Energy-dispersive x-ray diffraction equipment for fluids at extreme conditions of high temperatures and high pressures

Abstract

An energy-dispersive x-ray diffraction technique for fluid materials under high pressure, up to 2000 bar, and high temperature, up to 1650 °C, has been developed using an x-ray source with high energy up to 70 keV, a high-pressure vessel with Be windows pressurized with He gas, and a new sample cell made of single crystal sapphire. Using this technique one can overcome several difficulties intrinsic with x-ray diffraction measurements of fluids, such as high vapor pressure and high x-ray absorption constant of samples, x-ray scattering and absorption by sample cells, and x-ray absorption by high-pressure vessels. In order to show an excellent potential of the equipment, examples of the experiments for the liquid-vapor subcritical fluid Hg and Se are reported.