JPS62150644A - Supporting structure of electron discharge electrode - Google Patents

Abstract

PURPOSE:To prevent the excessive alkali at an electronic multiplier of the alkali to feed to a photoelectron cathode normally from around an anode of a photoelectron multiplier tube, by applying optimum numbers of frame-form black spacers. CONSTITUTION:A dynode 21 has a net-form electrode 14 and a sloped secondary electron discharge surface 22, and at the frame to support these components, four lugs are furnished. The plain net-form electrode 14 is combined by a spot welding, while an insulating spacer 15 has brims almost same as those of the dynode 21, and at the bottom of each brim, a projection is furnished to respond to each lug of the dynode 21. The each of projection has a penetrating hole responding to the hole of the lug of the dynode 21. The insulating dynode consists mainly of aluminum oxide, added very small amount of a metal thereto, and the color of the surface is black.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a support structure for an electron-emitting electrode that can be used as a dynode support structure of a photomultiplier tube.

(Prior Art) A conventional dynode support structure of a photomultiplier tube will be explained with reference to FIG.

FIG. 5 is a perspective view showing a dynode support structure of a conventional photomultiplier tube.

The electron-emitting electrodes have the same shape, and FIG. 5 shows an N-stage electron-emitting electrode 42n and an N-1-stage electron-emitting electrode 4.
2(n-1).

Each electron-emitting electrode is provided with protruding ears 45 on the rectangular frame and the abdomen of the can rim.

Each ear portion 45 is provided with a hole through which an alumina pipe 47 passes.

Each electron emitting electrode 42 is provided with a large number of secondary electron emitting slopes 44 for forming a Venetian blind dynode, and a mesh is provided on the front surface thereof.

The distance between each electron emitting electrode 42 is determined by cylindrical spacers 41...4.
1 is maintained. The cylindrical spacer 41 and the hole of the ear portion 45 are penetrated by an alumina pipe 47, and a Kinbaku vibrator 43 is inserted into the alumina pipe 47.

(Problems to be Solved by the Invention) In the above-described structure, the respective electron-emitting electrodes 42 are kept spaced apart from each other by the cylindrical spacer 41 and are insulated, but there are the following problems.

The dark current-applied voltage characteristic of a photomultiplier tube using a dynode assembly with the above structure is t at high applied voltage.
The g current value loses linearity and increases.

When the applied voltage is further increased, internal light emission (glow, electroluminescence), which is not directly related to the electron multiplication process, finally occurs.

Ionization of residual gas also occurs, further degrading the characteristics.

Generally, these unwanted light sources create current "noise" due to unwanted electron flow reaching the anode.

For example, unwanted light emission in the electron multiplier section within a photomultiplier tube creates undesirable "afterpulses" in the output signal as it travels back to the electron source or photocathode.

The return of the unnecessary electron radiation source and the unnecessary light emission source to the photocathode within the photomultiplier tube causes loss of linearity in the applied voltage-output current characteristic.

Therefore, the maximum applied voltage of the photomultiplier tube is limited, and the ability to amplify current is also limited.

An object of the present invention is to provide a support structure for an electron-emitting electrode that can solve the aforementioned problems such as increase in dark current.

(Means for Solving the Problems) In order to achieve the above object, the support structure for an electron-emitting electrode according to the present invention includes a planar support structure having a peripheral edge for attachment that emits electrons corresponding to incidence of charged particles. multiple electron-emitting electrodes;
One or more insulating spacers having a certain thickness and an opening through which electrons can pass, and having a black surface and having a plurality of through holes corresponding to the mounting holes of each of the electrodes on the peripheral edge, and the above-mentioned spacer between each of the electrodes. It is comprised of a fixing means for arranging insulating spacers and fixing each of the electrodes using the through holes.

(Example) Hereinafter, the present invention will be described in more detail with reference to the drawings and the like.

FIG. 1 is a perspective view showing an embodiment of an electron-emitting electrode support structure according to the present invention.

The Venetian blind type dynode 21 is
This structure is common to the one explained in the drawings, and the dynodes 21 are stacked in multiple stages to form an electron multiplier.

This dynode 21 has a mesh electrode 14 and an inclined secondary electron emitting surface 22, and a frame supporting these is provided with four ears.

The flat mesh electrodes 14 are connected by spot welding.

