JPH03202680A - Cryopump - Google Patents

Abstract

PURPOSE:To facilitate achievement to extremely high vacuum by using an oxygen free copper for extremely low temperature for a radiant shield in a cryopump and a plurality of materials of the cryopump so as to cool evenly and rapidly the entire body of each of the above parts. CONSTITUTION:As for a cryopump, one end is connected to an exhaust port 10 of an exhausted container and a small freezer 2 is provided in a casing 9. First and second cold stages 2 and 3 are fixed to the small freezer 1, and a radiant shield 4 and a baffle 7 are provided at the first cold stage 2. At the second cold stage 3, first and second cryopanels 5 and 8 are provided respec tively, and an activated carbon 6 is pasted on both their inner and outside surfaces. In the above constitution, an oxygen free copper for extremely low temperature is used as materials of the shield 4 and respective panels 5 and 8.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a cryopump, which is used in ultra-high vacuum equipment and is a distant relative of ultra-high vacuum, and particularly aims to shorten the time required to reach ultra-high vacuum. Regarding cryopumps.

(Prior art and its problems) As shown in FIG. 1, an example of a conventional cryopump has one end connected to an exhaust port 10 of a container to be evacuated, and a casing 9
A small refrigerator 1 is provided inside. First and second cold stages 2.3 are fixed to the middle and upper ends of this small refrigerator 1, respectively. A cup-shaped radiation shield 4 is connected upward to the first cold stage 2, and a baffle 7 is provided at the opening at the upper end of the radiation shield 4.

A kelp-shaped first cryopanel 5 is provided in the second cold stage 3 facing downward and inside the radiation shield 4.
Furthermore, a second cryopanel 8 is provided inside the first cryopanel 5 and close to the second cold stage 3.

Activated carbon 6 is attached to the inner surface of the first cryopanel 5 and the outer surface of the second cryopanel 8.

When the cryopump having such a configuration is operated, after roughing with a roughing vacuum pump (not shown), the small refrigerator 1 is operated to cool the first and second cold stages 2.3. Radiation shield 4, first cryopanel 5, second cryopanel 8 and activated carbon 6 fixed to these
are also cooled by heat conduction from the fixed portions of each cold stage 2.3.

However, in conventional cryopumps, the radiation shield 4, the first cryopanel 5, and the second cryopanel 8 are made of general industrial copper or copper alloy whose thermal conductivity at low temperatures is not considered. For this reason, there was a large temperature difference between the parts of each panel 4.5.8 fixed to each stage 2.3 and the parts far from them, making it difficult to maintain a uniformly low temperature throughout the panel. .

Therefore, each cold stage of each panel 4.5.8
2.3 The parts far from the fixed part were not sufficiently cooled, making it difficult to adsorb residual gases such as hydrogen even in extremely high vacuum, making it difficult to reach extremely high vacuum. .

Moreover, it takes a long time to reach an extremely high vacuum.

An object of the present invention is to solve the above-mentioned problems and provide a cryopump that can easily reach extremely high vacuum.

(Means for achieving the object) In order to achieve the above object, a first and second cold stage 2.3 provided in a vacuum chamber, and one end of the first or second cold stage 2.3 are provided. A fixed radiation shield 4, a first cryopanel 5, and a second cryopanel 8 are provided, and the radiation shield 4, first cryopanel 5, and second cryopanel 8 are passed through each of the cold stages 2.3 to an extremely low temperature. In this cryopump, each of the panels 4, 5, and 8 is made of cryogenic oxygen-free copper.

(Function) As shown in Figure 3, it has better thermal conductivity in the cryogenic region than conventional oxygen-free copper, and as shown in Figure 2, it has a low amount of outgassing from the material itself. By using each panel made of low-temperature oxygen-free copper, it is possible to increase the cooling efficiency from each cold stage and uniformly and rapidly cool down to the tip of each panel.

(Embodiment) The structure is the same as the conventional example described above. That is, as shown in FIG. 1, one end is connected to the exhaust port 10 of the evacuated container, and a small refrigerator 1 is provided inside the casing 9. First and second cold stages 2.3 are fixed at the middle and upper end of this small refrigerator l. A cup-shaped radiation shield 4 is connected upward to the first cold stage 2, and a baffle 7 is provided at the opening at the upper end of the radiation shield 4.

A kelp-shaped first cryopanel 5 is provided in the second cold stage 3 facing downward and inside the radiation shield 4.
Furthermore, a second cryopanel 8 is provided inside the first cryopanel 5 and close to the periphery of the small refrigerator 1. Activated carbon 6 is attached to the inner surface of the first cryopanel 5 and the outer surface of the second cryopanel 8.

In the above configuration, the radiation shield 4, the first cryopanel 5, and the second cryopanel 8 are made of cryogenic oxygen-free copper. As oxygen-free copper for cryogenic use,
For example, the product name rCG-OFCJ manufactured by Hitachi Cable is used.

Furthermore, it is preferable to use cryogenic oxygen-free copper for the baffle 7 as well.

Note that the shapes of the radiation shield 4, first cryopanel 5, second cryopanel 8, and baffle 7 do not have to be the shape shown in FIG. Any shape is acceptable as long as it is difficult for the gas molecules that enter it to escape.

Next, the operation of the cryopump of the present invention will be explained.

After roughing with the roughing vacuum pump, the small refrigerator 1 is operated to cool each cold stage, and this cold energy is transferred from the first and second cold stages 2.3 to the radiation shield 4.
The radiation is transmitted to the first cryopanel 5 and second cryopanel 8, but the radiation shield 4, first and second cryopanels 5.8 are made of cryogenic oxygen-free f having high thermal conductivity even at cryogenic temperatures.
Since it is made by iJ, the whole can be easily cooled uniformly.

Note that if the baffle 7 is also made of oxygen-free copper for cryogenic temperatures, this portion also tends to have a uniform temperature.

As a result, as shown in FIG. 3, there is a noticeable difference, especially in the extremely low temperature range, compared to the case where conventional oxygen-free copper is used.

Furthermore, as shown in FIG. 2, the amount of outgassing is significantly smaller than when stainless steel or copper alloy is used, making it easier to prevent the exhaust speed from decreasing.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of an example of a cryopump, Figure 2 is a characteristic diagram of the amount of outgassing depending on the material, and Figure 3 is the temperature and heat of the cryogenic oxygen-free copper used in the present invention and the conventional oxygen-free copper. It is a relationship diagram of conductivity. 2: First cold stage, 3: Second cold stage, 4: Radiation shield, 5: First cryopanel, 8: Second cryopanel. $30 Procedural amendment (voluntary) Taraio Bonp Co., Ltd. Japan Steel Works, Ltd.

Claims (1)

[Claims] A first and second cold stage provided in a vacuum chamber, a radiation shield, a first cryopanel, and a second cryopanel each having one end fixed to the first or second cold stage, the radiation shield, A cryopump that cools a first cryopanel and a second cryopanel to a cryogenic temperature through each of the cold stages, characterized in that each of the panels is made of cryogenic oxygen-free copper.