Theoretical consideration for the outgassing characteristics of an unbaked vacuum system

Recently the outgassing rate of an unbaked vacuum chamber has been measured with a variable orifice pumping by the author, and it has been shown that the outgassing rate q obeys the power law of pumping time t as q = qO(t1/t)X, 0.8 < x < 1.1 and the initial outgassing rate qO is dependent on the pumping speed S of orifice as qO ∝ Sm, 0 < m < 1. This paper describes the theoretical verification for the outgassing characteristics in the light of adsorption - desorption of molecules on the wall surface and the pump-down of gas phase molecules out of the chamber. (author)