charged particle detector

Abstract

To provide a charged particle detector capable of stably acquiring a detection signal from a multi-dynode.SOLUTION: A charged particle detector 1 includes: a microchannel plate 2 having an input surface 2a on which electrons (charged particles) are input, multiplication portions 5A, 5B performing multiplication of electrons while maintaining positional information of the electrons, and an output surface 2b outputting electrons multiplied by the multiplication portions 5A, 5B; a multi-dynode 3 having a plurality of dynodes 12 multiplying the electrons output from the output surface 2b, and insulation regions 13 positioned between the dynodes 12, 12; and an anode 4 disposed in a spatial region between the output surface 2b and the multi-dynode 3, and having collection portions 21 for collecting electrons multiplied by the dynodes 12 and aperture portions 22 for allowing electrons output from the output surface 2b to pass therethrough to a dynodes 12 side. All of the insulation regions 13 overlap the collection portions 21 when viewed in an output direction of the electrons from the output surface 2b.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Charged particle detectors equipped with microchannel plates are required to improve the output linearity of the microchannel plates. The output linearity of a microchannel plate is inversely proportional to the resistance of the microchannel plate. Therefore, it is essential to reduce the resistance of the microchannel plate. However, the improvement in output linearity achieved by reducing the resistance is already approaching its limit.

[0003] From another perspective, in order to improve output linearity, a triode structure combining a microchannel plate with a mesh anode and multiple dynodes has been considered. An example of a conventional charged particle detector having a triode structure is the electron multiplier device described in Patent Document 1. This conventional electron multiplier device includes at least one microchannel plate that emits secondary electrons. The microchannel plate has an input surface and an output surface, and a dynode and a lattice-shaped anode are arranged parallel to the output surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 57-196466 Summary of the Invention [Problem to be solved by the invention]

[0005] In Figure 4 of Patent Document 1, a multi-dynode, consisting of multiple independent elements arranged on an insulating substrate, is arranged parallel to the output surface of a microchannel plate together with a lattice-shaped anode. However, in this configuration, charging of the inter-element regions (insulating regions) of the insulating substrate that constitutes the multi-dynode becomes a problem. If charging occurs in the insulating regions, it is thought that acquisition of detection signals from the multi-dynode will become unstable.

[0006] The present disclosure has been made to solve the above-mentioned problems, and has an object to provide a charged particle detector that can stably acquire detection signals from multiple dynodes. [Means for solving the problem]

[0007] A charged particle detector according to one aspect of the present disclosure comprises a microchannel plate having an input surface into which charged particles are input, a multiplier section that multiplies electrons based on the input of the charged particles while maintaining positional information of the charged particles with respect to the input surface, and an output surface that outputs electrons multiplied by the multiplier section, a multi-dynode having a plurality of dynodes that multiply the electrons output from the output surface and insulating regions located between the dynodes, and an anode that is disposed in a spatial region between the output surface and the multi-dynode and has a collector section that collects the electrons multiplied by the dynodes, and an opening that allows the electrons output from the output surface to pass towards the multi-dynode, wherein the entire insulating region overlaps with the collector section when viewed from the direction in which electrons are output from the output surface.

[0008] In this charged particle detector, the entire insulating region of the multi-dynode overlaps with the collecting portion of the anode when viewed from the direction of electron output from the output surface of the microchannel plate. This prevents electrons from the output surface from entering the insulating region, preventing charging of the insulating region. This also reduces crosstalk between dynodes due to capacitive coupling. Therefore, this charged particle detector can stably acquire detection signals from the multi-dynode.

[0009] The anode may be positioned closer to the multi-dynode than the midpoint between the output surface and the multi-dynode. In this case, electrons multiplied by each dynode of the multi-dynode can be efficiently collected by the anode. This makes it possible to increase the effective electron multiplication factor and improve the dynamic range of the charged particle detector.

