JP2512129B2 - Cryopump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention condenses and adsorbs gas molecules having a boiling point higher than the panel temperature on a cryopanel surface cooled to an extremely low temperature, thereby rapidly transferring a large amount of gas. Regarding a cryopump for exhausting.

[Conventional technology]

As described in JP-A-61-169682, a conventional apparatus has a single flat surface cryopanel cooled to an extremely low temperature with liquid helium or the like, at a right angle to the surface of the gas inlet and at a constant interval. Are arranged in multiple. This cryopanel is radiated from the high temperature portion on the gas inflow surface side. A front shield plate cooled with liquid nitrogen is placed at a part of the gas inlet so as not to be heated by radiant heat, and a louver blind also cooled with liquid nitrogen is provided on the side surface of the cryopanel. The gas molecules pass through the gap of the louver blind and are solidified and adsorbed by the cryopanel. A rear shield cooled by liquid nitrogen is also provided on the rear side of the cryopanel.

The front shield plate, the rear shield plate, and the surface of the louver blind are black-treated to absorb radiant heat, and external light rays are reflected by these shield plates once and reach the cryopanel. Has been done.

The gas molecules to be exhausted flow into the cryopump from the inlet between the adjacent front shield plates. The gas molecule is
Collisions with the louver blind or the rear shield plate are repeated once or several times, some molecules flow out from the inlet, and some molecules reach the cryopanel and are condensed / adsorbed. If the ratio of the gas molecules condensed and adsorbed is increased, the pumping speed of the cryopump can be increased.

[Problems to be Solved by the Invention]

In the conventional cryopump, it is arranged with an inclination of an angle α with respect to the plane perpendicular to the gas molecule inflow surface.
The normal line standing on the louver blind surface (A surface) facing the inflow port was oriented toward the inflow port. Further, the reflected gas molecules have the highest probability of advancing in the normal direction of the collision surface according to the cosine law. Therefore, the number of gas molecules that collide with the A surface of the louver blind is greater than the number of molecules that go back to the cryopanel side after reflection,
In particular, the gas molecules that collide with the A surface of the louver blind near the inflow port increase in the ratio of flowing out from the inflow port after being reflected. Therefore, in the conventional cryopump, the ratio of molecules condensed and adsorbed on the cryopanel, that is,
There was a problem that the passing probability was small and the exhaust speed did not increase.

Further, in the conventional louver blind cryopump, since the cryopanel surface is one flat surface, it is not possible to exhaust a low boiling point gas such as helium gas that cannot be condensed / adsorbed on the single panel surface.

An object of the present invention is to provide a cryopump capable of increasing the passage probability (that is, the trapping probability) of gas molecules in the cryopump, increasing the exhaust speed, and simultaneously exhausting gas helium.

[Means for solving the problem]

In order to achieve the above object, the cryopump with a heat shield plate of the present invention is a cryopanel cooled to an extremely low temperature for condensing and adsorbing gas molecules, and a radiant heat cooled to a low temperature for protecting the cryopanel from high temperature radiant heat. In a cryopump provided with a shield plate, the radiant heat shield plate is arranged in a plurality of rows so that the shield surface is substantially parallel to the gas molecule cryopump inlet surface, and the shield plate is The cryopanels are arranged in a row in the depth direction in substantially the same width and in multiple stages, the cryopanels are arranged in the direction opposite to the molecular inlet surface of each shield plate, and the shield plates are folded on the side surface side of the cryopanels. It is characterized by being formed by bending.
Furthermore, an adsorbent is integrated in a part thereof.

The cryopump of the present invention is characterized by the configurations described in the claims.

In the specification of the application, the terms "rear surface" and "B surface" are expressions corresponding to the rear surface when the side closer to the gas inlet is defined as "front surface" and "A surface". Indicates the back side.

[Action]

When the A surface of the louver blind is substantially parallel to the inflow surface and arranged in a stack in the depth direction, the gas particles that collide with the louver blind A surface are more likely to collide with the louver blind than the inflow direction. The probability that the louver collides with the louver before the louver increases, and the louver is reflected again there, and gas molecules further advance in the depth direction of the pump. Therefore, the probability of exiting the gas inlet is reduced and the capture probability is increased.

Further, by disposing the cryopanel on the back side of the louver blind A surface, the gas molecules (for example, hydrogen gas molecules) reflected on the A surface can be condensed and adsorbed by this panel, and the trapping probability is further improved. Further, by providing an adsorbent on a part of the curved surface, helium gas can be selectively adsorbed and exhausted.

If the radiation shield plate is placed parallel to the gas inlet surface, there is a high probability that gas particles will collide with the shield plate surface (omotemen) and jump out in the normal direction. Gas particles are easily trapped in the panel.

