JPH0381692A - Fuel supply device of magnetic field confinment type nuclear fusion device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fuel supply system for a magnetic field confinement type nuclear fusion device, and more specifically to a type of fuel supply system that supplies fuel gas from a limiter that determines the shape of plasma. It is related to the device.

[Prior Art] As is well known, a magnetic field confinement type nuclear fusion device supplies fuel to a vacuum container evacuated to an ultra-high vacuum and generates plasma by applying an electric or magnetic field. It is also known that the temperature, density, etc. of the generated plasma are greatly affected by the fuel supply method and supply amount. Furthermore, in order to stably maintain the generated plasma for a long time, it is necessary to replenish fuel and exhaust impurities during plasma ignition.

As described above, in a magnetic field confinement type fusion device, supplying fuel is important, and conventionally, two fuel supply methods are known. One method is to cool the fuel gas to a low temperature, solidify it, make it into pellets, and inject it into the plasma at high speed. This method has the advantage of being able to supply fuel directly to the hot plasma center; however, this method cannot be used in the absence of plasma;
Furthermore, since the fuel is supplied in the form of pellets, there are problems such as the inability to provide continuous fuel supply, so this fuel supply method cannot be used alone and is used in conjunction with the second fuel supply method described below.

The second method is called the gas puff method, in which fuel is supplied in a gaseous state from a fuel release opening provided in a vacuum container, and an example of its principle is shown in Figure 5. ing. That is, a gas supply port 5 for supplying fuel gas is provided above the donut-shaped vacuum container 1, and a limiter 4 that determines the shape of plasma is provided on the side. When fuel gas is supplied into the vacuum container 1 from the fuel supply port 5 and plasma is generated, the plasma 2 is confined inside the lines of magnetic force that are in contact with the limiter 4. Then, a soflave-off layer 3 is formed outside this plasma.

The soflave-off layer 3 is a layer of fuel particles and impurity particles leaked out from inside the plasma by diffusion in a low-temperature plasma state.

Generally, the center of the plasma 2 is at a high temperature, so almost all particles are in a completely ionized state, but the sflave-off layer 3
Because of the low temperature, particles in various ionization states exist in the surrounding area, and particles undergo repeated ionization and recombination. The so-called recycling phenomenon is actively occurring and is a cause of energy loss from the plasma.

In the fuel supply device shown in FIG. 5, when fuel gas is injected from the fuel gas supply port 5 in the presence of the plasma 2 or the sflobe-off layer 3, the fuel gas particles are transferred to the low-temperature plasma center before reaching the high-temperature plasma center. Therefore, in the conventional method described above, in order to increase the density of the plasma center, a large amount of fuel must be injected. There is a problem in that the ionization of fuel particles occurring in the vicinity of layer 3 also increases the loss of energy from the plasma periphery, causing the temperature of the plasma periphery to drop and the entire plasma to disappear.

A solution to the drawbacks or problems of the conventional gas buffing method as described above is described, for example, in Journal of Nuclear Materials, Vol. 121 (1984), pp. 285 to 29.
Page 3 (“Journal of Nuclear M
materialg"121 (1984) PP285-2
39). The essential parts of the device for this improved gas puff method are shown in FIG. 6. As shown in FIG. A mouth 5 is provided.

[Problems to be Solved by the Invention] The conventional device shown in FIG. 6 has the fuel gas supply port 5 closest to the plasma, so it is difficult to solve the conventional gas puff method shown in FIG. Compared to a fuel supply device, the effect of increasing the number of fuel particles reaching the plasma center can be expected; however, the following two
There are two problems.

The first problem is that since the tip of the limiter 4 has a curvature in the opposite direction to the plasma 2, not only the plasma 2 but also the soufflé and eve-off layer 3 come into contact with the tip of the limiter 4. This means that low-temperature impurity particles ejected from the plasma exist close to the fuel gas supply port 5, which prevents the fuel particles from penetrating into the center of the plasma.

