JP7033501B2 - 1st stage dynode and photomultiplier tube - Google Patents

Description

The present invention relates to a first stage dynode and a photomultiplier tube.

As a first-stage dynode used for a photomultiplier tube, those exhibiting various shapes have been proposed. For example, Patent Document 1 describes a first-stage dynode for the purpose of improving photoelectron collection efficiency, which has a teacup shape having a flat bottom surface. In the first stage dynode described in Patent Document 1, the electron emission surface is formed by a flat bottom surface having a teacup shape. Further, Patent Document 2 describes, as a first-stage dynode for the purpose of acquiring a signal current independent of the incident position of the photocathode, a funnel-shaped receptacle into which photoelectrons are incident. In the first stage dynode described in Patent Document 2, the electron emission surface is composed of three planes and one curved surface which are connected so as to be curved in a concave shape, and the electron emission surface is orthogonal to the electron emission surface. A pair of side surfaces are provided on both sides.

U.S. Pat. No. 4,112,325 Special Fair 8-12772 Gazette

However, in the first-stage dynode described in Patent Document 1, since the electron emission surface is formed by the flat bottom surface having a teacup shape, the secondary electrons from the first-stage dynode to the second-stage dynode It becomes difficult to adjust the traveling time, and as a result, there may be a difference in the traveling time of the secondary electrons from the first stage die node to the second stage die node. Further, in the first-stage dynode described in Patent Document 2, since a pair of side surfaces are provided on both sides of the electron emission surface so as to be orthogonal to the electron emission surface, the electrons are emitted from the central region of the electron emission surface. While the secondary electrons travel linearly, the secondary electrons emitted from the region near the side surface of the electron emitting surface may repel the side surface of the same potential and travel, and as a result, the first stage dynode There may be a difference in the traveling time of secondary electrons from to the second stage dynode. Therefore, in the first stage dynode described in Patent Documents 1 and 2, the electron traveling time difference (Cathode Transit Time Difference) and the electron traveling time expansion (TTS) in the photomultiplier tube are used. .: It is expected that it will be difficult to suppress Transit Time Spread).

Therefore, an object of the present invention is to provide a first-stage die node capable of suppressing an electron traveling time difference and an electron traveling time spread in a photomultiplier tube, and a photomultiplier tube provided with such a first-stage die node.

The first-stage dynode of the present invention is a first-stage dynode used for a photomultiplier tube, and is a pair of side wall portions extending from both ends of the bottom wall portion and the bottom wall portion in a predetermined direction to one side. A bottom is provided with a first holding portion extending outward from the end portion of the bottom wall portion and a pair of second holding portions extending outward from both ends of the pair of side wall portions in a predetermined direction. A bottom surface on one side of the wall and a pair of sides on one side of the pair of side walls constitute an electron emitting surface facing one electron passage opening, the bottom surface having a cross section perpendicular to a predetermined direction. It is a curved surface that curves concavely in the above, and each of the pair of side surfaces is a curved surface that curves concavely in a cross section parallel to a predetermined direction.

In this first stage dynode, each of the pair of side surfaces constituting the electron emission surface is a curved surface curved in a concave shape in a cross section parallel to a predetermined direction. Therefore, the farther each side surface is from the center of the electron emitting surface in a predetermined direction, the closer to one electron passing opening. As a result, both the mileage of the photoelectrons incident on each side surface and the mileage of the secondary electrons emitted from each side surface are shortened by the amount that each side surface approaches one electron passage opening. Further, the bottom surface constituting the electron emission surface is a curved surface that is concavely curved in a cross section perpendicular to a predetermined direction. Therefore, it becomes easy to adjust the traveling time of the secondary electrons from the first stage die node to the second stage die node. Further, since both the photoelectrons incident on the electron emission surface and the secondary electrons emitted from the electron emission surface pass through one (that is, the same) electron passage opening, the dependence of the electron traveling time on the incident position of the photoelectrons. Becomes smaller. Therefore, according to this first-stage dynode, it is possible to suppress the electron traveling time difference and the electron traveling time spread in the photomultiplier tube.

In the first stage dynode of the present invention, the first holding portion may have a flat plate shape. According to this configuration, the first stage dynode can be easily and stably attached to the support member provided inside the photomultiplier tube by using the first holding portion.

