Mirror for guiding a radiation beam

A mirror (8) serves to guide a radiation beam. The mirror (8) has a base body (21) and the reflectivity of the mirror (8) enhancing coating (22) a reflecting surface (19) of the base body (21). A heat sink (24) serves for the discharge of the coating (22) of deposited heat (23). The heat dissipation means (24) has at least one Peltier element (25). The coating (22) is directly applied to the Peltier element (25). A temperature setting device (20) has at least one temperature sensor (28) for a temperature of the reflecting surface (19). A control device (30) of the temperature setting device (30) is connectable to the at least one Peltier element (25) and communicating with the at least one temperature sensor (28) in signal communication. The result is a mirror in which a heat removal capacity of the heat sink is improved.