Kiminori Ito

X-ray photon correlation spectroscopy using a fast pixel array detector with a grid mask resolution enhancer

The performance of a fast pixel array detector with a grid mask resolution enhancer has been demonstrated for X-ray photon correlation spectroscopy experiments.

Time-resolved X-ray diffraction studies of laser-induced acoustic pulse generation in semiconductors using synchrotron radiation

Laser-induced lattice deformation generating acoustic pulses has been studied by time-resolved X-ray diffraction method using a brilliant synchrotron radiation source. We constructed a time-resolved X-ray diffraction system equipped with a synchronized femtosecond pulsed laser at an undulator beamline of SPring-8 facility, and observed laser-induced acoustic pulse in a semiconductor wafer of GaAs, where the laser irradiation causes initial strain of expansion with a response time of around 200 ps. High resolution X-ray diffractometry in asymmetric configuration combined with laser-pump X-ray probe method revealed that the strain is formed with coherent longitudinal acoustic phonons and lattice expansion along the surface normal. The laser power dependence shows the saturation of the lattice expansion ratio with the lengthened relaxation time for high power excitation.

X-ray Photon Correlation Spectroscopy of Silica Particles Grafted with Polymer Brush in Polystyrene Matrix

X-ray photon correlation spectroscopy system was setup at SPring-8, BL19LXU, and the partial coherence scattering data from the silica particles grafted with polymer brush in polystyrene matrix were measured. Firstly, the static speckle patterns were checked. Below the glass transition temperature of polystyrene (Tg), speckles were clearly observed, on the other hand, above Tg, the scattering patterns became smooth and speckles were hardly observed. These variances of the speckle patterns result from the particle motion. Secondly, from the time variance of the speckle data, time autocorrelation functions g2(q,t) are calculated. While the flat behaviour of g2(q,t) without relaxation were observed below Tg, the relaxation behavior with relaxation time~100–101 were observed above Tg

X-ray beam deflection control with a flexible capillary

X-ray beam deflection control method using a single flexible glass capillary is proposed to illuminate a fixed sample at a target position with different incidence angle. A 700 mm-long capillary with a bore diameter of 50 micron and an outer diameter of 2 mm, which gives suitable flexibility for the critical curvature, was employed for the test experiment in SPring-8. The X-ray beam with a wavelength of 0.1 nm was introduced into the capillary, whose axis at the input side was finely adjusted to be parallel to the X-ray beam axis with swivel-, rotation- and translation stages. The divergence angle of output beam was measured and is 1–2 mrad. By moving the output-side capillary-support transversely to the beam axis, the beam deflection angle was changed over the range of about 80 mrad. The maximum throughput was larger than 60 % in efficiency, and 8 × 1010 photons/s in flux. Mapping with the beam deflection system has also been demonstrated for X-ray absorption measurement of a test sample composed of copper and nickel films. The materials were identified by changing the X-ray photon energy around their absorption edges.

System of laser pump and synchrotron radiation probe microdiffraction to investigate optical recording process.

We have developed a system of laser-pump and synchrotron radiation probe microdiffraction to investigate the phase-change process on a nanosecond time scale of Ge2Sb2Te5 film embedded in multi-layer structures, which corresponds to real optical recording media. The measurements were achieved by combining (i) the pump-laser system with a pulse width of 300 ps, (ii) a highly brilliant focused microbeam with wide peak-energy width (ΔE∕E ~ 2%) made by focusing helical undulator radiation without monochromatization, and (iii) a precise sample rotation stage to make repetitive measurements. We successfully detected a very weak time-resolved diffraction signal by using this system from 100-nm-thick Ge2Sb2Te5 phase-change layers. This enabled us to find the dependence of the crystal-amorphous phase change process of the Ge2Sb2Te5 layers on laser power.

Long-Working-Distance Kirkpatrick-Baez Mirrors for Hard X-ray Beamlines at SPring-8

We designed and installed two types of long‐working‐distance Kirkpatrick‐Baez (KB) mirrors and mirror manipulators, which were customized into each experiment for hard x‐ray undulator beamlines at SPring‐8. For the BL32XU RIKEN Targeted Proteins beamline, 400‐mm‐long KB focusing mirrors for a beam size of 1 μm with a 730‐mm‐long working distance were designed for carrying out the structural analysis of protein microcrystals. We realized a focusing beam size of 0.9×0.9 μm2 (FWHM) and a focusing intensity of 6×1010 (photons/s) at an x‐ray energy of 12.4 keV. For the BL19LXU RIKEN SR Physics beamline, we developed KB mirrors for 100‐nm focusing with a 100‐mm‐working distance for the purpose of nano‐focus x‐ray diffraction. A focusing beam size of 100×100 nm2 (FWHM) and a high focusing intensity of 3.7×1010 (photons/s) at an x‐ray energy of 12.4 keV were realized.