JPH07176916A - Waveguide and carbon based thin film generator - Google Patents

Abstract

PURPOSE:To obtain the waveguide suitable for transmission and radiation of a large output microwave in which no multipactor discharge takes place by forming a gas plasma of a carbon compound comprising hydrogen and a gas in the inside of the waveguide through which an electromagnetic wave propagates and forming a carbon based thin film on the inner face by the chemical gas phase growing method. CONSTITUTION:After the inside of the waveguide 7 is exhausted, a gas including a carbon compound comprising hydrogen and gas is injected to the waveguide from a gas supply system and a pressure in the waveguide 7 is kept constant and a plasma is generated in the waveguide 7 by providing a microwave into the waveguide. The carbon of the carbon compound separated by the stimulating action of the plasma 4 is vapor-depositted on copper plating 7a applied to the inner face of the stainless-steel made waveguide 7 to form a carbon group thin film 13 by the chemical gas phase growing method. A secondary electron emission factor of the carbon based thin film 13 is one or below, no multipactor discharge takes place and a microwave is stably transmitted even when a large output microwave is propagated by forming the carbon based thin film 13 to the inner side of the waveguide 7 in this way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency heating device for heating plasma or the like of a nuclear fusion device with electromagnetic waves, for example, microwaves, and particularly to a waveguide suitable for high-power microwave transmission and radiation. The present invention relates to a carbon thin film generator.

[0002]

2. Description of the Related Art There are various types of high frequency heating apparatus for heating plasma of a nuclear fusion apparatus depending on the frequency used, and one of them is a low frequency hybrid wave high frequency heating apparatus whose operating frequency is several GHz. . An example thereof is shown in FIG.

That is, as shown in FIG. 5, this high-frequency heating apparatus generates a high-power microwave and a microwave oscillator 1 for amplifying the microwave, and a microwave generator 1 for generating a microwave. A microwave transmission system 3 for transmitting up to 2 and a high frequency coupling system 5 connected to the microwave transmission system 3 for radiating microwaves to the plasma 4 in the vacuum container 8 are provided. In the fusion device 2, a toroidal magnetic field coil 9 is installed on the outer circumference of the vacuum container 8 in order to confine the plasma 4 in the vacuum container 8. Reference numeral 6 is a vacuum sealing window provided in the microwave transmission system 3.

As the microwave transmission system 3 and the high frequency coupling system 5, a bundle of a plurality of waveguides 7 shown in FIG. 6 is used, and the high frequency coupling system 5 is used in vacuum. Generally, the material of the waveguide 7 is made of stainless steel, and the inner surface thereof is plated with copper 7a to reduce the loss of the microwave tube wall.

[0005]

By the way, when high-power microwaves such as the high-frequency coupling system 5 are transmitted using the waveguide 7 in vacuum, the electrons are accelerated by the microwave electric field, and the accelerated electrons are generated. Hit the wall to emit secondary electrons,
Causes multipactor discharge. Particularly, in the nuclear fusion device 2, multipactor discharge is likely to occur in the waveguide 7 in the region where the magnetic field created by the toroidal magnetic field coil 9 becomes the resonance magnetic field of electrons.

To prevent this multipactor discharge, 2
It is effective to thinly coat the inner surface of the waveguide 7 with a material having a secondary electron emission coefficient of 1 or less. Carbon is one of the materials having a secondary electron emission coefficient of 1 or less. Conventionally, carbon is adhered to the inner surface of the waveguide 7 by coating, spraying, dipping or the like with a carbon colloid liquid.

However, in such a method, the adhesive force is weak, and the plasma 4 of the nuclear fusion device 2 is contaminated with impurities by peeling due to thermal expansion or the like, or by causing discharge by a released gas such as a solvent solution of a colloid solution. There was a risk of There is a method of vapor deposition using a physical vapor deposition (PVD) apparatus, a chemical vapor deposition (CVD) apparatus, or the like to obtain a carbon film having a strong adhesive force, but the carbon is uniformly applied to the inner surface of the long waveguide 7. It is difficult to deposit a film using a general PVD apparatus or a CVD apparatus.

