JPH0487247A - Multiple channel plate - Google Patents

Abstract

PURPOSE:To increase an electron multiplication factor without lengthening a unit channel and generating any misalignment of input and output image information by gradually reducing the diameter of the channel from an electron incident side toward an electron emitting side. CONSTITUTION:A diameter of a unit channel 12 is formed smaller from an electron incident side 16 toward an electron emitting side 17. The gradual decrease in cross section of the unit channel 12 from the electron beam incident side 16 toward the electron beam emitting side 17 can increase the number of times of electron collision to an electron multiplying surface 13 of the unit channel 12. Therefore, an electron multiplication factor can be increased without lengthening the unit channel and generating any misalignment of input and output image information.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a multichannel plate used for image intensifiers, photomultipliers, etc., and particularly aims at improving the channel shape. Regarding multichannel plates.

(Prior Art) In recent years, demands for image devices have been increasing toward higher performance, such as higher density, higher sensitivity, faster operation, and wider dynamic range. A multichannel plate is a planar device with a structure in which many micro-sized electron multiplier tubes are densely integrated.
Its resolution.

It has excellent linearity and dynamic range. It is used as a key device in systems that require high-performance signal amplification, especially of plane image information, such as image intensifiers.

The electron multiplier function of the multichannel plate is similar to that of a general electron multiplier, in which electrons accelerated by an electric field collide with the semi-insulating channel walls provided inside the insulating or semi-insulating substrate. This is due to the mechanism in which multiple secondary electrons are generated. Therefore, the electron multiplication factor of the device mainly depends on the number of times electrons collide with the wall surface and their energy. Therefore, in order to increase the electron multiplication factor, it is effective to lengthen the channel.

However, the method of increasing the electron multiplication factor of a device by lengthening the channel without changing the opening area of the channel requires increasing the operating voltage of the device, which not only makes it difficult to use, but also causes residual gas on the wall surface. This is not a desirable remedy as it has the drawback of increasing damage caused by ion bombardment. Furthermore, such a multichannel plate has the disadvantage that when irradiated from a direction parallel to the channels, the electrons do not collide with the walls of the channels, and therefore do not have an electron multiplication function.

As an improvement plan to compensate for these weaknesses, a method has been proposed in which the direction of the channels is arranged obliquely with respect to the plane of the multichannel plate. FIG. 8 shows a schematic diagram of the structure of a multichannel plate using this method. (a) is a perspective view showing the overall configuration, (b) is a perspective view showing the main part structure in an enlarged manner, and (C) is a sectional view showing the main part structure in an enlarged manner. 1 is an insulating substrate, 2 is a unit channel, 3 is an electron multiplication surface, 4 is a cathode electrode, 5 is an anode electrode, and 6 is a channel entrance.

In the above configuration, since the thin annular channel 2 is formed at an angle that is not perpendicular to the plate surface, the particle beam irradiated perpendicularly collides near the entrance of the plate surface, resulting in a high electron increase. The device becomes operational at the magnification. However, such a multichannel plate has a new drawback in that the positions of the incident image information and the output image information are misaligned.

(Problems to be Solved by the Invention) As described above, in the conventional multichannel plate configuration, it has been difficult to increase the electron multiplication factor without causing new performance defects.

The present invention has been made in consideration of the above-mentioned circumstances, and its purpose is to increase the number of electrons without increasing the length of the channel and without causing any displacement of input/output image information. An object of the present invention is to provide a multichannel plate that can increase magnification.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is to gradually reduce the cross-sectional area of the unit channels constituting the multi-channel plate from the electron beam incident side to the electron beam output side. As a structure like this,
The purpose is to increase the number of collisions of electrons with the channel wall.

That is, the present invention consists of an insulating base and a plurality of holes penetrating the base substantially perpendicularly, and a semi-insulating electron multiplier surface is formed on the wall of the hole to emit secondary electrons by collision of electrons. A multi-channel plate comprising a plurality of channels, and electrodes formed on at least a portion of both surfaces of the base for applying a predetermined voltage to the electron multiplication surface of the channels, wherein It is formed so that the size gradually decreases from the electron incidence side to the electron emission side.

