JPS61169682A - Cryopump - Google Patents

Abstract

PURPOSE:To improve the efficiency of a cryopump by increasing the rate of the arrival of the inflow gas particles into a cryopanel by reducing the number of pieces of louver blinds by installing an intermediate shielding plate between the cryopanels. CONSTITUTION:An intermediate shielding plate 7 parallel to a cryopanel 2 is installed into the intermediate part of cryopanels 2 and 2. Said intermediate shielding plate 7 is similarly cooled as other shielding plates 3 and 6 by liquid nitrogen, etc. Louver blinds 4 and 4 are arranged so that the cryopanel 2 is not directly seen from the edge part C of the intermediate shielding plate 7, and the number of pieces of the louver blinds 4 is reduced in comparison with the case where the edge part A is set as standard when the intermediate shielding plate 7 is not provided.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a method for producing a large amount of hydrogen gas by solidifying and adsorbing hydrogen gas on the surface of a cryopanel cooled to an extremely low temperature using liquid helium (LHe) K. This relates to a cryopump that pumps out gas at high speed, and is intended to further improve the pumping speed.

The main uses of this cryopump include neutral particle injection devices (NBL) used for plasma heating in nuclear fusion reactors,
There are space chambers for testing rockets and artificial satellites.

[Conventional technology]

FIG. 1 shows a cross-sectional perspective view of a conventional louver blind type Lyopong. A plurality of cryopanels 2 cooled with liquid helium are arranged at regular intervals perpendicular to the surface of the gas inlet 1. The cryopanel 2 is protected from being heated by the room temperature outside the cryopump or by the heat rays radiated from the high-temperature parts by shielding plates 5. and is covered on three sides by a rear outer peripheral shield plate 6.

A front shield plate 3 is placed on a part of the gas inlet in contact with the end face of the cryopanel 2, and a front shield plate 3 is placed on the front surface of the cryopanel 2 to allow gas molecules to pass through but to block heat rays entering from the gas inlet 1. A louver blind 4 is provided to block heat rays from entering the cryopanel 2.

Louver blind 4. The inner surfaces of the front shield plate 3 and the outer shield plates 55 and 6 are painted or surface-treated black to absorb heat rays, and the intensity of the heat rays reflected by them is large. Become tenth of -. In this way, the heat rays from outside the cryopump are prevented from placing unnecessary heat load on the cryopanel 4.

When the conventional cryopump shown in FIG. 1 is viewed from the ■-■ cross section, it becomes as shown in FIG. 2. Regarding FIG. 2, in order to consider the operation of the cryopump, we look at typical trajectories of gas molecules that have passed through the net opening length.

Gas molecules (B)...reflected by the back shield plate 6 and adsorbed to the cryopanel 2, gas molecules (B)...reflected by the louver blind 4,
Adsorbed to the cryopanel 2, gas molecules (c)...reflected by the back shield plate 6 and exited the cryopump.

(to gas molecules)...Reflects at Rhubarb 2 India 4 and exits the cryopump. All the gas molecules that flowed into the cryopump in this way are not adsorbed by the cryopanel 2, and many gas molecules become gas molecules. It comes out of the cryopump like (c), ni). Therefore, in order to improve the efficiency of the cryopump, it is necessary to increase the rate at which the gas molecules flowing into the cryopump are adsorbed by the cryopanel 2 (arrival rate).

The rate at which gas molecules reach the cryopanel in a cryopump with a certain opening length N changes depending on the following factors.

(1) Opening length N/depth D...No matter how large or small, the reach rate is lower, and there is an optimum value.

(2) Net length/Front shield width B: Although larger is better, the front shield width B is determined structurally.

(3) Number of 40 louver blinds and inclination...The smaller the number, the better, and the smaller the inclination α, the better. However, in order to block the incidence of heat rays from outside the cryopump, as shown in Figure 2, when looking at the end A of the opposing front shield plate 3, set the angle α so that the cryovanel 2 cannot be seen through. You need to choose the number.

In the conventional method, among the above factors, (1) N/D # (
2) After optimizing L/B, the inclination a and the number of Louvab 2 India were determined so that the cryopanel 2 could not be seen from the end A of the opposing front shield plate 3.

[Problem that the invention seeks to solve]

As described above, in the conventional technology, the net opening length is determined by optimizing the opening length N, depth D, and front shield width B. As for the inclination α of the louver blind 4 and the number of louver blinds, it is better to choose one over the other, and there was no way to further increase the rate at which incoming gas molecules reach the cryopanel 2 in order to improve the efficiency of the cryopump. .

[Means for solving problems]

Multiple cryopanels that are cooled to an extremely low temperature and solidify or adsorb incoming gas molecules are arranged at regular intervals in a direction perpendicular or almost perpendicular to the plane formed by the gas inlet of the cryopump. At the same time, in order to prevent heat rays radiated from room temperature or high temperature parts outside the cryopump from directly entering the cryopanel, the areas other than the gas inlet are
It is covered with a shield plate cooled with liquid nitrogen or the like, and a shield plate is also provided at a part of the gas inlet that touches the end face of the cryopanel to prevent the heat rays entering from the gas inlet from entering the cryopanel.

