JPH0781554B2 - Cryopump with heat shield plate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a cryopump that condenses and adsorbs gas molecules on a cryopanel surface cooled to an extremely low temperature and exhausts it at high speed.

[Conventional technology]

The conventional apparatus, as described in JP-A-61-169682, has a single flat surface cryopanel cooled to an extremely low temperature with liquid helium or the like at a substantially right angle to the gas inlet surface.
In addition, a plurality of sheets are arranged at regular intervals. To prevent this cryopanel from being heated from the high temperature outside the pump, place a front heat shield plate cooled to a low temperature with liquid nitrogen etc. on the gas inlet face in front of the cryopanel, and on both sides of the cryopanel. Similarly, a louver blind type heat shield plate cooled by liquid nitrogen is arranged. Further, a rear heat shield plate cooled with liquid nitrogen is provided also in the depth direction of the cryopanel, that is, on the rear side of the cryopanel. The gas molecules pass through the louver gap, collide with a cryogenic cryopanel, and are solidified and adsorbed there.

The back surface of the front heat shield plate, the rear heat seal plate, and the surface of the louver are treated with black so as to absorb the radiant heat. Designed to reach the panel.

The gas molecules to be exhausted flow into the cryopump through the gas inlet between the front heat shield plates adjacent to the front of the pump. While the gas molecules repeatedly collide with the louver or the rear heat shield plate once or several times, some gas molecules flow out from the inflow port, and some gas molecules reach the cryopanel and are solidified and adsorbed. If the proportion of gas molecules that are solidified and adsorbed is increased, the pumping speed of the cryopump can be increased.

[Problems to be Solved by the Invention]

In the conventional cryopump, the louvers are arranged in multiple stages with an inclination of an angle α with respect to the cryopanel. Now, the gas molecules collide with the surface facing the gas inlet, the surface A, and are reflected, and again collide with the flow surface of surface A, B of another louver, and are reflected again. In some cases, after colliding with the back side of the A side and the B side and reflecting, it collides with the heat shield plate several times and flows out of the pump from the gas inlet. As a result, there is a problem that the ratio of the number of outflowing gas molecules to the number of inflowing gas molecules increases, the probability of passage of gas molecules decreases, and the exhaust speed decreases.

An object of the present invention is to increase the probability of gas molecules passing through the cryopump to increase the exhaust speed.

[Means for Solving the Problems]

In order to achieve the above object, the cryopump with a heat shield plate of the present invention is arranged substantially perpendicular to the gas molecule inflow surface, and a main cryopanel cooled to an extremely low temperature in order to solidify or adsorb gas molecules, In a cryopump having a heat shield plate cooled to a low temperature to protect the main cryopanel from high-temperature radiant heat, a multistage sub-cryopanel is branched from the main cryopanel in a branch shape, It is characterized in that low-temperature heat shield plates are arranged in multiple stages on the gas molecule inflow surface side.

[Action]

By arranging the partition plate on the B surface side of the louver, all the gas molecules that collide with the A surface of the louver and reflect, and again collide with the B surface of another louver, are solidified by this partition plate. Can be adsorbed. As a result, the probability of passage of gas molecules increases.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. Low temperature front heat shield plate 1 placed in front of the cryopump
Gas molecules to be exhausted flow into the cryopump in the direction of the dashed arrow from between. The cryogenic main cryopanel 2,
The cryopump gas molecule is almost perpendicular to the inlet surface,
It is placed behind the front heat shield plate 1 and on the left and right sides of it.
Three groups of low temperature louvers inclined by an angle α are provided. On the B side of the louver, a partition plate 4 inclined by an angle α is provided so as to be thermally integrated with the main cryopanel 2 with a slight gap from the louver 3 and is cooled to an extremely low temperature. A partition plate 5 integrated with the main cryopanel 2 is also arranged behind the front heat shield plate 1. A low temperature rear heat shield plate 6 is provided behind the pump in the depth direction.

Cryogenic main cryopanel 2, partition plate 4 and partition plate 5
Are arranged so that they cannot be directly seen from the direction of the cryopump inlet. The gas molecules flowing into the cryopump from the inflow port repeatedly collide with the louver 3 and the rear heat shield plate, while a certain gas molecule collides with the rear heat shield plate or the louver A face and then directly flows out from the inflow port. However, by providing a partition plate, the gas molecules that have hitherto collided and reflected on the louver B surface and the back surface of the front heat shield plate are surely solidified by the partition plates 4 and 5.
It can be adsorbed and the ratio of gas molecules flowing out can be reduced. Therefore, according to the present embodiment, the exhaust speed of gas can be made higher than that of the conventional louvered cryo-pump.

FIG. 2 shows another embodiment of the present invention, in which the main cryopanel 2 is a gas inlet in the direction of the broken line arrow, and is protected from external radiant heat by the Sieblon type heat shield plate 7. There is. A partition plate 8 integrated with the main cryopanel 2 is arranged behind the bent portion of the heat shield plate 7.

Also in this embodiment, since the gas molecules that have been conventionally reflected by the curved surface and flow back to the inlet and flow out can be reliably exhausted by the partition plate 8, the exhaust speed is set higher than that of the conventional Sieblon type cryopump. be able to. The present embodiment also has an advantage that the depth of the pump can be made smaller than that of the louvered cryo-pump shown in FIG.

FIG. 3 shows another embodiment of the present invention. The difference from FIG. 1 is that the inclination α of the louver 3 is substantially zero, and the partition plate 4 is arranged behind it and parallel to the louver 3. The heat shield plate 7 is integrated with the louver 3 on the main cryopanel 2 side. The heat shield plate 7 thermally protects the main cryopanel 2. According to this embodiment, since the inclination α of the louver 3 is almost zero, the gas molecules colliding with the louver 3 are directly
Alternatively, the probability of reaching the partition plate 4 after being reflected by the heat shield plate 7 is further increased as compared with the case of FIG.

〔The invention's effect〕

According to the present invention, a cryogenic sub-cryopanel (partition plate) cooled to the same temperature as the main cryopanel can be provided on the back surface of the louver and the front heat shield plate. After colliding with the plate and being reflected, the probability of reaching the multi-stage sub-cryo panel from the main cryopump is increased, and the gas exhaust speed can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a panel arrangement of a cryopump for explaining an embodiment of the present invention, FIG. 2 is a partial sectional view of a panel arrangement according to another example, and FIG. It is a panel layout sectional view of a cryopump concerning other examples. 1 ... Front heat shield plate, 2 ... Main cryopanel, 3
...... Louver, 4 ...... Partition board, 5 …… Partition board.

Claims (1)

[Claims] 1. A main cryopanel which is arranged substantially at right angles to a gas molecule inflow surface and is cooled to an extremely low temperature for solidifying or adsorbing gas molecules, and for protecting the main cryopanel from high-temperature radiant heat. In a cryopump having a heat shield plate cooled to a low temperature, a multi-stage sub-cryo panel is extended in a plate shape from the main cryopanel, and a multi-stage low-temperature heat shield plate is provided on a gas molecule inflow side of each sub-cryo panel. A cryopump with a heat shield plate characterized by being arranged.