(Function) According to the present invention, by forming the channel structure as described above, it is possible to improve the electron multiplication factor without causing a positional shift of input/output image information.

Since it is easy to understand that the positional shift of input and output image information does not occur because the axis of the unit channel is perpendicular to the plate surface, an explanation will be given here regarding improving the electron multiplication factor. FIG. 7 is a cross-sectional view showing a comparison of equipotential lines A and electron trajectories B for each unit channel of multi-channel plates of the conventional example and the present invention. The circled numbers in the figure indicate the number of collisions between electrons and the electron multiplier surface 3. As can be seen from the figure, in the present invention, from the emission angle of secondary electrons caused by the angle between equipotential line A and the channel wall surface (electron multiplication surface 3), electron The number of collisions with surface 3 increases.

That is, in the present invention, the electron multiplication factor is improved compared to the conventional example. In addition, in multichannel plates having the same gain, there is an advantage that the output becomes more stable when the number of collisions is greater. Further, since the potentials applied to the multi-channel plates are the same, there is no significant difference in the acceleration energy of positive ions in the residual gas, and the number of collisions is also small, so damage to the channel walls does not increase.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is for explaining the schematic structure of a multi-channel plate according to the first embodiment of the present invention, and (a)
is a perspective view showing the overall configuration, (b) is an enlarged perspective view showing the main part structure (the area surrounded by the broken line in (a)), and (c) is an enlarged cross-sectional view showing the main part structure. . As shown in the figure,
For example, the insulating substrate 11 made of glass includes a plurality of truncated conical hollow unit channels 1 that vertically penetrate the substrate 11.
2 are formed. On the surface of the unit channel 12, there is a semi-insulating material (for example, made of partially reduced glass).
An electron multiplier surface 13 of high resistance) is formed. Furthermore, electrodes 14 and 15 made of a high melting point metal such as Mo or W of a multi-channel nel plate have been formed.

During use, the cathode electrode 14 is located on the channel population 16 side with a larger diameter (φ1), and the anode electrode is on the channel exit 17 side with a smaller diameter (φ2). Note that the unit channels 12 are regularly arranged on the plate surface.

In this embodiment, it is preferable that the diameter of the unit channel 12 satisfies the following condition with respect to the thickness (d) of the multichannel plate, from the viewpoint of multiplication efficiency.

200×φ1≧d≧20×φ2 This means that the gain characteristic of the multi-channel plate is 103
The above is a guideline to prevent the ion feedback effect from becoming noticeable. Furthermore, from the viewpoint of improving the electron multiplication factor, φ1>φ2 is indispensable, or in order to make the effect noticeable, it is desirable that the following conditions not be satisfied.

That is, for a given plate thickness (d) and incident particle beam angle, φ1 and φ2 are conditioned so that statistically speaking, the number of collisions is at least one more than that of a channel with an equal cross-sectional area. Establish. This is related to the applied voltage during use.

Also, as a more desirable embodiment, which is not shown in the figure, by bringing the electron multiplier surface 13 into contact with the electrode asymmetrically (at a constant angle with respect to the plate surface),
Create equipotential lines inside the channel (at a constant angle to the plate surface) at least near the channel mouth.
It may be distributed asymmetrically. In this case, even with respect to electron irradiation from a direction parallel to the channel, the trajectory of the electrons can be bent to provide sensitivity. The asymmetry of the equipotential lines is preferably from several degrees to several degrees with respect to the plate surface near the channel mouth.

Multi-channel plates with this structure can be produced using the conventional two-stage tube drawing method, which involves heating and softening bundled glass tubes, stretching them, turning them over multiple times, and then cutting them into plates. Difficult to manufacture. Therefore, an example of the method for manufacturing the multi-channel plate of this embodiment will be explained with reference to the partial cross-sectional view of FIG.