The insulating spacer 15 has an edge having substantially the same shape as the dynode 21, and a protrusion corresponding to the ear of the dynode 21 is provided on the abdomen of each wire.

A through hole 20 corresponding to the through hole provided in the ear portion of the dynode 21 is provided in this protruding portion.

The insulating dynode is made of aluminum oxide with a trace amount of metal added, and has a black surface.

FIG. 2 shows a sectional view of the rear part of an electron multiplier using the support structure.

Final stage electrode 1 that functions as a reflective dynode
The dynode 2 is connected to the dynode 6 via the three-stage insulating spacer 15.
1n are stacked on top of each other, and dynodes 21 (n-1) are stacked on top of each other with one stage of insulating spacer 15 interposed therebetween.

A flat mesh anode 17 is fixed to the final stage electrode via a cylindrical spacer 18.

In use, the highest voltage is applied to the anode 17 and the final stage electrode 16. Dynode 21n, dynode 21
Voltages that gradually decrease in the order of (n-1) are applied.

FIG. 3 is a diagram showing an embodiment of a photomultiplier tube having an electron multiplier section in which multiple stages of dynodes are stacked on top of the electron multiplier.

A photomultiplier tube 8 using the support structure according to the present invention has a spherical envelope 9, and a hemispherical portion on the top surface is a face plate 10.
A photocathode surface is formed inside.

A base 12 is fixed to the cylindrical base of the envelope 9.

This embodiment uses an electron multiplier in which dynodes 21 having the shape described above are stacked in 13 stages with insulating spacers 15.

13 is a focus electrode.

Note that the shape of the anode and the like are as described above with reference to FIG. 2.

FIG. 4 is a graph showing the dark current-voltage characteristics of the photomultiplier tube.

In order to facilitate comparison with the conventional structure, a photoelectron multiplier with a conventional structure using an electron multiplier in which two dynodes of the same shape as described above are stacked in 13 stages with the structure shown in FIG. The characteristics of the tube are shown by dashed lines.

The maximum applied voltage of a photomultiplier tube with a conventional structure is 200
0V, electron multiplication ability is about 5×108.

On the other hand, in the phototube of the above-mentioned example using the structure according to the present invention, even when the applied voltage is 3000 V, the linearity of the dark current with respect to the applied voltage is not lost, and the electron multiplication ability is 1.
It has reached X101' or more.

In the conventional structure, the electron multiplication factor and dark current lose linearity when the applied voltage approaches a certain range for the following reason.

When the applied voltage approaches 2000 V, an internal luminescence phenomenon occurs due to an electron radiation source that is not directly related to the electron multiplication process in the photomultiplier tube, and electrode glow occurs.

Unwanted light sources such as electroluminescence and ionization of residual gas begin to occur.

This emitted light is reflected and scattered by electrodes and the like, passes through a gap in the tube or inside the outer container, is fed back, and light or ions are incident on the front stage of the electron multiplier tube or the photocathode.

As a result, photoelectron or secondary electron emission unrelated to the incident light increases at an accelerated rate, and the linearity is greatly disrupted as shown by the broken line in the figure.

In contrast, the structure according to the present invention uses a frame-shaped insulating spacer, so that the light or ions generated during the electron multiplication process are directly shielded.

At the same time, since the material of the insulating spacer itself is black, it does not reflect light, but rather absorbs it, eliminating leakage of light or ions to areas other than the electron multiplier path, and preventing light from entering the front stage of the photocathode or electron multiplier. positive feedback to the electrode can be completely eliminated.

(Modifications) Various modifications can be made to the embodiments described in detail above within the scope of the present invention.

In the above embodiment, an example of multiplying photoelectrons has been described.

It can be similarly used in a multiplier in which the first-stage electron-emitting electrode is collided with a particle beam other than photoelectrons to emit electrons, and the electrons are multiplied by the subsequent dynodes.

Further, although a Venetian blind dynode is shown as an example of the electron emitting electrode, other dynodes, such as a mesh-like dynode or a box-and-grid dynode, can be used in the same manner.

(Effects of the Invention) As explained in detail above, the electron-emitting electrode support structure according to the present invention includes a plurality of planar electron-emitting electrodes each having a mounting peripheral portion that emits electrons corresponding to incident charged particles. ,
One or more insulating spacers having a certain thickness and an opening through which electrons can pass, and having a black surface and having a plurality of through holes corresponding to the mounting holes of each of the electrodes on the peripheral edge, and the above-mentioned spacer between each of the electrodes. It is comprised of a fixing means for arranging insulating spacers and fixing each of the electrodes using the through holes.