If the radiation shield plates are arranged in multiple rows and have substantially the same width, the gas particles are less likely to be blocked by the exposed part of the shield plate facing the gas inlet part of the shield plate (on the rear stage side), so that the gas particles can be protected from the back. Can lead up to.

Even if a plurality of rows of the radiation shield plate group are arranged, since there is no partition wall between the group rows, it is possible to sufficiently capture the gas particles blown from the adjacent row groups.

If the cryopanel is corrugated, the area of the panel surface is enlarged.

If an adsorption-only panel is provided behind the cryopanel, only the adsorbent panel can be replaced independently.

If the depression for embedding the adsorbent is provided in the cryopanel, the adsorbent is prevented from falling off.

Molecular sieve and activated carbon are suitable as the adsorbent.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 2 shows a bird's-eye view of FIG. Gas molecules to be exhausted flow into the cryopump from between the radiant heat shield plates 1 arranged on the front surface in the direction of the broken line arrow. The group of radiant heat shield plates 1 is arranged in the depth direction of the pump and on the same row at a predetermined interval. Radiant heat shield plate 1
Is cooled to a low temperature with liquid nitrogen and the temperature is maintained at about 80K. On the back surface of the radiant heat shield plate 1, a cryopanel 2 that is cooled to an extremely low temperature with liquid helium or the like is arranged. A radiation heat shield plate 3 cooled by liquid nitrogen or the like is provided on the back, top and bottom of the cryopump, respectively.
To provide. Further, the inner surfaces of the radiant heat shield plate 1 and the radiant heat shield plate 3 in the second and subsequent stages are treated black to increase the radiative rate of the surface. Further, both ends of the radiant heat shield plate 1 are bent at a right angle to the cryopanel 2 side so that the cryopanel 2 cannot be seen directly from the gas inlet port, and a high-temperature heat ray is prevented from entering the cryopanel 2. , Thermally protected.

Table 1 shows an example of performance comparison between the cryopump in the present embodiment and the conventional louver blind type cryopump.

In this way, by disposing the radiant heat shield plate 1 parallel to the inflow port surface and having the same width in multiple stages in the depth direction, gas molecules are drawn deeper into the pump and the heat shield is provided. The gas molecules reflected by the plate 1 have a higher probability of reaching the cryopanel 2 facing them in the preceding stage. Therefore, in the present embodiment, there is an effect that the probability that gas molecules are condensed and adsorbed on the cryopanel 2, that is, the capture probability is increased by about 32% as compared with the conventional type.

FIG. 3 shows another embodiment according to the present invention. This embodiment is different from that shown in FIG. 1 in that the bending angle of both ends of the radiation heat shield 1 of the second and subsequent stages is bent by 90 ° or more, and the bending surface 4 is directed toward the depth direction of the cryopump. is there. According to the present embodiment, when the gas molecules that collide with the bent surface 4 are reflected, the probability that the gas molecules travel in the depth direction of the pump increases, and the probability that the gas molecules flow out from the inflow port decreases. Therefore, there is an effect that the capture probability is further increased.

Another embodiment according to the present invention is shown in FIG. The present embodiment differs from FIG. 1 in that a low temperature partition plate 5 is provided on the radiant heat shield plate 1 after the second stage. This collision plate 5
It also serves as a heat radiation shield plate. By providing this partition plate 5, the gas molecules that should go from the pump back point toward the inlet point are reflected by the partition plate 5 and the probability of being condensed / adsorbed at the point of the cryopanel 2 increases. Has the effect of increasing.

Another embodiment according to the present invention is shown in FIG. The present embodiment is different from the example shown in FIG. 2 in that the cryopanel is composed of a wave-shaped heat conducting panel 6, and a liquid helium tube 7 is provided.
And the contact part is integrated. According to the present embodiment, since the surface area of the cryopanel 6 can be made large, more gas molecules can be condensed if the permissible gas condensation / adsorption amount per unit area is constant, so that the gas exhaust capacity is increased. be able to. Therefore, the cryopump can be continuously operated for a longer time.

FIG. 6 shows another embodiment of the present invention, which is different from that shown in FIG. 1 in that the cryopanel 6 is provided with a through hole 8 and the rear surface of the cryopanel 6 is provided with, for example, activated carbon. And the adsorbent 9 such as the above are thermally integrated. According to the present embodiment, for example, gas molecules that cannot be condensed / adsorbed directly on the surface of the cryopanel such as helium gas are generated in the holes 8
After passing through the inside, a new effect is produced in which the gas molecules reflected by the radiation shield plate collide with the adsorbent 9 and can be adsorbed and exhausted.

