Ultrasonic measurements in a diamond anvil cell

Abstract

Advances in ultrasonic and electronic technology have made it practical to make elastic wave measurements with wavelengths which are near the optical range, i.e. in the micro meter range. Ultrasonic interferometry has been adapted to a diamond anvil cell and thus expands the tools available for material property measurements under high pressure and temperature. Sound waves with a frequency of 1 GHz were propagated through an H 2O sample in a diamond anvil cell. Starting at room temperature and a pressure of approximately 1.2 GPa a single crystal of ice VI was heated until it was completely liquid. Good signal transmission was observed in the solid, two phase and liquid states. While the sample was in the two phase region the velocity of propagation of the phase boundary between the solid and the liquid and its roughness were observed. At a propagation velocity of 2 μ s −1 the phase boundary is smooth on the order of 1 μ. Compressional wave travel time measurements at ∼ 2.5 GPa through a ∼ 200-μ thick garnet sample illustrate the capability of the technique for solids. No frequency dispersion in the travel time is observed for this sample from 600 MHz to 1.3 GHz.