SBIR/STTR Award attributes
The performance of the X-ray beam-lines at the Department of Energy’s synchrotron light sources is limited by the quality of the focusing mirrors in those beam-lines, wherein the quality of the mirrors in turn is limited during their manufacture by the capabilities of the metrology equipment used to measure the mirror surfaces. In the proposed Phase II project a novel metrology system – originally assembled in Phase I – will be further researched and developed in order to prove that the underlying technology can obtain X-ray mirror surface measurement accuracies at or better than 100 picometers, which, when incorporated into the mirror fabrication process, is thought to be sufficient to completely resolve the beam-line limitations caused by the mirror. Researchers using X-ray beam-lines know that to obtain diffraction limited nanometer-scale focal spot sizes the peak-to-valley surface error of the beam-line mirrors must be approximately a nanometer, and the metrology error, which should consume less than 10% of the surface error budget, should have performance on the order of 100 picometers. Unfortunately, state of the art surface metrology is currently no better than several nanometers. To address this metrology shortcoming, a metrology system has been conceptualized that utilizes a new confocal chromatic interferometric probe. Utilizing the probe with a motion control system which causes the probe to scan across multiple sub-apertures of the surface of the mirror, combining the probe with a unique referencing and spatial localization sub-system, and further augmenting the system with sub-aperture stitching methods, allows for the surface of an X-ray mirror to be measured to 100 picometers accuracy over its entire length. In Phase II we propose to continue the R&D work begun in Phase I and demonstrate that the metrology technology can indeed perform at the 100pm accuracy level over the length of an 8” X-ray mirror. Work tasks include developing a machine model of the metrology system, calibrating and removing the effects of surface errors in the reference flats, improving the probe’s wavelet-fitting algorithm, and significantly improve the performance and capabilities of the current motion control system. The proposed surface-measuring system will significantly advance the state of the art of large-aperture optical surface metrology. While the system can measure the surface of nearly any optical element (e.g., lenses, mirrors, etc.), those devices having extraordinarily stringent surface tolerances over large surface areas will benefit most, such as X-ray beamline mirrors, space telescope mirror segments, and projection optics used in semiconductor fab equipment (i.e., “steppers”). The proposed Phase II project will be performed at OptiPro facilities in Ontario, NY, just outside of Rochester. The project is expected to last 24 months.
