Patent Number: 
Section: claims

1. 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; anda 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; andthe 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. 2. A gas discharge source as claimed in claim 1, wherein the gas pressure in a part-area of the gas-filled intermediate electrode space defined by the diaphragm and the second electrode is greater than in a part-area of the gas-filled intermediate electrode space defined by the diaphragm and the first electrode. 3. A gas discharge source as claimed in claim 1, wherein at least a portion of the diaphragm comprises a ceramic material. 4. A gas discharge source as claimed in claim 1, wherein the diaphragm comprises a discharge-resistant material adjacent the discharge opening. 5. A gas discharge source as claimed in claim 1, wherein the diaphragm comprises multiple metallic diaphragms and multiple isolators for separating the diaphragms. 6. A gas discharge source as claimed in claim 1, wherein, along the axis of symmetry, the diaphragm extends between 1 mm and 20 mm. 7. A gas discharge source as claimed in claim 1, wherein the opening of the diaphragm has a diameter between 4 mm and 20 mm. 8. A gas discharge source as claimed in claim 1, wherein the first electrode gas inlet has a first opening facing toward a first part-area of the intermediate electrode space defined by the diaphragm and by the first electrode, wherein the second electrode gas inlet has an opening facing toward a second part-area of the intermediate electrode space defined by the diaphragm and by the second electrode. 9. A gas discharge source as claimed in claim 8, wherein the intermediate electrode space is adapted for containing a working gas used for the gas discharge and at least one further filler gas exhibiting lower radiation losses than the working gas. 10. A gas discharge source as claimed in claim 9, wherein the first part-area contains a greater proportion of the working gas than the filler gas, and the second part-area contains a greater proportion of the filler gas than the working gas. 11. A gas discharge source as claimed in claim 1, wherein the first electrode opening is adapted for evacuation of the intermediate electrode space (3). 12. A gas discharge source as claimed in claim 1, wherein the second electrode comprises a cathode. 13. A gas discharge source as claimed in claim 1, wherein a spacing and a gas pressure between the first and the second electrode are selected such that the gas discharge takes place on a left branch of a Paschen curve.