Vacuum pumps, capture adsorption

Adsorption pump, vacuum (vacuum technology) A capture-type vacuum pump that pumps by cryocondensation or cryotrapping on a surface of temperature less than — 150°C. See also Vacuum pump. 

Vacuum pump, cryopump A capture-type pump that operates by condensation and/or adsorption on cold surfaces. Typically there are several stages of cold surfaces and one of the stages will have a temperature below 120 K. See also Cryopanel Cryosorption pump. 

Vacuum pump, sorption pump A capture-type vacuum pump that operates by cryocon-densation of gases on a large-adsorption-area, cryogenically cooled (< — 150°C) surface. 

To pump out larger vessels, several adsorption pumps are used in parallel or in series. First, the pressure is reduced from atmospheric pressure to a few millibars by the first stage in order to capture many noble gas molecules of helium and neon. After the pumps of this stage have been saturated, the valves to these pumps are closed and a previously closed valve to a further adsorption pump still containing clean adsorbent is opened so that this pump may pump down the vacuum chamber to the next lower pressure level. This procedure can be continued until the ultimate pressure cannot be further improved by adding further clean adsorption pumps. 

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