Initial Study of the Effect of Cryosurface Geometry on Cryopumping

Abstract

An experimental study of cryogenic pumping using siEveral cryosurfaces in the pressure ranges of 10-4 and 1C-3 mm Hg is presented. At these pressures, where the mean free path of the condensable gas is on the order of the cryosurface dimensions, it is shown that the pumping rate is no longer a constant as it is in free-molecular flow, but increases through what is terme.d the transition range and presumably approaches a higher constant value in the continum flow regime. Flow in the gas kinetic, gas dynamic, and transition regimes is discussed.Experimental results are presented showing the effects on cryopumping of the addition of fins or ribs to a cryosurface, and the effect of pumping with parallel cryosurfaces at different separations.ii