Reduced vacuum cryopump

摘要

A cryopump 20 for differentially pumping water vapor and inert gases from a work space comprising a two stage refrigerator 45 in which a radiation shield 32 substantially encloses a second stage cryopanel 40. The radiation shield 32 incorporates a baffle plate 34 which condenses higher condensing temperature gases and restricts passage of low condensing temperature gases through orifices 36 to the second stage cryopanel 40. Backside pumping ports 38 provide a flow path to the second stage refrigerator for residual gases within the cryopump 20. This creates a high vacuum within the cryopump and allows it to operate at maximum efficiency.