JPH0234799Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a high-frequency heating device for additionally heating the plasma of a nuclear fusion device, and particularly relates to a Faraday shield for an ion cyclotron frequency band high-frequency heating device.

[Technical background of the invention and its problems]

For plasma heating in nuclear fusion devices, in addition to Joule heating, which heats the plasma by passing an electric current through it, neutral particle injection heating, high frequency heating, and the like are used as second-stage heating methods.

The high-frequency heating method is a method of increasing the temperature of the plasma by absorbing high-frequency electromagnetic energy into the plasma.
There are various methods depending on the frequency used, one of which is the ion cyclotron frequency band (hereinafter referred to as
There is a high frequency heating device (abbreviated as ICRF).

As shown in Figure 3, the ICRF high-frequency heating device includes a high-frequency oscillator 1 that generates and amplifies high-output high-frequency waves in the 100 MHz band, a coaxial tube 2 that transmits the high-frequency output generated from the high-frequency oscillator 1, and a coaxial tube 2 that transmits the high-frequency output generated from the high-frequency oscillator 1. The coupling system 5 corresponds to an antenna that is connected to the plasma container 3 and emits high-frequency output to the plasma 4 in the plasma container 3.

The coupling system 5 includes a T-shaped rigid waveguide system and a loop antenna system from the viewpoint of compatibility with the tokamak vessel 3, but the loop antenna system will be considered here.

The coupling system 5 of this loop antenna method is a coaxial tube 2
A flange 6 provided on the outer periphery of the tokamak container 3
connected directly to. An antenna conductor 7 is attached to the tip of the coaxial tube 2, and a Faraday shield 8 is attached to the plasma 4 side of the antenna conductor 7. The Faraday shield 8 allows the magnetic field created by the high frequency current flowing through the antenna conductor 7 to pass through to the plasma side, but serves to electrostatically shield the antenna conductor 7. Since the tokamak container 3 is in a high vacuum, the space between the outer conduit 2a and the inner conduit 2b of the coaxial tube 2 is vacuum-sealed by the feedthrough 9. Further, the Faraday shield 8 suffers from high frequency loss and when combined with the irradiation heat from the plasma 4, receives a high heat load under high vacuum.

By the way, as nuclear fusion research progresses and the plasma 4 becomes hotter and denser, the high-frequency heating equipment also has to operate at a higher capacity for longer periods of time, increasing the heat load on the Faraday shield 8.
100W/cm ² for 10 seconds is becoming extremely large.

Therefore, the conventional Faraday Shield 8 is also
As shown in the figure, a jacket 11 is provided on the side surface of the antenna casing 10, and a plurality of pipes 12 are connected to the jacket 11 so that a cooling medium is passed through the pipes 12 for cooling.

Further, electromagnetic force also acts on the pipe 12 of the Faraday shield 8 due to the toroidal magnetic field and the poloidal magnetic field during plasma disruption. Figure 5 is a model diagram showing the action of electromagnetic force at this time, where B _T is a toroidal magnetic field, B _P is a poloidal magnetic field, and F _T is the effect between the toroidal magnetic field B _T and the current I induced in the pipe 12. The electromagnetic force, F _P , is the electromagnetic force generated by the poloidal magnetic field B _P. Therefore, the pipe 12 needs to have sufficient strength against F _T and F _P. On the other hand, the front side 12a of the antenna conductor 7 of the pipe 12 is approximately 100W/cm ² -10 seconds/10 due to irradiation heat from the plasma 4, high frequency loss, etc.
Due to the heat load, the temperature reaches several hundred degrees, causing thermal expansion. This thermal expansion needs to be absorbed by deforming the pipe 12b on the side surface of the antenna conductor 7.

To increase the amount of absorption due to deformation, pipe 12
There is a method of increasing the length of b or decreasing its rigidity, but increasing the length increases the electromagnetic force F _T , which is disadvantageous. Also, if the stiffness is reduced, F _T and
There are problems with the strength of F _P. Therefore, the conventional Faraday shield 8 could not cope with the increase in electromagnetic force and increase in thermal load associated with increased capacity and long-term operation of the device.

[Purpose of invention]

The purpose of the present invention is to provide a Faraday shield that prevents electromagnetic force from occurring during plasma disruption and can withstand high thermal loads.

