WO1998057353A1

WO1998057353A1 - Electron multiplier and photomultiplier

Info

Publication number: WO1998057353A1
Application number: PCT/JP1998/002568
Authority: WO
Inventors: Yutaka Hasegawa; Hiroyuki Kyushima
Original assignee: Hamamatsu Photonics K.K.
Priority date: 1997-06-11
Filing date: 1998-06-11
Publication date: 1998-12-17
Also published as: JP4146529B2; AU7673698A; JPH113677A

Abstract

An electron multiplier which cascade-multiplies incident electrons and a photomultiplier provided with the electron multiplier. The electron multiplier and the photomultiplier are each provided with a discharge suppressing structure which effectively suppresses the occurrence of noise by preventing the discharge between respective dynodes laminated in a plurality of stages. The discharge suppressing structures provides the dynodes with various structures, but, particularly for the first and second dynodes (11A and 11B) which are arranged adjacently to each other with a spacer in between, the positions of the edges (120) of the electron emitting surfaces of the first dynodes (11A) facing the second dynodes (11B) are shifted from the positions of the edges (130) of the electron entering surfaces of the second dynodes (11B) facing the first dynodes (11A) in the direction perpendicular to the direction of laminating the dynodes.

Description

Satsuki Itoda ¾ Technical field of electron multiplier and photomultiplier tube

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron multiplier for cascade multiplying electrons made incident into a vacuum vessel by a multi-layered dynode, and a photomultiplier provided with the electron multiplier. . Background art

A conventional electron multiplier is disclosed, for example, in Japanese Patent Application Laid-Open No. Hei 6-314145. The electron multiplier described in this publication has an electron multiplier disposed in a vacuum vessel. The electron multiplier has a plate-like dynode having electron multiplier holes arranged in a matrix. Have a multi-layered configuration. Furthermore, the dynodes are integrated by bonding two dynode thin plates and welding the corners (corners) of the dynode thin plates. Each dynode is provided with a notch at the corner of the dynode so as to avoid the welding marks of the adjacent dynode, thereby suppressing the electric field discharge caused at the welding site. Disclosure of the invention

The inventors have found the following problems as a result of studying the above-described conventional technology. That is, since the conventional electron multiplier is configured as described above, a notch is provided at a corner of each dyno to suppress electric field discharge at a welding site. However, since the distance between the dynodes is very narrow, 0.16 to 0.17 mm, electric field discharge is likely to occur at the edge of each adjacent dynode, and noise caused by this electric field discharge There was a problem that would occur. The present invention has been made in order to solve the above-mentioned problems, and has an electron multiplier having a structure for effectively suppressing noise generation due to discharge between dynodes, and an electron multiplier having the structure. It is an object of the present invention to provide a photomultiplier tube provided with the same.

Generally, the electron multiplier has an electron multiplier having a plurality of stages of dynodes stacked through a spacer of an insulating material along a predetermined stacking direction coinciding with the incident direction of incident electrons. An anode for capturing secondary electrons cascade-multiplied by the electron multiplier is provided, and the photomultiplier tube sandwiches the electron multiplier together with the anode together with the electron multiplier and the anode. And a photocathode arranged at In particular, the electron multiplier according to the present invention further includes a discharge suppressing structure in addition to the electron multiplier and the anode in order to achieve the above object. This discharge suppressing structure is provided for the first and second dynodes of the plurality of dynodes that are adjacent to each other via the spacer and that emit electrons facing the second dynode of the first dynode. The position of the edge of the surface and the position of the edge of the electron incident surface of the second dynode facing the first dynode are determined from the stacking direction of the plurality of dynodes (coincident with the incident direction of incident electrons). It is characterized in that they are shifted along the direction perpendicular to the laminating direction when viewed.

The present inventors have found that an electric field discharge is generated between adjacent dynodes between edges located in the peripheral portion of each dynode, and this is greatly involved in generating noise. Therefore, the electron multiplier and the photomultiplier according to the present invention focus on the peripheral portions of the dynodes adjacent to each other, and the positions of the edges directly adjacent via the spacer are viewed from the stacking direction of the dynodes. Thus, the shape of each dynode was changed so as to be shifted along the direction perpendicular to the lamination direction. As a result, while the distance between adjacent edges is increased, it is possible to effectively suppress electric field discharge between the edges without increasing the distance between adjacent dynodes.

