This research disclosure relates lo a collector protection gas delivery syslem which is applicable to, but not limited to sources of EUV radiation such as used in conjunction with EUV lithographic scanners. Lithographic scanners, in particular EUV scanners, comprise a radiation source and a lithographic apparatus. The radiation source is configured to generate an extreme ultraviolet (EUV) radiation beam. The radiation source may be a type referred to as a laser produced plasma source. A laser, which may for example be a CO_2 laser, is arranged to deposit energy via a laser beam into a fuel, such as tin (Sn) which is provided from a fuel emitter. Although tin is most commonly used, any suitable fuel may be used. The fuel may for example be in liquid form, and may for example be a metal or alloy. Droplets of fuel are emitted from the fuel emitter and a laser is incident upon the fuel droplets which creates a plasma. Radiation, including EUV radiation, is emitted from the plasma during de-excitation and recombination of ions of the plasma.
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