Diffraction-limited microbeam with Fresnel zone plate optics in hard X-ray regions

X-ray microbeam using Fresnel zone plate as a beam focusing device has been tested at an undulator beamline of SPring-8. The zone material is tantalum with thickness of I mum, and the zone structure is fabricated by using electron beam lithography technique. The outermost zone width of the zone plate is 0.25 mum. By utilizing a fully coherent illumination, a focused spot size near to the diffraction-limit (0.3 mum) has been achieved at an X-ray energy of 8 keV. The measured beam profiles shows good agreement with the theoretical profile. The measured diffraction efficiency agrees well with theoretical value within an X-ray energy region from 6 keV to 10 keV. A scanning microscopy experiment has also been performed in order to evaluate the spatial resolution. Fine structures of up to 0.2 mum are clearly observed in the measured image. The modulation transfer function derived from the measured image is 10 % at 0.2 mum line and 0.2,mum space.