In the first stage dynode of the present invention, each of the pair of second holding portions may have a flat plate shape. According to this configuration, the first stage dynode can be easily and stably attached to the support member provided inside the photomultiplier tube by using the pair of second holding portions.

In the first stage dynode of the present invention, the bottom wall portion, the pair of side wall portions, the first holding portion, and the pair of second holding portions may be integrally formed of a metal plate. According to this configuration, it is possible to facilitate the manufacture of the first stage dynode and simplify the structure.

In the first stage dynode of the present invention, the radius of curvature of each of the pair of side surfaces may be larger than 2 mm. According to this configuration, the electron traveling time difference and the electron traveling time spread can be suitably suppressed in the photomultiplier tube.

In the first stage dynode of the present invention, if the width of the electron emission surface in a predetermined direction is L and the radius of curvature of each of the pair of side surfaces is R, then R ≧ 0.1 L may be established. According to this configuration, the electron traveling time difference and the electron traveling time spread can be suitably suppressed in the photomultiplier tube.

The photomultiplier tube of the present invention includes a photocathode, a plurality of stages of dynodes, and an anode, and the plurality of stages of dynodes include first-stage dynodes and second-stage dynodes arranged on a predetermined surface. The first-stage dynode includes a bottom wall portion, a pair of side wall portions extending from both ends of the bottom wall portion in a predetermined direction perpendicular to a predetermined surface to the photocathode side and the second-stage dynode side, and a bottom wall portion. The first holding portion extending from the end on the photocathode side to the side opposite to the second stage dynode, and the both ends of the pair of side wall portions in a predetermined direction extend to the photocathode side and the second stage dynode side. It has a pair of second holding portions, and in the first stage dynode, the photocathode side and the bottom surface of the second stage dynode side in the bottom wall portion, and the photocathode side and the second stage dynode side in the pair of side wall portions. The pair of side surfaces constitutes an electron emission surface facing one electron transfer opening, the bottom surface is a curved surface that curves concavely in a cross section perpendicular to a predetermined direction, and each of the pair of side surfaces is oriented in a predetermined direction. It is a curved surface that curves concavely in a parallel cross section.

According to this photomultiplier tube, it is possible to suppress the electron traveling time difference and the electron traveling time spread for the above-mentioned reason.

According to the present invention, it is possible to provide a first-stage die node capable of suppressing an electron traveling time difference and an electron traveling time spread in a photomultiplier tube, and a photomultiplier tube provided with such a first-stage die node.

It is sectional drawing of the photomultiplier tube of one Embodiment. FIG. 3 is a cross-sectional view of an electron multiplier and an anode shown in FIG. It is a perspective view of the 1st stage dynode of one Embodiment. It is sectional drawing of the 1st stage dynode along the IV-IV line shown in FIG. It is sectional drawing of the 1st stage dynode along the VV line shown in FIG. It is a perspective view of the 1st stage dynode of the comparative example. It is a schematic diagram for demonstrating the traveling trajectory of an electron. It is a figure which shows the electron traveling time difference and the electron traveling time spread of the photomultiplier tube which used the 1st stage dynode of 1st Example. It is a figure which shows the electron traveling time difference and the electron traveling time spread of the photomultiplier tube which used the 1st stage dynode of the 2nd Example. It is a figure which shows the electron traveling time difference and the electron traveling time spread of the photomultiplier tube which used the 1st stage dynode of the 3rd Example. It is a figure which shows the electron traveling time difference and the electron traveling time spread of the photomultiplier tube which used the 1st stage dynode of 4th Example. It is a figure which shows the electron traveling time difference of the photomultiplier tube which used the 1st stage dynode of the 1st comparative example, and the photomultiplier tube which used the 1st stage dynode of 5th Example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same or corresponding parts are designated by the same reference numerals, and duplicate description will be omitted.
[Structure of photomultiplier tube]

As shown in FIG. 1, the photomultiplier tube 1 includes a tube body 2, a photocathode 3, an acceleration electrode 4, a convergence electrode 5, an electron multiplier 6, and an anode 7. .. The electron multiplier 6 has a plurality of stages (for example, 10 stages) of dynodes 10. In the following description, the side on which light is incident on the photomultiplier tube 1 is referred to as "front" and the opposite side is referred to as "rear". Further, the tube axis (central axis) of the tube body 2 is the "Z axis", and the axes orthogonal to the surface (the surface including the Z axis) in which the dynodes 10 of a plurality of stages are arranged are the "X axis", the Z axis and the X axis. The axis orthogonal to is defined as the "Y axis".

