High-precision measurement of Wolter-I mandrel for X-ray microscopy by using double confocal probes

The Wolter-type X-ray microscope, known for its high resolution and collecting area, is replacing KB-type X-ray microscopy in advanced light sources and high-energy lasers. A notable method for fabricating Wolter-type X-ray mirrors is nickel electroforming, where the surface accuracy and quality of the replication mandrel crucially impact mirror performance. Preparing the mandrel requires high-precision inspection technology, yet traditional equipment struggles to measure the circumferentially symmetric surface profile of the Wolter type. To address this challenge, we developed an offline detection device using a non-contact probe to measure the mandrel's middle and low frequency surface profile. Systematic and random errors in the detection device were analyzed, and we employed a dual-probe calibration method with a standard mirror, reducing the peak-to-valley (PV) value of drift due to temperature and humidity to 23 nm. A comparative experiment between our detection device and the CGH interferometric detection method showed a deviation of approximately 60 nm in the PV value of the surface test results for the Wolter mandrel, validating the effectiveness and accuracy of our detection method. © 2024 Chinese Academy of Sciences. All rights reserved.