DE2455712A1 - Cryogenic adsorption vacuum pump - has metal plates with adsorbent lacquer within insulated casing shielded from radiation - Google Patents

Abstract

The pump has a cylindrical casing with flanges at both ends. It is connected to a first stage pump by one of the flanges, and contains a number of metal plates arranged to form a pyramid like shape. The plates are made of a good conductor such as silver, copper or aluminium and are sprayed or painted with a lacquer of adsorbent material such as aluminium oxide. The mechanical and thermal properties of this arrangement enable very low pressures to be achieved at higher temperatures than has previously been possible. The pump also contains a liquid nitrogen reservoir which is connected to the lacquered metal plates to chill them and contains radiation shields protecting the plates from heat gain.

Description

Cryo-sorption pump The invention relates to a cryo-sorption pump for a vacuum systems. Such pumps are particularly suitable for achieving propellant-free Residual gas atmospheres in vacuum and UHV technology, in particular, they enable the generation of extremely low residual gas pressures.

In the case of cryo-sorption pumps, the behavior of sorbents such as aluminum oxide (zeolite) or activated carbon exploited at low temperatures to increase their adsorptive capacity considerably. With this it is possible to reduce the pressure in pre-evacuated vacuum vessels from about 10 2 to 10 3 Torr to values below i0-8 Degrade torr. In the previous systems, therefore, these sorbents in the form of small grains with a possibly for better heat conduction with copper powder mixed adhesive applied to coolable metal surfaces. The disadvantages this method is that the production of the sorption surface is very time consuming and cumbersome and that the thermal coupling of the sorbent to the cooling surface is by no means optimal. These pumps are therefore usually only used at temperatures operated from about 10 to 20 0K.

The invention is based on the object of a manufacturing method indicate for the sorption surfaces that these Does not have any disadvantages and to describe a pump arrangement which can also be used at higher temperatures (e.g. 77 0K) -6 provides a usable final pressure of 10 Torr to 10 7 Torr.

This object is achieved according to the invention in that the sorption surfaces by coating with a sorption varnish (Pat. No. P 24 51 717.7). Due to the excellent adhesive strength of this varnish, even at low temperatures and due to its good thermal properties and high sorption capacity are the achievable final pressures at a temperature of 77 0K between 10 5 Torr and 10 7 Torr and at a temperature of 10 to 200K below 10-8 Torr.

The advantages achieved by the invention are, in particular, that the production of the sorption surfaces is very simple, since the paint is dipped, Spraying or brushing can be applied to any surface.

Finally, there is the mechanical and thermal coupling of the paint on the base so well that the sorption capacity is sufficient at approx. 77 ° K, to achieve oil-free pressures of 1 x 10 Torr and lower. With further cooling of the adsorber with a commercially available refrigerator to 10 to 20 0K are final pressures scored below 10 8 torr.

The cryopump effect of the sorption varnish makes it possible in particular to keep the residual gas pressure in evacuated containers low. It is also possible by coating liquid nitrogen cold traps with the sorption varnish Manufacture cryo-sorption pumps that guarantee oil-free ultimate vacuums in the 10 6 Torr range.

An embodiment of the invention is shown in FIG.

and is explained in more detail below.

The actual cryo-sorption pump is located in a cylinder-shaped one Flanged vessel (1) made of a suitable material on the front sides, preferably VA steel. For connection to a backing pump, this has Outer vessel a flange (9). With a radiation shield cooled by a bar (6) (3) and an optically tight, cooled baffle (17) are the cryo-sorption surfaces (16) shielded from the outside against thermal radiation. For cooling they come with a liquid nitrogen storage vessel (15) connected. To enlarge the sorption areas are both the outer walls of the liquid nitrogen vessel (15) and the baffle holding cylinder (2) and the baffle (17) itself coated with sorption varnish. To achieve a good pumping effect, it is advantageous if these parts consist of a well-thermally conductive Material like silver, copper, aluminum or special alloys are made. The volume of the adsorber can be determined by suitable shaping of the cryo-sorption surfaces vary within wide limits. One embodiment is a pyramidal layer on top of one another of metal plates that are detachably or permanently connected to one another.

