Small cryopump.

Many cryopumps have been used to produce clean vacuum for LSI manufacturing equipment and experimental equipment of fusion reactor, etc. In this paper, the pumping principle of cryopump is described. A structure and operation of the cryopump with a closed-cycle refrigerator are also described. Recently, some types of cryopumps which are just suitable to the function of particular purposes have been developed. For examples of these cryopumps, cryopump for ultra high vacuum, cryopump with high pumping speed and cryopump for sputtering equipment are also introduced.