Patent Number: 
Section: claims

1. A system for an extreme ultraviolet light source, the system comprising:one or more optical elements positioned to receive a reflected amplified light beam and to direct the reflected amplified light beam into first, second, and third channels, the reflected amplified light beam comprising a reflection of at least a portion of an irradiating amplified light beam that interacts with a target material, and the first, second, and third channels being three separate paths along which light propagates;a first sensor that senses light from the first channel;a second sensor that senses light from the second channel and the third channel, the second sensor having a lower acquisition rate than the first sensor; andan electronic processor coupled to a computer-readable storage medium, the medium storing instructions that, when executed, cause the processor to:receive data from the first sensor and the second sensor, anddetermine, based on the received data, a location of the irradiating amplified light beam relative to the target material in more than one dimension. 2. The system of claim 1, wherein the medium further stores instructions that, when executed, cause the processor to determine an adjustment to the irradiating amplified light beam based on the determined location. 3. The system of claim 2, wherein the determined adjustment comprises distances, in more than one dimension, to move the irradiating amplified light beam. 4. The system of claim 1, wherein the instructions to cause the processor to determine a location of the irradiating amplified light beam comprise instructions that, when executed cause the processor to:determine a location of a focus position of the irradiating amplified light beam relative to the target material in a direction that is parallel to a direction of propagation of the irradiating amplified light beam, anddetermine a location of the focus position of the irradiating amplified light beam relative to the target material in a first transverse direction that is perpendicular to the direction of propagation of the irradiating amplified light beam. 5. The system of claim 4, wherein the instructions further comprise instructions that, when executed, cause the processor to determine a location of the expected focus position of the irradiating amplified light beam in a second transverse direction that is perpendicular to the first transverse direction and perpendicular to the direction of propagation of the irradiating amplified light beam. 6. The system of claim 1, further comprising an astigmatic optical element, positioned in the third channel, that modifies a wavefront of the reflected amplified light beam. 7. The system of claim 1, further comprising multiple partially reflective non-astigmatic optical elements, each positioned at a different location in the third channel and each receiving at least part of the reflected amplified light beam, each of the multiple partially reflective optical elements forming a beam that follows a path of a different length between the target material and the second sensor. 8. The system of claim 1, wherein the first, second, and third channels each comprise one or more refractive or reflective optical elements that direct a portion of the reflected amplified light beam. 9. The system of claim 1, wherein the reflected amplified light beam comprises a reflection of a pre-pulse beam and a drive beam, the drive beam being an amplified light beam that converts the target material to plasma upon interaction, and the pre-pulse and drive beams comprising different wavelengths, and the system further comprises one or more spectral filters that are transparent to only one of the pre-pulse beam and the drive beam. 10. The system of claim 1, whereinthe first sensor senses light pointing at a high acquisition rate from the first channel;the second sensor comprises a two-dimensional imaging sensor that senses light and measures intensity distribution of the light from the second channel and the third channel; andthe instructions that, when executed, cause the processor to determine, based on the received data, a location of the irradiating amplified light beam, cause the processor to determine a focus position of the irradiating amplified light beam relative to the target material in more than one dimension. 11. An extreme ultraviolet light system comprising:a source that produces an irradiating amplified light beam;a steering system that steers and focuses the irradiating amplified light beam toward a target material in a vacuum chamber;a beam positioning system comprising:one or more optical elements positioned to receive a reflected amplified light beam that is reflected from the target material and to direct the reflected amplified light beam into first, second, and third channels, the first, second, and third channels being three separate paths along which light propagates;a first sensor that senses light from the first channel;a second sensor, comprising a two-dimensional imaging sensor, that senses light from the second channel and the third channel, the second sensor having a lower acquisition rate than the first sensor; andan electronic processor coupled to a computer-readable storage medium, the medium storing instructions that, when executed, cause the processor to:receive data from the first sensor and the second sensor, anddetermine, based on the received data, a location of the irradiating amplified light beam relative to the target material in more than one dimension. 12. The system of claim 11, wherein the medium further stores instructions that, when executed, cause the processor to determine an adjustment to the location of the irradiating amplified light beam based on the determined location. 13. The system of claim 12, wherein the determined adjustment comprises an adjustment in more than one dimension. 14. The system of claim 13, wherein the instructions to cause the processor to determine a location of the irradiating amplified light beam relative to the target material comprise instructions that, when executed cause the processor to:determine a location of a focus of the irradiating amplified light beam relative to the target material in a direction that is parallel to a direction of propagation of the irradiating amplified light beam, anddetermine a location of the irradiating amplified light beam focus relative to the target material in first and second transverse directions, each of which are perpendicular to the direction of propagation of the irradiating amplified light beam. 15. The system of claim 11, wherein the instructions further comprise instructions that, when executed, cause the processor to:determine an adjustment to the amplified light beam based on the determined location of the amplified light beam, andprovide the generated output to the steering system.