photomultiplier tube

Abstract

A photomultiplier tube of the present application includes a photoelectric surface, N stages (N is an integer of 2 or more) of dynodes that multiply electrons emitted from the photoelectric surface, and an anode that collects the electrons multiplied by the dynodes. The mth stage (m is an integer of 2 or more and N or less) of the dynodes is disposed in opposition to the (m-1)th stage of the dynodes. In the long side direction of the dynodes, the width of the end edge of the mth stage of the dynodes on the side of the (m-1)th stage of the dynodes is smaller than the width of the (m-1)th stage of the dynodes. In the long side direction, the end edge of the mth stage of the dynodes is contained inside the (m-1)th stage of the dynodes.

Description

Technical Field

[0001] This disclosure relates to a photomultiplier tube. Background Technology

[0002] A photomultiplier tube is known, comprising: a photoelectric surface; an N-stage (N is an integer greater than or equal to 2) dynode that multiplies electrons emitted from the photoelectric surface; and an anode that collects electrons multiplied by the dynode (see, for example, Patent Document 1). In this photomultiplier tube, the m-th stage (m is an integer greater than or equal to 2 and less than or equal to N) dynode is arranged opposite to the (m-1)-th stage dynode. Existing technical documents Patent documents

[0003] Patent document 1: Japanese Patent Application Publication No. 2002-42720. Summary of the Invention The problem that the invention aims to solve

[0004] In photomultiplier tubes like the one described above, there is a desire to further improve the timing characteristics. One strategy to improve timing characteristics is to bring the opposing dynodes closer together to increase the electric field strength between the stages (dynodes). However, when the m-th dynode is brought close to the (m-1)-th dynode, discharge may occur between the m-th and (m-1)-th dynodes, which are applied with different potentials.

[0005] This disclosure was made in view of the above-mentioned circumstances, and its purpose is to provide a photomultiplier tube that can improve timing characteristics and prevent discharge between multiplier electrodes. Technical means for solving problems

[0006] The photomultiplier tube disclosed herein is, [1] "a photomultiplier tube comprising: a photoelectric surface; an N-level (N is an integer greater than or equal to 2) multiplier electrode that multiplies electrons emitted from the photoelectric surface; and an anode that collects electrons multiplied by the multiplier electrode, wherein the m-th level (m is an integer greater than or equal to 2 and less than or equal to N) multiplier electrode is arranged opposite to the (m-1)-th level multiplier electrode, and in the long side direction of the multiplier electrode, the width of the end edge of the (m-1)-th level multiplier electrode side of the m-th level multiplier electrode is less than the width of the (m-1)-th level multiplier electrode, and in the long side direction, the end edge of the m-th level multiplier electrode is contained inside the (m-1)-th level multiplier electrode."

[0007] As a result of in-depth research, the inventors have obtained the following insight: Discharge between dynodes tends to occur at the end along the long side direction (hereinafter also simply referred to as the "long side direction") of the dynode. Therefore, in the photomultiplier tube of this disclosure, the width of the long side direction of the edge of the (m-1)th dynode side of the m-th dynode is set to be smaller than the width along the long side direction of the (m-1)th dynode. Furthermore, this edge of the m-th dynode is included inside the (m-1)th dynode in the long side direction. This allows the opposing dynodes to be brought closer together to increase the inter-stage electric field strength, and ensures that the end of the m-th dynode along the long side direction is kept away from the end of the (m-1)th dynode, thus preventing discharge. In other words, it improves the timing characteristics and prevents discharge between dynodes.

[0008] The photomultiplier tube disclosed herein can also be, [2] "According to the photomultiplier tube of [1], wherein the cross-section of the dynode intersecting the long side direction is arc-shaped, and when viewed from the long side direction, the end edge of the m-th dynode extends into the (m-1)-th dynode." In this case, it is possible to prevent discharge between the m-th dynode and the (m-1)-th dynode and bring them close together, thereby increasing the electric field strength between them.

[0009] The photomultiplier tube disclosed herein may also be, [3] "the photomultiplier tube according to [1] or [2], wherein, in the long side direction of the multiplier, the width of the first-stage multiplier is greater than the width of the second to Nth-stage multiplier, and in the long side direction, the second to Nth-stage multiplier is contained within the first-stage multiplier." In this case, the ends of the second to Nth-stage multiplier in the long side direction can be moved away from the ends of the first-stage multiplier in the long side direction, ensuring the distance between these ends and preventing discharge.

[0010] The photomultiplier tube disclosed herein may also be, [4] "a photomultiplier tube according to any one of [1] to [3], wherein the dynode of the k-th stage (k is 2 or more and N or less, and is an integer other than m) is arranged opposite to the dynode of the (k-1)-th stage, and the width of the dynode of the k-th stage is equal to the width of the dynode of the (k-1)-th stage in the long side direction of the dynode." In this case, the electron arrival efficiency (so-called interstage efficiency) of the k-th stage dynode and the (k-1)-th stage dynode can be improved. Invention Effects

[0011] According to this disclosure, a photomultiplier tube that can improve timing characteristics and prevent discharge between multiplier electrodes can be provided. Attached Figure Description

