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.