In a cryopump that has multiple shield plates made up of louver blinds on the front side of the cryopanel, the main point is that a shield plate cooled with liquid nitrogen or the like is installed in the middle of the cryopanel almost parallel to the cryopanel. It has the following.

[Effect]

FIG. 4 shows a sectional view of a cryopump according to the present invention. The intermediate shield plate 7 provided in the middle of the cryopanel 2 is according to the present invention, and by providing this intermediate shield plate 7, the number of louver blinds 4 in the prior art is reduced.
When the angle α is constant (for example, 30°), the standard for determining the corner OA part of the front shield plate 3 is to Changes to 0 parts. As a result, when the inclination of the louver blind 4 is kept constant as shown in the figure,
It becomes possible to reduce the number of sheets.

This increases the permeability of gas molecules in the louver blind 4 in front of the cryopanel 2, which in turn increases the rate of inflow gas molecules reaching the cryopanel for the entire 2-ion pump), thereby improving the efficiency of the cryopump. is measured.

〔Example〕

A typical embodiment of the present invention is shown in FIG. 3, in which cryopanels 2 are arranged in a direction perpendicular to the plane formed by the gas inlet of the cryopump to be described.

The cryopanel 2 is kept at an extremely low temperature by liquid helium inside, and is designed to solidify and adsorb gas molecules on its front page and exhaust the gas molecules. The cryopump, except for its gas inlet, is surrounded by a side outer peripheral shield plate 5 and a side outer peripheral shield plate 6, which are cooled with liquid nitrogen, to prevent hot rays from outside the cryopump from entering the cryopanel 2. . In addition, a front shield plate 3 is placed on a part of the gas inlet that touches the end of the cryopanel 2, and a louver is placed on the front of the cryopanel 2 so that the heat rays entering from the gas inlet do not enter the cryopanel 2. Shield plates 4 made up of blinds are provided, and these shield plates 4 are also cooled with liquid nitrogen or the like.

Further, an intermediate shield plate 7 cooled with liquid nitrogen is provided between the cryopanels. As shown in the cross-sectional view of FIG. 4, the louver blind 4 is constructed so that the cryopanel 2 cannot be directly seen when viewed from the end portion 0 of the intermediate shield plate 7. To prevent the heat rays incident from the gas inlet from being reflected by these shield plates and louver blinds and reaching the cryopanel, the surfaces of the shield plates and louver blinds should be painted black with high heat ray absorption, or Surface treatment is performed.

Although the intermediate shield plate is shown as a simple flat plate in FIG. 3, it can also have a V-shape or a 7-shape that opens toward the rear outer peripheral shield plate 6. Table 1 shows an example of performance comparison between the cryopump of the present invention and the conventional louver blind type 2-ion pump.

Table 1■ [Effects of the Invention] By configuring the cryopump of the present invention, the number of louver blinds can be reduced compared to the conventional one, and as a result, the gas molecules flowing into the cryopump (through the gas inlet) are By increasing the rate at which the cryopump reaches the panel, the efficiency of the cryopump can be increased, and manufacturing costs can be reduced.

[Brief explanation of drawings]

Figure 1 is a cross-sectional perspective view of a conventional louver-blind type cryopump, Figure 2 is a cross-sectional view of the louver-blind type cryopump in Figure 1 as seen in the -■ direction, and Figure 3 is a louver-blind type cryopump of the present invention. FIG. 4 is a cross-sectional perspective view of the embodiment of FIG.
A cross-sectional view of the cryopong shown in the figure is shown in the IV-ff direction. 1.- Gas inlet 2... Cryopanel 3... Front shield plate 4... Louver blind 5... Side outer circumference shield plate 6... Rear outer circumference shield plate 7... Intermediate shield plate A. −・Front shield end B・−・Front shield width C−・Intermediate shield plate end D・−・Depth L・・・Net opening length N・・・Opening length

Claims (1)

[Claims] Multiple cryopanels, which are cooled to extremely low temperatures and solidify and adsorb incoming gas molecules, are arranged at regular intervals in a direction perpendicular or almost perpendicular to the plane formed by the gas inlet of the cryopump. At the same time, to prevent heat rays emitted from room temperature or high-temperature parts outside the cryopump from directly entering the cryopanel, the area other than the gas inlet is covered with a shield plate cooled with liquid nitrogen, etc. In order to prevent the hot rays from entering the cryopanel, a shield plate was installed on a part of the gas inlet that touches the end face of the cryopanel, and multiple shield plates made of louver blinds were installed on the front side of the cryopanel. A cryopump characterized in that a shield plate cooled with liquid nitrogen is provided in the middle of the cryopanel almost parallel to the cryopanel.