[0010] The anode may further include an auxiliary collector spanning the opening, in which case the electrons multiplied by each dynode of the multi-dynode structure can be collected more efficiently by the anode.

[0011] The width of the auxiliary collector may be smaller than the width of the collector, in which case electrons multiplied by each dynode of the multi-dynode can be efficiently collected by the anode while maintaining transparency of electrons from the anode to the multi-dynode.

[0012] The dynodes are composed of an insulating substrate, an electrode layer, and a multiplication layer provided on the insulating substrate, and the width of the multiplication layer may be smaller than the width of the electrode layer. In this case, the multiplication layer is spaced apart from the insulating substrate, thereby preventing capacitive coupling between the dynodes. This further reliably suppresses crosstalk between the dynodes.

[0013] When the divergence angle of electrons output from the output surface is θ, the height of the dynode is h, the width of the insulating region is D, and the distance from the anode to the bottom surface of the dynode is Y, the width W of the collecting region may satisfy W = 2(Yh) tan θ + D. By satisfying this condition, it is possible to more reliably prevent electrons output from the output surface with a divergence angle θ from entering the insulating region.

[0014] The device may have a positioning mechanism for positioning the anode and multi-dynode, the positioning mechanism including a first end electrode on the microchannel plate side and a second end electrode on the multi-dynode side, and the anode and multi-dynode may be fixed by screws while sandwiched between the first end electrode and the second end electrode. This positioning mechanism allows the anode and multi-dynode to be easily positioned. As a result, the relative positions of the insulating region of the multi-dynode and the collecting portion of the anode can be accurately aligned as designed. [Effects of the Invention]

[0015] According to the present disclosure, a charged particle detector capable of stably acquiring detection signals from multiple dynodes is provided. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic cross-sectional view illustrating a configuration example of a charged particle detector according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a plan view showing an example of a multi-dynode. [Figure 3] FIG. 2 is a schematic cross-sectional view showing the layer structure of a dynode included in a multi-dynode. [Figure 4] FIG. 2 is a plan view illustrating an example of an anode. [Figure 5] FIG. 2 is a schematic cross-sectional view showing the positional relationship between the insulating region of the multi-dynode and the collecting portion of the anode. [Figure 6] 10(a) to 10(c) are plan views showing modified examples of the multi-dynode. [Figure 7] 10(a) to 10(c) are plan views showing modified examples of the anode. [Figure 8] FIG. 10 is a plan view showing an example of an anode having an auxiliary collector. [Figure 9] FIG. 10 is a plan view showing another example of an anode having an auxiliary collector. [Figure 10] 1 is a schematic partial cross-sectional view showing an example of the configuration of a charged particle detector including a positioning mechanism for an anode and a multi-dynode. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, preferred embodiments of a charged particle detector according to one aspect of the present disclosure will be described in detail with reference to the drawings.

[0018] 1 is a schematic cross-sectional view showing an example of the configuration of a charged particle detector according to an embodiment of the present disclosure. Here, the charged particles include electrons, ions, etc. The charged particle detector 1 shown in FIG. 1 is configured as a multi-dynode electron detector used in, for example, X-ray photoelectron spectroscopy (XPS).

[0019] X-ray photoelectron spectroscopy is a technique that measures the kinetic energy of electrons (photoelectrons) emitted by irradiating a sample with monochromatic X-rays, and obtains information about the types, abundance, and chemical bonding state of elements present on the very surface of the sample. The photoelectron trajectory is deflected by an electric field on its way to the electron detector, and is input to different positions on the electron detector for each energy. In this case, the positional information of the electron detection is related to the energy of the photoelectron, so the electron detector must have high position detection performance.

[0020] As shown in FIG. 1, the charged particle detector 1 comprises a microchannel plate 2, a multi-dynode 3, and an anode 4. In this embodiment, the microchannel plate 2, the multi-dynode 3, and the anode 4 are all disk-shaped. The charged particle detector 1 is electrically connected to an external power supply and a bleeder circuit (not shown). The bleeder circuit applies a voltage with a predetermined potential gradient to the microchannel plate 2, the multi-dynode 3, and the anode 4. The highest voltage is applied to the anode 4, followed by the multi-dynode 3 and the output surface 2b of the microchannel plate 2.

