JPH02291655A - Photo-electron multiplier - Google Patents

Abstract

PURPOSE:To efficiency emit electrons from dynodes in the inward side to dynodes in the outward side by providing projected electrodes for the dynodes in the inward side of a photo-electron multiplier in such a way as to prevent the electrodes from being affected by potential in the one step ahead stage. CONSTITUTION:A grid 2 and a photo-electric surface 3 are provided for the light introducing side of a tube body 1 in a photo-electron multiplier, No.2, 4, 6, and 8 inside dynodes 5, 7, 9 and 11 roughly in a linear line form are interposed within the tube body 1, and No.1, 3, 5, 7 and 9 outside dynodes 4, 6, 8, 10 and 12 in a recessed surface form are arranged around said inside dynodes in such a way that a circle line is described so that an anode 13 is located at the focal point of No.9 dynode 12. In addition, a projected electrode section 14 is provided at least for one dynode out of the inside dynodes 5 through 11. And it is so constituted that the projected electrode section 14 is located close to the dynode in the one step ahead stage in such a way as to be bent roughly normal to the secondary electron emitting surface sides of sections 5a, 7a,... affected by the dynodes in the one step ahead stage wherein the effective area for emitting secondary electrons from the inside dynodes is widened so as to let a multiplication be thereby improved.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention relates to a photomultiplier tube that multiplies photoelectrons generated when light is incident on a photocathode using a plurality of dynodes and outputs an output from an anode. It is related to. "Prior Art" FIG. 5 shows a conventional example of a circular cage type photomultiplier tube. In the figure, (1) is a glass tube,
(2) is grit, (3) is photocathode, (4) to (12)
(13) is a dynode, and (13) is an anode, to which, for example, as shown in the figure, a voltage that increases sequentially from Ov to IOOOV is applied. When light enters the photocathode (3) through the grid (2), photoelectrons are emitted from the photocathode, and each dynode (4) to
(12), secondary electrons are emitted one after another, multiplied, and taken out as output from the anode (13).

"Problem to be solved by the invention" The dynode in the circular cage type has a concave surface on the outside (4) (6) (8) (10)
(12) and a substantially linear dynode (5) inside.
(7) Place (9) and (11). Among these, the inner dynode (5) exhibits an equipotential distribution like the dotted line curve in FIG.

However, the part (5a) near the previous stage dynode (4)
In this case, since the secondary electrons are affected by the potential of the dynode (4) in the previous stage, even if the secondary electrons are emitted, they are confined and cannot go to the dynode (6) outside the next stage. This means that the other dynode inside (7
) (9) The same applies to (11). As a result, there was a problem in that the multiplication factor of the dynode decreased.

An object of the present invention is to obtain a device in which secondary electrons are more effectively emitted from the inner dynode and the multiplication factor is improved.

"Means for Solving the Problems" The present invention aims to increase secondary electrons by alternating and sequentially using photoelectrons generated when light is incident on a photocathode between an outer dynode group and an inner dynode group that are arranged approximately circularly. In a circular cage type photomultiplier tube in which the output is extracted from the anode, at least one dynode of the inner dynode group has a portion close to the preceding dynode and is affected by its potential. A protruding electrode portion is provided on the secondary electron emitting surface of the device.

"Operation" By providing the protruding electrode portion on the inner dynode so as to prevent the influence of the potential of the previous stage, secondary electrons traveling from the inner dynode to the outer dynode are efficiently emitted. Therefore, the effective area for secondary electron emission is widened, the efficiency is improved, and the multiplication factor is also improved.

"Embodiment" An embodiment of the present invention will be described below with reference to FIGS. 1 to 4. Note that the same parts as in FIG. 5 are given the same reference numerals.

