JPS6056224B2 - Metal vapor deposition method on the inner surface of a vacuum vessel for a torus-shaped fusion device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for depositing metals such as titanium and molybdenum on the inner surface of a vacuum vessel for a toroidal fusion device.

In order to realize a nuclear fusion reactor, it is essential to reduce the amount of impurities in plasma.

For this purpose, the inner wall surface of the vacuum vessel for the fusion device, which has a large interaction with the plasma, must be kept in a clean state with few adsorbed molecules. Recently, a method has been adopted in which metals such as titanium and molybdenum are deposited on the inner wall of the vacuum chamber while the chamber is evacuated, and this method has been experimentally confirmed to be highly effective. Conventionally, the method for performing this vapor deposition is to attach metal wires or hollow metal balls made of titanium, molybdenum, etc. to each port of a donut-shaped vacuum container, and then connect them to leads pulled out from each port. A method is used in which the material is connected to an external power source via a wire and vapor-deposited by resistance heating.

With this method, vapor deposition can be performed while the vacuum is drawn, but even if several ports are used, metal wires and metal balls are attached to each port separately, so the toroidal direction of the vacuum vessel It is difficult to deposit uniformly on the surface.

Also, if you try to deposit it uniformly, you will need quite a lot of metal wires,
A metal bulb must be used, which requires many ports and a heating power source, which is not economical. An object of the present invention is to provide a method capable of uniformly depositing metals such as titanium, molybdenum, etc. in a toroidal direction on the inner surface of a donut-shaped vacuum container, while eliminating the drawbacks of the prior art described above.

In order to achieve this object, the present invention involves winding a metal wire made of titanium, molybdenum, etc. over almost the entire circumference in the toroidal direction of a donut-shaped vacuum container, and then, while the inside of the vacuum container is evacuated, It is characterized by passing a current through a metal wire to heat it resistance, and depositing metals such as titanium and molybdenum on the inner surface of the vacuum container. Hereinafter, one embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2. FIG.

FIG. 1 is a schematic configuration diagram showing an entire apparatus for carrying out a vapor deposition method according to an embodiment of the present invention, and FIG. 2 is an enlarged sectional view of essential parts showing a poloidal cross section of a vacuum container in this apparatus.

In these figures, reference numeral 1 denotes a donut-shaped vacuum container used in a toroidal fusion device, in which a metal wire 2 made of titanium, molybdenum, etc. is wound around once in a toroidal direction. There is.

3 is a current transformer for flowing a plasma current into the vacuum vessel 1, and is composed of an iron core 4 that forms a closed magnetic path interlinking with the vacuum vessel 1, and a primary coil 5 wound around this iron core. .

In order to prevent current from flowing in the toroidal direction, the vacuum container 1 may be completely insulated in the toroidal direction by providing an insulating material such as ceramic in a part thereof, or a part of the vacuum container may be formed with a thin bellows or the like. Appropriate resistance value (usually 1mΩ
However, in this embodiment, it is assumed that the toroidal direction is completely insulated. The vacuum container 1 is provided with about 4 to 8 cylindrical boats 6 spaced apart from each other in the toroidal direction.
A bellows 8 is attached to the boat 6 via an insulating flange 7, and a support rod 9 for supporting the metal wire 2 is attached to the bellows 8 in an airtight manner. Note that in FIG. 2, CL indicates the center line. Therefore,
When a current is passed through the primary coil 5 of the current transformer 3 while the inside of the vacuum container 1 is evacuated, gold. Since the metal wire 2 corresponds to the secondary coil of the current transformer 3, an induced current flows through it, resistance heating occurs, and metals such as titanium and molybdenum are uniformly deposited in the toroidal direction on the inner surface of the vacuum vessel 1.

Note that the metal wire 2 is connected to 4 to 8 locations by the support rod 9. Since it is supported to a certain extent, it will not sag much even if it is resistively heated as described above.

In addition, if the metal wire 2 is left as it is after vapor deposition, it will get in the way of plasma generation, so the boat 6
To do this, for example, a motor drive mechanism for moving each support rod 9 in the vertical direction is provided for each boat 6, and these motor drive mechanisms are synchronized with each other. By operating it, the ring-shaped metal wire 2 may be lowered while maintaining a substantially horizontal state.

