An EUV source for generating a beam of EUV radiation, has a droplet generator with a nozzle assembly to emit droplets of fuel from a nozzle towards a plasma formation location. The nozzle assembly receives the fuel from a reservoir. The nozzle assembly has a pump chamber receiving the fuel from the reservoir and an actuator to vibrate a membrane that forms a wall of the pump chamber. The wall is oriented perpendicularly to a direction wherein the nozzle emits the fuel. The nozzle assembly has first and second nozzle filters non-adjacently arranged in series in a path of the fuel from the pump chamber to the nozzle.