Specifically, for the first and second dynodes that are adjacent to each other, the discharge suppression structure includes a side surface of the first dynode facing the inner wall of the vacuum vessel and the vacuum container. Preferably, the distance from the inner wall of the vessel is longer or shorter than the distance between the side of the second dynode facing the inner wall of the vacuum vessel and the inner wall of the vacuum vessel. With such a structure, the electron multiplier has a simple configuration in which the side surfaces of adjacent dynodes are alternately arranged.

Further, the discharge suppressing structure may be configured such that, for each of the plurality of stages of dynodes, an area of an electron incident surface located on a side where electrons are incident is set to an electron emitting surface facing the electron incident surface (located on the anode side). Surface) may be larger or smaller. In this structure, for each of the plurality of dynodes, a side surface facing the inner wall of the vacuum vessel is inclined by a predetermined angle with respect to a side wall of the vacuum vessel so that the cross-sectional area changes along the laminating direction. This can be realized by: In addition, in the case of this structure, the electron multiplier can increase the interval between adjacent edge portions even if the side surfaces of each dynode are aligned in a straight line. In addition, the positions of the side surfaces of each of the dinos in the vacuum vessel can be aligned substantially all around.

Further, each of the plurality of stages of dynodes may have a structure including a first dynode plate and a second dynode plate directly contacted with the first dynode plate. In this case, the discharge suppressing structure is provided on each of the plurality of dynodes on a side facing the inner wall of the vacuum vessel, from the inner wall of the vacuum vessel to the side of the first dynode plate facing the inner wall. This can be realized by providing a step by changing the distance and the distance from the side wall of the vacuum vessel to the side surface of the second dynode plate facing the side wall. With this structure, the electron multiplier can have a step at the edge of each of the dies, and the outer peripheral portion of each of the dies can be made to have the same shape. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram showing a schematic structure of a photomultiplier tube (including an electron multiplier) according to the present invention. FIG. 2 is an enlarged perspective view showing a main part of an electron multiplier applicable to the electron multiplier shown in FIG.

FIG. 3 is a cross-sectional view of the electron multiplier shown in FIG. 2, which is taken along the line III-III in FIG.

FIG. 4 is a plan view showing the structure of each dynode applicable to the electron multiplier shown in FIG.

FIG. 5 is an enlarged perspective view showing a first modification of the electron multiplier applicable to the electron multiplier and the photomultiplier according to the present invention.

6 is a cross-sectional view of the electron multiplier shown in FIG. 5, which is taken along the line VI-VI in FIG.

FIG. 7 is a plan view showing the structure of each of the dynodes applicable to the electron multiplier shown in FIG.

FIG. 8 is a plan view showing the back surface (the anode side) of the dynode shown in FIG. FIG. 9 is an enlarged perspective view showing a second modification of the electron multiplier applicable to the electron multiplier and the photomultiplier according to the present invention.

FIG. 10 is a cross-sectional view of the electron multiplier shown in FIG. 9, which is taken along the line XX in FIG.

FIG. 11 is a plan view showing the structure of each dynode applicable to the electron multiplier shown in FIG.

Fig. 12 is a plan view showing the back side (anode side) of the dynode shown in Fig. 11.

Hereinafter, the electron multiplier and the photomultiplier according to the present invention will be described.

This will be described with reference to FIGS. In the drawings, the same parts and components are denoted by the same reference numerals, and redundant description will be omitted. FIG. 1 is a diagram showing a schematic configuration of a photomultiplier according to the present invention (including the electron multiplier according to the present invention). The photomultiplier tube 1 shown in Fig. 1 converts weak light into electrons (photoelectrons) and cascade multiplies the electrons. This photomultiplier tube 1 includes a cylindrical metal side tube 2 having both ends opened, and a glass light receiving surface plate 3 for receiving incident light is fixed to one open end of the side tube 2. At the other open end, a disc-shaped stem 5 in which a plurality of stem bins 4 are arranged is fixed. The side tube 2, the light receiving face plate 3, and the stem 5 constitute a vacuum vessel 6, and an electron multiplier 7 is disposed inside the vacuum vessel 6.

