JPS6111440B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a neutral particle injection device, and particularly to a neutral particle injection device for plasma heating in a nuclear fusion device. In a fusion device, the temperature of the plasma does not reach a temperature at which a fusion reaction occurs unless by means of additional heating. As a means for this additional heating, methods such as injecting high-speed neutral particles or using high-frequency heating have been proposed. Among these methods, a method of performing additional heating by the injection of neutral particles has recently been viewed as promising as a reliable heating means. Conventionally, as a vacuum evacuation device for a neutral particle injection device, cryopumps, cryosorption pumps, titanium getter pumps (evaporative getter pumps) made of metallic gas absorbers, and Al-Zr getter pumps made of metallic gas absorbers have been used. (Non-evaporative getter pump) etc. have been proposed. When using the cryopump, tritium is adsorbed on the surface of the cryopanel of the cryopump, and as this amount of adsorption increases, the solidification thickness of tritium increases, making it difficult for the low temperature of the cryopanel to be transmitted. Therefore, the pumping speed of the cryopump decreases. This point is the end of the cryopump's lifespan, and normally the exhaust operation is stopped at this point, the cryopump is stopped, and the temperature of the cryopanel is increased to evaporate the tritium that has solidified on the surface of the cryopanel. This evaporated tritium is released into the atmosphere by an auxiliary evacuation device. However, releasing tritium into the atmosphere is extremely dangerous.
Titanium getter pumps also have the same drawbacks as cryopumps because they are evaporative. However, on the other hand, the Al-Zr getter pump
The pump that adsorbs tritium and has a reduced pumping speed can be removed as is, and the removed pump can be disposed of in a suitable treatment device, so there is no drawback that tritium will be released into the atmosphere. Here, the following Tables 1 and 2 show the exhaust characteristics of the Al--Zr getter pump.

