Abstract
As a new type of actual-sized cryopump with high pumping speed, a parallel-louvre-blind type cryopump of a rectangular cross section with opening distance B, width C and depth D, is proposed and is produced as a trial pump unit designed as actual size. The influence of pump depth size ratio Rd(=D/B) and number of secondary cryopanels on the transmission Probability Pbc of the pump unit is calculated by Monte Carlo simulation, and the hydrogen pumping speed is measured by experiments. The following results are obtained. (1) The transmission probability of a cryopump designed with dimensional ratio of Rd=1.3 is calculated to be 0.66 at ratios of Rc(=β/C)=0.88, which means that hydrogen pumping speed of cryopumps of this size can attain 294 m3·s-1/m2 per opening area. (2) The real hydrogen pumping speed of the trial pump unit with 30 secondary cryopanels is measured as 295m3·s-1/m2.
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