ИСТИНА

PROBLEM TO BE SOLVED: To provide a method for cleaning elements of a lithographic device, for example, optical elements such as a collector mirror. ; SOLUTION: The method for cleaning the elements includes the steps of: providing a gas 155 containing nitrogen; generating nitrogen radicals from at least a part of the gas, thereby forming a radical containing gas 165; and providing at least a part of the radical containing gas to the one or more elements 100 of the apparatus. The lithographic apparatus includes a source and an optical element 100, and an electrical discharge generator 200 arranged so as to generate a radio frequency discharge.