The present invention has been made in view of the above circumstances, and provides a waveguide suitable for high-power microwave transmission / radiation in which multipactor discharge is unlikely to occur, and also has an adhesive force on the inner surface of the waveguide. An object of the present invention is to provide a carbon-based thin film generation apparatus capable of forming a strong carbon thin film.

[0009]

The waveguide according to the present invention comprises:
In order to solve the above-mentioned problems, as described in claim 1, in a waveguide that transmits and radiates electromagnetic waves, a gas plasma of hydrogen and a gas carbon compound is formed inside the propagating electromagnetic waves to form an inner surface. The carbon thin film is formed by chemical vapor deposition.

A second aspect of the present invention is characterized in that the carbon-based thin film of the first aspect is at least one selected from carbon, graphite, diamond and diamond-like carbon.

The carbon thin film forming apparatus according to the present invention is
In order to solve the above-mentioned problem, as described in claim 3, a microwave oscillator connected to one end of a waveguide through a vacuum sealing window and another end of the waveguide are connected. A vacuum pumping apparatus and a gas supply system for injecting a gas containing hydrogen and a gaseous carbon compound into the waveguide are provided.

A fourth aspect of the present invention is characterized in that a solenoid coil is installed on the outer circumference of the waveguide according to the third aspect, and an electron resonance magnetic field region is formed in the waveguide. A fifth aspect of the present invention is characterized in that the solenoid coil according to the fourth aspect is installed so as to be movable in the axial direction of the waveguide.

[0013]

In the carbon-based thin film generator having the above-described structure, the inside of the waveguide is evacuated, and then a gas containing hydrogen and a gaseous carbon compound is injected from the gas supply system to reduce the pressure inside the waveguide. When the microwave is output from the microwave oscillator while keeping it constant, plasma is generated in the waveguide. Due to the exciting action of this plasma, carbon of a carbon compound is deposited on the inner surface of the waveguide to form a carbon-based thin film.

Further, in the waveguide according to the present invention, since the secondary electron emission coefficient of the carbon-based thin film is 1 or less,
Even if a high-power microwave is transmitted, the multipactor discharge does not occur, and the microwave can be stably transmitted.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing a first embodiment of a carbon-based thin film production apparatus according to the present invention. The same or corresponding portions as those of the conventional configuration will be described using the same reference numerals as those in FIGS. 5 and 6. As shown in FIG. 1, a vacuum sealing window 6 is provided at one end of a waveguide 7 for transmitting and radiating electromagnetic waves.
The microwave oscillator 1 is connected via the, and the vacuum exhaust device 10 is connected to the other end of the waveguide 7.

Further, a gas supply system 11 for injecting a gas containing hydrogen 11a and a gaseous carbon compound 11b is attached via a valve 12 to the vacuum sealing window 6 side of the waveguide 7 for forming a carbon thin film. Has been.

Next, the operation of the carbon thin film forming apparatus of this embodiment will be described. After the valve 12 is closed and the inside of the waveguide 7 is evacuated to 10 ^-5 to 10 ^-7 Torr by the vacuum exhaust device 10,
The valve 12 is opened to inject a gas (hydrocarbon such as CH ₄ or CO, CO ₂ ) containing hydrogen 11a and a gaseous carbon compound 11b from the gas supply system 11 to keep the pressure in the waveguide 7 constant. When microwaves are output from the microwave oscillator 1, plasma 4 is generated in the waveguide 7.

The carbon of the carbon compound 11b dissociated by the exciting action of the plasma 4 is vapor-deposited on the inner surface of the waveguide 7 to form the carbon-based thin film 13. That is, as shown in FIG. 2, the material of the waveguide 7 is made of stainless steel, and the inner surface of the waveguide 7 is copper-plated 7a in order to reduce the microwave tube wall loss.
The carbon-based thin film 13 is formed on the copper plating 7a by the chemical vapor deposition method. The carbon-based thin film 13 is at least one selected from carbon, graphite, diamond, and diamond-like carbon depending on the bonding state of carbon resulting from the state of plasma 4.

