DEVELOPMENT OF A BAKEABLE CRYOPUMP FOR EXTREME HIGH-VACUUM

For the production of extreme high vacuum with a cryopump we have developed a new cryopump/refrigerator system in which the refrigerator is separated from the cryopanel housing to keep its cold head below 70-degrees-C during 200-degrees-C bakeout. The cryopanels are cooled by circulating helium gas from a two-stage refrigerator. For a stainless steel test dome polished by electro-chemical buffering technique, the lowest total pressures attained were 5.3 X 10(-8) Pa before bakeout, and less than 6 X 10(-9) Pa after 30 h bakeout at 130-degrees-C.