JPH0480690A - Plasma opposed machinery - Google Patents

Abstract

PURPOSE:To efficiently remove the high heat load from plasma by alternately arranging protective plates composed of a high m.p. material and cooling pipe structures to connect the same. CONSTITUTION:A loop antenna 7 is provided in a casing 11 and a coaxial pipe 3a is connected to the antenna 7 to allow high frequency power to be incident to plasma and the front surface of the antenna 7 is covered with Faraday shields 8 in a screen state to short-circuit an unnecessary electric field component not contributing to plasma heating. Cooling passages 19 are formed in the conductors 12 of the shields 8 and protective plates 18 composed of a high m.p. material are laminated so as to hold the conductors 12 on both sides thereof to constitute a laminated structure 20. As the material of the protective plates 18, aluminum nitride high in heat conductivity, low in high frequency loss and low in emission loss within plasma even when driven out by sputtering because constituted of an element of a low atomic number is used. When the structure 20 is integrally fastened by bolts 21, the high heat load from plasma can be efficiently removed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a plasma facing device that faces the plasma of a nuclear fusion device.

(Prior art) For example, in a tokamak-type nuclear fusion device, the equipment that makes up the innermost part of the torus-shaped structure is exposed to a harsh environment where it is repeatedly irradiated with high-energy particles, neutrons, etc. in addition to high heat loads from plasma. It is in. That is, when high-energy particles collide with the surface of a plasma-facing device, sputtering occurs in which atoms on the surface are ejected, resulting in deterioration of the device, and if the depletion rate is large, the life of the device will be shortened.

Furthermore, since it is subjected to a high heat load, it may melt if the heat removal capacity of the plasma facing equipment is small.

Furthermore, atoms ejected by sputtering mix into the plasma, and when the atomic number is large, radiation loss increases and plasma performance deteriorates.

Therefore, as a material for the surface of plasma facing equipment, the loss rate due to sputtering is small and the thermal conductivity is good.
In addition, a material with a small atomic number is desired. On the other hand, the inside of the equipment must have a cooling piping structure with excellent heat removal ability.
Conventionally, there has been no suitable material that satisfies both of these conditions.

Plasma facing equipment must also consider the following conditions: In other words, in a toroidal plasma, there is a phenomenon called disruption in which the plasma current disappears in a very short time, and a large induced current is generated due to electromagnetic induction in a conductor that forms a closed circuit facing the plasma, and the external magnetic field is A large electromagnetic force is applied to a conductor. Therefore, the conductor must be mounted in a rigid structure.

Furthermore, among the plasma facing devices, those used in combination with the high-frequency heating device must be located between the antenna and the plasma, so that they do not interfere with electromagnetic waves directed toward the plasma, but on the other hand, they must protect the antenna from radiation from the plasma.

The conventional technology will be introduced below using a specific example. FIG. 6 shows a schematic configuration of a high frequency heating device for heating plasma, particularly an ion cyclotron frequency band (hereinafter abbreviated as ICRF) high frequency heating device.

In FIG. 6, the high-frequency heating device includes a high-frequency oscillator 1 that generates high-power high-frequency waves in the band of several tens to 100 MHz, and a high-frequency output generated by the high-frequency oscillator 1 that is transmitted to the tokamak main body 2, as shown in the figure. coaxial tube 3 and this coaxial tube 3
and an antenna 5 which is connected to and emits the high frequency output to the plasma 4 of the fusion device. antenna 5
is connected to the tokamak body 2 via a flange 6. A loop antenna conductor 7 is attached to the tip of the inner conductor 3a of the coaxial tube 3, and a Faraday shield 8 is attached to the plasma 4 side of the loop antenna conductor 7.

A typical structure of the antenna 5 facing the plasma is shown in FIG. This antenna 5 includes a loop antenna 7 through which a high-frequency current flows, a casing 11 that serves as a return path for the high-frequency current,
It mainly consists of a Faraday shield 8 disposed in front of the loop antenna 7. Usually, high frequency power is fed to such an antenna 5 through the coaxial feed line 3. At this time, the inner conductor 3a of the coaxial feed line 3 is connected to the loop antenna 7, and the outer conductor 3b is connected to the casing 11.

As shown in FIG. 5, the Faraday shield 8 is constructed by arranging a plurality of conductors 12 in the form of a blind. Each conductor 12 is arranged along the direction of the magnetic field 13 that confines the plasma, shields electric fields that do not contribute to plasma heating, and can send out only electric field components perpendicular to the magnetic field 13.

Since the conductor of the Faraday shield 8 is usually made of a metal material, it is not preferable to directly oppose the plasma 4 . Figure 4 shows an example in which the plasma side of the Faraday shield 8 is covered with a material having a low atomic number. It is mechanically bonded to the conductor 12 and actively protects the Faraday shield 8 from wear and tear caused by particles from the plasma 4. On the other hand, internal heat generation due to thermal loads, neutrons, and high frequencies can be absorbed by the cooling channel 19 by making the conductor 12 into a cooling pipe structure. A method is used to remove this by flowing a cooling medium (for example, water) through it.