For example, as shown in Figure 2(a), high lead glass (
A mask] 8 in the shape of a channel outlet with a small diameter (diameter φ2) is formed on one surface of an insulating substrate 11 made of a material (S io2, B2 03 , Bad, etc.). Next, the insulating substrate 1] is selectively etched as shown in FIG. Drill a through hole (channel)] 2 in the hole. At this time, the etching start surface (mask side) has a large diameter channel entrance shape (diameter φ
Expand to 1).

Next, as shown in FIG. 2(C), after removing the mask 18, high vacuum (IX], 0-5 torr or less)
The surface of the substrate 1 is cleaned by heat treatment (at 300° C. or higher) inside the substrate. Furthermore, heat treatment is performed in a reducing gas atmosphere such as hydrogen, and as shown in FIG.
Modify to 3.

Next, using a fixture that rotates with an axis perpendicular to the surface of the substrate 1, a high melting point metal film 14 such as MO is deposited on the surface of the substrate 1 by electron beam evaporation, as shown in FIG. 2(e). ′ is deposited. At this time, the evaporation material in electron beam evaporation is made to be incident on the substrate surface from a shallow angle. Similarly, as shown in FIG. 2(f), the base 1
A high melting point metal film] 5' is also deposited on the other surface of 1. These metal films are electrically connected to a semi-insulating electron multiplication surface 13. Note that if the equipotential lines inside the channel are to be distributed asymmetrically, this can be similarly achieved by tilting the rotation axis several degrees with respect to the axis perpendicular to the plate surface.

Finally, as shown in FIG. 2(g), the end face of the plate is cut off to complete the multi-channel plate. Note that the metal film 14' deposited above
15' is the electrode 14.15.

As described above, according to this embodiment, the diameter (cross-sectional area) of the channel 12 is formed so as to gradually become smaller from the channel population 16 side (electron incidence side) to the channel exit side (electron emission side). The number of collisions between the electrons entering the channel 12 and the electron multiplication surface 3 can be increased, and the electron multiplication factor can be improved. In this case, since the channel 12 is formed at an angle perpendicular to the plate surface, there is no problem such as misalignment between the incident image information and the output image information.

Note that for multichannel plates with the same gain, the output is more stable when the number of collisions is greater. Therefore, in this embodiment, compared to the conventional example, the electrode 14.15
If the voltages applied between them are set to the same value, the electron multiplication factor will increase, and if the electron multiplication factors are set to the same value, the output can be stabilized. In addition, the shape of channel] 2 in this embodiment can be easily realized by a tri-etching method, etc., which is common in semiconductor manufacturing technology, without requiring special techniques, such as complicated processes such as a two-stage tube drawing method. I can do it.

FIG. 3 is for explaining the schematic structure of the second embodiment of the present invention, in which (a) is a perspective view showing the overall structure, (b) is a perspective view showing the main part structure in an enlarged manner, and ( c) is a sectional view showing an enlarged configuration of main parts. In addition, 21 to 27 in the figure are the first
They correspond to 11 to 17 in the figure.

This embodiment differs from the previously described embodiments in that a transparent material is used as the insulating substrate and the electrodes formed on both surfaces thereof. That is, on both sides of the transparent insulating substrate 21, electrodes 24 and 25 made of a transparent conductor such as ITO are provided.
or is formed. When in use, the caliber is large (
φ1) The cathode electrode 24 is on the channel population 26 side, and the anode electrode 25 is on the small diameter (φ2) channel exit 27 side. Striped or mesh-like electrodes 28 and 29 made of a high melting point metal such as MoW are formed between the transparent insulating substrate 21 and the electrode 2425 made of a transparent conductor. These electrodes 28, 29 are transparent electrodes 24
．． The purpose is to prevent a voltage drop across the 15 resistors. The configuration other than this is completely the same as that in FIG. 1.

An example of the method for manufacturing the multi-channel plate of this embodiment will be explained with reference to the partial cross-sectional view of FIG.

