There is provided a projection exposure system operable in a scanning mode
along a scanning direction. The projection exposure system includes a
collector that receives light having a wavelength .ltoreq.193 nm and
illuminates a region in a plane. The plane is defined by a local
coordinate system having a y-direction parallel to the scanning direction
and an x-direction perpendicular to the scanning direction. The collector
includes (a) a first mirror shell, (b) a second mirror shell within the
first mirror shell, and (c) a fastening device for fastening the first
and second mirror shells. The mirror shells are substantially rotational
symmetric about a common rotational axis. The fastening device has a
support spoke that extends in a radial direction of the mirror shells,
and the support spoke, when projected into the plane, yields a projection
that is non-parallel to the y-direction.