Double-edge scan wavefront metrology and its application in crystal diffraction wavefront measurements

Area of Science:

• Optics and Photonics
• Materials Science
• Synchrotron Radiation Technology

Background:

• Fourth-generation synchrotron radiation sources require monochromator crystals capable of preserving wavefronts over extensive ranges for diffraction-limited performance.
• Existing methods lack the precision for absolute crystal diffraction wavefront measurement needed for these advanced sources.
• There is a critical need for novel metrology techniques to characterize crystal optics.

Purpose of the Study:

• To develop and validate a novel technique for absolute crystal diffraction wavefront measurement.
• To enable precise characterization of monochromator crystals for next-generation synchrotron radiation facilities.
• To establish a critical feedback mechanism for crystal fabrication.

Main Methods:

• Development of a novel edge scan wavefront metrology technique at the Beijing Synchrotron Radiation Facility (BSRF).
• Implementation of a double-edge tracking method for enhanced measurement precision.
• Characterization of flat crystals within a 6 mm range using the developed technique.

Main Results:

• The double-edge scan (DES) technique achieved an equivalent diffraction surface slope error below 70 nrad (4.57% wavefront phase error) r.m.s.
• Exceptional slope error reproducibility below 15 nrad (< λ/100 phase error reproducibility) was demonstrated, even on a first-generation synchrotron source.
• The technique proved effective for measuring wavefront errors across a significant crystal surface range.

Conclusions:

• The novel double-edge scan (DES) technique provides a viable solution for absolute crystal diffraction wavefront measurement.
• DES enables diffraction-limited level metrology, crucial for the development of advanced monochromator crystals.
• The technique is now a critical feedback tool in the fabrication process for next-generation synchrotron optics.