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What is it exactly?
What does it do?
[edited by: defanjos at 6:52 pm (utc) on Oct. 5, 2002]
A vacuum pump in which pressure is reduced by condensing gases on surfaces maintained at about 20 K by means of liquid hydrogen or at 4 K by means of liquid helium. Pressures down to 10-8 mmHg (10-6 Pa) can be maintained; if they are used in conjunction with a diffusion pump, pressures as low as 10-15 mmHg (10-13 Pa) can be reached.