TIME RESOLVED DIFFRACTION STUDY UNDER EXTREME CONDITION. T. Yamanaka, and T. Nagai, Department of Earth and Space Science, Faculty of Science, Osaka University, 1-16 Machikaneyama Toyonaka, Osaka, 560 Japan

Time-resolved diffraction studies and kinetic studies of the phase transition and solid reactions have been made by in situ observation under high pressure and temperature. Diffraction intensity measurement was made using X-ray from synchrotron radiation and rotated anode generator together with curved position sensitive detector(PSD). A streamer mode rather than proportional mode fulfills the function as an effective detector having an extremely high quantum efficiency. Dynamical range in full range of 120deg. and a maximum count rate are 10⁵cps and 5000cps, respectively. A delay line positioning system ensures the angular resolution of 0.06deg. in MoK[[alpha]] radiation using Kr (ethane 15%) gas with 4.2bar compression with high bias voltage of 9600V. A computer aided measurement and control (CAMAC) module enables us to make the time-resolved diffraction intensity measurement with an interval of 10 mil seconds under compression. A fast spectroscopy ADC with maximum of 16,384 channel having 450MHz converter and histogramming memory is installed in the CAMAC crate controller.

We designed a new oil-pressure control diamond anvil pressure cell (DAC) with heating system. A desired pressure was automatically regulated by pressure sensitive semiconductor and electromotive micro piston. A ring platinum micro heater with DC current supplier and thermocouple are installed in DAC. Sample temperature is controlled by PID system. Both pressure and temperature can be controlled from the outside of the station in SR facility.

The kinetic study of the structure transition from [[alpha]]-quartz (P3₂21, z=3) to rutile form (P4₂mnm, z=2) structure has been made by the above described diffraction apparatus. The transformation mechanisms of dehydration, melting and pressure-induced amorphization etc of monometal dioxides and hydrates have been also elucidated by profile analysis including size and strain effect. Their transformation rate were determined by intensity ratios with time between initial and final products. The kinetic study of the pressure-induced first order transition indicates five stages: initial process, inductance period, acceleratory period, steady reaction and deceleration period.