JPS6355756B2 - - 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 suitable for use in a plasma confinement type nuclear fusion device.

FIG. 1 shows an outline of a conventional neutral particle injection device. In the figure, 1 is an ion source that discharges gas to extract and accelerate ions in the discharge, and 2 is an ion source 1.
Extraction acceleration electrode that selectively extracts only ions,
Reference numeral 3 denotes a cell for neutralizing the charges of extracted ions, which is housed in a vacuum container 4 for a neutral particle injection device.
A beam dump 6 and a cryopump 9 for evacuating the inside are housed in the vacuum chamber 4 for the neutral particle injection device, and the cryopump 9 is connected to the external refrigeration equipment 1.
Connected to 0. The end of the vacuum vessel 4 for a neutral particle injection device on the side opposite to the ion source 1 side is connected to a vacuum vessel 11 for a nuclear fusion device that houses a plasma 12 therein. 5 is a gas introduction system that supplies gas from the supply gas source 13 into the neutralization cell 3 via a gas pulse introduction valve; 8 is a trajectory of a fast neutron beam; and 7 is a trajectory of an ion beam without charge exchange. .

In such a configuration, the high-speed ion beam extracted from the ion source 1 collides with the gas remaining or floating inside the neutralization cell 3 to become a high-speed neutral particle beam that does not lose its charge, and the target plasma is 12 and heats the plasma 12.

By the way, in order to improve the neutralization efficiency within the neutralization cell 3, the gas introduction system 5 is connected to the supply gas source 13.
A gas is introduced into the neutralization cell 3 through the ion source 1, and the high-energy ion beam from the ion source 1 collides with the neutral gas to obtain a neutral particle beam.

However, since the temperature of the introduced gas is not normally controlled, it is necessary to increase the gas flow rate in order to obtain effective neutralization efficiency. This increases the gas load on the exhaust equipment attached to the device, making the equipment huge. Furthermore, although a cryopump 9 has conventionally been used for vacuum evacuation, the heat load on the cryopanel also increases and the capacity of the refrigeration equipment becomes enormous.

That is, in order to effectively collide the high-speed ions extracted from the ion source 1 with the residual gas, the neutralization cell 3 needs to maintain a predetermined pressure. Because it often enters the plasma 12, it is necessary to maintain an ultra-high vacuum, which requires an exhaust system with a large exhaust capacity. The pressure in the neutralization cell 3 is determined by the amount of introduced gas and the above-mentioned pumping speed, but it also depends on the ease of gas flow (conductance) in the neutralization cell 3. but,
The conductance of this neutralization cell 3 is determined by its geometrical shape, and the geometrical shape is also determined by the ion source and other factors.

If we consider a cylinder as the neutralization cell 3, this conductance C _N1 is where d: Diameter of cylinder l: Length of cylinder Mg: Mass number of introduced gas T: Temperature of introduced gas.

Note that d and l are determined by the geometrical shape, and in order to obtain a large-capacity beam, it is preferable to make d large and l short, and Mg is determined by the intended test. It is.

Therefore, the temperature of the introduced gas should be kept as low as possible, and the conductance C _N1 should be lowered while keeping the geometrical shape easy for the ion beam to pass through, which in turn reduces the gas supply amount and neutralizes the gas. It can increase efficiency.

By the way, as an idea to reduce the gas consumption of the neutralization cell, it is possible to lower the temperature of the gas colliding with the neutralization cell wall by cooling the neutralization cell itself to a low temperature.
Although there are attempts to reduce the speed of gas movement,
The neutralization cell is installed immediately behind the extraction electrode of the ion source, and not only is it structurally difficult to cool it sufficiently from the heat from the ion source, but it is also expected that the gas and the neutralization cell will repeatedly collide. Therefore, its effectiveness is low in terms of efficiency.

The present invention has been made in view of the above points, and its purpose is to maintain the pressure in the neutralization cell with a small amount of gas supply and to improve the neutralization efficiency of the ion beam. The objective is to provide a neutral particle injection device that can be used.