The tube 2 accommodates a photocathode 3, an accelerating electrode 4, a converging electrode 5, an electron multiplier 6 and an anode 7 in a vacuumed space. The tube body 2 is a glass bulb having light transmission. The tubular body 2 has a oblate spherical portion 2a having a Z-axis as a central axis and a cylindrical portion 2b having a Z-axis as a central axis on the rear side of the oblate spherical portion 2a. The oblate spherical portion 2a and the cylindrical portion 2b are integrally formed as one glass bulb. As an example, the outer diameter of the oblate spherical portion 2a when viewed from the front side is about 200 mm, and the outer diameter of the cylindrical portion 2b is about 85 mm.

The photocathode 3 is provided on the inner surface of the tube body 2. Specifically, the photocathode 3 is provided on the inner surface of the region of the front half of the oblate spherical portion 2a. The photocathode 3 constitutes a transmissive photoelectric surface, and is formed of, for example, an antimonyated potassium-cesium type (bialkali) material or another well-known material. When light is incident on the photocathode 3 from the front side, optoelectronics are emitted from the photocathode 3 to the rear side due to the photoelectric effect. As an example, the outer diameter of the photocathode 3 (that is, the effective diameter of the photomultiplier tube 1) when viewed from the front side is about 200 mm. The broken line shown in FIG. 1 indicates the orbital (typical orbital) of the photoelectrons emitted from the photocathode 3.

The accelerating electrode 4 is arranged behind the photocathode 3. A predetermined voltage is applied to the accelerating electrode 4. The accelerating electrode 4 is configured to accelerate the photoelectrons emitted from the photocathode 3 toward the electron multiplier 6. The focusing electrode 5 is arranged behind the accelerating electrode 4. A predetermined voltage is applied to the focusing electrode 5. The focusing electrode 5 is configured to converge the photoelectrons emitted from the photocathode 3 toward the electron multiplier 6.

The electron multiplier 6 is arranged behind the focusing electrode 5. The plurality of dynodes 10 are arranged on a YZ plane (a plane including the Y axis and the Z axis). Each dynode 10 is made of, for example, stainless steel. A predetermined voltage is applied to each of the plurality of stages of dynodes 10. The electron multiplier 6, that is, the multi-stage dynode 10, is configured to multiply the photoelectrons emitted from the photocathode 3. The anode 7 is arranged on the YZ plane so as to face the final stage dynode 10. A predetermined voltage is applied to the anode 7. The anode 7 is configured to output secondary electrons emitted from the final stage dynode 10 as a signal current.

The accelerating electrode 4, the converging electrode 5, each dynode 10 of the electron multiplier 6, and the anode 7 are supported by a support member (not shown) in the tubular body 2. The support member is attached to a stem (not shown) that seals the rear end portion of the columnar portion 2b. The stem is provided with wiring for applying voltage and wiring for signal current output as stem pins or cables.
[Structure of electron multiplier]

As shown in FIG. 2, in the electron multiplier 6, the plurality of stages of die nodes 10 include a first stage die node 11, a second stage die node 12, and a third stage die node 13. In the following description, each die node including the first stage die node 11, the second stage die node 12, and the third stage die node 13 are collectively referred to as a die node 10. Further, the electron emission surface of each dynode including the electron emission surface 11a of the first stage dynode 11, the electron emission surface 12a of the second stage dynode 12, and the electron emission surface 13a of the third stage dynode 13, thereby incidenting electrons. The surface that emits secondary electrons) is collectively referred to as the electron emission surface 10a.

The first-stage dynode 11 is arranged so that the electron emission surface 11a faces the photocathode 3 (see FIG. 1) and the electron emission surface 12a of the second-stage dynode 12. The second-stage dynode 12 is arranged so that the electron emission surface 12a faces the electron emission surface 11a of the first-stage dynode 11 and the electron emission surface 13a of the third-stage dynode 13. Similarly, each of the third and subsequent dynodes 10 except the dynode 10 in the final stage is arranged so that the electron emission surface 10a faces the electron emission surface 10a of the dynode 10 in the previous stage and the electron emission surface 10a of the dynode 10 in the subsequent stage. Has been done. The final stage dynode 10 is arranged so that its electron emission surface 10a faces the electron emission surface 10a and the anode 7 of the previous stage dynode 10.

