JP2002198701A - Output window and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an output window with high reliability and high performance, which can sufficiently suppress emission of secondary electrons from the surface of a ceramic disk and multipactor discharge. SOLUTION: In the output window where a ceramic disk 2 is placed in the center of a round waveguide 1 and which is air-tight sealed by a circumferential part of the ceramic disk 2 and an inner wall face of the waveguide 1, a coating film 3 with a uniform thickness made of a titanium nitride, titanium oxide or chromium oxide thin film or the like is formed on the surface of the ceramic disk 2. Or the ceramic disk 2 is coated such that the film thickness at the outer circumferential part of the ceramic disk 2 is thicker than the film thickness of the center part. Thus, the secondary electron emission coefficient at the center part and the outer circumferential part of the ceramic disk 2, and especially a triple junction is decreased and the multipactor discharge can be suppressed. Moreover, since the coating film 3 has a proper thickness on the entire surface of the ceramic disk 2, no microwave is reflected and the output window with high reliability and high performance can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a traveling wave tube,
The present invention relates to an electron tube such as a klystron, or an output window provided between a vacuum section and an external waveguide or device in a device such as a heating device or an accelerating tube that uses microwave or millimeter-wave power of the electron tube. .

[0002]

2. Description of the Related Art Electron tubes such as traveling wave tubes, klystrons or gyrotrons, and gyro klystrons,
An electron gun that emits an electron beam, a collector that supplements the electron beam, and a microwave amplification unit that amplifies microwaves (similarly for millimeter waves and high frequencies; hereinafter omitted for millimeter waves and high frequencies) by interaction with the electron beams. , And an input / output coupling section that serves as a connection section between the microwave amplification section and the external waveguide. In the input / output coupling section, an output window is used for maintaining the airtightness inside the electron tube and transmitting microwaves without loss. In order to transmit a microwave without reflecting it, it is necessary that the impedance of the output window be matched. FIG.
Is a conventional general output window described, for example, in JP-A-4-272637. In the figure, 1 is a circular waveguide, 2 is a ceramic disk, 4 is a flange, and 5 is a rectangular waveguide. The ceramic disk 2 is hermetically brazed in the middle of the circular waveguide 1. In general, a circular waveguide 1 and a ceramic disk 2
Is used because the cross-sectional area of the waveguide is large, the electric field intensity is reduced, and the allowable microwave power is increased.

[0003]

However, when a high-power microwave is passed through the above-described conventional output window, the ceramic disk 2 is broken and the airtightness becomes insufficient. there were. Such destruction is caused by the material itself of the ceramic disk 2 which may be broken by internal discharge due to insufficient dielectric strength or heat generated by dielectric loss, and locally due to the multipactor discharge or the like. There are cracks caused by an excessive temperature rise and pinholes caused by melting, which are caused by the characteristics of the surface of the ceramic disk 2. Among them, destruction caused by the material itself of the ceramic disk 2 can be improved by using aluminum ceramic having a high dielectric strength.

On the other hand, the destruction caused by the characteristics of the surface of the ceramic disk 2 is about 1 to 2 nm formed of a thin film of titanium nitride, titanium oxide, chromium oxide or the like having a low secondary electron emission coefficient on the surface of the ceramic disk 2. A considerable improvement can be achieved by forming a coating film. What is multipactor discharge?
A phenomenon that occurs when electrons are incident on a dielectric material with a high secondary electron emission coefficient, and the generated secondary electrons are incident on the dielectric again under a high microwave electric field and are amplified in an avalanche shape. It is. Secondary electrons are likely to be generated in the output window at the center of the ceramic disk 2 having a high electric field and at the outer periphery of the ceramic disk 2 hermetically sealed. Especially the outer part,
As shown in FIG. 10, the ceramic disk 2 and the circular waveguide 1
And is called a triple junction 7. In order to suppress the multipactor discharge and the like, it is desirable that the above-mentioned coating film is sufficiently thick. However, if the coating film is too thick, there is a problem that microwaves are reflected and characteristics as an output window deteriorate.

