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Cryopump

A vacuum cryopump typically consists of a vacuum-tight vessel with a valved inlet, containing a highly absorbent material such as a synthetic zeolite microporous on the scale of 1 to 10 Å (Angstrom units), and an enclosing cryogenic vessel. In industrial cryopumps, the vessel will typically be a Dewar flask, but homespun sorption pumps may be as simple as a labglass flask of zeolite in a styrofoam cooler filled with liquid nitrogen.

Sorption pumps are often used as roughing pumps to reduce pressures from the range of atmospheric to on the order of 10-3 torr, while lower pressures are achieved using a finishing pump (q.v. vacuum). As the sorbent saturates, the effectiveness of a sorption pump decreases, but can be recharged by heating the zeolite material (preferrably under conditions of low pressure) to a temperature near but below the breakdown point of the zeolite material's porous structure.



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