DEVELOPMENT OF THE AUTOMATIC OIL-PRESSURE CONTROLER AND IN SITU OBSERVATION OF PRESSURE-INDUCED TRANSITION

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Earth interious change their structures with physical conditions as pressure and temperature around them. In situ observations of the structure changes have been executed by X-ray diffaractometry and Raman spectroscopy as a function of pressure and temperature. Recently kinetics of the structure transformations has paied a larte attention as well as thermodynamical phase studies or equilibrium problems. An automatic controller of diamond anvil high pressure apparatus by oil-press was newly devised for the strcture study under compression. an ability test of this appratus was conducted in advance. Specification and capability of the controller were described below.(1) Alognment and remount of X-ray diffraction are no more required after changing pressure. therefore the measuring condition can assure the continuity.(2) The consistent pressure hold was confirmed for a long period.(3) A constant pressure in the diamond anvil pressure cell is automatically kept by semiconductor pressure sen … More sor. this controller is an effective apparatus for the study of pressure-induced transformation with volume change.(4) Load pressure is transmitted through flexible oil pipe. The aimed pressure is achieved from the outside of hutch, when the high pressure X-ray diffraction study is undertaken using synchrotron radiation X-ray at Photon Factory, National Insutitute of High Energy Physics. A remote control of pressure is capable.By using this controlling system an continuously raising and reducing pressure enable us to perform the kinetic study of phase transition under high pressure. This system can apply for the phase study of earth interiou and for measurement of the compressibility and bulk modulous. A newly devised system may throu a light on the new field jin the high pressure sciences, especially for the study of the metastable phase analysis and precursor phenomena of pressure-induced phase transition. Our X-ray diffraction experiments using the system are listed below.Example 1. Pressure-induced amorphization of GeO_2 having a similar polymorphic transition to SiO_2.Example 2. In situ observation of the precursor structure change of Ca(OH)_2 for its phase transformation under compression.Example 3. Comparison between molecular dynamic calculation and high pressure experiment for pressure-induced transition of olivine Mg_2SiO_4. Less