In-vacuum metrology platform for high precision x-ray mirror surface figure characterization

In situ x-ray mirror surface figure metrology under vacuum and high heat loads is essential for monitoring deformations and enabling adaptive corrections. This study introduces a high-precision vacuum metrology system based on a pentaprism long trace profiler, designed to monitor clamping and thermal deformations while enabling adaptive wavefront corrections. The pentaprism and scanning stage are vacuum-internal, with an external detector to minimize window errors. Two different optical configurations were studied: the Internal Optical Path with External Detector (IOP-ED) configuration and the external optical head configuration. Vacuum evaluations improved to sub-0.1 μrad RMS slope repeatability, yielding 0.23 μrad RMS systematic errors for the IOP-ED configuration, with a scan range of 150 mm on a flat mirror at a vacuum level of 200 Pa. Future enhancements include full-vacuum integration to eliminate residual instabilities.