ULTRASONIC MEASUREMENTS IN A DIAMOND-ANVIL CELL

Advances in ultrasonic and electronic technology have made it practica l to make elastic wave measurements with wavelengths which are near th e optical range, i.e. in the micro meter range. Ultrasonic interferome try has been adapted to a diamond anvil cell and thus expands the tool s available for material property measurements under high pressure and temperature. Sound waves with a frequency of 1 GHz were propagated th rough an H2O sample in a diamond anvil cell. Starting at room temperat ure and a pressure of approximately 1.2 GPa a single crystal of ice VI was heated until it was completely liquid. Good signal transmission w as observed in the solid, two phase and liquid states. While the sampl e was in the two phase region the velocity of propagation of the phase boundary between the solid and the liquid and its roughness were obse rved. At a propagation velocity of 2 mu s(-1) the phase boundary is sm ooth on the order of 1 mu. Compressional wave travel time measurements at similar to 2.5 GPa through a similar to 200-mu thick garnet sample illustrate the capability of the technique for solids. No frequency d ispersion in the travel time is observed for this sample from 600 MHz to 1.3 GHz.