Ryo Hashimoto

Frank–Kasper σ phase in polybutadiene-poly(ε-caprolactone) diblock copolymer/polybutadiene blends

Microphase-separated structures in a polybutadiene-poly(ε-caprolactone) diblock copolymer (PB-PCL)/polybutadiene homopolymer (PB) blend were investigated by small-angle x-ray scattering (SAXS). Non-equilibrium spherical micelles were observed at temperatures ranging between 60 and 100 °C. An SAXS profile with  >60 scattering peaks was recorded at 140 °C. All the peak positions were in good agreement with theoretical Frank-Kasper σ phase peak positions. Thus, these results indicate the formation of a Frank-Kasper σ phase in the PB-PCL/PB blend at 140 °C.

Evaluation of a pulse counting type SOI pixel using synchrotron radiation X-ray

Silicon-On-Insulator (SOI) technology was used to develop a fine pixelated detector with high performance. The first beam test for a prototype pulse-counting-type SOI chip, CPIXTEG3b, was performed at beamline BL-14A of the Photon Factory, KEK. CPIXTEG3b was designed using double SOI technology for decreasing crosstalk and increasing radiation hardness. It has a 64 × 64 pixel array wherein each pixel size is 50 μm × 50 μm. The sensitivity to incident X-rays was measured for each pixel with an X-ray beam 10 μm in diameter. We used the X-ray energy of 16 keV. Because of its small size, the pixel response was sensitive to the charge-sharing effect. We also considered the point spread function of the sensor. The discriminator of each pixel circuit was calibrated using a pulse generator, and performance was checked using flat-field X-rays.

Development of a new high-speed readout system for SOI pixel detectors

Abstract We are developing a new high-speed readout system for silicon on insulator (SOI) pixel detectors. The SOI detector is a monolithic radiation imaging detector based on a 0.2 μ m FD-SOI CMOS process. Previously, we used a Xilinx Virtex-4/5 FPGA readout board for the SOI detector and developed many facilities for this board. However, the Virtex-4/5 FPGA is now obsolete and does not have sufficiently high performance for recent experiments that require more than 1-kHz high-speed imaging with a large number of pixels. Thus, we started to develop a new high-speed readout system using the KC705, which is the evaluation board for the Xilinx Kintex-7 FPGA. We developed a new data acquisition structure that has backward compatibility with the previous environment on this board and implements several functions for practical purposes such as micro Computed Tomography. The transfer speed achieved by the new system is 95.3 fps for a 426k pixel detector in continuous data-taking mode, and 762.5 fps in maximum-speed mode. The details of the new readout system are presented.

Synchrotron beam test of a photon counting pixel prototype based on Double-SOI technology

The overall noise performances and first synchrotron beam measurement results of CPIXETEG3b, the first counting type Silicon-On-Insulator (SOI) pixel sensor prototype without crosstalk issue, are reported. The prototype includes a 64 × 64 pixel matrix with 50 μm pitch size. Each pixel consists of an N-in-P charge collection diode, a charge sensitive preamplifier, a shaper, a discriminator with thresholds adjustable by an in-pixel 4-bit DAC, and a 6-bit counter. The study was performed using the beam line 14A at KEK Photon Factory (KEK-PF) . The homogeneous response of the prototype, including charging-sharing effects between pixels were studied. 16 keV and 8 keV monochromatic small size (~ 10 μm diameter) X-ray beams were used for the charge sharing study, and a flat-field was added for homogenous response investigation. The overall detector homogeneity and the influence of basic detector parameters on charge sharing between pixels has been investigated.

Application of the SOPHIAS Detector to Synchrotron Radiation X-Ray Experiments

Application of synchrotron radiation science to structural analysis for functional materials is attracting considerable interest. When a low-emittance synchrotron ring is used, higher performance is required from an X-ray area detector used in experiments. The charge-integrating-type detector SOPHIAS, which was designed for the SACLA free-electron laser experiments, was developed by RIKEN using silicon-on-insulator technology. The SOPHIAS detector has a 2157 × 891 pixel array consisting of 30 μm square pixels. SOPHIAS is a powerful tool for X-ray structural analysis because of its high definition and high dynamic range. The application of SOPHIAS to synchrotron radiation experiments has begun at the Photon Factory, KEK (KEK/PF). Focusing on small angle X-ray scattering (SAXS) measurements of block copolymers, synchrotron radiation X-ray experiments were conducted using SOPHIAS at KEK/PF. The SAXS pattern of a sample, polybutadiene-poly(e-caprolactone) diblock copolymer/polybutadiene blend, has complicated peaks structure originating in Frank–Kasper σ phase; thus, the fine pixel array of SOPHIAS was very important for resolving the peaks. We report the results of experiments using SOPHIAS.