[0005] The coating film is formed by a DC sputtering device or an RF sputtering device. In these devices, the thickness of the central portion of the ceramic disk 2 generally tends to be larger than that of the outer peripheral portion. And it was difficult to form a uniform thickness. The electric field of the microwave passing through the output window is larger in the central portion, and the conventional coating film having a thick central portion is inconvenient. That is, when a coating film having an appropriate thickness is formed at the center, the thickness of the coating film is insufficient at the outer peripheral portion, and secondary electrons are easily generated. Conversely, when a coating film having an appropriate thickness is formed on the outer peripheral portion, the thickness of the coating film becomes too thick at the central portion, and there is a problem that microwaves are reflected.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has a small influence on the reflection of microwaves and sufficiently suppresses secondary electron emission from the surface of the ceramic disk and Macchipactor discharge. It is an object of the present invention to provide a reliable and high-performance output window and a method for manufacturing the same.

[0007]

In the output window according to the present invention, a ceramic disk is disposed in the middle of a circular waveguide, and the output window is hermetically sealed by a peripheral portion of the ceramic disk and an inner wall surface of the circular waveguide. In the output window, the surface of the ceramic disk is uniformly coated with a thin film of titanium nitride, titanium oxide, chromium oxide or the like. In addition, a ceramic disk is disposed in the middle of the circular waveguide, and at the output window hermetically sealed by the circumference of the ceramic disk and the inner wall surface of the circular waveguide, titanium nitride is formed on the surface of the ceramic disk. The ceramic disk is coated with a thin film of titanium oxide, chromium oxide, or the like such that the thickness of the outer peripheral portion is greater than the thickness of the central portion.

Further, according to the method of manufacturing an output window according to the present invention, in a process of manufacturing an output window in which a ceramic disk is disposed in the middle of a circular waveguide, titanium nitride, titanium nitride, A method of coating a thin film of titanium oxide, chromium oxide, or the like, wherein a step of forming a thin film on the entire surface of a ceramic disk and a step of forming a thin film only on the outer peripheral portion by covering the center of the ceramic disk with a mask It is made to be manufactured including.
Further, a step of installing a desired target in the sputtering apparatus, a step of displacing the center axis of the ceramic disk in the sputtering apparatus by an arbitrary distance from the center axis of the target, and installing the ceramic disk in the center thereof. The method includes a step of forming a thin film on the surface of a ceramic disk while rotating the film about an axis. Further, the manufacturing method includes a step of installing a desired target having a shape having a hole at the center in the sputtering apparatus and a step of forming a thin film on the surface of the ceramic disk.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing an output window according to Embodiment 1 of the present invention. In the figure, reference numeral 10 denotes an output window in the present embodiment,
1 is a circular waveguide, 2 is a ceramic disk arranged in the middle of the circular waveguide 1, and 3 is a thin film of titanium nitride, titanium oxide, chromium oxide or the like uniformly coated on the surface of the ceramic disk 2. The coating films 5 and 5 indicate rectangular waveguides provided on both sides of the circular waveguide 2, respectively. In the present embodiment, the ceramic disk 2 is arranged in the middle of the circular waveguide 1, and the output window hermetically sealed by the circumference of the ceramic disk 2 and the inner wall surface of the circular waveguide 1 has a ceramic structure. The surface of the disk 2 is uniformly coated with a thin film of titanium nitride, titanium oxide, chromium oxide or the like, and a coating film 3 having a uniform thickness is formed on the entire surface of the ceramic disk 2. In addition, the thickness of the coating film 3 is set to about 1 to 2 nm which can sufficiently reduce the secondary electron emission coefficient and does not cause microwave reflection.

A method for manufacturing an output window according to the embodiment;
That is, a method of uniformly forming a coating film 3 of titanium nitride, titanium oxide, chromium oxide, or the like on the surface of the ceramic disk 2 by a sputtering device or the like will be described in Embodiments 3 to 5 described later. Will be omitted. According to the present embodiment, since the thickness of the coating film 3 on the surface of the ceramic disk 2 is uniform over the entire surface, the secondary electron emission coefficient at the center and the outer periphery of the ceramic disk 2, particularly at the triple junction, is reduced. It is possible to suppress multipactor discharge. In addition, since the coating film 3 has an appropriate thickness on the entire surface of the ceramic disk 2, no microwave reflection occurs, and a highly reliable and high-performance output window can be obtained.

