The invention is directed to a device for generating flows of gas for filtering the radiation emitted in plasma-based radiation sources. It is the object of the invention to find a novel possibility for generating a gas curtain in the immediate vicinity of a radiating plasma so as to permit a simple arrangement and design and a long life of the device for generating the gas curtain under extreme thermal stress. According to the invention, this object is met in that a slit nozzle is formed of a plurality of partial bodies comprising different materials to form a supersonic nozzle profile for the generation of a broad gas curtain in order to accommodate the slit nozzle to different thermal and precision-mechanical requirements in the gas inlet region and in the gas outlet region.