A radiation system includes a contamination barrier, e.g., a foil trap, between a collector, for example a normal incidence collector, and a radiation source, such that radiation coming from the source passes the foil trap twice. The radiation passes the contamination barrier once before hitting the collector and a second time after reflection by the collector. The foil trap includes lamellas that are parallel to both the radiation coming from the light source, and to the radiation reflected by the collector. The radiation is thus not obstructed by the foil trap. In this way, a normal incidence collector, which is used with a plasma produced source, can be protected from debris coming from a EUV source.