Yasuhiko Imai

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A multislit collimator was designed and fabricated for basic studies on microbeam radiation therapy (MRT) with an x-ray energy of about 100 keV. It consists of 30 slits that are 25 microm high, 30 mm wide, and 5 mm thick in the beam direction. The slits were made of 25 microm-thick polyimide sheets that were separated by 175 microm-thick tungsten sheets.(More)
Two-dimensional crystals, especially graphene and transition metal dichalcogenides (TMDs), are attracting growing interests because they provide an ideal platform for novel and unconventional electronic band structures derived by thinning. The thinning may also affect collective phenomena of electrons in interacting electron systems and can lead to exotic(More)
The electrochemical oxidation behaviors of the surfaces of platinum nanoparticles, one of the key phenomena in fuel cell developments, were investigated in situ and in real time, via time-resolved hard X-ray diffraction and energy dispersive X-ray absorption spectroscopy. Combining two complementary structural analyses, dynamical and inhomogenous structural(More)
A displacement sensor using a pair of flat Panda fiber coils with a 90 degrees connection is demonstrated. The dual coils are squeezed differentially. The phase retardations caused by the compression are constructively added, while the retardations caused by the environmental temperature are destructively added, thereby removing the temperature effect. Both(More)
It was pointed out in a previous paper [Okitsu et al. (2006), Acta Cryst. A62, 237-244] that an n-beam Takagi-Taupin (T-T) equation can be solved for a crystal of arbitrary shape. The procedure to integrate the n-beam T-T equation is to let all the Fourier coefficients of the electric susceptibility be zero at positions inside the Borrmann pyramid but(More)
We have developed new microdiffraction system at the SPring-8. This system used a focused beam produced using a phase zone plate combined with a narrow slit, which made a focused beam with a small size and a small angular divergence. Furthermore we can use the two-dimensional x-ray CCD detector, which enable us to measure local reciprocal space maps at many(More)
A high-Ge-content Si1-yGey/compositionally graded Si1-xGex-stacked structure grown on Si(001) is now considered to be an important platform for the realization of advanced nanometer-scale complementary metal oxide semiconductor devices with high-mobility channel materials, such as III-V materials and Ge, and monolithically integrated photonic modules. The(More)
A 'six-beam X-ray section topograph' experiment was performed whose images are in excellent agreement with the images computer-simulated using the theory derived by one of the authors [Okitsu (2003). Acta Cryst. A59, 235-244] based on the Takagi-Taupin dynamical theory. X-rays whose wavefront was limited to 0.1 x 0.1 mm were incident on a [1 1; 1]-oriented(More)
X-ray six-beam pinhole topograph images were obtained for a silicon crystal with incident synchrotron X-rays. The polarization state of X-rays incident on the sample crystal was controlled by using a four-quadrant phase-retarder system [Okitsu et al. (2002). Acta Cryst. A58, 146-154] that can be rotated around the transmitted beam axis to generate(More)
Thermal effects on the conversion efficiency of four-photon mixing (FPM) power in a silica optical fiber are measured. When the temperature of the fiber changes from 9 to 350 degrees C, the first Stokes power decreases with a temperature coefficient of -0.33%/ degrees C as the temperature increases to 200 degrees C and then becomes saturated with a further(More)