An extreme ultraviolet (EUV) source includes a source vessel enclosing at least in part a volume in which, when in use, EUV light is transmitted by a collector from a primary focus to an intermediate focus along an optical axis: a shaft, the shaft having a length extending from a first end to a second end of the shaft.Math.the shaft including a passage, the passage extending at least partially along the length of the shaft, the first end of the shaft attached to an interior surface of the source vessel and the second end positioned inside the source vessel; a head (130) connected to the second end of the shaft, the head intersecting the optical axis, the head having an exposed surface (134) exposed to the primary focus, the exposed surface having one or more apertures therein, the one or more apertures being in fluid communication with the passage.

An EUV light generation apparatus includes a chamber in which a target is irradiated with laser light, a light concentrating mirror reflecting EUV light toward an external apparatus, a differential exhaust chamber arranged on an optical path of the EUV light reflected by the light concentrating mirror, a gas supply port through which gas is supplied to a space between the differential exhaust chamber and the light concentrating mirror, a first partition wall having a gas inlet port through which the gas flows into the plasma generation region side from the light concentrating mirror side and through which the EUV light traveling from the plasma generation region toward the light concentrating mirror passes, a gas main exhaust port through which the gas is exhausted, and a constriction member allowing the EUV light to pass therethrough and constrict a gas flow from the gas supply port toward the gas inlet port.

An extreme ultraviolet light generation apparatus generating extreme ultraviolet light by irradiating a droplet with laser light includes a tank storing a target substance in a liquid state; a nozzle outputting the target substance stored in the tank; a piezoelectric element applying vibration reflecting an electric signal to the target substance to be output from the nozzle to generate the droplet of the target substance; a first sensor measuring a passage interval of the droplets output from the nozzle; a second sensor measuring a parameter related to the droplet; and a processor setting a prohibited band of a duty of the electric signal based on data in which the duty and the parameter at the duty are associated with each other, and setting the duty of the electric signal to be applied to the piezoelectric element while avoiding the prohibited band.