[0021] The microchannel plate 2 has an input surface 2a to which electrons (charged particles) are input, a pair of multiplier units 5A and 5B that perform electron multiplication (secondary electron multiplication) based on the input electrons while maintaining positional information of the electrons relative to the input surface 2a, and an output surface 2b that outputs the electrons multiplied by the multiplier units 5A and 5B. Each of the multiplier units 5A and 5B is a secondary electron multiplier unit having a plurality of microchannel structures that are independent of each other. In the multiplier units 5A and 5B, a plurality of microchannel structures are two-dimensionally arranged.

[0022] Each channel of the multiplier units 5A and 5B has an inner diameter of about 10 μm and is inclined at about 10° with respect to the normal direction of the input surface 2a (electron input direction). The inclination direction of each channel is reversed between the multiplier units 5A and 5B. In the multiplier units 5A and 5B, the output surface 2b side is at a higher potential than the input surface 2a side. Electrons generated in response to the arrival of electrons at the input surface 2a are multiplied by the multiplier units 5A and 5B, and the multiplied electrons are output from the output surface 2b.

[0023] The multi-dynode 3 is an electrode that multiplies the electrons output from the microchannel plate 2. In each channel (each dynode 12) of the multi-dynode 3, a current is generated according to the amount of electrons multiplied during electron multiplication. By extracting this current value as a detection signal from each channel, positional information on electron detection can be obtained.

[0024] 1, the multi-dynode 3 is arranged on the output surface 2b side of the microchannel plate 2 and parallel to the output surface 2b. The multi-dynode 3 has an insulating substrate 11 and a plurality of dynodes 12 provided on the insulating substrate 11. The insulating substrate 11 is made of, for example, a ceramic substrate or a glass epoxy substrate, and has electrical insulation properties.

[0025] The dynodes 12 are components that multiply the electrons output from the output surface 2b. In this embodiment, the dynodes 12 are arranged on an insulating substrate 11 in a striped divided pattern, as shown in FIG. 2. The divided pattern of the dynodes 12 can be formed by etching, for example. When viewed in plan of the multi-dynode 3, each dynode 12 extends in one direction with a predetermined width. Each dynode 12 is electrically connected to the above-mentioned bleeder circuit and output coupling circuit via lead wires 14 (see FIG. 1).

[0026] Adjacent dynodes 12, 12 are spaced apart by a predetermined distance. As a result, the regions between adjacent dynodes 12, 12 are dead spaces where no dynodes 12 are arranged, and form insulating regions 13 where the insulating substrate 11 is exposed. In the example of Figure 2, the dynodes 12 are arranged on the insulating substrate 11 in a divided stripe pattern, and therefore the arrangement pattern of the insulating regions 13 is also a stripe pattern.

[0027] As shown in Fig. 3, the dynode 12 is composed of an electrode layer 15 and a multiplication layer 16. The electrode layer 15 is, for example, a copper foil electrode, and is laminated on the insulating substrate 11. The surface of the electrode layer 15 may be subjected to a gold flash treatment. The multiplication layer 16 is composed of a secondary electron emitting material, for example, MgO, MgF2, or Al2O3, and is laminated on the electrode layer 15. The electron deficiency in the multiplication layer 16 due to the emission of multiplied electrons is neutralized by the supply of electrons from the underlying electrode layer 15.

[0028] The thickness T1 of the electrode layer 15 is greater than the thickness T2 of the multiplication layer 16. The width F1 of the electrode layer 15 and the width F2 of the multiplication layer 16 are both sufficiently greater than the width D of the insulating region 13 between the dynodes 12, 12. In this embodiment, the width F2 of the multiplication layer 16 is smaller than the width F1 of the electrode layer 15. As a result, when the dynode 12 is viewed from the thickness direction, both edge portions of the electrode layer 15 in the width direction are exposed from the multiplication layer 16.