[0012] Figure 1 This is a cross-sectional view of a photomultiplier tube according to one embodiment. Figure 2 It means Figure 1 Cross-sectional view of the electron multiplier and anode. Figure 3 It is an enlarged representation Figure 2 A partial 3D image. Figure 4 It means Figure 1 A three-dimensional view of the electron multiplier and anode. Figure 5 This refers to the view from the Y direction. Figure 1 Diagram of electron multiplier and anode. Figure 6 It means Figure 1 A three-dimensional view of a portion of the electron multiplier. Figure 7 This refers to the view from the Y direction. Figure 1 A diagram of a portion of the electron multiplication region. Figure 8 (a) shows the simulation results of the electron trajectory from the 8th dynode to the 9th dynode in the electron multiplier of the comparative example. Figure 8 (b) shows the simulation results of the electron trajectory of the electron multiplier from the 9th dynode to the 10th dynode in the comparative example. Figure 8 (c) represents the simulation results of the electron trajectory from the 10th dynode to the anode in the electron multiplier of the comparative example. Figure 9 (a) is a simulation result showing the electron trajectory of the electron multiplier from the 8th dynode to the 9th dynode in the embodiment. Figure 9 (b) shows the simulation results of the electron trajectory of the electron multiplier from the 9th dynode to the 10th dynode in the embodiment. Figure 9 (c) shows the simulation results of the electron trajectory from the 10th dynode to the anode in the electron multiplier section of the embodiment. Figure 10 (a) is a graph showing the simulation results of the rise time for the comparative example and the embodiment. Figure 10 (b) is a graph showing the simulation results of the descent time for the comparative example and the embodiment. Figure 11 (a) is a graph representing the measured values ​​of the output signal from the anode in the comparative example. Figure 11 (b) is a graph representing the measured values ​​of the output signal from the anode in the embodiment. Figure 12 (a) is a perspective view showing a section of the electron multiplication part of the first modified example. Figure 12 (b) is a perspective view showing a section of the electron multiplication part of the second variation. Figure 13 This is a perspective view showing a portion of the electron multiplication part in the third variation. Figure 14 This is a diagram showing a portion of the electron multiplication part of the third modified example when viewed from the Y direction. Figure 15 This is a perspective view showing a portion of the electron multiplication part in the fourth variation. Figure 16 This is a diagram showing a portion of the electron multiplication part of the fourth modified example when viewed from the Y direction. Figure 17 This is a diagram showing a portion of the electron multiplication part of the fourth modified example when viewed from the X direction. Figure 18 This is a cross-sectional view showing the electron multiplication part of the fifth modified example. Detailed Implementation

[0013] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. In the drawings, the same or equivalent parts are labeled with the same symbols, and repeated descriptions are omitted.

[0014] like Figure 1 As shown, the photomultiplier tube 1 includes a tube body 2, a photoelectric surface 3, a focusing electrode 5, an electron multiplier section 6, an anode 7, and a partition (wall) 20. The electron multiplier section 6 has a so-called line-focusing type N-stage (N is an integer greater than 2) dynode 10. In the following description, the side on which light is incident on the photomultiplier tube 1 is designated as "front", and the opposite side is designated as "rear". In addition, the tube axis (central axis) of the tube body 2 is designated as the "Z-axis", the axis orthogonal to the surface on which the multi-stage dynode 10 is arranged (including the surface of the Z-axis) is designated as the "X-axis", and the axis orthogonal to both the Z-axis and the X-axis is designated as the "Y-axis".

[0015] The tube body 2 houses the photoelectric surface 3, the focusing electrode 5, the electron multiplier 6, and the anode 7 within a vacuum-sealed space. The tube body 2 is a transparent glass bulb. The tube body 2 has a flattened spherical portion 2a centered on the Z-axis, and a cylindrical portion 2b centered on the Z-axis on the rear side of the flattened spherical portion 2a. The flattened spherical portion 2a and the cylindrical portion 2b are integrally formed as a single glass bulb.

[0016] The photoelectric surface 3 is disposed on the inner surface of the tube body 2. Specifically, the photoelectric surface 3 is disposed on the inner surface of the front half of the oblate spherical portion 2a. The photoelectric surface 3 constitutes a transmission-type photocathode, for example, formed of a potassium antimonide-cesium type (dual alkali) material or other known materials. When light is incident on the photoelectric surface 3 from the front, electrons (photoelectrons) are emitted from the photoelectric surface 3 to the rear through the photoelectric effect.

[0017] The focusing electrode 5 is positioned further back than the photoelectric surface 3. A predetermined voltage is applied to the focusing electrode 5. The focusing electrode 5 is configured to focus electrons emitted from the photoelectric surface 3 toward the electron multiplier 6.

[0018] The electron multiplier 6 is positioned further rearward than the focusing electrode 5. The electron multiplier 6, also known as the N-stage dynode 10, multiplies (secondary electron multiplication) the electrons emitted from the photoelectric surface 3. The dynode 10 is formed, for example, of stainless steel. The dynode 10 is a long strip-shaped member with the X-direction as its long side. The dynode 10 is configured to include a bottom wall 13B with an arc-shaped cross-section along the YZ plane (a plane including the Y-axis and Z-axis). Figure 6 ), and the side walls 13W located at both ends of the bottom wall 13B in the X direction (see reference). Figure 6 On the side wall 13W of the dynode 10, as a structure for holding the dynode 10 within the tube body 2, a retaining piece (not shown) protruding outward in the X direction is provided.

[0019] The N-stage dynodes 10 each have a secondary electron emitting surface 11 for multiplying electrons. The secondary electron emitting surface 11 emits secondary electrons upon electron incidence. The secondary electron emitting surface 11 is disposed on the inner surface of the bottom wall 13B of the dynode 10, and its cross-section along the YZ plane is arc-shaped. That is, the cross-section of the dynode 10 intersecting the long side direction is arc-shaped. Different potentials are applied to each dynode 10.

[0020] Anode 7 is configured opposite to the Nth-stage dynode 10, which is the final stage. A predetermined voltage is applied to anode 7. Anode 7 collects electrons multiplied by the Nth-stage dynode 10. Anode 7 is configured to output the electrons emitted from the Nth-stage dynode 10 as a signal current. In other words, the electrode that has the function of collecting electrons that can be used as a signal current is anode 7.

[0021] The focusing electrode 5, each dynode 10 of the electron multiplier section 6, and the anode 7 are supported within the tube body 2 by support members (not shown) such as an insulating support substrate. These support members are mounted on a tube socket (not shown) that seals the rear end of the cylindrical portion 2b. Furthermore, wiring for voltage application and signal current output is provided on this tube socket as tube socket steam pins or cables.

[0022] The electron multiplier 6 in this embodiment, such as Figure 1 and Figure 2As shown, it has 10 dynodes 10 (i.e., N=10). The 10 dynodes 10, from the front side as the upstream side to the rear side as the downstream side, include: 1st dynode 10a, 2nd dynode 10b, 3rd dynode 10c, 4th dynode 10d, 5th dynode 10e, 6th dynode 10f, 7th dynode 10g, 8th dynode 10h, 9th dynode 10i, and 10th dynode 10j.

