Patent ID: 8632194

Claim:
A system having an optical path along which EUV radiation passes through the system during use of the system, the system comprising: an optical mirror comprising a substrate supporting a surface, the surface comprising a reflective surface and/or diffractive surface, the surface being in the optical path along which EUV radition passes through the system during use of the system; a heating device configured to heat the optical mirror; and a radiational cooling element configured to cool the optical mirror by radiation heat transfer, wherein: the optical mirror is configured so that, during use of the system, the optical mirror receives heat from the heating device while the surface is in the optical path along which the EUV radiation passes through the system; the heating device is configured to heat a mirror heat transfer area of the optical mirror; the radiational cooling element is configured to receive thermal radiation from the mirror heat transfer area; and the mirror heat transfer area is selected from the group consisting of an area substantially arranged at a periphery of the optical mirror and an area substantially facing a rear surface of the substrate of the optical mirror.