(Problem to be solved by the invention) Now, when a phenomenon called disruption in which plasma 4 disappears in an extremely short time occurs, the plasma current IP of several MA
disappears at about lo + ss, so in the antenna facing the plasma 4, a large induced current 115 as shown by the dotted line is generated due to electromagnetic induction in the closed circuit formed by the casing 11 and the Faraday shield 8 as shown in FIG. .

A magnetic field Br (this is called a toroidal magnetic field) 13 is applied from the outside in a direction along the donut to keep the plasma 4 stable.

Since a large electromagnetic force F16 is applied to the conductor 12 by the vertical magnetic field Bv14 and the induced current 115, there is a problem that the conductor 12 may be deformed or torn off.

Particularly for large plasma currents exceeding IOMA expected in recent tokamak designs, a full-scale Faraday shield 8
There are challenges that cause destruction.

On the other hand, as shown in FIG.
The protective plate 18 attached to the protective plate 2 receives a thermal load, and since its thermal expansion when the temperature rises is different from that of the conductor, thermal stress is generated on the joint surface. In particular, tokamak-type fusion devices are subject to repeated thermal stress due to their principle of pulse operation. Protective plate 18
Since it is made of a material with good conductivity, it is limited to the same width as the conductor I8, so there is no space for strong contact with bolts, so brazing or diffusion bonding is used.

However, it is difficult to prevent the protection plate 18 from cracking or peeling due to repeated thermal stress over a long period of time or displacement of the conductor due to electromagnetic force during the above-mentioned disruption.

The present invention has been made in order to solve the above problems, and a material made of a low atomic number with a small depletion rate is arranged on the surface facing the plasma, and it has excellent thermal contact with the cooling piping that removes high heat loads. 6 [Structure of the Invention] (To solve the problem) The present invention has a plurality of protection plates made of a high melting point material shaped to cover the space between the conductors having a cooling tube structure and the plasma facing surface, It is characterized by the fact that the equipment is connected together.

Another feature is that the plasma facing device is attached to the front of the high frequency heating device antenna, and fine ceramics made of aluminum nitride is used as the high melting point material.

(Function) Because the high melting point material with this structure is in close contact with the conductor having the cooling pipe structure, the high heat load from the plasma is efficiently removed, and the surfaces where thermal stress occurs are compressed by fastening. Since the bonded surface is exposed to heat, the bonded surface will not separate even if the heat load is repeated.

Similarly, even if electromagnetic force due to plasma disruption acts on the conductor, the high melting point material and the conductor are rigidly connected, so the cooling pipe structure will not be damaged or peeled from the protective plate, and its integrity will be maintained. It is maintained.

(Example) An example of the present invention will be described in detail using FIGS. 1 and 2.

In FIG. 1, the reference numeral 5 indicates an antenna, and the antenna 5 that injects high frequency waves into the plasma is attached to the casing 11.
A loop antenna 7 is installed inside the loop antenna 7.
A coaxial tube 3a is connected to the rear part of the . In front of the loop antenna 7, a Faraday shield 8 is attached to the casing 1 in order to short-circuit unnecessary electric field components that do not contribute to plasma heating.
It is covered in a blind shape so as to connect both sides of 1. A cooling channel 19 is formed inside the conductor 12 of the Faraday shield 8 .

Protective plates 18 made of a high melting point material are laminated to sandwich the conductor 12 of the Faraday shield 8 from both sides.
As is clear from the figure, the shape has a groove in which approximately half of the conductor 12 is filled.

Therefore, by stacking the conductors 12 and the protection plates 18 alternately, almost the entire periphery of the conductor 12 can be brought into contact with the protection plates 18. As the material of the protection plate 18, aluminum nitride, which has been developed as a fine ceramic, is used. Aluminum nitride has the same high dielectric strength as alumina, 15 KV/am, but has a thermal conductivity of 200Ω/K, which is 4 to 1O times higher. Since the dielectric loss tangent is relatively small (LM)lz, 5×10-', there is little high frequency loss, making it ideal as a window material through which high frequencies can pass. The constituent elements of aluminum nitride have an atomic number as low as alumina or silicon carbide, and even if they are knocked out by sputtering, radiation loss in plasma is lower than that of metal conductors, making it suitable for plasma-facing equipment. Suitable for surface materials.

Now, when the laminated structure 20 of the protection plate 18 and the conductor 12 is mechanically and firmly connected together with bolts 21 etc. from the outermost end so that the conductor 18 and the conductor 12 receive compressive force,
The thermal resistance between the protection plate 18 and the conductor 12 can be lowered. Therefore, the high heat flow velocity from the plasma can be efficiently removed in the cooling channel 19 from the side surface of the protection plate 18, which has good heat transfer characteristics, through the conductor 12. Compared to the conventional bonding of the protection plate and the cooling pipe structure by brazing, this embodiment is a plasma-facing device with an extremely reliable heat removal function.

