ON THE EFFECT OF BAKEOUT FOR THE PUMPING SPEED DEPENDENCE OF OUTGASSING RATE IN A STAINLESS STEEL CHAMBER

摘要

In order to investigate the effect of bakeout on the dependence of outgassing rate on pumping speed in a vacuum system, the outgassing rates of a test chamber at room temperature without baking and after bakeout at 100 and 250 degrees C were measured as a function of pumping speed. The measuresd outgassing rate q(Torr . l/s . cm(2)) obeys power law q = C(SIA)(m) where C and m (0 < m < 1) are constants, S/A is the pumping parameter defined as the ratio of the pumping speed S(l)/s) and the surface area A(cm(2)) of the chamber, and the variable range of S/A is from 2.46 x 10(-5) to 1.26 x 10(-2) (l/s . cm(2). The obtained power laws at RT and 100 degrees C have two different exponents but that at 250 degrees has only one exponent. The experiment shows that the bakeout weakens the pumping speed dependence on outgassing rate. In addition the theoretical consideration for the effect suggests that the sticking probability of the wall plays an important role on the pumping speed dependence. Copyright (C) 1996 Elsevier Science Ltd. [References: 5]