FIG. 7 shows another embodiment of the present invention. The difference from FIG. 6 is that the cryopanel 10 is composed of a group of L-shaped heat conducting segments and is attracted to the upward surface of the panel 10. Agent 9
It is in the place where it was thermally integrated. That is, according to the present embodiment, the helium gas that could not be exhausted on the L-shaped inner surface 11 reaches the adsorbent 9 and is exhausted after being reflected there. In the embodiment of FIG. 5, since only the helium gas that has passed through the hole 8 is exhausted, the probability of trapping the helium gas is small. However, in the present embodiment, the helium gas is directly or after being reflected on the inner surface 11, the adsorbent The probability of reaching 9 is high, the probability of capturing helium gas can be increased, and the exhaust rate of helium gas can be increased. By narrowing the surface on which the adsorbent 9 is provided, it is possible to easily reduce the exhaust speed of the helium gas.

FIG. 8 shows another embodiment according to the present invention. The difference from FIG. 7 is that the cryopanel is composed of 12 groups of chevron-shaped segments and is located on the rear surface of the lower panel of the radiation heat shield plate 1 side. This is where the adsorbent is thermally integrated. According to the present embodiment, when the cryopanel surface is viewed from the radiation heat shield plate 1 and the reflection side, the adsorbent is not directly visible. Therefore, the adsorbent 9 can be directly exhausted on the surface of the cryopanel 12, for example, nitrogen gas, hydrogen gas, or tritium gas, which is much larger than helium gas, is not adsorbed by the adsorbent 9, and the adsorbent 9 is short in adsorption saturation with these gases. It will never arrive in time. Therefore, the adsorbent can adsorb mainly helium gas, and has the effect of maintaining its exhaust effect for a long time.

FIG. 9 shows another embodiment according to the present invention, which is different from that shown in FIG. 8 in that the cryopanel is composed of 13 louver-shaped segments cooled by the liquid helium tube 7. A panel surface 15 cooled by a liquid helium pipe 14 is installed behind the adsorbent 9 and the adsorbent 9 is thermally integrated with the surface. According to the present embodiment, since the area of the panel surface holding the adsorbent 9 is provided separately from the cryopanel, the condensation / adsorption surface of the cryopanel is not reduced and the exhaust rate of hydrogen gas or the like is reduced. Instead, the passage probability of gas helium can be made larger than that of the chevron type, and there is an effect that the pumping speed of gas helium can be increased. Further, in this case, only the panel surface 15 in which the adsorbent is integrated can be easily replaced separately from the cryopanel.

FIG. 10 shows another embodiment according to the present invention, which is different from that shown in FIG. 7 in that a concave recess 16 is formed on the upward surface of the cryopanel 10 to form a pellet-shaped adsorbent 17. The point is that it is embedded in this and thermally integrated. According to this embodiment, since the adsorbent 17 can be deeply fixed in the recess 16 with an epoxy resin adhesive or the like, even when subjected to repeated thermal cycles such as cool down and warm up of the cryopanel, adsorption It has an effect that the agent 17 does not drop off from the panel 10. In this case, a similar effect can be obtained by using a concave continuous groove instead of the recess 16. At this time, the area of the downward surface of the cryopanel 10 is increased, and the exhaust capacity of hydrogen gas condensed / adsorbed on the downward surface is also increased.

FIG. 11 shows another embodiment according to the present invention, which is different from that shown in FIG. 5 in that the cryopanels 18 are separated from each other and the cooling pipe is made of stainless steel or the like having a large electric resistance. The point is that copper or aluminum having a high thermal conductivity is selected as the material of the cryopanel 18. Therefore, according to the present embodiment, even when an eddy current is generated in the cryopanel due to an external magnetic field variation, the cryopanel groups, which have a small electric resistance and easily generate an eddy current, are separated from each other. Is small and the generation of Joule heat is also small. Therefore, it is possible to prevent an increase in heat load on the liquid helium flowing in the cooling pipe 7. Further, in this case, if the material of the radiation heat shield plate that protects the cryopanel is copper or aluminum, Joule heat loss due to eddy current can be absorbed by the liquid nitrogen that cools the radiation heat shield plate. Because you can protect
The heat load of liquid helium can be further reduced, and the evaporation of liquid helium can be further reduced.

〔The invention's effect〕

Since the present invention is configured as described above,
The following effects are achieved.

The radiant heat shield plates are arranged almost parallel to the gas molecule inlet face, and they are arranged in multiple stages in the depth direction of the cryopump with almost the same width.The cryopanels are placed in the direction opposite to the molecular inlet face of these shield plates. Since the shield plate is provided by bending the side surface of the cryopanel, the gas molecules are drawn in the pump back direction and collide with the radiant heat shield plate, for example, hydrogen gas molecules reflected on the front cryopanel. The probability of arrival is increased, the probability of capture is increased, and the gas exhaust rate can be increased by about 25% compared to the conventional type.

