle formed between the first imaginary plane K1 and the second imaginary plane K2 is greater than 0 degrees and less than 60 degrees, but the angle formed between the first imaginary plane K1 and the second imaginary plane K2 may be greater than 60 degrees.

[0050] In the ion detector 1, the electron multiplier section 4 has a dynode structure, but the electron multiplier section 4 may be a channel-type electron multiplier section, a microchannel plate, or a semiconductor detector. The electron multiplier section 4 may also be a combination of a microchannel plate and a semiconductor detector, or a combination of a scintillator and a photomultiplier tube.

[0051] In the ion detector 1, the conversion region 3a does not have to face the electron incident surface 42b of the electron multiplier section 4 across the aperture 5a of the aperture electrode 5. As an example, the conversion region 3a may face one side (the center line A2 side) in the X-axis direction on the plane α. When viewed from the Y-axis direction, the outer edge of the aperture 5a may be located outside the outer edge of the conversion region 3a.

[0052] In the ion detector 1, the potential applying unit 6 applies a first potential (e.g., −10 kV) to the conversion dynode 3, applies a second potential (e.g., −2 kV) to the first stage dynode 42a of the electron multiplier unit 4, and applies a third potential (e.g., −9.5 kV) to the aperture electrode 5, but the values ​​of the first potential, second potential, and third potential are not limited to the above values. As another example, when detecting negative ions as the ions P, the potential applying unit 6 may apply a first potential (e.g., +10 kV) to the conversion dynode 3, apply a second potential (e.g., +11 kV) to the first stage dynode 42a of the electron multiplier unit 4, and apply a third potential (e.g., +10.5 kV) to the aperture electrode 5. In other words, the potential application section 6 may apply a predetermined potential to each of the conversion dynode 3, the electron multiplier section 4 and the aperture electrode 5 so that the difference between the first potential and the third potential is greater than or equal to the difference between the second potential and the third potential.

[0053] The ion detector 1 may be used as a part of a mass spectrometer that uses TOF (Time of Flight), or may be used as a part of a mass spectrometer that uses plasma as an ion source. [Explanation of symbols]

[0054] Reference Signs List: 1... ion detector, 2... partition section, 3... conversion dynode, 3a... conversion region, 4... electron multiplier section, 5... aperture electrode, 5a... aperture, 6... potential application section, 21a... ion entrance port, 42b... electron entrance surface, 200... mass spectrometer (analytical device), A1, A2... center line, E... electrons, K1... first virtual plane, K2... second virtual plane, P... ions.

Claims

1. a conversion dynode having a conversion region that emits electrons when ions are incident thereon; an electron multiplier unit having an electron incident surface on which the electrons are incident; an aperture electrode having an aperture for passing the electrons traveling from the conversion region to the electron incident surface; The conversion region is a region that is convex toward a space side from which the electrons are emitted.

2. The ion detector according to claim 1 , wherein the conversion region faces the electron incident surface of the electron multiplier section across the aperture of the aperture electrode.

3. 3. The ion detector according to claim 2, wherein the conversion region is a convex region that is line-symmetrical with respect to a center line of the aperture when viewed in a direction perpendicular to the center line.

4. The ion detector according to claim 3 , wherein the conversion region is formed such that the convex region extends in a direction intersecting a center line of the aperture.

5. a partition having an ion inlet for introducing the ions incident on the conversion dynode, the ion entrance is disposed such that a center line of the ion entrance intersects with a center line of the aperture and an extension direction of the conversion region, The ion detector according to claim 4 , wherein the electron incident surface of the electron multiplier section extends along an extending direction of the conversion region.

6. 6. The ion detector according to claim 5, wherein the partition, together with the aperture electrode, forms an enclosing space enclosing the conversion dynode.

7. 7. The ion detector according to claim 1, wherein the conversion region is a curved region.

8. 7. The ion detector according to claim 1, wherein an angle formed between a first imaginary plane tangent to a vertex of the conversion region and a second imaginary plane tangent to a point other than the vertex in the conversion region is greater than 0 degrees and less than or equal to 60 degrees.

9. a potential applying unit that applies a first potential to the conversion dynode, applies a second potential to the electron incident surface of the electron multiplier unit, and applies a third potential to the aperture electrode, the second potential is higher than the first potential, The ion detector according to any one of claims 1 to 6, wherein the third potential is equal to or greater than the first potential and is less than the second potential.

10. The ion detector of claim 9 , wherein a difference between the first potential and the third potential is less than a difference between the second potential and the third potential.

11. An analytical device using the ion detector according to any one of claims 1 to 6.

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