The second problem is that the contact point between the plasma 2 and the limiter 4 coincides with the fuel gas supply port 5 as shown in the figure. Generally, the temperature of the plasma is lowest at the contact point, and it has been experimentally confirmed that the recycling phenomenon, which is the repeated ionization and recombination of particles, occurs most actively at this contact point. On the other hand, at the contact point, the temperature of the limiter 4 is the highest, and the evaporation of the limiter material and the release of particles that have been diffused and adsorbed into the limiter are most active. In this way, in the device shown in Figure 6, fuel particles are injected from a place where the plasma temperature is low and impurity particles are actively released, so the plasma is increased through active recycling and charge exchange with impurity particles. There is a high possibility that the surrounding area will be cooled.

Therefore, the present invention provides a gas puff fuel supply device in a magnetic field confinement type fusion device that allows fuel particles to penetrate or inject to the plasma center and that reduces the temperature drop in the peripheral area of the plasma even when fuel is supplied. It is intended to. A further object of the present invention is to provide a fuel supply device that is easy to maintain and inspect, and that also has a high efficiency in exhausting impurity particles.

[Means for Solving the Problem] In order to achieve the above object, a fuel gas supply device for a magnetic field confinement type nuclear fusion device of the present invention has the features described in the claims.

[Function] According to the present invention, the limiter forms a closed space between it and the plasma, and this space forms a space that is distinct from the plasma and the space inside the vacuum container, and this space forms a closed space between the limiter and the plasma. Since it is isolated from the surface of the part, the scrape-off layer formed within the closed space is always thinner than the scrape-off layer in other areas. Furthermore, since the opening for supplying fuel gas faces the closed space, the opening for supplying fuel gas can be separated from the contact area between the plasma and the limiter. Therefore, according to the present invention, the fuel gas discharged from the fuel gas supply opening avoids the contact between the low temperature plasma and the limiter, and can reach the plasma only through the thin scrape-off layer, and Less cooling of peripheral areas.

C implementation example An embodiment of the present invention will be described with reference to FIGS. 1 and 2.

Figure 1 is a diagram showing only the limiter and its surroundings in the magnetic field confinement type fusion device of this embodiment, and 2 is a diagram showing the plasma,
3 is a scrap-off layer, 4 is a limiter, 5 is a fuel gas supply port, 6 is a closed space formed by the plasma 2 and the limiter 4, 7 is a contact portion between the plasma 2 and the limiter 4, 3
' is formed in the closed space 6 of the scrape-off layer 3. Figure 2 shows the limiter 4 shown in Figure 1.
FIG.

In this embodiment, the tip of the limiter 4 is expanded into a trumpet shape as shown in the figure, and the tip of the limiter 4 is shaped so as to threaten the contact portion 7 that comes into contact with the plasma throughout the edge of the trumpet shape. Processed. When the limiter 4 having such a shape is inserted into the plasma, the plasma 2 is changed as shown in FIG.
A closed space 6 is formed between the plasma 2 and the limiter 4, which is distinguished from the plasma 2 and the space inside the vacuum container. The scrape-off layer 3 formed outside the plasma 2 is composed of particles that have come out from the plasma by diffusion across the plasma surface. Therefore, the thickness of the scrape-off layer 3 is
It is determined by the size of the plasma surface area connected to it.
The smaller the plasma surface area, the thinner it is. In the closed space 6, the plasma surface area facing the closed space 6 is very small compared to the total plasma surface area, so the thickness of the scrape-off layer 3' in the space 6 is smaller than that of the scrape-off layer 3 in other parts. Become thin.

Further, in this embodiment, the fuel gas supply port 5 is connected to the plasma 2
and the closed space 6 farthest from the contact part 7 with the limiter 4
The limiter 4 is provided facing inward. For this reason, the fuel gas supply port 5 is located away from the contact portion 7 where the plasma temperature is low and the amount of impurity released is large.