[0023] The i-th stage (i is an integer greater than 2 and less than N) dynode 10 is arranged opposite to the (i-1)-th stage dynode 10. In other words, the N-th stage dynode 10 is arranged such that the secondary electron emission surfaces 11, 11 between adjacent dynodes 10, 10 are opposite to each other. A higher potential than that of the (i-1)-th stage dynode 10 is applied to the i-th stage dynode 10. A negative potential, for example, the same voltage as the focusing electrode 5, is applied to the first stage dynode 10a. The N-th stage dynodes 10 are arranged with their centers aligned in the X direction.

[0024] like Figure 2 and Figure 3 As shown, the anode 7 is configured to include a bottom wall 71 with an arc-shaped cross-section along the YZ plane, and side walls 72 disposed at both ends of the bottom wall 71 in the X direction. The outer surface of the bottom wall 71 has an electron collecting surface 73. The electron collecting surface 73 is opposite to the secondary electron emission surface 11j of the 10th stage dynode 10j, and at least a portion of it extends along the secondary electron emission surface 11j. Here, the electron collecting surface 73 extends in accordance with the secondary electron emission surface 11j. In the illustrated example, the cross-section of the electron collecting surface 73 along the YZ plane is arc-shaped.

[0025] The anode 7 is positioned between the 9th dynode 10i and the 10th dynode 10j. A portion of the anode 7 extends into the 10th dynode 10j. Thus, the electron collecting surface 73 is close to the secondary electron emitting surface 11j. The anode 7 does not have electron passage holes along the electron path from the 9th dynode 10i to the 10th dynode 10j. The anode 7 is a solid plate-shaped metal component. The electron passage holes are formed by holes that allow electrons to pass through, for example, in a grid structure, honeycomb structure, or porous structure. That is, the anode 7 does not have at least any one of a grid structure, honeycomb structure, or porous structure along the electron path from the 9th dynode 10i to the 10th dynode 10j. A potential higher than that of the 10th dynode 10 is applied to the anode 7. The potential of the anode 7 is, for example, set to 0V.

[0026] A separator 20 is disposed between the 9th stage dynode 10i and the anode 7. The separator 20 prevents electron injection from the 9th stage dynode 10i to the anode 7 and from the 8th stage dynode 10h to the anode 7. The separator 20 is also disposed between the 9th stage dynode 10i and the 10th stage dynode 10j. The separator 20 is a flat plate extending along the X direction. The width of the separator 20 in the X direction is greater than the width of the dynode 10 in the X direction, and also greater than the width of the anode 7 in the X direction (see reference). Figure 5 The partition 20 is made of, for example, stainless steel.

[0027] A potential equal to or greater than that of the 9th-stage dynode 10i is applied to the separator 20. For example, a potential equal to that of the 10th-stage dynode 10j is applied to the separator 20. The separator 20 is configured to be separate from the 10th-stage dynode 10j. For example, ... Figure 3 As shown, electrons emitted from the 9th stage dynode 10i pass through the space K between the end of the 10th stage dynode 10j side of the partition 20 and the 10th stage dynode 10j, and are incident on the 10th stage dynode 10j (refer to the dashed arrow in the figure).

[0028] like Figure 2 , Figure 4 , Figure 5 , Figure 6 and Figure 7 As shown, the sidewall 13W of the dynode 10 extends along the YZ plane, and the width of the dynode 10 in the X direction (hereinafter, the width in the X direction will also be simply referred to as "width") is constant. The width of the end edge E on the (m-1)th stage dynode 10 side of the m-th stage (m is an integer greater than 2 and less than N) dynode 10 is smaller than the width of the (m-1)th stage dynode 10. In other words, the width of the end edge E on the (m-1)th stage dynode 10 side of the m-th stage dynode 10 becomes a structure different from the width of the (m-1)th stage dynode 10 (hereinafter, also referred to as "nested structure"). In this embodiment, the m-th stage dynode 10 refers to a plurality of odd-numbered stages (excluding the first stage) of dynode 10 that are different from each other.

[0029] Specifically, the width of the 3rd-stage dynode 10c is smaller than the width of the 2nd-stage dynode 10b. The width of the 5th-stage dynode 10e is smaller than the width of the 4th-stage dynode 10d. The width of the 7th-stage dynode 10g is smaller than the width of the 6th-stage dynode 10f. The width of the 9th-stage dynode 10i is smaller than the width of the 8th-stage dynode 10h. The widths of the 3rd, 5th, 7th, and 9th-stage dynodes 10c, 10e, 10g, and 10i, which are multiple distinct odd-stage dynodes, are equal to each other. The widths of the 2nd, 4th, 6th, 8th, and 10th-stage dynodes 10b, 10d, 10f, 10h, and 10j, which are multiple distinct even-stage dynodes, are equal to each other.

[0030] In the X direction, the edge E of the m-th dynode 10 is contained inside the (m-1)-th dynode 10. That is, in the X direction, one sidewall 13W of the m-th dynode 10 is located more inner than one sidewall 13W of the (m-1)-th dynode 10, and the other sidewall 13W of the m-th dynode 10 is located more inner than the other sidewall 13W of the (m-1)-th dynode 10. In this embodiment, in the X direction, the 3rd dynode 10c is contained inside the 2nd dynode 10b, the 5th dynode 10e is contained inside the 4th dynode 10d, the 7th dynode 10g is contained inside the 6th dynode 10f, and the 9th dynode 10i is contained inside the 8th dynode 10h.

[0031] In the X direction, the width of the first-stage dynode 10a is greater than the width of the second to tenth-stage dynodes 10b to 10j. In the X direction, the second to tenth-stage dynodes 10b to 10j are contained within the first-stage dynode 10a. In other words, in the X direction, one end of the second to tenth-stage dynodes 10b to 10j is located further inside than one end of the first-stage dynode 10a, and the other end of the second to tenth-stage dynodes 10b to 10j is located further inside than the other end of the first-stage dynode 10a.

