Observation of Two Ion-Acoustic Waves in a Two-Species Laser-Produced Plasma with Thomson Scattering.

We report the first observations of two separate ion acoustic waves in a two ion species plasma with Thomson scattering. A flat disk coated with thin multilayers of gold and beryllium was irradiated with one laser beam, and the resulting two-ion-species plasma was probed with a second laser at a distance of 500{mu}m. The phase velocities of the ion-acoustic waves are shown to be a sensitive function of the relative concentrations of the two ion species. Moreover, an accurate measurement of the ion temperature can be derived from the relative damping of the two-ion-acoustic waves. {copyright} {ital 1996 The American Physical Society.}