A photoelectric conversion surface (photocathode) 8 made of a GaAs semiconductor crystal is provided on a surface of the light-receiving surface plate 3 located inside the vacuum vessel 6 (the back surface of the light-receiving surface plate 3). A focusing electrode 9 is arranged between the electron multiplier 7 and the electron multiplier 7. Therefore, the trajectory of the photoelectrons emitted from the photoelectric conversion surface 8 is converged by the influence of the focusing electrode 9, and is incident on a predetermined region of the electron multiplier 7.

The electron multiplying unit 7 includes a plate-like dynode 11 having electron multiplying holes 10 arranged in parallel through a spacer 110 made of an insulating material such as ceramic, as indicated by lines in the figure. It is configured to be multi-tiered along the indicated direction. The direction indicated by the line L is the incident direction of the weak light incident on the photomultiplier tube 1, the traveling direction of the photoelectrons from the photoelectric conversion surface 8 to the electron multiplier 7 (the incident direction of the photoelectrons). Also, the stacking direction of each dynode 11 is shown. Below the stacked dynodes 11, a final dynode 12 that reflects the secondary electrons output from the dynode 11 is disposed, and between the final dynode 12 and the dynode 11 is: An anode 13 for receiving electrons is arranged. The dynode 11, the last dynode 12, and the anode 13 are connected and fixed to the respective stem pins 4.

As shown in FIGS. 2 to 4, the square dynode 11 has two types of dynodes 11 A and 11 B, and the dynode 11 A is connected to the n (1) stage. In this case, dynode 1 1 B becomes the n + 1st dynode (Fig. 2). The n-th dynode 11A has a plurality of electron multiplying holes 1 OA arranged in parallel as shown in FIG. 4, and has a wide periphery so as to surround all the electron multiplying holes 1 OA. Section 12 is provided. On the other hand, the n + 1st dynode 11B also has a plurality of electron multiplier holes 10B arranged in parallel as shown in FIG. 4, and has a width surrounding the electron multiplier holes 10B. A narrow peripheral portion 13 is provided. In the dynodes 11A and 11B, the side surface 12a of the dynode 11A (the surface facing the inner wall of the vacuum vessel 6) is connected to the surfaces 12c (electron incident surface) and 12b (electron emitting surface) of the dynode 11A. The dynode 11B is formed at right angles to the side surface 13a (the surface facing the inner wall of the vacuum vessel 6) of the dynode 11B, and at right angles to the surfaces 13c (electron incident surface) and 13b (electron emitting surface) of the dynode 11B. Is formed. Therefore, when the electron multiplier 7 is assembled so that the electron multiplier hole 1OA of the nth dynode 11A and the electron multiplier hole 10B of the n + 1th dynode 11B face each other, the nth dynode 11 The side 12a of the peripheral part 12 of A protrudes outward (to the side of the side tube 2 of the vacuum vessel 6), and the side 13a of the peripheral part 13 of the n + first stage dynode 11B is inside (the tube of the vacuum vessel 6). (Axis L side). As a result, when comparing the peripheral portion 12 of the n-th dynode 11A with the peripheral portion 13 of the (n + 1) th dynode 11B, the edges 120 and n on the electron emission surface 12b of the n-th dynode 11A are compared. + The edge 130 on the electron incident surface 13c of the first-stage dynode 11B faces in an oblique direction, and the facing edges 120 and 130 are perpendicular to the stacking direction when viewed from the stacking direction L. (See Fig. 3).

In this way, merely by alternately stacking the dynode 11A of the same type as the dynode 11A of the nth stage and the dynode 11B of the same type as the n + 1st dynode 11B (see FIGS. 2 and 3), the adjacent edge 120, The distance between 130 and 130 can be increased, and the generation of electric field discharge between these edges 120 and 130 can be effectively suppressed. Therefore, according to the present invention, the distance between the dynodes 11 is maintained as a minute space of about 0.16 to 0.17 mm as in the conventional electron multiplier, The electric field discharge can be further suppressed.