[0029] The anode 4 is an electrode whose role is to collect electrons amplified by each dynode 12 of the multi-dynode 3 and prevent them from returning towards the multi-dynode 3. As shown in Fig. 4, the anode 4 is a so-called mesh-type anode, having a collector 21 that collects electrons multiplied by the dynodes 12, and an opening 22 that allows electrons output from the output surface 2b to pass towards the dynode 12. As shown in Fig. 1, the anode 4 is disposed in the spatial region between the output surface 2b and the multi-dynode 3. In the example of Fig. 1, the anode 4 is disposed parallel to the output surface 2b and the multi-dynode 3, at a position closer to the multi-dynode 3 than midpoint C between the output surface 2b and the multi-dynode 3.

[0030] The collecting portions 21 are arranged in a pattern that corresponds to the division pattern of the dynodes 12 in the multi-dynode 3 (i.e., the arrangement pattern of the insulating regions 13). In the example of Figure 4, the arrangement pattern of the collecting portions 21 is a striped pattern that corresponds to the striped division pattern of the dynodes 12. The width W of the collecting portions 21 is equal to or greater than the width D of the insulating regions 13 (see Figure 3).

[0031] The anode 4 is disposed in the spatial region between the output surface 2b and the multi-dynode 3 so that the widthwise center of the collecting portion 21 coincides with the widthwise center of the insulating region 13. This results in the entire insulating region 13 overlapping with the collecting portion 21 when viewed from the output direction Z (see FIG. 1 ) of the electrons e1 from the output surface 2b. The entire insulating region 13 overlapping with the collecting portion 21 prevents the electrons e1 from the output surface 2b from entering the insulating region 13.

[0032] If the anode 4 is not positioned in the spatial region between the output surface 2b and the multi-dynode 3, electrons emitted from the secondary electron surface (the surface of the multiplication layer 16) of the dynode 12 may return towards the multi-dynode 3. In this case, the electrons that return towards the multi-dynode 3 re-enter the secondary electron surface and are absorbed. Because the electrons absorbed by the secondary electron surface are not extracted as a detection signal from the dynode 12, the inherent electron multiplication ability of the secondary electron emitting material in the dynode 12 is not exerted, which may make it difficult to improve the dynamic range of the charged particle detector 1.

[0033] In contrast, in the charged particle detector 1, an anode 4 is placed in the spatial region between the output surface 2b and the multi-dynode 3. By placing the anode 4, as shown in Figure 1, electrons e2 emitted from the secondary electron surface of the dynode 12 are collected by the collector 21, preventing them from returning to the multi-dynode 3. This makes it possible to increase the effective electron multiplication factor of the dynode 12, and improve the dynamic range of the charged particle detector 1.

[0034] The detection signal output from the anode 4 is theoretically equal to the sum of the detection signals from each dynode 12 of the multi-dynode 3 (however, the polarity of the detection signal from the anode 4 is inverted relative to the polarity of the detection signal from each dynode 12). Therefore, the detection signal output from the anode 4 can be used to detect electron count errors (count losses) in each dynode 12. Detection of count errors ensures measurement accuracy in X-ray photoelectron spectroscopy.

[0035] The width W of the collecting region 21 may be adjusted by the distance between the anode 4 and the multi-dynode 3 in the output direction Z of the electrons e1. The electrons e1 output from the output surface 2b of the microchannel plate 2 proceed toward the multi-dynode 3 with a certain divergence angle. For this reason, the closer the anode 4 is to the microchannel plate 2, the smaller the width W of the collecting region 21 of the anode 4 may be.