The first stage die node 11 has a bottom wall portion 111, a pair of side wall portions 112, a first holding portion 113, and a pair of second holding portions 114 (details will be described later). The electron emission surface 11a of the first stage dynode 11 is the photocathode 3 side and the bottom surface of the second stage dynode 12 side of the bottom wall portion 111, and the photocathode 3 side and the second stage dynode 12 side of the pair of side wall portions 112. It is composed of a pair of sides.

The second stage die node 12 has a bottom wall portion 121 and a pair of holding portions 122. The electron emission surface 12a of the second stage die node 12 is composed of the bottom surface of the bottom wall portion 121 on the side of the first stage die node 11 and the side of the third stage die node 13. The pair of holding portions 122 extend from both ends of the bottom wall portion 121 in the X-axis direction (direction parallel to the X-axis) to the first-stage die node 11 side and the third-stage die node 13 side.

The third stage die node 13 has a bottom wall portion 131 and a pair of holding portions 132. The electron emission surface 13a of the third-stage die node 13 is composed of the bottom surface of the bottom wall portion 131 on the second-stage die node 12 side and the fourth-stage die node 10 side. The pair of holding portions 132 extend from both ends of the bottom wall portion 131 in the X-axis direction to the second stage die node 12 side and the fourth stage die node 10 side.

A pair of electron lens forming electrodes 14 are provided in a region between the first-stage dynode 11, the second-stage dynode 12, and the third-stage dynode 13. Specifically, the one electron lens forming electrode 14 is integrally formed with the one holding portion 132 so as to extend to the region between the one second holding portion 114 and the one holding portion 122. ing. The other electron lens forming electrode 14 is integrally formed with the other holding portion 132 so as to extend to the region between the other second holding portion 114 and the other holding portion 122. A predetermined voltage applied to the third stage dynode 13 is applied to the pair of electron lens forming electrodes 14. As a result, the potential distribution in the X-axis direction is flattened in the region between the first stage die node 11 and the second stage die node 12.
[1st stage die node configuration]

As shown in FIGS. 3, 4 and 5, the first stage dynode 11 has a bottom wall portion 111, a pair of side wall portions 112, a first holding portion 113, and a pair of second holding portions 114. There is. The pair of side wall portions 112 are provided on one side (photocathode 3 side and second stage dynode 12 side) (see FIGS. 1 and 2) from both ends of the bottom wall portion 111 in the X-axis direction (predetermined direction perpendicular to a predetermined surface). )). The first holding portion 113 is outside from the end of the front side (photocathode 3 side (see FIGS. 1 and 2)) of the bottom wall portion 111 (the side opposite to the second stage die node (see FIGS. 1 and 2)). It is extended to. The pair of second holding portions 114 extend to one side from both ends of the pair of side wall portions 112 in the X-axis direction.

The first holding portion 113 has a flat plate shape (for example, a rectangular plate shape) parallel to the XY plane. Each of the pair of second holding portions 114 has a flat plate shape parallel to the YZ plane. The first stage die node 11 is attached to a support member provided in the pipe body 2 via a first holding portion 113 and a pair of second holding portions 114.

The electron emission surface 11a of the first stage dynode 11 is composed of a bottom surface 111a on one side of the bottom wall portion 111 and a pair of side surfaces 112a on one side of the pair of side wall portions 112. The electron emission surface 11a faces one electron passage opening 11b. In the first stage dynode 11, one electron passage opening 11b is defined by the bottom wall portion 111, the pair of side wall portions 112, and the one-sided edge portion of the pair of second holding portions 114. That is, both the photoelectrons incident on the electron emission surface 11a and the secondary electrons emitted from the electron emission surface 11a pass through one (that is, the same) electron passage opening 11b.