Furthermore, the laminated structure 20 of the protection plate 18 and the conductor 12 is attached to the casing 1 through the holes 22 and bolt holes 23.
It is firmly fixed at 1. Therefore, the electromagnetic force applied to the conductor 12 at the time of disruption can be received by the protective plate 18 made of fine ceramics that is resistant to compressive force, and can be supported by the casing with a strong structure. 1 of conductor 12
Since each book is fixed with hard fine ceramics, the cooling structure will not be damaged and has excellent soundness.

The effects of this embodiment are not limited to those described above.

In the conventional technology, a portion of the loop antenna 7 is directly irradiated with plasma, which may change the electrical properties of the surface through which high-frequency current flows.

On the other hand, in this embodiment, the loop antenna 7 is connected to the protective plate 1.
8, so the above-mentioned fear does not exist, and
It is difficult to sinter, form and process a large fine ceramic that covers the surface of a plasma facing device as one piece, but in this embodiment, it is divided into many parts to make it smaller, so it is easy to manufacture and process.

Next, another embodiment of the present invention will be explained with reference to FIG.

This embodiment is an example of application to a diverter where impurities and high-energy particles in plasma are concentrated and the heat load is severe.

Graphite and carbon-based composite materials are examples of materials that can withstand heat load from plasma and irradiation with high-energy particles, have a high melting point, a low sputtering ratio, and a low atomic number. All of these materials have electrical conductivity, so if insulation is particularly required, the aforementioned aluminum nitride, which has excellent thermal conductivity, is suitable. Diverter 2
5, it is common to provide a so-called heat sink material behind the protective plate to efficiently transfer high heat flux to the cooling medium, and copper or copper alloy with good thermal conductivity is used. In this embodiment, the protection plate 18 is arranged so as to be in contact with the heat sink material z6 mainly at a surface 27 perpendicular to the plasma facing surface. That is, the heat sink material 2 having the cooling flow path 19
6 and protection plates 18 are alternately arranged and firmly fastened with fastening bolts 21, the thermal resistance of the mechanical contact surface 27 is reduced. The protection plate 18 is a heat sink material 26
A thin gap is created between the protective plate 18 and the adjacent protective plate 18 to escape thermal expansion caused by sudden heat load.

According to this embodiment, the high heat load from the plasma can be efficiently removed from the side surface of the heat sink material, and even if the heat load is repeated, the integrity of the contact surface can be maintained, thereby increasing the heat removal capacity. No deterioration occurs.

When graphite is used for the protection plate 18, the effect of this embodiment will be further enhanced if the direction of good thermal conductivity is parallel to the contact surface 27. Further, if an electrical closed circuit is a problem, by using the aforementioned aluminum nitride for the protection plate 18, adjacent heat sink materials 26 can be insulated. Even when electromagnetic force is applied to the heat sink material 26 due to disruption, the heat sink material 26 is not mechanically rigid.
is integrated with the protection plate 18, and can be supported as a whole by, for example, a key structure 29, resulting in excellent soundness.

〔Effect of the invention〕

According to the present invention, by alternately arranging and mechanically fastening the protective plates made of a high melting point material and the cooling pipe structure, the high heat load from the plasma can be efficiently removed.
Heat transfer between the protection plate and the cooling pipe structure can be maintained even after repeated heat loads.

Further, since the electromagnetic force applied to the cooling pipe structure due to disruption is supported integrally with the more rigid protection plate, the integrity of one device can be maintained.

Furthermore, if aluminum nitride is used as a protective plate, it can be attached to the front of the antenna of a high-frequency heating device and used as a highly reliable Faraday shield.

[Brief explanation of the drawing]

1 and 2 are for explaining one embodiment of the present invention, and FIG. 1 is a partially cutaway perspective view showing the plasma and opposing equipment placed in front of the high-frequency heating device antenna;
FIG. 2 is a sectional view of FIG. 1. FIG. 3 is a perspective view showing another embodiment of the present invention, FIGS. 4 and 5 are for explaining a conventional example, and FIG. 4 is a perspective view showing a Faraday shield joined to a protective plate. , 5th
The figure is a perspective view showing the heating device antenna, and FIG. 6 is a system diagram schematically showing the heating device. 1... High frequency oscillator 2... Tokamak body 3.
... Coaxial tube 4 ... Plasma 5 ... Antenna 8 ... Faraday shield 11 ... Casing 12 ... Conductor 16 ...
- Electromagnetic force 18... Protective plate 19... Cooling channel 21... Fastening bolt 25... Diverter 26... Heat sink

Claims (1)

[Claims] In a plasma facing device having an array of cooling tubes facing the plasma, a plurality of protection plates made of a high melting point material are disposed between the plasma facing surface of the cooling tube and the gap between the adjacent cooling tube and are brought into contact with the cooling tube. , A plasma facing device characterized in that the cooling pipe array and a plurality of protection plates are collectively fastened together.