An extreme ultraviolet light (EUL) source device is disclosed, the device comprising: a chamber in which a gas flow and a droplet stream are provided; a droplet generator through which target material is changed into the droplet stream; and a shroud positioned along the droplet stream, the shroud shielding the droplet stream from the gas flow, wherein the droplet stream is irradiated by laser to produce plasma and generate an extreme ultraviolet light. The shroud includes flow guide surface features that guide accumulated target material away from a collector mirror that reflects and focuses the EUL.