Furthermore, since the vacuum container 1 is insulated in the toroidal direction, if the metal wire 2 has a resistance value of 1 mΩ or more as described above, it will not have any adverse effect on plasma generation, and when generating plasma. Since the resistance of the plasma is orders of magnitude smaller, no current flows through the metal wire 2. According to this embodiment, the metal wire 2 is wound around the vacuum vessel 1 in the toroidal direction, and the metal wire 2 is resistance-heated and vapor-deposited, so that titanium, molybdenum, etc. are deposited on the inner surface of the vacuum vessel 1. Metal can be uniformly deposited in a toroidal direction. Furthermore, since the induced current is passed through the metal wire 2 using the existing current transformer 3 for passing the plasma current, there is no need to install a dedicated heating power supply, and lead wires can be drawn out from each boat 6. evaporation can be easily performed using inexpensive equipment. Furthermore, FIG. 3 shows an apparatus in which the vapor deposition method of the present invention is applied to a vacuum container that is partially formed of thin-walled bellows, etc., has an appropriate resistance value, and is not completely insulated in the toroidal direction. This is a schematic configuration diagram, and illustration of a current transformer 3 for flowing plasma current is omitted here.

The difference between this embodiment and the previous embodiment is that in the above embodiment, the metal wire 2 is wound around the metal wire 2 in a toroidal direction and closed in a ring shape. 2 is cut in at least one place in the toroidal direction as shown by the broken line, both ends of which are supported by support rods 9 made of a conductive material, and the ends of these support rods 9 that protrude outside the vacuum vessel 1 are cut. Electrical connection is made by a connecting rod 10 made of a conductive material.

Therefore, if a current is passed through the primary coil of a current transformer (not shown) while the inside of the vacuum container 1 is evacuated, metals such as titanium, molybdenum, etc. can be uniformly deposited in the toroidal direction.

By the way, if the vacuum container 1 is not completely insulated in the toroidal direction, in order to cause an induced current to flow through the metal wire 2,
The resistance value of the metal wire 2 must be made smaller than the resistance value of the vacuum vessel 1, but if this is done, the plasma current will not be able to flow effectively when plasma is generated.

Therefore, when generating plasma, the metal wire 2
It is necessary to electrically disconnect at least one place in the toroidal direction. However, in this example, after deposition,
Since the metal wire 2 can be electrically disconnected by removing the connecting rod 10, it can be easily applied to vapor deposition in a vacuum container that is not completely insulated in the toroidal direction.

In this embodiment as well, it goes without saying that the metal wire 2 is lowered to the boat after the vapor deposition. As described above, according to the present invention, metals such as titanium and molybdenum can be uniformly deposited in the toroidal direction on the inner surface of the doughnut-shaped vacuum container in a vacuum state.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a schematic configuration diagram showing the entire apparatus for carrying out a vapor deposition method according to an embodiment of the present invention, and Fig. 2 is a main part showing a poloidal cross section of a vacuum container in this apparatus. The enlarged sectional view and FIG. 3 are schematic configuration diagrams showing an apparatus for carrying out a vapor deposition method according to another embodiment of the present invention. 1... Vacuum container, 2... Metal wire, 3.
・・・・・・Current transformer for flowing plasma current.

Claims (1)

[Claims] 1. With the inside of a doughnut-shaped vacuum container being evacuated, a current is passed through a metal body placed in the vacuum container to heat it resistance, and the metal body is placed on the inner surface of the vacuum container. An inner surface of a vacuum vessel for a torus-shaped nuclear fusion device, characterized in that a metal wire is used as the metal body, and the metal wire is wound almost the entire circumference of the vacuum vessel in the toroidal direction. metal vapor deposition method. 2. The method of metal vapor deposition on the inner surface of a vacuum vessel for a torus fusion device, characterized in that an induced current is passed through the metal wire using a current transformer according to claim 1. 3. A metal vapor deposition method on the inner surface of a vacuum vessel for a torus-shaped nuclear fusion device according to claim 2, characterized in that a current transformer for flowing a plasma current is used as the current transformer.