According to this embodiment configured as described above, the fuel particles discharged from the fuel gas supply port 5 are thin scraped off particles,
Since the fuel particles can reach the plasma surface only through 1513', the rate of fuel particles reaching the plasma is higher than in the prior art.

FIG. 3 is a perspective view of the vicinity of the limiter of a magnetic field confinement type fusion device which is another embodiment of the present invention.

In this figure, 1 is a vacuum vessel, and a limiter 4 and a fuel gas supply port 5 are each separately provided in the vacuum vessel 1. The fuel gas supply port 5 opens at the bottom of the space 6 inside the limiter 4. The limiter 4 is approximately box-shaped, but its tip is shaped to form a contact portion 7 with the plasma.

Also in this embodiment, the contact portion 7 between the plasma and the limiter 4
Since a closed air M6 is formed by this, the same effect as in the first embodiment can be obtained.

Furthermore, in this embodiment, in addition to this, since the limiter 4 and the fuel gas supply port 5 are separate, there is an effect that the limiter 4 can be easily replaced and maintained.

FIG. 4 shows a poloidal cross-sectional view of a magnetic field confinement type fusion device which is still another embodiment of the present invention.

In this figure, parts that are equivalent to those in other figures are given the same numbers. 8 is an exhaust pump, 9 is an arrow indicating the direction of incidence of fuel particles, and 10 is an arrow indicating the direction of flow of impurity particles. . In this embodiment, the structure of the limiter 4 and the fuel supply port 5 is the same as that of the embodiment shown in FIGS. The box body 12 is attached to a wall 13 connected to the vacuum vessel 1, and is different in that an exhaust pump 8 is provided inside the box body. By operating the exhaust pump 8, the particles diffused out of the plasma 2 are led behind the limiter 4 through the scrape-off layer 3, and are exhausted through the through hole 14 in the end wall of the box 12. Therefore, according to this embodiment, not only the fuel supply efficiency can be improved as in the first embodiment, but also the efficiency of exhausting impurity particles and the like can be improved.

[Effects of the Invention] As described above, according to the present invention, the limiter forms a closed space between itself and the plasma that can be distinguished from the plasma and the space inside the vacuum container, and the fuel gas is injected into this closed space. Since the supply opening is facing, the scrape-off layer in front of the fuel gas supply opening is thinner than the scrape-off layer in other areas, and the point of contact between the plasma and the limiter is close to the fuel gas supply opening. Since the plasma is separated from the surrounding area, the efficiency of fuel supply to the plasma is increased and the peripheral area of the plasma is less likely to be cooled.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing only the main parts of one embodiment of the present invention, FIG. 2 is a perspective view of the limiter shown in FIG. 1, and FIG. 3 is a perspective view showing the main parts of another embodiment of the invention. 4 are sectional views of essential parts of still another embodiment, and FIGS. 5 and 6 are sectional views showing different conventional examples. l...Vacuum container 2...Plasma 3.3'...
・Scrape-off layer 4...Limiter 5...Fuel gas supply opening 6...Closed space 8...Exhaust pump (1 other person) Fig. 2 Afsuma 6 Fig. Fig. Fig. Fig. Fig. Fuel gas

Claims (1)

[Scope of Claims] 1. A fuel supply device for a magnetic field confinement type nuclear fusion device in which fuel gas is supplied to the plasma from a limiter for contacting the plasma and determining its shape in a vacuum vessel, wherein the limiter A magnetic field confinement type nuclear fusion device characterized in that it is configured in a shape that forms a closed space between it and the plasma, and that an opening for injecting fuel gas faces into the closed space. fuel supply system. 2. The fuel supply system for a magnetic field confinement type fusion device according to claim 1, wherein the limiter is removable from the vacuum vessel independently of the opening for fuel gas injection. 3. The fuel supply system for a magnetic field confinement type fusion device according to claim 1 or 2, wherein an exhaust pump is provided on a side of the limiter far from the plasma.