A Scheme of Initial Start of a Large Vacuum System with Sputter Ion Pump without Baking Procedure

An analysis on an initial start of an ion pump system is made, being taken into account the heat generation in the pump and temperature and time dependences of gas desorption rate of the chamber wall. In the starting process, the status of the system is represented as a point in \dotT-\ddotT plane. The relative position of the point with respect to the "marginal line", which is derived in the analysis, decides the sign of changing rate of pressure, \dotp, of the system.