Embodiment 2 FIG. 2 is a sectional view showing an output window according to Embodiment 2 of the present invention. In the figure,
Reference numeral 10a denotes an output window in the present embodiment, and 3a denotes a coating film made of a thin film of titanium nitride, titanium oxide, chromium oxide or the like coated on the surface of the ceramic disk 2, and the outer peripheral portion of the ceramic disk 2 has a film thickness. It is formed to be thicker than the film thickness at the center. In the drawings, the same or corresponding parts have the same reference characters allotted, and description thereof will not be repeated. As shown in FIG. 3, the coating film 3a on the surface of the ceramic disk 2 in the present embodiment is formed such that the film thickness at the outer peripheral portion of the ceramic disk 2 is larger than the film thickness at the central portion. Thereby, the secondary electron emission coefficient at the outer peripheral portion of the ceramic disk 2 can be further reduced. Further, since the electric field at the outer peripheral portion of the ceramic disk 2 is significantly smaller than that at the central portion, the reflection of microwaves caused by the thick coating film 3a is negligible. In addition, the manufacturing method of the output window in the present embodiment is as follows.
A description will be given later in Embodiments 3 to 5, and a description thereof will be omitted.

FIG. 4 is a diagram showing a comparison between the output window according to the present embodiment and a conventional output window in terms of the amount of heat generated when passing through a microwave. In the figure, A indicates the heat value of the output window according to the present embodiment, and B indicates the heat value of the conventional output window. The output window in the present embodiment generates less heat than the conventional product,
The effect of the present embodiment can be confirmed. According to the present embodiment, by forming the coating film 3a on the surface of the ceramic disk 2 such that the thickness of the outer peripheral portion is larger than the thickness of the central portion, the outer peripheral portion of the ceramic disk 2, particularly, It is possible to reduce the secondary electron emission coefficient at the triple junction and suppress multipactor discharge, and obtain a highly reliable and high performance output window.

The present embodiment and the first embodiment are described.
In the output window, the circular waveguide 1 is mirror-finished by electric field polishing or the like and the C-chamfer usually provided on the outer peripheral portion of the ceramic disk 2 is used to reduce the secondary electron emission coefficient at the triple junction. Can be further reduced. Further, in the present embodiment and the first embodiment, the case of the microwave is described as an example. However, the same effect can be obtained for the millimeter wave and the high frequency, and the present invention is effective.

FIG. 5 shows an example in which the output window in the present embodiment and the first embodiment is applied to a device using microwaves.
Shown in In the figure, 20 is an electron tube, 30 is a device using microwaves, and the output window 10a (or 10) is attached to the device 30. Output window 10a (or 1)
0) transmits microwaves from the electron tube 20 to the device 30 and also separates the electron tube 20 from the device 30. As described above, the output window 10a (or 10) in the present embodiment and the above-described first embodiment is not only an electron tube that generates microwaves, but also a heating device, an accelerator, or a processing device that uses microwave or millimeter-wave power. Widely used for etc.

Embodiment 3 FIG. 6 is a diagram showing a method of manufacturing an output window according to Embodiment 3 of the present invention, and shows the inside of a sputtering apparatus when a thin film of titanium nitride, titanium oxide, chromium oxide, or the like is coated on the surface of a ceramic disk. ing. In the figure, 2 is a ceramic disk, 8
Denotes a target for forming a desired thin film, and 9 denotes a mask. In the present embodiment, a thin film of titanium nitride, titanium oxide, chromium oxide, or the like is formed on the surface of the ceramic disk 2 by a sputtering device in a process of manufacturing an output window in which the ceramic disk 2 is disposed in the middle of the circular waveguide. As a method of coating, the method includes a step A of forming a thin film on the entire surface of the ceramic disk 2 and a step B of forming a thin film only on the outer peripheral part by covering the center of the ceramic disk 2 with a mask 9. It is. In the sputtering apparatus, generally, in the step A of forming a thin film on the entire surface of the ceramic disk 2, the thickness of the center of the ceramic disk 2 tends to be larger than that of the outer periphery. According to the manufacturing method in the embodiment, since the thin film is formed only in the outer peripheral portion in the step B, the coating film 3 (FIG. 1) having a uniform overall surface shown in the first embodiment or the outer peripheral film shown in the second embodiment is used. It is possible to form the coating film 3a (FIG. 2) in which the thickness of the portion is larger than the thickness of the central portion.
In addition, the order of the process A and the process B may be reversed, and a lift-off method may be used. First, the central portion of the ceramic disk 2 is covered with a mask 9 to form a thin film only on the outer peripheral portion.
Is removed, a similar coating film 3 (or 3a) can be formed even if a thin film is formed on the entire surface of the ceramic disk 2.