The present invention is provided in the middle of the trajectory of ions extracted from an ion source that discharges gas and extracts and accelerates ions during the discharge via an extraction accelerating electrode, and is external to a neutralization cell that neutralizes the charge of the ions. A gas cooling device is installed in the middle of the gas supply means that introduces more gas, and after cooling with this gas cooling device, the gas is introduced into the neutralization cell to achieve the intended purpose. It is.

The present invention will be described below based on embodiments shown in the drawings. Incidentally, the same reference numerals are used for the same parts as in the past.

FIG. 2 shows an embodiment of the present invention. Since its schematic structure is almost the same as that of the conventional one, detailed explanation will be omitted here.

In this embodiment shown in the figure, a gas cooling device 14 is provided in the middle of the gas introduction system 5 that supplies gas into the neutralization cell 3, and the supplied gas coming out of the gas source 13 is passed through the gas cooling device 14. The gas is cooled to a low temperature and introduced into the neutralization cell 3 through a gas introduction system 5. By using this embodiment, the low temperature gas stays in the neutralization cell for a longer time than room temperature gas, so the pressure in the neutralization cell 3 can be reduced without increasing the amount of gas supplied. In addition to being able to retain the ions, it is also possible to efficiently neutralize the ions extracted from the ion source.

3 and 4 show an example of a gas cooling device. The one shown in FIG.
I try to cool it down at 6. For example, if liquid nitrogen is used as the liquefied gas, the conductance will be lower than that at room temperature. In other words, it becomes about 1/2, which makes it possible to reduce the gas supply amount and also reduce the heat load on the cryopanel. In the system shown in Fig. 4, the gas cooling device 14 is cooled by a helium refrigerator 18 compressed by a helium compressor 17, and the effect of this is expected to be equal to or greater than that shown in Fig. 3. can.

According to the neutral particle injection device of the present invention described above, a gas cooling device is provided in the middle of the gas supply means that introduces gas into the neutralization cell from the outside, and after cooling with this gas cooling device, the gas is Since the low-temperature gas is introduced into the neutralization cell, the time that the low-temperature gas remains in the neutralization cell is extended, so the pressure inside the neutralization cell can be maintained without increasing the amount of gas supplied. This makes it possible to efficiently neutralize the ions extracted from the ion source, and is very effective when employed in this type of neutral particle injection device.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a conventional neutral particle injection device, FIG. 2 is a schematic configuration diagram showing an embodiment of the neutral particle injection device of the present invention, and FIGS. It is a figure showing an example of the gas cooling device adopted. 1...Ion source, 2...Extraction acceleration electrode, 3...
Neutralization cell, 4...neutral particle injection device vacuum container,
5... Gas introduction system, 6... Beam dump, 7...
Ion orbit, 8... Neutral particle trajectory, 9... Cryopump, 10... Refrigeration equipment, 11... Nuclear fusion device main body, 12... Plasma, 13... Gas source, 1
4... Gas cooling device, 15... Liquefied gas container, 1
6...Liquefied gas, 17...Helium compressor, 18...Helium refrigerator.

Claims (1)

[Scope of Claims] 1. An ion source that discharges a gas and extracts and accelerates the ions being discharged, and an ion source that is provided on the trajectory of the ions extracted from the ion source via an extraction accelerating electrode and that neutralizes the electric charge of the ions. A neutralization cell for sexualization,
A neutral particle injection device comprising: a vacuum tube that guides the neutral particles neutralized in the neutralization cell to the injection target device; and a gas supply means that introduces gas from the outside into the neutralization cell. . A neutral particle injection device, characterized in that a gas cooling device is provided in the middle of the gas supply means, and the gas is introduced into the neutralization cell after being cooled by the gas cooling device. 2. Claim 1, characterized in that cooling in the gas cooling device is performed using liquefied gas.
Neutral particle injection device described in Section 1. 3. The neutral particle injection device according to claim 1, wherein the gas cooling device is a helium refrigerator.