[0036] However, if the anode 4 is placed too close to the microchannel plate 2, there is a risk that electrons e1 from the output surface 2b will be collected directly by the anode 4 and will not reach the multi-dynode 3. In this embodiment, taking this into consideration, the anode 4 is positioned closer to the multi-dynode 3 than the midpoint C between the output surface 2b and the multi-dynode 3. Therefore, it is preferable that the width W of the collecting region 21 be greater than the width D of the insulating region 13.

[0037] Regarding the positional relationship between the insulating region 13 and the collecting unit 21, in the charged particle detector 1, as shown in FIG. 5, when the divergence angle of the electrons e1 output from the output surface 2b is θ, the height of the dynode 12 (the sum of the thickness T1 of the electrode layer 15 and the thickness T2 of the multiplication layer) is h, the width of the insulating region 13 is D, and the distance from the anode 4 (its bottom surface) to the bottom surface of the dynode 12 is Y, the width W of the collecting unit 21 satisfies W=2(Yh)tanθ+D.

[0038] 5, if the width of the portion of the collecting portion 21 that overlaps with the dynode 12 when viewed from the output direction Z of the electrons from the output surface 2b is ω, then the width ω is given by ω = (Yh) tan θ. The width W of the collecting portion 21 is given by W = 2ω + D, and therefore the above formula can be derived. By satisfying this positional relationship, it is possible to more reliably prevent the electrons output from the output surface 2b from entering the insulating region 13, relative to the divergence angle θ of the electrons.

[0039] The apertures 22 are portions that allow electrons output from the output surface 2b to pass through to the multi-dynode 3 side. The arrangement pattern of the apertures 22 is a striped pattern that corresponds to the arrangement pattern of the dynodes 12, as shown in FIG. 4. The aperture ratio of the anode 4 defined by the apertures 22 is set appropriately, for example, according to the width of the dynode 12 (here, the width F1 of the electrode layer 15). The aperture ratio of the anode 4 is set, for example, so that it increases as the width of the dynode 12 increases. When the width of the dynode 12 is 1.0 mm, the aperture ratio of the anode 4 is set, for example, to about 80%. When the width of the dynode 12 is 2.0 mm, the aperture ratio of the anode 4 is set, for example, to about 90%.

[0040] As described above, in the charged particle detector 1, the insulating region 13 of the multi-dynode 3 entirely overlaps with the collector 21 of the anode 4 when viewed from the output direction Z of electrons output from the output surface 2b of the microchannel plate 2. This prevents electrons from the output surface 2b from entering the insulating region 13, preventing charging of the insulating region 13. This reduces crosstalk between the dynodes 12 due to capacitive coupling. Preventing charging of the insulating region 13 not only reduces crosstalk between the dynodes 12, but also prevents changes in the trajectory of incident electrons and the generation of spurious signals due to discharge. Therefore, the charged particle detector 1 can stably acquire detection signals from the multi-dynode 3. When applied to an electron detector in X-ray photoelectron spectroscopy, the charged particle detector 1 can exhibit high position detection performance as an electron detector.

[0041] In the charged particle detector 1, the anode 4 is positioned closer to the multi-dynode 3 than an intermediate position C between the output surface 2b and the multi-dynode 3. This allows the anode 4 to efficiently collect electrons multiplied by each dynode 12 of the multi-dynode 3. This makes it possible to increase the effective electron multiplication factor, thereby improving the dynamic range of the charged particle detector 1.

[0042] In the charged particle detector 1, the dynode 12 is composed of an insulating substrate 11, and an electrode layer 15 and a multiplication layer 16 provided on the insulating substrate 11. Furthermore, the width F2 of the multiplication layer 16 is smaller than the width F1 of the electrode layer 15. With this configuration, the multiplication layer 16 is spaced apart from the insulating substrate 11, thereby preventing capacitive coupling between the dynodes 12, 12. Therefore, the occurrence of crosstalk between the dynodes 12, 12 can be more reliably suppressed.

