Patent ID: 8343429

Claim:
A target supply unit to be used in an extreme ultraviolet light source apparatus for generating extreme ultraviolet light by irradiating a target material with a laser beam to turn the target material into plasma, said target supply unit comprising: a target container configured to accommodate the target material; a target nozzle configured to inject the target material supplied from said target container; a reducing gas supply unit configured to supply a reducing gas into said target container; an exhaust pipe configured to exhaust a gas within said target container; a gas analysis unit configured to measure concentration of a reaction product of the reducing gas in said exhaust pipe to output a signal representing the concentration of the reaction product of the reducing gas; and a control unit configured to control said reducing as supply unit to stop supply of the reducing gas when the concentration of the reaction product of the reducing gas becomes not more than a predetermined value according to the signal outputted from said gas analysis unit.