Patent ID: 7734014

Claim:
A gas discharge source for generating extreme ultraviolet and/or soft X-radiation, comprising: a first electrode having an opening therein defining an axis of symmetry and providing an outlet for a discharge of radiation; a second electrode comprising a hollow electrode substantially completely surrounding a cavity save for an opening therethrough positioned along the axis of symmetry, the second electrode opening facing the first electrode; and a diaphragm positioned between the first and the second electrode and having an opening positioned along the axis of symmetry, the diaphragm acting as a differential pump stage, a space between the diaphragm and the first and the second electrode comprising an intermediate electrode space adapted for being filled with a gas, wherein: the first electrode has a gas inlet leading into the intermediate electrode space from exterior the first electrode; and the second electrode has a gas inlet leading into the intermediate electrode space from exterior the second electrode, the second electrode gas inlet not in direct fluid communication with the cavity.