[0043] In the charged particle detector 1, the width W of the collecting region 21 satisfies W=2(Yh)tanθ+D, where θ is the divergence angle of electrons output from the output surface 2b, h is the height of the dynode 12, D is the width of the insulating region 13, and Y is the distance from the anode 4 to the bottom surface of the dynode 12. By satisfying this condition, it is possible to more reliably prevent electrons output from the output surface 2b with a divergence angle θ from entering the insulating region 13.

[0044] The present disclosure is not limited to the above-described embodiment. For example, in the above-described embodiment, the anode 4 and the multi-dynode 3 are positioned so that the widthwise center of the collecting portion 21 coincides with the widthwise center of the insulating region 13. However, as long as the entire insulating region 13 overlaps with the collecting portion 21 when viewed from the direction in which electrons are output from the output surface 2b, the widthwise center of the collecting portion 21 does not necessarily have to coincide with the widthwise center of the insulating region 13.

[0045] In the above embodiment, the height of each dynode 12 in the multi-dynode 3 is constant (see FIG. 1). However, the height of each dynode 12 may also be different. For example, in X-ray photoelectron spectroscopy, the flight trajectory of photoelectrons is controlled so that the detection position of the electrons in the electron detector changes for each energy. Because the secondary electron emission ratio of the secondary electron emitting material changes depending on the energy of the primary electrons, in the charged particle detector 1 acting as an electron detector, the microchannel plate 2 may have an in-plane distribution of gain depending on the energy of the electrons input to the input surface 2a.

[0046] On the other hand, when the energy of the primary electrons incident on the secondary electron-emitting material is the same, such as the electrons flying between the output surface 2b of the microchannel plate 2 and the multi-dynode 3, the characteristics of the secondary electron-emitting material that contribute to the gain are specific to the material, and so the apparent secondary electron emission ratio changes depending on the thickness of the secondary electron-emitting material. Therefore, by varying the height (thickness) of each dynode 12, it becomes possible to correct the in-plane distribution of gain in the microchannel plate 2 on the multi-dynode 3 side.

[0047] In the above embodiment, the dynodes 12 are arranged on the insulating substrate 11 in a striped division pattern, but various modifications can be made to the division pattern of the dynodes 12. For example, the division pattern of the dynodes 12 may be an arc-shaped pattern with its origin located outside the multi-dynode 3, as shown in Figure 6(a). In X-ray photoelectron spectroscopy, the energy distribution of photoelectrons when they reach the charged particle detector 1 acting as an electron detector is an arc-shaped distribution with its origin located outside, as shown in Figure 6(a). Therefore, by matching the division pattern of the dynodes 12 to the energy distribution of the photoelectrons, it is possible to obtain positional information of electron detection with high accuracy.

[0048] The division pattern of the dynode 12 may be a concentric pattern with the center of the multi-dynode 3 as the origin, as shown in Figure 6(b), or may be a fan-shaped pattern divided (here, into four parts) around the center of the multi-dynode 3, as shown in Figure 6(c).

[0049] The arrangement pattern of the collecting units 21 on the anode 4 can also be modified in accordance with the modifications shown in Figures 6(a) to 6(c). For the division pattern of the dynode 12 shown in Figure 6(a), the arrangement pattern of the collecting units 21 corresponds to the insulating region 13 in Figure 6(a) and can be an arc-shaped pattern with its origin outside the multi-dynode 3, as shown in Figure 7(a). For the division pattern of the dynode 12 shown in Figure 6(b), the arrangement pattern of the collecting units 21 corresponds to the insulating region 13 in Figure 6(b) and can be a concentric pattern with its origin at the centre of the multi-dynode 3, as shown in Figure 7(b). For the division pattern of the dynode 12 shown in Figure 6(c), the arrangement pattern of the collecting units 21 corresponds to the insulating region 13 in Figure 6(c) and can be a cross-shaped pattern passing through the centre of the multi-dynode 3, as shown in Figure 7(c).

