Vacuum system for immersion photolithography

A vacuum system for extracting a stream of a multi-phase fluid from a photolithography tool comprises a pumping arrangement for drawing the fluid from the tool, and an extraction tank located upstream from the pumping arrangement for separating the fluid drawn from the tool into gas and liquid phases. The pumping arrangement comprises a first pump for extracting gas from the tank, and a second pump for extracting liquid from the tank. In order to minimize any pressure fluctuations transmitted from the vacuum system back to the fluid within the tool, a pressure control system maintains a substantially constant pressure in the tank by regulating the amounts of liquid and gas within the tank.