In consideration of the electrical connection between each dynode 11A, 1 IB and each stem pin 4, the inner wall of the vacuum vessel 6 (side pipe 2) ) Is provided in the outer periphery of the dynodes 11A and 1IB, and a part of the side surfaces 12a and 13a is interrupted by the ears. However, the electric field discharge between the tip of the ear and the edge of the periphery of the adjacent die is negligibly small. In this embodiment, the n-th dynode 11 A is integrated by bonding two dynode thin plates A and B and welding these dynode thin plates A and B. Similarly, the (n + 1) th dynode 11B is integrated with the dynode thin plates C and D (see FIGS. 2 and 3).

Next, a first application example of the electron multiplier applicable to the electron multiplier and the photoelectric multiplier according to the present invention will be described with reference to FIGS. The configuration other than the dynode 21 described later is the same as that of the photomultiplier tube 1 described above, and the overlapping description will be omitted below.

As shown in FIGS. 5 to 8, the square dynode 21 is provided with two types of dynodes 21A and 2IB, and the dynode 21A is used as the n (1) th dynode. In this case, the dynode 21B becomes the (n + 1) th dynode (see FIG. 5). The n-th dynode 21A has a plurality of electron multiplier holes 2OA arranged in parallel as shown in FIGS. 7 and 8, and surrounds all the electron multiplier holes 2OA. Is provided with a peripheral portion 22. On the other hand, the (n + 1) th stage dynode 21B has a plurality of electron multiplier holes 20B arranged in parallel as shown in FIGS. A peripheral portion 23 is provided so as to surround 20B.

As shown in FIGS. 5 and 6, in the dynodes 21A and 2IB, the side surface 22a of the dynode 21A (the surface facing the side wall of the vacuum vessel 6) is a dyno. Is a taper surface formed at an acute angle with respect to the surface 22 c (electron incident surface) of the node 22 A, and the side surface 22 b (surface facing the side wall of the vacuum vessel 6) of the dynode 21 B is It is a taper surface formed at an acute angle to the surface 23 c (electron incident surface) of dynode 21B.

Therefore, the electron multiplying unit 7A is assembled so that the electron multiplying hole 2OA of the nth dynode 21A and the electron multiplying hole 20B of the n + 1th dynode 21B are opposed to each other. The outermost peripheral line 2 2 d of the side surface 2 2 a in the n-th dynode 21 A and the outermost peripheral line 23 d of the side surface 23 a in the n + 1-stage dynode 21 B are Line up along the direction of extension of the tube axis L (see Fig. 1). As a result, when the periphery 22 of the n-th dynode 21A is compared with the periphery 23 of the n + 1th dynode 21B, the n-th dynode 2 The side 2 2 a of 1 A and the side 23 a of the n + 1st dynode 2 1 B face each other in an inclined state, and the pages 22 0 and 230 facing each other are When viewed from the stacking direction of the dynodes 21A and 21B, the dynodes can be shifted from each other along a direction perpendicular to the stacking direction. Even with this configuration, the distance between the edges 220 and 230 is increased without changing the distance between the dynodes 21 A and 21 B, so that the generation of electric field discharge at this portion is effectively suppressed. It becomes possible.

Thus, even if the side surface 22a of the dynode 21A and the side surface 23a of the dynode 21B are aligned in parallel and along the pipe axis L direction, the adjacent dynodes 21A and 21B The distance between the directly opposite edges 220 and 230 can be increased. Moreover, the positions of the side surface 22a of the dynode 21A and the side surface 23a of the dynode 21B in the vacuum vessel 6 can be aligned over substantially the entire circumference. The n-th dynode 21 A is integrally formed by bonding two dynode thin plates A 1 and B 1 and welding the dynode thin plates A 1 and B 1. Similarly, the n + 1st stage dynode 2 1 B is integrated by the dynode thin plates C 1 and D 1 (Figs. 5 and 6). Further, a second application example of the electron multiplier applicable to the electron multiplier and the photomultiplier according to the present invention will be described with reference to FIGS. The configuration other than the dynode 31 described later is the same as that of the photomultiplier tube 1 described above, and a duplicate description will be omitted below.