[0032] Viewed from the X direction, the edge E of the m-th dynode 10 extends into the (m-1)-th dynode 10. Specifically, viewed from the X direction, the edges E of multiple distinct odd-numbered dynodes 10 (excluding the 1st and 3rd dynodes) extend into the adjacent dynode 10 upstream of that dynode 10. More specifically, consider a nested structure where the edge E of the 5th dynode 10e and the 4th dynode 10d have different widths, in which the edge E of the 5th dynode 10e extends into the internal space of the 4th dynode 10d (the space defined by the sidewall 13W and the bottom wall 13B). Consider a nested structure where the edge E of the 7th dynode 10g and the 6th dynode 10f have different widths, in which the edge E of the 7th dynode 10g extends into the internal space of the 6th dynode 10f. Consider a nested structure where the edge E of the 9th dynode 10i has a different width from that of the 8th dynode 10h. In this nested structure, the edge E of the 9th dynode 10i extends into the internal space of the 8th dynode 10h. In other words, the 4th dynode 10d side of the 5th dynode 10e enters the internal space of the 4th dynode 10d, the 6th dynode 10f side of the 7th dynode 10g enters the internal space of the 6th dynode 10f, and the 8th dynode 10h side of the 9th dynode 10i enters the internal space of the 8th dynode 10h.

[0033] Furthermore, viewed from the X direction, the edge E of the second-stage dynode 10b extends into the first-stage dynode 10a. Specifically, it is designed as a nested structure where the edge E of the second-stage dynode 10b and the first-stage dynode 10a have different widths, and in this nested structure, the edge E of the second-stage dynode 10b extends into the internal space of the first-stage dynode 10a. Additionally, the third-stage dynode 10c does not extend into the second-stage dynode 10b and is configured separately from it. The fourth-stage dynode 10d does not extend into the third-stage dynode 10c and is configured separately from it. The sixth-stage dynode 10f does not extend into the fifth-stage dynode 10e and is configured separately from it. The eighth-stage dynode 10h does not extend into the seventh-stage dynode 10g and is configured separately from it. The 10th stage dynode 10j does not extend into the 9th stage dynode 10i and is configured separately from the 9th stage dynode 10b.

[0034] In the photomultiplier tube 1 configured as described above, when measuring light is incident on the photoelectric surface 3, electrons are emitted from the photoelectric surface 3. These electrons are focused by the focusing electrode 5 and sent to the electron multiplier section 6. In the electron multiplier section 6, electrons are sequentially incident on the secondary electron emission surfaces 11a-11j of the first to tenth stage multiplier electrodes 10a-10j and multiplied. Then, the multiplied electrons are collected by the electron collecting surface 73 of the anode 7 and extracted from the anode 7 as an output signal.

[0035] Figure 8 of (a) Figure 8 (b) and Figure 8 (c) represents a portion of the electron orbitals in the electron multiplier 906 of the comparative example. Figure 9 of (a) Figure 9 (b) and Figure 9 Figure (c) shows a simulation result representing a portion of the electron orbitals in the electron multiplication unit 6 of the embodiment. In each figure, multiple thin lines represent electron orbitals. Figure 8 As shown in (a), the electron multiplier 906 of the comparative example differs from the electron multiplier 6 in that it replaces the plurality of multiplier electrodes 10 (see Figure 6). Figure 3 ) and has multiple multiplier electrodes 910, replacing anode 7 (refer to Figure 3 It has an anode 907 but no partition 20 (see reference). Figure 3 ).

[0036] The widths of the multiple dynodes 910 are equal. The m-th dynode 910 does not extend into the (m-1)-th dynode 10 and is arranged separately from the (m-1)-th dynode 10. The cross-section of the 10th dynode 910j along the YZ plane is U-shaped with an opening on the front side. The secondary electron emission surface 911 of the 10th dynode 910j is provided on the outer surface of the rear side of the dynode 910 and is straight along the YZ plane. The anode 907 has a grid structure 930 containing multiple electron passage holes H0 for electrons to pass through along the electron path from the 9th dynode 910i to the 10th dynode 910j.

[0037] In the electron multiplier section 906, a portion of the electrons emitted from the 8th-stage dynode 910h skips the 9th-stage dynode 910i and the 10th-stage dynode 910j and enters the anode 907. For example... Figure 8 As shown in (b), a portion of the electrons emitted from the 9th dynode 910i skips the 10th dynode 10j and enters the anode 907. Furthermore, as... Figure 8 As shown in (c), a portion of the electrons emitted from the 10th-stage dynode 910j wanders near the grid structure 930 before being collected by the anode 907. Specifically, a portion of the electrons emitted from the 10th-stage dynode 910j moves back and forth between the 9th-stage dynode 910i and the 10th-stage dynode 910j multiple times before colliding with the anode 907.

[0038] In contrast, such as Figure 9 As shown in (a), in the electron multiplication section 6 of the embodiment, a portion of the electrons emitted from the 8th dynode 10h attempt to bypass the 9th dynode 10i and the 10th dynode 10j and be incident on the anode 7, but are blocked by the partition 20, and the incident is prevented.

[0039] like Figure 9 As shown in (b), some of the electrons emitted from the 9th-stage dynode 10i attempt to bypass the 10th-stage dynode 10j and enter the anode 7, but are blocked by the partition 20, thus preventing this entry. The electrons emitted from the 9th-stage dynode 10i pass through the space K formed between the partition 20 and the 10th-stage dynode 10j and enter the 10th-stage dynode 10j. Furthermore, as... Figure 9 As shown in (c), electrons emitted from the 10th stage dynode 10j are collected by the electron collection surface 73 of the anode 7.

[0040] As described above, the photomultiplier tube 1 includes: a photoelectric surface 3; an N-stage (N=10 here) dynode 10 that multiplies electrons emitted from the photoelectric surface 3; and an anode 7 that collects electrons multiplied by the dynode 10. In the photomultiplier tube 1, the anode 7, which is opposite to the secondary electron emission surface 11j of the 10th-stage dynode 10j (the final stage), extends along the secondary electron emission surface 11j. Therefore, electrons can easily be incident from the final-stage dynode 10j onto the anode 7. At the same time, the anode 7 does not have an electron passage hole in the electron path from the previous stage, the 9th-stage dynode 10i, toward the final-stage dynode 10j, thus preventing electron migration caused by the electron passage hole. As a result, the timing characteristics of the anode 7 can be improved. In particular, by preventing electron migration, the fall time characteristic of the signal waveform output from the anode 7 can be improved.

