Cryogenic Vacuum Pumping

Abstract

Cryogenically cooled baffles are now considered an integral part of space-simulation systems, and often serve as an important part of the pumping system. The design of such baffles requires a knowledge of their ability to cool and capture gas molecules colliding with the cold surface. This ability, in turn, depends upon the forces between the gas molecule and the bound surface molecule with which it collides, upon the rate of collisions with the surface, and upon the velocity energy difference between the two molecules. Surface coatings with interstices in the matrix structure may be used to cause a number of collisions to occur while the gas molecule is on the cooled surface, thus materially increasing the cooling and sticking probability.