Sub-100 nm Hard X-Ray Microbeam Generation with Fresnel Zone Plate Optics

A hard X-ray focusing test of a Fresnel zone plate has been performed with a synchrotron radiation source at the undulator beamline 20XU of SPring-8. A Fresnel zone plate with a radius of 150 µm, and an outermost zone width of 100 nm was used for the X-ray focusing device. The 248-m-long beamline provides fully coherent illumination for the focusing device. The focused beam was evaluated by the knife-edge-scan method and scanning microscope test using test charts. Nearly diffraction-limited focusing with a size of 120 nm was achieved for the first-order diffraction at 10 keV X-ray. Evaluation for the third-order diffraction was also performed at 8 keV X-ray, and a focal size of 50 nm has been obtained.