[0050] The anode 4 may further include an auxiliary collector 25 spanning the opening 22. The auxiliary collector 25 can be formed integrally with the collector 21 by, for example, etching. Figure 8 shows an example of an anode 4 in which auxiliary collectors 25 are applied to the collector 21 having the striped pattern shown in Figure 4. In the example of Figure 8, the auxiliary collectors 25 are arranged at equal intervals in a direction perpendicular to the striped arrangement of the collectors 21. When the anode 4 is provided with auxiliary collectors 25, electrons multiplied by each dynode 12 of the multi-dynode 3 can be collected more efficiently by the anode 4.

[0051] When the anode 4 is provided with an auxiliary collector 25, the width Wa of the auxiliary collector 25 may be smaller than the width W of the collector 21. This allows the anode 4 to efficiently collect electrons multiplied by each dynode 12 of the multi-dynode 3, while maintaining the transparency of electrons from the anode 4 to the multi-dynode 3.

[0052] The shape (planar shape) of the auxiliary collector 25 is not limited to being linear or curved, and may also be a honeycomb shape as shown in Fig. 9. Fig. 9 shows an example of an anode 4 in which a honeycomb-shaped auxiliary collector 25 is applied to a collector 21 having the cross pattern shown in Fig. 7(c). With this shape, as in the case of Fig. 8, electron transparency from the anode 4 to the multi-dynode 3 is maintained, while electrons multiplied by each dynode 12 of the multi-dynode 3 can be efficiently collected by the anode 4. Furthermore, by making the auxiliary collector 25 honeycomb-shaped, it is possible to ensure sufficient strength of the auxiliary collector 25 even when the width Wa of the auxiliary collector 25 is narrower than the width W of the collector 21.

[0053] The charged particle detector 1 may have a positioning mechanism 31 that positions the anode 4 and multi-dynode 3. Fig. 10 is a schematic partial cross-sectional view showing an example configuration of a charged particle detector including the anode and multi-dynode positioning mechanism. As shown in Fig. 10, the positioning mechanism 31 includes a first end electrode 32A on the microchannel plate 2 side and a second end electrode 32B on the multi-dynode 3 side. The anode 4 and multi-dynode 3 are sandwiched between the first end electrode 32A and the second end electrode 32B and fixed in place with screws.

[0054] 10, the microchannel plate 2, multi-dynode 3, and anode 4 are assembled using an IN electrode 33 and an OUT electrode 34 of the microchannel plate, a plurality of insulating spacers 35, and a substrate electrode 40. The IN electrode 33 and the OUT electrode 34 are annular and are arranged so as to sandwich the microchannel plate 2 therebetween.

[0055] The insulating spacers 35 are annular and are arranged between the OUT electrode 34 and the anode 4, between the anode 4 and the multi-dynode 3, and between the multi-dynode 3 and the substrate electrode 40. The substrate electrode 40 is disc-shaped and is arranged outside the insulating spacer 35 between the multi-dynode 3 and the substrate electrode 40. The IN electrode 33 corresponds to the first end electrode 32A, and the substrate electrode 40 corresponds to the second end electrode 32B.

[0056] The edges of the IN electrode 33, OUT electrode 34, insulating spacer 35, multi-dynode 3, and anode 4 are each provided with an insertion hole 36 into which a fixing screw S1 can be inserted, and an insertion hole 37 into which a positioning screw S2 can be inserted. The edge of the board electrode 40 is provided with a screw hole 38 into which the fixing screw S1 can be threaded, and a screw hole 39 into which the positioning screw S2 can be threaded. When assembling these components, first the positioning screw S2 is threaded into the screw hole 39 of the board electrode 40. Using the positioning screw S2 as a support, the IN electrode 33, OUT electrode 34, anode 4, and multi-dynode 3 are stacked on the board electrode 40 by passing the positioning screw S2 through the insertion hole 37.