For example, as shown in Figure 4(a), high lead glass (
Sio2. A high melting point metal film 28', for example 10, is deposited on one surface of the transparent insulating substrate 21 made of a material such as B203, Bad, etc.) by, for example, electron beam evaporation. Similarly, as shown in FIG. 4(b), the base 2
A high melting point metal film 29' is also deposited on the other surface of 1. 5. As shown in FIG. 4(C), the high melting point metal films 28' and 29' are selectively etched by a photoetching process to form a striped or mesh electrode pattern 28.
Form 29.

Next, as shown in FIGS. 4(d) to 4(g), a mask 30 is formed on one surface of the insulating substrate 11 in the same manner as in the previous embodiment, and the substrate 21 is coated with anisotropic dry eratin.
A channel 22 is formed by selective etching, and a semi-insulating electron multiplier surface 23 is further formed. Next, as shown in FIGS. 4(h) to (j), transparent conductors 24' and 25' such as ITO are formed on both sides of the substrate 11 by electron beam evaporation in the same manner as in the previous embodiment. By cutting off the end face of the plate, a multi-channel plate is completed.

In the method for manufacturing the multi-channel plate shown in Figure 4, is the surface of the insulating substrate under the transparent conductor film also modified into a semi-insulating electron multiplier surface, or is it necessary to avoid attenuation of light in this area? If so, the manufacturing process may be changed as shown in FIG.

First, striped or mesh electrode patterns 28 and 29 are formed on both sides of the transparent insulating substrate 21 in the same manner as in the steps shown in FIGS. 4(a) to 4(c). Next, as shown in FIG. 5(a), a Cr film 31, for example, is deposited on one surface of the base 21 by electron beam evaporation, and a Cr film 31 is similarly deposited on the other surface.
Deposit r31 film.

Thereafter, as shown in FIG. 5(b), a window opening pattern 3233 is formed on both sides by a photo-etching process.

Next, as shown in FIGS. 5(c) and 5(d), a channel 80 having a small diameter (diameter φ2) is formed as in the previous embodiment.
A mask 30 is formed, and then the base 21 is selectively etched by anisotropic dry etching to form the channel 22. Next, as shown in FIG. 5(e), after removing the mask 30, a high vacuum (I x 10-5 torr
The surface is cleaned by heat treatment (300° C. or higher) in the following). Further, heat treatment is performed in a reducing gas atmosphere such as hydrogen to modify the surface of the channel 22 into a semi-insulating electron multiplication surface 23, as shown in FIG. 5(f). after that,
As shown in FIG. 5(g), the window opening pattern 32.
33 from both sides of the face.

Next, after cleaning the surface by heat treatment (at least 300° C.) in a high vacuum (I x 10-5 torr or less), as shown in FIGS. Then, ITO was deposited on both sides of the substrate by electron beam evaporation.
A multi-channel plate is completed by forming transparent conductors 24', 25', etc., and cutting off the end faces of the plate.

A feature of the second embodiment is that the electrodes 24, 25 for applying voltage to the multichannel plate are made of a transparent conductor. This configuration allows optical signals to be transmitted via channels 22 in both directions of the multichannel plate.

Next, an application example of the second embodiment element will be described. FIG. 6 shows a light reflection amplification plate, which is an applied system that extracts an optical signal from the electron exit side to the light incidence side. The system configuration is as follows. Transparent sealing body 41.4
The area surrounded by 2 is a high vacuum 30 (I x 10-5t
orr) and is held in a transparent sealing body 41.
A multi-channel plate shown in FIG. 3 is arranged between 42 and 42.

The diameter of this multi-channel plate is large (φ1)
On the channel entrance side, a photocathode 43 for converting incident light P into an electron beam Q is formed at a position of the sealing body 41 facing the channel entrance. Further, on the channel exit side, phosphor screens 45 are formed on the sealing body 45 with collector electrodes 44 interposed therebetween at regular intervals. The potential applied to the phosphor screen 45 is kept at a much more positive potential than the electron exit side potential of the multichannel plate necessary for light emission. Furthermore, a separation electrode 46 is formed between the phosphor screens 45.