Embodiment 4 FIG. 7 is a diagram showing a method of manufacturing an output window according to Embodiment 4 of the present invention, showing the inside of a sputtering apparatus when a thin film of titanium nitride, titanium oxide, chromium oxide, or the like is coated on the surface of a ceramic disk. ing. In the figure, 2 is a ceramic disk, 2
a indicates the central axis of the ceramic disk 2, 8 indicates a target for forming a desired thin film, and 8a indicates the central axis of the target 8. In the present embodiment, a thin film of titanium nitride, titanium oxide, chromium oxide, or the like is coated on the surface of the ceramic disk 2 by a sputtering device in a manufacturing process of the output window in which the ceramic disk 2 is disposed in the middle of the circular waveguide. As a coating method, a step of installing a desired target 8 in a sputtering apparatus, and installing the ceramic disk 2 in the sputtering apparatus by shifting the center axis 2a of the ceramic disk 2 by an arbitrary distance r from the center axis 8a of the target 8 And a step of forming a thin film on the surface of the ceramic disk 2 while rotating the ceramic disk 2 about the center thereof as an axis. In the sputtering apparatus, generally, when the ceramic disk 2 and the target 8 are installed coaxially, the thickness of the central portion of the ceramic disk 2 tends to be larger than that of the outer peripheral portion. According to the manufacturing method, the ceramic disk 2
By displacing the center axis 2a of the target 8 and the center axis 8a of the target 8, the coating film 3 (FIG. 1) uniform over the entire surface shown in the first embodiment or the film at the outer peripheral portion shown in the second embodiment is used. It is possible to form the coating film 3a (FIG. 2) whose thickness is larger than the thickness of the central portion.

Embodiment 5 FIG. 8 is a diagram showing a method of manufacturing an output window according to Embodiment 5 of the present invention, and shows the inside of a sputtering apparatus when a thin film of titanium nitride, titanium oxide, chromium oxide, or the like is coated on the surface of a ceramic disk. ing. In the figure, 2 is a ceramic disk, 8
Reference numeral 8 denotes a target, and 88a denotes a hole provided at the center of the target 88. In the present embodiment, a thin film of titanium nitride, titanium oxide, chromium oxide, or the like is formed on the surface of the ceramic disk 2 by a sputtering device in a process of manufacturing an output window in which the ceramic disk 2 is disposed in the middle of the circular waveguide. As a method of coating, the method includes a step of installing a desired target 88 having a shape with a hole 88a in the center thereof in a sputtering apparatus and a step of forming a thin film on the surface of the ceramic disk 2. In the sputtering apparatus, when the ceramic disk 2 and a normal target are installed coaxially, the central part of the ceramic disk 2 tends to be thicker than the outer peripheral part. According to the method, the hole 88a in the center
By using the open target 88, the amount of the thin film material reaching the outer peripheral portion of the ceramic disk 2 increases, so that the uniform coating film 3 shown in the first embodiment is used.
(FIG. 1) or a coating film 3a (FIG. 2) in which the thickness of the outer peripheral portion is larger than that of the central portion shown in the second embodiment.
Can be formed.

