Patent ID: 8258492

Claim:
A differential evacuation system comprising: a light generation chamber that generates EUV (Extreme Ultra Violet) light; an illumination optical chamber in which optical processing is performed by using the EUV light; a light converging mirror arranged in the light generation chamber and converging the EUV light thus generated; a chamber connecting passage that connects together the light generation chamber and the illumination optical chamber to allow the EUV light to pass therethrough; an optical element arranged in the illumination optical chamber and reflecting the EUV light that has passed through the chamber connecting passage; a flow path constricting portion provided in the chamber connecting passage and obstructing a gas to pass therethrough; said flow path constriction portion with a smallest inner diameter and being increased in inner diameter in a conical tube shape at portions thereof that are at opposite sides, respectively, of said flow path constriction portion; and one or a plurality of vacuum pumps disposed in a position closer to the light generation chamber than the flow path constricting portion and evacuating the chamber connecting passage.