With such a configuration, the incident light P is converted into electrons Q by the photocathode 43, the electrons Q are multiplied by the multichannel plate, and finally collected by the collector electrode 44. At this time, a fluorescent screen 45 is placed on the collector electrode 44.
is formed, electrons collide with the phosphor screen 45 and fluorescence is emitted from the phosphor screen 45. From here on, R is the transparent insulating base 21. Transparent electrodes 24, 25 and transparent sealing body 41
The light passes through and is output in the opposite direction to the incident light.

Since this output light R is subjected to electron multiplication during photo-electron-light conversion, it has higher brightness than the incident light P. That is, the light is output after being amplified by the light.

Here, in order to effectively and accurately extract the light emitted from the phosphor screen 45, it is necessary to limit the channel aperture ratio. That is, in a multi-channel plate in which channels are formed in a high density, the light output through the transparent insulating substrate 21 is multiple scattered on the channel wall surface, causing blurring and attenuation of the optical signal. . However, on the other hand, in order to multiply the signal as a system, it is necessary to satisfy at least the following conditions.

A-B-C-D/E≧1 However, A is the photoelectric conversion rate, B is the MCP multiplication factor, C is the luminescence rate, D is the channel opening area (the opening area on the light incidence side), and E
is the unit element area. Under more desirable conditions, the above value is 100 or more.

In this application example, the present invention has effects other than the multiplication factor that are superior to the conventional example. That is, noise caused by re-excited electrons generated by light emitted from the fluorescent screen 45 is reduced.

This is because the incident cross-sectional area of light emitted from the phosphor screen 45 is smaller in this embodiment. This advantage is significant in systems that transmit optical signals in both directions across a multichannel plate. Further, by appropriately selecting the photocathode 43 and the fluorescent screen 45, it is easy to change the wavelength using the light reflection amplification plate. Furthermore, if a particle beam or ultraviolet light is used, for example, the channel wall surface can be directly excited to generate electrons without a photocathode.

Note that the present invention is not limited to the embodiments described above, and can be implemented with various modifications without departing from the gist thereof.

[Effects of the Invention] As detailed above, according to the present invention, the cross-sectional area of the unit channels constituting the multi-channel play 1 is gradually decreased from the electron beam incident side to the electron beam output side. As the structure does not increase the number of collisions of electrons with the wall surface of the channel, the electron multiplication factor can be improved without increasing the length of the channel and without causing misalignment of input and output image information. It is possible to realize a multichannel plate that can increase the

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the schematic structure of a multi-channel plate according to a first embodiment of the present invention, FIG. 2 is a process sectional view showing an example of the manufacturing method of the first embodiment, and FIG. A diagram for explaining the schematic configuration of the second embodiment of the present invention, FIGS. 4 and 5 are process cross-sectional views showing an example of the manufacturing method of the second embodiment, and FIG. 6 is a diagram for explaining the second embodiment. FIG. 7 is a schematic diagram for explaining the basic principle of the present invention, and FIG. 8 is a diagram for explaining a conventional technique. 11.21... Insulating substrate, 12.22... Unit channel, 13.23... Electron multiplication surface, 14.24... Cathode electrode, 15.25... Anode electrode, 16.26 ...Channel population, 17.27...Channel exit, 18.30...Etching mask, 28.29-...Striped electrode, 32.33...Window pattern, 41.42...Transparent Sealing body, 43-... Photocathode, 44-... Fluorescent screen, 45... Collector electrode. 16 Shiinofuru? ＼D ノ 1 1 3 Electric goba call sound i convex / (d) 27+, Noru exit fig fig fig fig

Claims (1)

[Claims] It consists of an insulating base and a plurality of holes penetrating the base almost vertically, and a plurality of channels in which a semi-insulating electron multiplier surface is formed on the wall of the hole to emit secondary electrons by collision of electrons. , formed on at least a portion of both surfaces of the base,
A multi-channel plate comprising an electrode for applying a predetermined voltage to an electron multiplier surface of the channel, characterized in that the diameter of the channel is gradually reduced from the electron incidence side to the electron emission side. Multi-channel plate.