[0041] In the photomultiplier tube 1, the anode 7 is positioned between the 9th dynode 10i and the 10th dynode 10j. In this case, it is easy to position the anode 7 close to the 10th dynode 10j, which can improve the electric field strength between the anode 7 and the 10th dynode 10j.

[0042] The photomultiplier tube 1 includes a separator 20 disposed between the 9th dynode 10i and the anode 7, which prevents the incidence of electrons from the 9th dynode 10i onto the anode 7. In this configuration, electrons are prevented from skipping the 10th dynode 10j from the 9th dynode 10i and entering the anode 7. As a result, the timing characteristics (especially the rise time characteristics) of the anode 7 are improved.

[0043] In the photomultiplier tube 1, the separator 20 is applied with a potential higher than that of the 9th dynode 10i. In this case, the separator 20 can effectively prevent electrons from entering the anode 7 from the 9th dynode 10i.

[0044] In photomultiplier tube 1, a separator 20 is disposed between the 9th dynode 10i and the 10th dynode 10j. Electrons emitted from the 9th dynode 10i pass through the space K between the separator 20 and the 10th dynode 10j and are incident on the 10th dynode 10j. In this case, the space K between the separator 20 and the 10th dynode 10j allows electrons to be incident from the 9th dynode 10i onto the Nth dynode 10j.

[0045] As a result of in-depth research, the inventors have obtained the following insight: Discharge between the dynodes 10 tends to occur from the end in the X direction, which is the long side of the dynode 10. Therefore, in the photomultiplier tube 1, the width of the edge E of the 3rd, 5th, 7th, and 9th stage dynodes 10c, 10e, 20g, and 10i in the X direction is set to be smaller than the width of the 2nd, 4th, 6th, and 8th stage dynodes 10b, 10d, 10f, and 10h in the X direction. Furthermore, the edge E of the 3rd, 5th, 7th, and 9th stage dynodes 10c, 10e, 20g, and 10i is contained within the inner side of the 2nd, 4th, 6th, and 8th stage dynodes 10b, 10d, 10f, and 10h in the X direction. Therefore, by bringing the opposing dynodes 10 closer together to increase the electric field strength between stages, and by moving the ends of the 3rd, 5th, 7th, and 9th stage dynodes 10c, 10e, 20g, and 10i in the X direction away from the ends of the 2nd, 4th, 6th, and 8th stage dynodes 10b, 10d, 10f, and 10h in the X direction, the distance between these ends can be ensured to prevent discharge.

[0046] That is, in the photomultiplier tube 1, the m-th dynode 10 is arranged opposite to the (m-1)-th dynode 10. In the X direction, which is the long side direction of the dynode 10, the width of the end edge E of the (m-1)-th dynode 10 side of the m-th dynode 10 is smaller than the width of the (m-1)-th dynode 10. In the X direction, this end edge E of the m-th dynode 10 is contained inside the (m-1)-th dynode 10. This improves the timing characteristics and prevents discharge between the dynodes 10. In other words, reducing the electrode distance between the dynodes 10 used to prevent discharge improves the electric field strength and timing characteristics.

[0047] In photomultiplier tube 1, the cross-sectional shape of the dynode 10 along the YZ plane is arc-shaped. Furthermore, in photomultiplier tube 1, viewed from the X direction, the end edges E of the 5th, 7th, and 9th stage dynodes 10e, 10g, and 10i are nested with the 4th, 6th, and 8th stage dynodes 10d, 10f, and 10h, each with a different width. The end edges E of the 5th, 7th, and 9th stage dynodes 10e, 10g, and 10i extend into the 4th, 6th, and 8th stage dynodes 10d, 10f, and 10h, respectively. This allows the 4th and 5th stage dynodes 10d and 10e to approach each other while preventing discharge, thus increasing the electric field strength between them. It also allows the 6th and 7th stage dynodes 10f and 10g to approach each other while preventing discharge, and the 8th and 9th stage dynodes 10h and 10i to approach each other while preventing discharge, thus increasing the electric field strength between them.

[0048] Furthermore, by setting the adjacent dynodes 10, 10 in a nested structure, electrons with extremely long or short migration times can be cut off (it can be configured such that electrons with extremely long or short migration times collide with the surface opposite to the secondary electron emission surface 11 of the dynode 10), and the electron group collected at the anode 7 becomes an electron group with a small migration time difference, which can easily improve the time characteristics.

[0049] Furthermore, by setting at least the adjacent dynodes 10, 10 on the upstream side of the N-stage dynodes 10 into a nested structure, electrons with extremely long or short migration times can be cut off before they are multiplied. This also prevents the feedback of ions generated by the increase of electrons inside the dynodes 10 to the photoelectric surface 3.

[0050] In the photomultiplier tube 1, in the X direction, the width of the first-stage dynode 10a is greater than the width of the second to tenth-stage dynodes 10b to 10j. In the X direction, the second to tenth-stage dynodes 10b to 10j are arranged in a nested structure contained within the first-stage dynode 10a. In this case, the X-direction ends of the second to tenth-stage dynodes 10b to 10j can be moved away from the X-direction end of the first-stage dynode 10a, ensuring the distance between these ends and preventing discharge.

[0051] Figure 10 (a) is a graph showing the simulation results of the rise time for the comparative example and the embodiment. Figure 10 (b) is a graph showing the simulation results of the fall time for the comparative example and the embodiment. The rise time is the time it takes for the output pulse peak to rise from 10% to 90%. The fall time is the time it takes for the output pulse peak to fall back from 90% to 10%. It can be said that shorter rise and fall times indicate better time characteristics. The comparative example corresponds to the electron multiplier 906 (see reference 906). Figure 8 ), the embodiment corresponds to electron multiplier 6 (refer to Figure 9 The graph in the figure compares the values ​​of 10j and 910j for the 10th stage dynode with the values ​​of 7 and 907 for the anode. (For example...) Figure 10 (a) and Figure 10 As shown in (b), it is confirmed that in the comparative example, both the rise time and fall time are longer (worsened) during the electron multiplication process from the 10th stage dynode 10j to the anode 7. In contrast, in the embodiment, both the rise time and fall time are maintained.

