Saturation of Ion Waves in Cross-Beam Energy Transfer

The tunable OMEGA port 9 (TOP9) laser on OMEGA was used to perform cross-beam energy transfer (CBET) experiments in a gas-jet plasma. The TOP9 laser is a wavelength{\-}tunable UV beam ($\Delta \lambda $\textasciitilde 3nm) that enables CBET experiments in a stationary plasma. TOP9 was interacted with either one or four other 351-nm UV pump beams to study CBET using the time-resolved transmitted beam diagnostic (TBD). The frequency of the TOP9 beam was set so that the beat frequency generated with the UV pump beams was resonant with the ion-acoustic wave frequency of the gas-jet plasma. At low TOP9 intensities, where ion-wave amplitudes were small ($\delta n$/$n$ \textless 1.0{\%}), TBD measurements agreed well with linear CBET theory. At high TOP9 intensities, TBD measurements show ion-wave amplitudes that are initially large ($\delta n$/$n$ \textgreater 3.0{\%}) and then decrease to smaller amplitudes ($\delta n$/$n \quad \approx $ 1.0{\%}) over approximately 300 ps.