Development of micro-tomography system with Fresnel zone plate optics at SPring-8

Abstract

X-ray micro-tomography system has been developed at BL47XU in SPring-8. A Fresnel zone plate (FZP) was used as an objective to achieve the 100-nm-order spatial resolution. The system consists of a light source, a Si(111) double crystal monochromator, a beam diffuser made by graphite powder, a condenser zone plate (CZP), high precision stages for sample rotation, FZP objective and an X-ray image detector. The X-ray energy was selected between 7keV and 10keV to obtain fine images for various samples. The FZP and CZP were fabricated by the electron-beam lithography technique. The material of the zone structure is tantalum with thickness of 1μm. The outermost zone width of FZP is 100 nm, and periodic zone width of the CZP is 200 nm (400 nm in pitch). The measured spatial resolution of the optical system was about 160 nm, which had a good agreement with the theoretical value derived from Hopkins' imaging theory. From a tomographic measurement of a concentric resolution test pattern, cross-sectional image with a spatial resolution of better than 300 nm was successfully reconstructed. A small meteorite and some kinds of minerals were successfully observed.