[0052] Figure 11 (a) is a graph showing the measured values ​​of the output signal from anode 907 in the comparative example. Figure 11 (b) is a graph representing the measured values ​​of the output signal from anode 7 in the embodiment. exist Figure 11 (a) and Figure 11 In (b), their timelines correspond to each other. For example... Figure 11 (a) and Figure 11 As shown in (b), it is confirmed that a significant improvement in the rise time and fall time of anode 7 can be achieved in the embodiment compared to the comparative example.

[0053] Furthermore, in this embodiment, N, which serves as the total number of stages of the multiplier 10, is set to 10. However, N is not particularly limited and can be any integer greater than 2. In this embodiment, m, which serves as the stage of the multiplier 10 with a smaller width, is set to 3, 5, 7, or 9 (odd-numbered stages). However, m is not particularly limited and can be any even-numbered stage, as long as it is an integer greater than 2 and less than N.

[0054] In this embodiment, the edge E of the fifth, seventh, and ninth stage pyroelectric multipliers 10e, 10g, and 10i, which have smaller widths, extends into the upstream pyroelectric multiplier 10, but this is not a limitation. All edge E of the third, fifth, seventh, and ninth stage pyroelectric multipliers 10c, 10e, 10g, and 10i may extend into the upstream pyroelectric multiplier 10. Alternatively, any edge E of the fifth, seventh, and ninth stage pyroelectric multipliers 10e, 10g, and 10i may extend into the upstream pyroelectric multiplier 10. That is, at least any edge E of the plurality of smaller pyroelectric multipliers 10 may extend into the upstream pyroelectric multiplier 10. Alternatively, the edge E of the fifth, seventh, and ninth stage pyroelectric multipliers 10e, 10g, and 10i may not extend into the upstream pyroelectric multiplier 10. That is, the N-stage dynode 10 can also be configured such that adjacent dynodes 10, 10 are separated from each other when viewed from the X direction.

[0055] In this embodiment, it is sufficient to make the width of the edge E of the m-th dynode 10 smaller than the width of the (m-1)-th dynode 10. Therefore, for example, the width of the part other than the edge E of the m-th dynode 10 can be greater than the width of the (m-1)-th dynode 10.

[0056] In this embodiment, on the sidewalls 13W of the 5th, 7th, and 9th stage dynodes 10e, 10g, and 10i extending into the upstream side of the dynode 10, a retaining sheet (not shown) for holding to the insulating support substrate may be provided on the side away from the upstream side of the dynode 10. In this case, the timing characteristics can be improved and discharge between the dynodes 10 can be further prevented.

[0057] Furthermore, in the field of photomultiplier tubes, improving the timing characteristics of the anode is synonymous with suppressing the degradation of timing characteristics caused by deviations in the electron's travel and / or movement paths; therefore, suppressing this degradation becomes important. In this regard, the photomultiplier tube 1 of this embodiment, as described above, can effectively suppress the degradation of timing characteristics caused by deviations in the electron's travel and / or movement paths, and is therefore particularly effective.

[0058] The present invention is not limited to the above-described embodiments.

[0059] Figure 12 (a) is a perspective view showing a section cut across a portion of the electron multiplication unit 106 in the first modified example. Figure 12 As shown in (a), the electron multiplier 106 differs from the embodiment described above in that the 10th stage dynode 10j is replaced (see Figure 10j). Figure 3 It possesses a multiplier electrode of 110J, replacing the anode 7 (refer to...). Figure 3 It has an anode 107 and a grid electrode 130.

[0060] The 10th stage dynode 110j includes a straight portion 11L with a straight cross-section along the YZ plane, and a bent portion 11R with a bent cross-section along the YZ plane. The bent portion 11R extends in a manner that bends from the end of the straight portion 11L toward the 9th stage dynode 10i. The other structures of the dynode 110j are configured in the same way as those of the dynode 10j.

[0061] The cross-section of the anode 107 along the YZ plane is L-shaped. The outer surface of the anode 107 on the 10th stage dynode 110j side has an electron collecting surface 173. The electron collecting surface 173 faces the secondary electron emission surface 111j of the 10th stage dynode 110j, and at least a portion extends along the secondary electron emission surface 111j. Here, the electron collecting surface 173 extends in a planar shape following the secondary electron emission surface 111j of the straight portion 11L. In other respects, the anode 107 is constructed similarly to the anode 7.

[0062] The grid electrode 130 is disposed on the electron path from the 10th-stage dynode 110j toward the anode 107. That is, the grid electrode 130 is disposed between the anode 107 and the 10th-stage dynode 110j. The grid electrode 130 causes electrons to be drawn out from the 10th-stage dynode 110j. The grid electrode 130 is disposed close to the secondary electron emission surface 111j of the 10th-stage dynode 110j. The grid electrode 130 includes a plurality of electron passage holes 130H for allowing electrons to pass through.

[0063] A potential higher than that of the 10th-stage dynode 110j is applied to the grid electrode 130. Preferably, the grid electrode 130 is not electrically connected to the anode 107. The grid electrode 130 constitutes an extraction electrode for electrons drawn from the 10th-stage dynode 110j, improving output linearity (dynamic range). The grid electrode 130 improves the time characteristics of the anode 107 by increasing the electric field strength between the anode 107 and the 10th-stage dynode 110j, thereby accelerating electrons flying from the 10th-stage dynode 110j towards the anode 107.

[0064] In this first modification, the aforementioned effect of improving the timing characteristics of the anode 107 is also achieved. Furthermore, the aforementioned effect of improving timing characteristics and preventing discharge between the dynodes 10 is achieved. In this first modification, the grid electrode 130 can promote electron extraction from the 10th-stage dynode 110j, thereby improving output linearity (dynamic range).

[0065] Furthermore, in the first modification, a potential higher than that of the 10th-stage dynode 110j is applied to the grid electrode 130. In this case, the grid electrode 130 can efficiently extract electrons. In the first modification, the grid electrode 130 is used as an extraction electrode. In this case, the grid electrode 130 can facilitate the extraction of electrons from the 10th-stage dynode 110j.

