Patent Number: 
Section: abstract

An optical collector (15) for collecting extreme ultraviolet radiation or EUV light generated at a central EUV production site comprises a reflective shell (25). To cope with thermal loading of the collector and avoid deformations, the reflective shell (25) is mounted on a support structure (24), such that a cooling channel (29) is established between the back side of the reflective shell (25) and the support structure (24), the thickness of the reflective shell (25) is substantially reduced, such that the convective heat transfer between the back side of the reflective shell (25) and a cooling medium (26) flowing through the cooling channel (29) dominates the process of removing heat from the reflective shell (25) with respect to heat conduction, and a cooling circuit (33) is connected to the cooling channel (29); to supply a cooling medium (26) to the cooling channel (29) with a controlled coolant pressure and/or mass flow.