【table】

[Table] Multiply.
However, as a feature of the Getter pump,
As shown by the solid line in Figure 1, when a metallic gas absorber is exposed to air, the surface of the metallic gas absorber gradually becomes oxidized and is exhausted by exposure to atmospheric pressure air approximately 15 times. Speed is reduced by about 50%. On the other hand, the first
As shown by the dotted line in the figure, no significant decrease in pumping speed is observed even when the metallic gas absorber is exposed to nitrogen. However, in the beamline vacuum chamber of a conventional neutral particle injection device, the neutralization cell, beam dump, beam limiter, calorimeter, etc. need to be repaired after a certain period of time, and during this repair, the beamline vacuum chamber will be exposed to atmospheric air. In this case, the metallic gas absorber of the Al-Zr getter pump, which is connected to the beam line vacuum chamber, will also be exposed to air, so the number of exposures will depend on the number of exposures, as shown in Figure 1. The drawback was that the hydrogen pumping speed was reduced. An object of the present invention is to provide a neutral particle injection device that prevents oxidation of a metallic gas absorber during maintenance of the neutral particle injection device and does not reduce the pumping speed of a getter pump. The present invention allows a valve body to be put in and taken out between a beam line vacuum chamber and a vacuum device, thereby making it possible to disconnect and communicate between the beam line vacuum chamber and the vacuum device, and to repair neutralization cells and beam dumps. The valve body prevents air from entering the vacuum device during maintenance, thereby preventing oxidation of the metallic gas absorber. In the present invention, since a valve device is interposed between the beam line vacuum chamber and the evacuation device in which the metallic gas absorber is arranged, the valve device is also used when repairing equipment in the beam line vacuum chamber. There is no risk that the metallic gas absorber in the vacuum evacuation device will be exposed to air due to the blockage. Embodiments of the neutral particle injection device according to the present invention will be described in detail below with reference to the accompanying drawings. In FIG. 2, a member designated by reference numeral 1 is an ion source, and a cylindrical neutralization cell 2 extends below the ion source 1. In FIG. The positive ions accelerated in the ion source 1 then exchange charge with the neutral gas in the neutralization cell 2, and about 40% of the neutral high-speed particles are now injected into the fusion device. ing. A beam line vacuum chamber 3 is provided below the neutralization cell 2, and a vacuum valve 4 is provided between the neutralization cell 2 and the beam line vacuum chamber 3. 2 and the beam line vacuum chamber 3 can be disconnected from each other. A vacuum evacuation device 5 and an auxiliary evacuation device 6 are provided on both sides of the beam line vacuum chamber 3, respectively. The evacuation device 5 is provided with a metallic gas absorber 5A, and can maintain the vacuum state within the beam line vacuum chamber 3. On the other hand, the auxiliary evacuation device 6 is
It is used to evacuate to a degree of vacuum at which the evacuation device 5 can operate effectively, and typically a turbo cellular pump, rotary pump, or the like is used. A vacuum valve 7 is interposed between the beam line vacuum chamber 3 and the evacuation device 5,
Communication between the beam line vacuum chamber 3 and the evacuation device 5 can be interrupted. The vacuum valve 7 is
As shown in FIG. 3, it has a valve body 7A that can be slid up and down by a drive 7B, and when the valve body 7A moves downward, communication between the beam line vacuum chamber 3 and the evacuation device 5 is interrupted. do. A partition 8 is provided in the beam line vacuum chamber 3, and a beam dump 9 is provided below the partition 8. The beam dump 9 receives high-speed ions that cannot be neutralized and converts them into a neutral gas. I can do it. Further, a beam limiter 11 is arranged below the calorimeter 10, and the beam limiter 11 can trim the tail of the Gaussian-distributed neutral beam. A nuclear fusion device main body (not shown in FIG. 2) is provided below the beam line vacuum chamber 3, and a vacuum valve 12 is interposed between the nuclear fusion device main body and the beam line vacuum chamber 3. The neutral particle injection device configured as described above operates as follows. First, the vacuum valves 4 and 7 are opened, and the vacuum valve 12 is closed. In this state, the beam line vacuum chamber 3 is removed using the auxiliary evacuation device 6.
The degree of vacuum inside is reduced to a level where the exhaust device 5 can operate. When a certain degree of vacuum is reached by the auxiliary evacuation device 6, the vacuum degree in the beam line vacuum chamber 3 is increased using the evacuation device 5. Next, hydrogen gas is sealed into the ion source 1, and the ion source 1
The accelerated positive ions are neutralized in the neutralization cell 2, and the vacuum valve 12 is opened to allow the neutral high-speed particles to enter the main body of the fusion device (not shown). On the other hand, if the partition 8, beam dump 9, calorimeter 10, beam limiter 11, etc. in the beam line vacuum chamber 3 need repair, first close the vacuum valve 7 and then close the vacuum valve 12. In this state, open the lid of the beam line vacuum chamber 3 and install the partition 8, beam dump 9, calorimeter 10,
Repair the beam limiter 11, etc. In this case, even if the lid of the beam line vacuum chamber 3 is opened and exposed to the atmosphere, the metallic gas absorber 5A in the vacuum exhaust device 5 will not be exposed to the air because the vacuum valve 7 is closed. , the exhaust characteristics will not deteriorate. After the repair is completed, the lid of the beam line vacuum chamber 3 is closed again, and the auxiliary vacuum evacuation device 6 is driven to raise the vacuum in the beam line vacuum chamber 3 to a predetermined degree of vacuum, and the vacuum degree in the vacuum evacuation device 5 is increased. Vacuum to the same level as . After the beam line vacuum chamber 3 reaches a certain degree of vacuum, the vacuum valve 7 is opened, and the vacuum valve 12 is also opened to inject neutral particles into the fusion device main body (not shown) in the same manner as described above. This raises the temperature of the plasma to the required temperature. As explained above, according to the neutral particle injection device according to the present invention, there is a valve between the beam line vacuum chamber and the evacuation device that is provided in connection with the beam line vacuum chamber and is made of a metallic gas absorber. Since the body is interposed between the body and the valve body, if the valve body is closed, the connection between the beamline vacuum chamber and the vacuum evacuation equipment will be severed, and even if the beamline vacuum chamber is exposed to the atmosphere, the metallic gas absorber will not be exposed to the atmosphere. It is not exposed to the atmosphere and, as a result, there is no risk that the exhaust characteristics of the metallic gas absorber will deteriorate.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the relationship between the number of exposures in air and nitrogen and the pumping speed of hydrogen in an Al-Zr getter pump, and Fig. 2 shows the structure of an embodiment of the neutral particle injection device according to the present invention. Front view showing,
FIG. 3 is a cross-sectional view taken along the top line in FIG. 2. 3... Beam line vacuum chamber, 5... Exhaust device,
7... Vacuum valve, 5A... Metallic gas absorber, 7A
...Valve body, 7B...Driver.

Claims (1)

[Claims] 1. A beam line vacuum chamber connected to the ion source via a neutralization cell, a vacuum evacuation device equipped with a metallic gas absorber provided adjacent to this beam line vacuum chamber, and this evacuation device and the beam A neutral particle injection device characterized by comprising a valve body that communicates with and shuts off communication with a line vacuum chamber, and a drive machine that moves the valve body in and out between the evacuation device and the beam line vacuum chamber. .