[0066] Furthermore, in the first modification, the grid electrode 130 is not electrically connected to the anode 107, but the grid electrode 130 can also be electrically connected to the anode 107. In this case, the grid electrode 130 is not an electrode that collects electrons that can be used as signal current, and does not function as the anode 107. In addition, since the number of electrons colliding with the grid electrode 130 is not zero, the signal caused by the electrons incident on the grid electrode 130 sometimes overlaps with the output of the anode 107, but the probability of electrons drawn from the 10th stage dynode 110j colliding with the grid electrode 130 is low (because the number of colliding electrons is extremely small), so it has little impact on the timing characteristics of the anode 107. Thus, by electrically connecting the grid electrode 130 to the anode 107, the number of components can be reduced, and the ease of assembly can be improved.

[0067] Figure 12 (b) is a perspective view showing a section cut across a portion of the electron multiplication unit 206 in the second modified example. Figure 12 As shown in (b), the electron multiplier 206 differs from the embodiment described above in that it does not have a 10th multiplier electrode 10j (see Figure 10). Figure 3 ), replacing the 9th stage multiplier 10i (refer to Figure 3 It features a 210i multiplier electrode, replacing the anode 7 (see reference). Figure 3 It has an anode 207, replacing the separator 20 (see reference). Figure 3 It has a partition 220.

[0068] In the electron multiplier section 206, N is set to 9, and it has 9 dynodes 10. The 9th dynode 210i includes a straight portion 21L with a straight cross-section along the YZ plane, and a bent portion 21R with a bent cross-section along the YZ plane. The bent portion 21R extends in a manner that bends from the end of the straight portion 21L toward the 8th dynode 10h side. The other structures of the dynode 210i are configured in the same way as those of the dynode 10i.

[0069] Anode 207 is disposed between the 8th dynode 10h and the 9th dynode 210i. The cross-section of anode 207 along the YZ plane is formed along the 9th dynode 210i. The outer surface of anode 207 on the 9th dynode 210i side has an electron collecting surface 273. The electron collecting surface 273 is opposite to the secondary electron emission surface 211i of the 9th dynode 210i, and at least a portion extends along the secondary electron emission surface 211i. In other respects, anode 207 is constructed similarly to anode 7.

[0070] A separator 220 is disposed between the 8th stage dynode 10h and the anode 207. The separator 220 prevents electrons from entering the anode 207 from the 8th stage dynode 10h. A separator 220 is also disposed between the 8th stage dynode 10h and the 9th stage dynode 210i. The separator 220 is a flat plate extending in the X direction. The separator 220 is integrally formed with the 9th stage dynode 210i. The separator 220 is continuous with the end of the curved portion 21R of the 9th stage dynode 210i. An opening 220H is formed in the separator 220, extending through its thickness direction. The opening 220H forms a space K. Electrons emitted from the 8th stage dynode 10h pass through the space K of the separator 220 and enter the 9th stage dynode 210i. The separator 220 is applied with a potential higher than that of the 8th stage dynode 10h. In other respects, partition 220 is constructed in the same manner as partition 20.

[0071] In this second modification, the aforementioned effect of improving the timing characteristics of the anode 207 is also achieved. Furthermore, the aforementioned effect of improving timing characteristics and preventing discharge between the dynodes 10 is also achieved. Additionally, in this second modification, since the separator 220 is integrally formed with the final stage dynode 210i, the separator 220 can be easily installed using the final stage dynode 210i.

[0072] Figure 13 This is a perspective view showing a portion of the electron multiplier 306 in the third modified example. Figure 14 This is a diagram showing a portion of the electron multiplication unit 306 in the third modified example as viewed from the Y direction. (See diagram below.) Figure 13 and Figure 14As shown, the electron multiplication section 306 differs from the above embodiment in that the 5th, 7th, and 9th stage multiplication electrodes 10e, 10g, and 10i are replaced (see reference). Figure 3 It possesses multiplier poles 310e, 310g, and 310i.

[0073] The sidewalls 31W at both ends of the fifth-stage dynode 310e in the X direction extend obliquely relative to the YZ plane, expanding outwards with respect to the fourth-stage dynode 10d. The width of the fifth-stage dynode 310e is smallest at the end edge E1 on the side of the fourth-stage dynode 10d and increases with respect to the fourth-stage dynode 10d; the end edge Z1 on the opposite side of end edge E1 corresponds to the width of the fourth-stage dynode 10d. The other structures of the dynode 310e are configured similarly to those of the dynode 10e.

[0074] The sidewalls 32W at both ends of the 7th dynode 310g in the X direction extend obliquely relative to the YZ plane, expanding outwards as they move away from the 6th dynode 10f. The width of the 7th dynode 310g is smallest at the end edge E2 on the side of the 6th dynode 10f and increases as it moves away from the 6th dynode 10f; the end edge Z2 on the opposite side of end edge E2 corresponds to the width of the 6th dynode 10f. The other structures of the dynode 310g are configured similarly to those of the dynode 10g.

[0075] The sidewalls 33W at both ends of the 9th dynode 310i in the X direction extend obliquely relative to the YZ plane, expanding outwards with distance from the 8th dynode 10h. The width of the 9th dynode 310i is smallest at the end edge E3 on the side of the 8th dynode 10h and increases with distance from the 8th dynode 10h; the end edge Z3 on the opposite side of end edge E3 corresponds to the width of the 8th dynode 10h. The other structures of the dynode 310i are configured similarly to those of the dynode 10i.

[0076] In this third variation, the aforementioned effect of improving the timing characteristics of the anode 207 is also achieved. Furthermore, the aforementioned effect of improving timing characteristics and preventing discharge between the dynodes 10 is also achieved.

[0077] Figure 15 This is a perspective view showing a portion of the electron multiplier 406 in the fourth modified example. Figure 16 This is a diagram showing a portion of the electron multiplication unit 406 in the fourth modified example as viewed from the Y direction. Figure 17 This is a diagram showing a portion of the electron multiplication unit 406 in the fourth modified example, viewed from the X-direction. Figure 15 , Figure 16 and Figure 17As shown, the electron multiplier 406 differs from the above embodiment in that it replaces the 7th stage pyrolysis electrode 10g (see reference). Figure 3 It has a multiplier of 410g.

