Abstract: The invention relates to a measurement system for a projection system of a lithographic apparatus, comprising: —a sensor plate; —a detector comprising an array of detector areas; —a randomly ordered optical fiber bundle; —a positioner to position the sensor plate in the projection system; and —a control unit to control the positioning of the sensor plate and to obtain measurement data from an output of the detector, wherein a first free end of the optical fiber bundle is arranged to receive light from the sensor plate, wherein a second free end of the optical fiber bundle opposite the first free end of the optical fiber bundle is aligned with the array of detector areas of the detector, and wherein the control unit is configured to match each detector area with a corresponding location in a pupil plane of the projection system by collecting measurement data corresponding to different positions of the sensor plate relative to the projection system.

Abstract: A patterning device support (1100) for controlling a temperature of a patterning device (1102) can include a movable component (1104). The movable component can include a gas inlet (1108) for supplying a gas flow across a surface of the patterning device and a gas outlet (1110) for extracting the gas flow. The patterning device support can also include a gas flow generator (1118) coupled to a duct (1114, 1116) for recirculating the gas flow from the gas outlet to the gas inlet.