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Equipment

  " VACUUM & CRYOGENIC  SYSTEMS"

("VACRIS" Co. Ltd)

Ultra-high Vacuum Systems with Cryopumps 

            Scientific production company " VACUUM & CRYOGENIC  SYSTEMS"  ("VACRYS" Co. Ltd) has designed and produces several modifications of ultra high vacuum units, consists of: cryogenic filling pumps in which liquid or solid nitrogen or liquid helium are used as cryogenic media, and also angle valves with metallic seal, ultra high vacuum chambers with special coatings giving possibility to receive pressure 10-8 Pa without heat these chambers.  

         Purpose and Application 

             The cryopumps developed allow solving many problems of evacuation and long autonomous support of ultra-clean oil-free vacuum with operating pressures between 105 to 10-11 Pa when pumping the chambers of 10-3 to 102 m3.

             Most efficiently these pumps are used in vacuum systems of wide application and research instrument systems, e.g. for pumping the systems used for the surface analysis of solids materials, molecular beam epitaxy, ion lithography, various mass spectrometers, monocrystal growing systems, super pure materials, industrial production of electronics elements and semiconductor materials, for pumping out plasma-chemical devices, charged-particle accelerator chambers space simulation chambers, thermonuclear installations and other systems used in the vacuum industry. 

           Merits of Cryosystems

 1.High specific pumping speed.

 2. Wide range of working pressures.

 3. Low specific consumption of cryogenic agents.

 4. Easy and economic maintenance.

 5. No moving parts, vibration, magnetic and electric fields, high voltage.  

 6. Full independence of power, water and pneumatic supply.       

 7. No need in heat regeneration.         

 8. Super pure hydrocarbon-free residual gas content.                              

 9. Low specific metal content.                                                                                                                                                 

10. High reliability in operation providing at last 10-year warranty life. 

Modifications of Cryosystems 

          Cryosystems with Sorption Cryopumps cooled by Liquid Nitrogen 

             The cryosystems are mainly intended to provide oil-free fore-vacuum within the pressure range of 105 - 10-1 Pa, or 102 - 10-5 Pa. 

Design Features 

             Units consist of cryogenic pool pump in which liquid nitrogen is used as cryogenic media, angle valves NW 16, NW 40, NW 63, NW  100 with metallic sea, pressure sensors with measuring range from 105 to 10-1 and from 10-1 to 10-8 Pa.

            The pumps incorporate a sorbing element cooled by cyogenic medium contained in a vessel, a housing which envelopes the sorbing  element arranged with a gap, a floating screen located within the gap. The sorbing element consists of heat lines, activated carbon used as an adsorber and a porous gas permeable screen efficiently  protecting the chamber to be evacuated from adsorbent dust. Pocket with adsorbent in cavity gap is situated on liquid nitrogen vessel. Once in a few years the security vacuum cavity is pumped to pressure 100 - 40 Pa via the valve NW 16 with metallic seal. After the vessel is filled with liquid nitrogen its own protecting vacuum is formed in the cavity of the gap with the pressure below 10-4 Pa, which is independent on the admission pressure. The vessel with a cryogenic medium incorporates also a built-in adequately conductive and optically dense tube which can be used, if necessary, as a permanently cold oil-vapour trap of the fore-vacuum mechanical pump. For that purpose, one end of the tube can be connected to the fore-vacuum mechanical pump, the other end through a valve - to the evacuated chamber. Where necessary, such assembly can be used for oil-free fore evacuation of the chamber from pressures of 105 - 102 down to pressures of 1 Pa and under. Two modifications of the pumps have been developed, namely: with 63 mm and 100 mm bore joint flanges. They are capable of operating with an inlet either directed upwards or downwards. Their main characteristics are given in the table. 

Cryosystems with Sorption Cryopumps cooled by Solid Nitrogen 

               The cryosystems are mainly intended for pumping out vacuum deposition units, magnetron sputtering units, plasma and chemical plasma cells with a high gas load (to 50 m3.Pa/s) of any gases other then helium but including active and corrosive gases, within a wide range of working pressures (102 - 10-6 Pa). Units with cryopumps cooled by solid or liquid nitrogen have no prototypes in the world practice.

 Design Features 

           Units consist of cryogenic pool pump cooled by solid nitrogen, angle valves NW 16, NW 40, NW 63, NW 100 with metallic seal  pressure sensors. The pump incorporates a sorbing element which is similar in its design to that used in the pump of the above modification but cooled by vessel with nitrogen whose temperature is reduced down to 50 ± 5 K by means of pumping off vapours of first liquid and then of solidified nitrogen. The outer surface of the sorbing element and the vessel with solid nitrogen which cools the element is surrounded by a screen cooled by another vessel containing liquid nitrogen at a temperature 77,4 K. As in the above modification, arranged inside the vessel is an oil-vapour trap of the fore-vacuum mechanical pump. The nitrogen consumption from the sorbing element vessel is approximately by an order less than from the screen cooling vessel. Three modifications of the pumps are available, with NW 100, NW 250, NW 400 joint flanges located on the top the pump with the next pumping speed - 0,2 , 1 and 5 m3/s. Their main characteristics are given in the table. 

