The principle of pumping mechanism and basic construction for the cryopump cooled by a small refrigerator are described. Also some applications of the cryopump are described. Two-staged Gifford-McMahon cycle or modified Solvay cycle refrigerator are commonly used for the cryopump. The first stage cold station cools a baffle and a radiation shield which condenses water vapour and blocks thermal radiation to the cryopanel. The cryopanel cooled by the second stage cold station condenses most gases except neon, hydrogen and helium which are adsorbed by charcoal attached to the cryopanel. Pumping speed for a cryopanel is led from the statistical mechanics. An operating procedure based upon a typical cryopump system is also described.
