Conditions for the Observation of Two Ion-Acoustic Waves via Thomson Scattering

Observationof two ion-acoustic waves via Thomson scattering can provide precise measurements of plasma parameters. The conditions for the observation of two ion-acoustic modes in a two-ion plasma are discussed.The ratio of electron temperature Te to ion temperature Ti is the critical parameter for the presence of two ion-acoustic modes, which should be in the range of 4/ZL ≤ Te/Ti ≤ 2AH/ZHAL, where ZL,H are the charge states of light and heavy ions, and AL,H are the atomic numbers of light and heavy ions, respectively. As the temperature ratio varies in this range, the concentration of heavy ions must increase with the ratio Te/Ti so that the two ion-acoustic modes can have the same fluctuation levels.