Abstract
Three types of cryopumping system using with a Claude cycle refrigerator (Cryogenerator), a Gifford-McMahon cycle refrigerator, and a liquid helium vessel (vertical and horizontal type) were constructed. The pump-down characteristics and the nitrogen-hydrogen trapping phenomena were investigated. The measured pumping speed of nitrogen, argon, and hydrogen were 3.8, 2.7, and 13.4 l/sec·cm2, respectively. These values were nearly equal to the caulated pumping speeds. The heat of condensation of nitrogen was estimated from the vaporization rate of liquid helium (or hydrogen) and the flow rate of introduced nitrogen gas.
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