The spectroscopic study and the evaluation study of optics for soft x-ray region. The evaluation of Schwarzschild mirror for soft x-ray region

The Schwarzschild optics is often adapted to the optics in soft X-ray region as its less aberration. However the efficiency measurements of larger one which can gain more effective angle needs the special measurement instruments corresponding to the optical arrangement. We report the efficiency measurements using the reflectometer for the optical elements at Rits SR BL-11. The measured Schwarzschild optics is designed for microdivision measurements at the wavelength 13 nm. It was constructed from Fused Silica Concave mirror (D=φ 120 mm, R=220 mm) and Fused Silica Convex mirror (D=φ 20 mm, R=65 mm), coated with Mo-Si Multilayers (80 layers) which had peak reflectivity at 13.05 nm and aligned well. By using the narrow light beam (φ 2 mm), the transmissive efficiencies were measured at some points in the effective area, and total efficiency was estimated to about 20% by the calculation from those values. The performance of the LPX microfocusing system using this optics for the under 100 nm focusing spot is also reported. (author)