The bottom surface 111a constituting the electron emission surface 11a is a curved surface curved in a concave shape in a cross section perpendicular to the X-axis direction (see particularly FIG. 4). In the present embodiment, the bottom surface 111a is a cylindrical surface (elliptical column surface, bi-curved column surface, radial column surface, composite surface thereof, etc.) whose longitudinal direction is the X-axis direction (the height direction of the cylinder). Each of the pair of side surfaces 112a constituting the electron emission surface 11a is a curved surface curved in a concave shape in a cross section parallel to the X-axis direction (see particularly FIG. 5). In the present embodiment, each side surface 112a corresponds to a chamfered surface when a round-shaped inner chamfer is applied to a corner portion (corner portion) formed by the bottom surface 111a and the inner surface of each second holding portion 114. The bottom surface 111a and each side surface 112a are connected to each other so that the curvatures are continuous. Further, the side surfaces 112a and the inner surfaces of the second holding portions 114 are also connected to each other so that the curvatures are continuous.

Assuming that the width of the electron emission surface 11a in the X-axis direction is L and the radius of curvature of each of the pair of side surfaces 112a is R (see FIG. 5), R ≧ 0.1L is established in the first stage die node 11. Further, the radius of curvature R of each of the pair of side surfaces 112a is larger than 2 mm. As an example, the width L of the electron emission surface 11a in the X-axis direction is larger than 20 mm and smaller than 50 mm.

The first stage dynode 11 having the above shape is integrally formed of a metal plate (for example, a stainless steel plate having a thickness of about 0.3 mm). That is, the bottom wall portion 111, the pair of side wall portions 112, the first holding portion 113, and the pair of second holding portions 114 are integrally formed by the metal plate. Here, being integrally formed by a metal plate means that the metal plate is formed by subjecting it to plastic working such as press working.
[Action and effect]

In the first stage dynode 11, each of the pair of side surfaces 112a constituting the electron emission surface 11a is a curved surface curved in a concave shape in a cross section parallel to the X-axis direction. Therefore, the farther each side surface 112a is from the center of the electron emission surface 11a in the X-axis direction, the closer to one electron passage opening 11b. As a result, both the mileage of the photoelectrons incident on each side surface 112a and the mileage of the secondary electrons emitted from each side surface 112a are shortened by the amount that each side surface 112a approaches one electron passage opening 11b. Further, the bottom surface 111a constituting the electron emission surface 11a is a curved surface curved in a concave shape in a cross section perpendicular to the X-axis direction. Therefore, it becomes easy to adjust the traveling time of the secondary electrons from the first stage die node 11 to the second stage die node 12. Further, since both the photoelectrons incident on the electron emission surface 11a and the secondary electrons emitted from the electron emission surface 11a pass through one (that is, the same) electron passage opening 11b, the electron traveling time with respect to the incident position of the photoelectrons Dependency becomes smaller. Therefore, according to the first stage dynode 11, it is possible to suppress the electron traveling time difference and the electron traveling time spread in the photomultiplier tube 1.

Even if the entire electron emission surface is formed into a spherical shape, for example, in the first stage die node having such an electron emission surface, the traveling time of the secondary electrons from the first stage die node to the second stage die node is adjusted. It becomes difficult to effectively suppress the difference in electron traveling time and the spread of electron traveling time in the photomultiplier tube. Further, in order to suppress the difference in electron traveling time and the spread of electron traveling time, it is considered that the electron emission surface is formed only by the bottom surface 111a without providing the pair of side surfaces 112a, and the width of the electron emission surface in the X-axis direction is increased. Will be. However, since the size of the first-stage dynode having such an electron emitting surface is large, the outer diameter of the columnar portion 2b of the tube 2 must also be increased, and the water pressure resistance of the tube 2 must be increased. It becomes difficult to secure. Further, when the size of the first stage dynode becomes large, it becomes difficult to form the first stage dynode by subjecting the metal plate to plastic working such as press working. According to the first-stage dynode 11 described above, it is possible to suppress the electron traveling time difference and the electron traveling time spread in the photomultiplier tube 1 while suppressing the increase in the size.

Further, in the first stage die node 11, the first holding portion 113 has a flat plate shape. With this configuration, the first stage dynode 11 can be easily and stably attached to the support member provided in the tube body 2 of the photomultiplier tube 1 by using the first holding portion 113.

Further, in the first stage dynode 11, each of the pair of second holding portions 114 has a flat plate shape. With this configuration, the first stage dynode 11 can be easily and stably attached to the support member provided in the tube body 2 of the photomultiplier tube 1 by using the pair of second holding portions 114.

