Optical Design of Soft X-ray Focusing System with Ellipsoidal Mirror for Laboratory-Based Sources

摘要

The ellipsoidal mirror is one of the most effective achromatic focusing optic with large aperture and nanofocusing ability. Because of the large aperture of mm-order size, this optic is suitable for a laboratory-based light source that has a large divergence angle. Recently, soft X-rays produced by high-order harmonics have become available. Such a beam has high spatial coherency but relatively large divergence angle. This light in combination with an ellipsoidal mirror will generate a highly intense focusing nanobeam that will contribute to various experiments and analyses such as those of photoelectron spectroscopy and nonlinear optical phenomena. In this paper, we present the optical design for a lab-based soft X-ray beamline and the results of optical simulation considering the parameters of the source. Finally, we introduce a two-stage focusing system with an axisymmetric mirror as a promising soft X-ray focusing system.