[Summary of the idea]

The Faraday shield according to the present invention consists of a pair of jackets attached to both sides of the antenna casing at the tip of the coupling system, and a number of pipes connected to each jacket and through which coolant passes. It is fixed or supported on the antenna casing via an object to prevent the creation of an electrical closed circuit, to prevent electromagnetic force from acting on the pipe, and to easily absorb thermal expansion due to high heat loads.

[Example of idea]

An embodiment of the present invention will be described below with reference to FIG. Note that the same parts as in FIGS. 3 to 5 are given the same reference numerals, and detailed explanation thereof will be omitted.

In the figure, 11a and 11b are a pair of jackets, and the jackets 11a and 11b are connected by a pipe 12, and the cooling medium supplied from the outside through a supply pipe 13 enters the jacket 11a, passes through the pipe 12, enters the jacket 11b, and enters the exhaust pipe. It is discharged to the outside at 14. The jacket 11a is attached to the antenna casing 10 by welding or bolting so as to be in electrical contact with the antenna casing 10, and the jacket 11b is attached to the antenna casing with an insulating bolt 16 and an insulating washer 17 via an insulator 15 (ceramics plate, ceramic spraying, etc.). It is attached to 10.

In the Faraday shield 8 configured in this way, the jacket 11b and the antenna casing 1
0 is electrically insulated, a current I as shown in FIG. 5 is not induced in the Faraday shield 8 during plasma degeneration, and no electromagnetic force is generated due to a toroidal magnetic field or a poloidal magnetic field. Therefore, there are no restrictions on electromagnetic force regarding the cross-sectional dimensions of the pipe 12 or the length of the pipe 12b, and only the high frequency loss and the heat load from the plasma 4 need to be considered. Therefore, thermal expansion of the pipe 12a due to thermal load can be easily absorbed by the pipe 12b. As a result, the stress on the pipe 12 is significantly reduced, and there is no fear of breakage of the pipe 12 or leakage of the cooling medium due to breakage, and the life and reliability can be greatly improved.

Note that it is preferable that the insulator 15 and the insulating bolt 16 be fixed to only one side of the antenna casing 10. On the other hand, the potential of the pipe 12 is fixed by connecting metals.

Next, another embodiment of the present invention will be briefly described. Fig. 2 shows another embodiment in which the jacket 11b is supported slidably in the longitudinal direction by insulating pins 18, and the jacket 11b is divided into 12 pipes each. pipe 12
Thermal expansion of each pipe 12a can be absorbed without deformation of pipe b.

[Effect of idea]

As described above, according to the present invention, since no electromagnetic force acts on the Faraday shield, it becomes easier to absorb the thermal expansion of the pipe due to thermal load, and as a result, it is possible to significantly reduce the stress on the pipe. Become.
Therefore, it is possible to provide a Faraday shield that can withstand large-capacity and long-time operation.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing a Faraday shield according to an embodiment of the present invention, Fig. 2 is a partial perspective view showing another embodiment, Fig. 3 is a schematic configuration diagram of a high frequency heating device, and Fig. 4 is a conventional FIG. 5 is a perspective view of the tip of the coupling system using the Faraday shield, and FIG. 5 is a model diagram of the action of electromagnetic force. 2... Coaxial tube, 5... Coupling system, 7... Antenna conductor, 8... Faraday shield, 10... Antenna casing, 11... Jacket, 12...
Pipe, 13... Supply pipe, 14... Discharge pipe, 15
... Insulator, 16 ... Insulation bolt, 17 ... Insulation washer, 18 ... Insulation pin.

Claims (1)

[Claims for Utility Model Registration] (1) A device that is attached via an insulator to the side of an antenna casing that supports an antenna conductor at the tip of a coupling system of an ion cyclotron frequency band high-frequency heating device of a nuclear fusion device and supplies or supplies a cooling medium. A Faraday shield comprising: a jacket from which the antenna conductor is discharged; and a pipe through which a cooling medium flows, which is attached to the jacket through the front surface of the antenna conductor. (2) The Faraday shield according to claim 1, wherein the jacket is attached to the antenna casing by an insulating pin, and the jacket is slidable in the length direction of the insulating pin. (3) The Faraday shield according to claim 1 of the utility model registration, characterized in that the jacket is divided into a plurality of pieces.