Development of a high performance surface slope measuring system for two-dimensional mapping of x-ray optics

Abstract

The research and development work on the Advanced Light Source (ALS) upgrade to a diffraction limited storage ring light source, ALS-U, has brought to focus the need for near-perfect x-ray optics, capable of delivering light to experiments without significant degradation of brightness and coherence. The desired surface quality is characterized with residual (after subtraction of an ideal shape) surface slope and height errors of <50−100 nrad (rms) and <1−2 nm (rms), respectively. The ex-situ metrology that supports the optimal usage of the optics at the beamlines has to offer even higher measurement accuracy. At the ALS X-Ray Optics Laboratory, we are developing a new surface slope profiler, the Optical Surface Measuring System (OSMS), capable of two-dimensional (2D) surface-slope metrology at an absolute accuracy below the above optical specification. In this article we provide the results of comprehensive characterization of the key elements of the OSMS, a NOM-like high-precision granite gantry system with air-bearing translation and a custom-made precision air-bearing stage for tilting and flipping the surface under test. We show that the high performance of the gantry system allows implementing an original scanning mode for 2D mapping. We demonstrate the efficiency of the developed 2D mapping via comparison with 1D slope measurements performed with the same hyperbolic test mirror using the ALS developmental long trace profiler. The details of the OSMS design and the developed measuring techniques are also provided.

Ex situ metrology and data analysis for optimization of beamline performance of aspherical pre-shaped x-ray mirrors at the advanced light source

“…The accuracy of the measurement is estimated to be on the level of 60 nrad (RMS). For the surface slope metrology with the mirrors, we have used the DLTP [12][13][14] and verified the results via comparison with that of obtained with the new OSMS, [15][16][17] both available at the ALS XROL. The measurements suggest that the QERLIN SM1 and SM2 mirrors are fabricated with shapes significantly different from the ideal shapes (corresponding to the central values of the specified conjugate parameters) with the PV deviations of 31 µrad and 6.5 µrad, respectively.…”

“…Because of the dramatic deviation of the slope profiles of SM1 and SM2 mirrors, as measured with the DLTP, from the ideal shapes corresponding to the central values of the specified conjugate parameters, we have also verified the DLTP results via comparison with the measurements with the new OSMS profiler, [15][16][17] also available at the ALS XROL. The NOM 28,29 -like gantry system of the OSMS is capable of twodimensional surface slope metrology over the spatial range from the sub-mm scale to the clear aperture.…”

“…The high efficacy of the developed measurement and data analysis procedures is demonstrated by results of measurements and performance optimization of hyperbolic (SM1) and elliptical (SM2) cylinder mirrors fabricated for the ALS QERLIN beamline. 11 For surface slope metrology with the mirrors, we used the Developmental Long Trace Profiler (DLTP) [12][13][14] and verified the results via comparison with that of obtained with the new Optical Surface Measuring System (OSMS), [15][16][17] both available at the ALS XROL.…”

Transfer of autocollimator calibration for use with scanning gantry profilometers for accurate determination of surface slope and curvature of state-of-the-art x-ray mirrors

“…The developed approaches are rather universal and, therefore, widely applicable. Figure 1 shows the XROL OSMS experimental set-up [49,50] based on the multifunctional translation system, including 2D gantry and a custom tilt-flip-Z-translation stage (TFZS) and four electronic autocollimators ELCOMAT-3000 [53]. The AC in the surface-under-test (SUT) measuring (sample) channel, AC˗1, is placed vertically on the OSMS X-axis translation carriage.…”

“…[50]. [49,50] based on the multifunctional translation system, including 2D gantry and custom tilt-flip-Z-translation stage (TFZS), and four electronic autocollimators ELCOMAT-3000 [53], with a fixed distance AC-1 in the sample arm [38]. AC-2 monitors the X-axis carriage wobbling error.…”