A debris trapping system for trapping debris particles released with the generation of radiation by a radiation source in a lithographic apparatus includes first and second sets of channels. Each channel of the first set enables radiation from a radiating source to propagate therethrough and has an inner wall for catching debris particles. The second set of channels is situated downstream of the first set with respect to a propagation direction of the radiation. Each channel of the second set enables radiation from the radiating source to also propagate therethrough and has an inner wall for catching debris particles. A gas supply and a gas exhaust are configured to provide between the first set and the second set of channels a gas flow having a net flow direction substantially across the propagation direction of the radiation from a radiating source.