Vacuum systems

Abstract

An evacuation process from atmospheric pressure to an extremely low pressure involves four stages: Removal of volume gas in a vacuum chamber, outgassing of gas adsorbed on the chamber surface, release of gas diffused to the surface from the inside of the chamber wall, and release of hydrogen gas permeated through the chamber wall. These stages are explained numerically to help understand the evacuation process. Mathematical descriptions of pumping time at the first stage of evacuation are presented using a tube between a vacuum chamber and a vacuum pump and also without using a tube. The tube can be ignored in the design of a vacuum system if its conductance is large. This will help readers in designing a vacuum system according to their own conditions.