VACUUM PUMPING SYSTEM

摘要

The present invention relates to a vacuum pumping system (10) for evacuating a vacuum chamber (12), the system comprising: a vacuum pump (16); and a plurality of forelines (22, 24) for conveying gas to the vacuum pump wherein in a first low vacuum stage of chamber evacuation a first foreline arrangement (22) can be connected for conveying gas to the vacuum pump and in a second higher vacuum stage of chamber evacuation a second foreline arrangement (22, 24) comprising one or more of said forelines can be connected for conveying gas to the vacuum pump, wherein the second foreline arrangement has a total cross-sectional area for conveying fluid which is larger than a total cross-sectional area of the first foreline arrangement.