abstracts
X-ray Free-Electron Laser facility, SACLA has been operational for more than 2 years. During the user runs, multi-port charge coupled device (MPCCD) detectors has been extensively used to deliver novel scientific results. In order to strengthen the facility capability, we are developing new variants of the MPCCD detectors[1]. Because some of the features such as high peak signal detection cannot be implemented by CCD technology, novel monolithic process based on silicon-on-insulator (SOI) sensor technology is under development. By employing the novel process, we are developing SOPHIAS sensor targeting the peak signal of 40000 photons at 7 keV within 100 micrometer square[2]. The SPring-8 site has proposed an upgrade of the storage ring to SPring-8 II. After the upgrades, we will obtain brighter x-rays, for example, 10^13 photons/second within a diameter of 100 nanometer. With this kind of bright X-ray sources, X-ray imaging detector with higher count rate, higher frame rate, and higher quantum efficiency up to 20-30 keV region is required. Detector development plan toward these targets are also discussed.
abstracts
Cubic boron nitride (c-BN) has some outstanding properties, such as hardness, chemical inertness, high temperature stability, and high thermal conductivity. The Raman spectrum of c-BN exhibits two intense lines at 1054 and 1305 cm-1 under ambient conditions, corresponding to the Brillouin zone center transverse optical (TO) and longitudinal optical (LO) modes, respectively. Previous studies have reported the pressure and temperature dependences of the frequency shift of the modes up to 40 GPa and 2300 K. The Raman line of the LO mode overlaps an intense Raman line of diamond at pressures higher than 3 GPa. Therefore, it is difficult to observe the LO line in high-pressure experiments using the diamond anvil cell. In contrast, previous studies proposed that the TO mode could be used as the pressure calibrant in diamond anvil cells under high pressure and temperature conditions. In this study, we used a diamond anvil cell high-pressure apparatus [1] combined with a Raman spectrometer system to investigate changes in the Raman line of c-BN. The use of a synchrotron radiation source made it possible to determine the precise pressure in the sample chamber. In this study, the temperature and pressure dependences of the Raman spectrum of the TO mode of cubic boron nitride were calibrated for applications to a Raman spectroscopy pressure sensor in optical cells to about 800 K and 90 GPa. A significant deviation from linearity of the pressure dependence is confirmed at pressures above 20 GPa. At ambient temperature, dv/dP slopes are 3.41 and 2.04 cm-1/GPa at 0 and 90 GPa, respectively. The pressure dependence does not significantly change with temperature, as determined from experiments conducted up to 800 K. At pressures above 90 GPa, the Raman spectrum of the TO mode cannot be observed because of an overlap of the signals of cubic boron nitride and diamond used as the anvils in the high-pressure cell.