Apparatus having a chamber with an interior wall and a region within the chamber from which a contaminating material emanates when the apparatus is in operation. A plurality of vanes is positioned on a portion of the interior wall, each of the vanes having a first surface which is oriented along a direction between the vane and the region and a second surface adjacent the first surface which is oriented to deflect the contaminating material striking the second surface away from the region, the second surfaces being dimensioned and juxtaposed with respect to one another such that the second surfaces substantially prevent the contaminating material from striking the portion of the interior wall. At least part of each of the vanes may be covered with a mesh. The vanes may be heated, and may be heated at least to a melting point of the contaminating material. The apparatus is especially applicable to protecting multilayer mirrors serving as collectors in systems for generating EUV light for use in semiconductor photolithography.
