Abstract
X-ray mirrors are widely used in beamlines and laboratories as focusing or collimating optics. As well as the highly accurate processes used to fabricate them, optimized alignment of X-ray mirrors also plays an important role in achieving an ideal X-ray beam. Currently, knife-edge scans are the most often used method for aligning X-ray mirrors, which can characterize the focal size and tune the alignment iteratively. However, knife-edge scanning provides only one-dimensional information and this method suffers from being time-consuming and requiring a high-resolution piezo translation stage. Here we describe a straightforward and non-iterative method for mirror alignment by measuring the relationship between the tilt aberration and the misaligned pitch angle, which is retrieved by an at-wavelength metrology technique using a randomly shaped wavefront modulator. Software and a graphical user interface have been developed to automate the alignment process. Combining the user-friendly interface and the flexibility of the at-wavelength metrology technique, we believe the proposed method and software can benefit researchers working at synchrotron facilities and on laboratory sources.
Highlights
Reflecting mirrors operating at grazing angles are an important component in many beamlines and laboratories for focusing or collimating X-ray beams with high efficiency
There are several different approaches that are commonly used for alignment of X-ray focusing mirrors including characterizing either the focal spot size4,5 or the ray or wavefront error6–10 as feedback for iterations of alignment
For 1D focusing mirrors, the regions of interest (ROIs) pixel values input here are only defined in the direction orthogonal to the focusing direction because the focusing direction is automatically defined in the software for each pitch angle scan
Summary
Reflecting mirrors operating at grazing angles are an important component in many beamlines and laboratories for focusing or collimating X-ray beams with high efficiency. X-ray near-field speckle patterns have been widely applied in phase-contrast imaging techniques and at-wavelength metrology.. X-ray near-field speckle patterns have been widely applied in phase-contrast imaging techniques and at-wavelength metrology.10,14 These speckle-based techniques have drawn increased attention due to their costefficiency and flexibility compared with other wavefront sensing techniques. The process has the simplicity of a pencil-beam scan but is able to provide 3D information because the speckle-based technique utilizes a 2D randomly shaped wavefront modulator rather than the 1D slit used in traditional pencil-beam scanning techniques. This method does not require iterative processes and, the image acquisition and data processing can be conveniently separated. The independent software we have developed is not restricted to any specific hardware control and can be used by any beamline or laboratory
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