Stitching methods at the European Synchrotron Radiation Facility (ESRF)

Area of Science:

• Optics and Metrology
• Materials Science
• X-ray Optics

Background:

• X-ray mirror quality has significantly improved, with manufacturers achieving slope errors below 0.2 μrad.
• Maintaining the intrinsic quality of long X-ray mirrors is challenging due to mounting and bending, which can introduce parasitic deformations like twist.

Purpose of the Study:

• To develop and evaluate advanced metrology techniques for measuring the 3D topography of X-ray optical surfaces.
• To assess the performance of new stitching interferometry systems for characterizing mirrors with varying curvatures and lengths.

Main Methods:

• Development of three distinct stitching interferometry systems based on Fizeau sub-aperture measurements.
• Application of the relative angle determinable stitching interferometry (RADSI) method for short, strongly curved mirrors and longer mirrors with intermediate curvature.
• Utilizing micro-stitching interferometry for measuring deeply curved aspherical profiles, including Kirkpatrick-Baez mirror systems.

Main Results:

• The study describes the measurement setups for each developed system.
• Initial results from the new stitching interferometry methods are presented and discussed.
• Demonstration of micro-stitching interferometry's suitability for aspherical mirror characterization with examples from nano-focusing systems.

Conclusions:

• Advanced stitching interferometry techniques are crucial for preserving the quality of high-precision X-ray mirrors.
• The developed methods offer versatile solutions for measuring diverse mirror geometries, from flat to deeply curved.
• These metrology advancements are essential for enabling next-generation X-ray applications, such as nano-focusing.