The MA8 system can generate relatively uniform pressure and get a large sample volume to including heating system. As an anvil material we have employed tungsten carbide. However, the efficiency of high pressure generation above 20 GPa is reduced because of plastic deformation of anvil top . Sintered diamond which has the highest compressive strength and no cleavage plane is the most promising choice as the alternative for anvil material. The purpose of this study is to develop the high

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... apparatus with sintered diamond anvils including internal heating capable under ultra high pressures and to establish condition for the reliable experiments. In this system we succeed in generating pressures over 30 GPa and temperature about 2000 •Ž in a sample volume of about lmm3. We confirmed of decomposition of forstrite to perovskite and periclace by X-ray diffraction analysis.