On the Difference of Outgassing Rates Measured by the Pressure Rise and the Throughput Methods in An Unbaked Vacuum System

Abstract

When the ouutgassing rate of an unbaked vacuum chamber is measured by the pressure rise and the throughput methods, the difference between two outgassing rates is often observed. Why the different outgassing rates are measured by the two methods is discussed by referring the theoretical pumpdown model and the experimental results. It is shown that the disagreement between the measured outgassing rates may be caused by the dependence of water outgassing rate on pumping speed because of the reversible adsorption of water.