[0018]

As described above, according to the present invention, the ceramic disk is arranged in the middle of the circular waveguide, and the ceramic disk is hermetically sealed with the circumferential portion and the inner wall surface of the circular waveguide. In the output window, the surface of the ceramic disk is coated with a thin film of titanium nitride, titanium oxide, chromium oxide, or the like, or the outer peripheral portion of the ceramic disk is thicker than the central portion. As a result, secondary electron emission and Macchipactor discharge from the entire surface of the ceramic disk, particularly from the outer peripheral portion, can be sufficiently suppressed, and a highly reliable and high-performance output window can be obtained.

According to the method for manufacturing an output window of the present invention, a thin film of titanium nitride, titanium oxide, chromium oxide, or the like is uniformly formed on the surface of the ceramic disk, or the thickness of the outer peripheral portion of the ceramic disk is centered. Since the coating can be performed so as to be thicker than the film thickness of the portion, an inexpensive, highly reliable and high-performance output window can be manufactured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an output window according to Embodiment 1 of the present invention.

FIG. 2 is a sectional view showing an output window according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a film thickness distribution of a coating film of an output window according to a second embodiment of the present invention.

FIG. 4 is a diagram comparing the amount of heat generated between an output window according to Embodiment 2 of the present invention and a conventional output window.

FIG. 5 is a diagram illustrating an application example of an output window according to the first embodiment and the second embodiment of the present invention.

FIG. 6 is a cross-sectional view illustrating a method for manufacturing an output window according to Embodiment 3 of the present invention.

FIG. 7 is a cross-sectional view illustrating a method for manufacturing an output window according to Embodiment 4 of the present invention.

FIG. 8 is a sectional view illustrating a method for manufacturing an output window according to a fifth embodiment of the present invention.

FIG. 9 is a sectional view showing a conventional output window.

FIG. 10 is a partially enlarged sectional view showing a triple junction of an output window.

[Explanation of symbols]

Reference Signs List 1 circular waveguide, 2 ceramic disc, 2a ceramic disc central axis, 3 3a coating film, 4 flange, 5 rectangular waveguide, 6 brazing material, 7 triple junction, 8 target, 8a target central axis,
9 mask, 10 and 10a output window, 20 electron tube, 3
0 equipment, 88 target, 88a hole.

Claims (5)

[Claims] A ceramic disk is disposed in the middle of a circular waveguide, and the ceramic disk is provided at an output window hermetically sealed by a circumferential portion of the ceramic disk and an inner wall surface of the circular waveguide. An output window characterized in that a thin film of titanium nitride, titanium oxide, chromium oxide, or the like is uniformly coated on the surface of the device. 2. A ceramic disk is disposed in the middle of a circular waveguide, and an output window hermetically sealed by a peripheral portion of the ceramic disk and an inner wall surface of the circular waveguide. An output window, characterized in that the surface of the output window is coated with a thin film of titanium nitride, titanium oxide, chromium oxide or the like so that the thickness of the outer peripheral portion of the ceramic disk is greater than the thickness of the central portion. 3. A process for manufacturing an output window in which a ceramic disk is disposed in the middle of a circular waveguide, wherein a thin film of titanium nitride, titanium oxide, chromium oxide, or the like is coated on the surface of the ceramic disk by a sputtering device or the like. A method of forming the thin film on the entire surface of the ceramic disk, and a step of covering the central portion of the ceramic disk with a mask and forming the thin film only on the outer peripheral portion. Output window manufacturing method. 4. In a manufacturing process of an output window in which a ceramic disk is arranged in the middle of a circular waveguide, a thin film of titanium nitride, titanium oxide, chromium oxide or the like is coated on the surface of the ceramic disk by a sputtering device or the like. A step of installing a desired target on the sputtering apparatus, and disposing the ceramic disk on the sputtering apparatus by shifting a center axis of the ceramic disk by an arbitrary distance from a center axis of the target. And a step of forming the thin film on the surface of the ceramic disk while rotating the ceramic disk about its center as an axis. 5. In a manufacturing process of an output window in which a ceramic disk is disposed in the middle of a circular waveguide, the surface of the ceramic disk is coated with a thin film of titanium nitride, titanium oxide, chromium oxide or the like by a sputtering device or the like. A step of installing a desired target having a shape with a hole in the center thereof in the sputtering apparatus, and a step of forming the thin film on the surface of the ceramic disk. Production method.