Free radicals that combine with debris that is created by converting a target mixture to plasma that emits EUV light are received at a first opening defined by a first end of a conduit, the conduit including a material that passes the free radicals and the conduit including a sidewall that extends away from the first opening and defines at least one other opening, the at least one other positioned to release the free radicals toward an element that accumulates the debris on a surface. The free radicals in the conduit are directed toward the at least one other opening. The free radicals are passed through the at least one other opening and to the surface of the element to remove the debris from the surface of the element without removing the element from the EUV light source.