Further, in the first stage die node 11, the bottom wall portion 111, the pair of side wall portions 112, the first holding portion 113, and the pair of second holding portions 114 are integrally formed by a metal plate. With this configuration, it is possible to facilitate the manufacture of the first stage dynode 11 and simplify the structure.

Further, in the first stage die node 11, the radius of curvature R of each of the pair of side surfaces 112a is larger than 2 mm. With this configuration, the electron traveling time difference and the electron traveling time spread can be suitably suppressed in the photomultiplier tube 1.

Further, in the first stage dynode 11, if the width of the electron emission surface 11a in the X-axis direction is L and the radius of curvature of each of the pair of side surfaces 112a is R, then R ≧ 0.1 L is established. With this configuration, the electron traveling time difference and the electron traveling time spread can be suitably suppressed in the photomultiplier tube 1.

Here, in the first-stage die node 11 described above, the reason why the difference in the traveling time of the secondary electrons up to the second-stage die node 12 is unlikely to occur will be described in more detail.

FIG. 6 is a perspective view of the first stage dynode 15 of the comparative example. As shown in FIG. 6, the first stage die node 15 of the comparative example is not provided with a pair of side wall portions 112, and the pair of second holding portions 114 intersect with the bottom wall portion 111. It is mainly different from the first stage dynode 11 described above. In the first stage die node 15 of the comparative example, the bottom surface 111a constitutes an electron emission surface 15a facing one electron passage opening 15b.

In the first stage dynode 15 of the comparative example, as shown in FIG. 7A, the secondary electrons emitted from the central region due to the photoelectrons incident on the central region on the electron emitting surface 15a in the orbit A1 are generated. , Travels linearly on track B1. On the other hand, the secondary electrons emitted from the vicinity region by the photoelectrons incident on the orbit A2 in the vicinity region of the second holding portion 114 on the electron emission surface 15a repel the second holding portion 114 having the same potential. Then, it runs on the track B2. As a result, in the first stage die node 15 of the comparative example, a difference in the traveling time of the secondary electrons up to the second stage die node 12 is likely to occur.

On the other hand, in the first-stage dynode 11 described above, as shown in FIG. 7 (b), secondary electrons emitted from the central region when photoelectrons are incident on the central region on the electron emission surface 11a in the orbit A1. Travels linearly on track B1. On the other hand, the secondary electrons emitted from the vicinity region (that is, the side surface 112a) of the second holding portion 114 on the electron emission surface 11a due to the incident of the photoelectrons in the orbit A2 are the second electrons having the same potential. Although it repels the holding portion 114 and travels in the orbit B2, the side surface 112a has the electron passage opening 11b for both the mileage of the photoelectrons incident on the vicinity region and the mileage of the secondary electrons emitted from the vicinity region. It becomes shorter as it gets closer. As a result, in the first-stage die node 11 described above, it is unlikely that there will be a difference in the traveling time of the secondary electrons up to the second-stage die node 12.

Next, in the first stage dynode 11, the reason why it is more preferable that the radius of curvature R of each of the pair of side surfaces 112a constituting the electron emission surface 11a is larger than 2 mm will be described together with the simulation results.

First, as a simulation model, a first-stage die node of the first embodiment, a first-stage die node of the second embodiment, a first-stage die node of the third embodiment, and a first-stage die node of the fourth embodiment were prepared. Each first-stage dynode corresponds to a stainless steel plate having a thickness of 0.3 mm formed by pressing. In each first stage die node, the width L of the electron emission surface in the X-axis direction was set to 30.6 mm.

Each first-stage die node has the same configuration as the first-stage die node 11 described above, and differs from each other only in the following points. That is, the radius of curvature R of the first-stage die node of the first embodiment is 2 mm, the radius of curvature R of the first-stage die node of the second embodiment is 4 mm, and the radius of curvature R of the first-stage die node of the third embodiment is 6 mm. In the first stage dynode of the fourth embodiment, the radius of curvature R was set to 8 mm.

The first stage die node of the first embodiment, the first stage die node of the second embodiment, the first stage die node of the third embodiment and the first stage die node of the fourth embodiment are attached to the same photomultiplier tube, respectively. In the simulation corresponding to the case where the photomultiplier tube was operated under the same conditions, the electron traveling time difference and the electron traveling time spread in the X-axis direction were measured.