To enlarge the surface, you can also use one-sided instead closed hollow cylinders are plugged into one another.

Suitable materials for making the sorption surfaces are good thermally conductive metals such as silver, copper, aluminum or special alloys.

If the cryo-sorption pump is to work at temperatures below 770K, a commercially available refrigerator can be used with the aid of an opening in the base plate (10) (11) to which the cryo-sorption surface (16) is now attached. Liquid nitrogen container (15), holding cylinder (2) and baffle (17) take over in In this case, in addition to their sorption capacity for gases, especially oil vapor> still the task of a radiation shield (770K). If the cooling capacity of the Refrigerators can dispense with the liquid nitrogen storage vessel and the entire outer part of the refrigerator either by conduction or via Thermal radiation can be cooled. Here comes the special property of the "carbon sorption varnish" comes into its own, in addition to its sorption capacity for gases, it also has a high emission factor to own for thermal radiation. For operation, the pump is switched on with the splash (1) connected to a recipient 0

Claims (11)

X a t e n t a n s p r ü c h e W Oryo sorption pump d a d u r c h gek e n n -z e i c h n e t that the coolable adsorber surfaces (16) are optically sealed and protected by a radiation shield (3) in one provided with splashing cylindrical vessel (1) made of metal or another suitable material, which is closed on one side and with the open side to a vacuum recipient can be flanged. 2. Cryo-sorption pump according to claim 1, d a d u r c h g e k e n n show that the adsorber surface (16) consists of a number of suitably shaped, For example, pyramid-shaped, detachable or firmly seated plates or Hollow cylinders sitting inside one another, which are open on one side, are coated with sorption varnish are coated. 3. Cryo-sorption pump according to one of the preceding claims, d a d u r c h e k e n n n z e i c h n e t that the connection to a recipient the open side of the vessel serving is optically sealed by a baffle (17), which is also coated with sorption varnish and cooled. 4. Cryo-sorption pump according to one of the preceding claims, d a d u r c h g e k e n n n z e i c h n e t that the cooling of the adsorber surface is carried out Attachment to a storage vessel for liquid nitrogen (15) is made possible, which is also coated with sorption varnish and to reduce radiation losses is surrounded by a radiation shield (3). 5. cryo-sorption pump according to one of the preceding claims, d a d u r c h e k e n n n z e i c h n e t that to achieve lower temperatures and lower final pressures, the adsorber surface (16) also with a commercially available refrigerator (11) can be connected. 6. Gryo sorption pump according to one of the preceding claims, d a d u- r c h e k e n n n z e i c h n e t that the coating of the liquid nitrogen container (15), the outer cylinder (2) and the baffle (17) with carbon sorption lacquer are used to on the one hand to lower the reflection factors and on the other hand to lower the cryosorption surfaces for gases and oil vapors to increase. 7. cryo-sorption pump according to one of the preceding claims, d a d u r c h e k e k e n n n n z e i c h n e t that the pump body without the outer cylinder (1) Can be flanged directly to a vacuum container. 8. Oryo sorption pump according to one of the preceding claims, d a d u r c h e k e n n n z e i c h n e t that with a sufficiently high output of the refrigerator (11) Outer jacket (2) and baffle (17) of the pump arrangement through the refrigerator Thermal conduction or thermal radiation can be cooled sufficiently deep. 9. cryo-sorption pump according to one of the preceding claims, d a d u r c h e k e n n n z e i c h n e t. that the pumping action and propellant-free Vacuum also by coating a commercially available liquid nitrogen cold trap or a commercially available liquid nitrogen baffle with sorption varnish can. 10. Gryo sorption pump according to claim 9 or one of the preceding Claims that such cryo-sorption pumps in combination with a backing pump are suitable for cooling to 77 0K oil-free vacuums of 1 x 10 Torr and lower to achieve-. 11. Cryo-sorption pump according to one of the preceding claims, d a d u r c h g e k e n n n z e i c h n e t that by enlarging the sorption area these pumps are suitable for vacuum systems without the use of backing pumps from atmospheric pressure to evacuate.