[0078] The width of the 7th dynode 410g in the X direction is constant, and the sidewall 13W extends along the YZ plane. The width of the 7th dynode 410g is equal to the width of the 6th dynode 10f. That is, in the 4th variation, the kth dynode 10 (k is an integer other than m, where k=7) is arranged opposite to the (k-1)th dynode 10, and the width of the kth dynode 10 in the X direction is equal to the width of the (k-1)th dynode 10.

[0079] The edge E4 of the 7th dynode 410g does not extend into the 6th dynode 10f. Viewed from the X direction, the 7th dynode 410g is arranged separately from the 6th dynode 10f. That is, the above-described nesting structure is adopted only in any one of the multiple stages (between the dynodes 10) of the plurality of dynodes 10 contained in the electron multiplication section 406 (here, between the stages of the 4th and 5th dynodes 10d and 10e and between the stages of the 8th and 9th dynodes 10h and 10i). The other structures of the dynode 410g are configured in the same way as those of the dynode 10g.

[0080] In this fourth variation, the aforementioned effect of improving the timing characteristics of the anode 207 is also achieved. Furthermore, the aforementioned effect of improving timing characteristics and preventing discharge between the dynodes 10 is also achieved.

[0081] Furthermore, in the fourth variation, the k-th dynode 410g is configured opposite to the (k-1)-th dynode 410f. In the X direction, the width of the k-th dynode 410g is equal to the width of the (k-1)-th dynode 410f. In this case, the electron arrival efficiency (so-called interstage efficiency) of both the k-th and (k-1)-th dynodes 410f can be improved. A nested structure is used in interstages where time characteristics deteriorate to improve time performance, while electron arrival efficiency can be improved in non-deteriorated interstages. This achieves a balance between time characteristics and electron multiplication number.

[0082] Figure 18 This is a cross-sectional view showing the electron multiplier 506 in the fifth modified example. (As shown) Figure 18 As shown, the electron multiplier 506 differs from the embodiment described above in that the 10th stage dynode 10j is replaced (see Figure 10j). Figure 3 ) and possesses a multiplier electrode 510J, replacing the anode 7 (refer to Figure 3 It has an anode 507 but no partition 20 (see reference). Figure 3 ).

[0083] The width of the 10th-stage dynode 510j in the X direction is constant. The width of the 10th-stage dynode 510j is equal to the width of the 9th-stage dynode 10i. The cross-section of the 10th-stage dynode 510j along the YZ plane is U-shaped with an opening on the front side. The secondary electron emission surface 511 of the 10th-stage dynode 510j is provided on the front outer surface of the 10th-stage dynode 510j (the surface opposite to the anode 507), and its cross-section along the YZ plane is straight. The anode 507 has a grid structure 530 containing multiple electron passage holes H0 along the electron path from the 9th-stage dynode 10i to the 10th-stage dynode 510j.

[0084] In this fifth variation, the aforementioned effects are also achieved, such as improving timing characteristics and preventing discharge between the 10 dynodes (especially between the 4th and 5th dynodes 10d and 10e, between the 6th and 7th dynodes 10f and 10e, and between the 8th and 9th dynodes 10h and 10i).

[0085] In the above embodiments and modifications, the entire region of the electron collecting surfaces 73, 173, and 273 of the anodes 7, 107, and 207 may not extend along the secondary electron emission surface 11 of the Nth-stage dynode 10; at least a portion of the electron collecting surfaces 73, 173, and 273 of the anodes 7, 107, and 207 may extend along the secondary electron emission surface 11 of the Nth-stage dynode 10. In the above embodiments and modifications, nested structures may also be alternately applied from the upstream side to the downstream side among the multiple stages of the Nth-stage dynode 10.

[0086] In the above embodiments and variations, partitions 20 and 220 are provided. However, any component that constitutes a wall portion that prevents electrons from entering the anode 7 from the (N-1)th stage dynode 10 can be used instead of partitions 20 and 220.

[0087] The structures in the above embodiments and modifications are not limited to the materials and shapes described above; various materials and shapes can be used. Furthermore, the structures in the above embodiments and modifications can be arbitrarily applied to structures in other embodiments or modifications. Explanation of reference numerals in the attached figures

[0088] 1… Photomultiplier tube, 3… Photoelectric surface, 7, 107, 207, 507… Anode, 10, 10a~10j, 110j, 210i, 310e, 310g, 310i, 410g, 510j… Multiplier electrode, 11, 11j, 111j, 211i, 511… Secondary electron emission surface, 20, 220… Partition (wall), 73, 173, 273… Electron collection surface, E, E1~E4… Edge, K… Space.

Claims

1. A photomultiplier tube, wherein, have: Photoelectric surface; The N-order dynode multiplies electrons emitted from the photoelectric surface, where N is an integer greater than or equal to 2; and The anode collects electrons multiplied by the multiplying electrode. The multiplication poles of the m-th stage are configured opposite to the multiplication poles of the (m-1)-th stage, where m is an integer greater than 2 and less than N. In the direction of the long side of the multiplier, the width of the end edge of the (m-1)th stage of the multiplier is smaller than the width of the (m-1)th stage of the multiplier. In the direction of the long side, the edge of the m-th stage multiplier is contained inside the (m-1)-th stage multiplier.

2. The photomultiplier tube according to claim 1, wherein, The cross-section of the multiplier pole intersecting the long side direction is arc-shaped. Viewed from the long side direction, the edge of the m-th stage multiplier extends into the (m-1)-th stage multiplier.

3. The photomultiplier tube according to claim 1 or 2, wherein, In the direction of the long side of the multiplication electrode, the width of the first-stage multiplication electrode is greater than the width of the second to Nth stages of the multiplication electrode. In the direction of the long side, the second to Nth stages of the multiplication pole are contained inside the first stage of the multiplication pole.

4. The photomultiplier tube according to claim 1 or 2, wherein, The k-th stage multiplication pole is configured opposite to the (k-1)-th stage multiplication pole, where k is 2 or more and N or less, and is an integer other than m. In the direction of the long side of the multiplier, the width of the k-th stage multiplier is equal to the width of the (k-1)-th stage multiplier.

Images