In addition, the cryopanel is formed in a corrugated shape, an L-shape, a chevron shape, etc., and an adsorbent is provided on a part of the surface of the cryopanel, so that the exhaust capacity of the hydrogen gas is not lowered and the cryopanel bare surface is exhausted. It is possible to exhaust even helium gas that cannot be discharged.

[Brief description of drawings]

FIG. 1 is a sectional view of a panel arrangement of a cryopump according to an embodiment of the present invention, FIG. 2 is a bird's eye view of FIG. 1, and FIGS. 3 and 4 are other embodiments of the present invention. Panel layout sectional view of the cryopump, FIG. 5, FIG. 6, FIG. 7, and FIG.
FIG. 9, FIG. 10, FIG. 10 and FIG. 11 are partial cross-sectional bird's-eye views of a pair of a heat shield plate and a cryopanel combination for explaining another embodiment of the present invention. 1 ...... Radiant heat shield plate, 2 ...... Cryopanel.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kaichi Ono 1-1-1, Kokubun-cho, Hitachi City, Ibaraki Prefecture Inside the Kokubun Plant of Hitachi, Ltd. Hitachi Ltd. Mechanical Research Laboratory (72) Inventor Takeo Nemoto 502 Jinrachicho, Tsuchiura City, Ibaraki Prefecture Hitachi Mechanical Research Laboratory (56) Reference JP-A-60-159383 (JP, A) JP-A-59- 60081 (JP, A) JP-A-60-249678 (JP, A)

Claims (13)

(57) [Claims] 1. A cryopump comprising: a cryopanel cooled to an extremely low temperature for condensing and adsorbing gas molecules; and a radiant heat shield plate cooled to a low temperature for protecting the cryopanel from a radiant heat of a high temperature. The plates are arranged in a plurality of rows so that the shield surface is substantially parallel to the gas molecule cryopump inlet surface, and the shield plates are arranged in the same row in the depth direction of the cry pump in substantially the same width in multiple stages. The cryopump is characterized in that the cryopanels are arranged in a direction opposite to the molecular inlet surface of each shield plate, and the shield plate is formed by bending on the side surface side of the cryopanel. . 2. A cryopump provided with a cryopanel cooled to an extremely low temperature for condensing and adsorbing gas molecules, and a radiant heat shield plate cooled to a low temperature for protecting the cryopanel from radiant heat of a high temperature. Plates are arranged in multiple stages such that the shield surface is substantially parallel to the gas molecule cryopump inlet surface, and the cryopanels are arranged in the opposite direction to the molecular inlet surface of each shield plate, Further, the cryopump is formed by bending the shield plate on a side surface side of the cryopanel. 3. A cryopump provided with a cryopanel cooled to an extremely low temperature for condensing and adsorbing gas molecules, and a radiant heat shield plate cooled to a low temperature for protecting the cryopanel from radiant heat of a high temperature. The plates are arranged in multiple rows in multiple rows so that the shield surface is substantially parallel to the gas molecule cryopump inlet surface, and a single wall is provided without partition walls between the groups of shield plates. The cryopump is characterized in that the cryopanels are arranged in a direction opposite to the molecular inlet surface of each shield plate, and the shield plate is formed by bending on the side surface side of the cryopanel. . 4. A partition plate is arranged on the gas inlet side of at least a part of the plurality of radiant heat shield plates,
The cryopump according to any one of claims 1 to 3, wherein each partition plate is arranged so as to form a gap between the partition plate and the cryopanel of the preceding stage. 5. The cryopump according to any one of claims 1 to 4, wherein each of the cryopanels is formed in a corrugated plate shape. 6. The cryopump according to claim 1, wherein each cryopanel comprises a pipe and a plurality of panel members. 7. The cryopump according to claim 6, wherein the pipe is a member having a larger electric resistance than the panel member. 8. The cryopump according to any one of claims 1 to 7, wherein an adsorbent is applied to the cryopanel. 9. The cryopump according to claim 6, wherein an adsorbent is attached to the panel member. 10. The cryopump according to claim 9, wherein an adsorbent embedding liquid is previously attached to each panel member. 11. The adsorbent panel according to claim 1, wherein an adsorbent is attached to the cryopanel or another panel provided on the back surface of the panel member to provide an adsorbent. Cryo pump. 12. The cryopump according to any one of claims 1 to 7, wherein an adsorbent is thermally integrated with at least a part of the bent surface of the cryopanel. 13. The cryopanel comprises a cooling pipe having a large electric resistance value and a panel segment group having a small electric resistance value which is thermally integrated with the cooling pipe so that the respective segments do not come into direct contact with each other. The cryopump according to any one of claims 1 to 12, wherein the cryopump is arranged.