As shown in FIGS. 9 to 12, the square dynode 31 has two types of dynodes 31 A and 3 IB, and the dynode 31 A is connected to the n-th dynode. In this case, dynode 31 B becomes the n + 1st dynode (see Fig. 9). The n-th dynode 31 A has a plurality of electron multiplier holes 3 OA arranged in parallel as shown in FIG. 11 and FIG. A peripheral portion 32 is provided so as to surround it. Similarly, the n + 1st dynode 31B has a plurality of electron multiplier holes 30B arranged in parallel as shown in FIG. 11 and FIG. A peripheral portion 33 is provided so as to surround the double hole 30B. As shown in FIG. 9 and FIG. 10, the n-th dynode 31 A is formed by laminating the first dynode thin plate A 2 and the second dynode thin plate B 2 and forming these dynode thin plates A 2 , B2 are welded together to achieve integration. In this case, the side surface 32aA of the first dynode thin plate A2 and the side surface 32aB of the second dynode thin plate B2 are not arranged on the same plane, The side surface 32aA of the first dynode thin plate A2 and the side surface 32aB of the second dynode thin plate B2 are shifted from each other in a direction perpendicular to the laminating direction when viewed from the laminating direction. With this configuration, the side surface 32a of the first dynode thin plate A2 protrudes outward (the side tube 2 of the vacuum vessel 6), and the side surface 32aB of the second dynode thin plate B2. Is drawn inside (tube axis L of vacuum vessel 6). Similarly, the n + 1st dynode 31 B is integrated by the dynode thin plates C2 and D2, and the side surface 33aC of the first dynode thin plate C2 protrudes outward, Dynode thin plate D 2 side 3 3 a D is drawn inward.

Thus, the electron multiplier 7 B is set so that the electron multiplier hole 3 OA of the n-th side node 31 A and the electron multiplier hole 30 B of the n + 1st dynode 31 B are opposed to each other. Assemble And the side surface 3 2 a of the n-th dynode 31 A and the side surface 33 a of the n + 1-th dynode 31 B in the direction in which the pipe axis L (see FIG. 1) of the side pipe 2 extends. Line up along the line. As a result, when comparing the peripheral portion 3 2 of the n-th dynode 3 1 A with the peripheral portion 3 3 of the n + 1-th dynode 3 1 B, the edge 3 2 b and the edge n of the n-th dynode 3 1 A + The edge 3 3b of the first-stage dynode 3 1B faces diagonally, and these facing edge portions 3 2b and 3 3b extend along the direction perpendicular to the laminating direction when viewed from the laminating direction. Can be shifted from each other.

Thus, even if the side surfaces 3 2a of the dynodes 31A and the side surfaces 33a of the dynodes 31B are aligned with each other along the pipe axis L direction, the distance between the adjacent edges 32b, 33b can be increased. The electric field discharge between these adjacent edges 32b and 33b can be effectively suppressed. Moreover, the positions of the side surfaces 32a of the dynodes 31A and the side surfaces 33a of the dynodes 31B in the vacuum vessel 6 can be aligned substantially all around.

Note that the present invention is not limited to the various embodiments described above. For example, the above-mentioned dynode may be a mesh type dynode. The photoelectric conversion surface (photocathode) 8 does not need to be a GaAs semiconductor crystal, but the GaAs type photoelectric conversion surface 8 has a small effective area and has a wide dynode edge. It is easy to devise the side of the edge. Further, in the above-described embodiment, the photomultiplier having the photoelectric conversion surface has been described. However, an electron multiplier having no photoelectric conversion surface may be used. Industrial applicability

Since the electron tube and the photomultiplier according to the present invention are configured as described above, the following effects can be obtained. That is, an electric field discharge is prevented from occurring between edges of dynodes adjacent to each other in a direction perpendicular to the stacking direction of the dynodes when viewed from the stacking direction of the dynodes. Due to This has the effect of effectively suppressing the generation of noise.

