Abstract: Method for regenerating a surface of an optical element in a radiation source for electromagnetic radiation with a wavelength in the extreme ultraviolet wavelength range, H (EUV, XUV) in particular with a wavelength in the wavelength range between 10 nm and 15 nm, this radiation source comprising at least a chamber for arranging therein a plasma generating XUV or EUV radiation and the optical element, in particular a collector for bundling XUV or EUV radiation generated by the plasma and causing it to exit the chamber, according to which method a first Si, C or metal compound is arranged in the chamber which reacts in an equilibrium reaction with the material of the surface of the collector to form respectively a second Si, C or metal compound bonded to this surface, and XUV or EUV radiation source adapted for such a method.