FIG. 8A is a diagram showing the difference in electron travel time of the photomultiplier tube using the first stage dynode of the first embodiment, and FIG. 8B is a diagram showing the electron travel time expansion in that case. It is a figure which shows. FIG. 9A is a diagram showing the difference in electron travel time of the photomultiplier tube using the first stage dynode of the second embodiment, and FIG. 9B is a diagram showing the electron travel time expansion in that case. It is a figure which shows. FIG. 10A is a diagram showing the difference in electron travel time of the photomultiplier tube using the first stage dynode of the third embodiment, and FIG. 10B is a diagram showing the electron travel time expansion in that case. It is a figure which shows. FIG. 11A is a diagram showing the difference in electron travel time of the photomultiplier tube using the first stage dynode of the fourth embodiment, and FIG. 11B is a diagram showing the electron travel time expansion in that case. It is a figure which shows.

As shown in (a) of FIG. 8, (a) of FIG. 9, (a) of FIG. 10 and (a) of FIG. 11, the first stage dynode of the second embodiment and the first of the third embodiment. In the photomultiplier tube using the stage die node and the first stage die node of the fourth embodiment, the electron traveling time difference in the X-axis direction is larger than that of the photomultiplier tube using the first stage die node of the first embodiment. It was made even more uniform at both ends in the X-axis direction. Further, as shown in (b) of FIG. 8, (b) of FIG. 9, (b) of FIG. 10 and (b) of FIG. 11, the first stage dynode of the second embodiment and the third embodiment In the photomultiplier tube using the 1st stage die node and the 1st stage die node of the 4th embodiment, the electron traveling in the X-axis direction is compared with the photomultiplier tube using the 1st stage die node of the 1st embodiment. The time spread has been further reduced.

From the above simulation results, the fact that the radius of curvature R of each of the pair of side surfaces constituting the electron emission surface is larger than 2 mm further suppresses the electron traveling time difference and the electron traveling time spread in the photomultiplier tube. It can be said that it is suitable.

Next, in the first stage dynode 11, the reason why it is more preferable that R ≧ 0.1L is satisfied will be described together with the simulation results.

From the above-mentioned simulation results, R ≧ 0.1 L was not established in the first stage die node (L: 30.6 mm, R: 2 mm) of the first embodiment, and the first stage die node (L:) of the second embodiment was not established. 30.6 mm, R: 4 mm), 1st stage die node (L: 30.6 mm, R: 6 mm) of the 3rd embodiment and 1st stage die node (L: 30.6 mm, R: 8 mm) of the 4th embodiment. Then, R ≧ 0.1L is established. Therefore, even if the width L of the electron emission surface in the X-axis direction is not 30.6 mm, the fact that R ≧ 0.1 L is established in the first stage die node causes an electron traveling time difference and an electron traveling time expansion in the photomultiplier tube. It was confirmed by simulation whether it can be said that it is more suitable for suppressing.

First, as a simulation model, a first-stage die node of the first comparative example and a first-stage die node of the fifth embodiment were prepared. Each first-stage dynode corresponds to a stainless steel plate having a thickness of 0.3 mm formed by pressing. In the first stage dynode of the first comparative example, the width L of the electron emitting surface in the X-axis direction is 34 mm, and the radius of curvature R of each of the pair of side surfaces is 0 mm (that is, the first stage dynode of the first comparative example). Has the same configuration as the first stage dynode 15 shown in FIG. 6). In the first stage dynode of the fifth embodiment, the width L of the electron emitting surface in the X-axis direction is 34 mm, and the radius of curvature R of each of the pair of side surfaces is 5 mm (that is, the first stage dynode of the fifth embodiment). Has the same configuration as the first-stage die node 11 described above).

In the simulation corresponding to the case where the first stage dynode of the first comparative example and the first stage dynode of the fifth embodiment are attached to the same photomultiplier tube and the photomultiplier tube is operated under the same conditions, X is used. The difference in electronic travel time in the axial direction was measured. FIG. 12A is a diagram showing the difference in electron traveling time of the photomultiplier tube in which the first stage dynode of the first comparative example is used, and FIG. 12B is the first diagram of the fifth embodiment. It is a figure which shows the electron traveling time difference of the photomultiplier tube which used the stage dynode.

