Standard design and evaluation of monolithic Wolter mirror for x-ray focusing at SPring-8

This paper describes a monolithic Wolter mirror, a standard micron-focusing element at SPring-8, which achieves highly stable and efficient micro-focusing. The mirror is composed of an ellipsoidal and a hyperboloidal surface on a single substrate in a Wolter type-I configuration. This configuration forms a focusing optical system that is achromatic, highly stable, and readily adjustable. An optical design methodology was developed, taking into consideration beamline spatial constraints, energy-dependent reflectivity, and manufacturability. Ray-tracing analysis indicated that the fabrication of this mirror requires a high degree of precision. However, the results indicate mirror resilience to alignment errors and exhibit stable focusing performance. Preliminary experimental evaluation at the beamline confirmed the high reflectivity and micron-order focusing size. On the other hand, the vertical focusing condition is influenced by upstream optical elements, such as crystals in monochromators and mirrors. The simulation evaluations indicated that this effect would be more apparent in next-generation SPring-8-II.