Search

Zemike phase-contrast microscopy was realized using a micro-capillary X-ray refractive lens. Using a gold N4-phase plate, positive phase contrast images were successfully taken. The microscope system was designed so that the ID & 2D phase contrast images can be taken with various sizes of the phase plates and the absorption contrast images, switchable by moving the phase plate. Thc profiles of the observed images are compared with the theoretically expected ones and they qualitatively agreed with each other. The sensitivity of the system was checked by detecting weakly absorbing materials, such as the SiC particles with the diameter of less than 5 micrometer.

Development of microfocusing optics for scanning microscopy and image forming optics for imaging microscopy are now in progress in SPring-8 by using varieties of optical devices: refractive lens, total reflection mirrors. Fresnel zone plates, and sputtered-sliced Fresnel zone plates. Spatial resolution of 100 nm has been achieved in scanning microscopy using highly coherent X-ray beam at a 248 m-long beamline 20XU and F2P' focusing optics. Recent results on development of optical systems are described.

High-sensitive differential phase imaging has been performed with hard x-ray scanning transmission microscope optics and an imaging detector. A microbeam with the size of 60 nm at 8 keV x ray is generated by highly-coherent illuminated beam at x-ray undulalor beamline BL20XU of SPring-8. The differential phase image is reconstructed by data set consists of diffraction images of each scan position. Advantages for absorption imaging are shown with some objects.

X-ray microbeam generated by a Kirkpatrik-Baez (KB) mirror optics with a set of two parabolic-shaped reflective surfaces was tested at an undulator beamline BL47XU of SPring-8. The KB mirror used in the experiment was fabricated by numerically-controlled polishing technique at Cannon Co. Ltd. Measured focal spot size at the x-ray energy of 8 keV in the vertical and the horizontal were 0.75 μm and 0.32 μm, respectively. The photon flux of the focal spot was 2 x 10'° [photons / s / 100 mA ring current]. Tantalum test pattern of the 0.2 μm line width was clearly observed with raster scan.

A wave-front dividing interferometer was devised in which half of a highly spatially coherent beam deflected by an x-ray prism is overlapped with another half. By placing the samples in the two beams and the x-ray imaging detector closely downstream of the sample, the differential phase of the sample is recorded on the imaging detector. The separation of the two paths at the sample plane, the amount of shear, was approximately 2 pm in the present experiment. This is easily controllable by changing the distance between the sample and the imaging detector. Phase retrieval using the fringe scanning method was successfully demonstrated for various kinds of weakly absorbing samples.

Present status of our developments of x-ray holographic microscopes at SPring-8 BL20XU is described. A combination of the x-ray undulator and a zone plate enabled us to make a coherent x-ray source of around 0.1 μm size. Using this secondary source, two types of x-ray holographic microscopes were investigated. First, a Gabor microscope in point-projection geometry was tested. A tantalum 0.2 μm line-and-space pattern could be resolved. Second, using a zone plate as a beam splitter, a Fourier transform holographic microscope was tested. A tantalum 0.2 μm line-and-space pattern could be observed. Polystyrene beads of 2.8 μmand 0.8 μm in diameter could be observed. In Fourier transform holography, a reconstructed image of a specimen that is located out of the plane of the reference source is blurred. Numerical focusing of such an x-ray hologram could be successfully demonstrated.

We are planning to develop a kinoform zone plate (ZP) for hard X-ray using a sputtered-sliced (SS) method with two materials (Cu/Al). The SS kinoform ZP is composed of a Cu/Al multilayer that is based on radial modulation of the refractive indices of deposition materials. The X-ray through the zones interferes constructively at the focal point. The kinoform ZP, therefore, has an advantage of high focusing efficiency. According to the our theoretical calculation, the focusing efficiency of the Cu/Al kinoform PZP is up to 86% in the 0-30 keV X-ray energy region, while one of the conventional Cu/Al multilayer Fresnel zone plate is up to 38%.