When the carbon thin film 13 is formed on the inner surface of the waveguide 7 as described above, even if a high power microwave is transmitted,
Since the secondary electron emission coefficient of the carbon-based thin film 13 is 1 or less, multipactor discharge does not occur and microwaves can be stably transmitted.

FIG. 3 is a block diagram showing a second embodiment of the carbon thin film forming apparatus according to the present invention. The same parts as those of the first embodiment are designated by the same reference numerals and described. In this embodiment, a solenoid coil 14 is arranged on the outer circumference of the waveguide 7, and the solenoid coil 14 is energized to generate electron resonance plasma in the waveguide 7. As a result, the plasma exciting action becomes active, and a high quality film can be formed. The rest of the configuration and operation are the same as in the first embodiment, so a description thereof will be omitted.

FIG. 4 is a block diagram showing a third embodiment of the carbon thin film forming apparatus according to the present invention. The same parts as those of the first embodiment are designated by the same reference numerals and described. In this embodiment, if the solenoid coil 14 is made short and the region of electron resonance plasma is narrowed, a stronger plasma can be locally produced.

In this case, the solenoid coil 14 is configured to be movable in the axial direction by the drive mechanism 15, so that a high quality film can be formed over the entire length of the waveguide 7.
The rest of the configuration and operation are the same as in the first embodiment, so a description thereof will be omitted.

[0023]

As described above, according to the waveguide of the present invention, in the waveguide that transmits and radiates electromagnetic waves, gas plasma of hydrogen and a gas carbon compound is propagated inside the electromagnetic waves. By forming a carbon-based thin film on the inner surface by chemical vapor deposition, it is possible to provide a waveguide suitable for high-power microwave transmission / radiation in which multipactor discharge does not occur.

Further, according to the carbon thin film generator of the present invention, the microwave oscillator connected to one end of the waveguide through the vacuum sealing window and the other end of the waveguide are connected. By providing a vacuum exhaust device and a gas supply system for injecting a gas containing hydrogen and a carbon compound of a gas into the waveguide, it is possible to strongly adhere to the inner surface of the waveguide without using another CVD. A carbon thin film can be formed.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a carbon-based thin film production apparatus according to the present invention.

FIG. 2 is a perspective view showing a waveguide in which a carbon-based thin film is formed by the carbon-based thin film generation device of the first embodiment.

FIG. 3 is a configuration diagram showing a second embodiment of a carbon-based thin film generation apparatus according to the present invention.

FIG. 4 is a configuration diagram showing a third embodiment of a carbon-based thin film generator according to the present invention.

FIG. 5 is a schematic configuration diagram showing an overall configuration of a general high-frequency heating device.

FIG. 6 is a perspective view showing a conventional waveguide.

[Explanation of Codes] 1 Microwave oscillator 4 Plasma 7 Waveguide 7a Copper plating 10 Vacuum exhaust device 11 Gas supply system 11a Hydrogen 11b Carbon compound 12 Valve 13 Carbon thin film 14 Solenoid coil

Claims (5)

[Claims] 1. In a waveguide for transmitting and radiating an electromagnetic wave, a gas plasma of hydrogen and a carbon compound of a gas is created inside the electromagnetic wave propagating inside, and a carbon-based thin film is formed on the inner surface by a chemical vapor deposition method. A waveguide characterized in that 2. The waveguide according to claim 1, wherein the carbon-based thin film is at least one selected from carbon, graphite, diamond and diamond-like carbon. 3. A microwave oscillator connected to one end of the waveguide through a vacuum sealing window, a vacuum exhaust device connected to the other end of the waveguide, and hydrogen and gas in the waveguide. And a gas supply system for injecting a gas containing the carbon compound as described above. 4. The carbon-based thin film generator according to claim 3, wherein a solenoid coil is installed on the outer periphery of the waveguide to create an electron resonance magnetic field region in the waveguide. 5. The solenoid coil is installed so as to be movable in the axial direction of the waveguide.
The carbon-based thin film generator described.