Stitching interferometry for synchrotron mirror metrology at NSLS-II (Conference Presentation)

With the progressive development in synchrotron radiation facilities and free electron lasers (FELs), the requirement of the X-ray mirror is getting higher with tighter specifications. It challenges the X-ray mirror metrology in two major application scenes. On one hand, a reliable mirror measurement technique is needed to provide trustable feedback to the deterministic polishing in mirror fabrication or re-polishing process. On the other hand, it demands a more accurate mirror metrology technique to offer better services for the X-ray mirror inspection at synchrotrons and FELs to control the quality of X-ray mirrors to be installed into beamlines. Since the stitching interferometry can provide two-dimensional laterally extendable (stitched) results with sub-nanometer height resolution and precision, several stitching interferometric techniques are studied for synchrotron mirror metrology. It is not only to enhance the mirror inspection capability in NSLS-II optical metrology laboratory but also to act in concert with the ongoing ion beam figuring project at NSLS-II. Various stitching methods with different stitching parameters are investigated at our stitching interferometric platform. Some experimental results are revealed to demonstrate the validity and performance of the developed system and stitching methods.