Patent Number: 
Section: claims

1. An extreme ultraviolet light generating apparatus, comprising:a light collecting mirror that reflects and focuses extreme ultraviolet light; anda magnet that generates a magnetic field;the light collecting mirror including:a first mirror portion that includes a first reflective surface which is formed by a portion of a spheroidal surface; anda second mirror portion that includes a second reflective surface having a focal point at substantially the same position as a focal point of the first reflective surface, and is formed by a portion of a spheroid surface different from that of the first reflective surface, the second reflective surface being provided at a position at which a magnetic flux density caused by the magnetic field is lower than that of the first reflective surface. 2. An extreme ultraviolet light generating apparatus as defined in claim 1, further comprising:a chamber in which the extreme ultraviolet light is generated from plasma which is generated at a plasma generating region in the interior thereof,wherein the first and second mirror portions are provided within the chamber such that:the first and second reflective surfaces reflect the extreme ultraviolet light, and focus the extreme ultraviolet light at a predetermined focal point at a position farther from the first and second reflective surfaces than the plasma generating region;a first focal point of each of the first and second reflective surfaces is positioned at the plasma generating region, while a second focal point of each of the first and second reflective surfaces is positioned at the predetermined focal point; andthe second reflective surface is provided at a position at which the magnetic flux density is lower than that of the first reflective surface in a direction from the second focal point to the first focal point. 3. An extreme ultraviolet light generating apparatus as defined in claim 2, wherein:the magnet is constituted by a pair of magnets which are provided outside a wall of the chamber and face each other with the plasma generating region interposed therebetween;the magnetic field causes ions which radiate from the plasma to travel from the plasma generating region toward the wall of the chamber at which the pair of magnets are provided; andthe first and second mirror portions are arranged such that the distance, in the direction of an axis that passes through the first and second focal points, from a central axis of the magnetic field to the second reflective surface is greater than the distance from the central axis of the magnetic field to the first reflective surface. 4. An extreme ultraviolet light generating apparatus as defined in claim 3, wherein:the first and second mirror portions are configured such that each of the first and second reflective substances is exposed to the plasma generating region across the entirety thereof. 5. An extreme ultraviolet light generating apparatus as defined in claim 3, wherein:the second mirror portion is constituted by a pair of second mirrors which are arranged along the central axis of the magnetic field. 6. An extreme ultraviolet light generating apparatus as defined in claim 5, wherein:the first mirror portion is constituted by a pair of first mirrors which are arranged between the pair of second mirrors in a direction along the central axis of the magnetic field. 7. An extreme ultraviolet light generating apparatus as defined in claim 5, wherein:the first mirror portion is constituted by one first mirror which is arranged between the pair of second mirrors in a direction along the central axis of the magnetic field. 8. An extreme ultraviolet light generating apparatus as defined in claim 5, further comprising:a pair of exhaust ports which are provided to face each other in a wall of the chamber that intersects with the central axis of the magnetic field, configured to exhaust the ions to the exterior of the chamber; wherein:the magnetic field causes the ions to travel from the plasma generating region toward each of the pair of exhaust ports.