In Figure 1, (1) is a sealed glass tube, and on the light introduction side of this tube (1) there is a grid (2) and a photocathode (
3) is provided. In addition, inside the tube body (1), there are approximately linear inner second, fourth, sixth, and eighth dynodes (5).
(7) (9) (11) and the concave first part on its outer periphery
, third, fifth, seventh, and ninth outer dynodes (4) (6
) (8), (10), and (12) are arranged in a circle, and the anode (1) is placed at the focal position of the ninth dynode (12).
3) is located. Among the above dynodes, a protruding electrode portion (14) is formed on at least one of the inner dynodes (5) to (11). This protruding electrode part (l
4) is a part close to the previous stage dynode and is affected by the potential of the previous stage dynode (5a) (7a
)... is bent approximately 90 degrees on the secondary electron emitting surface side. The height of this protruding electrode part (14) is 2
This is to prevent the secondary electron emitting surface from being affected by the dynode potential of the previous stage, but if it is set too high, the secondary electrons emitted from the outer dynode (4) of the previous stage will be The dynode (5)...8 will get in the way when it is incident, so it should be set to a level that does not block it. The protruding electrode part (14) is made by bending the same component as the dynode (5) by 90 degrees as shown in Fig. 3(a), and by welding nine rods as shown in Fig. 3(b). Things, (C
As shown in (d), the bent portions of the same component may be rounded, or as shown in (d), square rods may be welded together.

In the above configuration, the photocathode (3) has an OV and a first
, 2nd, 3rd, 4th, 5th, 6th, 7th, 8th, and 9th dynodes (4) to (l2) respectively 100 V, 20
0V. 300V, 400V, 500V. 600V.
Apply 700V, 800V, 900V, and 1000V to the anode (13).

Here, light enters the photocathode (3) through the grid (2), and photoelectrons are emitted. When this photoelectron enters the first dynode (4), a primary electron is emitted, and a secondary electron is emitted from the first dynode (4), which leads to the second dynode (5).
Sent to. Since this second dynode (5) has a protruding electrode portion (14), as shown by the dotted line in FIG.
The effective area for secondary electron emission from the dynode (5) toward the third dynode (6) on the outside can be increased. Thereafter, secondary electrons are emitted one after another in the same manner and are multiplied. The multiplied secondary electrons are transferred to the anode (
13) and output from there.

In the above embodiment, a so-called side-on type case in which the glass tube (1) has a cylindrical shape and light enters from the side has been described, but the invention is not limited to this, and as shown in FIG. It can also be used in a so-called head-on type case where the tube body (1) is cylindrical and the light enters from the head. In this Figure 4, (3) is the photocathode, (15) is the focus electrode, (l6) and (4) to (12) are the first
~10th dynode. (13) is an anode. The arrangement and multiplication of the dynodes (16), (4) to (12) are the same as in FIG. 1.

"Effects of the Invention" As described above, the present invention provides the inner dynode with a protruding electrode portion to prevent it from being affected by the potential of the previous stage dynode, so the effective area for secondary electron emission in the inner dynode is expands, and the efficiency of secondary electrons traveling from the inner dynode to the outer dynode improves. According to actual measurements, when the protruding electrode part is attached, the multiplication factor is 2 times higher than when it is not attached.
~3 times larger.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a first embodiment of the photomultiplier tube according to the present invention, FIG. 2 is an enlarged view of the main part of FIG. 1, and FIG. 3 is a side view showing different embodiments of the inner dynode. FIG. 4 is a sectional view of a second embodiment of the present invention, FIG. 5 is a sectional view of a conventional example, and FIG. 6 is an enlarged view of the main part of FIG. (1)...tube, (2)...grit, (3)...
- Photocathode, (4) to (12) (16)...Dynode, (13)...Anode, (14)...Protruding electrode portion. (15)... Focus electrode. Applicant Hamamatsu Photonics Co., Ltd. Figure 1 Figure 4 Figure 0 Figure 2

Claims (4)

[Claims] (1) The photoelectrons generated when light is incident on the photocathode are alternately and sequentially multiplied by the outer dynode group and the inner dynode group, which are arranged in a substantially circular manner, and the output is extracted from the anode. In the circular cage type photomultiplier tube, at least one dynode of the inner dynode group is provided with a protruding electrode portion on a secondary electron emitting surface of a portion close to the preceding dynode and affected by the potential thereof. A photomultiplier tube comprising: (2) The photomultiplier tube according to claim (1), wherein all of the inner dynode groups are provided with protruding electrode portions. (3) The photomultiplier tube according to claim 1 or 2, wherein the protruding electrode portion is formed by integrally bending the constituent members of the dynode. (4) The photomultiplier tube according to claim (1) or (2), wherein the protruding electrode portion is formed by welding a member different from the constituent members of the dynode.