A lithographic apparatus includes a radiation system including a radiation source for the production of a radiation beam, and a contaminant trap arranged in a path of the radiation beam. The contaminant trap includes a plurality of foils or plates defining channels which are arranged substantially parallel to the direction of propagation of said radiation beam. The foils or plates are oriented substantially radially with respect to an optical axis of the radiation beam. The contaminant trap is provided with a gas injector which is configured to inject gas at least at two different positions directly into at least one of the channels of the contaminant trap.