Claims

Scope of word blue

1. An electron multiplier for cascade multiplication of incident electrons,

A vacuum container,

An electron multiplying unit housed in the vacuum vessel and having a plurality of stages of dynodes stacked along a direction of incidence of the incident electrons via a spacer of an insulating material;

An anode that is housed in the vacuum vessel and captures secondary electrons multiplied by the electron multiplier;

Of the dynodes of the plurality of stages, regarding the first and second dynodes that are adjacent to each other via the spacer, the position of the edge of the electron emission surface of the first dynode that faces the second dynode. The position of the edge of the electron incident surface of the second dynode facing the first dynode is shifted along a direction perpendicular to the stacking direction when viewed from the stacking direction of the plurality of tiers. An electron multiplier comprising: a discharge suppression structure;

2. The discharge suppressing structure is configured such that, for the first and second dynodes, a distance between a side face of the first dynode facing the inner wall of the vacuum vessel and an inner wall of the vacuum vessel is determined. The electron multiplier according to claim 1, further comprising a structure that is longer or shorter than a distance between a side surface facing the inner wall of the vacuum vessel and an inner wall of the vacuum vessel.

3. The discharge suppression structure includes a structure in which, for each of the plurality of dynodes, the area of the electron incident surface is larger or smaller than the electron exit surface facing the electron incident surface. 2. The electron multiplier according to claim 1, wherein:

4. The discharge suppressing structure is configured such that, for each of the plurality of dynodes, 4. The vacuum container according to claim 3, wherein a side surface facing the inner wall of the vacuum container is inclined at a predetermined angle with respect to a side wall of the vacuum container so that a cross-sectional area thereof changes along a stacking direction. Electron multiplier.

5. Each of the plurality of stages of dynodes includes a first dynode plate and a second dynode plate directly contacted with the first dynode plate, and the discharge suppressing structure includes a plurality of dynodes of each of the plurality of stages. A distance from an inner wall of the vacuum vessel to a side face of the first die plate facing the inner wall, a side face facing the inner wall of the vacuum vessel, and a side face facing the side wall of the vacuum vessel. 4. The electron multiplier according to claim 3, further comprising a structure in which a step is provided by changing a distance from a side surface of the second dynode plate.

6. An electron multiplier for cascade multiplying incident electrons,

A vacuum container,

A photocathode housed in the vacuum vessel and receiving the incident electrons and outputting photoelectrons;

An electron multiplier section having a plurality of dynodes which are housed in the vacuum vessel and are stacked along a direction of incidence of photoelectrons from the photocathode via a spacer made of an insulating material; An anode provided on the opposite side of the photocathode with respect to the electron multiplying unit in a state in which the secondary electrons have been multiplied by the electron multiplying unit;

Of the plurality of dynodes, the first and second dynodes that are adjacent to each other via the spacer are formed on an edge of an electron emission surface of the first dynode that faces the second dynode. A discharge in which the position and the position of the edge of the electron incident surface of the second dynode facing the first dynode are respectively shifted along a direction perpendicular to the stacking direction when viewed from the stacking direction of the plurality of dynodes. With a restraining structure and Photomultiplier tube.

7. The discharge suppressing structure may be configured such that, for the first and second dynodes, a distance between a side of the first dynode facing the inner wall of the vacuum vessel and an inner wall of the vacuum vessel is determined by: The photomultiplier tube according to claim 6, comprising a structure that is longer or shorter than a distance between a side surface facing the inner wall of the vacuum vessel and an inner wall of the vacuum vessel.

8. The discharge suppressing structure includes a structure in which, for each of the plurality of dynodes, the area of the electron incident surface is larger or smaller than the electron emitting surface facing the electron incident surface. 7. The photomultiplier tube according to claim 6, wherein

9. The discharge suppressing structure is configured such that, for each of the plurality of dynodes, a side surface facing the inner wall of the vacuum vessel is predetermined with respect to a side wall of the vacuum vessel so that a cross-sectional area changes along the stacking direction. 9. The photomultiplier tube according to claim 8, including a structure inclined by an angle.

10. Each of the plurality of stages of dynodes includes a first dynode plate and a second dynode plate directly contacted with the first dynode plate,

The discharge suppressing structure may further include, on each of the plurality of stages of dynodes, a side face facing the inner wall of the vacuum vessel, and a distance from the inner wall of the vacuum vessel to a side face of the first dynode plate facing the inner wall. 9. The photomultiplier tube according to claim 8, further comprising: a step provided by changing a distance from a side wall of the vacuum vessel to a side surface of the second dynode plate facing the side wall.