Patent ID: 6987278

Claim:
A lithographic projection apparatus comprising: a radiation system constructed and arranged to supply a projection beam of radiation; a first object table for holding a mask; a second object table for holding a substrate; a projection system constructed and arranged to image an irradiated portion of the mask onto a target portion of the substrate; and a gas structure constructed and arranged to supply a substantially laminar flow of flushing gas across at least a part of a path of said projection beam to displace ambient air therefrom, said flushing gas being substantially non-absorbent of said radiation such that said substantially laminar flow of flushing gas traverses a substantially non-obstructed region in said projection apparatus, wherein said gas structure comprises: a supply of flushing gas, a gas flow regulator, an evacuator constructed and arranged to remove flushing gas from said part of said beam path, and a gas recovery system constructed and arranged to recover at least part of the flushing gas for further use in the apparatus.