Modeling of outgassing or pumping functions of the constituent elements such as chamber walls and high-vacuum pumps

Chamber walls, subjected to ``in situʹʹ baking, sometimes show a pumping function for a high vacuum, while a highvacuum pump sometimes shows outgassing in an ultrahigh vacuum. Such functions of the system elements can be represented by the internal pressures PX. All the system elements, such as chamber walls, pumps, and pin holes through a pipe wall, can be replaced by a pressure generator with the internal pressure PX and the internal ¯ow impedance RX in the equivalent vacuum circuit. The internal pressure PX of the chamber wall varies depending on the wall history under high vacuum. The equivalent vacuum circuit composed of many characteristic values (PX, RX) and ¯ow impedances R can represent the gas ¯ows in the original high-vacuum system. # 2001 Elsevier Science B.V. All rights reserved.