Focusing mirror for coherent hard X-rays

Abstract

The development of high-precision x-ray mirrors is described. Atomistic surface polishing technique, elastic emission machining (EEM), was developed more than 30 years ago. This chapter describes how the polishing technique was improved to successfully apply to the synchrotron radiation and XFEL mirrors. The key was actually the figure metrology. The metrology was dramatically advanced by using coherent x-rays at the 1-km beamline of SPring-8, where classical ray-tracing approach was no more valid so that wave-optical approach was developed. Various optical references were developed to improve the global surface figures of mirrors. Successful development of elliptical mirrors helped attaining less than 100 nm focal spot in the conventional beamlines using Kirkpatrick-Baez focusing configuration, reaching 7 nm at the 1-km beamline. The speckle-free mirrors and focusing mirrors were used in XFEL facilities. These mirrors have been applied for various types of scanning nano-probes, imaging system, and generation of high-intensity photon fields for nonlinear xray optical experiments.