An ultrahigh-pressure apparatus based on high presure produced by constraining thermal expansion and its application

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A method of producing ultrahigh pressures to several hundred gigapascals by constraining thermal expansion is investigated taking into account its application. In this method, high pressure is generated by applying pulse laser light to a sample compressed with transparent anvils. The generated ultrahigh pressures are measured by the ruby R-line fluorescence method. In order to avoid direct light radiated from high-temperature region that prevents the measurement of the R-line fluorescence, opaque solid materials are used as pressure medium and a ruby crystal for the pressure measurement is placed on the pressure face of the anvil opposite to that irradiated by pulse laser light. An optical instrument for adjusting the position and the diameter of the illuminated spot to those of the sample is proposed which enable one to apply the light to the sample without giving damage to the anvil. The results are as follows :R_1 fluorescence light of ruby which contains wavelengths emitted from ruby under a pressure of 1 Tpa is observed when a graphite sample compressed with sapphire anvils is irradiated by a pulse laser light with a energy of 1 J ;A part of the graphite sample is shown to be heated up to temperatures above 3200 ℃ in terms of the radiation spectrum measurement;The temperature distribution calculated on the basis of the above experimental results shows that the graphite sample includes a relatively large region beyond 4000 ℃ of which the greater part is considered to be evaporated ; andthe duration of several hundred gigapascals generated in the apparatus is several orders in magnitude longer than those of all other conventional shock compression method. The ultrahigh-pressure apparatus using sapphire anvils will be a powerful tool for industrial production because a large sapphire crystal is easy to make.