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

An energy-dispersive x-ray diffraction technique for fluid materials under high pressure, up to 2000 bar, and high temperature, up to 1650 degrees C, has been developed using an x-ray source with high energy up to 70 keV, a h igh-pressure vessel with Be windows pressurized with He gas, and a new samp le cell made of single crystal sapphire. Using this technique one can overc ome several difficulties intrinsic with x-ray diffraction measurements of f luids, such as high vapor pressure and high x-ray absorption constant of sa mples, x-ray scattering and absorption by sample cells, and x-ray absorptio n by high-pressure vessels. In order to show an excellent potential of the equipment, examples of the experiments for the liquid-vapor subcritical flu id Hg and Se are reported. (C) 1999 American Institute of Physics. [S0034-6 748(99)04601-8].