Cryosystems with Condensation Sorption Cryopumps

          Cooled by Liquid Helium 

             Units consist of condensation sorption pool cryopump cooling by liquid helium, sorption cryopump cooling by liquid nitrogen (NW 63) for previous evacuation of working chambers and vessel of helium cryopump for the first startup angle valves NW 16 and NW 63 with metallic seal, pressure sensors with measuring range from 105 to 10-1 Pa and from 10-1 to 10-11 Pa. These are single pumping means, which have the lowest limit pressures (under 10-11Pa). They are particularly efficient in precision research. They have the highest specific pumping speed and are capable of pumping all gases including hydrogen and helium in the condensation sorption regime. The optimum application is for operation pressures between 10-5 to 10-10 Pa.  

Design Features 

             The pump incorporates a vessel filled with liquid helium. The part of the vessel surface (usually its bottom or cover) is used for pumping. The vessel surface is covered by a screen which is cooled by a vessel filled with liquid nitrogen. A part of the screen on the side of the pumping surface is made as a herringbone black screen. The pumping element with the screen is arranged in its own housing which has a joint flange in its upper or lower part on the side of the herringbone screen. The surfaces of the pump assemblies facing the vacuum gap are carefully polished and coated by a film with very low emissivity factor (down to 2.10-3 - 6.10-4 at T=4,2 K), due to which the pumps have the lowest specific evaporation rate of cryoagents (under 0,1 litre/day of  He per each 1 m3/s of the pumping speed). In addition to the traditional designs of helium cryopumps with flatly parallel arrangement of herringbone screen and pumping surfaces, cryopumps with a so-called enveloped pumping zone have been developed, these pumps having trapping efficiency on Hand He equal to 1,7 and 3,1 times more, respectively, comparing to the efficiencies of traditionally designed pumps having the same casing diameter. The pumps with the enveloped pumping zone have no analogs in world practice. Most efficient helium cryopumps with enveloped pumping zone are used in monocrystals  growing systems, proton accelerators, thermonuclear devices, space simulation chambers.There have been developed eight modifications with pumping speeds for N2, H2 and He from 0,2 to 10 m3/s, from 0,5 to 30 m3/s and from 0,2 to 20 m3/s, respectively. Five of cryopumps are provided with joint flanges arranged at the bottom and three at the top. The cryopumps are made of titanium and aluminum and have the lowest possible specific weight, from 30 to 6 kg on 1 m3/s pumping speed.

           Main characteristics are summarized in the table.

          Patents have been obtained for the pumps of all three types in a number of countries.

         In order to attain ultimate pressure without heating of units and reduce gas desorption from surface ~ 104 times and order to get chemical protection from aggressive gases, all elements of units from vacuum side are covered by special films according to specific technology.   

PRIMING CRYOPUMPS COOLED BY LIQUID AND SOLID CRYOGENIC AGENTS  

 

 

Parameters of cryopumps

Sorption pumps

Condensation sorption pumps cooled by liquid He

Cooled by liquid N2

Cooled by solid N2

With bottom-located connection flange

With top-located connection flange

1.

Connection flange NW, mm

63

100

100

250

400

100

160

250

400

630

100

250

400

2.

Pumping speed for N2, m3/s

0,06

0,25

0,20

1

5

0,2

0,5

2,5

5,0

10

0,5

2,0

4,0

3.

Ultimate pressure, Pa

3.10-5

5.10-7

10-11

4.

Operation pressure range, Pa

105 - 10-4

102 - 10-6

10-4 - 10-10

5.

Cryoagent consumption

                

liquid N2, l/day

1,1

 2,4

2,5

8,0

 20

1,2

4

 7

14

20

 5

 8

16

solid N2 , l/day

0,1

0,3

0,8

-

liquid He, l/day

                        -

0,05

0,07

0,2

0,5

1,0

0,08

0,3

0,6

6.

Holding time for

liquid N2, hours

65

100

95

75

80

65

65

72

75

80

65

70

75

solid N2, days

-

30

25

30

-

liquid He, monthes

                        -

1

3

7.

Sorption capacity for Ar, N2 at  Pw=10-3 Pa, m3.Pa

600

2.103

4.104

1.105

5.105

-

8.

Operation temperature, K

77,4 ±  0.3

50 ± 5

4,2 - 1,5

9.

Regeneration temperature, oC

20 ± 10

10.

Overall dimensions, mm height casing diameter

420

490

700

780

1000

450

800

700

700

900

800

700

700

180

350

300

480

800

160

250

400

650

800

300

480

650

11.

Weight, kg

12

28

32

80

100

7

16

25

40

60

20

30

50

12.

Price (2008), thousand Euro

5

9

11

15

36

8

12

15

22

28

14

18

26

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  For additional information about unit parameters, conditions of usage, application, time of manufacturing and delivery, cost and other information, please contact us.

                                         General director                 M. Larin

 

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