[0057] The diameter of the insertion holes 37 (insertion holes 37A) in the multi-dynode 3 and anode 4 is smaller than the diameter of the insertion holes 37 (insertion holes 37B) in the IN electrode 33 and OUT electrode 34. Therefore, the IN electrode 33 and OUT electrode 34 are positioned by the positioning screws S2, while the anode 4 and multi-dynode 3 are positioned with high precision by the positioning screws S2.

[0058] Next, the microchannel plate 2 is placed between the IN electrode 33 and the OUT electrode 34. Furthermore, insulating spacers 35 are placed between the OUT electrode 34 and the anode 4, between the anode 4 and the multi-dynode 3, and between the multi-dynode 3 and the substrate electrode 40. After that, fixing screws S1 are inserted into the insertion holes 36 of each component from the IN electrode 33 side, and the tips of the fixing screws S1 are screwed into the threaded holes 38 of the substrate electrode 40. This completes the assembly of the components, with the multi-dynode 3 and anode 4 positioned with high precision. After assembly, the setting screws S2 can be removed.

[0059] The positioning mechanism 31 described above makes it possible to easily position the anode 4 and the multi-dynode 3. As a result, the positional relationship between the insulating region 13 of the multi-dynode 3 and the collecting portion 21 of the anode 4 can be accurately aligned as designed.

[0060] In the above embodiment, an electron detector is exemplified as the charged particle detector 1, but the charged particle detector of the present disclosure can also be applied to other uses, such as an ion detector. When the charged particle detector is used as an ion detector, ions (charged particles) are input to the detector. The input ions are converted into secondary electrons in a microchannel plate, and electrons are output as a result. [Explanation of symbols]

[0061] 1...charged particle detector, 2...microchannel plate, 2a...input surface, 2b...output surface, 3...multiple dynode, 4...anode, 5A, 5B...multiplication section, 12...dynode, 13...insulating region, 15...electrode layer, 16...multiplication layer, 21...collection section, 22...opening, 25...auxiliary collection section, 31...positioning mechanism, 32A...first end electrode, 32B...second end electrode, C...intermediate position.

Claims

1. a microchannel plate having an input surface to which charged particles are input, a multiplier unit that multiplies electrons based on the input of the charged particles while maintaining positional information of the charged particles with respect to the input surface, and an output surface that outputs electrons multiplied by the multiplier unit; a multi-dynode including a plurality of dynodes that multiply the electrons output from the output surface and an insulating region located between the dynodes; an anode, the anode being disposed in a spatial region between the output surface and the multi-dynode, the anode having a collector for collecting electrons multiplied by the dynode, and an opening for allowing electrons output from the output surface to pass toward the multi-dynode; A charged particle detector, wherein the insulating region entirely overlaps the collecting portion when viewed from the direction in which the electrons are output from the output surface.

2. 2. A charged particle detector according to claim 1, wherein the anode is disposed closer to the multi-dynode than an intermediate position between the output surface and the multi-dynode.

3. 3. A charged particle detector according to claim 1, wherein the anode further comprises an auxiliary collector spanning the opening.

4. 4. The charged particle detector of claim 3, wherein the width of the auxiliary collector is smaller than the width of the collector.

5. the dynode is composed of an insulating substrate, and an electrode layer and a multiplication layer provided on the insulating substrate; 5. The charged particle detector according to claim 1, wherein the width of the multiplication layer is smaller than the width of the electrode layer.

6. 6. The charged particle detector according to claim 1, wherein a width W of the collecting portion satisfies W = 2(Y - h) tan θ + D, where θ is a divergence angle of electrons output from the output surface, h is a height of the dynode, D is a width of the insulating region, and Y is a distance from the anode to a bottom surface of the dynode.

7. a positioning mechanism for positioning the anode and the multi-dynode; the positioning mechanism includes a first end electrode on the microchannel plate side and a second end electrode on the multi-dynode side; 7. A charged particle detector according to claim 1, wherein the anode and the multi-dynode are fixed by screws while being sandwiched between the first end electrode and the second end electrode.

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