Radiant heating source

A radiant source for heating a workpiece such as a semiconductor wafer includes a plurality of radiant heating elements, arranged in an array that is generally concentric about a source center axis. A reflector has a reflecting surface that bounds a cavity or channel that contains the heating elements, the reflector comprising walls that extend around the center axis and that are finished for reflecting radiant energy emitted by the heating elements to a region occupied by a wafer. The channel reflecting surfaces comprise at least a part of a plane and/or cylinder and/or a cone and/or a convex to the heating elements curved surface of revolution bordering or spanning two or more adjacent heating elements.