AN OPTIMALLY STAGED CRYOPUMP

摘要

A cryopump having at least two temperature stages (20, 32) for pumping gases at their optimal temperatures. A first embodiment has a third temperature stage (36) that is surrounded by and separated from the second temperature stage (32) which is surrounded by and separated from the first temperature stage (20). Adsorbent (34, 36) placed on the second and third stages are operated at different temperatures to prevent gases with higher critical mobility temperatures from becoming immobilized at the entrance of pores and wells along the surface of the adsorbent. Another embodiment has at least a second stage (32), a temperature sensor (46), and a heater (44) to maintain the second stage (32) temperature at the optimal level for the gas being pumped.