Precision Machining of Electroless Nickel Mandrel and Fabrication of Replicated Mirrors for a Soft X-Ray Microscope

摘要

A Wolter type Ⅰ aspheric mirror which is a key optical element used in a soft X-ray microscope requires super smooth surface and highly accurate figure. This paper deals with fabrication of the Wolter type Ⅰ microscope mirror by an epoxy replication method. The required figure accuracy of the mirror optimized with surface roughness of 2 nm rms and photon energy of 539 eV was estimated for a prototype soft X-ray microscope. A master mandrel was prepared by single-point diamond turning and polishing, and a precise aspheric gold mirror with axial symmetry was successfully obtained from the master mandrel through replication processes. The fabricated mirror showed surface roughness of 1.12 nm Ra and figure error of 34 nm rms, and several mirrors could be obtained from only one master mandrel without destroying its surface roughness and shape.