As shown in FIGS. 12 (a) and 12 (b), in the photomultiplier tube in which the first stage dynode of the fifth embodiment was used, the photomultiplier tube in which the first stage dynode of the first comparative example was used was used. Compared to the photomultiplier tube, the electron traveling time difference in the X-axis direction was made uniform at both ends in the X-axis direction. From this simulation result, it can be said that it is more preferable that R ≧ 0.1L is satisfied in the first stage dynode in order to suppress the electron traveling time difference and the electron traveling time spread in the photomultiplier tube.
[Modification example]

The present invention is not limited to the embodiments described above. For example, the material and shape of each configuration are not limited to the above-mentioned materials and shapes, and various materials and shapes can be adopted. As an example, the first holding portion 113 is not limited to the rectangular plate shape, and may have another shape such as a semicircular plate shape.

Further, the edge portion on one side of each of the pair of second holding portions 114 may be formed so as to protrude from the edge portion on one side of the bottom wall portion 111 and the pair of side wall portions 112. Alternatively, it may be formed so as to be recessed from the edge portion on one side of the bottom wall portion 111 and the pair of side wall portions 112.

Further, the bottom wall portion 111, the pair of side wall portions 112, the first holding portion 113, and the pair of second holding portions 114 may not be formed in a plate shape. As an example, the bottom wall portion 111, the pair of side wall portions 112, the first holding portion 113, and the pair of second holding portions 114 are formed in a block shape, and the electron emission surface 11a as described above is formed by cutting or the like. It may have been done.

1 ... Photomultiplier tube, 3 ... Photocathode, 7 ... Anode, 10 ... Dynode, 11 ... First stage dynode, 11a ... Electron emission surface, 11b ... Electron passage opening, 12 ... Second stage dynode, 111 ... Bottom wall Section, 111a ... bottom surface, 112 ... side wall portion, 112a ... side surface, 113 ... first holding portion, 114 ... second holding portion.

Claims (7)

It is a first-stage dynode used for photomultiplier tubes.
The bottom wall and
A pair of side wall portions extending from both ends of the bottom wall portion in a predetermined direction to one side,
A first holding portion extending outward from the end of the bottom wall portion,
A pair of second holding portions extending from both ends of the pair of side wall portions in the predetermined direction to the one side thereof are provided.
The bottom surface on one side of the bottom wall portion and the pair of side surfaces on the one side of the pair of side wall portions constitute an electron emission surface facing one electron passage opening.
The bottom surface is a curved surface that curves concavely in a cross section perpendicular to the predetermined direction.
Each of the pair of side surfaces is a first-stage dynode that is a curved surface that curves concavely in a cross section parallel to the predetermined direction. The first stage dynode according to claim 1, wherein the first holding portion has a flat plate shape. The first stage dynode according to claim 1 or 2, wherein each of the pair of second holding portions has a flat plate shape. The aspect according to any one of claims 1 to 3, wherein the bottom wall portion, the pair of side wall portions, the first holding portion, and the pair of second holding portions are integrally formed by a metal plate. The first stage die node of. The first stage dynode according to any one of claims 1 to 4, wherein the radius of curvature of each of the pair of side surfaces is larger than 2 mm. The aspect according to any one of claims 1 to 5, wherein if the width of the electron emitting surface in the predetermined direction is L and the radius of curvature of each of the pair of side surfaces is R, then R ≧ 0.1 L is satisfied. First stage die node. Photocathode and
With multiple stages of dynodes
With an anode,
The plurality of stage dynodes include a first stage dynode and a second stage dynode arranged on a predetermined surface.
The first stage dynode is
The bottom wall and
A pair of side wall portions extending from both ends of the bottom wall portion in a predetermined direction perpendicular to the predetermined surface to the photocathode side and the second stage dynode side.
A first holding portion extending from the end of the bottom wall portion on the photocathode side to the side opposite to the second stage dynode.
It has a pair of second holding portions extending from both ends of the pair of side wall portions in a predetermined direction to the photocathode side and the second stage dynode side.
In the first stage dynode, the photocathode side and the bottom surface of the second stage dynode side of the bottom wall portion, and the pair of side surfaces of the photocathode side and the second stage dynode side of the pair of side wall portions. An electron emission surface facing one electron passage opening is configured.
The bottom surface is a curved surface that curves concavely in a cross section perpendicular to the predetermined direction.
Each of the pair of side surfaces is a photomultiplier tube that is a curved surface that curves concavely in a cross section parallel to the predetermined direction.

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