A lithographic apparatus comprising a projection system configured to project a patterned radiation beam to form an exposure area on a substrate, a cooling apparatus located in use above the substrate adjacent to the exposure area, the cooling apparatus being configured to remove heat from the substrate during use, a plasma vessel located below the cooling apparatus with its opening facing towards the cooling apparatus, and a gas supply for supplying gas to the plasma vessel and an aperture for receipt of a radiation beam. In use, supplied gas and a received radiation beam react to form a plasma within the plasma vessel that is directed towards a surface of the cooling apparatus which faces the opening of the plasma vessel.