The advent of free-electron lasers and diffraction-limited storage rings has raised the bar for precision in the fabrication of the curved mirrors used to direct and focus x-rays. Such high-quality x-ray optics are now available from a number of vendors who have access to advanced, expensive, computer-controlled polishing techniques.
However, there is still a need to optimize a mirror in the context of its intended beamline. This painstaking and time-consuming process requires careful characterization and analysis of the mirror in conjunction with beamline parameters such as focal-point distances and grazing-incidence angles.
At the X-Ray Optics Laboratory (XROL) of the Advanced Light Source (ALS), researchers have developed an original procedure along with dedicated software for optimizing the performance of pre-shaped hyperbolic and elliptical mirrors, including improvements in the aperture configurations used in scanning a mirror’s surface. The Optical Surface Measuring System (OSMS) does in a day what used to take many days, by combining precise surface metrology with computer analysis of the optimal alignment of a mirror in a beamline that effectively preserves the mirror’s desired shape.
The system’s high efficacy has been demonstrated in measurements of aspherical optics designed and fabricated for the ALS QERLIN beamline. The unprecedented performance of the OSMS is needed, in particular, for state-of-the-art optics in ALS Upgrade Project (ALS-U) beamlines.
The work was a collaboration between the ALS XROL, Berkeley Lab’s Engineering Division, Physikalisch-Technische Bundesanstalt (Germany’s national metrology institute), Helmholtz-Zentrum Berlin (HZB)/BESSY-II, and the Leibniz Institute of Surface Engineering (Germany).
V.V. Yashchuk, I. Lacey, G.S. Gevorkyan, W.R. McKinney, B.V. Smith, and T. Warwick, “Ex situ metrology and data analysis for optimization of beamline performance of aspherical pre-shaped x-ray mirrors at the Advanced Light Source,” Rev. Sci. Instrum. 90, 021711 (2019), doi: 10.1063/1.5057441; and I. Lacey, R.D. Geckeler, A. Just, F. Siewert, T. Arnold, H. Paetzelt, B.V. Smith, and V.V. Yashchuk, “Optimization of the size and shape of the scanning aperture in autocollimator-based deflectometric profilometers,” Rev. Sci. Instrum. 90, 021717 (2019), doi: 10.1063/1.5058710.