A radiation source is configured to produce extreme ultraviolet radiation. The radiation source includes a chamber in which, in use, a plasma is generated, and an evaporation surface configured to evaporate a material formed as a by-product from the plasma and that is emitted to the evaporation surface. A method for removing a by-product material in or from a plasma radiation source of a lithographic apparatus includes evaporating a material which, in use, is emitted to that surface from the plasma.