To provide an electron multiplier that has a high electron multiplication factor and reduces the generation of dark current because an insulating spacer can block unwanted light emission and ions generated in a multiplication space. I can do it.

In particular, when the structure according to the present invention is utilized in a photomultiplier tube, the following effects can be obtained in the manufacturing process.

It is necessary to maintain an alkaline balance between the photocathode and the secondary electron emitting surface in the electron multiplier tube. be.

The alkaline balance is the balance of the amount of alkali to obtain a good photocathode and secondary electron emitting surface.

Generally, the photocathode is located away from the alkali generation source, and the amount of alkali is limited by a focus electrode or the like.

On the other hand, the electron multiplier part, especially near the anode, is close to the alkali generation source, and there is no object such as a focus electrode that restricts the alkali.

Due to this difference, the secondary electron emitting surface can obtain a good electron emitting surface in a shorter time than the photocathode because alkali easily flows into the secondary electron emitting surface.

The amount of alkali in the photocathode at this point is clearly insufficient. Furthermore, when the photocathode activity is advanced and a good photocathode is obtained, a large amount of alkali has already adhered to the secondary electron emitting surface, making it unsuitable as a secondary electron emitting surface.

Therefore, it is necessary to control the amount of reaction between the photocathode and the total alkali such as antimony on the secondary electron emitting surface. By changing the thickness of the antimony and physically adjusting the path through which the alkali penetrates, the photocathode and secondary electron emitting surface are made to have an optimal amount of alkali reaction.

This alkaline balance can be appropriately adjusted by the number of spacers used.

In the conventional structure, depending on the activation temperature and time during fabrication, it was necessary to fabricate the photocathode or the secondary electron emitting surface mainly.

However, the frame-shaped black frame according to the present invention.

By using an optimal number of pacers, it is possible to prevent excess alkali in the electron multiplier portion of the alkali, which is normally sent from the vicinity of the anode of the photomultiplier tube to the photocathode, through the alkali absorption of the frame-shaped black spacer according to the present invention. can.

[Brief explanation of drawings]

FIG. F is a perspective view showing an embodiment of a support structure for an electron-emitting electrode according to the present invention. FIG. 2 is a cross-sectional view of an electron multiplier using the support structure. FIG. 3 is a schematic diagram showing an embodiment of a photomultiplier tube using the electron-emitting electrode support structure. FIG. 4 shows a comparison of dark current-voltage characteristics and current multiplication factor-voltage characteristics of a photomultiplier tube using the electron-emitting electrode support structure according to the present invention and a photomultiplier tube using a conventional support structure. This is a graph. Figure 5 is a perspective view showing an example of the assembly structure of a conventional electron-emitting electrode. 8... Photomultiplier tube 9 using the support structure according to the present invention
... Photomultiplier tube envelope 10 ... Face plate 11 ... Lead pin 12 ... Base 13 ... Focus electrode 14 ... Net electrode 15 ... Insulating spacer 16 ... Final stage dynode 17... Anode 18... Cylindrical spacer for anode fixing 19... Insulating spacer opening 20... Through hole 21 for electrode fixing... Venetian blind dynode 41...
..... Cylindrical spacer 42 ..... N-stage electron emitting electrode 43 ..... Total pressure pipe 44 ..... Secondary electron emitting surface 45 ..... 2 Edge 47 of the secondary electron emission electrode...
・Alumina Pipe Patent Applicant Hamamatsu Photonics Co., Ltd. Agent Patent Attorney Hisao Inoro Name: Electron-emitting electrode support structure 3, relationship with the amended case Patent applicant 4, agent

Claims (2)

[Claims] (1) A plurality of planar electron-emitting electrodes each having a periphery for attachment that emits electrons corresponding to the incidence of charged particles, and each electrode having a certain thickness and an opening through which electrons pass through the periphery. one or more insulating spacers having a black surface and having a plurality of through holes corresponding to the mounting holes, and arranging the insulating spacer between each of the electrodes, and using the through holes to connect each of the electrodes. A support structure for an electron-emitting electrode consisting of fixing means for fixing it. (2) The support structure for an electron-emitting electrode according to claim 1, wherein the insulating spacer is made of aluminum oxide as a main component and has a black color by adding a trace amount of metal.